UC-NRLF 


c  3  D37  ^^^ 


Gift  of 
Llrs.  Rawlins  Cadwallader 


W^>-6X-^>OtJ^)^/^ 


Digitized  by  the  Internet  Archive 

in  2007  with  funding  from 

IVIicrosoft  Corporation 


http://www.archive.org/details/anatodescripsurgOOgrayrich 


A  N  A  T  O  M  Y, 


DESCRIPTIVE  AND  SURGICAL 


BY 


HENRY  KiEAY,  F.R.S., 

FELLOW    OF  THE    ROYAL   COLLEOE    OF   SUROEONS;    LECTURER   ON   ANATOMY   AT   ST.    QEORGk's 
HOSPITAL   MEDICAL  SCHOOL,    LONDON. 


EDITED  BY 

T.  PICKERING  PICK,  F.R.C.S., 

CONSULTING   SURGEON   TO   ST.  GEORGe's    HOSPITAL   AND   TO   THE   VICTORIA    HOSPITAL   FOR   CHILDREN,  LONDON; 
H.  M.    INSPECTOR   OF   ,\NATOMY   IN    ENGLAND   AND   WALES, 

AND 

ROBERT  HOWDEN,  M.A.,  M.B.,  CM., 

PROFESSOR  OF  ANATOMY  IN  THE  UNIVERSITY  OF  DURHAM;    EXAMINER  IN  ANATOMY  IN  THE  UNIVERSITIES 
OF  DURHAM  AND  EDINBURGH,  AND  TO  THE  BOARD  OF  EDUCATION,  SOUTH  KENSINGTON. 

NEW  AMERICAN  EDITION. 


THOROUGHLY  REVISED  AND  RE-EDITED  WITH  ADDITIONS 


BY 

JOHN  CHALMERS  Da  COSTA,  M.D„, 

PROFESSOR   OF   PRINCIPLES   OF   SURGERY    AND    PROFESSOR    OF   CLINICAL  SURGERY    I  .V    JEFFERSON    MEDICAL  COLLEGE 
PHILADELPHIA;    SURGEON   TO   THE    PHILADELPHIA    HOSPITAL;    CONSULTING   SURGEON 

TO  ST    Joseph's  hospital 


ILLUSTRATED  WITH   1132   ELABORATE  ENGRAVINGS. 


6^77 


I.EA   BROTHERS   &   CO., 
PHILADELPHIA  AND  NEW  YORK. 


Copyright,  1905,  by  Lea  Brothers  &  Co, 
Copyright,  1907,  by  T.ea  Brothers  &  Co. 


Revised,  printed  and  copyrighted,  1905.     Reprinted,  1906. 
Reprinted  with  alterations  and  recopyrighted,  August,  1907. 


THIS 


NEW  AMERICAN  EDITION  OF  GRAY'S  ANATOMY 


IS  DEDICATED    TO 


WILLIAM  W.  KEEN,  M.D,  LL.D.,  Hon.  F.KC.S.  [Eng.  and  Edin.] 

THE    DISTINGUISHED    PROFESSOR    OF    SURGERY    IN    JEFFERSON 
MEDICAL    COLLEGE 


AS    AN    EVIDENCE    OF 


THE    ADMIRATION,    THE    AFFECTION    AND    THE    GRATITUDE    OF    HIS    COLLEAGUE 


AND    FORMER    ASSISTANT 


THE  EDITOR 


74978 


PREFACE. 


In  this  revision  of  Gray's  Anatomy,  the  Editor  has  endeavored  to  reflect  the 
development  of  the  subject  since  the  appearance  of  the  last  edition,  and  has 
sought  to  accoinpHsh  this  without  sacrificing  those  practical  and  didactic  char- 
acteristics that  have  ever  been  the  most  notable  features  of  the  book.  Radical 
innovations  were  undesirable,  and  original  exposition  was  neither  desirable  nor 
possible.  The  P^ditor  is  responsible  for  some  eliminations,  many  alterations, 
and  a  great  number  of  additions;  and  it  has  been  deemed  unwise  even  to  attempt 
to  designate,  by  brackets  or  any  other  device,  so  great  a  number  of  changes  and 
additions. 

In  order  that  its  pages  might  represent  the  world's  best  knowledge,  American, 
English,  French,  and  German  text-books,  monographs,  and  journal-articles  have 
been  freely  consulted.  In  using  statements  from  these  numerous  sources,  the 
aim  has  been  to  give,  in  every  instance,  proper  credit  to  the  author.  If,  in  some 
cases,  this  has  not  been  done,  the  failure  is  the  result  of  accident,  and  never  of 
design. 

Among  the  many  works  thus  utilized  may  be  mentioned  the  three  composite 
treatises  edited  by  Gerrish,  Cunningham,  and  Morris,  respectively;  Poirier  and 
Charpy,  Testut,  Spalteholz  (which  has  recently  been  translated  into  English 
and  edited  by  Professor  Barker);  Hughes's  Practical  Anatomy,  edited  and  coni- 
pleted  by  Keith;  McClellan's  Regional  Anatomy;  Deaver's  Surgical  Anatomy  ; 
Treves's  Applied  Anatomy;  Owens's*  Manual  of  Anatomy;  Eisendrath's  Clinical 
Anatomy;  Byron  Robinson,  on  the  Peritoneum;  and  the  text-books  of  Quain 
and  MacAUister.  Special  credit  is  due  to  the  chapter  on  the  "Lymphatics"  in 
Poirier  and  Charpy  (translated  and  edited  by  Leaf) ;  to  the  admirable  section 
on  the  "Nervous  System,"  written  by  Professor  Cunningham  in  his  text-book; 
and  to  Professor  Santee's  extremely  valuable  monograph  on  the  Anatomy  of  the 
Brain  and  Spinal  Cord. 

The  Latin,  new  or  international  nomenclature  has  been  introduced  in 
parentheses,  following  the  names  still  currently  used  in  English-speaking  coun- 
tries. This  system  of  coupling  the  current  and  the  new  names  answers  the  needs 
of  all  students,  and  will  facilitate  the  much-to-be-desired  adoption  of  the  new 
nomenclature.  The  Latin  nomenclature  was  recommended  by  an  international 
(committee,  was  published  by  Wilhelm  His,  and  has  been  generally  accepted  by 
anatomists.  Owing  to  its  accuracy  and  its  simplicity,  it  seems  destined  eventu- 
ally to  succeed  the  older  methods  of  designation;  but  in  this  country  at  least, 
the  older  nomenclature  is  still  too  firmly  fixed  to  be  entirely  and  suddenly 
abandoned. 

Gray's  Anatomy  has  been  noted  for  the  extent  and  the  elaborate  nature  of  its 
illustrations.  This  new  edition  exceeds  its  predecessor  in  the  number  of  engrav- 
ings and  in  the  use  of  colors.  The  series  now  aggregates  over  eleven  hundred,  of 
which  about  five  hundred  are  new  in  this  edition.  Particular  acknowledgment  for 
originals  is  due  to  Spalteholz,  Cunningham,  Poirier  and  Charpy,  Testut,  Gerrish, 
Byron  Robinson,  and  the  Atlas  of  Human  Anatomy  by  Carl  Toldt,  assisted  by 

(V) 


vi  PREFACE 

A.  D.  Rosa  (recently  translated  into  English  and  edited  by  M.  Eden  Paul).  The 
pictures  taken  from  these  various  sources  have  been  re-engraved,  and  in  some 
instances  have  been  modified. 

In  this  edition  the  special  articles  on  "Histology"  and  "Embryology,"  hitherto 
placed  at  the  end  of  the  book,  have  been  eliminated.  The  extent,  the  importance, 
and  the  technical  nature  of  these  great  subjects  have  led  to  the  creation  of  special 
chairs  for  their  teaching;  and  it  seems  desirable  that  the  text-books  used  by 
the  students  should  be  those  written  by  men  devoted  to  these  specialties.  No 
single  volume,  in  these  days,  can  offer  adequate  instruction  on  anatomy,  histology, 
and  embryology;  and  to  attempt  it  would  be  unwise.  The  bearings  of  histology 
and  embryology  upon  anatomy  are  close  and  highly  important.  The  Editor  has 
set  forth  the  essential  points  of  these  subjects  when  the  elucidation  of  the  text 
demanded  it  by  means  of  resumes.  For  these,  he  has  drawn  chiefly  upon  the 
excellent  sections  in  the  previous  edition  of  Cray  (which  were  edited  by  Robert 
Howden),  supplementing  them  from  the  Hisiology  and  Microscopic  Anatomy 
by  Szymonowicz  (translated  by  John  Bruce  MacCallum),  the  text-book  of 
Histology  by  Bohm  and  von  Davidoff  (edited  by  G.  Carl  Huber),  and  the  text- 
book of  Embryology  by  John  Clement  Heisler.  The  clear  and  instructive  surgical 
notes  of  Mr.  Pick  have,  of  course,  been  retained;  although,  here  and  there,  they 
have  been  modified  or  added  to,  in  accordance  with  the  views  of  the  day. 
Because  of  an  oversight  the  foot-notes,  thirty-five  in  number,  from  page  49  to 
page  497  inclusive,  are  not  credited  to  the  Editors  of  the  15th  English  edition. 
Subsequent  to  page  497  proper  credit  is  given  for  foot-notes  from  the  English 
editors. 

The  Editor  desires  cordially  to  express  his  sense  of  indebtedness  and  gratitude 
to  Dr.  Howard  Dehoney,  Senior  Assistant  Demonstrator  of  Anatomy  in  the 
Jefferson  Medical  College,  for  his  able  and  conscientious  aid  and  collaboration. 
When  a  book  has  been  edited  many  times  by  many  men,  the  views  and  the 
style  of  the  author  are  sure  to  be  more  or  less  obscured.  The  Editor  of  this 
edition  hopes  that  Gray's  Anatomy  has  not  suffered  too  many  things  at  his 
hands. 

John  Chalmers  Da  Costa. 

Philadelphia,  1905. 


PUBLISHERS'  NOTE. 


Henry  Gray  ilied  young,  but  left  in  his  masterpiece  imperishable  evidence 
of  his  two-fold  genius,  on  the  one  hand  a  profound  capacity  to  grasp  the  struc- 
ture of  the  human  body,  and  on  the  other  an  equal  insight  into  the  mind  and 
the  best  method  of  imparting  knowledge.  His  work  immediately  attained  its 
merited  pre-eminence,  a  position  which  the  many  excellent  treatises  of  the  past 
fifty  years  have  only  rendered  more  conspicuous. 

During  this  period  fretiuent  revisions  have  kept  Gray  always  abreast  of  the 
active  development  of  its  subject.  Among  its  editors  it  has  numbered  many 
of  the  ablest  anatomists  on  both  sides  of  the  Atlantic.  The  services  of  Dr. 
Da  Costa  were  sought  by  the  Publishers  by  reason  of  his  combined  qualifications 
as  an  anatomist,  a  teacher  and  a  surgeon.  He  has  borne  in  mind  the  Author's 
original  purpose,  namely,  to  facilitate  to  the  utmost  the  work  of  instructors  and 
students,  antl  to  afford  the  physician  and  surgeon  the  assistance  necessary  in 
practice.  He  has  revised  every  page,  elaborating  the  text  where  necessary  to 
cover  the  latest  developments,  and  to  ensure  due  proportion,  and  has  greatly 
enriched  the  illustrations  both  in  number  and  in  the  use  of  col  )rs.  The  names 
of  the  parts  are  engraved  directly  upon  them,  a  feature  original  with  Gray  and 
peculiar  to  hi?  work.  The  advantage  is  obvious.  Ample  directions  are  given 
for  dissection.  The  new  nomenclature  has  been  introduced  in  parentheses 
following  the  names  still  in  common  use,  an  arrangement  preferable  to  either  system 
alone.  The  book  is  thoroughly  organized  in  its  headings  and  with  heavy  type 
catchwords  in  the  text,  so  that  the  student  readily  gains  a  knowledge  of  the  parts 
in  their  anatomical  dependence. 

From  the  foregoing  outline  it  is  not  difficult  to  appreciate  the  reasons  for  the 
fact  often  observed  that  Gray  is  the  easiest  work  from  which  to  teach,  to  learn, 
to  prepare  for  examinations  for  collegiate  degrees  and  state  licenses,  and  to  use 
for  reference  in  the  practice  of  medicine  and  surgery. 

Grateful  acknowledgment  is  made  by  the  Publishers  to  Dr.  William  T.  Eckley, 
Dr  D.  Kerfoot  Shute,  Dr.  E.  C.  Henry,  Dr.  William  Keiller,  Dr.  A.  Primrose. 
Dr  Samuel  H.  Childs,  Dr.  William  D.  Sumpter,  Dr.  William  Perrin  Nicolson,  Dr. 
Charles  L.  Mix,  Dr.  L.  F.  Barker,  Dr.  Norman  E.  Jobes,  Dr.  John  E.  Hays,  Dr, 
A.  C.  Pole.  Dr.  Isaac  R.  Trimble,  Prof.  J.  P.  McMurrich,  Dr.  Daniel  Da  Ferte, 
Dr.  Kenneth  Gonsolus,  Dr,  George  J.  Gordon,  Dr.  Norman  Driesbach,  Dr. 
Charles  A.  Erdman,  Dr.  George  H.  Hoxie,  Dr.  Howard  Hill,  Prof.  A.  C.  Eycle- 
shymer.  Dr.  Peter  Potter,  Dr.  Robert  J.  Terry,  Dr.  V.  P.  Blair,  Dr.  Joseph  D. 
Craig,  Dr.  James  A.  Gibson,  Dr.  Abram  T.  Kerr,  Dr.  George  M.  Price.  Dr.  Josiah 
Medbery,  Dr.  Louis  D.  Barbot,  Dr.  Elmer  E.  Francis,  Dr.  Samuel  S.  Briggs, 
Dr.  Ira  C.  Chase,  Dr.  Henry  C.  Tinkham,  Dr  William  P.  Mathews,  Dr.  William 
G.  Doern,  and  many  other  eminent  anatomists  and  teachers  whose  kindly  criti- 
cisms and  intelligent  suggestions  have  aided  so  materially  in  bringing  Gray  to 
its  present  excellence. 

(vii) 


CONTENTS. 


DESCRIPTIVE  AND  SURGICAL  ANATOMY. 


OSTEOLOGY— THE   SKELETON. 


PAGE 

The  Skeleton 33 

Number  of  the  Bones 33 

Form  of  Bones 33 

Long  Bones 33 

Short  Bones 33 

Flat  Bones 34 

Irregular  Bones 34 

Surfaces  of  Bones 34 

Structure  of  Bone 34 

Bloodvessels  of  Bone 39 

Chemical  Composition  of  Bone    ....  41 

Ossification  and  Growth  of  Bone      ...  42 

The  Vertebk.\l  or  Spin.\l,  Column. 

General  Characters  of  a  Vertebra. 

The  Cervical  Vertebrie 49 

Atlas 50 

Axis 52 

Seventh  Cervical         53 

The  Thoracic  or  Dorsal  Vertebra;      ...  53 

Peculiar  Dorsal  Vertebrae     ....  55 

The  Lumbar  Vertebrte 56 

Structure  of  the  Vertebra; 58 

Development  of  the  Vertebrsje      ....  58 

I3evelopnient  of  the  Atlas 59 

Development  of  the  Axis 59 

Development  of  the  Seventh  Cervical    .       .  60 
Development  of  the  Lumbar  Vertebrae        .  60 
Progress  of  Ossification  in  the  Spine  Gener- 
ally        60 

The  Sacral  and  Coccygeal  Vertebra;      .  61 

Sacrum 61 

Differences  in  the  Sacrum  of  the 

Male  and  Female        ....  64 

Peculiarities  of  the  Sacrum  64 

Coccyx 65 

The  Vertebral  Column  or  Spine  in  General  .  67 

Surface  Form  of  the  Vertebral  Column  .       .  69 

Surgical  Anatomy  of  the  Vertebral  Column  69 

The  Skull. 

The  Cerebral  Cranium. 

The  Occipital  Bone ;  71 

The  Parietal  Bone 76 

The  Frontal  Bone 79 

Vertical  Portion  of  the  Frontal  Bone  .  79 
Horizontal   or   Orbital   Portion   of   the 

Frontal  Bone 81 

The  Temporal  Bone 83 

Sfjuamous    Portion    of    the    Temporal 

Bone 83 

The  Mastoid  Portion  of  the  Temporal 

Bone 85 

The  Petrous  Portion  of  the  Temporal 

Bone 88 


PACK 

The  Sphenoid  Bone 92 

The  Body  of  the  Sphenoid  Bone    .      .  92 
The  Greater  or  Temporal  Wings  of  the 

Sphenoid  Bone 95 

The    Lesser    or    Orbital    Wings    of   the 

Sphenoid   Bone 96 

The  Pterygoid  Processes  of  the  Sphe- 
noid Bone 96 

The  Sphenoidal  Spongy  Bone    ...  97 

The  Ethmoid  Bone 98 

The   Horizontal   Lamina  or  Cribriform 

Plate  of  the  Ethmoid  Bone   ...  99 
The  Vertical  or  Perpendicular  Lamina 

or  Plate  of  the  Ethmoid  Bone    .  100 
The  Lateral  Mass  or  Labyrinth  of  the 

Ethmoid  Bone 100 

Development  of  the  Cranium      ....  102 

The  Fontanelles 102 

Supernumerary  or  Wormian  Bones      .  103 

Congenital  Fissures  and  Gaps   .             .  104 

Bones  of  the  Face. 

The  Nasal  Bones    . 104 

The  Superior  Maxillary  Bones    ....  105 
The  Body  of  the  Superior  Maxilla  .  105 
The  Processes  of  the  Superior  Maxillse  109 
Malar  Process  of  the  Superior  Max- 
illa           109 

Nasal  Process  of  the  Superior  Max- 
illa           109 

Alveolar   Process   of   the   Superior 

Maxilla 109 

Palate    Process    of    the    Superior 

Maxilla 110 

Changes  Produced  in  the  Upper  Jaw  by  Age  112 

The  Lachrvmal  Bone 112 

The  Malar"  Bone 113 

The  Palate  Bone 115 

The    Horizontal    Plate   of    the    Palate 

Bone 116 

The  Vertical  or  Perpendicular  Plate  of 

the  Palate   Bone 117 

The  Inferior  Turbinated  Bone            .  119 

The  Vomer 120 

The  Maxillary  Bone,  Inferior  Maxilla,  Man- 
dible or  Lower  Jaw 122 

The  Horizontal  Portion  or  Body  of  the 

Mandible 122 

The  Perpendicular  Portion  or  Rami  of 

the  Mandible 124 

Changes   Produced   in    the    Lower   Jaw   by 

Age ".125 

The  Sutures 127 

The  Skidl  as  a  Whole. 

The  Vertex  of  the  Skull 129 

The  Base  of  the  Skull 130 


CONTENTS 


PAGK 

The  Lateral  Region  of  tlie  Skull      .      .      .  136 

The  Temporal  Fossa 137 

The  Mastoid  Portion 138 

The  Zygomatic  or  Infratemporal  Fossa  138 
The  Spheno-maxillary  or  Pterygo-pala- 

tine   Fossa 139 

The  Anterior  Region  of  the  Skull    .       ^  139 

Orbits,  Orbital  Cavities  or  Orbital  Fosste  140 

The  Nasal  Cavity 142 

Difference  in  Size  and  Form  of  the  Cranium  146 

Surface  Form  of  the  Skull 147 

P'ixed  Points  for  Measurement  of  the  Skull  149 

Surgical  Anatomy  of  the  Skull   ....  149 

The  Hyoid  or  Lingual  Bone 153 

The  Thor.^^x. 

The  Sternum 155 

The  Ribs 159 

Common  Characters  of  the  Ribs    .       .  161 

Peculiar  Ribs 162 

The  Costal  Cartilages 164 

Surface  Form  of  the  Chest 165 

Surgical  Anatomy  of  the  Chest  .       .      .      .  165 

The  Upper  Extremity. 
The  Shoulder  Girdle. 

The  Clavicle 167 

Surface  Form  of  the  Clavicle    .      .      .  170 

Surgical  Anatomy  of  the  Clavicle   .       .  170 

The  Scapula 171 

Surface  Form  of  the  Scapula  176 

Surgical  Anatomy  of  the  Scapula  .      .  177 

The  Arm. 

The  Humerus   .7 .177 

Surface  Form  of  the  Humerus  .       .       .  183 

Surgical  Anatomy  of  the  Humerus  183 

The  Forearm. 

The  Ulna 184 

Surface  Form  of  the  Ulna           .      .  189 

The  Radius 190 

Surface  Form  of  the  Radius            .      .  192 
Surgical  Anatomy  of  the   Radius  and 

Ulna 192 

The  Hand. 

The  Carpus  . 193 

Common  Characters  of  the  Carpal  Bones  193 

Bones  of  the  Upper  Row            .  195 

Scaphoid  or  Navicular  Bone    .       .  195 

Semilunar  Bone 196 

Cuneiform  Bone 197 

Pisiform  Bone 197 

Bones  of  the  Lower  Row            .      .  198 

Trapezium 198 

Trapezoid 198 

Os  Magnum 199 

Unciform 199 


PAGE 

The  Metacarpus      .       .      7      .       ."     7      .       .  200 
Common  Characters  of  the  Metacarpal 

Bones 200 

PecuUar  Characters  of  the  Metacarpal 

Bones 201 

The  Phalanges  of  the  Hand 204 

Surface  Form  of  the  Bones  of  the  Hand  204 

Surgical  Anatomy  of  the  Bones  of  the  Hand  205 

Development  of  the  liones  of  the  Hand      .  205 

The  Lower  Extremity. 
The  Pelvic  Girdle. 

The  Os  Innominatum 207 

The  Ilium 207 

The  Ischium 210 

The  Pubis 212 

The  Cotyloid  Cavity  or  Acetabulum    .  213 

The  Obturator  or  Thyroid  Foramen    .  214 

The  Pelvis 215 

The  False  Pelvis 215 

The  True  Pelvis 216 

Position  of  the  PelvLs 218 

Axes  of  the  Pelvis 218 

Differences  between  the  Male  and    the 

Female  Pelvis 219. 

Surface  Form  of  the  Pelvis  ....  220 

Surgical  Anatomy  of  the  Pelvis      .  220 

The  Thigh. 

The  Femur  or  Thigh  Bone 221 

Surface  Form  of  the  Femur      .       .       .  229 

Surgical  Anatomy  of  the  Femur     .  229 

The  Leg. 

The  Patella  or  Knee-cap 230 

Surface  Form  of  the  Patella      .      .       .231 

Surgical  Anatomy  of  the  Patella     .  231 

The  Tibia  or  Shin  Bone 233 

Surface  Form  of  the  Tibia   ....  236 

The  Fibula  or  Calf  Bone 237 

Surface  Form  of  the  Fibula  .  239 

Surgical  Anatomy  of  Bones  of  the  Leg  239 

The  Foot. 

The  Tarsus 242 

The  Calcaneus  or  Heel  Bone  .  242 

The  Astragalus  or  Ankle  Bone  .       .  244 

The  Cuboid 245 

Scaphoid  or  Navicular  Bone     .  246 

Cuneiform  or  Wedge  Bones  ....  247 

The  Metatarsal  Bones 249 

Common  Characters  of  Metatarsal  Bones  249 

Peculiar  Characters  of  Metatarsal  Bones  249 

The  Phalanges  of  the  Foot 252 

Development  of  the  Foot 253 

Construction  of  the  Foot  a-s  a  Whole     .  254 

Surface  Form  of  the  Foot 255 

Surgical  Anatomy  of  the  Foot    ....  256 

Sesamoid  Bones 257 


THE  ARTICULATIONS  OR  JOINTS. 


Structures  Composing  the  Joints  .       .  259 

Bone 259 

Cartilage     .       .  .       .      .  .      .  259 

Ligament.s 261 

Synovial  Membranes 262 

Forms  of  Articulation: 

Synarthrosis 264 

Amphiarthrosis 264 

Diarthrosis 265 

The    Kinds    of     Movement    Admitted     in 

Joints 266 

Ligamentous  Action  of  Muscles  ....  268 


Articulations  of  the  Trunk. 

.\rticulations  of  the  Vertebral  Column  .  269 

Articulations  of  the  Atlas  with  the  Axis      .      274 

Articidations  of  the  Spine  with  the  Cranium. 

Articulation  of  the  Atlas  with  the  Occipital 

Bone .276 

Articulation  of  the  Axis  with  the  Occipital 

Bone  278 

Surgical   Anatomv   of   Articulations   of   the 

Spine         .      .  ■ 279 


CONTENTS 


XI 


290 
290 

290 
292 
292 


Articulation  of   the  Lower  Jaw  or  the  Tem- 

poro-inandibular  Articulation  280 

Surface  Form 282 

Surgical  Anatomy 282 

Articulations  of  the  Ribs  with  the  Vertebrje 

or  tlie  Costo-vortebral  Articulations  .       .      283 
Articulation  of  the  Cartilages  of  the  Ribs 
with  the  Sternum,  etc.,  or  the  Costo- 

sternal  Articulations 287 

Articulations  of  the  Cartilages  of  the 
Ribs  with  Each  Other  or  the  Inter- 
chondral  Articulations  ....  289 
Articulations  of  the  Ribs  with  tiieir  (Car- 
tilages or  the  Costo-chondral  Artic- 
ulations          

Articulations  of  the  Sternum       .... 
Articulations  of  the  Vertebral  Column  with 

the  Pelvis 

Articulations  of  the  Pelvis 

Articulation  of  the  Sacrum  and  Ilium  . 
Ligaments  passing  between  the  Sacnnn 

and  Ischium 292 

Articulation  of  the  Sacrum  and  Coccy.x     294 
Articulation  of  the  Ossa  Pubis  .  .      296 

Articul.\tio.ns  of  the   Uppek   E.xtremity. 

Sterno-clavicular  Articulation      ....  237 

Surface  Form 299 

Surgical  Anatomy 299 

Acromio-clavicular  Articulation  or  Scapulo- 
clavicular Articulation       ....  299 

Surface  Form 301 

Surgical  Anatomy 301 

Proper  Ligaments  of  the  Scapula     .      .      .  301 

The  Shoulder-joint 303 

Surface  Form  of  the  Shoulder-joint  307 
Surgical    Anatomy    of    the    Shoulder- 
joint        307 

The  El  bow- joint 308 

Surface  Form  of  tlie  Elbow-joint   .       .  312 

Surgical  Anatomy  of  the  Elbow-joint  .  312 

Radio-ulnar  Articulation 313 

Superior  or  Pro.ximal  Radio-ulnar  Artic- 
ulation          314 

Surface  Form 314 

Surgical  Anatomy 314 

Middle  Radio-ulnar  Ligaments  .       .       .  314 
Inferior   or    Distal    Radio-ulnar    Artic- 
ulation          315 

Surface  Form 317 

Radio-carpal  or  Wrist-joint 317 

Surface  Form  of  V/rist-joint      .       .      .  318 

Surgical  Anatomy  o"  Wrist-joint     .      .  318 

Articulations  of  the  Carpus 319 

Articulations  of  the  First  Row  of  Carpal 

Bones 319 

Articulations  of  the  Second  Row  of  Car- 
pal Bones 319 

Articulations  of  the  Two  Rows  of  Car- 
pal Bones 320 


PAGE 

Carpo-metacarpal  Articulations  .       .      .       .  321 
Articulation  of  the  Metacarpal  Bone  of 

the  Thumb  with  the  Trapezium       .  321 
Articulations  of  the  Metacarpal  Bones  of 

the  Four  Inner  Fingers  witli  the  Carpus  322 
Articulations  of  the  Metacarpal  Bones 

with  Each  Other 324 

Metacarpo-phalangeal  Articulations        .  324 
Surface  Form  of  Metacarpo-phalangeal 

Articulations 324 

Articulations  of  the  Phalanges     ....  325 

Articul.\tioxs  of  the  Lower  Extre.mity. 

The  Hip-joint 325 

Surface  Form  of  the  Hip-joint  .  .  333 

Surgical  Anatomy  of  the  Hip-joint      .  333 

Tlie  Knee-joint 334 

Surface  Form  of  the  Knee-joint  .  343 

Surgical  Anatomy  of  the  Knee-joint   .  343 

Tibio-fibular  Articulation 345 

Superior  Tibio-fibular  Articulation  345 
Middle  Tibio-fibular  Ligament  or  Inter- 
osseous Membrane 346 

Inferior  Tibio-fibular  Articulation  .       .  346 

The  Tibl-o-tar.sal  Articulation  or  Ankle-joint  347 

Surface  Form  of  Ankle-joint  .  351 

Surgical  Anatomy  of  Ankle-joint    .  351 

Articulations  of  the  Tarsus 352 

Articulation  of  the  Os  Calcis  and  A.s- 
tragalus  or  the  Calcaneo-astragaloid 

Articulation        . 352 

Articulation  of  the  Os  Calcis  with  the 
Cuboid  or  the  Calcaneo-cuboid  Artic- 
ulation      353 

The  Ligaments  connecting  the  Os  Calcis 
and  Scaphoid   or   the  Calcaneo- 

scaphoid  Articulation  Ligaments  353 

Surgical  Anatomy 354 

Articulation  of  the  Astragalus  with  the 
Scaphoid    Bone     or    the    Astragalo- 

scaphoid  Articulation         ....  354 
The  Articulation  of  the  Scaphoid  with 

the  Cuneiform  Bones 355 

The  Articulation  of  the  Scaphoid  with 

the  Cuboid 355 

The    Articulations    of    the    Cuneiform 
Bones  with  Each  Other  or  the  Inter- 
cuneiform Articulations     ....  355 
The  Articulation  of  the  External  Cunei- 
form Bone  with  the  Cuboid      .  356 

Surgical  Anatomy 356 

Tarso-metatarsal  Articulations     ....  357 
Articulations  of  the  Metatarsal  Bones  with 

Each  Other 358 

The  Synovial  Membranes  in  the  Tarsal 

and  Metatarsal  Joints 358 

Metatarso-phalangeal  Articulations         .       .  359 

Articulations  of  the  Phalanges     ....  359 

Surface  Form 360 

Surgical  Anatomy 360 


THE  MUSCI.es  and  FASCLE. 


Oeneral  Description  of  Muscles    ....  361 

General  Description  of  Tendons         .       .       .  363 

General  l)(>scri])ti()n  of  Aponeuroses        .       .  363 

General  Descrijition  of  Fasciae      ....  364 

Muscles  .\xd  F.\,sci.«  of  the  Cr.\nium  .\nd 
Face. 

Subdivision  into  Groups 365 

The  Cranial  Region 366 

Dissection 366 

Superficial  Fascia 366 

Surgical  Anatomy 367 

The  Occipito-frontalis 367 

Surgical  Anatomy 368 


Tlie  Auricular  Region        ......  369 

Dissection         369 

Attrahens  Auriculam  or  Aurem       .  369 

Attollens  Auriculam  or  Aurem .       .       .  369 

Retrahens  Auriculam  or  Aurem       .       .  369 

The  Palpebral  Region 370 

Dissection         370 

Orbicularis  Palpebraruni       ....  370 

Corrugator  Supercilii 371 

Levator  Palpebral 371 

Tensor  Tarsi  or  Horner's  Muscle     .      .  371 

The  Orbital  Region 372 

Levator  Palpebrse  Superioris     .       .      .  372 

Superior  Rectus 373 

Inferior  Rectus 373 


xu 


CONTENTS 


The  Orbital  Region — 

External  Rectus 373 

Superior  Oblique 373 

Inferior  Oblique 374 

Fascia;  of  the  Orbit 374 

Surgical  Anatomy 575 

The  >Jasal  Region 575 

Pyraniidalis  Nasi 375 

Levator  Labii  Superioris  Alaeque  Nasi  375 

Dilator  Naris  Posterior 376 

Dilator  Naris  Anterior 376 

Compressor  Nasi         376 

Compressor  Narium  Minor  ....  376 

Depressor  Alas  Nasi 376 

The  Superior  Maxillary  Region   ....  376 

Levator  Labii  Superioris       ....  376 

Levator  Anguli  Oris 377 

Zygomaticus  Major 377 

Zygomaticus  Minor 377 

The  Mandibular  Region 377 

Dissection 377 

Levator    Labii    Inferioris    or    Levator 

Menti 378 

Depressor  Labii  Inferioris  or  Quadratus 

Menti 378 

Depre.ssor  Anguli  Oris  or  Triangularis 

Menti 378 

The  Intermaxillary  Region 378 

Dissection 378 

Orbicularis  Oris 378 

Buccinator 380 

Risorius  or  Santorini's  Muscle    .       .       .  380 

The  Tenaporo-mandibular  Region                    .  381 

Masseteric  Fascia 381 

Masse ter  Muscle 381 

Temporal  Fascia 381 

Dissection 382 

Temporal  Muscle 382 

The  Pterygo-mandibular  Region  383 

Dissection 383 

External  Pterygoid  Muscle   ....  383 

Internal  Pters'goid  Muscle     ....  383 

Surface  Form  of  Muscles  of  Head  and  Face  385 

MUSCLE.S    AND    FaSCIvI'"    OF    THE    NeCK. 

Subdivision  in  Groups                    .       .       .       .  385 

The  Superficial  Cervical  Region  ....  386 

Dissection 386 

Superficial  Cervical  Fascia  ....  386 

Platysma  Myoides 386 

Deep  Cervical  Fascia 387 

Surgical  Anatomy 380 

St«mo-mastoid  orSterno-cleido-mastoid  389 

Surface  Form 391 

Surgical  Anatomy 391 

The  Infra-hyoid  Region 391 

Dissection 391 

Stemo-hyoid 391 

Sterno-thvroid 392 

Thyro-liybid 392 

Omo-hyoid 393 

The  Supra-iivoid  Region 393 

Dissection 393 

Diga-stric 393 

Stvlo-hvoid 394 

Mylo-hyoid 394 

Dissection 395 

Genio-hyoid 395 

The  Lingual"  Region     .       .       .      .      .       .  396 

Di-ssection 396 

Genio-hyo-glossus 396 

Hyo-glossus 397 

Chondro-glossus 397 

Stylo-glossus 397 

Palato-glossus    or    Constrictor    Isthmi 

Faucium 398 

Muscular  Substance  of  the  Tongue      .  398 

Surgical  Anatomy 400 


The  Pharyngeal  Region 400 

Dissection 400 

Inferior  Constrictor 400 

Middle  Constrictor 401 

Superior  Constrictor 401 

Stylo-pliaryngeus 403 

The  Palatal  Region 403 

Dissection 403 

Levator  Palati 4(J3 

Circumflexus  or  Tensor  Palati   .       .      .  404 

Palatine  Aponeurosis 404 

Azygos  Uvula' 405 

Palato-glossus    or    Constrictor    Isthmi 

Faucium 405 

Palato-pharyngeus 405 

Salpingo-pharyngeus 405 

Surgical  Anatomy 406 

The  Anterior  Vertebral  Region   ....  406 
Rectus  Capitis  Anticus  Major  or  Longus 

Capitis 406 

Rectus  Capitis  Anticus  Minor  .       .  407 

Rectus  Capitis  Lateralis        ....  407 

Longus  Colli 407 

The  Lateral  Vertebral  Region     ....  408 

Scalenus  Anticus 408 

Scalenus  Posticus 409 

Surface  Form  of  Muscles  of  the  Neck   .      .  409 

Muscles  and  Fasci-k  of  the  Trunk. 

Subdivision  into  Groups 41t) 

Muscles  of  the  Back. 

Subdivision  into  Groups 410 

The  Urst  Layer 410 

Dissection 410 

Superficial  Fascia 411 

Deep  Fascia 411 

Trapezius 411 

Ligamentum  Nuchse 413 

Latissimus  Dorsi 413 

The  Second  Layer 414 

Dissection 414 

Levator  Anguli  SrapulsD        ....  414 

Rhomboideus  Minor 414 

Rhomboideus  Major 414 

The  Third  Layer 415 

Dissection 415 

Serratus  Posticus  Superior    .       .       .       .  415 

Serratiis  Posticus  Inferior     .       .       .  415 

Vertebral  Aponeurosis 416 

Lumbar  Fascia  or  Aponeurosis        .  416 

Splenius 416 

Splenius  Capitis 416 

Splenius  Colli 416 

The  Fourth  Layer 417 

Dissection 417 

Erector  Spinse 417 

lUo-costalis  or  Sacro-lumbalis   .  419 
Musculus    Accessorius   ad   Ilio-cos- 

talem 419 

Cervicalis  Ascendens      ....  419 

Longissimus  Dorsi 419 

Transversalis    Cervicis    or    Trans- 

versalis  Colli 419 

Trachelo-mastoid 419 

Spinalis  Dorsi 419 

Spinalis  Colli 420 

Complexus 420 

The  Fifth  Layer 420 

Dissection         420 

Semispinalis  Dorsi 421 

Semispinalis  Colli 421 

Multifidus  Spina;         421 

Rotatores  Spinse 421 

Supraspinales 421 

Interspinales 421 

Extensor  Coccygis 422 

Intertransversales 422 

Rectus  Capitis  Posticus  Major  .  .  422 


CONTENTS 


The  Fifth  Layer— 

Rectus  Capitis  Posticus  Minor  . 
Obliquus  Capitis  Inferior 
Obliquus  Capitis  Superior 

Surface  Form  of  Muscles  of  the  Back 


PAGE 

422 
422 
422 
424 


Muscles  and  Fasciae  of  the  Thorax. 

Intercostal  Fascia 424 

Intercostal  Mviscles 425 

External  Intercostals 425 

Internal  Intercostals 425 

Infracostales 425 

Triangularis  Sterni 425 

Levatores  Costarum 426 

Diaphragm 427 

Ligainentum  Arcuatura  Internum  .       .  427 

Ligamentum  Arcuatum  Externum       .  427 

Central  Tendon  of  the  Diaphragm  .       .  429 

The  Openings  of  the  Diaphragm  .  429 

Muscles  of  Inspiration  and  Expiration  432 

Muscles  of  the  Abdomen. 

The  Superficial  Muscles  of  the  Abdomen     .  432 

Dissection 432 

Superficial  Fascia 433 

Deep  Fascia 433 

External  or  Descending  Oblique  .  433 
Aponeurosis  of  External  Oblitiue  .  434 
External  Abdominal  Ring  .  .  436 
External  Pillar  or  Inferior  Crus  .  436 
Internal  Pillar  or  Superior  Crus  .  436 
Intercolumnar  Fibres  ....  436 
Poupart's  Ligament  ....  436 
Gimbernat's  Ligament  437 
Triangular  Fascia  or  CoUes's  Liga- 
ment       437 

Ligament  of  Cooper       ....  437 

Suspensory  Ligament  of  the  Penis  437 

Suspensory  Ligament  of  the  Clitoris  437 

Internal  or  Ascending  Oblique  .       .       .  437 

Aponeurosis  of  Internal  Oblique    .  439 

Cremaster  Muscle 439 

Transversalis 442 

Dissection 442 

Rectus  Abdominis 442 

Pyramidalis 444 

The  Linea  Alba 444 

The  Lineae  Semilunares       .       .       .  445 

The  Lineae  Trans\'ers;e  ....  445 

The  Transversalis  Fascia      ....  445 

Internal  or  Deep  Abdominal   Ring      .  446 

The  Inguinal  or  Spermatic  Canal   .       .  448 

The  Deep  Crural  Arch 448 

Cooper's  Ligament 448 

Surface  Forms  of  Muscles  of  the  Abdomen  448 

The  Deep  Muscles  of  the  Abdomen  .  449 

The    Fascia    Covering    the    Quadratus 

Lumborum 449 

Quadratus  Lumborum 449 

Muscles  of  the  Pelvic  Outlet: 

The  Muscles  of  the  Ischio-rectal  Region      .  449 

The  Corrugator  Cutis  Ani     ....  449 

External  Sphincter  Ani 450 

Internal  Sphincter  Ani 451 

Levator  Ani 451 

Pubococcygeus  Muscle  ....  452 

Iliococcygeus  Muscle      ....  454 

Coccygeus 455 

The  Muscles  and  Fasciae  of  the  Perinaeum  in 

the  Male 455 

Superficial  Fascia 455 

The    Central    Tendinous    Point   of    the 

Perinaeum 456 

Transversus  Perinei  Superficialis     .       .  457 

Accelerator  Urinae 457 

Erector  Penis 458 

Triangular  Ivigament      ....  458 

Compressor  or  Constrictor  Urethras      .  460 


PAGE 

The  Muscles  of  the  Perinaeum  in  the  Female  460 

Transversus  Perinei  Superficialis     .      .  460 

Sphincter  Vaginje 461 

Erector  Clitoridis 461 

Triangular  Ligament      ....  462 

Compressor  Urethras 462 

Muscles  and  Fascitk  of  the  Uppeu 
Extremity. 

Subdivision  into  Groups 462 

Dissection  of  Pectoral  Region  and  Axilla     .  463 

The  Mziscles  and  Fascice  of  the  Thoracic 
Region. 

The  Anterior  Thoracic  Region     ....  463 

Superficial  Fascia 463 

Deep  Fascia 463 

Pectoralis  Major 464 

Dissection 467 

Costo-coracoid  Membrane  or  Clavipec- 

toral  P^ascia 467 

Pectoralis  Minor 468 

Subclavius 468 

The  Lateral  Thoracic  Region       ....  468 

Serratus  Magnus         468 

Surgical  Anatomy 469 

Dissection 470 

Muscles  and  Fascia:  of  Shoulder  and  Arm. 

Superficial  Fascia 470 

Deep  Fascia 470 

The  Acromial  Region 470 

Deep  Fascia 470 

Deltoid 470 

Surgical   Anatomy 471 

The  Anterior  Scapular  Region    ....  471 

Dissection 471 

The  Subscapular  Fascia 471 

Sub.scapularis 471 

The  Posterior  Scapular  Region   ....  472 

Dissection 472 

Supraspinatus  Fascia 472 

Supraspinatus  Muscle 472 

Infraspinatus  Fascia 472 

Infraspinatus  Muscle 472 

Teres  Minor 473 

Teres  Major 474 

The  Mii.icles  and  Fasciae  of  the  Arm. 

The  Anterior  Humeral  Region    ....  474 

Dissection 474 

Deep  Fascia 474 

Coraco-brachialis 475 

Biceps  or  Biceps  Flexor  Cubiti  .  475 

Brachialis  Anticus 476 

The  Postesrior  Humeral  Region   ....  477 

Triceps  or  Triceps  Extensor  Cubiti  477 

Subanconeus 478 

Surgical  Anatomy 478 

Muscles  and  Fascice  of  the  Forearm. 

Dissection 478 

Deep  Fascia 478 

The  Anterior  Radio-ulnar  Region                  .  479 

The  Superficial  Layer 479 

Pronator  Radii  Teres     ....  479 

Surgical  Anatomy  ....  479 

Flexor  Carpi  Radialis     ....  479 

Palmaris  Longus 480 

Flexor  Carpi  Ulnari.s     ....  480 

Flexor  Sublimis  Digitorum  481 

The  Deep  Layer 482 

Dissection 482 

Flexor  Profundus  Digitorum   .  482 

Flexor  Longus  Pollicis  ....  482 

Pronator  Quadratus       ....  483 

Surgical  Anatomy 484 


XIV 


CONTENTS 


The  Radial  Region 484 

Dissection 484 

Supinator  Longus 484 

Extensor  Carpi  Radialis  Longior     .      .  485 

Extensor  Carpi  Radialis  Brevior     .      .  485 

The  Posterior  Radio-uhiar  Region    .  .  486 

The  Superficial  Layer 486 

Extensor  Communis  IJigitoruni     .  486 

Extensor  Minimi  Digiti       .      .      .  487 

Extensor  Carpi  Ulnaris       .      .       .  487 

Anconeus 487 

The  Deep  Layer 487 

Supinator  Radii  Brevis  .  487 

Extensor  Ossis   Metacarpi   PoUicis  489 

Extensor  Brevis  Pollicis     .      .      .  489 

Extensor  Longus  Pollicis    .      .      .  489 

Extensor  Indicis 490 

Surgical  Anatomy 490 

Muscles  and  Fasciae  of  the.  Hand. 

Dissection 491 

Ligamentum  Carpi  Volare 491 

Anterior  Annular  Ligament 491 

The  Synovial  Membranes  of  the  Flexor  Ten- 
dons at  the  Wrist 492 

Surgical  Anatomy 492 

Burs*  about  the  Hand  and  Wrist   .       .       .  492 

Posterior  Annular  Ligament 493 

The  Deep  Palmar  Fascia 493 

The  Superficial  Transverse  Ligament  of 

the  Fingers 494 

Surgical  Anatomy 494 

The  Radial  Region 495 

Abductor  Pollicis 495 

Opponens  Pollicis 496 

Flexor  Brevis  Pollicis 497 

Adductor  Obliquus  Pollicis  ....  497 

Adductor  Transversus  Pollicis  .       .      .  497 

The  Ulnar  Region 498 

Palmaris  Brevis 498 

Abductor  Minimi  Digiti 498 

Flexor  Brevis  Minimi  Digiti       .       .      .  498 

Opponens  Minimi  Digiti        ....  498 

T,he  Middle  Palmar  Region 499 

Lumbricales 499 

Interossei  499 

Surface  Form  of  Muscles  of  the  Upper  Ex- 
tremity       500 

Surgical  Anatomy  of  Muscles  of  the  Upper 

Extremity ;:03 

Muscles  and  Fasci.e  of  the  Lower 

Extremity. 

Subdivision  into  Groups 507 

Muscles  and  Fascice  of  the  Iliac  Region. 

Dissection 508 

Iliac  Fascia 508 

Psoas  Magnus 509 

Psoas  Parvus 510 

Iliacus 510 

Surgical  Anatomy 511 

Muscles  and  Fasciae  of  the  Thigh. 

The  Anterior  Femoral  Region     .       .       .       .  512 

Dissection 512 

Superficial  Fascia 512 

Deep  Fascia  or  Fascia  Lata      .       .       .  513 

Surgical  Anatomy 515 

Tensor  Fasciae  Femoris 515 

Sartorius 516 

Quadriceps  Extensor 516 

Rectus  J'emoris 516 

Vastus  Extern  us 517 

Vastus  Intern  us 517 

Crureus 517 

Subcrureus 518 

Surgical  Anatomy 518 


PAGK 

The  Internal  Femoral  Region     ....  519 

Dissection 51& 

Gracilis 519 

Pectineus 519 

Adductor  Longus 519 

Adductor  Brevis 520 

Adductor  Magnus 520 

Hunter's  Canal 521 

Surgical  Anatomy 522 

The  Muscles  and  Fasciae  of  the  Hip. 

The  Gluteal  Region 522 

Dissection         .522 

Gluteus  Maximus 523 

Gluteus  Medius 523 

Gluteus  Minimus 523 

Pyriformis 524 

Obturator  Internus 525 

GemelU 526 

Gemellus  Superior 526 

Gemellus  Inferior 527 

Quad  rat  us  Femoris 527 

Obturator  Externus 528 

Surgical   Anatomy 528 

The  Posterior  Femoral  Region    ....  529 

Dissection 529 

Biceps  or  Biceps  Flexor  Cruris  .      .      .  529 

Semitendinosus 530 

Semimembranosus 530 

Surgical  Anatomy 531 

Muscles  and  Fasciae  of  the  Leg. 

The  Anterior  Tibio-fibular  Region    .      .       .  531 

Dissection         532 

Deep  Fascia  of  the  Leg 532 

Tibialis  Anticus 532 

Extensor  Proprius  Hallucis  ....  532 

Extensor  Longus  Digitorum       .      .      .  533 

Peroneus  Tertius         534 

The  Posterior  Tibio-fibular  Region   .      .       .  534 

Dissection 534 

The  Superficial  Layer 534 

Gastrocnemius 534 

Soleus 535 

Tendo-Achillis 535 

The  Deep  Layer 537 

Dissection 537 

Deep  Transverse  Fascia      .       .       .  537 

Popliteus 537 

Flexor  Longus  Hallucis       .      .       .  538 

Flexor  Longus  Digitorum  .      .      .  538 

Tibialis  Posticus 538 

The  Fibular  Region 539 

Dissection 539 

Peroneus  Longiis 539 

Peroneus  Brevis 540 

Surgical  Anatomy  of  Tendons  around  Ankle  541 

Muscles  and  Fascice  of  the  Foot.  * 

Dissection 541 

Anterior  Annular  Ligament 541 

Internal  Annular  Ligament 542 

External  Annular  Ligament 542 

Dissection  of  the  Sole  of  the  Foot    .       .       .  542 

Plantar  Fascia         542 

Central  Portion  of  Plantar  Fascia  .  542 

Lateral   Portions  of  Plantar  Fascia      .  543 

Bursse  about  the  Ankle  and  Pool    .  543 

Surgical  Anatomy 543 

The  Dorsal  Region 543 

Fascia 543 

Extensor  Brevis  Digitonun  ....  543 

The  Plantar  Region 544 

The  First  Layer 544 

Dissection 544 

Abductor  Hallucis 544 

Flexor  Brevis  Digitorum     .             .  544 
Fibrous  Sheaths  of  the  Flexor 

Tendons 545 

Abductor  Minimi   Digiti      .      .      .  545 


CONTENTS 


XV 


PAOK 

The  Plantar  Region — 

The  Second   Layer     .      ;     7     ".      .      .  546 

Flexor  Accessorius 546 

Lumbricales 546 

The  Third  Layer 546 

Flexor  Brevis  Hallucis  ....  546 

Adductor   Obliquus   Hallucis    .  546 

Flexor  Brevis  Minimi  Digiti            .  547 

Adductor  Tran.sversus  Hallucis  548 


PAaB 

The  Plantar  Region — 

The  P'ourth  Layer 548 

Interossei  Muscles 548 

rjorsal   Interossei    ....  548 
Plantar  Interossei         .       .  548 
Surface  Form  of  Muscles  of  the  Lower  Ex- 
tremity       549 

Surgical  Anatomy  of  Muscles  of  the  Lower 

Extremity 551 


THE  Br>OOD-V.\SCULAR  SYSTEM. 


The  Circulation  of  the  Blood      ....  555 

The  Cavity  of  the  Thorax 556 

The  Upper  Opening  of  the  Thorax  .       .  556 

The  Lower  Opening  of  the  Thorax  .       .      .  556 

The  Pericardium. 

Structure  of  the  Pericardium      ....  558 

Fibrous  Layer 558 

Serous  Pericardium 560 

Arteries  of  the  Pericardium  ....  561 

Nerves  of  the  Pericardium  ....  581 

The  Vestigial  Fold  of  the  Pericardium  561 

Surgical  Anato.-ny  of  the  Pericardium   .       .  561 

The  Heart. 

Position  of  the  Heart 562 

Size  and  Weight  of  the  Heart     ....  564 

Capacity  of  the  Cavities  of  the  Heart   .      .  564 

Fat  upon  the  Heart 564 


Component  Parts  of  the  Heart  ....  565 

Right  Auricle 565 

Left  Auricle 568 

Right  Ventricle 569 

Left  Ventricle 571 

Structure  of  the  Heart 574 

Endocardium         574 

Myocardium 574 

Muscular  Structure  of  the  Heart   .       .  575 

Fibres  of  the  Auricles   ....  575 

Fibres  of  the  Ventricles      .      .      .  575 

Ves.sels  and  Nerves  of  the  Heart      .      .      .  577 

Surface  Form  of  the  Heart 577 

Surgical  Anatomy  of  the  Heart  ....  578 

Peculiarities  of  Vascular  System  in  Foetus.  578 

The  Foramen  Ovale 578 

The  Eustachian  Valve 578 

The   Ductus  Arteriosus 579 

The  Umbilical  Arteries 579 

P'cetal  Circulation 579 

Changes  in  the  Vascular  System  at  Birth  .  581 


THE  ARTERIES. 


Distribution  of  the  Arteries  ."     7      .'      .  583 

Anastomosis  of  the  Arteries 583 

Histology  of  the  Capillaries  and  Arteries    .  584 

Blood-vessels  of  the  Blood-vessel  Wall  586 

Lymphatics  of  Arteries 586 

Nerves  of  Arteries 586 

Arterial  Sheath 586 

Pulmonary  Artery. 

Right  Pulmonary  Artery 587 

Left  Pulmonary  Artery 587 

The  Aorta. 

The  Ascending  Aorta. 

Relations  of  the  Ascending  Aorta  589 

Branches  of  the  Ascending  Aorta    .             .  590 

The  Coronary  Arteries 590 

Right  Coronary  Artery 590 

Left  Coronary  Artery 590 

Peculiarities  of  Coronary  Arteries  .  591 

The  Arch  of  the  Aorta. 

Relations  of  the  Arch  of  the  Aorta  .  591 

Peculiarities  of  the  Arch  of  the  Aorta    .  591 

Surgical  Anatomy  of  the  Arch  of  the  Aorta  592 

Branches  of  the  Arch  of  the  Aorta  .  593 

Peculiarities  of  the  Branches     .  593 

The  Innominate  Artery 593 

Relations 593 

Branches 594 

Thyroidea  Ima 594 

Peculiarities .  594 

Surgical  Anatomy 594 

Arteries  of  the  Head  and  Neck. 

The  Common  Carotid  Artery. 

Relations  of  the  Common  Carotid  Artery  .  596 

Peculiarities  of  the  Common  Carotid  Arterv  598 


Surface    Marking   of   the    Common   Carotid 

Artery 593 

Surgical  Anatomy  of  the  Common  Carotid 

Artery 593 

The  External  Carotid  Artery       ....  600 

Relations 600 

Surface  Marking 601 

Surgical  Anatomy 601 

Branches 601 

Superior  Thyroid  Artery  601 

Branches      ......  602 

Surgical  Anatomy  ....  603 

Lingual  Artery 603 

Relations 603 

Branches 603 

Surgical  Anatomy  ....  604 

Facial  or  External  Maxillary  Artery  604 

Relations '.  605 

Branches 60.5 

Peculiarities 607 

Surgical  Anatomy  ....  607 

Occipital  Artery       .       .             .  608 

Branches 609 

Posterior  Auricular  Arterv  609 

Branches 610 

Ascending  Pharyngeal  Artery  610 

Branches     " 610 

Surgical  .\natomy  .      .  .611 

Superficial  Temporal  Artery    .       .611 

Branches 611 

Surgical  Anatomy  .      .  .612 

Internal  Maxillary  Art«ry  .  612 

Branches  of  First  Portion  613 

Surgical  Anatomy  614 

Branches  of  Second  Portion   .  614 

Branches  of  Third  Portion  615 

Surgical  Anatomy  615 

Surgical  Anatomy  of  the  Triangles  of  the 

Neck 616 

Anterior  Triangle  of  the  Nock   .  616 

Posterior  Triangle  of  the  Neck  .  618 


CONTENTS 


PAGE 

The  Internal  Carotid  Artery  .      .  619 

Cervical  Portion 620 

Relations 620 

Petrous  Portion 620 

Cavernous  Portion 621 

Cerebral  Portion 621 

Peculiarities 621 

Surgical  Anatomy 621 

Branches 621 

Tympanic 622 

Arteriaj  Receptaculi       ....  622 

Anterior  Meningeal         ....  622 

Ophthahnic 622 

Branches 622 

Anterior  Cerebral 626 

Branches 626 

Middle  Cerebral 627 

Branches 628 

Posterior  Communicating   .             .  628 

Anterior  Choroid 628 

The  Bloodvessels  of  the  Brain. 

The  Central  Ganglionic  System   ....  630 
The  Cortical  Arterial  System        .      .       .       .631 

Arteries  of  the  Upper  Extremity. 

The  Subclavian  Artery. 

First  Part  of  the  Right  Subclavian  Artery  .  632 

Relations 632 

First  Part  of  the  Left  Subclavian  Artery     .  633 

Relations 633 

Second  and  Third  Parts  of  Subclavian  Artery  633 

Relations 634 

Third  Portion  of  the  Subclavian  Artery      .  634 

Peculiarities  of  the  Subclavian  Artery  .       .  635 

Surface  Marking  of  the  Subclavian  Artery  .  635 

Surgical  Anatomy  of  the  Subclavian  Artery  635 

Branches  of  the  Subclavian  Artery  .       .      .  637 

Vertebral  Artery 637 

Relations 637 

Branches 638 

Surgical  Anatomy 639 

Basilar  Artery 639 

Branches 639 

Circle  of  AA'illis 640 

Tliyroid  Axis 640 

Branches 641 

Internal  Mammary  Artery   ....  643 

Relations 644 

Branches 644 

Surgical  Anatomy 644 

Superior  Intercostal  Artery  .       .       .       .  645 

Deep  Cervical  Branch   ....  645 

Surgical  Anatomy  of  the  Axilla   ....  645 

Boundaries 645 

Contents 646 

Surgical  Anatomy 646 

The  Axillary  Artery. 

Relations  of  the  Axillary  Artery      7      .      .  648 

Peculiarities  of  the  Axillary  Artery  649 

Surface  Marking  of  the  Axillary  Artery  649 

Surgical  Anatomy  of  the  Axillary  Arterj'    .  649 

Branches  of  the  Axillary  Artery       .       .       .  650 

Superior  Thoracic  Artery      ....  650 
Acromial  Thoracic  Arterv  or  Thoracic 

Axis       ........  651 

Branches 651 

Long  Thoracic  or  External  Mammary 

Artery 651 

Alar  Thoracic  Artery 651 

Subscapular  Artery    ." 651 

Circumflex   Arteries    .      ' 651 

The  Brachial  Artery. 

Relations  of  the  Brachial  Artery      .       .       .  652 

Surgical  Anatomy  of  the  Bend  of  the  Elbow  653 

Peculiarities  of  the  Brachial  Artery      .  653 

Surface  Marking  of  the  Brachial  Artery  654 

Surgical  Anatomy  of  the  Brachial  Artery    .  654 


PAGE 

Branches  of  the  Brachial  Artery      .       .  655 

Superior  Profunda  Artery     ....  655 

Nutrient  Artery    ........  656 

Inferior  Profunda  Artery      ....  656 

Anastomotica  Magna 656 

Muscular  Branches 656 

The  Anastomosis  around  the  Elbow-joint  657 

The  Radial  Artery 557 

Relations 657 

The  Deep  Palmar  Arch 658 

Peculiarities 658 

Surface  Marking 658 

Surgical  Anatomy 658 

Branches 659 

Radial  Recurrent 659 

Muscular  Branches 659 

Anterior  Radial  Carpal        .             .  659 

Superficialis  Vola; 659 

Posterior  Radial  Carpal      .             .  659 

Dorsalis  Pollicis 659 

Dorsalis  Indicis 659 

Princeps  Pollicis 660 

Radialis  Indicis 660 

Perforating  Arteries       ....  660 

Palmar  Interosseous       ....  660 

Palmar  Recurrent  Branches    .  660 

The  Ulnar  Artery 660 

Relations 661 

Peculiarities 661 

Surface  Marking 661 

Surgical  Anatomy 661 

Branches 662 

Anterior  Ulnar  Recurrent  .       .       .  662 

Posterior  Ulnar  Recurrent  662 

Interosseous  Artery       ....  662 

Muscular  Branches 663 

Anterior  Carpal 663 

Posterior  Carpal 663 

Deep  Palmar  Arch 664 

Superficial  Palmar  Arch      .      .  664 

Relations 664 

Branches 664 

Surface  Marking     ....  665 

Surgical  Anatomy  ....  665 

Arteries  of  the  Trunk. 

The  Descending  Aorta. 

The  Thoracic  Aorta 665 

Relations 665 

Surface  Marking 666 

Surgical  Anatomy 666 

Branches 666 

Bronchial  Arteries 666 

(Esophageal  Arteries      ....  666 

Pericardiac  Arteries       ....  666 

Posterior  Mediastinal  Arteries       .  666 

Interco.stal  Arteries  and   Branches  667 

Surgical  Anatomy  ....  668 

The  Abdominal  Aorta 668 

Relations 669 

Surface  Marking 670 

Surgical  Anatomy 670 

Branches 671 

The  C(»liac  Axis  or  Artery      .       .  671 

Relations 671 

Branches 671 

Surgical  Anatomy  ....  674 

The  Superior  Mesenteric  Artery  675 

Branches 675 

Blood-supply  of  the  Right  Iliac 

Fossa 676 

The  Inferior  Mesenteric  Artery      .  677 

Suprarenal  Artery 678 

The  Renal  Arteries        ....  678 

The  Spermatic  Arteries  679 

The  Ovarian  Arteries     ....  680 

The  Inferior  Phrenic  Arteries    .       .  680 

The  Lumbar  Arteries      ....  680 

Branches         681 


CONTENTS 


The  Comtrion  Iliac  Arlrrics. 
Branches  of  Coinuiou  Iliac  Arteries 
Peculiarities  of  Coininou  Iliac  Arteries. 
Surface  Marking  of   Conunon  Iliac  Arteries 
Surgical  Anatomy  of  Common  Iliac  Arteries 

The  Internal  Iliac  Artery 

Relations  

Peculiarities 

Surgical  Anatomy 

Branches 

Superior  Vesical   Artery 
MidfUe  Vesical  Artery    .... 
Inferior  Vesical  .\rtery  .... 
Middle   Ilseniorrhoidal    .Vrtery 

Uterine  Artery 

Vaginal  Artery 

Surgical  Anatomy  .... 

Obturator  Artery 

Branches       

Peculiarities 

Internal  Pudic  Artery  .... 

Relations 

Peculiarities 

Surgical  Anatomy  .... 

Branches 

Sciatic  Artery 

Branches      

Lateral  Sacral  Artery    .... 

Branches 

Gluteal  Artery 

Branches      

Surface  Marking     .... 
Surgical  .\natomy  .... 

The  External   Iliac  Artery 

Relations 

Surface  Marking 

Surgical  Anatomy 

Branches    

Int,eriial  or  Deep  Epigastric  .\rt(!ry 

Branches 

Peci'.liarities 

Surgical  .-Vnat-omy  .... 
Deep  Circumflex  Iliac  Artery  . 


682 

682 

682 

682 

683 

683 

685 

685 

686 

686 

686 

686 

687 

687 

687 

688 

688 

()88 

68!) 

689 

690 

690 

690 

690 

692 

693 

693 

693 

694 

694 

694 

694 

694 

694 

695 

695 

696 

696 

696 

696 

697 

697 


Arteriks  of  the  Lower  Extremity. 
The  Femoral  Artery. 

Scarpa's  Triangle 697 

Hunter's  ('anal  or  the  .\dductor  Canal  .  698 

The  Common  Femoral  .\rtery     ....  699 

Relations 700 

The  Superficial  Femoral  Artery  ....  700 

Relations "    .      .      .      .  700 

Peculiarities 700 

Surface  Marking 701 

Surgical  Anatomy      ......  701 

Branches 704 

Superficial  Epigastric     ....  704 

Superfici.al  Circumflex  Iliac  .  704 

Superficial  External  Pudic        .       .  704 

Deep  External  Pudic     ....  704 

Deep  Femoral  or  Profunda  Femoris  704 

Relations 704 

Branches 705 


The  Superficial  Femoral  Artery — 

Muscular  Branches 707 

Auastomotica  Magna     ....  707 

Branches 707 

The  Popliteal  Artery. 

The  Popliteal  Space 707 

Dissection 707 

Boundaries 707 

Position  of  Contained  Parts       .       .      .  708 

PecuUarities 70e 

Surface  Marking 709 

Surgical  Anatomy 709 

Branches 710 

Superior  Muscular  Branches           .  710 

Inferior  Muscular  Branches            .  710 
Cutaneous  liranches              .       .       .710 

Superior   Articular  Arteries      .       .  710 
Azygos  Articular  Artery     .              .711 

Inferior  Articular  Arteries  .      .  711 

Circumpatellar  Anastomosis     .      .  711 

The  Anterior  Tibial  Artery 711 

Relations 711 

Peculiarities 712 

Surface  Marking 712 

Surgical  Anatomy 712 

Branches 712 

Posterior  Recurrent  Tibial  713 

Superior  Fibular 713 

Anterior  Recurrent  Tibial  .  713 

Muscular  Branches 713 

Malleolar  .\rteries 713 

The  Dorsalis  Pedis  Artery 714 

Relations 714 

Peculiarities 715 

Surface  Marking 715 

Surgical  Anatomy 715 

Branches 715 

Cutaneous  Branches  715 

Tarsal  Artery 715 

Metatarsal  .\rtery 715 

Communicating  .\rtery        .      .      .  716 

The  Posterior  Tibial  Artery 716 

Relations 716 

Peculiarities 717 

Surface  Marking 717 

Surgical  Anatomy 717 

Branches 717 

Peroneal  Artery 717 

Relations 718 

Peculiarities 718 

Branches 718 

Cutaneous  Branches       .      .      .      .  718 

Nutrient   Artery 719 

Muscular  Branches 719 

Communicating  Branch                    .  719 
Malleolar     or    Internal     Malleolar 

Artery 719 

Internal  Calcanean  Arteries     .  719 

Internal  Plantar  Artery             .  719 

External  Plantar  Artery           .      .  720 

Surface  Marking     ....  720 

Surgical  Anatomy  ....  720 

Branches 720 


THE  VEINS. 


Subdivisions  of  the  Veins 721 

Anastomosis  of  Veins 722 

Histology  of  the  Veins 723 

The  Superficial  or  Cutaneous  Veins  .       .       .  723 

The  Deep  Veins 723 

The  Pulmon.\ry  Vkins. 

The  Systemic  Veins. 

Vein.s  of  the  Head  and  Neck. 

Veins  of  the  p'.xt,<;rior  of  the  Head  and  Face  725 


Veins  of  the  Exterior  of  the  Head  and  Face — 

Frontal  Vein 725 

Supraorbital  Vein 726 

Angular  Vein 726 

Anterior  Facial  Vein        .....  726 

Common  Facial  Vein 726 

Superficial  Temporal  Vein     ....  727 
The  Pterygoid  Plexus  and  the  Internal 

Maxillary  Vein 727 

Temporo-maxillary  Vein       ....  727 

Posterior  Auricular  Vein       ....  727 

Occipital  Vein 727 


XVlll 


CONTENT!^ 


The  Veins  of  the  Neck 728 

External  Jugular  Vein 728 

Posterior  External  Jugular  Vein     .  728 

Anterior  Jugular  Vein 728 

Internal  Jugular  Vein 729 

Lingual  Veins 729 

Pharyngeal  Veins 730 

Superior  Thyroid  Vein  ....  730 

Middle  Thyroid  Vein     ....  730 
Veins  of  the  Thyroid  Gland     .       .731 

Surgical  Anatoniv 732 

Vertebral  Vei.i       .      ." 732 

Anterior    Vertebral     or    Anterior 

Deep  Cervical  Vein     ....  733 
Posterior    Vertebral    or   Posterior 

Deep  Cervical  Vein     ....  733 

The  Veins  of  the  Diploe 733 

The  Meningeal  Veins 734 

The  Cerebral  Vein 734 

Superficial  or  Cortical  Cerebral  Veins    .  735 

Superior  Cerebral  Veins       .       .  735 

Median  Cerebral  Veins  ....  735 

Inferior  Cerebral  Veins  735 

Deep  Cerebral,  Central  or  Ventricular 

Veins,  Veins  of  Galen             .  735 

Vena  Corporis  Striati      ....  735 

Choroid  Vein 735 

Basilar  Vein 735 

Superficial  Orebellar  Veins  ....  730 

Deep  Cerebellar  Veins 736 

Veins  of  the  Pons  Varoli  736 

Veins  of  the  Medulla  Oblongata    .  736 
The  Sinuses  of  the  Dura  Mater,  Ophthalmic 

Veins  and  Emissary  Veins     .      .  730 

Superior   Longitudinal  Sinus            .      .  736 

Torcular  Etrcphili 737 

Inferior  Longitudinal  Sinus  ....  738 

Straight  Sinus 738 

Lateral  Sinus 738 

Surgical  Anatomy 739 

Occipital  Sinus 7S9 

Cavernous  Sinus 739 

Surgical  Anatomy 740 

Spheno-parietal    Sinus    or    Sinus    Ala- 

Parva} 740 

Ophthalmic  Veins 740 

Circular  Sinus 742 

Superior  Petrosal  Sinus 742 

Inferior  Petrosal  Sinus 742 

Transverse  or  Basilar  Sinus       .       .       .  743 

Emissary  Veins 743 

Surgical  Anatomy 743 

Veins  of  the  Upper  Extremity  and  Thorax. 

The  Superficial  Veins  of  Upper  Extremity   .  745 
Superficial  Veins  of  the  Hand  and  Fin- 
gers    745 

Anterior  Ulnar  Vein 745 

Posterior  or  Dorsal  Ulnar  Vein       .  745 

Common  Ulnar  Vein 745 

Radial  Vein 745 

Median  Vein 745 

Median  Cephalic  Vein 740 

Median  Basilic  Vein       ....  746 

Basilic  Vein 746 

Cephalic   Vein 747 

The  Deep  Veins  of  the  Upper  Extremity     .  747 

Interosseous  Veins 747 

Deep  Palmar  Veins 747 

Brachial  Veins 747 

Axillary  Vein 747 

Branches 748 

Surgical  Anatomy 748 

Subclavian  Vein 749 

Innominate  or  Brachio-cephalic  Veins  750 

Right  Innominate  Vein 750 

Left  Innominate  Vein 750 

Peculiarities          7,50 


The  Deep  Veins  of  the  Upper  Extremity — 

Internal  Mammary  Vein 750 

Inferior  Thyroid  Veins 751 

Intercostal   Veins 752 

Superior  Vena  Cava 752 

Relations 752 

Azygos  Veins  752 

Surgical  Anatomy 753 

Bronchial  Veins 753 

The  Spinal  Veins 753 

Dorsi-spinal  Veins 753 

Meningo-rachidian  Veins       ....  754 
Veins  of  the  Bodies  of  the  Vertebrip  or 

Vense  Basis  Vertebrarum   ....  755 
Veins  of   the  Spinal   Cord  or  Medulli- 

spinal  Veins 755 

Veins  of  the  Lower  Extremiiy,  Abdomen 
and  Pelvis. 

The  Superficial  Veins  of  the  Lower  Extrem- 
ity       756 

The  Superficial  Veins  of  the  Foot  .       .  756 

Internal  or  Long  Saphenous  Vein        .  756 

External  or  Sliort  Saphenous  Vein       .  756 

Surgical  Anatomy 757 

The  Deep  Veins  of  the  Lower  Extremity     .  758 

The  Deep  Veins  of  the  Foot      .      .      .  758 

Posterior  Tibial  Veins 758 

Anterior  Tibial  Veins 758 

PopHteal  Vein 758 

Femoral  Vein 758 

External  Iliac  Vein 759 

Deep  Epigastric  Vein 759 

Deep  Circumflex  Iliac  Vein        .      .  759 

Hypogastric  or  Internal  Iliac  Vein  760 

Surgical  Anatomy 761 

Obturator  Vein 761 

Sciatic  Veins 761 

Gluteal  Veins 761 

Superior  Vesical  Plexus         ....  761 

Prostatic  or  Prostatico-vesical  Plexus  .  761 

Inferior  Vesical  Plexus 762 

Surgical  Anatomy 762 

The  Dorsal  Veins  of  the  Penis  .      .       .  762 

The  Vaginal  Plexuses  and   Veins    .       .  763 

The  Uterine  Plexuses  and  Veins     .  763 

Common  lUac  Vein 764 

Peculiarities 764 

Ascending  or  Inferior  Vena  Cava    .       .  764 

Relations 764 

Peculiarities         764 

Lumbar  Veins 765 

Spermatic  Veins 765 

Surgical  Anatomy         .  .  766 

Ovarian  Veins 766 

Renal  Veins         767 

Suprarenal  Veins 767 

Phrenic  Veins 767 

Hepatic  Veins 767 


The  Portal  System  of  Veins. 

Superior  Mesenteric  Vein 768 

Splenic  Vein 768 

Inferior  Mesenteric  Vein 768 

Gastric  Veins 768 

Cystic  Vein 769 

Portal  Vein 769 

The  Cardiac  Veins. 

Great  Cardiac  or  Left  Coronary  Vein    .       .  770 

Posterior  or  Middle  Cardiac  Vein  771 

Left  Cardiac  Vein         771 

Anterior  Cardiac  Vein 771 

Right  Cardiac  or  Small  Coronary  Vein  .       .  771 

Coronary  Sinus 771 

Venaj  Thebe.sii          771 


CONTENTS 


XIX 


THE  LYMPHATIC  SYSTEM. 


PAQE 

Subdivision  into  Superficial  and  Deep  Sets     773 
Lymphatic  or  Conglobate  Glands  .  774 

The  Thoracic   Duct   and   the   Right 
Lymphatic  Duct. 

Radicals  of  Origin  and  Tributaries  of  Tho- 
racic  Duct 777 

Structure  of  the  Thoracic  Duct  ....  778 

The  Right  Lymphatic  Duct 778 

Tributaries 779 

Lymphatics  of  thk  Cranial  Region,  Face 
and  Neck. 

The  Lymphatic   Glancis  of   the    Head   and 

Face 780 

The  Occipital  or  Suboccipital  Glands    .      780 
The  Posterior  Auricular,  Retro-auricu- 
lar or  Mastoid  Glands        ....      780 

Parotid  Lymph  Glands 781 

The  Subparotid  Glands 782 

The  Internal  Maxillary  or  Zj'gomatic 

Glands 782 

The  Facial  Glands  or  Genial  Glands    .      782 
The  Lymphatic  Vessels  of  the  Cranial  Region     782 
The  Lymphatic  Vessels  of  the  Face,  the  In- 
terior of  the  No.se,  Tongue,  Floor  of  the 
Mouth,    Pharynx,    Larynx    and    Thyroid 

Gland 782 

The  Lymphatic  Glands  of  the  Neck      .      .      784 
The  Superficial  Cervical  Glands      .       .      784 
The    Submaxillary    or    Lateral    Supra- 
hyoid Glands 784 

The  Submental  or  Median  Suprahyoid 

Glands 785 

The  Retro-pharyngeal  or  Post-pharyn- 

geal  Glands 785 

The  Deep  Cervical,  (^arotid,  or  Sterno- 

mastoid  Glands 786 

The  Lymphatic  Vessels  of  the  Neck            .      787 
Surgical  Anatomy 787 

The  Lymphatics  of  the  Upper  Extre.viity. 

The   Lymphatic  Glands  of  the   Upper  Ex- 
tremity   788 

The  Superficial    Lymphatic   Glands      .      788 
The   Deep   Lymphatic   or  the   Axillary 

Glands    .' 790 

The   Lymphatic   Vessels  of  the   Upper  Ex- 

"tremity  792 

The   Superficial   Lymphatic   Vessels  of 

the  Upper  Extremity 792 

The    Deep    Lymphatic    Vessels    of    the 

Upper"  Extremity        ....      792 
Surgical  Anatomy 792 

The  Lymphatics  of  the  Lower  Extremity. 

The   Lymphatic  Glands  of   the   Lower   Ex- 

•    tremity 793 

The    Superficial    Inguinal     Lymphatic 

Glands 793 

Surgical  Anatomy 794 

The    Deep    Lymphatic    Glands    of    the 

Lower  Extremity        ....      795 
The  Deep  Inguinal  or  Deep  Fem- 
oral Lymphatic  Glands  .      .       .      795 
The  Anterior  Tibial  Gland              .      795 
The  Popliteal  Glands     ....      795 
The  Gluteal  and  Ischiatic  Glands     797 
The   Lymphatic  Vessels  of  the  Lower  Ex- 
tremity   797 

The  Superficial   liymphatic  Vessels  of 

the  Lower  Extremity 797 

The    Deep    Lymphatic    Vessels   of   the 

Lower  Extremity 797 


The  Lymph.\tics  of  the  Pelvis  and 
Abdomen. 

The  Iliac  or  llio-pelvic  Glands  ....  797 
The  External  Iliac  Glands  ....  797 
The  Internal  Iliac  or  Hypogastric  Glands  799 
The  Common  Iliac  Gland  ....  799 
The  Abdomino-aortic  Glands  ....  799 
The  Right  Juxta-aortic  Glands  .  .  800 
The  Left  Ju.xta-aortic  Glands     .  800 

The  Retro-aortic  Glands       ....      800 
The  Pre-aortic  Glands 800 

The  Glands   along  the  Mesenteric 

Arteries 800 

The    Glands    connected    with    the 

Coeliac  Axis  and  its  Branches     .      800 

The  Gastric  Glands 800 

The  Splenic  Glands 800 

The  Hepatic  Glands       ....      801 
The  Lymphatic  Vessels  of  the  Abdomen  and 

Pelvis 801 

The   Superficial    Lymphatic    Vessels   of 

the  Walls  of  the  Abdomen    .       .      801 

The  Superficial  Lymphatic  Vessels 

of  the  Gluteal  Region      .      .       .      801 

The  Superficial  Lymphatic  Vessels 

of  the  Scrotum  and  Perina;um  .      801 

The  Superficial  Lymphatic  Vessels 

of  the  Penis 801 

The    Deep    Lymphatic    Vessels    of    the 

Abdominal  Wall 801 

The  Lymphatic  Ves.sels  of  the  Um- 
bilicus    802 

The  Lymphatic  Vessels  of  the  Peri- 
toneum        802 

The-    Lymphatic     Vessels    of    the 

Bladder 802 

The  Lymphatic  Vessels  of  the  Pros- 
tate Gland 803 

The  Lymphatic  Vessels  of  the  Male 

Urethra 803 

The  Lymphatic  Vessels  of  the  F'e- 

male  Urethra 803 

The     Lymphatic     Vessels    of    the 

Uterus 803 

The  Lymphatic  Vessels  of  the  Fal- 
lopian Tube 804 

The     Lymphatic     Vessels    of    the 

Ovary 804 

The  Lymphatic  Vessels  of  the 
Vagina 804 

The     Lymphatic     Vessels    of     the 

Testicle 804 

The     Lymphatic     Vessels    of    the 

Vas  Deferens  804 

The     Lymphatic     Vessels     of    the 

Seminal  Vesicles 804 

The  Lymphatic  Ves.sels  of  the 
Kidney,  Ureter,  and  Suprarenal 
Capsule 804 

The  Lymphatic  Vessels  of  the  Liver     805 

The     Lymphatic     Vessels    of    the 

Bile-ducts 806 

The     Lymphatic    Vessels    of    the 

Stomach 806 

The     Lymphatic     Vessels     of    the 

Pancreas 807 

The     Lymphatic     Vessels    of    the 

Spleen         807 

The  Lymph,\tic  System  of  the  Intestines. 

The  Lymphatic  Glands  of  the  Small  Intestine  807 

The  Ijymphatic  Vessels  of  the  Small  Intestine  808 

The  Lymphatic  Glands  of  the  Large  Intestine  808 

The  Colic  Glands 808 

The  Rectal  Glands 809 


XX 


CONTENTS 


The  Lymphatic  Vessels  of  the  Large  Intestine  809 

Lymphatics  of  the  Anus  and  Rectum    .       .  809 

The  Lymphatics  of  the  Thorax. 

The  Lymphatic  Glands  of  the  Thoracic  Wall 

or  the  Parietal  Lymphatics    .       .       .  810 

The  Internal  Mammary  Glands      .       .  810 

The  Intercostal  Glands 810 

The  Diaphragmatic  Lymphatics     .       .  810 

The  Visceral  Lymphatics      .       .       .       .811 

The  Anterior  Mediastinal  Glands  .  811 

The   Posterior  Mediastinal  Glands  812 

The   Peritracheo-bronchial  Glands  812 


The  Lymphatic  Vessels  of  the  Thoracic  Wail 
The  Cutaneous  Lymphatics 
Lymphatics  of  the  Mammary  Gland     . 
Lymphatics  of  the  Great  Pectoral 

Muscle 

Surgical  Anatomy 

The  Pulmonary   Lymphatics 
The  Pleural  Lymphatics 
The  Cardiac   Lymphatics      .... 
The  Thymic  Lymphatic  Vessels 
The  Lymphatic  Vessels  of  the  (Esoph- 
agus   

The  Lymphatic  Vessels  of  the  Thoracic 
Trachea         


PAGE 

812 
812 
812 

814 
814 
815 
815 
815 
815 

815 

815 


THE  NERVOUS  SYSTExM. 


Structure    of    the    Cerebro-spinal    Nervous 

System 817 

Nerve-cells    or    the   Cell-bodies   of    the 

Neurones 818 

Unipolar  cells 820 

Bipolar  cells 820 

Multipolar  cells 821 

The  Axone 821 

The  Dendrites 821 

The  Theory  of  Neurones      .       .      .      .821 

Nerve-fibres 822 

Development  of  Nerve-cells  and  Fibres      .  823 

Chemical  Composition  of  Nervous  Tissue      .  824 

Origin  and  Termination  of  Nerves   .       .       .  826 

Peripheral  Termination  of  Nerves  .       .  826 

Termination  in  Fibrilla; 827 

Neuro-tendinous  Spindles     ....  829 

Neuro-muscular  Spindles       ....  829 

The  Cerebro-spinal  Axis. 

The  Spinal  Cord  and  its  Membranes. 

Dissection 832 

Membranes  of  the  Cord. 

The  Spinal  Dura  Mater 832 

Structure 834 

The  Arachnoid  Membrane 834 

Structure 834 

The  Pia  Mater  of  the  Cord    .       .       .       .      .835 

Structure 835 

Surgical  Anatomy 836 

The  Spinal  Cord. 

Fissures  and  Grooves 837 

Columns  of  the  Cord 838 

Structures  of  the  Cord 839 

Blood  Supply  of  the  Cord 840 

Minute  Anatomy  of  the  Cord      ....  840 

The  Meninges  or  Meningeal  Membranes  of 
the  Brain. 

Dissection 847 

The  Dura  Mater  of  the  Brain      ....  847 

Structure 848 

Processes  of  the  Dura  Mater      .      .      .  849 

The  Arachnoid  Membrane 851 

The  Subarachnoid  Space      ....  852 

Structure 853 

GlanduliB  Pacchioni,  Luschka's  Villi  or  the 

Arachnoid  Villi 854 

The  Pia  Mater  of  the  Brain 854 

The  Velum  Interpositum  or  the   Tela 

Chorioidea  Superior 854 

The  Brain. 
The  Development  of  the  Brain   ....  857 
General  Considerations  and  Divisions    .       .  864 
The  Hemispheres  of  the  Cerebrum   .       .       .  864 
The  Constituent  Parts  of    the   Hemi- 
sphere       864 


The  Hemispheres  of  the  Cerebrum — 

The  Surface  of  the  Cerebrum    .       .       .865 
Fissures  and  Sulci  of  the  Outer  Surface 

of  the  Hemisphere 865 

The  Lobes  on  the  External  Surface  869 
The  Fissures,    Sulci  and   Lobes  of  the 

Mesial  and  Tentorial  Surfaces     .  869 

The  Frontal  Lobe 872 

The  Parietal  Lobe 875 

The  Occipital  Lobe 876 

The  Temporal  Lobe 877 

The    Central    Lobe    or    Island    of    Reil 

(Insula) 878 

Limbic  Lobe 878 

The  Olfactory  Lobe  or  Rhinencephalon  880 

Under  Surface  or  Base  of  Encephalon  .  881 
General     Arrangement    of     the     Parts 

composing  the  Cerebrum  ....  885 

Fibres  of  tlie  Internal  Capsule  .       .       .  892 

The  Inter-brain 901 

The  Third  Ventricle         901 

The  Optic  Thalamus 903 

The    Pineal    Bodj-,    Epiphysis   Cerebri, 

Conarium  or  Pineal  Gland     .       .      .  905 

The  Mid-brain         906 

Crusta  or  Pes 907 

The  Tegmentum 908 

The  Substantia  Nigra 910 

The    Corpora    or    Tubercula     Quadri- 

gemina 911 

The  Corpora  Geniculata 911 

The  Aqueduct  of  Sylvius  or  Iter  a  Tertio 

ad  Quartum  Ventriculum        .       .       .  912 

Subthalamic  region 913 

Structure  of  the  Cerebrum   .             .  913 

The  Hind-brain 922 

Pons  Varolii 923 

The  Cerebellum  or  Little  Brain      .       .  926 

The  Medulla  Oblongata 938 

The  Pyramid 939 

The  Lateral  Colunm  or  Lateral  Area    .  940 
The  Olive,    Olivary    Body    or    Olivary 

Eminence 941 

The    Funiculus    or    Fasciculus    of    Ro- 
lando         941 

The  Cuneate  Fasciculus         ....  941 

The  Fasciculus  Gracilis 941 

The  Restiform  Body 941 

The  Posterior  Surface   of   the   Medulla 

Oblongata 942 

The  Fourth  Ventricle 942 

The  Roof  or  Posterior  Wall            .  943 

The  Floor  or  Anterior  Wall            .  944 
The  Internal  Structure  of  the  Medulla 

Oblongata 945 

The  Posterior  Area         ....  946 

The  Lower  Part  of  the  Medulla     ..  946 

The  Upper  Part  of  the  Medulla     .  948 


Cerebral  Localization  and  Topography. 
Cranio-cerebral  Topography 


954 


CONTENTS 


XXI 


The  Nerve-paths. 

The  Motor,  Efferent  or  Descending  Tract     .  959 

The  Sensory,  Afferent  or  Ascending  Tract    .  961 

The  Spinal  Nerves. 

The  Roots  of  the  Spinal  Nerves       .       .       .  965 

The  Anterior  or  Ventral  Root  .      .      .  965 

The  Posterior  or  Dorsal  Root  .      .      .  965 

The  GangUa  of  the  Spinal  Nerves    .       .       .  966 

Distribution  of  the  Spinal  Nerves    .       .       .  967 

Points  of  Emergence  of  the  Spinal  Nerve    .  967 

The  Cervical  Nerves. 

The  Roots  of  the  Cervical  Nerves  ...  968 
The    Posterior   or    Dorsal    Division    of    the 

Cervical  Nerves 968 

The  Anterior  Divi.sion  of  the  Cervical  Nerves  971 

The  Cervical  Plexus 972 

Superficial  Branches 972 

Deep  Branches,   Internal  Series      .       .  974 

Surgical  Anatomy 976 

Deep  Branches,  External  Series      .       .  976 

Surgical  Anatomy 977 

The  Brachial  Plexus 977 

Relations 980 

Branches 981 

Surgical  Anatomy 991 

The  Thoracic  or  Dorsal  Nerves. 

The  Roots  of  the  Thoracic  or  Dorsal  Nerves  993 
The  Posterior  Divisions  of  the   Thoracic  or 

Dorsal  Nerves 993 

The  Internal  Branches 993 

The  External  Branches 993 

The  Cutaneous  Branches  ....  993 
The  Anterior  Divisions  of  the  Thoracic  or 

Dorsal     Nerves    or    the    Intercostal 

Nerves 993 

The    Anterior    Division    of    the    First 

Thoracic  or  First  Dorsal  Nerve  .  .  995 
The   Anterior   Divisions  of    the  Upper 

Thoracic  or  Dorsal  Nerves  .  .  .  995 
The   Anterior   Divisions  of   the   Lower 

Thoracic  or  Dorsal  Nerves     .      .      .  996 

The  Last  Thoracic  or  Dorsal  Nerve  996 

Surgical  Anatomy 996 

The  Lumbar  Nerves. 

The  Roots  of  the  Lmnbar  Nerves  .  .  .  997 
The    Posterior    Divisions    of    the    Lumbar 

Nerves 997 

Internal  Branches 998 

External  Branches 998 

The  Anterior  Divisions  of  the  Lumbar  Nerves  998 

The  Lumbar  Plexus 998 

Branches 999 

The  Sacral  and  Coccygeal  Nerves. 

The  Roots  of  the  Upper  Sacral  Nerves        .  1006 

The  Posterior  Divisions  of  the  Sacral  Nerves  1006 

The  Upper  Sacral  Nerves     ....  1006 

The  Lower  Sacral  Nerves     ....  1007 

The  Anterior  Divisions  of  the  Sacral  Nerves  1007 
The   Posterior   Divisions   of   the   Coccvgeal 

Nerve ".       .  1008 

The    Anterior    Division    of    the    Coccygeal 

Nerve 1009 

The  Sacral  or  Sciatic  Plexus  and  the  Pudic 

or  Pudendal  Plexus 1009 

Branches    .      ■■. 1010 

Surgical  Anatomy 1017 

The  Cerebral  or  Cranial  Nerves. 

The  First  or  Olfactory  Nerve. 

Surgical  Anatomy 1021 


The  Second  or  Optic  Nerve. 

The  Optic  Tract 1021 

The  Optic  Commissure 1021 

The  Optic  Path 1022 

Surgical  Anatomy 1022 


The  Third  or  Motor  Oculi  Nerve. 
Surgical  Anatomy 


1025 


The  Fourth  or  Trochlear  Nerve. 

Branches  of  Communication 1026 

Branches  of  Distribution 1026 

Surgical  Anatomy 1026 

The  Fifth,   Trigeminal  or  Trifacial  Nerve. 

The  Gasserian  or  Semilunar  Ganglion   .       .  1027 

Ophthalmic  Nerve 1028 

Branches 1028 

The  Superior  Maxillary  Nerve    ....  1031 

Branches 1032 

The  Mandibular  or  Inferior  Maxillary  Nerve  1036 

Branches 1036 

Surface  Marking 1041 

Surgical  Anatomy 1041 

The  Sixth  or  Abducent  Nerve. 

Branches  of  Communication 1043 

Surgical  Anatomy 1044 


The  Seventh  or  Facial  Nerve. 
Branches  of  Communication  .       .      .      . 

Branches  of  Distribution 

Surgical  Anatomy 


The  Eighth  or  Auditory  Nerve. 
The  Origin  of  the   Eighth  Nerve 

The  Auditory  Paths 

Surgical  Anatomy 


Tlie  Ninth  or  Glosso-Pharyngeal  Nerve 
The  Superior  or  Jugular  Ganglion 
The  Inferior  or  Petrous  Ganglion 

Branches  of  Communication 

Branches  of  Distribution 
The  Gustatory  Path  .  .  •  . 
Surgical  Anatomy 


1046 
1046 
1049 


1050 
1053 
1054 


1056 
1056 
1056 
1056 
1056 
1057 


The  Tenth  or  Pneumogastric  Nerve. 
The  Ganglion  of  the  Root  of  the  Pneumo- 
gastric Nerve 1059 

Connecting  Branches 1059 

The  Ganglion  of  the  Trunk  of  the  Pneumo- 
gastric Nerve 1059 

Connecting  Branches 1059 

Surgical  Anatomy 1062 

The  Eleventh  or  Spinal  Accessory  Nerve. 
The  Bulbar  or  Accessory  Part  of  the  Spinal 

Accessory  Nerve 1063 

The  Spinal  Portion  of  the  Spinal  Accessory 

Nerve 1063 

Surgical  Anatomy 1063 

The  Twelfth  or  Hypoglossal  Nerve. 

Branches  of  Communication 1065 

Branches  of  Distribution 1066 

Surgical  Anatomy 1066 


The  Symp.\thetic  Nftrve. 
Structure  of  the  Sympathetic  System 


1068 


The  Gangliated  Cord. 

The  Cervical  Portion  of  the  Gangliated  Cord   1071 

The  Superior  Cervical  Ganglion  .    1072 

The  Inferior  Cervical  Ganglion       .       .    1077 

Surgical  Anatomy 1077 


XXll 


CONTENTS 


The  Thoracic  Portion  of  the  Gangliated  Cord   1078  \  The  Cardiac  Plexus- 


The  Lumbar  Portion  of  the  Garighated  Cord   1079 
The  Pelvic  or  Sacral  Portion  of  the  GangU- 

ated  Cord 1080 

The  Great  Plexuses  of  the  Sympathctics . 

The  Cardiac  Plexus 1081 

The  Great  or  Deep  Cardiac  Plexus      .    1081 


The    Superficial    or    Anterior    Cardiac 

Plexus 1081 

The  Pulmonary  Plexus 1081 

The  CEsophageal  Plexus 1082 

The  Epigastric  or  Solar  Plexus   ....  1083 

The  Hypogastric  Plexus 1085 

The  Pelvic  or  Sacral  Plexus       ....  1086 


THE  ORGANS  OF  SPECIAL  SENSE. 


The  Tongue. 

The  Body 1087 

The  Base  or  Root 1087 

The  Apex  or  Tip 1087 

The  Margin  of  the  Tongue 1087 

The  Under  or  Inferior  Surface    ....  1087 

Structure  of  the  Tongue 1088 

Surgical  Anatomy 1093 

The  Nose. 
The  Outer  Nose. 

Structure 1096 

The  Nasal  Fossce. 

The  Anterior  Nares 1098 

The  Posterior  Nares 1098 

Outer  Wall 1099 

The  Inner  Wall 1100 

Surgical  Anatomy 1102 

The  Eye. 

The  Fascia  or  Capsule  of  T^non     .      .      .  1103 

The  Tunics  of  the  Eye. 
The  Fibrous  or  External  Coat :  The  Sclerotic 

and  Cornea 1107 

The  Sclera  or  Sclerotic  Coat      .             .  1107 

The  Cornea 1108 

Dissection 1111 

The  Choroid,  Ciliary    Body,  and    Iris;    the 

Tunica  Media;  the  Uveal  Tract  .       .  1111 

The  Choroid 1111 

The  Ciliary  Body 1115 

The  Iris      .      .     V 1117 

The  Tunica  Interna  or  Retina     .  .      ..  1120 

The  Refracting  Media. 

The  Aqueous  Humor 1128 

The  Vitreous  Body 1129 

The  Crystalline  Lens 1130 

Surgical  Anatomy  of  the  Eye      .       .       .       .  1134 

The  Appendages  of  the  Eye. 

The  Eyebrow 1137 

The  Eyelid         1137 

The  Meibomian  or  Tarsal  Glands    .       .  1139 


The  Conjunctiva 1140 

The  Lachrymal  Apparatus 1141 

The  Lachrymal  Glands 1141 

The  Lachrymal  Sac 1142 

The  Nasal  Duct 1142 

Surface  Form 1142 

Surgical  Anatomy 1143 

The   Ear. 
The  External  Ear. 

The  Pinna  or  Auricle 1144 

Structure  of  the  Pinna 1146 

The  External  Auditory  Canal     ....  1148 

The  Cartilaginous  Portion     ....  1148 

The  Osseous  Portion 1149 

Surface  Form 1150 

The  Middle  Ear,  Drum  or  Tympanum. 

The  Tympanic  Cavity 1150 

The  Drumhead  or  Membrana  Tympani      .    1155 

The  Ossicles  of  the  Tympanum   ....    1158 

The  Malleus  or  Hammer       .       .       .       .1158 

The  Incus  or  Anvil 1159 

The  Stapes  or  Stirrup 1160 

The  Internal  Ear  or  Labyrinth. 

The  Osseous  Labyrinth 1164 

The  Vestibule 1164 

The  Semicircular  Canals        ....  1165 

The  Cochlea 1165 

The  Membranous  Labyrinth 1169 

The  Utricle 1169 

The  Saccule 1170 

The  Membranous  Semicircular  Canals  .  1170 

Surgical  Anatomy .1176 

The  Skin. 

The  Corium,   Cutis   Vera,    Dermis  or  True 

Skin 1180 

The  Cuticle,  Scarf  Skin  or  Epidermis     .       .1181 

The  Appendages  of  the  Skin       ....  1185 

The  Nails 1185 

The  Hairs 1187 

The  Sudoriferous  or  Sweat-glands  .       .  1190 

The  Sebaceous  Glands 1191 


THE  ORGANS  OF  DIGESTION. 


The  AlLIMENTARY  C.\N.\L. 

The  Mouth,  Oral  or  Buccal  Cavity. 

The  Vestibule 

The  Cavity  of  the  Mouth  Proper 

The  Lips 

The  Cheeks 

The  Gums    .^ 

The  Teeth 

General  Characters 

Temporary,  Deciduous  or  Milk  Teeth 

Permanent  Teeth 

Arrangement  of  the  Teeth   . 

Structure  of  the  Teeth    .... 

Development  of  the  Teeth  . 
The  Palate 

The  Hard  Palate 


1194 
1194 
1194 
1195 
1195 
1195 
1195 
1196 
1196 
1198 
1200 
1204 
1210 
1210 


The  Palate— 

The  Soft    Palate  or  Velum  Pendulum 

Palati 1211 

The  Tonsil  or  Amvgdala       ....  1213 

The  Salivarv  Glands    ." 1214 

The  Parotid  Gland 1214 

Surface  Form      ...'...  1215 

The  Submaxillary  Gland      ....  1216 

The  Sublingual  Gland 1217 

Structure  of  Salivary  Glands     .       .       .  1217 

Surface  Form 1219 

The  Pharynx. 

The  Nasal  Part 1221 

The  Oral  Part 1221 

The  Larvngeal  Part 1222 

Structure 1222 


CONTENTS 


XXlll 


PAGE 

Surgical  Anatomy  of  the  Mouth,  Cheeks, 
Lips,  Gums,  Tonsils,  Palate,  Salivary 
Glands  and  Pharynx 1224 

The  (Esophagus. 

Relations 1227 

Anomalies 1228 

Structure 1228 

Movements  antl  Innervations  of  the  (Esoph- 
agus      1230 

Surgical  Anatomy 1230 

Thk  Audomen. 

Boundaries 1231 

Development  of  the  Alimentary  Canal,  Vis- 
cera and  Peritoneum 1235 

Development  of  the  Alimentary  Canal  .       .    1236 

The  Peritoneum. 

Structure  of  the  Peritoneum       ....    1245 

Retro-peritoneal  Fossae 1260 

Surgical  Anatomy 1264 

The  Stomach. 

Relations  of  the  Stomach 1269 

Surfaces 1269 

The  Cardia 1270 

The  Pylorus 1270 

Alterations  in  Position 1271 

Supports  of  the  Stomach 1272 

Structure 1273 

Movements  and  Innervation  of  Stomach    .  1280 

Surface  Form 1280 

Surgical  Anatomy 1280 

The  Small  Intestine. 

The  Duodenum 1282 

The  First  or  Superior  Portion  .  .  ,  1284 
The  Second  or  Descending  Portion  .  1285 
The    Third,    Pre-aortic,    Horizontal    or 

Transverse  Portion 1285 

The   Fourth  or   Ascending   Portion      .    1286 

The  Jejunum  and  Ileum 1289 

Differences  between  the  Jejvmum  and 

Ileum 1289 

The  Jejunum         1289 

The  Ileum 1289 

Structure  of  the  Small  Intestine,  including 
the  Duodenum 1290 


PAGE 

The  Large  hUestine. 

The  CiECum 13(M) 

The  Vermiform  Appendix     ....    1303 
The  Ileo-caical  Valve  or  the  Valve  of 

Bauhin 1308 

The  Colon 1309 

The  Ascending  Colon 1309 

The  Transverse  Colon 1309 

The  Descending  Colon 1309 

The  Sigmoid  Flexure,  Pelvic  Colon  or 

Sigmoid  Colon 1311 

The  Rectum 1312 

The  Common  Anal  Canal  .  .1315 

Structure  of  the  Large  Intestine  .       .    1316 

Movements  and  Innervations  of  the  Intes- 
tines     1322 

Surface  Form  of  the  Intestines   ....    1323 

Surgical  Anatomy  of  the  Intestines  .    1324 

The  Liver. 

The  Superior  Area  or  Surface      ....  1327 

The  Anterior  Area  or  Surface      ....  1327 

The  Lateral  or  Right  Area  or  Surface   .       .  1329 

The  Under  or  Visceral  Area  or  Surface        .  1329 

The  Posterior  Area  or  Surface     ....  1329 

Fissures  of  the  Liver 1331 

Lobes  of  the  Liver 1332 

Supports  and  Movability  of  the  Liver  .       .  1334 

Abnormalities  of  the  Liver 1335 

Structure  of  the  Liver 1337 

The  Excretory  Apparatus  of  the  Liver       .  1342 

The  Hepatic  Duct 1342 

The  Gall-bladder 1342 

The  Cystic  Duct         1344 

Surface  Relations  of  the  Liver     ....  1346 

Surgical  Anatomy  of  the  Liver  ....  1346 

The  Pancreas. 

Dissection 1348 

The  Right  Extremity  or  Head  of  the  Pan- 
creas    1348 

The  Neck  of  the  Pancreas 1350 

The  Body  and  Tail  of  the  Pancrea-s      .       .1350 

Structure  of  the  Pancreas 1352 

Surface  Form 1353 

Surgical  Anatomy 1353 

The  Spleen. 

Surface  of  the  Spleen 1354 

Supports  and  Movability  of  the  Spleen      .  1356 

Surface   Form 1359 

Surgical  Anatomy 1359 


ORGANS  OF  VOICE  AND  RESPIRATION. 


The  Larynx. 

The  Cartilages  of  the  Larynx      ....  1362 

The  Thyroid  Cartilage 1362 

The  Cricoid  Cartilage 1363 

The  Arytenoid  Cartilages     ....  1364 
The   Cornicula   Laryngis  or  Cartilages 

of  Santorini 1365 

The  Cuneiform  Cartilages  or  Cartilages 

of  Wri.sberg 1365 

The  Epiglottis  or  the  Cartilage  of  Epi- 
glottis       1365 

Structure  of  the  Larynx 1365 

Interior  of  the  Larynx 1368 

The  Tk.\che.'V  and  Bronchi. 

Relations 1376 

The  Right  Bronchus 1376 

The  Left  Bronchus 1378 

Structure  of  the  Trachea 1378 

Surface  Form  of  Larynx 1380 

Surgical  Anatomy  of  Larynx  and  Trachea  .  1381 


The  Pi.eur^. 

Reflections  of  the  Pleura 1384 

Structure  of  the  Pleura 1387 

Surgical  Anatomy 1387 

The  Mediastinal,  Space.  Interpleural  Space 
OR  Mediastinum. 

The  Superior  Mediastinum     .....  1388 

The  Anterior  Mediastinum 1389 

The  Middle  Mediastinum 1389 

The  Posterior  Mediastinum 1389 


The  Lungs. 

Apex  of  the  Lungs 1390 

Base  of  the  Lungs 1391 

Surfaces  of  the  I.,ungs 1391 

Borders  of  the  Lungs 1392 

Lobes  of  the  Limgs 1392 


XXIV 


CONTENTS 


PAGE 

The  Root  of  the  Lung 1394 

The  Fu^tal  Lung 1394 

Structure  of  tlie  Lung 1394 

The  Bronchus 1395 


Changes  in  tlie  Structure  of  the  Bronchi  in 

the  Lungs 1395 

Surface  Form  of  the  Lungs 1397 

Surgical  Anatomy  of  the  Lungs        .  .  1397 


THE  DUCTLESS  GLANDS. 


The  Thyroid  Body  or  Gland. 

Accessory  Thyroids 1403 

Structure  of  the  Thyroid 1403 

Surgical  Anatomy 1405 

Parathyroids 1408 

Structure  of 1406 


The  Thymus  Gland. 
Structure  of  the  Thymus  Gland       .  .    1408 

The  Carotid  Gland  or  Carotid  Body. 

Surgical  Anatomy 1409 

The  Coccygeal  Gland  or  Coccygeal  Body  1410 


THE  URINARY  ORGANS. 


The  Kidneys. 

Surfaces  of  the  Kidneys 1412 

Borders  of  the  Kidneys 1415 

General  Structure  of  the  Kdney       .  .  1415 

Surface  Form 1425 

Surgical  Anatomy 1425 

The  Ureter. 

The  Ureter  Proper 1426 

Relations  of  the  Ureter 1427 

Structure  of  the  Ureter 1427 

Surgical  Anatomy 1428 

The  Suprarenal  Capsule  or  Gland. 

Relations  of  the  Suprarenal  Capsule      .       .  1428 

Accessory  Suprarenal  Glands       ....  1430 

Structure  of  Suprarenal  Glands  ....  1430 

The  Cavity  of  the  Pelvis. 

Boundaries 1431 

Contents 1431 


The  Urinary  Bladder. 

Surfaces 1433 

The  Fundus  or  Base 1433 

The  Summit  or  Apex 1435 

The  Urachus  or  Middle  Umbilical  Ligament  1435 

Structure  of  tlie  Bladder 1437 

Objects  Seen  on  the  Inner  Surface  of  Bladder  1 438 

Surface  Form 1440 

Surgical  Anatomy 1440 

The  Male  Urethra. 
The  First  or  Prostatic  Portion     ....    1441 
The  Second,  Muscular  or  Membranous  Por- 
tion      1442 

The  Third,  Penile,  Pendulous,  Cavernous  or 

Spongy  Portion 1443 

Structure  of  Male  Urethra 1444 

Surgical  Anatomy 1445 

The  Female  Bladder  and  Urethra. 

The  Female  Urethra 1446 

Structure 1446 


THE  MALE  ORGANS  OF  GENERATION. 


The  Prostate  Gland. 

The  Base 1451 

The  Apex 1451 

Surfaces 1451 

The  Lateral  Lobes 1451 

The  So-called  Middle  Lobe 1451 

Structure 1452 

Surgical  Anatomy 1452 

Cowper's  Glands. 

Structure 1453 

The  Penis. 

The  Root 1454 

The  Body  of  the  Penis 1455 

Structure  of  the  Penis 1455 

Surgical  Anatomy 1460 

The  Testicles  and  their  Coverings. 

Descent  of  the  Testis. 

Surgical  Anatomy 1462 


The  Coverings  of  the  Testicle. 

The  Testicular  Bag  or  Scrotum    ....  1462 

The  Intercolumnar  or  Spermatic  Fascia       .  1463 

The  Cremasteric  Fascia 1464 

The  Infundibuliform  Fascia 1464 

The  Tunica  Vaginalis 1465 

The  Spermatic  Cord. 

Structure 1466 

Surgical  Anatomy 1468 

The  Testicles. 

Structure  of  the  Testicle  and  Epididymis     .  1471 

Surgical  Anatomy 1473 

The  Seminal  Vesicles. 

The  Ejaculatory  Ducts 1476 

Structure      .      '. 1476 


THE  FEMAIvE  ORGANS  OF  GENERATION. 


External  Organs. 
The  Mons  Veneris  .      7     .'     7     7     .      .      .    1477 


The  Large  Lips  or  Labia  Majora 

The  Small  Lips,  Nymphae  or  Labia  Minora 


1477 
1478 


The  Vestibule 1481 

The  Orifice  of  the  Urethra  or  the  Meatus 

Urinarius 1481 

The  Hymen 1481 

Glands  of  Bartholin 1482 


The  Clitoris 1479  ''  The  Vaginal  Bulb  or  Bulb  of  the  Vestibule    1483 


CONTENTS 


XXV 


PAQE 

Internal  Organs. 
The  Vagina. 

Relations 1484 

Structure 1484 

The  Wo7nh  or  Uterus. 

The  Fundus 1487 

The  Body  of  the  Uterus 1487 

The  Neck  or  Cervix  Uteri 1488 

Folds  and  Ligaments 1489 

The  Cavity  of  the  Uterus 1491 

The  Cavity  of  the  Cervix  or  Cervical  Canal  1491 

Surgical  Anatomy 1496 

The  Adnexa  or  Appendages  of  Uterus. 

The  Fallopian  Tube. 

Structure  of  the  Fallopian  Tube      .      .      7  1498 


The  Epo-ophoron,  Parovarium  or  Organ  of 

Rosenmiiller 1499 

The  Paro-ophoron 1499 

The  Ovary. 

Supports  and  Connections  of  the  Ovary     .  1500 

Descent  of  the  Ovary 150I 

The  Ovary  at  Different  Ages     .       .       .  1501 

Structure 1501 

Surgical  Anatomy  of  the  Appendages  .      .  1503 

The  Mammary  Gland. 

Description  of  a  Well-developed  Breast      .  1503 

The  Nipple 1504 

Prolongation  of  Mammary  Tissue    .      .      .  1505 

Structure  of  Mammary  Gland  and  Nipple    .  1505 

Surgical  Anatomy 1508 

The  Male  Breast     .      . 1509 

Surgical  Anatomy 1509 


THE   SURGICAr.  ANATOMY  OF  INGUINAL  AND  FEMORAL 

HERNIA. 


Dissection 1511 

Inguinal  Hernia. 

Obli<iue  Inguinal  Hernia 1520 

Congenital  Hernia 1523 

Infantile  and  Encysted  Hernia       .      .  1523 


Hernia  into  Funicular  Process 
Direct  Inguinal  Hernia     . 


Femoral  Hernia. 
Varieties  of  Femoral  Hernia 


1523 
1523 


1534 


SURGICAL  ANATOMY  OF  THE  PERINiEUM. 


Dissection ."     7      .    1535 


Ischio-reclal   Region. 
Dissection 1536 

The  PcrincBum,  Proper  in  the  Male. 
Position  of  the  Viscera  at  the  Outlet  of  the 

Pelvis 1540 


Surgical  Anatomy 1541 


The   Female  PerincBum,. 

The  Pelvic  Fascia 1544 

The  Obturator  Fascia 154G 

The   Recto-vesical    Fascia  or  the   Visceral 

Layer  of  the  Pelvic  Fascia       ....    1546 


Chronological  T,\ble  of  the  Development  of  the  Fcetus      .......      7      .   1547 

Index I549 


DESCRIPTIVE  AND  SURaiOAL 

AI^ATOMY. 


OSTEOLOGY -THE  SKELETON. 


T 


HE  entire  skeleton  in  the  adult  consists  of  200  distinct  bones.    These  are: 

The  spine  or  vertebral  column  (sacrum  and  coccyx  included)     ....  26 

Cranium 8 

Face 14 

Hyoid   bone,  sternum,  and   ribs 26 

Upper  extremities 64 

Lower  extremities 62 

200 

In  this  enumeration  the  patellae  are  included  as  separate  bones,  but  the  smaller 
sesamoid  bones  and  the  ossicula  auditus  are  not  reckoned.  The  teeth  belong  to 
the  tegumentary  system.  Different  anatomists  make  different  computations  as 
to  the  number  of  bones  in  the  skeleton.  Some  describe  the  skeleton  as  containing 
206  distinct  bones,  adding  the  ossicles  of  the  ear  to  the  previously  stated  number. 
By  adding  the  epipteric  bones,  the  sphenoidal  turbinal  bones,  the  sesamoid  bones, 
and  others,  the  number  may  be  greatly  augmented. 

Bones  are  divisible,  according  to  their  shape,  into  four  classes:  long,  short,  flat, 
and  irregular. 

Long  Bones. — The  long  bones  are  found  in  the  limbs,  where  they  form  a 
system  of  levers,  which  sustain  the  weight  of  the  trunk  and  confer  the  power 
of  locomotion.  A  long  bone  consists  of  a  shaft  and  two  extremities.  The  shaft 
is  a  hollow  cylinder,  contracted  and  narrowed  to  afford  greater  space  for  the 
bellies  of  the  muscles;  the  walls  consist  of  dense,  compact  tissue  of  great  thick- 
ness in  the  middle,  but  becoming  thinner  toward  the  extremities;  the  spongy 
tissue  is  scanty,  and  the  bone  is  hollowed  out  in  its  interior  to  form  the  medullary 
canal.  The  extremities  are  generally  somewhat  expanded  for  greater  convenience 
of  mutual  connection,  for  the  purpose  of  articulation,  and  to  afford  a  broad 
surface  for  muscular  attachment.  Here  the  bone  is  made  up  of  spongy  tissue 
with  only  a  thin  coating  of  compact  substance.  The  long  bones  are  not  straight, 
but  curved,  the  curve  generally  taking  place  in  two  directions,  thus  affording 
greater  strength  to  the  bone.  The  bones  belonging  to  this  class  are  the  clavicle, 
humerus,  radius,  ulna,  femur,  tibia,  fibula,  metacarpal  and  metatarsal  bones,  and 
the  phalanges. 

Short  Bones. — Where  a  part  of  the  skeleton  is  intended  for  strength  and  com- 
pactness, and  its  motion  is  at  the  same  time  slight  and  limited,  it  is  divided  into 
a  number  of  small  pieces  united  together  by  ligaments,  and  the  separate  bones 
are  short  and  compressed,  such  as  the  bones  of  the  carpus  and  tarsus.  These 
bones,  in  their  structure,  are  spongy  throughout,  excepting  at  their  surface,  where 

.s  ( 33  ) 


34  THE  SKELETON 

there  is  a  thin  crust  of  compact  substance.    The  patellae  also,  together  with  the 
other  sesamoid  bones,  are  by  some  regarded  as  short  bones. 

Flat  Bones. — Where  the  principal  requirement  is  either  extensive  protection 
or  the  provision  of  broad  surfaces  for  muscular  attachment,  we  find  the  osseous 
structure  expanded  into  broad,  flat  plates,  as  is  seen  in  the  bones  of  the  skull 
and  the  shoulder-blades.  Flat  bones  are  composed  of  two  thin  layers  of  com- 
pact tissue  enclosing  between  them  a  variable  quantity  of  cancellous  tissue.  In 
the  cranial  bones  these  layers  of  compact  tissue  are  familiarly  known  as  the  tables 
of  the  skull;  the  outer  table  is  thick  and  tough;  the  inner  table  is  thinner,  denser, 
and  more  brittle,  and  hence  is  termed  the  vitreous  table.  The  intervening  can- 
cellous tissue  is  called  the  diploe.  The  flat  bones  are:  the  occipital,  parietal,  frontal, 
nasal,  lachrymal,  vomer,  scapula,  os  innominatum,  sternum,  ribs,  and  patella. 

Irregular  Bones. — -The  irregular  or  mixed  bones  are  such  as,  from  their  pecu- 
liar form,  cannot  be  grouped  under  either  of  the  preceding  heads.  Their  structure 
is  similar  to  that  of  other  bones,  consisting  of  a  layer  of  compact  tissue  externally 
and  of  spongy,  cancellous  tissue  within.  The  irregular  bones  are:  the  vertebrae, 
sacrum,  coccyx,  temporal,  sphenoid,  ethmoid,  malar,  superior  maxilla,  inferior  maxilla, 
palate,  inferior  turbinated,  and  hyoid. 

Surfaces  of  Bones. — If  the  surface  of  any  bone  is  examined,  certain  eminences 
and  depressions  are  seen,  to  which  descriptive  anatomists  have  given  the  following 
names. 

These  eminences  and  depressions  are  of  two  kinds:  articular  and  non-articular. 
Well-marked  examples  of  articular  eminences  are  found  in  the  heads  of  the 
humerus  and  femur  and  of  articular  depressions  in  the  glenoid  cavity  of  the 
scapula  and  the  acetabulum.  Non-articular  eminences  are  designated  according 
to  their  form.  Thus  a  broad,  rough,  uneven  elevation  is  called  a  tuberosity;  a 
small,  rough  prominence,  a  tubercle;  a  sharp,  slender,  pointed  eminence,  a  spine; 
a  narrow,  rough  elevation,  running  some  way  along  the  surface,  a  ridge,  line,  or 
crest. 

The  non-articular  depressions  are  also  of  very  variable  form,  and  are  described 
as  fossae,  grooves,  furrows,  fissures,  notches,  sulci,  etc.  These  non-articular  emi- 
nences and  depressions  may  receive  blood-vessels,  nerves,  tendons,  ligaments,  or 
portions  of  organs,  or  may  serve  to  increase  the  extent  of  surface  for  the  attach- 
ment of  ligaments  and  muscles.  They  are  usually  well  marked  in  proportion  to 
the  muscular  development  of  the  subject. 

A  prominent  process  projecting  from  the  surface  of  a  bone  which  it  has  never 
been  separate  from  or  movable  upon  is  termed  an  apophysis  (from  d-6</'tj(Ti^,  an 
excrescence) ;  but  if  such  process  is  developed  as  a  separate  piece  from  the  rest  of 
the  bone,  to  which  it  is  afterward  joined,  it  is  termed  an  epiphysis  (from  iTiiifom^, 
an  accretion).  The  main  part  of  the  bone,  or  shaft,  which  is  formed  from  the 
primary  centre  of  ossification,  is  termed  the  diaphysis,  and  is  separated,  during 
growth,  from  the  epiphysis  by  a  layer  of  cartilage,  at  which  growth  in  length  of 
the  bone  takes  place.  Some  bones  are  hollow  and  contain  sinuses,  which  are 
spaces  for  air.  Canals  or  foramina  are  channels  or  openings  in  bone  through 
which  nerves  or  vessels  pass. 

Structure  of  Bone. — Bone  is  a  highly  specialized  form  of  connective  tissue. 
In  reality,  it  is  white  fibrous  tissue,  calcified  and  structurally  modified  until  it 
becomes  osseous  tissue.  Bone  is  not  simply  a  crude  mass  resulting  from  the 
calcification  of  cartilage  or  fibrous  tissue;  it  is  a  distinct  tissue,  of  a  definite  struc- 
ture, the  constituent  parts  of  which  are  arranged  symmetrically,  Its  structure 
varies  somewhat  in  different  vertebrates.^ 

1  Arquitectura  del  Aparato  de  Sustentacion  en  los  Vertebrados.     Por  el  Dr.  Saturnine  Garcia  Hurtado.     Our 
description  applies  to  human  bone. 


STRUCTURE    OF   BONE 


35 


There  are  two  varieties  of  bone:  dense  or  compact  bone  {substantia  compacta), 
and  cancellous,  loose,  or  spongy  bone  {substantia  spongiosa). 

Compact  Bone  is  dense,  like  ivory,  and  is  always  placed  upon  the  exterior  of 
bones.  Even  this  apparently  compact  tissue  is  porous;  it  differs  from  cancellous 
bone  in  the  greater  density  of  its  tissue  and  in  the  arrangement  of  its  osseous 
plates  into  Haversian  systems.     Compact  bone  is  surrounded  by  periosteum. 


OSTEOQENETIO 

CELLS 


LAMELL/E 

LACUN/E 

CANALICUL 

HAVERSIAN 

CANAL 


COMPLETE 
HAVERSIAN 
SYSTEM 


Fig.  1. — Diagram  of  the  structure  of  osseous  tissue.  A  small  part  of  a  transverse  section  of  the  shaft  of  a  long 
JDone  is  shown.  At  the  uppermost  part  is  the  periosteum  covering  the  outside  of  the  bone  ;  at  the  lowermost  part 
is  the  endosteum  lining  the  marrow-cavity.  Between  these  is  the  compact  tissue,  consisting  largely  of  a  series  of 
Haversian  systems,  each  being  circular  in  outline  and  perforated  by  a  central  canal.  In  the  first  one  is  shown 
only  the  area  occupied  by  a  system",  in  the  second  is  seen  the  concentric  arrangement  of  the  lamelte;  and  in  the 
others,  respectively,  canaliculi;  lacunae;  lacuna"  and  canaliculi;  the  contents  of  the  canal,  artery,  vein,  lymphatic 
and  areolar  tissue;  lamella?,  lacunae,  and  canaliculi;  and,  finall.y,  all  of  the  structures  composing  a  complete  sys- 
tem. Between  the  systems  are  circumferential  and  intermediate  lamella>,  only  a  few  of  which  are  represented  as 
lodging  lacuna>,  though  it  is  to  be  understood  that  the  lacuna;  are  in  all  parts.  The  periosteum  is  seen  to  be 
made  up  of  a  fibrous  layer  and  a  vascular  layer,  and  to  have  upon  its  attached  surface  a  stratum  of  cells.  From 
the  fibrous  layer  project  inward  the  rivet-like  fibres  of  Sharpey.     (F.  H.  Gerrish.) 


The  outer  portion  of  the  wall  of  a  long  bone,  the  cortex  of  the  head  of  a  bone, 
and  the  outer  and  inner  layers  of  a  flat  bone  are  composed  of  compact  osseous 
tissue,  which  is  the  hardest  substance  in  the  body  with  the  exception  of  dentine 
and  enamel;  it  is  tough  and  elastic,  and  much  force  is  required  to  break  it. 

Cancellous  Bone  is  found  in  the  interior  of  bones.  The  name,  which  means 
lattice-work,  indicates  the  structure,  which  consists  of  slender  fibres  and  lamellse 
joined  to  form  a  reticulum,  the  small  meshes  of  which  are  marrow-spaces.     The 


36  THE  SKELETON 

spicules  of  cancellous  bone  contain  lacunae  and  canaliculi,  but  no  Haversian 
systems.  In  some  regions  the  inner  portion  of  the  wall  of  a  long  bone,  about  the 
marrow-cavity,  is  composed  of  cancellous  bone.  Toward  each  extremity  of  the 
shaft  the  amount  of  cancellous  tissue  increases,  the  marrow-cavity  diminishes  in 
size,  and  the  cancellous  tissue  is  arranged  in  lines  that  approach  each  other  toward 
the  extremity,  like  the  sides  of  an  arch,  and  form  a  support  for  the  epiphysis 
(Fig.  131).  In  the  epiphysis  the  bone-plates  are,  as  a  rule,  at  right  angles  to 
the  plane  of  the  articular  surface  (the  lines  of  greatest  pressure) ;  and  they  are 
bound  together  or  strengthened  by  other  bone-fibres,  which  are  usually  in  corre- 
spondence with  the  planes  of  the  articulation  (the  lines  of  greatest  tension)  (Fig. 
163).  The  nearer  the  bone-spicules  are  to  the  medullary  cavity  the  stronger  they 
are  (Hurtado). 

In  the  flat  and  the  irregular  bones,  the  cancellous  tissue  is  between  the  layers 
of  compact  bone,  and  is  called  the  diploe. 

A  Short  Bone  is  composed  chiefly  of  cancellous  tissue,  which  is  encased  in  a 
thin  coat  of  compact  substance  [substantia  corticalis). 

A  Long  Bone  consists  of  a  shaft,  or  diaphysis,  and  two  extremities,  or  epiphyses. 
The  shaft  is  an  osseous  tube,  the  outer  layer  of  which  is  compact,  and  the  inner 
layer  of  which  is  cancellous.  It  surrounds  the  medullary  cavity  (cavum  medullar e), 
which,  in  the  recent  condition,  contains  the  medulla,  or  marrow  [medulla  ossium), 
which  substance  enters  into  the  nearest  Haversian  canals.  '  This  cavity  is  widest 
at  the  centre  of  the  shaft,  and  narrows  toward  the  ends,  where  it  is  encroached 
upon  by  the  cancellous  layer  which  lies  within  the  compact  layer. 

There  are  two  varieties  of  marrow:  Yellow  marrow  [medulla  ossium  flava)  is 
found  in  the  medullary  cavities  of  the  shafts  of  the  long  bones.  It  is  composed 
of  a  network  of  fibrous  tissue  carrying  many  blood-vessels,  fat-cells,  and  a  few 
large  nucleated  masses  of  protoplasm — the  true  marrow-cells,  or  myelocytes. 
The  yellow  color  of  the  marrow  is  due  to  fat.  Yellow  marrow  is  derived  from 
red  marrow  by  an  increase  in  fat  and  diminution  in  marrow  elements;  it  plays 
no  part  in  blood-formation.  At  the  periphery  of  the  marrow  cavity  the  fibrous 
tissue  of  the  network  forms  a  firm,  fibrous  membrane  lining  the  eavity.  This 
represents  an  inner  periosteum,  and  is  called  the  endosteum. 

Red  marrow  (medulla  ossium  rubra)  is  found  in  the  diploe  of  the  cranial  bones,  in 
the  cancellous  tissue  of  the  vertebrae,  ribs,  and  sternum,  and  in  the  articular  ends 
of  the  long  bones.  Red  marrow  contains  much  less  fat  and  is  less  solid  than  yellow 
marrow.  It  consists  of  a  delicate  network  of  connective  tissue,  supporting  a 
dense  capillary  plexus ;  some  fat;  and  numerous  cellular  elements.  The  delicate 
fibrous  membrane  surrounding  red  marrow  is  called  the  endosteum.  The 
cellular  elements  of  red  marrow  (Fig.  2)  comprise,  first,  marrow-cells,  or  myelocytes, 
which  are  protoplasmic  masses,  capable  of  amceboid  movements,  and  containing 
large  nuclei.  They  are  not  found  in  normal  blood,  but  are  abundant  in  leukaemia; 
second,  small,  nucleated,  reddish  cells  called  erythroblasts,  resembhngthe  nucleated 
red  cells  of  the  blood  of  the  embryo,  and  eventually  by  the  loss  of  their  nuclei 
becoming  red  blood-corpuscles;  third,  non-nucleated  red  blood-corpuscles;  fourth, 
giant-cells  containing  one  or  more  nuclei.  They  are  varieties  of  leukocytes.  The 
leukocyte  group  also  contains  the  osteoclasts,  eosinophiles,  and  mast-cells. 

Gelatinous  or  mucoid  marrow  is  formed  by  the  absorption  of  the  fat  and  the 
cellular  elements  of  yellow  marrow,  and  by  the  serous  infiltration  of  the  inter- 
cellular substance.  It  is  produced  by  starvation,  old  age,  and  certain  pathological 
conditions. 

Each  extremity  of  a  long  bone  is  separated  from  the  shaft  by  a  layer  of  car- 
tilage known  as  the  cambium  layer,  the  epiphysial  cartilage,  or  the  epiphysial 
disk  (Fig.  8).  Growth  from  the  cartilages  causes  an  increase  in  the  length  of 
the  bone.     The  cartilages  ossify  during  development,  and  effect  a  bony  union 


STRUCTURE    OF  BONE 


37 


between    the   shaft    and  the   head  of    the    bone.     Certain   bony   processes   are 
separated  from  the  bone  by  cartilage,  which  later  ossifies. 

A  Flat  Bone  is  composed  of  two  layers  of  compact  bone  with  a  layer  of  can- 
cellous bone  (the  diploe)  interposed.  There  is  no  general  marrow-cavity;  but 
the  spaces  between  the  bone-spicules  intercomm.unicate  and  contain  marrow. 


9        ^ 


f®  o  c«)  %  Q  *  I  SDiXI  ® 

i     y-        /fe  i.  m.  n,       ^      p        q  r  ^  ^ 


Fig.  2. — Cells  of  red  marrow  of  the  guinea-iiiK-     a-'''-  Myelo-plaques.     c-i.  Marrow-cells  proper,    j-i.  Erythro- 
blasts — some  in  process  of  division.      (Schiifer.) 

The  Periosteum  is  a  fibrous  membrane  adhering  to  the  surface  of  the  bone  in 
nearly  every  part  except  at  the  cartilage-covered  extremities.  When  strong  ten- 
dons or  ligaments  are  attached  to  the  bone,  the  periosteum  is  incorporated  with 
them.  By  means  of  the  periosteum  many  vessels  reach  and  enter  the  hard  bone 
through  Volkmann's  canals.  This  is  shown  by  stripping  the  periosteum-  from  the 
surface  of  Hving  bone,  when  small  bleeding  points  are  seen,  each  of  which 
marks  the  entrance  of  a  vessel  from  the  periosteum.  It  thus  becomes  obvious 
that  the  loosening  of  the  periosteum,  by  depriving  a  portion  of  the  bone  of  its 
nourishment,  may  produce  necrosis.  The  membrane  is  firmly  attached  to  the 
bone  by  trabecular  of  fibrous  tissue,  which  pene- 
trate the  bone  at  right  angles  to  its  surface,  and 
carry  blood-vessels.  These  trabeculse  are  called 
the  fibres  of  Sharpey  (Fig.  3).  They  do  not  di- 
rectly enter  the  Haversian  systems,  but  only  the 
circumferential  and  intermediate  lamellae — parts 
that  are  formed  by  periosteal  action.  Prolonga- 
tions from  some  of  these  vessels  reach  the  Haver- 
sian canals,  and  even  the  bone-marrow.  In  the 
extremities  of  a  long  bone,  vessels  from  the  peri- 
osteum penetrate  the  layer  of  compact  bone  and 
reach  the  cancellous  tissue.  In  the  newborn  and 
in  the  young  the  periosteum  is  composed  of  three 
layers:  an  outer  or  fibrous  layer,  containing  some 
blood-vessels,  and  composed  of  bundles  of  white 
fibrous  tissue;  a  middle  or  fibro-elastic  layer,  con- 
taining some  blood-vessels,  fibrous  tissue,  and 
much  elastic  tissue;  and  an  inner  or  osteogenetic  layer,  which  is  very  vascular  and 
contains  numerous  cells,  which  are  converted  into  osteoblasts.  These  are  the 
cells  that  form  osseous  tissue. 


Fig.  3. — Fibres  of  Sharpey  from  the 
parietal  bone  (adult  man)  isolated  by 
dissociation.      (After  Kolliker.) 


38  THE  SKELETON 

Transverse  Section  of  Compact  Bone  (Figs.  1,4,  and  6). — As  previously  stated, 
dense  bone  differs  from  cancellous  bone  in  the  fact  that  the  bone-plates  of  the 
former  are  arranged  in  Haversian  systems,  so  named  from  the  anatomist 
Havers.  A  Haversian  system  consists  of  a  central  canal,  running  in  a  more  or 
less  longitudinal  or  slightly  curved  or  spiral  direction  and  called  the  Haversian 
canal;  from  five  to  ten  bone-plates,  or  lamellae,  arranged  concentrically  around  the 
canal;  gaps,  called  lacunae,  between  the  lamellae,  which  spaces  contain  bone-cor- 
puscles; minute  channels,  or  canaliculi,  radiating  from  the  lacunae  and  passing 
through  the  lamellae — some  reaching  other  lacunae,  some  reaching  the  Haver- 
sian canal,  and  others  passing  to  adjacent  Haversian  systems.  The  canaliculi 
contain  processes  from  the  bone-corpuscle.  From  a  study  of  transverse  sections 
it  would  be  thought  that  the  lamellae  always  run  longitudinally  in  straight  lines 
or  in  curves  determined  by  pressure  and  tension;  but  Prof.  Dixon  proved  that 
in  the  human  femur  many  of  the  bone-plates  are  arranged  spirally,  and  thus 
increased  strength  is  obtained.     The  same  is  probably  true  of  other  bones. 


Fig.  4. — Transverse  section  of  compact  tissue  of  bone.     Magnified  about  150  diameters.      (Sharpey.) 


There  are  four  varieties  of  lamellae:  (1)  the  periosteal,  peripheral,  superficial, 
or  external;  (2)  the  Haversian,  or  concentric;  (3)  the  interstitial,  ground,  or  inter- 
mediate; and  (4)  the  perimeduUary,  or  internal.  The  periosteal  lamellae  are  some- 
times called  primary,  as  they  are  the  first  to  appear,  and  are  formed  by  the  direct 
transformation  of  the  inner  layer  of  the  periosteum  into  bone.  In  the  shaft  of 
a  long  bone  there  are  several  layers  of  periosteal  lamellae,  but  no  one  layer  is 
extensive  enough  to  surround  the  bone  completely. 

In  the  outer  surface  of  the  layer  of  periosteal  lamellae  depressions  exist  that 
are  known  as  Howship's  foveolse,  or  lacunae.  These  depressions  are  made  by 
large  cells,  called  osteoclasts,  which  destroy  bone.  There  are  no  Haversian 
canals  in  this  outer  layer,  but  there  are  some  large  channels  that  convey  blood- 
vessels into  the  bone,  and  are  known  as  Volkmann's  canals.  Many  small  arteries 
from  the  periosteum  enter  the  periphery  of  the  shaft,  and  also  of  the  epiphyses. 
A  large  trunk  enters  the  shaft  by  the  nutrient  foramen  (foramen  nutricius),  pass 
along  the  nutrient  canal  [canalis  nutricius),  and  reaches  the  medullary  canal. 
This  vessel  is  called  the  nutrient  artery. 

The  Haversian  or  concentric  lamellae  are  circular  layers  arranged  around  a 
central  space,  or  canal,  known  as  the  Haversian  canal.  There  is  no  fixed  num- 
ber of  these  layers,  there  being  usually  from  five  to  ten.  The  layers  of  each  system 
are  parallel  to  one  another,  but  the  layers  of  different  systems  cross  at  various 


BLOOD-VESSELS  OF  BONE 


39 


angles.  Between  these  layers  are  small,  irregular  spaces,  called  lacunse;  and 
extending  radially  out  from  the  lacunte  and  piercing  the  various  lamellae  are 
delicate  canals,  known  as  canaliculi,  which  connect  the  lacunse.  The  lacuna 
nearest  to  the  Haversian  canal  communicates  with  it  by  means  of  canalicuH; 
and  canaliculi  also  communicate  with  other  Haversian  systems.  The  Haversian 
canal  contains  blood-vessels — an  artery  or  a  vein,  or  both  an  artery  and  a  vein — 
and  a  nerve.  The  vessel  in  the  canal  is  covered  with  endothelial  cells,  and  the 
canal  itself  is  lined  with  them.  The  space  thus  formed  is  a  lymph-space,  and 
into  these  lymph-spaces  the  canaliculi  empty.  Beneath  the  periosteum  and  at 
the  periphery  of  the  medullary  cavity  there  are  lymph-spaces  that  are  in  direct 
communication  with  the  canaliculi  of  the  Haversian  systems.  In  each  lacuna  is 
a  bone-cell — a  corpuscle  that  almost  fills  the  space,  and  sends  arms,  or  processes, 
out  into  the  canaliculi  (Fig.  5j.      This  bone-cell  is  an  osteoblast. 

The  interstitial  or  intermediate  lamellse  occupy  the  spaces  between  the 
Haversian  systems.  They  represent  the  remains  of  peripheral  lamellae.  They 
are  usually  short  and  very 
irregular,  but  possess  lacunse 
and  canaliculi,  which  are  ar- 
ranged as  in  the  Haversian 
systems.  The  perimedullary 
lamellae  are  irregular  and  few 
in  number. 


Fig.  5. — Nucleated  bone-cells  and  their 
processes,  contained  in  the  bone-lacuna  and 
their  canaliculi,  respectively.  From  a  section 
through  the  vertebra  of  an  adult  mouse. 
(Klein  and  Noble  Smith.) 


Fig.  6. — Combined  transverse  and  longitudinal  section  of 
compact  bone.  CH.  Longitudinal  Haversian  canal  and 
anastomosing  canals,  o.  Communicating  with  medullary 
cavity.  <S'j.  Intermediate  systems.  Spe.  Circumferential 
lamella;.  Spi.  Perimedullary  lamellae.  os.  Osteoblasts, 
(Poirier  and  Charpy.) 


The  osteoblasts  are  irregular,  flattened,  stellate  masses  of  protoplasm,  pos- 
sessing a  number  of  processes.  The  protoplasm  is  granular,  and  each  cell  con- 
tains a  large  and  distinct  nucleus.  Osteoblasts  are  met  with  in  the  deeper  layer 
of  the  periosteum,  in  the  endosteum,  and  in  the  lacunae. 

Longitudinal  Section  of  Compact  Bone  (Figs.  6  and  7). — We  do  not  see  con- 
centric rings,  as  in  a  transverse  section,  but  rows  of  lacunae  parallel  to  the  course 
of  the  Haversian  canals — and  these  canals  appear  like  half-tubes  instead  of 
circular  spaces.  The  tubes  are  seen  to  branch  and  communicate,  so  that  each 
separate  Haversian  canal  runs  only  a  short  distance.  In  other  respects  the 
structure  closely  resembles  that  of  a  transverse  section. 

Lamellae  of  Cancellous  Bone. — There  are  no  Haversian  canals,  and  canaliculi 
open  into  the  medullary  spaces,  which  act  as  do  the  Haversian  canals  in  com- 
pact bone. 

Blood-vessels  of  Bone. — Small  arteries  derived  from  the  periosteum  enter 
the  minute  orifices  of   the  compact  bone  (Volkmann's  canals)  and  reach   the 


40  THE   SKELETON 

Haversian  canals  of  the  bony  substance.  Prolongations  from  these  vessels 
reach  the  marrow  and  communicate  with  branches  from  the  nutrient  artery. 
The  cancellous  tissue  is  supplied  by  fewer  but  larger  vessels,  which  are  derived 
from  the  periosteum,  and  which  often  penetrate  the  cortex  of  compact  bone 
and  ramify  in  the  cavities  of  the  spongy  tissue. 


Fig.  7. — From  a  groiind  longitudinal  sri'iion  t  !iroiicrh  the  dianlivsis  of  tlie  human   vilna.      All  canals  are  filled 
with  pigment,  which  is  here  black.      Ihuersian  canals  are  cut  longitudinally.      X  90.      (Szymonowicz.) 

The  medullary  canal  of  a  long  bone  is  supplied  by  a  large  artery  (sometimes 
more  than  one)  called  the  nutrient  artery.  It  enters  the  bone  by  the  nutrient 
foramen,  which  is  usually  near  the  centre  of  the  shaft,  runs  in  an  oblique  canal 
through  the  compact  structure,  giving  off  branches  to  this  structure,  and  enters 
the  medullary  cavity,  and  sends  branches  upward  and  downward.  These  branches 
communicate  with  branches  from  the  periosteal  vessels  and  subdivide  into  capil- 
laries, which  pass  into  comparatively  large  vessels.  The  walls  of  the  vessels  are 
very  thin,  and  in  some  places  deficient;  the  venous  blood  enters  the  spaces  of 
the  red  marrow,  and  the  current  becomes  extremely  slow.  Small  veins  collect 
the  venous  blood  and  emerge  from  the  bone. 

In  the  humerus  the  nutrient  canal  is  directed  toward  the  elbow-joint;  in  the 
radius  and  the  ulna  the  nutrient  canals  are  directed  toward  the  elbow-joint;  in 
the  femur,  the  canal  is  directed  toward  the  hip-joint;  and  in  the  tibia  and  the 
fibula,  the  canals  are  directed  toward  the  ankle-joint.  As  Professor  Cunningham 
states  it:    "In  the  upper  limb  the  vessels  flow  toward  the  elbow;  while  in  the 


CHEMICAL   COMPOSITION  OF  BONE  41 

lower  limb  they  pass  from  the  knee."  The  red  marrow  of  the  extremities  and 
the  medulla  of  the  entire  shaft,  and  the  bone  of  the  shaft,  except  the  circum- 
ferential lamellae,  are  supplied  by  the  nutrient  artery.  The  circumferential 
lamellae,  wholly,  and  the  cancellous  tissue  of  the  extremities,  in  part,  and  the 
medulla  of  the  shaft  to  a  very  small  extent  are  supplied  by  vessels  from  the 
periosteum.  The  extremities  of  a  bone  also  receive  articular  arteries.  In  most 
of  the  flat  bones,  and  in  some  of  the  short  bones,  one  or  more  large  apertures  exist 
for  the  passage  of  blood-vessels  to  the  central  parts  of  the  bone. 

Veins  emerge  from  the  long  bones  in  three  places:  1.  One  or  two  large  veins 
accompany  the  nutrient  artery.  2.  Numerous  veins  emerge  at  the  articular 
extremities.  3.  Many  small  veins  arise  in  and  emerge  from  compact  substance. 
The  latter  two  classes  do  not  accompany  arteries.  The  veins  in  the  marrow 
and  in  the  bone  are  devoid  of  valves;  but  immediately  after  emerging  from  the 
bone  they  have  numerous  valves. 

In  the  flat  cranial  bones  the  veins  are  numerous  and  large;  as  seen  in  diploic 
canals,  the  walls  of  which  are  composed  of  osseous  tissue,  perforated,  here  and 
there,  for  branches  from  adjacent  cancelli.  In  all  cancellous  tissue  the  venous 
channels  are  similarly  arranged,  and  the  veins  have  very  thin  coats  and  are 
without  valves.  When  the  bone  is  divided,  the  vessels  remain  open;  they  do 
not  retract  into  their  bony  canals,  and  readily  absorb  any  septic  matter  that 
may  be  present. 

The  lymphatics  are  chiefly  periosteal ;  but  some  enter,  the  bone,  along  with  the 
vessels.  Cruikshank  has  traced  them  into  the  substance  of  the  bone  and  Klein 
has  described  them  as  running  in  the  Haversian  canals.  The  perivascular  spaces 
of  the  Haversian  canals  are  lymph-spaces. 

Nerves  are  partly  medullated  and  partly  non-medullated,  are  distributed  freely 
to  the  periosteum,  and  some  of  the  fibres  terminate  in  this  structure  as  Pacinian 
corpuscles.  Nerves  accompany  the  nutrient  arteries  into  the  interior  of  the 
bone,  and  also  reach  the  marrow  from  the  periosteum  by  way  of  Volkmann's 
canals  and  the  Haversian  canals.  They  certainly  supply  the  arterial  coats. 
It  is  not,  as  yet,  determined  whether  nerves  do  or  do  not  terminate  in  bone-tissue. 
Stroh  maintains  that  occasionally  they  terminate  in  bone-corpuscles.  According 
to  Kolliker  nerves  are  most  numerous  in  the  articular  extremities  of  the  long 
bones,  in  the  vertebnie,  and  the  large  flat  bones. 

Chemical  Composition  of  Bone. — Bone  consists  of  an  animal  and  an  earthy 
part  intimately  combined. 

The  animal  part  may  be  obtained  by  immersing  the  bone  for  a  considerable 
time  in  dilute  mineral  acid,  after  which  process  the  bone  comes  out  exactly  the 
same  shape  as  before,  but  perfectly  flexible,  so  that  a  long  bone  (one  of  the  ribs, 
for  example)  can  easily  be  tied  into  a  knot.  If  now  a  transverse  section  is  made, 
the  same  general  arrangement  of  the  Haversian  canals,  lamellae,  lacunae,  and 
canaliculi  is  seen,  though  not  so  plainly,  as  in  the  ordinary  section. 

The  earthy  part  may  be  obtained  separate  by  calcination,  by  which  the  animal 
matter  is  completely  burned  out.  The  bone  will  still  retain  its  original  form,  but 
it  will  be  white  and  brittle,  will  have  lost  about  one-third  of  its  original  weight, 
and  will  crumble  with  the  slightest  force.  The  earthy  matter  confers  on  bone 
its  hardness  and  rigidity,  and  the  animal  matter  its  tenacity. 

The  mineral  matter  consists  of  phosphate,  carbonate,  and  fluoride  of  calcium, 
chloride  of  sodium,  and  phosphate  of  magnesium. 

The  animal  basis  is  largely  composed  of  ossein,  or  fat  collagen.  When  boiled 
with  water,  especially  under  pressure,  fat  collagen  is  almost  entirely  resolved 
into  gelatin. 

The  organic  matter  of  bone  forms  about  one-third;  the  inorganic  matter, 
two-thirds.     The  exact  composition,  according  to  Professor  Cunningham,  is,  of 


42  THE  SKELETON 

organic  matter,  31.04  parts;  of  inorganic  matter,  68.97  parts.  Of  the  earthy 
matter,  five-sixths  is  calcium  phosphate.  Even  after  the  removal  of  all  the 
marrow  a  small  percentage  of  fat  is  still  found  in  bone. 

Some  of  the  diseases  to  which  bones  are  liable  mainly  depend  on  the  dispro- 
portion between  the  two  constituents  of  bone.  Thus  in  the  disease  called  rickets, 
so  connnon  in  the  children  of  the  poor,  the  bones  become  bent  and  curved,  either 
from  the  superincumbent  weight  of  the  body  or  under  the  action  of  certain  mus- 
cles. This  depends  upon  some  defect  of  nutrition  by  which  bone  becomes  deprived 
of  its  normal  proportion  of  earthy  matter,  while  the  animal  matter  is  of  unhealthy 
quality.  In  the  vertebrae  of  a  rickety  subject  Bostock  found  in  100  parts  79.75 
animal  and  20.25  earthy  matter.  Osteomalacia  is  a  disease  of  adults  charac- 
terized by  the  decalcification  of  existing  bone  and  by  the  failure  in  calcification 
of  new  osteoid  material.  In  this  disease  the  bone  shows  a  diminution  in 
inorganic  and  an  increase  in  organic  material.  Senile  atrophy  renders  bones 
porous  and  brittle,  and  portions  of  bone  may  actually  be  absorbed,  as  is  seen  in 
the  disappearance  of  the  alveolae  in  old  age.  In  senile  atrophy  of  the  calvaria 
the  outer  table  becomes  very  thin,  porous,  and  brittle,  and  the  inner  table  often 
becomes  rough  and  thicker  from  the  formation  of  new  bone.  In  senile  atrophy 
of  a  long  bone  there  is  absorption  of  bone  from  the  surface  by  osteoclasts  in 
Howship's  lacunae,  and  absorption  of  the  inner  surface.  The  bone  becomes 
porous  and  the  medulla  becomes  more  fatty.     This  change  is  not,  as  was  so 

long  taught,  a  decrease  in  organic  matter 
and  an  increase  in  mineral  matter,  but  is  an 
actual  alteration  in  the  structure  of  the  bone. 
Ossification  and  Growth  of  Bone. — For 
the  early  development  of  the  skeleton  the 
reader  is  referred  to  text-books  on  embry- 
ology. Embryonic  connective-tissue  cells  of 
the  mesoblast  develop  membrane.  Membrane 
may  become  bone  directly  or  cartilage  may  be 
deposited,  which  cartilage  by  the  process  of 
ossification  is  formed  into  bone.  The  tissue 
which  is  eventually  to  become  bone  contains 
cellular  elements  which  evolve  into  osteoblasts, 
^^^tf  ^^^ffffl  or  bone-forming  cells.    Osteoblasts  exist  in  the 

I  B  X  ^  I  ' «   I  I  connective  tissues  which  become  bone  by  in- 

"  *  tramembranous  ossification,  and  in  the  deeper 

Fig.  8.— Schematic  diagram  showing  epi-     lavers  of  the  tissuc  Called  perichondrium  which 

physis  and  diaphysis  and  line  of  ossification.        .    •'  i       i  •    i     i  i 

Ep.  Epiphysis  of  endochondral  bone.    zpt.     mvests  Cartilage  and  whicli  bccomcs  the  osteo- 

Zone  of  proliferation,     zc.   Zone  of  calcifica-  .       ,  »       i  •       ,  t  •  e 

tion.     ca.  Cartilage.     (Poirier  and  Charpy.)        gCnctlC    layer  OI     the    pcriOStCUm.       lU   VlCW  OI 

the  fact  that  in  the  foetal  skeleton  some  bones 
are  preceded  by  membrane  (parietal  bones,  frontal  bone,  upper  part  of  tabular 
surface  of  occipital  bone,  most  of  bones  of  the  face),  and  others  are  preceded  by 
rods  of  cartilage  (the  long  bones),  two  kinds  of  ossification  are  described — viz., 
the  intramembranous  and  the  intracartilaginous.  Professor  Cunningham  says  all 
true  bone  may  be  correctly  regarded  as  of  membranous  origin,  though  its  appear- 
ance is  preceded  in  some  instances  by  the  deposition  of  cartilage ;  in  this  case 
calcification  of  the  cartilage  is  an  essential  stage  in  the  process  of  bone  forma- 
tion, but  the  ultimate  conversion  into  true  bone,  with  characteristic  Haversian 
systems,  leads  to  the  absorption  and  disappearance  of  this  primitive  calcified 
cartilage.  Intramembranous  ossification  forms  membrane  bones,  that  is,  forms 
bone  directly  from  fibrous  tissue,  there  being  no  intermediate  cartilaginous 
stage. 

Intracartilaginous  ossification  consists  in  the  ossification  of  cartilage. 


OSSIFICATION  AND   GROWTH  OF  BONE 


43 


Intramembranous  Ossification. — In  the  case  of  bones  which  are  developed  in 
membrane  no  cartilaginous  mould  precedes  the  appearance  of  the  bone-tissue. 
The  membrane,  which  occupies  the  place  of  the  future  bone,  is  of  the  nature  of 
connective  tissue,  and  ultimately  forms  the  periosteum.  At  this  stage  it  is  seen 
to  be  composed  of  fibres  and  granular  cells  in  a  matrix.  The  outer  portion  is 
more  fibrous,  while  internally  the  cells  or  osteoblasts  predominate;  the  whole 
tissue  is  richly  supplied  with  blood-vessels.  At  the  outset  of  the  process  of  bone- 
formation  a  little  network  of  bony  spiculse  is  first  noticed  radiating  from  the  point 
or  centre  of  ossification.  When  these  rays  of  growing  bone  are  examined  with  a 
microscope,  they  are  found  to  consist  at  their  growing  point  of  a  network  of  fine, 
clear  fibres  and  granular  corpuscles,  with  an  intervening  ground  substance 
(Fig.  9).    The  fibres  are  termed  osteogenetic  fibres,  and  are  made  up  of  fine  fibrils 


Union  of— 

adjacent 

spicules. 


Osteoblasts. <-:^ 


Osteogenetic 

fibres. 


Calcific  deposit 

between  the 
fibres. 


Bony 
spicules. 

Fig.  9. — Part  of  the  growing  edge  of  the  developing  parietal  bone  of  a  fcetal  cat.     (After  J.  Lawrence.) 

differing  little  from  those  of  white  fibrous  tissue.  Like 'them,  they  are  probably 
deposited  in  the  matrix  through  the  influence  of  the  cells — in  this  case  the  osteo- 
blasts. The  osteogenetic  fibres  soon  assume  a  dark  and  granular  appearance  from 
the  deposition  of  calcareous  granules  in  the  fibres  and  in  the  intervening  matrix, 
and  as  they  calcify  they  are  found  to  enclose  some  of  the  granular  corpuscles  or 
osteoblasts.  By  the  fusion  of  the  calcareous  granules  the  bony  tissue  again  assumes 
a  more  transparent  appearance,  but  the  fibres  are  no  longer  so  distinctly  seen. 
The  involved  osteoblasts  form  the  corpuscles  of  the  future  bone,  the  spaces  in 
which  they  are  enclosed  constituting  the  lacunae.  As  the  osteogenetic  fibres  grow 
out  to  the  periphery  they  continue  to  calcify,  and  give  rise  to  fresh  bone-spicules. 
Thus  a  network  of  bone  is  formed,  the  meshes  of  which  contain  the  blood-vessels 
and  a  delicate  connective  tissue  crowded  with  osteoblasts.  The  bony  trabecular 
thicken  by  the  addition  of  fresh  layers  of  bone  formed  by  the  osteoblasts  on  their 
surface,  and  the  meshes  are  correspondingly  encroached  upon.  Subsequently 
successive  layers  of  bony  tissue  are  deposited  under  the  periosteum  and  around 
the  larger  vascular  channels,  which  become  the  Haversian  canals,  so  that  the  bone 
increases  much  in  thickness. 

Intracartilaginous  Ossification. — Just  before  ossification  begins  the  bone  is 
entirely  cartilaginous,  and  in  the  long  bone,  which  may  be  taken  as  an  example,  the 
process  commences  in  the  centre  and  proceeds  toward  the  extremities,  which  for 
some  time  remain  cartilaginous.    Subsequently  a  similar  process  commences  in  one 


44 


THE  SKELETON 


or  more  places  in  those  extremities  and  gradually  extends  through  them.  The 
extremities  do  not,  however,  become  joined  to  the  shaft  by  bony  tissue  until  growth 
has  ceased,  but  are  attached  to  it  by  a  layer  of  cartilaginous  tissue  termed  the 
epiphysial  cartilage  (Fig.  8). 

The  first  step  in  the  ossification  of  the  cartilage  is  that  the  cartilage-cells,  at 
the  point  where  ossification  is  commencing  and  which  is  termed  a  centre  of  ossifica- 
tion, enlarge  and  arrange  themselves  in  rows  (Fig.  10).  The  matrix  in  which  they 
are  embedded  increases  in  quantity,  so  that  the  cells  become  further  separated 
from  each  other.    A  deposit  of  calcareous  material  now  takes  place  in  this  matrix, 


Fig.  10. — Section  of  fcetal  bone  of  cat.  ir.  Irruption 
of  the  subperiosteal  tissue,  p.  Fibrous  layer  of  the  peri- 
osteum, o.  Layer  of  osteoblasts.  im,.  Subperiosteal 
bony  deposit.      (From  Quain's  Anatomy,  E.  A.  Schafer.) 


Fig.  11. — Part  of  a  longitudinal  section  of 
the  developing  femur  of  a  rabbit,  o.  Flat- 
tened cartilage-cells,  h.  Enlarged  cartilage- 
cells,  c,  d.  Newly  formed  bone.  e.  Osteo- 
blasts. /.  Giant-cells  or  osteoclasts.  .0,  h. 
Shrunken  cartilage-cells.  (From  Atlas  of  His- 
tology, Klein  and  Noble  Smith.) 


between  the  rows  of  cells,  so  that  they  become  separated  from  each  other  by  longi- 
tudinal columns  of  calcified  matrix,  presenting  a  granular  and  opaque  appearance. 
Here  and  there  the  matrix  between  two  cells  of  the  same  row  also  becomes  calci- 
fied, and  transverse  bars  of  calcified  substance  stretch  across  from  one  calcareous 
column  to  another.  Thus  there  are  longitudinal  groups  of  the  cartilage-cells 
enclosed  in  oblong  cavities,  the  walls  of  which  are  formed  of  calcified  matrix, 
which  cuts  off  all  nutrition  from  the  cells,  and  they,  in  consequence,  waste,  leav- 
ing spaces  called  the  primary  areolae  (Sharpey). 

At  the  same  time  that  this  process  is  going  on  in  the  centre  of  the  solid  bar  of 
cartilage  of  which  the  foetal  bone  consists,  certain  changes  are  taking  place  on 


OSSIFICATION  AND   GROWTH  OF  BONE 


45 


its  surface.  This  is  covered  by  a  very  vascular  membrane,  the  perichondrium, 
entirely  similar  to  the  embryonic  connective  tissue  already  described  as  constituting 
the  basis  of  membrane-bone,  on  the  inner  surface  of  which,  that  is  to  say,  on  the 
surface  in  contact  with  the  cartilage,  are  gathered  the  formative  cells,  the  osteo- 
blasts. By  the  agency  of  these  cells  a  thin  layer  of  bony  tissue  is  being  formed 
between  the  perichondrium  and  the  cartilage,  by  the  intramemhranous  mode  of 
ossification  just  described.  There  are,  then,  in  this  first  stage  of  ossification,  two 
processes  going  on  simultaneously:  in  the  centre  of  the  cartilage  the  formation 
of  a  number  of  oblong  spaces,  formed  of  calcified  matrix  and  containing  the 
withered  cartilage-cells,  and  on  the  surface  of  the  cartilage  the  formation  of  a 
layer  of  true  membrane-bone.  The  second  stage  consists  in  the  prolongation 
into  the  cartilage  of  processes  of  the 
deeper  or  osteogenetic  layer  of  the 
perichondrium,  which  has  now  be- 
come periosteum  (Fig.  10,  ir).  The 
processes  consist  of  blood-vessels  and 
cells — osteoblasts,  or  bone -formers,  and 
osteoclasts,  or  bone -destroyers.  The 
latter  are  similar  to  the  giant-cells 
(myelo-plaques)  found  in  marrow, 
and  they  excavate  passages  through 


Fig.  12. — Transverse  section  from  the  femur  of  a 
human  embryo  about  eleven  weeks  old.  a.  A  med- 
ullary sinus  cut  transversely,  and  ft,  another,  longi- 
tudinally. C.  Osteoblasts,  d.  Newly  formed  os.seous 
substance  of  a  lighter  color,  e.  That  of  greater  age. 
/.  Lacunip  with  their  cells,  g.  A  cell  still  united  to 
an  osteoblast. 


Fig.  13. — Vertical  section  from  the  edge  of  the 
ossifying  portion  of  the  diaphysis  of  a  metatar- 
sal bone  from  a  fojtal  calf.  a.  Ground-mass  of 
the  cartilage,  b.  Of  the  bone.  C.  Newly  formed 
bone-cells  in  profile,  more  or  less  embedded  in  in- 
tercellular substance,  d.  Medullary  canal  in  pro- 
cess of  formation,  with  vessels  and  medullary 
cells.  «,/.  Bone-cells  on  their  broad  aspect,  g. 
Cartilage-capsules  arranged  in  rows,  and  partly 
with  shrunken  cell-bodies.     (After  Miiiler.) 


the  new-formed  bony  layer  by  absorption,  and  pass  through  it  into  the  cal- 
cified matrix  (Fig.  10).  Wherever  these  processes  come  in  contact  with  the 
calcified  walls  of  the  primary  areolae  they  absorb  it,  and  thus  cause  a  fusion 
of  the  original  cavities  and  the  formation  of  larger  spaces,  which  are  termed 
the  secondary  areolae  (Sharpey),  or  medullary  spaces  (Miiiler).  In  these  second- 
ary spaces  the  original  cartilage-cells,  having  disappeared,  become  filled 
with  embryonic  marrow,  consisting  of   osteoblasts  and  vessels,  and  derived  in 


46 


THE  SKELETON 


the    manner  described   above,  from   the  osteogenetic  layer  of   the  periosteum 
(Fig.  11). 

Thus  far  there  has  been  traced  the  formation  of  enlarged  spaces  (secondary 
areolae),  the  perforated  walls  of  which  are  still  formed  by  calcified  cartilage- 
matrix,  containing  an  embryonic  marrow,  derived  from  the  processes  sent  in 
from  the  osteogenetic  layer  of  the  periosteum,  and  consisting  of  blood-vessels 
and  round-cells,  osteoblasts  (Fig,  11),  The  walls  of  these  secondary  areolae  are 
at  this  time  of  only  inconsiderable  thickness,  but  they  become  thickened  by 
the  deposition  of  layers  of  new  bone  on  their  interior.  This  process  takes  place 
in  the  following  manner:  Some  of  the  osteoblasts  of  the  embryonic  marrow, 
after  undergoing  rapid  division,  arrange  themselves  as  an  epithelioid  layer  on 
the  surface  of  the  wall  of  the  space  (Fig.  12),  This  layer  of  osteoblasts  form  a 
bony  stratum,  and  thus  the  wall  of  the  space  becomes  gradually  covered  with  a 
layer  of  true  osseous  substance.  On  this  a  second  layer  of  osteoblasts  arrange 
themselves,  and  in  their  turn  form  an  osseous  layer.  By  the  repetition  of  this 
process  the  original  cavity  becomes  very  much  reduced  in  size,  and  at  last  only 
remains  as  a  small  circular  hole  in  the  centre,  containing  the  remains  of  the 
embryonic  marrow — that  is,  a  blood-vessel  and  a  few  osteoblasts.  This  small 
cavity  constitutes  the  Haversian  canal  of  the  perfectly  ossified  bone.  The  successive 
layers  of  osseous  matter  which  have  been  laid  down  and  which  encircle  this  central 

canal  constitute  the  lamellae  of 
which,  as  we  have  seen,  each 
Haversian  system  is  made  up. 
As  the  successive  layers  of  os- 
teoblasts form  osseous  tissue, 
certain  of  the  osteoblastic  cells 
remain  included  between  the 
various  bony  layers.  These 
persist  as  the  corpuscles  of  the 
future  bone,  the  spaces  enclos- 
ing them  forming  the  lacimae 
(Figs.  12  and  14).  The  canal- 
iculi,  at  first  extremely  short,  are 
supposed  to  be  extended  by  ab- 
sorption, so  as  to  meet  those  of 
neighboring  lacunae. 

Such  are  the  changes  which 
may  be  observed  at  one  partic- 
ular point,  the  centre  of  ossifi- 
cation. While  they  have  been  going  on  here  a  similar  process  has  been  set  up 
in  the  surrounding  parts  and  has  been  gradually  proceeding  toward  the  end  of 
the  shaft,  so  that  in  the  ossifying  bone  all  the  changes  described  above  may  be 
seen  in  different  parts,  from  the  true  bone  in  the  centre  of  the  shaft  to  the  hyaline 
cartilage  at  the  extremities.  The  bone  thus  formed  differs  from  the  bone  of  the 
adult  in  being  more  spongy  and  less  regularly  lamellated. 

Thus  far,  then,  we  have  followed  the  steps  of  a  process  by  which  a  solid  bony 
mass  is  produced,  having  vessels  running  into  it  from  the  periosteum,  Haversian 
canals  in  which  those  vessels  run,  medullary  spaces  filled  with  foetal  marrow, 
lacunae  with  their  contained  bone-cells,  and  canaliculi  growing  out  of  these 
lacunae. 

This  process  of  ossification,  however,  is  not  the  origin  of  the  whole  of  the 
skeleton,  for  even  in  those  bones  in  which  the  ossification  proceeds  in  a  great 
measure  from  a  single  centre,  situated  in  the  cartilaginous  shaft  of  a  long  bone,  a 
considerable  part  of  the  original  bone  is  formed  by  intramembranous  ossification 


Fig.  14. — Osteoblasts  from  the  parietal  bone  of  a  human  embryo 
thirteen  weeks  old.  a.  Bony  septa  with  the  cells  of  the  lacunse. 
0.  Layers  of  osteoblasts,  c.  The  latter  in  transition  to  bone- 
corpuscles.     (After  Gegenbauer.) 


OSSIFICATION  AND  GROWTH  OF  BONE  47 

beneath  the  perichondrium  or  periosteum ;  so  that  the  girth  of  the  bone  is  increased 
by  bony  deposit  from  the  deeper  layer  of  this  membrane.  The  shaft  of  the  bone 
is  at  first  sohd,  but  a  tube  is  hollowed  out  in  it  by  absorption  around  the  vessels 
passing  into  it,  which  becomes  the  medullary  canal.  This  absorption  is  supposed 
to  be  brought  about  by  large  "giant-cells,"  the  so-called  osteoclasts  of  KoUiker 
(Fig.  11).  They  vary  in  shape  and  size,  and  are  known  by  containing  a  large 
number  of  clear  nuclei,  sometimes  as  many  as  twenty.  The  occurrence  of 
similar  cells  in  some  tumors  of  bones  has  led  to  such  tumors  being  denominated 
"myeloid." 

As  more  and  more  bone  is  removed  by  this  process  of  absorption  from  the 
interior  of  the  bone  to  form  the  medullary  canal,  so  more  and  more  bone  is 
deposited  on  the  exterior  from  the  periosteum,  until  at  length  the  bone  has  attained 
the  shape  and  size  which  it  is  destined  to  retain  during  adult  life.  As  the  ossifi- 
cation of  the  cartilaginous  shaft  extends  toward  the  articular  ends  it  carries  with 
it,  as  it  were,  a  layer  of  cartilage,  or  the  cartilage  grows  as  it  ossifies,  and  thus  the 
bone  is  increased  in  length.  During  this  period  of  growth  the  articular  end,  or 
epiphysis,  remains  for  some  time  entirely  cartilaginous ;  then  a  bony  centre  appears 
in  it,  and  it  commences  the  same  process  of  intracartilaginous  ossification;  but 
this  process  never  extends  to  any  great  distance.  The  epiphyses  remain  separated 
from  the  shaft  by  a  narrow  cartilaginous  layer  for  a  definite  time  (Fig.  8). 
This  layer  ultimately  ossifies,  the  distinction  between  shaft  and  epiphysis  is 
obliterated,  and  the  bone  assumes  its  completed  form  and  shape.  The  same 
remarks  also  apply  to  the  processes  of  bone  which  are  separately  ossified,  such  as 
the  trochanters  of  the  femur.  The  bones,  having  been  formed,  -continue  to 
grow  until  the  body  has  acquired  its  full  stature.  They  increase  in  length  by 
ossification  continuing  to  extend  in  the  epiphysial  cartilage,  which  goes  on  grow- 
ing in  advance  of  the  ossifying  process.  They  increase  in  circumference  by 
deposition  of  new  bone,  from  the  deeper  layer  of  the  periosteum,  on  their  external 
surface,  and  at  the  same  time  an  absorption  takes  place  within,  by  which  the 
medullary  cavity  is  increased. 

The  medullary  spaces  which  characterize  the  cancellous  tissue  are  produced  by 
the  absorption  of  the  original  foetal  bone  in  the  same  way  as  the  original  medul- 
lary canal  is  formed.  The  distinction  between  the  cancellous  and  compact  tissue 
appears  to  depend  essentially  upon  the  extent  to  which  this  process  of  absorption 
has  been  carried ;  and  we  may  perhaps  remind  the  reader  that  in  morbid  states  of 
the  bone  inflammatory  absorption  produces  exactly  the  same  change,  and  con- 
verts portions  of  bone  naturally  compact  into  cancellous  tissue. 

The  number  of  ossific  centres  is  different  in  different  bones.  In  most  of  the 
short  bones  ossification  commences  by  a  single  point  in  the  centre,  and  proceeds 
toward  the  circumference.  In  the  long  bones  there  is  a  central  point  of  ossifica- 
tion for  the  shaft  or  diaphysis;  and  one  or  more  for  each  extremity,  the  epiphysis. 
That  for  the  shaft  is  the  first  to  appear.  The  union  of  the  epiphyses  with  the 
shaft  takes  place  in  the  reverse  order  to  that  in  which  their  ossification  began,  with 
the  exception  of  the  fibula,  and  appears  to  be  regulated  by  direction  of  the  nutrient 
artery  of  the  bone.  Thus  the  nutrient  arteries  of  the  bones  of  the  arm  and  fore- 
arm are  directed  toward  the  elbow,  and  the  epiphyses  of  the  bones  forming  this 
joint  become  united  to  the  shaft  before  those  at  the  shoulder  and  wrist.  In  the 
lower  limb,  on  the  other  hand,  the  nutrient  arteries  pass  in  a  direction  from  the 
knee;  that  is,  upward  in  the  femur,  downward  in  the  tibia  and  fibula;  and  in 
them  it  is  observed  that  the  upper  epiphysis  of  the  femur  and  the  lower  epiphysis 
of  the  tibia  and  fibula  become  first  united  to  the  shaft. 

Where  there  is  only  one  epiphysis,  the  medullary  artery  is  directed  toward 
that  end  of  the  bone  where  there  is  no  additional  centre,  as  toward  the  acromial 
end  of  the  clavicle,  toward  the  distal  end  of  the  metacarpal  bone  of  the  thumb 


48  THE  SKELETON 

and  great  toe,  and  toward  the  proximal  end  of  the  other  metacarpal  and  meta- 
tarsal bones. 

Besides  these  epiphyses  for  the  articular  ends,  there  are  others  for  projecting 
parts  or  processes,  which  are  formed  separately  from  the  bulk  of  the  bone.  For 
an  account  of  these  the  reader  is  referred  to  the  description  of  the  individual 
bones  in  the  sequel. 

A  knowledge  of  the  exact  periods  when  the  epiphyses  become  joined  to  the 
shaft  is  often  of  great  importance  in  medico-legal  inquiries.  It  also  aids  the  sur- 
geon in  the  diagnosis  of  many  of  the  injuries  to  which  the  joints  are  liable;  for  it 
not  infrequently  happens  that  on  the  application  of  severe  force  to  a  joint  the 
epiphysis  becomes  separated  from  the  shaft,  and  such  an  injury  may  be 
mistaken  for  a  fracture  or  dislocation. 

THE   VERTEBRAL   OR    SPINAL   COLUMN    (THE  SPINE) 
(COLUMNA  VERTEBRALIS). 

The  spine  is  a  flexuous  and  flexible  column  formed  of  a  series  of  bones  called 
vertebrae  (from  vertere,  to  turn). 

The  vertebrae  are  thirty-three  in  number,  and  have  received  the  names  cervical, 
dorsal  or  thoradc,  lumbar,  sacral,  and  coccygeal,  according  to  the  position  which 
they  occupy;  seven  being  found  in  the  cervical  region,  twelve  in  the  dorsal,  five 
in  the  lumbar,  five  in  the  sacral,  and  four  in  the  coccygeal. 

This  number  is  sometinies  increased  by  an  additional  vertebra  in  one  region,  or 
the  number  may  be  diminished  in  one  region,  the  deficiency  being  supplied  by 
an  additional  vertebra  in  another.  These  observations  do  not  apply  to  the  cervical 
portion  of  the  spine,  the  number  of  bones  forming  which  is  seldom  increased  or 
diminished. 

The  vertebrae  in  the  upper  three  regions  of  the  spine  remain  separate  through- 
out life,  and  are  known  as  true  or  movable  vertebrae;  but  those  found  in  the 
sacral  and  coccygeal  regions  are  in  the  adult  firmly  united,  so  as  to  form  two 
bones — five  entering  into  the  formation  of  the  upper  bone  or  sacrum,  and  four  into 
the  terminal  bone  of  the  spine  or  coccyx.  The  fused  vertebrae  are  known  as 
false  or  immovable  vertebrae. 

GENERAL  CHARACTERS  OF  A  VERTEBRA. 

Each  vertebra  consists  of  two  essential  parts — an  anterior  solid  segment,  the 
body,  or  centrum,  and  a  posterior  segment,  the  arch  (arcus  vertebra;),  or  the  neural 
arch.  The  neural  arch  is  formed  of  two  pedicles  and  two  laminae,  supporting 
seven  processes — viz.,  four  articular,  two  transverse,  and  one  spinous. 

The  bodies  of  the  vertebrae  are  piled  one  upon  the  other,  forming  a  strong 
pillar  for  the  support  of  the  cranium  and  trunk;  the  arches  forming  a  hollow 
cylinder  behind  the  bodies  for  the  protection  of  the  spinal  cord  (spinal  canal  or 
neural  canal).  The  different  vertebrae  are  connected  too:ether  bv  means  of  the 
articular  processes  and  the  intervertebral  fibrocartilages;  while  the  transverse 
and  spinous  processes  serve  as  levers  for  the  attachment  of  muscles  which 
move  the  different  parts  of  the  spine.  Lastly,  between  each  pair  of  vertebrae 
apertures  exist  through  which  the  spinal  nerves  pass  from  the  cord.  Each  of 
these  constituent  parts  must  now  be  separately  examined. 

Body,  or  Centrum  (corpus  vertebra'). — The  body  is  the  largest  part  of  a  vertebra. 
Above  and  below  it  is  flattened;  its  upper  and  lower  surfaces  are  rough  for  the 
attachment  of  the  intervertebral  fibro-cartilages,  and  each  presents  a  rim  around 
its  circumference.  In  front  it  is  convex  from  side  to  side,  concave  from  above 
downward.     Behind  it  is  flat  from  above  downward  and  slightly  concave  from 


THE    CERVICAL     VERTEBRA  49 

side  to  side.  Its  anterior  surface  is  perforated  by  a  few  small  apertures,  for 
the  passage  of  nutrient  vessels;  while  on  the  posterior  surface  is  a  single  large, 
irregular  aperture,  or  occasionally  more  than  one,  for  the  exit  of  veins  from  the 
body  of  the  vertebra — the  venae  basis  vertebrae. 

Pedicles. — The  pedicles  are  two  short,  thick  pieces  of  bone,  which  project 
backward,  one  on  each  side,  from  the  upper  part  of  the  body  of  the  vertebra,  at 
the  line  of  junction  of  its  posterior  and  lateral  surfaces.  Each  pedicle  {radix 
arcus  i^ertebra')  is  a  root  of  the  vertebral  arch.  The  concavities  above  and  below 
the  pedicles  are  the  superior  and  inferior  intervertebral  notches  or  grooves  (incisura 
vertehralis  superior  et  inferior) ;  they  are  four  in  number,  two  on  each  side,  the 
inferior  ones  being  generally  the  deeper.  When  the  vertebrae  are  articulated  the 
notches  of  each  contiguous  pair  of  bones  form  the  intervertebral  foramina  {jora- 
mina  intervertebralia) ,  which  communicate  with  the  spinal  canal  and  transmit 
the  spinal  nerves  and  bloodvessels. 

Laminse. — The  lamin*  are  two  broad  plates  of  bone  which  complete  the  neural 
arch  by  fusing  together  in  the  middle  line  behind.  They  enclose  a  foramen,  the 
spinal  or  vertebral  foramen  (foramen  vertebrale),  which  serves  for  the  protection  of 
the  spinal  cord.  When  the  vertebrte  are  joined  they  form,  with  their  ligaments, 
the  vertebral  canal  {spinal  or  neural  canal,  canalis  vertehralis).  The  laminse  are 
connected  to  the  body  by  means  of  the  pedicles.  Their  upper  and  lower  borders 
are  rough,  for  the  attachment  of  the  ligamenta  subflava. 

Processes.  Spinous  Process  {processus  spinosus). — The  spinous  process  projects 
backward  from  the  junction  of  the  two  laminse,  and  serves  for  the  attachment  of 
muscles  and  ligaments. 

Articular  Processes. — The  articular  processes  {zygapophyses),  four  in  number, 
two  on  each  side,  spring  from  the  junction  of  the  pedicles  with  the  laminse.  Each 
superior  process  (processus  articularis  superior)  projects  upward,  its  articular 
surface  (fades  articularis  superior)  being  directed  more  or  less  backward;  each 
inferior  process  (processus  articularis  inferior)  projects  downward,  its  articular 
surface  (fades  articularis  inferior)  looking  more  or  less  forward.^ 

Transverse  Processes  (processus  transversi). — The  transverse  processes,  two  in 
number,  project  one  at  each  side  from  the  point  where  the  lamina  joins  the 
pedicle,  between  the  superior  and  inferior  articular  processes.  They  also  serve 
for  the  attachment  of  muscles  and  ligaments. 

The  Cervical  Vertebrae  (Vertebrae  Cervicales)  (Fig.  15). 

The  cervical  vertebrae  are  smaller  than  those  in  any  other  region  of  the  spine, 
and  may  be  readily  distinguished  by  the  foramen  in  the  transverse  process,  which 
does  not  exist  in  the  transverse  process  of  either  a  dorsal  or  lumbar  vertebra. 

Body. — The  body  (centrum)  is  small,  comparatively  dense,  and  broader  from 
side  to  side  than  from  before  backward.  The  anterior  and  posterior  surfaces 
are  flattened  and  of  equal  depth;  the  former  is  placed  on  a  lower  level  than  the 
latter,  and  its  inferior  border  is  prolonged  downward,  so  as  to  overlap  the  upper 
and  fore  part  of  the  vertebra  below.  Its  upper  surface  is  concave  transversely, 
and  presents  a  projecting  lip  on  each  side;  its  lower  surface  is  convex  from  side 
to  side,  concave  from  before  backward,  and  presents  laterally  a  shallow  concavity 
which  receives  the  corresponding  projecting  lip  of  the  adjacent  vertebra. 

Pedicles. — The  pedicles  are  directed  outward  and  backward,  and  are 
attached  to  the  body  midway  between  the  upper  and  lower  borders,  so  that 
the  superior  intervertebral  notch  is  as  deep  as  the  inferior,  but  it  is,  at  the  same 
time,  narrower. 

'  It  may,  perhaps,  be  as  well  to  remind  the  reader  that  the  direction  of  a  surface  is  determined  by  that  of  a 
line  drawn  at  right  angles  to  it. 

4 


50 


THE  SKELETON 


Laminae. — The  laminae  are  narrow,  long,  thinner  above  than  below,  and 
overlap  each  other,  enclosing  the  spinal  foramen,  which  is  very  large,  and  of  a 
triangular  form. 

Processes.  Spinous  Process. — The  spinous  process  is  short,  and  bifid  at  the 
extremity,  to  afford  greater  extent  of  surface  for  the  attachment  of  muscles,  the 
two  divisions  being  often  of  unequal  size.  They  increase  in  length  from  the  fourth 
to  the  seventh  vertebra. 


Anterior  tubercle  of  trans- 
verse process, 

Costo-transverse  foramen  for 

vertebral  artery  and  vein  and 

sympathetic  plexus.^ 

Posterior  tubercle  of 
transverse  process. 


Costal  cartilage. 


Transverse  process. 


^-Superior  articular 
process. 
Inferior  articular  process. 


Fig.  15. — Cervical  vertebra. 


Articular  Processes. — The  articular  processes  are  flat,  oblique,  and  of  an  oval 
form :  the  superior  are  directed  backward  and  upward ;  the  inferior  forward  and 
downward. 

Transverse  Processes. — The  transverse  processes  are  short,  directed  down- 
ward, outward,  and  forward,  bifid  at  their  extremity,  and  marked  by  a 
groove  along  their  upper  surface,  which  runs  dowmward  and  outward  from  the 
superior  intervertebral  notch  and  serves  for  the  transmission  of  one  of  the  cer- 
vical nerves.  They  are  situated  in  front  of  the  articular  processes  and  on  the 
outer  side  of  the  pedicles.  The  transverse  processes  are  pierced  at  their  base  by 
a  foramen,  for  the  transmission  of  the  vertebral  artery,  vein,  and  a  plexus  of 
sympathetic  nerves.  This  foramen  is  known  as  the  transverse  foramen,  the  costo- 
transverse foramen,  and  the  vertebrarterial  foramen  (foramen  transversarium) . 
Each  process  is  formed  by  two  roots:  the  anterior  root,  sometimes  called  the 
costal  process,  arising  from  the  side  of  the  body,  and  is  the  homologue  of  the  rib 
in  the  dorsal  region  of  the  spine;  the  posterior  root  springs  from  the  junction  of 
the  pedicle  with  the  lamina,  and  corresponds  with  the  transverse  process  in  the 
dorsal  region.  It  is  by  the  junction  of  the  two  that  the  foramen  for  the  vertebral 
vessels  is  formed.  The  extremity  of  each  of  the  anterior  roots  forms  the  anterior 
tubercle  {tubercidum  anterius)  and  the  extremity  of  each  of  the  posterior  roots  the 
posterior  tubercle  {tuhercvlum  'posterius)  of  the  transverse  processes.^ 

The  peculiar  vertebrae  in  the  cervical  regions  are  the  first,  or  atlas;  the  second, 
or  axis;  and  the  seventh,  or  vertebra  prominens.  The  great  modifications  in  the 
form  of  the  atlas  and  axis  are  designed  to  admit  of  the  nodding  and  rotatory 
movements  of  the  head. 

Atlas. — The  atlas  (Fig.  16)  is  so  named  from  supporting  the  globe  of  the  head. 
The  chief  peculiarities  of  this  bone  are  that  it  has  neither  body  nor  spinous  process. 
The  body  is  detached  from  the  rest  of  the  bone,  and  forms  the  odontoid  process  of 

_  '  The  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  is  of  large  size,  and  is  some- 
^vmeii  known  as  "  Chassaignac's "  or  the  "carotid  tubercle"  (tubercidum  caroticum).  It  is  in  close  relation 
with  the  carotid  artery,  which  lies  in  front  and  a  little  external  to  it;  so  that,  as  was  first  pointed  out  by 
Lhassaignac,  the  vessel  can  with  ease  be  compressed  against  it. 


THE    CERVICAL    VERTEBRA 


51 


the  second  vertebra;  while  the  parts  corresponding  to  the  pedicles  join  in  front  to 
form  the  anterior  arch.  The  atlas  is  ring-like,  and  consists  of  an  anterior  arch,  a 
posterior  arch,  and  two  lateral  masses.  The  anterior  arch  (arcus  anterior)  forms  about 
one-fifth  of  the  ring;  its  anterior  surface  is  convex,  and  presents  about  its  centre  a 
tubercle  (tuberculum  anterius),  for  the  attachment  of  the  Longus  colli  muscle;  pos- 
teriorly it  is  concave,  and  marked  by  a  smooth,  oval  facet,  called  the  circular  facet 
(fovea  c^cn^t^),  covered  with  cartilage,  for  articulation  with  the  odontoid  process  of  the 


Tubercle. 


Diagram  of  section  of  odontoid 
process. 

Diagram  of  section  of 
transverse  ligament. 

Foramen  for 
vertebral  artery. 


Groove  for  vertebral  artery 
and  1st  cervical  nerve. 


Budimentary  spinous  process. , 

Fig.  16. — F'irst  cervical  vertebra,  or  atlas. 

axis.  The  upper  and  lower  borders  give  attachment  to  the  anterior  occipito-atlantal 
and  the  anterior  atlanto-axial  ligaments,  which  connect  it  with  the  occipital  bone 
above  and  the  axis  below.  The  posterior  arch  [arcus  'posterior)  forms  about  two- 
fifths  of  the  circumference  of  the  bone;  it  terminates  behind  in  a  tubercle  {tuber- 
culum posterius),  which  is  the  rudiment  of  a  spinous  process,  and  gives  origin  to 
the  Rectus  capitis  posticus  minor.  The  diminutive  size  of  this  process  prevents 
any  interference  in  the  movements  between  the  atlas  and  the  cranium.  The  pos- 
terior part  of  the  arch  presents  above  and  behind  a  rounded  edge  for  the  attach- 
ment of  the  posterior  occipito-atlantal  ligament,  while  in  front,  immediately 
behind  each  superior  articular  process,  is  a  groove  (sulcus  arterice  vertehralis), 
sometimes  converted  into  a  foramen  by  a  delicate  bony  spiculum,  which  arches 
backward  from  the  posterior  extremity  of  the  superior  articular  process.  These 
grooves  represent  the  superior  intervertebral  notches,  and  are  peculiar  from  being 
situated  behind  the  articular  processes,  instead  of  in  front  of  them,  as  in  the 
other  vertebrse.  They  serve  for  the  transmission  of  the  vertebral  artery,  which, 
ascending  through  the  foramen  in  the  transverse  process,  winds  round  the  lateral 
mass  in  a  direction  backward  and  inward.  They  also  transmit  the  suboccipital 
(first  spinal)  nerve.  On  the  under  surface  of  the  posterior  arch,  in  the  same 
situation,  are  two  other  grooves,  placed  behind  the  lateral  masses,  and  repre- 
senting the  inferior  intervertebral  notches  of  other  vertebrae.  They  are  much 
less  marked  than  the  superior.  The  lower  border  also  gives  attachment  to  the 
posterior  atlanto-axial  ligament,  which  connects  it  with  the  axis..  The  lateral 
masses  (massoe.  laterales)  are  the  most  bulky  and  solid  parts  of  the  atlas,  in  order 
to  support  the  weight  of  the  head;  they  present  two  articulating  surfaces  above, 
and  two  below.  Each  superior  process  (fovea  articularis  superior)  is  of  large  size, 
oval,  concave,  and  approaches  its  companion  in  front,  but  diverges  from  it 
behind;  it  is  directed  upward,  inward,  and  a  little  backward,  forming  a  kind  of 
cup  for  the  corresponding  condyle  of  the  occipital  bone.  The  two  processes  are 
admirably  adapted  to  the  nodding  movements  of  the  head.  Not  infrequently 
they  are  partially  subdivided  by  a  more  or  less  deep  indentation,  which  encroaches 
upon  each  lateral  margin.   Each  inferior  articular  process  (fades  articularis  inferior) 


52 


THE  SKELETON 


is  circular  in  form,  flattened  or  slightly  concave,  and  directed  downward  and 
inward,  articulating  with  the  axis.  The  inferior  processes  permit  the  rotatory 
movements.  Just  below  the  inner  margin  of  each  superior  articular  surface  is 
a  small  tubercle,  for  the  attachment  of  the  transverse  ligament,  which,  stretching 
across  the  ring  of  the  atlas,  divides  it  into  two  unequal  parts  or  arches;  the  anterior 
or  smaller  segment  receiving  the  odontoid  process  of  the  axis,  the  posterior  allow- 
ing the  transmission  of  the  spinal  cord  and  its  membranes.  This  part  of  the 
spinal  canal  is  of  considerable  size,  to  afford  space  for  the  spinal  cord  r  and  hence 
lateral  displacement  of  the  atlas  may  occur  without  compression  of  this  structure. 
The  transverse  processes  are  of  large  size,  project  directly  outward  and  down- 
ward from  the  lateral  masses,  and  serve  for  the  attachment  of  special  muscles 
which  assist  in  rotating  the  head.  They  are  long,  not  bifid,  and  perforated  at 
their  base  by  a  canal  for  the  vertebral  artery,  which  is  directed  from  below, 
upward,  and  backward. 


Odontoid  process. 


Bough  surface  for  check  ligaments. 
Articviar  surface  for  transverse  ligament. 


Articular  surface  for 
atlas. 


Spinous  process: 


Inferior  artictdar  process. 
Fig.  17. — Second  cervical  vertebra,  or  axis. 

Axis. — The  axis  (epistropheus)  (Fig.  17)  is  the  pivot  upon  which  the  first 
vertebra,  carrying  the  head,  rotates,  hence  the  name,  axis.  The  most  distinctive 
character  of  this  bone  is  the  strong,  prominent  process,  tooth-like  in  form  (hence 
the  name  odontoid  process,  or  dens),  which  rises  perpendicularly  from  the  upper 
surface  of  the  body.  The  body  is  deeper  in  front  than  behind,  and  prolonged 
downward  anteriorly  so  as  to  overlap  the  upper  and  fore  part  of  the  next 
vertebra.  It  presents  in  front  a  median  longitudinal  ridge,  separating  two 
lateral  depressions,  for  the  attachment  of  the  Longus  colli  muscle  of  either  side. 
The  odontoid  process  presents  two  articulating  surfaces  covered  with  cartilage : 
one  in  front,  of  an  oval  form,  for  articulation  with  the  atlas  (fades  articularis 
anterior);  another  behind  (fades  articularis  posterior),  for  the  transverse  ligament 
— the  latter  frequently  encroaching  on  the  sides  of  the  process.  The  apex  is 
pointed,  and  gives  attachment  to  the  middle  odontoid  ligament  (ligamentum 
apids  dentis).  Below  the  apex  the  process  is  somewhat  enlarged,  and  presents 
on  either  side  a  rough  impression  for  the  attachment  of  the  lateral  fasciculi  of 
the  odontoid  or  check  ligaments,  which  connect  it  to  the  occipital  bone;  the  base 
of  the  process,  where  it  is  attached  to  the  body,  is  constricted,  so  as  to  prevent 
displacement  from  the  transverse  ligament,  which  binds  it  in  this  situation  to  the 
anterior  arch  of  the  atlas.  Sometimes,  however,  this  process  does  become  di.s- 
placed,  especially  in  children,  in  whom  the  ligaments  are  more  relaxed:  instant 
death  is  the  result  of  this  accident.  The  internal  structure  of  the  odontoid  process 
is  more  compact  than  that  of  the  body.  The  pedicles  are  broad  and  strong,  espe- 
cially their  anterior  extremities,  which  coalesce  with  the  sides  of  the  body  and  the 


THE    THORACIC    OB    DORSAL    VERTEBRA 


53 


Body. 


root  of  the  odontoid  process.  The  laminae  are  thick  and  strong,  and  the  spinal 
foramen  large,  but  smaller  than  that  of  the  atlas.  The  transverse  processes  are  very 
small,  not  bifid,  and  each  is  perforated  by  the  foramen  for  the  vertebral  artery, 
which  is  directed  obli(|uely  upward  and  outward.  The  superior  articular  surfaces 
{fades  articulares  swperiores)  are  round,  slightly  convex,  directed  upward  and 
outward,  and  are  peculiar  in  being  supported  on  the  body,  pedicles,  and  trans- 
verse processes.  The  inferior 
articular  surfaces  (fades  articu- 
lares inferiores)  have  the  same 
direction  as  those  of  the  other 
cervical  vertebra\  The  superior 
intervertebral  notches  are  very 
shallow,  and  lie  behind  the  artic- 
ular processes ;  the  inferior  in 
front  of  them,  as  in  the  other 
cervical  vertebriie.  The  spinous 
process  is  of  large  size,  very 
strong,  deeply  channelled  on  its 
under  surface,  and  presents  a 
bifid,  tubercular  extremity  for 
the  attachment  of  muscles  which 
serve  to  rotate  the  head  upon 
the  spine. 

Seventh  Cervical  (Fig.  18).— 
The  most  distinctive  character 
of  this  vertebra  is  the  existence 
of  a  very  long  and  prominent 
spinous  process;  hence  the  name  vertebra  prominens.  This  process  is  thick,  nearly 
horizontal  in  direction,  not  bifurcated,  and  has  attached  to  it  the  lower  end  of  the 
ligamentum  nuchse.  The  transverse  process  is  usually  of  large  size,  its  posterior 
tubercles  are  large  and  prominent,  while  the  anterior  are  small  and  faintly  marked; 
its  upper  surface  has  usually  a  hollow  groove,  and  it  seldom  presents  more  than  a 
trace  of  bifurcation  at  its  extremity.  The  foramen  in  the  transverse  process  is 
sometimes  as  large  as  in  the  other  cervical  vertebme,  but  is  usually  smaller  on  one 
or  both  sides,  and  is  sometimes  wanting.  On  the  left  side  it  occasionally  gives 
passage  to  the  vertebral  artery;  more  frequently  the  vertebral  vein  traverses  it  on 
both  sides;  but  the  usual  arrangement  is  for  both  artery  and  vein  to  pass  in  front 
of  the  transverse  process,  and  not  through  the  foramen.  Occasionally  the  anterior 
root  of  the  transverse  process  exists  as  a  separate  bone,  and  attains  a  large  size. 
It  is  then  known  as  a  cervical  rib. 


Spinous  process. 
Fig.  18. — Seventh  cervical  vertebra,  or  vertebra  prominens. 


The  Thoracic  or  Dorsal  Vertebrae  (Vertebrae  Thoracales). 

The  dorsal  vertebrae  are  intermediate  in  size  between  those  in  the  cervical  and 
those  in  the  lumbar  region,  and  increase  in  size  from  above  downward,  the  upper 
vertebrre  in  this  segment  of  the  spine  being  much  smaller  than  those  in  the 
lower  part  of  the  region.  The  dorsal  vertebrre  may  be  at  once  recognized  by  the 
presence  on  the  sides  of  the  body  of  one  or  more  facets  or  half-facets  for  the  heads 
of  the  ribs. 

Bodies. — The  bodies  of  the  dorsal  vertebrae  resemble  those  in  the  cervical  and 
lumbar  regions  at  the  respective  ends  of  this  portion  of  the  spine;  but  in  the  middle 
of  the  dorsal  region  their  form  is  very  characteristic,  being  heart-shaped,  and  as 
broad  in  the  anteroposterior  as  in  the  lateral  direction.  They  are  thicker  behind 
than  in  front,  flat  above  and  below,  convex  and  prominent  in  front,  deeply  con- 


54  THE  SKELETON 

cave  behind,  slightly  constricted  in  front  and  at  the  sides,  and  marked  on  each 
side,  near  the  root  of  the  pedicle,  by  two  demi-facets,  one  above,  the  other  below 
{fovea  costalis  superior  et  inferior).  These  are  covered  with  cartilage  in  the  recent 
state,  and,  when  articulated  with  the  adjoining  vertebrae,  form,  with  the  inter- 
vening fibro-cartilage,  oval  surfaces  for  the  reception  of  the  heads  of  the  corre- 
sponding ribs.  The  tenth,  eleventh,  and  twelfth  dorsal  vertebrse  each  possesses 
one  complete  facet  for  the  head  of  the  rib,  instead  of  two  demi-facets. 


Superior  articular  process.- ._^_-»™v  r^     •  /. 

'    "^"^^  Demi-facet  for  head  of  no. 


Facet  for  tubercle  of  rib 


Demi-facet  for  head  of  Hb. 
Inferior  articular  process. 


Fig.  19.— a  dorsal  vertebra. 

Pedicles. — The  pedicles  are  directed  backward,  and  the  inferior  intervertebral 
notches  are  of  large  size,  and  deeper  than  in  any  other  region  of  the  spine. 

Laminae. — ^The  laminae  are  broad,  thick,  and  imbricated — that  is  to  say,  over- 
lapping one  another  like  tiles  on  a  roof.  The  spinal  foramen  is  small,  and  of  a 
circular  form. 

Processes.  Spinous  Processes. — Each  spinous  process  is  long,  triangular  on 
transverse  section,  directed  obliquely  downward,  and  terminates  in  a  tubercular 
extremity.  They  overlap  one  another  from  the  fifth  to  the  eighth  vertebra,  but 
are  less  oblique  in  direction  above  and  below. 

Articular  Processes. — The  articular  processes  are  flat,  nearly  vertical  in 
direction,  and  project  from  the  upper  and  lower  part  of  the  pedicles;  the 
superior  being  directed  backward  and  slightly  outward  and  upward,  the  inferior 
forward  and  a  little  inward  and  downward. 

Transverse  Processes. — The  transverse  processes  arise  from  the  same  parts 
of  the  arch  as  the  posterior  roots  of  the  transverse  processes  in  the  neck,  and 
are  situated  behind  the  articular  processes  and  pedicles;  they  are  thick,  strong, 
and  of  great  length,  directed  obliquely  backward  and  outward,  presenting  a 
clubbed  extremity,  which  is  tipped  on  its  anterior  part  by  a  small  concave  surface, 
for  articulation  with  the  tubercle  of  a  rib  {fovea  costalis  transversalis) .  The 
twelfth,  the  eleventh,  and  sometimes  the  tenth  dorsal  vertebra  has  no  facet  on 
the  transverse  process.  Besides  the  articular  facet  for  the  rib,  three  indistinct 
tubercles  may  be  seen  arising  from  the  transverse  processes:  one  at  the  upper 
border,  one  at  the  lower  border,  and  one  externally.  In  man  they  are  compara- 
tively of  small  size,  and  serve  only  for  the  attachment  of  muscles.  But  in  some 
animals  they  attain  considerable  magnitude,  either  for  the  purpose  of  more  closely 


THE    THORACIC    OB   DORSAL    VERTEBRA 


55 


connecting  the  segments  of  this  portion  of  the  spine  or  for  muscular  and  liga- 
mentous attachment. 

The  peculiar  dorsal  vertebrje  are  the  first,  ninth,  tenth,  eleventh,  and  twelfth 
(Fig.  20). 


f  An  entire  facet  above; 
\     a  demi-facet  below. 


'—A  demi-facet  above. 


— One  entire  facet. 


2/1  (  An  entire  facet. 

II  I  No  facet  on  transverse 
process,  which  is  ru- 
dimentary. 


An  entire  facet. 

Ko  facet  on  trans- 
verse process. 
I  Inferior  articular 
process,  convex 
and  turned  out- 
ward. 


Fig.  20. — Peculiar  dorsal  vertebrae. 

First  Dorsal  Vertebra. — The  first  dorsal  vertebra  presents,  on  each  side  of 
the  body,  a  single  entire  articular  facet  for  the  head  of  the  first  rib  and  a  half 
facet  for  the  upper  half  of  the  second.  The  body  is  like  that  of  a  cervical  vertebra, 
being  broad  transversely  its  upper  surface  is  concave,  and  lipped  on  each  side. 
The  articular  surfaces  are  oblique,  and  the  spinous  process  thick,  long,  and  almost 
horizontal. 

Ninth  Dorsal  Vertebra.— The  ninth  dorsal  has  no  demi-facet  below.  In  some 
subjects,  however,  the  ninth  has  two  demi-facets  on  each  side;  when  this  occurs 
the  tenth  has  only  a  demi-facet  at  the  upper  part. 


56  THE  SKELETON 

Tenth  Dorsal  Vertebra. — The  tenth  dorsal  has  (except  in  the  cases  just  men- 
tioned) an  entire  articular  facet  on  each  side,  above,  which  is  partly  placed  on 
the  outer  surface  of  the  pedicle.    It  has  no  demi-facet  below. 

Eleventh  Dorsal  Vertebra. — In  the  eleventh  dorsal  the  body  approaches  in  its 
form  and  size  to  the  lumbar.  The  articular  facets  for  the  heads  of  the  ribs,  one 
on  each  side,  are  of  large  size,  and  placed  chiefly  on  the  pedicles,  which  are 
thicker  and  stronger  in  this  and  the  next  vertebra  than  in  any  other  part  of  the 
dorsal  region.  The  spinous  process  is  short,  and  nearly  horizontal  in  direction. 
The  transverse  processes  are  very  short,  tubercular  at  their  extremities,  and  have 
no  articular  facets  for  the  tubercles  of  the  ribs. 

Twelfth  Dorsal  Vertebra. — The  twelfth  dorsal  has  the  same  general  characters 
as  the  eleventh,  but  may  be  distinguished  from  it  by  the  inferior  articular  processes, 
being  convex  and  turned  outward,  like  those  of  the  lumbar  vertebrae;  by  the 
general  form  of  the  body,  laminae,  and  spinous  process,  approaching  to  that  of 
the  lumbar  vertebrae;  and  by  the  transverse  processes  being  shorter,  and  marked 
by  three  elevations,  the  superior,  inferior,  and  external  tubercles,  which  corre- 
spond to  the  mammillary,  accessory,  and  transverse  processes  of  the  lumbar  ver- 
tebrae. Traces  of  similar  elevations  are  usually  to  be  found  upon  the  other  dorsal 
vertebrae  {vide  ut  supra). 

The  Lumbar  Vertebrae  (Vertebrae  Lumbales). 

The  lumbar  vertebrae  (Fig.  21)  are  the  largest  segments  of  the  vertebral 
column,  and  can  at  once  be  distinguished  by  the  absence  of  the  foramen  in 
the  transverse  process,  the  characteristic  point  of  the  cervical  vertebrae,  and  by 
the  absence  of  any  articulating  facet  on  the  side  of  the  body,  the  distinguishing 
mark  of  the  dorsal  vertebrae. 


Superior  articular  process. 


Fig.  21. — Lumbar  vertebra. 

Body. — The  body  is  large,  and  has  a  greater  diameter  from  side  to  side  than 
from  before  backward,  slightly  thicker  in  front  than  behind,  flattened  or  slightly 
concave  above  and  below,  concave  behind,  and  deeply  constricted  in  front  and  at 
the  sides,  presenting  prominent  margins,  which  afford  a  broad  basis  for  the  sup- 
port of  the  superincumbent  weight. 

Pedicles. — The  pedicles  are  very  strong,  directed  backward  from  the  upper 
part  of  the  bodies;  consequently,  the  inferior  intervertebral  notches  are  of  con- 
siderable depth. 

Laminae. — The  laminae  are  broad,  short,  and  strong,  and  the  spinal  fora- 
men triangular,  larger  than  in  the  dorsal,  smaller  than  in  the  cervical,  region. 


THE    LUMBAR     VERTEBRA 


57 


Processes.  Spinous  Processes. — The  spinous  processes  are  thick  and  broad, 
somewhat  quadrilateral,  horizontal  in  direction,  thicker  below  than  above,  and 
terminating  by  a  rough,  uneven  border. 

Articular  Processes. — The  superior  articular  processes  are  concave,  and  look 
backward  and  inward;  the  inferior  are  convex,  and  look  forward  and  outward; 
the  former  are  separated  by  a  much  wider  interval  than  the  latter,  embracing 
the  lower  articulating  processes  of  the  vertebra  above. 

Transverse  Processes. — The  transverse  processes  are  long,  slender,  directed 
transversely  outward  in  the  upper  three  lumbar  vertebrae,  slanting  a  little  upward 
in  the  lower  two.  They  are  situated  in  front  of  the  articular  processes,  instead 
of  behind  them,  as  in  the  dorsal  vertebme,  and  are  homologous  with  the  ribs.  Of 
the  three  tubercles  noticed  in  connection  with  the  transverse  processes  of  the 
twelfth  dorsal  vertebra,  the  superior  one  on  each  side  becomes  connected  in  this 
region  with  the  back  part  of  the  superior  articular  process,  and  has  received  the 


Inf.  articular  process. 


Mammillary  process. 
Accessory  process. 


Sup.  articular  process. 


Fig.  22. — Lumbar  vertebra. 


name  of  mammillary  process  {jyrocessus  mammillaris) ;  the  inferior  is  represented 
by  a  small  process  pointing  downward,  situated  at  the  back  part  of  the  base  of 
the  transverse  process,  and  called  the  accessory  process  {processus  accessorius): 
these  are  the  true  transverse  processes,  v/hich  are  rudimental  in  this  region  of 
the  spine.  The  external  one  is  the  so-called  transverse  process,  the  homologue 
of  the  rib,  and  hence  sometimes  called  the  costal  process  {processus  costarius) 
(Fig.  22).  Although  in  man  the  costal  processes  are  comparatively  small,  in  some 
animals  they  attain  considerable  size,  and  serve  to  lock  the  vertebrae  more 
closely  together. 

Fifth  Lumbar  Vertebra. — The  fifth  lumbar  vertebra  is  characterized  by  having 
the  body  much  thicker  in  front  than  behind,  which  accords  with  the  prominence 
of  the  sacro-vertebral  articulation;  by  the  smaller  size  of  its  spinous  process;  by 
the  wide  interval  between  the  inferior  articulating  processes;  and  by  the  greater 
size  and  thickness  of  its  transverse  processes,  which  spring  from  the  body  as  well 
as  from  the  pedicles. 


58 


THE  SKELETON 


Structure  of  the  Vertebrae. — The  body  is  composed  of  light,  spongy,  cancel- 
lous tissue,  having  a  thin  coating  of  compact  tissue  on  its  external  surface  per- 
forated by  numerous  orifices,  some  of  large  size,  for  the  passage  of  vessels;  its 
interior  is  traversed  by  one  or  two  large  canals,  for  the  reception  of  veins,  which 
converge  toward  a  single  large,  irregular  aperture  or  several  small  apertures  at  the 
posterior  part  of  the  body  of  each  bone.  The  arch  and  processes  projecting  from 
it  have,  on  the  contrary,  an  exceedingly  thick  covering  of  compact  tissue  (Fig.  23). 


Fig  23. — Bony  structure  of  a  lumbar  vertebra.      (Poirier  and  Charpy.) 

Development. — Each  vertebra  is  formed  of  four  primary  centres  of  ossification 
(Fig.  24),  one  for  each  lamina  and  its  processes,  and  two  for  the  body.^  Ossifica- 
tion commences  in  the  laminae  about  the  sixth  week  of  foetal  life,  in  the  situation 
where  the  transverse  processes  afterward  project,  the  ossific  granules  shooting 
backward  to  the  spine,  forward  into  the  pedicles,  and  outward  into  the  transverse 
and  articular  processes.  Ossification  in  the  body  commences  in  the  middle  of 
the  cartilage  about  the  eighth  week  by  two  closely  approximated  centres,  which 


By  Jf  primary  centres. 

^^  [Sfor  body  (8th  week). 


By  4  secondary  centres. 


Ifor  each  lamina  (6th  week). 
Fig.  24. — Development  of  a  vertebra. 


By  2  additional  plates. 

T^Igtb  -1  for  upper  surface 
aw  of  body, 

^1  for  under  surface 

of  body. 
Fig.  25. 


•  f  i  years. 


1  for  each  trans- 
verse process, 
16  years. 


[sometimes  1)  for  spinous  process  (16  years). 
Fig.  26. 


speedily  coalesce  to  form  one  central  ossific  point.  According  to  some  authors, 
ossification  commences  in  the  laminae  only  in  the  upper  vertebrae — i.  e.,  in  the 
cervical  and  upper  dorsal.  The  first  ossific  points  in  the  lower  vertebrae  are  those 
which  are  to  form  the  body,  the  osseous  centres  for  the  laminte  appearing  at  a 
subsequent  period.  At  birth  these  three  pieces  are  perfectly  separate.  During 
the  first  year  the  laminae  become  united  behind,  the  union  taking  place  first  in 
the  lumbar  region  and  then  extending  upward  through  the  dorsal  and  lower  cer- 
vical regions.  About  the  third  year  the  body  is  joined  to  the  arch  on  each  side  in 
such  a  manner  that  the  body  is  formed  from  the  three  original  centres  of  ossifica- 

1  By  many  observers  it  is  asserted  that  the  bodies  of  the  vertebra  are  developed  from  a  single  centre  which 
speedily  becomes  bilobed,  so  as  to  give  the  appearance  of  two  nuclei;  but  that  there  are  two  centres,  at  all 
events  sometimes,  is  evidenced  by  the  fact  that  the  two  halves  of  the  body  of  the  vertebra  may  remain  distinct 
throughout  life  and  be  separated  by  a  fissure  through  which  a  protrusion  of  the  spinal  menibrane  may  take 
place,  constituting  an  anterior  spina  bifida. 


THE   LUMBAR    VERTEBRjE 


59 


By  S  centres. 


tion,  the  amount  contributed  by  the  pedicles  increasing  in  extent  from  below 
upward.  Thus  the  bodies  of  the  sacral  vertebrse  are  formed  almost  entirely  from 
the  central  nuclei;  the  bodies  of  the  lumbar  are  formed  laterally  and  behind  by  the 
pedicles;  in  the  dorsal  region  the  pedicles  advance  as  far  forward  as  the  articular 
depressions  for  the  head  of  the  ribs,  forming  these  cavities  of  reception;  and  in 
the  neck  the  lateral  portions  of  the  bodies  are  formed  entirely  by  the  advance  of 
the  pedicles.  The  line  along  which  union  takes  place  between  the  body  and  the 
neural  arch  is  named  neuro -central  suture.  Before  puberty  no  other  changes  occur, 
excepting  a  gradual  increase  in  the  growth  of  these  primary  centres;  the  upper 
and  under  surfaces  of  the  bodies  and  the  ends  of  the  transverse  and  spinous  pro- 
cesses being  tipped  with  cartilage,  in  which  ossific  granules  are  not  as  yet  deposited. 
At  sixteen  years  (Fig.  26)  three  secondary  centres  appear,  one  for  the  tip  of 
each  transverse  process,  and  one  for  the  extremity  of  the  spinous  process.  In 
some  of  the  lumbar  vertebra,  especially  the  first,  second,  and  third,  a  second 
ossifying  centre  appears  at  the  base  of  the  spinous  process.  At  twenty-one  years 
(Fig.  25)  a  thin,  circular,  epiphysial  plate  of  bone  is  formed  in  the  layer  of  cartilage 
situated  on  the  upper  and  under  surfaces  of  the  body,  the  former  being  the  thicker 
of  the  two.  All  these  become  joined,  and  the  bone  is  completely  formed  between 
the  twenty-fifth  and  thirtieth  year  of  life. 

Exceptions  to  this  mode  of  development  occur  in  the  first,  second,  and  seventh 
cervical,  and  in  the  vertebra?  of  the  lumbar  region. 

Atlas  (Fig.  27). — The  number  of  centres  of  ossification  of  the  atlas  is  very  vari- 
able. It  may  be  developed  from  two,  three,  four,  or  five  centres.  The  most 
frequent  arrangement  is  by  three 
centres.  Two  of  these  are  destined 
for  the  two  lateral  or  neural  masses, 
the  ossification  of  which  commences 
about  the  seventh  week  near  the 
articular  processes,  and  extend 
backward;  these  portions  of  bone 
are  separated  from  one  another  be- 
hind, at  birth,  by  a  narrow  interval 
filled  in  with  cartilage.  Between 
the  third  and  fourth  years  they  unite 
either  directly  or  through  the  me- 
dium of  a  separate  centre  developed 
in  the  cartilage  in  the  middle  line. 
The  anterior  arch,  at  birth,  is  al- 
together cartilaginous,  and  in  this 
a  separate  nucleus  appears  about 
the  end  of  the  first  year  after  birth, 
and,  extending  laterally,  joins  the 
neural  processes  in  front  of  the  pedi- 
cles. Sometimes  there  are  two  nu- 
clei developed  in  the  cartilage,  one 
on  either  side  of  the  median  line, 
which  join  to  form  a  single  mass. 
And  occasionally  there  is  no  sepa- 
rate centre,  but  the  anterior  arch  is  formed  by  the  gradual  extension  forward 
and  ultimate  junction  of  the  two  neural  processes. 

Axis. — The  axis  (Fig.  28)  is  developed  by  seven  centres.  The  body  and  arch 
of  this  bone  are  formed  in  the  same  manner  as  the  corresponding  parts  in  the  other 
vertebrje:  one  centre  (or  two,  which  speedily  coalesce)  for  the  lower  part  of  the 
body,  and  one  for  each  lamina.    The  centres  for  the  laminae  appear  about  the 


anterior  arch  {1st  year), 

not  constant. 
1  for  each 
lateral  mass 


I  befori 


e  birth. 


Fig.  27.— Atlas. 


By  7  centres. 


2d  year. 


6th  month. 

1  for  each  lateral  mass. 

1  for  body  (4th  month). 
1  for  under  surface  of 
body. 


Pig.  28.— Axis. 
S  additional  centres. 


for  tubercles  on  superior  artictdar  process. 
Fig.  29. — Lumbar  vertebra. 


60  THE  SKELETON 

seventh  or  eighth  week,  that  for  the  body  about  the  fourth  month.  The  odontoid 
process  consists  originally  of  an  extension  upward  of  the  cartilaginous  mass  in 
which  the  lower  part  of  the  body  is  formed.  At  about  the  sixth  month  of  foetal 
life  two  osseous  nuclei  make  their  appearance  in  the  base  of  this  process;  they 
are  placed  laterally,  and  join  before  birth  to  form  a  conical  bilobed  mass  deeply 
cleft  above;  the  interval  between  the  cleft  and  the  summit  of  the  process  is  formed 
by  a  wedge-shaped  piece  of  cartilage,  the  base  of  the  process  being  separated 
from  the  body  by  a  cartilaginous  interval,  which  gradually  becomes  ossified  at 
its  circumference,  but  remains  cartilaginous  in  its  centre  until  advanced  age.^ 
Finally,  as  Humphry  has  demonstrated,  the  apex  of  the  odontoid  process  has 
a  separate  nucleus,  which  appears  in  the  second  year  and  joins  about  the  twelfth 
year.  .  In  addition  to  these  there  is  a  secondary  centre  for  a  thin  epiphysial  plate 
on  the  under  surface  of  the  body  of  the  bone.  J.  Bland  Sutton  and  others  main- 
tain that  the  odontoid  process  is  the  "dissociated  body  of  the  atlas."^ 

Seventh  Cervical. — The  anterior  or  costal  part  of  the  transverse  process  of  the 
seventh  cervical  is  developed  from  a  separate  osseous  centre  at  about  the  sixth 
month  of  foetal  life,  and  joins  the  body  and  posterior  division  of  the  transverse 
process  between  the  fifth  and  sixth  years.  Sometimes  this  process  continues  as 
a  separate  piece,  and,  becoming  lengthened  outward,  constitutes  what  is  known 
as  a  cervical  rib.  This  separate  ossific  centre  for  the  costal  process  has  also  been 
found  in  the  fourth,  fifth,  and  sixth  cervical  vertebrae. 

Lumbal  Vertebrae. — The  lumbar  vertebrae  (Fig.  29)  have  two  additional  centres 
(besides  those  peculiar  to  the  vertebrae  generally)  for  the  mammillary  tubercles, 
which  project  from  the  back  part  of  the  superior  articular  processes.  The  trans- 
verse process  of  the  first  lumbar  is  sometimes  developed  as  a  separate  piece,  which 
may  remain  permanently  unconnected  with  the  remaining  portion  of  the  bone, 
thus  forming  a  lumbar  rib — a  peculiarity  that  is  rarely  met  with. 

Progress  of  Ossification  in  the  Spine  Generally. — Ossification  of  the  laminae  of 
the  vertebrae  commences  in  the  cervical  region  of  the  spine,  and  proceeds  gradually 
downward.  Ossification  of  the  bodies,  on  the  other  hand,  commences  a  little 
below  the  centre  of  the  spinal  column  (about  the  ninth  or  tenth  dorsal  vertebra), 
and  extends  both  upward  and  downward.  Although  the  ossific  nuclei  make  their 
first  appearance  in  the  lower  dorsal  vertebrae,  the  lumbar  and  first  sacral  ver- 
tebrae are  those  in  which  these  nuclei  are  largest  at  birth. 

Attachment  of  Muscles. — To  the  Atlas  are  attached  nine  pairs:  the  Longus 
colli,  Rectus  capitis  anticus  minor.  Rectus  lateralis,  Obliquus  capitis  superior  and 
inferior,  Splenius  colli,  Ivcvator  anguli  scapuUe,  First  Intertransverse,  and  Rectus 
capitis  posticus  minor. 

To  the  Axis  are  attached  eleven  pairs:  the  Longus  colli,  I>evator  anguli  scapulae, 
Splenius  colli.  Scalenus  medius,  Transversalis  colli,  Intertransversales,  Obliquus 
capitis  inferior.  Rectus  capitis  posticus  major,  Semispinalis  colli,  Multifidus  spinae, 
Interspinales. 

To  the  remaining  vertebrae,  generally,  are  attached  thirty-five  pairs  and  a 
single  muscle:  anteriorly,  the  Rectus  capitis  anticus  major,  Longus  colli.  Scalenus 
anticus  medius  and  posticus,  Psoas  magnus  and  parvus,  Quadratus  lumborum. 
Diaphragm,  Obliquus  abdominis  internus,  and  Transversalis  abdominis;  pos- 
teriorly, the  Trapezius,  Latissimus  dorsi.  Levator  anguli  scapulae,  Rhomboideus 
major  and  minor,  Serratus  posticus  superior  and  inferior,  Splenius,  Erector  spinae, 
Ilio-costalis,  I>,ongissimus  dorsi.  Spinalis  dorsi,  Cervicalis  ascendens,  Transversalis 
colli,  Trachelo-mastoid,  Complexus,  Biventer  cervicis,  Semispinalis  dorsi  and  colli, 
Multifidus  spinae,  Rotatores  spinae,  Interspinales,  Supraspinales,  Intertransversales, 
Levatores  costarum. 

^  See  Cunningham,  Jour.  Anat.,  vol.  xx.  p.  238.  ^  Ligaments:  their  Nature  and  Morphology. 


THE  SACRAL    AND    COCCYGEAL    VERTEBBjE 


61 


The  Sacral  and  Coccygeal  Vertebrae  (False  or  Immovable  Vertebrae). 

The  sacral  and  coccygeal  vertebrae  consist,  at  an  early  period  of  life,  of  nine 
separate  pieces,  which  are  united  in  the  adult  so  as  to  form  two  bones,  five  enter- 
ing into  the  formation  of  the  sacrum,  four  into  that  of  the  coccyx.  Occasionally, 
the  coccyx  consists  of  five  bones.^ 

Sacrum  {os  sacrum). — The  os  sacrum  (sacer,  sacred),  the  sacred  bone. 
So  called,  according  to  some,  because  it  was  the  part  selected  in  sacrifices. 
Another  view  is  that  the  name  is  derived  from  an  opinion  of  the  Jewish  rabbis, 
that  this  part  of  the  skeleton  strongly  resists  decay  and  becomes  the  germ  from 
which  the  new  body  will  be  raised.  The  sacrum  is  a  large,  triangular  bone  (Fig. 
30),  situated  at  the  lower  part  of  the  vertebral  column,  and  at  the  upper  and 
back  part  of  the  pelvic  cavity,  where  it  is  inserted  like  a  wedge  between  the  two 
innominate  bones;  its  upper  part  or  base  articulating  with  the  last  lumbar  ver- 
tebra, its  apex  with  the  coccyx.  It  is  composed  of  five  segments  of  bone  (sacral 
vertebrae,  or  vertebrw  sacrales).  The  sacrum  is  curved  upon  itself,  and  placed 
very  obliquely,  its  upper  extremity  projecting  forward,  and  forming,  with  the 
last  lumbar  vertebra,  a  very  prominent  angle,  called  the  promontory  (promontorium) , 
or  sacro -vertebral  angle;  while  its  central  part  is  directed  backward,  so  as  to  give 
increased  capacity  to  the  pelvic  cavity.  It  presents  for  examination  an  anterior  and 
posterior  surface,  two  lateral  surfaces,  a  base,  an  apex,  and  a  central  canal. 


Fig.  30. — Sacrum,  anterior  surface. 

Surfaces.  Anterior  or  Pelvic  Surface  (fades  pelvina). — The  anterior  surface 
is  concave  from  above  downward,  and  slightly  so  from  side  to  side.  In  the 
middle  are  seen  four  transverse  ridges  (linear  transversoB) ,  indicating  the  original 
division  of  the  bone  into  five  separate  pieces.     The  portions  of  bone  intervening 

'  Sir  George  Humphry  describes  this  as  the  usual  composition  of  the  coccyx.     On  the  Skeleton,  p.  456. 


62 


THE  SKELETON 


between  the  ridges  correspond  to  the  bodies  of  the  vertebrae.  The  body  of  the  first 
segment  is  of  large  size,  and  in  forra  resembles  that  of  a  lumbar  vertebra;  the  suc- 
ceeding ones  diminish  in  size  from  above  downward,  are  flattened  from  before 
backward,  and  curved  so  as  to  accommodate  themselves  to  the  form  of  the  sacrum, 
being  concave  in  front,  convex  behind.  At  each  end  of  the  ridges  above  men- 
tioned are  seen  the  anterior  sacral  foramina  (foramina  sacralia  anteriora) ,  analogous 
to  the  intervertebral  foramina,  four  in  number  on  each  side,  somewhat  rounded 
in  form,  diminishing  in  size  from  above  downward,  and  directed  outward  and 
forward;  they  transmit  the  anterior  branches  of  the  sacral  nerves  and  the  lateral 
sacral  arteries.  External  to  these  foramina  is  the  lateral  mass  {'pars  lateralis), 
consisting  at  an  early  period  of  life  of  separate  segments;  these  become  blended, 

in  the  adult,  with  the  bodies,  with  each 
other,  and  with  the  posterior  transverse 
processes.  Each  lateral  mass  is  traversed 
by  four  broad,  shallow  grooves,  which 
lodge  the  anterior  sacral  nerves  as  they 
pass  outward,  the  grooves  being  sepa- 
rated by  prominent  ridges  of  bone,  which 
give  attachment  to  the  slips  of  the 
Pyriformis  muscle. 

If  a  vertical  section  is  made  through 
the  centre  of  the  sacrum  (Fig.  31),  the 
bodies  are  seen  to  be  united  at  their  cir- 
cumference by  bone,  a  wide  interval  being 
left  centrally,  which,  in  the  recent  state, 
is  filled  by  intervertebral  substance.  In 
some  bones  this  union  is  more  complete 
between  the  lower  segments  than  between 
the  upper  ones. 

Posterior  or  Dorsal  Sm:face  {fades  dor- 
salis) . — The  posterior  surface  (Fig.  32)  is 
convex  and  much  narrower  than  the  ante- 
rior. In  the  middle  line  are  three  or  four 
tubercles,  which  represent  the  rudimen- 
tary spinous  processes  of  the  sacral  verte- 
brae. Of  these  tubercles,  the  first  is 
usually  prominent,  and  perfectly  distinct 
from  the  rest;  the  second  and  third  are 
either  separate  or  united  into  a  tubercular 
ridge  {crista  sacralis  media),  which  dimin- 
ishes in  size  from  above  downward;  the 
fourth  usually,  and  the  fifth  always, 
remaining  undeveloped.  The  gap  which  results  from  failure  of  the  lamina?  to 
meet  in  the  mid-line  is  called  the  hiatus  sacralis.  External  to  the  spinous  pro- 
cesses on  each  side  are  the  laminae,  broad  and  well  marked  in  the  first  three 
pieces;  sometimes  the  fourth,  and  generally  the  fifth,  are  only  partially  developed 
and  fail  to  meet  in  the  middle  line.  These  partially  developed  laminae  are  prolonged 
downward  as  rounded  processes,  the  sacral  comua  (cornua  sacralia) ,  and  are  con- 
nected to  the  cornua  of  the  coccyx.  Between  them  the  bony  wall  of  the  lower  end 
of  the  sacral  canal  is  imperfect.  External  to  the  laminae  is  a  linear  series  of 
indistinct  tubercles  representing  the  articular  processes  {cristoe  sacrales  articulares) ; 
the  upper  pair  are  large,  well  developed,  and  correspond  in  shape  and  direction 
to  the  superior  articulating  processes  of  a  lumbar  vertebra;  the  second  and  third 
are  small;  the  fourth  and  fifth  (usually  blended  together)  are  situated  on  each 


Fig.  31. — Vertical  section  of  the  sacrum. 


THE  SACRAL    AND    COCCYGEAL    VERTEBRA 


63 


side  of  the  sacral  canal  and  assist  in  forming  the  sacral  cornua.  External  to  the 
articular  processes  are  the  four  posterior  sacral  foramina  {foramina  sacralia  pos- 
ter iora);  they  are  smaller  in  size  and  less  regular  in  form  than  the  anterior, 
and  transmit  the  posterior  branches  of  the  sacral  nerves.    On  the  outer  side  of 


Erector  spinae. 


Latissimus  dorai. 


Erector  spinse. 


Upper  half  of  fifth 
erior  sacral  foramen. 


Fig.  32. — Sacrum,  posterior  surface. 


the  posterior  sacral  foramina  is  a  series  of  tubercles,  the  rudimentary  transverse 
processes  of  the  sacral  vertebrae  (cristcB  sacrales  laterales) .  The  first  pair  of  trans- 
verse tubercles  are  large,  very  distinct,  and  correspond  with  each  superior  angle  of 
the  bone;  they  together  with  the  second  pair,  which  are  of  small  size,  give  attach- 
ment to  the  horizontal  part  of  the  sacro-iliac  ligament ;  the  third  gives  attachment 
to  the  oblique  fasciculi  of  the  posterior  sacro-iliac  ligaments ;  and  the  fourth 
and  fifth  to  the  great  sacro-sciatic  ligaments.  The  interspace  between  the  spinous 
and  transverse  processes  on  the  back  of  the  sacrum  presents  a  wide,  shallow 
concavity,  called  the  sacral  groove:  it  is  continuous  above  with  the  vertebral 
groove,  and  lodges  the  origin  of  the  Multifidus  spinjie. 

Lateral  Surface. — The  lateral  surface,  broad  above,  becomes  narrowed  into  a 
thin  edge  below.  Its  upper  half  presents  in  front  a  broad,  ear-shaped  surface  for 
articulation  with  the  ilium.  This  is  called  the  auricular  surface  (fades  auricularis) , 
and  in  the  fresh  state  is  coated  with  fibro-cartilage.  It  is  bounded  posteriorly  by 
deep  and  uneven  impressions,  for  the  attachment  of  the  posterior  sacro-iliac  liga- 
ments. The  chief  prominence  is  called  the  tuberosity  (tuberositas  sacralis).  The 
lower  half  is  thin  and  sharp,  and  terminates  in  a  projection  called  the  inferior  lateral 
angle;  below  this  angle  is  a  notch,  which  is  converted  into  a  foramen  by  articula- 
tion with  the  transverse  process  of  the  upper  piece  of  the  coccyx,  and  transmits 
the  anterior  division  of  the  fifth  sacral  nerve.  This  lower,  sharp  border  gives 
attachment  to  the  greater  and  lesser  sacro-sciatic  ligaments,  and  to  some  fibres 
of  the  Gluteus  maximus  posteriorly,  and  to  the  Coccygeus  in  front. 


y 


64  THE  SKELETON 

Base  (basis  oss.  sacri) . — The  base  of  the  sacrum,  which  is  broad  and  expanded,  is 
directed  upward  and  forward.  In  the  middle  is  seen  a  large  oval  articular  surface, 
which  is  connected  with  the  under  surface  of  the  body  of  the  last  lumbar  vertebra 
by  a  fibro-cartilaginous  disk.  It  is  bounded  behind  by  the  large,  triangular  orifice 
of  the  sacral  canal.  The  orifice  is  formed  behind  by  the  lamina?  and  spinous  process 
of  the  first  sacral  vertebra:  the  superior  articular  processes  project  from  it  on  each 
side;  they  are  oval,  concave,  directed  backward  and  inward,  like  the  superior 
articular  processes  of  a  lumbar  vertebra;  and  in  front  of  each  articular  process  is 
an  intervertebral  notch,  which  forms  the  lower  part  of  the  foramen  between  the 
last  lumbar  and  first  sacral  vertebra.  Lastly,  on  each  side  of  the  large  oval  articular 
plate  is  a  broad  and  flat  triangular  surface  of  bone,  which  extends  outward, 
supports  the  Psoas  magnus  muscle  and  lumbo-sacral  cord,  and  is  continuous 
on  each  side  with  the  iliac  fossa.  This  is  called  the  ala  of  the  sacrum  (ala 
sacralis) ,  and  gives  attachment  to  a  few  of  the  fibres  of  the  Iliacus  muscle.  The 
posterior  part  of  the  ala  represents  the  transverse  process  of  the  first  sacral 
segment. 

Apex  {a'pex  OSS.  sacri). — The  apex,  directed  downward  and  slightly  forward, 
presents  a  small,  oval,  concave  surface  for  articulation  with  the  coccyx. 

Spinal  Canal. — The  spinal  canal  in  this  region  is  called  the  sacral  canal  (canalis 
sacralis).  It  runs  throughout  the  greater  part  of  the  bone;  it  is  large  and  tri- 
angular in  form  above,  small  and  flattened,  from  before  backward,  below.  In 
this  situation  its  posterior  wall  is  incomplete,  from  the  non-development  of  the 
lamince  and  spinous  processes  (hiatus  sacralis).  It  lodges  the  sacral  nerves, 
and  is  perforated  by  the  anterior  and  posterior  sacral  foramina,  through  which 
these  pass  out. 

Structure. — It  consists  of  much  loose,  spongy  tissue  within,  invested  externally 
by  a  thin  layer  of  compact  tissue. 

Differences  in  the  Sacrum  of  the  Male  and  Female. — The  sacrum  in  the 
female  is  shorter  and  wider  than  in  the  male;  the  lower  half  forms  a  greater 
angle  with  the  upper,  the  upper  half  of  the  bone  being  nearly  straight,  the  lower 
half  presenting  the  greatest  amount  of  curvature.  The  bone  is  also  directed  more 
obliquely  backward,  which  increases  the  size  of  the  pelvic  cavity;  but  the  sacro- 
vertebral  angle  projects  less.  In  the  male  the  curvature  is  more  evenly  dis- 
tributed over  the  whole  length  of  the  bone,  and  is  altogether  greater  than  in 
the  female. 

Peculiarities  of  the  Sacrum. — This  bone,  in  some  cases,  consists  of  six  pieces; 
occasionally,  the  number  is  reduced  to  four.  Sometimes  the  bodies  of  the  first 
and  second  segments  are  not  joined  or  the  laminae  and  spinous  processes  have  not 
coalesced.  Occasionally,  the  upper  pair  of  transverse  tubercles  are  not  joined  to 
the  rest  of  the  bone  on  one  or  both  sides ;  and,  lastly,  the  sacral  canal  may  be  open 
for  nearly  the  lower  half  of  the  bone,  in  consequence  of  the  imperfect  development 
of  the  laminte  and  spinous  processes.  The  sacrum,  also,  varies  considerably  with 
respect  to  its  degree  of  curvature.  From  the  examination  of  a  large  number  of 
skeletons  it  would  appear  that  in  one  set  of  cases  the  anterior  surface  of  this  bone 
was  nearly  straight,  the  curvature,  which  was  very  slight,  affecting  only  its  lower 
end.  In  another  set  of  cases  the  bone  was  curved  throughout  its  whole  length, 
but  especially  toward  its  middle.  In  a  third  set  the  degree  of  curvature  was  less 
marked,  and  affected  especially  the  lower  third  of  the  bone. 

Development  (Fig.  33). — The  sacrum,  formed  by  the  union  of  five  vertebrae, 
has  thirty-five  centres  of  ossification. 

The  bodies  of  the  sacral  vertebrae  have  each  three  ossific  centres:  one  for  the 
central  part,  and  one  for  the  epiphysial  plates  on  its  upper  and  under  surface. 
Occasionally  the  primary  centres  for  the  bodies  of  the  first  and  second  piece  of  the 
sacrum  are  double. 


SACBAL    AND    COCCYGEAL     VERTEBRA 


65 


The  arch  of  each  sacral  vertebra  is  developed  by  two  centres,  one  for  each 
lamina.    These  unite  with  each  other  behind,  and  subsequently  join  the  body. 

The  lateral  masses  have  six  additional  centres,  two  for  each  of  the  first  three 
vertebrse.  These  centres  make  their  appearance  above  and  to  the  outer  side  of 
the  anterior  sacral  foramina  (Fig.  33),  and  are  developed  into  separate  segments 
(Fig.  34);  they  are  subsequently  blended  with  each  other,  and  with  the  bodies 
and  transverse  processes  to  form  the  lateral  mass. 

Lastly,  each  lateral  surface  of  the  sacrum  is  developed  by  two  epiphysial  plates 
(Fig.  35):  one  for  the  auricular  surface,  and  one  for  the  remaining  part  of  the 
thin  lateral  edge  of  the  bone. 


Additional  centres 
for  the  first  three  pieces. 


At  birth. 


At4i 


Two  epiphysial  laminx 
for  each  lateral  surface.'^ 


At 
S5th  year. 


Fig.  33. — Development  of  the  sacrum. 


Fig.  34. 


Fig.  35. 


Period  of  Development. — At  about  the  eighth  or  ninth  week  of  foetal  life  ossifi- 
cation of  the  central  part  of  the  bodies  of  the  first  three  vertebrae  commences, 
and  at  a  somewhat  later  period  that  of  the  last  two.  Between  the  sixth  and 
eighth  months  ossification  of  the  laminae  takes  place;  and  at  about  the  same 
period  the  centres  for  the  lateral  masses  for  the  first  three  sacral  vertebrae  make 
their  appearance.  The  period  at  which  the  arch  becomes  completed  by  the  junc- 
tion of  the  laminae  with  the  bodies  in  front  and  with  each  other  behind  varies  in 
different  segments.  The  junction  between  the  laminae  and  the  bodies  takes  place 
first  in  the  lower  vertebrae  as  early  as  the  second  year,  but  is  not  affected  in  the 
uppermost  until  the  fifth  or  sixth  year.  About  the  sixteenth  year  the  epiphyses 
for  the  upper  and  under  surfaces  of  the  bodies  are  formed,  and  between  the  eigh- 
teenth and  twentieth  years  those  for  each  lateral  surface  of  the  sacrum  make  their 
appearance.  The  bodies  of  the  sacral  vertebrae  are,  during  early  life,  separated 
from  each  other  by  intervertebral  disks.  But  about  the  eighteenth  year  the  two 
lowest  segments  become  joined  together  by  ossification  extending  through  the 
disk.  This  process  gradually  extends  upward  until  all  the  segments  become 
united,  and  the  bone  is  completely  formed  from  the  twenty-fifth  to  the  thirtieth 
year  of  life. 

Articulations. — With  four  bones:  the  last  lumbar  vertebra,  coccyx,  and  the 
two  innominate  bones. 

Attachment  of  Muscles. — To  eight  pairs:  in  front,  the  Pyriformis  and  Coc- 
cygeus,  and  a  portion  of  the  Iliacus  to  the  base  of  the  bone;  behind,  the  Gluteus 
maximus,  Latissimus  dorsi,  Multifidus  spinae,  and  Erector  spinae,  and  sometimes 
the  Extensor  coccygis. 

Coccyx  (os  coccygis). — The  coccyx  [xoxxuq,  cuckoo),  so  called  from  having 
been  compared  to  a  cuckoo's  beak  (Fig.  36),  is  usually  formed  of  four  small 
segments  of  bone,  the  most  rudimentary  parts  of  the  vertebral  column  (vertebrae 
coccygeae  or  caudate  vertebrae).  In  each  of  the  first  three  segments  may  be  traced 
a  rudimentary  body,  articular  and  transverse  processes;   the  last  piece  (some- 

5 


66 


THE  SKELETON 


times  the  third)  is  a  mere  nodule  of  bone,  without  distinct  processes.  All  the 
segments  are  destitute  of  pedicles,  laminte,  and  spinous  processes,  and,  conse- 
quently, of  intervertebral  foramina  and  spinal  canal.  The  first  segment  is  the 
largest;  it  resembles  the  lowermost  sacral  vertebra,  and  often  exists  as  a  separate 


Cornua. 


Anterior  surface. 


'*ct'eR 

Posterior  surface. 


Pig.  36. — Coccyx. 


piece;  the  last  three,  diminishing  in  size  from  above  downward,  are  usually 
blended  together  so  as  to  form  a  single  bone.  The  gradual  diminution  in  the  size 
of  the  pieces  gives  this  bone  a  triangular  form,  the  base  of  the  triangle  joining 
the  end  of  the  sacrum.  It  presents  for  examination  an  anterior  and  posterior  sur- 
face, two  borders,  a  base,  and  an  apex. 

Surfaces.  Anterior  Surface. — The  anterior  surface  is  slightly  concave,  and 
marked  with  three  transverse  grooves,  indicating  the  points  of  junction  of  the 
different  pieces.  It  has  attached  to  it  the  anterior  sacro-coccygeal  ligament  and 
Levator  ani  muscle,  and  supports  the  lower  end  of  the  rectum. 

Posterior  Surface. — The  posterior  surface  is  convex,  marked  by  transverse  grooves 
similar  to  those  on  the  anterior  surface;  and  presents  on  each  side  a  lineal  row 
of  tubercles,  the  rudimentary  articular  processes  of  the  coccygeal  vertebrae.  Of 
these,  the  superior  pair  are  large,  and  are  called  the  cornua  of  the  coccyx  (cornua 
coccygea) ;  they  project  upward,  and  articulate  with  the  cornua  of  the  sacrum,  the 
junction  between  these  two  bones  completing  the  fifth  posterior  sacral  foramen  for 
the  transmission  of  the  posterior  division  of  the  fifth  sacral  nerve. 

Borders. — The  lateral  borders  are  thin,  and  present  a  series  of  small  eminences, 
which  represent  the  transverse  processes  of  the  coccygeal  vertebr*.  Of  these, 
the  first  on  each  side  is  the  largest,  flattened  from  before  backward,  and  often 
ascends  to  join  the  lower  part  of  the  thin  lateral  edge  of  the  sacrum,  thus  com- 
pleting the  fifth  anterior  sacral  foramen  for  the  transmission  of  the  anterior 
division  of  the  fifth  sacral  nerve;  the  others  diminish  in  size  from  above  down- 
ward, and  are  often  wanting.  The  borders  of  the  coccyx  are  narrow,  and  give 
attachment  on  each  side  to  the  sacro-sciatic  ligaments,  to  the  Coccygeus  muscles 
in  front  of  the  ligaments,  and  to  the  Gluteus  maximus  behind  them. 

Base. — The  base  presents  an  oval  surface  for  articulation  with  the  sacrum. 
This  articulation  is  known  as  the  sacro-coccygeal  symphysis  (symphysis  sacro- 
coccygea) . 

Apex. — The  apex  is  rounded,  and  has  attached  to  it  the  tendon  of  the  external 
Sphincter  muscle.  It  is  occasionally  bifid,  and  sometimes  deflected  to  one  or 
other  side. 

Development. — The  coccyx  is  developed  by  four  centres,  one  for  each  piece. 
Occasionally  one  of  the  first  three  pieces  of  this  bone  is  developed  by  two  centres, 
placed  side  by  side.  The  ossific  nuclei  make  their  appearance  in  the  following 
order:  in  the  first  segment,  shortly  after  birth;  in  the  second  piece,  at  from  five 


THE   VERTEBRAL    COLUMN 


67 


to  ten  years;  in  the  third,  from  ten  to  fifteen 
years;  in  the  fourth,  from  fifteen  to  twenty 
years.  As  age  advances  these  various  seg- 
ments become  united  with  each  other  from 
below  upward,  the  union  between  the  first 
and  second  segments  being  frequently  delayed 
until  after  the  age  of  twenty-five  or  thirty. 
At  a  late  period  of  life,  especially  in  females, 
the  coccyx  often  becomes  joined  to  the  end 
of  the  sacrum. 

Articulation. — AYith  the  sacrum. 

Attachment  of  Muscles. — To  four  pairs 
and  one  single  muscle :  on  either  side,  the 
Coccygeus ;  behind,  the  Gluteus  maximus 
and  Extensor  coccygis,  when  present ;  at  the 
apex,  the  Sphincter  ani ;  and  in  front,  the 
Levator  ani. 

The  Vertebral  Colunm  or  Spine  in  General. 

"^llie  spinal  column  (columna  vertehralis) , 
formed  by  the  junction  of  the  vertebrae,  is 
situated  in  the  median  line,  at  the  posterior 
part  of  the  trunk;  its  average  length  is  about 
two  feet  two  or  three  inches,  measuring  along 
the  curved  anterior  surface  of  the  column. 
Of  this  length  the  cervical  part  measures 
about  five,  the  dorsal  about  eleven,  the  lum- 
bar about  seven  inches,  and  the  sacrum  and 
coccyx  the  remainder.  The  female  spine  is 
about  one  inch  less  than  that  of  the  male. 

Viewed  in  front,  the  ventral  surface  presents 
two  pyramids  joined  together  at  their  bases, 
the  upper  one  being  formed  by  all  the  verte- 
bra from  the  second  cervical  to  the  last  lum- 
bar, the  lower  one  by  the  sacrum  and  coccyx. 
AVhen  examined  more  closely,  the  upper 
pyramid  is  seen  to  be  formed  of  three  smaller 
pyramids.  The  uppermost  of  these  consists 
of  the  six  lower  cervical  vertebrae,  its  apex 
being  formed  by  the  axis  or  second  cervical, 
its  base  by  the  first  dorsal.  The  second 
pyramid,  which  is  inverted,  is  formed  by  the 
four  upper  dorsal  vertebrae,  the  base  being  at 
the  first  dorsal,  the  smaller  end  at  the  fourth. 
The  third  pyramid  commences  at  the  fourth 
dorsal,  and  gradually  increases  in  size  to  the 
fifth  lumbar. 

Viewed  laterally  (Fig.  37),  the  spinal  column 
presents  several  curves  which  correspond  to 
the  different  regions  of  the  column,  and  are 
called  cervical,  dorsal,  lumbar,  and  pelvic. 
The  cervical  curve  commences  at  the  apex  of 
the  odontoid  process,  and  terminates  at  the 


1st  cervical 
or  Atlas. 


1st  lumbar 


Coccyx. 
Fig.  37. — Lateral  view  of  the  spine. 


68  THE  SKELETON 

middle  of  the  second  dorsal  vertebra ;  it  is  convex  in  front,  and  is  the  least 
marked  of  all  the  curves.  The  dorsal  curve,  which  is  concave  forward,  com- 
mences at  the  middle  of  the  second,  and  terminates  at  the  middle  of  the  twelfth 
dorsal  vertebra.  Its  most  prominent  point  behind  corresponds  to  the  spine 
of  the  seventh  dorsal  vertebra.  The  lumbar  curve  commences  at  the  middle 
of  the  last  dorsal  vertebra,  and  terminates  at  the  sacro-vertebral  angle.  It  is 
convex  anteriorly;  the  convexity  of  the  lower  three  vertebrae  being  much  greater 
than  that  of  the  upper  two.  The  pelvic  curve  commences  at  the  sacro-verte- 
bral articulation  and  terminates  at  the  point  of  the  coccyx.  It  is  concave 
anteriorly.  The  dorsal  and  pelvic  curves  are  the  primary  qurves,  and  begin  to 
be  formed  at  an  early  period  of  foetal  life,  and  are  due  to  the  shape  of  the  bodies 
of  the  vertebrae.  The  cervical  and  lumbar  curves  are  compensatory  or  secondary, 
and  are  developed  after  birth  in  order  to  maintain  the  erect  position.  They  are 
due  mainly  to  the  shape  of  the  intervertebral  disks. 

Some  writers  teach  that  the  spine  has  a  normal  deviation  to  the  right  side. 
Quain,  Hyrtl,  and  others  maintain  this  view.  The  curve  is  said  to  be  in  the 
dorsal  region.  Bichat  assigned  muscular  action  as  the  chief  cause  of  the  curve. 
Most  persons  use  the  right  arm  in  preference  to  the  left,  especially  in  making 
long-continued  efforts,  when  the  body  is  curved  to  the  right  side.  In  support 
of  this  explanation  is  the  observation  made  by  Beclard  that  in  some  individuals 
who  were  left-handed  the  lateral  curvature  was  directed  to  the  left  side.  Sappey 
and  others  deny  the  existence  of  this  curve. 

The  movable  part  of  the  spinal  column  presents  for  examination  an  anterior, 
a  posterior,  and  two  lateral  surfaces;  a  base,  a  summit,  and  the  spinal  canal. 

Surfaces.  Anterior  Surface. — The  anterior  or  ventral  surface  presents  the  bodies 
of  the  vertebrae  separated  in  the  recent  state  by  the  intervertebral  disks.  The  bodies 
are  broad  in  the  cervical  region,  narrow  in  the  upper  part  of  the  dorsal,  and 
broadest  in  the  lumbar  region.  The  whole  of  this  surface  is  convex  transversely, 
concave  from  above  downward  in  the  dorsal  region,  and  convex  in  the  same 
direction  in  the  cervical  and  lumbar  regions. 

Posterior  Surface. — The  posterior  or  dorsal  surface  presents  in  the  median  line 
the  spinous  processes.  These  are  short,  horizontal,  with  bifid  extremities,  in  the 
cervical  region.  In  the  dorsal  region  they  are  directed  obliquely  above,  assume 
almost  a  vertical  direction  in  the  middle,  and  are  horizontal  below,  as  are  also 
the  spines  of  the  lumbar  vertebrae.  They  are  separated  by  considerable  intervals 
in  the  loins,  by  narrower  intervals  in  the  neck,  and  are  closely  approximated  in 
the  middle  of  the  dorsal  region.  Occasionally  one  of  these  processes  deviates  a 
little  from  the  median  line — a  fact  to  be  remembered  in  practice,  as  irregularities 
of  this  sort  are  attendant  also  on  fractures  or  displacements  of  the  spine.  On 
either  side  of  the  spinous  processes,  extending  the  whole  length  of  the  column, 
is  the  vertebral  groove  formed  by  the  laminae  in  the  cervical  and  lumbar  regions, 
where  it  is  shallow,  and  by  the  laminae  and  transverse  processes  in  the  dorsal 
region,  where  it  is  deep  and  broad.  In  the  recent  state  these  grooves  lodge  the 
deep  muscles  of  the  back.  External  to  each  vertebral  groove  are  the  articular 
processes,  and  still  more  externally  is  the  transverse  process.  In  the  dorsal  region 
the  latter  processes  stand  backward,  on  a  plane  considerably  posterior  to  the 
same  processes  in  the  cervical  and  lumbar  regions.  In  the  cervical  region  the 
transverse  processes  are  placed  in  front  of  the  articular  processes,  and  on  the 
outer  side  of  the  pedicles,  between  the  intervertebral  foramina.  In  the  dorsal 
region  they  are  posterior  to  the  pedicles,  intervertebral  foramina,  and  articular 
processes.  In  the  lumbar  region  they  are  placed  also  in  front  of  the  articular 
processes,  but  behind  the  intervertebral  foramina. 

Lateral  Surfaces. — The  lateral  surfaces  are  separated  from  the  posterior  surface 
by  the  articular  processes  in  the  cervical  and  lumbar  regions,  and  by  the  trans- 


THE    VERTEBRAL    COLUMN  69 

verse  processes  in  the  dorsal  region.  These  surfaces  present  in  front  the  sides  of 
the  bodies  of  the  vertebrie,  marked  in  the  dorsal  region  by  the  facets  for  articula- 
tion with  the  heads  of  the  ribs.  I\Iore  posteriorly  are  the  intervertebral  foramina, 
formed  by  the  juxtaposition  of  the  intervertebral  notches,  oval  in  shape,  smallest 
in  the  cervical  and  upper  part  of  the  dorsal  regions,  and  gradually  increasing  in 
size  to  the  last  lumbar  vertebra.  They  are  situated  between  the  transverse  pro- 
cesses in  the  neck,  anfl  in  front  of  them  in  the  back  and  loins,  and  transmit  the 
spinal  nerves. 

Base. — The  base  of  that  portion  of  the  vertebral  column  formed  by  the  twenty- 
four  movable  vertebne  is  formed  by  the  under  surface  of  the  body  of  the  fifth 
lumbar  vertebra;  and  the  summit  by  the  upper  surface  of  the  atlas. 

Spinal  Canal  {canalis  vertehralis) . — The  vertebral  or  spinal  canal  follows  the 
different  curves  of  the  spine;  it  is  largest  in  those  regions  in  which  the.  spine 
enjoys  the  greatest  freedom  of  movement,  as  in  the  neck  and  loins,  where  it  is 
wide  and  triangular;  and  is  narrow  and  rounded  in  the  back,  where  motion  is 
more  limited.  The  centre  of  gravity  of  the  spine  is  in  the  upper  lumbar  region, 
slightly  to  the  right  of  the  median  plane  (Struthers). 

Sm"face  Form. — The  only  parts  of  the  vertebral  column  which  lie  closely  under  the  skin,  and 
so  directly  influence  surface  form,  are  the  apices  of  the  spinous  processes.  These  are  always  distin- 
guishable at  the  bottom  of  a  median  furrow,  which,  more  or  less  evident,  runs  down  the  mesial 
line  of  the  back  from  the  external  occipital  protuberance  above  to  the  middle  of  the  sacrum  below. 
In  the  cervical  region  the  furrow  is  between  the  Trapezii  muscles ;  in  the  back  and  loins  it  is  between 
the  Erector  spinae  muscles.  In  the  neck  the  furrow  is  broad,  and  terminates  in  a  conspicuous 
projection,  which  is  caused  by  the  spinous  process  of  the  seventh  cervical  vertebra  (vertebra 
prominens).  Above  this  the  spinous  process  of  the  sixth  cervical  vertebra  may  sometimes  be 
seen  to  form  a  projection;  the  other  cervical  spines  are  sunken,  and  are  not  visible,  though  the 
spine  of  the  axis  can  be  felt,  and  generally  also  the  spines  of  the  third,  fourth,  and  fifth  cervical 
vertebne.  In  the  dorsal  region  the  furrow  is  shallow,  and  during  stooping  disappears,  and  then 
the  spinous  processes  become  more  or  less  visible.  The  markings  produced  by  these  spines  are 
small  and  close  together.  In  the  lumbar  region  the  furrow  is  deep,  and  the  situation  of  the  lumbar 
spines  is  frequently  indicated  by  Httle  pits  or  depressions,  especially  if  the  muscles  in  the  loins 
are  well  developed  and  the  spine  incurved.  They  are  much  larger  and  farther  apart  than  in  the 
dorsal  region.  In  the  sacral  region  the  furrow  is  shallower,  presenting  a  flattened  area  which 
terminates  below  at  the  most  prominent  part  of  the  posterior  surface  of  the  sacrum,  formed  by 
the  spinous  process  of  the  third  sacral  vertebra.  At  the  bottom  of  the  furrow  may  be  felt  the 
irregular  posterior  surface  of  the  bone.  Below  this,  in  the  deep  groove  leading  to  the  anus,  the 
coccyx  may  be  felt.  The  only  other  portions  of  the  vertebral  column  which  can  be  felt  from  the 
surface  are  the  transverse  processes  of  three  of  the  cervical  vertebrae — viz.,  the  first,  the  sixth, 
and  the  seventh.  The  transverse  process  of  the  atlas  can  be  felt  as  a  rounded  nodule  of  bone 
just  below  and  in  front  of  the  apex  of  the  mastoid  process,  along  the  anterior  border  of  the  sterno- 
mastoid.  The  transverse  process  of  the  sixth  cervical  vertebra  is  of  surgical  importance.  If 
deep  pressure  be  made  in  the  neck  in  the  course  of  the  carotid  artery,  opposite  the  cricoid  carti- 
lage, the  prominent  anterior  tubercle  of  the  transverse  process  of  the  sixth  cervical  vertebra  can 
be  felt.  This  has  been  named  Chassaignac's  tubercle,  and  against  it  the  carotid  artery  may  be 
most  conveniently  compressed  by  the  finger.  The  transverse  process  of  the  seventh  cervical 
vertebra  can  also  often  be  felt.  Occasionally  the  anterior  root,  or  costal  process,  is  large  and 
.segmented  ofi',  forming  a  cervical  rib. 

Surgical  Anatomy. — It  is  frequently  necessary  to  locate  certain  vertebrae.  Several  of  them 
can  be  easily  found  and  identified.  The  seventh  cervical  spine  is  conspicuously  prominent,  and 
when  the  skin  above  it  has  been  marked  with  a  blue  pencil  the  spine  of  the  sixth  cervical  above 
and  of  the  first  dorsal  below  may  be  located.  The  spine  of  the  third  dorsal  vertebra  is  on  a  level 
with  the  root  of  the  spine  of  the  scapula.  The  spine  of  the  fourth  lumbar  vertebra  is  on  a  level 
with  the  highest  point  of  the  iliac  crest.  When  one  or  two  vertebrae  have  been  definitely  recog- 
nized the  other  ones  can  be  found  by  counting  the  spines  from  a  fixed  point  or  from  fixed  points. 
Over  the  fifth  lumbar  spine  there  is  no  prominence,  but  a  depression.  The  third  sacral  spine 
is  on  a  level  with  the  posterior  superior  spines  of  the  ilium.  The  level  at  which  the  spinal  cord 
terminates  should  be  known  to  the  surgeon  if  he  proposes  to  tap  the  dural  sac  {lumbar  pmicture), 
for  diagnostic  or  therapeutic  purposes  or  as  a  preliminary  to  the  injection  of  cocaine  oreucaine 
(spinal  anaesthesia).  In  an  adult  the  cord  terminates  at  the  lower  border  of  the  first  lumbar 
vertebra,  and  the  dural  sac  terminates  opposite  the  body  of  the  third  sacral  vertebra.  In  a  child 
the  cprd  terminates  opposite  the  body  of  the  third  lumbar  vertebra,  and  the  dural  sac  ends  at 


70  THE  SKELETON 

about  the  same  level  as  in  an  adult.  Hence,  in  either  a  child  or  an  adult,  a  puncture  below  the 
level  of  the  fourth  lumbar  vertebra  will  inflict  no  injury  upon  the  cord.  In  children  the  puncture 
is  made  just  beneath  the  vertebral  spine,  and  in  adults  about  one-half  an  inch  to  either  side  of 
the  vertebral  spine,  although,  even  in  adults,  the  needle  is  made  to  enter  the  dura  in  the  middle 
line.  In  either  case  the  needle  is  directed  upward  and  forward.  As  previously  pointed  out,  the 
surgical  anatomy  of  an  infant's  spine  is  not  identical  with  the  surgical  anatomy  of  an  adult's 
spine.  An  infant's  spine  is  larger  comparatively  than  an  adult's  spine,  because  the  lower  limbs 
are  less  developed  in  the  former  (A.  H.  Tubby).  The  umbilicus  of  an  infant  is  opposite  the  body 
of  the  fourth  lumbar  vertebra;  in  an  adult  it  is  opposite  the  spine  of  the  third  lumbar  vertebra. 
In  an  infant  the  base  of  the  sternum  is  on  a  level  with  the  top  of  the  seventh  cervical  spine,  and 
in  an  adult  of  the  second  dorsal  spine  (A.  H.  Tubby). 

Occasionally  the  coalescence  of  the  laminae  is  not  completed,  and  consequently  a  cleft  is  left 
in  the  arches  of  the  vertebrae,  through  which  a  protrusion  of  the  spinal  membranes  (dura  mater 
and  arachnoid),  and  sometimes  of  the  spinal  cord  itself,  takes  place,  constituting  a  malformation 
known  as  s-pina  bifida  or  hydrorrhachitis.  This  disease  is  most  common  in  the  lumbosacral 
region;  but  it  may  occur  in  the  dorsal  or  cervical  region,  or  the  arches  throughout  the  whole 
length  of  the  canal  may  remain  unapproximated.  In  some  rare  cases,  in  consequence  of  the 
non-coalescence  of  the  two  primary  centres  from  which  the  body  is  formed,  a  similar  condition 
may  occur  in  front  of  the  canal,  the  bodies  of  the  vertebrae  being  found  cleft  and  the  tumor  pro- 
jecting into  the  thorax,  abdomen,  or  pelvis,  between  the  lateral  halves  of  the  bodies  affected. 

The  construction  of  the  spinal  column  of  a  number  of  pieces,  securely  connected  together 
and  enjoying  only  a  slight  degree  of  movement  between  any  two  individual  pieces,  though  per- 
mitting of  a  very  considerable  range  of  movement  as  a  whole,  allows  a  sufficient  degree  of 
mobility  without  any  material  diminution  of  strength.  The  main  joints  of  which  the  spine  is 
composed,  together  with  the  very  varied  movements  to  which  it  is  subjected,  render  it  liable  to 
strains,  which  may  complicate  other  injuries  or  may  exist  alone;  but  so  closely  are  the  individual 
vertebrae  articulated  that  these  sprains  are  seldom  severe,  and  an  amount  of  violence  sufficiently 
great  to  produce  tearing  of  the  ligaments  would  tend  to  cause  a  dislocation  or  fracture.  The 
further  safety  of  the  column  and  its  less  liability  to  injury  is  provided  for  by  its  disposition 
in  curves  instead  of  in  one  straight  line.  For  it  is  an  elastic  column,  and  must  first  bend  before 
it  breaks:  under  these  circumstances,  being  made  up  of  three  curves,  it  represents  three  columns, 
and  greater  force  is  required  to  produce  bending  of  a  short  column  than  of  a  longer  one  that  is 
equal  to  it  in  breadth  and  material.  Again,  the  safety  of  the  column  is  provided  for  by  the  inter- 
position of  the  intervertebral  disks  between  the  bodies  of  the  vertebrae,  which  act  as  admirable 
buffers  in  counteracting  the  effects  of  violent  jars  or  shocks.  Fracture  dislocation  of  the  spine 
may  be  caused  by  direct  or  indirect  violence,  or  by  a  combination  of  the  two,  as  when  a  person, 
falling  from  a  height,  strikes  against  some  prominence  and  is  doubled  over  it.  The  fractures 
from  indirect  violence  are  the  more  common,  and  here  the  bodies  of  the  vertebrae  are  compressed, 
whilst  the  arches  are  torn  asunder;  whilst  in  fractures  from  direct  violence  the  arches  are  com- 
pressed and  the  bodies  of  the  vertebrae  separated  from  each  other.  It  will  therefore  be  seen  that 
in  both  classes  of  injury  the  spinal  marrow  is  the  part  least  likely  to  be  injured,  and  may  escape 
damage  even  where  there  has  been  considerable  lesion  of  the  bony  framework.  For,  as  Mr. 
Jacobson  states,  "being  lodged  in  the  centre  of  the  column,  it  occupies  neutral  ground  in  respect 
to  forces  which  might  cause  fracture.  For  it  is  a  law  in  mechanics  that  when  a  beam,  as  of  timber, 
is  exposed  to  breakage  and  the  force  does  not  exceed  the  limits  of  the  strength  of  the  material, 
one  division  resists  compression,  another  laceration  of  the  particles,  while  the  third,  between 
the  two,  is  in  a  negative  condition."^  Applying  this  principle  to  the  spine  it  will  be  seen  that, 
v^hether  the  fracture  dislocation  be  produced  by  direct  violence  or  by  indirect  force,  one  segment, 
either  the  anterior  or  posterior,  will  be  exposed  to  compression,  the  other  to  laceration,  and  the 
intermediate  part,  where  the  cord  is  situated,  will  be  in  a  neutral  state.  When  a  fracture  dis- 
location is  produced  by  indirect  violence  the  displacement  is  almost  always  the  same,  the  upper 
segment  being  driven  for\vard  on  the  lower,  so  that  the  cord  is  compressed  between  the  body  of 
the  vertebra  below  and  the  arch  of  the  vertebra  above. 

The  parts  of  the  spine  most  liable  to  be  injured  are  (1)  the  dorso-lumbar  region,  for  this  part 
is  near  the  middle  of  the  column,  and  there  is  therefore  a  greater  amount  of  leverage,  and  more- 
over the  portion  above  is  comparatively  fixed,  and  the  vertebrae  which  form  it,  though  much 
smaller,  have  nevertheless  to  bear  almost  as  great  a  weight  as  those  below;  (2)  the  cervico-dorsal 
region,  because  here  the  flexible  cervical  portion  of  the  spine  joins  the  more  fixed  dorsal  region; 
and  (3)  the  atlanto-axial  region,  because  it  enjoys  an  extensive  range  of  movement,  and,  being 
near  the  skull,  is  influenced  by  violence  applied  to  the  head.  In  fracture  dislocation  spinous 
processes  and  portions  of  the  laminae  may  be  removed  {laminectomy)  in  order  to  free  the  cord 
from  pressure,  and  to  permit  the  surgeon  to  explore,  to  arrest  hemorrhage,  to  remove  bone 
fragments,  or  to  apply  sutures.  Laminectomy  is  also  resorted  to  in  some  cases  of  paraplegia  due 
to  Pott's  disease  of  the  spine. 

1  Holmes's  System  of  Surgery,  vol.  i.  p.  529,  1883. 


THE    OCCIPITAL    BONE 


71 


THE  SKULL. 

The  skeleton  of  the  head  is  called  the  skull.  The  cranium  is  the  skull  without 
the  mandible.  The  calvaria  or  cerebral  cranium  is  the  skull  without  the  bones  of 
the  face.  The  skull  is  supported  on  the  summit  of  the  vertebral  column,  and  is 
of  an  oval  shape,  wider  behind  than  in  front.  It  is  composed  of  a  series  of  flat- 
tened or  irregularly  shaped  bones  which,  with  one  exception  (the  lower  jaw),  are 
immovably  joined  together.  It  is  divided  into  two  parts,  the  cerebral  cranium  or 
calvaria  an^l  the  visceral  cranium  or  face,  the  former  of  which  constitutes  a  case 
for  the  accommodation  and  protection  of  the  brain,  while  opening  on  the  face 
are  the  orifices  of  the  nose  and  mouth;  between  the  cerebral  cranium  above  and 
the  face  below  the  orbital  cavities  are  situated.  The  cerebral  cranium  (xpduo^,  a 
helmet)  is  composed  of  eight  bones — viz.,  the  occipital,  two  parietal,  frontal,  two 
temporal,  sphenoid,  and  ethmoid.  The  face  is  composed  of  fourteen  bones — 
viz.,  the  two  nasal,  two  superior  maxillary,  two  lachrymal,  two  malar,  two  palate, 
two  inferior  turbinated,  vomer,  and  inferior  maxillary  or  mandible.  The  ossiculi 
auditus,  the  teeth,  and  Wormian  bones  are  not  included  in  this  enumeration. 

Occipital. 
Two  Parietal. 

''Cranium,  8  bones    .  i  m       m  i 

iwo   lemporal. 

I  Sphenoid. 

L  Ethmoid. 

Two  Nasal. 

Two  Superior  Maxillary. 

Two  Lachrymal. 

Two  Malar. 
}  Two  Palate. 

Two  Inferior  Turbinated. 

Vomer. 
L  Inferior  Maxillary  or  Mandible. 

The  Hyoid  Bone,  situated  at  the  root  of  the  tongue  and  attached  to  the  base 
of  the  skull  by  ligaments,  has  also  to  be  considered  in  this  section. 


Skull,  22  bones' 


Face,  14  bones 


THE  CEREBRAL  CRANIUM  (CRANIUM  CEREBRALE)  (THE  CALVARIA). 

The  Occipital  Bone  (Os  Occipitale). 

The  occipital  bone  (ob,  caput,  against  the  head)  is  situated  at  the  back  part 
and  base  of  the  cranium,  is  trapezoid  in  shape  and  is  much  curved  on  itself  (Fig. 
38).  It  presents  at  its  front  and  lower  part  a  large  oval  aperture,  the  foramen 
magnum  (foramen  occipitale  magnum) ,  by  which  the  cranial  cavity  communicates 
with  the  spinal  canal.  The  portion  of  bone  behind  this  opening  is  flat  and 
expanded  and  forms  the  tabula,  tabular  portion,  or  squamous  part  {squama 
occipitalis) ;  the  portion  in  front  is  a  thick,  el  ngated  mass  of  bone,  the  basilar 
process  (pars  basilaris) ;  while  on  each  side  of  the  foramen  is  situated  a  lateral 
or  condylic  portion  {pars  lateralis),  bearing  the  condyle,  by  which  the  bone  articu- 
lates with  the  atlas.  The  bone  presents  for  examination  two  surfaces,  four  borders, 
and  four  angles. 

Surfaces.  External  Surface. — The  external  surface  is  convex.  Midway  between 
the  summit  of  the  bone  and  the  posterior  margin  of  the  foramen  magnum  is  a 
prominent   tubercle,  the  inion   or  external  occipital  protuberance   {protuberantia 


72 


THE  SKELETON 


occipitalis  externa,  and,  descending  from  it  as  far  as  the  foramen,  a  vertical 
rido-e,  the  external  occipital  crest  {crista  occipitalis  externa).  This  protuberance 
and  crest  give  attachment  to  the  hgamentum  nuchre,  and  vary  in  prominence 
in  different  skulls.  Passing  outward  from  the  occipital  protuberance  is  a  semi- 
circular ridge  on  each  side,  the  superior  curved  or  superior  nuchal  line  (linea 
nuchas  superior).  Above  this  line  there  is  often  a  second  less  distinctly 
marked  ridge,  called  the  highest  curved  line  (linea  nuchce  suprema) ;  to  it  the  epi- 
cranial aponeurosis  is  attached.  The  bone  between  these  two  lines  is  smoother 
and  denser  than  the  rest  of  the  surface.  Running  parallel  with  these  from  the 
middle  of  the  crest  is  another  semicircular  ridge  on  each  side,  the  inferior  curved 
or  inferior  nuchal  line  (linea  nuchce  inferior).  The  surface  of  the  bone  above  the 
linea  suprema  is  rough  and  porous,  and  in  the  recent  state  is  covered  by  the 


lAnea 
suprema 


SUPERIOR 
CONSTRICTOR 

of  Pharynx. 


IfusvlctT  Jrrcic. 
Fig.  38. — Occipital  bone.     Outer  surface. 


Occipito-frontalis  muscle.  It  is  called  the  occipital  portion  or  the  planum 
occipitale.  The  superior  and  inferior  curved  lines,  together  with  the  surfaces  of 
bone  between  and  below  them,  serve  for  the  attachment  of  several  muscles. 
The  superior  curved  line  gives  attachment  internally  to  the  Trapezius,  externally 
to  the  muscular  origin  of  the  Occipito-frontalis,  and  to  the  Sterno-cleido-mastoid 
to  the  extent  shown  in  Fig.  38;  the  depressions  between  the  curved  lines  to  the 
Complexus  internally,  the  Splenius  capitis  and  Obliquus  capitis  superior  exter- 
nally. The  inferior  curved  line  and  the  depressions  below  it  afford  insertion  to 
the  Rectus  capitis  posticus,  major  and  minor.  The  portion  of  the  tabula  below 
the  superior  curved  line  is  called  the  nuchal  plane  (planum  nuchale) ,  and  it  gives 
attachment  to  certain  of  the  neck  muscles. 

The  foramen  magnum  (foramen  occipitale  magnum)  is  a  large,  oval  aperture,  its 
long  diameter  extending  from  before  backward.     It  transmits  the  lower  portion 


THE    OCCIPITAL    BONE  73 

of  the  medulla  oblongata  and  its  membranes,  the  spinal  accessory  nerves,  the 
vertebral  arteries,  the  anterior  and  posterior  spinal  arteries,  and  the  occipito- 
axial  ligaments.  Its  back  part  is  wide  for  the  transmission  of  the  medulla,  and 
the  corresponding  margin  rough  for  the  attachment  of  the  dura  mater  enclosing 
it;  the  fore  part  is  narrower,  being  encroached  upon  by  the  condyles;  it  has  pro- 
jecting toward  it,  from  below,  the  odontoid  process,  and  its  margins  are  smooth 
and  bevelled  internally  to  support  the  medulla  oblongata.  The  middle  of  the 
anterior  wall  of  the  foramen  magnum  is  called  by  Broca  the  basion.  The  lateral 
or  condylic  portions  {partes  laterales)  are  on  either  side  of  the  foramen  magnum 
and  bear  the  condyles  for  articulation  with  the  atlas.  Each  condyle  (condylus 
occipitalis)  is  convex,  oval,  or  reniform  in  shape,  and  directed  downward  and 
outward.  The  condyles  converge  in  front,  and  encroach  slightly  upon  the  anterior 
segment  of  the  foramen.  On  the  inner  border  of  each  condyle  is  a  rough  tubercle 
for  the  attachment  of  the  ligaments  (check)  which  connect  this  bone  with  the 
odontoid  process  of  the  axis;  while  external  to  them  is  a  rough  tubercular  promi- 
nence, the  transverse  or  jugular  process  (processus  jugularis),  channelled  in  front 
by  a  deep  notch  (incisura  jugularis),  which  forms  part  of  the  jugular  foramen 
or  foramen  laceruin  posterius.  The  under  surface  of  this  process  presents  an 
eminence  (processus  intrajugularis)  which  represents  the  paramastoid  process  of 
some  mammals.  The  eminence  is  occasionally  large,  and  extends  as  low  as  the 
transverse  process  of  the  atlas.  This  surface  affords  attachment  to  the  Rectus 
capitis  lateralis  muscle  and  to  the  lateral  occipito-atlantal  ligament;  its  upper  or 
cerebral  surface  presents  a  deep  groove  which  lodges  part  of  the  lateral  sinus, 
while  its  external  surface  is  marked  by  a  quadrilateral  rough  facet,  covered  with 
cartilage  in  the  fresh  state,  and  articulating  with  a  similar  surface  on  the  petrous 
portion  of  the  temporal  bone.  On  the  outer  side  of  each  condyle,  near  its  fore 
part,  is  a  foramen,  the  anterior  condyloid  foramen  (canalis  hypoglossi  or  the  hypo- 
glossal canal) ;  it  is  directed  downward,  outward,  and  forward,  and  transmits  the 
hypoglossal  nerve,  and  occasionally  a  meningeal  branch  of  the  ascending  pharyn- 
geal artery.  This  foramen  is  sometimes  double.  Behind  each  condyle  is  a 
fossa^  (fossa  condyloideus) ,  sometimes  perforated  at  the  bottom  by  a  foramen, 
the  posterior  condyloid  foramen  (canalis  condyloideus),  for  the  transmission  of  a 
vein  to  the  lateral  sinus.  The  basilar  process  (pars  hasilaris)  is  a  strong  quadri- 
lateral plate  of  bone,  which  is  wider  behind  than  in  front,  and  is  situated  in  front 
of  the  foramen  magnum.  Its  under  surface,  which  is  rough,  presents  in  the 
median  line  a  tubercular  ridge,  the  pharjmgeal  spine  or  tubercle  (tuherculum 
pharyngeum) ,  for  the  attachment  of  the  tendinous  raph^  and  Superior  con- 
strictor of  the  pharynx;  and  on  each  side  of  it  rough  depressions  for  the  attach- 
ment of  the  Rectus  capitis  anticus,  major  and  minor. 

Internal  Surface. — The  internal  or  cerebral  surface  (Fig.  39)  is  deeply  concave. 
The  posterior  or  tabular  part  is  divided  by  a  crucial  ridge  into  four  fossa?.  The 
two  superior  fossse  receive  the  occipital  lobes  of  the  cerebrum,  and  present  slight 
eminences  and  depressions  corresponding  to  their  convolutions.  The  two  inferior, 
which  receive  the  hemispheres  of  the  cerebellum,  are  larger  than  the  former,  and 
comparatively  smooth;  l)oth  are  marked  by  slight  grooves  for  the  lodgement  of 
arteries.  At  the  point  of  meeting  of  the  four  divisions  of  the  crucial  ridge  is  an 
eminence,  the  internal  occipital  protuberance  (protuherantia  occipitalis  interna).  It 
nearly  corresponds  to  that  on  the  outer  surface,  though  it  is  often  on  a  slightly 
higher  level,  and  is  perforated  by  one  or  more  large  vascular  foramina.  From 
this  eminence  the  superior  division  of  the  crucial  ridge  runs  upward  to  the  supe- 
rior angle  of  the  bone;  it  presents  a  deep  groove,  the  sagittal  sulcus  (sulcus  sagii- 

*  This  fossa  presents  many  variations  in  size.  It  is  usually  shallow,  and  the  foramen  small;  occasionally 
wanting  on  one  or  both  sides.  Sometimes  both  fossa  and  foramen  are  large,  but  confined  to  one  side  only; 
more  rarely,  the  fossa  and  foramen  are  very  large  on  both  sides. 


74 


THE  SKELETON 


talis),  for  the  superior  longitudinal  sinus.  The  margins  of  the  groove  give  attach- 
ment to  the  falx  cerebri.  The  inferior  division,  the  internal  occipital  crest  {crista 
occipitalis  interna),  runs  to  the  posterior  margin  of  the  foramen  magnum,  on  the 
edge  of  which  it  becomes  gradually  lost;  this  ridge,  which  is  bifurcated  below, serves 


Superior  angle. 


Inferior  angle. 
Fig.  39. — Occipital  bone.     Inner  surface. 


for  the  attachment  of  the  falx  cerebelli.  It  is  usually  marked  by  a  single  groove, 
which  commences  at  the  back  part  of  the  foramen  magnum  and  lodges  the  occip- 
ital sinus.  Occasionally  the  groove  is  double  where  two  sinuses  exist.  A 
transverse  groove  (sulcus  transversus)  passes  outward  on  each  side  to  the  lateral 
angle.  The  grooves  are  deep  channels  for  the  lodgement  of  the  lateral  sinuses,  their 
prominent  margins  affording  attachment  to  the  tentorium  cerebelli.^  At  the  point 
of  meeting  of  these  grooves  is  a  depression,  the  torcular  Herophili,^  placed  a  little 
to  one  or  the  other  side  of  the  internal  occipital  protuberance.  ]More  anteriorly 
is  the  foramen  magnum,  and  on  each  side  of  it,  but  nearer  its  anterior  than  its 
posterior  part,  the  internal  openings  of  the  anterior  condyloid  foramen.  On  the 
superior  aspect  of  the  lateral  portion  of  the  bone  the  jugular  tubercle  (tuherculum 
jugulare)  is  seen.  This  corresponds  to  the  portion  of  bone  which  roofs  in  the 
anterior  condyloid  foramen.     The  internal  openings  of  the  posterior  condyloid 

1  Usually  one  of  the  transverse  grooves  is  deeper  and  broader  than  the  other;  occasionally,  both  grooves  are 
of  equal  depth  and  breadth,  or  both  equally  indistinct.  The  broader  of  the  two  transverse  grooves  is  nearly 
always  continuous  with  the  vertical  groove  for  the  superior  longitudinal  sinus. 

-  The  columns  of  blood  coming  in  different  directions  were  supposed  to  be  pressed  together  at  this  point 
(torcular,  a  wine-press). 


THE    OCCIPITAL    BONE  75 

foramina  are  a  little  external  alid  posterior  to  the  openings  of  the  anterior  con- 
dyloid foramina,  protected  by  a  small  arch  of  bone.  At  this  part  of  the  internal 
surface  there  is  a  very  deep  groove  in  which  the  posterior  condyloid  foramen, 
when  it  exists,  has  its  termination.  This  groove  is  continuous,  in  the  complete 
skull,  with  the  transverse  groove  on  the  posterior  part  of  the  bone,  and  lodges 
the  end  of  the  same  sinus,  the  lateral.  In  front  of  the  foramen  magnum  is  the 
basilar  process,  presenting  a  shallow  depression,  the  basilar  groove  (clivus),  which 
slopes  from  behind,  upward  and  forward,  and  supports  the  medulla  oblongata 
and  part  of  the  pons  Varolii,  and  on  each  side  of  the  basilar  process  is  a  narrow 
channel,  which,  when  united  with  a  similar  channel  on  the  petrous  portion  of 
the  temporal  bone,  forms  a  groove  (sulcus  petrosus  inferior)  which  lodges  the 
inferior  petrosal  sinus. 

Borders.  Superior  Border. — The  superior  border,  lambdoidal  margin  (mar go 
lambdoideus) ,  extends  on  each  side  from  the  superior  to  the  lateral  angle,  is 
deeply  serrated  for  articulation  with  the  parietal  bone,  and  forms,  by  this  union, 
the  lambdoid  suture. 

Inferior  Border. — The  inferior  border  extends  from  the  lateral  to  the  inferior 
angle;  its  upper  half,  mastoid  margin  (margo  mastoideus) ,  is  rough,  and  articu- 
lates with  the  mastoid  portion  of  the  temporal,  forming  the  masto -occipital  suture ; 
the  inferior  half  articulates  with  the  petrous  portion  of  the  temporal,  forming 
the  petro-occipital  suture;  these  two  portions  are  separated  from  one  another  by 
the  jugular  process.  In  front  of  this  process  is  a  deep  notch,  which,  with  a 
similar  one  on  the  petrous  portion  of  the  temporal,  forms  the  jugular  foramen 
(foramen  lacerum  posterius).  This  notch  is  occasionally  subdivided  into  two 
parts  by  a  small  process  of  bone  (processus  intrajugularis) ,  and  it  generally 
presents  an  aperture  at  its  upper  part,  the  internal  opening  of  the  posterior 
condyloid*  foramen. 

Angles.  Superior  Angle .^ — The  superior  angle  is  received  into  the  interval 
between  the  posterior  superior  angles  of  the  two  parietal  bones;  it  corresponds 
with  that  part  of  the  skull  in  the  foetus  which  is  called  the  posterior  fontanelle 
(lambda). 

Inferior  Angle. — The  inferior  angle  is  represented  by  the  square-shaped  surface 
of  the  basilar  process.  At  an  early  period  of  life  a  layer  of  cartilage  separates  this 
part  of  the  bone  from  the  sphenoid, 
but  in  the  adult  the  union  between 
them  is  osseous. 

Lateral  Angles. — The  lateral  an- 
gles correspond  to  the  outer  ends  of  ^^^-l*  ^^^B^/or  ocdpitai 
the  transverse  grooves,  and  are  re-  ^^^^%'7      ""^"^^^    portion. 
ceived  into  the  interval  between  the 
posterior  inferior  angles  of  the  pari- 
etal and  the  mastoid  portion  of  the    ^^^'^^^JJ^^  0^         ^m^^i  for  each  condyloid  .  -^ 
temporal.     The  junction  of  the  oc-     separate.    \q\  )■  ^J  portion. 
cipital,  parietal,  and  temporal  bones 
was  named  the  asterion  by  Broca.                              ""g^ — —1  for  basilar  portimi.    j 

Structure. The    occipital    bone    Fig.  40.— Development  of  occipital  bone.    By  seven  centres. 

consists  of    two    compact    laminae, 

called  the  outer  and  inner  tables,  having  between  them  the  diploic  tissue;  this  bone 
is  especially  thick  at  the  ridges,  protuberances,  condyles,  and  anterior  part  of  the 
basilar  process;  while  at  the  bottom  of  the  fossae,  especially  the  inferior,  it  is  thin, 
semitransparent,  and  destitute  of  diploe. 

Development  (Fig.  40). — At  birth  the  bone  consists  of  four  distinct  parts:  a 
tabular  squamous  or  expanded  pcrtion,  which  lies  behind  the  foramen  magnum ;  two 
condylic  parts,  which  form  the  sides  of  the  foramen;  and  a  basilar  part,  which  lies 


76  THE  SKELETON 

in  front  of  the  foramen.  The  number  of  nuclei  for  the  tabular  part  vary.  As 
a  rule,  there  are  four,  but  there  may  be  only  one  (Blandin)  or  as  many  as  eight 
(Meckel).  They  appear  about  the  eighth  week  of  foetal  life,  and  soon  unite  to 
form  a  single  piece,  which  is,  however,  fissured  in  the  direction  indicated  in 
Fig.  40.  The  basilar  and  two  condyloid  portions  are  each  developed  from  a  single 
nucleus,  which  appears  a  little  later.  The  upper  portion  of  the  tabular  surface 
— that  is  to  say,  the  portion  above  the  transverse  fissure — is  developed  from  mem- 
brane, and  may  remain  separated  from  the  rest  of  the  bone  throughout  life,  when 
it  constitutes  the  interparietal  bone,  which  is  called  the  os  incae,  because  of  its  fre- 
quent occurrence  in  Peruvian  skulls.  The  rest  of  the  bone  is  developed  from 
cartilage.  At  about  the  fourth  year  the  tabular  and  the  two  condyloid  pieces 
join,  and  about  the  sixtii  year  the  bone  consists  of  a  single  piece.  At  a  later  period, 
between  the  eighteenth  and  twenty-fifth  years,  the  occipital  and  sphenoid  become 
united,  forming  a  single  bone. 

Articulations. — With  six  bones:  two  parietal,  two  temporal, sphenoid, and  atlas. 

Attachment  of  Muscles. — To  twelve  pairs:  to  the  superior  curved  line  are 
attached  the  Occipito-frontalis,  Trapezius,  and  Sterno-cleido-mastoid.  To  the 
space  between  the  curved  lines,  the  Complexus,^  Splenius  capitis,  and  Obliquus 
capitis  superior;  to  the  inferior  curved  line,  and  the  space  between  it  and  the 
foramen  magnum,  the  Rectus  capitis  posticus,  major  and  minor;  to  the  transverse 
process,  the  Rectus  capitis  lateralis;  and  to  the  basilar  process,  the  Rectus  capitis 
anticus,  major  and  minor,  and  Superior  constrictor  of  the  pharynx. 

The  Parietal  Bone  (Os  Parietale). 

The  parietal  bones  (paries,  a  wall)  are  paired  bones  and  form,  by  their  union,  the 
sides  and  roof  of  the  cerebral  cranium.  Each  bone  is  of  an  irregular  quadrilateral 
form,  and  presents  for  examination  two  surfaces,  four  borders,  and  four  angles. 

Surfaces.  External  Surface  (fades  parietalis). — The  external  surface  (Fig.  41) 
is  convex,  smooth,  and  marked  about  its  centre  by  an  eminence  called  the 
parietal  eminence  (tuber  parietale),  which  indicates  the  point  where  ossification 
commenced.  Crossing  the  middle  of  the  bone  in  an  arched  direction  are  two 
well-marked  curved  lines  or  ridges,  the  upper  and  lower  temporal  lines  or  ridges 
(linea  temporalis  superior  et  inferior);  the  former  gives  attachment  to  the  tem- 
poral fascia,  while  the  latter  indicates  the  upper  limit  of  the  origin  of  the 
Temporal  muscle.  These  lines  form  the  temporal  crest.  Above  these  ridges 
the  surface  of  the  bone  is  rough  and  porous,  and  covered  by  the  aponeurosis 
.  of  the  Occipito-frontalis ;  between  them  the  bone  is  smoother  and  more  polished 
than  the  rest;  below  them  the  bone  forms  part  of  the  temporal  fossa.  This 
portion  of  bone  is  called  the  planum  temporale,  and  affords  attachment  to  the 
Temporal  muscle.  The  superior  stephanion  is  the  intersection  of  the  upper 
temporal  ridge  with  the  coronal  suture.  The  inferior  stephanion  is  the  intersec- 
tion of  the  lower  temporal  ridge  with  the  coronal  suture.  At  the  back  part  of 
the  superior  border,  close  to  the  sagittal  suture,  is  a  small  foramen,  the  parietal 
foramen  (foramen  parietale),  which  transmits  the  emissary  vein  of  Santorini  from 
the  scalp  to  the  superior  longitudinal  sinus.  It  sometimes  also  transmits  a 
small  branch  of  the  occipital  artery.  Its  existence  is  not  constant,  and  its 
size  varies  considerably.  The  point  on  the  sagittal  suture,  between  the  parietal 
foramina,  is  the  obelion. 

Internal  or  Cerebral  Surface  (fades  cerebralis) . — The  internal  surface  (Fig.  42)  is 
concave,  presents  depressions  for  lodging  the  convolutions  of  the  cerebrum  and 
numerous  furrows,   for  the  ramifications  of  the  middle  meningeal  artery;  the 

1  To  these  the  Biventer  cervicis  should  be  added,  if  it  is  regarded  as  a  separate  muscle. 


THE  PARIETAL    BONE 


77 


Articulates 


Posterior 

superior 

angle. 


';/;'l':'''i"'",..  ^Anterior 
.,, ..■,...    -,...,     ■■'■'  J    sriperior 


Posterior 

inferior 

angle. 


FiQ.  42. — Left  parietal  bone.     Internal  surface. 


i 

-/  Anterior 
inferior 
angle. 


78  THE  SKELETON 

latter  runs  upward  and  backward  from  the  anterior  inferior  angle  and  from  the 
central  and  posterior  part  of  the  lower  border  of  the  bone.  The  depression  for 
the  middle  meningeal  artery  at  the  anterior  and  inferior  portions  of  the  cerebral 
surface  of  the  bone  is  called  the  sulcus  arteriosus.  Sometimes  a  distinct  canal 
exists  for  the  artery,  but  it  never  remains  a  canal  for  a  long  distance.  Along 
the  upper  margin  of  the  bone  is  part  of  a  shallow  groove,  which,  when  joined 
to  the  opposite  parietal,  forms  a  channel  for  the  superior  longitudinal  sinus  (the 
sulcus  sagittalis).  The  elevated  edges  of  the  groove  afford  attachment  to  the 
falx  cerebri.  Near  the  groove  are  seen  several  depressions,  Pacchionian  depressions 
(foveoloe  granulares  [Pacchioni]).  They  are  most  frequently  found  in  the  skulls 
of  old  persons,  and  lodge  the  Pacchionian  bodies.  The  internal  opening  of  the 
parietal  foramen  is  also  seen  when  that  aperture  exists.  On  the  inner  surface  of 
the  posterior  inferior  portion  of  the  bone  is  a  portion  of  the  groove  for  the  lodge- 
ment of  the  lateral  sinus  (sulcus  transversus). 

Borders.  Superior  Border. — The  superior  border,  sagittal  margin  (margo  sagit- 
talis), the  longest  and  thickest,  is  dentated  to  articulate  with  its  fellow  of  the 
opposite  side,  forming  the  sagittal  suture. 

Inferior  Border. — The  inferior  border,  squamous  margin  (margo  squamosus),  is 
divided  into  three  parts:  of  these,  the  anterior  is  thin  and  pointed,  bevelled  at 
the  expense  of  the  outer  surface,  and  overlapped  by  the  tip  of  the  great  wing 
of  the  sphenoid;  the  middle  portion  is  arched,  bevelled  at  the  expense  of  the 
outer  surface,  and  overlapped  by  the  squamous  portion  of  the  temporal;  the 
posterior  portion  is  thick  and  serrated  for  articulation  with  the  mastoid  portion 
of  the  temporal. 

Anterior  Border. — The  anterior  border,  frontal  margin  (margo  frontalis),  deeply 
serrated,  is  bevelled  at  the  expense  of  the  outer  surface  above  and  of  the  inner 
below;  it  articulates  with  the  frontal  bone,  forming  the  coronal  suture. 

Posterior  Border. — The  posterior  border,  occipital  margin  (margo  occipitalis), 
deeply  denticulated,  articulates  with  the  occipital,  forming  the  lambdoid  suture. 

Angles.  Anterior  Superior  Angle  (angulus  frontalis). — The  anterior  superior 
or  frontal  angle,  thin  and  pointed,  corresponds  with  that  portion  of  the  skull 
which  in  the  foetus  is  membranous,  and  is  called  the  anterior  fontanelle  (bregma). 

Anterior  Inferior  Angle  (angulus  sphenoidalis) . — The  anterior  inferior  or 
sphenoidal  angle  is  thin  and  lengthened,  being  received  in  the  interval  between 
the  great  wing  of  the  sphenoid  and  the  frontal.  Its  inner  surface  is  marked  by  a 
deep  groove,  sometimes  a  canal,  for  the  anterior  branch  of  the  middle  meningeal 
artery.  At  the  anterior  inferior  angle  the  parietal,  temporal,  and  frontal  bones 
and  the  greater  wing  of  the  sphenoid  bone  meet.  This  spot  is  called  the 
pterion. 

Posterior  Superior  Angle  (angulus  occipitalis) . — The  posterior  superior  or  occip- 
ital angle  corresponds  with  the  jimction  of  the  sagittal  and  lambdoid  sutures.  In 
the  foetus  this  part  of  the  skull  is  membranous,  and  is  called  the  posterior  fonta- 
nelle (lambda). 

Posterior  Inferior  Angle  (angulus  mastoideus. — The  posterior  inferior  or  mas- 
toid angle  articulates  with  the  mastoid  portion  of  the  temporal  bone,  and 
generally  presents  on  its  inner  surface  a  broad,  shallow  groove  for  lodging  part 
of  the  lateral  sinus. 

Development. — The  parietal  bone  is  formed  in  membrane,  being  developed 
by  one  centre,  which  corresponds  with  the  parietal  eminence,  and  makes  its  first 
appearance  about  the  seventh  or  eighth  week  of  foetal  life.  Ossification  gradually 
extends  from  the  centre  to  the  circumference  of  the  bone:  the  angles  are  conse- 
quently the  parts  last  formed,  and  it  is  in  their  situation  that  the  fontanelles  exist 
previous  to  the  completion  of  the  growth  of  the  bone.  Occasionally  the  parietal 
bone  is  divided  into  two  parts,  upper  and  lower,  by  an  antero-posterior  suture. 


THE    FRONTAL    BONE 


79 


Articulations. — ^Yith  five  bones:  the  opposite  parietal,  the  occipital,  frontal, 
temporal,  and  sphenoid. 
Attachment  of  Muscles. — One  only,  the  Temporal. 

The  Frontal  Bone  (Os  Frontale). 

The  frontal  bone  (frons,  the  forehead)  resembles  a  cockle-shell  in  form,  and 
consists  of  two  portions — a  vertical  or  frontal  portion,  situated  at  the  anterior 
part  of  the  cranium,  forming  the  forehead;  and  a  horizontal  or  orbital  portion, 
which  enters  into  the  formation  of  the  roof  of  the  orbits  and  nasal  fossae. 

Vertical  Portion  of  the  Frontal  Bone  (Pars  Frontalis). 

Surfaces.  External  Surface  (fades  frontalis)  (Fig.  43). — In  the  median  line, 
traversing  the  bone  from  the  upper  to  the  lower  part,  is  occasionally  seen  a 
slightly  elevated  ridge,  and  in  young  subjects  a  suture,  the  frontal  (metopic) 
suture,  which   represents  the  line  of  union  of  the  two  lateral  halves  of  which  the 


,  ,„  -  ,  External 

m  angtdar  process.        angular  process. 

Nasal  i   spine. 

Fig.  43. — Frontal  bone.     Outer  surface. 

bone  consists  at  an  early  period  of  life;  in  the  adult  this  suture  is  usually  oblit- 
erated and  the  bone  forms  one  piece;  traces  of  the  obliterated  suture  are,  how- 
ever, generally  perceptible  at  the  lower  part.  On  either  side  of  this  ridge,  a  little 
below  the  centre  of  the  bone,  is  a  rounded  eminence,  the  frontal  eminence  (tuber 
frontale).  These  eminences  vary  in  size  in  different  individuals,  and  are  occa- 
sionally unsymmetrical  in  the  same  subject.  They  are  especially  prominent  in 
cases  of  well-marked  cerebral  development.  The  whole  surface  of  the  bone 
above  this  part  is  smooth,  and  covered  by  the  aponeurosis  of  the  Occipito- 
frontalis  muscle.     Below  the  frontal  eminence  and  separated  from  it  by  a  slight 


go  THE   SKELETON 

groove  is  the  superciliary  ridge  (arcus  swperciliaris) ,  broad  internally,  where  it 
is  continuous  with  the  nasal  eminence,  but  less  distinct  as  it  arches  outward. 
These  ridges  are  caused  by  the  projection  outward  of  the  frontal  air  sinuses,^ 
and  give  attachment  to  the  Orbicularis  palpebrarum  and  Corrugator  supercilii. 
Between  the  two  superciliary  ridges  is  a  smooth,  flat  surface,  the  glabella. 
Nearly  corresponding  with  the  glabella  is  the  ophryon,  a  point  in  the  mid-line 
on  a  level  with  the  upper  border  of  the  eyebrows,  which  is  the  centre  of  the 
narrowest  transverse  diameter  of  the  forehead.  Beneath  the  superciliary  ridge 
is  the  orbital  margin  or  supraorbital  arch  (margo  supraorbitalis) ,  a  curved  and 
prominent  margin,  which  forms  the  upper  boundary  of  the  orbit  and  separates 
the  vertical  from  the  horizontal  portion  of  the  bone.  The  outer  part  of  the 
arch  is  sharp  and  prominent,  affording  to  the  eye,  in  that  situation,  considerable 
protection  from  injury;  the  inner  part  is  less  prominent.  At  the  junction  of  the 
internal  and  middle  third  of  this  arch  is  a  notch,  sometimes  converted  into  a 
foramen,  and  called  the  supraorbital  notch  or  foramen  (incisura  supraorbitalis  or 
foramen  supraorbitale) .  It  transmits  the  supraorbital  artery,  vein,  and  nerve.  A 
small  aperture  is  seen  in  the  upper  part  of  the  notch,  which  transmits  a  vein 
from  the  diploe  to  join  the  supraorbital  vein.  To  the  median  side  of  the 
supraorbital  notch  there  is  often  a  notch  (incisura  frontalis)  for  the  passage 
of  the  frontal  artery  and  frontal  nerve.  The  supraorbital  arch  terminates 
externally  in  the  external  angular  process  (processus  zygomaticus)  and  internally 
in  the  internal  angular  process.  The  external  angular  process  is  strong,  prominent, 
and  articulates  with  the  malar  bone;  running  upward  and  backward  from  it  are 
two  well-marked  lines,  which,  commencing  together  from  the  external  angular 
process  as  the  temporal  ridge,  crest  or  line  (linea  temporalis),  soon  diverge  from 
each  other  and  run  in  a  curved  direction  across  the  bone.  These  are  the 
upper  and  lower  temporal  ridges;  the  upper  gives  attachment  to  the  temporal 
fascia,  the  lower  to  the  Temporal  muscle.  Beneath  them  is  a  slight  concavity 
that  forms  the  anterior  part  of  the  temporal  fossa  and  gives  origin  to  the 
Temporal  muscle.  The  internal  angular  processes  are  less  marked  than  the 
external,  and  articulate  with  the  lachrymal  bones.  Between  the  internal  angular 
processes  is  a  rough,  uneven  interval,  the  nasal  notch,  which  articulates  in  the 
middle  line  with  the  nasal  bone,  and  on  either  side  with  the  nasal  process  of  the 
superior  maxillary  bone.  From  the  concavity  of  this  notch  projects  a  process, 
the  nasal  process,  which  extends  beneath  the  nasal  bones  and  nasal  processes  of 
the  superior  maxillary  bones  and  supports  the  bridge  of  the  nose.  On  the  under 
surface  of  this  is  a  long,  pointed  process,  the  nasal  or  frontal  spine  (spina  nasalis 
or  frontalis),  and  on  either  side  a  small  grooved  surface  enters  into  the  formation 
of  the  roof  of  the  nasal  fossa.  The  nasal  spine  forms  part  of  the  septum  of  the 
nose,  articulating  in  front  with  the  nasal  bones  and  behind  with  the  perpen- 
dicular plate  of  the  ethmoid.  The  junction  of  the  nasal  and  frontal  bones  is 
called  the  nasion. 

Internal  Surface  (cerebral  surface,  fades  cerebralis)  (Fig.  44). — Along  the  middle 
line  is  a  vertical  groove,  the  sulcus  sagittalis,  the  edges  of  which  unite  below  to 
form  a  ridge,  the  frontal  crest  (crista  frontalis) ;  the  groove  lodges  the  superior 
longitudinal  sinus,  whilst  its  margins  afford  attachment  to  the  falx  cerebri.  The 
crest  terminates  below  at  a  small  notch  which  is  converted  into  a  foramen  by 
articulation  with  the  ethmoid.  It  is  called  the  foramen  caecum,  and  varies  in 
size  in  different  subjects:  it  is  sometimes   partially  or  completely  impervious, 

1  Some  confusion  is  occasioned  to  students  commencing  the  study  of  anatomy  by  the  name  "  sinuses  "  having 
been  given  to  two  perfectly  different  kinds  of  spaces  connected  with  the  skull.  It  may  be  as  well,  therefore,  to 
state  here  at  the  outset,  that  the  "  sinuses  "  in  the  interior  of  the  cranium  which  produce  the  grooves  on  the 
mner  surface  of  the  bones  are  venous  channels  along  which  the  blood  runs  in  its  passage  back  from  the  brain, 
wbile  the  "sinuses  "  external  to  the  cranial  cavity  (the  frontal  sphenoidal,  ethmoidal,  and  maxillary)  are  hollow 
spaces  m  the  bones  themselves  which  communicate  with  the  nostrils,  and  contain  air. 


THE    FRONTAL    BONE 


81 


lodges  a  process  of  the  falx  cerebri,  and  when  open  transmits  a  vein  from  the 
Hning  membrane  of  the  nose  to  the  superior  longitudinal  sinus.  On  either 
side  of  the  groove  the  bone  is  deeply  concave,  presenting  depressions  for  the 
convolutions  of    the  brain,  and  numerous  small  furrows  for  lodging    the  rami- 


With  superior  maxillary! 

With  na^al' 

I 
With  perpendicular  plate  of  ethmoid. 

Fig.  44. — Frontal  bone. 


Frontal  sinus. 


Under  surface  of  nasal  process, 
forming  part  of  roof  of  nose. 
Inner  surface. 


fications  of  the  anterior  branches  of  the  middle  meningeal  arteries.  Several 
small  irregular  fossie  are  seen  also  on  either  side  of  the  groove,  for  the  reception 
of  the  Pacchionian  bodies. 

Border. — The  border  of  the  vertical  portion  is  thick,  strongly  serrated,  bevelled 
at  the  expense  of  the  internal  table  above,  where  it  rests  upon  the  parietal  bones, 
and  at  the  expense  of  the  external  table  at  each  side,  where  it  receives  the  lateral 
pressure  of  those  bones;  this  border  is  continued  below  into  a  triangular  rough 
surface  which  articulates  with  the  great  wing  of  the  sphenoid. 

Structure. — The  vertical  portion  and  external  angular  processes  are  very  thick, 
consisting  of  diploic  tissue  contained  between  two  compact  laminae. 

Horizontal  or  Orbital  Portion  of  the  Frontal  Bone  (Pars  Orbitalis). 

This  portion  of  the  bone  consists  of  two  thin  plates,  the  orbital  plates,  which 
form  the  vault  of  the  orbit,  separated  from  one  another  by  a  median  gap,  the 
ethmoidal  notch. 

Surfaces.  External  Surface. — The  inferior  or  external  surface  of  each  orbital 
plate  (fades  orbitalis)  consists  of  a  smooth,  concave,  triangular  lamina  of  bone, 
marked  at  its  anterior  and  external  part  (immediately  beneath  the  external 
angular  process)  by  a  shallow  depression,  the  lachrymal  fossa  (fossa  glandular 
lacrimalis)  for  lodging  the  lachrymal  gland;  and  at  its  anterior  and  internal  part 

6 


82 


THE   SKELETON 


by  a  depression  (sometimes  a  small  tubercle),  the  trochlear  fossa  (fovea  trochlearis) , 
for  the  attachment  of  the  cartilaginous  pulley  of  the  Superior  oblique  muscle  of 
the  eye.  The  ethmoidal  notch  (incisura  ethmoidalis)  separates  the  two  orbital 
plates;  it  is  quadrilateral,  and  filled  up,  when  the  bones  are  united,  by  the  cribri- 
form plate  of  the  ethmoid.  The  margins  of  this  notch  present  several  half-cells, 
which,  when  united  with  corresponding  half-cells  on  the  upper  surface  of  the  eth- 
moid, complete  the  ethmoidal  cells ;  two  grooves  are  also  seen  crossing  these  edges 
transversely;  they  are  converted  into  canals  by  articulation  with  the  ethmoid,  and 
are  called  the  anterior  and  posterior  ethmoidal  foramina  or  canals  {foramen  ethmoi- 
dale  anterius  and  foramen  ethmoidale  posterius) :  they  open  on  the  inner  wall  of  the 
orbit.  The  anterior  one  transmits  the  nasal  nerve  and  anterior  ethmoidal  vessels, 
the  posterior  one  the  posterior  ethmoidal  vessels.  In  front  of  the  ethmoidal 
notch,  on  each  side  of  the  nasal  spine,  is  the  opening  of  the  frontal  air  sinus  (sinus 
frontalis).  These  are  two  irregular  cavities,  which  extend  upward  and  outward,  a 
variable  distance,  between  the  two  tables  of  the  skull,  and  are  separated  from  one 
another  by  a  thin,  bony  septum  (septum  sinuum  frontalium) ,  which  is  often  dis- 
placed to  one  side.  Within  the  sinuses  imperfect  trabeculffi  of  bone  often  exist.  The 
sinuses  are  beneath  and  give  rise  to  the  prominences  above  the  supraorbital  arches 
called  the  superciliary  ridges  (arcus  superciliares) .  The  frontal  air  sinuses  are  absent 
at  birth,  become  apparent  about  the  seventh  year  of  life,  and  from  this  period  until 
the  age  of  twenty  increase  gradually  in  size.  Sometimes,  however,  the  sinuses 
remain  very  small  or  never  develop  at  all — or  one  side  may  be  large  and  the  other 
small — or  one  may  exist  on  one  side  and  be  absent  on  the  other.^  The  right  sinus 
is  usually  the  larger.  These  cavities  are  larger  in  men  than  in  women.  The  floor 
of  each  sinus  is  very  thin  and  is  over  the  orbit  and  the  upper  border  of  the  lateral 
mass  of  the  ethmoid.  The  thinnest  portion  of  the  floor  is  at  the  upper  and 
inner  angle  of  the  orbit,  and  at  this  point  pus  is  apt  to  point  in  cases  of 
empyema  of  the  sinus.  The  frontal  sinuses  are  lined  by  mucous  membrane 
and  each  sinus  communicates  with  the  middle  meatus  of  the  nose  by  the  infun- 
dibulum  and  part  of  the  semilunar  hiatus.  In  some  cases  the  sinuses  commu- 
nicate with  each  other  by  means  of  an  aperture  in  the  septum  and  occasionally 
join  the  sinus  in  the  crista  galli  of  the  ethmoid.^ 

Internal  Surface  (cerebral  surface,  fades  cerebralis). — The  internal  surface  of 
the  horizontal  portion  presents  the  convex  upper  surfaces  of  the  orbital  plates, 

separated  from  each  other  in  the  mid- 
dle line  by  the  ethmoidal  notch,  and 
marked  by  eminences  and  depressions  for 
the  convolutions  of  the  frontal  lobes  of 
the  brain. 

Border. — The  border  of  the  horizontal 
portion  is  thin,  serrated,  and  articulates 
with  the  lesser  wing  of  the  sphenoid. 

Structure. — The  horizontal  portion  is 
thin,  translucent,  and  composed  entirely 
of  compact  tissue;  hence  the  facility  with 
which  instruments  can  penetrate  the 
cranium  through  this  part  of  the  orbit. 

Development  (Fig.  45).— The  frontal 

bone    is    formed    in    membrane,  being 

developed  by  two  centres,  one  for  each  lateral  half,  which  make  their  appearance 

about  the  seventh  or  eighth  week,  above  the  orbital  arches.     From  this  point 

ossification  extends,  in  a  radiating  manner,  upward  into  the  forehead  and  back- 


FiG.  45. — Frontal  bone  at  birth.      Developed  by 
two  lateral  halves. 


'  Dr.  D.  Kerfoot  Shute.     Article  on  the  Skull,  in  Reference  Handbook  of  the  Medical  Sciences. 


Ibid. 


THE    TEMPORAL    BONE 


83 


ward  over  the  orbit.  At  birth  the  bone  consists  of  two  pieces,  which  afterward 
become  united,  along  the  middle  line,  by  a  suture  which  runs  from  the  vertex 
to  the  root  of  the  nose.  This  suture  usually  becomes  obliterated  within  a  few 
years  after  birth;  but  it  occasionally  remains  throughout  life,  constituting  the 
metopic  suture.  Secondary  centres  of  ossification  appear  for  the  nasal  spine — 
one  on  either  side  of  the  internal  angular  process  where  it  articulates  with  the 
lachrymal  bone;  and  sometimes  there  is  one  on  either  side  at  the  lower  end  of 
the  coronal  suture.  This  latter  centre  sometimes  remains  ununited,  and  is 
known  as  the  pterion  ossicle,  or  it  may  join  with  the  parietal,  sphenoid,  or  tem- 
poral bone. 

Articulations. — With  twelve  bones:  two  parietal,  the  sphenoid,  the  ethmoid, 
two  nasal,  two  superior  maxillary,  two  lachrymal,  and  two  malar. 

Attachment  of  Muscles. — To  three  pairs:  the  Corrugator  supercilii,  Orbicu- 
laris palpebrarum,  and  Temporal,  on  each  side. 

The  Temporal  Bone  (Os  Temporale). 

The  temporal  ones  (tempus,  time)  are  paired  liones,  situated  at  the  sides  and 
base  of  the  skull.  Each  presents  for  examination  a  squamous,  mastoid,  and  petrous 
portion. 

Squamous  Portion  of  the  Temporal  Bone  (Squama  Temporalis) . 

The  squamous  portion  (squama,  a  scale),  the  anterior  and  upper  part  of  the 
bone,  is  scale-like  in  form,  and  thin  and  translucent  in  texture  (Fig.  46). 


SQUAMOUS  SUTURE 


SULCUS  ron  middle 

TEMPORAL  ARTERY 


REMAINS  OF 
SQUAMOSO- 
MASTOID 


X  OF  PETROUS 
PORTION 


MASTOID 
FORAMEN 


MASTOID 
PORTION 

EXTERNAL  AUDITORY  MEATUS      TYMPANIC  PORTION 

Fig.  46. — Right  temporal  bone,  from  without.     (Spaltebolz.) 

Surfaces.  Outer  Surface  (fades  temporalis) . — Its  outer  surface  is  smooth,  convex, 
and  grooved  at  its  back  part  for  the  middle  or  deep  temporal  artery  {sulcus  a. 
temporalis  media');  it  affords  attachment  to  the  Temporal  muscle  and  forms  part 
of  the  temporal  fossa.  At  its  back  part  may  be  seen  a  curved  ridge — part  of  the 
temporal  ridge  or  line;  it  serves  for  the  attachment  of  the  temporal  fascia  and 


84  THE  SKELETON 

limits  the  origin  of  the  Temporal  muscle.  The  boundary  between  the  squamous 
and  mastoid  portions  of  the  bone,  as  indicated  by  traces  of  the  original  suture, 
lies  fully  half  an  inch  below  this  ridge.  Projecting  from  the  lower  part  of  the 
squamous  portion  is  a  long,  arched  process  of  bone,  the  zygoma  or  zygomatic 
process  (processus  zygomaticus).  This  process  is  at  first  directed  outward,  its 
two  surfaces  looking  upward  and  downward;  it  then  appears  as  if  twisted 
upon  itself,  and  runs  forward,  its  surfaces  now  looking  inward  and  outward. 
The  superior  border  of  the  process  is  long,  thin,  and  sharp,  and  serves  for  the 
attachment  of  the  temporal  fascia.  The  inferior,  short,  thick,  and  arched,  has 
attached  to  it  some  fibres  of  the  Masseter  muscle.  Its  outer  surface  is  convex 
and  subcutaneous;  its  inner  is  concave,  and  also  affords  attachment  to  the 
Masseter.  The  extremity,  broad  and  deeply  serrated,  articulates  with  the  malar 
bone.  The  zygomatic  process  is  connected  to  the  temporal  bone  by  three  divi- 
sions, called  its  roots — an  anterior,  middle,  and  posterior.  The  anterior,  which 
is  short,  but  broad  and  strong,  is  directed  inward,  to  terminate  in  a  rounded 
eminence,  the  eminentia  articularis  or  articular  eminence  (tuberculum  articulare) 
(Fig.  46).  This  eminence  forms  the  front  boundary  of  the  glenoid  or  mandibular 
fossa  (fossa  Tnandihularis),  and  in  the  recent  state  is  covered  with  cartilage. 
The  middle  root  is  known  as  the  post-glenoid  process  or  tubercle,  and  is  very 
prominent  in  young  bones.  It  separates  the  mandibular  portion  of  the  glenoid 
fossa  from  the  external  auditory  meatus,  and  terminates  at  the  commencement 
of  a  well-marked  fissure,  the  Glaserian  (petro-tympanic)  fissure  (fissura  petro- 
tympanica  [Glaseri]).  The  posterior  root,  which  is  strongly  marked,  runs  from 
the  upper  border  of  the  zygoma  backward  over  the  external  auditory  meatus. 
It  is  termed  the  supramastoid  or  temporal  crest,  and  forms  part  of  the  lower 
temporal  ridge.  At  the  junction  of  the  anterior  root  with  the  zygoma  is  a 
projection,  called  the  tubercle,  for  the  attachment  of  the  external  lateral  liga- 
ment of  the  lower  jaw;  and  between  the  anterior  and  middle  roots  is  an  oval 
depression,  forming  part  of  the  glenoid  (Tnandihular)  fossa  (ylrjvri,  a  socket),  for 
the  reception  of  the  condyle  of  the  lower  jaw.  This  fossa  is  bounded,  in  front, 
by  the  eminentia  articularis;  behind,  by  the  tympanic  plate,  which  separates  it 
from  the  external  auditory  meatus;  it  is  divided  into  two  parts  by  a  narrow  slit, 
the  Glaserian  or  petro -tympanic  fissure.  The  anterior  or  mandibular  part,  formed 
by  the  squamous  portion  of  the  bone,  is  smooth,  covered  in  the  recent  state  with 
cartilage,  and  articulates  with  the  condyle  of  the  lower  jaw.  This  part  of  the 
glenoid  fossa  presents  posteriorly  a  small  conical  eminence,  the  post-glenoid 
process,  already  referred  to.  This  process  is  the  representative  of  a  prominent 
tubercle  which,  in  some  of  the  mammalia,  descends  behind  the  condyle  of  the 
jaw,  and  prevents  it  being  displaced  backward  during  mastication  (Humphry). 
The  posterior  part  of  the  glenoid  fossa,  which  lodges  a  portion  of  the  parotid 
gland,  is  formed  chiefly  by  the  tympanic  plate,  which  constitutes  the  anterior 
wall  of  the  tympanum  and  external  auditory  meatus.  The  plate  of  bone  termi- 
nates above  in  the  Glaserian  fissure,  and  below  forms  a  sharp  edge,  the  vaginal 
process  of  the  styloid  (vagina  processus  styloidei),  which  gives  origin  to  some  of 
the  fibres  of  the  Tensor  palati  muscle.  The  Glaserian  fissure,  which  leads  into 
the  tympanum,  lodges  the  processus  gracilis  of  the  malleus,  and  transmits  the 
tympanic  branch  of  the  internal  maxillary  artery.  The  chorda  tympani  nerve 
passes  through  a  separate  canal,  parallel  to  the  Glaserian  fissure,  the  canal  of 
Huguier  (canaliculus  chorda^  tympani),  on  the  outer  side  of  the  Eustachian 
tube,  in  the  retiring  angle  between  the  squamous  and  petrous  portions  of  the 
temporal  bone.^    Between  the  posterior  bony  wall  of  the  external  auditory  meatus 

^  This  small  fissure  must  not  be  confounded  with  the  large  canal  which  lies  above  the  Eustachian  tube  and 
transmits  the  Tensor  tympani  muscle. 


THE    TEMPORAL    BONE 


85 


and  the  posterior  root  of  the  zygoma  is  the  area  called  the  suprameatal  triangle  of 
Prof.  Macewen.  Through  this  space  the  surgeon  pushes  the  gauge  in  order  to 
carry  it  into  the  antrum  of  the  mastoid  process. 

Internal  Surface  (cerebral  surface,  fades  cerebralis). — The  internal  surface  of 
the  squamous  portion  (Fig.  47)  is  concave,  presents  numerous  eminences  and 
depressions  for  the  convolutions  of  the  cerebrum,  and  two  well-marked  grooves 
for  the  branches  of  the  middle  meningeal  artery. 


parietal 


Aqiixductus  vestibuli. 

Depression  for  dura  mater 

Meatus  auditorius  internus. 


Eminence  for  superior  semicircular  canal. 
Hiatus  Fallopii. 

Opening  for  smaller  petrosal  nerve. 
Depression  for  Gasserian  Ganglion. 
Bristle  passed  through  carotid  canal. 


Fig.  47. — Left  temporal  bone.     Inner  surface.  , 

Borders.  Superior  Border. — The  superior  border,  parietal  margin  (margo 
parietalis),  is  thin,  bevelled  at  the  expense  of  the  internal  surface,  so  as  to 
overlap  the  lower  border  of  the  parietal  bone,  forming  the  squamous  suture. 

Anterior  Inferior  Border. — The  anterior  inferior  border,  sphenoidal  margin  (margo 
sphenoidal  is),  is  thick,  serrated,  and  bevelled,  alternately  at  the  expense  of  the 
inner  and  outer  surfaces,  for  articulation  with  the  great  wing  of  the  sphenoid. 

Posterior  Inferior  Border. — The  posterior  inferior  border,  occipital  margin 
(margo  occipitalis),  is  serrated  and  articulates  with  the  occipital  bone. 

The  Mastoid  Portion  of  the  Temporal  Bone  (Pars  Mastoidea) . 

The  mastoid  portion  (/mazo^,  a  nipple  or  teat)  is  situated  at  the  posterior  part 
of  the  bone  (Figs.  46,  48,  and  49). 

Surfaces.  Outer  Surface. — The  outer  surface  of  the  mastoid  is  rough,  and 
gives  attachment  to  the  Occipito-frontalis  and  Retrahens  aurem  muscles.  It 
is  perforated  by  numerous  foramina;  one  of  these,  of  large  size,  situated  at  the 
posterior  border  of  the  bone,  is  termed  the  mastoid  foramen  (foramen  mastoideum) ; 
it  transmits  a  vein  to  the  lateral  sinus  and  a  small  artery  from  the  occipital  to 
supply  the  dura  mater.  The  position  and  size  of  this  foramen  are  very  variable. 
It  is  not  always  present;  sometimes  it  is  situated  in  the  occipital  bone  or  in  the 
suture  between  the  temporal  and  the  occipital.    The  mastoid  portion  is  con- 


86 


THE   SKELETON 


tinned  below  into  a  conical  projection,  the  mastoid  process  (processus  mastoideus) , 
the  size  and  form  of  which  vary  somewhat.  Tlie  mastoitl  process  begins  to 
develop  during  the  second  year  and  does  not  attain  full  size  until  after  puberty. 
This  process  serves  for  the  attachment  of  the  Sterno-mastoid,  Splenius  capitis, 
and  Trachelo-mastoid  muscles.  On  the  inner  side  of  the  mastoid  process  is  a 
deep  groove,  the  digastric  fossa  (incisura  mastoidea),  for  the  attachment  of  the 
Digastric  muscle;  and,  running  parallel  with  it,  but  more  internal,  the  occipital 
groove  (sidcus  a.  occipitalis),  which  lodges  the  occipital  artery.  The  suprameatal 
triangle  of  Prof.  Macewen  is  bounded  by  the  posterior  root  of  the  zygoma,  the 
posterior  bony  wall  of  the  external  auditory  meatus,  and  an  imaginary  line  join- 
ing these  two.  Through  this  triangle  the  surgeon  enters  his  instrument  in  order 
to  reach  the  mastoid  antrum.  Behind  the  suprameatal  spine  is  a  depression 
known  as  the  mastoid  fossa  [fossa  mastoidea),  which  contains  numerous  small 
openings  for  bloodvessels. 


Tensor  tympani. 
Proc.  cochleariformis. 

Eustachian  tube, 
'arotid  canal. 


Carotid  canw 
Fenestra  rotunda. 

Pyramid, 


Aqueductus  Fallopii. 
Marrow  cells. 


Fig.  48.- 


-Section  through  the  petrous  and  mastoid  portions  of  the  temporal  bone,  showing  the  communication 
•  of  the  cavity  of  the  tympanum  with  the  mastoid  antrum. 


Internal  Surface. — The  internal  surface  of  the  mastoid  portion  presents  a  deep, 
curved  groove,  the  sigmoid  fossa  or  sulcus  (sulcus  sigmoideus) ,  which  lodges  part 
of  the  lateral  sinus;  and  into  it  may  be  seen  opening  the  mastoid  foramen, 
which  transmits  an  emissary  vein  from  the  lateral  sinus  to  the  posterior  auricular 
or  occipital  vein  and  a  small  artery,  the  mastoid  branch  of  the  occipital  artery 
(ramus  mastoideus) .  The  groove  for  the  lateral  sinus  is  separated  from  the  inner- 
most of  the  mastoid  air-cells  by  only  a  thin  lamina  of  bone,  and  even  this  may  be 
partly  deficient.  A  section  of  the  mastoid  process  (Figs.  48  and  49)  shows  it  to  be 
hollowed  out  into  a  number  of  cellular  spaces,  communicating  with  each  other, 
called  the  mastoid  cells  (cellules  mastoidece),  which  exhibit  the  greatest  possible 
variety  as  to  their  size  and  number,  and  which  do  not  exist  at  birth,  but  develop 
with  the  growth  of  the  mastoid  process.  At  the  upper  and  front  part  of  the 
bone  these  cells  are  large  and  irregular,  and  contain  air.  They  diminish  in  size 
toward  the  lower  part  of  the  bone,  those  situated  at  the  apex  of  the  mastoid 
process  being  quite  small  and  usually  containing  marrow.  These  pneumatic 
cells  extend  far  beyond  the  mastoid.    Some  may  reach  the  floor  of  the  Eustachian 


THE    TEMPORAL    BONE 


87 


canal;  others  the  jugular  portion  of  the  occipital  bone;  others  the  roof  of  the 
external  auditory  canal,  and  some  pass  up  toward  the  squamous  portion.^  Occa- 
sionally they  are  entirely  absent,  and  the  mastoid  is  solid  throughout.  In  addi- 
tion to  these  pneumatic  cells  may  be  seen  a  large,  irregular  cavity  (Figs.  48  and 
49),  situated  at  the  upper  and  front  part  of  the  section.  It  is  called  the  mastoid  or 
tympanic  antrum  (antrum  tympanicum) ,  and  must  be  distinguished  from  the  mas- 
toid cells,  though  it  communicates  with  them.  The  mastoid  cells  are  not  developed 
until  after  puberty,  but  the  mastoid  antrum  is  almost  as  large  at  birth  as  it  is  in 
the  adult. 

It  is  filled  with  air,  and  is  lined  with  a  prolongation  of  the  mucous  membrane 
of  the  tympanum,  which  extends  into  it  through  an  opening,  by  which  it  com- 
municates with  the  cavity  of  the  tympanum.  The  mastoid  antrum  is  bounded 
above  by  a  thin  plate  of  bone,  the  tegmen  tympani,  which  separates  it  from  the 
middle  fossa  of  the  base  of  the  skull  on  the  anterior  surface  of  the  petrous  portion 


PROMINENCE  OVER 
SEMICIRCULAR   CANAL 


FENESTRA  OVALIS 
OR  VCSTIBULI 


PROCESSUS 
COCHLEARIFORMIS 

AQUEDUCT  of/ 

FALLOPIUS 

SEPTUM    OF 
EUSTACHIAN  TUBE 


PROBE  IN 
TYMPANIC 
CANAL 


Fig.  49. — Right  temporal  bone  cut  open.     Lateral  view  of  medial  half  of  bone.     X  2.     (Spalteholz.) 

of  the  temporal  bone;  below  by  the  mastoid  process;  externally  by  the  squamous 
portion  of  the  bone  just  below  the  supramastoid  crest;  and  internally  by  the 
external  semicircular  canal  of  the  internal  ear,  which  projects  into  its  cavity. 
The  opening  by  which  it  communicates  with  the  tympanum  is  situated  at  the 
superior  internal  angle  of  the  posterior  wall  of  that  cavity;  it  is  a  triangular 
opening  into  that  portion  of  the  tympanic  cavity  which  is  known  as  the  tympanic 
attic  or  epitympanic  recess  or  space  (aditus  ad  antrum) — that  is  to  say,  that 
portion  of  the  tympanum  which  is  above  the  level  of  the  membrana  tympani. 

In  consequence  of  the  communication  which  exists  between  the  tympanum  and  mastoid  cells, 
mflammation  of  the  lining  membrane  of  the  former  cavity  may  easily  travel  backward  to  that 
of  the  antrum,  leading  to  caries  and  necrosis  of  their  walls  and  the  risk  of  transference  of  the 
inflammation  to  the  lateral  sinus  or  encephalon. 


'  Dr.  D.  Kerfoot  Shute,  in  Reference  Handbook  of  the  Medical  Sciences.- 


88  THE  SKELETON 

Borders.  Superior  Border. — The  superior  border  of  the  mastoid  portion  is 
broad  and  rough,  its  serrated  edge  sloping  outward,  for  articulation  with  the 
posterior  inferior  angle  of  the  parietal  bone. 

Posterior  Border. — The  posterior  border,  also,  uneven  and  serrated,  articu- 
lates with  the  inferior  border  of  the  occipital  bone  between  its  lateral  angle  and 
jugular  process. 

The  Petrous  Portion  of  the  Temporal  Bone  (Pars  Petrosa  [Pyramis])  (Fig.  47). 

The  petrous  portion  (Trsrpo^,  a  stone),  so  named  from  its  extreme  density  and 
hardness,  is  a  pyramidal  process  of  bone  wedged  in  at  the  base  of  the  skull 
between  the  sphenoid  and  occipital  bones.  Its  direction  from  without  is  inward, 
forward,  and  a  little  downward.  It  presents  for  examination  a  base,  an  apex, 
three  surfaces,  and  three  borders,  and  contains,  in  its  interior,  the  essential  parts 
of  the  organ  of  hearing. 

Base. — The  base  is  applied  against  the  internal  surface  of  the  squamous  and 
mastoid  portions,  its  upper  half  being  concealed;  but  its  lower  half  is  exposed 
by  the  divergence  of  those  two  portions  of  the  bone,  which  brings  into  view  the 
oval,  expanded  orifice  of  a  canal  leading  into  the  tympanum,  the  meatus  audi- 
torius  externus  {meatus  acusticu^  externus).  The  curved  tympanic  plate  or  part 
{fars  tympanica)  forms  the  anterior  wall,  the  floor,  and  a  part  of  the  posterior 
wall  of  this  meatus,  while  the  squamous  portion  of  the  temporal  completes  it 
above  and  behind.  The  entrance  to  the  meatus  is  bounded  throughout  the 
greater  part  of  its  circumference  by  the  auditory  process,  which  is  the  name 
applied  to  the  free  rough  margin  of  the  tympanic  plate,  and  which  gives  attach- 
ment to  the  cartilaginous  portion  of  the  meatus.  Superiorly  tlie  entrance  to 
the  meatus  is  limited  by  the  posterior  root  of  the  zygoma.  At  the  upper  and 
posterior  portion  of  the  bony  meatus  is  a  spine  of  bone  known  as  the  suprameatal 
spine  or  spine  of  Henle  (spina  suprameatum) ,  which  is  a  valuable  surgical  land- 
mark.    In  most  skulls  it  is  distinctly  marked. 

Apex  {apex  pyramidis). — The  apex  of  the  petrous  portion,  rough  and  uneven, 
is  received  into  the  angular  interval  between  the  posterior  border  of  the  greater 
wing  of  the  sphenoid  and  the  basilar  process  of  the  occipital;  it  presents  the  anterior 
or  internal  orifice  of  the  carotid  canal  (foramen  caroticum  internum) ,  and  forms 
the  posterior  and  external  boundary  of  the  foramen  lacerum  medium. 

Surfaces.  Anterior  Surface  (fades  anterior  pyramidis). — The  anterior  surface 
of  the  petrous  portion  (Fig.  47)  forms  the  posterior  part  of  the  middle  fossa  of 
the  skull.  This  surface  is  continuous  with  the  squamous  portion,  to  which  it  is 
united  by  a  suture,  the  petro-squamous  suture,  the  remains  of  which  are  distinct  even 
at  a  late  period  of  life.  It  presents  six  points  for  examination:  (1)  An  eminence 
{eminentia  arcuata)  near  the  centre,  which  indicates  the  situation  of  the 
superior  semicircular  canal.  (2)  In  front  and  a  little  to  the  outer  side  of  this 
eminence  a  depression  indicating  the  position  of  the  tympanum ;  here  the  layer 
of  bone  which  separates  the  tympanum  from  the  cranial  cavity  is  extremely  thin, 
and  is  known  as  the  tegmen  tympani.  (.3)  A  shallow  groove,  sometimes  double, 
leading  outward  and  backward  to  an  oblique  opening,  the  hiatus  Fallopii  (hiatus 
canalis  facialis) ,  for  the  passage  of  the  greater  petrosal  nerve  and  the  petrosal 
branch  of  the  middle  meningeal  artery.  (4)  A  smaller  opening  (apertura  superior 
canalicidi  tympanici) ,  occasionally  seen  external  to  the  latter,  for  the  passage  of 
the  smaller  petrosal  nerve.  (5)  Xear  the  apex  of  the  bone,  the  termination  of  the 
carotid  canal,  the  internal  carotid  foramen  (foramen  caroticum  internum),  the  wall 
of  which  in  this  situation  is  deficient  in  front.  (6)  Above  the  canal  a  shallow 
depression,  the  trigeminal  depression  (impressio  trigeminy),  for  the  reception  of  the 
Gasserian  ganglion. 


THE    TEMPORAL    BONE 


89 


Posterior  Surface  (fades  posterior  pyramidis). — The  posterior  surface  forms  the 
front  part  of  the  posterior  fossa  of  the  skull,  and  is  continuous  with  the  inner 
surface  of  the  mastoid  portion  of  the  bone.  It  presents  three  points  for  exami- 
nation: 1.  About  its  centre,  a  large  orifice,  the  meatus  auditorius  internus  (meatus 
acusticus  internus),  whose  size  varies  considerably;  its  margins  are  smooth  and 
rounded,  and  it  leads  into  a  short  canal,  about  four  lines  in  length,  which  runs 
directly  outward  and  is  closed  by  a  vertical  plate,  the  lamina  cribrosa,  which  is 
divided  by  a  horizontal  crest,  the  falciform  crest  (crista  falciformis) ,  into  two  unequal 
portions  ( Fig.  50) .  Each  portion  is  subdivided  by  a  little  vertical  crest  into  two  parts, 
named,  respectively,  anterior  and  posterior.  The  lower  portion  presents  three  sets 
of  foramina:  one  group  just  below  the  poste- 
rior part  of  the  crest,  the  area  cribro«a  media, 
consisting  of  a  number  of  small  openings 
for  the  nerves  to  the  saccule;  below  and 
posterior  to  this,  the  foramen  singulare,  or 
opening  for  the  nerve  to  the  posterior  semi- 
circular canal;  in  front  and  below  the  first, 
the  tractus  spiralis  foraminosus,  consisting 
of  a  numlier  of  small,  spirally  arranged 
openings  which  terminate  in  the  canalis 
centralis  cochleae  and  transmit  the  nerve  to 
the  cochlea;  the  upper  portion,  that  above 
the  crista,  presents  behind  a  series  of  small 
openings  the  area  cribrosa  superior,  for  the 
passage  of  filaments  to  the  utricle  and  supe- 
rior and  external  semicircular  canal,  and,  in 
front,  one  large  opening,  the  commence- 
ment of  the  aquaeductus  Fallopii  (canalis 
facialis),  for  the  passage  of  the  facial  nerve. 

2.  Behind  the  meatus  auditorius,  a  small 
slit  (apertura  externa  aqiioeducfus  vestihidi), 
almost  hidden  by  a  thin  plate  of  bone,  lead- 
ing to  a  canal,  the  aquaeductus  vestibuli, 
which  transmits  the  ductus  endolymphaticus 
together  with  a  small  artery  and  vein.     In 

the  interval  between  these  two  openings,  but  above  them,  is  an  angular  depression 
(fossa  subarcuata)  which  lodges  a  process  of  the  dura  mater,  and  transmits  a 
small  vein  into  the  cancellous  tissue  of  the  bone.  In  the  child  this  depression 
is  representefl  by  a  large  fossa,  the  floccular  fossa,  which  extends  backward  as  a 
blind  tunnel  under  the  superior  semicircular  canal. 

Inferior  Surface  (fades  inferior  pyramidis) . — The  inferior  or  basilar  surface  (Fig. 
51)  is  rough  and  irregular,  and  forms  part  of  the  base  of  the  skull.  Passing  from 
the  apex  to  the  base,  this  surface  presents  eleven  points  for  examination:  1.  A 
rough  surface,  quadrilateral  in*  form,  which  serves  partly  for  the  attachment  of 
the  Levator  palati  and  Tensor  tympani  muscles.  2.  The  large,  circular  aperture 
of  the  carotid  canal,  the  external  carotid  foramen  (foramen  caroticum  externum) ;  the 
canal  ascends  at  first  vertically,  and  then,  making  a  bend,  runs  horizontally  for- 
ward and  inward;  it  transmits  the  internal  carotid  artery  and  the  carotid  plexus. 
Within  the  carotid  canal  are  several  openings  (canaliculi  carotico  tympanici)  which 
transmit  tympanic  branches  of  the  internal  carotid  artery  and  of  the  carotid  plexus. 

3.  The  opening  of  the  aquaeductus  cochleae  (apertura  externa  canaliculi  cochleoe),  a 
small  triangular  opening,  lying  on  the  inner  side  of  the  latter,  close  to  the  posterior 
border  of  the  petrous  portion;  it  transmits  a  vein  from  the  cochlea,  which  joins 
the  internal  jugular.    4.  Behind  these  openings  a  deep  depression,  the  jugular  fossa 


Fig.  50. —  Diagrammatic  view  of  the  fundus 
of  the  internal  auditory  meatus:  1.  Falciform 
crest.  2.  Anterior  superior  cribriform  area.  2'. 
Internal  opening  of  the  aquaeductus  Fallopii. 
3.  Vertical  crest  which  separates  the  anterior 
and  po-sterior  superior  cribriform  areas.  4.  Pos- 
terior superior  cribriform  area,  with  (4')  open- 
ings for  nerve-filaments.  5.  Anterior  inferior 
cribriform  area.  5'.  Spirally  arranged,  sieve-like 
openings  for  the  nerves  to  the  cochlea.  5".  Open- 
ing of  the  central  canal  of  the  cochlea.  6.  Crest 
which  separates  the  anterior  and  posterior  infe- 
rior cribriform  areas.  7.  Posterior  inferior  crib- 
riform area.  7'.  Orifices  for  the  branches  of  the 
nerve  to  the  saccule.  8.  Foramen  singulare  of 
Morgagni,  with  the  anterior  portion  of  the  canal 
which  gives  passage  to  the  nerve  to  the  posterior 
semicircular  canal.     (Testut) 


90 


THE  SKELETON 


(fossa  jugularis),  which  varies  in  depth  and  size  in  different  skulls;  it  lodges  the 
lateral  sinus,  and,  with  a  similar  depression  on  the  margin  of  the  jugular  process  of 
the  occipital  bone,  forms  the  foramen  lacerum  posterius  or  jugular  foramen.  5.  A 
foramen  which  is  the  opening  of  a  small  canal  (canaliculus  tympanicus) ,  for  the 


Canals  for  Eustachian  tube  and 

TENSOR   TYMPANI    MUSCLE 
LEVATOR    PALATI 


Rough  quadrilateral  surface. 

Opening  of  carotid  canal. 

Canal  for  Jacohson's  nerve. 

Aquseductus  cochlese. 

Canal  for  Arnold's  nerve. 

Jugular  fossa. 

Vaginal  process. 

Styloid  process. 
Stylo-mastoid  foramen: 
Jugular  surface. 
Auricular  fissure. 


STYL0-PHARVNGEU8. 


Fig.  51. — Petrous  portion.     Inferior  surface. 

passage  of  Jacobson's  nerve  (the  tympanic  branch  of  the  glosso-pharyngeal) ; 
this  foramen  is  seen  in  front  of  the  bony  ridge  dividing  the  carotid  canal  from 
the  jugular  fossa.  6.  A  small  foramen  on  the  wall  of  the  jugular  fossa,  for  the 
entrance  of  the  auricular  branch  of  the  pneumogastric  (Arnold's)  nerve.  7.  Behind 
the  jugular  fossa  a  smooth,  square-shaped  facet,  the  jugular  surface;  it  is  covered 
with  cartilage  in  the  recent  state,  and  articulates  with  the  jugular  process  of 
the  occipital  bone.  8.  The  vaginal  process  (vagina  processus  sUjloidea),  a  very 
broad,  sheath-like  plate  of  bone,  which  extends  backward  from  the  carotid  canal 
and  gives  attachment  to  part  of  the  Tensor  palati  muscle;  this  plate  divides 
behind  into  two  laminae,  the  outer  of  which  is  continuous  with  the  tympanic 
plate,  the  inner  with  the  jugular  process.  9.  Between  these  laminae  is  the  ninth 
point  for  examination,  the  styloid  process  (processus  styloideus),  a  sharp  spine, 
about  an  inch  in  length;  it  is  directed  downward,  forward,  and  inward,  varies 
in  size  and  shape,  and  sometimes  consists  of  several  pieces  united  by  cartilage;  it 
affords  attachment  to  three  muscles,  the  Stylo-pharyngeus,  Stylo-hyoideus,  and 
Stylo-glossus,  and  two  ligaments,  the  stylo-hyoid  and  stylo-maxillary.  10.  The 
stylo-mastoid  foramen  (foramen  stylomastoideum) ,  a  rather  large  orifice,  placed 
between  the  styloid  and  mastoid  processes;  it  is  the  termination  of  the  aquaeductus 
Fallopii,  and  transmits  the  facial  nerve  and  stylo-mastoid  artery.  11.  The  auricular 
fissure  (fissura  tympanomastoidea) ,  situated  between  the  tympanic  plate  and 
mastoid  processes,  for  the  exit  of  the  auricular  branch  of  the  pneumogastric  nerve 


THE    TEMPORAL    BONE 


91 


(Arnold's  nerve).     This  fissure  is  the  external  opening  of  the  canaliculus  mas- 
toideus,  which  passes  to  the  aqueduct  of  Fallopius. 

Borders.  Superior  Border  {angulus  superior  pyramidis) . — The  superior,  the 
longest,  is  grooved  for  the  superior  petrosal  sinus,  and  has  attached  to  it  the  ten- 
torium cere})elli ;  at  its  inner  extremity  is  a  semilunar  notch,  upon  which  the  fifth 
nerve  lies. 

Posterior  Border  {angulus  posterior  pyramidis). — The  posterior  border  is  inter- 
mediate in  length  between  the  superior  and  the  anterior.  Its  inner  half  is  marked 
by  a  groove,  which,  when  completed  by  its  articulation  with  the  occipital,  forms 
the  channel  for  the  inferior  petrosal  sinus.  Its  outer  half  presents  a  deep  excava- 
tion, the  jugular  fossa  Qossa  jugidaris),  which,  with  a  similar  notch  on  the  occipital, 
forms  the  foramen  lacerum  posterius.  A  projecting  eminence  of  bone  occasionally 
stands  out  from  the  centre  of  the  notch,  and  divides  the  foramen  into  two  parts. 

Anterior  Border  (angulus  anterior  pyramidis) . — The  anterior  border  is  divided 
into  two  parts — an  outer,  joined  to  the  squamous  portion  by  a  suture,  the  remains 
of  which  are  distinct;  an  inner,  free,  articulating  with  the  spinous  process  of  the 
sphenoid.  At  the  angle  of  junction  of  the  petrous  and  squamous  portions  is 
seen  the  opening  of  the  canalis  musculotubarius.  This  canal  is  completely  or 
partially  divided  into  two  canals,  separated  from  one  another  by  a  thin  plate  of 
bone,  the  processus  cochleariformis  (septum  canalis  musculotubarii) ;  they  both  lead 
into  the  tympanum,  the  upper  one  (semicanalis  m.  tensoris  tympani)  transmitting 
the  Tensor  tympani  muscle,  the  lower 
one  (semicanalis  tubes  auditivce)  form- 
ing the  bony  part  of  the  Eustachian 
tube  or  canal. 

Structure. — The  squamous  portion 
is  like  that  of  the  other  cranial  bones: 
the  mastoid  portion,  cellular;  and  the 
petrous  portion,  dense  and  hard. 

Development  (Fig.  52). — The  tem- 
poral bone  is  developed  by  ten  centres, 
exclusive  of  those  for  the  internal  ear 
and  the  ossicula  —  viz.,  one  of  the 
squamous  portion  including  the  zygo- 
ma, one  for  the  tympanic  plate,  six  for 
the  petrous  and  mastoid  parts,  and  two 
for  the  styloid  process.  Just  before  the 
close  of  foetal  life  the  temporal  bone 
consists  of  four  parts :  1 .  The  squamo- 
zygomatic  part,  ossified  in  membrane 
from  a  single  nucleus,  which  appears 
at  its  lower  part  about  the  second 
month.  2.  The  tympanic  plate,  an  imperfect  ring,  in  the  concavity  of  which  is 
a  groove,  the  sulcus  tympanicus,  for  the  attachment  of  the  circumference  of  the 
tympanic  membrane.  This  is  also  ossified  from  a  single  centre,  which  appears 
about  the  third  month.  3.  The  petro-mastoid  part  is  developed  from  six  cen- 
tres, which  appear  about  the  fifth  or  sixth  month.  Four  of  these  are  for  the 
petrous  portion,  and  are  placed  around  the  labyrinth,  and  two  for  the  mastoid 
(Vrolik).  According  to  Huxley,  the  centres  are  more  numerous,  and  are  dis- 
posed so  as  to  form  three  portions:  (1)  including  most  of  the  labyrinth,  with  a 
part  of  the  petrous  and  mastoid,  he  has  named  prootic;  (2)  the  rest  of  the  petrous, 
the  opisthotic;  and  (3)  the  remainder  of  the  mastoid,  the  epiotic.  The  petro- 
mastoid  is  ossified  in  cartilage.  4.  The  styloid  process  is  also  ossified  in  cartilage 
from  two  centres:  one  for  the  base,  which  appears  before  birth,  and  is  termed  the 


1  for 
squamous 
portion, 
including 
zygoma  : 
2d  month. 


1  for  tympanic 
plate. 


6  for  petrous 

and  mastoid 

portions. 


2  for  styloid  process. 

Fig.  52. — Development  of  the  temporal  bone, 
ten  centres. 


By 


92  THE  SKELETON 

t3nQDipanohyal;  the  other,  comprising  the  rest  of  the  process,  is  named  the  stylohyal, 
and  does  not  appear  until  after  birth.  Shortly  before  birth  the  tympanic  plate  joins 
with  the  squamous.  The  petrous  and  mastoid  join  with  the  squamous  during 
the  first  year,  and  the  tympanohyal  portion  of  the  styloid  process  about  the  same 
time.  The  stylohyal  does  not  join  the  rest  of  the  bone  until  after  puberty,  and 
in  some  skulls  never  becomes  united.  The  subsequent  changes  in  this  bone  are, 
that  the  tympanic  plate  extends  outward  and  backward,  so  as  to  form  the  meatus 
auditorius.  The  extension  of  the  tympanic  plate,  however,  does  not  take  place  at 
an  equal  rate  all  around  the  circumference  of  the  ring,  but  occurs  most  rapidly 
on  its  anterior  and  posterior  portions,  and  these  outgrowths  meet  and  blend,  and 
thus,  for  a  time,  there  exists  in  the  floor  of  the  meatus  a  foramen,  the  foramen  of 
Buschke;  this  foramen  may  persist  throughout  life.  The  glenoid  cavity  is  at  first 
extremely  shallow,  and  looks  outward  as  well  as  downward;  it  becomes  deeper 
and  is  ultimately  directed  downward.  Its  change  in  direction  is  accounted  for 
as  follows :  the  part  of  the  squamous  temporal  which  supports  it  lies  at  first  helow 
the  level  of  the  zygoma.  As,  however,  the  base  of  the  skull  increases  in  width, 
this  lower  part  of  the  squama  is  directed  horizontally  inward  to  contribute  to 
the  middle  fossa  of  the  skull,  and  its  surfaces  therefore  come  to  look  upward  and 
downward.  The  mastoid  portion  is  at  first  quite  flat,  and  the  stylo-mastoid  fora- 
men and  rudimentary  styloid  process  lie  immediately  behind  the  entrance  to  the 
auditory  meatus.  With  the  development  of  the  air-cells  the  outer  part  of  the 
mastoid  portion  grows  downward  and  forward  to  form  the  mastoid  process,  and 
the  styloid  process  and  stylo-mastoid  foramen  now  come  to  lie  on  the  under  sur- 
face. The  descent  of  the  foramen  is  necessarily  accompanied  by  a  corresponding 
lengthening  of  the  aqueduct  of  Fallopius. 

The  downward  and  forward  growth  of  the  mastoid  process  also  pushes  forward 
the  tympanic  plate,  so  that  the  portion  of  it  which  formed  the  original  floor  of 
the  meatus  and  containing  the  foramen  of  Huschke  is  ultimately  found  in  the 
anterior  wall.  With  the  gradual  increase  in  size  of  the  petrous  portion  the  floc- 
cular  fossa  or  tunnel  under  the  superior  semicircular  canal  becomes  filled  up 
and  almost  obliterated. 

Articulations. — With  five  bones — occipital,  parietal,  sphenoid,  inferior  maxil- 
lary, and  malar. 

Attachment  of  Muscles. — To  fifteen  :  to  the  squamous  portion,  the  Tem- 
poral; to  the  zygoma,  the  Masseter;  to  the  mastoid  portion,  the  Occipito- 
frontalis,  Sterno-mastoid,  Splenius  capitis,  Trachelo-mastoid,  Digastricus,  and 
Retrahens  aurem;  to  the  styloid  process,  the  Stylo-pharyngeus,  Stylo-hyoideus, 
and  Stylo-glossus  ;  and  to  the  petrous  portion,  the  Levator  palati,  Tensor 
tympani.  Tensor  palati,  and  Stapedius. 

The  Sphenoid  Bone  (Os  Sphenoidale). 

The  sphenoid  bone  {oipr^v,  a  wedge)  is  situated  at  the  anterior  part  of  the  base 
of  the  skull,  articulating  with  all  the  other  cranial  bones,  which  it  binds  firmly 
and  solidly  together.  In  its  form  it  somewhat  resembles  a  bat  with  its  wings 
extended;  and  is  divided  into  a  central  portion  or  body,  two  greater  and  two  lesser 
wings  extending  outward  on  each  side  of  the  body,  and  two  processes — the  ptery- 
goid processes — which  project  from  it  below. 

The  Body  of  the  Sphenoid  Bone. 

The  body  (eorpiis)  is  of  large  size  and  hollowed  out  in  its  interior  so  as  to  form  a 
mere  shell  of  bone.  It  presents  for  examination  jour  surfaces — a  superior,  an 
inferior,  an  anterior,  and  a  posterior. 


THE  SPHENOID    BONE 


93 


Surfaces.  Superior  Surface  (fades  cerehralis)  (Fig.  53). — In  front  is  seen  a  promi- 
nent spine,  the  ethmoidal  spine,  for  articulation  with  the  cribriform  plate  of  the  eth- 
moid ;  behind  this  a  smooth  surface  presenting,  in  the  median  line,  a  slight  longi- 
tudinal eminence,  with  a  depression  on  each  side  for  lodging  the  olfactory  lobes. 
This  surface  is  bounded  behind  by  a  ridge,  which  forms  the  anterior  border  of  a 
narrow,  transverse  groove,  the  optic  groove  {sulcus  chiasmatis),  behind  which  lies  the 
optic  chiasm ;  the  groove  is  continuous  on  each  side  with  the  optic  foramen  (foramen 
opticum) ,  for  the  passage  of  the  optic  nerve  and  ophthalmic  artery.    Behind  the 


Middle  chnoid  process. 
_Posterior  clinoid  process 

\ 


Ethmoidal 


Foramen  opticum... 

Foramen  laceriim  ante- 

rius  or  Sphenoidal 

fissure. 

Foramen  rotundum. 

Foramen  Vesalii. 

Foramen  ovale.' 

Foramen  spinosum. 


Fig.  53. — Sphenoid  bone.     Superior  surface. 


optic  groove  is  a  small  eminence,  olive-like  in  shape,  the  olivary  process  or  eminence 
{tuberculum  sellce) ;  and  still  more  posteriorly,  a  deep  depression,  the  pituitary  fossa, 
or  sella  turcica  (fossa  hypophyseos) ,  which  lodges  the  circular  sinus  and  the  pituitary 
body  (hypophysis).  This  fossa  is  perforated  by  numerous  foramina,  for  the  trans- 
mission of  nutrient  vessels  into  the  substance  of  the  bone.  It  is  bounded  in  front 
by  the  olivary  eminence,  and  also  by  two  small  eminences,  one  on  either  side,  called 
the  middle  clinoid  processes  (processus  clinoidei  medii)  (x/cvrj,  a  bed),  which  are 
sometimes  connected  by  a  spiculum  of  bone  to  the  anterior  clinoid  processes.  It 
is  bounded  behind  by  a  square-shaped  plate  of  bone,  the  dorsum  ephippii  or  dorsum 
sellse,  terminating  at  each  superior  angle  in  a  tubercle,  the  posterior  clinoid  process 
(processus  clinoideu^  posterior).  The  size  and  form  of  these  processes  vary  con- 
siderably in  different  individuals.  They  deepen  the  pituitary  fossa,  and  serve  for 
the  attachment  of  prolongations  from  the  tentoriimi  cerebelli.  The  sides  of  the 
dorsum  ephippii  are  notched  for  the  passage  of  the  sixth  pair  of  nerves,  and 
below  present  a  sharp  process,  the  petrosal  process,  which  is  joined  to  the  apex 
of  the  petrous  portion  of  the  temporal  bone,  forming  the  inner  boundary  of  the 
middle  lacerated  foramen.  Behind  this  plate  the  bone  presents  a  shallow  depres- 
sion, which  slopes  obliquely  backward,  and  is  continuous  with  the  basilar  groove 
of  the  occipital  bone;  it  is  called  the  clivus,  and  supports  the  upper  part  of  the 
pons  Varolii.  On  either  side  of  the  body  is  a  broad  groove,  curved  something  like 
the  italic  letter  /;  it  lodges  the  internal  carotid  artery  and  the  cavernous  sinus, 
and  is  called  the  carotid  or  cavernous  groove  (sul&iis  caroticus).  Along  the  outer 
margin  of  this  groove,  at  its  posterior  part,  is  a  ridge  of  bone  in  the  angle 
between  the  body  and  greater  wing,  called  the  lingula  (lingula  sphenoidalis) . 

Posterior  Surface. — The  posterior  surface,  quadrilateral  in  form,  is  joined  to  the 
basilar  process  of  the  occipital  bone.    During  childhood  these  bones  are  separated 


94 


THE  SKELETON 


by  a  layer  of  cartilage;  but  in  after-life  (between  the  eighteenth  and  twenty-fifth 
years)  this  becomes  ossified,  ossification  commencing  above  and  extending  down- 
ward; and  the  two  bones  then  form  one  piece. 

Anterior  Surface. — The  anterior  surface  (Fig.  54)  presents,  in  the  middle  line,  a 
vertical  ridge  of  bone,  the  ethmoidal  or  sphenoidal  crest  (crista  sphenoidalis) ,  which 
articulates  in  front  with  the  perpendicular  plate  of  the  ethmoid,  forming  part  of 
the  septum  of  the  nose.  On  either  side  of  it  are  irregular  openings  leading  into 
the  sphenoidal  cells  or  sinuses  (sinus  sphenoidales).  These  are  two  large,  irregular 
cavities  hollowed  out  of  the  interior  of  the  body  of  the  sphenoid  bone,  often 


Pterygoid  ridge, 


Internal  pterygoid  plate-Si- 
HamuLar  process.-^ 

Fig.  54. — Sphenoid  bone.    Anterior  surface.^ 

extending  into  the  pterygoid  processes  and  base  of  the  greater  wings  of  the  bone, 
and  separated  from  one  another  by  a  more  or  less  complete  perpendicular  bony 
septum  (septum  sinuum  sphenoidalium).  Occasionally  they  extend  into  the  basilar 
process  of  the  occipital  nearly  as  far  as  the  foramen  magnum.  Their  form  and 
size  vary  considerably;  they  are  seldom  symmetrical,  and  are  often  partially  sub- 
divided by  irregular,  osseous  laminte.  One  sinus  or  both  sinuses  may  be  absent. 
The  septum  is  seldom  quite  vertical,  being  commonly  bent  to  one  or  the  other 
side.  These  sinuses  do  not  exist  in  very  young  children,  but  appear,  according 
to  lyaurent,  in  the  seventh  year,  and,  according  to  Tillaux,  not  until  the  twen- 
tieth year.  After  once  appearing  they  increase  in  size  as  age  advances.  They 
are  partially  closed,  in  front  and  below,  by  two  thin,  curved  plates  of  bone, 
the  sphenoidal,  spongy,  or  turbinated  bones  (conchce  sphenoidales).  At  the  upper 
part  of  each  is  a  round  opening  (apertura  sinus  sphenoidalis)  by  which  the  sinus 
communicates  with  the  upper  and  back  part  of  the  nose,  and  occasionally  with 
the  posterior  ethmoidal  cells  or  sinuses.  The  lateral  margins  of  this  surface 
present  a  serrated  edge,  which  articulates  with  the  os  planum  of  the  ethmoid, 
completing  the  posterior  ethmoidal  cells;  the  lower  margin,  also  rough  and  ser- 
rated, articulates  with  the  orbital  process  of  the  palate  bone,  and  the  upper 
margin  with  the  orbital  plate  of  the  frontal  bone. 

Inferior  Surface. — The  inferior  surface  presents,  in  the  middle  line,  a  triangular 
spine,  the  rostrum  (rostrum  sphenoidalis),  which  is  continuous  with  the  sphenoidal 
crest  on  the  anterior  surface,  and  is  received  into  a  deep  fissure  between  the  alse 

1  ^'V^'?!?  figure,  both  the  anterior  and  inferior  surfaces  of  the  body  of  the  sphenoid  bone  are  shown,  the  bone 
being  held  with  the  pterygoid  processes  almost  horizontal. 


THE  SPHENOID    BONE  95 

of  the  vomer.  On  each  side  may  be  seen  a  projecting  lamina  of  bone,  which  runs 
horizontally  inward  from  near  the  base  of  the  pterygoid  process:  these  plates,  termed 
the  vaginal  processes,  articulate  with  the  edges  of  the  vomer.  Close  to  the  root  of 
the  pterygoid  process  is  a  groove  (sulcus  pterygopalatinus) ,  formed  into  a  complete 
canal  when  articulated  with  the  sphenoidal  process  of  the  palate  bone;  it  is  called 
the  pterygo-palatine  canal,  and  transmits  the  pterygo-palatine  vessels  and  pharyngeal 
nerve. 

The  Greater  or  Temporal  Wings  of  the  Sphenoid  Bone  (Alae  Magnse). 

The  greater  wings  are  two  strong  processes  of  bone  which  arise  from  the  sides 
of  the  body,  and  are  curved  in  a  direction  upward,  outward,  and  backward,  each 
being  prolonged  behind  into  a  sharp-pointed  extremity,  the  alar  or  sphenoidal 
spine  (spina  angularis) .     Each  wing  presents  three  surfaces  and  a  circumference. 

Surfaces.  Superior  Surface  (fades  cerebralis) . — The  superior  or  cerebral  surface 
(Fig.  53)  forms  part  of  the  middle  fossa  of  the  skull;  it  is  deeply  concave,  and  pre- 
sents eminences  and  depressions  for  the  convolutions  of  the  brain.  At  its  anterior 
and  internal  part  is  seen  a  circular  aperture,  the  foramen  rotundum,  for  the  transmis- 
sion of  the  second  division  of  the  fifth  nerve.  Behind  and  external  to  this  is  a  large, 
oval  foramen,  the  foramen  ovale,  for  the  transmission  of  the  third  division  of  the 
fifth  nerve,  the  small  meningeal  artery,  and  sometimes  the  small  petrosal  nerve.^ 
At  the  inner  side  of  the  foramen  ovale  a  small  aperture  may  occasionally  be  seen 
opposite  the  root  of  the  pterygoid  process;  it  is  the  foramen  Vesalii,  transmitting 
a  small  vein.  Lastly,  in  the  posterior  angle,  near  to  the  spine  of  the  sphenoid,  is 
a  short  canal,  sometimes  double,  the  foramen  spinosum;  it  transmits  the  middle 
meningeal  artery. 

External  Surface. — The  external  surface  (Fig.  54)  is  convex  and  divided  by  a 
transverse  ridge,  the  pterygoid  ridge  or  infratemporal  crest  (crista  infratemporalis) , 
into  two  portions.  The  superior  or  larger,  convex  from  above  downward,  concave 
from  before  backward,  enters  into  the  formation  of  the  temporal  fossa,  and  gives 
attachment  to  part  of  the  Temporal  muscle.  The  inferior  portion,  smaller  in  size 
and  concave,  enters  into  the  formation  of  the  zygomatic  fossa,  and  affords  attach- 
ment to  the  External  pterygoid  muscle.  It  presents,  at  its  posterior  part,  a  sharp- 
pointed  eminence  of  bone,  the  spine,  to  which  are  connected  the  internal  lateral 
ligament  of  the  lower  jaw  and  the  Tensor  palati  muscle.  The  pterygoid  ridge, 
dividing  the  temporal  and  zygomatic  portions,  gives  attachment  to  part  of  the 
External  pterygoid  muscle.  At  its  inner  and  anterior  extremity  is  a  triangular 
spine  of  bone,  which  serves  to  increase  the  extent  of  origin  of  this  muscle. 

Anterior  Surface  (fades  orbitalis) . — The  anterior  or  orbital  surface,  smooth  and 
quadrilateral  in  form,  assists  in  forming  the  outer  wall  of  the  orbit.  It  is  bounded 
above  by  a  serrated  edge,  for  articulation  with  the  frontal  bone;  below,  by  a  rounded 
border  which  enters  into  the  formation  of  the  spheno-maxillary  fissure.  Internally,  it 
presents  a  sharp  border,  which  forms  the  lower  boundary  of  the  sphenoidal  fissure, 
and  has  projecting  from  about  its  centre  a  little  tubercle  of  bone,  which  gives 
origin  to  one  head  of  the  External  rectus  muscle  of  the  eye;  and  at  its  upper  part 
is  a  notch  for  the  transmission  of  a  recurrent  branch  of  the  lachrymal  artery; 
externally  it  presents  a  serrated  margin  for  articulation  with  the  malar  bone.  One 
or  two  small  foramina  may  occasionally  be  seen  for  the  passage  of  branches  of 
the  deep  temporal  arteries;  they  are  called  the  external  orbital  foramina. 

Circumference  (Fig.  53). — Commencing  from  behind,  that  portion  of  the  cir- 
cumference from  the  body  of  the  sphenoid  to  the  spine  is  serrated  and  articulates 
by  its  outer  half  with  the  petrous  portion  of  the  temporal  bone,  while  the  inner 
half  forms  the  anterior  boundary  of  the  foramen  lacerum  mediiun,  and  presents 

^  The  small  petrosal  nerve  sometimes  passes  through  a  special  foramen  between  the  foramen  ovale  and 
foramen  spinosum. 


96  THE  SKELETON 

the  posterior  aperture  of  the  Vidian  canal  (canalis  ptenjgoideus)  for  the  passage  of  the 
Vidian  nerve  and  artery.  In  front  of  the  spine  the  circumference  of  the  great  wing 
presents  a  serrated  edge,  bevelled  at  the  expense  of  the  inner  table  below  and  of  the 
external  above,  which  articulates  with  the  squamous  portion  of  the  temporal  bone. 
At  the  tip  of  the  great  wing  a  triangular  portion  is  seen,  bevelled  at  the  expense  of 
the  internal  surface,  for  articulation  with  the  anterior  inferior  angle  of  the  parietal 
bone.  Internal  to  this  is  a  triangular,  serrated  surface,  for  articulation  with  the 
frontal  bone;  this  surface  is  continuous  internally  with  the  sharp  inner  edge  of 
the  orbital  plate,  which  assists  in  the  formation  of  the  sphenoidal  fissure,  and 
externally  with  the  serrated  margin  for  articulation  with  the  malar  bone. 

The  Lesser  or  Orbital  Wings  of  the  Sphenoid  Bone  (Alae  Parvae). 

The  lesser  wings  (processes  of  Ingrassias)  are  two  thin,  triangular  plates  of 
bone  which  arise  from  the  upper  and  lateral  parts  of  the  body  of  the  sphenoid, 
and,  projecting  transversely  outward,  terminate  in  a  sharp  point  (Fig.  53).  The 
superior  surface  of  each  is  smooth,  flat,  broader  internally  than  externally,  and 
supports  part  of  the  frontal  lobe  of  the  brain.  The  inferior  surface  forms  the 
back  part  of  the  roof  of  the  orbit  and  the  upper  boundary  of  the  orbital  or  sphe- 
noidal fissure  or  foramen  lacenim  anterius  (fissura  orhitalis  superior) .  This  fissure  is 
of  a  triangular  form,  and  leads  from  the  cavity  of  the  cranium  into  the  orbit;  it  is 
bounded  internally  by  the  body  of  the  sphenoid — above,  by  the  lesser  wing; 
below,  by  the  internal  margin  of  the  orbital  surface  of  the  great  wing — and  is 
converted  into  a  foramen  by  the  articulation  of  this  bone  with  the  frontal.  It 
transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic  division 
of  the  fifth,  the  sixth  nerve,  some  filaments  from  the  cavernous  plexus  of  the 
sympathetic,  the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent 
branch  from  the  lachrymal  artery  to  the  dura  mater  and  the  ophthalmic  vein. 
The  anterior  border  of  the  lesser  wing  is  serrated  for  articulation  with  the 
frontal  bone;  the  posterior  border,  smooth  and  rounded,  is  received  into  the  fissure  of 
Sylvius  of  the  brain.  Each  inner  extremity  of  this  border  forms  an  anterior  clinoid 
process  (processus  clinoideus  anterior).  The  lesser  wing  is  connected  to  the  side 
of  the  body  by  two  roots,  the  upper  thin  and  flat,  the  lower  thicker,  obliquely 
directed,  and  presenting  on  its  outer  side,  near  its  junction  with  the  body,  a  small 
tubercle,  for  the  attachment  of  the  common  tendon  of  origin  of  three  of  the  muscles 
of  the  eye.  Between  the  two  roots  is  the  optic  foramen  (foramen  opticum),  for 
the  transmission  of  the  optic  nerve  and  ophthalmic  artery. 

The  Pterygoid  Processes  of  the  Sphenoid  Bone  (Processus  Pterygoidei) . 

The  pterygoid  processes  (Tzripu^,  a  wing;  slda:,  likeness),  one  on  each  side, 
descend  perpendicularly  from  the  point  where  the  body  and  greater  wing  unite 
(Fig.  55).  Each  process  consists  of  an  external  and  an  internal  lamina  or  plate, 
which  are  joined  together  by  their  anterior  borders  above,  but  are  separated  below, 
leaving  an  angular  cleft,  the  pterygoid  notch  or  fissure  (fissura  pterygoidea) ,  in  which 
the  pterygoid  process  or  tuberosity  of  the  palate  bone  is  received.  The  two  plates 
diverge  from  each  other  from  their  line  of  connection  in  front,  so  as  to  form  a  V- 
shaped  fossa,  the  pterygoid  fossa  (fossa  pterygoidea) .  The  external  pterygoid  plate 
(lamina  lateralis  processus  pterygoidei)  is  broad  and  thin,  turned  a  little  outward, 
and,  by  its  outer  surface,  forms  part  of  the  inner  wall  of  the  zygomatic  fossa,  giving 
attachment  to  the  External  pterygoid;  its  inner  surface  forms  part  of  the  pterygoid 
fossa,  and  gives  attachment  to  the  Internal  pterygoid.  The  internal  pterygoid  plate 
(lamina  medialis  processus  pterygoidei)  is  much  narrower  and  longer,  curving 
outward,  at  its  extremity,  into  a  hook-like  process  of  bone,  the  hamular  process 


THE  SPHENOID    BONE  97 

(hamulus  pterygoideus) ,  around  which  turns  the  tendon  of  the  Tensor  palati 
muscle.  The  outer  surface  of  this  plate  forms  part  of  the  pterygoid  fossa,  the 
inner  surface  forming  the  outer  boundary  of  the  posterior  aperture  of  the  nares. 
On  the  posterior  surface  of  the  base  of  the  process,  above  the  pterygoid  fossa,  is  a 
small,  oval,  shallow  depression,  the  scaphoid  fossa  (fossa  scaphoidea),  from  which 
arises  the  Tensor  palati,  and  above  which  is  seen  the  posterior  orifice  of  the  Vidian 
canal  {canalis  pterygoideus  [Vidii]).    Below  and  to  the  inner  side  of  the  Vidian 


Fig.  55. — Sphenoid  bone.     Posterior  surface. 

canal,  on  the  posterior  surface  of  the  base  of  the  internal  plate,  is  a  little  promi- 
nence, which  is  known  by  the  name  of  the  pterygoid  tubercle.  The  Superior 
constrictor  of  the  pharynx  is  attached  to  the  posterior  edge  of  the  internal  plate. 
The  anterior  surface  of  the  pterygoid  process  is  very  broad  at  its  base,  and  forms 
the  posterior  wall  of  the  spheno-maxillary  fossa.  It  supports  Meckel's  ganglion. 
It  presents,  above,  the  anterior  orifice  of  the  Vidian  canal ;  and  below,  a  rough 
margin,  which  articulates  with  the  perpendicular  plate  of  the  palate  bone. 

The  Sphenoidal  Spongy  Bone. 

The  sphenoidal  spongy,  turbinal  or  turbinated  bones  (the  hones  of  Bertin,  conchcB 
sphenoidales)  are  two  thin,  curved  plates  of  bones,  which  exist  as  separate  pieces 
until  puberty,  and  occasionally  are  not  joined  to  the  sphenoid  in  the  adult.  They 
are  situated  at  the  anterior  and  inferior  part  of  the  body  of  the  sphenoid,  an 
aperture  (apertura  sinus  sphenoidalis)  of  variable  size  being  left  in  the  anterior  wall 
of  each,  through  which  the  sphenoidal  sinuses  open  into  the  nasal  fossae.  They  are 
irregular  in  form  and  taper  to  a  point  behind,  being  broader  and  thinner  in  front. 
Their  upper  surface,  which  looks  toward  the  cavity  of  the  sinus,  is  concave ;  their 
under  surface  convex.  Each  bone  articulates  in  front  with  the  ethmoid,  exter- 
nally with  the  palate;  its  pointed  posterior  extremity  is  placed  above  the  vomer, 
and  is  received  between  the  root  of  the  pterygoid  process  on  the  outer  side  and 
the  rostrum  of  the  sphenoid  on  the  inner. ^ 

Development. — Up  to  about  the  eighth  month  of  fcetal  life  the  sphenoid  bone 
consists  of  two  distinct  parts:  a  posterior  or  post-sphenoid  part,  which  comprises 
the  pituitary  fossa,  the  greater  wings,  anfl  the  pterygoid  processes;  and  an  anterior 
or  pre-sphenoid  part,  to  which  the  anterior  part  of  the  body  and  lesser  wings 
belong.  It  is  developed  by  fourteen  centres:  eight  for  the  posterior  sphenoid 
division,  and  six  for  the  anterior  sphenoid.    The  eight  centres  for  the  posterior 

1  A  small  portion  of  the  .sphenoidal  turbinated  bone  sometimes  enters  into  the  formation  of  the  inner  wall  of 
the  orbit,  between  the  os  planum  of  the  ethmoid  in  front,  the  orbital  plate  of  the  palate  below,  and  the  frontal 
above. — Cleland,  Roy.  Soe.  Trans..  1862. 


98  THE  SKELETON 

sphenoid  are:  one  for  each  greater  wing  and  external  pterygoid  plate,  one  for 
each  internal  pterygoid  plate,  two  for  the  posterior  part  of  the  body,  and  one  on 
each  side  for  the  lingula.  The  six  for  the  anterior  sphenoid  are:  one  for  each 
lesser  wing,  two  for  the  anterior  part  of  the  body,  and  one  for  each  sphenoidal 
turbinated  bone. 

Post-sphenoid  Division. — The  first  nuclei  to  appear  are  those  for  the  greater 
wings  (ali-sphenoids).    They  make  their  appearance  between  the  foramen  rotun- 

dum  and  foramen  ovale  about  the  eighth 
one  for  each    two  for  anterior  week,  and  from  them  the  external  pterygoid 

lesser  wing,   ^art  of  body.  pktes    are   also    formed.      Soon   after,  the 

nuclei  for  the  posterior  part  of   the  body 
appear,  one  on  either  side  of  the  sella  turcica, 
and    become   blended   together   about   the 
\  r\w/(*7<-T-3i  ;<scn:«       •  middle  of   foetal   life.      About   the  fourth 

'     yv/f^  T^^^V^V     \  month  the  remaining  four  centres  appear, 

one  for  each  i£rnai,Ai""  '  \         *^^.^^  ^^\  *^^^  internal  pterygoid  plates  being 

pterygoid  plate.      '-'  \        ossified  in  membrane  and  becoming  joined 

me  for       for^ each  lingula.        \      to  the  external  pterygoid  plate  about  the 

each  great  wing  and  external  ptery-  sixth  month.  The  centres  for  the  linguhe 
onefor  each  Sphenoidal  turbinated  bme^^^'''"'  speedily  beCOme  joined  tO  the  rest  of  the 
Fig.  66. — Plan  of  development  of  the  sphenoid.  _    '        ,  .,_....  rr\,  n  i    • 

By  fourteen  centres.  Pie-sphenoid   Division. —  1  lie    hrst   nuclci 

to  appear  are  those  for  the  lesser  wings 
(orbito-sphenoids).  They  make  their  appearance  about  the  ninth  week,  at  the 
outer  borders  of  the  optic  foramina.  A  second  pair  of  nuclei  appear  on  the  inner 
side  of  the  foramina  shortly  after,  and,  becoming  united,  form  the  front  part  of 
the  body  of  the  bone.  The  remaining  two  centres  for  the  sphenoidal  turbinated 
bones  make  their  appearance  about  the  fifth  month.  At  birth  they  consist  of  small 
triangular  laminae,  and  it  is  not  till  the  third  year  that  they  become  hollowed  out 
and  cone-shaped.  About  the  fourth  year  they  become  fused  with  the  lateral 
masses  of  the  ethmoid,  and  hence,  from  an  embryological  point  of  view,  may  be 
regarded  as  belonging  to  the  ethmoid. 

The  pre-sphenoid  is  united  to  the  body  of  the  post-sphenoid  about  the  eighth 
month,  so  that  at  birth  the  bone  consists  of  three  pieces — viz.,  the  body  in  the 
centre,  and  on  each  side  the  great  wings  with  the  pterygoid  processes.  The  lesser 
wings  become  joined  to  the  body  at  about  the  time  of  birth.  At  the  first  year 
after  birth  the  greater  wings  and  body  are  united.  From  the  tenth  to  the  twelfth 
year  the  spongy  bones  are  partially  united  to  the  sphenoid,  their  junction  being 
complete  by  the  twentieth  year.  Lastly,  the  sphenoid  joins  the  occipital  from  the 
eighteenth  to  the  twenty-fifth  year. 

Articulations. — The  sphenoid  articulates  with  all  the  bones  of  the  cranium, 
and  five  of  the  face — the  two  malar,  the  two  palate,  and  vomer;  the  exact  extent 
of  articulation  with  each  bone  is  shown  in  the  accompanying  figures.^ 

Attachment  of  Muscles. — To  eleven  pairs:  the  Temporal,  External  pterygoid, 
Internal  pterygoid,  Superior  constrictor.  Tensor  palati,  Levator  palpebrae,  Ob- 
liquus  oculi  superior,  Superior  rectus.  Internal  rectus,  Inferior  rectus.  External 
rectus. 

The  Ethmoid  Bone  (Os  Ethmoidale). 

The  ethmoid  (/jd/jto^,  a  sieve)  is  an  exceedingly  light,  spongy  bone,  of  a  cubical 
form,  situated  at  the  anterior  part  of  the  base  of  the  cranium,  between  the  two 
orbits  at  the  root  of  the  nose,  and  contributing  to  form  each  of  these  cavities. 

'  It  also  sometimes  articulates  with  the  tuberosity  of  the  superior  maxilla. 


THE   ETHMOID    BONE 


99 


It  consists  of  three  parts:  a  horizontal  plate,  which  forms  part  of  the  base  of  the 
cranium;  a  perpendicular  plate,  which  forms  part  of  the  septum  nasi;  and  two 
lateral  masses  of  cells. 

The  Horizontal  Lamina  or  Cribriform  Plate  {lamina  crihrosa)  (Fig.  57)  forms 
part  of  the  anterior  fossa  of  the  base  of  the  skull,  and  is  received  into  the  ethmoid 
notch  of  the  frontal  bone  be- 
tween the  two  orbital  plates. 
Projecting  upward  from  the 
middle  line  of  this  plate  is  a 
thick,  smooth,  triangular  pro- 
cess of  bone,  the  crista  galli,  so 
called  from  its  fancied  resem- 
blance to  a  cock's  comb.  Its 
base  joins  the  cribriform  plate. 
Its  posterior  border,  long,  thin, 
and  slightly  curved,  serves  for 
the  attachment  of  the  falx  cere- 
bri. Its  anterior  border,  short 
and  thick,  articulates  with  the 
frontal  bone,  and  presents  two 
small  projecting  alae  (processus 
alares),  which  are  received  in- 
to corresponding  depressions 
in  the  frontal,  completing  the 
foramen  caecum  behind.  Its  sides  are  smooth  and  sometimes  bulging;  in  which 
case  it  is  found  to  enclose  a  small  sinus.*  On  each  side  of  the  crista  galli  the  cribri- 
form plate  is  narrow  and  deeply  grooved,  to  support  the  bulb  of  the  olfactory  tract, 
and  is  perforated  by  foramina  for  the  passage  of  the  olfactory  nerves.    These  fora- 


FiG.  57.- 


With  inferior  turbinated  bone. 


-Ethmoid  bone.     Outer  surface  of  right  lateral  mass 
(enlarged). 


LAMINA  CRIBROSA 


CRISTA  GALLI 

ALAR  PROCESS 

MINA  CRIBROSA 


UNCIFORM 
PROCESS 


ETHMOIDAL 
LABYRINTH 

Fig.  .58. — Ethmoid  bone  from  behind,  somewhat 
schematic.    (Spalteholz.) 


PERPENDICU- 
LAR  LAMINA 


POSTERIOR 
ETHMOIDAL 
FORAMEN 


ANTERIOR 

ETHMOIDAL 

FORAMEN 


RISTA  GALLI 


ALAR    PROCESS 


Fig.  59. — Ethmoid  bone  from  above.     (Spalteholz.) 


mina  are  arranged  in  three  rows:  the  innermost,  which  are  the  largest  and  least 
numerous,  are  lost  in  grooves  on  the  upper  part  of  the  septum;  the  foramina  of  the 
outer  row  are  continued  on  to  the  surface  of  the  upper  spongy  bone.  The  fora- 
mina of  the  middle  row  are  the  smallest;  they  perforate  the  bone  and  transmit 
nerves  to  the  roof  of  the  nose.     At  the  front  part  of  the  cribriform  plate,  on  each 


'  Sir  George  Humphry  states  that  the  crista  galli  is  commonly  inclined  to  one  side,  usually  the  opposite  to 
that  toward  which  the  lower  part  of  the  perpendicular  plate  is  bent. — The  Human  Skeleton,  1858,  p.  277. 


100 


THE  SKELETON 


wAl,  Ethmoidal 


Fig 


side  of  the  crista  galli,  is  a  small  fissure,  which  transmits  the  nasal  branch  of  the 
ophthalmic  nerve;  and  at  its  posterior  part  a  triangular  notch,  which  receives  the 
ethmoidal  spine  of  the  sphenoid. 

The  Vertical  or  Perpendicular  Lamina  or  Plate  (lamina  perpendicularis  or 
mesethmoid)  (Fig.  60)  is  a  thin,  flattened  lamella  of  bone,  which  descends  from  the 
under  surface  of  the  cribriform  plate,  and  assists  in  forming  the  septum  of  the  nose. 
It  is  much  thinner  in  the  middle  than  at  the  circumference,  and  is  generally  deflected 
a  little  to  one  side.  Its  anterior  border  articulates  with  the  nasal  spine  of  the  frontal 
bone  and  crest  of  the  nasal  bones.    Its  posterior  border,  divided  into  two  parts, 

articulates  by  its  upper 
half  with  the  sphenoidal 
crest  of  the  sphenoid,  by 
its  lower  half  with  the 
vomer.  The  inferior  bor- 
der serves  for  the  attach- 
ment of  the  triangular  car- 
tilage of  the  nose.  On 
each  side  of  the  perpen- 
dicular plate  numerous 
grooves  and  canals  are 
seen,  leading  from  the  for- 
amina on  the  cribriform 
plate;  they  lodge  filaments 
of  the  olfactory  nerves. 

The  Lateral  Mass  or 
Labyrinth  (labyrinthus 
ethmoidalis)  of  the  ethmoid 
consists  of  a  number  of 
thin-walled  cellular  cavities,  the  ethmoidal  cells  (cellulw  etkmoidales)  interposed  be- 
tween two  vertical  plates  of  bone,  the  outer  one  of  which  forms  part  of  the  orbit, 
and  the  inner  one  part  of  the  nasal  fossa  of  the  corresponding  side.  There  are  two 
lateral  masses,  one  on  each  side.  The  ethmoidal  cells  are  not  present  at  birth, 
but  appear  during  the  fifth  year.  In  the  disarticulated  bone  many  of  these  cells 
appear  to  be  broken;  but  when  the  bones  are  articulated  they  are  closed  in  at 
every  part,  except  where  they  open  into  the  nasal  fossi«.  The  wpper  surface  of 
each  lateral  mass  presents  a  number  of  apparently  half-broken  cellular  spaces; 
these  are  closed  in,  when  articulated,  by  the  edges  of  the  ethmoidal  notch  of  the 
frontal  bone.  Crossing  this  surface  are  two  grooves  on  each  side,  converted  into 
canals  by  articulation  with  the  frontal ;  they  are  the  anterior  and  posterior  ethmoidal 
canals  {canalis  ethmoidale  anterius  and  posterius),  and  open  on  the  inner  wall  of 
the  orbit.  The  posterior  surface  also  presents  large,  irregular  cellular  cavities, 
which  are  closed  in  by  articulation  with  the  sphenoidal  turbinated  bones  and 
the  orbital  process  of  the  palate.  The  cells  at  the  anterior  surface  are  completed 
by  the  lachrymal  bone  and  nasal  process  of  the  superior  maxillary,  and  those 
below  also  by  the  superior  maxillary.  The  older  surface  of  each  lateral  mass  is 
formed  of  a  thin,  smooth,  oblong  plate  of  bone,  called  the  os  planum  [lamina 
papyracea) ;  it  forms  part  of  the  inner  wall  of  the  orbit,  and  articulates,  above, 
with  the  orbital  plate  of  the  frontal ;  below,  with  the  superior  maxillary;  in 
front,  with  the  lachrymal;  and  behind,  with  the  sphenoid  and  orbital  process  of 
the  palate. 

From  the  inferior  part  of  each  lateral  mass,  immediately  beneath  the  os  planum, 
there  projects  downward  and  backward  an  irregular  lamina  of  bone,  called  the 
unciform  process  (processus  uncinatus) ,  from  its  hook-like  form ;  it  serves  to  close 
in  the  upper  part  of  the  orifice  of  the  antrum,  and  articulates  with  the  ethmoidal 


60. — Perpendicular  plate  of  ethmoid  (enlarged),  shown  by 
removing  the  right  lateral  mass. 


THE   ETHMOID    BONE  101 

process  of  the  inferior  turbinated  bone.  It  is  often  broken  in  disarticulating  the 
bones. 

The  inner  surface  of  each  lateral  mass  forms  part  of  the  outer  wall  of  the  nasal 
fossa  of  the  corresponding  side.  It  is  formed  of  a  thin  lamella  of  bone,  which 
descends  from  the  under  surface  of  the  cribriform  plate,  and  terminates  below  in 
a  free,  convoluted  margin,  the  middle  turbinated  or  the  inferior  ethmoidal  turbinate 
bone  (concha  nasalis  media).  The  middle  turbinated  bone  may  contain  a  cell  or 
cells,  which  are  really  ethmoidal  cells.  Howard  A.  Lothrop^  studied  1000  speci- 
mens, and  found  cells  in  9  per  cent, 
of  them.  He  never  found  cells  in 
children.  As  a  rule,  a  turbinate  cell 
communicates  with  a  posterior  eth- 
moidal cell,  but  may  join  an  anterior 
ethmoidal  cell.  The  cells  may  open 
into  the  superior  meatus  or  into  the 
middle  meatus.  The  whole  of  this 
surface  is  rough  and  marked  above 
by  numerous  grooves,  which  run  nearly 
vertically  downward  from  the  cribri- 
form plate;  they  lodge  branches  of  the 

IP,  1*1,  j'i*Vj.J      Fig.  61. — Ethmoid  bone.     Inner  surface  of  right  lateral 

olfactory  nerve,  which  are  distributed  mass  (enlarged). 

on  the  mucous  membrane  covering  the 

bone.  The  back  part  of  this  surface  is  subdivided  by  a  narrow  oblique  fissure,  the 
superior  meatus  of  the  nose  (meatus  nasi  superior) ,  bounded  above  by  a  thin,  curved 
plate  of  bone,  the  superior  turbinated  bone  (concha  nasalis  superior).  By  means  of  an 
orifice  at  the  upper  part  of  this  fissure  the  posterior  ethmoitlal  cells  open  into  the 
nose.  Below,  and  in  front  of  the  superior  meatus,  is  seen  the  convex  surface  of 
the  middle  turbinated  bone.  It  extends  along  the  whole  length  of  the  inner  sur- 
face of  each  lateral  mass;  its  lower  margin  is  free  and  thick,  and  its  concavity, 
directed  outward,  assists  in  forming  the  middle  meatus.  It  is  by  a  large  orifice 
at  the  upper  and  front  part  of  the  middle  meatus  that  the  anterior  ethmoidal  cells, 
and  through  them  the  frontal  sinuses,  communicate  with  the  nose  by  means  of  a 
funnel-shaped  canal,  the  infundibulum  (infundibulum  ethmoidale).  The  cellular 
cavities  of  each  lateral  mass,  thus  walled  in  by  the  os  planum  on  the  outer  side  and 
by  the  other  bones  already  mentioned,  are  divided  by  a  thin  transverse  bony  parti- 
tion into  two  sets,  which  do  not  communicate  with  each  other;  they  are  termed 
the  anterior  and  posterior  ethmoidal  cells  or  sinuses.  The  former,  more  numerous, 
communicate  with  the  frontal  sinuses  above  and  the  middle  meatus  below  by 
means  of  a  long,  flexuous  canal,  the  infundibulum;  the  posterior,  less  numerous, 
open  into  the  superior  meatus  and  communicate  (occasionally)  with  the  sphe- 
noidal sinuses.  In  some  cases  the  ethmoidal  sinuses  communicate  with  the  maxil- 
lary sinus.  In  some  cases  the  os  planum  never  develops,  and  the  ethmoidal 
sinuses  are  separated  from  the  orbit  inerely  by  membrane. 

Development. — By  three  centres:  one  for  the  perpendicular  lamella,  and  one 
for  each  lateral  mass.  The  lateral  masses  are  first  developed,  ossific  granules 
making  their  appearance  in  the  os  planum  between  the  fourth  and  fifth  months 
of  foetal  life,  and  extending  into  the  spongy  bones.  At  birth  the  bone  consists  of 
the  two  lateral  masses,  which  are  small  and  ill-developed.  During  the  first  year 
after  birth  the  perpendicular  plate  and  crista  galli  begin  to  ossify,  from  a  single 
nucleus,  and  become  joined  to  the  lateral  masses  about  the  beginning  of  the  second 
year.  The  cribriform  plate  is  ossified  partly  from  the  perpendicular  plate  and 
partly  from  the  lateral  masses.  The  formation  of  the  ethmoidal  cells,  which  com- 
pletes the  bone,  does  not  commence  until  the  end  of  the  fourth  year. 

'  Annals  of  Surgery,  May,  1903. 


102  THE  SKELETON 

Articulations. — With  fifteen  bones:  the  sphenoid,  two  sphenoidal  turbinated, 
the  frontal,  and  eleven  of  the  face — the  two  nasal,  two  superior  maxillary,  two 
lachrymal,  two  palate,  two  inferior  turbinated,  and  the  vomer.  No  muscles  are 
attached  to  this  bone. 

DEVELOPMENT  OF  THE  CRANIUM. 

The  cerebral  vesicles  became  enclosed  by  an  envelope  of  membrane  derived  from  the  em- 
bryonic connective  tissue  about  the  head  end  of  the  chorda.  This  sac  from  the  mesoderm 
is  converted  into  fibrous  tissue,  and  is  known  as  the  membranous  cranium.  In  adult  Hfe 
the  dura  mater  represents  the  membranous  cranium. 

In  mammals  the  base  and  part  of  the  sides  of  the  membranous  cranium  become  cartilaginous, 
but  the  roof  and  the  remaining  part  of  the  sides  remain  membi'anous.  Ossification  com- 
mences in  the  roof  and  begins  at  a  later  period  in  the  base.  Although  ossification  begins  in 
the  membrane  bones  before  it  does  in  the  cartilage  bones,  and  the  bones  of  the  roof  appear 
before  the  bones  of  the  base  and  make  considerable  progress  in  their  growth,  at  birth  ossification 
is  more  advanced  in  the  base,  this  portion  of  the  skull  forming  a  solid,  immovable  groundwork. 

The  Skull  at  Different  Ages. — The  skull  at  birth  is  relatively  of  large  size  as  compared 
with  the  body.  The  cerebral  cranium  is  large  and  the  face  is  small.  The  fontanelles  are 
open  (see  below).  There  are  no  sutures,  but  the  margins  of  adjacent  bones  are  widely  sepa- 
rated by  fibrous  tissue  which  runs  from  the  periosteum  to  the  dura  mater.  The  bones  of  the 
vault  have  no  diploe  and  digital  impressions  are  absent  on  the  cranial  surfaces.  The  parietal 
eminences  and  the  frontal  eminences  are  very  distinct.' 

The  orbits  and  parietal  bones  are  large.  If  the  base  is  examined  it  is  noted  that  the 
mastoid  processes  are  absent,  that  the  lower  border  of  the  symphysis  of  the  jaw  is  on  a  level 
with  the  condyles  of  the  occipital  bone,  and  that  the  pterygoid  plates  form  "  a  large  angle  with 
the  skull  base,  whereas  in  the  adult  the  angle  is  almost  a  right  one." '  The  lower  jaw  at  birth 
is  shown  in  Fig.  91 . 

The  development  of  individual  bones  is  considered  under  the  appropriate  headings.  At 
puberty  various  pneumatic  cells  develop  in  bone  and  alter  the  form  of  the  head  and  face. 

After  the  eruption  of  the  first  set  of  teeth  the  age  can  be  determined  with  reasonable  cer- 
tainty, and  the  degree  of  obliteration  of  the  sutures  will  also  give  valuable  information.  In 
the  vast  majority  of  individuals  the  metopic  suture  becomes  a  mere  trace  during  the  fifth  or 
sixth  years.  Ossification  at  the  junction  of  the  coronal  and  sagittal  sutures  and  osseous  union 
of  the  sphenoid  and  basilar  portion  of  the  occipital  occur  during  maturity.  The  lower  jaw  of 
an  adult  is  shown  in  Fig.  93. 

In  old  age  much  of  the  diploe  disappears  and  the  bones  become  thinner  and  more  porous. 
The  alveolar  surfaces  of  the  jaws  are  absorbed  if  the  teeth  are  lost,  and  the  lower  jaw  alters 
its  form  (Fig.  94). 

Sexual  Differences. — It  is  not  always  possible  to  tell  with  certainty  a  woman's  skull  from 
a  man's,  but  certain  features  are  of  value  in  reaching  a  conclusion.  Virchow  maintained  that 
in  non-European  races  it  is  very  difficult  to  determine  the  sex  from  the  skull,  though  among 
some  savage  races  the  differences  may  be  great.^  It  is  always  to  be  borne  in  mind  that  a 
woman's  skull  may  he  of  the  masculine  type  and  a  man's  skull  mmj  he  of  the  feminine  type. 
There  is  no  constant  characteristic  significant  of  the  male  or  female  skull.  As  a  general  rule, 
the  female  skull  is  smaller  than  the  male;  it  is  lighter,  the  muscular  ridges  and  processes  are 
less  distinct,  the  mastoid  processes  are  of  less  size,  the  orbital  margins  are  thin  and  sharp 
(Cunningham),  the  forehead  is  more  vertical  and  the  vertex  is  more  flattened  (Cunningham), 
and  the  edge  of  the  tympanic  plate  is  "  rounder  and  more  tuberculous  "  (Cunningham).  The 
frontal  air  sinuses  are  smaller  in  women  than  in  men,  one  reason  why  the  glabella  is  more 
prominent  in  men.  The  flattening  of  the  vertex  in  women,  previously  referred  to,  causes 
the  top  of  the  head  to  be  at  a  more  marked  angle  with  the  forehead  than  in  men  (Ecker). 
This  characteristic  was  recognized  by  the  Greek  sculptors  (Havelock  Ellis).  The  cephalic 
index,  which  shows  the  relation  of  skull  breadth  to  skull  length,  is  of  doubtful  value  in 
determining  sex. 

The  Fontanelles   (Fonticuli). 

Before  birth  the  bones  at  the  vertex  and  side  of  the  skull  are  separated  from  each  other  by 
membranous  intervals  in  which  bone  is  deficient.  These  intervals  are  principally  found  at  the 
four  angles  of  the  parietal  bones.  Hence  there  are  six  fontanelles.  Their  formation  is  due  to 
the  wave  of  ossification  being  circular  and  the  bones  quadrilateral ;  the  ossific  matter  first  meets 
at  the  margins  of  the  bones,  at  the  points  nearest  to  their  centres  of  ossification,  and  vacuities 

1  J.  Bland  Sutton  in  Henry  Morris'  Human  Anatomy.  ^  Ibid. 

*  Man  and  Woman,  by  Havelock  Ellis. 


8UPEBNUMEBABY,    WORMIAN  OB  SUTUBAL  BONES 


103 


or  spaces  are  left  at  the  angles,  which  are  called  fontanelles,  so  named  from  the  pulsations  of 
the  brain,  which  are  perceptible  at  the  anterior  fontanelle,  were  likened  to  the  rising  of  water 
in  a  fountain.  The  anterior  or  bregmatic  fontanelle  {fonticulus  frontalis)  is  the  largest;  it  is 
lozenge-shaped,  and  corresponds  to  the  junction  of  the  sagittal  and  coronal  sutures;  the  pos- 
terior fontanelle  {fonticulus  occipitalis),  of  smaller  size,  is  triangular,  and  is  situated  at  the 
junction  of  the  sagittal  and  lambdoid  sutures;  the  remaining  ones,  the  antero-lateral  and  the 
postero-lateral  fontanelles  {fonticulus  sphenoidalis  et  fonticulus  mastoideus),  are  situated  at  the 
inferior  angles  of  each  parietal  bone.  The  latter  are  closed  soon  after  birth;  the  two  at  the  two 
superior  angles  remain  open  longer;  the  posterior  being  closed  in  a  few  months  after  birth;  the 
anterior  remaining  open  until  the  first  or  second  year.  These  spaces  are  gradually  filled  in  by  an 
extension  of  the  ossifying  process  or  by  the  development  of.  a  Wormian  bone.  Sometimes  the  ante- 
rior fontanelle  remains  open  beyond  two  years,  and  is  occasionally  persistent  throughout  life. 

Supernumerary,  Wormian,^  Sutural  or  Epactal  Bones  (Ossa  Triquetra). 

In  addition  to  the  constant  centres  of  ossification  of  the  skull,  additional  ones  are  occasion- 
ally found  in  the  course  of  the  sutures.  These  form  irregular,  isolated  bones,  interposed  between 
the  cranial  bones,  and  have  been  termed  Wormian  bones  or  OSSa  triquetra.    They  are  most 


Fig.  62. — Skull  at  birth,  showing  the  anterior  and 
posterior  fontanelles. 


Fig.  63. — The  lateral  fontanelles. 


frequently  found  in  the  course  of  the  lambdoid  suture,  but  occasionally  also  occupy  the  situation 
of  the  fontanelles,  especially  the  posterior  and,  more  rarely,  the  anterior.  Frequently  one  is 
found  between  the  anterior  inferior  angle  of  the  parietal  bone  and  the  greater  wing  of  the 


Fig.  64. — Wormian  bones. 


Fig.  65. 


Fig.  66. 


sphenoid,  the  epicteric  bone  or  the  pterion  ossicle  (Fig.  63).  They  have  a  great  tendency  to  be 
symmetrical  on  the  two  sides  of  the  .skull,  and  they  vary  much  in  size,  being  in  some  cases  not 
larger  than  a  pin's  head,  and  confined  to  the  outer  table;  in  other  cases  so  large  that  one  pair  of 
these  bones  may  form  the  whole  of  the  occipital  bone  above  the  superior  curved  lines,  as  described 


*  Wormius,  a  physician  of  Copenhagen,  is  said  to  have  given  the  first  detailed  description  of  these  bones. 


104 


THE  SKELETON 


by  B^clard  and  Ward.  Their  number  is  generally  limited  to  two  or  three,  but  more  than  a 
hundred  have  been  found  in  the  skull  of  an  adult  hydrocephalic  skeleton.  In  their  development, 
structure,  and  mode  of  articulation  they  resemble  the  other  cranial  bones. 

Congenital  Fissures  and  Gaps. 

An  arrest  in  the  ossifying  process  may  give  rise  to  deficiencies  or  gaps;  or  to  fissures,  which 
are  of  importance  in  a  medico-legal  point  of  view,  as  they  are  liable  to  be  mistaken  for  fractures. 
The  fissures  generally  extend  from  the  margins  toward  the  centre  of  the  bone,  but  the  gaps 
may  be  found  in  the  middle  as  well  as  at  the  edges.  In  course  of  time  they  may  become  covered 
with  a  thin  lamina  of  bone. 

BONES  OF  THE  FACE    (OSSA  FACIEI). 

The  Facial  Bones  are  fourteen  in  number — viz.,  the 
Two  Nasal.  Two  Palate. 

Two  Superior  Maxillae.  Two  Inferior  Turbinated. 

Two  Lachrymal.  Vomer. 

Two  Malar.  Inferior  Maxilla  or  Mandible. 

"Of  these,  the  upper  and  lower  jaws  are  the  fundamental  bones  for  mastication^ 
and  the  others  are  accessories;  for  the  chief  function  of  the  facial  bones  is  to 
provide  an  apparatus  for  mastication,  while  subsidiary  functions  are  to  provide  for 
the  sense  organs  (eye,  nose,  tongue)  and  a  vestibule  to  the  respiratory  and  vocal 
organs.  Hence  the  variations  in  the  shape  of  the  face  in  man  and  the  lower 
animals  depend  chiefly  on  the  question  of  the  character  of  their  food  and  their 
mode  of  obtaining  it."^ 

The  Nasal  Bones  (Ossa  Nasalia). 

The  nasal  {nasus,  the  nose)  are  two  small  oblong  bones,  varying  in  size  and 
form  in  different  individuals;  they  are  placed  side  by  side  at  the  middle  and  upper 


Nasal  bone. 


Nasal  proc ^ 

/ 


Lachrymal  hone. 


Orbital  surface. 
Infra-orbital 
groove. 


Infra-orbital 
foramen 


Ant.  nasal  spine.- 


■Artie,  with  malar. 


Maxillary 
tuberosity. 


Fig.  67. — Nasal  and  lachrymal   bones  in  situ. 


part  of  the  face,  forming,  by  their  junction,  "the  bridge"  of  the  nose  (Fig.  67). 
Each  bone  presents  for  examination  two  surfaces  and  four  borders. 


1  W.  W.  Keen,  American  edition,  1887,  p.  185. 


THE  SUPEBIOB    MAXILLARY  BONES 


105 


Surfaces.  Outer  Surface. — The  outer  surface  is  concave  from  above  downward, 
convex  from  side  to  side;  it  is  covered  by  the  Pyramidalis  and  Compressor  nasi 
muscles,  and  gives  attachment  at  its  upper  part  to  a  few  fibres  of  the  Occipito- 
frontahs  muscle  (Theile).  It  is  marked  by  numerous  small  arterial  furrows,  and 
perforated  about  its  centre  by  a  foramen  {foramen  nasale),  sometimes  double, 
for  the  transmission  of  a  small  vein. 

Inner  Surface. — The  inner  surface  is  concave  from  side  to  side,  convex  from 
above  downward;  in  which  direction  it  is  traversed  by  a  longitudinal  groove 
(sometimes    a    canal),    for    the 

With  frontal  bone. 

With 


With 
'opposite  bone. 


Outer  Surface. 

Fig.  68. — Right  nasal  bone. 


frontal  spine. 

Crest. 

With 
perpendicular 
plate  of 
ethmoid. 


Groove  for  nasal  nerve. 


Inner  Surface. 

Fig.  69. — Left  nasal  bone. 


passage  of  a  branch  of  the  nasal 
nerve. 

Borders.  Superior  Border. — 
The  superior  border  is  narrow, 
thick,  and  serrated,  for  articula- 
tion with  the  nasal  notch  of  the 
frontal  bone. 

Inferior  Border. — The  inferior 
border  is  broad,  thin,  sharp,  in- 
clined obliquely  downward,  out- 
ward, and  backward,  and  serves 
for  the  attachment  of  the  lateral 
cartilage  of  the  nose.  This  bor- 
der presents,  about  its  middle,  a  notch,  through  which  passes  the  branch  of  the 
nasal  nerve  above  referred  to,  and  is  prolonged  at  its  inner  extremity  into  a  sharp 
spine,  which,  when  articulated  with  the  opposite  bone,  forms  the  nasal  angle. 

External  Border. — The  external  border  is  serrated,  bevelled  at  the  expense  of 
the  internal  surface  above  and  of  the  external  below,  to  articulate  with  the  nasal 
process  of  the  superior  maxillary. 

Internal  Border. — The  internal  border,  thicker  above  than  below,  articulates 
with  its  fellow  of  the  opposite  side,  and  is  prolonged  behind  into  a  vertical  crest, 
which  forms  part  of  the  septum  of  the  nose;  this  crest  articulates  above  down- 
ward with  the  nasal  spine  of  the  frontal  above,  and  the  perpendicular  plate  of 
the  ethmoid,  and  the  triangular  septal  cartilage  of  the  nose. 

Development.— By  one  centre  for  each  bone,  which  appears  about  the  eighth  week. 

Articulations. — With  four  bones:  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  opposite  nasal  and  the  superior  maxillary. 

Attachment  of  Muscles. — A  few  fibres  of  the  Occipito-frontalis  muscle. 

The  Superior  Maxillary  Bones  (Upper  Jaw  Bones  or  Maxillae). 

The  superior  maxillje  (maxilla,  the  jaw  bone)  are  the  most  important  bones 
of  the  face  from  a  surgical  point  of  view,  on  account  of  the  number  of  diseases  to 
which  some  of  their  parts  are  liable.  Their  careful  examination  becomes,  there- 
fore, a  matter  of  considerable  interest.  They  are  the  largest  bones  of  the  face, 
excepting  the  lower  jaw,  and  form,  by  their  union,  the  whole  of  the  upper  jaw. 
Each  maxilla  assists  in  the  formation  of  three  cavities,  the  roof  of  the  mouth,  the 
floor  and  outer  wall  of  the  nasal  fossse,  and  t!ie  floor  of  the  orbit,  and  also  enters 
into  the  formation  of  two  fossae,  the  zygomatic  and  spheno-maxillary,  and  two 
fissures,  the  spheno-maxillary  and  pterygo-maxillary.  The  bone  presents  for  exam- 
ination a  body  and  four  processes — malar,  nasal,  alveolar,  and  palate. 

The  Body  of  the  Superior  Maxilla  (Corpus  Maxlllas). 

The  body  is  somewhat  cuboid  and  is  hollowed  out  in  its  interior  to  form  a 
large  cavity,  the  antrum  of  Highmore  (sinus  maxillaris) .     Its  surfaces  are  four — 


106 


THE  SKELETON 


an  external  or  facial,  a  posterior  or  zygomatic,  a  superior  or  orbital,  and   an 
internal  or  nasal. 

Surfaces.  External  Surface  (fades  anterior) . — The  external  anterior  or  facial 
surface  (Fig.  70)  is  directed  forward  and  outward.  It  presents  at  its  lower  part  a 
series  of  eminences  corresponding  to  the  position  of  the  anterior  five  alveoli  (juga 
alveolaria) .  Just  above  those  for  the  incisor  teeth  is  a  depression,  the  incisive  or 
m3niiiform  fossa,  which  gives  origin  to  the  Depressor  alie  nasi ;  and  below  it  to  the 
alveolar  border  is  attached  a  slip  of  the  Orbicularis  oris.  Above  and  a  little  exter- 
nal to  it  the  Compressor  nasi  arises.  More  external  is  another  depression,  the 
canine  fossa  (fossa  canina) ,  larger  and  deeper  than  the  incisive  fossa,  from  which  it 
is  separated  by  a  vertical  ridge,  the  canine  eminence,  corresponding  to  the  socket  of 
the  canine  tooth.  The  canine  fossa  gives  origin  to  the  Levator  anguli  oris.  Above 
the  canine  fossa  is  the  infraorbital  foramen  {foramen  infraorhitale) ,  the  termination 

Outer  Surface. 


TENDO    OCULI 


Incisive  fossa.- 


Posterior  dental 
canals. 


Maxillary  tuberosity. 


'»»««.     Bicuspids. 
Fig.  70. — Left  superior  maxilla.     Outer  surface. 


of  the  infraorbital  canal;  it  transmits  the  infraorbital  vessels  and  nerve.  Some- 
times the  infraorbital  canal  opens  by  two,  very  rarely  by  three,  orifices  on  the 
face.  Above  the  infraorbital  foramen  is  the  margin  of  the  orbit  (margo  infraor- 
bitalis),  which  affords  partial  attachment  to  the  Levator  labii  superioris  proprius. 
To  the  sharp  margin  of  bone  which  bounds  this  surface  in  front  and  separates 
it  from  the  internal  surface  is  attached  the  Dilator  naris  posterior. 

Posterior  Surface  (fades  infratemporalis) . — The  posterior  or  zygomatic  or  infra- 
temporal surface  is  convex,  directed  backward  and  outward,  and  forms  part  of  the 
zygomatic  fossa.  It  is  separated  from  the  facial  surface  by  a  strong  ridge  of  bone, 
the  malar  process,  which  extends  upward  from  the  socket  of  the  second  molar 
tooth.  It  presents  about  its  centre  several  apertures  leading  to  canals  in  the 
substance  of  the  bone;  they  are  termed  the  posterior  dental  canals  (foramina  alveo- 
laria), and  transmit  the  posterior  dental  vessels  and  nerves.  At  the  lower  part  of 
this  surface  is  a  rounded  eminence,  the  maxillary  tuberosity  (tuber  maxillare), 
especially  prominent  after  the  growth  of  the  wisdom-tooth,  rough  on  its  inner 


THE  SUPERIOR    MAXILLARY  BONES  107 

side  for  articulation  with  the  tuberosity  of  the  palate  bone,  and  sometimes  with 
the  external  pterygoid  plate.  It  gives  attachment  to  a  few  fibres  of  origin  of 
the  Internal  pterygoid  muscle.  Immediately  above  this  is  a  smooth  surface, 
which  forms  the  anterior  boundary  of  the  spheno-maxillary  fossa;  it  presents  a 
groove  which,  running  obliquely  downward,  is  converted  into  a  canal  by  articu- 
lation with  the  palate  bone,  forming  the  posterior  palatine  or  palato-maxillary  canal 
for  the  descending  palatine  artery  and  great  palatine  nerve. 

Superior  Surface  (fades  orhitalis). — The  superior  or  orbital  surface  is  thin, 
smooth,  triangular,  and  forms  part  of  the  floor  of  the  orbit.  It  is  bounded  in- 
ternally by  an  irregular  margin  which  in  front  presents  a  notch,  the  lachrymal  notch 
{incisura  lacrimalis) ,  which  receives  the  lachrymal  bone;  in  the  middle  articulates 
with  the  OS  planum  of  the  ethmoid,  and  behind  with  the  orbital  process  of  the 
palate  bone;  bounded  externally  by  a  smooth,  rounded  edge  which  enters  into  the 
formation  of  the  spheno-maxillary  fissure,  and  which  sometimes  articulates  at  its 
anterior  extremity  with  the  orbital  plate  of  the  sphenoid;  bounded  in  front  by  part 
of  the  circumference  of  the  orbit,  which  is  continuous  on  the  inner  side  with  the 
nasal,  on  the  outer  side  with  the  malar  process.  Along  the  middle  hne  of  the  orbital 
surface  is  a  deep  groove,  the  infraorbital  groove  {sulcus  infraorbitalis) ,  for  the  pas- 
sage of  the  infraorbital  vessels  and  nerve.  The  groove  commences  at  the  middle 
of  the  outer  border  of  this  surface,  and,  passing  forward,  terminates  in  a  canal, 
which  subdivides  into  two  branches.  One  of  the  canals,  the  infraorbital  canal 
(canalis  infraorbitalis),  opens  just  below  the  margin  of  the  orbit;  the  other,  which 
is  smaller,  runs  downward  in  the  substance  of  the  anterior  wall  of  the  antrum; 
it  is  called  the  anterior  dental  canal,  and  transmits  the  anterior  dental  vessels 
and  nerve  to  the  front  teeth  of  the  upper  jaw.  From  the  back  part  of  the 
infraorbital  canal  a  second  small  canal  is  sometimes  given  off,  which  runs  down- 
w^ard  in  the  outer  wall  of  the  antrum,  and  conveys  the  middle  dental  nerve  to 
the  bicuspid  teeth.  Occasionally  this  canal  is  derived  from  the  anterior  dental. 
At  the  inner  and  fore  part  of  the  orbital  surface,  just  external  to  the  lachrymal 
groove  for  the  nasal  duct,  is  a  depression  which  gives  origin  to  the  Inferior  oblique 
muscle  of  the  eye. 

Internal  Surface  (fades  nasalis). — The  internal  or  nasal  surface  (Fig.  71)  is 
unequally  divided  into  two  parts  by  a  horizontal  projection  of  bone,  the  palate 
process  (processus  palatinus) :  the  portion  above  the  palate  process  forms  part  of 
the  outer  wall  of  the  nasal  fossa? ;  that  below  it  forms  part  of  the  cavity  of  the 
mouth.  The  superior  division  of  this  surface  presents  a  large,  irregular  opening, 
the  maxillary  hiatus  (hiatus  maxillaris) ,  leading  into  the  antrum  of  Highmore. 
At  the  upper  border  of  this  aperture  are  numerous  broken  cellular  cavities,  which 
in  the  articulated  skull  are  closed  in  by  the  ethmoid  and  lachrymal  bones.  Below 
the  aperture  is  a  smooth  concavity  which  forms  part  of  the  inferior  meatus  of  the 
nasal  fossae,  and  behind  it  is  a  rough  surface  which  articulates  with  the  perpendic- 
ular plate  of  the  palate  bone,  traversed  by  a  groove  which,  commencing  near  the 
middle  of  the  posterior  border,  runs  obliquely  downward  and  forward,  and  forms, 
when  completed  by  its  articulation  with  the  palate  bone,  the  posterior  palatine  or 
palato-maxillary  canal.  In  front  of  the  opening  of  the  antrum  is  a  deep  groove, 
converted  into  a  canal  (canalis  nasolacrimalis)  by  the  lachrymal  and  inferior 
turbinated  bones.  The  groove  is  called  the  lachrymal  groove  (sulcus  lacrimalis), 
and  lodges  the  nasal  duct.  More  anteriorly  is  a  well-marked  rough  ridge,  the 
inferior  turbinated  crest  (crista  conchalis),  for  articulation  with  the  inferior  turbin- 
ated bone.  The  shallow  concavity  above  this  ridge  forms  part  of  the  middle 
meatus  of  the  nose,  while  that  below  it  forms  part  of  the  inferior  meatus.  The 
portion  of  this  surface  below  the  palate  process  is  concave,  rough,  and  uneven, 
and  perforated  by  numerous  small  foramina  for  the  passage  of  nutrient  vessels. 
It  enters  into  the  formation  of  the  roof  of  the  mouth. 


108 


THE   ^SKELETON 


The  Antrum  of  Highmore,  Maxillary  Antrum,  or  Maxillary  Sinus  {sinus  maxil- 
laris),  is  a  pyramidal  cavity  hollowed  out  of  the  body  of  the  maxillary  bone. 
It  varies  much  in  size.  It  is  in  most  cases  a  large  cavity,  but  in  some  is  very 
small.    The  apex  of  the  antrum,  directed  outward,  is  formed  by  the  malar  process; 


Bones  partially  dosing  orifice  of  antrum 
marked  in  outline. 


Ethmoid. 

Inferior  turbinated. 

Palate. 


^u!la,. 


Anterior  nasal  spine. 


Bristle  passed 
through  anterior 
palatine  canal. 


Fig.  71. — Left  superior  maxilla.     Internal  surface. 

its  base  by  the  outer  wall  of  the  nose.  Its  walls  are  everywhere  exceedingly  thin, 
and  correspond  to  the  orbital,  facial,  and  zygomatic  surfaces  of  the  body  of  the 
bone.  The  antral  floor  is,  in  most  persons,  on  a  level  with  the  floor  of  the  nasal 
fossa,  but  in  some  individuals  it  is  on  a  lower  level.  Not  unusually  the  inner 
wall  of  the  antrum  will  be  found  to  contain  depressions  or  pockets.  In  rare 
instances  an  antral  cavity  is  made  into  two  by  a  bony  septum.  Its  inner  wall  or 
base  presents,  in  the  disarticulated  bone,  a  large,  irregular  aperture  {hiatus 
maxillaris),  which  communicates  with  the  nasal  fossa.  The  margins  of  this 
aperture  are  thin  and  ragged,  and  the  aperture  itself  is  much  contracted  by  its 
articulation  with  the  ethmoid  above,  the  inferior  turbinated  below,  and  the 
palate  bone  behind.^  In  the  articulated  skull  this  cavity  communicates  with 
the  middle  meatus  of  the  nasal  cavity,  generally  by  two  small  apertures  left 
between  the  above-mentioned  bones.  In  the  recent  state  usually  only  one  small 
opening  exists,  near  the  upper  part  of  the  cavity,  sufficiently  large  to  admit  the 
end  of  a  probe,  the  other  being  closed  by  the  lining  membrane  of  the  sinus.  That 
the  opening  into  the  nasal  fossa  does  not  afford  the  best  drainage  is  demon- 
strated, when  we  note  that  it  is  at  the  highest  and  not  at  the  lowest  point  of  the 
antrum.  "In  rare  instances  the  antrum  communicates  with  the  anterior  eth- 
moidal cells,  or  the  orbital  and  posterior  ethmoidal  cells  and  sphenoidal  sinuses."^ 
At  birth  the  antrum  exists,  though  in  a  rudimentary  state.  It  attains  its  full 
size  from  the  twelfth  to  the  fourteenth  year. 

Crossing  the  cavity  of  the  antrum  are  often  seen  several  projecting  laminae  of 
bone,  similar  to  those  seen  in  the  sinuses  of  the  cranium ;  and  on  its  posterior  wall 


1  In  some  cases,  at  any  rate,  the  lachrymal  bone  encroaches  slightly  on  the  anterior  superior  portion  of  the 
opening,  and  assists  in  forming  the  inner  wall  of  the  antrum. 

-  D.  Kerfoot  Shute,  in  the  Reference  Handbook  of  the  Medical  Sciences. 


THE   SUPERIOR    MAXILLARY  BONES  109 

are  the  posterior  dental  canals,  transmitting  the  posterior  dental  vessels  and  nerves 
to  the  teeth.  Projecting  into  the  floor  are  several  conical  processes,  corresponding 
to  the  roots  of  the  first  and  second  molar  teeth;'  in  some  cases  the  floor  is  per- 
forated by  the  teeth  in  this  situation. 

It  is  from  the  extreme  thinness  of  the  walls  of  this  cavity  that  we  are  enabled  to  explain  how 
a  tumor  growing  from  the  antrum  encroaches  upon  the  adjacent  parts,  pushing  up  the  floor  of 
the  orbit,  and  displacing  the  eyeball,  projecting  inward  into  the  nose,  protruding  forward  on 
to  the  cheek,  and  making  its  way  backward  into  the  zygomatic  fossa  and  downward  into  the 
mouth. 

The  Processes  of  the  Superior  Maxillae. 

Malar  Process  (processus  zygomaticus). — The  malar  process  is  a  rough,  trian- 
gular eminence,  situated  at  the  angle  of  separation  of  the  facial  from  the  zygo- 
matic surface.  In  front  it  is  concave,  forming  part  of  the  facial  surface;  behind 
it  is  also  concave,  and  forms  part  of  the  zygomatic  fossa;  above  it  is  rough  and 
serrated  for  articulation  with  the  malar  bone;  whilst  below  a  prominent  ridge 
marks  the  division  between  the  facial  and  zygomatic  surfaces.  A  small  part  of 
the  Masseter  muscle  arises  from  this  process. 

Nasal  Process  (processus  frontalis). — The  nasal  process  is  a  strong,  triangular 
plate  of  bone,  which  projects  upward,  inward,  and  backward  by  the  side  of  the 
nose,  forming  part  of  its  lateral  boundary.  Its  external  surface  is  concave,  smooth, 
perforated  by  numerous  foramina,  and  gives  attachment  to  the  Levator  labii 
superioris  aheque  nasi,  the  Orbicularis  palpebrarum,  and  Tendo  oculi.  Its 
internal  surface  forms  part  of  the  outer  wall  of  the  nasal  fossse;  at  its  upper 
part  it  presents  a  rough,  uneven  surface,  which  articulates  with  the  ethmoid 
bone,  closing  in  the  anterior  ethmoidal  cells;  below  this  is  a  transverse  ridge,  the 
superior  turbinated  crest  (crista  ethmoidalis),  for  articulation  with  the  middle  tur- 
binated bone  of  the  ethmoid,  bounded  below  by  a  shallow,  smooth  concavity 
which  forms  part  of  the  middle  meatus;  below  this  again  is  the  inferior  turbinated 
crest  (already  described),  where  the  process  joins  the  body  of  the  bone.  Its  upper 
border  articulates  with  the  frontal  bone.  The  anterior  border  of  the  nasal  process 
is  thin,  directed  obliquely  downward  and  forward,  and  presents  a  serrated  edge  for 
articulation  with  the  nasal  bone;  its  posterior  border  is  thick,  and  hollowed  into 
a  groove,  the  lachrjrmal  groove  (sulcus  lacrimalis) ,  for  the  naso-lachrymal  duct:  of 
the  two  margins  of  this  groove,  the  inner  one  articulates  with  the  lachrymal  bone; 
the  outer  one  forms  part  of  the  circumference  of  the  orbit.  Just  where  the  latter 
joins  the  orbital  surface  is  a  srnall  tubercle,  the  lachrymal  tubercle;  this  serves  as 
a  guide  to  the  position  of  the  lachrymal  sac  in  the  operation  for  fistula  laclirymalis. 
The  lachrymal  groove  in  the  articulated  skull  is  converted  into  a  canal  (canalis 
lacrimalis)  by  the  lachrymal  bone  and  lachrymal  process  of  the  inferior  turbin- 
ated; it  is  directed  downward,  and  a  little  backward  and  outward,  is  about  the 
diameter  of  a  goose-quill,  slightly  narrower  in  the  middle  than  at  either  extremity, 
and  terminates  below  in  the  inferior  meatus.    'It  lodges  the  nasal  duct. 

Alveolar  Process  (processus  alveolaris). — The  alveolar  process  is  the  thickest 
and  most  spongy  part  of  the  bone,  broader  behind  than  in  front,  and  excavated 
into  deep  cavities  for  the  reception  of  the  teeth  (alveoli  dentales).  These  cavities 
are  eight  in  number,  and  vary  in  size  and  depth  according  to  the  teeth  they  con- 
tain. That  for  the  canine  tooth  is  the  deepest;  those  for  the  molars  are  the 
widest,  and  subdivided  into  minor  cavities  by  septa;  those  for  the  incisors  are 
single,  but  deep  and  narrow.  The  limbus  alveolaris  is  the  broad  inferior  margin 
of  the  alveolar  process.     On  the  anterior  surface  are  five  projections  correspond- 

'  The  number  of  teeth  whose  fangs  are  in  relation  to  the  floor  of  the  antrum  is  variable.  The  antrum  "  may 
extend  so  as  to  be  in  relation  to  all  the  teeth  of  the  true  maxilla,  from  the  canine  to  the  dens  sapientise."  (See 
Mr.  Salter  on  Abscess  of  the  Antrum,  in  a  System  of  Surgery,  edited  by  T.  Holmes,  2d  ed.,  vol.  iv.  p.  356). 


110 


THE  SKELETON 


Foramen  of  Stenson. 


Foramen  of  Scarpa. 


Palate  process  of 
maxillary  bone. 


Horizontal  plate 
of  palate  bone 


rior  palatine  canal. 


ing  to  the  five  anterior  alveoli.  They  are  called  juga  alveolaria.  The  cavities 
for  the  teeth  are  separated  by  septa  inter  alveolar  la.  "^Fhe  Buccinator  muscle  arises 
from  the  outer  surface  of  this  process  as  far  forward  as  the  first  molar  tooth. 

Palate  Process  {processus  palatinus). — The  palate  process,  thick  and  strong, 
projects  horizontally  inward  from  the  inner  surface  of  the  bone.    It  is  much  thicker 

in  front  than  behind,  and 
Anterior  palatine  canal.  forms  a  considerable  part 

of  the  floor  of  the  nostril 
and  the  roof  of  the  mouth. 
Its  inferior  surface  (Fig. 
72)  is  concave,  rough  and 
uneven,  contains  numer- 
ous little  cavities  for  the 
glands  of  the  mucous 
membrane,  and  forms 
part  of  the  roof  of  the 
mouth.  This  surface  is 
perforated  by  niunerous 
foramina  for  the  passage 
of  the  nutrient  vessels, 
chaimelled  at  the  back 
part  of  its  alveolar  bor- 
der by  a  longitudinal 
groove,  sometimes  a  canal, 
for  the  transmission  of 
the  posterior  palatine 
vessels,  and  the  great  pos- 
terior palatine  nerve  from 
Meckel's  ganglion,  and 
presents  little  depressions 
for  the  lodgement  of  the  palatine  glands.  When  the  two  superior  maxillae 
bones  are  articulated  together,  a  large  orifice  may  be  seen  in  the  middle 
line,  immediately  behind  the  incisor  teeth.  This  is  the  anterior  palatine  fossa 
{foramen  incisivum).  On  examining  the  bottom  of  this  fossa  four  canals  are 
seen :  two  branch  off  laterally  to  the  right  and  left  nasal  fossfe,  and  two,  one  in 
front  and  one  behind,  lie  in  the  middle  line.  The  former  pair  of  these  openings 
are  named  the  incisor  foramina  or  foramina  of  Stenson;  they  are  the  openings  of 
the  forking  incisor  canal  {canalis  incisiviis),  through  which  pass  the  anterior  or 
terminal  branches  of  the  descending  or  posterior  palatine  arteries,  which  ascend 
from  the  mouth  to  the  nasal  fossae,  and  they  contain  the  remains  of  Jacobson's 
organ.  The  canals  in  the  middle  line  are  termed  the  foramina  of  Scarpa,  and 
transmit  the  naso-palatine  nerves,  the  left  passing  through  the  anterior,  and  the 
right  through  the  posterior,  canal.  Occasionally  in  adults'  skulls,  often  in  chil- 
dren's skulls,  on  the  palatal  surface  of  the  process  a  delicate  linear  suture  may 
sometimes  be  seen  extending  from  the  anterior  palatine  fossa  to  the  interval 
between  the  lateral  incisor  and  the  canine  tooth.  This  marks  out  the  inter- 
maxillary or  pre-maxillary  bones  or  the  incisive  bone  {os  incisivum)  on  each  side. 
It  is  the  portion  of  the  upper  jaw  which  is  in  front  of  the  anterior  palatine 
foramen,  and  which  in  some  animals  exists  permanently  as  a  separate  piece. 
It  includes  the  whole  thickness  of  the  alveolus,  the  corresponding  part  of  the  floor 
of  the  nose,  and  the  anterior  nasal  spine,  and  contains  the  sockets  of  the  incisor 
teeth.  The  pre-maxillary  bone  has  a  separate  centre  of  ossification  and  develops 
in  association  with  the  vertical  plate  of  the  ethmoid  and  the  vomer.  The  incisive 
bones,  which  are  always  present  in  the  foetus,  usually  join  the  rest  of  the  bone 


1 


Accessory  palatine  foramen. 
Fig.  72. — The  palate  and  alveolar  arch. 


THE   SUPERIOR  MAXILLARY   BONES 


111 


early  in  development,  more  or  less  well-marked  sutures  (sutura  incisiva)  indi- 
cating the  lines  of  union.  In  double  hare-lip  the  incisive  bones  covered  by  the 
median  part  of  the  lip  are  frequently  not  joined  to  the  palate  processes  of  the 
superior  maxillary  bones,  but  are  fixed  to  the  nasal  septum.  Albrecht  maintains 
that  instead  of  two  intermaxillary  seg- 
ments or  incisive  bones,  each  carrying 
two  incisor  teeth,  there  are  originally 
four,  each  carrying  the  rudiment  of 
one  tooth  and  each  of  a   triangular 


CNDOGNATHION 

SUTURE    I  CNOO-MESOGNATHION 

SUTURE 
MESOGNATHION 


ENOOGNATHION 


EXOGNATHION 


CNOO-EXOGNATHION 
SUTURE 


MESO- EXOGNATHION 
SUTURE 


Fig.  73. — The  pre-maxilla  and  its  sutures.     (Albrecht.) 


shape,  the  apices  approaching  at  the 
anterior  palatine  canal.  The  seg- 
ments are  separated  by  five  sutures. 
The  maxilla  is  called  the  exo-gnathion, 
each  mesial  segment  is  called  an  endo- 
gnathion,  and  each  lateral  segment 
a  meso-gnathion.    In  hare-lip  the  cleft 

may  l^e  {)urely  in  the  soft  parts,  but  may  pass  into  the  nostril,  the  alveolar  portion 
of  the  maxilla,  or  through  the  palate  bone  (cleft  palate).  In  hare-lip  with  cleft 
palate  (alveolar  hare-lip)  Kolliker  believes  that  the  cleft  is  between  the  maxilla  and 
the  intermaxillary  bone;  that  is,  between  the  exo-gnathion  and  the  meso-gnathion. 
Albrecht  is  of  the  opinion  that  the  cleft  is  between  the  endo-gnathion  and  the  meso- 
gnathion.  In  some  cases  of  double  hare-lip  the  pre-maxillary  segment  contains  the 
germs  of  four  incisors,  and  in  such  a  case  the  cleft  must  be  between  the  exo- 
gnathion  and  the  meso-gnathion.  In  other  cases  it  contains  but  two,  and  in  such 
a  case  the  cleft  must  be  as  indicated  by  Albrecht,  as  Fergusson's  explanation  is 
not  in  accordance  with  our  knowledge  of  development.  Fergusson  believed  that 
if  the  germs  of  four  incisors  are  not  present  the  missing  ones  were  lost  in  the  gap. 
The  upper  surface  of  the  palate  process  is  concave  from  side  to  side,  smooth,  and 
forms  part  of  the  floor  of  the  nose.     It  presents  the  upper  orifices  of  the  foramina  of 


Fig.  74. — KoUiker's  theory  of  alveolar  hare-lip. 
(Poirier  and  Charpy.) 


Fig.  75. — Alveolar  hare-lip  according  to  the  theory  of 
Albrecht.     (Poirier  and  Charpy.) 


Stenson  and  Scarpa,  the  former  being  on  each  side  of  the  middle  line,  the  latter 
being  situated  in  the  intermaxillary  suture,  and  therefore  not  visible  unless  the  two 
bones  are  placed  in  apposition.  The  outer  border  of  the  palate  process  is  incorpor- 
ated with  the  rest  of  the  bone.  The  inner  border  is  thicker  in  front  than  behind,  and 
is  raised  above  into  a  ridge,  the  nasal  crest  (crista  nasalis),  which,  with  the  corre- 
sponding ridge  in  the  opposite  bone,  forms  a  groove  for  the  reception  of  the  vomer. 
In  front  this  crest  rises  to  a  considerable  height,  and  this  portion  is  named  the  incisor 
crest.  The  anterior  margin  is  bounded  by  the  thin,  concave  border  of  the  opening 
of  the  nose,  prolonged  forward  internally  into  a  sharp  process,  forming,  with  a 
similar  process  of  the  opposite  bone,  the  anterior  nasal  spine  (spina  nasalis  anterior). 
The  posterior  border  is  serrated  for  articulation  with  the  horizontal  plate  of  the 
palate  bone. 


112 


THE   SKELETON 


Anterior  Surface. 


Development. — This  bone  commences  to  ossify  at  a  very  early  period,  and 
ossification  proceeds  in  it  with  great  rapidity,  so  that  it  is  difficult  to  ascertain  with 
certainty  its  precise  number  of  centres.  It  appears,  however,  probable  that  it  is 
ossified  from  four  centres,  which  are  deposited  in  membrane.  1.  One  which  forms 
that  portion  of  the  body  of  the  bone  which  lies  internal 
to  the  infraorbital  canal,  including  the  floor  of  the  orbit, 
the  outer  wall  of  the  nasal  fossa,  and  the  nasal  process, 
2.  A  second  which  gives  origin  to  that  portion  of  the 
bone  which  lies  external  to  the  infraorbital  canal  and  the 
malar  process.  3.  A  third  from  which  is  developed  the 
palatine  process  posterior  to  Stenson's  canal  and  the  ad- 
joining part  of  the  nasal  wall.  4.  And  a  fourth  for  the 
front  part  of  the  alveolus  which  carries  the  incisor  teeth 
and  corresponds  to  the  pre-maxillary  bone  of  the  lower 
animals.  These  centres  appear  about  the  eighth  week, 
and  by  the  tenth  week  the  three  first-named  centres 
have  become  fused  together  and  the  bone  consists  of  two 
portions,  one  the  maxilla  proper,  and  the  other  the  pre- 
maxillary  portion.  The  suture  between  these  two  por- 
tions on  the  palate  persists  till  middle  life,  but  is  not  to 
be  seen  on  the  facial  surface.  This  is  believed  by  Cal- 
lender  to  be  due  to  the  fact  that  the  front  wall  of  the 
sockets  of  the  incisive  teeth  is  not  formed  by  the  pre- 
FiG.  76.  —  Development  of    maxillary  bouc,  but  by  an  outgrowth  from  the  facial  part 

superior    maxillary    bone.     At         „  ^,  ''        .  .,,  r^\^  i  i      i 

birth.  oi  the  superior  maxilla.     1  he  antrum  appears  as  a  shal- 

low groove  on  the  inner  surface  of  the  bone  at  an  ear\ier 
period  than  any  of  the  other  nasal  sinuses,  its  development  commencing  about 
the  fourth  month  of  f«etal  life.  The  sockets  for  the  teeth  are  formed  by  the 
growing  downward  of  two  plates  from  the  dental  groove,  which  subsequently 
becomes  divided  by  partitions  jutting  across  from  the  one  to  the  other.  If  the 
two  palate  processes  fail  to  unite  partially  or  completely,  a  partial  or  complete 
cleft  palate  results. 

Articulations. — With  nine  bones:  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  seven  of  the  face — viz.,  the  nasal,  malar,  lachrymal,  inferior  turbinated,  palate, 
vomer,  and  its  fellow  of  the  opposite  side.  Sometimes  it  articulates  with  the  orbital 
plate  of  the  sphenoid,  and  sometimes  with  its  external  pterygoid  plate. 

Attachment  of  Muscles. — To  twelve:  the  Orbicularis  palpebrarum,  Obliquus 
oculi  inferior.  Levator  labii  superioris  aljeque  nasi,  I>evator  labii  superioris  pro- 
prius.  Levator  anguli  oris.  Compressor  nasi,  Depressor  ahe  nasi.  Dilatator  naris 
posterior,  Masseter,  Buccinator,  Internal  pterygoid,  and  Orbicularis  oris. 


Inferior  Surface. 


CHANGES  PRODUCED  IN  THE  UPPER  JAW  BY  AGE. 

At  birth  and  during  infancy  the  diameter  of  the  bone  is  greater  in  an  antero-posterior  than 
in  a  vertical  direction.  Its  nasal  process  is  long,  its  orbital  surface  large,  and  its  tuberosity 
well  marked.  In  the  adult  the  vertical  diameter  is  the  greater,  owing  to  the  development  of 
the  alveolar  process  and  the  increase  in  size  of  the  antrum.  In  old  age  the  bone  approaches 
again  in  character  to  the  infantile  condition:  its  height  is  diminished,  and  after  the  loss  of  the 
teeth  the  alveolar  process  is  absorbed,  and  the  lower  part  of  the  bone  contracted  and  diminished 
in  thickness. 


The  Lachrymal  Bone  (Os  Lacrimale). 

The  lachrymal  {lachryma,  a  tear)  is  the  smallest  and  most  fragile  bone  of 
the  face.  There  are  two  lachrymal  bones.  They  are  situated  at  the  front  part 
of  the  inner  wall  of  the  orbit  (Fig.  67),  and  resemble  somewhat  in  form,  thinness, 


THE   MALAR    BONE  113 

and  size  a  finger-nail;  hence  they  are  termed  theossa  unguis.    Each  bone  presents 
for  examination  two  surfaces  and  four  borders. 

Surfaces.  External  Surface. — The  external  or  orbital  surface  (Fig.  77)  is  divided 
bv  a  vertical  ridge,  the  lachrymal  crest  (crista  lacrimalis  posterior),  into  two  parts. 
The  portion  of  bone  in  front  of  this  ridge,  the  lachr3mial  sulcus  (sulcus  lacrimalis), 
presents  a  smooth,  concave,  longitudinal  groove,  the  free  margin  of  which  unites 
with  the  nasal  process  of  the  superior  maxillary  bone,  completing  the  lachrymal 
groove.  The  upper  part  of  this  groove  (fossa  sacci  lacrimalis) 
lodges  the  lachrymal  sac;  the  lower  part  (sulcus  lacrimalis)  wuhfronmi. 

lodges  the  nasal  duct.  The  portion  of  bone  behind  the  ridge 
is  smooth,  slightly  concave,  and  forms  part  of  the  inner  wall 
of  the  orbit.  The  ridge,  with  a  part  of  the  orbital  surface 
inmiediately  behind  it,  affords  attachment  to  the  Tensor  tarsi 
muscle:  it  terminates  below  in  a  small,  hook-like  projection, 
the  hamular  process  (hamulus  lacrimalis),  which  articulates 
with  the  lachrymal  tubercle  of  the  superior  maxillary  bone, 
and  completes  the  upper  orifice  of  the  lachrymal  groove. 
It  sometimes  exists  as  a  separate  piece,  which  is  then  called  ^^  fl^^^v, 
the  lesser  lachrymal  bone.  in/*''"^'"" 

Internal  Surface. — The  internal  or  nasal  surface  presents       Fig.  77.  —  Left  lachry- 

,  ,    „  !•  J       ,1  •  1  -i  J  mal  bone.      External  sur- 

a  depressed  furrow,  correspondmg  to  the  ridge  on  its  outer    face.    (Siightiy  enlarged.) 
surface.    The  surface  of  bone  in  front  of  this  forms  part  of 
the  middle  meatus,  and  that  behind  it  articulates  with  the  ethmoid  bone,  fill- 
ing in  the  anterior  ethmoidal  cells. 

Borders. — Of  the  four  borders,  the  anterior  is  the  longest,  and  articulates  with 
the  nasal  process  of  the  superior  maxillary  bone.  The  posterior,  thin  and  uneven, 
articulates  with  the  os  planum  of  the  ethmoid.  The  superior,  the  shortest  and 
thickest,  articulates  with  the  internal  angular  process  of  the  frontal  bone.  The 
inferior  is  divided  by  the  lower  edge  of  the  vertical  crest  into  two  parts;  the  poste- 
rior part  articulates  with  the  orbital  plate  of  the  superior  maxillary  bone;  the 
anterior  portion  is  prolonged  downward  into  a  pointed  process,  which  articulates 
with  the  lachrymal  process  of  the  inferior  turbinated  bone  and  assists  in  the  forma- 
tion of  the  lachrymal  groove. 

Development. — By  a  single  centre,  which  makes  its  appearance  soon  after  ossifi- 
cation of  the  vertebrfe  has  commenced. 

Articulations. — With  four  bones:  two  of  the  cranium,  the  frontal  and  ethmoid, 
and  two  of  the  face,  the  superior  maxillary  and  the  inferior  turbinated. 

Attachment  of  Muscles. — To  one  muscle,  the  Tensor  tarsi. 

The  Malar  Bone  (Os  Zygomaticum). 

The  name  malar  is  derived  from  mala,  the  cheek.  The  malar  or  yoke  bone  is 
also  called  the  cheek  bone.  There  are  two  malar  bones.  Plach  is  a  small,  quad- 
rangular bone,  situated  at  the  upper  and  outer  part  of  the  face.  They  form 
the  prominence  of  the  cheek,  part  of  the  outer  wall  and  floor  of  the  orbit,  and 
part  of  the  temporal  and  zygomatic  fossa?  (Fig.  78).  Each  bone  presents  for 
examination  an  external  and  an  internal  surface;  four  processes,  the  frontal, 
orbital,  maxillary,  anfl  zygomatic  processes;  and  four  borders. 

Surfaces.  External  or  Malar  Surface  (fades  malaris). — The  external  surface 
(Fig.  79)  is  smooth,  convex,  perforated  near  its  centre  by  a  small  aperture,  the 
malar  foramen  (foramen  zygomaticofaciale),  for  the  passage  of  nerves  and  vessels 
from  the  orbit.  The  malar  surface  is  covered  by  the  Orbicularis  palpebrarum 
muscle,  and  affords  attachment  to  the  Zygomaticus  major  and  minor  muscles. 

8 


114 


THE  SKELETON 


Internal  or  Temporal  Surface  (fades  temporalis). — The  internal  surface  (Fig.  80), 
directed  backward  and  inward,  is  concave,  presenting  internally  a  rough, 
triangular  surface,  for  articulation  with  the  superior  maxillary  bone;  and  exter- 
nally, a  smooth  concave  surface,  which  above  forms  the  anterior  boundary  of 


Zygoma- 
tic proc. 


Fig.  78. — Malar  bone  in  situ. 


the  temporal  fossa,  and  below,  where  it  is  wider,  forms  part  of  the  zygomatic 
fossa.  This  surface  presents,  a  little  above  its  centre,  the  aperture  of  a  malar 
canal  (foramen  zygomaticotemporale) ,  and  affords  attachment  to  a  portion  of  the 
Masseter  muscle  at  its  lower  part. 


Bristles  passed 

through  temporo- 

malar  canals. 


yfiih  frontal. 


Fig.  79. — Left  malar  bone.     Outer  surface. 


Fig.  80. — Left  malar  bone.     Inner  surface. 


Processes.  Frontal  Process  (processus  frontosphenoidalis).—Oi  the  four 
processes,  the  frontal  is  thick  and  serrated,  and  articulates  with  the  external 
angular  process  of   the   frontal    bone.     To  its  orbital  margin   is  attached  the 


external  tarsal  ligament. 


Orbital  Process. — The  orbital  process  is  a  thick  and  strong  plate,  which  projects 
backward  from  the  orbital  margin  of  the  bone.    Its  supero-internal  surface  (fades 


1 


THE  PALATE   BONE  115 

orbitalis),  smooth  and  concave,  forms,  by  its  junction  with  the  orbital  surface  of  the 
superior  maxillary  bone  and  with  the  great  wing  of  the  sphenoid,  part  of  the  floor 
and  outer  wall  of  the  orbit.  Its  infero-external  surface,  smooth  and  convex,  forms  part 
of  the  zygomatic  and  temporal  fossa?.  Its  anterior  marcjin  is  smooth  and  rounded, 
forming  part  of  the  circumference  of  the  orbit.  Its  superior  margin,  rough  and 
directed  horizontally,  articulates  with  the  frontal  bone  behind  the  external  angular 
process.  Its  posterior  margin  is  rough  and  serrated  for  articulation  with  the 
sphenoid;  internally  it  is  also  serrated  for  articulation  with  the  orbital  surface  of 
the  superior  maxillary.  At  the  angle  of  junction  of  the  sphenoidal  and  maxillary- 
portions  a  short,  rounded,  non-articular  margin  is  generally  seen;  this  forms  the 
anterior  boundary  of  the  spheno-maxillary  fissure:  occasionally  no  such  non- 
articular  margin  exists,  the  fissure  being  completed  by  the  direct  junction  of  the 
maxillary  and  sphenoid  bones  or  by  the  interposition  of  a  small  Wormian  bone  in 
the  angular  interval  between  them.  On  the  upper  surface  of  the  orbital  process 
are  seen  a  single  or  double  temporo -malar  foramen  {foramen  zygoTnaticoorhitale), 
the  entrance  of  the  temporo-malar  canal.  This  canal  may  be  bifurcated,  or 
there  may  be  two  canals  from  the  beginning;  one  of  these  usually  opens  on  the 
posterior  surface,  the  other  (occasionally  two)  on  the  facial  surface:  they  transmit 
filaments  (temporo-malar)  of  the  orbital  branch  of  the  superior  maxillary  nerve. 

Maxillary  Process. — The  maxillary  process  is  a  rough,  triangular  surface  which 
articulates  with  the  malar  process  of  the  superior  maxillary  bone. 

Zygomatic  Process  (processus  temporalis). — The  zygomatic  process,  long,  narrow, 
and  serrated,  articulates  with  the  zygomatic  process  of  the  temporal  bone. 

Borders. — Of  the  four  borders,  the  antero- superior  or  orbital  border  is  smooth, 
arched,  and  forms  a  considerable  part  of  the  circumference  of  the  orbit.  The 
antero-inferior  or  maxillary  border  is  rough,  and  bevelled  at  the  expense  of  its 
inner  ta})le,  to  articulate  with  the  superior  maxillary  bone;  affording  attachment 
by  its  margin  to  the  Levator  labii  superioris  proprius,  just  at  its  point  of  junction 
with  the  superior  maxillary.  The  postero-superior  or  temporal  border,  curved  like 
an  italic  letter  /,  is  continuous  above  with  the  commencement  of  the  temporal 
ridge ;  below,  with  the  upper  border  of  the  zygomatic  arch :  it  affords  attachment 
to  the  temporal  fascia.  The  poster o-inferior  or  zygomatic  border  is  continuous 
with  the  lower  border  of  the  zygomatic  arch,  affording  attachment  by  its  rough 
edge  to  the  Masseter  muscle. 

Development. — The  malar  bone  ossifies  generally  from  three  centres,  which 
appear  about  the  eighth  week — one  for  the  zygomatic  and  two  for  the  orbital 
portion — and  fuse  about  the  fifth  month  of  fcetal  life.  The  bone  is  sometimes, 
after  birth,  seen  to  be  divided  by  a  horizontal  suture  into  an  upper  and  larger 
and  a  lower  and  smaller  division.  In  some  quadrumana  the  malar  bone  consists 
of  two  parts,  an  orbital  and  a  malar,  which  are  ossified  by  separate  centres. 

Articulations. — With  four  bones:  three  of  the  cranium,  frontal,  sphenoid,  and 
temporal;  and  one  of  the  face,  the  superior  maxillary. 

Attachment  of  Muscles. — To  four:  the  Levator  labii  superioris  proprius, 
Zygomaticus  major  and  minor,  and  Masseter. 

The  Palate  Bone  (Os  Palatinum). 

The  palate  bones  {palatum,  the  palate)  are  situated  at  the  back  part  of  the 
nasal  fossse:  they  are  wedged  in  between  the  superior  maxillary  bones  and  the 
pterygoid  processes  of  the  sphenoid  (Fig.  81).  Each  bone  assists  in  the  formation 
of  three  cavities:  the  floor  and  outer  wall  of  the  nose,  the  roof  of  the  mouth,  and 
the  floor  of  the  orbit,  and  enters  into  the  formation  of  two  fossje,  the  spheno- 
maxillary {fossa  pterygopalatina)  and  pterygoid  fossae  {fossa  pterygoidea) ;  and  one 
fissure,  the  spheno-maxillary  fissure  {fissura  orbitalis  inferior).    In  form  the  palate 


116 


THE   SKELETON 


bone  somewhat  resembles  the  letter  L,  and  may  be  divided  into  an  inferior  or 
horizontal  plate  and  a  superior  or  vertical  plate. 


Orbital  process. 

Spheno-palatine  for. 

Sphenoidal  process 

Sup.  turbinated  crest 

Inf.  turbi7iated  crest. 


Nasal  process. 

Sup.  turbinated  crest. 


Inf.  turbinated  crest. 


— 'Ant.  nasal  spine. 


Fig.  81. — Palate  bone  in  silu. 


The  Horizontal  Plate  of  the  Palate  Bone  (Pars  Horizcntalis)    (Fig.  83). 

The  horizontal  plate  is  of  a  quadrilateral  form,  and  presents  two  surfaces  and 
four  borders. 

Surfaces.  Superior  Surface  (fades  nasalis). — The  superior  or  nasal  surface, 
concave  from  side  to  side,  forms  the  back  part  of  the  floor  of  the  nasal  cavity. 

Inferior  Surface  [jades  palatina). — The  inferior  or  palatine  surface,  slightly 
concave  and  rough,  forms  the  back  part  of  the  hard  palate.  At  its  posterior  part 
may  be  seen  a  transverse  ridge,  more  or  less  marked,  for  the  attachment  of  part 
of  the  aponeurosis  of  the  Tensor  palati  muscle.  At  the  outer  extremity  of  this 
ridge  is  a  deep  groove,  the  pterygopalatine  groove  (sulcus  pterygopalatinus), 
converted  into  a  canal  by  its  articulation  with  the  tuberosity  of  the  superior 
maxillary  bone,  and  forming  the  lower  end  of  the  posterior  palatine  canal  (canalis 
pterygopalatinus) ,  the  opening  of  which  is  called  the  great  palatine  foramen  (fora- 
men palatinum  majus).  Near  this  groove  the  orifices  (foramiria  palatina  minora) 
of  one  or  two  small  canals,  accessory  posterior  palatine  canals  (canales  palatini) 
may  be  seen.  Through  the  posterior  palatine  canal  emerge  the  descending 
palatine  artery  and  the  great  posterior  palatine  nerve. 

Borders. — The  anterior  border  is  serrated,  bevelled  at  the  expense  of  its  inferior 
surface,  and  articulates  with  the  palate  process  of  the  superior  maxillary  bone. 
The  posterior  border  is  concave,  free,  and  serves  for  ,the  attachment  of  the  soft 
palate.  Its  inner  extremity  is  sharp  and  pointed,  and,  when  united  with  the 
opposite  bone,  forms  a  projecting  process,  the  posterior  nasal  or  palatine  spine 
(spina  nasalis  posterior),  for  the  attachment  of  the  Azygos  uvulfe  muscle.  The 
external  border  is  united  with  the  lower  part  of  the  perpendicular  plate  almost 
at  right  angles.  The  internal  border,  the  thickest,  is  serrated  for  articulation  with 
its  fellow  of  the  opposite  side;  its  superior  edge  is  raised  into  a  ridge,  which,  united 
with  the  opposite  bone,  forms  a  crest  (crista  nasalis)  into  which  the  vomer  is 
received. 


THE    PALATE   BONE 


117 


Orbital  process. 

Orhiud  surface. 


Maxillary  surface. 


Superior  meatus. 
Spheno-palatine  foramen.-^ 


■^      Maxillary 
process. 


The  Vertical  or  Perpendicular  Plate  of  the  Palate  Bone  (Pars  Perpendicularis). 

The  vertical  or  perpendicular  plate  (Figs.  82  and  83)  is  thin,  of  an  oblong 
form,  and  directed  upward  and  a  little  inward.  It  presents  two  surfaces,  an 
external  and  an  internal,  and  four  borders. 

Surfaces.  Internal,  Medial,  or  Nasal  Surface  (fades  nasalis). — The  internal  sur- 
face presents  at  its  lower  part  a  broad,  shallow  depression,  which  forms  part  of 
the  inferior  meatus  of  the  nose. 
Immediately  above  this  is  a 
well-marked  horizontal  ridge, 
the  inferior  turbinated  crest 
(crista  conchalis),  for  articula- 
tion with  the  inferior  turbin- 
ated bone;  above  this,  a  second 
broad,  shallow  depression, 
which  forms  part  of  the  mid- 
dle meatus,  surmounted  above 
by  a  horizontal  ridge  less 
prominent  than  the  inferior, 
the  superior  turbinated  crest 
(crista  ethmoidalis) ,  for  articu- 
lation with  the  middle  turbin- 
ated bone.  Above  the  superior 
turbinated  crest  is  a  narrow, 
horizontal  groove,  which  forms 
part  of  the  superior  meatus. 

External,  Lateral,  or  Maxillary 
Surface    (fades  maxillaris) . — 
The  external  surface  is  rough  and  irregular  throughout  the  greater  part  of  its  extent, 
for  articulation  with  the  inner  surface  of  the  superior  maxillary  bone,  its  upper 

and  back  part  being  smooth  where  it  enters 
into  the  formation  of  the  spheno-maxillary 
fossa;  it  is  also  smooth  in  front,  where  it 
covers  the  orifice  of  the  antrum.  Toward 
the  back  part  of  this  surface  is  a  deep 
groove,  the  pterygo -palatine  groove,  converted 
into  a  canal,  the  posterior  palatine  canal,  by 
its  articulation  with  the  superior  maxillary 
bone.  It  transmits  the  posterior  or  descend- 
ing palatine  vessels  and  the  great  posterior 
palatine  nerve  from  Meckel's  ganglion. 

Borders.  Anterior  Border  (Fig.  82).— The 
anterior  border  is  thin,  irregular,  and  pre- 
sents opposite  the  inferior  turbinated  crest 
a  pointed,  projecting  lamina,  the  maxillary 
process  (processus  maxillaris),  which  is  di- 
rected forward,  and  closes  in  the  lower  and 
back  part  of  the  opening  of  the  antrum. 

Posterior   Border. — The   posterior  border 

(Fig.  S3)  presents  a  deep  groove,  the  edges 

of  which  are  serrated  for  articulation  with 

the  pterygoid  process  of  the  sphenoid.    At  the  lower  part  of  this  border  is  seen  a 

pyramidal  process  of  bone,  the  pterygoid  process  or  tuberosity  of  the  palate  (processus 

pyramidalis) ,  which  is  received  into  the  angular  interval  between  the  two  pterygoid 


Horizontal  Plate. 

Fig.  82. — Left  palate  bone.     Internal  view.      (Enlarged.) 


Orbital  process, 
,  surface. 


^Sphenoidal  palatine 
foramen. 

js.  ^  Sphenoidal  process. 
/  Y~ 'Artic^llar  portion, 
ii on-articular  portion. 


""ill/. 


Fig.  83.— Left  palate  bone. 
(Enlarged.) 


External  Surface. 


Posterior 
.  nasal  spine. 

Horizontal 

Plate. 

Posterior  view. 


118  THE   SKELETON 

plates  of  the  sphenoid  at  their  inferior  extremity.  This  process  presents  at  its  back 
part  a  median  groove  and  two  lateral  surfaces.  The  groove  is  smooth,  and  forms 
part  of  the  pterygoid  fossa,  affording  attachment  to  the  Internal  pterygoid  muscle; 
whilst  the  lateral  surfaces  are  rough  and  uneven,  for  articulation  with  the  anterior 
border  of  each  pterygoid  plate,  A  few  fibres  of  the  Superior  constrictor  arise  from 
the  tuberosity  of  the  palate  bone.  The  base  of  this  process,  continuous  with  the 
horizontal  portion  of  the  bone,  presents  the  aperture  of  the  accessory  descending 
palatine  canals,  through  which  pass  the  two  smaller  descending  branches  of 
Meckel's  ganglion ;  whilst  its  outer  surface  is  rough  for  articulation  with  the 
inner  surface  of  the  body  of  the  superior  maxillary  bone. 

Superior  Border. — The  superior  border  of  the  vertical  plate  presents  two  well- 
marked  processes  separated  by  an  intervening  notch  or  foramen.  The  anterior, 
or  larger,  is  called  the  orbital  process;  the  posterior,  the  sphenoidal  process. 

Processes.  Orbital  Process  {processus  orbitalis). — The  orbital  process,  directed 
upward  and  outward,  is  placed  on  a  higher  level  than  the  sphenoidal.  It  presents 
five  surfaces,  which  enclose  a  hollow  cellular  cavity,  and  is  connected  with  the  per- 
pendicular plate  by  a  narrow,  constricted  neck.  Of  these  five  surfaces,  three  are 
articular,  two  non-articular  or  free  surfaces.  The  three  articular  are  the  anterior  or 
maxillary  surface,  which  is  directed  forward,  outward,  and  downward,  is  of  an 
oblong  form,  and  rough  for  articulation  with  the  superior  maxillary  bone.  The  pos- 
terior or  sphenoidal  surface  is  directed  backward,  upward,  and  inward.  It  ordinarily 
presents  a  small,  open  cell,  the  orbital  sinus  {sinus  orbitalis) ,  which  communicates 
with  the  sphenoidal  cells,  and  the  margins  of  which  are  serrated  for  articulation  with 
the  vertical  part  of  the  sphenoidal  turbinated  bone.  "  The  orbital  may  connnunicate 
not  only  with  the  sphenoidal  sinus  and  the  ethmoidal  cells,  but,  in  rare  instances, 
with  the  maxillary  antrum."^  The  internal  or  ethmoidal  surface  is  directed  inward, 
upward,  and  forward,  and  articulates  with  the  lateral  mass  of  the  ethmoid  bone. 
In  some  cases  the  cellular  cavity  opens  on  the  internal  surface  of  the  bone;  it  then 
communicates  with  the  posterior  ethmoidal  cells.  More  rarely  it  opens  on  both 
surfaces,  and  then  communicates  v/ith  both  the  posterior  ethmoidal  and  the 
sphenoidal  cells.  The  non-articular  or  free  surfaces  are  the  superior  or  orbital 
surface,  directed  upward  and  outward,  of  triangular  form,  concave,  smooth,  and 
forming  the  back  part  of  the  floor  of  the  orbit ;  and  the  external  or  zygomatic  surface, 
directed  outward,  backward,  and  downward,  of  an  oblong  form,  smooth,  lying  in 
the  spheno-maxillary  fossa,  and  looking  into  the  zygomatic  fossa.  The  latter 
surface  is  separated  from  the  orbital  by  a  smooth,  rounded  border,  which  enters 
into  the  formation  of  the  spheno-maxillary  fissure. 

Sphenoidal  Process  {processus  sphenoidalis) . — The  sphenoidal  process  of  the 
palate  bone  is  a  thin,  compressed  plate,  much  smaller  than  the  orbital,  and 
directed  upward  and  inward.  It  presents  three  surfaces  and  two  borders.  The 
superior  surface,  the  smallest  of  the  three,  articulates  with  the  under  surface  of 
the  sphenoidal  turbinated  bone;  it  presents  a  groove,  which  contributes  to  the 
formation  of  the  pterygo-palatine  canal.  The  internal  surface  is  concave,  and 
forms  part  of  the  outer  wall  of  the  nasal  fossa.  The  external  surface  is  divided 
into  an  articular  and  a  non-articular  portion:  the  former  is  rough,  for  articulation 
with  the  inner  surface  of  the  internal  pterygoid  plate  of  the  sphenoid;  the  latter  is 
smooth,  and  forms  part  of  the  spheno-maxillary  fossa.  The  anterior  border  forms 
the  posterior  boundary  of  the  spheno-palatine  notch.  The  posterior  border, 
serrated  at  the  expense  of  the  outer  table,  articulates  with  the  inner  surface  of 
the  internal  pterygoid  plate. 

The  orbital  and  sphenoidal  processes  are  separated  from  one  another  by  a  deep 
notch,  the  spheno-palatine  notch  {incisura  sphenopalatinum) ,  which  is  converted 

1  Dr.  D.  Kerfoot  Shute,  in  the  Reference  Handbook  of  the  Medical  Sciences. 


THE    INFERIOR    TURBINATED    BONE 


119 


into  a  foramen,  the  spheno-palatine  foramen  {foramen  sphenopalatinwn) ,  by  articu- 
lation with  the  under  surface  of  the  body  of  the  sphenoid  bone.  Sometimes  the 
two  processes  are  united  above,  and  form  between  them  a  complete  foramen  (Figs. 
82  and  83) ,  or  the  notch  is  crossed  by  one  or  more  spicuUe  of  bone,  so  as  to  form 
two  or  more  foramina.  In  the  articulated  skull  this  foramen  is  seen  to  pass  from 
the  spheno-maxillary  fossa  into  the  back  part  of  the  superior  meatus.  It  trans- 
mits the  spheno-palatine  vessels  and  the  superior  nasal  and  naso-palatine  nerves. 

Development. — From  a  single  centre,  which  makes  its  appearance  about  the 
second  month  at  the  angle  of  junction  of  the  two  plates  of  the  bone.  From  this 
point  ossification  spreads  inward  to  the  horizontal  plate,  downward  into  the 
tuberosity,  and  upward  into  the  vertical  plate.  In  the  foetus  the  horizontal  plate 
is  much  larger  than  the  vertical,  and  even  after  it  is  fully  ossified  the  whole  bone 
is  at  first  remarkable  for  its  shortness. 

Articulations. — With  six  bones:  the  sphenoid,  ethmoid,  superior  maxillary, 
inferior  turbinated,  vomer,  and  opposite  palate. 

Attachment  of  Muscles.- -To  four:  the  Tensor  palati,  Azygos  uvulae,  Internal 
pterygoid,  and  Superior  constrictor  of  the  pharynx. 

The  Inferior  Turbinated  Bone  (Concha  Nasalis  Inferior). 

The  inferior  turbinal  or  turbinated  bones  (turbo,  a  whirl)  are  situated  one  on 
each  side  of  the  outer  wall  of  the  nasal  fossae.  Each  inferior  turbinated  bone 
(concha  nasalis  inferior)  consists  of  a  layer  of  thin,  spongy  bone,  curled  upon 


NASO-PHARYNGEAU 
MEATUS 


Fig.  84. — Nasal  cavity,  right  lateral  wall,  from  the  left.      (Spalteholz.) 


itself  like  a  scroll — hence  its  name  "turbinated" — and  extends  horizontally 
along  the  outer  wall  of  the  nasal  fossa,  immediately  below  the  orifice  of  the 
antrum  (Fig.  84).  Each  bone  presents  two  surfaces,  two  borders,  and  two 
extremities. 


120 


THE    SKELETON 


Surfaces. — The  internasal  surface  (Fig.  85)  is  convex,  perforated  by  numerous 
apertures,  and  traversed  by  longitudinal  grooves  and  canals  for  the  lodgement 
of  arteries  and  veins.  In  the  recent  state  it  is  covered  by  the  lining  membrane  of 
the  nose.  The  external  surface  is  concave  (Fig.  86),  and  forms  part  of  the  inferior 
meatus. 


Fig.  85. — Right  inferior  turbinated  bone, 
surface. 


Internal 


Fig.  86. 


-Right  inferior  turbinated  bone. 
External  surface. 


Borders. — Its  upper  border  is  thin,  irregular,  and  connected  to  various  bones 
along  the  outer  wall  of  the  nose.  It  may  be  divided  into  three  portions :  of  these, 
the  anterior  articulates  with  the  inferior  turbinated  crest  of  the  superior  maxillary 
bone;  the  posterior  with  the  inferior  turbinated  crest  of  the  palate  bone;  the  middle 
portion  of  the  superior  border  presents  three  well-marked  processes,  which  vary 
much  in  their  size  and  form.  Of  these,  the  anterior  and  smallest  is  situated  at 
the  junction  of  the  anterior  fourth  with  the  posterior  three-fourths  of  the  bone: 
it  is  small  and  pointed,  and  is  called  the  lachrymal  process  (processus  lacrimalis) ; 
it  articulates  by  its  apex  with  the  anterior  inferior  angle  of  the  lachrymal  bone, 
and  by  its  margins  with  the  groove  on  the  back  of  the  nasal  process  of  the  supe- 
rior maxillary,  and  thus  assists  in  forming  the  canal  for  the  nasal  duct.  At  the 
junction  of  the  two  middle  fourths  of  the  bone,  but  encroaching  on  its  posterior 
fourth,  a  broad,  thin  plate,  the  ethmoidal  process  (processus  ethmoidalis) ,  ascends 
to  join  the  unciform  process  of  the  ethmoid;  from  the  lower  border  of  this  pro- 
cess a  thin  lamina  of  bone  curves  downward  and  outward,  hooking  over  the 
lower  edge  of  the  orifice  of  the  antrum,  which  it  narrows  below:  it  is  called  the 
maxillary  process  (processus  maxillaris),  and  fixes  the  bone  firmly  to  the  outer  wall 
of  the  nasal  fossa.  The  inferior  border  is  free  and  thick,  more  especially  in  the 
middle  of  the  bone.  Bone  extremities  are  more  or  less  narrow  and  pointed,  the 
posterior  being  the  more  tapering.  If  the  bone  is  held  so  that  its  outer  concave 
surface  is  directed  backward  (i.  e.,  toward  the  holder),  and  its  superior  border,  from 
which  the  lachrymal  and  ethmoidal  processes  project,  upward,  the  lachrymal  pro- 
cess will  be  directed  to  the  side  to  which  the  bone  belongs.^  In  a  study  of  1000  speci- 
mens, Howard  A.  Lothrop^  did  not  discover  cells  in  the  inferior  turbinated  bone. 

Development. — By  a  single  centre,  which  makes  its  appearance  about  the 
middle  of  foetal  life. 

Articulations.^ With  four  bones:  one  of  the  cranium,  the  ethmoid,  and  three 
of  the  face,  the  superior  maxillary,  lachrymal,  and  palate. 

No  muscles  are  attached  to  this  bone. 

The  Vomer  (Ploughshare  Bone). 

The  vomer  (vomer,  a  ploughshare)  is  a  single  bone,  situated  vertically  at  the 
back  part  of  the  nasal  fossae,  forming  part  of  the  septum  of  the  nose  (Fig.  87). 
It  is  thin,  somewhat  like  a  ploughshare  in  form;  but  it  varies  in  different  indi- 
viduals, being  frequently  bent  to  one  or  the  other  side;  it  presents  for  examination 
two  surfaces  and  four  borders. 


If  the  lachrymal  process  is  broken  off,  as  is  often  the  case,  the  side  to  which  the  bone  belongs  may  be  known 
by  recollecting  that  the  maxillary  process  is  nearer  the  back  than  the  front  of  the  bone. 
-  Annals  of  Surgery,  May,  1903. 


THE    VOMER 


121 


Surfaces. — The  lateral  surfaces  are  smooth,  marked  by  small  furrows  for  the 
lodgement  of  blood-vessels,  and  })y  a  groove  on  each  side,  sometimes  a  canal,  the 
naso-palatine  groove  or  canal,  which  runs  obliquely  downward  and  forward  to  the 
intermaxillary  suture;  it  transmits  the  naso-palatine  nerve. 


Frontal  sinuses. 


Sphenoidal  sinuses. 


Perpendicnlar 
plute  of  eth- 
moid. 

Space  for  triangular 
cartilage  of  septum, 

Vomer. 


Rostrum  of  sphenoid. 
Palate  process. 
Int.  pterygoid  plate. 


Fig.  87. — Vomer  in  situ. 

Borders. — The  superior  border,  the  thickest,  presents  a  deep  groove,  bounded 
on  each  side  by  a  horizontal  projecting  leaf  of  bone;  these  leaves  are  the  alae 
(alcB  vomeris).  The  groove  formed  by  the  a\se  receives  the  rostrum  of  the 
sphenoid,  while  the  alse  are  overlapped  and  retained  by  the  vaginal  processes,  which 
project  from  the  under  surface  of  the  body  of  the  sphenoid  at  the  base  of  the 
pterygoid  processes.  At  the  front 
of  the  groove  a  fissure  is  left  for 
the  transmission  of  blood-vessels 
to  the  substance  of  the  bone.  The 
inferior  border,  the  longest,  is 
broad  and  imeven  in  front,  where 
it  articulates  with  the  two  supe- 
rior maxillary  bones ;  thin  and 
sharp  behind,  where  it  joins  with 
the  palate  bones.  The  upper  \s; 
half  of  the  anterior  border  usually  ^^  ^ 


With  sup.  maxill.  hones  and  palate. 

Fig.  88. — The  vomer. 


consists  of  two  laminae  of  bone, 

in  the  groove  between  which  is 

received  the  perpendicular  plate 

of  the  ethmoid;  the  lower  half, 

also  separated  into  two  lamellae,  receives  between  them  the  lower  margin  of  the 

septal  cartilage  of  the  nose.     The  posterior  border  is  free,  concave,  and  separates 

the  nasal  fossae  behind.     It  is  thick  and  bifid  above,  thin  below. 

The  surfaces  of  the  vomer  are  covered  by  mucous  membrane,  which  is  inti- 
mately connected  with  the  periosteum,  with  the  intervention  of  very  little,  if  any, 


122 


THE  SKELETON 


submucous  connective  tissue.  Hence  polypi  are  rarely  found  growing  from  this 
surface,  though  they  frequently  grow  from  the  outer  wall  of  the  nasal  fossae, 
where  the  submucous  tissue  is  abundant. 

Development. — The  vomer  at  an  early  period  consists  of  two  laminae,  separated 
by  a  very  considerable  interval,  and  enclosing  between  them  a  plate  of  cartilage, 
the  vomerine  cartilage,  which  is  prolonged  forward  to  form  the  remainder  of  the 
septum.  Ossification  commences  in  the  membrane  at  the  postero-inferior  part  of 
this  cartilage  by  two  centres,  one  on  each  side  of  the  middle  line,  which  extend 
to  form  the  two  laminje.  They  begin  to  coalesce  at  the  lower  part,  but  their 
union  is  not  complete  until  after  puberty. 

Articulations.- -With  5ix  bones:  two  of  the  cranium,  the  sphenoid  and  ethmoid; 
and  four  of  the  face,  the  superior  maxillary  and  the  two  palate  bones;  and  with 
the  cartilage  of  the  septum. 

The  vomer  has  no  muscles  attached  to  it. 


The  Maxillary  Bone,  Inferior  Maxilla,  Mandible  or  Lower  Jaw  (Mandibula) . 

The  mandible,  the  largest  and  strongest  bone  of  the  face,  serves  for  the 
reception  of  the  lower  teeth.  It  consists  of  a  curved,  horizontal  portion,  the 
body,  and  two  perpendicular  portions,  the  rami,  which  join  the  back  part  of 
the  body  nearly  at  right  angles. 

The  Horizontal  Portion  or  Body  of  the  Mandible  (Corpus  Mandibulse). 

The  horizontal  portion  or  body  (Fig.  89)  is  convex  in  its  general  outline,  and 
curved  somewhat  like  a  horseshoe.  It  presents  for  examination  two  surfaces  and 
two  borders. 

Coronoid  process.  Condyle. 


Mental, 
process 


Groove  for  facial  artery. 
Fig.  89. — The  mandible.     Outer  surface.     Side  view. 


Surfaces.  External  Surface. — The  external  surface  is  convex  from  side  to  side, 
concave  from  above  downward.  In  the  median  line  is  a  vertical  ridge,  the  symphy- 
sis, which  extends  from  the  upper  to  the  lower  border  of  the  bone,  and  indicates 
the  point  of  junction  of  the  two  pieces  of  which  the  bone  is  composed  at  an  early 
period  of  life.  The  lower  part  of  the  ridge  terminates  in  a  prominent  triangular 
eminence,  the  mental  process  or  protuberance  (protuberantia  mentalis) .  This  emi- 
nence is  rounded  below,  and  often  presents  a  median  depression  separating  two 
processes,  the  mental  tubercles  (tubera  meritalia).  It  forms  the  chin,  a  feature 
peculiar  to  the  human  skull.    On  either  side  of  the  symphysis,  just  below  the 


THE   3£AXILLAIiY  BONE 


123 


cavities  for  the  incisor  teeth,  is  a  depression,  the  incisive  or  incisor  fossa,  for  the 
attachment  of  the  Levator  menti  (or  Levator  labii  inferioris) ;  more  externally  is 
attached  a  portion  of  the  Orbicularis  oris  (accessorii  orbicularis  inferioris),  and, 
still  more  externally,  a  foramen,  the  mental  foramen  (foramen  mentale),  for  the 
passage  of  the  mental  vessels  and  nerve.  This  foramen  is  placed  just  below  the 
interval  between  the  two  bicuspid  teeth.  Running  outward  from  the  base  of  the 
mental  process  on  each  side  is  a  ridge,  the  external  oblique  line  (linea  obliqua). 
The  ridge  is  at  first  nearly  horizontal,  but  afterward  inclines  upw^ard  and  back- 
ward, and  is  continuous  with  the  anterior  border  of  the  ramus :  it  affords  attach- 
ment to  the  Depressor  labii  inferioris  and  Depressor  anguli  oris;  below  it  the 
Platysma  myoides  is  attached. 

Internal  Surface.- — The  internal  surface  (Fig.  90)  is  concave  from  side  to  side, 
convex  from  above  downward.    In  the  middle  line  is  an  indistinct  linear  depres- 


QENIO-HYO-QLOSS 


QENIO-HYOIOEUS. 


Mylo-hyoid  ridge. 

Body. 

Fig.  90. — The  mandible.     Inner  surface.     Side  view. 

sion,  corresponding  to  the  symphysis  externally;  on  either  side  of  this  depression, 
just  below  its  centre,  are  four  prominent  tubercles,  placed  in  pairs,  two  above  and 
two  below;  they  are  called  the  genial  tubercles  or  mental  spines  (spinoB  mentales) ,  and 
afford  attachment,  the  upper  pair  to  the  Genio-hyo-glossi,  the  lower  pair  to  the 
Genio-hyoidei,  muscles.  Sometimes  the  tubercles  on  each  side  are  blended  into 
one;  at  others  they  all  unite  into  an  irregular  eminence;  or,  again,  nothing  but  an 
irregularity  may  be  seen  on  the  surface  of  the  bone  at  this  part.  On  either  side  of 
the  genial  tubercles  is  an  oval  depression,  the  sublingual  fossa  {fovea  sublingualis) , 
for  lodging  the  sublingual  gland;  and  beneath  the  fossa  a  rough  depression  on 
each  side  which  gives  attachment  to  the  anterior  belly  of  the  Digastric  muscle, 
the  digastric  fossa  (fossa  digastrica) .  At  the  back  part  of  the  sublingual  fossa  the 
internal  oblique  line  or  mylo-hyoid  ridge  (linea  mylohyoidea)  commences;  it  is  at 
first  faintly  marked,  but  becomes  more  distinct  as  it  passes  upward  and  outward, 
and  is  especially  prominent  opposite  the  last  two  molar  teeth;  it  affords  attach- 
ment throughout  its  whole  extent  to  the  Mylohyoid  muscle;  the  Superior  con- 
strictor of  the  pharynx  with  the  pterygo-m axillary  ligament  being  attached  above 
its  posterior  extremity,  near  the  alveolar  margin.  The  portion  of  the  bone  above 
this  ridge  is  smooth  and  covered  by  the  mucous  membrane  of  the  mouth;  the 
portion  below  presents  an  oblong  depression,  the  submaxillary  fossa  (fovea  sub- 
maxillaris) ,  wider  behind  than  in  front,  for  the  lodgement  of  the  submaxillary 


124  THE  SKELETON 

gland.  The  external  oblique  line  and  the  internal  or  mylo-hyoidean  line  divide 
the  body  of  the  bone  into  a  superior  or  alveolar  and  an  inferior  or  basilar  portion. 
Borders. — The  superior  or  alveolar  'portion  of  the  body  {jpars  alveolaris]  has 
above  a  narrow  border  which  is  wider  and  the  margins  of  which  are  thicker 
behind  than  in  front.  Its  narrow  margin  is  called  the  limbus  alveolaris.  It  is 
hollowed  into  numerous  cavities  {alveoli  dentales) ,  for  the  reception  of  the  teeth ; 
these  cavities  are  sixteen  in  number,  and  vary  in  depth  and  size  according  to  the 
teeth  which  they  contain.  The  cavities  are  separated  from  one  another  by  septa 
interalveolaria.  The  juga  alveolaria  are  prominences  on  the  outer  surface  over  the 
three  front  alveoli.  To  the  outer  side  of  the  alveolar  border  the  Buccinator  muscle 
is  attached  upon  the  buccinator  crest  (crista  huccinatoria)  as  far  forward  as  the 
first  molar  tooth.  The  inferior  or  basilar  portion  (basis  mandibulcB)  is  rounded, 
longer  than  the  superior,  and  thicker  in  front  than  behind;  it  presents  a  shallow 
groove,  just  where  the  body  joins  the  ramus,  over  which  the  facial  artery  turns. 

The  Perpendicular  Portions  or  Rami  of  the  Mandible  (Rami  Mandibulae). 

The  perpendicular  portions  or  rami  are  of  a  quadrilateral  form.  Each  presents 
for  examination  two  surfaces,  four  borders,  and  two  processes. 

Surfaces.  External  Surface. — The  external  surface  is  flat,  marked  with  ridges, 
and  gives  attachment  throughout  nearly  the  whole  of  its  extent  to  the  Masseter 
muscle. 

Internal  Surface. — The  internal  surface  presents  about  its  centre  an  oblique 
foramen  (foramen  mandibulare)  of  the  inferior  dental  canal  (canalis  mandibuloe) ,  for 
the  passage  of  the  inferior  dental  vessels  and  nerve.  The  margin  of  this  opening 
is  irregular;  it  presents  in  front  a  prominent  ridge,  surmounted  by  a  sharp  spine, 
the  lingula  (lingula  mandibuloe),  which  gives  attachment  to  the  internal  lateral 
ligament  of  the  lower  jaw,  and  at  its  lower  and  back  part  a  notch  leading  to 
a  groove,  the  mylo-hyoidean  groove  (sulcus  mylohyoideus) ,  which  runs  obliquely 
downward  to  the  back  part  of  the  submaxillary  fossa,  and  lodges  the  mylo-hyoid 
vessels  and  nerve.  Behind  the  groove  is  a  rough  surface,  for  the  insertion  of  the 
Internal  pterygoid  muscle.  The  inferior  dental  canal  runs  obliquely  downward 
and  forward  in  the  substance  of  the  ramus,  and  then  horizontally  forward  in  the 
body;  it  is  here  placed  under  the  alveoli,  with  which  it  communicates  by  small 
openings.  On  arriving  at  the  incisor  teeth,  it  turns  back  to  communicate  with 
the  mental  foramen,  giving  off  two  small  canals,  which  run  forward,  to  be  lost  in 
the  cancellous  tissue  of  the  bone  beneath  the  incisor  teeth.  This  canal,  in  the 
posterior  two-thirds  of  the  bone,  is  situated  nearer  the  internal  surface  of  the 
jaw;  and  in  the  anterior  third,  nearer  its  external  surface.  Its  walls  are  com- 
posed of  compact  tissue  at  either  extremity,  and  of  cancellous  in  the  centre.  It 
contains  the  inferior  dental  vessels  and  nerve,  from  which  branches  are  distributed 
to  the  teeth  through  small  apertures  at  the  bases  of  the  alveoli. 

Borders. — The  lower  border  of  the  ramus  is  thick,  straight,  and  continuous 
with  the  body  of  the  bone.  At  its  junction  with  the  posterior  border  is  the  angle 
of  the  jaw  (angulus  inandibulce).  The  outer  portion  of  the  angle  is  called  the 
gonion.  The  angle  is  either  inverted  or  everted,  and  marked  by  rough,  oblique 
ridges  on  each  side,  for  the  attachment  of  the  Masseter  externally,  and  the 
Internal  pterygoid  internally;  the  stylo-maxillary  ligament  is  attached  to  the  angle 
between  these  muscles.  The  anterior  border  is  thin  above,  thicker  below,  and 
continuous  with  the  external  oblique  line.  The  posterior  border  is  thick, 
smooth,  rounded,  and  covered  by  the  parotid  gland.  The  upper  border  of  the 
ramus  is  thin,  and  presents  two  processes,  separated  by  a  deep  concavity,  the 
sigmoid  notch  (incisura  mandibuloe).  Of  these  processes,  the  anterior  is  the 
coronoid,  the  posterior  the  condyloid. 


THE    MAXILLARY  BONE  125 

Coronoid  Process  (processus  coronoideus) . — The  coronoid  process  is  a  thin,  flat- 
tened, triangular  eminence  of  bone,  which  varies  in  shape  and  size  in  different 
subjects,  and  serves  chiefly  for  the  attachment  of  the  Temporal  muscle.  Its  external 
surface  is  smooth,  and  aftbrds  attachment  to  the  Temporal  and  Masseter  muscles. 
Its  internal  surface  gives  attachment  to  the  Temporal  muscle  and  presents  the 
commencement  of  a  longitudinal  ridge,  which  is  continued  to  the  posterior  part 
of  the  alveolar  process.  On  the  outer  side  of  this  ridge  is  a  deep  groove,  con- 
tinued below  on  the  outer  side  of  the  alveolar  process;  this  ridge  and  part  of  the 
groove  afford  attachment,  above,  to  the  Temporal;  below,  to  the  Buccinator 
muscle. 

Condyloid  Process  (processus  condyloideus) . — The  condyloid  process,  shorter  but 
thicker  than  the  coronoid,  consists  of  two  portions:  the  condyle  (capitulum  man- 
dibulcB),  and  the  constricted  portion  which  supports  the  condyle,  the  neck  (collum 
mandihulw).  The  condyle  is  of  an  oblong  form,  its  long  axis  being  transverse,  and 
set  obliquely  on  the  neck  in  such  a  manner  that  its  outer  end  is  a  little  more 
forward  and  a  little  higher  than  its  inner.  It  is  convex  from  before  backward 
and  from  side  to  side,  the  articular  surface  extending  farther  on  the  posterior 
than  on  the  anterior  aspect.  At  its  outer  extremity  is  a  small  tubercle  for  the 
attachment  of  the  external  lateral  ligament  of  the  temporo-mandibular  joint. 
The  neck  of  the  condyle  is  flattened  from  before  backward,  and  strengthened 
by  ridges  which  descend  from  the  fore  part  and  sides  of  the  condyle.  Its  lateral 
margins  are  narrow,  the  external  one  giving  attachment  to  part  of  the  external 
lateral  ligament.  Its  posterior  surface  is  convex;  its  anterior  is  hollowed  out  on 
its  inner  side  by  a  depression,  the  pterygoid  depression  (fovea  pterygoidea) ,  for  the 
attachment  of  the  External  pterygoid  muscle. 

The  Sigmoid  Notch  (incisura  mandibidoe) ,  separating  the  two  processes,  is  a 
deep  semilunar  depression,  crossed  by  the  masseteric  vessels  and  nerve. 

Development. — The  lower  jaw  is  developed  principally  from  membrane,  but 
partly  from  cartilage.  The  process  of  ossification  commences  early — earlier  than 
in  any  other  bone  except  the  clavicle.  The  greater  part  of  the  bone  is  formed  from 
a  centre  of  ossification  (dentary),  which  appears  between  the  fifth  and  sixth  week 
in  the  membrane  on  the  outer  surface  of  Meckel's  cartilage.  A  second  centre 
(splenial)  appears  in  the  membrane  on  the  inner  surface  of  the  cartilage,  and 
from  this  centre  the  inner  wall  of  the  sockets  of  the  teeth  is  formed;  this  termi- 
nates above  in  the  lingula.  The  anterior  extremity  of  INleckel's  cartilage  becomes 
ossified,  forming  the  body  of  the  bone  on  each  side  of  the  symphysis.  Two  supple- 
mental patches  of  cartilage  appear  at  the  condyle  and  at  the  angle,  in  each  of 
which  a  centre  of  ossification  for  these  parts  appears;  the  coronoid  process  is  also 
ossified  from  a  separate  centre.  At  birth  the  bone  consists  of  two  halves,  united 
by  a  fibrous  symphysis,  in  which  ossification  takes  place  during  the  first  year. 

Articulation. — With  the  glenoid  fossae  of  the  two  temporal  bones. 

Attachment  of  Muscles. ^ — To  fifteen  pairs:  to  its  external  surface,  commencing 
at  the  symphysis,  and  proceeding  backward :  Levator  menti,  Depressor  labii  infe- 
rioris,  Depressor  anguli  oris,  Platysma  myoides.  Buccinator,  Masseter;  a  portion 
of  the  Orbicularis  oris  fAccessorii  orbicularis  inferioris)  is  also  attached  to  this 
surface.  To  its  internal  surface,  commencingat  the  same  point :  Genio-hyo-glossus, 
Genio-hyoideus,  Mylo-hyoideus,  Digastric,  Superior  constrictor.  Temporal,  Inter- 
nal pterygoid.  External  pterygoid. 

CHANGES  PRODUCED  IN  THE  LOWER  JAW  BY  AGE. 

The  changes  which  the  lower  jaw  undergoes  after  birth  relate  (1)  to  the  alterations  effected 
in  the  body  of  the  bone  by  the  first  and  second  dentitions,  the  loss  of  the  teeth  in  the  aged,  and 
the  subsequent  absorption  of  the  alveoli;  (2)  to  the  size  and  situation  of  the  dental  canal;  and 
(3)  to  the  angle  at  which  the  ramus  joins  with  the^ody. 


126 


THE   SKELETON 


Side  View  of  the  Lower  Jaw  at  Different  Periods  of  Life. 


At  birth  (Fig.  91 )  the  bone  consists  of  lateral  halves,  united  by  fibrous  tissue.  The  body  is 
a  mere  shell  of  bone,  containing  the  sockets  of  the  two  incisor,  the  canine,  and  the  two  tem- 
porary molar  teeth,  imperfectly  partitioned  from  one  another.  The  dental  canal  is  of  large  size, 
and  runs  near  the  lower  border  of  the  bone,  the  mental  foramen  opening  beneath  the  socket  of 
the  first  molar.  The  angle  is  obtuse  (175  degrees),  and  the  condyloid  portion  nearly  in  the 
same  horizontal  line  with  the  body;  the  neck  of  the  condyle  is  short,  and  bent  backward.  The 
coronoid  process  is  of  comparatively  large  size,  and  situated  at  right  angles  with  the  rest  of 
the  bone. 


Fig.  91. — Lower  jaw  bone  in  newborn.  (Spalteholz.) 


Fig.  92.- 


-In  child  six  to  seven  years  of  age. 
(Spalteiiolz.) 


After  birth  (Fig.  92)  the  two  segments  of  the  bone  become  joined  at  the  symphysis,  from 
below  upward,  in  the  first  year;  but  a  trace  of  separation  may  be  visible  in  the  beginning  of  the 
second  year  near  the  alveolar  margin.  The  body  becomes  elongated  in  its  whole  length,  but 
more  especially  behind  the  mental  foramen,  to  provide  space  for  the  three  additional  teeth 
developed  in  this  part.  The  depth  of  the  body  becomes  greater,  owing  to  increased  growth  of 
the  alveolar  part,  to  afford  room  for  the  fangs  of  the  teeth,  and  by  thickening  of  the  subdental 
portion,  which  enables  the  jaw  to  withstand  the  powerful  action  of  the  masticatory  muscles;  but 
the  alveolar  portion  is  the  deeper  of  the  two,  and,  consequently,  the  chief  part  of  the  body  lies 
above  the  oblique  line.  The  dental  canal  after  the  second  dentition  is  situated  just  above  the 
level  of  the  mylo-hyoid  ridge,  and  the  mental  foramen  occupies  the  position  usual  to  it  in  the 
adult.  The  angle  becomes  less  obtuse,  owing  to  the  separation  of  the  jaws  by  the  teeth.  (About 
the  fourth  year  it  is  140  degrees.) 


Fig.  93.— In  the  adult.     (Spalteholz.) 


In  the  adult  (Fig.  93)  the  alveolar  and  basilar  portions  of  the  body  are  usually  of  equ^l 
depth.    The  mental  foramen  opens  midway  between  the  upper  and  lower  border  of  the  bone, 


THE  SUTURES  127 

and  the  dental  canal  runs  nearly  parallel  with  the  mylo-hyoid  line.    The  ramus  is  almost  vertical 
in  direction,  and  joins  the  body  nearly  at  right  angles. 

In  old  age  (Fig.  94)  the  bone  becomes  greatly  reduced  in  size;  for  with  the  loss  of  the  teeth 
the  alveolar  process  is  absorbed,  and  the  basilar  part  of  the  bone  alone  remains,  consequently, 


Fig.  94. — In  old  age.     (Spalteholz.) 

the  chief  part  of  the  bone  is  heloio  the  oblique  line.  The  dental  canal,  with  the  mental  foramen 
opening  from  it,  is  close  to  the  alveolar  border.  The  rami  are  oblique  in  direction,  the  angle 
obtuse,  and  the  neck  of  the  condyle  more  or  less  bent  backward. 

The  Sutures. 

The  bones  of  the  cranium  and  face  are  connected  to  each  other  by  means  of 
sutures.  That  is,  the  articulating  surfaces  or  edges  of  the  bones  are  more  or  less 
roughened  or  uneven,  and  are  closely  adapted  to  each  other,  a  small  amount  of 
intervening  fibrous  tissue,  the  sutural  ligament,  fastening  them  together.  The 
cranial  sutures  may  be  divided  into  three  sets:  1.  Those  at  the  vertex  of  the 
skull.    2.  Those  at  the  side  of  the  skull.    3.  Those  at  the  base. 

The  sutures  at  the  vertex  of  the  skull  are  four:  the  metopic,  the  sagittal,  the 
coronal,  and  the  lambdoid. 

The  Metopic  or  Frontal  Suture  {sutura  frontalis)  is  usually  noted  in  adults  as  a 
trivial  fissure,  just  above  the  glabella.  At  birth  the  two  halves  of  the  frontal 
bone  are  separated  by  the  suture.  This  suture  is,  as  a  rule,  almost  completely 
or  completely  closed  during  the  fifth  or  sixth  year,  but  occasionally  it  remains 
intact  (in  about  8  per  cent,  of  Europeans  according  to  Prof.  Cunningham). 

The  Interparietal  or  Sagittal  Suture  (sutura  sagittalis)  is  formed  by  the  junction 
of  the  two  parietal  bones,  and  extends  from  the  middle  of  the  frontal  bone  back- 
ward to  the  superior  angle  of  the  occipital.  This  suture  is  sometimes  perforated, 
near  its  posterior  extremity,  by  the  parietal  foramen ;  and  in  front,  where  it  joins 
the  coronal  suture,  a  space  is  occasionally  left  which  encloses  a  large  Wormian 
bone. 

The  Fronto -parietal  or  Coronal  Suture  {sutura  coronalis)  extends  transversely 
across  the  vertex  of  the  skull,  and  connects  the  frontal  with  the  parietal  bones. 
It  commences  at  the  extremity  of  the  greater  wing  of  the  sphenoid  on  one  side, 
and  terminates  at  the  same  point  on  the  opposite  side.  The  dentations  of  the 
suture  are  more  marked  at  the  sides  than  at  the  summit,  and  are  so  constructed 
that  the  frontal  rests  on  the  parietal  above,  whilst  laterally  the  frontal  supports 
the  parietal. 


128  THE  SKELETON 

The  Occipito -parietal  or  Lambdoid  Suture  (sutura  lamhdoidea) ,  so  called  from 
its  resemblance  to  the  Greek  letter  A,  connects  the  occipital  with  the  parietal 
bones.  It  commences  on  each  side  at  the  mastoid  portion  of  the  temporal  bone, 
and  inclines  upward  to  the  end  of  the  sagittal  suture.  The  dentations  of  this 
suUire  are  very  deep  and  distinct,  and  are  often  interrupted  by  several  small 
Wormian  bones. 

The  sutures  at  the  side  of  the  skull  extend  from  the  external  angular  process  of 
the  frontal  bone  to  the  lower  end  of  the  lambdoid  suture  behind.  Theanterior  'portion 
is  formed  between  the  lateral  part  of  the  frontal  bone  above  and  the  malar  and  great 
wing  of  the  sphenoid  below,  forming  the  fronto-malar  suture  {sutura  zijgomatico- 
frontalis)  and  fronto-sphenoidal  suture  (sutura  spheno frontalis).  These  sutures 
can  also  be  seen  in  the  orbit,  and  form  part  of  the  so-called  transverse  facial 
suture.  The  posterior  portion  is  formed  between  the  parietal  bone  above  and 
the  great  wing  of  the  sphenoid,  the  squamous  and  mastoid  portions  of  the  temporal 
bone  below,  forming  the  spheno -parietal,  squamo-parietal,  and  masto-parietal  sutures. 

The  spheno-parietal  {sutura  sphenoparietalis)  is  very  short;  it  is  formed  by  the 
tip  of  the  great  wing  of  the  sphenoid,  which  overlaps  the  anterior  inferior  angle 
of  the  parietal  bone. 

The  squamo-parietal  or  squamous  suture  (sutura  squamosa)  is  arched.  It  is 
formed  by  the  squamous  portion  of  the  temporal  bone  overlapping  the  middle 
division  of  the  lower  border  of  the  parietal. 

The  masto-parietal  (sutura  parietomastoidea)  is  a  short  suture,  deeply  dentated, 
formed  by  the  posterior  inferior  angle  of  the  parietal  and  the  superior  border  of 
the  mastoid  portion  of  the  temporal. 

The  sutures  at  the  base  of  the  skull  are  the  basilar  in  the  centre,  and  on  each 
side  the  petro-occipital,  the  masto-occipital,  the  petro-sphenoidal,  and  the  squamo- 
sphenoidal. 

The  Basilar  Suture  (fissura  sphenooccipitalis)  is  formed  by  the  junction  of  the 
basilar  surface  of  the  occipital  bone  with  the  posterior  surface  of  the  body  of 
the  sphenoid.  At  an  early  period  of  life  a  thin  plate  of  cartilage  exists  between 
these  bones,  but  in  the  adult  they  become  fused  into  one  (synchondrosis  spheno- 
occipitalis) .  Between  the  outer  extremity  of  the  basilar  suture  and  the  termina- 
tion of  the  lambdoid  an  irregular  suture  exists,  which  is  subdivided  into  two  por- 
tions. The  inner  portion,  formed  by  the  union  of  the  petrous  part  of  the  temporal 
with  the  occipital  bone,  is  termed  the  petro-occipital  fissure  (fissura  petrooccipitalis) . 
The  outer  portion,  formed  by  the  junction  of  the  mastoid  part  of  the  temporal 
with  the  occipital,  is  called  the  masto-occipital  suture  (sutura  occipitomastoidea) . 
Between  the  bones  forming  the  petro-occipital  suture  a  thin  plate  of  cartilage 
exists;  in  the  masto-occipital  is  occasionally  found  the  opening  of  the  mastoid 
foramen.  Between  the  outer  extremity  of  the  basilar  suture  and  the  spheno- 
parietal an  irregular  suture  may  be  seen,  formed  by  the  union  of  the  sphenoid 
with  the  temporal  bone.  The  inner  and  smaller  portion  of  this  suture  is  termed 
the  petro-sphenoidal  fissure  (fissura  spheno petrosa) ;  it  is  formed  between  the 
petrous  portion  of  the  temporal  and  the  great  wing  of  the  sphenoid;  the  outer 
portion,  of  greater  length  and  arched,  is  formed  between  the  squamous  portion 
of  the  temporal  and  the  great  wing  of  the  sphenoid ;  it  is  called  the  squamo- 
sphenoidal  suture  (sutura  spheno  squamosa) . 

The  cranial  bones  are  connected  with  those  of  the  face,  and  the  facial  bones 
with  each  other,  by  numerous  sutures,  which,  though  distinctly  marked,  have 
received  no  special  names.  The  only  remaining  suture  deserving  especial  con- 
sideration is  the  transverse  suture.  This  extends  across  the  upper  part  of  the  face, 
and  is  formed  by  the  junction  of  the  frontal  with  the  facial  bones:  it  extends  from 
the  external  angular  process  of  one  side  to  the  same  point  on  the  opposite  side, 
and  connects  the  frontal  with  the  malar,  the  sphenoid,  the  ethmoid,  the  lachrymal, 


THE    VERTEX    OF    THE   SKULL  129 

the  superior  maxillary,  and  the  nasal  bones  on  each  side  (sutura  zygomatico- 
frontalis;  the  orbital  portion  of  the  sutura  sphenofrontalis,  sutura  fronto- 
cthmoidalis ,  sutura  frontolacrimalis,  sutura  frontomaxillaris,  sutura  nasofrontalis) . 
Tlie  sutures  remain  separate  for  a  considerable  period  after  the  complete  for- 
mation of  the  skull.  It  is  probable  that  they  serve  the  purpose  of  permitting  the 
growth  of  the  bones  at  their  margins,  while  their  peculiar  formation,  together 
with  the  interposition  of  the  sutural  ligament  between  the  bones  forming  them, 
prevents  the  dispersion  of  blows  or  jars  received  upon  the  skull.  Humphry 
remarks,  "that,  as  a  general  rule,  the  sutures  are  first  obliterated  at  the  parts  in 
which  the  ossification  of  the  skull  was  last  completed — viz.,  in  the  neighborhood 
of  the  fontanelles;  and  the  cranial  bones  seem  in  this  respect  to  observe  a  similar 
law  to  that  which  regulates  the  union  of  the  epiphyses  to  the  shafts  of  the  long 
bones."  The  same  author  remarks  that  the  time  of  their  disappearance  is  ex- 
tremely variable:  they  are  sometimes  found  well  marked  in  skulls  edentulous 
with  age,  while  in  others  which  have  only  just  reached  maturity  they  can  hardly 
be  traced.  The  obliteration  of  the  sutures  takes  place  sooner  on  the  inner  than 
on  the  outer  surface  of  the  skull.  The  sagittal  and  coronal  sutures  are  as  a  rule 
the  first  to  become  ossified — the  process  starting  near  the  posterior  extremity  of 
the  former  and  the  lower  ends  of  the  latter. 

THE  SKULL  AS  A  WHOLE. 

The  skull,  formed  by  the  union  of  the  several  cranial  and  facial  bones  already 
described,  when  considered  as  a  whole  is  divisible  into  five  regions:  a  superior 
region  or  vertex,  an  inferior  region  or  base,  two  lateral  regions,  and  an  anterior 
region,  the  face. 

The  Vertex  of  the  Skull. 

The  superior  region,  or  vertex,  presents  two  surfaces,  an  external  and  an 
internal. 

Surfaces.  External  Surface.  (This  surface  as  seen  from  above  is  called  the 
norma  verticalis.) — The  external  surface  is  bounded,  in  front,  by  the  glabella 
and  supraorbital  ridges;  behind,  by  the  occipital  protuberance  and  superior 
curved  lines  of  the  occipital  bone;  laterally,  by  an  imaginary  line  extending  from 
the  outer  end  of  the  superior  curved  line,  along  the  temporal  ridge,  to  the  exter- 
nal angular  process  of  the  frontal  bone.  This  surface  includes  the  greater  pai't  of 
the  vertical  portion  of  the  frontal,  the  greater  part  of  the  parietal,  and  the  superior 
third  of  the  occipital  bone;  it  is  smooth,  convex,  of  an  elongated  oval  form,  crossed 
transversely  by  the  coronal  suture,  and  from  before  backward  by  the  sagittal, 
which  terminates  behind  in  the  lambdoid.  The  point  of  junction  of  the  coronal 
and  sagittal  sutures  is  named  the  bregma,  and  is  represented  by  a  line  drawn  verti- 
cally upward  from  the  external  auditory  meatus,  the  head  being  in  its  normal  posi- 
tion. The  point  of  junction  of  the  sagittal  and  lambdoid  sutures  is  called  the 
lambda,  and  is  about  2f  inches  above  the  external  occipital  protuberance.  From 
before  backward  may  be  seen  the  frontal  eminences  and  remains  of  the  suture 
connecting  the  two  lateral  halves  of  the  frontal  bone;  on  each  side  of  the  sagittal 
siiture  are  the  parietal  foramen  and  parietal  eminence,  and  still  more  posteriorly 
the  convex  surface  of  the  occipital  bone.  In  the  neighborhood  of  the  parietal 
foramen  the  skull  is  often  flattened,  and  the  name  of  obelion  is  sometimes  given 
to  that  point  of  the  sagittal  suture  which  lies  exactly  opposite  to  the  parietal 
foramen. 

Internal  or  Cerebral  Surface. — The  internal  surface  is  concave,  presents  depres- 
sions for  the  convolutions  of  the  cerebrum,  and  numerous  furrows  for  the  lodge- 
ment of   branches  of  the  meningeal  arteries.    Along  the  middle  line  of    this 


130  THE  SKELETON 

surface  is  a  longitudinal  groove,  narrow  in  front,  where  it  commences  at  the 
frontal  crest,  but  broader  behind,  where  it  lodges  the  superior  longitudinal 
sinus,  and  by  its  margin  affords  attachment  to  the  falx  cerebri.  On  either  side 
of  it  are  several  depressions  for  the  Pacchionian  bodies,  and  at  its  back  part 
the  internal  openings  of  the  parietal  foramina.  This  surface  is  crossed,  in  front, 
by  the  coronal  suture;  from  before  backward  by  the  sagittal;  behind,  by  the 
lambdoid. 

The  Base  of  the  Skull  (the  Skull  being  without  the  Mandible). 

The  inferior  region,  or  base  of  the  skull,  presents  two  surfaces — an  internal 
or  cerebral,  and  an  external  or  basilar. 

Surfaces.  Internal  Upper  or  Cerebral  Surface. — The  internal  or  cerebral  surface 
(Fig.  95)  presents  three  fossaj,  called  the  anterior,  middle,  and  posterior  fossse  of  the 
cranium. 

Anterior  Fossa  (fossa  cranii  anterior). — The  anterior  fossa  is  formed  by  the 
orbital  plates  of  the  frontal,  the  cribriform  plate  of  the  ethmoid,  the  anterior 
third  of  the  superior  surface  of  the  body,  and  the  upper  surface  of  the  lesser  wings 
of  the  sphenoid  bone.  It  is  the  most  elevated  of  the  three  fosste,  convex  exter- 
nally where  it  corresponds  to  the  roof  of  the  orbit,  concave  in  the  median  line  in 
the  situation  of  the  criliriform  plate  of  the  ethmoid.  It  is  traversed  by  three  sutures, 
the  ethmo-frontal,  ethmo-sphenoidal,  and  fronto-sphenoidal,  and  lodges  the  frontal 
lobe  of  the  cerebrum.  It  presents,  in  the  median  hne,  from  before  backward,  the 
commencement  of  the  groove  for  the  superior  longitudinal  sinus  and  the  frontal 
crest  for  the  attachment  of  the  falx  cerebri;  the  foramen  caecum,  an  aperture  formed 
between  the  frontal  bone  and  the  crista  galli  of  the  ethmoid,  which,  if  pervious, 
transmits  a  small  vein  from  the  nose  to  the  superior  longitudinal  sinus;  behind  the 
foramen  cjecum,  the  crista  galli,  the  posterior  margin  of  which  affords  attachment 
to  the  falx  cerebri;  on  either  side  of  the  crista  galli,  the  cribriform  plate,  which  sup- 
ports the  olfactory  bulb,  and  presents  three  rows  of  foramina  for  the  transmission 
of  its  nervous  filaments,  and  in  front  a  slit-like  opening  for  the  nasal  branch  of 
the  ophthalmic  division  of  the  fifth  nerve.  On  the  outer  side  of  each  olfactory 
groove  are  the  internal  openings  of  the  anterior  and  posterior  ethmoidal  foramina; 
the  former,  situated  about  the  middle  of  the  outer  margin  of  the  olfactory 
groove,  transmits  the  anterior  ethmoidal  vessels  and  the  nasal  nerve,  which  latter 
runs  in  a  depression  along  the  surface  of  the  ethmoid  to  the  slit-like  opening  abov^e 
mentioned;  while  the  posterior  ethmoidal  foramen  opens  at  the  back  part  of  this 
margin  under  cover  of  the  projecting  lamina  of  the  sphenoid,  and  transmits  the 
posterior  ethmoidal  vessels.  Farther  back  in  the  middle  line  is  the  ethmoidal  spine, 
bounded  behind  by  a  slight  elevation,  separating  two  shallow  longitudinal  grooves 
which  support  the  olfactory  lobes.  Behind  this  is  a  transverse  sharp  ridge,  run- 
ning outward  on  either  side  to  the  anterior  margin  of  the  optic  foramen,  and  sepa- 
rating the  anterior  from  the  middle  fossa  of  the  l)ase  of  the  skull.  The  anterior 
fossa  presents,  laterally,  depressions  for  the  convolutions  of  the  brain  and  grooves 
for  the  lodgement  of  the  anterior  meningeal  arteries. 

Middle  Fossa  (fossa  cranii  media). — The  middle  fossa,  deeper  than  the  pre- 
ceding, is  narrow  in  the  middle  line,  but  becomes  wider  at  the  side  of  the  skull.  It 
is  bounded  in  front  by  the  posterior  margin  of  the  lesser  wing  of  the  sphenoid,  the 
anterior  clinoid  process,  and  the  ridge  forming  the  anterior  margin  of  the  optic 
groove;  behind,  by  the  superior  border  of  the  petrous  portion  of  the  temporal  and 
the  dorsum  ephippii;  externally  by  the  squamous  portion  of  the  temporal  anterior 
inferior  angle  of  the  parietal  bone,  and  greater  wing  of  the  sphenoid.  It  is  trav- 
ersed by  four  sutures,  the  squamo-parietal,  spheno-parietal,  squamo-sphenoidal, 
and  petro-sphenoidal.     In  the  middle  line,  from  before  backward,  is  the  optic 


I 


THE  BASE    OF    THE  SKULL 


131 


groove,  behind  which  Hes  the  optic  commissure;  the  groove  terminates  on  each  side 
in  the  optic  foramen,  for  the  passage  of  the  optic  nerve  and  ophthalmic  artery; 


Groove  for  superior  longitudinal  sinus. 

Grooves  for  anterior  meningeal  artery. 

Foramen  cseeum. 

Crista  galli. 

Slit  for  nasal  nerve. 

Groove  for  7iasal  nerve. 

Anterior  ethinoidal  foramen. 

Orifices  for  olfactory  nerves. 

Postei'ior  ethmoidal  foramen. 

Ethmoidal  spine. 


Olfactory  grooves. 

Optic  foramen. 

Optic  groove. f 

Olivary  process.- G^^' 

Anterior  clinoid  process. 
Middle  clinoid  process. 


Postei-ior  clinoid  process. 

Groove  for  6th  nerve. 

Foramen  lacerum  medium. 

Orifice  of  carotid  canal. 

Depression  for  Gasserian  ganglion. 


Meatus  auditorius  internus. 

Slit  for  dura  mater. 

Superior  petrosal  groove. 

Foramen  lacerum  posterius. 

Anterior  condyloid  foramen. 

Aquxductus  vestibuli. 

Posterior  condyloid  foramen. 


Mastoid  foramen. 
Posterior  meningeal  grooves. 


Fig.  95. — Base  of  the  .skull.     Inner  or  cerebral  surface. 


behind  the  optic  groove  is  the  olivaxy  process  and  laterally  the  anterior  clinoid  pro- 
cesses, to  which  are  attached  processes  of  the  tentorium  cerebelH.  Farther  back  is 
the  sella  tm-cica,  a  deep  depression  which  lodges  the  pituitary  gland,  bounded  in 


132  THE  SKELETON 

front  by  a  small  eminence  on  either  side,  the  middle  clinoid  process,  and  behind  by 
a  broad,  square  plate  of  bone,  the  dorsum  ephippii,  surmounted  at  each  superior 
angle  by  a  tubercle,  the  posterior  clinoid  process;  beneath  the  latter  process  is 
a  notch,  for  the  sixth  nerve.  On  each  side  of  the  sella  turcica  is  the  cavernous 
groove:  it  is  broad,  shallow,  and  curved  somewhat  like  the  italic  letter  /;  it  com- 
mences behind  at  the  foramen  lacerum  medium,  and  terminates  on  the  inner 
side  of  the  anterior  clinoid  process,  and  presents  along  its  outer  margin  a  ridge 
of  bone.  This  groove  lodges  the  cavernous  sinus,  the  internal  carotid  artery, 
and  the  nerves  of  the  orbit.  The  sides  of  the  middle  fossa  are  of  considerable 
depth;  they  present  depressions  for  the  convolutions  of  the  brain  and  grooves 
for  the  branches  of  the  middle  meningeal  artery;  the  latter  commence  on  the 
outer  side  of  the  foramen  spinosum,  and  consist  of  two  large  branches,  an  anterior 
and  a  posterior;  the  former  passing  upward  and  forward  to  the  anterior  inferior 
angle  of  the  parietal  bone,  the  latter  passing  upward  and  backward.  The  fol- 
lowing foramina  may  also  be  seen  from  before  backward:  Most  anteriorly  is  the 
foramen  lacerum  anterius,  or  sphenoidal  fissure  (fissura  orhitaLis  superior),  formed 
above  by  the  lesser  wing  of  the  sphenoid;  below,  by  the  greater  wi  ig;  internally,  by 
the  body  of  the  sphenoid ;  and  sometimes  completed  externally  by  the  orbital  plate 
of  the  frontal  bone.  It  transmits  the  third,  the  fourth,  the  three  branches  of  the 
ophthalmic  division  of  the  fifth,  the  sixth  nerve,  some  filaments  from  the  cavernous 
plexus  of  the  sympathetic,  the  orbital  branch  of  the  middle  meningeal  artery,  a 
recurrent  branch  from  the  lachrymal  artery  to  the  dura  mater,  and  the  ophthalmic 
vein.  Behind  the  inner  extremity  of  the  sphenoidal  fissure  is  the  foramen  rotundum, 
for  the  passage  of  the  second  division  of  the  fifth  or  the  superior  maxillary  nerve; 
still  more  posteriorly  is  seen  a  small  orifice,  the  foramen  Vesalii.an  opening  situated 
between  the  foramen  rotundum  and  ovale,  a  little  internal  to  both:  it  varies  in  size 
in  different  individuals,  and  is  often  absent;  when  present  it  transmits  a  small  vein. 
It  opens  below  into  the  pterygoid  fossa,  just  at  the  outer  side  of  the  scaphoid 
depression.  Behind  and  external  to  the  latter  opening  is  the  foramen  ovale,  which 
transmits  the  third  division  of  the  fifth  or  the  inferior  maxillary  nerve,  the  small 
meningeal  artery,  and  the  small  petrosal  nerve.^  On  the  outer  side  of  the  foramen 
ovale  is  the  foramen  spinosum,  for  the  passage  of  the  middle  meningeal  artery;  and 
on  the  inner  side  of  the  foramen  ovale  is  the  foramen  lacerum  medium.  The  lower 
part  of  this  aperture  is  filled  with  cartilage  in  the  recent  state.  The  Vidian  nerve 
and  a  meningeal  branch  from  the  ascending  pharyngeal  artery  pierce  this  car- 
tilage. On  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone  is 
seen,  from  without  inward,  the  eminence  caused  by  the  projection  of  the  superior 
semicircular  canal;  in  front  of  and  a  little  outside  this  is  a  depression  corresponding 
to  the  roof  of  the  tympanum;  the  groove  leading  to  the  hiatus  Fallopii,  for  the 
transmission  of  the  petrosal  branch  of  the  Vidian  nerve  and  the  petrosal  branch 
of  the  middle  meningeal  artery;  beneath  it,  the  smaller  groove,  for  the  passage 
of  the  lesser  petrosal  nerve;  and,  near  the  apex  of  the  bone,  the  depression  for 
the  Gasserian  ganglion;  and  the  internal  orifice  of  the  carotid  canal  {foramen 
caroticum  internum),  for  the  passage  of  the  internal  carotid  artery  and  carotid 
plexus  of  nerves. 

Posterior  Fossa  (fossa  cranii  posterior). — The  posterior  fossa,  deeply  concave, 
is  the  largest  of  the  three,  and  situated  on  a  lower  level  than  either  of  the  preceding. 
It  is  formed  by  the  posterior  third  of  the  superior  surface  of  the  bodv  of  the  sphe- 
noid, by  the  occipital,  the  petrous  and  mastoid  portions  of  the  temporal,  and  the 
posterior  inferior  angle  of  the  parietal  bone;  it  is  crossed  by  four  sutures,  the  petro- 
occipital,  the  masto-occipital,  the  masto-parietal,  and  the  basilar;  and  lodges  the 
cerebellum,  pons  Varolii,  and  medulla  oblongata.     It  is  separated  from  the  middle 

*  See  footnote,  p.  95. 


THE   BASE    OF   THE  SKULL  133 

fossa  in  the  median  line  by  the  dorsum  ephippii,  and  on  each  side  by  the  superior 
border  of  the  petrous  portion  of  the  temporal  bone.  This  border  serves  for  the 
attachment  of  the  tentorium  cerebelli,  is  grooved  for  the  superior  petrosal  sinus, 
and  at  its  inner  extremity  presents  a  notch,  upon  which  rests  the  fifth  nerve.  The 
circumference  of  the  fossa  is  bounded  posteriorly  by  the  grooves  for  the  lateral 
sinuses.  In  the  centre  of  this  fossa  is  the  foramen  magnum,  bounded  on  either 
side  by  a  rough  tubercle,  which  gives  attachment  to  the  odontoid"  or  check  liga- 
ments; and  a  little  above  these  are  seen  the  internal  openings  of  the  anterior 
condyloid  foramina,  through  which  pass  the  hypoglossal  nerves  and  meningeal 
branches  from  the  ascending  pharyngeal  arteries.  In  front  of  the  foramen  mag- 
num is  a  grooved  surface,  formed  by  the  basilar  process  of  the  occipital  bone  and 
by  the  posterior  third  of  the  superior  surface  of  the  body  of  the  sphenoid,  which 
supports  the  medulla  oblongata  and  pons  Varolii,  and  articulates  on  each  side 
with  the  petrous  portion  of  the  temporal  bone,  forming  the  petro-occipital  suture, 
the  anterior  half  of  which  is  grooved  for  the  inferior  petrosal  sinus,  the  posterior 
half  being  encroached  upon  by  the  foramen  lacerum  posterius  or  jugular  foramen 
(foramen  jugulare).  This  foramen  presents  three  compartments :  through  the  ante- 
rior passes  the  inferior  petrosal  sinus ;  through  the  posterior,  the  lateral  sinus  and 
some  meningeal  branches  from  the  occipital  and  ascending  pharyngeal  arteries; 
and  through  the  middle,  the  glosso-pharyngeal,  pneumogastric,  and  spinal  acces- 
sory nerves.  Above  the  jugular  foramen  is  the  internal  auditory  meatus,  for  the 
facial  and  auditory  nerves  and  auditory  artery;  behind  and  external  to  this  is  the 
slit-like  opening  leading  into  the  aquaeductus  vestibuli,  which  lodges  the  ductus 
endolymphaticus;  while  between  the  two  latter,  and  near  the  superior  border  of 
the  petrous  portion,  is  a  small,  triangular  depression,  the  remains  of  the  floccular 
fossa,  which  lodges  a  process  of  the  dura  mater  and  occasionally  transmits  a  small 
vein  into  the  substance  of  the  bone.  Behind  the  foramen  magnum  are  the  inferior 
occipital  fossae,  which  lodge  the  hemispheres  of  the  cerebellum,  separated  from 
one  another  by  the  internal  occipital  crest,  which  serves  for  the  attachment  of  the 
falx  cerebelli  and  lodges  the  occipital  sinus.  The  posterior  fossae  are  surmounted 
above  by  the  deep  transverse  grooves  for  the  lodgement  of  the  lateral  sinuses. 
These  channels,  in  their  passage  outward,  groove  the  occipital  bone,  the  posterior 
inferior  angle  of  the  parietal,  the  mastoid  portion  of  the  temporal,  and  the  jugular 
process  of  the  occipital,  and  terminate  at  the  back  part  of  the  jugular  foramen. 
Where  this  sinus  grooves  the  mastoid  portion  of  the  temporal  bone  the  orifice  of 
the  mastoid  foramen  may  be  seen.  Just  previous  to  the  termination  of  the  groove 
the  posterior  condyloid  foramen  opens  into  it.    Neither  foramen  is  constant. 

External  Under  or  Basilar  Surface  (the  view  from  below  is  called  the  norma 
basalis). — The  external  surface  of  the  base  of  the  skull  (Fig.  96)  is  extremely 
irregular.  It  is  bounded  in  front  by  the  incisor  teeth  in  the  upper  jaw;  behind 
by  the  superior  curved  lines  of  the  occipital  bone;  and  laterally  by  the  alve- 
olar arch,  the  lower  border  of  the  malar  bone,  the  zygoma,  and  an  imaginary  line 
extending  from  the  zygoma  to  the  mastoid  process  and  extremity  of  the  superior 
curved  line  of  the  occiput.  It  is  formed  by  the  palate  processes  of  the  superior 
maxillary  and  palate  bones,  the  vomer,  the  pterygoid  processes,  under  surface 
of  the  great  wing,  spinous  processes  and  part  of  the  body  of  the  sphenoid,  the 
under  surface  of  the  squamous,  mastoid,  and  petrous  portions  of  the  temporal, 
and  the  under  surface  of  the  occipital  bone.  The  anterior  part  of  the  base  of  the 
skull  is  raised  above  the  level  of  the  rest  of  this  surface  (when  the  skull  is  turned 
over  for  the  purpose  of  examination),  surrouhded  by  the  alveolar  process,  which  is 
thicker  behind  than  in  front,  and  excavated  by  sixteen  depressions  for  lodging  the 
teeth  of  the  upper  jaw,  the  cavities  varying  in  depth  and  size  according  to  the  teeth 
they  contain.  Immefliately  behind  the  incisor  teeth  is  the  anterior  palatine  fossa 
(foramen  incisivum) .  At  the  bottom  of  this  fossa  may  usually  be  seen  four  apertures : 


134 


THE    SKELETON 


two  placed  laterally,  the  foramina  of  Stenson,  which  open  above,  one  in  the  floor  of 
each  nostril,  and  transmit  the  anterior  branch  of  the  posterior  palatine  vessels,  and 


,c<'- 


Anterior  palatine  fossa. 

Transmits  left  naso-palatine  nerve. 
Transmits  anterior  palatine  vessel. 
Transmits  right  naso-palatine  nerve. 


Accessory  palatine  foramina. 
Posterior  nasal  spine. 

AZYQOS   UVUL>E. 

Hamular  process. 


Sphenoid  process  of  palate. 
Ptery  go-palatine  canal. 


-TENSOR    TYMPANI. 

■Pharyngeal  spine  for 

SUPERIOR    CONSTRICTOR. 

Situation  of  Eustachian  tube  and 
canal  for  tensor  tvmpani. 

TENSOR    PALATI. 

Canal  for  Jacobson's  nerve. 
Aquxductus  cochlem. 
Foramen  lacerum  posterius. 
Canal  for  Arnold's  nerve. 
~  Auricular  fissure. 


Fig.  96. — Base  of  the  skull.     External  surface. 


THE   BASE    OF    THE  SKULL  I35 

two  in  the  median  line  in  the  intermaxillary  suture,  the  foramina  of  Scarpa,  one 
in  front  of  the  other,  the  anterior  transmitting  the  left,  and  the  posterior  (the 
larger)  the  right,  naso-palatine  nerve.  These  two  lateral  canals  are  sometimes 
wanting,  or  they  may  join  to  form  a  single  one,  or  one  of  them  may  open  into  one 
of  the  lateral  canals  above  referred  to.  The  palatine  vault  is  concave,  uneven, 
perforated  by  numerous  foramina,  marked  by  depressions  for  the  palatine  glands, 
anfl  crossed  by  a  crucial  suture,  formed  by  the  junction  of  the  four  bones  of  which 
it  is  composed.  At  the  front  part  of  this  surface  a  delicate  hnear  suture  may 
frequently  be  seen,  passing  outward  and  forward  from  the  anterior  palatine  fossa 
to  the  interval  between  the  lateral  incisor  and  canine  teeth,  and  marking  off  the 
pre -maxillary  portion  of  the  bone.  At  each  posterior  angle  of  the  hard  palate  is 
the  posterior  palatine  foramen,  for  the  transmission  of  the  posterior  palatine  vessels 
and  great  descending  palatine  nerve;  and  running  forward  and  inward  from  it  a 
groove,  for  the  same  vessels  and  nerve.  Behind  the  posterior  palatine  foramen 
is  the  tuberosity  of  the  palate  bone,  perforated  by  one  or  more  accessory  posterior 
palatine  canals,  and  marked  by  the  commencement  of  a  ridge  which  runs  trans- 
versely inward,  and  serves  for  the  attachment  of  the  tendinous  expansion  of  the 
Tensor  palati  muscle.  Projecting  backward  from  the  centre  of  the  posterior 
border  of  the  hard  palate  is  the  posterior  nasal  spine,  for  the  attachment  of  the 
Azygos  uvulffi  nmscle.  Behind  and  above  the  hard  palate  is  the  posterior  aper- 
ture of  the  nares,  divided  into  two  parts  by  the  vomer,  bounded  above  by  the 
body  of  the  sphenoid,  below  by  the  horizontal  plate  of  the  palate  bone,  and  lat- 
erally by  the  internal  pterygoid  plate  of  the  sphenoid.  Each  aperture  measures 
about  an  inch  in  the  vertical  and  about  half  an  inch  in  the  transverse  direction. 
At  the  base  of  the  vomer  may  be  seen  the  expanded  alte  of  this  bone,  receiving 
between  them,  on  each  side,  the  rostrum  of  the  sphenoid.  Near  the  lateral  margins 
of  the  vomer,  at  the  root  of  the  pterygoid  processes,  are  the  pterygo-palatine  canals. 
The  pterygoid  process,  which  bounds  the  posterior  nares  on  each  side,  presents 
near  its  base  the  pterygoid  or  Vidian  canal  (canalis  pterygoideus)  ,ior  the  Vidian  nerve 
and  artery.  Each  process  consists  of  two  plates,  which  bifurcate  at  the  extremity  to 
receive  the  tuberosity  of  the  palate  bone,  and  are  separated  behind  by  the  ptery- 
goid fossa,  which  lodges  the  Internal  pterygoid  muscle.  The  internal  plate  is 
long  and  narrow,  presenting  on  the  outer  side  of  its  base  the  scaphoid  fossa,  for 
the  origin  of  the  Tensor  palati  muscle,  and  at  its  extremity  the  hamular  process, 
around  which  the  tendon  of  this  muscle  turns.  The  external  pterygoid  plate  is 
broad,  forms  the  inner  boundary  of  the  zygomatic  fossa,  and  affords  attachment 
by  its  outer  surface  to  the  External  pterygoid  muscle. 

Behind  the  nasal  fossae  in  the  middle  line  is  the  basilar  surface  of  the  occipital 
bone,  presenting  in  its  centre  the  pharsmgeal  spine,  for  the  attachment  of  the 
Superior  constrictor  muscle  of  the  pharynx,  with  depressions  on  each  side  for 
the  insertion  of  the  Rectus  capitis  anticiis  major  and  minor.  At  the  base  of  the 
exteriial  pterygoid  plate  is  the  foramen  ovale,  for  the  transmission  of  the  third 
division  of  the  fifth  nerve,  the  small  meningeal  artery,  and  sometimes  the  small 
petrosal  nerve;  behind  this,  the  foramen  spinosum,  w^hich  transmits  the  middle 
meningeal  artery,  and  the  prominent  spinous  process  of  the  sphenoid,  which  gives 
attachment  to  the  internal  lateral  ligament  of  the  lower  jaw'  and  the  Tensor  palati 
muscle.  External  to  the  spinous  process  is  tlie  glenoid  fossa,  divided  into  two  parts 
by  the  Glaserian  fissure  (page  84),  the  anterior  portion  concave,  smooth,  bounded 
in  front  by  the  eminentia  articularis,  and  serving  for  the  articulation  of  the  condyle 
of  the  lower  jaw;  the  posterior  portion  rough,  bounded  behind  by  the  tympanic 
plate,  and  serving  for  the  reception  of  part  of  the  parotid  gland.  Emerging  from 
between  the  laminae  of  the  vaginal  process  of  the  tympanic  plate  is  the  styloid 
process,  and  at  the  base  of  this  process  is  the  stylo-mastoid  foramen,  for  the  exit  of 
the  facial  nerve  and  entrance  of  the  stylo-mastoid  artery.    External  to  the  stylo- 


136  THE  SKELETON 

mastoid  foramen  is  the  auricular  fissure,  for  the  auricular  branch  of  the  pneumo- 
gastric,  bounded  behind  by  the  mastoid  process.  Upon  the  inner  side  of  the  mas- 
toid process  is  a  deep  groove,  the  digastric  fossa;  and  a  little  more  internally  the 
occipital  groove,  for  the  occipital  artery.  At  the  base  of  the  internal  pterygoid  plate 
is  a  large  and  somewhat  triangular  aperture,  the  foramen  lacerum  medium,  bounded 
in  front  by  the  great  wing  of  the  sphenoid,  behind  by  the  apex  of  the  petrous  por- 
tion of  the  temporal  bone,  and  internally  by  the  body  of  the  sphenoid  and  basilar 
process  of  the  occipital  bone :  it  presents  in  front  the  posterior  orifice  of  the  Vidian 
canal;  behind,  the  aperture  of  the  carotid  canal.  The  basilar  surface  of  this  open- 
ing is  filled  in  the  recent  state  by  fibro-cartilaginous  substance;  across  its  upper 
or  cerebral  aspect  passes  the  internal  carotid  artery.  External  to  this  aperture  the 
petro-sphenoidal  sutiure  is  observed,  at  the  outer  termination  of  which  is  seen  the 
orifice  of  the  canal  for  the  Eustachian  tube  and  that  for  the  Tensor  tympani 
muscle.  Behind  this  suture  is  seen  the  under  surface  of  the  petrous  portion  of  the 
temporal  bone,  presenting,  from  within  outward,  the  quadrilateral,  rough  surface, 
part  of  which  affords  attachment  to  the  Levator  palati  and  Tensor  tympani  mus- 
cles; external  to  this  surface  the  orifices  of  the  carotid  canal  (foramen  caroticum 
externum)  and  the  aquaeductus  cochleae,  the  former  transmitting  the  internal 
carotid  artery  anrl  the  ascending  branches  of  the  superior  cervical  ganglion 
of  the  sympathetic,  the  latter  serving  for  the  passage  of  a  small  artery  and  vein 
to  the  cochlea.  Behind  the  carotid  canal  is  a  large  aperture,  the  jugular  foramen, 
formed  in  front  by  the  petrous  portion  of  the  temporal,  and  behind  by  the 
occipital;  it  is  generally  larger  on  the  right  than  on  the  left  side,  and  is  divided 
into  three  compartments  by  processes  of  dura  mater.  The  anterior  is  for  the 
passage  of  the  inferior  petrosal  sinus;  the  posterior,  for  the  lateral  sinus  and 
some  meningeal  branches  from  the  occipital  and  ascending  pharyngeal  arteries; 
the  central  one,  for  the  glosso-pharyngeal,  pneumogastric,  and  spinal  accessory 
nerves.  On  the  ridge  of  bone  dividing  the  carotid  canal  from  the  jugular  fora- 
men is  the  small  foramen  for  the  transmission  of  Jacobson's  nerve;  and  on  the 
wall  of  the  jugular  foramen,  near  the  root  of  the  styloid  process,  is  the  small 
aperture  for  the  transmission  of  Arnold's  nerve.  Behind  the  basilar  surface  of 
the  occipital  bone  is  the  foramen  magnum,  bounded  on  each  side  by  the  con- 
dyles, rough  internally  for  the  attachment  of  the  check  or  odontoid  ligaments,  and 
presenting  externally  a  rough  surface,  the  jugular  process,  which  serves  for  the 
attachment  of  the  Rectus  capitis  lateralis  muscle  and  the  lateral  occipito-atlantal 
ligament.  On  either  side  of  each  condyle  anteriorly  is  the  anterior  condyloid  fossa, 
perforated  by  the  anterior  condyloid  foramen,  for  the  passage  of  the  hypoglossal 
nerve  and  often  a  meningeal  branch  of  the  ascending  pharyngeal  artery.  Behind 
each  condyle  is  the  posterior  condyloid  fossa,  perforated  by  the  posterior  condyloid 
foramen,  for  the  transmission  of  a  vein  to  the  lateral  sinus.  Behind  the  foramen 
magnum  is  the  external  occipital  crest,  terminating  above  at  the  external  occipital 
protuberance,  whilst  on  each  side  are  seen  the  superior  and  inferior  curved  lines; 
these,  as  well  as  the  surfaces  of  bone  between  them,  are  rough  for  the  attachment 
of  the  muscles,  which  are  enumerated  on  page  76. 

The  Lateral  Region  of  the  Skull. 

The  view  of  the  lateral  region  of  the  skull  from  the  side  is  known  as  the  norma 
lateralis.  The  lateral  region  is  of  a  somewhat  triangular  form,  the  base  of  the  tri- 
angle being  formed  by  a  line  extending  from  the  external  angular  process  of  the 
frontal  bone  along  the  temporal  ridge  backward  to  the  outer  extremity  of  the  supe- 
rior curved  line  of  the  occiput;  and  the  sides  by  two  lines,  the  one  drawn  down- 
ward and  backward  from  the  external  angular  process  of  the  frontal  bone  to  the 
angle  of  the  lower  jaw,  the  other  from  the  angle  of  the  jaw  upward  and  back- 


THE   LATERAL    REGION    OF    THE   SKULL 


137 


ward  to  the  outer  extremity  of  the  superior  curved  line.  This  region  is  divisible  into 
three  portions — temporal  fossa,  mastoid  portion,  and  zygomatic  or  infratemporal  fossa. 
The  Temporal  Fossa  {fossa  temporalis). — The  temporal  fossa  is  bounded  above 
and  behind  by  the  temporal  ridges,  which  extend  from  the  external  angular  process 
of  the  frontal  upward  and  backward  across  the  frontal  and  parietal  bones,  curving 
downward  behind  to  terminate  in  the  posterior  root  of  the  zygomatic  process,  supra- 


|'<:^//('V/''V>/ 


Y 

5       :A}^'^ 


M^f 


^m%-  * 


r 


/  / 


Oc< 


■,f 


■l^-/ 


y 


Fig.  97. — Side  view  of  the  skull.     (Cryer.) 

mastoid  crest.  In  front  it  is  bounded  by  the  frontal,  malar,  and  great  wing  of  the 
sphenoid;  externally  by  the  zygomatic  arch  formed  conjointly  by  the  malar  and 
temporal  bones;  below,  it  is  separated  from  the  zygomatic  fossa  by  the  pterygoid 
ridge,  seen  on  the  outer  surface  of  the  great  wing  of  the  sphenoid.  This  fossa  is 
formed  by  five  bones,  part  of  the  frontal,  great  wing  of  the  sphenoid,  parietal,  squa- 
mous portion  of  the  temporal  and  malar  bones,  and  is  traversed  by  six  sutures,  part  of 
the  transverse  facial,  spheno-malar,  coronal,  spheno-parietal,  squamo-parietal,  and 
squamo-sphenoidal.  The  point  where  the  coronal  suture  crosses  the  superior  tem- 
poral ridge  is  sometimes  named  the  stephanion ;  and  the  region  where  the  four  bones, 
the  parietal,  the  frontal,  the  squamous,  and  the  greater  wing  of  the  sphenoid,  meet, 
at  the  anterior  inferior  angle  of  the  parietal  bone,  is  named  the  pterion.  This  point 
is  about  on  a  level  with  the  external  angular  process  of  the  frontal  bone  and  about 
one  and  a  half  inches  behind  it.  This  fossa  is  deeply  concave  in  front,  convex 
behind,  traversed  by  grooves  which  lodge  branches  of  the  deep  temporal  arteries, 
and  filled  by  the  Temporal  muscles. 


138 


THE   SKELETON 


The  Mastoid  Portion. — The  mastoid  portion  of  the  side  of  the  skull  is  bounded 
in  front  by  the  tubercle  of  the  zygoma;  above,  by  a  line  which  runs  from  the  pos- 
terior root  of  the  zygoma  to  the  end  of  the  mastoid-parietal  suture;  behind  and 
below  by  the  masto-occipital  suture.  It  is  formed  by  the  mastoid  and  part  of  the 
squamous  and  petrous  portions  of  the  temporal  bone;  its  surface  is  convex  and 
rough  for  the  attachment  of  muscles,  and  presents,  from  behind  forward,  the 
mastoid  foramen,  the  mastoid  process,  the  external  auditory  meatus  surrounded  by 
the  tympanic  plate,  and,  most  anteriorly,  the  temporo-maxillary  articulation.  The 
point  where  the  posterior  inferior  angle  of  the  parietal  meets  the  occipital  bone 
and  mastoid  portion  of  the  temporal  is  named  the  asterion. 

The  Zygomatic  or  Infratemporal  Fossa  {jossa  infratemporalis) . — The  zygo- 
matic fossa  is  an  irregularly  shaped  cavity,  situated  below  and  on  the  inner  side 
of  the  zygoma;  bounded  in  front  by  the  zygomatic  surface  of  the  superior  maxil- 
lary bone  and  the  ridge  which  descends  from  its  malar  process;  behind,  by  the 
posterior  border  of  the  external  pterygoid  plate  and  the  eminentia  articularis; 
above,  by  the  pterygoid  ridge  on  the  outer  surface  of  the  great  wing  of  the 
sphenoid  and  the  under  part  of  the  squamous  portion  of  the  temporal;  below, 
by  the  alveolar  border  of  the  superior  maxilla;  internally,  by  the  external  pterygoid 
plate;  and  externally,  by  the  zygomatic  arch  and  ramus  of  the  lower  jaw  (Fig.  98). 


Ext.  auditory        y^ 

Spheno-      ^^U 

maxillary     ^^H 

fissure.       ^H 

meatus.          Styloid 

/^ 

process. 

Ext. 

pterygoid 
plate. 

Fig.  98. — Zygomatic  fossa. 

It  contains  the  lower  part  of  the  Temporal,  the  External  and  Internal  pterygoid 
muscles,  the  internal  maxillary  artery  and  vein,  and  inferior  maxillary  nerve  and 
their  branches.  At  its  upper  and  inner  part  may  be  observed  two  fissures,  the 
spheno-maxillary  and  pterygo-maxillary  fissures. 

The  Spheno-maxillary  Fissure  {fissura  orhitalis  inferior),  horizontal  in  direction, 
opens  into  the  outer  and  back  jmrt  of  the  orbit.  It  is  formed  above  by  the  lower 
border  of  the  orbital  surface  of  the  great  wing  of  the  sphenoid ;  below,  by  the  exter- 
nal border  of  the  orbital  surface  of  the  superior  maxilla  and  a  small  part  of  the 
palate  bone;  externally,  by  a  small  part  of  the  malar  bone:*  internally,  it  joins  at 

1  Occasionally  the  superior  maxillary  bone  and  the  sphenoid  articulate  with  each  other  at  the  anterior 
extremity  of  this  fissure  ;  the  malar  is  then  excluded  from  entering  into  its  formation. 


THE  ANTERIOR    REGION   OF    THE  SKULL  139 

right  angles  with  the  pterygo-maxillary  fissure.  This  fissure  opens  a  communication 
from  the  orbit  into  three  fossae — the  temporal,  zygomatic,  and  spheno -maxillary  fossa ; 
it  transmits  the  superior  maxillary  nerve  and  its  orbital  branch,  the  infraorbital 
vessels,  and  ascending  branches  from  the  spheno-palatine  or  Meckel's  ganglion. 

The  Pterygo-maxillary  Fissm^e  is  vertical,  and  descends  at  right  angles  from  the 
inner  extremity  of  the  preceding;  it  is  a  V-shaped  interval,  formed  by  the  diver- 
gence of  the  superior  maxillary  bone  from  the  pterygoid  process  of  the  sphenoid. 
It  serves  to  connect  the  spheno-maxillary  fossa  with  the  zygomatic  fossa,  and 
transmits  the  internal  maxillary  artery. 

The  Spheno-maxillary  or  Pterygo-palatine  Fossa  {fossa  pterygopalatina). — 
The  spheno-maxillary  fossa  is  a  small,  triangular  space  situated  at  the  angle 
of  junction  of  the  spheno-maxillary  and  pterygo-maxillary  fissures,  and  placed 
beneath  the  apex  of  the  orbit.  It  is  formed  above  by  the  under  surface  of  the 
body  of  the  sphenoid  and  by  the  orbital  process  of  the  palate  bone;  in  front, 
by  the  superior  maxillary  bone;  behind,  by  the  anterior  surface  of  the  base  of 
the  pterygoid  process  and  lower  part  of  the  anterior  surface  of  the  great  wing  of 
the  sphenoid;  internally,  by  the  vertical  plate  of  the  palate.  This  fossa  has 
three  fissures  terminating  in  it — the  sphenoidal,  spheno-maxillary,-  and  pterygo- 
maxillary;  it  communicates  with  the  orbit  by  the  spheno-maxillary  fissure ;  with  the 
nasal  fossae  by  the  spheno-palatine  foramen,  and  with  the  zygomatic  fossa  by  the 
pterygo-maxillary  fissure.  It  also  communicates  with  the  cavity  of  the  cranium, 
and  has  opening  into  it  five  foramina.  Of  these,  there  are  three  on  the  posterior 
wall :  the  foramen  rotmidum  above ;  below  and  internal  to  this,  the  Vidian  canal ;  and 
still  more  inferiorly  and  internally,  the  pterygo-palatine  canal.  On  the  inner  wall 
is  the  spheno-palatine  foramen,  by  which  the  spheno-maxillary  communicates  with 
the  nasal  fossa;  and  below  is  the  superior  orifice  of  the  posterior  palatine  canal, 
besides  occasionally  the  orifices  of  the  accessory  posterior  palatine  canals.  The 
fossa  contains  the  superior  maxillary  nerve  and  Meckel's  ganglion,  and  the  termi- 
nation of  the  internal  maxillary  artery. 

The  Anterior  Region  of  the  Skull. 

The  view  of  the  anterior  region  of  the  skull  from  the  front  is  known  as  the 
norma  frontalis.  It  forms  the  face,  is  of  an  oval  form,  presents  an  irregular 
surface,  and  is  excavated  for  the  reception  of  two  of  the  organs  of  sense,  the 
eye  and  the  nose.  It  is  bounded  above  by  the  glabella  and  margins  of  the 
orbit;  below,  by  the  prominence  of  the  chin;  on  each  side  by  the  malar  bone 
and  anterior  margin  of  the  ramus  of  the  jaw.  In  the  median  line  are  seen  from 
above  downward  the  glabella,  and  diverging  from  it  are  the  superciUary  ridges, 
which  indicate  the  situation  of  the  frontal  sinuses  and  supports  the  eyebrow. 
Beneath  the  glabella  is  the  fronto-nasal  suture,  the  mid-point  of  which  is  termed 
the  nasion,  and  below  this  is  the  arch  of  the  nose,  formed  by  the  nasal  bones,  and 
the  nasal  processes  of  the  superior  maxillary.  The  nasal  arch  is  convex  from  side 
to  side,  concave  from  above  downward,  presenting  in  the  median  line  the  inter- 
nasal  suture  {sutura  inter nasalis) ,  formed  between  the  nasal  bones,  laterally  the 
naso-maxillary  suture  {sutura  nasomaxillaris) ,  formed  between  the  nasal  bone  and 
the  nasal  process  of  the  superior  maxillary  bone.  Below  the  nose  is  seen  the 
opening  of  the  anterior  nares,  which  is  heart-shaped,  with  the  narrow  end 
upward,  and  presents  laterally  the  thin,  sharp  margins  serving  for  the  attach- 
ment of  the  lateral  cartilages  of  the  nose,  and  in  the  middle  line  below  a 
prominent  process,  the  anterior  nasal  spine,  bounded  by  two  deep  notches. 
Below  this  is  the  intermaxillary  suture  {sutura  intermaxillaris) ,  and  on  each  side 
of  it  the  iricisive  fossa.  Beneath  this  fossa  are  the  alveolar  processes  of  the 
upper  and  lower  jaws,  containing  the  incisor  teeth,  and  at  the  lower  part  of  the 


140 


THE  SKELETON 


median  line  the  symphysis  of  the  chin,  the  mental  process,  with  its  two  mental 
tubercles,  separated  by  a  median  groove,  and  the  incisive  fossa  of  the  lower  jaw. 

On  each  side,  proceeding  from  above  downward,  is  the  supraorbital  ridge, 
terminating  externally  in  the  external  angular  process  at  its  junction  with  the 
malar,  and  internally  in  the  internal  angular  process;  toward  the  inner  third  of 
this  ridge  is  the  supraorbital  notch  or  foramen,  for  the  passage  of  the  supraorbital 
vessels  and  nerve.  Beneath  the  supraorbital  ridge  is  the  opening  of  the  orbit, 
bounded  externally  by  the  orbital  ridge  of  the  malar  bone;  below,  by  the  orbital 
ridge  formed  by  the  malar  and  superior  maxillary  bones;  internally,  by  the  nasal 
process  of  the  superior  maxillary  and  the  internal  angular  process  of  the  frontal 
bone.  On  the  outer  side  of  the  orbit  is  the  quadrilateral  anterior  surface  of  the 
malar  bone,  perforated  by  one  or  two  small  malar  foramina.  Below  the  inferior 
margin  of  the  orbit  is  the  infraorbital  foramen,  the  termination  of  the  infraorbital 
canal,  and  beneath  this  the  canine  fossa,  which  gives  attachment  to  the  Levator 
anguli  oris;  still  lower  are  the  alveolar  processes,  containing  the  teeth  of  the  upper 
and  lower  jaws.  Beneath  the  alveolar  arch  of  the  lower  jaw  is  the  mental  foramen, 
for  the  passage  of  the  mental  vessels  and  nerve,  the  external  oblique  line,  and  at 
the  lower  border  of  the  bone,  at  the  point  of  junction  of  the  body  with  the  ramus, 
a  shallow  groove  for  the  passage  of  the  facial  artery. 

Orbits,  Orbital  Cavities,  or  Orbital  Fossae. — The  orbits  (from  orhis,  a  circle) 
(Fig.  99)  are  two  quadrilateral  pyramidal  cavities,  situated  at  the  upper  and  anterior 


TENDO  OCULI 


\<Tiooiefor 
facial  artery 


[ueiice 

Fig.  99. — Antero-lateral  region  of  the  skull.     (Cryer.) 


THE   ANTERIOR    REGION   OF   THE  SKULL  141 

part  of  the  face,  their  bases  being  directed  forward  and  outward,  and  their  apices 
backward  and  inward,  so  that  the  axes  of  the  two,  if  continued  backward,  would 
meet  over  the  body  of  the  sphenoid  bone.  The  wide  orbital  opening  or  mouth  is 
called  the  aditus  orbitce.  The  orbit  is  lined  with  periosteum,  the  periorbita.  Each 
orbit  (orbita)  is  formed  of  seveji  bones,  the  frontal,  sphenoid,  ethmoid,  superior 
maxillary,  malar,  lachrymal,  and  palate;  but  three  of  these,  the  frontal,  ethmoid, 
and  sphenoid,  enter  into  the  formation  of  both  orbits,  so  that  the  two  cavities  are 
formed  of  eleven  bones  only.  Each  cavity  presents  for  examination  a  roof,  a  floor, 
an  inner  and  an  outer  wall,  four  angles,  a  circumference  or  base,  and  an  apex. 

The  Roof  (paries  superior). — The  roof  is  concave,  directed  downward  and 
slightly  forward,  and  formed  in  front  by  the  orbital  plate  of  the  frontal;  behind, 
by  the  lesser  wing  of  the  sphenoid.  This  surface  presents  internally  the  depres- 
sion for  the  cartilaginous  pidley  of  the  Superior  oblique  muscle;  externally,  the 
depression  for  the  lachrymal  gland;  and  posteriorly,  the  suture  connecting  the 
frontal  and  lesser  wing  of  the  sphenoid. 

The  Floor  (paries  inferior). — The  floor  is  directed  upward  and  outward,  and 
is  of  less  extent  than  the  roof;  it  is  formed  chiefly  by  the  orbital  process  of 
the  superior  maxillary;  in  front,  to  a  small  extent,  by  the  orbital  process  of  the 
malar,  and  behind,  by  the  superior  surface  of  the  orbital  process  of  the  palate. 
This  surface  presents  at  its  anterior  and  internal  part,  just  external  to  the  lachrymal 
groove,  a  depression  for  the  attachment  of  the  Inferior  oblique  muscle;  externally, 
the  sutu  re  between  the  malar  and  superior  maxillary  bones ;  near  its  middle,  the  infra- 
orbital groove ;  and  posteriorly,  the  suture  between  the  maxillary  and  palate  bones. 

Inner  or  Medial  Wall  (paries  medialis). — The  inner  wall  is  flattened,  nearly 
vertical,  and  formed  from  before  backward  by  the  nasal  process  of  the  superior 
maxillary,  the  lachrymal,  os  planum  of  the  ethmoid,  and  a  small  part  of  the  body  of 
the  sphenoid.  This  surface  presents  the  lachrymal  groovie  and  crests  of  the  lachrymal 
bone,  and  the  sutures  connecting  the  lachrymal  with  the  superior  maxillary,  the 
ethmoid  with  the  lachrymal  in  front,  and  the  ethmoid  with  the  sphenoi<l  behind. 

Outer  or  Lateral  Wall  (paries  lateralis). — The  outer  wall  is  directed  forward 
and  inward,  and  is  formed  in  front  by  the  orbital  process  of  the  malar  bone; 
behind,  by  the  orbital  surface  of  the  greater  wing  of  the  sphenoid.  On  it  are 
seen  the  orifices  of  one  or  two  malar  canals,  and  the  suture  connecting  the  sphenoid 
and  malar  bones. 

Angles. — The  superior  external  angle  is  formed  by  the  junction  of  the  upper 
and  outer  walls;  it  presents  from  before  backward,  the  suture  connecting  the 
frontal  with  the  malar  in  front  and  with  the  great  wing  of  the  sphenoid  behind; 
quite  posteriorly  is  the  foramen  lacerum  anterius,  or  sphenoidal  fissure,  which 
transmits  the  third,  the  fourth,  the  three  branches  of  the  ophthalmic  division  of 
the  fifth,  the  sixth  nerve,  some  filaments  from  the  cavernous  plexus  of  the  sym- 
pathetic, the  orbital  branch  of  the  middle  meningeal  artery,  a  recurrent  branch 
from  the  lachrymal  artery  to  the  dura  mater,  and  the  ophthalmic  vein.  The 
superior  internal  angle  is  formed  by  the  junction  of  the  upper  and  inner  wall,  and 
presents  the  suture  connecting  the  frontal  bone  with  the  lachrymal  in  front  and 
with  the  ethmoid  behind.  The  point  of  junction  of  the  anterior  border  of  the 
lachrymal  with  the  frontal  has  been  named  the  dacryon.  This  angle  presents  two 
foramina,  the  anterior  and  posterior  ethmoidal  foramina,  the  former  transmitting  the 
anterior  ethmoidal  vessels  and  nasal  nerve,  the  latter  the  posterior  ethmoidal  vessels. 
The  inferior  external  angle,  formed  by  the  junction  of  the  outer  wall  and  floor,  pre- 
sents the  spheno-maxillary  fissure,  which  transmits  the  superior  maxillary  nerve  and 
its  orliital  branches,  the  infraorbital  vessels,  and  the  ascending  branches  from  the 
spheno-palatine  or  jNIeckel's  ganglion.  The  inferior  internal  angle  is  formed  by 
the  union  of  the  lachrymal  bone  and  the  os  planum  of  the  ethmoid  with  the 
superior  maxillary  and  palate  bones. 


142 


THE   SKELETON 


Circumference. — The  circumference  or  base  of  the  orbit,  quadrilateral  in  form, 
is  bounded  above  (margo  swpraorhitalis)  by  the  supraorbital  ridge;  below  (margo 
infraorb (talis) ,  by  the  anterior  border  of  the  orbital  plate  of  the  malar  and  supe- 
rior maxillary  bones;  externally,  by  the  external  angular  process  of  the  frontal 
and  malar  bones;  internally,  by  the  internal  angular  process  of  the  frontal  and  the 
nasal  process  of  the  superior  maxillary.  The  circumference  is  marked  by  three 
sutures,  the  fronto-maxillary  internally,  the  fronto-malar  externally,  and  the  malo- 
maxillary  below;  it  contributes  to  the  formation  of  the  lachrymal  groove,  and 
presents,  above,  the  supraorbital  notch  (or  foramen),  for  the  passage  of  the  supra- 
orbital vessels  and  nerve. 

Apex. — The  apex,  situated  at  the  back  of  the  orbit,  corresponds  to  the  optic 
foramen,^  a  short  circular  canal  which  transmits  the  optic  nerve  and  ophthalmic 
artery.  It  will  thus  be  seen  that  there  are  nine  openings  communicating  with  each 
orbit — viz.,  the  optic  foramen,  sphenoidal  fissure,  spheno-maxillary  fissure,  supra- 
orbital foramen,  infraorbital  canal,  anterior  and  posterior  ethmoidal  foramina, 
malar  foramina,  and  the  canal  for  the  nasal  duct. 


>E  FROM    FRONTAL 

SINUS  IN  THE 

INFUNDIBULUM 


LACHRYMAL   CANAL  PALATE  BONE 

Fig.  100. — Nasal  cavity,  right  lateral  wall,  from  the  left.     (Spalteholz.) 

The  Nasal  Cavity  (cavum  nasi). — The  nasal  cavities  or  nasal  fossae  CFigs. 
84  and  100)  are  two  l^arge,  irregular  cavities  situated  on  either  sidfe  of  th&  middle 
line  of  the  face,  extending  from  the  base  of  the  craniiim  to  the  roof  of  the 
mouth,  and  separated  from  each  other  by  a  thin  vertical  g^ptuffi;  the  Bepfcuni;  of 
the  nose  (septum  nasi  osseum),  formed  by  the  perpendicular  plate  of  the  ethmoid 
and  by  the  vomer.  Each  cavity  communicates  by  a  large  aperture,  the  anterior 
nasal  aperture  (apertura  pyriformis)  ^  with  the  front  of  the  face,  and  by  the  two 
posterior  nares  {choanae)  with  the  naso-pharynx  behind.     These  fossse  are  much 

1  Quain,  Testut,  and  others  give  the  apex  of  the  orbit  as  oorresponding  with  the  inner  end  of  the  sphenoidal 
fissure.  It  seentis  better,  however,  to  adopt  the  statement  in  the  text,  since  the  muscles  of  the  eyeball  take 
origin  around  the  optic  foramen,  and  diverge  from  it  to  the  globe  of  the  eye. 

2  In  the  skull  freed  of  soft  parts,  the  anterior  nasal  cavities  open  in  front  by  the  apertura  pyriformis.  In  the 
skull  with  the  soft  parts  in  place  they  open  by  the  antenoi  nares 


THE    ANTERIOR    REGION    OF    THE  SKULL  143 

narrower  above  than  below,  and  in  the  middle  than  at  the  anterior  or  posterior 
openings;  their  depth,  which  is  considerable,  is  much  greater  in  the  middle  than  at 
either  extremity.  "The  nasal  fossae  are  surrounded  by  four  other  fossae — above  is 
the  cranial  fossa;  laterally,  the  orbital  fossae;  and  below,  the  cavity  of  the  mouth."^ 
Each  nasal  fossa  communicates  with  four  sinuses,  the  frontal  above,  the  sphenoidal 
behind,  and  the  maxillary  and  ethmoidal  on  the  outer  wall.  Each  fossa  also  com- 
municates with  four  cavities:  with  the  orbit  by  the  lachrymal  groove,  with  the 
mouth  by  the  anterior  palatine  canal,  with  the  cranium  by  the  olfactory  foramina, 
and  with  the  spheno-maxillary  fossa  by  the  spheno-palatine  foramen ;  and  they  occa- 
sionally communicate  with  each  other  by  an  aperture  in  the  septum.  The  bones 
entering  into  their  formation  are  fourteen  in  number:  three  of  the  cranium,  the 
frontal,  sphenoid,  and  ethmoid,  and  all  the  bones  of  the  face,  excepting  the  malar 
and  lower  jaw.   Each  cavity  is  bounded  by  a  roof,  a  floor,  an  inner  and  an  outer  wall. 

Upper  Wall. — The  upper  wall,  or  roof  (Fig.  101),  is  long,  narrow,  and  horizontal 
in  its  centre,  but  slopes  downward  at  its  anterior  and  posterior  extremities;  it  is 
formed  in  front  by  the  nasal  bones  and  nasal  spine  of  the  frontal,  which  are 
directed  downward  and  forward;  in  the  middle,  by  the  cribriform  plate  of  the 
ethmoid,  which  is  horizontal;  and  behind,  by  the  under  surface  of  the  body  of  the 
sphenoid  and  sphenoidal  turbinated  bones,  the  ala  of  the  vomer  and  the  sphenoidal 
process  of  the  palate  bone,  which  are  directed  downward  and  backward.  This 
surface  presents,  from  before  backward,  the  internal  aspect  of  the  nasal  bones; 
on  their  outer  side,  the  suture  formed  between  the  nasal  bone  and  the  nasal  process 
of  the  superior  maxillary;  on  their  inner  side,  the  elevated  crest  which  receives  the 
nasal  spine  of  the  frontal  and  the  perpendicular  plate  of  the  ethmoid,  and  articu- 
lates with  its  fellow  of  the  opposite  side;  whilst  the  surface  of  the  bones  is  perforated 
by  a  few  small  vascular  apertures,  and  presents  the  longitudinal  groove  for  the 
nasal  nerve;  farther  back  is  the  transverse  suture,  connecting  the  frontal  with  the 
nasal  in  front,  and  the  ethmoid  behind,  the  olfactory  foramina  and  nasal  slit  on 
the  under  surface  of  the  cribriform  plate,  and  the  suture  between  it  and  the  sphe- 
noid behind;  quite  posteriorly  are  seen  the  sphenoidal  turbinated  bones,  the  ori- 
fices of  the  sphenoidal  sinuses,  and  the  articulation  of  the  alse  of  the  vomer  with 
the  under  surface  of  the  body  of  the  sphenoid. 

Floor  (Figs.  84,  100,  and  101) . — The  floor  is  flattened  from  before  backward, 
concave  from  side  to  side,  and  wider  in  the  middle  than  at  either  extremity.  It 
is  formed  in  front  by  the  palate  process  of  the  superior  maxillary;  behind,  by  the 
I  palate  process  of  the  palate  bone.  This  surface  presents,  from  before  backward, 
the  anterior  nasal  spine ;  behind  this,  the  upper  orifices  of  the  anterior  palatine  canal ; 
[internally,  the  elevated  crest  which  articulates  with  the  vomer;  and  behind,  the 
suture  between  the  palate  and  superior  maxillary  bones,  and  the  posterior  nasal  spine. 

Inner  or  Medial  Wall. — The  inner  wall,  or  septum  (Figs.  101  and  103),  is  a  thin 
vertical  partition  which  separates  the  nasal  fossae  from  each  other;  it  is  occasionally 
.perforated,  so  that  the  fossje  communicate,  and  it  is  frequently  deflected  consid- 
erably to  one  side.^  It  is  formed,  in  front,  by  the  crest  of  the  nasal  bones  and 
[nasal  spine  of  the  frontal;  in  the  middle,  by  the  perpendicular  plate  of  the  ethmoid; 
[behind,  by  the  vomer  and  rostrum  of  the  sphenoid;  below,  by  the  crests  of  the 
superior  maxillary  and  palate  bones.  It  presents,  in  front,  a  large,  triangular 
[notch,  which  receives  the  septal  cartilage  of  the  nose;  and  behind,  the  grooved 
[edge  of  the  vomer.  Its  surface  is  marked  by  numerous  vascular  and  nervous 
[canals  and  the  groove  for  the  naso-palatine  nerve,  and  is  traversed  by  sutures 
[connecting  the  bones  of  which  it  is  formed. 

Outer  or  Lateral  Wall. — The  outer  wall  (Figs.  84  and  101)  is  formed,  in  front, 
[by  the  nasal  process  of  the  superior  maxillary  and  lachrymal  bones;  in  the  middle, 

1  Howard  A.  Lothrop,  in  Annals  of  Surgery,  May,  1903.  '^  See  footnote,  p.  99. 


144 


THE   SKELETON 


by  the  ethmoid  and  inner  surface  of  the  body  of  the  superior  maxillary  and  inferior 
turbinated  bones;  behind,  by  the  vertical  plate  of  the  palate  bone  and  the  internal 
pterygoid  plate  of  the  sphenoid.    Upon  this  outer  wall  are  two  marked  projections 


UNCIFORM 

PROCESS  OF 

ETHMOID 

INFERIOR 
TURBINATED 


THIRD  MOLAR 
TOOTH 


MIDDLE 
TURBINATED 


Fig.  101. — Coronal  section  of  the  face,  passing  through  the  third  molar  tooth.     (Poirier  and  Charpy.) 


of  bone  (Figs.  84  and  101).    One  is  known  as  the  inferior  turbinated  bone  and  the 
other  as  the  middle  turbinated  bone.    The  superior  turbinated  bones  or  bodies  appear 


ANTRUM  O 
HIGHMOR 


STLE   PASSED  THROUGH 
FUNDIBULUM    FROM 
ONTAL  SINUS  TO 
DOLE  MEATUS 


PROBE  PASSED 
THROUGH  LACH- 
RYMAL CANAL 


RONTAL  CANAL 


f— NASAL  CANAL 


Fig.  102. — Cranial  section  through  the  frontal  sinus  and  nasal  fossa.       (Poirier  and  Charpy.) 


as  less  distinct  bony  projections.  This  surface  presents  three  irregular  longitudinal 
passages,  or  meatuses,  termed  the  superior,  middle,  and  inferior  meatuses  of  the 
nose  (Figs.  84,  101,  and  102).     The  superior  meatus  {meatus  nasi  superior),  the 


THE    ANTERIOR    REGION   OF   THE  SKULL 


145 


smallest  of  the  three,  is  situated  at  the  upper  and  back  part  of  each  nasal  fossa,  occu- 
pying the  posterior  third  of  the  outer  wall.  It  is  situated  between  the  superior 
turbinated  bone,  and  has  opening  into  it  two  foramina,  the  spheno-palatine  foramina 
at  the  back  of  its  outer  wall,  and  the  posterior  ethmoidal  cells  at  the  front  part  of 
the  outer  wall.  The  sphenoidal  sinus  opens  into  a  recess,  the  spheno -ethmoidal 
recess  {recessus  sphenoethmoidalis) ,  which  is  situated  above  and  behind  the 
superior  turbinated  bone.  The  middle  meatus  (meatus  nasi  medius)  is  situated 
external  to  the  middle  turbinated  bone,  and  above  the  inferior  turbinated  bone, 
and  extends  from  the  anterior  end  of  the  inferior  turbinated  bone  to  the  spheno- 
palatine foramen  of  the  outer  wall  of  the  nasal  fossa.  Anteriorly  it  terminates  in 
a  depression,  the  atrium  of  the  nasal  meatus.  The  bulla  ethmoidalis,  an  elevated 
area  disclosed  by  removing  the  middle  turbinated  bone.  Below  and  in  front  of  the 
bulla  is  a  groove,  the  semilunar  hiatus  (hiatus  semilunaris) ,  into  which  open  the 
antrum  and  the  anterior  ethmoidal  cells.  The  middle  meatus  presents  in  front 
the  orifice  of  the  infundibulum  (infundibulum  ethmoidale) ,  by  which  the  middle 
meatus  communicates  with  the  anterior  ethmoidal  cells,  and  through  these  with 


Crest  of  nasal  bone 

Nasal  spine  of 
frontal  bone. 


Space  for  triangular^ 
cartilage  of  septum^ 


Crest  of  palate  bone. 
I Crest  of  superior  maxilla. 


Fig.  103. — Inner  wall  of  nasal  fossse,  or  septum  of  nose. 

the  frontal  sinuses.  The  middle  ethmoidal  cells  also  open  into  this  meatus,  while 
at  the  centre  of  the  outer  wall  is  the  orifice  of  the  maxillary  antrum  (hiatus  maxil- 
laris),  which  varies  somewhat  as  to  its  exact  position  in  different  skulls.  The 
inferior  meatus  (meatus  nasi  inferior),  the  largest  of  the  three,  is  the  space  between 
the  inferior  turbinated  bone  and  the  floor  of  the  nasal  fossa.  It  extends  along 
the  entire  length  of  the  outer  wall  of  the  nose,  is  broader  in  front  than  behind, 
and  presents  anteriorly  the  lower  orifice  of  the  canal  for  the  nasal  duct  (canalis 
nasolacrimalis).  The  anterior  nares  present  a  heart-shaped  or  pyriform  opening 
(apertura  piriformis)  whose  long  axis  is  vertical  and  narrow  extremity  upward. 
This  opening  in  the  recent  state  is  much  contracted  by  the  cartilages  of  the  nose. 
It  is  bounded  above  by  the  inferior  border  of  the  nasal  bone;  laterally  by  the  thin, 
sharp  margin  which  separates  the  facial  from  the  nasal  surface  of  the  superior 

10 


146 


THE  SKELETON 


maxillary  bone;  and  below  by  the  same  border,  where  it  slopes  inward  to  join  its 
fellow  of  the  opposite  side  at  the  anterior  nasal  spine.  The  posterior  naxes,  or 
choance,  are  the  two  posterior  oval  openings  of  the  nasal  fossae,  by  which  they 
communicate  with  the  upper  part  of  the  naso-pharynx.  They  are  situated  imme- 
diately in  front  of  the  basilar  process,  and  are  bounded  above  by  the  under 
surface  of  the  body  of  the  sphenoid  and  alse  of  the  vomer;  below,  by  the  posterior 
border  of  the  horizontal  plate  of  the  palate  bone;  externally,  by  the  inner  surface 
of  the  internal  pterygoid  plate;  and  internally,  in  the  middle  line,  they  are 
separated  from  each  other  by  the  posterior  border  of  the  vomer. 

Difference  in  Size  and  Form  of  the  Cranium. — These  differences  are  thus 
set  forth  by  Mr.  Arthur  Thomson  in  Professor  D.  J.  Cunningham's  Text-book 
of  Anatomy: 

Microcephalic  skulls  have  a  capacity  of  less  than  1350  c.c.  Mesocephalic  skulls 
have  a  capacity  of  from  1350  c.c.  to  1450  c.c.  Megacephalic  skulls  have  a  capacity 
over  1450  c.c. 

What  is  known  as  the  cephalic  index  is  the  proportion  borne  by  the  greatest 

breadth  of  the  skull  to  the  greatest  length,  assuming  that  the  latter  is  equal  to  100. 

Thomson  gives  the  following  formula: 

Maximum  length  X  100  i    i-    •    i 

. ,  j-j =  cephalic  mdex. 

maximum  breadth 

The  cephalic  index  is  used  to  determine  the  form  of  the  skull :  Dolichocephalic 
(long  antero-posterior  diameter)  (Figs.  105  and  107),  having  a  cephalic  index 


Fig.  104. — Brachycephalic  cranium. 
(Poirier  and  Charpy.) 


Fig.  105. — Dolichocephalic  cranium. 
(Poirier  and  Charpy.) 


Fig.  106. — Brachycephalic  cranium. 
(Poirier  and  Charpy.) 


Fig.  107. — Dolichocephalic  cranium. 
Poirier  and  Charpy.) 


THE  ANTERIOR   REGION   OF   THE  SKULL  147 

below  75.  Mesaticephalic  (median  head),  having  a  cephahc  index  from  75  to  80. 
Brachycephahc  (short  antero-posterior  diameter)  (Figs.  104  and  106),  having  a 
cephalic  index  over  80. 

Surface  Form. — The  various  bony  prominences  or  landmarks  which  are  to  be  easily  felt  and 
recognized  in  the  head  and  face,  and  which  afford  the  means  of  mapping  out  the  important 
structures  comprised  in  this  region,  are  as  follows: 

1.  Supraorbital  arch.  8.  Parietal  eminences. 

2.  Internal  angular  process.  9.  Temporal  ridge. 

3.  External  angular  process.  10.  Frontal  eminences. 

4.  Zygomatic  arch.  11.  Superciliary  ridges. 

5.  Mastoid  process.  12.  Nasal  bones. 

6.  External  occipital  protuberance.  13.  Lower  margin  of  orbit. 

7.  Superior  curved  line  of  occipital  bone.  14.  Lower  jaw. 

1 .  The  supraorbital  arches  are  to  be  felt  throughout  their  entire  extent,  covered  by  the  eye- 
brows. They  form  the  upper  boundary  of  the  circumference  or  base  of  the  orbit,  and  separate 
the  face  from  the  forehead.  They  are  strong  and  arched,  and  terminate  internally  on  each  side 
of  the  root  of  the  nose  in  the  internal  angular  process,  which  articulates  with  the  lachrymal 
bone.  Externally  they  terminate  in  the  external  angular  process,  which  articulates  with  the 
malar  bone.  This  arched  ridge  is  sharper  and  more  defined  in  its  outer  than  in  its  inner  half, 
and  forms  an  overhanging  process  which  protects  and  shields  the  lachrymal  gland.  It  thus  pro- 
tects the  eye  in  its  most  exposed  situation  and  in  the  direction  from  which  blows  are  most  likely 
to  descend.  The  supraorbital  arch  varies  in  prominence  in  different  individuals.  It  is  more 
marked  in  the  male  than  in  the  female,  and  in  some  races  of  mankind  than  others.  In  the  less 
civilized  races,  as  the  forehead  recedes  backward,  the  supraorbital  arch  becomes  more  prominent, 
and  approaches  more  to  the  characters  of  the  monkey  tribe,  in  which  the  supraorbital  arches  are 
very  largely  developed,  and  acquire  additional  prominence  from  the  oblique  direction  of  the 
frontal  bone.  2.  The  internal  angular  process  is  scarcely  to  be  felt.  Its  position  is  indicated 
by  the  angle  formed  by  the  supraorbital  arch  with  the  nasal  process  of  the  superior  maxillary 
bone  and  the  lachrymal  bone  at  the  inner  side  of  the  orbit.  Between  the  internal  angular  pro- 
cesses of  the  two  sides  is  a  broad  surface  which  assists  in  forming  the  root  of  the  nose,  and 
immediately  above  this  a  broad,  smooth,  somewhat  triangular  surface,  the  glabella,  situated 
between  the  superciliary  ridges.  3.  The  external  angular  process  is  much  more  strongly  marked 
than  the  internal,  and  is  plainly  to  be  felt.  It  is  formed  by  the  junction  or  confluence  of  the  supra- 
orbital and  temj)oral  ridges,  and,  articulating  with  the  malar  bone,  it  serves  to  a  very  consider- 
able extent  to  support  the  bones  of  the  face.  In  carnivorous  animals  the  external  angular  pro- 
cess does  not  articulate  with  the  malar,  and  therefore  this  lateral  support  to  the  bones  of  the  face 
is  not  present.  4.  The  zygomatic  arch  is  plainly  to  be  felt  throughout  its  entire  length,  being 
situated  almost  immediately  under  the  skin.  It  is  formed  by  the  malar  bone  and  the  zygomatic 
process  of  the  temporal  bone.  At  its  anterior  extremity,  where  it  is  formed  by  the  malar  bone, 
it  is  broad  and  forms  the  prominence  of  the  cheek;  the  posterior  part  is  narrower,  and  termi- 
nates just  in  front  and  a  little  above  the  tragus  of  the  external  ear.  The  lower  border  is 
more  plainly  to  be  felt  than  the  upper,  in  consequence  of  the  dense  temporal  fascia  being 
attached  to  the  latter,  which  somewhat  obscures  its  outline.  Its  shape  differs  very  much  in  indi- 
viduals and  in  different  races  of  mankind.  In  the  most  degraded  type  of  skull — as,  for  instance, 
in  the  skull  of  the  negro  of  the  Guinea  Coast — the  malar  bones  project  forward  and  not  outward, 
and  the  zygoma  at  its  posterior  extremity  extends  farther  outward  before  it  is  twisted  on  itself  to 
be  prolonged  forward.  This  makes  the  zygomatic  arch  stand  out  in  bold  relief,  and  affords 
greater  space  for  the  Temporal  muscle.  In  skulls  which  have  a  more  pyramidal  shape,  as  in  the 
Esquimaux  or  Greenlander,  the  malar  bones  do  not  project  forward  and  downward  under  the 
eyes,  as  in  the  preceding  form,  but  take  a  direction  outward,  forming  with  the  zygoma  a  large, 
rounded  sweep  or  segment  of  a  circle.  Thus  it  happens  that  if  two  lines  are  drawn  from  the 
zygomatic  arches,  touching  the  temporal  ridges,  they  meet  above  the  top  of  the  head,  instead  of 
being  parallel,  or  nearly  so,  as  in  the  European  skull,  in  which  the  zygomatic  arches  are  not 
nearly  so  prominent.  This  gives  to  the  face  a  more  or  less  oval  type.  5.  Behind  the  ear  is  the 
mastoid  portion  of  the  temporal  bone,  plainly  to  be  felt,  and  terminating  below  in  a  nipple- 
shaped  process.  Its  anterior  border  can  be  traced  immediately  behind  the  concha,  and  its  apex 
is  on  about  a  level  with  the  lobule  of  the  ear.  It  is  rudimentary  in  infancy,  but  gradually 
develops  in  childhood,  and  is  more  marked  in  the  negro  than  in  the  European.  6.  The  external 
occipital  protuberance  is  always  plainly  to  be  felt  just  at  the  level  where  the  skin  of  the  neck 
joins  that  of  the  head.  At  this  point  the  skull  is  thick  for  the  purposes  of  safety,  while  radiating 
from  it  are  numerous  curved  arches  or  buttresses  of  bone  which  give  to  this  portion  of  the 
skull  further  security.  7.  Running  outward  on  either  side  from  the  external  occipital  protu- 
berance is  an  arched  ridge  of  bone,  which  can  be  more  or  less  plainly  perceived.  This  is  the 
superior  curved  line  of  the  occipital  bone,  and  gives  attachment  to  some  of  the  muscles  which 


148  THE  SKELETON 

keep  the  head  erect  on  the  spine;  accordingly,  we  find  it  more  developed  in  the  negro  tribes,  in 
whom  the  jaws  are  much  more  massive,  and  therefore  require  stronger  muscles  to  prevent  their 
extra  weight  carrying  the  head  forward.  Below  this  line  the  surface  of  hone  at  the  back  of  the 
head  is  obscured  by  the  overlying  muscles.  Above  it,  the  vault  of  the  cranium  is  thinly  covered 
with  soft  structures,  so  that  the  form  of  this  part  of  the  head  is  almost  exactly  that  of  the  upper 
partion  of  the  occipital,  the  parietal,  and  the  frontal  bones  themselves;  and  in  bald  persons, 
even  the  lines  of  junction  of  the  bones,  especially  the  junction  of  the  occipital  and  parietal  at 
the  lambdoid  suture,  may  be  defined  as  a  slight  depression,  caused  by  the  thickening  of  the 
borders  of  the  bones  in  this  situation.  8.  In  the  line  of  the  greatest  transverse  diameter  of  the 
head,  on  each  side  of  the  middle  line,  are  generally  to  be  found  the  parietal  eminences,  one  on 
each  side  of  the  middle  line,  though  sometimes  these  eminences  are  not  situated  at  the  point  of 
the  greatest  transverse  diameter,  which  is  at  some  other  prominent  part  of  the  parietal  region. 
They  denote  the  point  where  ossification  of  the  parietal  bone  began.  They  are  much  more 
prominent  and  well-marked  in  early  life,  in  consequence  of  the  sharper  curve  of  the  bone  at 
this  period,  so  that  it  describes  the  segment  of  a  smaller  circle.  Later  in  life,  as  the  bone  grows, 
the  curve  spreads  out  and  forms  the  segment  of  a  larger  circle,  so  that  the  eminence  becomes 
less  distinguishable.  In  consequence  of  this  sharp  curve  of  the  bone  in  early  life,  the  whole  of 
the  vault  of  the  skull  has  a  squarer  shape  than  it  has  in  later  life,  and  this  appearance  may  per- 
sist in  some  rickety  skulls.  The  eminence  is  more  apparent  in  the  negro's  skull  than  in  that  of 
the  European.  This  is  due  to  greater  flattening  of  the  temporal  fossa  in  the  former  skull  to 
accommodate  the  larger  Temporal  muscle  which  exists  in  these  races.  The  parietal  eminence 
is  particularly  exposed  to  injury  from  blows  or  falls  on  the  head,  but  fracture  is  to  a  certain 
extent  prevented  by  the  shape  of  the  bone,  which  forms  an  arch,  so  that  the  force  of  the  blow 
is  diffused  over  the  bone  in  every  direction.  9.  At  the  side  of  the  head  may  be  felt  the  temporal 
ridge.  Commencing  at  the  external  angular  process,  it  may  be  felt  as  a  curved  ridge,  passing 
upward  and  then  curving  backward,  on  the  frontal  bone,  separating  the  forehead  from  the 
temporal  fossa.  It  may  then  be  traced  passing  backward  in  a  curved  direction,  over  the  parietal 
bone,  and,  though  less  marked,  still  generally  to  be  recognized.  Finally,  the  ridge  curves  down- 
ward, and  terminates  in  the  posterior  root  of  the  zygoma,  which  separates  the  squamous  from 
the  subcutaneous  mastoid  portion  of  the  temporal  bone.  Sir  Victor  Horsley  has  recently  shown 
in  an  article  on  the  "Topography  of  the  Cerebral  Cortex,"  that  the  second  temporal  ridge  (see 
page  76)  can  be  made  out  on  the  living  body.  10.  The  frontal  eminences  vary  a  good  deal  in 
different  individuals,  being  considerably  more  prominent  in  some  than  in  others,  and  they  are 
often  not  symmetrical  on  the  two  sides  of  the  body,  the  one  being  much  more  pronounced  than 
the  other.  This  is  often  especially  noticeable  in  the  skull  of  the  young  child  or  infant,  and 
becomes  less  marked  as  age  advances.  The  prominence  of  the  frontal  eminences  depends 
more  upon  the  general  shape  of  the  whole  bone  than  upon  the  size  of  the  protuberances  them- 
selves. As  the  skull  is  more  highly  developed  in  consequence  of  increased  intellectual  capacity, 
so  the  frontal  bone  becomes  more  upright  and  the  frontal  eminences  stand  out  in  bolder  relief. 
Thus  they  may  be  considered  as  affording,  to  a  certain  extent,  an  indication  of  the  development 
of  the  hemispheres  of  the  brain  beneath,  and  of  the  mental  powers  of  the  individual.  They 
are  not  so  much  exposed  to  injury  as  the  parietal  eminences.  In  falls  forward  the  upper  extrem- 
ities are  involuntarily  thrown  out,  and  break  the  force  of  the  fall,  and  thus  shield  the  frontal 
bone  from  injury.  11.  Below  the  frontal  eminences  on  the  forehead  are  the  superciliary  ridges, 
which  denote  the  position  of  the  frontal  sinuses,  and  vary  according  to  the  size  of  the  sinuses 
in  difTerent  individuals,  being,  as  a  rule,  small  in  the  female,  absent  in  children,  and  some- 
times unusually  prominent  in  the  male,  when  the  frontal  sinuses  are  largely  develo])ed.  They 
commence  on  either  side  of  the  glabella,  and  at  first  present  a  rounded  form,  which  gradually 
fades  away  at  their  outer  ends.  12.  The  nasal  bones  form  the  prominence  of  the  nose.  They 
vary  much  in  size  and  shape,  and  to  them  is  due  the  varieties  in  the  contour  of  this  organ  and 
much  of  the  character  of  the  face.  Thus,  in  the  Mongolian  or  Ethiopian  they  are  flat,  broad, 
and  thick  at  their  base,  giving  to  these  races  the  flattened  nose  by  which  they  are  characterized, 
and  differing  very  decidedly  from  the  Caucasian,  in  whom  the  nose,  owing  to  the  shape  of  the  ■ 
nasal  bones,  is  narrow,  elevated  at  the  bridge,  and  elongated  downward.  Below,  the  nasal 
bones  are  thin  and  connected  with  the  cartilages  of  the  nose,  and  the  angle  or  arch  formed  by ' 
their  union  serves  to  throve  out  the  bridge  of  the  nose,  and  is  much  more  marked  in  some  indi- 
viduals than  others.  13.  The  lower  margin  of  the  orbit,  formed  by  the  superior  maxillary  bone 
and  the  malar  bone,  is  plainly  to  be  felt  throughout  its  entire  length.  It  is  continuous  inter-  i 
nally  with  the  nasal  process  of  the  superior  maxillary  bone,  which  forms  the  inner  boundary 
of  the  orbit.  At  the  point  of  junction  of  the  lower  margin  of  the  orbit  with  the  nasal  process 
is  to  be  felt  a  little  tubercle  of  bone,  which  can  be  plainly  perceived  by  running  the  finger  along 
the  bone  in  this  situation.  This  tubercle  serves  as  a  guide  to  the  position  of  the  lachrymal  sac, 
which  is  situated  above  and  behind  it.  14.  The  outline  of  the  lower  jaw  is  to  be  felt  throughout 
its  entire  length.  Just  in  front  of  the  tragus  of  the  external  ear,  and  below  the  zygomatic  arch, 
the  condyle  can  be  made  out.  When  the  mouth  is  opened  this  prominence  of  bone  can  be  per- 
ceived advancing  out  of  the  glenoid  fossa  on  to  the  eminentia  articularis,  and  receding  again 


THE  ANTERIOR    REGION   OF   THE   SKULL  149 

when  the  mouth  is  closed.  From  the  condyle  the  posterior  border  of  the  ramus  can  be  felt 
extending  down  to  the  angle.  A  line  drawn  from  the  condyle  to  the  angle  would  indicate  the 
exact  position  of  this  border.  From  the  angle  to  the  symphysis  of  the  chin  the  lower,  rounded 
border  of  the  body  of  the  bone  is  plainly  to  be  felt.  At  the  point  of  junction  of  the  two  halves 
of  the  bone  is  a  well-marked  triangular  eminence,  the  mental  process,  which  forms  the  promi- 
nence of  the  chin. 

Fixed  Points  for  Measurement. — In  order  to  determine  the  location  of  regions  of  surgical 
importance  within  the  skull  (bony  spaces,  vessels,  fissures,  centres,  and  convolutions  of  the 
i)rain)  and  in  order  to  estimate  cranial  capacity,  measurements  are  made  and  these  measure- 
ments are  taken  from  fixed  points.    The  following  are  the  chief  fixed  points: 

The  Nasion.    The  middle  of  the  naso-frontal  suture. 

The  Glabella.    Midway  between  the  two  superciliary  ridges. 

The  Obelion.    A  point  in  the  sagittal  suture  between  the  parietal  foramina. 

The  IxiON.    The  external  occipital  protuberance. 

The  Basion.    The  middle  of  the  anterior  edge  of  the  foramen  magnum. 

The  Opisthion.    The  middle  of  the  posterior  edge  of  the  foramen  magnum. 

The  Lambda.    The  point  of  junction  of  the  sagittal  and  lambdoid  sutures. 

The  Pterion.  The  site  of  the  antero-lateral  fontanelle,  where  the  frontal,  parietal,  squa- 
mous portion  of  the  temporal  and  greater  wing  of  the  sphenoid  are  in  relation. 

The  AsTERiON.  The  region  of  the  postero-lateral  fontanelle,  at  the  posterior  inferior  margin 
of  the  parietal  bone. 

The  Bregma.  The  site  of  the  anterior  fontanelle,  where  the  sagittal  and  coronal  sutures 
meet. 

The  Superior  Stephanion.  The  point  where  the  superior  temporal  ridge  meets  the  coronal 
suture. 

The  Inferior  Stephanion.  The  point  where  the  inferior  temporal  ridge  meets  the  coronal 
suture. 

The  GoNiON.    The  outer  surface  of  the  angle  of  the  mandible. 

The  Ophryon.    The  middle  of  the  narrowest  transverse  diameter  of  the  forehead. 

The  Vertex.    The  highest  point  of  the  vault  of  the  skull. 

Besides  these  points  we  use  the  mastoid  process,  the  nasal  spine,  the  zygomatic  arch,  the 
frontal  eminences,  the  parietal  eminences,  the  supraorbital  ridges,  the  superciliary  ridges,  the 
mental  process,  suprameatal  spine,  the  external  and  internal  angular  processes,  and  the  canine 
fossa. 

Surgical  Anatomy. — The  thickness  of  the  skull  varies  greatly  in  different  regions  of  the  same 
skull  and  in  different  individuals.  The  average  thickness  of  the  skull-cap  is  about  one-fifth 
of  an  inch.  The  thickest  portions  are  the  occipital  protuberance,  the  inferior  portion  of  the 
frontal  bone,  and  the  mastoid  process.  The  thinnest  portions  are  the  occipital  fossae,  the  squa- 
mous portion  of  the  temporal  bone,  and  over  certain  sinuses  and  arteries.  An  arrest  in  the 
ossifying  process  may  give  rise  to  deficiencies  or  gaps,  or  to  fissures,  which  are  of  importance 
in  a  medico-legal  point  of  view,  as  they  are  liable  to  be  mistaken  for  fractures.  The  fissures 
generally  extend  from  the  margin  toward  the  centre  of  the  bone,  but  gaps  may  be  found  in  the 
middle  as  well  as  at  the  edges.  In  course  of  time  they  may  become  covered  with  a  thin  lamina 
of  bone. 

Occasionally  a  protrusion  of  the  brain  or  its  membranes  may  take  place  through  one  of  these 
gaps  in  an  imperfectly  developed  skull.  When  the  protrusion  consists  of  membranes  only,  and 
is  filled  with  cerebro-spinal  fluid,  it  is  called  a  meningocele ;  when  the  protrusion  consists  of  brain 
as  well  as  membranes,  it  is  termed  an  enCGphalocele  and  when  the  protruded  brain  is  a  prolonga- 
tion from  one  of  the  ventricles,  and  is  distended  by  a  collection  of  fluid  from  an  accumulation  in 
the  ventricle,  it  is  termed  an  hydrencephalocele.  This  latter  condition  is  sometimes  found  at  the 
root  of  the  nose,  where  a  protrusion  of  the  anterior  horn  of  the  lateral  ventricle  takes  place 
through  a  deficiency  of  the  fronto-nasal  suture.  These  malformations  are  usually  found  in  the 
middle  line,  and  most  frequently  at  the  back  of  the  head,  the  protrusion  taking  place  through 
the  fissures  which  separate  the  four  centres  of  ossification  from  w-hich  the  tabular  portion  of  the 
occipital  bone  is  originally  developed  (see  page  75).  They  most  frequently  occur  through  the 
upper  part  of  the  vertical  fissure,  which  is  the  last  to  ossify,  but  not  uncommonly  through  the 
lower  part,  when  the  foramen  magnum  may  be  incomplete.  More  rarely  these  protrusions 
have  been  met  with  in  other  situations  than  those  above  mentioned,  both  through  normal 
fissures,  as  the  sagittal,  lambdoid,  and  other  sutures,  and  also  through  abnormal  gaps  and 
deficiencies  at  the  sides,  and  even  at  the  base  of  the  skull.  Force  may  be  responsible  in  a  young 
person  for  separating  a  suture.  This  accident,  seldom  met  with  even  in  the  young,  is  only  occa- 
sionally encountered  in  older  persons. 

Fractures  of  the  skull  may  be  divided  into  those  of  the  vault  and  those  of  the  base.  Frac- 
tures of  the  vault  are  usually  produced  by  direct  violence.  This  portion  of  the  skull  varies  in 
thickness  and  strength  in  different  individuals,  but,  as  a  rule,  is  sufficiently  strong  to  resist  a  very 
considerable  amount  of  violence  without  being  fractured.     This  is  due  to  several  causes:  the 


150  THE  SKELETON 

rounded  shape  of  the  head  and  its  construction  of  a  number  of  secondary  elastic  arches,  each 
made  up  of  a  single  bone;  the  fact  that  it  consists  of  a  number  of  bones,  united,  at  all  events  in 
early  life,  by  a  sutural  ligament,  which  acts  as  a  sort  of  buffer  and  interrupts  the  continuity  of 
any  violence  applied  to  the  skull ;  the  presence  of  arches  or  ridges,  both  on  the  inside  and  outside 
of  the  skull,  which  materially  strengthen  it;  and  the  mobility  of  the  head  upon  the  spine,  which 
further  enables  it  to  withstand  violence.  The  elasticity  of  the  bones  of  the  head  is  especially 
marked  in  the  skull  of  the  child,  and  this  fact,  together  with  the  wide  separation  of  the  indi- 
vidual bones  from  each  other,  and  the  interposition  between  them  of  other  and  softer  structures 
render  fracture  of  the  bones  of  the  head  a  very  uncommon  event  in  infants  and  quite  young 
children;  as  age  advances  and  the  bones  become  joined,  fracture  is  more  common,  though  still 
less  liable  to  occur  than  in  the  adult.  Fractures  of  the  vault  may,  and  generally  do,  involve  the 
whole  thickness  of  the  bone;  but  sometimes  one  table  may  be  fractured  without  any  correspond- 
ing injury  to  the  other.  Thus,  the  outer  table  of  the  skull  may  be  splintered  and  driven  into  the 
diploe,  or  in  the  frontal  or  mastoid  regions  into  the  frontal  or  mastoid  cells,  without  any  injury 
to  the  internal  table.  And  on  the  other  hand,  the  internal  table  has  been  fractured,  and  por- 
tions of  it  depressed  and  driven  inward,  without  any  fracture  of  the  outer  table.  As  a  rule,  in 
fractures  of  the  skull  the  inner  table  is  more  splintered  and  comminuted  than  the  outer,  and 
this  is  due  to  several  causes.  It  is  thinner  and  more  brittle;  the  force  of  the  violence  as  it  passes 
inward  becomes  broken  up,  and  is  more  diffused  by  the  time  it  reaches  the  inner  table;  the 
bone,  being  in  the  form  of  an  arch,  bends  as  a  whole  and  spreads  out,  and  thus  presses  the 
particles  together  on  the  convex  surface  of  the  arch — i.  e.,  the  outer  table — and  forces  them 
asunder  on  the  concave  surface  or  inner  table;  and,  lastly,  there  is  nothing  firm  under  the  inner 
table  to  support  it  and  oppose  the  force.  Fractures  of  the  vault  may  be  simple  fissures  or  starred 
and  comminuted  fractures,  and  these  may  be  depressed  or  elevated.  These  latter  cases  of 
fracture  with  elevation  of  the  fractured  portion  are  uncommon,  and  can  only  be  produced  by 
direct  wound.  In  comminuted  fracture  a  portion  of  the  skull  is  broken  into  several  pieces, 
the  lines  of  fracture  radiating  from  a  centre  where  the  chief  impact  of  the  blow  was  felt;  if 
depressed,  a  fissure  circumscribes  the  radiating  line,  enclosing  a  portion  of  skull.  If  this  area 
is  circular,  it  is  termed  a  pond  fracture,  and  would  in  all  probability  have  been  caused  by 
a  round  instrument,  as  a  life-preserver  or  hammer;  if  elliptical  in  shape,  it  is  termed  a  gutter 
fracture,  and  would  owe  its  shape  to  the  instrument  which  had  produced  it,  as  a  poker.  A 
fracture  may  take  place  along  the  line  of  an  ossified  or  partly  ossified  suture.  When  a  surgeon 
explores  the  vault  of  the  skull  through  a  wouftd  he  must  not  mistake  a  Wormian  bone  for  a  frag- 
ment produced  by  a  fracture.  A  Wormian  bone  which  may  lead  to  mistake  is  encountered  at 
the  anterior  inferior  angle  of  the  parietal  bone.  Wormian  bones  are  most  frequently  found 
along  the  lambdoid  suture. 

Fractures  of  the  base  are  most  frequently  produced  by  the  extension  of  a  fissure  from  the 
vault,  as  in  falls  on  the  head,  where  the  fissure  starts  from  the  part  of  the  vault  which  first 
struck  the  ground.  Sometimes,  however,  they  are  caused  by  direct  violence,  when  foreign 
bodies  have  been  forced  through  the  thin  roof  of  the  orbit,  through  the  cribriform  plate  of  the 
ethmoid  from  being  thrust  up  the  nose,  or  through  the  roof  of  the  pharynx.  Other  cases  of 
fracture  of  the  base  occur  from  indirect  violence,  as  in  fracture  of  the  occipital  bone  from  impac- 
tion of  the  spinal  column  against  its  condyles  in  falls  on  the  buttocks,  knees,  or  feet,  or  in  cases 
where  the  glenoid  cavity  has  been  fractured  by  the  violent  impact  of  the  condyle  of  the  lower  jaw 
against  it  from  blows  on  the  chin. 

The  most  common  place  for  fracture  of  the  base  to  occur  is  through  the  middle  fossa,  and 
here  the  fissure  usually  takes  a  fairly  definite  course.  Starting  from  the  point  struck,  which  is 
generally  somewhere  in  the  neighborhood  of  the  parietal  eminence,  it  runs  downward  through  the 
parietal  bone  and  the  squamous  portion  of  the  temporal  bone  and  across  the  petrous  portion  of  this 
bone,  frequently  traversing  and  implicating  the  internal  auditory  meatus,  to  the  middle  lacerated 
foramen.  From  this  it  may  pass  across  the  body  of  the  sphenoid,  through  the  pituitary  fossa  to 
the  middle  lacerated  foramen  of  the  other  side,  and  may  indeed  travel  round  the  whole  cranium, 
so  as  to  completely  separate  the  anterior  from  the  posterior  part.  The  course  of  the  fracture 
should  be  borne  in  mind,  as  it  explains  the  symptoms  to  which  fracture  in  this  region  may  give 
rise;  thus,  if  the  fissure  pass  across  the  internal  auditory  meatus,  injury  to  the  facial  and  auditory 
nerves  may  result,  with  consequent  facial  paralysis  and  deafness;  or  the  tubular  prolongation 
of  the  arachnoid  around  these  nerves  in  the  meatus  may  be  torn,  and  thus  permit  of  the  escape 
of  the  cerebro-spinal  fluid  should  there  be  a  communication  between  the  internal  ear  and  the 
tympanum  and  the  membrana  tympani  be  ruptured,  as  is  frequently  the  case;  again,  if  the 
fissure  passes  across  the  pituitary  fossa  and  the  muco-periosteum  covering  the  under  surface 
of  the  body  of  the  sphenoid  is  torn,  blood  will  find  its  way  into  the  pharynx  and  be  swallowed, 
and  after  a  time  vomiting  of  blood  will  result.  Fractures  of  the  anterior  fossa,  involving  the 
bones  forming  the  roof  of  the  orbit  and  nasal  fossa,  are  generally  the  results  of  blows  on  the  fore- 
head; but  fracture  of  the  cribriform  plate  of  the  ethmoid  may  be  a  complication  of  fracture  of 
the  nasal  bone.  When  the  fracture  implicates  the  roof  of  the  orbit,  the  blood  finds  its  way 
into  this  cavity,  and,  travelling  forward,  appears  as  a  subconjunctival  ecchymosis.     Subcon- 


THE   ANTERIOR    REGION   OF    THE  SKULL 


151 


junctival  ecchyraosis  can  also  be  caused  by  fracture  of  the  malar  bone.  If  the  roof  of  the  nasal 
fossa  be  fractured,  the  blood  escapes  from  the  nose.  In  rare  cases  there  may  be  also  escape  of 
cerebro-spinal  fluid  from  the  nose  where  the  dura  mater  and  arachnoid  have  been  torn.  In 
fractures  of  the  posterior  fossa  extravasation  of  blood  takes  place  beneath  the  deep  fascia  and 
discoloration  of  the  skin  is  soon  observed  in  the  course  of  the  posterior  auricular  artery,  the  dis- 
coloration first  appearing  in  the  skin  over  the  tip  of  the  mastoid  process  of  the  temporal  bone 
(Battle's  sign).  Some  of  the  blood  which  was  extra vasated  beneath  the  deep  fascia  approaches 
the  surface  through  the  openings  in  the  deep  fascia  for  the  passage  of  vessels  and  nerves. 

The  bones  of  the  skull  are  frequently  the  seat  of  nodes,  and  not  uncommonly  necrosis  results 
from  this  cause,  also  from  injury.  Necrosis  may  involve  the  entire  thickness  of  the  skull,  but 
is  usually  confined  to  the  external  table.  Necrosis  of  the  internal  table  alone  is  rarely  met  with. 
The  bones  of  the  skull  are  also  sometimes  the  seat  of  sarcomatous  tumor. 

The  skull  in  rickets  is  peculiar:  the  forehead  is  high,  square,  and  projecting,  and  the  antero- 
posterior diameter  of  the  skull  is  long  in  relation  to  the  transverse  diameter.  The  bones  of  the 
face  are  small  and  ill-developed,  and  this  gives  the  appearance  of  a  larger  head  than  actually 
exists.  The  bones  of  the  head  are  often  thick,  especially  in  the  neighborhood  of  the  sutures, 
and  the  anterior  fontanelle  is  late  in  closing,  sometimes  remaining  unclosed  till  the  fourth  year. 
The  condition  of  craniotabes  has  by  some  been  also  believed  to  be  the  result  of  rickets,  by  others 
is  believed  to  be  due  to  inherited  syphilis.  In  all  probability  it  is  due  to  both.  In  these  cases 
the  bone  undergoes  atrophic  changes  in  patches,  so  that  it  becomes  greatly  thinned  in  places, 
generally  where  there  is  pressure,  as  from  the  pillow  or  nurse's  arm.  It  is,  therefore,  usually 
met  with  in  the  parietal  bone  and  vertical  plate  of  the  occipital  bone. 

In  congenital  syphilis  deposits  of  porous  bone  are  often  found  at  the  angles  of  the  parietal 
bones  and  two  halves  of  the  frontal  bone  which  bound  the  anterior  fontanelle.  These  deposits 
are  separated  by  the  coronal  and  sagittal  sutures,  and  give  to  the  skull  an  appearance  like  a  hot 
cross  bun.  They  are  known  as  Parrot's  nodes,  and  such  a  skull  has  received  the  name  of  nati- 
form,  from  its  fancied  resemblance  to  the  buttocks.  When  the  surgeon  wishes  to  effect  an  entrance 
into  the  interior  of  the  mastoid  antrum  (Fig.  108)  he  applies  his  bur  or  gouge  in  the  swprameatal 
triangle  1  cm.  posterior  to  the  suprameatal  spine,  being  careful  to  keep  below  the  posterior  root  of 
the  zygoma  and  the  level  of  the  superior  wall  of  the  bony  meatus.  If  the  instrument  is  entered 
at  a  higher  level  it  will  open  the  cerebral  cavity;  the  instrument  should  be  carried  inward,  for- 
ward, and  a  little  upward,  that  is,  in  the  direction  of  the  auditory  canal.  The  antrum  is  usually 
reached  after  the  penetration  of  from  1  to  1^  cm.  of  bone.  The  depth  at  which  the  antrum  is  sit- 
uated is  not  constant.  "It  is  safe  to  say  that  if  the  instrument  penetrates  deeper  than  1^  cm.  and 
be  directed  too  far  forward  or  downward,  the  horizontal  semicircular  canal  or  the  aqujeduetus 
Fallopii  will  be  encountered.  If  the 
former  were  opened  in  a  purulent  otitis 
media  the  pus  would  travel  along  it  to 
the  vestibule  and  from  there  into  the 
internal  auditory  meatus,  producing  a 
pachymeningitis  or  extradural  (epidural) 
abscess  of  the  posterior  fossa  of  the  skull ; 
or  from  the  vestibule  through  the  perpen- 
dicular semicircular  canal,  which  if  ac- 
companied by  erosion  of  its  bony  cover- 
ing would  lead  to  involvement  of  the 
meninges  of  the  middle  fossa;  the  same 
would  hold  good  for  the  posterior  semi- 
circular canal,  affecting  the  posterior 
fossa.  If  the  latter  (the  aquseductus  Fal- 
lopii) were  opened  an  inflammation  of 
the  facial  nerve  which  is  contained  there- 
in would  result,  producing  paralysis  of 
that  side  of  the  face.  The  inflammatory 
process  might  also  find  its  way  through 
the  entire  canal  to  the  internal  auditory 
meatus,  causing  a  pachymeningitis  or 
extradural  abscess  as  mentioned  above; 
or,  travelling  along  the  nerve  to  its  cere- 
bral attachment,  would  produce  a  men- 
ingitis or  subdural  (intradural)  abscess. 
The  direction  of  the  penetrating  instru- 
ment must  also  V)e  forward,  in  order  to  avoid  injuring  the  lateral  dnus"  ("Anatomy  and  Sur- 
gerv  of  the  Temporal  Bone,"  bv  A.  E.  Schmitt,  M.D.,  American  Journal  of  the  Medical  Sciences, 
April,  1903).  In  the  operation  for  infective  thrombosis  of  the  lateral  sinus  the  sinus  is  deliber- 
ately exposed  and  opened  (Fig.  108). 


Fig.  108. — Division  of  the  mastoid  process  into  four  equal 
parts.  An  opening  in  the  upper  anterior  quadrant  reaches  the 
mastoid  antrum  ;  into  the  upper  posterior  quadrant  reaches 
the  lateral  sinus  ;  the  lower  anterior  quadrant  into  mastoid 
cells  ;  a  superficial  opening  into  the  lower  posterior  quadrant 
reaches  mastoid  cells  ;  a  deep  opening  reaches  the  descending 
limb  of  the  lateral  sinus.     (A.  E.  Schmitt.) 


152  THE   SKELETON 

Hartley  divides  the  mastoid  process  into  four  parts  as  follows:  The  upper  margin  is  the 
posterior  root  of  the  zygoma.  The  anterior  margin  is  the  anterior  border  of  the  mastoid.  The 
posterior  margin  is  a  vertical  line  dropped  from  the  masto-occipital  junction.  The  lower  mar- 
gin is  an  imaginary  line  backward  from  the  mastoid  tip.  This  space  is  divided  into  four  equal 
parts.  Points  upon  it  may  be  designated  as  on  a  map.  Take  the  left  side  for  demonstration. 
An  opening  in  the  N.  W.  quadrant  enters  the  antrum,  one  into  the  N.  E.  quadrant  exposes  the 
lateral  sinus,  one  into  the  S.  W.  quadrant  enters  mastoid  cells,  and  a  superficial  one  into  the 
S.  E.  quadrant  enters  mastoid  cells,  but  a  deep  one  exposes  the  descending  portion  of  the  lateral 
sinus. 

When  pus  breaks  through  the  mastoid  process  it  may  enter  the  sheath  of  the  digastric  or  sterno- 
cleido-mastoid  muscle  and  point  a  considerable  distance  away  from  the  bone,  Bezold's  abscesS; 

In  connection  with  the  bones  of  the  face  a  common  malformation  is  cleft  palate,  owing  to 
the  non-union  of  the  palatal  processes  of  the  maxillary  or  pre-oral  arch.  This  cleft  may  involve 
the  whole  or  only  a  portion  of  the  hard  palate,  and  usually  involves  the  soft  palate  also.  The 
cleft  is  in  the  middle  line,  except  it  involves  the  alveolus  in  front,  when  it  follows  the  suture 
between  the  main  portion  of  the  bone  and  the  pre-maxillary  bone.  Sometimes  the  cleft  runs 
on  either  side  of  the  pre-maxillary  bone,  so  that  this  bone  is  quite  isolated  from  the  maxillary 
bones  and  hangs  from  the  end  of  the  vomer.  In  such  a  case  the  pre-maxillary  bone  usually 
contains  the  germs  of  the  central  incisors  only.  In  some  cases  there  is  no  pre-maxillary  bone 
and  the  great  gap  in  the  lip  is  in  the  median  line.  Cleft  palate  (Fig.  92)  is  usually  associated 
with  hare-lip,  which,  when  single,  is  almost  always  on  one  side,  corresponding  to  the  position 
of  the  suture  between  the  lateral  incisor  and  canine  tooth.  Some  few  cases  of  median  hare- 
lip have  been  described.  In  double  hare-lip  there  is  a  cleft  on  each  side  of  the  middle  line  (see 
page  111). 

The  outlines  and  the  height  of  the  arch  of  the  palate  vary  greatly  in  different  persons.  A 
narrow  palate  with  a  high  arch  is  common  in  idiots  and  certain  degenerates. 

The  bones  of  the  face  are  sometimes  fractured  as  the  result  of  direct  violence.  The  two 
most  commonly  broken  are  the  nasal  bone  and  the  mandible,  and  of  these  the  latter  is  by 
far  the  most  frequently  fractured  of  all  the  bones  of  the  face.  Fracture  of  the  nasal  bone  is 
for  the  most  part  transverse,  and  takes  place  about  half  an  inch  from  the  free  margin.  The 
broken  portion  may  be  displaced  backward  or  more  generally  to  one  side  by  the  force  which 
produced  the  lesion,  as  there  are  no  muscles  here  which  can  cause  displacement.  The  malar 
bone  is  probably  never  broken  alone;  that  is  to  say,  unconnected  with  a  fracture  of  the  other 
bones  of  the  face.  The  zygomatic  arch  is  occasionally  fractured,  and  when  this  occurs  from 
direct  violence,  as  is  usually  the  case,  the  fragments  may  be  displaced  inward.  This  lesion  is 
often  attended  with  great  difficulty  or  even  inability  to  open  and  shut  the  mouth,  and  this  has 
been  stated  to  be  due  to  the  depressed  fragments  perforating  the  temporal  muscle,  but  would 
appear  rather  to  be  caused  by  the  injury  done  to  the  bony  origin  of  the  Masseter  muscle. 
Fractures  of  the  superior  maxilla  may  vary  much  in  degree,  from  the  chipping  off  of  a  portion 
of  the  alveolar  arch,  a  frequent  accident  when  the  "old  key"  instrument  was  used  for  the 
extraction  of  teeth,  to  an  extensive  comminution  of  the  whole  bone  from  severe  violence,  as 
the  kick  of  a  horse.  The  most  common  situation  for  a  fracture  of  the  mandible  bone  is  in  the 
neighborhoad  of  the  canine  tooth,  as  at  this  spot  the  jaw  is  weakened  by  the  deep  socket  for 
the  fang  of  this  tooth;  it  is  next  most  frequently  fractured  at  the  angle;  then  at  the  symphysis, 
and  finally  the  neck  of  the  condyle  or  the  coronoid  process  may  be  broken.  Occasionally  a 
double  fracture  may  occur,  one  in  either  half  of  the  bone.  The  fractures  are  usually  compound, 
from  laceration  of  the  mucous  membrane  covering  the  gums.  The  displacement  is  mainly  the 
result  of  the  same  violence  as  producsd  the  injury,  but  may  be  further  increased  by  the  action 
of  the  muscles  passing  from  the  neighborhood  of  the  symphysis  to  the  hyoid  bone. 

The  superior  and  inferior  maxillary  bones  are  both  of  them  frequently  the  seat  of  necrosis, 
though  the  disease  affects  the  lower  much  more  frequently  than  the  upper  jaw.  It  may  be  the 
result  of  periostitis,  from  tooth  irritation,  injury,  or  the  action  of  some  specific  poison,  as  syphilis, 
or  from  salivation  by  mercury;  it  not  infrequently  occurs  in  children  after  attacks  of  the  exan- 
thematous  fevers,  and  a  special  form  occurs  from  the  action  of  the  fumes  of  phosphorus  in 
persons  engaged  in  the  manufacture  of  matches. 

Tumors  attack  the  jaw  bones  not  infrequently,  and  these  may  be  either  innocent  or  malig- 
nant: in  the  upper  jaw  cysts  may  occur  in  the  antrum,  constituting  the  so-called  dropsy  of  the 
antrum;  or,  again,  cysts  may  form  in  either  jaw  in  connection  with  the  teeth:  either  cysts  con- 
nected with  the  roots  of  fully  developed  teeth,  the  "dental  cyst;"  or  cysts  connected  with  im- 
perfectly developed  teeth,  the  "dentigerous  cyst."  Solid  innocent  tumors  include  the  fibroma, 
the  chondroma,  and  the  osteoma.  Of  malignant  tumors  there  are  the  endotheliomata,  the 
sarcomata,  and  the  epitheliomata.  The  sarcomata  are  of  various  kinds,  the  spindle-celled, 
the  round-celled,  which  are  of  a  very  malignant  character,  and  the  myeloid  sarcomata,  prin- 
cipally affecting  the  alveolar  margin  of  the  bone.  Of  the  epitheliomata  we  find  the  squamous 
variety  spreading  to  the  bone  from  the  palate  or  gum,  and  the  cylindrical  epithelioma  origin- 
ating in  the  antrum  or  nasal  fossae. 


THE  HYOID    OB   LINGUAL    BONE  153 

Both  superior  and  inferior  maxillary  bones  occasionally  require  excision  for  tumors  and  in 
some  other  conditions.  The  upper  jaw  is  removed  by  an  incision  from  the  inner  canthus  of  the 
eye,  along  the  side  of  the  nose,  round  the  ala,  and  down  the  middle  line  of  the  upper  lip.  A 
second  incision  is  carried  outward  from  the  inner  canthus  of  the  line  along  the  lower  margin  of 
the  orbit  as  far  as  the  prominence  of  the  malar  bone.  The  flap  thus  formed  is  reflected  outward 
and  the  surface  of  the  bone  exposed,  and  the  central  incisor  of  the  diseased  side  is  removed. 
The  connections  of  the  bone  to  the  other  bones  of  the  face  are  then  divided  with  a  narrow  saw  and 
bone-cutting  forceps.  They  are  (1)  the  junction  with  the  malar  bone,  passing  into  the  spheno- 
maxillary fissure;  (2)  the  nasal  process;  a  small  portion  of  its  upper  extremity,  connected  with  the 
nasal  bone  in  front,  the  lachrymal  bone  behind,  and  the  frontal  bone  above,  being  left;  (3)  the 
connection  with  the  bone  on  the  opposite  side  and  the  palate  in  the  roof  of  the  mouth.  The 
bone  is  now  firmly  grasped  with  lion-jaw  forceps,  and  by  means  of  a  rocking  movement  upward 
and  downward  the  remaining  attachments  of  the  orbital  plate  with  the  ethmoid  and  the 
back  of  the  bone  with  the  palate,  broken  through.  The  soft  palate  is  first  separated  from 
the  hard  with  a  scalpel,  and  is  not  removed.  Occasionally  in  removing  the  upper  jaw  it 
will  be  found  that  the  orbital  plate  can  be  spared,  and  this  should  always  be  done  if  possible. 
A  horizontal  saw-cut  is  to  be  made  just  below  the  infraorbital  foramen  and  the  bone  cut  through 
with  a  chisel  and  mallet.  Lockwood  has  pointed  out  that  in  removing  the  upper  jaw  the  sur- 
geon must  be  careful  in  dividing  the  nasal  process  of  the  superior  maxilla  to  preserve  the  inter- 
nal orbital  or  palpebral  ligament  (Tendo  oculi),  because  this  ligament  arises  from  the  palpebral 
fascia,  and  if  it  is  interfered  with  the  eye  will  inevitably  drop  downward.  Removal  of  one-half 
of  the  lower  jaw  is  sometimes  required.  If  possible,  the  section  of  the  bone  should  be  made 
to  one  side  of  the  symphysis,  so  as  to  save  the  genial  tubercles  and  the  origin  of  the  genio-hyo- 
glossus  muscle,  as  otherwise  the  tongue  tends  to  fall  backward  and  may  produce  suffocation. 
Having  extracted  the  central  or  preferably  the  lateral  incisor  tooth,  a  vertical  incision  is  made 
down  to  the  bone,  commencing  at  the  free  margin  of  the  lip,  and  carried  to  the  lower  border 
of  the  bone;  it  is  then  carried  along  its  lower  border  to  the  angle  and  up  the  posterior  margin 
of  the  ramus  to  a  level  with  the  lobule  of  the  ear.  The  flap  thus  formed  is  raised  by  separating 
all  the  structures  attached  to  the  outer  surface  of  the  bone.  The  jaw  is  now  sawn  through 
at  the  point  where  the  tooth  has  been  extracted,  and  the  knife  passed  along  the  inner  side  of 
the  jaw,  separating  the  structures  attached  to  this  surface.  The  jaw  is  then  grasped  by  the 
surgeon  and  strongly  depressed,  so  as  to  bring  down  the  coronoid  process  and  enable  the  operator 
to  sever  the  tendon  of  the  Temporal  muscle.  The  jaw  can  be  now  further  depressed,  care  being 
taken  not  to  evert  it  nor  rotate  it  outward,  which  would  endanger  the  internal  maxillary  artery, 
and  the  External  pterygoid  muscle  is  torn  through  or  divided.  The  capsular  ligament  is  now 
opened  in  front  and  the  lateral  ligaments  divided,  and  the  jaw  removed  with  a  few  final  touches 
of  the  knife. 

The  antrum  of  Highmore  occasionally  requires  tapping  for  suppuration.  This  may  be  done 
through  the  socket  of  a  tooth,  preferably  the  first  molar,  the  fangs  of  which  are  most  intimately 
connected  with  the  antrum,  or  through  the  facial  aspect  of  the  bone  above  the  alveolar  process. 
This  latter  method  does  not  perhaps  afford  such  efficient  drainage,  but  there  is  less  chance  of 
food  finding  its  way  into  the  cavity.  The  operation  may  be  performed  by  incising  the  mucous 
membrane  above  the  second  molar  tooth,  and  driving  a  trocar  or  any  sharp-pointed  instrument 
into  the  cavity. 

THE  HYOID  OR  LINGUAL  BONE  (OS  HYOIDEUM). 

The  hyoid  bone  (Fig.  109)  is  named  from  its  resemblance  to  the  Greek  upsilon; 
it  is  also  called  the  lingual  hone,  because  it  supports  the  tongue  and  gives  attach- 
ment to  its  numerous  muscles.  It  is  a  bony  arch,  shaped  like  a  horseshoe,  and 
consisting  of  five  segments:  a  body,  two  greater  comua,  and  two  lesser  comua.  It 
is  suspended  from  the  tip  of  the  styloid  processes  of  the  temporal  bone  by  liga- 
mentous bands,  the  stylo-hyoid  ligaments. 

Body  {corpus  ossei  Jnjoidei).- — The  body,  or  basi-hyal,  forms  the  central  part 
of  the  bone,  and  is  of  a  quadrilateral  form. 

Surfaces. — Its  anterior  surface  (Fig.  109),  convex,  directed  forward  and  upward, 
is  divided  into  two  parts  by  a  vertical  ridge  which  descends  along  the  median 
line  and  is  crossed  at  right  angles  by  a  horizontal  ridge,  so  that  this  surface  is 
divided  into  four  spaces  or  depressions.  At  the  point  of  meeting  of  these  two  lines 
is  a  prominent  elevation,  the  tubercle.  The  portion  above  the  horizontal  ridge  is 
directed  upward,  and  is  sometimes  described  as  the  superior  border.  The  anterior 
surface  gives  attachment  to  the  Genio-hyoid  in  the  greater  part  of  its  extent;  above, 


154 


THE  SKELETON 


THYRO-HVOIO 


STYLO-HYOID. 


OMO-HYOID. 


GENIO-HYOID.  STERNO-HYOID.  MYLO-HYOIO. 

Fig.  109. — Hyoid  bone.     Anterior  surface.     (Enlarged.) 


to  the  Genio-hyo-glossus ;  below,  to  the  Mylo-hyoid,  Stylo-hyoid,  and  aponeurosis  of 
the.  Digastric  (suprahyoid  aponeurosis);  and  between  these  to  part  of  the  Hyo- 
glossus.  The  posterior  surface  is  smooth,  concave,  directed  backward  and  down- 
ward, and  separated  from  the  epiglottis  by  the  thyro-hyoid  membrane  and  by  a 
quantity  of  loose  areolar  tissue.  The  lateral  surfaces  after  middle  life  are  joined 
to  the  greater  cornua.  In  early  life  they  are  connected  to  the  cornua  by  carti- 
laginous surfaces,  and  held  together  by  ligaments,  and  occasionally  a  synovial 
membrane  is  found  between  them. 

Borders. — The  superior  border  is  rounded,  and  gives  attachment  to  the  thyro- 
hyoid membrane,  part  of  the  Genio-hyo-glossi  and  Chondro-glossi  muscles.  The 
inferior  border  gives  attachment,  in  front,  to  the  Sterno-hyoid ;  behind,  to  the  Omo- 
hyoid and  to  the  part  of  the  Thyro- 
hyoid at  its  junction  with  the  great 
cornu.  It  also  gives  attachment  to 
the  Levatore  glandule  thyroidese 
when  this  muscle  is  present. 

Greater  Cornua  (cornua  majora) . 
— The  greater  cornua  or  tiyro-hyals 
project  backward  from  the  lateral 
surfaces  of  the  body;  they  are  flat- 
tened from  above  downward,  di- 
minish in  size  from  before  back- 
ward, and  terminate  posteriorly  in 
a  tubercle  for  the  attachment  of 
the  lateral  thyro-hyoid  ligament. 
The  outer  surface  gives  attachment 
to  the  Hyo-glossus,  their  upper  border  to  the  Middle  constrictor  of  the  pharynx, 
their  lower  border  to  part  of  the  Thyro-hyoid  muscle. 

Lesser  Cornua  (cornua  minora). — The  lesser  cornua,  or  cerato-hyals,  are  two 
small,  conical-shaped  eminences  attached  by  their  bases  to  the  angles  of  junc- 
tion between  the  body  and  greater  cornua,  and  giving  attachment  by  their  apices 
to  the  stylo-hyoid  ligaments.^  The  smaller  cornua  are  connected  to  the  body  of 
the  bone  by  a  distinct  diarthrodial  joint,  which  usually  persists  throughout  life, 
but  occasionally  becomes  ankylosed. 

Development. — By  five  centres:  one  for  the  body,  and  one  for  each  cornu. 
Ossification  commences  in  the  body  about  the  eighth  month,  and  in  the  greater 
cornua  toward  the  end  of  foetal  life.  Ossification  of  the  lesser  cornua  commences 
some  years  after  birth.    Sometimes  there  are  two  centres  for  the  body. 

Attachment  of  Muscles. — Sterno-hyoid,  Thyro-hyoid,  Omo-hyoid,  aponeurosis 
of  the  Digastric,  Stylo-hyoid,  Mylo-hyoid,  Genio-hyoid,  Genio-hyo-glossus,  Chon- 
dro-glossus,  Hyo-glossus,  Middle  constrictor  of  the  pharynx,  and  occasionally  a 
few  fibres  of  the  Inferior  lingualis.  It  also  gives  attachment  to  the  thyro-hyoidean 
membrane  and  the  stylo-hyoid,  thyro-hyoid,  and  hyo-epiglottic  ligaments. 

Surface  Form. — The  hyoid  bone  can  be  felt  in  the  receding  angle  below  the  chin,  and  the 
finger  can  be  carried  along  the  whole  length  of  the  bone  to  the  greater  cornu,  which  is  situated 
just  below  the  angle  of  the  jaw.  This  process  of  bone  is  best  perceived  by  making  pressure  on 
one  cornu,  and  so  pushing  the  bone  over  to  the  opposite  side,  when  the  cornu  of  this  side  will 
be  distinctly  felt  immediately  beneath  the  skin.  This  process  of  bone  is  an  important  landmark 
in  ligature  of  the  lingual  artery. 

Surgical  Anatomy.— The  hyoid  bone  is  occasionally  fractured,  generally  from  direct  vio- 
lence, as  in  the  act  of  garroting  or  throttling.  It  is  frequently  found  broken  in  those  who  have 
been  hung.  The  great  cornu  is  the  part  of  the  bone  most  frequently  broken,  but  sometimes 
the  fracture  takes  place  through  the  body  of  the  bone.     In  consequence  of  the  muscles  of  the 


1  These  ligaments  in  many  animals  are  distinct  bones,  and  in  man  are  occasionally  ossified  to  a  certain  extent. 


THE   STERNUM  I55 

tongue  having  important  connections  with  this  bone,  there  is  great  pain  upon  any  attempt  being 
made  to  move  the  tongue,  as  in  speaking  or  swallowing. 

THE  THORAX. 

The  thorax,  or  chest,  is  an  osseo-cartilaginous  cage  the  cavity  of  which  (cavum 
thoracis)  contains  and  protects  the  principal  organs  of  respiration  and  circula- 
tion. It  is  conical  in  shape,  being  narrow  above  and  broad  below,  flattened 
from  before  backward,  and  longer  behind  than  in  front.  It  is  somewhat 
renifonn  on  transverse  section. 

Boundaries. — The  posterior  surface  is  formed  by  the  twelve  dorsal  vertebrae  and 
the  posterior  part  of  the  ribs.  It  is  concave  from  above  downward,  and  presents 
on  each  side  of  the  middle  line  a  deep  groove,  the  vertebral  groove,  in  conse- 
quence of  the  direction  backward  and  outward  which  the  ribs  take  from  their 
vertebral  extremities  to  their  angles.  The  anterior  surface  is  flattened  or  slightly 
convex,  and  inclined  forward  from  above  downward.  It  is  formed  by  the  sternum 
and  costal  cartilages.  The  lateral  surfaces  are  convex;  they  are  formed  by  the 
ribs,  separated  from  each  other  by  spaces.  Each  space  is  called  an  intercostal 
space  (spatium  intercostale) .  These  are  eleven  in  number,  and  are  occupied  by 
the  intercostal  muscles. 

The  superior  or  upper  opening  or  aperture  of  the  thorax,  the  inlet  (apertura 
thoracis  superior),  is  reniform  in  shape,  being  broader  from  side  to  side  than 
from  before  backward.  It  is  formed  by  the  first  dorsal  vertebra  behind,  the 
upper  margin  of  the  sternum  in  front,  and  the  first  rib  on  each  side.  It  slopes 
downward  and  forward,  so  that  the  anterior  part  of  the  ring  is  on  a  lower  level 
than  the  posterior.  The  antero-posterior  diameter  is  about  two  inches,  and  the 
transverse  al)out  four.  The  inferior  or  lower  opening  (apertura  thoracis  inferior) 
is  formed  by  the  twelfth  dorsal  vertebra  behind,  by  the  twelfth  rib  at  the  sides, 
and  in  front  by  the  cartilages  of  the  eleventh,  tenth,  ninth,  eighth,  and  seventh 
ribs,  which  ascend  on  either  side  and  form  an  angle,  the  subcostal  angle  {anguine 
infrasternalis) ,  from  the  apex  of  which  the  ensiform  cartilage  projects.  It  is 
wider  transversely  than  from  before  backward.  It  slopes  obliquely  downward 
and  backward,  so  that  the  cavity  of  the  thorax  is  much  deeper  behind  than  in 
front.    The  Diaphragm  closes  in  the  opening  forming  the  floor  of  the  thorax. 

In  the  female  the  thorax  differs  as  follows  from  the  male:  1.  Its  general  capa- 
city is  less.  2.  The  sternum  is  shorter.  3.  The  upper  margin  of  the  sternum 
is  on  a  level  with  the  lower  part  of  the  body  of  the  third  dorsal  vertebra,  whereas 
in  the  male  it  is  on  a  level  with  the  lower  part  of  the  body  of  the  second  dorsal 
vertebra.  4.  The  upper  ribs  are  more  movable,  and  so  allow  a  greater  enlarge- 
ment of  the  upper  part  of  the  thorax  than  in  the  male. 

The  Sternum  or  Breast  Bone. 

The  sternum  (azipvov,  the  chest),  or  breast  bone  (Figs.  110,  111),  is  a  flat, 
narrow  bone,  situated  in  the  median  line  of  the  front  of  the  chest,  and  con- 
sisting, in  the  adult,  of  three  portions.  It  has  been  likened  to  an  ancient 
sword;  the  upper  piece,  representing  the  handle,  is  termed  the  manubrium 
stemi  (presternum);  the  middle  and  largest  piece,  which  represents  the  chief 
part  of  the  blade,  is  termed  the  gladiolus  (mesosternum  or  corpus  stemi);  and 
the  inferior  piece,  which  is  likened  to  the  point  of  the  sword,  is  termed  the 
ensiform  or  xiphoid  process  or  appendix  (processus  xiphoideus  or  metasternum) . 
In  early  youth  the  sternum  is  composed  of  six  pieces  or  stemebrse.  In  adult  life 
the  upper  piece  remains  as  the  manubrium;  the  inferior  piece  remains  as  the 
xiphoid;  and  the  other  four  pieces  fuse  together  to  form  the  gladiolus.     In  its 


156 


THE   SKELETON 


STERNO-OLEIDOMASTOID.  % 
SUBCLAVIUS. 


Fig.  110. — Sternum  and  costal  cartilages. 


Fig.  111. — Posterior  surface  of  sternum. 


THE  STERNUM  I57 

natural  position  its  inclination  is  oblique  from  above  downward  and  forward.  It 
is  slightly  convex  in  front,  concave  behind,  broad  above,  becoming  narrowed  at 
the  point  where  the  first  and  second  pieces  are  connected,  after  which  it  again 
widens  a  little,  and  is  pointed  at  its  extremity.  Its  average  length  in  the  adult  is 
about  seven  inches,  being  rather  longer  in  the  male  than  in  the  female.  At  the 
junction  of  the  manubrium  and  gladiolus  is  a  distinct  angle,  the  angulus  stemi 
{angle  of  Ludovic  or  angle  of  'Louis),  the  maimbrium  looking  forward,  the 
gladiolus  also  looking  forward,  but  to  a  less  degree.  This  angle  is  on  a  level 
with  the  second  rib,  and  is  produced  by  retraction  of  the  upper  portion  of  the 
thorax. 

WilSt  Piece. — The  first  piece  of  the  sternum,  or  the  manubrium  sterni  (pre- 
sternum), is  of  a  somewhat  triangular  form,  broad  and  thick  above,  narrow 
below  at  its  junction  with  the  middle  piece. 

Surfaces. — Its  anterior  surface,  convex  from  side  to  side,  concave  from  above 
downward,  is  smooth,  and  affords  attachment  on  each  side  to  the  Pectoralis 
major  aud  sternal  origin  of  the  Sterno-cleido-mastoid  muscle.  In  well-marked 
bones  the  ridges  limiting  the  attachment  of  these  muscles  are  very  distinct.  Its 
posterior  surface,  concave  and  smooth,  affords  attachment  on  each  side  to  the 
Sterno-hyoid  and  Sterno-thyroid  muscles. 

Borders. — The  superior  border,  the  thickest,  presents  at  its  centre  the  pre-stemal 
notch  (incisura  jugularis),  and  on  each  side  an  oval  articular  surface,  the 
clavicular  facet  (incisura  clavicularis) ,  directed  upward,  backward,  and  outward, 
for  articulation  with  the  sternal  end  of  the  clavicle.  The  inferior  border  presents 
an  oval,  rough  surface,  covered  in  the  recent  state  with  a  thin  layer  of  cartilage, 
for  articulation  with  the  second  portion  of  the  bone  (synchondrosis  sternalis). 
The  junction  of  the  manubrium  with  the  gladiolus  is  marked  by  a  transverse 
ridge,  which  corresponds  to  the  attachment  on  each  side  of  the  cartilage  of 
the  second  rib.  The  lateral  borders  are  marked  above  by  a  depression  (incisura 
costalis  I)  for  the  first  costal  cartilage,  and  below  by  a  small  facet,  which,  with  a 
similar  facet  on  the  upper  angle  of  the  middle  portion  of  the  bone,  forms  a 
notch  (incisura  costalis  II)  for  the  reception  of  the  costal  cartilage  of  the  second 
rib.  These  articular  surfaces  are  separated  by  a  narrow,  curved  edge,  which 
slopes  from  above  downward  and  inward. 

Second  Piece. — The  second  piece  of  the  sternum,  the  corpus  sterni  or  gladiolus 
(mesosternum) ,  considerably  longer,  narrower,  and  thinner  than  the  first  piece,  is 
broader  below  than  above. 

Surfaces. — Its  anterior  surface  (planum  sternale)  is  nearly  flat,  directed  upward 
and  forward,  and  marked  by  three  transverse  lines  which  cross  the  bone  opposite 
the  third,  fourth,  and  fifth  articular  depressions.  These  lines  are  produced  by  the 
union  of  the  four  separate  pieces  of  which  this  part  of  the  bone  consists  at  an  early 
period  of  life.  iVt  the  junction  of  the  third  and  fourth  pieces  is  occasionally  seen 
an  orifice,  the  sternal  foramen;  it  varies  in  size  and  form  in  different  individuals, 
and  pierces  the  bone  from  before  backward.  This  surface  affords  attachment 
on  each  side  to  the  sternal  origin  of  the  Pectoralis  major.  The  posterior  surface, 
slightly  concave,  is  also  marked  by  three  transverse  lines,  but  they  are  less  dis- 
tinct than  those  in  front:  this  surface  affords  attachment  below,  on  each  side, 
to  the  Triangularis  sterni  muscle,  and  occasionally  presents  the  posterior  opening 
of  the  sternal  foramen. 

Borders. — The  superior  border  presents  an  oval  surface  for  articulation  with  the 
manubrium.  The  inferior  border  is  narrow,  and  articulates  with  the  ensiform 
appendix.  Each  lateral  border  presents,  at  each  superior  angle,  a  small  facet, 
whicii,  with  a  similar  facet  on  the  manubrium,  forms  a  cavity  for  the  cartilage  of 
the  second  rib;  the  four  succeeding  angular  depressions  receive  the  cartilages  of 
the  third,  fourth,  fifth,  and  sixth  ribs;  whilst  each  inferior  angle  presents  a  small 


158 


THE  SKELETON 


facet,  which,  with  a  corresponding  one  on  the  ensiform  appendix,  forms  a  notch 
for  the  cartilage  of  the  seventh  rib.  These  articular  depressions  are  known  as 
incisurcB  costales.  They  are  separated  by  a  series  of  curved  interarticular  inter- 
vals, which  diminish  in  length  from  above  downward,  and  correspond  to  the 
intercostal  spaces.  Most  of  the  cartilages  belonging  to  the  true  ribs,  as  will  be 
seen  from  the  foregoing  description,  articulate  with  the  sternum  at  the  line  of 
junction  of  two  of  its  primitive  component  segments.  This  is  well  seen  in  many 
of  the  lower  animals,  where  the  separate  parts  of  the  bone  remain  ununited 
longer  than  in  man.  In  this  respect  a  striking  analogy  exists  between  the  mode 
of  connection  of  the  ribs  with  the  vertebral  column  and  the  connection  of  the 
costal  cartilages  with  the  sternum. 

Third  Piece. — The  third  piece  of  the  sternum,  the  ensiform  or  xiphoid  appendix 
{'processus  xiphoideus  or  metasternuTn),  is  the  smallest  of  the  three;  it  is  thin  and 
elongated  in  form,  cartilaginous  in  structure  in  youth,  but  more  or  less  ossified 
at  its  upper  part  in  the  adult. 

Surfaces. — Its  anterior  surface  affords  attachment  to  the  chondro-xiphoid 
ligament;  its  posterior  surface,  to  some  of  the  fibres  of  the  Diaphragm  and 
Triangularis  sterni  muscles;  its  lateral  borders,  to  the  aponeurosis  of  the  abdom- 
inal muscles.  Above  it  articulates  with  the  lower  end  of  the  gladiolus,  and  at  each 
superior  angle  presents  a  facet  (incisura  costalis  VII),  for  the  lower  half  of  the 
cartilage  of  the  seventh  rib;  below,  by  its  pointed  extremity,  it  gives  attachment 
to  the  linea  alba.  This  portion  of  the  sternum  is  very  various  in  appearance, 
being  sometimes  pointed,  broad,  and  thin,  sometimes  bifid  or  perforated  by  a 
round  hole,  occasionally  curved  or  deflected  considerably  to  one  or  the  other  side. 

Structure. — The  bone  is  composed  of  delicate  cancellous  structure,  covered  by 
a  thin  layer  of  compact  tissue,  which  is  thickest  in  the  manubrium  between  the 
articular  facets  for  the  clavicles. 

Development. — The  cartilaginous  sternum  originally  consists  of  two  bars,  situ- 
ated one  on  either  side  of  the  mesial  plane  and  connected  with  the  rib  cartilages  of 
its  own  side.  These  two  bars  fuse  with  each  other  along  the  middle  line,  and 
the  bone,  including  the  ensiform  appendix,  is  developed  by  six  centres :  one  for  the 
first  piece  or  manubrium,  four  for  the  second  piece  or  gladiolus,  and  one  for  the 
ensiform  appendix.    Up  to  the  middle  of  foetal  life  the  sternum  is  entirely  car- 


for  first  piece,  two  or  more  centres. 

for  second  piece,  usually  one. 

for  third    ] 
I 
for  fourth  \  2,  placed  laterally. 

for  fifth     J 


Fig.  112. — Development  of  the  sternum  by  six 
centres.     Time  of  appearance. 


Arrest  of  development 
of  lateral  pieces,  producing 


-Sternal  fissure,  and 
.Sternal  foramen. 


Fig.  113. — Time  of  union  of  sternum. 


tilaginous,  and  when  ossification  takes  place  the  ossific  granules  are  deposited  in 
the  mitldle  of  the  intervals  between  the  articular  depressions  for  the  costal  car- 
tilages, in  the  following  order  (Fig.  112):  In  the  first  piece,  between  the  fifth  and 
sixth  months;  in  the  second  and  third,  between  the  sixth  and  seventh  months;  in 
the  fourth  piece,  at  the  ninth  month;  in  the  fifth,  within  the  first  year  or  between 
the  first  and  second  years  after  birth;  and  in  the  ensiform  appendix,  between  the 


THE  BIBS 


]59 


second  and  the  seventeenth  or  eighteenth  years,  by  a  single  centre  which  makes 
its  appearance  at  the  upper  part  and  proceeds  gradually  downward.  To  these 
may  be  added  the  occasional  existence,  as  described  by  Breschet,  of  two  small 
episternal  centres,  which  make  their  appearance  one  on  each  side  of  the  pre-sternal 
notch.  They  are  probably  vestiges  of  the  episternal  bone  of  the  monotremata 
and  lizards.  It  occasionally  happens  that  some  of  the  segments  are  formed  from 
more  than  one  centre,  the  number  and  position  of  which  vary  (Fig.  114).  Thus, 
the  first  piece  may  have  two,  three,  or  even  six  centres.  When  two  are  present, 
they  are  general y  situated  one  above  the  other,  the  upper  one  being  the  larger;^ 
the  second  piece  has  seldom  more  than  one;  the  third,  fourth,  and  fifth  pieces 
are  often  formed  from  two  centres  placed  laterally,  the  irregular  union  of  which 
will  serve  to  explain  the  occasional  occurrence  of  the  sternal  foramen  (Fig.  113), 


1  for  M  piece  \  ^^^^^  month  foetal, 
or  manubrium  J  •' 


4  for  2nd  piece 
or  gladiolus 


6-7th  month. 


Jf     9ih  month. 

5    1st  year  after 
birth. 


Iforensifo^-m  ]  ^nd  to  18th  year 
cartilage       J  " 


Fig.  114. — Peculiarities  in  number  of  centres  of 
sternum. 


Rarely  unite, 
except  in  old  age. 


Between  puberty 
j  and  the  25th  year. 

Soon  after  puberty. 


Partly  cartilaginous  to 
advanced  life. 


Fig.  115. — Peculiarities  in  mode  of  union 
of  sternum. 


or  of  the  vertical  fissure  which  occasionally  intersects  this  part  of  the  bone  (Fig.  113), 
and  which  is  further  explained  by  the  manner  in  which  the  cartilaginous  matrix, 
in  which  ossification  takes  place,  is  formed.  Union  of  the  various  centres  of  the 
gladiolus  commences  about  puberty,  from  below,  and  proceeds  upward,  so  that  by 
the  age  of  twenty-five  they  are  all  united,  and  this  portion  of  bone  consists  of  one 
piece.  The  ensiform  cartilage  becomes  joined  to  the  gladiolus  about  forty.  The 
manubrium  is  occasionally  but  seldom  joined  to  the  gladiolus  in  advanced  life 
by  bone.  When  this  union  takes  place,  however,  it  is  generally  only  superficial,  a 
portion  of  the  centre  of  the  sutural  cartilage  remaining  unossified. 

Articulations. — With  the  clavicles  and  seven  costal  cartilages  on  each  side. 

Attachment  of  Muscles. — To  nine  pairs  and  one  single  muscle:  the  Pectoralis 
major,  Sterno-cleido-mastoid,  Sterno-hyoid,  Ster no- thyroid.  Triangularis  sterni, 
aponeuroses  of  the  Obliquus  externus,  Obliquus  internus,  Transversalis,  Rectus 
muscles,  and  Diaphragm. 

The  Ribs  (Costse). 

The  ribs  are  elastic  arches  of  hone,  which  form  the  chief  part  of  the  thoracic 
walls.  They  are  twelve  in  number  on  each  side;  but  this  number  may  be  increased 
by  the  development  of  a  cervical  or  lumbar  rib,  or  may  be  diminished  to  eleven. 
The  first  seven  are  connected  behind  with  the  spine  and  in  front  with  the  sternum, 
through  the  intervention  of  the  costal  cartilages;  they  are  called  true,  sternal,  or 
vertebro-stemal   ribs    (cosioB  veroe).^    The    remaining   five   are   false   ribs   {costw 


'  Sir  George  Humphry  states  that  this  is  "probably  the  more  complete  condition." 

^  Sometimes  the  eighth  rib  cartilage  articiilates  with  the  sternum;  this  condition  occurs  more  frequently  on 
the  right  than  on  the  left  side. 


160 


THE  SKELETON 


spurice) ;  of  these,  the  first  three  have  their  cartilages  attached  to  the  cartilage  of 
the  rib  above,  and  are  called  the  vertebro-chondral  ribs;  the  last  two  are  free  at  their 


^Tuberosity, 


Articular  part  of  tuberosity: 


iNeck. 


-Subcostal  groove 


Head.' 


anterior  extremities;  they  are  termed  floating  or 
vertebral  ribs.  The  ribs  vary  in  their  direction, 
the  upper  ones  being  less  oblique  than  the  lower. 
The  extent  of  obliquity  reaches  its  maximum  at 
the  ninth  rib,  and  gradually  decreases  from  that 
rib  to  the  twelfth.  The  ribs  are  situated  one  be- 
low the  other  in  such  a  manner  that  spaces  are 
left  between  them.  Each  space  is  called  an  inter- 
costal space  (spatium  intercostale).  The  length  of 
these  spaces  corresponds  to  the  length  of  the  ribs 
and  their  cartilages;  their  breadth  is  greater  in 
front  than  behind,  and  between  the  upper  than 
between  the  lower  ribs.  The  ribs  increase  in 
length  from  the  first  to  the  seventh,  when  they 
again  diminish  to  the  twelfth.  In  breadth  they 
decrease  from  above  downward ;  in  the  upper  ten 
the  greatest  breadth  is  at  the  sternal  extremity. 


^Body 
or  shaft. 


Common  Characters  of  the  Ribs. 

A  rib  from  the  middle  of  the  series  should  be 
taken  in  order  to  studv  the  common  characters  of 
the  ribs  (Figs.  116,  "ll 7,  and  118).  Each  rib 
presents  two  extremities,  a  posterior  or  vertebral, 
an  anterior  or  sternal,  and  an  intervening  portion 
— the  body  or  shaft. 

Posterior  Extremity. — The  posterior  or  ver- 
tebral extremity  presents  for  examination  a  head, 
neck,  and  tuberosity. 

The  Head  {capitulum  costcB). — The  head  (Fig. 
118)  is  marked  by  a  kidney  shaped  articular 
surface,  divided  by  a  horizontal  ridge  {crista 
capituli)  into  two  facets  for  articulation  with  the 
costal  cavity  formed  by  the  junction  of  the  bodies 
of  two  contiguous  dorsal  vertebrae;  the  upper 
facet  is  small,  the  inferior  one  of  larger  size; 
the  ridge  separating  them  serves  for  the  attach- 
ment of  the  interarticular  ligament. 

The  Neck  (collum  costoe), — The  neck  is  that  flattened  portion  of  the  rib  which 
extends  outward  from  the  head;  it  is  about  an  inch  long,  and  is  placed  in  front 


Fig.  116. — A  central  rib  of  right  side. 


COMMON   CHARACTERS   OF   THE  RIBS 


161 


of  the  transverse  process  of  the  lower  of  the  two  vertebrae  with  which  the  head 
articulates.  Its  anterior  surface  is  flat  and  smooth,  its  posterior  surface  is  rough 
for  the  attachment  of  the  middle  costo-transverse  ligament,  and  is  perforated  by 
numerous  foramina,  the  direction  of  which  is  less  constant  than  those  found  on 
the  inner  surface  of  the  shaft.  Of  its  two  borders  the 
superior  border  presents  a  rough  crest  {crista  colli  costce) 
for  the  attachment  of  the  anterior  costo-transverse  liga- 
ment; its  inferior  border  is  rounded.  On  the  posterior 
surface  of  the  neck,  just  where  it  joins  the  shaft,  and 
nearer  the  lower  than  the  upper  border,  is  an  eminence 
— the  tuberosity,  or  tubercle. 

Tuberosity  (tuberculum  costce). — The  tuberosity,  or 
tubercle,  consists  of  an  articular  and  a  non-articular  por- 
tion. The  axticular  portion  (fades  articularis  tuber culi 
costce),  the  more  internal  and  inferior  of  the  two,  pre- 
sents a  small,  oval  surface  for  articulation  with  the  ex- 
tremity of  the  transverse  process  of  the  lower  of  the  two 
vertebrfe  to  which  the  head  is  connected.  The  non- 
articulax  portion  is  a  rough  elevation,  which  affords  at- 
tachment to  the  posterior  costo-transverse  ligament. 
The  tubercle  is  much  more  prominent  in  the  upper  than 
in  the  lower  ribs. 

Anterior  Extremity. — ^The  anterior  or  sternal  extremity  is  flattened,  and  pre- 
sents a  porous,  oval,  concave  depression,  into  which  the  costal  cartilage  is  received. 

The  Shaft  {corpus  costae). — The  shaft  is  thin  and  flat,  so  as  to  present  two  sur- 
faces, an  external  and  an  internal,  and  two  borders,  a  superior  and  an  inferior. 


Fig.  117. — Ribs  and  ar- 
ticulations of  the  vertebrsB. 
(Sappey.) 


■Facet  for  body  of  upper  dorsal  vertebra. 
■Ridge  for  interarticular  ligament. 
■Facet  for  body  of  lower  dorsal  vertebra. 

Articular  part  of  tuberosity. 


Non-articular  part  of  tuberosity. 
Fig.  118. — Vertebral  extremity  of  a  rib.     External  surface. 


Surfaces. — The  external  surface  is  convex,  smooth  and  marked  at  its  back  part,  a 
little  in  front  of  the  tuberosity,  by  a  prominent  line,  directed  obliquely  from  above 
downward  and  outward;  this  gives  attachment  to  a  tendon  of  the  Ilio-costalis 
muscle  or  of  one  of  its  accessory  portions,  and  is  called  the  angle  {angulus  costae) . 
At  this  point  the  rib  is  bent  in  two  directions.  If  the  rib  is  laid  upon  its  lower 
border,  it  will  be  seen  that  the  portion  of  the  shaft  in  front  of  the  angle  rests  upon 
this  border,  while  the  portion  of  the  shaft  behind  the  angle  is  bent  inward  and  at 
the  same  time  tilted  upward.  The  interval  between  the  angle  and  the  tuberosity 
increases  gradually  from  the  second  to  the  tenth  rib.  The  portion  of  bone  between 
these  two  parts  is  rounded,  rough,  and  irregular,  and  serves  for  the  attachment  of 
the  Longissimiis  dorsi  muscle.  The  portion  of  bone  between  the  tubercle  and 
sternal  extremity  is  also  slightly  twisted  upon  its  own  axis,  the  external  surface 
looking  downward  behind  the  angle,  a  little  upward  in  front  of  it.  This  surface 
presents,  toward  its  sternal  extremity,  an  oblique  line,  the  anterior  angle.  The 
internal  surface  is  concave,  smooth,  directed  a  little  upward  behind  the  angle,  a 
little  downward  in  front  of  it.    This  surface  is  marked  by  a  ridge  which  com- 

11 


162  THE  SKELETON 

mences  at  the  lower  extremity  of  the  head;  it  is  strongly  marked  as  far  as  the 
inner  side  of  the  angle,  and  gradually  becomes  lost  at  the  junction  of  the  anterior 
with  the  middle  third  of  the  bone.  '^J^'he  interval  between  it  and  the  inferior  border 
presents  a  groove,  subcostal  groove  {sulcus  costce),  for  the  intercostal  vessels  and 
nerve.  At  the  back  part  of  the  bone  this  groove  belongs  to  the  inferior  border, 
but  just  in  front  of  the  angle,  where  it  is  deepest  and  broadest,  it  corresponds  to 
the  internal  surface.  The  superior  edge  of  the  groove  is  rounded;  it  serves  for 
the  attachment  of  the  Internal  intercostal  muscle.  The  inferior  edge  corresponds 
to  the  lower  margin  of  the  rib  and  gives  attachment  to  the  External  intercostal 
muscle.  Within  the  groove  are  seen  the  orifices  of  numerous  small  foramina 
which  traverse  the  wall  of  the  shaft  obliquely  from  before  backward. 

Borders.— The  superior  border,  thick  and  rounded,  is  marked  by  an  external 
and  an  internal  lip,  more  distinct  behind  than  in  front;  they  serve  for  the  attach- 
ment of  the  External  and  Internal  intercostal  muscles.  The  inferior  border,  thin, 
and  sharp,  has  attached  to  it  the  External  intercostal  muscle. 

Peculiar  Ribs, 

The  ribs  which  require  especial  consideration  are  five  in  number — viz.,  the 
first,  second,  tenth,  eleventh,  and  twelfth. 

First  Rib. — The  first  rib  (Fig.  119)  is  the  shortest  and  the  most  curved  of 
all  the  ribs;  it  is  broad  and  flat,  its  surface  looking  upward  and  downward,  and 
its  borders  inward  and  outward.  The  head  is  of  small  size,  rounded,  and  presents 
only  a  single  articular  facet  for  articulation  with  the  body  of  the  first  dorsal  ver- 
tebra. The  neck  is  narrow  and  rounded.  The  tuberosity,  thick  and  prominent, 
rests  on  the  outer  border.  There  is  no  angle,  but  in  this  situation  the  rib  is  slightly 
bent,  with  the  convexity  of  the  bend  upward,  so  that  the  head  of  the  bone  is 
directed  downward.  The  upper  surface  of  the  shaft  is  marked  by  two  shallow 
depressions,  separated  by  a  small  rough  surface  (tuberculum  scaleni)  for  the 
attachment  of  the  Scalenus  anticus  muscle — the  shallow  groove  in  front  of  it 
transmitting  the  subclavian  vein,  the  deeper  groove  behind  it  (sulcus  subclaviae) 
the  subclavian  artery.  Between  the  groove  for  the  subclavian  artery  and 
the  tuberosity  is  a  rough  surface,  for  the  attachment  of  the  Scalenus  medius 
muscle.  The  under  surface  is  smooth,  and  destitute  of  the  groove  observed  on  the 
other  ribs.  The  outer  border  is  convex,  thick,  and  rounded,  and  at  its  posterior 
part  gives  attachment  to  the  first  serration  of  the  Serratus  magnus;  the  inner  is 
concave,  thin,  and  sharp,  and  marked  about  its  centre  by  the  commencement  of 
the  rough  surface  for  the  Scalenus  anticus.  The  anterior  extremity  is  larger  and 
thicker  than  any  of  the  other  ribs. 

Second  Rib. — The  second  rib  (Fig.  120)  is  much  longer  than  the  first,  but  bears 
a  very  considerable  resemblance  to  it  in  the  direction  of  its  curvature.  The  non- 
articular  portion  of  the  tuberosity  is  occasionally  only  slightly  marked.  The  angle 
is  slight  and  situated  close  to  the  tuberosity,  and  the  shaft  is  not  twisted,  so  that 
both  ends  touch  any  plane  surface  upon  which  it  may  be  laid;  but  there  is  a  similar 
though  slighter  bend,  with  its  convexity  upward,  to  that  found  in  the  first  rib.  The 
shaft  is  not  horizontal,  like  that  of  the  first  rib,  its  outer  surface,  which  is  convex, 
looking  upward  and  a  little  outward.  It  presents,  near  the  middle,  a  rough  emi- 
nence, tuberositas  costse  II,  for  the  attachment  of  the  second  and  third  digitations 
of  the  Serratus  magnus;  behind  and  above  which  is  attached  the  Scalenus 
posticus.  The  inner  surface,  smooth  and  concave,  is  directed  dowmward  and  a 
little  inward;  it  presents  a  short  groove  toward  its  posterior  part. 

Tenth  Rib. — The  tenth  rib  (Fig.  121)  has  only  a  single  articular  facet  on  its  head. 

Eleventh  and  Twelfth  Ribs.— The  eleventh  and  twelfth  ribs  (Figs.  122  and 
123)  have  each  a  single  articular  facet  on  the  head,  which  is  of  rather  large  size; 


PECULIAR    JRIBS 


163 


they  have  no  neck  or  tuberosity,  and  are  pointed  at  the  extremity.  The  eleventh 
has  a  slight  angle  and  a  shallow  groove  on  the  lower  border.  The  twelfth  has 
neither,  and  is  much  shorter  than  the  eleventh,  and  the  head  has  a  slight  inclina- 
tion downward.     Sometimes  the  twelfth  rib  is  even  shorter  than  the  first. 


.\,Avgi«  <s>-, 


Angle 

slightly  marked 

and  close  to 

tuberosity. 


Single  articular  facet 


Single  articular  facet. 


Figs.   119-123.— Peculiar  ribs. 


Structure. — The  ribs  consist  of  cancellous  tissue  enclosed  in  a  thin,  compact 
layer. 

Development. — Each  rib,  with  the  exception  of  the  last  two,  is  developed  by 
three  centres:  one  for  the  shaft,  one  for  the  head,  and  one  for  the  tubercle.  The 
last  two  have  only  two  centres,  that  for  the  tubercle  being  wanting.  Ossification 
commences  in  the  shaft  of  the  ribs  at  a  very  early  period,  before  its  appearance  in 
the  vertebrae.  The  epiphysis  of  the  head,  which  is  of  slightly  angular  shape,  and 
that  for  the  tubercle,  of  a  lenticular  form,  make  their  appearance  between  the  six- 
teenth and  twentieth  years,  and  are  not  united  to  the  rest  of  the  bone  until  about 
the  twenty-fifth  year. 


164  THE  SKELETON 

Attachment  of  Muscles. — To  nineteen:  The  Internal  and  External  intercostals, 
Scalenus  anticus,  Scalenus  medius,  Scalenus  posticus,  Pectoralis  minor,  Serratus 
magnus,  Obliquus  externus,  Quadratus  lumborum,  Diaphragm,  Latissimus  dorsi, 
Serratus  posticus  superior,  Serratus  posticus  inferior,  Ilio-costalis,  Musculus  acces- 
sorius  ad  ilio-costalem,  Longissimus  dorsi,  Cervicalis  ascendens,  Levatores  costa- 
rum,  and  Infracostales. 

The  Costal  Cartilages. 

The  costal  cartilage  (cartilago  costalis)  (Fig.  110)  is  white,  hyaline  cartilage.  The 
cartilages  serve  to  prolong  the  ribs  forward  to  the  front  of  the  chest,  and  they 
contribute  very  materially  to  the  elasticity  of  its  walls.  The  first  seven  are  con- 
nected with  the  sternum,  the  next  three  with  the  lower  border  of  the  cartilage  of 
the  preceding  rib.  The  cartilages  of  the  last  two  ribs  have  pointed  extremities, 
which  terminate  in  free  ends  in  the  walls  of  the  abdomen.  Like  the  ribs,  the 
costal  cartilages  vary  in  their  length,  breadth,  and  direction.  They  increase  in 
length  from  the  first  to  the  seventh,  then  gradually  diminish  to  the  last.  They 
diminish  in  breadth,  as  well  as  the  intervals  between  them,  from  the  first  to  the 
last.  They  are  broad  at  their  attachment  to  the  ribs,  and  taper  toward  their  sternal 
extremities,  excepting  the  first  two,  which  are  of  the  same  breadth  throughout, 
and  the  sixth,  seventh,  and  eighth,  which  are  enlarged  where  their  margins  are 
in  contact.  In  direction  they  also  vary:  the  first  descends  a  little,  the  second  is 
horizontal,  the  third  ascends  slightly,  while  all  the  rest  follow  the  course  of  the 
ribs  for  a  short  extent,  and  then  ascend  to  the  sternum  or  preceding  cartilage. 
Each  costal  cartilage  presents  two  surfaces,  two  borders,  and  two  extremities. 

Surfaces. — The  anterior  surface  is  convex,  and  looks  forward  and  upward:  that 
of  the  first  gives  attachment  to  the  costo-clavicular  ligament  and  the  Subclavius 
muscle;  that  of  the  second,  third,  fourth,  fifth,  and  sixth,  at  their  sternal  ends, 
to  the  Pectoralis  major.^  The  others  are  covered  by,  and  give  partial  attachment 
to,  some  of  the  great  flat  muscles  of  the  abdomen.  The  ^posterior  surface  is  con- 
cave, and  directed  backward  and  downward,  the  first  giving  attachment  to  the 
Sterno-thyroid,  the  third  to  the  sixth  inclusive  to  the  Triangularis  sterni,  and 
the  six  or  seven  inferior  ones  to  the  Trans versalis  muscle  and  the  Diaphragm. 

Borders. — Of  the  two  borders,  the  superior  border  is  concave,  the  inferior  con- 
vex; they  afford  attachment  to  the  internal  Intercostal  muscles,  the  upper  border 
of  the  sixth  giving  attachment  to  the  Pectoralis  major  muscle.  The  contiguous 
borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the  ninth  and  tenth, 
costal  cartilages  present  small,  smooth,  oblong-shaped  facets  at  the  points  where 
they  articulate. 

Extremities. — Of  the  two  extremities,  the  outer  extremity  is  continuous  with  the 
osseous  tissue  of  the  rib  to  which  it  belongs.  The  inner  extremity  of  the  first  is 
continuous  with  the  sternum;  the  six  succeeding  ones  have  rounded  extremities, 
which  are  received  into  shallow  concavities  on  the  lateral  margins  of  the  sternum. 
The  inner  extremities  of  the  eighth,  ninth,  and  tenth  costal  cartilages  are  pointed, 
and  are  connected  with  the  cartilage  above.  Those  of  the  eleventh  and  twelfth 
are  free  and  pointed. 

The  costal  cartilages  are  most  elastic  in  youth,  those  of  the  false  ribs  being 
more  so  than  the  true.  In  old  age  they  become  of  a  deep  yellow  color,  and  are 
prone  to  calcify. 

Attachment  of  Muscles. — To  nine:  the  Subclavius,  Sterno-thyroid,  Pectoralis 
major,  Internal  oblique,  Transversalis,  Rectus,  Diaphragm,  Triangularis  sterni, 
and  Internal  intercostals. 

1  The  first  and  seventh  also,  occasionally,  give  origin  to  the  same  muscle. 


THE    COSTAL    CARTILAGES  165 

Surface  Form. — The  bones  of  the  chest  are  to  a  very  considerable  extent  covered  by  mus- 
cles, so  that  in  the  strongly  developed  muscular  subject  they  are  for  the  most  part  concealed. 
In  the  emaciated  subject,  on  the  other  hand,  the  ribs,  especially  in  the  lower  and  lateral  region, 
stand  out  as  prominent  ridges  with  the  sunken,  intercostal  spaces  between  them. 

In  the  middle  line,  in  front,  the  superficial  surface  of  the  sternum  is  to  be  felt  throughout 
its  entire  length,  at  the  bottom  of  a  deep  median  furrow  situated  between  the  two  great  pectoral 
muscles  and  called  the  Sternal  fuiTOW.  These  muscles  overlap  the  anterior  surface  somewhat,  so 
that  the  whole  of  the  sternum  in  its  entire  width  is  not  subcutaneous;  and  this  overlapping  is 
greater  opposite  the  centre  of  the  bone  than  above  and  below,  so  that  the  furrow  is  wider  at  its 
upper  and  lower  parts,  but  narrower  in  the  middle.  The  centre  of  the  upper  border  of  the  ster- 
num is  visible,  constituting  the  pre-stemal  notch,  but  the  lateral  parts  of  this  border  are  obscured 
by  the  tendinous  origins  of  the  Sterno-mastoid  muscles,  which  present  themselves  as  oblique 
tendinous  cords,  which  narrow  and  deepen  the  notch.  Lower  down  on  the  subcutaneous  surface 
a  well-defined  transverse  ridge,  the  angle  of  Ludovic,  is  always  to  be  felt.  This  denotes  the  line 
of  junction  of  the  manubrium  and  body  of  the  bone,  and  is  a  useful  guide  to  the  second  costal 
cartilage,  and  thus  to  the  identity  of  any  given  rib.  The  second  rib  being  found  through  its 
costal  cartilage,  it  is  easy  to  count  downward  and  find  any  other.  From  the  middle  of  the 
sternum  the  furrow  spreads  out,  and,  exposing  more  of  the  surface  of  the  body  of  the  bone, 
terminates  below  in  a  sudden  depression,  the  infrastemal  depression  or  pit  of  the  stomach 
{scrobiculus  cordis),  which  corresponds  to  the  ensiform  cartilage.  This  depression  lies  between 
the  cartilages  of  the  seventh  ribs,  and  in  it  the  ensiform  cartilage  may  be  felt.  The  sternum  in 
its  vertical  diameter  presents  a  general  convexity  forward,  the  most  prominent  point  of  which 
is  at  the  joint  between  the  manubrium  and  gladiolus. 

On  each  side  of  the  sternum  the  costal  cartilages  and  ribs  on  the  front  of  the  chest  are  par- 
tially obscured  by  the  great  pectoral  muscles;  through  which,  however,  they  are  to  be  felt  as 
ridges,  with  yielding  intervals  between  them,  corresponding  to  the  intercostal  spaces.  Of  these 
spaces,  the  one  between  the  second  and  third  ribs  is  the  widest,  the  next  two  somewhat  nar- 
rower, and  the  remainder,  with  the  exception  of  the  last  two,  comparatively  narrow. 

The  lower  border  of  the  Pectoralis  major  muscle  corresponds  to  the  fifth  rib,  and  below 
this,  on  the  front  of  the  chest,  the  broad,  flat  outline  of  the  ribs,  as  they  begin  to  ascend,  and 
the  more  rounded  outline  of  the  costal  cartilages,  are  often  visible.  The  lower  boundary  of 
the  front  of  the  thorax,  the  abdomino-thoracic  arch,  which  is  most  plainly  seen  by  arching  the 
body  backward,  is  formed  by  the  ensiform  cartilage  and  the  cartilages  of  the  seventh,  eighth, 
ninth,  and  tenth  ribs,  and  the  extremities  of  the  eleventh  and  twelfth  ribs  or  their  cartilages. 

On  each  side  of  the  chest,  from  the  axilla  downward,  the  flattened  external  surfaces  of  the 
ribs  may  be  defined  in  the  form  of  oblique  ridges,  separated  by  depressions  corresponding  to  the 
intercostal  spaces.  They  are,  however,  covered  by  muscles,  which  obscure  their  outline  to  a 
certain  extent  in  the  strongly  developed.  Nevertheless,  the  ribs,  with  the  exception  of  the  first, 
can  generally  be  followed  over  the  front  and  sides  of  the  chest  without  difficulty.  The  first  rib, 
being  almost  completely  covered  by  the  clavicle  and  scapula,  can  only  be  distinguished  in  a 
small  portion  of  its  extent.  At  the  back  the  angles  of  the  ribs  form  a  slightly-marked  oblique 
line  on  each  side  of  and  some  distance  from  the  vertebral  spines.  This  line  diverges  some- 
what as  it  descends,  and  external  to  it  is  a  broad,  convex  surface  caused  by  the  projection  of 
the  ribs  beyond  their  angles.  Over  this  surface,  except  where  covered  by  the  scapula,  the 
individual  ribs  can  be  distinguished. 

Surgical  Anatomy. — Malformations  of  the  sternum  present  nothing  of  surgical  importance 
beyond  the  fact  that  abscesses  of  the  mediastinum  may  sometimes  escape  through  the  sternal 
foramen.  Frax'tures  of  the  sternum  are  by  no  means  common,  owing,  no  doubt,  to  the  elasticity 
of  the  ribs  and  their  cartilages,  which  support  it  like  so  many  springs.  When  broken  it  is  fre- 
quently associated  with  fracture  of  the  spine,  and  may  be  caused  by  forcibly  bending  the  body 
either  backward  or  forw^ard  until  the  chin  becomes  impacted  against  the  top  of  the  sternum.  It 
may  also  be  fractured  by  direct  violence  or  by  muscular  action.  The  fracture  usually  occurs  in 
the  upper  half  of  the  body  of  the  bone.  Dislocation  of  the  gladiolus  from  the  manubrium  also 
takes  place,  and  is  sometimes  described  as  a  fracture. 

The  bone,  cancellous  in  structure  and  being  subcutaneous,  is  frequently  the  seat  of  gummatous 
tumors,  and  not  uncommonly  is  affected  with  caries.  Occasionally  the  bone,  and  especially 
its  ensiform  appendix,  becomes  altered  in  shape  and  driven  inward  by  the  pressure,  in  work- 
men, of  tools  against  the  chest. 

The  ribs  are  frequently  broken,  though  from  their  connections  and  shape  they  are  able  to 
withstand  great  force,  yielding  under  the  injury  and  recovering  themselves  like  a  spring.  The 
middle  of  the  series  are  the  ones  most  liable  to  fracture.  The  first,  and  to  a  less  extent  the 
second,  being  protected  by  the  clavicle,  are  rarely  fractured;  and  the  eleventh  and  twelfth,  on 
account  of  their  loose  and  floating  condition,  enjoy  a  like  immunity.  The  fracture  generally 
occurs  from  indirect  violence,  from  forcible  compression  of  the  chest-wall,  and  the  bone  then 
gives  way  at  its  weakest  part — i.  e.,  just  in  front  of  the  angle.  But  the  ribs  may  also  be  broken 
by  direct  violence,  when  the  bone  gives  away  and  is  driven  inward  at  the  point  struck,  or  they 


166  THE   SKELETON 

may  be  broken  by  muscular  action.  It  seems  probable,  however,  that  in  the  latter  case  the 
bone  has  undergone  some  atrophic  changes.  Fracture  of  the  ribs  is  frequently  complicated  with 
some  injury  to  the  viscera  contained  within  the  thorax  or  upper  part  of  the  abdominal  cavity, 
and  this  is  most  likely  to  occur  in  fractures  from  direct  violence. 

Fracture  of  the  costal  cartilages  may  also  take  place,  though  it  is  a  comparatively  rare  injury. 

The  thorax  is  frequently  found  to  be  altered  in  shape  in  certain  diseases. 

The  shape  of  the  rickety  thorax  is  produced  chiefly  by  atmospheric  pressure.  The  balance 
between  the  air  on  the  inside  of  the  chest  and  the  outside  during  some  stage  of  respiration  is  not 
equal,  the  preponderance  being  in  favor  of  the  air  outside;  and  this,  acting  on  the  softened  ribs, 
causes  them  to  be  forced  in  at  the  junction  of  the  cartilages  with  the  bones,  which  is  the  weakest 
part.  In  consequence  of  this  the  sternum  projects  forward,  with  a  deep  depression  on  either  side 
caused  by  the  sinking  in  of  the  softened  ribs.  The  depression  is  less  on  the  left  side,  on  account 
of  the  ribs  being  supported  by  the  heart.  The  condition  is  known  as  pigeon-breast.  The 
lower  ribs,  however,  are  not  involved  in  this  deformity,  as  they  are  prevented  from  falling  in  by 
the  presence  of  the  stomach,  liver,  and  spleen.  And  when  the  liver  and  spleen  are  enlarged, 
as  they  sometimes  are  in  rickets,  the  lower  ribs  may  be  pushed  outward:  this  causes  a  trans- 
verse constriction  just  above  the  costal  arch.  The  anterior  extremities  of  the  ribs  are  usually 
enlarged  in  rickets,  giving  rise  to  what  has  been  termed  the  rickety  rosary.  The  phthisical 
chest  is  often  long  and  narrow,  flattened  from  before  backward,  and  with  great  obliquity  of  the 
ribs  and  projection  of  the  scapulae.  In  pulmonary  emphysema  the  chest  is  enlarged  in  all  its 
diameters,  and  presents  on  section  an  almost  circular  outline.  It  has  received  the  name  of  the 
barrel-shaped  chest.  In  severe  cases  of  lateral  curvature  of  the  spine  the  thorax  becomes 
much  distorted.  In  consequence  of  the  rotation  of  the  bodies  of  the  vertebrae  which  takes 
place  in  this  disease  the  ribs  opposite  the  convexity  of  the  dorsal  curve  become  extremely  con- 
vex behind,  being  thrown  out  and  bulging,  and  at  the  same  time  flattened  in  front,  so  that  the 
two  ends  of  the  same  rib  are  almost  parallel.  Coincident  with  this,  the  ribs  on  the  opposite 
side,  on  the  concavity  of  the  curve,  are  sunk  and  depressed  behind  and  bulging  and  convex  in 
front.     In  addition  to  this  the  ribs  become  occasionally  welded  together  by  bony  material. 

The  ribs  are  frequently  the  seat  of  caries  leading  to  abscesses  and  sinuses,  which  may 
burrow  to  a  considerable  extent  over  the  wall  of  the  chest.  The  only  special  anatomical  point 
in  connection  with  abscesses  and  sinuses  is  that  care  must  be  taken  in  dealing  with  them  that 
the  intercostal  space  is  not  punctured  and  the  pleural  cavity  opened  or  the  intercostal  vessels 
wounded,  as  the  necrosed  portion  of  bone  is  generally  situated  on  the  internal  surface  of  the  rib. 

In  cases  of  empyema  the  chest  requires  opening  ft  evacuate  the  pus.  There  is  consider- 
able difference  of  opinion  as  to  the  best  position  to  do  this.  Probably  the  best  place  for  inter- 
costal drainage  is  between  the  fifth  and  sixth  ribs,  in  or  a  little  in  front  of  the  mid-axillary  line. 
This  is  the  last  part  of  the  cavity  to  be  closed  by  the  expansion  of  the  lung;  it  is  not  thickly 
covered  by  soft  parts;  the  space  between  the  two  ribs  is  sufficiently  great  to  allow  of  the  intro- 
duction of  a  fair-sized  drainage-tube,  and  when  the  patient  is  confined  to  bed  he  does  not  lie 
upon  the  drainage-tube  as  he  does  when  the  opening  is  posterior.  Better  than  intercostal  drain- 
age in  the  vast  majority  of  cases  is  rib  resection  and  drainage.  A  portion  of  the  fifth  or  sixth 
rib  should  be  removed  in  the  mid-axillary  line.  In  chronic  empyema  the  lung  becomes  shrunken 
and  adherent  and  simple  drainage  will  not  bring  about  a  cure.  It  is  necessary  in  such  cases 
to  do  an  operation  that  will  permit  of  collapse  of  the  chest  wall.  Esilander's  operation  consists 
in  resecting  a  portion  of  every  rib  which  overlies  the  cavity  of  the  empyema.  Schede's  opera- 
tion consists  in  removing  ribs  from  the  second  rib  down  over  the  empyema  cavity.  The  ribs 
are  removed  from  cartilages  to  angles,  and  intercostal  muscles  and  the  parietal  layer  of  the 
pleura  are  also  taken  away.  Fowler  and  de  Lorme  not  only  practice  extensive  rib  resection 
and  remove  the  parietal  layer  of  the  pleura,  but  also  remove  the  pulmonary  pleura  {total  pleu- 
rectomy  or  pulmonary  decortication). 

THE  EXTREMITIES. 

The  extremities,  or  limbs,  are  those  long,  jointed  appendages  of  the  body 
which  are  connected  with  the  trunk  by  one  end  and  free  in  the  rest  of  their  extent. 
They  are  four  in  number:  an  upper  or  thoracic  pair,  connected  with  the  thorax 
through  the  intervention  of  the  shoulder,  and  subservient  mainly  to  prehension; 
and  a  lower  pair,  connected  with  the  pelvis,  intended  for  support  and  locomotion. 
Both  pairs  of  limbs  are  constructed  after  one  common  type,  so  that  they  present 
numerous  analogies,  while  at  the  same  time  certain  differences  are  observed 
between  the  upper  and  lower  pair,  dependent  on  the  peculiar  offices  they  have 
to  perform. 


THE    CLAVICLE  167 

The  bones  by  which  the  upper  and  lower  limbs  are  attached  to  the  trunk  are 
named  respectively  the  shoulder  and  pelvic  girdles,  and  they  are  constructed  on  the 
same  general  type,  though  presenting  certain  modifications  relating  to  the  different 
uses  to  which  the  upper  and  lower  limbs  are  respectively  applied.  The  shoulder 
girdle  is  formed  by  the  scapulae  and  clavicles,  and  is  imperfect  in  front  and  behind. 
In  front,  however,  the  girdle  is  completed  by  the  upper  end  of  the  sternum,  with 
which  the  inner  extremities  of  the  clavicle  articulate.  Behind,  the  girdle  is  widely 
imperfect  and  the  scapula  is  connected  to  the  trunk  by  muscles  only.  The  pelvic 
girdle  is  formed  by  the  innominate  bones,  and  is  completed  in  front  through  the 
symphysis  pubis,  at  which  the  two  innominate  bones  articulate  with  each  other. 
It  is  imperfect  behind,  but  the  intervening  gap  is  filled  in  by  the  upper  part  of 
the  sacrum.  The  pelvic  girdle,  therefore,  presents,  with  the  sacrum,  a  complete 
ring,  comparatively  fixed,  and  presenting  an  arched  form  which  confers  upon  it  a 
solidity  manifestly  intended  for  the  support  of  the  trunk,  and  in  marked  contrast 
to  the  lightness  and  mobility  of  the  shoulder  girdle. 

With  regard  to  the  morphology  of  these  girdles,  the  blade  of  the  scapula  is 
generally  believed  to  correspond  to  the  ilium;  but  with  regard  to  the  clavicles 
there  is  some  difference  of  opinion:  formerly  it  was  believed  that  they  corre- 
sponded to  the  ossa  pubis,  meeting  at  the  symphysis,  but  it  is  now  generally 
taught  that  the  clavicle  has  no  homologue  in  the  pelvic  girdle,  and  that  the  os 
pubis  and  ischium  are  represented  by  the  small  coracoid  process  in  man  and 
most  mammals. 


i 


THE  UPPER  EXTREMITY. 


The  bones  of  the  upper  extremity  consist  of  those  of  the  shoulder  girdle,  of  the 
arm,  the  forearm,  and  the  hand. 

THE  SHOULDER  GIRDLE. 

The  shoulder  girdle  consists  of  the  clavicle  and  the  scapula. 

The  Clavicle  or  Collar  Bone  (Clavicula). 

The  clavicle  or  key  bone  (clavis,  a  key)  obtains  it  name  from  its  supposed 
resemblance  to  the  key  used  by  the  Romans.  It  forms  the  anterior  portion  of  the 
shoulder  girdle.  It  is  a  long  bone,  curved  somewhat  like  the  italic  letter  /,  and 
placed  nearly  horizontally  at  the  upper  and  anterior  part  of  the  thorax,  imme- 
diately above  the  first  rib.  It  articulates  by  its  inner  extremity  with  the  upper 
border  of  the  sternum,  and  by  its  outer  extremity  with  the  acromion  process  of  the 
scapula,  serving  to  sustain  the  upper  extremity  in  the  various  positions  which  it 
assumes,  whilst  at  the  same  time  it  allows  of  great  latitude  of  motion  in  the  arm.' 
It  presents  a  double  curvature  when  looked  at  in  front,  the  convexity  being  for- 
ward at  the  sternal  end  and  the  concavity  at  the  scapular  end.  Its  outer  third  is 
flattened  from  above  downward,  and  extends,  in  the  natural  position  of  the  bone, 
from  a  point  opposite  the  coracoid  process  to  the  acromion.  Its  inner  two-thirds 
are  of  a  prismatic  form,  and  extend  from  the  sternum  to  a  point  opposite  the  cora- 
coid process  of  the  scapula. 

Outer,  External,  or  Flattened  Portion. — ^The  outer  third  is  flattened  from  above 
downward,  so  as  to  present  two  surfaces,  an  upper  and  a  lower;  and  two  borders, 
an  anterior  and  a  posterior. 

'  The  clavicle  acts  especially  as  a  fulcrum  to  enable  the  muscles  to  give  lateral  motion  to  the  arm.  It  is 
accordingly  absent  in  those  animals  whose  fore  limbs  are  used  only  for  progression,  but  is  present  for  the  most 
part  in  those  animals  whose  anterior  extremities  are  clawed  and  used  for  prehension,  though  in  some  of  them — 
as,  for  instance,  in  a  large  number  of  the  carnivora — it  is  merely  a  rudimentary  bone  suspended  among  the 
muscles,  and  not  articulating  with  the  scapula  or  sternum. 


168  THE  SKELETON 

Surfaces. — The  upper  surface  is  flattened,  rough,  marked  by  impressions  for  the 
attachment  of  the  Deltoid  in  front  and  the  Trapezius  behind;  between  these  two 
impressions,  externally,  a  small  portion  of  the  bone  is  subcutaneous.  The  under 
surface  is  flattened.  At  its  posterior  border,  a  little  external  to  the  point  where  the 
prismatic  joins  with  the  flattened  portion,  is  a  rough  eminence,  the  conoid  tubercle 
(tuberositas  coracoidea) ;  this,  in  the  natural  position  of  the  bone,  surmounts  the 
coracoid  process  of  the  scapula  and  gives  attachments  to  the  conoid  ligament. 
From  this  tubercle  an  oblique  line,  occasionally  a  depression,  passes  forward 
and  outward  to  near  the  outer  end  of  the  anterior  border;  it  is  called  the  oblique 
line  or  trapezoid  ridge,  and  affords  attachment  to  the  trapezoid  ligament. 

Borders. — The  anterior  border  is  concave,  thin,  and  rough,  and  gives  attachment 
to  the  Deltoid;  it  occasionally  presents,  at  its  inner  end,  at  the  commencement  of 
the  deltoid  impression,  a  tubercle,  the  deltoid  tubercle,  which  is  sometimes  to  be 
felt  in  the  living  subject.  The  posterior  border  is  convex,  rough,  broader  than  the 
anterior,  and  gives  attachment  to  the  Trapezius. 

Inner,  Internal,  or  Prismatic  Portion. — The  prismatic  portion  forms  the  inner 
two-thirds  of  the  bone.  It  is  curved  so  as  to  be  convex  in  front,  concave  behind, 
and  is  marked  by  three  borders,  separating  three  surfaces. 

Borders. — The  anterior  border  is  continuous  with  the  anterior  margin  of  the  flat 
portion.  At  its  commencement  it  is  smooth,  and  corresponds  to  the  interval 
between  the  attachment  of  the  Pectoralis  major  and  Deltoid  muscles;  at  the  inner 
half  of  the  clavicle  it  forms  the  lower  boundary  of  an  elliptical  space  for  the 
attachment  of  the  clavicular  portion  of  the  Pectoralis  major,  and  approaches  the 
posterior  border  of  the  bone.  The  superior  border  is  continuous  with  the  posterior 
margin  of  the  flat  portion,  and  separates  the  anterior  from  the  posterior  surface. 
At  its  commencement  it  is  smooth  and  rounded,  becomes  rough  toward  the  inner 
third  for  the  attachment  of  the  Sterno-mastoid  muscle,  and  terminates  at  the 
upper  angle  of  the  sternal  extremity.  The  posterior  or  subclavian  border  separates 
the  posterior  from  the  inferior  surface,  and  extends  from  the  conoid  tubercle  to 
the  rhomboid  impression.  It  forms  the  posterior  boundary  of  the  groove  for  the 
Subclavius  muscle,  and  gives  attachment  to  a  layer  of  cervical  fascia  covering 
the  Omo-hyoid  muscle. 

Surfaces. — The  anterior  surface  is  included  between  the  superior  and  anterior 
borders.  It  is  directed  forward  and  a  little  upward  at  the  sternal  end,  outward 
and  still  more  upward  at  the  acromial  extremity,  where  it  becomes  continuous 
with  the  upper  surface  of  the  flat  portion.  Externally,  it  is  smooth,  convex, 
nearly  subcutaneous,  being  covered  only  by  the  Platysma;  but,  corresponding 
to  the  inner  half  of  the  bone,  it  is  divided  by  a  more  or  less  prominent  line  into 
two  parts:  a  lower  portion,  elliptical  in  form,  rough,  and  slightly  convex,  for  the 
attachment  of  the  Pectoralis  major;  and  an  upper  part,  which  is  rough,  for  the 
attachment  of  the  Sterno-cleido-mastoid.  Between  the  two  muscular  impressions 
is  a  small  subcutaneous  interval.  The  posterior  or  cervical  surface  is  smooth, 
flat,  and  looks  backward  toward  the  root  of  the  neck.  It  is  limited,  above,  by  the 
superior  border;  below,  by  the  subclavian  border;  internally,  by  the  margin  of  the 
sternal  extremity;  externally,  it  is  continuous  with  the  posterior  border  of  the  flat 
portion.  It  is  concave  from  within  outward,  and  is  in  relation,  by  its  lower  part, 
with  the  suprascapular  vessels.  This  surface,  at  about  the  junction  of  the  inner 
and  outer  curves,  is  also  in  close  relation  with  the  brachial  plexus  and  subclavian 
vessels.  It  gives  attachment,  near  the  sternal  extremity,  to  part  of  the  Sterno-hyoid 
muscle;  and  presents,  at  or  near  the  middle,  a  foramen,  nutrient  foramen  (foramen 
nutricium).  It  opens  into  a  canal,  nutrient  canal  (canalis  nutricius),  which  is 
directed  obliquely  outward  and  transmits  the  chief  nutrient  artery  of  the  bone. 
Sometimes  there  are  two  foramina  on  the  posterior  surface,  or  one  on  the 
posterior,  and  one  on  the  inferior  surface.    The  inferior  or  subclavian  surface 


THE    CLAVICLE 


169 


is  bounded,  in  front,  by  the  anterior  border;  behind,  by  the  subclavian  border. 
It  is  narrow  internally,  but  gradually  increases  in  width  externally,  and  is 
continuous  with  the  under  surface  of  the  flat  portion.  Commencing  at  the 
sternal  extremity  may  be  seen  a  small  facet,  the  costal  facet,  for  articulation 

This  is  continuous  with  the  articular  surface 


with  the  cartilage  of  the  first  rib 


Acromial  extremity. 


Sternal  exti-emity. 


Fig.  124. — Left  clavicle.     Superior  surface. 

at  the  sternal  end  of  the  bone.  External  to  this  is  a  broad,  rough  surface,  the 
rhomboid  impression  (tuberositas  costalis),  rather  more  than  an  inch  in  length,  for 
the  attachment  of  the  costo-clavicular  (rhomboid)  ligament.  The  remaining  part 
of  this  surface  is  occupied  by  a  longitudinal  groove,  the  subclavian  groove,  broad 
and  smooth  externally,  narrow  and  more  uneven  internally;  it  gives  attachment  to 
the  Subclavius  muscle,  and  by  its  margins  to  the  costo-coracoid  membrane, 
which  splits  to  enclose  the  muscle.  Not  infrequently  this  groove  is  subdivided 
into  two  parts  by  a  longitudinal  line,  which  gives  attachment  to  the  intermuscular 
septum  of  the  Subclavius  muscle. 


Fig.  125. — Left  clavicle.     Inferior  surface. 


Internal  or  Sternal  Extremity  (extremitas  sternalis). — The  internal  or  sternal 
extremity  of  the  clavicle  is  triangular  in  form,  dii'ected  inward  and  a  little  down- 
ward and  forward;  and  presents  an  articular  facet  {fades  articularis  sternalis), 
concave  from  before  backward,  convex  from  above  downward,  which  articulates 
with  the  sternum  through  the  intervention  of  an  interarticular  fibro-cartilage; 
the  circumference  of  the  articular  surface  is  rough,  for  the  attachment  of 
numerous  ligaments.  The  posterior  border  of  this  surface  is  prolonged  back- 
warfl,  so  as  to  increase  the  size  of  the  articular  facet;  the  upper  border  gives 
attachment  to  the  interarticular  fibro-cartilage,  and  the  lower  border  is  con- 
tinuous with  the  costal  facet  on  the  inner  end  of  the  inferior  or  subclavian  sur- 
face, which  articulates  with  the  cartilage  of  the  first  rib. 

Outer  or  Acromial  Extremity  (extremitas  acromialis) . — The  outer  or  acromial 
extremity,  directed  outward  and  forward,  presents  a  small,  flattened,  oval  facet. 


170 


THE   SKELETON 


acromial  surface  (facies  articularis  acromialis) ,  which  looks  obliquely  downward, 
for  articulation  with  the  acromion  process  of  the  scapula.  The  circumference 
of  the  articular  facet  is  rough,  especially  above,  for  the  attachment  of  the 
acromio-clavicular  ligaments. 

Peculiarities  of  the  Bone  in  the  Sexes  and  in  Individuals. — In  the  female  the. 
clavicle  is  generally  shorter,  thinner,  less  curved,  and  smoother  than  in  the  male.] 
In  those  persons  who  perform  considerable  manual  labor,  which  brings  into  con- 
stant action  the  muscles  connected  with  this  bone,  it  becomes  thicker  and  more 
curved,  its  ridges  for  muscular  attachment  become  prominently  marked.     The 
right  clavicle  is  generally  longer,  thicker,  and  rougher  than  the  left. 

Structure. — The  shaft,  as  well  as  the  extremities,  consists  of  cancellous  tissue,; 
invested  in  a  compact  layer  much  thicker  in  the  middle  than  at  either  end.  The 
clavicle  is  highly  elastic,  by  reason  of  its  curves.  From  the  experiments  of  Mr.j 
Ward  it  has  been  shown  that  it  possesses  sufficient  longitudinal  elastic  force  tc 
project  its  own  weight  nearly  two  feet  on  a  level  surface  when  a  smart  blow  is 
struck  on  it;  and  sufficient  transverse  elastic  force,  opposite  the  centre  of  it 
anterior  convexity,  to  throw  its  own  weight  about  a  foot.  This  extent  of  elastic 
power  must  serve  to  moderate  very  considerably  the  effect  of  concussions  receivec 
upon  the  point  of  the  shoulder. 

Development.^-By  two  centres:  one  for  the  shaft  and  outer  extremity  anc 
one  for  the  sternal  extremity.    The  centre  for  the  shaft   appears   very  early, 
before  any  other   bone — according  to  Beclard,  as  early  as  the  thirtieth  day.l 
The  centre  for  the  sternal  end  makes  its  appearance  about  the  eighteenth  oi 
twentieth  year,  and  unites  with  the  rest  of  the  bone  about  the  twenty-fifth  year.l 

Articulations. — With  the  sternum,  scapula,  and  cartilage  of  the  first  rib. 

Attachment  of  Muscles. — To  six  :  the  Sterno-cleido-mastoid,  Trapezius, 
Pectoralis  major.  Deltoid,  SubclaviuSj  and  Sterno-hyoid. 

Surface  Form. — The  clavicle  can  be  felt  throughout  its  entire  length,  even  in  persons  who 
are  very  fat.  Commencing  at  the  inner  end,  the  enlarged  sternal  extremity,  where  the  bone 
projects  above  the  upper  margin  of  the  sternum,  can  be  felt,  forming  with  the  sternum  and  the 
rounded  tendon  of  the  Sterno-mastoid  a  V-shaped  notch,  the  pre-stemal  notch.  Passing  out-^ 
ward,  the  shaft  of  the  bone  can  be  felt  immediately  under  the  skin,  with  its  convexity  forwarc 
in  the  inner  two-thirds,  the  surface  partially  obscured  above  and  below  by  the  attachments  of 
the  Sterno-mastoid  and  Pectoralis  major  muscles.  In  the  outer  third  it  forms  a  gentle  curve 
backward,  and  terminates  at  the  outer  end  in  a  somewhat  enlarged  extremity  which  articulates 
with  the  acromial  process  of  the  scapula.  The  direction  of  the  clavicle  is  almost,  if  not  quite, 
horizontal  when  the  arm  is  lying  quietly  by  the  side,  though  in  well-developed  subjects  it  may 
incline  a  little  upward  at  its  outer  end.  Its  direction  is,  however,  very  changeable,  altering 
with  the  varying  movements  of  the  shoulder-joint. 

Surgical  Anatomy. — The  clavicle  is  the  most  frequently  fractured  of  any  single  bone  in  the 
body.  This  is  due  to  the  fact  that  it  is  much  exposed  to  violence,  and  is  the  only  bony  connec- 
tion between  the  upper  limb  and  the  trunk.  The  bone,  moreover,  is  slender,  and  is  very  super- 
ficial. The  bone  may  be  broken  by  direct  or  indirect  violence  or  by  muscular  action.  The  most 
common  cause  is,  however,  from  indirect  violence,  and  the  bone  then  gives  way  at  the  junction 
of  the  fixed  outer  one-third  with  the  movable  inner  two-thirds  of  the  bone.  This  is  the  weakest 
and  most  slender  part  of  the  bone.  The  fracture  is  generally  oblique,  and  the  displacement 
of  the  outer  fragments  is  inward,  away  from  the  surface  of  the  body;  hence  compound 
fracture  of  the  clavicle  is  of  rare  occurrence.  The  iimer  fragment  as  a  rule  is  little  displaced 
(page  503).  Beneath  the  bone  the  main  vessels  of  the  upper  limb  and  the  great  nerve-cords  of 
the  brachial  plexus  lie  on  the  first  rib,  and  are  liable  to  be  wounded  in  fracture,  especially  in 
fracture  from  direct  violence,  when  the  force  of  the  blow  drives  the  broken  ends  inward.  For- 
tunately, the  Subclavius  muscle  is  interposed  between  these  structures  and  the  clavicle,  and 
this  often  protects  them  from  injury. 

The  clavicle  is  not  uncommonly  the  seat  of  sarcomatous  tumors,  rendering  the  operation 
of  excision  of  the  entire  bone  necessary.  This  operation  is  best  performed  by  exposing  the 
bone  freely,  disarticulating  at  the  acromial  end,  and  turning  it  inward.  The  removal  of 
the  outer  part  is  comparatively  easy,  but  resection  of  the  inner  part  is  fraught  with  difficulty,  the 
main  danger  being  the  risk  of  wounding  the  great  veins  which  are  in  relation  with  its  under 
surface. 


THE  SCAPULA 


The  Scapula  or  Shoulder  Blade. 


173 


The  scapula  {axaTzdvrj,  a  spade),  or  blade  bone,  forms  the  back  part  of 
the  shoulder  girdle.  It  is  a  large,  flat  bone,  triangular  in  shape,  situated  at 
the  posterior  aspect  and  side  of  the  thorax,  between  the  second  and  seventh,  or 
sometimes  the  eighth,  ribs,  its  internal  border  or  base  being  about  an  inch  from 
and  nearly  but  not  quite  parallel  with  the  spinous  processes  of  the  vertebrae,  so 
that  it  is  rather  closer  to  them  above  than  below.  It  presents  for  examination 
two  surfaces,  three  borders,  and  three  angles. 


Fig.  126. — Left  scapula.     Anterior  surface  or  venter. 


Surfaces.  Anterior  or  Costal  Surface,  Ventral  Aspect  or  Venter  (facies  costalis) . — 
The  anterior  surface  (Fig.  126)  presents  a  broad  concavity,  the  subscapular 
fossa  ijossa  subscapularis) .  It  is  marked,  in  the  inner  two-thirds,  by  several 
oblique  ridges  (linece  musculares) ,  which  pass  from  behind  outward  and  upward; 
the  outer  third  is  smooth.  The  oblique  ridges  give  attachment  to  the  tendinous 
mtersections,  and  the  surfaces  between  them  to  the  fleshv  fibres,  of  the  Sub- 


172  THE  SKELETON 

scapularis  muscle.  The  anterior  third  of  the  fossa,  which  is  smooth,  is  covered 
by,  but  does  not  afford  attachment  to,  the  fibres  of  this  muscle.  The  venter  is 
separated  from  the  internal  border  by  a  smooth,  triangular  margin  at  the  supe- 
rior and  inferior  angles,  and  in  the  interval  between  these  by  a  narrow  edge  which 
is  often  deficient.  This  marginal  surface  affords  attachment  throughout  its  entire 
extent  to  the  vSerratus  magnus  muscle.  The  subscapular  fossa  presents  a  trans- 
verse depression  at  its  upper  part,  where  the  bone  appears  to  be  bent  on  itself, 
forming  a  considerable  angle,  called  the  subscapulax  angle  (angulus  subscapularis) , 
thus  giving  greater  strength  to  the  body  of  the  bone  from  its  arched  form,  whilst 
the  summit  of  the  arch  serves  to  support  the  spine  and  acromion  process.  It  is  in 
this  situation  that  the  fossa  is  deepest,  so  that  the  thickest  part  of  the  Subscapu- 
laris muscle  lies  in  a  line  perpendicular  to  the  plane  of  the  glenoid  cavity,  and 
must  consequently  operate  most  effectively  on  the  head  of  the  humerus,  which 
is  contained  in  that  cavity.  The  portion  of  bone  between  the  suprascapular 
notch  and  the  infraglenoid  tubercle  is  sometimes  called  the  surgical  neck. 

Posterior  or  Dorsal  Surface  or  Dorsum  (facies  dorsalis) . — The  posterior  or  dorsal 
surface  (Fig.  127)  is  arched  from  above  downward,  alternately  concave  and 
convex  from  side  to  side.  It  is  subdivided  unequally  into  two  parts  by  the 
spine ;  the  portion  above  the  spine  is  called  the  supraspinous  fossa,  and  that  below 
it  the  infraspinous  fossa. 

The  supraspinous  fossa  {fossa  supraspinata) ,  the  smaller  of  the  two,  is  concave, 
smooth,  and  broader  at  the  vertebral  than  at  the  humeral  extremity.  It  affords 
attachment  by  its  inner  two-thirds  to  the  Supraspinatus  muscle. 

The  infraspinous  fossa  (fossa  infraspinata)  is  much  larger  than  the  preceding; 
toward  its  vertebral  margin  a  shallow  concavity  is  seen  at  its  upper  part;  its  centre 
presents  a  prominent  convexity,  whilst  toward  the  axillary  border  is  a  deep  groove 
which  runs  from  the  upper  toward  the  lower  part.  The  inner  two-thirds  of  this 
surface  affords  attachment  to  the  Infraspinatus  muscle;  the  outer  third  is  only  cov- 
ered by  it,  without  giving  origin  to  its  fibres.  This  surface  is  separated  from  the 
axillary  border  by  an  elevated  ridge,  which  runs  from  the  lower  margin  of  the  glenoid 
cavity  downward  and  backward  to  the  posterior  border,  about  an  inch  above  the  in- 
ferior angle.  The  ridge  serves  for  the  attachment  of  a  strong  aponeurosis  which 
separates  the  Infraspinatus  from  the  two  Teres  muscles.  The  surface  of  bone  between 
this  line  and  the  axillary  border  is  narrow  in  the  upper  two-thirds  of  its  extent, 
and  traversed  near  its  centre  by  a  groove  for  the  passage  of  the  dorsalis  scapulae 
vessels;  it  affords  attachment  to  the  Teres  minor  muscle.  Its  lower  third  presents  a 
broader,  somewhat  triangular  surface,  which  gives  origin  to  the  Teres  major,  and 
over  which  the  Latissimus  dorsi  glides;  sometimes  the  latter  muscle  takes  origin 
by  a  few  fibres  from  this  part.  The  broad  and  narrow  portions  of  bone  above 
alluded  to  are  separated  by  an  oblique  line  which  runs  from  the  axillary  border, 
downward  and  backward,  to  meet  the  elevated  ridge:  to  it  is  attached  the 
aponeurosis  separating  the  two  Teres  muscles  from  each  other. 

The  spine  {spina  scapuloe)  is  a  prominent  plate  of  bone  which  crosses  obliquely 
the  inner  four-fifths  of  the  dorsum  of  the  scapula  at  its  upper  part,  and  separates  the 
supra- from  the  infraspinous  fossa :  it  commences  at  the  vertebral  border  by  a  smooth, 
triangular  surface,  over  which  the  Trapezius  glides,  separated  from  the  bone  by  a 
bursa,  and,  gradually  becoming  more  elevated  as  it  passes  outward,  terminates  in 
the  acromion  process,  which  overhangs  the  shoulder-joint.  The  spine  is  triangular 
and  flattened  from  above  downward,  its  apex  corresponding  to  the  vertebral 
border,  its  base  (which  is  directed  outward)  to  the  neck  of  the  scapula.  It  pre- 
sents two  surfaces  and  three  borders.  Its  superior  surface  is  concave,  assists 
in  forming  the  supraspinous  fossa,  and  affords  attachment  to  part  of  the  Supra- 
spinatus muscle.  Its  inferior  surface  forms  part  of  the  infraspinous  fossa,  gives 
origin  to  part  of  the  Infraspinatus  muscle,  and  presents  near  its  centre  the  orifice 


THE   SCAPULA 


173 


of  a  nutrient  canal.  Of  the  three  borders,  the  anterior  is  attached  to  the  dorsum 
of  the  bone;  the  posterior,  or  crest  of  the  spine,  is  broad,  and  presents  two  hps 
and  an  intervening  rough  interval.  To  the  superior  hp  is  attached  the  Trapezius 
to  the  extent  shown  in  the  figure.  A  rough  tubercle  is  generally  seen  occupying 
that  portion  of  the  spine  which  receives  the  insertion  of  the  middle  and  inferior 
fibres  of  this  muscle.    To  the  inferior  lip,  throughout  its  whole  length,  is  attached 


Coracoi(f 


Vor  ^ 


Groove  for  Dorsalis 
Scapulx  Artery. 


inferior 
Fig.  127. — Left  scapula.     Posterior  surface  or  dorsum. 

the  Deltoid.  The  intervals  between  the  lips  is  also  partly  covered  by  the  tendinous 
fibres  of  these  muscles.  The  external  border,  or  base,  the  shortest  of  the  three,  is 
slightly  concave,  its  edge  thick  and  round,  continuous  above  with  the  under  sur- 
face of  the  acromion  process,  below  with  the  neck  of  the  scapula.  The  narrow 
portion  of  bone  external  to  this  border,  and  separating  it  from  the  glenoid  cavity, 
is  called  the  great  scapular  notch,  and  serves  to  connect  the  supra-  and  infraspinous 
fossae. 


174  THE  SKELETON 

The  acromion  process  (acromion),  so  called  from  forming  the  summit  of  the 
shoulder  (dxpou,  a  summit;  (h/io^,  the  shoulder),  is  a  large  and  somewhat  triangular 
or  oblong  process,  flattened  from  behind  forward,  directed  at  first  a  little  outward, 
and  then  curving  forward  and  upward,  so  as  to  overhang  the  glenoid  cavity.  Its 
upper  surface,  directed  upward,  backward,  and  outward,  is  convex,  rough,  and 
gives  attachment  to  some  fibres  of  the  Deltoid,  and  in  the  rest  of  its  extent  it  is 
subcutaneous.  Its  under  surface  is  smooth  and  concave.  Its  outer  border  is  thick 
and  irregular,  and  presents  three  or  four  tubercles  for  the  tendinous  origins  of  the 
Deltoid  muscle.  Its  inner  margin,  shorter  than  the  outer,  is  concave,  gives  attach- 
ment to  a  portion  of  the  Trapezius  muscle,  and  presents  about  its  centre  a  small 
oval  surface  for  articulation  with  the  acromial  end  of  the  clavicle.  Its  apex,  which 
corresponds  to  the  point  of  meeting  of  these  two  borders  in  front,  is  thin,  and 
has  attached  to  it  the  coraco-acromial  ligament. 

Margins  or  Borders  of  the  Scapula.  Superior  Border  (margo  superior) . — Of  the 
three  borders  of  the  scapula,  the  superior  is  the  shortest  and  thinnest;  it  is  concave 
and  extends  from  the  superior  angle  to  the  coracoid  process.  At  its  outer  part  is  a 
deep,  semicircular  notch,  the  suprascapular  notch  {incisura  scapulae) ,  formed  partly 
by  the  base  of  the  coracoid  process.  This  notch  is  converted  into  a  foramen  by  the 
transverse  ligament,  and  serves  for  the  passage  of  the  suprascapular  nerve.  Some- 
times this  foramen  is  entirely  surrounded  by  bone.  The  adjacent  margin  of  the 
superior  border  affords  attachment  to  the  Omo-hyoid  muscle. 

External  or  Axillary  Border  {margo  axillaris)  .—The  external  or  axillary  border 
is  the  thickest  of  the  three.  It  commences  above  at  the  lower  margin  of  the 
glenoid  cavity,  and  inclines  obliquely  downward  and  backward  to  the  inferior 
angle.  Immediately  below  the  glenoid  cavity  is  a  rough  impression,  the  infra- 
glenoid  tubercle  {tuberositas  infraglenoidalis) ,  about  an  inch  in  length,  which 
affords  attachment  to  the  long  head  of  the  Triceps  muscle;  in  front  of  this  is 
a  longitudinal  groove,  which  extends  as  far  as  the  lower  third  of  the  axillary 
border  and  affords  origin  to  part  of  the  Subscapularis  muscle.  The  inferior 
third  of  this  border,  which  is  thin  and  sharp,  serves  for  the  attachment  of  a  few 
fibres  of  the  Teres  major  behind  and  the  Subscapularis  in  front. 

Internal  or  Vertebral  Border  {margo  vertebralis) . — The  internal  or  vertebral  bor- 
der, also  named  the  base,  is  the  longest  of  the  three,  and  extends  from  the  superior  to 
the  inferior  angle  of  the  bone.  It  is  arched,  is  intermediate  in  thickness  between  the 
superior  and  the  external  borders,  and  the  portion  of  it  above  the  spine  is  bent  con- 
siderably outward,  so  as  to  forai  an  obtuse  angle  with  the  lower  part.  The  vertebral 
border  presents  an  anterior  lip,  a  posterior  lip,  and  an  intermediate  space.  The  ante- 
rior lip  affords  attachment  to  the  Serratus  magnus ;  the  posterior  lip,  to  the  Supra- 
spinatus  above  the  spine,  the  Infraspinatus  below;  the  interval  between  the  two  lips, 
to  the  Levator  anguli  scapulae  above  the  triangular  surface  at  the  commencement 
of  the  spine,  the  Rhomboideus  minor  to  the  edge  of  that  surface;  the  Rhomboideus 
major  being  attached  by  means  of  a  fibrous  arch  connected  above  to  the  lower 
part  of  the  triangular  surface  at  the  base  of  the  spine,  and  below  to  the  lower  part 
of  the  posterior  border. 

Angles.  Superior  or  Mesial  Angle  {angulus  medialis) . — Of  the  three  angles,  the 
superior,  formed  by  the  junction  of  the  superior  and  internal  borders,  is  thin, 
smooth,  rounded,  somewhat  inclined  outward,  and  gives  attachment  to  a  few 
fibres  of  the  Levator  anguli  scapulae  muscle. 

Inferior  Angle  (angulus  inferior). — The  inferior  angle,  thick  and  rough,  is 
formed  by  the  union  of  the  vertebral  and  axillary  borders,  its  outer  surface 
affording  attachment  to  the  Teres  major  and  frequently  to  a  few  fibres  of  the 
Latissimus  dorsi. 

Anterior  or  Lateral  Angle  {angidus  lateralis) . — The  anterior  angle  is  the  thickest 
part  of  the  bone,  and  forms  what  is  called  the  head  of  the  scapula.    The  head 


THE  SCAPULA 


175 


presents  a  shallow,  pyriforra,  articular  surface,  the  glenoid  surface  or  cavity  {cav- 
itas  glenoidalis ,  from  y/rjvT^,  a  socket),  whose  longest  diameter  is  from  above 
downward,  and  its  direction  outward  and  forward.  It  is  broader  below  than 
above.  Just  above  it  is  a  rough  surface,  the  supraglenoid  tubercle  or  tuberosity 
(tuberositas  supraglenoidalis) ,  to  which  is  attached  the  long  tendon  of  the  Biceps 
muscle.  The  glenoid  cavity  is  covered  with  cartilage  in  the  recent  state;  and 
its  margins  are  slightly  raised  and  give  attachment  to  a  fibro-cartilaginous  struc- 
ture, the  glenoid  ligament,  by  which  its  cavity  is  deepened.  The  anatomical  neck 
of  the  scapula  (collum  scajmlae)  is  the  slightly  depressed  surface  which  surrounds 
the  head ;  it  is  more  distinct  on  the  posterior  than  on  the  anterior  surface,  and 
below  than  above.  In  the  latter  situation  it  has  arising  from  it  a  thick  prominence, 
the  coracoid  process. 

The  coracoid  process  (processus  coracoideus) ,  so  called  from  its  fancied  resemblance 
to  a  crow's  beak  (x6(>a^,  a  crow),  is  a  thick,  curved  process  of  bone  which  arises  by 
a  broad  base  from  the  upper  part  of  the  neck  of  the  scapula;  it  is  directed  at  first 
upward  and  inward,  then,  becoming  smaller,  it  changes  its  direction  and  passes  for- 
ward and  outward.  The  ascending  portion,  flattened  from  before  backward,  pre- 
sents in  front  a  smooth,  concave 

surface  over  which  passes  the     ^/J^  ^foi-  ^ 

Subscapularis     muscle.       The     '^^  "  "  ^^ 

horizontal  portion  is  flattened 
from  above  downward,  its  upper 
surface  is  convex  and  irregular, 
and  gives  attachment  to  the 
Pectoralis  minor;  its  under  sur- 
face is  smooth ;  its  inner  border 
is  rough,  and  gives  attachment 
to  the  Pectoralis  minor;  its  outer 
border  is  also  rough  for  the 
coraco-acromial  ligament,  while 
the  apex  is  embraced  by  the 
conjoined  tendon  of  origin  of 
the  short  head  of  the  Biceps 
and  of  the  Coraco-brachialis 
and  gives  attachment  to  the 
costo-coracoid  ligament.  At  the 
inner  side  of  the  root  of  the 
coracoid  process  is  a  rough  im- 
pression for  the  attachment  of 
the  conoid  ligament;  and  run- 
ning from  it  obliquely  forward 
and  outward  on  the  upper  sur- 
face of  the  horizontal  portion, 
an  elevated  ridge  for  the  attach- 
ment of  the  trapezoid  ligament. 

Structure.— In  the  head,  pro- 
cesses, and  all  the  thickened 
parts  of  the  bone  the  scapula  is  composed  of  cancellous  tissue,  while  in  the  rest  of 
its  extent  it  is  composed  of  a  thin  layer  of  dense,  compact  tissue.  "  The  centre  part 
of  the  supraspinous  fossa  and  the  upper  part  of  the  infraspinous  fossa,  but  especially 
the  former,  are  usually  so  thin  as  to  be  semitransparent ;  occasionally  the  bone  is 
found  wanting  in  this  situation,  and  the  adjacent  muscles  come  into  contact. 

Development  (Fig.  128). — By  seven  or  more  centres:  one  for  the  body,  two  for 
the  coracoid  process,  two  for  the  acromion,  one  for  the  vertebral  border,  and  one 


fifenot 


Fig.  128. — Plan  of  the  development  of  the  scapula.  By  seven 
centres.  The  epiphyses  (except  one  for  the  coracoid  process) 
appear  from  fifteen  to  seventeen  years,  and  unite  between  twenty- 
two  and  twenty-five  years  of  age. 


176  THE  SKELETON 

For  the  inferior  angle.  Ossification  of  the  body  of  the  scapula  commences  about 
the  second  month  of  f(»*tal  life  by  tiie  fonn.ition  of  an  invfj^nhir  (|na(lrihiteral 
plate  of  bone  ininiediately  behind  the  j^lenoid  cavity.  This  plate  extends  itself  so 
as  to  form  the  chief  part  of  the  bone,  the  spine  growing  up  from  its  posterior, 
surface  about  the  third  month.  At  birth  a  large  j)art  of  the  scapula  is  osseous, 
but  the  glenoid  cavity,  coracoid  and  acromion  processes,  the  |)osterior  border,  and 
inferior  angle  are  cartilaginous.  From  the  fifteenth  to  the  eighteenth  month  after 
birth  ossification  takes  place  in  the  middle  of  the  coracoid  process,  which  usually 
becomes  joined  with  the  rest  of  the  bone  at  the  time  when  the  other  centres  make 
their  aj)pearance.  Between  the  fourteenth  and  twentieth  years  ossification  of  the 
remaining  centres  takes  place  in  (juick  succession,  and  in  the  following  onler: 
first,  in  the  root  of  the  coracoid  process,  in  the  form  of  a  broad  scale;  secondly, 
near  the  base  of  the  acromion  process;  thirdly,  in  the  inferior  angle  and  contigu- 
ous part  of  the  posterior  border;  fourthly,  near  the  extremity  of  the  acromion; 
fifthly,  in  the  posterior  border.  The  acromion  process,  besides  !)eing  formed  of 
two  se{)arate  nuclei,  has  its  base  formed  by  an  extension  into  it  of  tlie  centre  of 
ossification  which  belongs  to  the  spine,  the  extent  of  which  varies  in  different 
cases.  The  two  separate  nuclei  unite,  and  then  join  with  the  extension  from  the 
spine.  These  various  epiphyses  become  joined  to  the  bone  between  the  ages  of 
twenty-two  and  twenty-five  years.  Sometimes  failure  of  union  between  the 
acromion  process  and  spine  occurs,  the  junction  being  effected  by  fibrous  tissue 
or  by  an  imperfect  articulation;  in  some  cases  of  supposed  fracture  of  the  acromion 
with  ligamentous  union  it  is  probable  that  the  detached  segment  was  never  united 
to  the  rest  of  the  bone.  The  upper  third  of  the  glenoid  cavity  is  usually  ossified 
from  a  separate  centre  (subcoracoid)  which  makes  its  appearance  between  the 
tenth  and  eleventh  years.  Very  often,  in  addition,  an  epiphysis  appears  for  the 
lower  part  of  the  glenoid  cavity. 

Articulations.     With  the  humerus  and  clavicle. 

Attachment  of  Muscles. — To  seventeen:  to  the  anterior  surface,  the  Subscapu- 
laris;  posterior  surface,  Supraspinatus,  Infraspinatus;  spine.  Trapezius,  Deltoid; 
superior  border,  Omo-hyoid;  vertebral  border,  Serratus  magnus,  Levator  anguli 
scapida\  Hhomboideus  minor  and  major;  axillary  border.  Triceps,  Teres  minor, 
Teres  major;  apex  of  glenoid  cavity,  long  head  of  the  Biceps;  coracoid  process, 
short  head  of  the  Hice{)s,  Coraco-brachialis,  Pectoralis  minor;  and  to  the  inferior 
angle  occasionally  a  few  fibres  of  the  Latissimus  dorsi. 

Surface  Form.— The  only  parts  of  the  scapula  which  are  truly  subcutaneous  are  the  spine 
and  acromion  process,  but,  in  addition  to  those,  the  coracoid  process,  the  internal  or  vcrteoral 
l)order  and  inferior  anjjfe,  and,  to  a  less  extent,  the  axillary  border,  may  be  defined.  TIic  acro- 
mion process  and  s}>ine  of  the  scapula  are  easily  felt  throuji;hout  their  entiiv  leno;th,  forming, 
with  tile  clavicle,  the  ar<'li  of  the  shoulder.  The  acromion  can  be  ascertained  to  be  connected 
to  the  clavicle  at  the  acromio-clavicular  joint  by  runninji  the  finjier  alonjj;  it,  its  position  being 
often  indicated  bv  an  irrcfjularity  or  bony  outjjrowth  from  the  clavicle  close  to  the  joint.  The 
acronuon  can  be  tclt  forming  the  point  of  the  shoulder,  and  from  this  can  be  traced  backward  to 
join  the  spine  of  the  scapula.  The  plai'c  of  junction  is  usually  denoted  by  a  prominence,  which  is 
sumctimes  called  the  acromial  angle.  From  here  the  spine  of  the  scapula  can  be  felt  as  a  promi- 
nent ridge  of  bone,  marked  on  the  surface  as  an  oblicjuc  depression,  which  becomes  less  and  less 
distinct,  and  terminates  a  little  external  to  the  spinous  processes  of  the  vertebra'.  Its  termination  is 
usually  indicated  by  a  slight  chniple  in  the  skin  on  a  level  with  the  interval  between  the  third  and 
fourth  dorsal  spines,  below  this  point  the  vertebral  border  of  the  scapula  may  be  trai-etl,  running 
downward  and  outward,  and  thus  diverging  from  the  vertebral  spines,  to  the  inferior  angle  of 
the  bone,  which  can  be  recognized,  although  covered  by  the  Latissimus  dorsi  muscle.  From 
this  angle  the  axillary  border  can  usually  be  traced  through  this  thick  nuiscular  covering,  form- 
ing, with  the  nniscles,  the  posterior  fold  of  the  axilla.  The  coracoid  nroccss  may  be  felt  about 
an  inch  below  the  junction  of  the  middle  and  outer  thirds  of  the  clavicle.  Here  it  is  covered  by 
the  anterior  bonier  of  the  deltoid  and  lies  a  little  to  the  outer  side  of  a  slight  depression  which 
corresponds  to  the  interval  l)etwecn  the  IVctoralis  major  and  Deltoid  nniscles.  When  the  arms 
are  hanging  by  the  side,  the  upper  angle  of  the  scapula  corresponds  to  the  upper  bonier  of  tlie 


THE   HUMERUS  177 

second  rih  or  (lie  iiilcrval  between  the  first  and  second  dorsal  spines,  the  inferior  anple  to  the 
upper  lionlcr  of  i\w.  eiffhth  rih  or  the  interval  between  tlu^  seventh  and  eifjhth  dorsal  spines. 

Surgical  Anatomy.  Fnuiurr.i  of  the  body  of  the  scapula  are  ran;,  owinj^  to  the  mobility  of  the 
bone,  the  thick  layer  of  muscles  by  which  it  is  encased  on  both  surfaces,  and  the  elasticity  of  the 
ribs  on  which  it  rests.  Fracture  of  the  neck  of  the  bone  is  also  uncommon.  'I'hc;  most  fre(juent 
course  of  a  line;  of  fracture  of  the  neck  is  from  the  su|)rascapular  notch  to  the  infraglenoid 
tubercle  {nurt/ictil  neck),  and  it  derives  its  princi|)al  interest  from  its  simulation  to  a  subj^lenoid 
dislocation  of  the  humerus.  The  diagnosis  can  be  made  by  noting  the  alteration  in  the  position 
of  the  coracoid  process.  A  fracture  of  the  neck  external  to,  and  not  including,  the  coracoid 
process  {analoiiiiad  nrric)  is  said  to  occur,  but  it  is  exceedingly  doubtful  whether  such  an 
accident  ever  tak(!s  place.  The  acromion  process  is  more  frc(juently  broken  than  any  other 
part  of  the  bone,  and  there  is  sometimes,  in  young  subjects,  a  separation  of  the  epiphysis.  It 
IS  believed  that  many  of  the  cases  of  supposed  fracture  of  the  acromion,  with  fibrous  union, 
which  have  been  found  on  post-mortem  examination  are  really  cases  of  imperfectly  united 
e])iphysis.  !^ir  Astley  C.ooper  believed  that  most  fractures  of  this  bone  united  by  fibrous 
tissue,  and  the  cause  of  this  mode  of  um'on  was  the  difficulty  there  was  in  keeping  the  frac- 
tured ends  in  constant  ap|)osition.  TIk;  <'oraeoi(l  proces.s  is  occasionally  broken  off,  either  from 
direct  violence  or  perhaps,  rarely,  from  mus<"ular  action. 

Tumor.i  of  various  kinds  grow  from  the  scapula.  Of  the  innocent  form  of  tumors  probably 
the  osteomata  are  th(!  most  coirnnon.  When  an  osteoma  grows  from  the  venter  of  the  sca|)ida,  as  it 
sometimes  <loes,  it  is  of  the  compact  variety,  such  as  usually  grows  from  membrane-formed  bones, 
as  the  bones  of  the  skull.  This  wouhl  app(!ar  to  afford  evidence  that  this  i)ortion  of  the  bone 
is  foruKnl  from  membrane,  and  not,  like;  the  rest  of  the  bone,  from  cartilage.  Sarcomatous 
tumors  somctiiiK's  grow  from  the  scapula,  and  may  necessitate  removal  of  the  bone,  with  or 
witlDUt  amputation  of  the  up|)er  limb.  Removal  of  the  upper  limb  with  th<;  scapula  and  the 
outer  two-thirds  of  the  clavicle  is  known  as  the  intrrncajmlo-tlioracic,  arnputntinn.  The 
scapula  may  be  partially  res(!cted  or  completely  excised.  There  are  several  methods  of  com- 
plete ex<'ision.  'I'lie  bone  may  be  excised  by  a  T-sha{)ed  incision,  and,  the  flaps  being  reflected, 
the  removal  is  commenced  from  the  oosterior  or  vertebral  border,  so  that  the  subscapular 
vessels  which  lie  along  the  axillary  boraer  are  among  the  last  structures  divided,  and  can  be 
at  once  secured. 

THE  ARM. 

The  arm  is  tluit  portion  of  the  upj)er  extremity  which  i.s  situated  between  the 
.shoulder  and  the  elhow.     Its  skeleton  consists  of  a  single  bone,  the  humerus. 

The  Humerus  or  Upper  Arm  Bone  (Figs.  129,  130). 

The  hmnerus  (from  humerus,  or  more  correctly  umerus,  the  .shoulder)  is  the 
longest  and  largest  bone  of  the  upper  extremity;  it  presents  for  examination  a 
shaft  and  two  extremities. 

Upper  Extremity. — The  upper  extremity  presents  a  large,  rounded  head, 
joined  to  the  shaft  by  a  constricted  portion,  called  the  neck,  and  two  other  emi- 
nences, the  greater  and  lesser  tuberosities. 

The  Head  (caput  humeri). — The  head,  nearly  hemispherical  in  form,*  is  directed 
upward,  inward,  and  slightly  backward,  and  articulates  with  the  glenoid  cavity 
of  the  scapula;  its  surface  is  smooth  and  coated  with  cartilage  in  the  recent  .state. 
The  circumference  of  its  articular  surface  is  slightly  constricted,  and  is  termed 
the  anatomical  neck,  in  contradistinction  to  th(^  constriction  which  exists  below  the 
tiibcrosilics.  The  latter  is  called  the  surgical  neck  (collum  chirurgicum) ,hom  its 
often  being  the  seat  of  fracture.  It  should  be  remembered,  however,  that  frac- 
ture of  the  anatomical  neck  does  sometimes,  though  rarely,  occur. 

A.N'ATO.MiCAL  Nkck  (collurri  anatomicum). — The  anatomical  neck  is  oblicjuely 
directed,  forming  an  obtuse  angle  with  the  shaft.  It  is  more  distinctly  marked  in 
the  lower  half  of  its  circiunference  than  in  the  upper  half,  where  it  presents  a  nar- 
row groove,  .separating  the  head  from  the  tuberosities.    Its  circumference  affords 

'  ThouKh  the  head  is  nearly  heminpherical  in  form,  its  marfcin,  an  Sir  ('•.  Humphry  haw  xhown,  is  by  no  meanH 
a  true  circle.  U-s  greatest  measurement  is  from  the  top  of  the  l)icipital  groove  in  a  (jirection  downward,  inward, 
and  backward.  Hence  it  follows  that  the  greatest  elevation  of  the  arm  can  be  obtained  by  rolling  the  articular 
surface  in  this  direction-  that  is  to  say,  obliquely  upward,  outward,  and  forward. 

12 


178 


THE  SKELETON 


Surgical  nech.- 


>SUPINATOR    RADII    LONQUS. 


^■m 


^EXTENSOR    CARPI    RADIALI8 
LONQIOR. 


Common  origin  of- 

FLEXOR    CARPI    RADIALIS. 
PALMARIS    LONQUS. 
FLEXOR    SUBLIMIS    DIQITORUM. 
FLEXOR    CARPI    ULNARIS. 


'i'^.. 


Common  origin  of 

i  EXTENSOR    CARPI     RADIALIS    BREVISt 
(•  ■■       COMMUNIS    DIOITORUM. 

"       MINIMI    DIQITI. 
'         CARPI    ULNARIS. 
SUPINATOR    BREVIS. 


Fig.  129. — Left  humerus.     Anterior  view. 


THE  HUMERUS  179 

attachment  to  the  capsular  hgament  and  is  perforated  by  numerous  vascular 
foramina. 

Greater  Tuberosity  (tuberculum  ma  jus). — The  greater  tuberosity  is  situated  on 
the  outer  side  of  the  head  and  lesser  tuberosity.  Its  upper  surface  is  rounded  and 
marked  by  three  flat  facets,  separated  by  two  slight  ridges:  the  highest  facet  gives 
attachment  to  the  tendon  of  the  Supraspinatus;  the  middle  one,  to  the  Infra- 
spinatus; the  inferior  facet  and  the  shaft  of  the  bone  below  it,  to  the  Teres  minor. 
The  outer  surface  of  the  great  tuberosity  is  convex,  rough,  and  continuous  with 
the  outer  side  of  the  shaft. 

Lesser  Tuberosity  (tuberculum  minus). — The  lesser  tuberosity  is  more  promi- 
nent, although  smaller  than  the  greater:  it  is  situated  in  front  of  the  head,  and 
is  directed  inward  and  forward.  Its  summit  presents  a  prominent  facet  for  the 
insertion  of  the  tendon  of  the  Subscapularis  muscle.  The  tuberosities  are  sepa- 
rated from  one  another  by  a  deep  groove,  the  bicipital  groove  (sulcus  intertuber- 
cularis).  This  groove  lodges  the  long  tendon  of  the  Biceps  muscle,  with  which 
runs  a  branch  of  the  anterior  circumflex  artery.  It  commences  above  between 
the  two  tuberosities,  passes  obliquely  downward  and  a  little  inward,  and  ter- 
minates at  the  junction  of  the  upper  with  the  middle  third  of  the  bone.  It  is 
deep  and  narrow  at  the  commencement,  and  becomes  shallow  and  a  little  broader 
as  it  descends.  Its  borders  are  called,  respectively,  the  external  or  posterior  bicipital 
ridge  {crista  tuberculi  majoris)  and  the  internal  or  anterior  bicipital  ridge  (crista 
tuherculi  minoris),  and  form  the  upper  part  of  the  anterior  and  internal  borders 
of  the  shaft  of  the  bone.  In  the  recent  state  it  is  covered  with  a  thin  layer  of 
cartilage,  lined  by  a  prolongation  of  the  synovial  membrane  of  the  shoulder- 
joint,  and  receives  the  tendon  of  insertion  of  the  I-atissimus  dorsi  muscle. 

The  Shaft  (corpus  humeri) . — The  shaft  of  the  humerus  is  almost  cylindrical  in 
the  upper  half  of  its  extent,  prismatic  and  flattened  below,  and  presents  three 
borders  an<l  three  surfaces  for  examination. 

Anterior  Border. — The  anterior  border  runs  from  the  front  of  the  great  tuber- 
osity above  to  the  coronoid  depression  below,  separating  the  internal  from  the 
external  surface.  Its  upper  part  is  very  prominent  and  rough,  and  forms  the 
outer  lip  of  the  bicipital  groove.  It  is  sometimes  called  the  posterior  bicipital, 
external  bicipital,  or  pectoral  ridge  (crista  tuberculi  majoris),  and  serves  for  the 
attachment  of  the  tendon  of  the  Pectoralis  major.  About  its  centre  it  forms  the 
anterior  boundary  of  the  rough  deltoid  eminence  or  impression  (tuberositas  deltoidea) ; 
below,  it  is  smooth  and  rounded,  affording  attachment  to  the  Brachialis  anticus 
muscle. 

External  Border  (margo  lateralis). — The  external  border  runs  from  the  back 
part  of  the  greater  tuberosity  to  the  external  condyle,  and  separates  the  external 
from  the  posterior  surface.  It  is  rounded  and  indistinctly  marked  in  its  upper 
half,  serving  for  the  attachment  of  the  lower  part  of  the  insertion  of  the  Teres 
minor  muscle,  and  below  this  of  the  external  head  of  the  Triceps  muscle ;  its  centre  is 
traversed  by  a  broad  but  shallow,  oblique  depression,  the  musculo-spiral  groove 
(sulcus  nervi  radialis) ;  its  lower  part  is  marked  by  a  prominent,  rough  margin, 
a  little  curved  from  behind  forward,  the  external  supracondylar  or  epicondylic  ridge 
(marr/o  lateralis),  which  presents  an  anterior  lip  for  the  attachment  of  the  Supin- 
ator longus  above  and  Extensor  carpi  radialis  longior  below,  a  posterior  lip  for 
the  Triceps,  and  an  intermediate  space  for  the  attachment  of  the  external  inter- 
muscular septum. 

Internal  Border  (margo  medialis). — The  internal  border  extends  from  the  lesser 
tuberosity  to  the  internal  condyle.  Its  upper  third  is  marked  by  a  prominent 
ridge,  forming  the  posterior  lip  of  the  bicipital  groove,  and  gives  attachment  to 
the  tendon  of  the  Teres  major.  About  its  centre  is  an  impression  for  the  attach- 
ment of  the  Coracobrachialis,  and  just  below  this  is  seen  the  entrance  of  the 


180 


THE   SKELETON 


'«^. 


Fig.  130. — Left  humerus.    Posterior  surface. 


nutrient  canal,  directed  downward.  Sometimes 
there  is  a  second  canal  situated  at  the  com- 
mencement of  the  musculo-spiral  groove,  for  a 
nutrient  artery  derived  from  the  superior  pro- 
funda branch  of  the  brachial  artery.  The  in- 
ferior third  of  this  border  is  raised  into  a  slig-ht 
ridge,  the  internal  supracondylar  or  epicondylic 
ridge  (margo  medialis),  which  becomes  very 
prominent  below;  it  presents  an  anterior  lip 
for  the  attachment  of  the  Brachialis  anticus 
muscle,  a  posterior  lip  for  the  internal  head  of 
the  Triceps  muscle,  and  an  intermediate  space 
for  the  attachment  of  the  internal  intermuscular 
septum. 

External  Surface  (facies  anterior  lateralis). — 
The  external  surface  is  directed  outward  above, 
where  it  is  smooth,  rounded,  and  covered  by  the 
Deltoid  muscle ;  forward  and  outward  below, 
where  it  is  slightly  concave  from  above  down- 
ward, and  gives  origin  to  part  of  the  Brachi- 
alis anticus  muscle.  About  the  middle  of  this 
surface  is  seen  a  rough,  triangular  impression 
for  the  insertion  of  the  Deltoid  muscle,  deltoid 
impression  (tuberositas  deltoidea) ;  and  below  it 
the  musculo-spiral  groove,  directed  obliquely 
from  behind,  forward  and  downward,  and  trans- 
mitting the  musculo-spiral  nerve  and  superior 
profunda  artery. 

Internal  Surface  (facies  anterior  medialis). — 
The  internal  surface,  less  extensive  than  the  ex- 
ternal, is  directed  inward  above,  forward  and 
inward  below;  at  its  upper  part  it  is  narrow  and 
forms  the  floor  of  the  bicipital  groove:  to  it  is 
attached  the  Latissimus  dorsi.  The  middle  part 
of  this  surface  is  slightly  rough  for  the  attach- 
ment of  some  of  the  fibres  of  the  tendon  of 
insertion  of  the  Coraco-brachialis ;  its  loweM 
part  is  smooth,  concave  from  above  downward^ 
and  gives  attachment  to  the  Brachialis  anticus 
muscle.^  A  little  below  the  middle  of  the  shafl 
is    the    nutrient    foramen    (foramen  nutriciwmn 

'  A  small,  hook-shaped  process  of  bone,  the  supracondylar  prt^ 
cess,  varying  from  '/lo  to  ^/4  of  an  inch  in  length,  is  not  infrequentl 
found  projecting  from  the  inner  surface  of  the  shaft  of  the  humeru 
two  inches  above  the  internal  condyle.  It  is  curved  downward 
forward,  and  inward,  and  its  pointed  extremity  is  connected  t 
the  internal  border,  just  above  the  inner  condyle,  by  a  ligamel 
or  fibrous  band,  which  gives  origin  to  a  portion  of  the  Pronato 
radii  teres;  through  the  arch  completed  by  this  fibrous  band  tb 
median  nerve  and  brachial  artery  pass  when  these  structun 
deviate  from  their  usual  course.  Sometimes  the  nerve  alone  i 
transmitted  through  it,  or  the  nerve  may  be  accompanied  by  tfc 
ulnar  artery  in  cases  of  high  division  of  the  brachial.  A  well-marke 
groove  is  usually  found  behind  the  process  in  which  the  nerve  and 
artery  are  lodged.  This  space  is  analogous  to  the  .supracondyloi^ 
foramen  in  many  animals,  and  probably  serves  in  them  to  protei 
the  nerve  and  artery  from  compression  during  the  contractio 
of  the  muscles  in  this  region.  A  detailed  account  jf  this  procea 
is  given  by  Dr.  Struthers,  in  his  Anatomical  and  Physiologiea 
Observations,  p.  202.  An  acces.sory  portion  of  the  Coraco-bra 
chialis  muscle  is  frequently  connected  with  this  process,  accordint 
to  Mr.  J.  Wood  (Journal  of  Anat.  and  Phys.,  No.  1,  November 
1866.  p.  47). 


THE  HUMERUS  181 

This  leads  into  a  nutrient  canal  (canalis  nutricius),  which  is  directed  toward  the 
elbow-joint  (distally) . 

Posterior  Surface  (fades  posterior), — The  posterior  surface  (Fig.  130)  appears 
somewhat  twisted,  so  that  its  upper  part  is  directed  a  little  inward,  its  lower  part 
backward  and  a  little  outward.  Nearly  the  whole  of  this  surface  is  covered  by 
the  external  and  internal  heads  of  the  Triceps,  the  former  of  which  is  attached 
to  its  upper  and  outer  part,  the  latter  to  its  inner  and  back  part,  the  two  being 
separated  by  the  musculo-spiral  groove. 

Lower  Extremity. — The  lower  extremity  is  flattened  from  before  back- 
ward, and  curved  slightly  forward;  it  terminates  below  in  a  broad,  articular 
surface  which  is  divided  into  two  parts  by  a  slight  ridge.  Projecting  on 
either  side  are  the  external  and  internal  condyles  (epicondyliis  lateralis  and 
epicondylus  medialis).  By  some  anatomists  the  external  condyle  is  called  the 
external  epicondyle  and  the  internal  condyle  is  called  the  internal  epicondyle. 
Others  call  the  internal  condyle  the  epitrochlea.  The  articular  surface  extends  a 
little  lower  than  the  condyles,  and  is  curved  slightly  forward,  so  as  to  occupy  the 
more  anterior  part  of  the  bone;  its  greatest  breadth  is  in  the  transverse  diameter, 
and  it  is  obliquely  directed,  so  that  its  inner  extremity  occupies  a  lower  level  than 
the  outer.  The  outer  portion  of  the  articular  surface  presents  a  smooth,  rounded 
eminence,  which  has  received  the  name  of  the  capitellum,  or  radial  head  of  the 
humerus  {capitulum  humeri);  it  articulates  with  the  cup-shaped  depression  on 
the  head  of  the  radius,  and  is  limited  to  the  front  and  lower  part  of  the  bone, 
not  extending  as  far  back  as  the  other  portion  of  the  articular  surface.  On  the 
inner  side  of  this  eminence  is  a  shallow,  groove,  in  which  is  received  the  inner 
margin  of  the  head  of  the  radius.  Above  the  front  part  of  the  capitellum  is  a 
slight  depression,  the  radial  fossa  (fossa  radialis),  which  receives  the  anterior 
bonier  of  the  head  of  the  radius  when  the  forearm  is  flexed.  The  inner  por- 
tion of  the  articular  surface,  the  trochlea  (trochlea  humeri),  presents  a  deep 
depression  between  two  well-marked  borders.  This  surface  is  convex  from 
before  backward,  concave  from  side  to  side,  and  occupies  the  anterior,  lower, 
and  posterior  parts  of  the  bone.  The  external  border,  less  prominent  than  the 
internal,  corresponds  to  the  interval  between  the  radius  and  the  ulna.  The 
internal  border  is  thicker,  more  prominent,  and  consequently  of  greater  length, 
than  the  external.  The  grooved  portion  of  the  articular  surface  fits  accurately 
within  the  greater  sigmoid  cavity  of  the  ulna:  it  is  broader  and  deeper  on  the  pos- 
terior than  on  the  anterior  aspect  of  the  bone,  and  is  inclined  obliquely  from 
behind  forward  and  from  without  inward.  Above  the  front  part  of  the  trochlear 
surface  is  seen  a  smaller  depression,  the  coronoid  fossa  (fossa  coronoidea),  which 
receives  the  coronoid  process  of  the  ulna  during  flexion  of  the  forearm.  Above 
the  back  part  of  the  trochlear  surface  is  a  deep,  triangular  depression,  the 
olecranon  fossa  (fossa  olecrani),  in  which  is  received  the  summit  of  the  olecranon 
process  in  extension  of  the  forearm.  These  fossae  are  separated  from  one  another  by 
a  thin,  transparent  lamina  of  bone,  which  is  sometimes  perforated  by  a  foramen, 
the  supratrochlear  foramen;  their  upper  margins  afford  attachment  to  the  anterior 
and  posterior  ligaments  of  the  elbow-joint,  and  they  are  lined,  in  the  recent  state, 
by  the  synovial  membrane  of  this  articulation.  The  articular  surfaces,  in  the 
recent  state,  are  covered  with  a  thin  layer  of  cartilage.  The  external  epicon- 
dyle (epicondylus  lateralis)  is  a  small,  tubercular  eminence,  less  prominent 
than  the  internal,  curved  a  little  forward,  and  giving  attachment  to  the  external 
lateral  ligament  of  the  elbow-joint,  and  to  a  tendon  common  to  the  origin  of  some 
of  the  extensor  and  supinator  muscles.  The  internal  epicondyle  (epitrochlea  or 
epicondylus  medialis),  larger  and  more  prominent,  and  therefore  more  liable  to 
fracture,  than  the  external,  is  directed  a  little  backward:  it  gives  attachment  to 
the  internal  lateral  ligament,  to  the  Pronator  radii  teres,  and  to  a  tendon  common 


182 


THE  SKELETON 


to  the  origin  of  some  of  the  flexor  muscles  of  the  forearm.  The  ulnar  nerve  runs 
in  a  groove,  the  ulnar  groove  (sulcus  nervi  ulnaris),  at  the  back  of  the  internal 
condyle,  or  between  it  and  the  olecranon  process.  These  condyles  are  directly 
continuous  above  with  the  external  and  internal  supracondylar  ridges. 

Structure. — The  extremities  consist  of  cancellous  tissue,  covered  with  a  thin 
compact  layer;  the  shaft  is  composed  of  a  cylinder  of  compact  tissue,  thicker  at 
the  centre  than  at  the  extremities,  and  hollowed  out  by  a  large  medullary  canal, 
which  extends  along  its  whole  length.  In  the  head  of  the  humerus  the  plates 
of  the  cancellous  tissue  are  arranged  in 
curves  (Fig.  131)  known  as  pressure  curves. 
Most  of  the  bone-plates  are  at  right  angles 
to  the  plane  of  the  articular  surface  (the 
lines  of  greatest  pressure),  and  they  are 
bound  together  by  other  bone-fibres,  which 
usually  correspond    to   the    plane  of   the 


Epiphyses  of  head  and  1      ^^ 
tuberosities  Mend   at     %-/^ 
5th  year,  and  unite  \        ' 
with   shaft    at   2(Hh 


year. 


Fig.  131. — Diagram  showing  the  architecture  of  the  supe- 
rior extremity  of  the  humerus.    (Poirier  and  Charpy.) 


Unites  with  shaft  ]  c5 
at  18th  year.      J 


Sha/t  at 

Fig.   132.^Plan  of   the  development  of   the 
humerus  by  seven  centres. 


articulation  (the  lines  of  greatest  tension) .  This  arch-like  arrangement  strength- 
ens the  head  of  the  bone,  and  it  is  further  strengthened  by  the  binding  fibres. 

Development. — By  seven,  or  occasionally  eight,  centres  (Fig.  132) :  one  for  the 
shaft,  one  for  the  head,  one  for  the  tuberosities,  one  for  the  radial  head,  one  for 
the  trochlear  portion  of  the  articular  surface,  and  one  for  each  condyle.  The 
nucleus  for  the  shaft  appears  near  the  centre  of  the  bone  in  the  eighth  week,  and 
soon  extends  toward  the  extremities.  At  birth  the  humerus  is  ossified  nearly  in 
its  whole  length,  the  extremities  remaining  cartilaginous.  During  the  first  year, 
sometimes  even  before  birth,  ossification  commences  in  the  head  of  the  bone,  and 
during  the  third  year  the  centre  for  the  tuberosities  makes  its  appearance,  usually 
by  a  single  ossific  point,  but  sometimes,  according  to  Beclard,  by  one  for  each 
tuberosity,  that  for  the  lesser  being  small  and  not  appearing  until  the  fifth  year. 
By  the  sixth  year  the  centres  for  the  head  and  tuberosities  have  increased  in  size 
and  become  joined,  so  as  to  form  a  single  large  epiphysis. 

The  lower  end  of  the  humerus  is  developed  in  the  following  manner:  At  the 
end  of  the  second  year  ossification  commences  in  the  capitellum,  and  from  this 
point  extends  inward,  so  as  to  form  the  chief  part  of  the  articular  end  of  the  bone, 


THE   HUMERUS  183 

the  centre  for  the  inner  part  of  the  trochlea  not  appearing  until  about  the  age  of 
twelve.  Ossification  commences  in  the  internal  condyle  about  the  fifth  year,  and 
in  the  external  one  not  until  about  the  thirteenth  or  fourteenth  year.  About  six- 
teen or  seventeen  years  the  outer  condyle  and  both  portions  of  the  articulating 
surface  (which  have  already  joined)  unite  with  the  shaft;  at  eighteen  years  the  inner 
condyle  becomes  joined;  while  the  upper  epiphysis,  although  the  first  formed,  is 
not  united  until  about  the  twentieth  year. 

Articulations. — With  the  glenoid  cavity  of  the  scapula  and  with  the  ulna  and 
radius. 

Attachment  of  the  Muscles. — To  twenty-four:  to  the  greater  tuberosity,  the 
Supraspinatus,  Infraspinatus,  and  Teres  minor;  to  the  lesser  tuberosity,  the 
Subscapularis ;  to  the  anterior  bicipital  ridge,  the  Pectoralis  major;  to  the  posterior 
bicipital  ridge,  the  Teres  major;  to  the  bicipital  groove,  the  Latissimus  dorsi;  to 
the  shaft,  the  Deltoid,  Coraco-brachialis,  Brachialis  anticus,  external  and  internal 
heads  of  the  Triceps;  to  the  internal  condyle,  the  Pronator  radii  teres,  and  common 
tendon  of  the  Flexor  carpi  radialis,  Palmaris  longus,  Flexor  sublimis  digitorum, 
and  Flexor  carpi  ulnaris;  to  the  external  condyloid  ridge,  the  Supinator  longus 
and  Extensor  carpi  radialis  longior;  to  the  external  condyle,  the  common  tendon 
of  the  Extensor  carpi  radialis  brevior.  Extensor  communis  digitorum,  Extensor 
minimi  digiti,  Extensor  carpi  ulnaris,  and  Supinator  brevis;  to  the  back  of  the 
external  condyle,  the  Anconeus, 

Surface  Form. — The  humerus  is  almost  entirely  clothed  by  the  muscles  which  surround  it, 
and  the  only  ])arts  of  this  bone  which  are  strictly  subcutaneous  are  small  portions  of  the 
internal  and  external  condyles.  In  addition  to  these,  the  tuberosities  and  a  part  of  the  head 
of  the  bone  can  be  felt  under  the  skin  and  muscles  by  which  they,  are  covered.  Of  these  the 
greater  tuberosity  forms  the  most  prominent  bony  point  of  the  shoulder,  extending  beyond  the 
acromion  process  and  covered  by  the  Deltoid  muscle.  It  influences  materially  the  surface  form 
of  the  shoulder.  It  is  best  felt  while  the  arm  is  lying  loosely  by  the  side;  if  the  arm  be  raised, 
it  recedes  from  under  the  finger.  The  lesser  tuberosity,  directed  forward  and  inward,  is  to  be 
felt  to  the  inner  side  of  the  greater  tuberosity,  just  below  the  acromio-clavicular  joint.  Between 
the  two  tuberosities  lies  the  bicipital  groove.  This  can  be  defined  by  placing  the  finger  and 
making  firm  pressure  just  internal  to  the  greater  tuberosity;  then,  by  rotating  the  humerus,  the 
groove  will  be  felt  to  pass  under  the  finger  as  the  bone  is  rotated.  With  the  arm  abducted  from 
the  side,  by  pressing  deeply  in  the  axilla  the  lower  part  of  the  head  of  the  bone  is  to  be  felt. 
On  each  side  of  the  elbow-joint,  and  just  above  it,  the  internal  and  external  condyles  of  the 
bone  are  to  be  felt.  Of  these  the  internal  is  the  more  prominent,  but  the  ridge  passing  upward 
from  it,  the  internal  condyloid  ridge,  is  much  less  marked  than  the  external,  and,  as  a  rule,  is 
not  to  be  felt.  Occasionally,  however,  we  find  along  this  border  the  hook-shaped  process  men- 
tioned above.  The  external  condyle  is  most  plainly  to  be  seen  during  semiflexion  of  the  fore- 
arm, and  its  position  is  indicated  by  a  depression  between  the  attachment  of  the  adjacent  mus- 
cles. From  it  is  to  be  felt  a  strong  bony  ridge  running  up  the  outer  border  of  the  shaft  of  the 
bone.  This  is  the  external  supracondylar  ridge;  it  is  concave  forward,  and  corresponds  with 
the  curved  direction  of  the  lower  extremity  of  the  humerus. 

Surgical  Anatomy. — There  are  several  points  of  surgical  interest  connected  with  the 
humerus.  First,  as  regards  its  development.  The  upper  end,  though  the  first  to  ossify,  is  the 
last  to  join  the  shaft,  and  the  length  of  the  bone  is  mainly  due  to  growth  from  this  upper 
epiphysis.  Hence,  in  cases  of  amputation  of  the  arm  in  young  subjects  the  humerus  continues 
to  grow  considerably,  and  the  end  of  the  bone,  which  immediately  after  the  operation  was  cov- 
ered with  a  thick  cushion  of  soft  tissue,  begins  to  project,  thinning  the  soft  parts  and  rendering 
the  stump  conical.  This  may  necessitate  another  operation,  which  consists  in  the  removal  of  a 
couple  of  inches  or  so  of  the  bone,  and  even  after  this  operation  a  recurrence  of  the  conical  stump 
may  take  place. 

There  are  several  points  of  surgical  interest  in  connection  with  fractures.  First,  as  regard 
their  causation:  the  bone  may  be  broken  by  direct  or  indirect  violence  like  the  other  long  bones, 
but,  in  addition  to  this,  it  is  probably  more  frequently  fractured  by  muscular  action  than  any 
other  of  this  class  of  bone  in  the  body.  It  is  usually  the  shaft,  just  below  the  insertion  of  the 
Deltoid,  which  is  thus  broken.  Mr.  Pick  has  seen  the  accident  happen  from  throwing  a  stone,  and 
in  an  apparently  healthy  adult  from  cutting  a  piece  of  hard  "cake  tobacco"  on  a  table.  In  this 
latter  case  there  was  no  disease  of  the  bone  that  could  be  discovered.  Fractures  of  the  upper 
end  may  take  place  through  the  anatomical  neck,  through  the  surgical  neck,  or  separation  of  the 


184  "J" HE  SKELETON 

greater  tuberosity  may  occur.  Fracture  of  the  anatomical  neck  is  a  very  rare  accident ;  in  fact, 
it  is  doubted  by  some  whether  it  ever  occurs.  These  fractures  are  usually  considered  to  be 
intracapsular,  but  they  are  probably  partly  within  and  partly  without  the  capsule,  as  the  lower 
part  of  the  capsule  is  inserted  some  little  distance  below  the  anatomical  neck,  while  the  upper 
part  is  attached  to  it.  They  may  be  impacted  or  non-impacted.  In  most  cases  there  is  little  or 
no  displacement  on  account  of  the  capsule,  in  whole  or  in  part,  remaining  attached  to  the  lower 
fragment.  But  occasionally  a  very  remarkable  alteration  in  position  takes  place;  the  upper 
fragment  turns  on  its  own  axis,  so  that  the  cartilaginous  surface  of  the  head  rests  against  the 
upper  end  of  the  lower  fragment.  When  the  fractured  end  is  entirely  separated  from  all  its 
surroundings,  its  vascular  supply  must  be  entirely  cut  off,  and  one  would  expect  it,  theoretically, 
to  necrose.  But  this  must  be  exceedingly  rare,  for  Gurlt  was  unable  to  find  a  single  authenti- 
cated case  recorded.  Separation  of  the  upper  epiphysis  of  the  humerus  sometimes  occurs  in  the 
young  subject,  and  is  marked  by  a  characteristic  deformity  by  which  the  lesion  may  be  at  once 
recognized.  This  consists  in  the  presence  of  an  abrupt  projection  at  the  front  of  the  joint  some 
short  distance  below  the  coracoid  process,  caused  by  the  upper  end  of  the  lower  fragment.  In 
fractures  of  the  shaft  of  the  humerus  the  lesion  may  take  place  at  any  point,  but  appears  to  be 
more  common  in  the  lower  than  in  the  upper  part  of  the  bone.  The  points  of  interest  in  con- 
nection with  these  fractures  are:  (1)  That  the  musculo-spiral  nerve  may  be  injured  as  it  lies  in  the 
groove  on  the  bone,  or  may  become  involved  in  the  calluL  which  is  subsequently  thrown  out; 
and  (2)  the  frequency  of  non-union.  This  is  believed  to  be  more  common  in  the  humerus  than 
in  any  other  bone,  and  various  causes  have  been  assigned  for  it.  It  would  seem  most  probably 
to  be  due  to  the  difficulty  that  there  is  in  fixing  the  shoulder-joint  and  the  upper  fragment,  and 
possibly  the  elbow-joint  and  lower  fragment  also.  Other  causes  which  have  been  assigned 
for  the  non-union  are:  (1)  That  in  attempting  passive  motion  of  the  elbow-joint  to  overcome 
any  rigidity  which  may  exist,  the  movement  does  not  take  place  at  the  articulation,  but  at  the 
seat  of  fracture;  or  that  the  patient,  in  consequence  of  the  rigidity  of  the  elbow,  in  attempting 
to  flex  or  extend  the  forearm  moves  the  fragment  and  not  the  joint.  (2)  The  presence  of  small 
portions  of  muscular  tissue  between  the  broken  ends.  (3)  Want  of  support  to  the  elbow,  so 
that  the  weight  of  the  arm  tends  to  drag  the  lower  fragment  away  from  the  upper.  An  impor- 
tant distinction  to  make  in  fractures  of  the  lower  end  of  the  humerus  is  between  those  that 
involve  the  elbow-joint  and  those  which  do  not;  the  former  are  always  serious,  as  they  may  lead 
to  stiffness  of  the  joint  and  impairment  of  the  utility  of  the  limb.  They  include  the  T-shaped 
fracture  and  oblique  fractures  which  involve  the  articular  surface.  The  fractures  which  do  not 
involve  the  joint  are  the  transverse  above  the  condyles  and  the  so-called  epitrochlear  fracture, 
in  which  the  tip  of  the  internal  condyle  is  broken  off,  generally  by  direct  violence. 

Under  the  head  of  separation  of  the  lower  epiphysis  two  separate  injuries  have  been  described: 
One  where  the  whole  oi  the  four  ossific  centres  which  form  the  lower  extremity  of  the  bone  are 
separated  from  the  shaft;  and  secondly,  where  the  articular  portion  is  alone  separated,  the  two 
condyles  remaining  attached  to  the  shaft  of  the  bone.  The  epiphysial  line  between  the  shaft 
and  lower  end  runs  across  the  bone  just  above  the  tips  of  the  condyles,  a  point  to  be  borne  in 
mind  in  performing  the  operation  of  excision. 

Tumors  originating  from  the  humerus  are  of  frequent  occurrence.  A  not  uncommon  place 
for  a  chondroma  tc  grow  from  is  the  shaft  of  the  bone  somewhere  in  the  neighborhood  of  the 
insertion  of  the  deltoid.     Sarcomata  frequently  grow  from  this  bone. 


THE  FOREARM. 

The  forearm  is  that  portion  of  the  upper  extremity  which  is  situated  between 
the  elbow  and  the  wrist.  Its  skeleton  is  composed  of  two  bones,  the  ulna  and 
radius. 

The  Ulna  or  Elbow  Bone. 

The  ulna  (Figs.  133  and  134),  so  called  from  its  forming  the  elbow  {coXivrj),  is  a 
long  bone,  prismatic  in  form,  placed  at  the  inner  side  of  the  forearm,  parallel  with 
the  radius.  It  is  the  larger  and  longer  of  the  two  bones.  Its  upper  extremity,  of 
great  thickness  and  strength,  forms  a  large  part  of  the  articulation  of  the  elbow- 
joint;  it  diminishes  in  size  from  above  downward,  its  lower  extremity  being  very 
small,  and  excluded  from  the  wrist-joint  by  the  interposition  of  an  interarticular 
fibro-cartilage.  It  is  divisible  into  a  shaft  and  two  extremities. 
.  Upper  Extremity. — The  upper  extremity,  the  strongest  part  of  the  bone, 
presents  for  examination  two  large,  curved  processes,  the  olecranon  process  and 


THE    ULNA 


185 


Ulna 


FLEXOR    DIQITORUM 
SUBLIMIS. 


PRONATOR 
RADII    TERES 


Radius. 


i^^lr^^^-^ii&. 


Occasional  origin  of 

FLEXOR    LONQUS    POLLICIS. 


Radial  orifjin  o/flexob 

DIQITORUM    SUBLIMIS. 


SUPINATOR    LONQUS. 

Groove  for  ext.  ossis 

METACARPI    POLLICIS 
and  EXT,   BREV.   POLL. 


Styloid  process. 
Fig.  133. — Bones  of  the  left  forearm.     Anterior  surface. 


186  'J'HE   SKELETON 

the  coronoid  process;  and  two  concave,  articular  cavities,  the  greater  and  lesser 
sigmoid  cavities. 

Olecranon  Process  {olecranon). — The  olecranon  process  {ioXivrj,  elbow;  xpaucuv, 
head)  is  a  large,  thick,  curved  eminence  situated  at  the  upper  and  back  part  of 
the  ulna.  It  is  curved  forward  at  the  summit  so  as  to  present  a  prominent  tip 
which  is  received  into  the  olecranon  fossa  of  the  humerus  in  extension  of  the  fore- 
arm ;  its  base  being  contracted  where  it  joins  the  shaft.  This  is  the  narrowest  part 
of  the  upper  end  of  the  ulna,  and,  consequently,  the  most  usual  seat  of  fracture. 
The  posterior  surface  of  the  olecranon,  directed  backward,  is  triangular,  smooth, 
subcutaneous,  and  covered  by  a  bursa.  Its  upper  surface  is  of  a  quadrilateral 
form,  marked  behind  by  a  rough  impression  for  the  attachment  of  the  Triceps 
muscle;  and  in  front,  near  the  margin,  by  a  slight  transverse  groove  for  the 
attachment  of  part  of  the  posterior  ligament  of  the  elbow-joint.  Its  interior  sur- 
face is  smooth,  concave,  covered  with  cartilage  in  the  recent  state,  and  forms  the 
upper  and  back  part  of  the  great  sigmoid  cavity.  The  lateral  borders  present 
a  continuation  of  the  same  groove  that  was  seen  on  the  margin  of  the  superior 
surface;  they  serve  for  the  attachment  of  ligaments — viz.,  the  back  part  of  the 
internal  lateral  ligament  internally,  the  posterior  ligament  externally.  To  the 
inner  border  is  also  attached  a  part  of  the  Flexor  carpi  ulnaris,  while  to  the  outer 
border  is  attached  the  Anconeus  muscle. 

Coronoid  Process  {processus  coronoideus) . — ^The  coronoid  process  {xopcovfj,  any- 
thing hooked  like  a  crow's  beak)  is  a  triangular  eminence  of  bone  which  projects 
horizontally  forward  from  the  upper  and  front  part  of  the  ulna.  Its  base  is  con- 
tinuous with  the  shaft,  and  of  considerable  strength;  so  much  so  that  fracture  of 
it  is  an  accident  of  rare  occurrence.  Its  apex  is  pointed,  slightly  curved  upward, 
and  is  received  into  the  coronoid  depression  of  the  humerus  in  flexion  of  the  forearm. 
Its  upper  surface  is  smooth,  concave,  and  forms  the  lower  part  of  the  greater  sig- 
moid cavity.  The  under  surface  is  concave.  At  the  junction  of  this  surface  with 
the  shaft  is  a  rough  eminence,  the  tubercle  of  the  ulna  {tuberositas  ulnae),  for  the 
attachment  of  the  oblique  ligament  of  the  superior  radio-ulnar  articulation  and  the 
Brachialis  anticus  muscle.  Its  outer  surface  presents  a  narrow,  oblong,  articular 
depression,  the  lesser  sigmoid  cavity.  The  inner  surface,  by  its  prominent,  free 
margin,  serves  for  the  attachment  of  part  of  the  internal  lateral  ligament.  At 
the  front  part  of  this  surface  is  a  small,  rounded  eminence  for  the  attachment  of 
one  head  of  the  Flexor  sublimis  digitorum ;  behind  the  eminence,  a  depression  for 
part  of  the  origin  of  the  Flexor  profundus  digitorum;  and,  descending  from  the 
eminence,  a  ridge  which  gives  attachment  to  one  head  of  the  Pronator  radii  teres. 
Generally,  the  Flexor  longus  pollicis  has  an  origin  from  the  lower  part  of  the 
coronoid  process  by  a  rounded  bundle  of  muscular  fibres. 

Greater  Sigmoid  Cavity  {incisura  semilunaris). — ^The  greater  sigmoid  cavity,  so 
called  from  its  resemblance  to  the  old  shape  of  the  Greek  letter  2',  is  a  semi- 
lunar depression  of  large  size,  formed  by  the  olecranon  and  coronoid  processes, 
and  serving  for  articulation  with  the  trochlear  surface  of  the  humerus.  About 
the  middle  of  either  lateral  border  of  this  cavity  is  a  notch  which  contracts  it 
somewhat,  and  serves  to  indicate  the  junction  of  the  two  processes  of  which  it  is 
formed.  The  cavity  is  concave  from  above  downward,  and  divided  into  two 
lateral  parts  by  a  smooth,  elevated  ridge  which  runs  from  the  summit  of  the 
olecranon  to  the  tip  of  the  coronoid  process.  Of  these  two  portions,  the  internal 
is  the  larger,  and  is  slightly  concave  transversely;  the  external  portion  is  convex 
above,  slightly  concave  below.  The  articular  surface,  in  the  recent  state,  is 
covered  with  a  thin  layer  of  cartilage. 

Lesser  Sigmoid  Cavity  {incisura  radialis). — The  lesser  sigmoid  cavity  is  a  narrow,, 
oblong,  articular  depression,  placed  on  the  outer  side  of  the  coronoid  process,  and 
receives  the  lateral  articular  surface  of  the  head  of  the  radius.    It  is  concave  from 


THE    ULKA 
Ulna. 


187 


For  EXT.  CARPI    RAD.  LON' 

extensor  carpi  radialis  brevl'or. 

extensor  lonqus  pollici 
Fig.  134. 


FLEXOR   SUBLIMIS    DIOITORUM. 


For    EXTENSOR   CARPI    ULNAHI8. 
For    EXTENSOR    MINIMI    D;OITI. 


J!br| 
Bones  of  the  left  forearm 


EXTENSOR    INDICIS. 

EXTENSOR    COMMUNIS   DIQITORUM. 


Posterior  surface. 


188  THE   SKELETON 

before  backward,  and  its  extremities,  which  are  prominent,  serve  for  the  attach- 
ment of  the  orbicular  Hgament.  In  the  recent  state  it  is  covered  with  a  thin  layer 
of  cartilage. 

The  Shaft  {corpus  ulnos). — The  shaft,  at  its  upper  part,  is  prismatic  in  form,  and 
curved  from  behind  forward  and  from  without  inward,  so  as  to  be  convex  behind 
and  externally;  its  central  part  is  quite  straight;  its  lower  part  rounded,  smooth, 
and  bent  a  little  outward;  it  tapers  gradually  from  above  downward,  and  presents 
for  examination  three  borders  and  three  surfaces. 

Anterior  or  Palmar  Border  (margo  volaris). — The  anterior  border  commences 
above  at  the  prominent  inner  angle  of  the  coronoid  process,  and  terminates  below 
in  front  of  the  styloid  process.  It  is  well  marked  above,  smooth  and  rounded  in 
the  middle  of  its  extent,  and  affords  attachment  to  the  Flexor  profundus  digitorum : 
its  lower  fourth,  marked  off  from  the  rest  of  the  border  by  the  commencement  of 
an  oblique  ridge  on  the  anterior  surface,  serves  for  the  attachment  of  the  Pronator 
quadratus.     It  separates  the  anterior  from  the  internal  surface. 

Posterior  or  Dorsal  Border  {margo  dor  sails) . — The  posterior  border  commences 
above  at  the  apex  of  the  triangular  subcutaneous  surface  at  the  back  part  of  the 
olecranon,  and  terminates  below  at  the  back  part  of  the  styloid  process;  it  is  well 
marked  in  the  upper  three-fourths,  and  gives  attachment  to  the  aponeurosis  com- 
mon to  the  Flexor  carpi  ulnaris,  the  Extensor  carpi  ulnaris,  and  the  Flexor  pro- 
fundus digitorum  muscles;  its  lower  fourth  is  smooth  and  rounded.  This  border 
separates  the  internal  from  the  posterior  surface. 

External  or  Interosseous  Border  (crista  interossea). — The  external  or  interosseous 
border  commences  above  by  the  union  of  two  lines,  which  converge  one  from  each 
extremity  of  the  lesser  sigmoid  cavity,  enclosing  between  them  a  triangular  space 
for  the  attachment  of  part  of  the  Supinator  brevis.  The  external  line  is  the 
crista  m.  supinatoris.  The  interosseous  border  of  the  ulna  terminates  below  at 
the  middle  of  the  head  of  the  ulna.  Its  two  middle  fourths  are  very  prominent; 
its  lower  fourth  is  smooth  and  rounded.  This  border  gives  attachment  to  the 
interosseous  membrane,  and  separates  the  anterior  from  the  posterior  surface. 

Anterior  or  Palmar  Surface  (fades  volaris) . — The  anterior  surface,  much  broader 
above  than  below,  is  concave  in  the  upper  three-fourths  of  its  extent,  and  affords 
attachment  to  the  Flexor  profundus  digitorum;  its  lower  fourth,  also  concave,  is 
covered  by  the  Pronator  quadratus.  The  lower  fourth  is  separated  from  the 
remaining  portion  of  the  bone  by  a  prominent  ridge,  directed  obliquely  from 
above  downward  and  inward;  this  ridge,  the  oblique  or  pronator  ridge,  marks  the 
extent  of  attachment  of  the  Pronator  quadratus.  At  the  junction  of  the  upper 
with  the  middle  third  of  the  bone  is  the  nutrient  foramen  (foramen  nutricium). 
It  opens  into  the  nutrient  canal  (canalis  nutricius),  which  is  directed  obliquely 
upward  and  inward  (proximally) . 

Posterior  or  Dorsal  Surface  (facies  dorsalis) . — The  posterior  surface,  directed  back- 
ward and  outward,  is  broad  and  concave  above,  somewhat  narrower  and  convex  in 
the  middle  of  its  course,  narrow,  smooth,  and  rounded  below.  It  presents,  above,  an 
oblique  ridge,  which  runs  from  the  posterior  extremity  of  the  lesser  sigmoid  cavity, 
downward  to  the  posterior  border;  the  triangular  surface  above  this  ridge  receives 
the  insertion  of  the  Anconeus  muscle,  whilst  the  upper  part  of  the  ridge  itself  affords 
attachment  to  the  Supinator  brevis.  The  surface  of  bone  below  this  is  subdivided 
by  a  longitudinal  ridge,  sometimes  called  the  perpendicular  line,  into  two  parts; 
the  internal  part  is  smooth,  and  covered  by  the  Extensor  carpi  ulnaris;  the  exter- 
nal portion,  wider  and  rougher,  gives  attachment  from  above  downward  to  part 
of  the  Supinator  brevis,  the  Extensor  ossis  metacarpi  pollicis,  the  Extensor  longus 
pollicis,  and  the  Extensor  indicis  muscles. 

Internal  Surface  (facies  medialis). — The  internal  surface  is  broad  and  concave 
above,  narrow  and  convex  below.    It  gives  attachment  by  its  upper  three-fourths 


THE     ULNA 


189 


to  the  Flexor  profundus  digitorura  muscle:   its  lower  fourth  is  subcutaneous. 
The  anterior  and  the  inner  surfaces  constitute  the  flexor  surface. 

Lower  Extremity. — The  lower  extremity  of  the  ulna  is  of  small  size,  and 
excluded  from  the  articulation  of  the  wrist-joint.  It  presents  for  examination  two 
eminences,  the  outer  and  larger  of  which  is  a  rounded,  articular  eminence,  termed 
the  head  of  the  ulna  (capitulum  ulnae),  the  inner,  narrower  and  more  projecting, 
is  a  non-articular  eminence,  the  styloid  process  (processiis  styloideus) .  The  head- 
presents  an  articular  facet,  part  of  which,  of  an  oval  or  semilunar  form,  is 
directed  downward,  and  articulates  with  the  upper  surface  of  the  interarticular 
fibro-cartilage  which  separates  it  from  the  wrist-joint;  the  remaining  portion, 
directed  outward,  is  narrow,  convex,  and  received  into  the  sigmoid  cavity  of  the 
radius.  The  peripheral  margin  of  the  portion  of  the  head  which  articulates  with 
the  ulna  is  called  the  articular  circumference  (circumferentia  ariicularis).  The 
styloid  process  projects  from  the  inner  and  back  part  of  the  bone,  and  descends 
a  little  lower  than  the  head,  terminating  in  a  rounded  summit,  which  affords 
attachment  to  the  internal  lateral  ligament  of  the  wrist.  The  head  is  separated 
from  the  styloid  process  by  a  depression  for  the  attachment  of  the  triangular 
interarticular  fibro-cartilage;  and  behind,  by  a  shallow  groove  for  the  passage  of 
the  tendon  of  the  Extensor  carpi  ulnaris. 

Structure. — Similar  to  that  of  the  other  long  bones. 

Development. — By  three  centres :  one  for  the  shaft,  one  for  the  inferior  extrem- 
ity, and  one  for  the  olecranon  (Fig.  135).  Ossification  commences  near  the 
middle  of  the  shaft  about  the  eighth  week,  and 
soon  extends  through  the  greater  part  of  the  bone. 
At  birth  the  ends  are  cartilaginous.  About  the 
fourth  year  a  separate  osseous  nucleus  appears  in 
the  middle  of  the  head,  which  soon  extends  into  the 
styloid  process.  About  the  tenth  year  ossific  matter 
appears  in  the  olecranon  near  its  extremity,  the  chief 
part  of  this  process  being  formed  from  an  extension 
of  the  shaft  of  the  bone  into  it.  At  about  the  six- 
teenth year  the  upper  epiphysis  becomes  joined,  and 
at  about  the  twentieth  year  the  lower  one. 

Articulations. — With  the  humerus  and  radius. 

Attachment  of  Muscles. — To  sixteen :  to  the  ole- 
cranon, the  Triceps,  Anconeus,  and  one  head  of  the 
Flexor  carpi  ulnaris.  To  the  coronoid  process,  the 
Brachialis  anticus.  Pronator  radii  teres,  Flexor  sub- 
limis  digitorum,  and  Flexor  profundus  digitorum; 
generally  also  the  Flexor  longus  pollicis.  To  the 
shaft,  the  Flexor  profundus  digitorum,  Pronator 
quadratus.  Flexor  carpi  ulnaris.  Extensor  carpi 
ulnaris.  Anconeus,  Supinator  brevis,  Extensor  ossis 
metacarpi  pollicis.  Extensor  longus  pollicis,  and 
Extensor  indicis. 


Olecranon. 
Appears  aCr^s£^^-Jom.s  shaft  at 


10th  year. 


16th  year. 


Appears  at  f 
4th  year. 


Joins  shaft  at 
20th  year. 


Inferior  extremity. 
Fig.  135. — Plan  of  the  development 
Surface  Form.— The  most  prominent  part  of  the  ulna  on         "^  ^^^  ^l"**-    ^^  ^^'^^  ''^''^'^^■ 
the  surface  of  the  body  is  the  olecranon  process,  which  can 

ahvays  be  felt  at  the  back  of  the  elbow-joint.  When  the  forearm  is  flexed,  the  upper  quadri- 
lateral surface  can  be  feU,  directed  backward;  during  extension  it  recedes  into  the  olecranon 
fossa,  and  the  contracting  fibres  of  the  triceps  prevent  its  being  perceived.  At  the  back  of 
the  olecranon  is  the  smooth,  triangular,  subcutaneous  surface,  which  below  is  continuous 
with  the  posterior  border  of  the  shaft  of  the  bone,  and  felt  in  every  position  of  the  forearm. 
During  extension  the  upper  border  of  the  olecranon  is  slightly  above  the  level  of  the  internal 
condyle,  and  the  process  itself  is  nearer  to  this  condyle  than  the  outer  one.  Running  down 
the  back  of  the  forearm,  from  the  apex  of  the  triangular  surface  which  forms  the  posterior 


190  THE   SKELETON 

surface  of  the  olecranon,  is  a  prominent  ridge  of  bone,  the  posterior  border  of  the  ulna. 
This  is  to  be  felt  throughout  the  entire  length  of  the  shaft  of  the  bone,  from  the  olecranon 
above  to  the  styloid  process  below.  As  it  passes  down  the  forearm  it  pursues  a  sinuous  course 
and  inclines  to  the  inner  side,  so  that,  though  it  is  situated  in  the  middle  of  the  back  of 
the  limb  above,  it  is  on  the  inner  side  of  the  wrist  at  its  termination.  It  becomes  rounded  off 
in  its  lower  third,  and  may  be  traced  below  to  the  small,  subcutaneous  surface  of  the  styloid 
process.  Internal  to  this  border  the  lower  fourth  of  the  inner  surface  is  to  be  felt.  The  styloid 
process  is  to  be  felt  as  a  prominent  tubercle  of  bone,  continuous  above  with  the  posterior  sub- 
cutaneous border  of  the  ulna,  and  terminating  below  in  a  blunt  apex,  which  lies  a  little  internal 
and  behind,  but  on  a  level  with,  the  wrist-joint.  The  styloid  process  is  best  felt  when  the  hand 
is  in  the  same  line  as  the  bones  of  the  forearm,  and  in  a  position  midway  between  supination 
and  pronation.  If  the  forearm  is  pronated  while  the  finger  is  placed  on  the  process,  it  will  be 
felt  to  recede,  and  another  prominence  of  bone  will  appear  just  behind  and  above  it.  This 
is  the  head  of  the  ulna,  which  articulates  with  the  lower  end  of  the  radius  and  the  triangular 
interarticular  fibro-cartilage,  and  now  projects  between  the  tendons  of  the  Extensor  carpi  ulnaris 
and  the  Extensor  minimi  digiti  muscles. 


The  Radius. 

The  radius  {radius,  a  ray,  or  spoke  of  a  wheel)  is  so  called  because  it  is  the 
rotary  bone  of  the  forearm.  It  is  situated  on  the  outer  side  of  the  forearm,  lying 
side  by  side  with  the  ulna,  which  exceeds  it  in  length  and  size  (Figs.  133  and 
134).  Its  upper  end  is  small,  and  forms  only  a  small  part  of  the  elbow-joint; 
but  its  lower  end  is  large,  and  forms  the  chief  part  of  the  wrist.  It  is  one  of  the 
long  bones,  prismatic  in  form,  slightly  curved  longitudinally,  and,  like  other 
long  bones,  has  a  shaft  and  two  extremities. 

Upper  Extremity. — ^The  upper  extremity  presents  a  head,  neck,  and  tuberosity. 

The  Head. — The  head  (capitulum  radii)  is  of  a  cylindrical  form,  depressed  on 
its  upper  surface  into  a  shallow  cup  (fovea  capitidi  radii),  which  articulates  with 
the  capitellum  or  radial  head  of  the  humerus.  In  the  recent  state  it  is  covered 
with  a  layer  of  cartilage  which  is  thinnest  at  its  centre.  Around  the  circumference 
of  the  head  is  a  smooth,  articular  surface  (circumferentia  articularis) ,  broad  inter- 
nally where  it  articulates  with  the  lesser  sigmoid  cavity  of  the  ulna;  narrow  in 
the  rest  of  its  circumference,  where  it  rotates  within  the  orbicular  ligament.  It 
is  coated  with  cartilage  in  the  recent  state.  The  head  is  supported  on  a  round, 
smooth,  and  constricted  portion  of  bone,  called  the  neck  (collum  radii),  which 
presents,  behind,  a  slight  ridge,  for  the  attachment  of  part  of  the  Supinator  brevis. 
Beneath  the  neck,  at  the  inner  and  front  aspect  of  the  bone,  is  a  rough  eminence, 
the  bicipital  tuberosity  (tuberositas  radii).  Its  surface  is  divided  into  two  parts  by 
a  vertical  line — a  posterior,  rough  portion,  for  the  insertion  of  the  tendon  of  the 
Biceps  muscle;  and  an  anterior,  smooth  portion,  on  which  a  bursa  is  interposed 
between  the  tendon  and  the  bone.  • 

The  Shaft  (corpus  radii). — The  shaft  of  the  bone  is  prismoid  in  form,  narrower 
above  than  below,  and  slightly  curved,  so  as  to  be  convex  outward.  It  presents 
three  surfaces,  separated  by  three  borders. 

Anterior  or  Palmar  Border  (margo  volaris) . — ^The  anterior  border  extends  from 
the  lower  part  of  the  tuberosity  above  to  the  anterior  part  of  the  base  of  the  styloid 
process  below.  It  separates  the  anterior  from  the  external  surface.  Its  upper 
third  is  very  prominent;  and  from  its  oblique  direction,  downward  and  outward, 
has  received  the  name  of  the  oblique  line  of  the  radius.  It  gives  attachment  exter- 
nally to  the  Supinator  brevis,  internally  to  the  Flexor  longus  pollicis,  and  between 
these  to  the  Flexor  sublimis  digitorum.  The  middle  third  of  the  anterior  border 
is  indistinct  and  rounded.  Its  lower  fourth  is  sharp,  prominent,  affords  attach- 
ment to  the  Pronator  quadratus  and  to  the  posterior  annular  ligament  of  the  wrist, 
and  terminates  in  a  small  tubercle  at  the  base  of  the  styloid  process,  into  which 
is  inserted  the  tendon  of  the  Supinator  longus. 


THE    RADIUS  191 

Posterior  or  Dorsal  Border  (margo  dorsalis). — The  posterior  border  commences 
above  at  the  back  part  of  the  neck  of  the  radius,  and  terminates  below  at  the 
posterior  part  of  the  base  of  the  styloid  process;  it  separates  the  posterior  from 
the  external  surface.  It  is  indistinct  above  and  below,  but  well  marked  in  the 
middle  third  of  the  bone. 

Internal  or  Interosseous  Border  (crista  interossea). — The  internal  or  interosseous 
border  commences  above  at  the  back  part  of  the  tuberosity,  where  it  is  rounded 
anti  indistinct,  becomes  sharp  and  prominent  as  it  descends,  and  at  its  lower  part 
divides  into  two  ridges,  which  descend  to  the  anterior  and  posterior  margins  of 
the  sigmoid  cavity.  This  border  separates  the  anterior  from  the  posterior  sur- 
face, and  has  the  interosseous  membrane  attached  to  it  throughout  the  greater 
part  of  its  extent. 

Anterior  or  Palmar  or  Flexor  Surface  (fades  volaris). — ^The  anterior  surface  is 
concave  for  its  upper  three-fourths,  and  gives  attachment  to  the  Flexor  longus 
pollicis  muscle;  it  is  broad  and  flat  for  its  lower  fourth,  and  gives  attachment  to 
the  Pronator  quadratus.  A  prominent  ridge  limits  the  attachment  of  the  Pro- 
nator quadratus  below,  and  between  this  and  the  inferior  border  is  a  triangular 
rough  surface  for  the  attachment  of  the  anterior  ligament  of  the  wrist-joint.  At 
the  junction  of  the  upper  and  middle  third  of  this  surface  is  the  nutrient  foramen 
(foramen  nidricium) ,  the  opening  of  the  nutrient  canal  (canalis  nutricius),  which 
is  directed  obliquely  upward  (proximally) . 

Posterior  or  Dorsal  or  Extensor  Surface  (facies  dorsalis). — ^The  posterior  surface 
is  rounded,  convex,  and  smooth  in  the  upper  third  of  its  extent,  and  covered  by 
the  Supinator  brevis  muscle.  Its  middle  third  is  broad,  slightly  concave,  and  gives 
attachment  to  the  Extensor  ossis  metacarpi  pollicis  above,  the  Extensor  brevis  pol- 
licis below.  Its  lower  third  is  broad,  convex,  and  covered  by  the  tendons  of  the 
muscles,  which  subsequently  run  in  the  grooves  on  the  lower  end  of  the  bone. 

External  Surface  (facies  lateralis) . — The  external  surface  is  rounded  and  convex 
throughout  its  entire  extent.  Its  upper  third  gives  attachment  to  the  Supinator 
brevis  muscle.  About  its  centre  is  seen  a  rough  ridge,  for  the  insertion  of  the  Pro- 
nator radii  teres  muscle.  Its  lower  part  is  narrow,  and  covered  by  the  tendons 
of  the  Extensor  ossis  metacarpi  pollicis  and  Extensor  brevis  pollicis  muscles. 

Lower  Extremity. — The  lower  extremity  of  the  radius  is  large,  of  quadri- 
lateral form,  and  provided  with  two  articular  surfaces — one  at  the  extremity,  for 
articulation  with  the  carpus,  and  one  at  the  inner  side  of  the  bone,  for  articulation 
with  the  ulna.  The  carpal  articular  surface  (facies  articularis  carpea)  is  of  tri- 
angular form,  concave,  smooth,  and  divided  by  a  slight  antero-posterior  ridge 
into  two  parts.  Of  these,  the  external  is  of  a  triangular  form,  and  articulates  with 
the  scaphoid  bone;  the  inner  is  quadrilateral  and  articulates  with  the  semilunar 
bone.  The  articular  surface  for  the  head  of  the  ulna  is  called  the  sigmoid  cavity 
of  the  radius  (incisura  ulnaris);  it  is  narrow,  concave,  smooth,  and  articulates 
with  the  head  of  the  ulna.  The  circumference  of  this  end  of  the  bone  presents 
three  surfaces — an  anterior,  external,  and  posterior.  The  anterior  surface,  rough 
and  irregular,  affords  attachment  to  the  anterior  ligament  of  the  wrist-joint.  The 
external  surface  is  prolonged  obliquely  downward  into  a  strong,  conical  projec- 
tion, the  styloid  process  (processus  styloideus),  which  gives  attachment  by  its  base 
to  the  tendon  of  the  Supinator  longus,  and  by  its  apex  to  the  external  lateral  liga- 
ment of  the  wrist-joint.  The  outer  surface  of  this  process  is  marked  by  a  flat 
groove,  which  runs  obliquely  downward  and  forward,  and  gives  passage  to  the 
tendons  of  the  Extensor  ossis  metacarpi  pollicis  and  the  Extensor  brevis  pollicis. 
The  posterior  surface  is  convex,  affords  attachment  to  the  posterior  ligament  of 
the  wrist,  and  is  marked  by  three  grooves.  Proceeding  from  without  inward,  the 
first  groove  is  broad  but  shallow,  and  subdivided  into  two  by  a  slightly  elevated 
ridge:  the  outer  of  these  two  transmits  the  tendon  of  the  Extensor  carpi  radialis 


192 


THE  SKELETON 


Appears  atj 
5th  year. 


Unites  with  shaft 
about  puberty. 


longior,  the  inner  the  tendon  of  the  Extensor  carpi  radialis  brevior.  The  second^ 
which  is  near  the  centre  of  the  bone,  is  a  deep  but  narrow  groove,  bounded  on  its 
outer  side  by  a  sharply-defined  ridge;  it  is  directed  obHquely  from  above,  down- 
ward and  outward,  and  transmits  the  tendon  of  the  Extensor  longus  polHcis- 
The  third,  lying  most  internally,  is  a  broad  groove,  for  the  passage  of  the  tendons 
of  the  Extensor  indicis  and  Extensor  communis  digitorum. 
Structure. — Similar  to  that  of  the  other  long  bones. 

Development  (Fig.  136). — By  three  centres:  one  for  the  shaft  and  one  for  each 
extremity.    That  for  the  shaft  makes  its  appearance  near  the  centre  of  the  bone, 

about  the  eighth  week  of   foetal  life.     About 
Head.  the  end  of  the  second  year  ossification  com- 

mences in  the  lower  epiphysis,  and  about  the 
fifth  year  in  the  upper  end  At  the  age  of 
seventeen  or  eighteen  the  upper  epiphysis  be- 
comes joined  to  the  shaft,  the  lower  epiphysis 
becoming  united  about  the  twentieth  year. 

Articulation. — With  four  bones:  the  humerus, 
ulna,  scaphoid,  and  semilunar. 

Attachment  of  Muscles. — To  nine:  to  the 
tuberosity,  the  Biceps,  to  the  oblique  ridge,  the 
Supinator  brevis,  Flexor  subhmis  digitorum, 
and  Flexor  longus  pollicis;  to  the  shaft  (its 
anterior  surface),  the  Flexor  longus  pollicis^ 
and  Pronator  quadratus ;  (its  posterior  surface) , 
the  Extensor  ossis  metacarpi  pollicis  and  Exten- 
sor brevis  pollicis;  (its  outer  surface),  the  Pro- 
nator radii  teres;  and  to  the  styloid  process, 
the  Supinator  longus. 


Appears  at^ 
2d  year. 


Unites  with  shaft 
'  about  20th  year. 


Lower  extremity. 

Fig.  136. — Plan  of  the  development  of  the 
radius.     By  three  centres. 


Surface  Form.— Just  below  and  a  little  in  front  of 
the  posterior  surface  of  the  external  condyle  a  part  of 
the  head  of  the  radius  may  be  felt,  covered  by  the 
orbicular  and  external  lateral  ligaments.  There  is  in 
this  situation  a  little  dimple  in  the  skin,  which  is  most 
visible  when  the  arm  is  extended;  and  which  marks  the 
position  of  the  head  of  the  bone.  If  the  finger  is  placed  on  this  dimple  and  the  forearm  pro- 
nated  and  supinated,  the  head  of  the  bone  will  be  distinctly  perceived  rotating  in  the  lesser 
sigmoid  cavity.  The  upper  half  of  the  shaft  of  the  radius  cannot  be  felt,  as  it  is  surrounded  by 
the  fleshy  bellies  of  the  muscles  arising  from  the  external  condyle.  The  lower  half  of  the  shaft 
can  be  readily  examined,  though  covered  by  tendons  and  muscles  and  not  strictly  subcutaneous- 
If  traced  downward,  the  shaft  will  be  felt  to  terminate  in  a  lozenge-shaped,  convex  surface 
on  the  outer  side  of  the  base  of  the  styloid  process.  This  is  the  only  subcutaneous  part  of  the 
bone,  and  from  its  lower  extremity  the  apex  of  the  styloid  process  will  be  felt  bending  inward 
toward  the  wrist.  About  the  middle  of  the  posterior  aspect  of  the  lower  extremity  of  the  bone 
is  a  well-marked  ridge,  best  perceived  when  the  hand  is  slightly  flexed  on  the  wrist.  It  forms 
the  outer  boundary  of  the  oblique  groove  on  the  posterior  surface  of  the  bone,  through  which 
the  tendon  of  the  Extensor  longus  pollicis  runs,  and  serves  to  keep  that  tendon  in  place. 

Surgical  Anatomy  of  the  Radius  and  Ulna. — The  two  bones  of  the  forearm  are  more  often 
broken  together  than  is  either  the  radius  or  ulna  separately.  It  is  therefore  convenient  to  consider 
fractures  of  both  bones  in  the  first  instance,  and  subsequently  to  mention  the  principal  fractures 
which  take  place  in  each  bone  individually.  These  fractures  may  be  produced  by  either  direct 
or  indirect  violence,  though  more  commonly  by  direct  violence.  When  indirect  force  is  applied 
to  the  forearm  the  radius  generally  alone  gives  way,  though  both  bones  may  suffer.  The 
fracture  from  indirect  force  generally  takes  place  somewhere  about  the  middle  of  the  bones; 
fracture  from  direct  violence  may  occur  at  any  part,  more  often,  however,  in  the  lower  half  of 
the  bone.  The  fracture  is  usually  transverse,  but  may  be  more  or  less  oblique.  A  point  of 
interest  in  connection  with  these  fractures  is  the  tendency  that  there  is  for  the  two  bones  to  unite 
across  the  interosseous  membrane;  the  limb  should  therefore  be  put  up  in  a  position  midway 
between  supination  and  pronation,  which  is  not  only  the  most  comfortable  position,  but  also  sep- 
arates the  bones  most  widely  from  each  other,  and  therefore  diminishes  the  risk  of  the  bones 


THE    CARPUS  193 

becoming  united  across  the  interosseous  membrane.  The  splints,  anterior  and  posterior,  which 
are  apphed  in  these  cases  should  be  rather  wider  than  the  limb,  so  as  to  prevent  any  lateral 
pressure  on  the  bones.  In  these  cases  there  is  a  greater  liability  to  gangrene  from  the  pressure 
of  the  splints  than  in  other  parts  of  the  body.  This  is  no  doubt  due  principally  to  two  causes: 
(1)  the  flexion  of  the  forearm  compressing  to  a  certain  extent  the  brachial  artery  and  retarding 
the  flow  of  blood  to  the  limb;  and  (2)  the  superficial  position  of  the  two  main  arteries  of  the 
forearm  in  a  part  of  their  course,  and  their  liability  to  be  compressed  by  the  splints.  The  special 
fractures  of  the  ulna  are — (1)  Fracture  of  the  olecranon.  This  may  be  caused  by  direct  violence, 
falls  on  the  elbow,  with  the  forearm  flexed,  or  by  muscular  action  by  the  sudden  contraction  of 
the  triceps,  The  most  common  place  for  the  fracture  to  occur  is  at  the  constricted  portion 
where  the  olecranon  joins  the  shaft  of  the  bone,  and  the  fracture  may  be  either  transverse  or 
oblique;  but  any  part  may  be  broken,  even  a  thin  shell  may  be  torn  off.  Fractures  from  direct 
violence  are  occasionally  comminuted.  The  displacement  is  sometimes  very  slight,  owing  to  the 
fibrous  structures  around  the  process  not  being  torn.  (2)  Fracture  of  the  coronoid  process  some- 
times occurs  as  a  complication  of  dislocation  backward  of  the  bones  of  the  forearm,  but  it  is 
doubtful  if  it  ever  occurs  as  an  uncomplicated  injury.  (3)  Fractures  of  the  shaft  of  the  ulna 
may  occur  at  any  part,  but  usually  takes  place  at  the  middle  of  the  bone  or  a  little  below  it. 
They  are  almost  always  the  result  of  direct  violence.  (4)  The  styloid  process  may  be  knocked 
off  by  direct  violence.  Fractures  of  the  radius  consist  of — (1)  Fracture  of  the  head  of  the  bone; 
this  generally  occurs  in  conjunction  with  some  other  lesion,  but  may  occur  as  an  uncomplicated 
injury.  (2)  Fracture  of  the  neck  may  also  take  place,  but  is  generally  complicated  with  other 
injury  (3)  Fractures  of  the  shaft  of  the  radius  are  very  common,  and  may  take  place  at  any 
part  of  the  bone.  They  may  take  place  from  either  direct  or  indirect  violence.  In  fractures  of  the 
upper  third  of  the  shaft  of  the  bone,  that  is  to  say,  above  the  insertion  of  the  Pronator  radii  teres, 
the  displacement  is  very  great.  The  upper  fragment  is  strongly  supinated  by  the  Biceps  and  Supi- 
nator brevis,  and  flexed  by  the  Biceps,  while  the  lower  fragment  is  pronated  and  drawn  toward 
the  ulna  by  the  two  pronators.  If  such  a  fracture  is  put  up  in  the  ordinary  position,  midway 
between  supination  and  pronation,  the  fracture  will  unite  with  the  upper  fragment  in  a  position 
of  supination,  and  the  lower  one  in  the  mid-position,  and  thus  considerable  impairment  of  the 
movements  of  the  hand  will  result.  The  limb  should  be  put  up  with  the  forearm  supinated.  (4) 
The  most  important  fracture  of  the  radius  is  that  of  the  lower  end  {Colles's  fracture).  The 
fracture  is  transverse,  and  generally  takes  place  about  an  inch  from  the  lower  extremity.  It  is 
caused  by  falls  on  the  palm  of  the  hand,  and  is  an  injury  of  advanced  life,  occurring  more  fre- 
(|uently  in  the  female  than  the  male.  In  consequence  of  the  manner  in  which  the  fracture  is 
caused,  the  upper  fragment  becomes  driven  into  the  lower,  and  impaction  is  the  result;  or  else 
the  lower  fragment  becomes  split  up  into  two  or  more  pieces,  so  that  no  fixation  occurs.  Sepa- 
ration of  the  lower  epiphysis  of  the  radius  may  take  place  in  the  young.  This  injury  and  Colles's 
fracture  may  be  distinguished  from  other  injuries  in  this  neighborhood — especially  dislocation, 
with  which  it  is  liable  to  be  confounded — by  observing  the  relative  positions  of  the  styloid 
processes  of  the  ulna  and  radius.  In  the  natural  condition  of  parts,  with  the  arm  hanging  by  the 
side,  the  styloid  process  of  the  radius  is  on  a  lower  level  than  that  of  the  ulna;  that  is  to  say, 
nearer  the  ground.  After  fracture  or  separation  of  the  epiphysis  this  process  is  on  the  same  or 
a  higher  level  than  that  of  the  ulna,  whereas  it  would  be  unaltered  in  position  in  dislocation. 


THE  HAND. 

The  skeleton  of  the  hand  is  subdivided  into  three  segments — the  carpus  or  wrist 
ones ;  the  metacarpus  or  bones  of  the  palm ;  and  the  phalanges  or  bones  of  the  digits . 

The  Carpus  (Ossa  Carpi)  (Figs.  137,  138). 

The  bones  of  the  carpus  {xapiioQ,  the  wrist),  eight  in  number,  are  arranged 
in  two  rows.  Those  of  the  upper  row,  enumerated  from  the  radial  to  the  ulnar 
side,  are  the  scaphoid,  semilunar,  cuneiform,  and  pisiform;  those  of  the  lower 
row,  enumerated  in  the  same  order,  are  the  trapezium,  trapezoid,  os  magnum, 
and  unciform. 

Common  Characters  of  the  Carpal  Bones. — Each  bone  (excepting  the  pisiform) 
presents  six  surfaces.  Of  these  the  anterior,  'palmar,  or  volar,  and  the  posterior  or 
dorsal  are  rough  for  ligamentous  attachment,  the  dorsal  surface  being  the  broader, 
except  in  the  scaphoicl  and  semilunar.  The  superior  or  proximal  and  inferior  or 
distal  are  articular,  the  superior  generally  convex,  the  inferior  concave;  and  the 

13 


194 


THE  SKELETON 


internal  and  external  are  also  articular  when  in  contact  with  contiguous  bones, 
otherwise  rough  and  tubercular.     The  structure  in  all  is  similar,  consisting  of 


^i^^^^&i^\ 


I 


EXTKNSOR   CARPI 
FACIALIS    LONQIOR. 


EXTENSOR    CARPI 
RAOIALIS    BREVIOR. 


Metacarpus,  \ 


EXTENSOR   BREVIS 
POLtlCIS 


EXTENSOR   LONQUS 
POLLICIS 


EXTENSOR    D1QITORUM 

COMMUNIS  and 

EXTENSOR    INDICIS 


Fig.  137. — Bones  of  the  left  hand.     Dorsal  surface. 

cancellous  tissue  enclosed  in  a  layer  of  compact  bone.    Each  bone  is  also  develope( 
from  a  single  centre  of  ossification. 


THE   CARPUS 


195 


Bones  of  the  Upper  Row. 

Scaphoid  or  Navicular  Bone  {os  naviculare  manus,  the  boat-like  hone)  (Fig, 
139). — The  scaphoid  ((Txd<fT^,  a  boat,  £cdo(;,  like)  is  the  largest  bone  of  the  first 


FLEXOR    CARPI    ULNARIS. 


FLEXOR    BREVIS    MINIMI    DIQITI. 


FLEXOR    0SS1S    METACARPI. 
MINIMI    DIQITI. 


Groove  for  tendon  of 

FLEXOR  CARPI   RADIALIS. 

FLEXOR    OSSIS 
METACARPI     POLLICIS. 
FLEXOR   BREVIS    POLL. 

EXTEN.   OS.   METACARP.   POLL. 

EXTENSOR    OSSIS 
METACARPI    POLLICIS. 


Metacarpus. 


FLEX.    BREVIS 

and 

ABDUCTOR 
MINIMI    DIQTI. 


FLEXOR 

IQITORUM 
PROFUNDUS. 


Fig.  138. — Bones  of  the  left  hand.     Palmar  .surface. 


row.     It  has  received  its  name  from  its  fancied  resemblance  to  a  boat,  being 
broad  at  one  end  and  narrowed  like  a  prow  at  the  opposite.     It  is  situated  at 


196 


THE  SKELETON 


the  upper  and  outer  part  of  the  carpus,  its  long  axis  being  from  above  down- 
ward, outward,  and  forward. 

Surfaces. — The  superior  surface  is  convex,  smooth,  of  triangular  shape,  and 
articulates  with  the  lower  end  of  the  radius.     The  inferior  surface,  directed 


For  radius. 


Tuberosity 


For  trapezium. 


For  semilunar. 


For  OS  magntim. 
For  trapezoid. 

Fig.  139. — The  left  scaphoid. 

downward,  outward,  and  backward,  is  smooth,  convex,   also  triangular,   and' 
divided  by  a  slight  ridge  into  two  parts,  the  external  of  which  articulates  with 
the  trapezium,  the  inner  with  the  trapezoid.     The  posterior  or  dorsal  surface 
presents  a  narrow,  rough  groove  which  runs  the  entire  length  of  the  bone  andj 
serves  for  the  attachment  of  ligaments.    The  anterior  or  palmar  surface  is  concave 
above,  and  elevated  at  its  lower  and  outer  part  into  a  prominent  rounded  tuber- 
osity {tuberculum  ossis  navicularis) ,  which  projects  forward  from  the  front  of  the] 
carpus  and  gives  attachment  to  the  anterior  annular  ligament  of  the  wrist  and 
sometimes  a  few  fibres  of  the  Abductor  pollicis.     The  external  surface  is  rough 
and  narrow,  and  gives  attachment  to  the  external  lateral  ligament  of  the  wrist. 
The  internal  surface  presents  two  articular  facets:  of  these,  the  superior  or  smaller] 
one  is  flattened,  of  semilunar  form,  and  articulates  with  the  semilunar;  the  inferior 
or  larger  is  concave,  forming,  with  the  semilunar  bone,  a  concavity  for  the  head  i 
of  the  OS  magnum. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  superior  or  radial 
convex,  articular  surface  upward,  and  the  posterior  surface — i.  e.,  the  narrow,: 
non-articular,  grooved  surface — toward  you.  The  tubercle  on  the  outer  surface] 
points  to  the  side  to  which  the  bone  belongs.^ 

Articulations. — With  five  bones:    the   radius  above,  trapezium  and  trapezoid] 
below,  OS  magnum  and  semilunar  internally. 

Attachment  of  Muscles. — Occasionally  a  few  fibres  of  the  Abductor  pollicis. 

Semilunar  (os  lunatum)  (Fig.  140). — The  semilunar  {semi,  half;  luna,  moon) 
bone  may  be  distinguished  by  its  deep  concavity  and  crescentic  outline.     It  isl 


For  cuneiform. 


For  radius. 


For  unciform. 

For  OS  magnum 
Fig.  140. — The  left  semilunar, 


For 
scaphoid. 


situated  in  the  centre  of  the  upper  row  of  the  carpus,  between  the  scaphoid  and 
cuneiform. 

Surfaces. — The  superior  surface,  convex,  smooth,  and  bounded  by  four  edges, 
articulates  with  the  radius.    The  inferior  surface  is  deeply  concave,  and  of  greater  I 

'  In  these  directions  each  bone  is  supposed  to  be  placed  in  its  natural  position — that  is,  such  a  position  as  it 
would  occupy  when  the  arm  is  hanging  by  the  side,  the  forearm  in  a  position  of  supination,  the  thumb  being 
directed  outward,'  and  the  palm  of  the  hand  looking  forward. 


THE    CABPUS  197 

extent  from  before  backward  than  transversely :  it  articulates  with  the  head  of  the 
OS  magnum  and  by  a  long,  narrow  facet  (separated  by  a  ridge  from  the  general 
surface)  with  the  unciform  bone.  The  anterior  or  palmar  and  'posterior  or  dorsal 
surfaces  are  rough,  for  the  attachment  of  iigaments,  the  former  being  the  broader 
and  of  a  somewhat  rounded  form.  The  external  surface  presents  a  narrow,  flat- 
tened, semilunar  facet  for  articulation  with  the  scaphoid.  The  internal  surface 
is  marked  by  a  smooth,  quadrilateral  facet,  for  articulation  with  the  cuneiform. 

Hold  it  with  the  convex  articular  surface  for  the  radius  upward,  and  the  nar- 
rowest non-articular  surface  toward  you.  The  semilunar  facet  for  the  scaphoid 
will  be  on  the  side  to  which  the  bone  belongs. 

Articulations, — With  five  bones:  the  radius  above,  os  magnum  and  unciform 
below,  scaphoid  and  cuneiform  on  either  side. 

Cuneiform  (as  triquetrum,  the  wedge-shaped  bone)  (Fig.  141). — ^The  cuneiform 
(cuneus,  a   wedge;   forma,   likeness)   may   be    distinguished    by   its    pyramidal 
shape,  and  by  its  having  an  oval,  isolated  facet  for  articu- 
lation with  the  pisiform  bone.    It  is  situated  at  the  upper  For  semilunar. 
and  inner  side  of  the  carpus.                                                         ForpisiM 

Surfaces. — The  superior  surface  presents  an  internal,  rough, 
non-articular  portion,  and  an  external  or  articular  portion, 
which  is  convex,  smooth,  and  articulates  with  the  triangular 
interarticular  fibro-cartilage  of  the  wrist.    The  inferior  sur-  -^*""  v,nciform. 

face,  directed  outward,  is  concave,  sinuously  curved,  and  ^'g- i^i— T^kftcunei- 
smooth  for  articulation  with  the  unciform.  The  posterior 
or  dorsal  surface  is  rough,  for  the  attachment  of  ligaments.  The  anterior  or 
palmar  surface  presents,  at  its  inner  side,  an  oval  facet,  for  articulation  with 
the  pisiform;  and  is  rough  externally,  for  ligamentous  attachment.  The  exter- 
nal surface,  the  base  of  the  pyramid,  is  marked  by  a  flat,  quadrilateral,  smooth 
facet,  for  articulation  with  the  semilunar.  The  internal  surface,  the  summit  of 
the  pyramid,  is  pointed  and  roughened,  for  the  attachment  of  the  internal  lateral 
ligament  of  the  wrist. 

Hold  the  bone  with  the  surface  supporting  the  pisiform  facet  away  from  you, 
and  the  concavo-convex  surface  for  the  unciform  downward.  The  base  of  the 
wedge  (i.  e.,  the  broad  end  of  the  bone)  will  be  on  the  side  to  which  it  belongs. 

Articulations. — With  three  bones:  the  semilunar  externally,  the  pisiform  in 
front,  the  unciform  below;  and  with  the  triangular,  interarticular  fibro-cartilage 
which  separates  it  from  the  lower  end  of  the  ulna. 

Pisiform  (os  pisiforme)  (Fig.  142). — The  pisiform  (pisum,  a  pea;  forma,  like- 
ness) may  be  known  by  its  small  size  and  by  its  presenting  a  single  articular 
facet.     It  is  situated  on  a  plane  anterior  to  the  other  bones  of 

For  .       .  .  . 

cuneiform.  the  carpus;  it  is   spheroidal  in  form,  with  its  long  diameter 

#  directed  vertically. 

Surfaces. — Its  posterior  surface  is  a  smooth,  oval  facet,  for 
articulation  with  the  cuneiform.     This  facet   approaches  the 
superior,  but  not  the  inferior  border  of  the  bone.    The  anterior 
'°  pisifOTm.^  ^*      or  palmar  surface  is  rounded  and  rough,  and  gives  attachment 
to   the   anterior  annular    ligament  and    to  the   Flexor  carpi 
ulnaris  and  Abductor  minimi  digiti  muscles.     The  outer  and  inner  surfaces  are 
also  rough,  the  former  being  concave,  the  latter  usually  convex. 

Hold  the  bone  with  the  posterior  surface — that  which  presents  the  articular 
facet — toward  you,  in  such  a  manner  that  the  faceted  portion  of  the  surface  is 
uppermost.    The  outer,  concave  surface  will  point  to  the  side  to  which  it  belongs. 
Articulations. — With  one  bone,  the  cuneiform. 

Attachment  of  Muscles. — To  two:  the  Flexor  carpi  ulnaris  and  Abductor 
minimi  digiti;  and  to  the  anterior  annular  ligament. 


198 


THE   SKELETON 


Bones  of  the  Lower  Row. 

Trapezium  {os  multangulmn  majus)  (Fig.  143). — The  trapezium  (zf)dz£^a,  a 
table)  is  of  very  irregular  form.    It  may  be  distinguished  by  a  deep  groove,  for 


Groove. 


For  scaphoid. 


For  Sd 
metacarpal. 


Ridge. 


For  1st  metacarpal. 

Fig.  143. — The  left  trapezium. 


For  trapezoid. 


For  2d  metacarpal. 


the  tendon  of  the  Flexor  carpi  radiahs  muscle.  It  is  situated  at  the  external  and 
inferior  part  of  the  carpus  between  the  scaphoid  and  first  metacarpal  bone. 

Surfaces. — The  superior  surface,  concave  and  smooth,  is  directed  upward  and 
inward,  and  articulates  with  the  scaphoid.  The  inferior  surface,  directed  down- 
ward and  inward,  is  oval,  concave  from  side  to  side,  convex  from  before  backward, 
so  as  to  form  a  saddle-shaped  surface,  for  articulation  with  the  base  of  the  first 
metacarpal  bone.  The  anterior  or  palmar  surface  is  narrow  and  rough.  At  its 
upper  part  is  a  deep  groove  running  from  above  obliquely  downward  and  inward ; 
it  transmits  the  tendon  of  the  Flexor  carpi  radialis,  and  is  bounded  externally 
by  a  prominent  ridge,  the  oblique  ridge  of  the  trapezium  (tuherculum  ossis  mul- 
tanguli  majoris).  This  surface  gives  attachment  to  the  Abductor  pollicis.  Flexor 
ossis  metacarpi  pollicis,  and  Flexor  brevis  pollicis  muscles,  and  the  anterior 
annular  ligament.  The  posterior  or  dorsal  surface  is  rough.  The  external  sur- 
face is  also  broad  and  rough,  for  the  attachment  of  ligaments.  The  internal 
surface  presents  two  articular  facets:  the  upper  one,  large  and  concave,  articu- 
lates with  the  trapezoid;  the  lower  one,  small  and  oval,  with  the  base  of  the 
second  metacarpal  bone. 

Hold  the  bone  with  the  saddle-shaped  surface  downward  and-  the  grooved 
surface  away  from  you.  The  prominent,  rough,  non-articular  surface  points  to 
the  side  to  which  the  bone  belongs. 

Articulations. — With  four  bones:  the  scaphoid  above,  the  trapezoid  and  second 
metacarpal  bones  internally,  the  first  metacarpal  below. 

Attachment  of  Muscles. — Abductor  pollicis,  Flexor  ossis  metacarpi  pollicis,  and 
part  of  the  Flexor  brevis  pollicis. 

Trapezoid  (os  multangulum  minus)  (Fig.  144). — The  trapezoid  is  the  smallest 
bone  in  the  second  row.    It  may  be  known  by  its  wedge-shaped  form,  the  broad 


For  scaphoid. 


Anterior  surface. 

For  trapezium. 


Post,  surface 

Fig.  144. 


OS  magnum. 

For  2d  metacarpal. 
The  left  trapezoid. 


end  of  the  wedge  forming  the  dorsal,  the  narrow  end  the  palmar,  surface,  and  by 
its  having  four  articular  surfaces  touching  each  other  and  separated  by  sharp 
edges. 

Surfaces.^The  superior  surface,  quadrilateral  in  form,  smooth,  and  slightly  con- 
cave, articulates  with  the  scaphoid.    The  inferior  surface  articulates  with  the  upper 


THE    CARPUS 


199 


end  of  the  second  metacarpal  bone ;  it  is  convex  from  side  to  side,  concave  from  before 
backward,  and  subdivided  by  an  elevated  ridge  into  two  unequal  lateral  facets. 
The  posterior  or  dorsal  and  anterior  or  palmar  surfaces  are  rough,  for  the  attach- 
ment of  ligaments,  the  former  being  the  larger  of  the  two.  The  external  surface, 
convex  and  smooth,  articulates  with  the  trapezium.  The  internal  surface  is  con- 
cave and  smooth  in  front,  for  articulation  with  the  os  magnum;  rough  behind, 
for  the  attachment  of  an  interosseous  ligament. 

Hold  the  bone  with  the  larger,  non-articular  surface  toward  you,  and  the 
smooth,  quadrilateral  articular  surface  upward.  The  convex  articular  surface 
will  point  to  the  side  to  which  the  bone  belongs.^ 

Articulations. — ^With  four  bones:  the  scaphoid  above,  second  metacarpal  bone 
below,  trapezium  externally,  os  magnum  internally. 

Os  Magnum  (os  capitatum)  (Fig.  145). — The  os  magnum  is  the  largest  bone 
of  the  carpus,  and  occupies  the  centre  of  the  wrist.    It  presents,  above,  a  rounded 


For  semilunar. 


For  scaphoid. 

For 
trapezoid. 

For  2d 
metacarpal. 


For  semUunar. 


For  unciform. 


For  4th 
metacarpal. 


For  3d     For  4th  metacarpal, 
metacarpal. 

Fig.  145. — The  left  os  magnum 


Ant.  surface. 


portion  or  head,  which  is  received  into  the  concavity  formed  by  the  scaphoid  and 
semilunar  bones;  a  constricted  portion  or  neck;  and,  below,  the  body. 

Surfaces. — The  superior  surface  is  rounded,  smooth,  and  articulates  with  the  semi- 
lunar. The  inferior  surface  is  divided  by  two  ridges  into  three  facets  for  articulation 
with  the  second,  third,  and  fourth  metacarpal  bones,  that  for  the  third  (the  middle 
facet)  being  the  largest  of  the  three.  The  posterior  or  dorsal  surface  is  broad  and 
rough;  the  anterior  or  palmar,  narrow,  rounded,  and  also  rough,  for  the  attachment 
of  ligaments  and  a  part  of  the  Adductor  obliquus  pollicis.  The  external  surface 
articulates  with  the  trapezoid  by  a  small  facet  at  its  anterior  inferior  angle,  behind 
which  is  a  rough  depression  for  the  attachment  of  an  interosseous  ligament. 
Above  this  is  a  deep  and  rough  groove,  which  forms  part  of  the  neck  and  serves  , 
for  the  attachment  of  ligaments,  bounded  superiorly  by  a  smooth,  convex  surface, 
for  articulation  with  the  scaphoid.  The  internal  surface  articulates  with  the  unci- 
form by  a  smooth,  concave,  oblong  facet  which  occupies  its  posterior  and  superior 
parts,  and  is  rough  in  front,  for  the  attachment  of  an  interosseous  ligament. 

Hold  the  bone  with  the  broader,  non-articular  surface  toward  you,  and  the 
head  upward.  The  small,  articular  facet  at  the  anterior  inferior  angle  of  the 
external  surface  will  point  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  seven  bones:  the  scaphoid  and  semilunar  above;  the 
second,  third,  and  fourth  metacarpal  below;  the  trapezoid  on  the  radial  side;  and 
the  unciform  on  the  ulnar  side. 

Attachment  of  Muscles. — Part  of  the  Adductor  obliquus  pollicis. 

Unciform  (os  hamatum)  (Fig.  146). — ^The  unciform  or  hook  bone  (uncus,  a  hook; 
forma,  likeness)  may  be  readily  distinguished  by  its  wedge-shaped  form  and  the 
hook-like  process  that  projects  from  its  palmar  surface.    It  is  situated  at  the  inner 


'  Occa.'iionally  in  a  badly  marked  bone  there  is  some  difficulty  in  ascertaining  to  which  side  the  bone  belongs; 
the  following  method  will  sometimes  be  found  useful  :  Hold  the  bone  with  its  broader,  non-articular  surface 
upward,  so  that  its  sloping  border  is  directed  toward  you.  The  border  will  slope  to  the  side  to  which, the  bone 
belongs. 


200 


THE  SKELETON 


and  lower  angle  of  the  carpus,  with  its  base  downward,  resting  on  the  two  inner 
metacarpal  bones,  and  its  apex  directed  upward  and  outward. 

Surfaces. — The  superior  surface,  the   apex  of  the  wedge,  is   narrow,  convex, 
smooth,  and  articulates  with  the  semilunar.    The  inferior  surface  articulates  with 


For  semilunar. 


For  cuneiform. 


For  OS  magnum. 


For  fourth  meta 
tarsal. 


Unciform  process. 


fifth 
metatarsal. 


Fig.  146. — The  left  unciform. 


the  fourth  and  fifth  metacarpal  bones,  the  concave  surface  for  each  being  sepa- 
rated by  a  ridge  which  runs  from  before  backward.    The  posterior  or  dorsal\ 
surface  is  triangular  and  rough,  for  ligamentous  attachment.    The  anterior  orj 
palmar  surface  presents,  at  its  lower  and  inner  side,  a  curved,  hook-like  pro- 
cess of  bone,  the  unciform  process   (hamulus  ossis  hamati),  directed  from  the] 
palmar  surface  forward  and  outward.     It  gives  attachment  by  its  apex  to  thej 
annular  ligament  and  Flexor  carpi  ulnaris;  by  its  inner  surface  to  the  Flexor  brevis 
minimi  digiti  and  the  Opponens  minimi  digiti;   and  is  grooved  on  its  outer] 
side,  for  the  passage  of  the  Flexor  tendons  into  the  palm  of  the  hand.    This  isj 
one  of   the   four  eminences   on   the  front  of  the  carpus  to  which  the  anterior 
annular  ligament  is  attached,  the  others  being  the  pisiform  internally,  the  oblique} 
ridge  of  the  trapezium  and  the  tuberosity  of  the  scaphoid  externally.    The  internall 
surface  articulates  with  the  cuneiform  by  an  oblong  facet  cut  obliquely  from  above,} 
downward  and  inward.    The  external  surface  articulates  with  the  os  magnum  byj 
its  upper  and  posterior  part,  the  remaining  portion  being  rough,  for  the  attach- 
ment of  ligaments. 

Hold  the  bone  with  the  hooked  process  away  from  you,  and  the  articular  sur- 
face, divided  into  two  parts,  for  the  metacarpal  bones,  downward     The  concavity! 
of  the  process  will  be  on  the  side  to  which  the  bone  belongs. 

Articulations. — -With  five  bones:    the  semilunar  above,  the  fourth  and    fiftl 
metacarpal  below,  the  cuneiform  internally,  the  os  magnvim  externally. 

Attachment  of  Muscles. — To  three:  the  Flexor  brevis  minimi  digiti,  the  Opponens 
minimi  digiti,  the  Flexor  carpi  ulnaris. 


The  Metacarpus  (Ossa  Metacarpalia)  (Figs.  137,  138). 

The  metacarpal  bones  are  five  in  number,  and  they  are  numbered  from  1  to-l 
5  inclusive,  the  first  being  the  metacarpal   bone  of   the  thumb,  the  fifth   the 
metacarpal  bone  of  the  index  finger.     They  are  long,  cylindrical  bones,  pre- 
senting for  examination  a  shaft  and  two  extremities. 

Common  Characters  of  the  Metacarpal  Bones.  The  Shaft  (corpus)  .—The\ 
shaft  is  prismoid  in  form  and  curved  longitudinally,  so  as  to  be  convex  in  the] 
longitudinal  direction  behind,  concave  in  front.  It  presents  three  surfaces; 
two  lateral  and  one  posterior.  The  two  lateral  surfaces  constitute  the  palmar  or) 
volar  surface.  The  lateral  surfaces  are  concave,  for  the  attachment  of  the  Inter-j 
ossei  muscles,  and  separated  from  one  another  by  a  prominent  anterior  ridge.  [ 
The  posterior  or  dorsal  surface  presents  in  its  distal  half  a  smooth,  triangular,  flat-j 
tened  area  which  is  covered,  in  the  recent  state,  by  the  tendons  of  the  Extensor 
muscles.    This  triangular  surface  is  bounded  by  two  lines,  which  commence  inj 


THE  METACABPUS 


201 


small  tubercles  situated  on  the  dorsal  aspect  on  either  side  of  the  digital  extremity, 
and,  running  backward,  converge  to  meet  together  a  little  behind  the  centre  of 
the  bone  and  form  a  ridge  which  runs  along  the  rest  of  the  dorsal  surface  to  the 
carpal  extremity.  This  ridge  separates  two  lateral,  sloping  surfaces  for  the 
attachment  of  the  Dorsal  interossei  muscles/  To  the  tubercles  on  the  digital 
extremities  are  attached  the  lateral  ligaments  of  the  metacarpo-phalangeal  joints. 
On  the  palmar  surface  of  each  metacarpal  bone  is  a  nutrient  foramen  (foramen 
nidricium) ,  which  opens  into  a  nutrient  canal  {canalis  nutricius).  In  the  thumb 
metacarpal  the  direction  of  this  foramen  is  toward  the  periphery  (distally).  In 
each  of  the  other  metacarpals  it  is  from  the  periphery  (proximally). 

Carpal  or  Proximal  Extremity  or  Base  (basis) . — The  carpal  extremity,  or  base, 
is  of  a  cuboidal  form,  and  broader  behind  than  in  front;  it  articulates  above 
with  the  carpus,  and  on  each  side  with  the  adjoining  metacarpal  bones ;  its  dorsal 
and  palmar  surfaces  are  rough,  for  the  attachment  of  tendons  and  ligaments. 

Digital  or  Distal  Extremity  or  Head  (capitulum). — The  digital  extremity,  or  head, 
presents  an  oblong  surface,  markedly  convex  from  before  backward,  less  so  from 
side  to  side,  and  flattened  laterally;  it  articulates  with  the  proximal  phalanx;  it  is 
broader  and  extends  farther  forward  on  the  palmar  than  on  the  dorsal  aspect.  It 
is  longer  in  the  antero-posterior  than  in  the  transverse  diameter.  On  either  side  of 
the  head  is  a  tubercle  for  the  attachment  of  the  lateral  ligament  of  the  metacarpo- 
phalangeal joint.  The  posterior  surface,  broad  and  flat,  supports  the  Extensor 
tendons;  the  anterior  surface  is  grooved  in  the  middle  line  for  the  passage  of  the 
Flexor  tendons,  and  marked  on  each  side  by  an  articular  eminence  continuous  with 
the  terminal  articular  surface.  The  metacarpal  spaces  (spatia  interossea  metacarpi) 
are  the  intervals  between  the  metacarpal  bones.  They  are  occupied  by  the 
Interossei  muscles.  The  broadest  space  is  between  the  metacarpal  bones  of  the 
thumb  and  index  finger. 

Peculiar  Characters  of  the  Metacarpal  Bones. — The  Metacarpal  Bone  of  the 
Thumb  (os  metacarpale  I)  (Fig.  147)  is  shorter  and  wider  than  the  rest,  diverges  to  a 
greater  degree  from  the  carpus,  and  its  palmar  sur- 
face is  directed  inward  toward  the  palm.  The  shaft 
is  flattened  and  broad  on  its  dorsal  aspect,  and 
does  not  present  the  ridge  which  is  found  on  the 
other  metacarpal  bones ;  it  is  concave  from  above 
downward,  on  its  palmar  surface.  The  carpal 
extremity,  or  base,  presents  a  concavo-convex  sur- 
face, for  articulation  with  the  trapezium;  it  has 
no  lateral  facets,  but  presents  externally  a  tubercle 
for  the  insertion  of  the  Extensor  ossis  metacarpi 
pollicis.  The  digital  extremity  is  less  convex  than 
that  of  the  other  metacarpal  bones,  broader  from 
side  to  side  than  from  before  backward.  It  pre- 
sents on  its  palmar  aspect  two  distinct  articular 
eminences  for  the  two  sesamoid  bones  in  the  ten- 
dons of  the  Flexor  brevis  pollicis,  the  outer  one 
being  the  larger  of  the  two. 

The  side  to  which  this  bone  belongs  may  be  known  by  holding  it  in  the  position 
it  occupies  in  the  hand,  with  the  carpal  extremity  upward  and  the  dorsal  surface 
backward;  the  tubercle  for  the  Extensor  ossis  metacarpi  pollicis  will  point  to  the 
side  to  which  it  belongs. 

Attachment  of  Muscles. — To  four:  the  Flexor  ossis  metacarpi  pollicis,  the  Extensor 
ossis  metacarpi  pollicis,  the  Flexor  brevis  pollicis,  and  the  First  dorsal  interosseous. 


Tubercle. 
For  trapezium 


For  trnpezium. 


Fig.  147. — The  fir.st  metacarpal.    (Left.) 


'  By  these  .sloping  surfaces  the  metacarpal  bones  of  the  hand  may  be  at  once  differentiated  from  the  meta- 
tarsal bone  of  the  foot. 


202 


THE  SKELETON 


The  Metacarpal  Bone  of  the  Index  Finger  {os  metacarpale  II)  (Fig.  148)  is  the 
longest  and  its  base  the  largest  of  the  other  four.  Its  carpal  extremity  is  prolonged 
upward  and  inward,  forming  a  prominent  ridge.  The  dorsal  and  palmar  surfaces 
of  this  extremity  are  rough,  for  the  attachment  of  tendons  and  ligaments.  It  pre- 
sents four  articular  facets :  three  on  the  upper  aspect  of  the  base :  the  middle  one  of 
the  three  is  the  largest,  concave  from  side  to  side,  convex  from  before  backward,  for 
articulation  with  the  trapezoid;  the  external  one  is  a  small,  flat,  oval  facet,  for 
articulation  with  the  trapezium ;  the  internal  one  on  the  summit  of  the  ridge  is  long 
and  narrow,  for  articulation  with  the  os  magnum.  The  fourth  facet  is  on  the  inner 
or  ulnar  side  of  the  extremity  of  the  bone,  and  is  for  articulation  with  the  third 
metacarpal  bone. 

The  side  to  which  this  bone  belongs  is  indicated  by  the  absence  of  the  lateral 
facet  on  the  outer  (radial)  side  of  its  base,  so  that  if  the  bone  is  placed  with  the 
base  toward  the  student  and  the  palmar  surface  upward,  the  side  on  which  there 
is  no  lateral  facet  will  be  that  to  which  it  belongs. 


■t^For  trapezium. 
For  trapezoid. 


1    For  third  metacarpal. 
For  OS  magnum. 


Fig.  148. — The  second  metacarpal.     (Left.) 


Styloid   For  second  \  For  fourth 

process,  metacarpal.    \  metacarpal. 

For  OS  magnum. 

Fig.  149. — The  third  metacarpal.     (Left.) 


Attachment  of  Muscles. — To  six:  Flexor  carpi  radialis,  Extensor  carpi  radialis 
longior,  Adductor  obliquus  pollicis.  First  and  Second  dorsal  interosseous,  and 
First  palmar  interosseous. 

The  Metacarpal  Bone  of  the  Middle  Finger  (os  metacarpale  III)  (Fig.  149)  is  a 
little  smaller  than  the  preceding:  it  presents  a  pyramidal  eminence,  the  styloid 
process  (processus  styloideus) ,  on  the  radial  side  of  its  base  (dorsal  aspect),  which 
extends  upward  behind  the  os  magnum;  immediately  below  this,  on  the  dorsal 
aspect,  is  a  rough  surface  for  the  attachment  of  the  Extensor  carpi  radialis  brevior. 
The  carpal,  articular  facet  is  concave  behind,  flat  in  front,  and  articulates  with  the 
OS  magnum.  On  the  radial  side  is  a  smooth,  concave  facet,  for  articulation  with 
the  second  metacarpal  bone,  and  on  the  ulnar  side  two  small,  oval  facets,  for  articu- 
lation with  the  fourth  metacarpal. 

The  side  to  which  this  bone  belongs  is  easily  recognized  by  the  styloid  process 
on  the  radial  side  of  its  base.  With  the  palmar  surface  uppermost  and  the  base 
toward  the  student,  this  process  points  toward  the  side  to  which  the  bone  belongs. 


THE   METACARPUS 


203 


Attachment  of  Muscles. — To  six:  Extensor  carpi  radialis  brevior,  Flexor  carpi 
radialis,  Adductor  transversus  pollicis,  Adductor  obliquus  pollicis,  and  Second  and 
Third  dorsal  interosseous. 

The  Metacarpal  Bone  of  the  Ring  Finger  {os  metacarpale  IV)  (Fig.  150)  is  shorter 
and  smaller  than  the  preceding,  and  its  base  small  and  quadrilateral;  the  carpal 
surface  of  the  base  presenting  two  facets,  a  large  one  externally,  for  articulation 
with  the  unciform,  and  a  small  one  internally,  for  the  os  magnum.  On  the  radial 
side  are  two  oval  facets,  for  articulation  with  the  third  metacarpal  bone;  and  on 
the  ulnar  side  a  single  concave  facet,  for  the  fifth  metacarpal. 

If  this  bone  is  placed  with  the  base  toward  the  student  and  the  palmar  surface 
upward,  the  radial  side  of  the  base,  which  has  two  facets  for  articulation  with  the 
third  metacarpal  bone,  will  be  on  the  side  to  which  it  belongs.  If,  as  sometimes 
happens  in  badly  marked  bones,  one  of  these  facets  is  indistinguishable,  the  side 
may  be  known  by  selecting  the  surface  on  which  the  larger  articular  facet  is  present. 
This  facet  is  for  the  fifth  metacarpal  bone,  and  would  therefore  be  situated  on  the 
ulnar  side — that  is,  the  one  to  which  the  bone  does  not  belong. 


Fig.  150. 


For  fift  h  metor 
For  OS  I  carpal 

magnum.  For  unciform. 

— The  fourth  metacarpal.     (Left.) 


For  cuneiform. 


For  fourth 
metacarpal. 
Fig.  151. — The  fifth  metacarpal. 


(Left.) 


Attachment  of  Muscles. — ^To  three:  the  Third  and  Fourth  dorsal  and  Second 
pahnar  intercsseous. 

The  Metacarpal  Bone  of  the  Little  Finger  (os  metacarpale  V)  (Fig.  151)  presents  on 
its  base  one  facet,  which  is  concavo-convex,  and  which  articulates  with  the  unciform 
bone,  and  one  lateral,  articular  facet,  which  articulates  with  the  fourth  metacarpal 
bone.  On  its  ulnar  side  is  a  prominent  tubercle,  for  the  insertion  of  the  tendon  of 
the  Extensor  carpi  ulnaris.  The  dorsal  surface  of  the  shaft  is  marked  by  an  oblique 
ridge  which  extends  from  near  the  uhiar  side  of  the  upper  extremity  to  the  radial 
side  of  the  lower.  The  outer  division  of  this  surface  serves  for  the  attachment  of 
the  Fourth  dorsal  interosseous  muscle;  the  inner  division  is  smooth  and  covered 
by  the  Extensor  tendons  of  the  little  finger. 

If  this  bone  is  placed  with  its  base  toward  the  student  and  its  palmar  surface 
upward,  the  side  of  the  head  which  has  a  lateral  facet  will  be  that  to  which  the 
bone  belongs. 

Attachment  of  Muscles. — To  five:  the  Extensor  carpi  ulnaris.  Flexor  carpi 
ulnaris,  Flexor  ossis  metacarpi  minimi  digiti,  Fourth  dorsal,  and  Third  palmar 
interosseous. 


204  THE    SKELETON 

Articulations. — Besides  the  phalangeal  articulations,  the  first  metacarpal  bone 
articulates  with  the  trapezium;  the  second  with  the  trapezium,  trapezoid,  os 
magnum,  and  third  metacarpal  bones;  the  third  with  the  os  magnum  and  second 
and  fourth  metacarpal  bones;  the  fourth  with  the  os  magnum,  unciform,  and 
third  and  fifth  metacarpal  bones;  and  the  fifth  with  the  unciform  and  fourthj 
metacarpal. 

The  first  has  no  lateral  facets  on  its  carpal  extremity;  the  second  has  no  lateral] 
facet  on  its  radial  side,  but  one  on  its  ulnar  side;  the  third  has  one  on  its  radial! 
and  two  on  its  ulnar  side;  the  fourth  has  two  on  its  radial  and  one  on  its  ulnarj 
side;  and  the  fifth  has  only  one  on  its  radial  side. 

The  Phalanges  of  the  Hand  (Phalanges  Digitorum  Manus). 

The  phalanges  (internodia)  are  the  bones  of  the  fingers;  they  are  fourteen  ir 
number,  three  for  each  finger,  and  two  for  the  thumb.  In  numbering  them  the 
proximal  bone  is  designated  as  the  first  phalanx  (phalanx  I) .  They  are  long  bones  J 
and  present  for  examination  a  shaft  and  two  extremities.  The  shaft  (corpus 
phalangis)  tapers  from  above  downward,  is  convex  posteriorly,  concave  in  front 
from  above  downward,  flat  from  side  to  side,  and  marked  laterally  by  rougl 
ridges,  which  give  attachment  to  the  fibrous  sheaths  of  the  Flexor  tendons, 
nutrient  foramen  on  the  palmar  surface  leads  into  a  nutrient  canal  which  runs 
toward  the  periphery  (distalward) .  The  metacarpal  extremity  or  base  (hasiA 
phalangis)  of  each  phalanx  in  the  first  row  presents  an  oval,  concave,  articular 
surface,  broader  from  side  to  side  than  from  before  backward;  and  the  samt 
extremity  in  the  other  two  rows,  a  double  concavity,  separated  l)y  a  longitudinal] 
median  ridge,  extending  from  before  backward.  The  distal  extremity  of  the  first 
phalanx  of  the  thumb  and  of  the  first  and  second  phalanx  of  each  of  the  fingers  is 
smaller  than  the  base,  and  terminates  in  two  small,  lateral  condyles,  separatee 
by  a  slight  groove  (trochlea  phalangis) ;  the  articular  surface  being  prolonged  far- 
ther forward  on  the  palmar  than  on  the  dorsal  surface,  especially  in  the  first  row.] 

The  Ungual  Phalanges  (distal)  are  convex  on  their  dorsal,  flat  on  their  palmar^ 
surfaces;  they  are  recognized  by  their  small  size  and  by  a  roughened,  elevatec 
surface  of   a  horseshoe  form  on  the  palmar  aspect  of    their  ungual  extremity 
(tuberositas  unguicularis) ,  which  serves  to  support  the  sensitive  pulp  of  the  finger.] 

Articulations. — The  first  row,  with  the  metacarpal  bones  and  the  second  row  of 
phalanges;  the  second  row,  with  the  first  and  third;  the  third,  with  the  second  row.] 

Attachment  of  Muscles. — To  the  base  of  the  first  phalanx  of  the  thumb,  five 
muscles:  the  Extensor  brevis  polHcis,  Flexor  brevis  pollicis.  Abductor  polHcis,] 
Adductor  transversus  and  Obliquus  pollicis.     To  the  second  phalanx,  two :  the 
Flexor  longus  pollicis  and  the  Extensor  longus  pollicis.    To  the  base  of  the  first 
phalanx  of  the  index  finger,  the  First  dorsal  and  the  First  palmar  interosseous;  tc 
that  of  the  middle  finger,  the  Second  and  Third  dorsal  interosseous;  to  that  of 
the  ring  finger,  the  Fourth  dorsal  and  the  Second  palmar  interosseous ;  and  to  that 
of  the  little  finger,  the  Third  palmar  interosseous,  the  Flexor  brevis  minimi  digiti,] 
and  Abductor  minimi  digiti.    To  the  second  phalanges,  the  Extensor  sublimis  digi- 
torum. Extensor  communis  digitorum,  and,  in  addition,  the  Extensor  indicis  tc 
the  index  finger,  the  Extensor  minimi  digiti  to  the  little  finger.     To  the  third] 
phalanges,  the  Flexor  profundus  digitorum  and  Extensor  communis  digitorum. 

Surface  Form. — On  the  front  of  the  wrist  are  two  subcutaneous  eminences,  one  on  the 
radial  side,  the  larger  and  flatter,  due  to  the  tuberosity  of  the  scaphoid  and  the  ridge  on  the 
trapezium;  the  other,  on  the  ulnar  side,  caused  by  the  pisiform  bone.  The  tubercle  of  the 
scaphoid  is  to  be  felt  just  below  and  in  front  of  the  apex  of  the  styloid  process  of  the  radius.  It 
is  best  perceived  by  extending  the  hand  on  the  forearm.  Immediately  below  is  to  be  felt 
another  prominence,  better  marked  than  the  tubercle;  this  is  the  ridge  on  the  trapezium  whichj 
gives  attachment  to  some  of  the  short  muscles  of  the  thumb.     On  the  inner  side  of  the  front  of 


DEVELOPMENT  OF  THE  BONES  OF  THE  HAND  205 

the  wrist  the  pisiform  bone  is  to  be  felt,  forming  a  small  but  prominent  projection  in  this  situa- 
tion. It  is  some  distance  below  the  styloid  process  of  the  ulna,  and  may  be  said  to  be  just  below 
the  level  of  the  styloid  process  of  the  radius.  The  rest  of  the  front  of  the  carpus  is  covered  by 
tendons  and  the  annular  ligament,  and  entirely  concealed,  with  the  exception  of  the  hooked 
process  of  the  unciform,  which  can  only  be  made  out  with  difficulty.  The  back  of  the  carpus  is 
convex  and  covered  by  the  Extensor  tendons,  so  that  none  of  the  posterior  surfaces  of  the  bones 
are  to  be  felt,  with  the  exception  of  the  cuneiform  on  the  inner  side.  Below  the  carpus  the 
dorsal  surfaces  of  the  metacarpal  bones,  except  the  fifth,  are  covered  by  tendons,  and  are  scarcely 
visible  except  in  very  thin  hands.  The  dorsal  surface  of  the  fifth  is,  however,  subcutaneous 
throughout  almost  its  whole  length,  and  is  plainly  to  be  perceived  and  felt.  In  addition  to  this, 
slightly  external  to  the  middle  line  of  the  hand,  is  a  prominence,  frequently  well  marked,  but 
occasionally  indistinct,  formed  by  the  base  of  the  metacarpal  of  the  middle  finger.  The  heads  of 
the  metacarpal  bones  are  plainly  to  be  felt  and  seen,  rounded  in  contour  and  standing  out  in  bold 
relief  under  the  skin,  when  the  fist  is  clenched.  It  should  be  borne  in  mind  that  when  the  fin- 
gers are  flexed  on  the  hand,  the  articular  surfaces  of  the  first  phalanges  glide  off  the  heads  of  the 
metacarpal  bones  on  to  their  anterior  surfaces,  so  that  the  head  of  these  bones  form  the  prom- 
inence of  the  knuckles  and  receive  the  force  of  any  blow  which  may  be  given.  The  head  of  the 
third  metacarpal  bone  is  the  most  prominent,  and  receives  the  greater  part  of  the  shock  of  the 
blow.  This  bone  articulates  with  the  os  magnum,  so  that  the  concussion  is  carried  through  this 
bone  to  the  scaphoid  and  semilunar,  with  which  the  head  of  the  os  magnum  articulates,  and  by 
these  bones  is  transferred  to  the  radius,  along  which  it  may  be  carried  to  the  capitellum  of  the 
humerus.  The  enlarged  extremities  of  the  phalanges  are  to  be  ])lainly  felt:  they  form  the 
joints  of  the  fingers.  When  the  digits  are  bent  the  proximal  phalanges  of  the  joints  form 
prominences,  which  in  the  joint  between  the  first  and  second  phalanges  is  slightly  hollowed,  in 
accordance  with  the  grooved  shape  of  their  articular  surfaces,  whilst  at  the  last  row  the  prom- 
inence is  flattened  and  square-shaped.  In  the  palm  of  the  hand  the  four  inner  metacarpal  bones 
are  covered  by  muscles,  tendons,  and  the  palmar  fascia,  and  no  part  of  them  but  their  heads 
is  to  be  distinguished.  With  regard  to  the  thumb,  on  the  dorsal  aspect  the  base  of  the  meta- 
carpal bone  forms  a  prominence  below  the  styloid  process  of  the  radius;  the  shaft  is  to  be  felt, 
covered  by  tendons,  terminating  at  its  head  in  a  flattened  prominence,  in  front  of  which  can  be 
felt  the  sesamoid  bones. 

Surgical  Anatomy. — The  carpal  bones  are  not  very  liable  to  fracture,  except  from  extreme 
violence,  when  the  parts  may  be  so  comminuted  as  to  necessitate  amputation.  Occasionally  they 
.  are  the  seat  of  tuberculous  disease.  The  metacarpal  bones  and  the  phalanges  are  not  unfrequently 
broken  by  direct  violence.  The  first  metacarpal  bone  is  the  one  most  commonly  fractured; 
then  the  second,  the  fourth,  and  the  fifth,  the  third  being  the  one  least  frequently  broken.  There 
are  two  diseases  of  the  metacarpal  bones  and  phalanges  which  require  special  mention  on 
account  of  the  frequency  of  their  occurrence.  One  is  tuberculous  dactylitis,  consisting  in  a 
deposit  of  tuberculous  material  in  the  medullary  canal,  expanding  the  bone,  with  subsequent 
caseation  and  resulting  necrosis.  The  other  is  chondroma,  which  is  perhaps  more  frequently 
found  in  connection  with  the  metacarpal  bones  and  phalanges  than  with  any  other  bones.  When 
chondromatous  growth  takes  place  there  are  usually  multiple  tumors,  and  they  may  spring 
either  from  the  medullary  canal  or  from  the  periosteum. 


• 


Development  of  the  Bones  of  the  Hand. 


The  Carpal  Bones  are  each  developed  by  a  single  centre.  At  birth  they  are 
all  cartilaginous.  Ossification  proceeds  in  the  following  order  (Fig.  152):  In  the 
OS  magnum  and  unciform  an  ossific  point  appears  during  the  first  year,  the  former 
preceding  the  latter;  in  the  cuneiform,  at  the  third  year;  in  the  trapezium  and 
semilunar,  at  the  fifth  year,  the  former  preceding  the  latter;  in  the  scaphoid,  at 
the  sixth  year;  in  the  trapezoid,  during  the  eighth  year;  and  in  the  pisiform,  about 
the  twelfth  year. 

Occasionally  an  additional  bone,  the  os  cenirale,  is  found  in  the  carpus,  lying 
between  the  scaphoid,  trapezoid,  and  os  magnum.  During  the  second  month  of 
foetal  life  it  is  represented  by  a  small  cartilaginous  nodule,  which,  however, 
fuses  with  the  cartilaginous  scaphoid  about  the  third  month.  Sometimes  the 
styloid  process  of  the  third  metacarpal  is  detached  and  forms  an  additional 
ossicle. 

The  Metacarpal  Bones  are  each  developed  by  two  centres:  one  for  the  shaft 
and  one  for  the  digital  extremity  for  the  four  inner  metacarpal  bones;  one  for  the 
shaft  and  one  for  the  base  for  the  metacarpal  bone  of  the  thumb,  which  in  this 


206 


THE   SKELETON 


respect  resembles  the  phalanges/  Ossification  commences  in  the  centre  of  the 
shaft  about  the  eighth  or  ninth  week,  and  gradually  proceeds  to  either  end  of  the 
bone:  about  the  third  year  the  digital  extremities  of  the  four  inner  metacarpal 
bones  and  the  base  of  the  first  metacarpal  begin  to  ossify,  and  they  unite  about 
the  twentieth  year. 


Carpus. 

One  centre  for  each  hone.        ^^ 
All  cartilaginous  at  birth.      ^/ 


Metacarpus. 

Two  centres  for  each  hone  : 
One  for  shaft, 
One  for  digital  extremity, 
except  first. 


Phalanges. 

Two  centres  for  each  hone 
One  for  shaft, 
One  for  metacarpal 
extremity. 


Appears  Srd  year. 

Vs^^S.  f/mfe  20th  year. 

"^        Appears  8th  week. 


^-Appears  Uth-Sth  year. 
I  Unite  ISth-SOlh  year. 
Appears  8th  week. 

Appears  Uh-Sth  year. 
\  Unite  mh-30  year. 
'—Appears  8th  week. 

Fig.  152. — Plan  of  the  development  of  the  hand. 

The  Phalanges  are  each  developed  by  two  centres ;  one  for  the  shaft  and  one 
for  the  base.  Ossification  commences  in  the  shaft,  in  all  three  rows,  at  about  the 
eighth  week,  and  gradually  involves  the  whole  of  the  bone  excepting  the  upper 
extremity.  Ossification  of  the  base  commences  in  the  first  row  between  the  third 
and  fourth  years,  and  a  year  later  in  those  of  the  second  and  third  rows.  The  two 
centres  become  united,  in  each  row,  between  the  eighteenth  and  twentieth  years. 

In  the  ungual  phalanges  the  centre  for  the  shaft  appears  at  the  distal  extremity 
of  the  phalanx,  instead  of  at  the  middle  of  the  shaft,  as  is  the  case  with  the  other 
phalanges. 

THE  LOWER  EXTREMITY. 

The  bones  of  the  lower  extremity  consist  of  those  of  the  pelvic  girdle,  of  the 
thigh,  of  the  leg,  and  of  the  foot. 


'  Allan  Thomson  has  demonstrated  the  fact  that  the  first  metacarpal  bone  is  often  developed  from  three 
centres;  that  is  to  say,  there  is  a  separate  nucleus  for  the  di.stal  end,  forming  a  distinct  epiphysis,  visible  at  the 
age  of  seven  or  eight  years.  He  also  states  that  there  are  traces  of  a  proximal  epiphysis  in  the  second  meta- 
carpal bone. — Journal  of  Anatomy,  1869. 


THE   OS  INNOMINATUM  207 


THE  PELVIC  GIRDLE. 

The  pelvic  girdle  consists  of  a  single  bone,  the  os  innominatum,  by  which  the 
thigh  is  connected  to  the  trunk. 

The  Os  Innominatum,  called  also  Os  Coxae,  Hip  Bone,  Haunch  Bone, 
the  Nameless  Bone  (Figs.  153,  154). 

The  OS  innominatum  {in,  not;  nomino,  I  name)  is  so  called  from  bearing  no 
resemblance  to  any  known  object.  It  is  a  large,  irregularly  shaped,  flat  bone,  con- 
stricted in  the  centre  and  expanded  above  and  below.  With  its  fellow  of  the 
opposite  side  it  forms  the  sides  and  anterior  wall  of  the  pelvic  cavity.  In  young 
subjects  it  consists  of  three  separate  parts,  which  meet  and  form  the  large,  cup- 
like cavity,  the  acetabulum,  situated  near  the  middle  of  the  outer  surface  of  the 
bone;  and,  although  in  the  adult  these  have  become  united,  it  is  usual  to  describe 
the  bone  as  divisible  into  three  portions — the  ilium,  the  ischium,  and  the  pubis. 

The  iUum,  so  called  from  its  supporting  the  flank  (ilium  or  ileuin,  the  flank), 
is  the  superior,  broad,  and  expanded  portion  which  runs  upward  from  the 
acetabulum  and  forms  the  prominence  of  the  hip. 

The  ischium  {iayj.ov,  the  hip)  is  the  inferior  and  strongest  portion  of  the  bone ; 
it  proceeds  downward  from  the  acetabulum,  expands  into  a  large  tuberosity,  and 
then,  curving  forward,  forms,  with  the  descending  ramus  of  the  os  pubis,  a  large 
aperture,  the  obturator  foramen. 

The  OS  pubis  is  that  portion  which  extends  inward  and  downward  from  the 
acetabulum  to  articulate  in  the  middle  line  with  the  l)one  of  the  opposite  side:  it 
forms  the  front  of  the  pelvis,  supports  the  external  organs  of  generation,  and  has 
received  its  name  from  the  skin  over  it  being  covered  with  hair  (pubes). 

The  Ilium  {os  ilium). — The  lower  or  constricted  part  of  the  ilium  is  thick, 
though  narrower  than  the  expanded  portion.  It  aids  in  the  formation  of  the 
acetabulum  and  is  called  the  body  {corpus  ossis  ilium).  The  broad  expanded 
portion  of  the  ilium  is  thin  in  many  places.  It  is  called  the  ala  {ala  ossis  ilium). 
The  ilium  presents  for  examination  two  surfaces,  an  external  and  an  internal;  a 
crest,  and  two  borders,  an  anterior  and  a  posterior. 

External  Surface  or  Dorsum  of  the  Ilium  (Fig.  153). — The  posterior  part  of  this 
surface  is  directed  backward  and  outward;  its  front  part,  downward  and  outward. 
It  is  smooth,  convex  in  front,  deeply  concave  behind;  bounded  above  by  the  crest, 
below  by  the  upper  border  of  the  acetabulum ;  in  front  and  behind  by  the  anterior 
and  posterior  borders.  This  surface  is  crossed  in  an  arched  direction  by  three 
semicircular  lines — the  superior,  middle,  and  inferior  curved  lines.  The  superior 
curved  line,  or  the  posterior  gluteal  line  {linea  glutaea  'posterior),  the  shortest  of  the 
three,  commences  at  the  crest,  about  two  inches  in  front  of  its  posterior  extremity; 
it  is  at  first  distinctly  marked,  but  as  it  passes  downward  and  backward  to  the 
upper  part  of  the  great  sacro-sciatic  notch,  where  it  terminates,  it  becomes  less 
marked,  and  is  often  altogether  lost.  Behind  this  line  is  a  narrow  semilunar 
surface,  the  upper  part  of  which  is  rough  and  affords  attachment  to  part  of 
the  Gluteus  maximus;  the  lower  part  is  smooth  and  has  no  muscular  fibres 
attached  to  it.  The  middle  curved  line,  or  the  anterior  gluteal  line  {linea  glutaea 
anterior),  the  longest,  of  the  three,  commences  at  the  crest,  about  an  inch 
behind  its  anterior  extremity,  and,  taking  a  curved  direction  downward  and 
backward,  terminates  at  the  upper  part  of  the  great  sacro-sciatic  notch.  The 
space  between  the  superior  and  middle  curved  lines  and  the  crest  is  concave, 
and  affords  attachment  to  the  Gluteus  medius  muscle.  Near  the  central  part 
of  this  line  may  often  be  observed  the  orifice  of  a  nutrient  foramen.     The  inferior 


208 


THE   SKELETON 


curved  or  inferior  gluteal  line  (linea  glutaea  inferior),  the  least  distinct  of  the  three, 
commences  in  front  at  the  notch  on  the  anterior  border,  and,  taking  a  curved 
direction  backward  and  downward,  terminates  at  the  middle  of  the  great  sacro- 
sciatic  notch.     The  surface  of  bone  included  between  the  middle  and  inferior 


nierior  superior 
spine. 


OEMELLUS   SUPERIOR. 

Bpine  of  ischium. 


OEMKLLUS  INFERIOR. 


PYRAMIOALIS. 
DDUCTOR  LOi 


Fig.  153. — Right  os  innominatum.     External  surface. 

curved  lines  is  concave  from  above  downward,  convex  from  before  backward,  andj 
affords  attachment  to  the  Gluteus  minimus  muscle.    Beneath  the  inferior  curvec 
line,  and  corresponding  to  the  upper  part  of  the  acetabulum,  is  a  roughened  sur-1 
face  (sometimes  a  depression),  to  which  is  attached  the  reflected  tendon  of  the] 
Rectus  femoris  muscle. 

Internal  Surface. — The  internal  surface  (Fig.  154)  of  the  ilium  is  bounded  abovej 
by  the  crest;  below  it  is  continuous  with  the  pelvic  surface  of  the  os  pubis  andj 
ischium,  a  faint  line  only  indicating  the  place  of  union;  and  before  and  behind  itj 


THE    OS   INNOMINATUM 


209 


is  bounded  by  the  anterior  and  posterior  borders.  It  presents  a  large,  smooth, 
concave  surface,  called  the  iliac  fossa,  or  venter  ilii  (fossa  iliaca) ,  which  lodges  the 
Iliacus  muscle,  and  presents  at  its  lower  part  the  orifice  of  a  nutrient  canal  (fora- 
men nutricium) ;  and  below  this  a  smooth,  rounded  border,  the  ilio-pectineal  line 


COMPRESSOR    URETHR/E. 


TRANSVERSUS    PERINEI. 

Crus  penis.'  erector  penis. 

Fig.  154. — Right  os  innominatum.     Internal  surface. 


or  the  linea  ilio-pectinea  (linea  arcuata) ,  which  separates  the  iliac  fossa  from  that 
portion  of  the  internal  surface  which  enters  into  the  formation  of  the  true  pelvis, 
and  which  gives  attachment  to  part  of  the  Obturator  internus  muscle.  Behind 
the  iliac  fossa  is  a  rough  surface  divided  into  two  portions,  an  anterior  and 
a  posterior.  The  anterior  or  auricular  surface  (fades  auricularis) ,  so  called  from 
its  resemblance  in  shape  to  the  ear,  is  coated  with  cartilage  in  the  recent  state, 
and  articulates  with  a  surface  of  similar  shape  on  the  side  of  the  sacrum.  The 
posterior  portion  (tuberositas  iliaca)  is  rough,  for  the  attachment  of  the  posterior 
sacro-iliac  ligaments  and  |or  a  part  of  the  origin  of  the  Erector  and  Multifidus 

14 


210  THE  SKELETON 

spinse.  In  many  bones  a  furrow  exists  in  front,  under  and  behind  the  auricular 
surface.  This  furrow  is  the  paraglenoid  sulcus  (sulcus  paraglenoidalis) ,  and  it 
affords  attachment  to  the  sacro-sciatic  ligaments. 

The  Crest  of  the  Ilium  (crista  iliaca). — The  crest  of  the  ilium  is  convex  in  its 
general  outline  and  sinuously  curved,  being  concave  inward  in  front,  concave 
outward  behind.     It  is  longer  in  the  female  than  in  the  male,  very  thick  behind, 
and  thinner  at  the  centre  than  at  the  extremities.     It  terminates  at  either  end  inj 
a  prominent  eminence,  the  anterior  superior  and  posterior  superior  spinous  processj 
(spina  iliaca  anterior  superior  et  spina  iliaca  posterior  superior) .    The  surface  of  j 
the  crest  is  broad,  and  divided  into  an  external  lip  (labium  externum) ,  an  inter- 
nal lip  (labium  internum),  and  an  intermediate  space  (linea  intermedia).     About 
two  inches  behind  the  anterior  superior  spinous  process  there  is  a  prominent 
tubercle  on  the  outer  lip.     To  the  external  lip  is  attached  the  Tensor  fascif 
femoris,   Obliquus   externus  abdominis,   and   Latissimus   dorsi,   and   along  its! 
whole  length,  the  fascia  lata;  to  the  space  between  the  lips,  the  Internal  oblique;! 
to  the  internal  lip,  the  Transversalis,  Quadratus  lumborum,  and  Erector  spinse,] 
the  Iliacus,  and  the  fascia  iliaca. 

Anterior  Border. — The  anterior  border  of  the  ilium  is  concave.    It  presents  twol 
projections,  separated  by  a  notch.    Of  these,  the  uppermost,  situated  at  the  junc-j 
tion  of  the  crest  and  anterior  border,  is  called  the  anterior  superior  spinous  processj 
of  the  ilium  (spina  iliaca  anterior  superior),  the  outer  border  of   which  gives 
attachment  to  the  fascia  lata  and  the  origin  of  the  Tensor  fasciae  femoris  (teri5or| 
vagincB  femoris) ;  its  inner  border,  to  the  Iliacus;  while  its  extremity  affords  attach- 
ment to  Poupart's  ligament  and  the  origin  of  the  Sartorius.    Beneath  this  emi- 
nence is  a  notch  which  gives  attachment  to  the  Sartorius  muscle,  and  across 
which   passes   the   external   cutaneous   nerve.     Below  the  notch  is  the  anterior 
inferior  spinous  process  (spina  iliaca  anterior  inferior),  which  terminates  in  thel 
upper  lip  of  the   acetabulum;   it  gives   attachment  to  the  straight  tendon  of] 
the  Rectus  femoris  muscle  and  the  ilio-femoral  ligament.    On  the  inner  side  of  thej 
anterior  inferior  spinous  process  is  a  broad,  shallow  groove,  over  which  passes 
the  Ilio-psoas  muscle.     This  groove  is  bounded  internally  by  an  eminence,  thel 
ilio-pectineal  eminence  (eminentia  iliopectinea) ,  which  marks  the  point  of  union] 
of  the  ilium  and  os  pubis. 

Posterior  Border. — -The  posterior  border  of  the  ilium,  shorter  than  the  anterior,! 
also  presents  two  projections  separated  by  a  notch,  the  posterior  superior  spinous! 
process  (spina  iliaca  posterior  superior)  and  the  posterior  inferior  spinous  process! 
(spina  iliaca  posterior  inferior).  The  former  corresponds  with  that  portion  ofj 
the  inner  surface  of  the  ilium  which  serves  for  the  attachment  of  the  oblique! 
portion  of  the  sacro-iliac  ligaments  and  the  Multifidus  spinae  muscle;  the  latter,! 
to  the  auricular  portion  which  articulates  with  the  sacrum.  Below  the  pos- 
terior inferior  spinous  process  is  a  deep  notch,  the  great  sciatic,  ilio-sciatic,  orl 
the  great  sacro-sciatic  notch  (incisura  isckiadica  major). 

The  Ischium  (os  ischii). — The  ischium  forms  the  lower  and  back  part  of  thej 
OS  innominatum.  It  is  divisible  into  a  thick  and  solid  portion — the  body;  a  large,] 
rough  eminence,  on  which  the  trunk  rests  in  sitting — the  tuberosity;  and  a  thin! 
part  which  passes  forward  and  slightly  upward — the  ramus. 

The  Body  (corpus  ossis  ischii). — The  body,  somewhat  triangular  in  form,  pre- 
sents three  surfaces,  external,  internal,  and  posterior;  and  three  borders,  external, 
internal,  and  posterior.     The  external  surface  corresponds  to  that  portion  of  the 
acetabulum  formed   by  the  ischium;   it  is  smooth   and   concave,  and   forms   ai 
little  more  than  two-fifths  of  the  acetabular  cavity;  its  outer  margin  is  bounded] 
by  a  prominent  rim  or  lip,  the  external   border,   to  which   the  cotyloid  fibro- 
cartilage  is  attached.     Below  the  acetabulum,  between  it  and  the  tuberosity,  is] 
a  deep  groove,  along  which  the  tendon  of  the  Obturator  externus  muscle  runs 


THE    OS  INNOMINATUM  211 

as  it  passes  outward  to  be  inserted  into  the  digital  fossa  of  the  femur.  The 
internal  surface  is  smooth,  concave,  and  enters  into  the  formation  of  the  lateral 
boundary  of  the  true  pelvic  cavity.  This  surface  is  perforated  by  two  or  three 
large,  vascular  foramina,  and  affords  attachment  to  part  of  the  Obturator  inter- 
nus  muscle.  The  'posterior  surface  is  quadrilateral  in  form,  broad  and  smooth. 
Below,  where  it  joins  the  tuberosity,  it  presents  a  groove,  the  obturator  groove 
(sulcus  obturatorius) ,  continuous  with  that  on  the  external  surface,  for  the  tendon 
of  the  Obturator  externus  muscle.  The  lower  edge  of  this  groove  is  formed  by 
the  tuberosity  of  the  ischium,  and  affords  attachment  to  the  Gemellus  inferior 
muscle.  This  surface  is  limited,  externally,  by  the  margin  of  the  acetabulum; 
behind,  by  the  posterior  border;  it  supports  the  Pyriformis,  the  two  Gemelli,  and 
the  Obturator  internus  muscles  in  their  passage  outward  to  the  great  trochanter. 
The  external  border  forms  the  prominent  rim  of  the  acetabulum,  and  separates 
the  posterior  from  the  external  surface.  To  it  is  attached  the  cotyloid  fibro- 
cartilage.  The  internal  border  is  thin,  and  forms  the  outer  circumference  of  the 
obturator  foramen.  The  posterior  border  of  the  body  of  the  ischium  presents,  a 
little  below  the  centre,  a  thin  and  pointed,  triangular  eminence,  the  spine  of  the 
ischium  (spina  ischiadica) ,  more  or  less  elongated  in  different  subjects;  its  exter- 
nal surface  gives  attachment  to  the  Gemellus  superior,  its  internal  surface  to 
the  Coccygeus  and  Levator  ani;  whilst  to  the  pointed  extremity  is  connected  the 
lesser  sacro-sciatic  ligament.  Above  the  spine  is  a  notch  of  large  size,  the  great 
sacro-sciatic  notch  (incisura  ischiadica  major),  converted  into  a  foramen,  the  great 
sacro-sciatic  foramen  (foramen  ischiadicum  majus),  by  the  lesser  sacro-sciatic  liga- 
ment; it  transmits  the  Pyriformis  muscle,  the  gluteal  vessels,  and  superior  and 
inferior  gluteal  nerves;  the  sciatic  vessels,  the  greater  and  lesser  sciatic  nerves, 
the  internal  pudic  vessels  and  nerve,  and  the  nerves  to  the  Obturator  internus  and 
Quadratus  femoris.  Of  these,  the  gluteal  vessels  and  superior  gluteal  nerve  pass 
out  above  the  Pyriformis  muscle,  the  other  structures,  below  it.  Below  the  spine 
is  a  smaller  notch,  the  lesser  sacro-sciatic  notch  (incisura  ischiadica  minor) ;  it  is 
smooth,  coated  in  the  recent  state  with  cartilage,  the  surface  of  which  presents 
two  or  three  ridges  corresponding  to  the  subdivisions  of  the  tendon  of  the  Obtu- 
rator internus,  which  winds  over  it.  It  is  converted  into  a  foramen,  the  lesser 
sacro-sciatic  foramen  (foramen  ischiadicum  minus),  by  the  sacro-sciatic  ligaments, 
and  transmits  the  tendon  of  the  Obturator  internus,  the  nerve  which  supplies 
that  muscle,  and  the  internal  pudic  vessels  and  nerve. 

The  Tuberosity  of  the  Ischium  (tuber  ischiadicum). — The  tuberosity  of  the 
ischium  is  the  portion  of  bone  between  the  body  and  the  ascending  ramus. 
Some  anatomists  name  this  portion  of  bone  the  descending  or  superior  ramus 
(ramus  superior  ossis  ischii),  and  restrict  the  term  tuberosity  to  the  surface  of 
the  bone  which  is  rough,  and  is  directed  backward  and  outward.  The  tuber- 
osity presents  for  examination  three  surfaces:  external,  internal,  and  posterior. 
The  external  surface  is  quadrilateral  in  shape,  and  rough  for  the  attachment  of 
muscles.  It  is  bounded  above  by  the  groove  for  the  tendon  of  the  Obturator 
externus;  in  front  it  is  limited  by  the  posterior  margin  of  the  obturator  foramen, 
and  below  it  is  continuous  with  the  ramus  of  the  bone;  behind,  it  is  bounded  by 
a  prominent  margin  which  separates  it  from  the  posterior  surface.  In  front  of 
this  margin  the  surface  gives  attachment  to  the  Quadratus  femoris,  and  anterior 
to  this  to  some  of  the  fibres  of  origin  of  the  Obturator  externus.  The  lower  part 
of  the  surface  gives  origin  to  part  of  the  Adductor  magnus.  The  internal  sur- 
face forms  part  of  the  bony  wall  of  the  true  pelvis.  In  front  it  is  limited  by  the 
posterior  margin  of  the  obturator  foramen.  Behind,  it  is  bounded  by  a  sharp 
ndge,  for  the  attachment  of  a  falciform  prolongation  of  the  great  sacro-sciatic 
ligament;  it  sometimes  presents  a  groove  on  the  inner  side  of  this  ridge  for  the 
lodgement  of  the  internal  pudic  vessels  and  nerve;  and,  more  anteriorly,  has 


212  THE  SKELETON 

attached  the  Transversus  perinaei  and  Erector  penis  muscles.  The  'posterior 
surface  is  divided  into  two  portions — a  lower  rough,  somewhat  triangular  part, 
and  an  upper  smooth,  quadrilateral  portion.  The  anterior  portion  is  subdivided 
by  a  prominent  vertical  ridge,  passing  from  base  to  apex,  into  two  parts;  the 
outer  one  gives  attachment  to  the  Adductor  magnus;  the  inner  to  the  great  sacro- 
sciatic  ligament.  The  upper  portion  is  subdivided  into  two  facets  by  an  oblique 
ridge  which  runs  downward  and  outward;  from  the  upper  and  outer  facet  arises 
the  Semimembranosus;  from  the  lower  and  inner,  the  Biceps  and  Semitendinosus. 

The  Ramus  or  Inferior  Ramus  or  Ascending  Ramus  of  the  Ischium  {ramus  inferior 
ossis  ischii) . — The  ramus  is  the  thin,  flattened  part  of  the  ischium  which  ascends 
from  the  tuberosity  upward  and  inward,  and  joins  the  descending  ramus  of  the 
OS  pubis,  their  point  of  junction  being  indicated  in  the  adult  by  a  rough  line. 
The  outer  surface  of  the  ramus  is  rough,  for  the  attachment  of  the  Obturator 
externus  muscle,  and  also  some  fibres  of  the  Adductor  magnus;  its  inner  sur- 
face forms  part  of  the  anterior  wall  of  the  pelvis.  Its  inner  border  is  thick, 
rough,  slightly  everted,  forms  part  of  the  outlet  of  the  pelvis,  and  presents  two 
ridges  and  an  intervening  space.  The  ridges  are  continuous  with  similar  ones 
on  the  descending  ramus  of  the  os  pubis:  to  the  outer  one  is  attached  the  deep 
layer  of  the  superficial  perineal  fascia,  and  to  the  inner,  the  superficial  layer  of 
the  triangular  ligament  of  the  urethra.  If  these  two  ridges  are  traced  downward, 
they  will  be  found  to  join  with  each  other  just  behind  the  point  of  origin  of  the 
Transversus  perinsei  muscle;  here  the  two  layers  of  fascia  are  continuous  behind 
the  posterior  border  of  the  muscle.  To  the  intervening  space,  just  in  front  of  the 
point  of  junction  of  the  ridges,  is  attached  the  Transversus  perinsei  muscle,  and 
in  front  of  this  a  portion  of  the  crus  penis  vel  clitoridis  and  the  Erector  penis  vel 
clitoridis  muscle.  Its  outer  border  is  thin  and  sharp,  and  forms  part  of  the  inner 
margin  of  the  obturator  foramen. 

The  Pubis  {os  pubis). — The  OS  pubis  forms  the  anterior  part  of  the  os  innomi- 
natum,  and,  with  the  bone  of  the  opposite  side,  forms  the  front  boundary  of  the 
true  pelvic  cavity.    It  is  divisible  into  a  body,  an  ascending  and  a  descending  ramus. 

The  Body  {corpus  ossis  pubis) . — The  body  is  the  broad  portion  of  bone  formed 
by  the  junction  of  the  two  rami.  It  is  somewhat  quadrilateral  in  shape,  and 
presents  for  examination  two  surfaces  and  three  borders.  The  anterior  surface 
is  rough,  directed  downward  and  outward,  and  serves  for  the  attachment  of 
various  muscles.  To  the  upper  and  inner  angle,  immediately  below  the  crest, 
is  attached  the  Adductor  longus;  lower  down,  from  without  inward,  are  attached 
the  Obturator  externus,  the  Adductor  brevis,  and  the  upper  part  of  the  Gracilis. 
The  posterior  surface,  convex  from  above  downward,  concave  from  side  to  side, 
is  smooth,  and  forms  part  of  the  anterior  wall  of  the  pelvis.  It  gives  attach- 
ment to  the  Levator  ani.  Obturator  internus,  a  few  muscular  fibres  prolonged 
from  the  bladder,  and  the  pubo-prostatic  ligaments.  The  upper  border  presents 
fer  examination  a  prominent  tubercle,  which  projects  forward  and  is  called  the 
spine  {tuberculum  pubicum) ;  to  it  are  attached  the  outer  pillar  of  the  external 
abdominal  ring  and  Poupart's  ligament.  Passing  upward  and  outward  from 
this  is  a  prominent  ridge,  forming  part  of  the  ilio-pectineal  line  {linea  arcuMta), 
and  called  the  pecten  ossis  pubis.  It  marks  the  brim  of  the  true  pelvis:  to  it  are 
attached  a  portion  of  the  conjoined  tendon  of  the  Internal  oblique  and  Trans- 
versalis  muscles,  Gimbernat's  ligament,  and  the  triangular  fascia  of  the  abdomen. 
Internal  to  the  spine  of  the  os  pubis  is  the  crest,  which  extends  from  this  process 
to  the  iimer  extremity  of  the  bone.  It  affords  attachment,  anteriorly,  to  the  con- 
joined tendon  of  the  Internal  obhque  and  Transversalis ;  and  posteriorly,  to  the 
Rectus  and  Pyramidalis  muscles.  The  point  of  junction  of  the  crest  with  the 
inner  border  of  the  bone  (symphysis)  is  called  the  angle ;  to  it,  as  well  as  to  the 
symphysis,  is  attached  the  internal  pillar  of  the  external  abdominal  ring.     The 


THE    OS  INNOMINATUM  213 

internal  border  is  articular;  it  is  oval,  covered  by  eight  or  nine  transverse  ridges, 
or  a  series  of  nipple-like  processes  arranged  in  rows,  separated  by  grooves;  they 
serve  for  the  attachment  of  a  thin  layer  of  cartilage,  placed  between  it  and  the 
central  fibro-cartilage.  The  outer  border  presents  a  sharp  margin,  which  forms 
part  of  the  circumference  of  the  obturator  foramen  and  affords  attachment  to 
the  obturator  membrane. 

The  Ascending  or  Superior  Ramus  of  the  Pubis  {ramus  superior  ossis  pubis). — 
The  ascending  or  superior  ramus  extends  from  the  body  to  the  point  of  junction 
of  the  OS  pubis  with  the  ilium,  and  forms  the  upper  part  of  the  circumference  of 
the  obturator  foramen.  It  presents  for  examination  a  superior,  inferior,  and 
posterior  surface,  and  an  outer  extremity,  The  superior  surface  presents  a  con- 
tinuation of  the  ilio-pectineal  line,  already  mentioned  as  commencing  at  the 
pubic  spine.  In  front  of  this  ridge  the  surface  of  bone  is  triangular  in  form, 
wider  externally  than  internally,  smooth,  and  is  covered  by  the  Pectineus  muscle. 
The  surface  is  bounded  externally  by  a  rough  eminence,  the  ilio-pectineal  emi- 
nence (eminentia  iliopectinea) ,  which  serves  to  indicate  the  point  of  junction  of 
the  ilium  and  os  pubis,  and  gives  attachment  to  the  Psoas  parvus,  when  this 
muscle  is  present.  The  triangular  surface  is  bounded  below  by  a  prominent 
ridge,  the  obturator  crest  (crista  obturatoria) ,  which  extends  from  the  cotyloid 
notch  to  the  spine  of  the  os  pubis.  The  inferior  surface  forms  the  upper  bound- 
ary of  the  obturator  foramen,  and  presents  externally  a  broad  and  deep  oblique 
groove,  the  obturator  groove  (sulcus  obturatorius) ,  for  the  passage  of  the  obturator 
vessels  and  nerve;  and  internally  a  sharp  margin  which  forms  part  of  the  cir- 
cumference of  the  obturator  foramen,  and  to  which  the  obturator  membrane  is 
attached.  The  posterior  surface  forms  part  of  the  anterior  boundary  of  the  true 
pelvis.  It  is  smooth,  convex  from  above  downward,  and  affords  attachment  to 
.some  fibres  of  the  Obturator  internus.  The  outer  extremity,  the  thickest  part  of 
the  ramus,  forms  one-fifth  of  the  cavity  of  the  acetabulum. 

The  Descending  or  Inferior  Ramus  of  the  Pubis  (ramus  inferior  ossis  pubis) . — 
The  descending  or  inferior  ramus  of  the  os  pubis  is  thin  and  flattened.  It  passes 
outward  and  downward,  becoming  narrower  as  it  descends,  and  joins  with  the 
ramus  of  the  ischium.  Its  anterior  surface  is  rough,  for  the  attachment  of  muscles 
— the  Gracilis  along  its  inner  border;  a  portion  of  the  Obturator  externus  where  it 
enters  into  the  formation  of  the  foramen  of  that  name;  and  between  these  two 
muscles  the  Adductores  brevis  and  magnus  from  within  outward.  The  posterior 
surface  is  smooth,  and  gives  attachment  to  the  Obturator  internus,  and,  close  to 
the  inner  margin,  to  the  Compressor  urethrae.  The  inner  border  is  thick,  rough, 
and  everted,  especially  in  females.  It  presents  two  ridges,  separated  by  an  inter- 
vening space.  The  ridges  extend  downward,  and  are  continuous  with  similar 
ridges  on  the  ascending  ramus  of  the  ischium;  to  the  external  one  is  attached 
the  deep  layer  of  the  superficial  perineal  fascia,  and  to  the  internal  one  the  super- 
ficial layer  of  the  triangular  ligament  of  the  urethra.  The  outer  border  is  thin 
and  sharp,  forms  part  of  the  circumference  of  the  obturator  foramen,  and  gives 
attachment  to  the  obturator  membrane. 

The  Cotyloid  Cavity  or  Acetabulum. — The  cotyloid  cavity,  or  acetabulum,  is 
a  deep,  cup-shaped,  hemispherical  depression,  directed  downward,  outward,  and 
forward;  formed  internally  by  the  os  pubis,  above  by  the  ilium,  behind  and  below 
by  the  ischium,  a  little  less  than  two-fifths  being  formed  by  the  ilium,  a  little  more 
than  two-fifths  by  the  ischium,  and  the  remaining  fifth  by  the  pubic  bone.  It  is 
bounded  by  a  prominent,  uneven  rim,  which  is  thick  and  strong  above,  and  serves 
for  the  attachment  of  the  cotyloid  ligament,  which  contracts  its  orifice  and  deepens 
the  surface  for  articulation.  It  presents  below  a  deep  notch,  the  cotyloid  notch 
(mcisura  acetabuli),  which  is  continuous  with  a  circular  depression,  the  fossa  of 
the  acetabulum  (fossa  acetabuli),  at  the  bottom  of  the  cavity:  this  depression  is 


214 


THE   SKELETON 


perforated  by  numerous  apertures,  lodges  a  mass  of  fat,  and  its  margins,  as  well 
as  those  of  the  notch,  serve  for  the  attachment  of  the  ligamentum  teres.  In  fronts 
above  and  behind  the  fossa  acetabuli,  is  a  concave  rim  of  bone  (fades  lunata) .  The 
cotyloid  notch  is  converted,  in  the  natural  state,  into  a  foramen  by  a  dense  liga- 
mentous band  which  passes  across  it.  Through  this  foramen  the  nutrient  vessels 
and  nerves  enter  the  joint. 

The  Obturator  or  Thyroid  Foramen  (foramen  ohturatum) . — The  obturator  or 
thyroid  foramen  is  a  large  aperture  situated  between  the  ischium  and  os  pubis. 
In  the  male  it  is  large,  of  an  oval  form,  its  longest  diameter  being  obliquely  from 
before  backward;  in  the  female  it  is  smaller  and  more  triangular.  It  is  bounded 
by  a  thin,  uneven  margin,  to  which  a  strong  membrane  is  attached,  and  presents, 
anteriorly,  a  deep  groove,  the  obturator  groove  (sulcus  ohturatorius) ,  which  runs 
from  the  pelvis  obliquely  inward  and  downward.  This  groove  is  converted  into 
a  foramen  by  the  obturator  membrane,  and  transmits  the  obturator  vessels  and 
nerve. 

Structure. — This  bone  consists  of  much  cancellous  tissue,  especially  where  itl 
is  thick,  enclosed  between  two  layers  of  dense,  compact  tissue.  In  the  thinnerj 
parts  of  the  bone,  as  at  the  bottom  of  the  acetabulum  and  centre  of  the  iliac 
fossa,  it  is  usually  semitransparent,  and  composed  entirely  of  compact  tissue. 

Development  (Fig.  155). — ^y  eight  centres:  three  primary — one  for  the  ilium  J 
one  for  the  ischium,  and  one  for  the  os  pubis;  and  five  secondary — one  for  the) 

By  eight  centres  \  l^"""^  primary  {Ilium,  Ischium,  and  Os  Pubis). 
"     "  (  Five  secondary. 


8.  Symphysis  pubis. 


The  three  primary  centres  unite  through  a  \-shaped  piece  about  puberty. 
Epiphyses  appear  about  puberty,  and  unite  about  the  twenty-fifth  year. 

Fig.  155. — Plan  of  the  development  of  the  os  innominatum. 


crest  of  the  ilium,  one  for  the  anterior  inferior  spinous  process  (said  to  occur  more: 
frequently  in  the  male  than  in  the  female),  one  for  the  tuberosity  of  the  ischium, 
one  for  the  symphysis  pubis  (more  frequent  in  the  female  than  the  male),  and  one 
or  more  for  the  Y-shaped  piece  at  the  bottom  of  the  acetabulum.    These  various 
centres  appear  in  the  following  order:    First,  in  the  ilium,  at  the  lower  part  of 


THE  PELVIS  215 

the  bone,  immediately  above  the  sciatic  notch,  at  about  the  eighth  or  ninth  week; 
secondly,  in  the  body  of  the  ischium,  at  about  the  third  month  of  foetal  hfe; 
thirdly,  in  the  body  of  the  os  pubis,  between  the  fourth  and  fifth  months.  At 
birth  the  three  primary  centres  are  quite  separate,  the  crest,  the  bottom  of  the 
acetabulum,  the  ischial  tuberosity,  and  the  rami  of  the  ischium  and  pubes  being 
still  cartilaginous.  At  about  the  seventh  or  eighth  year  the  rami  of  the  os  pubis 
and  ischium  are  almost  completely  united  by  bone.  About  the  thirteenth  or 
fourteenth  year  the  three  divisions  of  the  bone  have  extended  their  growth  into 
the  bottom  of  the  acetabulum,  being  separated  from  each  other  by  a  Y-shaped 
portion  of  cartilage,  which  now  presents  traces  of  ossification,  often  by  two  or 
more  centres.  One  of  these,  the  os  acetabuli,  appears  about  the  age  of  twelve, 
between  the  ilium  and  os  pubis,  and  fuses  with  them  about  the  age  of  eighteen. 
It  forms  the  pubic  part  of  the  acetabulum.  The  ilium  and  ischium  then  become 
joined,  and  lastly  the  os  pubis  to  the  ischium,  through  the  intervention  of  this 
Y-shaped  portion.  At  about  the  age  of  puberty  ossification  takes  place  in  each 
of  the  remaining  portions,  and  they  become  joined  to  the  rest  of  the  bone 
between  the  twentieth  and  twenty-fifth  years.  Separate  centres  are  frequently 
found  for  the  pubic  and  ischial  spines 

Articulations. — With  its  fellow  of  the  opposite  side,  the  sacrum,  and  femur. 

Attachment  of  Muscles. — To  the  ilium,  sixteen.  To  the  outer  lip  of  the  crest, 
the  Tensor  vaginje  femoris,  Obliquus  externus  abdominis,  and  Latissimus  dorsi; 
to  the  internal  lip,  the  Iliacus,  Transversalis,  Quadratus  lumborum,  and  Erector 
spintie;  to  the  interspace  between  the  lips,  the  Obliquus  internus.  To  the  outer 
surface  of  the  ilium,  the  Gluteus  maximus,  Gluteus  medius.  Gluteus  minimus, 
reflected  tendon  of  the  Rectus;  to  the  upper  part  of  the  great  sacro-sciatic  notch,  a 
portion  of  the  Pyriformis;  to  the  internal  surface,  the  Iliacus;  to  that  portion  of 
the  internal  surface  below  the  linea  ilio-pectinea,  the  Obturator  internus  to  the 
internal  surface  of  the  posterior  superior  spine,  and  the  Multifidus  spinse;  to  the 
anterior  border,  the  Sartorius  and  straight  tendon  of  the  Rectus.  To  the  ischium, 
thirteen.  To  the  outer  surface  of  the  ramus,  the  Obturator  externus  and  Adductor 
magnus;  to  the  internal  surface,  the  Obturator  internus  and  Erector  penis.  To  the 
spine,  the  Gemellus  superior.  Levator  ani,  and  Coccygeus.  To  the  tuberosity,  the 
Biceps,  Semitendinosus,  Semimembranosus,  Quadratus  femoris.  Adductor  mag- 
nus, Gemellus  inferior,  Transversus  periniei,  Erector  penis.  To  the  pubis, 
sixteen:  Obliquus  externus,  Obliquus  internus,  Transversalis,  Rectus,  Pyramid- 
alis,  Psoas  parvus,  Pectineus,  Adductor  magnus,  Adductor  longus,  Adductor 
brevis.  Gracilis,  Obturator  externus  and  internus,  Levator  ani,  Compressor 
urethrie,  and  occasionally  a  few  fibres  of  the  Accelerator  urinae. 

The  Pelvis  (Figs.  156,  157). 

The  pelvis,  so  c^led  from  its  resemblance  to  a  basin  (L.  pelvis),  is  stronger 
and  more  massively  constructed  than  either  the  cranial  or  thoracic  cavity;  it  is  a 
bony  ring,  interposed  between  the  lower  end  of  the  spine,  which  it  supports,  and 
the  lower  extremities,  upon  which  its  rests.  It  is  composed  of  four  bones:  the  two 
ossa  innominata,  which  bound  it  on  either  side  and  in  front,  and  the  sacrum  and 
coccyx,  which  complete  it  behind.  The  pelvis  is  divided  by  an  oblique  plane 
passing  through  the  prominence  of  the  sacrum,  the  linea  ilio-pectinea,  and  the 
upper  margin  of  the  symphysis  pubis  into  the  false  and  true  pelvis. 

The  False  Pelvis  (pelvis  major)  .—The  false  pelvis  is  the  expanded  portion  of 
the  pelvic  cavity  which  is  situated  above  this  plane.  It  is  bounded  on  each  side 
by  the  ossa  ilii;  in  front  it  is  incomplete,  presenting  a  wide  interval  between  the 
spinous  processes  of  the  ilia  on  either  side,  which  is  filled  up  in  the  recent  state  by 
the  parietes  of  the  abdomen;  behind,  in  the  middle  line,  is  a  deep  notch.,   This 


216 


THE  SKELETON 


broad,  shallow  cavity  is  fitted  to  support  the  intestines  and  to  transmit  part  of 
their  weight  to  the  anterior  wall  of  the  abdomen,  and  is,  in  fact,  really  a  portion 
of  the  abdominal  cavity.    The  term  false  pelvis  is  incorrect,  and  this  space  ought 


Fig.  156. — Male  pelvis  (adult). 


more  properly  to  be  regarded  as  part  of  the  hypogastric  and  iliac  regions  of  the 
abdomen. 

The  True  Pelvis  (pelvis  minor) . — The  true  pelvis  is  that  part  of  the  pelvic 
cavity  which  is  situated  beneath  the  plane.    It  is  smaller  than  the  false  pelvis, 


Fig.  157. — Female  pelvis  (adult). 


but  its  walls  are  more  perfect.  For  convenience  of  description  it  is  divided 
into  a  superior  circumference  or  inlet,  an  inferior  circumference  or  outlet,  and  a 
cavity. 


THE  PELVIS  217 

The  Superior  Circumference  or  Inlet  (apertura  pelvis  superior) . — The  superior  cir- 
cumference forms  the  brim  of  the  pelvis,  the  included  space  being  called  the  inlet. 
It  is  formed  by  the  linea  ilio-pectinea,  completed  in  front  by  the  crests  of  the 
pubic  bones,  and  behind  by  the  anterior  margin  of  the  base  of  the  sacrum  and 
sacro-vertebral  angle.  The  brim  of  the  pelvis  is  the  name  often  given  to  the 
marofin  of  the  inlet.  The  inlet  of  the  pelvis  is  somewhat  heart-shaped,  obtusely 
pointed  in  front,  diverging  on  either  side,  and  encroached  upon  behind  by  the 
projection  forward  of  the  promontory  of  the  sacrum.  It  has  three  principal 
diameters:  antero-posterior  (sacro-pubic),  transverse,  and  oblique.  The  antero- 
posterior or  conjugate  diameter  (conjugata)  extends  from  the  sacro-vertebral  angle 
to  the  symphysis  pubis.  The  anatomical  conjugate  (conjugata  anatomica)  is  the 
distance  between  the  sacro-vertebral  angle  and  the  top  of  the  symphysis  pubis. 
Its  average  measurement  is  four  inches  in  the  male  and  four  and  three-fifths  inches 
in  the  female.  The  true,  available,  or  obstetric  conjugate  {conjugata  gyncecologica) 
is  the  distance  between  the  sacro-vertebral  angle  and  the  nearest  point  upon  the 
symphysis.  This  point  is  a  little  behind  and  below  the  upper  margin  (Webster). 
The  average  distance  in  women  is  four  and  three-eighths  inches.  The  diagonal 
conjugate  (diagonalconjugata)  is  measured  from  the  sacro-vertebral  angle  to  the 
subpubic  ligament.  The  distance  exceeds  the  true  conjugate  by  one-half  or  two- 
thirds  of  an  inch.  The  transverse  diameter  (diameter  transversa)  extends  across 
the  greatest  width  of  the  inlet,  from  the  middle  of  the  brim  on  one  side  to  the 
same  point  on  the  opposite;  its  average  measurement  is  five  inches  in  the  male, 
five  and  one-fourth  inches  in  the  female.  The  oblique  diameter  (diameter  ohliqua) 
extends  from  the  margin  of  the  pelvis,  corresponding  to  the  ilio-pectineal  eminence 
on  one  side,  to  the  sacro-iliac  articulation  on  the  opposite  side;  its  average 
measurement  is  four  and  a  quarter  inches  in  the  male  and  five  in  the  female.  The 
oblique  diameters  are  named  right  or  left  oblique,  according  to  the  sacro-iliac 
joint  from  which  the  measurement  is  taken. 

The  Cavity.— The  cavity  of  the  true  pelvis  is  bounded  in  front  by  the  symphysis 
pubis;  behind,  by  the  concavity  of  the  sacrum  and  coccyx,  which,  curving  forward 
above  and  below,  contracts  the  inlet  arid  outlet  of  the  canal;  and  laterally  it  is 
bounded  by  a  broad,  smooth,  quadrangular  surface  of  bone,  corresponding  to  the 
inner  surface  of  the  body  of  the  ischium  and  that  part  of  the  ilium  which  is  below 
the  ilio-pectineal  line.  The  cavity  is  shallow  in  front,  measuring  at  the  symphy- 
sis an  inch  and  a  half  in  depth,  three  inches  and  a  half  in  the  middle,  and  four 
inches  and  a  half  posteriorly.  From  this  description  it  will  be  seen  that  the  cavity 
of  the  pelvis  is  a  short,  curved  canal,  considerably  deeper  on  its  posterior  than 
on  its  anterior  wall.  This  cavity  contains,  in  the  recent  subject,  the  rectum, 
bladder,  and  part  of  the  organs  of  generation.  The  rectum  is  placed  at  the  back 
of  the  pelvis,  and  corresponds  to  the  curve  of  the  sacro-coccygeal  column;  the 
bladder  in  front,  behind  the  symphysis  pubis.  In  the  female  the  uterus  and 
vagina  occupy  the  interval  between  these  viscera. 

The  Lower  Circumference  or  Outlet  (apertura  pelvis  inferior). — The  lower  cir- 
cumference of  the  pelvis  is  very  irregular,  and  forms  what  is  called  the  outlet. 
It  is  bounded  by  three  prominent  eminences :  one  posterior,  formed  by  the  point 
of  the  coccyx;  and  one  on  each  side,  the  tuberosities  of  the  ischia.  These  emi- 
nences are  separated  by  three  notches ;  one  in  front,  the  pubic  arch  (arcus  pubis) , 
formed  by  the  convergence  of  the  rami  of  the  ischia  and  pubic  bones  on  each 
side.  The  other  notches,  one  on  each  side,  are  formed  by  the  sacrum  and  coccyx 
behind,  the  ischium  in  front,  and  the  ilium  above;  they  are  called  the  sacro-sciatic 
notches;  in  the  natural  state  they  are  converted  into  foramina  by  the  lesser  and 
greater  sacro-sciatic  ligaments.  In  the  recent  state,  when  the  ligaments  are  in 
situ,  the  outlet  of  the  pelvis  is  lozenge-shaped,  bounded  in  front  by  the  subpubic 
ligament  and  the  rami  of  the  os  pubis  and  ischium;  on  each  side  by  the  tuber- 


218 


THE  SKELETON 


osities  of  the  ischia;  and  behind  by  the  great  sacro-sciatic  Hgaments  and  the  tip 
of  the  coccyx. 

The  diameters  of  the  outlet  of  the  pelvis  are  two,  antero-posterior  and  trans- 
verse. The  antero-posterior  (conjugate)  diameter  (diameter  recta  of  the  outlet) 
extends  from  the  tip  of  the  coccyx  to  the  lower  part  of  the  symphysis  pubis ;  its 
average  measurement  is  three  and  three-quarter  inches  in  the  male  and  four  and 
one-half  inches  in  the  female.  The  antero-posterior  diameter  varies  with  the 
length  of  the  coccyx,  and  is  capable  of  increase  or  diminution  on  account  of  the 
mobility  of  that  bone.  During  labor  the  coccyx  may  be  bent  back  so  that  the 
conjugate  is  increased  one  inch,  or  even  one  and  one-fourth  inches.  The  trails- 
verse  diameter  extends  from  the  posterior  part  of  one  ischiatic  tuberosity  to  the 
same  point  on  the  opposite  side:  the  average  measurement  is  three  and  a  half 
inches  in  the  male  and  four  and  three-fourths  in  the  female.^ 

Oblique  diameters  are  not  employed,  as  there  are  no  fixed  points  from  which 
to  measure  them. 

Position  of  the  Pelvis. — In  the  erect  posture  the  pelvis  is  placed  obliquely  with 
regard  to  the  trunk  of  the  body:  the  bony  ring,  which  forms  the  brim  of  the  true 
pelvis,  is  placed  so  as  to  form  an  angle  of  about  60  to  65  degrees  with  the  ground 
on  which  we  stand  (inclinatio  pelvis).  The  pelvic  surface  of  the  symphysis  pubis 
looks  upward  and  backward,  the  concavity  of  the  sacrum  and  coccyx  downward 
and  forward,  the  base  of  the  sacrum  in  well-formed  female  bodies  being  nearly 
four  inches  above  the  upper  border  of  the  symphysis  pubis,  and  the  apex  of  the 

coccyx  a  little  more  than  half  an  inch  above  its 
lower  border.  In  consequence  of  the  obliquity 
of  the  pelvis  the  line  of  gravity  of  the  head, 
which  passes  through  the  middle  of  the  odontoid 
process  of  the  axis  and  through  the  points  of 
junction  of  the  curves  of  the  vertebral  column  to 
the  sacro-vertebral  angle,  descends  toward  the 
front  of  the  cavity;  so  that  it  bisects  a  line 
drawn  transversely  through  the  middle  of  the 
heads  of  the  thigh  bones.  And  thus  the  centre 
of  gravity  of  the  head  is  placed  immediately 
over  the  heads  of  the  thigh  bones  on  which  the 
trunk  is  supported. 

Axes  of  the  Pelvis  (Fig.  158).— The  plane  of 
the  inlet  of  the  true  pelvis  will  be  represented  by 
a  line  drawn  from  the  base  of  the  sacrum  to  the 
upper  margin  of  the  symphysis  pubis.  A  line 
carried  at  right  angles  with  this  at  its  middle 
would  correspond  at  one  extremity  with  the 
umbilicus,  and  at  the  other  with  the  middle  of 
the  coccyx:  the  axis  of  the  inlet  is  therefore  directed  downward  and  backward. 
The  axis  of  the  outlet,  produced  upward,  would  touch  the  base  of  the  sacrum, 
and  is  therefore  directed  downward  and  forward.  The  axis  of  the  cavity  is  curved 
like  the  cavity  itself:  this  curve  corresponds  to  the  concavity  of  the  sacrum 
and  coccyx,  the  extremities  being  indicated  by  the  central  points  of  the  inlet  and 


pi^W  "'^*'«*- 


Fig.  158. — ;- Vertical   section  of   the  pelvis 
with  lines  indicating  the  axis  of  the  pelvis. 


_  ^  The  measurements  of  the  pelvis  given  above  are.  I  believe,  fairly  accurate,  but  different  measurements  are 
given  by  various  authors,  no  doubt  due  in  a  great  measure  to  differences  in  the  physique  and  stature  of  the 
population  from  whom  the  measurements  have  been  taken.  The  accompanying  chart  has  been  formulated  to 
show  the  measurements  of  the  pelvis  which  are  adopted  by  many  obstetricians. — ]']d. 

Diameters  of  the  True  Pelvis  in  Woman. 


Antero-posterior. 

Oblique. 

Transverse. 

Of  inlet 

.     4'''/5  inches  (118  mm.) 

5  inches  (127  mm.) 

S%  inches  (135  mm.) 

Of  outlet    . 

.     4%  inches  (115  mm. ) 

4%  inches  (120  mm.) 

THE    PELVIS 


219 


outlet.  A  knowledge  of  the  direction  of  these  axes  serves  to  explain  the  course 
of  tlie  foetus  in  the  passage  through  the  pelvis  during  parturition.  It  is  also 
important  to  the  surgeon,  as  indicating  the  direction  of  the  force  required  in  the 
removal  of  calculi  from  the  bladder  by  the  sub-pubic  operation,  and  as  deter- 
mining the  direction  in  which  instruments  should  be  used  in  operations  upon  the 
pelvic  viscera. 

Differences  between  the  Male  and  the  Female  Pelvis. — The  female  pelvis, 
looked  at  as  a  whole,  is  distinguished  from  the  male  by  the  bones  being  more 
delicate,  by  its  width  being  greater  and  its  depth  smaller.  The  whole  pelvis  is 
less  massive,  and  its  bones  are  lighter  and  more  slender,  and  its  muscular  impres- 
sions are  slightly  marked.  The  iliac  fossjT?  are  shallow,  and  the  anterior  iliac  spines 
widely  separated;  hence  the  greater  prominence  of  the  hips.  The  inlet  in  the 
female  is  larger  than  in  the  male ;  it  is  more  nearly  circular,  and  the  sacro-vertebral 
angle  projects  less  forward.  The  cavity  is  shallower  and  wider;  the  sacrum  is 
shorter,  wider,  and  less  curved;  the  obturator  foramina  are  triangular,  and  smaller 
in  size  than  in  the  male.  The  outlet  is  larger  and  the  coccyx  more  movable.  The 
spines  of  the  ischia  project  less  inward.  The  tuberosities  of  the  ischia  and  the 
acetabula  are  wider  apart.  The  pubic  arch  is  wider  and  more  rounded  than  in  the 
male,  where  it  is  an  angle  rather  than  an  arch.  In  consequence  of  this  the  width  of 
the  fore  part  of  the  pelvic  outlet  is  much  increased  and  the  passage  of  the  foetal 
head  facilitated. 

The  size  of  the  pelvis  varies,  not  only  in  the  two  sexes,  but  also  in  different 
members  of  the  same  sex.    This  does  not  appear  to  be  influenced  in  any  way  by 


Fig.  159. — Diameters  of  the  pelvic  inlet. 


the  height  of  the  individual.  Women  of  short  stature,  as  a  rule,  have  broad  pelves. 
Occasionally  the  pelvis  is  equally  contracted  in  all  its  dimensions,  so  much  so  that 
all  its  diameters  measure  an  inch  less  than  the  average,  and  this  even  in  women 
of  average  height  and  otherwise  well  formed.  The  principal  divergences,  however, 
are  found  at  the  inlet,  and  affect  the  relation  of  the  antero-posterior  to  the  trans- 
verse diameter.  Thus  we  may  have  a  pelvis  the  inlet  of  which  is  elliptical  either 
in  a  transverse  or  antero-posterior  direction;  the  transverse  diameter  in  the  former 
and  the  antero-posterior  in  the  latter  greatly  exceeding  the  other  diameters.  Again, 
the  inlet  of  the  pelvis  in  some  instances  is  seen  to  be  almost  circular.  The  same 
differences  are  found  in  various  races.     European  women  are  said  to  have  the 


220 


THE  SKELETON 


most  roomy  pelves.  That  of  the  negress  is  smaller,  circular  in  shape,  and  with  a 
narrow  pubic  arch.  The  Hottentots  and  Bushwomen  possess  the  smallest  pelves. 
In  the  foetus  and  for  several  years  after  birth  the  pelvis  is  small  in  proportion 
to  that  of  the  adult.  The  cavity  is  deep,  and  the  projection  of  the  sacro-vertebral 
angle  less  marked.  The  generally  accepted  opinion  that  the  female  pelvis  does 
not  acquire  its  sexual  characters  until  after  puberty  has  been  shown  by  recent 


Fig.  160. — Diameters  of  the  pelvic  outlet. 

observations^  to  be  erroneous,  the  characteristic  differences  between  the  male  and 
female  pelvis  being  distinctly  indicated  as  early  as  the  fourth  month  of  foetal  life. 
At  birth  these  differences  are  distinct  (Romiti),  the  female  pelvis  possessing  less 
straight  ilia,  a  broader  subpubic  arch,  and  less  height  than  the  male. 

Surface  Form. — The  pelvic  bones  are  so  thickly  covered  with  muscles  that  it  is  only  at 
certain  points  that  they  approach  the  surface  and  can  be  felt  through  the  skin.  In  front, 
the  anterior  superior  spinous  process  is  easily  recognized;  a  portion  of  it  is  subcutaneous, 
and  in  thin  subjects  may  be  seen  to  stand  out  as  a  prominence  at  the  outer  extremity  of  the  fold 
of  the  groin.  In  fat  subjects  its  position  is  marked  by  an  oblique  depression  amongst  the  sur- 
rounding fat,  at  the  bottom  of  which  the  bony  process  may  be  felt.  Proceeding  upward  and 
outward  from  this  process,  the  crest  of  the  ilium  may  be  traced  throughout  its  whole  length, 
sinuously  curved.  It  is  represented,  in  muscular  subjects,  on  the  surface,  by  a  groove  or  fur- 
row, the  iliac  furrow,  caused  by  the  projection  of  fleshy  fibres  of  the  External  oblique  muscles 
of  the  abdomen ;  the  iliac  furrow  lies  slightly  below  the  level  of  the  crest.  It  terminates  behind 
in  the  posterior  superior  spinous  process,  the  position  of  which  is  indicated  by  a  slight  depression 
on  a  level  with  the  spinous  process  of  the  second  sacral  vertebra.  Between  the  two  posterior 
superior  spinous  processes,  but  at  a  lower  level,  is  to  be  felt  the  spinous  process  of  the  third - 
sacral  vertebra  (see  page  69).  Another  part  of  the  bony  pelvis  easily  accessible  to  touch  is  the 
tuberosity  of  the  ischium,  situated  beneath  the  gluteal  fold,  and,  when  the  hip  is  flexed,  it  is 
easily  felt,  as  it  is  then  to  a  great  extent  uncovered  by  muscle.  Finally,  the  spine  of  the  os 
pubis  can  always  be  readily  felt,  and  constitutes  an  important  surgical  guide,  especially  in  con- 
nection with  the  subject  of  hernia.  It  is  nearly  in  the  same  horizontal  line  with  the  upper  edge 
of  the  great  trochanter.  In  thin  subjects  it  is  very  apparent,  but  in  the  obese  it  is  obscured  by 
the  pubic  fat.  It  can,  however,  be  detected  by  following  up  the  tendon  of  origin  of  the 
Adductor  longus  muscle. 

Surgical  Anatomy. — There  is  arrest  of  development  in  the  bones  of  the  pelvis  in  cases 
of  extroversion  of  the  bladder ;  the  anterior  part  of  the  pelvic  girdle  being  deficient,  the  bodies 
of  the  pubic  bones  imperfectly  developed,  and  the  symphysis  absent.  The  pubic  bones  are 
separated  to  the  extent  of  from  two  to  four  inches,  the  superior  rami  shortened  and  directed 
forward,  and  the  obturator  foramen  diminished  in  size,  narrowed,  and  turned  outward.     The 


'  Fehling,  Zeitschr.  fiir  Geburt.  u.  Gynaek.,  Bd.  ix.  und  x.;   and  Arthur  Thomson,  Journal  of  Anatomy  and 
Physiology,  vol.  xxxiii. 


THE   FEMUR,    OB    THIGH   BONE  221 

iliac  bones  are  straightened  out  more  than  normal.  The  sacrum  is  very  peculiar.  The  lateral 
curve,  instead  of  being  concave,  is  flattened  out  or  even  convex,  with  the  ilio-sacral  facets  turned 
more  outward  than  normal,  while  the  vertical  curve  is  straightened.' 

Fractures  of  the  pelvis  are  divided  into  fractures  of  the  false  pelvis  and  of  the  true  pelvis. 
Fractures  of  the  false  pelvis  vary  in  extent:  a  small  portion  of  the  iliac  crest  may  be  broken  or 
one  of  the  spinous  processes  may  be  torn  off,  and  this  may  be  the  result  of  muscular  action;  or 
the  bone  may  be  extensively  comminuted.  This  latter  accident  is  the  result  of  some  crushing 
violence,  and  may  be  complicated  with  fracture  of  the  true  pelvis.  These  cases  may  be  accom- 
panied by  injury  to  the  intestine  as  it  lies  in  the  hollow  of  the  bone,  or  to  the  iliac  vessels  as 
they  course  along  the  margin  of  the  true  pelvis.  Fractures  of  the  true  pelvis  generally  occur 
through  the  ascending  ramus  of  the  os  pubis  and  the  ramus  of  the  ischium,  as  this  is  the  weakest 
part  of  the  bony  ring,  and  may  be  caused  either  by  crushing  violence  applied  in  an  antero- 
posterior direction,  when  the  fracture  occurs  from  direct  force,  or  by  compression  laterally, 
when  the  acetabula  are  pressed  together,  and  the  bone  gives  way  in  the  same  place  from  indirect 
violence.  Occasionally  the  injury  may  be  double,  a  break  occurring  on  both  sides  of  the  body. 
In  fracture  of  the  true  pelvis  the  contained  viscera  are  liable  to  be  damaged:  the  small  intestines, 
the  urethra,  the  bladder,  the  rectum,  the  vagina,  and  even  the  uterus,  in  the  female,  have  all 
been  lacerated  by  a  displaced  fragment.  Fractures  of  the  acetabulum  are  occasionally  met  with: 
either  a  portion  of  the  rim  may  be  broken  off,  or  a  fracture  may  take  place  through  the  bottom 
of  the  cavity,  and  the  head  of  the  femur  may  be  driven  inward  and  project  into  the  pelvic  cavity. 
Separation  of  the  Y-shaped  cartilage  at  the  bottom  of  the  acetabulum  may  also  occur  in  the 
young  subject,  dispersing  the  bone  into  its  three  anatomical  portions. 

The  sacrum  is  seldom  broken.  The  cause  is  direct  violence — i.  e.,  blows,  kicks,  or  falls 
on  the  part.  The  lesion  may  be  complicated  with  injury  to  the  nerves  of  the  sacral  plexus, 
leading  to  paralysis  and  loss  of  sensation  in  the  lower  extremity  or  to  incontinence  of  fseces  from 
paralysis  of  the  Sphincter  ani. 

The  pelvic  bones  often  undergo  important  deformity  in  rickets,  the  effect  of  which  in  the 
adult  woman  may  interfere  seriously  with  childbearing.  The  deformity  *is  due  mainly  to  the 
weight  of  the  spine  and  trunk,  which  presses  on  the  sacro-vertebral  angle  and  greatly  increases 
it,  so  that  the  antero-posterior  diameter  of  the  pelvis  is  diminished.  But,  in  addition  to  this, 
the  weight  of  the  viscera  on  the  venter  ilii  causes  those  bones  to  expand  and  the  tuberosities  of 
the  ischia  to  incurve.  In  osteomalacia  also  great  deformity  may  occur.  The  weight  of  the 
trunk  causes  an  increase  in  the  sacro-vertebral  angle  and  a  lessening  of  the  antero-posterior 
diameter  of  the  inlet,  and  at  the  same  time  the  pressure  of  the  acetabula  on  the  heads  of  the 
thigh-bones  causes  these  cavities,  with  the  adjacent  bone,  to  be  pushed  upward  and  backward, 
so  that  the  oblique  diameters  of  the  pelvis  are  also  diminished,  and  the  cavity  of  the  pelvis 
assumes  a  triradiate  shape,  with  the  symphysis  pubis  pushed  forward. 

THE  THIGH. 

The  thigh  is  that  portion  of  the  lower  extremity  which  is  situated  between  the 
pelvis  and  the  knee.    It  consists  in  the  skeleton  of  a  single  bone,  the  femur. 

The  Femur,  or  Thigh  Bone  (Figs.  161,  162). 

The  femur  (femur,  the  thigh)  is  the  longest,^  largest,  and  strongest  bone  in  the 
skeleton,  and  almost  perfectly  cylindrical  throughout  the  greater  part  of  its  extent. 
In  the  erect  posture  it  is  not  vertical,  being  separated  from  its  fellow  above  by 
a  considerable  interval,  which  corresponds  to  the  entire  breadth  of  the  pelvis,  but 
inclining  gradually  downward  and  inward,  so  as  to  approach  its  fellow  toward 
its  lower  part,  for  the  purpose  of  bringing  the  knee-joint  near  the  line  of  gravity 
of  the  body.  The  degree  of  this  inclination  varies  in  different  persons,  and 
is  greater  in  the  female  than  the  male,  on  account  of  the  greater  breadth  of 
the  pelvis.  The  femur,  like  other  long  bones,  is  divisible  into  a  shaft  and  two 
extremities. 

Upper  Extremity. — The  upper  extremity  presents  for  examination  a  head, 
a  neck,  and  a  great  and  lesser  trochanters. 

Head  of  the  Femur  {caput  femoris)  .—The  head,  which  is  globular,  and 
forms  rather  more  than  a  hemisphere,  i^  directed  upward,  inward,  and  a  little 

'  Wood.     Heath's  Dictionary  of  Practical  Surgery,  i.,  426. 

2  In  a  man  six  feet  high  it  measures  eighteen  inches — one-fourth  of  the  whole  body. 


222 


THE  SKELETON 


OBTURATOR   INTERNUS 
and  QEMELLI. 
PVRIFORMIS. 


'  Depression  for 

LIQAMENTUM    TERES. 


Fig.  161.— Right  femur. 


Anterior  surface. 


forward,  the  greater  part  of   its 
convexity  being  above  and  in  front. 
Its  surface  is  smooth,  coated  with 
cartilage  in  the  recent  state,  ex- 
cept at  a  Httle  behind  and    below  its  centre, 
where   is   an    ovoid    depression    (fovea   capitis 
jemoris),  for  the  attachment  for  the  Ligamen- 
tiim  teres. 

The  Neck  of  the  Femur  (collum  jemoris). — The 
neck  is  a  flattened  pyramidal  process  of  bone 
which  connects  the  head  with  the  shaft.  It 
varies  in  length  and  obliquity  at  various  periods 
in  life  and  under  different  circumstances.  The 
angle  is  widest  in  infancy,  and  becomes  lessened 
during  growth,  so  that  at  puberty  it  forms  a 
gentle  curve  from  the  axis  of  the  shaft.  In  the 
adult  it  forms  an  angle  of  about  130  degrees 
with  the  shaft,  but  varies  in  inverse  proportion 
to  the  development  of  the  pelvis  and  the  stature. 
In  consequence  of  the  prominence  of  the  hips 
and  widening  of  the  pelvis  in  the  female,  the 
neck  of  the  thigh  bone  forms  more  nearly  a  right 
angle  with  the  shaft  than  it  does  in  man.  It  has 
been  stated  that  the  angle  diminishes  in  old  age 
and  the  direction  of  the  neck  becomes  hori- 
zontal, but  this  statement  is  founded  on  insuffi- 
cient evidence.  Sir  George  Humphry  states 
that  the  angle  decreases  during  the  period  of 
growth,  but  after  full  growth  has  been  attained 
it  does  not  usually  undergo  any  change,  even 
in  old  age.  He  further  states  that  the  angle 
varies  considerably  in  different  persons  of  the 
same  age.  It  is  smaller  in  short  than  in  long 
bones,  and  when  the  pelvis  is  wide.^  The  neck 
is  flattened  from  before  backward,  contracted  in 
the  middle,  and  broader  at  its  outer  extremity, 
where  it  is  connected  with  the  shaft,  than  at 
its  summit,  where  it  is  attached  to  the  head. 
The  vertical  diameter  of  the  outer  half  is  in- 
creased by  the  thickening  of  the  lower  edge, 
which  slopes  downward  to  join  the  shaft  at  the 
lesser  trochanter,  so  that  the  outer  half  of  the 
neck  is  flattened  from  before  backward,  and  its 
vertical  diameter  measures  one-third  more  than 
the  antero-posterior.  The  inner  half  is  smaller 
and  of  a  more  circular  shape.  The  anterior 
surface  of  the  neck  is  perforated  by  numerous 
vascular  foramina.  The  posterior  surface  is 
smooth,  and  is  broader  and  more  concave  than 
the  anterior;  it  gives  attachment  to  the  posterior 
part  of  the  capsular  ligament  of  the  hip-joint, 
about  half  an  inch  above  the  posterior  intertro- 
chanteric line.    The  superior  border  is  short  and 

'  Journal  of  Anatomy  and  Physiology. 


THE   FEMUB,    OB    THIGH   BONE  223 

thick,  and  terminates  externally  at  the  great  trochanter;  its  surface  is  perforated 
by  large  foramina.  The  inferior  border,  long  and  narrow,  curves  a  little  back- 
ward, to  terminate  at  the  lesser  trochanter. 

The  Trochanters. — The  trochanters  (Tf)uydco,  to  run  or  roll)  are  prominent  pro- 
cesses of  bone  which  afford  leverage  to  the  muscles  which  rotate  the  thigh  on  its 
axis.    They  are   two  in  number,  the  greater  and  the  lesser. 

The  great  trochanter  (trochanter  major)  is  a  large,  irregular,  quadrilateral  eminence, 
situated  at  the  outer  side  of  the  neck,  at  its  junction  with  the  upper  part  of  the  shaft. 
It  is  directed  a  little  outward  and  backward,  and  in  the  adult  is  about  three-quarters 
of  an  inch  lower  than  the  head.  It  presents  for  examination  two  surfaces  and  four 
borders.  The  external  surface,  quadrilateral  in  form,  is  broad,  rough,  convex,  and 
marked  by  a  prominent  diagonal  impression,  which  extends  from  the  posterior 
superior  to  the  anterior  inferior  angle,  and  serves  for  the  attachment  of  the  tendon 
of  the  Gluteus  medius.  Above  the  impression  is  a  triangular  surface,  sometimes 
rough  for  part  of  the  tendon  of  the  same  muscle,  sometimes  smooth  for  the  inter- 
position of  a  bursa  between  that  tendon  and  the  bone.  Below  and  behind  the 
diagonal  line  is  a  smooth,  triangular  surface,  over  which  the  tendon  of  the  Gluteus 
maximus  muscle  plays,  a  bursa  being  interposed.  The  internal  surface  is  of  much 
less  extent  than  the  external,  and  presents  at  its  base  a  deep  depression,  the  digital 
or  trochanteric  fossa  (fossa  trochanter ica) ,  for  the  attachment  of  the  tendon  of  the 
Obturator  externus  muscle:  above  and  in  front  of  this  an  impression  for  the  attach- 
ment of  the  Obturator  internus  and  Gemelli.  The  superior  border  is  free;  it  is  thick 
and  irregular,  and  marked  near  the  centre  by  an  impression  for  the  attachment  of 
the  Pyriformis.  The  inferior  border  corresponds  to  the  point  of  junction  of  the  base 
of  the  trochanter  with  the  outer  surface  of  the  shaft;  it  is  marked  by  a  rough,  promi- 
nent, slightly  curved  ridge,  which  gives  attachment  to  the  upper  part  of  the  Vastus 
externus  muscle.  The  anterior  border  is  prominent,  somewhat  irregular,  as  well 
as  the  surface  of  bone  immediately  below  it;  it  affords  attachment  at  its  outer 
part  to  the  Gluteus  minimus.  The  posterior  border  is  very  prominent,  and  appears 
as  a  free,  rounded  edge,  which  forms  the  back  part  of  the  digital  fossa. 

The  lesser  trochanter  (trochanter  minor)  is  a  conical  eminence  which  varies  in  size 
in  different  subjects ;  it  projects  from  the  lower  and  back  parts  of  the  base  of  the  neck. 
Its  base  is  triangular,  and  connected  with  the  adjacent  parts  of  the  bone  by  three 
well-marked  borders:  two  of  these  are  above — the  internal  border,  continuous  with 
the  lower  border  of  the  neck,  the  external  border  with  the  posterior  intertrochan- 
teric line — while  the  inferior  border  is  continuous  with  the  middle  division  of  the 
linea  aspera.  Its  summit,  which  is  directed  inward  and  backward,  is  rough,  and 
gives  insertion  to  the  tendon  of  the  Ilio-psoas.  The  Iliacus  is  also  inserted  into 
the  shaft  below  the  lesser  trochanter  between  the  Vastus  internus  in  front  and  the 
Pectineus  behind. 

A  well-marked  prominence  of  variable  size,  which  projects  from  the  upper  and 
front  part  of  the  neck  at  its  junction  with  the  great  trochanter,  is  called  the  tuber- 
cle of  the  femur;  it  is  the  point  of  meeting  of  five  muscles:  the  Gluteus  minimus 
externally,  the  Vastus  externus  below,  and  the  tendon  of  the  Obturator  internus 
and  Gemelli  above.  Running  obliquely  downward  and  inward  from  the  tubercle 
is  the  spiral  line  of  the  femur,  or  anterior  intertrochanteric  line  (linea  intertrochan- 
terica);  it  winds  round  the  inner  side  of  the  shaft,  below  the  lesser  trochanter,  and 
terminates  in  the  linea  aspera,  about  two  inches  below  thi^  eminence.  Its  upper 
half  is  rough,  and  affords  attachment  to  the  ilio-femoral  ligament  of  the  hip-joint; 
its  lower  half  is  less  prominent,  and  gives  attachment  to  the  upper  part  of  the 
Vastus  internus.  Running  obliquely  downward  and  inward  from  the  summit  of 
the  great  trochanter  on  the  posterior  surface  of  the  neck  is  a  very  prominent, 
well-marked  ridge,  the  posterior  intertrochanteric  line  (crista  intertrochanterica). 
Its  upper  half  forms  the  posterior  border  of  the  great  trochanter,  and  its  lower 


224 


THE  SKELETON 


OBTURATOR    EXTERNUS. 


Groove  for  tendon  of 

POPLITEUS. 


Fig.  162. — Right  femur.     Posterior  surface. 


half  runs  downward  and  inward 
to  the  upper  and  back  part  of 
the  lesser  trochanter,  A  slight 
ridge  sometimes  commences  about 
the  middle  of  the  posterior  inter- 
trochanteric line,  and  passes  ver- 
tically downward  for  about  two 
inches  along  the  back  part  of  the 
shaft:  it  is  called  the  linea  quadrati, 
and  gives  attachment  to  the 
Quadratus  femoris  and  a  few 
fibres  of  the  Adductor  magnus. 
muscles/ 

The  Shaft  of  the  Femur  {corpus 
femoris) . — The  shaft,  almost  cylin 
drical  in  form,  is  a  little  broader 
above   than   in    the   centre,  and 
somewhat  flattened  below,  from 
before   backward.     It   is  slightly 
arched,  so  as  to  be  convex  in  front 
and  concave  behind,  where  it  is. 
strengthened  by  a  prominent  lon- 
gitudinal ridge,  the  linea  aspera 
It  presents  for  examination  three 
borders,  separating  three  surfaces 
Of  the  three  borders,  one,  the  linea 
aspera,  is  posterior;  the  other  two 
are  placed  laterally. 

The  Linea  Aspera.  —  The  linea 
aspera  (Fig.  162)  is  a  prominent 
longitudinal  ridge  or  crest,  on  the 
middle  third  of  the  bone,  present 
ing  an  external  lip  (labium  laterale) ,. 
an  internal  lip  {labium  mediale), 
and  a  rough  intermediate  space. 
Above,  this  crest  is  prolonged  by 
three  ridges.  The  most  external 
ridge  is  very  rough,  and  is  con 
tinned  almost  vertically  upward  to- 
the  base  of  the  great  trochanter, 
It  is  sometimes  termed  the  gluteal 
ridge  {tuberositas  glutoea) ,  and  gives 
attachment  to  part  of  the  Gluteus 
maximus  muscle;  its  upper  part  is 
sometimes  elongated  into  a  rough- 
ened crest,  on  which  is  a  more  or 
less  well-marked,  rounded  tuber- 
cle, a  rudimental  third  trochanter 
{trochanter  tertius).  The  middle 
ridge  (linea  pectinea) ,  the  least  dis- 


1  Generally  there  is  merely  a  slight  thickening- 
about  the  centre  of  the  intertrochanteric  line, 
marking  the  point  of  attachment  of  the  Quad- 
ratus femoris.  This  is  termed  by  some  anato- 
mists the  tubercle  of  Uie  Quadratus. 


I 


THE  FEMUR,    OB    THIGH  BONE  225 

tinct,  is  continued  to  the  base  of  the  trochanter  minor,  and  the  Internal  ridge  is 
lost  above  in  the  spiral  line  of  the  femur.  Below,  the  linea  aspera  is  prolonged 
by  two  ridges,  which  pass  to  the  condyles  and  enclose  between  them  a  triangular 
space,  the  popliteal  surface  (planum  popliteum),  upon  which  rests  the  popliteal 
artery.  Of  these  two  ridges,  the  outer  one  is  the  more  prominent,  and  descends 
to  the  summit  of  the  outer  condyle.  The  inner  one  is  less  marked,  especially  at 
its  upper  part,  where  it  is  crossed  by  the  femoral  artery.  It  terminates,  below, 
at  the  summit  of  the  internal  condyle,  in  a  small  tubercle,  the  adductor  tubercle, 
which  affords  attachment  to  the  tendon  of  the  Adductor  magnus.  To  the  inner 
lip  of  the  linea  aspera  and  its  inner  prolongation  above  and  below  is  attached 
the  Vastus  internus,  and  to  the  outer  lip  and  its  outer  prolongation  above  is 
attached  the  Vastus  externus.  The  Adductor  magnus  is  attached  to  the  linea 
aspera,  to  its  outer  prolongation  above  and  its  inner  prolongation  below.  Be- 
tween the  Vastus  externus  and  the  Adductor  magnus  are  attached  two  muscles 
— viz.,  the  Gluteus  maximus  above,  and  the  short  head  of  the  Biceps  below. 
Between  the  Adductor  magnus  and  the  Vastus  internus  four  muscles  are  attached : 
the  Iliacus  and  Pectineus  above,  the  Adductor  brevis  and  Adductor  longus  below. 
A  little  below  the  centre  of  the  linea  aspera  is  the  nutrient  foramen  (foramen 
nutricium),  the  orifice  of  the  nutrient  canal  (canalis  nutricius),  which  is  directed 
obHquely  upward  (proximally) . 

Lateral  Borders. — The  two  lateral  borders  of  the  femur  are  only  slightly  marked, 
the  outer  one  extending  from  the  anterior  inferior  angle  of  the  great  trochanter 
to  the  anterior  extremity  of  the  external  condyle;  the  inner  one  from  the  spiral  line 
at  a  point  opposite  the  trochanter  minor,  to  the  anterior  extremity  of  the  internal 
condyle.  The  internal  border  marks  the  limit  of  attachment  of  the  Crureus  muscle 
internally. 

Anterior  Surface. — The  anterior  surface  includes  that  portion  of  the  shaft  which 
is  situated  between  the  two  lateral  borders.  It  is  smooth,  convex,  broader  above 
and  below  than  in  the  centre,  slightly  twisted,  so  that  its  upper  part  is  directed 
forward  and  a  little  outward,  its  lower  part  forward  and  a  little  inward.  To  the 
upper  three-fourths  of  this  surface  the  Crureus  is  attached;  the  lower  fourth  is 
separated  from  the  muscle  by  the  intervention  of  the  synovial  membrane  of  the 
knee-joint  and  a  bursa,  and  affords  attachment  to  the  Subcrureus  to  a  small  extent. 

External  Surface. — The  external  surface  includes  the  portion  of  bone  between 
the  external  border  and  the  outer  lip  of  the  linea  aspera :  it  is  continuous  above 
with  the  outer  surface  of  the  great  trochanter,  below  with  the  outer  surface  of 
the  external  condyle ;  to  its  upper  three-fourths  is  attached  the  outer  portion  of 
the  Crureus  muscle. 

Internal  Surface. — The  internal  surface  includes  the  portion  of  bone  between 
the  internal  border  and  the  inner  hp  of  the  linea  aspera;  it  is  continuous  above 
with  the  lower  border  of  the  neck,  below  with  the  inner  side  of  the  internal  con- 
dyle: it  is  covered  by  the  Vastus  internus  muscle. 

Lower  Extremity. — The  lower  extremity,  larger  than  the  upper,  is  of  a  cuboid 
form,  flattened  from  before  backward,  and  divided  into  two  large  eminences, 
the  condyles  (condyli,  from  ;f6vrJu/oc,  a  knuckle),  by  an  interval  which  presents  a 
smooth  depression  in  front  called  the  trochlea  (fades  patellaris) ,  and  a  notch  of  con- 
siderable size  behind — the  intercondyloid  notch  (fossa  intercondyloidea) .  The  exter- 
nal condyle  (condylus  lateralis)  is  the  more  prominent  anteriorly,  and  is  the  broader 
both  in  the  antero-posterior  and  transverse  diameters.  The  internal  condyle  (con- 
dylus medialis)  is  the  narrower,  longer,  and  more  prominent  inferiorly.  This 
difference  in  the  length  of  the  two  condyles  is  only  observed  when  the  bone  is 
perpendicular  and  depends  upon  the  obliquity  of  the  thigh  bones,  in  consequence 
of  their  separation  above  at  the  articulation  with  the  pelvis.  If  the  femur  is 
held  obliquely,  the  surfaces  of  the  two  condyles  will  be  seen  to  be  nearly  hori- 

15. 


226 


THE  SKELETON 


zontal.  The  two  condyles  are  directly  continuous  in  front,  and  form  a  smooth, 
trochlear  surface,  the  trochlea,  which  articulates  with  the  patella.  It  presents 
a  median  groove,  which  extends  downward  and  backward  to  the  intercondyloid 
notch;  and  two  lateral  convexities,  of  which  the  external  is  the  broader,  more 
prominent,  and  prolonged  farther  upward  upon  the  front  of  the  outer  condyle. 
The  external  border  of  this  articular  surface  is  also  more  prominent,  and  ascends 
higher  than  the  internal  one.  The  intercondyloid  notch  lodges  the  crucial  liga- 
ments ;  it  is  bounded  laterally  by  the  opposed  surfaces  of  the  two  condyles,  and 
in  front  by  the  lower  end  of  the  shaft.  Between  the  popliteal  surface  and  the  I 
floor  of  the  intercondyloid  notch  is  an  elevation  {linea  intercondyloidea) ,  which  i 
affords  attachment  to  the  posterior  ligament  of  the  knee-joint. 

Outer  or  External  Condyle  {condylus  lateralis). — The  outer  surface  of  the  external  i 
condyle  presents,  a  little  behind  its  centre,  an  eminence,  the  outer  tuberosity  {e'pi- 
condylus  lateralis) ;  it  is  less  prominent  than  the  inner  tuberosity,  and  gives  attach- 
ment to  the  external  lateral  ligaments  of  the  knee.    Immediately  beneath  it  is  a] 
groove,  the  popliteal  groove  (sulcus  popliieus),  which  commences  at  a  depression  a 
little  behind  the  centre  of  the  lower  border  of  this  surface :  the  front  part  of  this 
depression  gives  origin  to  the  Popliteus  muscle,  the  tendon  of  which  is  lodged! 
in  the  groove  during  flexion  of  the  knee.    The  groove  is  smooth,  covered  with] 
cartilage  in  the  recent  state,  and  runs  upward  and  backward  to  the  posterior 
extremity  of  the  condyle.    The  inner  surface  of  the  outer  condyle  forms  one  of 
the  lateral  boundaries  of  the  intercondyloid  notch,  and  gives  attachment,  by  its' 
posterior  part,  to  the  anterior  crucial   ligament.     The  inferior  surface  is  convex, 
smooth,  and  broader  than  that  of  the  internal  condyle.    The  posterior  extremity) 
is  convex  and  smooth:  just  above  and  to  the  outer  side  of  the  articular  surface] 
is  a  depression  for  the  tendon  of  the  outer  head  of  the  Gastrocnemius,  above 
which  is  the  origin  of  the  Plantaris. 

Inner  or  Internal  Condyle  {condylus  medialis) . — The  inner  surface  of  the  inner  | 
condyle  presents  a  convex  eminence,  the  inner  tuberosity  (epicondylu^  medialis), 
rough  for  the  attachment  of  the  internal  lateral  ligament.    The  outer  side  of  the; 

inner  condyle  forms  one  of  the  lateral  bound- 
aries of  the  intercondyloid  notch,  and  gives 
attachment,  by  its  anterior  part,  to  the  posterior  1 
crucial  ligament.  Its  inferior  or  articular  sur- 
face is  convex,  and  presents  a  less  extensive 
surface  than  the  external  condyle.  Just  above ' 
the  articular  surface  of  the  condyle,  behind, 
is  a  depression  for  the  tendon  of  origin  of  the 
inner  head  of  the  Gastrocnemius. 

Structure. — The  shaft  of  the  femur  is  a 
cylinder  of  compact  tissue,  hollowed  by  a 
large  medullary  canal.  The  cylinder  is  of  great 
thickness  and  density  in  the  middle  third  of 
the  shaft,  where  the  bone  is  narrowest  and  the 
medullary  canal  well  formed;  but  above  and 
below  this  the  cylinder  gradually  becomes 
thinner,  owing  to  a  separation  of  the  layers  of 
the  bone  into  cancelli,  which  project  into  the 
medullary  canal  and  finally  obliterate  it,  so 
that  the  upper  and  lower  ends  of  the  shaft,  and 
the  articular  extremities  more  especially,  consist  of  cancellated  tissue  invested 
by  a  thin,  compact  layer. 

The  arrangement  of  the  cancelli  in  the  ends  of  the  femur  is  remarkable.     In 
the  upper  end  they  are  arranged  in  two  sets.    One,  starting  from  the  top  of  the 


Tension         Pressure 
planes.  planes 

Fig.  163. — Diagram  showing  the  arrangement 
of  the  bone-fibres  of  the  neck  of  the  femur. 


THE  FEMUB^   OB    THIGH  BONE  227 

head,  the  upper  surface  of  the  n(  <  Is,  and  the  great  trochanter,  converge  to  the  inner 
circumference  of  the  shaft  (Figs.  163  and  164);  these  are  placed  in  the  direction  of 
greatest  pressure,  and  serve  to  support  the  vertical  weight  of  the  body.  The  second 
set  are  planes  of  lamellfe  intersecting  the  former  nearly  at  right  angles,  and  are 


Fig.  164. — Right  femur,  upper  extremity,  ground  frontal  section,  from  in  front.     (Spalteholz.) 


situated  in  the  line  of  the  greatest  tension — that  is  to  say,  along  the  lines  in  which 
the  muscles  and  ligaments  exert  their  traction.  In  the  head  of  the  bone  these 
planes  are  arranged  in  a  curv^ed  form,  in  order  to  strengthen  the  bone  when  exposed 
to  pressure  in  all  directions.  In  the  midst  of  the  cancellous  tissue  of  the  neck  is 
a  vertical  plane  of  compact  bone,  the  femoral  spur  {calcar  femorale),  which  com- 


228 


THE  SKELETON 


mences  at  the  point  where  the  neck  joins  the  shaft  midway  between  the  lesser 
trochanter  and  the  internal  border  of  the  shaft  of  the  bone,  and  extends  in  the 
direction  of  the  digital  fossa  (Fig.  165).  This  materially  strengthens  this  portion 
of  the  bone.  Another  point  in  connection  with  the  structure  of  the  neck  of  the 
femur  requires  mention,  especially  on  account  of  its  influence  on  the  productionjij 
of  fracture  in  this  situation.  It  will  be  noticed  that  a  considerable  portion  of  the  «l 
great  trochanter  lies  behind  the  level  of  the  posterior  surface  of  the  neck;  and  if  a 
section  be  made  through  the  trochanter  at  this  level,  it  will  be  seen  that  the  pos- 
terior wall  of  the  neck  is  prolonged  into  the  trochanter.  This  prolongation  is 
termed  by  Bigelow  the  true  neck,^  and  forms  a  thin,  dense  plate  of  bone,  which 
passes  beneath  the  posterior  intertrochanteric  ridge  toward  the  outer  surface  of 
the  bone.  In  the  lower  end  the  cancelli  spring  on  all  sides  from  the  inner  surface 
of  the  cyUnder,  and  descend  in  a  perpendicular  direction  to  the  articular  surface, 


Great  trochanter. 


_  Digital  fossa. 


Appears  at    ^th 
year;  joins  shaft  ■^ 
about  18th  year. 


Appears  at 
9th  month 
(fatal). 


Appears  at  end 
of  1st  year ; 

joins  shaft  about 
18th  year. 


£  Appears  ISth-lJ^th  year  ; 
5-    joins  shaft  about  18th 


Joins  shaft  at  20th 
year. 


Fig.  165. — Calcar  femorale. 


Lower  extremity. 

Fig.  166. — Plan  of  the  development  of  the  femur, 
five  centres. 


the  cancelli  being  strongest  and  having  a  more  accurately  perpendicular  course 
above  the  condyles.  In  addition  to  this,  however,  horizontal  planes  of  cancellous 
tissue  are  to  be  seen,  so  that  the  spongy  tissue  in  this  situation  presents  an  appear*] 
ance  of  being  mapped  out  into  a  series  of  rectangular  areas. 

Articulations. — With  three  bones:  the  os  innominatum,  tibia,  and  patella. 

Development  (Fig.  166). — The  femur  is  developed  by  five  centres:  one  for  th| 
shaft,  one  for  each  extremity,  and  one  for  each  trochanter.  Of  all  the  long  bonesi 
except  the  clavicle,  it  is  the  first  to  show  traces  of  ossification :  this  commences  ii 
the  shaft,  at  about  the  seventh  week  of  foetal  life,  the  centres  of  ossification  in  th^ 
epiphyses  appearing  in  the  following  order:  First,  in  the  lower  end  of  the  bonej 
at  the  ninth  month  of  foetal  life^  (from  this  the  condyles  and  tuberosities  ai 


1  Bigelow  on  the  Hip,  p.  121. 

*  This  is  said  to  be  the  only  epiphysis  in  which  cssification  begins  before  birth;  though  according  to  som^ 
observers,  the  centre  for  the  upper  epiphysis  of  the  tibia  also  appears  before  birth. 


THE  FEMUB,   OB    THIGH  BONE  229 

formed);  in  the  head  at  the  end  of  the  first  year  after  birth;  in  the  great  tro- 
chanter, during  the  fourth  year;  and  in  the  lesser  trochanter,  between  the  thir- 
teenth and  fourteenth.  The  order  in  which  the  epiphyses  are  joined  to  the  shaft 
is  the  reverse  of  that  of  their  appearance:  their  junction  does  not  commence  until 
after  puberty,  the  lesser  trochanter  being  first  joined,  then  the  great,  then  the 
head,  and,  lastly,  the  inferior  extremity  (the  first  in  Avhich  ossification  commenced), 
which  is  not  united  until  the  twentieth  year. 

Attachment  of  Muscles. — To  twenty-three.  To  the  great  trochanter:  the  Glu- 
teus medius.  Gluteus  minimus,  Pyriformis,  Obturator  internus.  Obturator  externus, 
Gemellus  superior.  Gemellus  inferior,  and  Quadratus  femoris.  To  the  lesser 
trochanter:  the  Psoas  magnus  and  the  Iliacus  below  it.  To  the  shaft:  the  Vastus 
externus.  Gluteus  maximus,  short  head  of  the  Biceps,  Vastus  internus,  Adductor 
magnus,  Pectineus,  Adductor  brevis.  Adductor  longus,  Crureus,  and  Subcrureus. 
To  the  condyles:  the  Gastrocnemius,  Plantaris,  and  Popliteus. 

Surface  Form. — The  femur  is  covered  with  muscles,  so  that  in  fairly  muscular  subjects  the 
shaft  is  not  to  be  detected  through  its  fleshy  covering,  and  the  only  parts  accessible  to  the  touch 
are  the  outer  surface  of  the  great  trochanter  and  the  lower  expanded  end  of  the  bone.  The 
external  surface  of  the  great  trochanter  is  to  be  felt,  especially  in  certain  positions  of  the  limb.  Its 
position  is  generally  indicated  by  a  depression,  owing  to  the  thickness  of  the  Gluteus  medius  and 
minimus,  which  project  above  it.  When,  however,  the  thigh  is  flexed,  and  especially  if  crossed 
over  the  opposite  one,  the  trochanter  produces  a  blunt  eminence  on  the  surface.  The  upper 
border  is  about  on  a  line  with  the  spine  of  the  os  pubis,  and  its  exact  level  is  indicated  by  a 
line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium,  over  the  outer  side  of  the 
hip,  to  the  most  prominent  point  of  the  tuberosity  of  the  ischium.  This  is  known  as  Nelaton's 
line.  The  outer  and  inner  condyles  of  the  lower  extremity  are  easily  to  be  felt.  The  outer  one 
is  more  subcutaneous  than  the  inner  one  and  readily  felt.  The  tuberosity  on  it  is  comparatively 
little  developed,  but  can  be  more  or  less  easily  recognized.  The  inner  condyle  is  more  thickly 
covered,  and  this  gives  a  general  convex  outline  to  this  part,  especially  when  the  knee  is  flexed. 
The  tuberosity  on  it  is  easily  felt,  and  at  the  upper  part  of  the  condyle  the  sharp  tubercle  for  the 
insertion  of  the  tendon  of  the  Adductor  magnus  can  be  recognized  without  difficulty.  When 
the  knee  is  flexed,  and  the  patella  situated  in  the  interval  between  the  condyles  and  the  upper 
end  of  the  tibia,  a  part  of  the  trochlear  surface  of  the  femur  can  be  made  out  above  the  patella. 

Surgical  Anatomy. — There  are  one  or  two  points  about  the  ossification  of  the  femur  bear- 
ing on  practice  to  which  allusion  must  be  made.  It  has  been  stated  above  that  the  lower  end 
of  the  femur  is  the  only  epiphysis  in  which  ossification  has  commenced  at  the  time  of  birth. 
The  presence  of  the  ossific  centre  in  newly  born  children  found  dead  is,  therefore,  a  proof 
that  the  child  has  arrived  at  the  full  period  of  utero-gestation,  and  is  always  relied  upon  in 
medico-legal  investigations.  The  position  of  the  epiphysial  line  should  be  carefully  noted.  It 
is  on  a  level  with  the  adductor  tubercle,  and  the  epiphysis  does  not,  therefore,  form  the  whole 
of  the  cartilage-clad  portion  of  the  lower  end  of  the  bone.  It  is  essential  to  bear  this  point  in 
mind  in  performing  excision  of  the  knee,  since  growth  in  length  of  the  femur  takes  place  chiefly 
from  the  lower  epiphysis,  and  any  interference  with  the  epiphysial  cartilage  in  a  young  child 
would  involve  such  ultimate  shortening  of  the  limb,  from  want  of  growth,  as  to  render  it  almost 
useless.  Separation  of  the  lower  epiphysis  may  take  place  up  to  the  age  of  twenty,  at  which 
time  it  becomes  completely  joined  to  the  shaft  of  the  bone;  but,  as  a  matter  of  fact,  few  cases 
occur  after  the  age  of  sixteen  or  seventeen.  The  epiphysis  of  the  head  of  the  femur  is  of  interest 
principally  on  account  of  its  being  the  seat  of  origin  of  a  large  number  of  cases  of  tuberculous 
disease  of  the  hip-joint.  The  disease  commences  in  the  majority  of  cases  in  the  highly  vascular 
and  growing  tissue  in  the  neighborhood  of  the  epiphysis,  and  from  here  extends  into  the  joint. 
In  the  condition  known  as  coxa  vara  the  head  of  the  femur  falls  to  a  lower  level  than  normal. 
The  angle  between  the  neck  and  shaft  is  greatly  diminished  and  may  become  a  right  angle  or 
the  head  may  actually  descend  to  a  lower  level  than  that  of  the  trochanter.  The  neck  is  also 
bent  with  a  convexity  forward;  coxa  vara  is  due  to  rickets. 

Fractures  of  the  femur  are  divided,  like  those  of  the  other  long  bones,  into  fractures  of  the 
upper  end;  of  the  shaft;  and  of  the  lower  end.  The  fractures  of  the  upper  end  may  be  classi- 
fied into  (1)  fracture  of  the  neck;  (2)  fracture  at  the  junction  of  the  neck  with  the  great  trochanter; 
(3)  fracture  of  the  great  trochanter;  and  (4)  separation  of  the  epiphysis,  either  of  the  head  or 
of  the  great  trochanter.  The  first  of  these,  fracture  of  the  neck,  is  usually  termed  intracapsular 
fracture,  but  this  is  scarcely  a  correct  designation,  as  owing  to  the  attachment  of  the  capsular 
ligament,  the  fracture  may  be  partly  within  and  partly  without  the  capsule,  when  the  fracture 
occurs  at  the  lower  part  of  the  neck.  It  generally  occurs  in  old  people,  principally  women,  and 
usually  from  a  very  slight  degree  of  indirect  violence.     Probably  the  main  cause  of  the  fracture 


230  THE  SKELETON 

taking  place  in  old  people  is  in  consequence  of  the  degenerative  changes  which  the  bone  has 
undergone.  Merkel  believes  that  it  is  mainly  due  to  the  absorption  of  the  calcar  femorale. 
These  fractures  are  occasionally  impacted.  As  a  rule  they  unite  by  fibrous  tissue,  and  frequently 
no  union  takes  place,  and  the  surfaces  of  the  fracture  become  smooth  and  eburnated.  The 
lack  of  reparative  power  in  intracapsular  fracture  is  due  to  lack  of  apposition  of  the  fragments  and 
diminution  in  the  amount  of  blood  sent  to  the  smaller  fragment.  The  head  of  the  bone  receives 
blood  from  the  neck  through  the  reflected  portions  of  the  capsule  and  through  the  Ligamentum 
teres.     A  fracture  cuts  off  the  supply  by  the  neck  and  by  the  reflected  portions  of  the  capsule. 

Fractures  at  the  junction  of  the  neck  with  the  great  trochanter  are  usually  termed  extra- 
capsular, but  this  designation  is  also  incorrect;  as  the  fracture  is  partly  within  the  capsule, 
owing  to  its  attachment  in  front  to  the  anterior  intertrochanteric  line,  which  is  situated  below 
the  line  of  fracture.  These  fractures  are  produced  by  direct  violence  to  the  great  trochanter,  as 
from  a  blow  or  fall  laterally  on  the  hip.  From  the  manner  in  which  the  accident  is  caused,  the 
neck  of  the  bone  is  driven  into  the  trochanter,  where  it  may  remain  impacted  or  the  trochanter 
may  be  split  up  into  two  or  more  fragments,  and  thus  no  fixation  takes  place. 

Fractures  of  the  great  trochanter  may  be  either  "oblique  fracture  through  the  trochanter 
major,  without  implicating  the  neck  of  the  bone"  (Astley  Cooper),  or  seyjaration  of  the  great 
trochanter.  Most  of  the  recorded  cases  of  this  latter  injury  occurred  in  young  persons,  and 
were  probably  cases  of  separation  of  the  epiphysis  of  the  great  trochanter.  Separation  of  the 
epiphysis  of  the  head  of  the  femur  has  been  said  to  occur,  but  has  probably  never  been  verifii 
by  post-mortem  examination. 

Fractures  of  the  shaft  may  occur  at  any  part,  but  the  most  usual  situation  is  at  or  near  th( 
centre  of  the  bone.  They  may  be  caused  by  direct  or  indirect  violence  or  by  muscular  action. 
Fractures  of  the  upper  third  of  the  shaft  are  almost  always  the  result  of  indirect  violence,  whilst 
those  of  the  lower  third  are  the  result,  for  the  most  part,  of  direct  violence.  In  the  middle  third 
fractures  occur  from  both  forms  of  injury  in  about  equal  proportions.  Fractures  of  the  shaft 
are  generally  oblique,  but  they  may  be  transverse,  longitudinal,  or  spiral.  The  transverse 
fracture  occurs  most  frequently  in  children.  The  fractures  of  the  lower  end  of  the  femur  include 
transverse  fracture  above  the  condyles,  the  most  common;  and  this  may  be  complicated  by  a 
vertical  fracture  between  the  condyles,  constituting  the  T-shaped  fracture.  In  these  cases  the 
popliteal  artery  is  in  danger  of  being  wounded.  Oblique  fracture,  separating  either  the  internal 
or  external  condyle,  and  a  longitudinal  incomplete  fracture  between  the  condyles,  may  also  tak 
place. 

The  femur  and  also  the  bones  of  the  leg  are  frequently  the  seat  of  acute  osteomyelitis  in  younj^ 
children.  This  is  no  doubt  due  to  their  greater  exposure  to  injury,  which  is  often  the  exciting 
cause  of  this  disease.  Tumors  not  unfrequently  are  found  growing  from  the  femur:  the  most 
common  forms  being  sarcoma,  which  may  grow  either  from  the  periosteum  or  from  the  medullary 
tissue  within  the  interior  of  the  bone;  and  exostosis,  which  is  commonly  found  originating  in 
the  neighborhood  of  the  epiphysial  cartilage  of  the  lower  end. 

Genu  varum  is  a  form  of  bow-leg  in  which  the  tibia  and  femur  are  curved  outward,  the  knee: 
being  widely  separated.  Both  extremities  are  usually  affected.  In  early  life  the  disease  is  due 
to  rickets.  In  elderly  people  it  may  be  due  to  arthritis  deformans.  Genu  valgum  (knock-knee) 
is  a  condition  in  which  the  knees  are  close  together,  the  feet  are  wide  apart,  and  the  internal 
lateral  ligament  of  the  knee-joint  is  stretched.  It  is  due  to  excessive  growth  of  the  inner  con- 
dyle of  the  femur,  the  shaft  of  the  femur  curving  inward.  It  may  be  due  to  rickets,  attitude  o: 
an  occupation,  or  flat-foot,  and  one  or  both  knees  may  be  affected. 

THE  LEG. 

The  skeleton  of  the  leg  consists  of  three  bones:  the  patella,  a  large  sesamoic 
bone,  placed  in  front  of  the  knee;  the  tibia;  and  the  fibula. 

The  Patella,  or  Knee-cap  (Figs.  167,  168). 

The  patella  (patella,  a  small  pan),  the  knee-cap  or  knee-pan,  is  a  flat,  triangularl 
bone,  situated  at  the  anterior  part  of  the  knee-joint.  It  is  usually  regarded  as  a| 
sesamoid  bone,  developed  in  the  tendon  of  the  Quadriceps  extensor.  It  resembles] 
these  bones  (1)  in  its  being  developed  in  a  tendon;  (2)  in  its  centre  of  ossification 
presenting  a  knotty  or  tuberculated  outline;  (3)  in  its  structure  being  composed; 
mainly  of  dense  cancellous  tissue,  as  in  the  other  sesamoid  bones.  It  serves  to  I 
protect  the  front  of  the  joint,  and  increases  the  leverage  of  the  Quadriceps  extensor 
by  making  it  act  at  a  greater  angle.  It  presents  an  anterior  and  a  posterior  sur-J 
face,  three  borders,  and  an  apex. 


I 


I 

it 

I 


THE   PATELLA,    OB    KNEE-CAP 


231 


Fig.  167.— Right  patella. 
Anterior  surface. 


Fig.  168.— Right  patella. 
Posterior  surface. 


Surfaces.  Anterior  Surface. — The  anterior  surface  is  convex,  perforated  by 
small  apertures,  for  the  passage  of  nutrient  vessels,  and  marked  by  numerous 
rough,  longitudinal  striie.  This  surface  is  covered,  in  the  recent  state,  by  an 
e.xpansion  from  the  tendon  of 
the  Quadriceps  extensor,  which 
is  continuous  below  with  the 
superficial  fibres  of  the  liga- 
mentum  patellae.  It  is  sepa- 
rated from  the  integument  Ly 
a  bursa. 

Posterior  Surface. — The  pos- 
terior surface  presents  a 
smooth,  oval-shaped,  articular 
surface  {fades  articularis) ,  cov- 
ered with  cartilage  in  the  re- 
cent state,  and  divided  into  two  facets  by  a  vertical  ridge,  which  descends  from 
the  superior  border  toward  the  inferior  angle  of  the  bone.  The  ridge  corresponds 
to  the  groove  on  the  trochlear  surface  of  the  femur,  and  the  two  facets  to  the 
articular  surfaces  of  the  two  condyles ;  the  outer  facet,  for  articulation  with  the 
outer  condyle,  being  the  broader  and  deeper.  This  character  serves  to  indicate 
the  side  to  which  the  bone  belongs.  Below  the  articular  surface  is  a  rough,  convex, 
non-articular  depression,  the  lower  half  of  which  gives  attachment  to  the  liga- 
mentum  patellae,  the  upper  half  being  separated  from  the  head  of  the  tibia  by 
adipose  tissue. 

Borders.  Superior  Border. — The  superior  border  (basis  patelloB)  is  thick,  and 
sloped  from  behind,  downward  and  forward:  it  gives  attachment  to  that  portion 
of  the  Quadriceps  extensor  which  is  derived  from  the  Rectus  and  Crureus  muscles. 

Lateral  Borders. — The  lateral  borders  are  thinner,  converging  below.  They 
give  attachment  to  that  portion  of  the  Quadriceps  extensor  derived  from  the 
external  and  internal  Vasti  muscles. 

The  Apex  (apex  patellce). — The  apex  is  pointed,  and  gives  attachment  to  the 
ligamentum  patellae. 

Structure. — It  consists  of  a  nearly  uniform,  dense  cancellous  tissue  covered 
by  a  thin  compact  lamina.  The  cancelli  immediately  beneath  the  anterior  surface 
are  arranged  parallel  with  it.  In  the  rest  of  the  bone  they  radiate  from  the  pos- 
terior articular  surface  toward  the  other  parts  of  the  bone. 

Development. — By  a  single  centre,  which  makes  its  appearance,  according  to 
B^clard,  about  the  third  year.  In  two  instances  Mr.  Pick  haS  seen  this  bone  car- 
tilaginous throughout,  at  a  much  later  period  (six  years).  More  rarely,  the  bone  is 
developed  by  two  centres,  placed  side  by  side.  Ossification  is  completed  about 
the  age  of  puberty.  ;. 

Articulations. — With  the  two  condyles  of  the  femur. 

Attachment  of  Muscles. — To  four:  the  Rectus,  Crureus,  Vastus  internus,  and 
Vastus  externus.  These  muscles,  joined  at  their  insertion,  constitute  the  Quadri- 
ceps extensor  cruris. 


Surface  Form. — The  external  surface  of  the  patella  can  be  seen  and  felt  Jn  front  of  the 
knee.  In  the  extended  position  of  the  limb  the  internal  border  is  a  little  more  prominent  than 
the  outer,  and  if  the  Quadriceps  extensor  is  relaxed  the  bone  can  be  moved  from  side  to  side  and 
appears  to  be  loosely  fixed.  If  the  joint  is  flexed,  the  patella  recedes  into  the  hoUox^  between  the 
condyles  of  the  femur  and  the  upper  end  of  the  tibia,  and  becomes  firmly  fixed  against  the  femur. 

Surgical  Anatomy. — The  main  surgical  interest  about  the  patella  is  in  connection  with 
fractures,  which  are  of  common  occurrence.  They  may  be  produced  by  muscular  action;  that 
IS  to  say,  by  violent  contraction  of  the  Quadriceps  extensor  while  the  limb  is  in  a  position  of 
semi-flexion,  so  that  the  bone  is  snapped  across  the  condyles;  or  by  direct  violence,  such  as 


232 


THE  SKELETON 


Head. 

Styloid  process. 


Tibia. 


^rticulrt^"". 


Internal  malleolus. 
External  malleolus. 

Fig.  169. — Bones  of  the  right  leg.    Anterior  surface. 


Styloid  proces. 


Fibula. 


Fig.  170. — Bones  of  the  right  leg.    Posterior  surface. 


THE   TIBIA,    OR  SHIN  BONE  233 

falls  on  the  knee.  Most  fractures  are  due  to  muscular  action ;  in  fact,  the  patella  is  more  often 
broken  by  muscular  action  than  is  any  other  bone.  In  fractures  by  muscular  action  the  line  of 
fracture  is  transverse.  In  fractures  by  direct  force  the  line  of  fractuure  may  be  oblique,  longi- 
tudinal, stellate,  or  the  bone  variously  comminuted.  The  principal  interest  in  these  cases 
attaches  to  their  treatmennt.  Owing  to  the  wide  separation  of  the  fragments,  and  the  diffi- 
culty there  is  in  maintaining  them  in  apposition,  union  takes  place  by  fibrous  tissue,  and  this 
may  subsequently  stretch,  producing  wide  separation  of  the  fragments  and  permanent  lame- 
ness. Various  plans,  including  opening  the  joint  and  suturing  the  fragments,  have  been  advo- 
cated for  overcoming  this  difficulty.  In  many  cases  a  portion  of  fascia  or  capsule  gets  between 
the  fragments.     In  such  a  condition  operation  is  necessary. 

In  the  larger  number  of  cases  of  fracture  of  the  patella  the  knee-joint  is  involved,  the  car- 
tilage which  covers  its  posterior  surface  being  torn,  the  synovial  membrane  lacerated,  the  lateral 
fibrous  expansions  ruptured,  and  the  patellar  bursa  torn  open.  In  cases  of  fracture  from 
direct  violence,  however,  this  need  not  necessarily  happen,  the  lesion  may  involve  only  the 
superficial  part  of  the  bone;  and,  as  Morris  has  pointed  out,  it  is  an  anatomical  possibility,  in 
complete  fracture,  if  the  lesion  involve  only  the  lower  and  non-articular  part  of  the  bone,  for 
it  to  take  place  without  injury  to  the  synovial  membrane. 

The  Tibia,  or  Shin  Bone  (Figs.  169,  170). 

The  tibia  {tibia,  a  flute  or  pipe)  is  situated  at  the  front  and  inner  side  of  the 
leg,  and,  excepting  the  femur,  is  the  longest  and  largest  bone  in  the  skeleton.  It 
is  prismoid  in  form,  expanded  above,  where  it  enters  into  the  knee-joint,  more 
slightly  enlarged  below.  In  the  male  its  direction  is  vertical  and  parallel  with 
the  bone  of  the  opposite  side;  but  in  the  female  it  has  a  slightly  oblique  direction 
downward  and  outward,  to  compensate  for  the  oblique  direction  of  the  femur 
inward.    It  presents  for  examination  a  shaft  and  two  extremities. 

Upper  Extremity. — The  upper  extremity,  or  head,  is  large,  and  expanded 
on  each  side  into  two  lateral  eminences,  the  internal  and  external  tuberosities 
(condylus  medialis  and  condylus  lateralis).  Superiorly,  each  tuberosity  presents 
a  smooth,  concave  surface  (fades  articularis  superior),  which  articulates  with 


ATTACHMENT  OF  POSTERIOR    __,_,„  „_  po-TroinB    ATTACHMENT  OF  POSTERIOR 

EXTREMITY  OF  EXTERNAL  i^     ^T^    "  EXTR  EM  ITY  OF  I NTERN  AL 

SEMILUNAR  CARTILAGE        ,.-,,-    'V  ,""^Z^,      SEMI  LUNAR  CARTI LAGC 


ATTACHMENT  OF  ANTERIOR^    ooiPiM  nr  .mtc-     ^ATTACHMENT  OF  ANTERIOR 

EXTREMITY   OF  EXTERNAL    „,„''„  °^*Jo\j.,     EXTREM ITY  OF  INTERN  AL 

SEMILUNAR  CARTILAGE    ""","  EATERIMAL  SEMILUNAR  CARTILAGE 


Fig.  171. — Upper  articular  surface  of  the  tibia,  showing  the  attachments  of  the  ligaments. 

(Poirier  and  Charpy.) 

a  condyle  of  the  femur.  The  internal,  articular  surface  is  longer,  deeper,  and 
narrower  than  the  external,  oval  from  before  backward,  to  articulate  with  the  in- 
ternal condyle;  the  external  one  is  broader  and  more  circular,  concave  from  side 
to  side,  but  slightly  convex  from  before  backward^especially  at  its  posterior  part, 
where  it  is  prolonged  on  to  the  posterior  surface  for  a  short  distance,  to  articulate 
with  the  external  condyle.  Between  the  two  articular  surfaces,  and  nearer  the  pos- 
terior than  the  anterior  aspect  of  the  bone,  is  an  eminence,  the  spinous  process 
of  the  tibia  (eminentia  intercondyloidea) ;  surmounted  by  a  prominent  tubercle  on 
each  side  (the  tuberculum  intercondyloideum  mediale  and  the  tuherculum  inter- 
condyloideum  laterale),  on  to  the  lateral  aspect  of  which  the  facets  just  described 
are  prolonged;  in  front  and  behind  the  spinous  process  is  a  rough  depression 


234  'J^HE  SKELETON 

(fossa  intercondyloidea  anterior  and  the  fossa  inter condyloidea  ^posterior)  for  the 
attachment  of  the  anterior  and  posterior  crucial  Ugaments  and  the  semilunar 
fibro-cartilages  (Fig.  171). 

The  anterior  surfaces  of  the  tuberosities  are  continuous  with  one  another,  form- 
ing a  single  large  surface,  which  is  somewhat  flattened:  it  is  triangular,  broad 
above,  and  perforated  by  large  vascular  foramina;  narrow  below,  where  it  ter- 
minates in  a  prominent  oblong  elevation  of  large  size,  the  tubercle  of  the  tibia  , 
{tuberositas  tibce);  the  lower  half  of  this  tubercle  is  rough,  for  the  attachment  of  ■! 
the  ligamentum  patellae;  the  upper  half  presents  a  smooth  facet  supporting,  in  the 
recent  state,  a  bursa  which  separates  the  ligament  from  the  bone.  Posteriorly  the 
tuberosities  are  separated  from  each  other  by  a  shallow  depression,  the  popliteal 
notch  (incisura  poplitea),  which  gives  attachment  to  part  of  the  posterior  crucial 
ligament  and  part  of  the  posterior  ligament  of  the  knee-joint.  The  inner  tuberosity 
presents  posteriorly  a  deep  transverse  groove,  for  the  insertion  of  one  of  the  fas- 
ciculi of  the  tendon  of  the  Semi-membranosus.  Its  lateral  surface  is  convex, 
rough,  and  prominent,  and  gives  attachment  to  the  internal  lateral  ligament.  The 
outer  tuberosity  presents  posteriorly  a  flat  articular  facet  (fades  articular  is  fibularis), 
nearly  circular  in  form,  directed  downward,  backward,  and  outward,  for  articu- 
lation with  the  fibula.  Its  lateral  surface  is  convex  and  rough,  more  prominent 
in  front  than  the  internal,  and  presents  a  prominent  rough  eminence,  situated  on 
a  level  with  the  upper  border  of  the  tubercle  of  the  tibia  at  the  junction  of  its 
anterior  and  outer  surfaces,  for  the  attachment  of  the  ilio-tibial  band.  Just  below 
this  the  Extensor  longus  digitorum  and  a  slip  from  the  Biceps  are  attached.  The 
infraglenoid  margin  (margo  infraglenoidalis)  is  at  the  outer  edge  of  the  superior 
articular  surface.     From  this  point  the  bone  rapidly  narrows  distally. 

Shaft  of  the  Tibia  (corpus  tibice). — The  shaft  of  the  tibia  is  of  a  triangular 
prismoid  form,  broad  above,  gradually  decreasing  in  size  to  its  most  slender  part, 
at  the  commencement  of  its  lower  fourth,  where  fracture  most  frequently  occurs; 
it  then  enlarges  again  toward  its  lower  extremity.  It  presents  for  examination 
three  borders  and  three  surfaces. 

Anterior  Border. — ^The  anterior  border,  the  most  prominent  of  the  three,  is 
called  the  crest  of  the  tibia  (crista  anterior),  or,  in  popular  language,  the  shin;  it 
commences  above  at  the  tubercle,  and  terminates  below  at  the  anterior  margin 
of  the  inner  malleolus.  This  border  is  very  prominent  in  the  upper  two-thirds  of 
its  extent,  smooth  and  rounded  below.  It  presents  a  very  flexuous  course,  being 
usually  curved  outward  above  and  inward  below;  it  gives  attachment  to  the 
deep  fascia  of  the  leg. 

Internal  Border  (margo  medialis) . — ^The  internal  border  is  smooth  and  rounded 
above  and  below,  but  more  prominent  in  the  centre;  it  commences  at  the  back 
part  of  the  inner  tuberosity,  and  terminates  at  the  posterior  border  of  the  inter- 
nal malleolus;  its  upper  part  gives  attachment  to  the  internal  lateral  ligament  of 
the  knee  to  the  extent  of  about  two  inches,  and  to  some  fibres  of  the  Fopliteus 
muscle,  and  its  middle  third  to  some  fibres  of  the  Soleus  and  Flexor  longus 
digitorum  muscles. 

External  Border  (crista  interossea). — The  external  border,  or  interosseous  ridge, 
is  thin  and  prominent,  especially  its  central  part,  and  gives  attachment  to  the 
interosseous  membrane;  it  commences  above  in  front  of  the  fibular  articular  facet, 
and  bifurcates  below,  to  form  the  boundaries  of  a  triangular  rough  surface,  for 
the  attachment  of  the  interosseous  ligament  connecting  the  tibia  and  fibula. 

Internal  Surface  (fades  medialis). — The  internal  surface  is  smooth,  convex^ 
and  broader  above  than  below;  its  upper  third,  directed  forward  and  inward,  is 
covered  by  the  aponeurosis  derived  from  the  tendon  of  the  Sartorius,  and  by  the 
tendons  of  the  Gracilis  and  Semitendinosus,  all  of  which  are  inserted  nearly  as 
far  forward  as  the  anterior  border;  in  the  rest  of  its  extent  it  is  subcutaneous. 


THE    TIBIA,    OB    SHIN  BONE  235 

External  Surface  (fades  lateralis). — The  external  surface  is  narrower  than  the 
internal;  its  upper  two-thirds  presents  a  shallow  groove  for  the  attachment  of 
the  Tibialis  anticus  muscle;  its  lower  third  is  smooth,  convex,  curves  gradually 
forward  to  the  anterior  aspect  of  the  bone,  and  is  covered  from  within  outward  by 
the  tendons  of  the  following  muscles:  Tibialis  anticus.  Extensor  proprius  hallucis, 
Extensor  longus  digitorum. 

Posterior  Surface  (fades  posterior). — The  posterior  surface  (Fig.  170)  presents, 
at  its  upper  part,  a  prominent  ridge,  the  popliteal  line  or  the  oblique  line  of  the 
tibia  (linea  poplitea),  which  extends  from  the  back  part  of  the  articular  facet 
for  the  fibula  obliquely  downward,  to  the  internal  border,  at  the  junction  of 
its  upper  and  middle  thirds.  It  marks  the  lower  limit  for  the  insertion  of  the 
Popliteus  muscle,  and  serves  for  the  attachment  of  the  popliteal  fascia  and  part 
of  the  Soleus,  Flexor  longus  digitorum,  and  Tibialis  posticus  muscles;  the  tri- 
angular concave  surface,  above  and  to  the  inner  side  of  this  line,  gives  attach- 
ment to  the  Popliteus  muscle.  The  middle  third  of  the  posterior  surface  is 
divided  by  a  vertical  ridge  into  tAvo  lateral  halves:  the  ridge  is  well  marked  at 
its  commencement  at  the  oblique  Hne,  but  becomes  gradually  indistinct  below; 
the  inner  and  broader  half  gives  attachment  to  the  Flexor  longus  digitorum,  the 
outer  and  narrower  to  part  of  the  Tibialis  posticus.  The  remaining  part  of  the 
bone  presents  a  smooth  surface  covered  by  the  Tibialis  posticus,  Flexor  longus 
digitorum,  and  Flexor  longus  hallucis  muscles.  Immediately  below  the  oblique 
line  is  the  nutritive  foramen  (foramen  nutridum),  which  is  large  and  directed 
obliquely  downward.  It  is  the  opening  of  the  nutrient  canal,  which  is  directed 
toward  the  periphery. 

Lower  Extremity. — The  lower  extremity,  much  smaller  than  the  upper, 
presents  five  surfaces;  it  is  prolonged  downward,  on  its  inner  side,  to  a  strong 
process,  the  internal  malleolus  (malleolus  medialis) . 

Inferior  Surface  (fades  articularis  inferior). — The  inferior  surface  of  the  bone 
is  quadrilateral,  and  smooth  for  articulation  with  the  astragalus.  This  surface 
is  concave  from  before  backward,  and  broader  in  front  than  behind.  It  is  trav- 
ersed from  before  backward  by  a  slight  elevation,  separating  two  lateral  depres- 
sions. It  is  narrow  internally,  where  the  articular  surface  becomes  continuous 
with  that  on  the  inner  malleolus  (fades  articularis  malleolaris) . 

Anterior  Surface. — The  anterior  surface  of  the  lower  extremity  is  smooth  and 
rounded  above,  and  covered  by  the  tendons  of  the  Extensor  muscles  of  the  toes; 
its  lower  margin  presents  a  rough  transverse  depression,  for  the  attachment  of 
the  anterior  ligament  of  the  ankle-joint. 

Posterior  Surface. — The  posterior  surface  presents  a  superficial  groove  directed 
obliquely  downward  and  inward,  continuous  with  a  similar  groove  on  the  posterior 
surface  of  the  astragalus,  and  serving  for  the  passage  of  the  tendon  of  the  Flexor 
longus  hallucis. 

External  Surface. — The  external  surface  presents  a  triangular  rough  depression 
for  the  attachment  of  the  interior  interosseous  ligament,  connecting  it  with  the 
fibula;  the  lower  part  of  this  depression,  the  fibular  notch  (incisura  fibularis),  is 
smooth,  covered  with  cartilage  in  the  recent  state,  and  articulates  with  the  fibula. 
This  surface  is  bounded  by  two  prominent  borders,  continuous  above  with  the 
interosseous  ridge;  they  afford  attachment  to  the  anterior  inferior  and  posterior 
inferior  tibio-fibular  ligaments. 

Internal  Smrface. — The  internal  surface  of  the  lower  extremity  is  prolonged 
downward  to  form  a  strong  pyramidal  process,  flattened  from  without  inward — 
the  internal  malleolus  (malleolus  medialis).  The  inner  surface  of  this  process  is 
convex  and  subcutaneous;  its  outer  surface  is  smooth  and  slightly  concave,  and 
articulates  with  the  astragalus;  its  anterior  border  is  rough,  for  the  attachment  of 
the  anterior  fibres  of  the  internal  lateral  or  Deltoid  ligament;  its  posterior  border 


236 


THE    SKELETON 


Upper  extremity. 


Appears  at. 
birth. 


,Johis  shaft  about 
20th  year. 


presents  a  broad  and  deep  groove  (sulcus  malleolaris) ,  directed  obliquely  down- 
ward and  inward,  which  is  occasionally  double:  this  groove  transmits  the  tendons 
of  the  Tibialis  posticus  and  Flexor  longus  digitorum  muscles.  The  summit  of  the 
internal  malleolus  is  marked  by  a  rough  depression  behind,  for  the  attachment  of 
the  internal  lateral  ligament  of  the  ankle-joint. 

Structure. — Like  that  of  the  other  long  bones.    At  the  junction  of  the  middle 

and  lower  third,  where  the  bone  is  smallest,  the  wall  of  the  shaft  is  thicker  than 

in  other  parts,  in  order  to  compensate  for  the  smallness  of  the  calibre  of  the  bone. 

Development. — By  three  centres  (Fig.  172):   one   for  the  shaft  and  one  for 

each  extremity.     Ossification  commences  in  the  centre  of  the  shaft  about  the 

seventh  week,  and  gradually  extends  to- 
ward either  extremity.  The  centre  for 
the  upper  epiphysis  appears  before  or 
shortly  after  birth;  it  is  flattened  in  form, 
and  has  a  thin,  tongue-shaped  process  in 
front  which  forms  the  tubercle.  That 
for  the  lower  epiphysis  appears  in  the 
second  year.  The  lower  epiphysis  joins 
the  shaft  at  about  the  eighteenth,  and 
the  upper  one  about  the  twentieth  year. 
Two  additional  centres  occasionally  exist 
— one  for  the  tongue-shaped  process  of 
the  upper  epiphysis,  which  forms  the 
tubercle,  and  one  for  the  inner  malleolus. 
Articulations. — With  three  bones :  the 
femur,  fibula,  and  astragalus. 

Attachment  of  Muscles. — To  twelve: 
to  the  inner  tuberosity,  the  Semimem- 
branosus; to  the  outer  tuberosity,  the 
Tibialis  anticus  and  Extensor  longus  digi- 
torum and  Biceps;  to  the  shaft,  its  in- 
ternal surface,  the  Sartorius,  Gracilis,  and 
Semitendinosus;  to  its  external  surface, 
the  Tibialis  anticus;  to  its  posterior  sur- 
face, the  Pppliteus,  Soleus,  Flexor  longus 
digitorum,  and  Tibiahs  posticus;  to  the 
tubercle,  the  ligamentum  patellae,  by  which  the  Quadriceps  extensor  muscle  is 
inserted  into  the  tibia.  In  addition  to  these  muscles,  the  Tensor  fasciae  femoris  is 
inserted  indirectly  into  the  tibia,  through  the  ilio-tibial  band,  and  the  Peroneus 
longus  occasionally  derives  a  few  fibres  of  origin  from  the  outer  tuberosity. 

Surface  Form. — A  considerable  portion  of  the  tibia  is  subcutaneous  and  easily  to  be  felt. 
At  the  upper  extremity  the  tuberosities  are  to  be  recognized  just  below  the  knee.  The  internal 
one  is  broad  and  smooth,  and  merges  into  the  subcutaneous  surface  of  the  shaft  below.  The 
external  one  is  narrower  and  more  prominent,  and  on  it,  about  midway  between  the  apex  of  the 
patella  and  the  head  of  the  fibula,  may  be  felt  a  prominent  tubercle  for  the  insertion  of  the  illo- 
tibial  band.  In  front  of  the  upper  erid  of  the  bone,  between  the  tuberosities,  is  the  tubercle  of 
the  tibia,  forming  an  oval  eminence  which  is  continuous  below  with  the  anterior  border  or  crest 
of  the  bone.  This  border  can  be  felt,  forming  the  prominence  of  the  shin,  in  the  upper  two- 
thirds  of  its  extent  as  a  sharp  and  flexuous  ridge,  curved  outward  above  and  inward  below.  In 
the  lower  third  of  the  leg  the  border  disappears,  and  the  bone  is  concealed  by  the  tendons  of 
the  muscles  on  the  front  of  the  leg.  Internal  to  the  anterior  border  is  to  be  felt  the  broad 
internal  surface  of  the  tibia,  slightly  encroached  upon  by  the  muscles  in  front  and  behind.  It 
commences  above  at  the  wide  expanded  inner  tuberosity,  and  terminates  below  at  the  internal 
malleolus.  The  internal  malleolus  is  a  broad  prominence  situated  on  a  higher  level  and  some- 
what farther  forward  than  the  external  malleolus.  It  overhangs  the  inner  border  of  the  arch 
of  the  foot.  Its  anterior  border  is  nearly  straight;  its  posterior  border  presents  a  sharp  edge 
which  forms  the  inner  margin  of  the  groove  for  the  tendon  of  the  Tibialis  posticus  muscle. 


Appears  at  2nd^ 
year. 


Joins  shaft  about 
18th  year. 


Lower  extremity. 


Fig.  172.- 


-Plan  of  the  development  of  the  tibia. 
By  tiiree  centres. 


THE  FIBULA,    OR    CALF  BONE  237 


The  Fibula,  or  Calf  Bone  (Figs.  169,  170). 

The  fibula  (fibula,  a  clasp)  is  situated  at  the  outer  side  of  the  leg.  It  is  the 
smaller  of  the  two  bones,  and,  in  proportion  to  its  length,  the  most  slender  of  all 
the  long  bones;  it  is  placed  on  the  outer  side  of  the  tibia,  with  which  it  is  con- 
nected above  and  below.  Its  upper  extremity  is  small,  placed  toward  the  back  of 
the  head  of  the  tibia  and  below  the  level  of  the  knee-joint,  and  excluded  from  its 
formation;  the  lower  extremity  inclines  a  little  forward,  so  as  to  be  on  a  plane 
anterior  to  that  of  the  upper  end,  projects  below  the  tibia,  and  forms  the  outer 
ankle.    It  presents  for  examination  a  shaft  and  two  extremities. 

Upper  Extremity. — The  upper  extremity,  or  head  (capitulum  fibulce),  is  of 
an  irregular  quadrate  form,  presenting  above  a  flattened  articular  facet,  directed 
upward,  forward,  and  inward,  for  articulation  with  a  corresponding  facet  on  the 
external  tuberosity  of  the  tibia.  On  the  outer  side  is  a  thick  and  rough  promi- 
nence, continued  behind  into  a  pointed  eminence,  the  styloid  process  of  the  fibula. 
(apex  capituli  fibulce),  which  projects  upward  from  the  posterior  part  of  the 
head.  The  prominence  gives  attachment  to  the  tendon  of  the  Biceps  muscle 
and  to  the  long  external  lateral  ligament  of  the  knee,  the  ligament  dividing  the 
tendon  into  two  parts.  The  summit  of  the  styloid  process  gives  attachment  to 
the  short  external  lateral  ligament.  The  remaining  part  of  the  circumference  of  the 
head  is  rough,  for  the  attachment  of  muscles  and  ligaments.  It  presents  in  front 
a  tubercle  for  the  origin  of  the  upper  and  anterior  part  of  the  Peroneus  longus,  and 
the  adjacent  surface  gives  attachment  to  the  anterior  superior  tibio-fibular  liga- 
ment; and  behind,  another  tubercle  for  the  attachment  of  the  posterior  superior 
tibio-fibular  ligament  and  the  upper  fibres  of  the  Soleus  muscle. 

Shaft  of  the  Fibula  (corpus  fibulce). — The  shaft  presents  four  borders — 
the  antero-external,  the  antero-internal,  the  postero-external,  and  the  postero- 
internal; and  four  surfaces — anterior,  posterior,  internal,  and  external. 

Antero-external  Border  (crista  anterior). — The  antero-external  border  commences 
above  in  front  of  the  head,  runs  vertically  downward  to  a  little  below  the  middle  of 
the  bone,  and  then,  curving  somewhat  outward,  bifurcates  so  as  to  embrace  the 
triangular  subcutaneous  surface  immediately  above  the  outer  surface  of  the  exter- 
nal malleolus.  This  border  gives  attachment  to  an  intermuscular  septum,  which 
separates  the  extensor  muscles  on  the  anterior  surface  of  the  leg  from  the  Peroneua 
longus  and  brevis  muscles  on  the  outer  surface. 

Antero-intemal  Border  (crista  interossea) . — The  antero-internal  border,  or  inter- 
osseous ridge,  is  situated  close  to  the  inner  side  of  the  preceding,  and  runs  nearly 
parallel  with  it  in  the  upper  third  of  its  extent,  but  diverges  from  it  so  as  to 
include  a  broader  space  in  the  lower  two-thirds.  It  commences  above,  just 
beneath  the  head  of  the  bone  (sometimes  it  is  quite  indistinct  for  about  an 
inch  below  the  head),  and  terminates  below  at  the  apex  of  a  rough  triangular 
surface  inmiediately  above  the  articular  facet  of  the  external  malleolus.  It  serves 
for  the  attachment  of  the  interosseous  membrane,  which  separates  the  extensor 
muscles  in  front  from  the  flexor  muscles  behind. 

Postero-external  Border  (crista  lateralis) . — The  postero-external  border  is  promi- 
nent; it  commences  above  at  the  base  of  the  styloid  process,  and  terminates  below 
in  the  posterior  border  of  the  outer  malleolus.  It  is  directed  outward  above,  back- 
ward in  the  middle  of  its  course,  backward  and  a  little  inward  below,  and  gives 
attachment  to  an  aponeurosis  which  separates  the  Peronei  muscles  on  the  outer 
surface  of  the  shaft  from  the  flexor  muscles  on  its  posterior  surface. 

Postero-intemal  Border  (crista  medialis). — The  postero-internal  border,  some- 
times called  the  oblique  line,  commences  above  at  the  inner  side  of  the  head, 
and  terminates  by  becoming  continuous  with  the  antero-internal  border  or  inter- 


238  THE  SKELETON 

osseous  ridge  at  the  lower  fourth  of  the  bone.  It  is  well  marked  and  promi- 
nent at  the  upper  and  middle  parts  of  the  bone.  It  gives  attachment  to  an 
aponeurosis  which  separates  the  Tibialis  posticus  from  the  Soleus  above  and  the 
Flexor  longus  hallucis  below. 

Anterior  Surface  (fades  anterior)  ,-^The  anterior  surface  is  the  interval  between 
the  antero-external  and  antero-internal  borders.  It  is  extremely  narrow  and  flat 
in  the  upper  third  of  its  extent;  broader  and  grooved  longitudinally  in  its  lower 
third;  it  serves  for  the  attachment  of  three  muscles,  the  Extensor  longus  digitorum, 
Peroneus  tertius,  and  Extensor  proprius  hallucis. 

External  Surface  (facies  lateralis). — The  external  surface  is  the  space  between 
the  antero-external  and  postero-external  borders.  It  is  much  broader  than  the 
preceding,  and  often  deeply  grooved,  is  directed  outward  in  the  upper  two-thirds 
of  its  course,  backward  in  the  lower  third,  where  it  is  continuous  with  the  poste- 
rior border  of  the  external  malleolus.  This  surface  is  completely  occupied  by 
the  Peroneus  longus  and  brevis  muscles. 

Internal  Surface  (facies  medialis). — The  internal  surface  is  the  interval  included 
between  the  antero-internal  and  the  postero-internal  borders.  It  is  directed 
inward,  and  is  grooved  for  the  attachment  of  the  Tibialis  posticus  muscle. 

Posterior  Surface  (facies  posterior). — ^The  posterior  surface  is  the  space  included 
between  the  postero-external  and  the  postero-internal  borders,  it  is  continuous 
below  with  the  rough  triangular  surface  above  the  articular  facet  of  the  outer 
malleolus;  it  is  directed  backward  above,  backward  and  inward  at  its  middle, 
directly  inward  below.  Its  upper  third  is  rough,  for  the  attachment  of  the  Soleus 
muscle;  its  lower  part  presents  a  triangular  rough  surface,  connected  to  the  tibia 
by  a  strong  interosseous  ligament,  and  between  these  two  points  the  entire  surface 
is  covered  by  the  fibres  of  origin  of  the  Flexor  longus  hallucis  muscle.  At  about 
the  middle  of  this  surface  is  the  nutrient  foramen  (foramen  nutricium) .  It  opens 
into  the  nutrient  canal  (canalis  nutricius) ,  which  is  directed  downward. 

Lower  Extremity. — The  lower  extremity,  or  external  malleolus  (malleolus 
lateralis),  is  of  a  pyramidal  form,  somewhat  flattened  from  without  inward,  and 
is  longer,  and  descends  lower  than  the  internal  malleolus.  Its  external  surface  is 
convex,  subcutaneous,  and  continuous  with  the  triangular  (also  subcutaneous) 
surface  on  the  outer  side  of  the  shaft.  The  internal  surface  presents  in  front  a 
smooth  triangular  facet  (facies  articularis  malleoli) .  broader  above  than  below,  and 
convex  from  above  downward,  which  articulates  with  a  corresponding  surface  on 
the  outer  side  of  the  astragalus.  Behind  and  beneath  the  articular  surface  is  a 
rough  depression  which  gives  attachment  to  the  posterior  fasciculus  of  the  external 
lateral  ligament  of  the  ankle.  The  anterior  border  is  thick  and  rough,  and  marked 
below  by  a  depression  for  the  attachment  of  the  anterior  fasciculus  of  the  external 
lateral  ligament.  The  posterior  border  is  broad  and  niarked  by  a  shallow  groove 
(sulcus  malleolaris) ,  for  the  passage  of  the  tendons  of  the  Peroneus  longus  and 
brevis  muscles.  The  summit  is  rounded,  and  gives  attachment  to  the  middle 
fasciculus  of  the  external  lateral  ligament. 

In  order  to  distinguish  the  side  to  which  the  bone  belongs,  hold  it  with  the 
lower  extremity  downward  and  the  broad  groove  for  the  Peronei  tendons  back- 
ward— i.e.,  toward  the  holder;  the  triangular  subcutaneous  surface  will  then  be 
directed  to  the  side  to  which  the  bone  belongs. 

Articulations. — With  two  bones:  the  tibia  and  astragalus. 

Development. — By  three  centres  (Fig.  173):  one  for  the  shaft,  and  one  for 
each  extremity.  Ossification  commences  in  the  shaft  about  the  eighth  week  of 
foetal  life,  a  little  later  than  in  the  tibia,  and  extends  gradually  toward  the  extrem- 
ities. At  birth  both  ends  are  cartilaginous.  Ossification  commences  in  the  lower 
end  in  the  second  year,  and  in  the  upper  one  about  the  fourth  year.  The  lower 
■epiphysis,  the  first  in  which  ossification  commences,  becomes  united  to  the  shaft 


THE   FOOT 


239 


Upper  extremity. 

Appears  about  /-^^VUnite^  about 
y,h  year.     ^  ^Sm    ^^^^  V^^- 


about  the  twentieth  year;  the  upper  epiphysis  joins  about  the  twenty-fifth  year. 
Ossification  appearing  first  in  the  lower  epiphysis  is  contrary  to  the  rule  which 
prevails  with  regard  to  the  commencement  of  ossification  in  epiphyses — viz., 
that  epiphysis  toward  which  the  nutrient  artery  is 
directed  commences  to  ossify  last;  but  it  follows  the 
rule  which  prevails  with  regard  to  the  union  of  epi- 
physes, by  uniting  first. 

Attachment  of  Muscles. — ^To  nine:  to  the  head, 
the  Biceps,  Soleus,  and  Peroneus  longus;  to  the  shaft, 
its  anterior  surface,  the  Extensor  longus  digitorum, 
Peroneus  tertius,  and  Extensor  proprius  hallucis;  to 
the  internal  surface,  the  Tibialis  posticus;  to  the 
posterior  surface,  the  Soleus  and  Flexor  longus 
hallucis;  to  the  external  surface,  the  Peroneus  longus 
and  brevis. 

Surface  Form. — The  only  parts  of  the  fibula  which  are  to 
be  felt  are  the  head  and  the  lower  part  of  the  external  surface 
of  the  shaft  and  the  external  malleolus.  The  head  is  to  be 
seen  and  felt  behind  and  to  the  outer  side  of  the  outer  tuber- 
osity of  the  tibia.  It  presents  a  small,  prominent  triangular 
eminence  slightly  above  the  level  of  the  tubercle  of  the  tibia. 
The  external  malleolus  presents  a  narrow  elongated  promi- 
nence, situated  on  a  plane  posterior  to  the  internal  malleolus 
and  reaching  to  a  lower  level.     From  it  may  be  traced  the 

lower  third  or  half  of  the  external  surface  of  the  shaft  of  the         Appears  o<__fliP  Pni<cs  about 
bone  in  ihe  interval  between  the  Peroneus  tertius  in  front  and  ^"'^  2/«o»'-     \  w  /  ^^''^  J'^"'"- 

the  other  two  Peronei  tendons  behind. 

Surgical  Anatomy. — In  fractures  of  the  bones  of  the  leg  both 
bones  are  usually  fractured,  but  either  bone  may  be  broken 
separately,  the  fibula  more  frequently  than  the  tibia.  Fracture 
of  both  bones  may  be  caused  either  by  direct  or  indirect  violence.  When  it  occurs  from  indirect 
force,  the  fracture  in  the  tibia  is  usually  at  the  junction  of  the  middle  and  lower  third  of  the  bone. 
Many  causes  conduce  to  render  this  the  weakest  part  of  the  bone.  The  fracture  of  the  fibula 
is  usually  at  rather  a  higher  level.  These  fractures  present  great  variety,  both  as  regards 
their  direction  and  condition.  They  may  be  oblique,  transverse,  longitudinal,  or  spiral.  When 
oblique,  they  are  usually  the  result  of  indirect  violence,  and  the  direction  of  the  fracture  is  from 
behind,  downward,  forward,  and  inward  in  many  cases,  but  may  be  downward  and  outward 
or  downward  and  backward.  When  transverse,  the  fracture  is  often  at  the  upper  part  of  the 
bone,  and  is  the  result  of  direct  violence.  The  spiral  fracture  usually  commences  as  a  vertical 
fissure,  involving  the  ankle-joint,  and  is  associated  with  fracture  of  the  fibula  higher  up.  It  is 
the  result  of  torsion,  from  twisting  of  the  body  whilst  the  foot  is  fixed. 

Fractures  of  the  tibia  alone  are  almost  always  the  result  of  direct  violence,  except  where  the 
malleolus  is  broken  of?  by  twists  of  the  foot.  Fractures  of  the  fibula  alone  may  arise  from  indi- 
rect or  direct  force,  those  of  the  lower  end  being  usually  the  result  of  the  former,  and  those 
higher  up  being  caused  by  a  direct  blow  on  the  part. 

The  tibia  and  fibula,  like  the  femur,  are  frequently  the  seat  of  acute  osteomyelitis.  Tuberculous 
<ibscess  is  more  frequently  met  with  in  the  cancellous  tissue  of  the  head  and  lower  end  of  the 
tibia  than  in  any  other  bone  of  the  body.  The  abscess  is  of  small  sizC;  very  chronic,  and  prob- 
ably the  result  of  tuberculous  osteitis  in  the  highly  vascular  growing  tissue  at  the  end  of  the  shaft 
near  the  epiphysial  cartilage  in  the  young  subject.  Such  an  abscess  in  bone  is  called  Brodie's 
abscess. 

The  tibia  is  the  bone  which  is  most  frequently  and  most  extensively  distorted  in  rickets.  It 
gives  way  at  the  junction  of  the  middle  and  lower  third,  its  weakest  part,  and  presents  a  curve 
forward  and  outward.  Bow-leg  is  due  to  outward  curvature  of  the  femur,  tibia,  and  fibula, 
the  bend  being  about  the  junction  of  the  shafts  and  lower  extremities. 


Lower  extremity. 

Fig.  173. — Plan  of  the  development 
of  the  fibula.    By  three  centres. 


THE  FOOT  (Figs.  174,  175). 

The  skeleton  of  the  foot  consists  of  three  divisions:  the  tarsus,  metatarsus,  and 
phalanges. 


240 


THE  SKELETON 


Groove Jor  peroncus  lonqus. 
Groove  for  peroneus  brevis, 


PERONEUS  TERTIUS 
PERONEUS  BREVIS 


Groove  for  tendon  of 

FLEXOR    LONQUS   HALLUCIS. 


Tarsus. 


Metatarsus. 


Innermost  tendon  of 

EXTENSOR    BREVIS    DIQITORUM. 


i'^Shaftj    Phalanges. 

y 

i!A.—.;5rT~  EXTENSOR    LONQUS    HALLUCIS. 


Fig.  174.— Bones  of  the  right  foot.     Dorsal  surface. 


THE    FOOT 


241 


A9DUCT0R    HALLUCIS 


OUTER   HEAD   Or   ACCESSORIUS, 


rtCXOR    BREVIS    HALLU0I8. 


FLEXOR  BREVia 
,  „....  ABDUCTOR 
(   MINIMI    DIQITI. 


FLEXOR    BREVIS    OIQlTORUM. 


FLEXOR    LONQUS    DIQITORUM. 


Fig.  175. — Bones  of  the  right  foot.     Plantar  surface. 

16 


242 


THE  SKELETON 
The  Tarsus  (Ossa  Tarsi). 


The  bones  of  the  tarsus  are  seven  in  number — viz.,  the  calcaneus  or  os  calcis, 
astragalus,  cuboid,  scaphoid,  internal,  middle,  and  external  cuneiform. 

The  Calcaneus,  or  Heel  Bone  (Fig.  176).— It  is  also  called  the  os  calcis.  The 
name  is  derived  from  calx,  the  heel.  The  heel  bone  is  the  largest  and  strongest  of 
the  tarsal  bones.    It  is  irregularly  cuboidal  in  form,  having  its  long  axis  directed  for- 

A 


Peroneal  tubercle 
Groove  for 
Peroneus  brevis 


Groove  for 
Peroneus  longus.  Tubercle  for  ext.  lat.  lig. 


For  astragalus. 


For  cuboid, 
tali. 

Groove  for  Flex, 
long,  hallucis. 

Fig.  176. — The  left  os  calcis.     A.  Postero-external  view.     B.  Antero-internal  view. 

ward  and  outv^^ard.  It  is  situated  at  the  lov^^er  and  back  bart  of  the  foot,  serving  to 
transmit  the  weight  of  the  body  to  the  ground,  and  forming  a  strong  lever  for  the 
muscles  of  the  calf.  It  is  composed  of  a  body  (corpus  calcanei) ,  an  anterior  extremity 
or  greater  process,  and  a  posterior  extremity  or  tuberosity  (tuber  calcanei).  It  pre- 
sents for  examination  six  surfaces:  superior,  inferior,  external,  internal,  anterior, 
and  posterior. 

Superior  Surface. — The  superior  surface  is  formed  behind  by  the  upper  aspect 
of  that  part  of  the  os  calcis  which  projects  backward  to  form  the  heel.  It  varies 
in  length  in  different  individuals ;  is  convex  from  side  to  side,  concave  from  before 
backward,  and  corresponds  above  to  a  mass  of  adipose  substance  placed  in 
front  of  the  tendo  Achillis.  In  the  middle  of  the  superior  surface  are  two  (some- 
times three)  articular  facets,  separated  by  a  broad  shallow  groove  (sulcus  cal- 
canei), which  is  directed  obliquely  forward  and  outward,  and  is  rough  for  the 
attachment  of  the  interosseous  ligament  connecting  the  astragalus  and  os  calcis. 
When  the  calcaneus  is  in  contact  with  the  astragalus  this  groove  is  converted  into 
a  canal  (sinus  tarsi) .  Of  the  articular  surfaces,  the  external  or  posterior  articular 
surface  (fades  articularis  calcanea  posterior)  is  the  larger,  and  is  situated  on  the  body 


THE    TARSUS  243 

of  the  bone:  it  is  of  an  oblong  form,  wider  behind  than  in  front,  and  convex  from 
before  backward.  The  internal  or  anterior  articular  surface  is  usually  divided  into 
two  facets.  The  anterior  facet  is  the  ]acies  articularis  calcanea  anterior,  and  it 
supports  the  head  of  the  astragalus.  The  more  posteriorly  situated  facet  is  the 
fades  articularis  calcanea  media.  It  articulates  with  the  middle  facet  on  the 
under  surface  of  the  astragalus.  The  internal  articular  surface  is  supported  on 
a  projecting  process  of  bone,  called  the  lesser  process  of  the  calcaneus  (susten- 
taculum tali) ;  it  is  also  oblong,  concave  longitudinally,  and  sometimes  subdivided 
into  two  parts,  which  differ  in  size  and  shape.  More  anteriorly  is  seen  the  upper 
surface  of  the  greater  process  of  the  calcaneus,  marked  by  a  rough  depression 
for  the  attachment  of  numerous  ligaments,  and  a  tubercle  for  the  origin  of  the 
Extensor  brevis  digitorum  muscle. 

Inferior  Surface. — The  inferior  surface  is  narrow,  rough,  uneven,  wider  behind 
than  in  front  and  convex  from  side  to  side,  it  is  bounded  posteriorly  by  two  tuber- 
cles separated  by  a  rough  depression ;  the  external  tubercle  (processus  lateralis  tuheris 
calcanei),  small,  prominent,  and  rounded,  gives  attachment  to  part  of  the  Abductor 
minimi  digiti :  the  internal  tubercle  (processus  medialis  tuheris  calcanei) ,  broader 
and  larger,  for  the  support  of  the  heel,  gives  attachment,  by  its  prominent  inner 
margin,  to  the  Abductor  hallucis,  and  in  front  to  the  Flexor  brevis  digitorum 
muscles  and  plantar  fascia;  the  depression  between  the  tubercles  gives  attach- 
ment to  the  Abductor  minimi  digiti.  The  rough  surface  in  front  of  the  tubercles 
gives  attachment  to  the  long  plantar  ligament  and  to  the  outer  head  of  the  Flexor 
accessorius  muscle;  while  to  a  prominent  tubercle  nearer  the  anterior  part  of 
this  surface,  as  well  as  to  a  transverse  groove  in  front  of  it,  is  attached  the 
short  plantar  ligament. 

External  Surface. — The  external  surface  is  broad,  flat,  and  almost  subcutaneous; 
it  presents  near  its  centre  a  tubercle,  for  the  attachment  of  the  middle  fasciculus 
of  the  external  lateral  ligament.  At  its  upper  and  anterior  part  this  surface 
gives  attachment  to  the  external  calcaneo-astragaloid  ligament;  and  in  front  of 
the  tubercle  it  presents  a  narrow  surface  marked  by  two  oblique  grooves,  sepa- 
rated by  an  elevated  ridge  which  varies  much  in  size  in  different  bones;  it  is 
named  the  peroneal  spine  or  tubercle  (processus  trochlearis) ,  and  gives  attachment 
to  a  fibrous  process  from  the  external  annular  ligament.  The  superior  groove 
transmits  the  tendon  of  the  Peroneus  brevis;  the  inferior  groove  the  tendon  of 
the  Peroneus  longus. 

Internal  Surface. — The  internal  surface  is  deeply  concave;  it  is  directed  obliquely 
downward  and  forward,  and  serves  for  the  transmission  of  the  plantar  vessels 
nd  nerves  into  the  sole  of  the  foot;  it  affords  attachment  to  part  of  the  Flexor 

cessorius  muscle.     At  its  upper  and  fore  part  it  presents  an  eminence  of  bone, 

e  lesser  process  of  the  calcaneum  (sustentaculum  tali),  which  projects  horizon- 
tally inward,  and  to  it  a  slip  of  the  tendon  of  the  Tibialis  posticus  is  attached. 
This  process  is  concave  above,  and  supports  the  anterior  articular  surface  of 
the  astragalus;  below,  it  is  grooved  for  the  tendon  of  the  Flexor  longus  hallucis. 
Its  free  margin  is  rough,  for  the  attachment  of  part  of  the  internal  lateral  liga- 
ment of  the  ankle-joint. 

Anterior  Surface  (fades  articularis  cuboidea). — The  anterior  surface,  of  a  some- 
what triangular  form,  articulates  with  the  cuboid.  It  is  concave  from  above 
downward  and  outward,  and  convex  in  the  opposite  direction.  Its  inner  border 
gives  attachment  to  the  inferior  calcaneo-scaphoid  ligament. 

Posterior  Surface. — The  posterior  surface  is  rough,  prominent,  convex,  and 
wider  below  than  above.  The  posterior  extremity  is  the  projection  of  the  heel. 
It  is  called  the  tuberosity  (tuber  calcanei).  Its  lower  part  is  rough,  for  the  attach- 
ment of  the  tendo  Achillis  and  the  tendon  of  the  Plantaris  muscle;  its  upper  part 
is  smooth,  and  is  covered  by  a  bursa  which  separates  the  tendons  from  the  bone. 


^ 

'^^. 


244 


THE    SKELETON 


Articulations. — With  two  bones:  the  astragalus  and  cuboid. 

Attachment  of  Muscles. — To  eight :  part  of  the  Tibiahs  posticus,  the  tendo 
AchilHs,  Plantaris,  Abductor  hallucis,  Abductor  minimi  digiti,  Flexor  brevis  digi- 
torum,  Flexor  accessorius,  and  Extensor  brevis  digitorum. 

The  Astragalus,  or  Ankle  Bone  (talus)  (Fig.  177). — The  astragalus  (daTfjayah}::, 
a  die)  is  the  largest  of  the  tarsal  bones,  next  to  the  os  calcis.  It  occupies  thei 
middle  and  upper  part  of  the  tarsus,  supporting  the  tibia  above,  articulating 
with  the  malleoli  on  either  side,  resting  below  upon  the  os  calcis,  and  joined  inj 
front  to  the  scaphoid.  This  bone  may  easily  be  recognized  by  its  large  roundec 
head,  by  the  broad  articular  facet  on  its  upper  convex  surface,  and  by  the  tw( 
articular  facets  separated  by  a  deep  groove  on  its  under  concave  surface.     II 


For 
navicular.    Neck. 


Sup.  surface 
for  tibia. 

■   / 


For  inner 
malleolus. 

For  navicular. 


For  ext. 
malleolus 


^For  inferior 
calc.  navic.  lig. 


Groove  for  ^_^^^' 

Flex.  long.  hall.  ««  ^'"'«*«- 

Fig.   177. — The  left  astragalus.     A.  Superior  and  external  view.     B.  Inferior  and  internal  view, 


is  divided  into  a  body  (corpus  tali),  which  supports  the  trochlear  surface;  the 
head  (caput  tali),  which  is  in  front  of  the  body;  and  the  neck  (collum  tali),  the 
constricted  part  between  the  head  and  body.  The  astragalus  presents  si? 
surfaces  for  examination. 

Superior   Surface. — The  superior  surface  presents,   behind,   a  broad   smootl 
trochlear  surface  (trochlea  tali)  for  articulation  with  the  tibia.     The  trochlea  is| 
broader  in  front  than  behind,  convex  from  before  backward,  slightly  concave 
from   side  to   side;   in   front   of  it   is   the   upper   surface  of  the   neck  of  the 
astragalus,  rough  for  the  attachment  of  ligaments. 

Inferior  Surface. — The  inferior  surface  presents  two  articular  facets  separatee 
by  a  deep  groove  (sulcus  tali).  The  groove  runs  obliquely  forward  and  outward, 
becoming  gradually  broader  and  deeper  in  front:  it  corresponds  with  a  similar 
groove  upon  the  upper  surface  of  the  calcaneus,  and  forms,  when  articulated  wit! 
that  bone,  a  canal  (sinus  tarsi) ,  filled  up  in  the  recent  state  by  the  interosseous 
calcaneo-astragaloid  ligament.  Of  the  two  articular  facets,  the  posterior  articula 
facet  (fades  articularis  calcanea  posterior)  is  the  larger,  of  an  oblong  form  an( 
deeply  concave  from  side  to  side;  the  anterior  articular  facet  is  shorter  and  nar- 
rower, of  an  elongated  oval  form,  convex  longitudinally,  and  often  subdivided  intq 
two  by  an  elevated  ridge;  of  these,  the  posterior  (fades  articularis  calcanea  media) 
articulates  with  the  lesser  process  of  the  os  calcis ;  the  anterior  (fades  articulari 
calcanea  anterior) ,  with  the  upper  surface  of  the  inferior  calcaneo-scaphoid  ligamentj 

Internal  Surface. — The  internal  surface  presents  at  its  upper  part  a  pear-shapec 
articular  facet  (fades  malleolaris  medialis)  for  the  inner  malleolus,  continuous 
above  with  the  trochlear  surface;  below  the  articular  surface  is  a  rougl 
depression,  for  the  attachment  of  the  deep  portion  of  the  internal  lateral  ligament^ 

External  Surface. — The  external  surface  presents  a  large  triangular  facet  (faciei 
malleolaris  lateralis) ,  covered  with  cartilage  and  concave  from  above  downwai 


THE    TARSUS 


245 


for  articulation  with  the  external  malleolus;  it  is  called  the  external  process  {'pro- 
cessus lateralis  tali),  and  passes  outward  and  downward  from  the  triangular  facet. 
The  triangular  facet  is  continuous  above  with  the  trochlear  surface;  and  in  front 
of  it  is  a  rough  depression  for  the  attachment  of  the  anterior  fasciculus  of  the 
external  lateral  ligament  of  the  ankle-joint. 

Anterior  Surface  {jades  articularis  navicularis) . — The  anterior  surface  of  the 
h?ad  of  the  astragalus  is  convex  and  rounded,  smooth,  of  an  oval  form,  and 
directed  obliquely  inward  and  downward;  it  articulates  with  the  scaphoid.  On 
its  under  and  inner  surface  is  a  small  facet,  continuous  in  front  with  the  articular 
surface  of  the  head,  and  behind  with  the  smaller  facet  for  the  os  calcis.  This 
rests  on  the  inferior  calcaneo-scaphoid  ligament,  being  separated  from  it  by  the 
synovial  membrane,  which  is  prolonged  from  the  anterior  calcaneo-astragaloid 
joint  to  the  astragalo-scaphoid  joint.  The  head  is  surrounded  by  a  constricted 
portion,  the  neck  of  the  astragalus  {collum  tali). 

Posterior  Surface. — The  posterior  surface  is  narrow,  and  traversed  by  a  groove 
{sulcus  m.  flexor  is  hallucis  longi),  which  runs  obliquely  downward  and  inward, 
and  transmits  the  tendon  of  the  Flexor  longus  hallucis,  external  to  which  is 
the  prominent  external  tubercle  {processus  posterior  tali),  to  which  the  posterior 
fasciculus  of  the  external  lateral  ligament  is  attached.  This  tubercle  is  some- 
times separated  from  the  rest  of  the  astragalus,  and  is  then  known  as  the  os 
trigonum.    To  the  inner  side  of  the  groove  is  the  less  marked  internal  tubercle. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  broad  articular 
surface  upward,  and  the  rounded  head  forward;  the  lateral  triangular  articular 
surface  foi'  the  external  malleolus  will  then  point  to  the  side  to  which  the  bone 
belongs. 

Articulations. — With  four  bones:  tibia,  fibula,  os  calcis,  and  scaphoid. 

The  Cuboid  {os  cuhoideaim)  (Fig.  178). — The  cuboid,  from  zt>/9oc,  a  cube; 
eidoQ,  like,  is  placed  on  the  outer  side  of  the  foot,  in  front  of  the  os  calcis,  and 


isionnl  facet. 
•  navicular. 


For  ext. 
cuneiform. 


For  fourth 
metatarml. 


Groove  for 
Peroneus  longus.    For  os  calcis. 
For  fifth  metatarsal. 
Fig.  178. — The  left  cuboid.     A.  Antero-internal  view.     B.  Postero-external  view. 


)ehind  the  fourth  and  fifth  metatarsal  bones.  It  is  of  a  pyramidal  shape,  its 
base  being  directed  inward,  its  apex  outward.  It  may  be  distinguished  from 
the  other  tarsal  bones  by  the  existence  of  a  deep  groove  on  its  under  surface, 
for  the  tendon  of  the  Peroneus  longus  muscle.  It  presents  for  examination  six 
surfaces:  three  articular  and  three  non-articular. 

Non-articular  Surfaces. — The  non-articular  surfaces  are  the  superior,  inferior,  and 
external.  The  superior  or  dorsal  surface,  directed  upward  and  outward,  is  rough, 
for  the  attachment  of  numerous  ligaments.  The  inferior  or  plantar  surface  presents 
in  front  a  deep  groove,  the  peroneal  groove  {sulcus  m.  peronoei  longi),  which 
runs  obliquely  from  without,  forward  and  inward;  it  lodges  the  tendpn  of  the 
Peroneus  longus,  and  is  bounded  behind  by  a  prominent  ridge,  to  which  is 
attached  the  long  calcaneo-cuboid  ligament.  The  ridge  terminates  externally 
in  an  eminence,  the  tuberosity  of  the  cuboid  {tuberositas  ossis  cuboidei),  the  sur- 
face of  which  presents  a  convex  facet,  for  articulation  with  the  sesamoid  bone 


246 


THE  SKELETON 


of  the  tendon  contained  in  the  groove.  The  surface  of  bone  behind  the  groove 
is  rough,  for  the  attachment  of  the  short  plantar  ligament,  a  few  fibres  of  the 
Flexor  brevis  hallucis,  and  a  fasciculus  from  the  tendon  of  the  Tibialis  posticus. 
The  external  surface,  the  smallest  and  narrowest  of  the  three,  presents  a  deep 
notch  formed  by  the  commencement  of  the  peroneal  groove. 

Articular  Surfaces. — The  articular  surfaces  are  the  posterior,  anterior,  and] 
internal.  The  'posterior  surface  is  smooth,  triangular,  and  concavo-convex,  foi 
articulation  with  the  anterior  surface  of  the  os  calcis.  The  anterior  surface,  o{ 
smaller  size,  but  also  irregularly  triangular,  is  divided  by  a  vertical  ridge  intc 
two  facets;  the  inner  one,  quadrilateral  in  form,  articulates  with  the  fourtl: 
metatarsal  bone;  the  outer  one,  larger  and  more  triangular,  articulates  witl 
the  fifth  metatarsal.  The  internal  surface  is  broad,  rough,  irregularly  quadrin 
lateral,  presenting  at  its  middle  and  upper  part  a  smooth  oval  facet,  for  articula-i 
tion  with  the  external  cuneiform  bone;  and  behind  this  (occasionally)  a  smallei 
facet,  for  articulation  with  the  navicular;  it  is  rough  in  the  rest  of  its  extent,  for 
the  attachment  of  strong  interosseous  ligaments. 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  so  that  its  under  surface] 
marked  by  the  peroneal  groove,  looks  downward,  and  the  large  concavo-convex! 
articular  surface  backward  toward  the  holder:  the  narrow  non-articular  surface,! 
marked  by  the  commencement  of  the  peroneal  groove,  will  point  to  the  side  toj 
which  the  bone  belongs. 

Articulations. — With  four  bones:  the  os  calcis,  external  cuneiform,  and  the 
fourth  and  fifth  metatarsal  bones;  occasionally  with  the  scaphoid. 

Attachment  of  Muscles. — Part  of  the  Flexor  brevis  hallucis  and  a  slip  from] 
the  tendon  of  the  Tibialis  posticus. 

Scaphoid  or  Navicular  Bone  {os  naviculare  pedis)  (Fig.  179). — The  scaphoid) 
is  situated  at  the  inner  side  of  the  tarsus,  between  the  astragalus  behind  and] 


J^ur  mid.  cuneiform. 


For  int. 
cuneiform, 


For  ext. 
cuneiform. 


For  cuboid 
(occasional).  For  astragalus. 

Fig.  179. — The  left  scaphoid.     A.  Antero-external  view.     B.  Postero-internal  view. 


the  three  cuneiform  bones  in  front.     It  may  be  distinguished  by  its  form,  bein^ 
concave  behind,  convex  and  subdivided  into  three  facets  in  front. 

Surfaces. — The  anterior  surface,  of  an  oblong  form,  is  convex  from  side  to  side,| 
and  subflivided  by  two  ridges  into  three  facets,  for  articulation  with  the  three 
cuneiform  bones.     The  posterior  surface  is  oval,  concave,  broader  externally! 
than  internally,  and  articulates  with  the  rounded  head  of  the  astragalus.     Tbej 
superior  surface  is  convex  from  side  to  side,  and  rough  for  the  attachment  oi 
ligaments.     The  inferior  is  irregular,  and  also  rough  for  the  attachment  of  liga- 
ments.     The    internal   surface   presents    a   rounded    tubercular   eminence,    thej 
tuberosity  (tuberositas  ossis  navicularis) ,  the  lower  part  of  which  projects,  andl 
gives  attachment  to  part  of  the  tendon  of  the  Tibialis  posticus.     The  external] 
surface  is  rough  and  irregular,  for  the  attachment  of  ligamentous  fibres,  andf 
occasionally  presents  a  small  facet  for  articulation  with  the  cuboid  bone. 


THE    TARSUS  247 

To  ascertain  to  which  foot  the  bone  belongs,  hold  it  with  the  concave  articular 
surface  backward,  and  the  convex  dorsal  surface  upward;  the  external  surface — 
i.  e.,  the  surface  opposite  the  tubercle — will  point  to  the  side  to  which  the  bone 
belongs. 

Articulations. — With  four  bones:  astragalus  and  three  cuneiform;  occasionally 
also  with  the  cuboid. 

Attachment  of  Muscles. — Part  of  the  Tibialis  posticus. 

Cuneiform  or  Wedge  Bones. — The  cuneiform  bones  have  received  their 
name  from  their  wedge-like  shape  {cuneus,  a  wedge;  forma,  likeness).  They 
form,  with  the  cuboi(l,  the  anterior  row  of  the  tarsus,  being  placed  between 
the  scaphoid  behind,  the  three  innermost  metatarsal  bones  in  front,  and  the 
cuboid  externally.  They  are  called  the  first,  second,  and  third,  counting  from 
the  inner  to  the  outer  side  of  the  foot,  and,  from  their  position,  internal,  middle, 
and  external. 

Internal  or  First  Cuneiform  (os  cuneiforme  primum)  (Fig.  180). — The  inter- 
nal cuneiform  is  the  largest  of  the  three.  It  is  situated  at  the  inner  side  of 
the  foot,  between  the  scaphoid  behind  and  the  base  of  the  first  metatarsal  in 
front.    It  may  be  distinguished  from  ^^^.^^^^         ^^^^^^^^^^     For  middle 

the    other    two    by   its   large   size,   and  metatarsal.  metatarsal.       cuneiform. 

by  its  not  presenting  such  a  distinct 
wedse-like  form.  Without  the  others 
■  it  may  be  known  by  the  large,  kidney- 
shaped  anterior  articulating  surface 
and  by  the  prominence  on  the  in- 
'erior  or  plantar  surface  for  the  at- 
tachment of  the  Tibialis  posticus.  It 
presents  for  examination  six  surfaces. 
Surfaces. — The   internal  surface   is 

subcutaneous,   and   forms  part   of  the   ■f"'"  tendon  of  Tibialis  ant.  For  navicular. 

;^.,^v.   Vx^,.J,,«  ^t    *^V..r.  f^r^+.    ;+    Ic.    U^^o^l  Fig.    180. — The  left    internal  cuneiform.     A.    Antero- 

inner   border  Ot    the  toot;    it   is    broad,  internal  view.     B.  Postero-extemal  view. 

cjuadrilateral,  and  presents  at  its  an- 
terior inferior  angle  a  smooth  oval  facet,  into  which  the  tendon  of  the  Tibialis 
anticus  is  partially  inserted;  in  the  rest  of  its  extent  it  is  rough,  for  the  attachment 
of  ligaments.  The  external  surface  is  concave,  presenting,  along  its  superior  and 
posterior  borders,  a  narrow,  reversed,  L-shaped  surface,  for  articulation  with  the 
middle  cuneiform  behind  and  second  metatarsal  bone  in  front;  in  the  rest  of  its 
extent  it  is  rough,  for  the  attachment  of  ligaments  and  part  of  the  tendon  of  the 
eroneus  longus.  The  anterior  surface,  kidney-shaped,  much  larger  than  the  poste- 
or,  articulates  with  the  metatarsal  bone  of  the  great  toe.  The  posterior  surface 
is  triangular,  concave,  and  articulates  with  the  innermost  and  largest  of  the  three 
facets  on  the  anterior  surface  of  the  scaphoid.  The  inferior  or  plantar  surface 
is  rough,  and  presents  a  prominent  tuberosity  at  its  back  part  for  the  attachment 
of  part  of  the  tendon  of  the  Tibialis  posticus.  It  also  gives  attaphment  in  front 
to  part  of  the  tendon  of  the  Tibialis  anticus.  The  superior  surface  is  the  narrow- 
pointed  end  of  the  wedge,  which  is  directed  upward  and  outward;  it  is  rough 
for  the  attachment  of  ligaments. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  so  that  its  superior  narrow 
edge  looks  upward,  and  the  long,  kidney-shaped,  articular  surface  forward;  the 
external  surface,  marked  by  its  vertical  and  horizontal  articular  facets,  will 
point  to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones:  scaphoid,  middle  cuneiform,  first  and  second 
metatarsal  bones. 

Attachment  of  Muscles. — To  three :  the  Tibialis  anticus  and  posticus,  and 
Peroneus  longus. 


m 


248 


THE  SKELETON 


Middle  or  Second  Cuneiform  {os  cuneiforme  secundum)  (Fig.  181). — The 
middle  cuneiform,  the  smallest  of  the  three,  is  of  very  regular  wedge-like  form, 
the  broad  extremity  being  placed  upward,  the  narrow  end  downward.  It  is 
situated  between  the  other  two  bones  of  the  same  name,  and  articulates  with  the 
scaphoid  behind  and  the  second  metatarsal  in  front.  It  is  smaller  than  the  external 
cuneiform  bone,  from  which  it  may  be  further  distinguished  by  the  L-shaped 
articular  facet,  which  runs  round  the  upper  and  back  part  of  its  inner  surface. 

Surfaces. — The  anterior  surface,  triangular  in  form  and  narrower  than  the  poste- 
rior, articulates  with  the  base  of  the  second  metatarsal  bone.     The  posterior  sur- 
face, also  triangular,  articulates  with  the  scaphoid.     The  internal  surface  presents] 
a  reversed  L-shaped  articular  facet,  running  along  the  superior  and  posteriori 
borders,  for  articulation  with  the  internal  cuneiform,  and  is  rough  in  the  rest] 
of  its  extent,  for  the  attachment  of  ligaments.     The  external  surface  presents 
posteriorly  a  smooth  facet  for  articulation  with  the  external  cuneiform  bone. 
The  superior  surface  forms  the  base  of  the  wedge;  it  is  quadrilateral,  broader: 
behind  than  in  front,  and  rough  for  the  attachment  of  ligaments.    The  inferior' 
surface,  pointed  and  tubercular,  is  also  rough  for  ligamentous  attachment  and 
for  the  insertion  of  a  slip  from  the  tendon  of  the  Tibialis  posticus. 


For  int.  cuneiform. 


For  navicular. 


For  navicular. 

For  mid.  cuneiform. 


For  ext.  cuneiform. 


Fig.  181. — The  left  middle  cuneiform.  A.  Antero- 
internal  view.     B.  Posteroexternal  view. 


For  fourth     For  cuboid, 
metatarsal.  I 


Fig.  182. 


For  For  third 

second  metatarsal,  metatarsal. 

-The  left  external  cuneiform.   A.  Postero-internal 
view.     B.  Antero-external  view. 


To  ascertain  to  which  foot  the  bone  belongs,  hold  its  superior  or  dorsal  surface ' 
upward,  the  broadest  edge  being  toward  the  holder:  the  smooth  facet  (limited 
to  the  posterior  border)  will  then  point  to  the  side  to  which  it  belongs. 

Articulations. — With  four  bones:   scaphoid,  internal  and  external  cuneiform, 
and  second  matatarsal  bone. 

Attachment  of  Muscles. — A  slip  from  the  tendon  of  the  Tibialis  posticu-s  is  I 
attached  to  this  bone. 

External  or  Third  Cuneiform  (os  cuneiforme  tertium)  (Fig.  182). — The  exter- 
nal cuneiform,  intermediate  in  size  between  the  two  preceding,  is  of   a  very! 
regular  wedge-like  form,  the  broad  extremity  being  placed  upward,  the  narrow  < 
end  downward.     It  occupies  the  centre  of  the  front  row  of  the  tarsus,  between 
the  middle  cuneiform  internally,  the  cuboid  externally,  the  scaphoid  behind,  and 
the  third  metatarsal  in  front.     It  is  distinguished  from  the  internal  cuneiform  i 
bone  by  its  more  regular  wedge-like  shape  and  by  the  absence  of  the  kidney- j 
shaped  articular  surface:  from   the  middle  cuneiform,  by  the  absence  of  thei 
reversed  L-shaped  facet,  and  by  the  two  articular  facets  which  are  present  onj 
both  its  inner  and  outer  surfaces.     It  has  six  surfaces  for  examination. 

Surfaces. — The  anterior  surface,  triangular  in  form,  articulates  with  the  thirdj 
metatarsal  bone.  The  posterior  surface  articulates  with  the  most  external  facet 
of  the  scaphoid,  and  is  rough  below  for  the  attachment  of  ligamentous  fibres.. 
The  internal  surface  presents  two  articular  facets,  separated  by  a  rough  depres-l 
sion;  the  anterior  one,  sometimes  divided  into  two,  articulates  with  the  outer  side  J 
of  the  base  of  the  second  metatarsal  bone;  the  posterior  one  skirts  the  posteriori 
border  and  articulates  with  the  middle  cuneiform;  the  rough  depression  between! 


THE  3IETATABSAL    BONES  249 

the  two  gives  attachment  to  an  interosseous  Hgament.  The  external  surface  also 
presents  two  articular  facets,  separated  by  a  rough  non-articular  surface;  the 
anterior  facet,  situated  at  the  superior  angle  of  the  bone,  is  small,  and  articulates 
with  the  inner  side  of  the  base  of  the  fourth  metatarsal;  the  posterior  and  larger 
one  articulates  with  the  cuboid;  the  rough,  non-articular  surface  serves  for  the 
attachment  of  an  interosseous  ligament.  The  three  facets  for  articulation  with 
the  three  metatarsal  bones  are  continuous  with  one  another,  and  covered  by  a 
prolongation  of  the  same  cartilage;  the  facets  for  articulation  with  the  middle 
cuneiform  and  scaphoid  are  also  continuous,  but  that  for  articulation  with  he 
cuboid  is  usually  separate.  The  superior  or  dorsal  surface  is  of  an  oblong  square 
form,  its  posterior  external  angle  being  prolonged  backward.  The  inferior  or 
plantar  surface  is  an  obtuse  rounded  margin,  and  serves  for  the  attachment  of 
part  of  the  tendon  of  the  Tibialis  posticus,  part  of  the  Flexor  brevis  hallucis, 
and  ligaments. 

To  ascertain  to  which  side  the  bone  belongs,  hold  it  with  the  broad  dorsal 
surface  upward,  the  prolonged  edge  backward;  the  separate  articular  facet  for 
the  cuboid  will  point  to  the  proper  side. 

Articulations. — With  six  bones:  the  scaphoid,  middle  cuneiform,  cuboid,  and 
second,  third,  and  fourth  metatarsal  bones. 

Attachment  of  Muscles. — To  two:  part  of  the  Tibialis  posticus,  and  Flexor 
brevis  hallucis. 

The  number  of  tarsal  bones  may  be  reduced  owing  to  congenital  ankylosis 
which  may  occur  between  the  os  calcis  and  cuboid,  the  os  calcis  and  scaphoid, 

e  OS  calcis  and  astragalus,  or  the  astragalus  and  scaphoid. 


tf 


The  Metatarsal  Bones  (Ossa  Metatarsalia). 


The  metatarsal  bones  are  five  in  number,  and  are  numbered  one  to  five,  in 
accordance  with  their  position  from  within  outward;  they  are  long  bones,  and 
])resent  for  examination  a  shaft  and  two  extremities. 

Common  Characters. — The  shaft  (corpus)  is  prismoid  in  form,  tapers  gradually 
from  the  tarsal  to  the  phalangeal  extremity,  and  is  slightly  curved  longitudinally, 
so  as  to  be  concave  below,  slightly  convex  above.  On  the  plantar  surface  of  the 
shaft  of  each  bone  is  a  nutrient  foramen  corresponding  to  the  nutrient  foramen 
in  each  metacarpal  bone.  The  posterior  or  proximal  extremity,  or  base  (basis), 
is  wedge-shaped,  articulating  by  its  terminal  surface  with  the  tarsal  bones,  and 
by  its  lateral  surfaces  with  the  contiguous  metatarsal  bones,  its  dorsal  and  plantar 
surfaces  being  rough  for  the  attachment  of  ligaments.  The  anterior  or  distal 
extremity,  or  head  (capitulum) ,  presents  a  terminal  rounded  articular  surface, 
oblong  from  above  downward,  and  extending  farther  backward  below  than 
above.  Its  sides  are  flattened  and  present  a  depression,  surmounted  by  a 
tubercle,  for  ligamentous  attachment.  Its  under  surface  is  grooved  in  the 
middle  line  for  the  passage  of  the  Flexor  tendon,  and  marked  on  each  side  by 
an  articular  eminence  continuous  with  the  terminal  articular  surface. 

Peculiar  Characters.  First  Metatarsal  Bone  or  the  Metatarsal  Bone  of  the  Great 
Toe  {as  metatarsale  I). — The  first  (Fig.  183)  is  remarkable  for  its  great  thickness, 
but  is  the  shortest  of  all  the  metatarsal  bones.  The  shaft  is  strong  and  of  well- 
marked  prismoid  form.  The  posterior  extremity  presents,  as  a  rule,  no  lateral 
articular  facet,  but  occasionally  on  the  outer  side  there  is  an  oval  facet  by  which 
it  articulates  with  the  second  metatarsal  bones.  Its  terminal  articular  surface  is  of 
large  size  and  kidney-shaped;  its  circumference  is  grooved,  for  the  tarso-metatarsal 
ligaments,  and  internally  gives  attachment  to  part  of  the  tendon  of  the  Tibialis 
anticus  muscle;  its  inferior  angle  presents  a  rough  oval  prominence,  the  tuberosity 
(tuberositas  ossis  metatarsalis  I) ,  for  the  insertion  of  the  tendon  of  the  Peroneus 


250 


THE  SKELETON 


longus.  The  head  is  of  large  size;  on  its  plantar  surface  are  two  grooved  facets, 
over  which  glide  sesamoid  bones ;  the  facets  are  separated  by  a  smooth  elevated 
ridge. 

This  bone  is  known  by  the  single  kidney-shaped  articular  surface  on  its  base, 
the  deeply  grooved  appearance  of  the  plantar  surface  of  its  head,  and  its  great 

thickness  relatively  to  its  length.      . 
When  it  is  placed  in  its  natural^! 
position,  the  concave  border  of 
the  kidney-shaped  articular  sur- 
face on   its  base   points  to  the^f 
side  to  which  the  bone  belongs.  ^" 

Attachment    of    Muscles. — To 
three:  part  of  the  Tibialis  anti-- 
cus,  the   Peroneus   longus,  and] 
the  First  dorsal  interosseous. 

Second  Metatarsal  {os  metatarA 
sale  II)  .—The  second  (Fig.  184)] 
is  the  longest  and  largest  of  the 
remaining  metatarsal  bones,  be-J 
ing  prolonged  backward  into  the 
recess  formed  between  the  three! 
cuneiform  bones.     Its  tarsal  ex- 
tremity is   broad  above,  narrow! 
and    rough  belovv^.     It  presents! 
four  articular  surfaces:  one  be-j 
hind,  of  a  triangular  form,  for  articulation  with  the  middle  cuneiform ;  one  at  thej 
upper  part  of  its  internal  lateral  surface,  for  articulation  with  the  internal  cunei-j 


For  internal  cuneiform. 

J'iG.  183. — The  first  metatarsal 


Occasional  facet  fui 
second  metatarsal. 


(Left.) 


Occasional 
facet  for  first 
!  metatarsal. 

For  middle  cuneiform. 

Fig.  184. — The  second  metatarsal. 


For  external 
cuneiform. 

(Left.) 


/  For  second  melahirsal. 
For  middle  cuneiform. 


For  foiirfh 
metatarsal. 


Fig.  185. — The  third  metatarsal.     (Left.) 


form ;  and  two  on  its  external  lateral  surface — an  upper  and  a  lower,  separated  by 
a  rough  non-articular  interval.  Each  of  these  articular  surfaces  is  divided  by  a] 
vertical  ridge  into  two  facets,  thus  making  four  facets;  the  two  anterior  of  thesel 


THE   METATARSAL    BONES 


251 


articulate  with  the  third  metatarsal ;  the  two  posterior  (sometimes  continuous)  with 
the  external  cuneiform.  In  addition  to  these  articular  surfaces  there  is  occasion- 
ally a  fifth  when  this  bone  articulates  with  the  first  metatarsal  bone.  It  is  oval  in 
shape,  and  is  situated  on  the  inner  side  of  the  shaft  near  the  base. 

The  facets  on  the  tarsal  extremity  of  the  second  metatarsal  bone  serve  at  once 
to  distinguish  it  from  the  rest,  and  to  indicate  the  foot  to  which  it  belongs;  there 
being  one  facet  at  the  upper  angle  of  the  internal  surface,  and  two  facets,  each 
subdivided  into  two  parts,  on  the  external  surface,  pointing  to  the  side  to  which 
the  bone  belongs.  The  fact  that  the  two  posterior  subdivisions  of  these  external 
facets  sometimes  run  into  one  should  not  be  forgotten. 

Attachment  of  Muscles. — To  ]our :  the  Adductor  obliquus  halhicis,  First  and 
Second  dorsal  interosseous,  and  a  slip  from  the  tendon  of  the  Tibialis  posticus; 
occasionally  also  a  slip  from  the  Peroneus  longus. 

Third  Metatarsal  {os  metaiarsale  HI) . — The  third  metatarsal  (Fig.  185)  articu- 
lates behind,  by  means  of  a  triangular  smooth  surface,  with  the  external  cunei- 
form; on  its  inner  side,  by  two  facets,  with  the  second  metatarsal;  and  on  its 
outer  side,  by  a  single  facet,  with  the  fourth  metatarsal.  The  latter  facet  is  of 
circular  form  and  situated  at  the  upper  angle  of  the  base. 

The  third  metatarsal  is  known  by  its  having  at  its  tarsal  end  two  undivided 
facets  on  the  inner  side,  and  a  single  facet  on  the  outer.  This  distinguishes  it 
from  the  second  metatarsal,  in  which  the  two  facets,  found  on  one  side  of  its 
tarsal  end,  are  each  subdivided  into  two.  The  single  facet  (when  the  bone  is  put 
in  its  natural  position)  is  on  the  side  to  which  the  bone  belongs. 

Attachment  of  Muscles. — To  five :  Adductor  obliquus  hallucis.  Second  and 
Third  dorsal,  and  First  plantar  interosseous,  and  a  slip  from  the  tendon  of  the 
Ti])ialis  posticus. 

Fourth  Metatarsal  {os  metaiarsale  IV). — The  fourth  metatarsal  (Fig.  186)  is 
smaller  in  size  than  the  preceding;  its  tarsal  extremity  presents  a  terminal  quad- 


For  cuboid. 
For  ext.  cuneiform. 


For  fifth 
metatarsal. 


Fig.  186.— The  fourth  metatarsal.     (Left.) 


For  fourth     \ 

metatarsal.     \  ^  »"<='"--»• 

Fnr  ciiboid. 
Fig.  187.— The  fifth  metatarsal.     (Left.) 


rilateral  surface,  for  articulation  with  the  cuboid;  a  smooth  facet  on  the  inner 
side,  divided  by  a  ridge  into  an  anterior  portion  for  articulation  with  the  third 


252  "THE  SKELETON 

metatarsal,  and  a  posterior  portion  for  artic'iilatioi>  with  the  external  cuneiform; 
on  the  outer  side  a  sinjijle  facet,  for  articulation  with  the  fifth  metatarsal. 

The  fourth  metatarsal  is  known  by  its  haviufj^  a  sino;le  facet  on  either  side  of 
the  tarsal  extremity,  that  on  the  inner  side  heinjjj  divided  into  two  })arts.  If  this 
subdivision  be  not  recognizable,  the  fact  that  its  tarsal  end  is  bent  somewhatf^ 
outward  will  indicate  the  side  to  which  it  belonj^s. 

Attachment  of  Muscles. — To  five:  Adductor  obliquus  hallucis,  Third  anc 
Fourth  dorsal,  and  Second  plantar  interosseous,  and  a  slip  from  the  tendon  of  the 
Tibialis  posticus. 

Fifth  Metatarsal  Bone,  or  the  Metatarsal  Bone  of  the  Little  Toe  {os  met  afar  sale  V)\ 
— The  fifth  metatarsal  (Fii;;.  1S7)  is  rec()ti;ni/ed  by  the  tubercl'*  (fnheroslfas  ossis' 
mefatarsalis   V)   on  the  outer  side  of  its  base.     It  articulates  behind,  by  a  tri- 
an<2^ular  surface  cut  oblicpiely  from  without  inward,  with  the  cuboid,  and  int.T-" 
nally  with  the  fourth  metatarsal. 

The  projection  on  the  outer  side  of  this  bone  at  its  tarsal  end  at  once  distinJ 
guishes  it  from  the  others,  and  points  to  the  side  to  which  it  belongs. 

Attachment  of  Muscles. — To  six :  the  Peroneus  brevis,  Peroneus  tertius 
Flexor  brevis  minimi  digiti,  Adductor  transversus  hallucis,  Fourth  dorsal,  am 
Third  plantar  interossei. 

Articulations. — Each  bone  articulates  with  the  tarsal  bones  by  one  extremity 
and  by  the  other  with  the  first  row  of  phalanges.    The  number  of  tarsal  boneij 
with  which  each  metatarsal  articulates  is  t)ne  for  the  first,  three  for  the  secon(" 
one  for  the  third,  two  for  the  fourth,  and  one  for  the  fifth. 

The  Phalanges  of  the  Foot  (Phalanges  Digitoram  Pedis). 

The  phalanges  of  the  foot,  both  in  number  and  general  arrangement,  resembU 
those  in  the  hand;  there  being  two  in  the  great  toe  and  three  in  each  of  th^ 
other  toes.  The  nutritive  foramina  correspond  to  those  in  the  phalanges  of  th^ 
hand. 

The  first  or  proximal  phalanx  (phalanx  prima)  resembles  closely  the  correspond^ 
ing  bone  of  the  hand.     The  shaft  also  is  compressed  from  side  to  side,  convex 
above,  concave  below.     The   posterior  extremity  is  concave;   and  the  anteric 
extremitif  presents  a  trochlear  surface,  for  articulation  with  the  second  phalanx. 

The  second  phalanx  (phalanx  secunda)  is  remarkably  small  and  short,  \n\\ 
rather  broader  than  the  first  ])halanx. 

The  ungual  or  distal  phalanx  (phalanx  tcriia)  in  form  resembles  the  bone  of  th* 
corresponding  finger,  l)ut  is  smaller,  flattened  from  above  downward,  presenting 
broad  base  for  articulation  with  tlie  second  phalanx,  and  an  expanded  extremity 
for  the  sup))ort  of  the  nail  and  end  of  the  toe. 

Articulation.^The  first  row,  with  the  metatarsal  bones  behind  and  secon( 
phalanges  in  front;  the  second  row  of  the  four  outer  toes,  with  the  first  and  thirc 
phalanges;  of  the  great  toe,  with  the  first  phalanx;  the  third  row  of  the  four  outei 
toes,  with  the  second  phalanges. 

Attachment  of  Muscles. — To  the  first  phalanges.  Great  toe,  five  muscles^ 
innermost  tendon  of  Extensor  brevis  digitorum,  Abductor  hallucis.  Adductor 
obliquus  hallucis,  Flexor  brevis  hallucis.  Adductor  transversus  hallucis.  Second 
toe,  three  muscles:  First  and  Second  dorsal  interosseous  and  First  lumbrical. 
Third  toe,  three  muscles:  Third  dorsal  and  First  plantar  interosseous  and  Second 
lumbrical.  Fourth  toe,  three  muscles:  Fourth  dorsal  and  Second  plantar  inter- 
osseous and  Third  lumbrical.  Fifth  toe,  four  muscles:  Flexor  brevis  minimi 
digiti.  Abductor  minimi  digiti,  and  Third  plantar  interosseous,  and  Fourth! 
lumbrical. — Second  phalanges.  (Ireat  toe;  Extensor  longus  hallucis.  Flexor! 
longus  hallucis.     Other  toes;  Flexor  brevis  digitorum,  one  slip  of  the  commor 


DEVELOrMKI^T   OF    TUi:    FOOT 


253 


Icndoii  of  (lie  FiXtcnsor  loii^us  uiid  hirvis  di^iloniin.'- — Tliinl  pliulaii^c.s:  (wo  sli|),s 
from  the  coiiimoii  tendon  of  the  KxliMi.sor  loii^u.s  and  Extensor  hrevis  digitoruni, 
and  the  Flexor  lon<fiis  dif^itornni. 


Development  of  the  Foot  {V\\^.  I.S8). 

The  Tarsal  Bones  are  each  developed  hy  a  Hincflc  centre,  excepting  the  os  calcis 

I     which  hiis  an  ej)iphy.sis  for  its  posterior  extn-niity.    The  centres  nMd\e  their  appear- 
',     ance  in  Ih*-  following  order:  os  caU'is,  at  the  sixth  month  of  fo'tai  life;  astragalus, 

y  H  i  8. 

"^  ^a^HMEEk, Appenm  VHh  year ; 

.  *^i'//'/  •'"**'"  \        uniivs  after  puberty. 

Tarmis.  Walei.//. 

One  centre  for  eneh  bone,       nJ^^''""§\ 

exccnt  OS  cald».  \  yWrinKiL 


MdatnrHioi. 

Tu'o  mil rm  for  rach  bone 
Out'  for  HhafI, 
One  for  difiilnl  extremity 
except  lat. 


Appear$  7th  week. 

Unite  18th-20th  year. 
Appi'drn  lird  year, 

Appearn  ^Ih  year..—,^^ 

Unite  17-lHth  year. 

Phalanges.    Appears  2nd-/tlh  monlh.- 

Tuio  centres  for  each  bone : 

One  for  shnfl, 

Oneformelalarsal       Appears  mh -7th  year. ^        ^ 

extremity.  f/„//,,  77//,   igih  year.  .[ '  *^  £ 

'  V'kl 

Appears  '£n<l-4lh  month.  t»-''»i 

Appears  (llh  year.^^  si 

Unite  17th- IKIh  year.-r^.  - 

Appears  7th  week.^ij)'^^ 


f^-J^        Appears  /5th  year, 
WHS^  I  Unite  mh~20  year. 

\~  Appears  7th  week. 


Fio,  188. — Plan  of  the  (iovelopment  of  the  foot, 

al)out  the  seventh  month;  enhoid,  at  the  ninth  month;  external  cuneiform,  dur- 
ing the  first  y^'iir;  internal  cuneiform  in  the  third  year;  middle  cuneiform  and 
sca[)hoid  in  the  fourth  year.  The  ej)ij)hysis  for  the  posterior  tnlx'rosity  of  the 
OS  calcis  ap|)ears  at  the  tenth  year,  and  unites  with  the  rest  of  the  hone  soon 
after  |)ul)erty. 

The  Metatarsal  Bones  are  each  developed  hy  two  centres:  one  for  the  shaft 
and  one  for  tlx'  digital  extremity  in  the  ff)ur  outer  metatarsal;  one  for  the  shaft 
and  one  for  the  base  in  the  metatarsal  hone  of  the  great  toe,''     Ossification  com- 

'  Except  the  ttecond  phalanx  of  the  fifth  toe,  which  receive*  no  »iHp  from  the  Kxtennor  brevln  diBltoriirn. 
»  Ah  waH  nijtcil  in  the  firHt  inctaciiroiil  bono,  no  in  th<i  firMt  niPtatiirHal,  there  i«  often  to  be  oljwrved  a  ten<lency 
to  the  formation  of  n  xecond  epiphynlH  in  tiic  (iiMliil  extremity. 


254 


THE   SKELETON 


mences  in  the  centre  of  the  shaft  about  the  ninth  week,  and  extends  toward 
either  extremity.  The  centre  in  the  proximal  end  of  the  first  metatarsal  bone 
appears  about  the  third  year,  the  centre  in  the  distal  end  of  the  other  bones 
between  the  fifth  and  eighth  years;  they  become  joined  between  the  eighteenth 
and  twentieth  years. 

The  Phalanges  are  developed  by  two  centres  for  each  bone:  one  for  the  shaft 
and  one  for  the  metatarsal  extremity.  The  centre  for  the  shaft  appears  about  the 
tenth  week,  that  for  the  epiphysis  between  the  fourth  and  tenth  years;  they  join 
the  shaft  about  the  eighteenth  year. 

Construction  of  the  Foot  as  a  Whole  (Figs.  189,  190). 

The  foot  is  constructed  on  the  same  principles  as  the  hand,  but  modified  to  form 
a  firm  basis  of  support  for  the  rest  of  the  body  when  in  the  erect  position.  It 
is  more  solidly  constructed,  and  its  component  parts  are  less  movable  on  each 
other  than  in  the  hand.    This  is  especially  the  case  with  the  great  toe,  which  has 


Fig.  189. — Skeleton  of  the  foot,  internal  border.     (Poirier  and  Charpy.) 

to  assist  in  supporting  the  body,  and  is  therefore  constructed  with  greater  solidity; 
it  lies  parallel  with  the  other  toes,  and  has  a  very  limited  degree  of  mobility, 
whereas  the  thumb,  which  is  occupied  in  numerous  and  varied  movements,  is 
constructed  in  such  a  manner  as  to  permit  of  great  mobility.    Its  metacarpal  bone 


SECOND  CUNEIFORM 


SECOND  METATARSAL 


Fig.  190. — Skeleton  of  the  foot,  external  border.     (Poirier  and  Charpy.) 


is  directed  away  from  the  others,  so  as  to  form  an  acute  angle  with  the  second, 
and  it  enjoys  a  considerable  range  of  motion  at  its  articulation  with  the  carpus. 
The  foot  is  placed  at  right  angles  to  the  leg — a  position  which  is  almost  peculiar 
to  man,  and  has  relation  to  the  erect  position  which  he  maintains.  In  order  to 
allow  of  its  supporting  the  weight  of  the  whole  body  in  this  position  with  the 
least  expenditure  of  material,  it  is  constructed  in  the  form  of  an  arch.  This 
antero-posterior  or  longitudinal  arch  is  made  up  of  two  unequal  limbs.     The 


CONSTRUCTION  OF   THE    FOOT  AS  A     WHOLE  255 

hinder  one,  which  is  made  up  of  the  os  calcis  and  the  posterior  part  of  the 
astragahis,  is  about  half  the  length  of  the  anterior  limb,  and  measures  about 
three  inches.  The  anterior  limb  consists  of  the  rest  of  the  tarsal  and  the  meta- 
tarsal bones,  and  measures  about  seven  inches.  It  may  be  said  to  consist  of  two 
parts,  an  inner  segment  made  up  of  the  head  of  the  astragalus,  the  scaphoid, 
the  three  cuneiform,  and  the  three  inner  metatarsal  bones;  and  an  outer  segment 
composed  of  the  os  calcis,  the  cuboid,  and  the  two  outer  metatarsal  bones.  The 
summit  of  the  arch  is  at  the  superior  articular  surface  of  the  astragalus;  and  its 
tw^o  extremities — that  is  to  say,  the  two  piers  on  which  the  arch  rests  in  standing 
— are  the  tubercles  on  the  under  surface  of  the  os  calcis  posteriorly,  and  the  heads 
of  the  metatarsal  bones  anteriorly.  The  weakest  part  of  the  arch  is  the  joint 
between  the  astragalus  and  scaphoid,  and  here  it  is  more  liable  to  yield  in  those 
who  are  overweighted,  and  in  those  in  whom  the  ligaments  which  complete  and 
preserve  the  arch  are  relaxed.  This  weak  point  in  the  arch  is  braced  on  its  con- 
cave surface  by  the  inferior  calcaneo-scaphoid  ligament,  which  is  more  elastic 
than  most  other  ligaments,  and  thus  allows  the  arch  to  yield  from  jars  or  shocks 
applied  to  the  anterior  portion  of  the  foot  and  quickly  restores  it  to  its  pristine 
condition.  This  ligament  is  supported  internally  by  blending  with  the  Deltoid 
ligament,  and  inferiorly  by  the  tendon  of  the  Tibialis  posticus  muscle,  which  is 
spread  out  into  a  fan-shaped  insertion,  and  prevents  undue  tension  of  the  ligament 
or  such  an  amount  of  stretching  as  would  permanently  elongate  it. 

In  addition  to  this  longitudinal  arch  the  foot  presents  a  transverse  axch,  at  the 
anterior  part  of  the  tarsus  and  hinder  part  of  the  metatarsus.  This,  however,  can 
scarcely  be  described  as  a  true  arch,  but  presents  more  the  character  of  a  half- 
dome.  The  inner  border  of  the  central  portion  of  the  longitudinal  arch  is  elevated 
from  the  ground,  and  from  this  point  the  bones  arch  over  to  the  outer  border, 
w^hich  is  in  contact  with  the  ground,  and,  assisted  by  the  longitudinal  arch,  pro- 
duce a  sort  of  rounded  niche  on  the  inner  side  of  the  foot,  which  gives  the  appear- 
ance of  a  transverse  as  well  as  a  longitudinal  arch. 

The  line  of  the  foot,  from  the  point  of  the  heel  to  the  toes,  is  not  quite  straight, 
but  is  directed  a  little  outward,  so  that  the  inner  border  is  a  little  convex  and  the 
outer  border  concave.  This  disposition  of  the  bones  becomes  more  marked  when 
the  longitudinal  arch  of  the  foot  is  lost,  as  in  the  disease  known  under  the  name 
of  "flat-foot." 

Surface  Form.—  On  the  dorsum  of  the  foot  the  individual  bones  are  not  to  be  distinguished 
with  the  exception  of  the  head  of  the  astragalus,  which  forms  a  rounded  projection  in  front  of 
the  ankle-joint  when  the  foot  is  forcibly  extended.  The  whole  surface  forms  a  smooth  convex 
outline,  the  summit  of  which  is  the  ridge  formed  by  the  head  of  the  astragalus,  the  scaphoid, 
the  middle  cuneiform,  and  the  second  metatarsal  bones;  from  this  it  gradually  inclines  outward 
and  more  rapidly  inward.  On  the  inner  side  of  the  foot,  the  internal  tuberosity  of  the  OS  Calcis 
and  the  ridge  separating  the  inner  from  the  posterior  surface  of  the  bone  may  be  felt  most  poste- 
riorly. In  front  of  this,  and  below  the  internal  malleolus,  may  be  felt  the  projection  of  the 
sustentaculum  tali.  Passing  forward  is  the  well-marked  tuberosity  of  the  scaphoid  bone,  situ- 
ated about  an  inch  or  an  inch  and  a  quarter  in  front  of  the  internal  malleolus.  Further  toward 
the  front,  the  ridge  formed  by  the  base  of  the  first  metatarsal  bone  can  be  obscurely  felt,  and 
from  this  the  shaft  of  the  bone  can  be  traced  to  the  expanded  head  articulating  with  the  base 
of  the  first  phalanx  of  the  great  toe.  Immediately  beneath  the  base  of  this  phalanx,  the  internal 
sesamoid  bone  is  to  be  felt.  Lastly,  the  expanded  ends  of  the  bones  forming  the  last  joint  of 
the  great  toe  are  to  be  felt.  On  the  outer  side  of  the  foot  the  most  posterior  bony  point  is  the 
outer  tuberosity  of  the  os  calcis,  with  the  ridge  separating  the  posterior  from  the  outer  surface 
of  the  bone.  In  front  of  this  the  greater  part  of  the  external  surface  of  the  os  calcis  is  subcu- 
taneous; on  it,  below  and  in  front  of  the  extern^,!  malleolus,  may  be  felt  the  peroneal  ridge,  when 
this  process  is  present.  Farther  forward,  the  base  of  the  fifth  metatarsal  bone  forms  a  prom- 
inent and  well-defined  landmark,  and  in  front  of  this  the  shaft  of  the  bone,  with  its  expanded 
head,  and  the  base  of  the  first  phalanx  may  be  defined.  The  sole  of  the  foot  is  almost  entirely 
covered  by  soft  parts,  so  that  but  few  bony  parts  are  to  be  made  out,  and  these  somewhat 
obscurely.     The  hinder  part  of  the  under  surface  of  the  os  calcis  and  the  heads  of  the  metatarsal 


256  THE  SKELETON 

bones,  with  the  exception  of  the  first,  which  is  concealed  by  the  sesamoid  bones,  may  be  recog- 
nized. 

Surgical  Anatomy. — Considering  the  injuries  to  which  the  foot  is  subjected,  it  is  surpris- 
ing how  seldom  the  tarsal  bones  are  fractured.  This  is  no  doubt  due  to  the  fact  that  the  tarsus 
is  composed  of  a  number  of  bones,  articulated  by  a  considerable  extent  of  surface  and  joined 
together  by  very  strong  ligaments,  which  serve  to  mitigate  the  intensity  of  violence  applied  to  this 
part  of  the  body.  When  fracture  does  occur,  these  bones,  being  composed  for  the  most  part 
of  a  soft  cancellous  structure,  covered  only  by  a  thin  shell  of  compact  tissue,  are  often  extensively 
comminuted,  especially  as  most  of  the  fractures  are  produced  by  direct  violence.  As  the  bones 
have  only  a  very  scanty  amount  of  soft  parts  over  them,  fractures  are  very  often  compound,  and 
amputation  is  frequently  necessary. 

When  fracture  occurs  in  the  anterior  group  of  tarsal  bones,  it  is  almost  invariably  the  result 
of  direct  violence;  but  fractures  of  the  posterior  group,  that  is,  of  the  calcaneum  and  astrag- 
alus, are  most  frequently  produced  by  falls  from  a  height  on  to  the  feet;  though  fracture  of  the 
OS  calcis  may  be  caused  by  direct  violence  or  by  muscular  action.  The  posterior  part  of  the 
bone,  that  is,  the  part  behind  the  articular  surfaces,  is  almost  always  the  seat  of  the  fracture, 
though  some  few  cases  of  fracture  of  the  sustentaculum  tali  and  of  vertical  fracture  between 
the  two  articulating  facets  have  been  recorded.  The  neck  of  the  astragalus,  being  the  weakest 
part  of  the  bone,  is  most  frequently  fractured,  though  fractures  may  occur  in  any  part  and 
almost  in  any  direction,  either  associated  or  not  with  fracture  of  other  bones. 

In  cases  of  club-foot,  especially  in  congenital  cases,  the  bones  of  the  tarsus  become  altered 
in  shape  and  size,  and  displaced  from  their  proper  positions.  This  is  especially  the  case  in  con- 
genital equino-varus,  in  which  the  astragalus,  particularly  about  the  head,  becomes  twisted  and 
atrophied,  and  a  similar  condition  may  be  present  in  the  other  bones,  more  especially  the  sca- 
phoid. The  tarsal  bones  are  peculiarly  liable  to  become  the  seat  of  tuberculous  caries,  and  this 
condition  may  arise  after  comparatively  trivial  injuries.  There  are  several  reasons  to  account 
for  this.  They  are  composed  of  a  delicate  cancellated  structure,  surrounded  by  intricate  synovial 
membranes.  They  are  situated  at  the  farthest  point  from  the  central  organ' of  the  circulation 
and  exposed  to  vicissitudes  of  temperature;  and,  moreover,  on  their  dorsal  surface  are  thinly 
clad  with  soft  parts  which  have  but  a  scanty  blood-supply.  And  finally,  after  slight  injuries, 
they  are  not  maintained  in  a  condition  of  rest  to  the  same  extent  as  structures  suffering  from 
similar  injuries  in  some  other  parts  of  the  body.  Caries  of  the  calcaneus  or  astragalus 
may  remain  limited  to  the  one  bone  for  a  long  period,  but  when  one  of  the  other  bones  is 
affected,  the  remainder  frequently  become  involved,  in  consequence  of  the  disease  spreading 
through  the  large  and  complicated  synovial  membrane  which  is  more  or  less  common  to  these 
bones. 

Amputation  of  the  whole  or  a  part  of  the  foot  is  frequently  required  either  for  injury  or 
disease.  The  principal  amputations  are  as  follows:  (1)  Syme's :  amputation  at  the  ankle-joint 
by  a  heel-flap,  with  removal  of  the  malleoli  and  a  thin  slice  from  the  lower  end  of  the  tibia. 
(2)  Roux's :  amputation  at  the  ankle-joint  by  a  large  internal  flap.  (3)  Pirogoff's  amputa- 
tion .•  removal  of  the  whole  of  the  tarsal  bones,  except  the  posterior  part  of  the  os  calcis..  A  thin 
slice  is  sawn  from  the  tibia  and  fibula,  including  the  two  malleoli.  The  sawn  surface  of  the  os 
calcis  is  then  turned  up  and  united  to  the  similar  surface  of  the  tibia.  (4)  Subastragaloid 
amputation :  removal  of  the  foot  below  the  astragalus  through  the  joint  between  it  and  the  os 
calcis.  This  operation  has  been  modified  by  Hancock,  who  leaves  the  posterior  third  of  the  os 
calcis  and  turns  it  up  against  the  denuded  surface  of  the  astragalus.  This  latter  operation  is  of 
doubtful  utility  and  is  rarely  performed.  (.5)  ChopaH's  or  medio-tarsal :  removal  of  the  ante- 
rior part  of  the  foot  with  all  the  tarsal  bones  except  the  os  calcis  and  astragalus;  disarticula- 
tion being  effected  through  the  astragalo-scaphoid  and  calcaneo-cuboid  joints.  (6)  Lisfrancs : 
amputation  of  the  anterior  part  of  the  foot  through  the  tarso-metatarsal  joints.  This  was 
modified  by  Hey,  who  disarticulated  through  the  joints  of  the  four  outer  metatarsal  bones  with 
the  tarsus,  and  sawed  off  the  projecting  internal  cuneiform;  and  by  Skey,  who  sawed  off  the  base 
of  the  second  metatarsal  bone  and  disarticulated  the  others. 

The  bones  of  the  tarsus  occasionally  require  removal  individually.  This  is  especially  the 
case  with  the  astragalus  and  os  calcis  for  disease  limited  to  the  one  bone,  or  again  the  astragalus 
may  require  excision  in  cases  of  subastragaloid  dislocation,  or,  as  recommended  by  M.r  Lund, 
m  cases  of  inveterate  talipes.  The  cuboid  has  been  removed  for  the  same  reason  by  Mr.  Solly, 
cut  the  latter  two  operations  have  fallen  into  disuse,  and  have  been  superseded  bv  resection 
ot  a  wedge-shaped  piece  of  bone  from  the  outer  side  of  the  tarsus.  Finally,  Mickulicz  and 
Watson  have  devised  operations  for  the  removal  of  more  extensive  portions  of  the  tarsus. 
Mickuhcz  s  operation  consists  in  the  removal  of  the  os  calcis  and  astragalus,  along  with  the 
articular  surfaces  of  the  tibia  and  fibula,  and  also  of  the  scaphoid  and  cuboid.  The  remain- 
ing portion  of  the  tarsus  is  then  brought  into  contact  with  the  sawn  surfaces  of  the  tibia  and 
fabula,  and  fixed  there.  The  result  is  a  position  of  the  shortened  foot  resembling  talipes 
equinus.  Watsons  operation  is  adapted  to  those  cases  where  the  disease  is  confined  to  the 
anterior  tarsal  bones.     By  two  lateral  incisions  he  saws  through  the  bases  of  the  metatarsal 


SESAMOID    BONES 


257 


bones  in  front  and  opens  up  the  joints  between  the  scaphoid  and  astragalus,  and  the  cuboid  and 
OS  calcis,  and  removes  the  intervening  bones. 

Fractures  of  the  metatarsal  bones  and  phalanges  are  nearly  always  due  to  direct  violence,  and 
in  many  cases  the  injury  is  the  result  of  severe  crushing  accidents,  necessitating  amputation. 
The  metatarsal  bones,  and  especially  the  metatarsal  bone  of  the  great  toe,  are  frequently  dis- 
eased, either  in  tuberculous  subjects  or  in  perforating  ulcer  of  the  foot. 


Sesamoid  Bones  (Ossa  Sesamoidea)  (Figs.  191,  192). 

These  are  small  rounded  masses,  cartilaginous  in  early  life,  osseous  in  the  adult, 
which  are  developed  in  those  tendons  which  exert  a  great  amount  of  pressure  upon 
the  parts  over  which  they  glide.  It  is  said  that  they  are  more  commonly  found  in 
the  male  than  in  the  female,  and  in  persons  of  an  active  muscular  habit  than  in 
those  who  are  weak  and  debilitated.  They  are  invested  throughout  their  whole 
surface  by  the  fibrous  tissue  of  the  tendon  in  which  they  are  found,  excepting  upon 
that  side  which  lies  in  contact  with  the  part  over  which  they  play,  where  they 
present  a  free  articular  facet.  They  may  be  divided  into  two  kinds:  those  which 
glide  over  the  articular  surfaces  of  the  joints,  and  those  which  play  over  the  cartilag- 
inous facets  found  on  the  surfaces  of  certain  bones. 


Fig.  191. — Sesamoid  bones  of  the  hand.     (Poirier 
and  Charpy.) 


Fig.  192. — Sesamoid  bones  of  the 
foot.     (Poirier  and  Charpy.) 


The  sesamoid  bones  of  the  joints  in  the  upper  extremity  are  two  on  the  palmar 
surface  of  the  metacarpo-phalangeal  joint  in  the  thumb,  developed  in  the  tendons 
of  the  Flexor  brevis  poUicis;  one  on  the  palmar  surface  of  the  interphalangeal 
joint  of  the  thumb;  occasionally  one  or  two  opposite  the  metacarpo-phalangeal 
articulations  of  the  fore  and  little  fingers;  and,  still  more  rarely,  one  opposite 
the  same  joints  of  the  third  and  fourth  fingers.  In  the  lower  extremity,  the 
patella,  which  is  developed  in  the  tendon  of  the  Quadriceps  extensor;  two 
small  sesamoid  bones,  found  in  the  tendons  of  the  flexor  brevis  hallucis,  opposite 
the  metatarso-phalangeal  joint  of  the  great  toe;  one  sometimes  over  the  inter- 
phalangeal joint  of  the  great  toe;  and  occasionally  one  in  the  metatarso-phalan- 
geal joint  of  the  second  toe,  the  little  toe,  and,  still  more  rarely,  the  third  and 
fourth  toes. 

17 


258  THE  SKELETON 

Those  found  in  the  tendons  which  glide  over  certain  bones  occupy  the  following 
situations:  one  sometimes  found  in  the  tendon  of  the  Biceps  cubiti,  opposite  the 
tuberosity  of  the  radius:  one  in  the  tendon  of  the  Peroneus  longus,  where  it  glides 
through  the  groove  in  the  cuboid  bone;  one  appears  late  in  life  in  the  tendon  of  the 
Tibialis  anticus,  opposite  the  smooth  facet  of  the  internal  cuneiform  bone;  one  is 
found  in  the  tendon  of  the  Tibialis  posticus,  opposite  the  inner  side  of  the  head 
of  the  astragalus;  one  in  the  outer  head  of  the  Gastrocnemius,  behind  the  outer 
condyle  of  the  femur;  and  one  in  the  conjoined  tendon  of  the  Psoas  and  Iliacus, 
where  it  glides  over  the  Os  pubis.  Sesamoid  bones  are  found  occasionally  in  the 
tendon  of  the  Gluteus  maximus,  as  it  passes  over  the  great  trochanter,  and  in 
the  tendons  which  wind  round  the  inner  and  outer  malleoli. 


THE  AKTIOULATIONS  OR  JOINTS. 


THE  various  bones  of  which  the  Skeleton  consists  are  connected  together  at 
different  parts  of  their  surfaces,  and  such  a  connection  is  designated  by  the 
name  of  joint  or  articulation.  Arthrology  is  the  branch  of  anatomy  which  treats  of 
the  joints.  If  the  joint  is  immovable,  as  between  the  cranial  and  most  of  the 
facial  bones,  the  adjacent  margins  of  the  bones  are  applied  in  almost  close  con- 
tact, a  thin  layer  of  fibrous  membrane,  the  sutural  ligament,  and,  at  the  base  of 
the  skull,  in  certain  situations,  a  thin  layer  of  cartilage,  being  interposed.  Where 
slight  movement  is  required,  combined  with  great  strength,  the  osseous  surfaces 
are  united  by  tough  and  elastic  fibro -cartilages,  as  in  the  joints  between  the 
vertebral  bodies  and  interpubic  articulations;  but  in  the  movable  joints  the  bones 
forming  the  articulation  are  generally  expanded  for  greater  convenience  of  mutual 
connection,  covered  by  cartilage,  held  together  by  strong  bands  or  capsules  of 
fibrous  tissue  called  ligaments,  and  partially  lined  by  a  membrane,  the  synovial 
membrane,  which  secretes  a  fluid  to  lubricate  the  various  parts  of  which  the  joint 
is  formed;  so  that  the  structures  which  enter  into  the  formation  of  a  joint  are 
bone,  cartilage,  fibro-cartilage,  ligament,  and  sjmovial  membrane. 

Bone. — Bone  constitutes  the  fundamental  element  of  all  the  joints.  In  the 
long  bones  the  extremities  are  the  parts  which  form  the  articulations;  they  are 
generally  somewhat  enlarged,  consisting  of  spongy  cancellous  tissue,  with  a  thin 
coating  of  compact  substance.  In  the  flat  bones  the  articulations  usually  take 
place  at  the  edges,  and,  in  the  short  bones,  at  various  parts  of  their  surface.  The 
layer  of  compact  bone  which  forms  the  articular  surface,  and  to  which  the  car- 
tilage is  attached,  is  called  the  articular  lamella.  It  is  of  a  white  color,  extremely 
dense,  and  varies  in  thickness.  Its  structure  differs  from  ordinary  bone-tissue 
in  this  respect,  that  it  contains  no  Haversian  canals,  and  its  lacunar  are  much 
larger  than  in  ordinary  bone  and  have  no  canaliculi.  The  vessels  of  the  can- 
cellous tissue,  as  they  approach  the  articular  lamella,  turn  back  in  loops,  and 
do  not  perforate  it;  this  layer  is  consequently  more  dense  and  firmer  than  ordinary 
bone,  and  is  evidently  designed  to  form  a  firm  and  unyielding  support  for  the 
articular  cartilage. 

Cartilage. — Cartilage  is  material  which  is  a  transition  stage  of  connective  tissue 
into  bone.  When  boiled  it  yields  chondrin.  Cartilage  is  not  vascular  and  is  found 
in  various  parts  of  the  body;  in  adult  life  chiefly  in  the  joints,  in  the  parietes  of 
the  thorax,  and  in  various  tubes,  which  are  to  be  kept  permanently  open,  such  as 
the  air  passages,  nostrils,  and  ears.  In  the  foetus  in  an  early  period  the  greater  part 
of  the  skeleton  is  cartilaginous.  As  this  cartilage  is  replaced  by  bone,  it  is  called 
temporary  in  contradistinction  to  that  which  remains  unossified  during  life,  and 
which  is  called  permanent.    Cartilage  is  divided  into: 

1.  Hyaline  cartilage. 

2.  Elastic  cartilage. 

3.  Fibro-cartilage. 

Hyaline  Cartilage. — This  structure  is  found  in  the  nose,  larynx,  trachea,  bronchi, 
and  in  symphyses  and  synchondroses;  costal  cartilage  and  epiphyseal  cartilage 
are  composed  of  it,  and  as  articular  cartilage  (cartilago  articularis)  it  covers  joint 

(259) 


2G0  ^^^'   ARTICULATIONS    OB    JOINTS 

surfaces.  It  is  a  bluish  or  pearly  hued  substance,  in  reality  a  modified  connective 
tissue,  but  mych  harder  than  most  connective  tissues.  The  investing  membrane, 
the  perichondrium,  is  composed  of  two  layers:  an  outer  fibrous  layer  which  carries 
blood-vessels  and  an  inner  or  chondrogenetic  layer,  which  contains  cartilage- 
forming  cells  (chondroblasts). 

Cartilage  does  not  contain  blood-vessels  except  in  regions  of  very  active  growth 
or  of  ossification.  In  such  regions  vessels  may  be  formed.  Hyaline  cartilage  is 
composed  of  round  or  oval  cells  and  intercellular  substance.  Each  cell  contains 
granular  protoplasm  and  a  nucleus,  and  the  nucleus  contains  one  or  two  nucleoli. 
The  cells  are  placed  in  the  so-called  cartilage  spaces  of  the  ground  substance,  and  the 
ground  substance  immediately  surrounding  a  space  is  called  a  cartilage  capsule. 
The  cells  are  placed  in  groups  and  near  the  surface  are  arranged  in  rows,  and  in 
some  regions  are  flattened  by  pressure.  The  intercellular  or  ground  substance 
(matrix)  is  an  apparently  homogeneous  and  structureless  material  between  the 
cartilage  spaces.  By  certain  methods,  however,  fibres  can  be  demonstrated  in  it. 
These  fibrils  in  general  are  parallel.  In  some  of  the  lower  animals  canals  have 
been  demonstrated.  In  man  it  has  not  been  proved  that  canals  exist,  and  it  has 
been  suggested  that  the  fibrils  act  as  paths  of  conduction  for  nutritive  fluid. 

Articular  cartilage  forms  a  thin  incrustation  upon  the  joint-surfaces  of  the 
bones,  and  its  elasticity  enables  it  to  break  the  force  of  any  concussion,  while  its 
smoothness  affords  ease  and  freedom  of  movement.  It  varies  in  thickness  accord- 
ing to  the  shape  of  the  articular  surface  on  which  it  lies;  where  this  is  convex  the 
cartilage  is  thickest  at  the  centre,  where  the  greatest  pressure  is  received;  and  the 
reverse  is  the  case  on  the  concave  articular  surfaces.  Articular  cartilage  appears 
to  derive  its  nutriment  partly  from  the  vessels  of  the  neighboring  synovial  mem- 
brane, partly  from  those  of  the  bone  upon  which  it  is  implanted.  Toynbee  has 
shown  that  the  minute  vessel  of  the  cancellous  tissue  as  they  approach  the  articular 
lamella  dilate  and  form  arches,  and  then  return  into  the  substance  of  the  bone. 

The  hyaline  cartilages,  especially  in  adult  and  advanced  life,  are  prone  to 
calcify — that  is  to  say,  to  have  their  matrix  permeated  by  the  salts  of  lime  without 
any  appearance  of  true  bone.  The  process  of  calcification  occurs  also,  and  still 
more  frequently,  according  to  Rollett,  in  such  cartilages  as  those  of  the  trachea 
and  in  the  costal  cartilages,  which  are  prone  afterward  to  conversion  into  true 
bone. 

Elastic  Cartilage. — In  this  structure  there  are  elastic  fibres  in  the  matrix,  which 
fibres  at  the  periphery  of  the  cartilage  enter  into  the  perichondrium.  Such  carti- 
lage is  not  blue-white  in  color,  but  is  a  very  light  yellow,  and  is  not  to  be  regarded 
as  identical  with  elastic  fibrous  tissue.  Elastic  cartilage  is  found  in  the  epiglottis 
and  the  cartilages  of  the  larynx. 

Fibro-cartilage  is  composed  of  wliite  fibrous  tissue  and  cartilage  in  varying  pro- 
portions; it  is  to  the  first  of  these  two  constituents  that  its  flexibility  and  toughness  are 
chiefly  owing,  and  to  the  latter  its  elasticity;  the  cells  are  fewer  in  number,  but  are 
possessed  of  more  definite  capsules  than  are  those  of  hyaline  cartilage,  and  they 
are  usually  arranged  in  groups  surrounded  by  small  islands  of  hyaline  matrix, 
which  may  be  concentrically  striated.  The  hyaline  islands  are  separated  from 
one  another  by  bundles  of  white  fibrous  tissue  that  pursue  a  markedly  wavy 
course. 

Fibro-cartilage  is  found  at  the  point  of  insertion  of  the  ligamentum  teres  into 
the  head  of  the  femur,  in  the  intervertebral  disks,  in  the  pubic  symphysis,  and  in 
the  interarticular  cartilages. 

The  fibro-cartilages  admit  of  arrangement  into  four  groups:  interarticular,  con- 
necting, circumferential,  and  stratiform. 

1.  The  interarticular  fibro-cartilages  {menisci')  are  flattened,  fibro-cartilaginous 
plates,  of  a  round,  oval,  triangular,  or  sickle-like  form,  interposed  between  the 


LIGAMENTS  261 

articular  cartilages  of  certain  joints.  They  are  free  on  both  surfaces,  thinner 
toward  their  centre  than  at  their  circumference,  and  held  in  position  by  the  attach- 
ment of  their  margins  and  extremities  to  the  surrounding  ligaments.  The  synovial 
membrane  of  the  joint  is  prolonged  over  them  a  short  distance  from  their  attached 
margins.  They  are  fouiid  in  the  temporo-mandibular,  sterno-clavicular,  acromio- 
clavicular, wrist-  and  knee-joints.  These  cartilages  are  usually  found  in  those 
joints  which  are  most  exposed  to  violent  concussion  and  subject  to  frequent  move- 
ment. Their  use  is  to  maintain  the  apposition  of  the  opposed  surfaces  in  their 
various  motions;  to  increase  the  depth  of  the  articular  surfaces  and  give  ease  to 
the  gliding  movement;  to  moderate  the  effects  of  great  pressure  and  deaden  the 
intensity  of  the  shocks  to  which  the  parts  may  be  subjected.  Humphry  has  pointed 
out  that  these  interarticular  fibro-cartilages  serve  an  important  purpose  in  increasing 
the  variety  of  movements  in  a  joint.  Thus,  in  the  knee-joint  there  are  two  kinds 
of  motion — viz.,  angular  movement  and  rotation — although  it  ijs  a  hinge  joint,  in 
which,  as  a  rule,  only  one  variety  of  motion  is  permitted ;  the  foimer  movement  takes 
place  between  the  condyles  of  the  femur  and  the  interarticular  cartilage,  the  latter 
between  the  cartilage  and  the  head  of  the  tibia.  So,  also,  in  the  temporo-man- 
dibular joint,  the  upward  and  downward  movement  of  opening  and  shutting  the 
mouth  takes  place  between  the  fibro-cartilage  and  the  jaw-lwne,  the  grinding 
movement  between  the  glenoid  cavity  and  the  fibro-cartilage,  the  latter  moving 
with  the  jaw-bone. 

Interarticular  cartilages  may  divide  the  joint  into  two  distinct  cavities,  as  in  the 
temporo-maxillary  articulation.  The  periphery  of  an  articular  cartilage  is  attached 
particularly  to  the  capsule  and  may  also  be  attached  to  the  non-articular  portion 
of  the  bone.  The  semilunar  cartilages  of  the  knee  resemble  tendon  more  than 
they  do  cartilage.  The  fibres  are  arranged  in  dense,  more  or  less  parallel  bundles, 
separated  by  small,  scattered  hyaline  cells,  and  the  disks  are  attached  to  the  bone 
by  thin  layers  of  hyaline  cartilage. 

2.  The  connecting  fibro-cartilages  are  interposed  between  the  bony  surfaces  of 
those  joints  which  admit  of  only  slight  mobility,  as  between  the  bodies  of  the 
vertebrae  and  between  the  pubic  bones.  They  form  disks  which  adhere  closely  to 
both  of  the  opposed  surfaces,  antl  are  composed  of  concentric  rings  of  fibrous 
tissue,  with  cartilaginous  laminae  interposed,  the  former  tissue  predominating 
toward  the  circumference,  the  latter  toward  the  centre. 

3.  The  circumferential  fibro-cartilages  consist  of  a  rim  of  fibro-cartilage,  which 
surrounds  the  margin  of  some  of  the  articular  cavities,  as  the  cotyloid  cavity  of 
the  hip  and  the  glenoid  cavity  of  the  shoulder;  they  serve  to  deepen  the  articular 
surface,  and  to  protect  its  edges. 

4.  The  stratiform  fibro-cartilages  are  those  which  form  a  thin  coating  to  osseous 
grooves  through  which  the  tendons  of  certain  muscles  glide.  Small  masses  of 
fibro-cartilages  are  developed  also  in  the  tendons  of  some  muscles,  where  they 
glide  over  bones,  as  in  tendons  of  the  Peroneus  longus  and  the  Tibialis  posticus. 

Ligaments. — Ligaments  consist  of  bands  of  various  forms,  serving  to  connect 
together  the  articular  extremities  of  l)ones,  and  are  composed  mainly  of  coarse 
bundles  of  very  dense  white  fibrous  tissue  placed  parallel  with,  or  closely  inter- 
laced with,  one  another,  and  presenting  a  white,  shining,  silvery  aspect.  These 
bundles  are  called  fasciculi.  They  are  held  together  by  a  cement  substance 
containing  cells  which  resemble  those  of  tendon.  A  ligament  is  pUant  and 
flexible,  so  as  to  allow  of  the  most  perfect  freedom  of  movement,  but  it  is 
strong,  tough,  and  inextensile,  so  as  not  readily  to  yield  under  the  most 
severely  applied  force;  it  is  consequently  well  adapted  to  serve  as  the  connecting- 
medium  between  the  bones.  Some  ligaments  consist  entirely  of  yellow  elastic 
tissue  {elastic  fibrous  tissue),  the  elastic  fibres  branching  considerably,  but  main- 
taining in  general  a  parallel  course.     The  fibres  are  in  bundles,  between  which 


202  THE   ARTICULATIONS   OR   JOINTS 

areolar  connective  tissue  lies.  The  ligamenta  subflava,  which  connect  together 
the  adjacent  arches  of  the  vertebrae  in  man  and  the  ligamentum  nuchae  in  the 
lower  animals  are  composed  of  yellow  elastic  tissue.  In  these  cases  it  will  be 
observed  that  the  elasticity  of  the  ligament  is  intended  to  act  as  a  substitute  for 
muscular  power. 

Synovial  Membranes. — These  membranes  are  serous  in  character.  A  synovial 
membrane  consists  of  loose  connecting  tissue  (subendothelial  tissue),  containing  fat, 
vessels,  and  nerves,  its  inner  surface  being  lined  with  a  single  layer  of  flat  endothelial 
cells.  The  endothelial  cells  are  polyhedral,  and  each  cell  possesses  a  flattened  oval 
nucleus.  The  cells  are  held  together  by  intercellular  cement.  It  is  believed  by  some 
that  little  openings  occur  at  intervals  in  the  intercellular  cement,  but  it  is  held  by 
many  that  the  supposed  openings  are  artifacts.  Synovial  cavities  contain  a  little 
fluid.  A  non-articular  synovial  membrane  does  not  actually  secrete  fluid,  but  it  is 
moistened  by  lymph  which  passes  through  the  membrane  and  into  the  cavity  by 
osmosis. 

Joint  cavities  and  bursa?  communicating  with  joints  contain  a  characteristic 
fluid  which  is  a  secretion  of  the  membrane.  It  is  yellowish-white  or  slightly  red- 
dish, somewhat  cloudy,  viscid  like  the  white  of  an  egg,  having  a  strongly  alkaline 
reaction  and  a  slightly  saline  taste.  It  consists  of  fats,  salts,  albumins,  extract- 
ives from  lymph,  a  mucinous  body  known  as  S3moviii,^  and  another  mucin-like 
body,  which  is  rich  in  phosphorus  (Simon).  The  nature  of  synovin  is  uncertain, 
but  it  is  neither  a  nucleo-albumin  nor  a  mucin  (Simon).  The  second  mucin-like 
body  is  probably  a  nucleo-albumin  (Simon).  The  quantitative  composition  of 
synovial  fluid  varies  with  motion  and  rest  (Frerichs,  Simon).  During  exercise  the 
mucin-like  bodies,  the  albumins,  and  the  extractives  increase,  and  the  salts  and 
water  diminish.^  The  synovial  membranes  found  in  the  body  admit  of  sub- 
division into  three  kinds — articular,  bursal,  and  vaginal. 

Articular  Synovial  Membrane. — Articular  synovial  membrane  is  found  in  every 
freely  movable  joint.  It  lines  the  capsule  of  the  joint  and  is  reflected  upon  the 
non-articular  intracapsular  portion  of  the  bones  which  enter  into  the  formation 
of  the  joint.  In  the  fcetus  this  membrane  is  said,  by  Toynbee,  to  be  continued 
over  the  surface  of  the  cartilages;  but  in  the  adult  it  merely  encroaches  for  a 
short  distance  upon  the  margins  of  the  cartilages,  to  which  it  is  firmly  attached; 
it  then  invests  the  inner  surface  of  the  capsular  or  other  ligaments  enclosing  the 
joint,  and  is  reflected  over  the  surface  of  any  tendons  passing  through  its  cavity,  as 
the  tendon  of  the  Popliteus  in  the  knee  and  the  tendon  of  the  Biceps  in  the 
shoulder.  Hence  the  articular  synovial  membrane  may  be  regarded  as  a  short 
wide  tube,  attached  by  its  open  ends  to  the  margins  of  the  articular  cartilages,  and 
covering  the  inner  surface  of  the  various  ligaments  which  connect  the  articular 
surfaces,  so  that  along  with  the  cartilages  it  completely  encloses  the  joint-cavity. 
In  some  of  the  joints  the  synovial  membrane  is  thrown  into  folds,  which  pass 
across  the  cavity.  They  are  called  synovial  ligaments,  and  are  especially  distinct  in 
the  knee.  In  some  joints  there  are  flattened  folds,  subdivided  at  their  margins  into 
fringe-like  processes  (synovial  villi) ,  the  vessels  of  which  have  a  convoluted  arrange- 
ment. These  latter  generally  project  from  the  synovial  membrane  near  the  margin 
of  the  cartilage  and  lie  flat  upon  its  surface.  They  consist  of  connective  tissue  cov- 
ered with  endothelium,  and  contain  fat-cells  in  variable  quantities,  and,  more  rarely, 
isolated  cartilage-cells.  The  larger  folds  often  contain  considerable  quantities  of 
fat.  They  were  described  by  Clopton  Havers  as  mucilaginous  glands,  and  as  the 
source  of  the  synovial  secretion.  Under  certain  diseased  conditions  similar  pro- 
cesses are  found  covering  the  entire  surface  of  the  synovial  membrane,  forming  a 

'  Simon's  Physiological  Chemistry. 

'  Frerichs'  analysis,  in  Simon's  Physiological  Chemistry. 


SYNOVIAL   MEMBRANES 


263 


mass  of  pedunculated  fibro-fatty  growths  which  project  into  the  joint.     Similar 
structures  are  also  found  in  some  of  the  bursal  and  vaginal  synovial  membranes. 

Bursal  Synovial  Membrane. — The  bursal  synovial  membranes  are  sacs  inter- 
posed between  surfaces  which  move  upon  each  other,  producing  friction,  as  in  the 
gliding  of  a  tendon  or  of  the  integument  over  projecting  bony  surfaces.  There  are 
two  groups  of  synovial  bursae  designated  according  to  situation :  1.  Those  situated 
between  the  integument  and  a  prominent  process  of  bone.  Such  a  bursa  is  called 
a  subcutaneous  synovial  bursa  {bursa  mucosa  subcutanea)  (Fig.  246).  Subcuta- 
neous bursa'  are  found  between  the  integument  and  the  front  of  the  patella, 
over  the  olecranon,  the  malleoli,  and  other  prominent  parts.  2.  Those  situated 
between  tendons  or  muscles  and  the  bony  or  cartilaginous  surfaces  over  which 
the    tendons  or   nmscles   glide    (Figs.  193  and  194).     Such  a  bursa  is  called  a 


Fig.  193. 


-Scheme  of  a  serous  bursa. 
and  Charpy.) 


(Poirier 


Fig.  194. 


C  SUBTENDINOUS        J 
BURSA  J 


-Scheme  of  a  serous  bursa.     (Poirier 
and  Charpy.) 


subtendinous  synovial  bursa  {bursa  mucosa  subtendinea) .  For  example,  a  bursa 
is  placed  between  the  Glutei  muscles  and  the  surface  of  the  great  trochanter. 
Subtendinous  bursae  are  found  often  about  joints  and  not  unusually  communicate 
directly  with  the  cavity  of  the  joint  by  means  of  an  opening  in  the  joint  capsule, 
the  synovial  membrane  of  the  joint  being  continuous  with  the  synovial  mem- 
brane of  the  bursa.  For  instance,  the  bursa  between  the  tendon  of  the  Psoas 
and  Iliacus  muscles  and  the  capsular  ligament  of  the  hip  communicates  with 
the  hip-joint;  and  the  bursa  between  the  under  surface  of  the  Subscapularis 
muscle  and  the  neck  of  the  scapula  communicates  with  the  shoulder-joint. 
Bursae  consist  of  a  thin  wall  of  connective  tissue,  partially  covered  by  patches 
of  cells,  and  contain  a  viscid  fluid. 

Vaginal  Synovial  Membrane  (Fig.  326). — A  vaginal  synovial  membrane  (52/rioi;iaZ 
sheath,  thecal  synovial  bursa,  vagina  mucosa  tendinis)  serves  to  facilitate  the  gliding 
of  a  tendon  in  the  osseo-fibrous  canal  through  which  it  passes.  The  membrane 
is  here  arranged  in  the  form  of  a  sheath,  one  laver  of  which  adheres  to  the  wall 
of  the  canal,  and  the  other  is  reflected  upon  the  surface  of  the  contained  tendon, 
the  space  between  the  two  free  surfaces  of  the  membrane  containing  synovia. 
These  sheaths  are  chiefly  found  surrounding  the  tendons  of  the  Flexor  and  Ex- 
tensor muscles  of  the  fingers  and  toes  as  they  pass  through  the  osseo-fibrous 
canals  in  the  hand  or  foot.  A  vaginal  sheath  covers  the  long  head  of  the  biceps 
muscle  from  its  origin  to  the  surgical  neck  of  the  humerus  (Fig.  222). 

Pads  of  adipose  tissue  {synovial  fat  pads)  are  found  in  certain  joints  between 
the  synovial  membrane  and  the  surface  beneath  it.  These  pads  fill  up  certain 
joint  intervals,  and  by  adapting  themselves  to  changes  of  position  maintain  the 
form  of  the  joint  during  movement. 

The  articulations  are  divided  into  three  classes:  synarthrosis,  or  immovable; 
amphiarthrosis,  or  mixed;  and  diarthrosis,  or  movable  joints. 


264  'THE  ARTICULATIONS    OB    JOINTS 

Synarthrosis  (Immovable  Articulation). 

Synarthrosis  includes  all  those  articulations  in  which  the  surfaces  of  the  bones 
are  in  almost  direct  contact,  being  fastened  together  by  an  intervening  mass  of 
connective  tissue,  and  in  which  there  is  no  joint  cavity  and  no  appreciable  motion. 
Examples  of  synarthrosis  are  the  joints  between  the  bones  of  the  cranium  and 
of  the  face,  excepting  those  of  the  lower  jaw.  The  varieties  of  synarthrosis  are 
four  in  number:  sutura,  schindylesis,  gomphosis,  and  synchondrosis. 

Sutura. — Sutura  (a  seam)  is  that  form  of  articulation  met  with  only  in  the 
skull,  where  the  contiguous  margins  of  flat  bones  are  apparently  but  not  really 
in  immediate  contact,  a  thin  layer  of  fibrous  tissue,  sutural  membrane,  being 
interposed.  This  membrane  is  continuous  externally  with  the  pericranium  and 
internally  with  the  dura  mater.  In  some  of  the  sutures  the  sutural  membrane 
gradually  disappears  as  age  advances  and  the  two  bones  form  an  osseous  fusion. 
Where  the  articulating  surfaces  are  connected  by  a  series  of  processes  and  inden- 
tations interlocked  together,  it  is  termed  a  tme  suture  or  sutura  vera,  of  which  there 
are  three  varieties:  sutura  dentata,  serrata,  and  limbosa.  The  sutura  dentata  {dens, 
a  tooth)  is  so  called  from  the  tooth-like  form  of  the  projecting  articular  processes, 
as  in  the  suture  between  the  parietal  bones.  In  the  sutura  serrata  (serra,  a  saw) 
the  edges  of  the  two  bones  forming  the  articulation  are  serrated  like  the  teeth 
of  a  fine  saw,  as  between  the  two  portions  of  the  frontal  bone.  In  the  sutura 
limbosa  (limbus,  a  selvage),  besides  the  dentated  processes,  there  is  a  certain 
d agree  of  bevelling  of  the  articular  surfaces,  so  that  the  bones  overlap  one  another, 
as  in  the  suture  between  the  parietal  and  frontal  bones.  When  the  articulation 
is  formed  by  roughened  surfaces  placed  in  apposition  with  one  another,  it  is 
termed  the  false  suture  (sutura  notha),  of  which  there  are  two  kinds:  the  sutura 
squamosa  {squama,  a  scale),  formed  by  the  overlapping  of  two  contiguous  bones 
by  broad  bevelled  margins,  as  in  the  squamo-parietal  (squamous)  suture;  and 
the  sutura  harmonia  {kpixovla,  a  joining  together),  where  there  is  simple  apposition 
of  two  contiguous,  rough,  bony  surfaces,  as  in  the  articulation  between  the  two 
superior  maxillary  bones  or  of  the  horizontal  plates  of  the  palate  bones. 

Schindylesis. — Schindylesis  {ayivdbhjotz,  a  fissure)  is  that  form  of  articulation 
in  which  a  thin  plate  of  bone  is  received  into  a  cleft  or  fissure  formed  })y  the  sep- 
aration of  two  laminae  in  another  bone,  as  in  the  articulation  of  the  rostrum  of  the 
sphenoid  and  perpendicular  plate  of  the  ethmoid  with  the  vomer,  or  in  the  recep- 
tion of  the  latter  in  the  fissure  between  the  superior  maxillary  and  palate  bones. 

Gomphosis. — Gomphosis  {yofupo!^,  a  nail)  is  an  articulation  formed  by  the 
insertion  of  a  conical  process  into  a  socket,  as  a  nail  is  driven  into  a  board;  this 
is  not  illustrated  by  any  articulation  between  bones,  properly  so  called,  but  is 
seen  in  the  articulation  of  the  teeth  with  the  alveoli  of  the  maxillary  bones. 

Synchondrosis. — Where  the  connecting  medium  is  cartilage  the  joint  is  termed 
a  synchondrosis.  This  is  a  temporary  form  of  joint,  because  the  hyaline  cartilage 
becomes  converted  into  bone  before  adult  life.  wSuch  a  joint  is  found  between 
the  epiphyses  and  shafts  of  long  bones.  Another  example  of  a  synchondrosis  is 
the  occipito-sphenoid  articulation. 

Amphiarthrosis  (Mixed  Articulation). 

In  this  form  of  articulation  the  contiguous  osseous  surfaces  may  be  connected 
together  by  broad  flattened  disks  of  fibro-cartilage,  of  a  more  or  less  complex 
structure,  which  adhere  to  the  end  of  each  bone,  as  in  the  articulation  between 
the  bodies  of  the  vertebrae  and  the  pubic  symphyses.  This  is  termed  symphysis. 
In  a  symphysis  there  is  a  partial  joint  cavity  which  may  exhibit  an  incomplete 
synovial  membrane.    Each  constituent  bone  is  coated  with  hyaline  cartilage  and 


DIARTHBOSIS  265 

the  bones  are  held  together  by  Hgaments  and  intervening  fibro-cartilage.  The 
bony  surfaces  of  an  amphiarthrodial  joint  may  be  united  by  an  interosseous  hga- 
ment,  as  in  the  inferior  tibio-fibular  articulation.  To  such  an  articulation  the 
term  syndesmosis  is  applied.     A  mixed  articulation  permits  limited  motion. 

Diarthrosis  (Movable  Articulation). 

This  form  of  articulation  includes  the  greater  number  of  the  joints  in  the  body, 
mobility  being  their  distinguishing  character.  They  are  formed  by  the  approxi- 
mation of  two  contiguous  bony  surfaces  covered  with  cartilage,  connected  by 
ligaments  and  lined  by  synovial  membrane.  The  varieties  of  joints  in  this  class 
have  been  determined  by  the  kind  of  motion  permitted  in  each.  There  are  two 
varieties  in  which  the  movement  is  uniaxial;  that  is  to  say,  all  movements  take 
place  around  one  axis.  In  one  form,  the  ginglymus  or  hinge-joint,  this  axis  is, 
practically  speaking,  transverse;  in  the  other,  the  trochoid  or  pivot-joint,  it  is 
longitudinal.  There  are  two  varieties  where  the  movement  is  biaxial  or  around 
two  horizontal  axes  at  right  angles  to  each  other  or  at  any  intervening  axis 
between  the  two.  These  are  the  condyloid-joint  and  the  saddle-joint.  There  is 
one  form  of  joint  where  the  movement  is  polyaxial,  the  enarthrosis  or  ball-and- 
socket  joint.  And  finally  there  are  the  arthrodia  or  gliding  joints.  In  a  diarthrosis 
there  is  always  a  joint  cavity  lined  with  synovial  membrane — the  articular  sur- 
faces of  the  bones  are  covered  with  hyaline  cartilage  and  the  bones  are  held  in 
contact  by  ligaments. 

Ginglymus  or  Hinge-joint  {yiyfAoiioz,  a  hinge). — In  this  form  of  joint  the 
articular  surfaces  are  moulded  to  each  other  in  such  a  manner  as  to  permit  motion 
only  in  one  plane,  forward  and  backward ;  the  extent  of  motion  at  the  same  time 
being  considerable.  The  direction  which  the  distal  bone  takes  in  this  motion  is 
never  in  the  same  plane  as  that  of  the  axis  of  the  proximal  bone,  and  there  is 
always  a  certain  amount  of  alteration  from  the  straight  line  during  flexion.  The 
articular  surfaces  are  connected  together  by  strong  lateral  ligaments,  which  form 
their  chief  bond  of  union.  The  most  perfect  forms  of  ginglymus  are  the  inter- 
phalangeal  joints  and  the  joint  between  the  humerus  and  ulna;  the  knee  and 
ankle  are  less  perfect,  as  they  allow  a  slight  degree  of  rotation  or  lateral  move- 
ment in  certain  positions  of  the  limb. 

Trochoid  or  Pivot-joint  or  Rotary-joint. — Where  the  movement  is  limited  to 
rotation,  the  joint  is  formed  by  a  pivot-like  process  turning  within  a  ring,  or  the 
ring  on  the  pivot,  the  ring  being  formed  partly  of  bone,  partly  of  ligament.  In 
the  superior  radio-ulnar  articulation  the  ring  is  formed  partly  by  the  lesser  sig- 
moid cavity  of  the  ulna;  in  the  rest  of  its  extent,  by  the  orbicular  ligament;  here 
the  head  of  the  radius  rotates  within  the  ring.  In  the  articulation  of  the  odontoid 
process  of  the  axis  with  the  atlas  the  ring  is  formed  in  front  by  the  anterior  arch 
of  the  atlas;  behind,  by  the  transverse  ligament;  here  the  ring  rotates  round  the 
odontoid  process. 

Condyloid  or  Biaxial  Articulation. — In  this  form  of  joint  an  ovoid  articular 
head,  or  condyle,  is  received  into  an  elliptical  cavity  in  such  a  manner  as  to  per- 
mit of  flexion  and  extension,  adduction  and  abduction  and  circumduction,  but 
no  axial  rotation.  The  articular  surfaces  are  connected  together  by  anterior, 
posterior,  and  lateral  ligaments.  An  example  of  this  form  of  joint  is  found  in 
the  wrist. 

Articulation  by  Reciprocal  Reception  or  Saddle-joint. — In  this  variety  the 
articular  surfaces  are  concavo-convex;  that  is  to  say,  they  are  inversely  convex  in 
one  direction  and  concave  in  the  other.  The  movements  are  the  same  as  in  the 
preceding  form;  that  is  to  say,  there  is  flexion,  extension,  adduction,  abduction, 
and  circumduction,  but  no  axial  rotation.    The  articular  surfaces  are  connected 


266 


THE   ARTICULATIONS    OR    JOINTS 


by  a  capsular  ligament.  The  best  example  of  this  form  of  joint  is  the  carpo- 
metacarpal joint  of  the  thumb. 

Enarthrosis,  or  Ball-and-socket-joint,  is  that  form  of  joint  in  which  the  distal 
bone  is  capable  of  motion  around  an  indefinite  number  of  axes  which  have  one 
common  centre.  It  is  formed  by  the  reception  of  a  globular  head  into  a  deep 
cup-like  cavity  (hence  the  name  "ball-and-socket"),  the  parts  being  kept  in 
apposition  by  a  capsular  ligament  strengthened  by  accessory  ligamentous  bands. 
Examples  of  this  form  of  articulation  are  found  in  the  hip  and  shoulder. 

Arthrodia. — Arthrodia  is  that  form  of  joint  which  admits  of  a  gliding  move- 
ment; it  is  formed  by  the  approximation  of  plane  surfaces  or  one  slightly  concave, 
the  other  slightly  convex,  the  amount  of  motion  between  them  being  limited  by 
the  ligaments,  or  osseous  processes,  surrounding  the  articulation;  as  in  the  articu- 
lar processes  of  the  vertebrae,  the  carpal  joints,  except  that  of  the  os  magnum 
with  the  scaphoid  and  semilunar  bones,  and  the  tarsal  joints  with  the  exception 
of  the  joint  between  the  astragalus  and  the  scaphoid. 

Below,  in  tabular  form,  are  the  names,  distinctive  characters,  and  examples 
of  the  different  kinds  of  articulations. 


The  Kinds  of  Movement  Admitted  in  Joints. 

The  movements  admissible  in  joints  may  be  divided  into  four  kinds:  gliding, 
angular  movement,  circumduction,  and  rotation.  These  movements  are  often, 
however,  more  or  less  combined  in  the  various  joints,  so  as  to  produce  an  infinite 
variety,  and  it  is  seldom  that  we  find  only  one  kind  of  motion  in  any  particular  joint. 

D  entata,  having 
tooth-like  processes. 

As  in  interparietal 
suture. 

Serrata,  havinsf  ser- 
rated  edges  like  the 
teeth  of  a  saw. 

As  in  interfrontal 
suture. 

L  imbosa,  having 
bevelled  margins  and 
dentated  processes. 

As  in  fronto-parie- 
tal  suture. 

Squamosa,  formed 
by  thin  bevelled  mar- 
gins, overlapping  each 
other. 

As  in  squamo-parie- 


Synarthrosis,  or 
Immovable  Joint. 
Surfaces  separated 
by  fibrous  mem- 
brane or  by  line 
of  cartilage,  with- 
out any  interven- 
ing  synovial 
cavity,  and  im- 
movably  con- 
nected  with  each 
other. 

As  in  joints  of 
cranium  and  face 
(except  lower 
jaw). 


Sutura.  Ar- 
ticulation by 
processes  and 
indentations 
i  nterlocked 
together. 


Sutura  vera 
(true),  articulate 
by  indented  bor- 
ders. 


Sutur a    notha 
(false),     articulate^  tal  suture 
by  rough  surfaces.        //armo/n'a,  formed  by 
the  apposition  of  con- 
tiguous rough  surfaces. 
As  in  intermaxillary 
^  suture. 

Schindylesis. — Articulation  formed  by  the  reception  of  a 
thin  plate  of  one  bone  into  a  fissure  of  another. 

As  in  articulation  of  rostrum  of  sphenoid  with  vomer. 
Gomphosis. — Articulation  formed  by  the  insertion  of  a 
conical  process  into  a  socket:  the  teeth. 


THE   KIND:^    of  3I0VEMENT  ADMITTED    IN   JOINTS        267 


f     Symphysis. — Surfaces  connected  by  fibro-cartilage.  There 
J       i-.r       •     I  is  a  partial  joint  cavity  and  may  be  an  incomplete  synovial 
^  membrane.     Mas    limited    motion.     As   in    joints   between 

bodies  of  vertebrae. 

Syndesmosis. — Surfaces  united  by  an  interosseous  liga- 


Mixed      Articula 
tion 


< 


Diarthro'sis, 
Movable  Joint. 


Lment.     As  in  the  inferior  tibio-fibular  articulation. 

Ginglymus. — Hinge-joint;  motion  limited  to  two  directions, 
forwaid  and  backward.  Articular  surfaces  fitted  together 
so  as  to  permit  of  movement  in  one  plane.  As  in  the  inter- 
phalangeal  joints  and  the  joint  between  the  humerus  and  the 
ulna. 

Trochoides,  or  Pivot-joint. — Articulation  by  a  pivot  process 
turning  within  a  ring  or  ring  around  a  pivot.  As  in  superior 
radio-ulnar  articulation  and  atlanto-axial  joint. 

Condyloid.— Ow Old  head  received  into  elliptical  cavity. 
Movements  in  every  direction  except  axial  rotation.  As  the 
wrist-joint. 

Reciprocal  Reception  (saddle-joint). — Articular  surfaces 
inversely  convex  in  one  direction  and  concave  in  the  other. 
Movement  in  every  direction  except  axial  rotation.  As  in 
the  carpo-metacarpal  joint  of  the  thumb. 

Enarthrosis. — Ball-and-socket  joint;  capable  of  motion  in 
all  directions.  Articulations  by  a  globular  head  received 
into  a  cup-like  cavity.    As  in  hip-  and  shoulder-joints. 

Arthrodia. — Gliding  joint;  articulations  by  plane  surfaces, 
which  glide  upon  each  other.  As  in  carpal  and  tarsal  articu- 
^  lations. 

Gliding  movement  is  the  most  simple  kind  of  motion  that  can  take  place  in  a 
joint,  one  surface  gliding  or  moving  over  another  without  any  angular  or  rotatory 
movement.  It  is  common  to  all  movable  joints,  but  in  some,  as  in  the  articu- 
lations of  the  carpus  and  tarsus,  it  is  the  only  motion  permitted.  This  movement 
is  not  confined  to  plane  surfaces,  but  may  exist  between  any  two  contiguous 
surfaces,  of  whatever  form,  limited  by  the  ligaments  which  enclose  the  articu- 
lation. Gliding  over  a  wide  range,  as  is  seen  in  the  sliding  of  the  patella  over 
the  femur,  is  called  coaptation. 

Angular  movement  occurs  only  between  the  long  bones,  and  by  it  the  angle 
between  the  two  bones  is  increased  or  diminished.  It  may  take  place  in  four 
directions:  forward  and  backward,  constituting  flexion  or  bending  and  extension 
or  straightening,  or  inward  toward  and  outward  from  the  mesial  line  of  the  body, 
constituting  adduction  and  abduction.  Abduction  of  a  limb  is  movement  away  from 
the  mesial  fine  of  the  body.  Adduction  of  a  limb  is  movement  toward  the  mesial 
line  of  the  body.  In  the  fingers  and  toes  the  significance  of  the  terms  are  different; 
abduction  means  movement  of  the  fingers  away  from  the  middle  finger  or  of  the 
toes  away  from  the  second  toe;  adduction  means  movement  of  fingers  toward 
the  middle  finger  or  of  the  toes  toward  the  second  toe.  The  strictly  ginglymoid 
or  hinge-joints  admit  of  flexion  and  extension  only.  Abduction  and  adduction, 
combined  with  flexion  and  extension,  are  met  with  in  the  more  movable  joints; 
as  in  the  hip-,  shoulder-,  and  metacarpal-joint  of  the  thumb,  and  partially  in 
the  wrist.  When  two  anterior  surfaces  are  brought  nearer  together,  as  by 
bending  the  elbow  or  wrist,  we  speak  of  the  movement  as  ventral,  anterior,  or 
palmar  flexion.  If  two  posterior  surfaces  are  brought  nearer  together,  as  by 
bending  the  knee  or  wrist,  we  speak  of  the  movement  as  posterior  or  dorsalt 
flexion. 


268  '-^'HE  ARTICULATIONS   OB    JOINTS 

At  the  wrist-joint  the  bending  of  the  uhiar  margin  of  the  hand  toward  the 
ulnar  side  of  the  forearm  is  ulnar  flexion;  the  bending  of  the  radial  margin  of 
the  hand  toward  the  radial  side  of  the  forearm  is  radial  flexion. 

Circumduction  is  that  limited  degree  of  motion  which  takes  place  between  the 
head  of  the  bone  and  its  articular  cavity,  whilst  the  extremity  and  sides  of  the  limb 
are  made  to  circumscribe  a  conical  space,  the  base  of  which  corresponds  with  the 
inferior  extremity  of  the  limb,  the  apex  with  the  articular  cavity;  this  kind  of 
motion  is  best  seen  in  the  shoulder-  and  hip-joints. 

Rotation  is  the  movement  of  a  bone  upon  an  axis,  which  is  the  axis  of  the  pivot 
on  which  the  bone  turns,  as  in  the  articulation  between  the  atlas  and  axis,  when 
the  odontoid  process  serves  as  a  pivot  around  which  the  atlas  turns;  or  else  is  the 
axis  of  a  pivot-like  process  which  turns  within  a  ring,  as  in  the  rotation  of  the 
radius  upon  the  humerus. 

Ligamentous  Action  of  Muscles. — The  movements  of  the  different  joints  of 
a  limb  are  combined  by  means  of  the  long  muscles  which  pass  over  more  than  one 
joint,  and  which,  when  relaxed  and  stretched  to  their  greatest  .extent,  act  as 
elastic  ligaments  in  restraining  certain  movements  of  one  joint,  except  when 
combined  with  corresponding  movements  of  the  other,  these  latter  movements 
being  usually  in  the  opposite  direction.  Thus  the  shortness  of  the  hamstring 
muscles  prevents  complete  flexion  of  the  hip,  unless  the  knee-joint  is  also  flexed, 
so  as  to  bring  their  attachments  nearer  together.  The  uses  of  this  arrangement 
are  threefold:  1.  It  co-ordinates  the  kinds  of  movement  which  are  the  most 
habitual  and  necessary,  and  enables  them  to  be  performed  with  the  least  expendi- 
ture of  power.  "Thus  in  the  usual  gesture  of  the  arms,  whether  in  grasping  or 
rejecting,  the  shoulder  and  the  elbow  are  flexed  simultaneously,  and  simultane- 
ously extended,"  in  consequence  of  the  passage  of  the  Biceps  and  Triceps  cubiti 
over  both  joints.  2.  It  enables  the  short  muscles  which  pass  over  only  one  joint 
to  act  upon  more  than  one.  "Thus,  if  the  Rectus  femoris  remain  tonically  of 
such  length  that,  when  stretched  over  the  extended  hip,  it  compels  extension  of 
the  knee,  then  the  Gluteus  maximus  becomes  not  only  an  extensor  of  the  hip,  but 
an  extensor  of  the  knee  as  well."  3.  It  provides  the  joints  with  ligaments  which, 
while  they  are  of  very  great  power  in  resisting  movements  to  an  extent  incom- 
patible with  the  mechanism  of  the  joint,  at  the  same  time  spontaneously  yield 
when  necessary.  "Taxed  beyond  its  strength,  a  ligament  will  be  ruptured, 
whereas  a  contracted  muscle  is  easily  relaxed;  also,  if  neighboring  joints  be 
united  by  ligaments,  the  amount  of  flexion  or  extension  of  each  must  remain  in 
constant  proportion  to  that  of  the  other;  while,  if  the  union  be  by  muscles,  the 
separation  of  the  points  of  attachment  of  those  muscles  may  vary  considerably 
in  different  varieties  of  movement,  the  muscles  adapting  themselves  tonically 
to  the  length  required."  The  quotations  are  from  a  very  interesting  paper  by 
Dr.  Cleland  in  the  Journal  of  Anatomy  and  Physiology,  No.  1,  1866,  p.  85;  by 
whom  I  believe  this  important  fact  in  the  mechanism  of  joints  was  first  clearly 
pointed  out,  though  it  has  been  independently  observed  afterward  by  other 
anatomists.  Dr.  W.  W.  Keen  points  out  how  important  it  is  "that  the  surgeon 
should  remember  this  ligamentous  action  of  muscles  in  making  passive  motion — 
for  instance,  at  the  wrist  after  Colles's  fracture.  If  the  fingers  be  extended,  the 
wrist  can  be  flexed  to  a  right  angle.  If,  however,  they  be  first  flexed,  as  in  'mak- 
ing a  fist,'  flexion  at  the  wrist  is  quickly  limited  to  from  40  to  50  degrees  in 
different  persons,  and  is  very  painful  beyond  that  point.  Hence  passive  motion 
here  should  be  made  with  the  fingers  extended.  In  the  leg,  when  flexing  the  hip, 
the  knee  should  be  flexed."  Dr.  Keen  further  points  out  that  "a  beautiful  illus- 
tration of  this  is  seen  in  the  perching  of  birds,  whose  toes  are  forced  to  clasp  the 
perch  by  just  such  a  passive  ligamentous  action  so  soon  as  they  stoop.  Hence 
they  can  go  to  sleep  and  not  fall  ofi^  the  perch." 


ARTICULATIONS    OF   THE    VERTEBRAL    COLUMN  269 

The  articulations  may  be  arranged  into  those  of  the  trunk,  those  of  the  upper 
extremity,  and  those  of  the  lower  extremity. 

ARTICULATIONS  OF  THE  TRUNK. 

These  may  be  divided  into  the  following  groups,  viz. : 


I.  Of  the  vertebral  column. 
II.  Of  the  atlas  Vv-^ith  the  axis. 
III.  Of   the   atlas    with   the   occipital 

l^one. 
V\  .  Of  the  axis  with  the  occipital  bone. 
V.  Of  the  lower  jaw. 
VI.  Of  the  ribs  with  the  vertebrae. 


VII.  Of  the  cartilages  of  the  ribs  with 
the  sternum  and  with  each  other. 
VIII.  Of  the  sternum. 
IX.  Of  the  vertebral  column  with  the 

pelvis. 
X.  Of  the  pelvis. 


I.  Articulations  of  the  Vertebral  Column. 

The  different  segments  of  the  spine  are  connected  together  by  spinal  ligaments 
(Ugamenta  columnoB  vertebraLs) ,  which  may  be  divided  into  five  sets:  1.  Those 
connecting  the  bodies  of  the  vertebrae.  2,  Those  connecting  the  laminae. 
3.  Those  connecting  the  articular  processes.  4.  Those  connecting  the  spinous 
processes.    5.  Those  of  the  transverse  processes. 

The  articulations  of  the  bodies  of  the  vertebras  with  each  other  form  a  series  of 
amphiarthrodial  joints;  those  between  the  articular  processes  form  a  series  of 
arthrodial  joints. 

1.  The  Ligaments  of  the  Vehtebral  Bodies  or  Centra  (Intercentral 

Ligaments). 

Anterior  Common  Ligament  (anterior  longitudinal  ligament). 
Posterior  Common  Ligament  (posterior  longitudinal  ligament). 
Intervertebral  Substance  (intervertebral  disk,  fibro-cartilage). 

The  Anterior  Common  or  Anterior  Longitudinal  Ligament  (ligamentum  longitu- 
dinale  anterius)  (Figs.  197,  199,  and  203)  is  a  broad  and  strong  band  of  longi- 
tudinal fibres  which  extends  along  the  anterior  (ventral)  surface  of  the  bodies  of 
the  vertebra?  from  the  axis  to  the  sacrum.  It  is  broader  below  than  above,  thicker 
in  the  dorsal  than  in  the  cervical  or  lumbar  regions,  and  somewhat  thicker 
opposite  the  front  of  the  body  of  each  vertebra  than  opposite  the  intervertebral 
substance.  It  is  attached,  above,  to  the  body  of  the  axis  by  a  pointed  process, 
where  it  is  continuous  with  the  anterior  atlanto-axial  ligament,  is  connected 
with  the  tendon  of  insertion  of  the  Longus  colli  muscle,  and  extends  down  as  far 
as  the  upper  bone  of  the  sacrum.  It  consists  of  dense  longitudinal  fibres,  which 
are  intimately  adherent  to  the  intervertebral  substance  and  the  prominent  margins 
of  the  vertebrae,  but  less  closely  to  the  middle  of  the  bodies.  In  the  latter 
situation  the  fibres  are  exceedingly  thick,  and  serve  to  fill  up  the  concavities 
on  their  front  surface  and  to  make  the  anterior  surface  of  the  spine  more  even. 
This  ligament  is  composed  of  several  layers  of  fibres,  which  vary  in  length,  but 
are  closely  interlaced  with  each  other.  The  most  superficial  or  longest  fibres 
extend  between  four  or  five  vertebrae.  A  second  subjacent  set  extends  between 
two  or  three  vertebrae,  whilst  a  third  set,  the  shortest  and  deepest,  extends  from 
one  vertebra  to  the  next.  At  the  side  of  the  bodies  the  ligament  consists  of  a 
few  short  fibres,  which  pass  from  one  vertebra  to  the  next,  separated  from  the 
median  portion  by  large  oval  apertures  for  the  passage  of  vessels. 


270 


THE  ARTICULATIONS    OB    JOINTS 


The  Posterior  Common  or  Posterior  Longitudinal  Ligament  (ligamentum  longi- 
tudinale  posterius)  (Figs.  195,  197,  202,  and  203)  is  situated  within  the  spinal 
canal,  and  extends  along  the  posterior  (dorsal)  surface  of  the  bodies  of  the  ver- 
tebrae from  the  body  of  the  axis  above,  where  it  is  continuous  with  the  posterior 


INTERVERTE- 
BFIAL  FIBRO- 
CARTILAGE 


ROOT  OF 
VERTEBRAL 


Fig.  196. — Intervertebral    disk,  with  the    adjacent 
vertebral  bodies,  from  in  front.     (Spalteholz.) 


POSTERIOR   COMMON 
LIGAMENT 

Fig.  195. — Vertebral    bodies    with    ligaments,    from 
behind.      (Spalteholz.) 


occipito-axial  ligament,  to  the  sacrum 
below.  It  can  be  separated  from  the 
posterior  occipito-axial  ligament,  as  is 
shown  in  Fig.  203,  and  may  be  regarded 
as  really  arising  from  the  clivus.  It  is 
broader  above  than  below,  and  thicker  in 
the  dorsal  than  in  the  cervical  or  lumbar 
regions.  In  the  situation  of  the  intervertebral  substance  and  contiguous  margins 
of  the  vertebrie,  where  the  ligament  is  more  intimately  adherent,  it  is  broad,  and 
presents  a  series  of  dentations  with  intervening  concave  margins;  but  it  is  narrow 
and  thick  over  the  centre  of  the  bodies,  from  which  it  is  separated  by  the  vense 
basis  vertebrae.  This  ligament  is  composed  of  smooth,  shining,  longitudinal 
fibres,  denser  and  more  compact  than  those  of  the  anterior  ligament,  and  formed 
of  a  superficial  layer  occupying  the  interval  between  three  or  four  vertebrae,  and 
of  a  deeper  layer  which  extends  between  one  vertebra  and  the  next  adjacent 
to  it.  It  is  separated  from  the  dura  mater  of  the  spinal  cord  by  some  loose 
connective  tissue,  which  is  very  liable  to  serous  infiltration. 

The  Intervertebral  Fibro-cartilages,  Disks,  or  Substances  (fibrocartilagines  inter- 
vertebrales)  (Figs.  196  and  197).— Each  fibrocartilaginous  disk  is  of  lenticular 
form  and  of  composite  structure.  The  disks  are  interposed  between  the  adjacent 
surfaces  of  the  bodies  of  the  vertebrae  from  the  axis  to  the  sacrum,  and  form 
the  chief  bonds  of  connection  between  those  bones.  In  young  children  inter- 
vertebral substance  exists  in  the  coccyx.  These  disks  vary  in  shape,  size,  and 
thickness  in  different  parts  of  the  spine.  In  shape  they  accurately  correspond 
with  the  surfaces  of  the  bodies  between  which  they  are  placed,  being  oval  in  the 
cervical  and  lumbar  regions,  and  circular  in  the  dorsal.  Their  size  is  greatest 
in  the  lumbar  region.  In  thickness  they  vary  not  only  in  the  different  regions 
of  the  spine,  but  in  different  parts  of  the  same  disk:  thus,  they  are  thicker  in 
front  than  behind  in  the  cervical  and  lumbar  regions,  while  they  are  uniformly 
thick  in  the  dorsal  region.  The  intervertebral  disks  form  about  one-fourth  of 
the  spinal  column,  exclusive  of  the  first  two  vertebrae;  they  are  not  equally  dis- 
tributed, however,  between  the  various  bones;  the  dorsal  portion  of  the  spine 


ARTICULATIONS    OF    THE    VERTEBBAL    COLUMN 


271 


having,  in  proportion  to  its  length,  a  much  smaller  quantity  than  in  the  cervical 
and  lumbar  regions,  which  necessarily  gives  to  the  latter  parts  greater  pliancy 
and  freedom  of  movement.  The  intervertebral  disks  are  adherent,  by  their  sur- 
faces, to  a  thin  layer  of  hyaline  cartilage  which  covers  the  upper  and  under  sur- 
faces of  the  bodies  of  the  vertebme,  and  in  which,  in  early  life,  the  epiphysial 
plate  develops,  and  by  their  circinnference  are  closely  connected  in  front  to  the 
anterior,  and  behind  to  the  posterior  common  ligament;  whilst  in  the  dorsal 
region  they  are  connected  laterally,  by  means  of  the  interarticular  ligament,  to 
the  heads  of  those  ribs  which  articulate  with  two  vertebrae;  they,  consequently, 
form  part  of  the  articular  cavities  in  which  the  heads  of  these  bones  are  received. 


POSTERIOR  COMMON 
LIGAMENT 


Fig.  197.- 


-  Median  section  of  a  piece  of  the  lumbar  spinal  column,  right  half  of  sections  viewed  from  the 
left.     (Spalteholz.) 


Structure  of  the  Intervertebral  Substance. — The  outer  portion  of  the  intervertebral 
substance  is  composed  of  many  layers  of  fibrous  connective  tissue.  This  envel- 
oping portion  is  called  the  annulus  fibrosus.  The  central  portion  of  the  disk  is 
composed  of  soft,  pulpy,  highly  elastic  fibro-cartilage,  containing  some  bantls  of 
connective  tissue.  It  is  called  the  nucleus  pulposus,  is  of  a  yellowish  color,  and 
rises  up  considerably  above  the  surrounding  level  when  the  disk  is  divided  hori- 
zontally. This  pulpy  substance,  which  is  especially  well  developed  in  the  lumbar 
region,  is  the  remains  of  the  chorda  dorsalis,  and,  according  to  Luschka,  contains  a 
small  synovial  cavity  in  its  centre.  The  outer  layers  of  the  disk  are  arranged  con- 
centrically one  within  the  other,  the  outermost  consisting  of  ordinary  fibrous  tissue, 
but  the  others  and  more  numerous  consisting  of  white  fibro-cartilage.  These 
plates  are  not  quite  vertical  in  their  direction,  those  near  the  circumference  being 
curved  outward  and  closely  approximated;  whilst  those  nearest  the  centre  curve 
in  the  opposite  direction,  and  are  somewhat  more  widely  separated.  The  fibres  of 
which  each  plate  is  composed  are  directed,  for  the  most  part,  obliquely  from  above 
downward,  the  fibres  of  adjacent  plates  passing  in  opposite  directions  and  varying 
in  every  layer;  so  that  the  fibres  of  one  layer  are  directed  across  those  of  another, 
like  the  limbs  of  the  letter  X.  This  laminar  arrangement  belongs  to  about  the 
outer  half  of  each  disk.  The  pulpy  substance  presents  no  concentric  arrangement, 
and  consists  of  a  fine  fibrous  matrix,  containing  angular  cells,  united  to  form  a 


272 


THE  ARTICULATIONS    OR    JOINTS 


reticular  structure.  J.  Bland  Sutton^  calls  attention  to  the  fact  that  in  the  human 
foetus  a  transverse  ligamentous  band  crosses  the  dorsal  aspect  of  the  intervertebral 
disk  and  is  continuous  with  the  interosseous  ligaments  of  the  heads  of  the  ribs; 
and  also  that  a  foetal  ligamentous  band  exists  in  the  ventral  surface  of  the  inter- 
vertebral disk  which,  after  development,  becomes  the  middle  fasciculus  of  the 
stellate  ligament.  These  bands  are  named  by  Sutton  the  posterior  conjugal 
ligaments  and  the  anterior  conjugal  ligaments. 

Interneural    Articulations   include    the    ligaments  of   the  laminae;   articular 
processes,  spinous  processes,  and  transverse  processes. 


2.  Ligaments  connecting  the  Lamina. 
Ligamenta  Subflava. 

The  Ligamenta  Subflava  {ligamenta  flava,  ligamenta  intercruralia)  (Figs.  197 
and  198)  are  interposed  between  the  laminae  of  the  vertebrae,  from  the  axis  to 
the  sacrum.  They  are  most  distinct  when  seen  from  the  interior  of  the  spinal 
canal;  when  viewed  from  the  outer  surface  they  appear  short,  being  over- 
lapped by  the  laminae.  Each  ligamentum  subflavmn  consists  of  two  lateral 
portions,  which  commence  on  each  side  at  the  root  of  either  articular  process, 
and  pass  backward  to  the  point  where  the  laminae  converge  to  form  the  spi- 
nous process,  where  their  margins  are  in  contact  and  to  a  certain  extent  united; 
slight  intervals  being  left   for  the  passage  of   small  vessels.     These  ligaments 

consist  of  yellow  elastic  tissue,  the 
fibres  of  which,  almost  perpendic- 
ular in  direction,  are  attached  to 
the  anterior  surface  of  the  laminae 
above,  some  distance  from  its  in- 
ferior margin,  and  to  the  posterior 
surface,  as  well  as  to  the  margin 
,of  the  lamina  below.  In  the  cer- 
vical region  they  are  thin  in  tex- 
ture, but  very  broad  and  long; 
they  become  thicker  in  the  dorsal 
region,  and  in  the  lumbar  acquire 
very  considerable  thickness.  Their 
highly  elastic  property  serves  to 
preserve  the  upright  posture  and 
to  assist  in  resuming  it  after  the 
spine  has  been  flexed.  These  liga- 
ments do  not  exist  between  the 
occiput  and  atlas  or  between .  the 
atlas  and  axis. 

3.  Ligaments  connecting   the 
Articular  Processes. 

Capsular  Ligaments. 

The  Capsular  Ligaments  (capsidce 
articidares)  (Fig.  198)  are  thin  and 
loose  ligamentous  sacs,  attached 
to  the  contiguous  margins  of  the  articulating  processes  of  each  vertebra  through 
the  greater  part  of  their  circumference,  and  completed  internally  by  the  ligamenta 


Fig.  198. 


-Vertebral  arches  with  ligamenta  flava. 
(Spalteholz.) 


1  J.  Bland  Sutton.     Ligaments:  Their  Nature  and  Morphology. 


ARTICULATIONS    OF   THE    VERTEBRAL    COLVMN  273 

subflava.  They  are  longer  and  looser  in  the  cervical  than  in  the  dorsal  or  lumbar 
regions.  The  capsular  ligaments  are  lined  on  their  inner  surface  by  synovial 
membrane. 

4.  Ligaments  connecting  the  Spinous  Processes. 

Supraspinous  Ligament.     Interspinous  Ligaments. 

The  Supraspinous  Ligament  {Ugainentum  supraspinale)  (Fig.  197)  is  a  strong 
fibrous  cord,  which  connects  together  the  apices  of  the  spinous  processes  from  the 
seventh  cervical  to  the  spinous  processes  of  the  sacrum.  It  is  thicker  and  broader 
in  the  lumbar  than  in  the  dorsal  region,  and  intimately  blended,  in  both  situa- 
tions, with  the  neighboring  aponeurosis.  The  most  superficial  fibres  of  this 
ligament  connects  three  or  four  vertebrae;  those  deeper-seated  pass  between  two 
or  three  vertebra;  whilst  the  deepest  connect  the  contiguous  extremities  of 
neighboring  vertebrte.  It  is  continued  upward  to  the  external  occipital  protu- 
berance as  the  ligamentum  nuchse,  which,  in  the  human  subject,  is  thin  and 
forms  merely  an  intermuscular  septum. 

The  Interspinous  Ligaments  (ligamenta  interspinalia)  (Fig.  197),  thin  and 
membranous,  are  interposed  between  the  spinous  processes.  Each  ligament 
extends  from  the  root  to  the  summit  of  each  spinous  process  and  connects  together 
their  adjacent  margins.  They  meet  the  ligamenta  subflava  in  front  and  the 
supraspinous  ligament  behind.  They  are  narrow  and  elongated  in  the  dorsal 
region;  broader,  cjuadrilateral  in  form,  and  thicker  in  the  lumbar  region;  and 
only  slightly  developed  in  the  neck. 

5.  Liga:ments  connecting  the  Transverse  Processes. 
Intertransverse  Ligaments. 

The  Intertransverse  Ligaments  (ligamenta  intertransversaria)  (Fig.  210)  consist 
of  bundles  of  fibres  interposed  between  the  transverse  processes.  In  the  cervical 
region  they  consist  of  a  few  irregular,  scattered  fibres;  in  the  dorsal,  they  are 
rounded  cords  intimately  connected  with  the  deep  muscles  of  the  back;  in  the 
lumbar  region  they  are  thin  and  membranous. 

Actions. — The  movements  permitted  in  the  spinal  column  are,  flexion,  exten- 
sion, lateral  movement,  circwmduction,  and  rotation. 

In  flexion  {forward  flexion),  or  movement  of  the  spine  forward,  the  anterior 
common  ligament  is  relaxed,  and  the  intervertebral  substances  are  compressed 
in  front,  while  the  posterior  common  ligament,  the  ligamenta  subflava,  and  the 
inter-  and  supra-spinous  ligaments  are  stretched,  as  well  as  the  posterior  fibres 
of  the  intervertebral  disks.  The  interspaces  between  the  laminae  are  widened, 
and  the  inferior  articular  processes  of  the  vertebrae  above  glide  upward  upon 
the  articular  processes  of  the  vertebrae  below.  Flexion  is  the  most  extensive  of 
all  the  movements  of  the  spine. 

In  extension  (backward  flexion),  or  movement  of  the  spine  backward,  an  exactly 
opposite  disposition  of  the  parts  takes  place.  This  movement  is  not  extensive, 
being  limited  by  the  anterior  common  ligament  and  by  the  approximation  of  the 
spinous  processes. 

Flexion  and  extension  are  free  in  the  lower  part  of  the  lumbar  region  between 
the  third  and  fourth  and  fourth  and  fifth  lumbar  vertebne;  above  the  third 
they  are  much  diminished,  and  reach  their  minimum  in  the  middle  and  upper 
part  of  the  back.  They  increase  again  in  the  neck,  the  capability  of  motion 
backward  from  the  upright  position  being  in  this  region  greater  than  that  of  the 
motion  forward,  whereas  in  the  lumbar  region  the  reverse  is  the  case. 

In  lateral  flexion,  the  sides  of  the  intervertebral  disks  are  compressed,  the 
extent  of  motion  being  limited  by  the  resistance  offered  by  the  surrounding  liga- 

18 


274  '^HE   ARTICULATIONS    OB   JOINTS 

ments  and  by  the  approximation  of  the  transverse  processes.  This  movement 
may  take  place  in  any  part  of  the  spine,  but  is  most  free  in  the  neck  and  loins. 

Circumduction  is  very  limited,  and  is  produced  merely  by  a  succession  of  the 
preceding  movements. 

Rotation  is  produced  by  the  twisting  of  the  intervertebral  substances;  this, 
although  only  slight  between  any  two  vertebrae,  produces  a  considerable  extent  of 
movement  when  it  takes  place  in  the  whole  length  of  the  spine,  the  front  of  the 
upper  part  of  the  column  being  turned  to  one  or  the  other  side.  This  movement 
takes  place  only  to  a  slight  extent  in  the  neck,  but  is  freer  in  the  upper  part  ot 
the  dorsal  region,  and  is  altogether  absent  in  the  lumbar  region. 

It  is  thus  seen  that  the  cervical  region  enjoys  the  greatest  extent  of  each  variety 
of  movement,  flexion  and  extension  especially  being  very  free.  In  the  dorsal 
region  the  three  movements  of  flexion,  extension,  and  circumduction  are  per- 
mitted only  to  a  slight  extent,  while  rotation  is  very  free  in  the  upper  part  and 
ceases  below.  In  the  lumbar  region  there  is  free  flexion,  extension,  and  lateral 
movement,  but  no  rotation. 

As  Sir  George  Humphry  has  pointed  out,  the  movements  permitted  are  mainly 
due  to  the  shape  and  position  of  the  articulating  processes.  In  the  loins  the  infe- 
rior articulating  processes  are  turned  outward  and  are  embraced  by  the  superior; 
this  renders  rotation  in  this  region  of  the  spine  impossible,  while  there  is  nothing 
to  prevent  a  sliding  upward  and  downward  of  the  surfaces  on  each  other,  so  as  to 
allow  of  flexion  and  extension.  In  the  dorsal  region,  on  the  other  hand,  the 
articulating  processes,  by  their  direction  and  mutual  adaptation,  especially  at  the 
upper  part  of  the  series,  permit  of  rotation,  but  prevent  extension  and  flexion, 
while  in  the  cervical  region  the  greater  obliquity  and  lateral  slant  of  the  articular 
processes  allow  not  only  flexion  and  extension,  but  also  rotation. 

The  principal  muscles  which  produce  flexion  are  the  Sterno-mastoid,  Rectus 
capitis  anticus  major,  and  Longus  coUi;  the  Scaleni;  the  abdominal  muscles  and 
the  Psoas  magnus.  Extension  is  produced  by  the  fourth  layer  of  the  muscles 
of  the  back,  assisted  in  the  neck  by  the  Splenius,  Semispinalis  dorsi  et  colli,  and 
the  Multifidus  spinae.  Lateral  motion  is  produced  by  the  fourth  layer  of  the 
muscles  of  the  back,  by  the  Splenius  and  the  Scaleni,  the  muscles  of  one  side  only 
acting;  and  rotation  by  the  action  of  the  following  muscles  of  one  side  only — viz. 
the  Sterno-mastoid,  the  Rectus  capitis  anticus  major,  the  Scaleni,  the  Multifidus 
spinse,  the  Complexus,  and  the  abdominal  muscles. 

II.  Articulation  of  the  Atlas  with  the  Axis  (Articulatio  Atlantoepistrophica). 

The  articulation  of  the  atlas  with  the  axis  is  of  a  complicated  nature,  compris- 
ing no  fewer  than  four  distinct  joints.  There  is  a  pivot  articulation  between  the 
odontoid  process  of  the  axis  and  the  ring  formed  between  the  anterior  arch  of  the 
atlas  and  the  transverse  ligament  (see  Fig.  201).  Here  there  are  two  joints:  one  in 
front  between  the  posterior  surface  of  the  anterior  arch  of  the  atlas  and  the  front 
of  the  odontoid  process,  the  atlanto-odontoid  joint  of  Cruveilhier;  the  other  between 
the  anterior  surface  of  the  transverse  ligament  and  the  back  of  the  process,  the 
syndesmo-odontoid  joint.  Between  the  articular  processes  of  the  two  bones  there 
is  a  double  arthrodia  or  gliding  joint.  The  ligaments  which  connect  these  bones 
are  the 

Anterior  Atlanto-axial.  Transverse. 

Posterior  Atlanto-axial.  Two  Capsular. 

The  Anterior  Atlanto-axial  or  the  Anterior  Atlo-axoid  Ligament  (Figs.  199  and  203) 
is  a  strong,  membranous  layer,  attached,  above,  to  the  lower  border  of  the  anterior, 
arch  of  the  atlas;  below,  to  the  base  of  the  odontoid  process  and  to  the  front  of 


ARTICULATION    OF    THE  ATLAS    WITH    THE  AXIS 


275 


the  body  of  the  axis.  It  is  strengthened  in  the  middle  Kne  by  a  rounded  cord,  which 
is  attached,  above,  to  the  tubercle  on  the  anterior  arch  of  the  atlas,  and  below  to 
the  body  of  the  axis,  being  a  continuation  upward  of  the  anterior  common  liga- 
ment of  the  spine.  Some  anatomists  regard  this  ligament  as  being  a  part  of  the 
anterior  common  ligament.  The  ligament  is  in  relation,  in  front,  with  the  Recti 
antici  majores. 

The  Posterior  Atlanto-axial  or  the  Posterior  Atlo-axoid  Ligament  (Figs.  200  and 
203)  is  a  broad  and  thin  membranous  layer,  attached,  above,  to  the  lower  border 
of  the  posterior  arch  of  the  atlas;  below,  to  the  upper  edge  of  the  laminae  of 
the  axis.  This  ligament  supplies  the  place  of  the  ligamenta  subflava,  and  is 
in  relation,  behind,  with  the  Inferior  oblique  muscles. 

The  Transverse  Ligament  of  the  Atlas^  (ligamentum  transversum  atlantis)  (Figs. 
201,  202,  and  203)  is  a  thick,  strong  band,  which  arches  across  the  ring  of  the 
atlas,  and  serves  to  retain  the  odontoid  process  in  firm  connection  with  its  anterior 
arch.  This  ligament  is  flattened  from  before  backward,  broader  and  thicker  in 
the  middle  than  at  either  extremity,  and  firmly  attached  on  each  side  to  a  small 
tubercle  on  the  inner  surface  of  the  lateral  mass  of  the  atlas.  As  it  crosses  the 
odontoid  process,  a  small  fasciculus  is  derived  from  its  upper,  and  another  from 
its  lower,  border;  the  former  passing  upward,  to  be  inserted  into  the  anterior  sur- 


PHARYNGEAL 
TUBERCLE 


BASILAR  PORTION  OF 
CIPITAL  BONE 


ANTERIOR  OCCIPITO- 
ATLANTAL  LIGAMENT 


ANTERIOR    CONDYLOID 
ORAMEN 


CIPITO-ATLANTAL 
ICULATION 


TRANSVERSE 
PROCESS  OF 
ATLAS 

ANTERIOR    ATLANTO- 
AXIAL LIGAMENT 


JOINT  BETWEEN 

BODY  CF  VERTEBRA 

AND   INTERVER-. 

TEBRAL  FIBRO- 

CARTILAGE 


TRANSVERSE 
PROCESS  OF 
AXIS 


TRANSVERSE  PROCESS 
OF  THIRD  CERVICAL 
VERTEBRA 


INTERVERTEBRAL 
FIBROCARTILAGE 


ANTERIOR  COMMON 
LIGAMENT 


Fig.  199. — Occipital  bone  and  first  three  cervical  vertebrae  with  ligaments,  from  in  front.     (Spalteholz.) 

face  of  the  foramen  magnum  of  the  occipital  bone;  the  latter,  downward,  to  be 
attached  to  the  posterior  surface  of  the  body  of  the  axis;  hence,  the  whole  ligament 
has  received  the  name  of  cruciform  ligament  (ligamentum  cruciatum  atlantis). 
A  synovial  surface  is  interposed  between  the  odontoid  process  and  the  trans- 
verse ligament,  and  one  is  placed  between  the  anterior  surface  of  the  odontoid 
process  and  the  anterior  arch  of  the  atlas.     The  transverse  ligament  divides  the 


'  It  hasi  been  found  necessary  to  describe  the  transverse  ligament  with  those  of  the  atlas  and  axis;  but  the 
student  mu.«t  remember  that  it  is  really  a  portion  of  the  mechanism  by  which  the  movements  of  the  head  on  the 
spine  are  regulated;  so  that  the  connections  between  the  atlas  and  axis  ought  always  to  be  studied  together  with 
those  between  the  latter  bones  and  the  skull. 


276  THE  ARTICULATIONS   OB   JOINTS 

ring  of  the  atlas  into  two  unequal  parts :  of  these,  the  posterior  and  larger  serves 
for  the  transmission  of  the  cord  and  its  membranes  and  the  spinal  accessory 
nerves ;  the  anterior  and  smaller  contains  the  odontoid  process.  Since  the  space 
between  the  anterior  arch  of  the  atlas  and  the  transverse  ligament  is  smaller  at 
the  lower  part  than  the  upper  (because  the  transverse  ligament  embraces  tightly 
the  narrow  neck  of  the  odontoid  process),  this  process  is  retained  in  firm  connec- 
tion with  the  atlas  after  all  the  other  ligaments  have  been  divided. 

The  Capsular  Ligaments  (capsuloB  articulares)  (Figs.  199,  200,  and  202)  are  two 
thin  and  loose  capsules,  connecting  the  lateral  masses  of  the  atlas  with  the  superior 
articular  surfaces  of  the  axis,  the  fibres  being  strengthened  at  the  posterior  and 
inner  part  of  each  articulation  by  an  accessory  ligament,  which  is  attached  below 
to  the  body  of  the  axis  near  the  base  of  the  odontoid  process. 

Synovial  Membranes  (Fig.  201). — There  are  jour  synovial  membranes  in  this 
articulation:  one  lining  the  inner  surface  of  each  of  the  capsular  ligaments;  one 
between  the  anterior  surface  of  the  odontoid  process  and  the  anterior  arch  of 
the  atlas,  the  atlanto-odontoid  joint;  and  one  between  the  posterior  surface  of 
the  odontoid  process  and  the  transverse  ligament,  the  syndesmo-odontoid  joint. 
The  latter  often  communicates  with  those  between  the  condyles  of  the  occipital 
bone  and  the  articular  surfaces  of  the  atlas. 

Actions. — This  joint  allows  the  rotation  of  the  atlas  (and,  with  it,  of  the  cra- 
nium) upon  the  axis,  the  extent  of  rotation  being  limited  by  the  odontoid  ligaments. 

The  principal  muscles  by  which  this  action  is  produced  are  the  Sterno-mastoid 
and  Complexus  of  one  side,  acting  with  the  Rectus  capitis  anticus  major,  Sple- 
nius,  Trachelo-mastoid,  Rectus  capitis  posticus  major,  and  Inferior  oblique  of  the 
other  side. 


ARTICULATIONS  OF  THE  SPINE  WITH  THE  CRANIUM. 

The  ligaments  connecting  the  spine  with  the  cranium  may  be  divided  into  two 
sets — those  connecting  the  occipital  bone  with  the  atlas,  and  those  connecting  the 
occipital  bone  with  the  axis. 

III.  Articulation  of  the  Atlas  with  the  Occipital  Bone  (Articulatio 

Atlantooccipitalis) . 

This  articulation  is  a  double  condyloid  joint.    Its  ligaments  are  the 

Anterior  Occipito-atlantal.  Posterior  Occipito-atlantal. 

Two  Capsular. 

The  Anterior  Occipito-atlantal  Ligament  or  Membrane  (memhrana  atlantooccipitalis 
anterior,  anterior  occipito-atloid  ligament)  (Figs.  199  and  203)  is  a  broad  membra- 
nous layer,  composed  of  densely  woven  fibres,  which  passes  between  the  anterior 
margin  of  the  foramen  magnum  above,  and  the  whole  length  of  the  upper  border 
of  the  anterior  arch  of  the  atlas  below.  Laterally,  it  is  continuous  with  the  cap- 
sular ligaments.  In  the  middle  line  in  front  it  is  strengthened  by  a  strong,  narrow, 
rounded  cord,  which  is  attached,  above,  to  the  basilar  process  of  the  occiput,  and, 
below,  to  the  tubercle  on  the  anterior  arch  of  the  atlas,  and  which  is  a  continua- 
tion of  the  anterior  common  ligament.  This  ligament  is  in  relation,  in  front, 
with  the  Recti  antici  minores;  behind,  with  the  odontoid  ligaments. 

The  Posterior  Occipito-atlantal  Ligament  or  Membrane  (memhrana  atlantooccipitalis 
posterior,  posterior  occipito-atloid  ligament)  (Figs.  200  and  203)  is  a  very  broad  but 
thin  membranous  lamina  intimately  blended  with  the  dura  mater.  It  is  connected, 
above,  to  the  posterior  margin  of  the  foramen  magnum ;  below,  to  the  upper  border 


ARTICULATION  OF  THE  ATLAS  WITH  THE  OCCIPITAL  BONE    277 

of  the  posterior  arch  of  the  atlas.  This  hgament  is  incomplete  at  each  side,  and 
forms,  with  the  superior  intervertebral  notch,  an  opening  for  the  passage  of  the 
vertebral  artery  and  suboccipital  nerve.  The  fibrous  band  which  arches  over  the 
artery  and  nerve  sometimes  becomes  ossified.  The  ligaments  are  in  relation, 
behind,  with  the  Recti  postici  minores  and  Obliqui  superiores;  in  front,  with  the 
dura  mater  of  the  spinal  canal,  to  which  they  are  intimately  adherent. 


POSTERIOR  OC 

CIPITO-ATLANTA 

LIGAMEN 


POSTERIOR 
CIPITO-ATLAN 
LIGAME 


TRANSVERSE 
PROCESS  OF 
ATLAS 


POSTE 
AT  LAN  TO 


Fig.  200. — Occipital  bone,  first  and  second  cervical  vertebra?  with  ligaments  from  behind.     (Spalteholz.) 


The  Capsular  Ligaments  {capsvloB  articvlares)  (Fig.  202)  surround  the  condyles 
of  the  occipital  bone,  and  connect  them  with  the  articular  processes  of  the  atlas; 
they  consist  of  thin  and  loose  capsules,  which  enclose  the  synovial  membranes 
of  the  articulations. 

S3movial  Membranes. — There  are  two  synovial  membranes  in  this  articulation, 
one  lining  the  inner  surface  of  each  of  the  capsular  ligaments.  These  occasionally 
communicate  with  that  between  the  posterior  surface  of  the  odontoid  process  and 
the  transverse  lisament. 


Fig.  201. — Articulation  between  odontoid  process  and  atlas. 

Actions. — The  movements  permitted  in  this  joint  are  flexion  and  extension, 
which  give  rise  to  the  ordinary  forward  and  backward  nodding  of  the  head.  Slight 
lateral  motion  to  one  or  the  other  side  may  also  take  place.  When  either  of  these 
actions  is  carried  beyond  a  slight  extent,  the  whole  of  the  cervical  portion  of  the  spine 
assists  in  its  production.  Flexion  is  mainly  produced  by  the  action  of  the  Rectus 
capitis  anticus  major  et  minor  and  the  Sterno-mastoid  muscles;  extension  by  the 


278 


THE   ARTICULATIONS    OR    JOINTS 


Rectus  capitis  posticus  major  et  minor,  the  Superior  oblique,  the  Complexus,  Sple- 
nius,  and  upper  fibres  of  the  Trapezius.  The  Recti  laterales  are  concerned  in  the 
lateral  movement,  assisted  by  the  Trapezius,  Splenius,  Complexus,  and  the  Sterno- 
mastoid  of  the  same  side,  all  acting  together.  According  to  Cruveilhier,  there  is 
a  slight  motion  of  rotation  in  this  joint. 

rV.  Articulation  of  the  Axis  with  the  Occipital  Bone. 
The  ligaments  of  this  articulation  are  the 

Occipito-axial.         Three  Odontoid. 

To  expose  these  ligaments  the  spinal  canal  should  be  laid  open  by  removing 
the  posterior  arch  of  the  atlas,  the  laminae  and  spinal  process  of  the  axis,  and  the 
portion  of  the  occipital  bone  behind  the  foramen  magnum,  as  seen  in  Fig.  192. 

The  Posterior  Occipito-axial  Ligament  (posterior  occipito-axoid  ligament ,  membrana 
tedoria,  apparatus  ligamentosus  colli)  (Figs.  202  and  203)  is  situated  within  the  spinal 
canal.  It  is  a  broad,  strong  band,  w^hich  covers  the  odontoid  process  and  its  liga- 
ments, and  appears  to  be  a  prolongation  upward  of  or  a  membrane  due  to  fusion 
with  the  posterior  common  ligament  of  the  spine.  It  is  attached,  below,  to  the 
posterior  surface  of  the  body  of  the  axis,  and,  becoming  expanded  as  it  ascends, 
is  inserted  into  the  basilar  groove  of  the  occipital  bone,  in  front  of  the  foramen 
magnum,  where  it  becomes  blended  with  the  dura  mater  of  the  skull. 


Tfie  vertical  portion  of 

ODONTOID    LIQAWENTS. 


CAPSULAR    LIGAMENT 

and  synovial 
membrane. 


fCAPSULAR    LIGAMENT 

(.        membrane. 


Fig.  202. — Occipito-axial  and  atlanto-axial  ligaments.     Posterior  view,  obtained  by  removing  the  arches  of 
the  vertebrce  and  the  posterior  part  of  the  skull. 

Relations. — By  its  anterior  surface  with  the  transverse  ligament;  by  its  posterior 
surface  with  the  posterior  common  ligament. 

The  Lateral  Odontoid  or  Check  Ligaments  (ligamenta  alaria)  (Figs.  202  and  203) 
are  strong,  rounded,  fibrous  cords,  which  arise  one  on  either  side  of  the  upper 
part  of  the  odontoid  process,  and,  passing  obliquely  upward  and  outward,  are 
inserted  into  the  rough  depressions  on  the  inner  side  of  the  condyles  of  the 


ARTICULATION  OF  THE  AXIS    WITH   THE   OCCIPITAL   BONE    279 

occipital  bone.  In  the  triangular  interval  left  between  these  ligaments  another 
strong  fibrous  cord,  ligamentum  suspensorium,  or  middle  odontoid  ligament  {liga- 
mentum  apicis  dentis),  may  be  seen,  which  passes  almost  perpendicularly  from 
the  apex  of  the  odontoid  process  to  the  anterior  margin  of  the  foramen  mag- 
num, being  intimately  blended  with  the  deep  portion  of  the  anterior  occipito- 
atlantal  ligament  and  upper  fasciculus  of  the  transverse  ligament  of  the  atlas. 

Actions. — The  odontoid  ligaments  serve  to  limit  the  extent  to  which  rotation 
of  the  cranium  may  be  carried;  hence,  they  have  received  the  name  of  check 
ligaments. 

In  addition  to  these  ligaments,  which  connect  the  atlas  and  axis  to  the  skull, 
the  ligamentum  nuchse  must  be  regarded  as  one  of  the  ligaments  by  which  the 
spine  is  connected  with  the  cranium.    It  is  described  on  page  273. 

Surgical  Anatomy. — The  ligaments  which  unite  the  component  parts  of  the  vertebrae 
together  are  so  strong,  and  these  bones  are  so  interlocked  by  the  arrangement  of  their  articu- 
lating processes,  that  dislocation  is  very  uncommon,  and,  indeed,  unless  accompanied  by  fracture, 
seldom  occurs,  except  in  the  upper  part  of  the  neck.     Dislocation  of  the  occiput  from  the  atlas 


THIN   LAYER  OF  POSTERIOR  COMMON 
LIGAMENT  SEPARATED  FROM  THE 
POSTERIOR  OCCIPITO-AXIAL  LIGAMENT 


HYPOGLOSSAL 
NERVE 


ANTERIOR  OCCIPITO- 
ATLOID    LIGAMENT 

POSTERIOR   OCCIPITO- 
AXIAL  LIGAMENT 
CRUCIFORM 

LIGAMENT         i    j 
MIDDLE  ODONTOID 
LIGAMENT 

ANTERIOR   ARCH 
OF  ATLAS 
ODONTOID   PROC- 
ESS OF  AXIS 
ARTICULAR 
CAVITY 
TRANSVERSE    LIGA 
MENT  OF  ATLAS 

ANTERIOR  ATLO- 
AXOID    LIGAMENT 


intervertebral 
fibro-cartilage" 


ANTERIOR  COMMON 
LIGAMENT' 


.     B  Q  O^l^' 


POSTERIOR    COMMON 
LIGAMENT 

Fig.  203. — Median  section  through  the  occipital  bone  and  first  three  cervical  vertebrae  with  ligaments. 

(Spalteholz.) 


has  only  been  recorded  in  one  or  two  cases ;  but  dislocation  of  the  atlas  from  the  axis,  with  rup- 
ture of  the  transverse  ligament,  is  much  more  common:  it  is  the  mode  in  which  death  is  produced 
in  many  cases  of  execution  by  hanging.  Occipito-atloid  dislocation  is  certainly  fatal.  Recoveries 
are  on  record  after  atlo-axoid  dislocation.  Immediate  death  occurs  if  the  transverse  ligament 
is  torn  or  the  odontoid  process  is  broken.  In  the  lower  part  of  the  neck — that  is,  below  the 
third  cervical  vertebra — dislocation  unattended  by  fracture  occasionally  takes  place. 


280 


THE    ARTICULATIONS    OB   JOINTS 


V.  Articulation  of  the  Lower  Jaw,  or  the  Temporo-mandibular  Articulation 

(Articulatio  Mandibularis). 

This  is  a  ginglymo-arthrodial  joint:  the  parts  entering  into  its  formation  on 
each  side  are,  above,  the  anterior  part  of  the  glenoid  cavity  of  the  temporal  bone 
and  the  eminentia  articularis;  and,  below,  the  condyle  of  the  lower  jaw.  The 
ligaments  are  the  following: 

External  liateral.  Stylo-mandibular. 

Internal  Lateral.  Capsular. 

Interarticular  Fibro-cartilage. 

The  External  Lateral  Ligament  {ligamentum  temporomandibulare)  (Fig.  204)  is  a 
short,  thin,  and  narrow  fasciculus,  attached,  above,  to  the  outer  surface  of  the  zygoma 
and  to  the  tubercle  on  its  lower  border;  below,  to  the  outer  surface  and  posterior 
border  of  the  neck  of  the  lower  jaw.    It  is  broader  above  than  below;  its  fibres  are 


Fig.  204. — Temporo-mandibular  articulation. 

placed  parallel  with  one  another,  and  directed  obliquely  downward  and  backward. 
Externally,  it  is  covered  by  the  parotid  gland  and  by  the  integument.  Internally 
it  is  in  relation  with  the  capsular  ligament,  of  which  it  is  an  accessory  band,  and 
from  which  it  is  not  separable. 

The  Internal  Lateral  Ligament  (ligamentum  sphenomandibulare)  (Fig.  205)  is  a 
flat,  thin  band  which  is  attached  above  to  the  spinous  process  of  the  sphenoid 
bone,  and,  becoming  broader  as  it  descends,  is  inserted  into  the  margin  of  the 
mandibular  or  dental  fofamen  and  the  portion  of  bone,  the  lingula,  which  over- 
hangs the  foramen  in  front.  Its  outer  surface  is  in  relation,  above,  Avith  the 
External  pterygoid  muscle;  lower  down  it  is  separated  from  the  neck  of  the 
condyle  by  the  internal  maxillary  artery;  and  still  more  inferiorly,  the  inferior 
dental  vessels  and  nerve  separate  it  from  the  ramus  of  the  jaw.  The  inner  surface 
is  in  relation  with  the  Internal  pterygoid.  It  is  really  the  fibrous  covering  of  a 
part  of  Meckel's  cartilage. 


ARTICULATION    OF    THE    LOWER    JAW 


281 


Fig.  205. — Temporo-mandibular  articulation.     Internal  view 


The  Stylo-mandibulax  or  Stylo -maxillary  Ligament  {ligamentum  stylomandihulare) 
(Fig.  205)  is  a  specialized  band  of  the  cervical  fascia,  which  extends  from  near  the 
apex  of  the  styloid  process  of  the  temporal  bone  to  the  angle  and  posterior  border 
of  the  ramus  of  the  lower  jaw,  between  the  Masseter  and  Internal  pterygoid  mus- 
cles. This  ligament  separates  the  parotid  from  the  submaxillary  gland,  and  has 
attached  to  its  inner  side  part  of 
the  fibres  of  origin  of  the  Stylo- 
glossus muscle.  Although  usually 
classed  among  the  ligaments  of  the 
jaw,  it  can  be  considered  only  as 
an  accessory  to  the  articulation. 

The  Capsular  Ligament  (capsida 
articularis)  (Figs.  204  and  205) 
forms  a  thin  and  loose  capsule, 
passing  from  the  circumference  of 
the  glenoid  cavity  and  the  articular 
surface  immediately  in  front  to  the 
upper  margin  of  the  articular  disk, 
and  from  the  lower  margin  of  the 
articular  disk  to  the  neck  of  the 
condyle  of  the  lower  jaw.  It  con- 
sists of  very  thin  fibres,  and  is  com- 
plete. It  forms  two  joint  cavities, 
distinct  from  each  other,  and  sepa- 
rated by  the  articular  disk.  So 
thin  is  it  that  it  is  hardly  to  be 
considered  as  a  distinct  ligament;  it  is  thickest  at  the  back  part,  and  thinnest 
on  the  inner  side  of  the  articulation.* 

The  Interarticular  Fibro-cartilage  or  Meniscus  (discus  articularis)  (Fig.  206)  is  a 
thin  plate  of  an  oval  form,  placed  horizontally  between  the  condyle  of  the  jaw  and 

the  glenoid  cavity.  Its  upper  surface 
is  concavo-convex  from  before  back- 
ward, and  a  little  convex  transversely, 
to  accommodate  itself  to  the  form  of 
the  glenoid  cavity.  Its  under  surface, 
where  it  is  in  contact  with  the  con- 
dyle, is  concave.  Its  circumference  is 
connected  to  the  capsular  ligament, 
and  in  front  to  the  tendon  of  the  Ex- 
ternal pterygoid  muscle.  It  is  thicker 
at  its  circumference,  especially  be- 
hind, than  at  its  centre.  The  fibres 
of  which  it  is  composed  have  a  con- 
centric arrangement,  more  apparent 
at  the  circumference  than  at  the 
centre.  Its  surfaces  are  smooth.  It  divides  the  joint  into  two  cavities,  each 
of  which  is  furnished  with  a  separate  synovial  membrane  from  the  capsular 
ligament. 

Synovial  Membranes  (Fig.  206) . — The  synovial  membranes,  two  in  number,  are 
placed,  one  above,  and  the  other  below,  the  fibro-cartilage.  The  upper  one,  the 
larger  and  looser  of  the  two,  is  continued  from  the  margin  of  the  cartilage  covering 


Fig.  206. — Vertical  section  of  temporo-mandibular 
articulation. 


'  Sir  G.  Humphry  describes  the  internal  portion  of  the  capsular  lijjament  .separately  as  the  short  internal  lateral 
ligament:  and  it  certainly  seems  as  deserving  of  a  separate  description  as  is  the  external  lateral  ligament. 


282  THE  ARTICULATIONS    OB   JOINTS 

the  glenoid  cavity  and  eminentia  articularis  on  to  the  upper  surface  of  the  fibro- 
cartilage.  The  lower  one  passes  from  the  under  surface  of  the  fibro-cartilage  to 
the  neck  of  the  condyle  of  the  jaw,  being  prolonged  downward  a  little  farther 
behind  than  in  front.  The  interarticular  cartilage  is  sometimes  perforated  in  its 
centre;  the  two  synovial  sacs  then  communicate  with  each  other. 

The  nerves  of  this  joint  are  derived  from  the  auriculo-temporal  and  masseteric 
branches  of  the  inferior  maxillary.  The  arteries  are  derived  from  the  temporal 
branch  of  the  external  carotid. 

Actions. — The  movements  possible  in  this  articulation  are  very  extensive.  Thus, 
the  jaw  may  be  depressed  or  elevated,  or  it  may  be  carried  forward  or  backward. 
It  must  be  borne  in  mind  that  there  are  two  distinct  joints  in  this  articula- 
tion— that  is  to  say,  one  between  the  condyle  of  the  jaw  and  the  interarticular 
fibro-cartilage,  and  another  between  the  fibro-cartilage  and  the  glenoid  fossa; 
when  the  jaw  is  depressed,  as  in  opening  the  mouth,  the  movements  which  take 
place  in  these  two  joints  are  not  the  same.  In  the  lower  compartment,  that  between 
the  condyle  and  the  fibro-cartilage,  the  movement  is  of  a  ginglymoid  or  hinge-like 
character,  the  condyle  rotating  on  a  transverse  axis  on  the  fibro-cartilage;  while  in 
the  upper  compartment  the  movement  is  of  a  gliding  character,  the  fibro-cartilage, 
together  with  the  condyle,  gliding  forward  on  to  the  eminentia  articularis.  These 
two  movements  take  place  simultaneously — the  condyle  and  fibro-cartilage  move 
forward  on  the  eminence,  and  at  the  same  time  the  condyle  revolves  on  the  fibro- 
cartilage.  In  the  opposite  movement  of  shutting  the  mouth  the  reverse  action  takes 
place;  the  fibro-cartilage  glides  back,  carrying  the  condyle  with  it,  and  this  at  the 
same  time  revolves  back  to  its  former  position.  When  the  jaw  is  carried  horizon- 
tally forward,  as  in  protruding  the  lower  incisors  in  front  of  the  upper,  the  move- 
ment takes  place  principally  in  the  upper  compartment  of  the  joint:  the  fibro- 
cartilage,  carrying  with  it  the  condyle,  glides  forward  on  the  glenoid  fossa.  This 
is  because  this  movement  is  mainly  effected  by  the  External  pterygoid  muscles, 
which  are  inserted  into  both  condyle  and  interarticular  fibro-cartilage.  The  grind- 
ing or  chewing  movement  is  produced  by  the  alternate  movement  of  one  condyle, 
with  its  fibro-cartilage,  forward  and  backward,  while  the  other  condyle  moves 
simultaneously  in  the  opposite  direction;  at  the  same  time  the  condyle  undergoes  a 
vertical  rotation  on  its  own  axis  on  the  fibro-cartilage  in  the  lower  compartment. 
One  condyle  advances  and  rotates,  the  other  condyle  recedes  and  rotates,  in  alter- 
nate succession. 

The  lower  jaw  is  depressed  by  its  own  weight,  assisted  by  the  Platysma,  the 
Digastric,  the  Mylo-hyoid,  and  the  Genio-hyoid  muscles.  It  is  elevated  by  the 
anterior  part  of  the  Temporal,  Masseter,  and  Internal  pterygoid.  It  is  drawn  for- 
ward by  the  simultaneous  action  of  the  External  pterygoid  and  the  superficial  fibres 
of  the  Masseter;  and  it  is  drawn  backward  by  the  deep  fibres  of  the  Masseter  and 
the  posterior  fibres  of  the  Temporal  muscle.  The  grinding  movement  is  caused  by 
the  alternate  action  of  the  two  External  pterygoids. 

Surface  Form. — The  temporo-mandibular  articulation  is  quite  superficial,  situated  below  the 
base  of  the  zygoma,  in  front  of  the  tragus  and  external  auditory  meatus,  and  behind  the  poste- 
rior border  of  the  upper  part  of  the  Masseter  muscle.  Its  exact  position  can  be  at  once  ascer- 
tained by  feehng  for  the  condyle  of  the  jaw,  the  working  of  which  can  be  distinctly  felt  in  the 
movements  of  the  lower  jaw  in  opening  and  shutting  the  mouth.  When  the  mouth  is  opened 
wide,  the  condyle  advances  out  of  the  glenoid  fossa  on  to  the  eminentia  articularis,  and  a  depres- 
sion is  felt  in  the  situation  of  the  joint. 

Surgical  Anatomy.— Genuine  dislocation  of  the  lower  jaw  is  always  forward.  Croker, 
Kmg,  and  Theim,  however,  have  reported  posterior  displacement.  Dislocation  is  caused  by 
violence  or  muscular  action.  When  the  mouth  is  open,  the  condyle  is  situated  on  the  eminentia 
articularis,  and  any  sudden  violence,  or  even  a  sudden  muscular  spasm,  as  during  a  convulsive 
yawn,  may  displace  the  condyle  forward  into  the  zygomatic  fossa.  The  displacement  may  be 
unilateral  or  bilateral,  according  as  one  or  both  of'  the  condyles  are  displaced.     The  latter  of 


ARTICULATIONS    OF   THE   BIBS    WITH    THE    VERTEBRA    283 

the  two  is  the  more  common.     The  interarticular  fibro-cartilage  adheres  to  the  condyle  till  it 
passes  over  the  eminentia  articularis,  but  at  this  point  remains  behind. 

Sir  Astley  Cooper  described  a  condition  which  he  termed  "subluxation."  It  occurs  princi- 
pally in  delicate  women,  and  is  believed  by  some  to  be  due  to  the  relaxation  of  the  ligaments, 
permitting  too  free  movement  of  the  bone.  Others  believe  it  is  due  to  displacement  of  the  inter- 
articular fibro-cartilage.  Still  others  attribute  the  symptoms  to  gouty  or  rheumatic  changes  in 
the  joint.  In  close  relation  to  the  condyle  of  the  jaw  is  the  external  auditory  meatus  and  the 
tympanum;  any  force,  therefore,  applied  to  the  bone  is  liable  to  be  attended  with  damage  to 
these  parts,  or  inflammation  in  the  joint  may  extend  to  the  ear,  or  on  the  other  hand  inflam- 
mation of  the  middle  ear  may  involve  the  articulation  and  cause  its  destruction,  thus  leading 
to  ankylosis  of  the  joint.  In  children,  arthritis  of  this  joint  may  follow  the  exanthemata,  and 
in  adults  it  occurs  as  the  result  of  some  constitutional  conditions,  as  rheumatism  or  gout.  The 
temporo-mandibular  joint  is  also  occasionally  the  seat  of  osteo-arthritis,  leading  to  great  suffer- 
ing during  efforts  of  mastication.  A  peculiar  affection  sometimes  attacks  the  neck  and  condyle 
of  the  lower  jaw,  consisting  in  hypertrophy  and  elongation  of  these  parts  and  consequent  protru- 
sion of  the  chin  to  the  opposite  side. 

VI.  Articulations  of    the  Ribs  with  the  Vertebrse  or  the  Costo-vertebral 
Articulations  (Articulationes  Costovertebrales). 

The  articulations  of  the  ribs  with  the  vertebral  column  may  be  divided  into 
two  sets:  1.  Those  which  connect  the  heads  of  the  ribs  with  the  bodies  of  the 
vertebrae;  costo-central.  2.  Those  which  connect  the  necks  and  tubercles  of  the 
ribs  with  the  transverse  processes;  costo-transverse. 

1.  Articulations   between  the  Heads  of  the  Ribs  and  the  Bodies  of 
THE  Vertebra  or  the  Costo-central  Articulations  (Articu- 
lationes Capitulorum)  (Figs.  207  and  208). 

These  constitute  a  series  of  arthrodial  joints,  formed  by  the  articulation  of  the 
heads  of  the  ribs  with  the  cavities  on  the  contijiuous  margins  of  the  bodies  of  the 


FOVEA  COSTALIS 
TRANSVERSALIS 


rNTCRVERTEBRAL 
FIBROCARTILAGC 


Fig.  207. — Spinal  column  with  ligament,  from  in  front.     (Spalteholz.) 


284 


THE  ARTICULATIONS    OB   JOINTS 


INTEBARTICULAR   LIGA- 
MENT OF  HEAD  OF  RIB 


dorsal  vertebrae  and  the  intervertebral  substance  between  them,  except  in  the  case 
of  the  first,  tenth,  eleventh,  and  twelfth  ribs,  where  the  cavity  is  formed  by  a  single 
vertebra.    The  bones  are  connected  by  the  following  ligaments: 

Anterior  Costo-vertebral  or  Stellate. 
Capsular.  Interarticular. 

The  Anterior  Costo-vertebral  or  Stellate  Ligament  {ligamentum  capitvli  costcB  radi- 
atum)  (Figs.  207  and  210)  connects  the  anterior  part  of  the  head  of  each  rib  with  the 
sides  of  the  bodies  of  two  vertebrae  and  the  intervertebral  disk  between  them.  It 
consists  of  three  flat  bundles  of  ligamentous  fibres,  which  are  attached  to  the  ante- 
rior part  of  the  head  of  the  rib,  just  beyond  the  articular  surface.     The  superior 

fibres  pass  upward  to  be  con- 
nected with  the  body  of  the 
vertebra  above;  the  inferior 
one  descends  to  the  body  of 
the  vertebra  below;  and  the 
middle  one,  the  smallest  and 
least  distinct,  passes  horizon- 
tally inward,  to  be  attached 
to  the  intervertebral  sub- 
stance. 

Relations. — In  front,  with 
the  thoracic  ganglia  of  the 
sympathetic,  the  pleura,  and, 
on  the  right  side,  with  the  vena 
azygos  major;  behind,  with 
the  interarticular  ligament 
and  synovial  membranes. 

On  the  first  rib,  which 
articulates  with  a  single  ver- 
tebra, this  ligament  does  not 
present  a  distinct  division 
into  three  fasciculi ;  its  fibres, 
however,  radiate,  and  are  at- 
tached to  the  body  of  the  last  cervical  vertebra,  as  well  as  to  the  body  of  the 
vertebra  with  which  the  rib  articulates.  In  the  tenth,  eleventh,  and  twelfth  ribs 
also,  which  likewise  articulate  with  a  single  vertebra,  the  division  does  not  exist; 
but  the  fibres  of  the  ligament  in  each  case  radiate  and  are  connected  with  the 
vertebra  above,  as  well  as  that  with  which  the  ribs  articulate. 

The  Capsular  Ligament  (capsula  articularis)  is  a  thin  and  loose  ligamentous  bag, 
which  surrounds  the  joint  between  the  head  of  the  rib  and  the  articular  cavity 
formed  by  the  intervertebral  disk  and  the  adjacent  vertebra.  It  is  very  thin, 
firmly  connected  with  the  anterior  ligament,  and  most  distinct  at  the  upper  and 
lower  parts  of  the  articulation.  Behind,  some  of  its  fibres  pass  through  the  inter- 
vertebral foramen  to  the  back  of  the  intervertebral  disk.  This  is  the  analogue  of 
the  ligamentum  conjugale  of  some  mammals,  which  unites  the  heads  of  opposite 
ribs  across  the  back  of  the  intervertebral  disk. 

The  Interarticular  Ligament  {ligamentum  capituli  costce  interarticulare)  (Figs.  208 
and  209)  is  situated  in  the  interior  of  the  joint.  It  consists  of  a  short  band  of 
fibres,  flattened  from  above  downward,  attached  by  one  extremity  to  the  sharp 
crest  which  separates  the  two  articular  facets  on  the  head  of  the  rib,  and  by  the 
other  to  the  intervertebral  disk.  It  divides  the  joint  into  two  cavities,  which 
have  no  communication  with  each  other.     In  the  first,  tenth,  eleventh,  and 


Fig.  208.— Ribs  and  corresponding  vertebral  bodies  with  their 
ligaments,  viewed  from  the  right.    (Spalteholz.) 


ARTICULATIONS    OF    THE  BIBS    WITH   THE    VEBTEBBjE    285 

twelfth  ribs  the  interarticular  ligament  does  not  exist;  consequently  there  is  but 
one  synovial  membrane. 

Synovial  Membranes  (Figs.  208  and  209). — There  are  hoo  synovial  membranes 
in  each  of  the  articulations  in  which  there  is  an  interarticular  hgament,  one  on 
each  side  of  this  structure. 


2.  Articulations  of  the  Necks  and  Tubercles  of  the  Ribs  with   the 

Transverse  Processes  or  the  Costo-transverse  Articulations 

(Articulationes  Costotransversari^)  (Fig.  209). 

The  articular  portion  of  the  tubercle  of  the  rib  and  adjacent  transverse  process 
form  an  arthrodial  joint. 

In  the  eleventh  and  twelfth  ribs  this  articulation  is  wanting. 
The  ligaments  connecting  these  parts  are  the 


Anterior  Superior  Costo-transverse. 
Middle  Costo-transverse  (Interosseous). 


Posterior  Costo-transverse 
Capsular. 


The  Anterior  Superior  or  Long  Costo-traiisverse  Ligament  (ligamentum  costo- 
transversarium  anterius)  (Figs.  207,208,209,  and  210)  consists  of  two  sets  of  fibres: 
the  one  (anterior)  is  attached   below  to   the  sharp  crest  on   the   upper  border 


Fig.  209. — Costo-transverse  articulation.     Seen  from  above. 

of  the  neck  of  each  rib,  and  passes  obliquely  upward  and  outward  to  the  lower 
border  of  the  transverse  process  immediately  above;  the  other  (posterior)  is 
attached  below  to  the  neck  of  the  rib,  and  passes  upward  and  inward  to  the  base 
of  the  transverse  process  and  outer  border  of  the  lower  articular  process  of  the 
vertebra  above.  This  ligament  is  in  relation,  in  front,  with  the  intercostal  vessels 
and  nerves;  behind,  with  the  Longissimus  dorsi  muscle.  Its  internal  border  is 
thickened  and  free,  and  bounds  an  aperture  through  which  pass  the  posterior 
branches  of  the  intercostal  vessels  and  nerves.  Its  external  border  is  continuous 
with  a  thin  aponeurosis  which  covers  the  External  intercostal  muscle. 

The  first  rib  has  no  anterior  costo-transverse  ligament.    In  the  twelfth  rib  the 
ligament  is  absent  or  is  a  mere  vestige. 


286 


THE  ARTICULATIONS    OB    JOINTS 


ARTICULAR  SURFACE 

FOR    TUBCRCLE  W 
OF  RIB 


ANTERIOR 
COSTO-TRANS- 
VERSE    LIGAMENT 
INTERTRANS- 
VERSE  LIGAMENT 


5  SUPERIOR  ARTICULAR 
.n  SURFACE   FOR  HEAD 


INTERVERTE- 
BRAL FIBRO- 
CARTILAGE 


The  Middle  Costo-transverse  or  Interosseous  Ligament  (ligamentum  colli  costoe) 
(Fig.  209)  consists  of  short  but  strong  fibres  which  pass  between  the  rough  sur- 
face on  the  posterior  part  of  the  neck  of  each  rib  and  the  anterior  surface  of  the 
adjacent  transverse  process.  In  order  fully  to  expose  this  ligament,  a  horizontal 
section  should  be  made  across  the  transverse  process  and  corresponding  part  of 
the  rib;  or  the  rib  may  be  forcibly  separated  from  the  transverse  process  and  the 
fibres  of  the  ligament  put  on  the  stretch. 

In  the  eleventh  and  twelfth  ribs  this  ligament  is  quite  rudimentary  or  wanting. 

The  Posterior  Costo-transverse  Ligament  (ligamentumcostotransversarium  posterius) 

(Fig.  209)  is  a  short  but  thick  and  strong  fasciculus  which  passes  obliquely  from  the 

summit  of  the  transverse 
*'^^'^'  process  to  the  rough  non- 

articular  portion  of  the 
tubercle  of  the  rib.  This 
ligament  is  shorter  and 
more  oblique  in  the  upper 
than  in  the  lower  ribs. 
Those  corresponding  to 
the  superior  ribs  ascend, 
while  those  of  the  inferior 
ribs  descend  slightly. 

In  the  eleventh  and 
twelfth  ribs  this  ligament 
is  wanting. 

The  Capsular  Ligament 
(capsula  articularis)  is  a 
thin,  membranous  sac  at- 
tached to  the  circumfer- 
ence of  the  articulari  sur- 
faces, and  enclosing  a 
small  synovial  membrane. 
In  the  eleventh  and 
twelfth  ribs  this  ligament 
is  absent. 

Actions. — The  heads  of 
the  ribs  are  so  closely 
connected  to  the  bodies 
of  the  vertebrae  by  the 
stellate  and  interarticular 
ligaments,  and  the  necks 
and  tubercles  of  the  ribs  to  the  transverse  processes,  that  only  a  slight  sliding 
movement  of  the  articular  surfaces  on  each  other  can  take  place  in  these  articula- 
tions. The  result  of  this  gliding  movement  with  respect  to  the  six  upper  ribs  con- 
sists in  an  elevation  of  the  front  and  middle  portion  of  the  rib,  the  hinder  part 
being  prevented  from  performing  any  upward  movement  by  its  close  connection 
with  the  spine.  In  this  gliding  movement  the  rib  rotates  on  an  axis  corresponding 
with  a  line  drawn  through  the  two  articulations,  costo-central  and  costo-transverse, 
which  the  rib  forms  with  the  spine.  With  respect  to  the  seventh,  eighth,  ninth,  and 
tenth  ribs,  each  one,  besides  rotating  in  a  similar  manner  to  the  upper  six,  also 
rotates  on  an  axis  corresponding  with  a  line  drawn  from  the  head  of  the  rib  to  the 
sternum.  By  the  first  movement — that  of  rotation  of  the  rib  on  an  axis  correspond- 
ing with  a  line  drawn  through  the  two  articulations  which  this  bone  forms  with 
the  spine — an  elevation  of  the  anterior  part  of  the  rib  takes  place,  and  a  consequent 
enlargement  of  the  antero-posterior  diameter  of  the  chest.     None  of  the  ribs  lie  in 


Fig. 


INFERIOR   ARTICULAR 
SURFACE  FOR  HEAD 
OF  RIB 
INFERIOR  ARTIC- 
ULAR   PROCESS 

210. — Ribs  and  corresponding  vertebrae  with  ligaments,  viewed 
from  the  right.      (Spalteholz.) 


ARTICULATION   OF   CARTILAGES    OF  BIBS   WITH   STEBNUM    287 


a  truly  horizontal  plane;  they  are  all  directed  more  or  less  obliquely,  so  that  their 
anterior  extremities  lie  on  a  lower  level  than  their  posterior,  and  this  obliquity 
increases  from  the  first  to  the  seventh,  and  then  again  decreases.  If  we  examine 
any  one  rib — say,  that  in  which  there  is  the  greatest  obliquity— we  shall  see  that 
it  is  obvious  that  as  its  sternal  extremity  is  carried  upward,  it  must  also  be  thrown 
forward ;  so  that  the  rib  may  be 
regarded  as  a  radius  moving  on 
the  vertebral  joint  as  a  centre,  and 
causing  the  sternal  attachment  to 
describe  an  arc  of  a  circle  in  the 
vertical  plane  of  the  body.  Since 
all  the  ribs  are  oblique  and  con- 
nected in  front  to  the  sternum  by 
the  elastic  costal  cartilages,  they 
must  have  a  tendency  to  thrust 
the  sternum  forward,  and  so  in- 
crease the  antero-posterior  diam- 
eter of  the  chest.  By  the  second 
movement — that  of  the  rotation 
of  the  rib  on  an  axis  correspond- 
ing with  a  line  drawn  from  the 
head  of  the  rib  to  the  sternum — 
an  elevation  of  the  middle  portion 
of  the  rib  takes  place,  and  conse- 
quently an  increase  in  the  trans- 
verse diameter  of  the  chest.  For 
the  ribs  not  only  slant  downward 
and  forward  from  their  vertebral 
attachment,  but  they  are  also  ob- 
lique in  relation  to  their  transverse 
plane — that  is  to  say,  their  middle 
is  on  a  lower  level  than  either 
their  vertebral  or  sternal  extremi- 
ties. It  results  from  this  that  when 
the  ribs  are  raised,  the  centre  por- 
tion is  thrust  outward,  somewhat 
after  the  fashion  in  which  the 
handle  of  a  bucket  is  thrust  away 
from  the  side  when  raised  to  a 
horizontal  position,  and  the  lateral 
diameter  of  the  chest  is  increased 
(see  Fig.  21 1).  The  mobility  of  the  different  ribs  varies  very  much.  The  first  rib 
is  more  fixed  than  the  others,  on  account  of  the  weight  of  the  upper  extremity  and 
the  strain  of  the  ribs  beneath ;  but  on  the  freshly  dissected  thorax  it  moves  as  freely 
as  the  others.  From  the  same  causes  the  movement  of  the  second  rib  is  also  not 
very  extensive.  In  the  other  ribs  this  mobility  increases  successively  down  to  the 
last  two,  which  are  very  movable.  The  ribs  are  generally  more  movable  in  the 
female  than  in  the  male. 

VII.  Articulation  of  the  Cartilages  of  the  Ribs  with  the  Sternum,  etc.,  or 

the  Costo-stemal  Articulations  (Articulationes 

Stemocostales)   (Fig.  212). 

The  articulations  of  the  cartilages  of  the  true  ribs  with  the  sternum  are  arthro- 
dial  joints,  with  the  exception  of  the  first,  in  which  the  cartilage  is  almost  always 


Fig.  211. — Diagrams  showing  the  axis  of  rotation  of  the 
ribs  in  the  movements  of  respiration.  The  one  axis  of  rota- 
tion corresponds  with  the  line  drawn  through  the  two  articu- 
lations which  the  rib  forms  with  the  spine  (a,  b),  and  the  other 
with  a  line  drawn  from  the  head  of  the  rib  to  the  sternum 
{A,  B).     (From  Kirke's  Handbook  of  Physiology.) 


288  THE  ARTICULATIONS   OR   JOINTS 

directly  united  with  the  sternum,  and  which  must  therefore  be  regarded  as  a 
synarthrodia!  articulation.     The  ligaments  connecting  them  are  the 

Anterior  Chondro-sternal.  Capsular. 

Posterior  Chondro-sternal.  Interarticular  Chondro-sternal. 

Chondro-xiphoid. 

The  Anterior  Chondro-sternal  or  Stemo-costal  Ligament  (ligamentum  sternocostale 
radiatum)  (Fig.  212)  is  a  broad  and  thin  membranous  band  that  radiates  from 
the  front  of  the  inner  extremity  of  the  cartilages  of  the  true  ribs  to  the  anterior 
surface  of  the  sternum.  It  is  composed  of  fasciculi  which  pass  in  different  direc- 
tions. The  superior  fasciculi  ascend  obliquely,  the  inferior  fasciculi  pass  obliquely 
downward,  and  the  middle  fasciculi  pass  horizontally.  The  superficial  fibres  of  this 
ligament  are  the  longest:  they  intermingle  with  the  fibres  of  the  ligaments  above 
and  below  them,  with  those  of  the  opposite  side,  and  with  the  tendinous  fibres  of 
origin  of  the  Pectoralis  major,  forming  a  thick  fibrous  membrane  which  covers 
the  surface  of  the  sternum  {memhrana  sterni).  This  is  more  distinct  at  the  lower 
than  at  the  upper  part.  According  to  the  modern  nomenclature,  this  ligament 
and  the  posterior  chondro-sternal  ligament  are  called  ligamenta  stemocostalia 
radiata.  The  two  chondro-sternal  ligaments  form  a  sheath  for  the  sternum 
anteriorly  and  posteriorly,  the  membrana  sterni. 

The  Posterior  Chondro-sternal  or  Stemo-costal  Ligament  {ligamentum  sterno- 
costale radiatum),  less  thick  and  distinct  than  the  anterior,  is  composed  of  fibres 
which  radiate  from  the  posterior  surface  of  the  sternal  end  of  the  cartilages  of 
the  true  ribs  to  the  posterior  surface  of  the  sternum,  becoming  blended  with  the 
periosteum. 

The  Capsular  Ligament  (capsida  articidaris)  surrounds  the  joint  formed  between 
the  cartilage  of  a  true  rib  and  the  sternum.  It  is  very  thin,  intimately  blended 
with  the  anterior  and  posterior  Hgaments,  and  strengthened  at  the  upper  and  lower 
part  of  the  articulation  by  a  few  fibres  which  pass  from  the  cartilage  to  the  side 
of  the  sternum.    These  ligaments  protect  the  synovial  membranes. 

The  Interarticular  Chondro-sternal  or  Sterno-costal  Ligament  {ligamentum  sterno- 
costale interarticuLare)  (Fig,  212). — This  is  found  between  the  second  costal  car- 
tilage and  the  sternum.  The  cartilage  of  the  second  rib  is  connected  with  the 
sternum  by  means  of  an  interarticular  ligament  attached  by  one  extremity  to  the 
cartilage  of  the  second  rib,  and  by  the  other  extremity  to  the  cartilage  which  unites 
the  first  and  second  pieces  of  the  sternum.  This  articulation  is  provided  with  tioo 
synovial  membranes.  The  cartilage  of  the  third  rib  is  also  connected  with  the  ster- 
num by  means  of  an  interarticular  ligament  which  is  attached  by  one  extremity  to 
the  cartilage  of  the  third  rib,  and  by  the  other  extremity  to  the  point  of  junction 
of  the  second  and  third  pieces  of  the  sternum.  This  articulation  may  be  provided 
with  two  synovial  membranes.  In  the  other  joints  interarticular  ligaments  may 
exist,  but  they  rarely  completely  divide  the  joint  into  two  cavities. 

The  Anterior  Chondro-xiphoid  or  Costo-xiphoid  Ligament  {ligamentum  costo- 
xiphoidea)  (Fig.  212). — This  is  a  band  of  ligamentous  fibres  which  connects 
the  anterior  surface  of  the  seventh  costal  cartilage,  and  occasionally  also  that 
of  the  sixth,  to  the  anterior  surface  of  the  ensiform  appendix.  It  varies  in 
length  and  breadth  in  different  subjects.  A  similar  band  of  fibres  on  the  inter- 
nal or  posterior  surface,  though  less  thick  and  distinct,  may  be  demonstrated. 
It  is  spoken  of  as  the  posterior  chondro-xiphoid  or  costo-xiphoid  ligament. 

Synovial  Membranes  (Fig.  212). — There  is  no  synovial  membrane  between  the 
first  costal  cartilage  and  the  sternum,  as  this  cartilage  is  directly  continuous  with 
the  sternum.  There  are  two  synovial  membranes,  both  in  the  articulation  of  the 
second  and  third  costal  cartilages  to  the  sternum.  There  is  generally  one  syno- 
vial membrane  in  each  of  the  joints  between  the  fourth,  fifth,  sixth,  and  seventh 


ARTICULATION    OF   CARTILAGES    OF  RIBS    WITH  STERNUM    289 

costal  cartilages  to  the  sternum;  but  it  is  sometimes  absent  in  the  sixth  and 
seventh  chondro-sternal  joints.  Thus  there  are  usually  eight  synovial  cavities  on 
each  side  in  the  articulations  between  the  costal  cartilages  of  the  true  ribs  and 
the  sternum.     After  middle  life  the  articular  surfaces  lose  their  polish,  become 


Fig.  212. — Sternum  and  ribs  with  ligaments,  from  in  front.  In  the  left  half  of  the  figure  the  most  anterior 
layer  has  been  removed  and  the  joint  sUts  have  been  opened  ;  the  parts  are  separated  somewhat  from  one 
another  on  the  left  side.     (Spalteholz.) 

roughened,  and  the  synovial  membranes  appear  to  be  wanting.  In  old  age  the 
articulations  do  not  exist,  the  cartilages  of  most  of  the  ribs  becoming  continuous 
with  the  sternum. 

Actions. — The  movements  which  are  permitted  in  the  chondro-sternal  articu- 
lations are  limited  to  elevation  and  depression,  and  these  only  to  a  slight  extent. 

Articulations  of  the  Cartilages  of  the  Ribs  with  Each  Other  or  the  Inter- 
chondral   Articulations    (articidationes   interchondrales)   (Fig.  212). — The  con- 

19 


290  THE   ARTICULATIONS    OB   JOINTS 

tiguous  borders  of  the  sixth,  seventh,  and  eighth,  and  sometimes  the  ninth  and 
tenth,  costal  cartilages  articulate  with  each  other  by  small,  smooth,  oblong-shaped 
facets.  Each  articulation  is  enclosed  in  a  thin  capsular  ligament  lined  by  syno- 
vial membrane,  and  strengthened  externally  and  internally  by  ligamentous  fibres, 
external  and  internal  interchondral  ligaments  {ligamenta  intercostalia  externa  et 
interna),  which  pass  from  one  cartilage  to  the  other.  Sometimes  the  fifth  costal 
cartilao-e,  more  rarely  that  of  the  ninth,  articulates,  by  its  lower  border,  with  the 
adjoining  cartilage  by  a  small  oval  facet;  more  frequently  they  are  connected 
too-ether  by  a  few  ligamentous  fibres.  Occasionally  the  articular  surfaces  above 
mentioned  are  wanting. 

Articulations  of  the  Ribs  with  their  Cartilages  or  the  Costo-chondral 
Articulations  (Fig.  212). — The  outer  extremity  of  each  costal  cartilage  is  re- 
ceived into  a  depression  in  the  sternal  ends  of  the  ribs,  and  the  two  are  held 
together  by  the  periosteum.  There  is  no  real  joint.  Occasionally  a  synovial 
membrane  exists  between  the  first  rib  and  the  corresponding  cartilage. 

VIII.  Articulations  of  the  Sternum  (Fig.  212). 

The  first  piece  of  the  sternum  is  united  to  the  second  either  by  an  amphi- 
arthrodial  joint — a  single  piece  of  true  fibro-cartilage  uniting  the  segments — or 
by  a  diarthrodial  joint,  in  which  each  bone  is  clothed  with  a  distinct  lamina  of 
cartilage,  adherent  on  one  side,  free  and  lined  with  synovial  membrane  on  the 
other.  In  the  latter  case  the  cartilage  covering  the  gladiolus  is  continued  without 
interruption  on  to  the  cartilages  of  the  second  ribs.  Mr.  Rivington  has  found  the 
diarthrodial  form  of  joint  in  about  one-third  of  the  specimens  examined  by  him; 
Mr.  Maisonneuve  more  frequently.  It  appears  to  be  rare  in  childhood,  and  is 
formed,  in  Mr.  Rivington's  opinion,  from  the  amphiarthrodial  form  by  absorption. 
The  diarthrodial  joint  seems  to  have  no  tendency  to  ossify  at  any  age,  while  the 
amphiarthrodial  is  more  liable  to  do  so,  and  has  been  found  ossified  as  early  as 
thirty-four  years  of  age.  Professor  Cunningham^  says :  "It  is  not  usual  to  find  the 
manubri-gladiolar  joint  obliterated  by  the  ossification  of  the  two  bony  segments. 
Even  in  advanced  life  it  remains  open,  and  the  joint  partakes  of  the  nature  of 
an  amphiarthrosis,  although  a  joint  cavity  is  not  found  under  any  circumstances 
in  the  plate  of  fibro-cartilage  which  intervenes  between  the  manubrium  and  the 
gladiolus."     The  two  segments  are  further  connected  by  an 

Anterior  Intersternal  Ligament.         Posterior  Intersternal  Ligament. 

The  Anterior  Intersternal  Ligament  consists  of  a  layer  of  fibres,  having  a  longi- 
.tudinal  direction;  it  blends  with  the  fibres  of  the  anterior  chondro-sternal  liga- 
ments on  both  sides  (membrani  sterni),  and  with  the  tendinous  fibres  of  origin 
of  the  Pectoralis  major  muscle.  This  ligament  is  rough,  irregular,  and  much 
thicker  below  than  above. 

The  Posterior  Intersternal  Ligament  is  disposed  in  a  somewhat  similar  manner 
on  the  posterior  surface  of  the  articulation. 

IX.  Articulation  of  the  Vertebral  Column  with  the  Pelvis. 

The  ligaments  connecting  the  last  lumbar  vertebra  with  the  sacrum  are  similar 
to  those  which  connect  the  segments  of  the  spine  with  each  other — viz.:  1.  The 
continuation  downward  of  the  anterior  and  posterior  common  ligaments.  2.  The 
intervertebral  substance  connecting  the  flattened  oval  surfaces  of  the  two  bones 

1  Text-book  of  Anatomy,  p.  264. 


ARTICULATION   OF    VERTEBRAL    COLUMN  WITH    PELVIS    291 

and  forming  an  amphiarthrodial  joint.  3.  Ligamenta  subflava,  connecting  the 
arch  of  the  last  lumbar  vertebra  with  the  posterior  border  of  the  sacral  canal. 
4.  Capsular  ligaments  connecting  the  articulating  processes  and  forming  a  double 
arthrodia.     5.  Inter-  and  supraspinous  ligaments. 

The  two  proper  ligaments  connecting  the  pelvis  with  the  spine  are  the  lumbo- 
sacral and  ilio-lumbar. 

The  Lumbo-sacral  Ligament  (Fig.  213)  is  a  short,  thick,  triangular  fascic- 
ulus, which  is  connected  above  to  the  lower  and  front  part  of  the  trans- 
verse process  of  the  last  lumbar  vertebra,  passes  obliquely  outward,  and  is 
attached  below  to  the  lateral  surface  of  the  base  of  the  sacrum.  It  is  closely 
blended  with  the  anterior  sacro-iliac  ligament  and  with  the  ilio-lumbar 
ligament,  and  is  to  be  regarded  as  a  portion  of  the  ilio-lumbar  ligament. 
This  ligament  is  in  relation,  in  front,  with  the  Psoas  muscle.  The  in- 
ternal border  of  the  lumbo-sacral  ligament  margins  the  foramen  of  the  last 
lumbar  nerve. 

The  Ilio-liimbar  Ligament  (I ig amentum  iliolumhale)  (Fig.  213)  passes  horizon- 
tally outward  from  the  apex  of  the  transverse  process  of  the  last  lumbar  vertebra 


Aperture  of  communication 
vnth 
PSOAS  and  iliacus. 


Fig.  213. — Articulations  of  the  pelvis  and  hip.     Anterior  view. 


to  the  crest  of  the  ilium  immediately  in  front  of  the  sacro-iliac  articulation.  It 
is  of  a  triangular  form,  thick  and  narrow  internally,  broad  and  thinner  exter- 
nally. It  is  in  relation,  in  front,  with  the  Psoas  muscle ;  behind,  with  the 
muscles  occupying  the  vertebral  groove;  above,  with  the  Quadratus  lum- 
borum.  It  blends  in  places  with  the  lumbo-sacral  ligament,  and  its  cres- 
centic  inner  margin  marks  the  limit  of  the  foramen  for  the  fourth  lumbar  nerve. 
These  ligaments  are  thick  prolongations  from  the  anterior  layer  of  the  lumbar 
fascia. 


292  THE  ARTICULATIONS    OB    JOINTS 

X.  Articulations  of  the  Pelvis. 

The  ligaments  connecting  the  bones  of  the  pelvis  with  each  other  may  be 
divided  into  four  groups:  1.  Those  connecting  the  sacrum  and  ilium.  2.  Those 
passing  between  the  sacrum  and  ischiimi.  3.  Those  connecting  the  sacrum  and 
coccyx.    4.  Those  between  the  two  pubic  bones. 

1.  Articulation  0¥  the  Sacrum  and  Ilium  (Articulatio  Sacroiliaca.) 

The  sacro-iliac  articulation  is  an  amphiarthrodial  joint,  formed  between  the 
lateral  surfaces  of  the  sacrum  and  ilium.  Tlie  anterior  or  auricular  portion  of  each 
articular  surface  is  covered  with  a  thin  plate  of  cartilage,  thicker  on  the  sacrum 
than  on  the  ilium.  These  are  in  close  contact  with  each  other,  and  to  a  certain 
extent  united  together  by  irregular  patches  of  softer  fibro-cartilage,  and  at  their 
upper  and  posterior  part  by  fine  fibres  of  interosseous  fibrous  tissue.  Throughout 
a  considerable  part  of  their  extent,  especially  in  advanced  life,  they  are  not 
connected  together,  but  are  separated  by  a  space  containing  a  synovial-like  fluid, 
and  hence  the  joint  presents  the  characters  of  a  diarthrosis. 

The  ligaments  connecting  these  surfaces  are  the 

Anterior  Sacro-iliac.  Posterior  Sacro-iliac. 

Interosseous. 

The  Anterior  Sacro-iliac  Ligaments  (ligamenta  sacroiliaca  anteriora)  (Fig.  213) 
consists  of  numerous  thin  bands  which  connect  the  anterior  surfaces  of  the  sacrum 
and  ilium. 

The  Posterior  Sacro-iliac  Ligament  {lig amentum  sacroiliacum  posterius)  (Fig.  214) 
is  a  strong  interosseous  ligament,  situated  in  a  deep  depression  between  the  sacrum 
and  ilium  behind,  and  forming  the  chief  bond  of  connection  between  those  bones. 
It  consists  of  numerous  strong  fasciculi  which  pass  between  the  bones  in  various 
directions.  Three  of  these  are  of  large  size:  the  two  superior  fasciculi  constitute 
the  short  sacro-iliac  ligament  {ligamentum  sacroiHacum  posterius  breve) .  They  are 
nearly  horizontal  in  direction,  arise  from  the  first  and  second  transverse  tuber- 
cles on  the  posterior  surface  of  the  sacrum,  and  are  inserted  into  the  rough, 
uneven  surface  at  the  posterior  part  of  the  inner  surface  of  the  iHum.  The 
third  fasciculus,  oblique  in  direction,  is  attached  by  one  extremity  to  the  third 
transverse  tubercle  on  the  posterior  surface  of  the  sacrum,  and  by  the  other  to 
the  posterior  superior  spine  of  the  ilium;  it  is  sometimes  called  the  long  or  oblique 
sacro-iliac  ligament  (ligamentum  sacroiliacum  posterius  longum). 

The  Interosseous  Ligaments  {ligamenta  sacroiliaca  inter ossea)  are  completely 
covered  by  the  posterior  sacro-iliac  ligament,  and  are  not  visible  when  the  joint 
is  unopened.  The  fibres  are  short  and  run  obliquely  and  completely  fill  the 
hollow  which  exists  posterior  to  the  joint. 

The  position  of  the  sacro-ihac  joint  is  indicated  by  the  posterior  superior  spine  of  the  iHum. 
This  process  is  immediately  behind  the  centre  of  the  articulation. 

2.  Ligaments  passing  between  the  Sacrum  and  Ischium  (Fig.  214). 

The  Great  Sacro-sciatic  (Posterior). 
The  Lesser  Sacro-sciatic  (Anterior). 

The  Great  or  Posterior  Sacro-sciatic  Ligament  {ligamentum  sacrotuherosum)  (Figs. 
214  and  215)  is  situated  at  the  lower  and  back  part  of  the  pelvis.  It  is  flat,  and 
triangular  in  form;  narrower  in  the  middle  than  at  the  extremities;  attached  by  its 
broad  base  to  the  posterior  inferior  spine  of  the  ilium,  to  the  fourth  and  fifth  trans- 


ARTICULATIONS    OF    THE   PELVIS 


293 


verse  tubercles  of  the  sacrum,  and  to  the  lower  part  of  the  lateral  margin  of  that  bone 
and  the  coccyx.  Passing  obliquely  downward,  outward,  and  forward,  it  becomes 
narrow  and  thick,  and  at  its  insertion  into  the  inner  margin  of  the  tuberosity  of 
the  ischium  it  increases  in  breadth,  and  is  prolonged  forward  along  the  inner 
margin  of  the  ramus,  forming  what  is  known  as  the  falciform  process  of  the 
great  sacro-sciatic  ligament  or  the  falciform  ligament  (processus  falciformis) .  The 
free  concave  edge  of  this  prolongation  has  attached  to  it  the  obturator  fascia, 
with  which  it  forms  a  kind  of  groove,  protecting  the  internal  pudic  vessels  and 
nerve.  One  of  its  surfaces  is  turned  toward  the  perinoeum,  the  other  toward 
the  Obturator  internus  muscle. 


Fig.  214. — Articulations  of  pelvis  and  hip.     Posterior  view. 


The  posterior  surface  of  this  ligament  gives  origin,  by  its  whole  extent,  to  fibres 
of  the  Gluteus  maximus  muscle.  Its  anterior  surface  is  united  to  the  lesser  sacro- 
sciatic  ligament.  Its  external  border  forms,  above,  the  posterior  boundary  of  the 
great  sacro-sciatic  foramen,  and,  below,  the  posterior  boundary  of  the  lesser  sacro- 
sciatic  foramen.  Its  lower  border  forms  part  oi  the  boundary  of  the  perinseum.  It 
is  pierced  by  the  coccygeal  branch  of  the  sciatic  artery  and  the  coccygeal  nerve. 

The  Lesser  or  Anterior  Sacro-sciatic  Ligament  (ligamentum  sacrospinosum)  (Figs. 
214  and  215),  much  shorter  and  smaller  than  the  preceding,  is  thin,  triangular  in 
form,  attached  by  its  apex  to  the  spine  of  the  ischium,  and  internally,  by  its  broad 
base,  to  the  lateral  margin  of  the  sacrum  and  coccyx,  anterior  to  the  attachment 
of  the  great  sacro-sciatic  ligament,  with  which  its  fibres  are  intermingled. 

It  is  in  relation,  anteriorly,  with  the  Coccygeus  muscle;  posteriorly,  it  is  covered 
by  the  great  sacro-sciatic  ligament  and  crossed  by  the  internal  pudic  vessels  and 
nerve.  Its  superior  border  forms  the  lower  boundary  of  the  great  sacro-sciatic 
foramen;  its  inferior  border,  part  of  the  lesser  sacro-sciatic  foramen. 


294  THE   ARTICULATIONS    Oli   JOINTS 

These  two  ligaments  convert  the  sacro-sciatic  notches  into  foraminao  The 
superior  or  great  sacro-sciatic  foramen  (foramen  ischiadicum  majus)  (Figs.  214  and 
215)  is  bounded,  in  front  and  above,  by  the  posterior  border  of  the  os  innominatum; 
behind,  by  the  great  sacro-sciatic  ligament;  and  below,  by  the  lesser  sacro-sciatic 
ligament.  It  is  partially  filled  up,  in  the  recent  state,  by  the  Pyriformis  muscle, 
which  passes  through  it.  Above  this  muscle  the  gluteal  vessels  and  superior  gluteal 
nerve  emerge  from  the  pelvis,  and,  below  it,  the  sciatic  vessels  and  nerves,  the  inter- 
nal pudic  vessels  and  nerve,  the  inferior  gluteal  nerve,  and  the  nerves  to  the  obtu- 
rator internus  and  quadratus  femoris.  The  inferior  or  lesser  sacro-sciatic  foramen 
(foramen  ischiadicum  minus)  (Figs.  214  and  215)  is  bounded,  in  front,  by  the 


POUPAHTS 
LIGAMENT 


ANT.   SACRO-ILlAa 
LIGAMENT. 


GREAT   SACRO- 
SCIATIC    LIGA- 
MENT. 


LESSER  SACRO- 
SCIATIC  LIGA- 
MENT. 


GREAT   SACRO- 
SCIATIC    LIGA- 
MENT. 


Obturator 
membrane 


Fig.  215. — Side  view  of  pelvis,  showing  the  greater  and  lesser  sacro-sciatic  ligaments. 

tuber  ischii;  above,  by  the  spine  and  lesser  sacro-sciatic  ligament;  behind,  by  the- 
greater  sacro-sciatic  ligament.  It  transmits  the  tendon  of  the  Obturator  internus 
muscle,  its  nerve,  and  the  internal  pudic  vessels  and  nerve. 

3.  Articulation  of  the  Sacrum  and  Coccyx  (Symphysis  Sacrococcygea) . 

This  articulation  is  an  amphiarthrodial  joint,  formed  between  the  oval  surface 
at  the  apex  of  the  sacrum  and  the  base  of  the  coccyx.  It  is  analogous  to  the 
joints  between  the  bodies  of  the  vertebrte.    The  ligaments  are  the 

Anterior  Sacro-coccygeal.  Lateral  Sacro-coccygeal. 

Posterior  Sacro-coccygeal.  Interposed  Fibro-cartilage. 

The  Anterior  Sacro-coccygeal  Ligament  (ligamenium  sacrococcygeum  anterius) 
consists  of  a  few  irregular  fibres  which  descend  from  the  anterior  surface  of  the 
sacrum  to  the  front  of  the  coccyx,  becoming  blended  with  the  periosteum.  It  is 
a  continuation  of  the  anterior  common  ligament. 

The  Posterior  Sacro-coccygeal  Ligament  (ligamentum  sacrococcygeum  posterius) 
(Fig.  216)  is  divided  into  two  portions,  the  deep  and  the  superficial.     The  deep' 


ARTICULATIONS    OF    THE   PELVIS 


295 


portion  of  the  posterior  sacro -coccygeal  ligament  {ligamentum  sacrococcygeum  posterius 
profundum) ,  which  is  a  continuation  of  the  posterior  common  ligament,  is  a  flat 
band  of  a  pearly  tint,  which  arises  from  the  margin  of  the  lower  orifice  of  the  sacral 
canal,  and  descends  to  be  inserted  into  the  posterior  surface  of  the  coccyx.  This 
ligament  completes  the  lower  and  back  part  of  the  sacral  canal.  Its  superficial 
fibres  are  much  longer  than  the  more  deeply  seated.  This  ligament  is  in  rela- 
tion, behind,  with  the  Gluteus  maximus. 

The  superficial  portion  of  the  posterior  sacro-coccygeal  ligament  (ligamentum 
sacrococcygeum  posterius  superficiale)  is  composed  of  longitudinal  fibrous  bands 
which  extend  from  the  lower  portion  of  the  middle  sacral  ridge  to  the  posterior 
surface  of  the  coccyx  and  closes  partly  the  hiatus  sacralis;  and  of  fibrous  bands 
which  extend  from  the  sacral  cornua  to  the  coccygeal  cornua.  A  portion  of  this 
ligament  corresponds  to  the  ligamenta  subflava  and  the  balance  to  the  capsular 
ligament. 

A  Lateral  Sacro-coccygeal  or  Intertransverse  Ligament  (ligamentum  sacrococcygeum 
later  ale)  (Fig.  216)  connects  the  transverse  process  of  the  coccyx  to  the  lower 
lateral  angle  of  the  sacrum  on  each  side. 


APEX  OF  SACRUM 
LATERAL  SACRO- 
COCCYGEAL   LIGAMENT 
SUPERFICIAL    PORTION   OF    POST 
SACRO-COCCYGEAL  LIGAMENT 
DEEP  PORTION  OF  POSTERIOR 
SACRO-COCCYGEAL    LIGAMENT 


Fig.  216. — Ligaments  between  the  sacrum  and  the  coccyx.     (Spalteholz.) 

A  Fibro-cartilage  is  interposed  between  the  contiguous  surfaces  of  the  sacrum 
and  coccyx;  it  differs  from  that  interposed  between  the  bodies  of  the  vertebrae  in 
being  thinner,  and  its  central  part  firmer  in  texture.  It  is  somewhat  thicker  in 
front  and  behind  than  at  the  sides.  Occasionally,  a  synovial  membrane  is  found 
and  the  coccyx  is  freely  movable.     This  is  especially  the  case  during  pregnancy. 

The  different  segments  of  the  coccyx  are  connected  together  by  an  extension 
downward  of  the  anterior  and  posterior  sacro-coccygeal  ligaments,  a  thin  annular 
disk  of  fibro-cartilage  being  interposed  between  each  of  the  bones.  In  the  adult 
male  all  the  pieces  become  ossified,  but  in  the  female  this  does  not  commonly 
occur  until  a  later  period  of  life.  The  separate  segments  of  the  coccyx  are  first 
united,  and  at  a  niore  advanced  age  the  joint  between  the  sacrum  and  coccyx  is 
obliterated. 

Actions.— The  movements  which  take  place  between  the  sacrum  and  coccyx, 
and  between  the  different  pieces  of  the  latter  bone,  are  forward  and  backward^ 
and  are  very  limited.    Their  extent  increases  during  pregnancy. 


296 


THE  ARTICULATIONS    OB   JOINTS 


4.  Articulation  of  the  Ossa  Pubis  (Symphysis  Ossium  Pubis)  (Figs.  213, 217). 

The  articulation  between  the  pubic  bones  is  an  amphiarthrodial  joint,  formed 
by  the  junction  of  the  two  oval  articular  surfaces  of  the  ossa  pubis.  The  liga- 
ments of  this  articulation  are  the 


Anterior  Pubic. 
Posterior  Pubic. 


Superior  Pubic. 
Inferior  Pubic. 


Hyaline  cartilage  covering  bone. 


Intermediate  fibro-cartilaqe. 
Cavity  at  upper 
and  hack  part 


Interpubic  Disk. 

The  Anterior  Pubic  Ligament  (ligamentum  pubicum  anterius)  (Fig.  213)  consists 
of  several  superimposed  layers  which  pass  across  the  front  of  the  articulation.  The 
superficial  fibres  pass  obliciuely  from  one  bone  to  the  other,  decussating  and  form- 
ing an  interlacement  with  the  fibres  of  the  aponeurosis  of  the  External  oblique  and 
the  tendon  of  the  Rectus  muscles.  The  deep  fibres  pass  transversely  across  the 
symphysis,  and  are  blended  with  the  fibro-cartilage. 

The  Posterior  Pubic  Ligament  {ligamentum  pubicum  posterius)  consists  of  a 
few  thin,  scattered  fibres  which  unite  the  two  pubic  bones  posteriorly. 

The  Superior  Pubic  Ligament  {liga- 
mentum pubicum  super  ius)  (Fig.  213) 
is  a  band  of  fibres  which  connects  to- 
gether the  two  pubic  bones  superiorly. 
The  Inferior  Pubic  or  Subpubic 
Ligament  {ligamentum  arcuatum 
pubis)  (Fig.  213)  is  a  thick,  tri- 
angular arch  of  ligamentous  fibres, 
connecting  together  the  two  pubic 
bones  below  and  forming  the  upper 
boundary  of  the  pubic  arch.  Above, 
it  is  blended  with  the  interarticular 
fibro-cartilage;  laterally  it  is  united 
with  the  descending  rami  of  the 
pubis.  Its  fibres  are  closely  con- 
nected and  have  an  arched  direction. 
Its  lower  margin  is  separated  from 
the  triangular  ligament  of  the  per- 
inffium  by  a  gap,  through  w^hich  runs 
the  dorsal  vein  of  the  penis. 
The  Interpubic  Disk  {lamina  fibrocartilaginea  interpubica)  (Fig.  217)  consists  of  a 
disk  of  cartilage  and  fibro-cartilage  connecting  the  surfaces  of  the  pubic  bones  in 
front.  Each  of  the  two  surfaces  is  covered  by  a  thin  layer  of  hyaline  cartilage  which 
is  firmly  connected  to  the  bone  by  a  series  of  nipple-like  processes  which  accu- 
rately fit  within  corresponding  depressions  on  the  osseous  surfaces.  These  opposed 
cartilaginous  surfaces  are  connected  together  by  an  intermediate  stratum  of  fibrous 
tissue  and  fibro-cartilage  which  varies  in  thickness  in  different  subjects.  It  often 
contains  a  cavity  {cavum  articulare)  in  its  centre,  probably  formed  by  the  soften- 
ing and  absorption  of  the  fibro-cartilage,  since  it  rarely  appears  before  the  tenth' 
year  of  life,  and  is  not  lined  by  synovial  membrane.  It  is  larger  in  the  female 
than  in  the  male,  but  it  is  very  questionable  whether  it  enlarges,  as  was  formerly 
supposed,  during  pregnancy.  It  is  most  frequently  limited  to  the  upper  and  back 
part  of  the  joint,  but  it  occasionally  reaches  to  the  front,  and  may  extend  the 
entire  length  of  the  cartilage.  This  cavity  may  be  easily  demonstrated  by  making 
a  vertical  section  of  the  symphysis  pubis  near  its  posterior  surface  (Fig.  217). 

The  Obturator  Ligament  is  more  properly  regarded  as  analogous  to  the  muscular 
fasciae,  with  which  it  will  be  described. 


Fig.  217. — Vertical  section  of  the  symphysis  pubis. 
Made  near  its  posterior  surface. 


^TERNO  CLAVICULAR   ARTICULATION 


297 


ARTICULATIONS  OF  THE  UPPER  EXTREMITY. 

The  articulations  of  the  upper  extremity  may  be  arranged  in  the  following 
groups : 


I.  Sterno-clavicular  Articulation.  VII, 

II.  Acromio-clavicular  Articulation.  VIII. 

III.  Ligaments  of  the  Scapula.  IX. 

IV.  Shoulder-joint.  X. 
V.  Elbow-joint. 

VI.  Radio-ulnar  Articulations.  XI. 


Wrist-joint. 

Articulations  of  the  Carpal  Bones. 
Carpo-metacarpal  Articulations. 
Metacarpo-phalangeal    Articula- 
tions. 
Articulations  of  the  Phalanges. 


I.  Stemo-clavicular  Articulation  (Articulatio  Steraoclavicularis)  (Fig.  218). 

The  sterno-clavicular  is  regarded  by  most  anatomists  as  an  arthrodial  joint, 
but  Cruveilhier  considers  it  to  be  an  articulation  by  reciprocal  reception.  Probably 


Fig.  218. — Sterno-clavicular  articulation.     Anterior  view. 

the  former  opinion  is  the  correct  one,  the  varied  movement  which  the  joint  enjoys 
being  due  to  the  interposition  of  an  interarticular  fibro-cartilage  between  the 
joint  surfaces.  The  parts  entering  into  its  formation  are  the  sternal  end  of  the 
clavicle,  the  upper  and  lateral  part  of  the  first  piece  of  the  sternum,  and  the 
cartilage  of  the  first  rib.  The  articular  surface  of  the  sternum  is  covered  with 
cartilage.  The  articular  surface  of  the  clavicle  is  much  larger  than  that  of  the 
sternum,  and  invested  with  a  layer  of  cartilage^  which  is  considerably  thicker  than 
that  on  the  latter  bone.    The  ligaments  of  this  joint  are  the 

Capsular.  Interclavicular. 

Anterior  Sterno-clavicular.  Costo-clavicular. 

Posterior  Sterno-clavicular.  Interarticular  Fibro-cartilage. 

The  Capsular  Ligament  (capsula  articularis)  completely  surrounds  the  articula- 
tion, consisting  of  fibres  of  varying  degrees  of  thickness  and  strength.  Those  in 
front  and  behind  are  of  considerable  thickness,  and  form  the  anterior  and  posterior 
sterno-clavicular  ligaments;  but  those  above  and  below,  especially  in  the  latter 
situation,  are  thin  and  scanty,  and  partake  more  of  the  character  of  connective 
tissue  than  true  fibrous  tissue. 


1  According  to  Bruch,  the  sternal  end  of  the  clavicle   is  covered  by  a  tissue  which  is  rather  fibrous  than 
cartilaginous  in  structure. 


298  THE  ARTICULATIONS    OB    JOINTS 

The  Anterior  Sterao-clavicular  Ligament  (ligamentum  sternoclaviculare)  (Fig.  218) 
is  a  part  of  the  capsule.  It  is  a  broad  band  of  fibres  which  covers  the  anterior  sur- 
face of  the  articulation,  being  attached,  above,  to  the  upper  and  front  part  of  the 
inner  extremity  of  the  clavicle,  and,  passing  obliquely  downward  and  inward, 
is  attached,  below,  to  the  upper  and  front  part  of  the  first  piece  of  the  sternum. 
This  ligament  is  covered,  in  front,  by  the  sternal  portion  of  the  Sterno-cleido- 
mastoid  and  the  integument;  behind,  it  is  in  relation  with  the  interarticular 
fibro-cartilage  and  the  two  synovial  membranes. 

The  Posterior  Stemo -clavicular  Ligament,  also  a  part  of  the  capsule,  is  a  band  of 
fibres  which  covers  the  posterior  surface  of  the  articulation,  being  attached,  above, 
to  the  upper  and  back  part  of  the  inner  extremity  of  the  clavicle,  and,  passing 
obliquely  downward  and  inward,  is  attached,  below,  to  the  upper  and  back  part 
of  the  first  piece  of  the  sternum.  It  is  in  relation,  in  front,  with  the  interartic- 
ular fibro-cartilage  and  synovial  membranes;  behind,  with  the  Sterno-hyoid  and 
Sterno-thyroid  muscles. 

The  Interclavicular  Ligament  {ligamentum  interciaviculare)  (Fig.  218j  is  a  flat- 
tened band  which  varies  considerably  in  form  and  size  in  different  individuals;  it 
passes  in  a  curved  direction  from  the  upper  part  of  the  inner  extremity  of  one 
clavicle  to  the  other,  and  is  also  attached  to  the  upper  margin  of  the  sternum.  It 
is  in  relation,  in  front,  with  the  integument;  behind,  with  the  Sterno-thyroid 
muscles. 

The  Costo-clavicular  or  Rhomboid  Ligament  '{ligamentum  costoclavicular e) 
(Fig.  218)  is  short,  flat,  and  strong;  it  is  of  a  rhomboid  form,  attached,  below,  to 
the  upper  and  inner  part  of  the  cartilage  of  the  first  rib :  it  ascends  obliquely  back- 
ward and  outward,  and  is  attached,  above,  to  the  rhomboid  depression  on  the 
under  surface  of  the  clavicle.  It  is  in  relation,  in  front,  with  the  tendon  of 
origin  of  the  Subclavius;  behind,  with  the  subclavian  vein. 

The  Literarticular  Fibro-cartilage  {discus  articularis)  (Fig.  218)  is  a  flat  and  nearly 
circular  meniscus,  interposed  between  the  articulating  surfaces  of  the  sternum  and 
clavicle.  It  is  attached,  above,  to  the  upper  and  posterior  border  of  the  articular 
surface  of  the  clavicle;  below,  to  the  cartilage  of  the  first  rib,  at  its  junction  with  the 
sternum ;  and  by  its  circumference,  to  the  anterior  and  posterior  sterno-clavicular 
and  the  interclavicular  ligaments.  It  is  thicker  at  the  circumference,  especially 
its  upper  and  back  part,  than  at  its  centre  or  below.  It  divides  the  joint  into  two 
cavities,  each  of  which  is  furnished  with  a  separate  synovial  membrane. 

Synovial  Membrane. — Of  the  two  synovial  membranes  found  in  this  articulation, 
one  is  reflected  from  the  sternal  end  of  the  clavicle  over  the  adjacent  surface  of  the 
fibro-cartilage  and  cartilage  of  the  first  rib;  the  other  is  placed  between  the  articular 
surface  of  the  sternum  and  adjacent  surface  of  the  fibro-cartilage;  the  latter  is  the 
larger  of  the  two. 

Actions. — This  articulation  is  the  centre  of  the  movements  of  the  shoulder,  and 
admits  of  a  limited  amount  of  motion  in  nearly  every  direction — upward,  down- 
ward, backward,  forward — as  well  as  circumduction.  When  these  movements  take 
place  in  the  joint,  the  clavicle  in  its  motion  carries  the  scapula  with  it,  this  bone 
gliding  on  the  outer  surface  of  the  chest.  This  joint  therefore  forms  the  centre 
from  which  all  movements  of  the  supporting  arch  of  the  shoulder  originate,  and 
is  the  only  point  of  articulation  of  this  part  of  the  skeleton  with  the  trunk.  "The 
movements  attendant  on  elevation  and  depression  of  the  shoulder  take  place 
between  the  clavicle  and  the  interarticular  fibro-cartilage,  the  bone  rotating  upon 
the  ligament  on  an  axis  drawn  from  before  backward  through  its  own  articular 
facet.  When  the  shoulder  is  moved  forward  and  backward,  the  clavicle,  with 
the  interarticular  fibro-cartilage,  rolls  to  and  fro  on  the  articular  surface  of  the 
sternum,  revolving,  with  a  sliding  movement,  round  an  axis  drawn  nearly  vertically 
through  the  sternum.    In  the  circumduction  of  the  shoulder,  which  is  compounded 


ACBOMIO-CLAVICULAR    ARTICULATION  299 

of  these  two  movements,  the  clavicle  revolves  upon  the  interarticular  fibro-carti- 
lage,  and  the  latter,  with  the  clavicle,  rolls  upon  the  sternum."^  Elevation  of  the 
clavicle  is  principally  hmited  by  the  costo-clavicular  ligament;  depression  bv  the 
interclavicular.  The  muscles  which  raise  the  clavicle,  as  in  shrugging  the  shoulder, 
are  the  upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapulae,  the  clavicular 
head  of  the  Sterno-mastoid,  assisted  to  a  certain  extent  by  the  two  Rhomboids, 
which  pull  the  vertebral  border  of  the  Scapula  backward  and  upward,  and  so 
raise  the  clavicle.  The  degression  of  the  clavicle  is  principally  effected  by  gravity, 
assisted  by  the  Subclavius,  Pectoralis  minor,  and  lower  fibres  of  the  Trapezius. 
It  is  drawn  backward  by  the  Rhomboids  and  the  middle  and  lower  fibres  of  the 
Trapezius;  and  forward  by  the  Serratus  magnus  and  Pectoralis  minor. 

Surface  Form. — The  position  of  the  sterno-clavicular  joint  may  be  easily  ascertained  by  feel- 
ing the  enlarged  sternal  end  of  the  collar-bone  just  external  to  the  long,  cord-like,  sternal  origin 
of  the  Sterno-mastoid  muscle.  If  this  muscle  is  relaxed  by  bending  the  head  forward,  a  depres- 
sion just  internal  to  the  end  of  the  clavicle,  and  between  it  and  the  sternum,  can  be  felt,  indi- 
cating the  exact  position  of  the  joint,  which  is  subcutaneous.  When  the  arm  hangs  by  the  side, 
the  cavity  of  the  joint  is  V-shaped.  If  the  arm  is  raised,  the  bones  become  more  closely  approx- 
imated, and  the  cavity  becomes  a  mere  slit. 

Surgical  Anatomy. — The  strength  of  this  joint  mainly  depends  upon  its  ligaments,  and 
it  is  because  of  the  ligaments  and  because  the  force  of  a  blow  is  generally  transmitted  along  the 
long  axis  of  the  clavicle,  that  dislocation  so  rarely  occurs,  and  that  the  bone  is  generally  broken 
rather  than  displaced.  When  dislocation  does  occur,  the  course  which  the  displaced  bone  takes 
depends  more  upon  the  direction  in  which  the  violence  was  applied  than  upon  the  anatomical 
construction  of  the  joint;  it  may  be  either  forward,  backward,  or  upward.  A  complete  upward 
dislocation  is  also  inward.  A  complete  forward  or  backward  dislocation  is  also  inward  and 
downward.  The  chief  point  worthy  of  note,  as  regards  the  construction  of  the  joint,  in  regard 
to  dislocations,  is  the  fact  that,  owing  to  the  shape  of  the  articular  surfaces  being  so  little 
adapted  to  each  other,  and  that  the  strength  of  the  joint  mainly  depends  upon  the  ligaments, 
the  displacement  when  reduced  is  very  liable  to  recur,  and  hence  it  is  extremely  difficult  to 
keep  the  end  of  the  bone  in  its  proper  place,  and  it  may  be  necessary  to  incise  the  soft  parts 
and  wire  the  bone  in  place. 

II.  Acromio-clavicular  Articulation  or  Scapulo-clavicular  Articulation 
(Articulatio  Acromioclavicularis)  (Fig.  219). 

The  acromio-clavicular  is  an  arthrodial  joint  formed  between  the  outer  extrem- 
ity of  the  clavicle  and  the  inner  margin  of  the  acromion  process  of  the  scapula. 
The  ligaments  which  surround  the  joint  form  a  capsule.  The  ligaments  of  this 
articulation  are  the 

Superior  Acromio-clavicular.  (Trapezoid. 

Inferior  Acromio-clavicular.  Coraco-clavicular  <       and 

Interarticular  Fibro-cartilage.  I  Conoid. 

The  Superior  Acromio-clavicular  Ligament  (ligamentum  acromioclavicidare)  (Figs. 
219  and  220)  is  a  portion  of  the  joint  capsule.  It  is  a  quadrilateral  band  which 
covers  the  superior  part  of  the  articulation,  extending  between  the  upper  part  of 
the  outer  end  of  the  clavicle  and  the  adjoining  part  of  the  upper  surface  of  the 
acromion.  It  is  composed  of  parallel  fibres  wliich  interlace  with  the  aponeurosis 
of  the  Trapezius  and  Deltoid  muscles;  below,  it  is  in  contact  with  the  inter- 
articular fibro-cartilage  (when  it  exists)  and  the  synovial  membranes. 

The  Inferior  Acromio-clavicular  Ligament,  somewhat  thinner  than  the  pre- 
ceding, and  like  it  a  portion  of  the  capsule,  covers  the  under  part  of  the  articula- 
tion, and  is  attached  to  the  adjoining  surfaces  of  the  two  bones.  It  is  in  relation, 
above,  with  the  synovial  membranes,  and  in  rare  cases  with  the  interarticular 
fibro-cartilage;  below,  with  the  tendon  of  the  Supraspinatus.     These  two  liga- 

•  Humphry.    On  the  Human  Skeleton,  p.  402. 


300  'J'HE    ARTICULATIONS    OR   JOINTS 

ments  are  continuous  with  each  other  in  front  and  behind,  and  form  a  complete 
capsule  round  the  joint. 

The  Interarticular  Fibro-cartilage  (discus  articularis)  is  frequently  absent  in  this 
articulation.  When  the  meniscus  exists  it  is  generally  incomplete  and  only  par- 
tially separates  the  articular  surfaces,  and  occupies  the  upper  part  of  the  articu- 
lation.   More  rarely  it  completely  separates  the  joint  into  two  cavities. 


Fig.  219. — The  left  shoulder-joint,  scapulo-clavicular  articulations,  and  proper  ligaments  of  scapula. 

The  Sjmovial  Membrane. — There  is  usually  only  one  synovial  membrane  in 
this  articulation,  but  when  a  complete  interarticular  fibro-cartilage  exists  there  are 
two  synovial  membranes. 

The  Coraco-clavicular  Ligament  (ligamentum  coracoclaviculare)  (Figs.  219  and 
220)  serves  to  connect  the  clavicle  with  the  coracoid  process  of  the  scapula.  It  does 
not  properly  belong  to  this  articulation,  but  as  it  forms  a  most  efficient  means  in 
retaining  the  clavicle  in  contact  with  the  acromial  process,  it  is  usually  described 
with  it.     It  consists  of  two  fasciculi,  called  the  trapezoid  and  conoid  ligaments. 

The  trapezoid  ligament  (ligamentum  trapezoideum) ,  the  anterior  and  external 
fasciculus,  is  broad,  thin,  and  quadrilateral;  it  is  placed  obliquely  between  the 
coracoid  process  and  the  clavicle.  It  is  attached,  below,  to  the  upper  surface 
of  the  coracoid  process;  above,  to  the  obHque  line  on  the  under  surface  of  the 
clavicle.  Its  anterior  border  is  free ;  its  posterior  border  is  joined  with  the  conoid 
ligament,  the  two  forming  by  their  junction  a  projecting  angle. 

The  conoid  ligament  (ligamentum  conoideum) ,  the  posterior  and  internal  fas- 
ciculus, is  a  dense  band  of  fibres,  conical  in  form,  the  base  being  directed  upward, 
the  summit  downward.  It  is  attached  by  its  apex  to  a  rough  impression  at  the 
base  of  the  coracoid  process,  internal  to  the  preceding;  above,  by  its  expanded 


PROPER    LIGAMENTS    OF    THE   SCAPULA  301 

base,  to  the  conoid  tubercle  on  the  under  surface  of  the  clavicle,  and  to  a  line 
proceeding  internally  from  it  for  half  an  inch.  These  ligaments  are  in  relation, 
in  front,  with  the  Subclavius  and  Deltoid;  behind,  with  the  Trapezius.  They 
serve  to  limit  rotation  of  the  scapula,  the  Trapezoid  limiting  rotation  forward, 
and  the  Conoid  backward. 

Actions. — The  movements  of  this  articulation  are  of  two  kinds:  1.  A  gliding 
motion  of  the  articular  end  of  the  clavicle  on  the  acromion.  2.  Rotation  of  the 
scapula  forward  and  backward  upon  the  clavicle,  the  extent  of  this  rotation  being 
limited  by  the  two  portions  of  the  coraco-clavicular  ligament. 

The  acromio-clavicular  joint  has  important  functions  in  the  movements  of  the 
upper  extremity.  It  has  been  well  pointed  out  by  Sir  George  Humphry  that  if 
there  had  been  no  joint  between  the  clavicle  and  scapula  the  circular  movement  of 
the  scapula  on  the  ribs  (as  in  throwing  both  shoulders  backward  or  forward)  would 
have  been  attended  with  a  greater  alteration  in  the  direction  of  the  shoulder  than  is 
consistent  with  the  free  use  of  the  arm  in  such  position,  and  it  would  have  been 
impossible  to  give  a  blow  straight  forward  with  the  full  force  of  the  arm ;  that  is  to 
say,  with  the  combined  force  of  the  scapula,  arm,  and  forearm.  "This  joint,"  as 
he  happily  says,  "is  so  adjusted  as  to  enable  either  bone  to  turn  in  a  hinge-like 
manner  upon  a  vertical  axis  drawn  through  the  other,  and  it  permits  the  surfaces 
of  the  scapula,  like  the  baskets  in  a  roundabout  swing,  to  look  the  same  way  in 
every  position  or  nearly  so."  Again,  when  the  whole  arch  formed  by  the  clavicle 
and  scapula  rises  and  falls  (in  elevation  or  depression  of  the  shoulders),  the  joint 
between  these  two  bones  enables  the  scapula  still  to  maintain  its  lower  part  in 
contact  with  the  ribs. 

Surface  Form. — The  position  of  the  acromio-clavicular  joint  can  generally  be  ascertained  by 
the  slightly  enlarged  extremity  of  the  outer  end  of  the  clavicle,  which  causes  it  to  project  above 
the  level  of  the  acromion  process  of  the  scapula.  Sometimes  this  enlargement  is  so  considerable 
as  to  form  a  rounded  eminence,  which  is  easily  to  be  felt.  The  joint  lies  in  the  plane  of  a  ver- 
tical line  passing  uj)  the  middle  of  the  front  of  the  arm. 

Surgical  Anatomy. — Owing  to  the  slanting  shape  of  the  articular  surfaces  of  this  joint, 
the  commonest  dislocation  is  the  passing  of  the  acromion  process  of  the  scapula  under  the 
outer  end  of  the  clavicle;  but  dislocations  in  the  opposite  direction  have  been  described.  The 
first  form  of  dislocation  is  produced  by  violent  force  applied  to  the  scapula  so  as  to  drive  the 
shoulder  forward.  The  displacement  in  acromio-clavicular  dislocation  is  often  incomplete,  on 
account  of  the  strong  coraco-clavicular  ligaments  which  remain  untorn.  The  same  difficulty 
exists,  as  in  the  sterno-clavicular  dislocation,  in  maintaining  the  ends  of  the  bone  in  apposition  after 
reduction,  and  it  may  become  necessary  to  wire  them  in  place  after  incision  of  the  soft  parts. 

III.  Proper  Ligaments  of  the  Scapula  (Figs.  219, 220). 

The  proper  ligaments  of  the  scapula  pass  between  portions  of  that  bone,  but 
are  not  parts  of  an  articulation.     They  are  the 

Coraco-acromial.  Superior  Transverse. 

Inferior  Transverse. 

The  Coraco-acromial  Ligament  (ligamentum  coracoccromicle)  is  a  strong  trian- 
gular band,  extending  between  the  coracoid  and  acromial  processes.  It  is  attached, 
by  its  apex,  to  the  summit  of  the  acromion  just  in  front  of  the  articular  surface 
for  the  clavicle,  and  by  its  broad  base  to  the  whole  length  of  the  outer  border  of 
the  coracoid  process.  Its  posterior  fibres  are  directed  inward,  its  anterior  fibres 
forward  and  inward.  This  ligament  completes  the  vault  formed  by  the  coracoid  and 
acromion  processes  for  the  protection  of  the  head  of  the  humerus.  It  is  in  relation, 
above,  with  the  clavicle  and  under  surface  of  the  Deltoid  muscle;  below,  with  the 
tendon  of  the  Supraspinatus  muscle,  a  bursa  being  interposed.  Its  outer  border  is 
continuous  with  a  dense  lamina  that  passes  beneath  the  Deltoid  upon  the  tendons 


302 


THE   ARTICULATIONS    OR    JOINTS 


of  the  Supra-  and  Infraspinatus  muscles.  This  Hgament  is  sometimes  described  as 
consisting  of  two  marginal  bands  and  a  thinner  intervening  portion,  the  two  bands 
being  attached  respectively  to  the  apex  and  base  of  the  coracoid  process,  and  join- 
ing together  at  their  attachment  into  the  acromion  process.  When  the  Pectoralis 
minor  is  inserted,  as  sometimes  is  the  case,  into  the  capsule  of  the  shoulder-joint 
instead  of  into  the  coracoid  process,  it  passes  between  these  two  bands,  and  the 
intervening  portion  is  then  deficient. 

The  Superior  Transverse,  Coracoid  or  Suprascapular  Ligament  (lig amentum  trans- 
versum  scapuloe  super ius)  (Figs.  219,  220,  and  222J  converts  the  suprascapular 


SUPERIOR 

ACROMIOCLAVICULAR 

LIGAMENT 


GLENOID 

LIGAMENT 


Fig.  220.- 


-Right  clavicle  and  shoulder-blade  with  ligament,  from  without  and  somewhat  from  in  front. 

(Spaltenolz.) 


notch  into  a  foramen.  It  is  a  thin  and  flat  fasciculus,  narrower  at  the  middle 
than  at  the  extremities,  attached  by  one  end  to  the  base  of  the  coracoid  process, 
and  by  the  other  to  the  inner  extremity  of  the  scapular  notch.  The  suprascapular 
nerve  passes  through  the  foramen;  the  suprascapular  vessels  pass  over  the  liga- 
ment. 

An  additional  ligament,  the  Inferior  Transverse  or  Spino-glenoid  Ligament  (liga- 
menium  transversum  scapuloe  inferius),  is  sometimes  found  on  the  scapula,  stretch- 
ing from  the  outer  border  of  the  spine  to  the  margin  of  the  glenoid  cavity.  When 
present,  it  forms  an  arch  under  which  the  suprascapular  vessels  and  nerve  pass  as 
they  enter  the  infraspinous  fossa. 

Movements  of  Scapula. — The  scapula  is  capable  of  being  moved  upward  and 
downward,  forward  and  backward,  or,  by  a  combination  of  these  movements,  cir- 
cumducted on  the  wall  of  the  chest.  The  muscles  which  raise  the  scapula  are  the 
upper  fibres  of  the  Trapezius,  the  Levator  anguli  scapulre,  and  the  two  Rhom- 
boids; those  which  depress  it  are  the  lower  fibres  of  the  Trapezius,  the  Pectoralis 
minor,  and,  through  the  clavicle,  the  Subclavius.  The  scapula  is  drawn  hackioard 
by  the  Rhomboids  and  the  middle  and  lower  fibres  of  the  Trapezius,  and  forward 


THE  SHOULDER- JOINT 


303 


by  the  Serratus  magnus  and  Pectoralis  minor,  assisted,  when  the  arm  is  fixed,  by 
the  PectoraHs  major.  The  mobihty  of  the  scapula  is  very  considerable,  and 
greatly  assists  the  movements  of  the  arm  at  the  shoulder-joint.  Thus,  in  raising 
the  arm  from  the  side  the  Deltoid  and  Supraspinatus  can  only  lift  it  to  a  right 


DELTOID.      SUPRA-SPINATUS. 


TERES    MAJOR 


SUl 

TERES  MAJOR.      Circumjiex  vessels.  Circumflex  vessels.  scapularis. 

Fig.  221. — Vertical  sections  through  the  shoulder-joint,  the  arm  being  vertical  and  horizontal.     (After  Henle.) 

angle  with  the  trunk,  the  further  elevation  of  the  limb  being  effected  by  the 
Trapezius  and  Serratus  magnus  moving  the  scapula  on  the  wall  of  the  chest. 
This  mobility  is  of  special  importance  in  ankylosis  of  the  shoulder-joint,  the 
movement  of  this  bone  compensating  to  a  very  great  extent  for  the  immobility 
of  the  joint. 

IV.  The  Shoulder-joint  (Articulatio  Humeri)  (Figs.  219,  220,  221,  222). 

The  shoulder  is  an  enarthrodial  or  ball-and-socket  joint.  The  bones  entering 
into  its  formation  are  the  large  globular  head  of  the  humerus,  which  is  received 
into  the  shallow  glenoid  cavity  of  the  scapula — an  arrangement  which  permits  of 
very  considerable  movement,  whilst  the  joint  itself  is  protected  against  displace- 
ment by  the  tendons  which  surround  it  and  by  atmospheric  pressure.  The  liga- 
ments do  not  maintain  the  joint  surfaces  in  apposition,  because  when  they  alone 
remain  the  humerus  can  be  separated  to  a  considerable  extent  from  the  glenoid 
cavity ;  their  use,  therefore,  is  to  limit  the  amount  of  movement.  Above,  the  joint 
is  protected  by  an  arched  vault,  formed  by  the  under  surfaces  of  the  ccracoid  and 
acromion  processes,  and  the  coraco-acromial  ligament.  The  articular  surfaces 
are  covered  by  a  layer  of  cartilage:  that  on  the  head  of  the  humerus  is  thicker  at 
the  centre  than  at  the  circumference,  the  reverse  being  the  case  in  the  glenoid 
cavity.    The  ligaments  of  the  shoulder  are  the 

Capsular.  Transverse  humeral. 

Coraco-huraeral.  Glenoid.^ 

The  Capsular  Ligament  (capsula  articularis)  (Figs.  219,  220,  and  222)  completely 
encircles  the  articulation,  being  attached,  above,  to  the  circumference  of  the  glenoid 
cavity  beyond  the  glenoid  ligament,  below,  to  the  anatomical  neck  of  the  humerus, 
approaching  nearer  to  the  articular  cartilage  above  than  in  the  rest  of  its  extent. 
It  is  thicker  above  and  below  than  elsewhere,  and  is  remarkably  loose  and  lax,  and 


1  The  long  tendon  of  origin  of  the  Biceps  muscle  also  acts  as  one  of  the  liganients  of  this  joint, 
observations  on  p.  268  on  the  function  of  the  muscles  passing  over  more  than  one  joint. 


See  the 


304 


THE  ARTICULATIONS    OB    JOINTS 


much  larger  and  longer  than  is  necessary  to  keep  the  bones  in  contact,  allowing 
them  to  be  separated  from  each  other  more  than  an  inch — an  evident  provision 
for  that  extreme  freedom  of  movement  which  is  peculiar  to  this  articulation.  Its 
superficial  surface  is  strengthened,  above,  by  the  Supraspinatus;  below,  by  the 
long  head  of  the  Triceps;  behind,  by  the  tendons  of  the  Infraspinatus  and  Teres 
minor;  and  in  front,  by  the  tendon  of  the  Subscapularis.  The  capsular  ligament 
usually  presents  three  openings:  One  anteriorly,  below  the  coracoid  process, 
establishes  a  communication  between  the  synovial  membrane  of  the  joint  and  a 


ARTICULAR 
CAPSULE 


LONG  HEAD  OF 
BICEPS   MUSCLE 


SPINE   OF   SCAPULA 

(sawed  off  at  its  origin) 


Fig.  222. — Right  shoulder-joint,  frontal  section,  from  behind.     (Spalteholz.) 


bursa  beneath  the  tendon  of  the  Subscapularis  muscle.  The  second,  which  is 
not  constant,  is  at  the  posterior  part,  where  a  communication  sometimes  exists 
between  the  joint  and  a  bursal  sac  belonging  to  the  Infraspinatus  muscle.  The 
third  is  seen  between  the  two  tuberosities,  for  the  passage  of  the  long  tendon 
of  the  Biceps  muscle.  It  transmits  a  sac-like  prolongation  of  the  synovial 
membrane,  which  ends  as  a  blind  pouch  opposite  the  surgical  neck  of  the  bone. 
This  synovial  sac  is  called  the  vagina  mucosa  intertubercularis. 

The  Coraco-humeral  Ligament  {lig amentum  coracohumerale)  (Fig.  219)  is  a  broad 
band  which  strengthens  the  upper  part  of  the  capsular  ligament.  It  arises  from 
the  outer  border  of  the  coracoid  process,  and  passes  obliquely  downward  and  out- 
ward to  the  front  of  the  great  tuberosity  of  the  humerus,  being  blended  with  the 
tendon  of  the  Supraspinatus  muscle.  This  ligament  is  intimately  united  to  the 
capsular  ligament  throughout  the  greater  part  of  its  extent. 

Supplemental  Bands  of  the  Capsular  Ligament. — In  addition  to  the  coraco- 
humeral  ligament,  the  capsular  ligament  is  strengthened  by  supplemental  bands  in 
the  interior  of  the  joint.  One  of  these  bands  is  situated  on  the  inner  side  of  the 
joint,  and  passes  from  the  inner  edge  of  the  glenoid  cavity  to  the  lower  part  of  the 
lesser  tuberosity  of  the  humerus.    This  is  sometimes  known  as  Flood's  ligament> 


THE  SHOULDER-  JOINT  305 

and  is  supposed  to  correspond  with  the  Hgamentum  teres  of  the  hip-joint.  A 
second  of  these  bands  is  situated  at  the  lower  part  of  the  joint,  and  passes  from  the 
under  edge  of  the  glenoid  cavity  to  the  under  part  of  the  neck  of  the  humerus,  and 
is  known  as  Schlemm's  ligament.  A  third,  called  the  gleno-humeral  ligament,  is 
situated  at  the  upper  part  of  the  joint,  and  projects  into  its  interior,  so  that  it  can 
be  seen  only  when  the  capsule  is  opened.  It  is  attached  above  to  the  apex  of  the 
glenoid  cavity,  close  to  the  root  of  the  coracoid  process,  and,  passing  downward 
along  the  inner  edge  of  the  tendon  of  the  Biceps,  is  attached  below  to  the  lesser 
tuberosity  of  the  humerus,  where  it  forms  the  inner  boundary  of  the  upper  part  of 
the  bicipital  groove.  It  is  a  thin,  ribbon-like  band,  occasionally  quite  free  from 
the  capsule. 

The  Transverse  Humeral  Ligament  is  a  prolongation  of  the  capsular  ligament. 
It  is  a  broad  band  of  fibrous  tissue  passing  from  the  lesser  to  the  greater  tuber- 
osity of  the  humerus,  and  always  limited  to  that  portion  of  the  bone  which  lies 
above  the  epiphysial  line.  It  converts  the  bicipital  groove  into  an  osseo-aponeu- 
rotic  canal,  and  is  the  analogue  of  the  strong  process  of  bone  which  connects  the 
summits  of  the  two  tuberosities  in  the  musk  ox. 

The  Glenoid  Ligament  (lahrum  glenoidale)  (Figs.  220  and  222)  is  a  fibro- 
cartilaginous rim,  attached  round  the  margin  of  the  glenoid  cavity.  It  is  trian- 
gular on  section,  the  thickest  portion  being  fixed  to  the  circumference  of  the  cavity, 
the  free  edge  being  thin  and  sharp.  It  is  continuous  above  with  the  long  tendon 
of  the  Biceps  muscle,  which  bifurcates  at  the  upper  part  of  the  cavity  into  two 
fasciculi,  and  becomes  continuous  with  the  fibrous  tissue  of  the  glenoid  ligament. 
This  ligament  deepens  the  cavity  for  articulation,  and  protects  the  edges  of  the 
bone.     It  is  lined  by  the  synovial  membrane. 

Synovial  Membrane  (Fig.  222). — The  synovial  membrane  is  reflected  from  the 
margin  of  the  glenoid  cavity  over  the  fibro-cartilaginous  rim  surrounding  it:  it  is 
then  reflected  over  the  internal  surface  of  the  capsular  ligament,  covers  the  lower 
part  and  sides  of  the  anatomical  neck  of  the  humerus  as  far  as  the  cartilage  cover- 
ing the  head  of  the  bone.  The  long  tendon  of  the  Biceps  muscle  which  passes 
through  the  capsular  ligament  is  enclosed  in  a  tubular  sheath  of  synovial  membrane 
{vagina  mucosa  intertvbercularis) ,  which  is  reflected  upon  it  at  the  point  where  it 
perforates  the  capsule,  and  is  continued  around  it  as  far  as  the  level  of  the  surgical 
neck  of  the  humerus.  The  tendon  of  the  Biceps  is  thus  enabled  to  traverse  the 
articulation,  but  it  is  not  contained  in  the  interior  of  the  synovial  cavity. 

Bm'sse. — A  large  bursa  exists  between  the  joint  capsule  and  the  tendon  of  the 
Subscapularis  muscle.  It  is  called  the  subscapular  bursa.  This  sac  communicates 
with  the  shoulder-joint  by  means  of  an  opening  at  the  inner  side  of  the  capsular 
ligament.  The  subscapular  bursa  is  constant.  Occasionally  another  and  smaller 
bursa  exists  jjeneath  the  tendon  of  the  infraspinatus.  It  is  called  the  infraspinatus 
bursa,  and  communicates  with  the  shoulder-joint  by  means  of  an  opening  in  the  outer 
surface  of  the  capsule.  The  subdeltoid  or  subacromial  bursa  is  placed  between  the 
under  surface  of  the  Deltoid  muscle  and  the  outer  surface  of  the  capsule.  It  does 
not  communicate  with  the  joint.  The  subcutaneous  acromial  bursa  is  between  the 
surface  and  the  summit  of  the  acromion  process.  There  is  a  bursa  beneath 
the  Coraco-brachialis  muscle — one  beneath  the  teres  major — and  one  beneath 
the  tendinous  portion  of  the  latissimus  dorsi.  There  is  also  a  bursa  between  the 
tendon  of  insertion  of  the  Pectoralis  major  muscle  and  the  long  head  of  the 
biceps. 

The  Muscles  in  relation  with  the  joint  are,  above,  the  Supraspinatus ;  below,  the 
long  head  of  the  Triceps;  in  front,  the  Subscapularis;  behind,  the  Infraspinatus 
and  Teres  minor;  within,  the  long  tendon  of  the  Biceps.  The  Deltoid  is  placed 
most  externally,  and  covers  the  articulation  on  its  outer  side,  as  well  as  in  front 
and  behind. 

20 


306  THE  ARTICULATIONS   OB   JOINTS 

The  Arteries  supplying  the  joint  are  articular  branches  of  the  anterior  and 
posterior  circumflex,  and  the  suprascapular. 

The  Nerves  are  derived  from  the  circumflex  and  suprascapular. 

Actions. — The  shoulder-joint  is  capable  of  movement  in  every  direction,  forward, 
backward,  abduction,  adduction,  circumduction,  and  rotation.  The  humerus  is 
drawn  forward  by  the  Pectoralis  major,  anterior  fibres  of  the  Deltoid,  Coraco- 
brachialis,  and  by  the  Biceps  when  the  forearm  is  flexed ;  backward,  by  the  Latis- 
simus  dorsi,  Teres  major,  posterior  fibres  of  the  Deltoid,  and  by  the  Triceps  when 
the  forearm  is  extended;  it  is  abducted  (elevated)  by  the  Deltoid  and  Supraspinatus; 
it  is  adducted  (depressed)  by  the  Subscapularis,  Pectoralis  major,  liatissimus  dorsi, 
and  Teres  major;  it  is  rotated  outward  by  the  Infraspinatus  and  Teres  minor; 
and  it  is  rotated  inward  by  the  Subscapularis,  Latissimus  dorsi.  Teres  major,  and 
•Pectoralis  major. 

The  most  striking  peculiarities  in  this  joint  are:  1.  The  large  size  of  the  head 
of  the  humerus  in  comparison  with  the  depth  of  the  glenoid  cavity,  even  when 
supplemented  by  the  glenoid  ligament.  2.  The  looseness  of  the  capsule  of  the 
joint.  3.  The  intimate  connection  of  the  capsule  with  the  muscles  attached  to  the 
head  of  the  humerus.     4.  The  peculiar  relation  of  the  biceps  tendon  to  the  joint. 

It  is  in  consequence  of  the  relative  size  of  the  two  articular  surfaces  that  the 
joint  enjoys  such  free  movement  in  every  possible  direction.  When  these  move- 
ments of  the  arm  are  arrested  in  the  shoulder-joint  by  the  contact  of  the  bony  sur- 
faces and  by  the  tension  of  the  corresponding  fibres  of  the  capsule,  together  with 
that  of  the  muscles  acting  as  accessory  ligaments,  they  can  be  carried  considerably 
farther  by  the  movements  of  the  scapula,  involving,  of  course,  motion  at  the 
acromio-  and  sterno-clavicular  joints.  These  joints  are  therefore  to  be  regarded 
as  accessory  structures  to  the  shoulder-joint.^  The  extent  of  these  movements  of 
the  scapula  is  very  considerable,  especially  in  extreme  elevation  of  the  arm,  which 
movement  is  best  accomplished  when  the  arm  is  thrown  somewhat  forward  and 
outward,  because  the  margin  of  the  head  of  the  humerus  is  by  no  means  a  true 
circle;  its  greatest  diameter  is  from  the  bicipital  groove  downward,  inward,  and 
backward,  and  the  greatest  elevation  of  the  arm  can  be  obtained  by  rolling  its 
articular  surface  in  the  direction  of  the  measurement.  The  great  width  of  the 
central  portion  of  the  humeral  head  also  allows  of  very  free  horizontal  movement 
when  the  arm  is  raised  to  a  right  angle,  in  which  movement  the  arch  formed  by  the 
acromion,  the  coracoid  process,  and  the  coraco-acromial  ligament  constitutes  a 
sort  of  supplemental  articular  cavity  for  the  head  of  the  bone. 

The  looseness  of  the  capsule  is  so  great  that  the  arm  will  fall  about  an  inch 
from  the  scapula  when  the  muscles  are  dissected  from  the  capsular  ligament  and 
an  opening  made  in  it  to  remove  the  atmospheric  pressure.  The  movements  of 
the  joint,  therefore,  are  not  regulated  by  the  capsule  so  much  as  by  the  surrounding 
muscles  and  by  the  pressure  of  the  atmosphere — an  arrangement  which  "renders 
the  movements  of  the  joint  much  more  easy  than  they  would  otherwise  have  been, 
and  permits  a  swinging,  pendulum-like  vibration  of  the  limb  when  the  muscles 
are  at  rest"  (Humphry).  The  fact,  also,  that  in  all  ordinary  positions  of  the  joint 
the  capsule  is  not  put  on  the  stretch  enables  the  arm  to  move  freely  in  all  direc- 
tions. Extreme  movements  are  checked  by  the  tension  of  appropriate  portions  of 
the  capsule,  as  well  as  by  the  interlocking  of  the  bones.  Thus  it  is  said  that 
"  abduction  is  checked  by  the  contact  of  the  great  tuberosity  with  the  upper  edge  of 
the  glenoid  cavity,  adduction  by  the  tension  of  the  coraco-humeral  ligament" 
(Beaunis  et  Bouchard).  Cleland^  maintains  that  the  limitations  of  movement  at 
the  shoulder-joint  are  due  to  the  structure  of  the  joint  itself,  the  glenoid  ligament 
fitting,  in  different  positions  of  the  elevated  arm,  into  the  anatomical  neck  of  the 
humerus. 

1  See  p.  301.  *  Journal  of  Anatomy  and  Physiology,  1884,  vol.  xviii. 


THE  SHOULDER-  JOINT  307 

Cathcart^  has  pointed  out  that  in  abducting  the  arm  and  raising  it  above  the 
liead,  the  scapula  rotates  throughout  the  whole  movement  with  the  exception  of 
a  short  space  at  the  beginning  and  at  the  end;  that  the  humerus  moves  on  the 
scapula  not  only  from  the  hanging  to  the  horizontal  position,  but  also  in  passing 
upward  as  it  approaches  the  vertical  above;  that  the  clavicle  moves  not  only 
during  the  second  half  of  the  movement  but  in  the  first  as  well,  though  to  a  less 
extent — i.  e.,  the  scapula  and  clavicle  are  concerned  in  the  first  stage  as  well  as  in 
the  second;  and  that  the  humerus  is  partly  involved  in  the  second  as  well  as 
chiefly  in  the  first. 

The  intimate  union  of  the  tendons  of  the  four  short  muscles  with  the  capsule 
converts  these  muscles  into  elastic  and  spontaneously  acting  ligaments  of  the  joint, 
and  it  is  regarded  as  being  also  intended  to  prevent  the  folds  into  which  all  portions 
of  the  capsule  would  alternately  fall  in  the  varying  positions  of  the  joint  from  being 
driven  between  the  bones  by  the  pressure  of  the  atmosphere. 

The  peculiar  relations  of  the  Biceps  tendon  to  the  shoulder-joint  appear  to  sub- 
serve various  purposes.  In  the  first  place,  by  its  connection  with  both  the  shoulder 
and  elbow  the  muscle  harmonizes  the  action  of  the  two  joints,  and  acts  as  an 
elastic  ligament  in  all  positions,  in  the  manner  previously  adverted  to.^  Next,  it 
strengthens  the  upper  part  of  the  articular  cavity,  and  prevents  the  head  of  the 
humerus  from  being  pressed  up  against  the  acromion  process,  when  the  Deltoid 
contracts,  instead  of  forming  the  centre  of  motion  in  the  glenoid  cavity.  By  its 
passage  along  the  bicipital  groove  it  assists  in  rendering  the  head  of  the  humerus 
steady  in  the  various  movements  of  the  arm.  When  the  arm  is  raised  from  the 
side  it  assists  the  Supra-  and  Infraspinatus  in  rotating  the  head  of  the  humerus  in 
the  glenoid  cavity.  It  also  holds  the  head  of  the  bone  firmly  in  contact  with  the 
glenoid  cavity,  and  prevents  its  slipping  over  its  lower  edge,  or  being  displaced  by 
the  action  of  the  Latissimus  dorsi  and  Pectoralis  major,  as  in  climbing  and  many 
other  movements. 

Surface  Form. — The  direction  and  position  of  the  shoulder-joint  may  be  indicated  by  a  line 
drawn  from  the  middle  of  the  coraco-acromial  ligament,  in  a  curved  direction,  with  its  con- 
vexity inward,  to  the  innermost  part  of  that  portion  of  the  head  of  the  humerus  which  can  be 
felt  in  the  axilla  when  the  arm  is  forcibly  abducted  from  the  side.  When  the  arm  hangs  by  the 
side,  not  more  than  one-third  of  the  head  of  the  bone  is  in  contact  with  the  glenoid  cavity,  and 
three-fjuarters  of  its  circumference  is  in  front  of  a  vertical  line  drawn  from  the  anterior  border 
of  the  acromion  process. 

Surgical  Anatomy. — Owing  to  the  construction  of  the  shoulder-joint  and  the  freedom  of 
movement  which  it  enjoys,  as  well  as  in  consequence  of  its  exposed  situation,  it  is  more  frequently 
dislocated  than  any  other  joint  in  the  body.  Dislocations  of  the  shoulder  contribute  about  forty 
per  cent,  of  the  cases  in  tables  of  dislocations.  Dislocation  occurs  when  the  arm  is  thrown  into 
<?xtreme  abduction,  and  when,  therefore,  the  head  of  the  humerus  presses  against  the  lower  and 
froiit  part  of  the  capsule,  which  is  the  thinnest  and  least  supported  part  of  the  ligament.  The 
rent  in  the  capsule  almost  invariably  takes  place  in  this  situation,  between  the  tendon  of  the  Sub- 
scapularis  and  the  Triceps,  and  through  it  the  head  of  the  bone  escapes,  so  that  the  dislocation 
in  most  instances  is  primarily  subglenoid.  The  head  of  the  bone  does  not  usually  remain  in  this 
situation,  but  generally  assumes  some  other  position,  which  varies  according  to  the  direction  and 
amount  of  force  producing  the  dislocation  and  the  relative  strength  of  the  muscles  in  front  and 
behind  the  joint.  In  consequence  of  the  muscles  at  the  back  being  weaker  than  those  in  front, 
and  especially  on  account  of  the  long  head  of  the  Triceps  preventing  the  bone  passing  backward, 
dislocation  forward  is  much  more  common  than  backward.  The  most  frequent  position  which 
the  head  of  the  humerus  ultimately  assumes  is  on  the  front  of  the  neck  of  the  scapula,  beneath 
the  coracoid  process,  and  hence  named  subcoracoid  dislocation.  Occasionally,  in  consequence 
probably  of  a  greater  amount  of  force  being  brought  to  bear  on  the  limb,  the  head  is  driven 
farther  inward,  and  rests  on  the  upper  part  of  the  front  of  the  chest,  beneath  the  clavicle  (sub- 
clavicular). If  the  head  of  the  bone  passes  under  the  Subscapularis  muscle  and  also  under 
the  Teres  major  or  the  lower  border  of  the  Pectoralis  major,  the  arm  remains  abducted,  or  even 
with  the  elbow  raised  above  the  head  {luxatio  erecta).  Sometimes  the  humerus  remains  in  the 
position  in  which  it  was  primarily  displaced,  resting  on  the  axillary  border  of  the  scapula  (sub- 

'  Journal  of  Anatomy  and  Physiology,  1884,  vol.  xviii.  *  See  p.  26Sr 


308  'I'HE  ARTICULATIONS    OB   JOINTS 

glenoid),  and  rarely  it  passes  backward  and  remains  in  the  infraspinatous  fossa  beneath  the 
spine  (subspinous).  If  dislocation  frequently  recurs  the  condition  may  be  amended  in  some 
cases  by  exposing  the  capsule  and  putting  tucks  in  it  by  means  of  sutures. 

An  old  unreduced  dislocation  is  sometimes  treated  by  incising  the  soft  parts  and  returning 
the  head  of  the  humerus  into  the  glenoid  cavity.  In  other  cases  the  head  of  the  humerus  is 
excised.  Dislocation  of  the  long  tendon  of  the  Biceps  muscle  from  the  bicipital  groove  is  a  rare 
accident.  When  it  occurs  the  arm  is  rigid  in  abduction,  but  the  head  of  the  humerus  is  found 
to  be  in  the  glenoid  cavity.  It  is  reduced  by  flexion  of  the  elbow  and  rotation  of  the  arm. 
Rupture  of  the  long  tendon  of  the  biceps  is  more  common  than  dislocation  of  the  tendon. 

After  this  injury  the  belly  of  the  muscle  is  relaxed  and  is  nearer  than  normal  to  the  elbow; 
flexion  of  the  forearm  is  much  weakened,  and  is  weaker  in  supination  than  it  is  in  pronation. 
The  head  of  the  humerus  passes  forward  and  inward,  and  the  condition  is  often  mistaken  for 
dislocation  of  the  bone. 

If  we  desire  to  aspirate  the  shoulder- joint,  place  the  arm  against  the  side,  flex  the  forearm  at 
a  right  angle  to  the  arm,  carry  the  forearm  across  the  front  of  the  chest,  and  enter  the  trocar 
below  the  acromion  (De  Vos). 

The  shoulder-joint  is  sometimes  the  seat  of  all  those  inflammatory  affections,  both  acute  and 
chronic,  which  attack  joints,  though  perhaps  it  suffers  less  frequently  than  some  other  joints  of 
equal  size  and  importance.  Acute  synovitis  may  result  from  injury,  rheumatism,  or  pysemia,  or 
may  follow  secondarily  on  the  so-called  acute  epiphysitis  of  infants.  It  is  attended  with  effusion 
into  the  joint,  and  when  this  occurs  the  capsule  is  evenly  distended  and  the  contour  of  the  joint 
rounded.  Special  projections  may  occur  at  the  site  of  the  openings  in  the  capsular  ligament. 
Thus  a  swelling  may  appear  just  in  front  of  the  joint,  internal  to  the  lesser  tuberosity,  from  effu- 
sion into  the  bursa  beneath  the  Subscapularis  muscle;  or,  again,  a  swelling  which  is  sometimes 
bilobed  may  be  seen  in  the  interval  between  the  Deltoid  and  Pectoralis  major  muscles,  from  effu- 
sion into  the  diverticulum,  which  runs  down  the  bicipital  groove  with  the  tendon  of  the  biceps. 
The  effusion  into  the  synovial  membrane  can  be  best  ascertained  by  examination  from  the  axilla, 
where  a  soft,  elastic,  fluctuating  swelling  can  usually  be  felt.  The  bursa  beneath  the  deltoid  is 
sometimes  ruptured  by  violence,  and  sometimes  inflames,  suppurates,  or  becomes  tuberculous. 

Tuberculous  arthritis  not  unfrequently  attacks  the  shoulder-joint,  and  may  lead  to  total 
destruction  of  the  articulation,  when  ankylosis  may  result  or  long-protracted  suppuration  may 
necessitate  excision.  This  joint  is  also  one  of  those  which  is  most  liable  to  be  the  seat  of  osteo- 
arthritis, and  may  also  be  affected  in  gout  and  rheumatism;  or  in  locomotor  ataxia,  when  it 
occasionally  becomes  the  seat  of  Charcot's  disease. 

Excision  of  the  shoulder-joint  may  be  required  in  cases  of  arthritis  (especially  the  tuber- 
culous form)  which  have  gone  on  to  destruction  of  the  articulation;  in  compound  dislocations  and 
fractures,  particularly  those  arising  from  gunshot  injuries,  in  which  there  has  been  extensive 
injury  to  the  head  of  the  bone;  in  some  cases  of  old  unreduced  dislocation,  where  there  is  much 
pain;  and  possibly  in  some  few  cases  of  growth  connected  with  the  upper  end  of  the  bone.  The 
operation  is  best  performed  by  making  an  incision  from  the  middle  of  the  coraco-acromial  liga- 
ment down  the  arm  for  about  three  inches:  this  will  expose  the  bicipital  groove  and  the  tendon 
of  the  Biceps,  which  may  be  either  divided  or  hooked  out  of  the  way,  according  as  to  whether  it 
is  implicated  in  the  disease  or  not.  The  capsule  is  then  freely  opened,  and  the  muscles  attached 
to  the  greater  and  lesser  tuberosities  of  the  humerus  divided.  The  head  of  the  bone  can  then 
be  thrust  out  of  the  wound  and  sawn  off,  or  divided  with  a  narrow  saw  in  sitn  and  subsequently 
removed.  The  section  should  be  made,  if  possible,  just  below  the  articular  surface,  so  as  to 
leave  the  bone  as  long  as  possible.  The  glenoid  cavity  must  then  be  examined,  and  gouged 
if  carious. 

V.  The  Elbow- joint  (Articulatio  Cubiti)  (Figs.  223,  224,  225,  226). 

The  elbow  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  forma- 
tion are  the  trochlea  of  the  humerus,  which  is  received  into  the  greater  sigmoid 
cavity  of  the  ulna  {articulatio  humeroulnaris ) ,  and  admits  of  the  movements 
peculiar  to  this  joint — viz.,  flexion  and  extension;  whilst  the  capitellum  or  radial 
head  of  the  humerus  articulates  with  the  cup-shaped  depression  on  the  head  of 
the  radius  (articulatio  Jiumeroradialis) ;  the  circumference  of  the  head  of  the 
radius  articulates  with  the  lesser  sigmoid  cavity  of  the  ulna  {articulatio  radio- 
ulnaris  proximalis) ,  allowing  of  the  movement  of  rotation  of  the  radius  on  the 
ulna,  the  chief  action  of  the  superior  radio-ulnar  articulation.  The  articular 
surfaces  are  covered  with  a  thin  layer  of  cartilage,  and  connected  together  by  a 
capsular  ligament  {capsula  articularis)  (Fig.  225)  of  unequal  thickness,  being 
especially  thickened  on  its  two  sides  and,  to  a  less  extent,  in  front  and  behind. 


THE  ELBOW- JOINT 


309 


These  thickened  portions  are  usually  described  as  distinct  ligaments  under  the 

following  names: 

Anterior.  Internal  Lateral 

Posterior.  External  Lateral. 

The  orbicular  ligament  of  the  upper  radio-ulnar  articulation  must  also  be 
reckoned  among  the  ligaments  of  the  elbow. 

The  Anterior  Ligament  (Fig.  223)  is  a  broad  and  thin  fibrous  layer  which  covers 
the  anterior  surface  of  the  joint.  It  is  attached  to  the  front  of  the  internal  condyle 
and  to  the  front  of  the  humerus  immediately  above  the  coronoid  and  radial  fossae; 
below,  to  the  anterior  surface  of  the  coronoid  process  of  the  ulna  and  to  the 
orbicular  ligament,  being  continuous  on  each  side  with  the  lateral  ligaments.    Its 


Fig.  223. — Left  elbow-joint,  showing  anterior 
and  internal  ligaments. 


Fig.  224. — Left  elbow-joint,  showing  posterior 
and  external  ligaments. 


superficial  fibres  pass  obliquely  from  the  inner  condyle  of  the  humerus  outward  to 
the  orbicular  ligament.  The  middle  fibres,  vertical  in  direction,  pass  from  the 
upper  part  of  the  coronoid  depression  and  become  partly  blended  with  the  pre- 
ceding, but  are  mainly  inserted  into  the  anterior  surface  of  the  coronoid  process. 
The  deep  or  transverse  set  intersects  these  at  right  angles.  This  ligament  is  in 
relation,  in  front,  with  the  Brachialis  anticus  muscle,  except  at  its  outermost 
part;  behind,  it  is  in  relation  with  the  synovial  membrane. 

The  Posterior  Ligament  (Fig.  224)  is  a  tliin  and  loose  membranous  fold,  attached, 
above,  to  the  lower  end  of  the  humerus,  above  and  at  the  sides  of  the  olecranon 


310 


THE  ARTICULATIONS    OB    JOINTS 


CORONOID 
PROCESS 


OLECRANON 
FOSSA 


ARTICULAR 
CAPSULE 


fossa;  below,  to  the  groove  on  the  upper  and  outer  surfaces  of  the  olecranon.  The 
superficial  or  transverse  fibres  pass  between  the  adjacent  margins  of  the  olecranon 
fossa.  The  deeper  portion  consists  of  vertical  fibres,  some  of  which,  thin  and 
weak,  pass  from  the  upper  part  of  the  olecranon  fossa  to  the  margin  of  the  olec- 
ranon; others,  thicker  and  stronger,  pass  from  the  back  of  the  capitellum  of  the 
humerus  to  the  posterior  border  of  the  lesser  sigmoid  cavity  of  the  ulna.  This 
ligament  is  in  relation,  behintl,  with  the  tendon  of  the  Triceps  muscle  and  the 
Anconeus  muscle;  in  front,  with  the  synovial  membrane. 

The  Internal  Lateral  Ligament  (ligamentum  collaterale  ulnare)  (Fig.  223)  is  a 
thick  triangular  band  consisting  of  two  portions,  an  anterior  and  posterior,  united 
by  a  thinner  intermediate  portion.  The  anterior  portion,  directed  obhquely  forward, 

is  attached,  above,  by  its  apex, 
to  the  front  part  of  the  in- 
ternal condyle  of  the  humerus ; 
and,  below,  by  its  broad  base, 
to  the  inner  margin  of  the 
coronoid  process.  The  poste- 
rior portion,  also  of  triangular 
form,  is  attached,  above,  by 
its  apex,  to  the  lower  and  back 
part  of  the  internal  condyle; 
below,  to  the  inner  margin  of 
the  olecranon.  Between  these 
two  bands  a  few  intermediate 
fibres  descend  from  the  inter- 
nal condyle  to  blend  with  a 
transverse  band  of  ligament- 
ous tissue  which  bridges 
across  the  notch  between  the 
olecranon  and  coronoid  pro- 
cesses. This  ligament  is  in 
relation,  internally,  with  the 
Triceps  and  Flexor  carpi 
ulnaris  muscles  and  the  ulnar 
nerve,  and  gives  origin  to  part 
of  the  Flexor  sublimis  digi- 
torum  muscle. 

The  External  Lateral  Liga- 
ment (ligamentum  collaterale 
radiale)  (Fig.  224)  is  a  short 
and  narrow  fibrous  band  less 
distinct  than  the  internal,  at- 
tached, above,  to  a  depression 
below  the  external  condyle  of 
the  humerus;  below,  to  the 
orbicular  ligament,  some  of  its 
most  posterior  fibres  passing  over  that  ligament,  to  be  inserted  into  the  outer 
margin  of  the  ulna.  This  ligament  is  intimately  blended  with  the  tendon  of 
origin  of  the  Supinator  brevis  muscle. 

Synovial  Membrane  (Fig.  225). — The  synovial  membrane  is  very  extensive.  It 
covers  the  margin  of  the  articular  surface  of  the  humerus,  and  lines  the  coronoid 
and  olecranon  fossa  on  that  bone;  from  these  points  it  is  reflected  over  the  anterior, 
posterior,  and  lateral  ligaments,  and  forms  a  pouch  (recessus  sacciformis)  between 
the  lesser  sigmoid  cavity,  the  internal  surface  of  the  orbicular  ligament,  and  the 


EPIPHYSrAL 
JUNCTION 


EPIPHYSEAL 
JUNCTION 


Fig.  225. — Right  elbow-joint,  cut  through  at  right  angles  to  the 
axis  of  the  trochlea  humeri,  from  the  ulnar  side.     (Spalteholz.) 


THE   ELBOW- JOINT 


311 


circumference  of  the  head  of  the  radius.  Projecting  into  the  cavity  is  a  crescentic 
fold  of  synovial  membrane,  between  the  radius  and  ulna,  suggesting  the  division  of 
the  joint  into  two :  one  the  humero-radial,  the  other  the  humero-ulnar. 

Between  the  capsular  ligament  and  the  synovial  membrane  are  three  masses 
of  fat:  one,  the  largest,  above  the  olecranon  fossa,  which  is  pressed  into  the  fossa  by 
the  Triceps  during  flexion;  a  second,  over  the  coronoid  fossa;  and  a  third,  over 
the  radial  fossa.  The  two  last-named  pads  are  pressed  into  their  respective  fossae 
during  extension. 

The  muscles  (Fig.  226)  in  relation  with  the  joint  are,  in  front,  the  Brachialis 
anticus;  behind,  the  Triceps  and  Anconeus;  externallij,  the  Supinator  brevis  and 
the  common  tendon  of  origin  of  the  Ex- 
tensor muscles  ;  internally,  the  common 
tendon  of  origin  of  the  Flexor  muscles,  and 
the  Flexor  carpi  ulnaris,  with  the  ulnar 
nerve. 

The  arteries  supplying  the  joint  are  de- 
rived from  the  anastomosis  between  the 
superior  profunda,  inferior  profunda,  and 
anastomotica  magna,  bi  inches  of  the 
brachial,  with  the  anterior,  posterior,  and 
interosseous  recurrent  branches  of  the 
ulnar  and  the  recurrent  branch  of  the 
radial.  These  vessels  form  a  complete 
chain  of  inosculation  around  the  joint. 

The  nerves  are  derived  from  the  ulnar 
as  it  passes  between  the  internal  condyle 
and  the  olecranon  ;  a  filament  from  the 
musculo-cutaneous  (Riidinger),  and  two 
filaments  from  the  median  (Macalister). 

Bursse. — The  olecranon  bursa  (bursa  sub- 
cutaneous olecrani)  is  placed  between  the 
olecranon  process  and  the  cutaneous  sur- 
face. A  bursa  exists  between  the  tendon 
of  the  Biceps  and  the  tubercle  of  the 
radius  {bursa  bicipitoradialis)  —  another 
between  the  Triceps  tendon  and  the  olec- 
ranon process  (bursa  subtendinea  olecrani) 
— another  between  the  cutaneous  surface 

and  the  external  condyle  (bursa  subcutanea  epicondyli  humeri  lateralis) — another 
between  the  cutaneous  surfr.ce  and  the  internal  condyle  (bursa  subcutanea 
epicondyli  humeri  medialis — another  within  the  Triceps  tendon  at  its  insertion  on 
the  olecranon  (bursa  intratendinea  olecrani). 

Actions. — The  elbow-joint  comprises  three  different  portions — viz.,  the  joint 
between  the  ulna  and  humerus,  that  between  the  head  of  the  radius  and  the 
humerus,  and  the  superior  radio-ulnar  articulation,  described  below.  All  these 
articular  surfaces  are  invested  by  a  common  synovial  membrane,  and  the  move- 
ments of  the  whole  joint  should  be  studied  together.  The  combination  of  the 
movements  of  flexion  and  extension  of  the  forearm  with  those  of  pronation  and 
supination  of  the  hand,  which  is  ensured  by  the  two  being  performed  at  the 
same  joint,  is  essential  to  the  accuracy  of  the  various  minute  movements  of  the 
hand. 

The  portion  of  the  joint  between  the  ulna  and  humerus  is  a  simple  hinge- 
joint,  and  allows  of  movements  of  flexion  and  extension  only.  Owing  to  the 
obliquity  of  the  trochlear  surface  of  the  humerus,  this  movement  does  not  take 


Fig.  226. — Sagittal  section  of  the  right  elbow- 
joint,  taken  somewhat  obliquely  and  seen  from  the 
radial  aspect.     (After  Braune.) 


312  THE  ARTICULATIONS   OR    JOINTS 

place  in  a  straight  line;  so  that  when  the  forearm  is  extended  and  supinated 
the  axis  of  the  arm  and  forearm  is  not  in  the  same  line,  but  the  one  portion  of  the 
limb  forms  an  angle  with  the  others,  and  the  hand,  with  the  forearm,  is  directed 
outward.  During  flexion,  on  the  other  hand,  the  forearm  and  the  hand  tend  to 
approach  the  middle  line  of  the  body,  and  thus  enable  the  hand  to  be  easily 
carried  to  the  face.  The  shape  of  the  articular  surface  of  the  humerus,  with  its 
prominences  and  depressions  accurately  adapted  to  the  opposing  surfaces  of 
the  olecranon,  prevents  any  lateral  movement.  Flexion  is  produced  by  the 
action  of  the  Biceps  and  Brachialis  anticus,  assisted  by  the  muscles  arising  from 
the  internal  condyle  of  the  humerus  and  the  Supinator  longus;  extension,  by  the 
Triceps  and  Anconeus,  assisted  by  the  extensors  of  the  wrist  and  by  the  Extensor 
communis  digitorum  and  Extensor  minimi  digiti. 

The  joint  between  the  head  of  the  radius  and  the  capitellum  or  radial  head  of 
the  humerus  is  an  arthrodial  joint.  The  bony  surfaces  would  of  themselves  con- 
stitute an  enarthrosis,  and  allow  of  movement  in  all  directions  were  it  not  for  the 
orbicular  ligament  by  which  the  head  of  the  radius  is  bound  down  firmly  to  the 
sigmoid  cavity  of  the  ulna,  and  which  prevents  any  separation  of  the  two  bones 
laterally.  It  is  to  the  same  ligament  that  the  head  of  the  radius  owes  its  security 
from  dislocation,  which  would  otherwise  constantly  occur  as  a  consequence  of  the 
shallowness  of  the  cup-like  surface  on  the  head  of  the  radius.  In  fact,  but  for 
this  ligament  the  tendon  of  the  biceps  would  be  liable  to  pull  the  head  of  the 
radius  out  of  the  joint. ^  In  complete  extension  the  head  of  the  radius  glides  so 
far  back  on  the  outer  condyle  that  its  edge  is  plainly  felt  at  the  back  of  the  articu- 
lation. Flexion  and  extension  of  the  elbow-joint  are  limited  by  the  tension  of 
the  structures  on  the  front  and  back  of  the  joint,  the  limitation  of  flexion  being 
also  aided  by  the  soft  structures  of  the  arm  and  forearm  coming  in  contact. 

In  combination  with  any  position  of  flexion  or  extension  the  head  of  the  radius 
can  be  rotated  in  the  upper  radio-ulnar  joint,  carrying  the  hand  with  it.  The 
hand  is  directly  articulated  to  the  lower  surface  of  the  radius  only,  and  the  concave 
or  sigmoid  surface  on  the  lower  end  of  the  radius  travels  round  the  lower  end  of 
the  ulna.  The  latter  bone  is  excluded  from  the  wrist-joint  (as  will  be  seen  in 
the  sequel)  by  the  interarticular  fibro-cartilage.  Thus,  rotation  of  the  head  of  the 
radius  round  an  axis  which  passes  through  the  centre  of  the  radial  head  of  the 
humerus  imparts  circular  movement  to  the  hand  through  a  very  considerable 
arc. 

Surface  Form. — If  the  forearm  be  slightly  flexed  on  the  arm,  a  curved  crease  or  fold  with 
its  convexity  downward  may  be  seen  running  across  the  front  of  the  elbow,  extending  from  one 
condyle  to  the  other.  The  centre  of  this  fold  is  some  slight  distance  above  the  line  of  the  joint. 
The  position  of  the  radio-humeral  portion  of  the  joint  can  be  at  once  ascertained  by  feehng  for  a 
slight  groove  or  depression  between  the  head  of  the  radius  and  the  capitellum  of  the  humerus  at 
the  back  of  the  articulation. 

Surgical  Anatomy.^From  the  great  breadth  of  the  joint,  and  the  manner  in  which  the 
articular  surfaces  are  interlocked,  and  also  on  account  of  the  strong  lateral  ligaments  and 
the  support  which  the  joint  derives  from  the  mass  of  muscles  attached  to  each  condyle  of  the 
humerus,  lateral  displacement  of  the  bones  is  very  uncommon,  whereas  antero-posterior  disloca- 
tion, on  account  of  the  shortness  of  the  antero-posterior  diameter,  the  weakness  of  the  anterior 
and  posterior  ligaments,  and  the  want  of  support  of  muscles,  much  more  frequently  takes  place, 
dislocation  backward  taking  place  when  the  forearm  is  in  a  position  of  extension,  and  forward 
when  in  a  position  of  flexion.  For,  in  the  former  position,  that  of  extension,  the  coronoid  process 
is  not  interlocked  into  the  coronoid  fossa,  and  loses  its  grip  to  a  certain  extent,  whereas  th(: 
olecranon  process  is  in  the  olecranon  fossa,  and  entirely  prevents  displacement  forward.  On 
the  other  hand,  during  flexion,  the  coronoid  process  is  in  the  coronoid  fossa,  and  prevents  dis- 
location backward,  while  the  olecranon  loses  its  grip  and  is  not  so  efficient,  as  during  extension, 
in  preventing  a  forward  displacement.  When  lateral  dislocation  does  take  place,  it  is  generally 
incomplete. 

1  Humphry,  op  cit.,  p.  419. 


RADIO- ULNAR   ARTICULATION  313 

Dislocation  of  the  elbow-joint  is  of  common  occurrence  in  children,  far  more  common  than 
dislocation  of  any  other  articulation,  for,  as  a  rule,  fracture  of  a  bone  more  frequently  takes 
place,  under  the  application  of  any  severe  violence,  in  young  persons  than  dislocation.  In 
lesions  of  this  joint  there  is  often  very  great  difficulty  in  ascertaining  the  exact  nature  of  the 
injury.  Sprain  of  the  elbow  is  a  very  common  injury  in  childhood.  Injury  to  the  radio- 
humeral  joint  is  frequently  produced  by  lifting  a  child  by  the  hand,  as  in  swinging  it  over  a 
gutter.  The  supinator  brevis,  which  under  normal  circumstances  would  retain  the  head  of  the 
radius  against  the  capitellum  of  the  humerus,  is  unable  to  do  so,  the  radio-humeral  articulation 
receives  the  force  and  the  orbicular  ligament  undergoes  upward  displacement,  is  caught 
between  the  head  of  the  radius  and  the  capitellum  and  jams  the  joint. ^  This  injury  is  often 
called  subluxation  of  the  head  of  the  radius. 

The  elbow-joint  is  occasionally  the  seat  of  acute  synovitis.  The  synovial  membrane  then 
becomes  distended  with  fluid,  the  bulging  showing  itself  principally  around  the  olecranon  process ; 
that  is  to  say,  on  its  inner  and  outer  sides  and  above,  in  consequence  of  the  laxness  of  the  poste- 
rior ligament.  Occasionally  a  well-marked,  triangular  projection  may  be  seen  on  the  outer 
side  of  the  olecranon,  from  bulging  of  the  synovial  membrane  beneath  the  Anconeus  muscle. 
Again,  there  is  often  some  swelling  just  above  the  head  of  the  radius,  in  the  line  of  the  radio- 
humeral  joint.  There  is  generally  not  much  swelling  at  the  front  of  the  joint,  though  sometimes 
deep-seated  fulness  beneath  the  Brachialis  anticus  may  be  noted.  When  suppuration  occurs  the 
abscess  usually  points  at  one  or  other  border  of  the  Triceps  muscle;  occasionally  the  pus  dis- 
charges itself  in  front,  near  the  insertion  of  the  Brachialis  anticus  muscle.  Chronic  synovitis, 
usually  of  tuberculous  origin,  is  of  common  occurrence  in  the  elbow-joint:  under  these  circum- 
stances the  forearm  tends  to  assume  the  position  of  semi-flexion,  which  is  that  of  greatest  ease 
and  relaxation  of  ligaments.  It  should  be  borne  in  mind  that  should  ankylosis  occur  in  this  or 
the  extended  position,  the  limb  will  not  be  nearly  so  useful  as  if  it  becomes  ankylosed  in  a  position 
of  rather  less  than  a  right  angle.  Loose  cartilages  are  sometimes  met  with  in  the  elbow-joint,  not 
so  commonly,  however,  as  in  the  knee;  nor  do  they,  as  a  rule,  give  rise  to  such  urgent  symptoms. 
They  rarely  require  operative  interference.  The  elbow-joint  is  also  sometimes  affected  with 
osteo-arthritis ,  but  this  affection  is  less  common  in  this  articulation  than  in  some  other  of  the 
larger  joints.  Bursitis  about  the  elbow  is  not  uncommon.  Enlargement  of  the  subcutaneous 
bursa  over  the  olecranon  is  known  as  miners'  elbow.  Enlargement  of  any  one  of  the  bursse 
may  occur. 

Excision  of  the  elbow  is  principally  required  for  one  of  three  conditions — viz.,  tuberculous 
arthritis,  injury  and  its  results,  and  ankylosis  in  a  position  which  greatly  impairs  the.  useful- 
ness of  the  limb;  but  may  be  necessary  for  some  other  rarer  conditions,  such  as  disorganizing 
arthritis  after  pyaemia,  unreduced  dislocation,  and  osteo-arthritis.  The  results  of  the  opera- 
tion are,  as  a  rule,  more  favorable  than  those  of  excision  of  any  other  joint,  and  it  is  one, 
therefore,  that  the  surgeon  should  never  hesitate  to  perform,  especially  in  the  first  three  of 
the  conditions  mentioned  above.  The  operation  is  best  performed  by  a  single  vertical  incision 
down  the  back  of  the  joint,  a  transverse  incision,  over  the  outer  condyle,  being  added  if  the 
p:irts  are  much  thickened  and  fixed.  A  straight  incision  is  made  about  four  inches  long,  the 
mid-point  of  which  is  on  a  level  with  and  a  little  to  the  inner  side  of  the  tip  of  the  olecra- 
non. This  incision  is  made  down  to  the  bone,  through  the  substance  of  the  Triceps  muscle. 
The  operator  with  the  point  of  his  knife,  and  guarding  the  soft  parts  with  his  thumb-nail, 
separates  them  from  the  bone.  In  doing  this  there  are  two  structures  which  he  should 
carefully  avoid:  the  ulnar  nerve,  which  lies  parallel  to  his  incision,  but  a  little  internal,  as  it 
courses  down  between  the  internal  condyle  and  the  olecranon  process,  and  the  prolongation  of 
the  Triceps  into  the  deep  fascia  of  the  forearm  over  the  Anconeus  muscle.  Having  cleared  the 
bones  and  divided  the  lateral  and  posterior  ligaments,  the  forearm  is  strongly  flexed  and  the 
ends  of  the  bone  turned  out  and  sawn  off.  The  section  of  the  humerus  should  be  through 
the  base  of  the  condyles,  that  of  the  ulna  and  radius  should  be  just  below  the  level  of  the  lesser 
sigmoid  cavity  of  the  ulna  and  the  neck  of  the  radius.  In  this  operation  the  object  is  to  obtain 
such  fibrous  union  as  shall  allow  free  motion  of  the  bones  of  the  forearm;  and,  therefore,  passive 
motion  must  be  commenced  early,  that  is  to  say,  about  the  tenth  day. 

VI.  Radio-ulnar  Articulation  (Articulatio  Radioulnaris). 

The  articulation  of  the  radius  with  the  ulna  is  effected  by  ligaments  which 
connect  together  both  extremities  as  well  as  the  shafts  of  these  bones.  It  may, 
consequently,  be  subdivided  into  three  articulations :  (1)  the  superior  radio-ulnar, 
which  is  a  portion  of  the  elbow-joint;  (2)  the  middle  radio-ulnar;  and  (3)  the  infe- 
rior radio-ulnar  articulations. 

^  Mr.  Jonathan  Hutchinson,  Jr.,  in  Annals  of  Surgery,  August,  1885. 


314  THE  ARTICULATIONS    OB    JOINTS 

1.  Superior  or  Proximal  Radio-ulnar  Articulation  (Articulatio 
Radioulnaris  Proximalis). 

This  articulation  is  a  trochoid  or  pivot-joint.  The  bones  entering  into  its  forma- 
tion are  the  inner  side  of  the  circumference  of  the  head  of  the  radius  rotating  within 
the  lesser  sigmoid  cavity  of  the  ulna.     Its  only  ligament  is  the  annular  or  orbicular. 

The  Orbicular  or  Annular  Ligament  {ligamentum  annulare  radii)  (Figs.  223,  224, 
and  227)  is  a  strong,  flat  band  of  ligamentous  fibres  which  surrounds  the  head  of 
the  radius  and  retains  it  in  firm  connection  with  the  lesser  sigmoid  cavity  of  the 
ulna.  It  forms  about  four-fifths  of  an  osseo-fibrous  ring,  attached  by  each  end  to 
the  extremities  of  the  lesser  sigmoid  cavity,  and  is  smaller  at  the  lower  part  of  its 
circumference  than  above,  by  which  means  the  head  of  the  radius  is  more  securely 
held  in  its  position.  Its  outer  surface  is  strengthened  by  the  external  lateral 
ligament  of  the  elbow,  and  affords  origin  to  part  of  the  Supinator  brevis  muscle. 
Its  inner  surface  is  smooth,  and  lined  by  synovial  membrane.  The  synovial 
membrane  is  continuous  with  that  which  lines  the  elbow-joint. 

Actions. — ^The  movement  which  takes  place  in  this  articulation  is  limited  to 
rotation  of  the  head  of  the  radius  within  the  orbicular  ligament,  and  upon  the 
lesser  sigmoid  cavity  of  the  ulna,  rotation  forward  being  called  pronation;  rotation 
backward,  supination.  Supination  is  performed  by  the  Biceps  and  Supinator 
brevis,  assisted  to  a  slight  extent  by  the  Extensor  muscles  of  the  thumb  and, 
in  certain  positions,  by  the  Supinator  longus.  Pronation  is  performed  by  the 
Pronator  radii  teres  and  the  Pronator  quadratus,  assisted,  in  some  positions,  by 
the  Supinator  longus. 

Surface  Form. — The  position  of  the  superior  radio-ulnar  joint  is  marked  on  the  surface  of 
the  body  by  the  little  dimple  on  the  back  of  the  elbow  which  indicates  the  position  of  the  head 
of  the  radius. 

Surgical  Anatomy. — Dislocation  of  the  head  of  the  radius  alone  is  not  an  uncommon  acci- 
dent, and  occurs  most  frequently  in  young  persons  from  falls  on  the  hand  when  the  forearm  is 
extended  and  supinated,  the  head  of  the  bone  being  displaced  forward.  It  is  attended  by  rup- 
ture of  the  orbicular  ligament.  Occasionally  a  peculiar  injury,  which  is  supposed  to  be  a  sub- 
luxation, occurs  in  young  children  in  lifting  them  from  the  ground  by  the  hand  or  forearm.  It 
is  believed  that  the  head  of  the  radius  is  displaced  downward  or  the  orbicular  ligament  upward, 
and  the  upper  border  of  the  ligament  becomes  folded  over  the  head  of  the  radius,  between  it  and 
the  capitellum  of  the  humerus. 

2.  Middle  Radio-ulnar  Ligaments. 

The  interval  between  the  shafts  of  the  radius  and  ulna  is  occupied  by  two 
ligaments. 

Oblique.  Interosseous. 

The  Oblique  or  Round  Ligament  (chorda  obliqua)  (Figs.  223  and  225)  is  a  small^ 
flattened  fibrous  band  which  extends  obliquely  downward  and  outward  from  the 
tubercle  of  the  ulna  at  the  base  of  the  coronoid  process  to  the  radius  a  little  below 
the  bicipital  tuberosity.  Its  fibres  run  in  the  opposite  direction  to  those  of  the 
interosseous  ligament,  and  it  appears  to  be  placed  as  a  substitute  for  it  in  the 
upper  part  of  the  interosseous  interval.    This  ligament  is  sometimes  wanting. 

The  Interosseous  Membrane  (membrana  interossea  antibrachii)  (Fig.  227)  is  a 
broad  and  thin  plane  of  fibrous  tissue  descending  obliquely  downward  and  inward, 
from  the  interosseous  ridge  on  the  radius  to  that  on  the  ulna.  It  is  deficient  above, 
commencing  about  an  inch  beneath  the  tubercle  of  the  radius;  is  broader  in  the 
middle  than  at  either  extremity;  and  presents  an  oval  aperture  just  above  its 
lower  margin  for  the  passage  of  the  anterior  interosseous  vessels  to  the  back  of 
the  forearm.  This  ligament  serves  to  connect  the  bones  and  to  increase  the 
extent  of  surface  for  the  attachment  of  the  deep  muscles.     Between  its  upper 


BADIO-  ULNAR    ARTICULATION 


315 


ANNULAR  LIGAMENT 
OF  RADI 


TENDON  OF 
BICEPS  MUSCL 

(cut  through) 


OBLIQUE 
LICAMENT 


INTEROSSEOUS 
MEMBRANE 


border  and  the  oblique  ligament  an  interval  exists  through  which  the  posterior 
interosseous  vessels  pass  to  the  dorsum  of  the  forearm.  Two  or  three 
fibrous  bands  are  occasionally  found 
on  the  posterior  surface  of  this  mem- 
brane which  descend  obliquely  from 
the  ulna  toward  the  radius,  and  which 
have  consequently  a  direction  contrary 
to  that  of  the  other  fibres.  It  is  in 
relation,  in  front,  by  its  upper  three- 
fourths  with  the  Flexor  longus  pollicis 
on  the  outer  side,  and  with  the  Flexor 
profundus  digitorum  on  the  inner,  lying 
upon  the  interval  between  which  are 
the  anterior  interosseous  vessels  and 
nerve  ;  by  its  lower  fourth,  with  the 
Pronator  quadratus;  behind,  with  the 
Supinator  brevis.  Extensor  ossis  meta- 
carpi  pollicis,  Extensor  brevis  pollicis, 
Extensor  longus  pollicis,  Extensor  in- 
dicis;  and,  near  the  wrist,  with  the 
anterior  interosseous  artery  and  poste- 
rior interosseous  nerve. 

3.  Inferior  or  Distal  Radio-ulnar 
Articulation  (Articulatio  Ra- 

DIOULNARIS  DiSTALIS). 

■  This  is  a  pivot-joint,  formed  by  the 
sigmoid  cavity  at  the  inner  side  of  the 
lower  end  of  the  radius  receiving  the 
head  of  the  ulna.  The  articular  sur- 
faces are  covered  by  a  thin  layer  of 
cartilage,  and  connected  together  by  a 
capsule  (capsula  articularis) ,  portions 
of  which  are  usually  described  as  dis- 
tinct ligaments.  The  ligaments  of  the 
articulation  are: 

Anterior  Radio-ulnar. 
Posterior  Radio-ulnar. 
Triangular   Interarticular   Fibro- 
cartilage. 

The  Anterior  Radio-ulnax  Ligament 
(Fig.  228)  is  a  narrow  band  of  fibres 
extending  from  the  anterior  margin  of 
the  sigmoid  cavity  of  the  radius  to  the 
anterior  surface  of  the  head  of  the  ulna. 

The  Posterior  Radio-ulnar  Ligament 
(Fig,  229)  extends  between  similar 
points  on  the  posterior  surface  of  the 
articulation. 

The  Triangular  Interarticular  Fibro-cartilage  (discus  articularis)  (Figs.  227  and  231) 
is  triangular  in  shape,  and  is  placed  transversely  beneath  the  head  of  the  ulna, 
binding  the  lower  end  of  this  bone  and  the  radius  firmly  together.    Its  periphery 


Fig.  227. — Bones  of  the  right  forearm,  with  ligaments 
from  the  volar  .surface.     (Spalteholz.) 


31G 


THE    ARTICULATIONS    OB    JOINTS 


is  thicker  than  its  centre,  which  is  thin  and  occasionally  perforated.  It  is  attached 
by  its  apex  to  a  depression  which  separates  the  styloid  process  of  the  ulna  from 
the  head  of  that  bone;  and  by  its  base,  which  is  thin,  to  the  prominent  edge  of 


Inferior  radio-ulnar 
articulation. 


■joint. 


ticulations. 


metacarpal 
•ulations. 


Fig.  228. — Ligament.s  of  wrist  and  hand.     Anterior  view. 

the  radius,  which  separates  the  sigmoid  cavity  from  the  carpal  articulating  sur- 
face. Its  margins  are  united  to  the  ligaments  of  the  wrist-joint.  Its  iipper  sur- 
face, smooth  and  concave,  articulates  with  the  head  of  the  ulna,  forming  an 


Inferior  radio-iUnar 

articulation 


Wrist-joint 
Carpal  articulations. 


Carpo-metacarpal 

articulations, 


Fig.  229. — Ligaments  of  wrist  and  hand.     Posterior  view. 

arthrodial  joint;  its  under  surface,  also  concave  and  smooth,  forms  part  of  the 
wrist-joint  and  articulates  with  the  cuneiform  and  inner  part  of  the  semilunar 
bone.     Both  surfaces  are  lined  by  a  synovial  membrane — the  upper  surface,  by 


RADIO -CARPAL    OR    WRIST -JOINT 


317 


one  peculiar  to  the  radio-ulnar  articulation;  the  under  surface,  by  the  synovial 
membrane  of  the  wrist. 

Synovial  Membrane. — The  synovial  membrane  (Fig.  231)  of  this  articulation 
has  been  called,  from  its- extreme  looseness,  the  membrana  sacciformis.  It  projects 
horizontally  inward  between  the  head  of  the  ulna  and  the  interarticular  fibro- 
cartilage,  and  upward  between  the  radius  and  the  ulna,  forming  a  very  loose 
cul-de-sac  {recessus  sacciformis).  The  quantity 
of  synovia  which  it  contains  is  usually  consider- 
able. The  inferior  radio-ulnar  joint  does  not 
communicate  with  the  wrist-joint. 

Actions.— The  movement  in  the  inferior  radio- 
ulnar articulation  is  just  the  reverse  of  that  in 
the  superior  radio-ulnar  joint.  It  consists  of  a 
movement  of  rotation  of  the  lower  end  of  the 
radius  round  an  axis  which  corresponds  to  the 
centre  of  the  head  of  the  ulna.  When  the  radius 
rotates  forward,  pronation  of  the  forearm  and 
hand  is  the  result;  and  when  backward,  supina- 
tion. It  will  thus  be  seen  that  in  pronation  and 
supination  of  the  forearm  and  hand  the  radius 
describes  a  segment  of  a  cone,  the  axis  of  which 
extends  from  the  centre  of  the  head  of  the  radius 
to  the  middle  of  the  head  of  the  ulna.  In  this 
movement,  however,  the  ulna  is  not  quite  sta- 
tionary, but  rotates  a  little  in  the  opposite  direc- 
tion. So  that  it  also  describes  the  segment  of  a 
cone,  though  of  smaller  size  than  that  described 
by  the  radius.  The  movement  which  causes  this 
alteration  in  the  position  of  the  head  of  the  ulna 
takes  place  principally  at  the  shoulder-joint  by  a 
rotation  of  the  humerus,  but  possibly  also  to  a 
slight  extent  at  the  elbow-joint.^ 

Surface  Form. — The  position  of  the  inferior  radio- 
ulnar joint  may  be  ascertained  by  feeling  for  a  slight 
groove  at  the  back  of  the  wrist,  between  the  prominent 
head  of  the  ulna  and  the  lower  end  of  the  radius,  when 
the  forearm  is  in  a  state  of  almost  complete  pronation. 


VII.  Radio-carpal  or  Wrist-joint  (Articulatio 
Radiocarpea)  (Figs.  228,  229,  231). 

The  wrist  is  a  condyloid  articulation.  The 
parts  entering  into  its  formation  are  the  lower 
end  of  the  radius  and  under  surface  of  the 
interarticular  fibro-cartilage,  which  form  together 
the  receiving  cavity,  and  the  scaphoid,  semilunar, 
and  the  cuneiform  bones,  which  form  the  condyle.  The  articular  surface  of  the 
radius  and  the  under  surface  of  the  interarticular  fibro-cartilage  are  the  receiving 
cavity,  forming  together  a  transversely  elliptical  concave  surface.  The  articular 
surfaces  of  the  scaphoid,  semilunar,  and  cuneiform  bones  form  together  a  smooth, 
convex  surface,  the  condyle,  which  is  received  into  the  concavity  above  men- 
tioned.   All  the  bony  surfaces  of  the  articulation  are  covered  with  cartilage,  and 


Fig.  230. — Longitudinal  section  of  the 

right    forearm,    hand,     and    third  finger, 

viewed    from    the    ulnar    aspect.  (Afier 
Braune.) 


1  See  Journal  of  Anatomy  and  Physiology,  vol.  xix.,  parts  ii.,  iii.,  and  iv. 


318  THE  ARTICULATIONS    OB   JOINTS 

connected  together  by  a  loose  capsule  (capsula  articularis) ,  which  is  divided  into 
the  following  ligaments : 

External  Lateral.  Anterior. 

Internal  Lateral.  Posterior. 

• 

The  External  Lateral  Ligament  ( ligamentum  collaterale  carpi  radiate)  (Fig.  228) 
extends  from  the  summit  of  the  styloid  process  of  the  radius  to  the  outer  side  of 
the  scaphoid,  some  of  its  fibres  being  prolonged  to  the  trapezium  and  annular 
ligament. 

The  Internal  Lateral  Ligament  {ligamentum  collaterale  carpi  ulnare)  (Fig.  228) 
is  a  rounded  cord,  attached,  above,  to  the  extremity  of  the  styloid  process  of  the 
ulna,  and  dividing  below  into  two  fasciculi,  which  are  attached,  one  to  the  inner 
side  of  the  cuneiform  bone,  the  other  to  the  pisiform  bone  and  annular  ligament. 

The  Anterior  or  Volar  Ligament  {ligamentum  radiocarpeum  volare)  (Fig.  228j 
is  a  broad,  membranous  band,  attached,  above,  to  the  anterior  margin  of  the 
lower  end  of  the  radius,  its  styloid  process,  and  the  ulna :  its  fibres  pass  downward 
and  inward  to  be  inserted  i^to  the  palmar  surface  of  the  scaphoid,  semilunar, 
and  cuneiform  bones,  some  of  the  fibres  being  continued  to  the  os  magnum.  In 
addition  to  this  broad  membrane  there  is  a  distinct  rounded  fasciculus,  superficial 
to  the  rest,  which  passes  from  the  base  of  the  styloid  process  of  the  ulna  to 
the  semilunar  and  cuneiform  bones.  This  ligament  is  perforated  by  numerous 
apertures  for  the  passage  of  vessels,  and  is  in  relation,  in  front,  with  the  tendons 
of  the  Flexor  profundus  digitorum  and  Flexor  longus  pollicis;  behind,  with  the 
synovial  membrane  of  the  wrist-joint. 

The  Posterior  or  Dorsal  Ligament  (ligamentum  radiocarpeum  dorsale)  (Fig.  229), 
less  thick  and  strong  than  the  anterior,  is  attached,  above,  to  the  posterior  border 
of  the  lower  end  of  the  radius;  its  fibres  pass  obliquely  downward  and  inward,  to 
be  attached  to  the  dorsal  surface  of  the  scaphoid,  semilunar,  and  cuneiform  bones, 
being  continuous  with  those  of  the  dorsal  carpal  ligaments.  This  ligament  is  in 
relation,  behind,  with  the  extensor  tendons  of  the  fingers;  in  front,  with  the  syno- 
vial membrane  of  the  wrist. 

S3movial  Membrane. — The  synovial  membrane  (Fig.  231)  lines  the  inner  sur- 
face of  the  ligaments  above  described,  extending  from  the  lower  end  of  the  radius 
and  interarticular  fibro-cartilage  above  to  the  articular  surfaces  of  the  carpal  bones 
below.    It  is  loose  and  lax,  and  presents  numerous  folds,  especially  behind. 

Relations. — The  wrist-joint  is  covered  in  front  by  the  flexor  and  behind  by  the 
extensor  tendons  (Fig;  230);  it  is  also  in  relation  with  the  radial  and  ulnar 
arteries. 

The  arteries  supplying  the  joint  are  the  anterior  and  posterior  carpal  branches 
of  the  radial  and  ulnar,  the  anterior  and  posterior  interosseous,  and  some  ascend- 
ing branches  from  the  deep  palmar  arch. 

The  nerves  are  derived  from  the  ulnar  and  posterior  interosseous. 

Actions. — The  movements  permitted  in  this  joint  are  flexion,  extension,  abduc- 
tion, adduction,  and  circumduction.  Its  actions  will  be  further  studied  with  those 
of  the  carpus,  with  which  they  are  combined. 

Surface  Form. — The  line  of  the  radio-carpal  joint  is  on  a  level  with  the  apex  of  the  styloid 
process  of  the  ulna. 

Surgical  Anatomy. — The  wrist-joint  is  rarely  dislocated,  its  strength  depending  mainly 
upon  the  numerous  strong  tendons  which  surround  the  articulation.  Its  security  is  further  pro- 
vided for  by  the  number  of  small  bones  of  which  the  carpus  is  made  up,  and  which  are  united 
by  very  strong  ligaments.  The  slight  movement  which  takes  place  between  the  several  bones 
serves  to  break  the  jars  that  result  from  falls  or  blows  on  the  hand.  Dislocation  backward, 
which  is  the  more  common  dislocation,  simulates  to  a  considerable  extent  Colles's  fracture  of  the 
radius,  and  is  liable  to  be  mistaken  for  it.  The  diagnosis  can  be  easily  made  out  by  observing 
the  relative  position  of  the  styloid  processes  of  the  radius  and  the  ulna.  "  In  the  natural  condition 


ARTICULATIONS    OF    THE    CARPUS  319 

the  styloid  process  of  the  radius  is  on  a  lower  level — i.  e.,  nearer  the  ground — when  the  arm  hangs 
by  the  side,  than  that  of  the  ulna,  and  the  same  would  be  the  case  in  dislocation.  In  Colles's 
fracture,  on  the  other  hand,  the  styloid  process  of  the  radius  is  on  the  same  or  even  a  higher 
level  than  that  of  the  ulna. 

The  wrist-joint  is  occasionally  the  seat  of  (wute  synovitis,  the  result  of  traumatism  or  arising 
in  the  rheumatic  or  pya?mic  state.  When  the  synovial  sac  is  distended  with  fluid,  the  swelling 
is  greatest  on  the  dorsal  aspect  of  the  wrist,  showing  a  general  fulness,  with  some  bulging  between 
the  tendons.  The  inflammation  is  prone  to  extend  to  the  intercarpal  joints  and  to  attack  also 
the  sheaths  of  the  tendons  in  the  neighborhood.  Chronic  inflammation  of  the  wrist  is  generally 
tuberculous,  and  often  leads  to  similar  disease  in  the  synovial  sheaths  of  adjacent  tendons  and  of 
the  intercarpal  joints.  The  disease,  therefore,  when  progressive,  often  leads  to  necrosis  of  the 
car{>al  bones,  and  the  result  is  often  unsatisfactory. 

VIII.  Articulations  of  the  Carpus  (Articulatio  Intercarpea) 

(Figs.  228,  229,  231). 

These  articulations  may  be  subdivided  into  three  sets: 

1.  The  Articulations  of  the  First  Row  of  Carpal  Bones. 

2.  The  Articulations  of  the  Second  Row  of  Carpal  Bones. 

3.  The  Articulations  of  the  Two  Rows  with  each  other. 

1.  Articulations  of  the  First  Row  of  Carpal  Bones. 

These  are  arthrodial  joints.  The  ligaments  connecting  the  scaphoid,  semi- 
lunar, and  cuneiform  bones  are — 

Dorsal.  Palmar. 

Two  Interosseous 

The  Dorsal  Ligaments  (ligamenta  intercarpea  dorsalia)  are  placed  transversely 
behind  the  bones  of  the  first  row;  they  connect  the  scaphoid  and  semilunar  and 
the  semilunar  and  cuneiform. 

The  Palmar  or  Volar  Ligaments  {ligamenta  intercarpea  volaria)  connect  the 
scaphoid  and  semilunar  and  the  semilunar  and  cuneiform  bones;  they  are  less 
strong  than  the  dorsal,  and  placed  very  deeply  below  the  anterior  ligament  of 
the  wrist. 

The  Interosseous  Ligaments  {ligamenta  intercarpea  interossea)  (Fig.  231)  are  two 
narrow  bundles  of  fibrous  tissue  connecting  the  semilunar  bone  on  one  side  with 
the  scaphoid,  and  on  the  other  with  the  cuneiform.  They  are  on  a  level  with 
the  superior  surfaces  of  these  bones,  and  close  the  upper  part  of  the  spaces 
between  them.  Their  upper  surfaces  are  smooth,  and  form  with  the  bones  the 
convex  articular  surfaces  of  the  wrist-joint. 

The  ligaments  connecting  the  pisiform  bone  are — 

Capsular.  Two  Palmar  Ligaments. 

The  Capsular  Ligament  {capsula  articularis)  is  a  thin  membrane  which  con- 
nects the  pisiform  bone  to  the  cuneiform.  It  is  lined  with  a  separate  synovial 
membrane. 

The  Two  Palmar  Ligaments  are  two  strong  fibrous  bands  which  connect  the 
pisiform  to  the  unciform,  the  piso-uncinate  ligament  (ligamentum  pisohamatum) , 
and  to  the  base  of  the  fifth  metacarpal  bone,  the  piso-metacarpal  ligament  {liga- 
mentum pisometacarpeum) . 

2.  Articulations  of  the  Second  Row  of  Carpal  Bones. 

These  are  also  arthrodial  joints.  The  articular  surfaces  are  covered  with 
cartilage,  and  connected  by  the  following  ligaments: 

Dorsal.  Palmar. 

Three  Interosseous. 


320  THE   ARTICULATIONS    OB    JOINTS 

The  Dorsal  Ligaments  (ligamenta  intercarpea  dorsalia)  extend  transversely  from 
one  bone  to  another  on  the  dorsal  surface,  connecting  the  trapezium  with  the  trape- 
zoid, the  trapezoid  with  the  os  magnum,  and  the  os  magnum  with  the  unciform. 

The  Palmar  or  Volar  Ligaments  (ligamenta  intercarpea  volaria)  have  a  similar 
arrangement  on  the  palmar  surface. 

The  Three  Interosseous  Ligaments  (ligamenta  intercarpea  interossea)  (Fig.  231) 
much  thicker  than  those  of  the  first  row,  are  placed  one  between  the  os  magnum 
and  the  unciform,  a  second  between  the  os  magnum  and  the  trapezoid,  and  a 
third  between  the  trapezium  and  trapezoid.  The  first  of  these  is  much  the 
strongest,  and  the  third  is  sometimes  wanting. 

3.  Articulations  of  the  Two  Rows  of  Carpal  Bones  with  Each  Other 

(Figs.  228,229,  231). 

The  joint  between  fhe  scaphoid,  semilunar,  and  cuneiform,  and  the  second  row 
of  the  carpus,  or  the  mid-carpal  joint,  is  made  up  of  three  distinct  portions;  in  the 
centre  the  head  of  the  os  magnum  and  the  superior  surface  of  the  unciform 
articulate  with  the  deep,  cup-shaped  cavity  formed  by  the  scaphoid  and  semi- 
lunar bones,  and  constitute  a  sort  of  ball-and-socket  joint.  On  the  outer  side 
the  trapezium  and  trapezoid  articulate  with  the  scaphoid,  and  on  the  inner  side 
the  unciform  articulates  with  the  cuneiform,  forming  gliding  joints. 

The  ligaments  are : 

Anterior.  External  Lateral. 

Posterior.  Internal   Lateral. 

The  Anterior,  Palmar,  or  Volar  Ligaments  {ligamenta  intercarpea  volaria)  consist 
of  short  fibres,  which  pass,  for  the  most  part,  from  the  palmar  surface  of  the  bones 
of  the  first  row  to  the  front  of  the  os  magnum. 

The  Posterior  or  Dorsal  Ligaments  (ligamenta  intercarpea  dorsalia)  consist  of 
short,  irregular  bundles  of  fibres  passing  between  the  bones  of  the  first  and  second 
row  on  the  dorsal  surface  of  the  carpus. 

The  Lateral  Ligaments  are  very  short:  they  are  placed,  one  on  the  radial,  the 
other  on  the  ulnar  side  of  the  carpus;  the  former,  the  stronger  and  more  distinct, 
connecting  the  scaphoid  and  trapezium  bones,  the  latter  the  cuneiform  and  unci- 
form; they  are  continuous  with  the  lateral  ligaments  of  the  wrist-joint.  In  addi- 
tion to  these  ligaments,  a  slender  interosseous  band  sometimes  connects  the  os 
magnum  and  the  scaphoid. 

Synovial  Membrane  (Fig.  231). — The  synovial  membrane  of  the  carpus  is  very 
extensive:  it  passes  from  the  under  surface  of  the  scaphoid,  semilunar,  and  cunei- 
form bones  to  the  upper  surface  of  the  bones  of  the  second  row,  sending  upward 
two  prolongations — between  the  scaphoid  and  semilunar  and  the  semilunar  and 
cuneiform ;  sending  downward  three  prolongations  between  the  four  bones  of  the 
second  row,  which  are  further  continued  onward  into  the  carpo-metacarpal 
joints  of  the  four  inner  metacarpal  bones,  and  also  for  a  short  distance  between 
the  metacarpal  bones.  There  is  a  separate  synovial  membrane  between  the 
pisiform  and  cuneiform  bones. 

Actions. — The  articulation  of  the  hand  and  wrist,  considered  as  a  whole,  is 
divided  into  three  parts:  (1)  the  radius  and  the  i ntef articular  fibro-cartilage ; 
(2)  the  meniscus,  formed  by  the  scaphoid,  semilunar,  and  cuneiform,  the  pisiform 
bone  having  no  essential  part  in  the  movements  of  the  hand;  (3)  the  hand  proper, 
the  metacarpal  bones  with  the  four  carpal  bones  on  which  they  are  supported — viz., 
the  trapezium,  trapezoid,  os  magnum,  and  imciform.  These  three  elements  form 
two  joints:  (1)  the  superior,  wrist-joint  proper,  between  the  meniscus  and  bones 
of  the  forearm;  (2)  the  inferior,  between  the  hand  and  meniscus,  transverse  or 
mid-carpal  joint. 


CARPO- METACARPAL    ARTICULATIONS  321 

(1)  The  articulation  between  the  forearm  and  carpus  is  a  true  condyloid  artic- 
ulation, and  therefore  all  movements  but  rotation  are  permitted.  Flexion  and 
extension  are  the  most  free,  and  of  these  a  greater  amount  of  extension  than 
flexion  is  permitted  on  account  of  the  articulating  surfaces  extending  farther  on 
the  dorsal  than  on  the  palmar  aspect  of  the  carpal  bones.  In  this  movement  the 
carpal  bones  rotate  on  a  transverse  axis  drawn  between  the  tips  of  the  styloid 
processes  of  the  radius  and  ulna.  A  certain  amount  of  adduction  (or  ulnar 
flexion)  and  abduction  (or  radial  flexion)  is  also  permitted.  Of  these  the  former 
is  considerably  greater  in  extent  than  the  latter.  In  this  movement  the  carpus 
revolves  upon  an  antero-posterior  axis  drawn  through  the  centre  of  the  wrist. 
Finally,  circumduction  is  permitted  by  the  consecutive  movements  of  adduction, 
extension,  abduction,  and  flexion,  with  intermediate  movements  between  them. 
There  is  no  rotation,  but  this  is  provided  for  by  the  supination  and  pronation 
of  the  radius  on  the  ulna.  The  movement  of  flexion  is  performed  by  the  Flexor 
carpi  radialis,  the  Flexor  carpi  ulnaris,  and  the  Palmaris  longus;  extension, 
by  the  Extensor  carpi  radialis  longior  et  brevior  and  the  Extensor  carpi 
ulnaris;  adduction  (ulnar  flexion),  by  the  Flexor  carpi  ulnaris  and  the  Ex- 
tensor carpi  ulnaris;  and  abduction  (radial  flexion),  by  the  Extensors  of  the 
thumb  and  the  Extensor  carpi  radialis  longior  et  brevior  and  the  Flexor  carpi 
radialis. 

(2)  The  chief  movements  permitted  in  the  transverse  or  mid-carpal  joint  are 
flexion  and  extension  and  a  slight  amount  of  rotation.  In  flexion  and  extension, 
which  is  the  movement  most  freely  enjoyed,  the  trapezium  and  trapezoid  on  the 
radial  side  and  the  unciform  on  the  ulnar  side  glide  forward  and  backward  on  the 
scaphoid  and  cuneiform  respectively,  while  the  head  of  the  os  magnum  and  the 
superior  surface  of  the  unciform  rotate  in  the  cup-shaped  cavity  of  the  scaphoid 
anfl  semilunar.  Flexion  at  this  joint  is  freer  than  extension.  A  very  trifling 
amount  of  rotation  is  also  permitted,  the  head  of  the  os  magnum  rotating  round  a 
vertical  axis  drawn  through  its  own  centre,  while  at  the  same  time  a  slight  gliding 
movement  takes  place  in  the  lateral  portions  of  the  joint. 

IX.  Carpo-metacarpal  Articulations  (Articulationes  Carpometacarpese) 

(Figs.  228,  229,  231). 

1.  Articulation  of  the  Metacarpal  Bone  of  the  Thumb  with  the 
Trapezium  (Articulatio  Carpometacarpea  Pollicis). 

This  is  a  joint  of  reciprocal  reception,  and  enjoys  great  freedom  of  movement, 
on  account  of  the  configuration  of  its  articular  surfaces,  which  are  saddle-shaped, 
so  that,  on  section,  each  bone  appears  to  be  received  into  a  cavity  in  the  other, 
according  to  the  direction  in  which  they  are  cut.  The  joint  is  surrounded  by  a 
capsular  ligament. 

The  Capsular  Ligament  (capsula  articularis)  is  thick  and  fibrous,  but  loose, 
and  passes  from  the  circumference  of  the  upper  extremity  of  the  meta- 
carpal bone  to  the  rough  edge  bounding  the  articular  surface  of  the  trape- 
zium; it  is  thickest  externally  and  behind,  and  lined  by  a  separate  synovial 
membrane. 

Movements. — In  the  articulation  of  the  metacarpal  bone  of  the  thumb  w^ith  the 
trapezium  the  movements  permitted  are  flexion,  extension,  adduction,  abduction, 
and  circumduction.  When  the  joint  is  flexed  the  metacarpal  bone  is  brought  in 
front  of  the  palm  and  the  thumb  is  gradually  turned  to  the  fingers.  It  is  by  this 
peculiar  movement  that  the  tip  of  the  thumb  is  opposed  to  the  other  digits;  for 
by  slightly  flexing  the  fingers  the  palmar  surface  of  the  thumb  can  be  brought  in 
contact  with  their  palmar  surfaces  one  after  another. 

21 


322 


THE  ARTICULATIONS    OB    JOINTS 


2.  Articulations  of  the  Metacarpal  Bones  of  the  Four  Inner  Fingers 
WITH  THE  Carpus  (Articulationes  Carpometacarpe.^). 

The  joints  formed  between  the  carpus  and  four  inner  metacarpal  bones  are 
arthrodial  joints.     The  Hgaments  are — 


Dorsal. 


Palmar. 


Interosseous. 


The  Dorsal  Ligaments  (Hgamenta  carpometacarpea  dorsalia),  the  strongest  and 
most  distinct,  connect  the  carpal  and  metacarpal  bones  on  their  dorsal  surface. 


EPIPHYSEAL 
JUNCTION 

MEMBRANA  SACCI- 

FORMIS  OF  INFERIOR 

RADIO-ULNAR 

ARTICULATION 


TRIANGULAR 
FIBRO-CARTILAGE 

STYLOID  PROCESS 
OF  ULNA 


EPIPHYSEAL 
JUNCTION 


RADIO-CARPAL 
ARTICULATION 


INTEROSSEOUS 
LIGAMENT 


INTEROSSEOUS 
LIGAMENT 


INTERMETACARPAL 
ARTICULATION 


INTERCARPAL 
ATION 


RTICULATION  OF 
RAPEZIUM  AND 

ETACARPAL  BONE 

F  THUMB 

A RPO- METACARPAL 
RTICULATION 


METACARPAL  BONES 

Fig.  231. — Joints  of  the  right  hand,  from  the  back  of  the  hand.      (Spalteholz.) 


The  second  metacarpal  bone  receives  two  fasciculi — one  from  the  trapezium, 
the  other  from  the  trapezoid;  the  third  metacarpal  receives  two — one  from 
the  trapezoid  and  one  from  the  os  magnum;  the  fourth  two — one  from  the  os 
magnum  and  one  from  the  unciform;  the  fifth  receives  a  single  fasciculus  from 
the  unciform  bone,  which  is  continuous  with  a  similar  ligament  on  the  palmar 
surface,  forming  an  incomplete  capsule. 

The  Palmar  or  Volar  Ligaments  (liqamenta  carpometacarpea  volaria)  have  a 
somewhat  similar  arrangement  on  the  palmar  surface,  with  the  exception  of 
the  third  metacarpal,  which    has    three    ligaments — an  external   one  from  the 


CABPO  -  METACARPAL    ARTICULATIONS 


323 


trapezium,  situated  above  the  sheath  of  the  tendon  of  the  Flexor  carpi  radialis; 
a  middle  one,  from  the  os  magnum;  and  an  internal  one,  from  the  unciform. 

The  Interosseous  Ligaments  consist  of  short,  thick  fibres,  which  are  limited  to 
one  part  of  the  carpo-metacarpal  articulation ;  they  connect  the  contiguous  inferior 
angles  of  the  os  magnum  and  unciform  with  the  adjacent  surfaces  of  the  third 
and  fourth  metacarpal  bones. 

Synovial  Membrane. — The  synovial  membrane  is  a  continuation  of  that  between 
the  two  rows  of  carpal  bones.  Occasionally,  the  articulation  of  the  unciform 
with  the  fourth  and  fifth  metacarpal  bones  has  a  separate  synovial  membrane. 

The  synovial  membranes  of  the  wrist  and  carpus  (Fig.  231)  are  thus  seen  to 
be  five  in  number.  The  first,  the  membrana  sacciformis  or  the  recessus  sacciformis 
of  the  inferior  radio-ulnar  articulation,  passes  from  the  lower  end  of  the  ulna  to 


TENDON  OF  FLEXOR 
8UBLIMIS  OIGITORUM 


TENDON    OF   FLEXOR 
PROFUNDUS   OIGITORUM 


ANTERIOR 

OR  VAGINAL 

LIGAMENT 


TRANSVERSE 

METACARPAL 

LIGAMENT 


LATERAL 
LIGAMENT 


SECOND   LUM- 
BRICAL  MUSCLE 


ANTERIOR  OR  SECOND 

VAGINAL  LIGAMENT  PALMAR 

INTEROSSEOUS 
MUSCLE 


ANTERIOR  OR 
VAGINAL  LIGAMENT 


Fig.  232. — Metacarpal  bones  and  first  phalanges  of  the  second  to  the  fifth  finger  of  the  right  hand,  with 
ligaments,  from  the  volar  surface.     (Spalteholz.) 

the  sigmoid  cavity  of  the  radius,  and  lines  the  upper  surface  of  the  interarticular 
fibro-cartilage.  The  second  passes  from  the  lower  end  of  the  radius  and  inter- 
articular fibro-cartilage  above  to  the  bones  of  the  first  row  below,  The  third, 
the  most  extensive,  passes  between  the  contiguous  margins  of  the  two  rows  of 
carpal  l)ones— between  the  bones  of  the  second  row  to  the  carpal  extremities  of 
the  four  inner  metacarpal  bones.  The  fourth,^  from  the  margin  of  the  trapezium 
to  the  metacarpal  bone  of  the  thumb.  The  fifth,  between  the  adjacent  margins 
of  the  cuneiform  and  pisiform  bones. 

Actions. — The  movement  permitted  in  the  carpo-metacarpal  articulations  of  the 
four  inner  fingers  is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  each 
other,  the  extent  of  which  varies  in  the  difi'erent  joints.  Thus  the  articulation  of  the 
metacarpal  bone  of  the  little  finger  is  most  movable,  then  that  of  the  ring  finger. 
The  metacarpal  bones  of  the  index  and  middle  fingers  are  almost  immovable. 


324 


THE   ARTICULATIONS    OB    JOINTS 


»nO  ^ft^ 


3.  Articulations  of  the  Metacarpal  Bones  with  Each  Other  (Articu- 
LATiONES  Intermetacarpe^  (Figs.  228,  229,  231). 

The  carpal  extremities  of  the  four  inner  metacarpal  bones  articulate  with 
one  another  at  each  side  by  small  surfaces  covered  with  cartilages,  and  connected 
together  by  dorsal,  palmar,  and  interosseous  ligaments. 

The  Dorsal  Ligaments  {ligamenta  hasium  oss.  7netacarp.  dorsalia)  and  Palmar 
Ligaments  (ligamenta  hasium  oss.  metacarp.  volaria)  pass  transversely  from  one 

bone  to  another  on  the  dorsal  and  palmar  sur- 
faces. 

The  Interosseous  Ligaments  (ligamenta  hasium 
oss.  metacarp.  interossea)  pass  between  their  con- 
tiguous surfaces,  just  beneath  their  lateral  artic- 
ular facets. 

Synovial  Membrane  (Fig.  231). — The  synovial 
membrane  between  the  lateral  facets  is  a  reflec- 
tion from  that  between  the  two  rows  of  carpal 
bones. 

The  Transverse  Metacarpal  Ligament  {Uga- 
nentum  capitulorum  oss.  metacarpalium  trans- 
versum)  (Fig.  232)  is  a  narrow,  fibrous  band 
which  passes  transversely  across  the  anterior  sur- 
faces of  the  digital  extremities  of  the  four  inner 
^\\"^^3I  metacarpal  bones,  connecting  them  together.     It 

is  blended  anteriorly  with  the  palmar  ligaments 
of  the  metacarpo-phalangeal  articulations.  To 
its  posterior  border  is  connected  the  fascia  which 
covers  the  Interossei  muscles.  Its  anterior  sur- 
face is  concave  where  the  flexor  tendons  pass 
over  it.  Behind  it  the  tendons  of  the  Interossei 
muscles  pass  to  their  insertion. 


X.  Metacarpo-phalangeal  Articulations  f  Artic- 

ulationes  Metacarpo-phalangeae; 

(Figs.  232,  233). 

These  articulations  are  of  the  condyloid  kind, 
formed  by  the  reception  of  the  rounded  head  of 
the  metacarpal  bone  into  a  shallow  cavity  in  the 
extremity  of  the  first  phalanx.  The  expansion 
of  the  extensor  tendon  acts  as  a  dorsal  ligament. 
There  is  a  capsular  ligament  which  at  certain 
points  has  strengthening  ligaments.  The  liga- 
ments are — 


ARTICULAR 
CAPSULC 


LATERAL 

'ligament 


ARTICULAR. 
CAPSULE 


LATERAL 

'ligament 


articular 
capsule' 


LATERAL 
'LIGAMEM 


Anterior. 


Two   Lateral. 


The    Anterior,    Palmar,    or    Vaginal    Ligament 

(glenoid  ligament  of  Cruveilhier,  ligamentum 
_  vaginale)   is    a   thick,   dense,  fibrous   structure, 

phai'aAges  ofThefSfing^r"ofthe'lfght  placed  on  the  palmar  surface  of  the  joint  in  the 
(sArhoS^'"""*''''""'^"''"^'"'"^"-   interval  between  the  lateral  ligaments,  to  which 

it  is  connected ;  it  is  loosely  united  to  the  meta- 
carpal bone,  but  very  firmly  to  the  base  of  the  first  phalanx.  Its  palmar  surface 
is  intimately  blended  with  the  transverse  metacarpal  ligament,  and  presents  a 


THE  HIP -JOINT 


325 


groove  for  the  passage  of  the  flexor  tendons,  the  sheath  surrounding  which  is 
connected  to  each  side  of  the  groove.  By  its  deep  surface  it  forms  part  of  the 
articular  surface  for  the  head  of  the  metacarpal  bone,  and  is  lined  by  a  synovial 
membrane. 

The  Lateral  or  Collateral  Ligaments  (ligamenta  collateralia)  are  strong,  rounded 
cords  placed  one  on  each  side  of  the  joint,  each  being  attached  by  one  extremity 
to  the  posterior  tubercle  on  the  side  of  the  head  of  the  metacarpal  bone,  and  by 
the  other  to  the  contiguous  extremity  of  the  phalanx. 

Actions.  —  The  movements  which  occur  in  these  joints  are  flexion,  extension, 
adduction,  abduction,  and  circumduction ;  the  lateral  movements  are  very  limited. 

Surface  Form. — The  prominences  of  the  knuckles  do  not  correspond  to  the  position  of  the 
joints  either  of  the  metacarpo-phalangeal  or  interphalangeal  articulations.  These  prominences 
are  invariably  formed  by  the  distal  ends  of  the  proximal  bone  of  each  joint,  and  the  line  indi- 
cating the  position  of  the  joint  must  be  sought  considerably  in  front  of  the  middle  of  the  knuckle. 
The  usual  rule  for  finding  these  joints  is  to  flex  the  distal  phalanx  on  the  proximal  one  to  a  right 
angle;  the  position  of  the  joint  is  then  indicated  by  an  imaginary  line  drawn  along  the  middle  of 
the  lateral  aspect  of  the  proximal  phalanx. 

XI.  Articulations  of  the  Phalanges  (Articulationes  Digitorum  Manus) 

(Fig.  233). 

These  are  ginglymus  joints.  Each  joint  has  a  capsule,  and  certain  accentuated 
portions  are  regarded  as  definite  ligaments.     These  ligaments  are — 


Anterior  or  Palmar. 


Two  Lateral  (ligamenta  collateralia). 


The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metacarpo- 
phalangeal articulations;  the  extensor  tendon  supplies  the  place  of  a  dorsal 
ligament. 

Actions. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion 
and  extension;  these  movements  are  more  extensive  between  the  first  and  second 
phalanges  than  between  the  second  and  third.  The  movement  of  flexion  is  very 
considerable,  but  extension  is  limited  by  the  anterior  and  lateral  ligaments. 

ARTICULATIONS  OF  THE  LOWER  EXTREMITY. 


The  articulations  of  the  Lower  Extremity  comprise  the  following  groups: 


L  The  Hip-joint. 
IL  The  Knee-joint. 
in.  The    Articulations    between    the 

Tibia  and  Fibula. 
IV.  The  Ankle-joint. 
V.  The  Articidations  of  the  Tarsus. 


VI.  TheTarso-metatarsal  Articulations. 
VII.  Articulations    of     the     Metatarsal 

Bones  with  each  other. 
VIII.  The    Metatarso-phalangeal   Artic- 
ulations. 
IX.  The  Articulations  of  the  Phalanges. 


I.  The  Hip-joint  (Articulatio  Coxae)  (Figs.  234,  235,  236,  237,  238,  239). 

This  articulation  is  an  enarthrodial  or  ball-and-socket  joint,  formed  by  the 
reception  of  the  head  of  the  femur  into  the  cup-shaped  cavity  of  the  acetabulum. 
The  articulating  surfaces  are  covered  with  cartilage,  that  on  the  head  of  the  femur 
being  thicker  at  the  centre  than  at  the  circumference,  and  covering  the  entire 
surface,  with  the  exception  of  a  depression  just  below  its  centre  for  the  ligamen- 
tum  teres;  that  covering  the  acetabulum  is  much  thinner  at  the  centre  than  at 
the  circumference.  It  forms  an  incomplete  cartilaginous  ring  of  a  horseshoe 
shape,  being  deficient  below,  where  there  is  a  circular  depression,  which  is  occu- 


326 


THE   ARTICULATIONS    OB    JOINTS 


pied  in  the  recent  state  by  a  mass  of  fat  covered  by  synovial  membrane.    The 
ligaments  of  the  joints  are  the 


Capsular. 
Ilio-femoral. 


Transverse. 


Teres. 
Cotyloid. 


The  Capsular  Ligament  {capsula  articularis)  (Figs.  234,  235,  237,  and  239)  is  a 
strong,  dense,  ligamentous  capsule,  embracing  the  margin  of  the  acetabulum 
above  and  surrounding  the  neck  of  the  femur  below.     Its  upper  circumference 


ANTERIOR  INFERIOR 1 

SPINE  OF  ILIUM 


rElMO  R  A« 


AiviEN-y^^y/^V^y;^ 


LESSER 
TROCHANTER 


Fig.  234. — Right  hip-joint,  from  in  front.     (Spalteholz.) 

is  attached  to  the  acetabulum,  above  and  behind,  two  or  three  lines  external 
to  the  cotyloid  ligament;  but  in  front  it  is  attached  to  the  outer  margin  of 
this  ligament,  and  opposite  to  the  notch,  where  the  margin  of  this  cavity  is 
deficient,  it  is  connected  to  the  transverse  ligament,  and  by  a  few  fibres  to 
the  edge  of  the  obturator  foramen.  Its  lower  circumference  surrounds  the  neck 
of  the  femur,  being  attached,  in  front,  to  the  spiral  or  anterior  intertrochanteric 
line;  above,  to  the  base  of  the  neck;  behind,  to  the  neck  of  the  bone,  about  half 


THE   HIP- JOINT 


327 


an  inch  above  tl;ie  posterior  intertrochanteric  Hne.  From  this  insertion  the  fibres 
are  reflected  upward  over  the  neck  of  the  femur,  forming  a  sort  of  tubular  sheath, 
the  cervical  reflection,  which  blends  with  the  periosteum  and  can  be  traced  as  far 
as  the  articular  cartilage.  On  the  surface  of  the  neck  of  the  femur  some  of  these 
reflected  fibres  are  raised  into  longitudinal  folds,  termed  retinacula.  It  is  much 
thicker  at  the  upper  and  forepart  of   the  joint,  where  the  greatest  amount  of 


•■?#// 


I    i_   I    U    M 


Fig.  235. — Right  hip-joint,  from  behind.     (The  joint  capsule,  except  for  the  strengthening  ligaments,  has 

been  removed.)     (Spalteholz.) 


resistance  is  required,  than  below  and  internally,  where  it  is  thin,  loose,  and 
longer  than  in  any  other  part.  It  consists  of  two  sets  of  fibres,  circular  and  lon- 
gitudinal. The  circular  fibres,  zona  orbicularis  (Fig.  237) ,  are  most  abundant  at  the 
lower  and  back  part  of  the  capsule,  and  form  a  sling  or  collar  around  the  neck  of 
the  femur.  Anteriorly  they  blend  with  the  deep  surface  of  the  ilio-femoral  liga- 
ment, and  through  its  medium  reach  the  anterior  inferior  spine  of  the  ilium.  The 
longitudinal  fibres  are  greatest  in  amount  at  the  upper  and  front  part  of  the  cap- 
sule, where  they  form  distinct  Imnds  or  accessory  ligaments,  of  which  the  most 
important  is  the  ilio-femoral.     Other  accessory  bands  are  known  as  the  pubo- 


328 


THE   ARTICULATIONS    OB    JOINTS 


femoral  or  pubo-capsular  ligament  (ligamentum  pubocapsulare) ,  passing  from  the 
outer  portion  of  the  horizontal  pubic  ramus,  the  iho-pectineal  eminence,  the 
obturator  crest  and  the  obturator  membrane,  to  the  front  of  the  capsule;  and 
ischio-capsular  ligament  or  ligament  of  Bertin  (ligamentum  ischiocapsulare) , 
passing  from  the  ischium,  just  below  the  acetabulum,  to  blend  with  the  circular 
fibres  at  the  lower  part  of  the  joint.  The  external  surface  is  rough,  covered  by 
numerous  muscles,  and  separated  in  front  from  the  Psoas  and  Iliacus  muscles  by 
a  synovial  bursa,  which  not  infrequently  communicates,  by  a  circular  aperture, 
with  the  cavity  of  the  joint.  It  differs  from  the  capsular  ligament  of  the  shoulder 
in  being  much  less  loose  and  lax,  and  in  not  being  perforated  for  the  passage  of 
a  tendon. 


ANTERIOR 

INFERIOR 

SPINE  OF  ILIUM 


,'«..ii,lj,|(i.,.,, 


SPINE  OF 
ISCHIUM 


TRANSVERSE 
LIGAMENT  OF 
ACETABULUM 


TUBEROSITY 
OF  ISCHIUM 


Fig.  236.- 


-Right  hip-joint  from  the  medial  side.     (The  bottom  of  the  acetabulum  has  been  chiselled  away 
suflBciently  to  make  the  head  of  the  femur  visible.)     (Spalteholz.) 


The  Ilio-femoral  or  Y-ligament  or  Ligament  of  Bigelow  (ligamentum  ilio- 
femorale)  (Figs.  234,  235,  237,  and  238)  is  an  accessory  band  of  fibres  extending 
obliquely  across  the  front  of  the  joint;  it  is  intimately  connected  with  the  cap- 
sular ligament,  and  serves  to  strengthen  it  in  this  situation.  It  is  attached, 
above,  to  the  lower  part  of  the  anterior  inferior  spine  of  the  ilium  and  the 
adjacent  rim  of  the  acetabulum;  and,  diverging  below,  forms  two  bands,  of 
which  one  passes  downward  to  be  inserted  into  the  lower  part  of  the  anterior 
intertrochanteric  line;  the  other  passes  downward  and  outward  to  be  inserted 
into  the  upper  part  of  the  same  line  and  the  adjacent  part  of  the  neck  of  the 
femur.  Between  the  two  bands  is  a  thinner  part  of  the  capsule.  Sometimes 
there  is  no  division,  but  the  ligament  spreads  out  into  a  flat,  triangular  band, 
which  is  attached  below  into  the  whole  length  of  the  anterior  intertrochanteric 
line.     This  ligament  is  frequently  called  the  Y-shaped  ligament  of  Bigelow;  and 


THE   HIP -JOINT 


329 


the  outer  or  upper  of  the  two  bands  is  sometimes  described  as  a  separate  liga- 
ment, under  the  name  of  the  ilio -trochanteric  ligament. 

The  Ligamentum  Teres,  or  the  Interarticular  Ligament  (ligamentum  teres  femoris) 
(Figs.  236,  237,  and  239)  is  a  triangular  band  implanted  by  its  apex  into  the 
depression  a  little  behind  and  below  the  centre  of  the  head  of  the  femur,  and  by 
its  broad  base  into  the  margins  of  the  cotyloid  notch,  becoming  blended  with  the 
transverse  ligament.  It  is  formed  of  connective  tissue,  surrounded  by  a  tubular 
sheath  of  synovial  membrane.  Sometimes  only  the  synovial  fold  exists.  Very 
rarely  it  is  absent.    The  ligament  is   made   tense  when  the  hip  is  semiflexed, 


ILIOLUMBAR   LIGAMENT 


ANTERIOR  SACRO- 
ILIAC LIGAMENT 


CAPSULAR   LIGAMENT, 

FIBROUS    PORTION 

CAPSULAR    LIGAMENT, 

SYNOVIAL  PORTION 


ILIOFEMORAL 
LIGAMENT 


ZONA 
ORBICULARIS 
GREAT 
TROCHANTER 


/COOPER'S  LIGAMtNT 
/     SPINE  OF  PUBIS 


PUBOFEMORAL 
LIGAMENT 

OBTURATOR   LIGAMENT 
ZONA  ORBICULARIS 
SMALL  SYNOVIAL  MEMBRANE  COVERING 

TROCHANTER  NECK  OF  FEMUR 


Fig.  237. — The  right  hip-joint,  seen  from  before.     (Toldt.) 

and  the  limb  adducted  and  rotated  outward;  it  is,  on  the  other  hand,  relaxed 
when  the  limb  is  abducted.  It  has,  however,  but  little  influence  as  a  ligament, 
though  it  may  to  a  certain  extent  limit  movement,  and  would  appear  to  be 
merely  a  "vestigial  and  practically  useless  ligament."^  It  is  probably  a  modifi- 
cation of  the  folds  which  in  other  joints  fringe  the  margins  of  reflection  of  synovial 
membranes. 

The  Cotyloid  Ligament  (lahrum  glenoidale)  (Fig.  239)  is  a  fibro-cartilaginous  rim 
attached  to  the  margin  of  the  acetabulum,  the  cavity  of  which  it  deepens;  at  the 


*  J.  Bland  Sutton.     Ligaments:  Their  Nature  and  Morphology. 


330 


THE   ABTICULATIOS    OB    JOINTS 


same  time  it  protects  the  edges  of  the  bone  and  fills  up  the  inequalities  on  its  sur- 
face.    It  bridges  over  the  notch  as  the  transverse  ligament  of  the  acetabulum,  and 

thus  forms  a  complete  circle,  which  closely  sur- 
rounds the  head  of  the  femur,  and  assists  in 
holding  it  in  its  place,  acting  as  a  sort  of  valve. 
It  is  prismoid  on  section,  its  base  being  attached 
to  the  margin  of  the  acetabulum  and  its  op- 
posite edge  being  free  and  sharp;  whilst  its 
two  surfaces  are  invested  by  synovial  mem- 
brane, the  external  one  being  in  contact  with 
the  capsular  ligament,  the  internal  one  being 
inclined  inward,  so  as  to  narrow  the  acetab- 
ulum and  embrace  the  cartilaginous  surface 
of  the  head  of  the  femur.  It  is  much  thicker 
above  and  behind  than  below  and  in  front, 
and  consists  of  close,  compact  fibres,  which 
arise  from  different  points  of  the  circumference 
of  the  acetabulum  and  interlace  with  each  other 
at  very  acute  angles. 

The  transverse  ligament  of  the  acetabulum 
(ligamentum  transversum  acetabuli)  (Figs.  230 
and  239)  is  in  reality  a  portion  of  the  cotyloid 
ligament,  though  differing  from  it  in  having 
no  cartilage-cells  amongst  its  fibres.  It  con- 
sists of  strong,  flattened  fibres,  which  cross  the 
notch  at  the  lower  part  of  the  acetabulum  and 
convert  it  into  a  foramen.  Thus  an  interval 
is  left  beneath  the  ligament  for  the  passage  of 
nutrient  vessels  to  the  joint. 
Synovial  Membrane  (Figs.  237  and  239). — The  synovial  membrane  is  very 
extensive.  Commencing  at  the  margin  of  the  cartilaginous  surface  of  the  head 
of  the  femur,  it  covers  all  that  portion  of  the  neck  which  is  contained  within  the 
joint;  from  the  neck  it  is  reflected  on  the  internal  surface  of  the  capsular  liga- 
ment, covers  both  surfaces  of  the  cotyloid  ligament  and  the  mass  of  fat  contained 
in  the  depression  at  the  bottom  of  the  acetabulum,  and  is  prolonged  in  the  form 
of  a  tubular  sheath  around  the  ligamentum  teres,  as  far  as  the  head  of  the  femur. 
It  sometimes  communicates  through  a  hole  in  the  capsular  ligament  between 
the  inner  band  of  the  Y-shaped  ligament  and  the  pubo-femoral  ligament  with 
a  bursa  situated  on  the  under  surface  of  the  Ilio-psoas  muscle. 

The  muscles  in  relation  with  the  joint  (Fig.  240)  are,  in  front,  the  Psoas  and 
Iliacus,  separated  from  the  capsular  ligament  by  a  synovial  bursa;  above,  the 
reflected  head  of  the  Rectus  and  Gluteus  minimus,  the  latter  being  closely  adherent 
to  the  capsule;  internally,  the  Obturator  externus  and  Fectineus;  behind,  the  Pyri- 
formis,  Gemellus  superior.  Obturator  internus,  Gemellus  inferior.  Obturator  exter- 
nus, and  Quadratus  femoris. 

The  arteries  supplying  the  joint  are  derived  from  the  obturator,  sciatic,  internal 
circumflex,  and  gluteal. 

The  nerves  are  articular  branches  from  the  sacral  plexus,  great  sciatic,  obtu- 
rator, accessory  obturator,  and  a  filament  from  the  branch  of  the  anterior  crural 
supplying  the  rectus. 

Bursse. — Numerous  bursse  exist  in  the  neighborhood  of  the  hip-joint.  Some 
anatomists  have  counted  twenty-one  (Synnestredt).  The  chief  ones  are :  1.  The 
ilio-pectineal  bursa  (bursa  iliopectinea)  (Fig.  240),  between  the  ilio-psoas  tendon 
and  the  capsule  of  the  joint.    It  often  communicates  with  the  hip-joint.    2.  The 


Fig.  238. — Hip-joint,  showing  the  ilio-femoral 

ligament.     (After  Bigelow.) 


THE   HIP -JOINT 


331 


subtendinous  iliac  bursa  (bursa  iliaca  subtendinea) ,  between  the  tendon  of  the  psoas 
and  iUacus  and  the  lesser  trochanter.  3.  The  ischio -gluteal  bursa  (bursa  ischiadica 
m.  glutei  maximi) ,  between  the  Gluteus  maximus  muscle  and  the  tuberosity  of  the 
ischium  (not  constant).  4.  The  bursa  of  the  great  trochanter  (bursa  trochanterica  m. 
glutoei  maximi),  between  the  great  trochanter  and  the  Gluteus  maximus  muscle 
near  the  muscular  insertion.  5.  Two  or  three  gluteo-femcral  bursae  (bursa; 
glutaojemorales)  below.  6.  The  obturator  bursa  (bursa  m.  obturatorii  interni), 
between  the  margin  of  the  great  sacro-sciatic  notch  and  the  tendon  of  the 
Obturator  internus  muscle.      7.  The  subcutaneous  trochanteric  bursa  (bursa  tro- 


GREAT. 

TROCHANTER       / 


EPIPHVSEAL 
JUNCTION 


EPIPHYSEAL 
JUNCTION 


LIGAMENTUM 
TERES 

TRANSVERSE 
LIGAMENT  OF 
ACETABULUM 


Fig.  239. — Right  hip-joint.     Frontal  section.     Posterior  half,  viewed  from  in  front.     (The  joint  surfaces 
have  been  .somewhat  pulled  apart.)     (Spalteholz.) 


chanterica  subcufanea),  between  the  cutaneous  surface  and  the  great  trochanter. 
Besides  these  there  is  a  bursa  between  the  great  trochanter  and  the  anterior  part 
of  the  Gluteus  medius — between  the  great  trochanter  and  the  posterior  part  of 
the  Gluteus  medius — between  the  great  trochanter  and  the  Gluteus  minimus — 
beneath  the  Pyriformis  muscle — between  the  small  trochanter  and  the  Quad- 
ratus  femoris  muscle,  and  there  are  bursae  beneath  the  Biceps  femoris  muscle. 

Actions. — The  movements  of  the  hip  are  very  extensive,  and  consist  of  flexion, 
extension,  adduction,  abduction,  circumduction,  and  rotation. 


332 


THE   ARTICULATIONS    OB   JOINTS 


The  hip-joint  presents  a  very  striking  contrast  to  the  shoulder-joint  in  the 
much  more  complete  mechanical  arrangements  for  its  security  and  for  the  limita- 
tion of  its  movements.  In  the  shoulder,  as  we  have  seen,  the  head  of  the  humerus 
is  not  adapted  at  all  in  size  to  the  glenoid  cavity,  and  is  hardly  restrained  in  any 
of  its  ordinary  movements  by  the  capsular  ligament.  In  the  hip-joint,  on  the 
contrary,  the  head  of  the  femur  is  closely  fitted  to  the  acetabulum  for  a  distance 
extending  over  nearly  half  a  sphere,  and  at  the  margin  of  the  bony  cup  it  is  still 
more  closely  embraced  by  the  cotyloid  ligament,  so  that  the  head  of  the  femur 
is  held  in  its  place  by  that  ligament  even  when  the  fibres  of  the  capsule  have  been 
quite  divided  (Humphry).  The  anterior  portion  of  the  capsule,  described  as  the 
ilio-femoral  ligament,  is  the  strongest  of  all  the  ligaments  in  the  body,  and  is  put 
on  the  stretch  by  any  attempt  to  extend  the  femur  beyond  a  straight  line  with  the 
trunk.  That  is  to  say,  this  ligament  is  the  chief  agent  in  maintaining  the  erect 
position  without  muscular  fatigue;  for  a  vertical  line  passing  through  the  centre 
of  gravity  of  the  trunk  falls  behind  the  centres  of  rotation  in  the  hip-joints,  and 


Isch.  capn 
ligament 


RECT.    FEM. 


Ileo-fem.  ligament 


Pub.  fern,  ligament 


Fig.  240. — Relation  of  muscles  to  hip-joint.     (Henle.) 

therefore  the  pelvis  tends  to  fall  backward,  but  is  prevented  by  the  tension  of 
the  ilio-femoral  and  capsular  ligaments.  The  security  of  the  joint  may  be  also 
provided  for  by  the  two  bones  being  directly  united  through  the  ligamentum 
teres;  but  it  is  doubtful  whether  this  so-called  ligament  can  have  much  influence 
upon  the  mechanism  of  the  joint.  Flexion  of  the  hip-joint  is  arrested  by  the  soft 
parts  of  the  thigh  and  abdomen  being  brought  into  contact  when  the  leg  is  flexed 
on  the  thigh ;  and  by  the  action  of  the  hamstring  muscles  when  the  leg  is  extended  ;* 
extension,  by  the  tension  of  the  ilio-femoral  ligament  and  front  of  the  capsule; 
adduction,  by  the  thighs  coming  into  contact;  adduction,  with  flexion  by  the 
outer  band  of  the  ilio-femoral  ligament,  the  outer  part  of  the  capsular  ligament; 


'  The  hip-joint  cannot  be  completely  flexed,  in  most  persons,  without  at  the  same  time  flexing  the  knee,  on 
account  of  the  shortness  of  the  hamstring  muscles. — Cleland,  Jour,  of  Anat.  and  Phys.,  No.  1,  Old  Series,  p.  87. 


THE  HIP -JOINT  .  333 

abduction,  by  the  inner  band  of  the  iho-femoral  Hgament  and  the  pubo-femoral 
band;  rotation  outward,  by  the  outer  band  of  the  iUo-femoral  Hgament;  and 
rotation  inward,  by  the  ischio-capsular  Hgament  and  the  hinder  part  of  the  cap- 
sule. The  muscles  which  f.ex  the  femur  on  the  pelvis  are  the  Psoas,  Iliacus, 
Rectus,  Sartorius,  Pectineus,  Adductor  longus  and  brevis,  and  the  anterior  fibres 
of  the  Gluteus  medius  and  minimus.  Extension  is  mainly  performed  by  the 
Gluteus  maximus,  assisted  by  the  hamstring  muscles.  The  thigh  is  adducted  by 
the  Adductor  magnus,  longus,  and  brevis,  the  Pectineus,  the  Gracilis,  and  lower 
part  of  the  Gluteus  maximus,  and  abducted  by  the  Gluteus  medius  and  minimus 
and  upper  part  of  the  Gluteus  maximus.  The  muscles  which  rotate  the  thigh 
inward  are  the  anterior  fibres  of  the  Gluteus  medius,  the  Gluteus  minimus,  and  the 
Tensor  fasciae  f emoris ;  while  those  which  rotate  it  outward  are  the  posterior  fibres 
of  the  Gluteus  medius,  the  Pyriformis,  Obturator  externus  and  internus,  Gemellus 
superior  and  inferior,  Quadratus  femoris,  Iliacus,  Gluteus  maximus,  the  three 
Adductors,  the  Pectineus,  and  the  Sartorius. 

Surface  Form, — A  line  drawn  from  the  anterior  superior  spinous  process  of  the  ilium  to 
the  most  prominent  part  of  the  tuberosity  of  the  ischium  (Nelaton's  line)  runs  through  the 
centre  of  the  acetabulum,  and  would,  therefore,  indicate  the  level  of  the  hip-joint;  or,  in  other 
words,  the  upper  border  of  the  great  trochanter,  which  lies  on  Nelaton's  line,  is  on  a  level  with 
the  centre  of  the  hip-joint. 

Surgical  Anatomy. — Inflammation  of  bursw  about  the  hip-joint  gives  rise  to  confusing 
symptoms.  Inflammation  of  one  of  the  bursse  over  the  great  trochanter  is  not  uncommon. 
Great  pain  is  produced  if  any  movement  of  the  gluteal  muscles  is  permitted. 

Enlargement  of  the  bursa  over  the  ischial  tuberosity  was  long  called  weaver's  button.  Enlarge- 
ment of  the  bursa  beneath  the  ilio-psoas  may  produce  a  large  swelling.  Bursal  inflammation  is 
not  unusually  mistaken  for  hip-joint  disease 

In  dislocation  of  the  hip  "the  head  of  the  thigh  bone  may  rest  at  any  point  around  its  socket" 
(Bryant);  but  whatever  position  the  head  ultimately  assumes,  the  primary  displacement  is 
generally  downward  and  inward,  the  capsule  giving  way  at  its  weakest — that  is,  its  lower  and 
inner — part.  The  situation  that  the  head  of  the  bone  subsequently  assumes  is  determined 
by  the  degree  of  flexion  or  extension,  and  of  outward  or  inward  rotation  of  the  thigh  at  the 
moment  of  luxation,  influenced,  no  doubt,  by  the  ilio-femoral  ligament,  which  is  not  easily 
ruptured.  When,  for  instance,  the  head  is  forced  backward,  this  ligament  forms  a  fixed  axis, 
round  which  the  head  of  the  bone  rotates,  and  the  head  is  thus  driven  on  to  the  dorsum  of  the  ilium. 
The  ilio-femoral  ligament  also  influences  the  position  of  the  thigh  in  the  various  dislocations: 
in  the  dislocations  backward  it  is  tense,  and  produces  inversion  of  the  limb;  in  the  dislocation 
on  to  the  pubes  it  is  relaxed,  and  therefore  allows  the  external  rotators  to  evert  the  thigh;  while 
in  the  thyroid  dislocation  it  is  tense  and  produces  flexion.  The  muscles  inserted  into  the  upper 
part  of  the  femur,  with  the  exception  of  the  Obturator  internus,  have  very  little  direct  influence 
in  determining  the  position  of  the  bone.  But  Bigelow  has  endeavored  to  show  that  the  Obtu- 
rator internus  is  the  principal  agent  in  determining  whether  in  the  backward  dislocations  the 
head  of  the  bone  shall  be  ultimately  lodged  on  the  dorsum  of  the  ilium  or  in  or  near  the  sciatic 
notch.  In  both  dislocations  the  head  passes,  in  the  first  instance,  in  the  same  direction;  but, 
as  Bigelow  asserts,  in  the  displacement  on  to  the  dorsum,  the  head  of  the  bone  travels  up  behind 
the  acetabulum,  in  front  of  the  muscle;  while  in  the  dislocation  into  the  sciatic  notch,  the  head 
passes  behind  the  muscle,  and  is  therefore  prevented  from  reaching  the  dorsum,  in  consequence 
of  the  tendon  of  the  muscle  arching  over  the  neck  of  the  bone,  and  so  remains  in  the  neighbor- 
hood of  the  sciatic  notch.  Bigelow,  therefore,  distinguishes  these  two  forms  of  dislocation  by 
describing  them  as  dislocations  backward,  "above  and  below,"  the  Obturator  internus. 

The  ilio-femoral  ligament  is  rarely  torn  in  dislocations  of  the  hip,  and  this  fact  is  taken 
advantage  of  by  the  surgeon  in  reducing  these  dislocations  by  manipulation.  It  is  made  to  act 
as  a  fulcrum  to  a  lever,  of  which  the  long  arm  is  the  shaft  of  the  femur,  and  the  short  arm  the 
neck  of  the  bone. 

The  hip-joint  is  rarely  the  seat  of  acute  synovitis  from  injury,  on  account  of  its  deep  position 
and  its  thick  covering  of  soft  parts.  Acute  inflammation  may,  and  does,  frequently  occur  as 
the  result  of  constitutional  conditions,  as  rheumatism,  pytemia,  etc.  When,  in  these  cases, 
effusion  takes  place,  and  the  joint  becomes  distended  with  fluid,  the  swelling  is  not  very  easy 
to  detect  on  account  of  the  thickness  of  the  capsule  and  the  depth  of  the  articulation.  It  is 
principally  to  be  found  on  the  front  of  the  joint,  just  internal  to  the  ilio-femoral  ligament;  or 
behind,  at  the  lower  and  back  part.  In  these  two  places  the  capsule  is  thinner  than  elsewhere. 
Disease  of  the  hip-joint  is  much  more  frequently  of  a  chronic  character  and  is  usually  of  tuber- 
culous origin.     It  begins  either  in  the  bones  or  in  the  synovial  membrane,  more  frequently  in  the 


334  •  '^HE   ARTICULATIONS    OR   JOINTS 

former,  and  probably,  in  most  cases,  in  the  growing,  highly  vascular  tissue  in  the  neighborhood 
of  the  epiphysial  cartilage.  In  this  respect  it  differs  very  materially  from  tuberculous  arthritis 
of  the  knee,  where  the  disease  often  commences  in  the  synovial  membrane.  The  reasons  why 
hip-disease  so  frequently  begins  near  the  epiphysial  cartilage  are  twofold:  first,  this  part  being 
the  centre  of  rapid  growth,  its  nutrition  is  unstable  and  inflammation  is  easily  awakened; 
and,  secondly,  great  strain  is  thrown  upon  it,  from  the  frequency  of  falls  and  blows  upon  the  hip, 
which  causes  crushing  of  the  epiphysial  cartilage  or  the  cancellous  tissue  in  its  neighborhood, 
with  the  results  likely  to  follow  such  an  injury.  In  addition  to  these,  the  depth  of  the  joint 
protects  it  from  the  causes  of  synovitis. 

In  chronic  hip-disease  the  affected  limb  assumes  an  altered  position,  the  cause  of  which  it 
is  important  to  understand.  In  the  early  stage  of  a  typical  case  the  limb  is  flexed,  abducted, 
and  rotated  outward.  In  this  position  all  the  ligaments  of  the  joint  are  relaxed:  the  front  of 
the  capsule  by  flexion;  the  outer  band  of  the  ilio-femoral  ligament  by  abduction;  and  the  inner 
band  of  this  ligament  and  the  back  of  the  capsule  by  rotation  outward.  It  is,  therefore,  the 
position  of  the  greatest  ease.  The  condition  is  not  quite  obvious  at  first  upon  examining  a 
patient.  If  the  patient  is  laid  in  the  supine  position,  the  affected  limb  will  be  found  to  be 
extended  and  parallel  with  the  other.  But  it  will  be  found  that  the  pelvis  is  tilted  downward 
on  the  diseased  side  and  the  limb  apparently  longer  than  its  fellow,  and  that  the  lumbar  spine 
is  arched  forward  (lordosis).  If  now  the  thigh  is  abducted  and  flexed,  the  tilting  down- 
ward and  the  arching  forward  of  the  pelvis  disappears.  The  condition  is  thus  explained.  A 
limb  which  is  flexed  and  abducted  is  obviously  useless  for  progression,  and,  to  overcome  the 
difficulty,  the  patient  depresses  the  affected  side  of  his  pelvis  in  order  to  produce  parallelism 
of  his  limbs,  arid  at  the  same  time  rotates  his  pelvis  on  its  transverse  horizontal  axis,  so  as  to 
direct  the  limb  downward  instead  of  forward.  In  the  latter  stages  of  the  disease  the  limb 
becomes  flexed,  adducted,  and  inverted.  The  position  probably  depends  upon  muscular 
action,  at  all  events  as  regards  the  adduction.  The  Adductor  muscles  are  supplied  by  the 
obturator  nerve,  which  also  largely  supplies  the  joint.  These  muscles  are  therefore  thrown  into 
reflex  action  by  the  irritation  of  the  peripheral  terminations  of  this  nerve  in  the  inflamed  artic- 
ulation. Osteo-arthritis  is  not  uncommon  in  the  hip-joint,  and  it  is  said  to  be  more  common  in 
the  male  than  in  the  female,  in  whom  the  knee-joint  is  more  frequently  affected.  It  is  a  disease 
of  middle  age  or  more  advanced  period  of  life. 

Congenital  dislocation  is  more  commonly  met  with  in  the  hip-joint  than  in  any  other  articula- 
tion. The  displacement  usually  takes  place  on  to  the  dorsum  ilii.  It  gives  rise  to  extreme 
lordosis,  and  a  waddling  gait  is  noticed  as  soon  as  the  child  commences  to  walk. 

Excision  of  the  hip  may  be  required  for  disease  or  for  injury,  especially  for  gunshot  wound. 
It  may  be  performed  either  by  an  anterior  or  an  external  incision.  The  former  one  entails 
less  interference  with  important  structures,  especially  muscles,  than  the  posterior  one,  but  permits 
of  less  efficient  drainage.  In  these  days,  however,  when  the  surgeon  aims  at  securing  healing 
of  his  wound  without  suppuration,  this  second  advantage  is  not  of  so  much  importance.  In 
the  operation  in  front  the  surgeon  makes  an  incision  three  or  four  inches  in  length,  starting 
immediately  below  and  external  to  the  anterior  superior  spinous  process  of  the  ilium,  down- 
ward and  inward  between  the  Sartorius  and  Tensor  fascite  femoris,  to  the  neck  of  the  bone, 
dividing  the  capsule  at  its  upper  part.  A  narrow-bladed  saw  now  divides  the  neck  of  the  femur, 
and  the  head  of  the  bone  is  extracted  with  sequestrum  forceps.  All  diseased  tissue  is  carefully 
removed  with  a  sharp  spoon  or  scissors,  and  the  cavity  thoroughly  flushed  with  a  hot  aseptic 
fluid. 

The  external  method  consists  in  making  an  incision  three  or  four  inches  long,  commencing 
midway  between  the  top  of  the  great  trochanter  and  the  anterior  superior  spine,  and  ending 
over  the  shaft,  just  below  the  trochanter.  The  muscles  are  detached  from  the  great  trochanter, 
and  the  capsule  opened  freely.  The  head  and  neck  are  freed  from  the  soft  parts  and  the  bone 
sawn  through  just  below  the  top  of  the  trochanter  with  a  narrow  saw.  The  head  of  the  bone  is 
then  levered  out  of  the  acetabulum.  In  both  operations,  if  the  acetabulum  is  eroded,  it  must  be 
freely  gouged. 

II.  The  Knee-joint  (Articulatio  Genu). 

The  knee-joint  was  formerly  described  as  a  ginglymus  or  hinge-joint,  but  is 
really  of  a  much  more  complicated  character.  It  must  be  regarded  as  consist- 
ing of  three  articulations  in  one :  one  between  each  condyle  of  the  femur  and  the 
corresponding  tuberosity  of  the  tibia,  which  are  condyloid  joints,  and  one  between 
the  patella  and  the  femur,  which  is  partly  arthrodial,  but  not  completely  so,  since 
the  articular  surfaces  are  not  mutually  adapted  to  each  other,  so  that  the  movement 
is  not  a  simple  gliding  one.  This  view  of  the  construction  of  the  knee-joint  receives 
confirmation  from  the  study  of  the  articulation  in  some  of  the  lower  mammals, 


THE   KNEE-JOINT 


335 


where  three  synovial  membranes  are  sometimes  found,  corresponding  to  these 
three  subdivisions,  either  entirely  distinct  or  only  connected  together  by  small 
communications.  This  view  is  further  rendered  probable  by  the  existence 
of  the  two  crucial  ligaments  within  the  joint,  which  must  be  regarded  as  the 
external  and  internal  lateral  ligaments  of  the  inner  and  outer  joints  respectively. 
The  existence  of  the  ligamentum  mucosum  would  further  indicate  a.  tendency 
to  separation  of  the  synovial  cavity  into  two  minor  sacs,  one  corresponding  to 
each  joint. 

The  bones  entering  into  the  formation  of  the  knee-joint  are  the  condyles  of  the 
femur  above,  the  head  of  the  tibia  below,  and  the  patella  in  front.  The  bones  are 
connected  together  by  ligaments,  some  of  which  are  placed  on  the  exterior  of  the 
joint,  while  others  occupy  its  interior. 


External  Ligaments. 

Anterior,  or  Ligamentum  Patellae. 

Posterior. 

Internal  Lateral. 

Two  External  Lateral.  (The  long 
external  ligament  is  constant.  The 
short  external  ligament  is  not  always 
present.) 

Capsular. 


Interior  Ligaments. 

Anterior,  or  External  Crucial. 

Posterior,  or  Internal  Crucial. 

Two  Semilunar  Fibro-cartilages. 

Transverse. 

Coronary. 

T .  ,  f  Processes  of 

Ligamentum  mucosum.       o         •  i 
T  .^  .      1     •  ^    fevnovial 

Ligamenta  alaria.  tvt      u 

'^  Membrane. 


The  Anterior  Ligament,  or  Ligamentum  Patellae  (Figs.  241,  245,  and  246),  is  the 
central  portion  of  the  common  tendon  of  the  Extensor  muscles  of  the  thigh,  which 
is  continued  from  the  patella  to  the  tubercle  of  the  tibia,  supplying  the  place  of  an 
anterior  ligament.  It  is  a  strong,  flat,  ligamentous  band  about  three  inches  in 
length,  attached,  above,  to  the  apex  of  the  patella  and  the  rough  depression  on  its 
posterior  surface ;  below,  to  the  lower  part  of  the  tubercle  of  the  tibia,  its  superficial 
fibres  being  continuous  over  the  front  of  the  patella  with  those  of  the  tendon  of  the 
Quadriceps  extensor.  The  lateral  portions  of  the  tendon  of  the  Extensor  muscles 
pass  down  on  either  side  of  the  patella,  and  are  attached  to  the  borders  of  this  bone. 
The  deep  fascia  and  the  quadriceps  extensor  muscle  are  inserted  into  the  patella. 
Prolongations  from  the  fascia  and  from  the  fibrous  expansion  of  the  muscle  pass 
from  the  edges  of  the  patella  and  from  the  ligament  of  the  patella  to  the  upper 
extremity  of  the  tibia  on  each  side  of  the  tubercle ;  externally,  and  to  the  head  of 
the  fibula.  They  are  termed  lateral  patellar  ligaments  (retinaculum  patelloB  mediate 
and  retinaculum,  'patelloe  laterale),  and  merge  into  the  capsule.  The  posterior 
surface  of  the  ligamentum  patellae  is  separated  from  the  front  of  the  capsular 
ligament  by  a  mass  of  fat. 

The  Posterior  Ligament  (ligamentum  popliteum  ohliquum)  (Fig.  241)  is  a  broad, 
flat,  fibrous  band,  formed  of  fasciculi  separated  from  one  another  by  apertures 
for  the  passage  of  vessels  and  nerves.  It  is  attached,  above,  to  the  upper  margin 
of  the  intercondyloid  notch  of  the  femur,  and,  below,  to  the  posterior  margin  of 
the  head  of  the  tibia.  Superficial  to  the  main  part  of  the  ligament  and  forming 
a  portion  of  it  is  a  strong  fasciculus  derived  from  the  tendon  of  the  Semi- 
membranosus, and  passing  from  the  back  part  of  the  inner  tuberosity  of  the  tibia 
obliquely  upward  and  outward  to  the  back  part  of  the  outer  condyle  of  the  femur. 
This  expansion  from  the  tendon  of  the  Semimembranosus  muscle  is  called  the 
posterior  ligament  of  Winslow  (ligamentum  posticum  Winslowii),  and  it  merges 
with  the  posterior  ligament.  The  posterior  ligament  forms  part  of  the  floor  of 
the  popliteal  space,  and  the  popliteal  artery  rests  upon  it. 

The  Internal  Lateral  Ligament  (ligamentum  collaterale  tihiale)  (Figs.  241  and  242) 
is  a  broad,  flat,  membranous  band,  thicker  behind  than  in  front,  and  situated 


336 


THE   ARTICULATIONS    OB    JOINTS 


nearer  to  the  back  than  the  front  of  the  joint.  It  is  attached,  above,  to  the  inner 
tuberosity  of  the  femur;  below,  to  the  inner  tuberosity  and  inner  surface  of  the 
shaft  of  the  tibia  to  the  extent  of  about  two  inches.  It  is  crossed,  at  its  lower 
part,  by  the  tendons  of  the  Sartorius,  GraciUs,  and  Semitendinosus  muscles,  a 
synovial  bursa  being  interposed.  Its  deep  surface  covers  the  anterior  portion  of 
the  tendon  of  the  Semimembranosus,  with  which  it  is  connected  by  a  few  fibres, 
the  synovial  membrane  of  the  joint,  and  the  inferior  internal  articular  vessels  and 
nerve;  it  is  intimately  adherent  to  the  internal  semilunar  fibro-cartilage. 


Fig.  241. — Right  knee-joint.     Anterior  view. 


Fig.  242. — Right  knee-joint.     Posterior  view. 


The  External  Lateral  or  Long  External  Lateral  Ligament  (  Ugamentum  collaterale 
fbulare)  (Figs.  242  and  246)  is  a  strong,  rounded,  fibrous  cord  situated  nearer 
to  the  back  than  the  front  of  the  joint.  It  is  attached,  above,  to  the  back  part 
of  the  outer  tuberosity  of  the  femur;  below,  to  the  outer  part  of  the  head  of  the 
fibula.  Its  outer  surface  is  covered  by  the  tendon  of  the  Biceps,  which  divides  at 
its  insertion  into  two  parts,  separated  by  the  ligament.  The  ligament  has,  pass- 
ing beneath  it,  the  tendon  of  the  Popliteus  muscle  and  the  inferior  external 
articular  vessels  and  nerve. 

The  Short  External  Lateral  Ligament  {Ugamentum  laterale  externum  breve  sen 
posticum)  (Fig.  242)  is  not  a  constant  structure.  It  is  an  accessory  bundle  of 
fibres  placed  behind  and  parallel  with  the  preceding,  attached,  above,  to  the 
lower  and  back  part  of  the  outer  tuberosity  of  the  femur;  below,  to  the  summit 
of  the  styloid  process  of  the  fibula.  This  ligament  is  intimately  connected  with 
the  capsular  ligament,  and  has,  passing  beneath  it,  the  tendon  of  the  Popliteus 
muscle  and  the  inferior  external  articular  vessels  and  nerve. 


THE  KNEE-JOINT 


337 


Femur 


The  Capsular  Ligament  (capsula  articularis)  (Fig.  241)  consists  of  an  exceedingly 
thin  but  strong,  fibrous  membrane  which  fills  in  the  intervals  left  between  the 
stronger  bands  above  described,  and  is  inseparably  connected  with  them.  In  front 
it  blends  with  and  forms  part  of  the  lateral 
patellar  ligaments  and  fills  in  the  interval 
between  the  anterior  and  lateral  ligaments  of 
the  joints,  with  which  latter  structures  it  is 
closely  connected.  It  is  deficient  above  the 
joint  and  beneath  the  tendon  of  the  quadri- 
ceps extensor.  Behind,  it  is  formed  chiefly 
of  vertical  fibres,  which  arise  above  from 
the  condyles  and  intercondyloid  notch  of 
the  femur,  and  is  connected  below  with  the 
back  part  of  the  head  of  the  tibia,  being 
closely  united  with  the  origins  of  the  Gas- 
trocnemius, Plantaris,  and  Popliteus  muscles. 
It  passes  in  front  of,  but  is  inseparably  con- 
nected with,  the  posterior  ligament. 

The  Crucial  Ligaments  (ligamenta  cruciata 
genu)  (Figs.  171,  243,  and  244)  are  two  inter- 
osseous ligaments  of  considerable  strength 
situated  in  the  interior  of  the  joint,  nearer  its 
posterior  than  its  anterior  part.  They  are 
called  crucial  because  they  cross  each  other 
somewhat  like  the  lines  of  the  letter  X;  and 
have  received  the  names  anterior  crucial  and 
posterior  crucial,  from  the  position  of  their  at- 
tachment to  the  tibia. 

The  anterior  or  external  crucial  ligament 
{ligamentum  cruciatum  anterius)  (Fig.  243)  is 
attached  to  the  depression  in  front  of  the 
spine  of  the  tibia,  being  blended  with  the  anterior  extremity  of  the  external 
semilunar  fibro-cartilage,  and,  passing  obliquely  upward,  backward,  and  out- 
ward, is  inserted  into  the  iimer  and  back  part  of  the  outer  condyle  of  the  femur. 
The  posterior  or  internal  crucial  ligament  (ligamentum  cruciatum  posterius) 
is  stronger,  but  shorter  and  less  oblique  in  its  direction  than  the  anterior.    It 

is  attached  to  the  back  part 
of  the  depression  behind  the 
spine  of  the  tibia,  to  the  pop' 
liteal  notch,  and  to  the  poste- 
rior extremity  of  the  external 
semilunar  fibro-cartilage;  and 
passes  upward,  forward,  and 
inward,  to  be  inserted  into 
the  outer  and  forepart  of  the 
inner  condyle  of  the  femur. 
It  is  in  relation,  in  front,  with 
the  anterior  crucial  ligament; 
behind,  with  the  capsular  liga- 
ment. 

The  Semilunar  Fibro-cartil- 
a,ges(menisic)  (Figs.  171,243, 
244,  245,  and  246)  are  two  crescentic  lamellae  which  serve  to  deepen  the  surface 
of  the  head  of  the  tibia,  for  articulation  with  the  condyles  of  the  femur.    The 

22 


Fig.  243.- 


Right  knee-joint.    Showing  internal 
ligaments. 


Fig.  244. 


-Head  of  tibia,  with  semilunar  cartilages,  etc. 
from  above.     Right  side. 


Seen 


338 


THE  ARTICULATIONS    OB   JOINTS 


circumference  of  each  cartilage  is  thick,  convex,  and  attached  to  the  inside  of  the 
capsule  of  the  knee ;  the  inner  border  is  thin,  concave,  and  free.  Their  uy^er 
surfaces  are  concave,  and  in  relation  with  the  condyles  of  the  femur;  their  lower 
surfaces  are  flat,  and  rest  upon  the  head  of  the  tibia.  Each  cartilage  covers 
nearly  the  outer  two-thirds  of  the  corresponding  articular  surface  of  the  tibia, 
leaving  the  inner  third  uncovered ;  both  surfaces  are  smooth  and  invested  by 
svnovial  membrane. 


ARTICULAR 
CAVITY 


LIGAMENTA 
ALARIA 


SE 
FIBRO-CA 


LIGAMENTUM 
PATELL/E 


DEEP  INFRA- 
PATELLAR BURSA 


EPIPHYSEAL 
JUNCTION 


Fig.  245. — Right  knee-joint.  Sagittal  section  through  the  external  condyle  of  the  femur.  Medial  half  of 
section,  from  the  lateral  side.  (The  knee  is  slightly  flexed;  the  joint  surfaces  have  been  pulled  a  little  aparv.) 
(Spalteholz.) 


The  internal  semilunar  fibro-caxtilage  {meniscus  medialis)  is  nearly  semicircular 
in  form,  a  little  elongated  from  before  backward,  and  broader  behind  than  in  front; 
its  anterior  extremity,  thin  and  pointed,  is  attached  to  a  depression  on  the  anterior 
margin  of  the  head  of  the  tibia,  in  front  of  the  anterior  crucial  ligament;  its 
'posterior  extremity  is  attached  to  the  depression  behind  the  spine,  between  the 
attachments  of  the  external  semilunar  fibro-cartilage  and  the  posterior  crucial 
ligaments. 


THE  KNEE-JOINT 


339 


The  external  semilunar  fibro-cartilage  {meniscus  lateralis)  forms  nearly  an 
entire  circle,  covering  a  larger  portion  of  the  articular  surface  than  the  internal 
one.  It  is  grooved  on  its  outer  side  for  the  tendon  of  the  Popliteus  muscle.  Its 
extremities,  at  their  insertion,  are  interposed  between  the  two  extremities  of  the 
internal  semilunar  fibro-cartilage ;  the  anterior  extremity  being  attached  in  front 
of  the  spine  of  the  tibia  to  the  outer  side  of,  and  behind,  the  anterior  crucial 


TENDON  OF  QUAD- 
RICEPS EXTENSOR 
FEMORIS 

SUPRAPATELLAR 
BURSA 


ARTICULAR 
CAVITY 


LONG   EXTERNAL 

LATERAL 

LIGAMENT 

TENDON  OF 

POPLITEUS 

MUSCLE 

popliteal 
bursa' 


HEAD  OF    li 
FIBULA 


PREPATELLAR 
BURSA 


EXTERNAL  SEMI- 
LUNAR FIBRO- 
CARTILAGE 


LIGAMENTUM 
PATELUE 


DEEP  INFRAPATEL- 
LAR BURSA 


TUBEROSITIES 
OF  TIBIA 


Fig.  246. 


-Right  knee-joint,  from  the  lateral  surface.       (The  joint  cavity  and  several  bursse  have  been  injecteu 

with  a  stiffening  medium  and  then  dissected  out.)     (Spalteholz.) 


ligament,  with  which  it  blends;  the  posterior  extremity  being  attached  behind  the 
spine  of  the  tibia,  in  front  of  the  posterior  extremity  of  the  internal  semilunar 
fibro-cartilage.  Just  before  its  insertion  posteriorly  it  gives  off  a  strong  fasciculus, 
the  ligament  of  Wrisberg,  which  passes  obliquely  upward  and  outward,  to  be 
inserted  into  the  inner  condyle  of  the  femur,  close  to  the  attachment  of  the  poste- 
rior crucial  ligament.  Occasionally  a  small  fasciculus  is  given  off  which  passes 
forward  to  be  inserted  into  the  back  part  of  the  anterior  crucial  ligament.    The 


340  THE  ARTICULATIONS    OR    JOINTS 

external  semilunar  fibro-cartilage  gives  off  from  its  anterior  convex  margin  a 
fasciculus  which  forms  the  transverse  ligament. 

The  Transverse  Ligament  (ligamentum  transversum  genu)  (Fig.  244)  is  a  band  of 
fibres  which  passes  transversely  from  the  anterior  convex  margin  of  the  external 
semilunar  fibro-cartilage  to  the  anterior  convex  margin  of  the  internal  semilunar 
fibro-cartilage;  its  thickness  varies  considerably  in  different  subjects,  and  it  is 
sometimes  absent  altogether. 

The  Coronary  Ligaments  (ligamenfa  coronaria)  are  merely  portions  of  the  cap- 
sular ligament,  which  connect  the  circumference  of  each  of  the  semilunar  fibro- 
cartilages  with  the  margin  of  the  head  of  the  tibia. 

Synovial  Membrane  (Figs.  245  and  246) . — The  synovial  membrane  encloses  the 
articular  cavity  (cavum  articulare)  of  the  knee-joint.  It  is  the  largest  and  most 
extensive  synovial  membrane  in  the  body.  Commencing  above  the  upper  border 
of  the  patella,  it  forms  a  short  cul-de-sac  beneath  the  Quadriceps  extensor  tendon  of 
the  thigh,  on  the  lower  part  of  the  front  of  the  shaft  of  the  femur;  this  connnuni- 
cates,  by  an  orifice  of  variable  size,  with  a  synovial  bursa  interposed  between  the 
tendon  "and  the  front  of  the  femur  (bursa  suprapaiellaris) .  On  each  side  of  the 
patella  the  synovial  membrane  extends  beneath  the  aponeurosis  of  the  Vasti 
muscles,  and  more  especially  beneath  that  of  the  Vastus  internus.  Below  the 
patella  it  is  separated  from  the  anterior  ligament  by  the  anterior  part  of  the 
capsule  and  a  considerable  quantity  of  adipose  tissue,  known  as  the  infrapatellar 
pad  (Fig.  245) .  In  this  situation  the  synovial  membrane  sends  off  a  triangular 
prolongation,  containing  a  few  ligamentous  fibres,  which  extends  from  the  ante- 
rior part  of  the  joint  below  the  patella  to  the  front  of  the  intercondyloid  notch. 
This  fold  has  been  termed  the  ligamentum  mucosum  (plica  synovialis  patellar  is). 
It  also  sends  off  two  fringe-like  folds,  called  the  ligamenta  alaria  (plicre  alares) 
(Fig.  245),  which  extend  from  the  sides  of  the  ligamentum  mucosum,  upward 
and  laterally  between  the  patella  and  femur.  On  either  side  of  the  joint  it  passes 
downward  from  the  femur,  lining  the  capsule  to  its  point  of  attachment  to  the 
semilunar  cartilages ;  it  may  then  be  traced  over  the  upper  surfaces  of  these  car- 
tilages to  their  free  borders,  and  from  thence  along  their  under  surfaces  to  the 
tibia.  At  the  back  part  of  the  external  one  it  forms  a  cul-de-sac  between  the 
groove  on  its  surface  and  the  tendon  of  the  Popliteus;  it  surrounds  the  crucial 
ligaments  and  lines  the  inner  surface  of  the  ligaments  which  enclose  the  joint. 
The  pouch  of  synovial  membrane  between  the  Extensor  tendon  and  front  of  the 
femur  is  supported,  during  the  movements  of  the  knee,  by  a  small  muscle,  the 
Subcrureus,  which  is  inserted  into  the  upper  part  of  the  capsular  ligament. 

The  folds  of  synovial  membrane  and  the  fatty  processes  contained  in  them  act, 
as  it  seems,  mainly  in  padding  to  fill  up  interspaces  and  obviate  concussions. 
Sometimes  the  bursa  beneath  the  Quadriceps  extensor  is  completely  shut  off  from 
the  rest  of  the  synovial  cavity,  thus  forming  a  closed  sac  between  the  Quadriceps 
and  the  lower  part  of  the  front  of  the  femur;  sometimes  it  communicates  with  the 
synovial  cavity  by  a  minute  aperture;  usually  the  two  cavities  are  incompletely 
separated  by  a  synovial  fold. 

Bursae.^-The  bursa?  about  the  knee-joint  are  the  following:  In  front  there 
are  jour  bursse:  one  is  interposed  between  the  patella  and  the  skin.  It  is 
known  as  the  prepatellar  bursa  (bursa  prcepatellaris  suhcutanea) ;  another,  of 
small  size,  between  the  upper  part  of  the  tuberosity  of  the  tibia  and  the 
ligamentum  patellae  is  called  the  deep  infrapatellar  bursa  (bursa  injrapateUaris 
profunda);  and  a  third  between  the  lower  part  of  the  tuberosity  of  the  tibia 
and  the  skin,  the  subcutaneous  tibial  bursa  (bursa  subcutanea  tuberositaUs  tibiw). 
A  fourth  bursa  exists  in  front,  the  suprapatellar  bursa  (bursa  suprapateUaris) . 
It  lies  between  the  anterior  surface  of  the  lower  end  of  the  femur  and  the 
posterior    surface  of   the  quadriceps  feraoris.     Spalteholz  says  that  the  supra- 


THE   KNEE-JOINT  34I 

patellar  bursa  is  closely  connected  with  the  quadriceps  tendon  and  is  usually 
incompletely  shut  off  from  the  cavity  of  the  joint.^  Occasionally  there  is  a 
bursa  between  the  expansion  of  the  fascia  lata  and  the  Quadriceps  and  the 
patella  (bursa  prcepatellaris  subfascialis) ,  and  sometimes  one  between  the  tendon 
of  the  quadriceps  and  the  anterior  surface  of  the  patella  (bursa  prcBpatellaris 
siibtendinea) .  On  the  outer  side  there  are  Jour  bursse:  (1)  one  beneath  the  outer 
head  of  the  Gastrocnemius  (which  sometimes  communicates  with  the  joint); 
(2)  one  above  the  external  lateral  ligament  between  it  and  the  tendon  of  the 
Biceps;  (3)  one  beneath  the  external  lateral  ligament  between  it  and  the  tendon 
of  the  Popliteus  (this  is  sometimes  only  an  expansion  from  the  next  bursa); 

(4)  one  beneath  the  tendon  of  the  Popliteus  (bursa  musculi  poplitei)  between  it 
and  the  condyle  of  the  femur,  which  is  almost  always  an  extension  from  the  syno- 
vial membrane  of  the  joint.  On  the  inner  side  there  are  fivehursee:  (1)  one 
beneath  the  inner  head  of  the  Gastrocnemius,  which  sends  a  prolongation  between 
the  tendons  of  the  Gastrocnemius  and  Semimembranosus :  this  bursa  often  com- 
municates with  the  joint;  (2)  one  above  the  internal  lateral  ligament  between  it 
and  the  tendons  of  the  Sartorius,  Gracilis,  and  Semitendinosus;  (3)  one  beneath 
the  internal  lateral  ligament  between  it  and  the  tendon  of  the  Semimembra- 
nosus: this  is  sometimes  only  an  expansion  from  the  next  bursa;  (4)  one  beneath 
the  tendon  of  the  Semimembranosus,  between  it  and   the   head   of  the  tibia; 

(5)  sometimes  there  is  a  bursa  between  the  tendons  of  the  Semimembranosus 
and  of  the  Semitendinosus. 

Structures  around  the  Joint. — In  front  and  at  the  sides,  the  Quadriceps  extensor; 
on  the  outer  side,  the  tendons  of  the  Biceps  and  the  Popliteus  and  the  external 
popliteal  nerve;  on  the  inner  side,  the  Sartorius,  Gracilis,  Semitendinosus,  and 
Semimembranosus;  behind,  an  expansion  from  the  tendon  of  the  Semimembra- 
nosus, the  popliteal  vessels,  and  the  internal  popliteal  nerve,  the  Popliteus,  the 
Plantaris,  and  the  inner  and  outer  heads  of  the  Gastrocnemius,  some  lymphatic 
glands,  and  fat. 

The  arteries  supplying  the  joint  are  derived  from  the  anastomotica  magna 
branch  of  the  femoral,  articular  branches  of  the  popliteal,  anterior  and  posterior 
recurrent  branches  of  the  anterior  tibial,  and  a  descending  branch  from  the 
external  circumflex  of  the  Profunda. 

The  nerves  are  derived  from  the  obturator,  anterior  crural,  and  external  and 
internal  popliteal. 

Actions. — The  knee-joint  permits  of  movements  of  flexion  and  extension,  and, 
in  certain  positions,  of  slight  rotation  inward  and  outward.  The  movement  of 
flexion  and  extension  does  not,  however,  take  place  in  a  simple,  finger-like  man- 
ner, as  in  other  joints,  but  is  a  complicated  movement,  consisting  of  a  certain 
amount  of  gliding  and  rotation;  so  that  the  same  part  of  one  articular  surface  is 
not  always  applied  to  the  same  part  of  the  other  articular  surface,  and  the  axis 
of  motion  is  not  a  fixed  one.  If  the  joint  is  examined  while  in  a  condition  of 
extreme  flexion,  the  posterior  part  of  the  articular  surfaces  of  the  tibia  will  be 
found  to  be  in  contact  with  the  posterior  rounded  extremities  of  the  condyles  of 
the  femur;  and  if  a  simple  hinge-like  movement  were  to  take  place,  the  axis, 
round  which  the  revolving  movement  of  the  tibia  occurs,  would  be  in  the  back 
part  of  the  condyle.  If  the  leg  is  now  brought  forward  into  a  position  of  semi- 
flexion, the  upper  surface  of  the  tibia  will  be  seen  to  glide  over  the  condyles  of 
the  femur,  so  that  the  middle  part  of  the  articular  facets  are  in  contact,  and  the 
axis  of  rotation  must  therefore  have  shifted  forward  to  nearer  the  centre  of  the 
condyles.  If  the  leg  is  now  brought  into  the  extended  position,  a  still  further 
gliding  takes  place  and  a  further  shifting  forward  of  the  axis  of  rotation.    This 

1  Spalteholz's  Hand  Atlas  of  Human  Anatomy.     Translated  by  Lewellys  F.  Barker. 


342  THE  ARTICULATIONS    OR    JOINTS 

is  not,  however,  a  simple  movement,  but  is  accompanied  by  a  certain  amount  of 
rotation  outward  round  a  vertical  axis  drawn  through  the  centre  of  the  head  of 
the  tibia.  This  rotation  is  due  to  the  greater  length  of  the  internal  condyle,  and 
to  the  fact  that  the  anterior  portion  of  its  articular  surface  is  inclined  obliquely 
outward.  In  consequence  of  this  it  will  be  seen  that  toward  the  close  of  the 
movement  of  extension — that  is  to  say,  just  before  complete  extension  is  effected 
— the  tibia  glides  obliquely  upward  and  outward  over  this  oblique  surface  on  the 
inner  condyle,  and  the  leg  is  therefore  necessarily  rotated  outward.  In  flexion 
of  the  joint  the  converse  of  these  movements  takes  place:  the  tibia  glides  backward 
round  the  end  of  the  femur,  and  at  the  commencement  of  the  movement  the  tibia 
is  directed  downward  and  inward  along  the  oblique  curve  of  the  inner  condyle, 
thus  causing  an  inward  rotation  to  the  leg. 

During  flexion  and  extension  the  patella  moves  on  the  lower  end  of  the  femur, 
but  this  movement  is  not  a  simple  gliding  one;  for  if  the  articular  surface  of  this 
bone  is  examined,  it  will  be  found  to  present  on  each  side  of  the  central  vertical 
ridge  two  less  marked  transverse  ridges,  which  divide  the  surface,  except  a  small 
portion  along  the  inner  border,  which  is  cut  off  by  a  slight  vertical  ridge  into 
six  facets  (see  Fig.  247),  and  therefore  does  not  present  a  uniform  curved  surface 

as  would  be  the  case  if  a  simple  gliding  movement  took 
place.  These  six  facets — three  on  each  side  of  the 
median  vertical  ridge — correspond  to  and  denote  the 
parts  of  the  bone  respectively  in  contact  with  the  con- 
dyles of  the  femur  during  flexion,  semiflexion,  and  exten- 
sion. In  flexion  only  the  upper  facets  on  the  patella  are 
in  contact  with  the  condyles  of  the  femur;  the  lower 
two-thirds  of  the  bone  rests  upon  the  mass  of  fat  which 
occupies  the  space  between  the  femur  and  tibia.  In  the 
semiflexed  position  of  the  joint  the  middle  facets  on  the 
Fig  247  —View  of  the  pos-  Patella  rcst  upon  the  most  prominent  portion  of  the  con- 
terior  surface  of  the  patella,     dvlcs,  and  thus  afford  greater  leverage  to  the  Quadriceps 

showing  diagrammatically  the       ,"'.  .         .,.         "^^  ^  ».  i 

areas  of  contact  with  the  femur     by  mcrcasiug  its  distaucc  irom  the  Centre  oi  motion.     In 

in    different    positions    of     the  ,     .  ,  .  ,,  j    ii      •       i  ,i      ,  i 

knee.  Complete  extension  the  patella  is  drawn  up,  so  that  only 

the  lower  facets  are  in  contact  with  the  articular  sur- 
faces of  the  condyles.  The  narrow  strip  along  the  inner  border  is  in  contact 
with  the  outer  aspect  of  the  internal  condyle  when  the  leg  is  fully  flexed  at 
the  knee-joint.  As  in  the  elbow,  so  it  is  in  the  knee — the  axis  of  rotation  in 
flexion  and  extension  is  not  precisely  at  right  angles  to  the  axis  of  the  bone,  but 
during  flexion  there  is  a  certain  amount  of  alteration  of  plane;  so  that,  whereas  in 
flexion  the  femur  and  tibia  are  in  the  same  plane,  in  extension  the  one  bone  forms 
an  angle  of  about  10  degrees  with  the  other.  There  is,  however,  this  difference 
between  the  two  extremities:  that  in  the  upper,  during  extension,  the  humeri  are 
parallel  and  the  bones  of  the  forearm  diverge;  in  the  lower,  the  femora  converge 
below  and  the  tibia  are  parallel. 

In  addition  to  the  slight  rotation  during  flexion  and  extension,  the  tibia  enjoys 
an  independent  rotation  on  the  condyles  of  the  femur  in  certain  positions  of  the 
joint.  This  movement  takes  place  between  the  interarticular  fibro-cartilages  and 
the  tibia,  whereas  the  movement  of  flexion  and  extension  takes  place  between  the 
interarticular  fibro-cartilages  and  the  femur.  So  that  the  knee  may  be  said  to 
consist  of  two  joints,  separated  by  the  fibro-cartilages:  an  upper,  menisco-femoral, 
in  which  flexion  and  extension  take  place;  and  a  lower,  menisco-tibial,  allowing 
of  a  certain  amount  of  rotation.  This  latter  movement  can  only  take  place  in  the 
semiflexed  position  of  the  limb,  when  all  the  ligaments  are  relaxed.  • 

During  flexion  the  ligamentum  patellae  is  put  upon  the  stretch,  as  is  also  the 
posterior  crucial  ligament  in  extreme  flexion.    The  other  ligaments  are  all  relaxed 


THE   KNEE   JOINT  343 

by  flexion  of  the  joint,  though  the  relaxation  of  the  anterior  crucial  ligament  is 
very  trifling.  During  life  flexion  is  checked  by  the  contact  of  the  leg  with  the 
thigh.  In  the  act  of  extending  the  leg  upon  the  thigh  the  ligamentuin  patellse  is 
tightened  by  the  Quadriceps  extensor;  but  when  the  leg  is  fully  extended,  as  in  the 
erect  posture,  the  ligament  becomes  relaxed,  so  as  to  allow  free  lateral  movement  to 
the  patella,  which  then  rests  on  the  front  of  the  lower  end  of  the  femur.  The  other 
ligaments,  with  the  exception  of  the  posterior  crucial,  which  is  partly  relaxed,  are  all 
on  the  stretch.  When  the  limb  has  been  brought  into  a  straight  line,  extension  is 
checked  mainly  by  the  tension  of  all  the  ligaments  except  the  posterior  crucial  and 
ligamentum  patellae.  The  movements  of  rotation  of  which  the  knee  is  capable  are 
permitted  in  the  semiflexed  condition  by  the  partial  relaxation  of  both  crucial  liga- 
ments, as  well  as  of  the  lateral  ligaments.  Rotation  inward  appears  to  be  limited 
by  the  tension  of  the  anterior  crucial  ligament,  and  by  the  interlocking  of  the  two 
ligaments;  but  rotation  outward  does  not  appear  to  be  checked  by  either  crucial 
ligament,  since  they  uncross  during  the  execution  of  this  movement,  but  it  is 
checked  by  the  lateral  ligaments,  especially  the  internal.  The  main  function  of 
the  crucial  ligaments  is  to  act  as  a  direct  bond  of  union  between  the  tibia  and 
femur,  preventing  the  former  bone  from  being  carried  too  far  backward  or 
forward.  Thus  the  anterior  crucial  ligament  prevents  the  tibia  being  carried 
too  far  forward  by  the  extensor  tendons,  and  the  posterior  crucial  checks  too 
great  movement  backward  by  the  flexors.  They  also  assist  the  lateral  ligaments 
in  resisting  any  lateral  bending  of  the  joint.  The  interarticular  cartilages  are 
intended,  as  it  seems,  to  adapt  the  surface  of  the  tibia  to  the  shape  of  the  femur 
to  a  certain  extent,  so  as  to  fill  up  the  intervals  which  would  otherwise  be  felt 
in  the  varying  positions  of  the  joint,  and  to  interrupt  the  jars  which  would  be 
so  frequently  transmitted  up  the  limb  in  jumping  or  falls  on  the  feet;  also  to 
permit  of  the  two  varieties  of  motion,  flexion  and  extension,  and  rotation,  as 
explained  above.  The  patella  is  a  great  defence  to  the  knee-joint  from  any 
injury  inflicted  in  front,  and  it  distributes  upon  a  large  and  tolerably  even  sur- 
face during  kneeling  the  pressure  which  would  otherwise  fall  upon  the  prominent 
ridges  of  the  condyles ;  it  also  affords  leverage  to  the  Quadriceps  extensor  muscle 
when  it  acts  upon  the  tibia;  and  Mr.  Ward  has  pointed  out^  how  this  leverage 
varies  in  the  various  positions  of  the  joint,  so  that  the  action  of  the  muscles  pro- 
duces velocity  at  the  expense  of  force  in  the  commencement  of  extension,  and,  on 
the  contrary,  at  the  close  of  extension  tends  to  diminish  velocity,  and  therefore 
the  shock  to  the  ligaments  at  the  moment  tension  of  the  structures  takes  place. 
Extension  of  the  leg  on  the  thigh  is  performed  by  the  Quadriceps  extensor; 
flexion  by  the  hamstring  muscles,  assisted  by  the  Gracilis  and  Sartorius,  and, 
indirectly,  by  the  Gastrocnemius,  Popliteus,  and  Plantaris;  rotation  outward,  by 
the  Biceps;  and  rotation  inward  by  the  Popliteus,  Semitendinosus,  and,  to  a  slight 
extent,  the  Semimembranosus,  the  Sartorius,  and  the  Gracilis. 

Surface  Form. — The  interval  between  the  two  bones  entering  into  the  formation  of  the  knee- 
joint  can  always  easily  be  felt.  If  the  limb  is  extended,  it  is  situated  on  a  slightly  higher  level 
than  the  apex  of  the  patella;  but  if  the  limb  is  slightly  flexed,  a  knife  carried  horizontally  back- 
ward immediately  below  the  apex  of  the  patella  would  pass  directly  into  the  joint.  When  the 
knee-joint  is  distended  with  fluid,  the  outline  of  the  synovial  membrane  at  the  front  of  the  knee 
may  be  fairly  well  mapped  out. 

Surgical  Anatomy. — The  bursa;  about  the  knee  are  frequently  the  seat  of  inflammation. 
Enlargement  of  the  prepatellar  bursa  constitutes  housemaid'  s  knee.  The  bursa  beneath  the 
Semimembranosus  may  enlarge  greatly.  It  communicates  with  the  knee-joint  and  can  frequently 
be  made  to  disappear  bv  pressure  when  the  knee  is  flexed.  Treves  points  out  that  enlargement 
of  the  bursa  between  the  biceps  tendon  and  the  external  lateral  ligament  causes  great  pain 
because  the  peroneal  nerve  crosses  the  sac.^ 

From  a  consideration  of  the  construction  of  the  knee-joint  it  would  at  first  sight  appear  to  be 

1  Human  Osteology,  p.  405.  ^  Applied  Anatomy. 


344  THE  ARTICULATIONS    OB   JOINTS 

one  of  the  least  secure  of  any  of  the  joints  in  the  body.  It  is  formed  between  the  two  longest 
bones,  and  therefore  the  amount  of  leverage  which  can  be  brought  to  bear  upon  it  is  very  con- 
siderable; the  articular  surfaces  are  but  ill  adapted  to  each  other,  and  the  range  and  variety  of 
motion  which  it  enjoys  is  great.  All  these  circumstances  tend  to  render  the  articulation  very 
insecure;  but,  nevertheless,  on  account  of  the  very  powerful  ligaments  which  bind  the  bones 
together,  the  joint  is  one  of  the  strongest  in  the  body,  and  dislocation  from  traumatism  is  of 
very  rare  occurrence.  When,  on  the  other  hand,  the  ligaments  have  been  softened  or  destroyed 
by  disease,  partial  displacement  is  very  liable  to  occur,  and  is  frequently  brought  about  by  the 
mere  action  of  the  muscles  displacing  the  articular  surfaces  from  each  other.  The  tibia  may 
be  dislocated  in  any  direction  from  the  femur — forward,  backward,  inward,  or  outward;  or  a 
combination  of  two  of  these  dislocations  may  occur — that  is,  the  tibia  may  be  dislocated  for- 
ward and  laterally,  or  backward  and  laterally,  and  any  of  these  dislocations  may  be  complete 
or  incomplete.  As  a  rule,  however,  the  antero-posterior  dislocations  are  complete,  the  lateral 
ones  incomplete. 

One  or  other  of  the  semilunar  cartilages  may  become  displaced  and  nipped  between  the 
femur  and  tibia.  The  accident  is  produced  by  a  twist  of  the  leg  when  the  knee  is  flexed,  and  is 
accompanied  by  a  sudden  pain  and  fixation  of  the  knee  in  a  flexed  position.  The  cartilage  may 
be  displaced  either  inward  or  outward:  that  is  to  say,  either  inward  toward  the  tibial  spine,  so 
that  the  cartilage  becomes  lodged  in  the  intercondyloid  notch;  or  outward,  so  that  the  car- 
tilage projects  beyond  the  margin  of  the  articular  surface.  Acute  synovitis,  the  result  of  trau- 
matism or  exposure  to  cold,  is  very  common  in  the  knee,  on  account  of  its  superficial  position. 
When  distended  with  fluid,  the  swelling  shows  itself  above  and  at  the  sides  of  the  patella,  reach- 
ing about  an  inch  or  more  above  the  trochlear  surface  of  the  femur,  and  extending  a  little  higher 
under  the  Vastus  internus  than  the  Vastus  externus.  Occasionally  the  swelling  may  extend 
two  inches  or  more.  At  the  sides  of  the  patella  the  swelling  extends  lower  at  the  inner  side 
than  it  does  on  the  outer  side.  The  lower  level  of  the  synovial  membrane  is  just  above  the 
level  of  the  upper  part  of  the  head  of  the  fibula.  In  the  middle  line  it  covers  the  upper  third 
of  the  ligamentum  patellae,  being  separated  from  it,  however,  by  the  capsule  and  a  pad  of  fat. 
Chronic  synovitis  principally  shows  itself  in  the  form  of  pulpy  degeneration  of  the  synovial  mem- 
brane, the  result  of  tuberculous  arthritis.  The  reasons  why  tuberculous  disease  of  the  knee 
so  often  commences  in  the  synovial  membrane  appear  to  be  the  complex  and  extensive  nature  of 
this  sac;  the  extensive  vascular  supply  to  it;  and  the  fact  that  injuries  are  generally  diffused 
and  applied  to  the  front  of  the  joint  rather  than  to  the  ends  of  the  bones.  Syphilitic  disease 
not  unfrequently  attacks  the  knee-joint.  In  the  hereditary  form  of  the  disease  it  is  usually 
symmetrical,  attacking  both  joints,  which  become  filled  with  synovial  effusion,  and  is  very  intract- 
able and  difficult  to  cure.  In  the  tertiary  stage  of  acquired  syphilis  gummatous  infiltration  of 
the  synovial  membrane  may  take  place.  The  knee  is  one  of  the  joints  most  commonly  affected  with 
osteo-arthritis,  and  is  said  to  be  more  frequently  the  seat  of  this  disease  in  women  than  in  men. 
The  occurrence  of  the  so-called  loose  cartilage  is  almost  confined  to  the  knee,  though  loose  cartilages 
are  occasionally  met  with  in  the  elbow,  and,  rarely,  in  some  other  joints.  Many  of  them  occur  in 
cases  of  osteo-arthritis,  in  which  calcareous  or  cartilaginous  material  is  formed  in  one  of  the  synovial 
fringes  and  constitutes  the  foreign  body,  and  may  or  may  not  become  detached,  in  the  former 
case  only  meriting  the  usual  term,  "  loose  "  cartilage.  In  other  cases  they  have  their  origin  in  the 
exudation  of  inflammatory  lymph,  and  possibly,  in  some  rare  instances,  a  portion  of  the  articular 
cartilage  or  one  of  the  semilunar  cartilages  becomes  detached  and  constitutes  the  foreign  body. 

Genu  valgum,  or  knock-knee,  is  a  common  deformity  of  childhood,  in  which,  owing  to 
changes  in  and  about  the  joint,  the  angle  between  the  outer  border  of  the  tibia  and  femur  is 
diminished,  so  that  as  the  patient  stands  the  two  internal  condyles  of  the  femora  are  in  contact, 
but  the  two  internal  malleoli  of  the  tibise  are  more  or  less  widely  separated  from  each  other. 
When,  however,  the  knees  are  flexed  to  a  right  angle,  the  two  legs  are  practically  parallel  with 
each  other.  At  the  commencement  of  the  disease  there  is  a  yielding  of  the  internal  lateral  liga- 
ment and  other  fibrous  structures  on  the  inner  side  of  the  joint;  as  a  result  of  this  there  is  a 
constant  undue  pressure  of  the  outer  tuberosity  of  the  tibia  against  the  outer  condyle  of  the 
femur.  This  extra  pressure  causes  arrest  of  growth  and,  possibly,  wasting  of  the  outer  con- 
dyle, and  a  consequent  tendency  for  the  tibia  to  become  separated  from  the  internal  condyle. 
To  prevent  this  the  internal  condyle  becomes  depressed;  probably,  as  was  first  pointed  out  by 
Mikulicz,  by  an  increased  growth  of  the  lower  end  of  the  diaphysis  on  its  inner  side,  so  that  the 
line  of  the  epiphysis  becomes  oblique  instead  of  transverse  to  the  axis  of  the  bone,  with  a  direc- 
tion downward  and  inward.  It  is  often  said  that  the  deformity  is  produced  by  undue  length 
of  the  inner  condyle,  but  in  reality  the  condyle  grows  as  the  deformity  progresses. 

Excision  of  the  knee-joint  is  most  frequently  required  for  tuberculous  disease  of  this  articula- 
tion, but  is  also  practised  in  cases  of  disorganization  of  the  knee  after  rheumatic  fever,  pyaemia, 
etc.,  in  osteo-arthritis,  and  in  ankylo^s.  It  is  also  occasionally  called  for  in  cases  of  injury,  gun- 
shot or  otherwise.  The  operation  is  best  performed  either  by  a  horseshoe  incision,  starting  from 
one  condyle,  descending  as  low  as  the  tubercle  of  the  tibia,  where  it  crosses  the  leg,  and  is  then 
earned  upward  to  the  other  condyle;  or  by  a  transverse  incision  across  the  patella.     In  this 


TIBIO- FIBULAR    ARTICULATION 


345 


TUBEROSITY 
OF  TIBIA 


latter  incision  the  patella  is  either  removed  or  sawn  across,  and  the  halves  subsequently  sutured 
together.  The  bones  having  been  cleared,  and  in  those  cases  where  the  operation  is  performed 
for  tuberculous  disease  all  pulpy  tissue  having  been  carefully  removed,  the  section  of  the  femur 
is  first  made.  This  should  never  include,  in  children,  more  than,  at  the  most,  two-thirds  of 
the  articular  surface,  otherwise  the  epiphysial  cartilage  will  be  involved,  with  disastrous  results 
as  regards  the  growth  of  the  limb.  Afterward  a  thin  slice  should  be  removed  from  the  upper 
end  of  the  tibia,  not  more  than  half  an  inch.  If  any  diseased  tissue  still  appears  to  be  left  in  the 
bones,  it  should  be  removed  with  the  gouge  rather  than  by  making  a  further  section  of  the  bones. 

III.     Tibio-fibular    Articulation 
(Articulatio  Tibiofibularis) . 

The  articulations  between  the  tibia 
and  fibula  are  effected  by  ligaments 
which  connect  both  extremities,  as 
well  as  the  shafts  of  the  bones.  It 
may,  consequently,  be  subdivided 
into  three  articulations:  1.  The 
superior  tibio-fibulax  articulation.  2. 
The  middle  tibio-fibular  ligament  or 
interosseous  membrane.  3.  The 
inferior  tibio-fibular  articulation. 


1.  Superior  Tibio-fibular  Artic- 
ulation   (Articulatio 
Tibiofibularis)  . 

This  articulation  is  an  arthrodial 
joint.  The  contiguous  surfaces  of 
the  bones  present  two  flat,  oval 
facets  covered  with  cartilage,  and 
connected  together  by  the  following 
ligaments : 

Capsular. 

Anterior  Superior  Tibio-fibular. ' 

Posterior  Superior  Tibio-fibular. 

The  Capsular  Ligament  (capsula 
articularis)  consists  of  a  membra- 
nous bag  which  surrounds  the  artic- 
ulation, being  attached  around  the 
margins  of  the  articular  facets  on 
the  tibia  and  fibula,  and  is  much 
thicker  in  front  than  behind. 

The  new  nomenclature  considers 
the  anterior  and  posterior  ligaments 
as  one  ligament  {ligamentum  capitidi 
fibulce). 

The  Anterior  Superior  Ligament 
(Fig.  248)  consists  of  two  or  three 
broad  and  flat  bands  which  pass 
obliquely  upward  and  inward  from 
the  front  of  the  head  of  the  fibula 
to  the  front  of  the  outer  tuberosity 
of  the  tibia. 

The  Posterior  Superior  Ligament 
(Fig.  241)    is    a    single    thick    and 


INNER 
MALLEOLUS 


OUTER 
MALLEOLUS 


TERIOR     LIGAMENT 
OF    LATERAL 
MALLEOLUS 


Fig.  248. — Ligaments  of  the  right  leg,  from  in  front. 
(Spalteholz.) 


346  THE  ARTICULATIONS    OR    JOINTS 

broad  band  which  passes  upward  and  inward  from  the  back  part  of  the  head  of 
the  fibula  to  the  back  part  of  the  outer  tuberosity  of  the  tibia.  It  is  covered  by 
the  tendon  of  the  Pophteus  muscle. 

Synovial  Membrane. — A  synovial  membrane  lines  this  articulation,  which  at  its 
upper  and  back  part  is  occasionally  continuous  with  that  of  the  knee-joint. 

2.  Middle  Tibio-fibular  Ligament  or  Interosseous  Membrane 
(Membrana  Interossea  Cruris)  (Fig.  248). 

An  interosseous  membrane  extends  between  the  contiguous  margins  of  the 
tibia,  and  fibula  and  separates  the  muscles  on  the  front  from  those  on  the  back 
of  the  leg.  It  consists  of  a  thin,  aponeurotic  lamina  composed  of  oblique  fibres 
which  for  the  most  part  pass  downward  and  outward  between  the  interosseous 
ridges  on  the  two  bones;  some  few  fibres,  however,  pass  in  the  opposite  direction, 
downward  and  inward.  It  is  broader  above  than  below.  Its  upper  margin  does 
not  quite  reach  the  superior  tibio-fibular  joint,  but  presents  a  free  concave  bprder, 
above  which  is  a  large,  oval  aperture  for  the  passage  of  the  anterior  tibial  vessels 
forward  to  the  anterior  aspect  of  the  leg.  At  its  lower  part  is  an  opening  for  the 
passage  of  the  anterior  peroneal  vessels.  It  is  continuous  below  with  the  inferior 
interosseous  ligament,  and  is  perforated  in  numerous  places  for  the  passage  of  small 
vessels.  It  is  in  relation,  in  front,  with  the  Tibialis  anticus.  Extensor  longus  digi- 
torum.  Extensor  proprius  hallucis,  Peroneus  tertius,  and  the  anterior  tibial  vessels 
and  nerve ;  behind,  with  the  Tibialis  posticus  and  Flexor  longus  hallucis. 

3.  Inferior  Tibio-fibular  Articulation  (Syndesmosis  Tibiofibularis) 

(Figs.  250,  251,  252). 

This  articulation  is  formed  by  the  rough,  convex  surface  of  the  inner  side  of 
the  lower  end  of  the  fibula,  connected  with  a  concave  rough  surface  on  the  outer 
side  of  the  tibia.  Below,  to  the  extent  of  about  two  lines,  these  surfaces  are  smooth, 
and  covered  with  cartilage,  which  is  continuous  with  that  of  the  ankle-joint.  The 
ligaments  of  this  joint  are- 
Anterior  Inferior  Tibio-fibular.  .  Transverse  or  Inferior. 
Posterior  Inferior  Tibio-fibular.  Inferior  Interosseous. 

The  Anterior  Inferior  Ligament  (ligamentum  malleoli  lateralis  anterius)  (Figs.  248 
and  252)  is  a  flat,  triangular  band  of  fibres,  broader  belowthan  above,  which  extends 
obliquely  downward  and  outward,  between  the  adjacent  margins  of  the  tibia  and 
fibula,  on  the  front  aspect  of  the  articulation.  It  is  in  relation,  in  jront,  with  the 
Peroneus  tertius,  the  aponeurosis  of  the  leg,  and  the  integument;  behind,  with 
the  inferior  interosseous  ligament;  and  lies  in  contact  with  the  cartilage  covering 
the  astragalus. 

The  Posterior  Inferior  Ligament  {ligamentum  malleoli  lateralis  posterius)  (Fig. 
252),  smaller  than  the  preceding,  is  disposed  in  a  similar  manner  on  the  posterior 
surface  of  the  articulation. 

The  Transverse  Ligament  or  Inferior  Ligament  lies  under  cover  of  the  posterior 
ligament,  and  is  a  strong,  thick  band  of  yellowish  fibres  which  passes  transversely 
across  the  back  of  the  joint,  from  the  external  malleolus  to  the  posterior  border  of 
the  articular  surface  of  the  tibia,  almost  as  far  as  its  malleolar  process.  This  liga- 
ment projects  below  the  margin  of  the  bones,  and  forms  part  of  the  articulating 
surface  for  the  astragalus. 

The  Inferior  Interosseous  Ligament  (Fig.  250)  consists  of  numerous  short,  strong, 
fibrous  bands  which  pass  between  the  contiguous  rough  surfaces  of  the  tibia  and 
fibula,  and  constitute  the  chief  bond  of  union  between  the  bones.  This  ligament 
is  continuous  above  with  the  interosseous  membrane. 


THE    TIBIO- TARSAL    ARTICULATION 


347 


Synovial  Membrane. — The  synovial  membrane  lining  the  articular  surface  is 
derived  from  that  of  the  ankle-joint  (Fig.  250). 

Actions. — The  movement  permitted  in  these  articulations  is  limited  to  a  very 
slight  gliding  of  the  articular  surfaces  one  upon  another. 

IV.  The  Tibio-tarsal  Articulation  or  Ankle-joint  (Articulatio  Talocruralis) 

(Figs.  249,  250,  251,  252). 

The  ankle  is  a  ginglymus  or  hinge-joint.  The  bones  entering  into  its  formation 
are  the  lower  extremity  of  the  tibia  and  its  malleolus  and  the  external  malleolus 


Tarso-metatar 
articulations 


Tarsal  articulations. 


Fig.  249. — Ankle-joint:  tarsal  and  tarso-metatarsal  articulations.     Internal  view.     Right  side. 


of  the  fibula,  which  forms  a  mortise  (Fig.  248)  to  receive  the  upper  convex  surface 
of  the  astragalus  and  its  two  lateral  facets.  The  bony  surfaces  are  covered  with  car- 
tilage and  connected  together  by  a  capsule  (capsula  articularis) ,  which  in  places 
forms  thickened  bands  constituting  the  following  ligaments: 

Anterior.  Internal  Lateral. 

Posterior.  External  Lateral. 

The  Anterior  Tibio-tarsal  Ligament  {ligamentum  talotihiale  anterius)  is  a  broad, 
thin,  membranous  layer,  attached,  above,  to  the  anterior  margin  of  the  lower 
extremity  of  the  tibia;  below,  to  the  margin  of  the  astragalus,  in  front  of  its  artic- 
ular surface.  It  is  in  relation,  in  front,  with  the  Extensor  tendons  of  the  toes,  with 
the  tendons  of  the  TibiaHs  anticus  and  Peroneus  tertius,  and  the  anterior  tibial 
vessels  and  nerve;  behind,  it  lies  in  contact  with  the  synovial  membrane. 

The  Posterior  Tibio-tarsal  Ligament  {ligamentum  talotihiale  posterius)  is  very 
thin,  and  consists  principally  of  transverse  fibres.  It  is  attached,  above,  to  the 
margin  of  the  articular  surface  of  the  tibia,  blending  with  the  transverse  tibio- 
fibular ligament;  below,  to  the  astragalus,  behind  its  superior  articular  facet. 
Externally,  where  a  somewhat  thickened  band  of  transverse  fibres  is  attached  to 
the  hollow  on  the  inner  surface  of  the  external  malleolus,  it  is  thicker  than  inter- 
nally. 


348 


THE   ARTICULATIONS    OB    JOINTS 


The  Internal  Lateral  or  Deltoid  Ligament  (ligamentum  calcaneotib  iale  or  ligamentum 
deltoideum)  (Figs.  249,  250,  and  251)  is  a  strong,  flat,  triangular  band,  attached, 
above,  to  the  apex  and  anterior  and  posterior  borders  of  the  inner  malleolus. 
The  most  anterior  fibres  pass  forward  to  be  inserted  into  the  scaphoid  bone  and 
the  inferior  calcaneo-scaphoid  ligament;  the  middle  descend  almost  perpendicu- 
larly to  be  inserted  into  the  sustentaculum  tali  of  the  os  calcis;  and  the  posterior 
fibres  pass  backward  and  outward  to  be  attached  to  the  inner  side  of  the  astragalus. 
This  ligament  is  covered  by  the  tendons  of  the  Tibialis  posticus  and  Flexor  longus 
digitorum  muscles. 

The  External  Lateral  Ligament  {ligamenta  talofibularia  et  calcaneofibulare)  (Figs. 
251  and  252)  consists  of  three  distinctly  specialized*  fasciculi  of  the  capsule, 
taking  different  directions  and  separated  by  distinct  intervals;  for  which  reason 
it  is  described  by  some  anatomists  as  three  distinct  ligaments.^ 

The  anterior  fasciculus  (ligamentum  talofibulare  anterius),  the  shortest  of  the 
three,  passes  from  the  anterior  margin  of  the  external  malleolus  forward  and 
inward  to  the  astragalus,  in  front  of  its  external  articular  facet. 


INTEROSSEOUS. 
LIGAME 


SYNOVIAL 
ADIPOSE    PAD 


PERONE 
IREVIS  MUSC 


PERONEU 
LONGUS  MUSCL 


NTERNAL  LATERAL 
LIGAMENT 
TIBIALIS    POSTICUS 

NTEROSSEOUS  CAL- 
NEO  ASTRAGALOID 
GAMENT 

EXOR  LONGUS 

GITORUM 

EXOR   LONGUS 
HALLUCIS 
POSTERIOR 
TIBIAL  VESSELS 


Fig.  250. — Frontal  section  through  the  ankle-joint  and  the  calcaneo-astragaloid  articulation. 
(Poirier  and  Charpy). 

The  posterior  fasciculus  {ligamentum  talofibulare  posterius),  the  most  deeply  seated, 
passes  inward  from  the  depression  at  the  inner  and  back  part  of  the  external  mal- 
leolus to  a  prominent  tubercle  on  the  posterior  surface  of  the  astragalus.  Its  fibres 
are  almost  horizontal  in  direction. 

The  middle  fasciculus  (ligamentum  calcaneofibulare)  (Figs.  251  and  252),  the 
longest  of  the  three,  is  a  narrow,  rounded  cord  passing  from  the  apex  of  the 
external  malleolus  downward  and  slightly  backward  to  a  tubercle  on  the  outer 
surface  of  the  os  calcis.  It  is  covered  by  the  tendons  of  the  Peroneus  longus  and 
brevis. 

Sjmovial  Membrane. — The  synovial  membrane  (^Fig.  250)  invests  the  inner 
surface  of  the  ligaments,  and  sends  a  duplicature  upward  between  the  lower 
extremities  of  the  tibia  and  fibula  for  a  short  distance. 


^  Humphry.     On  the  Skeleton,  p.  559. 


THE    TIBIO- TARSAL    ARTICULATION 


349 


Relations. — The  tendons,  vessels,  and  nerves  in  connection  with  the  joint  are, 
in  jront,  from  within  outward,  the  TibiaHs  anticus,  Extensor  proprius  hallucis, 
anterior  tibial  vessels,  anterior  tibial  nerve,  Extensor  longus  digitorum,  and  Pero- 
neus  tertius;  behind,  from  within  outward,  the  Tibialis  posticus,  Flexor  longus 


INTERNAL 

INTEROSSEOUS 

LIGAMENT 


TARSO- 
METATARSAL 
ARTICULATIONS 


INTEROSSEOUS 
LIGAMENT 


ASTRAGALO- 

SCAPHOID 

ARTICULATION 


TENDON  OF  POS 
TERIOR  TIBIAL 
MUSCLE 


INTEROSSEOUS 
LIGAMENTS 


INTERMETATARSAL 
ARTICULATIONS 


INTEROSSEOUS 
LIGAMENT 


CALCANEO-SCAPHOID 
LIGAMENT 


CALCANEO-CUBOID 
ARTICULATION 


INTEROSSEOUS 
LIGAMENT 


ASTRAGALO-CALCANEAL 
RTICULATION 


ANKLE-JOINT 

MIDDLE  FASCICULUS 
OF  THE  EXTERNAL 
LATERAL  LIGAMENT 

INFERIOR  TIBIO- 
FIBULAR ARTICULATION 


Fig.  251. — Joints  of  the  right  foot,  from  the  back  of  the  foot.     (Spalteholz.) 

digitorum,  posterior  tibial  vessels,  posterior  tibial  nerve,  Flexor  longus  hallucis; 
and  in  the  groove  behind  the  external  malleolus,  the  tendons  of  the  Peroneus 
longus  and  brevis. 

The  arteries  supplying  the  joint  are  derived  from  the  malleolar  branches  of 
the  anterior  tibial  and  the  peroneal. 


350 


THE  ARTICULATIONS    OH    JOINTS 


The  nerves  are  derived  from  the  anterior  and  posterior  tibial. 

Actions. — The  movements  of  the  joint  are  those  of  flexion  and  extension. 
Flexion  consists  in  the  approximation  of  the  dorsum  of  the  foot  to  the  front  of  the 
leg,  while  in  extension  the  heel  is  drawn  up  and  the  toes  pointed  downward.  The 
malleoli  tightly  embrace  the  astragalus  in  all  positions  of  the  joint,  so  that  any 
slight  degree  of  lateral  movement  which  may  exist  is  simply  due  to  stretching 
of  the  inferior  tibio-fibular  ligaments  and  slight  bending  of  the  shaft  of  the  fibula. 
Of  the  ligaments,  the  internal,  or  deltoid,  is  of  very  great  power — so  much  so 
that  it  usually  resists  a  force  which  fractures  the  process  of  bone  to  which  it  is 
attached.  Its  middle  portion,  together  with  the  middle  fasciculus  of  the  external 
lateral  ligament,  binds  the  bones  of  the  leg  firmly  to  the  foot  and  resists  displace- 
ment in  every  direction.  Its  anterior  and  posterior  fibres  limit  extension  and 
flexion  of  the  foot  respectively,  and  the  anterior  fibres  also  limit  abduction.  The 
posterior  portion  of  the  external  lateral  ligament  assists  the  middle  portion  in 
resisting  the  displacement  of  the  foot  backward,  and  deepens  the  cavity  for  the 


Inferior  tibio-fibidar  articulation. 


Tarsal  articulations. 

Tarso-metatar.sal 

articulations. 


Fig.  252. — Ankle-joint:  tarsal  and  tarso-metatarsal  articulations.     External  view.     Right  side. 


reception  of  the  astragalus.  The  anterior  fasciculus  is  a  security  against  the  dis- 
placement of  the  foot  forward,  and  limits  extension  of  the  joint.  The  movements 
of  inversion  and  eversion  of  the  foot,  together  with  the  minute  changes  in  form  by 
which  it  is  applied  to  the  ground  or  takes  hold  of  an  object  in  climbing,  etc.,  are 
mainly  effected  in  the  tarsal  joints,  the  one  which  enjoys  the  greatest  amount  of 
motion  being  that  between  the  astragalus  and  os  calcis  behind  and  the  scaphoid 
and  cuboid  in  front.  This  is  often  called  the  transverse  or  medio-taxsal  joint,  and 
it  can,  with  the  subordinate  joints  of  the  tarsus,  replace  the  ankle-joint  in  a  great 
measure  when  the  latter  has  become  ankylosed. 

Extension  of  the  tarsal  bones  upon  the  tibia  and  fibula  is  produced  by  the 
Gastrocnemius,  Soleus,  Plantaris,  Tibialis  posticus,  Peroneus  longus  and  brevis, 
Flexor  longus  digitorum,  and  Flexor  longus  hallucis;  flexion,  by  the  Tibialis  anti- 
cus,  Peroneus  tertius,  Extensor  longus  digitorum,  and  Extensor  proprius  hallucis* 


'  The  student  must  bear  in  mind  that  the  Extensor  longus  digitorum  and  Extensor  proprius  hallucis  are 
extensors  of  the  toes,  but/ea:oj-s  of  the  ankle,  and  that  the  Flexor  longus  digitorum  and  Flexor  longus  hallucis  are 
flexors  of  the  toes,  but  extensors  of  the  ankle. 


THE    TIBIO- TARSAL    ARTICULATION 


351 


(Fig.  251) ;  imsrsion,  in  the  extended  position,  is  produced  by  the  Tibialis  anticus 
and  posticus;  and  eversion  by  the  Peronei, 


Fig. 


263. — Section  of  the  right  foot  near  its  inner  border,  dividing  the  tibia,  astragalus,  scaphoid,  internal 

cuneiform,  and  first  metatarsal  bone,  and  the  first  phalanx  of  the  great  toe.      (After  Braune.) 


Surface  Form. — The  line  of  the  ankle-joint  may  be  indicated  by  a  transverse  line  drawn 
across  the  front  of  the  lower  part  of  the  leg,  about  half  an  inch  above  the  level  of  the  tip  of  the 
internal  malleolus. 

Surgical  Anatomy. — Displacement  of  the  trochlear  surface  of  the  astragalus  from  the  tibio- 
fibular mortise  is  not  of  common  occurrence,  as  the  ankle-joint  is  a  very  strong  and  powerful 
articulation,  and  great  force  is  required  to  produce  dislocation.  Nevertheless,  dislocation  does 
occasionally  occur,  both  in  an  antero-posterior  and  a  lateral  direction.  In  the  latter,  which  is  the 
most  common,  fracture  is  a  necessary  accompaniment  of  the  injury.  The  dislocation  in  these  cases 
is  somewhat  peculiar,  and  is  not  a  displacement  in  a  horizontally  lateral  direction,  such  as  usually 
occurs  in  lateral  dislocations  of  ginglymoid  joints,  but  the  astragalus  undergoes  a  partial  rotation 
round  an  antero-posterior  axis  drawn  through  its  own  centre,  so  that  the  superior  surface,  instead 
of  being  directed  upward,  is  inclined  more  or  less  inward  or  outward  according  to  the  variety  of 
the  displacement. 

The  ankle-joint  is  more  frequently  sprained  than  any  joint  in  the  body,  and  this  may  lead 
to  acute  synovitis.  In  these  cases,  when  the  synovial  sac  is  distended  with  fluid,  the  bulging 
appears  principally  in  the  front  of  the  joint,  beneath  the  anterior  tendons,  and  on  either  side, 
between  the  tibialis  anticus  and  the  internal  lateral  ligament  on  the  inner  side,  and  between  the 
Peroneus  tertius  and  the  external  lateral  ligament  on  the  outer  side.  In  addition  to  this,  bulging 
frequently  occurs  posteriorly,  and  a  fluctuating  swelling  may  be  detected  on  either  side  of  the 
tendo  Achillis. 

Chronic  synovitis  may  result  from  frequent  sprains,  and  when  once  this  joint  has  been 
sprained  it  is  more  liable  to  a  recurrence  of  the  injury  than  it  was  before;  chronic  synovitis 
may  be  tuberculous  in  its  origin,  the  disease  usually  commencing  in  the  astragalus  and  extending 
to  the  joint,  though  it  may  commence  as  a  synovitis  the  result  probably  of  some  slight  strain  in 
a  tuberculous  subject. 

Excision  of  the  ankle-joint  is  not  often  performed  for  two  reasons.  In  the  first  place,  disease 
of  the  articulation  for  which  this  operation  is  indicated  is  frequently  associated  with  disease  of 
the  tarsal  bones,  which  prevents  its  performance;  and,  secondly,  the  foot  after  excision  is  fre- 
quently of  very  little  use;  far  less,  in  fact,  than  after  a  Syme's  amputation,  which  is  often,  there- 
fore, a  preferable  operation  in  these  cases.  Excision  may,  however,  be  attempted  in  a  case  of 
tuberculous  arthritis  in  a  young  and  otherwise  healthy  subject,  where  the  disease  is  limited  to 
the  bones  forming  the  joint.  It  may  also  be  required  after  injury  where  the  vessels  and  nerves 
have  not  been  damaged  and  the  patient  is  young  and  free  from  visceral  disease.  The  excision  is 
best  performed  through  two  lateral  incisions.  One  commencing  two  and  a  half  inches  above  the 
external  malleolus,  carried  down  the  posterior  border  of  the  fibula,  round  the  end  of  the  bone, 
and  then  forward  and  downward  as  far  as  the  calcaneo-cuboid  joint,  midway  between  the  tip 
of  the  external  malleolus  and  the  tuberosity  on  the  fifth  metatarsal  bone.     Through  this  incision 


352  THE   ARTICULATIONS    OR    JOINTS 

the  fibula  is  cleared,  the  external  lateral  ligament  is  divided,  and  the  bone  sawn  through  about 
half  an  inch  above  the  level  of  the  ankle-joint  and  removed.  A  similar  curved  incision  is  now 
made  on  the  inner  side  of  the  foot,  commmencing  two  and  a  half  inches  above  the  lower  end  of 
the  tibia,  carried  down  the  posterior  border  of  the  bone,  round  the  internal  malleolus,  and  for- 
ward and  downward  to  the  tuberosity  of  the  scaphoid  bone.  Through  this  incision  the  tibia  is 
cleared  in  front  and  behind,  the  internal  lateral,  the  anterior  and  posterior  ligaments  divided, 
and  the  end  of  the  tibia  protruded  through  the  wound  by  displacing  the  foot  outward,  and  sawn 
off  sufficiently  high  to  secure  a  healthy  section  of  bone.  The  articular  surface  of  the  astragalus 
is  now  to  be  sawn  off  or  the  whole  bone  removed.  In  cases  where  the  operation  is  performed 
for  tuberculous  arthritis  the  latter  course  is  probably  preferable,  as  the  injury  done  by  the  saw  is 
frequently  the  starting  point  of  fresh  caries;  and  after  removal  of  the  whole  bone  the  shortening 
is  not  appreciably  increased,  and  the  result  as  regards  union  appears  to  be  as  good  as  when  two 
sawn  surfaces  of  bone  are  brought  into  apposition. 

V.  Articulations  of  the  Tarsus  (Articulationes  Intertarsese)  (Figs.  249, 

251,  252,  254,  255). 

1.   Articulation  of  the  Os  Calcis  and  Astragalus  or  the    Calcaneo- 

ASTRAGALOID  ARTICULATION  (ArTICULATIO  TaLOCALCANEA)    (Fig.  251). 

The  articulations  between  the  os  calcis  and  astragalus  are  two  in  number — 
anterior  and  posterior.  They  are  arthrodial  joints.  The  bones  are  connected 
together  by  a  capsule  (capsula  articularis) ,  which  is  at  certain  points  accentuated 
into  definite  ligaments.     There  are  five  ligaments  in  this  articulation: 

External  Calcaneo-astragaloid,  Anterior  Calcaneo-astragaloid. 

Internal  Calcaneo-astragaloid.  Posterior  Calcaneo-astragaloid. 

Interosseous. 

The  External  Calcaneo-astragaloid  Ligament  (ligainentum  talocalcaneum  laterale) 
(Fig.  252)  is  a  short,  strong,  fasciculus  passing  from  the  outer  surface  of  the 
astragalus,  immediately  beneath  its  external  malleolar  facet,  to  the  outer  surface 
of  the  OS  calcis.  It  is  placed  in  front  of  the  middle  fasciculus  of  the  external 
lateral  ligament  of  the  ankle-joint,  with  the  fibres  of  which  it  is  parallel. 

The  Internal  Calcaneo-astragaloid  Ligament  {ligainentum  talocalcaneum  mediale) 
is  a  band  of  fibres  connectino-  the  internal  tubercle  of  the  back  of  the  astragalus 
with  the  back  of  the  sustentaculum  tali.  Its  fibres  blend  with  those  of  the  inferior 
calcaneo-scaphoid  ligament. 

The  Anterior  Calcaneo-astragaloid  Ligament  (ligamentum  talocalcaneum  anterius) 
passes  from  the  front  and  outer  surface  of  the  neck  of  the  astragalus  to  the  supe- 
rior surface  of  the  os  calcis. 

The  Posterior  Calcaneo-astragaloid  Ligament  (ligamentum  talocalcaneum  posterius) 
connects  the  external  tubercle  of  the  astragalus  with  the  upper  and  inner  part 
of  the  OS  calcis ;  it  is  a  short  band,  the  fibres  of  which  radiate  from  their  narrow 
attachment  to  the  astragalus. 

The  Interosseous  Ligament  {ligamentum  talocalcaneum  interosseum)  (Figs.  250, 
251,  and  255)  forms  the  chief  bond  of  union  between  the  bones.  It  consists  of 
numerous  vertical  and  oblique  fibres  attached  by  one  extremity  to  the  groove 
between  the  articulating  facets  on  the  under  surface  of  the  astragalus;  by  the 
other  to  a  corresponding  depression  on  the  upper  surface  of  the  os  calcis.  It 
is  very  thick  and  strong,  being  at  least  an  inch  in  breadth  from  side  to  side, 
and  serves  to  unite  the  os  calcis  and  astragalus  solidly  together. 

SjTiovial  Membrane. — The  synovial  membranes  (Fig.  255)  are  two  in  num- 
ber: one  for  the  posterior  calcaneo-astragaloid  articulation;  a  second  for  the 
anterior  calcaneo-astragaloid  joint.  The  latter  synovial  membrane  is  con- 
tinued forward  between  the  contiguous  surfaces  of  the  astragalus  and  scaphoid 
bones. 


ARTICULATIONS    OF    THE    TARSUS  353 

Actions. — The  movements  permitted  between  the  astragalus  and  os  calcis  are 
limited  to  a  ghding  of  the  one  bone  on  the  other  in  a  direction  from  before  back- 
ward, and  from  side  to  side. 

2.   Articulation  of  the  Os  Calcis  with  the  Cuboid  or  the  Calcaneo- 
cuboid Articulation  (Articulatio  Calcaneocuboidea)  (Fig.  251). 

In  this  joint  the  articular  capsule  {capsula  articularis)  is  strengthened  at 
certain  points  by  definite  ligaments. 

The  ligaments  connecting  the  os  calcis  with  the  cuboid  are  four  in  number: 

Dorsal  or  Superior  Calcaneo-cuboid.         T       PI     t      ^  Long  Calcaneo-cuboid. 
The  Internal  Calcaneo-cuboid.  \  Short  Calcaneo-cuboid. 

The  Superior  Calcaneo-cuboid  Ligament  {ligamentum  calcaneocuhoideum  dorsale) 
(Fig.  252)  is  a  broad  portion  of  the  capsule  which  passes  between  the  contiguous 
surfaces  of  the  os  calcis  and  cuboid  on  the  dorsal  surface  of  the  joint. 

The  Internal  Calcaneo-cuboid  or  the  Interosseous  Ligament  {'pars  calcaneo- 
cuboidea ligamenti  bifurcati)  is  a  short  but  thick  and  strong  band  of  fibres 
arising  from  the  cfs  calcis,  in  the  deep  hollow  which  intervenes  between  it  and 
the  astragalus,  and  closely  blended,  at  its  origin,  with  the  superior  calcaneo- 
scaphoid  ligament.  These  two  ligaments  are  often  regarded  as  a  single  bifur- 
cated ligament  (ligamentum  bijurcatum).  The  internal  calcaneo-cuboid  liga- 
ment is  inserted  into  the  inner  side  of  the  cuboid  bone.  This  ligament  forms 
one  of  the  chief  bonds  of  union  between  the  first  and  second  rows  of  the  tarsus. 

The  Long  Calcaneo-cuboid  or  Long  Plantar  or  Superficial  Long  Plantar  Ligament 
(ligamentum  plantar e  longum)  (Fig.  254),  the  more  superficial  of  the  two  plantar 
ligaments,  is  the  longest  of  all  the  ligaments  of  the  tarsus :  it  is  attached  to 
the  under  surface  of  the  os  calcis,  from  near  the  tuberosities,  as  far  forward  as 
the  anterior  tubercle;  its  fibres  pass  forward  to  be  attached  to  the  ridge  on  the 
under  surface  of  the  cuboid  bone,  the  more  superficial  fibres  being  continued 
onward  to  the  bases  of  the  second,  third,  and  fourth  metatarsal  bones.  This 
ligament  crosses  the  groove  on  the  under  surface  of  the  cuboid  bone,  converting 
it  into  a  canal  for  the  passage  of  the  tendon  of  the  Peroneus  longus. 

The  Short  Calcaneo-cuboid  or  Short  Plantar  Ligament  {ligamentum  calcaneo- 
cuhoideum plantare)  (Fig.  254)  lies  nearer  the  bones  than  the  preceding,  from 
which  it  is  separated  by  a  little  areolar  tissue.  It  is  exceedingly  broad,  about 
an  inch  in  length,  and  extends  from  the  tubercle  and  the  depression  in  front  of 
it,  on  the  forepart  of  the  under  surface  of  the  os  calcis,  to  the  inferior  surface  of 
the  cuboid  bone  behind  the  peroneal  groove. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  in  this  joint  is  distinct. 
It  lines  the  inner  surface  of  the  ligaments. 

Actions. — The  movements  permitted  between  the  os  calcis  and  cuboid  are 
limited  to  a  slight  gliding  upon  each  other. 

3.  The  Ligaments  Connecting  the  Os  Calcis  and  Scaphoid  or  the 
Calcaneo-scaphoid  Articulation  Ijgaments. 

Though  these  two  bones  do  not  directly  articulate,  they  are  connected  together 
by  two  ligaments: 

Superior  or  External  Calcaneo-scaphoid. 
Inferior  or  Internal  Calcaneo-scaphoid. 

The  Superior  or  External  Calcaneo-scaphoid  or  Calcaneo -navicular  {pars  cal- 
caneonavicular is  ligamenti  bifurcati)  arises,  as  already  mentioned,  with  the 
internal  calcaneo-cuboid  in  the  deep  hollow  between  the  astragalus  and  os  calcis, 

23 


354 


THE  ARTICULATIONS    OR    JOINTS 


constituting  a  part  of  the  ligamentum  bifurcatum ;  it  passes  forward  from  the 
upper  surface  of  the  anterior  extremity  of  the  os  calcis  to  the  outer  side  of  the 
scaphoid  bone.  These  two  hgaments  resemble  the  letter  Y,  being  blended  together 
behind,  but  separated  in  front. 

The  Inferior  or  Internal  Oalcaneo-scaphoid  or  Galcaneo-navicular  (ligamentum 
calcaneonavicular e  plantarc)  (Fig.  254)  is  by  far  the  larger  and  stronger  of  the  two 
ligaments  between  these  bones;  it  is  a  broad  and  thick  band  of  fibres,  which 

passes  forward  and  inward  from  the  anterior 
margin  of  the  sustentaculum  tali  of  the  os 
calcis  to  the  under  surface  of  the  scaphoid 
bone.  This  ligament  not  only  serves  to 
connect  the  os  calcis  and  scaphoid,  but  sup- 
ports the  head  of  the  astragalus,  forming 
part  of  the  articular  cavity  in  which  it  is 
received.  The  upper  surface  presents  a 
fibro-cartilaginous  facet,  lined  by  the  syn- 
ovial membrane  continued  from  the  ante- 
rior calcaneo-astragaloid  articulation,  upon 
which  a  portion  of  the  head  of  the  astragalus 
rests.  Its  under  surface  is  in  contact  with 
the  tendon  of  the  Tibialis  posticus  muscle;^ 
its  inner  border  is  blended  with  the  forepart 
of  the  Deltoid  ligament,  thus  completing 
the  socket  for  the  head  of  the  astragalus. 

Surgical  Anatomy. — The  inferior  calcaneo- 
scaphoid  ligament,  by  supporting  the  head  of  the 
astragalus,  is  principally  concerned  in  maintaining 
the  arch  of  the  foot,  and  when  it  yields  the  head  of 
the  astragalus  is  pressed  downward,  inward,  and 
forward  by  the  weight  of  the  body,  and  the  foot 
becomes  flattened,  expanded,  and  turned  outward, 
constituting  the  disease  known  as  flat-foot.  This 
ligament  contains  a  considerable  amount  of  elastic 
fibre,  so  as  to  give  elasticity  to  the  arch  and  spring  to 
the  foot;  hence  it  is  sometimes  called  the  "spring" 
ligament.  It  is  supported,  on  its  under  surface,  by 
the  tendon  of  the  Tibialis  posticus,  which  spreads 
out  at  its  insertion  into  a  number  of  fasciculi  which 
are  attached  to  most  of  the  tarsal  and  metatarsal 
bones;  this  prevents  undue  stretching  of  the  ligament 
and  is  a  protection  against  the  occurrence  of  fiat-foot. 


Fig.  254. 


-Ligaments  of  the  plantar  surface 
of  the  foot. 


4.   Articulation  of  the   Astragalus  with  the  Scaphoid   Bone  or   the 

ASTRAGALO-SCAPHOID    ARTICULATION    (ArTICULATIO    TaLONAVICULARIS) 

(Fig.  251). 
The  articulation  between  the  astragalus  and  scaphoid  is  an  arthrodial  joint: 
the  rounded  head  of  the  astragalus  being  received  into  the  concavity  formed  by 
the  posterior  surface  of  the  scaphoid,  the  anterior  articulating  surface  of  the 
calcaneum,  and  the  upper  surface  of  the  inferior  calcaneo-scaphoid  ligament, 
which  fills  up  the  triangular  interval  between  these  bones.  The  only  ligament  of 
this  joint  is  the  superior  astragalo-scaphoid  (Fig.  249).  It  is  a  broad  band, 
which  passes  obliquely  forward  from  the  neck  of  the  astragalus  to  the  superior 
surface  of  the  scaphoid  bone.  It  is  thin,  and  weak  in  texture,  and  covered  by  the 
Extensor  tendons.  The  inferior  calcaneo-scaphoid  ligament  supplies  the  place  of 
an  inferior  astragalo-scaphoid  ligament. 


1  Mr.  Hancock  describes  an  extension  of  this  ligament  upward  on  the  inner  side  of  the  foot,  which  completes 
the  socket  of  the  joint  in  that  direction  (Lancet,  1866,  vol.  i.  p.  618). 


ARTICULATIONS    OF    THE    TARSUS  355 

Synovial  Membrane  (Fig.  255) . — The  synovial  membrane  which  lines  the  joint 
is  continued  forward  from  the  anterior  calcaneo-astragaloid  articulation. 

Actions. — This  articulation  permits  of  considerable  mobility,  but  its  feebleness 
is  such  as  to  allow  occasionally  of  dislocation  of  the  other  bones  of  the  tarsus 
from  the  astragalus. 

The  transverse  tarsal  or  medio-tarsal  joint  [articulatio  tarsi  transversa  [Choparti]) 
(Figs.  251  and  256)  is  formed  by  the  articulation  of  the  os  calcis  with  the  cuboid, 
and  by  the  articulation  of  the  astragalus  with  the  scaphoid.  The  movement  which 
takes  place  in  this  joint  is  more  extensive  than  that  in  the  other  tarsal  joints,  and 
consists  of  a  sort  of  rotation  by  means  of  which  the  sole  of  the  foot  may  be 
slightly  flexed  and  extended  or  carried  inward  (inverted)  and  outward  (everted). 

5.  The  Articulation  of  the  Scaphoid  with  the  Cuneiform  Bones 
(Articulatio  Cuneonavicularis)  (Fig.  251). 

The  scaphoid  is  connected  to  the  three  cuneiform  bones  by 
Dorsal  and  Plantar  ligaments. 

The  Dorsal  Ligaments  {ligamenta  navicular icuneiformia  dorsalia)  (Figs.  249  and 
251)  are  s^nall,  longitudinal  bands  of  fibrous  tissue  arranged  as  three  bundles,  one 
to  each  of  the  cuneiform  bones.  That  bundle  of  fibres  which  connects  the  scaphoid 
with  the  internal  cuneiform  is  continued  round  the  inner  side  of  the  articulation  to 
be  continuous  with  the  plantar  ligament  which  connects  these  two  bones. 

The  Plantar  Ligaments  (ligamenta  navicularicuneiforrnia  plantaria)  (Fig.  254) 
have  a  similar  arrangement  to  those  on  the  dorsum.  They  are  strengthened  by 
processes  given  off  from  the  tendon  of  the  Tibialis  posticus. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  of  these  joints  is 
part  of  the  great  tarsal  synovial  membrane. 

Actions. — The  movements  permitted  between  the  scaphoid  and  cuneiform 
bones  are  limited  to  a  slight  gliding  upon  each  other. 

6.  The  Articulation  of  the  Scaphoid  with  the  Cuboid  (Articulatio 

Cubonavicularis)  . 

The  scaphoid  bone  is  connected  with  the  cuboid  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligament  (ligamentum  cuboideonaviculare  dorsale)  (Fig.  252)  con- 
sists of  a  band  of  fibrous  tissue  which  passes  obliquely  forward  and  outward 
from  the  scaphoid  to  the  cuboid  bone. 

The  Plantar  Ligament  (ligamentum  cuboideonaviculare.  plantare)  consists  of  a 
band  of  fibrous  tissue  which  passes  nearly  transversely  between  these  two  bones. 

The  Interosseous  Ligament  (Figs.  251  and  255)  consists  of  strong  transverse 
fibres  which  pass  between  the  rough  non-articular  portions  of  the  lateral  sur- 
faces of  these  two  bones. 

Synovial  Membrane  (Fig.  255). — The  synovial  membrane  of  this  joint  is  part 
of  the  great  tarsal  synovial  membrane. 

Actions. — The  movements  permitted  between  the  scaphoid  and  cuboid  bones 
are  limited  to  a  slight  gliding  upon  each  other. 

7.    The  Articulations  of  the   Cuneiform  Bones  with  Each  Other  or 
THE  Intercuneiform  Articulations  (Fig.  251). 

These  bones  are  connected  together  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 


356 


THE   ARTICULATIONS    OB    JOINTS 


The  Dorsal  Ligaments  (ligamenta  inter cuneiformia  dorsalia)  consist  of  two  bands 
of  fibrous  tissue  which  pass  transversely,  one  connecting  the  internal  with  the 
middle  cuneiform,  and  the  other  connecting  the  middle  with  the  external  cunei- 
form. 

The  Plantar  Ligaments  (ligamenta  intercuneijormia  'plantaria)  have  a  similar 
arrangement  to  those  oh  the  dorsum.  They  are  strengthened  by  the  processes 
given  off  from  the  tendon  of  the  TibiaUs  posticus. 

The  Interosseous  Ligaments  {ligamenta  intercuneijormia  interossea)  consist  of 
strong  transverse  fibres  which  pass  between  the  rough  non-articular  portions  of 
the  lateral  surfaces  of  the  first  and  second  and  the  second  and  third  cuneiform 
bones.  The  outer  portion  of  the  third  cuneiform  is  attached  to  the  cuboid  by 
the  ligamentum  cuneocuboideum  interosseum. 

Synovial  Membrane  (Fig.  255). — ^The  synovial  membrane  of  these  joints  is  part 
of  the  great  tarsal  synovial  membrane. 

Actions. — The  movements  permitted  between  the  cuneiform  bones  are  limited 
to  a  slight  gliding  upon  each  other. 

8.  The  Articulation  of  the  External  Cuneiform  Bone  with  the 

Cuboid  (Fig.  251). 

These  bones  are  connected  together  by 

Dorsal,  Plantar,  and  Interosseous  ligaments. 

The  Dorsal  Ligament  {ligamentum  cuneocuboideum  dorsale)  (Fig.  252)  consists 
of  a  band  of  fibrous  tissue  which  passes  transversely  between  these  two  bones. 

The  Plantar  Ligament  (ligamentum  cuneocuboideum  plantare)  has  a  similar 
arrangement.  It  is  strengthened  by  a  process  given  off  from  the  tendon  of  the 
Tibialis  posticus. 

The  Interosseous  Ligament  (ligamentum  cuneocuboideum  interosseum)  (Fig.  251) 
consists  of  strong  transverse  fibres  which  pass  between  the  rough  non-articular 
portions  of  the  lateral  surfaces  of  the  adjacent  sides  of  these  two  bones. 

Sjmovial  Membrane  (Fig.  255). — The  synovial  membrane  of  this  joint  is  part 
of  the  great  tarsal  synovial  membrane. 

Actions. — The  movements  permitted  between  the  external  cuneiform  and 
cuboid  are  limited  to  a  slight  gliding  upon  each  other. 

Nerve-supply. — All  the  joints  of  the  tarsus  are  supplied  by  the  anterior  tibial 
nerve. 

Surgical  Anatomy. — In  spite  of  the  great  strength  of  the  ligaments  which  connect  the  tarsal 
bones  together,  dislocation  at  some  of  the  tarsal  joints  does  occasionally  occur;  though,  on 
account  of  the  spongy  character  of  the  bones,  they  are  more  frequently  broken  than  dislocated, 
as  the  result  of  violence.  When  dislocation  does  occur,  it  is  most  commonly  in  connection  with 
the  astragalus;  for  not  only  may  this  bone  be  dislocated  from  the  tibia  and  fibula  at  the  ankle- 
joint,  but  the  other  bones  may  be  dislocated  from  it,  the  trochlear  surface  of  the  bone  remaining 
in  situ  in  the  tibio-fibular  mortise.  This  constitutes  what  is  known  as  the  subastragaloid  dis- 
location. Or,  again,  the  astragalus  may  be  dislocated  from  all  its  connections — from  the  tibia 
and  fibula  above,  the  os  calcis  below,  and  the  scaphoid  in  front — and  may  even  undergo  a 
rotation,  either  on  a  vertical  or  horizontal  axis.  In  the  former  case  the  long  axis  of  the  bone 
becoming  directed  across  the  joint,  so  that  the  head  faces  the  articular  surface  on  one  or  other 
malleolus;  or,  in  the  latter,  the  lateral  surfaces  becoming  directed  upward  and  downward,  so 
that  the  trochlear  surface  faces  to  one  or  the  other  side.  Finally,  dislocation  may  occur  at 
the  medio-tarsal  joint,  the  anterior  tarsal  bones  being  luxated  from  the  astragalus  and  cal- 
caneum.  The  other  tarsal  bones  are  also,  occasionally,  t)iough  rarely,  dislocated  from  their 
connections. 

Pes  planus,  flat-foot,  or  splay-foot  is  a  condition  in  which  there  is  abduction,  eversion,  and 
loss  of  both  the  longitudinal  and  the  transverse  arch.  The  head  of  the  astragalus  passes  down- 
ward and  inward ;  the  anterior  portion  of  the  foot  is  turned  outward  and  the  inner  side  of  the 
foot  is  lengthened  and  broadened.     Deformity  is  increased  when  standing.     In  severe  cases 


TABSO  -  METATARSAL    ARTICULATIONS  357 

the  patient  walks  on  the  inner  side  of  the  foot.  The  condition  is  due  to  yielding  of  the  tarsal 
ligaments.  Abduction  is  permitted  by  yielding  of  the  internal  lateral  and  calcaneo-astragaloid 
ligaments.  Yielding  of  the  calcaneo-scaphoid  ligament  permits  the  head  of  the  astragalus  to  pass 
downward  and  forward,  and  the  entire  arch  falls.  Further  deformity  is  induced  by  the  yielding 
of  the  ligaments. 

VI.  Tarso-metatarsal  Articulations  (Articulationes  Tarsometatarseae 

[Lisfranci])  (Figs.  249,  251,  252,  254,  257). 

These  are  arthrodial  joints.  The  bones  entering  into  their  formation  are  four 
tarsal  bones — viz.,  the  internal,  middle,  and  external  cuneiform  and  the  cuboid — 
which  articulate  with  the  metatarsal  bones  of  the  five  toes.  The  metatarsal  bone 
of  the  great  toe  articulates  with  the  internal  cuneiform;  that  of  the  second  is 
deeply  wedged  in  between  the  internal  and  external  cuneiform,  resting  against  the 
middle  cuneiform,  and  being  the  most  strongly  articulated  of  all  the  metatarsal 
bones;  the  third  metatarsal  articulates  with  the  extremity  of  the  external  cunei- 
form; the  fourth,  with  the  cuboid  and  external  cuneiform;  and  the  fifth,  with 
the  cuboid.  The  articular  surfaces  are  covered  with  cartilage,  lined  by 
synovial  membrane,  and  connected  together  by  capsules  and  by  the  following 
ligaments : 

Dorsal.  Plantar.  Interosseous. 

The  Dorsal  Ligaments  {ligamenta  tarsometatarsea  dorsalia)  consist  of  strong, 
flat,  fibrous  bands,  which  connect  the  tarsal  with  the  metatarsal  bones.  The 
first  metatarsal  is  connected  to  the  internal  cuneiform  by  a  single  broad,  thin, 
fibrous  band;  the  second  has  three  dorsal  ligaments,  one  from  each  cuneiform 
bone;  the  third  has  one  from  the  external  cuneiform;  the  fourth  has  two,  one 
from  the  external  cuneiform  and  one  from  the  cuboid;  and  the  fifth,  one  from 
the  cuboid. 

The  Plantar  Ligaments  {ligamenta  tarsometatarsea  plantaria)  consist  of  longi- 
tudinal and  oblique  fibrous  bands  connecting  the  tarsal  and  metatarsal  bones, 
but  disposed  with  less  regularity  than  on  the  dorsal  surface.  Those  for  the  first 
and  second  metatarsal  are  the  most  strongly  marked ;  the  second  and  third  meta- 
tarsal receive  strong  fibrous  bands  which  pass  obliquely  across  from  the  internal 
cuneiform;  the  plantar  ligaments  of  the  fourth  and  fifth  metatarsal  consist  of  a 
few  scanty  fibres  derived  from  the  cuboid. 

The  Interosseous  Ligaments  (ligamenta  cuneomeiatarsea  interossea)  are  three  in 
number— internal,  middle,  and  external.  The  internal  one  is  the  strongest  of  the 
three,  and  passes  from  the  outer  extremity  of  the  internal  cuneiform  to  the 
adjacent  angle  of  the  second  metatarsal.  The  middle  one,  less  strong  than  the 
preceding,  connects  the  external  cuneiform  with  the  adjacent  angle  of  the  second 
metatarsal.  The  external  interosseous  ligament  connects  the  outer  angle  of  the 
external  cuneiform  with  the  adjacent  side  of  the  third  metatarsal. 

Synovial  Membrane  (Fig.  255). — ^The  synovial  membrane  between  the  internal 
cuneiform  bone  and  the  first  metatarsal  bone  is  a  distinct  sac.  The  synovial 
membrane  between  the  middle  and  external  cuneiform  behind,  and  the  second 
and  third  metatarsal  bones  in  front,  is  part  of  the  great  tarsal  synovial  membrane. 
Two  prolongations  are  sent  forward  from  it — one  between  the  adjacent  sides  of 
the  second  and  third  metatarsal  bones,  and  one  between  the  third  and  fourth 
metatarsal  bones.  The  synovial  membrane  between  the  cuboid  and  the  fourth 
and  fifth  metatarsal  bones  is  a  distinct  sac.  From  it  a  prolongation  is  sent  for- 
ward between  the  fourth  and  fifth  metatarsal  bones. 

Actions. — The  movements  permitted  between  the  tarsal  and  metatarsal  bones 
are  limited  to  a  slight  gliding  upon  each  other. 


358 


THE  ARTICULATIONS    OB    JOINTS 


VII.  Articulations  of  the  Metatarsal  Bones  with  Each  Other 
(Articulationes  Intermetatarseae)   (Figs.  251,  252,  254). 

The  base  of  the  first  metatarsal  bone  is  not  connected  with  the  second  meta- 
tarsal bone  by  any  ligaments;  in  this  respect  it  resembles  the  thumb. 

The  bases  of  the  four  outer  metatarsal  bones  are  connected  together  by  dorsal, 
plantar,  and  interosseous  ligaments. 

The  Dorsal  Ligaments  (ligamenta  hasium  \oss.  metatarsi]  dorsalia)  consist  of 
bands  of  fibrous  tissue  which  pass  transversely  between  the  adjacent  metatarsal 
bones. 

The  Plantar  Ligaments  {ligamenta  hasium  \oss.  metatars.]  plantaria)  have  a 
similar  arrangement  to  those  on  the  dorsum. 

The  Interosseous  Ligaments  (ligamenta  basium  [oss.  metatars.]  interossea)  con- 
sist of  strong  transverse  fibres  which  pass  between  the  rough  non-articular  portions 
of  the  lateral  surfaces. 

Synovial  Membrane. — The  synovial  membrane  between  the  second  and  third 
and  the  third  and  fourth  metatarsal  bones  is  part  of  the  great  tarsal  synovial  mem- 
brane. The  synovial  membrane  between  the  fourth  and  fifth  metatarsal  bones  is 
a  prolongation  of  the  synovial  membrane  of  the  cubo-metatarsal  joint  (Fig.  255). 

Actions. — The  movement  permitted  in  the  tarsal  ends  of  the  metatarsal  bones 
is  limited  to  a  slight  gliding  of  the  articular  surfaces  upon  one  another. 

The  Synovial  Membranes  in  the  Tarsal  and  Metatarsal  Joints. 

The  synovial  membranes  (Fig.  255)  found  in  the  articulations  of  the  tarsus 
and  metatarsus  are  six  in  number;  one  for  the  posterior  calcaneo-astragaloid 


Fig.  255. — Oblique  section  of  the  articulations  of  the  tarsus  and  metatarsus.     Showing  the  six  synovial 

membranes. 

articulation;  a  second  for  the  anterior  calcaneo-astragaloid  and  astragalo- 
scaphoid  articulations;  a  third  for  the  calcaneo-cuboid  articulation;  and  a  fourth 
for  the  articulations  of  the  scaphoid  with  the  three  cuneiform,  the  three  cunei- 
form with  each  other,  the  external  cuneiform  with  the  cuboid,  and  the  middle  and 
external  cuneiform  with  the  bases  of  the  second  and  third  metatarsal  bones,  and 
the  lateral  surfaces  of  the  second,  third,  and  fourth  metatarsal  bones  with  each 
other;  a  fifth  for  the  internal  cuneiform  with  the  metatarsal  bone  of  the  great  toe; 
and  a  sixth  for  the  articulation  of  the  cuboid  with  the  fourth  and  fifth  metatarsal 
bones.  A  small  synovial  membrane  is  sometimes  found  between  the  contiguous 
surfaces  of  the  scaphoid  and  cuboid  bones. 


ARTICULATIONS    OF    THE  PHALANGES  359 

Nerve-supply. — The  nerves  supplying  the  tarso-metatarsal  joints  are  derived 
from  the  anterior  tibial. 

The  digital  extremities  of  all  the  metatarsal  bones  are  connected  together  by 
the  transverse  metatarsal  ligament. 

The  Transverse  Metatarsal  Ligament  is  a  narrow  fibrous  band  which  passes 
transversely  across  the  anterior  extremities  of  all  the  metatarsal  bones,  connecting 
them  together.  It  is  blended  anteriorly  with  the  plantar  {glenoid)  ligament  of 
each  metatarso-phalangeal  articulation.  To  its  posterior  border  is  connected  the 
fascia  covering  the  Interossei  muscles.  Its  inferior  surface  is  concave  where  the 
Flexor  tendons  pass  over  it.  Above  it  the  tendons  of  the  Interossei  muscles  pass 
to  their  insertion.  It  differs  from  the  transverse  metacarpal  ligament  in  that  it 
connects  the  metatarsal  bone  of  the  great  toe  with  the  rest  of  the  metatarsal  bones. 

VIII.  Metatarso-phalangeal  Articulations  (Articulationes  Metatarso- 

phalangeae). 

The  metatarso-phalangeal  articulations  are  of  the  condyloid  kind,  formed  by 
the  reception  of  the  rounded  head  of  the  metatarsal  bone  into  a  superficial  cavity 
in  the  extremity  of  the  first  phalanx.  Each  joint  has  a  capsule  and  certain 
other  ligaments. 

These  ligaments  are — 

Plantar.  Two  I^ateral. 

The  Plantar  Ligaments  or  the  Glenoid  Ligaments  of  Cruveilhier  (ligamenta 
accessoria  plaTitaria)  are  thick,  dense,  fibrous  structures.  Each  is  placed  on 
the  plantar  surface  of  the  joint  in  the  interval  between  the  lateral  ligaments, 
to  which  it  is  connected.  The  plantar  ligaments  are  loosely  united  to  the  meta- 
tarsal bones,  but  very  firmly  to  the  bases  of  the  first  phalanges.  The  plantar 
surface  of  each  is  intimately  blended  with  the  transverse  metatarsal  ligament, 
and,  except  in  the  great  toe,  presents  a  groove  for  the  passage  of  the  Flexor 
tendons,  the  sheath  surrounding  which  is  connected  to  each  side  of  the  groove. 
The  plantar  ligament  of  the  great  toe  contains  two  large  sesamoid  bones.  By 
their  deep  surface  they  form  part  of  the  articular  surface  for  the  head  of  the 
metatarsal  bone,  and  are  lined  by  synovial  membrane. 

The  Lateral  Ligaments  (ligamenta  collaieralia)  are  strong,  rounded  cords,  placed 
one  on  each  side  of  the  joint,  each  being  attached,  by  one  extremity,  to  the  poste- 
rior tubercle  on  the  side  of  the  head  of  the  metatarsal  bone;  and,  by  the  other,  to 
the  contiguous  extremity  of  the  phalanx. 

The  place  of  a  Posterior  Ligament  is  supplied  by  the  extensor  tendon  over  the 
back  of  the  joint. 

Actions. — The  movements  permitted  in  the  metatarso-phalangeal  articulations 
are  flexion,  extension,  abduction,  and  adduction. 

IX.  Articulations  of  the  Phalanges  (Articulationes  Digitorum  Pedis). 

The  articulations  of  the  phalanges  are  ginglymoid  joints.  Besides  the  cap- 
sular the  ligaments  are — 

Plantar.  Two  Lateral  (ligamenta  collateralia) . 

The  arrangement  of  these  ligaments  is  similar  to  those  in  the  metatarso-phalan- 
geal articulations;  the  extensor  tendon  supplies  the  place  of  a  posterior  ligament. 

Actions. — The  only  movements  permitted  in  the  phalangeal  joints  are  flexion 
and  extension;  these  movements  are  more  extensive  between  the  first  and  second 
phalanges  than  between  the  second  and  third.  The  movement  of  flexion  is  very 
considerable,  but  extension  is  limited  by  the  plantar  and  lateral  ligaments. 


3G0  THE  ARTICULATIONS    OB    JOINTS 

Surface  Form. — The  principal  joints  which  it  is  necessary  to  distinguish,  with  regard  to 
the  surgery  of  the  foot,  are  the  medio-tarsal  and  the  tarso-metatarsal.  The  joint  between  the 
astragalus  and  the  scaphoid  is  best  found  by  means  of  the  tubercle  of  the  scaphoid,  for 
the  line  of  the  joint  is  immediately  behind  this  process.  If  the  foot  is  grasped  and  forcibly 
extended,  a  rounded  prominence,  the  head  of  the  astragalus,  will  appear  on  the  inner  side  of 
the  dorsum  in  front  of  the  ankle-joint,  and  if  a  knife  is  carried  downward,  just  in  front  of  this 
prominence  and  behind  the  line  of  the  scaphoid  tubercle,  it  will  enter  the  astragalo-scaphoid 
joint.  The  calcaneo-cuboid  joint  is  situated  midway  between  the  external  malleolus  and  the 
prominent  end  of  the  fifth  metatarsal  bone.  The  plane  of  the  joint  is  in  the  same  line  as  that 
of  the  astragalo-scaphoid.  The  position  of  the  joint  between  the  fifth  metatarsal  bone  and  the 
cuboid  is  easily  found  by  the  projection  of  the  fifth  metatarsal  bone,  which  is  the  guide  to  it. 
The  direction  of  the  line  of  the  joint  is  very  oblique,  so  that,  if  continued  onward,  it  would 
pass  through  the  head  of  the  first  metatarsal  bone.  The  joint  between  the  fourth  metatarsal 
bone  and  the  cuboid  and  external  cuneiform  is  the  direct  continuation  inward  of  the  previous 
joint,  but  its  plane  is  less  oblique;  it  would  be  represented  by  a  line  drawn  from  the  outer  side 
of  the  articulation  to  the  middle  of  the  first  metatarsal  bone.  The  plane  of  the  joint  between 
the  third  metatarsal  bone  and  the  external  cuneiform  is  almost  transverse.     It  would  be  repre- 


FIFTH 


OS  CALCIS-f-    \  iK  METATARSAL  i        ft^j^         I    /  /    CUNEIFORM 


EXTERNAL 


FIRST 
METATARSAL 


Fig.  256. — Line  of  Chopart's  amputation.  Fig.  257. — Line  of  Lisfranc's  amputation. 

(Poirier.)  (Poirier.) 

sented  by  a  line  drawn  from  the  outer  side  of  the  joint  to  the  base  of  the  first  metatarsal  bone. 
The  tarso-metatarsal  articulation  of  the  great  toe  corresponds  to  a  groove  which  can  be  felt  by 
making  firm  pressure  on  the  inner  side  of  the  foot  one  inch  in  front  of  the  tubercle  on  the 
scaphoid  bone;  and  the  joint  between  the  second  metatarsal  bone  and  the  middle  cuneiform  is 
to  be  found  on  the  dorsum  of  the  foot,  half  an  inch  behind  the  level  of  the  tarso-metatarsal  joint 
of  the  great  toe.  The  line  of  the  joints  between  the  metatarsal  bones  and  the  first  phalanges 
is  about  an  inch  behind  the  webs  of  the  corresponding  toes. 

Surgical  Anatomy. — Chopart's  amputation  passes  through  the  middle  tarsal  joint  (astragalo- 
scaphoid  and  calcaneo-cuboid  articulation).  Fig.  256  shows  the  line  of  Chopart.  Lisfranc 
amputated  at  the  tarso-metatarsal  articulation.  Fig.  257  shows  the  line  of  Lisfranc.  In  Hey's 
amputation  the  fifth,  fourth,  third,  and  second  metatarsal  bones  are  disarticulated  from  the 
tarsus  and  the  internal  cuneiform  is  sawn  through.  In  the  operation  of  Forbes,  of  Toledo,  the 
cuneiform  bones  are  disarticulated  from  the  scaphoid,  the  cuboid  is  sawn  through  on  a  line 
with  the  surface  exposed  by  the  disarticulation. 


THE  MUSCLES  AND  FASCU). 


MYOLOGY  is  the  branch  of  anatomy  which  treats  of  the  muscles.  The 
muscles  are  formed  of  bundles  of  reddish  fibres,  endowed  with  the  property 
of  contractility.  The  two  principal  kinds  of  muscular  tissue  found  in  the 
body  are  voluntary  and  involiintaxy.  The  former  of  these,  from  the  character- 
istic appearances  which  its  fibres  exhibit  under  the  microscope,  is  known  as 
striated  or  striped  muscle,  and  from  the  fact  that  it  is  capable  of  being  put  into 
action  and  controlled  by  the  will,  as  voluntary  muscle.  The  fibres  of  the  latter 
do  not  present  any  cross-striped  appearance,  and  for  the  most  part  are  not 
under  the  control  of  the  will;  hence  they  are  known  as  unstriated,  unstriped,  or 
involuntary  muscle.  The  muscular  fibres  of  the  heart  differ  in  certain  partic- 
ulars from  both  these  groups,  and  they  are  therefore  separately  described  as 
cardiac  muscular  fibres. 

Thus  it  will  be  seen  that  there  are  three  varieties  of  muscular  fibres:  (1) 
Transversely  striated  muscular  fibres,  which  are  for  the  most  part  voluntary  and 
under  the  control  of  the  will,  but  some  of  which  are  not  so,  such  as  the  muscles 
of  the  pharynx  and  upper  part  of  the  oesophagus.  This  variety  of  muscle  is 
sometimes  called  skeletal.  (2)  Transversely  striated  muscular  fibres,  which  are 
not  under  the  control  of  the  will — i.  e.,  the  cardiac  muscles.  (3)  Plain  or  unstriped 
muscular  fibres,  which  are  involuntary  and  controlled  by  a  different  part  of  the 
nervous  system  from  that  which  controls  the  activity  of  the  voluntary  muscles. 
Such  are  the  muscular  walls  of  the  stomach  and  intestine,  of  the  uterus  and  bladder, 
of  the  blood-vessels,  etc. 

In  this  section  we  treat  of  the  skeletal  or  voluntary  muscles  only.  A  muscle  is 
composed  of  numerous  long,  narrow  muscle  cells  which  shorten  when  stimulated. 
The  wall  of  a  muscle  cell  is  called  the  sarcolemma.  Muscle  cells  end  either  by 
blending  with  tendon  or  aponeurosis  or  else  by  rounded  or  tapering  extremities, 
which  are  connected  to  neighboring  cells  by  means  of  the  sarcolemma.  Each 
muscle  is  composed  of  bundles  or  fasciculi  of  cells  or  fibres.  These  bundles  are 
connected  together  by  a  connective  tissue  which  is  known  as  the  epimysium  or 
external  perimysium  (perimysium  externum),  and  which  is  continuous  with  the 
sheath  of  the  muscle.  Each  bundle  of  muscle  fibres  is  surrounded  by  the  internal 
perimysium  (perimysium  internum).  The  internal  perimysium  joins  the  external 
perimysium  externally  and  the  sarcolemma,  or  tubular  sheath,  of  each  fibre 
internally. 

Each  muscle  cell  (fibre)  contains  numerous  nuclei  and  also  fibrillated  striated 
protoplasm.  A  muscle  cell  may  be  10  cm.  in  length,  and  may  even  extend  the 
entire  length  of  a  small  muscle  (Szymonowicz).  The  diameter  of  a  cell  is  from 
40//  to  60//.  The  striated  portion  of  a  cell  is  differentiated  protoplasm,  each  cell  is 
a  portion  of  unchanged  protoplasm  (sarcoplasm).    In  man  most  muscles  are  of 

*  The  Muscles  and  Fascise  are  described  conjointly,  in  order  that  the  student  may  consider  the  arrangement 
of  the  latter  in  his  dissection  of  the  former.  It  is  rare  for  the  student  of  anatomy  in  this  country  to  have 
the  opportunity  of  dissecting  the  fascia;  separately;  and  it  is  for  this  reason,  as  well  as  from  the  close  con- 
nection that  exists  between  the  muscles  and  their  investing  sheaths,  that  they  are  considered  together.  Some 
general  observations  are  first  made  on  the  histology  and  anatomy  of  the  muscles  and  fasciae,  the  special 
description  being  given  in  connection  with  the  different  regions. 

(  361  ) 


362  THE  MUSCLES   AND   FASCIA 

the  red  type,  but  some  (mixed  muscles)  contain  red  and  white  fibres.  A  red 
muscle  fibre  contains  a  considerable  quantity  of  sarcoplasm,  and  the  nuclei  are 
toward  the  centre  of  the  cell;  in  a  white  muscle  fibre  there  is  less  sarcoplasm,  the 
nuclei  are  toward  the  periphery,  and  striation  is  very  distinct/  Striation  is  due 
to  alteration  in  the  parts  of  the  fibre,  so  that  the  altered  material  has  a  different 
refractive  index  and  stains  differently  from  the  unaltered  portions  of  the  cell. 

The  Arteries  of  voluntary  muscles  pierce  the  external  perimysium  and  form 
superficial  and  deep  plexuses  that  anastomose  with  each  other.  These  vessels 
follow  the  trabeculse  between  the  bundles.  Branches  enter  the  bundles  and 
form  capillary  plexuses,  which  here  and  there  possess  dilatations  for  the  relief 
of  tension  during  muscular  action. 

Veins  accompany  the  arteries,  and  even  the  smaller  ones  possess  valves 
(Spalteholz). 

The  Nerve  Endings  in  voluntary  muscle  comprise  both  motor  and  sensory  ter- 
minations. A  motor  nerve  pierces  the  external  perimysium  and  breaks  up  into 
numerous  branches  to  form  an  interfascicular  plexus  in  the  internal  perimysium. 
From  this  plexus  nerve  fibrils  arise  and  usually  one  nerve  fibril  passes  to  each 
muscle  fibre.  The  nerve  fibril  pierces  the  sarcolemma,  the  neurilemma  and 
medullary  sheath  disappearing  before  the  nerve  fibril  reaches  the  muscle  fibre, 
and  probably  being  lost  by  fusing  with  the  sarcolemma.  The  naked  axis-cylinder 
beneath  the  sarcolemma  of  a  fibre  continues  to  the  surface  of  the  muscle  fibre  and 
undergoes  arborization  to  form  an  end  organ.  Around  the  end  organ  is  a  quantity 
of  granular  sarcoplasm,  which,  with  the  nerve  end  organ,  constitutes  a  sole-plate. 
A  sensory  nerve  takes  origin  from  a  muscle  spindle,  which  consists  of  a  bundle 
of  encapsuled  muscle  fibre  about  sensory  nerve  twigs.  From  a  muscle  spindle 
arise  from  two  to  eight  large  medullated  nerve  fibres. 

The  muscles  are  connected  with  the  bones,  cartilages,  ligaments,  and  skin, 
either  directly  or  through  the  intervention  of  fibrous  structures  called  tendons 
or  aponeuroses.  Where  a  muscle  is  attached  to  bone  or  cartilage,  the  fibres  ter- 
minate in  blunt  extremities  upon  the  periosteum  or  perichondrium,  and  do  not 
come  into  direct  relation  with  the  osseous  or  cartilaginous  tissue.  Where  muscles 
are  connected  with  the  skin,  they  either  lie  as  a  flattened  layer  beneath  it,  or  are 
connected  with  its  areolar  tissue  by  larger  or  smaller  bundles  of  fibres,  as  in  the 
muscles  of  the  face.  The  direct  continuation  of  the  tendon  of  a  muscle  is  known 
as  the  belly  or  venter.     The  origin  of  a  muscle  is  its  head  (caput). 

The  muscles  vary  extremely  in  their  form.  In  the  limbs  they  are  of  consid- 
erable length,  especially  the  more  superficial  ones,  the  deep  ones  being  generally 
broad;  they  surround  the  bones  and  form  an  important  protection  to  the  various 
joints.  In  the  trunk  they  are  broad,  flattened,  and  expanded,  forming  the  parietes 
of  the  cavities  which  they  enclose;  hence  the  reason  of  the  terms  long,  broad, 
short,  etc.,  used  in  the  description  of  a  muscle. 

There  is  a  considerable  variation  in  the  arrangement  of  the  fibres  of  certain 
muscles  with  reference  to  the  tendons  to  which  they  are  attached.  In  some,  the 
fibres  are  parallel  and  run  directly  from  their  origin  to  their  insertion;  these  are 
quadrilateral  muscles,  such  as  the  Thyro-hyoid.  A  modification  of  these  is  found  in 
the  fusiform  muscles  {m.  fusiformis),  in  which  the  fibres  are  not  quite  parallel,  but 
slightly  curved,  so  that  the  muscle  tapers  at  each  end;  in  their  action,  however,  they 
resemble  the  quadrilateral  muscles.  Secondly,  in  other  muscles  the  fibres  are  con- 
vergent; arising  by  a  broad  origin,  they  converge  to  a  narrow  or  pointed  insertion. 
This  arrangement  of  fibres  is  found  in  the  triangular  muscles — e.  g.,  the  Temporal. 
In  some  muscles,  which  otherwise  would  belong  to  the  quadrilateral  or  triangular 
type,  the  origin  and  insertion  are  not  in  the  same  plane,  but  the  plane  of  the  line 

^  A  Text-book  of  Histology.  By  Dr.  Ladislaus  Szymonowicz.  Translated  and  edited  by  Dr.  John  Bruce 
MacCallum. 


APONEUROSES  363 

of  origin  intersects  that  of  their  insertion;  such  is  the  case  in  the  Pectineus  muscle. 
Thirdly,  in  some  muscles  the  fibres  are  oblique  and  converge,  like  the  plumes 
of  a  pen,  to  one  side  of  a  tendon,  which  runs  the  entire  length  of  the  muscle. 
Such  a  muscle  is  rhomboidal  or  penniform  im.  unipennatus) ,  as  the  Peronei.  A 
modification  of  these  rhomboidal  muscles  is  found  in  those  cases  where  oblique 
fibres  converge  to  both  sides  of  a  central  tendon  which  runs  down  the  middle  of 
the  muscle;  these  are  called  bipenniform  (m.  bipennatus) ,  and  an  example  is  afforded 
in  the  Rectus  femoris.  Finally,  we  have  muscles  in  which  the  fibres  are  arranged 
in  curved  bimdles  in  one  or  more  planes,  as  in  an  orbicular  muscle  (m.  orbicularis) 
and  in  that  variety  of  orbicular  muscle  called  a  sphincter  muscle  (m.  sphincter). 
The  arrangement  of  the  muscular  fibres  is  of  considerable  importance  in  respect 
to  their  relative  strength  and  range  of  movement.  Those  muscles  where  the 
fibres  are  long  and  few  in  number  have  great  range,  but  diminished  strength; 
where,  on  the  other  hand,  the  fibres  are  short  and  more  numerous,  there  is 
great  power,  but  lessened  range. 

Muscles  differ  much  in  size:  the  Gastrocnemius  forms  the  chief  bulk  of  the 
back  of  the  leg,  and  the  fibres  of  the  Sartorius  are  nearly  two  feet  in  length,  whilst 
the  Stapedius,  a  small  muscle  of  the  internal  ear,  weighs  about  a  grain,  and  its 
fibres  are  not  more  than  two  lines  in  length. 

The  names  applied  to  the  various  muscles  have  been  derived — 1,  from  their 
situation,  as  the  Tibialis,  Radialis,  Ulnaris,  Peroneus;  2,  from  their  direction,  as 
the  Rectus  abdominis,  Obliquus  capitis,  Transversalis;  3,  from  their  uses,  as  Flexors, 
Extensors,  Abductors,  etc. ;  4,  from  their  shape,  as  the  Deltoid,  Trapezius,  Rhom- 
boideus;  5,  from  the  number  of  their  divisions,  as  the  Biceps,  the  Triceps;  6, 
from  their  points  of  attachment,  as  the  Sterno-cleido-mastoid,  Sterno-hyoid, 
Sterno-thyroid. 

In  the  description  of  a  muscle  the  term  origin  is  meant  to  imply  its  more  fixed 
or  central  attachment,  and  the  term  insertion,  the  movable  point  to  which  the 
force  of  the  muscle  is  directed;  but  the  origin  is  absolutely  fixed  in  only  a  very 
small  number  of  muscles,  such  as  those  of  the  face,  which  are  attached  by  one 
extremity  to  the  bone  and  by  the  other  to  the  movable  integument;  the  greater 
number  of  muscles  can  be  made  to  act  from  either  extremity. 

In  the  dissection  of  the  muscles  the  student  should  pay  especial  attention  to 
the  exact  origin,  insertion,  and  actions  of  each,  and  its  more  important  relations 
with  surrounding  parts.  An  accurate  knowledge  of  the  points  of  attachment  of 
the  muscles  is  of  great  importance  in  the  determination  of  their  action.  By  a 
knowledge  of  the  action  of  the  muscles  the  surgeon  is  able  to  explain  the  causes 
of  displacement  in  various  forms  of  fracture  and  the  causes  which  produce  dis- 
tortion in  various  deformities,  and,  consequently,  to  adopt  appropriate  treatment 
in  each  case.  The  relations,  also,  of  some  of  the  muscles,  especially  those  in 
immediate  apposition  with  the  larger  blood-vessels,  and  the  surface-markings  they 
produce,  should  be  especially  remembered,  as  they  form  useful  guides  to  the 
surgeon  who  operates  to  expose  and  ligate  them. 

Tendons. — Tendons  are  white,  glistening,  fibrous  cords,  varying  in  length  and 
thickness,  sometimes  round,  sometimes  flattened,  of  considerable  strength,  and 
devoid  of  elasticity.  They  consist  almost  entirely  of  white  fibrous  tissue,  the  fibrils 
of  which  have  an  undulating  course  parallel  with  each  other  and  are  firmly  united 
together.  They  are  very  sparingly  supplied  with  blood-vessels,  the  smaller  ten- 
dons presenting  in  their  interior  not  a  trace  of  them.  Nerves  also  are  not  present 
in  the  smaller  tendons,  but  the  larger  ones,  as  the  tendo  Achillis,  receive  nerves 
which  accompany  nutrient  vessels.  The  tendons  consist  principally  of  a  sub- 
stance w'hich  yields  gelatin. 

Aponeuroses. — Aponeuroses  are  flattened  or  ribbon-shaped  tendons,  of  a 
pearly-white  color,  iridescent,  glistening,  and  similar  in  structure  to  the  tendons. 


364 


THE  MUSCLES  AND    FASCIJE 


They  are  destitute  of  nerves,  and  the  thicker  ones  are  only  sparingly  supplied 
with  blood-vessels. 

The  tendons  and  aponeuroses  are  connected,  on  the  one  hand,  with  the  mus- 
cles, and,  on  the  other  hand,  with  movable  structures,  as  the  bones,  cartilages, 
ligaments,  fibrous  membranes  (for  instance,  the  sclerotic).  Where  the  muscular 
fibres  are  in  a  direct  line  with  those  of  the  tendon  or  aponeurosis,  the  two  are 
directly  continuous,  the  muscular  fibre  being  distinguishable  from  that  of  the 
tendon  only  by  its  striation.  But  where  the  muscular  fibres  join  the  tendon  or 
aponeurosis  at  an  oblique  angle  the  former  terminate,  according  to  Kolliker,  in 
rounded  extremities,  which  are  received  into  corresponding  depressions  on  the 
surface  of  the  latter,  the  connective  tissue  between  the  fibres  being  continuous 
with  that  of  the  tendon.  The  latter  mode  of  attachment  occurs  in  all  the  penni- 
form  and  bipenniform  muscles,  and  in  those  muscles  the  tendons  of  which  com- 
mence in  a  membranous  form,  as  the  Gastrocnemius  and  Soleus. 

Fasciae. — The  fasciae  {fascia,  a  bandage)  are  fibro-areolar  or  aponeurotic 
laminae  of  variable  thickness  and  strength,  found  in  all  regions  of  the  body, 
investing  the  softer  and  more  delicate  organs.  The  fasciae  have  been  sub- 
divided, from  the  situation  in  which  they  are  found,  into  two  groups,  superficial 
and  deep. 

Superficial  Fascia  (panniculus  adiposus). — The  superficial  fascia  is  found  imme- 
diately beneath  the  integument  over  almost  the  entire  surface  of  the  body.  It 
connects  the  skin  with  the  deep  or  aponeurotic  fascia,  and  consists  of  fibro-areolar 
tissue,  containing  in  its  meshes  pellicles  of  fat  in  varying  quantity.  In  the  eyelids 
and  scrotum,  where  adipose  tissue  is  rarely  deposited,  this  tissue  is  very  liable -to 
serous  infiltration.  The  superficial  fascia  varies  in  thickness  in  different  parts 
of  the  body:  in  the  groin  it  is  so  thick  as  to  be  capable  of  being  subdivided  in 
several  laminae.  Beneath  the  fatty  layer  of  the  superficial  fascia,  which  is  imme- 
diately subcutaneous,  there  is  generally  another  layer  of  the  same  structure,  com- 
paratively devoid  of  adipose  tissue,  in  which  the  trunks  of  the  subcutaneous  vessels 
and  nerves  are  found,  as  the  superficial  epigastric  vessels  in  the  abdominal  region, 
the  radial  and  ulnar  veins  in  the  forearm,  the  saphenous  veins  in  the  leg  and 
thigh,  and  the  superficial  lymphatic  glands;  certain  cutaneous  muscles  also  are 
situated  in  the  superficial  fascia,  as  the  Platysma  myoides  in  the  neck,  and  the 
Orbicularis  palpebrarum  around  the  eyelids.  This  fascia  is  most  distinct  at  the 
lower  part  of  the  abdomen,  the  scrotum,  perinaeum,  and  extremities;  is  very  thin 
in  those  regions  where  muscular  fibres  are  inserted  into  the  integument,  as  on 
the  side  of  the  neck,  the  face,  and  around  the  margin  of  the  anus.  It  is  very 
dense  in  the  scalp,  in  the  palms  of  the  hands  and  soles  of  the  feet,  forming  a  fibro- 
fatty  layer  which  binds  the  integument  firmly  to  the  subjacent  structure.  The 
superficial  fascia  connects  the  skin  to  the  subjacent  parts,  facilitates  the  move- 
ment of  the  skin,  serves  as  a  soft  medium  for  the  passage  of  vessels  and  nerves 
to  the  integument,  and  retains  the  warmth  of  the  body,  since  the  fat  contained  in 
its  areolae  is  a  bad  conductor  of  heat. 

Deep  Fascia. — The  deep  or  aponeurotic  fascia  is  a  dense,  inelastic,  unyielding 
fibrous  membrane,  forming  sheaths  for  the  muscles  and  affording  them  broad 
surfaces  for  attachment.  It  consists  of  shining  tendinous  fibres,  placed  parallel 
with  one  another,  and  connected  together  by  other  fibres  disposed  in  a  rectilinear 
manner.  It  is  usually  exposed  on  the  removal  of  the  superficial  fascia,  forming  a 
strong  investment,  which  not  only  binds  down  collectively  the  muscles  in  each 
region,  but  gives  a  separate  sheath  to  each,  as  well  as  to  the  vessels  and  nerves. 
The  fasciae  are  thick  in  unprotected  situations,  as  on  the  outer  side  of  a  limb,  and 
thinner  on  the  inner  side.  The  deep  fasciae  assist  the  muscles  in  their  action  by 
the  degree  of  tension  and  pressure  they  make  upon  their  surface;  and  in  certain 
situations  this  is  increased  and  regulated  by  muscular  action;  as,  for  instance,  by 


MUSCLES  AND   FASCIJS   OF   THE    CRANIUM  AND   FACE      365 

the  Tensor  fasciae  femoris  and  Gluteus  maximus  in  the  thigh,  by  the  Biceps  in 
the  upper  and  lower  extremities,  and  Palmaris  longus  in  the  hand.  In  the  limbs 
the  fasciae  not  only  invest  the  entire  limb,  but  give  off  septa  which  separate  the 
various  muscles,  and  are  attached  beneath  to  the  periosteum :  these  prolongations 
of  fasciae  are  usually  spoken  of  as  intermuscular  septa. 

The  Muscles  and  Fasciae  may  be  arranged,  according  to  the  general  division 
of  the  body,  into  those  of  the  cranium,  face,  and  neck;  those  of  the  trunk;  those  of 
the  upper  extremity;  and  those  of  the  lower  extremity. 


MUSCLES  AND  FASCI-ffi  OF  THE  CRANIUM  AND  FACE. 


The  muscles  of  the  cranium  and  face  consist  of  ten  groups,  arranged  according 
to  the  region  in  which  they  are  situated: 


1.  Cranial  Region. 

2.  Auricular  Region. 

3.  Palpebral  Region. 

4.  Orbital  Region. 

5.  Nasal  Region 


6.  Maxillary  Region. 

7.  Mandibular  Region. 

8.  Intermaxillary  Region. 

9.  Temporo-mandibular  Region. 
10.  Pterygo-mandibular  Region. 


The  muscles  contained  in  each  of  these  groups  are  the  following: 


1.  Cranial  Region. 
Occipito-frontalis. 

2.  Auricular  Region. 

Attrahens  auriculam. 
AttoUens  auriculam. 
Retrahens  auriculam. 

3.  Palpebral  Region. 

Orbicularis  palpebrarum. 
Corrugator  supercilii. 
Tensor  tarsi. 

4.  Orbital  Region. 

Levator  palpebrae. 
Rectus  superior. 
Rectus  inferior. 
Rectus  internus. 
Rectus  externus. 
Obliquus  superior. 
Obliquus  inferior. 

5.  Nasal  Region. 

Pyramidalis  nasi. 

Levator  labii  superioris  alseque 

nasi. 
Dilatator  naris  posterior. 
Dilatator  naris  anterior. 
Compressor  nasi. 
Compressor  narium  minor. 
Depressor  alae  nasi. 


6.  Maxillary  Region. 

Levator  labii  superioris. 
Levator  anguli  oris. 
Zygomaticus  major. 
Zygomaticus  minor. 


7.  Mandibular  Region. 

I^evator  labii  inferioris. 
Depressor  labii  inferioris. 
Depressor  anguli  oris. 


8.  Intermaxillary  Region. 

Buccinator. 
Risorius. 
Orbicularis  oris. 


9.  Temporo-mandibular  Region. 

Masseter. 
Temporal. 

10.  Pterygo-mandibular  Region. 

Pterygoideus  externus. 
Pterygoideus  internus. 


366 


THE    MUSCLES  AND    FASCIuE 


1.  The  Cranial  Region. 

Occipito-frontalis. 

Dissection  (Fig.  258). — The  head  being  shaved,  and  a  block  placed  beneath  the  back  of 
the  neck,  make  a  vertical  incision  through  the  skin  from  before  backward,  commencing  at 


1.  Dissection  of  scalp. 

2,  S,  of  auricular  region. 
4,  5,  6,  of  face. 

7,  8,  of  neck. 


Fig.  258. — Dissection  of  the  head,  face,  and  neck. 

the  root  of  the  nose  in  front,  and  terminating  behind  at  the  occipital  protuberance;  make  a 
second  incision  in  a  horizontal  direction  along  the  forehead  and  round  the  side  of  the  head, 
from  the  anterior  to  the  posterior  extremity  of  the  preceding.  Raise  the  skin  in  front,  from 
the  subjacent  muscle,  from  below  upward;  this  must  be  done  with  extreme  care,  removing 
the  integument  from  the  outer  surface  of  the  vessels  and  the  nerves  which  lie  immediately 
beneath  the  skin. 

The  Skin  of  the  Scalp. — This  is  thicker  than  in  any  other  part  of  tlie  body.  It 
is  intimately  adherent  to  the  superficial  fascia,  which  attaches  it  firmly  to  the 
underlying  aponeurosis  and  muscle.  Movements  of  the  muscle  move  the  skin. 
The  hair-follicles  are  very  closely  set  together,  and  extend  throughout  the  whole 
thickness  of  the  skin.    It  also  contains  a  number  of  sebaceous  glands. 


SUBCUTANEOUS   ADI- 
POSE TISSUE 

APONEUROSIS  OF 
CC I  PITO- FRONTALIS 

MUSCLE 


OCCIPITO-FRONTALIS 
MUSCLE 


BAPONEUROTIC 
SUE 


PERIOSTEUM 


OCCIPITO-FRONTALIS 
MUSCLE 


Fig.  259. — Epicranial  aponeurosis.     Antero-posterior  section.     (Schematic.)     (Poirier  and  Charpy.) 


Superficial  Fascia. — The  superficial  fascia  in  the  cranial  region  is  a  firm, 
dense,  fibro-fatty  layer,  intimately  adherent  to  the  integument,  and  to  the  occipito- 
frontalis  and  its  tendinous  aponeurosis;  it  is  continuous,  behind,  with  the  super- 


THE    CRANIAL    REGION 


367 


ficial  fascia  at  the  back  part  of  the  neck;  and,  laterally,  is  continued  over  the 
temporal  fascia.  It  contains  between  its  layers  the  superficial  vessels  and  nerves 
and  much  granular  fat. 

Surgical  Anatomy. — The  subcutaneous  tissue  is  composed  of  bands  of  fibrous  tissue  enclos- 
ing spaces  filled  with  fat.  The  fibrous  character  of  this  tissue  greatly  limits  discoloration  and 
swelling  when  inflammation  occurs.  The  edges  of  a  wound  which  does  not  involve  the  apon- 
eurosis or  muscle  do  not  retract,  hence  the  wound  does  not  gap.  The  blood-vessels  run  practi- 
cally in  the  skin,  and  as  they  lie  in  very  dense  tissue  and  are  adherent  to  it,  wounds  bleed 
profusely,  the  arteries  being  unable  to  freely  contract  and  retract.  It  is  very  difficult  or 
impossible  to  pick  up  with  forceps  a  vessel  in  the  skin  of  the  .scalp,  and  bleeding  must  be 
arrested  by  suture  ligatures  or  by  the  stitches  which  close  the  wound.  Sebaceous  glands  in 
the  skin  of  the  scalp  may  develop  into  sebaceous  cysts  (wens). 

The  Occipito-frontalis  {m.  epicranms)  (Fig.  260).— The  Occipito-frontalis 
is  a  broad  musculo-fibrous  laver,  which  covers  the  whole  of  one  side  of  the 


CORRUQATOR    SUPERCILM 


DILATATOR    NAHIS    ANTERIOR 

DILATATOR    MARIS     POSTERIOR 

COMPRESSOR    NARIUM     MINOR 

DEPRESSOR   AL/C    NASI. 


LEVATOR    MENTI 


Fio.  260. — Muscles  of  the  head,  face,  and  neck. 


368  THE  MUSCLES  AND    FASCIA 

vertex  of  the  skull,  from  the  occiput  to  the  eyebrow.  It  consists  of  two  mus- 
cular shps,  separated  by  an  intervening  tendinous  aponeurosis.  The  occipital 
portion,  the  occipitalis  muscle  {m.  occipitalis),  is  thin,  quadrilateral  in  form,  and 
about  an  inch  and  a  half  in  length;  it  arises  from  the  outer  two-thirds  of  the 
superior  curved  line  of  the  occipital  bone,  and  from  the  mastoid  portion  of  the 
temporal  bone.  Its  fibres  of  origin  are  tendinous,  but  they  soon  become  muscular, 
and  ascend  in  a  parallel  direction  to  terminate  in  a  tendinous  aponeurosis.  The 
frontal  portion,  the  frontalis  muscle  {m.  frontalis),  is  thin,  of  a  quadrilateral 
form,  and  intimately  adherent  to  the  superficial  fascia.  It  is  broader,  its  fibres 
are  longer,  and  their  structure  paler  than  the  occipital  portion.  Its  internal 
fibres  are  continuous  with  those  of  the  PyramidaHs  nasi.  Some  anatomists  con- 
sider the  Pyramidalis  muscle  as  simply  the  lower  fibres  of  the  frontalis,  and 
give  these  bundles  of  muscle  fibre  the  name  of  musculus  procerus.  Its  middle 
fibres  become  blended  with  the  Corrugator  supercilii  and  Orbicularis  palpebra- 
rum; and  the  outer  fibres  are  also  blended  with  the  latter  muscle  over  the  external 
angular  process.  According  to  Theile,  the  innermost  fibres  are  attached  to  the 
nasal  bones,  the  outer  to  the  external  angular  process  of  the  frontal  bone.  From 
these  attachments  the  fibres  are  directed  upward,  and  join  the  aponeurosis  below 
the  coronal  suture.  The  inner  margins  of  the  frontal  portions  of  the  two  muscles 
are  joined  together  for  some  distance  above  the  root  of  the  nose;  but  between  the 
occipital  portions  there  is  a  considerable,  though  variable,  interval,  which  is  occu- 
pied by  the  aponeurosis. 

The  middle  portion  of  the  Occipito-frontalis  muscle  or  the  aponeurosis  (epi- 
cranial aponeurosis,  Galea  aponeurotica)  covers  the  upper  part  of  .the  vertex 
of  the  skull,  being  continuous  across  the  middle  line  with  the  aponeurosis  of  the 
opposite  muscle.  Behind,  it  is  attached,  in  the  interval  between  the  occipital 
origins,  to  the  occipital  protuberance  and  highest  curved  lines  of  the  occipital 
bone;  in  front,  it  forms  a  short  and  narrow  prolongation  between  the  frontal  por- 
tions; and  on  each  side  it  has  connected  with  it  the  Attollens  and  Attrahens 
auriculam  muscles.  This  aponeurosis  is  closely  connected  to  the  integument  by 
the  firm,  dense,  fibro-fatty  layer  which  forms  the  superficial  fascia;  it  is  connected 
with  the  pericranium  by  loose  cellular  tissue,  which  allows  of  a  considerable 
degree  of  movement  of  the  integument.  It  is  continuous  with  the  temporal 
fascia  below  the  temporal  ridge,  and  it  is  in  reality  the  representative  of  the 
deep  fascia. 

Nerves. — The  frontal  portion  of  the  Occipito-frontalis  is  supplied  by  the  facial 
nerve;  its  occipital  portion  by  the  posterior  auricular  branch  of  the  facial. 

Actions. — The  frontal  portion  of  the  muscle  raises  the  eyebrows  and  the  skin 
over  the  root  of  the  nose,  and  at  the  same  time  draws  the  scalp  forward,  throwing 
the  integument  of  the  forehead  into  transverse  wrinkles.  The  posterior  portion 
draws  the  scalp  backward.  By  bringing  alternately  into  action  the  frontal  and 
occipital  portions  the  entire  scalp  may  be  moved  forward  and  backward.  In  the 
ordinary  action  of  the  muscles,  the  eyebrows  are  elevated,  and  at  the  same  time 
the  aponeurosis  is  fixed  by  the  posterior  portion,  thus  giving  to  the  face  the 
expression  of  surprise:  if  the  action  is  more  exaggerated,  the  eyebrows  are  still 
further  raised,  and  the  skin  of  the  forehead  thrown  into  transverse  wrinkles,  as  in 
the  expression  of  fright  or  horror. 

Surgical  Anatomy.— The  skull  is  covered  by  the  scalp  (Fig.  259).  This  consists  of  five  layers: 
(1)  the  pericranium;  (2)  a  layer  of  connective  tissue  beneath  the  Occipito-frontalis  aponeurosis 
(subaponeurotic  tissue) ;  (3)  the  Occipito-frontalis  muscle  and  aponeurosis;  (4)  subcutaneous  fat; 
(5)  skin.  If  a  wound  involves  the  muscle  or  aponeurosis,  it  gaps  widely,  the  greatest  amount 
of  gaping  being  observed  in  transverse  wounds.  The  space  between  the  aponeurosis  and  the 
pericranium  is  called  by  Treves  the  dangerous  area  of  the  scalp.  It  contains  a  layer  of  con- 
nective tissue  and  suppuration  in  this  tissue  spreads  widely.    An  abscess  in  the  dangerous  area 


THE   AURICULAR    REGION  369 

should  be  opened  above  the  superior  curved  line  of  the  occipital  bone,  above  the  eyebrow 
or  above  the  zygoma.  In  a  wound  or  contusion  above  the  aponeurosis  but  little  blood  can  be, 
effused  in  the  tissue  because  the  fibrous  structure  prevents  it,  and  abscesses  do  not  tend  to 
spread  widely.  Between  the  aponeurosis  and  the  pericranium  a  great  amount  of  blood  can  be 
effused.  An  effusion  of  blood  beneath  the  pericranium  is  called  a  cephalhcematoma.  Such 
a  condition  may  occur  from  pressure  during  birth.  An  extravasation  beneath  the  pericranium 
is  limited  to  the  surface  of  one  bone.  The  pericranium  is  tightly  attached  to  the  sutures,  but 
adheres  lightly  to  the  surface  of  the  bone,  and  abscess  beneath  the  pericranium  is  restricted 
to  the  surface  of  one  bone. 

2.  The  Auricular  Region  (Fig.  260). 

Attrahens  auriculam.  AttoUens  auriculam. 

Retrahens  auriculam. 

These  three  small  muscles  are  placed  immediately  beneath  the  skin  around  the 
external  ear.  In  man,  in  whom  the  external  ear  is  almost  immovable,  they  are 
rudimentary.  They  are  the  analogues  of  large  and  important  muscles  in  some 
of  the  mammalia. 

Dissection. — This  requires  considerable  care,  and  should  be  performed  in  the  following 
manner:  To  expose  the  Attollens  auriculam,  draw  the  pinna,  or  broad  part  of  the  ear,  downward, 
when  a  tense  band  will  be  felt  beneath  the  skin,  passing  from  the  side  of  the  head  to  the  upper 
part  of  the  concha;  by  dividing  the  skin  over  this  band  in  a  direction  from  below  upward, 
and  then  reflecting  it  on  each  side,  the  muscle  is  exposed.  To  bring  into  view  the  Attrahens 
auriculam,  draw  the  helix  backward  by  means  of  a  hook,  when  the  muscle  will  be  made 
tense,  and  may  be  exposed  in  a  similar  manner  to  the  preceding.  To  expose  the  Retrahens 
auriculam,  draw  the  pinna  forward,  when  the  muscle,  being  made  tense,  may  be  felt  beneath 
the  skin  at  its  insertion  into  the  back  part  of  the  concha,  and  may  be  exposed  in  the  same 
manner  as  the  other  muscles. 

The  Attrahens  Auriculam  or  Aurem  (m.  auricularis  anterior),  the  smallest  of  the 
three,  is  thin,  fan-shaped,  and  its  fibres  pale  and  indistinct;  they  arise  from  the 
lateral  edge  of  the  aponeurosis  of  the  Occipito-frontalis,  and  converge  to  be  inserted 
into  a  projection  on  the  front  of  the  helix. 

Relations. — Superficially,  with  the  skin;  deeply,  with  the  areolar  tissue  derived 
from  the  aponeurosis  of  the  Occipito-frontalis,  beneath  which  are  the  temporal 
artery  and  vein  and  the  temporal  fascia. 

The  AttoUens  Auriculam  or  Aurem  (m.  auricularis  superior),  the  largest  of  the 
three,  is  thin  and  fan-shaped :  its  fibres  arise  from  the  aponeurosis  of  the  Occipito- 
frontalis  and  converge  to  be  inserted  by  a  thin,  flattened  tendon  into  the  upper 
part  of  the  cranial  surface  of  the  pinna. 

Relations. — Superficially,  with  the  integument;  deeply,  with  the  areolar  tissue 
derived  from  the  aponeurosis  of  the  Occipito-frontalis,  beneath  which  is  the  tem- 
poral fascia. 

The  Retrahens  Auriculam  or  Aurem  (m.  auricularis  posterior)  consists  of  two  or 
three  fleshy  fasciculi,  which  arise  from  the  mastoid  portion  of  the  temporal  bone 
by  short  aponeurotic  fibres.  They  are  inserted  into  the  lower  part  of  the  cranial 
surface  of  the  concha. 

Relations. — Superficially,  with  the  integument;  deeply,  with  the  mastoid  portion 
of  the  temporal  bone  and  the  posterior  auricular  artery  and  nerve. 

Nerves. — The  Attrahens  and  Attollens  auriculam  are  supplied  by  the  temporal 
branch  of  the  facial ;  the  Retrahens  auriculam  is  supplied  by  the  posterior  auricu- 
lar branch  of  the  same  nerve. 

Actions. — In  man,  these  muscles  possess  very  little  action:  the  Attrahens  auric- 
ulam draws  the  ear  forward  and  upward;  the  Attollens  auriculam  slightly  raises 
it;  and  the  Retrahens  auriculam  draws  it  backward. 

24 


370  THE  MUSCLES  AND    FASCIjE 

3.  The  Palpebral  Region  (Fig.  260). 

Orbicularis  palpebrarum.  Levator  palpebrse. 

Corrugator  supercilii.  Tensor  tarsi. 

Dissection  (Fig.  257). — In  order  to  expose  the  muscles  of  the  face,  continue  the  longi- 
tudinal incision  made  in  the  dissection  of  the  Occipito-frontalis  down  the  median  line  of  the 
face  to  the  tip  of  the  nose,  and  from  this  point  onward  to  the  upper  lip;  and  carry  another 
incision  along  the  margin  of  the  lip  to  the  angle  of  the  mouth,  and  transversely  across  the  face 
to  the  angle  of  the  jaw.  Then  make  an  incision  in  front  of  the  external  ear,  from  the  angle  of 
the  jaw  upward,  to  join  the  transverse  incision  made  in  exposing  the  Occipito-frontalis.  These 
incisions  include  a  square-shaped  flap,  which  should  be  removed  in  the  direction  marked  in 
the  figure,  with  care,  as  the  muscles  at  some  points  are  intimately  adherent  to  the  integument. 

The  Orbicularis  Palpebrarum  (m.  orbicularis  oculi)  is  a  sphincter  muscle,  which 
surrounds  the  circumference  of  the  orbit  and  eyehds.  It  arises  from  the  internal 
angular  process  of  the  frontal  bone,  from  the  nasal  process  of  the  superior  maxil- 
lary bone  in  front  of  the  lachrymal  groove  for  the  nasal  duct,  and  from  the  anterior 
surface  and  borders  of  a  short  tendon,  the  tendo  oculi,  or  internal  taxsal  ligament, 
placed  at  the  inner  angle  of  the  orbit.  From  this  origin  the  fibres  are  directed 
outward,  forming  a  broad,  thin,  and  flat  layer,  which  covers  the  eyelids,  surrounds 
the  circumference  of  the  orbit,  and  spreads  out  over  the  temple  and  downward  on 
the  cheek.  The  internal  or  palpebral  portion  {pars  palpebralis)  of  the  Orbicularis  is 
thin  and  pale;  it  arises  from  the  bifurcation  of  the  tendo  palpebrarum,  and  forms 
a  series  of  concentric  curves,  which  are  on  the  outer  side  of  the  eyelids  inserted  into 
the  external  tarsal  ligament.  The  external  or  orbital  portion  (pars  orbitalis)  is 
thicker  and  of  a  reddish  color:  its  fibres  are  well  developed,  and  form  complete 
ellipses.  The  upper  fibres  of  this  portion  blend  with  the  Occipito-frontalis  and 
Corrugator  supercilii. 

Relations. — By  its  superficial  surface,  with  the  integument.  By  its  deep  surface, 
above,  with  the  Occipito-frontalis  and  Corrugator  supercilii,  with  which  it  is  inti- 
mately blended,  and  with  the  supraorbital  vessels  and  nerve ;  below,  it  covers  the 
lachrymal  sac,  and  the  origin  of  the  Levator  labii  superioris  alreque  nasi,  the 
I-,evator  labii  superioris,  and  the  Zygomaticus  minor  muscles.  Internally,  it  is 
occasionally  blended  with  the  Pyramidalis  nasi.  Externally ,  it  lies  on  the  temporal 
fascia.  On  the  eyelids  it  is  separated  from  the  conjunctiva  by  the  Levator  palpe- 
brse,  the  tarsal  ligaments,  the  tarsal  plates,  and  the  Meibomian  glands. 

The  tendo  oculi  or  internal  tarsal  ligament  (ligamentum  palpebrale  mediale)  is  a 
short  tendon,  about  two  lines  in  length  and  one  in  breadth,  attached  to  the  nasal 
process  of  the  superior  maxillary  bone  in  front  of  the  lachrymal  groove.  Crossing 
the  lachrymal  sac,  it  divides  into  two  parts,  each  division  being  attached  to  the 
inner  extremity  of  the  corresponding  tarsal  plate.  As  the  tendon  crosses  the  lach- 
rymal sac,  a  strong  aponeurotic  lamina  is  given  off  from  the  posterior  surface, 
which  expands  over  the  sac,  and  is  attached  to  the  ridge  on  the  lachrymal  bone. 
This  is  the  reflected  aponeurosis  of  the  tendo  oculi. 

The  external  tarsal  ligament  (raphe  palpebralis  lateralis)  is  a  much  weaker  struc- 
ture than  the  tendo  oculi.  It  is  attached  to  the  margin  of  the  frontal  process  of 
the  malar  bone,  and  passes  inward  to  the  outer  commissure  of  the  eyelids;  it 
coimects  together  the  outer  extremities  of  the  two  tarsal  cartilages. 

Use  of  Tendo  Oculi. — Besides  giving  attachment  to  part  of  the  Orbicularis 
palpebrarum  and  to  the  tarsal  plates,  it  serves  to  suck  the  tears  into  the  lachrymal 
sac,  by  its  attachment  to  the  sac.  Thus,  each  time  the  eyelids  are  closed,  the  tendo 
oculi  becomes  tightened,  through  the  action  of  the  Orbicularis,  and  draws  the  wall 
of  the  lachrymal  sac  outward  and  forward,  so  that  a  vacuum  is  made  in  the  sac, 
and  the  tears  are  sucked  along  the  lachrymal  canals  into  it. 


THE   PALPEBRAL    REGION 


371 


The  Comigatcr  Supercilii  (Figs.  259  and  260)  is  a  small  narrow,  pyramidal 
muscle,  placed  at  the  inner  extremity  of  the  eyebrow,  beneath  the  Occipito- 
frontalis  and  Orbicularis  palpebrarum  muscles.  It  arises  from  the  inner  extrem- 
ity of  the  superciliary  ridge,  from  whence  its  fibres  pass  upward  and  outward, 
and  are  inserted  into  the  deep  surface  of  the  skin,  opposite  the  middle  of  the 
orbital  arch. 

Relations. — By  its  anterior  surface  with  the  Occipito-frontalis  and  Orbicularis 
palpebrarum  muscles;  by  its  posterior  surface,  with  the  frontal  bone  and  supra- 
trochlear nerve. 

The  Levator  Palpebrae  will  be  described  with  the  muscles  of  the  orbital  region. 

The  Tensor  Tarsi  or  Homer's  Muscle  (pars  lacrimalis  of  the  orbicularis  pal- 
pebrarum) (Fig.  261)  is  a  small  thin  muscle  about  three  lines  in  breadth  and  six 
in  length,  situated  at  the  inner  side  of  the  orbit,  behind  the  tendo  oculi.  It  is 
usually  considered  to  be  composed  of  fibres  derived  from  the  Orbicularis  palpe- 
brarum.   It  arises  from  the  crest  and  adjacent  part  of  the  orbital  surface  of  the 


FRONTAL  SINUS 


CORRUGATOR 
SUPERCIUI 


PALPEBRAL  PORTION 

OF  ORBICULARIS 

PALPEBRARUM 


PUNCTA 
LACHRYMALIA 


'     ~77f LACHRYMAL 

'£  GROOVE 


ORBITAL  PORTION  OF 
ORBICULARIS  PALPEBRARUM 


ANTRUM   OF 
HIGHMORE 


Fig.  261. — The  three  portions  of  the  Orbicularis  palpebrarum  muscle,  and  the  relation  of  this  muscle  to  the 
Corrugator  supercilii  muscle,  seen  from  behind.     (Left  side.)     (Toldt.) 

lachrymal  bone,  and,  passing  across  the  lachrymal  sac,  divides  into  two  slips, 
which  cover  the  lachrymal  canals  and  are  inserted  into  the  tarsal  plates  internal 
to  the  puncta  lachrymalia.  Its  fibres  appear  to  be  continuous  with  those  of  the 
palpebral  portion  of  the  Orbicularis  palpebrarum;  it  is  occasionally  very  indistinct. 

Nerves. — The  Orbicularis  palpebrarum,  Corrugator  supercilii,  and  Tensor  tarsi 
are  supplied  by  the  facial  nerve.  Recent  investigations  tend  to  show  that  the 
Orbicularis  palpebrarum,  Corrugator  supercilii,  and  frontal  part  of  the  Occipito- 
frontalis  are  in  reality  supplied  by  fibres  of  the  third  nerve,  which  descend  through 
the  pons  varolii  to  join  the  facial  nerve. 

Actions. — The  Orbicularis  palpebrarum  is  the  sphincter  muscle  of  the  eyelids. 
The  palpebral  portion  acts  involuntarily,  closing  the  lids  gently,  as  in  sleep  or  in 
blinking;  the  orbicular  portion  is  subject  to  the  will.  When  the  entire  muscle  is 
brought  into  action,  the  skin  of  the  forehead,  temple,  and  cheek  is  drawn  inward 
toward  the  inner  angle  of  the  orbit,  and  the  eyelids  are  firmly  closed  as  in  photo- 


372 


THE   MUSCLES   AND   FASCIA 


phobia.  When  the  skin  of  the  forehead,  temple,  and  cheek  is  thus  drawn  inward 
by  the  action  of  the  muscle  it  is  thrown  into  folds,  especially  radiating  from  the 
outer  angle  of  the  eyelids,  which  give  rise  in  old  age  to  the  so-called  "crow's  feet." 
The  Levator  palpebrse  is  the  direct  antagonist  of  this  muscle;  it  raises  the  upper 
eyelid  and  exposes  the  globe.  The  Corrugator  supercilii  draws  the  eyebrow 
downward  and  inward,  producing  the  vertical  wrinkles  of  the  forehead.  It  is  the 
"  frowning"  muscle,  and  may  be  regarded  as  the  principal  agent  in  the  expression 
of  suffering.  The  Tensor  tarsi  draws  the  eyelids  inward  and  compresses  the  eye- 
lids and  the  extremities  of  the  lachrymal  canals  against  the  surface  of  the  globe 
of  the  eye;  thu&  placing  the  canals  in  the  most  favorable  situation  for  receiving 
the  tears.    It  serves,  also,  to  compress  the  lachrymal  sac. 

4.  The  Orbital  Region  (Fig.  262). 

Levator  palpebrse  superioris.  Rectus  internus. 

Rectus  superior.  Rectus  externus. 

Rectus  inferior.  Obliquus  oculi  superior. 

Obliquus  oculi  inferior. 

Dissection. — To  open  the  cavity  of  the  orbit,  remove  the  skull-cap  and  brain;  then  saw 
through  the  frontal  bone  at  the  inner  extremity  of  the  supraorbital  ridge,  and  externally  at  its 
junction  with  the  malar.  Break  in  pieces  the  thin  roof  of  the  orbit  by  a  few  slight  blows  of 
the  hammer,  and  take  it  away;  drive  forward  the  superciliary  portion  of  the  frontal  bone 


Fig.  262. — Muscles  of  the  right  orbit. 

by  a  smart  stroke,  but  do  not  remove  it,  as  that  would  destroy  the  pulley  of  the  Obliquus 
superior.  When  the  fragments  are  cleared  away,  the  periosteum  of  the  orbit  will  be  exposed; 
this  being  removed,  together  with  the  fat  which  fills  the  cavity  of  the  orbit,  the  several  muscles 
of  this  region  can  be  examined.  The  dissection  will  be  facilitated  by  distending  the  globe 
of  the  eye.  In  order  to  effect  this,  puncture  the  optic  nerve  near  the  eyeball  with  a  curved 
needle,  and  push  the  needle  onward  into  the  globe;  insert  the  point  of  a  blowpipe  through 
this  aperture,  and  force  a  little  air  into  the  cavity  of  the  eyeball;  then  apply  a  ligature  round 
the  nerve  so  as  to  prevent  the  air  escaping.  The  globe  being  now  drawn  forward,  the  muscles 
will  be  put  upon  the  stretch. 

The  Levator  Palpebrae  Superioris  is  thin,  flat,  and  triangular  in  shape.  It 
arises  from  the  under  surface  of  the  lesser  wing  of  the  sphenoid,  above  and  in 
front  of  the  optic  foramen,  from  which  it  is  separated  by  the  origin  of  the  Superior 
rectus  (Fig.  263).  At  its  origin  it  is  narrow  and  tendinous,  but  soon  becomes 
broad  and  fleshy,  and  finally  terminates  in  a  wide  aponeurosis,  which  is  inserted 
into  the  upper  margin  of  the  superior  tarsal  plate.  From  this  aponeurosis  a  thin 
expansion  is  continued  onward,  passing  between  the  fibres  of    the  Orbicularis 


THE    ORBITAL    REGION  373 

to  be  inserted  into  the  skin  of  the  Hd,  and  some  deeper  fibres  blend  with  an 
expansion  from  the  sheath  of  the  Superior  rectus  muscle,  and  are  with  it  pro- 
longed into  the  conjunctiva. 

Relations. — By  its  upper  surface,  with  the  frontal  nerve  and  supraorbital 
artery,  the  periosteum  of  the  orbit  and  lachrymal  gland;  and,  in  the  lid,  with  the 
inner  surface  of  the  tarsal  ligament ;  by  its  under  surface,  with  the  Superior  rectus, 
and,  in  the  lid,  with  the  conjunctiva.  A  small  branch  of  the  third  nerve  enters 
its  under  surface. 

The  Superior  Rectus  (m.  rectus  superior) ,  the  thinnest  and  narrowest  of  the 
four  Recti,  arises  from  the  upper  margin  of  the  optic  foramen  (Fig.  263)  beneath 
the  Levator  palpebrse,  and  from  the  fibrous  sheath  of  the  optic  nerve;  and  is 
inserted  by  a  tendinous  expansion  into  the  sclerotic  coat,  about  three  or  four 
lines  from  the  margin  of  the  cornea. 

Relations. — By  its  upper  surface,  with  the  Levator  palpebrse;  by  its  under  sur- 
face, with  the  optic  nerve,  the  ophthalmic  artery,  the  nasal  nerve,  and  the  branch 
of  the  third  nerve  which  supplies  it ;  and,  in  front,  with  the  tendon  of  the  Superior 
oblique  and  the  globe  of  the  eye. 

The  Inferior  Rectus  (m.  rectus  inferior)  and  the  Internal  Rectus  (m.  rectus 
medialis)  arise  by  a  common  tendon,  the  ligament  of  Zinn^  (annulus  tendineus 
communis),  which  is  attached  round  the  circumference  of  the  optic  foramen, 
except  at  its  upper  and  outer  part  (Fig.  263). 

The  External  Rectus  (m.  rectus  lateralis)  has  two  heads :  the  upper  one  arises 
from  the  outer  margin  of  the  optic  foramen  immediately  beneath  the  Superior 
rectus;  the  lower  head,  partly  from  the  ligament  of  Zinn  and  partly  from  a  small 
pointed  process  of  bone  on  the  lower  margin 
of  the  sphenoidal    fissure   (Fig.  263).     Each  Rectus stiperior 

muscle  passes  forward  in  the  position  implied  by  paipebZ^'lupenor. 
its  name,  to  be  inserted  by  a  tendinous  expan-  owquus  superior} 
sion,  the  tunica  albuginea,  into  the  sclerotic  coat, 
about  three  or  four  lines  from  the  margin  of 
the  cornea.  Between  the  two  heads  of  the  Ex- 
ternal rectus  is  a  narrow  interval,  through 
which  passes  the  third,  the  nasal  branch  of 
the  ophthalmic  division  of  the  fifth  and  sixth 
nerves,  and   the   ophthalmic   vein.     Although  sectus  inferior. 

nearly  all  of  these  muscles  present  a  common    ^^^..e'nt'oTtle  mSi^rortile  le^^ 
origin  and   are  inserted   in   a  similar  manner 

into  the  sclerotic  coat,  there  are  certain  differences  to  be  observed  in  them  as 
regards  their  length  and  breadth.  The  Liternal  rectus  is  the  broadest,  the 
External  is  the  longest,  and  the  Superior  is  the  thinnest  and  narrowest. 

The  Superior  Oblique  (w.  ohliquus  superior)  is  a  fusiform  muscle  placed  at  the 
upper  and  inner  side  of  the  orbit,  internal  to  the  Levator  palpebrse.  It  arises 
about  a  line  above  the  inner  margin  of  the  optic  foramen  (Fig.  263) ,  and,  pass- 
ing forward  to  the  inner  angle  of  the  orbit,  terminates  in  a  rounded  tendon, 
which  plays  in  a  ring  or  pulley,  the  trochlea  {trochlea  m.  ohliqui  superioris), 
formed  by  a  cartilaginous  tissue  attached  to  a  depression  beneath  the  internal 
angular  process  of  the  frontal  bone,  the  contiguous  surfaces  of  the  tendon  and 
ring  being  lined  by  a  delicate  synovial  membrane  and  enclosed  in  a  thin  fibrous 
investment.  The  tendon  is  reflected  backward,  outward,  and  downward  beneath 
the  Superior  rectus  to  the  outer  part  of  the  globe  of  the  eye,  and  is  inserted  into 

'  The  ligament  of  Zinn  ought,  perhaps  more  appropriately,  to  be  termed  the  aponeurosis  or  tendon  of  Zinn, 
Mr.  C.  B.  Lockwood  has  described  a  somewhat  similar  structure  on  the  under  surface  of  the  Superior  rectus 
muscle,  which  is  attached  to  the  lesser  wing  of  the  sphenoid,  forming  the  upper  and  outer  margin  of  the  optic 
foramen.  This  superior  tendon  give.s  origin  to  the  Rectus  superior,  the  superior  head  of  the  External  rectus, 
and  the  upper  part  of  the  Internal  rectus. — Journal  of  Anatomy  and  Physiology,  vol.  xx.  part  i.  p.  1. 


374  THE  MUSCLES  AND   FASCIA 

the  sclerotic  coat,  behind  the  equator  of  the  eyeball,  the  insertion  of  the  muscle 
lying  between  the  Superior  and  External  recti. 

Relations. — By  its  upper  surface,  with  the  periosteum  covering  the  roof  of  the 
orbit  and  the  fourth  nerve:  the  tendon,  where  it  lies  on  the  globe  of  the  eye, 
is  covered  by  the  Superior  rectus;  by  its  under  surface,  with  the  nasal  nerve, 
ethmoidal  arteries,  and  the  upper  border  of  the  internal  rectus. 

The  Inferior  Oblique  (m.  obliquus  inferior)  is  a  thin,  narrow  muscle  placed  near 
the  anterior  margin  of  the  orbit.  It  arises  from  a  depression  on  the  orbital  plate 
of  the  superior  maxillary  bone,  external  to  the  lachrymal  groove  (Fig.  262). 
Passing  outward,  backward,  and  upward  between  the  Inferior  rectus  and  the 
floor  of  the  orbit,  and  then  between  the  eyeball  and  the  External  rectus,  it  is 
inserted  into  the  outer  part  of  the  sclerotic  coat  between  the  Superior  and  External 
recti,  near  to,  but  somewhat  behind,  the  tendon  of  insertion  of  the  Superior  oblique. 

Relations. — By  its  ocular  surface,  with  the  globe  of  the  eye  and  with  the  Inferior 
rectus;  by  its  orbital  surface,  with  the  periosteum  covering  the  floor  of  the  orbit, 
and  with  the  External  rectus.  Its  borders  look  forward  and  backward ;  the  poste- 
rior one  receives  a  branch  of  the  third  nerve. 

The  orbital  muscle  or  Miiller's  muscle  {musculus  orbitalis),  which  spans  the 
spheno-maxillary  fissure  and  infraorbital  groove,  is  composed  of  non-striated 
fibres,  and  is  a  rudimentary  structure  continuous  with  the  periosteum  of  the  orbit.^ 

Nerves. — The  Levator  palpebree.  Inferior  oblique,  and  all  the  Recti  excepting 
the  External,  are  supplied  by  the  third  nerve;  the  Superior  oblique,  by  the  fourth; 
the  External  rectus,  by  the  sixth. 

Actions. — The  Levator  palpebrse  raises  the  upper  eyelid,  and  is  the  direct 
antagonist  of  the  Orbicularis  palpebrarum.  The  four  Recti  muscles  are  attached 
in  such  a  manner  to  the  globe  of  the  eye  that,  acting  singly,  they  will  turn  it  either 
upward,  downward,  inward,  or  outward,  as  expressed  by  their  names.  The 
movement  produced  by  the  Superior  or  Inferior  rectus  is  not  quite  a  simple  one, 
for,  inasmuch  as  they  pass  obliquely  outward  and  forward  to  the  eyeball,  the 
elevation  or  depression  of  the  cornea  must  be  accompanied  by  a  certain  deviation 
inward,  with  a  slight  amount  of  rotation,  which,  however,  is  corrected  by  the 
Oblique  muscles,  the  Inferior  oblique  correcting  the  deviation  inward  of  the 
Superior  rectus,  and  the  Superior  oblique  that  of  the  Inferior  rectus.  The  con- 
traction of  the  External  and  Internal  recti,  on  the  other  hand,  produces  a  purely 
horizontal  movement.  If  any  two  contiguous  recti  of  one  eye  act  together,  they 
carry  the  globe  of  the  eye  in  the  diagonal  of  these  directions — viz.,  upward  and 
inward,  upward  and  outward,  downward  and  inward,  or  downward  and  outward. 
The  movement  of  circumduction,  as  in  looking  round  a  room,  is  performed  by 
the  alternate  action  of  the  four  Recti.  The  Oblique  muscles  rotate  the  eyeball 
on  its  antero-posterior  axis,  this  kind  of  movement  being  required  for  the  correct 
viewing  of  an  object  when  the  head  is  moved  laterally,  as  from  shoulder  to  shoulder, 
in  order  that  the  picture  may  fall  in  all  respects  on  the  same  part  of  the  retina  of 
each  eye.^  It  should  be  noted  that  sometimes  the  corresponding  Recti  and  some- 
times the  opposite  ones  of  the  two  eyes  act  together;  for  instance,  the  two  superior 
and  inferior  Recti  carry  both  eyeballs  upward  and  downward,  respectively.  In 
looking  toward  the  right  the  right  External  and  left  Internal  recti  act  together, 
the  reverse  being  the  case  in  looking  toward  the  left.  In  turning  both  eyes  toward 
the  middle  line,  as  in  directing  our  vision  toward  an  object  less  than  twenty  feet 
distant,  the  two  internal  recti  act  together. 

Fasciae  of  the  Orbit. — The  connective  tissue  of  the  orbit  is  in  various  places 
condensed  into  thin  membranous  layers,  which  may  be  conveniently  described  as 

1  See  F.  Groyer,  in  the  Vienna  Sitzungsberichte  der  Kaiserlichen  Akademie  derWissenschaften,  1903,  Band  cxii. 
_  ^  On  the  Oblique  Muscles  of  the  Eye  in  Man  and  Vertebrate  Animals,  by  John  Struthers,  M.D.,  in  Anatom- 
ical and  Physiological  Observations.  For  a  fuller  account  of  the  various  co-ordinate  actions  of  the  muscles  of 
a  smgle  eye  and  of  both  eyes  than  our  space  allows  see  Dr.  M.  Foster's  Text-book  of  Physiology. 


THE  NASAL    REGION  375 

(1)  the  orbital  fascia;  (2)  the  sheaths  of  the  muscles;  and  (3)  the  covering  of  the 
eyeball. 

(1)  The  Orbital  Fascia. — This  forms  the  periosteum  of  the  orbit.  It  is  loosely 
connected  to  the  bones,  from  which  it  can  be  readily  separated.  Behind,  it  is 
connected  with  the  dura  mater  by  processes  which  pass  through  the  optic  foramen 
and  sphenoidal  fissure,  and  with  the  sheath  of  the  optic  nerve.  In  front  it  is 
connected  with  the  periosteum  at  the  margin  of  the  orbit,  and  sends  off  a  process 
which  assists  in  forming  the  palpebral  fascia.  From  its  internal  surface  two 
processes  are  given  off — one  to  enclose  the  lachrymal  gland,  the  other  to  hold  the 
pulley  of  the  Superior  oblique  muscle  in  position. 

(2)  The  Sheaths  of  the  Muscles. — The  sheaths  of  the  muscles  give  off  expansions 
to  the  margins  of  the  orbit  which  limit  the  action  of  the  muscles. 

(3)  The  Covering  of  the  Eyeball — Tenon's  capsule — surrounds  the  posterior 
two-thirds  of  the  eyeball ;  it  will  be  described  in  the  sequel. 

Surgical  Anatomy. — The  position  and  exact  point  of  insertion  of  the  tendons  of  the 
Internal  and  External  recti  muscles  into  the  globe  should  be  carefully  examined  from  the  front 
of  the  eyeball,  as  the  surgeon  is  often  required  to  divide  the  one  or  the  other  muscle  for  the  cure 
of  strabismus  (squint).  In  convergent  strabismus,  which  is  the  more  common  form  of  the  disease, 
the  eye  is  turned  inward,  requiring  the  division  of  the  Internal  rectus.  In  the  divergent  form, 
which  is  more  rare,  the  eye  is  turned  outward,  the  External  rectus  being  especially  implicated. 
The  deformity  produced  in  either  case  is  to  be  remedied  by  division  of  one  or  the  other  muscle. 
The  operation  is  thus  performed:  The  lids  are  to  be  well  separated;  the  eyeball  being  rotated 
outward  or  inward,  the  conjunctiva  should  be  raised  by  a  pair  of  forceps  and  divided  immediately 
beneath  the  lower  border  of  the  tendon  of  the  muscle  to  be  divided,  a  little  behind  its  insertion 
into  the  sclerotic;  the  submucous  areolar  tissue  is  then  divided,  and  into  the  small  aperture 
thus  made  a  blunt  hook  is  passed  upward  between  the  muscle  and  the  globe,  and  the  tendon  of 
the  muscle  and  conjunctiva  covering  it  divided  by  a  pair  of  blunt-pointed  scissors.  Or  the 
tendon  may  be  divided  by  a  subconjunctival  incision,  one  blade  of  the  scissors  being  passed 
upward  between  the  tendon  and  the  conjunctiva,  and  the  other  between  the  tendon  and  the 
sclerotic.  The  student,  when  dissecting  these  muscles,  should  remove  on  one  side  of  the  subject 
the  conjunctiva  from  the  front  of  the  eye,  in  order  to  see  more  accurately  the  position  of  the 
tendons,  while  on  the  opposite  side  the  operation  may  be  performed.  Inflammation  of  the 
synovial  membrane  lining  the  trochlea  of  the  Superior  oblique  may  lead  to  the  formation  of 
a  cyst  of  considerable  size. 

In  performing  enucleation  of  the  eyeball  the  conjunctiva  is  clipped  with  scissors  near  the 
cornea  and  the  capsule  of  T^non  is  divided  with  it.  One  rectus  muscle  after  another  is  caught 
up  on  a  blunt  hook  and  divided.  The  scissors  are  now  pushed  well  in  along  the  outer  orbital 
wall  and  the  optic  nerve  is  divided.  Finally  the  oblique  muscles,  the  ciliary  vessels  and  nerves, 
and  fragments  of  tissue  helping  to  retain  the  globe  are  cut  and  the  eyeball  is  enucleated. 

An  orbital  abscess  is  evacuated  by  making  an  incision  close  to  the  border  of  the  orbit,  above 
or  below  the  eyeball. 

5.  The  Nasal  Region  (Fig.  260). 

Pyramidalis  nasi.  Dilatator  naris  anterior, 

lycvator  labii  superioris  alseque  nasi.  Compressor  nasi. 

Dilatator  naris  posterior.  Compressor  narium  minor. 

Depressor  ate  nasi. 

The  Pyramidalis  Nasi  is  a  small  pyramidal  slip  placed  over  the  nasal  bone. 
Its  origin  is  by  tendinous  fibres  from  the  fascia  covering  the  lower  part  of  the  nasal 
bone  and  upper  part  of  the  cartilage,  where  it  blends  with  the  Compressor  nasi, 
and  it  is  inserted  into  the  skin  over  the  lower  part  of  the  forehead  between  the 
two  eyebrows,  its  fibres  decussating  with  those  of  the  Occipito-frontalis  (see 
page  368). 

Relations. — By  its  upper  surface,  with  the  skin;  by  its  under  surface,  with  the 
frontal  and  nasal  bones. 

The  Levator  Labii  Superioris  Alaeque  Nasi  is  a  thin  triangular  muscle  placed 
by  the  side  of  the  nose,  and  extending  between  the  inner  margin  of  the  orbit  and 


376  THE  MUSCLES  AND   FASCIA 

upper  lip.  It  arises  by  a  pointed  extremity  from  the  upper  part  of  the  nasal 
process  of  the  superior  maxillary  bone,  and,  passing  obliquely  downward  and 
outward,  divides  into  two  slips,  one  of  which  is  inserted  into  the  cartilage  of  the 
ala  of  the  nose  and  the  under  surface  of  the  skin  over  the  ala;  the  other  is  pro- 
longed into  the  upper  lip,  becoming  attached  to  the  urider  surface  of  the  skin 
and  blended  with  the  Orbicularis  oris  and  Levator  labii  superioris  proprius. 

Relations. — In  ]ront,  with  the  integument,  and  with  a  small  part  of  the  Orbicu- 
laris palpebrarum  above. 

The  Dilatator  Naris  Posterior  is  a  small  muscle  which  is  placed  partly  beneath 
the  elevator  of  the  nose  and  lip.  It  arises  from  the  margin  of  the  nasal  notch  of 
the  superior  maxilla  and  from  the  sesamoid  cartilages,  and  is  inserted  into  the 
skin  near  the  margin  of  the  nostril. 

The  Dilatator  Naris  Anterior  is  a  thin  delicate  fasciculus  passing  from  the 
cartilage  of  the  ala  of  the  nose  to  the  integument  near  its  margin.  This  muscle  is 
situated  in  front  of  the  preceding. 

The  Compressor  Nasi  is  a  small,  thin,  triangular  muscle  arising  by  its  apex 
from  the  superior  maxillary  bone,  above  and  a  little  external  to  the  incisive  fossa; 
its  fibres  proceed  upward  and  inward,  expanding  into  a  thin  aponeurosis  which 
is  attached  to  the  fibro-cartilage  of  the  nose  and  is  continuous  on  the  bridge  of 
the  nose  with  that  of  the  muscle  of  the  opposite  side  and  with  the  aponeurosis  of 
the  Pyraraidalis  nasi.  His  uses  the  term  musculus  nasalis  to  include  the  Com- 
pressor nasi  (transverse  portion  of  the  nasal  muscle),  and  the  Dilatator  naris 
posterior  and  the  Dilatator  naris  anterior  (alar  portion  of  the  nasal  muscle). 

The  Compressor  Narium  Minor  is  a  small  muscle  attached  by  one  end  to  the 
alar  cartilage,  and  by  the  other  to  the  integument  at  the  end  of  the  nose. 

The  Depressor  Alae  Nasi  (depressor  septi)  is  a  short  radiated  muscle  arising 
from  the  incisive  fossa  of  the  superior  maxilla;  its  fibres  ascend  to  be  inserted  into 
the  septum  and  back  part  of  the  ala  of  the  nose.  This  muscle  Hes  between  the 
mucous  membrane  and  muscular  structure  of  the  hp. 

Nerves. — All  of  the  muscles  of  this  group  are  supplied  by  the  facial  nerve. 

Actions. — The  Pyramidalis  nasi  draws  down  the  inner  angle  of  the  eyebrows 
and  produces  transverse  wrinkles  over  the  bridge  of  the  nose.  The  Levator  labii 
superioris  alseque  nasi  draws  upward  the  upper  lip  and  ala  of  the  nose ;  its  most 
important  action  is  upon  the  nose,  which  it  dilates  to  a  considerable  extent.  The 
action  of  this  muscle  produces  a  marked  influence  over  the  countenance,  and  it  is 
the  principal  agent  in  the  expression  of  contempt  and  disdain.  The  two  Dilatatores 
nasi  enlarge  the  aperture  of  the  nose.  Their  action  in  ordinary  breathing  is  to 
resist  the  tendency  of  the  nostrils  to  close  from  atmospheric  pressure,  but  in 
difficult  breathing  they  may  be  noticed  to  be  in  violent  action,  as  well  as  in  some 
emotions,  as  anger.  The  Depressor  aUe  nasi  is  a  direct  antagonist  of  the  other 
muscles  of  the  nose,  drawing  the  ala  of  the  nose  downward,  and  thereby  constrict- 
ing the  aperture  of  the  nares.  The  Compressor  nasi  depresses  the  cartilaginous 
part  of  the  nose  and  compresses  the  alse  together. 

6.  The  Superior  Maxillary  Region  (Fig.  260). 

Levator  labii  superioris.  Zygomaticus  major. 

Ivcvator  anguli  oris.  Zygomaticus  minor. 

By  the  term  musculus  quadratus  labii  superioris,  His  includes  three  muscles. 
The  caput  angulare  is  called  in  this  book  the  Levator  labii  superioris  alaeque  nasi. 
The  caput  infraorbitale  is  called  the  Levator  labii  superioris.  The  caput  zygomati- 
cum  is  called  the  Zygomaticus  minor. 

The  Levator  Labii  Superioris  (proprius)  is  a  thin  muscle  of  a  quadrilateral 
form.    It  arises  from  the  lower  margin  of  the  orbit  immediately  above  the  infra- 


THE   MANDIBULAR    REGION  377 

orbital  foramen,  some  of  its  fibres  being  attached  to  the  superior  maxilla,  others 
to  the  malar  bone;  its  fibres  converge  to  be  inserted  into  the  muscular  substance 
of  the  upper  lip. 

Relations. — By  its  swperjicial  surface  above,  with  the  lower  segment  of  the 
Orbicularis  palpebrarum;  below,  it  is  subcutaneous.  By  its  deep  surface  it  con- 
ceals the  origin  of  the  Compressor  nasi  and  Ijcvator  anguli  oris  muscles,  and  the 
infraorbital  vessels  and  nerve,  as  they  escape  from  the  infraorbital  foramen. 

The  Levator  Anguli  Oris  (r/i.  caninus)  arises  from  the  canine  fossa  immediately 
below  the  infraorbital  foramen ;  its  fibres  incline  downward  and  a  little  outward,  to 
be  inserted  into  the  deep  surface  of  the  skin  and  into  the  subcutaneous  tissue 
near  the  angle  of  the  mouth  and  intermingles  with  the  fibres  of  the  Zygomaticus 
major,  the  Depressor  anguli  oris,  and  the  Orbicularis. 

Relations. — By  its  superficial  surface,  with  the  Levator  labii  superioris  and 
the  infraorbital  vessels  and  nerves;  by  its  deep  surface,  with  the  superior  maxilla, 
the  Buccinator,  and  the  mucous  membrane. 

The  Zygomaticus  Major  (m.  zygomaticus)  is  a  slender  fasciculus  which 
arises  from  the  malar  bone,  in  front  of  the  zygomatic  suture,  and,  descending 
obliquely  downward  and  inward,  is  inserted  into  the  deep  surface  of  the  skin 
and  subcutaneous  tissue  at  the  outer  portion  of  the  upper  lip  and  into  the  angle 
of  the  mouth,  where  it  blends  with  the  fibres  of  the  Levator  anguli  oris,  the 
Orbicularis  oris,  and  the  Depressor  anguli  oris. 

Relations. — By  its  superficial  surface,  with  the  subcutaneous  adipose  tissue; 
by  its  deep  surface,  with  the  Masseter  and  Buccinator  muscles  and  the  facial  artery 
and  vein. 

The  Zygomaticus  Minor,  which  is  often  absent,  arises  from  the  malar  bone 
immediately  behind  the  maxillary  suture,  and,  passing  downward  and  inward,  is 
inserted  into  the  deep  surface  of  the  skin  and  the  adjacent  muscles  at  the  upper 
margin  of  the  exposed  vermilion  surface  of  the  lip  midway  between  the  middle 
line  of  the  lip  and  the  angle  of  the  mouth.  It  is  continuous  with  the  Orbicularis 
oris  at  the  outer  margin  of  the  I^evator  labii  superioris.  It  lies  in  front  of  the 
preceding. 

Relations. — By  its  superficial  surface,  with  the  integument  and  the  Orbicularis 
palpebrarum  above;  by  its  deep  surface,  with  the  Masseter,  Buccinator,  and 
Levator  anguli  oris,  and  the  facial  artery  and  vein. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Levator  labii  superioris  is  the  proper  elevator  of  the  upper  lip, 
carrying  it  at  the  same  time  a  little  forward.  It  assists  in  forming  the  naso-labial 
ridge,  which  passes  from  the  side  of  the  nose  to  the  upper  lip  and  gives  to  the 
face  an  expression  of  sadness.  The  Levator  anguli  oris  raises  the  angle  of  the 
mouth  and  draws  it  inward,  and  assists  the  Levator  labii  superioris  in  producing 
the  naso-labial  ridge.  The  Zygomaticus  major  draws  the  angle  of  the  mouth 
backward  and  upward,  as  in  laughing;  whilst  the  Zygomaticus  minor,  being 
inserted  into  the  outer  part  of  the  upper  lip  and  not  into  the  angle  of  the 
mouth,  draws  it  backward,  upward,  and  outward,  and  thus  gives  to  the  face 
an  expression  of  sadness, 

7.  The  Mandibular  Region  (Fig.  260). 

Levator  labii  inferioris.  Depressor  labii  inferioris. 

Depressor  anguli  oris. 

Dissection. — The  muscles  in  this  region  may  be  dissected  by  making  a  vertical  incision 
through  the  integument  from  the  margin  of  the  lower  lip  to  the  chin;  a  second  incision  should 
then  be  carried  along  the  margin  of  the  lower  jaw  as  far  as  the  angle,  and  the  integument  care- 
fully removed  in  the  direction  shown  in  Fig.  258. 


378  THE  MUSCLES  AND   FASCIA 

The  Levator  Labii  Inferioris  or  Levator  Menti  (m.  mentalis)  is  to  be  dissected 
by  everting  the  lower  Hp  and  raising  the  mucous  membrane.  It  is  a  small  conical 
fasciculus  placed  on  the  side  of  the  frsenum  of  the  lower  lip.  It  arises  from  the 
incisive  fossa,  external  to  the  symphysis  of  the  lower  jaw;  its  fibres  descend  to 
be  inserted  into  the  integument  of  the  chin. 

Relation. — On  its  inner  surface,  with  the  mucous  membrane;  in  the  median 
line,  it  is  blended  with  the  muscle  of  the  opposite  side;  and  on  its  outer  side,  with 
the  Depressor  labii  inferioris. 

The  Depressor  Labii  Inferioris  or  Quadratus  Menti  (m.  quadratus  labii 
inferioris)  (Fig.  264)  is  a  small  quadrilateral  muscle.  It  arises  from  the  external 
oblique  line  of  the  lower  jaw,  between  the  symphysis  and  mental  foramen,  and 
passes  obliquely  upward  and  inward,  to  be  inserted  into  the  integument  of  the 
lower  lip,  its  fibres  blending  with  the  Orbicularis  oris  and  with  those  of  its  fellow 
of  the  opposite  side.  It  is  continuous  with  the  fibres  of  the  Platysma  at  its  origin. 
This  muscle  contains  much  yellow  fat  intermingled  with  its  fibres. 

Relations. — By  its  superficial  surface,  with  part  of  the  Depressor  anguli  oris 
and  with  the  integument,  to  which  it  is  closely  connected;  by  its  deep  surface, 
with  the  mental  vessels  and  nerves,  the  mucous  membrane  of  the  lower  lip,  the 
labial  glands,  and  the  Levator  menti,  with  which  it  is  intimately  united. 

The  Depressor  Anguli  Oris  or  Triangularis  Menti  (m.  triangularis)  (Fig.  260) 
is  triangular  in  shape,  arising,  by  its  broad  base,  from  the  external  oblique  line  of 
the  lower  jaw,  from  whence  its  fibres  pass  upward,  to  be  inserted,  by  a  narrow 
fasciculus,  into  the  angle  of  the  mouth.  It  is  continuous  with  the  Platysma  at 
its  origin  and  with  the  Orbicularis  oris  and  Risorius  at  its  insertion,  and  some  of 
its  fibres  are  directly  continuous  with  those  of  the  Levator  anguli  oris.  Muscular 
fibres  connecting  the  two  muscles  below  the  chin  are  occasionally  met  with;  they 
constitute  the  Musculus  transversus  menti  of  His  and  Waldeyer. 

Relations. — By  its  superficial  surface,  with  the  integument;  by  its  deep  surface, 
with  the  Depressor  labii  inferioris  and  Buccinator. 

Nerves. — This  group  of  muscles  is  supplied  by  the  facial  nerve. 

Actions. — The  Levator  labii  inferioris  raises  the  lower  lip  and  protrudes  it 
forward,  and  at  the  same  time  wrinkles  the  integument  of  the  chin,  expressing 
doubt  or  disdain.  The  Depressor  labii  inferioris  draws  the  lower  lip  directly 
downward  and  a  little  outward,  as  in  the  expression  of  irony.  The  Depressor 
anguli  oris  depresses  the  angle  of  the  mouth,  being  the  antagonist  to  the  Levator 
anguli  oris  and  Zygomaticus  major;  acting  with  these  muscles,  it  will  draw  the 
angle  of  the  mouth  directly  backward. 

8.  The  Intermaxillary  Region. 
Orbicularis  oris.  Buccinator.  Risorius. 

Dissection. — The  dissection  of  these  muscles  may  be  considerably  facilitated  by  filling  the 
cavity  of  the  mouth  with  tow,  so  as  to  distend  the  cheeks  and  lips;  the  mouth  should  then  be 
closed  by  a  few  stitches  and  the  integument  carefully  removed  from  the  surface. 

The  Orbicularis  oris  (Figs.  260  and  264)  is  not  a  sphincter  muscle,  like  the  Orbic- 
ularis palpebrarum,  but  consists  of  numerous  strata  of  muscular  fibres,  having  dif- 
ferent directions,  which  surround  the  orifice  of  the  mouth.  These  fibres  are  par- 
tially derived  from  the  other  facial  muscles  which  are  inserted  into  the  lips,  and  are 
partly  fibres  proper  to  the  lips  themselves.  Of  the  former,  a  considerable  number 
are  derived  from  the  Buccinator  and  form  the  deeper  stratum  of  the  Orbicularis. 
Some  of  them — namely,  those  near  the  middle  of  the  muscle — decussate  at  the 
angle  of  the  mouth,  those  arising  from  the  upper  jaw  passing  to  the  lower  lip,  and 
those  from  the  lower  jaw  to  the  upper  lip.    Other  fibres  of  the  muscle,  situated  at 


THE  INTERMAXILLARY  REGION 


379 


its  upper  and  lower  part,  pass  across  the  lips  from  side  to  side  without  decussation. 
Superficial  to  this  stratum  is  a  second,  formed  by  the  Levator  and  Depressor 
anguli  oris,  which  cross  each  other  at  the  angle  of  the  mouth,  those  from  the 
Depressor  passing  to  the  upper  lip,  and  those  from  the  Levator  to  the  lower  lip, 
along  which  they  run  to  be  inserted  into  the  skin  near  the  median  line.    In  addi- 


Fio.  264. — Temporal  and  deep  muscles  about  the  mouth.     (Testut.) 

tion  to  these  there  are  fibres  from  the  other  muscles  inserted  into  the  lips — the 
Levator  labii  superioris,  the  Levator  labii  superioris  alseque  nasi,  the  Zygomatici, 
and  the  Depressor  labii  inferioris;  these  intermingle  with  the  transverse  fibres 
above  described,  and  have  principally  an  oblique  direction.  The  proper  fibres  of 
the  lips  are  oblique,  and  pass  from  the  under  surface  of  the  skin  to  the  mucous 
membrane  through  the  thickness  of  the  lip.    And  in  addition  to  these  are  fibres 


380  THE  MUSCLES  AND    FASCIA 

by  which  the  muscle  is  connected  directly  with  the  maxillary  bones  and  the 
septum  of  the  nose.  These  consist,  in  the  upper  lip,  of  four  bands,  two  of 
which  {m.  incisivus  superior)  arise  from  the  alveolar  border  of  the  superior 
maxilla,  opposite  the  lateral  incisor  tooth,  and,  arching  outward  on  each  side, 
are  continuous  at  the  angles  of  the  mouth  with  the  other  muscles  inserted  into 
this  part.  The  two  remaining  muscular  slips,  called  the  Nasolabialis,  connect 
the  upper  lip  to  the  back  of  the  septum  of  th&  nose:  as  they  descend  from  the 
septum  an  interval  is  left  between  them.  It  is  this  interval  which  forms  the  depres- 
sion seen  on  the  surface  of  the  skin  beneath  the  septum  of  the  nose,  which  is 
called  the  philtnim.  The  additional  fibres  for  the  lower  segment  {m.  incisivus 
inferior)  arise  from  the  inferior  maxilla,  externally  to  the  Levator  labii  inferioris, 
and  arch  outward  to  the  angles  of  the  mouth,  to  join  the  Buccinator  and  the  other 
muscles  attached  to  this  part. 

Relations. — By  its  superficial  surface,  with  the  integument,  to  which  it  is  closely 
connected;  by  its  deep  surface,  with  the  buccal  mucous  membrane,  the  labial 
glands,  and  coronary  vessels;  by  its  outer  circumference  it  is  blended  with  the 
numerous  muscles  which  converge  to  the  mouth  from  various  parts  of  the  face. 
Its  inner  circumference  is  free,  and  covered  by  the  mucous  membrane. 

The  Buccinator  (Fig.  264)  is  a  broad,  thin  muscle,  quadrilateral  in  form, 
which  occupies  the  interval  between  the  jaws  at  the  side  of  the  face.  It  arises 
from  the  outer  surface  of  the  alveolar  processes  of  the  upper  and  lower  jaws, 
corresponding  to  the  three  molar  teeth,  and,  behind,  from  the  anterior  border  of 
the  ptery go-maxillary  ligament.  The  fibres  converge  toward  the  angle  of  the 
mouth,  where  the  central  fibres  intersect  each  other,  those  from  below  being 
continuous  with  the  upper  segment  of  the  Orbicularis  oris,  and  those  from  above 
with  the  inferior  segment ;  the  highest  and  lowest  fibres  continue  forward  uninter- 
ruptedly into  the  corresponding  segment  of  the  lip,  without  decussation. 

Relations. — By  its  superficial  surface,  behind,  with  a  large  mass  of  fat,  the  sucking 
or  suctorial  pad  (corpus  adiposum  huccx),  which  separates  it  from  the  ramus  of  the 
lower  jaw,  the  Masseter,  and  a  small  portion  of  the  Temporal  muscle.  The  suck- 
ing pad  is  much  more  developed  relatively  in  children  than  in  adults.  It  assists 
sucking  by  aiding  the  cheek  to  resist  atmospheric  pressure.  The  buccinator 
muscle  is  in  relation,  anteriorly,  with  the  Zygomatici,  Risorius,  Levator  anguli 
oris.  Depressor  anguli  oris,  and  Stenson's  duct,  which  pierces  it  opposite  the 
second  molar  tooth  of  the  upper  jaw;  the  facial  artery  and  vein  cross  it  from  below 
upward;  it  is  also  crossed  by  the  branches  of  the  facial  and  buccal  nerves;  by 
its  internal  surface,  with  the  buccal  glands  and  mucous  membrane  of  the  mouth. 

The  Pterygo-maxillary  or  Pterygo-mandibular  Ligament  {raphe  pterygomandih- 
ularis)  separates  the  Buccinator  muscle  from  the  Superior  constrictor  of  the 
pharynx.  It  is  a  tendinous  thickening  of  the  bucco-pharyngeal  fascia,  attached  by 
one  extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other  to  the 
posterior  extremity  of  the  internal  oblique  line  of  the  lower  jaw.  Its  inner  surface 
corresponds  to  the  cavity  of  the  mouth,  and  is  lined  by  mucous  membrane.  Its 
outer  surface  is  separated  from  the  ramus  of  the  jaw  by  a  quantity  of  adipose 
tissue.  Its  posterior  border  gives  attachment  to  the  Superior  constrictor  of  the 
pharynx;  its  anterior  border,  to  the  fibres  of  the  Buccinator. 

The  Bucco-pharyngeal  fascia  (fascia  hiccophari/ngea)  is  a  thin  fascia  covering 
the  external  surface  of  the  Buccinator  muscle.  lit  is  gradually  lost  in  front  of  the 
angle  of  the  mouth.  Posteriorly  it  is  continued  over  the  external  surface  of  the 
throat  muscles.    Its  thickened  cord-like  portion  is  the  stylo-mandibular  ligament. 

The  Risorius  or  Santorini's  Muscle  (m.  risorius)  (Fig.  260)  consists  of  a 
narrow  bundle  of  fibres  which  arises  in  the  fascia  over  the  Masseter  muscle, 
and,  passing  horizontally  forward,  is  inserted  with  the  Depressor  anguli  oris  into 
the  subcutaneous  and  muscular  tissue  at  the  angle  of  the  mouth.     It  is  placed 


THE    TEMPORO  -  MANDIBULAR   REGION  381 

superficial  to  the  Platysraa,  and  is  broadest  at  its  outer  extremity.  This  muscle 
varies  much  in  its  size  and  form. 

Nerves. — The  muscles  in  this  group  are  all  supplied  by  the  facial  nerve.  The 
buccal  branch  of  the  inferior  maxillary  nerve  pierces  the  Buccinator  muscle,  and 
by  some  anatomists  is  regarded  as  partly  supplying  this  muscle.  Probably  it 
merely  pierces  it  on  its  way  to  the  mucous  membrane  of  the  cheek. 

Actions. — The  Orbicularis  oris  in  its  ordinary  action  produces  the  direct  closure 
of  the  lips;  by  its  deep  fibres,  assisted  by  the  oblique  ones,  it  closely  applies  the 
lips  to  the  alveolar  arch.  The  superficial  part,  consisting  principally  of  the  decus- 
sating fibres,  brings  the  lips  together  and  also  protrudes  them  forward.  The  Buc- 
cinators contract  and  compress  the  cheeks,  so  that,  during  the  process  of  mastica- 
tion, the  food  is  kept  under  the  immediate  pressure  of  the  teeth.  When  the  cheeks 
have  been  previously  distended  with  air,  the  Buccinator  muscles  expel  it  from 
between  the  lips,  as  in  blowing  a  trumpet.  Hence  the  name  (buccina,  a  trumpet). 
The  Risorius  retracts'  the  angles  of  the  mouth,  and  produces  the  unpleasant 
expression  which  is  sometimes  seen  in  tetanus,  and  is  known  as  risus  sardonicus,  the 
sardonic  laugh. 

9.  The  Temporo-mandibular  Region. 

Masseter.  Temporal. 

The  Masseteric  Fascia  (fascia  parotideomasseterica)  covers  the  outer  and  inner 
surfaces  of  the  parotid  gland  as  a  thick  membrane,  called  the  parotid  fascia.  It 
passes  forward,  and  becomes  thinner  to  cover  the  Masseter  muscle,  to  which  it 
is  firmly  connected.  It  is  derived  from  the  deep  cervical  fascia.  Above,  this 
fascia  is  attached  to  the  lower  border  of  the  zygoma.  It  is  lost  in  front  below 
the  Risorius  and  Platysma. 

The  Masseter  Muscle  is  exposed  by  the  removal  of  this  fascia  (Fig.  260) ;  it  is  a 
short,  thick  muscle,  somewhat  quadrilateral  in  form,  consisting  of  two  portions, 
superficial  and  deep.  The  superficial  portion,  the  larger,  arises  by  a  thick,  tendinous 
aponeurosis  from  the  malar  process  of  the  superior  maxilla,  and  from  the  anterior 
two-thirds  of  the  lower  border  of  the  zygomatic  arch:  its  fibres  pass  downward 
and  backward,  to  be  inserted  into  the  angle  and  lower  half  of  the  outer  surface 
of  the  ramus  of  the  jaw.  The  deep  portion  is  much  smaller  and  more  muscular 
in  texture;  it  arises  from  the  posterior  third  of  the  lower  border  and  the  whole  of 
the  inner  surface  of  the  zygomatic  arch;  its  fibres  pass  downward  and  forward, 
to  be  inserted  into  the  upper  half  of  the  ramus  and  outer  surface  of  the  coronoid 
process  of  the  jaw.  The  deep  portion  of  the  muscle  is  partly  concealed,  in  front 
by  the  superficial  portion;  behind,  it  is  covered  by  the  parotid  gland.  The  fibres 
of  the  two  portions  are  united  at  their  insertion. 

Relations. — By  its  superficial  surface,  with  the  Zygomatici,  the  parotid  gland 
and  Socia  parotidis,  and  Stenson's  duct;  the  branches  of  the  facial  nerve  and 
the  transverse  facial  vessels,  which  cross  it;  the  masseteric  fascia;  the  Risorius, 
Platysma  myoides,  and  the  integument;  by  its  deep  surface,  with  the  Temporal 
muscle  at  its  insertion,  the  ramus  of  the  jaw,  the  Buccinator  and  the  long 
buccal  nerve,  from  which  it  is  separated  by  a  mass  of  fat  (suctorial  or  sucking  pad). 
The  masseteric  nerve  and  artery  enter  in  on  its  under  surface.  Its  posterior  margin 
is  overlapped  by  the  parotid  gland.  Its  anterior  margin  projects  over  the  Bucci- 
nator muscle,  and  the  facial  vein  lies  on  it  below. 

Temporal  Fascia  (fascia  temporalis). — The  temporal  fascia  is  seen,  at  this  stage 
of  a  dissection,  covering  in  the  Temporal  muscle.  It  is  a  strong,  fibrous  invest- 
ment, covered,  on  its  outer  surface,  by  the  Attrahens  and  Attollens  auriculam  mus- 
cles, the  aponeurosis  of  the  Occipito-frontalis,  and  by  part  of  the  Orbicularis  palpe- 
brarum. The  temporal  vessels  and  the  auriculo-temporal  nerve  cross  it  from  below 
upward.     Above,  it  is  a  single  layer,  attached  to  the  entire  extent  of  the  upper  tem- 


382 


THE  MUSCLES   AND    FASCIA 


poral  ridge;  but  below,  where  it  is  attached  to  the  zygoma,  it  consists  of  two  layers, 
one  of  which  is  inserted  into  the  outer,  and  the  other  into  the  inner,  border  of  the 
zygomatic  arch.  A  small  quantity  of  fat,  the  orbital  branch  of  the  temporal  artery, 
and  a  filament  from  the  orbital,  or  temporo-malar,  branch  of  the  superior  maxillary 
nerve  are  contained  between  these  two  layers.  It  affords  attachment  by  its  inner 
surface  to  the  superficial  fibres  of  the  Temporal  muscle. 

Dissection. — In  order  to  expose  the  Temporal  muscle,  remove  the  temporal  fascia,  which 
may  be  effected  by  separating  it  at  its  attachment  along  the  upper  border  of  the  zygoma,  and 
dissecting  it  upward  from  the  surface  of  the  muscle.  The  zygomatic  arch  should  then 
be  divided  in  front  at  its  junction  with  the  malar  bone,  and  behind  near  the  external  auditory 
meatus,  and  drawn  downward  with  the  Masseter,  which  should  be  detached  from  its  inser- 
tion into  the  ramus  and  angle  of  the  jaw.  The  whole  extent  of  the  Temporal  muscle  is  then 
exposed. 


Fig.  265. — The  Temporal  muscle,  the  zygoma  and  Masseter  having  been  removed. 


The  Temporal  Muscle  (m.  temporalis)  (Figs.  264  and  265)  is  a  broad,  radiating 
muscle  situated  at  the  side  of  the  head  and  occupying  the  entire  extent  of  the  tem- 
poral fossa.  It  arises  from  the  whole  of  the  temporal  fossa  except  that  portion  of  it 
that  is  formed  by  the  malar  bone.  Its  attachment  extends  from  the  external  angular 
process  of  the  frontal  in  front  to  the  mastoid  portion  of  the  temporal  behind,  and 
from  the  curved  line  on  the  frontal  and  parietal  bones  above  to  the  pterygoid  ridge 
on  the  great  wing  of  the  sphenoid  below.  It  is  also  attached  to  the  inner  surface  of 
the  temporal  fascia.  Its  fibres  converge  as  they  descend,  and  terminate  in  an  apon- 
eurosis, the  fibres  of  which,  radiated  at  its  commencement,  converge  into  a  thick 
and  flat  tendon,  which  is  inserted  into  the  inner  surface,  apex,  and  anterior  border 
of  the  coronoid  process  of  the  jaw,  nearly  as  far  forward  as  the  last  molar  tooth. 

Relations. — By  its  superficial  surface,  with  the  integument,  the  Attrahens  and 
Attollens  auriculam  muscles,  the  temporal  vessels  and  nerves,  the  aponeurosis  of 
the  Occipito-frontalis,  the  temporal  fascia,  the  zygoma,  and  Masseter;  by  its 
deep  surface,  with  the  temporal  fossa,  the  External  pterygoid  and  part  of  the 
Buccinator  muscles,  the  internal  maxillary  artery  and  its  deep  temporal  branches, 
and  the  deep  temporal  nerves.  Behind  the  tendon  are  the  masseteric  vessels  and 
nerve,  and  in  front  of  it  the  buccal  vessels  and  nerve.  Its  anterior  border  is  sepa- 
rated from  the  malar  bone  by  a  mass  of  fat. 

Nerves. — Both  muscles  are  supplied  by  the  inferior  maxillary  nerve. 


THE  PTEBYGO- MANDIBULAR    REGION  383 

10.  The  Pterygo-mandibular  Region  (Figs.  266,  267). 
External  pterygoid.  Internal  pterygoid. 

Dissection. — The  Temporal  muscle  having  been  examined,  saw  through  the  base  of  the 
coronoid  process,  and  draw  it  upward,  together  with  the  Temporal  muscle,  which  should  be 
detached  from  the  surface  of  the  temporal  fossa.  Divide  the  ramus  of  the  jaw  just  below  the 
condyle,  and  also,  by  a  transverse  incision  extending  across  the  middle,  just  above  the  dental 
foramen;  remove  the  fragment,  and  the  Pterygoid  muscles  will  be  exposed. 

The  External  Pterygoid  Muscle  (m.  pterygoideus.  extemus)  is  a  short,  thick 
muscle,  somewhat  conical  in  form,  which  extends  ahiiost  horizontally  between  the 
zygomatic  fossa  and  the  condyle  of  the  jaw.  It  arises  by  two  heads,  separated 
by  a  slight  interval :  the  upper  head  arises  from  the  inferior  surface  of  the  greater 
wing  of  the  sphenoid  and  from  the  pterygoid  ridge,  which  separates  the  zygo- 
matic from  the  temporal  fossa ;  the  lower  head  from  the  outer  surface  of  the  external 
pterygoid  plate.  Its  fibres  pass  horizontally  backward  and  outward,  to  be  inserted 
into  a  depression  in  front  of  the  neck  of  the  condyle  of  the  lower  jaw  and  into  the 
corresponding  part  of  the  interarticular  fibro-cartilage. 


Fig.  266. — The  Pterygoid  muscles,  the  zygomatic  arch,  and  a  portion  of  the  ramus  of  the  jaw  having 

been  removed. 

Relations. — By  its  external  surface,  with  the  ramus  of  the  lower  jaw,  the  internal 
maxillary  artery,  which  crosses  it,^  the  tendon  of  the  Temporal  muscle,  and  the 
Masseter;  by  its  internal  surface  it  rests  against  the  upper  part  of  the  Internal 
pterygoid  muscle,  the  internal  lateral  ligament,  the  middle  meningeal  artery,  and 
inferior  maxillary  nerve;  by  its  upper  border  it  is  in  relation  with  the  temporal  and 
masseteric  branches  of  the  inferior  maxillary  nerve;  by  its  lower  border  it  is  in 
relation  with  the  inferior  dental  and  gustatory  nerves.  Through  the  interval 
between  the  two  portions  of  the  muscle,  the  buccal  nerve  emerges  and  the  internal 
maxillary  artery  passes,  when  the  trunk  of  this  vessel  lies  on  the  muscle. 

The  Internal  Pterygoid  Muscle  (m.  pterygoideu^  internus)  is  a  thick,  quadri- 
lateral muscle,  and  resembles  the  Masseter  in  form.  It  arises  from  the  pterygoid 
fossa,  being  attached  to  the  inner  surface  of  the  external  pterygoid  plate  and  to 

1  This  is  the  usual  relation,  but  in  many  cases  the  artery  will  be  found  below  the  muscle. 


384 


THE   3IUSCLE8   AND    FASCIA 


the  D-rooved  surface  of  the  tuberosity  of  the  palate  bone,  and  by  a  second  sHp  from 
the  outer  surface  of  the  tuberosities  of  the  palate  and  superior  maxillary  bones; 
its  fibres  pass  downward,  outward,  and  backward,  to  be  inserted,  by  a  strong,  ten- 
dinous lamina,  into  the  lower  and  back  part  of  the  inner  side  of  the  ramus  and 
angle  of  the  lower  jaw,  as  high  as  the  dental  foramen. 

Relations. — By  its  external  surface,  with  the  ramus  of  the  lower  jaw,  from 
which  it  is  separated,  at  its  upper  part,  by  the  External  pterygoid  muscle,  the 
internal  lateral  ligament,  the  internal  maxillary  artery,  the  dental  vessels  and 
nerves,  and  the  lingual  nerve,  and  a  process  of  the  parotid  gland.  By  its  internal 
surface,  with  the  Tensor  palati,  being  separated  from  the  Superior  constrictor  of 
the  pharynx  by  a  cellular  interval. 


Fig.  267. 


-Pterygoid  muscles,  viewed  from  behind,  the  back  portion  of  the  skull  having  been  removed. 

(Testut.) 


Nerves. — ^These  muscles  are  supplied  by  the  inferior  maxillary  nerve. 

Actions.— The  Temporal  and  Masseter  and  Internal  pterygoid  raise  the  lower 
jaw  against  the  upper  with  great  force.  The  superficial  portion  of  the  Masseter 
assists  the  External  pterygoid  in  drawing  the  lower  jaw  forward  upon  the  upper, 
the  jaw  being  drawn  back  again  by  the  deep  fibres  of  the  Masseter  and  posterior 
fibres  of  the  Temporal.  The  External  pterygoid  muscles  are  the  direct  agents  in 
the  trituration  of  the  food,  drawing  the  lower  jaw  directly  forward,  so  as  to  make 
the  lower  teeth  project  beyond  the  upper.  If  the  muscle  of  one  side  acts,  the 
corresponding  side  of  the  jaw  is  drawn  forward,  and,  the  other  condyle  remaining 
fixed,  the  symphysis  deviates  to  the  opposite  side.  The  alternation  of  these  move- 
ments on  the  two  sides  produces  trituration. 


3TUSCLES   AND    FASCIA    OF    THE   NECK  335 

Surface  Form. — The  outline  of  the  muscles  of  the  head  and  face  cannot  be  traced  on  the 
surface  of  the  body,  except  in  the  case  of  two  of  the  masticatory  muscles.  Those  of  the  head 
are  thin,  so  that  the  outline  of  the  bone  is  perceptible  beneath  them.  Those  in  the  face  are 
small,  covered  by  soft  skin,  and  often  by  a  considerable  layer  of  fat,  so  that  their  outline  is  con- 
cealed, but  they  serve  to  round  off  and  smooth  prominent  borders  and  to  fill  up  what  would  be 
otherwise .  unsightly  angular  depressions.  Thus,  the  Orbicularis  palpebrarum  rounds  off  the 
prominent  margin  of  the  orbit,  and  the  Pyramidalis  nasi  fills  in  the  sharp  depression  beneath 
the  glabella,  and  thus  softens  and  tones  down  the  abrupt  depression  which  is  seen  on  the 
unclothed  bone.  In  like  manner,  the  labial  muscles,  converging  to  the  lips  and  assisted  by  the 
superimposed  fat,  fill  in  the  sunken  hollow  of  the  lower  part  of  the  face.  Although  the  muscles 
of  the  face  are  usually  described  as  arising  from  the  bones  and  inserted  into  the  nose,  lips,  and 
corners  of  the  mouth,  they  have  fibres  inserted  into  the  skin  of  the  face  along  their  whole 
extent,  so  that  almost  every  point  of  the  skin  of  the  face  has  its  muscular  fibre  to  move  it; 
hence  it  is  that  when  in  action  the  facial  muscles  produce  alterations  in  the  skin-surface, 
giving  rise  to  the  formation  of  various  folds  or  wrinkles,  or  otherwise  altering  the  relative 
position  of  the  parts,  so  as  to  produce  the  varied  expressions  with  which  the  face  is  endowed; 
hence  these  muscles  are  termed  the  muscles  of  expression.  The  only  two  muscles  in  this 
region  which  greatly  influence  surface  form  are  the  Masseter  and  the  Temporal.  The  Masseter 
is  a  quadrilateral  muscle,  which  imparts  fulness  to  the  hinder  part  of  the  cheek.  When  the 
muscle  is  firmly  contracted,  as  when  the  teeth  are  clenched,  its  outline  is  plainly  visible; 
the  anterior  border  forms  a  prominent  vertical  ridge,  behind  which  is  a  considerable  fulness, 
especially  marked  at  the  lower  part  of  the  muscle;  this  fulness  is  entirely  lost  when  the 
mouth  is  opened  and  the  muscle  no  longer  in  a  state  of  contraction.  The  Temporal  muscle 
is  fan-shaped,  and  fills  the  Temporal  fossa,  substituting  for  it  a  somewhat  convex  form,  the 
anterior  part  of  which,  on  account  of  the  absence  of  hair  over  the  temple,  is  more  marked  than 
the  posterior,  and  stands  out  in  strong  relief  when  the  muscle  is  in  a  state  of  contraction, 

MUSCLES  AND  FASCIA  OF  THE  NECK. 

The  muscles  of  the  neck  may  be  arranged  into  groups  corresponding  with  the 
region  in  which  they  are  situated. 
These  groups  are  nine  in  number: 

1.  Superficial  Cervical  Region.  5.  Muscles  of  the  Pharynx. 

2.  Depressors  of  the  Os  Hyoideum  6.  Muscles  of  the  Soft  Palate. 

and  Larynx.  7.  Muscles  of  the  Anterior  Ver- 

3.  Elevators  of  the  Os  Hyoideum  tebral  Region. 

and  I..arynx.  8.  Muscles  of  the  Lateral  Ver- 

4.  Muscles  of  the  Tongue.  tebral  Region. 

9.  Muscles  of  the  Larynx. 

The  muscles  contained  in  each  of  these  groups  are  the  following: 

\.  Superficial  Region.  Lingual  Region. 

Platysma  myoides. 
Sterno-cleido-mastoid.  4.  Muscles  of  the  Tongue. 

Infra-hyoid  Region.  Genio-hyo-glossus. 

2.  Depressors  of  Os  hyoideum  and  Hyo-glossus. 

Larynx.  Chondro-glossus. 

Sterno-hyoid.  Stylo-glossus. 

Sterno-thyroid.  Palato-glossus. 

Thyro-hyoid. 
Omo-hyoid. 

Supra-hyoid  Region. 

3.  Elevators  of  Os  hyoideum  and  Larynx.  Inferior  constrictor. 

Digastric.  Middle  constrictor. 

Stylo-hyoid.  Superior  constrictor. 

Mylo-hyoid.  Stylo-pharyngeus. 

Genio-hyoid.  Palato-pharyngeus. 

25 


5.  Muscles  of  the  Pharynx, 


386  THE  MUSCLES  AND    FASCIA 

6.  Muscles  of  the  Soft  Palate.  8.  Muscles  of  the  Lateral  Vertebral 
Levator  palati.  Region. 

Tensor  palati. 

Azygos  uvulae.  Scalenus  anticus. 

Palato-glossus.  Scalenus  medius. 

Palato-pharyngeus.  Scalenus  posticus. 

Salpingo-pliaryngeus. 

7.  Muscles  of  the  A  nteriorV  ertehral  Region. 

Rectus  capitis  anticus  major.  ^    Muscles  of  the  Larynx. 

Rectus  capitis  anticus  minor. 

Rectus  capitis  lateralis.  Included    in  description    of    the 

Longus  colli.  Larynx. 

1.  The  Superficial  Cervical  Region. 

Platysma  myoides.  Sterno-cleido-mastoid. 

Dissection. — A  block  having  been  placed  at  the  back  of  the  neck,  and  the  face  turned  to 
the  side  opposite  that  to  be  dissected,  so  as  to  place  the  parts  upon  the  stretch,  make  two  trans- 
verse incisions:  one  from  the  chin,  along  the  margin  of  the  lower  jaw,  to  the  mastoid  jjrocess, 
and  the  other  along  the  upper  border  of  the  clavicle.  Connect  these  by  an  oblique  incision 
made  in  the  course  of  the  Sterno-mastoid  muscle,  from  the  mastoid  process,  to  the  sternum ;  the 
two  flaps  of  integument  having  been  removed  in  the  direction  shown  in  Fig.  257,  the  superficial 
fascia  will  be  exposed. 

Superficial  Cervical  Fascia. — The  superficial  cervical  fascia  is  a  thin,  apon- 
eurotic lamina  which  is  hardly  demonstrable  as  a  separate  membrane.  Beneath 
it  is  found  the  Platysma  myoides  muscle. 

The  Platysma  Myoides  (m.  'platysma)  (Fig.  260)  is  a  broad,  thin  plane  of  mus- 
cular fibres  placed  immediately  beneath  the  superficial  fascia  on  each  side  of  the 
neck.  It  arises  by  thin,  fibrous  bands  from  the  fascia  covering  the  upper  part  of  the 
Pectoral  and  Deltoid  muscles ;  its  fibres  pass  over  the  clavicle  and  proceed  obliquely 
upward  and  inward  along  the  side  of  the  neck.  The  anterior  fibres  interlace, 
below  and  behind  the  symphysis  menti,  with  the  fibres  of  the  muscle  of  the  oppo- 
site side;  the  posterior  fibres  pass  over  the  lower  jaw,  some  of  them  being  attached 
to  the  bone  below  the  external  oblique  line,  others  passing  on  to  be  inserted  into 
the  skin  and  subcutaneous  tissue  of  the  lower  part  of  the  face,  many  of  these  fibres 
blending  with  the  muscles  about  the  angle  and  lower  part  of  the  mouth.  Some- 
times fibres  can  be  traced  to  the  Zygomatic  muscles  or  to  the  margin  of  the 
Orbicularis  oris.  Beneath  the  Platysma  the  external  jugular  vein  may  be  seen 
descending  in  a  line  from  the  angle  of  the  jaw  to  the  middle  of  the  clavicle. 

Relations. — By  its  external  surface,  with  the  integument,  to  which  it  is  united 
moi'e  closely  below  than  above;  by  its  internal  surface,  with  the  Pectoralis  major 
and  Deltoid,  and  with  the  clavicle.  In  the  neck,  with  the  external  and  anterior 
jugular  veins,  the  deep  cervical  fascia,  the  superficial  branches  of  the  cervical 
plexus,  the  Sterno-mastoid,  Sterno-hyoid,  Omo-hyoid,  and  Digastric  muscles; 
behind  the  Sterno-mastoid  muscle  it  covers  in  the  posterior  triangle  of  the  neck. 
On  the  face  it  is  in  relation  with  the  parotid  gland,  the  facial  artery  and  vein, 
and  the  Masseter  and  Buccinator  muscles. 

Nerves. — ^The  lower  division  of  the  facial  nerve  chiefly  innervates  this  muscle, 
and  superficial  branches  from  the  cervical  plexus  also  reach  it. 

Action. — The  Platysma  myoides  produces  a  slight  wrinkling  of  the  surface  of 
the  skin  of  the  neck,  in  an  oblique  direction,  when  the  entire  muscle  is  brought 
into  action.  Its  anterior  portion,  the  thickest  part  of  the  muscle,  depresses  the 
lower  jaw;  it  also  serves  to  draw  down  the  lower  lip  and  angle  of  the  mouth  on 
each  side,  being  one  of  the  chief  agents  in  the  expression  of  melancholy.  In  the 
pressure  upon  the  blood-vessels  of  the  neck  induced  by  strong  inspiratory  effort, 


THE  SUPERFICIAL   CERVICAL  REGION 


387 


this  muscle  draws  away  the  skin  and  fascia,  and  by  so  doing,  greatly  diminishes 
the  pressure  on  the  veins. 

Deep  Cervical  Fascia  {jascia  colli)  (Fig.  268).— The  deep  cervical  fascia 
lies  under  cover  of  the  Platysma  myoides  muscle  and  constitutes  a  complete 
investment  for  the  neck.  It  also  forms  a  sheath  for  the  carotid  vessels,  and,  in 
addition,  is  prolonged  deeply  in  the  shape  of  certain  processes  or  lamellae,  which 
come  into  close  relation  with  the  structures  situated  in  front  of  the  vertebral  column. 


SPACE  BETWEEN  THE 
TWO  LAYERS  OF  FASCIA 


STERNOTHYROID 

DEEP   FASCIA    OF  NECK 
lOHYOID 


OESOPHAGUS 


PREVERTEBRAL 
FASCIA 


MOHYOID 

COMMON  CAROTID 
ERV 

DESCENDENS  HYPO- 
GLOSSI   NERVE 

PNEUMOGASTRIC 
NERVE 

LYMPHATIC 
GLANDS 

SYMPATHETIC 
NERVE 
PHRENIC 
NERVE 
INTERNAL 
JUGULAR 
VEIN 

BRACHIAL 
PLEXUS 


SUPERFICIAL 
FASCIA  OF 
NECK 


Fig.  268. — Transverse  section  through  the  neck  at  the  level  of  the  seventh  cervical  vertebra.     (Spalteholz.) 

The  investing  portion  of  the  fascia  is  attached,  behind,  to  the  ligamentum 
nuchae  and  to  the  spine  of  the  seventh  cervical  vertebra.  Along  this  line  it  splits 
to  enclose  the  Trapezius  muscle,  at  the  anterior  border  of  which  the  two  enclosing 
lamellie  unite  and  form  a  strong  membrane,  which  extends  forward  so  as  to  roof 
in  the  posterior  triangle  of  the  neck.  Along  the  hinder  edge  of  the  Sterno-mastoid 
the  membrane  divides  to  enclose  this  muscle,  at  the  anterior  edge  of  which  it  once 
more  forms  a  single  lamellae,  which  roofs  in  the  anterior  triangle  of  the  neck, 
and,  reaching  forward  to  the  middle  line,  is  continuous  with  the  corresponding 
part  from  the  opposite  side  of  the  neck.  In  the  middle  line  of  the  neck  it  is  attached 
to  the  symphysis  menti  and  to  the  body  of  the  liyoid  bone. 


388  THE  MUSCLES  AND  FASCIA 

AboDe,  the  fascia  is  attached  to  the  superior  curved  Hne  of  the  occiput,  to  the 
mastoid  process  of  the  temporal,  and  to  the  whole  length  of  the  body  of  the  jaw. 
Opposite  the  angle  of  the  jaw  the  fascia  is  very  strong,  and  binds  the  anterior 
edge  of  the  Sterno-mastoid  firmly  to  that  bone.  Between  the  jaw  and  the  mastoid 
process  it  ensheaths  the  parotid  gland — the  layer  which  covers  the  gland  extending 
upward  under  the  name  of  the  parotid  fascia  to  be  fixed  to  the  zygomatic  arch. 
Thg  parotid  fascia  is  prolonged  forward  to  cover  the  masseter  muscle,  the  masse- 
teric fascia.  From  the  layer  which  passes  under  the  parotid  a  strong  band, 
the  stylo-mandibular  ligament,  reaches  from  the  styloid  process  to  the  angle  of 
the  jaw.  The  parotid  and  masseteric  fascite  constitute  the  fascia  parotideo- 
masseterica. 

Below,  the  cervical  fascia  is  attached  to  the  acromion  process,  the  clavicle,  and 
to  the  manubrium  sterni.  Some  little  distance  above  the  last-named  point,  how- 
ever, it  splits  into  two  layers,  superficial  and  deep.  The  former  is  attached  to 
the  anterior  border  of  the  manubrium,  the  latter  to  its  posterior  border  and  to 
the  interclavicular  ligament.  Between  these  two  layers  is  a  slit-like  interval,  the 
suprasternal  space  or  space  of  Bums  (spatium  swpr aster nale).  It  contains  a  small 
quantity  of  areolar  tissue,  and  sometimes  a  lymphatic  gland;  the  lower  portions 
of  the  anterior  jugular  veins  and  their  transverse  connecting  branch;  and  also 
the  sternal  heads  of  the  Sterno-mastoid  muscles. 

The  fascia  which  lines  the  deep  aspect  of  the  Sterno-mastoid  gives  off  certain 
important  processes,  viz. :  (1)  A  process  to  envelop  the  tendon  of  the  Omo-hyoid, 
and  bind  it  down  to  the  sternum  and  first  costal  cartilage.  (2)  A  strong  sheath, 
the  carotid  sheath,  for  the  large  vessels  of  the  neck,  enclosed  within  which  are  the 
carotid  artery,  internal  jugular  vein,  the  vagus,  and  descendens  hypoglossi  nerves. 
(3)  The  prevertebral  fascia  {fascia  prcevertebralis) ,  which  extends  inward  behind 
the  carotid  vessels,  where  it  assists  in  forming  their  sheath,  and  passes  in  front 
of  the  prevertebral  muscles.  It  thus  forms  the  posterior  limit  of  a  fibrous  com- 
partment which  contains  the  larynx  and  trachea,  the  thyroid  gland,  and  the 
pharynx  and  oesophagus.  The  prevertebral  fascia  is  fixed  above  to  the  base  of 
the  skull,  while  below  it  is  continued  into  the  thorax  in  front  of  the  Longus  colli 
muscles.  Parallel  to  the  carotid  vessels  and  along  their  inner  aspect  it  gives  off 
a  thin  lamina,  the  bucco-pharyngeal  fascia  (fascia  buccopharyngea) ,  which  closely 
invests  the  constrictor  muscles  of  the  pharynx,  and  is  continued  forward  from 
the  Superior  constrictor  on  to  the  Buccinator.  It  is  attached  to  the  prever- 
tebral layer  by  loose  connective  tissue  only,  and  thus  an  easily  distended  space, 
the  retro-pharyngeal  space  (spatium  retropharyjigea) ,  is  found  between  them.  This 
space  is  limited  above  by  the  base  of  the  skull,  while  below  it  extends  behind  the 
oesophagus  into  the  thorax,  where  it  is  continued  into  the  posterior  mediastinum. 
The  prevertebral  fascia  is  prolonged  downward  and  outward  behind  the  carotid 
vessels  and  in  front  of  the  Scaleni  muscles,  and  forms  a  sheath  for  the  brachial 
plexus  of  nerves  and  for  the  subclavian  vessels  in  the  posterior  triangle  of  the  neck, 
and,  continuing  under  the  clavicle  as  the  axillary  sheath,  is  attached  to  the  deep 
surface  of  the  costo-coracoid  membrane.  Immediately  above  the  clavicle  an 
areolar  space  exists  between  the  investing  layer  and  the  sheath  of  the  subclavian 
vessels,  and  in  it  are  found  the  lower  part  of  the  external  jugular  vein,  the  descend- 
ing clavicular  nerves,  the  suprascapular  and  transversalis  colli  vessels,  and  the 
posterior  belly  of  the  Omo-hyoid  muscle.  This  space  extends  downward  behind 
the  clavicle,  and  is  limited  below  by  the  fusion  of  the  costo-coracoid  membrane 
with  the  anterior  wall  of  the  axillary  sheath.  (4)  The  pre-tracheal  fascia,  which 
extends  inward  in  front  of  the  carotid  vessels,  and  assists  in  forming  the  carotid 
sheath.  It  is  further  continued  behind  the  Depressor  muscles  of  the  hyoid  bone, 
and,  after  enveloping  the  thyroid  body,  is  prolonged  in  front  of  the  trachea  to 
meet  the  corresponding  layer  of  the  opposite  side.    Above,  it  is  fixed  to  the  hyoid 


THE  INFRAHYOID  REGION  39I 

Actions. — When  only  one  Sterno-mastoid  muscle  acts,  it  draws  the  head  toward 
the  shoulder  of  the  same  side,  assisted  by  the  Splenius  and  the  Obliquus  capitis 
inferior  of  the  opposite  side.  At  the  same  time  it  rotates  the  head  so  as  to  carry 
the  face  toward  the  opposite  side.  When  the  two  muscles  act  together  they 
flex  the  head  upon  the  neck.  If  the  head  is  fixed,  the  two  muscles  assist  in 
elevating  the  thorax  in  forced  inspiration. 

Surface  Form. — The  anterior  edge  of  the  muscle  forms  a  very  prominent  ridge  beneath  the 
skin,  which  it  is  important  to  notice,  as  it  forms  a  guide  to  the  surgeon  in  making  the  necessary 
incisions  for  Hgature  of  the  common  carotid  artery  and  for  oesophagotomy. 

Surgical  Anatomy. — The  relations  of  the  sternal  and  clavicular  parts  of  the  Sterno-mastoid 
should  be  carefully  examined,  as  the  surgeon  is  sometimes  required  to  divide  one  or  both  portions 
of  the  muscle  in  wry-neck  (torticollis).  One  variety  of  this  distortion  is  produced  by  spasmodic 
contraction  or  rigidity  of  the  Sterno-mastoid ;  the  head  being  carried  down  toward  the  shoulder 
of  the  same  side,  and  the  face  turned  to  the  opposite  side  and  fixed  in  that  position.  When  there 
is  permanent  shortening,  subcutaneous  division  of  the  muscle  is  resorted  to  by  some  surgeons. 
This  is  performed  by  introducing  a  tenotomy  knife  beneath  it,  close  to  its  origin,  and  dividing 
it  from  behind  forward  whilst  the  muscle  is  put  well  upon  the  stretch.  There  is  seldom  any 
difficulty  in  dividing  the  sternal  portion  by  making  a  puncture  on  the  inner  side  of  the  tendon, 
and  then  pushing  a  blunt  tenotome  behind  it,  and  cutting  forward.  In  dividing  the  clavicular 
portion  care  must  be  taken  to  avoid  wounding  the  external  jugular  vein,  which  runs  parallel 
with  the  posterior  border  of  the  muscle  in  this  situation,  or  the  anterior  jugular  vein,  which 
crosses  beneath  it.  If  the  external  jugular  vein  lies  near  the  muscle,  it  is  safer  to  make  the 
first  puncture  at  the  outer  side  of  the  tendon,  and  introduce  a  blunt  tenotome  from  without 
inward.  Many  surgeons  prefer  dividing  the  muscle  by  open  incision,  because  by  this  method 
all  of  the  contracted  fibres,  muscular  and  facial,  can  be  certainly  and  safely  divided.  An  incision 
is  made  over  the  origin  of  the  muscle,  the  origin  is  exposed,  a  director  is  passed  underneath  it, 
and  it  is  then  divided.  With  care  and  attention  to  asepsis  this  plan  of  treatment  is  devoid  of 
risk,  and  in  this  way  the  accidental  division  of  vessels  can  be  avoided.  Some  of  the  fibres  of 
the  Sterno-mastoid  muscle  are  occasionally  torn  during  birth,  especially  in  breech  presenta- 
tions; this  is  accompanied  by  hemorrhage  and  formation  of  a  swelling  within  the  substance  of 
the  muscle.  This  by  some  is  believed  to  be  one  of  the  causes  of  wry-neck,  the  scar  tissue 
which  is  formed  contracting  and  shortening  the  muscle. 

2.  The  Infra-hyoid  Region  (Figs.  269,  270). 
Depressors  of  the  Os  Hyoideum  and  Larynx. 

Sterno-hyoid.  Thyro-hyoid. 

Sterno-thyroid.  Omo-hyoid. 

Dissection. — The  muscles  in  this  region  may  be  exposed  by  removing  the  deep  fascia  from  the 
front  of  the  neck.  In  order  to  see  the  entire  extent  of  the  Omo-hyoid  it  is  necessary  to  divide 
the  sterno-mastoid  at  its  centre,  and  turn  its  ends  aside,  and  to  detach  the  Trapezius  from  the 
clavicle  and  scapula.    This,  however,  should  not  be  done  until  the  Trapezius  has  been  dissected. 

The  Stemo-hyoid  (m.  sternohyoideus)  is  a  thin,  narrow,  ribbon-like  muscle, 
which  arises  from  the  inner  extremity  of  the  clavicle,  the  posterior  sterno- 
clavicular ligament,  and  the  upper  and  posterior  part  of  the  first  piece  of  the 
sternum ;  passing  upward  and  inward,  it  is  inserted,  by  short,  tendinous  fibres, 
into  the  lower  border  of  the  body  of  the  hyoid  bone.  This  muscle  is  separated, 
below,  from  its  fellow  by  a  considerable  interval;  but  the  two  muscles  come  into 
contact  with  one  another  in  the  middle  of  their  course,  and  from  this  upward 
lie  side  by  side.  It  sometimes  presents,  immediately  above  its  origin,  a  trans- 
verse tendinous  intersection,  like  those  in  the  Rectus  abdominis.  As  a  rule, 
two  bursse,  the  stemo-hyoid  bursae  (hursce  sternohyoidii) ,  lie  between  the  crico- 
thyroid membrane,  on  one  hand,  and  the  Stemo-hyoid  muscle  and  the  cervical 
fascia,  on  the  other.  Sometimes  there  is  one  large  median  bursa  instead  of  two 
lateral  bursae.    Not  unusually  there  is  no  bursa  at  all. 

Relations. — By  its  superficial  surface,  below,  with  the  sternum,  the  sternal  end 
of  the  clavicle,  and  the  Sterno-mastoid ;  and  above,  with  the  Platysma  and  deep 
cervical  fascia;  by  its  deep  surface,  with  the  Sterno-thyroid,  Crico-thyroid,  and 


392 


THE  MUSCLES  AND  FASCIA 


Thyro-hyoid  muscles,  the  thyroid  gland,  the  superior  thyroid  vessels,  the  thyroid 
cartilage,  the  crico-thyroid  and  thyro-hyoid  membranes. 

The  Stemo-thyroid  {m.  sternoihyreoideus)  is  situated  beneath  the  preceding 
muscle,  but  is  shorter  and  wider  than  it.  It  arises  from  the  posterior  surface  of 
the  first  piece  of  the  sternum,  below  the  origin  of  the  Sterno-hyoid,  and  from  the 
edge  of  the  cartilage  of  the  first  rib,  occasionally  of  the  second  rib  also,  and  is 
inserted  into  the  oblique  line  on  the  side  of  the  ala  of  the  thyroid  cartilage. 
This  muscle  is  in  close  contact  with  its  fellow  at  the  lower  part  of  the  neck,  and 
is  occasionally  traversed  by  a  transverse  or  oblique  tendinous  intersection,  like 
those  in  the  Rectus  abdominis. 

Symphysis 
of  jaw. 


Fig.  270. — Muscles  of  the  neck.     Anterior  view. 


Relations. — By  its  anterior  surface,  with  the  Sterno-hyoid,  Omo-hyoid,  and 
Sterno-mastoid ;  by  its  'posterior  surface,  from  below  upward,  with  the  trachea, 
vena  innominata,  common  carotid  (and  on  the  right  side  the  arteria  innominata), 
the  thyroid  gland  and  its  vessels,  and  the  lower  part  of  the  larynx  and  pharynx. 
The  inferior  thyroid  vein  lies  along  its  inner  border,  a  relation  which  it  is  impor- 
tant to  remember  in  the  operation  of  tracheotomy.  On  the  left  side  the  deep 
surface  of  the  muscle  is  in  relation  to  the  oesophagus. 

The  Thyro-hyoid  (m.  thyreohyoideus)  is  a  small,  quadrilateral  muscle  appear- 
ing like  a  continuation  of  the  Stemo-thyroid.  It  arises  from  the  oblique  line  on 
the  side  of  the  thyroid  cartilage,  and  passes  vertically  upward  to  be  inserted  into 
the  lower  border  of  the  body  and  greater  cornu  of  the  hyoid  bone.  The  thyro- 
hyoid bursse  {hursce  thyreohyoidii)  lie  inferior  to  the  greater  cornua  of  the  hyoid 
bone  and  upon  the  thyro-hyoid  membrane.  There  is  one  bursa  on  each  side 
beneath  the  corresponding  Thyro-hyoid  muscle. 

Relations. — By  its  external  surface,  with  the  Sterno-hyoid  and  Omo-hyoid 
muscles;  by  its  internal  surface,  with  the  thyroid  cartilage,  the  thyro-hyoid  mem- 
brane, and  the  superior  laryngeal  vessels  and  nerve. 


THE  SUPRA- HYOID  REGION  393 

The  Omo-hyoid  (m.  omohyoideus)  passes  across  the  side  of  the  neck,  from 
the  scapula  to  the  hyoid  bone.  It  consists  of  two  fleshy  bellies,  united  by  a 
central  tendon.  It  arises  from  the  upper  border  of  the  scapula,  and  occasionally 
from  the  transverse  ligament  which  crosses  the  suprascapular  notch,  its  extent  of 
attachment  to  the  scapula  varying  from  a  few  lines  to  an  inch.  From  this  origin 
the  posterior  belly  (venter  inferior)  forms  a  flat,  narrow  fasciculus,  which  inclines 
forward  and  slightly  upward  across  the  lower  part  of  the  neck,  behind  the  Sterno- 
mastoid  muscle,  where  it  becomes  tendinous;  it  then  changes  its  direction,  forming 
an  obtuse  angle,  and  terminates  in  the  anterior  belly  (venter  superior),  which 
passes  almost  vertically  upward,  close  to  the  outer  border  of  the  Sterno-hyoid, 
to  be  inserted  into  the  lower  border  of  the  body  of  the  hyoid  bone,  just  external  to 
the  insertion  of  the  Sterno-hyoid.  The  central  tendon  of  this  muscle,  which  varies 
much  in  length  and  form,  is  held  in  position  by  a  process  of  the  deep  cervical 
fascia,  which  includes  it  in  a  sheath.  This  process  is  prolonged  down,  to  be 
attached  to  the  clavicle  and  first  rib.  It  is  by  this  means  that  the  angular  form  of 
the  muscle  is  maintained. 

This  muscle  subdivides  each  of  the  two  large  triangles  at  the  side  of  the  neck 
into  two  smaller  triangles;  the  two  posterior  ones  being  the  posterior  superior  or 
occipital  triangle,  and  the  posterior  inferior  or  subclavian  triangle;  the  two  anterior, 
the  anterior  superior  or  superior  carotid  triangle,  and  the  anterior  inferior  or  inferior 
carotid  triangle. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  the  Sterno-mastoid, 
deep  cervical  fascia,  Platysma,  and  integument;  by  its  deep  surface,  with  the 
Scaleni  muscles,  phrenic  nerve,  lower  cervical  nerves,  which  go  to  form  the  brachial* 
plexus,  the  suprascapular  vessels  and  nerve,  sheath  of  the  common  carotid  artery 
and  internal  jugular  vein,  the  Sterno-thyroid  and  Thyro-hyoid  muscles. 

Nerves. — The  Thyro-hyoid  is  supplied  by  the  hypoglossal;  the  other  muscles 
of  this  group  by  branches  from  the  loop  of  communication  between  the  descendens 
and  communicans  hypoglossi. 

Actions. — ^These  muscles  depress  the  larynx  and  hyoid  bone,  after  they  have 
been  drawn  up  with  the  pharynx  in  the  act  of  deglutition.  The  Omo-hyoid 
muscles  not  only  depress  the  hyoid  bone,  but  carry  it  backward  and  to  one  side. 
It  is  concerned  especially  in  prolonged  inspiratory  efforts;  for  by  tensing  the 
lower  part  of  the  cervical  fascia  it  lessens  the  inward  suction  of  the  soft  parts, 
which  would  otherwise  compress  the  great  vessels  and  the  apices  of  the  lungs. 
This  action  is  synergistic  with  that  of  the  Platysma.  The  Thyro-hyoid  may  act 
as  an  elevator  of  the  thyroid  cartilage  when  the  hyoid  bone  ascends,  drawing 
upward  the  thyroid  cartilage,  behind  the  hyoid  bone.  The  Sterno-thyroid  acts  as 
a  depressor  of  the  thyroid  cartilage. 

3.  The  Supra-hyoid  Region  (Figs.  269,  270). 

Elevators  of  the  Os  Hyoideum — Depressors  of  the  Lower  Jaw. 

Digastric.  Mylo-hyoid. 

Stylo-hyoid.  Genio-hyoid. 

Dissection. — To  dissect  these  muscles  a  block  should  be  placed  beneath  the  back  of  the 
neck,  and  the  head  drawn  backward  and  retained  in  that  position.  On  the  removal  of  the  deep 
fascia  the  muscles  are  at  once  exposed. 

The  Digastric  (m.  digastricus)  consists  of  two  fleshy  bellies  united  by  an  inter- 
mediate, rounded  tendon.  It  is  a  small  muscle,  situated  below  the  side  of  the 
body  of  the  lower  jaw,  and  extending,  in  a  curved  form,  from  the  side  of  the 
head  to  the  symphysis  of  the  jaw.  The  posterior  belly  (venter  posterior) ,  longer 
than  the  anterior,  arises  from  the  digastric  groove  on  the  inner  side  of  the  mas- 
toid process  of  the  temporal  bone,  and  passes  downward,  forward,  and  inward. 


394  THE  MUSCLES  AND  FASCIA 

The  anterior  belly  {venter  anterior)  arises  from  a  depression  on  the  inner  side 
of  the  lower  border  of  the  jaw,  close  to  the  symphysis,  and  passes  downward 
and  backward.  The  two  bellies  terminate  in  the  central  tendon  which  per- 
forates the  Stylo-hyoid,  and  is  held  in  connection  with  the  side  of  the  body 
and  the  greater  cornu  of  the  hyoid  bone  by  a  fibrous  loop,  lined  by  a  synovial 
membrane.  A  broad  aponeurotic  layer  is  given  off  from  the  tendon  of  the 
Digastric  on  each  side,  which  is  attached  to  the  body  and  great  cornu  of  the 
hyoid  bone:  this  is  termed  the  supra-hyoid  aponeurosis.  It  forms  a  strong  layer 
of  fascia  between  the  anterior  portion  of  the  two  muscles,  and  a  firm  investment 
for  the  other  muscles  of  the  supra-hyoid  region  which  lie  deeper. 

The  Digastric  muscle  divides  the  anterior  superior  triangle  of  the  neck  into 
two  smaller  triangles;  the  upper,  or  submaxillary  triangle,  being  bounded,  above,  by 
the  lower  border  of  the  body  of  the  jaw,  and  a  line  drawn  from  its  angle  to  the 
mastoid  process;  below,  by  the  posterior  belly  of  the  Digastric  and  the  Stylo- 
hyoid muscles ;  in  front,  by  the  middle  line  of  the  neck  and  the  anterior  belly  of  the 
Digastric,  the  lower  or  superior  carotid  triangle  being  bounded  above  by  the  poste- 
rior belly  of  the  Digastric,  behind  by  the  Sterno-mastoid,  below  by  the  anterior 
belly  of  the  Omo-hyoid, 

Relations. — By  its  superficial  surface,  with  the  mastoid  process,  the  Platysma,. 
Sterno-mastoid,  part  of  the  Splenius,  Trachelo-mastoid,  and  Stylo-hyoid  muscles, 
and  the  parotid  gland.  By  its  deep  surface,  the  anterior  belly  lies  on  the  Mylo- 
hyoid; the  posterior  belly  on  the  Stylo-glossus,  Stylo-pharyngeus,  and  Hyo-glossus 
muscles,  the  external  carotid  artery  and  its  occipital,  lingual,  facial,  and  ascending 
pharyngeal  branches,  the  internal  carotid  artery,  internal  jugular  vein,  and  hypo- 
glossal nerve. 

The  Stylo-hyoid  (m.  stylohyoideus)  is  a  small,  slender  muscle,  lying  in  front 
of,  and  above,  the  posterior  belly  of  the  Digastric.  It  arises  from  the  back  and 
outer  surface  of  the  styloid  process  of  the  temporal  bone,  near  the  base;  andy 
passing  downward  and  forward,  is  inserted  into  the  body  of  the  hyoid  bone,^ 
just  at  its  junction  with  the  greater  cornu,  and  immediately  above  the  Omo- 
hyoid, This  muscle  is  perforated,  near  its  insertion,  by  the  tendon  of  the 
Digastric, 

Relations. — By  its  superficial  surface  above  with  the  parotid  gland  and  deep 
cervical  fascia;  below  it  is  superficial,  being  situated  immediately  beneath  the  deep 
cervical  fascia.  By  its  deep  surface,  with  the  posterior  belly  of  the  Digastric,  the 
external  carotid  artery,  with  its  lingual  and  facial  branches,  the  Hyo-glossus 
muscle,  and  the  hypoglossal  nerve. 

The  Stylo-hyoid  Ligament  {ligamentum  stylohyoideus) . — In  connection  with  the 
Stylo-hyoid  muscle  may  be  described  a  ligamentous  band,  the  stylo-hyoid  ligament. 
It  is  a  fibrous  cord,  often  containing  a  little  cartilage  in  its  centre,  which  continues 
the  styloid  process  down  to  the  hyoid  bone,  being  attached  to  the  tip  of  the  former 
and  the  small  cornu  of  the  latter.  It  is  often  more  or  less  ossified,  and  in  many 
animals  forms  a  distinct  bone,  the  epihyal. 

The  anterior  belly  of  the  Digastric  should  be  removed,  in  order  to  expose  the  next  muscle. 

The  Mylo-hyoid  (m.  mylohyoideus)  (Fig.  271)  is  a  flat,  triangular  muscle^ 
situated  immediately  beneath  the  anterior  belly  of  the  Digastric,  and  forming, 
with  its  fellow  of  the  opposite  side,  a  muscular  floor  for  the  cavity  of  the  mouth- 
It  arises  from  the  whole  length  of  the  mylo-hyoid  ridge  of  the  lower  jaw,  extend- 
ing from  the  symphysis  in  front  to  the  last  molar  tooth  behind.  The  posterior 
fibres  pass  inward  and  slightly  downward,  to  be  inserted  into  the  body  of  the 
hyoid  bone.  The  middle  and  anterior  fibres  are  inserted  into  a  median  fibrous 
raphe,  extending  from  the  symphysis  of  the  lower  jaw  to  the  hyoid  bone,  where 
they  join  at  an  angle  with  the  fibres  of  the  opposite  muscle.    The  median  raph^ 


THE  SUPRA- HYOID  REGION 


395 


is  sometimes  wanting;  the  muscular  fibres  of  the  two  sides    are   then  directly 
continuous  with  one  another. 

Relations. — By  its  cutaneous  or  under  surface,  with  the  Platysma,  the  anterior 
belly  of  the  Digastric,  the  supra-hyoid  aponeurosis,  the  submaxillary  gland,  sub- 
mental vessels,  and  mylo-hyoid  vessels  and  nerve;  by  its  deep  or  superior  surface, 
with  the  Genio-hyoid,  part  of  the  Hyo-glossus  and  Stylo-glossus  muscles,  the  hypo- 
glossal and  lingual  nerves,  the  submaxillary  ganglion,  the  sublingual  gland,  the 
deep  portion  of  the  submaxillary  gland,  and  Wharton's  duct;  the  sublingual  and 
ranine  vessels,  and  the  buccal  mucous  membrane. 

Dissection. — The  Mylo-hvoid  should  now  be  removed,  in  order  to  expose  the  muscles  which 
lie  beneath;  this  is  effected  by  reflecting  it  from  its  attachments  to  the  hyoid  bone  and  jaw,  and 
separating  it  by  a  vertical  incision  from  its  fellow  of  the  opposite  side. 


Fig.  271. — Mylo-hyoid  muscle.     (Poirier  and  Charpy.) 

The  Genio-hyoid  (m.  geniohijoideus)  (Fig.  272)  is  a  narrow,  slender  muscle, 
situated  immediately  beneath^  the  inner  border  of  the  preceding.  It  arises  from 
the  inferior  genial  tubercle  on  the  inner  side  of  the  symphysis  of  the  jaw,  and 
passes  downward  and  backward,  to  be  inserted  into  the  anterior  surface  of  the 
body  of  the  hyoid  bone.  This  muscle  lies  in  close  contact  with  its  fellow  of  the 
opposite  side,  and  increases  slightly  in  breadth  as  it  descends. 

Relations. — It  is  covered  by  the  Mylo-hyoid  and  lies  along  the  lower  border 
of  the  Genio-hyo-glossus. 

Nerves. — The  anterior  belly  of  the  Digastric  is  supplied  by  the  mylo-hyoid 
branch  of  the  inferior  dental;  its  posterior  belly,  by  the  facial;  the  Stylo-hyoid 
is  supplied  by  the  facial;  the  Mylo-hyoid,  by  the  mylo-hyoid  branch  of  the 
inferior  dental;  the  Genio-hyoid,  by  the  hypoglossal. 

Actions. — This  group  of  muscles  performs  two  very  important  actions.  They 
raise  the  hyoid  bone,  and  with  it  the  base  of  the  tongue,  during  the  act  of  degluti- 
tion; or,  when  the  hyoid  bone  is  fixed  by  its  depressors  and  those  of  the  larynx, 
they  depress  the  lower  jaw.  During  the  first  act  of  deglutition,  when  the  mass 
is  being  driven  from  the  mouth  into  the  pharynx,  the  hyoid  bone,  and  with  it  the 
tongue,  is  carried  upward  and  forward  by  the  anterior  belly  of  the  Digastric,  the 
Mylo-hyoid,  and  Genio-hyoid  muscles.    In  the  second  act,  when  the  mass  is  pass- 

1  This  refers  to  the  depth  of  the  muscles  from  the  skin  in  the  order  of  dissection.  In  the  erect  position  of 
the  body  the  Genio-hyoid  is  above  the  Mylo-hyoid. 


396 


THE  MUSCLES  AND  FASCIjE 


ing  through  the  pharynx,  the  direct  elevation  of  the  hyoid  bone  takes  place  by  the 
combined  action  of  all  the  muscles;  and  after  the  food  has  passed,  the  hyoid  bone 
is  carried  upward  and  backward  by  the  posterior  belly  of  the  Digastric  and  Stylo- 
hyoid muscles,  which  assist  in  preventing  the  return  of  the  morsel  into  the  mouth. 

4.   The  Lingual  Region  (Figs.  272,  273,  274). 

Genio-hyo-glossus.  Stylo-glossus. 

Hyo-glossus.  Palato-glossus. 

Chondro-glossus. 

Dissection. — After  completing  the  dissection  of  the  preceding  muscles,  saw  through  the 
lower  jaw  just  external  to  the  symphysis.  Then  draw  the  tongue  forward,  and  attach  it,  by  a 
stitch,  to  the  nose;  when  its  muscles,  which  are  thus  put  on  the  stretch,  may  be  examined. 


Fig.  272. — Muscles  of  the  tongue.     Left  side. 

The  Gsnio-hyo-glossus  (m.  genioglossus)  has  received  its  name  from  its  triple 
attachment  to  the  jaw,  hyoid  bone,  and  tongue,  but  it  is  better  to  name  it  the 
Genio-glossus,  since  its  attachment  to  the  hyoid  bone  is  very  slight  or  altogether 
absent.  It  is  a  flat,  triangular  muscle,  placed  vertically  on  either  side  of  the 
middle  line,  its  apex  corresponding  with  its  point  of  attachment  to  the  lower  jaw,  its 
base  with  its  insertion  into  the  tongue  and  hyoid  bone.  It  arises  by  a  short  tendon 
from  the  superior  genial  tubercle  on  the  inner  side  of  the  symphysis  of  the  jaw,  im- 
mediately above  the  Genio-hyoid ;  from  this  point  the  muscle  spreads  out  in  a  fan- 
like form,  a  few  of  the  inferior  fibres  passing  downward,  to  be  attached  by  a  thin 
aponeurosis  into  the  upper  part  of  the  body  of  the  hyoid  bone,  a  few  fibres  passing 
between  the  Hyo-glossus  and  Chondro-glossus  to  blend  with  the  Constrictor  mus- 
cles of  the  pharynx;  the  middle  fibres  passing  backward,  and  the  superior  ones 
upward  and  forward,  to  enter  the  whole  length  of  the  under  surface  of  the  tongue, 
from  the  base  to  the  apex.    The  two  muscles  lie  on  either  side  of  the  median  plane; 


THE  LING  UAL  REGION 


397 


behind  (Fig.  273),  they  are  quite  distinct  from  each  other,  and  are  separated  at 
their  insertion  into  the  under  surface  of  the  tongue  by  a  tendinous  raph^,  which 
extends  through  the  middle  of  the  organ;  in  front,  the  two  muscles  are  more  or 
less  blended:  distinct  fasciculi  are  to  be  seen  passing  off  from  one  muscle, 
crossing  the  middle  line,  and  intersecting  with  bundles  of  fibres  derived  from 
the  muscle  on  the  other  side. 

Relations. — By  its  internal  surface  it  is  in  contact  with  its  fellow  of  the  opposite 
side;  by  its  external  surface,  with  the  Inferior  lingualis,  the  Hyo-glossus,  the  lin- 
gual artery  and  hypoglossal  nerve,  the  lingual 
nerve,  and  sublingual  gland;  by  its  upper  bor- 
der, with  the  mucous  membrane  of  the  floor  of 
the  mouth  (frtenum  linguae) ;  by  its  lower  border 
with  the  Genio-hyoid. 

The  Hyo-glossus  (m.  hyoglossv^)  is  a  thin, 
flat,  quadrilateral  muscle  which  arises  from  the 
side  of  the  body  and  whole  length  of  the  greater 
cornu  of  the  hyoid  bone,  and  passes  almost  ver- 
tically upward  to  enter  the  side  of  the  tongue, 
between  the  Stylo-glossus  and  Lingualis.  Those 
fibres  of  this  muscle  which  arise  from  the  body 
are  directed  upward  and  backward,  overlajv 
ping  those  arising  from  the  greater  cornu,  which 
are  directed  upward  and  forward. 

Relations. — By  its  external  surface,  with  the 
Digastric,  the  Stylo-hyoid,  Stylo-glossus,  and 
Mylo-hyoid  muscles,  the  submaxillary  ganglion, 
the  lingual  and  hypo-glossal  nerves,  Wharton's 
duct,  the  ranine  vein,  the  sublingual  gland,  and 
the  deep  portion  of  the  submaxillary  gland.  By 
its  deep  surface,  with  the  Stylo-hyoid  ligament, 
the  Genio-hyo-glossus,  Lingualis,  and  Middle 
constrictor,  the  lingual  vessels,  and  the  glosso- 
pharyngeal nerve. 

The  Chondro-glossus  (to.  chondroglossus)  is 
a  distinct  muscular  slip,  though  it  is  sometimes 
described  as  a  part  of  the  Hyo-glossus,  from 
which,  however,  it  is  separated  by  the  fibres  of 
the  Genio-hyo-glossus,  which  pass  to  the  side  of 

the  pharynx.  It  is  about  three-quarters  to  an  inch  in  length,  and  arises  from  the 
inner  side  and  base  of  the  lesser  cornu  and  contiguous  portion  of  the  body  of  the 
hyoid  bone,  and  passes  directly  upward  to  blend  with  the  intrinsic  muscular 
fibres  of  the  tongue,  between  the  Hyo-glossus  and  Genio-hyo-glossus.  A  small 
slip  of  muscular  fibre  is  occasionally  found,  arising  from  the  cartilago  triticia 
in  the  thyro-hyoid  ligament,  and  passing  upward  and  forward  to  enter  the 
tongue  with  the  hindermost  fibres  of  the  Hyo-glossus. 

The  Stylo-glossus  (to.  styloglossus),  the  shortest  and  smallest  of  the  three  styloid 
muscles,  arises  from  the  anterior  and  outer  side  of  the  styloid  process,  near  its  apex, 
and  from  the  stylo-mandibular  ligament,  to  which  its  fibres,  in  most  cases,  are 
attached  by  a  thin  aponeurosis.  Passing  downward  and  forward  between  the  inter- 
nal and  external  carotid  arteries,  and  becoming  nearly  horizontal  in  its  direction, 
it  divides  upon  the  side  of  the  tongue  into  two  portions:  one  longitudinal,  which 
enters  the  side  of  the  tongue  near  its  dorsal  surface,  blending  with  the  fibres  of  the 
Lingualis  in  front  of  the  Hyo-glossus;  the  other  oblique,  which  overlaps  the 
Hyoglossus  muscle  and  decussates  with  its  fibres. 


CHONDRO-GLOSSUS. 


Fig.  273. — Muscles  of  the  tongue  from  be~ 
low.  (From  a  preparation  in  the  Museum  of 
the  Royai  College  of  Surgeons  of  England.) 


THE  MUSCLES  AND  FASCIA 


Relations. — By  its  external  surface,  from  above  downward,  with  the  parotid 
gland,  the  Internal  pterygoid  muscle,  the  lingual  nerve,  and  the  mucous  membrane 
of  the  mouth;  by  its  internal  surface,  with  the  tonsil,  the  Superior  constrictor,  and 
the  Hyo-glossus  muscle. 

The  Palato-glossus  or  Constrictor  Isthmi  Faucium  (m.  glossopalatinus) , 
although  it  is  one  of  the  muscles  of  the  tongue,  serving  to  draw  its  base  upward 
during  the  act  of  deglutition,  is  more  nearly  associated  with  the  soft  palate,  both 
in  its  situation  and  function ;  it  will  consequently  be  described  with  that  group  of 
muscles. 

Nerves. — The  Palato-glossus  is  probably  innervated  by  the  spinal  accessory 
nerve,  through  the  pharyngeal  plexus;  the  remaining  muscles  of  this  group,  by  the 
hypo-glossal. 

Muscular  Substance  of  the  Tongue  (Figs.  273,  274,  and  275).— The  muscular 
fibres  of  the  tongue  run  in  various  directions.  These  fibres  are  divided  into  two 
sets — Extrinsic  and  Intrinsic.  The  extrinsic  muscles  of  the  tongue  are  those 
which  have  their  origin  external,  and  only  their  terminal  fibres  contained  in  the 
substance  of  the  organ.  They  are:  the  Stylo-glossus,  the  Hyo-glossus,  the  Palato- 
glossus, the  Genio-hyo-glossus,  and  part  of  the 
Superior  constrictor  of  the  pharynx  (Pharyngeo- 
glossus).  The  intrinsic  muscles  are  those  which 
are  contained  entirely  within  the  tongue,  and 
form  the  greater  part  of  its  muscular  struc- 
ture. 

/         9 


CUT    EDGE    OF  SUPERIOR    LINGUALIS. 

Fig.  274. — Muscles  on  the  dorsum  of  the 
tongue. 


■'""'iiJ/Zllli 


Fig.  275. — ;Coronal  section  of  tongue.  Showing  intrinsic 
muscles,  a.  lingual  artery;  b.  Inferior  lingualis,  cut  through; 
C,  fibres  of  Hyo-glossus;  d.  oblique  fibres  of  Stylo-glo.ssus;  e,  in- 
sertion of  Transverse  lingualis;  /,  Superior  lingualis;  fir,  papillae 
to  tongue;  h,  vertical  fibres  of  Genio-hyo-glossus  intersecting 
Transverse  lingualis;  i,  septum.     (Altered  from  Krause.) 


The  tongue  consists  of  symmetrical  halves  separated  from  each  other  in  the 
middle  line  by  a  fibrous  septum  (septum  linguoe).  Each  half  is  composed  of 
muscular  fibres  arranged  in  various  directions,  containing  much  interposed  fat, 
and  supplied  by  vessels  and  nerves. 

To  demonstrate  the  various  fibres  of  the  tongue,  the  organ  should  be  subjected  to 
prolonged  boiling,  in  order  to  soften  the  connective  tissue;  the  dissection  may  then 
be  commenced  from  the  dorsum  (Figs.  274  and  275).  Immediately  beneath  the 
mucous  membrane  is  a  submucous,  fibrous  layer,  into  which  the  muscular  fibres 
which  terminate  on  the  surface  of  the  tongue  are  inserted.    Upon  removing  this, 


THE  LINGUAL  REGION  399 

with  the  mucous  membrane,  the  first  stratum  of  muscular  fibres  is  exposed. 
This  belongs  to  the  group  of  intrinsic  muscles,  and  has  been  named  the  Superior 
lingualis  {m.  longitudinalis  superior).  It  consists  of  a  thin  layer  of  oblique  and 
longitudinal  fibres  which  arise  from  the  submucous  fibrous  layer,  close  to  the 
Epiglottis,  and  from  the  fibrous  septum,  and  pass  forward  and  outward  to  the 
edges  of  the  tongue.  Between  its  fibres  pass  some  vertical  fibres  derived  from 
the  Genio-hyo-glossus  and  from  the  vertical  intrinsic  muscle,  which  will  be  de- 
scribed later  on.  Beneath  this  layer  is  the  second  stratum  of  muscular  fibres, 
derived  principally  from  the  extrinsic  muscles.  In  front  it  is  formed  by  the  fibres 
derived  from  the  Stylo-glossus,  running  along  the  side  of  the  tongue,  and  sending 
one  set  of  fibres  over  the  dorsum  which  run  obliquely  forward  and  inward  to  the 
middle  line,  and  another  set  of  fibres  seen  at  a  later  period  of  the  dissection,  on  to 
the  under  surface  of  the  sides  of  the  anterior  part  of  the  tongue,  which  run  forward 
and  inward,  between  the  fibres  of  the  Hyo-glossus,  to  the  middle  line.  Behind  this 
layer  of  fibres,  derived  from  the  Stylo-glossus,  are  fibres  derived  from  the  Hyo- 
glossus,  assisted  by  some  few  fibres  of  the  Palato-glossus.  The  Hyo-glossus,  enter- 
ing the  side  of  the  under  surface  of  the  tongue,  between  the  Stylo-glossus  and 
Inferior  lingualis,  passes  round  its  margin  and  spreads  out  into  a  layer  on  the  dor- 
sum, which  occupies  the  middle  third  of  the  organ,  and  runs  almost  transversely 
inward  to  the  septum.  It  is  reinforced  by  some  fibres  from  the  Palato-glossus; 
other  fibres  of  this  muscle  pass  more  deeply  and  intermingle  with  the  next  layer. 
The  posterior  part  of  the  second  layer  of  the  muscular  fibres  of  the  tongue  is 
derived  from  those  fibres  of  the  Hyo-glossus  which  arise  from  the  lesser  cornu  of 
thehyoid  bone,  and  are  here  described  as  a  separate  muscle — theChondro-glossus. 
The  fibres  of  this  muscle  are  arranged  in  a  fan-shaped  manner,  and  spread  out  over 
the  posterior  third  of  the  tongue.  Beneath  this  layer  is  the  great  mass  of  the  intrin- 
sic muscles  of  the  tongue,  intersected  at  right  angles  by  the  terminal  fibres  of  one  of 
the  extrinsic  muscles — the  Genio-hyo-glossus.  This  portion  of  the  tongue  is  paler 
in  color  and  softer  in  texture  than  that  already  described,  and  is  sometimes 
designated  the  medullary  portion  in  contradistinction  to  the  firmer  superficial  part, 
which  is  termed  the  cortical  portion.  It  consists  largely  of  transverse  fibres,  the 
Transverse  lingualis  (m.  iransversus  lingua;),  and  of  vertical  fibres,  the  Vertical 
lingualis  (m.  veriicdis  lingua').  The  Transverse  lingualis  forms  the.largest  portion 
of  the  third  layer  of  muscular  fibres  of  the  tongue.  The  fibres  arise  from  the 
median  septum,  and  pass  outward  to  be  inserted  into  the  submucous  fibrous  layer 
at  the  sides  of  the  tongue.  Intermingled  with  these  transverse  intrinsic  fibres  are 
transverse  extrinsic  fibres  derived  from  the  Palato-glossus  and  the  Superior  con- 
strictor of  the  pharynx.  These  transverse  extrinsic  fibres,  however,  run  in  the 
opposite  direction,  passing  inward  toward  the  septum.  Intersecting  the  transverse 
fibres  are  a  large  number  of  vertical  fibres  derived  partly  from  the  Genio-hyo- 
glossus  and  partly  from  intrinsic  fibres,  the  Vertical  lingualis.  The  fibres  derived 
from  the  Genio-hyo-glossus  enter  the  under  surface  of  the  tongue  on  each  side  of 
the  median  septum  from  base  to  apex.  They  ascend  in  a  radiating  manner  to  the 
dorsum,  being  inserted  into  the  submucous  fibrous  layer  covering  the  tongue  on 
each  side  of  the  middle  line.  The  Vertical  lingualis  is  found  only  at  the  borders 
of  the  forepart  of  the  tongue,  external  to  the  fibres  of  the  Genio-hyo-glossus. 
Its  fibres  extend  from  the  upper  to  the  under  surface  of  the  organ,  decussating 
with  the  fibres  of  the  other  muscles,  and  especially  with  the  Transverse  lingualis. 
The  fourth  layer  of  muscular  fibres  of  the  tongue  consists  partly  of  extrinsic  fibres 
derived  from  the  Stylo-glossus,  and  partly  of  intrinsic  fibres,  the  Inferior  lingualis 
(m.  longitudinalis  inferior).  At  the  sides  of  the  under  surface  of  the  organ  are 
some  fibres  derived  from  the  Stylo-glossus,  which,  as  it  runs  forward  at  the  side  of 
the  tongue,  gives  off  fibres  which,  passing  forward  and  inward  between  the  fibres 
of  the  Hyo-glossus,  form  an  inferior  oblique  stratum  which  joins  in  front  with  the 


400  THE  MUSCLES  AND    FASCIA 

anterior  fibres  of  the  Inferior  lingualis.  The  Inferior  Ungualis  is  a  longitudinal 
band,  situated  on  the  under  surface  of  the  tongue,  and  extending  from  the  base  to 
the  apex  of  the  organ.  Behind,  some  of  its  fibres  are  connected  with  the  body  of 
the  hyoid  bone.  It  Hes  between  the  Hyo-glossus  and  the  Genio-hyo-glossus,  and 
in  front  of  the  Hyo-glossus  it  enters  into  relation  with  the  Stylo-glossus,  with  the 
fibres  of  which  it  blends.  It  is  in  relation  by  its  under  surface  with  the  ranine 
artery. 

Surgical  Anatomy. — The  fibrous  septum  which  exists  between  the  two  halves  of  the  tongue 
is  very  complete,  so  that  the  anastomosis  between  the  two  lingual  arteries  is  not  very  free, 
a  fact  often  illustrated  by  injecting  one-half  of  the  tongue  with  colored  size,  while  the  other 
half  is  left  uninjected  or  is  injected  with  size  of  a  different  color. 

This  is  a  point  of  considerable  importance  in  connection  with  removal  of  one-half  of  the 
tongue  for  cancer,  an  operation  which  is  now  frequently  resorted  to  when  the  disease  is  strictly 
confined  to  one  side  of  the  anterior  portion  of  the  tongue.  If  the  mucous  membrane  is  divided 
longitudinally  exactly  in  the  middle  line,  the  tongue  can  be  split  into  halves  along  the  median 
raphe  without  any  appreciable  hemorrhage,  and  the  diseased  half  can  then  be  removed. 

Actions. — The  movements  of  the  tongue,  although  numerous  and  complicated,^ 
may  be  understood  by  carefully  considering  the  direction  of  the  fibres  of  its 
muscles.  The  Genio-hyo-glossi  muscles,  by  means  of  their  posterior  fibres,  draw 
the  base  of  the  tongue  forward,  so  as  to  protrude  the  apex  from  the  mouth.  The 
anterior  fibres  draw  the  tongue  back  into  the  mouth.  The  whole  length  of  these 
two  muscles,  acting  along  the  middle  line  of  the  tongue,  draw  it  downward,  so  as  to 
make  it  concave  from  side  to  side,  forming  a  channel  along  which  fluids  may  pass 
toward  the  pharynx,  as  in  sucking.  The  Hyo-glossi  muscles  depress  the  tongue 
and  draw  down  its  sides,  so  as  to  render  it  convex  from  side  to  side.  The  Stylo- 
glossi muscles  draw  the  tongue  upward  and  backward.  The  Palato-glossi  muscles 
draw  the  base  of  the  tongue  upward.  With  regard  to  the  intrinsic  muscles,  both 
the  Superior  and  Inferior  linguales  tend  to  shorten  the  tongue,  but  the  former,  in 
addition,  turn  the  tip  and  sides  upward  so  as  to  render  the  dorsum  concave,  while 
the  latter  pull  the  tip  downward  and  cause  the  dorsum  to  become  convex.  The 
Transverse  lingualis  narrows  and  elongates  the  tongue,  and  the  Vertical  lingualis 
flattens  and  broadens  it.  The  complex  arrangement  of  the  muscular  fibres  of 
the  tongue,  and  the  various  directions  in  which  they  run,  give  to  this  organ  the 
power  of  assuining  the  various  forms  necessary  for  the  enunciation  of  the  different 
consonantal  sounds;  and  Dr.  Macalister  states  that  "there  is  reason  to  believe 
that  the  musculature  of  the  tongue  varies  in  different  races  owing  to  the  hereditary 
practice  and  habitual  use  of  certain  motions  required  for  enunciating  the  several 
vernacular  languages." 

5.  The  Pharyngeal  Region  (Figs.  276,  277,  278). 

Inferior  constrictor.  Superior  constrictor. 

Middle  constrictor.  Stylo-pharyngeus. 

Palato-pharyngeus.      1  .^  ,        x-      \ 

c^  ^   •  ■>  r         (See  next  section.) 

Salpmgo-pharyngeus.  J  ^ 

Dissection  (Fig.  276). — In  order  to  examine  the  muscles  of  the  pharynx,  cut  through  the 
trachea  and  oesophagus  just  above  the  sternum,  and  draw  them  upward  by  dividing  the  loose 
areolar  tissue  connecting  the  pharynx  with  the  front  of  the  vertebral  column.  The  parts  being 
drawn  well  forward,  apply  the  edge  of  the  saw  immediately  behind  the  styloid  processes,  and 
saw  the  base  of  the  skull  through  from  below  upward.  The  pharynx  and  mouth  should  then 
be  stuffed  with  tow,  in  order  to  distend  its  cavity  and  render  the  muscles  tense  and  easier  of 
dissection. 

The  Inferior  Constrictor  (w.  constrictor  pharipigis  inferior),  the  most  superficial 
and  thickest  of  the  three  constrictors,  arises  from  the  sides  of  the  cricoid  and 
thyroid  cartilages.    To  the  cricoid  cartilage  it  is  attached  in  the  interval  between 


THE   PHARYNGEAL    REGION 


401 


the  Crico-thyroid  muscle  in  front  and  the  articular  facet  for  the  thyroid  cartilage 
behind.  To  the  thyroid  cartilage  it  is  attached  to  the  oblique  line  on  the  side  of 
the  great  ala,  the  cartilaginous  surface  behind  it,  nearly  as  far  as  its  posterior  border, 
and  to  the  inferior  cornu.  From  these  attachments  the  fibres  spread  backward  and 
inward,  to  be  inserted  into  the  fibrous  raphd  in  the  posterior  median  line  of  the 
pharynx.  The  inferior  fibres  are  horizontal,  and  continuous  with  the  fibres  of  the 
oesophagus :  the  rest  ascend,  increasing  in  obliquity,  and  overlap  the  Middle  con^ 
stricter. 

Relations. — It  is  covered  by  a  thin  membrane  which  surrounds  the  entire 
pharynx,  bucco-pharyngeal  fascia  (fascia  buccopharyngea) .  Behind,  it  is  in 
relation  with  the  vertebral  column 
and  the  prevertebral  fascia  and  mus- 
cles; laterally,  with  the  thyroid  gland, 
the  common  carotid  artery,  and  the 
Sterno-thyroid  muscle;  by  its  internal 
surface,  with  the  Middle  constrictor, 
the  Stylo-pharyngeus,  Palato-pharyn- 
geus,  the  fibrous  coat  and  mucous 
membrane  of  the  pharynx.  The  in- 
ternal laryngeal  nerve  and  the  laryn- 
geal branch  of  the  Superior  Thyroid 
artery  pass  near  the  upper  border,  and 
the  inferior,  or  recurrent  laryngeal 
nerve,  and  the  laryngeal  branch  of  the 
Inferior  Thyroid  artery,  beneath  the 
lower  border  of  this  muscle,  previous  to 
their  entering  the  larynx. 

The  Middle  Constrictor  (m.  constric- 
tor jyharyngis  medius)  is  a  flattened, 
fan-shaped  muscle,  smaller  than  the 
preceding.  It  arises  from  the  whole 
length  of  the .  upper  border  of  the 
greater  cornu  of  the  hyoid  bone,  from 
the  lesser  cornu,  and  from  the  stylo- 
hyoid ligament.  The  fibres  diverge 
from  their  origin,  the  lower  ones  de- 
scending beneath  the  Inferior  con- 
stricter,  the  middle  fibres  passing 
transversely,  and  the  upper  fibres  ascending  and  overlapping  the  Superior  con- 
strictor. The  muscle  is  inserted  into  the  posterior  median  fibrous  raphe,  blending 
in  the  middle  line  with  the  one  of  the  opposite  side. 

Relations. — Between  this  muscle  and  the  Superior  constrictor  are  the  glosso- 
pharyngeal nerve,  the  Stylo-pharyngeus  muscle  and  the  stylo-hyoid  ligament; 
and  between  it  and  the  Inferior  constrictor  is  the  superior  laryngeal  nerve. 
Behind,  it  lies  on  the  vertebral  column,  the  Longus  colli,  and  the  Rectus  capitis 
anticus  major.  On  each  side  it  is  in  relation  with  the  carotid  vessels,  the  pharyn- 
geal plexus,  and  some  lymphatic  glands.  Near  its  origin  it  is  covered  by  the 
Hyo-glossus,  the  lingual  vessels  being  placed  between  the  two  muscles.  It  lies 
upon  the  Superior  constrictor,  the  Stylo-pharyngeus,  the  Palato-pharyngeus,  the 
fibrous  coat,  and  the  mucous  membrane  of  the  larynx. 

The  Superior  Constrictor  (to.  constrictor  pharyngis  superior)  is  a  quadrilateral 
muscle,  thinner  and  paler  than  the  other  constrictors,  and  situated  at  the  upper 
part  of  the  pharynx.  It  arises  from  the  lower  third  of  the  posterior  margin  of  the 
internal  pterygoid  plate  and  its  hamular  process,  from  the  contiguous  portion  of  the 

26 


Fig.  276. — Muscles  of  the  pharynx.     External  view. 


402 


THE   3fUSCLES   AND    FASCIA 


palate  bone  and  the  reflected  tendon  of  the  Tensor  palati  muscle,  from  the  pterygo- 
maxillary  ligament,  from  the  alveolar  process  above  the  posterior  extremity  of  the 
mylo-hyoid  ridge,  and  by  a  few  fibres  from  the  side  of  the  tongue.  From  these 
points  the  fibres  curve  backward,  to  be  inserted  into  the  median  raphe,  being  also 
prolonged  by  means  of  a  fibrous  aponeurosis  to  the  pharyngeal  spine  on  the  basilar 
process  of  the  occipital  bone.  The  superior  fibres  arch  beneath  the  I^evator  palati 
and  the  Eustachian  tube,  the  interval  between  the  upper  border  of  the  muscle  and 
the  basilar  process  being  deficient  in  muscular  fibres  and  closed  by  a  portion 
of  the  pharyngeal  aponeurosis  [fascia  pharyngobasilaris) .  This  interval  is  known  as 
the  sinus  of  Morgagni. 


ACCESSORY  BUN 
FROM  PETROSA 
TION  OF  TEMPOI 


STYLOID  PROC 


EXPANSION  OF 
STYLO-PHARYNGEUS 


g       EXPANSION  OF 

PALATO-PHARYNGEUS 


Fig.  277. — The  muscles  of  the  pharynx.    On  the  right  side  most  of  the  inferior  constrictor  has  been  removed, 
on  the  left  side  the  Digastric  and  Stylo-hyoid  have  been  removed.     (Spalteholz.) 


Relations. — By  its  outer  surface,  with  the  prevertebral  fascia  and  muscles, 
the  vertebral  column,  the  internal  carotid  and  ascending  pharyngeal  arteries,  the 
internal  jugular  vein  and  pharyngeal  venous  plexus,  the  glosso-pharyngeal,  pneu- 
mogastric,  spinal  accessory,  hypoglossal,  lingual,  and  sympathetic  nerves,  the 
Middle  constrictor  and  Internal  pterygoid  muscles,  the  Styloid  process,  the  Stylo- 


THE  PALATAL    REGION  403 

hyoid  ligament,  and  the  Stylo-pharyngeus.  By  its  internal  surface,  with  the 
Palato-pharyngeus,  the  tonsil,  the  fibrous  coat  and  mucous  membrane  of  the 
pharynx. 

The  Stylo-pharyngeus  (m.  stylopharyngeus)  is  a  long,  slender  muscle,  round 
above,  broad  and  thin  below.  It  arises  from  the  inner  side  of  the  base  of  the 
styloid  process  of  the  temporal  bone,  passes  downward  along  the  side  of  the 
pharynx  between  the  Superior  and  Middle  constrictors,  and  spreads  out  beneath 
the  mucous  membrane,  where  some  of  its  fibres  are  lost  in  the  Constrictor  muscles; 
and  others,  joining  with  the  Palato-pharyngeus,  are  inserted  into  the  posterior 
border  of  the  thyroid  cartilage.  The  glosso-pharyngeal  nerve  runs  on  the  outer 
side  of  this  muscle,  and  crosses  over  it  in  passing  forward  to  the  tongue. 

Relations. — Externally,  with  the  Stylo-glossus  muscle,  the  parotid  gland,  the 
external  carotid  artery,  and  the  ^Middle  constrictor;  internally,  with  the  internal 
carotid,  the  internal  jugular  vein,  the  Superior  constrictor,  Palato-pharyngeus, 
and  mucous  membrane. 

Nerves.— The  Constrictors  are  supplied  by  branches  from  the  pharyngeal 
plexus.  The  Inferior  constrictor  also  receives  an  additional  branch  from  the 
external  laryngeal  nerve  and  one  frcm  the  recurrent  laryngeal.  The  Stylo- 
pharyngeus  is  supplied  by  the  glosso-pharyngeal  nerve. 

Actions. — When  deglutition  is  about  to  be  performed,  the  pharynx  is  drawn 
upward  and  dilated  in  different  directions,  to  receive  the  morsel  propelled  into  it 
from  the  mouth.  The  Stylo-pharyngei,  which  are  much  farther  removed  from 
one  another  at  their  origin  than  at  their  insertion,  draw  the  sides  of  the  pharynx 
upward  and  outward,  and  so  increase  its  transverse  diameter,  its  breadth  in  the 
antero-posterior  direction  being  increased  by  the  larynx  and  tongue  being  carried 
forward  in  their  ascent.  As  soon  as  the  morsel  is  received  in  the  pharynx,  the 
Elevator  muscles  relax,  the  bag  descends,  and  the  Constrictors  contract  upon 
the  morsel,  and  convey  it  gradually  downward  into  the  oesophagus.  Besides  its 
action  in  deglutition,  the  pharynx  also  exerts  an  important  influence  in  the  modu- 
lation of  the  voice,  especially  in  the  production  of  the  higher  tones. 

6.  The  Palatal  Region  (Fig.  278.) 

Levator  palati.  Palato-glossus. 

Tensor  palati.  Palato-pharyngeus. 

Azygos  uvulae.  Salpingo-pharyngeus. 

Dissection  (Fig.  278). — Lay  open  the  pharynx  from  behind  by  a  vertical  incision  extending 
from  its  upper  to  its  lower  part,  and  partially  divide  the  occipital  attachment  by  a  transverse 
incision  on  each  side  of  the  vertical  one;  the  posterior  surface  of  the  soft  palate  is  then  exposed. 
Having  fixed  the  uvula  so  as  to  make  it  tense,  the  mucous  membrane  and  glands  should  be 
carefully  removed  from  the  posterior  surface  of  the  soft  palate,  and  the  muscles  of  this  part 
are  at  once  exposed. 

The  Levator  Palati  (m.  levator  veil  palatini)  is  a  long,  thick,  rounded  muscle, 
placed  on  the  outer  side  of  the  posterior  nares.  It  arises  from  the  under  surface  of 
the  apex  of  the  petrous  portion  of  the  temporal  bone,  and  from  the  inner  surface 
of  the  cartilaginous  portion  of  the  Eustachian  tube;  after  passing  into  the  pharynx, 
above  the  upper  concave  margin  of  the  Superior  constrictor,  it  passes  obliquely 
downward  and  inward,  its  fibres  spreading  out  in  the  soft  palate  as  far  as  the 
middle  line,  where  they  blend  with  those  of  the  opposite  side. 

Relations. — Externally,  with  the  Tensor  palati  and  Superior  constrictor  and 
Eustachian  tube;  internally,  with  the  mucous  membrane  of  the  pharynx;  pos- 
teriorly, with  the  posterior  fasciculus  of  the  Palato-pharyngeus,  the  Azygos  uvulae, 
and  the  mucous  lining  of  the  soft  palate. 


404 


THE   3rU^CLES   AND    FASCIA 


The  Gircumfiexus  or  Tensor  Palati  {m.  tensor  veli  palatini)  is  a  broad,  thin, 
ribbon-Uke  muscle,  placed  on  the  outer  side  of  the  Levator  palati,  and  consisting  of 
a  vertical  and  a  horizontal  portion.  The  vertical  portion  arises  by  a  flat  lamella 
from  the  scaphoid  fossa  at  the  base  of  the  internal  pterygoid  plate;  from  the  spine 
of  the  sphenoid  and  the  outer  side  of  the  cartilaginous  portion  of  the  Eustachian 
tube:  descending  vertically  between  the  internal  pterygoid  plate  and  the  inner  sur- 
face of  the  Internal  pterygoid  muscle,  it  terminates  in  a  tendon,  which  winds  round 
the  hamular  process,  being  retained  in  this  situation  by  some  of  the  fibres  of  origin 
of  the  Internal  pterygoid  muscle.  Between  the  hamular  process  and  the  tendon  is 
a  small  bursa  (bursa  m.  tensoris  veli  palati).   The  tendon  or  horizontal  portion  then 


<>  p  h  a 
Fig.  278. — Muscles  of  the  soft  palate,  the  pharynx  being  laid  open  from  behind. 


passes  horizontally  inward,  and  is  inserted  into  a  broad  aponeurosis,  the  palatini 
aponeurosis,  and  into  the  transverse  ridge  on  the  horizontal  portion  of  the  palate 
bone. 

Relations. — Externally,  with  the  Internal  pterygoid;  internally,  with  the  Levator 
palati,  from  which  it  is  separated  by  the  Eustachian  tube  and  Superior  constrictor 
and  with  the  internal  pterygoid  plate.  In  the  soft  palate  its  tendon  and  the  pala- 
tine aponeurosis  are  anterior  to  those  of  the  I^evator  palati,  being  covered  by  the 
Palato-glossus  and  the  mucous  membrane. 

Palatine  Aponeurosis. — Attached  to  the  posterior  border  of  the  hard  palate  is 
a  thin,  firm,  fibrous  lamella  which  supports  the  muscles  and  gives  strength  to  the 
soft  palate.  It  is  thicker  above  than  below,  where  it  becomes  very  thin  and 
difficult  to  define.     Laterally,  it  is  continuous  with  the  pharyngeal  aponeurosis. 


THE   PALATAL    REGION  405 

The  Azygos  Uvulae  {m.  uvuhc)  is  not  a  single  muscle,  as  would  be  inferred  from 
its  name,  but  a  pair  of  narrow  cylindrical  fleshy  fasciculi  placed  on  either  side  of  the 
median  line  of  the  soft  palate.  Each  muscle  arises  from  the  posterior  nasal  spine 
of  the  palate  bone  and  from  the  contiguous  tendinous  aponeurosis  of  the  soft  palate, 
and  descends  to  be  inserted  into  the  uvula. 

Relations. — Anteriorly,  with  the  tendinous  expansion  of  the  Levatores  palati; 
behind,  with  the  posterior  fasciculus  of  the  Palato-pharyngeus  and  the  mucous 
membrane. 

The  next  two  muscles  are  exposed  by  removing  the  mucous  membrane  from  the  pillars  of 
the  fauces  throughout  nearly  their  whole  extent. 

The  Palato-glossus  or  the  Constrictor  Isthmi  Faucium  (to.  glossopalatinns) 
is  a  small  fleshy  fasciculus,  narrower  in  the  middle  than  at  either  extremity, 
forming,  with  the  mucous  membrane  covering  its  surface,  the  anterior  pillar  of 
the  soft  palate.  It  arises  from  the  anterior  surface  of  the  soft  palate  on  each 
side  of  the  uvula,  and,  passing  downward,  forward,  and  outward  in  front  of  the 
tonsil,  is  inserted  into  the  side  of  the  tongue,  some  of  its  fibres  spreading  over 
the  dorsum,  and  others  passing  deeply  into  the  substance  of  the  organ  to  inter- 
mingle with  the  Transverse  lingualis.  In  the  soft  palate  the  fibres  of  this  muscle 
are  continuous  with  those  of  the  muscle  of  the  opposite  side. 

The  Palato-pharyngeus  (to.  pharyngopalatinus)  is  a  long,  fleshy  fasciculus, 
narrower  in  the  middle  than  at  either  extremity,  forming,  with  the  mucous 
membrane  covering  its  surface,  the  posterior  pillar  of  the  soft  palate.  It  is  sepa- 
rated from  the  Palato-glossus  by  an  angular  interval,  in  which  the  tonsil  is 
lodged.  It  arises  from  the  soft  palate  by  an  expanded  fasciculus,  which  is 
divided  into  two  parts  by  the  Levator  palati  and  Azygos  uvulae.  The  posterior 
fasciculus  lies  in  contact  with  the  mucous  membrane,  and  also  joins  with  the 
corresponding  muscle  in  the  middle  line;  the  anterior  fasciculus,  the  thicker,  lies 
in  the  soft  palate  between  the  Levator  and  Tensor,  and  joins  in  the  middle  line 
the  corresponding  part  of  the  opposite  muscle.  Passing  outward  and  downward 
behind  the  tonsil,  the  Palato-pharyngeus  joins  the  Stylo-pharyngeus,  and  is 
inserted  with  that  muscle  into  the  posterior  border  of  the  thyroid  cartilage,  some 
of  its  fibres  being  lost  on  the  side  of  the  pharynx,  and  others  passing  across  the 
middle  line  posteriorly  to  decussate  with  the  muscle  of  the  opposite  side. 

Relations. — In  the  soft  palate  its  posterior  svrface  is  covered  by  mucous  mem- 
brane, from  which  it  is  separated  by  a  layer  of  palatine  glands.  By  its  anterior 
surface  it  is  in  relation  with  the  Tensor  palati.  Where  it  forms  the  posterior  pillar 
of  the  fauces  it  is  covered  by  mucous  membrane,  excepting  on  its  outer  surface.  In 
the  pharynx  it  lies  between  the  mucous  membrane  and  the  Constrictor  muscles. 

The  Salpingo-pharyngeus  arises  from  the  inferior  part  of  the  Eustachian  tube 
near  its  orifice ;  it  passes  downward  and  blends  with  the  posterior  fasciculus  of 
the  Palato-pharyngeus. 

In  a  dissection  of  the  soft  palate  from  its  posterior  or  nasal  surface  to  its  ante- 
rior or  oral  surface,  the  muscles  Avould  be  exposed  in  the  following  order — viz.,  the 
posterior  fasciculus  of  the  Palato-pharyngeus,  covered  over  by  the  mucous  mem- 
brane reflected  from  the  floor  of  the  nasal  fossa?;  the  Azygos  uvulae;  the  Levator 
palati;  the  anterior  fasciculus  of  the  Palato-pharyngeus;  the  aponeurosis  of  the 
Tensor  palati,  and  the  Palato-glossus,  covered  over  by  a  reflection  from  the  oral 
mucous  membrane. 

Nerves. — The  Tensor  palati  is  supplied  by  a  branch  from  the  otic  ganglion; 
the  remaining  muscles  of  this  group  are  in  all  probability  supplied  by  the  internal 
branch  of  the  spinal  accessory,  whose  fibres  are  distributed  along  with  certain 
branches  of  the  pneumogastric  through  the  pharyngeal  plexus.^    It  is  possible, 

1  Journal  of  Anatomy  anrt  Physiology,  vol.  xxiii.  p.  523. 


406 


THE   MUSCLES  AND    FASCIA 


however,  that  the  Levator  palati  may  be  suppHed  by  the  facial  through  the  Petrosal 
branch  of  the  Vidian. 

Actions. — During  the  first  stage  of  deglutition  the  morsel  of  food  is  driven 
back  into  the  fauces  by  the  pressure  of  the  tongue  against  the  hard  palate,  the 
base  of  the  tongue  being,  at  the  same  time,  retracted,  and  the  larynx  raised  with 
the  pharynx,  and  carried  forward  under  it.  During  the  second  stage  the  entrance 
to  the  larynx  is  closed,  not,  as  was  formerly  supposed,  by  the  folding  backward 
of  the  epiglottis  over  it,  but,  as  Anderson  Stuart  has  shown,  by  the  drawing 
forward  of  the  arytenoid  cartilages  toward  the  cushion  of  the  epiglottis — a  move- 
ment produced  by  the  contraction  of  the  External  thyro-arytenoid,  the  Arytenoid, 
and  Aryteno-epiglottidean  muscles. 

The  morsel  of  food  after  leaving  the  tongue  passes  on  to  the  posterior  or  laryn- 
geal surface  of  the  epiglottis,  and  glides  along  this  for  a  certain  distance;^  then 
the  Palato-glossi  muscles,  the  constrictors  of  the  fauces,  contract  behind  the  food; 
the  soft  palate  is  slightly  raised  by  the  Levator  palati,  and  made  tense  by  the 
Tensor  palati;  and  the  Palato-pharyngei,  by  their  contraction,  pull  the  pharynx 
upward  over  the  morsel  of  food,  and  at  the  same  time  come  nearly  together,  the 
uvula  filling  up  the  slight  interval  between  them.  By  these  means  the  food  is 
prevented  passing  into  the  upper  part  of  the  larynx  or  the  posterior  nares;  at 
the  same  time  the  latter  muscles  form  an  inclined  plane,  directed  obliquely  down- 
ward and  backward,  along  the  under  surface  of  which  the  morsel  descends  into 
the  lower  part  of  the  pharynx.  The  Salpingo-pharyngeus  raises  the  upper  and 
lateral  part  of  the  pharynx — i.  e.,  that  part  which  is  above  the  point  where  the 
Stylo-pharyngeus  is  attached  to  the  pharynx. 

Surgical  Anatomy. — The  muscles  of  the  soft  palate  should  be  carefully  dissected,  the  rela- 
tions they  bear  to  the  surrounding  parts  especially  examined,  and  their  action  attentively  studied 
upon  the  dead  subject,  as  the  surgeon  is  required  to  divide  one  or  more  of  these  muscles  in  the 
operation  of  staphylorraphy.  Sir  W.  Fergusson  was  the  first  to  show  that  in  the  congenital 
deficiency  called  clep,  palate  the  edges  of  the  fissure  are  forcibly  separated  by  the  action  of  the 
Levatores  palati  and  Palato-pharyngei  muscles,  producing  very  considerable  impediment  to  the 
healing  process  after  the  performance  of  the  operation  for  uniting  their  margins  by  adhesion ;  he 
consequently  recommended  the  division  of  these  muscles  as  one  of  the  most  important  steps  in 
the  operation.  This  he  effected  by  an  incision  made  with  a  curved  knife  introduced  behind  the 
soft  palate.  The  incision  is  to  be  half-way  between  the  hamular  process  and  Eustachian  tube 
and  perpendicular  to  a  line  drawn  between  them.  This  incision  perfectly  accomplishes  the 
division  of  the  Levator  palati.  The  Palato-pharyngeus  may  be  divided  by  cutting  across  the 
posterior  pillar  of  the  soft  palate,  just  below  the  tonsil,  with  a  pair  of  blunt-pointed  curved 
scissors;  and  the  anterior  pillar  may  be  divided  also.  To  divide  the  Levator  palati  the  plan 
recommended  by  Mr.  Pollock  is  to  be  greatly  preferred.  The  soft  palate  being  put  upon  the 
stretch,  a  double-edged  knife  is  passed  through  it  just  on  the  inner  side  of  the  hamular  process 
and  above  the  line  of  the  Levator  palati.  The  handle  being  now  alternately  raised  and  depressed, 
a  sweeping  cut  is  made  along  the  posterior  surface  of  the  soft  palate,  and  the  knife  withdrawn, 
leaving  only  a  small  opening  in  the  mucous  membrane  on  the  anterior  surface.  If  this  operation 
is  performed  on  the  dead  body  and  the  parts  afterward  dissected,  the  Levator  palati  will  be 
found  completely  divided.  In  the  present  day,  however,  this  division  of  the  muscles,  as  part 
of  the  operation  of  staphylorraphy,  is  not  so  much  insisted  upon.  All  tension  is  prevented  by 
making  longitudinal  incisions  on  either  side,  parallel  to  the  cleft  and  just  internal  to  the  hamular 
process,  in  such  a  position  as  to  avoid  the  posterior  palatine  artery. 

7.  The  Anterior  Vertebral  Region  (Fig.  279). 

Rectus  capitis  anticus  major.  Rectus  capitis  lateralis. 

Rectus  capitis  anticus  minor.  Longus  colli. 

The  Rectus  Capitis  Anticus  Major  or  the  Longus  Capitis,  broad  and 
thick  above,  narrow  below,   appears  hke   a    continuation   upward  of  the   Sca- 

^  We  now  know  that  normal  deglutition  can  be  carried  out  when  the  epiglottis  is  so  small  that  it  cannot  coyer 
the  opening  into  the  larynx,  or  when  it  has  been  removed  surgically.  In  such  cases  the  sphincter  muscles  which 
surround  the  laryngeal  aperture  contract  during  swallowing  and  prevent  the  entrance  of  foreign  bodies  mto  the 
larynx. — Ed. 


THE   ANTERIOR    VERTEBRAL    REGION 


407 


leniis  anticus.  It  arises  by  four  tendinous  slips  from  the  anterior  tubercles  of 
the  transverse  processes  of  the  third,  fourth,  fifth,  and  sixth  cervical  vertebrae,  and 
ascends,  converging  toward  its  fellow  of  the  opposite  side,  to  be  inserted  into  the 
basilar  process  of  the  occipital  bone. 

Relations. — By  its  anterior  surface,  with  the  pharynx,  the  sympathetic  nerve, 
and  the  sheath  enclosing  the  internal  and  common  carotid  artery,  internal  jugular 
vein,  and  pneumogastric  nerve;  by  its  ^posterior  surface,  with  the  Longus  colli,  the 
Rectus  capitis  anticus  minor,  and  the  upper  cervical  vertebrae. 


Fig.  279. — The  prevertebral  muscles. 

The  Rectus  Capitis  Anticus  Minor  is  a  short,  flat  muscle,  situated  imme- 
diately behind  the  upper  part  of  the  preceding.  It  arises  from  the  anterior 
surface  of  the  lateral  mass  of  the  atlas  and  from  the  root  of  its  transverse  process, 
and,  passing  obliquely  upward  and  inward,  is  inserted  into  the  basilar  process 
immediately  behind  the  preceding  muscle. 

Relations. — By  its  anterior  surface,  with  the  Rectus  capitis  anticus  major;  by 
its  posterior  surface,  with  the  front  of  the  occipito-atlantal  articulation. 

The  Rectus  Capitis  Lateralis  is  a  short,  flat  muscle,  which  arises  from  the 
upper  surface  of  the  transverse  process  9f  the  atlas,  and  is  inserted  into  the  under 
surface  of  the  jugular  process  of  the  occipital  bone. 

Relations. — By  its  anterior  surface,  with  the  internal  jugular  vein;  by  its  'pos- 
terior surface,  with  the  vertebral  artery.  On  its  outer  side  lies  the  occipital  artery; 
on  its  inner  side,  the  suboccipital  nerve. 

The  Longus  Colli  is  a  long,  flat  muscle,  situated  on  the  anterior  surface  of  the 
spine,  between  the  atlas  and  the  third  dorsal  vertebra.    It  is  broad  in  the  middle, 


408 


THE  MUSCLES  AND    FASCIA 


narrow  and  pointed  at  each  extremity,  and  consists  of  three  portions:  a  superior 
obhque,  an  inferior  obUque,  and  a  vertical  portion.  The  superior  oblique  portion 
arises  from  the  anterior  tubercles  of  the  transverse  processes  of  the  third,  fourth, 
and  fifth  cervical  vertebrae,  and,  ascending  obliquely  inward,  is  inserted  by  a  nar- 
row tendon  into  the  tubercle  on  the  anterior  arch  of  the  atlas.  The  inferior  oblique 
portion,  the  smallest  part  of  the  muscle,  arises  from  the  front  of  the  bodies  of  the 
first  two  or  three  dorsal  vertebrae,  and,  ascending  oblicjuely  outward,  is  inserted 
into  the  anterior  tubercles  of  the  transverse  processes  of  the  fifth  and  sixth  cervi- 
cal vertebrae.  The  vertical  portion  lies  directly  on  the  front  of  the  spine;  it  arises, 
below,  from  the  front  of  the  bodies  of  the  upper  three  dorsal  and  lower  three  cer- 
vical vertebrae,  and  is  inserted  above  into  the  front  of  the  bodies  of  the  second, 
third,  and  fourth  cervical  vertebrae. 

Relations. — By  its  anterior  surface,  with  the  prevertebral  fascia,  the  pharynx, 
the  oesophagus,  sympathetic  nerve,  the  sheath  of  the  great  vessels  of  the  neck, 
the  inferior  thyroid  artery,  and  recurrent  laryngeal  nerve;  by  its  ^posterior  surface, 
with  the  cervical  and  dorsal  portions  of  the  spine.  Its  inner  border  is  separated 
from  the  opposite  muscle  by  a  considerable  interval  below,  but  they  approach 
each  other  above. 


8.   The  Lateral  Vertebral  Region  (Figs.  279,  280). 


Scalenus  anticus. 


Scalenus  medius. 


Scalenus  posticus. 

The   Scalenus   Anticus   (w.  scalenus  anterior)  is  a   conical-shaped    muscle, 
situated    deeply    at    the    side   of    the    neck,    behind    the    Sterno-mastoid.      It 

arises  from  the  anterior  tubercles  of 
the  transverse  processes  of  the  third, 
fourth,  fifth,  and  sixth  cervical  verte- 
brae, and,  descending  almost  vertically, 
is  inserted  by  a  narrow,  flat  tendon 
into  the  Scalene  tubercle  on  the  inner 
border  and  upper  surface  of  the  first 
rib.  The  lower  part  of  this  muscle  sep- 
arates the  subclavian  artery  and  vein, 
the  latter  being  in  front,  and  the  former, 
with  the  brachial  plexus,  behind. 

Relations. — In  front,  with  the  clav- 
icle, the  Subclavius,  Sterno-mastoid, 
and  Omo-hyoid  muscles,  the  Trans- 
versalis  colli,  the  suprascapular  and 
ascending  cervical  arteries,  the  subcla- 
vian vein,  and  the  phrenic  nerve;  by 
its  'posterior  surface,  with  the  Scalenus 
medius,  pleura,  subclavian  artery,  and 
brachial  plexus  of  nerves.  It  is  sep- 
arated from  the  Longus  colli,  on  the 
inner  side,  by  the  vertebral  artery. 
On  the  anterior  tubercles  of  the  trans- 
verse processes  of  the  cervical  vertebrae, 
between  the  attachments  of  the  Scale- 
nus anticus  and  Longus  colli,  lies  the 
ascending  cervical  branch  of  the  infe- 
rior thyroid  artery. 

The  Scalenus  Medius,  the  largest  and  longest  of  the  three  Scaleni,  arises  from 
the  posterior  tubercles  of  the  transverse  processes  of  the  lower  six  cervical  vertebrae, 


Fig.  280. — Scaleni  muscles.     (Poirier  and  Charpy.) 


THE   LATERAL    VERTEBRAL    REGION  409 

and,  descending  along  the  side  of  the  vertebral  column,  is  inserted  by  a  broad 
attachment  into  the  upper  surface  of  the  first  rib,  behind  the  groove  for  the  sub- 
clavian artery,  as  far  back  as  the  tubercle.  It  is  separated  from  the  Scalenus 
anticus  by  the  subclavian  artery  below  and  the  cervical  nerves  above.  The  pos- 
terior thoracic,  or  nerve  of  Bell,  is  formed  in  the  substance  of  the  Scalenus  medius 
and  emerges  from  it.    The  nerve  to  the  Rhomboids  also  pierces  it. 

Relations. — By  its  anterior  surface,  with  the  Sterno-mastoid;  it  is  crossed  by 
the  clavicle,  the  Omo-hyoid  muscle,  subclavian  artery,  and  cervical  nerves.  To 
its  outer  side  is  the  Levator  anguli  scapulae  and  the  Scalenus  posticus  muscle. 

The  Scalenus  Posticus  (m.  scalenus  posterior),  the  smallest  of  the  three  Scaleni, 
arises,  by  two  or  three  separate  tendons,  from  the  posterior  tubercles  of  the  trans- 
verse processes  of  the  lower  two  or  three  cervical  vertebrae,  and,  diminishing  as  it 
descends,  is  inserted  by  a  thin  tendon  into  the  outer  surface  of  the  second  rib, 
behind  the  attachment  of  the  Serratus  magnus.  This  is  the  most  deeply  placed  of 
the  three  Scaleni,  and  is  occasionally  blended  with  the  Scalenus  medius. 

Nerves.— The  Rectus  capitis  anticus  major  and  minor  and  the  Rectus  lateralis 
are  supplied  by  the  first  cervical  nerve,  and  from  the  loop  formed  between  it  and 
the  second;  the  I>ongus  colli  and  Scaleni,  by  branches  from  the  anterior  divisions 
of  the  lower  cervical  nerves  (fifth,  sixth,  seventh,  and  eighth)  before  they  form  the 
brachial  plexus.  The  Scalenus  medius  also  receives  a  filament  from  the  deep 
external  branches  of  the  cervical  plexus. 

Actions. — The  Rectus  anticus  major  and  minor  are  the  direct  antagonists  of  the 
muscles  at  the  back  of  the  neck,  serving  to  restore  the  head  to  its  natural  position 
after  it  has  been  drawn  backward.  These  muscles  also  serve  to  flex  the  head,  and, 
from  their  obliquity,  rotate  it,  so  as  to  turn  the  face  to  one  or  the  other  side.  The 
Longus  colli  flexes  and  slightly  rotates  the  cervical  portion  of  the  spine.  The 
Scaleni  muscles,  when  they  take  their  fixed  point  from  above,  elevate  the  first  and 
second  ribs,  and  are,  therefore,  inspiratory  muscles.  When  they  take  their  fixed 
point  from  below,  they  bend  the  spinal  column  to  one  or  the  other  side.  If  the 
muscles  of  both  sides  act,  lateral  movement  is  prevented,  but  the  spine  is  slightly 
flexed.    The  Rectus  lateralis,  acting  on  one  side,  bends  the  head  laterally. 

Surface  Form. — The  muscles  in  the  neck,  with  the  exception  of  the  Platysma  myoides,  are 
invested  by  the  deep  cervical  fascia,  which  softens  down  their  form,  and  is  of  considerable 
importance  in  connection  with  deep  cervical  abscesses  and  tumors,  modifying  the  direction  of 
the  growth  of  tumors  and  of  the  enlargement  of  abscesses,  and  causing  them  to  extend 
laterally  instead  of  toward  the  surface.  The  Platysma  myoides  does  not  influence  surface 
form  except  when  in  action,  when  it  produces  wrinkling  of  the  skin  of  the  neck,  which  is 
thrown  into  oblique  ridges  parallel  with  the  fasciculi  of  the  muscle.  Sometimes  this  con- 
traction takes  place  suddenly  and  repeatedly  as  a  sort  of  spasmodic  twitching,  the  result  of 
a  nervous  habit.  The  Sterno-cleido-mastoid  is  the  most  important  muscle  of  the  neck  as 
regards  its  surface  form.  If  the  muscle  is  put  into  action  by  drawing  the  chin  downward  and 
to  the  opposite  shoulder,  its  surface  form  will  be  plainly  outlined.  The  sternal  origin  will 
stand  out  as  a  sharply-defined  ridge,  while  the  clavicular  origin  will  present  a  flatter  and  not  so 
prominent  an  outline.  The  fleshy  middle  portion  will  appear  as  an  oblique  roll  or  elevation, 
Avith  a  thick  rounded  anterior  border  gradually  becoming  less  marked  above.  On  the  opposite 
side — i.  e.,  on  the  side  to  which  the  head  is  turned — the  outline  is  lost,  its  place  being  occupied 
by  an  oblique  groove  in  the  integument.  When  the  muscle  is  at  rest  its  anterior  border  is  still 
visible,  forming  an  oblique  rounded  ridge,  terminating  below  in  the  sharp  outline  of  the  sternal 
head.  The  posterior  border  of  the  muscle  does  not  show  above  the  clavicular  head.  The 
anterior  border  is  defined  by  drawing  a  line  from  the  tip  of  the  mastoid  process  to  the  sterno- 
clavicular joint.  It  is  an  important  surface-marking  in  the  operation  of  ligature  of  the  common 
carotid  artery  and  in  some  other  operations.  Between  the  sternal  and  clavicular  heads  is  a  slight 
depression,  most  marked  when  the  muscle  is  in  action.  This  is  bounded  below  by  the  prominent 
sternal  extremity  of  the  clavicle.  Between  the  sternal  origins  of  the  two  muscles  is  a  V-shaped 
space,  the  suprasternal  notch,  more  pronounced  below,  and  becoming  toned  down  above,  where 
the  vSterno-hyoid  and  Sterno-thyroid  muscles,  lying  upon  the  trachea,  become  more  prominent. 
Above  the  hyoid  bone,  in  the  middle  line,  the  anterior  belly  of  the  Digastric  to  a  certain  extent 
influences  surface  form.     It  corresponds  to  a  line  drawn  from  the  symphysis  of  the  lower  jaw  to 


410 


THE  MUSCLES  AND   FASCl^ 


the  side  of  the  body  of  the  hyoid  bone,  and  renders  this  part  of  the  hyo-mental  region  convex. 
In  the  posterior  triangle  of  the  neck,  the  posterior  belly  of  the  Omo-hyoid,  when  in  action,  forms 
a  conspicuous  object,  especially  in  thin  necks,  presenting  a  cord-like  form  running  across  this 
region,  almost  parallel  with,  and  a  little  above,  the  clavicle. 


MUSCLES  AND  FASCIA  OF  THE  TRUNK. 

The  muscles  of  the  Trunk  may  be  arranged  in  four  groups,  corresponding 
with  the  region  in  which  they  are  situated. 

I.  The  Back.  III.  The  Abdomen. 


II.  The  Thorax. 


IV.  The  Perinseum. 


I.  MUSCLES  OF  THE  BACK. 

The  muscles  of  the  Back  are  very  numerous,  and  may  be  subdivided  into  five 
layers : 

First  Layer. 


Trapezius. 
Latissimus  dorsi. 

Second  Layer. 

Levator  anguli  scapulae. 
Rhomboideus  minor. 
Rhomboideus  major. 

Third  Layer. 

Serratus  posticus  superior. 
Serratus  posticus  inferior. 
Splenius  capitis. 
Splenius  colli. 

Fourth  Layer. 
Sacral  and  Lumbar  Regions. 
Erector  spinse. 

Dorsal  Region. 

Ilio-costalis. 

Musculus  accessorius  ad  ilio-costalem. 


Longissimus  dorsi. 
Spinalis  dorsi. 

Cervical  Region. 

Cervicalis  ascendens. 
Transversalis  cervicis. 
Trachelo-mastoid. 
Complexus. 
Biventer  cervicis. 
Spinalis  colli. 

Fifth  Layer. 

Semispinalis  dorsi. 
Semispinalis  colli. 
Multifidus  spinse. 
Rotatores  spinee. 
Supraspinales. 
Interspinales. 
Extensor  coccygis. 
Intertransversalis. 
Rectus  capitis  posticus  major. 
Rectus  capitis  posticus  minor. 
Obliquus  capitis  inferior. 
Obliquus  capitis  superior. 


The  First  Layer  (Fig.  282). 
Trapezius.  I>atissimus  dorsi. 

Dissection  (Fig.  281). — Place  the  body  in  a  prone  position,  with  the  arms  extended  over 
the  sides  of  the  table,  and  the  chest  and  abdomen  supported  by  several  blocks,  so  as  to  render 
the  muscles  tense.  Then  make  an  incision  along  the  middle  line  of  the  back  from  the  occipital 
protuberance  to  the  coccyx.  Make  a  transverse  incision  from  the  upper  end  of  this  to  the  mas- 
toid process,  and  a  third  incision  from  its  lower  end,  along  the  crest  of  the  ilium  to  about  its 
middle.  This  large  intervening  space  should,  for  convenience  of  dissection,  be  subdivided  by 
a  fourth  incision,  extending  obliquely  from  the  spinous  process  of  the  last  dorsal  vertebra,  upward 
and  outward,  to  the  acromion  process.  This  incision  corresponds  with  the  lower  border  of  the 
Trapezius  muscle.  The  flaps  of  integument  are  then  to  be  removed  in  the  direction  shown  in 
the  figure. 


OF    THE   BACK 


411 


Superficial  Fascia. — The  superficial  fascia  is  exposed  upon  removing  the  skin 
from  the  back.  It  forms  a  layer  of  considerable  thickness  and  strength,  in  which 
a  quantity  of  granular  pinkish  fat  is  contained.  It  is  continuous  with  the  super- 
ficial fascia  in  other  parts  of  the  body. 

Deep  Fascia. — The  deep  fascia  is  a  dense  fibrous  layer  attached  to  the 
occipital  bone,  the  spines  of  the  vertebrse,  the  crest  of  the  ilium,  and  the  spine 
of  the  scapula.  It  covers  over  the  superficial 
muscles,  forming  sheaths  for  them,  and  in  the 
neck  forms  the  posterior  part  of  the  deep  cer- 
vical fascia;  in  the  thorax  it  is  continuous  with 
the  deep  fascia  of  the  axilla  and  chest,  and  in 
the  abdomen  with  that  covering  the  abdominal 
muscles.  In  the  back  of  the  thoracic  region 
the  deep  fascia  is  called  the  vertebral  aponeurosis 
or  the  aponeurosis  of  the  latissimus  dorsi  muscle. 
It  covers  the  erector  spinte  muscles,  and  is  the 
posterior  layer  of  the  lumbar  fascia. 

The  Trapezius  is  a  broad,  flat,  triangular 
muscle,  placed  immediately  beneath  the  skin 
and  fascia,  and  covering  the  upper  and  back 
part  of  the  neck  and  shoulders.  It  arises  from 
the  external  occipital  protuberance  and  the 
inner  third  of  the  superior  curved  line  of  the 
occipital  bone;  from  the  ligamentum  nuchae,  the 
spinous  process  of  the  seventh  cervical,  and  the 
spinous  processes  of  all  the  dorsal  vertebrae;  and 
from  the  corresponding  portion  of  the  supra- 
spinous ligament.  From  this  origin  the  supe- 
rior fibres  proceed  downward  and  outward, 
the  inferior  ones  upward  and  outward,  and 
the  middle  fibres  horizontally,  and  are  in- 
serted, the  superior  ones  into  the  outer  third  of 
the  posterior  border  of  the  clavicle ;  the  middle 
fibres  into  the  inner  margin  of  the  acromion 

process,  and  into  the  superior  lip  of  the  posterior  border  or  crest  of  the  spine 
of  the  scapula;  the  inferior  fibres  converge  near  the  scapula,  and  terminate  in  a 
triangular  aponeurosis,  which  glides  over  a  smooth  surface  at  the  inner  extremity 
of  the  spine,  to  be  inserted  into  a  tubercle  at  the  outer  part  of  this  smooth  surface. 
The  Trapezius  is  fleshy  in  the  greater  part  of  its  extent,  but  tendinous  at  its  origin 
and  insertion.  At  its  occipital  origin  it  is  connected  to  the  bone  by  a  thin  fibrous 
lamina,  firmly  adherent  to  the  skin,  and  wanting  the  lustrous,  shining  appearance 
of  aponeuroses.  At  its  origin  from  the  spines  of  the  vertebrae  it  is  connected  to 
the  bones  by  means  of  a  broad  semi-elliptical  aponeurosis,  which  occupies  the 
space  between  the  sixth  cervical  and  the  third  dorsal  vertebrae,  and  forms,  with 
the  aponeurosis  of  the  opposite  nmscle,  a  tendinous  ellipse.  The  rest  of  the 
muscle  arises  by  numerous  short  tendinous  fibres.  If  the  Trapezius  is  dissected 
on  both  sides,  the  two  muscles  resemble  a  trapezium  or  diamond-shaped  quad- 
rangle ;  two  angles  corresponding  to  the  shoulders ;  a  third  to  the  occipital  pro- 
tuberance; and  the  fourth  to  the  spinous  process  of  the  last  dorsal  vertebra.  The 
clavicular  insertion  of  this  muscle  varies  as  to  the  extent  of  its  attachment;  it 
sometimes  advances  as  faV  as  the  middle  of  the  clavicle,  and  may  even  become 
blended  with  the  posterior  edge  of  the  Sterno-mastoid  or  overlap  it.  This  should 
be  borne  in  mind  in  the  operation  for  tying  the  third  part  of  the  subclavian 
artery.  ♦ 


Fig.  281. — Dissection  of  the  muscles  of 
the  back. 


412 


THE   31USCLES    AND    FASCIA 


Fig.  282. — Muscles  of  the  back.     On  the  left  side  is  exposed  the  first  layer;  on  the  right  side,  the  second  layer 

and  part  of  the  third. 


OF    THE  BACK  413 

Relations. — By  its  superficial  surface,  with  the  integument;  by  its  deep  sur- 
face, in  the  neck,  with  the  Complexus,  Splenius,  Levator  anguH  scapulae,  and 
Rhomboideus  minor;  in  the  back,  with  the  Rhomboideus  major,  Supraspinatus, 
Infraspinatus,  and  Vertebral  aponeurosis  (which  separates  it  from  the  prolonga- 
tions of  the  Erector  spinae),  and  the  Latissimus  dorsi.  The  spinal  accessory  nerve 
and  the  superficial  cervical  artery  and  branches  from  the  third  and  fourth  cervical 
nerves  pass  beneath  the  anterior  border  of  this  muscle.  The  anterior  margin  of  its 
cervical  portion  forms  the  posterior  boundary  of  the  posterior  triangle  of  the  neck, 
the  other  boundaries  being  the  Sterno-mastoid  in  front  and  the  clavicle  below. 

The  Ligamentum  nuchse  (Fig.  282)  is  a  fibrous  membrane,  which,  in  the  neck, 
represents  the  supraspinous  and  interspinous  ligaments  of  the  lower  vertebrae. 
It  extends  from  the  external  occipital  protuberance  to  the  spinous  process  of  the 
seventh  cervical  vertebra.  From  its  anterior  border  a  fibrous  lamina  (fascia 
nuAihoe)  is  given  off,  which  is  attached  to  the  external  occipital  crest,  the  posterior 
tubercle  of  the  atlas,  and  the  spinous  process  of  each  of  the  cervical  vertebrae,  so 
as  to  form  a  septum  between  the  muscles  on  each  side  of  the  neck.  In  man  it  is 
merely  the  rudiment  of  an  important  elastic  ligament,  which,  in  some  of  the  lower 
animals,  serves  to  sustain  the  weight  of  the  head. 

The  Latissimus  Dorsi  is  a  broad  flat  muscle,  which  covers  the  lumbar  and  the 
lower  half  of  the  dorsal  regions,  and  is  gradually  contracted  into  a  narrow  fascic- 
ulus at  its  insertion  into  the  humerus.  It  arises  by  tendinous  fibres  from  the 
spinous  processes  of  the  six  inferior  dorsal  vertebrae  and  from  the  posterior  layer 
of  the  lumbar  fascia  (see  page  416),  by  which  it  is  attached  to  the  spines  of  the 
lumbar  and  sacral  vertebnB  and  to  the  supraspinous  ligament.  It  also  arises 
from  the  external  lip  of  the  crest  of  the  ilium,  behind  the  origin  of  the  External 
oblique,  and  by  fleshy  digitations  from  the  three  or  four  lower  ribs,  which  are 
interposed  between  similar  processes  of  the  External  oblique  muscle  (Fig.  289, 
page  434).  From  this  extensive  origin  the  fibres  pass  in  different  directions,  the 
upper  ones  horizontally,  the  middle  obliquely  upward,  and  the  lower  vertically 
upward,  so  as  to  converge  and  form  a  thick  fasciculus,  which  crosses  the  inferior 
angle  of  the  scapula,  and  occasionally  receives  a  few  fibres  of  origin  from  it.  The 
muscle  then  curves  around  the  lower  border  of  the  Teres  major,  and  is  twisted 
upon  itself  so  that  the  superior  fibres  become  at  first  posterior  and  then  inferior, 
and  the  vertical  fibres  at  first  anterior  and  then  superior.  It  then  terminates  in  a 
short  quadrilateral  tendon,  about  three  inches  in  length,  which,  passing  in  front  of 
the  tendon  of  the  Teres  major,  is  inserted  into  the  bottom  of  the  bicipital  groove 
of  the  humerus,  its  insertion  extending  higher  on  the  humerus  than  that  of  the 
tendon  of  the  Pectoralis  major.  The  lower  border  of  the  tendon  of  this  muscle  is 
united  with  that  of  the  Teres  major,  the  surfaces  of  the  two  being  separated  by  a 
bursa;  another  bursa  is  sometimes  interposed  between  the  muscle  and  the  inferior 
angle  of  the  scapula.  This  muscle  at  its  insertion  gives  off  an  expansion  to  the 
deep  fascia  of  the  arm. 

A  muscular  slip,  the  axillary  arch,  varying  from  3  to  4  inches  in  length,  and  from  J  to  f  of  an 
inch  in  breadth,  occasionally  arises  from  the  upper  edge  of  the  Latissimus  dorsi  about  the  mid- 
dle of  the  posterior  fold  of  the  axilla,  and  crosses  the  axilla  in  front  of  the  axillary  vessels  and 
nerves,  to  join  the  under  surface  of  the  tendon  of  the  Pectoralis  major,  the  Coraco-brachialis, 
or  the  fascia  over  the  Biceps.  The  position  of  this  abnormal  slip  is  a  point  of  interest  in  its 
relation  to  the  axillary  artery,  as  it  crosses  the  vessel  just  above  the  spot  usually  selected  for  the 
application  of  a  ligature,  and  may  mislead  the  surgeon  during  the  operation.  It  may  be  easily 
recognized  by  the  transverse  direction  of  its  fibres.  Dr.  Struther  found  it,  in  8  out  of  105  sub- 
jects, occurring  seven  times  on  both  sides.  In  most  subjects  there  is  a  fibrous  axillary  arch, 
in  only  a  few  is  the  arch  muscular. 

There  is  usually  a  fibrous  slip  which  passes  from  the  lower  border  of  the  tendon  of  the  Latis- 
simus dorsi,  nearits  insertion,  to  the  long  head  of  the  Triceps.  This  is  occasionally  muscular, 
and  is  the  representative  of  the  Dorso-epitrochlearis  muscle  of  apes. 


414  THE  3IU8CLES   ANB   FASCIA 

Relations. — Its  superficial  surface  is  subcutaneous,  excepting  at  its  upper  part, 
where  it  is  covered  by  the  Trapezius,  and  at  its  insertion,  where  its  tendon  is 
crossed  by  the  axillary  vessels  and  the  brachial  plexus  of  nerves.  By  its  deep 
surface  it  is  in  relation  with  the  lumbar  fascia,  the  Serratus  posticus  inferior, 
the  lower  External  intercostal  muscles  and  ribs,  inferior  angle  of  the  scapula, 
Rhomboideus  major.  Infraspinatus,  and  Teres  major.  Its  outer  margin  is  sepa- 
rated below  from  the  External  oblique  by  a  small  triangular  interval,  the  triangle 
of  Petit  (trigonum  lumbale  [Petiti]) ;  and  another  triangular  interval  exists  between 
its  upper  border  and  the  margin  of  the  Trapezius,  in  which  the  Rhomboideus 
major  muscle  is  exposed. 

Nerves. — The  Trapezius  is  supplied  by  the  spinal  accessory,  and  by  branches 
from  the  anterior  divisions  of  the  third  and  fourth  cervical  nerves :  the  Latissimus 
dorsi,  by  the  middle  or  long  subscapular  nerve. 

The  Second  Layer  (Fig.  282). 

Levator  anguli  scapulae.  Rhomboideus  minor. 

Rhomboideus  major. 

Dissection.— The  Trapezius  must  be  removed,  in  order  to  expose  the  next  layer;  to  effect 
this,  detach  the  muscle  from  its  attachment  to  the  clavicle  and  spine  of  the  scapula,  and  turn 
it  back  toward  the  spine. 

The  Levator  Ang^uli  Scapulae  (m.  levator  scapulae)  is  situated  at  the  back  part 
and  side  of  the  neck.  It  arises  by  tendinous  slips  from  the  transverse  process  of 
the  atlas,  and  from  the  posterior  tubercles  of  the  transverse  processes  of  the  second, 
third,  and  fourth  cervical  vertebrae;  these,  becoming  fleshy,  are  united  so  as  to 
form  a  flat  muscle,  which,  passing  downward  and  backward,  is  inserted  into  the 
posterior  border  of  the  scapula,  between  the  superior  angle  and  the  triangular 
smooth  surface  at  the  root  of  the  spine. 

Relations. — By  its  superficial  surface,  with  the  integument.  Trapezius,  and 
Sterno-mastoid;  by  its  deep  surface,  with  the  Splenius  colli,  Transversalis  cervicis, 
Cervicalis  ascendens,  and  Serratus  posticus  superior  muscles,  and  with  the  pos- 
terior scapular  artery  and  the  nerve  to  the  Rhomboids. 

The  Rhomboideus  Minor  arises  from  the  ligamentum  nuchse  and  spinous 
processes  of  the  seventh  cervical  and  first  dorsal  vertebrae.  Passing  downward 
and  outward,  it  is  inserted  into  the  margin  of  the  triangular  smooth  surface  at  the 
root  of  the  spine  of  the  scapula.  This  small  muscle  is  usually  separated  from  the 
Rhomboideus  major  by  a  slight  cellular  interval. 

Relations. — By  its  superficial  (posterior)  surface,  with  the  Trapezius;  by  its  deep 
{anterior)  surface,  with  the  same  structures  as  the  Rhomboideus  major. 

The  Rhomboideus  Major  is  situated  immediately  below  the  preceding,  the 
adjacent  margins  of  the  two  being  occasionally  united.  It  arises  by  tendinous 
fibres  from  the  spinous  processes  of  the  four  or  five  upper  dorsal  vertebrae  and  the 
supraspinous  ligament,  and  is  inserted  into  a  narrow  tendinous  arch  attached 
above  to  the  lower  part  of  the  triangular  surface  at  the  root  of  the  spine;  below, 
to  the  inferior  angle,  the  arch  being  connected  to  the  border  of  the  scapula  by  a 
thin  membrane.  When  the  arch  extends,  as  it  occasionally  does,  but  a  short 
distance,  the  muscular  fibres  are  inserted  into  the  scapula  itself. 

Relations. — By  its  superficial  (posterior)  surface,  with  the  Trapezius  and  Latis- 
simus dorsi;  by  its  deep  (anterior)  surface,  with  the  Serratus  posticus  superior, 
posterior  scapular  artery,  the  vertebral  aponeurosis  which  separates  it  from  the 
prolongations  from  the  Erector  spinae,  the  Intercostal  muscles,  and  ribs. 

Nerves. — The  Rhomboid  muscles  are  supplied  by  branches  from  the  anterior 
division  of  the  fifth  cervical  nerve;    the  Levator  anguli  scapulae,  by  the  anterior 


OF   THE  BACK  4I5 

divisions  of  the  third  and  fourth  cervical  nerves,  and  frequently  by  a  branch  from 
the  nerve  to  the  Rhomboids. 

Actions. — The  movements  effected  by  the  preceding  muscles  are  numerous,  as 
may  be  conceived  from  their  extensive  attachment.  The  whole  of  the  Trapezius 
when  in  action  retracts  the  scapula  and  braces  back  the  shoulder;  if  the  head  is 
fixed,  the  upper  part  of  the  Trapezius  will  elevate  the  point  of  the  shoulder,  as  in 
supporting  weights;  when  the  lower  fibres  are  brought  into  action,  they  assist 
in  depressing  the  bone.  The  middle  and  lower  fibres  of  the  muscle  rotate  the 
scapula,  causing  elevation  of  the  acromion  process.  If  the  shoulders  are  fixed,  both 
Trapezii,  acting  together,  will  draw  the  head  directly  backward;  or  if  only  one 
acts  the  head  is  drawn  to  the  corresponding  side.  The  Latissimus  dorsi,  when  it 
acts  upon  the  humerus,  depresses  it,  draws  it  backward,  adducts,  and  at  the  same 
time  rotates  it  inward.  It  is  the  muscle  which  is  principally  employed  in  giving  a 
downward  blow,  as  in  felling  a  tree  or  in  sabre  practice.  If  the  arm  is  fixed,  the 
muscle  may  act  in  various  ways  upon  the  trunk;  thus,  it  may  raise  the  lower  ribs 
and  assist  in  forcible  inspiration;  or,  if  both  arms  are  fixed,  the  two  muscles  may 
assist  the  Abdominal  and  great  Pectoral  muscles  in  suspending  and  drawing  the 
whole  trunk  forward,  as  in  climbing  or  walking  on  crutches.  The  Levator  anguli 
scapula?  raises  the  superior  angle  of  the  scapula,  and  by  so  doing  depresses  the 
point  of  the  shoulder.  It  assists  the  Trapezius  in  bearing  weights  and  in  shrugging 
the  shoulders.  If  the  shoulder  be  fixed,  the  Levator  anguli  scapulte  inclines  the 
neck  to  the  corresponding  side  and  rotates  it  in  the  same  direction.  The  Rhom- 
boid muscles  carry  the  inferior  angle  backward  and  upward,  thus  producing  a 
slight  rotation  of  the  scapula  upon  the  side  of  the  chest,  the  Rhomboideus  major 
acting  especially  on  the  lower  angle  of  the  scapula  through  the  tendinous  arch  by 
which  it  is  inserted.  The  Rhomboid  muscles,  acting  together  with  the  middle  and 
inferior  fibres  of  the  Trapezius,  will  draw  the  scapula  directly  backward  toward 
the  spine. 

The  Third  Layer. 

Serratus  posticus  superior.  Serratus  posticus  inferior. 

^  ,     .        f  Splenius  capitis. 
Splenms   |  g^j^^j^^  J^^ 

Dissection. — To  bring  into  view  the  third  layer  of  muscles,  remove  the  whole  of  the  second, 
together  with  the  Latissimus  dorsi,  by  cutting  through  the  Levator  anguli  scapulae  and  Rhom- 
boid muscles  near  their  origin,  and  reflecting  them  downward,  and  by  dividing  the  Latissimus 
dorsi  in  the  middle  by  a  vertical  incision  carried  from  its  upper  to  its  lower  part,  and  reflecting 
the  two  halves  of  the  muscle. 

The  Serratus  Posticus  Superior  {m.  serratus  'posterior  superior)  is  a  thin,  flat, 
quadrilateral  muscle  situated  at  the  upper  and  back  part  of  the  thorax.  It  arises 
by  a  thin  and  broad  aponeurosis  from  the  ligamentum  nuchae,  and  from  the  spinous 
processes  of  the  last  cervical  and  two  or  three  upper  dorsal  vertebrae  and  from  the 
supraspinous  ligament.  Inclining  downward  and  outward,  it  becomes  muscular, 
and  is  inserted,  by  four  fleshy  digitations  into  the  upper  borders  of  the  second, 
third,  fourth,  and  fifth  ribs,  a  little  beyond  their  a  gles. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  Rhomboidei,  and 
Levator  anguli  scapulae;  by  its  deep  surface,  with  the  Splenius  and  the  vertebral 
aponeurosis,  which  separates  it  from  the  prolongations  of  the  Erector  spinae,  and 
with  the  Intercostal  muscles  and  ribs. 

The  Serratus  Posticus  Inferior  (m.  serratus  posterior  inferior)  (Fig.  282)  is 
situated  at  the  junction  of  the  dorsal  and  lumbar  regions ;  it  is  of  an  irregularly 
quadrilateral  form,  broader  than  the  preceding,  and  separated  from  it  by  a  consid- 
erable interval.  It  arises  by  a  thin  aponeurosis  from  the  spinous  processes  of  the 
last  two  dorsal  and   two  or  three  upper  lumbar  vertebrae,  and  from  the  supra- 


41G  THE  MUSCLES   AND    FASCIA 

spinous  ligaments.  Passing  obliquely  upward  and  outward,  it  becomes  fleshy, 
and  divides  into  four  flat  digitations,  which  are  inserted  into  the  lower  borders  of 
the  four  lower  ribs,  a  little  beyond  their  angles.  The  thin  aponeurosis  of  origin 
is  intimately  blended  with  the  lumbar  fascia. 

Relations. — By  its  superficial  surface,  with  the  Latissimus  dorsi.  By  its  deep 
surface,  with  the  Erector  spinae,  ribs,  and  Intercostal  muscles.  Its  upper  margin 
is  continuous  with  the  vertebral  aponeurosis. 

The  vertebral  aponeurosis  is  a  thin,  fibrous  lamina,  extending  along  the  whole 
length  of  the  back  part  of  the  thoracic  region,  serving  to  bind  down  the  long 
Extensor  muscles  of  the  back  which  support  the  spine  and  head,  and  separate  them 
from  those  muscles  which  connect  the  spine  to  the  upper  extremity.  It  consists  of 
longitudinal  and  transverse  fibres  blended  together,  forming  a  thin  lamella,  which 
is  attached  in  the  median  line  to  the  spinous  processes  of  the  dorsal  vertebrae; 
externally,  to  the  angles  of  the  ribs ;  and  below,  to  the  upper  border  of  the  Serratus 
posticus  inferior  and  a  portion  of  the  lumbar  fascia,  which  gives  origin  to  the  Latis- 
simus dorsi ;  above,  it  passes  beneath  the  Serratus  posticus  superior  and  the  Splenius, 
and  blends  with  the  deep  fascia  of  the  neck. 

The  lumbar  fascia  or  aponeurosis  (Fig^.  282  and  295),  which  may  be  regarded 
as  the  posterior  aponeurosis  of  the  Transversalis  abdominis  muscle,  consists 
of  three  laminae,  which  are  attached  as  follows:  the  posterior  layer,  to  the 
spines  of  the  lumbar  and  sacral  vertebrae  and  their  supraspinous  ligaments;  the 
middle  layer,  to  the  tips  of  the  transverse  processes  of  the  lumbar  vertebne  and 
their  intertransverse  ligaments;  the  anterior  layer,  to  the  roots  of  the  lumbar 
transverse  processes.  The  posterior  layer  is  continued  above  as  the  vertebral 
aponeurosis,  while  inferiorly  it  is  fixed  to  the  outer  lip  of  the  iliac  crest.  With  this 
layer  are  blended  the  aponeurotic  origin  of  the  Serratus  posticus  inferior  and  part 
of  that  of  the  Latissimus  dorsi.  The  middle  layer  is  attached  above  to  the  last 
rib,  and  below  to  the  iliac  crest;  the  anterior  layer  is  fixed  below  to  the  ilio-lumbar 
ligament  and  iliac  crest ;  while  above  it  is  thickened  to  form  the  external  arcuate 
ligament  of  the  Diaphragm,  and  stretches  from  the  tip  of  the  last  rib  to  the  trans- 
verse process  of  the  first  or  second  lumbar  vertebra.  These  three  layers,  together 
with  the  vertebral  column,  enclose  two  spaces,  the  posterior  of  which  is  occupied 
by  the  Erector  spinae  muscle,  and  the  anterior  by  the  Quadratus  lumborum. 

Now  detach  the  Serratus  posticus  superior  from  its  origin,  and  turn  it  outward,  when  the 
Splenius  muscle  will  be  brought  into  view. 

The  Splenius  (Fig.  282)  is  situated  at  the  back  of  the  neck  and  upper  part 
of  the  dorsal  region.  At  its  origin  it  is  a  single  muscle,  which  soon  after  its 
origin  becomes  broad,  and  divides  into  two  portions,  which  have  separate  inser- 
tions. It  arises,  by  tendinous  fibres,  from  the  lower  half  of  the  ligamentum 
nuchae,  from  the  spinous  processes  of  the  last  cervical  and  of  the  six  upper 
dorsal  vertebrae,  and  from  the  supraspinous  ligament.  From  this  origin  the  fleshy 
fibres  proceed  obliquely  upward  and  outward,  forming  a  broad  flat  muscle,  which 
divides  as  it  ascends  into  two  portions,  the  Splenius  capitis  and  Splenius  colli. 

The  Splenius  capitis  (m.  splenius  capitis)  is  inserted  into  the  mastoid  process  of 
the  temporal  bone,  and  into  the  rough  surface  on  the  occipital  bone  just  beneath 
the  superior  curved  line. 

The  Splenius  colli  (m.  splenius  cervicis)  is  inserted,  by  tendinous  fasciculi,  into  the 
posterior  tubercles  of  the  transverse  processes  of  the  two  or  three  upper  cervical 
vertebrae. 

The  Splenius  is  separated  from  its  fellow  of  the  opposite  side  by  a  triangular 
interval,  in  which  is  seen  the  Complexus. 

Relations. — By  its  superficial  surface,  with  the  Trapezius,  from  which  it  is  sepa- 
rated below  by  the  RhomJboidei  and  the  Serratus  posticus  superior.    It  is  covered 


OF   THE  BACK  41 7 

at  its  insertion  by  the  Sterno-mastoid,  and  at  the  lower  and  back  part  of  the  neck 
by  the  Levator  anguH  scapulae ;  by  its  deep  surface,  with  the  Spinalis  dorsi,  Longis- 
simus  dorsi,  Semispinalis  colli,  Complexus,  Trachelo-mastoid,  and  Transversalis 
cervicis. 

Nerves. — The  Splenius  is  supplied  from  the  external  branches  of  the  posterior 
divisions  of  the  cervical  nerves;  the  Serratus  posticus  superior  is  supplied  by  the 
external  branches  of  the  posterior  divisions  of  the  upper  dorsal  nerves;  the  Ser- 
ratus posticus  inferior  by  the  external  branches  of  the  posterior  divisions  of  the 
lower  dorsal  nerves. 

Actions. — The  Serrati  are  respiratory  muscles.  The  Serratus  posticus  supe- 
rior elevates  the  ribs;  it  is  therefore  an  inspiratory  muscle;  while  the  Serratus 
inferior  draws  the  lower  ribs  downward  and  backward,  and  thus  elongates  the 
thorax.  It  also  fixes  the  lower  ribs,  thus  aiding  the  downward  action  of  the 
diaphragm  and  resisting  the  tendency  which  it  has  to  draw  the  lower  ribs  upward 
and  forward.  It  must  therefore  be  regarded  as  a  muscle  of  inspiration.  This 
muscle  is  also  probably  a  tensor  of  the  vertebral  aponeurosis.  The  Splenii  muscles 
of  the  two  sides,  acting  together,  draw  the  head  directly  backward,  assisting  the 
Trapezius  and  Complexus;  acting  separately,  they  draw  the  head  to  one  or  the 
other  side,  and  slightly  rotate  it,  turning  the  face  to  the  same  side.  They  also 
assist  in  supporting  the  head  in  the  erect  position. 

The  Fourth  Layer  (Fig.  283). 

I.  Erector  spinse. 
a.  Outer  Column.  h.  Middle  Column. 

Ilio-costalis.  Longissimus  dorsi. 

Musculus  accessorius.  Transversalis  cervicis. 

Cervicalis  ascendens.  Trachelo-mastoid. 

c.  Inner  Column. 
Spinalis  dorsi.  Spinalis  colli. 

II.  Complexus. 

Dissection. — To  expose  the  muscles  of  the  fourth  layer,  remove  entirely  the  Serrati  and  the 
vertebral  and  lumbar  fasciae.  Then  detach  the  Splenius  by  separating  its  attachment  to  the 
spinous  processes  and  reflecting  it  outward. 

The  Erector  Spinse  {m.  sacrospinalis)  and  its  prolongations  in  the  dorsal 
and  cervical  regions  fill  up  the  vertebral  groove  on  each  side  of  the  spine.  It 
is  covered  in  the  lumbar  region  by  the  lumbar  fascia;  in  the  dorsal  region,  by 
the  Serrati  muscles  and  the  vertebral  aponeurosis;  and  in  the  cervical  region,  by 
a  layer  of  cervical  fascia  continued  beneath  the  Trapezius  and  the  Splenius.  This 
large  muscular  and  tendinous  mass  varies  in  size  and  structure  at  different  parts 
of  the  spine.  In  the  sacral  region  the  Erector  spina?  is  narrow  and  pointed,  and 
its  origin  chiefly  tendinous  in  structure.  In  the  lumbar  region  the  muscle  becomes 
enlarged,  and  forms  a  large  fleshy  mass.  In  the  dorsal  region  it  subdivioes  into 
two  parts,  which  gradually  diminish  in  size  as  they  ascend  to  be  inserted  into  the 
vertebrae  and  ribs. 

The  Erector  spinae  arises  from  the  anterior  surface  of  a  very  broad  and  thick 
tendon,  which  is  attached,  internally,  to  the  spines  of  the  sacrum,  to  the  spinous 
processes  of  the  lumbar  and  the  eleventh  and  twelfth  dorsal  vertebrae,  and  the 
supraspinous  ligament;  externally,  to  the  back  part  of  the  inner  lip  of  the  crest  of 
the  ilium,  and  to  the  series  of  eminences  on  the  posterior  part  of  the  sacrum,  which 
represents  the  transverse  processes,  where  it  blends  with  the  great  sacro-sciatic  and 
posterior  sacro-iliac  ligaments.    Some  of  its  fibres  are  continuous  with  the  fibres 

27 


■418 


THE  MUSCLES   AND   FASCIA 


MULTIFIDUS   SPINiE 


First  dorsal  vertebra.- — 


First  lumbar  vertebra. 


First  sacral  vertebra 


Fig.  283. — Muscles  of  the  back.     Deep  layers. 


OF   THE   BACK  41 9 

of  origin  of  the  Gluteus  maximus.  The  muscular  fibres  form  a  single  large  fleshy 
mass,  bounded  in  front  by  the  transverse  processes  of  the  lumbar  vertebrae  and  by 
the  middle  lamella  of  the  lumbar  fascia.  Opposite  the  last  rib  it  divides  into  two 
parts,  the  Ilio-costalis  and  the  Longissimus  dorsi;  the  Spinalis  dorsi  is  given  off 
from  the  latter  in  the  upper  dorsal  region. 

The  Ilio-costalis  or  Sacro-lumbalis  (w.  iliocostalis  lumhorum),  the  external  por- 
tion of  the  Erector  spinse,  is  inserted,  generally,  by  six  or  seven  flattened  tendons  into 
the  inferior  borders  of  the  angles  of  the  six  or  seven  lower  ribs.  The  number  of  the 
tendons  of  this  muscle  is,  however,  very  variable,  and  therefore  the  number  of  ribs 
into  which  it  is  inserted  vary.  Frequently  it  is  found  to  possess  nine  or  ten 
tendons,  and  sometimes  as  many  tendons  as  there  are  ribs,  and  is  then  inserted 
into  the  angles  of  all  the  ribs.  If  this  muscle  is  reflected  outward,  it  will  be 
seen  to  be  reinforced  by  a  series  of  muscular  sHps  which  arise  from  the  angles 
of  the  ribs ;  by  means  of  these  the  IHo-costalis  is  continued  upward  to  the  upper 
ribs  and  cervical  portion  of  the  spine.  The  accessory  portions  form  two  additional 
muscles,  the  Musculus  accessorius  and  the  Cervicalis  ascendens. 

The  Musculus  accessorius  ad  ilio-costalem  {m.  iliocostalis  dorsi)  arises,  by  separate 
flattened  tendons,  from  the  upper  borders  of  the  angles  of  the  six  lower  ribs:  these 
become  muscular,  and  are  finally  inserted,  by  separate  tendons,  into  the  upper 
borders  of  the  angles  of  the  six  upper  ribs  and  into  the  back  of  the  transverse 
processes  of  the  seventh  cervical  vertebra. 

The  Cervicalis  ascendens*  (w.  iliocostalis  cervicis)  is  the  continuation  of  the  Acces- 
sorius upward  into  the  neck;  it  is  situated  on  the  inner  side  of  the  tendons  of  the 
Accessorius,  arising  from  the  angles  of  the  four  or  five  upper  ribs,  and  is  inserted 
by  a  series  of  slender  tendons  into  the  posterior  tubercles  of  the  transverse  processes 
of  the  fourth,  fifth,  and  sixth  cervical  vertebrae. 

The  Longissimus  dorsi  is  the  middle  and  largest  portion  of  the  Erector  spinse. 
In  the  lumbar  region,  where  it  is  as  yet  blended  with  the  Ilio-costalis,  some  of  the 
fibres  are  attached  to  the  whole  length  of  the  posterior  surface  of  the  transverse 
processes  and  the  accessory  processes  of  the  lumbar  vertebrae,  and  to  the  middle 
layer  of  the  lumbar  fascia.  In  the  dorsal  region,  the  Longissimus  dorsi  is  inserted, 
by  long  thin  tendons,  into  the  tips  of  the  transverse  processes  of  all  the  dorsal  ver- 
tebrae, and  into  from  seven  to  eleven  of  the  lower  ribs  between  their  tubercles  and 
angles.  This  muscle  is  continued  upward  to  the  cranium  and  cervical  portion  of 
the  spine  by  means  of  two  additional  muscles,  the  Transversalis  cervicis  and 
Trachelo-mastoid. 

The  Transversalis  cervicis  or  Transversalis  colli  {m.  longissimus  cervicis),  placed 
on  the  inner  side  of  the  Longissimus  dorsi,  arises  by  long  thin  tendons  from  the 
summits  of  the  transverse  processes  of  the  six  upper  dorsal  vertebrae,  and  is 
inserted  by  similar  tendons  into  the  posterior  tubercles  of  the  transverse  pro- 
cesses of  the  cervical  vertebrae,  from  the  second  to  the  sixth  inclusive. 

The  Trachelo-mastoid  (m.  longissimus  capitis)  lies  on  the  inner  side  of  the  preced- 
ing, V)etween  it  and  the  Complexus  muscle.  It  arises,  by  tendons,  from  the  trans- 
verse processes  of  the  five  or  six  upper  dorsal  vertebrae,  and  the  articular  processes 
of  the  three  or  four  lower  cervical.  The  fibres  form  a  small  muscle,  which  ascends 
to  be  inserted  into  the  posterior  margin  of  the  mastoid  process,  beneath  the  Splenius 
and  vSterno-mastoid  muscles.  This  small  muscle  is  almost  always  crossed  by  a 
tendinous  intersection  near  its  insertion  into  the  mastoid  process.^ 

The  Spinalis  dorsi  connects  the  spinous  processes  of  the  upper  lumbar  and  the 
dorsal  vertebrae  together  by  a  series  of  muscular  and  tendinous  slips  which  are 

'  This  muscle  is  sometimes  called  "Cervicalis  deseendens."  The  student  should  remember  that  these  long 
muecles  take  their  fixed  point  from  above  or  from  below,  according  to  circumstances. 

^  These  two  muscles  (Transversalis  cervicis  and  Trachelo-mastoid)  are  sometirnes  described  as  one,  having 
a  common  origin,  but  dividing  above  at  their  insertion.  The  Trachelo-mastoid  is  then  termed  the  Transver- 
salis capitis. 


420  THE  MUSCLES   AND   FASCIA 

intimately  blended  with  the  Longissimus  dorsi.  It  is  situated  at  the  inner  side 
of  the  Longissimus  dorsi,  arising,  by  three  or  four  tendons,  from  the  spinous 
processes  of  the  first  two  lumbar  and  the  last  two  dorsal  vertebrae:  these, 
uniting,  form  a  small  muscle,  which  is  inserted,  by  separate  tendons,  into  spinous 
processes  of  the  dorsal  vertebrae,  the  number  varying  from  four  to  eight.  It  is 
intimately  united  with  the  Semispinalis  dorsi,  which  lies  beneath  it. 

The  Spinalis  colli  (m.  spinalis  cervicis)  is  a  small  muscle,  connecting  together  the 
spinous  processes  of  the  cervical  vertebrae,  and  analogous  to  the  Spirialis  dorsi  in 
the  dorsal  region.  It  varies  considerably  in  its  size  and  in  its  extent  of  attachment 
to  the  vertebrae,  not  only  in  different  bodies,  but  on  the  two  sides  of  the  same  body. 
It  usually  arises  by  fleshy  or  tendinous  slips,  varying  from  two  to  four  in  number, 
from  the  spinous  processes  of  the  fifth,  sixth,  and  seventh  cervical  vertebrae,  and 
occasionally  from  the  first  and  second  dorsal,  and  is  inserted  into  the  spinous 
process  of  the  axis,  and  occasionally  into  the  spinous  processes  of  the  two  vertebrae 
below  it.    This  muscle  was  found  absent  in  five  cases  out  of  twenty-four. 

Relations. — The  Erector  spinae  and  its  prolongations  are  bound  down  to  the 
vertebrae  and  ribs  in  the  lumbar  and  dorsal  regions  by  the  lumbar  fascia  and 
the  vertebral  aponeurosis.  The  inner  part  of  these  muscles  covers  the  muscles 
of  the  fifth  layer.  In  the  neck  they  are  in  relation,  by  their  superficial  surface,  with 
the  Trapezius  and  Splenius;  by  their  deep  surface,  with  the  Semispinalis  dorsi  et 
colli  and  the  Recti  and  Obliqui. 

The  Gomplexus  (m.  semispinalis  capitis)  is  a  broad  thick  muscle,  situated  at  the 
upper  and  back  part  of  the  neck,  beneath  the  Splenius,  and  internal  to  the  Trans- 
versalis  cervicis  and  Trachelo-mastoid.  It  arises,  by  a  series  of  tendons,  from 
the  tips  of  the  transverse  processes  of  the  upper  six  or  seven  dorsal  and  the  last 
cervical  vertebrae,  and  from  the  articular  processes  of  the  three  cervical  above 
this.  The  tendons,  uniting,  form  a  broad  muscle,  which  passes  obliquely  upward 
and  inward,  and  is  inserted  into  the  innermost  depression  between  the  two  curved 
lines  of  the  occipital  bone.  This  muscle,  about  its  middle,  is  traversed  by  a  trans- 
verse tendinous  intersection.  The  biventer  cervicis  is  a  small  fasciculus,  situated 
on  the  inner  side  of  the  preceding,  and  in  the  majority  of  cases  blended  with  it; 
it  has  received  its  name  from  having  a  tendon  intervening  between  two  fleshy 
bellies.  It  is  sometimes  described  as  a  part  of  the  Complexus.  It  arises  by  from 
two  to  four  tendinous  slips,  from  the  transverse  processes  of  as  many  of  the  upper 
dorsal  vertebrae,  and  is  inserted,  on  the  inner  side  of  the  Complexus,  into  the  supe- 
rior curved  line  of  the  occipital  bone. 

Relations. — The  Complexus  is  covered  by  the  Splenius  and  the  Trapezius.  It 
lies  on  the  Rectus  capitis  posticus  major  and  minor,  the  Obliquus  capitis  superior 
and  inferior,  and  on  the  Semispinalis  colli,  from  which  it  is  separated  by  the  pro- 
funda cervicis  artery,  the  princeps  cervicis  artery,  and  branches  of  the  posterior 
primary  divisions  of  the  cervical  nerves.  The  Biventer  cervicis  is  separated  from 
its  fellow  of  the  opposite  side  by  the  ligamentum  nuchae. 

The  Fifth  Layer  (Fig.  283). 

Semispinalis  dorsi.  Extensor  coccygis. 

Semispinalis  colli.  Intertransversales. 

Multifidus  spinae.  Rectus  capitis  posticus  major. 

Rotatores  spinae.  Rectus  capitis  posticus  minor. 

Supraspinales.  Obliquus  capitis  inferior. 

Interspinales.  Obliquus  capitis  superior. 

Dissection. — Remove  the  muscles  of  the  preceding  layer  by  dividing  and  turning  aside  the 
Complexus;  then  detach  the  Spinalis  and  Longissimus  dorsi  from  their  attachments,  divide  the 
Erector  spinae  at  its  connection  below  to  the  sacral  and  lumbar  spines  and  turn  it  outward.  The 
muscles  filling  up  the  interval  between  the  spinous  and  transverse  processes  are  then  exposed. 


OF    THE  BACK  42i 

The  Semispinalis  Dorsi  consists  of  thin,  narrow,  fleshy  fasciculi  interposed 
between  tendons  of  considerable  length.  It  arises  by  a  series  of  small  tendons 
from  the  transverse  processes  of  the  lower  dorsal  vertebrae,  from  the  tenth  or 
eleventh  to  the  fifth  or  sixth;  and  is  inserted,  by  five  or  six  tendons,  into  the 
spinous  processes  of  the  upper  four  dorsal  and  lower  two  cervical  vertebrae. 

The  Semispinalis  Colli  [in.  semispinalis  cervicis),  thicker  than  the  preceding, 
arises  by  a  series  of  tendinous  and  fleshy  fibres  from  the  transverse  processes  of 
the  upper  five  or  six  dorsal  vertebrae,  and  is  inserted  into  the  spinous  processes  of 
four  cervical  vertebrae,  from  the  axis  to  the  fifth  cervical.  The  fasciculus  con- 
nected with  the  axis  is  the  largest,  and  chiefly  muscular  in  structure. 

Relations.— By  their  superficial  surface,  from  below  upward,  with  the  Spinalis 
dorsi,  Longissimus  dorsi,  Splenius,  Complexus,  the  profunda  cervicis  artery,  the 
princeps  cervicis  artery,  and  the  internal  branches  of  the  posterior  divisions  of 
the  first,  second,  and  third  cervical  nerves;  by  their  deep  surface,  with  the  Mul- 
tifidus  spinse. 

The  Multifidus  Spinse  (m.  multifidus)  consists  of  a  number  of  fleshy  and  ten- 
dinous fasciculi  which  fill  up  the  groove  on  either  side  of  the  spinous  processes  of  the 
vertebrae,  from  the  sacrum  to  the  axis.  In  the  sacral  region  these  fasciculi  arise  from 
the  back  of  the  sacrum,  as  low  as  the  fourth  sacral  foramen,  and  from  the  aponeu- 
rosis of  origin  of  the  Erector  spinae;  from  the  inner  surface  of  the  posterior  superior 
spine  of  the  ilium  and  posterior  sacro-iliac  ligaments;  in  the  lumbar  regions,  from 
the  articular  processes;  in  the  dorsal  region,  from  the  transverse  processes;  and  in 
the  cervical  region,  from  the  articular  processes  of  the  three  or  four  lower  vertebrae. 
Each  fasciculus,  passing  obliquely  upward  and  inward,  is  inserted  into  the  whole 
length  of  the  spinous  process  of  one  of  the  vertebrae  above.  These  fasciculi  vary 
in  length:  the  most  superficial,  the  longest,  pass  from  one  vertebra  to  the  third  or 
fourth  above;  those  next  in  order  pass  from  one  vertebra  to  the  second  or  third 
above;  whilst  the  deepest  connect  two  contiguous  vertebrae. 

Relations. — By  its  superficial  surface,  with  the  Longissimus  dorsi.  Spinalis  dorsi, 
Semispinalis  dorsi,  and  Semispinalis  colli;  by  its  deep  surface,  with  the  laminae 
and  spinous  processes  of  the  vertebrae,  and  with  the  Rotatores  spinae  in  the  dorsal 
region. 

The  Rotatores  Spinse  (mm.  rotatores)  are  found  only  in  the  dorsal  region  of  the 
spine,  beneath  the  Multifidus  spinae;  they  are  eleven  in  number  on  each  side.  Each 
muscle  is  small  and  somewhat  quadrilateral  in  form;  it  arises  from  the  upper  and 
back  part  of  the  transverse  process,  and  is  inserted  into  the  lower  border  and  outer 
surface  of  the  lamina  of  the  vertebra  above,  the  fibres  extending  as  far  inward  as 
the  root  of  the  spinous  process.  The  first  is  found  between  the  first  and  second 
dorsal ;  the  last,  between  the  eleventh  and  twelfth.  Sometimes  the  number  of  these 
muscles  is  diminished  by  the  absence  of  one  or  more  from  the  upper  or  lower  end. 

The  Supraspinales  consist  of  a  series  of  fleshy  bands  which  lie  on  the  spinous 
processes  in  the  cervical  region  of  the  spine. 

The  Interspinales  are  short  muscular  fasciculi,  placed  in  pairs  between  the 
spinous  processes  of  the  contiguous  vertebrae,  one  on  each  side  of  the  interspinous 
ligament.  In  the  cervical  region  they  are  most  distinct,  and  consist  of  six  pairs, 
the  first  being  situated  between  the  axis  and  third  vertebra,  and  the  last  between 
the  last  cervical  and  the  first  dorsal.  They  are  small  narrow  bundles,  attached, 
above  and  below,  to  the  apices  of  the  spinous  processes.  In  the  dorsal  region 
they  are  found  between  the  first  and  second  vertebrae,  and  occasionally  between 
the  second  and  third;  and  below,  between  the  eleventh  and  twelfth.  In  the 
lumbar  region  there  are  four  pairs  of  these  muscles  in  the  intervals  between  the 
five  lumbar  vertebrae.  There  is  also  occasionally  one  in  the  interspinous  space, 
between  the  last  dorsal  and  first  lumbar,  and  between  the  fifth  lumbar  and  the 
sacrum. 


422  THE  MUSCLES  AND    FASCIA 

The  Extensor  Coccygis  is  a  slender  muscular  fasciculus,  occasionally  present, 
which  extends  over  the  lower  part  of  the  posterior  surface  of  the  sacrum  and 
coccyx.  It  arises  by  tendinous  fibres  from  the  last  bone  of  the  sacrum  or  first 
piece  of  the  coccyx,  and  passes  downward  to  be  inserted  into  the  lower  part  of 
the  coccyx.  It  is  a  rudiment  of  the  Extensor  muscle  of  the  caudal  vertebrae  of 
the  lower  animals. 

The  Intertransversales  {mm.  intertransversarii)  are  small  muscles  placed 
between  the  transverse  processes  of  the  vertebrae.  In  the  cervical  region  they  are 
most  developed,  consisting  of  rounded  muscular  and  tendinous  fasciculi,  which  are 
placed  in  pairs,  passing  between  the  anterior  and  the  posterior  tubercles  of  the 
transverse  processes  of  two  contiguous  vertebrae,  separated  from  one  another  by 
the  anterior  division  of  the  cervical  nerve,  which  lies  in  the  groove  between  them. 
In  this  region  there  are  seven  pairs  of  these  nmscles,  the  first  pair  being  between 
the  atlas  and  axis,  and  the  last  pair  between  the  seventh  cervical  and  first  dorsal 
vertebrae.  In  the  dorsal  region  they  are  least  developed,  consisting  chiefly  of 
rounded  tendinous  cords  in  the  intertransverse  spaces  of  the  upper  dorsal  vertebrae; 
but  between  the  transverse  processes  of  the  lower  three  dorsal  vertebrae,  and 
between  the  transverse  processes  of  the  last  dorsal  and  the  first  lumbar,  they  are 
muscular  in  structure.  In  the  lumbar  region  they  are  arranged  in  pairs,  on  either 
side  of  the  spine,  one  set  occupying  the  entire  interspace  between  the  transverse 
processes  of  the  lumbar  vertebrae,  the  intertransversales  laterales  {mm.  intertrans- 
versarii laterales) ;  the  other  set,  intertransversales  mediales  {mm.  intertransversarii 
mediates) ,  passing  from  the  accessory  process  of  one  vertebra  to  the  mammillary 
process  of  the  next. 

The  Rectus  Capitis  Posticus  Major  {m.  rectus  capitis  posterior  major)  arises  by 
a  pointed  tendinous  origin  from  the  spinous  process  of  the  axis,  and,  becoming 
broader  as  it  ascends,  is  inserted  into  the  inferior  curved  line  of  the  occipital  bone 
and  the  surface  of  bone  immediately  below  it.  As  the  muscles  of  the  two  sides  pass 
upward  and  outward,  they  leave  between  them  a  triangular  space,  in  which  are 
seen  the  Recti  capitis  postici  minores  muscles. 

Relations. — By  its  superficial  surface,  with  the  Complexus,  and,  at  its  insertion, 
with  the  Superior  oblique;  by  its  deep  surface,  with  part  of  the  Rectus  capitis 
posticus  minor,  the  posterior  arch  of  the  atlas,  the  posterior  occipito-atlantal  liga- 
ment, and  part  of  the  occipital  bone. 

The  Rectus  Capitis  Posticus  Minor  (w.  rectus  capitis  posterior  minor),  the  small- 
est of  the  four  muscles  in  this  region,  is  of  a  triangular  shape;  it  arises  by  a  narrow 
pointed  tendon  from  the  tubercle  on  the  posterior  arch  of  the  atlas,  and,  becom- 
ing broader  as  it  ascends,  is  inserted  into  the  rough  surface  beneath  the  inferior 
curved  line,  nearly  as  far  as  the  foramen  magnum,  nearer  to  the  middle  line  than 
the  preceding. 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  the  Rectus  capitis 
posticus  major;  by  its  deep  surface,  with  the  posterior  occipito-atlantal  ligament. 

The  Obliquus  Capitis  Inferior,  the  larger  of  the  two  Oblique  muscles,  arises 
from  the  apex  of  the  spinous  process  of  the  axis,  and  passes  outward  and  slightly 
upward,  to  be  inserted  into  the  lower  and  back  part  of  the  transverse  process  of 
the  atlas. 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  with  the  pos- 
terior division  of  the  second  cervical  nerve,  which  crosses  it;  by  its  deep  surface, 
with  the  vertebral  artery  and  posterior  atlanto-axial  ligament. 

The  Obliquus  Capitis  Superior,  narrow  below,  wide  and  expanded  above, 
arises  by  tendinous  fibres  from  the  upper  surface  of  the  transverse  process  of  the 
atlas,  joining  with  the  insertion  of  the  preceding,  and,  passing  obliquely  upward 
and  inward,  is  inserted  into  the  occipital  bone,  between  the  two  curved  lines, 
external  to  the  Complexus. 


OF    THE  BACK  423 

Relations. — By  its  superficial  surface,  with  the  Complexus  and  Trachelo-mastoid 
and  occipital  artery.   By  its  deep  surf  ace, with  the  posterior  occipito-atlantal  Hgament. 

Between  the  two  obhque  muscles  and  the  Rectus  capitis  posticus  major  a  trian- 
gular interval  exists,  the  suboccipital  triangle.  This  triangle  is  bounded,  above 
and  internally,  by  the  Rectus  capitis  posticus  major;  above  and  externally,  by  the 
Obliquus  capitis  superior;  below  and  externally,  by  the  Obliquus  capitis  inferior. 
It  is  covered  in  by  a  layer  of  dense  fibro-fatty  tissue,  situated  beneath  the  Com- 
plexus muscle.  The  floor  is  formed  by  the  posterior  occipito-atlantal  ligament 
and  the  posterior  arch  of  the  atlas.  It  contains  the  vertebral  artery,  as  it  runs  in 
a  deep  groove  on  the  upper  surface  of  the  posterior  arch  of  the  atlas,  and  the  pos- 
terior division  of  the  suboccipital  nerve. 

Nerves.— The  third,  fourth,  and  fifth  layers  of  the  muscles  of  the  back  are 
supplied  by  the  posterior  primary  divisions  of  the  spinal  nerves. 

Actions. — When  both  the  Spinales  dorsi  contract,  they  extend  the  dorsal  region 
of  the  spine;  when  only  one  muscle  contracts,  it  helps  to  bend  the  dorsal  por- 
tion of  the  spine  to  one  side.  The  Erector  spinse,  comprising  the  Ilio-costalis  and 
the  Ivongissimus  dorsi  with  their  accessory  muscles,  serves,  as  its  name  implies, 
to  maintain  the  spine  in  the  erect  posture;  it  also  serves  to  bend  the  trunk  back- 
ward when  it  is  required  to  counterbalance  the  influence  of  any  weight  at  the 
front  of  the  body,  as,  for  instance,  when  a  heavy  weight  is  suspended  from  the 
neck,  or  when  there  is  any  great  abdominal  distention,  as  in  pregnancy  or  dropsy; 
the  peculiar  gait  under  such  circumstances  depends  upon  the  spine  being  drawn 
backward  by  the  counterbalancing  action  of  the  Erector  spinse  muscles.  The 
muscles  which  form  the  continuation  of  the  Erector  spinse  upward  steady  the 
head  and  neck,  and  fix  them  in  the  upright  position.  If  the  Ilio-costalis  and 
Longissimus  dorsi  of  one  side  act,  they  serve  to  draw  down  the  chest  and  spine  to 
the  corresponding  side.  The  Cervicales  ascendens,  taking  their  fixed  points  from 
the  cervical  vertebrae,  elevate  those  ribs  to  which  they  are  attached;  taking  their 
fixed  points  from  the  ribs,  both  muscles  help  to  extend  the  neck;  while  one  muscle 
bends  the  neck  to  its  own  side.  The  Trans versalis  cervicis,  when  both  muscles  act, 
taking  their  fixed  point  from  below,  bend  the  neck  backward.  The  Trachelo- 
mastoid,  when  both  muscles  act,  taking  their  fixed  point  from  below,  bend  the  head 
backward;  while,  if  only  one  muscle  acts,  the  face  is  turned  to  the  side  on  which 
the  muscle  is  acting,  and  then  the  head  is  bent  to  the  shoulder.  The  two  Recti 
muscles  draw  the  head  backward.  The  Rectus  capitis  posticus  major,  owing  to 
its  obliquity,  rotates  the  cranium,  with  the  atlas,  round  the  odontoid  process, 
turning  the  face  to  the  same  side.  The  Multifidus  spinte  acts  successively  upon  the 
different  parts  of  the  spine;  thus,  the  sacrum  furnishes  a  fixed  point  from  which 
the  fasciculi  of  this  muscle  act  upon  the  lumbar  region;  these  then  become  the 
fixed  points  for  the  fasciculi  moving  the  dorsal  region,  and  so  on  throughout  the 
entire  length  of  the  spine;  it  is  by  the  successive  contraction  and  relaxation  of 
the  separate  fasciculi  of  this  and  other  muscles  that  the  spine  preserves  the  erect 
posture  without  the  fatigue  that  would  necessarily  have  been  produced  had  this 
position  been  maintained  by  the  action  of  a  single  muscle.  The  Multifidus  spinae, 
besides  preserving  the  erect  position  of  the  spine,  serves  to  rotate  it,  so  that  the 
front  of  the  trunk  is  turned  to  the  side  opposite  to  that  from  which  the  muscle 
acts,  this  muscle  being  assisted  in  its  action  by  the  Obliquus  externus  abdominis. 
The  Complexi  draw  the  head  directly  backward:  if  one  muscle  acts,  it  draws 
the  head  to  one  side,  and  rotates  it  so  that  the  face  is  turned  to  the  opposite 
side.  The  Superior  oblique  draws  the  head  backward,  and,  from  the  obliquity 
in  the  direction  of  its  fibres,  will  slightly  rotate  the  cranium,  turning  the  face  to 
the  opposite  side.  The  Obliquus  capitis  inferior  rotates  the  atlas,  and  with  it  the 
cranium,  round  the  odontoid  process,  turning  the  face  to  the  same  side.  The 
Semispinales,  when  the  muscles  of  the  two  sides  act  together,  help  to  extend  thq 


424  THE  MUSCLES  AND    FASCIA 

spine;  when  the  muscles  of  one  side  only  act,  they  rotate  the  dorsal  and  cervical 
parts  of  the  spine,  turning  the  body  to  the  opposite  side.  The  Supraspinales  and 
Interspinales  by  approximating  the  spinous  processes  help  to  extend  the  spine. 
The  Intertransversales  approximate  the  transverse  processes,  and  help  to  bend  the 
spine  to  one  side.  The  Rotatores  spinie  assist  the  Multifidus  spinse  to  rotate  the 
spine,  so  that  the  front  of  the  trunk  is  turned  to  the  side  opposite  to  that  from 
which  the  muscle  acts. 

Surface  Forms. — The  surface  forms  produced  by  the  muscles  of  the  back  are  numerous  and 
difficult  to  analyze  unless  they  are  considered  in  systematic  order.  The  most  superficial  layer, 
consisting  of  large  strata  of  muscular  substance,  influences  to  a  certain  extent  the  surface  form, 
and  at  the  same  time  reveals  the  forms  of  the  layers  beneath.  The  Trapezius  at  the  upper  part 
of  the  back,  and  in  the  neck,  covers  over  and  softens  down  the  outline  of  the  underlying  muscles. 
Its  anterior  border  forms  the  posterior  boundary  of  the  posterior  triangle  of  the  neck.  It  forms 
a  slight  undulating  ridge  which  passes  downward  and  forward  from  the  occiput  to  the  junction 
of  the  middle  and  outer  third  of  the  clavicle.  The  tendinous  ellipse  formed  by  a  part  of  the 
origin  of  the  two  muscles  at  the  back  of  the  neck  is  always  to  be  seen  as  an  oval  depression, 
more  marked  when  the  muscle  is  in  action.  A  slight  dimple  on  the  skin  opposite  the  interval 
between  the  spinous  processes  of  the  third  and  fourth  dorsal  vertebrae  marks  the  triangular 
aponeurosis  by  which  the  inferior  fibres  are  inserted  into  the  root  of  the  spine  of  the  scapula. 
From  this  point  the  inferior  border  of  the  muscle  may  be  traced  as  an  undulating  ridge  to  the 
spinous  process  of  the  twelfth  dorsal  vertebra.  In  like  manner  the  Latissimus  dorsi  softens 
down  and  modulates  the  underlying  structures  at  the  lower  part  of  the  back  and  lower  part  of 
the  side  of  the  chest.  In  this  way  it  modulates  the  outline  of  the  Erector  spinae;  of  the  Serratus 
posticus  inferior,  which  is  sometimes  to  be  discerned  through  it,  and  is  sometimes  entirely 
obscured  by  it;  of  part  of  the  Serratus  magnus  and  Superior  oblique,  which  it  covers;  and  of 
the  convex  oblique  ridges  formed  by  the  ribs  with  the  intervening  intercostal  spaces.  The 
anterior  border  of  the  muscle  is  the  only  part  which  gives  a  distinct  surface  form.  This  border 
may  be  traced,  when  the  muscle  is  in  action,  as  a  rounded  edge,  starting  from  the  crest  of  the 
ilium,  and  passing  obliquely  forward  and  upward  to  the  posterior  border  of  the  axilla,  where  it 
combines  with  the  Teres  major  in  forming  a  thick  rounded  fold,  the  posterior  boundary  of  the 
axillary  space.  The  muscles  in  the  second  layer  influence  to  a  very  considerable  extent  the  sur- 
face form  of  the  back  of  the  neck  and  upper  part  of  the  trunk.  The  Levator  anguli  scapulae 
reveals  itself  as  a  prominent  divergent  line,  running  downward  and  outward,  from  the  trans- 
verse processes  of  the  upper  cervical  vertebrae  to  the  angle  of  the  scapula,  covered  over  and 
toned  down  by  the  overlying  Trapezius.  The  Rhomboidei  produce,  when  in  action,  a  vertical 
eminence  between  the  vertebral  border  of  the  scapula  and  the  spinal  furrow,  varying  in  intensity 
according  to  the  condition  of  contractioij  or  relaxation  of  the  Trapezius  muscle,  by  which  they 
are  for  the  most  part  covered.  The  lowermost  part  of  the  Rhomboideus  major  is  uncovered 
by  the  Trapezius,  and  forms  on  the  surface  an  oblique  ridge  running  upward  and  inward  from 
the  inferior  angle  of  the  scapula.  Of  the  muscles  of  the  third  layer  of  the  back,  the  Serratus 
posticus  superior  does  not  in  any  way  influence  surface  form.  The  Serratus  posticus  inferior, 
when  in  strong  action,  may  occasionally  be  revealed  as  an  elevation  beneath  the  Latissimus 
dorsi.  The  Splenii  by  their  divergence  serve  to  broaden  out  the  upper  part  of  the  back  of  the 
neck  and  produce  a  local  fulness  in  this  situation,  but  do  not  otherwise  influence  surface  form. 
Beneath  all  these  muscles  those  of  the  fourth  layer — the  Erector  spince  and  its  continuations — 
influence  the  surface  form  in  a  decided  manner.  In  the  loins,  the  Erector  spinse,  bound  down 
by  the  lumbar  fascia,  forms  a  rounded  vertical  eminence,  which  determines  the  depth  of  the 
spinal  furrow,  and  which  below  tapers  to  a  point  on  the  posterior  surface  of  the  sacrum  and 
becomes  lost  there.  In  the  back  it  forms  a  flattened  plane  which  gradually  becomes  lost.  In 
the  neck  the  only  part  of  this  group  of  muscles  which  influences  surface  form  is  the  Trachelo- 
mastoid,  which  produces  a  short  convergent  line  across  the  upper  part  of  the  posterior  triangle 
of  the  neck,  appearing  from  under  cover  of  the  posterior  border  of  the  Sterno-mastoid  and 
being  lost  below  beneath  the  Trapezius. 

II.  MUSCLES  AND  FASCIiE  OF  THE  THORAX. 

The  muscles  belonging  exclusively  to  this  region  are  few  in  number.  They  are  the 

Intercostales  externi.  Triangularis  sterni. 

Intercostales  interni.  I^evatores  costarum. 

Infracostales.  Diaphragm. 

Intercostal  Fascia. — A  thin  but  firm  layer  of  fascia  covers  the  outer  surface  of 
the  External  intercostal  and  the  inner  surface  of  the  Internal  intercostal  muscles; 


OF    THE    THORAX  425 

and  a  third  layer,  more  delicate,  is  interposed  between  the  two  planes  of  muscular 
fibres.  These  are  the  intercostal  fasciae,  external,  viiddle,  and  internal;  they  are  best 
marked  in  those  situations  where  the  muscular  fibres  are  deficient,  as  between  the 
External  intercostal  muscles  and  sternum,  in  front,  and  between  the  Internal 
intercostals  and  spine,  behind. 

The  Intercostal  Muscles  (Figs.  291  and  315)  are  two  thin  planes  of  muscular 
and  tendinous  fibres,  placed  one  over  the  other,  filling  up  the  intercostal  spaces, 
and  being  directed  obliquely  between  the  margins  of  the  adjacent  ribs.  They 
have  received  the  name  external  and  internal  from  the  position  they  bear  to  one 
another.  The  tendinous  fibres  are  longer  and  more  numerous  than  the  muscular; 
hence  the  walls  of  the  intercostal  spaces  possess  very  considerable  strength,  to 
which  the  crossing  of  the  muscular  fibres  materially  contributes. 

The  External  Intercostals  (mm.  intercostales  externi)  are  eleven  in  number  on 
each  side.  They  extend  from  the  tubercles  of  the  ribs,  behind,  to  the  commence- 
ment of  the  cartilages  of  the  ribs,  in  front,  where  they  terminate  in  a  thin  mem- 
brane, the  anterior  intercostal  membrane,  which  is  continued  forward  to  the  sternum. 
They  arise  from  the  lower  border  of  the  rib  above,  and  are  inserted  into  the  upper 
border  of  the  rib  below.  In  the  two  lowest  spaces  they  extend  to  the  ends  of  the 
cartilages,  and  in  the  upper  two  or  three  spaces  they  do  not  quite  extend  to  the  ends 
of  the  ribs.  Their  fibres  are  directed  obliquely  downward  and  forward,  in  a 
similar  direction  with  those  of  the  External  oblique  muscle  of  the  abdomen. 
They  are  thicker  than  the  Internal  intercostals. 

Relations. — By  their  oider  surface,  with  the  muscles  which  immediately  invest 
the  chest — viz.,  the  Pectoralis  major  and  minor,  Serratus  magnus,  and  Rhom- 
boideus  major,  Serratus  posticus  superior  and  inferior.  Scalenus  posticus,  Ilio- 
costalis,  Longissimus  dorsi,  Cervicalis  ascendens,  Transversalis  cervicis,  I>eva- 
tores  costarum,  Obliquus  externus  abdominis,  and  the  Latissimus  dorsi;  by  their 
internal  surface,  with  the  middle  intercostal  fascia,  which  separates  them  from  the 
intercostal  vessels  and  nerve  and  the  Internal  intercostal  muscles,  and,  behind, 
from  the  pleura. 

The  Internal  Intercostals  (mw.  intercostales  interni)  are  also  eleven  in  number  on 
each  side.  They  commence  anteriorly  at  the  sternum  in  the  interspaces  between 
the  cartilages  of  the  true  ribs,  and  from  the  anterior  extremities  of  the  cartilages 
of  the  false  ribs,  and  extend  backward  as  far  as  the  angles  of  the  ribs,  whence  they 
are  continued  to  the  vertebral  column  by  a  thin  aponeurosis,  the  'posterior  inter- 
costal membrane.  They  arise  from  the  ridge  on  the  inner  surface  of  the  rib  above, 
as  well  as  from  the  corresponding  costal  cartilage,  and  are  inserted  into  the  upper 
border  of  the  rib  below.  Their  fibres  are  directed  obliquely  downward  and  back- 
ward, passing  in  the  opposite  direction  to  the  fibres  of  the  External  intercostal 
muscle. 

Relations. — By  their  external  surface,  with  the  intercostal  vessels  and  nerves 
and  the  External  intercostal  muscles;  near  the  sternum,  with  the  anterior  inter- 
costal membrane  and  the  Pectoralis  major.  By  their  internal  surface,  with  the 
pleura  costalis.  Triangularis  sterni,  and  Diaphragm. 

The  Infracostales  (mm.  subcostales)  consist  of  muscular  and  aponeurotic  fas- 
ciculi, which  vary  in  number  and  length;  they  are  placed  on  the  inner  surface  of  the 
ribs,  where  the  Internal  intercostal  muscles  cease;  they  arise  from  the  inner  sur- 
face of  one  rib,  and  are  inserted  into  the  inner  surface  of  the  first,  second,  or  third 
rib  below.  Their  direction  is  most  usually  oblique,  like  the  Internal  intercostals. 
They  are  most  frequent  between  the  lower  ribs. 

The  Triangularis  Sterni  (m.  transversus  thoracis)  (Fig.  284)  is  a  thin  plane  of 
muscular  and  tendinous  fibres,  situated  upon  the  inner  wall  of  the  front  of  the  chest. 
It  arises  from  the  lower  third  of  the  posterior  surface  of  the  sternum,  from  the 
posterior  surface  of  the  ensiform  cartilage,  and  from  the  sternal  ends  of  the  costal 


426 


THE  MUSCLES  AND   FASCIAE 


cartilages  of  the  three  or  four  lower  true  ribs.  Its  fibres  diverge  upward  and  out- 
ward, to  be  inserted  by  digitations  into  the  lower  borders  and  inner  surfaces  of  the 
costal  cartilages  of  the  second,  third,  fourth,  fifth,  and  sixth  ribs.  The  lowest 
fibres  of  this  muscle  are  horizontal  in  their  direction,  and  are  continuous  with 
those  of  the  Transversalis ;  those  which  succeed  are  oblique,  whilst  the  superior 
fibres  are  almost  vertical.  This  muscle  varies  much  in  its  attachment,  not  only  in 
different  bodies,  but  on  opposite  sides  of  the  same  body. 

Relations. — In  front,  with  the  sternum,  ensiform  cartilage,  costal  cartilages, 
Internal  intercostal  muscles,  and  internal  mammary  vessels;  behind,  with  the 
pleura,  pericardium,  and  anterior  mediastinum. 


STERNO-MASTOID 


SUBCLAVIUS 


SUBCLAVIUS. 


Internal  mam,' 
mary  artery. 


TRIANGULARIS 
STERN  I. 


TRANSVERSALIS    ABDOMINIS. 


Fig.  284. — Posterior  surface  of  sternum  and  costal  cartilages,  showing  Triangularis  sterni  muscle      (From  a 
preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

The  Levatores  Costarum  (Fig.  283),  twelve  in  number  on  each  side,  are  small 
tendinous  and  fleshy  bundles  which  arise  from  the  extremities  of  the  transverse 
processes  of  the  seventh  cervical  and  eleven  upper  dorsal  vertebrae,  and,  passing 
obliquely  downward  and  outward,  are  inserted  into  the  upper  border  of  the  rib 
below  them,  between  the  tubercle  and  the  angle.  The  Inferior  levatores  divide 
into  two  fasciculi,  one  of  which  is  inserted  as  above  described;  the  other  fasciculus 
passes  down  to  the  second  rib  below  its  origin ;  thus,  each  of  the  lower  ribs  receives 
fibres  from  the  transverse  processes  of  two  vertebrfe. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  intercostal  nerves. 


OF   THE    THORAX 


427 


The  Diaphragm  (diaphragma,  from  d:d(foayna,  a  partition  wall)  (Figs.  285,  286, 
and  287)  is  a  thin,  musculo-fibrous  septum,  consisting  of  muscular  fibres  externally, 
which  arise  from  the  circumference  of  the  thoracic  cavity  and  pass  upward  and 
inward  to  converge  to  a  central  tendon.  It  is  placed  obliquely  at  the  junction  of 
the  upper  with  the  middle  third  of  the  trunk,  and  separates  the  thorax  from  the 
abdomen,  forming  the  floor  of  the  former  cavity  and  the  roof  of  the  latter.  It  is 
elliptical,  its  longest  diameter  being  from  side  to  side;  is  somewhat  fan-shaped,  the 
broad  elliptical  portion  being  horizontal,  the  narrow  part,  the  crura,  which  repre- 
sents the  handle  of  the  fan,  vertical,  and  joined  at  right  angles  to  the  former.  It 
is  from  this  circumstance  that  some  anatomists  describe  it  as  consisting  of  two 
portions,  the  upper  or  great  muscle  of  the  Diaphragm,  and  the  lower  or  lesser 
muscle.  It  arises  from  the  whole  of  the  internal  circumference  of  the  thorax, 
being  attached,  in  front,  by  fleshy  fibres  to  the  ensiform  cartilage,  sternal  portion 
of  the  Diaphragm  (pars  sternalis);  on  either  side,  to  the  inner  surface  of  the 
cartilages  and  bony  portions  of  the  six  or  seven  inferior  ribs,  costal  portion  (pars 
costalis),  interdigitating  with  the  Transversalis;  and  behind,  to  two  aponeurotic 
arches,  named  the  ligamentum  arcuatum  externum  and  the  ligamentum  arcuatum 
internum,  and  by  the  crura,  to  the  lumbar  vertebrae,  lumbar  portion  (pars  lumhalis). 
The  fibres  from  these  sources  vary  in  length:  those  arising  from  the  ensiform 
appendix  are  very  short  and  occasionally  aponeurotic;  those  from  the  ligamenta 
arcuata,  and  more  especially  those  from  the  cartilages  of  the  ribs  at  the  side 
of  the  chest,  are  longer,  describe  well-marked  curves  as  they  ascend,  and  finally 
converge  to  be  inserted  into  the  circumference  of  the  central  tendon.  Between 
the  sides  of  the  muscular  slip  from  the  ensiform  appendix  and  the  cartilages  of 
the  adjoining  ribs  the  fibres  of  the  Diaphragm  are  deficient,  the  interval  being 
filled  by  areolar  tissue,  covered  on  the  thoracic  side  by  the  pleurae;  on  the  abdom- 
inal, by  the  peritoneum.  This  is,  consequently,  a  weak  point,  and  a  portion  of 
the  contents  of  the  abdomen  may  protrude  through  it  into  the  chest,  forming  a 
phrenic  or  diaphragmatic  hernia,  or  a  collection  of  pus  in  the  mediastinum  may 
descend  through  it,  so  as  to  point  at  the  epigastrium.  A  triangular  gap  is  some- 
times seen  between  the  fibres  springing  from  the  internal  and  those  arising  from 
the  external  arcuate  ligament.  When  it  exists,  the  kidney  is  separated  from  the 
pleura  only  by  fatty  and  areolar  tissue. 

A  congenital  deficiency  in  the  Diaphragm  may  produce  diaphragmatic  hernia; 
in  deficiency  of  the  central  tendon  the  hernia  passes  into  the  pericardial  sac;  in 
deficiency  of  one  of  the  lateral  portions  the  hernia  passes  into  the  pleural  sac. 

There  are  five  arcuate  ligaments,  two  internal,  two  external,  and  one  middle. 

The  Ligamentum  Arcuatum  Internum  (arcus  lumbocostalis  medialis)  is  a  tendinous 
arch,  thrown  across  the  upper  part  of  the  Psoas  magnus  muscle,  on  each  side  of 
the  spine.  It  is  connected,  by  one  end,  to  the  outer  side  of  the  body  of  the  first  or 
second  lumbar  vertebra,  being  continuous  with  the  outer  side  of  the  tendon  of 
the  corresponding  crus ;  and,  by  the  other  end,  to  the  front  of  the  transverse  process 
of  the  first,  and  sometimes  also  to  that  of  the  second,  lumbar  vertebra. 

The  Ligamentum  Arcuatimi  Externum  (arcus  lumbocostalis  lateralis)  is  the  thick- 
ened upper  margin  of  the  anterior  lamella  of  the  lumbar  fascia;  it  arches  across 
the  upper  part  of  the  Quadratus  lumborum,  being  attached,  by  one  extremity,  to 
the  front  of  the  transverse  process  of  the  first  lumbar  vertebra,  and,  by  the  other, 
to  the  apex  and  lower  margin  of  the  last  rib. 

The  arch  of  fibrous  tissue  which  connects  the  crura  of  the  diaphragm  in  front 
of  the  aorta  is  sometimes  called  the  middle  arcuate  ligament.  The  Diaphragm  is 
connected  to  the  spine  by  two  crura  or  pillars,  which  are  situated  on  the  bodies  of 
lumbar  vertebrae,  on  each  side  of  the  aorta.  The  crura,  at  their  origin,  are  ten- 
dinous in  structure;  the  right  crus,  larger  and  longer  than  the  left,  arising  from 
the  anterior  common  ligament  and  intervertebral  substances  of  the  three  or  four 


428 


THE  MUSCLES   AND    FASCIAE 


upper  lumbar  vertebrse;  the  left,  from  the  two  upper  lumbar  vertebrae.     These 
tendinous  portions  of  the  crura  pass  forward  and  inward,  and  gradually  con- 


CESOPHAGUS 


FORAMEN    QUADRATUM 
FOR  VENA  CAVA 


CENTRAL  TENDON, 
LEFT  SIDE 


AORTA  CENTRAL  TENDON, 

RIGHT  SIDE 

Fig.  285. — The  Diaphragm,  seen  from  above.      (Poirier  and  Charpy.) 


Fig.  286.— The  Diaphragm,  Meised  from  in  front.     (Testut.) 

verge  to  meet  in  the  middle  line,  forming  an  arch,  beneath  which  passes  the 
aorta,  vena  azygos  major,  and  thoracic  duct.  From  this  tendinous  arch  muscular 
fibres  arise,  which  diverge,  the  outermost  portion  being  directed  upward  and 


OF    THE    THORAX 


429 


outward  to  the  central  tendon;  the  innermost  decussating  in  front  of  the  aorta 
and  then  diverging,  so  as  to  surround  the  oesophagus  before  ending  in  the  central 
tendon.  The  fibres  derived  from  the  right  crus  are  the  most  numerous  and  pass 
in  front  of  those  derived  from  the  left.  His  and  Spalteholz  teach  that  three  crura 
exist  on  each  side — viz.,  the  crus  mediale,  arising  from  the  third  and  fourth  lumbar 
vertebrae;  the  crus  intermedium,  from  the  second  and  third  lumbar  vertebrte;  and 
the  crus  laterale,  from  the  second  or  first  lumbar  vertebrae,  and  from  the  band  of 
fascia  which  is  stretched  between  the  lateral  part  of  the  body  of  the  first  lumbar 
vertebra  and  the  transverse  process  of  the  second  lumbar  vertebra  in  front  of  the 
Psoas  muscle. 

The  Central  or  Cordiform  Tendon  of  the  Diaphragm  {centrum  tendineum)  is  a  thin 
but  strong  tenflinous  aponeurosis,  situated  at  the  centre  of  the  vault  formed  by 
the  muscle,  immediately  below  the  pericardium,  with  which  it  is  partly  blended. 
It  is  shaped  somewhat  like  a  trefoil  leaf,  consisting  of  three  divisions,  or  leaflets. 


Fig.  287. — The  Diaphragm,  viewed  from  below.    (Testut.) 

separated  from  one  another  by  slight  indentations.  The  right  leaflet  is  the  largest; 
the  middle  one,  directed  toward  the  ensiform  cartilage,  the  next  in  size;  and  the 
left,  the  smallest.  In  structure,  the  tendon  is  composed  of  several  planes  of  fibres 
which  intersect  one  another  at  various  angles,  and  unite  into  straight  or  curved 
bundles — an  arrangement  which  affords  it  additional  strength. 

The  Openings. — The  openings  connected  with  the  Diaphragm  are  three  large 
and  several  smaller  apertures.  The  former  are  the  aortic,  the  oesophageal,  and  the 
opening  for  the  vena  cava. 

The  Aortic  Opening  (hiatus  aorticus)  is  the  lowest  and  the  most  posterior  of  the 
three  large  apertures  connected  with  this  muscle,  being  at  the  level  of  the  first 
lumbar  vertebra.  It  is  situated  slightly  to  the  left  of  the  middle  line,  immediately 
in  front  of  the  bodies  of  the  vertebrsTp;  and  is,  therefore,  behind  the  Diaphragm,  not 
in  it.  It  is  an  osseo-aponeurotic  aperture,  formed  by  a  tendinous  arch  thrown 
across  the  front  of  the  bodies  of  the  vertebrae,  from  the  crus  on  one  side  to  that 
on  the  other,  and  transmits  the  aorta,  vena  azygos  major,  and  thoracic  duct. 
Sometimes  the  vena  azygos  major  is  transmitted  upward  through  the  right  crus. 


430  THE  MUSCLES  AND    FASCIA 

Occasionally  some  tendinous  fibres  are  prolonged  across  the  bodies  of  the  ver- 
tebrae from  the  inner  part  of  the  lower  end  of  the  crura,  passing  behind  the  aorta, 
and  thus  converting  the  opening  into  a  fibrous  ring. 

The  OEsophageal  Opening  {hiatus  cesophageus)  is  situated  at  the  level  of  the  tenth 
dorsal  vertebrae;  it  is  elliptical  in  form,  oblique  in  direction,  muscular  in  structure, 
and,  formed  by  the  decussating  fibres  of  the  two  crura,  is  placed  above,  and,  at 
the  same  time,  anterior,  and  a  little  to  the  left  of  the  preceding.  It  transmits  the 
oesophagus  and  pneumogastric  nerves  and  some  small  oesophageal  arteries.  The 
anterior  margin  of  this  aperture  is  occasionally  tendinous,  being  formed  by  the 
margin  of  the  central  tendon.  The  posterior  and  lateral  margins  are  thick  and 
the  gullet  is  in  contact  with  them  for  about  half  an  inch.  The  right  margin  of 
the  oesophageal  opening  is  particularly  prominent  and  lies  in  the  oesophageal 
groove  on  the  posterior  surface  of  the  left  lobe  of  the  liver. 

The  Opening  for  the  Vena  Cava  or  the  Foramen  Quadratum  (foramen  vence  cavoe) 
is  the  highest  opening,  being  about  on  the  level  of  the  disk  between  the  eighth 
and  ninth  dorsal  vertebrae;  it  is  quadrilateral  in  form,  tendinous  in  structure,  and 
placed  at  the  junction  of  the  right  and  middle  leaflets  of  the  central  tendon, 
its  margins  being  adherent  to  the  wall  of  the  inferior  vena  cava. 

The  right  cms  transmits  the  greater  and  lesser  splanchnic  nerves  of  the  right 
side;  the  left  crus  transmits  the  greater  and  lesser  splanchnic  nerves  of  the  left 
side,  and  the  vena  azygos  minor.  The  gangliated  cords  of  the  sympathetic 
usually  enter  the  abdominal  cavity  by  passing  behind  the  internal  arcuate  liga- 
ments. 

Serous  Membranes. — The  serous  membranes  in  relation  with  the  Diaphragm  are 
four  in  number:  three  lining  its  upper  or  thoracic  surface;  one,  its  abdominal.  The 
three  serous  membranes  on  its  upper  surface  are  the  pleura  on  either  side  and  the 
pericardium,  which  covers  the  middle  portion  of  the  tendinous  centre.  The 
serous  membrane  covering  the  under  surface  of  the  Diaphragm  is  a  portion  of 
the  general  peritoneal  membrane  of  the  abdominal  cavity. 

The  Diaphragm  is  arched,  being  convex  toward  the  chest  and  concave  toward  the 
abdomen.  The  right  portion  forms  a  complete  arch  from  before  backward,  being 
accurately  moulded  over  the  convex  surface  of  the  liver,  and  having  resting  upon 
it  the  concave  base  of  the  right  lung.  The  left  portion  is  arched  from  before  back- 
ward in  a  similar  manner;  but  the  arch  is  narrower  in  front,  being  encroached  upon 
by  the  pericardium,  and  lower  than  the  right,  at  its  summit,  by  about  three-quarters 
of  an  inch.  It  supports  the  base  of  the  left  lung,  and  covers  the  great  end  of  the 
stomach,  the  spleen,  and  left  kidney.  At  its  circumference  the  Diaphragm  is 
higher  in  the  mesial  line  of  the  body  than  at  either  side;  but  in  the  middle  of  the 
thorax  the  central  portion,  which  supports  the  heart,  is  on  a  lower  level  than  the 
two  lateral  portions. 

Nerves. — The  Diaphragm  is  supplied  by  the  phrenic  nerves,  the  lower  inter- 
costal nerves  and  the  phrenic  plexus  of  the  sympathetic. 

Actions. — The  Intercostals  are  the  chief  agents  in  the  movement  of  the  ribs 
in  ordinary  respiration.  When  the  first  rib  is  elevated  and  fixed  by  the  Scaleni,  the 
External  intercostals  raise  the  other  ribs,  especially  their  forepart,  and  so  increase 
the  capacity  of  the  chest  from  before  backward ;  at  the  same  time  they  evert  their 
lower  borders,  and  so  enlarge  the  thoracic  cavity  transversely.  The  Internal 
intercostals,  at  the  side  of  the  thorax,  depress  the  ribs  and  invert  their  lower 
borders,  and  so  diminish  the  thoracic  cavity;  but  at  the  forepart  of  the  chest  these 
muscles  assist  the  External  intercostals  in  raising  the  cartilages.*    The  Levatores 

^  The  view  of  the  action  of  the  Intercostal  muscles  given  in  the  text  is  that  which  is  taught  by  Hutchinson 
(Cycl.  of  Anat.  and  Phys.,  art.  Thorax),  and  is  usually  adopted  in  our  schools.  It  is,  however,  much  dis- 
puted. Hamberger  believed  that  the  External  intercostals  act  as  elevators  of  the  ribs,  or  muscles  of  inspira- 
tion, while  the  internal  act  in  expiration.  Haller  taught  that  both  sets  of  muscles  act  in  common — viz.,  as  muscles 
of  inspiration — and  this  view  is  adopted  by  many  of  the  best  anatomists  of  the  Continent,  and  appears  sup- 


OF    THE    THORAX  43 1 

costarum  assist  the  External  intercostals  in  raising  the  ribs.  The  Triangularis 
sterni  draws  flown  the  costal  cartilages;  it  is  therefore  an  expiratory  muscle. 

The  Diaphragm  is  the  principal  muscle  of  inspiration.  When  in  a  condition 
of  rest  the  muscle  presents  a  domed  surface,  concave  toward  the  abdomen;  and 
consists  of  a  circumferential  muscular  and  a  central  tendinous  part.  When 
the  muscular  fibres  contract,  they  become  less  arched,  or  nearly  straight,  and 
thus  cause  the  central  tendon  to  descend,  and  in  consequence  the  level  of  the 
chest-wall  is  lowered,  the  vertical  diameter  of  the  chest  being  proportionally 
increased.  In  this  descent  the  different  parts  of  the  tendon  move  unequally. 
The  left  leaflet  descends  to  the  greatest  extent;  the  right  to  a  less  extent,  on 
account  of  the  liver;  and  the  central  leaflet  the  least,  because  of  its  connection  to 
the  pericardium.  In  descending  the  Diaphragm  presses  on  the  abdominal  viscera, 
and  so  to  a  certain  extent  causes  a  projection  of  the  abdominal  wall;  but  in  conse- 
quence of  these  viscera  not  yielding  completely,  the  central  tendon  becomes  a  fixed 
point,  and  enables  the  circumferential  muscular  fibres  to  act  from  it,  and  so  elevate 
the  lower  ribs  and  expand  the  lower  part  of  the  thoracic  cavity;  and  Duchenne 
has  shown  that  the  Diaphragm  has  the  power  of  elevating  the  ribs,  to  which  it 
is  attached,  by  its  contraction,  if  the  abdominal  viscera  are  in  situ,  but  that  if  these 
organs  are  removed,  this  power  is  lost.  When  at  the  end  of  inspiration  the  Dia- 
phragm relaxes,  the  thoracic  walls  return  to  their  natural  position  in  consequence 
of  their  elastic  reaction  and  of  the  elasticity  and  weight  of  the  displaced  viscera.^ 

In  all  expulsive  acts  the  Diaphragm  is  called  into  action,  to  give  additional 
power  to  each  expulsive  effort.  Thus,  before  sneezing,  coughing,  laughing,  and 
crying,  before  vomiting,  previous  to  the  expulsion  of  the  urine  and  faeces,  or  of 
the  foetus  from  the  womb,  a  deep  inspiration  takes  place. 

The  height  of  the  Diaphragm  is  constantly  varying  during  respiration,  the 
muscle  being  carried  upward  or  downward  from  the  average  level;  its  height  also 
varies  according  to  the  degree  of  distention  of  the  stomach  and  intestines,  and  the 
size  of  the  liver.  After  a  forced  expiration,  the  right  arch  is  on  a  level,  in  front, 
with  the  fourth  costal  cartilage;  at  the  side,  with  the  fifth,  sixth,  and  seventh 
ribs;  and  behind,  with  the  eighth  rib,  the  left  arch  being  usually  from  one  to  two 
ribs'  breadth  below  the  level  of  the  right  one.  In  a  forced  inspiration,  it  descends 
from  one  to  two  inches;  its  slope  would  then  be  represented  by  a  fine  drawn 
from  the  ensiform  cartilage  toward  the  tenth  rib.  Prof.  Wm.  S.  Forbes^  is  of  the 
opinion  that  the  Diaphragm  is  an  appendage  of  the  circulatory  apparatus  rather 
than  the  chief  agent  in  respiration.  He  maintains  that  the  opening  in  the 
vena  cava  is  stationary  and  holds  a  constant  relation  to  the  ninth  dorsal  verte- 
bra. He  emphasizes  the  fact  that  the  base  of  the  pericardium  is  attached  to  the 
central  tendon  of  the  Diaphragm,  and  on  the  anterior  and  left  side.  The  muscular 
fibres  of  the  Diaphragm  ascend  upon  and  are  attached  to  the  pericardium.  Pro- 
longations of  the  fibrous  pericardium  pass  upward  as  the  pericardial  ligaments. 
These  ligaments  form  fibrous  planes  reaching  from  each  side  of  the  central 
tendon  of  the  Diaphragm  to  the  "  bony  apex  of  the  thoracic  line  "  and  to  the 
fascia  stretched  across  the  thoracic  apex,  and  they  may  be  called  the  "  superior 
tendinous  crura."  It  is  thus  evident  that  the  deep  cervical  fascia  is  connected 
to  the  lateral  and  superior  parts  of  the  pericardium.     At  birth  the  muscular 

ported  by  many  observations  made  on  the  human  subject  under  various  conditions  of  disease,  and  on  living 
animals  after  the  muscles  have  been  exposed  under  chloroform.  The  reader  may  consult  an  interestmg  paper 
bv  Dr.  Cleland  in  the  Journal  of  Anat.  and  Phys.,  No.  II.,  May,  1867,  p.  209,  On  the  Hutchmsonian  Theory 
of  the  Action  of  the  Intercostal  Muscles,  who  refers  also  to  Henle,  Luschka,  Budge,  and  Baumler,  Observa- 
tions on  the  Action  of  the  Intercostal  Muscles,  Eriangen,  1860.  (In  New  Syd.  Soc.  s  Year-book  for  1861,  p.  69.) 
Dr.  W.  W.  Keen  has  come  to  the  conclusion,  from  experiments  made  upon  a  crimmal  executed  by  hangmg, 
that  the  External  intercostals  are  muscles  of  expiration,  as  they  pulled  the  ribs  down,  while  the  Internal  inter- 
costals pulled  the  ribs  up  and  are  muscles  of  inspiration  (Trans.  Coll.  Phys.,  Philadelphia,  Third  beries,  vol.  i., 

>  For  a  detailed  description  of  the  general  relations  of  the  Diaphragm,  and  its  action,  refer  to  Dr.  Sibson's 
Medical  Anatomy. 

*  American  Journal  of  the  Medical  Sciences,  July,  1880. 


432  THE  MUSCLES   AND   FASCIAE 

fibres  of  the  Diaphragm  contract  at  the  first  inspiration.  The  ductus  arteriosus 
is  lodged  in  an  elhptical  opening  of  a  tendinous  scaflolding.  The  contractions 
of  the  Diaphragm  cause  the  tendinous  scafi^olding  to.  compress  the  ductus  arteri- 
osus "  and  eventually  close  it."  The  chief  agents  in  the  compression  are  the 
muscular  fibres  which  pass  from  the  Diaphragm  to  the  pericardium.  When  the 
lateral  wings  of  the  Diaphragm  descend  they  tend  to  form  a  vacuum  in  the  thorax 
and  thus  assist  the  venous  circulation. 

"  The  descent  of  the  Diaphragm  is  not  necessary  to  respiration,"  but  it  "  is 
necessary  in  order  to  protect  the  heart  from  the  movement  of  surrounding 
viscera,  and  in  order  to  promote  the  free  circulation  of  the  blood  through  the 
vessels  forming  the  cardiac  roots." 

Muscles  of  Inspiration  and  Expiration. — The  muscles  which  assist  the  action 
of  the  Diaphragm  in  ordinary  tranquil  inspiration  are  the  Intercostals  and  the 
Levatores  costarum,  as  above  stated,  and  the  Scaleni.  When  the  need  for  more 
forcible  action  exists,  the  shoulders  and  the  base  of  the  scapula  are  fixed,  and  then 
the  powerful  muscles  of  forced  inspiration  come  into  play;  the  chief  of  these  are 
the  Trapezius,  the  Pectoralis  minor,  the  Serratus  posticus  superior  and  inferior, 
and  the  Rhomboidei.  The  lower  fibres  of  the  Serratus  magnus  may  possibly  assist 
slightly  in  dilating  the  chest  by  raising  and  everting  the  ribs.  The  Sterno-mastoid 
also,  when  the  head  is  fixed,  assists  in  forced  inspiration  by  drawing  up  the  sternum 
and  by  fixing  the  clavicle,  and  thus  affording  a  fixed  point  for  the  action  of  the 
muscles  of  the  chest.  The  Ilio-costalis  and  Quadratus  lumborum  assist  in  forced 
inspiration  by  fixing  the  last  rib. 

The  ordinary  action  of  expiration  is  hardly  effected  by  muscular  force,  but 
results  from  a  return  of  the  walls  of  the  thorax  to  a  condition  of  rest,  owing  to 
their  own  elasticity  and  to  that  of  the  lungs.  Forced  expiratory  actions  are  per- 
formed mainly  by  the  flat  muscles  (Obliqui  and  Transversalis)  of  the  abdomen^ 
assisted  by  the  Rectus.  Other  muscles  of  forced  expiration  are  the  Internal 
intercostals  and  Triangularis  sterni  (as  above  mentioned).^ 

III.  MUSCLES  OF  THE  ABDOMEN. 

The  muscles  of  the  abdomen  may  be  divided  into  two  groups:  1.  The  super- 
ficial muscles  of  the  abdomen.    2.  The  deep  muscles  of  the  abdomen. 

1.  The  Superficial  Muscles  of  the  Abdomen. 

The  Muscles  in  this  region  are,  the 

External  Oblique.  Transversalis. 

Internal  Obhque.  Rectus. 

Pyramidalis. 

Dissection  (Fig.  288). — To  dissect  the  abdominal  muscles,  make  a  vertical  incision  from  the 
ensiform  cartilage  to  the  symphysis  pubis;  a  second  incision  from  the  umbilicus  obliquely  upward 
and  outward  to  the  outer  surface  of  the  chest,  as  high  as  the  lower  border  of  the  fifth  or  sixth 
rib;  and  a  third,  commencing  midway  between  the  umbilicus  and  pubes,  transversely  outward 
to  the  anterior  superior  iliac  spine,  and  along  the  crest  of  the  ilium  as  far  as  its  posterior  third. 
Then  reflect  the  three  flaps  included  between  these  incisions  from  within  outward,  in  the  lines 
of  direction  of  the  muscular  fibres.  If  necessary,  the  abdominal  muscles  may  be  made  tense 
by  inflating  the  peritoneal  cavity  through  the  umbilicus. 

>  A.  M.  Patterson  (article  on  Myology,  in  D.  J.  Cunningham's  Text-book  of  Anatomy)  states  that  the  move- 
ment of  expiration  is  performed  by  the  elasticity  of  the  lungs,  the  weight  of  the  chest-wall,  the  elevation  of 
the  Diaphragm,  the  action  of  the  Triangularis  sterni  and  muscles  of  the  abdominal  wall,  possiblv  aided  by  the 
interosseous  fibres  of  the  Internal  intercostal  muscles.  The  same  author  states  that  the  movement  of  inspira- 
tion IS  performed  ordinarily  by  the  descent  of  the  Diaphragm  and  the  action  of  this  muscle  in  elevating  the 
ribs,  the  action  of  the  External  intercostals  and  Levatores  costarum,  probably  the  action  of  the  whole  of  each 
Iriternal  intercostal,  of  the  Scaleni,  and  of  the  Serrati  postici.  The  accessory  muscles  of  respiration  are  employed 
when  voluntary  respiratory  effort  is  necessary.  Patterson  names  them  as  follows:  The  Quadratus  lumborum, 
Pectorales,  Serratus  magnus,  Sterno-mastoid,  Latissimus  dorsi,  Infra-hyoid  muscles,  Extensors  of  the  spine. 


OF   THE  ABDOMEN 


433 


Superficial  Fascia. — The  superficial  fascia  of  the  abdomen  consists,  over  the 
greater  part  of  the  abdominal  wall,  of  a  single  layer  of  fascia,  which  contains  a 
variable  amount  of  fat;  but  as  this  layer  approaches  the  groin  it  is  easily  divisible 
into  two  layers,  between  which  are  found  the  superficial  vessels  and  nerves  and 
the  superficial  inguinal  lymphatic  glands.  The  superficial  layer  of  the  superficial 
fascia,  or  the  fascia  of  Camper,  is  thick,  areolar  in  texture,  containing  adipose  tissue 
in  its  meshes,  the  quantity  of  which  varies  in  different  subjects.  Below  it  passes 
over  Poupart's  ligament,  and  is  continuous  with  the  outer  layer  of  the  superficial 
fascia  of  the  thigh.  In  the  male  this  fascia  is  continued  over  the  penis  and  outer  sur- 
face of  the  cord  to  the  scrotum,  where  it  helps  to 
form  the  dartos.  As  it  passes  to  the  scrotum  it 
changes  its  character,  becoming  thin,  destitute  of 
adipose  tissue,  and  of  a  pale  hue,  it  has  a  reddish 
color,  and  in  the  scrotum  it  acquires  some  invol- 
untary muscular  fibres.  From  the  scrotum  it  may 
be  traced  backward  to  be  continuous  with  the 
superficial  fascia  of  the  perinseum.  In  the  female 
this  fascia  is  continued  into  the  labia  majora. 
The  deep  layer  of  the  superficial  fascia  or  the  fascia 
of  Scarpa,  is  thinner  and  more  membranous  in 
character  than  the  superficial  layer.  In  the  mid- 
dle line  it  is  intimately  adherent  to  the  linea  alba  g  Dig. 
and  to  the  symphysis  pubis,  and  is  prolonged  on  section  of 
to  the  dorsum  of  the  penis,  forming  the  suspen-  ^hernia. 
sory  ligament  of  the  penis;  above,  it  joins  the 
superficial  layer  and  is  continuous  with  the 
superficial  fascia  over  the  rest  of  the  trunk; 
below,  it  blends  with  the  fascia  lata  of  the 
thigh  a  little  below  Poupart's  ligament;  and 
below  and  internally  it  is  continued  over  the 
penis  and  spermatic  cord  to  the  scrotum,  where 
it  helps  to  form  the  dartos.  From  the  scrotum 
it  may  be  traced  backward  to  be  continuous  with  the  deep  layer  of  the  super- 
ficial fascia  of  the  perinseum.  In  the  female  it  is  continued  into  the  labia 
majora. 

Deep  Fascia. — The  deep  fascia  invests  the  external  oblique  muscle,  but  is  so 
thin  over  the  aponeurosis  of  the  muscle  as  to  be  scarcely  recognizable. 

The  External  or  Descending  Oblique  Muscle  (m.  obliquus  extemus  abdominis) 
(Fig.  289)  is  situated  on  the  side  and  forepart  of  the  abdomen;  being  the  largest 
and  the  most  superficial  of  the  three  flat  muscles  in  this  region.  It  is  broad,  thin, 
and  irregularly  quadrilateral,  its  muscular  portion  occupying  the  side,  its  aponeu- 
rosis the  anterior  wall,  of  the  abdomen.  It  arises,  by  eight  fleshy  digitations, 
from  the  external  surface  and  lower  borders  of  the  eight  inferior  ribs;  these 
digitations  are  arranged  in  an  oblique  line  running  downward  and  backward; 
the  upper  ones  being  attached  close  to  the  cartilages  of  the  corresponding  ribs; 
the  lowest,  to  the  apex  of  the  cartilage  of  the  last  rib;  the  intermediate  ones,  to 
the  ribs  at  some  distance  from  their  cartilages.  The  five  superior  serrations 
increase  in  size  from  above  downward,  and  are  received  between  corresponding 
processes  of  the  Serratus  magnus;  the  three  lower  ones  diminish  in  size  from 
above  downward,  receiving  between  them  corresponding  processes  from  the  Latis- 
simus  dorsi.  From  these  attachments,  the  fleshy  fibres  proceed  in  various  direc- 
tions. Those  from  the  lowest  ribs  pass  nearly  vertically  downward,  to  be  inserted 
into  the  anterior  half  of  the  outer  lip  of  the  crest  of  the  ilium ;  the  middle  and 
upper  fibres,  directed  downward  and  forward,  terminate  in  an  aponeurosis,  oppo- 

28 


Fig.  288. — Dissection  of  abdomen. 


434 


THE  MUSCLES  AND    FASCIAE 


site  a  line  drawn  from  the  prominence  of  the  ninth  costal  cartilage  to  the  anterior 
superior  spinous  process  of  the  ilium. 

Aponeurosis  of  External  Oblique. — The  aponeurosis  of  the  external  oblique  is  a 
thin,  but  strong  membranous  aponeurosis,  the  fibres  of  which  are  directed 
obliquely  downward  and  inward.  It  is  joined  with  that  of  the  opposite  muscle 
along  the  median  line,  covers  the  whole  of  the  front  of  the  abdomen;  above,  it  is 
connected  with  the  lower  border  of  the  Pectoralis  major;  below,  its  fibres  are  closely 


External  abdo- 
minal ring. 
GimbernaVs 
ligament. 


\Pubes. 
Fig.  289. — The  External  oblique  muscle. 


aggregated  together,  and  extend  obliquely  across  from  the  anterior  superior  spine 
of  the  ilium  to  the  spine  of  the  os  pubis  and  the  linea  ilio-pectinea.  In  the  median 
line  it  interlaces  with  the  aponeurosis  of  the  opposite  muscle,  forming  the  linea 
alba,  which  extends  from  the  ensiform  cartilage  to  the  symphysis  pubis. 

That  portion  of  the  aponeurosis  which  extends  between  the  anterior  superior 
spine  of  the  ilium  and  the  spine  of  the  os  pubis  is  a  broad  band,  folded  inward, 
and  continuous  below  with  the  fascia  lata;  it  is  called  Poupart's  ligament  or  the 


OF    THE   ABDOMEN 


435 


ligament  of  Fallopius.  The  portion  which  is  reflected  from  Poupart's  ligament 
at  the  spine  of  the  os  pubis  along  the  pectineal  line  is  called  Gimbemat's  ligament. 
From  the  point  of  attachment  of  the  latter  to  the  pectineal  line,  a  few  fibres 
pass  upward  and  inward,  behind  the  inner  pillar  of  the  ring,  to  the  linea  alba. 
They  diverge  as  they  ascend,  and  form  a  thin,  triangular,  fibrous  layer,  which  is 
called  the  triangular  fascia  of  the  abdomen  or  Oolles's  ligament  {ligamentum 
inguinale  reflexum).  The  point  of  the  triangle  is  at  the  origin  of  Colles's  ligament; 
the  base  is  at  the  linea  alba.  Colles's  ligament  is  in  front  of  the  conjoined  tendon, 
the  Rectus  muscle,  and  the  Pyramidalis  muscle. 

In  the  aponeurosis  of  the  External  oblique,  immediately  above  the  crest  of  the 
OS  pubis,  is  a  triangular  opening,  the  external  abdominal  ring,  formed  by  a  separa- 
tion of  the  fibres  of  the  aponeurosis  in  this  situation. 


POUPART'S 
LIGAMENT 


INTERCOLUMNAR 
FIBRES 


GIMBERNAT'S 
LIGAMENT 

SAPHENOUS 
OPENING 


LONG 

SAPHENOUS 

VEIN 


EXTERNAL 
■ABDOMINAL 
RING 


CRU3 
SUPERIOR 


Fig.  290.— Right  external  abdominal  ring  and  saphenous  opening  in  the  male.     (Spalteholz.) 

Relations.— By  its  external  surface,  with  the  superficial  fascia,  superficial  epi- 
gastric and  circumflex  iliac  vessels,  and  some  cutaneous  nerves;  by  its  internal 
surface,  with  the  Internal  oblique,  the  lower  part  of  the  eight  inferior  ribs,  and 
Intercostal  muscles,  the  Cremaster,  the  spermatic  cord  in  the  male,  and  round  liga- 
ment in  the  female.  Its  posterior  border,  extending  from  the  last  rib  to  the  crest 
of  the  ilium,  is  fleshy  throughout  and  free;  it  is  occasionally  overlapped  by  the 
Latissimus  dorsi,  though  generally  a  triangular  interval  exists  between  the  two 
muscles  near  the  crest  of  the  ilium,  in  which  is  seen  a  portion  of  the  internal 
oblique.  This  triangle,  Petit's  triangle  (trigonum  lumhale),  is  therefore  bounded 
in  front  by  the  External  oblique,  behind  by  the  Latissimus  dorsi,  below  by  the 
crest  of  the  ilium,  while  its  floor  is  formed  by  the  Internal  oblique  (Fig.  289). 

The  following  parts  of  the  aponeurosis  of  the  External  oblique  muscle  require 
to  be  further  described — viz.,  the  external  abdominal  ring,  the  intercolumnar  fibres 
and  fascia,  Poupart's  ligament,  Gimbemat's  ligament,  and  the  triangular  fascia  of 
the  abdomen. 


436  THE   MUSCLES  AND   FASCIA 

The  External  Abdominal  Ring  {annulus  inguinalis  subcutaneous)  (Fig.  290). — 
Just  above  and  to  the  outer  side  of  the  crest  of  the  os  pubis  an  interval  is  seen  in  the 
aponeurosis  of  the  External  oblique,  called  the  external  abdominal  ring.  The  aper- 
ture is  oblique  in  direction,  somewhat  triangular  in  form,  and  corresponds  with 
the  course  of  the  fibres  of  the  aponeurosis.  It  usually  measures  from  base  to  apex 
about  an  inch,  and  transversely  about  half  an  inch.  It  is  bounded  below  by  the 
crest  of  the  os  pubis;  above,  by  a  series  of  curved  fibres,  the  external  spermatic,  or 
the  intercolumnar  fibres  (fibrce  intercrurales) ,  which  pass  across  the  upper  angle  of 
the  ring,  so  as  to  increase  its  strength;  and  on  each  side,  by  the  margins  of  the 
opening  in  the  aponeurosis,  which  are  called  the  columns  or  pillars  of  the  ring. 

The  External  Pillar  or  inferior  cms  (crus  inferius)  is  inferior  from  the  obliquity 
of  its  direction.  It  is  stronger  than  the  internal  pillar;  it  is  formed  by  that 
portion  of  Poupart's  ligament  which  is  inserted  into  the  spine  of  the  os  pubis;  it  is 
curved  so  as  to  form  a  kind  of  groove,  upon  which  the  spermatic  cord  rests. 

The  Internal  Pillar  or  superior  crus  (crus  swperius)  is  a  broad,  thin,  flat  band, 
which  is  attached  to  the  front  of  the  symphysis  pubis,  interlacing  with  its  fellow 
of  the  opposite  side. 

The  external  abdominal  ring  gives  passage  to  the  spermatic  cord  in  the  male 
{funiculus  spermaticus)  and  round  ligament  in  the  female  (ligamentum  teres  uteri) : 
it  is  much  larger  in  men  than  in  women,  on  account  of  the  large  size  of  the  sper- 
matic cord,  and  hence  the  greater  frequency  of  inguinal  hernia  in  men. 

Intercolumnar  Fibres  {jihrcs  intercrurales)  (Fig.  290). — The  intercolumnar  fibres 
are  a  series  of  curved  tendinous  fibres,  which  arch  across  the  lower  part  of 
the  aponeurosis  of  the  External  oblique.  They  have  received  their  name  from 
stretching  across  between  the  two  pillars  of  the  external  ring,  describing  a  curve 
with  the  convexity  downward.  They  are  much  thicker  and  stronger  at  the  outer 
margin  of  the  external  ring,  where  they  are  connected  to  the  outer  third  of  Pou- 
part's ligament,  than  internally,  where  they  are  inserted  into  the  linea  alba.  They 
are  more  strongly  developed  in  the  male  than  in  the  female.  The  inter- 
columnar fibres  increase  the  strength  of  the  lower  part  of  the  aponeurosis, 
and  prevent  the  divergence  of  the  pillars  from  one  another. 

These  intercolumnar  fibres  as  they  pass  across  the  external  abdominal  ring 
are  themselves  connected  together  by  delicate  fibrous  tissue,  thus  forming  a  fascia, 
which  as  it  is  attached  to  the  pillars  of  the  ring  covers  it  in,  and  is  called  the 
intercolumnar  fascia  or  the  external  spermatic  fascia.  This  intercolumnar  fascia 
is  continued  down  as  a  tubular  prolongation  around  the  outer  surface  of  the 
cord  and  testis  or  of  the  round  ligament,  and  encloses  them  in  a  distinct  sheath. 

The  sac  of  an  inguinal  hernia,  in  passing  through  the  external  abdominal  ring,  receives  an 
investment  from  the  intercolumnar  fascia. 

If  the  finger  is  introduced  a  short  distance  into  the  external  abdominal  ring 
and  the  limb  is  then  extended  and  rotated  outward,  the  aponeurosis  of  the  External 
oblique,  together  with  the  iliac  portion  of  the  fascia  lata,  will  be  felt  to  become 
tense,  and  the  external  ring  much  contracted;  if  the  limb  is,  on  the  contrary,  flexed 
upon  the  pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax  and  the 
external  abdominal  ring  sufficiently  enlarged  to  admit  the  finger  with  compara- 
tive ease;  hence  the  patient  should  always  be  put  in  the  latter  position  when  the 
taxis  is  applied  for  the  reduction  of  an  inguinal  hernia  in  order  that  the  abdominal 
walls  may  be  relaxed  as  much  as  possible. 

Poupart's  Ligament  (ligamentum  inguinale). — The  portion  of  Poupart's  ligament 
in  front  of  the  crural  ring  is  called  the  superficial  crural  arch.  Poupart's  ligament 
is  the  lower  border  of  the  aponeurosis  of  the  External  oblique  muscle,  and  extends 
from  the  anterior  superior  spine  of  the  ilium  to  the  pubic  spine.  From  this 
latter  point  it  is  reflected  outward  to  be  attached  to  the  pectineal  line  for  about 


OF   THE   ABDOMEN  437 

half  an  inch,  forming  Gimbemat's  ligament.  Its  general  direction  is  curved  down- 
ward toward  the  thigh,  where  it  is  continuous  with  the  fascia  lata.  Its  outer  half 
is  rounded  and  oblique  in  direction.  Its  inner  half  gradually  widens  at  its  attach- 
ment to  the  OS  pubis,  is  more  horizontal  in  direction,  and  lies  beneath  the  spermatic 
cord.  Nearly  the  whole  of  the  space  included  between  the  crural  arch  and  the 
innominate  bone  is  filled  in  by  the  parts  which  descend  from  the  abdomen  into 
the  thigh  (Fig.  298).    These  will  be  referred  to  again  on  a  subsequent  page. 

Gimbemat's  Ligament  (ligamentum  lacunare)  (Figs.  290  and  298). — Gimbernat's 
ligament  is  that  part  of  the  aponeurosis  of  the  External  oblique  muscle  which  is 
reflected  upward  and  outward  from  the  spine  of  the  os  pubis  to  be  inserted  into  the 
pectineal  line.  It  is  about  half  an  inch  in  length,  larger  in  the  male  than  in  the 
female,  almost  horizontal  in  direction  in  the  erect  posture,  and  of  a  triangular  form 
with  the  base  directed  outward.  Its  base,  or  outer  margin,  is  concave,  thin,  and 
sharp,  and  lies  in  contact  with  the  crural  sheath,  forming  the  inner  boundary  of 
the  femoral  or  crural  ring  (antiulus  femoralis) .  Its  apex  corresponds  to  the  spine 
of  the  OS  pubis.  Its  posterior  margin  is  attached  to  the  pectineal  line,  and  is  con- 
tinuous with  the  pubic  portion  of  the  fascia  lata.  Its  anterior  margin  is  continuous 
with  Poupart's  ligament.     Its  surfaces  are  directed  upward  and  downward. 

Triangular  Fascia  or  CoUes's  Ligament  (ligamentum  inguinal  reflexum). — The 
triangular  fascia  of  the  abdomen  is  a  layer  of  tendinous  fibres  of  a  triangular 
shape,  which  is  attached  by  its  apex  to  the  pectineal  line,  where  it  is  continuous 
with  Gimbernat's  ligament.  It  passes  inward  beneath  the  spermatic  cord,  and 
expands  into  a  somewhat  fan-shaped  fascia,  lying  behind  the  inner  pillar  of  the 
external  abdominal  ring,  and  in  front  of  the  conjoined  tendon,  and  interlaces  with 
the  ligament  of  the  other  side  at  the  linea  alba. 

Ligament  of  Cooper  (Fig.  298). — This  is  a  strong  ligamentous  band,  which  was 
first  described  by  Sir  Astley  Cooper.  It  extends  upward  and  backward  from  the 
base  of  Gimbernat's  ligament  along  the  ilio-pectineal  line,  to  which  it  is  attached. 
It  is  strengthened  by  the  fascia  transversalis,  by  the  pectineal  aponeurosis,  and 
by  a  lateral  expansion  from  the  lower  attachment  of  the  linea  alba  (adminicidum 
lineoe  alhoe). 

Suspensory  Ligament  of  the  Penis  {ligamentum  fundiforme  penis). — The  suspen- 
sory ligament  of  the  penis  arises  from  the  linea  alba,  the  anterior  portion  of 
the  sheath  of  the  Rectus  muscle,  and  the  superficial  fascia.  It  splits  into  two 
portions,  blends  with  the  inserting  fascia  of  the  penis,  and  passes  into  the  scrotum. 

Suspensory  Ligament  of  the  Clitoris  (ligamentum  fundiforme  clitoridis). — The 
suspensory  ligament  of  the  clitoris  corresponds  in  the  female  to  the  suspen- 
sory ligament  of  the  penis  in  the  male. 

Dissection — Detach  the  External  oblique  by  dividing  it  across,  just  in  front  of  its  attach- 
ment to  the  ribs,  as  far  as  its  posterior  border,  and  separate  it  below  from  the  crest  of  the  ihum 
as  far  as  the  anterior  superior  spine;  then  separate  the  muscle  carefully  from  the  Internal  oblique, 
which  lies  beneath,  and  turn  it  toward  the  opposite  side. 

The  Internal  or  Ascending  Oblique  Muscle  (m.  obliquus  intemus  abdominis) 
(Fig.  291),  thinner  and  smaller  than  the  preceding,  beneath  which  it  lies,  is  of 
an  irregularly  quadrilateral  form,  and  is  situated  at  the  side  and  forepart  of  the 
abdomen.  It  arises,  by  fleshy  fibres,  from  the  outer  half  of  Poupart's  ligament, 
being  attached  to  the  groove  on  its  upper  surface;  from  the  anterior  two-thirds 
of  the  middle  lip  of  the  crest  of  the  ilium,  and  from  the  posterior  lamella  of  the 
lumbar  fascia  (Fig.  295).  From  this  origin  the  fibres  diverge:  those  from  Poupart's 
ligament,  few  in  number  and  paler  in  color  than  the  rest,  arch  downward  and 
inward  across  the  spermatic  cord  in  the  male  and  the  round  ligament  in  the 
female,  and,  becoming  tendinous,  are  inserted,  conjointly  with  those  of  the  Trans- 
versalis, into  the  crest  of  the  os  pubis  and  pectineal  line,  to  the  extent  of  half  an  inch 
or  more,  forming  what  is  known  as  the  conjoined  tendon  of  the  Internal  oblique  and 


438 


THE   MUSCLES    AND    FASCIA 


Transversalis ;  those  from  the  anterior  tliird  of  the  ihac  origin  are  horizontal  in 
their  direction,  and,  becoming  tendinous  along  the  lower  fourth  of  the  linea 
semilunaris,  pass  in  front  of  the  Rectus  muscle  to  be  inserted  into  the  linea  alba; 
those  which  arise  from  the  middle  third  of  the  origin  from  the  crest  of  the 
ilium  pass  obliquely  upward  and  inward,  and  terminate  in  an  aponeurosis  wdiich 
divides  at  the  outer  border  of  the  Rectus  muscle  into  two  lamellae  (Fig.  296), 
which  are  continued  forward,  in  front  and  behind  this  muscle,  to  the  linea  alba, 
the  posterior  lamella  being  also  connected  to  the  cartilages  of  the  seventh,  eighth, 
and  ninth  ribs;  the  most  posterior  fibres  pass  almost  vertically  upward,  to  be 
inserted  into  the  lower  borders  of  the  cartilages  of  the  three  lower  ribs,  being  con- 
tinuous with  the  Internal  intercostal  muscles. 


Conjoined  tendon.-jj 

CREMASTER 

Puhes. 


Fig.  291. — The  Internal  oblique  muscle. 

The  conjoined  tendon  of  the  Inte.nal  obhque  and  Transversalis  is  inserted  into 
the  crest  of  the  os  pubis  and  pectineal  line,  immediately  behind  the  external 
abdominal  ring,  serving  to  protect  what  would  otherwise  be  a  weak  point  in  the 
abdominal  wall.  Sometimes  this  tendon  is  insufficient  to  resist  the  pressure  from 
within,  and  is  carried  forward  in  front  of  a  protrusion  through  the  external  ring, 
forming  one  of  the  coverings  of  direct  inguinal  hernia ;  or  the  hernia  forces  its  way 
through  the  fibres  of  the  conjoined  tendon.  The  conjoined  tendon  is  sometimes 
divided  into  an  outer  and  an  inner  portion — the  former  being  termed  the  liga- 
ment of  Hesselbach  {ligamentum  interjoveolare) ;  the  latter,  the  ligament  of  Henle 
(Fig.  292). 


OF    THE  ABDOMEN 


439 


Aponeurosis  of  Internal  Oblique. — The  aponeurosis  of  the  Internal  oblique  is 
continued  forward  to  the  middle  line  of  the  abdomen,  where  it  joins  with  the 
aponeurosis  of  the  opposite  muscle  at  the  linea  alba,  and  extends  from  the  margin 
of  the  thorax  to  the  os  pubis.  At  the  outer  margin  of  the  Rectus  muscle  this 
aponeurosis,  for  the  upper  three-fourths  of  its  extent,  divides  into  two  lamellae, 
which  pass,  one  in  front  and  the  other  behind  the  muscle,  enclosing  it  in  a  kind  of 
sheath,  and  reuniting  on  its  inner  border  of  the  linea  alba;  the  anterior  layer  is 
blended  with  the  aponeurosis  of  the  External  obli(}ue  muscle;  the  posterior  layer 
with  that  of  the  Transversalis.  Along  the  lower  fourth  the  aponeurosis  passes 
altogether  in  front  of  the  Rectus  without  any  separation.    Where  the  aponeurosis 


SEMILUNAR   FOLD 
OF  DOUGLAS 


TRANSVERSALIS 


RECTUS 
ABDOMINIS 


DEEP  EPI- 
GASTRIC ARTERY 
AND  VEIN 


INTERNAL 
OBL4QUe 


iiGAMENT  OF  HENLE  LIGAMENT  OF  HESSELBACH 

Fig.  292. — The  deep  epigastric  artery  and  veins,  ligament  of  Henle  and  ligament  of  Hesselbach,  seen 
from  in  front.     (Modified  from  Braune.) 

ceases  to  split,  and  passes  altogether  in  front  of  the  Rectus  muscle,  a  deficiency  is 
left  in  the  sheath  of  the  muscle  behind;  this  is  marked  above  by  a  sharp  lunated 
margin  having  its  concavity  downward.  This  is  known  as  the  semilunar  fold  of 
Douglaft  (linea  semicircularis)  (Fig.  293). 

Relations. — By  its  external  surface,  with  the  External  oblique,  Latissimus  dorsi, 
spermatic  cord,  and  external  ring;  by  its  internal  surface,  with  the  Transversalis 
muscle,  the  lower  intercostal  vessels  and  nerves,  the  ilio-hypogastric  and  the  ilio- 
inguinal nerves.  Near  Poupart's  ligament  it  lies  on  the  fascia  transversalis, 
internal  ring,  and  spermatic  cord.  Its  lower  border  forms  the  upper  boundary 
of  the  inguinal  canal. 

The  Cremaster  muscle  (Fig.  291)  is  a  thin,  muscular  layer,  composed  of  a  num- 
ber of  fasciculi  which  arise  from  the  inner  part  of  Poupart's  ligament,  where  its 
fibres  are  continuous  with  those  of  the  Internal  oblique  and  also  occasionally  with 
the  Transversalis.  It  passes  along  the  outer  side  of  the  spermatic  cord,  descends 
with  it  through  the  external  abdominal  ring  upon  the  front  and  sides  of  the  cord, 
and  forms  a  series  of  loops  which  differ  in  thickness  and  length  in  different  sub- 
jects. Those  at  the  upper  part  of  the  cord  are  exceedingly  short,  but  they  become 
in  succession  longer  and  longer,  the  longest  reaching  down  as  low  as  the  testicle, 
where  a  few  are  inserted  into  the  tunica  vaginalis.  These  loops  are  united  together 
by  areolar  tissue,  and  form  a  thin  covering  over  the  cord  and  testis,  the  middle 


440 


THE  MUSCLES  AND    FASCIyE 


spermatic  fascia  (fascia  cremasterica).  The  fibres  ascend  along  the  inner  side  of 
the  cord,  and  are  inserted  by  a  small  pointed  tendon  into  the  crest  of  the  os 
pubis  and  front  of  the  sheath  of  the  Rectus  muscle. 


'5    POSTERIOR  LEAF 

^ OF  SHEATH  OF 

■'  RECTUS  ABDOMINIS 


LINEA  SEMILUNARIS 


TRANSVERSALI8 


SEMILUNAR   FOLD 
OF  DOUGLAS 


RECTUS  ABDOMINIS 

(cut  through) 


ANTERIOR  LEAF 

F  SHEATH   OF 
RECTUS  ABDOMINIS 


Fig.  293. — The  muscles  of  the  abdomen,  showing  the  semilunar  fold  of  Douglas.     Viewed  from  in  front. 

(Spalteholz.) 

It  will  be  observed  that  the  origin  and  insertion  of  the  Cremaster  is  precisely 
similar  to  that  of  the  lower  fibres  oif  the  Internal  oblique.  This  fact  affords  an  easy 
explanation  of  the  manner  in  which  the  testicle  and  cord  are  invested  by  this 
muscle.  At  an  early  period  of  fretal  life  the  testis  is  placed  at  the  lower  and  back 
part  of  the  abdominal  cavity,  but  during  its  descent  toward  the  scrotum,  which 
takes  place  before  birth,  it  passes  beneath  the  arched  fibres  of  the  Internal  oblique. 
In  its  passage  beneath  this  muscle  some  fibres  are  derived  from  its  lower  part 
which  accompany  the  testicle  and  cord  into  the  scrotum.    It  occasionally  happens 


OF    THE   ABDOMEN 


441 


that  the  loops  of  the  Cremaster  surround  the  cord,  some  lying  behind  as  well  as  in 
front.  It  is  probable  that  under  these  circumstances  the  testis,  in  its  descent, 
passed  through  instead  of  beneath  the  fibres  of  the  Internal  oblique. 

In  the  descent  of  an  ol)lique  inguinal  hernia,  which  takes  the  same  course  as 
the  spermatic  cord,  the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle 
becomes  largely  developed  in  cases  of  hydrocele  and  large  old  scrotal  hernia.  The 
Cremaster  muscle  is  found  only  in  the  male,  but  almost  constantly  in  the  female 


JAnea  alba. 


Fig.  294. — The  Transversalis,  Rectus,  and  Pyramidalis  muscles. 

a  few  muscular  fibres  may  be  seen  on  the  surface  of  the  round  ligament,  which 
correspond  to  this  muscle,  and  in  cases  of  oblique  inguinal  hernia  in  the  female  a 
considerable  amount  of  muscular  fibre  may  be  found  covering  the  sac. 

Dissection. — Detach  the  Internal  oblique  in  order  to  expose  the  Transversalis  beneath.  This 
may  be  effected  by  dividing  the  muscle,  above,  at  its  attachment  to  the  ribs;  below,  at  its  con- 
nection with  Poupart's  ligament  and  the  crest  of  the  ilium;  and  behind,  by  a  vertical  incision 


442  THE    MUSCLES   AND    FASCIA 

extending  from  the  last  rib  to  the  crest  of  the  ihum.  The  muscle  should  previously  be  made 
tense  by  drawing  upon  it  with  the  fingers  of  the  left  hand,  and  if  its  division  is  carefully  effected, 
the  cellular  interval  between  it  and  the  Transversalis,  as  well  as  the  direction  of  the  fibres  of  the 
latter  muscle,  will  aft'ord  a  clear  guide  to  their  separation;  along  the  crest  of  the  ilium  the  cir- 
cumflex iliac  vessels  are  interposed  between  them,  and  form  an  important  guide  in  separating 
them.     The  muscle  should  then  be  thrown  inward  toward  the  linea  alba. 

The  Transversalis  Muscle  {m.  transversus  abdominis)  (Fig.  294),  so  called 
from  the  direction  of  its  fibres,  is  the  most  internal  flat  muscle  of  the  abdomen, 
being  placed  immediately  beneath  the  Internal  oblique.  It  arises  by  fleshy  fibres 
from  the  outer  third  of  Poupart's  ligament;  from  the  inner  lip  of  the  crest  of  the 
ilium  for  its  anterior  three-fourths ;  from  the  inner  surface  of  the  cartilages  of  the 
six  lower  ribs,  interdigitating  with  the  Diaphragm;  and  from  the  lumbar  fascia 
(Fig.  295),  which  may  be  regarded  as  the  posterior  aponeurosis  of  the  muscle. 
The  muscle  terminates  in  front  in  a  broad  aponeurosis,  the  lower  fibres  of 
which  curve  downward  and  inward,  and  are  inserted,  together  with  those  of  the 
Internal  oblique,  into  the  lower  part  of  the  linea  alba,  the  crest  of  the  os  pubis 
and  pectineal  line  forming  what  is  known  as  the  conjoined  tendon  of  the  Internal 
oblique  and  Transversalis.  The  lowermost  fibres  help  to  form  the  posterior  wall 
of  the  inguinal  canal.  Throughout  the  rest  of  its  extent  the  aponeurosis  passes 
horizontally  inward,  and  is  inserted  into  the  linea  alba,  its  upper  three-fourths 
passing  behind  the  Rectus  muscle,  blending  with  the  posterior  lamella  of  the 
Internal  oblique;  its  lower  fourth  passing  in  front  of  the  Rectus.  The  external 
portion  of  the  lower  fibres  of  the  conjoined  tendon  is  known  as  the  ligament  of 
Hesselbach;  the  internal  portion  as  the  ligament  of  Henle. 

Relations. — By  its  external  surface,  with  the  Internal  oblique,  the  lower  inter- 
costal nerves,  and  the  inner  surface  of  the  cartilages  of  the  lower  ribs;  by  its 
internal  surface,  with  the  fascia  transversalis,  which  separates  it  from  the  periton- 
eum.   Its  lower  border  forms  the  upper  boundary  of  the  inguinal  canal. 

Dissection. — To  expose  the  Rectus  muscle,  open  its  sheath  by  a  vertical  incision  extending 
from  the  margin  of  the  thorax  to  the  os  pubis,  and  then  reflect  the  two  portions  from  the  surface 
of  the  muscle,  which  is  easily  done,  excepting  at  the  linefe  transversse,  where  so  close  an  adhesion 
exists  that  the  greatest  care  is  requisite  in  separating  them.  Now  raise  the  outer  edge  of  the 
muscle,  in  order  to  examine  the  posterior  layer  of  the  sheath.  By  dividing  the  muscle  in  the 
centre,  and  turning  its  lower  part  downward,  the  point  where  the  posterior  wall  of  the  sheath 
terminates  in  a  thin  curved  margin  will  be  seen. 

The  Rectus  Abdominis  (Figs.  292,  294  and  296)  is  a  long  flat  muscle,  which 
extends  along  the  whole  length  of  the  front  of  the  abdomen,  being  separated  from 
its  fellow  of  the  opposite  side  by  the  linea  alba.  It  is  much  broader,  but  thinner, 
above  than  below,  and  arises  by  two  tendons,  the  external  or  larger  being  attached 
to  the  crest  of  the  os  pubis,  the  internal,  smaller  portion  interlacing  with  its  fellow  of 
the  opposite  side,  and  being  connected  with  the  ligaments  covering  the  front  of  the 
symphysis  pubis.  The  fibres  ascend,  and  the  muscle  is  inserted  by  three  portions  of 
unequal  size  into  the  cartilages  of  the  fifth,  sixth,  and  seventh  ribs.  The  upper  por- 
tion, attached  principally  to  the  cartilage  of  the  fifth  rib,  usually  has  some  fibres  of 
insertion  into  the  anterior  extremity  of  the  rib  itself.  Some  fibres  are  occasionally 
connected  with  the  costo-xiphoid  ligaments  and  side  of  the  ensiform  cartilage. 

The  Rectus  muscle  is  traversed  by  tendinous  intersections,  three  in  number, 
which  have  received  the  name  of  lineae  transversae.  One  of  these  is  usually 
situated  opposite  the  umbilicus,  and  two  above  that  point;  of  the  latter,  one 
corresponds  to  the  extremity  of  the  ensiform  cartilage,  and  the  other  to  the  inter- 
val between  the  ensiform  cartilage  and  the  umbilicus.  These  intersections  pass 
transversely  or  obliquely  across  the  muscle  in  a  zigzag  course;  they  rarely  extend 
completely  through  its  substance,  sometimes  they  pass  only  half-way  across  it,  and 
are  intimately  adherent  in  front  to  the  sheath  in  which  the  muscle  is  enclosed. 


OF   THE   ABDOMEN 


443 


Sometimes  one  or  two  additional  lines  may  be  seen,  one  usually  below  the 
umbilicus;  the  position  of  the  other,  when  it  exists,  is  variable.  These  addi- 
tional lines  are  for  the  most  part  incomplete. 


Fig.  295. — A  transverse  section  of  the  abdomen  in  the  lumbar  region. 

The  Rectus  is  enclosed  in  a  sheath,  the  rectus  sheath  {vagina  m.  recti  abdominis) 
(Figs.  295  and  296),  formed  by  the  aponeurosis  of  the  Oblique  and  Trans versalis 


SHEATH    OF 
RECTUS  ABDOMINIS 

(anterior  leaf) 


Posterior  leaf       Anterior  leaf 


SHEATH  OF  RECTUS  ABDOMINIS 

Fig.  296. — Transition  of  the  tendon  of  the  right  internal  oblique  into  the  sheath  of  the  rectus.     (Spalteholz.) 

muscles,  which  are  arranged  in  the  following  manner.    When  the  aponeurosis  of  the 
Internal  oblique  arrives  at  the  outer  margin  of  the  Rectus  it  divides  into  two  lamellae. 


444  THE  MUSCLES  AND   FASCIA 

one  of  which  passes  in  front  of  the  Rectus,  blending  with  the  aponeurosis  of  the 
External  oblique;  the  other,  behind  it,  blending  with  the  aponeurosis  of  the  Trans- 
versalis;  and  these,  joining  again  at  its  inner  border,  are  inserted  into  the  linea  alba. 
This  arrangement  of  the  aponeuroses  exists  along  the  upper  three-fourths  of  the 
muscle:  at  the  commencement  of  the  lower  fourth,  the  posterior  wall  of  the  sheath 
terminates  in  a  thin  curved  margin,  the  semilunar  fold  of  Douglas  {linea  semicir- 
cularis)  (Fig.  293),  the  concavity  of  which  looks  downward  toward  the  pubes;  the 
aponeuroses  of  all  three  muscles  passing  in  front  of  the  Rectus  without  any  sepa- 
ration. A  very  thin  aponeurotic  layer  does  pass  behind  the-  lower  one-fourth  of 
the  muscle,  but  it  is  trivial  as  compared  with  the  thickness  of  the  layer  behind  the 
upper  three-fourths  of  the  muscle.  This  sudden  thinning  causes  the  semilunar 
fold  of  Douglas.  The  extremities  of  the  fold  of  Douglas  descend  as  pillars  to  the 
OS  pubis.  The  inner  pillar  is  attached  to  the  symphysis  pubis;  the  outer  pillar 
passes  downward  as  a  distinct  band  on  the  inner  side  of  the  internal  abdominal 
ring  to  join  with  the  outer  fibres  of  the  conjoined  tendon,  and  assist  to  form 
the  ligament  of  Hesselbach.  There  its  fibres  divide  into  two  sets,  internal 
and  external;  the  internal  fibres  are  attached  to  the  ascending  ramus  of  the  os 
pubis  and  the  pectineal  fascia;  the  external  ones  pass  to  the  Psoas  fascia,  to 
the  deep  surface  of  Poupart's  ligament,  and  to  the  tendon  of  the  Transversalis  on 
the  outer  side  of  the  ring.  The  Rectus  muscle,  in  the  situation  where  its  sheath 
is  deficient,  is  separated  from  the  peritoneum  by  the  transversalis  fascia.  The 
convex  outer  border  of  the  Rectus  muscle  corresponds  to  the  linea  semilunaris. 

The  P3n:amidalis  is  a  small  muscle,  triangular  in  shape,  placed  at  the  lower 
part  of  the  abdomen,  in  front  of  the  Rectus,  and  contained  in  the  same  sheath 
with  that  muscle.  It  arises  by  tendinous  fibres  from  the  front  of  the  os  pubis 
and  the  anterior  pubic  ligament;  the  fleshy  portion  of  the  muscle  passes  upward, 
diminishing  in  size  as  it  ascends,  and  terminates  by  a  pointed  extremity,  which  is 
inserted  into  the  linea  alba,  midway  between  the  umbilicus  and  the  os  pubis.  This 
muscle  is  sometimes  found  wanting  on  one  or  both  sides;  the  lower  end  of  the 
Rectus  then  becomes  proportionately  increased  in  size.  Occasionally  it  has  been 
found  double  on  one  side,  or  the  muscles  of  the  two  sides  are  of  unequal  size. 
Sometimes  its  length  exceeds  what  is  stated  above. 

Besides  the  Rectus  and  Pyramidalis  muscles,  the  sheath  of  the  Rectus  contains 
the  superior  and  deep  epigastric  arteries,  the  terminations  of  the  lumbar  arteries 
and  of  the  lower  intercostal  arteries  and  nerves. 

Nerves. — The  abdominal  muscles  are  supplied  by  the  lower  intercostal  nerves. 
The  Transversalis  and  Internal  oblique  also  receive  filaments  from  the  hypogastric 
branch  of  the  ilio-hypogastric  and  sometimes  from  the  ilio-inguinal.  The  Cremas- 
ter  is  supplied  by  the  genital  branch  of  the  Genito-crural. 

In  the  description  of  the  abdominal  muscles  mention  has  frequently  been  made 
of  the  linea  alba,  lineae  semilunares,  and  linese  transversae;  when  the  dissection  of 
the  muscles  is  completed  these  structures  should  be  examined. 

The  Linea  Alba  (Figs.  293  and  296). — The  linea  alba  is  a  tendinous  raph^  seen 
along  the  middle  line  of  the  abdomen,  extending  from  the  ensiform  cartilage  to  the 
symphysis  pubis,  to  which  it  is  attached.  It  is  placed  between  the  inner  borders  of 
the  Recti  muscles,  and  is  formed  by  the  blending  of  the  aponeuroses  of  the  Obliqui 
and  Transversales  muscles.  It  is  narrow  below,  corresponding  to  the  narrow  inter- 
val existing  betwee^  the  Recti ;  but  broader  above,  as  these  muscles  diverge  from  one 
another  in  their  ascent,  becoming  of  considerable  breadth  when  there  is  great  dis- 
tention of  the  abdomen  from  pregnancy  or  ascites.  It  presents  numerous  apertures 
for  the  passage  of  vessels  and  nerves :  the  largest  of  these  is  the  umbilicus  (Fig.  297). 
The  umbilicus  is  a  fibrous  ring  formed  by  the  fibres  of  the  aponeurosis  of  the  linea 
alba,  is  filled  with  scar  tissue;  in  the  foetus  transmits  the  umbilical  vein,  the  two 
hypogastric  arteries,  the  allantoic  duct,  and  the  vitello-intestinal  duct;  but  in  the 


OF    THE   ABDOMEN 


445 


UMBILICAL 
VEIN 


LINEA  ALBA 


INTERVASCULAR 


HYPOGASTRIC 
ARTERY 


Fig.  297.— The  umbilicus  of  the  fcetus 
seen  from  within  the  abdomen.  (Poirier 
and  Charpy.) 


adult  is  obliterated,  the  cicatrix  being  stronger  than  the  neighboring  parts;  hence 
umbilical  hernia  occurs  in  the  adult  near  the  umbilicus,  whilst  in  the  foetus  it  occurs 
at  the  umbilicus.  The  remains  of  the  foetal  structures  are  cord-like  in  character, 
and  they  diverge  from  the  umbilicus  within  the 
abdomen.  The  remains  of  the  umbilical  vein  con- 
stitute the  round  ligament  of  the  liver,  and  this 
cord  passes  upward  (Pig.  297).  The  remains  of 
the  hypogastric  arteries  pass  downward  (Pig.  297). 
The  remains  of  the  allantois  become  the  urachus, 
which  passes  to  the  summit  of  the  bladder  (Fig. 
297).  The  depression  of  the  umbilicus  was 
created  by  the  urachus.  The  linea  alba  is  in  re- 
lation, in  ^ront,  with  the  integument,  to  which  it 
is  adherent,  especially  at  the  umbilicus;  behind, 
it  is  separated  from  the  peritoneum  by  the  trans- 
versalis  fascia;  and  below,  by  the  urachus,  and 
the  bladder  when  that  organ  is  distended. 

The  Lineae  Semilunares  (Fig.  289). — The  linese 
semilunares  are  two  curved  tendinous  lines  placed 
one  on  each  side  of  the  linea  alba.  Each  corre- 
sponds with  the  outer  border  of  the  Rectus  mus- 
cle, extends  from  the  cartilage  of  the  ninth  rib 
to  the  pubic  spine,  and  is  formed  by  the  aponeu- 
rosis of  the  Internal  oblique  at  its  point  of  division  to  enclose  the  Rectus,  where 
it  is  reinforced  in  front  by  the  External  oblique  and  behind  by  the  Transversalis. 

The  Lineae  Transversse  (inscriptiones  tendinew)  (Fig.  289). — The  line.T  trans- 
versje  are  narrow  transverse  lines  which  intersect  the  Recti  muscles,  as  already 
mentioned;  they  connect  the  lineae  semilunares  with  the  linea  alba. 

Actions. — The  abdominal  muscles  perform  a  threefold  action: 

When  the  pelvis  and  thorax  are  fixed,  they  compress  the  abdominal,  viscera,  by 
constricting  the  cavity  of  the  abdomen,  in  which  action  they  are  materially  assisted 
by  the  descent  of  the  Diaphragm.  By  these  means  the  foetus  is  expelled  from  the 
uterus,  the  faeces  from  the  rectum,  the  urine  from  the  bladder,  and  the  contents  of 
the  stomach  in  vomiting. 

If  the  pelvis  and  spine  are  fixed,  these  muscles  compress  the  lower  part  of  the 
thorax,  materially  assisting  expiration.  If  the  pelvis  alone  is  fixed,  the  thorax  is 
bent  directly  forward  when  the  muscles  of  both  sides  act,  or  to  either  side  when 
those  of  the  two  sides  act  alternately,  rotation  of  the  trunk  at  the  same  time  taking 
place  to  the  opposite  side. 

If  the  thorax  is  fixed,  these  muscles,  acting  together,  draw  the  pelvis  upward, 
as  in  climbing;  or,  acting  singly,  they  draw  the  pelvis  upward,  and  bend  the 
vertebral  column  to  one  side  or  the  other.  The  Recti  muscles,  acting  from  below, 
depress  the  thorax,  and  consequently  flex  the  vertebral  column;  when  acting  from 
above,  they  flex  the  pelvis  upon  the  vertebral  column.  The  Pyramidalis  are 
tensors  of  the  linea  alba. 

The  Transversalis  Fascia  (fascia  transversalis). — The  fascia  transversalis  is  a 
thin  aponeurotic  membrane  which  lies  between  the  inner  surface  of  the  Transversalis 
muscle  and  the  extra-peritoneal  fat.  It  forms  part  of  the  general  layer  of  fascia 
which  lines  the  interior  of  the  abdominal  and  pelvis  cavities,  and  is  directly  continu- 
ous with  the  iliac  and  pelvic  fasciae.  In  the  inguinal  region  the  transversalis  fascia  is 
thick  and  dense  in  structure,  and  joined  by  fibres  from  the  aponeurosis  of  the  Trans- 
versalis muscle,  but  it  becomes  thin  and  cellular  as  it  ascends  to  the  Diaphragm, 
and  blends  with  the  fascia  covering  this  muscle.  In  front,  it  unites  across  the 
middle  line  with  the  fascia  on  the  opposite  side  of  the  body,  and  behind  it  becomes 


446 


THE   MUSCLES   AND    FASCIA 


lost  in  the  fat  which  covers  the  posterior  surfaces  of  the  kidneys.  Below,  it  has 
the  folloAving  attachments:  posteriorly,  it  is  connected  to  the  whole  length  of  the 
crest  of  the  ilium,  between  the  attachments  of  the  Transversalis  and  Iliacus 
muscles;  between  the  anterior  superior  spine  of  the  ilium  and  the  femoral  vessels 
it  is  connected  to  the  posterior  margin  of  Poupart's  ligament,  and  is  there  con- 
tinuous with  the  iliac  fascia.  Internal  to  the  femoral  vessels  it  is  thin  and  attached 
to  the  OS  pubis  and  pectineal  line,  behind  the  conjoined  tendon,  with  which  it  is 
united;  and,  corresponding  to  the  point  where  the  femoral  vessels  pass  into  the 
thigh,  this  fascia  descends  in  front  of  them,  forming  the  anterior  wall  of  the  crural 
sheath.  Beneath  Poupart's  ligament  it  is  strengthened  by  a  band  of  fibrous  tissue, 
which  is  only  loosely  connected  to  Poupart's  ligament,  and  is  specialized  as  the 
deep  crural  arch.  The  spermatic  cord  in  the  male  and  the  round  ligament  in  the 
female  pass  through  this  fascia;  the  point  where  they  pass  through  is  called  the 
internal  abdominal  ring.  This  opening  is  not  visible  externally,  owing  to  a  pro- 
longation of  the  transversalis  fascia  on  these  structures,  forming  the  infundibuliform 
fascia. 

The  internal  or  deep  abdominal  ring  {annulus  inguinalis  abdominis)  (Figs.  292 
and  298)    is   situated  in  the  transversalis  fascia,  midway  between  the  anterior 


TRANSVERSALIS 
FASCIA 


INTERNAL 

ABDOMINAL 

RING 


CRURAL  NERVE 


FEMORAL  ARTERY. 


ILIAC  FASCIA 


GIMBERNAT'S 
LIGAMENT 


COOPER'S 
LIGAMENT 


Fig.  298.— The  relation  of  the  femoral  and  internal  abdominal  rings,  seen  from  within  the  abdomen  after 
removal  of  the  peritoneum.      (Poirier  and  Charpy.) 


superior  spine  of  the  ilium  and  the  symphysis  pubis,  and  about  half  an  inch  above 
Poupart's  ligament.  It  is  of  an  oval  form,  the  extremities  of  the  oval  directed 
upward  and  downward,  varies  in  size  in  different  subjects,  and  is  much  larger  in 
the  male  than  in  the  female.  Its  lower  border  is  strengthened  by  the  collection  of 
fibres  called  Hesselbach's  ligament,  lying  directly  in  front  of  the  deep  epigastric 
artery.  It  is  the  outer  portion  of  the  conjoined  tendon  fused  with  the  outer 
pillar  of  the  semilunar  fold  of  Douglas.  The  internal  ring  is  bounded,  above 
and  externally,  by  the  arched  fibres  of  the  Transversalis;  below  and  internally, 
by  the  deep  epigastric  vessels.  It  transmits  the  spermatic  cord  in  the  male 
and  the  round  ligament  in  the  female.  From  its  circumference  a  thin  funnel- 
shaped  membrane,  the  infmidibuliform  or  internal  spermatic  fascia,  is  continued 
round  the  cord  and  testis,  enclosing  them  in  a  distinct  pouch. 


OF    THE   ABDOMEN 


447 


,    EXTERNAL  OBLIQUE 

(reflected  downward) 


EXTERNAL.OBLIQUE 

(reflected  inward; 


POSTERIOR  WALL  OF 

INGUINAL  CANAL 


INTERNAL    ORIGIN 
OF  CRENASTER 


Fig.  299. — The  right  inguinal  canal  in  the  male,  second  layer,  viewed  from  in  front.     (The  first  layer 
is  shown  in  Fig.  290.)     (Spalteholz.) 


INTERNAL  OBLIQUE 

(reflected  inward) 


INTERNAL 
OBLIQUE 


EXTERNAL  OBLIQUE 

(reflected  inward) 


Fio.  300. — The  right  inguinal  canal  in  the  male,  third  layer,  viewed  from  in  front.     (Spalteholz.) 


448  THE   3IUSCLES  AND    FASCIA 

When  the  sac  of  an  oblique  inguinal  hernia  passes  through  the  internal  or  deep  abdominal 
ring,  the  infundibuliform  process  of  the  transversalis  fascia  forms  one  of  its  coverings. 

The  Inguinal  or  Spermatic  Canal  (canalis  ingumaUs)  (Figs.  299  and  300). — The 
ino-uinal  or  spermatic  canal  contains  the  spermatic  cord  {funiculus  spermaticus)  in 
the  male  and  the  round  ligament  {ligamentum  teres  uteri)  in  the  female.  It  is  an 
oblique  canal  about  an  inch  and  a  half  in  length,  directed  downward  and  inward, 
and  placed  parallel  to  and  a  little  above  Poupart's  ligament.  It  commences  above 
at  the  internal  or  deep  abdominal  ring,  which  is  the  point  where  the  cord  enters 
the  spermatic  canal,  and  terminates  below  at  the  external  ring.  It  is  bounded 
in  front  by  the  integument  and  superficial  fascia,  by  the  aponeurosis  of  the 
External  oblique  throughout  its  whole  length,  and  by  the  Internal  oblique  for 
its  outer  third;  behind,  by  the  triangular  fascia,  the  conjoined  tendon  of  the 
Internal  obHque  and  Transversalis,  transversalis  fascia,  and  the  subperitoneal 
fat  and  peritoneum ;  above,  by  the  arched  fibres  of  the  Internal  oblique  and  Trans- 
versalis; below,  by  Gimbernat's  ligament,  and  by  the  union  of  the  fascia  trans- 
versalis with  Poupart's  ligament.  The  median  aspect  of  the  floor  of  the  canal  is 
strengthened  by  dense  fibres  which  are  attached  to  the  pubis  and  to  the  Rectus 
muscle.  These  fibres  constitute  the  falx  inguinalis.  The  deep  epigastric  artery 
passes  upward  and  inward  behind  the  canal  lying  close  to  the  inner  side  of  the 
internal  abdominal  ring  (Fig.  292).  The  interval  between  this  artery  and  the 
outer  edge  of  the  Rectus  is  named  Hesselbach's  triangle,  the  base  of  which  is 
formed  by  Poupart's  ligament. 

That  form  of  protrusion  in  which  the  intestine  follows  the  course  of  the  spermatic  cord  along 
ihe  spermatic  canal  is  called  oblique  inguinal  hernia. 

The  Deep  Crural  Arch. — Curving  over  the  vessels,  just  at  the  point  where  they 
become  femoral,  on  the  abdominal  side  of  Poupart's  ligament  and  loosely  con- 
nected with  it,  is  a  thickened  band  of  fibres  called  the  deep  crural  arch.  It  is 
apparently  a  thickening  of  the  fascia  transversalis,  joining  externally  to  the  centre 
of  Poupart's  ligament,  and  arching  across  the  front  of  the  crural  sheath  to  be 
inserted  by  a  broad  attachment  into  the  spine  of  the  os  pubis  and  ilio-pectineal 
line,  behind  the  conjoined  tendon.  In  some  subjects  this  structure  is  not  very 
prominently  marked,  and  not  infrequently  it  is  altogether  wanting. 

Cooper's  Ligament  or  the  Reflected  Tendon  of  Cooper  (Fig.  298)  is  a  small  reflection 
from  the  tendon  of  the  Transversalis  which  passes  downward  and  outward  behind 
Gimbernat's  ligament. 

Surface  Form. — The  only  two  muscles  of  this  group  which  have  any  considerable  influ- 
ence on  surface  form  are  the  External  oblique  and  Rectus  muscles  of  the  abdomen.  With 
regard  to  the  External  oblique,  the  upper  digitations  of  its  origin  from  the  ribs  are  well  marked, 
intermingled  with  the  serrations  of  the  Serratus  magnus;  the  lower  digitations  are  not  visible, 
being  covered  by  the  thick  border  of  the  Latissimus  dorsi.  Its  attachment  to  the  crest  of  the 
ilium,  in  conjunction  with  the  Internal  oblique,  forms  a  thick  oblique  roll,  which  determines  the 
iliac  furrow.  Sometimes  on  the  front  of  the  lateral  region  of  the  abdomen  an  undulating  out- 
line marks  the  spot  where  the  muscular  fibres  terminate  and  the  aponeurosis  commences.  The 
outer  border  of  the  Rectus  is  defined  by  the  tinea  sryailunaris,  which  may  be  exactly  defined  by 
putting  the  muscle  into  action.  It  corresponds  with  a  curved  line,  with  its  convexity  outward, 
drawn  from  the  end  of  the  cartilage  of  the  ninth  rib  to  the  spine  of  the  os  pubis,  so  that  the 
centre  of  the  line,  at  or  near  the  umbilicus,  is  three  inches  from  the  median  line.  The  inner 
border  of  the  Rectus  corresponds  to  the  tinea  alba,  marked  on  the  surface  of  the  body  by  a 
groove,  the  abdominal  furrow,  which  extends  from  the  infrasternal  fossa  to,  or  to  a  little  below, 
the  umbilicus,  where  it  gradually  becomes  lost.  The  surface  of  the  Rectus  presents  three  trans- 
verse furrows,  the  luiese  transversse.  The  upper  two  of  these,  one  opposite  or  a  little  below  the 
tip  of  the  ensiform  cartilage,  and  another,  midway  between  this  point  and  the  umbilicus,  are 
usually  well  marked;  the  third,  opposite  the  umbilicus,  is  not  so  distinct.  The  umbilicus,  situ- 
ated in  the  linea  alba,  varies  very  much  in  position  as  regards  its  level.  It  is  always  situated 
above  a  zone  drawn  round  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium,  gen- 
erally being  about  three-quarters  of  an  inch  to  an  inch  above  this  line.  It  usually  corresponds, 
therefore,  to  the  fibro-cartilage  between  the  third  and  fourth  lumbar  vertebrae. 


OF   THE  18CHI0- RECTAL   REGION  449 

2.  The  Deep  Muscles  of  the  Abdomen. 

Psoas  magnus,  Iliacus. 

Psoas  parvus.  Quadratus  lumborum. 

The  Psoas  magnus,  the  Psoas  parvus,  and  the  IHacus  muscles,  with  the  fascia 
covering  them,  will  be  described  with  the  Muscles  of  the  Lower  Extremity. 

The  Fascia  Covering  the  Quadratus  Lumborum  (Fig.  295).— This  is  the  most 
anterior  of  the  three  layers  of  the  lumbar  fascia.  It  is  a  thin  layer  of  fascia,  which, 
passing  over  the  anterior  surface  of  the  Quadratus  lumborum,  is  attached,  inter- 
nally, to  the  bases  of  the  transverse  processes  of  the  lumbar  vertebrae;  below,  to 
the  ilio-lumbar  ligament ;  and  above,  to  the  apex  and  lower  border  of  the  last  rib. 

The  portion  of  this  fascia  which  extends  from  the  transverse  process  of  the 
first  lumbar  vertebra  to  the  apex  and  lower  border  of  the  last  rib  constitutes  the 
ligamentum  arcuatum  externum. 

The  Quadratus  Lumborum  (Fig.  283)  is  situated  in  the  lumbar  region.  It  is 
irregularly  quadrilateral  in  shape,  and  broader  below  than  above.  It  arises  by 
aponeurotic  fibres  from  the  ilio-lumbar  ligament  and  the  adjacent  portion  of  the 
crest  of  the  ilium  for  about  two  inches,  and  is  inserted  into  the  lower  border  of 
the  last  rib  for  about  half  its  length,  and  by  four  small  tendons,  into  the  apices 
of  the  transverse  processes  of  the  four  upper  lumbar  vertebrae.  Occasionally  a 
second  portion  of  this  muscle  is  found  situated  in  front  of  the  preceding.  This 
arises  from  the  upper  borders  of  the  transverse  processes  of  three  or  four  of  the 
lower  lumbar  vertebrae,  and  is  inserted  into  the  lower  margin  of  the  last  rib.  The 
Quadratus  lumborum  is  contained  in  a  sheath  formed  by  the  anterior  and  middle 
lamellae  of  the  lumbar  fasciae. 

Relations. — Its  anterior  surface  (or  rather  the  fascia  which  covers  its  anterior 
surface)  is  in  relation  with  the  colon,  the  kidney,  the  Psoas  muscle,  and  the 
Diaphragm.  Between  the  fascia  and  the  muscle  are  the  last  dorsal,  ilio-hypogas- 
tric,  and  ilio-inguinal  nerves.  Its  posterior  surface  is  in  relation  with  the  middle 
lamella  of  the  lumbar  fascia,  which  separates  it  from  the  Erector  spinae.  The 
Quadratus  lumborum  extends,  however,  beyond  the  outer  border  of  the  Erector 
spinae. 

Nerve-supply. — The  anterior  branches  of  the  last  dorsal  and  first  lumbar  nerves; 
sometimes  also  a  branch  from  the  second  lumbar  nerve. 

Actions. — ^The  Quadratus  lumborum  draws  down  the  last  rib.  It  acts  as  a 
muscle  of  inspiration  by  helping  to  fix  the  origin  of  the  Diaphragm.  If  the  thorax 
and  spine  are  fixed,  it  may  act  upon  the  pelvis,  raising  it  toward  its  own  side 
when  only  one  muscle  is  put  in  action;  and  when  both  muscles  act  together,  either 
from  below  or  above,  they  flex  the  trunk. 

IV.  MUSCLES  OF  THE  PELVIC  OUTLET. 

The  muscles  of  this  region  are  situated  at  the  pelvic  outlet  in  the  ischio-rectal 
region  and  the  perinaeum.    They  include  the  following: 

1.  Muscles  of  the  ischio-rectal  region. 

2.  Muscles  of  the  perinaeum  in  the  male. 

3.  Muscles  of  the  perinaeum  in  the  female. 

1.  The  Muscles  of  the  Ischio-rectal  Region. 

Corrugator  cutis  ani.  Internal  sphincter  ani. 

External  sphincter  ani.  Levator  ani. 

Coccygeus. 
The  Corrugator  Cutis  Ani. — Around  the  anus  is  a  thin  stratum  of  involuntary 
muscular  fibre,  which  radiates  from  the  orifice.     Internally,  the  fibres  fade  off 

29 


450 


THE  MUSCLES  AND   FASCIA 


into  the  submucous  tissue,  while  externally  they  blend  with  the  true  skin.     By 
its  contraction  it  raises  the  skin  into  ridges  around  the  margin  of  the  anus. 

The  External  Sphincter  Ani  (m.  sphincter  ani  externus)  (Figs.  301,  306, 307,  and 
308)  is  a  thin,  flat  plane  of  muscular  fibres,  elliptical  in  shape  and  intimately  adher- 


FRCNUM  OF 
PREPUCE 


TUBEROSITY 
OF  ISCHIUM 


INFERIOR 
LAYER   OF 
TRIANGULAR 
LIGAMENT 

TRANSVERSUS 
—  PERINEI 

SUPERFICIALiS 


ISCHIO-RECTAL 
fOSSA 


ANO-COCCYGEAL  LIGAMENT 

Fig.  301. — The  muscles  of  the  male  perinseum,  viewed  from  below.      (Spalteholz.) 

ent  to  the  integument  surrounding  the  margin  of  the  anus.  It  measures  about 
three  or  four  inches  in  length  from  its  anterior  to  its  posterior  extremity,  being 
about  an  inch  in  breadth  opposite  the  anus.  It  arises  from  the  tip  and  back  of 
the  coccyx  by  a  narrow  tendinous  band,  and  from  the  superficial  fascia  in  front 


OF   THE  ISCHIO-BECTAL   BEGION 


451 


of  that  bone ;  and  is  inserted  into  the  raphe  of  the  Accelerator  urinse  muscle  and 
into  the  central  tendinous  point  of  the  perinseum,  joining  with  the  two  Superficial 
transverse  perineal,  the  Levator  ani,  and  the  Accelerator  urinse  muscles.  Many 
of  the  fibres  are  continuous  with  the  Accelerator  urinje  in  the  male  and  with  the 
Sphincter  vaginae  in  the  female.  Often  some  of  the  fibres  are  continuous  with  the 
Transverse  perineal  muscles.  It  is  continuous  above  with  the  Levator  ani.  Like 
other  sphincter  muscles,  it  consists  of  two  planes  of  muscular  fibre,  which  sur- 
round the  margin  of  the  anus  and  join  in  a  commissure  in  front  and  behind, 
some  fibres  crossing  from  side  to  side  in  front  and  behind  the  anus. 

Nerve-supply. — A  branch  from  the  anterior  division  of  the  fourth  sacral  and 
the  inferior  hfemorrhoidal  branch  of  the  internal  pudic. 

Actions. — The  action  of  this  muscle  is  peculiar:  1.  It  is,  like  other  sphincter 
muscles,  always  in  a  state  of  tonic  contraction,  and  having  no  antagonistic  muscle, 
it  keeps  the  anal  orifice  closed.    2.  It  can  be  put  into  a  condition  of  greater  con- 


PECTINEUS 
ADDUCTOR 
LONGUS 
GRACILIS. 


Epididymis. 


Ampxina. 


Ampulla  of  vasn 
deferens. 


Testicle. 

Ascending  ramus  of 

ISCHIUM 

Internal  ptidic 
vessels  and  nerve. 


Fig.  302.-— Side  view  of  pelvis,  showing  Levator  ani.     (From  a  preparation  in  the  Museum  of  the  Royal 

College  of  Surgeons.) 

traction  under  the  influence  of  the  will,  so  as  to  occlude  more  firmly  the  anal 
aperture  in  expiratory  eft'orts  unconnected  with  defecation.  3.  Taking  its  fixed 
point  at  the  coccyx,  it  helps  to  fix  the  central  point  of  the  perinaeum,  so  that  the 
Accelerator  urinae  may  act  from  this  fixed  point. 

The  Internal  Sphincter  Ani  {in.  sphincter  ani  intemus)  is  a  muscular  ring 
which  surrounds  the  lower  extremity  of  the  rectum  for  about  an  inch,  its  inferior 
border  being  contiguous  to,  but  quite  separate  from,  the  External  sphincter. 
This  muscle  is  about  two  lines  in  thickness,  and  is  formed  by  an  aggregation 
of  the  involuntary  circular  fibres  of  the  intestine.  It  is  paler  in  color  and  less 
coarse  in  texture  than  the  External  sphincter. 

Actions. — Its  action  is  entirely  involuntary.  It  helps  the  External  sphincter 
to  occlude  the  anal  aperture. 

The  Levator  Ani  (Figs.  302,  303,  304,  and  305)  is  a  broad,  thin  muscle, 
situated  on  each  side  of  the  pelvis.     It  is  attached  to  the  inner  surface  of  the 


452 


THE  MUSCLES  AND   FASCIjE 


sides  of  the  true  pelvis,  and,  descending,  unites  with  its  fellow  of  the  opposite  side 
to  form  the  floor  of  the  pelvic  cavity.  It  supports  the  viscera  in  this  cavity  and 
surrounds  the  various  structures  which  pass  through  it.  It  is  usually  possible  to 
detect  an  interval  between  the  fibres  rising  from  the  pubis  and  those  rising  from 
the  pelvic  fascia,  and  this  interval  marks  the  fact  that  the  muscle  described  as  one 
is  really  two.  The  pubic  fibres  constitute  the  Pubococcygeus  muscle  and  the 
other  fibres  the  Iliococcygeus  muscle.^ 

The  Pubococcygeus  muscle  takes  origin  from  the  posterior  aspect  of  the  ramus 
of  the  pubis  and  from  the  most  anterior  portion  of  the  tendinous  arch  of  the 
Levator  ani  muscle.  The  fibres  of  origin  from  the  pubis  surround  anteriorly  the 
origin  of  the  Internal  obturator  muscle.  The  muscle  is  a  band,  about  one  inch  in 
width,  thickest  at  its  outer  border,  where  it  overlaps  the  Iliococcygeus.  It  passes 
backward,  downward,  and  inward,  "near  the  prostate  in  the  male,  the  urethra 
and  vagina  in  the  female,"^  and  near  to  the  rectum.    Most  of  the  fibres  pass  back 


ANTERIOR  SACRO- 
COCCYGEAL   LIGAMENT 


GREAT  SACRO- 
SCIATtC  LIGAMENT 


OBTURATOR 
CANAL 


SUPERIOR   LAYER 
OF  TRIANGULAR 
LIGAMENT 


Fig.  303. — The  Levator  ani  of  the  male,  viewed  from  above.     (Spalteholz.) 


of  the  rectum,  where  they  meet  and  join  with  the  corresponding  fibres  of  the 
opposite  side.  These  united  fibres  form  a  thick,  tendinous  aponeurosis.  "This 
is  continued  upward  in  front  of  the  coccyx  for  some  distance,  and  finally  divides 
into  two  lateral  portions,  which  have  been  named  the  ligamenta  sacro-coccygea 
anterior.  They  are  situated  on  either  side  of  the  middle  sacral  artery,  and  are 
finally  inserted  into  the  last  one  or  two  pieces  of  the  sacrum  and  the  first  piece 
of  the  coccyx."^     A  few  of  the  fibres  of  the  Pubococcygeus  muscle  pass  to  the 

1  Peter  Thompson.     The  Myology  of  the  Pelvic  Floor. 
^  Spalteholz's  Atlas.     Translated  and  edited  by  Barker. 
*  Peter  Thompson.     The  Myology  of  the  Pelvic  Floor. 


OF   THE  ISCHIO- RECTAL    REGION 


453 


central  tendon  of  the  perinseum,  come  in  contact  with  but  do  not  terminate  in  the 
rectal  wall,  descend  in  front  of  and  close  to  the  anterior  rectal  wall,  and  terminate 
in  the  anterior  portion  of  the  sphincter  ani  and  in  the  skin  of  the  anus  (Peter 
Thompson). 

Luschka  and  others  believe  that  these  anterior  fibres  descend  among  the  longi- 
tudinal fibres  of  the  rectum.     It  is  certain  that  the  most  anterior  fibres  of  the 


COWPER-S      SUPCRFICIAL  TRANS- 
GLANDS  VERSUS   PERINEI 


Fig.  304.— The  right  Levator  ani  in  the  male,  viewed  from  the  left.     (Spalteholz.) 

Pubococcygeus  muscle  pass  to  the  central  point  of  the  perinseum.  They  pass 
"backward  and  downward  on  the  side  of  the  prostate,  and  in  some  cases  on  the 
side  of  the  urethra  immediately  it  emerges  from  the  prostate."^  These  anterior 
fibres  in  the  female  descend  upon  the  side  of  the  vagina.  The  anterior  fibres 
are  the  preanal  fibres  of  the  Levator  ani.    They  constitute  what  Santorini  named 


»  Peter  Thompson.     The  Myology  of  the  Pelvic  Floor. 


454 


THE  MUSCLES   AND    FASCIA 


the  levator  prostatas,  because  he  regarded  them  as  constituting  a  distinct 
muscle,  which  surrounds  the  prostate  as  a  sling.  Krause  calls  these  fibres 
the  levator  urethrae ;  Testut,  the  fibres  pr^-rectales,  and  Prout,  the  Recto-urethralis 
muscle. 

The  Iliococcygeus  muscle  arises  from  the  tendinous  arch  of  the  Levator  ani  muscle 
(arcus  fendineus  m.  levatoris  ani).  This  arch  is  concave  upward.  The  anterior 
end  of  the  arch  begins  on  the  posterior  surface  of  the  superior  ramus  of  the 
pubis.  "The  posterior  end  can  be  followed  as  far  as  the  linea  arcuata  of  the 
ilium,  between  these  two  points  it  descends  for  a  variable  distance,  but  always 
leaves  the  canalis  obturatorius  free."^  The  fibres,  coursing  internally  and  down- 
ward, pass  below  the  posterior  portion  of  the  Pubococcygeus.  The  anterior 
fibres  join  the  fibres  of  the  other  side,  between  the  anus  and  the  tip  of  the  coccyx 
in  a  median  raph^. 

The  posterior  fibres  are  inserted  into  the  sides  of  the  last  two  pieces  and  into 
the  tip  of  the  coccyx.  Peter  Thompson  points  out  that  the  Iliococcygeus  muscle 
is  liable  to  variations.  It  is  strongly  developed  in  but  few,  is  usually  thin,  the 
muscular  bundles  being  separated  by  membranous  intervals;  it  may  be  replaced 
by  fibrous  tissue  and  may  even  be  absent.^ 


INTERNAL 
ILIAC  artery' 


obturator 
nerve' 


ANTERIOR   LAYER  OF 

TRIANGULAR  LIGAMENT 

POSTERIOR   LAYER  OF 

TRIANGULAR  LIGAMENT 


PARIETAL 
PELVIC  FASCIA 
ATTACHMENT  TO 
ISCHIAL  SPINE 


WHITE  LINE 
ORIGIN  OF 
LEVATOR    ANI 
ITE  LINE 


VISCERAL 
PELVIC  FASCIA 


OBTURATOR 
FASCIA 


Fig.  305. — The  outer  wall  of  the  pelvis  (pelvic  fascia).     (Cunningham.) 

Relations  of  the  Levator  Ani. — By  its  inner  or  pelvic  surface,  with  the  recto- 
vesical fascia,  which  separates  it  from  the  viscera  of  the  pelvis  and  from  the 
peritoneum.  By  its  outer  or  perineal  surface,  it  forms  the  inner  boundary 
of  the  ischio-rectal  fossa,  and  is  covered  by  a  thin  layer  of  fascia,  the  ischio- 
rectal or  anal  fascia,  given  off  from  the  obturator  fascia.  Its  posterior  border  is 
free  and  separated  from  the  Coccygeus  muscle  by  a  cellular  interspace.  Its 
anterior  border  is  separated  from  the  muscle  of  the  opposite  side  by  a  triangular 
space,  through  which  the  urethra,  and  in  the  female  the  vagina,  passes  from  the 
pelvis. 

Nerve-supply. — A  branch  from  the  anterior  division  of  the  fourth  sacral  nerve 
and  a  branch  from  the  pudic  nerve,  which  is  sometimes  derived  from  the  perineal 
and  sometimes  from  the  inferior  hemorrhoidal  division. 

Actions. — The  entire  Levator  ani  muscle  enters  into  the  formation  of  the 
diaphragm  of  the  pelvis  and  aids  in  supporting  the  rectum,  vagina,  and  bladder. 


1  Spalteholz's  Atlas.     Translated  and  edited  by  Barker. 


2  Myology  of  Muscles. 


OF    THE  PERINEUM  IN    THE  MALE  455 

The  two  parts  of  the  muscle  have  different  functions.  The  IHococcygei  have 
no  other  function  than  that  of  supporting  the  viscera.  In  early  life  they  flex  the 
vertebrae  of  the  coccyx  on  one  another  and  flex  the  coccyx  on  the  sacrum,  but  do 
not  act  directly  at  any  age  on  the  rectum  or  pelvic  viscera  (Peter  Thompson). 
The  Pubococcygei,  especially  in  the  female,  have  most  important  functions. 
They  are  the  most  influential  supports  of  the  pelvic  floor  and  restore  the  pelvic 
floor  to  its  proper  position  after  the  depression  induced  by  parturition,  defecation, 
and  efforts  at  urination.^  Normally,  they  pull  the  perinseum  upward  after  the 
descending  head  has  pulled  it  down.  In  some  cases  the  contraction  of  the  muscles 
actually  obstructs  the  descent  of  the  head  (Peter  Thompson).  The  muscles  are 
strongly  developed  in  females,  and,  acting  with  the  Sphincter  vaginae,  they  aid 
in  contracting  the  vaginal  canal.  The  muscles  constrict  the  rectum  and  also  lift 
the  rectum  with  the  pelvic  floor.  During  defecation  the  position  of  the  rectal 
contents  is  maintained  by  intra-abdominal  pressure,  the  muscles  lift  the  perinseum 
over  the  fecal  matter  (Goffe).  The  Levator  ani  is  also  a  muscle  of  forced 
expiration. 

The  Coccygeus  is  a  flat,  triangular  muscle  situated  behind  and  parallel  with 
the  preceding.  It  is  a  triangular  plane  of  muscular  and  tendinous  fibres,  arising, 
by  its  apex,  from  the  spine  of  the  ischium,  the  obturator  fascia,  the  edge  of  the 
great  sacro-sciatic  notch,  and  from  the  lesser  sacro-sciatic  ligament,  and  inserted, 
by  its  base,  into  the  side  of  the  lower  two  vertebrae  of  the  sacrum  and  the  upper 
two  vertebrae  of  the  coccyx.  It  assists  the  Levator  ani  and  Pyriformis  in  closing 
in  the  back  part  of  the  outlet  of  the  pelvis. 

Relations. — By  its  inner  or  'pelvic  surface,  with  the  rectum.  By  its  external 
surface,  with  the  lesser  sacro-sciatic  ligament.  The  lower  border  is  in  relation 
with  the  posterior  border  of  the  Levator  ani,  but  separated  from  it  by  a 
cellular  interval:  its  upper  border  is  in  relation  with  the  lower  border  of  the 
Pyriformis,  but  separated  from  it  by  the  sciatic  and  internal  pudic  vessels  and 
nerve. 

Nerve-supply. — A  branch  from  the  fourth  and  fifth  sacral  nerves. 

Action. — The  Coccygei  muscles  raise  and  support  the  coccyx,  after  it  has  been 
pressed  backward  during  defecation  or  parturition. 


2.  The  Muscles  and  Fasciae  of  the  Perinseum  in  the  Male  (Figs.  301, 

306,  307,  308). 

Transversus  perinei  superficialis.  Erector  penis. 

Accelerator  urinae.  Compressor  urethrae. 

Superficial  Fascia  (fascia  superficialis  perinei). — The  superficial  fascia  of  the 
perinaeum  consists  of  two  layers,  superficial  and  deep,  as  in  other  regions  of  the 
body.  The  superficial  fascia  over  the  posterior  portion  of  the  perinaeum  is 
arranged  in  fatty  layers  which  fill  the  ischio-rectal  fossa  on  each  side  of  the 
rectum  and  anus.  The  superficial  fascia  over  the  anterior  portion  of  the  peri- 
naeum (urethral  region)  requires  fuller  consideration. 

The  Superficial  Layer  is  thick,  loose,  areolar  in  texture,  and,  except  toward  the 
scrotum,  contains  much  adipose  tissue  in  its  meshes,  the  amount  of  which  varies 
in  different  subjects.  In  front,  it  is  continuous  with  the  dartos  of  the  scrotum; 
behind,  it  is  continuous  with  the  subcutaneous  areolar  tissue  surrounding  the 
anus;  and,  on  either  side,  with  the  same  fascia  on  the  inner  side  of  the  thighs.  In 
the  middle  line  it  is  adherent  to  the  skin  of  the  raphe  and  to  the  deep  layer  of 

1  Peter  Thompson.     The  Myology  of  the  Pelvic  Floor. 


456 


THE  MUSCLES  AND   FASCIA 


the  superficial  fascia.    This  layer  should  be  carefully  removed  after  it  has  been 
examined,  when  the  deep  layer  will  be  exposed. 

The  Deep  Layer  of  Superficial  Fascia  or  the  Fascia  of  Colles  is  thin,  aponeurotic 
in  structure,  and  of  considerable  strength,  serving  to  bind  down  the  muscles  of  the 
root  of  the  penis.  It  is  continuous,  in  front,  with  the  deep  fascia  of  the  penis, 
and  the  dartos  of  the  scrotum,  the  fascia  of  the  spermatic  cord,  and  Scarpa's 
fascia  upon  the  anterior  portion  of  the  abdomen;  on  either  side  it  is  firmly 
attached  to  the  margins  of  the  rami  of  the  os  pubis  and  ischium,  external  to 
the  crus  penis,  and  as  far  back  as  the  tuberosity  of  the  ischium;  posteriorly, 
it  curves  down  behind  the  Superficial  transverse  perineal  muscles  (reflected 
portion  of  fascia)  to  join  the  lower  margin  of  the  triangular  ligament,  which 
structure  is  a  prolongation  of  the  deep  layer  of  the  superficial  fascia.  The 
deep  layer  is  attached  to  the  superficial  layer  in  the  median  line  and  to  the 


Fig.  306. — The  perinseum.     The  integument  and  superficial  layer  of  superficial  fascia  reflected. 

median  septum  of  the  Accelerator  urinse  muscle.  At  the  central  tendon  of  the 
perineum  the  reflected  portion  of  the  fascia  becomes  blended  with  the  inser- 
tions of  the  External  anal  sphincter,  the  two  Superficial  transverse  perineal 
muscles,  and  the  Accelerator  urinse.  This  fascia  not  only  covers  the  muscles 
in  this  region,  but  sends  upward  a  vertical  septum  from  its  deep  surface,  which 
separates  the  back  part  of  the  subjacent  space  into  two,  the  septum  being 
incomplete  in  front. 

The  Central  Tendinous  Point  of  the  Perinseum. — This  is  a  fibrous  point  in  the 
middle  line  of  the  perinseum,  between  the  urethra  and  the  rectum,  being  about 
half  an  inch  in  front  of  the  anus.  At  this  point  four  muscles  converge  and  are 
attached — viz.,  the  External  sphincter  ani,  the  Accelerator  urinae,  and  the  two 
Superficial  transverse  perineal ;  so  that  by  the  contraction  of  these  muscles,  which 
extend  in  opposite  directions,  it  serves  as  a  fixed  point  of  support. 


OF    THE   PERINJEUM  IN    THE   MALE 


457 


The  Transversus  Perinei  Superficialis  is  a  narrow  muscular  slip,  which  passes 
more  or  less  transversely  across  the  back  part  of  the  perineal  space.  It  arises 
by  a  small  tendon  from  the  inner  and  forepart  of  the  tuberosity  of  the  ischium, 
and,  passing  inward,  is  inserted  into  the  central  tendinous  point  of  the  perinseum, 
joining  in  this  situation  with  the  muscle  of  the  opposite  side,  the  External 
sphincter  ani  behind,  and  the  Accelerator  urinse  in  front.  The  base  of  the  tri- 
angular ligament  lies  just  beneath  this  muscle. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their  contraction  they  serve  to  fix  the  central  tendinous  point  of 
the  perinseum. 

The  Accelerator  Urinse,  called  also  the  Ejaculator  seminis  and  the  Ejaculator 
urinse  (m.  hulhocavernosus) ,  is  placed  in  the  middle  line  of  the  perinaeum,  imme- 
diately in  front  of  the  anus.  It  consists  of  two  symmetrical  halves,  united 
along  the  median  line  by  a  tendinous  raph^.     It  arises  from  the  central  tendon 


Transversus  perinei 
superficialis 


GREAT  SACRO- 
SCIATIC   LIGAMENT 


Superficial  perineal  artery. 
Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


Fig.  307. — The  superficial  muscles  and  vessels  of  the  perinseum. 

of  the  peringeum,  and  from  the  median  raph^  in  front.  From  this  point  its  fibres 
diverge  like  the  plumes  of  a  pen;  the  most  posterior  form  a  thin  layer,  which  is 
lost  on  the  anterior  surface  of  the  triangular  ligament;  the  middle  fibres  encircle 
the  bulb  and  adjacent  parts  of  the  corpus  spongiosum,  and  join  with  the  fibres 
of  the  opposite  side,  on  the  upper  part  of  the  corpus  spongiosum,  in  a  strong 
aponeurosis;  the  anterior  fibres,  the  longest  and  most  distinct,  spread  out  over 
the  sides  of  the  corpus  cavernosum,  to  be  inserted  partly  into  that  body,  anterior 
to  the  Erector  penis,  occasionally  extending  to  the  os  pubis;  partly  terminating 
in  a  tendinous  expansion,  which  covers  the  dorsal  vessels  of  the  penis.  The  latter 
fibres  are  best  seen  by  dividing  the  muscle  longitudinally,  and  dissecting  it  out- 
ward from  the  surface  of  the  urethra.  Many  fibres  of  the  External  sphincter 
ani  and  of  the  Superficial  transverse  perineal  muscles  pass  into  this  muscle. 

Action. — ^This  muscle  serves    to  empty  the  canal  of    the  urethra,  after  the 
bladder  has  expelled  its  contents;  during  the  greater  part  of  the  act  of  micturition 


458 


THE  MUSCLES   AND    FASCIA 


its  fibres  are  relaxed,  and  it  only  comes  into  action  at  the  end  of  the  process. 
The  middle  fibres  are  supposed,  by  Krause,  to  assist  in  the  erection  of  the  corpus 
spongiosum,  by  compressing  the  erectile  tissue  of  the  bulb.  The  anterior  fibres, 
on  each  side,  which  are  known  as  Houston's  muscles,  according  to  Tyrrel,  also 
contribute  to  the  erection  of  the  penis,  as  they  are  inserted  into,  and  continuous 
with,  the  fascia  of  the  penis,  compressing  the  dorsal  vein  during  the  contraction 
of  the  muscle. 

The  Erector  Penis  (m.  ischiocavernosus)  covers  part  of  the  crus  penis.  It  is  an 
elongated  muscle,  broader  in  the  middle  than  at  either  extremity,  and  situated  on 
either  side  of  the  lateral  boundary  of  the  perinaeum.  It  arises  by  tendinous  and 
fleshy  fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium,  behind  the 
crus  penis,  from  the  surface  of  the  crus,  and  from  the  adjacent  portion  of  the 
ramus  of  the  ischium.  From  these  points  fleshy  fibres  succeed,  which  end 
in  an  aponeurosis  which  is  inserted  into  the  sides  and  under  surface  of  the 
crus  penis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 


Anterior  layer  of 

deep  peHneal  fascia  removed, 

showing 

COMPRESSOR   URETHRC 

_Jnternal  pudic  artery. 
Artery  of  the  bulb. 
Cowper's  gland. 


Fig.  308. — Triangular  ligament  or  deep  perineal  fascia.     On  the  left  side  the  anterior  layer  has  been  removed. 


Actions. — It  compresses  the  crus  penis  and  retards  the  return  of  the  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

Between  the  muscles  just  examined  a  triangular  space  exists,  bounded  inter- 
nally by  the  Accelerator  urinse,  externally  by  the  Erector  penis,  and  behind  by 
the  Transversus  perinei  superficialis.  The  floor  of  this  space  is  formed  by  the 
triangular  ligament  of  the  urethra  (deep  perineal  fascia),  and  running  from  behind 
forward  in  it  are  the  superficial  perineal  vessels  and  nerves,  the  long  pudendal 
nerve,  and  the  transverse  perineal  artery  coursing  along  the  posterior  boundary 
of  the  space  on  the  Transversus  perinei  superficialis. 

The  Triangulax  Ligament  or  the  Deep  Perineal  Fascia  (trigonum  or  diaphragma 
urogenitale)  (Figs.  305,  309,  and  310)  is  stretched  almost  horizontally  across  the 
pubic  arch,  so  as  to  close  in  the  front  part  of  the  outlet  of  the  pelvis.     It  con- 


OF    THE   PERINEUM  IN    THE   HALE 


459 


sists  of  two  dense  musculo-membranous  laminae,  which  are  united  along  their 
posterior  borders,  but  are  separated  in  front  by  intervening  structures.  The 
superficial  of  these  two  layers,  the  superficial,  anterior,  or  inferior  layer  of  the 
triangular  ligament  (fascia  trigoni  urogenitalis  inferior),  is  triangular  in  shape 
and  about  an  inch  and  a  half  in  depth.  Its  apex  is  directed  forward,  and  is 
separated  from  the  subpubic  ligament  by  an  oval  opening  for  the  transmission 
of  the  dorsal  vein  of  the  penis.    The  apex  of  the  triangular  ligament  is  called  the 


DEEP  LAYER  OF 
SUPERFICIAL  FASCIA 


PERITONEUM 

PROSTATIC 
FASCIA 

DEEP    LAYER 
OF  TRIANGULAR 
'^       LIGAMENT 


OMPRESSOR 
URETHR>E 
MUSCLE 
SUPERFICIAL  LAYER  OF 
TRIANGULAR  LIGAMENT 


Fig.  309. — The  aponeurosis  of  the  perinseum.    (Denonvilliers.) 


transverse  perineal  or  transverse  pelvic  ligament  (ligamentum  transversum  pelvis). 
The  lateral  margins  of  the  inferior  layer  of  the  triangular  ligament  are  attached 
on  each  side  to  the  rami  of  the  ischium  and  os  pubis,  above  the  crura  penis. 
The  fusion  of  the  two  leaves  posteriorly  takes  place  beneath  the  Superficial 
transverse  perineal  muscles.  The  region  of  fusion  of  the  two  leaflets  posteriorly 
is  called  the  base.     The  base  is  directed  toward  the  rectum,  and  connected  to 


DORSAL  VEIN 

OF    PENIS 

DORSAL  NERVE 

OF    PEN 

DORSAL  ARTERY 

OF  PENIS 


ARTERY  TO 

BULB 

COMPRESSOR 

URETHR/E 


conpus. 

SPONGIOSUM 


ERECTOR 
PENIS 


CORPUS 
CAVERNOSUM 
TRIANGULAR 
LIGAMENT 

(upper  margin) 


Fig   310 — The  superficial  layer  of  the  triangular  liRament.     The  Compressor  urethrse  muscle  lies  behind  the 
superficial  layer  of  the  triangular  ligament  and  is  shown  in  the  figure  for  convenience.    (Poirier  and  Charpy.) 


the  central  tendinous  point  of  the  perinseum.  It  is  continuous  with  the  deep 
layer  of  the  superficial  fascia  behind  the  Superficial  transverse  perineal  muscles, 
and  with  a  thin  fascia  which  covers  the  cutaneous  surface  of  the  Levator  ani 
muscle,  the  anal  or  ischio-rectal  fascia. 

This  layer  of  the  triangular  ligament  is  perforated,  about  an  inch  below  the 
symphysis  pubis,  by  the  urethra,  the  aperture  for  which  is  circular  in  form  and 


460  THE  MUSCLES  AND    FASCIA 

about  three  or  four  lines  in  diameter;  by  the  arteries  to  the  bulb  and  the  ducts  of 
Cowper's  glands  close  to  the  urethral  orifice;  by  the  arteries  to  the  corpora  caver- 
nosa— one  on  each  side,  close  to  the  pubic  arch  and  about  half-way  along  the 
attached  margin  of  the  ligament ;  by  the  dorsal  arteries  and  nerves  of  the  penis  near 
the  apex  of  the  ligament.  Its  base  is  also  perforated  by  the  superficial  perineal 
vessels  and  nerves,  while  between  its  apex  and  the  subpubic  ligament  the  dorsal 
nerve  of  the  penis  and  the  dorsal  vein  of  the  penis  passes  upward  into  the 
pelvis. 

If  this  superficial  or  inferior  layer  of  the  triangular  ligament  is  detached  on 
either  side,  the  following  structures  will  be  seen  between  it  and  the  deeper 
layer:  the  dorsal  vein  of  the  penis;  the  membranous  portion  of  the  urethra, 
arid  the  Compressor  urethrse  muscle;  Cowper's  glands  and  their  ducts;  the 
pudic  vessels  and  dorsal  nerve  of  the  penis;  the  artery  and  nerve  of  the  bulb, 
and  a  plexus  of  veins.  The  two  layers  join  the  urethral  wall  and  vagina 
medianward. 

The  deep,  posterior,  or  superior  layer  (fascia  trigoni  urogenitalis  superior)  of  the 
triangular  ligament  is  derived  from  the  obturator  fascia  and  stretches  across 
the  pubic  arch.  If  the  obturator  fascia  is  traced  inward  after  covering  the 
Obturator  internus  muscle,  it  will  be  found  to  be  attached  by  some  of  its 
deeper  or  anterior  fibres  to  the  inner  margin  of  the  ischio-pubic  ramus,  while  its 
superficial  or  posterior  fibres  pass  over  this  attachment  to  become  the  superior 
layer  of  the  triangular  ligament.  Behind,  this  layer  of  the  fascia  is  continuous 
with  the  inferior  layer  and  with  the  fascia  of  Colles,  and  in  front  it  is  separated 
from  the  apex  of  the  prostate  gland  through  the  intervention  of  a  prolongation  of 
the  recto-vesical  fascia.  It  is  pierced  by  the  urethra,  or  rather  consists  of  two 
halves  which  are  separated  in  the  middle  line  by  the  urethra  passing  between 
them. 

The  Compressor  or  Constrictor  Urethrae  (m.  constrictor  urethrce)  in  the  male 
surrounds  the  whole  length  of  the  membranous  portion  of  the  urethra,  and  is 
contained  between  the  two  layers  of  the  triangular  ligament.  It  arises,  by  apon- 
eurotic fibres,  from  the  junction  of  the  rami  of  the  os  pubis  and  ischium,  to  the 
extent  of  half  or  three-quarters  of  an  inch:  the  point  where  the  crura  penis  joins 
the  transverse  ligament  of  the  perineum  and  the  layers  of  the  triangular  liga- 
ment; each  segment  of  the  muscle  passes  inward,  and  divides  into  twofascicuH, 
which  surround  the  membranous  urethra  and  unite,  at  the  upper  and  lower 
surfaces  of  this  tube,  with  the  muscle  of  the  opposite  side  by  means  of  a  tendinous 
raphe.  The  Compressor  urethne  is  continuous  posteriorly  with  the  m.  prostaticus 
and  is  continuous  anteriorly  with  the  circular  fibres  of  the  cavernous  portion  of 
the  urethra.  This  muscle  is  frequently  in  two  portions,  an  anterior  and  a 
posterior,  separated  by  a  distinct  interval.  In  such  cases  the  posterior  fibres  are 
called  the  transversus  perinei  profundus,  and  the  anterior  fibres  are  called  the 
sphincter  urethrae  membranacese. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — The  muscles  of  both  sides  act  together  as  a  sphincter,  compressing 
the  membranous  portion  of  the  urethra.  During  the  transmission  of  fluids  they, 
like  the  Acceleratores  urinte,  are  relaxed,  and  come  into  action  only  at  the  end  of 
the  process,  to  eject  the  last  drops  of  the  fluid. 

3.  The  Muscles  of  the  Perinaeum  in  the  Female  (Fig.  311). 

Transversus  perinei  superficialis.  Erector  clitoridis. 

Sphincter  vaginae.  Compressor  urethrae. 

The  Transversus  Perinei  Superficialis  in  the  female  is  a  narrow  muscular  slip, 
which  passes  more  or  less  transversely  across  the  back  part  of  the  perineal  space. 


OF    THE   PERINjEUM  IN   THE   FEMALE 


461 


It  arises  by  a  small  tendon  from  the  inner  and  forepart  of  the  tuberosity  of  the 
ischium,  and,  passing  inward,  is  inserted  into  the  central  point  of  the  perinseum, 
joining  in  this  situation  with  the  muscle  of  the  opposite  side,  the  External  sphinc- 
ter ani  behind,  and  the  Sphincter  vaginae  in  front. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — By  their  contraction  they  serve  to  fix  the  central  tendinous  point  of 
the  perinseum. 

The  Sphincter  Vaginae  (m.  hulbocavemosus)  surrounds  the  orifice  of  the 
vagina,  and  is  analogous  to  the  Accelerator  urinse  in  the  male.  It  is  attached 
posteriorly  to  the  central  tendinous  point  of  the  perinseum,  where  it  blends  with 


TRANSVERSUS 
PERINjCI. 


LIBER    ISCHII. 


Fig.  311. — Muscles  of  the  female  perinajum. 


the  External  sphincter  ani.  Its  fibres  pass  forward  on  each  side  of  the  vagina,  to 
be  inserted  into  the  corpora  cavernosa  of  the  clitoris,  a  fasciculus  crossing  over 
the  body  of  the  organ  so  as  to  compress  the  dorsal  vein. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  diminishes  the  orifice  of  the  vagina.  The  anterior  fibres  contribute 
to  the  erection  of  the  clitoris,  as  they  are  inserted  into  and  are  continuous  with  the 
fascia  of  the  clitoris;  compressing  the  dorsal  vein  during  the  contraction  of  the 
muscle. 

The  Erector  Clitoridis  (m.  ischiocavemosus)  resembles  the  Erector  penis  in  the 
male,  but  is  smaller  than  it.  It  covers  the  unattached  part  of  the  crus  clitoridis. 
It  is  an  elongated  muscle,  broader  at  the  middle  than  at  either  extremity,  and 
situated  on  either  side  of  the  lateral  boundary  of  the  perinseum.  It  arises  by 
tendinous  and  fleshy  fibres  from  the  inner  surface  of  the  tuberosity  of  the  ischium, 
behind  the  crus  clitoridis  from  the  surface  of  the  crus,  and  from  the  adjacent 
portion  of  the  ramus  of  the  ischium.    From  these  points  fleshy  fibres  succeed, 


462 


THE   3IU8CLES  AND   FASCIA 


which  end  in  an  aponeurosis,  which  is  inserted  into  the  sides  and  under  surface 
of  the  crus  chtoridis. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 

Actions. — It  compresses  the  crus  clitoridis  and  retards  the  return  of  blood 
through  the  veins,  and  thus  serves  to  maintain  the  organ  erect. 

The  Triangular  Ligament  (trigonum  urogenitale)  in  the  female  is  not  so  strong 
as  in  the  male.  It  is  divided  in  the  middle  line  by  the  aperture  of  the  vagina, 
with  the  external  coat  of  which  it  becomes  blended,  and  in  front  of  this  is 
perforated  by  the  urethra.  Its  posterior  border  is  continuous,  as  in  the  male, 
with  the  deep  layer  of  the  superficial  fascia  around  the  Transversus  perinei 
muscle. 

Like  the  triangular  ligament  in  the  male,  it  consists  of  two  layers,  between 
which  are  to  be  found  the  following  structures:  the  dorsal  vein  of  the  clitoris, 
a  portion  of  the  urethra  and  the  Compressor  urethrae  muscle,  the  glands  of  Bar- 
tholin and  their  ducts;  the  pudic  vessels  and  the  dorsal  nerve  of  the  clitoris;  the 
arteries  of  the  bulbi  vestibuli,  and  a  plexus  of  veins. 

The  Compressor  Urethrae  (m.  constrictor  urethrce)  arises  on  each  side  from  the 
margin  of  the  descending  ramus  of  the  os  pubis.  The  fibres,  passing  inward, 
divide  into  two  sets:  those  of  the  forepart  of  the  muscle  are  directed  across  the 
subpubic  arch  in  front  of  the  urethra  to  blend  with  the  muscular  fibres  of  the 
opposite  side;  while  those  of  the  hinder  and  larger  part  pass  inward  to  blend  with 
the  wall  of  the  vagina  behind  the  urethra. 

Nerve-supply. — The  perineal  branch  of  the  internal  pudic. 


MUSCLES  AND  FASCI-ffi  OF  THE  UPPER  EXTREMITY. 


The  muscles  of  the  Upper  Extremity  are  divisible  into  groups,  corresponding 
with  the  different  regions  of  the  limb. 


I.  Of  the  TfjORACic  Region. 

1.  Anterior  Thoracic  Region. 

Pectoralis  major.     Pectoralis  minor. 
Subclavius. 

2.  Lateral  Thoracic  Region. 

Serratus  magnus. 

II.  Of  the  Shoulder  and  Arm. 

3.  Acromial  Region. 

Deltoid. 

4.  Anterior  Scapular  Region. 

Subscapularis. 

5.  Posterior  Scapular  Region. 

Supraspinatus.  Teres  minor. 

Infraspinatus.  Teres  major. 


6.  Anterior  Humeral  Region. 

Coraco-brachialis.  Biceps. 

Brachialis  anticus. 

7.  Posterior  Humeral  Region. 
Triceps.  Subanconeus. 

III.  Of  the  Forearm. 

8.  Anterior  Radio-ulnar  Region. 

Pronator  radii  teres. 

Flexor  carpi  radialis. 

Palmaris  longus. 

Flexor  carpi  ulnaris. 
L  Flexor  sublimis  digitorum. 
f  Flexor  profundus  digitorum. 
j  Flexor  longus  pollicis. 
[Pronator  quadratus. 


.2 


9.  Radial   Region. 

Supinator  longus. 

Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevior. 


^_^ 

.2 

*5 

t-l 

^ 

0) 

rf    1 

^^  1 

02 

Oh 

o 

b5 
1— 1 

yff^  ANTERIOR    THORACIC  REGION  463 

10.  Posterior   Radio-Ulnar  Region.       Flexor  brevis  pollicis. 

J?  ^  ^^„^\c,  ^;^,-+^^,,rv.  Adductor  obliquus  pollicis. 

Extensor  communis  aigitorum.  .  ,  ,     ,  ,      ^         ^        „.  . 

t:,   ,  •   •_•  ,1-  :+;  Adductor  transversus  pollicis. 

Extensor  minimi  digiti.  ^ 

Extensor  carpi  ulnaris. 

Anconeus.  1*^-  Ulnar  Region. 

Supinator  brevis.  Palmaris  brevis. 

Extensor  ossis  metacarpi  poUici.    Abductor  minimi  digiti. 

Extensor  brevis  pollicis.  Ylexor  brevis  minimi  digiti. 

Extensor  longus  pollicis.  p^g^^j.  ossis  metacarpi   minimi  digiti 

Extensor  indicis.  (Opponens  minimi  digiti). 

IV.  Of  the  Hand. 

11.  Radial  Region.  l^-  ^'^^^'  ^^^^«^  ^'d^""' 

Abductor  pollicis.  Lumbricales. 

Flexor  ossis  metacarpi  pollicis  Interossei  palmares. 

(Opponens  pollicis).  Interossei  dorsales. 

Dissection  of  Pectoral  Region  and  Axilla  (Fig.  312). — The  arm  being  drawn  away  from 
the  side  nearly  at  right  angles  with  the  trunk  and  rotated  outward,  make  a  vertical  incision 
through  the  integument  in  the  median  line  of  the  chest,  from  the  upper  to  the  lower  part  of  the 
sternum;  a  second  incision  along  the  lower  border  of  the  Pectoral  muscle,  from  the  ensiform 
cartilage  to  the  inner  side  of  the  axilla ;  a  third,  from  the  sternum  along  the  clavicle,  as  far  as  its 
centre;  and  a  fourth,  from  the  middle  of  the  clavicle  obliquely  downward,  along  the  interspace 
between  the  Pectoral  and  Deltoid  muscles,  as  low  as  the  fold  of  the  armpit.  The  flap  of  integu- 
ment is  then  to  be  dissected  off  in  the  direction  indicated  in  the  figure,  but  not  entirely  removed, 
as  it  should  be  replaced  on  completing  the  dissection.  If  a  transverse  incision  is  now  made 
from  the  lower  end  of  the  sternum  to  the  side  of  the  chest,  as  far  as  the  posterior  fold  of  the 
armpit,  and  the  integument  reflected  outward,  the  axillary  space  will  be  more  completely  exposed. 

I.  THE  MUSCLES  AND  FASGIiE  OF  THE  THORACIC  REGION. 
1.  The  Anterior  Thoracic  Region. 

Pectoralis  major.  Pectoralis  minor. 

Subclavius. 

Superficial  Fascia. — ^The  superficial  fascia  of  the  thoracic  region  is  a  loose 
cellulo-fibrous  layer  enclosing  masses  of  fat  in  its  spaces.  It  is  continuous  with 
the  superficial  fascia  of  the  neck  and  upper  extremity  above,  and  of  the  abdomen 
below.  Opposite  the  mamma  it  divides  into  two  layers,  one  of  which  passes  in 
front,  the  other  behind,  that  gland;  and  from  both  of  these  layers  numerous  septa 
pass  into  its  substance,  supporting  its  various  lobes :  from  the  anterior  layer  fibrous 
processes  pass  forward  to  the  integument  and  nipple.  These  processes  were  called 
by  Sir  A.  Cooper  the  suspensory  ligaments  (ligamenta  suspensoria) ,  from  the  sup- 
port they  afford  to  the  gland  in  this  situation. 

Deep  Fascia. — The  deep  thoracic  fascia  is  a  thin  aponeurotic  lamina,  cover- 
ing the  surface  of  the  great  Pectoral  muscle,  and  sending  numerous  prolongations 
between  its  fasciculi:  it  is  attached,  in  the  middle  line,  to  the  front  of  the  sternum, 
and  above  to  the  clavicle;  externally  and  below  it  becomes  continuous  with  the 
fascia  over  the  shoulder,  axilla,  and  thorax.  It  is  very  thin  over  the  upper  part 
of  the  muscle,  thicker  in  the  interval  between  the  Pectoralis  major  and  Eatissimus 
dorsi,  where  it  closes  in  the  axillary  space,  and  is  known  as  the  axillary  fascia  (fascia 
axillaris).  It  passes  behind  into  the  fascia  of  the  Latissimus  dorsi  and  Teres 
major,  in  front  into  the  fascia  of  the  deltoid  and  outward  into  the  brachial 
fascia.  The  fascia  of  the  liatissimus  dorsi  divides  at  the  outer  margin  of  the 
muscle  into  two  layers,  one  of  which  passes  in  front  and  the  other  behind  it;  these 
proceed  as  far  as  the  spinous  processes  of  the  dorsal  vertebrae,  to  which  they  are 


464 


THE  MUSCLES  AND   FASCIA 


attached.  As  the  axillary  fascia  leaves  the  lower  edge  of  the  Pectoralis  major  to 
pass  across  the  floor  of  the  axilla  it  sends  a  layer  upward  under  cover  of  the 
muscle,  deep  pectoral  fascia:  this  lamina  splits  to  envelop  the  Pectoralis  minor,  at 
the  upper  edge  of  which  it  becomes  continuous  with  the  costo-coracoid  membrane, 
or  the  clavi-pectoral  fascia.  The  hollow  of  the  armpit,  seen  when  the  arm  is 
abducted,  is  mainly  produced  by  the  traction  of  this  fascia  on  the  axillary  floor, 
the  axillary  fascia  (fascia  axillaris),  and  hence  it  is  sometimes  named  the 
suspensory  ligament  of  the  axilla.  The  axillary  fascia  (Fig.  313)  is  not  a  dis- 
tinct and  complete  rigid  floor  of  the  axillary  space.  Like  all  other  fasciae,  it 
follows  muscular  planes,  and  splits  to  encompass  vessels,  nerves,  and  muscles. 
In  it  are  numerous  perforations.  In  this  fascia  is  a  curved  arch  which  often 
contains  muscular  fibres  and  which  passes  from  the  tendon  of  the  great  Pectoral, 


S.  Dissection  of 
Shoulder  and  Arm, 


1.  Dissection  of 
Pectoral  Region 
and  Axilla. 


2.  Bend  of  Elbow. 


Jf,  Forearm. 


B.  Palm  of  Hand. 


Fig.  312. — Dissection  of  upper  extremity. 

the  Coraco-brachialis  or  the  fascia  over  the  biceps  to  the  tendon  of  the  Latissimus 
dorsi.  This  is  called  the  axillary  arch.  Langer  showed  many  years  ago  that  there 
is  an  opening  in  the  centre  of  the  dense  axillary  fascia,  the  foramen  of  Langer. 
Through  this  opening  axillary  glands  not  unusually  protrude.  The  axillary  arch 
is  the  inner  margin  of  the  foramen  of  Langer.  At  the  lower  part  of  the  thoracic 
region  the  deep  thoracic  fascia  is  well  developed,  and  is  continuous  with  the 
fibrous  sheath  of  the  Recti  muscles. 

The  Pectoralis  Major  (Fig.  314)  is  a  broad,  thick,  triangular  muscle,  situated 
at  the  upper  and  forepart  of  the  chest,  in  front  of  the  axilla.  It  arises  from  the 
anterior  surface  of  the  sternal  half  of  the  clavicle;  from  half  the  breadth  of  the 
anterior  surface  of  the  sternum,  as  low  down  as  the  attachment  of  the  cartilage 
of  the  sixth  or  seventh  rib ;  this  portion  of  its  origin  consists  of  aponeurotic  fibres, 
which  intersect  with  those  of  the  opposite  muscle;  it  also  arises  from  the  carti- 


THE   ANTERIOR    THORACIC  REGION 


465 


lages  of  all  true  ribs,  with  the  exception,  frequently,  of  the  first  or  of  the  seventh, 
or  both;  and  from  the  aponeurosis  of  the  External  oblique  muscle  of  the  abdo- 
men. The  fibres  from  this  extensive  origin  converge  toward  its  insertion,  giving 
to  the  muscle  a  radiated  appearance.  Those  fibres  which  arise  from  the  clavicle 
pass  obliquely  outward  and  downward  and  are  usually  separated  from  the  rest 
by  a  cellular  interval :  those  from  the  lower  part  of  the  sternum,  and  the  cartilages 
of  the  lower  true  ribs,  pass  upward  and  outward,  whilst  the  middle  fibres  pass 
horizontally.  They  all  terminate  in  a  flat  tendon,  about  two  inches  broad,  which 
is  inserted  into  the  outer  bicipital  ridge  of  the  humerus.  This  tendon  consists  of 
two  laminae,  placed  one  in  front  of  the  other,  and  usually  blended  together  below. 
The  anterior,  the  thicker,  receives  the  clavicular  and  upper  half  of  the  sternal 
portion  of  the  muscle;  and  its  fibres  are  inserted  in  the  same  order  as  that  in 
which  they  arise;  that  is  to  say,  the  outermost  fibres  of  origin  from  the  clavicle  are 


SUBSCAPULAR 
ARTERY  AND  VelN 


Fig.  313. — The  fa.scia  of  the  right  axilla,  viewed  from  below.      (Spalteholz.) 


inserted  at  the  uppermost  part  of  the  tendon;  the  upper  fibres  of  origin  from  the 
sternum  pass  down  to  the  lowermost  part  of  this  anterior  lamina  of  the  tendon 
and  extend  as  low  as  the  tendon  of  the  Deltoid  and  join  with  it.  The  posterior 
lamina  of  the  tendon  receives  the  attachment  of  the  lower  half  of  the  sternal  por- 
tion and  the  deeper  part  of  the  muscle  from  the  costal  cartilages.  These  deep 
fibres,  and  particularly  those  from  the  lower  costal  cartilages,  ascend,  the  higher, 
turning  backward  successively  behind  the  superficial  and  upper  ones,  so  that  the 
tendon  appears  to  be  twisted.  The  posterior  lamina  reaches  higher  on  the  humerus 
than  does  the  anterior  one,  and  from  it  an  expansion  is  given  off  which  covers 
the  bicipital  groove  and  blends  with  the  capsule  of  the  shoiilder-joint.  From  the 
deepest  fibres  of  this  lamina  at  its  insertion  an  expansion  is  given  off  which  lines 
the  bicipital  groove  of  the  humerus,  while  from  the  lower  border  of  the  tendon  a 
third  expansion  passes  downward  to  the  fascia  of  the  arm.     Between  the  poste- 

30 


466 


THE   MUSCLED   AND    FASCIA 


rior  surface  of  the  tendon  of  the  great  pectoral  and  the  anterior  surface  of  the 
long  head  of  the  biceps  there  is  usually  a  bursa  {bursa  m.  pectoralis  majoris). 

Relations. — By  its  anterior  surface,  with  the  integument,  the  superficial  fascia, 
the  Platysma,  some  of  the  branches  of  the  descending  cervical  nerves,  the  mam- 
mary gland,  and  the  deep  fascia;  by  its  posterior  surface:  its  thoracic  'portion,  with 
the  sternum,  the  ribs  and  costal  cartilages,  the  costo-coracoid  membrane,  the  Sub- 
clavius,  Pectoralis  minor,  Serratus  magnus,  and  the  Intercostals ;  its  axillary  por- 


FiG.  314. — Muscles  of  the  chest  and  front  of  the  arm.     Superficial  view. 


tion  forms  the  anterior  wall  of  the  axillary  space,  and  covers  the  axillary  vessels  and 
nerves,  the  Biceps  and  Coraco-brachialis  muscles.  Its  upper  border  lies  parallel 
with  the  Deltoid,  from  which  it  is  separated  by  a  slight  interspace  in  which  lie  the 
cephalic  vein  and  humeral  branch  of  the  acromial  thoracic  artery.  Its  lower  border 
forms  the  anterior  margin  of  the  axilla,  being  at  first  separated  from  the  Latissimus 
dorsi  by  a  considerable  interval;  but  both  muscles  gradually  converge  toward  the 
outer  part  of  the  space. 


THE   ANTERIOR    THORACIC   REGION 


407 


Dissection.— Detach  the  Pectoralis  major  by  dividing  the  muscle  along  its  attachment  to 
the  clavicle,  and  by  making  a  vertical  incision  through  its  substance  a  little  external  to  its  line  of 
attachment  to  the  sternum  and  costal  cartilages.  The  muscle  should  then  be  reflected  outward, 
and  its  tendon  carefully  examined.  The  Pectoralis  minor  is  now  exposed,  and  immediately 
above  it,  in  the  interval  between  its  upper  border  and  the  clavicle,  a  strong  fascia,  the  costo- 
coracoid  membrane. 

The  Costo-coracoid  Membrane  or  the  Clavipectoral  Fascia  is  a  strong  fascia, 
situated  under  cover  of  the  clavicular  portion  of  the  Pectorahs  major  muscle.  It 
occupies  the  interval  between  the  Pectoralis  minor  and  Subclavius  muscle,  and  pro- 
tects the  axillary  vessels  and  nerves.  Traced  upward,  it  splits  to  enclose  the  Sub- 
clavius muscle,  and  its  two  layers  are  attached  to  the  clavicle,  one  in  front  of  and 
the  other  behind  the  muscle;  the  latter  layer  fuses  with  the  deep  cervical  fascia  and 


Fig.  315.^ — Muscles  of  the  chest  and  front  of  the  arm,  showing  some  of  the  boundaries  of  the  axilla. 

with  the  sheath  of  the  axillary  vessels.  Internally,  it  blends  with  the  fascia  covering 
the  first  two  intercostal  spaces,  and  is  attached  also  to  the  first  rib  internal  to  the 
origin  of  the  Subclavius  muscle.  Externally  it  is  very  thick  and  dense,  and  is 
attached  to  the  coracoid  process.  The  portion  extending  from  its  attachment  to 
the  first  rib  to  the  coracoid  process  is  often  whiter  and  denser  than  the  rest;  this 
is  sometimes  called  the  costo-coracoid  ligament.  Below,  it  is  thin,  and  at  the  upper 
border  of  the  Pectoralis  minor  it  splits  into  two  layers  to  invest  the  muscle;  from 
the  lower  border  of  the  Pectoralis  minor  it  is  continued  downward  to  join  the  axil- 
lary fascia,  and  outward  to  join  the  fascia  over  the  short  head  of  the  Biceps.  The 
costo-coracoid  membrane  is  pierced  by  the  cephalic  vein,  the  acromial  thoracic 
artery  and  vein,  superior  thoracic  artery,  and  anterior  thoracic  nerves. 


468  'J'HE  MUSCLES  AND   FASCIA 

The  Pectoralis  Minor  (Fig.  315)  is  a  thin,  flat,  triangular  muscle,  situated  at 
the  upper  part  of  the  thorax,  beneath  the  Pectoralis  major.  It  arises  by  three 
tendinous  digitations  from  the  upper  margin  and  outer  surface  of  the  third,  fourth, 
and  fifth  ribs,  near  their  cartilages,  and  from  the  aponeurosis  covering  the  Inter- 
costal muscles;  the  fibres  pass  upward  and  outward,  and  converge  to  form  a  flat 
tendon,  which  is  inserted  into  the  inner  border  and  upper  surface  of  the  coracoid 
process  of  the  scapula. 

Relations. — By  its  anterior  surface,  with  the  Pectoralis  major  and  the  thoracic 
branches  of  the  acromial  thoracic  artery.  By  its  'posterior  surface,  with  the 
ribs,  Intercostal  muscles,  Serratus  magnus,  the  axillary  space,  and  the  axillary 
vessels  and  brachial  plexus  of  nerves.  Its  upper  border  is  separated  from  the 
clavicle  by  a  triangular  interval,  broad  internally,  narrow  externally,  which  is 
occupied  by  the  costo-coracoid  membrane.  This  space  contains  the  first  part  of 
the  axillary  vessels  and  the  axillary  nerves.  Running  parallel  to  the  lower  border 
of  the  muscle  is  the  long  thoracic  artery. 

The  costo-coracoid  membrane  should  now  be  removed,  when  the  Subclavius  muscle  will 
be  seen. 

The  Subclavius  is  a  small  triangular  muscle,  placed  in  the  interval  between  the 
clavicle  and  the  first  rib.  It  arises  by  a  short,  thick  tendon  from  the  first  rib  and 
its  cartilage  at  their  junction,  in  front  of  the  rhomboid  ligament;  the  fleshy  fibres 
proceed  obliquely  upward  and  outward,  to  be  inserted  into  a  deep  groove  on  the 
under  surface  of  the  clavicle.  An  extension  from  the  aponeurosis  of  this  muscle 
lies  upon  the  subclavian  vein. 

Relations. — By  its  upper  surface,  with  the  clavicle.  By  its  deep  surface  it  is 
separated  from  the  first  rib  by  the  subclavian  vessels  and  brachial  plexus  of  nerves. 
Its  anterior  surface  is  separated  from  the  Pectoralis  major  by  the  costo-coracoid 
membrane,  which,  with  the  clavicle,  forms  an  osseo-fibrous  sheath  in  which  the 
muscle  is  enclosed. 

If  the  costal  attachment  of  the  Pectoralis  minor  is  divided  across,  and  the  muscle  reflected 
outward,  the  axillary  vessels  and  nerves  are  brought  fully  into  view,  and  should  be  examined. 

Nerves. — The  Pectoral  muscles  are  supplied  by  the  anterior  thoracic  nerves; 
the  Pectoralis  major  through  these  nerves  receives  filaments  from  all  the  spinal 
nerves  entering  into  the  formation  of  the  brachial  plexus;  the  Pectoralis  minor 
receives  its  fibres  from  the  eighth  cervical  and  first  dorsal  nerves.  The  Subclavius 
is  supplied  by  a  filament  from  the  fifth  cervical  nerve. 

Actions. — If  the  arm  has  been  raised  by  the  Deltoid,  the  Pectoralis  major  will, 
conjointly  with  the  Latissimus  dorsi  and  Teres  major,  depress  it  to  the  side  of  the 
chest.  If  acting  alone,  it  adducts  and  draws  forward  the  arm,  bringing  it  across 
the  front  of  the  chest,  and  at  the  same  time  rotates  it  inward.  The  Pectoralis  minor 
depresses  the  point  of  the  shoulder,  drawing  the  scapula  downward  and  inward 
to  the  thorax,  and  throwing  the  inferior  angle  backward.  The  Subclavius  de- 
presses the  shoulder,  drawing  the  clavicle  downward  and  forward.  When  the 
arms  are  fixed,  all  three  muscles  act  upon  the  ribs,  drawing  them  upward  and 
expanding  the  chest,  and  thus  becoming  very  important  agents  in  forced  inspira- 
tion. Asthmatic  patients  always  assume  an  attitude  which  fixes  the  shoulders,  so 
that  all  these  muscles  may  be  brought  into  action  to  assist  in  dilating  the  cavity 
of  the  chest. 

2.  The  Lateral  Thoracic  Region. 

Serratus  magnus. 

The  Serratus  Magnus  (m.  serratus  anterior)  (Figs.  315  and  316)  is  a  thin,  irregu- 
larly quadrilateral  muscle,  situated  between  the  ribs  and  the  scapula  at  the  upper 


THE   LATERAL    THORACIC  REGION 


469 


Slip  of  SERRATUS 

MAGNUS  to  first  rib. 


Spine  of 
scapula. 


and  lateral  part  of  the  chest.  It  arises  by  nine  digitations  or  slips  from  the  outer 
surface  and  upper  border  of  the  eight  upper  ribs  (the  second  rib  giving  origin  to 
two  slips),  and  from  the  aponeurosis  covering  the  corresponding  intercostal  muscles. 
From  this  extensive  attachment  the  fibres  pass  backward,  closely  applied  to  the 
chest- wall,  and  reach  the  vertebral  border  of 
the  scapula,  and  are  inserted  into  its  ventral 
aspect  in  the  following  manner.  The  upper 
two  digitations — i.  e.,  the  one  from  the  first 
rib  and  the  higher  of  the  two  from  the  second 
rib — converge  to  be  inserted  into  a  triangular 
area  on  the  ventral  aspect  of  the  superior 
angle.  The  next  two  digitations  spread  out 
to  form  a  thin  triangular  sheet,  the  base  of 
which  is  directed  backward  and  is  inserted 
into  nearly  the  whole  length  of  the  ventral 
aspect  of  the  vertebral  border.  The  lower 
five  digitations  converge,  as  they  pass  back- 
ward from  the  ribs,  to  form  a  fan-shaped 
structure,  the  apex  of  which  is  inserted, 
partly  by  muscular  and  partly  by  tendinous 
fibres,  into  a  triangular  impression  on  the 
ventral  aspect  of  the  inferior  angle.  The 
lower  four  slips  interdigitate  at  their  origin 
with  the  upper  five  slips  of  the  External 
oblique  muscle  of  the  abdomen. 

Relations. — This  muscle  is  partly  covered, 
in  front,  by  the  Pectoral  muscles;  l)ehind, 
by  the  Subscapularis.  The  axillary  vessels 
and  nerves  lie  upon  its  upper  part,  while  its 
deep  surface  rests  upon  the  ribs  and  inter- 
costal muscles. 

Nerve. — The  Serratus  magnus  is  supplied 
by  the  posterior  thoracic  nerve,  which  is  de- 
rived from  the  fifth,  sixth,  and  generally  the 
seventh  cervical  nerves. 

Actions. — The  Serratus  magnus,  as  a 
whole,  carries  the  scapula  forward,  and  at 
the  same  time  raises  the  vertebral  border  of 
the  bone.  It  is  therefore  concerned  in  the 
action  of  pushing.  Its  lower  and  stronger  fibres  move  forward  the  lower  angle 
and  assist  the  Trapezius  in  rotating  the  bone  round  an  axis  through  its  centre, 
and  thus  assists  this  muscle  in  raising  the  acromion  and  supporting  weights  upon 
the  shoulder.  It  is  also  an  assistant  to  the  Deltoid  in  raising  the  arm,  inasmuch  as 
during  the  action  of  this  latter  muscle  it  fixes  the  scapula  and  so  steadies  the  glen- 
oid cavity  on  which  the  head  of  the  humerus  rotat'es.  After  the  Deltoid  has  raised 
the  arm  to  a  right  angle  with  the  trunk,  the  Serratus  magnus  and  the  Trapezius, 
by  rotating  the  scapula,  raise  the  arm  into  an  almost  vertical  position.  It  is  pos- 
sible that  when  the  shoulders  are  fixed  the  lower  fibres  of  the  Serratus  magnus  may 
assist  in  raising  and  everting  the  ribs;  but  it  is  not  the  important  inspiratory  muscle 
which  it  was  formerly  believed  to  be. 


EXTERNAL 
OBLIQUE. 


Eighth  rib. 


Fig.  316. — Serratus  magnus.  (From  a  prepa- 
ration in  the  Museum  of  the  Royal  College  of  Sur- 
geons of  England.) 


Surgical  Anatomy.— When  the  muscle  is  paralyzed,  the  vertebral  border,  and  especially 
the  lower  angle  of  the  scapula,  leaves  the  ribs  and  stands  out  prominently  on  the  surface,  giving 
a  peculiar  "winged"  appearance  to  the  back.     The  patient  is  unable  to  raise  the  arm,  and  an 


470  THE  MUSCLES  AND    FASCIA 

attempt  to  do  so  is  followed  by  a  further  projection  of  the  lower  angle  of  the  scapula  from  the 
back  of  the  thorax. 

Dissection.— After  completing  the  dissection  of  the  axilla,  if  the  muscles  of  the  back  have 
been  dissected,  the  upper  extremity  should  be  separated  from  the  trunk.  Saw  through  the 
clavicle  at  its  centre,  and  then  cut  through  the  muscles  which  connect  the  scapula  and  arm  with 
the  trunk — viz.,  the  Pectoralis  minor  in  front,  Serratus  magnus  at  the  side,  and  the  Levator 
anguli  scapulae,  the  Rhomboids,  Trapezius,  and  Latissimus  dorsi  behind.  These  muscles  should 
be  cleaned  and  traced  to  their  respective  insertions.  Then  make  an  incision  through  the  integu- 
ment, commencing  at  the  outer  third  of  the  clavicle,  and  extending  along  the  margin  of  that 
bone,  the  acromion  process,  and  spine  of  the  scapula;  the  integument  should  be  dissected  from 
above  downward  and  outward,  when  the  fascia  covering  the  Deltoid  is  exposed  (Fig.  312,  No.  3). 

II.  MUSCLES  AND  FASCIiE  OF  THE  SHOULDER  AND  ARM. 

Superficial  Fascia. — ^The  superficial  fascia  of  the  upper  extremity  is  a  thin 
cellulb-fibrous  layer,  containing  the  superficial  veins  and  lymphatics,  and  the 
cutaneous  nerves;  It  is  most  distinct  in  front  of  the  elbow,  and  contains  very  large 
superficial  veins  and  nerves ;  in  the  hand  it  is  hardly  demonstrable,  the  integument 
being  closely  adherent  to  the  deep  fascia  by  dense  fibrous  bands.  Small  sub- 
cutaneous bursse  are  found  in  this  fascia  over  the  acromion,  the  olecranon,  and 
the  knuckles. 

Deep  Fascia. — The  deep  fascia  of  the  upper  extremity  comprises  the  aponeurosis 
of  the  shoulder,  arm,  and  forearm,  the  anterior  and  posterior  annular  ligaments  of 
the  carpus,  and  the  palmar  fascia.  These  will  be  considered  in  the  description 
of  the  muscles  of  the  several  regions. 

3.  The  Acromial  Region. 
Deltoid. 

Deep  Fascia. — The  deep  fascia  covering  the  Deltoid,  and  known  as  the  deltoid 
aponeurosis,  is  a  fibrous  layer  which  covers  the  outer  surface  of  the  muscle,  thick 
and  strong  behind,  where  it  is  continuous  with  the  infraspinatus  fascia,  thinner 
over  the  rest  of  its  extent.  It  sends  down  numerous  prolongations  between  the 
fasciculi  of  the  muscle.  In  front,  it  is  continuous  with  the  fascia  covering  the 
great  Pectoral  muscle;  behind,  with  that  covering  the  Infraspinatus;  above,  it 
is  attached  to  the  clavicle,  the  acromion,  and  spine  of  the  scapula;  below,  it  is 
continuous  with  the  deep  fascia  of  the  arm. 

The  Deltoid  (m.  deltoideus)  (Fig.  314)  is  a  large,  thick,  triangular  muscle,  which 
gives  the  rounded  outline  to  the  shoulder,  and  has  received  its  name  from  its  resem- 
blance to  the  Greek  letter  a  reversed.  It  surrounds  the  shoulder-joint  in  the  greater 
part  of  its  extent,  covering  it  on  its  outer  side,  and  in  front  and  behind.  It  arises 
from  the  outer  third  of  the  anterior  border  and  upper  surface  of  the  clavicle;  from 
the  outer  margin  and  upper  surface  of  the  acromion  process,  and  from  the  lower  lip 
of  the  posterior  border  of  the  spine  of  the  scapula,  as  far  back  as  the  triangular  sur- 
face at  its  inner  end.  From  this  extensive  origin  the  fibres  converge  toward  their 
insertion,  the  middle  passing  vertically,  the  anterior  obliquely  backward,  the  pos- 
terior obliquely  forward;  they  unite  to  form  a  thick  tendon,  which  is  inserted  into 
a  rough  triangular  prominence  on  the  middle  of  the  outer  side  of  the  shaft  of  the 
humerus.  At  its  insertion  the  muscle  gives  off  an  expansion  to  the  deep  fascia  of 
the  arm.  This  muscle  is  remarkably  coarse  in  texture,  and  the  arrangement  of 
its  muscular  fibres  is  somewhat  peculiar;  the  central  portion  of  the  muscle — that 
is  to  say,  the  part  arising  from  the  acromion  process — consists  of  oblique  fibres, 
which  arise  in  a  bipenniform  manner  from  the  sides  of  tendinous  intersections, 
generally  four  in  number,  which  are  attached  above  to  the  acromion  process  and 
pass  downward  parallel  to  one  another  in  the  substance  of  the  muscle.     The 


THE  ANTERIOR  SCAPULAR    REGION  471 

oblique  muscular  fibres  thus  formed  are  inserted  into  similar  tendinous  intersec- 
tions, generally  three  in  number,  which  pass  upward  from  the  insertion  of  the 
muscle  into  the  humerus  and  alternate  with  the  descending  septa.  The  portions 
of  the  muscle  which  arise  from  the  clavicle  and  spine  of  the  scapula  are  not 
arranged  in  this  manner,  but  pass  from  their  origin  above,  to  be  inserted  into  the 
margins  of  the  inferior  tendon. 

Relations. — By  its  superficial  surface,  with  the  integument,  the  superficial  and 
deep  fasciae,  Platysma,  and  supra-acromial  nerves.  Its  deep  surface  is  separated 
from  the  head  of  the  humerus  by  a  large  sacculated  synovial  bursa,  the  subdeltoid 
bursa  (bursa  suhdeltoidea) .  It  often  communicates  with  the  subacromial  bursa 
(bursa  subacromialis),  which  is  between  the  acromial  process  and  the  coraco- 
acromial  ligament  above  and  the  capsule  of  the  shoulder-joint  and  the  Supra- 
spinatus  muscle  below.  The  deep  surface  of  the  deltoid  covers  the  coracoid 
process,  coraco-acromial  ligament,  Pectoralis  minor,  Coraco-brachialis,  both  heads 
of  the  Biceps,  the  tendon  of  the  Pectoralis  major,  the  insertions  of  the  Supra- 
spinatus,  Infraspinatus,  and  Teres  minor,  the  scapular  and  external  heads  of  the 
Triceps,  the  circumflex  vessels  and  nerve,  and  the  humerus.  Its  anterior  border 
is  separated  at  its  upper  part  from  the  Pectoralis  major  by  a  cellular  interspace, 
which  lodges  the  cephalic  vein  and  humeral  branch  of  the  acromial  thoracic  artery : 
lower  down  the  two  muscles  are  in  close  contact.  Its  posterior  border  rests  on  the 
Infraspinatus  and  Triceps  muscles. 

Nerves. — The  Deltoid  is  supplied  by  the  fifth  and  sixth  cervical  through  the 
circumflex  nerve. 

Actions. — The  Deltoid  raises  the  arm  directly  from  the  side,  so  as  to  bring  it 
at  right  angles  with  the  trunk,  but  this  act  cannot  be  performed  without  the  aid 
of  the  Serratus  magnus,  which  muscle  steadies  the  lower  angle  of  the  scapula. 
Its  anterior  fibres,  assisted  by  the  Pectoralis  major,  draw  the  arm  forward;  and  its 
posterior  fibres,  aided  by  the  Teres  major  and  Latissimus  dorsi,  draw  it  backward. 

Surgical  Anatomy. — The  Deltoid  is  very  liable  to  atrophy,  and  when  in  this  condition 
simulates  dislocation  of  the  shoulder-joint,  as  there  is  flattening  of  the  shoulder  and  apparent 
prominence  of  the  acromion  process;  upon  examination,  however,  it  will  be  found  that  the 
relative  position  of  the  great  tuberosity  of  the  humerus  to  the  acromion  and  coracoid  process  is 
unchanged.  Atrophy  of  the  Deltoid  may  be  due  to  disuse  or  loss  of  trophic  influence,  either 
from  injury  to  the  circumflex  nerve  or  cord  lesions,  as  in  infantile  paralysis. 

4.  The  Anterior  Scapular  Region. 

Subscapularis. 

Dissection. — Divide  the  Deltoid  across,  near  its  upper  part,  by  an  incision  carried  along  the 
margin  of  the  clavicle,  the  acromion  process  and  spine  of  the  scapula,  and  reflect  it  downward, 
when  the  structures  under  cover  of  it  will  be  seen. 

The  Subscapular  Fascia  {fascia  subscapularis). — The  subscapular  fascia  is  a 
thin  membrane  attached  to  the  entire  circumference  of  the  subscapular  fossa,  and 
affording  attachment  by  its  inner  surface  to  some  of  the  fibres  of  the  Subscapu- 
laris muscle :  when  this  is  removed,  the  Subscapularis  muscle  is  exposed. 

The  Subscapularis  (Fig.  315)  is  a  large  triangular  muscle  which  fills  up  the 
subscapular  fossa,  arising  from  its  internal  two-thirds,  with  the  exception  of  a 
narrow  margin  along  the  posterior  border,  and  the  surfaces  at  the  superior  and 
inferior  angles  which  afford  attachment  to  the  Serratus  magnus :  it  also  arises  from 
the  lower  two-thirds  of  the  groove  on  the  axillary  border  of  the  bone.  Some  fibres 
arise  from  tendinous  laminae,  which  intersect  the  muscle,  and  are  attached  to  ridges 
on  the  bone;  and  others  from  an  aponeurosis,  which  separates  the  muscles  from  the 
Teres  major  and  the  long  head  of  the  Triceps.  The  fibres  pass  outward,  and, 
gradually  converging,  terminate  in  a  tendon,  which  is  inserted  into  the  lesser 


472  THE   MUSCLES   AND   FASCIA 

tuberosity  of  the  humerus.  Those  fibres  which  arise  from  the  axillary  border  of 
the  scapula  are  inserted  into  the  neck  of  the  humerus  to  the  extent  of  an  inch  below 
the  tuberosity.  The  tendon  of  the  muscle  is  in  close  contact  with  the  anterior  part 
of  the  capsular  ligament  of  the  shoulder-joint,  and  glides  over  a  large  bursa,  the- 
bursa  of  the  subscapularis  muscle  (bursa  m.  subscapular  is,  which  separates  it  from 
the  base  of  the  coracoid  process.  This  bursa  communicates  with  the  cavity  of  the 
joint  by  an  aperture  in  the  capsular  ligament. 

Relations. — Its  anterior  surface  forms  a  considerable  part  of  the  posterior  wall 
of  the  axilla,  and  is  in  relation  with  the  Serratus  magnus,  Coraco-brachialis,  and 
Biceps,  the  axillary  vessels  and  brachial  plexus  of  nerves,  and  the  subscapular 
vessels  and  nerves.  By  its  posterior  surface,  with  the  scapula  and  the  capsular 
ligament  of  the  shoulder-joint.  Its  lower  border  is  contiguous  with  the  Teres  major 
and  Latissimus  dorsi. 

Nerves. — It  is  supplied  by  the  fifth  and  sixth  cervical  nerves  through  the  upper 
and  lower  subscapular  nerves. 

Actions. — The  Subscapularis  rotates  the  head  of  the  humerus  inward;  when 
the  arm  is  raised,  it  draws  the  humerus  forward  and  downward.  It  is  a  powerful 
defence  to  the  front  of  the  shoulder-joint,  preventing  displacement  of  the  head  of 
the  bone. 

5.  The  Posterior  Scapular  Region  (Fig.  317). 

Supraspinatus.  Teres  minor. 

Infraspinatus.  Teres  major. 

Dissection. — To  expose  these  muscles,  and  to  examine  their  mode  of  insertion  into  the 
humerus,  detach  the  deltoid  and  Trapezius  from  their  attachment  to  the  spine  of  the  scapula 
and  acrorfiion  process.  Remove  the  clavicle  by  dividing  the  ligaments  connecting  it  with  the 
coracoid  process,  and  separate  it  at  its  articulation  with  the  scapula:  divide  the  acromion  process 
near  its  root  with  a  saw.  The  fragments  being  removed,  the  tendons  of  the  posterior  Scapular 
muscles  will  be  fully  exposed,  and  can  be  examined.  A  block  should  be  placed  beneath  the 
shoulder-joint,  so  as  to  make  the  muscles  tense. 

The  Supraspinatus  Fascia  (fascia  supraspinata) . — The  supraspinatus  fascia  is 
a  thick  and  dense  membranous  layer,  which  completes  the  osseo-fibrous  case 
in  which  the  Supraspinatus  muscle  is  contained,  affording  attachment,  by  its 
inner  surface,  to  some  of  the  fibres  of  the  muscle.  It  is  thick  internally,  but 
thinner  externally  under  the  coraco-acromial  ligament.  VSTien  this  fascia  is 
removed,  the  Supraspinatus  muscle  is  exposed. 

The  Supraspinatus  Muscle  occupies  the  whole  of  the  supraspinatus  fossa, 
arising  from  its  internal  two-thirds  and  from  the  strong  fascia  which  covers  its  sur- 
face. The  muscular  fibres  converge  to  a  tendon  which  passes  across  the  upper 
part  of  the  capsular  ligament  of  the  shoulder-joint,  to  which  it  is  intimately  adher- 
ent, and  is  inserted  into  the  highest  of  the  three  facets  on  the  great  tuberosity  of 
the  humerus. 

Relations. — By  its  upper  surface,  with  the  Trapezius,  the  clavicle,  the  acromion, 
the  coraco-acromial  ligament,  and  the  Deltoid;  by  its  under  surface,  with  the 
scapula,  the  suprascapular  vessels  and  nerve,  and  upper  part  of  the  shoulder-joint. 

The  Infraspinatus  Fascia  {fascia  infraspinata). — The  infraspinatus  fascia  is 
a  dense  fibrous  membrane,  covering  in  the  Infraspinatus  muscle  and  attached 
to  the  circumference  of  the  infraspinatus  fossa;  it  affords  attachment,  by  its  inner 
surface,  to  some  fibres  of  that  muscle.  At  the  point  where  the  Infraspinatus 
commences  to  be  covered  by  the  Deltoid,  this  fascia  divides  into  two  layers:  one 
layer  passes  over  the  Deltoid  muscle,  helping  to  form  the  Deltoid  fascia  already 
described;  the  other  passes  beneath  the  Deltoid  to  the  capsule  of  the  shoulder-joint. 

The  Infraspinatus  is  a  thick,  triangular  muscle,  which  occupies  the  chief  part 
of  the  infraspinatus  fossa,  arising  by  fleshy  fibres  from  its  internal  two-thirds,  and 


THE  POSTEBIOB    SCAPULAR    REGION 


473 


by  tendinous  fibres  from  the  ridges  on  its  surface:  it  also  arises  from  a  strong 
fascia  which  covers  it  externally,  and  separates  it  from  the  Teres  major  and  minor. 
The  fibres  converge  to  a  tendon  which  glides  over  the  external  border  of  the 
spine  of  the  scapula,  and,  passing  across  the  posterior  part  of  the  capsular  ligament 
of  the  shoulder-joint,  is  inserted  into  the  middle  facet  on  the  great  tuberosity  of 
the  humerus.  The  tendon  of  this  muscle  has  interposed  between  it  and  the  joint 
capsule  a  synovial  bursa,  the  bursa  of  the  Infraspinatus  muscle  {bursa  m.  infra- 
spinati),  Avhich  communicates  with  the  synovial  cavity  of  the  shoulder-joint. 

Relations. — By  its  posterior  surface,  with  the  Deltoid,  the  Trapezius,  Latissimus 
dorsi,  and  the  integument;  by  its  anterior  surface,  with  the  scapula,  from  which 
it  is  separated  by  the  suprascapular  and  dorsalis  scapulae  vessels,  and  with  the 


Fig.  317. — Muscles  on  the  dorsum  of  the  Scapula  and  the  Triceps. 


capsular  ligament  of  the  shoulder-joint.  Its  lower  border  is  in  contact  with  the 
Teres  minor,  occasionally  united  with  it,  and  with  the  Teres  major. 

The  Teres  Minor  is  a  narrow,  elongated  muscle,  which  arises  from  the  dorsal 
surface  of  the  axillary  border  of  the  scapula  for  the  upper  two-thirds  of  its  extent, 
and  from  two  aponeurotic  laminae,  one  of  which  separates  this  muscle  from  the 
Infraspinatus,  the  other  from  the  Teres  major;  its  fibres  pass  obliquely  upward 
and  outward,  and  terminate  in  a  tendon  which  is  inserted  into  the  lowest  of  the 
three  facets  on  the  great  tuberosity  of  the  humerus,  and,  by  fleshy  fibres,  into  the 
humerus  immediately  below  it.  The  tendon  of  this  muscle  passes  across  the 
posterior  part  of  the  capsular  ligament  of  the  shoulder-joint. 

Relations. — By  its  posterior  surface,  with  the  Deltoid  and  the  integument; 
by  its  anterior  surface,  with  the  scapula  and  dorsal  branch  of  the  subscapular 
artery,  the  long  head  of  the  Triceps,  and  the  shoulder-joint;  by  its  upper  border, 


474  THE  MUSCLES  AND   FASCIAE 

with  the  Infraspinatus;  by  its  lower  border,  with  the  Teres  major,  from  which  it 
is  separated  anteriorly  by  the  long  head  of  the  Triceps. 

The  Teres  Major  is  a  thick  but  somewhat  flattened  muscle,  which  arises  from 
the  oval  surface  on  the  dorsal  aspect  of  the  inferior  angle  of  the  scapula,  and  from 
the  fibrous  septa  interposed  between  it  and  the  Teres  minor  and  Infraspinatus ;  the 
fibres  are  directed  upward  and  outward,  and  terminate  in  a  flat  tendon,  about  two 
inches  in  length,  which  is  inserted  into  the  inner  bicipital  ridge  of  the  humerus. 
The  tendon  of  this  muscle,  at  its  insertion  into  the  humerus,  lies  behind  that  of  the 
Latissimus  dorsi,  from  which  it  is  separated  by  a  synovial  bursa,  the  bursa  of  the 
Latissimus  dorsi  muscle  (bursa  m.  latissimi  dorsi),  the  two  tendons  being,  however, 
united  along  their  lower  borders  for  a  short  distance.  Between  the  tendon  of 
the  Teres  major  and  the  bone  is  the  bursa  m.  teretis  majoris. 

Relations. — By  its  posterior  surface,  with  the  Latissimus  dorsi  below,  and  the 
long  head  of  the  Triceps  above.  By  its  anterior  surface,  with  the  Subscapularis, 
Latissimus  dorsi,  Coraco-brachialis,  short  head  of  the  Biceps,  the  axillary  vessels, 
and  brachial  plexus  of  nerves.  Its  upper  border  is  at  first  in  relation  with  the 
Teres  minor,  from  which  it  is  afterward  separated  by  the  long  head  of  the  Triceps. 
Its  lower  border  forms,  in  conjunction  with  the  Latissimus  dorsi,  part  of  the  pos- 
terior boundary  of  the  axilla.  The  Latissimus  dorsi  at  first  covers  the  origin  of 
the  Teres  major,  then  wraps  itself  obliquely  round  its  lower  border,  so  that  its 
tendon  ultimately  comes  to  lie  in  front  of  that  of  the  Teres  major. 

Nerves. — ^The  Supra-  and  Infraspinatus  muscles  are  supplied  by  the  fifth  and 
sixth  cervical  nerves  through  the  suprascapular  nerve;  the  Teres  minor,  by  the 
fifth  cervical,  through  the  circumflex;  and  the  Teres  major,  by  the  fifth  and  sixth 
cervical,  through  the  lower  subscapular. 

Actions. — The  Supraspinatus  assists  the  Deltoid  in  raising  the  arm  from  the 
side,  and  fixes  the  head  of  the  humerus  in  the  glenoid  cavity.  The  Infraspinatus 
and  Teres  minor  rotate  the  head  of  the  humerus  outward :  when  the  arm  is  raised, 
they  assist  in  retaining  it  in  that  position  and  carrying  it  backward.  One  of  the 
most  important  uses  of  these  three  muscles  is  the  great  protection  they  afford  to 
the  shoulder-joint,  the  Supraspinatus  supporting  it  above,  and  preventing  displace- 
ment of  the  head  of  the  humerus  upward,  while  the  Infraspinatus  and  Teres  minor 
protect  it  behind,  and  prevent  dislocation  backward.  The  Teres  major  assists  the 
Latissimus  dorsi  in  drawing  the  humerus  downward  and  backward,  when  pre- 
viously raised,  and  rotating  it  inward;  when  the  arm  is  fixed,  it  may  assist  the 
Pectoral  and  Latissimus  dorsi  muscles  in  drawing  the  trunk  forward. 

THE  MUSCLES  AND  FASCIiE  OF  THE  ARM. 

6.  The  Anterior  Humeral  Region  (Fig.  315). 
Coraco-brachialis.  Biceps.  Brachialis  anticus. 

Dissection. — The  arm  being  placed  on  the  table,  with  the  front  surface  uppermost,  make 
a  vertical  incision  through  the  integument  along  the  middle  line,  from  the  clavicle  to  about 
two  inches  below  the  elbow-joint,  where  it  should  be  joined  by  a  transverse  incision,  extending 
from  the  inner  to  the  outer  side  of  the  forearm;  the  two  flaps  being  reflected  on  either  side, 
the  fascia  should  be  examined  (Fig.  312). 

Deep  Fascia  (fascia  brae hii). — ^The  deep  fascia  of  the  arm  is  continuous  with 
that  covering  the  Deltoid  and  the  great  Pectoral  muscles,  by  means  of  which  it  is 
attached,  above,  to  the  clavicle,  acromion,  and  spine  of  the  scapula,  and  is  also 
continuous  with  the  axillary  fascia.  It  forms  a  thin,  loose,  membranous  sheath 
investing  the  muscles  of  the  arm,  sending  down  septa  between  them,  and  com- 
posed of  fibres  disposed  in  a  circular  or  spiral  direction,  and  connected  together 
by  vertical  and  oblique  fibres.     It  differs  in  thickness  at  different  parts,  being 


THE  ANTERIOR    HUMERAL   REGION  475 

thin  over  the  Biceps,  but  thicker  where  it  covers  the  Triceps,  and  over  the 
condyles  of  the  humerus;  it  is  strengthened  by  fibrous  aponeuroses,  derived 
from  the  PectoraHs  major  and  Latissimus  dorsi  on  the  inner  side,  and  from  the 
Deltoid  externally.  On  either  side  it  gives  off  a  strong  intermusculax  septum, 
which  is  attached  to  the  supracondylar  ridge  and  condyle  of  the  humerus.  These 
septa  serve  to  separate  the  muscles  of  the  anterior  from  those  of  the  posterior 
brachial  region.  The  external  intermusculax  septum  (septum  intermuscular e 
laterale)  extends  from  the  lower  part  of  the  anterior  bicipital  ridge,  along  the 
external  supracondylar  ridge,  to  the  outer  condyle;  it  is  blended  with  the  tendon 
of  the  Deltoid,  gives  attachment  to  the  Triceps  behind,  to  the  Brachiailis  anticus, 
Supinator  longus,  and  Extensor  carpi  radialis  longior,  in  front,  and  is  perforated 
by  the  musculo-spiral  nerve  and  superior  profunda  artery.  The  internal  inter- 
muscular septum  {septum  intermuscular e  mediale),  thicker  than  the  preceding, 
extends  from  the  lower  part  of  the  posterior  lip  of  the  bicipital  groove  below  the 
Teres  major,  along  the  internal  supracondylar  ridge  to  the  inner  condyle;  it  is 
blended  with  the  tendon  of  the  Coraco-brachialis,  and  affords  attachment  to  the 
Triceps  behind,  and  the  Brachialis  anticus  in  front.  It  is  perforated  by  the  ulnar 
nerve  and  the  inferior  profunda  and  anastomotic  arteries.  At  the  elbow  the  deep 
fascia  is  attached  to  all  the  prominent  points  round  the  joint — viz.,  the  condyles  of 
the  humerus  and  the  olecranon  process  of  the  ulna — and  is  continuous  with  the 
deep  fascia  of  the  forearm.  Just  below  the  middle  of  the  arm,  on  its  inner  side,  in 
front  of  the  intermuscular  septum,  is  an  oval  opening  in  the  deep  fascia  which 
transmits  the  basilic  vein  and  some  lymphatic  vessels.  On  the  removal  of  this 
fascia  the  muscles,  vessels,  and  nerves  of  the  anterior  humeral  region  are  exposed. 

The  Coraco-brachialis,  the  smallest  of  the  three  muscles  in  this  region,  is 
situated  at  the  upper  and  inner  part  of  the  arm.  It  arises  by  fleshy  fibres  from 
the  apex  of  the  coracoid  process,  in  common  with  the  short  head  of  the  Biceps, 
and  from  the  intermuscular  septum  between  the  two  muscles;  the  fibres  pass 
downward,  backward,  and  a  little  outward,  to  be  inserted  by  means  of  a  flat 
tendon  into  an  impression  at  the  middle  of  the  inner  surface  and  internal  border 
of  the  shaft  of  the  humerus  between  the  origins  of  the  Triceps  and  Brachialis 
anticus.  It  is  perforated  by  the  musciilo-cutaneous  nerve.  The  inner  border  of 
the  muscle  forms  a  guide  to  the  position  of  the  brachial  artery  in  tying  the  vessel 
in  the  upper  part  of  its  course.  Between  the  tendon  of  the  subscapularis, 
the  coracoid  process  and  the  tendon  of  the  Coraco-brachialis,  is  the  bursa  of  the 
Coraco-brachialis  muscle  (bursa  m.  coracobrachialis). 

Relations. — By  its  anterior  surface,  with  the  Pectoralis  major  above,  and  at 
its  insertion  with  the  brachial  vessels  and  median  nerve  which  cross  it;  by  its 
posterior  surface,  with  the  tendons  of  the  Subscapularis,  Latissimus  dorsi,  and 
Teres  major,  the  inner  head  of  the  Triceps,  the  humerus,  and  the  anterior  circum- 
flex vessels;  by  its  inner  border,  with  the  brachial  artery,  and  the  median  and 
musculo-cutaneous  nerves;  by  its  outer  border,  with  the  short  head  of  the  Biceps 
and  Brachialis  anticus. 

The  Biceps  or  the  Biceps  Flexor  Cubiti  (m.  biceps  brachii)  is  a  long  fusiform 
muscle,  occupying  the  whole  of  the  anterior  surface  of  the  arm,  and  divided  above 
into  two  portions  or  heads,  from  which  circumstance  it  has  received  its  name.  The 
short  head  (caput  breve)  arises  by  a  thick  flattened  tendon  from  the  apex  of  the  cora- 
coid process,  in  common  with  the  Coraco-brachialis.  The  long  head  (caput  longum) 
arises  from  the  upper  margin  of  the  glenoid  cavity,  and  is  continuous  with  the 
glenoid  ligament.  This  tendon  arches  over  the  head  of  the  humerus,  being  enclosed 
in  a  special  sheath  of  the  synovial  membrane  of  the  shoulder-joint;  it  then  passes 
through  an  opening  in  the  capsular  ligament  at  its  attachment  to  the  humerus, 
and  descends  in  the  bicipital  groove,  in  which  it  is  retained  by  a  fibrous  prolonga- 
tion from  the  tendon  of  the  Pectoralis  major.    Each  tendon  is  succeeded  by  an 


476  THE  MUSCLES  AND   FASCIA 

elongated  muscular  belly,  and  the  two  bellies,  although  closely  applied  to  each 
other,  can  readily  be  separated  until  within  about  three  inches  of  the  elbow-joint. 
Here  they  end  in  a  flattened  tendon,  which  is  inserted  into  the  back  part  of  the 
tuberosity  of  the  radius,  a  synovial  bursa  {bursa  bicipito-radialis) ,  being  interposed 
between  the  tendon  and  the  front  of  the  tuberosity,  and  another  bursa  {bursa 
cubitalis  interossea)  is  often  interposed  between  the  ulna  and  the  tendon.  As  the 
tendon  of  the  muscle  approaches  the  radius  it  becomes  twisted  upon  itself,  so  that 
its  anterior  surface  becomes  external  and  is  applied  to  the  tuberosity  of  the 
radius  at  its  insertion :  opposite  the  bend  of  the  elbow  the  tendon  gives  off,  from 
its  inner  side,  a  broad  aponeurosis,  the  bicipital  or  semilunar  fascia  {lacertus 
fibrosus),  which  passes  obliquely  downward  and  inward  across  the  brachial 
artery,  and  is  continuous  with  the  deep  fascia  of  the  forearm  (Fig.  314).  The 
inner  border  of  this  muscle  forms  a  guide  to  the  position  of  the  vessel  in  tying  the 
brachial  artery  in  the  middle  of  the  arm.^ 

Relations. — Its  anterior  surface  is  overlapped  above  by  the  Pectoralis  major 
and  Deltoid;  in  the  rest  of  its  extent  it  is  covered  by  the  superficial  and  deep 
fasciae  and  the  integument.  Its  posterior  surface  rests  above  on  the  shoulder- 
joint  and  upper  part  of  the  humerus;  below  it  rests  on  the  Brachialis  anticus, 
with  the  musculo-cutaneous  nerve  intervening  between  the  two,  and  on  the 
Supinator  brevis.  Its  inner  border  is  in  relation  with  the  Coraco-brachialis,  and 
overlaps  the  brachial  vessels  and  median  nerve;  its  outer  border,  with  the  Deltoid 
and  Supinator  longus. 

The  Brachialis  Anticus  (w.  brachialis)  is  a  broad  muscle,  which  covers  the  elbow- 
joint  and  the  lower  half  of  the  front  of  the  humerus.  It  is  somewhat  compressed 
from  before  backward,  and  is  broader  in  the  middle  than  at  either  extremity.  It 
wises  from  the  lower  half  of  the  outer  and  inner  surfaces  of  the  shaft  of  the  humerus, 
and  commences  above  at  the  insertion  of  the  Deltoid,  which  it  embraces  by  two 
angular  processes.  Its  origin  extends  below,  to  within  an  inch  of  the  margin  of 
the  articular  surface,  and  is  limited  on  each  side  by  the  external  and  internal 
borders  of  the  shaft  of  the  humerus.  It  also  arises  from  the  intermuscular  septa 
on  each  side,  but  more  extensively  from  the  inner  than  the  outer,  from  which  it  is 
separated  below  by  the  Supinator  longus  and  Extensor  carpi  radialis  longior.  Its 
fibres  converge  to  a  thick  tendon,  which  is  inserted  into  a  rough  depression  on 
the  anterior  surface  of  the  coronoid  process  of  the  ulna,  being  received  into  an 
interval  between  two  fleshy  slips  of  the  Flexor  profundus  digitorum. 

Relations. — By  its  anterior  surface,  with  the  Biceps,  the  brachial  vessels,  mus- 
culo-cutaneous, and  median  nerves;  by  its  posterior  surface,  with  the  humerus 
and  front  of  the  elbow-joint;  by  its  inner  border,  with  the  Triceps,  ulnar  nerve, 
and  Pronator  radii  teres,  from  which  it  is  separated  by  the  intermuscular  septum; 
by  its  outer  border,  with  the  musculo-spiral  nerve,  radial  recurrent  artery,  the 
Supinator  longus,  and  Extensor  carpi  radialis  longior. 

Nerves. — The  muscles  of  this  group  are  supplied  by  the  musculo-cutaneous 
nerve.  The  Brachialis  anticus  usually  receives  an  additional  filament  from  the 
musculo-spiral.  The  Coraco-brachialis  receives  its  supply  primarily  from  the 
seventh  cervical,  the  Biceps  and  Brachialis  anticus  from  the  fifth  and  sixth  cer- 
vical nerves. 

Actions. — The  Coraco-brachialis  draws  the  humerus  forward  and  inward,  and 
at  the  same  time  assists  in  elevating  it  toward  the  scapula.  The  Biceps  is  a  flexor 
of  the  forearm;  it  is  also  a  powerful  supinator,  and  serves  to  render  tense  the 
deep  fascia  of  the  forearm  by  means  of  the  broad  aponeurosis  given  off  from 

'  A  third  head  to  the  Biceps  is  occasionally  found  (Theile  says  as  often  as  once  in  eight  or  nine  subjects), 
arising  at  the  upper  and  inner  part  of  the  Brachialis  anticus,  with  the  fibres  of  which  it  is  continuous,  and  inserted 
into  the  bicipital  fascia  and  inner  side  of  the  tendon  of  the  Biceps.  In  most  cases  this  additional  slip  passes 
behind  the  brachial  artery  in  its  course  down  the  arm.  Occasionally  the  third  head  con.sists  of  two  slips  which 
pass  down,  one  in  front,  the  other  behind  the  artery,  concealing  the  vessel  in  the  lower  half  of  the  arm. 


THE   POSTERIOR    HUMERAL    REGION  477 

its  tendon.  The  Brachialis  anticus  is  a  flexor  of  the  forearm,  and  forms  an  impoi^ 
tant  defence  to  the  elbow-joint.  When  the  forearm  is  fixed,  the  Biceps  and 
BrachiaUs  anticus  flex  the  arm  upon  the  forearm,  as  is  seen  in  efforts  at  climbing. 

7.  The  Posterior  Humeral  Region. 
Triceps.  Subanconeus. 

The  Triceps  or  the  Triceps  Extensor  Cubiti  (m.  trice'ps  hrachii)  (Fig.  317)  is 
situated  on  the  back  of  the  arm,  extending  the  entire  length  of  the  posterior  surface 
of  the  humerus.  It  is  of  large  size,  and  divided  above  into  three  parts;  hence  its 
name.  These  three  portions  have  been  named  (1 )  the  middle,  scapular,  or  long  head ; 
(2)  the  external  or  long  humeral  head;  and  (3)  the  internal  or  short  humeral  head. 

The  Middle,  Long,  or  Scapular  Head  (caput  longum)  arises,  by  a  flattened  tendon, 
from  a  rough  triangular  depression  on  the  scapula,  immediately  below  the  glenoid 
cavity,  being  blended  at  its  upper  part  with  the  capsular  ligament;  the  muscular 
fibres  pass  downward  between  the  two  other  portions  of  the  muscle,  and  join  with 
them  in  the  common  tendon  of  insertion. 

The  External  Head  {caput  laterale)  arises  from  the  posterior  surface  of  the  shaft 
of  the  hinnerus,  between  the  insertion  of  the  Teres  minor  and  the  upper  part  of 
the  musculo-spiral  groove;  from  the  external  border  of  the  humerus  and  the 
external  intermuscular  septum:  the  fibres  from  this  origin  converge  toward  the 
common  tendon  of  insertion. 

The  Internal  Head  {caput  mediale)  arises  from  the  posterior  surface  of  the  shaft 
of  the  humerus,  below  the  groove  for  the  musculo-spiral  nerve;  commencing  above, 
narrow  and  pointed,  below  the  insertion  of  the  Teres  major,  and  extending  to 
within  an  inch  of  the  trochlear  surface :  it  also  arises  from  the  internal  border  of 
the  humerus,  and  from  the  back  of  the  whole  length  of  the  internal  and  lower  part 
of  the  external  intermuscular  septum.  The  fibres  of  this  portion  of  the  muscle  are 
directed,  some  downward  to  the  olecranon,  whilst  others  converge  to  the  common 
tendon  of  insertion. 

The  Common  Tendon  of  the  Triceps  commences  about  the  middle  of  the  back  part 
of  the  muscle :  it  consists  of  two  aponeurotic  laminae,  one  of  which  is  subcutaneous 
and  covers  the  posterior  surface  of  the  muscle  for  the  lower  half  of  its  extent;  the 
other  is  more  deeply  seated  in  the  substance  of  the  muscle:  after  receiving  the 
attachment  of  the  muscular  fibres,  they  join  together  above  the  elbow,  and  are 
inserted,  for  the  most  part,  into  the  back  part  of  the  upper  surface  of  the  olecranon 
process;  a  band  of  fibres  is,  however,  continued  downward,  on  the  outer  side, 
over  the  Anconeus,  to  blend  with  the  deep  fascia  of  the  forearm.  A  small  bursa 
(bursa  suhtendinea  olecrani)  occasionally  multilocular,  is  situated  on  the  front  part 
of  this  surface,  beneath  the  tendon.  The  subcutaneous  olecranon  bursa  (bursa  sub- 
cutanea  olecrani)  is  situated  between  the  olecranon  process  and  the  skin.  Within 
the  tendon  of  the  triceps  is  often  found  the  bursa  intratendinea  olecrani. 

The  long  head  of  the  Triceps  descends  between  the  Teres  minor  and  Teres 
major,  dividing  the  triangular  space  between  these  two  muscles  and  the  humerus 
into  two  smaller  spaces,  one  triangular,  the  other  quadrangular  (Fig.  317).  The 
triangular  space  contains  the  dorsalis  scapulae  vessels;  it  is  bounded  by  the  Teres 
minor  above,  the  Teres  major  below,  and  the  scapular  head  of  the  Triceps  exter- 
nally: the  quadrangular  space  transmits  the  posterior  circumflex  vessels  and  the 
circumflex  nerve;  it  is  bounded  by  the  Teres  minor  above,  the  Teres  major  below, 
the  scapular  head  of  the  Triceps  internally,  and  the  humerus  externally. 

Relations. — By  its  posterior  surface,  with  the  Deltoid  above:  in  the  rest  of  its 
extent  it  is  subcutaneous;  by  its  anterior  surface,  with  the  humerus,  musculo- 
spiral  nerve,  superior  profunda  vessels,  and  back  part  of  the  elbow-joint.     Its 


478  THE  MUSCLES  AND    FASCIA 

middle  or  long  head  is  in  relation,  behind,  with  the  Deltoid  and  Teres  minor;  in 
front,  with  the  Subscapularis,  Latissimus  dorsi,  and  Teres  major. 

The  Subanconeus  {m.  anconaeus)  is  a  name  given  to  a  few  fibres  from  the  under 
surface  of  the  lower  part  of  the  Triceps  muscle,  which  are  inserted  into  the  posterior 
ligament  of  the  elbow-joint.  By  some  authors  it  is  regarded  as  the  analogue  of 
the  Subcrureus  in  the  lower  limb,  but  it  is  not  a  separate  muscle. 

Nerves. — The  Triceps  is  supplied  by  the  seventh  and  eighth  cervical  nerves 
through  the  musculo-spiral  nerve. 

Actions. — The  Triceps  is  the  great  extensor  muscle  of  the  forearm,  serving, 
when  the  forearm  is  flexed,  to  extend  the  elbow-joint.  It  is  the  direct  antagonist 
of  the  Biceps  and  Brachialis  anticus.  When  the  arm  is  extended  the  long  head 
of  the  muscles  may  assist  the  Teres  major  and  Latissimus  dorsi  in  drawing  the 
humerus  backward  and  in  adducting  it  to  the  thorax.  The  long  head  of  the  Tri- 
ceps protects  the  under  part  of  the  shoulder-joint,  and  prevents  displacement  of 
the  head  of  the  humerus  downward  and  backward.  The  Subanconeus  draws 
up  the  posterior  ligament  during  extension  of  the  forearm. 

Surgical  Anatomy. — The  existence  of  the  band  of  fibres  from  the  Triceps  to  the  fascia  of 
the  forearm  is  of  importance  in  excision  of  the  elbow,  and  should  always  be  carefully  preserved 
from  injury  by  the  operator,  as  by  means  of  these  fibres  the  patient  is  enabled  to  extend  the 
forearm,  a  movement  which  would  otherwise  mainly  be  accomplished  by  gravity;  that  is  to  say, 
allowing  the  forearm  to  drop  from  its  own  weight. 

III.  MUSCLES  AND  FASCI.®  OF  THE  FOREARM. 

Dissection. — To  dissect  the  forearm,  place  the  limb  in  the  position  indicated  in  Fig.  312, 
make  a  vertical  incision  along  the  middle  line  from  the  elbow  to  the  wrist,  and  a  transverse 
incision  at  the  extremity  of  this;  the  superficial  structures  being  removed,  the  deep  fascia  of 
the  forearm  is  exposed. 

Deep  Fascia  {fascia  antibrachii). — ^The  deep  fascia  of  the  forearm,  continuous 
above  with  that  enclosing  the  arm,  is  a  dense,  highly  glistening  aponeurotic 
investment,  which  forms  a  general  sheath  enclosing  the  muscles  in  this  region; 
it  is  attached,  behind,  to  the  olecranon  and  posterior  border  of  the  ulna,  and  gives 
off  from  its  inner  surface  numerous  intermuscular  septa,  which  enclose  each  mus- 
cle separately.  Below,  it  is  continuous  in  front  with  the  anterior  annular  ligament 
{ligamentum  carpi  volar e) ,  and  forms  a  sheath  for  the  tendon  of  the  Palmaris  longus 
muscle,  which  passes  over  the  annular  ligament  to  be  inserted  into  the  palmar 
fascia.  Behind,  near  the  wrist-joint,  it  becomes  much  thickened  by  the  addition 
of  many  transverse  fibres,  and  forms  the  posterior  annular  ligament  {ligamentum 
carpi  dorsale).  It  consists  of  circular  and  oblique  fibres,  connected  together  by 
numerous  vertical  fibres.  It  is  much  thicker  on  the  dorsal  than  on  the  palmar  sur- 
face, and  at  the  lower  than  at  the  upper  part  of  the  forearm,  and  is  strengthened 
above  by  tendinous  fibres  derived  from  the  Brachialis  anticus  and  Biceps  in  front, 
and  from  the  Triceps  behind.  Its  deep  surface  gives  origin  to  muscular  fibres, 
especially  at  the  upper  part  of  the  inner  and  outer  sides  of  the  forearm,  and  forms 
the  boundaries  of  a  series  of  conical-shaped  cavities,  in  which  the  muscles  are 
contained.  Besides  the  vertical  septa  separating  each  muscle,  transverse  septa  are 
given  off  on  the  anterior  and  posterior  surfaces  of  the  forearm,  separating  the 
deep  from  the  superficial  layer  of  muscles.  Numerous  apertures  exist  in  the  fascia 
for  the  passage  of  vessels  and  nerves;  one  of  these,  of  large  size,  situated  at  the 
front  of  the  elbow,  serves  for  the  passage  of  a  communicating  branch  between 
the  superficial  and  deep  veins. 

The  muscles  of  the  forearm  may  be  subdivided  into  groups  corresponding  to 
the  region  they  occupy.  One  group  occupies  the  inner  and  anterior  aspect  of  the 
forearm,  and  comprises  the  Flexor  and  Pronator  muscles.  Another  group  occupies 
its  outer  side,  and  a  third  its  posterior  aspect.  The  two  latter  groups  include  all 
the  Extensor  and  Supinator  muscles. 


THE  ANTERIOR   RADIO -ULNAR   REGION  479 

8.  The  Anterior  Radio-ulnar  Region. 

The  muscles  in  this  region  are  divided  for  convenience  of  description  into  two 
groups  or  layers,  superficial  and  deep. 

The  Superficial  Layer. 

Pronator  radii  teres.  Palmaris  longus. 

Flexor  carpi  radialis.  Flexor  carpi  ulnaris. 

Flexor  sublimis  digitorum. 

These  muscles  take  origin  from  the  internal  condyle  of  the  humerus  by  a 
common  tendon. 

The  Pronator  Radii  Teres  (m.  pronator  teres)  arises  by  two  heads.  One,  the 
larger  and  more  superficial,  humeral  head  (caput  humerale) ,  arises  from  the  humerus, 
immediately  above  the  internal  condyle,  and  from  the  tendon  common  to  the 
origin  of  the  other  muscles ;  also  from  the  fascia  of  the  forearm  and  the  inter- 
muscular septum  between  it  and  the  Flexor  carpi  radialis.  The  other  head,  the 
ulnar  head  {caput  ulnare),  is  a  thin  fasciculus  which  arises  from  the  inner  side  of 
the  coronoid  process  of  the  ulna,  joining  the  preceding  at  an  acute  angle. 
Between  the  two  heads  the  median  nerve  enters  the  forearm.  The  muscle  passes 
obliquely  across  the  forearm  from  the  inner  to  the  outer  side,  and  terminates  in  a 
flat  tendon,  which  turns  over  the  outer  margin  of  the  radius,  and  is  inserted  into 
a  rough  impression  at  the  middle  of  the  outer  surface  of  the  shaft  of  that  bone. 

Relations. — By  its  anterior  surface,  throughout  the  greater  part  of  its  extent, 
with  the  deep  fascia;  at  its  insertion  it  is  crossed  by  the  radial  vessels  and  nerve, 
and  is  covered  by  the  Supinator  longus ;  by  its  posterior  surface,  with  the  Brachialis 
anticus.  Flexor  sublimis  digitorum,  the  median  nerve,  and  ulnar  artery,  the  small 
or  deep  head  being  interposed  })etween  the  two  latter  structures.  Its  outer  border 
forms  the  inner  boundary  of  a  triangular  space  in  which  are  placed  the  brachial 
artery,  median  nerve,  and  tendon  of  the  Biceps  muscle.  Its  inner  border  is  in 
contact  with  the  Flexor  carpi  radialis. 

Surgical  Anatomy. — This  muscle,  when  suddenly  brought  into  very  active  use,  as  in  the 
game  of  lawn  tennis,  is  apt  to  be  strained,  producing  slight  swelling  and  tenderness,  and  pain 
on  putting  the  muscle  into  action.    This  is  known  as  lawn-tennis  arm. 

The  Flexor  Carpi  Radialis  lies  on  the  inner  side  of  the  preceding  muscle.  It 
arises  from  the  internal  condyle  by  the  common  tendon,  from  the  fascia  of  the  fore- 
arm, and  from  the  intermuscular  septa  between  it  and  the  Pronator  radii  teres,  on 
the  outside,  the  Palmaris  longus  internally,  and  the  Flexor  sublimis  digitorum 
beneath.  Slender  and  aponeurotic  in  structure  at  its  commencement,  it  increases 
in  size,  and  terminates  in  a  tendon  which  forms  rather  more  than  the  lower  half 
of  its  length.  This  tendon  passes  through  a  canal  on  the  outer  side  of  the  annular 
ligament,  runs  through  a  groove  in  the  os  trapezium  (which  is  converted  into  a 
canal  by  a  fibrous  sheath,  and  is  lined  by  a  synovial  membrane),  and  is  inserted 
into  the  base  of  the  metacarpal  bone  of  the  index  finger,  and  by  a  slip  into  the  base 
of  the  metacarpal  bone  of  the  middle  finger.  The  radial  artery  lies  between  the 
tendon  of  this  muscle  and  the  Supinator  longus,  and  may  easily  be  tied  in  this 
situation.  In  the  hand  a  bursa  (bursa  m.  flexoris  carpi  radialis)  lies  between  the 
base  of  the  second  metacarpal  bone  and  the  tendon  (Spalteholz) . 

Relations.— By  its  superficial  surface,  with  the  deep  fascia  and  the  integument; 
by  its  deep  surface,  with  the  Flexor  subUmis  digitorum.  Flexor  longus  pollicis, 
and  wrist-joint;  by  its  outer  border,  with,  the  Pronator  radii  teres  and  the  radial 
vessels ;  by  its  inner  border,  with  the  Palmaris  longus  above  and  the  median 
nerve  below. 


480 


THE   MUSCLES  AND    FASCIA 


The  Palmaris  Longus  (Fig.  318)  is  a  slender,  fusiform  muscle  lying  on  the  inner 
side  of  the  preceding.  It  arises  from  the  inner  condyle  of  the  humerus  by  the  com- 
mon tendon,  from  the  deep  fascia,  and  the  inter- 
muscular septa  between  it  and  the  adjacent  mus- 
cles. It  terminates  in  a  slender  flattened  tendon, 
which  passes  over  the  upper  part  of  the  annular 
ligament,  to  end  in  the  central  part  of  the  palmar 
fascia  and  lower  part  of  the  annular  ligament, 
frequently  sending  a  tendinous  slip  to  the  short 
muscles  of  the  thumb.  This  muscle  is  often 
absent,  and  is  subject  to  very  considerable  varia- 
tions; it  may  be  tendinous  above  and  muscular 
below;  or  it  may  be  muscular  in  the  centre,  with 
a  tendon  above  and  below;  or  it  may  present  two 
muscular  bundles  with  a  central  tendon;  or 
finally  it  may  consist  simply  of  a  mere  tendinous 
band. 

Relations. — By  its  superficial  surface,  with  the 
deep  fascia.  By  its  deep  surface,  with  the  Flexor 
sublimis  digitorum.  Internally,  with  the  Flexor 
carpi  ulnaris.  Externally,  with  the  Flexor  carpi 
radialis.  The  median  nerve  lies  close  to  the 
tendon,  just  above  the  wrist,  on  its  inner  and 
posterior  side. 

The  Flexor  Carpi  Ulnaris  (Fig.  318)  lies  along 
the  ulnar  side  of  the  forearm.  It  arises  by  two 
heads,  connected  by  a  tendinous  arch,  beneath 
which  pass  the  ulnar  nerve  and  posterior  ulnar 
recurrent  artery.  One  head  arises  from  the  inner 
condyle  of  the  humerus,  humeral  head  {caput 
humerale) ,  by  the  common  tendon ;  the  other  from 
the  inner  margin  of  the  olecranon  and  from  the 
upper  two-thirds  of  the  posterior  border  of  the 
ulna,  ulnar  head  (caput  ulnare),  by  an  aponeu- 
rosis, common  to  it  and  the  Extensor  carpi 
ulnaris  and  Flexor  profundus  digitorum;  and  from 
the  intermuscular  septum  between  it  and  the 
Flexor  sublimis  digitorum.  The  fibres  terminate 
in  a  tendon  which  occupies  the  anterior  part  of 
the  lower  half  of  the  muscle,  and  is  inserted  into 
the  pisiform  bone,  and  is  prolonged  from  this  to 
the  fifth  metacarpal  and  unciform  bones,  by  the 
piso-metacarpal  and  piso-uncinate  ligaments:  it  is 
also  attached  by  a  few  fibres  to  the  annular  liga- 
ment. The  ulnar  artery  lies  on  the  outer  side  of 
the  tendon  of  this  muscle,  in  the  lower  two-thirds 
of  the  forearm,  the  tendon  forming  a  guide  in  tying  the  vessel  in  this  situation. 
A  bursa  (bursa  m.  flexoris  carpi  ulnaris)  is  placed  between  the  tendon  and  a 
part  of  the  pisiform  bone. 

Relations. — By  its  superficial  surface,  with  the  deep  fascia,  with  which  it  is 
intimately  connected  for  a  considerable  extent;  by  its  deep  surface,  with  the  Flexor 
sul)limis  digitorum,  the  Flexor  profundus  digitorum,  the  Pronator  quadratus,  and 
the  ulnar  vessels  and  nerve ;  by  its  outer  or  radial  border,  with  the  Palmaris  longus 
above  and  the  ulnar  vessels  and  nerve  below. 


Fig.  318. — Front  of  the  left  forearm. 
Superficial  muscles. 


THE  ANTERIOR    RADIO- ULNAR   REGION  481 

The  Flexor  Sublimis  Digitorum  (m.  jiexor  digitorum  suhlimis)  (Fig.  318) 
is  placed  beneath  the  preceding  muscles,  which  therefore  must  be  removed 
in  order  to  bring  its  attachment  into  view.  It  is  the  largest  of  the  muscles  of  the 
superficial  layer,  and  arises  by  t? iree  heads.  One  head,  the  humeral  head  {caput 
humerale),  arises  from  the  internal  condyle  of  the  humerus  by  the  common  ten- 
don, from  the  internal  lateral  ligament  of  the  elbow-joint,  and  from  the  intermus- 
cular septum  common  to  it  and  the  preceding  muscles.  The  second  head,  ulnar 
head  (caput  ulnar e),  arises  from  the  inner  side  of  the  coronoid  process  of  the  ulna, 
above  the  ulnar  origin  of  the  Pronator  radii  teres  (Fig.  133,  p.  185).  The  third 
head,  radial  head  [caput  radiate),  arises  from  the  oblique  line  of  the  radius,  extend- 
ing from  the  tubercle  to  the  insertion  of  the  Pronator  radii  teres.  The  fibres  pass 
vertically  downward,  forming  a  broad  and  thick  muscle,  which  speedily  divides  into 
two  planes  of  muscular  fibres,  superficial  and  deep:  the  superficial  plane  divides 
into  two  parts  which  end  in  tendons  for  the  middle  and  ring  fingers;  the  deep 
plane  also  divides  into  two  parts,  which  end  in  tendons  for  the  index  and  little 
fingers,  but  previously  to  having  done  so  it  gives  off  a  muscular  slip,  which  joins 
that  part  of  the  superficial  plane  which  is  intended  for  the  ring  finger.  As  the 
four  tendons  thus  formed  pass  beneath  the  annular  ligament  into  the  palm  of  the 
hand,  they  are  arranged  in  pairs,  the  superficial  pair  corresponding  to  the  middle 
and  ring  fingers,  the  deep  pair  to  the  index  and  little  fingers.  The  tendons  diverge 
from  one  another  as  they  pass  onward.  Opposite  the  bases  of  the  first  phalanges 
each  tendon  divides  into  two  slips  (chiasma  tendinum)  to  allow  of  the  passage  of 
the  corresponding  tendon  of  the  Flexor  profundus  digitorum ;  the  two  portions  of 
the  tendon  then  unite  and  form  a  grooved  channel  for  the  reception  of  the  accom- 
panying deep  flexor  tendon.  Finally  they  subdivide  a  second  time,  to  be  inserted 
into  the  sides  of  the  second  phalanges 
about  their  middle.  The  insertion  in  the 
index  finger  is  shown  in  Fig.  324.  After 
leaving  the  palm  the  tendons  of  the 
superficial  flexor,  accompanied  by  the  deep 
flexor  tendons,  lie  in  osseo-aponeurotic 
canals  (Fig.  320).  Each  canal  or  theca 
extends  from  the  metacarpo-phalangeal 
articulation  to  the  proximal  end  of  the 
distal  phalanx  (Fig.  231).     It  is  formed 

by  strong  fibrous  bands,  which  arch  across         Fig-  319.  — Section  passing  through  the  middle 

,"'  -P  ,  ,       ,  1       •  1  third  of  the  first  phalanx  of  the  middle  finger  (frozen 

the  tendons,  and  are  attached  on  each  side  section).       The  tendon  of  the  Flexor  subllmis  digi- 

,        ,1  •  i«   ii  1      1  /-\  torum  is  divided  into  two  small  bands,  which  spread 

to    the  margins  Ot   the   phalanges.       OppO-  laterally  and  engage  themselves  between  the  osse- 

site  the  middle  of  the  proximal  and  second  (XrfirTd'charly')  ^^'"°'"  ^^"^""^^"^  digitorum. 
phalanges  the  sheath  is  very  strong,  and 

the  fibres  pass  transversely;  but  opposite  the  joints  it  is  much  thinner,  and  the 
fibres  pass  obUquely.  It  is  very  thin  over  the  metacarpo-phalangeal  articulation. 
It  is  absent  over  the  distal  phalanx.  Each  sheath  is  lined  by  a  synovial  mem- 
brane, which  is  reflected  on  the  contained  tendons. 

Relations. — In  the  forearm,  by  its  superficial  surface,  with  the  deep  fascia  and 
all  the  preceding  superficial  muscles;  by  its  deep  surface,  with  the  Flexor  profundus 
digitorum.  Flexor  longus  pollicis,  the  ulnar  vessels  and  nerve,  and  the  median 
nerve.  In  the  hand  its  tendons  are  in  relation,  in  front,  with  the  palmar  fascia, 
superficial  palmar  arch,  and  the  branches  of  the  median  nerve;  behind,  with  the 
tendons  of  the  deep  Flexor  and  the  Lumbricales. 


31 


FLEXOR  PROFUNDUS 
DIGITiORUM 
SHEATH  OF,^                      ]                       /FLEXOR 

flexor\                          /'sublimis 
tendons    \^,0-   l-^^/     digitorum 
/^^ -,^-^v      digital 

ff^L'^  fr''Jh^Xi''  *''TERIES 
/./^"'•'iOiJ^^MJMl     *'*"  NERVES 

kjwb^J 

\^ps/. 

COMMON  TENDON  OF 
'extensor  MUSCLE 
OF  FINGERS 

FIRST  PHALANX 

482  THE  MUSCLES  AND   FASCIA 

The  Deep  Layer  (Fig.  320). 

Flexor  profundus  digitorum.  Flexor  longus  polllcis. 

Pronator  quadratus. 

Dissection. — Divide  each  of  the  superficial  muscles  at  its  centre,  and  turn  either  end  aside; 
the  deep  layer  of  muscles,  together  with  the  median  nerve  and  ulnar  vessels,  will  then  be  exposed. 

The  Flexor  Profundus  Digitorum  (m.  flexor  digitorum  profundiis)  (Fig.  320) 
is  situated  on  the  ulnar  side  of  the  forearm,  immediately  beneath  the  superficial 
Flexors.  It  arises  from  the  upper  three-fourths  of  the  anterior  and  inner 
surfaces  of  the  shaft  of  the  ulna,  embracing  the  insertion  of  the  Brachialis  anticus 
above,  and  extending,  below,  to  within  a  short  distance  of  the  Pronator  quadratus. 
It  also  arises  from  a  depression  on  the  inner  side  of  the  coronoid  process;  by  an  apo- 
neurosis from  the  upper  three-fourths  of  the  posterior  border  of  the  ulna,  in  common 
with  the  Flexor  and  Extensor  carpi  ulnaris;  and  from  the  ulnar  half  of  the  inter- 
osseous membrane.  The  fibres  form  a  fleshy  belly  of  considerable  size,  which  divides 
into  four  tendons :  these  pass  under  the  annular  ligament  beneath  the  tendons  of  the 
Flexor  sublimis  digitorum.  Opposite  the  first  phalanges  the  tendons  pass  through 
the  openings  in  the  two  slips  of  the  tendons  of  the  Flexor  sublimis  digitorum,  and 
are  finally  inserted  into  the  bases  of  the  last  phalanges.  The  portion  of  the  muscle 
for  the  index  finger  (Fig.  324)  is  usually  distinct  throughout,  but  the  tendons  for 
the  three  inner  fingers  are  connected  together  by  cellular  tissue  and  tendinous  slips 
as  far  as  the  palm  of  the  hand.  The  tendons  of  this  muscle  and  those  of  the  Flexor 
sublimis  digitorum,  whilst  contained  in  the  osseo-aponeurotic  canals  of  the  fingers, 
are  invested  in  a  synovial  sheath,  and  are  connected  to  each  other  and  to  the 
phalanges  by  slender  tendinous  filaments,  called  vincula  accessoria  tendinum  (vin~ 
culum  tendinum).  One  of  these  connects  the  deep  tendon  to  the  bone  before  it 
passes  through  the  superficial  tendon ;  a  second  connects  the  two  tendons  together, 
after  the  deep  tendons  have  passed  through;  and  a  third  connects  the  deep  ten- 
don to  the  head  of  the  second  phalanx.  This  last  consists  largely  of  yellow  elastic 
tissue,  and  may  assist  in  drawing  down  the  tendon  after  flexion  of  the  finger.^ 

Four  small  muscles,  the  Lumbricales,  are  connected  with  the  tendons  of  the  Flexor 
profundus  in  the  palm.    They  will  be  described  with  the  muscles  in  that  region. 

Relations. — By  its  superficial  surface,  in  the  forearm,  with  the  Flexor  sublimis 
digitorum,  the  Flexor  carpi  ulnaris,  the  ulnar  vessels  and  nerve,  and  the  median 
nerve;  and  in  the  hand,  with  the  tendons  of  the  superficial  Flexor;  by  its  deep 
surface,  in  the  forearm,  with  the  ulna,  the  interosseous  membrane,  the  Pronator 
quadratus;  and  in  the  hand,  with  the  Interossei,  Adductor  pollicis,  and  deep 
palmar  arch;  by  its  ulnar  border,  with  the  Flexor  carpi  ulnaris;  by  its  radial  border, 
with  the  Flexor  longus  pollicis,  the  anterior  interosseous  vessels  and  nerve  being 
interposed. 

The  Flexor  Longus  Pollicis  (m.  flexor  pollicis  longus)  (Fig.  320)  is  situated  on 
the  radial  side  of  the  forearm,  lying  on  the  same  plane  as  the  preceding.  It  arises 
from  the  grooved  anterior  surface  of  the  shaft  of  the  radius,  commencing  above, 
immediately  below  the  tuberosity  and  oblique  line,  and  extending  below  to  within 
a  short  distance  of  the  Pronator  quadratus.  It  also  arises  from  the  adjacent  part 
of  the  interosseous  membrane  and  generally  by  a  fleshy  slip  from  the  inner  border 
of  the  coronoid  process  or  from  the  internal  condyle  of  the  humerus.  The  fibres 
pass  downward,  and  terminate  in  a  flattened  tendon  which  passes  beneath  the 
annular  ligament,  is  then  lodged  in  the  interspace  between  the  outer  head  of  the 
Flexor  brevis  pollicis  and  the  Adductor  obliquus  polHcis,  and,  entering  an  osseo- 
aponeurotic  canal  similar  to  those  for  the  other  flexor  tendons,  is  inserted  into  the 
base  of  the  last  phalanx  of  the  thumb. 

1  Marshall,  Brit,  and  For.  Med  -Chir.  Rev.,  1853. 


THE  ANTERIOR   RADIO- ULNAR   REGION 


483 


Relations. — By  its  superficial  sur- 
face, with  the  Flexor  suhlimis  digi- 
torum,  Flexor  carpi  radialis,  Supi- 
nator longus,  and  radial  vessels;  by 
its  deep  surface,  with  the  radius, 
interosseous  membrane,  and  Pro- 
nator quadratus ;  by  its  ulnar  border, 
with  the  Flexor  profundus  digitorum, 
from  which  it  is  separated  by  the 
anterior  interosseous  vessels  and 
nerve. 

The  Pronator  Quadratus  (Figs. 
320  and  329)  is  a  small,  flat,  quadri- 
lateral muscle,  extendingtransversely 
across  the  front  of  the  radius  and 
ulna,  above  their  carpal  extremities. 
It  arises  from  the  oblique  or  pronator 
ridge  on  the  lower  part  of  the  ante- 
rior surface  of  the  shaft  of  the  ulna; 
from  the  lower  fourth  of  the  anterior 
surface  and  the  anterior  border  of 
the  ulna;  and  from  a  strong  aponeu- 
rosis which  covers  the  inner  third  of 
the  muscle.  The  fibres  pass  out- 
ward and  slightly  downward,  to  be 
inserted  into  the  lower  fourth  of  the 
anterior  surface  and  anterior  border 
of  the  shaft  of  the  radius. 

Relations. — By  its  superficial  sur- 
face, with  the  Flexor  profundus  digi- 
torum, the  Flexor  longus  polhcis, 
Flexor  carpi  radialis,  and  the  radial 
vessels;  by  its  deep  surface,  with  the 
radius,  ulna,  and  interosseous  mem- 
brane. 

Nerves.  —  All  the  muscles  of  the 
superficial  layer  are  supplied  by  the 
median  nerve,  excepting  the  Flexor 
carpi  ulnaris,  which  is  supplied  by  the 
ulnar  nerve.  The  Pronator  radii  teres 
and  the  Flexor  carpi  radialis  derive 
their  supply  primarily  from  the  sixth 
cervical;  the  Pahnaris  longus  from 
the  eighth  cervical;  the  Flexor  sub- 
limis  digitorum  from  the  seventh  and 
eighth  cervical  and  first  dorsal,  and 
the  Flexor  carpi  ulnaris  from  the 
eighth  cervical  and  first  dorsal  nerves. 
Of  the  deep  layer,  the  Flexor  pro- 
fundus digitorum  is  supplied  by  the 
eighth  cervical  and  first  dorsal 
through  the  ulnar  and  anterior  in- 
terosseous branch  of  the  median. 
The    remaining   two    muscles,    the 


Fro.  320. — Front  of  the  left  forearm.     Deep  muscles. 


484  THE  MUSCLES  AND    FASCIA 

Flexor  longus  pollicis  and  Pronator  quadratus,  are  also  supplied  by  the  eighth 
cervical  and  first  dorsal  through  the  anterior  interosseous  branch  of  the  median. 
Actions. — These  muscles  act  upon  the  forearm,  the  wrist,  and  hand.  The 
Pronator  radii  teres  helps  to  rotate  the  radius  upon  the  ulna,  rendering  the  hand 
prone:  when  the  radius  is  fixed  it  assists  the  other  muscles  in  flexing  the  forearm. 
The  Flexor  carpi  radialis  is  one  of  the  flexors  of  the  wrist;  when  acting  alone  it 
flexes  the  wrist,  inclining  it  to  the  radial  side.  It  can  also  assist  in  pronating  the 
forearm  and  hand,  and,  by  continuing  its  action,  in  bending  the  elbow.  The  Flexor 
carpi  ulnaris  is  one  of  the  flexors  of  the  wrist :  when  acting  alone  it  flexes  the  wrist, 
inclining  it  to  the  ulnar  side  (adducts  the  wrist),  and,  by  continuing  to  contract, 
it  bends  the  elbow.  The  Palmaris  longus  is  a  tensor  of  the  palmar  fascia,  and 
tension  of  this  fascia  protects  the  parts  beneath  it.  It  also  assists  in  flexing  the 
wrist  and  elbow.  The  Flexor  sublimis  digitorum  flexes  the  middle  phalanx  and 
then  assists  in  flexing  the  wrist  and  elbow.  The  Flexor  profundus  digitorum  is 
the  flexor  of  the  distal  phalanx.  After  the  Flexor  sublimis  has  bent  the  second 
phalanx,  the  Flexor  profundus  flexes  the  terminal  one,  but  it  cannot  do  so  until 
after  the  contraction  of  the  superficial  muscle.  After  flexing  the  distal  phalanx, 
it  assists  in  flexing  the  middle  phalanx,  the  proximal  phalanx,  and  the  wrist.  The 
Flexor  longus  pollicis  is  the  flexor  of  the  distal  phalanx  of  the  thumb.  When  the 
thumb  is  fixed  it  also  assists  in  flexing  the  wrist.  The  Pronator  quadratus  helps 
to  rotate  the  radius  upon  the  ulna,  rendering  the  hand  prone. 

Surgical  Anatomy. — -When  a  finger  is  amputated  so  that  the  fibrous  sheath  of  the  flexor  ten- 
dons is  divided  in  a  region  in  which  it  is  firm  and  dense,  the  tendon  contracts  but  the  theca  does 
not,  and  the  rigid  theca  constitutes  a  permeable  passage  to  the  palm.  If  the  parts  should  be 
infected  the  theca  will  draw  pus  toward  the  palm.  Hence  it  is  best  to  close  the  theca  by  sutures. 
"Over  the  terminal  phalanx,  and  over  the  joint  between  the  middle  and  terminal  phalanges, 
there  is  no  fibrous  sheath.  In  front  of  the  metacarpo-phalangeal  joint  it  is  scarcely  evident. 
Over  the  first  and  second  (proximal  and  middle)  phalanges,  and  in  front  of  the  joint  between 
these  bones,  the  fibrous  sheath  is  well  marked,  and  appears  as  a  rigid  tube  when  cut  across. 
As  the  sheath  crosses  the  metacarpo-phalangeal  and  first  interphalangeal  joints,  it  is  adherent 
to  the  glenoid  ligament,  and  is  easily  closed  by  two  fine  catgut  sutures  passed  vertically — i-  e., 
from  the  dorsal  to  the  palmar  wall.  Opposite  the  shafts  of  the  first  and  second  phalanges, 
however,  there  is  much  difficulty  in  effecting  closure,  since  the  sheath  is  united  to  the  periosteum, 
and  that  membrane  is  very  thin.  In  these  situations  the  periosteum  should  be  stripped  up  a 
little  from  the  palmar  aspect  of  the  bone,  and  the  orifice  of  the  tube  secured  by  two  fine  sutures 
passed  either  vertically  or  transversely,  as  may  appear  the  more  convenient.  This  stripping 
off  of  periosteum  should  be  effected  before  the  bone  is  divided. "• 

9.  The  Radial  Region  (Figs.  318,  321,  322). 

Supinator  longus.  Extensor  carpi  radialis  longior. 

Extensor  carpi  radialis  brevior. 

Dissection. — Divide  the  integument  in  the  same  manner  as  in  the  dissection  of  the  anterior 
brachial  region,  and,  after  having  examined  the  cutaneous  vessels  and  nerves  and  deep  fascia, 
remove  all  those  structures.  The  muscles  will  then  be  exposed.  The  removal  of  the  fascia 
will  be  considerably  facilitated  by  detaching  it  from  below  upward.  Great  care  should  be 
taken  to  avoid  cutting  across  the  tendons  of  the  muscles  of  the  thumb,  which  cross  obliquely 
the  larger  tendons  running  down  the  back  of  the  radius. 

The  Supinator  Longus  (m.  brachioradialis)  (Fig.  318)  is  the  most  superficial 
muscle  on  the  radial  side  of  the  forearm ;  it  is  fleshy  for  the  upper  two-thirds  of 
its  extent,  tendinous  below.  It  arises  from  the  upper  two-thirds  of  the  external 
supracondylar  ridge  of  the  humerus,  and  from  the  external  intermuscular  septum, 
being  limited  above  by  the  musculo-spiral  groove.  The  fibres  terminate  above 
the  middle  of  the  forearm  in  a  flat  tendon,  which  is  inserted  into  the  outer  side 
of  the  base  of  the  styloid  process  of  the  radius. 

^  Operative  Surgery.     By  Sir  Frederick  Treves. 


THE   RADIAL    REGION 


485 


Relations. — By  its  superficial  sur- 
face, with  the  integument  and  fascia 
for  the  greater  part  of  its  extent ;  near 
its  insertion  it  is  crossed  by  the  Ex- 
tensor ossis  metacarpi  polKcis  and  the 
Extensor  brevis  polhcis;  by  its  deep 
surface,  with  the  humerus,  the  Ex- 
tensor carpi  radiahs  longior  and  bre- 
vior,  the  insertion  of  the  Pronator 
radii  teres,  and  the  Supinator  brevis; 
by  its  inner  border,  above  the  elbow, 
with  the  BrachiaHs  anticus,  the  mus- 
culo-spiral  nerve,  and  the  radial  recur- 
rent artery;  and  in  the  forearm  with 
the  radial  vessels  and  nerve. 

The  Extensor  Carpi  Radialis 
Longior  (m.  extensor  carpi  radialis 
loncjus)  (Fig.  321)  is  placed  partly 
beneath  the  preceding  muscle.  It 
arises  from  the  lower  third  of  the  ex- 
ternal supracondylar  ridge  of  the 
humerus,  and  from  the  external  in- 
termuscular septum  by  a  few  fibres 
from  the  common  tendon  of  origin  of 
the  Extensor  muscles  of  the  forearm. 
The  fibres  terminate  at  the  upper  third 
of  the  forearm  in  a  flat  tendon,  which 
runs  along  the  outer  border  of  the 
radius,  beneath  the  extensor  tendons 
of  the  thumb;  it  then  passes  through 
a  groove  common  to  it  and  the  Ex- 
tensor carpi  radialis  brevior,  immedi- 
ately behind  the  styloid  process,  and 
is  inserted  into  the  base  of  the  meta- 
carpal bone  of  the  index  finger,  on 
its  radial  side. 

Relations. — By  its  superficial  sur- 
face, with  the  Supinator  longus  and 
fascia  of  the  forearm;  its  outer  side 
is  crossed  obliquely  by  the  extensor 
tendons  of  the  thumb;  by  its  deep 
surface,  with  the  elbow-joint,  the 
Extensor  carpi  radialis  brevior,  and 
back  part  of  the  wrist. 

The  Extensor  Carpi  Radialis 
Brevior  (m,  extensor  carpi  radialis 
brevis)  (Fig.  321)  is  shorter,  as  its 
name  implies,  and  thicker  than  the 
preceding  muscle,  beneath  which  it  is 
placed.  It  arises  from  the  external 
condyle  of  the  humerus  by  a  tendon 
common  to  it  and  the  three  following 
muscles ;  from  the  external  lateral 
ligament  of  the  elbow-joint,  from  a 
strong  aponeurosis  which  covers  its 


Fig.  321. 


-Posterior  surface  of  the  forearm, 
muscles. 


Superficial 


486  THE  MUSCLES  AND   FASCIAE 

surface,  and  from  the  intermuscular  septa  between  it  and  the  adjacent  muscles. 
The  fibres  terminate  about  the  middle  of  the  forearm  in  a  flat  tendon  which  is 
closely  connected  with  that  of  the  preceding  muscle,  and  accompanies  it  to  the 
wrist,  lying  in  the  same  groove  on  the  posterior  surface  of  the  radius ;  it  passes 
beneath  the  extensor  tendons  of  the  thumb,  then  beneath  the  annular  ligament, 
and,  diverging  somewhat  from  its  fellow,  is  inserted  into  the  base  of  the  meta- 
carpal bone  of  the  middle  finger,  on  its  radial  side.  There  is  often  a  bursa 
{bursa  m.  extensoris  carpi  radialis  brevis)  between  a  portion  of  the  base  of  the 
bone  and  the  tendon. 

The  tendons  of  the  two  preceding  muscles  pass  through  the  same  compartment 
of  the  annular  ligament,  and  are  lubricated  by  a  single  synovial  membrane,  but  are 
separated  from  each  other  by  a  small  vertical  ridge  of  bone  as  they  lie  in  the  groove 
at  the  back  of  the  radius. 

Relations. — By  its  superficial  surface,  with  the  Extensor  carpi  radialis  longior, 
and  with  the  Extensor  muscles  of  the  thumb  which  cross  it;  by  its  deep  surface, 
with  the  Supinator  brevis,  tendon  of  the  Pronator  radii  teres,  radius,  and  wrist- 
joint;  by  its  ulnar  border,  with  the  Extensor  communis  digitorum. 

10.  The  Posterior  Radio-ulnar  Region  (Fig.  321). 

The  muscles  in  this  region  are  divided  for  purposes  of  description  into  two 
groups  or  layers,  superficial  and  deep. 

The  Superficial  Layer. 

Extensor  communis  digitorum.  Extensor  carpi  ulnaris. 

Extensor  minimi  digiti.  Anconeus. 

The  Extensor  Communis  Digitorum  (m.  extensor  digitorum  communis)  is 
situated  at  the  back  part  of  the  forearm.  It  arises  from  the  external  condyle  of 
the  humerus  by  the  common  tendon,  from  the  deep  fascia,  and  the  intermus- 
cular septa  between  it  and  the  adjacent  muscles.  Just  below  the  middle  of 
the  forearm  it  divides  into  three  fleshy  masses,  from  which  tendons  proceed; 
these  pass,  together  with  the  Extensor  indicis,  through  a  separate  compartment 
of  the  annular  ligament,  lubricated  by  a  synovial  membrane.  The  tendons 
then  diverge,  the  innermost  one  dividing  into  two;  and  all,  after  passing  across  the 
back  of  the  hand,  are  inserted  into  the  second  and  third  phalanges  of  the  fingers  in 
the  following  manner:  the  outermost  tendon,  accompanied  by  the  Extensor  indicis, 
goes  to  the  index  finger  (Figs.  321,  323,  and  324) ;  the  second  tendon  is  sometimes 
connected  to  the  first  by  a  thin  transverse  band,  and  receives  a  slip  from  the  third 
tendon  (Fig.  321);  it  goes  to  the  middle  finger;  the  third  tendon  gives  off  the  slip 
to  the  second  (Fig.  321),  and  receives  a  very  considerable  part  of  the  fourth  tendon; 
the  fourth,  or  innermost  tendon,  divides  into  two  parts:  one  goes  to  join  the  third 
tendon;  the  other,  reinforced  by  the  Extensor  minimi  digiti,  goes  to  the  little 
finger.  Each  tendon  opposite  the  metacarpo-phalangeal  articulation  becomes 
narrow  and  thickened,  and  gives  off  a  thin  fasciculus  upon  each  side  of  the  joint, 
which  blends  with  the  lateral  ligaments  and  serves  as  the  posterior  ligament; 
after  having  passed  the  joint  it  spreads  out  into  a  broad  aponeurosis,  which  covers 
the  whole  of  the  dorsal  surface  of  the  first  phalanx,  being  reinforced,  in  this 
situation,  by  the  tendons  of  the  Interossei  and  Lumbricales.  Opposite  the  first 
phalangeal  joint. this  aponeurosis  divides  into  three  slips,  a  middle  and  two 
lateral:  the  former  is  inserted  into  the  base  of  the  second  phalanx;  and  the  two 
lateral,  which  are  continued  onward  along  the  sides  of  the  second  phalanx,  unite 
by  their  contiguous  margins,  and  are  inserted  into  the  dorsal  surface  of  the  last 
phalanx.  As  the  tendons  cross  the  phalangeal  joints  they  furnish  them  with  pos- 
terior ligaments.     The  accessory  slips  or  lateral  vincula  which  join  the  tendon 


THE  POSTERIOR   RADIO- ULNAR   REGION  437 

of  the  ring  finger  to  the  tendon  of  the  little  finger  and  the  tendon  of  the  middle 
finger  are  constant.  If  the  middle  and  little  fingers  are  held  flexed  the  lateral 
vincula  greatly  limit  the  range  of  extension  possible  in  the  ring  finger — a  limi- 
tation which  interferes  with  a  piano-player  (Prof.  William  S.  Forbes). 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  forearm  and  hand, 
the  posterior  annular  ligament,  and  integument;  by  its  deep  surface,  with  the 
Supinator  brevis,  the  Extensor  muscles  of  the  thumb  and  index  finger,  the  pos- 
terior interosseous  vessels  and  nerve,  the  wrist-joint,  carpus,  metacarpus,  and 
phalanges;  by  its  radial  border,  with  the  Extensor  carpi  radialis  brevior;  by  its 
ulnar  border,  with  the  Extensor  minimi  digiti  and  Extensor  carpi  ulnaris. 

The  Extensor  Minimi  Digiti  (m.  extensor  digiti  quinti  proprius)  is  a  slender 
muscle  placed  on  the  inner  side  of  the  Extensor  communis,  with  which  it  is  gen- 
erally connected.  It  arises  from  the  common  tendon  by  a  thin,  tendinous  slip,  and 
from  the  intermuscular  septa  between  it  and  the  adjacent  muscles.  Its  tendon 
runs  through  a  separate  compartment  in  the  annular  ligament  behind  the  inferior 
radio-ulnar  joint,  then  divides  into  two  as  it  crosses  the  hand,  the  outermost 
division  being  joined  by  the  slip  from  the  innermost  tendon  of  the  common  exten- 
sor. The  two  slips  thus  formed  spread  into  a  broad  aponeurosis,  which  after 
receiving  a  slip  from  the  Abductor  minimi  digiti  is  inserted  into  the  second  and 
third  phalanges.  The  tendon  is  situated  on  the  ulnar  side  of,  and  somewhat  more 
superficial  than,  the  common  extensor. 

The  Extensor  Carpi  Ulnaris  is  the  most  superficial  muscle  on  the  ulnar  side  of 
the  forearm.  It  arises  from  the  external  condyle  of  the  humerus  by  the  common 
tendon;  by  an  aponeurosis  from  the  posterior  border  of  the  ulna  in  common 
with  the  Flexor  carpi  ulnaris  and  the  Flexor  profundus  digitorum;  and  from  the 
deep  fascia  of  the  forearm.  This  muscle  terminates  in  a  tendon  which  runs 
through  a  groove  behind  the  styloid  process  of  the  ulna,  passes  through  a  separate 
compartment  in  the  annular  ligament,  and  is  inserted  into  the  prominent  tubercle 
on  the  ulnar  side  of  the  base  of  the  metacarpal  bone  of  the  little  finger. 

Relations. — By  its  superficial  surface,  with  the  deep  fascia  of  the  forearm;  by 
its  deep  surface,  with  the  ulna  and  the  muscles  of  the  deep  layer. 

The  Anconeus  {m.  anconceus)  is  a  small  triangular  muscle  placed  behind  and 
below  the  elbow-joint,  and  appears  to  be  a  continuation  of  the  external  portion  of 
the  Triceps.  It  arises  by  a  separate  tendon  from  the  back  part  of  the  outer  condyle 
of  the  humerus,  and  is  inserted  into  the  side  of  the  olecranon  and  upper  fourth  of 
the  posterior  surface  of  the  shaft  of  the  ulna;  its  fibres  diverge  from  their  origin, 
the  upper  ones  being  directed  transversely,  the  lower  obliquely  inward. 

Relations. — By  its  superficial  surface,  with  a  strong  fascia  derived  from  the 
Triceps;  by  its  deep  surface,  with  the  elbow-joint,  the  orbicular  ligament,  the 
ulna,  and  a  small  portion  of  the  Supinator  brevis. 

The  Deep  Layer  (Fig.  323). 

Supinator  radii  brevis.  Extensor  brevis  pollicis. 

Extensor  ossis  metacarpi  pollicis.  Extensor  longus  pollicis. 

Extensor  indicis. 

The  Supinator  Radii  Brevis  (w.  supinator)  (Figs.  322  and  323)  is  a  broad  muscle, 
of  hollow  cylindrical  form,  curved  round  the  upper  third  of  the  radius.  It  consists  of 
two  distinct  planes  of  muscular  fibres,  between  which  lies  the  posterior  interosseous 
nerve  (Fig.  322).  The  two  planes  arise  in  common :  the  superficial  one  by  tendin- 
ous, and  the  deeper  by  muscular,  fibres  from  the  external  condyle  of  the  humerus; 
from  the  external  lateral  ligament  of  the  elbow-joint  and  the  orbicular  ligament  of 
the  radius;  from  the  ridge  on  the  ulna,  which  runs  obliquely  downward  from  the 


488 


THE    MUSCLES    AND   FASCIjE 


posterior  extremity  of  the  lesser  sigmoid  cavity;  from  the  triangular  depression  in 
front  of  it;  and  from  a  tendinous  expansion  which  covers  the  surface  of  the  muscle. 


Int. 
Condyle. 


Coronoid 
proc. 

Head  of 
radius. 


TENDON    OF.\^ 
BICEPS 


Olecranon. 


Fig.  322. — Supinator  brevis.  (From  a  prepa- 
ration in  the  Museum  of  the  Royal  College  of 
Surgeons  of  England.) 


The  superficial  fibres  surround  the 
upper  part  of  the  radius,  and  are  in- 
serted intothe  outer  edge  of  the  bicip- 
ital tuberosity  and  into  the  oblique 
line  of  the  radius,  as  low  down  as  the 
insertion  of  the  Pronator  radii  teres. 
The  upper  fibres  of  the  deeper  plane 
form  a  sling-like  fasciculus,  which 
encircles  the  neck  of  the  radius 
above  the  tuberosity  and  is  at- 
tached to  the  back  part  of  its  inner 
surface :  the  greater  part  of  this  por- 
tion of  the  muscle  is  inserted  into 
the  posterior  and  external  surface 
of  the  shaft,  midway  between  the 
oblique   line   and  the  head  of   the 


Fig.  323. — Posterior  surface  of  the  forearm.    Deep  muscles. 

-  -    bone.     Between    the    insertion  of  the  two 

planes  the  posterior  interosseous  nerve  lies  on  the  shaft  of  the  bone  (Fig.  322). 


THE   POSTERIOR   RADIO- ULNAR   REGION 


489 


Relations. — By  its  superficial  surface,  with  the  superficial  Extensor  and  Supina- 
tor muscles,  and  the  radial  vessels  and  nerve;  by  its  deep  surface,  w^ith  the  elbow- 
joint,  the  interosseous  membrane,  and  the  radius. 

The  Extensor  Ossis  Metacarpi  PoUicis  (m.  abductor  pollicis  longus)  is  the  most 
external  and  the  largest  of  the  deep  extensor  muscles:  it  lies  immediately  below 
the  Supinator  brevis,  with  which  it  is  sometimes  united.  It  arises  from  the  outer 
part  of  the  posterior  surface  of  the  shaft  of  the  ulna  below  the  insertion  of  the 
Anconeus,  from  the  interosseous  membrane,  and  from  the  middle  third  of  the 
posterior  surface  of  the  shaft  of  the  radius.  Passing  obliquely  downward  and 
outward,  it  terminates  in  a  tendon  which  runs  through  a  groove  on  the  outer  side 
of  the  styloid  process  of  the  radius,  accompanied  by  the  tendon  of  the  Extensor 
brevis  pollicis,  and  is  inserted  into  the  base  of  the  metacarpal  bone  of  the  thumb. 
It  occasionally  gives  oft'  two  slips  near  its  insertion — one  to  the  Trapezium,  and  the 
other  to  blend  with  the  origin  of  the  Abductor  pollicis. 

Relations. — By  its  superficial  surface,  with  the  Extensor  communis  digitorum, 
Extensor  minimi  digiti,  and  fascia  of  the  forearm,  and  with  the  branches  of  the 
posterior  interosseous  artery  and  nerve  which  cross  it;  by  its  deep  surface,  with 
the  ulna,  interosseous  membrane,  radius,  the  tendons  of  the  Extensor  carpi  radialis 
longior  and  brevior,  which  it  crosses  obliquely,  and,  at  the  outer  side  of  the  wrist, 
with  the  radial  vessels;  by  its  upper  border,  with  the  Supinator  brevis;  by  its 
loiver  border,  with  the  Extensor  brevis  pollicis. 

The  Extensor  Brevis  Pollicis,  often  called  the  extensor  primi  intemodii  pollicis 
(m.  extensor  pollicis  brevis),  the  smallest  muscle  of  this  group,  lies  on  the  inner 
side  of  the  preceding.  It  arises  from  the  posterior  surface  of  the  shaft  of  the  radius, 
below  the  Extensor  ossis  metacarpi 
pollicis,  and  from  the  interosseous 
membrane.  Its  direction  is  similar  to 
that  of  the  Extensor  ossis  metacarpi 
poUicis,  its  tendon  passing  through  the 
same  groove  on  the  outer  side  of  the 
styloid  process,  to  be  inserted  into  the 
base  of  the  first  phalanx  of  the  thumb. 

Relations. — The  same  as  those  of 
the  Extensor  ossis  metacarpi  pollicis. 

The  Extensor  Longus  Pollicis, 
often  called  the  extensor  secundi  inter- 
nodii  pollicis  {m.  extensor  pollicis  longus) 
is  much  larger  than  the  preceding 
muscle,  the  origin  of  which  it  partly 
covers  in.  It  arises  from  the  outer 
part  of  the  posterior  surface  of  the 
shaft  of  the  ulna,  below  the  origin  of 
the  Extensor  ossis  metacarpi  pollicis, 
and  from  the  interosseous  membrane. 
It  terminates  in  a  tendon  which  passes 
through  a  separate  compartment  in 
the  annular  ligament,  lying  in  a  nar- 
row, oblique  groove  at  the  back  part 

of  the  lower  end  of  the  radius.  It  then  crosses  obliquely  the  tendons  of  the 
Extensor  carpi  radialis  longior  and  brevior,  being  separated  from  the  other 
extensor  tendons  of  the  thumb  by  a  triangular  interval,  in  which  the  radial  artery 
is  found,  and  is  finally  inserted  into  the  base  of  the  last  phalanx  of  the  thumb. 

Relations. — By  its  superficial  surface,  with  the  same  parts  as  the  Extensor  ossis 
metacarpi  pollicis ;  by  its  deep  surface,  with  the  ulna,  interosseous  membrane,  the 


LICAMENTUM 
BREVIS 


LICAMENTUM 
LONGUS 


LIGAMtNTUM  BREVIS 

FLEXOR  SUBLIMIS 
DIGITORUM 
EXPANSION   OF 
EXTENSOR  TENDON 
FLEXOR   PROFUNDUS 
TORUM 

ST  LUM8RICAL 
MUSCLE 

FIRST  DORSAL 
INTEROSSEOUS 
SOLE 

XTENSOR  INDICiS 
TENDON 


EXTENSOR  COMMUNIS 
DIGITORUM  TENDON 


Fig.  324.- 


-The  tendons  attached  to  the  index  finger. 
(Cunningham. ) 


490  THE   MUSCLES  AND   FASCIAE 

posterior  interosseous  nerve,  radius,  the  wrist,  the  radial  vessels,  and  metacarpal 
bone  of  the  thumb. 

The  Extensor  Indicis  (m.  extensor  indicis  proprius)  (Figs.  321,  323,  and  324)  is 
a  narrow,  elongated  muscle  placed  on  the  inner  side  of,  and  parallel  with,  the 
preceding.  It  arises  from  the  posterior  surface  of  the  shaft  of  the  ulna,  below 
the  origin  of  the  Extensor  longus  poUicis  and  from  the  interosseous  membrane. 
Its  tendon  passes  with  the  Extensor  communis  digitorum  through  the  same  canal 
in  the  annular  ligament,  and  subsequently  joins  the  tendon  of  the  Extensor 
communis  which  belongs  to  the  index  finger,  opposite  the  lower  end  of  the 
corresponding  metacarpal  bone,  lying  to  the  ulnar  side  of  the  tendon  from  the 
common  extensor. 

Relations. — ^The  relations  are  similar  to  those  of  the  preceding  muscles. 

Nerves. — The  Supinator  longus  is  supplied  by  the  sixth,  the  Extensor  carpi 
radialis  longior  by  the  sixth  and  seventh,  and  the  Anconeus  by  the  seventh  and 
eighth  cervical  nerves,  all  through  the  musculo-spiral  nerve;  the  remaining  muscles 
of  the  radial  and  posterior  brachial  region  are  supplied  through  the  posterior 
interosseous  nerve,  the  Supinator  brevis  being  supplied  by  the  sixth  cervical,  the 
Extensor  carpi  radialis  brevior  by  the  sixth  and  seventh  cervical,  and  all  the  other 
muscles  by  the  seventh  cervical. 

Actions. — The  muscles  of  the  radial  and  posterior  brachial  regions,  which 
comprise  all  the  extensor  and  supinator  muscles,  act  upon  the  forearm,  wrist,  and 
hand;  they  are  the  direct  antagonists  of  the  pronator  and  flexor  muscles.  The 
Anconeus  assists  the  Triceps  in  extending  the  forearm.  The  chief  action  of  the 
Supinator  longus  is  that  of  a  flexor  of  the  elbow-joint,  but  in  addition  to  this  it 
may  act  both  as  a  supinator  or  a  pronator;  that  is  to  say,  if  the  forearm  is  forcibly 
pronated  it  will  act  as  a  supinator,  and  bring  the  bones  into  a  position  midway 
between  supination  and  pronation;  and  vice  versa,  if  the  arm  is  forcibly  supinated, 
it  will  act  as  a  pronator,  and  bring  the  bones  into  the  same  position,  midway 
between  supination  and  pronation.  The  action  of  the  muscle  is  therefore  to  throw 
the  forearm  and  hand  into  the  position  they  naturally  occcupy  when  placed  across 
the  chest.  The  Supinator  brevis  is  a  supinator;  that  is  to  say,  when  the  radius 
has  been  carried  across  the  ulna  in  pronation  and  the  back  of  the  hand  is  directed 
forward,  this  muscle  carries  the  radius  back  again  to  its  normal  position  on  the 
outer  side  of  the  ulna,  and  the  palm  of  the  hand  is  again  directed  forward.  The 
Extensor  carpi  radialis  longior  extends  the  wrist  and  abducts  the  hand.  It  may 
also  assist  in  bending  the  elbow-joint;  at  all  events,  it  serves  to  fix  or  steady  this 
articulation.  The  Extensor  carpi  radialis  brevior  assists  the  Extensor  carpi 
radialis  longior  in  extending  the  wrist,  and  may  also  act  slightly  as  an  abductor  of 
the  hand.  The  Extensor  carpi  ulnaris  helps  to  extend  the  hand,  but  when  acting 
alone  inclines  it  toward  the  ulnar  side;  by  its  continued  action  it  extends  the 
elbow-joint.  The  Extensor  communis  digitorum  extends  the  phalanges,  then  the 
wrist,  and  finally  the  elbow.  It  acts  principally  on  the  proximal  phalanges,  the 
middle  and  terminal  phalanges  being  extended  by  the  Interossei  and  Lumbri- 
cales.  It  has  also  a  tendency  to  separate  the  fingers  as  it  extends  them.  The 
Extensor  minimi  digiti  extends  similarly  the  little  finger,  and  by  its  continued 
action  it  assists  in  extending  the  wrist.  It  is  owing  to  this  muscle  that  the  little 
finger  can  be  extended  or  pointed  whilst  the  others  are  flexed.  The  chief  action  of 
the  Extensor  ossis  metacarpi  pollicis  is  to  carry  the  thumb  outward  and  backward 
from  the  palm  of  the  hand,  and  hence  it  has  been  called  the  abductor  pollicis  longus. 
By  its  continued  action  it  helps  to  extend  and  abduct  the  wrist.  The  Extensor 
brevis  pollicis  extends  the  proximal  phalanx  of  the  thumb.  By  its  continued 
action  it  helps  to  extend  and  abduct  the  wrist.  The  Extensor  longus  pollicis 
extends  the  terminal  phalanx  of  the  thumb.  By  its  continued  action  it  helps  to 
extend  and  abduct  the  wrist.    The  Extensor  indicis  extends  the  index  finger,  and 


OF    THE   HAND  49I 

by  its  continued  action  assists  in  extending  the  wrist.    It  is  owing  to  this  muscle 
that  the  intlex  finger  can  be  extended  or  pointed  while  the  others  are  flexed. 

Surgical  Anatomy. — The  tendons  of  the  extensor  muscles  of  the  thumb  are  liable  to  become 
strained  and  their  sheaths  inflamed  after  excessive  exercise,  producing  a  sausage-shaped  swell- 
ing along  the  course  of  the  tendon,  and  giving  a  peculiar  creaking  sensation  to  the  finger  when 
the  muscle  acts.  In  consequence  of  its  often  being  caused  by  such  movements  as  wringing 
clothes,  it  is  known  as  washerwoman^ s  sprain.  In  piano-players  the  slips  which  join  the  ten- 
dons of  the  Extensor  communis  digitorum  may  limit  freedom  of  motion  in  individual  fingers. 
"  When  the  middle  finger  and  little  finger  of  the  hand  are  brought  down  by  the  flexor  muscles, 
and  their  balls  are  held  down  firmly  against  the  keys  of  a  musical  instrument,  as  in  perform- 
ing on  a  piano  for  the  purjxjse  of  producing  continuous  sounds,  and  when  at  the  same  time 
it  is  necessary  to  extend  and  then  to  flex  the  ring-finger  in  order  to  produce  accompanying 
sounds,  it  will  be  found  that  in  the  still-flexed  position  of  the  middle  and  little  fingers,  the 
ring  finger  can  be  but  very  slightly  extended.  Its  complete  extension,  without  operative  mter- 
ference,  can  only  be  brought  about  by  long-continued  exertion  in  practice,  when  elongation 
of  certain  accessory,  but  restricting,  tendons  is  made  by  nutritive  growth."'  If  there  is  much 
limitation  division  of  the  hindering  slips  is  proper.  This  was  suggested  by  Prof.  William  S. 
Forbes  in  1857. 

IV.  MUSCLES  AND  FASGIiE  OF  THE  HAND. 

The  muscles  of  the  hand  are  subdivided  into  tliree  groups:  1.  Those  of  the 
thumb,  which  occupy  the  radial  side  and  produce  the  thenar  eminence.  2.  Those 
of  the  little  finger,  which  occupy  the  ulnar  side  and  give  rise  to  the  hsrpothenar 
eminence.     3.  Those  in  the  middle  of  the  palm  and  within  the  interosseous  spaces. 

Dissection  (Fig.  312). — Make  a  transverse  incision  across  the  front  of  the  wrist,  and  a 
second  across  the  heads  of  the  metacarpal  bones:  connect  the  two  by  a  vertical  incision  in  the 
middle  line,  and  continue  it  through  the  centre  of  the  middle  finger.  The  anterior  and  poste- 
rior annular  ligaments  and  the  palmar  fascia  should  then  be  dissfected. 

ANTERIOR 
ANNULAR 
LIGAMENT, 

FLEXOR  LONGus  poLLicis.  /  Median  nerve. 

FLEXOR  CARPI  RADiALis.        \  I         I       .Ulnar  vessels. 

MUSCLES    OF   THUMB.^  \  \  /  /  / fPALMARIS    BREVrS. 

MUSCLES   OF 
^^^^^^^^  _        ^y  LITTLE 

1st  MetacarmlXi<lMB^''i^^B^^^^h--'-^~^~^-':^iiS)/f^^^^k^^Fi  n g e r. 


EXT.    PRIM 
INTERNOO 

POLL.  _ _  _  

EXT.    CARPI 

EXT.  SEC.  >i^:^^»>,^rN  i.tiTJ^^:  Sill  ■J'Jmry^'jf'.^  i-A^f&Hi.i'v^'y^AV/'^  ulnaris. 

INTERNOD. 
POLL. 

Trapezium."        /^'^^^^!>?tf.5ji|  W '^^'V-X'r*'s."%^^^^i^'<TENSOR 
Radial  vessels.    /  ^"^'^^^^^^^^L^fj^^^^^^^  digiti. 

EXT.   CARP.    RAD.    LONG.     X^^^^^^^^^^^^'^v  EXTENSOR 

Trapezoid.  /7      T~^^        ^communis 

/       /       I  digitorum. 

EXTENSOR    carpi    RADIALIs/  /      EXTENSOR    INDICIS. 


BREVIOR 


Os  magnum. 


Fig.  325. — Transverse  section  through  the  carpus,  showing  the  relative  positions  of  the  tendons,  vessels, 

and  nerves.     (Henle.) 

The  Ligamentum  Carpi  Volare  is  a  thickening  of  the  deep  fascia  of  the  forearm 
(fascia  antibrachii)  by  deep  fibres  just  above  the  wrist  (Fig.  330).  It  covers  the 
flexor  muscles  and  joins  the  anterior  annular  ligament. 

The  Anterior  Annular  Ligament  (ligamentum  carpi  transversum)  (Fig.  325)  is  a 
strong,  fibrous  band  which  arches  over  the  carpus,  converting  the  deep  groove 
on  the  front  of  the  carpal  bones  into  a  canal,  beneath  which  pass  the  flexor 
tendons  of   the  fingers.     It  is  attached,  internally,  to  the  pisiform  bone   and 

1  Prof.  WiUiam  S.  Forbes  in  the  Philadelphia  Medical  Journal,  January  15,  1898. 


492 


THE   3fUSCLES    AND    FASCIA 


the  hook  of  the  unciform  bone  {eminentia  carpi  ulnaris),  and  externally  to  the 
tuberosity  of  the  scaphoid  and  to  the  inner  part  of  the  anterior  surface  and 
the  ridge  of  the  trapezium  {eminentia  carpi  radialis).  It  is  continuous,  above, 
with  the  deep  fascia  of  the  forearm,  of  which  it  may  be  regarded  as  a  thickened 
portion,  and,  below,  with  the  palmar  fascia.  It  is  crossed  by  the  ulnar  vessels  and 
nerve  and  the  cutaneous  branches  of  the  median  and  ulnar  nerves.  At  its  outer 
extremity  is  the  tendon  of  the  Flexor  carpi  radialis,  which  lies  in  the  groove  on  the 

trapezium  between  the  attachments  of 
the  annular  ligaments  to  the  bone.  It 
has  inserted  into  its  anterior  surface  a 
part  of  the  tendon  of  the  Palmaris  longus 
and  part  of  the  tendon  of  the  Flexor 
carpi  ulnaris,  and  has  arising  from  it, 
below,  the  small  muscles  of  the  thumb 
and  little  finger.  Beneath  it  pass  the 
tendons  of  the  Flexor  sublimis  and  Pro- 
fundus digitorum,  the  Flexor  longus 
pollicis,  and  the  median  nerve. 

The  Synovial  Membranes  of  the  Flexor 
Tendons  at  the  Wrist. — ^There  are  two 
vaginal  synovial  membranes  which  en- 
close all  the  tendons  as  they  pass  be- 
neath this  ligament — one  for  the  Flexor 
sublimis  and  Profundus  digitorum,  the 
other  for  the  Flexor  longus  pollicis. 
They  extend  up  into  the  forearm  for 
about  an  inch  above  the  annular  liga- 
ment, and  downward  about  half-way 
along  the  metacarpal  bone,  where  they 
terminate  in  a  blind  diverticulum  around 
each  pair  of  tendons,  with  the  exception 
of  that  of  the  thumb  and  those  of  the 
little  finger — in  each  of  these  two  digits  the  diverticulum  is  continued  on,  and 
communicates  with  the  synovial  sheath  of  the  tendons  in  the  fingers.  In  the  other 
three  fingers  the  synovial  sheath  of  the  tendons  begins  as  a  blind  pouch  without 
communication  with  the  large  synovial  sac  (Fig.  326). 

Surgical  Anatomy. — This  arrangement  of  the  synovial  sheaths  explains  the  fact  that  thecal 
abscess  in  the  thumb  and  little  finger  is  liable  to  be  followed  by  abscesses  in  the  forearm,  from 
extension  of  the  inflammation  along  the  continuous  synovial  sheaths.  Tuberculous  inflamma- 
tion is  apt  to  occur  in  this  situation,  constituting  compound  palmar  ganglion ;  it  presents  an  hour- 
glass outline,  with  a  swelling  in  front  of  the  wrist  and  in  the  palm  of  the  hand,  and  a  constriction 
corresponding  to  the  annular  ligament  between  the  two.  The  fluid  can  be  forced  from  the  one 
swelling  to  the  other  under  the  ligament. 

Bursae  about  the  Hand  and  Wrist. — Bursse  usually  exist  between  the  distal 
extremities  of  the  metacarpal  bones  (burses  intermetacarpophalangece) ,  and  a  sub- 
cutaneous bursa  often  exists  over  the  dorsal  surface  of  the  head  of  the  fifth 
metacarpal  bone.  Subcutaneous  digital  dorsal  bursse  occur  "  almost  constantly 
in  the  first  finger-joints  (between  the  first  and  second  phalanx),  occasionally  in 
the  second  joint  of  the  second  and  fourth  fingers"^  (bursce  subcutanece  digitorum 
dorsales).  A  bursa  exists  between  the  tendon  of  the  Extensor  carpi  radialis 
brevior  and  the  base  of  the  third  metacarpal  bone;  another  between  the  Flexor 
carpi  ulnaris  and  the  pisiform  bone;  another  between  the  Flexor  carpi  radialis 
and  the  base  of  the  second  metacarpal  bone. 

1  Hand  Atlas  of  Human  Anatomy.    By  Werner  Spalteholz.  Translated  and  edited  by  Lewellys  F.  Barker. 


Fia.  326. — Diagram  showing  the  arrangement  of  the 
synovial  sheaths  of  the  palm  and  fingers. 


OF    THE   HAND  493 

The  Posterior  Annulax  Ligament  (ligamentum  carpi  dorsale)  is  a  strong  fibrous 
band  extending  obliquely  downward  and  inward  across  the  back  of  the  wrist,  and 
consisting  of  the  deep  fascia  of  the  back  of  the  forearm,  strengthened  by  the 
addition  of  some  transverse  fibres.  It  binds  down  the  extensor  tendons  in  their 
passage  to  the  fingers,  being  attached,  internally,  to  the  styloid  process  of  the  ulna, 
the  cuneiform  and  pisiform  bones;  externally,  to  the  margin  of  the  radius;  and,  in 
its  passage  across  the  wrist,  to  the  elevated  ridges  on  the  posterior  surface  of  the 
radius.  It  presents  six  compartments  for  the  passage  of  tendons,  each  of  which  is 
lined  by  a  separate  synovial  membrane 

(Fig.  327).    These  are,  from  without      ,^  ^^-'^^SM^ 

inward:  1.  On  the  outer  side  of  the 
styloid  process,  for  the  tendons  of  the 
Extensor  ossis  metacarpi  and  Extensor 
brevis  pollicis.  2.  Behind  the  styloid 
process,  for  the  tendons  of  the  Ex- 
tensor carpi  radialis  longior  and  bre- 
vior.  3.  About  the  middle  of  the 
posterior  surface  of  the  radius,  for  the 
tendon  of  the  Extensor  longus  pollicis. 

4.  To  the  inner  side  of  the  latter,  for  -"".  uln.«-^--     •-"«.    l?^^^^f-^V  ^^^  ^       ^^ 

the  tendons  of  the  Extensor  communis      ^     „„,     ^  ! """°'®"  ' 

...  ^     -r\  •      T    •  p-  *"'•  ^^'- — Transverse  section  through  the  wrist,  show- 

dlgltorum    and     Extensor    mdlClS.       5.    ing  the  annular  ligaments  and  the  canals  for  the  passage 

Opposite   the    interval    between   the 

radius  and  ulna,  for  the  Extensor  minimi  digiti.     6.  Grooving  the  back  of  the 

ulna,  for  the  tendon  of  the  Extensor  carpi  ulnaris.     The  synovial  membranes 

lining  these  sheaths  are  usually  very  extensive,  reaching  from  above  the  annular 

ligament  down  upon  the  tendons  for  a  variable  distance  on  the  back  of  the 

hand. 

The  Deep  Palmar  Fascia  (aponeurosis  palmaris). — The  deep  palmar  fascia 
(Fig.  32S)  forms  a  common  sheath  which  invests  the  muscles  of  the  hand. 
It  consists  of  a  central  and  two  lateral  portions. 

The  Central  Portion  occupies  the  middle  of  the  palm,  is  triangular  in  shape,  of 
great  strength  and  thickness,  and  binds  down  the  tendons  and  protects  the  vessels 
and  nerves  in  this  situation.  It  is  narrow  above,  where  it  is  attached  to  the  lower 
margin  of  the  annular  ligament,  and  receives  the  expanded  tendon  of  the  Pal- 
maris longus  muscle.  Below,  it  is  broad  and  expanded,  and  divides  into  four 
slips  for  the  four  fingers.  Each  slip  gives  off  superficial  fibres,  which  are  inserted 
into  the  skin  of  the  palm  and  finger,  those  to  the  palm  joining  the  skin  at  the 
furrow  corresponding  to  the  metacarpo-phalangeal  articulation,  and  those  to  the 
fingers  passing  into  the  skin  at  the  transverse  fold  at  the  base  of  the  fingers.  The 
deeper  part  of  each  slip  subdivides  into  two  processes,  which  are  inserted  into  the 
lateral  margins  of  the  anterior  (glenoid)  ligament  of  the  metacarpo-phalangeal 
joint.  From  the  sides  of  these  processes  offsets  are  sent  backward,  to  be  attached 
to  the  borders  of  the  lateral  surfaces  of  the  metacarpal  bones  at  their  distal  extrem- 
ities. By  this  arrangement  short  channels  are  formed  on  the  front  of  the  lower 
ends  of  the  metacarpal  bones,  through  which  the  flexor  tendons  pass.  Dr.  W.  W. 
Keen  describes  a  fifth  slip  as  frequently  found  passing  to  the  thumb.  The  inter- 
vals left  in  the  fascia  between  the  four  fibrous  slips  transmit  the  digital  vessels 
and  nerves  and  the  tendons  of  the  Lumbricales.  At  the  points  of  division  of  the 
palmar  fascia  into  the  slips  above  mentioned  numerous  strong,  transverse  fibres 
bind  the  separate  processes  together.  The  palmar  fascia  is  intimately  adherent 
to  the  integument  by  dense  fibro-areolar  tissue,  forming  the  superficial  palmar 
fascia,  and  gives  origin  by  its  inner  margin  to  the  Palmaris  brevis:  it  covers  the 
superficial  palmar  arch,  the  tendons  of  the  flexor  muscles,  and  the  branches  of 


494 


THE  MUSCLES  AND    FASCIA 


the  median  and  ulnar  nerves,  and  on  each  side  it  gives  off  a  vertical  septum,  which 
is  continuous  with  the  interosseous  aponeurosis  and  separates  the  lateral  from 
the  middle  palmar  group  of  muscles. 

The  Lateral  Portions  of  the  Palmar  Fascia  are  thin,  fibrous  layers,  which  cover, 
on  the  radial  side,  the  muscles  of  the  ball  of  the  thumb,  and,  on  the  ulnar  side,  the 
muscles  of  the  little  finger;  they  are  continuous  with  the  dorsal  fascia,  and  in  the 
palm  with  the  central  portion  of  the  palmar  fascia. 


Digital  artery 
Digital  nerves. 


Fig.  328. — Palmar  fascia.     (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 


The  Superficial  Transverse  Ligament  of  the  Fingers  is  a  thin,  fibrous  band  which 
stretches  across  the  roots  of  the  four  fingers,  and  is  closely  attached  to  the  skin 
of  the  clefts,  and  internally  to  the  fifth  metacarpal  bone,  forming  a  sort  of  rudi- 
mentary web.  Beneath  it  the  digital  vessels  and  nerves  pass  onward  to  their 
destination. 

Surgical  Anatomy. — The  palmar  fascia  is  liable  to  undergo  contraction,  producing  a  very 
inconvenient  deformity  known  as  Dupuytren's  contraction.  The  ring  and  little  fingers  are  most 
frequently  implicated,"but  the  middle,  index,  and  the  thumb  may  be  involved.  The  proximal 
phalanx  is  drawn  down  and  cannot  be  straightened,  and  the  two  distal  phalanges  become  simi- 
larly flexed  as  the  disease  advances. 


THE   BADIAL    REGION 


495 


11.  The  Radial  Region  (Figs.  329,  330). 


Abductor  pollicis. 
Opponens  pollicis. 


Flexor  brevis  pollicis. 
Adductor  obliquus  pollicis. 


Adductor  transversus  pollicis. 

The  Abductor  Pollicis  (m.  abductor  'pollicis  brevis)  (Fig.  330)  is  a  thin,  flat 
muscle,  placed  immediately  beneath  the  integument.  It  arises  from  the  anterior 
annular  ligament,  the  tuberosity  of  the  scaphoid,  and  the  ridge  of  the  trapezium, 


Fig.  329. — -Adductor  pollicis,  Opponens  pollicis,  and  Pronator  quadratus.     (Testut.) 

frequently  by  two  distinct  slips;  and,  passing  outward  and  downward,  is  inserted 
by  a  thin,  flat  tendon  into  the  radial  side  of  the  base  of  the  first  phalanx  of  the 
thumb,  sending  a  slip  to  join  the  tendon  of  the  Extensor  longus  pollicis. 


496  THE   MUSCLES  AND    FASCIA 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia  and  siiperficialis 
voloe  artery,  which  frequently  perforates  it.  By  its  deep  surface,  with  the  Opponens 
pollicis,  from  which  it  is  separated  by  a  thin  aponeurosis.  Its  inner  border  is 
separated  from  the  Flexor  brevis  pollicis  by  a  narrow  cellular  interval. 


Fig.  330. — Muscles  of  the  left  hand.     Palmar  surface. 


The  Opponens  Pollicis  (Figs.  329  and  330),  often  called  the  flexor  ossis  meta- 
carpi  pollicis,  is  a  small,  triangular  muscle,  placed  beneath  the  preceding.  It  arises 
from  the  palmar  surface  of  the  ridge  on  the  trapezium  and  from  the  annular 
ligament,  passes  downward  and  outward,  and  is  inserted  into  the  whole  length  of 
the  metacarpal  bone  of  the  thumb  on  its  radial  side. 


THE   RADIAL   REGION  497 

Relations. — By  its  superficial  surface,  with  the  Abductor  and  Flexor  brevis 
polHcis.  By  its  deep  surface,  with  the  trapezio-metacarpal  articulation.  By  its 
inner  border,  with  the  Adductor  obliquus  pollicis. 

The  Flexor  Brevis  Pollicis  (m.  flexor  pollicis  brevis)  (Fig.  330)  consists  of  two 
portions,  outer  and  inner.  The  outer  and  more  superficial  portion  arises  from  the 
outer  two-thirds  of  the  lower  border  of  the  anterior  annular  ligament,  and  passes 
along  the  outer  side  of  the  tendon  of  the  Flexor  longus  pollicis;  and,  becoming 
tendinous,  has  a  sesamoid  bone  developed  in  its  tendon,  and  is  inserted  into  the 
outer  side  of  the  base  of  the  first  phalanx  of  the  thumb.  The  inner  and  deeper 
portion  of  the  muscle  is  very  small,  and  arises  from  the  ulnar  side  of  the  first 
metacarpal  bone  beneath  the  Adductor  obliquus  pollicis,  and  is  inserted  into  the 
inner  side  of  the  base  of  the  first  phalanx  with  this  muscle. 

Relations. — By  its  superficial  surface,  with  the  palmar  fascia.  By  its  deep  sur- 
face, with  the  tendon  of  the  Flexor  longus  pollicis.  By  its  external  surface,  with 
the  Opponens  pollicis.    Behind,  with  the  Adductor  obliquus  poUicis. 

The  Adductor  Obliquus  Pollicis  (m.  adductor  pollicis)  (Figs.  329  and  330) 
arises  by  several  slips  from  the  os  magnum,  the  bases  of  the  second  and  third 
metacarpal  bones,  the  anterior  carpal  ligaments,  and  the  sheath  of  the  tendon 
of  the  Flexor  carpi  radialis.  From  this  origin  the  greater  number  of  fibres 
pass  obliquely  downward  and  converge  to  a  tendon,  which,  uniting  with  the 
tendons  of  the  deeper  portion  of  the  Flexor  brevis  pollicis  and  the  Adductor 
transversus,  is  inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  of  the 
thumb,  a  sesamoid  bone  being  developed  in  the  tendon  of  insertion.  A  consid- 
erable fasciculus,  however,  passes  more  obliquely  outward  beneath  the  tendon 
of  the  long  flexor  to  join  the  superficial  portion  of  the  short  flexor  and  the 
Abductor  pollicis.^ 

Relations. — By  its  superficial  surface,  with  the  Flexor  longus  pollicis  and  the 
outer  head  of  the  Flexor  brevis  pollicis.  Its  deep  surfdce  is  in  relation  with  the 
deep  palmar  arch,  which  passes  between  the  two  adductors. 

The  Adductor  Transversus  Pollicis  (Figs.  329  and  330)  is  the  most  deeply 
seated  of  this  group  of  muscles.  It  is  of  a  triangular  form,  arising,  by  its  broad 
base,  from  the  lower  two-thirds  of  the  metacarpal  bone  of  the  middle  finger  on 
its  palmar  surface;  the  fibres,  proceeding  outward,  converge  to  be  inserted,  with 
the  inner  part  of  the  Flexor  brevis  pollicis,  and  the  Adductor  obhquus  pollicis, 
into  the  ulnar  side  of  the  base  of  the  first  phalanx  of  the  thumb.  From  the 
common  tendon  of  insertion  a  slip  is  prolonged  to  the  Extensor  longus  pollicis. 
The  name  adductor  pollicis  is  frequently  used  to  mean  both  of  the  adductors 
(Figs.  329  and  3.30). 

Relations. — By  its  superficial  surface,  with  the  Adductor  obliquus  pollicis,  the 
tendons  of  the  Flexor  profundus,  and  the  Lumbricales.  Its  deep  surface  covers 
the  first  two  interosseous  spaces,  from  which  it  is  separated  by  a  strong  aponeu- 
rosis. 

Three  of  these  muscles  of  the  thumb,  the  Abductor,  the  Adductor  transversus, 
and  the  Flexor  brevis  pollicis,  at  their  insertions  give  off  fibrous  expansions  which 
join  the  tendon  of  the  Extensor  longus  pollicis.  This  permits  of  flexion  of  the 
proximal  phalanx  and  extension  of  the  terminal  phalanx  at  the  same  time.  These 
expansions,  originally  figured  by  Albinus,  have  been  more  recently  described  by 
M.  Duchenne.^ 

Nerves. — ^The  Abductor,  Opponens,  and  outer  head  of  the  Flexor  brevis  pollicis 
are  supplied  by  the  sixth  cervical  through  the  median  nerve;  the  inner  head  of  the 
Flexor  brevis,  and  the  Adductors,  by  the  eighth  cervical  through  the  ulnar  nerve. 

*  This  muscle  is  described  by  some  as  the  deep  portion  of  the  Flexor  brevis  pollicis. 
^  Physiologie  des  Mouvements. 

32 


498  THE  MUSCLES  AND   FASCIA 

Actions. — The  actions  of  the  muscles  of  the  thumb  are  almost  sufficiently  indi- 
cated by  their  names.  This  segment  of  the  hand  is  provided  with  three  extensors 
— an  extensor  of  the  metacarpal  bone,  an  extensor  of  the  first,  and  an  extensor  of 
the  second  phalanx;  these  occupy  the  dorsal  surface  of  the  forearm  and  hand. 
There  are  also  three  flexors  on  the  palmar  surface — a  flexor  of  the  metacarpal 
bone,  a  flexor  of  the  proximal,  and  a  flexor  of  the  terminal  phalanx;  there  is  also 
an  Abductor  and  two  Adductors.  The  Abductor  pollicis  moves  the  metacarpal 
bone  of  the  thumb  outward;  that  is,  away  from  the  index  finger.  The  Flexor 
ossis  metacarpi  pollicis  flexes  the  metacarpal  bone — that  is,  draws  it  inward  over 
the  palm — and  at  the  same  time  rotates  the  bone,  so  as  to  turn  the  ball  of  the 
thumb  toward  the  fingers,  thus  producing  the  movement  of  opposition.  The 
Flexor  brevis  pollicis  flexes  and  adducts  the  proximal  phalanx  of  the  thumb.  The 
Adductores  pollicis  move  the  metacarpal  bone  of  the  thumb  inward;  that  is, 
toward  the  index  finger.  These  muscles  give  to  the  thumb  its  extensive  range  of 
motion.  It  will  be  noticed,  however,  that  in  consequence  of  the  position  of  the 
first  metacarpal  bone,  these  movements  differ  from  the  corresponding  movements 
of  the  metacarpal  bones  of  the  other  fingers.  Thus  extension  of  the  thumb  more 
nearly  corresponds  to  the  motion  of  abduction  in  the  other  fingers,  and  flexion  to 
adduction. 

12.  The  Ulnar  Region  (Fig.  330). 

Palmaris  brevis.  Flexor  brevis  minimi  digiti. 

Abductor  minimi  digiti.  Opponens  minimi  digiti. 

The  Palmaris  Brevis  is  a  thin  quadrilateral  muscle  placed  beneath  the  integu- 
ment on  the  ulnar  side  of  the  hand.  It  arises  by  tendinous  fasciculi  from  the 
anterior  annular  ligament  and  palmar  fascia;  the  fleshy  fibres  pass  inward,  to  be 
inserted  into  the  skin  on  the  inner  border  of  the  palm  of  the  hand. 

Relations. — By  its  superficial  surface,  with  the  integument,  to  which  it  is  inti- 
mately adherent,  especially  by  its  inner  extremity;  by  its  deep  surface,  with  the 
inner  portion  of  the  palmar  fascia,  which  separates  it  from  the  ulnar  vessels  and 
nerve,  and  from  the  muscles  of  the  ulnar  side  of  the  hand. 

The  Abductor  Minimi  Digiti  (m.  abductor  digiti  quinti)  is  situated  on  the  ulnar 
border  of  the  palm  of  the  hand.  It  arises  from  the  pisiform  bone  and  from  the 
tendon  of  the  Flexor  carpi  ulnaris,  and  terminates  in  a  flat  tendon,  which  divides 
into  two  slips;  one  is  inserted  into  the  ulnar  side  of  the  base  of  the  first  phalanx 
of  the  little  finger.  The  other  slip  is  inserted  into  the  ulnar  border  of  the  aponeu- 
rosis of  the  Extensor  minimi  digiti. 

Relations. — By  its  superficial  surface,  with  the  inner  portion  of  the  palmar  fascia 
and  the  Palmaris  brevis;  by  its  deep  surface,  with  the  Opponens  minimi  digiti; 
by  its  outer  border,  with  the  Flexor  brevis  minimi  digiti. 

The  Flexor  Brevis  Minimi  Digiti  (m.  fiexor  digiti  quinti  brevis)  lies  on  the  same 
plane  as  the  preceding  muscle,  on  its  radial  side.  It  arises  from  the  convex  aspect 
of  the  hook  of  the  unciform  bone  and  anterior  surface  of  the  annular  ligament, 
and  is  inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  of  the  little  finger. 
It  is  separated  from  the  Abductor  at  its  origin  by  the  deep  branches  of  the  ulnar 
artery  and  nerve.  This  muscle  is  sometimes  wanting;  the  Abductor  is  then, 
usually,  of  large  size. 

Relations. — By  its  superficial  surface,  with  the  internal  portion  of  the  palmar 
fascia  and  the  Palmaris  brevis ;  by  its  deep  surface,  with  the  Opponens.  The  deep 
branch  of  the  ulnar  artery  and  the  corresponding  branch  of  the  ulnar  nerve  pass 
between  the  Abductor  and  Flexor  brevis  minimi  digiti  muscles. 

The  Opponens  Minimi  Digiti  {m.  opponens  digiti  quinti).— T\\\s  muscle  is 
sometimes  called  the  flexor  ossis  metacarpi  (Fig.  320),  is  of  a  triangular  form,  and 
placed  immediately  beneath  the  preceding  muscles.    It  arises  from  the  convexity 


THE   MIDDLE   PALMAR    REGION  499 

of  the  hook  of  the  unciform  bone  and  the  contiguous  portion  of  the  anterior 
annular  ligament;  its  fibres  pass  downward  and  inward,  to  be  inserted  into  the 
whole  length  of  the  metacarpal  bone  of  the  little  finger,  along  its  ulnar  margin. 

Relations. — By  its  superficial  surface,  with  the  Flexor  brevis  and  Abductor 
minimi  digiti ;  by  its  deep  surface,  with  the  Interossei  muscles  in  the  fourth  meta- 
carpal space,  the  metacarpal  bone,  and  the  Flexor  tendons  of  the  little  finger. 

Nerves. — All  the  muscles  of  this  group  are  supplied  by  the  eighth  cervical  nerve 
through  the  ulnar  nerve. 

Actions. — ^The  Abductor  minimi  digiti  abducts  the  little  finger  from  the  middle 
line  of  the  hand.  It  corresponds  to  a  dorsal  interosseous  muscle.  It  also  assists 
in  flexing  the  proximal  phalanx  and  extending  the  second  and  third  phalanges. 
The  Flexor  brevis  minimi  digiti  abducts  the  little  finger  from  the  middle  line  of 
the  hand.  It  also  assists  in  flexing  the  proximal  phalanx.  The  Opponens  minimi 
digiti  draws  forward  the  fifth  metacarpal  bone,  so  as  to  deepen  the  hollow  of  the 
palm.  The  Palmaris  brevis  corrugates  the  skin  on  the  inner  side  of  the  palm  of 
the  hand  and  probably  serves  to  protect  the  ulnar  nerve  and  artery  from  damage 
by  the  pressure  of  grasping  a  hard  object. 

13.  The  Middle  Palmar  Region. 

Lumbricales.  Interossei  dorsales. 

Interossei  palmares. 

The  Lumbricales  (Fig.  330)  are  four  small  fleshy  fasciculi,  accessories  to  the 
deep  Flexor  muscle.  They  arise  from  the  tendons  of  the  deep  Flexor:  the  first  and 
second,  from  the  radial  side  and  palmar  surface  of  the  tendons  of  the  index  and 
middle  fingers  respectively;  the  third,  from  the  contiguous  sides  of  the  tendons  of 
the  middle  and  ring  fingers;  and  the  fourth,  from  the  contiguous  sides  of  the 
tendons  of  the  ring  and  little  fingers.  They  pass  to  the  radial  side  of  the  corre- 
sponding fingers  and  opposite  the  metacarpo-phalangeal  articulation  each  tendon 
is  inserted  into  the  tendinous  expansion  of  the  Extensor  communis  digitorum, 
covering  the  dorsal  aspect  of  each  finger. 

The  Interossei  Muscles  (Figs.  331  and  332)  are  so  named  from  occupying 
the  intervals  between  the  metacarpal  bones,  and  are  divided  into  two  sets,  dorsal 
and  palmar. 

The  Dorsal  interossei  (mm.  interossei  dorsales)  are  four  in  number,  larger  than  the 
palmar,  and  occupy  the  intervals  between  the  metacarpal  bones.  They  are  bipen- 
niform  muscles,  arising  by  two  heads  from  the  adjacent  sides  of  the  metacarpal 
bones,  but  more  extensively  from  the  metacarpal  bone  of  the  finger  into  which  the 
muscle  is  inserted.  They  are  inserted  into  the  bases  of  the  first  phalanges  and  into 
the  aponeurosis  of  the  common  Extensor  tendon.  Between  the  double  origin  of 
each  of  these  muscles  is  a  narrow  triangular  interval,  through  the  first  of  which 
passes  the  radial  artery;  through  each  of  the  other  three  passes  a  perforating 
branch  from  the  deep  palmar  arch. 

The  First  dorsal  interosseous  muscle  or  Abductor  indicis  is  larger  than  the 
others.  It  is  flat,  triangular  in  form,  and  arises  by  two  heads,  separated  by  a 
fibrous  arch,  for  the  passage  of  the  radial  artery  from  the  dorsum  to  the  palm  of 
the  hand.  The  outer  head  arises  from  the  upper  half  of  the  ulnar  border  of  the 
first  metacarpal  bone;  the  inner  head,  from  almost  the  entire  length  of  the  radial 
border  of  the  second  metacarpal  bone;  the  tendon  is  inserted  into  the  radial  side 
of  the  index  finger.  The  second  and  third  dorsal  interossei  are  inserted  into  the 
middle  finger,  the  former  into  its  radial,  the  latter  into  its  ulnar  side.  The  fourth 
is  inserted  into  the  ulnar  side  of  the  ring  finger. 

The  Palmar  interossei  {mm.  interossei  volar es),  three  in  number,  are  smaller  than 
the  Dorsal,  and  placed  upon  the  palmar  surface  of  the  metacarpal  bones,  rather 


500 


THE  MUSCLES  AND   FASCIA 


than  between  them.  Each  muscle  arises  from  the  entire  length  of  the  meta- 
carpal bone  of  one  finger,  and  is  inserted  into  the  side  of  the  base  of  the  first 
phalanx  and  aponeurotic  expansion  of  the  common  extensor  tendon  of  the  same 
finger.  The  first  arises  from  the  ulnar  side  of  the  second  metacarpal  bone,  and 
is  inserted  into  the  same  side  of  the  first  phalanx  of  the  index  finger.  The  second 
arises  from  the  radial  side  of  the  fourth  metacarpal  bone,  and  is  inserted  into  the 


Fig.  331. — The  Dorsal  interossei  of  left  hand. 


Fig.  332. — The  Palmar  interossei  of  left  hand. 


same  side  of  the  ring  finger.  The  third  arises  from  the  radial  side  of  the  fifth 
metacarpal  bone,  and  is  inserted  into  the  same  side  of  the  little  finger.  From 
this  account  it  may  be  seen  that  each  finger  is  provided  with  two  Interosseous 
muscles,  with  the  exception  of  the  little  finger,  in  which  the  Abductor  muscle 
takes  the  place  of  one  of  the  pair. 

Nerves. — The  two  outer  Lumbricales  are  supplied  by  the  sixth  cervical  nerve, 
through  the  third  and  fourth  digital  branches  of  the  median  nerve:  the  two  inner 
I^umbricales  and  all  the  Interossei  are  supplied  by  the  eighth  cervical  nerve, 
through  the  deep  palmar  branch  of  the  ulnar  nerve.  Brooks  states  that  the  third 
lumbrical  received  a  twig  from  the  median  in  twelve  out  of  twenty-one  cases. 

Actions. — The  Palmar  interossei  muscles  adduct  the  fingers  to  an  imaginary 
line  drawn  longitudinally  through  the  centre  of  the  middle  finger;  and  the  Dorsal 
interossei  abduct  the  fingers  from  that  line.  In  addition  to  this,  the  Interossei,  in 
conjunction  with  the  Lumbricales,  jiex  the  first  phalanges  at  the  metacarpo-phalan- 
geal  joints,  and  extend  the  second  and  third  phalanges  in  consequence  of  their 
insertion  into  the  expansion  of  the  extensor  tendons.  The  Extensor  communis 
digitorum  is  believed  to  act  almost  entirely  on  the  first  phalanges. 


SURFACE  FORM  OF  THE  UPPER  EXTREMITY. 

The  Pectoralis  major  muscle  largely  influences  surface  form  and  conceals  a  considerable  part 
oi  the  thoracic  wall  in  front.  Its  sternal  origin  presents  a  festooned  border  which  bounds  and 
determines  the  width  of  the  sternal  furrow.  Its  clavicular  origin  is  somewhat  depressed  and  flat- 
tened, and  between  the  two  portions  of  the  muscle  is  often  an  oblique  depression  which  differen- 
tiates the  one  from  the  other.  The  outer  margin  of  the  muscle  is  generally  well  marked  above, 
and  bounds  the  infraclavicular  fossa,  a  triangular  interval  which  separates  the  Pectoralis  major 


SURFACE  FORM   OF  THE    UPPER   EXTREMITY  501 

from  the  Deltoid.  It  gradually  becomes  less  marked  as  it  approaches  the  tendon  of  insertion, 
and  becomes  more  closely  blended  with  the  Deltoid  muscle.  The  lower  border  of  the  Pectoralis 
major  forms  the  rounded  anterior  axillary  fold,  and  corresponds  with  the  direction  of  the  fifth  rib. 
The  Pectoralis  minor  muscle  influences  surface  form.  When  the  arm  is  raised  its  lowest  shp 
of  origin  produces  a  local  fulness  just  below  the  border  of  the  anterior  fold  of  the  axilla,  and  so 
serves  to  break  the  sharp  line  of  the  lower  border  of  the  Pectoralis  major  muscle,  which  is  pro- 
duced when  the  arm  is  in  this  position.  The  origin  of  the  SerratUS  magnus  muscle  produces  a 
very  characteristic  surface  marking.  When  the  arm  is  raised  from  the  side  in  a  well-developed 
subject,  the  five  or  six  lower  serrations  are  plainly  discernible,  forming  a  zigzag  line,  caused  by 
the  series  of  digitations,  which  diminish  in  size  from  above  downward,  and  have  their  apices 
arranged  in  the  form  of  a  curve.  W^hen  the  arm  is  lying  by  the  side,  the  first  serration  to 
appear,  at  the  lower  margin  of  the  Pectoralis  major,  is  the  one  attached  to  the  fifth  rib.  The 
Deltoid  muscle,  with  the  prominence  of  the  upper  extremity  of  the  humerus,  produces  the 
rounded  outline  of  the  shoulder.  It  is  rounder  and  fuller  in  front  than  behind,  where  it  presents 
a  somewhat  flattened  form.  Its  anterior  border,  above,  presents  a  rounded,  slightly  curved 
eminence,  which  bounds  externally  the  infraclavicular  fossa;  below,  it  is  closely  united  with  the 
Pectoralis  major.  Its  posterior  border  is  thin,  flattened,  and  scarcely  marked  above;  below,  it 
is  thicker  and  more  prominent.  When  the  muscle  is  in  action,  the  middle  portion  becomes 
irregular,  presenting  alternate  longitudinal  elevations  and  depressions,  the  elevations  correspond- 
ing to  the  fleshy  portions,  the  depressions  to  the  tendinous  intersections  of  the  muscle.  The 
insertion  of  the  Deltoid  is  marked  by  a  depression  on  the  outer  side  of  the  middle  of  the  arm. 
Of  the  scapular  muscles,  the  only  one  which  materially  influences  surface  form  is  the  Teres 
major,  which  assists  the  Latissimus  dorsi  in  forming  the  thick,  rounded  fold  of  the  posterior 
boundary  of  the  axilla.  When  the  arm  is  raised,  the  Goraco-brachialis  reveals  itself  as  a  long, 
narrow  elevation  which  emerges  from  under  cover  of  the  anterior  fold  of  the  axilla  and  runs 
downward,  internal  to  the  shaft  of  the  humerus.  When  the  arm  is  hanging  by  the  side,  its 
front  and  inner  part  presents  the  prominence  of  the  Biceps,  bounded  on  either  side  by  an  inter- 
muscular depression.  This  muscle  determines  the  contour  of  the  front  of  the  arm,  and  extends 
from  the  anterior  margin  of  the  axilla  to  the  bend  of  the  elbow.  Its  upper  tendons  are  con- 
cealed by  the  Pectoralis  major  and  the  Deltoid,  and  its  lower  tendon  sinks  into  the  space  at  the 
bend  of  the  elbow.  When  the  muscle  is  in  a  state  of  complete  contraction — that  is  to  say, 
when  the  forearm  has  been  flexed  and  supinated — it  presents  a  rounded  convex  form,  bulged 
out  laterally,  and  its  length  is  diminished.  On  each  side  of  the  Biceps,  at  the  lower  part  of 
the  arm,  the  Brachialis  anticus  is  discernible.  On  the  outer  side  it  forms  a  narrow  eminence 
which  extends  some  distance  up  the  arm  along  the  border  of  the  Biceps.  On  the  inner  side  it 
shows  itself  only  as  a  little  fulness  just  above  the  elbow.  On  the  back  of  the  arm  the  long  head 
of  the  Triceps  may  be  seen  as  a  longitudinal  eminence  emerging  from  under  cover  of  the  Deltoid, 
and  gradually  merging  into  the  longitudinal  flattened  plane  of  the  tendon  of  the  muscle  on  the 
lower  part  of  the  back  of  the  arm.  The  tendon  of  insertion  of  the  muscle  extends  about  half- 
way up  the  back  of  the  arm,  where  it  forms  an  elongated  flattened  plane  when  the  muscle  is  in 
action.  Under  similar  conditions  the  surface  forms  produced  by  the  three  heads  of  the  muscle 
are  well  seen.  On  the  anterior  aspect  of  the  elbow  are  to  be  seen  two  muscular  elevations, 
one  on  each  side,  separated  above  and  converging  below  so  as  to  form  a  triangular  space. 
Of  these,  the  inner  elevation,  consisting  of  the  flexors  and  pronator,  forms  the  prominence 
along  the  inner  side  and  front  of  the  forearm.  It  is  a  fusiform  mass,  pointed  above  at  the 
internal  condyle  and  gradually  tapering  off  below.  The  Pronator  radii  teres,  the  innermost 
muscle  of  the  group,  forms  the  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It 
is  shorter,  less  prominent,  and  more  oblique  than  the  outer  boundary.  The  most  prominent 
part  of  the  eminence  is  produced  by  the  Flexor  carpi  radialis,  the  muscle  next  in  order  on  the 
inner  side  of  the  preceding  one.  It  forms  a  rounded  prominence  above,  and  can  be  traced 
downward  to  its  tendon,  which  can  be  felt  lying  on  the  front  of  the  wrist,  nearer  to  the  radial 
than  to  the  ulnar  border,  and  to  the  inner  side  of  the  radial  artery.  The  Palmaris  long^s  pre- 
sents no  surface  marking  above,  but  below  is  the  most  prominent  tendon  on  the  front  of  the 
wrist,  standing  out,  when  the  muscle  is  in  action,  as  a  sharp,  tense  cord  beneath  the  skin.  The 
Flexor  sublimis  digitorum  does  not  directly  influence  surface  form.  The  position  of  its  four 
tendons  on  the  front  of  the  lower  part  of  the  forearm  is  indicated  by  an  elongated  depression 
between  the  tendons  of  the  Palmaris  longus  and  the  Flexor  carpi  ulnaris.  The  Flexor  carpi 
ulnaris  occupies  a  small  part  of  the  posterior  surface  of  the  forearm,  and  is  separated  from  the 
extensor  and  supinator  group,  which  occupies  the  greater  part  of  this  surface,  by  the  ulnar 
furrow,  produced  by  the  subcutaneous  posterior  border  of  the  ulna.  Its  tendon  can  be  perceived 
along  the  ulnar  border  of  the  front  of  the  forearm,  and  is  most  marked  when  the  hand  is  flexed 
and  adducted.  The  deep  muscles  of  the  front  of  the  forearm  have  no  direct  influence  on  sur- 
face form.  The  external  group  of  muscles  of  the  forearm,  consisting  of  the  extensors  and  supi- 
nators, occupy  the  outer  and  a  considerable  portion  of  the  posterior  surface  of  this  region.  It 
has  a  fusiform  outline,  which  is  altogether  on  a  higher  level  than  the  pronato-flexor  group.  Its 
apex  emerges  from  between  the  Triceps  and  Brachialis  anticus  muscles  some  distance  above  the 


502  THE  MUSCLES   AND    FASCIA 

elbow-joint,  and  acquires  its  greatest  breadth  opposite  the  external  condyle,  and  thence  gradually 
shades  off  into  a  flattened  surface.  About  the  middle  of  the  forearm  it  divides  into  two 
longitudinal  eminences  which  diverge  from  each  other,  leaving  a  triangular  interval  between 
them.  The  outer  of  these  two  groups  of  muscles  consists  of  the  Supinator  longus  and  the 
Extensor  carpi  radialis  longior  et  brevior,  which  form  a  longitudinal  eminence  descending  from 
the  external  condylar  ridge  in  the  direction  of  the  styloid  process  of  the  radius.  The  other  and 
more  posterior  group  consists  of  the  Extensor  communis  digitorum,  the  Extensor  minimi  digiti, 
and  the  Extensor  carpi  ulnaris.  It  commences  above  as  a  tapering  form  at  the  external  con- 
dyle of  the  humerus,  and  is  separated  behind  at  its  upper  part  from  the  Anconeus  by  a  well- 
marked  furrow,  and  below,  from  the  pronato-flexor  mass,  by  the  ulnar  furrow.  In  the  triangular 
interval  left  between  these  two  groups  the  extensors  of  the  thumb  and  index  finger  are  seen. 
The  only  two  muscles  of  this  region  which  require  special  mention  as  independently  influencing 
surface  form  are  the  Supinator  longus  and  the  Anconeus.  The  inner  border  of  the  Supinator 
longus  forms  the  outer  boundary  of  the  triangular  space  at  the  bend  of  the  elbow.  It  com- 
mences as  a  rounded  border  above  the  condyle,  and  is  longer,  less  oblique,  and  more  prominent 
than  the  inner  boundary.  Lower  down,  the  muscle  forms  a  full  fleshy  mass  on  the  outer  side  of 
the  upper  part  of  the  forearm,  and  below  tapers  into  a  tendon,  which  may  be  traced  down  to 
the  styloid  process  of  the  radius.  The  Anconeus  presents  a  well-marked  and  characteristic 
surface  form  in  the  shape  of  a  triangular,  slightly  elevated  surface,  immediately  external  to  the 
subcutaneous  posterior  surface  of  the  olecranon,  and  differentiated  from  the  common  extensor 
group  by  a  well-marked  oblique  longitudinal  depression.  The  upper  angle  of  the  triangle  corre- 
sponds to  the  external  condyle,  and  is  marked  by  a  depression  or  dimple  in  this  situation.  In 
the  interval  caused  by  the  divergence  from  each  other  of  the  two  groups  of  muscles  into  which 
the  extensor  and  supinator  group  is  divided  at  the  lower  part  of  the  forearm  an  oblique  elongated 
eminence  is  seen,  caused  by  the  emergence  of  two  of  the  extensors  of  the  thumb  from  their 
deep  origin  at  the  back  of  the  forearm.  This  eminence,  full  above  and  becoming  flattened 
out  and  partially  subdivided  below,  runs  downward  and  outward  over  the  back  and  outer  sur- 
face of  the  radius  to  the  outer  side  of  the  wrist-joint,  where  it  forms  a  ridge,  especially  marked 
when  the  thumb  is  extended,  which  passes  onward  to  the  posterior  aspect  of  the  thumb.  The 
tendons  of  most  of  the  extensor  muscles  are  to  be  seen  and  felt  at  the  level  of  the  wrist-joint. 
Most  externally  are  the  tendons  of  the  Extensor  ossis  metacarpi  pollicis  and  the  Extensor  brevis 
poUicis,  forming  a  vertical  ridge  over  the  outer  side  of  the  joint  from  the  styloid  process  of  the 
radius  to  the  thumb.  Internal  to  this  is  the  oblique  ridge  produced  by  the  tendon  of  the  Exten- 
sor longus  pollicis,  very  noticeable  when  the  muscle  is  in  action.  The  Extensor  carpi  radialis 
longior  is  scarcely  to  be  felt,  but  the  Extensor  carpi  radialis  brevior  can  be  distinctly  perceived 
as  a  vertical  ridge  emerging  from  under  the  inner  border  of  the  tendon  of  the  Extensor  longus 
pollicis,  when  the  hand  is  forcibly  extended  at  the  wrist.  Internal  to  this,  again,  can  be  felt 
the  tendons  of  the  Extensor  indicis.  Extensor  communis  digitorum,  and  Extensor  minimi  digiti; 
the  latter  tendon  being  separated  from  those  of  the  common  extensor  by  a  slight  furrow.  The 
muscles  of  the  hand  are  principally  concerned,  as  far  as  regards  surface-form,  in  producing 
the  thenar  and  hjrpothenar  eminences,  and  individually  are  not  to  be  distinguished,  on  the  sur- 
face, from  each  other.  The  Adductor  trans versus  pollicis  is,  however,  an  exception  to  this; 
its  anterior  border  gives  rise  to  a  ridge  across  the  web  of  skin  connecting  the  thumb  to  the  rest 
of  the  hand.  The  thenar  eminence  is  much  larger  and  rounder  than  the  hypothenar  one,  which 
presents  a  longer  and  narrower  eminence  along  the  ulnar  side  of  the  hand.  When  the  Palmaris 
brevis  is  in  action  it  produces  a  wrinkling  of  the  skin  over  the  hypothenar  eminence,  and  a  deep 
dimple  on  the  ulnar  border  of  the  hand.  The  anterior  extremities  of  the  Lumbrical  muscles 
help  to  produce  the  soft  eminences  just  behind  the  clefts  of  the  fingers,  separated  from  each 
other  by  depressions  corresponding  to  the  flexor  tendons  in  their  sheaths.  Between  the  thenar 
and  hypothenar  eminences,  at  the  wrist-joint,  is  a  slight  groove  or  depression,  widening  out  as 
it  approaches  the  fingers;  beneath  this  we  have  the  strong  central  part  of  the  palmar  fascia. 
Here  we  have  some  furrows,  which  are  pretty  constant  in  their  arrangement,  and  bear  some 
resemblance  to  the  letter  M.  One  of  these  furrows  passes  obliquely  outward  from  the  groove 
between  the  thenar  and  hypothenar  regions  near  the  wrist  to  the  head  of  the  metacarpal  bone 
of  the  index  finger.  A  second  passes  inward,  with  a  slight  inclination  upward,  from  the  ter- 
mination of  the  first  to  the  ulnar  side  of  the  hand.  A  third  runs  nearly  parallel  with  the  second 
and  about  three-quarters  of  an  inch  below  it.  Lastly,  crossing  these  two  latter  furrows,  is  an 
oblique  furrow  parallel  with  the  first.  The  skin  of  the  palm  of  the  hand  differs  considerably 
from  that  of  the  forearm.  At  the  wrist  it  suddenly  becomes  hard  and  dense,  and  covered  with 
a  thick  layer  of  cuticle.  The  skin  in  the  thenar  region  presents  these  characteristics  less  than 
elsewhere.  In  spite  of  this  hardness  and  density,  the  skin  of  the  palm  is  exceedingly  sensitive 
and  very  vascular.  It  is  destitute  of  hair,  and  no  sebaceous  follicles  have  been  found  in  this 
region.  Over  the  fingers  the  skin  again  becomes  thinner,  especially  at  the  flexures  of  the  joints, 
and  over  the  terminal  phalanges  it  is  thrown  into  numerous  ridges  in  consequence  of  the  arrange- 
ment of  the  papillse  in  it.  These  ridges  form,  in  different  individuals,  distinctive  and  permanent 
patterns,  which  may  be  used  for  purposes  of  identification.     The  superficial  fascia  in  the  palm 


SURGICAL   ANATOMY   OF   THE    UPPER   EXTREMITY        503 

is  made  up  of  dense  fibro-fatty  tissue.  This  tissue  binds  down  the  skin  so  firmly  to  the  deep 
palmar  fascia  that  very  little  movement  is  permitted  between  the  two.  On  the  back  of  the  hand 
the  Dorsal  interossei  produce  elongated  swellings  between  the  metacarpal  bones.  The  first 
dorsal  interosseous  (Abductor  indicis),  when  the  thumb  is  closely  adducted  to  the  hand,  forms 
a  prominent  fusiform  bulging;  the  other  interossei  are  not  so  marked. 


SURGICAL  ANATOMY  OF  THE  UPPER  EXTREMITY. 


The  student,  having  completed  the  dissection  of  the  muscles  of  the  upper  extremity,  should 
consider  the  effects  likely  to  be  produced  by  the  action  of  the  various  muscles  in  fracture  of  the 
bones. 

In  considering  the  actions  of  the  various  muscles  upon  fractures  of  the  upper  extremity,  the 
most  common  forms  of  injury  have  been  selected  both  for  illustration  and  description. 

Fracture  of  the  middle  of  the  clavicle  (Fig.  333)  is  always  attended  with  considerable  dis- 
placement; the  inner  end  of  the  outer  fragment  is  displaced  inward  and  backward,  while  the 
outer  end  of  the  same  fragment  is  rotated  forward.  The  whole  outer  fragment  is  somewhat 
depressed.  The  deformity  is  described  by  saying  that  the  shoulder  goes  downward,  forward, 
and  inward. 

The  displacement  is  produced  as  follows:  inward,  by  the  muscles  passing  from  the  chest  to 
the  outer  fragment  of  the  clavicle,  to  the  scapula,  and  to  the  humerus — viz.,  the  Subclavius  and 
the  Pectoralis  minor,  and,  to  a  less  extent,  the  Pectoralis  major  and  the  Latissimus  dorsi;  hack- 
ward,  in  consequence  of  the  rotation  of  the  outer  fragment.  The  Serratus  magnus  causes  the 
scapula  to  rotate  on  the  wall  of  the  chest;  this  carries  the  acromion  and  outer  end  of  the  outer 
fragment  of  the  clavicle  forward  and  causes  the  piece  of  bone  to  rotate  round  a  vertical  axis 
through  its  centre,  and  so  carries  the  inner  end  of  the  outer  portion  backward.  The  depression 
of  the  whole  outer  fragment  is  produced  by  the  weight 
of  the  arm  and  by  the  contraction  of  the  Deltoid.  The 
outer  end  of  the  inner  fragment  appears  to  be  elevated, 
the  skin  being  drawn  tensely  over  it  ;  this  is  owing  to 
the  depression  of  the  outer  fragment,  as  the  inner  frag- 
ment is  usually  kept  fixed  by  the  costo-clavicular  liga- 
ment and  by  the  antagonism  between  the  Sternomastoid 
and  Pectoralis  major  muscles.  But  it  may  be  raised  by 
an  unusually  strong  Sterno-mastoid,  or  by  the  inner  end 
of  the  outer  fragment  getting  below  and  behind  it.  The 
causes  of  displacement  having  been  ascertained,  it  is 
easy  to  apply  the  appropriate  treatment.  The  outer 
fragment  is  to  be  drawn  outward,  and,  together  with  the 
scapula,  raised  upward  to  a  level  with  the  inner  frag- 
ment, and  retained  in  that  position.  The  formula  for 
correcting  the  deformity  is  as  follows :  carry  the  shoulder 
upward,  outward,  and  backward. 

In  fracture  of  the  acromial  end  of  the  clavicle,  between 
the  conoid  and  trapezoid  ligaments,  only  slight  displace- 
ment occurs,  as  these  ligaments,  from  their  oblique  in- 
sertion, serve  to  hold  both  portions  of  the  bone  in  appo- 
sition. Fracture,  also,  of  the  sternal  end,  internal  to 
the  costoclavicular  ligament,  is  attended  with  only  slight 
displacement,  this  ligament  serving  to  retain  the  frag- 
ments in  close  apposition. 

Fracture  of  the  acromion  process  usually  arises  from 
violence  applied  to  the  upper  and  outer  part  of  the 
shoulder;  it  is  generally  known  by  the  rotundity  of  the 
shoulder  being  lost,  from  the  Deltoid  drawing  the  fractured  portion  downward  and  forward; 
and  the  displacement  may  easily  be  discovered  by  tracing  the  macgin  of  the  clavicle  outward, 
when  the  fragment  will  be  found  resting  on  the  front  and  upper  part  of  the  head  of  the 
humerus.  In  order  to  relax  the  anterior  and  outer  fibres  of  the  Deltoid  (the  opposing  muscle), 
the  arm  should  be  drawn  forward  across  the  chest  and  the  elbow  well  raised,  so  that  the  head 
of  the  bone  may  press  the  acromion  process  upward  and  retain  it  in  its  position. 

Fracture  of  the  coracoid  process  is  an  extremely  rare  accident,  and  is  usually  caused  by  a 
sharp  blow  on  the  point  of  the  shoulder.  Displacement  is  here  produced  by  the  combined 
actions  of  the  Pectoralis  minor,  short  head  of  the  Biceps,  and  Coraco-brachialis,  the  former 
muscle  drawing  the  fragment  inward,  and  the  latter  muscles  directly  downward,  the  amount  of 
displacement  being  limited  by  the  connection  of  this  process  to  the  acromion  by  means  of  the 
coraco-acromial  ligament.     In  many  cases  there  appears  to  have  been  little  or  no  displacement, 


Fig.  333. 


-Fracture  of  the  middle  of  the 
clavicle. 


504 


THE   MUSCLES   AND    FASCIA 


from  the  fact  that  the  coraco-clavicular  ligament  has  remained  intact,  and  has  kept  the  separated 
fragment  from  displacement.  In  order  to  relax  these  muscles  and  replace  the  fragments  in 
close  apposition,  the  forearm  should  be  flexed  so  as  to  relax  the  Biceps,  and  the  arm  drawn 
forward  and  inward  across  the  chest,  so  as  to  relax  the  Coraco-brachialis;  the  humerus  should 
then  be  pushed  upward  against  the  coraco-acromial  ligament,  and  the  arm  retained  in  that 
position. 

Fracture  of  the  surgical  neck  of  the  humerus  (Fig.  334)  is  very  common,  is  attended  with 
considerable  displacement,  and  its  appearances  correspond  somewhat  with  those  of  dislocation 
of  the  head  of  the  humerus  into  the  axilla.  The  upper  fragment  is  slightly  elevated  under  the 
coraco-acromial  ligament  by  the  muscles  attached  to  the  greater  and  lesser  tuberosities;  the 
lower  fragment  is  drawn  inward  by  the  Fectoralis  major,  Latissimus  dorsi,  and  Teres  major;  and 
the  humerus  is  thrown  obliquely  outward  from  the  side  by  the  Deltoid,  and  occasionally  elevated 

so  as  to  cause  the  upper  end  of  the  lower  fragment  to  project 
beneath  and  in  front  of  the  coracoid  process.  The  deformity 
is  reduced  by  fixing  the  shoulder,  and  drawing  the  arm  out- 
ward and  downward.  To  counteract  the  opposing  muscles, 
and  to  keep  the  fragments  in  position,  a  conical-shaped  pad 
should  be  placed  with  the  apex  in  the  axilla ;  while  the  fore- 
arm is  flexed  to  an  angle  of  90  degrees  the  shoulder  is  padded 
with  cotton,  a  shoulder-cap  of  plaster-of-Paris  is  applied  to 
cover  the  shoulder,  a  portion  of  the  chest  and  back,  and  the 
arm  down  to  the  external  condyle  (Scudder).  The  arm,  with 
the  elbow  slightly  forward,  is  bandaged  to  the  side.  In  some 
cases  a  splint  is  placed  between  the  axillary  pad  and  the 
inner  side  of  the  arm. 

In  fracture  of  the  shaft  of  the  humerus  below  the  insertion 
of  the  Fectoralis  major,  Latissimus  dorsi,  and  Teres  major, 
and  above  the  insertion  of  the  Deltoid,  there  is  also  consider- 
able deformity,  the  upper  fragment  being  drawn  inward  by 
the  first-mentioned  muscles,  and  the  lower  fragment  upward 
and  outward  by  the  Deltoid,  producing  shortening  of  the  limb 
and  a  considerable  prominence  at  the  seat  of  fracture,  from 
the  fractured  ends  of  the  bone  riding  over  one  another,  espe- 
cially if  the  fracture  takes  place  in  an  oblique  direction.  The 
fragments  may  be  brought  into  apposition  by  extension  from 
the  elbow,  and  are  retained  in  that  position  by  adopting  the  same  means  as  in  the  preceding 
injury,  or  by  the  use  of  an  internal  angular  splint  with  three  short  humeral  splints. 

In  fractures  of  the  shaft  of  the  humerus  immediately  below  the  insertion  of  the  Deltoid,  the 
amount  of  deformity  depends  greatly  upon  the  direction  of  the  fracture.  If  it  occurs  in  a  trans- 
verse direction,  only  slight  displacement  takes  place,  the  upper  fragment  being  drawn  a  little 
forward;  but  in  oblique  fracture  the  combined  actions  of  the  Biceps  and  Brachialis  anticus 
muscles  in  front  and  the  Triceps  behind  draw  upward  the  lower  fragment,  causing  it  to  glide 
over  the  upper  fragment,  either  backward  or  forward,  according  to  the  direction  of  the  fracture. 
Simple  extension  reduces  the  deformity,  and  the  application  of  an  internal  angular  splint  and 
three  short  humeral  splints  will  retain  the  fragments  in  apposition.  Care  should  be  taken  not 
to  raise  the  elbow,  but  the  forearm  and  hand  may  be  supported  in  a  sling. 

Fracture  of  the  humerus  (Fig.  335)  above  the  condyle  deserves  very  attentive  considera- 
tion, as  the  general  appearances  correspond  somewhat  with  those  produced  by  separation 
of  the  epiphysis  of  the  humerus,  and  with  those  of  dislocation  of  the  radius  and  ulna  back- 
ward. If  the  direction  of  the  fracture  is  oblique  from  above,  downward  and  forward,  the 
lower  fragment  is  drawn  upward  by  the  Brachialis  anticus  and  Biceps  in  front  and  the  Triceps 
behind ;  and  at  the  same  time  is  drawn  backward  behind  the  upper  fragment  by  the  Triceps. 
This  injury  may  be  diagnosticated  from  dislocation  by  the  increased  mobility  in  fracture,  the 
existence  of  crepitus,  and  the  fact  of  the  deformity  being  remedied  by  extension,  on  the  discon- 
tinuance of  which  it  is  reproduced.  The  age  of  the  patient  is  of  importance  in  distinguishing 
this  form  of  injury  from  separation  of  the  epiphysis.  If  fracture  occurs  in  the  opposite  direc- 
tion to  that  shown  in  Fig.  335,  the  lower  fragment  is  drawn  upward  and  forward,  causing  a 
considerable  prominence  in  front,  and  the  upper  fragment  projects  backward  beneath  the 
tendon  of  the  Triceps  muscle. 

Fractures  of  the  lower  extremity  of  the  humerus  are  spoken  of  as  fractures  in  the  neighbor- 
hood of  the  elbow-joint.  The  term  includes  fracture  of  the  external  condyle,  of  the  internal  condyle, 
at  the  base  of  the  condyles,  and  T-  or  Y-shaped  fracture,  the  two  condyles  being  separated 
from  each  other  and  from  the  shaft  of  the  humerus.  Such  injuries  are  followed  by  great  and 
rapid  swelling.  Whenever  possible  the  .r-rays  are  used  to  aid  in  diagnosis,  and  the  patient  is 
placed  under  ether,  to  set  and  dress  the  fracture. 

In  fracture  of  the  inner  condyle  the  fragment  with  the  ulna  passes  up  and  back,  and  when 


Fig.  334. — Fracture  of  the  surgical 
neck  of  the  humerus. 


SURGICAL    ANATOMY   OF    THE    UPPER    EXTREMITY 


505 


the  forearm  is  extended  the  ulna  projects  posteriorly.  The  "  carrying  function  "  of  the  arm  is 
lost,  because  the  forearm  deviates  to  the  ulnar  side. 

In  all  cases  of  fracture  of  the  lower  end  of  the  humerus,  except  fracture  at  the  base  of 
the  condyles,  effect  reduction  by  traction  upon  the  forearm,  and  supination,  extension,  and 
bending  the  forearm  slowly  into  acute  flexion.  In  transverse  fracture  above  the  condyles 
draw  the  forearm  and  the  lower  fragment  downward  and  forward  and  push  the  upper  frag- 
ment back.  A  case  can  be  treated  by  maintaining  a  position  of  acute  flexion  (Jones's  position) 
or  by  using  an  anterior  angular  splint.     Allis  and  others  treat  in  extension. 

Fracture  of  the  olecranon  process  (Fig.  336)  is  a  frequent  accident.  The  detached  fragment 
is  displaced  u]n\ard,  by  the  action  of  the  Triceps  muscle,  from  half  an  inch  to  two  inches;  the 
prominence  of  the  elbow  is  consequently  lost,  and  a  deep  hollow  is  felt  at  the  back  part  of  the 
joint,  which  is  much  increased  on  flexing  the  limb.  The  patient  at  the  same  time  loses,  more 
or  less,  the  power  of  extending  the  forearm.  The  treatment  consists  in  relaxing  the  Triceps  by 
extending  the  limb,  and  retaining  it  in  the  extended  position  by  means  of  a  long  straight  splint 
applied  to  the  front  of  the  arm;  the  fragments  are  thus  brought  into  close  apposition,  and 
may  be  further  approximated  by  drawing  down  the  upper  fragment.  Union  is  generally 
ligamentous. 

Fracture  of  the  neck  of  the  radius  is  an  exceedingly  rare  accident,  and  is  generally  caused 
by  direct  violence.  Its  diagnosis  is  somewhat  obscure,  on  account  of  the  slight  deformity  visible, 
the  injured  part  being  surrounded  by  a  large  number  of  muscles;  but  the  movements  of  prona- 
tion and  supination  are  entirely  lost.     The  upper  fragment  is  drawn  outward  by  the  Supinator 


Tig.  335. 


-Fracture  of  the  humerus  above 
the  condyles. 


Fig.  336. — Fracture  of  the  olecranon. 


brevis,  the  extent  of  displacement  being  limited  by  the  attachment  of  the  orbicular  ligament. 
The  lower  fragment  is  drawn  forward  and  slightly  upward  by  the  Biceps,  and  inward  by  the 
Pronator  radii  teres,  its  displacement  forward  and  upward  being  counteracted  in  some  degree 
by  the  Supinator  brevis.  The  treatment  essentially  consists  in  relaxing  the  Biceps,  Supinator 
brevis,  and  Pronator  radii  teres  muscles  by  flexing  the  forearm,  and  placing  it  in  a  position  mid- 
way between  pronation  and  supination,  extension  having  been  previously  made  so  as  to  bring 
the  parts  in  apposition. 

In  fracture  of  the  radius  below  the  insertion  of  the  Biceps,  but  above  the  insertion  of  the 
Pronator  radii  teres,  the  upper  fragment  is  strongly  supinated  by  the  Biceps  and  Supinator 
brevis,  and  at  the  same  time  drawn  forward  and  flexed  by  the  Biceps;  the  lower  fragment  is 
pronated  and  drawn  inward  toward  the  ulna  by  the  pronators.  Thus  there  is  extreme  dis- 
placement with  very  little  deformity.  In  treating  such  a  fracture  the  arm  must  be  put  up  in 
a  position  of  supination,  otherwise  union  will  take  place  with  great  impairment  of  the  move- 
ments of  the  hand.  In  fractures  of  the  radius  below  the  insertion  of  the  Pronator  radii  teres 
(Fig.  337),  the  upper  fragment  is  drawn  upward  by  the  Biceps  and  inward  by  the  Pronator 
radii  teres,  holding  a  position  midway  between  pronation  and  supination,  and  a  degree  of  fulness 
in  the  upper  half  of  the  forearm  is  thus  produced;  the  lower  fragment  is  drawn  downward  and 
inward  toward  the  ulna  by  the  Pronator  quadratus,  and  thrown  into  a  state  of  pronation  by  the 
same  muscle;  at  the  same  time,  the  Supinator  longus,  by  elevating  the  styloid  process,  into  which 


506 


THE  MUSCLES  AND    FASCIA 


it  is  inserted,  will  serve  to  depress  the  upper  end  of  the  lower  fragment  still  more  toward  the  ulna. 
In  order  to  relax  the  opposing  muscles  the  forearm  should  be  bent,  and  the  limb  placed  in  a 
position  midway  between  pronation  and  supination;  the  fracture  is  then  easily  reduced  by 
extension  from  the  wrist  and  elbow:  well-padded  splints  should  be  applied  on  both  sides  of 
the  forearm  from  the  elbow  to  the  wrist;  the  hand  being  allowed  to  fall,  will,  by  its  own  weight, 
counteract  the  action  of  the  Pronator  quadratus  and  Supinator  longus,  and  elevate  the  lower 
fragment  to  the  level  of  the  upper  one. 

In  fracture  of  the  sha]t  of  the  ulna  the  upper  fragment  retains  its  usual  position,  but  the 
lower  fragment  is  drawn  outward  toward  the  radius  by  the  Pronator  quadratus,  producing  a 
well-marked  depression  at  the  seat  of  fracture  and  some  fulness  on  the  dorsal  and  palmar  sur- 
faces of  the  forearm.  The  fracture  is  easily 
reduced  by  extension  from  the  wrist  and  fore- 
arm. The  forearm  should  be  flexed,  and 
placed  in  a  position  midway  between  pronation 
and  supination,  and  well-padded  splints  ap- 
plied from  the  elbow  to  the  ends  of  the  fingers. 
In  fracture  of  the  shafts  of  the  radius  and 
ulna  together  the  lower  fragments  are  drawn 
upward,  sometimes  forward,  sometimes  back- 
ward, according  to  the  direction  of  the  frac- 
ture, by  the  combined  actions  of  the  Flexor  and 
Extensor  muscles,  producing  a  degree  of  ful- 
ness on  the  dorsal  or  palmar  surface  of  the 
forearm;  at  the  same  time  the  two  fragments  are  drawn  into  contact  by  the  Pronator  quad- 
ratus, the  radius  being  in  a  state  of  pronation  :  the  upper  fragment  of  the  radius  is  drawn 
upward  and  inward  by  the  Biceps  and  Pronator  radii  teres  to  a  higher  level  than  the  ulna; 
the  upper  portion  of  the  ulna  is  slightly  elevated  by  the  Brachialis  anticus.  The  fracture  may 
be  reduced  by  extension  from  the  wrist  and  elbow,  and  the  forearm  should  be  placed  in  the 
same  position  as  in  fracture  of  the  ulna. 

In  fracture  of  the  lower  end  of  the  radius  {Colles'r  fracture)  (Fig.  338)  the  displacement 
which  is  produced  is  very  considerable,  and  bears  some  resemblance  to  dislocation  of  the 
carpus  backward,  from  which  it  should  be  carefully  distinguished.  The  lower  fragment  is 
displaced  backward  and  upward,  but  this  displacement  is  probably  due  to  the  force  of  the 
blow  driving  the  portion  of  the  bone  into  this  position  and  not  to  any  muscular  influence. 
The  upper  fragment  projects  forward,  often  lacerating  the  substance  of  the  Pronator  quad- 
ratus, and  is  drawn  by  this  muscle  into  close  contact  with  the  lower  end  of  the  ulna,  causing  a 


Fig.  337. — Fracture  of  the  shaft  of  the  radius. 


Fig.  338. — Fracture  of  the  lower  end  of  the  radius. 

projection  on  the  anterior  surface  of  the  forearm,  immediately  above  the  carpus,  from  the  flexor 
tendons  being  thrust  forward.  This  fracture  may  be  distinguished  from  dislocation  by  the 
deformity  being  removed  on  making  sufficient  extension,  when  crepitus  may  be  occasionally 
detected;  at  the  same  time,  on  extension  being  discontinued,  the  parts  immediately  resume 
their  deformed  appearance.  The  age  of  the  patient  will  also  assist  in  determining  whether 
the  injury  is  fracture  or  separation  of  the  epiphysis.  Reduction  is  effected  by  hyperextension, 
longitudinal  traction,  and  forced  flexion.'  The  posterior  straight  splint  with  suitable  pads  is 
the  best  dressing. 


^  R.  J.  Levis. 


OF   THE  LOWER   EXTREMITY 


507 


MUSCLES  AND  FASCI-ffi  OF  THE  LOWER  EXTREMITY. 

The  Muscles  of  the  liower  Extremity  are  subdivided  into  groups  corresponding 
with  the  different  regions  of  the  Umb. 


I.  Iliac  Region. 

Psoas  magnus. 
Psoas  parvus. 
Iliacus. 

11.  Thigh. 
1.  Anterior  Femoral  Region. 

Tensor  fascise  Femoris. 

Sartorius. 

Rectus. 


Quadriceps 
extensor. 


Vastus  externus. 
Vastus  internus. 
Crureus. 
Subcrureus. 


2.  Internal  Femoral  Region. 

Gracilis. 
Pectineus. 
Adductor  longus. 
Adductor  brevis. 
Adductor  magnus. 

3.  Gluteal  Region. 
Gluteus  maximus. 
Gluteus  medius. 
Gluteus  minimus 
Pyriformis. 
Obturator  internus. 
Gemellus  superior. 
Gemellus  inferior. 
Quadratus  femoris. 
Obturator  externus. 

4.  Posterior  Femoral  Region. 

Biceps. 

Semitendinosus. 

Semimembranosus. 

III.  Leg. 

5.  Anterior  Tibio-fibular  Region. 

Tibialis  anticus. 
Extensor  proprius  hallucis. 
Extensor  longus  digitorum. 
Peroneus  tertius. 


6.  Posterior  Tibio-fibular  Region. 

Superficial  Layer. 

Gastrocnemius. 
Soleus. 
,  Plantaris. 

Deep  Layer. 

Popliteus. 

Flexor  longus  hallucis. 
Flexor  longus  digitorum. 
Tibialis  posticus. 


7.  Fibular  Region. 

Peroneus  longus. 
Peroneus  brevis. 


IV.  Foot. 

8.  Dorsal  Region. 
Extensor  brevis  digitorum. 

9.  Plantar  Region. 

First  Layer. 

Abductor  hallucis. 
Flexor  brevis  digitorum. 
Abductor  minimi  digiti. 

Second  Layer. 

Flexor  accessorius. 
Lumbricales. 

Third  Layer. 

Flexor  brevis  hallucis. 
Adductor  obliquus  hallucis. 
Flexor  brevis  minimi  digiti. 
Adductor  transversus  hallucis. 

Fourth  Layer. 
The  Interossei. 


508 


THE   MUSCLES   AND    FASCIA 


I.  MUSCLES  AND  FASCI-ffl  OF  THE  ILIAC  REGION. 


Psoas  magnus. 


Psoas  parvus. 


Iliacus. 


Dissection. — No  detailed  description  is  required  for  the  dissection  of  these  muscles.  On 
the  removal  of  the  viscera  from  the  abdomen  they  are  exposed,  covered  by  the  peritoneum  and 
a  thin  layer  of  fascia,  the  iliac  fascia. 

Iliac  Fascia  {fascia  iliaca). — ^The  iliac  fascia^  is  the  aponeurotic  layer  which 
lines  the  back  part  of  the  abdominal  cavity,  and  covers  the  Psoas  and  Iliacus 
muscles  throughout  their  whole  extent.  It  is  thin  above,  and  becomes  gradually 
thicker  below  as  it  approaches  the  crural  arch. 

The  Portion  Covering  the  Psoas  is  attached,  above,  to  the  ligamentum  arcuatum 
internum;  internally,  by  a  series  of  arched  processes  to  the  intervertebral  sub- 
stances and  prominent  margins  of  the  bodies  of  the  vertebrae,  and  to  the  upper  part 
of  the  sacrum,  the  intervals  so  left,  opposite  the  constricted  portions  of  the  bodies, 

PELVIC 
ILIACUS      PERITONEUM 

FASCIA  ILIACA 


PELVIC  FASCIA 

EXTRA- PERITONEAL 

TISSUE 

PARIETAL  LAYER 
OF  PELVIC  FASCIA 


VISCERAL  LAYER 

OF  PELVIC  FASCIA 

FASCIAL  CANAL 

FAT  OF  ISCHIO- 
RECTAL FOSSA 


SPHINCTER 
ANI   EXTERNUS 

Fig.  339. — Oblique  section  across  the  pelvis,  to  show  the  disposition  of  the  pelvic  fascia  and  the 
boundaries  of  the  ischio-rectal  fossa.     (Cunningham. ) 

transmitting  the  lumbar  arteries  and  veins  and  filaments  of  the  sympathetic  cord. 
Externally,  above  the  crest  of  the  ilium,  this  portion  of  the  iliac  fascia  is  continu- 
ous with  the  anterior  lamella  of  the  lumbar  fascia,  but  below  the  crest  of  the 
ilium  it  is  continuous  with  the  fascia  covering  the  Iliacus. 

The  Portion  Investing  the  Iliacus  is  connected  externally  to  the  whole  length 
of  the  inner  border  of  the  crest  of  the  ilium,  and  internally  to  the  brim  of  the  true 
pelvis,  where  it  is  continuous  with  the  periosteum;  and  at  the  ilio-pectineal  emi- 
nence it  receives  the  tendon  of  insertion  of  the  Psoas  parvus,  when  that  muscle 
exists.  External  to  the  femoral  vessels,  this  fascia  is  intimately  connected  to  the 
posterior  margin  of  Poupart's  ligament,  and  is  continuous  with  the  fascia  transver- 
salis.  Immediately  to  the  outer  side  of  the  femoral  vessels  the  fascia  iliaca  is  pro- 
longed backward  and  inward  from  Poupart's  ligament  as  a  band,  the  ilio-pectineal 
ligament,  which  is  attached  to  the  ilio-pectineal  eminence.  This  ligament  divides 
the  space  between  Poupart's  ligament  and  the  innominate  bone  into  two  parts,  the 
inner  of  which  {lacuna  vasorum)  transmits  the  femoral  vessels,  and  contains  the 


*  The  student  must  not  confound  this  fascia  with  the  iliac  portion  of  the  fascia  lata  (see  p.  515). 


THE  ILIAC  REGION 


509 


margin  of  Gimbernat's  ligament  and  also  the  femoral  ring;  the  outer  {lacuna 
musculorum)  the  ilio-psoas  and  the  anterior  crural  nerve  (Fig.  340).  Internal  to 
the  vessels  the  iliac  fascia  is  attached  to  the  ilio-pectineal  line  behind  the  con- 
joined tendon,  where  it  is  again  continuous  with  the  transversalis  fascia;  and, 
corresponding  to  the  point  where  the  femoral  vessels  pass  into  the  thigh,  this 
fascia  descends  behind  them,  forming  the  posterior  wall  of  the  femoral  sheath. 
This  portion  of  the  iliac  fascia  which  passes  behind  the  femoral  vessels  is  also 
attached  to  the  ilio-pectineal  line  beyond  the  limits  of  the  attachment  of  the  con- 
joined tendon ;  at  this  part  it  is  continuous  with  the  pubic  portion  of  the  fascia  lata 
of  the  thigh.  The  external  iliac  vessels  lie  in  front  of  the  iliac  fascia,  but  all  the 
branches  of  the  lumbar  plexus  behind  it;  it  is  separated  from  the  peritoneum  by  a 
quantity  of  loose  areolar  tissue.    The  femoral  or  crural  sheath  {fascia  cruris)  is 


POUPART'S 
LIGAM  ENT 
ANTERIOR 
CRURAL  NERVE 

FEMORAL  ARTERY 

LIAC  FASCIA 

FEMORAL  VEIN 

GIMBERNAT'S 
LIGAMENT 


PECTINEUS 


Fig.  340. — Poupart's  ligament  and  the  relation  of  the  parts  passing  beneath  it.     (Poirier  and  Charpy.) 


formed  by  the  transversalis  fascia  in  front  of  the  vessels  and  the  iliac  fascia  back 
of  them.  The  fascia?  join  to  the  inner  side  of  the  femoral  vein,  a  space,  the 
femoral  canal,  intervening  between  the  vein  and  the  junction. 

Between  the  femoral  vein  and  the  edge  of  Gimbernat's  ligament  is  the  femoral  or 
crural  ring  {annulus  femoralis)  (Fig.  342).  The  crural  or  femoral  canal  {canalis 
femoralis)  is  the  interval  between  the  femoral  vein  and  the  inner  wall  of  the  femoral 
(crural)  sheath.  This  canal  extends  from  the  femoral  ring  to  the  saphenous 
opening.  The  femoral  ring  is  closed  by  the  septum  crurale  of  Cloquet  {septum 
femorale  [Cloqueti]) ,  which  is  a  process  of  transversalis  fascia. 

The  Psoas  Magnus  {rn.  psoas  major)  (Fig.  343)  is  a  long  fusiform  muscle  placed 
on  the  side  of  the  lumbar  region  of  the  spine  and  the  margin  of  the  pelvis.  It  arises 
from  the  front  of  the  bases  and  lower  borders  of  the  transverse  processes  of  the 


510  THE  MUSCLES  AND   FASCIA 

lumbar  vertebrae  by  five  fleshy  slips;  also  from  the  sides  of  the  bodies  and  the  corre- 
sponding intervertebral  substances  of  the  last  dorsal  and  all  the  lumbar  vertebrae. 
The  muscle  is  connected  to  the  bodies  of  the  vertebrae  by  five  slips;  each  slip  is 
attached  to  the  upper  and  lower  margins  of  two  vertebrae,  and  to  the  intervertebral 
substance  between  them,  the  slips  themselves  being  connected  by  the  tendinous 
arches  which  extend  across  the  constricted  part  of  the  bodies,  and  beneath  which 
pass  the  lumbar  arteries  and  veins  and  filaments  of  the  sympathetic  cord.  These 
tendinous  arches  also  give  origin  to  muscular  fibres,  and  protect  the  blood-vessels 
and  nerves  from  pressure  during  the  action  of  the  muscle.  The  first  slip  is  attached 
to  the  contiguous  margins  of  the  last  dorsal  and  first  lumbar  vertebrae;  the  last 
to  the  contiguous  margins  of  the  fourth  and  fifth  lumbar  vertebrae,  and  to  the 
intervertebral  substance.  From  these  points  the  muscle  descends  across  the 
brim  of  the  pelvis,  and,  diminishing  gradually  in  size,  passes  beneath  Pou- 
part's  ligament,  and  terminates  in  a  tendon  which,  after  receiving  nearly  the 
whole  of  the  fibres  of  the  Iliacus,  is  inserted  into  the  lesser  trochanter  of  the 
femur. 

Relations. — In  the  lumbax  region:  by  its  anterior  surface,  which  is  placed  behind 
the  peritoneum,  with  the  ihac  fascia,  the  ligamentumarcuatum  internum,  the  kidney, 
Psoas  parvus,  renal  vessels,  ureter,  spermatic  vessels,  genito-crural  nerve,  and  the 
colon.  In  many  cases  the  vermiform  appendix  rests  upon  the  Psoas  muscle  (page 
511).  By  its  posterior  surface,  with  the  transverse  processes  of  the  lumbar  vertebrae 
and  the  Quadratus  lumborum  muscle,  from  which  it  is  separated  by  the  anterior 
lamella  of  the  lumbar  fascia.  The  lumbar  plexus  is  situated  in  the  posterior  part 
of  the  substance  of  the  muscle.  By  its  inner  side  the  muscle  is  in  relation  with  the 
bodies  of  the  lumbar  vertebrae,  the  lumbar  arteries,  the  ganglia  of  the  sympathetic 
nerve,  and  their  branches  of  communication  with  the  spinal  nerves;  the  lumbar 
glands ;  the  vena  cava  inferior  on  the  right  and  the  aorta  on  the  left  side,  and  along 
the  brim  of  the  pelvis  with  the  external  iliac  artery.  In  the  thigh  it  is  in  relation, 
in  front,  with  the  fascia  lata;  behind,  with  the  capsular  ligament  of  the  hip,  from 
which  it  is  separated  by  a  synovial  bursa  (bursa  ilio-pectinea) ,  which  frequently 
communicates  with  the  cavity  of  the  joint  through  an  opening  of  variable  size; 
between  the  tendon  and  part  of  the  lesser  trochanter  is  the  bursa  iliaca  sub- 
tendinea  ;  by  its  inner  border,  with  the  Pectineus  and  internal  circumflex  artery, 
and  also  with  the  femoral  artery,  which  slightly  overlaps  it:  by  its  outer  border, 
with  the  anterior  crural  nerve  and  Iliacus  muscle. 

The  Psoas  Parvus  (m.  psoas  minor)  (Fig.  343)  is  a  long  slender  muscle  placed 
in  front  of  the  Psoas  magnus.  It  arises  from  the  sides  of  the  bodies  of  the  last 
dorsal  and  first  lumbar  vertebrae  and  from  the  intervertebral  substance  between 
them.  It  forms  a  small  flat  muscular  bundle,  which  terminates  in  a  long  flat 
tendon  inserted  into  the  ilio-pectineal  eminence,  and,  by  its  outer  border,  into 
the  iliac  fascia.  This  muscle  is  often  absent,  and,  according  to  Cruveilhier,  is 
sometimes  double. 

Relations. — It  is  covered  by  the  peritoneum,  and,  at  its  origin,  by  the  ligamentum 
arcuatum  internum;  it  rests  on  the  Psoas  magnus. 

The  Hiacus  (Fig.  343)  is  a  flat,  triangular  muscle  which  fills  up  the  whole  of  the 
iliac  fossa.  It  arises  from  the  upper  two-thirds  of  this  fossa  and  from  the  inner 
margin  of  the  crest  of  the  ilium;  behind,  from  the  ilio-lumbar  ligament  and  base 
of  the  sacrum;  in  front,  from  the  anterior  superior  and  anterior  inferior  spinous 
processes  of  the  ilium,  from  the  notch  between  them.  The  fibres  converge  to  be 
inserted  into  the  outer  side  of  the  tendon  of  the  Psoas,  some  of  them  being  pro- 
longed on  to  the  shaft  of  the  femur  for  about  an  inch  below  and  in  front  of  the 
lesser  trochanter.^     The  most  external  fibres  are  inserted  into  the  capsule  of  the 

^  The  Psoas  magnus,  Psoas  parvus,  and  Iliacus  are  regarded  by  His  and  others  as  a  single  muscle,  the  Ilio- 
psoas (Fig.  340). 


THE  ILIAC  REGION  511 

hip-joint.  If  these  fibres  are  separate  they  constitute  the  Ilio-capsularis  muscle  or 
the  niacus  minor. 

Relations. — Within  the  abdomen:  by  its  anterior  surface,  with  the  ihac  fascia, 
which  separates  the  muscle  from  the  peritoneum,  and  with  the  external  cutaneous 
nerve ;  on  the  right  side,  with  the  caecum ;  on  the  left  side,  with  the  sigmoid  flexure 
of  the  colon;  by  its  posterior  surface,  with  the  iliac  fossa;  by  its  inner  border,  with 
the  Psoas  magnus  and  anterior  crural  nerve.  In  the  thigh,  it  is  in  relation,  by  its 
anterior  surface,  with  the  fascia  lata,  the  Rectus  and  Sartorius  muscles,  and  the 
profunda  femoris  artery;  behind,  with  the  capsule  of  the  hip-joint,  a  synovial 
bursa  common  to  it  and  the  Psoas  magnus  being  interposed. 

Nerves. — The  Psoas  magnus  is  supplied  by  the  anterior  branches  of  the  second 
and  third  lumbar  nerves;  the  Psoas  parvus,  when  it  exists,  is  supplied  by  the 
anterior  branch  of  the  first  lumbar  nerve ;  and  the  Iliacus  by  the  anterior  branches 
of  the  second  and  third  lumbar  nerves  through  the  anterior  crural. 

Actions. — The  Psoas  and  Iliacus  muscles,  acting  from  above,  flex  the  thigh 
upon  the  pelvis.  Acting  from  below,  the  femur  being  fixed,  the  muscles  of 
both  sides  bend  the  lumbar  portion  of  the  spine  and  pelvis  forward.  They  also 
serve  to  maintain  the  erect  position,  by  supporting  the  spine  and  pelvis  upon 
the  femur,  and  assist  in  raising  the  trunk  when  the  body  is  in  the  recumbent 
posture. 

The  Psoas  parvus  is  a  tensor  of  the  iliac  fascia.  It  assists  in  flexing  the  lumbar 
spine  laterally,  the  pelvis  being  its  fixed  point. 

Surgical  Anatomy. — There  is  no  definite  septum  between  the  portions  of  the  iliac  fascia 
covering  the  Psoas  and  IHacus  respectively,  and  the  fascia  is  only  connected  to  the  subjacent 
muscles  by  a  quantity  of  loose  connective  tissue.  When  an  abscess  forms  beneath  this  fascia, 
as  it  is  very  apt  to  do,  the  matter  is  contained  in  an  osseo-fibrous  cavity,  which  is  closed  on  all 
sides  within  the  abdomen,  and  is  open  only  at  its  lower  part,  where  the  fascia  is  prolonged  over 
the  muscle  into  the  thigh. 

Abscess  within  the  sheath  of  the  Psoas  muscle  (psoas  abscess)  is  generally  due  to  tuberculous 
caries  of  the  bodies  of  the  lower  dorsal  or  of  the  lumliar  vertebrae.  When  the  disease  is  in  the  dorsal 
region,  the  matter  tracts  down  the  posterior  mediastinum,  in  front  of  the  bodies  of  the  vertebrae, 
and,  passing  beneath  the  ligamentum  arcuatum  internum,  enters  the  sheath  of  the  Psoas  muscle, 
down  which  it  passes  as  far  as  the  pelvic  brim ;  it  then  gets  beneath  the  iliac  portion  of  the  fascia 
and  fills  up  the  iliac  fossa.  In  consequence  of  the  attachment  of  the  fascia  to  the  pelvic  brim,  it 
rarely  finds  its  way  into  the  pelvis,  but  passes  by  a  narrow  opening  under  Poupart's  ligament 
into  the  thigh,  to  the  outer  side  of  the  femoral  vessels.  It  thus  follows  that  a  Psoas  abscess  may 
be  described  as  consisting  of  four  parts:  (1)  a  somewhat  narrow  channel  at  its  upper  part,  in  the 
Psoas  sheath;  (2)  a  dilated  sac  in  the  iliac  fossa;  (3)  a  constricted  neck  under  Poupart's  ligament; 
and  (4)  a  dilated  sac  in  the  upper  part  of  the  thigh.  When  the  lumbar  vertebrae  are  the  seat  of  the 
disease,  the  matter  finds  its  way  directly  into  the  substance  of  the  muscle.  If  a  Psoas  abscess 
forms  the  muscular  fibres  are  destroyed,  and  the  nervous  cords  contained  in  the  abscess  are  isolated 
and  exposed  in  its  interior;  the  femoral  vessels  which  lie  in  front  of  the  fascia  remain  intact,  and 
the  peritoneum  seldom  becomes  implicated.  All  Psoas  abscesses  do  not,  however,  pursue  this 
course:  the  matter  may  leave  the  muscle  above  the  crest  of  the  ilium,  and,  tracking  backward, 
may  point  in  the  loin  (lumbar  abscess) ;  or  it  may  point  above  Poupart's  ligament  in  the  inguinal 
region;  or  it  may  follow  the  course  of  the  iliac  Vessels  into  the  pelvis,  and,  passing  through  the 
^eat  sacro-sciatic  notch,  discharge  itself  on  the  back  of  the  thigh;  it  may  open  into  the  bladder 
or  find  its  way  into  the  perinaeum,  or  it  may  pass  down  the  thigh  to  the  popliteal  space  or  even 
lower.  Strain  of  the  Psoas  muscle  is  not  unusual,  and  induces  pain  which  may  be  mistaken 
for  appendicitis.  The  bursa  beneath  the  tendon  of  the  Psoas  and  Iliacus  and  the  hip-joint  or 
that  between  the  tendon  and  the  lesser  trochanter  may  greatly  enlarge  and  produce  pain  and 
disablement.  Byron  Robinson*  pointed  out  that  trauma  of  the  Psoas  muscle  may  be  an 
important  factor  in  the  etiology  of  appendicitis,  trauma  may  induce  periappendicular  adhe- 
sions and  adhesions  interfere  with  the  circulation  of  blood  and  faeces.  Robinson  says,  in  the 
previously  quoted  article,  that  in  46  per  cent,  of  men  and  in  20  per  cent,  of  women  the 
appendix  rests  on  the  Psoas  muscle. 

1  Annals  of  Surgery,  April,  1901. 


512 


THE  MUSCLES  AND   FASCIA 


II.  MUSCLES  AND  FASCIA  OF  THE  THIGH. 
1.  The  Anterior  Femoral  Region. 


Tensor  fascise  femoris. 
Sartorius. 


i  Rectus. 
Vastus  externus. 
Vastus  internus. 
Crureus. 
Subcrureus. 


1.  Dissection   of 
femoral  hernia, 

and    Scarpa's 

triangle. 


Dissection. — To  expose  the  muscles  and  fasciae  in  this  region,  make  an  incision  along 
Poupart's  ligament,  from  the  anterior  superior  spine  of  the  ilium  to  the  spine  of  the  os  pubis; 
a  vertical  incision  from  the  centre  of  this,  along  the  middle  of  the  thigh  to  below  the  knee-joint; 
and  a  transverse  incision  from  the  inner  to  the  outer  side  of  the  leg,  at  the  lower  end  of  the  ver- 
tical incision.  The  flaps  of  integument  having  been  removed,  the  superficial  and  deep  fasciae 
should  be  examined.  The  more  advanced  student  should  commence  the  study  of  this  region  by 
an  examination  of  the  anatomy  of  femoral  hernia  and  Scarpa's  triangle,  the  incisions  for  the 
dissection  of  which  are  marked  out  in  Fig.  341. 

Superficial  Fascia. — The  superficial  fascia  forms  a  continuous  layer  over  the 
whole  of  the  thigh.    It  consists  of  areolar  tissue,  containing  in  its  meshes  much  fat, 

and  is  capable  of  being  separated  into  two  or 
more  layers,  between  which  are  found  the  super- 
ficial vessels  and  nerves.  It  varies  in  thickness 
in  different  parts  of  the  limb:  in  the  groin  it 
is  thick,  and  the  two  layers  are  separated  from 
one  another  by  the  superficial  inguinal  lymphatic 
glands,  the  internal  saphenous  vein,  and  several 
smaller  vessels.  One  of  these  two  layers,  the 
superficial,  is  continuous  above  with  the  super- 
ficial fascia  of  the  abdomen  and  the  back.  In- 
ternally it  is  continuous  with  the  superficial 
fascia  of  the  perineum.  The  deep  layer  of  the 
superficial  fascia  is  a  very  thin  fibrous  layer, 
best  marked  on  the  inner  side  of  the  k)ng 
saphenous  vein  and  below  Poupart's  ligament. 
It  is  placed  beneath  the  subcutaneous  vessels 
and  nerves  and  upon  the  surface  of  the  fascia 
lata.  It  is  intimately  adherent  to  the  fascia  lata 
a  little  below  Poupart's  ligament.  It  covers  the 
saphenous  opening  (Fig.  342)  in  the  fascia  lata, 
being  closely  united  to  the  margins  of  the  open- 
ing, and  is  connected  to  the  sheath  of  the  fem- 
oral vessels  by  its  under  surface.  The  portion 
of  the  fascia  covering  this  aperture  is  perforated 
by  the  internal  saphenous  vein  and  by  numer- 
ous blood-  and  lymphatic  vessels;  hence  it  has 
been  termed  the  cribriform  fascia  (fascia  cribrosa), 
theopenings  for  these  vessels  having  been  Hkened 
to  the  holes  in  a  sieve.  The  cribriform  fascia 
adheres  closely  both  to  the  superficial  fascia  and 
to  the  fascia  lata,  so  that  it  is  described  by  some 
anatomists  as  part  of  the  fascia  lata,  but  is  usually 
considered  (as  in  this  work)  as  belonging  to  the 
superficial  fascia.  It  is  not  until  the  cribriform 
fascia  has  been  cleared  away  that  the  saphenous  opening  is  seen,  so  that  this  open- 
ing does  not  in  ordinary  cases  exist  naturally,  but  is  the  result  of  dissection.    Mr. 


g  \  ^.  Front  of  thigh. 


S.  Front  of  leg. 


^  /  ^  I  4.  Dorsum  of  foot. 


Fig.  341.- 


-Dissection  of  lower  extremity. 
Front  view. 


THE   ANTERIOR    FEMORAL    REGION 


513 


Callender,  however,  speaks  of  cases  in  which,  probably  as  the  result  of  pressure 
from  enlarged  inguinal  lymphatic  glands,  the  fascia  has  become  atrophied,  and  a 
saphenous  opening  exists  independent  of  dissection.  A  femoral  hernia  in  passing 
through  the  saphenous  opening  receives  the  cribriform  fascia  as  one  of  its  cover- 
ings. A  large  subcutaneous  bursa  (bursa  pra'patellaris  subcutanea)  is  found  in  the 
superficial  fascia  over  the  patella,  and  another  (bursa  trochanterica  subcutanea) 
in  the  superficial  fascia  over  the  great  trochanter. 

Deep  Fascia  or  Fascia  Lata  (Fig.  342). — The  deep  fascia  of  the  thigh  is  exposed 
on  the  removal  of  the  superficial  fascia,  and  is  named,  from  its  great  extent,  the  fascia 
lata;  it  forms  a  uniform  investment  for  the  whole  of  this  region  of  the  limb,  but  varies 
in  thickness  in  different  parts;  thus,  it  is  thicker  in  the  upper  and  outer  part  of 
the  thigh,  where  it  receives  a  fibrous  expansion  from  the  Gluteus  maximus  muscle, 
and  the  Tensor  fasciae  femoris  is  inserted  between  its  layers :  it  is  very  thin  behind, 
and  at  the  upper  and  inner  part  where  it  covers  the  Adductor  muscles,  and  again 


POUPART'S 
LIGAMENT 


INTERCOLUMNAR 
FIBRES 


GIMBERNAT'S 
LIGAMENT 

SAPHENOUS 

OPENING 

FEMORAL 

VEIN 

LONG 

SAPHENOUS 

VEIN 


EXTERNAL 
•ABDOMINAL 
RING 


Fig.  342.— Right  external  abdominal  ring  and  saphenous  opening  in  the  male.     (Spalteholz). 


becomes  stronger  around  the  knee,  receiving  fibrous  expansions  from  the  tendon  of 
the  Biceps  externally,  from  the  Sartorius  internally,  and  from  the  Quadriceps 
extensor  in  front.  The  fascia  lata  is  attached,  above  and  behind,  to  the  back  of 
the  sacrum  and  coccyx;  externally,  to  the  crest  of  the  ilium;  in  front,  to  Pou- 
part's  hgament  and  to  the  body  of  the  os  pubis;  and  internally,  to  the  descend- 
ing ramus  of  the  os  pubis,  to  the  ramus  and  tuberosity  of  the  ischium,  and  to  the 
lower  border  of  the  great  sacro-sciatic  ligament.  From  its  attachment  to  the  crest 
of  the  ilium  it  passes  down  over  the  Gluteus  medius  muscle  to  the  upper  border 
of  the  Gluteus  maximus,  where  it  splits  into  two  layers,  one  passing  superficial  to 
and  the  other  beneath  this  muscle.  At  the  lower  border  of  the  muscle  the  two  layers 
reunite.  Externally  the  fascia  lata  receives  the  greater  part  of  the  tendon  of  inser- 
tion of  the  Gluteus  maximus,  and  becomes  proportionately  thickened.  The 
portion  of  the  fascia  lata  arising  from  the  front  part  of  the  crest  of  the  ilium,  cor- 

33 


514 


THE   MUSCLES   AND    FASCIA 


Wf  I « 


llllt  V 


X 


''(o 


t^liW§BS!  responding  to  the  origin  of  the  Tensor  fasciae 
femoris,  passes  down  the  outer  side  of  the  thigh 
as  two  layers,  one  superficial  to  and  the  other 
beneath  this  muscle.  The  deep  layer  is  a  con- 
tinuation of  the  tendinous  fibres  of  the  Gluteus 
maximus  muscle  and  the  superficial  layer  is 
chiefly  a  continuation  of  the  tendinous  fibres  of 
the  Tensor  fasciae  femoris,  but  receives  some 
fibres  from  the  fascia  covering  the  Gluteus 
medius  muscle/  These  layers  at  the  lower 
end  of  the  muscle  become  blended  into  a  thick 
and  strong  band,  having  first  received  the  in- 
sertion of  the  muscle.  This  band  is  continued 
downward,  under  the  name  of  the  ilio-tibial  band 
(tractus  iliotibialis  [Maissiati]),  to  be  inserted 
into  the  external  tuberosity  of  the  tibia.  A 
strengthening  band  of  transverse  fibres  is  placed 
in  the  gluteal  groove  or  sulcus  {sulcus  glutceus)  and 
another  is  placed  across  the  roof  of  the  popliteal 
space.  Below,  the  fascia  lata  is  attached  to  all 
the  prominent  points  around  the  knee-joint — 
viz.,  the  condyles  of  the  fenmr,  tuberosities  of 
the  tibia,  and  head  of  the  fibula.  On  each  side 
of  the  patella  it  is  strengthened  by  transverse 
fibres  given  off  from  the  lower  part  of  the  Vasti 
muscles,  which  are  attached  to  and  support  this 
bone.  Of  these  the  outer  fibres  are  the  stronger, 
and  are  continuous  with  the  ilio-tibial  band. 
From  the  inner  surface  of  the  fascia  lata  are 
given  off  two  strong  intermuscular  septa,  which 
are  attached  to  the  whole  length  of  the  linea 
aspera  and  its  prolongations  above  and  below: 
the  external  intermuscular  septum  {septum  in- 
termusculare  laterale)  is  the  stronger.  It  extends 
from  the  insertion  of  the  Gluteus  maximus  to 
the  outer  condyle,  separates  the  Vastus  externus 
in  front  from  the  short  head  of  the  Biceps  be- 
hind, and  gives  partial  origin  to  these  muscles; 
the  internal  intermuscular  septum  {septum  inter- 
musculare  mediale),  the  thinner  of  the  two, 
separates  the  Vastus  internus  from  the  Adductor 
and  Pectineus  muscles.  Besides  these  there 
are  numerous  smaller  septa,  separating  the  in- 
dividual muscles  and  enclosing  each  in  a  dis- 
,\^''^    "T^^^f/  tinct  sheath.      At  the  upper  and  inner  part  of 

the  thigh,  a  little  below  Poupart's  ligament,  a 
large  oval-shaped  aperture  is  observed  after 
the  superficial  fascia  has  been  cleared  off:  it 
transmits  the  internal  saphenous  vein  and  other 
smaller  vessels,  and  is  termed  the  saphenous 
opening  {fossa  ovalis)  (Fig.  342) .  This  opening 
is  covered  by  a  portion  of  the  deep  layer  of  the 

Fig.  343.— Muscles  of  the  iliac  and  anterior         i  Werner  Spalteholz's  Hand  Atlas  of  Human  Anatomy.    Edited 
femoral  region.  and  translated  by  Lewellys  F.  Barker. 


Jr^r 


THE   ANTERIOR    FEMORAL    REGION  515 

superficial  fascia,  the  cribriform  fascia.  In  order  more  correctly  to  consider  the 
mode  of  formation  of  this  aperture,  the  fascia  lata  in  this  part  of  the  thigh  is 
described  as  consisting  of  two  portions — an  iliac  portion  and  a  pubic  portion. 

Iliac  Portion. — The  iliac  portion,  the  superficial  layer  of  the  fascia  lata  or  the 
Sartorial  portion  of  the  fascia  lata,  is  all  that  part  of  the  fascia  lata  on  the  outer 
side  of  the  saphenous  opening.  It  is  attached,  externally,  to  the  crest  of  the 
ilium  and  its  anterior  superior  spine,  to  the  whole  length  of  Poupart's  ligament  as 
far  internally  as  the  spine  of  the  os  pubis,  and  to  the  pectineal  line  in  conjunction 
with  Gimbernat's  ligament.  From  the  spine  of  the  os  pubis  it  is  reflected  down- 
ward and  outward,  forming  an  arched  margin,  the  falciform  process  or  the  falciform 
margin  of  Bm-ns  (margo  falciformw),  or  the  superior  comuof  the  saphenous  opening 
(cornu  superius).  This  margin  overlies  and  is  adherent  to  the  anterior  layer  of 
the  sheath  of  the  femoral  vessels:  to  its  edge  is  attached  the  cribriform  fascia; 
and,  below,  it  is  continuous  with  the  pubic  portion  of  the  fascia  lata.  The 
femoral  ligament,  or  the  ligament  of  Hey,  is  the  point  at  which  the  falciform 
process  joins  the  base  of  Gimbernat's  ligament. 

Pubic  Portion. — The  pubic  portion,  or  the  pectineal  portion,  or  the  deep  layer  of 
the  fascia  lata,  is  situated  at  the  inner  side  of  the  saphenous  opening :  at  the  lower 
margin  of  this  aperture  it  is  continuous  with  the  iliac  portion.  The  lower  concave 
margin  of  the  saphenous  opening  where  the  two  layers  of  fascia  are  continuous  is 
called  the  inferior  cornu  {cornu  injerim).  Traced  upward,  the  pubic  portion  covers 
the  surface  of  the  Pectineus,  Adductor  longus,  and  Gracilis  muscles,  and,  passing 
behind  the  sheath  of  the  femoral  vessels,  to  which  it  is  closely  united,  is  continu- 
ous with  the  sheath  of  the  Psoas  and  Iliacus  muscles,  and  is  attached  above  to 
the  ilio-pectineal  line,  where  it  becomes  continuous  with  the  iliac  fascia.  From 
this  description  it  may  be  observed  that  the  iliac  portion  of  the  fascia  lata  passes 
in  front  of  the  femoral  vessels,  and  the  pubic  portion  behind  them,  so  that  an 
apparent  aperture  exists  between  the  two,  through  which  the  internal  saphenous 
joins  the  femoral  vein.^ 

Surgflcal  Anatomy. — The  ilio-tibial  band  at  a  point  between  the  crest  of  the  ilium  and  the 
great  trochanter  is  so  tense  that  it  is  impossible  to  sink  the  fingers  in  deeply  in  this  region.  Dr. 
Allis  points  out  that  in  fracture  of  the  neck  of  the  femur  the  great  trochanter  mounts  toward 
the  iliac  crest,  the  ilio-tibial  band  relaxes,  and  the  fingers  can  be  sunk  deeply  into  the  space 
between  the  great  trochanter  and  the  iliac  crest — Alhs's  sign.  Allis's  sign  indicates  shorten- 
ing. A  Psoas  abscess  usually  points  at  the  termination  of  the  Psoas  muscle,  but  the  tuberculous 
matter  may  be  directed  down  the  thigh  beneath  the  fascia  lata,  and  it  may  reach  the  popliteal 
space  or  even  lower. 

The  fascia  should  now  be  removed  from  the  surface  of  the  muscles.  This  may  be  effected  by 
pinching  it  up  between  the  forceps,  dividing  it,  and  separating  it  from  each  muscle  in  the  course 
of  its  fibres. 

The  Tensor  FasciaB  Femoris  (w.  tensor  fascice  Iotas,  m.  tensor  vagina  femoris) 
(Fig.  ^43)' arises  from  the  anterior  part  of  the  outer  lip  of  the  crest  of  the  ilium, 
and  from  the  outer  surface  of  the  anterior  superior  spinous  process,  and  part  of 
the  outer  border  of  the  notch  below  it,  between  the  Gluteus  medius  and  Sartorius, 
and  from  the  surface  of  the  fascia  covering  the  Gluteus  medius.  It  is  inserted 
between  two  layers  of  the  fascia  lata,  about  one-fourth  down  the  outer  side  of 
the  thigh.  From  the  point  of  insertion  the  fascia  is  continued  downward  to  the 
external  tuberosity  of  the  tibia  as  a  thickened  band,  the  ilio-tibial  band. 

Relations. — By  its  superficial  surface,  with  the  fascia  lata  and  the  integument; 
by  its  deep  surface,  with  the  Gluteus  medius.  Rectus  femoris,  and  Vastus  externus 
muscles,  and  the  ascending  branches  of  the  external  circumflex  artery;  by  its 
anterior  border,  with  the  Sartorius,  from  which  it  is  separated  below  by  a  triangular 

1  These  parts  will  be  again  more  particularly  described  with  the  anatomy  of  Hernia. 


516  THE  MUSCLES  AND  FASCIA 

space,  in  which  is  seen  the  Rectus  femoris;  by  its  posterior  border,  with  the 
Gluteus  medius. 

The  Sartorius  (Fig.  343) ,  the  longest  muscle  in  the  body,  is  flat,  narrow,  and 
ribbon-like;  it  arises  by  tendinous  fibres  from  the  anterior  superior  spinous  process 
of  the  ilium  and  the  upper  half  of  the  notch  below  it,  passes  obliquely  across  the 
upper  and  anterior  part  of  the  thigh,  from  the  outer  to  the  inner  side  of  the  limb, 
then  descends  vertically,  as  far  as  the  inner  side  of  the  knee,  passing  behind  the 
inner  condyle  of  the  femur,  and  terminates  in  a  tendon  which,  curving  obliquely- 
forward,  expands  into  a  broad  aponeurosis,  inserted  in  front  of  the  Gracilis  and 
Semitendinosus,  into  the  upper  part  of  the  inner  surface  of  the  shaft  of  the  tibia, 
nearly  as  far  forward  as  the  crest.  The  upper  part  of  the  tendon  is  curved  back- 
ward over  the  upper  edge  of  the  tendon  of  the  Gracilis  so  as  to  be  inserted  behind 
it.  An  offset  is  derived  from  the  upper  margin  of  this  aponeurosis,  which  blends 
with  the  fibrous  capsule  of  the  knee-joint,  and  another,  given  off  from  its  lower 
border,  blends  with  the  fascia  on  the  inner  side  of  the  leg. 

The  relations  of  this  muscle  to  the  femoral  artery  should  be  carefully  examined, 
as  it  constitutes  the  chief  guide  in  tying  the  vessel.  In  the  upper  third  of  the 
thigh  it  forms  the  outer  side  of  a  triangular  space,  Scarpa's  triangle  (trigonum 
femorale) ,  the  inner  side  of  which  is  formed  by  the  inner  border  of  the  Adductor 
longus,  and  the  base,  which  is  turned  upward,  by  Poupart's  ligament;  the  femoral 
artery  passes  perpendicularly  through  the  middle  of  this  space  from  its  base  to 
its  apex.  In  the  middle  third  of  the  thigh  the  femoral  artery  lies  first  along 
the  inner  border,  and  then  behind  the  Sartorius. 

Relations. — By  its  superficial  surface,  with  the  fascia  lata  and  integument;  by 
its  deejp  surface,  with  the  Rectus,  Iliacus,  Vastus  internus,  anterior  crural  nerve, 
sheath  of  the  femoral  vessels.  Adductor  longus.  Adductor  magnus,  Gracilis, 
Semitendinosus,  long  saphenous  nerve,  and  internal  lateral  ligament  of  the  knee- 
joint.  Frequently  there  is  a  bursa  (bursa  to.  sartorii  propria)  between  the  tendon 
of  the  Sartorius  and  the  tendons  of  the  Gracilis  and  Semimembranosus.  It  may 
be  in  communication  with  the  bursa  anserina. 

The  Quadriceps  Extensor  (to.  quadriceps  femoris)  (Fig.  343)  includes  the  four 
remaining  muscles  on  the  front  of  the  thigh.  It  is  the  great  Extensor  muscle 
of  the  leg,  forming  a  large  fleshy  mass  which  covers  the  front  and  sides  of  the 
femur,  being  united  below  into  a  single  tendon,  attached  to  the  patella,  and 
above  subdivided  into  separate  portions,  which  have  received  distinct  names. 
Of  these,  one  occupying  the  middle  of  the  thigh,  connected  above  with  the  ilium, 
is  called  the  Rectus  femoris,  from  its  straight  course.  The  other  divisions  lie  in 
immediate  connection  with  the  shaft  of  the  femur,  which  they  cover  from  the 
trochanters  to  the  condyles.  The  portion  on  the  outer  side  of  the  femur  is 
termed  the  Vastus  extemus;  that  covering  the  inner  side,  the  Vastus  internus; 
and  that  covering  the  front  of  the  femur,  the  Crureus. 

The  Rectus  Femoris  is  situated  in  the  middle  of  the  anterior  region  of  the  thigh; 
it  is  fusiform  in  shape,  and  its  superficial  fibres  are  arranged  in  a  bipenniform 
manner,  the  deep  fibres  running  straight  down  to  the  deep  aponeurosis.  It  arises 
by  two  tendons:  one,  the  anterior  or  straight,  from  the  anterior  inferior  spinous 
process  of  the  ihum;  the  other,  the  posterior  or  reflected  tendon,  from  a  groove 
above  the  brim  of  the  acetabulum;  the  two  unite  at  an  acute  angle  and  spread 
into  an  aponeurosis,  which  is  prolonged  downward  on  the  anterior  surface  of  the 
muscle  and  from  which  the  muscular  fibres  arise.*  The  muscle  terminates  in  a 
broad  and  thick  aponeurosis,  which  occupies  the  lower  two-thirds  of  its  posterior 
surface,  and,  gradually  becoming  narrowed  into  a  flattened  tendon,  is  inserted 

1  Mr.  W.  R.  Williams,  in  an  interesting  paper  in  the  Jourh.  of  Anat.  and  Phys.,  vol.  xiii.  p.  204,  pomts 
out  that  the  reflected  tendon  is  the  real  origin  of  the  muscle,  and  is  alone  present  in  early  foetal  life.  The 
direct  tendon  is  merely  an  accessory  band  of  condensed  fascia.  The  paper  will  well  repay  perusal,  though  in 
some  particulars  I  think  the  description  in  the  text  more  generally  accurate. — Ed.  of  15th  English  edition. 


THE   ANTERIOR   FEMORAL    REGION  517 

into  the  patella  in  common  with  the  Vasti  and  Crureus.  Beiween  the  tendon  of 
origin  and  the  acetabulum  there  is  often  a  biirsa  {bursa  m.  recti  femoris). 

Relations. — By  its  superficial  surface,  with  the  anterior  fibres  of  the  Gluteus 
minimus,  the  Tensor  fasciae  femoris,  the  Sartorius,  and  the  Iliacus;  by  its  lower 
three-fourths,  with  the  fascia  lata.  By  its  posterior  surface,  with  the  hip-joint, 
the  external  circumflex  vessels,  branches  of  the  anterior  crural  nerve,  and  the 
Crureus  and  Vasti  muscles. 

The  Vastus  Extemus  (m.  vastus  lateralis)  is  the  largest  part  of  the  Quadriceps 
extensor.  It  arises  by  a  broad  aponeurosis,  which  is  attached  to  the  upper  half 
of  the  anterior  intertrochanteric  line,  to  the  anterior  and  inferior  borders  of  the 
root  of  the  great  trochanter,  to  the  outer  lip  of  the  gluteal  ridge,  and  to  the  upper 
half  of  the  outer  lip  of  the  linea  aspera;  this  aponeurosis  covers  the  upper  three- 
fourths  of  the  muscle,  and  from  its  inner  surface  many  fibres  take  origin.  A  few 
additional  fibres  arise  from  the  tendon  of  the  Gluteus  maximus,  and  from  the 
external  intermuscular  septum  between  the  Vastus  externus  and  short  head  of  the 
Biceps.  The  fibres  form  a  large  fleshy  mass,  which  is  attached  to  a  strong  aponeu- 
rosis, placed  on  the  under  surface  of  the  muscle  at  its  lower  part:  this  becomes 
contracted  and  thickened  into  a  flat  tendon,  which  is  inserted  into  the  outer 
border  of  the  patella,  blending  with  the  great  Extensor  tendon,  and  giving  an 
expansion  to  the  capsule  of  the  knee-joint.  Some  of  the  fibres  run  down  by  the 
side  of  the  patella  to  the  condyle  of  the  tibia,  and  are  called  the  retinacula  patellae 
laterals. 

Relations. — By  its  superficial  surface,  with  the  Rectus,  the  Tensor  fasciae  femoris, 
the  fascia  lata,  and  the  tendon  of  the  Gluteus  maximus,  from  which  it  is  separated 
by  a  synovial  bursa.  By  its  deep  surface,  with  the  Crureus,  some  large  branches 
of  the  external  circumflex  artery  and  anterior  crural  nerve  being  interposed. 

The  Vastus  Intemus  and  Crureus  appear  to  be  inseparably  united,  but  when 
the  Rectus  femoris  has  been  reflected,  a  narrow  interval  will  be  observed  extending 
upward  from  the  inner  border  of  the  patella  between  the  two  muscles.  Here  they 
can  be  separated,  and  the  separation  should  be  continued  upward  as  far  as  the 
lower  part  of  the  anterior  intertrochanteric  line,  where,  however,  the  two  muscles 
are  frequently  continuous. 

The  Vastus  Intemus  (m.  vastus  medialis)  arises  from  the  lower  half  of  the 
anterior  intertrochanteric  line,  the  spiral  line,  the  inner  lip  of  the  linea  aspera, 
the  upper  part  of  the  internal  supra-condylar  line,  and  the  tendon  of  the  Adductor 
magnus  and  the  internal  intermuscular  septum.  Its  fibres  are  directed  downward 
and  forward,  and  are  chiefly  attached  to  an  aponeurosis  which  lies  on  the  deep 
surface  of  the  muscle  and  is  inserted  into  the  inner  border  of  the  patella  and 
the  Quadriceps  extensor  tendon,  an  expansion  being  sent  to  the  capsule  of  the 
knee-joint.  Some  of  the  fibres  run  down  by  the  side  of  the  patella  to  the  con- 
dyle of  the  tibia  and  are  called  the  retinacula  patellae  mediale. 

The  Crureus  (m.  vastus  iniermedius)  arises  from  the  front  and  outer  aspect  of 
the  shaft  of  the  femur  in  its  upper  two-thirds  and  from  the  lower  part  of  the 
external  intermuscular  septum.  Its  fibres  end  in  a  superficial  aponeurosis,  which 
forms  the  deep  part  of  the  Quadriceps  extensor  tendon. 

Relations. — The  inner  edge  of  the  Crureus  is  in  contact  with  the  anterior  edge 
of  the  Vastus  internus,  but  when  separated  from  each  other,  as  directed  above,  the 
latter  muscle  is  seen  merely  to  overlap  the  inner  aspect  of  the  femoral  shaft  without 
taking  any  fibres  of  origin  from  it.  The  Vastus  internus  is  partly  covered  by  the 
Rectus  and  Sartorius,  but  where  these  separate  near  the  knee  it  becomes  superficial, 
and  produces  a  well-marked  prominence  above  the  inner  aspect  of  the  knee.  In 
the  middle  third  of  the  thigh  it  forms  the  outer  wall  of  Hunter's  canal  (canalis 
adductorius  [Hunteri]),  which  contains  the  femoral  vessels  and  the  long  saphenous 
nerve — the  roof  of  the  canal  being  formed  by  a  strong  fascia  which  extends  from 


518  THE  MUSCLES  AND  FASCIA 

the  Vastus  internus  to  the  Adductores  longus  and  magnus.  The  Crureus  is  almost 
completely  hidden  by  the  Rectus  femoris  and  Vastus  externus.  The  deep  surface 
of  the  two  muscles  is  in  relation  with  the  femur  and  Subcrureus  muscles.  A 
synovial  bursa  (bursa  suprapatellaris)  is  situated  between  the  femur  and  the 
portion  of  the  Quadriceps  extensor  tendon  above  the  patella;  in  the  adult  it 
communicates  with  the  synovial  cavity  of  the  knee-joint. 

The  tendons  of  the  different  portions  of  the  Quadriceps  extensor  unite  at  the 
lower  part  of  the  thigh,  so  as  to  form  a  single  strong  tendon,  which  is  inserted  into 
the  upper  part  of  the  patella,  some  few  fibres  passing  over  it  to  blend  with  the 
Ligamentum  patellae.  More  properly,  the  patella  may  be  regarded  as  a  sesamoid 
bone,  developed  in  the  tendon  of  the  Quadriceps;  and  the  Ligamentum  patellae, 
which  is  continued  from  the  lower  part  of  the  patella  to  the  tuberosity  of  the  tibia, 
as  the  proper  tendon  of  insertion  of  the  muscle.  A  synovial  bursa,  the  deep  patel- 
lar bursa  {bursa  infrapatellaris  profunda),  is  interposed  between  the  tendon  and 
the  upper  part  of  the  tuberosity  of  the  tibia;  and  another,  the  pre-patellar  bursa 
(bursa  proepatellaris  subcutanea),  is  placed  over  the  patella  itself.  This  latter 
bursa  often  becomes  enlarged,  constituting  "housemaid's  knee." 

The  Subcrureus  {m.  articularis  genu)  is  a  small  muscle,  usually  distinct  from 
the  Crureus,  but  occasionally  blended  with  it,  which  arises  from  the  anterior  sur- 
face of  the  lower  part  of  the  shaft  of  the  femur,  and  is  inserted  into  the  upper 
part  of  the  cul-de-sac  of  the  capsular  ligament  which  projects  upward  beneath 
the  Quadriceps  for  a  variable  distance.  It  sometimes  consists  of  several  separate 
muscular  bundles. 

Nerves. — The  Tensor  fasciae  femoris  is  supplied  by  the  fourth  and  fifth  lumbar 
and  first  sacral  nerves  through  the  superior  gluteal  nerve;  the  other  muscles  of 
this  region,  by  the  second,  third,  and  fourth  lumbar  nerves,  through  branches  of 
the  anterior  crural. 

Actions. — ^The  Tensor  fasciae  femoris  is  a  tensor  of  the  fascia  lata;  continuing 
its  action,  the  oblique  direction  of  its  fibres  enables  it  to  abduct  and  to  rotate  the 
thigh  inward.  In  the  erect  posture,  acting  from  below,  it  will  serve  to  steady  the 
pelvis  upon  the  head  of  the  femur,  and  by  means  of  the  ilio-tibial  band  it  steadies 
the  condyles  of  the  femur  on  the  articular  surfaces  of  the  tibia,  and  assists  the 
Gluteus  maximus  in  supporting  the  knee  in  the  extended  position.  The  Sartorius 
flexes  the  leg  upon  the  thigh,  and,  continuing  to  act,  flexes  the  thigh  upon  the 
pelvis;  it  next  rotates  the  thigh  outward.  It  was  formerly  supposed  to  adduct  the 
thigh,  so  as  to  cross  one  leg  over  the  other,  and  hence  received  its  name  of  Sar- 
torius, or  tailor's  muscle  (sartor, a  tailor),  because  it  was  supposed  to  assist  in  cross- 
ing the  legs  in  the  squatting  position.  When  the  knee  is  bent  the  Sartorius  assists 
the  Semitendinosus,  Semimembranosus,  and  Popliteus  in  rotating  the  tibia  inward. 
Taking  its  fixed  point  from  the  leg,  it  flexes  the  pelvis  upon  the  thigh,  and,  if  one 
muscle  acts,  assists  in  rotating  the  pelvis.  The  Quadriceps  extensor  extends  the 
leg  upon  the  thigh.  The  Rectus  muscle  assists  the  Psoas  and  Iliacus  in  supporting 
the  pelvis  and  trunk  upon  the  femur.  It  also  assists  in  flexing  the  thigh  on  the 
pelvis,  or  if  the  thigh  is  fixed  it  will  flex  the  pelvis.  The  Vastus  internus  draws 
the  patella  inward  as  well  as  upward. 

Surgical  Anatomy. — A  few  fibres  of  the  Rectus  muscle  are  liable  to  be  ruptured  from 
severe  strain.  This  accident  is  especially  liable  to  occur  during  the  games  of  football  and  cricket, 
and  is  sometimes  known  as  cricket  thigh.  The  patient  experiences  a  sudden  pain  in  the  part, 
as  if  he  had  been  struck,  and  the  Rectus  muscle  stands  out  and  is  felt  to  be  tense  and  rigid.  The 
accident  is  often  followed  by  considerable  swelling  from  inflammatory  effusion.  Occasionally  the 
Quadriceps  extensor  may  be  torn  away  from  its  insertion  into  the  patella,  or  the  tendon  of  the 
quadriceps  may  be  ruptured  about  an  inch  above  the  bone.  This  accident  is  caused  in  the  same 
manner  that  fracture  of  the  patella  by  muscular  action  is  produced — viz.,  by  a  violent  muscular 
effort  to  prevent  falling  whilst  the  knee  is  in  a  position  of  semiflexion.     A  distinct  gap  can  be 


THE  INTERNAL    FEMORAL   REGION  5I9 

felt  above  the  patella,  and,  owing  to  the  retraction  of  the  muscular  fibres,  union  may  fail  to  take 
place.  Sudden  and  powerful  contraction  of  the  Quadriceps  extensor  femoris  is  the  cause  of 
transverse  fracture  of  the  patella. 

2.  The  Internal  Femoral  Region. 

Gracilis.  Adductor  longus. 

Pectineus.  Adductor  brevis. 

Adductor  magnus. 

Dissection. — These  muscles  are  at  once  exposed  by  removing  the  fascia  from  the  forepart 
and  inner  side  of  the  thigh.  The  limb  should  be  abducted,  so  as  to  render  the  muscles  tense 
and  easier  of  dissection. 

The  Gracilis  (Figs.  343,  346,  and  349)  is  the  most  superficial  muscle  on  the 
inner  side  of  the  thigh.  It  is  thin  and  flattened,  broad  above,  narrowing  and  taper- 
ing below.  It  arises  by  a  thin  aponeurosis  from  the  lower  half  of  the  margin  of  the 
symphysis  and  the  anterior  half  of  the  pubic  arch.  The  fibres  pass  vertically  down- 
ward, and  terminate  in  a  rounded  tendon  which  passes  behind  the  internal  condyle 
of  the  femur,  and,  curving  round  the  inner  tuberosity  of  the  tibia,  becomes  flattened, 
and  is  inserted  into  the  upper  part  of  the  inner  surface  of  the  shaft  of  the  tibia,  below 
the  tuberosity.  A  few  of  the  fibres  of  the  lower  part  of  the  tendon  are  prolonged 
into  the  deep  fascia  of  the  leg.  The  tendon  of  this  muscle  is  situated  immediately 
above  that  of  the  Semitendinosus,  and  its  upper  edge  is  overlapped  by  the  tendon 
of  the  Sartorius,  with  which  it  is  in  part  blended.  As  it  passes  across  the  internal 
lateral  ligament  of  the  knee-joint  it  is  separated  from  it  by  a  synovial  bursa 
(bursa  anserina)  common  to  it  and  the  Semitendinosus  muscle. 

Relations. — By  its  superficial  surf  ace,  with  the  fascia  lata  and  the  Sartorius  below: 
the  internal  saphenous  vein  crosses  it  obliquely  near  its  lower  part,  lying  superficial 
to  the  fascia  lata;  the  internal  saphenous  nerve  emerges  between  its  tendon  and 
that  of  the  Sartorius ;  by  its  deep  surface,  with  the  Adductor  brevis  and  the  Adductor 
magnus  and  the  internal  lateral  ligament  of  the  knee-joint. 

The  Pectineus  (Fig.  343)  is  a  flat,  quadrangular  muscle,  situated  at  the  anterior 
part  of  the  upper  and  inner  aspect  of  the  thigh.  It  arises  from  the  linea  ilio-pec- 
tinea,  and  to  a  slight  extent  from  the  surface  of  the  bone  in  front  of  it  between  the 
pectineal  eminence  and  spine  of  the  os  pubis,  and  from  the  fascia  covering  the 
anterior  surface  of  the  muscle;  the  fibres  pass  downward,  backward,  and  outward, 
to  be  inserted  into  a  rough  line  leading  from  the  lesser  trochanter  to  the  linea  aspera. 

Relations. — By  its  anterior  surface,  with  the  pubic  portion  of  the  fascia  lata, 
which  separates  it  from  the  femoral  vessels  and  internal  saphenous  vein;  by  its 
posterior  surface,  with  the  capsular  ligament  of  the  hip-joint,  the  Adductor  brevis 
and  Obturator  externus  nuiscles,  the  obturator  vessels  and  nerve  being  interposed ; 
by  its  outer  border,  with  the  Psoas,  a  cellular  interval  separating  them,  through 
which  pass  the  internal  circumflex  vessels;  by  its  inner  border,  with  the  margin  of 
the  Adductor  longus.  There  is  usually  a  bursa  (bursa  m.  pectinei)  between  the 
pectineus  and  the  tendon  of  the  psoas  and  iliacus. 

The  Adductor  Longus  (Figs.  343  and  344),  the  most  superficial  of  the  three 
Adductors,  is  a  flat  triangular  muscle  lying  on  the  same  plane  as  the  Pectineus. 
It  arises,  by  a  flat  narrow  tendon,  from  the  front  of  the  os  pubis,  at  the  angle  of 
junction  of  the  crest  with  the  symphysis;  and  soon  expands  into  a  broad  fleshy 
belly,  which,  passing  downward,  backward,  and  outward,  is  inserted,  by  an 
aponeurosis,  into  the  linea  aspera,  between  the  Vastus  internus  and  the  Adductor 
magnus,  with  both  of  which  it  is  usually  blended. 

Relations. — By  its  anterior  surface,  with  the  fascia  lata,  the  Sartorius,  and,  near 
its  insertion,  with  the  femoral  artery  and  vein;  by  its  posterior  surface,  with  the 
Adductor  brevis  and  magnus,  the  anterior  branches  of  the  obturator  nerve,  and 


520 


THE  MUSCLES   AND    FASCIAE 


with  the  profunda  artery  and  vein  near  its  insertion;  by  its  outer  border,  with  the 
Pectineus;  by  its  inner  border,  with  the  GraeiUs. 

The  Pectineus  and  Adductor  longus  should  now 
be  divided  near  their  origin,  and  turned  down- 
ward, when  the  Adductor  brevis  and  Obturator  ex- 
ternus  will  be  exposed. 

The  Adductor  Brevis  (Fig.  344)  is  situ- 
ated immediately  behind  the  two  preceding 
muscles.  It  is  somewhat  triangular  in 
form,  and  arises  by  a  narrow  origin  from 
the  outer  surface  of  the  body  and  descend- 
ing ramus  of  the  os  pubis,  between  the 
Gracilis  and  Obturator  externus.  Its  fibres 
passing  backward,  outward,  and  downward, 
are  inserted,  by  an  aponeurosis,  into  the 
lower  part  of  the  line  leading  from  the  lesser 
trochanter  to  the  linea  aspera  and  the  upper 
part  of  the  same  line,  immediately  behind 
the  Pectineus  and  upper  part  of  the  Ad- 
ductor longus. 

Relations. — By  its  anterior  surface,  with 
the  Pectineus,  Adductor  longus,  profunda 
femoris  artery,  and  anterior  branches  of  the 
obturator  nerve;  by  its  'posterior  surface, 
with  the  Adductor  magnus  and  posterior 
branch  of  the  obturator  nerve ;  by  its  outer 
border,  with  the  internal  circumflex  artery, 
the  Obturator  externus,  and  conjoined  ten- 
don of  the  Psoas  and  Iliacus;  by  its  inner 
border,  with  the  Gracilis  and  Adductor 
magnus.  This  muscle  is  pierced,  near  its 
insertion,  by  the  second  or  by  the  first  and 
second  perforating  branches  of  the  pro- 
funda femoris  artery. 

The  Adductor  brevis  should  now  be  cut  away 
near  its  origin,  and  turned  outward,  when  the  en- 
tire extent  of  the  Adductor  magnus  will  be  exposed. 

The  Adductor  Magnus  (Fig.  344)  is  a 
large  triangular  muscle  forming  a  septum 
between  the  muscles  on  the  inner  and  those 
on  the  back  of  the  thigh.  It  arises  from  a 
small  part  of  the  descending  ramus  of  the 
OS  pubis,  from  the  ramus  of  the  ischium, 
and  from  the  outer  margin  of  the  inferior 
part  of  the  tuberosity  of  the  ischium.  Those 
fibres  which  arise  from  the  ramus  of  the  os 
pubis  are  very  short,  horizontal  in  direction, 
and  are  inserted  into  the  rough  line  leading 
from  the  great  trochanter  to  the  linea  aspera, 
internal  to  the  Gluteus  maximus.  They  are 
considered  by  some  a  distinct  muscle  and  called  the  Adductor  minimus.  The  fibres 
taking  origin  from  the  ramus  of  the  ischium  are  directed  downward  and  outward 


Fig.  344.- 


-Deep  muscles  of  the  internal  femoral 
region. 


THE  INTERNAL    FEMORAL    REGION  521 

with  different  degrees  of  obliquity,  to  be  inserted,  by  means  of  a  broad  aponeurosis, 
into  the  Unea  aspera  and  the  upper  part  of  its  internal  prolongation  below.  The 
internal  portion  of  the  muscle,  consisting  principally  of  those  fibres  which  arise  from 
the  tuberosity  of  the  ischium,  forms  a  thick  fleshy  mass  consisting  of  coarse  bundles 
which  descend  almost  vertically,  and  terminate  about  the  lower  third  of  the  thigh 
in  a  rounded  tendon,  which  is  inserted  into  the  Adductor  tubercle  on  the  inner 
condyle  of  the  femur,  being  connected  by  a  fibrous  expansion  to  the  line  leading 
upward  from  the  tubercle  to  the  linea  aspera.  Between  the  two  portions  of  the 
muscle  an  interval  is  left,  tendinous  in  front,  fleshy  behind,  for  the  passage  of  the 
femoral  vessels  from  Hunter's  canal  into  the  popliteal  space.  The  external  portion 
of  the  muscle  at  its  attachment  to  the  femur  presents  three  or  four  osseo-aponeurotic 
openings,  formed  by  tendinous  arches  attached  to  the  bone,  from  which  muscular 
fibres  arise.  The  three  superior  of  these  apertures  are  for  the  three  perforating 
arteries,  and  the  fourth,  when  it  exists,  is  for  the  terminal  branch  of  the  profunda. 

Relations. — By  its  anterior  surface,  with  the  Pectineus,  Adductor  brevis.  Ad- 
ductor longus,  and  the  femoral  and  profunda  vessels  and  obturator  nerve;  by  its 
posterior  surface,  with  the  great  sciatic  nerve,  the  Gluteus  maximus.  Biceps,  Semi- 
tendinosus,  and  Semimembranosus.  By  its  superior  or  shortest  border  it  lies 
parallel  with  the  Quadratus  femoris,  the  internal  circumflex  artery  passing  between 
them;  by  its  internal  or  longest  border,  with  the  Gracilis,  Sartorius,  and  fascia 
lata;  by  its  ex  ernal  or  attached  border  it  is  inserted  into  the  femur  behind  the  Ad- 
ductor brevis  and  Adductor  longus,  which  separate  it  from  the  Vastus  internus, 
and  in  front  of  the  Gluteus  maximus  and  short  head  of  the  Biceps,  which  sep- 
arate it  from  the  A'astus  externus. 

Nerves.  The  three  Adductor  muscles  and  the  Gracilis  are  supplied  by  the 
third  and  fourth  lumbar  nerves  through  the  obturator  nerve;  the  Adductor  mag- 
nus  receiving  an  additional  branch  from  the  sacral  plexus  through  the  great  sciatic. 
The  Pectineus  is  supplied  by  the  second,  third,  and  fourth  lumbar  nerves  through 
the  anterior  crural,  and  by  the  accessory  obturator,  from  the  third  lumbar,  when 
it  exists.     Occasionally  it  receives  a  branch  from  the  obturator  nerve.^ 

Actions. — The  Pectineus  and  three  Adductors  adduct  the  thigh  powerfully; 
they  are  especially  used  in  horse  exercise,  the  flanks  of  the  horse  being  grasped 
between  the  knees  by  the  actions  of  these  muscles.  In  consequence  of  the  obliquity 
of  their  insertion  into  the  linea  aspera  they  rotate  the  thigh  outward,  assisting 
the  external  Rotators,  and  when  the  limb  has  been  abducted  they  draw  it  inward, 
carrying  the  thigh  across  that  of  the  opposite  side.  The  Pectineus  and  Adductor 
brevis  and  longus  assist  the  Psoas  and  Iliacus  in  flexing  the  thigh  upon  the  pelvis. 
In  progression,  also,  all  these  muscles  assist  in  drawing  forward  the  hinder  limb. 
The  Gracilis  assists  the  Sartorius  in  flexing  the  leg  and  rotating  it  inward;  it  is 
also  an  adductor  of  the  thigh.  If  the  lower  extremities  are  fixed,  these  muscles 
may  take  their  fixed  point  from  below  and  act  upon  the  pelvis,  serving  to  maintain 
the  body  in  an  erect  posture,  or,  if  their  action  is  continued,  to  flex  the  pelvis 
forward  upon  the  femur. 

Hunter's  Canal  (canalis  adductorius  [Hunteri])  extends  from  the  apex  of  Scarpa's 
triangle  to  the  opening  in  the  Adductor  magnus  muscle.  The  antero-internal 
lx)undary  or  roof  of  Hunter's  canal  is  the  Sartorius  and  the  aponeurotic  expan- 
sion from  the  Adductors  to  the  Vastus  internus.  It  is  bounded  externally  by  the 
Vastus  internus.  The  Adductor  longus  and  Magnus  constitute  its  floor  or  the 
postero-internal  boundary.  The  canal  contains  the  femoral  artery,  femoral  vein, 
the  long  saphenous  nerve,  and  the  nerve  to  the  Vastus  internus.  The  anterior 
opening  of  Hunter's  canal  is  called  the  hiatus  tendinous. 

1  Professor  Paterson  describes  the  Pectineus  as  consisting  of  two  incompletely  separated  strata,  of  which 
the  outer  or  dorsal  stratum,  which  is  constant,  is  supplied  by  the  anterior  crural  nerve,  or  in  its  absence  by  the 
accessory  obturator,  with  which  it  is  intimately  related;  while  the  inner  or  ventral  stratum,  when  present,  is 
supplied  by  the  obturator  nerve. — Journ.  of  Anat.  and  Phys.,  vol.  xxvi.  p.  43. — Ed.  of  15th  lOnglish  edition. 


522 


THE  MUSCLES  AND   FASCIJE 


Surgical  Anatomy. — The  Adductor  longus  is  liable  to  be  severely  strained  in  those  who  ride 
much  on  horseback,  or  its  tendon  to  be  ruptured  by  suddenly  gripping  the  saddle.  Occasionally, 
especially  in  cowboys  and  cavalry  soldiers,  the  tendon  of  insertion  of  the  Adductor  magnus 
may  become  ossified,  constituting  the  rider's  bone. 


THE  MUSCLES  AND  FASCI.ffi  OF  THE  HIP. 


3.  The  Gluteal  Region  (Figs.  346,  347). 

Gluteus  maximus.  Obturator  internus. 

Gluteus  medius.  Gemellus  superior. 

Gluteus  minimus.  Gemellus  inferior. 

Pyriformis.  Quadratus  femoris. 

Obturator  externus. 

Dissection  (Fig.  345). — The  subject  should  be  turned  on  its  face,  a  block  placed  beneath 
the  pelvis  to  make  the  buttocks  tense,  and  the  limbs  allowed  to  hang  over  the  end  of  the  table, 
with  the  foot  inverted  and  the  thigh  abducted.    Make  an  incision  through  the  integument  along 

the  crest  of  the  ilium  to  the  middle  of  the  sacrum,  and 
thence  downward  to  the  tip  of  the  coccyx,  and  carry  a 
second  incision  from  that  point  obliquely  downward  and 
outward  to  the  outer  side  of  the  thigh,  four  inches  be- 
low the  great  trochanter.  The  portion  of  integument 
included  between  these  incisions  is  to  be  removed  in 
1.  Dissection  of  the  direction  shown  in  the  figure. 
gluteal  region. 

The  Gluteus  Maximus  (m.  glutceus  maximus) 
(Fig.  346),  the  most  superficial  muscle  in  the 
gluteal  region,  is  a  very  broad  and  thick,  fleshy 
mass  of  a  quadrilateral  shape,  which  forms  the 
prominence  of  the  buttock.  Its  large  size  is  one 
of  the  most  characteristic  points  in  the  mus- 
cular system  of  man,  connected  as  it  is  with 
the  power  he  has  of  maintaining  the  trunk  in 
the  erect  posture.  In  structure  the  muscle  is 
remarkably  coarse,  being  made  up  of  muscular 
fasciculi  lying  parallel  with  one  another,  and 
collected  together  into  large  bundles,  separated 
by  deep  cellular  intervals.  It  arises  from  the 
superior  curved  line  of  the  ilium  and  the  por- 
tion of  bone,  including  the  crest,  immediately 
above  and  behind  it;  from  the  posterior  sur- 
face of  the  lower  part  of  the  sacrum,  the  side  of 
the  coccyx,  the  aponeurosis  of  the  Erector  spinse 
muscle,  the  great  sacro-sciatic  ligament,  and 
the  fascia  covering  the  Gluteus  medius.  The 
fibres  are  directed  obliquely  downward  and 
outward;  those  forming  the  upper  and  large 
portion  of  the  muscle,  together  with  the  super- 
ficial fibres  of  the  lower  portion,  terminate  in 
a  thick  tendinous  lamina,  which  passes  across 
the  great  trochanter  and  is  inserted  into  the 
fascia  lata  covering  the  outer  side  of  the  thigh; 
the  deeper  fibres  of  the  lower  portion  of  the  muscles  are  inserted  into  the  rough 
line  leading  from  the  great  trochanter  to  the  linea  aspera  between  the  Vastus 
externus  and  Adductor  magnus. 


3.  Back  of  thigh. 


2.  Popliteal  space. 


Jf.  /  Jf.  Back  of  leg. 


5   \  5.  Sole  of  foot 


Fig.  345.- 


-Dissection  of  lower  extremity. 
Posterior  view. 


THE    GLUTEAL    REGION  523 

Several  synovial  bursae  are  found  in  relation  with  this  muscle.  One  of  these 
(bursa  trochanterica  m.  glutwi  maximi),  of  large  size,  and  generally  multilocular, 
separates  it  from  the  great  trochanter.  A  second  (bursa  ischiadica  m.  glutcBi 
maximi),  often  wanting,  is  situated  on  the  tuberosity  of  the  ischium.  A  third 
bursa  is  found  between  the  tendon  of  this  muscle  and  the  Vastus  externus.  Two 
or  three  small  bursse  (burs(B  glutaofemorales)  are  placed  between  the  tendon  of 
the  muscle  and  the  gluteal  ridge. 

Relations. — By  its  superficial  surface,  with  a  thin  fascia,  which  separates  it  from 
the  subcutaneous  tissue;  by  its  deep  surface,  from  above  downward,  with  the  ilium, 
sacrum,  coccyx,  and  great  sacro-sciatic  ligament,  part  of  the  Gluteus  medius, 
Pyriformis,  Gemelli,  Obturator  internus,  Quadratus  femoris,  the  tuberosity  of 
the  ischium,  great  trochanter,  the  origin  of  the  Biceps,  Semitendinosus,  Semimem- 
branosus, and  Adductor  magnus  muscles.  The  superficial  part  of  the  gluteal 
artery  reaches  the  deep  surface  of  the  muscle  by  passing  between  th?  Pyriformis 
and  the  Gluteus  medius;  the  sciatic  and  internal  pudic  vessels  and  nerves  and 
muscular  branches  from  the  sacral  plexus  issue  from  the  pelvis  below  the  Pyri- 
formis. The  first  perforating  artery  and  the  terminal  branches  of  the  internal  cir- 
cumflex artery  are  also  found  under  cover  of  the  muscle.  Its  upper  border  is  thin, 
and  connected  with  the  Gluteus  medius  by  the  fascia  lata.  Its  lower  border  is  free 
and  prominent. 

Dissection. — Divide  the  Gluteus  maximus  near  its  origin  by  a  vertical  incision  carried  from 
its  upper  to  its  lower  border;  a  cellular  interval  will  be  exposed,  separating  it  from  the  Gluteus 
medius  and  External  rotator  muscles  beneath.  The  upper  portion  of  the  muscle  is  to  be  alto- 
gether detached,  and  the  lower  portion  turned  outward;  the  loose  areolar  tissue  filling  up  the 
interspace  between  the  trochanter  major  and  tuberosity  of  the  ischium  being  removed,  the  parts 
already  enumerated  as  exposed  by  the  removal  of  this  muscle  will  be  seen. 

The  Gluteus  Medius  (m.  glutoem  medium)  (Fig.  346)  is  a  broad,  thick,  radiated 
muscle,  situated  on  the  outer  surface  of  the  pelvis.  Its  posterior  third  is  covered  by 
the  Gluteus  maximus;  its  anterior  two-thirds  by  the  fascia  lata,  which  separates 
it  from  the  integument.  It  arises  from  the  outer  surface  of  the  ilium,  between  the 
superior  and  middle  curved  lines,  and  from  the  outer  lip  of  that  portion  of  the 
crest  which  is  between  them ;  it  also  arises  from  the  dense  fascia,  the  gluteal  aponeu- 
rosis, covering  its  outer  surface.  The  fibres  converge  to  a  strong  flattened  tendon 
which  is  inserted  into  the  oblique  line  which  traverses  the  outer  surface  of  the 
great  trochanter.  A  synovial  bursa  (bursa  trochanterica  m.  glutcei  medii  anterior) 
separates  the  tendon  of  the  muscle  from  the  summit  of  the  great  trochanter. 
There  is  frequently  a  bursa  (bursa  trochanterica  m.  glutcei  medii  posterior)  between 
the  tendons  of  the  Gluteus  medius  and  Pyriformis. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  behind,  the 
Tensor  fascife  femoris  and  deep  fascia  in  front;  by  its  deep  surface,  with  the  Glu- 
teus minimus  and  the  gluteal  vessels  and  superior  gluteal  nerve.  Its  anterior  border 
is  blended  with  the  Gluteus  minimus.  Its  posterior  border  Hes  parallel  with  the 
Pyriformis,  the  gluteal  vessels  intervening. 

This  muscle  should  now  be  divided  near  its  insertion  and  turned  upward,  when  the  Gluteus 
minimus  will  be  exposed. 

The  Gluteus  Minimus  (m.  glutceu^  minimus)  (Fig.  346),  the  smallest  of  the 
three  Glutei,  is  placed  immediately  beneath  the  preceding.  It  is  fan-shaped, 
arising  from  the  outer  surface  of  the  ilium,  between  the  middle  and  inferior 
curved  lines,  and  behind,  from  the  margin  of  the  great  sacro-sciatic  notch;  the 
fibres  converge  to  the  deep  surface  of  a  radiated  aponeurosis,  which,  terminating 
in  a  tendon,  is  inserted  into  an  impression  on  the  anterior  border  of  the  great 
trochanter. 


524 


THE  MUSCLES  AND  FASCIA 


Inner  hamstring 
tendons. 


SEMIMI 

NOSUS 


Fig.  346. — Muscles  of  the  hip  and  thigh. 


Relations. — By  its  superficial 
surf  ace, vi'ith.  the  Gluteus  medius 
and  the  gluteal  vessels  and  supe- 
rior gluteal  nerve;  by  its  deep 
surface,  with  the  ilium,  the  re- 
flected tendon  of  the  Rectus 
femoris,  and  the  capsular  liga- 
ment of  the  hip-joint.  Its  ante- 
rior margin  is  blended  with  the 
Gluteus  medius;  its  posterior 
margin  is  in  contact  and  some- 
times joined  with  the  tendon  of 
the  Pyriformis.  There  is  a 
synovial  bursa  {bursa  m.  glutoei 
minimi)  between  the  tendon  of 
the  Gluteus  minimus  and  the 
great  trochanter. 

The  Pyriformis  (to.  pirifor- 
mis) (Figs.  346  and  347)  is 
a  flat  muscle,  pyramidal  in 
shape,  lying  almost  parallel 
with  the  posterior  margin  of  the 
Gluteus  medius.  It  is  situated 
partly  within  the  pelvis  at  its 
posterior  part  and  partly  at  the 
back  of  the  hip-joint.  It  arises 
from  the  front  of  the  sacrum 
by  three  fleshy  digitations  at- 
tached to  the  portions  of  bone 
between  the  first,  second,  third, 
and  fourth  anterior  sacral  fora- 
mina, and  also  from  the  groove 
leading  from  the  foramina:  a 
few  fibres  also  arise  from  the 
margin  of  the  great  sacro-sciatic 
foramen  and  from  the  anterior 
surface  of  the  great  sacro-sciatic 
ligament.  The  muscle  passes 
out  of  the  pelvis  through  the 
great  sacro-sciatic  foramen,  the 
upper  part  of  which  it  fills,  and 
is  inserted  by  a  rounded  tendon 
into  the  upper  border  of  the 
great  trochanter,  behind,  but 
often  partly  blended  with,  the 
tendon  of  the  Obturator  in- 
ternus  and  Gemelli  muscles. 

Relations.  —  By  its  anterior 
surface,  within  the  pelvis,  with 
the  Rectum  (especially  on  the 
left  side),  the  sacral  plexus  of 
nerves,  and  the  branches  of  the 
internal  iliac  vessels;  external 
to  the  pelvis,  with  the  posterior 


THE    GLUTEAL   REGION  525 

surface  of  the  ischium  and  the  capsular  ligament  of  the  hip-joint;  by  its  'posterior 
surface,  within  the  pelvis,  with  the  sacrum,  and  external  to  i^,  with  the  Gluteus 
maximus;  by  its  upper  border,  with  the  Gluteus  medius,  from  which  it  is 
separated  by  the  gluteal  vessels  and  superior  gluteal  nerve;  by  its  loiver  border, 
with  the  Gemellus  superior  and  Coccygeus,  the  sciatic  vessels  and  nerves,  the 
internal  pudic  vessels  and  nerve,  and  muscular  branches  from  the  sacral  plexus, 
passing  from  the  pelvis  in  the  interval  between  the  two  muscles.  There  is 
usually  a  bursa  {bursa  m.  piriformis)  between  the  tendon  of  the  pyriforaiis  and 
the  ilium. 

The  Obturator  Membrane  (membrana  obturatoria)  (Fig.  215)  is  a  thin  layer  of 
interlacing  fibres  which  closes  almost  completely  the  obturator  foramen.  It  is 
attached,  externally,  to  the  margin  of  the  foramen;  internally,  to  the  posterior 
surface  of  the  ischio-pubic  ramus,  below  and  internal  to  the  margin  of  the 
foramen.  It  presents  at  its  upper  and  outer  part  a  small  canal,  obturator  canal 
{canalis  obturator iu^s)  for  the  passage  of  the  obturator  vessels  and  nerve.  Both 
obturator  muscles  are  connected  with  this  membrane. 

Dissection. — The  next  muscle,  as  well  as  the  origin  of  the  Pyriformis,  can  only  be  seen  when 
the  pelvis  is  divided  and  the  viscera  removed. 

The  Obturator  Intemus(Figs.  346  and  347) ,  like  the  preceding  muscle,  is  situated 
partly  within  the  cavity  of  the  pelvis,  and  partly  at  the  back  of  the  hip-joint.  It  arises 
from  the  inner  surface  of  the  anterior  and  external  wall  of  the  pelvis,  where  it  sur- 
rounds the  greater  part  of  the  obturator  foramen,  being  attached  to  the  descending 
ramus  of  the  os  pubis  and  the  ramus  of  the  ischium,  and  at  the  side  to  the  inner  sur- 
face of  the  innominate  bone  below  and  behind  the  pelvic  brim,  reaching  from  the 
upper  part  of  the  great  sacro-sciatic  foramen  above  and  behind  to  the  thyroid 
foramen  below  and  in  front.  It  also  arises  from  the  inner  surface  of  the  obturator 
membrane  except  at  its  posterior  part,  from  the  tendinous  arch  which  completes 
the  canal  for  the  passage  of  the  obturator  vessels  and  nerve  and  to  a  slight  extent 
from  the  obturator  layer  of  the  pelvic  fascia,  which  covers  it.  The  fibres  converge 
rapidly,  and  are  directed  backward  and  downward,  and  terminate  in  four  or  five 
tendinous  bands,  which  are  found  on  its  deep  surface;  these  bands  are  reflected  at 
a  right  angle  over  the  inner  surface  of  the  tuberosity  of  the  ischium,  which  is 
grooved  for  their  reception;  the  groove  is  covered  with  cartilage,  and  lined  by  a 
synovial  bursa  {bursa  m.  obturatoris  interni).  The  muscle  leaves  the  pelvis  by 
the  lesser  sacro-sciatic  foramen ;  and  the  tendinous  bands  unite  into  a  single  flat- 
tened tendon,  which  passes  horizontally  outward,  and,  after  receiving  the  attach- 
ment of  the  Gemelli,  is  inserted  into  the  forepart  of  the  inner  surface  of  the  great 
trochanter  in  front  of  the  Obturator  externus.  A  synovial  bursa,  narrow  and 
elongated  in  form,  is  usually  found  between  the  tendon  of  this  muscle  and  the 
capsular  ligament  of  the  hip:  it  occasionally  communicates  with  the  bursa 
between  the  tendon  and  the  tuberosity  of  the  ischium,  the  two  forming  a 
single  sac. 

In  order  to  display  the  peculiar  appearances  presented  by  the  tendon  of  this  muscle,  it  must 
be  divided  near  its  insertion  and  reflected  inward. 

Relations. — Within  the  pelvis  this  muscle  is  in  relation,  by  its  anterior  surface, 
with  the  obturator  membrane  and  inner  surface  of  the  anterior  wall  of  the  pelvis; 
by  its  posterior  surface,  with  the  pelvic  and  obturator  fasciae,  which  separate  it 
from  the  Levator  ani;  and  it  is  crossed  by  the  internal  pudic  vessels  and  nerve. 
This  surface  forms  the  outer  boundary  of  the  ischio-rectal  fossa  (Fig.  339). 
External  to  the  pelvis  it  is  covered  by  the  Gluteus  maximus,  is  crossed  by  the 
great  sciatic  nerve,  and  rests  on  the  back  part  of  the  hip-joint.  As  the  tendon 
of  the  Obturator  internus  emerges  from  the  lesser  sacro-sciatic  foramen  it  is  over- 


526 


THE  MUSCLES   AND    FASCIA 


lapped  by  the  two  Gemelli,  while  nearer  its  insertion  the  Gemelli  pass  in  front  of  it 
and  form  a  groove  in  which  the  tendon  lies. 

The  Gemelli  (Fig.  346)  are  two  small  muscular  fasciculi,  accessories  to  the 
tendon  of  the  Obturator  internus,  which  is  received  into  a  groove  between  them. 
They  are  called  superior  and  inferior. 

The  Gemellus  Supenor,  the  smaller  of  the  two,  arises  from  the  outer  surface 
of  the  spine  of  the  ischium,  and,  passing  horizontally  outward,  becomes  blended 


Fig.  347. — Muscles  of  the  small  or  true  pelvis  on  the  right  side,  viewed  from  without  and  below.      (Spalteholz.) 


with  the  upper  part  of  the  tendon  of  the  Obturator  internus,  and  is  inserted  with 

it  into  the  inner  surface  of  the  great  trochanter.    This  muscle  is  sometimes  wanting. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  sciatic 

vessels  and  nerves;  by  its  deep  surface,  with  the  capsule  of  the  hip-joint;  by  its 


THE    GLUTEAL    BEGION 


527 


upper  border,  with  the  lower  margin  of  the  Pyriformis;  by  its  lower  border,  with 
the  tendon  of  the  Obturator  internus. 

The  Gemellus  Inferior  arises  from  the  upper  part  of  the  tuberosity  of  the  ischium, 
where  it  forms  the  lower  edge  of  the  groove  for  the  Obturator  internus  tendon, 
and,  passing  horizontally  outward,  is  blended  with  the  lower  part  of  the  tendon 
of  the  Obturator  internus,  and  is  inserted  with  it  into  the  inner  surface  of  the  great 
trochanter. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  sciatic 
vessels  and  nerves;  by  its  deep  surface,  with  the  scapular  ligament  of  the  hip-joint; 
by  its  upper  border,  with  the  tendon  of  the  Obturator  internus;  by  its  lower  border, 
with  the  tendon  of  the  Obturator  externus  and  Quadratus  femoris. 

The  Quadratus  Femoris  (Fig.  346)  is  a  short,  flat  muscle,  quadrilateral  in  shape 
(hence  its  name),  situated  between  the  Gemellus  inferior  and  the  upper  margin 
of  the  Adductor  magnus.  It  arises  from  the  upper  part  of  the  external  lip  of  the 
tuberosity  of  the  ischium,  and,  proceeding  horizontally  outward,  is  inserted  iato 
the  upper  part  of  the  linea  quadrata ;  that  is,  the  line  which  crosses  the  posterior 
intertrochanteric  line.  A  synovial  bursa  is  often  found  between  the  under  surface 
of  this  muscle  and  the  lesser  trochanter,  which  it  covers. 


Obturator 
artery. 


Anterior  division  of 
obturator  nerve. 


Antenor  inferior 
iliac  spine. 


Posterior  division 
of  obturator 
nerve. 


Internal  clrcum 
flex  artery 


liga- 
partly 
away. 


Fig.  348. 


-Obturator  externus  muscle.     (From  a  preparation  in  the  Museum  of  the  Royal  College  of 
Surgeons  of  England.) 


Relations. — By  its  posterior  surface,  with  the  Gluteus  maximus  and  the  sciatic 
vessels  and  nerves;  by  its  anterior  surface,  with  the  tendon  of  the  Obturator  exter- 
nus and  trochanter  minor  and  with  the  capsule  of  the  hip-joint;  by  its  upper 
border,  with  the  Gemellus  inferior.  Its  lower  border  is  separated  from  the  Adductor 
magnus  by  the  terminal  branches  of  the  internal  circumflex  vessels. 

Dissection. — In  order  to  expose  the  next  muscle  (the  Obturator  externus)  it  is  necessary 
to  remove  the  Psoas,  IHacus,  Pectineus,  and  Adductor  brevis  and  longus  muscles  from  the  front 


528  THE  MUSCLES  AND   FASCIA 

and  inner  side  of  the  thigh,  and  the  Gluteus  maximus  and  Quadratus  femoris  from  the  back 
part.  Its  dissection  should,  consequently,  be  postponed  until  the  muscles  of  the  anterior  and 
internal  femoral  regions  have  been  explained. 

The  Obturator  Externus  (Figs.  347  and  348)  is  a  flat,  triangular  muscle,  which 
covers  the  outer  surface  of  the  anterior  wall  of  the  pelvis.  It  arises  from  the  margin 
of  bone  immediately  around  the  inner  side  of  the  obturator  foramen — viz.,  from  the 
body  and  ramus  of  the  os  pubis  and  the  ramus  of  the  ischium ;  it  also  arises  from 
the  inner  two-thirds  of  the  outer  surface  of  the  obturator  membrane,  and  from 
the  tendinous  arch  which  completes  the  canal  for  the  passage  of  the  obturator 
vessels  and  nerves.  The  fibres  from  the  pubic  arch  extend  on  to  the  inner  sur- 
face of  the  bone,  from  which  they  obtain  a  narrow  origin  between  the  margin  of 
the  foramen  and  the  attachment  of  the  membrane.  The  fibres  converging 
pass  backward,  outward,  and  upward,  and  terminate  in  a  tendon  which  runs 
across  the  back  part  of  the  hip-joint,  and  is  inserted  into  the  digital  fossa  of  the 
femur. 

Relations. — By  its  anterior  surface,  with  the  Psoas,  Iliacus,  Pectineus,  Adductor 
magnus,  and  Adductor  brevis;  and  more  externally,  with  the  neck  of  the  femur 
and  capsule  of  the  hip-joint.  The  obturator  artery  and  vein  lie  between  this 
muscle  and  the  obturator  membrane;  the  superficial  part  of  the  obturator  nerve 
lies  above  the  muscle,  and  the  deep  branch  perforates  it;  by  its  'posterior  surface , 
with  the  obturator  membrane  and  Quadratus  femoris. 

Nerves. — ^The  Gluteus  maximus  is  supplied  by  the  fifth  lumbar  and  first  and 
second  sacral  nerves  through  the  inferior  gluteal  nerve  from  the  sacral  plexus; 
the  Gluteus  medius  and  minimus,  by  the  fourth  and  fifth  lumbar  and  first  sacral 
nerves  through  the  superior  gluteal;  the  Pyriformis  is  supplied  by  the  first  and 
second  sacral  nerves;  the  Gemellus  inferior  and  Quadratus  femoris  by  the  last 
lumbar  and  first  sacral  nerve;  the  Gemellus  superior  and  Obturator  internus  by 
the  fifth  lumbar  and  first  and  second  sacral  nerves,  and  the  Obturator  externus 
by  the  second,  third,  and  fourth  lumbar  nerves  through  the  obturator. 

Actions. — ^The  Gluteus  maximus,  when  it  takes  its  fixed  point  from  the  pelvis, 
extends  the  femur  and  brings  the  bent  thigh  into  a  line  with  the  body.  Taking 
its  fixed  point  from  below,  it  acts  upon  the  pelvis,  supporting  it  and  the  whole 
trunk  upon  the  head  of  the  femur,  which  is  especially  obvious  in  standing  on  one 
leg.  Its  most  powerful  actions  are  to  hold  the  head  of  the  femur  in  close  approxi- 
mation to  the  acetabulum  in  walking  and  to  cause  the  body  to  regain  the  erect 
position  after  stooping  by  drawing  the  pelvis  backward,  being  assisted  in  this  action 
by  the  Biceps,  Semitendinosus,  and  Semimembranosus.  The  Gluteus  maximus 
is  a  tensor  of  the  fascia  lata,  and  by  its  connection  with  the  ilio-tibial  band  it  steadies 
the  femur  on  the  articular  surface  of  the  tibia  during  standing,  when  the  Extensor 
muscles  are  relaxed.  The  lower  part  of  the  muscle  also  acts  as  an  adductor  and 
external  rotator  of  the  limb.  The  Gluteus  medius  and  minimus  abduct  the  thigh 
when  the  limb  is  extended,  and  are  principally  called  into  action  in  supporting 
the  body  on  one  limb,  in  conjunction  with  the  Tensor  fascipe  femoris.  Their 
anterior  fibres,  by  drawing  the  great  trochanter  forward,  rotate  the  thigh  inward, 
in  which  action  they  are  also  assisted  by  the  Tensor  fascite  femoris.  The  remain- 
ing muscles  are  powerful  rotators  of  the  thigh  outward.  In  the  sitting  posture, 
when  the  thigh  is  flexed  upon  the  pelvis,  their  action  as  rotators  cease,  and  they 
become  abductors,  with  the  exception  of  the  Obturator  externus,  which  still 
rotates  the  femur  outward.  When  the  femur  is  fixed,  the  Pyriformis  and  Obturator 
muscles  serve  to  draw  the  pelvis  forward  if  it  has  been  inclined  backward,  and 
assist  in  steadying  it  upon  the  head  of  the  femur. 

Surgical  Anatomy. — The  fascia  over  the  gluteal  region  is  extremely  dense  and  an  abscess 
beneath  it  may  pass  far  down  into  the  thigh. 


THE   POSTERIOR   FEMORAL    REGION 


529 


4.  The  Posterior  Femoral  Region. 

Biceps.  Semitendinosus.  Semimembranosus. 

{Hamstring  muscles.) 

Dissection  (Fig.  345).— Make  a  vertical  incision  along  the  middle  of  the  back  of  the  thigh, 
from  the  lower  fold  of  the  buttock  to  about  three  inches  below  the  back  of  the  knee-joint,  and 
there  connect  it  with  a  transverse  incision,  carried  from  the  inner  to  the  outer  side  of  the  leg. 
Make  a  third  incision  transversely  at  the  junction  of  the  middle  with  the  lower  third  of  the 
thigh.  The  integument  having  been  removed  from  the  back  of  the  knee,  and  the  boundaries 
of  the  popliteal  space  having  been  examined,  the  removal  of  the  integument  from  the  remaining 
T>art  of  the  thigh  should  be  continued,  when  the  fascia  and  muscles  of  this  region  will  be  exposed. 


BURSA  OF 
SCMIMCMBRANOSUS 


BURSA  OF 

APONEUROTIC 

EXPANSION 

OF  SARTORIUS 


Fig.  349. — Region  of  the  knee,  seen  obliquely  from  behind  and  within.     Right  limb.     (Toldt.) 

The  Biceps  or  Biceps  Flexor  Cruris  (m.  biceps  femoris)  is  a  large  muscle,  of 
considerable  length,  situated  on  the  posterior  and  outer  aspect  of  the  thigh 
(Figs.  346  and  349).  It  ariseshy  two  heads.  One,  the  long  head  (caput  longum), 
arises  from  the  lower  and  inner  impression  on  the  back  part  of  the  tuberosity 

34 


530  THE    MUSCLES  AND    FASCIA 

of  the  ischium,  by  a  tendon  common  to  it  and  the  Semitendinosus,  and  from 
the  lower  part  of  the  great  sacro-sciatic  Hgament.  Between  this  tendon  of 
origin  and  the  Semimembranosus  there  is  often  a  bursa  (bursa  m.  bicipitis 
femoris  superior).  The  femoral,  or  short  head  (caput  breve),  arises  from  the 
outer  Hp  of  the  Hnea  aspera,  between  the  Adductor  magnus  and  Vastus  externus, 
extending  up  almost  as  high  as  the  insertion  of  the  Gluteus  maximus;  from 
the  outer  prolongation  of  the  linea  aspera  to  within  two  inches  of  the  outer  con- 
dyle, and  from  the  external  intermuscular  septum.  The  fibres  of  the  long  head 
form  a  fusiform  belly,  which,  passing  obliquely  downward  and  a  little  out- 
ward, terminates  in  an  aponeurosis  which  covers  the  posterior  surface  of  the 
muscle,  and  receives  the  fibres  of  the  short  head:  this  aponeurosis  becomes 
gradually  contracted  into  a  tendon,  which  is  inserted  into  the  outer  side  of  the 
head  of  the  fibula,  and  by  a  small  slip  into  the  lateral  surface  of  the  external 
tuberosity  of  the  tibia.  At  its  insertion  the  tendon  divides  into  two  portions,  which 
embrace  the  long  external  lateral  ligament  of  the  knee-joint.  From  the  posterior 
border  of  the  tendon  a  thin  expansion  is  given  off  to  the  fascia  of  the  leg.  The 
tendon  of  this  muscle  forms  the  outer  hamstring.  Sometimes  there  is  a  bursa 
(bursa  bicipitogastrocnemialis)  between  the  tendon  of  insertion  of  the  Biceps  and 
the  origin  of  the  Gastrocnemius,  and  there  is  a  bursa  (bursa  m.  bicipitis  femoris 
inferior)  between  the  tendon  of  the  biceps  and  the  external  lateral  ligament. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  the  small 
sciatic  nerve,  the  fascia  lata,  and  integument.  By  its  deep  surface,  with  the  Semi- 
membranosus, Adductor  magnus,  and  Vastus  externus,  the  great  sciatic  nerve, 
and,  near  its  insertion,  with  the  external  head  of  the  Gastrocnemius,  the  Plantaris, 
the  superior  external  articular  artery,  and  the  external  popliteal  nerve. 

The  Semitendinosus  (Figs.  346  and  349),  remarkable  for  the  great  length 
of  its  tendon,  is  situated  at  the  posterior  and  inner  aspect  of  the  thigh.  It 
arises  from  the  lower  and  inner  impression  on  the  tuberosity  of  the  ischium 
by  a  tendon  common  to  it  and  the  long  head  of  the  Biceps ;  it  also  arises  from 
an  aponeurosis  which  connects  the  adjacent  surfaces  of  the  two  muscles  to 
the  extent  of  about  three  inches  after  their  origin.  There  is  a  bursa  (bursa 
m.  bicipitis  femoris  superior)  between  the  tendons  of  origin  of  the  Biceps  and 
Semitendinosus  on  one  side  and  the  tendon  of  origin  of  the  Semimembranosus 
on  the  other.  The  Semitendinosus  is  a  fusiform  muscle,  which,  passing  down- 
ward and  inward,  terminates  a  little  below  the  middle  of  the  thigh  in  a  long 
round  tendon  which  lies  along  the  inner  side  of  the  popliteal  space,  then 
curves  around  the  inner  tuberosity  of  the  tibia,  and  is  inserted  into  the  upper 
part  of  the  inner  surface  of  the  shaft  of  that  bone  nearly  as  far  forward  as  its 
anterior  border.  At  its  insertion  it  gives  off  from  its  lower  border  a  prolongation 
to  the  deep  fascia  of  the  leg.  This  tendon  lies  behind  the  tendon  of  the  Sar- 
torius,  and  below  that  of  the  Gracilis,  to  which  it  is  united.  A  tendinous  inter- 
section is  usually  observed  about  the  middle  of  the  muscles.  The  bursa  anserina 
lies  between  the  tendon  of  the  Semitendinosus  and  the  tibia.  This  bursa  was 
referred  to  in  speaking  of  the  Gracilis,  p.  519. 

Relations. — By  its  superficial  surface,  with  the  Gluteus  maximus  and  fascia  lata; 
by  its  deep  surface,  with  the  Semimembranosus,  Adductor  magnus,  inner  head  of 
the  Gastrocnemius,  and  internal  lateral  ligament  of  the  knee-joint. 

The  Semimembranosus  (Figs.  346  and  349),  so  called  from  its  membranous 
tendon  of  origin,  is  situated  at  the  back  part  and  inner  side  of  the  thigh.  It 
arises  by  a  thick  tendon  from  the  upper  and  outer  impression  on  the  back  part 
of  the  tuberosity  of  the  ischium,  above  and  to  the  outer  side  of  the  Biceps  and 
Semitendinosus,  and  is  inserted  into  the  groove  on  the  inner  and  back  part  of  the 
inner  tuberosity  of  the  tibia,  beneath  the  internal  lateral  ligament.  The  tendon  of 
the  muscle  at  its  origin  expands  into  an  aponeurosis  which  covers  the  upper  part 


THE   ANTERIOR     TIBIO- FIBULAR    REGION  531 

of  its  anterior  surface:  from  this  aponeurosis  muscular  fibres  arise,  and  converge 
to  another  aponeurosis,  which  covers  the  lower  part  of  its  posterior  surface  and 
contracts  into  the  tendon  of  insertion.  The  tendon  of  the  muscle  at  its  insertion 
o;ives  off  certain  fibrous  expansions;  one  of  these,  of  considerable  size,  passes 
upward  and  outward  to  be  inserted  into  the  back  part  of  the  outer  condyle  of 
the  femur,  forming  part  of  the  posterior  ligament  of  the  knee-joint;  a  second  is 
continued  downward  to  the  fascia  which  covers  the  Popliteus  muscle.  The 
tendon  also  sends  a  few  fibres  to  join  the  internal  lateral  ligament  of  the  joint. 

The  tendons  of  the  two  preceding  muscles,  with  that  of  the  Gracilis,  form 
the  inner  hamstrings. 

Relations.— By  its  superficial  surface,  with  the  Gluteus  maximus,  Semitendinosus, 
Biceps,  and  fascia  lata;  by  its  deep  surface,  with  the  origin  of  the  Quadratus 
femoris,  popliteal  vessels.  Adductor  magnus,  and  inner  head  of  the  Gastroc- 
nemius; by  its  inner  border,  with  the  Gracilis;  by  its  outer  border,  with  the  great 
sciatic  nerve,  and  its  internal  popliteal  branch.  There  is  a  bursa  between  the 
Gastrocnemius  and  Semimembranosus  and  another  bursa  between  the  Semi- 
membranosus and  the  inner  condyle  of  the  tibia.  The  first  bursa  usually  com- 
municates with  the  knee-joint.  These  two  bursae  are  in  communication  and  in 
reality  constitute  a  double  bursa  (bursa  m.  semimembranosi) . 

Nerves. — The  muscles  of  this  region  are  supplied  by  the  first,  second,  and 
third  sacral  nerves  through  the  great  sciatic  nerve. 

Actions. — The  hamstring  muscles  flex  the  leg  upon  the  thigh.  When  the  knee 
is  semiflexed,  the  Biceps,  in  consequence  of  its  obhque  direction  downward  and 
outward,  rotates  the  leg  slightly  outward;  and  the  Semitendinosus,  and  to  a 
slight  extent  the  Semimembranosus,  rotate  the  leg  inward,  assisting  the  Popliteus. 
Taking  their  fixed  point  from  below,  these  muscles,  especially  the  Semimem- 
branosus, serve  to  support  the  pelvis  upon  the  head  of  the  femur  and  to  draw 
the  trunk  directly  backward,  as  in  raising  it  from  the  stooping  position  or  in 
feats  of  strength,  when  the  body  is  thrown  backward  in  the  form  of  an  arch. 
When  the  leg  is  extended  on  the  thigh,  they  limit  the  amount  of  flexion  of  the 
trunk  on  the  lower  limbs. 

Surgical  Anatomy. — The  hamstring  tendons  are  occasionally  ruptured.  In  disease  of  the 
knee-joint  the  hamstrings  may  contract,  flexing  the  knee,  drawing  the  tibia  backward,  and  some- 
times causing  incomplete  dislocation.  The  tendons  of  these  muscles  occasionally  require  sub^ 
cutaneous  division  in  some  forms  of  spurious  ankylosis  of  the  knee-joint  dependent  upon 
permanent  contraction  and  rigidity  of  the  Flexor  muscles,  or  from  stiffening  of  the  ligamentous 
and  other  tissues  surrounding  the  joint,  the  result  of  disease.  Division  of  a  tendon  is  effected 
by  putting  the  tendon  upon  the  stretch,  and  inserting  a  narrow  sharp-pointed  knife  between 
it  and  the  skin:  the  cutting  edge  being  then  turned  toward  the  tendon,  it  should  be  divided, 
taking  great  care  that  the  wound  in  the  skin  is  not  at  the  same  time  enlarged.  The  relation  of  the 
external  popliteal  nerve  to  the  tendon  of  the  Biceps  must  always  be  borne  in  mind  in  dividing  this 
tendon. 

III.  MUSCLES  AND  FASCIA  OF  THE  LEG. 

These  may  be  divided  into  three  groups:  those  on  the  anterior,  those  on  the 
posterior,  and  those  on  the  outer  side  of  the  leg. 

5.  The  Anterior  Tibio-fibular  Region  (Fig.  350). 

Tibialis  anticus.  Extensor  longus  digitorum. 

Extensor  proprius  hallucis.^  Peroneus  tertius. 

'  There  is  no  such  word  as  '  'Hallux,  -cis."  It  is  the  result  of  some  ignorant  blunder,  copied  until  it  has  become 
established  by  usage;  it  has  been  thought  better,  therefore,  to  retain  it.  According  to  Lewis  and  Short,  the 
word  is  Allex,  masculine;  genitive,  Allicis,  the  great  toe,  and  the  correct  rendering  would  be  Extensor  pro- 
prius allicis.  It  is  a  rare  word,  and  is  sometimes  spelt,  but  not  so  correctly,  "Hallex.  It  is  used  by  Plautus, 
in  the  "Pcenulus,"  V.,  v.  31.  of  a  little  man,  as  we  might  say  "a  hop-o'-my-thumb."  "Tunc  hie  amator  audes 
esse,  allex  viri"  (To  think  of  you  daring  to  make  uo  to  her,  you  hop-o'-my-thumb!).  The  word  "alex,"  some- 
times spelt  "allex,"  a  fish  sauce,  is  probably  a  different  word  altogether.  It  is  used  by  Horace  and  Pliny. 
— Ed.  of  15th  English  edition. 


532  THE  MUSCLES   AND   FASCIA 

Dissection  (Fig.  341). — The  knee  should  be  bent,  a  block  placed  beneath  it,  and  the  foot 
kept  in  an  extended  position;  then  make  an  incision  through  the  integument  in  the  middle  line 
of  the  leg  to  the  ankle,  and  continue  it  along  the  dorsum  of  the  foot  to  the  toes.  Make  a  second 
incision  transversely  across  the  ankle,  and  a  third  in  the  same  direction  across  the  bases  of  the 
toes;  remove  the  flaps  of  integument  included  between  these  incisions  in  order  to  examine  the 
deep  fascia  of  the  leg. 

The  Deep  Fascia  of  the  Leg  (fascia  cruris)  forms  a  complete  investment  to 
the  muscles,  but  is  not  continuous  over  the  subcutaneous  surfaces  of  the  bones. 
It  is  continuous  above  with  the  fascia  lata,  receiving  an  expansion  from  the  tendon 
of  the  Biceps  on  the  outer  side,  and  from  the  tendons  of  the  Sartorius,  Gracilis, 
and  Semitendinosus  on  the  inner  side;  in  front  it  blends  with  the  periosteum 
covering  the  subcutaneous  surface  of  the  tibia,  and  with  that  covering  the  head 
and  external  malleolus  of  the  fibula;  below  it  is  continuous  with  the  annular  liga- 
ments of  the  ankle.  It  is  thick  and  dense  in  the  upper  and  anterior  part  of  the  leg, 
and  gives  attachment,  by  its  deep  surface,  to  the  Tibialis  anticus  and  Extensor 
longus  digitorum  muscles,  but  is  thinner  behind,  where  it  covers  the  Gastrocnemius 
and  Soleus  muscles.  Over  the  popliteal  space  it  is  much  strengthened  by  trans- 
verse fibres  which  stretch  across  from  the  inner  to  the  outer  hamstring  muscles, 
and  it  is  here  perforated  by  the  external  saphenous  vein.  Its  deep  surface  gives 
off,  on  the  outer  side  of  the  leg,  two  strong  intermuscular  septa  which  enclose  the 
Peronei  muscles,  and  separate  them  from  the  muscles  of  the  anterior  and  posterior 
tibial  regions.  It  also  gives  off  several  smaller  and  more  slender  processes 
which  enclose  the  individual  muscles  in  each  region;  at  the  same  time  a  broad 
transverse  intermuscular  septum,  called  the  deep  transverse  fascia  of  the  leg, 
intervenes  between  the  superficial  and  deep  muscles  in  the  posterior  tibio-fibular 
region. 

Remove  the  fascia  by  dividing  it  in  the  same  direction  as  the  integument,  excepting  opposite 
the  ankle,  where  it  should  be  left  entire.  Commence  the  removal  of  the  fascia  from  below, 
opposite  the  tendons,  and  detach  it  in  the  line  of  direction  of  the  muscular  fibres. 

The  Tibialis  Anticus  (m.  tibialis  anterior)  is  situated  on  the  outer  side  of  the 
tibia;  it  is  thick  and  fleshy  at  its  upper  part,  tendinous  below.  It  arises  from  the 
outer  tuberosity  and  upper  two-thirds  of  the  external  surface  of  the  shaft  of  the 
tibia;  from  the  adjoining  part  of  the  interosseous  membrane;  from  the  deep 
surface  of  the  fascia;  and  from  the  intermuscular  septum  between  it  and  the 
Extensor  longus  digitorum:  the  fibres  pass  vertically  downward,  and  terminate 
in  a  tendon  which  is  apparent  on  the  anterior  surface  of  the  muscle  at  the  lower 
third  of  the  leg.  After  passing  through  the  innermost  compartment  of  the  anterior 
annular  ligament,  it  is  inserted  into  the  inner  and  under  surface  of  the  internal 
cuneiform  bone  and  base  of  the  metatarsal  bone  of  the  great  toe.  There  is 
usually  a  bursa  (bursa  subtendinea  m.  tibialis  anterioris)  between  the  tendon  of 
the  tibialis  anticus  and  the  internal  cuneiform  bone. 

Relations. — By  its  anterior  surface,  with  the  fascia  and  with  the  annular  liga- 
ment; by  its  posterior  surface,  with  the  interosseous  membrane,  tibia,  ankle-joint, 
and  inner  side  of  the  tarsus :  this  surface  also  overlaps  the  anterior  tibial  vessels 
and  nerve  in  the  upper  part  of  the  leg.  By  its  inner  surface,  with  the  tibia;  by 
its  outer  surface,  with  the  Extensor  longus  digitorum  and  Extensor  proprius 
hallucis,  and  the  anterior  tibial  vessels  and  nerve. 

The  Extensor  Proprius  Hallucis  (m.  extensor  hallucis  longus)  is  a  thin,  elon- 
gated, and  flattened  muscle  situated  between  the  Tibialis  anticus  and  Extensor 
longus  digitorum.  It  arises  from  the  anterior  surface  of  the  fibula  for  about  the 
middle  two-fourths  of  its  extent,  its  origin  being  internal  to  that  of  the  Extensor 
longus  digitorum ;  it  also  arises  from  the  interosseous  membrane  to  a  similar 
extent.    The  fibres  pass  downward,  and  terminate  in  a  tendon  which  occupies 


THE   ANTEBIOll    TIBIO- FIBULAR    REGION 


533 


the  anterior  border  of  the  muscle,  passes  through  a 
distinct  compartment  in  the  lower  portion  of  the 
annular  ligament,  crosses  the  anterior  tibial  vessels 
near  the  bend  of  the  ankle,  and  is  inserted  into  the 
base  of  the  last  phalanx  of  the  great  toe.  Opposite 
the  metatarso-phalangeal  articulation  the  tendon 
gives  off  a  thin  prolongation  on  each  side,  which 
covers  the  surface  of  the  joint.  It  usually  sends  an 
expansion  from  the  inner  side  of  the  tendon,  to  be 
inserted  into  the  base  of  the  first  phalanx. 

Relations. — By  its  anterior  surface,  with  the  fascia 
and  the  anterior  annular  ligament;  by  its  posterior 
surface,  with  the  interosseous  membrane,  fibula, 
tibia,  and  ankle-joint;  by  its  outer  side,  with  the 
Extensor  longus  digitorum  above,  the  dorsalis  pedis 
vessels,  anterior  tibial  nerve,  and  Extensor  brevis 
digitorum  below;  by  its  inner  side,  with  the  Tibialis 
anticus  and  the  anterior  tibial  vessels  above.  The 
muscle  is  external  to  the  anterior  tibial  vessels  in 
the  upper  part  of  the  leg;  but  in  the  lower  third  its 
tendon  crosses  over  them,  so  that  it  lies  internal  to 
them  on  the  dorsum  of  the  foot. 

The  Extensor  Longus  Digitorum  (m.  extensor 
digitorum  longus)  is  an  elongated,  flattened,  penni- 
form  muscle  situated  the  most  externally  of  all  the 
muscles  on  the  forepart  of  the  leg.  It  arises  from 
the  outer  tuberosity  of  the  tibia;  from  the  upper 
three-fourths  of  the  anterior  surface  of  the  shaft  of 
the  fibula;  from  the  interosseous  membrane;  from 
the  deep  surface  of  the  fascia;  and  from  the  inter- 
muscular septa  between  it  and  the  Tibialis  anticus 
on  the  inner  and  the  Peronei  on  the  outer  side. 
The  tendon  enters  a  canal  in  the  annular  ligament 
with  the  Peroneus  tertius,  and  divides  into  four 
slips,  which  run  across  the  dorsum  of  the  foot  and 
are  inserted  into  the  second  and  third  phalanges  of 
the  four  lesser  toes.  The  mode  in  which  the  tendons 
are  inserted  is  the  following:  Each  of  the  three 
inner  tendons  opposite  the  metatarso-phalangeal 
articulation  is  joined,  on  its  outer  side,  by  a  ten- 
don from  the  Extensor  brevis  digitorum.  The  outer 
tendon  does  not  receive  such  a  tendinous  slip.  They 
all  receive  a  fibrous  expansion  from  the  Interossei 
and  Lumbricales,  and  then  spread  out  into  a  broad 
aponeurosis,  which  covers  the  dorsal  surface  of  the 
first  phalanx:  this  aponeurosis,  at  the  articulation  of 
the  first  with  the  second  phalanx,  divides  into  three 
slips — a  middle  one,  which  is  inserted  into  the  base 
of  the  second  phalanx,  and  two  lateral  slips,  which, 
after  uniting  on  the  dorsal  surface  of  the  second 
phalanx,  are  continued  onward,  to  be  inserted  into 
the  base  of  the  third. 

Relations. — By  its  anterior  surface,  with  the  fascia 
and  the  annular  ligament;   by  its   posterior  surface. 


I  A  I,  4! 


\hl' 


trl'd' 


Fig.  350.- 


the  front  of 


534  THE    3IUSCLE8   AND    FASCIA 

with  the  fibula,  interosseous  membrane,  ankle-joint,  and  Extensor  brevis  digi- 
torum;  by  its  inner  side,  with  the  Tibialis  anticus.  Extensor  proprius  hallucis, 
and  anterior  tibial  vessels  and  nerve ;  by  its  outer  side,  with  the  Peroneus  longus 
and  brevis. 

The  Peroneus  Tertius  {m.  peronoeus  tertius)  is  a  part  of  the  Extensor  longus 
digitorum,  and  might  be  described  as  its  fifth  tendon.  The  fibres  belonging  to 
this  tendon  arise  from  the  lower  fourth  of  the  anterior  surface  of  the  fibula,  from 
the  lower  part  of  the  interosseous  membrane,  and  from  an  intermuscular  septum 
between  it  and  the  Peroneus  brevis.  The  tendon,  after  passing  through  the  same 
canal  in  the  annular  ligament  as  the  Extensor  longus  digitorum,  is  inserted  into 
the  dorsal  surface  of  the  base  of  the  metatarsal  bone  of  the  little  toe.  This 
muscle  is  sometimes  wanting. 

Nerves. — These  muscles  are  supplied  by  the  fourth  and  fifth  lumbar  and  first 
sacral  nerves  through  the  anterior  tibial  nerve. 

Actions. — The  Tibialis  anticus  and  Peroneus  tertius  are  the  direct  flexors  of  the 
foot  at  the  ankle-joint;  the  former  muscle,  when  acting  in  conjunction  with  the 
Tibialis  posticus,  raises  the  inner  border  of  the  foot  {i.e.,  inverts  the  foot);  and 
the  latter,  acting  with  the  Peroneus  brevis  and  longus,  draws  the  outer  border  of 
the  foot  upward  and  the  sole  outward  (i.  e.,  everts  the  foot).  The  Extensor  longus 
digitorum  and  Extensor  proprius  hallucis  extend  the  phalanges  of  the  toes,  and, 
continuing  their  action,  flex  the  foot  upon  the  leg.  Taking  their  fixed  point  from 
below,  in  the  erect  posture,  all  these  muscles  serve  to  fix  the  bones  of  the  leg  in  the 
perpendicular  position,  and  give  increased  strength  to  the  ankle-joint. 

6.  The  Posterior  Tibio-fibular  Region  (Figs.  349,  352). 

Dissection  (Fig.  345). — Make  a  vertical  incision  along  the  middle  line  of  the  back  of  the 
leg,  from  the  lower  part  of  the  popliteal  space  to  the  heel,  connecting  it  below  by  a  transverse 
incision  extending  between  the  two  malleoli;  the  flaps  of  integument  being  removed,  the  fascia 
and  muscles  should  be  examined. 

The  muscles  in  this  region  of  the  leg  are  subdivided  into  two  layers — superficial 
and  deep.  The  superficial  layer  constitutes  a  powerful  muscular  mass,  forming 
the  calf  of  the  leg.  Their  large  size  is  one  of  the  most  characteristic  features  of 
the  muscular  apparatus  in  man,  and  bears  a  direct  connection  with  his  ordinary 
attitude  and  mode  of  progression. 

The  Superficial  Layer. 

Gastrocnemius.  Soleus.  Plantaris. 

The  Gastrocnemius  is  the  most  superficial  muscle,  and  forms  the  greater  part 
of  the  calf.  It  arises  by  two  heads,  which  are  connected  to  the  condyles  of  the  femur 
by  two  strong  flat  tendons.  The  inner  and  larger  head  {caput  inediale)  arises  from 
a  depression  at  the  upper  and  back  part  of  the  inner  condyle  and  from  the 
adjacent  part  of  the  femur.  There  is  a  bursa  (bursa  m.  gastrocnemii  mediahs) 
between  the  tendon  of  origin  and  the  inner  condyle.  The  outer  head  (caput 
laterale)  arises  from  an  impression  on  the  outer  side  of  the  external  condyle  and 
from  the  posterior  surface  of  the  femur  immediately  above  the  condyle.  There 
is  a  bursa  (bursa  m.  gastrocnemii  lateralis)  between  the  tendon  of  origin  and  the 
outer  condyle.  Both  heads,  also,  arise  by  a  few  tendinous  and  fleshy  fibres 
from  the  ridges  which  are  continued  upward  from  the  condyles  to  the  linea  aspera. 
Each  tendon  spreads  out  into  an  aponeurosis,  which  covers  the  posterior  surface 
of  that  portion  of  the  muscle  to  which  it  belongs ;  the  muscular  fibres  of  the 
inner  head  being  thicker  and  extending  lower  than  those  of  the  outer.  From 
the  anterior  surface  of  these  tendinous  expansions  muscular  fibres  are  given  off. 


THE  POSTERIOR    TIBIO- FIBULAR    REGION 


535 


The  fibres  in  the  median  line,  which  correspond  to  the  accessory  portions  of  the 
muscle  derived  from  the  bifurcations  of  the  linea  aspera,  unite  at  an  angle 
upon  a  median  tendinous  raphe  below:  the  remaining  fibres  converge  to  an 
aponeurosis  which  covers  the  anterior  surface  of  the  muscle,  and  this,  gradually 
contracting,  unites  with  the  tendon  of  the  Soleus,  and  forms  with  it  the  tendo 
Achillis. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  leg,  which  separates 
it  from  the  external  saphenous  vein  and  nerve;  by  its  deep  surface,  with  the  pos- 
terior ligament  of  the  knee-joint,  the  Popliteus,  Soleus,  Plantaris,  popliteal  vessels, 
and  internal  popliteal  nerve.  The  tendon  of  the  inner  head  corresponds  with  the 
back  part  of  the  inner  condyle,  from  which  it  is  separated  by  a  synovial  bursa, 
which,  in  some  cases,  communicates  with  the  cavity  of  the  knee-joint.  The 
tendon  of  the  outer  head  contains  a  sesamoid  fibro-cartilage  (rarely  osseous) 
where  it  plays  over  the  corresponding  outer  condyle;  and  one  is  occasionally 
found  in  the  tendon  of  the  inner  head. 


The  Gastrocnemius  should  be  divided  across,  just  below  its  origin,  and  turned  downward, 
in  order  to  expose  the  next  two  muscles. 

The  Soleus  is  a  broad  flat  muscle  situated  immediately  beneath  the  Gastroc- 
nemius.   It  has  received  its  name  from  its  resemblance  in  shape  to  a  sole-fish.    It 
arises  by  tendinous  fibres  from  the  back  part  of  the  head  of  the  fibula  and  from 
the  upper  third  of  the  posterior  surface  of  its  shaft; 
from  the  oblique  line  of  the  tibia  and  from  the  mid- 
dle third  of  its  internal  border;  some  fibres  also  arise 
from  a  tendinous  arch  placed  between  the  tibial  and 
fibular  origins   of    the    muscle,   beneath  which   the 
popliteal  vessels  and  internal  popliteal  nerve  pass. 
The  fibres  pass  backward  to  an  aponeurosis  which 
covers  the  posterior  surface  of  the  muscle,  and  this, 
gradually  becoming  thicker  and  narrower,  joins  with 
the  tendon  of  the  Gastrocnemius,  and  forms  with  it 
the  tendo  Achillis. 

The  triceps  surm  is  the  designation  in  the  new 
nomenclature  of  the  Gastrocnemius  and  Soleus. 

Relations.  —  By  its  superficial  surface,  with  the 
Gastrocnemius  and  Plantaris;  by  its  deep  surface, 
with  the  Flexor  longus  digitorum.  Flexor  longus 
hallucis,  Tibialis  posticus,  and  posterior  tibial 
vessels  and  nerve,  from  which  it  is  separated  by 
the  transverse  intermuscular  septum  or  deep  transverse  fascia  of  the  leg. 

The  Tendo  Achillis  (tendo  calcaneus),  the  common  tendon  of  the  Gastrocnemius 
and  Soleus,^  is  the  thickest  and  strongest  tendon  in  the  body.  It  is  about  six 
inches  in  length,  and  commences  about  the  middle  of  the  leg,  but  receives  fleshy 
fibres  on  its  anterior  surface  nearly  to  its  lower  end.  Gradually  becoming  con- 
tracted below,  it  is  inserted  into  the  lower  part  of  the  posterior  surface  of  the  os 
calcis,  a  synovial  bursa,  the  retro-calcaneal  bursa  (bursa  tendinis  calcanei 
[Achillis])  (Fig.  351),  being  interposed  between  the  tendon  and  the  upper  part 
of  this  surface.  The  tendon  spreads  out  somewhat  at  its  lower  end,  so  that  its 
narrowest  part  is  usually  about  an  inch  and  a  half  above  its  insertion.  The  tendon 
is  covered  by  the  fascia  and  the  integument,  a  bursa  (bursa  svbcutanea  calcanea) 
(Fig..  351)  being  often  interposed  between  the  tendon  and  the  fascia.    The  tendon 


BURSA  BETWEEN 
—  FASCIA  AND 
TENDON 


BURSA  BETWEEN 
TENDON    AND 
OS  CALCIS 


Fig.  351. — Bursse  of  the  tendo 
Achillis.    (Poirier  and  Charpy.) 


*  These  two  muscles  with  a  common  tendon  are  by  some  anatomists  classed  together  as  one  muscle,  the 
Trictps  surx,  the  two  heads  of  origin  of  the  Gastrocnemius  and  the  Soleus  constituting  the  three  heads  of  the 
Triceps,  and  the  tendo  Achillis  the  single  tendon  of  insertion. — Ed.  of  15th  English  edition. 


536 


THE  MUSCLES  AND    FASCIA 


is  separated  from  the  deep  muscles  and  vessels  by  a  considerable  interval  filled 
up  with  areolar  and  adipose  tissue.  Along  its  outer  side,  but  superficial  to  it,  is 
the  external  saphenous  vein. 


Tendons  of 

RONEUS    LONGUS 

and  BREvis. 


Femur. 


ilti- 


i>» 


mkiVi 


Fig.  352. — Muscles  of  the  back  of  the  leg. 
Superficial  layer. 


Fig.  3.53. — Muscles  of  the  back 
of  the  leg.     Deep  layer. 


The  Plantaris  is  an  extremely  diminutive  muscle  placed  between  the  Gas- 
trocnemius and  Soleus,  and  remarkable  for  its  long  and  delicate  tendon.    It  arises 


THE  POSTERIOR    TIBIO- FIBULAR    REGION  537 

from  the  lower  part  of  the  outer  prolongation  of  the  Unea  aspera  and  from  the  pos- 
terior Hgament  of  the  knee-joint.  It  forms  a  small  fusiform  belly,  about  three  or 
four  inches  in  length,  terminating  in  a  long  slender  tendon  which  crosses  obliquely 
between  the  two  muscles  of  the  calf,  and,  running  along  the  inner  border  of  the 
tendo  Achillis,  is  inserted  with  it  into  the  posterior  part  of  the  os  calcis.  This 
muscle  is  occasionally  double,  and  is  sometimes  wanting.  Occasionally  its  tendon 
is  lost  in  the  internal  annular  ligament  or  in  the  fascia  of  the  leg. 

Nerves. — The  Gastrocnemius  is  supplied  by  the  first  and  second  sacral  nerves, 
and  the  Plantaris  by  the  fourth  and  fifth  lumbar  and  first  sacral  nerves  through  the 
internal  pophteal.  The  Soleus  is  supplied  by  the  fifth  lumbar  and  first  and  second 
sacral  nerves  through  the  internal  popliteal  and  posterior  tibial. 

Actions.— The  muscles  of  the  calf  are  the  chief  extensors  of  the  foot  at  the 
ankle-joint.  They  possess  considerable  power,  and  are  constantly  called  into  use 
in  standing,  walking,  dancing,  and  leaping;  hence  the  large  size  they  usually  pre- 
sent. In  walking  these  muscles  draw  powerfully  upon  the  os  calcis,  raising  the 
heel,  and  with  it  the  entire  body,  from  the  ground;  the  body  being  thus  supported 
on  the  raised  foot,  the  opposite  limb  can  be  carried  forward.  In  standing,  the 
Soleus,  taking  its  fixed  point  from  below,  steadies  the  leg  upon  the  foot,  and  pre- 
vents the  body  from  falling  forward,  to  which  there  is  a  constant  tendency  from  the 
superincumbent  weight.  The  Gastrocnemius,  acting  from  below,  serves  to  flex  the 
femur  upon  the  tibia,  assisted  by  the  Popliteus.  The  Plantaris  is  the  rudiment  of 
a  large  muscle  which  exists  in  some  of  the  lower  animals  and  is  continued  over  the 
OS  calcis  to  be  inserted  into  the  plantar  fascia.  In  man  it  is  an  accessory  to  the 
Gastrocnemius,  extending  the  ankle  if  the  foot  is  free,  or  bending  the  knee  if  the 
foot  is  fixed.  Possibly,  acting  from  below,  by  its  attachment  to  the  posterior  liga- 
ment of  the  knee-joint,  it  may  pull  that  ligament  backward  during  flexion,  and  so 
protect  it  from  being  compressed  between  the  two  articular  surfaces. 

The  Deep  Layer  (Fig.  353). 

Popliteus.  Flexor  longus  digitorum. 

Flexor  longus  hallucis.  Tibialis  posticus. 

Dissection. — Detach  the  Soleus  from  its  attachment  to  the  fibula  and  tibia,  and  turn  it  down- 
ward, when  the  deep  layer  of  muscles  is  exposed,  covered  by  the  deep  transverse  fascia  of  the 
leg. 

Deep  Transverse  Fascia. — The  deep  transverse  fascia  of  the  leg  is  a  trans- 
versely placed,  intermuscular  septum,  between  the  superficial  and  deep  muscles 
in  the  posterior  tibio-fibular  region.  On  either  side  it  is  connected  to  the  margins 
of  the  tibia  and  fibula.  Above,  where  it  covers  the  Pophteus,  it  is  thick  and  dense, 
and  receives  an  expansion  from  the  tendon  of  the  Semimembranosus ;  it  is  thinner 
in  the  middle  of  the  leg,  but  below,  where  it  covers  the  tendons  passing  behind  the 
malleoli,  it  is  thickened  and  continuous  with  the  internal  annular  ligament. 

This  fascia  should  now  be  removed,  commencing  from  below  opposite  the  tendons,  and 
detaching  it  from  the  muscles  in  the  direction  of  their  fibres. 

The  Popliteus  (Fig.  349)  is  a  thin,  flat,  triangular  muscle,  which  forms  part  of 
the  floor  of  the  popliteal  space.  It  arises  by  a  strong  tendon,  about  an  inch  in 
length,  from  a  deep  depression  on  the  outer  side  of  the  external  condyle  of  the 
femur,  and  from  the  posterior  ligament  of  the  knee-joint.  A  bursa  (bursa  m. 
poplifei)  is  placed  between  the  condyle  and  the  muscle.  The  muscle  is  inserted 
into  the  inner  two-thirds  of  the  triangular  surface  above  the  oblique  line  on  the 
posterior  surface  of  the  shaft  of  the  tibia,  and  into  the  tendinous  expansion 
covering  the  surface  of  the  muscle.  The  tendon  of  the  muscle  is  covered  by 
that  of  the  Biceps  and  by  the  external  lateral  ligament  of  the  knee-joint;  it  grooves 


538  THE   MUSCLES  AND    FASCIA 

the  posterior  border  of  the  external  semikmar  fibro-cartilage,  and  is  invested  by 
the  synovial  membrane  of  the  knee-joint. 

Relations. — By  its  superficial  surface,  with  the  fascia  covering  it,  which  separates 
it  from  the  Gastrocnemius,  Plantaris,  popliteal  vessels,  and  internal  pophteal  nerve; 
by  its  deep  surface,  with  the  knee-joint  and  back  of  the  tibia. 

The  Flexor  LongUS  Hallucis  (m.  flexor  halhicis  longu^)  is  situated  on  the  fibular 
side  of  the  leg,  and  is  the  most  superficial  and  largest  of  the  three  next  muscles. 
It  arises  from  the  lower  two-thirds  of  the  posterior  surface  of  the  shaft  of  the 
fibula,  with  the  exception  of  an  inch  at  its  lowest  part;  from  the  lower  part  of 
the  interosseous  membrane;  from  an  intermuscular  septum  between  it  and  the 
Peronei,  externally;  and  from  the  fascia  covering  the  Tibialis  posticus  internally. 
The  fibres  pass  obliquely  downward  and  backward,  and  terminate  in  a  tendon 
which  occupies  nearly  the  whole  length  of  the  posterior  surface  of  the  muscle. 
This  tendon  occupies  a  groove  on  the  posterior  surface  of  the  lower  end  of  the 
tibia;  it  then  lies  in  a  second  groove  on  the  posterior  surface  of  the  astragalus,  and 
finally  in  a  third  groove,  beneath  the  sustentaculum  tali  of  the  os  calcis,  and 
passes  into  the  sole  of  the  foot,  where  it  runs  forward  between  the  two  heads  of 
the  Flexor  brevis  hallucis,  and  is  mserted  into  the  base  of  the  last  phalanx  of  the 
great  toe  (Fig.  355).  The  grooves  in  the  astragalus  and  os  calcis,  which  contain 
the  tendon  of  the  muscle,  are  converted  by  tendinous  fibres  into  distinct  canals 
lined  by  synovial  membrane;  and  as  the  tendon  crosses  the  sole  of  the  foot,  it  is 
connected  to  the  common  flexor  by  a  tendinous  slip. 

Relations. — By  its  superficial  surface,  with  the  Soleus  and  tendo  Achillis,  from 
which  it  is  separated  by  the  deep  transverse  fascia;  by  its  deep  surface,  with  the 
fibula.  Tibialis  posticus,  the  peroneal  vessels,  the  lower  part  of  the  interosseous 
membrane,  and  the  ankle-joint;  by  its  outer  harder,  with  the  Peronei;  by  its  inner 
border,  with  the  Tibialis  posticus  and  posterior  tibial  vessels  and  nerve.  In  the 
sole  of  the  foot  it  lies  above  the  Abductor  hallucis  and  Flexor  longus  digitorum. 

The  Flexor  Longus  Digitorum  (m.  flexor  digitorum  longus)  is  situated  on 
the  tibial  side  of  the  leg.  At  its  origin  it  is  thin  and  pointed,  but  gradually 
increases  in  size  as  it  descends.  It  arises  from  the  posterior  surface  of  the  shaft 
of  the  tibia,  immediately  below  the  oblique  line  to  within  three  inches  of  its 
extremity,  internal  to  the  tibial  origin  of  the  Tibialis  posticus;  some  fibres  also 
arise  from  the  fascia  covering  the  Tibialis  posticus.  The  fibres  terminate  in  a 
tendon  which  runs  nearly  the  whole  length  of  the  posterior  surface  of  the  muscle. 
This  tendon  passes  behind  the  internal  malleolus  in  a  groove,  common  to  it  and 
the  Tibialis  posticus,  but  separated  from  the  latter  by  a  fibrous  septum,  each 
tendon  being  contained  in  a  special  sheath  lined  by  a  separate  synovial  membrane. 
It  then  passes  obliquely  forward  and  outward,  superficial  to  the  internal  lateral 
ligament,  into  the  sole  of  the  foot  (Fig.  355),  where,  crossing  superficially  to  the 
tendon  of  the  Flexor  longus  hallucis,^  to  which  it  is  connected  by  a  strong 
tendinous  slip,  it  becomes  expanded,  is  joined  by  the  Flexor  accessorius,  and  finally 
divides  into  four  tendons  which  are  inserted  into  the  bases  of  the  last  phalanges 
of  the  four  lesser  toes,  each  tendon  passing  through  a  fissure  in  the  tendon  of  the 
Flexor  brevis  digitorum  opposite  the  base  of  the  first  phalanges  (Fig.  354). 

Relations. — In  the  leg:  by  its  super flcial  surface,  with  the  posterior  tibial  vessels 
and  nerve,  and  the  deep  transverse  fascia,  which  separates  it  from  the  Soleus 
muscle;  by  its  deep  surface,  with  the  Tibia  and  Tibialis  posticus.  In  the  foot  it  is 
covered  by  the  Abductor  hallucis  and  Flexor  brevis  digitorum,  and  crosses  super- 
ficial to  the  Flexor  longus  hallucis. 

The  Tibialis  Posticus  (m.  tibialis  posterior)  lies  between  the  two  preceding 
muscles,  and  is  the  most  deeply  seated  of  all  the  muscles  in  the  leg.    It  com- 

*  That  is,  in  the  order  of  dissection  of  the  sole  of  the  foot. 


THE    FIBULAR    REGION  539 

mences  above  by  two  pointed  processes,  separated  by  an  angular  interval, 
through  which  the  anterior  tibial  vessels  pass  forward  to  the  front  of  the  leg. 
It  arises  from  the  whole  of  the  posterior  surface  of  the  interosseous  membrane, 
excepting  its  lowest  part,  from  the  outer  portion  of  the  posterior  surface  of  the 
shaft  of  the  tibia,  between  the  commencement  of  the  oblique  line  above,  and  the 
junction  of  the  middle  and  lower  third  of  the  shaft  below;  and  from  the  upper 
two-thirds  of  the  internal  surface  of  the  fibula;  some  fibres  also  arise  from  the 
deep  transverse  fascia  and  from  the  intermuscular  septa,  separating  it  from  the 
adjacent  muscles  on  each  side.  This  muscle,  in  the  lower  fourth  of  the  leg, 
passes  in  front  of  the  Flexor  longus  digitorum,  and  terminates  in  a  tendon  which 
passes  through  a  groove  behind  the  inner  malleolus  with  the  tendon  of  that 
muscle,  but  enclosed  in  a  separate  sheath ;  it  then  passes  through  another  sheath, 
over  the  internal  lateral  ligament  into  the  foot,  and  then  beneath  the  inferior 
calcaneo-scaphoid  ligament,  and  is  inserted  into  the  tuberosity  of  the  scaphoid 
and  internal  cuneiform  bones  (Fig.  356).  The  tendon  of  this  muscle  contains  a 
sesamoid  fibro-cartilage  as  it  passes  over  the  scaphoid  bone,  and  gives  off  fibrous 
expansions,  one  of  which  passes  backward  to  the  sustentaculum  tali  of  the  os  calcis, 
others  outward  to  the  middle  and  external  cuneiform  and  cuboid,  and  some 
forward  to  the  base  of  the  second,  third,  and  fourth  metatarsal  bones  (Fig.  355). 

Relations. — By  its  superficial  surface,  with  the  Soleus,  from  which  it  is  separated 
by  the  deep  transverse  fascia,  the  Flexor  longus  digitorum,  the  posterior  tibial 
vessels  and  nerve,  and  the  peroneal  vessels;  by  its  deep  surface,  with  the  inter- 
osseous ligament,  the  tibia,  fibula,  and  ankle-joint. 

Nerves. — The  Popliteus  is  supplied  by  the  fourth  and  fifth  lumbar  and  first  sacral 
nerves,  through  the  internal  popliteal;  the  Flexor  longus  digitorum  and  Tibialis 
posticus  by  the  fifth  lumbar  and  first  sacral;  and  the  Flexor  longus  hallucis  by  the 
fifth  lumbar  and  first  and  second  sacral  nerves  through  the  posterior  tibial. 

Actions. — The  Popliteus  assists  in  flexing  the  leg  upon  the  thigh;  when  the  leg 
is  flexed,  it  will  rotate  the  tibia  inward.  It  is  especially  called  into  action  at  the 
commencement  of  the  act  of  bending  the  knee,  inasmuch  as  it  produces  a  slight 
inward  rotation  of  the  tibia,  which  is  essential  in  the  early  stage  of  this  movement. 
The  Tibialis  posticus  is  a  direct  extensor  of  the  foot  at  the  ankle-joint;  acting  in 
conjunction  with  the  Tibialis  anticus,  it  turns  the  sole  of  the  foot  inward  (i.  e., 
inverts  the  foot),  antagonizing  the  Peronei,  which  turn  it  outward  (evert  it).  In 
the  sole  of  the  foot  the  tendon  of  the  Tibialis  posticus  lies  directly  below  the  inferior 
calcaneo-scaphoid  ligament,  and  is  therefore  an  important  factor  in  maintaining 
the  arch  of  the  foot.  The  Flexor  longus  digitorum  and  Flexor  longus  hallucis  are 
the  direct  flexors  of  the  phalanges,  and,  continuing  their  action,  extend  the  foot 
upon  the  leg;  they  assist  the  Gastrocnemius  and  Soleus  in  extending  the  foot,  as  in 
the  act  of  walking  or  in  standing  on  tiptoe.  In  consequence  of  the  oblique  direction 
of  the  tendon  of  the  long  flexor  the  toes  would  be  drawn  inward  were  it  not  for  the 
Flexor  accessorius  muscle,  which  is  inserted  into  the  outer  side  of  its  tendon  and 
draws  it  to  the  middle  line  of  the  foot  during  its  action.  Taking  their  fixed  point 
from  the  foot,  these  muscles  serve  to  maintain  the  upright  posture  by  steadying 
the  tibia  and  fibula  perpendicularly  upon  the  ankle-joint.  They  also  serve  to  raise 
these  bones  from  the  oblique  position  they  assume  in  the  stooping  posture. 

7.  The  Fibular  Region  (Fig.  353). 
Peroneus  longus.  Peroneus  brevis. 

Dissection. — The  muscles  are  readily  exposed  by  removing  the  fascia  covering  their  surface, 
from  below  upward,  in  the  line  of  direction  of  their  fibres. 

The  Peroneus  Longus  (m.  peronoeu^  longu^s)  is  situated  at  the  upper  part  of 
the  outer  side  of  the  leg,  and  is  the  more  superficial  of  the  two  muscles.    It  arises 


540  THE  3IUSCLES  AND   FASCIA 

from  the  head  and  upper  two-thirds  of  the  outer  surface  of  the  shaft  of  the  fibula, 
from  the  deep  surface  of  the  fascia,  and  from  the  intermuscular  septa  between  it 
and  the  muscles  on  the  front,  and  those  on  the  back  of  the  leg,  occasionally  also 
by  a  few  fibres  from  the  outer  tuberosity  of  the  tibia.  Between  its  attachment 
to  the  head  and  to  the  shaft  of  the  fibula  there  is  a  small  interval  of  bone  from 
which  no  muscular  fibres  arise ;  through  this  gap  the  external  popliteal  nerve  passes 
beneath  the  muscle.  The  muscle  terminates  in  a  long  tendon,  which  passes  behind 
the  outer  malleolus,  in  a  groove  common  to  it  and  the  tendon  of  the  Peroneus 
brevis,  behind  which  it  lies,  the  groove  being  converted  into  a  canal  by  a  fibrous 
band,  and  the  tendons  being  invested  by  a  common  synovial  membrane;  it  is 
then  reflected  obliquely  forward  across  the  outer  side  of  the  os  calcis,  below  its 
peroneal  tubercle,  being  contained  in  a  separate  fibrous  sheath,  lined  by  a  pro- 
longation of  the  synovial  membrane  which  lines  the  groove  behind  the  malleolus. 
Having  reached  the  outer  side  of  the  cuboid  bone,  it  runs  in  a  groove  on  the 
under  surface  of  that  bone,  which  is  converted  into  a  canal  by  the  long  calcaneo- 
cuboid ligament,  and  is  lined  by  a  synovial  membrane:  the  tendon  then  crosses 
the  sole  of  the  foot  obliquely,  and  is  inserted  into  the  outer  side  of  the  base  of  the 
metatarsal  bone  of  the  great  toe  and  the  internal  cuneiform  bone  (Figs.  355  and 
356).  Occasionally  it  sends  a  slip  to  the  base  of  the  second  metatarsal  bone.  The 
tendon  changes  its  direction  at  two  points:  first,  behind  the  external  malleolus; 
secondly,  on  the  outer  side  of  the  cuboid  bone;  in  both  of  these  situations  the 
tendon  is  thickened,  and  in  the  latter  a  sesamoid  fibro-cartilage,  or  sometimes  a 
bone,  is  usually  developed  in  its  substance. 

Relations. — By  its  superficial  surface,  with  the  fascia  and  integument;  by  its 
deep  surface,  with  the  fibula,  external  popliteal  nerve,  the  Peroneus  brevis,  os 
calcis,  and  cuboid  bone;  by  its  anterior  border,  with  an  intermuscular  septum,, 
which  intervenes  between  it  and  the  Extensor  longus  digitorum;  by  its  posterior 
border,  with  an  intermuscular  septum,  which  separates  it  from  the  Soleus  above 
and  the  Flexor  longus  hallucis  below. 

The  Peroneus  Brevis  (w.  peronceus  brevis)  lies  beneath  the  Peroneus  longus, 
and  is  shorter  and  smaller  than  it.  It  arises  from  the  lower  two-thirds  of  the 
external  surface  of  the  shaft  of  the  fibula,  internal  to  the  Peroneus  longus,  and 
from  the  intermuscular  septa  separating  it  from  the  adjacent  muscles  on  the  front 
and  back  part  of  the  leg.  The  fibres  pass  vertically  downward,  and  terminate  in 
a  tendon  which  runs  in  front  of  that  of  the  preceding  muscle  through  the  same 
groove,  behind  the  external  malleolus,  being  contained  in  the  same  fibrous 
sheath  and  lubricated  by  the  same  synovial  membrane.  It  then  passes  through 
a  separate  sheath  on  the  outer  side  of  the  os  calcis,  above  that  for  the  tendon  of 
the  Peroneus  longus,  the  two  tendons  being  here  separated  by  the  peroneal 
tubercle,  and  is  finally  inserted  into  the  tuberosity  at  the  base  of  the  metatarsal 
bone  of  the  little  toe,  on  its  outer  side. 

Relations. — By  its  superficial  surface,  with  the  Peroneus  longus  and  the  fascia 
of  the  leg  and  foot;  by  its  deep  surface,  with  the  fibula  and  outer  side  of  the  os 
calcis. 

Nerves. — The  Peroneus  longus  and  brevis  are  supplied  by  the  fourth  and  fifth 
lumbar  and  first  sacral  nerves  through  the  musculo-cutaneous  branch  of  the 
external  popliteal  nerve. 

Actions. — The  Peroneus  longus  and  brevis  extend  the  foot  upon  the  leg,  in 
conjunction  with  the  Tibialis  posticus,  antagonizing  the  Tibialis  anticus  and 
Peroneus  tertius,  which  are  flexors  of  the  foot.  The  Peroneus  longus  also  everts 
the  sole  of  the  foot;  hence  the  extreme  eversion  occasionally  observed  in  fracture 
of  the  lower  end  of  the  fibula,  where  that  bone  offers  no  resistance  to  the  action 
of  this  muscle.  From  the  oblique  direction  of  the  Peroneus  longus  tendon  across 
the  sole  of  the  foot  it  is  an  important  agent  in  the  maintenance  of  the  transverse 


OF    THE   FOOT  544 

arch  of  the  foot.  Taking  their  fixed  point  below,  the  Peronei  serve  to  steady  the 
leg  upon  the  foot.  This  is  especially  the  case  in  standing  upon  one  leg,  when 
the  tendency  of  the  superincumbent  weight  is  to  throw  the  leg  inward:  the 
Peroneus  longus  overcomes  this  tendency  by  drawing  on  the  outer  side  of  the 
leg,  and  thus  maintains  the  perpendicular  direction  of  the  limb. 

Surgical  Anatomy. — The  student  should  now  consider  the  position  of  the  tendons  of  the 
various  muscles  of  the  leg,  their  relation  with  the  ankle-joint  and  surrounding  blood-vessels,  and 
especially  their  action  upon  the  foot,  as  their  rigidity  and  contraction  give  rise  to  one  or  other  of 
the  kinds  of  deformity  known  as  club-foot.  The  most  simple  and  common  deformity,  and  one 
that  is  rarely,  if  ever,  congenital,  is  the  talipes  equinus,  the  heel  being  raised  by  rigidity  and  con- 
traction of  the  Gastrocnemius  muscle,  and  the  patient  walking  upon  the  ball  of  the  foot.  In  the 
talipes  varus  the  foot  is  forcibly  adducted  and  the  inner  side  of  the  sole  raised,  sometimes  to  a 
right  angle  with  the  ground,  by  the  action  of  the  Tibialis  anticus  and  posticus.  In  the  talipes 
valgus  the  outer  edge  of  the  foot  is  raised  by  the  Peronei  muscles,  and  the  patient  walks  on  the 
inner  ankle.  In  the  talipes  calcaneus  the  toes  are  raised  by  the  Extensor  muscles,  the  heel  is 
depressed,  and  the  patient  walks  upon  it.  Other  varieties  of  deformity  are  met  with,  as  the 
talipes  equino-varus,  equino-valgus ,  and  calcaneo-valgus,  whose  names  sufficiently  indicate  their 
nature.  Of  these,  the  talipes  equino-varus  is  the  most  common  congenital  form:  the  heel  is 
raised  by  the  tendo  Achillis,  the  inner  border  of  the  foot  drawn  upward  by  the  Tibialis  anticus, 
the  anterior  two-thirds  twisted  inward  by  the  Tibialis  posticus,  and  the  arch  increased  by  the 
contraction  of  the  plantar  fascia,  so  that  the  patient  walks  on  the  middle  of  the  outer  border  of 
the  foot.  Each  of  these  deformities  may  sometimes  be  successfully  relieved  by  division  of  the 
opposing  tendons  and  fascia ;  by  this  means  the  foot  regains  its  proper  position,  and  the  tendons 
subsequently  heal.  The  operation  is  easily  performed  by  putting  the  contracted  tendon  upon 
the  stretch,  and  dividing  it  by  means  of  a  narrow,  sharp-pointed  knife  inserted  beneath  it. 
Pes  cavus  or  hollow  foot  is  accentuation  of  the  longitudinal  arch.  Pes  planus  or  flat-foot  has 
been  discussed  elsewhere. 

Rupture  of  a  few  of  the  fibres  of  the  Gastrocnemius  may  take  place.  Rupture  of  the  Plantaris 
tendon  not  uncommonly  occurs,  especially  in  men  somewhat  advanced  in  life,  from  some  sudden 
exertion,  and  frequently  occurs  during  the  game  of  lawn  tennis,  and  is  hence  known  as  lawn- 
tennis  leg.  The  accident  is  accompanied  by  a  sudden  pain,  and  produces  a  sensation  as  if  the 
individual  had  been  struck  a  violent  blow  on  the  part.  The  tendo  Achillis  is  also  sometimes 
ruptured.  It  is  stated  that  John  Hunter  ruptured  his  tendo  Achillis  whilst  dancing  at  the 
age  of  forty.  The  retro-calcaneal  bursa  is  interposed  between  the  posterior  surface  of  the  os 
calcis  and  the  tendo  Achillis,  just  above  the  point  of  insertion  of  the  tendon.  If  it  inflames 
it  produces  disabling  pain  (achillodynia,  or  Albert's  disease,  retro-calcaneal  bursitis).  This  bursa 
may  become  cartilaginous  or  osteophytes  may  form  on  the  surface  toward  the  os  calcis. 


IV.  MUSCLES  AND  FASCIA  OF  THE  FOOT. 

The  fibrous  bands,  or  thickened  portions  of  the  fascia  of  the  leg,  which  bind  down  the  tendons 
in  front  of  and  behind  the  ankle  in  their  passage  to  the  foot  should  now  be  examined;  they  are 
termed  the  annular  ligaments,  and  are  three  in  number — anterior,  internal,  and  external. 

The  Anterior  Annular  Ligament  (Fig.  350)  consists  of  a  superior  or  transverse  portion 
(ligamentum  transversum  cruris)  which  binds  down  the  Extensor  tendons  as  they 
descend  on  the  front  of  the  tibia  and  fibula;  and  an  inferior  or  Y-shaped  portion 
(ligamentum  cruciatum  cruris),  which  retains  them  in  connection  with  the  tarsus, 
the  two  portions  being  connected  by  a  thin  intervening  layer  of  fascia.  The 
transverse  portion  is  attached  externally  to  the  lower  end  of  the  fibula  and  inter- 
nally to  the  tibia;  above  it  is  continuous  with  the  fascia  of  the  leg;  it  contains 
only  one  synovial  sheath,  for  the  tendon  of  the  Tibialis  anticus;  the  other  tendons 
and  the  anterior  tibial  vessels  and  nerve  passing  beneath  it,  but  without  any  dis- 
tinct synovial  sheath.  The  Y-shaped  portion  is  placed  in  front  of  the  ankle-joint, 
the  stem  of  the  Y,  the  fimdiform  ligament  of  Retzius,  being  attached  externally  to 
the  upper  surface  of  the  os  calcis,  in  front  of  the  depression  for  the  interosseous 
ligament;  it  is  directed  inward,  as  a  double  layer,  one  lamina  passing  in  front, 
and  the  other  behind,  the  tendons  of  the  Peroneus  tertius  and  Extensor  longus 
digitorum.    At  the  inner  border  of  the  latter  tendon  these  two  layers  join  together. 


542  THE   MUSCLES  AND   FASCIA 

forming  a  sort  of  loop  or  sheath  in  which  the  tendons  are  enclosed,  surrounded 
by  a  synovial  membrane.  From  the  inner  extremity  of  this  loop  the  two  limbs 
of  the  Y  diverge:  one  passes  upward  and  inward,  to  be  attached  to  the  internal 
malleolus,  passing  over  the  Extensor  proprius  hallucis  and  the  vessels  and  nerves, 
but  enclosing  the  Tibialis  anticus  and  its  synovial  sheath  by  a  splitting  of  its 
fibres.  The  other  limb  extends  downward  and  inward  to  be  attached  to  the 
inner  border  of  the  plantar  fascia,  and  passes  over  the  tendons  of  the  Extensor 
proprius  hallucis  and  Tibialis  anticus  and  also  the  vessels  and  nerves.  These 
two  tendons  are  contained  in  separate  synovial  sheaths  situated  beneath  the 
ligament. 

The  Internal  Annular  Ligament  (ligamentum  laciniatum)  is  a  strong  fibrous 
band  which  extends  from  the  inner  malleolus  above  to  the  internal  margin  of  the 
OS  calcis  below,  converting  a  series  of  grooves  in  this  situation  into  canals  for  the 
passage  of  the  tendons  of  the  Flexor  muscles  and  vessels  into  the  sole  of  the  foot. 
It  is  continuous  by  its  upper  border  with  the  deep  fascia  of  the  leg,  and  by  its  lower 
border  with  the  plantar  fascia  and  the  fibres  of  origin  of  the  Abductor  hallucis 
muscle.  The  four  canals  which  it  forms  transmit,  counting  from  before  back- 
ward, first,  the  tendon  of  the  Tibialis  posticus;  second,  the  tendon  of  the  Flexor 
longus  digitorum ;  third,  the  posterior  tibial  vessels  and  nerve,  which  run  through 
a  broad  space  beneath  the  ligament;  lastly,  in  a  canal  formed  partly  by  the 
astragalus,  the  tendon  of  the  Flexor  longus  hallucis.  The  canals  for  the  tendons 
are  lined  by  a  separate  synovial  membrane. 

The  External  Aiinular  Ligament  is  divided  into  two  portions;  a  superior  por- 
tion (retinaculum  mm.  peroncBorum  siiperias),  which  extends  from  the  extremity 
of  the  outer  malleolus  to  the  outer  surface  of  the  os  calcis :  it  binds  down  the 
tendons  of  the  Peroneus  longus  and  brevis  muscles  in  their  passage  behind  the 
external  malleolus.  The  two  tendons  are  enclosed  in  one  synovial  sac.  An 
inferior  portion  (retinaculum  mm.  peronceorum  inferius),  which  bridges  the  Peronei 
on  the  side  of  the  os  calcis  and  is  attached  to  the  bone  above  and  below  them. 

Dissection  of  the  Sole  of  the  Foot. — The  foot  should  be  placed  on  a  high  block  with  the 
sole  uppermost,  and  firmly  secured  in  that  position.  Carry  an  incision  round  the  heel  and  along 
the  inner  and  outer  borders  of  the  foot  to  the  great  and  little  toes.  This  incision  should  divide 
the  integument  and  thick  layer  of  granular  fat  beneath  until  the  fascia  is  visible;  the  skin  and  fat 
should  then  be  removed  from  the  fascia  in  a  direction  from  behind  forward,  as  seen  in  Fig.  345. 

Plantar  Fascia  (aponeurosis  plantaris)  .—The  plantar  fascia,  the  densest  of  all 
the  fibrous  membranes,  is  of  great  strength,  and  consists  of  pearly-white  glisten- 
ing fibres,  disposed,  for  the  most  part,  longitudinally:  it  is  divided  into  a  central 
and  two  lateral  portions. 

Central  Portion. — The  central  portion,  the  thickest,  is  narrow  behind  and 
attached  to  the  inner  tubercle  of  the  os  calcis,  posterior  to  the  origin  of  the 
Flexor  brevis  digitorum,  and,  becoming  broader  and  thinner  in  front,  divides 
near  the  heads  of  the  metatarsal  bones  into  five  processes,  one  for  each  of  the  toes. 
Each  of  these  processes  divides  opposite  the  metatarso-phalangeal  articulation 
into  two  strata,  superficial  and  deep.  The  superficial  stratum  is  inserted  into 
the  skin  of  the  transverse  sulcus  which  divides  the  toes  from  the  sole.  The 
deeper  stratum  divides  into  two  slips  which  embrace  the  sides  of  the  flexor  tendons 
of  the  toes,  and  blend  with  the  sheaths  of  the  tendons,  and  laterally  with  the 
transverse  metatarsal  ligament,  thus  forming  a  series  of  arches  through  which 
the  tendons  of  the  short  and  long  flexors  pass  to  the  toes.  The  intervals  left 
between  the  five  processes  allow  the  digital  vessels  and  nerves  and  the  tendons 
of  the  Lumbricales  muscles  to  become  superficial.  At  the  point  of  division  of  the 
fascia  into  processes  and  slips  numerous  transverse  fibres  are  superadded,  which 
serve  to  increase  the  strength  of  the  fascia  at  this  part  by  binding  the  processes 


THE  DORSAL    BEG  ION  543 

together  and  connecting  them  with  the  integument.  The  central  portion  of  the 
plantar  fascia  is  continuous  with  the  lateral  portions  at  each  side,  and  sends 
upward  into  the  foot,  at  their  point  of  junction,  two  strong  vertical  intermuscular 
septa,  broader  in  front  than  behind,  which  separate  the  middle  from  the  external 
and  internal  plantar  group  of  muscles;  from  these,  again,  thinner  transverse 
septa  are  derived,  which  separate  the  various  layers  of  muscles  in  this  region. 
The  upper  surface  of  this  fascia  gives  attachment  behind  to  the  Flexor  brevis 
digitorum  muscle. 

Lateral  Portions. — The  lateral  portions  of  the  plantar  fascia  are  thinner  than 
the  central  piece,  and  cover  the  sides  of  the  foot.  The  outer  portion  covers  the 
under  surface  of  the  Abductor  minimi  digiti;  it  is  thick  behind,  thin  in  front,  and 
extends  from  the  os  calcis,  forward,  to  the  base  of  the  fifth  metatarsal  bone,  into 
the  outer  side  of  which  it  is  attached;  it  is  continuous  internally  with  the  middle 
portion  of  the  plantar  fascia,  and  externally  with  the  dorsal  fascia.  The  inner 
portion  is  very  thin,  and  covers  the  Abductor  hallucis  muscle;  it  is  attached 
behind  to  the  internal  annular  ligament,  and  is  continuous  around  the  side  of 
the  foot  with  the  dorsal  fascia,  and  externally  with  the  middle  portion  of  the 
plantar  fascia 

Bursas  about  the  Ankle  and  Foot. — (1)  A  subcutaneous  bursa  on  the  sole  of 
the  foot,  beneath  the  tuberosity  of  the  os  calcis.  (2)  A  subcutaneous  bursa 
over  the  tendo  Achillis  {bursa  subcutanea  calcanea).  (3)  The  retrocalcaneal 
bursa,  between  the  posterior  surface  of  the  os  calcis  and  the  insertion  of  the 
tendo  Achillis  (bursa  tendinis  calcanei  [Achillis]) .  (4)  A  bursa  between  the 
internal  cuneiform  bone  and  the  tendon  of  the  Tibialis  anticus  (bursa  subten- 
dinea  m.  iibialis  anierioris).  (5)  Bursse  between  the  heads  of  the  metatarsal 
bones  (bursx  infermetatarsophalangecB).  (6)  A  subcutaneous  bursa  over  the 
internal  malleolus  (bursa  subcutanea  malleoli  medialis).  (7)  Bursae  between  the 
scaphoid  and  middle  cuneiform  bones  on  the  one  hand  and  the  tendon  of  the 
Tibialis  posticus  on  the  other  (bursa  subtendinea  m.  iibialis  posterioris) .  (8)  Bursse 
between  the  Lumbricales  and  the  transverse  ligaments  (bursae  mm.  lumbricalium 
'pedis) .  (9)  A  bursa  over  the  external  malleolus  (bursa  subcutanea  malleoli  lateralis). 
(10)  A  bursa  over  the  head  of  the  first  metatarsal  bone.  Various  muscles  have 
tendon-sheaths  lined  with  synovial  membrane  (vaginal  sheaths). 

Surgical  Anatomy. — ^The  dense  plantar  fascia  aids  powerfully  in  maintaining  the  arch  of  the 
foot.  When  this  fascia  stretches  or  gives  way  flat-foot  forms.  In  some  forms  of  club-foot 
the  plantar  fascia  is  contracted.     This  contraction  is  usually  a  secondary  change. 

When  inflammation  causes  tenderness  and  enlargement  of  the  bursa  over  the  metatarso- 
phalangeal articulation  of  the  great  toe,  the  enlargement  is  called  a  bunion.  Enlargement  of 
the  retro-calcaneal  bursa  is  known  as  Albert's  disease,  or  achiUodynia. 

8.  The  Dorsal  Region  (Fig.  350). 
Extensor  brevis  digitorum. 

Fascia  (fascia  dorsalis  pedis). — The  fascia  on  the  dorsum  of  the  foot  is  a  thin 
membranous  layer  continuous  above  with  the  anterior  margin  of  the  annular 
ligament;  it  becomes  gradually  lost  opposite  the  heads  of  the  metatarsal  bones, 
And  on  each  side  blends  with  the  lateral  portions  of  the  plantar  fascia;  it  forms  a 
sheath  for  the  tendons  placed  on  the  dorsum  of  the  foot.  On  the  removal  of  this 
fascia  the  muscles  and  tendons  of  the  dorsal  region  of  the  foot  are  exposed. 

The  Extensor  Brevis  Digitorum  (m.  extensor  digitorum  brevis)  (Fig.  350) 
is  a  broad  thin  muscle  which  arises  from  the  forepart  of  the  upper  and 
outer  surfaces  of  the  os  calcis,  in  front  of  the  groove  for  the  Peroneus  brevis, 
from  the  external  calcaneo-astragaloid  ligament,  and  from  the  common  limb  of 
the  Y-shaped   portion   of  the  anterior  annular   ligament.     It   passes   obliquely 


544  THE  MUSCLES   AND    FASCIA 

across  the  dorsum  of  the  foot,  and  terminates  in  four  tendons.  The  innermost, 
which  is  the  largest,  is  inserted  into  the  dorsal  surface  of  the  base  of  the  first 
phalanx  of  the  great  toe,  crossing  the  dorsalis  pedis  artery;  the  other  three,  into 
the  outer  sides  of  the  long  extensor  tendons  of  the  second,  third,  and  fourth  toes. 

Relations. — By  its  superficial  surface,  with  the  fascia  of  the  foot,  the  tendons 
of  the  Extensor  longus  digitorum  and  Peroneus  tertius;  by  its  deej)  surface,  with 
the  tarsal  and  metatarsal  arteries  and  bones  and  the  Dorsal  interossei  muscles. 

Nerves. — It  is  supplied  by  the  anterior  tibial  nerve. 

Actions. — The  Extensor  brevis  digitorum  is  an  accessory  to  the  long  Extensor, 
extending  the  phalanges  of  the  four  inner  toes,  but  acting  only  on  the  first  phalanx 
of  the  great  toe.  The  obliquity  of  its  direction  counteracts  the  oblique  movement 
given  to  the  toes  by  the  long  Extensor,  so  that,  both  muscles  acting  together,  the 
toes  are  evenly  extended. 

9.  The  Plantar  Region  (Figs.  354,  355,  356,  357,  358). 

The  muscles  in  the  plantar  region  of  the  foot  may  be  divided  into  three  groups^ 
in  a  similar  manner  to  those  in  the  hand.  Those  of  the  internal  plantar  region 
are  connected  with  the  great  toe,  and  correspond  with  those  of  the  thumb;  those 
of  the  external  plantar  region  are  connected  with  the  little  toe,  and  correspond 
with  those  of  the  little  finger;  and  those  of  the  middle  plantar  region  are  con- 
nected with  the  tendons  intervening  between  the  two  former  groups.  But  in  order 
to  facilitate  the  dissection  of  these  muscles  it  will  be  found  more  convenient  to 
divide  them  into  four  layers,  as  they  present  themselves,  in  the  order  in  which 
they  are  successively  exposed. 

The  First  Layer. 

Abductor  hallucis.  Flexor  brevis  digitorum. 

Abductor  minimi  digiti. 

Dissection. — Remove  the  fascia  on  the  inner  and  outer  sides  of  the  foot,  commencing  in 
front  over  the  tendons  and  proceeding  backward.  The  central  portion  should  be  divided 
transversely  in  the  middle  of  the  foot,  and  the  two  flaps  dissected  forward  and  backward. 

The  Abductor  Hallucis  lies  along  the  inner  border  of  the  foot.  It  arises  from 
the  inner  tubercle  on  the  under  surface  of  the  os  calcis;  from  the  internal  annular 
ligament;  from  the  plantar  fascia;  and  from  the  intermuscular  septum  between  it 
and  the  Flexor  brevis  digitorum.  The  fibres  terminate  in  a  tendon  which  is 
inserted,  together  with  the  innermost  tendon  of  the  Flexor  brevis  hallucis,  into 
the  inner  side  of  the  base  of  the  first  phalanx  of  the  great  toe. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia;  by  its  deep  sur- 
face, with  the  Flexor  brevis  hallucis,  the  Flexor  accessorius,  and  the  tendons  of 
the  Flexor  longus  digitorum  and  Flexor  longus  hallucis,  the  Tibialis  anticus  and 
posticus,  the  plantar  vessels  and  nerves.  Its  outer  border  is  in  relation  to  the 
Flexor  brevis  digitorum. 

The  Flexor  Brevis  Digitorum  (m.  flexor  digitorum  brevis)  lies  in  the 
middle  of  the  sole  of  the  foot,  immediately  beneath^  the  plantar  fascia,  with 
which  it  is  firmly  united.  It  arises  by  a  narrow  tendinous  process,  from  the 
inner  tubercle  of  the  os  calcis,  from  the  central  part  of  the  plantar  fascia,  and 
from  the  intermuscular  septa  between  it  and  the  adjacent  muscles.  It  passes 
forward,  and  divides  into  four  tendons,  one  for  each  of  the  four  outer  toes. 
Opposite  the  bases  of  the  first  phalanges  each  tendon  divides  into  two  slips,  to 
allow  of  the  passage  of  the  corresponding  tendon  of  the  Flexor  longus  digitorum  ,• 

'  That  is,  in  order  of  dissection  of  the  sole  of  the  foot. 


THE  PLANTAR    REGION 


545 


the  two  portions  of  the  tendon  then  unite  and  form  a  grooved  channel  for  the 
reception  of  the  accompanying  long  flexor  tendon.  Finally,  they  divide  a  second 
time,  to  be  inserted  into  the  sides  of  the  second  phalanges  about  their  middle.  The 
mode  of  division  of  the  tendons  of  the  Flexor  brevis  digitorum  and  their  insertion 
into  the  phalanges  is  analogous  to  the  division 
and  insertion  of  the  Flexor  sublimis  digitorum 
in  the  hand. 

Relations. — By  its  superficial  surface,  with 
the  plantar  fascia;  by  its  deep  surface,  with  the 
Flexor  accessorius,  the  Lumbricales,  the  ten- 
dons of  the  Flexor  longus  digitorum,  and  the 
external  plantar  vessels  and  nerve,  from  which 
it  is  separated  by  a  thin  layer  of  fascia.  The 
outer  and  inner  borders  are  separated  from  the 
adjacent  muscles  by  means  of  vertical  pro- 
longations of  the  plantar  fascia. 

Fibrous  Sheaths  of  the  Flexor  Tendons. — 
These  are  not  so  well  marked  as  in  the  fingers. 
The  flexor  tendons  of  the  toes  as  they  run 
along  the  phalanges  are  retained  against  the 
bones  by  a  fibrous  sheath,  forming  osseo- 
aponeurotic  canals.  These  sheaths  are  formed 
by  strong  fibrous  bands  which  arch  across  the 
tendons  and  are  attached  on  each  side  to  the 
margins  of  the  phalanges.  Opposite  the  mid- 
dle of  the  proximal  and  second  phalanges  the 
sheath  is  very  strong,  and  the  fibres  pass 
transversely,  but  opposite  the  joints  it  is 
much  thinner,  and  the  fibres  pass  obliquely. 
Each  sheath  is  lined  by  a  synovial  mem- 
brane which  is  reflected  on  the  contained 
tendon. 

The  Abductor  Minimi  Digiti  (m.  abductor 
digiti  quinti)  lies  along  the  outer  border  of  the 
foot.  It  arises,  by  a  very  broad  origin,  from 
the  outer  tubercle  of  the  os  calcis,  from  the 
under  surface  of  the  os  calcis  between  the  two 
tubercles,  from  the  forepart  of  the  inner 
tubercle,  from  the  plantar  fascia  and  the  in- 
termuscular septum,  between  it  and  the  Flexor 
brevis  digitorum.  Its  tendon,  after  gliding 
over  a  smooth  facet  on  the  under  surface  of 
the  base  of  the  fifth  metatarsal  bone,  is  inserted 
with  the  short  Flexor  of  the  little  toe  into  the  outer  side  of  the  base  of  the  first 
phalanx  of  this  toe. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia;  by  its  deep  sur- 
face, with  the  Flexor  accessorius,  the  Flexor  brevis  minimi  digiti,  the  long  plantar 
ligament,  and  the  tendon  of  the  Peroneus  longus.  On  its  inner  side  are  the 
external  plantar  vessels  and  nerve,  and  it  is  separated  from  the  Flexor  brevis 
digitorum  by  a  vertical  septum  of  fascia. 

Dissection. — The  muscles  of  the  superficial  layer  should  be  divided  at  their  origin  by  insert- 
ing the  knife  beneath  each,  and  cutting  obliquely  backward,  so  as  to  detach  them  from  the 
bone;  they  should  then  be  drawn  forward,  in  order  to  expose  the  second  layer,  but  not  cut  away 
at  their  insertion.     The  two  layers  are  separated  by  a  thin  membrane,  the  deep  plantar  fascia, 

35 


Fig.  354. 


-Muscles  of  the  sole  of  the  foot. 
First  layer. 


546  THE  MUSCLES  AND    FASCIA 

on  the  removal  of  which  is  seen  the  tendon  of  the  Flexor  longus  digitorum,  the  Flexor  accessorius, 
the  tendon  of  the  Flexor  longus  hallucis,  and  the  Lumbricales.  The  long  flexor  tendons 
diverge  from  each  other  at  an  acute  angle;  the  Flexor  longus  hallucis  runs  along  the  inner  side 
of  the  foot,  on  a  plane  superior  to  that  of  the  Flexor  longus  digitorum,  the  direction  of  which  is 
obliquely  outward. 

The  Second  Layer. 
Flexor  accessorius.  Lumbricales. 

The  Flexor  Accessorius  (m.  quadratus  plantcc)  arises  by  two  heads,  which  are 
separated  from  each  other  by  the  long  plantar  ligament :  the  inner  or  larger  head, 
which  is  muscular,  being  attached  to  the  inner  concave  surface  of  the  os  calcis 
below  the  groove  which  lodges  the  tendon  of  the  Flexor  longus  digitorum;  the 
outer  head,  flat  and  tendinous,  to  the  outer  surface  of  the  os  calcis,  in  front  of  its 
lesser  tubercle,  and  to  the  long  plantar  ligament;  the  two  portions  join  at  an 
acute  angle,  and  are  inserted  into  the  outer  margin  and  upper  and  under  sur- 
faces of  the  tendon  of  the  Flexor  longus  digitorum,  forming  a  kind  of  groove  in 
which  the  tendon  is  lodged.^ 

Relations. — By  its  superficial  surface,  with  the  muscles  of  the  superficial  layer, 
from  which  it  is  separated  by  the  external  plantar  vessels  and  nerves;  by  its  deep 
surface,  with  the  os  calcis  and  long  calcaneo-cuboid  ligament. 

The  Lumbricales  are  four  small  muscles  accessory  to  the  tendons  of  the  Flexor 
longus  digitorum:  they  arise  from  the  tendons  of  the  long  Flexor,  as  far  back  as 
their  angle  of  division,  each  arising  from  two  tendons,  except  the  internal  one. 
Each  muscle  terminates  in  a  tendon,  which  passes  forward  on  the  inner  side  of 
the  four  lesser  toes  and  is  inserted  into  the  expansion  of  the  long  Extensor  tendon 
on  the  dorsum  of  the  first  phalanx  of  the  corresponding  toe. 

Dissection. — The  flexor  tendons  should  be  divided  at  the  back  part  of  the  foot,  and  the 
Flexor  accessorius  at  its  origin,  and  drawn  forward,  in  order  to  expose  the  third  layer. 

The  Third  Layer. 

Flexor  brevis  hallucis.  Flexor  brevis  minimi  digiti. 

Adductor  obliquus  hallucis.  Adductor  transversus  hallucis. 

The  Flexor  Brevis  Hallucis  (m.  flexor  hallucis  brevis)  arises,  by  a  pointed 
tendinous  process,  from  the  inner  part  of  the  under  surface  of  the  cuboid  bone, 
from  the  contiguous  portion  of  the  external  cuneiform,  and  from  the  prolongation 
of  the  tendon  of  the  Tibialis  posticus,  which  is  attached  to  that  bone.  The 
muscle  divides,  in  front,  into  two  portions,  which  are  inserted  into  the  inner 
and  outer  sides  of  the  base  of  the  first  phalanx  of  the  great  toe,  a  sesamoid  bone 
being  developed  in  each  tendon  at  its  insertion.  The  inner  portion  of  this 
muscle  is  blended  with  the  Abductor  hallucis  previous  to  its  insertion,  the  outer 
portion  with  the  Adductor  obliquus  hallucis,  and  the  tendon  of  the  Flexor 
longus  hallucis  lies  in  a  groove  between  them. 

Relations. — By  its  superficial  surface,  with  the  Abductor  hallucis  and  the  ten- 
don of  the  Flexor  longus  hallucis;  by  its  deep  surface,  with  the  tendon  of  the 
Peroneus  longus  and  metatarsal  bone  of  the  great  toe;  by  its  inner  border,  with 
the  Abductor  hallucis;  by  its  outer  border,  with  the  Adductor  obliquus  hallucis. 

The  Adductor  Obliquus  Hallucis  is  a  large,  thick,  fleshy  mass  passing  obliquely 
across  the  foot  and  occupying  the  hollow  space  between  the  four  inner  meta- 
tarsal bones.  It  arises  from  the  tarsal  extremities  of  the  second,  third,  and  fourth 
metatarsal  bones,  and  from  the  sheath  of  the  tendon  of  the  Peroneus  longus, 

'  According  to  Turner,  the  fibres  of  the  Flexor  accessorius  end  in  aponeurotic  bands,  which  contribute  slips 
to  the  second,  third,  and  fourth  digits. 


THE   PLANTAR    REGION 


547 


and  is  inserted,  together  with  the  outer  portion  of  the  Flexor  brevis  hallucis,  into 
the  outer  side  of  the  base  of  the  first  phalanx  of  the  great  toe. 

The  small  muscles  of  the  great  toe,  the  Abductor,  Flexor  brevis,  Adductor 
obliquus,  and  Adductor  transversus,  like  the  similar  muscles  of  the  thumb,  give 
off  fibrous  expansions,  at  their  insertions,  to  blend  with  the  long  Extensor  tendon. 


Fig.  355.- 


-  Muscles  of  the  sole  of  the  foot. 
Second  layer. 


Fig.  356. — Muscles  of  the  sole  of  the  foot. 
Third  layer. 


The  Flexor  Brevis  Minimi  Digiti  {m.  flexor  digiti  quinti  brevis)  lies  on  the  meta- 
tarsal bone  of  the  little  toe,  and  much  resembles  one  of  the  Interossei.  It  arises 
from  the  base  of  the  metatarsal  bone  of  the  little  toe,  and  from  the  sheath  of  the 
Peroneus  longus;  its  tendon  is  inserted  into  the  base  of  the  first  phalanx  of 
the  little  toe  on  its  outer  side.  Occasionally  some  of  the  deeper  fibres  of  the 
muscle  are  inserted  into  the  outer  part  of  the  distal  half  of  the  fifth  metatarsal 
bone;  these  are  described  by  some  as  a  distinct  muscle,  the  Opponens  minimi 
digiti. 

Relations. — By  its  superficial  surface,  with  the  plantar  fascia  and  tendon  of 
the  Abductor  minimi  digiti;  by  its  deep  surface,  with  the  fifth  metatarsal  bone. 


548 


THE    MUSCLES  AND    FASCIA 


The  Adductor  Transversus  Hallucis  (m.  transversus  pedis)  is  a  narrow,  flat, 
muscular  fasciculus,  stretched  transversely  across  the  heads  of  the  metatarsal  bones, 
between  them  and  the  flexor  tendons.  It  arises  from  the  inferior  metatarso- 
phalangeal ligaments  of  the  three  outer  toes,  sometimes  only  from  the  third  and 
fourth  and  from  the  transverse  ligament  of  the  metatarsus;  and  is  inserted  into 
the  outer  side  of  the  first  phalanx  of  the  great  toe,  its  fibres  being  blended  with 
the  tendon  of  insertion  of  the  Adductor  obliquus  hallucis. 

Relations. — By  its  superficial  surface,  with  the  tendons  of  the  long  and  short 
Flexors  and  Lumbricales;  by  its  deep  surface,  with  the  Interossei. 

The  Fourth  Layer. 

The  Interossei. 

The  Interossei  Muscles  in  the  foot  are  similar  to  those  in  the  hand,  with  this 
exception,  that  they  are  grouped  around  the  middle  line  of  the  second  toe,  instead 
of  the  middle  line  of  the  third  finger,  as  in  the  hand.  They  are  seven  in  number, 
and  consist  of  two  groups.  Dorsal  and  Plantar. 


Fig.  357. — The  Dorsal  interossei.     Left  foot. 


Fig.  358. — The  Plantar  interossei.     Left  foot. 


The  Dorsal  Interossei  (m.  interossei  dorsales), ionr  in  number,  are  situated  between 
the  metatarsal  bones.  They  are  bipenniform  muscles,  arising  by  two  heads  from 
the  adjacent  sides  of  the  metatarsal  bones,  between  which  they  are  placed;  their 
tendons  are  inserted  into  the  bases  of  the  first  phalanges,  and  into  the  aponeurosis 
of  the  common  extensor  tendon.  In  the  angular  interval  left  between  the  heads 
of  each  muscle  at  its  posterior  extremity  the  perforating  arteries  pass  to  the 
dorsum  of  the  foot,  except  in  the  First  interosseous  muscle,  where  the  interval 
allows  the  passage  of  the  communicating  branch  of  the  dorsalis  pedis  artery.  The 
First  dorsal  interosseous  muscle  is  inserted  into  the  inner  side  of  the  second  toe; 
the  other  three  are  inserted  into  the  outer  sides  of  the  second,  third,  and  fourth  toes. 

The  Plantar  Interossei  (m.  interossei  plantares),  three  in  number,  lie  beneath, 
rather  than  between,  the  metatarsal  bones.  They  are  single  muscles,  and  are 
each  connected  with  but  one  metatarsal  bone.     They  arise  from  the  base  and 


SURFACE  FORM    OF    THE    LOWER    EXTREMITY  549 

inner  sides  of  the  shaft  of  the  third,  fourth,  and  fifth  metatarsal  bones,  and  are 
inserted  into  the  inner  sides  of  the  bases  of  the  first  phalanges  of  the  same  toes, 
and  into  the  aponeurosis  of  the  common  extensor  tendon. 

Nerves. — The  Flexor  brevis  digitorum,  the  Flexor  brevis  and  Abductor  hallucis, 
and  the  innermost  LumbricaP  are  supplied  by  the  internal  plantar  nerve.  All 
the  other  muscles  in  the  sole  of  the  foot  by  the  external  plantar.  The  first  dorsal 
interosseous  muscle  frequently  receives  an  extra  filament  from  the  internal 
branch  of  the  anterior  tibial  nerve  on  the  dorsum  of  the  foot,  and  the  second 
dorsal  interosseous  a  twig  from  the  external  branch  of  the  same  nerve. 

Actions. — All  the  muscles  of  the  foot  act  upon  the  toes,  and  for  purposes  of 
description  as  regard  their  action  may  be  grouped  as  Abductors,  Adductors, 
Flexors,  or  Extensors.  The  Abductors  are  the  Dorsal  interossei,  the  Abductor 
hallucis,  and  the  Abductor  minimi  digiti.  The  Dorsal  interossei  are  abductors 
from  an  imaginary  line  passing  through  the  axis  of  the  second  toe,  so  that  the 
first  muscle  draws  the  second  toe  inward,  toward  the  great  toe;  the  second  muscle 
draws  the  same  toe  outward;  the  third  draws  the  third  toe,  and  the  fourth  draws 
the  fourth  toe,  in  the  same  direction.  Like  the  interossei  in  the  hand,  they  also 
flex  the  proximal  phalanges  and  extend  the  two  terminal  phalanges.  The  Abduc- 
tor hallucis  abducts  the  great  toe  from  the  others,  and  also  flexes  the  proximal 
phalanx  of  this  toe.  And  in  the  same  way  the  action  of  the  Abductor  minimi 
digiti  is  twofold — as  an  abductor  of  this  toe  from  the  others,  and  also  as  a  flexor 
of  the  proximal  phalanx.  The  Adductors  are  the  Plantar  interossei,  the  Adductor 
obliquus  hallucis,  and  the  Adductor  transversus  hallucis.  The  Plantar  inter- 
osseous muscles  adduct  the  third,  fourth,  and  fifth  toes  toward  the  imaginary 
line  passing  through  the  second  toe,  and  by  means  of  their  insertion  into  the 
aponeurosis  of  the  extensor  tendon  they,  with  the  dorsal  interossei,  flex  the  prox- 
imal phalanges  and  extend  the  two  terminal  phalanges.  The  Adductor  obliquus 
hallucis  is  chiefly  concerned  in  adducting  the  great  toe  toward  the  second  one, 
but  also  assists  in  flexing  this  toe.  The  Adductor  transversus  hallucis  approxi- 
mates all  the  toes,  and  thus  increases  the  curve  of  the  transverse  arch  of  the 
metatarsus.  The  Flexors  are  the  Flexor  brevis  digitorum,  the  Flexor  accessorius, 
the  Flexor  brevis  hallucis,  the  Flexor  brevis  minimi  digiti,  and  the  Lumbricales. 
The  Flexor  brevis  digitorum  flexes  the  second  phalanges  upon  the  first,  and,  con- 
tinuing its  action,  may  flex  the  first  phalanges  also  and  bring  the  toes  together. 
The  Flexor  accessorius  assists  the  Long  flexor  of  the  toes,  and  converts  the 
oblique  pull  of  the  tendons  of  that  muscle  into  a  direct  backward  pull  upon  the 
toes.  The  Flexor  brevis  hallucis  flexes  and  slightly  adducts  the  first  phalanx  of 
the  great  toe.  The  Flexor  brevis  minimi  digiti  flexes  the  little  toe  and  draws  its 
metatarsal  bone  downward  and  inward.  The  Lumbricales,  like  the  correspond- 
ing muscles  in  the  hand,  assist  in  flexing  the  proximal  phalanx,  and  by  their 
insertion  into  the  long  Extensor  tendon  aid  in  straightening  the  two  terminal 
phalanges.  The  only  muscle  in  the  Extensor  group  is  the  Extensor  brevis  digi- 
torum. It  extends  the  first  phalanx  of  the  great  toe,  and  assists  the  long  Exten- 
sor in  extending  the  next  three  toes,  and  at  the  same  time  gives  to  the  toes  an 
outward  direction  when  they  are  extended. 

SURFACE  FORM  OF  THE  LOWER  EXTREMITY. 

Of  the  muscles  of  the  thigh,  those  of  the  iliac  region  have  no  influence  on  surface  form, 
while  those  of  the  anterior  femoral  region,  being  to  a  great  extent  superficial,  largely  con- 
tribute  to   the   surface   form  of   this  part  of    the  body.     The  Tensor  fascise   femoris  pro- 

1  Formerly  the  two  inner  Lumbricales  were  described  as  being  supplied  by  the  internal  plantar  nerve.  Brooks 
(Journal  of  Anatomy,  vol.  xxi.  p.  575)  in  ten  dissections  found  that  in  nine  of  them  only  the  inner  Lumbrical 
obtained  its  nerve  supply  from  this  source.  In  the  tenth  instance  the  first  and  second  Lumbricales  were 
supplied  by  both  external  and  internal  plantar. 


550  THE  MUSCLES  AND   FASCIA 

duces  a  broad  elevation  immediately  below  the  anterior  portion  of  the  crest  of  the  ilium  and 
behind  the  anterior  superior  spinous  process.  From  its  lower  border  a  longitudinal  groove, 
corresponding  to  the  ilio-tibial  band,  may  be  seen  running  down  the  outer  side  of  the  thigh  to 
the  outer  side  of  the  knee-joint.  The  Sartorius  muscle,  when  it  is  brought  into  action  by  flexing 
the  leg  on  the  thigh  and  the  thigh  on  the  pelvis,  and  rotating  the  thigh  outward,  presents  a 
well-marked  surface  form.  At  its  upper  part,  where  it  constitutes  the  outer  boundary  of 
Scarpa's  triangle,  it  forms  a  prominent  oblique  ridge,  which  becomes  changed  into  a  flattened 
plane  below,  and  this  gradually  merges  in  a  general  fulness  on  the  inner  side  of  the  knee-joint. 
When  the  Sartorius  is  not  in  action,  a  depression  exists  between  the  Quadriceps  extensor  and  the 
Adductor  muscles,  running  obliquely  downward  and  inward  from  the  apex  of  Scarpa's  triangle 
to  the  inner  side  of  the  knee,  which  depression  corresponds  to  this  muscle.  In  the  depressed  angle 
formed  by  the  divergence  of  the  Sartorius  and  Tensor  fasci?e  femoris  muscles,  just  below  the 
anterior  superior  spinous  process  of  the  ilium,  the  Rectus  femoris  muscle  appears,  and,  below 
this,  determines  to  a  great  extent  the  convex  form  of  the  front  of  the  thigh.  In  a  well-developed 
subject  the  borders  of  the  muscle,  when  in  action,  are  clearly  to  be  defined.  The  Vastus  extemus 
forms  a  long  flattened  plane  on  the  outer  side  of  the  thigh,  traversed  by  the  longitudinal  groove 
formed  by  the  ilio-tibial  band.  The  Vastus  intemus,  on  the  inner  side  of  the  lower  half  of  the 
thigh,  gives  rise  to  a  considerable  prominence,  which  increases  toward  the  knee  and  terminates 
somewhat  abruptly  in  this  situation  with  a  full,  curved  outline.  The  Crureus  and  Subcrureus 
are  completely  hidden,  and  do  not  directly  influence  surface  form.  The  Adductor  muscles, 
constituting  the  internal  femoral  group,  are  not  to  be  individually  distinguished  from  each 
other,  with  the  exception  of  the  upper  tendon  of  the  Adductor  longus  and  the  lower  tendon  of 
the  Adductor  magnus.  The  upper  tendon  of  the  Adductor  longUS,  when  the  muscle  is  in  action, 
stands  out  as  a  prominent  ridge,  which  runs  obliquely  downward  and  outward  from  the  neigh- 
borhood of  the  pubic  spine,  and  forms  the  inner  boundary  of  a  flattened  triangular  space  on 
the  upper  part  of  the  front  of  the  thigh,  known  as  Scarpa's  triangle.  The  lower  tendon  of  the 
Adductor  magnus  can  be  distinctly  felt  as  a  short  ridge  extending  down  to  the  Adductor  tubercle 
on  the  internal  condyle,  between  the  Sartorius  and  Vastus  internus.  The  Adductor  group 
of  muscles  fills  in  the  triangular  space  at  the  upper  part  of  the  thigh,  formed  between  the  oblique 
femur  and  the  pelvic  wall,  and  to  them  is  due  the  contour  of  the  inner  border  of  the  thigh,  the 
Gracilis  largely  contributing  to  the  smoothness  of  the  outline.  These  muscles  are  not  marked 
off  on  the  surface  from  those  of  the  posterior  femoral  region  by  any  intermuscular  marking;  but 
on  the  outer  side  of  the  thigh  these  latter  muscles  are  defined  from  the  Vastus  externus  by  a 
distinct  marking,  corresponding  to  the  external  intermuscular  septum.  The  Gluteus  maximus 
and  a  part  of  the  Gluteus  medius  are  the  only  muscles  of  the  buttock  which  influence  surface 
form.  The  other  part  of  the  Gluteus  medius,  the  Gluteus  minimus,  and  the  External  rotators 
are  completely  hidden.  The  Gluteus  maximus  forms  the  full  rounded  outline  of  the  buttock; 
it  is  more  prominent  behind,  compressed  in  front,  and  terminates  at  its  tendinous  insertion  in 
a  depression  immediately  behind  the  great  trochanter.  Its  lower  border  does  not  correspond 
to  the  gluteal  fold,  but  is  much  more  oblique,  being  marked  by  a  line  drawn  from  the  side  of 
the  coccyx  to  the  junction  of  the  upper  with  the  lower  two-thirds  of  the  thigh  on  the  outer  side. 
From  beneath  the  lower  margin  of  this  muscle  the  Hamstring  muscles  appear,  at  first  narrow 
and  not  well  marked,  but  as  they  descend  becoming  more  prominent  and  widened  out,  and 
eventually  dividing  into  two  well-marked  ridges,  which  constitute  the  upper  boundaries  of  the 
popliteal  space,  and  are  formed  by  the  tendons  of  the  inner  and  outer  hamstring  muscles  respect- 
ively. In  the  upper  part  of  the  thigh  these  muscles  are  not  to  be  individually  distinguished 
from  each  other,  but  lower  down  the  separation  between  the  Semitendinosus  and  Semimem- 
branosus is  denoted  by  a  slight  intermuscular  marking.  The  external  hamstring  tendon  formed 
by  the  Biceps  is  seen  as  a  thick  cord  running  down  to  the  head  of  the  fibula.  The  inner  ham- 
string tendons  comprise  the  Semitendinosus,  the  Semimembranosus,  and  the  Gracilis.  The 
Semitendinosus  is  the  most  internal  of  these,  and  can  be  felt,  in  certain  positions  of  the  limb, 
as  a  sharp  cord;  the  Semimembranosus  is  thick,  and  the  Gracilis  is  situated  a  little  farther 
forward  than  the  other  two.  All  the  muscles  on  the  front  of  the  leg  appear  to  a  certain  extent 
somewhere  on  the  surface,  but  the  form  of  this  region  is  mainly  dependent  upon  the  Tibialis 
anticus  and  the  Extensor  longus  digitorum.  The  Tibialis  anticus  is  well  marked,  and  presents 
a  fusiform  enlargement  at  the  outer  side  of  the  tibia,  and  projects  beyond  the  crest  of  the  shin- 
bone.  From  the  muscular  mass  its  tendons  may  be  traced  downward,  standing  out  boldly, 
when  the  muscle  is  in  action,  on  the  front  of  the  tibia  and  ankle-joint,  and  coursing  down  to  its 
insertion  along  the  inner  border  of  the  foot.  A  well-marked  groove  separates  this  muscle  exter- 
nally from  the  Extensor  longus  digitorum,  which  fills  up  the  rest  of  the  space  between  the  upper 
part  of  the  shaft  of  the  tibia  and  fibula.  It  does  not  present  so  bold  an  outline  as  the  Tibialis 
anticus,  and  its  tendon  below,  diverging  from  the  tendon  of  the  Tibialis  anticus,  forms  with  the 
latter  a  sort  of  plane,  in  which  may  be  seen  the  tendon  of  the  Extensor  proprius  hallucis.  A 
groove  on  the  outer  side  of  the  extensor  longus  digitorum,  seen  most  plainly  when  the  muscle 
is  in  action,  separates  the  tendon  from  a  slight  eminence  corresponding  to  the  Peroneus  tertius. 
The  fleshy  fibres  of  the  Peroneus  longus  are  strongly  marked  at  the  upper  part  of  the  outer 


SURGICAL    ANATOMY    OF    THE   LOWER    EXTREMITY        551 

side  of  the  leg,  especially  when  the  muscle  is  in  action.  It  forms  a  bold  swelling,  separated  by 
furrows  from  the  Extensor  longus  digitorum  in  front  and  the  Soleus  behind.  Below,  the  fleshy 
fibres  terminate  abruptly  in  a  tendon  which  overlaps  the  more  flattened  form  of  the  Peroneus 
brevis.  At  the  external  malleolus  the  tendon  of  the  Peroneus  brevis  is  more  marked  than  that 
of  the  Peroneus  longus.  On  the  dorsum  of  the  foot  the  tendons  of  the  Extensor  muscles, 
emerging  from  beneath  the  anterior  annular  ligament,  spread  out  and  can  be  distinguished 
in  the  following  order:  The  most  internal  and  largest  is  the  Tibialis  anticus,  then  the  Extensor 
proprius  hallucis ;  next  comes  the  Extensor  longus  digitorum,  dividing  into  four  tendons  to 
the  four  outer  toes;  and  lastly,  most  externally,  is  the  Peroneus  tertius.  The  flattened  form  of 
the  dorsum  of  the  foot  is  relieved  by  the  rounded  outline  of  the  fleshy  belly  of  the  Extensor 
brevis  digitorum,  which  forms  a  soft  fulness  on  the  outer  side  of  the  tarsus  in  front  of  the  external 
malleolus,  and  by  the  Dorsal  interossei,  which  bulge  between  the  metatarsal  bones.  At  the 
back  of  the  knee  is  the  popliteal  space,  bounded  above  by  the  tendons  of  the  hamstring  muscle; 
below,  by  the  two  heads  of  the  Gastrocnemius.  Below  this  space  is  the  prominent  fleshy  mass 
of  the  calf  of  the  leg,  produced  by  the  Gastrocnemius  and  Soleus.  When  these  muscles  are 
in  action,  as  in  standing  on  tiptoe,  the  borders  of  the  Gastrocnemius  are  well  defined,  presenting 
two  curved  lines,  which  converge  to  the  tendon  of  insertion.  Of  these  borders,  the  inner  is 
more  prominent  than  the  outer.  The  fleshy  mass  of  the  calf  terminates  somewhat  abruptly 
below  in  the  tendo  Achillis,  which  stands  out  prominently  on  the  lower  part  of  the  back  of  the 
leg.  It  presents  a  somewhat  tapering  form  in  the  upper  three-fourths  of  its  extent,  but  widens 
out  slightly  below.  When  the  muscles  of  the  calf  are  in  action,  the  lateral  portions  of  the  Soleus 
may  be  seen,  forming  curved  eminences,  of  which  the  outer  is  the  longer,  on  either  side  of  the 
Gastrocnemius.  Behind  the  inner  border  of  the  lower  part  of  the  shaft  of  the  tibia  a  well- 
marked  ridge,  produced  by  the  tendon  of  the  Tibialis  posticus,  is  visible  when  this  muscle  is  in 
a  state  of  contraction.  On  the  sole  of  the  foot  the  superficial  layer  of  muscles  influences  surface 
form;  the  Abductor  minimi  digiti  most  markedly.  This  muscle  forms  a  narrow  rounded 
elevation  along  the  outer  border  of  the  foot,  while  the  Abductor  hallucis  does  the  same,  though 
to  a  less  extent,  on  the  inner  side.  The  Flexor  brevis  digitorum,  bound  down  by  the  plantar 
fascia,  is  not  very  apparent;  it  produces  a  flattened  form,  covered  by  the  thickened  skin  of  the 
sole,  which  is  here  thrown  into  numerous  wrinkles. 

SURGICAL  ANATOMY  OF  THE  LOWER  EXTREMITY. 

The  student  should  now  consider  the  effects  produced  by  the  action  of  the  various  muscles 
in  fractures  of  the  bones  of  the  lower  extremity.  The  more  common  forms  of  fractures  are 
selected  for  illustration  and  description. 


PYRIFORMIS. 
GEMELLUS   SUPERIOR. 
OBTURATOR    INTERNUS. 
GEMELLUS    INFERIOR. 
OBTURATOR    EXTERNUS. 
QUADRATUS    FEMORIS. 


Fig.  359.-  -Fracture  of  the  neck  of  the  femur  within  the  capsular  ligament. 

In  fracture  of  the  neck  of  the  femur  internal  to  the   capsular  ligament  (Fig.  359)  the  charac- 
teristic marks  are  slight  shortening  of  the  limb  and  eversion  of  the  foot,  neither  of  which  symp- 


552 


THE   MUSCLES    AND    FASCIJE 


toms  occurs,  however,  in  some  cases  until  some  time  after  the  injury.  The  eversion  is  caused 
by  the  weight  of  the  Hmb  rotating  it  outward.  The  shortening  is  produced  by  the  action  of  the 
Glutei,  and  by  the  Rectus  femoris  in  front  and  the  Biceps,  Semitendinosus,  and  Semimem- 
branosus behind.  The  treatment  is  extension  by  means  of  adhesive  plaster  and  weights  and 
counter-extension  by  raising  the  foot  of  the  bed,  eversion  being  corrected  by  sand-bags.  In 
some  cases  Thomas's  splint  is  used. 

In  fracture  of  the  femur  just  below  the  trochanters  (Fig.  360)  the  upper  fragment,  the  por- 
tion chiefly  displaced,  is  tilted  forward  almost  at  right  angles  with  the  pelvis  by  the  combined 

action  of  the  Psoas  and  Iliacus,  and,  at  the  same  time,  everted 
and  drawn  outward  by  the  External  rotator  and  Glutei  muscles, 
causing  a  marked  prominence  at  the  upper  and  outer  side  of  the 
thigh,  and  much  pain  from  the  bruising  and  laceration  of  the 
muscles.  The  limb  is  shortened,  in  consequence  of  the  lower 
fragment  being  drawn  upward  by  the  rectus  in  front,  and  the 
Biceps,  Semimembranosus,  and  Semitendinosus  behind,  and  is 
at  the  same  time  everted.  This  fracture  may  be  reduced  by 
direct  relaxation  of  all  the  opposing  muscles,  to  effect  which  the 
limb  should  be  put  up  in  such  a  manner  that  the  thigh  is  flexed 
on  the  pelvis  and  the  leg  on  the  thigh,  the  extremity  being  placed 


SEMI- 
MEMBRANOSUS. 
SEMI- 
/      TENDINOSUS. 


Fig.  360. — Fracture  of   the  femur 
below  the  trochanters. 


Fig.  361. — Fracture  of  the  femur 
above  the  condyles. 


Fig.  362.— Fracture  of 
the  patella 


upon  a  double  inclined  plane  and  extension  being  made  in  the  axis  of  the  partly  flexed 
thigh  by  means  of  adhesive  plaster  and  weights.  In  some  cases  it  is  necessary  to  incise  and 
wire  the  fragments  together. 

Oblique  fracture  of  the  femur  immediately  above  the  condyles  (Fig.  361)  is  a  formidable 
injury,  and  attended  with  considerable  displacement.  On  examination  of  the  limb  the  lower 
fragment  may  be  felt  deep  in  the  popliteal  space,  being  drawn  backward  by  the  Gastrocnemius 
and  Plantaris  muscles,  and  upward  by  the  Hamstring  and  Rectus  muscles.  The  pointed  end 
of  the  upper  fragment  is  drawn  inward  by  the  Pectineus  and  Adductor  muscles,  and  tilted  for- 
ward by  the  Psoas  and  Iliacus,  piercing  the  Rectus  muscle  and  occasionally  the  integument. 
Relaxation  of  these  muscles  and  direct  approximation  of  the  broken  fragments  are  effected  by 
placing  the  limb  on  a  double  inclined  plane.  The  greatest  care  is  requisite  in  keeping  the 
pointed  extremity  of  the  upper  fragment  in  proper  position;  otherwise,  after  union  of  the 
fracture,  the  power  of  extension  of  the  limb  is  partially  destroyed  from  the  Rectus  muscle  being 
held  down  by  the  fractured  end  of  the  bone,  and  from  the  patella,  when  elevated,  being  drawn 
upward  against  the  projecting  fragment. 

In  fracture  of  the  patella  (Fig.  362)  the  fragments  are  separated  by  the  efi'usion  which  takes 
place  into  the  joint,  and  by  the  action  of  the  Quadriceps  extensor;  the  extent  of  separation  of 
the  two  fragments  depending  upon  the  degree  of  laceration  of  the  ligamentous  structures 
around  the  bone.  Some  cases  may  be  treated  by  a  posterior  straight  splint,  the  fragments 
being  pulled  together  by  strips  of  adhesive  plaster.  In  many  cases  it  is  advisable  to  incise, 
remove  intervening  pieces  of  fibrous  tissue  and  wire  the  fragments  together. 


SURGICAL   ANATOMY   OF    THE   LOWER    EXTREMITY       553 

The  tibia  is  fractured  most  commonly  by  indirect  force  at  the  junction  of  the  middle  third 
with  the  lower  third  of  the  shaft.  Compound  fractures  are  more  common  in  the  leg  than 
in  any  other  region  of  the  body  because  the  tibia  is  such  a  superficial  bone  and  is  so  much 
exposed  to  injury.     Most  fractures  from  indirect  force  are  oblique. 

In  oblique  fracture  of  the  shaft  of  the  tibia  (Fig.  363),  if  the  fracture  has  taken  place  obliquely 
from  above,  downward  and  forward,  the  fragments  ride  over  one  another,  the  lower  fragments 
being  drawn  backward  and  upward  by  the  powerful  action  of  the  muscles  of  the  calf;  the 
pointed  extremity  of  the  upper  fragment  projects  forward  immediately  beneath  the  integu- 
ment, often  protruding  through  it  and  rendering  the  fracture  a  compound  one.  If  the  direc- 
tion of  the  fracture  is  the  reverse  of  that  shown  in  the  figure,  the  pointed  extremity  of  the  lower 
fragment  projects  forward,  riding  upon  the  lower  end  of  the  upper  one.     By  bending  the  knee. 


Fig.  363. — Oblique  fracture  of 
the  shaft  of  the  tibia. 


Fig.  364. — Fracture  of  the  fibula  with  dislocation  of 
the  foot  outward — "  Pott's  fracture." 


which  relaxes  the  opposing  muscles,  and  making  extension  from  the  ankle  and  counter- 
extension  at  the  knee,  the  fragments  may  be  brought  into  apposition.  It  is  often  necessary, 
however,  in  a  compound  fracture,  to  remove  a  portion  of  the  projecting  bone  with  the  saw 
before  complete  adaptation  can  be  effected. 

Fracture  of  the  fibula  with  dislocation  of  the  foot  outward  (Fig.  364),  commonly  known  as 
Pott's  fracture,  is  one  of  the  most  frequent  injuries  of  the  ankle-joint.  The  fibula  is  frac- 
tured about  three  inches  above  the  ankle;  in  addition  to  this  the  internal  malleolus  is  broken 
off,  or  the  deltoid  ligament  torn  through,  and  the  end  of  the  tibia  displaced  from  the  correspond- 
ing surface  of  the  astragalus.  The  foot  is  markedly  everted,  and  the  sharp  edge  of  the  upper 
end  of  the  fractured  malleolus  presses  strongly  against  the  skin;  at  the  same  time,  the  heel  is 
drawn  up  by  the  muscles  of  the  calf.  This  injury  can  generally  be  reduced  by  flexing  the  leg  at 
right  angles  with  the  thigh,  which  relaxes  all  the  opposing  muscles,  and  by  making  extension 
from  the  ankle  and  counter-extension  at  the  knee. 


^ 


THE  BLOOD-VASCULAE  SYSTEM. 


ANGIOLOGY  is  the  branch  of  anatomy  which  treats  of  the  blood-vessels. 
The  blood-vascular   system  comprises  the  heart  and  blood-vessels  with 
their  contained  fluid,  the  blood. 

The  Heart  is  the  central  organ  of  the  entire  system,  and  is  a  hollow  muscle; 
by  its  contraction  the  blood  is  pumped  to  all  parts  of  the  body  through  a  com- 
plicated series  of  tubes,  termed  arteries.  The  arteries  undergo  almost  infinite 
ramification  in  their  course  throughout  the  body,  and  end  in  very  minute  vessels, 
called  arterioles,  which  in  their  turn  open  into  a  close-meshed  network  of  micro- 
scopic vessels,  termed  capillaries .  After  the  blood  has  passed  through  the  capil- 
laries it  enters  into  minute  vessels  called  venules  and  from  them  it  is  collected 
into  a  series  of  larger  vessels,  called  veins,  by  which  it  is  returned  to  the  heart. 
The  passage  of  the  blood  through  the  heart  and  blood-vessels  constitutes  what  is 
termed  the  circulation  of  the  blood,  of  which  the  following  is  an  outline. 

The  human  heart  is  divided  by  a  septum  into  two  halves,  right  and  left,  each 
half  being  further  constricted  into  two  cavities,  the  upper  of  the  two  being  termed 
the  auricle  and  the  lower  the  ventricle.  The  heart  therefore  consists  of  four 
chambers  or  cavities,  two  forming  the  right  half,  the  right  auricle  and  right 
ventricle;  and  two  the  left  half,  the  left  auricle  and  left  ventricle.  The  right 
half  of  the  heart  contains  venous  or  impure  blood;  the  left,  arterial  or  pure  blood. 
From  the  cavity  of  the  left  ventricle  the  pure  blood  is  carried  into  a  large  artery, 
the  aorta,  through  the  numerous  branches  of  which  it  is  distributed  to  all  parts 
of  the  body,  with  the  exception  of  the  lungs.  In  its  passage  through  the  capil- 
laries of  the  body  the  blood  gives  up  to  the  tissues  the  materials  necessary  for 
their  growth  and  nourishment,  and  at  the  same  time  receives  from  the  tissues  the 
waste  products  resulting  from  their  metabolism,  and  in  doing  so  becomes  changed 
from  arterial  or  pure  blood  into  venous  or  impure  blood,  which  is  collected  by  the 
veins  and  through  them  returned  to  the  right  auricle  of  the  heart.  From  this 
cavity  the  impure  blood  passes  into  the  right  ventricle,  from  which  it  is  conveyed 
through  the  pulmonary  arteries  to  the  lungs.  In  the  capillaries  of  the  lungs  it 
again  becomes  arterialized,  and  is  then  carried  to  the  left  auricle  by  the  pulmonary 
veins.  From  this  cavity  it  passes  into  that  of  the  left  ventricle,  from  which  the 
cycle  once  more  begins. 

The  course  of  the  blood  from  the  left  ventricle  through  the  body  generally  to 
the  right  side  of  the  heart  constitutes  the  greater  or  systemic  circulation,  while  its 
passage  from  the  right  ventricle  through  the  lungs  to  the  left  side  of  the  heart  is 
termed  the  lesser  or  pulmonary  circulation. 

It  is  necessary,  however,  to  state  that  the  blood  which  circulates  through  the 
spleen,  pancreas,  stomach,  small  intestine,  and  the  greater  part  of  the  large  intes- 
tine is  not  returned  directly  from  these  organs  to  the  heart,  but  is  collected  into 
a  large  vein,  termed  the  portal  vein,  by  which  it  is  carried  to  the  liver.  In  the 
liver  this  vein  divides,  after  the  manner  of  an  artery,  and  ultimately  ends  in 
capillary  vessels,  from  which  the  rootlets  of  a  series  of  veins,  called  the  hepatic 
veins,  arise;  these  carry  the  blood  into  the  inferior  vena  cava,  which  conveys  it 
to  the  right  auricle. 

(  555  ) 


556 


THE  BLOOD -VASCULAR    SYSTEM 


Pulm onary  Camllaries 


From  this  it  will  be  seen  that  the  blood  contained  in  the  portal  vein  passes 
through  two  sets  of  capillary  vessels:  (1)  those  in  the  spleen,  pancreas,  stomach, 
etc.,  and  (2)  those  in  the  liver. 

Speaking  generally,  the  arteries  may  be  said  to  contain  pure,  and  the  veins 
impure,  blood.  This  is  true  of  the  systemic,  but  not  of  the  pulmonary,  vessels, 
since  it  has  been  seen  that  the  impure  blood  is  conveyed  from  the  heart  to  the 
lungs  by  the  pulmonary  arteries,  and  the  pure  blood  returned  from  the  lungs  to 

the  heart  by  the  pulmonary  veins.  Arteries, 
therefore,  must  be  defined  as  vessels  which 
convey  blood  from  the  heart,  and  veins  as 
vessels  which  return  blood  to  the  heart. 

The  heart  and  lungs  are  contained  within 
the  cavity  of  the  thorax,  the  walls  of  which 
afford  them  protection  (Fig.  366).  The  heart 
lies  between  the  two  lungs,  and  is  there 
enclosed  within  a  sero-membranous  bag,  the 
pericaxdium,  while  each  lung  is  invested  by  a 
serous  membrane,  the  pleura.  The  skeleton 
of  the  thorax  was  described  on  page  155. 

The  Cavity  of  the  Thorax  (cavum  tho- 
racis).— The  capacity  of  the  cavity  of  the 
thorax  does  not  correspond  with  its  apparent 
size  externally,  because  (1)  the  space  en- 
closed by  the  lower  ribs  is  occupied  by  some 
of  the  abdominal  viscera ;  and  (2)  the  cavity 
extends  above  the  first  rib  into  the  neck. 
The  size  of  the  cavity  of  the  thorax  is  con- 
stantly varying  during  life,  with  the  move- 
ments of  the  ribs  and  diaphragm,  and  with 
the  degree  of  distention  of  the  abdominal 
viscera.  From  the  collapsed  state  of  the 
lungs,  as  seen  when  the  thorax  is  opened, 
in  the  dead  body,  it  would  appear  as  if  the 
viscera  only  partly  filled  the  cavity  of  the 
thorax,  but  during  life  there  is  no  vacant 
space,  that  which  is  seen  after  death  being 
filled  up  during  life  by  the  expanded  lungs. 
The  Upper  Opening  of  the  Thorax 
{apertura  thoracis  superior) .  —  The  parts 
which  pass  through  the  upper  opening  of 
the  thorax  are,  from  before  backward  in  or 
near  the  middle  line,  the  Sterno-hyoid  and 
Sterno-thyroid  muscles,  the  remains  of  the 
thymus  gland,  the  trachea,  oesophagus,  thoracic  duct,  the  inferior  thyroid  veins, 
and  the  Longus  colli  muscle  of  each  side;  at  the  sides,  the  innominate  artery, 
the  left  common  carotid,  and  left  subclavian  arteries,  the  internal  mammary 
and  superior  intercostal  arteries,  the  right  and  left  innominate  veins,  the  pneu- 
mogastric,  cardiac,  phrenic,  and  sympathetic  nerves,  the  anterior  branch  of  the 
first  dorsal  nerve,  and  the  recurrent  laryngeal  nerve  of  the  left  side.  The 
apex  of  each  lung,  covered  by  the  pleura,  also  projects  through  this  aperture,  a 
little  above  the  margin  of  the  first  rib. 

The  Lower  Opening  of  the  Thorax  (apertura  thoracis  inferior)  is  wider  trans- 
versely than  from  before  backward.  It  slopes  obliquely  downward  and  back- 
ward, so  that  the  cavity  of  the  thorax  is  much  deeper  behind  than  in  front.     The 


Fig.  365.- 


-Diagram  to  show  the  course  of  the 
circulation  of  the  blood. 


THE   PERICARDIUM 


557 


Diaphragm  (see  page  427)  closes  in  the  opening,  forming  the  floor  of  the  thorax. 
The  floor  is  flatter  at  the  centre  than  at  the  sides,  and  is  higher  on  the  right  side 
than  on  the  left,  corresponding  in  the  dead  body  to  the  upper  border  of  the  fifth 


Fig.  366. — Front  view  of  the  thorax.  The  ribs  and  sternum  are  represented  in  relation  to  the  lungs,  heart, 
and  othpr  internal  organs.  1.  Pulmonary  orifice.  2.  Aortic  orifice.  3.  Left  auriculo- ventricular  orifice.  4. 
Right  auriculo-ventricular  orifice. 

costal  cartilage  on  the  former,  and  to  the  corresponding  part  of  the  sixth  costal 
cartilage  on  the  latter.  From  the  highest  point  on  each  side  the  floor  slopes  sud- 
denly downward  to  the  attachment  of  the  Diaphragm  to  the  ribs;  this  is  more 
marked  behind  than  in  front,  so  that  only  a  narrow  space  is  left  between  it  and 
the  wall  of  the  thorax. 


THE  PERICARDIUM. 

The  pericardium  (Figs.  367,  368,  369,  370,  371,  and  372)  is  a  conical  sero- 
membranous  sac,  placed  in  the  middle  mediastinum.  In  this  sac  the  heart  and 
the  commencement  of  the  great  vessels  are  contained.  It  is  placed  behind  the 
sternum  and  the  cartilages  of  the  third,  fourth,  fifth,  sixth,  and  seventh  ribs  of 
the  left  side,  in  the  interval  between  the  pleurae. 

Its  apex  is  directed  upward,  and  surrounds  the  great  vessels  about  two  inches 
above  their  origin  from  the  base  of  the  heart.  Its  base  is  attached  to  the  central 
tendon  and  to  the  left  part  of  the  adjoining  muscular  structure  of  the  Diaphragm. 
In  front  it  is  separated  from  the  sternum  by  the  remains  of  the  thymus  gland 


558 


THE    BLOOD -VASCULAR    SYSTEM 


above  and  a  little  loose  areolar  tissue  below,  and  is  covered  by  the  margins  of  the 
lungs,  especially  the  left.  Behind,  it  rests  upon  the  bronchi,  the  oesophagus,  and 
the  descending  aorta.  Laterally,  it  is  covered  by  the  pleurae,  and  is  in  relation  to 
the  inner  surface  of  the  lungs;  the  phrenic  nerve  with  its  accompanying  vessels 
descends  between  the  pericardium  and  pleura  on  either  side  (Fig.  371). 

Structure  of  the  Pericardium. — ^The  pericardium  is  a  fibro-serous  membrane, 
and  consi^s,  therefore,  of  two  layers,  an  external  fibrous  and  an  internal  serous. 


Right  common 
carotid  artery. 
Inferior  thyroid 
vein. 
Left  innomi- 
nate vein. 
Right  innomi- 
nate vein. 

Superior  vena 
cava. 


Right  pulmo 
nary  veins. 


Left  common 
carotid  art. 


Left  sub- 
chirian 
(trtery. 


]  Left  pul- 
>  monary 
J      veins. 


Fig.  367.- 


-Pericardium  from  in  front.     The  sac  has  been  distended  with  plaster.     (From  a  preparation 
in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 


The  Fibrous  Layer  is  a  strong,  dense,  connective-tissue  membrane.  Above,  it 
surrounds  the  great  vessels  arising  from  the  base  of  the  heart,  on  which  it  is 
continued  in  the  form  of  tubular  prolongations  which  are  gradually  lost  upon 
their  external  coat,  the  strongest  being  that  which  encloses  the  aorta.  The  peri- 
cardium may  be  traced  over  these  vessels,  to  become  continuous  with  the  deep 
layer  of  the  cervical  fascia.  The  prolongations  to  the  cervical  fascia  constitute  the 
vertebro-pericardial  ligaments  (Fig.  370).  In  front  the  pericardium  is  connected  to 
the  posterior  surface  of  the  sternum  by  two  fibrous  bands,  the  superior  and  inferior 
stemo-pericardiac  ligaments  or  ligaments  of  Luschka  (ligamenta  sternopericardiaca) 
(Fig.  370).     The  superior  sterno-pericardial  ligament,  called  also  the  stemocosto- 


THE   PERICARDIUM 


559 


pericardial  ligament  (Fig.  370),  passes  to  the  manubrium.  The  inferior  sterno- 
pericardial Hgament,  called  also  the  xipho-pericardial  ligament  (Fig.  370),  passes  to 
the  ensiform  cartilage.  On  each  side  of  the  ascending  aorta  the  pericardium  sends 
upward  a  diverticulum :  the  one  on  the  left  side,  somewhat  conical  in  shape,  passes 
upward  and  outward,  between  the  arch  of  the  aorta  and  the  pulmonary  artery, 
as  far  as  the  ductus  arteriosus,  where  it  terminates  in  a  csecal  extremity,  which  is 
attached  by  loose  connective  tissue  to  the  obliterated  duct  (Fig.  367).  The  one  on 
the  right  side  passes  upward  and  to  the  right,  between  the  ascending  aorta  and 


Left  subclavian  artery 
Bight  pulmonary  artery. 


Right  subclavian  artery. 
Left  common 
carotid  artery.  

Right  common 
carotid  artery. 

Inferior  thyroid 
_^__         vein. 

.      ./^^^^^ 

"Aj^i-..       c^^lj^    ~  Vena  azygos 

'"'■  *''    (y   f/         major. 


Right  pulmonary 
veins. 


Fig.  368. — Pericardium  from  behind.     (From  the  same  preparation  as  the  preceding  figure.) 


vena  cava  superior,  and  also  terminates  in  a  csecal  extremity.  Below,  the  fibrous 
layer  is  attached  to  the  central  tendon  of  the  Diaphragm,  and  on  the  left  side  to 
its  muscular  fibres.  The  pericardium  is  fixed  to  the  Diaphragm  by  the  anterior 
phreno-pericardial  ligament  and  by  the  lateral  phreno-pericardial  ligaments  (Fig.  370). 
The  vessels  receiving  fibrous  prolongations  from  this  membrane  are  the  aorta 
the  superior  vena  cava,  the  right  and  left  pulmonary  arteries,  and  the  four  pulmo- 
nary veins.  The  inferior  vena  cava  enters  the  pericardium  through  the  central 
tendon  of  the  Diaphragm,  and  consequently  it  receives  no  covering  from  the 
fibrous  layer  (Fig.  371). 


560 


THE   BLOOD -VASCULAB    SYSTEM 


The  Serous  Pericaxdium  invests  the  heart,  and  is  then  reflected  on  the  inner  sur- 
face of  the  fibrous  pericardium.  It  consists,  therefore,  of  a  visceral  layer  (epicar- 
dium)  and  a  parietal  layer.  The  former  invests  the  surface  of  the  heart,  and  the 
commencement  of  the  great  vessels,  to  the  extent  of  an  inch  and  a  half  from 
their  origin ;  from  these  it  is  reflected  upon  the  inner  surface  of  the  fibrous  layer. 
The  serous  membrane  encloses  the  aorta  and  pulmonary  artery  in  a  single  tube, 
so  that  a  passage,  termed  the  great  transverse  sinus  of  the  pericardium  (sinus  trans- 
versiis  'pericardii),  exists  between  these  vessels  in  front  and  the  auricle  behind. 
This  sinus  is  closed  above  and  below  but  often  to  the  right  and  left.  The  mem- 
brane only  partially  covers  the  superior  vena  cava  and  the  four  pulmonary  veins. 


RIGHT 

PULMONARY. 

VEIN 


PAR  I  ETA 
PERICARDIUM 


Fig.  369. — The  line  of  reflection  of  the  serous  pericardium.     (Modified  from  Poirier  and  Charpy.) 

and  scarcely  covers  the  inferior  cava,  as  this  vessel  enters  the  heart  almost  directly 
after  it  has  passed  through  the  Diaphragm.  A  deep  blind  recess  formed  by  the 
serous  pericardium  is  found  behind  the  heart  when  that  organ  is  raised  up. 
This  recess  runs  backward  between  the  left  auricle  and  the  posterior  portion  of 
the  fibrous  pericardium,  and  forms  a  diverticulum  between  the  heart  and  the 
oesophagus.  This  recess  is  called  the  oblique  sinus.  It  passes  upward  between 
the  inferior  vena  cava  and  the  lower  left  pulmonary  vein  and  terminates  between 
the  right  and  left  pulmonary  veins.  The  inner  surface  of  the  pericardium 
is  covered  with  endothelium,  which  rests  upon  a  mixture  of  fibrous  and 
elastic  tissue,  which  is  smooth  and  glistening,  and  secretes  a  serous  fluid  {liquor 


THE  PERICARDIUM 


561 


'pericardii) ,  which  serves  to  facilitate  the  movements  of  the  heart.  In  the  serous 
layer  of  the  pericardium  are  many  blood-vessels,  lymph  vessels,  and  nerves. 

Arteries  of  the  Pericaxdium. — These  are  derived  from  the  internal  mammary  and 
its  musculo-phrenic  branch,  and  from  the  descending  thoracic  aorta. 

Nerves  of  the  Pericaxdium. — These  are  branches  from  the  vagus,  the  phrenic, 
and  the  sympathetic. 

The  Vestigial  Fold  of  the  Pericardium. — Between  the  left  pulmonary  artery  and 
subjacent  pulmonary  vein  and  behind  the  left  extremity  of  the  transverse  sinus  is 
a  triangular  fold  of  the  serous  pericardium;  it  is  known  as  the  vestigial  fold  of 
Marshall  (ligamentum  v.  cavcB  sinisiroe) .  It  is  formed  by  the  duplicature  of  the 
serous  layer  over  the  remnant  of  the  lower  part  of  the  left  superior  vena   cava 


SUPERIOR 
VENA  CAVA 


INFERIOR 
VENA  CAVA 

PHRENO- 

PERICARDIAL 

LIGAMENTS 


OR  STERNO- 
RDIAL  LIG- 
TS 


TERIOR 
RFACE    OF 
RICARDIUM 


XIPHO- 

PERICARDIAL 

LIGAMENTS 


Fig.  370. — Ligaments  of  the  pericardium.  (Modified  from  Teutleben.)  Right  lateral  view,  showing  the  right 
vertebra — pericardial  ligaments,  the  right  phreno-pericardial,  and  the  superior  and  inferior  sterno-pericardial 
ligaments.     (Poirier  and  Charpy.) 


{v.  cava  sinistra)  or  the  duct  of  Cuvier,  which,  after  birth,  becomes  obliterated, 
and  remains  as  a  fibrous  band  stretching  from  the  left  superior  intercostal  vein 
to  the  left  auricle,  where  it  is  continuous  with  a  small  vein,  the  oblique  vein  of 
Marshall  {v.  ohliqua  atrii  sinistri  [Marshalli]) ,  which  opens  into  the  coronary 
sinus  and  is  a  remnant  of  the  foetal  left  superior  vena  cava. 

Surgical  Anatomy. — Aspiration  of  the  pericardium  (paracentesis  of  the  pericardium)  is  occa- 
sionally though  seldom  performed.  It  is  only  to  be  thought  of  when  pericardial  effusion  endangers 
life.    The  operation  is  very  dangerous,  because  the  effusion  lifts  the  heart  and  pushes  it  forward. 

36 


562 


THE  BLOOD -VASCULAR   SYSTEM 


and  the  needle  is  apt  to  wound  the  heart  or  even  enter  one  of  the  cavities.  There  is  also  danger 
of  wounding  the  internal  mammary  artery.  The  operation  is  never  to  be  thought  of  in  puru- 
lent pericarditis.  The  safest  way  to  aspirate  is  to  introduce  the  needle  in  the  fifth  interspace 
two  inches  to  the  left  of  the  sternum  and  push  it  straight  backward. 

A  better  operation,  even  in  a  case  of  serous  effusion,  and  one  invariably  selected  in  purulent 
pericarditis,  is  incision  (pericardotomy).  A  portion  of  the  cartilage  of  the  fifth  rib  of  the  left 
side  is  excised.  The  pericardium  is  exposed  and  is  punctured,  to  learn  the  nature  of  the 
contained  fluid,  and  is  then  incised.  By  this  method  the  surgeon  avoids  opening  the  pleural 
cavity,  and  can  obtain  free  drainage  if  pus  is  found. 

Porter  maintains  that  by  "reason  of  the  uncertain  and  varying  relations  of  the  pleura,  and 
also  of  the  anterior  position  of  the  heart,  whenever  the  pericardial  sac  is  distended  with  fluid, 
aspiration  of  the  pericardium  is  a  much  more  dangerous  procedure  than  open  incision  when 
done  by  skilled  hands." 


RIGHT 

PULMONARY 

VETNS 

PERICARDIUM 


PULMONARY 


PERICARDIUM 


DIAPriRAQM 


Fig.  371.— Posterior  wall  of  the  pericardium,  after  the  removal  of  the  heart,  .showing  the  relation  of  the  serous 
pericardium  to  the  great  vessels.     (From  a  formalin  preparation  by  Prof.  Birmingham.)     (Cunningham.) 


THE  HEART  (COR). 

The  heart  is  a  hollow  muscular  organ  of  a  conical  form,  placed  between  the 
lungs,  and  enclosed  in  the  cavity  of  the  pericardium. 

Position  (Fig.  372).— The  heart  is  placed  obliquely  in  the  chest:  the  broad 
attached  end,  or  base  (basis  cordis),  is  directed  upward,  backward,  and  to  the  right, 
and  corresponds  with  the  dorsal  vertebra,  from  the  fifth  to  the  eighth  inclusive;  the 
apex  (apex  cordis)  is  directed  downward,  forward,  and  to  the  left,  and  corresponds 
to  the  space  between  the  cartilages  of  the  fifth  and  sixth  ribs,  three-quarters  of  an 


THE   HEART 


563 


inch  to  the  inner  side,  and  an  inch  and  a  half  below  the  left  nipple,  or  about  three 
and  a  half  inches  from  the  middle  line  of  the  sternum.  The  heart  is  placed  behind 
the  sternum,  and  projects  farther  into  the  left  than  into  the  right  half  of  the  cavity 
of  the  chest,  extending  from  the  median  line  about  three  inches  in  the  former 
direction,  and  only  one  and  a  half  in  the  latter;  about  one-third  of  the  heart  lies 
to  the  right  and  two-thirds  to  the  left  of  the  mesial  plane.  The  antero-superior 
surface  (fades  sternocostalis)  is  round  and  convex,  directed  upward  and  forward, 
is  formed  chiefly  by  the  right  auricle  and  ventricle,  together  with  a  small  part  of 
the  left  ventricle.  It  lies  behind  the  middle  portion  of  the  sternum  and  the  costal 
cartilages  of  the  third,  fourth,  fifth,  and  sixth  ribs  on  both  sides.    On  account  of 


Fig.  372. — Pusition  of  the  heart.     The  pericardium  laid  open.     Adult  male.     (Poirier  and  Charpy.) 


the  heart's  inclination  to  the  left  side,  only  a  small  part  of  it  lies  behind  the  carti- 
lages of  the  right  ribs.  Lying  in  front  of  the  heart,  between  it  and  the  anterior 
chest-wall,  is  the  thin  anterior  margin  of  the  lungs,  covered  by  the  pleura.  On 
the  left  side,  however,  owing  to  the  notch  in  the  anterior  margin  of  the  left 
lung  (incisura  cardiaca),  there  is  a  portion  of  the  pericardium  lying  in  contact 
with  the  Triangularis  sterni  muscle.  This  area  is  called  the  area  of  greatest  or 
of  absolute  cardiac  duhiess  or  the  area  of  superficial  cardiac  dulness.  The  postero- 
inferior  surface  of  the  heart  (fades  dia^hragmatica) ,  which  looks  downward  rather 


564 


THE   BLOOD -VASCULAR   SYSTEM 


than  backward,  is  flattened  and  rests  upon  the  Diaphragm,  and  is  formed  chiefly 
by  the  left  ventricle.  The  right  or  lower  border  is  long,  thin,  and  sharp;  the  left 
or  upper  border  short,  but  thick  and  round. 

Size  and  Weight. — The  heart,  in  the  adult,  measures  five  inches  in  length, 
three  inches  and  a  half  in  breadth  in  the  broadest  part,  and  two  inches  and  a  half 
in  thickness.  The  prevalent  weight,  in  the  male,  varies  from  ten  to  twelve  ounces; 
in  the  female,  from  eight  to  ten:  its  proportions  to  the  body  being  as  1  to  169  in 
males;  1  to  149  in  females.  The  heart  continues  increasing  in  weight,  and  also 
in  length,  breadth,  and  thickness,  up  to  an  advanced  period  of  life:  this  increase 
is  more  marked  in  men  than  in  women. 


•"{,«-!nii.;i".r8i..i ,. 


LEFT  APPENDIX 

AURICUUE 

LEFT  AuniCULA 

VENTRICULA 

GROOVE 


CORONARY 
SINUS 


SULCUS 
TERMINALES 


INTERARTICULAR 
SULCUS 


(ESOPHAGUS 


'^*i£fitti/ 


Fig.  373. — Base  of  the  heart  in  place.     The  attachments  of  the  pericardium  are  outlined  in  red. 

(Poirier  and  Charpy.) 

Capacity  of  the  Cavities  of  the  Heart. — This  matter  is  in  dispute.  Professor 
Cunningham  believes  that  during  life  the  capacity  of  the  ventricles  is  nearly  iden- 
tical, each  holding  about  four  ounces  of  blood.  Each  auricle  holds  a  little  less 
than  four  ounces.  Stewart  maintains  that  at  each  heart  beat  each  ventricle 
throws  out  only  eighty-seven  grams  of  blood.  Morrant  Baker^  says  that,  "taking 
the  mean  of  various  estimates,  it  may  be  inferred  that  each  ventricle  is  able  to 
contain  four  to  six  ounces  of  blood."  / 

Fat  upon  the  Heart. — Normally  there  is  a  certain  amount  of  fat  upon  the 
surface  of  the  heart.  This  begins  to  appear  in  the  early  weeks  of  life  and 
increases  in  amount  as  age  advances.  It  is  found  upon  the  surface  of  the 
muscles  and  along  the  course  of  the  vessels.  Poirier  is  of  the  opinion  that  the 
cardiac  fat  on  the  anterior  surface  of  the  heart  is  arranged  in  three  movable 


^  Kirke's  Physiology,  10th  ed.,  p.  156. 


THE   HEART  555 

pads,  which  act  as  valves  and  fill  vacant  spaces  about  the  heart  created  during 
the  cardiac  contractions/ 

Component  Parts. — The  heart  is  subdivided  by  a  muscular  septum  into  two- 
lateral  halves,  which  are  named  respectively  the  right  or  pulmonary  heart  and  the 
left  or  systemic  heart;  and  a  transverse  constriction  subdivides  each  half  of  the 
organ  into  two  cavities,  the  upper  cavity  on  each  side  being  called  the  auricle, 
the  lower  the  ventricle.  The  course  of  the  blood  through  the  heart  cavities  and 
blood-vessels  has  already  been  described  (page  555). 

The  division  of  the  heart  into  four  cavities  is  indicated  by  grooves  upon  its  sur- 
face. The  groove  separating  the  auricles  from  the  ventricles  is  called  the  auriculo- 
ventricular  groove  (sulcus  coronarius).  It  is  deficient,  in  front,  where  it  is  crossed 
by  the  root  of  the  pulmonary  artery.  It  contains  the  trunks  of  the  nutrient  vessels 
of  the  heart.  The  auricular  portion  occupies  the  base  of  the  heart,  and  is  sub- 
divided into  two  cavities  by  a  median  septum.  The  two  ventricles  are  also  sepa- 
rated into  a  right  and  left  by  two  furrows,  the  interventricular  grooves  {sulci  longi- 
tudinales),  which  are  situated  one  on  the  anterior  (sulcus  longitudinalis  anterior), 
the  other  on  the  posterior  (sulcus  longitudinalis  posterior)  surface;  these  extend 
from  the  base  of  the  ventricular  portion  to  near  the  apex  of  the  organ ;  the  former 
being  situated  nearer  to  the  left  border  of  the  heart,  and  the  latter  to  the  right. 
It  follows,  therefore,  that  the  right  ventricle  forms  the  greater  portion  of  the 
anterior  surface  of  the  heart,  and  the  left  ventricle  more  of  its  posterior  surface. 
The  internal  surface  of  the  heart  is  lined  with  endocardium. 

The  auricular  portion  occupies  the  base  of  the  heart  and  is  subdivided  into  two 
cavities  or  auricles  (atria]  by  a  septum.  As  before  stated,  this  portion  of  the  heart 
corresponds  to  the  middle  segment  of  the  dorsal  spine.  Its  form  is  quadrilateral 
in  shape,  and  has  two  processes  extending  upward  from  its  two  upper  angles, 
called  the  auricular  appendices  (appendices  auriculce),  between  which  are  found 
the  aorta  and  the  pulmonary  artery.  The  greater  part  of  the  base  of  the  heart 
is  formed  by  the  left  auricle.  Its  boundaries  are,  above,  the  pulmonary  artery; 
below,  the  coronary  sinus;  on  the  left  it  is  bounded  by  the  left  superior  and 
inferior  pulmonary  veins,  while  on  the  right  side  it  is  limited  by  the  sulcus 
terminalis.  The  latter  corresponds  to  a  ridge  in  the  interior  of  the  auricle, 
called  the  crista  terminalis.  Running  vertically  on  this  surface,  just  to  the 
left  of  the  openings  of  the  two  venae  cavae,  is  the  interauricular  furrow,  which 
exactly  indicates  the  proportion  of  the  base  of  the  heart  formed  by  each 
auricle. 

Each  of  the  cavities  should  now  be  separately  examined. 

The  Right  Auricle^  (atrium  dextrum)  is  a  little  larger  than  the  left,  its  walls 
somewhat  thinner,  measuring  about  one  line.  It  consists  of  two  parts :  a  principal 
cavity,  the  sinus  venosus,  situated  posteriorly,  and  an  anterior,  smaller  portion, 
the  appendix  auriculae.  The  right  auricle  is  separated  from  the  left  auricle  by 
the  interauricular  septum  (septum  atriorum).  Part  of  tliis  septum  is  muscular; 
part  is  composed  of  connective  tissue. 

The  sinus  venosus  (sinu3  venarum)  is  the  large  quadrangular  cavity,  placed 
between  the  two  venae  cavse;  its  walls  are  extremely  thin;  it  is  connected  below 
with  the  right  ventricle,  and  internally  with  the  left  auricle,  being  free  in  the 
rest  of  its  extent.  It  is  derived  from  a  portion  of  the  sinus  reuniens  of  the 
fcetal  heart. 

The  right  auricular  appendix  (auricula  dextra) ,  so-called  from  its  fancied  resem- 
blance to  a  dog's  ear,  is  a  small  conical  muscular  pouch,  the  margins  of  which 
present  a  dentated  edge.  It  projects  from  the  sinus  forward  and  to  the  left 
side,  overlapping  the  root  of  the  aorta. 

'  L'appariel  sero-graisseux.     La  Presse  M6dicale,  December  7,  1904. 

2  In  the  new  nomenclature  the  auricle  is  called  the  atrium,  and  auricular  appendix  is  called  the  auricle. 


566 


THE   BLOOD -VASCULAR    SYSTEM 


To  examine  the  interior  of  the  right  auricle,  an  incision  should  be  made  along  its  right  border, 
from  the  entrance  of  the  superior  vena  cava  to  that  of  the  inferior.  A  second  cut  is  to  be  made 
from  the  centre  of  this  first  incision  to  the  tip  of  the  auricular  appendix,  and  the  flaps  raised. 

The  internal  surface  of  the  right  auricle  is  smooth,  except  in  the  appendix 
and  adjacent  part  of  the  anterior  wall  of  the  sinus  venosus,  where  the  muscular 
wall  is  thrown  into  parallel  ridges  resembling  the  teeth  of  a  comb  and  hence 
named  the  musculi  pectinati.    These  end  behind  on  a  vertical  smooth  ridge,  the 


Bristle  passed  through. 
Right  Auricula-  Ventricular  opening. 

Fig.  374. — The  right  auricle  and  ventricle  laid  open,  the  anterior  walls  of  both  being  removed. 

crista  terminalis  of  His,  the  position  of  which  is  indicated  on  the  surface  of  the 
distended  auricle  by  a  furrow,  the  sulcus  terminalis  of  His.  The  sulcus  terminalis 
passes  from  in  front  of  the  superior  vena  cava  to  the  left  of  the  inferior  vena  cava. 
It  represents  the  line  of  fusion  of  the  sinus  venosus  of  the  embryo  with  the  primi- 
tive auricle  proper. 

The  right  auricle  presents  the  following  parts  for  examination: 

Superior  cava. 
Inferior  cava. 
Openings  \  Coronary  sinus. 

Foramini  Thebesii. 
Auriculo-ventricular. 

Fossa  ovalis. 

Annulus  ovalis. 

Tuberculum  Loweri. 

Musculi  pectinati. 

The  superior  vena  cava  returns  the  blood  from  the  upper  half  of  the  body,  and 
opens  into  the  upper  and  back  part  of  the  auricle,  the  direction  of  its  orifice  being 
downward  and  forward.     The  superior  vena  cava  does  not  possess  valves. 

The  inferior  vena  cava,  larger  than  the  superior,  returns  the  blood  from  the 
lower  half  of  the  body,  and  opens  into  the  lowest  part  of  the  auricle  near  the 


Valves  I  Eustachian. 
C  Coronary. 


THE  HEART  567 

septum,  the  direction  of  its  orifice  being  upward  and  inward.  The  direction  of 
a  current  of  blood  through  the  superior  vena  cava  would  consequently  be  toward 
the  auriculo-ventricular  orifice,  whilst  the  direction  of  the  blood  through  the 
inferior  cava  would  be  toward  the  auricular  septum.  This  is  the  normal  direction 
of  the  two  currents  in  foetal  life.  The  inferior  vena  cava  does  not  possess  valves 
until  its  termination  at  the  right  auricle. 

The  coronary  sinus  (sinus  coronarius)  opens  into  the  auricle,  between  the  inferior 
vena  cava  and  the  auriculo-ventricular  opening.  It  returns  the  blood  from  the 
substance  of  the  heart,  and  is  protected  by  a  semicircular  fold  of  the  lining  mem- 
brane of  the  auricle,  the  coronary  valve  or  valve  of  Thebesius.  The  sinus,  before 
entering  the  auricle,  is  considerably  dilated — nearly  to  the  size  of  the  end  of  the 
little  finger.  Its  wall  is  partly  muscular,  and  at  its  junction  with  the  great  coronary 
vein  it  is  somewhat  constricted  and  is  furnished  with  a  valve  consisting  of  two 
unequal  segments. 

The  foramini  Thebesii  (foramina  venarum  minimarum)  are  numerous  minute 
fossse  or  apertures  on  various  parts  of  the  inner  surface  of  the  auricle.  Many  of 
these  foramina  have  at  their  points  the  minute  openings  of  small  veins  (vence 
TninimoB  cordis).  They  return  the  blood  directly  from  the  muscular  substance 
of  the  heart.  Some  of  these  foramina  are  minute  depressions  in  the  walls  of  the 
heart,  presenting  a  closed  extremity. 

The  right  auriculo-ventricular  opening  or  the  tricuspid  orifice  (ostium  venosum 
dextrum)  is  the  large  oval  aperture  of  communication  between  the  right  auricle 
and  the  ventricle,  to  be  presently  described. 

The  Eustachian  valve  (valvula  vencB  caves  inferioris  [Eu^tachii'\)  is  situated 
between  the  anterior  margin  of  the  inferior  vena  cava  and  the  auriculo-ventricular 
orifice.  It  is  semilunar  in  form,  its  convex  margin  being  attached  to  the  wall 
of  the  vein;  its  concave  margin,  which  is  free,  terminating  in  two  cornua,  of 
which  the  left  is  attached  to  the  anterior  edge  of  the  annulus  ovalis,  the  right 
being  lost  on  the  wall  of  the  auricle.  The  valve  is  formed  by  a  duplicature  of  the 
lining  membrane  of  the  auricle  and  contains  a  few  muscular  fibres. 

In  the  foetus  this  valve  is  of  large  size,  and  serves  to  direct  the  blood  from  the 
inferior  vena  cava,  through  the  foramen  ovale,  into  the  left  auricle. 

In  the  adidt  it  is  occasionally  large,  and  may  assist  in  preventing  the  reflux 
of  blood  into  the  inferior  vena  cava;  more  commonly  it  is  small,  and  its  free 
margin  presents  a  cribriform  or  filamentous  appearance;  occasionally  it  is  alto- 
gether wanting. 

The  coronary  valve  or  valve  of  Thebesius  (valvulce  sinv^  coronarii  [^ThebesHy) 
is  a  semicircular  fold  of  the  lining  membrane  of  the  auricle,  protecting 
the  orifice  of  the  coronary  sinus.  It  prevents  the  regurgitation  of  blood 
into  the  sinus  during  the  contraction  of  the  auricle.  This  valve  is  occasionally 
double. 

The  fossa  ovalis  is  an  oval  depression  corresponding  to  the  situation  of  the 
foramen  ovale  in  the  foetus.  It  is  situated  at  the  lower  part  of  the  septum  atriorum, 
above  and  to  the  left  of  the  orifice  of  the  inferior  vena  cava.  In  foetal  life  an 
opening,  the  foramen  ovale,  exists  at  this  point  between  the  two  auricles;  almost 
immediately  after  birth  the  valve-like  edge  is  pressed  down  by  the  increased 
pressure  in  the  left  auricle  and  by  the  tenth  day  it  passes  to  the  annulus  and 
closes  the  opening. 

The  annulus  ovalis  (limbus  josser  ovalis  [VieusseniiJ)  is  a  prominent  oval  margin 
which  surrounds  anteriorly  and  superiorly  the  fossa  ovalis.  It  is  most  distinct 
above  and  at  the  sides;  below,  it  is  deficient.  A  small  slit-like  valvular  opening 
is  occasionally  found,  at  the  upper  margin  of  the  fossa  ovalis,  which  leads 
upward  beneath  the  annulus  into  the  left  auricle,  and  is  the  remains  of  the 
aperture  between  the  two  auricles  in  the  foetus. 


568  THE  BLOOD -VASCULAR    SYSTEM 

The  tubercle  of  Lower  (tuherculum  intervenosum  {Loweri\)  is  a  small  projection 
on  the  interauricular  septum  between  the  fossa  ovalis  and  the  opening  of  the 
superior  vena  cava.  It  is  most  distinct  in  the  hearts  of  quadrupeds;  in  man  it 
is  scarcely  visible.  It  was  supposed  by  Lower  to  direct  the  blood  from  the 
superior  cava  toward  the  auriculo-ventricular  opening. 

The  Left  Auricle  {atrium  sinistrum)  is  rather  smaller  than  the  right;  its  walls 
are  thicker,  measuring  about  one  line  and  a  half;  and  it  consists,  like  the  right, 
of  two  parts,  a  principal  cavity,  or  sinus,  and  an  appendix  auriculae. 

The  sinus  is  cuboidal  in  form,  and  concealed  in  front  by  the  pulmonary  artery 
and  aorta;  internally,  it  is  separated  from  the  right  auricle  by  the  septum  auricu- 
larum  (septum  atriorum);  behind,  it  receives  on  each  side  two  pulmonary  veins, 
being  free  in  the  rest  of  its  extent. 

The  left  auricular  appendix  {auricula  sinistra)  is  somewhat  constricted  at  its 
junction  with  the  auricle;  it  is  longer,  narrower,  and  more  curved  than  that  of 
the  right  side,  and  its  margins  are  more  deeply  indented,  presenting  a  kind  of 
foliated  appearance.  Its  direction  is  forward  and  toward  the  right  side,  over- 
lapping the  root  of  the  pulmonary  artery. 

Within  the  auricle  the  following  parts  present  themselves  for  examination: 

The  openings  of  the  four  pulmonary  veins. 
Auriculo-ventricular  opening. 
Musculi  pectinati. 
Foramina  Thebesii. 

The  pulmonary  veins,  four  in  number,  open,  two  into  the  right  and  two  into 
the  left  side  of  the  auricle.  The  two  left  veins  frequently  terminate  by  a  common 
opening.    They  are  not  provided  with  valves. 

The  auriculo-ventricular  opening  or  mitral  orifice  {ostium  venosum  ventriculi 
sinistri)  is  the  large  oval  aperture  of  communication  between  the  left  auricle 
and  the  left  ventricle.  It  is  rather  smaller  than  the  corresponding  opening  on 
the  opposite  side  (see  note,  page  569). 

The  musculi  pectinati  are  fewer  in  number  and  smaller  than  on  the  right  side; 
they  are  confined  to  the  inner  surface  of  the  auricular  appendix. 

On  the  inner  surface  of  the  septum  atriorum  may  be  seen  a  lunated  impres- 
sion bounded  below  by  a  crescentic  ridge  the  concavity  of  which  is  turned  upward. 
The  depression  is  just  above  the  fossa  ovalis  in  the  right  auricle.  The  inner  sur- 
face of  the  auricle  shows  foramini  Thebesii  and  venae  minimis  cordis. 

To  examine  the  interior  of  the  left  ventricle,  make  an  incision  a  little  to  the  left  of  the  anterior 
interventricular  groove  from  the  base  to  the  apex  of  the  heart,  and  carry  it  up  from  thence, 
a  little  to  the  left  of  the  posterior  interventricular  groove,  nearly  as  far  as  the  auriculo-ventricular 
groove. 

The  ventricular  portion  of  the  heart  is  conical  in  shape  with  its  base  extending 
backward  and  upward  and  fitting  against  the  atrii  of  the  auricles.  Its  apex 
constitutes  the  apex  of  the  heart  {a'pex  cordis)  and  extends  to  the  fifth  intercostal 
space  three  and  a  quarter  inches  to  the  left  of  the  middle  line.  The  ventricles 
are  thick  and  muscular  and  have  an  antero -superior  surface  (fades  sternalis)  and 
a  postero-inferior  surface  (fades  diaphragmatic 2)  and  two  borders,  a  right  and  a 
left  border.  The  antero-superior  surface  is  composed  mainly  of  the  right  ven- 
tricle; coursing  on  this  surface,  nearer  the  left  border  than  the  right  from  the 
auriculo-ventricular  groove  to  the  apex,  is  the  anterior  interventricular  groove 
(sulcus  longitudinalis  anterior) .  The  inferior  surface  rests  on  the  diaphragm  and 
is  chiefly  made  by  the  left  ventricle ;  it  is  also  traversed  by  a  groove  called  the 
inferior  or  posterior  interventricular  groove  (sidcus  longitudinalis  posterior).  The 
two  grooves  meet  in  a  groove   (incisura  apicis  cordis)  at  the  right  side  of  the 


THE  HEART  569 

apex  of  the  heart.  Of  the  two  borders  of  the  ventricular  portion  the  right  is 
sharp  and  thin  (margo  acutus)  and  is  a  continuation  of  the  sulcus  terminahs  of 
the  base  of  the  heart.  It  extends  from  right  to  left.  The  left  border  is  thick 
and  rounded  {margo  ohtusus).  The  base  of  the  ventricles  is  perforated  by  four 
large  openings,  namely,  the  aorta,  the  pulmonary  artery,  the  right  and  left 
auriculo-ventricular  openings. 

The  Right  Ventricle  (ventriculus  dexter)  is  triangular  in  form,  and  extends 
from  the  right  auricle  to  near  the  apex  of  the  heart.  Its  antero-superior  surface 
is  rounded  and  convex,  and  forms  the  larger  part  of  the  front  of  the  heart.  Its 
inferior  surface  is  flattened,  rests  upon  the  Diaphragm,  and  forms  only  a  small 
part  of  the  back  of  the  heart.  Its  posterior  wall  is  formed  by  the  partition  between 
the  two  ventricles,  the  interventricular  septum  (septum  ventriculorum) ,  so  that  a 
transverse  section  of  the  cavity  presents  a  semilunar  outline.  The  surface  of 
the  septum  is  convex  and  bulges  into  the  cavity  of  the  right  ventricle.  The 
upper  and  inner  angle  of  the  ventricle  is  prolonged  into  a  conical  pouch,  the 
infundibulum  (conus  arteriosus),  from  which  the  pulmonary  artery  arises.  The 
balance  of  the  ventricle,  the  body,  is  the  portion  into  which  the  auriculo- 
ventricular  orifice  opens.  The  conus  arteriosus  is  marked  off  from  the  body  of 
the  ventricle  by  a  muscular  projection  (crista  swpraventricularis) .  The  walls  of 
the  right  ventricle  are  thinner  than  those  of  the  left,  the  proportion  between  them 
being  as  1  to  3.  The  wall  is  thickest  at  the  base,  and  gradually  becomes  thinner 
toward  the  apex. 

To  examine  the  interior  of  the  right  ventricle,  its  anterior  wall  should  be  turned  downward 
and  to  the  right  in  the  form  of  a  triangular  flap.  This  is  accomplished  by  making  two  incisions : 
(1)  from  the  pulmonary  artery  to  the  apex  of  the  ventricle  parallel  to,  but  a  little  to  the  right 
of,  the  anterior  interventricular  furrow;  (2)  another,  starting  from  the  upper  extremity  of  the 
first  and  carried  outward  parallel  to,  but  a  little  below,  the  auriculo-ventricular  furrow,  care 
being  taken  not  to  injure  the  auriculo-ventricular  valve. 

The  following  parts  present  themselves  for  examination: 

^       .        f  Auriculo-ventricular. 
P        ^    ^  Opening  of  the  pulmonary  artery. 

Valves       {Tricuspid. 
I  Semilunar. 

And  a  muscular  and  tendinous  apparatus  connected  with  the  tricuspid  valve: 

Columnse  carnese.  Chordae  tendinese. 

The  right  auriculo-ventriculax  opening  or  the  tricuspid  orifice  {ostium  venosum  ven- 
triculi  dextri)  is  the  large  oval  aperture  of  communication  between  the  auricle  and 
ventricle.  It  is  situated  at  the  base  of  the  ventricle,  near  the  right  border  of 
the  heart.  It  is  about  an  inch  and  a  half  in  diameter,^  oval  from  side  to  side, 
surrounded  by  a  fibrous  ring  and  covered  by  the  lining  membrane  of  the  heart; 
it  is  considerably  larger  than  the  corresponding  aperture  on  the  left  side,  being 
sufficient  to  admit  the  ends  of  four  fingers.  It  is  guarded  by  the  tricuspid 
valve. 

The  opening  of  the  pulmonary  artery  (ostium  arteriosum)  is  circular  in  form, 
and  is  situated  at  the  summit  of  the  conus  arteriosus,  close  to  the  septum  ven- 
triculorum.   It  is  placed  above  and  on  the  left  side  of  the  auriculo-ventricular 

'  In  the  Pathological  Transactions,  vol.  vi.  p.  119,  Dr.  Peacock  has  given  some  careful  researches  upon  the 
weight  and  tlimen.sions  of  the  heart  in  health  and  di.sease.  He  states,  as  a  result  of  his  investigations,  that 
in  the  healthy  athilt  heart  the  right  auriculo-ventricular  aperture  has  a  mean  circumference  of  54,4  lines,  or 
420/04  inches;  the  left  auriculo-ventricular  aperture  a  mean  circumference  of  44.3  lines,  or  3*;24  inches;  the  pulmonic 
orifice  of  40  lines,  or  3'-*/2i  inches;  and  the  aortic  orifice  of  35.5  lines,  or  3'--/o4  inches;  but  the  dimensions  of  the 
orifices  varied  greatly  in"different  cases,  the  right  auriculo-ventricular  aperture  having  a  range  of  from  40  to  50 
lines,  and  the  others  in  the  same  proportion. — Ed.  of  15th  English  edition. 


570  THE  BLOOD -VASCULAR   8Y8TEM 

opening,  upon  the  anterior  aspect  of  the  heart.  Its  orifice  is  guarded  by  the 
pulmonary  semilunar  valves. 

The  tricuspid  valve  (valvula  tricuspidalis)  consists  of  three  segments  or  cusps 
(cuspides)  of  a  triangular  or  trapezoidal  shape,  each  formed  by  a  duplicature  of 
the  lining  membrane  of  the  heart,  strengthened  by  a  layer  of  fibrous  tissue,  which 
contains,  according  to  Kiirschner  and  Senac,  muscular  fibres.  These  segments 
are  connected  by  their  bases  to  the  oval  fibrous  ring  surrounding  the  auriculo- 
ventricular  orifice  (annulus  fibrosus  dexter),  and  by  their  sides  with  one  another, 
so  as  to  form  a  continuous  annular  membrane,  which  is  attached  round  the 
margin  of  the  auriculo-ventricular  opening,  their  free  margins  and  ventricular 
surfaces  affording  attachment  to  a  number  of  delicate  tendinous  cords,  the 
chordae  tendineae.  The  largest  and  most  movable  segment  is  placed  toward 
the  left  side  of  the  auriculo-ventricular  opening,  and  is  interposed  between  that 
opening  and  the  infundibulum;  hence  it  is  called  the  left  or  infundibulax  cusp 
(cuspis  medialis).  Another  segment  corresponds  to  the  right  part  of  the  front 
of  the  ventricle,  the  right  or  marginal  cusp  {cuspis  anterior) ,  and  a  third  to  its 
posterior  wall,  the  posterior  or  septal  cusp  (cuspis  posterior) .  The  central  part  of 
each  segment  is  thick  and  strong:  the  lateral  margins  are  thin  and  translucent. 
The  chordse  tendineae  are  connected  with  the  adjacent  margins  of  the  principal 
segments  of  the  valve,  and  are  further  attached  to  each  segment  in  the  following 
manner:  1.  Three  or  four  reach  the  attached  margin  of  each  segment,  where 
they  are  continuous  with  the  auriculo-ventricular  tendinous  ring.  2.  Others,  four 
to  six  in  number,  are  attached  to  the  central  thickened  part  of  each  segment.  3. 
The  most  numerous  and  finest  are  connected  with  the  marginal  portion  of  each 
segment. 

The  columnse  cameae  (trabeculoe  earners)  are  the  rounded  muscular  columns 
which  project  from  nearly  the  whole  of  the  inner  surface  of  the  ventricle,  except- 
ing near  the  opening  of  the  pulmonary  artery,  where  the  wall  is  smooth.  They 
may  be  classified,  according  to  their  mode  of  connection  with  the  ventricle,  into 
three  sets.  The  first  set  merely  forms  prominent  ridges  on  the  inner  surface  of 
the  ventricle,  being  attached  by  their  entire  length  on  one  side,  as  well  as  by 
their  extremities.  The  second  set  are  attached  by  their  two  extremities,  but  are 
free  in  the  rest  of  their  extent;  while  the  third  set  (musculi  papillares)  are  attached 
by  one  extremity  to  the  wall  of  the  heart,  the  opposite  extremity  giving  attach- 
ment to  the  chordae  tendineae.  There  are  two  papillary  muscles,  the  anterior  and 
the  posterior:  of  these,  the  anterior  is  the  larger;  its  chordse  tendinse  are  connected 
with  the  right  and  left  segments  of  the  tricuspid  valve.  The  posterior  is  not 
always  single,  but  sometimes  consists  of  two  or  three  muscular  columns;  its 
chordae  tendineae  are  connected  with  the  posterior  and  the  right  segments  of  the 
tricuspid  valve.  In  addition  to  these,  some  few  chordae  may  be  seen  springing 
directly  from  the  ventricular  septum,  or  from  small  eminences  on  it,  and  passing 
to  the  left  and  posterior  segments.  A  fleshy  band,  well  marked  in  the  ox  and 
some  other  animals,  is  frequently  seen  passing  from  the  base  of  the  anterior 
papillary  muscle  to  the  interventricular  septum.  From  its  attachments  it  may 
assist  in  preventing  overdistention  of  the  auricle,  and  so  has  been  named  the 
moderator  band. 

The  right  auriculo-ventricular  orifice  allows  the  blood  to  pass  freely  from  the 
right  auricle  into  the  right  ventricle,  and  it  will  be  noted  that  the  surface  of  the 
tricuspid  valve  next  the  blood-current  is  quite  smooth.  When  the  right  ventricle 
contracts  to  force  the  blood  into  the  pulmonary  artery,  the  segments  of  the  tri- 
cuspid valve  come  together  and  close  the  auriculo-ventricular  opening,  and  so 
prevent  the  blood  from  passing  back  into  the  auricle.  The  papillary  muscles 
and  chordae  tendineae  moor  the  segments  of  the  valve  and  prevent  their  being 
forced  through  into  the  auricle  by  the  weight  of  blood  behind  them. 


THE  HEART  57I 

The  semilunar  valves  (valvulcB  semilunares  a.  pulmonalis) ,  three  in  number,* 
guard  the  orifice  of  the  pulmonary  artery.  They  consist  of  three  semicircular 
folds :  two  of  which  are  anterior  and  one  of  which  is  posterior.  They  are  formed 
by  duplicatures  of  the  lining  membrane  of  the  ventricle,  strengthened  by  fibrous 
tissue.  They  are  attached,  by  their  convex  margins,  to  the  wall  of  the  artery,  at  its 
junction  with  the  ventricle,  the  straight  border  being  free,  and  directed  upward  in 
the  lumen  of  the  vessel.  The  free  margin  of  each  is  somewhat  thicker  than  the  rest 
of  the  valve,  is  strengthened  by  a  bundle  of  tendinous  fibres,  and  presents,  at  its 
middle,  a  small  projecting  thickened  nodule,  consisting  of  bundles  of  interlacing 
connective-tissue  fibres  with  branched  connective-tissue  cells  and  some  few  elastic 
fibres.  Such  a  nodule  is  called  the  corpus  Arantii  or  body  cf  Arangi  {nodulus  valvules 
semilunaris  [Arantii^) .  From  this  nodule  tendinous  fibres  radiate  through  the  valve 
to  its  attached  margin,  and  these  fibres  form  a  constituent  part  of  its  substance 
throughout  its  whole  extent,  excepting  two  narrow  lunated  portions,  the  lunulas 
(lunulw  valvularum  semilunarium) ,  placed  one  on  each  side  of  the  nodule  imme- 
diately adjoining  the  free  margin;  here  the  valve  is  thin,' and  formed  merely  by  the 
Uning  membrane.  During  the  passage  of  the  blood  along  the  pulmonary  artery 
these  valves  are  opened,  and  the  course  of  the  blood  along  the  tube  is  uninter- 
rupted ;  but  during  the  ventricular  diastole,  when  the  current  of  blood  along  the 
pulmonary  artery  is  checked  and  partly  thrown  back  by  its  elastic  walls,  these 
valves  become  immediately  expanded,  and  effectually  close  the  entrance  of  the 
tube.  When  the  valves  are  closed,  the  lunated  portions  of  each  are  brought  into 
contact  with  one  another  by  their  opposed  surfaces,  the  three  corpora  Arantii  fill- 
ing up  the  small  triangular  space  that  would  be  otherwise  left  by  the  approxima- 
tion of  the  three  semilunar  valves. 

Between  the  semilunar  valves  and  the  commencement  of  the  pulmonary  artery 
are  three  pouches  or  dilatations,  one  behind  each  valve.  These  are  the  pulmonary 
sinuses  of  Valsalva.  Similar  sinuses  exist  between  the  semilunar  valves  and  the 
commencement  of  the  aorta;  they  are  larger  than  the  pulmonary  sinuses.  The 
blood,  in  its  regurgitation  toward  the  heart,  finds  its  way  into  these  sinuses,  and 
so  shuts  down  the  valve-flaps. 

In  order  to  examine  the  interior  of  the  left  auricle,  make  an  incision  on  the  posterior  surface 
of  the  auricle  from  the  pulmonary  veins  on  one  side  to  those  on  the  other,  the  incision  being 
carried  a  little  way  into  the  vessels.  Make  another  incision  from  the  middle  of  the  horizontal 
one  to  the  appendix. 

The  Left  Ventricle  (ventriculus  sinister)  is  longer  and  more  conical  in  shape 
than  the  right  ventricle,  and  on  transverse  section  its  cavity  presents  an  oval  or 
nearly  circular  outline.  It  forms  a  small  part  of  the  anterior  surface  of  the  heart 
and  a  considerable  part  of  its  posterior  surface.  It  also  forms  the  apex  of  the 
heart  by  its  projection  beyond  the  right  ventricle.  Its  walls  are  much  thicker 
than  those  of  the  right  side,  the  proportion  being  as  3  to  1 .  They  are  thickest  oppo- 
site the  widest  part  of  the  ventricle,  becoming  gradually  thinner  toward  the  base, 
and  also  toward  the  apex,  which  is  the  thinnest  part. 

The  following  parts  present  themselves  for  examination : 


J  Auriculo-ventricular.  ,,.  ,        ( Mitral. 

I  Aortic.  ^^^^^M  Semilunar. 

Chordae  tendinese.  Columnse  carnese. 


The  left  auriculo-ventricular  opening  or  the  mitral  orifice  (ostium  venosum  ven- 
triculi  sinistri)  is  placed  below  and  to  the  left  of  the  aortic  orifice.     It  is  a  little 

'  Thepulmonary  semilunar  valves  have  been  found  to  be  two  in  number  instead  of  three  (Dr.  Hand,  of  St. 
Paul,  Mjnn.,  in  North  Western  Med.  and  Surg.  Journ.,  July,  1873),  and  the  same  variety  is  more  frequently 
noticed  in  the  aortic  semilunar  valves. — Ed.  of  15th  English  edition. 


572 


THE   BLOOD -VASCULAB   SYSTEM 


smaller  than  the  corresponding  aperture  of  the  opposite  side,  admitting  only  two 
fingers;  but,  like  it,  is  broader  in  the  transverse  than  in  the  antero-posterior 
diameter.  Its  right,  posterior,  and  left  sides  are  surrounded  by  a  dense  horseshoe- 
shaped  fibrous  ring  (annulus  fibrosus  sinister) .  The  orifice  is  guarded  by  the 
mitral  valves,  which  are  covered  with  endocardium. 

The  aortic  opening  (ostium  arteriosum)  is  a  circular  aperture,  in  front  and  to 
the  right  side  of  the  auriculo-ventricular  opening,  from  which  it  is  separated  by 
one  of  the  segments  of  the  mitral  valve.  Its  orifice  is  guarded  by  the  semilunar 
valves.  The  portion  of  the  ventricle  immediately  below  the  aortic  orifice  is  often 
termed  the  aortic  vestibule  of  Sibson.  It  possesses  fibrous  instead  of  muscular 
walls,  and  so  does  not  collapse  during  the  ventricular  diastole ;  it  thus  gives  space 
for  the  segments  of  the  aortic  valve  during  its  closure. 


Bristle  passed  through  left 
auriculo-ventricular  opening. 


Passed  through  aortic  opening. 


Fig.  375. — The  left  auricle  and  ventricle  laid  open,  the  posterior  walls  of  both  being  removed. 

The  mitral  or  bicuspid  valve  (valvula  bicuspidalis)  is  attached  to  the  circumfer- 
ence of  the  auriculo-ventricular  orifice  in  the  same  way  that  the  tricuspid  valve  is 
on  the  opposite  side.  It  is  formed  by  a  duplicature  of  the  lining  membrane, 
strengthened  by  fibrous  tissue,  and  contains  a  few  muscular  fibres.  It  is  larger 
in  size,  thicker,  and  altogether  stronger  than  the  tricuspid,  and  consists  of  two 
segments  of  unequal  size.  The  larger  segment,  the  anterior  or  aortic  cusp  (cuspis 
anterior) ,  is  placed  in  front  and  to  the  right  between  the  auriculo-ventricular  and 
aortic  orifices,  the  smaller,  the  posterior  or  marginal  cusp  (cuspis  posterior),  is 
placed  to  the  left  and  behind  the  opening,  close  to  the  wall  of  the  ventricle.  Two 
smaller  segments  are  usually  found  at  the  angles  of  junction  of  the  larger.  The 
mitral  valve-flaps  are  furnished  with  chordae  tendinese,  the  mode  of  attachment 
of  which  is  precisely  similar  to  those  on  the  right  side;  but  they  are  thicker, 
stronger,  and  less  numerous. 

The  aortic  semilunar  valves  (valvules  semilunares  aortce)  surround  the  orifice  of 
the  aorta;  one  is   posterior  (valvula  semilunaris   posterior)',  one   right  (valvula 


THE   HEART 


573 


semilunaris  dextra) ,  and  one  left  {valvula  semilunaris  sinistra) :  they  are  similar  in 
structure  and  in  their  mode  of  attachment  to  those  of  the  pulmonary  artery.  They 
are,  however,  larger,  thicker,  and  stronger  than  those  of  the  right  side;  the  lunulas 
are  more  distinct  and  the  corpora  Arantii  larger  and  more  prominent.  Opposite 
each  segment  the  wall  of  the  aorta  presents  a  slight  dilatation  or  bulging,  the 
sinus  of  Valsalva. 

The  columnae  cameae  admit  of  a  subdivision  into  three  sets,  like  those  upon 
the  right  side;  but  they  are  smaller,  more  numerous,  and  present  a  dense  inter- 
lacement, especially  at  the  apex,  and  upon  the  posterior  wall.  Those  attached  by 
one  extremity  only,  the  musculi  papillares,  are  two  in  number,  being  connected 


kilmonary 
artery. 


Fig.  376. — Section  of  the  heart,  showing  the  interventricular  septum. 

one  to  the  anterior,  the  other  to  the  posterior  wall;   they  are  of  large  size,  and 
terminate  by  free  rounded  extremities,  from  which  the  chordae  tendineae  arise. 

The  septum  between  the  two  ventricles  {senium  ventriculorum)  is  thick  and 
muscular,  especially  below  (Fig.  376).  At  its  upper  part  it  suddenly  tapers  oflF, 
becomes  destitute  of  muscular  fibres,  and  consists  only  of  fibrous  tissue,  covered 
by  two  layers  of  endocardium;  and  on  the  right  side  also  covered,  during  dias- 
tole, by  one  of  the  flaps  of  the  tricuspid  valve.  This  upper  portion  is  termed 
the  undefended  or  membranous  part  of  the  septum  (septum  memhranaceum  ven- 
triculorum), and  is  continued  upward  and  forms  the  septum  between  the 
aortic  vestibule  and  the  right  auricle.  It  is  derived  from  the  lower  part  of 
the  aortic  septum  of  the  foetus,  and  an  abnormal  communication  may  exist  at 
this  part,  owing  to  defective  development  of  this  septum. 


574 


THE   BLOOD -VASCULAR   SYSTEM 


Structure  of  the  Heart. — The  heart  is  a  hollow  muscular  organ  and  its  walls 
are  divisible  into  three  layers :  the  endocardium,  myocardium,  and  visceral  layer  of 
the  pericardium  (page  560). 

The  Endocardium  is  the  lining  membrane  of  the  heart.  It  is  composed  of 
endothelial  cells  resting  upon  a  connective-tissue  membrane  which  contains 
unstriated  muscle  cells  and  elastic  tissue.  This  connective-tissue  membrane  of 
the  endocardium  is  attached  to  the  myocardium  by  loose  elastic  tissue.  The  endo- 
thelial layer  of  the  endocardium  is  continuous  with  the  endothelial  coat  of  the 
blood-vessels.  The  endocardium  is  more  opaque  on  the  left  than  on  the  right 
side  of  the  heart,  thicker  in  the  auricles  than  in  the  ventricles,  and  thickest  in 
the  left  auricle.  It  is  thin  on  the  musculi  pectinati  and  on  the  columnse  carneee, 
but  thicker  on  the  smooth  parts  of  the  auricular  and  ventricular  walls  and  on  the 
tips  of  the  musculi  papillares. 

The  Fibrous  Rings  {annuli  fibrosi)  surround  the  auriculo-ventricular  and  arterial 
orifices ;  they  are  stronger  upon  the  left  than  on  the  right  side  of  the  heart.  The 
auriculo-ventricular  rings  serve  for  the  attachment  of  the  muscular  fibres  of  the 
auricles  and  ventricles,  and  also  for  the  mitral  and  tricuspid  valves;  the  ring  on  the 


LEFT  AURICULO- 
VENTRICULAR    ORIFICE 


Fig.  377. — Fibrous  zones  at  the  base  of  the  ventricles.     (Poirier  and  Charpy.) 

left  side  is  closely  connected  by  its  right  margin  with  the  aortic  arterial  ring.  Be- 
tween these  and  the  right  auriculo-ventricular  ring  is  a  mass  of  fibrous  tissue,  and  in 
some  of  the  larger  animals,  as  the  ox  and  elephant,  a  nodule  of  bone,  the  os  cordis. 

The  fibrous  rings  surrounding  the  arterial  orifices  serve  for  the  attachment  of 
the  great  vessels  and  semilunar  valves.  Each  ring  receives,  by  its  ventricular 
margin,  the  attachment  of  the  muscular  fibres  of  the  ventricles;  its  opposite  margin 
presents  three  deep  semicircular  notches,  within  which  the  middle  coat  of  the 
artery  (which  presents  three  convex  semicircular  segments)  is  firmly  fixed,  the 
attachment  of  the  artery  to  its  fibrous  ring  being  strengthened  by  the  thin  cellular 
coat  and  serous  membrane  externally  and  by  the  endocardium  within.  It  is 
opposite  the  margins  of  these  semicircular  notches,  in  the  arterial  rings,  that  the 
endocardium  by  its  reduplication  forms  the  semilunar  valves,  the  fibrous  structure 
of  the  ring  being  continued  into  each  of  the  segments  of  the  valve  at  this  part. 
The  middle  coat  of  the  artery  in  this  situation  is  thin,  and  the  sides  of  the  vessel  are 
dilated  to  form  the  sinuses  of  Valsalva. 

The  Myocardium  is  composed  of  muscle  fibres  which  differ  from  ordinary  striated 
muscle  fibres,  and  are  called  cardiac  fibres.  Between  individual  fibres  and  be- 
tween bundles  of  fibres  is  connective  tissue  carrying  capillaries. 


THE   HEART 


575 


The  Muscular  Structure  of  the  heart  consists  of  bands  of  fibres  which  present 
an  exceedingly  intricate  interlacement.  They  are  of  a  deep  red  color  and  marked 
with  transverse  striae. 

The  muscular  fibres  of  the  heart  admit  of  a  subdivision  into  two  groups,  those 
of  the  auricles  and  those  of  the  ventricles,  which  are  quite  independent  of  one 
another. 

Fibres  of  the  Auricles  (Fig.  378). — These  are  disposed  in  two  layers — a 
superficial  layer  common  to  both  cavities,  and  a  deep  layer  proper  to  each.  The 
superficial  fibres  are  more  distinct  on  the  anterior  surface  of  the  auricles,  across 
the  bases  of  which  they  run  in  a  transverse  direction,  forming  a  thin  but  incomplete 
layer.  Some  of  these  fibres  pass  into  the  septum  atriorum.  The  internal  or  deep 
fibres  proper  to  each  auricle  consist  of  two  sets,  looped  and  annular  fibres.  The 
looped  fibres  pass  upward  over  each  auricle,  being  attached  by  two  extremities 
to  the  corresponding  auriculo-ventricular  rings  in  front  and  behind.  The  annular 
fibres  surround  the  whole  extent  of  the  auricular  appendices,  and  are  continued 
upon  the  walls  of  the  vente  cava?  and  coronary  sinus  on  the  right  side,  and  upon 
the  pulmonary  veins  on  the  left  side,  at  their  connection  with  the  heart.  In  the 
appendices  they  interlace  with  the  longitudinal  fibres. 


Fig.  378. — The  arrangement  of  the  muscles  of  the  auricles.     (Poirier  and  Charpy.) 

Fibres  of  the  Ventricles. — These  are  arranged  in  an  exceedingly  complex 
manner,  and  the  accounts  given  by  various  anatomists  differ  considerably.  This 
is  probably  due  partly  to  the  fact  that  the  various  layers  of  muscular  fibres  of 
which  the  heart  is  said  to  be  composed  are  not  independent,  but  their  fibres  are 
interlaced  to  a  considerable  extent,  and  therefore  any  separation  into  layers  must 
be  to  a  great  extent  artificial;  and  also  partly  to  the  fact,  pointed  out  by  Henle, 
that  there  are  varieties  in  the  arrangement  due  to  individual  differences.  If  the 
epicardium  and  the  subjacent  fat  are  removed  from  a  heart  which  has  been  sub- 
jected to  prolonged  boiling,  so  as  to  dissolve  the  connective  tissues,  the  superficial 
fibres  of  the  ventricles  will  be  exposed.  They  will  be  seen  to  commence  at  the  base 
of  the  heart,  where  they  are  attached  to  the  tendinous  rings  around  the  orifices, 
and  to  pass  obliquely  downward  toward  the  apex,  with  a  direction  from  right  to 
left.  At  the  apex  the  fibres  turn  suddenly  inward  into  the  interior  of  the  ventricle, 
forming  what  is  called  the  vortex  (Fig.  379).  On  the  back  of  the  heart  it  will  be 
seen  that  the  fibres  pass  continuously  from  one  ventricle  to  the  other  over  the  inter- 
ventricular groove;  and  the  same  thing  will  be  noticed  on  the  front  of  the  heart  at 
the  upper  and  lower  end  of  the  anterior  interventricular  groove,  but  in  the  middle 
portion  of  this  groove  the  fibres  passing  from  one  ventricle  to  the  other  are  inter- 


576 


THE   BLOOD -VASCULAR   SYSTEM 


rupted  by  fibres  emerging  from  the  septum  along  the  groove;  many  of  the  super- 
ficial fibres  pass  in  also  at  this  groove  to  the  septum.    The  vortex  is  produced, 

as  stated  above,  by  the  sudden  turning 
inward  of  the  superficial  fibres  in  a 
peculiar  spiral  manner  into  the  deepest 
portion  of  the  wall  of  the  ventricle. 
Those  fibres  which  descended  on  the 
posterior  surface  of  the  heart  enter  the 
left  ventricle  at  the  vortex,  and,  ascend- 
ing, form  the  posterior  part  of  the  inner 
layer  of  muscular  fibres  lining  this 
cavity  and  the  right  (posterior)  mus- 
culus  papillaris;  those  fibres  which 
descend  on  the  front  of  the  heart  to 
reach  the  apex  also  pass,  at  the  vortex, 
into  the  interior  of  the  ventricle,  where 
they  form  the  remainder  of  the  inner- 
most layer  of  the  ventricle  and  the  left 
(anterior)  musculus  papillaris.  The 
fibres  forming  the  inner  layer  of  the  wall  of  the  ventricle  ascend  to  be  attached 
to  the  fibrous  rings  around  the  orifices. 

By  dissection  these  superficial  fibres  may  be  removed  as  a  thin  stratum,  and  it 
will  then  be  found  that  the  ventricles  are  made  up  of  oblique  fibres  (Fig.  380),  super- 


FiG.  379. — The  muscular  arrangement  of  the  apex 
of  the  heart.      (Poirier  and  Charpy.) 


Fig.  380. — The  muscular  arrangement  of  the  ventricle.      (Poirier  and  Charpy.) 

imposed  in  layers  one  on  the  top  of  another,  and  assuming  gradually  a  less  pblique 
direction  as  they  pass  to  the  middle  of  the  thickness  of  the  ventricular  wall,  so  that 


THE    HEART  577 

in  the  centre  of  the  wall  the  fibres  are  transverse.  Internal  to  this  central  transverse 
layer  the  fibres  become  oblique  again,  but  in  the  opposite  direction  to  the  external 
ones.  This  division  into  distinct  layers  is,  however,  to  a  great  extent  artificial,  as  the 
fibres  pass  across  from  one  layer  to  another,  and  have  therefore  to  be  divided  in 
the  dissection,  and  the  change  in  the  direction  of  the  fibres  is  very  gradual.  These 
oblique  fibres  commence  above  at  the  fibrous  rings  at  the  base  of  the  heart,  and, 
descending  toward  the  apex,  they  enter  the  septum  near  its  lower  end.  In  the 
septum  the  fibres  which  form  the  left  ventricle  may  be  traced  in  three  directions: 
1.  Some  pass  upward  to  be  attached  to  the  central  mass  of  fibrous  tissue.  2. 
Others  pass  through  the  septum  to  become  continuous  with  the  fibres  of  the  right 
ventricle.  3.  The  remainder  pass  through  the  septum  to  encircle  the  ventricle 
as  annular  fibres.  Of  the  fibres  of  the  right  ventricle,  some  on  entering  the  septum 
pass  upward  to  be  attached  to  the  central  mass  of  fibrous  tissue;  some,  entering 
the  septum  from  behind,  pass  forward  to  become  continuous  with  the  fibres  on 
the  anterior  surface  of  the  left  ventricle;  and  others,  entering  in  front,  pass  back- 
ward to  join  the  fibres  on  the  posterior  wall  of  the  left  ventricle.  The  septum 
therefore  consists  of  three  varieties  of  fibres — viz.,  annular  fibres,  special  to  the  left 
ventricle;  ascending  fibres,  derived  from  both  ventricles  and  ascending  through 
the  septum  to  the  central  fibro-cartilage;  and  decussating  fibres,  derived  from  the 
anterior  wall  of  one  ventricle  and  passing  to  the  posterior  wall  of  the  other  ven- 
tricle, or  from  the  posterior  wall  of  the  right  ventricle  and  passing  to  the  anterior 
wall  of  the  left.  In  addition  to  these  fibres  there  are  a  considerable  number 
which  appear  to  encircle  both  ventricles  and  which  pass  across  the  septum  without 
turning  into  it. 

Vessels  and  Nerves. — The  arteries  supplying  the  heart  are  the  right  and  left 
coronary  from  the  aorta.  Branches  from  the  coronary  vessels  supply  the  mus- 
cular structure,  the  subendocardial,  and  the  subepicardial  tissue.  There  are  no 
vessels  in  the  endocardium.  The  valves  contain  no  vessels  unless  they  contain 
muscle,  in  which  case  minute  vessels  enter  them.  There  are  numerous  capillary 
networks  about  the  muscular  fibres. 

The  veins  accompany  the  arteries.  They  are:  the  anterior  or  great,  the  posterior, 
the  left,  and  the  anterior  cardiac  veins,  the  right  or  small,  and  the  left  or  great, 
coronary  sinuses.  The  coronary  sinus  receives  most  of  the  veins  of  the  heart  and 
empties  into  the  right  auricle.  Some  few  small  veins  open  directly  into  the  right 
and  left  auricles  and  into  the  ventricles.  They  are  the  venae  minimse  cordis.  The 
oblique  vein  of  the  left  auricle  is  known  as  the  oblique  vein  of  Marshall. 

The  lymphatics  are  arranged  in  two  networks:  one  in  the  muscle  beneath  the 
endocardium,  another  in  the  muscle  beneath  the  epicardium.  The  deep  empties 
into  the  superficial  network,  the  anterior  collecting  trunks  from  the  subepicardial 
network  pass  to  the  tracheo-bronchial  glands.  The  posterior  collecting  trunk 
terminates  in  the  same  group  of  glands." 

The  nerves  are  derived  from  the  superficial  and  deep  cardiac  plexuses,  and  from 
these  plexuses  obtain  fibres  of  the  pneumogastric,  spinal  accessory,  and  sympa- 
thetic. The  superficial  cardiac  plexus  lies  under  the  arch  of  the  aorta.  The 
deep  cardiac  plexus  is  in  front  of  the  tracheal  bifurcation.  The  nerves  from  the 
plexuses  are  freely  distributed  both  on  the  surface  and  in  the  substance  of  the 
heart,  the  separate  filaments  being  furnished  with  small  ganglia. 

Surface  Form. — In  order  to  show  the  extent  of  the  heart  in  relation  to  the  front  of  the  chest, 
draw  a  line  from  the  lower  border  of  the  second  left  costal  cartilage,  one  inch  from  the  sternum, 
to  the  upper  border  of  the  third  right  costal  cartilage,  half  an  inch  from  the  sternum.  This 
represents  the  base-line  or  upper  limit  of  the  organ.  Take  a  point  an  inch  and  a  half  below 
and  three-quarters  of  an  inch  internal  to  the  left  nipple — that  is,  about  three  and  a  half  inches 
Id  the  left  of  the  median  line  of  the  body.    This  represents  the  apex  of  the  heart.    Draw  a  line 

1  The  Lymphatics.     By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 

37 


578  THE  BLOOD -VASCULAR   SYSTEM 

from  this  apex-point,  with  a  slight  convexity  downward,  to  the  junction  of  the  seventh  right 
costal  cartilage  to  the  sternum.  This  represents  the  lower  limit  of  the  heart.  Join  the  right 
extremity  of  the  first  line — that  is,  the  base-line — ^with  the  right  extremity  of  this  line — that  is, 
to  the  seventh  right  chondro-sternal  joint — with  a  slight  curve  outward,  so  that  it  projects  about 
an  inch  and  a  half  from  the  middle  line  of  the  sternum.  Lastly,  join  the  left  extremity  of  the 
base-line  and  the  apex-point  by  a  line  curved  slightly  to  the  left. 

The  position  of  the  various  orifices  is  as  follows — viz.,  the  pulmonary  orifice  is  situated  in 
the  upper  angle  formed  by  the  articulation  of  the  third  left  costal  cartilage  with  the  sternum; 
the  aortic  orifice  is  a  little  below  and  internal  to  this,  behind  the  left  border  of  the  sternum, 
close  to  the  articulation  of  the  third  left  costal  cartilage  to  this  bone.  The  left  auriculo-ventric- 
ular  opening  is  behind  the  sternum,  rather  to  the  left  of  the  median  line,  and  opposite  the  fourth 
costal  cartilages.  The  right  auriculo-ventricular  opening  is  a  little  lower,  opposite  the  fourth 
interspace  and  in  the  middle  line  of  the  body  (Fig.  366). 

A  portion  of  the  area  of  the  heart  thus  mapped  out  is  uncovered  by  lung,  and  therefore 
gives  a  dull  note  on  percussion;  the  remainder,  being  overlapped  by  the  lung,  gives  a  more  or 
less  resonant  note.  The  former  is  known  as  the  area  of  superficial  cardiac  dulness;  the  latter 
as  the  area  of  deep  cardiac  dulness.  The  area  of  superficial  cardiac  dulness  is  included  between 
a  line  drawn  from  the  centre  of  the  sternum,  on  a  level  with  the  fourth  costal  cartilages,  to  the 
apex  of  the  heart  and  a  line  drawn  from  the  same  point  down  the  lower  third  of  the  middle  line 
of  the  sternum.  Below,  this  area  merges  into  the  dulness  which  corresponds  to  the  liver.  Dr. 
McClellan  states  that  the  area  of  superficial  cardiac  dulness  may  be  mapped  out  "  by  draw- 
ing a  line  from  the  middle  of  the  sternum  opposite  the  fourth  left  costal  cartilage  to  the  point 
of  junction  of  the  fiifth  rib  and  its  cartilage,  and  from  this  point  horizontally  back  to  the  mid- 
sternal  line." 

Surgical  Anatomy. — Wounds  of  the  heart  are  often  immediately  fatal,  but  not  necessarily 
so.  They  may  be  non-penetrating,  when  death  may  occur  from  hemorrhage,  if  one  of  the  coro- 
nary vessels  has  been  wounded,  or  subsequently  from  pericarditis;  or,  on  the  other  hand,  the 
patient  may  recover.  Even  a  penetrating  wound  is  not  necessarily  fatal,  if  the  wound  is  a  small 
one.  An  attempt  should  be  made  to  save  the  patient  by  means  of  a  surgical  operation.  A 
trap-door  flap  comprising  the  whole  thickness  of  the  thoracic  wall  should  be  made.  The  hinges 
of  the  trap-door  are  the  rib  cartilages.  The  pericardium  is  exposed  and  opened  freely,  clots  are 
removed,  the  wound  in  the  heart  is  sought  for,  and  when  discovered  is  sutured.  In  a  pene- 
trating wound  the  sutures  include  the  whole  thickness  of  the  heart,  except  the  endocardium. 
Interrupted  sutures  should  be  used,  and  each  one  had  better  be  tied  during  diastole.  A  number 
of  successful  operations  of  this  character  have  been  performed. 

Peculiarities  in  the  Vascular  System  of  the  Foetus  (Fig.  382). 

The  chief  peculiarities  in  the  heart  of  the  foetus  are  the  direct  communication 
between  the  two  auricles  through  the  foramen  ovale,  and  the  large  size  of  the 
Eustachian  valve.  There  are  also  several  minor  peculiarities.  Thus,  the  position 
of  the  heart  is  vertical  until  the  fourth  month,  when  it  commences  to  assume  an 
oblique  direction.  Its  size  is  also  very  considerable  as  compared  with  the  body, 
the  proportion  at  the  second  month  being  1  to  50;  at  birth  it  is  as  1  to  120;  whilst 
in  the  adult  the  average  is  about  1  to  160.  At  an  early  period  of  foetal  life  the 
auricular  portion  of  the  heart  is  larger  than  the  ventricular,  the  right  auricle  being 
more  capacious  than  the  left;  but  toward  birth  the  ventricular  portion  becomes 
the  larger.  The  thickness  of  both  ventricles  is  at  first  about  equal,  but  toward 
birth  the  left  becomes  much  the  thicker  of  the  two. 

The  foramen  ovale  (Fig.  381)  is  situated  at  the  lower  and  back  part  of  the  septum 
atriorum,  forming  a  communication  between  the  auricles.  It  remains  as  a  free 
oval  opening  until  the  middle  period  of  foetal  life.  About  this  period  a  fold 
grows  up  from  the  posterior  wall  of  the  auricle  to  the  left  of  the  foramen  ovale,  and 
advances  over  the  opening  so  as  to  form  a  sort  of  valve,  which  allows  the  blood 
to  pass  only  from  the  right  to  the  left  auricle,  and  not  in  the  opposite  direction. 

The  Eustachian  valve  (Fig.  381)  is  directed  upward  on  the  left  side  of  the 
opening  of  the  inferior  vena  cava,  and  serves  to  direct  the  blood  from  this  vessel 
through  the  foramen  ovale  into  the  left  auricle. 

The  peculiarities  in  the  arterial  system  of  the  foetus  are  the  communication 
between  the  pulmonary  artery  and  the  descending  aorta  by  means  of  the  ductus 


THE   HEART 


579 


arteriosus,  and  the  communication  between  the  internal  iliac  arteries  and  the 
placenta  by  means  of  the  umbilical  arteries. 

The  Ductus  Arteriosus  (Fig.  382) . — The  ductus  arteriosus  is  a  short  tube,  about 
half  an  inch  in  length  at  birth,  and  of  the  diameter  of  a  goose-quill.  In  the  early 
condition  it  forms  the  continuation  of  the  pulmonary  artery,  and  opens  into  the 
descending  aorta  just  below  the  origin  of  the  left  subclavian  artery,  and  so  con- 
ducts the  chief  part  of  the  blood  from  the  right  ventricle  into  this  vessel.  When 
the  branches  of  the  pulmonary  artery  have  become  larger  relatively  to  the  ductus 
arteriosus,  the  latter  is  chiefly  connected  to  the  left  pulmonary  artery;  and  the 
fibrous  cord  (ligamentum  arteriosum),  which  is  all  that  remains  of  the  ductus 
arteriosus  in  later  life,  will  be  found  to  be  attached  to  the  root  of  that  vessel. 

The  Umbilical  Arteries. — The  umbilical  or  hypogastric  arteries  arise  from  the 
internal  iliacs,  in  addition  to  the  branches  given  off  from  those  vessels  in  the 
adult.  Ascending  along  the  sides  of  the  bladder  to  its  apex,  they  pass  out  of 
the  abdomen  at  the  umbilicus  and  are  continued  along  the  umbilical  cord  to 
the  placenta,  coiling  round  the  umbilical  vein.  They  carry  to  the  placenta  the 
blood  which  has  circulated  in  the  system  of  the  foetus. 


CONUS 
ARTERIOSUS 


VALVE  OF 
FORAMEN  OVALE 


VALVE  OF     AURICULO-VENTRICULAR 
CORONARY  SINUS      OPENING 


Fig.  381. — The  right  auricle  of  a  foetal  heart  (eighth  month).     Enlarged.     (Spalteholz.) 

The  peculiarity  in  the  venous  system  of  the  foetus  is  the  communication  estab- 
lished between  the  placenta  and  the  liver  and  portal  vein  through  the  umbilical 
vein,  and  the  inferior  vena  cava  through  the  ductus  venosus. 

Foetal  Circulation. — The  blood  destined  for  the  nutrition  of  the  foetus  is 
returned  from  the  placenta  to  the  foetus  by  the  umbilical  vein.  This  vein  enters 
the  abdomen  at  the  umbilicus,  and  passes  upward  along  the  free  margin  of  the 
suspensory  ligament  of  the  liver  to  the  under  surface  of  that  organ,  where  it  gives 
ofT  two  or  three  branches  to  the  left  lobe,  one  of  which  is  of  large  size,  and  others 
to  the  lobus  quadratus  and  lobulus  Spigelii.  At  the  transverse  fissure  it  divides 
into  two  branches :  of  these,  the  larger  is  joined  by  the  portal  vein  and  enters  the 
right  lobe;  the  smaller  branch  continues  outward,  under  the  name  of  the  ductus 
venosus,  and  joins  the  left  hepatic  vein  at  the  point  of  junction  of  that  vessel  with 
the  inferior  vena  cava.  The  blood,  therefore,  which  traverses  the  umbilical  vein 
reaches  the  inferior  vena  cava  in  three  different  ways:  the  greater  quantity  cir- 
culates through  the  liver  with  the  portal  venous  blood  before  entering  the  vena 


580 


THE   BLOOD -VASCULAR   SYSTEM 


cava  by  the  hepatic  veins ;  some  enters  the  Uver  directly,  and  is  also  returned  to 
the  inferior  cava  by  the  hepatic  veins;  the  smaller  quantity  passes  directly  into  the 
vena  cava  by  the  junction  of  the  ductus  venosus  w^ith  the  left  hepatic  vein. 


Ductus  arteriosus. 


Internal  iliac  artery. 


Fig.  382.— Plan  of  the  foetal  circulation.     In  this  plan  the  figured  arrows  represent  the  kind  of  blood,  as  well 

as  the  direction  which  it  takes  in  the  vessels.     Thus,  arterial  blood  is  figured  >> — -->  ;  venous  blood, 

>> >;  mixed  (arterial  and  venous)  blood,  >>  ••  —  ••  — >. 

In  the  inferior  cava  the  blood  carried  by  the  ductus  venosus  and  hepatic  veins 
becomes  mixed  with  that  returning  from  the  lower  extremities  and  wall  of  the 
abdomen.  It  enters  the  right  auricle,  and,  guided  by  the  Eustachian  valve,  passes 
through  the  foramen  ovale  into  the  left  auricle,  where  it  becomes  mixed  with  a 
small  quantity  of  blood  returned  from  the  lungs  by  the  pulmonary  veins.  From 
the  left  auricle  it  passes  into  the  left  ventricle,  and  from  the  left  ventricle  into 


THE  HEART  581 

the  aorta,  by  means  of  which  it  is  distributed  almost  entirely  to  the  head  and 
upper  extremities,  a  small  quantity  being  probably  carried  into  the  descending 
aorta.  From  the  head  and  upper  extremities  the  blood  is  returned  by  the  tribu- 
taries of  the  superior  vena  cava  to  the  right  auricle,  where  it  becomes  mixed 
with  a  small  portion  of  the  blood  from  the  inferior  cava.  From  the  right  auricle 
it  descends  over  the  Eustachian  valve  into  the  right  ventricle,  and  from  the  right 
ventricle  passes  into  the  pulmonary  artery.  The  lungs  of  the  foetus  being  inactive, 
only  a  small  quantity  of  the  blood  of  the  pulmonary  artery  is  distributed  to  them 
by  the  right  and  left  pulmonary  arteries,  and  is  returned  by  the  pulmonary  veins 
to  the  left  auricle;  the  greater  part  passes  through  the  ductus  arteriosus  into  the 
commencement  of  the  descending  aorta,  where  it  becomes  mixed  with  a  small 
quantity  of  blood  transmitted  by  the  left  ventricle  into  the  aorta.  Through  this 
vessel  it  descends  to  supply  the  lower  extremities  and  viscera  of  the  abdomen 
and  pelvis,  the  chief  portion  being,  however,  conveyed  by  the  umbilical  arteries 
to  the  placenta. 

From  the  preceding  account  of  the  circulation  of  the  blood  in  the  foetus  it  will 
be  seen— 

1.  That  the  placenta  serves  the  purposes  of  nutrition  and  excretion,  receiving 
the  impure  blood  from  the  foetus,  and  returning  it  charged  with  additional  nutri- 
tive material. 

2.  That  nearly  the  whole  of  the  blood  of  the  umbilical  vein  traverses  the  liver 
before  entering  the  inferior  cava;  hence  the  large  size  of  this  organ,  especially  at 
an  early  period  of  foetal  life. 

3.  That  the  right  auricle  is  the  point  of  meeting  of  a  double  current,  the  blood 
in  the  inferior  cava  being  guided  by  the  Eustachian  valve  into  the  left  auricle, 
whilst  that  in  the  superior  cava  descends  into  the  right  ventricle.  At  an  early 
period  of  the  foetal  life  it  is  highly  probable  that  the  two  streams  are  quite  dis- 
tinct, for  the  inferior  cava  opens  almost  directly  into  the  left  auricle,  and  the 
Eustachian  valve  would  exclude  the  current  along  the  vein  from  entering  the 
right  ventricle.  At  a  later  period,  as  the  separation  between  the  two  auricles 
becomes  more  distinct,  it  seems  probable  that  some  mixture  of  the  two  streams 
must  take  place. 

4.  The  pure  blood  carried  from  the  placenta  to  the  foetus  by  the  umbilical  vein, 
mixed  with  the  blood  from  the  portal  vein  and  inferior  cava,  passes  almost  directly 
to  the  arch  of  the  aorta,  and  is  distributed  by  the  branches  of  that  vessel  to  the 
head  and  upper  extremities;  hence  the  large  size  and  perfect  development  of 
those  parts  at  birth. 

5.  The  blood  contained  in  the  descending  aorta,  chiefly  derived  from  that 
which  has  already  circulated  through  the  head  and  upper  limbs,  together  with  a 
small  quantity  from  the  left  ventricle,  is  distributed  to  the  lower  extremities; 
hence  the  small  size  and  imperfect  development  of  these  parts  at  birth. 

Changes  in  the  Vascular  System  at  Birth. 

At  birth,  when  respiration  is  established,  an  increased  amount  of  blood  from 
the  pulmonary  artery  passes  through  the  lungs,  which  now  perform  their  office 
as  respiratory  organs,  and  at  the  same  time  the  placental  circulation  is  cut  off. 
Almost  immediately  after  birth  the  foramen  ovale  is  closed  by  the  valvular  edge 
being  pressed  against  the  annulus  ovalis,  the  pressure  being  due  to  respiration, 
which  increases  the  pressure  in  the  left  auricle.  The  structures  fuse,  and  closure 
is  complete  by  about  the  tenth  day  after  birth.  The  valvular  fold  above  men- 
tioned becomes  adherent  to  the  margins  of  the  foramen  for  the  greater  part  of  its 
circumference,  but  above  a  slit-like  opening  is  left  between  the  two  auricles  which 
sometimes  remains  persistent. 


582  THE  BLOOD -VASCULAR  SYSTEM 

The  ductus  arteriosus  begins  to  contract  immediately  after  respiration  is  estab- 
lished, becomes  completely  closed  from  the  fourth  to  the  tenth  day,  and  ultimately 
degenerates  into  an  impervious  cord  which  serves  to  connect  the  left  pulmonary 
artery  to  the  descending  aorta.  When  respiration  begins,  the  caval  opening  of 
th3  diaphragm  being  fixed  and  the  balance  of  thi  muscle  rising  and  falling,  the 
ductus  arteriosus  is  compressed  by  the  muscular  structures  which  pass  from  the 
diaphragm  to  the  pericardium,  is  narrowed,  and  is  finally  obhterated  (Forbes). 

Of  the  umbilical  or  hypogastric  arteries,  the  portion  continued  on  to  the  bladder 
from  the  trunk  of  the  corresponding  internal  iliac  remains  pervious  as  the  superior 
vesical  artery,  and  the  part  extending  from  the  side  of  the  bladder  to  the  umbilicus 
becomes  obliterated  between  the  second  and  fifth  days  after  birth,  and  projects 
as  a  fibrous  cord  toward  the  abdominal  cavity,  carrying  on  it  a  fold  of  peritoneum 
and  separating  two  of  the  fossse  of  the  peritoneum  spoken  of  in  the  section  on  the 
surgical  anatomy  of  direct  inguinal  hernia. 

The  umbilical  vein  and  the  ductus  venosus  become  completely  obliterated 
between  the  second  and  fifth  days  after  birth,  and  ultimately  dwindle  to  fibrous 
cords,  the  former  becoming  the  round  ligament  of  the  liver,  the  latter  the  fibrous 
cord,  which  in  the  adult  may  be  traced  along  the  fissure  of  the  ductus  venosus. 


THE  ARTERIES. 


The  Arteries  are  cylindrical  tubular  vessels  which  serve  to  convey  blood  from 
both  ventricles  of  the  heart  to  every  part  of  the  body.  These  vessels  were  named 
arteries  {drjp,  air;  zr^pelu,  to  contain)  from  the  belief  entertained  by  the  ancients 
that  they  contained  air.  To  Galen  is  due  the  honor  of  refuting  this  opinion;  he 
showed  that  these  vessels,  though  for  the  most  part  empty  after  death,  contain 
blood  in  the  living  body. 

The  distribution  of  the  systemic  arteries  is  like  a  highly  ramified  tree,  the 
common  trunk  of  which,  formed  by  the  aorta,  commences  at  the  left  ventricle  of 
the  heart,  the  smallest  ramifications  corresponding  to  the  circumference  of  the 
body  and  the  contained  organs.  The  arteries  are  found  in  nearly  every  part  of 
the  body,  with  the  exception  of  the  hairs,  nails,  epidermis,  cartilages,  and  cornea; 
and  the  larger  trunks  usually  occupy  the  most  protected  situations,  running,  in 
a  limb,  along  the  flexor  side,  where  they  are  less  exposed  to  injury. 

There  is  considerable  variation  in  the  mode  of  division  of  the  arteries:  occa- 
sionally a  short  trunk  subdivides  into  several  branches  at  the  same  point,  as 
we  observe  in  the  coeliac  and  thyroid 

axes;  or  the  vessel  may  give  off  several  a  ^ 

branches  in  succession,  and  still  con- 
tinue as  the  main  trunk,  as  is  seen  in 
the  arteries  of  the  limbs;  but  the  usual 
division  is  dichotomous;  as,  for  instance, 
the  aorta  dividing  into  the  two  common 
iliacs,  and  the  common  carotid  into  the 
external  and  internal  carotids. 

The  branches  of  arteries  arise  at  very 
variable  angles:  some,  as  the  superior 
intercostal  arteries  from  the  aorta,  arise 
at  an  obtuse  angle:  others,  as  the  lumbar 
arteries,  at  a  right  angle;  or,  as  the 
spermatic,  at  an  acute  angle.  An  artery 
from  below  the  point  at  which  a  branch 
is  given  off  is  smaller  in  size  than  be- 
fore. It  retains  a  uniform  diameter 
until  a  second  branch  is  derived  from 
it.  A  branch  of  an  artery  is  smaller 
than  the  trunk  from  which  it  arises;  but 
if  an  artery  divides  into  two  branches, 
the  combined  area  of  the  two  vessels  is,  in  nearly  every  instance,  somewhat 
greater  than  that  of  the  trunk;  and  the  combined  area  of  all  the  arterial  branches 
greatly  exceeds  the  area  of  the  aorta;  so  that  the  arteries  collectively  may  be 
regarded  as  a  cone,  the  apex  of  which  corresponds  to  the  aorta,  the  base  to  the 
capillary  system. 

The  arteries,  in  their  distribution,  communicate  with  one  another,  forming 
what  is  called  an  anastomosis  {d.vd,  between;  azoixa,  mouth)  or  inosculation  (Fig, 
383) ;  and  this  communication  is  very  free  between  the  larger  as  well  as  between  the 

(583) 


Fig.  383. — Diagram  showing  the  anastomosis  of 
arteries.     (Poirier  and  Charpy.) 


584 


THE  BLOOD -VASCULAR    SYSTEM 


smaller  branches.  An  anastomosis  between  trunks  of  equal  size  is  found  where 
great  activity  of  the  circulation  is  requisite,  as  at  the  base  of  the  brain ;  here  the 
two  vertebral  arteries  unite  to  form  the  basilar,  and  the  two  internal  carotid 
arteries  are  connected  by  a  short  communicating  trunk;  it  is  also  found  in  the 
abdomen,  the  intestinal  arteries  having  very  ample  anastomoses  between  their 
larger  branches.  In  the  limbs  the  anastomoses  are  most  numerous  and  of 
largest  size  around  the  joints,  the  branches  of  an  artery  above  inosculating 
with  branches  from  the  vessels  below;  these  anastomoses  are  of  considerable 
interest  to  the  surgeon,  as  it  is  by  their  enlargement  that  a  collateral  circula- 
tion is  established  after  the  application  of  a  ligature  to  an  artery  for  the  cure 
of  aneurism.  The  smaller  branches  of  arteries  anastomose  more  frequently 
than  the  larger,  and  between  the  smallest  twigs  these  inosculations  become  so 

numerous  as  to  constitute  a  close  network 
that  pervades  nearly  every  tissue  of  the  body. 
A  terminal  artery  is  one  which  forms  no 
anastomoses.  Such  vessels  are  found  in  the 
brain,  spleen,  kidneys,  lungs,  and  mesen- 
tery. 

Throughout  the  body  generally  the  larger 
arterial  branches  pursue  a  perfectly  straight 
course,  but  in  certain  situations  they  are  tor- 
tuous; thus  the  facial  arteries  in  their  course 
over  the  face,  and  the  arteries  of  the  lips, 
are  extremely  tortuous  in  their  course,  to 
accommodate  themselves  to  the  movements 
of  the  parts.  The  uterine  arteries  are  also 
tortuous,  to  accommodate  themselves  to  the 
increase  of  size  which  the  organ  undergoes 
during  pregnancy.  Again,  the  internal 
carotid  and  vertebral  arteries,  previous  to 
their  entering  the  cavity  of  the  skull,  de- 
scribe a  series  of  curves,  which  are  evidently 
intended  to  diminish  the  velocity  of  the  cur- 
rent of  blood  by  increasing  the  extent  of 
surface  over  which  it  moves  and  adding  to 
the  resistance  which  is  produced  by  friction. 
The  arteries  are  dense  in  structure,  of 
considerable  strength,  highly  elastic,  and, 
when  divided,  they  preserve,  although  empty, 
their  cylindrical  form. 

Histology  of  the  Capillaries  and  Ar- 
teries. The  Capillaries  (Fig.  386). — The 
capillaries  are  very  small  endothelial  tubes 
which  connect  the  venous  system  with  the 
arterial  system.  In  diameter  they  vary  from  -gVro  ^^  2"oVo  ^^  ^^  inch,  in  length 
from  yV  to  ^V  of  an  inch.  The  nucleated  endothelial  cells  which  constitute  the 
wall  of  a  capillary  are  flat,  irregular  in  outline,  and  are  united  by  a  cement 
material.  Small  openings  (stomata)  are  frequently  noted  between  these  cells, 
but  they  are  probably  artifacts  and  do  not  exist  during  life. 

The  capillaries  anastomose  and  form  vast  networks.  When  an  artery  is  about 
to  become  a  capillary  the  muscular  coat  disappears.  The  endothelial  coat  which 
constitutes  the  capillaries  extends  as  a  system  of  endothelial  tubes  throughout  the 
entire  blood-vascular  system.  The  heart  is  a  great  muscular  thickening  around 
a  portion  of  the  system  of  endothelial  tubes.    An  artery  consists  of  an  endothelial 


Fig.  384. — Tran.sverse  section  through  a  small 
artery  and  vein  of  the  mucous  membrane  of  the 
epiglottis  of  a  child.  Magnified  about  350  diame- 
ters. A,  artery,  showing  the  nucleated  endothe- 
lium e,  which  lines  it:  the  vessel  being  con- 
tracted, the  endothelial  cells  appear  very  thick. 
Underneath  the  endothelium  is  the  wavy  elastic 
intima.  The  chief  part  of  the  wall  of  the  vessel 
is  occupied  by  the  circular  muscle-coat  ni;  the 
staff-shaped  nuclei  of  the  muscle-cells  are  well 
seen.  Outside  this  is  a,  part  of  the  adventitia. 
This  is  composed  of  bundles  of  connective-tissue 
fibres,  shown  in  section,  with  the  nuclei  of  the 
connective-tissue  corpuscles.  The  adventitia 
gradually  merges  into  the  surrounding  connective- 
tissue.  V,  vein  showing  a  thin  endothelial  mem- 
bra,ne  e,  raised  accidentally  from  the  intima, 
which  on  account  of  its  delicacy  is  seen  as  a  mere 
line  on  the  media  m.  This  latter  is  composed  of 
a  few  circular  unstriped  muscle-cells  ;  a,  the  ad- 
ventitia, similar  in  structure  to  that  of  an  artery. 
(Klein  and  Noble  Smith.) 


THE   ARTERIES 


585 


tube  covered  by  certain  accessory  coats.  The  wall  of  an  artery  diminishes 
greatly  in  thickness  (Fig.  387)  and  is  found  to  be  composed  of  endothelial  cells 
anfl  scattered  unstriated  muscle-fibres,  covered  merely  by  thin  connective  tissue 
or  elastic-tissue  sheath  (adventitia  capillaris).  Such  a  structure  is  known  as  an 
arteriole  or  a  precapillary  artery.  By  the  loss  of  its  thin  sheath  of  connective  or 
elastic  tissue  it  becomes  a  capillary.  A  capillary  takes  on  a  thin  sheath  and 
becomes  a  venule  or  precapillary  vein.  Nerves  do  not  terminate  in  capillaries, 
but  networks  of  nerve-filaments  often  encompass  these  small  vessels. 

An  artery  consists  of  an  internal  coat  or  tunica  intima,  a  middle  coat  or  tunica 
media,  and  an  external  coat  or  tunica  adventitia  (Figs.  384  and  385). 

The  Inner  Coat  (tunica  intima)  consists  of  endothelial  cells  and  yellow  elastic 
tissue.  In  some  cases  the  elastic  fibres  are  arranged  longitudinally,  but,  as  a  rule, 
they  form  a  distinct  fenestrated  membrane  known  as  the  fenestrated  membrane  of 


Endothelial   and   sub- 
etidothelial  layer  of 
■""     inner  coat. 
"Elastic  layer. 

_  Innermost  layers  of 
middle  coat. 


Outermost  layers  of 
middle  coat. 

_  Innermost  part 
outer  coat. 


^X:^-'' O ^-.  -'- ^f  - i 


^  I     Outer  part  of  outer 


coat. 


Fig.  385. — Section  of  a  medium-sized  artery.     (After  Griinstein.) 

Henle,  or  the  internal  elastic  coat.  In  medium-sized  vessels  the  elastic  layer  of  the 
intima  is  separated  from  the  endothelial  layer  by  a  layer  of  connective  tissue. 
In  the  large  arteries  the  interposed  layer  of  connective  tissue  is  thicker  and  con- 
tains elastic  fibres. 

The  Middle  Coat  {tunica  media)  consists  of  muscle,  elastic  tissue,  and  white 
fibrous  tissue,  and  it  is  often  called  the  elastomuscular  coat.  The  arterioles  con- 
tain scattered  unstriated  muscle  fibres.  In  the  small  arteries  they  constitute  a 
thin  but  definite  coat.  In  larger  arteries  the  muscular  coat  is  much  thicker.  The 
muscle  is  unstriated  and  the  fibres  are  arranged  circularly,  and  in  the  larger 
vessels  form  layers  which  are  separated  by  elastic  fibres.  Here  and  there  longi- 
tudinally-disposed muscle-fibres  exist.  The  larger  the  artery  the  greater  is  the 
amount  of  elastic  tissue  exi.sting  in  the  middle  coat.  In  the  aorta  and  in  some 
of  the  very  large  arteries  the  amount  of  elastic  tissue  exceeds  the  amount  of 


586 


THE  BLOOD -VASCULAR    SYSTEM 


muscular  tissue.  "In  the  first  part  of  the  aorta,  in  the  pulmonary  artery  and  in 
the  arteries  of  the  retina,  the  muscular  fibres  are  entirely  replaced  by  elastic 
tissue."^  The  arteries  within  the  skull  have  no  elastic  tissue  in  the  media, 
although  they  have  some  in  the  adventitia. 

The  External  Coat  {tunica  adventitia)  is  called  the  fibrous  coat.  It  contains 
fibrous  connective  tissue,  elastic  tissues,  and  in  some  arteries  fibres  of  unstriated 
muscle  arranged  longitudinally.  The  circular  elastic  membrane  which  sepa- 
rates the  outer  coat  from  the  middle  coat  is  known  as  the  external  elastic  mem- 
brane. 

Blood-vessels  of  the  Blood-vessel  Wall. — Many  small  blood-vessels  course  in  the 
external  and  middle  coats  of  arteries  of  large  and  of  moderate  size.  They  are 
mostly  in  the  adventitia.    They  may  arise  from  the  vessel  to  which  they  are  dis- 


FiG.  386.— Capillaries  from  the 
mesentery  of  a  guinea-pig  after  treat- 
ment with  solution  of  nitrate  of  silver. 
a,  cells;  b,  their  nuclei. 


Fig.  387. — Finest  vessels  on  the  arterial  aide.  From  the  human 
brain.  Magnified  300  times.  1,  small  artery;  2,  transition  vessel; 
3,  coarser  capillaries;  4,  finer  capillaries;  o,  structureless  mem- 
brane still  with  some  nuclei,  representative  of  the  tunica  adven- 
titia; h,  nuclei  of  the  muscular  fibre-cells;  c,  nuclei  within  the 
small  arterj;,  perhaps  appertaining  to  an  endothelium;  d,  nuclei 
in  the  transition  vessels. 


tributed  or  take  origin  from  an  adjacent  vessel.  These  small  arteries  are  called 
the  vasa  vasorum.  The  blood  is  returned  from  the  walls  of  the  vessels  by  small 
veins. 

Lymphatics. — Distinct  lymphatic  vessels  may  exist  in  the  adventitia,  but  are 
not  found  in  either  of  the  other  coats.  Lymph-capillaries  often  surround  small 
blood-vessels  or  a  small  blood-vessel  may  lie  in  a  perivascular  lymph-space. 

Nerves. — Arteries  are  supplied  with  nerves,  medullated  and  non-medullated. 
A  network  of  nerve-fibres  may  surround  a  vessel  and  usually  capillaries  are  so 
surrounded.  In  the  arteries  a  network  of  nerves  exists  in  the  media.  These  nerves 
supply  the  muscle-fibres  and  are  called  vasomotor  nerves. 

The  Arterial  Sheath  {vagina  vasis)  surrounds  the  artery.  It  is  composed  of  con- 
nective tissue  and  is  attached  to  the  vessel  at  numerous  points  by  fibrous  tissue. 


*  D.  J.  Cunningham.     Text-book  of  Anatomy. 


THE  AORTA  587 

PULMONARY  ARTERY  (A.  PULMONALIS)   (Fig.  389,  391). 

In  the  description  of  the  arteries  we  shall  first  consider  the  efferent  trunk  of 
the  pulmonic  circulation,  the  pulmonary  artery,  and  then  the  efferent  trunk  of  the 
systemic  circulation,  the  aorta  and  its  branches. 

The  pulmonary  artery  conveys  the  venous  blood  from  the  right  side  of  the  heart 
to  the  lungs.  It  is  a  short,  wide  vessel,  about  2  inches  in  length  and  li  inches 
(30  mm.)  in  diameter,  arising  from  the  left  side  of  the  base  (conus  arteriosus) 
of  the  right  ventricle,  in  front  of  the  aorta.  It  extends  obliquely  upward  and 
backward,  passing  at  first  in  front  of  and  then  to  the  left  of  the  ascending 
aorta,  as  far  as  the  under  surface  of  the  arch,  where  it  divides,  about  on  a  level 
with  the  intervertebral  substance  between  the  fifth  and  sixth  dorsal  vertebrae, 
into  two  branches  of  nearly  equal  size,  the  right  and  left  pulmonary  arteries. 

The  Right  Pulmonary  Artery  (ramus  dexter  a.  pulmonalis),  longer  and 
larger  than  the  left,  runs  horizontally  outward  to  the  root  of  the  right  lung,  where 
it  divides  into  two  branches,  of  which  the  lower  and  larger  supplies  the  middle 
and  lower  lobes;  the  upper  and  smaller  is  distributed  to  the  upper  lobe.  It  has 
in  front  of  it  the  ascending  aorta,  the  superior  vena  cava,  and  the  right  phrenic 
nerve.  It  has  behind  it  the  right  bronchus.  Above  it  is  the  transverse  portion  of 
the  arch  of  the  aorta.    Below  it  is  the  right  auricle. 

The  Left  Pulmonary  Artery  (ramus  sinister  a.  pulmonalis),  shorter  and 
somewhat  smaller  than  the  right,  passes  horizontally  to  the  root  of  the  left  lung, 
where  it  divides  into  two  branches  for  the  two  lobes.  In  front  of  it  and  below  it 
are  the  pulmonary  veins  of  the  left  side.  Behind  are  the  descending  aorta  and  the 
left  bronchus.  Above  it  are  the  arch  of  the  aorta,  the  left  recurrent  laryngeal 
nerve,  and  the  ductus  arteriosus.  The  left  bronchus  in  a  portion  of  its  course  lies 
below  as  well  as  behind. 

Relations. — The  whole  of  the  vessel  is  contained,  together  with  the  ascending 
aorta,  in  the  pericardium.  It  is  enclosed  with  the  aorta  in  a  single  tube  of  the 
serous  pericardium,  which  is  continued  upward  upon  them  from  the  base  of  the 
heart  and  connects  them  together.  The  fibrous  layer  of  the  pericardium  becomes 
gradually  lost  upon  the  external  coats  of  its  two  branches.  In  front,  the  pulmonary 
artery  is  separated  from  the  anterior  extrerpity  of  the  second  left  intercostal  space 
by  the  pleura  and  left  lung,  in  addition  to  the  pericardium;  it  rests  at  first  upon 
the  ascending  aorta,  and  higher  up  lies  in  front  of  the  left  auricle  on  a  plane 
posterior  to  the  ascending  aorta.  On  each  side  of  its  origin  is  the  appendix  of 
the  corresponding  auricle  and  a  coronary  artery,  the  left  coronary  artery  passing, 
in  the  first  part  of  its  course,  behind  the  vessel. 

The  root  of  the  left  pulmonary  artery  is  connected  to  the  under  surface  of  the 
arch  of  the  aorta  by  a  short  fibrous  cord,  the  ligamentum  arteriosum;  this  is  the 
remains  of  a  vessel  peculiar  to  foetal  life,  the  ductus  arteriosus. 

The  terminal  branches  of  the  pulmonary  artery  will  be  described  with  the 
anatomy  of  the  lung. 

THE  AORTA  (Figs.  388,  389,  390,  391). 

The  aorta  or  arteria  magna  (doprij)  is  the  main  trunk  of  a  series  of  vessels  which 
convey  the  oxygenated  blood  to  the  tissues  of  the  body  for  their  nutrition.  This 
vessel  commences  at  the  upper  part  of  the  left  ventricle,  where  it  is  aV)out  one  and 
one-eighth  inches  in  diameter,  and,  after  ascending  for  a  short  distance,  arches 
backward  and  to  the  left  side,  over  the  root  of  the  left  lung,  then  descends  within 
the  thorax  on  the  left  side  of  the  vertebral  column,  passes  through  the  aortic  open- 
ing in  the  Diaphragm,  and,  entering  the  abdominal  cavity,  terminates,  consider- 


588 


THE   BLOOD -VASCULAR    SYSTEM 


ably  diminished  in  size  (about  seven-tenths  of  an  inch  in  diameter),  opposite  the 
lower  border  of  the  fourth  lumbar  vertebra,  where  it  divides  into  the  right  and  left 
common  iliac  arteries.  Hence  it  is  divided  into  the  ascending  aorta,  the  arch  of 
the  aorta,  and  the  descending  aorta,  which  last  is  again  divided  into  the  thoracic  aorta 
and  the  abdominal  aorta,  from  the  position  of  these  parts. 

THE  ASCENDING  AORTA  (AORTA  ASGENDENS). 

The  ascending  aorta  is  about  two  inches  in  length.  It  commences  at  the 
upper  part  of  the  left  ventricle,  on  a  level  with  the  lower  border  of  the  third 
costal  cartilage,  behind  the  left  half  of  the  sternum ;  it  passes  obliquely  upward, 
forward,  and  to  the  right,  in  the  direction  of  the  heart's  axis,  as  high  as  the 


PNCUMOGASTRIC 
NERVE 


CARDIAC  NERVE 
SUPERIOR  INTER- 
COSTAL VEIN 
CARDIAC  NERVE 
ARTERIAL 
LIGAMENTS 


VENA  AZYGOS: 

MINOR 


SYMPATHETIC 
GANGLION 


SYMPATHETIC 
NERVE 


Fig.  388. — Arch  of  the  aorta  and  its  relations.      (Poirier  and  Charpy.) 


upper  border  of  the  second  right  costal  cartilage,  describing  a  slight  curve  in 
its  course,  and  being  situated,  when  distended,  about  a  quarter  of  an  inch  behind 
the  posterior  surface  of  the  sternum.  A  little  above  its  commencement  it  is  some- 
what enlarged  (bulhus  aortoe),  and  presents  three  small  dilatations,  one  of  which  is 
anterior,  two  of  which  are  posterior,  which  are  called  the  sinuses  of  Valsalva  {sinu» 
aortce).    Opposite  to  the  sinuses  are  attached  the  three  semilunar  valves  (Fig.  376), 


THE   ASCENDING    AORTA 


589 


which  serve  the  purpose  of  preventing  any  regurgitation  of  blood  into  the  cavity 
of  the  ventricle.  These  valves  are  placed  one  in  front  and  two  behind.  At  the 
union  of  the  ascending  with  the  transverse  part  of  the  aorta  the  calibre  of  the  vessel 
is  increased,  owing  to  a  bulging  outward  of  its  right  wall.  This  dilatation  is  termed 
the  great  sinus  of  the  aorta.  A  section  of  the  aorta  opposite  this  part  has  a  some- 
what oval  figure;  but  below  the  attachment  of  the  valves  it  is  circular.  This  por- 
tion of  the  aorta  is  contained  in  the  cavity  of  the  pericardium,  and,  together  with 
the  pulmonary  artery,  is  invested  in  a  tube  of  serous  membrane,  continued  on  to 
them  from  the  surface  of  the  heart. 


Eight  vagus 
Recurrent  laryngeal. 


Left  vagus. 
I — Left  phrenic. 
Thoracic  duct. 


Fig.  389. — The  arch  of  the  aorta  and  its  branches. 


Relations. — The  ascending  aorta  is  covered  at  its  commencement  by  the  trunk 
of  the  pulmonary  artery  and  the  right  auricular  appendix,  and,  higher  up,  is 
separated  from  the  sternum  by  the  pericardium,  the  right  pleura,  and  anterior 
margin  of  the  right  lung,  some  loose  areolar  tissue,  and  the  remains  of  the  thymus 
gland ;  behind,  it  rests  upon  the  right  pulmonary  artery,  left  auricle,  and  the  right 
bronchus.  On  the  right  side  it  is  in  relation  with  the  superior  vena  cava  and  right 
auricle;  on  the  left  side,  with  the  pulmonary  artery. 


590  THE   BLOOD -VASCULAR   SYSTEM 


Plan  of  the  Relations  of  the  Ascending  Aorta. 

In  front. 
Pulmonary  artery. 
Right  auricular  appendix. 
Pericardium. 
Right  pleura  and  lung. 
Remains  of  the  thymus  gland. 


Right  side. 

/       \ 

Left  side. 

Superior  vena  cava. 

Ascending 

Pulmonary  artery. 

Right  auricle. 

Aorta. 

\                         / 

Behind. 
Right  pulmonary  artery. 
Left  auricle. 
Right  bronchus. 

Branches — The  only  branches  of  the  ascending  aorta  are  the  coronary  arteries. 
They  supply  the  heart,  and  are  two  in  number,  right  and  left,  arising  near  the  com- 
mencement of  the  aorta,  immediately  above  the  free  margin  of  the  semilunar 
valves. 

The  Coronary  Arteries  (Fig.  389). 

The  Right  Coronary  Artery  (a.  coronaria  [cordis]  dextra),  about  the  size  of  a 
crow's  quill,  arises  from  the  anterior  sinus  of  Valsalva.  It  passes  forward  between 
the  pulmonary  artery  and  the  right  auricular  appendix,  then  runs  obliquely  to  the 
right  side,  in  the  groove  between  the  right  auricle  and  ventricle,  and,  curving 
around  the  right  border  of  the  heart,  runs  to  the  left  along  its  posterior  surface  as 
far  as  the  posterior  interventricular  groove,  where  it  divides  into  two  branches,  one 
of  which,  the  transverse,  continues  onward  in  the  groove  between  the  left  auricle 
and  ventricle,  and  anastomoses  with  the  left  coronary;  the  other,  the  descending 
{ramus  descendens  posterior  a.  coronarice  [cordis]  dextroe),  courses  along  the  posterior 
interventricular  furrow,  supplying  branches  to  both  ventricles  and  to  the  septum, 
and  anastomosing  at  the  apex  of  the  heart  with  the  descending  branches  of  the  left 
coronary.  This  vessel  sends  a  large  branch,  the  marginal,  along  the  thin  margin 
of  the  right  ventricle  to  the  apex,  which  in  its  course  gives  off  numerous  small 
branches  to  the  anterior  and  posterior  surfaces  of  the  ventricle.  It  also  gives  off 
a  branch,  the  infundibular,  which  ramifies  over  the  front  part  of  the  conus  arte- 
riosus of  the  right  ventricle. 

The  Left  Coronary  Artery  (a.  coronaria  [cordis]  sinistra),  larger  than  the 
former,  arises  from  the  left  posterior  sinus  of  Valsalva;  it  passes  forward  between 
the  pulmonary  artery  and  the  left  auricular  appendix,  and  divides  into  two 
branches.  Of  these,  one,  the  transverse,  passes  transversely  outward  in  the  left 
auriculo-ventricular  groove,  and  winds  around  the  left  border  of  the  heart  to  its 
posterior  surface,  where  it  anastomoses  with  the  transverse  branch  of  the  right 
coronary ;  the  other,  the  descending  (ramus  descendens  anterior  a.  coronarioe  [cordis] 
sinistroe),  passes  along  the  anterior  interventricular  groove  to  the  apex  of  the  heart, 
where  it  anastomoses  with  the  descending  branches  of  the  right  coronary.  The  left 
coronary  supplies  the  left  auricle  and  its  appendix,  gives  branches  to  both  ventri- 
cles, and  numerous  small  branches  to  the  pulmonary  artery  and  commencement 
of  the  aorta.^ 

*  According  to  Dr.  Samuel  West,  there  is  a  very  free  and  complete  anastomosis  between  the  two  coronary 
arteries  (Lancet,  June  2,  1883,  p.  945).  This,  however,  is  not  the  view  generally  held  by  anatomists,  for,  with 
the  exception  of  the  anastomosis  mentioned  above  in  the  auriculo-ventricular  and  interventricular  grooves,  it 
is  believed  that  the  two  arteries  only  communicate  by  very  small  vessels  in  the  substance  of  the  heart. — Ed.  of 
15th  English  edition. 


THE  ABCH   OF    THE   AORTA  591 

Peculiarities. — These  vessels  occasionally  arise  by  a  common  trunk,  or  their  number  may 
be  increased  to  three,  the  additional  branch  being  of  small  size.  More  rarely  there  are  two 
additional  branches. 

THE  ARCH  OF  THE  AORTA. 

The  arch,  or  transverse  aorta  (arcus  aort(B),  commences  at  the  upper  border  of 
the  second  chondro-sternal  articulation  of  the  right  side,  and  passes  at  first  upward 
and  backward  and  from  right  to  left,  and  then  from  before  backward,  to  the  left 
side  of  the  lower  border  of  the  fourth  dorsal  vertebra  behind.  Its  upper  border  is 
usually  about  an  inch  below  the  upper  margin  of  the  sternum. 

Between  the  origin  of  the  left  subclavian  artery  and  the  attachment  of  the 
ductus  arteriosus  the  lumen  of  the  foetal  aorta  is  considerably  narrowed,  forming 
what  is  termed  the  aortic  isthmus  (isthmus  aorte),  while  immediately  beyond  the 
ductus  arteriosus  the  vessel  presents  a  fusiform  dilatation  which  His  has  named 
the  aortic  spindle  (aortenspindel) — the  point  of  junction  of  the  two  parts  being 
marked  in  the  concavity  of  the  arch  by  an  indentation  or  angle.  These  con- 
ditions persist,  to  some  extent,  in  the  adult,  where  His  found  that  the  average 
diameter  of  the  spindle  exceeded  that  of  the  isthmus  by  3  mm.  (about  one-eighth 
of  an  inch). 

Relations. — Its  anterior  surface  is  covered  by  the  pleurae  and  lungs  (much 
more  by  the  left  lung  than  by  the  right)  and  the  remains  of  the  thymus  gland,  and 
crossed  toward  the  left  side  by  the  left  pneumogastric  and  phrenic  nerves  and 
superficial  cardiac  branches  of  the  left  sympathetic  and  vagus,  and  by  the  left 
superior  intercostal  vein.  Its  posterior  surface  lies  on  the  trachea,  just  above  its 
bifurcation,  on  the  great,  or  deep,  cardiac  plexus,  the  oesophagus,  thoracic  duct, 
and  left  recurrent  laryngeal  nerve.  Its  upper  border  is  in  relation  with  the  left 
innominate  vein,  and  from  its  upper  part  are  given  off  the  innominate,  left  com- 
mon carotid  and  left  subclavian  arteries.  Its  lower  border  is  in  relation  with  the 
bifurcation  of  the  pulmonary  artery,  the  remains  of  the  ductus  arteriosus,  which 
is  connected  with  the  left  division  of  that  vessel,  and  the  superficial  cardiac  plexus; 
the  left  recurrent  laryngeal  nerve  winds  round  it  from  before  backward,  whilst 
the  left  bronchus  passes  below  it. 

Plan  of  the  Relations  of  the  Arch  of  the  Aorta. 

Above. 

Left  innominate  vein. 
Innominate  artery. 
Left  carotid. 
Left  subclavian. 
In  Front.  Behind. 

Pleurae  and  lungs.  /"^      "^\  Trachea. 

Remains  of  thymus  gland.  /  \  Deep  cardiac  plexus. 

Left  pneumogastric  nerve.  (      Arch  of      j  Oesophagus. 

Left  phrenic  nerve.  I       '*^°'"'*-       /  Thoracic  duct. 

Superficial  cardiac  nerves.  \  /  Left  recurrent  nerve. 

Left  superior  intercostal  vein.  ^- ^ 

Below. 
Bifurcation  of  pulmonary  artery. 
Remains  of  ductus  arteriosus. 
Superficial  cardiac  plexus. 
Left  recurrent  nerve. 
Left  bronchus. 

Peculiarities. — The  height  to  which  the  aorta  rises  in  the  chest  is  usually  about  an  inch  below 
the  upper  border  of  the  sternum ;  but  it  may  ascend  nearly  to  the  top  of  that  bone.  Occasionally 
it  is  found  an  inch  and  a  half,  more  rarely  two  or  even  three  inches,  below  this  point. 


592 


THE   BLOOD -VASCULAR    SYSTEM 


In  Direction. — Sometimes  in  man,  as  is  normal  in  birds,  the  aorta  arches  over  the  root  of 
the  right  instead  of  the  left  lung,  and  passes  down  on  the  right  side  of  the  spine.  In  such  cases 
all  of  the  viscera  of  the  thoracic  and  abdominal  cavities  are  transposed.  Less  frequently,  the 
aorta,  after  arching  over  the  root  of  the  right  lung,  is  directed  to  its  usual  position  on  the  left 
side  of  the  spine,  this  peculiarity  not  being  accompanied  by  any  transposition  of  the  viscera. 

In  Conformation. — The  aorta  occasionally  divides,  as  in  some  quadrupeds,  into  an  ascend- 
ing and  descending  trunk,  the  former  of  which  is  directed  vertically  upward,  and  subdivides 
into  three  branches,  to  supply  the  head  and  upper  extremities.  Sometimes  the  aorta  subdivides 
soon  after  its  origin  into  two  branches,  which  soon  reunite.  In  one  of  these  cases  the  oesophagus 
and  trachea  were  found  to  pass  through  the  interval  left  by  the  division  of  the  aorta;  this  is 
the  normal  condition  of  the  vessel  in  the  reptilia. 

Surgical  Anatomy. — Of  all  the  vessels  of  the  arterial  system,  the  aorta,  and  more  especially 
its  arch,  is  most  frequently  the  seat  of  disease;  hence  it  is  important  to  consider  some  of  the 
consequences  that  may  ensue  from  aneurism  of  this  part. 

It  will  be  remembered  that  the  ascending  aorta  is  continued  in  the  pericardium,  just  behind 
the  sternum,  being  crossed  at  its  commencement  by  the  pulmonary  artery  and  right  auricular 
appendix,  and  having  the  right  pulmonary  artery  behind,  the  vena  cava  on  the  right  side,  and 
the  pulmonary  artery  and  left  auricle  on  the  left  side. 


Right  pulmonary 
vein. 

Right  pulmonary 
vein. 


Vena  asygos 
major. 


Left  subclavian 
artery. 

Left  common 
carotid  artery. 


-Left  innomi- 
nate vein. 


Inferior  thyroid 
vein. 


Right  innomi- 
nate vein. 

Right  subclavian  artery, 


Right  common  carotid  artery. 


Fig.  391. 


-Relation  of  great  vessels  at  base  of  heart,  seen  from  above.     (From  a  preparation  in  the  Museum 
of  the  Royal  College  of  Surgeons  of  England. ) 


Aneurism  of  the  ascending  aorta,  in  the  situation  of  the  sinuses  of  Valsalva,  in  the  great  major- 
ity of  cases,  affects  the  anterior  sinus;  this  is  mainly  owing  to  the  fact  that  the  regurgitation 
of  blood  upon  the  sinuses  takes  place  chiefly  on  the  anterior  aspect  of  the  vessel.  As  the  aneuris- 
mal  sac  enlarges  it  may  compress  any  or  all  of  the  structures  in  immediate  proximity  to  it, 
but  chiefly  projects  toward  the  right  anterior  side,  and,  consequently,  interferes  mainly  with 
those  structures  that  have  a  corresponding  relation  with  the  vessel.  In  the  majority  of  cases  it 
bursts  into  the  cavity  of  the  pericardium,  the  patient  suddenly  drops  dead,  and,  upon  a  post- 
mortem examination,  the  pericardial  sac  is  found  full  of  blood;  or  it  may  compre.ss  the  right 
auricle,  or  the  pulmonary  artery  and  adjoining  part  of  the  right  ventricle,  and  open  into  one  or 
the  other  of  these  parts,  or  may  press  upon  the  superior  vena  cava. 

Aneurism  of  the  ascending  aorta,  originating  above  the  sinuses,  most  frequently  implicates 
the  right  anterior  wall  of  the  vessel,  where,  as  has  been  explained,  there  exists  a  normal  dilata- 
tion, the  great  sinus  of  the  aorta;  this  is  probably  mainly  owing  to  the  blood  being  impelled 
against  this  part.  The  direction  of  the  aneurism  is  also  chiefly  toward  the  right  of  the  median 
line.  It  attains  a  large  size  and  projects  forward,  it  may  absorb  the  sternum  and  the  cartilages 
of  the  ribs,  usually  on  the  right  side,  and  appear  as  a  pulsating  tumor  on  the  front  of  the  chest, 
just  below  the  manubrium;  or  it  may  burst  into  the  pericardium,  or  may  compress  or  open  into 
the  right  lung,  the  trachea,  bronchi,  or  oesophagus. 


THE    INNOMINATE   ARTERY  593 

Regarding  the  transverse  aorta,  the  student  is  reminded  that  the  vessel  lies  on  the  trachea, 
the  oesophagus,  and  thoracic  duct;  that  the  recurrent  laryngeal  nerve  winds  around  it;  and  that 
from  its  upper  part  are  given  off  three  large  trunks,  which  supply  the  head,  neck,  and  upper 
extremities.  An  aneurismal  tumor,  taking  origin  from  the  posterior  part  of  the  vessel,  its  most 
usual  site,  may  press  upon  the  trachea,  impede  the  breathing,  or  produce  cough,  haemoptysis, 
or  stridulous  breathing,  or  it  may  ultimately  burst  into  that  tube,  producing  fatal  haemorrhage. 
Again,  its  pressure  on  the  laryngeal  nerves  may  give  rise  to  symptoms  which  so  accurately 
resemble  those  of  laryngitis  that  the  operation  of  tracheotomy  has  in  some  cases  been  resorted 
to,  from  the  supposition  that  disease  existed  in  the  larynx;  or  it  may  press  upon  the  thoracic 
duct  and  destroy  life  by  inanition;  or  it  may  involve  the  cesophagus,  producing  dysphagia;  or 
may  burst  into  the  oesophagus,  when  fatal  hemorrhage  will  occur.  Again,  the  innominate 
artery,  or  the  subclavian,  or  left  carotid,  may  be  so  obstructed  by  clots  as  to  produce  a  weakness, 
or  even  a  disappearance,  of  the  pulse  in  one  or  the  other  wrist  or  in  the  left  temporal  artery;  or 
the  tumor  may  present  itself  at  or  above  the  manubrium,  generally  either  in  the  median  line 
or  to  the  right  of  the  sternum,  and  may  simulate  an  aneurism  of  one  of  the  arteries  of  the  neck. 

Branches  (Figs.  389  and  390). — The  branches  given  off  from  the  arch  of  the 
aorta  are  three  in  number:  the  innominate,  the  left  common  carotid,  and  the  left 
subclavian  arteries. 

Peculiarities.  Position  of  the  Branches. — The  branches,  instead  of  arising  from  the  high- 
est part  of  the  arch  (their  usual  position),  may  be  moved  more  to  the  right,  arising  from  the 
commencement  of  the  transverse  or  upper  part  of  the  ascending  portion;  or  the  distance  from 
one  another  at  their  origin  may  be  increased  or  diminished,  the  most  frequent  change  in  this 
respect  being  the  approximation  of  the  left  carotid  toward  the  innominate  artery. 

The  Number  of  the  primary  branches  may  be  reduced  to  a  single  vessel,  or  more  commonly 
two:  the  left  carotid  arising  from  the  innominate  artery,  or  (more  rarely)  the  carotid  and  sub- 
clavian arteries  of  the  left  side  arising  from  the  innominate  artery.  But  the  number  may  be 
increased  to  four,  from  the  right  carotid  and  subclavian  arteries  arising  directly  from  the  aorta, 
the  innominate  being  absent.  In  most  of  these  latter  cases  the  right  subclavian  has  been  found 
to  arise  from  the  left  end  of  the  arch;  in  other  cases  it  was  the  second  or  third  branch  given  off 
instead  of  the  first.  Another  common  form  in  which  there  are  four  primary  branches  is  that 
in  which  the  left  vertebral  artery  arises  from  the  arch  of  the  aorta  between  the  left  carotid  and 
subclavian  arteries.  Lastly,  the  number  of  trunks  from  the  arch  may  be  increased  to  five  or 
six;  in  these  instances,  the  external  and  internal  carotids  arise  separately  from  the  arch,  the 
common  carotid  being  absent  on  one  or  both  sides.  In  some  cases,  where  six  branches  have 
been  found,  it  has  been  due  to  a  separate  origin  of  the  vertebral  on  both  sides. 

Number  as  Usual,  Arrangement  Different. — When  the  aorta  arches  over  to  the  right 
side,  the  three  branches  have  an  arrangement  the  reverse  of  what  is  usual,  the  innominate  sup- 
plying the  left  side,  and  the  carotid  and  subclavian  (which  arise  separately)  the  right  side.  In 
other  cases,  where  the  aorta  takes  its  usual  course,  the  two  carotids  may  be  joined  in  a  common 
trunk,  and  the  subclavians  arise  separately  from  the  arch,  the  right  subclavian  generally  arising 
from  the  left  end  of  the  arch.' 

In  some  instances  other  arteries  are  found  to  arise  from  the  arch  of  the  aorta.  Of  these  the 
most  common  are  the  bronchial,  one  or  both,  and  the  thyroidea  ima;  but  the  internal  mammary 
and  the  inferior  thyroid  have  been  seen  to  arise  from  this  vessel. 

The  Innominate  Artery  (A.  Anonyma)   (Figs.  389,  390,  391). 

The  innominate  or  brachio-cephalic  artery  is  the  largest  branch  given  off 
from  the  arch  of  the  aorta.  It  arises,  on  a  level  with  the  upper  border  of 
the  second  right  costal  cartilage,  from  the  commencement  of  the  arch  of  the 
aorta  in  front  of  the  left  carotid,  and,  ascending  obliquely  to  the  upper  border  of 
the  right  sterno-clavicular  articulation,  divides  into  the  right  common  carotid  and 
right  subclavian  arteries.  This  vessel  varies  from  an  inch  and  a  half  to  two  inches 
in  length. 

Relations. — In  front,  it  is  separated  from  the  first  piece  of  the  sternum  by  the 
Sterno-hyoid  and  Sterno-thyroid  muscles,  the  remains  of  the  thymus  gland,  the 
left  innominate  and  right  inferior  thyroid  veins  which  cross  its  root,  and  some- 
times the  inferior  cervical  cardiac  branch  of  the  right  pneumogastric.    Behind,  it 

'  The  anomalies  of  the  aorta  and  its  branches  are  minutely  described  by  Krause  in  Henle's  Anatomy  (Bruns- 
wick, 1868),  vol.  iii.  p.  203  et  seq.— Ed.  of  15th  English  edition 

38  -^ 


594  THE    BLOOD -VASCULAR   SYSTEM 

lies  upon  the  trachea,  which  it  crosses  obliquely,  and  continuing  upward  it  lies 
in  the  right  pleura.  On  the  right  side  is  the  right  innominate  vein,  right  pneumo- 
gastric  nerve,  and  the  pleura;  and  on  the  le]t  side,  the  remains  of  the  thymus  gland, 
the  origin  of  the  left  carotid  artery,  the  left  inferior  thyroid  vein,  and  the  trachea. 

Branches.— The  innominate  usually  gives  off  no  branches,  but  occasionally  a 
small  branch,  the  thjnroidea  ima,  is  given  off  from  this  vessel.  It  also  sometimes 
gives  off  a  thymic  or  bronchial  branch. 

The  Thjrroidea  Ima  (a.  thyroidea  ima),  which  is  occasionally  present,  ascends  in 
front  of  the  trachea  to  the  lower  part  of  the  thyroid  body,  which  it  supplies.  It 
varies  greatly  in  size,  and  appears  to  compensate  for  the  deficiency  or  absence  of 
one  of  the  other  thyroid  vessels.  It  occasionally  is  found  to  arise  from  the  right 
common  carotid  or  from  the  aorta,  the  subclavian,  or  internal  mammary  vessels. 

Plan  of  the  Relations  of  the  Innominate  Artery. 

In  front. 
Sternum. 

Sterno-hyoid  and  Sterno-thyroid  muscles. 
Remains  of  the  thymus  gland. 
Left  innominate  and  right  inferior  thyroid  veins. 
Inferior  cervical  cardiac  branch  from  right  pneumogastric  nerve. 

Right  side.  /  \  Left  side. 

Right  innominate  vein.  /  innominate   |  Remains  of  thymus. 

Right  pneumogastric  nerve.  I       Artery.       )  Left  carotid. 

Pleura.  \  /  Left  inferior  thyroid  vein. 

^-_^^^  Trachea. 

Behind. 

Trachea. 
Right  pleura. 

Peculiarities  in  Point  of  Division. — When  the  bifurcation  of  the  innominate  artery  varies 
from  the  point  above  mentioned  it  sometimes  ascends  a  considerable  distance  above  the  sternal 
end  of  the  clavicle;  less  frequently  it  divides  below  it.  In  the  former  class  of  cases  its  length 
may  exceed  two  inches,  and  in  the  latter  be  reduced  to  an  inch  or  less.  These  are  points  of  con- 
siderable interest  for  the  surgeon  to  remember  in  connection  with  the  operation  of  tying  this 
vessel. 

Position. — When  the  aorta  arches  over  to  the  right  side,  the  innominate  is  directed  to  the 
left  side  of  the  neck  instead  of  the  right. 

Collateral  Circulation. — Allan  Burns  demonstrated,  on  the  dead  subject,  the  possibility  of 
the  establishment  of  the  collateral  circulation  after  ligature  of  the  innominate  artery,  by  tying 
and  dividing  that  artery,  after  which,  he  says,  "Even  coarse  injection,  impelled  into  the  aorta, 
passing  freely  by  the  anastomosing  branches  into  the  arteries  of  the  right  arm,  filling  them  and 
all  the  vessels  of  the  head  completely."^  The  branches  by  which  this  circulation  would  be  car- 
ried on  are  very  numerous;  thus,  all  the  communications  across  the  middle  line  between  the 
branches  of  the  carotid  arteries  of  opposite  sides  would  be  available  for  the  supply  of  blood  to 
the  right  side  of  the  head  and  neck;  while  the  anastomosis  between  the  superior  intercostal  of 
the  subclavian  and  the  first  aortic  intercostal  (see  infra  on  the  collateral  circulation  after  oblitera- 
tion of  the  thoracic  aorta)  would  bring  the  blood,  by  a  free  and  direct  course,  into  the  right 
subclavian:  the  numerous  connections,  also,  between  the  intercostal  arteries  and  the  branches 
of  the  axillary  and  internal  mammary  arteries  would,  doubtless,  assist  in  the  supply  of  blood  to 
the  right  arm,  while  the  deep  epigastric,  from  the  external  iliac,  would,  by  means  of  its  anasto- 
mosis with  the  internal  mammary,  compensate  for  any  deficiency  in  the  vascularity  of  the  wall 
of  the  chest. 

Surgical  Anatomy. — The  innominate  artery  has  been  tied  at  least  thirty  times  and  in  six 
instances,  according  to  Mr.  Jacobson,  the  patient  survived.  Mott's  patient,  however,  on 
whom  the  operation  was  first  performed,  lived  nearly  four  weeks,  and  Graefe's  more  than 
two  months.  In  1895  Burrell,  of  Boston,  resected  the  right  sterno-clavicular  articulation  with 
the  upper  end  of  the  sternum  and  tied  the  innominate.     The  patient  lived  104  days.     The 

'  Surgical  Anatomy  of  the  Head  and  Neck,  p.  62. 


THE    COMMON   CAROTID    ARTERY  595 

ligation  was  first  successfully  performed  by  A.  W.  Smyth,  of  New  Orleans,  in  1864,  for  sub- 
clavian aneurism.  The  patient  died  ten  years  later  of  the  original  aneurism,  which  was  reformed 
by  the  collaterals.  The  chief  danger  of  the  operation  appears  to  be  the  frequency  of  secondary 
hemorrhage;  but  in  the  present  day,  with  the  practice  of  aseptic  surgery  and  our  greater 
knowledge  of  the  use  of  the  ligature,  more  favorable  results  may  be  anticipated.  Other  causes 
of  death  after  operation  are  pleurisy,  pericarditis,  and  suppurative  cellulitis.  The  main 
obstacles  to  the  operation  are,  as  the  student  will  perceive  from  his  dissection  of  this  vessel, 
the  deep  situation  of  the  artery  behind  and  beneath  the  sternum,  and  the  number  of  important 
structures  which  surround  it  in  every  part. 

In  order  to  apply  a  ligature  to  this  vessel,  the  patient  is  to  be  placed  upon  his  back,  with  the 
thorax  slightly  raised,  the  head  bent  a  little  backward,  and  the  shoulder  on  the  side  of  the  aneu- 
rism strongly  depressed,  so  as  to  draw  out  the  artery  from  behind  the  sternum  into  the  neck. 
An  incision  three  or  more  inches  long  is  then  made  along  the  anterior  border  of  the  Sterno-mas- 
toid  muscle,  terminating  at  the  sternal  end  of  the  clavicle.  From  this  point  a  second  incision  is 
carried  about  the  same  length  along  the  upper  border  of  the  clavicle.  The  skin  is  then  dissected 
back,  and  the  Platysma  divided  on  a  director:  the  sternal  end  of  the  Sterno-mastoid  is  now 
brought  into  view,  and,  a  director  being  passed  beneath  it  and  close  to  its  under  surface,  so  as  to 
avoid  any  small  vessels,  it  is  to  be  divided ;  in  like  manner  the  clavicular  origin  is  to  be  divided 
throughout  the  whole  or  greater  part  of  its  attachment.  By  pressing  aside  any  loose  cellular 
tissue  or  vessels  that  may  now  appear  the  Sterno-hyoid  and  Sterno-thyroid  muscles  will  be 
exposed,  and  must  be  divided,  a  director  being  previously  passed  beneath  them.  The  inferior 
thyroid  veins  may  come  into  view,  and  must  be  carefully  drawn,  either  upward  or  downward,  by 
means  of  a  blunt  hook,  or  tied  with  double  ligatures  and  divided.  After  tearing  through  a 
strong  fibro-cellular  lamina,  the  right  carotid  is  brought  into  view,  and,  being  traced  downward, 
the  arteria  innominata  is  arrived  at.  The  left  innominate  vein  should  now  be  depressed;  the 
right  innominate  vein,  the  internal  jugular  vein,  and  the  pneumogastric  nerve  drawn  to  the  right 
side;  and  a  curved  aneurism  needle  may  then  be  passed  around  the  vessel,  close  to  its  surface, 
and  in  a  direction  from  below  upward  and  inward,  care  being  taken  to  avoid  the  right  pleural 
sac,  the  trachea,  and  cardiac  nerves.  The  ligature  should  be  applied  to  the  artery  as  high  as 
possible,  in  order  to  allow  room  between  it  and  the  aorta  for  the  formation  of  the  coagulum. 
The  importance  of  avoiding  the  thyroid  plexus  of  veins  during  the  primary  steps  of  the  opera- 
tion, and  the  pleural  sac  whilst  including  the  vessel  in  the  ligature,  should  be  most  carefully  borne 
in  mind.  After  the  artery  has  been  secured,  the  common  carotid  should  be  tied  about  half  an 
inch  above  its  origin,  and  also  the  thyroidea  ima  if  the  vessel  is  of  any  size.  The  several  muscles 
are  united  by  buried  sutures.  An  easier  and  safer  plan  than  the  above  is  that  employed  by 
Burrell — viz.,  resection  of  the  right  sterno-clavicular  articulation  and  of  the  upper  end  of  the 
sternum. 

ARTERIES  OF  THE  HEAD  AND  NECK. 

The  chief  artery  which  supplies  the  head  and  neck  is  the  common  carotid:  it 
ascends  in  the  neck  and  divides  into  two  branches:  the  External  Carotid,  supply- 
ing the  superficial  parts  of  the  head  and  face  and  the  greater  part  of  the  neck; 
and  the  Internal  Carotid,  supplying  to  a  great  extent  the  parts  within  the  cranial 
cavity. 

THE  COMMON  CAROTID  ARTERY  (A.  CAROTIS  COMMUNIS)  (Figs.  388,  389, 

390,  392). 

The  common  carotid  arteries,  although  occupying  a  nearly  similar  position  in 
the  neck,  differ  in  position,  and,  consequently,  in  their  relation  at  their  origin. 
The  right  common  caxotid  (a.  carotis  communis  dextra)  arises  from  the  innom- 
inate artery,  behind  the  right  sterno-clavicular  articulation.  The  left  common 
caxotid  {a.  carotis  communis  sinistra)  arises  from  the  highest  part  of  the  arch  of 
the  aorta,  and  is,  consequently,  longer,  and  at  its  origin  is  contained  within 
the  thorax.  The  course  and  relations  of  that  portion  of  the  left  carotid  which 
intervenes  between  the  arch  of  the  aorta  and  the  left  sterno-clavicular  articulation 
will  first  be  described.     (See  Figs.  388,  389,  and  390.) 

The  left  carotid  within  the  thorax  ascends  obliquely  outward  from  the  arch  of 
the  aorta  to  the  root  of  the  neck.  In  front,  it  is  separated  from  the  first  piece 
of  the  sternum  by  the  Sterno-hyoid  and  Sterno-thyroid  muscles,  the  leftinnomi- 


596  THE   BLOOD -VASCULAR    SYSTEM 

nate  vein,  and  the  remains  of  the  thymus  gland;  behind,  it  Hes  on  the  trachea, 
oesophagus,  thoracic  duct,  and  the  left  recurrent  laryngeal  nerve.  Internally,  it 
is  in  relation  with  the  innominate  artery,  inferior  thyroid  veins  and  remains  of  the 
thymus  gland;  externally,  with  the  left  pneumogastric  nerve,  left  pleura,  and  left 
lung.    The  left  subclavian  artery  is  posterior  and  slightly  external  to  it. 

Plan  of  the  Relations  of  the  Left  Common  Carotid. 
Thoracic  Portion. 

In  front. 
Sternum. 

Sterno-hyoid  and  Sternothyroid  muscles. 
Left  innominate  vein. 
Remains  of  the  thymus  gland. 

Internally.  /Lft  c  \  Externally. 

Innominate  artery.  /      Caroua.       |  Left  pneumogastric  nerve. 

Inferior  thyroid  veins.  I      pui-Uoq^     I  Left  pleura  and  lung. 

Remains  of  the  thymus  gland.  V  y  Left  subclavian  artery. 

Behind. 
Trachea. 
(Esophagus. 
Thoracic  duct. 
Left  recurrent  laryngeal  nerve. 

In  the  neck  the  two  common  carotids  resemble  each  other  so  closely  that  one 
description  will  apply  to  both.  Each  vessel  passes  obliquely  upward  from  behind 
the  sterno-clavicular  articulation  to  a  level  with  the  upper  border  of  the  thyroid 
cartilage,  opposite  the  fourth  cervical  vertebra,  where  it  divides  into  the  external 
and  internal  carotid ;  these  names  being  derived  from  the  distribution  of  the  arteries 
to  the  external  parts  of  the  head  and  face  and  to  the  internal  parts  of  the  cranium 
and  orbit  respectively. 

At  the  lower  part  of  the  neck  the  two  common  carotid  arteries  are  separated 
from  each  other  by  a  small  interval,  which  contains  the  trachea;  but  at  the  upper 
part,  the  thyroid  body,  the  larynx  and  pharynx  project  forward  between  the 
two  vessels,  and  give  the  appearance  of  their  being  placed  farther  back  in  this 
situation.  The  common  carotid  artery  is  contained  in  a  sheath  derived  from  the 
deep  cervical  fascia,  which  also  encloses  the  internal  jugular  vein  and  pneumo- 
gastric nerve,  the  vein  lying  on  the  outer  side  of  the  artery,  and  the  nerve  between 
the  artery  and  vein,  on  a  plane  posterior  to  both.  On  opening  the  sheath  these 
three  structures  are  seen  to  be  separated  from  one  another,  each  being  enclosed  in 
a  separate  fibrous  investment. 

Relations. — At  the  lower  part  of  the  neck  the  common  carotid  artery  is  very 
deeply  seated,  being  covered  by  the  integument,  superficial  fascia,  Platysma,  and 
deep  cervical  fascia,  the  Sterno-mastoid,  Sterno-hyoid,  and  Sterno-thyroid  muscles, 
and  by  the  Omo-hyoid,  opposite  the  cricoid  cartilage;  but  in  the  upper  part  of  its 
course,  near  its  termination,  it  is  more  superficial,  being  covered  merely  by  the 
integument,  the  superficial  fascia,  Platysma,  deep  cervical  fascia,  and  inner  margin 
of  the  Sterno-mastoid,  and,  when  the  latter  is  drawn  backward,  it  is  seen  to  be 
contained  in  a  triangular  space,  bounded  behind  by  the  Sterno-mastoid,  above  by 
the  posterior  belly  of  the  Digastric,  and  below  by  the  anterior  belly  of  the  Omo- 
hyoid. This  part  of  the  artery  is  crossed  obliquely,  from  within  outward,  by  the 
sterno-mastoid  artery;  it  is  crossed  also  by  the  superior  and  middle  thyroid  veins, 
which  terminate  in  the  internal  jugular;  and,  descending  on  its  sheath  in  front,  is 
seen  the  descendens  hypoglossi  nerve,  this  filament  being  joined  by  one  or  two 
branches  from  the  cervical  nerves,  which  cross  the  vessel  from  without  inward. 


THE    COMMON   CAROTID   ARTERY 


597 


Sometimes  the  descendens  hypoglossi  is  contained  within  the  sheath.  The  middle 
thyroid  vein  crosses  the  artery  about  its  middle,  and  the  anterior  jugular  vein  below; 
the  latter,  however,  is  separated  from  the  artery  by  the  Sterno-hyoid  and  Sterno- 
thyroid muscles.  Behind,  the  artery  is  separated  from  the  transverse  processes  of 
the  vertebrae  by  the  Longus  colli  and  Rectus  capitis  anticus  major  muscles,  the 
sympathetic  nerve  being  interposed  between  it  and  the  muscles.    The  recurrent 


Fig.  392. — Surgical  anatomy  of  the  arteries  of  the  neck,  showing  the  carotid  and  subclavian  arteries. 

laryngeal  nerve  and  inferior  thyroid  artery  cross  behind  the  vessel  at  its  lower  part. 
Internally,  it  is  in  relation  with  the  trachea  and  thyroid  gland,  the  latter  overlapping 
it,  the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve  being  interposed: 
higher  up,  with  the  larv^nx  and  pharynx.  On  its  outer  side  are  placed  the  internal 
jugular  vein  and  pneumogastric  nerve.  At  the  lower  part  of  the  neck  the  internal 
jugular  vein  on  the  right  side  diverges  from  the  artery,  but  on  the  left  side  it 


598  THE   BLOOD -VASCULAR   SYSTEM 

approaches  it,  and  often  overlaps  its  lower  part.  This  is  an  important  fact  to  bear 
in  mind  during  the  performance  of  any  operation  on  the  lower  part  of  the  left 
common  carotid  artery.  In  this  region  the  relation  which  the  right  and  left  recur- 
rent laryngeal  nerves  bear  to  the  arteries  is  not  identical.  The  left  recurrent  laryn- 
geal nerve  lies  behind  the  thoracic  portion  of  the  left  common  carotid  artery  and 
internal  to  the  cervical  portion  of  the  vessel.  The  right  nerve  passes  obliquely 
upward  and  inward  behind  the  right  common  carotid  to  reach  its  inner  side. 

Plan  of  the  Relations  of  the  Common  Carotid  Artery. 

In  front. 

Integument  and  superficial  fascia.  Omo-hyoid. 

Deep  cervical  fascia.  Descendens  and  Communicans  hypoglossi 
Platysma.  nerves. 

Sterno-mastoid.  Sterno-mastoid  artery. 

Sterno-hyoid.  Superior  and  middle  thyroid  veins. 

Sterno-thyroid.  Anterior  jugular  vein. 


Externally. 

Internally. 

Internal  jugular  vein. 

^      ^\ 

Trachea. 

Pneumogastric  nerve. 

/               \^ 

Thyroid  gland. 

Common        | 

Recurrent  laryngeal  nerve, 

Carotid.         1 

Inferior  thyroid  artery. 
Larynx. 

V.___^ 

Pharynx. 

Behind. 
Longus  colli.  Sympathetic  nerve. 

Rectus  capitis  anticus  major.  Inferior  thyroid  artery. 

Recurrent  laryngeal  nerve. 

Peculiarities  as  to  Origin. — The  right  common  carotid  may  arise  above  or  below  the  upper 
border  of  the  sterno-clavicular  articulation.  This  variation  occurs  in  one  out  of  about  eight 
cases  and  a  half,  and  the  origin  is  more  frequently  below  than  above;  or  the  artery  may  arise 
as  a  separate  branch  from  the  arch  of  the  aorta  or  in  conjunction  with  the  left  carotid.  The 
left  common  carotid  varies  more  frequently  in  its  origin  than  the  right.  In  the  majority  of  abnor- 
mal cases  it  arises  with  the  innominate  artery,  or,  if  the  innominate  artery  is  absent,  the  two 
carotids  arise  usually  by  a  single  trunk.  It  rarely  joins  with  the  left  subclavian,  except  in  cases 
of  transposition  of  the  arch. 

Peculiarities  as  to  Point  of  Division. — The  most  important  peculiarities  of  this  vessel,  in 
a  surgical  point  of  view,  relate  to  its  place  of  division  in  the  neck.  In  the  majority  of  abnormal 
cases  this  occurs  higher  than  usual,  the  artery  dividing  into  two  branches  opposite  the  hyoid 
bone,  or  even  higher;  more  rarely  it  occurs  below,  opposite  the  middle  of  the  larynx  or  the  lower 
border  of  the  cricoid  cartilage;  and  one  case  is  related  by  Morgagni  where  the  common  carotid, 
only  an  inch  and  a  half  in  length,  divided  at  the  root  of  the  neck.  Very  rarely  the  common 
carotid  ascends  in  the  neck  without  any  subdivision,  the  internal  carotid  being  wanting;  and 
in  a  few  cases  the  common  carotid  has  been  found  to  be  absent,  the  external  and  internal  carotids 
arising  directly  from  the  arch  of  the  aorta.  This  peculiarity  existed  on  both  sides  in  some  instances, 
on  one  side  in  others. 

Occasional  Branches. — The  common  carotid  usually  gives  off  no  branch  previous  to  its 
bifurcation;  but  it  occasionally  gives  origin  to  the  superior  thyroid  or  its  laryngeal  branch,  the 
ascending  pharyngeal,  the  inferior  thyroid,  or,  more  rarely,  the  vertebral  artery. 

Surface  Marking. — The  carotid  arteries  are  covered  throughout  their  entire  extent  by  the 
Sterno-mastoid  muscle,  but  their  course  does  not  correspond  to  the  anterior  border  of  the  muscle, 
which  passes  in  a  somewhat  curved  direction  from  the  mastoid  process  to  the  sterno-clavicular 
joint.  The  course  of  the  artery  is  indicated  more  exactly  by  a  line  drawn  from  the  sternal  end 
of  the  clavicle  below,  to  a  point  midway  between  the  angle  of  the  jaw  and  the  mastoid  process 
above.  That  portion  of  the  line  below  the  level  of  the  upper  border  of  the  thyroid  cartilage 
would  represent  the  course  of  the  vessel. 

Surgical  Anatomy. — The  operation  of  tying  the  common  carotid  artery  may  be  necessary 
in  a  case  of  wound  of  that  vessel  or  its  branches,  in  aneurism,  or  in  a  case  of  pulsating  tumor  of 
the  orbit  or  skull.  If  the  wound  involves  the  trunk  of  the  common  carotid,  it  will  be  necessary 
to  tie  the  artery  through  the  wound  above  and  below  the  wounded  part.  If  the  wound  is  too  small 
to  admit  of  safe  and  rapid  work  it  must  be  enlarged.     In  cases  of  aneurism,  or  where  one  of 


THE    COMMON   CAROTID    ARTERY  599 

the  branches  of  the  common  carotid  is  wounded  in  an  inaccessible  situation,  it  may  be  judged 
necessary  to  tie  the  trunk.  In  such  cases  the  whole  of  the  artery  is  accessible,  and  any  part  may 
be  tied  except  close  to  either  end.  When  the  case  is  such  as  to  allow  of  a  choice  being  made, 
the  lower  part  of  the  carotid  should  never  be  selected  as  the  spot  upon  which  to  place  a  ligature, 
for  not  only  is  the  artery  in  this  situation  placed  very  deeply  in  the  neck,  but  it  is  covered  by 
three  layers  of  muscles,  and,  on  the  left  side,  in  the  great  majority  of  cases,  the  internal  jugular 
vein  passes  obliquely  in  front  of  it.  Neither  should  the  upper  end  be  selected,  for  here  the 
superior  thyroid  vein  and  its  tributaries  would  give  rise  to  very  considerable  difficulty  in  the  appli- 
cation of  a  ligature.  The  point  most  favorable  for  the  operation  is  that  part  of  the  vessel  which 
is  at  the  level  of  the  cricoid  cartilage.  It  occasionally  happens  that  the  carotid  artery  bifurcates 
below  its  usual  position:  if  the  artery  be  exposed  at  its  point  of  bifurcation,  both  divisions  of 
the  vessel  should  be  tied  near  their  origin,  in  preference  to  tying  the  trunk  of  the  artery  near  its 
termination;  and  if,  in  consequence  of  the  entire  absence  of  the  common  carotid  or  from  its 
early  division,  two  arteries,  the  external  and  internal  carotids,  are  met  with,  the  ligature  should 
be  placed  on  that  vessel  which  is  found  on  compression  to  be  connected  with  the  disease. 

Ligation  of  the  Caxotid  at  the  Level  of  the  Cricoid  Cartilage  {Ligation  in  the  Triangle  of 
Election). — The  triangle  of  election  is  bounded  jxisteriorly  by  the  anterior  edge  of  the  sterno- 
cleido-mastoid;  is  bounded  above  by  the  posterior  belly  of  the  digastric;  is  bounded  below  by  the 
anterior  belly  of  the  omohyoid.  In  this  operation  the  direction  of  the  vessel  and  the  inner 
margin  of  the  Sterno-mastoid  are  the  chief  guides  to  its  performance.  The  patient  should  be 
placed  on  his  back  with  the  head  thrown  back  and  turned  slightly  to  the  opposite  side:  an 
incision  is  to  be  made,  three  inches  long,  in  the  direction  of  the  anterior  border  of  the  Sterno- 
mastoid,  so  that  the  centre  corresponds  to  the  level  of  the  cricoid  cartilage;  after  dividing  the 
integument,  superficial  fascia,  and  Platysma,  the  deep  fascia  must  be  cut  through  on  a  director, 
so  as  to  avoid  wounding  numerous  small  veins  that  are  usually  found  beneath.  The  head 
may  now  be  brought  forward  so  as  to  relax  the  parts  somewhat,  and  the  margins  of  the  wound 
are  held  asunder  by  retractors.  The  descendens  hypoglossi  nerve  may  now  be  exposed,  and  must 
be  avoided,  and,  the  sheath  of  the  vessel  having  been  raised  by  forceps,  is  to  be  opened  to  a  small 
•extent  over  the  artery  at  its  inner  side.  The  internal  jugular  vein  may  present  itself  alternately 
•distended  and  relaxed ;  this  should  be  compressed  both  above  and  below,  and  drawn  outward, 
in  order  to  facilitate  the  operation.  The  aneurism  needle  is  passed  from  the  outside,  care 
being  taken  to  keep  the  needle  in  close  contact  with  the  artery,  and  thus  avoid  the  risk  of 
injuring  the  internal  jugular  vein  or  including  the  vagus  nerve.  Before  the  ligature  is  tied  it 
should  be  ascertained  that  nothing  but  the  artery  is  included  in  it. 

Ligation  of  the  Common  Carotid  at  the  Lower  Part  of  the  Neck  {Ligation  in  the  Triangle 
■of  Necessity). — The  triangle  of  necessity  is  bounded  above  by  the  anterior  belly  of  the  omo- 
hyoid; is  bounded  behind  by  the  anterior  margin  of  the  sterno-cleido-mastoid ;  is  bounded 
in  front  by  the  mid-lme  of  the  neck.  This  operation  is  sometimes  required  in  cases  of 
aneurism  of  the  upper  part  of  the  carotid,  especially  if  the  sac  is  of  large  size.  It  is  best 
performed  by  dividing  the  sternal  origin  of  the  Sterno-mastoid  muscle,  but  may  be  done 
m  some  cases,  if  the  aneurism  is  not  of  very  large  size,  by  an  incision  along  the  anterior 
border  of  the  Sterno-mastoid,  extendmg  down  to  the  sterno-clavicular  articulation,  and  by 
then  retractmg  the  muscle.  The  easiest  and  best  plan,  however,  is  to  make  an  incision  two 
•or  three  inches  long  down  the  lower  part  of  the  anterior  border  of  the  Sterno-mastoid  muscle 
to  the  sterno-clavicular  joint,  and  a  second  incision,  starting  from  the  termination  of  the  first, 
along  the  upper  border  of  the  clavicle  for  about  two  inches.  This  incision  is  made  through  the 
superficial  and  deep  fascia,  and  the  sternal  origin  of  the  muscle  is  exposed.  This  is  to  be  divided 
on  a  director,  and  turned  up,  with  the  superficial  structures,  as  a  triangular  flap.  Some  loose 
connective  tissue  is  to  be  divided  or  torn  through,  and  the  outer  border  of  the  Sterno-hyoid 
muscle  exposed.  In  doing  this  care  must  be  taken  not  to  wound  the  anterior  jugular  vein,  which 
•crosses  the  muscle  to  reach  the  external  jugular  or  subclavian  vein.  The  Sterno-hyoid,  and  with 
it  the  Stern o-thyroid,  are  to  be  drawn  inward  by  means  of  a  retractor,  and  the  sheath  of  the 
vessel  is  exposed.  This  must  be  opened  with  great  care  on  its  inner  or  tracheal  side,  so  as  to 
avoid  the  internal  jugular  vein.  This  is  especially  necessary  on  the  left  side,  where  the  artery 
is  commonly  overlapped  by  the  vein.  On  the  right  side  there  is  usually  an  interval  between  the 
artery  and  the  vein,  and  not  the  same  risk  of  woundmg  the  latter. 

The  common  carotid  artery,  being  a  long  vessel  without  any  branches,  is  particularly  suitable 
for  the  performance  of  Brasdor's  operation  for  the  cure  of  an  aneurism  of  the  lower  part  of  the 
vessel.  Brasdor's  procedure  consists  in  ligaturing  the  artery  on  the  distal  side  of  the  aneurism, 
and  in  the  case  of  the  common  carotid  there  are  no  branches  given  off  from  the  vessel  between 
the  aneurism  and  the  site  of  the  ligature;  hence  the  flow  of  blood  through  the  sac  of  the  aneurism 
is  diminished  and  cure  takes  place  in  the  usual  way,  by  the  deposit  of  laminated  fibrin. 

Collateral  Circulation. — After  ligature  of  the  common  carotid  the  collateral  circulation 
can  be  perfectly  established,  by  the  free  communication  which  exists  between  the  carotid  arteries 
of  opposite  sides,  both  without  and  within  the  cranium,  and  by  enlargement  of  the  branches  of 
the  subclavian  artery  on  the  side  corresponding  to  that  on  which  the  vessel  has  been  tied — the 


600  THE  BLOOD -VASCULAR    SYSTEM 

chief  communication  outside  the  skull  taking  place  between  the  superior  thyroid  from  the 
external  carotid  and  the  inferior  thyroid  from  the  subclavian,  the  profunda  cervicis  from  the 
subclavian  and  the  superior  intercostal  with  the  arteria  princeps  cervicis  of  the  occipital; 
the  vertebral  taking  the  place  of  the  internal  carotid  within  the  cranium. 

Sir  A.  Cooper  had  an  opportunity  of  dissecting,  thirteen  years  after  the  operation,  the  case 
in  which  he  first  successfully  tied  the  common  carotid  (the  second  case  in  which  he  performed 
the  operation).^  The  injection,  however,  does  not  seem  to  have  been  a  successful  one.  It  showed 
merely  that  the  arteries  at  the  base  of  the  brain  (circle  of  Willis)  were  much  enlarged  on  the 
side  of  the  tied  artery,  and  that  the  anastomosis  between  the  branches  of  the  external  carotid  on 
the  affected  side  and  those  of  the  same  artery  on  the  sound  side  was  free,  so  that  the  external 
carotid  was  pervious  throughout. 

The  Intercarotid  Body  {carotid  gland,  retrocarotid  corpuscle)  (see  the  Ductless 
Glands). 

The  External  Carotid  Artery  (A.  Carotis  Externa)  (Figs.  392,  393,  394). 

The  external  carotid  artery  commences  opposite  the  upper  border  of  the  thyroid 
cartilage,  and,  taking  a  slightly  curved  course,  passes  upward  and  forward,  and 
then  inclines  backward  to  the  space  between  the  neck  of  the  condyle  of  the  lower 
jaw  and  the  external  meatus,  where  it  divides  into  the  superficial  temporal  and 
internal  maxillary  arteries.  It  rapidly  diminishes  in  size  in  its  course  up  the 
neck,  owing  to  the  number  and  large  size  of  the  branches  given  off  from  it.  In 
the  child  it  is  somewhat  smaller  than  the  internal  carotid,  but  in  the  adult  the 
two  vessels  are  of  nearly  equal  size.  At  its  commencement  this  artery  is  more 
superficial,  and  placed  nearer  the  middle  line  than  the  internal  carotid,  and  is 
contained  in  the  triangular  space  bounded  by  the  Sterno-mastoid  behind,  the 
anterior  belly  of  the  Omo-hyoid  below,  and  the  posterior  belly  of  the  Digastric 
and  the  Stylo-hyoid  above.. 

Relations. — It  is  covered  by  the  skin,  superficial  fascia,  Platysma,  deep  fascia 
and  anterior  margin  of  the  Sterno-mastoid,  and  is  crossed  by  the  hypoglossal  nerve, 
and  by  the  lingual  and  facial  veins;  it  is  afterward  crossed  by  the  Digastric  and 
Stylo-hyoid  muscles,  and  higher  up  passes  deeply  into  the  substance  of  the  parotid 
gland,  where  it  lies  beneath  the  facial  nerve  and  the  junction  of  the  temporal  and 
internal  maxillary  veins.  Internally  is  the  hyoid  bone,  wall  of  the  pharynx,  the 
superior  laryngeal  nerve,  and  the  ramus  of  the  jaw,  from  which  it  is  separated  by 
a  portion  of  the  parotid  gland.  Externally,  in  the  lower  part  of  its  course,  is  the 
internal  carotid  artery.  Behind  it,  near  its  origin,  is  the  superior  laryngeal  nerve; 
and  higher  up,  it  is  separated  from  the  internal  carotid  by  the  Stylo-glossus  and 
Stylo-pharyngeus  muscles,  the  glosso-pharyngeal  nerve,  and  part  of  the  parotid 
gland. 

Plan  of  the  Relations  of  the  External  Carotid. 

In  front. 
Skin,  superficial  fascia. 
Platysma  and  deep  fascia. 
Anterior  border  of  Sterno-mastoid. 
Hypoglossal  nerve. 
Lingual  and  facial  veins. 
Digastric  and  Stylo-hyoid  muscles. 

Parotid  gland  with  facial  nerve  and    temporo-maxillary  vein 
in  its  substance. 


IntemcUly. 

X N 

Externally. 

Hyoid  bone. 

X          \ 

Internal  carotid  artery, 

Pharynx. 

/      External     \ 

Superior  laryngeal  nerve. 

1       Carotid.       1 

Parotid  gland. 

\                      / 

Ramus  of  jaw. 

^- -^ 

*  Guy's  Hospital  Reports,  i.,  56. 


THE  EXTERNAL    CAROTID   ARTERY  601 

Behind. 
Superior  laryngeal  nerve. 
Stylo-glossus. 
Stylo-pharyngeus. 
Glosso-pharyngeal  nerve. 
Parotid  gland. 

Surface  Maxkicg. — The  position  of  the  external  carotid  artery  may  be  marked  out  with 
sufficient  accuracy  by  a  line  drawn  from  the  front  of  the  meatus  of  the  external  ear  to  the  side 
of  the  cricoid  cartilage,  slightly  arching  the  line  forward. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  external  carotid  may  be  required 
in  case  of  wounds  of  this  vessel,  or  of  its  branches  when  these  cannot  be  tied,  and  in  some  cases 
of  pulsating  tumor  of  the  scalp  or  face.  The  operation  has  not  received  the  attention  which  it 
deserves,  owing  to  the  fear  which  surgeons  have  entertained  of  secondary  hemorrhage,  on  account 
of  the  number  of  branches  given  off  from  the  vessel.  This  fear,  however,  has  been  shown  by 
Mr.  Cripps  not  to  be  well  founded. >  Ligation  is  often  very  useful  as  a  means  of  prevent- 
ing excessive  hemorrhage  in  operations  about  the  face,  jaws,  and  mouth.  It  is  sometimes 
employed  with  the  hope  of  lessening  the  growth  of  tumors  by  cutting  off  the  blood  supply,  but 
ligation  is  useless  for  this  purpose.  Ligation  of  one  external  carotid  artery  arrests  the  circu- 
lation for  only  a  brief  period,  and  within  a  very  few  days  the  circulation  is  practically  freely 
re-established.  This  result  is  seen  to  be  inevitable  when  we  recall  the  numerous  branches  of  the 
external  carotid,  their  free  anastomoses,  and  the  fact  that  a  very  great  number  of  extremely  minute 
vessels  in  the  middle  line  join  the  external  carotid  system  of  one  side  to  that  of  the  other  side. 
Robert  H.  M.  Dawbarn  points  out  that  ligation  of  both  external  carotids  produces  only  temporary 
anaemia,  for  "inside  of  a  week  or  ten  days  thereafter  the  pulse  can  again  be  felt  in  the  temporals  and 
facials  upon  both  sides."^  Dawbarn  points  out  that  even  after  excision  of  the  external  carotids, 
with  separate  ligation  of  each  of  the  eight  branches,  blood  can  still  reach  the  nose,  tongue,  etc., 
from  outside  systems  by  twenty-nine  distinct  routes.  Whereas  ligation  of  even  both  carotids  will 
not  prevent  the  growth  of  a  malignant  tumor,  excision  of  each  external  carotid,  with  separate 
control  of  its  eight  branches,  will  sometimes  prove  of  great  value  in  retarding  the  progress  of  a 
growth.  It  "  starves  "  the  growth  and  may  cause  it  to  shrink  (Dawbarn's  operation).  To  tie  the 
external  carotid  near  its  origin,  below  the  point  where  it  is  crossed  by  the  Digastric,  an  incision 
about  three  inches  in  length  should  be  made  along  the  margin  of  the  Sterno-mastoid,  from  the 
angle  of  the  jaw  to  the  upper  border  of  the  thyroid  cartilage.  The  ligature  should  be  applied 
between  the  lingual  and  superior  thyroid  branches.  To  tie  the  vessel  above  the  Digastric, 
between  it  and  the  parotid  gland,  an  incision  should  be  made,  from  the  lobe  of  the  ear  to  the 
great  cornu  of  the  os  hyoides,  dividing  successfully  the  skin,  Platysma,  and  fascia.  By  drawing 
the  Sterno-mastoid  outward,  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid  muscles  down- 
ward, and  separating  them  from  the  parotid  gland,  the  vessel  will  be  exposed,  and  a  ligature  may 
be  applied  to  it.  The  circulation  is  at  once  re-established  by  the  free  communication  between 
most  of  the  large  branches  of  the  artery  (facial,  lingual,  superior  thyroid,  occipital)  and  the  corre- 
sponding arteries  of  the  opposite  side  and  by  the  anastomosis  of  its  branches  with  those  of  the 
internal  carotid,  and  of  the  occipital  with  the  branches  of  the  subclavian,  etc. 

Branches. — The  external  carotid  artery  gives  oflP  eight  branches,  which,  for 
convenience  of  description,  may  be  divided  into  four  sets.  (See  Fig.  393,  Plan  of 
the  Branches.) 

Anterior.  Posterior.  Ascending.                         Terminal. 

Superior  Thyroid.  Occipital.  Ascending  Phar-  Superficial  Temporal. 

I^iingual.  Posterior  Auric-  yngeal.  Internal  Maxillary. 

Facial.  ular. 

The  student  is  here  reminded  that  many  variations  are  met  with  in  the  number, 
origin,  and  course  of  these  branches  in  different  subjects;  but  the  above  arrange- 
ment is  that  which  is  found  in  the  great  majority  of  cases. 

The  Superior  Th3rroid  Artery  (a.  thyreoidea  superior)  (Figs.  392,  393,  and  3^6) 
is  the  first  branch  given  off  from  the  external  carotid,  being  derived  from  that  vessel 
just  below  the  great  cornu  of  the  hyoid  bone.  At  its  commencement  it  is  quite 
superficial,  being  covered  by  the  integument,  fascia,  and  Platysma,  and  is  contained 

>  Med.-Chir  Trans.,  Ixi.,  229.  *  The  Treatment  of  Certain  Malignant  Growths. 


602  THE   BLOOD -VASCULAR   SYSTEM 

in  the  triangular  space  bounded  by  the  Sterno-mastoid,  Digastric,  and  Omo-hyoid 
muscles.  After  running  upward  and  inward  for  a  short  distance,  it  curves  down- 
ward and  forward,  in  an  arched  and  tortuous  manner,  to  the  upper  part  of  the 
thyroid  gland,  passing  beneath  the  Omo-hyoid,  Sterno-hyoid,  and  Sterno-thyroid 
muscles,  and  supplying  them.  It  distributes  numerous  branches  to  the  upper  part 
of  the  gland,  anastomosing  with  its  fellow  of  the  opposite  side  and  with  the 
inferior  thyroid  arteries.  The  terminal  branches  supplying  the  gland  are  generally 
two  in  number:  one,  the  largest,  the  anterior  branch  {ramus  anterior) ,  descends 
at  the  anterior  border  of  the  lateral  lobe  of  the  gland,  reaches  the  upper  border 
of  the  isthmus,  and  then  passes  in  the  substance  of  the  isthmus  to  the  middle 
line  of  the  neck,  where  it  anastomoses  with  the  corresponding  artery  of  the 
opposite  side :  the  posterior  branch  {ramus  'posterior)  descends  along  the  posterior 
border  of  the  lateral  lobe  of  the  gland,  the  anterior  and  posterior  branches 
anastomose  with  each  other  and  with  branches  of  the  inferior  thyroid,  and  both 
of  them  send  branches  to  the  thyroid  gland  {rami  glandular es) .  Besides  the 
arteries  distributed  to  the  muscles  by  which  it  is  covered  and  to  the  substance 
of  the  gland,  the  branches  of  the  superior  thyroid  are  the  following: 

Hyoid.  Superior  Laryngeal. 

Superficial  Descending  Branch  (Sterno-mastoid).        Crico-thyroid. 

The  Hyoid  or  Infra-hyoid  {ramus  hyoideus)  is  a  small  branch  which  runs  along 
the  lower  border  of  the  os  hyoides  beneath  the  Thyro-hyoid  muscle;  after  sup- 
plying the  muscles  connected  to  that  bone,  it  forms  an  arch,  by  anastomosing 
with  the  vessel  of  the  opposite  side. 

The  Superficial  Descending  or  Sterno-mastoid  Branch  {ramus  sternocleidomas- 
toideus)  runs  downward  and  outward  across  the  sheath  of  the  common  carotid 
artery,  and  supplies  the  Sterno-mastoid  and  neighboring  muscles  and  integument. 
There  is  frequently  a  separate  branch  from  the  external  carotid  distributed  to  the 
Sterno-mastoid  muscle. 

The  Superior  Laryngeal  (a.  laryngea  superior),  larger  than  either  of  the  preceding, 
accompanies  the  internal  laryngeal  nerve,  beneath  the  Thyro-hyoid  muscle:  it 
pierces  the  thyro-hyoid  membrane,  and  supplies  the  muscles,  mucous  membrane, 
and  glands  of  the  larynx,  anastomosing  with  the  branch  from  the  opposite 
side. 

The  Crico-thyroid  {ramus  cricothyreoideus)  is  a  small  branch  which  runs  trans- 
versely across  the  crico-thyroid  membrane,  communicating  with  the  artery  of  the 
opposite  side. 

Arteries  of  the  Thyroid  Gland. — The  thyroid  gland  is  supplied  by  the  two 
superior  thyroids  from  the  external  carotid;  the  two  inferior  thyroids  from  the 
subclavian,  and  sometimes  also  by  the  thyreoidea  ima  from  the  innominate. 

The  superior  thyroid  joins  the  gland  at  the  summit  of  the  upper  horn,  passes 
down  the  posterior  surface  of  the  gland  toward  the  inner  surface  of  the  upper  horn, 
comes  forward  to  the  anterior  margin  of  the  inner  surface,  descends  to  the  isthmus, 
and  on  the  superior  border  of  the  isthmus  anastomoses  with  the  artery  from  the 
other  side.  The  superior  thyroid  artery  sends  numerous  branches  across  the 
anterior  surface  of  the  gland. 

The  inferior  thyroid  artery  is  larger  than  the  superior  artery.  It  passes  to 
the  posterior  surface  of  the  gland  and  divides  into  branches.  Some  of  the  branches 
enter  the  hilus;  others  track  across  the  posterior  surface  of  the  gland.  The  inferior 
thyroid  artery  is  close  to  the  recurrent  laryngeal  nerve.  The  artery,  as  a  rule, 
passes  behind-theJiervebief ore  it  divides  into  branches.  It  may  divide  first  and 
then  one  or  two  branches  may  be  in  front  of  the  nerve.  In  unusual  cases  the 
artery  before  division  is  in  front  of  the  nerve,  or  all  the  branches  are  in  front.' 

1  Berry.     Diseases  of  the  Thyroid  Gland. 


THE  EXTERNAL    CAROTID   ARTERY  603 

The  thyreoidea  ima  passes  to  the  lower  portion  of  the  gland.  Berry  points  out 
that  the  thyroid  arteries  communicate  very  freely  with  each  other;  only  the  small 
branches  pass  into  the  interior  of  the  gland;  the  larger  branches  "ramify  on  the 
surface  of  the  gland,  just  beneath  the  capsule."^ 

Surgical  Anatomy. — The  superior  thyroid,  or  one  of  its  branches,  is  often  divided  in  cases 
of  cut  throat,  giving  rise  to  considerable  hemorrhage.  In  such  cases  the  artery  should  be  secured, 
the  woiuid  being  enlarged  for  that  purpose,  if  necessary.  The  operation  may  be  easily  per- 
formed, the  position  of  the  artery  being  very  superficial,  and  the  only  structures  of  importance 
covering  it  being  a  few  small  veins.  The  operation  of  tying  the  superior  thyroid  artery  to  lessen 
the  size  of  a  bronchocele  has  been  performed  in  numerous  instances  with  partial  or  temporary 
success.  When,  however,  the  collateral  circulation  between  this  vessel  and  the  artery  of  the 
opposite  side,  and  the  inferior  thyroid,  is  completely  re-established,  the  tumor  usually  regains 
its  former  size,  and  hence  the  operation  has  been  given  up,  especially  as  better  results  are 
obtained  by  other  means.  Both  thyroid  arteries  on  the  same  side,  and  indeed  all  the  four 
thyroid  arteries,  have  been  tied  in  enlarged  thyroid.  The  superior  and  inferior  thyroid  arteries 
of  the  involved  side  are  ligated  before  extirpating  a  goitrous  lobe  of  the  thyroid. 

The  position  of  the  superficial  descending  branch  is  of  importance  in  connection  with  the 
operation  of  ligation  of  the  common  carotid  artery.  It  crosses  and  lies  on  the  sheath  of  this 
vessel,  and  may  chance  to  be  wounded  in  opening  the  sheath.  The  position  of  the  crico-thyroid 
branch  should  be  remembered,  as  it  may  prove  the  source  of  troublesome  hemorrhage  during 
the  operation  of  laryngotomy.  In  performing  the  operation  of  quick  laryngotomy  the  crico- 
thyroid membrane  should  be  incised  transversely  in  order  to  avoid  this  vessel. 

The  Lingual  Artery  (a.  lingualis)  (Figs.  392  and  393)  arises  from  the  external 
carotid  between  the  superior  thyroid  and  facial;  it  first  runs  obliquely  upward 
and  inward  to  the  great  cornu  of  the  hyoid  bone;  it  then  curves  downward  and 
forward,  forming  a  loop  which  is  crossed  by  the  hypoglossal  nerve,  and,  passing 
beneath  the  Digastric  and  Stylo-hyoid  muscles,  it  runs  horizontally  forward, 
beneath  the  Hyo-glossus,  and  finally,  ascending  almost  perpendicularly  to  the 
tongue,  turns  forward  on  its  under  surface  as  far  as  the  tip,  under  the  name  of 
the  ranine  artery. 

Relations. — Its  first,  or  oblique,  portion  is  superficial,  being  contained  in  the 
same  triangular  space  as  the  superior  thyroid  artery,  resting  upon  the  middle  con- 
strictor of  the  pharynx,  and  covered  by  the  Platysma  and  fascia  of  the  neck.  Its 
second,  or  curved,  portion  also  lies  upon  the  middle  constrictor,  being  covered  at 
first  by  the  tendon  of  the  Digastric  and  the  Stylo-hyoid  muscle,  and  afterward  by 
the  Hyo-glossus,  the  latter  muscle  separating  it  from  the  hypoglossal  nerve.  Its 
third,  or  horizontal,  portion  lies  between  the  Hyo-glossus  and  Genio-hyo-glossus 
muscles.  The  fourth,  or  terminal,  part,  under  the  name  of  the  ranine,  runs  along 
the  under  surface  of  the  tongue  to  its  tip:  it  is  very  superficial,  being  covered 
only  by  the  mucous  membrane,  and  rests  on  the  Lingualis  on  the  outer  side  of 
the  Genio-hyo-glossus.  The  hypoglossal  nerve  crosses  the  lingual  artery,  and  then 
becomes  separated  from  it,  in  the  second  part  of  its  course,  by  the  Hyo-glossus 
muscle. 

Branches. — The  branches  of  the  lingual  artery  are — the 

Hyoid.  Sublingual. 

Dorsalis  Linguae.  Ranine. 

The  Hyoid  or  Supra-hyoid  Branch  (ramus  hyoideus)  runs  along  the  upper  border 
of  the  hyoid  bone,  supplying  the  muscles  attached  to  it  and  anastomosing  with 
its  fellow  of  the  opposite  side. 

The  Dorsalis  Linguae  (ramus  dorsalis  linguae)  (Fig.  445)  arises  from  the  lingual 
artery  beneath  the  Hyo-glossus  muscle  (which,  in  the  figure,  has  been  partly  cut 
away,  to  show  the  vessel) ;  it  ascends  to  the  dorsum  of  the  tongue,  and  supplies  the 
mucous  membrane,  the  tonsil,  soft  palate,  and  epiglottis,  anastomosing  with  its 

1  Berry.    Diseases  of  the  Thyroid  Gland 


604  THE  BLOOD -VASCULAR    SYSTEM 

fellow  from  the  opposite  side.  This  artery  is  frequently  represented  by  two  or 
three  small  branches. 

The  Sublingual  (a.  siihlingualis) ,  which  may  be  described  as  a  branch  of  bifur- 
cation of  the  lingual  artery,  arises  at  the  anterior  margin  of  the  Hyo-glossus  muscle, 
and  runs  forward  between  the  Genio-hyo-glossus  and  the  sublingual  gland.  It 
supplies  the  substance  of  the  gland,  giving  branches  to  the  Mylo-hyoid  and 
neighboring  muscles,  the  mucous  membrane  of  the  mouth  and  gums.  One 
branch  runs  behind  the  alveolar  process  of  the  lower  jaw  in  the  substance  of  the 
gum  to  anastomose  with  a  similar  artery  from  the  other  side. 

The  Ranine  or  Deep  Lingual  (a.  profunda  lingua)  may  be  regarded  as  the  other 
branch  of  bifurcation.  It  is  usually  described  as  the  continuation  of  the  lingual 
artery;  it  runs  along  the  under  surface  of  the  tongue,  resting  on  the  Inferior 
lingualis,  and  covered  by  the  mucous  membrane  of  the  mouth;  it  lies  on  the  outer 
side  of  the  Genio-hyo-glossus,  accompanied  by  the  lingual  nerve.  On  arriving 
at  the  tip  of  the  tongue  it  is  said  to  anastomose  with  the  artery  of  the  opposite 
side,  but  this  is  denied  by  Hyrtl.  These  vessels  in  the  mouth  are  placed  one  on 
each  side  of  the  frtenum. 

Surgical  Anatomy. — The  lingual  artery  may  be  divided  near  its  origin  in  cases  of  cut  throat, 
a  complication  that  not  unfrequently  happens  in  this  class  of  wounds;  or  severe  hemorrhage 
which  cannot  be  restrained  by  ordinary  means  may  ensue  from  a  wound  or  deep  ulcer  of  the 
tongue.  In  the  former  case  the  primary  wound  may  be  enlarged  if  necessary,  and  the  bleeding 
vessels  secured.  In  the  latter  case  it  has  been  suggested  that  the  lingual  artery  should  be  tied 
near  its  origin.  Ligature  of  the  lingual  artery  is  also  occasionally  practised,  as  a  paUiative  measure, 
in  cases  of  cancer  of  the  tongue,  in  order  to  check  the  progress  of  the  disease  by  starving  the 
growth,  and  it  is  sometimes  tied  as  a  preliminary  measure  to  removal  of  the  tongue.  The  operation 
is  a  somewhat  difficult  one,  on  account  of  the  depth  of  the  artery,  the  number  of  important 
structures  by  which  it  is  surrounded,  the  loose  and  yielding  nature  of  the  parts  upon  which  it  is 
supported,  and  its  occasional  irregularity  of  origin.  An  incision  is  to  be  made  in  a  curved  direc- 
tion from  a  point  one  finger's  breadth  external  to  the  symphysis  of  the  jaw  downward  to  the 
cornu  of  the  hyoid  bone,  and  then  upward  to  near  the  angle  of  the  jaw.  Care  must  be  taken  not 
to  carry  this  incision  too  far  backward,  for  fear  of  endangering  the  facial  vein.  In  the  first 
incision  the  skin,  superficial  fascia,  and  Platysma  will  be  divided,  and  the  deep  fascia  exposed. 
The  deep  fascia  is  then  to  be  incised  and  the  submaxillary  gland  exposed  and  pulled  upward  by 
retractors.  A  triangular  space  is  now  exposed.  Leaser's  triangle,  bounded  internally  by  the  pos- 
terior border  of  the  Mylo-hyoid  muscle:  below  and  externally,  by  the  tendon  of  the  Digastric; 
and  above,  by  the  hypoglossal  nerve.  The  floor  of  the  space  is  formed  by  the  Hyo-glossus  muscle, 
beneath  which  the  artery  lies.  The  fibres  of  this  muscle  are  now  to  be  cut  through  horizontally 
and  the  vessel  exposed,  care  being  taken,  while  near  the  vessel,  not  to  open  the  pharynx. 

Troublesome  hemorrhage  may  occur  in  the  division  of  the  franum  in  children  if  the  ranine 
arteries,  which  lie  on  each  side  of  it,  are  wounded.  The  student  should  remember  that  the  opera- 
tion is  always  to  be  performed  with  a  pair  of  blunt-pointed  scissors,  and  the  mucous  membrane 
only  is  to  be  divided  by  a  very  superficial  cut,  which  cannot  endanger  any  vessel.  The  scissors, 
also,  should  be  directed  away  from  the  tongue.  Any  further  liberation  of  the  tongue  which  may 
be  necessary  can  be  effected  by  tearing. 

The  Facial  or  External  Maxillary  Artery  (a.  maxillaris  externa)  (Figs.  392, 
393,  394,  and  395)  arises  a  little  above  the  lingual,  and  passes  obliquely  upward, 
beneath  the  Digastric  and  Stylo-hyoid  muscles,  and  frequently  beneath  the  hypo- 
glossal nerve;  it  now  runs  forward  under  cover  of  the  body  of  the  lower  jaw,  lodged 
in  a  groove  on  the  posterior  surface  of  the  submaxillary  gland ;  this  may  be  called 
the  cervical  part  of  the  artery.  It  then  curves  upward  over  the  body  of  the  jaw 
at  the  anterior  inferior  angle  of  the  Masseter  muscle;  passes  forward  and  upward 
across  the  cheek  to  the  angle  of  the  mouth,  then  upward  along  the  side  of  the  nose, 
and  terminates  at  the  inner  canthus  of  the  eye,  under  the  name  of  the  angular  artery 
(a.  angularis).  The  facial  artery,  both  in  the  neck  and  on  the  face,  is  remarkably 
tortuous :  in  the  former  situation  its  tortuosity  enables  it  to  accommodate  itself  to 
the  movements  of  the  pharynx  in  deglutition,  and  in  the  latter  to  the  movements, 
of  the  jaw  and  the  lips  and  cheeks. 


THE   EXTERNAL    CAROTID    ARTERY 


605 


Relations. — In  the  neck  its  origin  is  superficial,  being  covered  by  the  integu- 
ment, Platysma,  and  fascia;  it  then  passes  beneath  the  Digastric  and  Stylo-hyoid 
muscles  and  part  of  the  submaxillary  gland.  It  lies  upon  the  middle  constrictor 
of  the  pharynx,  and  is  separated  from  the  Stylo-glossus  and  Hyo-glossus  muscles 
by  a  portion  of  the  submaxillary  gland.  On  the  face,  where  it  passes  over  the 
body  of  the  lower  jaw,  it  is  comparatively  superficial,  lying  immediately  beneath 
the  Platysma.  In  this  situation  its  pulsation  may  be  distinctly  felt,  and  compres- 
sion of  the  vessel  against  the  bone  can  be  effectually  made.  In  its  course  over  the 
face  it  is  covered  by  the  integument,  the  fat  of  the  cheek,  and,  near  the  angle  of  the 


A  rteria  septi  nast. 
iiperior  coronary. 


Inferior  coronary. 
Inferior  IcMal. 


Fig.  394. — The  arteries  of  the  face  and  scalp.* 

mouth,  by  the  Platysma,  Risorius,  and  Zygomatic  muscles.  It  rests  on  the  Bucci- 
nator, the  Levator  anguli  oris,  and  the  I^evator  labii  superioris  (sometimes  piercing 
or  else  passing  under  this  last  muscle).  The  facial  vein  lies  to  the  outer  side  of 
the  artery,  and  takes  a  more  direct  course  across  the  face,  where  it  is  separated 
from  the  artery  by  a  considerable  interval.  In  the  neck  it  lies  superficial  to  the 
artery.  The  branches  of  the  facial  nerve  cross  the  artery,  and  branches  of  the 
infraorbital  nerve  lie  beneath  it. 

Branches. — The  branches  of  this  vessel  may  be  divided  into  two  sets:  those 
^iven  off  below  the  jaw  (cervical),  and  those  on  the  face  (facial). 


*  The  muscular  tissue  of  the  lips  must  be  supposed  to  have  been  cut  away,  in  order  to  show  the  course  of  the 
■coronary  arteries 


606  THE   BLOOD -VASCULAR    SYSTEM 

Cervical  Branches.  Facial  Branches, 

Inferior  or  Ascending  Palatine.  Muscular. 

Tonsillar.  Inferior  Labial. 

Submaxillary.  Inferior  Coronary. 

Submental.  Superior  Coronary. 

Muscular.  Lateral  Nasal. 

Angular. 

The  Inferior  or  Ascending  Palatine  (a.  'palatine  ascendens)  passes  up  between 
the  Stylo-glossus  and  Stylo-pharyngeus  to  the  outer  side  of  the  pharynx,  along 
which  it  is  continued  between  the  Superior  constrictor  and  the  Internal  ptery- 
goid to  near  the  base  of  the  skull.  It  supplies  the  neighboring  muscles,  the 
tonsil,  and  Eustachian  tube,  and  divides,  near  the  Levator  palati,  into  two 
branches:  one  follows  the  course  of  the  Levator  palati,  and,  winding  over  the 
upper  border  of  the  Superior  constrictor,  supplies  the  soft  palate  and  the  palatine 
glands,  anastomosing  with  its  fellow  of  the  opposite  side  and  with  the  posterior 
palatine  branch  of  the  internal  maxillary  artery;  the  other  pierces  the  Superior 
constrictor  and  supplies  the  tonsil,  anastomosing  with  the  tonsillar  and  ascending 
pharyngeal  arteries. 

The  Tonsillar  (ramus  tonsillaris)  passes  up  between  the  Internal  pterygoid 
and  Stylo-glossus,  and  then  ascends  along  the  side  of  the  pharynx,  perforating 
the  Superior  constrictor,  to  ramify  in  the  substance  of  the  tonsil  and  root  of  the 
tongue. 


Fig.  395. — The  coronary  arteries,  the  glands  of  the  lips,  and  the  nerves  of  the  right  side  seen  from  the 
posterior  surface  after  removal  of  the  mucous  membrane.      (Poirier  and  Charpy.) 

The  Submaxillary  or  Glandular  Branches  (rami  glandulares)  consist  of  three  oi 
four  large  vessels,  which  supply  the  submaxillary  gland,  some  being  prolonged  to 
the  neighboring  muscles,  lymphatic  glands,  and  integument. 

The  Submental  (a.  submentalis)  (Fig.  392),  the  largest  of  the  cervical  branches, 
is  given  off  from  the  facial  artery  just  as  that  vessel  quits  the  submaxillary  gland : 
it  runs  forward  upon  the  Mylo-hyoid  muscle,  just  below  the  body  of  the  "jaw  and 
beneath  the  Digastric;  after  supplying  the  surrounding  muscles,  and  anastomosing 
with  the  sublingual  artery  by  branches  which  perforate  the  TVlylo-hyoid  muscle,  it 
arrives  at  the  symphysis  of  the  chin,  where  it  turns  over  the  border  of  the  jaw  and 
divides  into  a  superficial  and  a  deep  branch;  the  former  passes  between  the  integu- 
ment and  Depressor  labii  inferioris,  supplies  both,  and  anastomoses  with  the 
inferior  labial.  The  deep  branch  passes  between  the  latter  muscle  and  the  bone, 
supplies  the  lip,  and  anastomoses  with  the  inferior  labial  and  mental  arteries. 

The  Muscular  Branches  are  distributed  to  the  Internal  pterygoid  and  Stylo- 
hyoid in  the  neck,  and  to  the  Masseter  and  Buccinator  on  the  face. 


THE   EXTERNAL    CAROTID    ARTERY  607 

The  Inferior  Labial  (a.  labialis  inferior)  (Fig.  394)  passes  beneath  the  Depressor 
anguH  oris,  to  supply  the  muscles  and  integument  of  the  chin  and  lower  lip,  anas- 
tomosing with  the  inferior  coronary  and  submental  branches  of  the  facial,  and  with 
the  mental  branch  of  the  inferior  dental  artery. 

The  Inferior  Coronary  (Figs.  394  and  395)  is  derived  from  the  facial  artery,  near 
the  angle  of  the  mouth :  it  passes  upward  and  inward  beneath  the  depressor  anguli 
oris,  and,  penetrating  the  Orbicularis  oris  muscle,  runs  in  a  tortuous  course  along 
the  edge  of  the  lower  lip  between  this  muscle  and  the  mucous  membrane,  inoscu- 
lating with  the  artery  of  the  opposite  side.  This  artery  supplies  the  labial  glands, 
the  mucous  membrane,  and  muscles  of  the  lower  lip,  and  anastomoses  with  the 
inferior  labial  from  the  facial  and  the  mental  branch  of  the  inferior  dental  artery. 

The  Superior  Coronary  (a.  labialis  superior)  (Figs.  394  and  395)  is  larger  and  more 
tortuous  in  its  course  than  the  preceding.  It  follows  the  same  course  along  the 
edge  of  the  upper  lip,  lying  between  the  mucous  membrane  and  the  Orbicularis 
oris,  and  anastomoses  with  the  artery  of  the  opposite  side.  It  supplies  the  textures 
of  the  upper  lip,  and  gives  off  in  its  course  two  or  three  vessels  which  ascend  to  the 
nose.  One,  named  the  inferior  artery  of  the  septum,  ramifies  on  the  septum  of  the 
nostrils  as  far  as  the  point  of  the  nose,  and  there  anastomoses  with  the  naso- 
palatine artery;  another,  the  artery  of  the  ala,  supplies  the  ala  of  the  nose. 

The  Lateralis  Nasi  is  derived  from  the  facial,  as  that  vessel  is  ascending  along 
the  side  of  the  nose;  it  supplies  the  ala  and  dorsum  of  the  nose,  anastomosing 
with  its  fellow,  the  nasal  branch  of  the  ophthalmic,  the  inferior  artery  of  the  sep- 
tum, the  artery  of  the  ala,  and  the  infraorbital. 

The  Angular  Artery  (a.  angularis)  is  the  termination  of  the  trunk  of  the  facial; 
it  ascends  to  the  inner  angle  of  the  orbit,  embedded  in  the  fibres  of  the  Levator 
labii  superioris  ahieque  nasi,  and  accompanied  by  a  large  vein,  the  angular  vein; 
it  distributes  some  branches  on  the  cheek  which  anastomose  with  the  infraorbital. 
After  supplying  the  lachrymal  sac  and  Orbicularis  palpebrarum  muscle,  the 
angular  artery  terminates  by  anastomosing  with  the  nasal  branch  of  the  oph- 
thalmic artery. 

The  anastomoses  of  the  facial  artery  are  very  numerous,  not  only  with  the 
vessel  of  the  opposite  side,  but,  in  the  neck,  with  the  sublingual  branch  of  the 
lingual;  with  the  ascending  pharyngeal;  and  with  the  posterior  palatine,  a  branch  of 
the  internal  maxillary,  by  its  inferior  or  ascending  palatine  and  tonsillar  branches ; 
on  the  face,  with  the  mental  branch  of  the  inferior  dental  as  it  emerges  from  the 
mental  foramen,  with  the  transverse  facial,  a  branch  of  the  temporal;  with  the 
infraorbital,  a  branch  of  the  internal  maxillary,  and  with  the  nasal  branch  of 
the  ophthalmic. 

Peculiarities. — The  facial  artery  not  unfrequently  arises  by  a  common  trunk  with  the  lingual. 
This  vessel  is  also  subject  to  some  variations  in  its  size  and  in  the  extent  to  which  it  supplies 
the  face.  It  occasionally  terminates  as  the  submental,  and  not  unfrequently  supplies  the  face 
only  as  high  as  the  angle  of  the  mouth  or  nose.  The  deficiency  is  then  supplied  by  enlargement 
of  one  of  the  neighboring  arteries. 

Surgical  Anatomy. — The  passage  of  the  facial  artery  over  the  body  of  the  jaw  would  appear 
to  afford  a  favorable  position  for  the  application  of  pressure  in  case  of  hemorrhage  from  the 
lips,  the  result  either  of  an  accidental  wound  or  during  an  operation ;  but  its  application  is  useless, 
except  for  a  very  short  time,  on  account  of  the  free  communication  of  this  vessel  with  its  fellow 
and  with  numerous  branches  from  different  sources.  In  a  wound  involving  the  lip  it  is  better 
to  seize  the  part  between  the  fingers,  and  evert  it,  when  the  bleeding  vessel  may  be  at  once  secured 
with  pressure-forceps.  In  order  to  prevent  hemorrhage  in  cases  of  removal  of  diseased  growths 
from  the  part,  the  lip  should  be  compressed  on  each  side  between  the  fingers  and  thumb  or  by 
a  pair  of  specially  devised  clamp-forceps,  whilst  the  suigeon  excises  the  diseased  part.  In  order 
to  stop  hemorrhage  where  the  lip  has  been  divided  in  an  operation,  it  is  necessary,  in  uniting 
the  edges  of  the  wound,  to  pass  the  sutures  through  the  cut  edges  from  the  skin  alraost-as  deep 
as  the  mucous  surface;  by  these  means  not  only  are  the  cut  surfaces  more  neatly  and  securely 
adapted  to  each  other,  but  the  possibility  of  hemorrhage  is  prevented  by  including  in  the  suture 


608 


THE  BLOOD -VASCULAR    SYSTEM 


the  divided  artery.  If  the  suture  is,  on  the  contrary,  passed  through  merely  the  cutaneous 
portion  of  the  wound,  hemorrhage  occurs  into  the  cavity  of  the  mouth.  The  student  should, 
lastly,  observe  the  relation  of  the  angular  artery  to  the  lachrymal  sac,  and  it  will  be  seen  that, 
as  the  vessel  passes  up  along  the  inner  margin  of  the  orbit,  it  ascends  on  its  nasal  side.  In 
operating  for  fistula  lacrimalis  the  sac  should  always  be  opened  on  its  outer  side,  in  order  that 
this  vessel  may  be  avoided. 

The  Occipital  Artery  (a.  occipitalis)  (Figs.  392,  393,  394,  and  396)  arises  from 
the  posterior  part  of  the  external  carotid,  opposite  the  facial,  near  the  lower  margin 

Internal  jugular  vein. 
Occipital  artery 


Internal  maxil- 
lary artery. 

Facial 
nerve. 


Ijnqaal 

nerve. 
Inferior  dental 

nerve. 

Mylo-hyoiA 


SUPERIOR    OBLIQUE 
MUSCLE. 


Vertebral  artery 


INFERIOR     OBLIQUE 
MUSCLE. 

Pneumogastri 
nerve. 


Hypo-glossal 
nerve. 
Internal  carotid 


STERNO-MASTOI 
MUSCLE. 


Superior  thyroid 
artery. 
External  carotid 
artery. 


Fig.  396. — The  occipital  artery  and  its  relations.     (From  a  dissection  by  Mr.  Gerald  S.  Hughes.) 


of  the  Digastric  muscle.  At  its  origin  it  is  covered  by  the  posterior  belly  of  the 
Digastric  muscle  and  the  Stylo-hyoid  muscle,  and  the  hypoglossal  nerve  winds 
around  it  from  behind  forward;  higher  up,  it  passes  across  the  internal  carotid 
artery,  the  internal  jugular  vein,  and  the  pneumogastric  and  spinal  accessory  nerves; 


THE  EXTERNAL    CAROTID   ARTERF  609 

it  then  ascends  to  the  interval  between  the  transverse  process  of  the  atlas  and  the 
mastoid  process  of  the  temporal  bone,  and  passes  horizontally  backward,  groov- 
ing the  surface  of  the  latter  bone,  being  covered  by  the  Sterno-mastoid,  Splenius, 
Trachelo-mastoid,  and  Digastric  muscles,  and  resting  upon  the  Rectus  lateralis,  the 
Superior  oblique,  and  Complexus  muscles;  it  then  changes  its  course  and  passes 
vertically  upward,  pierces  the  fascia  which  connects  the  cranial  attachment  of 
the  Trapezius  with  the  Sterno-mastoid,  and  ascends  in  a  tortuous  course  over 
the  occiput,  as  high  as  the  vertex,  where  it  divides  into  numerous  branches  (rami 
occipifales).  It  is  accompanied  in  the  latter  part  of  its  course  by  the  great  occip- 
ital nerve,  and  occasionally  by  a  cutaneous  filament  from  the  suboccipital  nerve. 
Branches. — The  branches  given  off  from  this  vessel  are — 

Muscular.  Meningeal. 

Sterno-mastoid.  Mastoid. 

Auricular.  Arteria  Princeps  Cervicis. 

The  Muscular  Branches  (rami  musculares)  supply  the  Digastric,  Stylo-hyoid, 
Splenius,  and  Trachelo-mastoid  muscles. 

The  Sterno-mastoid  (a.  sternocleidomastoidea)  is  a  large  and  constant  branch, 
generally  arising  from  the  artery  close  to  its  commencement,  but  sometimes 
springing  directly  from  the  external  carotid.  It  first  passes  downward  and  back- 
ward over  the  hypoglossal  nerve,  and  enters  the  substance  of  the  muscle  in  com- 
pany with  the  spinal  accessory  nerve. 

The  Auricular  Branch  (ramus  auricidaris)  supplies  the  back  part  of  the  concha. 
It  frequently  gives  off  a  branch,  which  enters  the  skull  through  the  mastoid 
foramen  and  supplies  the  dura  mater,  the  diploe,  and  the  mastoid  cells. 

The  Meningeal  Branch  (ramus  meningeus)  ascends  with  the  internal  jugular 
vein,  and  enters  the  skull  through  the  foramen  lacerum  posterius,  or  through  the 
anterior  condyloid  foramen,  to  supply  the  dura  mater  in  the  posterior  fossa. 

The  Mastoid  Branch  (ramus  mastoideus)  is  a  small  vessel,  by  no  means  constant. 
It  passes  into  the  skull  through  the  mastoid  foramen  and  is  distributed  upon  the 
dura  mater  of  the  posterior  fossa. 

The  Arteria  Princeps  Cervicis  (ramu^  descendens),  the  largest  branch  of  the 
occipital,  descends  along  the  back  part  of  the  neck  and  divides  into  a  super- 
ficial and  a  deep  portion.  The  former  runs  beneath  the  Splenius,  giving  off 
branches  which  perforate  that  muscle  to  supply  the  Trapezius,  which  anastomose 
with  the  superficial  cervical  artery,  a  branch  of  the  Transversalis  colli :  the  latter 
passes  beneath  the  Complexus  between  it  and  the  Semispinalis  colli,  and  anasto- 
moses with  branches  from  the  vertebral  and  with  the  deep  cervical  artery,  a 
branch  of  either  the  superior  intercostal  or  the  subclavian.  The  anastomosis 
between  these  vessels  serves  mainly  to  establish  the  collateral  circulation  after 
ligation  of  the  carotid  or  subclavian  artery. 

The  cranial  branches  (rami  occipitales)  of  the  occipital  artery  are  distributed 
upon  the  occiput;  they  are  very  tortuous,  and  lie  between  the  integument  and 
Occipito-frontalis,  anastomosing  with  the  artery  of  the  opposite  side,  the  pos- 
terior auricular  and  temporal  arteries.  They  supply  the  back  part  of  the 
Occipito-frontalis  muscle,  the  integument,  and  pericranium. 

The  Posterior  Auricular  Artery  (a.  auricularis  posterior)  (Figs.  392,  393,  and 
394)  is  a  small  vessel  which  arises  from  the  external  carotid,  above  the  Digastric 
and  Stylo-hyoid  muscles,  opposite  the  apex  of  the  styloid  process.  It  ascends, 
under  cover  of  the  parotid  gland,  on  the  styloid  process  of  the  temporal  bone,  to 
the  groove  between  the  cartilage  of  the  ear  and  the  mastoid  process,  immediately 
above  which  it  divides  into  its  two  terminal  branches,  the  auricular  and  mastoid. 
Just  before  arriving  at  the  mastoid  process,  this  artery  is  crossed  by  the  facial 
nerve,  and  has  beneath  it  the  spinal  accessory  nerve. 

39 


610  THE  BLOOD -VASCULAR  SYSTEM 

Branches. — Besides  several  small  branches  to  the  Digastric,  Stylo-hyoid,  and 
Sterno-mastoid  muscles  and  to  the  parotid  gland,  this  vessel  gives  off  three 
branches : 

Stylo-mastoid.  Auricular.  Mastoid. 

The  Stylo-mastoid  Branch  {a.  siylomastoidea)  enters  the  stylo-mastoid  foramen^ 
and  supplies  the  tympanum,  mastoid  cells,  and  semicircular  canals.  In  the 
young  subject  a  branch  from  this  vessel  forms,  with  the  tympanic  branch  from 
the  internal  maxillary,  a  vascular  circle,  which  surrounds  the  membrana  tympani, 
and  from  which  delicate  vessels  ramify  on  that  membrane.  It  anastomoses  with 
the  petrosal  branch  of  the  middle  meningeal  artery  by  a  twig,  which  enters  the 
hiatus  Fallopii. 

The  Auricular  Branch  {ramus  auricularis) ,  one  of  the  terminal  branches,  ascends 
behind  the  ear,  beneath  the  Retrahens  auriculam  muscle,  and  is  distributed  to 
the  back  part  of  the  cartilage  of  the  ear,  upon  which  it  ramifies  minutely,  some 
branches  curving  round  the  margin  of  the  fibro-cartilage,  others  perforating  it, 
to  supply  its  anterior  surface.  It  anastomoses  with  the  posterior  branch  of  the 
superficial  temporal  and  also  with  the  anterior  auricular  branches. 

The  Mastoid  Branch  (ramus  mastoideus)  passes  backward,  over  the  Sterno- 
mastoid  muscle,  to  the  scalp  above  and  behind  the  ear.  It  supplies  the  posterior 
belly  of  the  Occipito-frontalis  muscles  and  the  scalp  in  this  situation.  It  anasto- 
moses with  the  occipital  artery. 

The  Ascending  Pharyngeal  Artery  (a.  pharyngea  ascendens)  (Figs.  392  and 
393),  the  smallest  branch  of  the  external  carotid,  is  a  long,  slender  vessel,  deeply 
seated  in  the  neck,  beneath  the  other  branches  of  the  external  carotid  and  the 
Stylopharyngeus  muscle.  It  arises  from  the  back  part  of  the  external  carotid,  near 
the  commencement  of  that  vessel,  and  ascends  vertically  between  the  internal 
carotid  and  the  side  of  the  pharynx,  to  the  under  surface  of  the  base  of  the  skull, 
lying  on  the  Rectus  capitis  anticus  major  muscle. 

Branches. — Its  branches  may  be  subdivided  into  four  sets: 

Prevertebral.  Pharyngeal.  Tympanic.  Meningeal. 

The  Prevertebral  Branches  are  numerous  small  vessels  which  supply  the  Recti 
capitis  antici  and  Longus  colli  muscles,  the  sympathetic,  hypoglossal,  and  pneu- 
mogastric  nerves,  and  the  lymphatic  glands.  They  anastomose  with  the  ascending 
cervical  artery. 

The  Pharyngeal  Branches  {rami  pharyngei)  are  three  or  four  in  number.  Two 
of  these  descend  to  supply  the  middle  and  inferior  Constrictors  and  the  Stylo- 
pharyngeus, ramifying  in  the  substance  of  the  muscles  and  in  the  submucous 
tissue  of  the  mucous  membrane  lining  them.  The  largest  of  the  pharyngeal 
branches  passes  inward,  running  upon  the  Superior  constrictor,  and  sends  rami- 
fications to  the  soft  palate  and  tonsil,  which  take  the  place  of  the  ascending 
palatine  branch  of  the  facial  artery  when  that  vessel  is  of  small  size.  A  twig 
from  this  branch  supplies  the  Eustachian  tube. 

The  Tympanic  Branch  {a.  tympanica  inferior)  is  a  small  artery  which  passes 
through  a  minute  foramen  in  the  petrous  portion  of  the  temporal  bone,  in  com- 
pany with  the  tympanic  branch  of  the  Glosso-pharyngeal  nerve  to  supply  the 
inner  wall  of  the  tympanum  and  anastomose  with  the  other  tympanic  arteries. 

The  Meningeal  Branches  consist  of  several  small  vess'els,  which  pass  through 
foramina  in  the  base  of  the  skull,  to  supply  the  dura  mater.  One,  the  posterior 
meningeal  (a.  meningea  posterior),  enters  the  cranium  through  the  foramen  lacerum 
posterius;  a  second  passes  through  the  foramen  lacerum  medium;  and  occasion- 
ally a  third  through  the  anterior  condyloid  foramen.  They  are  all  distributed 
to  the  dura  mater. 


THE   EXTERNAL    CAROTID    ARTERY  611 

Surgical  Anatomy. — The  ascending  pharyngeal  artery  has  been  wounded  from  the  throat, 
as  in  the  case  in  which  the  stem  of  a  tobacco-pipe  was  driven  into  the  vessel,  causing  fatal  hemor- 
rhage. After  removal  of  the  tonsil  there  is  sometimes  severe  bleeding.  This  is  almost  never 
due  to  wounding  of  the  internal  carotid  artery,  as  the  latter  vessel,  if  normally  placed,  is  too 
far  away  to  be  damaged.  The  bleeding  comes  from  branches  of  the  ascending  pharyngeal, 
tonsillar,  or  ascending  palatine  arteries. 

The  Superficial  Temporal  Artery  (a.  temporalis  superficialis)  (Fig.  392, 393,  and 
394),  the  smaller  of  the  two  terminal  branches  of  the  external  carotid,  appears,  from 
its  direction,  to  be  the  continuation  of  that  vessel.  It  commences  in  the  substance 
of  the  parotid  gland,  in  the  interspace  between  the  neck  of  the  lower  jaw  and  the 
external  auditory  meatus,  crosses  over  the  posterior  root  of  the  zygoma,  passes 
beneath  the  Attrahens  auriculam  muscle,  lying  on  the  temporal  fascia,  and 
divides,  about  two  inches  above  the  zygomatic  arch,  into  two  branches,  an  anterior 
and  a  posterior.      This  vessel  is  accompanied  by  the  auriculo-temporal  nerve. 

The  Anterior  Temporal  runs  tortuously  upward  and  forward  to  the  forehead, 
supplying  the  muscles,  integument,  and  pericranium  in  this  region,  and  anasto- 
moses with  the  supra-orbital  and  frontal  arteries.  The  terminal  portion  of  the 
anterior  branch  is  called  the  frontal  artery  {ramus  frontalis). 

The  Posterior  Temporal,  larger  than  the  anterior,  curves  upward  and  backward 
along  the  side  of  the  head,  lying  superficial  to  the  temporal  fascia,  and  inosculates 
with  its  fellow  of  the  opposite  side,  and  with  the  posterior  auricular  and  occipital 
arteries.  The  terminal  portion  of  the  posterior  branch  is  named  the  parietal 
artery  (ramus  parietalis) . 

The  superficial  temporal  artery,  as  it  crosses  the  zygoma,  is  covered  by  the 
Attrahens  auriculam  muscle,  and  by  a  dense  fascia  given  off  from  the  parotid 
gland :  it  is  crossed  by  the  temporo-facial  division  of  the  facial  nerve  and  one  or 
two  veins,  and  is  accompanied  by  the  auriculo-temporal  nerve,  which  lies  behind 
it.  Besides  some  twigs  to  the  parotid  gland,  the  articulation  of  the  jaw,  and  the 
Masseter  muscle. 

Branches. — The  branches  of  the  superficial  temporal  artery  are  the — 

Transverse  Facial.  Orbital. 

Middle  Temporal.  Anterior  Auricular. 

The  Transverse  Facial  Branch  (a.  transversa  faciei)  is  given  off  from  the  tem- 
poral before  that  vessel  quits  the  parotid  gland;  running  forward  through  its 
substance,  it  passes  transversely  across  the  face,  between  Stenson's  duct  and 
the  lower  border  of  the  zygoma,  and  divides  on  the  side  of  the  face  into  numerous 
branches,  which  supply  the  parotid  gland,  the  Masseter  muscle,  and  the  integu- 
ment, anastomosing  with  the  facial,  masseteric,  and  infra-orbital  arteries.  This 
vessel  rests  on  the  Masseter,  and  is  accompanied  by  one  or  two  branches  of  the 
facial  nerve.    It  is  sometimes  a  branch  of  the  external  carotid. 

The  Middle  Temporal  Artery  (a.  temporalis  media)  arises  immediately  above 
the  zygomatic  arch,  and,  perforating  the  temporal  fascia,  gives  branches  to  the 
Temporal  muscle,  anastomosing  with  the  deep  temporal  branches  of  the  internal 
maxillary.  It  occasionally  gives  off  an  orbital  branch,  which  runs  along  the  upper 
border  of  the  zygoma,  between  the  two  layers  of  the  temporal  fascia,  to  the  outer 
angle  of  the  orbit.  This  branch,  which  may  arise  directly  from  the  superficial 
temporal  artery,  supplies,  the  Orbicularis  palpebrarum,  and  anastomoses  with 
the  lachrymal  and  palpebral  branches  of  the  ophthalmic  artery. 

The  Orbital  Artery  (a.  zygomaticoorhitalis)  comes  off  from  the  temporal  just 
above  the  zygoma  and  is  distributed  to  the  upper  orbital  margin. 

The  Anterior  Auricular  Branches  (rami  auriculares  anteriores)  are  distributed 
to  the  anterior  portion  of  the  pinna,  the  lobule,  and  part  of  the  external  meatus, 
anastomosing  with  branches  of  the  posterior  auricular. 


612 


THE   BLOOD -VASCULAR    SYSTEM 


Surgical  Anatomy. — Formerly  the  operation  of  arteriotomy  was  performed  upon  this  vessel 
in  cases  of  inflammation  of  the  eye  or  brain,  but  at  the  present  time  the  operation  is  obsolete. 
If  the  student  will  consider  the  relations  of  the  trunk  of  the  vessels  as  it  crosses  the  zygomatic 
arch,  with  the  surrounding  structures,  he  will  observe  that  it  is  covered  by  a  thick  and  dense 
fascia,  crossed  by  one  of  the  main  divisions  of  the  facial  nerve  and  one  or  two  veins,  and  accom- 
panied by  the  auriculo-temporal  nerve.  The  anterior  branch,  on  the  contrary,  is  subcutaneous, 
and  is  a  large  vessel. 

The  Internal  Maxillary  Artery  (a.  maxillaris  interna)  (Figs.  397  and  398),  the 
larger  of  the  two  terminal  branches  of  the  external  carotid,  arises  from  that  vessel 
opposite  the  neck  of  the  condyle  of  the  lower  jaw,  and  is  at  first  imbedded  in  the 


Incisor. 


Fig.  397. — The  internal  maxillary  artery  and  its  branches. 


Bmall  Meningeal, 
middle  Meningeal 
Tympan 


Inferior  Dental- 


Jterygofalatine^         ^^^^ 

«5soS    /Descending  Palatin4 
Deep  ■^'^Po'-al^^/^^^^Spheno-paMine 

[^S' ■  "'■6,, 


Fig.  398. — Plan  of  the  branches. 

substance  of  the  parotid  gland;  it  passes  inward  between  the  ramus  of  the  jaw 
and  the  internal  lateral  ligament,  and  then  upon  the  outer  surface  of  the  External 
pterygoid  muscle  to  the  spheno-maxillary  fossa,  to  supply  the  deep  structures 
of  the  face.  For  convenience  of  description  it  is  divided  into  three  portions :  a 
maxillary,  a  pterygoid,  and  spheno-maxillary. 

In  the  first  part  of  its  course,  the  maxillary  portion,  the  artery  passes  horizontally 
forward  and  inward,  between  the  ramus  of  the  jaw  and  the  internal  lateral  liga- 
ment. The  artery  here  lies  parallel  to  and  a  little  below  the  auriculo-temporal 
nerve;  it  crosses  the  inferior  dental  nerve,  and  lies  along  the  lower  border  of  the 
External  pterygoid  muscle. 


THE   EXTERNAL    CAROTID    ARTERY  613 

In  the  second  part  of  its  course,  tli:  pterygoid  portion,  it  runs  obliquely  forward, 
and  upward  upon  the  outer  surface  of  the  External  pterygoid  muscle,  being 
covered  by  the  ramus  of  the  lower  jaw  and  lower  part  of  the  Temporal  muscle; 
or  it  may  pass  on  the  inner  surface  of  the  External  pterygoid  muscle  to  reach  the 
interval  between  its  two  heads,  between  which  it  passes  to  reach  the  spheno- 
maxillary fossa. 

In  the  third  part  of  its  course,  the  spheno-maxillaxy  portion,  it  approaches  the 
superior  maxillary  bone,  and  enters  the  spheno-maxillary  fossa  in  the  interval 
between  the  two  heads  of  the  External  pterygoid  nmscle,  where  it  lies  in  relation 
witli  Meckel's  ganglion,  and  gives  off  its  terminal  branches. 

The  branches  of  this  vessel  may  be  divided  into  three  groups,  corresponding 
with  its  three  divisions. 

Branches  of  the  First  or  Maxillary  Portion  (Fig.  398) ; 

Anterior  Tympanic.  Small  Meningeal. 

Deep  Auricular.  Inferior  Dental. 

Middle  Meningeal. 

The  Anterior  Tympanic  Branch  (a.  tympanica  anterior)  passes  upward  behind 
the  articulation  of  the  lower  jaw,  enters  the  tympanum  through  the  Glaserian 
fissure,  and  ramifies  upon  the  membrana  tympani,  forming  a  vascular  circle 
around  the  membrane  with  the  stylo-mastoid  artery,  and  anastomosing  with 
the  Vidian  and  the  tympanic  branch  from  the  internal  carotid. 

The  Deep  Auricular  Branch  (a.  auricularis  profunda)  often  arises  in  common 
with  the  preceding.  It  passes  upward  in  the  substance  of  the  parotid  gland, 
behind  the  temporo-maxillary  articulation,  pierces  the  cartilaginous  or  bony  wall 
of  the  external  auditory  meatus,  and  supplies  its  cuticular  lining  and  the  outer 
surface  of  the  membrana  tympani. 

The  Middle  Meningeal  Branch  (a.  meningea  media)  is  the  largest  of  the  branches 
which  supply  the  dura  mater.  It  arises  from  the  internal  maxillary,  between  the 
internal  lateral  ligament  and  the  neck  of  the  jaw,  and  passes  vertically  upward 
between  the  two  roots  of  tlie  auriculo-temporal  nerve  to  the  foramen  spinosum  of 
the  sphenoid  bone.  On  entering  the  cranium  it  divides  into  two  branches,  anterior 
and  posterior.  The  anterior  branch,  the  larger,  crosses  the  great  ala  of  the  sphenoid, 
and  reaches  the  groove,  or  canal,  in  the  anterior  inferior  angle  of  the  parietal 
bone;  it  then  divides  into  two  branches  which  spread  out  between  the  dura  mater 
and  internal  surface  of  the  cranium,  one  passing  upward  over  the  parietal  bone  as 
far  as  the  vertex,  and  sending  rami  backward  to  the  occipital  bone,  the  other 
passing  front  to  the  inner  surface  of  the  frontal  bone.  The  posterior  branch 
crosses  the  squamous  portion  of  the  temporal,  and  on  the  inner  surface  of  the 
parietal  bone  divides  into  branches  which  supply  the  posterior  part  of  the  dura 
mater  and  cranium.  The  branches  of  this  vessel  are  distributed  partly  to  the 
dura  mater,  but  chiefly  to  the  bones;  they  anastomose  with  the  arteries  of  the 
opposite  side,  and  with  the  anterior  and  posterior  meningeal  arteries. 

The  middle  meningeal  on  entering  the  cranium  gives  off  the  following  collateral 
branches:  1.  Numerous  small  vessels  to  the  Gasserian  ganglion,  and  to  the  dura 
mater  in  this  situation.  2.  A  branch,  the  petrosal  branch  {ramus  petrosus  super- 
ficialis),  which  enters  the  hiatus  Fallopii,  supplies  the  facial  nerve,  and  anasto- 
moses with  the  styio-mastoid  branch  of  the  posterior  auricular  artery.  3.  A 
minute  superior  tympanic  branch  (a.  tympanica  superior),  which  runs  in  the  canal 
for  the  Tensor  tympani  muscle,  and  supplies  this  muscle  and  the  lining  mem- 
brane of  the  canal.  4.  Orbital  branches,  which  pass  through  the  sphenoidal  fissure, 
or  through  separate  canals  in  the  great  wing  of  the  sphenoid  to  anastomose 
with  the  lachrymal  or  other  branches  of  the  ophthalmic  artery.  5.  Temporal 
or  anastomotic  branches,  which  pass  through  foramina  in  the  great  wing  of  the 


614  THE  BLOOD -VASCULAR   SYSTEM 

sphenoid  bone  and  anastomose  in  the  temporal  fossa  with  the  deep  temporal 
arteries. 

Surgical  Anatomy. — The  middle  meningeal  is  an  artery  of  considerable  surgical  importance, 
as  it  may  be  injured  in  fractures  of  the  temporal  region  of  the  skull.  The  vessel  may  be  ruptured 
by  traumatism,  even  though  the  skull  escapes  fracture.  Rupture  of  the  middle  meningeal  artery 
will  be  followed  by  considerable  hemorrhage  between  the  bone  and  dura  mater,  which  may  cause 
compression  of  the  brain  and  require  the  operation  of  trephining  for  its  relief.  This  artery 
crosses  the  anterior  inferior  angle  of  the  parietal  bone  at  a  point  1  ^  inches  behind  the  external 
angular  process  of  the  frontal  bone,  and  If  inches  above  the  zygoma.  From  this  point  the  ante- 
rior branch  passes  upward  and  slightly  backward  to  the  sagittal  suture,  lying  about  §  inch  to 
f  inch  behind  the  coronal  suture.  The  posterior  branch  passes  upward  and  backward  over  the 
squamous  portion  of  the  temporal  bone.  In  order  to  expose  the  artery  as  it  lies  in  the  groove  in 
the  parietal  bone,  a  semilunar  incision,  with  its  convexity  upward,  should  be  made,  commencing 
an  inch  behind  the  external  angular  process,  and  carried  backward  for  two  inches.  The  struc- 
tures cut  through  are:  (1)  skin;  (2)  superficial  fascia,  with  branches  of  the  superficial  temporal 
vessels  and  nerves;  (3)  the  fascia  continued  down  from  the  aponeurosis  of  the  Occipito-frontalis; 
(4)  the  two  layers  of  the  temporal  fascia;  (5)  the  temporal  muscle;  (6)  the  deep  temporal  vessels; 
(7)  the  pericranium.  The  bone  is  trephined,  the  clot  removed,  and  the  vessel  secured  by 
ligatures,  suture  ligatures,  or  gauze  packing. 

The  Small  Meningeal  Branch  (ramus  meningeus  accessorius)  is  sometimes  derived 
from  the  preceding,  usually  from  the  internal  maxillary.  It  enters  the  skull 
through  the  foramen  ovale,  and  supplies  the  Gasserian  ganglion  and  dura  mater. 

The  Mandibular,  Inferior  Alveolar  or  Inferior  Dental  Branch  (a.  alveolaris  inferior) 
descends  with  the  inferior  dental  nerve  to  the  foramen  on  the  inner  side  of  the 
ramus  of  the  jaw.  It  runs  along  the  dental  canal  in  the  substance  of  the  bone, 
accompanied  by  the  nerve,  and  opposite  the  first  bicuspid  tooth  divides  into  two 
branches,  the  incisor  and  mental ;  the  incisor  branch  is  continued  forward  beneath 
the  incisor  teeth  as  far  as  the  symphysis,  where  it  anastomoses  with  the  artery 
of  the  opposite  side;  the  mental  branch  (a.  mentalis)  escapes  with  the  nerve  at  the 
mental  foramen,  supplies  the  structures  composing  the  chin,  and  anastomoses 
with  the  submental,  inferior  labial  and  inferior  coronary  arteries.  Near  its  origin 
the  inferior  dental  artery  gives  off  a  lingual  branch,  which  descends  with  the  lingual 
(gustatory)  nerve  and  supplies  the  mucous  membrane  of  the  mouth.  As  the 
inferior  dental  artery  enters  the  foramen  it  gives  off  a  mylo-hyoid  branch  {ramus 
mylohyoideus) ,  which  runs  in  the  mylo-hyoid  groove,  and  ramifies  on  the  under 
surface  of  the  Mylo-hyoid  muscle.  The  dental  and  incisor  arteries  during  their 
course  through  the  substance  of  the  bone  give  off  a  few  twigs  which  are  lost  in 
the  cancellous  tissue,  and  a  series  of  branches  which  correspond  in  number  to 
the  roots  of  the  teeth:  these  enter  the  minute  apertures  at  the  extremities  of  the 
fangs  and  supply  the  pulp  of  the  teeth. 

Branches  of  the  Second  or  Pterygoid  Portion  (Fig.  398) : 

Deep  Temporal.  Masseteric. 

Pterygoid.  Buccal. 

These  branches  are  distributed,  as  their  names  imply,  to  the  muscles  in  the 
maxillary  region. 

The  Deep  Temporal  Branches,  two  in  number,  anterior  (a.  temporalis  profunda 
anterior)  and  posterior  (a.  temporalis  profunda  posterior),  each  occupy  that  part 
of  the  temporal  fossa  indicated  by  its  name.  Ascending  between  the  Temporal 
muscle  and  pericranium,  they  supply  that  muscle  and  anastomose  with  the  middle 
temporal  artery.  The  anterior  branch  communicates  with  the  lachrymal  artery 
through  small  branches  which  perforate  the  malar  bone  and  great  wing  of  the 
sphenoid. 

The  Pterygoid  Branches  (rami  pterygoidei) ,  irregular  in  their  number  and 
origin,  supply  the  Pterygoid  muscles. 


THE  EXTERNAL    CAROTID  ARTERY  615 

The  Masseteric  (a.  masseterica)  is  a  small  branch  which  passes  outward,  above 
the  sigmoid  notch  of  the  lower  jaw,  to  the  deep  surface  of  the  Masseter  muscle. 
It  supplies  that  muscle,  and  anastomoses  with  the  masseteric  branches  of  the 
facial  and  with  the  transverse  facial  artery. 

The  Buccal  (a.  huccinatoria)  is  a  small  branch  which  runs  obliquely  forward 
between  the  Internal  pterygoid  and  the  ramus  of  the  jaw,  to  the  outer  surface  of 
the  Buccinator,  to  which  it  is  distributed,  anastomosing  with  branches  of  the 
facial  artery. 

Branches  of  the  Third  or  Spheno -maxillary  Portion  (Fig.  398): 

Superior  Alveolar  or  Alveolar.  Vidian. 

Infraorbital.  Pterygo-palatine. 

Descending  or  Posterior  Palatine.  Naso-  or  Spheno-palatine. 

The  Superior  Alveolar,  Alveolar  or  Posterior  Dental  Branch  (a.  alveolaris  superior 
posterior)  is  given  off  from  the  internal  maxillary  by  a  common  branch  with  the 
infraorbital,  and  just  as  the  trunk  of  the  vessel  is  passing  into  the  spheno-maxillary 
fossa.  Descending  upon  the  tuberosity  of  the  superior  maxillary  bone,  it  divides 
into  numerous  branches,  some  of  which  enter  the  posterior  dental  canals,  to  supply 
the  upper  molar  and  bicuspid  teeth  and  the  lining  of  the  antrum,  and  others  are 
continued  forward  on  the  alveolar  process  to  supply  the  gums  of  the  upper  jaw. 

The  Infraorbital  (a.  infraorbitalis)  appears,  from  its  direction,  to  be  the  con- 
tinuation of  the  trunk  of  the  internal  maxillary.  It  arises  from  that  vessel  by  a 
•common  trunk  with  the  preceding  branch,  and  runs  along  the  infra-orbital 
canal  with  the  superior  maxillary  nerve,  emerging  upon  the  face  at  the  infra- 
orbital foramen,  beneath  the  Levator  labii  superioris  muscle.  Whilst  contained 
in  the  canal,  it  gives  off  branches  which  ascend  into  the  orbit,  and  assist 
in  supplyitig  the  Inferior  rectus  and  Inferior  oblique  muscles  and  the  lachrymal 
gland.  Other  branches,  anterior  dental  (aa.  alveolares  swperiores  anteriores) ,  descend 
through  the  anterior  dental  canals  in  the  bone,  to  supply  the  mucous  membrane  of 
the  antrum  and  the  front  teeth  of  the  upper  jaw.  On  the  face,  some  branches  pass 
upward  to  the  inner  angle  of  the  orbit  and  the  lachrymal  sac,  anastomosing  with 
the  angular  branch  of  the  facial  artery;  other  branches  pass  inward  toward  the 
nose,  anastomosing  with  the  nasal  branch  of  the  ophthalmic;  and  other  branches 
•descend  beneath  the  Levator  labii  superioris  muscle,  and  anastomose  with  the 
transverse  facial  and  buccal  arteries. 

The  four  remaining  branches  arise  from  that  portion  of  the  internal  maxillary 
which  is  contained  in  the  spheno-maxillary  fossa. 

The  Descending  or  Posterior  Palatine  (a.  palatina  descendens)  descends  through 
the  posterior  palatine  canal  with  the  anterior  palatine  branch  of  Meckel's  ganglion, 
and,  emerging  from  the  posterior  palatine  foramen,  runs  forward  in  a  groove  on 
the  inner  side  of  the  alveolar  border  of  the  hard  palate  to  the  anterior  palatine 
•canal,  where  the  terminal  branch  of  the  artery  passes  upward  through  the  fora- 
men of  Stenson  to  anastomose  with  the  naso-palatine  artery.  Its  branches  are 
distributed  to  the  gums,  the  mucous  membrane  of  the  hard  palate,  and  the 
palatine  glands.  Whilst  it  is  contained  in  the  palatine  canal  it  gives  off  branches 
which  descend  in  the  accessory  palatine  canals  to  supply  the  soft  palate  and 
tonsil,  anastomosing  with  the  ascending  palatine  artery. 

Surgical  Anatomy. — The  position  of  the  descending  palatine  artery  on  the  hard  palate 
should  be  borne  in  mind  in  performing  an  operation  for  the  closure  of  a  cleft  in  the  hard 
palate,  as  the  vessel  is  in  danger  of  being  wounded,  and  may  give  rise  to  formidable  hemor- 
rhage. In  case  it  should  be  wounded  it  may  be  necessary  to  plug  the  posterior  palatine 
canal  in  order  to  arrest  the  bleeding.  This  artery  may  bleed  furiously  in  the  operation  of 
resection  of  the  upper  jaw. 


616  THE  BLOOn -VASCULAR  SYSTEM 

The  Vidian  Branch  (a.  canalis  pterygoidei)  passes  backward  along  the  Vidian 
canal  with  the  Vidian  nerve.  It  is  distributed  to  the  upper  part  of  the  pharynx 
and  Eustachian  tube,  sending  a  small  branch  into  the  tympanum,  which  anasto- 
moses with  the  other  tympanic  arteries. 

The  Pterygo-palatine  is  a  very  small  branch,  which  passes  backward  through 
the  pterygo-palatine  canal  with  the  pharyngeal  nerve,  and  is  distributed  to  the 
upper  part  of  the  pharynx  and  Eustachian  tube. 

The  Naso-  or  Spheno -palatine  (a.  sfheno'palatina)  passes  through  the  spheno- 
palatine foramen  into  the  cavity  of  the  nose,  at  the  back  part  of  the  superior 
meatus,  and  divides  into  two  branches:  one  internal,  the  naso-palatin^  or  artery  of 
the  septum,  passes  obliquely  downward  and  forward  along  the  septum  nasi,  supplies 
the  mucous  membrane,  and  anastomoses  in  front  with  the  terminal  branch  of  the 
descending  palatine  and  the  inferior  artery  of  the  septum,  which  is  a  branch 
of  the  superior  coronary.  The  external  branches,  two  or  three  in  number,  supply 
the  mucous  membrane  covering  the  lateral  wall  of  the  nose,  the  antrum,  and 
the  ethmoid  and  sphenoid  cells. 

SURGICAL  ANATOMY  OF  THE  TRIANGLES  OF  THE  NECK 

(Fig.  269). 

The  student  having  considered  the  relative  anatomy  of  the  large  arteries  of  the 
neck  and  their  branches,  and  the  relations  they  bear  to  the  veins  and  nerves,  should 
now  examine  these  structures  collectively,  as  they  present  themselves  in  certain 
regions  of  the  neck,  in  each  of  which  important  operations  are  constantly  being 
performed. 

The  side  of  the  neck  presents  a  somewhat  quadrilateral  outline,  limited,  above^ 
by  the  lower  border  of  the  body  of  the  jaw,  and  an  imaginary  line  extending  from 
the  angle  of  the  jaw  to  the  mastoid  process;  below,  by  the  prominent  upper  border 
of  the  clavicle;  in  jront,  by  the  median  line  of  the  neck;  behind,  by  the  anterior 
margin  of  the  Trapezius  muscle.  This  space  is  subdivided  into  two  large  triangles 
by  the  Sterno-mastoid  muscle,  which  passes  obliquely  across  the  neck,  from  the 
sternum  and  clavicle  below  to  the  mastoid  process  above.  The  triangular  space 
in  front  of  this  muscle  is  called  the  anterior  triangle ;  and  that  behind  it,  the  poste- 
rior triangle. 

Anterior  Triangle  of  the  Neck. — The  anterior  triangle  is  bounded  in  front, 
by  an  imaginary  line  extending  from  the  chin  to  the  sternum;  behind,  by  the 
anterior  margin  of  the  Sterno-mastoid;  its  base,  directed  upward,  is  formed  by 
the  lower  border  of  the  body  of  the  jaw  and  an  imaginary  line  extending  from 
the  angle  of  the  jaw  to  the  mastoid  process;  its  apex  is  below,  at  the  sternum. 
This  space  is  subdivided  into  three  smaller  triangles  by  the  Digastric  muscle 
above  and  the  anterior  belly  of  the  Omo-hyoid  below.  These  smaller  triangles 
are  named,  from  below  upward,  the  inferior  carotid,  the  superior  carotid,  and  the 
submaxillary  triangle. 

The  Inferior  Carotid  Triangle  or  the  Triangle  of  Necessity  is  bounded,  in  jront, 
by  the  median  line  of  the  neck;  behind,  by  the  anterior  margin  of  the  Sterno- 
mastoid  ;  above,  by  the  anterior  belly  of  the  Omo-hyoid ;  and  is  covered  by  the 
integument,  superficial  fascia,  Platysma,  and  deep  fascia,  ramifying  between 
which  are  some  of  the  descending  branches  of  the  superficial  cervical  plexus. 
Beneath  these  superficial  structures  are  the  Sterno-hyoid  and  Sterno-thyroid 
muscles,  which,  together  with  the  anterior  margin  of  the  Sterno-mastoid,  conceal 
the  lower  part  of  the  common  carotid  artery.^    The  floor  of  this  triangle  is  formed 

_>  Therefore  the  common  carotid  artery  and  internal  jugular  vein  are  not,  strictly  speaking,  contained  in  this 
triangle,  since  they  are  covered  by  the  Sterno-mastoid  muscle,  that  is  to  say,  lie  behind  the  anterior  border  of 
that  muscle,  which  forms  the  posterior  border  of  the  triangle.  But,  as  they  lie  very  close  to  the  structure* 
which  are  really  contained  in  the  triangle,  and  whose  position  it  is  essential  to  remember  in  operating  on  thia 
part  of  the  artery,  it  has  seemed  expedient  to  study  the  relations  of  all  these  parts  together. — Ed.  of  15th 
English  edition. 


SURGICAL    ANATOMY   OF    THE    TRIANGLES    OF    THE    NECK    QYJ 

by  the  Longiis  colli  muscle  below  and  by  the  Scalenus  anticus  muscle  above,  between 
which  muscles  the  vertebral  artery  and  vein  will  be  found  passing  into  the  foramen 
of  the  transverse  process  of  the  sixth  cervical  vertebra.  A  small  portion  of  the  origin 
of  the  Rectus  capitis  anticus  major  may  also  be  seen  on  the  floor  of  the  space. 

The  common  carotid  artery  is  enclosed  within  its  sheath,  together  with  the 
internal  jugular  vein  and  pneumogastric  nerve;  the  vein  lying  on  the  outer  side 
of  the  artery  on  the  right  side  of  the  neck,  but  overlapping  it  below  on  the  left  side ; 
the  nerve  lying  between  the  artery  and  vein,  on  a  plane  posterior  to  both.  In 
front  of  the  sheath  are  a  few  filaments  descending  from  the  loop  of  communica- 
tion between  the  Descendens  and  communicans  hypoglossi;  behind  the  sheath 
are  seen  the  inferior  thyroid  artery,  the  recurrent  laryngeal  nerve,  and  the  sym- 
pathetic nerve;  and  on  its  inner  side,  the  trachea,  the  thyroid  gland — much  more 
prominent  in  the  female  than  in  the  male — and  the  lower  part  of  the  larynx.  By 
cutting  into  the  upper  part  of  this  space  and  slightly  displacing  the  Sterno-mastoid 
muscle  the  common  carotid  artery  may  be  tied  below  the  Omo-hyoid  muscle. 

The  Superior  Caxotid  Triangle  or  the  Triangle  of  Election  is  bounded,  behind, 
by  the  Sterno-mastoid;  below,  by  the  anterior  belly  of  the  Omo-hyoid;  and 
above,  by  the  posterior  belly  of  the  Digastric  muscle.  It  is  covered  by  the 
integument,  superficial  fascia,  Platysma,  and  deep  fascia,  ramifying  between 
which  are  branches  of  the  facial  and  superficial  cervical  nerves.  Its  floor  is 
formed  by  parts  of  the  Thyro-hyoid  and  Hyo-glossus  muscles,  and  the  Inferior 
and  Middle  constrictor  muscles  of  the  pharynx.  This  space,  when  dissected, 
is  seen  to  contain  the  upper  part  of  the  common  carotid  artery,  which  bifur- 
cates opposite  the  upper  border  of  the  thyroid  cartilage  into  the  external  and 
internal  carotid.  These  vessels  are  occasionally  somewhat  concealed  from  view 
by  the  anterior  margin  of  the  Sterno-mastoid  muscle,  which  overlaps  them. 
The  external  and  internal  carotid  lie  side  by  side,  the  external  being  the  more 
anterior  of  the  two.  The  following  branches  of  the  external  carotid  are  also 
met  with  in  this  space:  the  superior  thyroid,  running  forward  and  downward;  the 
lingual,  directly  forward;  the  facial,  forward  and  upward;  the  occipital,  back- 
ward; and  the  ascending  pharyngeal  directly  upward  on  the  inner  side  of  the 
internal  carotid.  The  veins  met  with  are:  the  internal  jugular,  which  lies  on  the 
outer  side  of  the  common  and  internal  carotid  arteries,  and  veins  corresponding  to 
the  above-mentioned  branches  of  the  external  carotid — viz.,  the  superior  thyroid, 
the  lingual,  facial,  ascending  pharyngeal,  and  sometimes  the  occipital,  all  of 
which  accompany  their  corresponding  arteries  and  terminate  in  the  internal  jugular. 
The  nerves  in  this  space  are  the  following:  In  front  of  the  sheath  of  the  common 
carotid  is  the  descendens  hypoglossi.  The  hypoglossal  nerve  crosses  both  the 
internal  and  external  carotids  above,  curving  round  the  occipital  artery  at  its 
origin.  Within  the  sheath,  between  the  artery  and  vein,  and  behind  both,  is  the 
pneumogastric  nerve;  behind  the  sheath,  the  sympathetic.  On  the  outer  side  of 
the  vessels  the  spinal  accessory  nerve  runs  for  a  short  distance  before  it  pierces 
the  Sterno-mastoid  muscle;  and  on  the  inner  side  of  the  external  carotid,  just 
below  the  hyoid  bone,  may  be  seen  the  internal  laryngeal  nerve;  and,  still  more 
inferiorly,  the  external  laryngeal  nerve.  The  upper  part  of  the  larynx  and  lower 
part  of  the  pharynx  are  also  found  in  the  front  part  of  this  space. 

The  Submaxillary  Triangle  corresponds  to  the  part  of  the  neck  immediately 
beneath  the  body  of  the  jaw.  It  is  bounded,  above,  by  the  lower  border  of  the 
body  of  the  jaw  and  a  line  drawn  from  its  angle  to  the  mastoid  process;  below,  by 
the  posterior  belly  of  the  Digastric  muscle  and  the  Stylo-hyoid  muscle;  in  jront, 
by  the  anterior  belly  of  the  Digastric.  It  is  covered  V)y  the  integument,  superficial 
fascia,  Platysma,  and  deep  fascia,  ramifying  between  which  are  branches  of  the 
facial  and  ascending  filaments  of  the  superficial  cervical  nerves.  Its  floor  is  formed 
by  the  Mylo-hyoid  and  Hyo-glossus  muscles.  This  space  contains,  in  front,  the  sub- 


618  THE   BLOOD 'VASCULAR    SYSTEM 

maxillary  gland,  superficial  to  which  is  the  facial  vein,  while  imbedded  in  it  are  the 
facial  artery  and  its  glandular  branches;  beneath  this  gland,  on  the  surface  of  the 
Mylo-hyoid  muscle,  are  the  submental  artery  and  the  mylo-hyoid  artery  and  nerve. 
The  posterior  part  of  this  triangle  is  separated  from  the  anterior  part  by  the  stylo- 
maxillary  ligament:  it  contains  the  external  carotid  artery,  ascending  deeply  in 
the  substance  of  the  parotid  gland :  this  vessel  here  lies  in  front  of,  and  superficial 
to,  the  internal  carotid,  being  crossed  by  the  facial  nerve,  and  gives  off  in  its 
course  the  posterior  auricular,  temporal,  and  internal  maxillary  branches:  more 
deeply  are  the  internal  carotid  artery,  the  internal  jugular  vein,  and  the  pneumo- 
gastric  nerve,  separated  from  the  external  carotid  by  the  Stylo-glossus  and  Stylo- 
pharyngeus  muscles  and  the  glosso-pharyngeal  nerve/ 

Posterior  Triangle  of  the  Neck. — The  posterior  triangle  is  bounded,  in  front, 
by  the  Sterno-mastoid  muscle;  behind,  by  the  anterior  margin  of  the  Trapezius; 
its  base  corresponds  to  the  middle  third  of  the  clavicle;  its  apex,  to  the  occiput. 
The  space  is  crossed,  about  an  inch  above  the  clavicle,  by  the  posterior  belly  of 
the  Omo-hyoid,  which  divides  it  unequally  into  two,  an  upper  or  occipital  and  a 
lower  or  subclavian  triangle. 

The  Occipital  Triangle,  the  larger  division  of  the  posterior  triangle,  is  bounded, 
in  front,  by  the  Sterno-mastoid;  behind,  by  the  Trapezius;  below,  by  the  Omo- 
hyoid. Its  floor  is  formed  from  above  downward  by  the  Splenius,  Levator  anguli 
scapulae,  and  the  Middle  and  posterior  scaleni  muscles.  It  is  covered  by  the 
integument,  the  Platysma  below,  the  superficial  and  deep  fasciae;  the  spinal 
accessory  nerve  is  directed  obliquely  across  the  space  from  the  Sterno-mastoid, 
which  it  pierces,  to  the  under  surface  of  the  Trapezius;  below,  the  descending 
branches  of  the  cervical  plexus  and  the  transversalis  colli  artery  and  vein  cross  the 
space.  A  chain  of  lymphatic  glands  is  also  found  running  along  the  posterior 
border  of  the  Sterno-mastoid,  from  the  mastoid  process  to  the  root  of  the  neck. 

The  Subclavian  Triangle,  the  smaller  of  the  two  posterior  triangles,  is  bounded, 
above,  by  the  posterior  belly  of  the  Omo-hyoid ;  below,  by  the  clavicle,  its  base, 
directed  forward,  being  formed  by  the  Sterno-mastoid.  The  size  of  the  subclavian 
triangle  varies  according  to  the  extent  of  attachment  of  the  clavicular  portion  of  the 
Sterno-mastoid  and  Trapezius  muscles,  and  also  according  to  the  height  at  which 
the  Omo-hyoid  crosses  the  neck  above  the  clavicle.  Its  height  also  varies  much 
according  to  the  position  of  the  arm,  being  much  diminished  by  raising  the  limb, 
on  account  of  the  ascent  of  the  clavicle,  and  increased  by  drawing  the  arm  down- 
ward, when  that  bone  is  depressed.  This  space  is  covered  by  the  integument, 
the  Platysma,  the  superficial  and  deep  fasciae,  and  crossed  by  the  descending 
branches  of  the  cervical  plexus.  Just  above  the  level  of  the  clavicle  the  third 
portion  of  the  subclavian  artery  curves  outward  and  downward  from  the  outer 
margin  of  the  Scalenus  anticus,  across  the  first  rib,  to  the  axilla.  Sometimes  this 
vessel  rises  as  high  as  an  inch  and  a  half  above  the  clavicle,  or  to  any  point  inter- 
mediate between  this  and  its  usual  level.  Occasionally  it  passes  in  front  of  the 
Scalenus  anticus  or  pierces  the  fibres  of  that  muscle.  The  subclavian  vein  lies 
behind  the  clavicle,  and  is  usually  not  seen  in  this  space;  but  it  occasionally  rises 
as  high  up  as  the  artery,  and  has  even  been  seen  to  pass  with  that  vessel  behind 
the  Scalenus  anticus.  The  brachial  plexus  of  nerves  lies  above  the  artery,  and 
in  close  contact  with  it.  Passing  transversely  behind  the  clavicle  are  the  supra- 
scapular vessels,  and  traversing  its  upper  angle  in  the  same  direction,  the  trans- 
versalis colli  artery  and  vein.  The  external  jugular  vein  runs  vertically  downward 
behind  the  posterior  border  of  the  Sterno-mastoid  muscle,  to  terminate  in  the 

The  same  remark  will  apply  to  this  triangle  as  was  made  about  the  inferior  carotid  triangle.  The  structures 
enumerated  as  contamed  m  the  back  part  of  the  space  lie,  strictly  speaking,  beneath  the  muscles  which  form 
ine  posterior  boundary  of  the  triangle;  but  as  it  is  very  important  to  bear  in  mind  their  close  relation  to  the 
parotid  gland  and  its  boundaries  (on  account  of  the  frequency  of  surgical  operations  on  this  gland),  all  these 
parts  are  spoken  of  together.— Ed.  of  15th  English  edition 


THE  INTERNAL    CAROTID   ARTERY 


619 


subclavian  vein ;  it  receives  the  transverse  cervical  and  suprascapular  veins,  which 
occasionally  form  a  plexus  in  front  of  the  artery,  and  a  small  vein  which  crosses 
the  clavicle  from  the  cephalic.  The  small  nerve  to  the  Subclavius  muscle  also 
crosses  this  triangle  about  its  middle.  A  lymphatic  gland  is  also  found  in  the  space. 
Its  floor  is  formed  by  the  first  rib  with  the  first  digitation  of  the  Serratus  magnus. 

The  Internal  Carotid  Artery  (A.  Carotis  Interna). 

The  internal  carotid  artery  supplies  the  anterior  part  of  the  brain,  the  eye, 
and  its  appendages,  and  sends  branches  to  the  forehead  and  nose.  Its  size 
in  the  adult  is  equal  to  that  of  the  external  carotid,  though  in  the  child  it  is 
larger  than  that  vessel.  It  is  remarkable  for  the  number  of  curvatures  that  it 
presents  in  different  parts  of  its  course.    It  occasionally  has  one    or  two  flexures 


Fig.  399. — The  internal  carotid  and  vertebral  arteries.     Right  side. 


620  THE  BLOOD -VASCULAR    SYSTEM 

near  the  base  of  the  skull,  whilst  in  its  passage  through  the  carotid  canal  and 
along  the  side  of  the  body  of  the  sphenoid  bone  it  describes  a  double  curve 
which  resembles  somewhat  the  letter  S  placed  horizontally.  These  curvatures  most 
probably  diminish  the  velocity  of  the  current  of  blood,  by  increasing  the  extent  of 
surface  over  which  it  moves  and  adding  to  the  impediment  produced  from  friction. 

In  considering  the  course  and  relations  of  this  vessel  it  may  be  conveniently 
divided  into  four  portions:  the  cervical,  petrous,  cavernous,  and  cerebral  portions. 

Cervical  Portion. — This  portion  of  the  internal  carotid  commences  at  the 
bifurcation  of  the  common  carotid,  opposite  the  upper  border  of  the  thyroid 
cartilage,  and  runs  perpendicularly  upward,  in  front  of  the  transverse  processes 
of  the  three  upper  cervical  vertebrae,  to  the  carotid  canal  in  the  petrous  portion 
of  the  temporal  bone.  It  is  superficial  at  its  commencement,  being  contained  in  the 
superior  carotid  triangle,  and  lying  on  the  same  level  as  the  external  carotid,  but 
behind  that  artery  overlapped  by  the  Sterno-mastoid  and  covered  by  the  deep 
fascia,  Platysma,  and  integument:  it  then  passes  beneath  the  parotid  gland,  being 
crossed  by  the  hypoglossal  nerve,  the  Digastric  and  Stylo-hyoid  muscles,  and 
the  occipital  and  posterior  auricular  arteries.  Higher  up,  it  is  separated  from  the 
external  carotid  by  the  Stylo-glossus  and  Stylo-pharyng^us  muscles,  the  glosso- 
pharyngeal nerve,  and  pharyngeal  branch  of  the  pneumogastric. 

Relations. — It  is  in  relation,  behind,  with  the  Rectus  capitis  anticus  major,  the 
superior  cervical  ganglion  of  the  sympathetic,  and  superior  laryngeal  nerve ;  exter- 
nally, with  the  internal  jugular  vein  and  pneumogastric  nerve,  the  nerve  lying 
on  a  plane  posterior  to  the  artery;  internally,  with  the  pharynx,  tonsil,  the  superior 
laryngeal  nerve,  and  ascending  pharyngeal  artery.  At  the  base  of  the  skull  the 
glosso-pharyngeal,  vagus,  spinal  accessory,  and  hypoglossal  nerves  lie  between 
the  artery  and  the  internal  jugular  vein. 

Plan  of  the  Relations  of  the  Internal  Carotid  Artery  in  the  Neck. 

In  front. 
Skin,  superficial  and  deep  fasciae. 
Platysma. 
Sterno-mastoid. 

Occipital  and  posterior  auricular  arteries. 
Hypoglossal  nerve. 
Parotid  gland. 

Stylo-glossus  and  Stylo-pharyngeus  muscles. 
Glosso-pharyngeal  nerve. 
Pharyngeal  branch  of  the  pneumogastric. 

Externally.  f  \  Internally. 

Internal  jugular  vein.  (       ^^^l^^     \  Pharynx. 

Pneumogastric  nerve.  \       Artery.       I  Superior  laryngeal  nerve. 

\  /  Ascending  pharyngeal  artery. 

^- -^  Tonsil. 

Behind. 
Rectus  capitis  anticus  major. 
Sympathetic. 
Superior  laryngeal  nerve. 

Petrous  Portion. — When  the  internal  carotid  artery  enters  the  canal  in  the 
petrous  portion  of  the  temporal  bone,  it  first  ascends  a  short  distance,  then  curves 
forward  and  inward,  and  again  ascends  as  it  leaves  the  canal  to  enter  the  cavity  of 
the  skull  between  the  lingula  and  petrosal  process.  In  this  canal  the  artery  lies 
at  first  in  front  of  the  cochlea  and  tympanum ;  from  the  latter  cavity  it  is  separated 
by  a  thin,  bony  lamella,  which  is  cribriform  in  the  young  subject,  and  is  often 
absorbed  in  old  age.  Farther  forward  it  is  separated  from  the  Gasserian  ganglion 
by  a  thin  plate  of  bone,  which  forms  the  floor  of  the  fossa  for  the  ganglion  and  the 
roof  of  the  horizontal  portion  of  the  canal.     Frequently  this  bony  plate  is  more 


THE  INTERNAL    CAROTID   ARTERY  621 

or  less  deficient,  and  then  the  ganghon  is  separated  from  the  artery  by  a  fibrous 
membrane.  The  artery  is  separated  from  the  bony  wall  of  the  carotid  canal  by  a 
prolongation  of  dura  mater,  and  is  surrounded  by  a  number  of  small  veins  and 
by  filaments  of  the  carotid  plexus,  derived  from  the  ascending  branch  of  the 
superior  cervical  ganglion  of  the  sympathetic. 

Cavernous  Portion.— The  internal  carotid  artery  in  this  part  of  its  course  is 
situated  between  the  layers  of  the  dura  mater  forming  the  cavernous  sinus,  but  is 
covered  by  the  lining  membrane  of  the  sinus.  It  at  first  ascends  to  the  posterior 
clinoid  process,  then  passes  forward  by  the  side  of  the  body  of  the  sphenoid  bone, 
and  again  curves  upward  on  the  inner  side  of  the  anterior  clinoid  process,  and 
perforates  the  dura  mater,  forming  the  roof  of  the  sinus.  In  this  part  of  its  course 
it  is  surrounded  by  filaments  of  the  sympathetic  nerve,  and  has  in  relation  with  it 
externally  the  sixth  nerve. 

Cerebral  Portion. — Having  perforated  the  dura  mater,  on  the  inner  side  of  the 
anterior  clinoid  process,  the  internal  carotid  passes  between  the  second  and  third 
cranial  nerves  to  the  anterior  perforated  spot  at  the  inner  extremity  of  the  fissure 
of  Sylvius,  where  it  gives  off  its  terminal  or  cerebral  branches.  This  portion 
of  the  artery  has  the  optic  nerve  on  its  inner  side,  and  the  third  nerve  externally. 

Peculiaxities. — The  length  of  the  internal  carotid  varies  according  to  the  length  of  the  neck, 
and  also  according  to  the  point  of  bifurcation  of  the  common  carotid.  Its  origin  sometimes 
takes  place  from  the  arch  of  the  aorta;  in  such  rare  instances  this  vessel  has  been  found  to  be 
placed  nearer  the  middle  line  of  the  neck  than  the  external  carotid,  as  far  upward  as  the  larynx, 
when  the  latter  vessel  crossed  the  internal  carotid.  The  course  of  the  vessel,  instead  of  being 
straight,  may  be  very  tortuous.  A  few  instances  are  recorded  in  which  this  vessel  was  altogether 
absent:  in  one  of  these  the  common  carotid  passed  up  the  neck,  and  gave  off  the  usual  branches 
of  the  external  carotid,  the  cranial  portion  of  the  internal  carotid  being  replaced  by  two  branches 
of  the  internal  maxillary,  which  entered  the  skull  through  the  foramen  rotundum  and  the  foramen 
ovale  and  joined  to  form  a  single  vessel. 

Surgical  Anatomy. — The  cervical  part  of  the  internal  carotid  is  very  rarely  wounded.  Mr. 
Cripps,  in  an  interesting  paper  in  the  Medico-Chirurgical  Transactions,  compares  the  rareness 
of  a  wound  of  the  internal  carotid  with  one  of  the  external  carotid  or  its  branches.  It  is,  however, 
sometimes  injured  by  a  stab  or  gunshot  wound  in  the  neck,  or  even  occasionally  by  a  stab  from 
within  the  mouth,  as  when  a  person  receives  a  thrust  from  the  end  of  a  parasol  or  falls  down 
with  a  tobacco-pipe  in  his  mouth.  It  used  to  be  believed  that  the  internal  carotid  was  occa- 
sionally wounded  in  the  removal  of  the  tonsil.  Such  an  accident  cannot  happen  if  the  artery  is 
normally  placed.  The  severe  and  sometimes  fatal  hemorrhage  which  has  followed  this  opera- 
tion in  a  few  instances  probably  had  as  its  source  enlarged  branches  of  the  ascending  pharyn- 
geal, tonsillar,  or  ascending  palatine  arteries.  Recently,  however,  Dr.  Gwilym  G.  Davis,  of 
Philadelphia,  demonstrated  a  specimen  in  which  the  internal  carotid  could  have  been  wounded 
by  incision  of  the  tonsil.  The  indications  for  ligature  are  wounds,  when  the  vessel  should  be 
exposed  by  a  careful  dissection  and  tied  above  and  below  the  bleeding  point;  and  aneurism, 
which  if  non-traumatic  may  be  treated  by  ligature  of  the  common  carotid,  but  if  traumatic  in 
origin  by  exposing  the  sac  and  tying  the  vessel  above  and  below.  The  incision  for  ligature  of 
the  cervical  portion  of  the  internal  carotid  should  be  made  along  the  anterior  border  of  the 
Sterno-mastoid,  from  the  angle  of  the  jaw  to  the  upper  border  of  the  thyroid  cartilage.  The 
superficial  structures  being  divided  and  the  Sterno-mastoid  defined  and  drawn  outward,  the 
cellular  tissue  must  be  carefully  separated  and  the  posterior  belly  of  the  Digastric  muscle  and 
the  hypoglossal  nerve  sought  for  as  guides  to  the  vessel.  When  the  artery  is  found  the  external 
carotid  should  be  drawn  inward  and  the  Digastric  muscles  upward,  and  the  aneurism  needle 
passed  from  without  inward. 

Branches. — The  branches  given  off  from  the  internal  carotid  artery  are — 

From  the  Petrous  portion        .     .     Tympanic  (internal  or  deep). 

[  Arterife  Receptaculi. 
From  the  Cavernous  portion  .     .  ]  Anterior  Meningeal. 


From  the  Cerebral  portion 


Ophthalmic. 
Anterior  Cerebral. 
Middle  Cerebral. 
Posterior  Communicating. 
Anterior  Choroid. 


622 


THE   BLOOD -VASCULAR   SYSTEM 


The  cervical  portion  of  the  internal  carotid  gives  off  no  branches. 

The  Tympanic  (ramiis  caroticotympanicus)  is  a  small  branch  from  the  petrous 
portion,  which  enters  the  cavity  of  the  tympanum  through  a  minute  foramen  in 
the  carotid  canal,  and  anastomoses  with  the  tympanic  branch  of  the  internal 
maxillary,  and  with  the  stylo-mastoid  artery. 

The  Arteriae  Receptaculi  are  numerous  small  vessels,  derived  from  the  inter- 
nal carotid  in  the  cavernous  sinus;  they  supply  the  pituitary  body,  the  Gasserian 
ganglion,  and  the  walls  of  the  cavernous  and  inferior  petrosal  sinuses.  Some  of 
these  branches  anastomose  with  branches  of  the  middle  meningeal. 

The  Anterior  Meningeal  (a.  meningea  anterior)  is  a  small  branch  which 
passes  over  the  lesser  wing  of  the  sphenoid  to  supply  the  dura  mater  of  the  ante- 
rior fossa;  it  anastomoses  with  the  meningeal  branch  from  the  posterior  ethmoidal 
artery. 

The  Ophthalmic  Artery  (a.  ophthalmica)  arises  from  the  internal  carotid, 
just  as  that  vessel  is  emerging  from  the  cavernous  sinus,  on  the  inner  side  of  the 
anterior  clinoid  process,  and  enters  the  orbit  through  the  optic  foramen,  below  and 


Nasal.        Palpebral. 
Frontal. 


a-orbital. 


Anterior  ethmoidal. 


Posterior  ethmoidal. 


Muscular. 


Temporal  branches 
of  lachrymal. 

centralis  retime. 

Lachrymal. 


OphthalmiC' 


Internal  carotid. 


Fig.  400. — The  ophthalmic  artery  and  its  branches,  the  roof  of  the  orbit  having  been  removed. 


on  the  outer  side  of  the  optic  nerve.  It  then  passes  over  the  nerve  to  the  inner  wall 
of  the  orbit,  and  thence  horizontally  forward,  beneath  the  lower  border  of  the 
Superior  oblique  muscle,  to  a  point  behind  the  internal  angular  process  of  the 
frontal  bone,  where  it  divides  into  two  terminal  branches,  the  frontal  and  nasal 
branches.  As  the  artery  crosses  the  optic  nerve  it  is  accompanied  by  the  nasal 
nerve,  and  is  separated  from  the  frontal  nerve  by  the  Rectus  superior  and 
Levator  palpebrse  superioris  muscles. 

Branches. — The  branches  of  this  vessel  may  be  divided  into  an  orbital  group, 
which  are  distributed  to  the  orbit,  and  surrounding  parts,  and  an  ocular  group^ 
which  supply  the  muscles  and  globe  of  the  eye: 


THE  INTERNAL    CAROTID    ARTERY  623 

Orbital  Group.  Ocular  Group. 

Lachrymal.  Short  CiUary. 

Supraorbital.  Long  Ciliary. 

Posterior  Ethmoidal.  Anterior  Ciliary. 

Anterior  Ethmoidal.  Arteria  Centralis  Retinae. 

Internal  Palpebral.  Muscular. 
Frontal. 
Nasal. 

The  Lachrymal  (a.  lachrimalis)  is  one  of  the  largest  branches  derived  from  the 
ophthalmic,  arising  close  to  the  optic  foramen;  not  infrequently  it  is  given  off  from 
the  ophthalmic  artery  before  it  enters  the  orbit.  It  accompanies  the  lachrymal  nerve 
along  the  upper  border  of  the  External  rectus  muscle,  and  is  distributed  to  the 
lachrymal  gland.  Its  terminal  branches,  escaping  from  the  gland,  are  distributed  to 
the  eyelids  and  conjunctiva :  of  those  supplying  the  eyelids,  two  are  of  considerable 
size  and  are  named  the  external  palpebral ;  they  run  inward  in  the  upper  and  lower 
lids  respectively,  and  anastomose  with  the  internal  palpebral  arteries,  forming  an 
arterial  circle  in  this  situation.  The  lachrymal  artery  gives  off  one  or  two  malar 
branches,  one  of  which  passes' through  a  foramen  in  the  malar  bone,  to  reach  the 
temporal  fossa,  and  anastomoses  with  the  deep  temporal  arteries;  the  other  appears 
on  the  cheek  through  the  malar  foramen,  and  anastomoses  with  the  transverse  facial. 
A  branch,  the  recurrent,  is  also  sent  backward  through  the  sphenoidal  fissure  to  the 
dura  mater,  which  anastomoses  with  a  branch  of  the  middle  meningeal  artery. 

Peculiarities. — The  lachrymal  artery  is  sometimes  derived  from  one  of  the  anterior  branches 
of  the  middle  meningeal  artery. 

The  Supraorbital  Artery  (a.  supraorbitalis)  arises  from  the  ophthalmic  as  that 
vessel  is  crossing  over  the  optic  nerve.  Ascending  so  as  to  arise  above  all  the  muscles 
of  the  orbit,  it  passes  forward,  with  the  supraorbital  nerve,  between  the  periosteum 
and  Levator  palpebrae  muscle;  and,  passing  through  the  supraorbital  foramen, 
divides  into  a  superficial  and  deep  branch,  which  supply  the  integument,  the 
muscles,  and  the  pericranium  of  the  forehead,  anastomosing  with  the  frontal,  the 
anterior  branch  of  the  temporal,  and  the  supraorbital  artery  of  the  opposite  side. 
This  artery  in  the  orbit  supplies  the  Superior  rectus  and  the  Levator  palpebral 
muscles,  and  sends  a  branch  inward,  across  the  pulley  of  the  Superior  oblique 
muscle,  to  supply  the  parts  at  the  inner  canthus.  At  the  supraorbital  foramen 
it  frequently  transmits  a  branch  to  the  diploe. 

The  Ethmoidal  Branches  are  two  in  number — posterior  (a.  ethmoidalis  posterior) 
and  anterior  (a.  ethmoidalis  anterior).  The  former,  which  is  the  smaller,  passes 
through  the  posterior  ethmoidal  foramen,  supplies  the  posterior  ethmoidal  cells, 
and,  entering  the  cranium,  gives  off  a  meningeal  branch,  which  supplies  the  adja- 
cent dura  mater,  and  nasal  branches  which  descend  into  the  nose  through  aper- 
tures in  the  cribriform  plate,  anastomosing  with  branches  of  the  spheno-palatine. 
The  anterior  ethmoidal  artery  accompanies  the  nasal  nerve  through  the  anterior 
ethmoidal  foramen,  supplies  the  anterior  ethmoidal  cells  and  frontal  sinuses,  and, 
entering  the  cranium,  gives  off  a  meningeal  branch,  which  supplies  the  adjacent 
dura  mater  and  nasal  branches,  which  descend  into  the  nose,  through  the  slit  by 
the  side  of  the  crista  galli,  and,  running  along  the  groove  on  the  under  surface  of 
the  nasal  bone,  supply  the  skin  of  the  nose. 

The  Internal  Palpebral  Arteries  (aa.  palpebrales  mediales),  two  in  number,  supe- 
rior and  inferior,  arise  from  the  ophthalmic,  opposite  the  pulley  of  the  Superior 
oblique  muscle;  they  leave  the  orbit  to  encircle  the  eyelids  near  their  free  margin, 
forming  a  superior  tarsal  arch  (arcus  tarseus  superior)  and  an  inferior  tarsal  arch  {arcus 
tarseus  inferior),  which  lie  between  the  Orbicularis  muscle  and  the  tarsal  plates; 


624 


THE   BLOOD -VASCULAR    SYSTEM 


the  superior  palpebral  inosculating  at  the  outer  angle  of  the  orbit  with  the  orbital 
branch  of  the  temporal  artery,  and  with  the  upper  of  the  two  external  palpebral 
branches  from  the  lachrymal  artery — the  inferior  palpebral  inosculating,  at  the 
outer  angle  of  the  orbit,  with  the  lower  of  the  two  external  palpebral  branches 


Fig.  401.— The  arteries  of  the  base  of  the  brain.  The  right  half  of  the  cerebellum  and  pons  have  been  removed. 
N.  B. — It  will  be  noticed  that  the  two  anterior  cerebral  arteries  have  been  drawn  at  a  considerable  distance  from 
«ach  other :    this  makes  the  anterior  communicating  artery  appear  very  much  longer  than  it  really  is. 

from  the  lachrymal  and  with  the  transverse  facial  artery,  and  at  the  inner  side 
of  the  lid  with  a  branch  from  the  angular  artery.  From  this  last  anastomosis  a 
branch  passes  to  the  nasal  duct,  ramifying  in  its  mucous  membrane,  as  far  as  the 
inferior  meatus. 


THE  INTERNAL    CAROTID   ARTERY 


625 


The  Frontal  Artery  (a.  frontalis),  one  of  the  terminal  branches  of  the  ophthal- 
mic, passes  from  the  orbit  at  its  inner  angle,  and,  ascending  on  the  forehead,  sup- 
plies the  integument,  muscles,  and  pericranium,  anastomosing  with  the  supra- 
orbital artery  and  with  the  frontal  artery  of  the  opposite  side. 

The  Nasal  Artery  (a.  dorsalis  nasi),  the  other  terminal  branch  of  the  ophthalmic, 
emerges  from  the  orbit  above  the  tendo  oculi,  and,  after  giving  a  branch  to  the 
upper  part  of  the  lachrymal  sac,  divides  into  two  branches,  one  of  which  crosses 
the  root  of  the  nose,  the  transverse  nasal,  and  anastomoses  with  the  angular  artery; 
the  other,  the  dorsalis  nasi,  runs  along  the  dorsum  of  the  nose,  supplies  its  outer 
surface,  and  anastomoses  with  the  artery  of  the  opposite  side  and  with  the  lateral 
nasal  branch  of  the  facial. 


Fissure  of 
Rolando 


Fig.  402. — Vascular  area  of  the  upper  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  external  and 
inferior  frontal  artery.  II.  The  part  supplied  by  the  ascending  frontal.  III.  The  part  supplied  by  the  ascending 
parietal.     IV.  The  part  supplied  by  the  parieto-sphenoidal  artery.    (After  Duret.) 

The  Ciliary  Arteries  (a.  ciliares)  are  divisible  into  three  groups,  the  short,  long, 
and  anterior.  The  short  ciliary  arteries  {aa.  ciliaris  posteriores  breves),  from  six 
to  twelve  in  number,  arise  from  the  ophthalmic  or  some  of  its  branches;  they  sur- 
round the  optic  nerve  as  they  pass  forward  to  the  posterior  part  of  the  eyeball, 
pierce  the  sclerotic  coat  around  the  entrance  of  the  nerve,  and  supply  the  choroid 
coat  and  ciliary  processes.  The  long  ciliary  arteries  (aa.  ciliares  posteriores  longce), 
two  in  number,  pierce  the  posterior  part  of  the  sclerotic  at  some  little  distance  from 
the  optic  nerve,  and  run  forward,  along  each  side  of  the  eyeball,  between  the 
sclerotic  and  choroid,  to  the  ciliary  muscle,  where  they  divide  into  two  branches; 
these  form  an  arterial  circle,  the  circulus  major,  around  the  circumference  of  the 
iris,  from  which  numerous  radiating  branches  pass  forward,  in  its  substance,  to 
its  free  margin,  where  they  form  a  second  arterial  circle,  the  circulus  minor,  around 
its  pupillary  margin.     The  anterior  ciliary  arteries  (aa.  ciliares  anteriores)  are 

40 


626 


THE   BLOOD -VASCULAR    SYSTEM 


derived  from  the  muscular  branches;  they  pass  to  the  front  of  the  eyeball  in  com- 
pany with  the  tendons  of  the  Recti  muscles,  form  a  vascular  zone  beneath  the 
conjunctiva,  and  then  pierces  the  sclerotic  a  short  distance  from  the  cornea  and 
terminate  in  the  circulus  major  of  the  iris. 

The  Arteria  Centralis  Retinae  is  the  first  and  one  of  the  smallest  branches  of  the 
ophthalmic  artery.  It  runs  for  a  short  distance  within  the  dural  sheath  of  the 
optic  nerve,  but  about  half  an  inch  behind  the  eyeball  it  pierces  the  optic  nerve 
obliquely,  and  runs  forward  in  the  centre  of  its  substance,  and  enters  the  globe 
of  the  eve  through  the  porus  opticus.  Its  mode  of  distribution  will  be  described 
in  the  account  of  the  anatomy  of  the  eye. 

The  Muscular  Branches  {rami  musculares) ,  two  in  number,  superior  and  inferior, 
frequently  spring  from  a  common  trunk.  The  superior,  the  smaller,  often  wanting, 
supplies  the  Levator  palpebrse,  Superior  rectus,  and  Superior  oblique.  The  infe- 
rior, more  constant  in  its  existence,  passes  forward,  between  the  optic  nerve  and 
the  Inferior  rectus  muscle,  and  is  distributed  to  the  External,  Internal,  and 
Inferior  recti,  and  Inferior  oblique.  This  vessel  gives  off  most  of  the  anterior 
ciliary  arteries.  Additional  muscular  branches  are  given  off  from  the  lachrymal 
and  supraorbital  arteries  or  from  the  ophthalmic  itself. 


Fissure  of  Rolando 


Fig.  403. — Vascular  area  of  the  internal  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  anterior 
internal  frontal.  II.  The  part  supplied  by  the  middle  internal  frontal.  III.  The  part  supplied  by  the  posterior 
internal  frontal.  IV.  The  part  supplied  by  the  posterior  temporal.  V.  The  part  supplied  by  the  occipital,  both 
terminal  branches  of  the  posterior  cerebral.      (After  Duret.) 

The  Anterior  Cerebral  (a.  cerebri  anterior)  arises  from  the  internal  carotid 
at  the  inner  extremity  of  the  fissure  of  Sylvius.  It  passes  forward  and  inward  across 
the  anterior  perforated  space,  above  the  optic  nerve,  to  the  commencement  of  the 
great  longitudinal  fissure.  Here  it  comes  into  close  relationship  with  the  anterior 
cerebral  artery  of  the  opposite  side,  and  the  two  vessels  are  connected  together  by 
a  short* anastomosing  trunk,  about  two  lines  in  length,  the  anterior  communicating 
artery.  From  this  point  the  two  vessels  run  side  by  side  in  the  longitudinal  fissure, 
curve  round  the  genu  of  the  corpus  callosum,  and,  turning  backward,  continue 
along  its  upper  surface  to  its  posterior  part,  where  they  terminate  by  anastomosing 
with  the  posterior  cerebral  arteries. 

Branches. — In  their  course  the  anterior  cerebral  arteries  give  off  the  following 
branches : 

Antero-median  ganglionic.  Anterior  internal  frontal. 

Inferior  internal  frontal.  Middle  internal  frontal. 

Posterior  internal  frontal. 


THE  INTERNAL    CAROTID    ARTERY 


627 


The  Antero-median  Ganglionic  is  a  group  of  small  arteries  which  arise  at  the 
commencement  of  the  anterior  cerebral  artery ;  they  pierce  the  anterior  perforated 
space  and  lamina  cinerea,  and  supply  the  head  of  the  caudate  nucleus. 

The  Inferior  Internal  Frontal  Branches  or  the  Internal  Orbital  Arteries,  two  or 
three  in  number,  are  distributed  to  the  orbital  surface  of  the  frontal  lobe,  where 
they  supply  the  olfactory  lobe,  gyrus  rectus,  and  internal  orbital  convolution. 

The  Anterior  Internal  Frontal  supplies  a  part  of  the  marginal  convolution,  and 
sends  branches  over  the  edge  of  the  hemisphere  to  the  superior  and  middle  frontal 
convolutions  and  upper  part  of  the  ascending  frontal  convolution. 

The  Middle  Internal  Frontal  supplies  the  corpus  callosum,  the  convolution  of  the 
corpus  callosum,  the  inner  surface  of  the  first  frontal  convolution,  and  the  upper 
part  of  the  ascending  frontal  convolution. 


Fig.  404. — Vascular  area  of  the  inferior  surface  of  the  cerebrum.  I.  The  part  supplied  by  the  anterior  tem- 
poral from  the  posterior  cerebral  artery.  II.  The  part  supplied  by  the  posterior  temporal  from  the  posterior 
cerebral  artery.     III.  The  part  supplied  by  the  occipital  from  the  posterior  cerebral  artery.     (After  Duret.) 

The  Posterior  Internal  Frontal  supplies  the  lobus  quadratus  and  adjacent  outer 
surface  of  the  hemisphere. 

The  Anterior  Communicating  Artery  (a.  communicans  anterior)  is  a  short  branch, 
about  two  lines  in  length,  but  of  moderate  diameter,  connecting  together  the  two 
anterior  cerebral  arteries  across  the  longitudinal  fissure.  Sometimes  this  vessel  is 
wanting,  the  two  arteries  joining  together  to  form  a  single  trunk,  which  afterward 
divides.  Or  the  vessel  may  be  wholly  or  partially  divided  into  two;  frequently  it 
is  longer  and  smaller  than  usual.  It  gives  off  some  of  the  antero-median  gan- 
glionic group  of  vessels,  which  are,  however,  principally  derived  from  the  anterior 
cerebral. 

The  Middle  Cerebral  Artery  (a.  cerebri  media)  (Fig.  405),  the  largest  branch 
of  the  internal  carotid,  passes  obliquely  outward  along  the  fissure  of  Sylvius,  and 
opposite  the  island  of  Reil  divides  into  its  terminal  branches. 


628 


THE   BLOOD -VASCULAR    SYSTEM 


Branches. — The  branches  of  the  middle  cerebral  artery  are — 


Antero-lateral  ganglionic. 
Inferior  external  frontal. 


Parieto-tem  poral . 


Ascending  frontal. 
Ascending  parietal. 


The  Antero-lateral  Ganglionic  Branches  are  a  group  of  small  arteries  which  arise 
at  the  commencement  of  the  middle  cerebral  artery;  they  pierce  the  anterior 
perforated  space  and  supply  the  greater  part  of  the  caudate  nucleus,  the  lenticular 
nucleus,  the  internal  capsule,  and  a  part  of  the  optic  thalamus.  One  artery  of  this 
group  (one  of  the  lenticulo-striate  arteries)  is  of  larger  size  than  the  rest,  and  is  of 
special  importance,  as  being  the  artery  in  the  brain  most  frequently  ruptured;  it 
has  been  termed  by  Charcot  the  artery  of  cerebral  hemorrhage.  It  passes  up  between 
the  lenticular  nucleus  and  the  external  capsule,  and  ultimately  ends  in  the  caudate 
nucleus. 


FISSURE  OP 
ROLANDO. 
/ 


Antero-lateraV 
Ganglionic  or  Per- 
forating Branches. 

Middle  Cerebral 
Artery. 
Fig.  405. — The  distribution  of  the  middle  cerebral  artery. 


(After  Charcot.) 


The  Inferior  External  Frontal  supplies  the  third  or  inferior  frontal  convolution, 
Broca's  convolution,  and  the  outer  part  of  the  orbital  surface  of  the  frontal  lobe. 

The  Ascending  Frontal  supplies  the  ascending  frontal  convolution. 

The  Ascending  Parietal  supplies  the  ascending  parietal  convolution  and  the 
lower  part  of  the  superior  parietal  convolution. 

The  Parieto-temporal  or  Parieto-sphenoidal  supplies  the  supramarginal,  the 
superior,  and  part  of  the  middle  temporal  convolutions,  and  the  angular  gyrus. 
It  sends  branches  to  the  temporal  lobe. 

The  Posterior  Communicating  Artery  (a.  communicans  posterior)  arises 
from  the  back  part  of  the  internal  carotid,  runs  directly  backward,  and  anasto- 
moses with  the  posterior  cerebral,  a  branch  of  the  basilar.  This  artery  varies 
considerably  in  size,  being  sometimes  small,  and  occasionally  so  large  that  the 
posterior  cerebral  may  be  considered  as  arising  from  the  internal  carotid  rather 
than  from  the  basilar.  It  is  frequently  larger  on  one  side  than  on  the  other  side. 
From  the  posterior  half  of  this  vessel  are  given  off  a  number  of  small  branches, 
the  postero-median  ganglionic  branches,  which,  with  similar  vessels  from  the  pos- 
terior cerebral,  pierce  the  posterior  perforated  space  and  supply  the  internal  sur- 
faces of  the  optic  thalami  and  the  walls  of  the  third  ventricle. 

The  Anterior  Choroid  (a.  chorioidea)  is  a  small  but  constant  branch  which 
arises  from  the  back  part  of  the  internal  carotid,  near  the  posterior  communicating 
artery.    Passing  backward  and  outward  between  the  temporal  lobe  and  the  crus 


THE    BLOOD-VESSELS    OF    THE   BRAIN 


629 


cerebri,  it  enters  the  descending  horn  of  the  lateral  ventricle  through  the  trans- 
verse fissure  and  ends  in  the  choroid  plexus.  It  is  distributed  to  the  hippocampus 
major,  corpus  fimbriatum,  velum  interpositum,  and  choroid  plexus. 


THE  BLOOD-VESSELS  OF  THE  BRAIN. 

Recent  investigations  have  tended  to  show  that  the  mode  of  distribution  of 
the  vessels  of  the  brain  has  an  important  bearing  upon  a  considerable  number  of 
the  anatomical  lesions  of  which  this  part  of  the  nervous  system  may  be  the  seat; 
it  therefore  becomes  important  to  consider  a  little  more  in  detail  the  way  in  which 
the  cerebral  vessels  are  distributed. 

The  cerebral  arteries  are  derived  from  the  internal  carotid  and  the  vertebral, 
which  at  the  base  of  the  brain  form  a  remarkable  anastomosis  known  as  the  circle 


—~~'  Anterior  cerebral  artery. 


I InterndC'carotid  artery. 


Middle  ch'ebral  artery. 


/Posterior  cef'ehral  artery. 


Fig.  406. — Diagram  of  the  arterial  circulation  at  the  base  of  the  brain.  I.  Antero-median  group  of  ganglionic 
branches.  II.  Postero-median  group.  III.  Right  and  left  antero-lateral  group.  IV.  Right  and  left  postero- 
lateral group.     The  dotted  line  shows  the  limit  of  the  ganglionic  circle.     (After  Charcot.) 


of  Willis  {circulus  arteriosus  \Willisi\)-  The  tortuosity  of  the  constituent  vessels 
of  the  anastomosis  lessens  the  impact  of  the  circulation  and  saves  the  brain  from 
damage.  The  outline  of  the  vessels  forming  the  so-called  circle  is  said  by  Sappey 
to  be  hexagonal,  and  by  Testut  to  be  heptagonal.  The  circle  of  Willis  is  formed 
in  front  by  the  anterior  cerebral  arteries,  branches  of  the  internal  carotid,  which 
are  connected  together  by  the  anterior  communicating;  behind  by  the  two  posterior 
cerebrals,  branches  of  the  basilar  which  are  connected  on  each  side  to  the  internal 
carotid  by  the  posterior  communicating  (Fig.  401).  The  parts  of  the  brain 
included  within  this  arterial  circle  are  the  lamina  cinerea,  the  commissure  of  the 
optic  nerves,  the  infundibulum,  the  tuber  cinereum,  the  corpora  albicantia,  and 
the  posterior  perforated  space.  This  arrangement  of  the  vessels  of  the  circle  of 
Willis  is  not  invariable;  according  to  Windle  it  is  maintained  in  little  more  than 
half  the  recorded  cases.     In  the  other  cases  there  are  various  anomalies. 


630 


THE    BLOOD -VASCULAR    SYSTEM 


From  the  circle  of  Willis  arise  the  three  trunks  which  together  supply  each 
cerebral  hemisphere.  From  its  anterior  part  proceed  the  two  anterior  cerebrals, 
from  its  antero-lateral  part  the  middle  cerebrals,  and  from  its  posterior  part  the 
posterior  cerebrals.  Each  of  these  principal  arteries  gives  origin  to  two  very 
different  systems  of  secondary  vessels.  One  of  these  systems  has  been  named  the 
central  ganglionic  system,  and  the  vessels  belonging  to  it  supply  the  central  ganglia 
of  the  brain;  the  other  has  been  named  the  cortical  arterial  system,  and  its  vessels 
ramify  in  the  pia  mater  and  supply  the  cortex  and  subjacent  medullary  matter. 
These  two  systems,  though  they  have  a  common  origin,  do  not  communicate  at  any 
point  of  their  peripheral  distribution,  and  are  entirely  independent  of  each  other. 
Though  some  of  the  arteries  of  the  cortical  system  approach,  at  their  terminations, 
the  regions  supplied  by  the  central  ganglionic  system,  no  communication  between 
the  two  sets  of  vessels  takes  place,  and  there  is  between  the  parts  supplied  by  the 
two  systems  a  borderland  of  diminished  nutritive  activity,  where,  it  is  said, 
softening  is  especially  liable  to  occur  in  the  brains  of  old  people. 

The  Central  Ganglionic  System. — All  the  vessels  belonging  to  this  system 
are  given  off  from  the  circle  of  Willis  or  from  the  vessels  immediately  after  their 
origin  from  it,  so  that  if  a  circle  is  drawn  at  a  distance  of  about  an  inch  from  the 
circle  of  Willis,  it  will  include  the  origin  of  all  the  arteries  belonging  to  this  system 
(Fig.  406).  The  vessels  of  this  system  form  six  principal  groups:  (I.)  the  antero- 
median group,  derived  from  the  anterior  cerebrals  and  anterior  communicating; 
(II.)  the  postero-median  group,  from  the  posterior  cerebrals  and  posterior  communi- 
cating; (III.)  the  right  and  left  antero-lateral  group,  from  the  middle  cerebrals;  and 
(IV.)  the  right  and  left  postero-lateral  group,  from  the  posterior  cerebrals,  after  they 
have  wound  round  the  crura  cerebri.    The  vessels  belonging  to  this  system  are 


Fig.  407. — Distribution  of  the  cortical  arteries.  1.  Medullary  arteries.  1'.  Group  of  medullary  arteries  in 
the  sulcus  between  two  adjacent  convolutions.  1".  Arteries  situated  among  the  short  association  fibres.  2,2. 
Cortical  arteries,  a.  Capillary  network  with  fairly  wide  meshes,  situated  beneath  the  pia  mater,  b.  Net- 
work with  more  compact,  polygonal  meshes,  situated  in  the  cortex.  C.  Transitional  network  with  wider 
meshes,     a.  Capillary  network  in  the  white  matter.      (After  Charcot.) 

larger  than  those  of  the  cortical  system,  and  are  what  Cohnheim  has  termed 
terminal  arteries ;  that  is  to  say,  vessels  which  from  their  origin  to  their  termination 
neither  supply  nor  receive  any  anastomotic  branches,  so  that  by  one  of  the  small 


THE   SUBCLAVIAN  ARTERY  631 

vessels  only  a  limited  area  of  the  central  ganglia  can  be  injected;  and  the  injection 
cannot  be  driven  beyond  the  area  of  the  part  supplied  by  the  particular  vessel  which 
is  the  subject  of  the  experiment. 

The  Cortical  Arterial  System. — The  vessels  forming  this  system  are  the  ter- 
minal branches  of  the  anterior,  middle,  and  posterior  cerebral  arteries,  described 
above.  These  vessels  divide  and  ramify  in  the  substance  of  the  pia  mater,  and  give 
off  nutrient  arteries  which  penetrate  the  cortex  perpendicularly.  These  nutrient 
vessels  are  divisible  into  two  classes — the  long  and  short.  The  long — or,  as  they 
are  sometimes  called,  the  medullary — arteries  pass  through  the  gray  matter  to  pene- 
trate the  centrum  ovale  to  the  depth  of  about  an  inch  and  a  half,  without  intercom- 
municating otherwise  than  by  very  fine  capillaries,  and  thus  constitute  so  many 
independent  small  systems.  The  short  vessels  are  confined  to  the  cortex,  where 
they  form  with  the  long  vessels  a  compact  network  in  the  middle  zone  of  the  gray 
matter,  the  outer  and  inner  zones  being  sparingly  supplied  with  blood  (Fig.  407). 
The  vessels  of  the  cortical  arterial  system  are  not  so  strictly  terminal  as  those  of  the 
central  ganglionic  system,  but  they  approach  this  type  very  closely,  so  that  injec- 
tion of  one  area  from  the  vessel  of  another  area,  though  it  may  be  possible,  is  fre- 
quently very  difficult,  and  is  only  effected  through  vessels  of  small  calibre.  As  a 
result  of  this,  oljstruction  of  one  of  the  main  branches  or  its  divisions  may  have 
the  effect  of  producing  softening  in  a  very  limited  area  of  the  cortex.^ 

ARTERIES  OF  THE  UPPER  EXTREMITY. 

The  artery  which  supplies  the  upper  extremity  continues  as  a  single  trunk 
from  its  commencement  down  to  the  elbow,  but  different  portions  of  it  have 
received  different  names  according  to  the  region  through  which  it  passes.  That 
part  of  the  vessel  which  extends  from  its  origin  to  the  outer  border  of  the  first 
rib  is  termed  the  subclavian  artery ;  beyond  this  point  to  the  lower  border  of  the 
axilla  it  is  termed  the  axillary  artery;  and  from  the  lower  margin  of  the  axillary  space 
to  the  bend  of  the  elbow  it  is  termed  the  brachial  artery;  here  the  single  trunk 
terminates  by  dividing  into  two  branches,  the  radial  and  ulnar — an  arrangement 
precisely  similar  to  what  occurs  in  the  lower  limb. 

THE  SUBCLAVIAN  ARTERY  (A.  SUBCLAVIA)  (Fig.  408). 

The  subclavian  artery  on  the  right  side  arises  from  the  innominate  artery 
opposite  the  right  sterno-clavicular  articulation;  on  the  left  side  it  arises  from 
the  arch  of  the  aorta.  It  follows,  therefore,  that  these  two  vessels  must,  in  the  first 
part  of  their  course,  differ  in  their  length,  their  direction,  and  their  relation  with 
neighboring  parts. 

In  order  to  facilitate  the  description  of  these  vessels,  more  especially  from  a 
surgical  point  of  view,  each  subclavian  artery  has  been  divided  into  three  parts. 
The  first  portion,  on  the  right  side,  passes  upward  and  outward  from  the  origin 
of  the  vessel  to  the  inner  border  of  the  Scalenus  anticus.  On  the  left  side  it  ascends 
nearly  vertically,  to  gain  the  inner  border  of  that  muscle.  The  second  part  passes 
outward,  behind  the  Scalenus  anticus;  and  the  third  part  passes  from  the  outer 
margin  of  that  muscle,  beneath  the  clavicle,  to  the  outer  border  of  the  first  rib, 
where  it  becomes  the  axillary  artery.  The  first  portion  of  these  two  vessels  differs 
so  much  in  its  course  and  in  its  relations  with  neighboring  parts  that  it  will  be 
described  separately.    The  second  and  third  parts  are  alike  on  the  two  sides. 

'  The  student  who  desires  further  information  on  this  subject  is  referred  to  Charcot's  Localization  of  Cerebral 
and  Spinal  Diseases,  p.  42  et  seq.,  whence  the  facts  above  given  have  been  principally  derived. — Ed.  of  15th 
English  edition. 


632 


THE  BLOOD -VASCULAR    SYSTEM 


First  Part  of  the  Right  Subclavian  Artery  (Figs.  389,  390,  392,  408). 

On  the  right  side  the  subclavian  artery  arises  from  the  arteria  innominata,  oppo- 
site the  upper  part  of  the  right  sterno-clavicular  articulation,  and  passes  upward 
and  outward  to  the  inner  margin  of  the  Scalenus  anticus  muscle  (Figs.  389,  390, 
and  408) .  In  this  part  of  its  course  it  ascends  a  little  above  the  clavicle,  the  extent 
to  which  it  does  so  varying  in  different  cases. 


Phrenic  nerve. 


Vertebral  artery. 

Inferior  thyroid  artery. 


Supra-scapular 
artery 
Supra- 

scapHlar\  ^i^  ^- 


eumo- 
gastric 
nerve. 


Subclavian 

artery. 
^External  jugu- 
lar vein. 
Eight  innomi- 
nate vein. 
Jnnomi- 

II life  artery. 


\ 


Fig.  408.- 


'  Profunda  artery. 
■  Musculo-spiral  nerve. 

-The  subclavian  artery,  showing  its  relations.     (From  a  preparation  in  the  Museum  of  the  Royal 
College  of  Surgeons  of  England.) 


Relations. — It  is  covered, m  front,hy  the  integument,  superficial  fascia,  Platysma^ 
deep  fascia,  the  clavicular  origin  of  the  Sterno-mastoid,  the  Sterno-hyoid,  and 
Sterno-thyroid  muscles,  and  a  second  layer  of  deep  fascia.  It  is  crossed  by  the 
internal  jugular  and  vertebral  veins,  and  by  the  pneumogastric  nerve  and  the 
cardiac  branches  of  the  sympathetic  nerve.  A  loop  of  the  sympathetic  nerve 
itself  also  crosses  the  artery,  forming  a  ring  around  the  vessels.  The  anterior 
jugular  vein  passes  outward  in  front  of  the  artery  but  is  not  in  contact  with  it, 
being  separated  from  it  by  the  Sterno-hyoid  and  Sterno-thyroid  muscles.  Below 
and  behind  the  artery  is  the  pleura,  which  separates  it  from  the  apex  of  the  lung; 
behind  is  the  cord  of  the  sympathetic  nerve;  the  recurrent  laryngeal  nerve  winds 
round  the  lower  and  back  part  of  the  vessel. 


THE  SUBCLAVIAN   ARTERY  633 

Plan  of  the  Relations  of  First  Portion  of  the  Right  Subclavian  Artery. 

In  front. 
Skin,  superficial  fascia. 
Platysma,  deep  fascia. 
Clavicular  origin  of  Sterno-mastoid. 
Sterno-hyoid  and  Sterno-thyroid. 

Anterior  jugular,  Internal  jugular,  and  vertebral  veins. 
Pneumogastric  and  cardiac  nerves. 
Loop  from  the  sympathetic. 

Beneath. 
Pleura. 
Recurrent  laryngeal  nerve. 

Behind. 
Recurrent  laryngeal  nerve. 
Sympathetic. 
Pleura  and  apex  of  lung. 

First  Part  of  the  Left  Subclavian  Artery  (Figs.  388,  389). 

The  left  subclavian  artery  arises  from  the  end  of  the  arch  of  the  aorta,  opposite 
the  fourth  dorsal  vertebra,  and  ascends  nearly  vertically  to  the  inner  margin  of 
the  Scalenus  anticus  muscle.  This  part  of  the  vessel  is,  therefore,  longer  than  the 
right,  is  situated  deeply  in  the  cavity  of  the  chest,  and  is  directed  nearly  vertically 
upward,  instead  of  arching  outward  like  the  vessel  of  the  opposite  side. 

Relations. — It  is  in  relation,  in  front,  with  the  pneumogastric,  cardiac,  and  phrenic 
nerves,  which  lie  parallel  with  it,  the  left  carotid  artery,  left  internal  jugular 
and  vertebral  veins,  and  the  commencement  of  the  left  innominate  vein  and  is 
covered  by  the  Sterno-thyroid,  Sterno-hyoid,  and  Sterno-mastoid  muscles;  behind, 
it  is  in  relation  with  the  oesophagus,  thoracic  duct,  inferior  cervical  ganglion  of  the 
sympathetic,  and  Longus  colli  muscle;  higher  up,  however,  the  oesophagus  and 
thoracic  duct  lie  to  its  right  side;  the  latter  ultimately  arching  over  the  vessel  to 
join  the  angle  of  union  between  the  subclavian  and  internal  jugular  veins.  To 
its  inner  side  are  the  oesophagus,  trachea,  and  thoracic  duct;  to  its  outer  side,  the 
left  pleura  and  lung. 

Plan  of  the  Relations  of  First  Portion  of  the  Left  Subclavian  Artery. 

In  front. 
Pneumogastric,  cardiac,  and  phrenic  nerves. 
Left  carotid  artery. 
Thoracic  duct. 

Left  internal  jugular,  vertebral,  and  innominate  veins. 
Sterno-thyroid,  Sterno-hyoid,  and  Sterno-mastoid  muscles. 

Inner  side.  /  \  Outer  side. 

Trachea.  /    „  .i^^ft        \  Pleura  and  left  lung, 

(lisophagus. 
Thoracic  duct. 

Behind. 
(Esophagus  and  thoracic  duct. 
Inferior  cervical  ganglion  of  sympathetic. 
Longus  colli. 

Second  and  Third  Parts  of  the  Subclavian  Artery  (Figs.  392,  408). 

The  Second  Portion  of  the  Subclavian  Artery  lies  behind  the  Scalenus  anticus 
muscle;  it  is  very  short,  and  forms  the  highest  part  of  the  arch  described  by  that 
vessel. 


634 


THE   BLOOD -VASCULAR   SYSTEM 


Relations. — It  is  covered,  in  front,  by  the  skin,  superficial' fascia,  Platysma, 
deep  cervical  fascia,  the  Sterno-mastoid  and  the  Scalenus  anticus  muscles.  On 
the  right  side  the  phrenic  nerve  is  separated  from  the  second  part  of  the  artery  by 
the  Scalenus  anticus  muscle,  while  on  the  left  side  the  nerve  crosses  the  first  part 
of  the  artery  immediately  to  the  inner  edge  of  the  muscle.  Behind,  it  is  in  rela- 
tion with  the  pleura  and  the  Scalenus  medius  muscle.  Above,  with  the  brachial 
plexus  of  nerves.  Below,  with  the  pleura.  The  subclavian  vein  lies  below  and 
in  front  of  the  artery,  separated  from  it  by  the  Scalenus  anticus  muscle. 

Plan  of  the  Relations  of  Second  Portion  of  Subclavian  Artery. 

In  front. 
Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 
Sterno-mastoid. 
Phrenic  nerve. 
Scalenus  anticus. 
Subclavian  vein. 

Above.  I     Artery!'''    ]  Below. 

Brachial  plexus.  1     p^^a.    J  Pleura. 

Behind. 
Pleura  and  Middle  Scalenus. 

The  Third  Portion  of  the  Subclavian  Artery  passes  downward  and  outward 
from  the  outer  margin  of  the  Scalenus  anticus  muscle  to  the  outer  border  of  the 
first  rib,  where  it  becomes  the  axillary  artery.  This  portion  of  the  vessel  is  the 
most  superficial,  and  is  contained  in  the  subclavian  triangle  (see  page  618). 

Relations. — It  is  covered,  in  front,  by  the  skin,  the  superficial  fascia,  the  Platysma 
the  descending  clavicular  branches  of  the  cervical  plexus,  and  the  deep  cervical 
fascia;  by  the  clavicle,  the  Subclavius  muscle,  the  suprascapular  artery  and 
vein,  and  the  transverse  cervical  vein;  the  nerve  to  the  Subclavius  muscle  passes 
vertically  downward  in  front  of  the  artery.  The  external  jugular  vein  crosses 
the  artery  at  its  inner  side,  and  receives  the  suprascapular  and  transverse  cervical 
veins,  which  frequently  form  a  plexus  in  front  of  it.  The  subclavian  vein  is 
below  and  in  front  of  the  artery,  lying  close  behind  the  clavicle.  Behind,  it  lies  on 
the  Middle  scalenus  muscle  and  the  lowest  cord  of  the  brachial  plexus,  formed 
by  the  union  of  the  last  cervical  and  first  dorsal  nerves.  Above  it,  and  to  its 
outer  side,  is  the  brachial  plexus  and  Omo-hyoid  muscle.  Below,  it  rests  on  the 
upper  surface  of  the  first  rib. 

Plan  of  the  Relations  of  Third  Portion  of  Subclavian  Artery. 

In  front. 
Skin  and  superficial  fascia. 
Platysma  and  deep  cervical  fascia. 

Descending  branches  of  cervical  plexus.     Nerve  to  Subclavius  muscle. 
Subclavius  muscle,  suprascapular  artery,  and  vein. 
The  external  jugular  and  transverse  cervical  veins. 
The  clavicle. 

. ,  /    Subclavian     \  „  , 

Above.  I  Artery.         ]  BelOW. 

Brachial  plexus.  I      portion.      /  First  rib. 


Omo-hyoid. 


Behind. 
Scalenus  medius. 
Lower  cord  of  brachial  plexus. 


THE   SUBCLAVIAN  ARTERY  635 

Peculiarities. — The  subclavian  arteries  vary  in  their  origin,  their  course,  and  the  height  to 
■which  they  rise  in  the  neck. 

The  origin  of  the  right  subclavian  from  the  innominate  takes  place,  in  some  cases,  above  the 
sterno-clavicular  articulation,  and  occasionally,  but  less  frequently,  in  the  cavity  of  the  thorax, 
below  that  point.  Or  the  artery  may  arise  as  a  separate  trunk  from  the  arch  of  the  aorta.  In 
such  cases  it  may  be  either  the  first,  second,  third,  or  even  the  last  branch  derived  from  that 
vessel ;  in  the  majority  of  cases  it  is  the  first  or  last,  rarely  the  second  or  third.  When  it  is  the  first 
branch,  it  occupies  the  ordinary  position  of  the  innominate  artery;  when  the  second  or  third,  it 
gains  its  usual  position  by  passing  behind  the  right  carotid;  and  when  the  last  branch,  it  arises 
from  the  left  extremity  of  the  arch,  at  its  upper  or  back  part,  and  passes  obliquely  toward  the 
right  side,  usually  behind  the  trachea,  oesophagus,  and  right  carotid,  sometimes  between  the 
<Esophagus  and  trachea  to  the  upper  border  of  the  first  rib,  whence  it  follows  its  ordinary  course. 
In  very  rare  instances  this  vessel  arises  from  the  thoracic  aorta,  as  low  down  as  the  fourth 
dorsal  vertebra.  Occasionally  it  perforates  the  Scalenus  anticus  muscle;  more  rarely  it  passes 
in  front  of  that  muscle.  Sometimes  the  subclavian  vein  passes  with  the  artery  behind  the 
Scalenus  anticus  muscle.  The  artery  may  ascend  as  high  as  an  inch  and  a  half  above  the 
clavicle  or  any  intermediate  point  between  this  and  the  upper  border  of  the  bone,  the  right 
subclavian  usually  ascending  higher  than  the  left. 

The  left  subclavian  is  occasionally  joined  at  its  origin  with  the  left  carotid. 

Surface  Marking. — The  course  of  the  subclavian  artery  in  the  neck  may  be  mapped  out 
by  describing  a  curve,  with  its  convexity  upward  at  the  base  of  the  posterior  triangle.  The  inner 
•end  of  this  curve  corresponds  to  the  sterno-clavicular  joint,  the  outer  end  of  the  centre  of  the 
lower  border  of  the  clavicle.  The  curve  is  to  be  drawn  with  such  an  amount  of  convexity  that 
its  mid-point  reaches  half  an  inch  above  the  upper  border  of  the  clavicle.  The  left  subclavian 
artery  is  more  deeply  placed  than  the  right  in  the  first  part  of  its  course,  and,  as  a  rule,  does  not 
reach  quite  as  high  a  level  in  the  neck.  It  should  be  borne  in  mind  that  the  posterior  border  of 
the  Sterno-mastoid  muscle  corresponds  to  the  outer  border  of  the  Scalenus  anticus  muscle,  so 
that  the  third  portion  of  the  artery,  that  part  most  accessible  for  operation,  lies  immediately 
external  to  the  posterior  border  of  the  Sterno-mastoid  muscle. 

Surgical  Anatomy. — The  relations  of  the  subclavian  arteries  of  the  two  sides  having  been 
examined,  the  student  should  direct  his  attention  to  a  consideration  of  the  best  position  in  which 
compression  of  the  vessel  may  be  effected,  or  in  what  situation  a  ligature  may  be  best  applied  in 
cases  of  aneurism  or  wound. 

Compression  of  the  subclavian  artery  is  required  in  cases  of  operations  about  the  shoulder, 
in  the  axilla,  or  at  the  upper  part  of  the  arm;  and  the  student  will  observe  that  there  is  only 
■one  situation  in  which  it  can  be  effectually  applied — viz.,  where  the  artery  passes  across  the 
upper  surface  of  the  first  rib.  In  order  to  compress  the  vessel  in  this  situation,  the  shoulder 
should  be  depressed,  and  the  surgeon,  grasping  the  side  of  the  neck,  should  press  with  his  thumb 
in  the  angle  formed  by  the  posterior  border  of  the  Sterno-mastoid  with  the  upper  border  of 
the  clavicle,  downward,  backward,  and  inward  against  the  rib;  if  from  any  cause  the  shoulder 
cannot  be  sufficiently  depressed,  pressure  may  be  made  from  before  backward,  so  as  to  compress 
the  artery  against  the  Scalenus  medius  muscle  and  the  transverse  process  of  the  seventh  cervical 
vertebra.  In  appropriate  cases,  a  preliminary  incision  may  be  made  through  the  cervical 
fascia,  and  the  finger  may  be  pressed  down  directly  upon  the  artery. 

Ligature  of  the  subclavian  artery  may  be  required  in  cases  of  wounds  or  of  aneurism  in 
the  axilla,  or  in  cases  of  aneurism  on  the  cardiac  side  of  the  point  of  ligature;  and  the  third  part 
•of  the  artery  is  that  which  is  most  favorable  for  an  operation,  on  account  of  its  being  compara- 
tively superficial  and  most  remote  from  the  origin  of  the  large  branches.  In  those  cases  where 
the  clavicle  is  not  displaced,  this  operation  may  be  performed  with  comparative  facility;  but 
where  the  clavicle  is  pushed  up  by  a  large  aneurismal  tumor  in  the  axilla  the  artery  is  placed  at 
a  great  depth  from  the  surface,  which  materially  increases  the  difficulty  of  the  operation.  Under 
these  circumstances  it  becomes  a  matter  of  importance  to  consider  the  height  to  which  this 
vessel  reaches  above  the  bone.  In  ordinary  cases  its  arch  is  about  half  an  inch  above  the  clavicle, 
occasionally  it  is  as  high  as  an  inch  and  a  half,  and  sometimes  so  low  as  to  be  on  a  level  with 
the  upper  border  of  the  clavicle.  If  the  clavicle  is  displaced,  these  variations  will  necessarily 
make  the  operation  more  or  less  difficult  according  as  the  vessel  is  more  or  less  accessible. 

The  chief  points  in  the  operation  of  tying  the  third  portion  of  the  subclavian  artery  are  as 
follows:  The  patient  being  placed  on  a  table  in  the  supine  position,  with  the  head  drawn  over  to 
the  opposite  side  and  the  shoulder  depressed  as  much  as  possible,  the  integument  should  be 
drawn  downward  over  the  clavicle,  and  an  incision  made  through  it,  upon  that  bone,  from  the 
anterior  border  of  the  Trapezius  to  the  posterior  border  of  the  Sterno-mastoid,  to  which  may  be 
added  a  short  vertical  incision  meeting  the  inner  end  of  the  preceding.  The  object  in  drawing 
the  skin  downward  is  to  avoid  any  risk  of  wounding  the  external  jugular  vein,  for  as  it  perforates 
the  deep  fascia  above  the  clavicle,  it  cannot  be  drawn  downward  with  the  skin.  The  soft  parts 
should  now  be  allowed  to  glide  up,  and  the  cervical  fascia  should  be  divided  upon  a  director, 
and  if  the  interval  between  the  Trapezius  and  Sterno-mastoid  muscles  be  insufficient  for  the  per- 


636  THE   BLOOD -VASCULAR   SYSTEM 

formance  of  the  operation,  a  portion  of  one  or  both  may  be  divided.  The  external  jugular  vein 
will  now  be  seen  toward  the  inner  side  of  the  wound :  this  and  the  suprascapular  and  transverse 
cervical  veins,  which  terminate  in  it,  should  be  held  aside.  If  the  external  jugular  vein  is  at  all 
in  the  way  and  exposed  to  injury,  it  should  be  tied  in  two  places  and  divided.  The  suprascapu- 
lar artery  should  be  avoided,  and  the  Omo-hyoid  muscle  held  aside  if  necessary.  In  the  space 
beneath  this  muscle  careful  search  must  be  made  for  the  vessel :  a  deep  layer  of  fascia  and  some 
connective  tissue  having  been  divided  carefully,  the  outer  margin  of  the  Scalenus  anticus  muscle 
must  be  felt  for,  and,  the  finger  being  guided  by  it  to  the  first  rib,  the  pulsation  of  the  subcla- 
vian artery  will  be  felt  as  it  passes  over  the  rib.  The  sheath  of  the  vessels  having  been  opened, 
the  aneurism  needle  may  then  be  passed  around  the  artery  from  above  downward  and  inward,  so 
as  to  avoid  including  any  of  the  branches  of  the  brachial  plexus.  If  the  clavicle  is  so  raised  by 
the  tumor  that  the  application  of  the  ligature  cannot  be  effected  in  this  situation,  the  artery  may 
be  tied  above  the  first  rib,  or  even  behind  the  Scalenus  anticus  muscle;  the  difficulties  of  the 
operation  in  such  a  case  will  be  materially  increased,  on  account  of  the  greater  depth  of  the  artery 
and  the  alteration  in  position  of  the  surrounding  parts. 

The  second  part  of  the  subclavian  artery,  from  being  that  portion  which  rises  highest  in 
the  neck,  has  been  considered  favorable  for  the  application  of  the  ligature  when  it  is  difficult  to 
tie  the  artery  in  the  third  part  of  its  course.  There  are,  however,  many  objections  to  the  opera- 
tion in  this  situation.  It  is  necessary  to  divide  the  Scalenus  anticus  muscle,  upon  which  lies 
the  phrenic  nerve,  and  at  the  inner  side  of  which  is  situated  the  internal  jugular  vein;  and  a 
wound  of  either  of  these  structures  might  lead  to  the  most  dangerous  consequences.  Again, 
the  artery  is  in  contact,  below,  with  the  pleura,  which  must  also  be  avoided;  and,  lastly,  the 
proximity  of  so  many  of  its  large  branches  arising  internal  to  this  point  must  be  a  still  further 
objection  to  the  operation.  In  cases,  however,  where  the  sac  of  an  axillary  aneurism  encroaches 
on  the  neck,  it  may  be  necessary  to  divide  the  outer  half  or  two-thirds  of  the  Scalenus  anticus 
muscle,  so  as  to  place  the  ligature  on  the  vessel  at  a  greater  distance  from  the  sac.  The  opera- 
tion is  performed  exactly  in  the  same  way  as  a  ligature  of  the  third  portion,  until  the  Scalenus 
anticus  is  exposed,  when  it  is  to  be  divided  on  a  director  (never  to  a  greater  extent  than  its  outer 
two-thirds),  and  it  immediately  retracts.  The  operation  is  therefore  merely  an  extension  of 
ligature  of  the  third  portion  of  the  vessel. 

In  those  cases  of  aneurism  of  the  axillary  or  subclavian  artery  in  which  the  aneurism 
encroaches  upon  the  outer  portion  of  the  Scalenus  muscle  to  such  an  extent  that  a  ligature 
cannot  be  applied  in  that  situation,  it  may  be  deemed  advisable,  as  a  last  resource,  to  tie  the 
first  portion  of  the  subclavian  artery.  On  the  left  side  this  operation  has  been  regarded  as 
almost  impracticable;  the  great  depth  of  the  artery  from  the  surface,  its  intimate  relation 
with  the  pleura,  and  its  close  proximity  to  the  thoracic  duct  and  to  so  many  important  veins 
and  nerves,  present  a  series  of  difficulties  which  it  is  very  difficult  to  overcome.  Nevertheless, 
Professor  Halsted  and  Schumpert  have  each  tied  successfully  the  first  portion  of  the  left  sub- 
clavian for  aneurism.  J.  K.  Rodgers,  of  New  York,  also  did  it  successfully.  On  the  right 
side  the  operation  is  practicable,  and  has  been  performed.  Dr.  Nassau,  of  Philadelphia,  suc- 
cessfully ligated  the  first  part  of  the  right  subclavian.  The  main  objection  to  the  operation 
in  this  situation  is  the  smallness  of  the  interval  which  usually  exists  between  the  com- 
mencement of  the  vessel  and  the  origin  of  the  nearest  branch.  The  operation  may  be  per- 
formed in  the  following  manner:  The  patient  being  placed  on  the  table  in  the  supine  position 
with  the  neck  extended,  an  incision  should  be  made  along  the  upper  border  of  the  inner  part 
of  the  clavicle,  and  a  second  along  the  inner  border  of  the  Sterno-mastoid,  meeting  the 
former  at  an  angle.  The  attachment  of  both  heads  of  the  Sterno-mastoid  must  be  divided 
on  a  director  and  turned  outward;  a  few  small  arteries  and  veins,  and  occasionally  the 
anterior  jugular  vein,  must  be  avoided,  or,  if  necessary,  ligatured  in  two  places  and  divided, 
and  the  Sterno-hyoid  and  Sterno-thyroid  muscles  are  to  be  divided  in  the  same  manner  as  the 
preceding  muscle.  After  tearing  through  the  deep  fascia  with  the  finger-nail,  the  internal  jugular 
vein  will  be  seen  crossing  the  subclavian  artery;  this  should  be  pressed  aside  and  the  artery 
secured  by  passing  the  needle  from  below  upward,  by  which  the  pleura  is  more  effectually 
avoided.  The  exact  position  of  the  vagus,  the  recurrent  laryngeal,  the  phrenic  and  sympa- 
thetic nerves  should  be  remembered,  and  the  ligature  should  be  applied  near  the  origin  of  the 
vertebral,  in  order  to  afford  as  much  room  as  possible  for  the  formation  of  a  coagulum 
between  the  ligature  and  the  orgin  of  the  vessel.  It  should  be  remembered  that  the  right  sub- 
clavian artery  is  occasionally  deeply  placed  in  the  first  part  of  its  course  when  it  arises  from 
the  left  side  of  the  aortic  arch,  and  passes  in  such  cases  behind  the  oesophagus  or  between  it 
and  the  trachea. 

Collateral  Circulation. — After  ligature  of  the  third  part  of  the  subclavian  artery  the  col- 
lateral circulation  is  mainly  established  by  three  sets  of  vessels,  thus  described  in  a  dissection: 

"1.  A  posterior  set,  consisting  of  the  suprascapular  and  posterior  scapular  branches  of  the 
subclavian,  anastomosing  with  the  subscapular  from  the  axillary. 

"2.  An  internal  set  produced  by  the  connection  of  the  internal  mammary  on  the  one  hand, 
with  the  superior  and  long  thoracic  arteries,  and  the  branches  from  the  subscapular  on  the  other. 


THE   SUBCLAVIAN  ARTERY  637 

"  3.  A  middle  or  axillary  set,  which  consisted  of  a  number  of  small  vessels  derived  from  branches 
of  the  subclavian,  above,  and,  passing  through  the  axilla,  terminated  either  in  the  main  trunk 
or  some  of  the  branches  of  the  axillary  below.  This  last  set  presented  most  conspicuously  the 
peculiar  character  of  the  newly  formed  or,  rather,  dilated  arteries,  being  excessively  tortuous, 
and  forming  a  complete  plexus. 

"The  chief  agent  in  the  restoration  of  the  axillary  artery  below  the  tumor  was  the  subscapular 
artery,  which  communicated  most  freely  with  the  internal  mammary,  suprascapular,  and  pos- 
terior scapular  branches  of  the  subclavian,  from  all  of  which  is  received  so  great  an  influx  of 
blood  as  to  dilate  it  to  three  times  its  natural  size."' 

When  a  ligature  is  applied  to  the  first  part  of  the  subclavian  aretry,  the  collateral  circulation 
is  carried  on  by — 1,  the  anastomosis  between  the  superior  and  inferior  thyroid;  2,  the  anasto- 
mosis of  the  two  vertebrals;  3,  the  anastomosis  of  the  internal  mammary  with  the  deep  epi- 
gastric and  the  aortic  intercostals ;  4,  the  superior  intercostal  anastomosing  with  the  aortic  inter- 
costals;  5,  the  profunda  cervicis  anastomosing  with  the  princeps  cervicis;  6,  the  scapular  branches 
of  the  thyroid  axis  anastomosing  with  the  branches  of  the  axillary;  and  7,  the  thoracic  branches 
of  the  axillary  anastomosing  with  the  aortic  intercostals. 

Branches. — The  branches  given  off  from  the  subclavian  artery  are: 
Vertebral.  Internal  mammary. 

Thyroid  axis.  Superior  intercostal. 

On  the  left  side  all  four  branches  generally  arise  from  the  first  portion  of  the 
vessel;  but  on  the  right  side,  the  superior  intercostal  usually  arises  from  the  second 
portion  of  the  vessel.  On  both  sides  of  the  body  the  first  three  branches  arise  close 
together  at  the  inner  margin  of  the  Scalenus  anticus;  in  the  majority  of  cases  a 
free  interval  of  from  half  an  inch  to  an  inch  exists  between  the  commencement  of 
the  artery  and  the  origin  of  the  nearest  branch;  in  a  smaller  number  of  cases  an 
interval  of  more  than  an  inch  exists,  but  it  never  exceeds  an  inch  and  three-quarters. 
In  a  very  few  instances  the  interval  has  been  found  to  be  less  than  half  an  inch. 
The  vertebral  artery  arises  from  the  upper  and  posterior  part  of  the  subclavian 
artery,  the  internal  mammary  from  the  lower  part  of  the  artery;  the  thyroid  axis 
from  in  front  and  the  superior  intercostal  from  behind. 

The  Vertebral  Artery  (a.  vertehralis)  (Fig.  399)  is  generally  the  first  and 
largest  branch  of  the  subclavian ;  it  arises  from  the  upper  and  back  part  of  the 
first  portion  of  the  vessel,  and,  passing  upward,  enters  the  foramen  in  the  trans- 
verse process  of  the  sixth  cervical  vertebra,^  and  ascends  through  the  foramina 
in  the  transverse  processes  of  all  the  vertebrae  above  this.  Above  the  upper  border 
of  the  axis  it  inclines  outward  and  upward  to  the  foramen  in  the  transverse  process 
of  the  atlas,  through  which  it  passes ;  it  then  winds  backward  behind  its  articular 
process,  runs  in  a  deep  groove  on  the  upper  surface  of  the  posterior  arch  of  this 
bone  (Fig.  16),  and,  passing  beneath  the  posterior  occipito-atlantal  ligament 
(Figs.  199  and  202),  pierces  the  dura  mater  and  arachnoid,  and  enters  the  skull 
through  the  foramen  magnum.  It  then  passes  forward  and  upward,  incHning 
from  the  lateral  aspect  to  the  front  of  the  medulla  oblongata.  It  unites  in  the 
middle  line  with  the  vessel  of  the  opposite  side  at  the  lower  border  of  the  pons 
Varolii  to  form  the  basilar  artery  (Fig.  401). 

Relations. — At  its  origin  it  is  situated  behind  the  internal  jugular  and  vertebral 
veins,  and  is  crossed  by  the  inferior  thyroid  artery:  it  lies  between  the  Longus 
colli  and  Scalenus  anticus  muscles,  having  the  thoracic  duct  in  front  of  it  on  the 
left  side.  It  rests  on  the  transverse  process  of  the  seventh  cervical  vertebra  and 
the  sympathetic  nerve.  Within  the  foramina  formed  by  the  transverse  processes 
of  the  vertebrae  it  is  accompanied  by  a  plexus  of  nerves  from  the  inferior  cervical 
ganglion  of  the  sympathetic,  and  is  surrounded  by  a  dense  plexus  of  veins  which 
unite  to  form  the  vertebral  vein  at  the  lower  part  of  the  neck.     It  is  situated  in 

'  Guy's  Hospital  Reports,  vol.  i.,  1836:  case  of  axillary  aneurism,  in  which  Mr.  Aston  Key  had  tied  the  sub- 
•clavian  artery  on  the  outer  edge  of  the  Scalenus  muscle  twelve  years  previously. 

2  The  vertebral  artery  sometimes  enters  the  foramen  in  the  transverse  process  of  the  fifth  vertebra.  Dr.  Smyth, 
who  tied  this  arter.v  in  the  livinjt  subject,  found  it,  in  one  of  his  dissections,  passing  into  the  foramen  in  the 
.seventh  vertebra. — Ed.  of  15th  English  edition. 


638  THE  BLOOD -VASCULAR   SYSTEM 

front  of  the  cervical  nerves,  as  they  issue  from  the  intervertebral  foramina.  WTiile 
winding  round  the  articular  process  of  the  atlas,  it  is  contained  in  a  triangular 
space,  the  suboccipital  triangle,  formed  by  the  Rectus  capitis  posticus  major,  the 
Superior  oblique  and  the  Inferior  oblique  muscles;  and  at  this. point  is  covered 
by  the  Complexus  muscle  (Fig.  283) .  The  suboccipital  nerve  here  lies  between 
the  artery  and  the  bone.  Within  the  skull,  as  the  artery  winds  round  the  medulla 
oblongata,  it  is  placed  between  the  hypoglossal  nerve  and  the  anterior  root  of  the 
suboccipital  nerve,  beneath  the  first  digitation  of  the  ligamentum  denticulatum, 
and  finally  ascends  between  the  basilar  process  of  the  occipital  bone  and  the 
anterior  surface  of  the  medulla  oblongata. 

Branches. — These  may  be  divided  into  two  sets — those  given  off  in  the  neck 
and  those  within  the  cranium. 

Cervical  Branches.  Cranial  Branches. 

Lateral  Spinal.  Posterior  Meningeal. 

Muscular.  Anterior  Spinal. 

Posterior  Spinal. 

Posterior  Inferior  Cerebellar. 

Bulbar. 

The  Lateral  Spinal  Branches  {rami  spinales)  enter  the  spinal  canal  through  the 
intervertebral  foramina  and  divide  into  two  branches.  Of  these,  one  passes  along 
the  roots  of  the  nerves  to  supply  the  spinal  cord  and  its  membranes,  anastomosing 
with  the  other  arteries  of  the  spinal  cord ;  the  other  divides  into  an  ascending  and 
a  descending  branch,  which  unite  with  similar  branches  from  the  artery  above  and 
below,  so  that  two  lateral  anastomotic  chains  are  formed  on  the  posterior  surface 
of  the  bodies  of  the  vertebrae  near  the  attachment  of  the  pedicles.  From  these 
anastomotic  chains  branches  are  given  off  to  supply  the  periosteum  and  the  bodies 
of  the  vertebrae,  and  to  communicate  with  similar  branches  from  the  opposite  side; 
from  these  communicating  branches  small  branches  are  given  off  which  join 
similar  branches  above  and  below,  so  that  a  central  anastomotic  chain  is  formed 
on  the  posterior  surface  of  the  bodies  of  the  vertebrae. 

Muscular  Branches  are  given  off  to  the  deep  muscles  of  the  neck,  where  the 
vertebral  artery  curves  round  the  articular  process  of  the  atlas.  They  anastomose 
with  the  occipital  and  with  the  ascending  and  deep  cervical  arteries. 

The  Posterior  Meningeal  {ramus  meningeus)  is  a  small  branch  given  off  from 
the  vertebral  opposite  the  foramen  magnum.  It  ramifies  between  the  bone  and 
dura  mater  in  the  cerebellar  fossae,  and  supplies  the  falx  cerebelli. 

The  Anterior  Spinal  (a.  spinalis  anterior)  is  a  small  branch  which  arises  near 
the  termination  of  the  vertebral,  and,  descending  in  front  of  the  medulla  oblongata, 
unites  with  its  fellow  on  the  opposite  side  at  about  the  level  of  the  foramen  magnum. 
One  of  these  vessels  is  usually  larger  than  the  other,  but  occasionally  they  are  about 
equal  in  size.  The  single  trunk  thus  formed  descends  on  the  front  of  the  spinal 
cord,  and  is  reinforced  by  a  succession  of  small  branches  which  enter  the  spinal 
canal  through  the  intervertebral  foramina;  these  branches  are  derived  from  the 
vertebral  artery  and  the  ascending  cervical  branch  of  the  inferior  thyroid  artery 
in  the  neck;  from  the  intercostal  in  the  dorsal  region;  and  from  the  lumbar, 
ilio-lumbar,  and  lateral  sacral  arteries  in  the  lower  part  of  the  spine.  They  unite, 
by  means  of  ascending  and  descending  branches,  to  form  a  single  anterior  median 
artery,  which  extends  as  far  as  the  lower  part  of  the  spinal  cord.  This  vessel  is 
placed  in  the  pia  mater  along  the  anterior  median  fissure;  it  supplies  that  mem- 
brane and  the  substance  of  the  cord,  and  sends  off  branches  at  its  lower  part  to 
be  distributed  to  the  cauda  equina,  and  ends  on  the  central  fibrous  prolongation 
of  the  cord. 


THE   SUBCLAVIAN    ARTERY  639 

The  Posterior  Spinal  (a.  spinalis  posterior)  arises  from  the  vertebral  at  the  side 
of  the  medulla  oblongata:  passing  backward  to  the  posterior  aspect  of  the  spinal 
cord,  it  descends  on  each  side,  lying  behind  the  posterior  roots  of  the  spinal 
nerves,  and  is  reinforced  by  a  succession  of  small  branches  which  enter  the 
spinal  canal  through  the  intervertebral  foramina,  and  by  which  it  is  continued  to 
the  lower  part  of  the  cord  and  to  the  cauda  equina.  Branches  from  these  vessels 
form  a  free  anastomosis  round  the  posterior  roots  of  the  spinal  nerves,  and  com- 
municate, by  means  of  very  tortuous  transverse  branches,  with  the  vessel  of  the 
opposite  side.  At  its  commencement  it  gives  off  an  ascending  branch,  which 
terminates  on  the  side  of  the  fourth  ventricle. 

The  Posterior  Inferior  Cerebellar  Artery  (a.  cerehelli  inferior  posterior)  (Fig.  401), 
the  largest  branch  of  the  vertebral,  winds  backward  round  the  upper  part  of  the 
medulla  oblongata,  passing  between  the  origin  of  the  pneumogastric  and  spinal 
accesssory  nerves,  over  the  restiform  body  to  the  under  surface  of  the  cerebellum, 
where  it  divides  into  two  branches — an  internal,  which  is  continued  backward 
to  the  notch  between  the  two  hemispheres  of  the  cerebellum ;  and  an  external, 
which  supplies  the  under  surface  of  the  cerebellum  as  far  as  its  outer  border, 
where  it  anastomoses  with  the  anterior  inferior  cerebellar  and  the  superior  cere- 
bellar branches  of  the  basilar  artery.  Branches  from  this  artery  supply  the 
choroid  plexus  of  the  fourth  ventricle. 

The  Bulbar  Arteries  comprise  several  minute  vessels  which  spring  from  the 
vertebral  and  its  branches  and  are  distributed  to  the  medulla  oblongata. 

Surgical  Anatomy. — The  vertebral  artery  has  been  tied  in  several  instances :  1 ,  for  wounds 
or  traumatic  aneurism ;  2,  after  ligation  of  the  innominate,  either  immediately  to  prevent  hem- 
orrhage, or  later  on  to  arrest  bleeding  where  it  has  occurred  at  the  seat  of  ligation;  and  3, 
in  epilepsy.  In  these  latter  cases  the  treatment  has  been  recommended  by  Dr.  Alexander,  of 
Liverpool,  in  the  hope  that  by  diminishing  the  supply  of  blood  to  the  posterior  part  of  the  brain 
and  the  spinal  corda  diminution  or  cessation  of  the  epileptic  fits  would  result.  But,  on  account 
of  the  uncertainty  as  to  what  cases,  if  any,  derived  benefit  from  the  operation,  it  has  now  been 
abandoned  as  a  treatment  for  epilepsy.  The  operation  of  ligation  of  the  vertebral  is  performed 
by  making  an  incision  along  the  posterior  border  of  the  Sterno-mastoid  muscle,  just  above  the 
clavicle.  The  muscle  is  pulled  to  the  inner  side,  and  the  anterior  tubercle  of  the  transverse 
process  of  the  sixth  cervical  vertebra  is  sought  for.  A  deep  layer  of  fascia  being  now  divided, 
the  interval  between  the  Scalenus  anticus  and  the  Longus  colli  muscles  just  below  their  attach- 
ment to  the  tubercle  is  defined,  and  the  artery  and  vein  are  found  in  the  interspace.  The  vein 
is  to  be  drawn  to  the  outer  side,  and  the  aneurism  needle  is  passed  from  without  inward.  Drs. 
Ramskill  and  Bright  have  pointed  out  that  severe  pain  at  the  back  of  the  head  may  be  symp- 
tomatic of  disease  of  the  vertebral  artery  just  before  it  enters  the  skull.  This  is  explained  by 
the  close  connection  of  the  artery  with  the  suboccipital  nerve  in  the  groove  on  the  posterior 
arch  of  the  atlas.  Disease  of  the  same  artery  has  been  also  said  to  aifect  speech,  from  pressure 
on  the  hypoglossal  nerve  where  it  is  in  relation  with  the  vessel,  leading  to  paralysis  of  the  muscles 
of  the  tongue. 

The  Basilar  Artery  (a.  basilaris)  (Fig.  401),  so  named  from  its  position  at  the 
base  of  the  skull,  is  a  single  trunk  formed  by  the  junction  of  the  two  vertebral 
arteries;  it  extends  from  the  posterior  to  the  anterior  border  of  the  pons  Varolii, 
lying  in  the  median  pontine  groove,  under  cover  of  the  arachnoid.  It  ends  by 
dividing  into  the  two  posterior  cerebral  arteries. 

Branches. — Its  branches  are,  on  each  side,  the  following: 

Transverse.  Anterior  Inferior  Cerebellar. 

Internal  Auditory.  Superior  Cerebellar. 

Posterior  Cerebral. 

The  Transverse  or  Pontal  Branches  (rami  ad  pontem)  supply  the  substance  of 
the  pons  Varolii. 

The  Internal  Auditory  (a.  auditiva  interna)  accompanies  the  auditory  nerve 
into  the  internal  auditory  meatus.      It  supplies  the  internal  ear. 


640  THE   BLOOD -VASCULAR   SYSTEM 

The  Anterior  Inferior  Cerebellar  Artery  (a.  cerebelli  inferior  anterior)  passes  back- 
ward across  the  crus  cerebelH,  to  be  distributed  to  the  anterior  border  of  the  under 
surface  of  the  cerebellum,  anastomosing  with  the  posterior  inferior  cerebellar 
branch  of  the  vertebral. 

The  Superior  Cerebellar  Artery  (a.  cerebelli  superior)  on  each  side  arises  near 
the  termination  of  the  basilar.  It  passes  outward,  immediately  behind  the  third 
nerve,  which  separates  it  from  the  posterior  cerebral,  winds  round  the  crus 
cerebri,  close  to  the  fourth  nerve,  and,  arriving  at  the  upper  surface  of  the 
cerebellum,  divides  into  branches  which  ramify  in  the  pia  mater  and,  reaching 
the  circumference  of  the  cerebellum,  anastomose  with  the  branches  of  the  inferior 
cerebellar  arteries.  Several  branches  are  given  to  the  pineal  gland,  the  valve  of 
Vieussens,  and  the  velum  interpositum. 

The  Posterior  Cerebral  Artery  (a.  cerebri  posterior)  (Figs.  401, 403, 404,  and  406) ,  on 
each  side,  is  the  terminal  branch  of  the  basilar.  It  is  larger  than  the  preceding,  from 
which  it  is  separated  near  its  origin  by  the  third  nerve.  Passing  outward,  parallel 
to  the  superior  cerebellar  artery,  and  receiving  the  posterior  communicating  from 
the  internal  carotid,  it  winds  round  the  crus  cerebri,  and  passes  to  the  under  surface 
of  the  occipital  lobes  of  the  cerebrum,  and  break  up  into  branches  for  the  supply  of 
the  temporal  and  occipital  lobes.    The  branches  of  the  posterior  cerebral  artery  are : 

Postero-median  ganglionic.  (  Anterior  temporal. 

Posterior  choroid.  Three  terminal  <  Posterior  temporal. 

Postero-lateral  ganglionic.  [  Occipital. 

The  postero-median  ganglionic  branches  (Fig.  406)  are  a  group  of  small  arteries 
which  arise  at  the  commencement  of  the  posterior  cerebral  artery;  these,  with  simi- 
lar branches  from  the  posterior  communicating,  pierce  the  posterior  perforated 
space,  and  supply  the  internal  surfaces  of  the  optic  thalamus  and  the  walls  of  the 
third  ventricle.  The  posterior  choroid  enters  the  interior  of  the  brain  beneath  the 
splenium  of  the  corpus  callosum,  and  supplies  the  velum  interpositum  and  the 
choroid  plexus.  The  postero-lateral  ganglionic  branches  are  a  group  of  small 
arteries  which  arise  from  the  posterior  cerebral  artery,  after  it  has  turned  round  the 
crus  cerebri;  they  supply  a  considerable  portion  of  the  optic  thalamus.  The 
terminal  branches  are  distributed  as  follows:  the  first,  or  the  anterior  temporal 
branches,  to  the  under  surface  of  the  anterior  portion  of  the  temporal  lobe;  the 
second,  or  the  posterior  temporal  branches,  to  the  external  occipital  and  the  third 
temporal  convolutions;  and  the  third,  or  the  occipital  branches,  to  the  inner  and 
outer  surfaces  of  the  occipital  lobe. 

Circle  of  Willis  {circulus  arteriosus  \Willisi\). — The  remarkable  anastomosis 
which  exists  between  the  branches  of  the  internal  carotid  and  vertebral  arteries  at 
the  base  of  the  brain  constitutes  the  circle  of  Willis.  It  is  formed  in  front,  by  the 
anterior  cerebral  arteries,  branches  of  the  internal  carotid,  which  are  connected 
together  by  the  anterior  communicating;  behind,  by  the  two  posterior  cerebrals, 
branches  of  the  basilar,  which  are  connected  on  each  side  with  the  internal  carotid 
by  the  posterior  communicating  arteries  (Fig.  401).  It  is  by  this  anastomosis 
that  the  cerebral  circulation  is  equalized,  and  provision  made  for  effectually 
carrying  it  on  if  one  or  more  of  the  branches  are  obliterated.  The  parts  of  the 
brain  included  within  this  arterial  circle  are — the  lamina  cinerea,  the  commissure 
of  the  optic  nerves,  the  infundibulum,  the  tuber  cinereum,  the  corpora  albicantia, 
and  the  posterior  perforated  space. 

The  ThjTToid  Axis  (truncus  thyreocervicalis)  (Figs.  392  and  410)  is  a  short  thick 
trunk  which  arises  from  the  forepart  of  the  first  portion  of  the  subclavian  artery, 
close  to  the  inner  border  of  the  Scalenus  anticus  muscle,  and  divides,  almost 
immediately  after  its  origin,  into  three  branches — the  inferior  thyroid,  supra- 
scapular, and  trans versalis  colli. 


THE   SUBCLAVIAN  ARTEBY  641 

The  Inferior  Thsrroid  Artery  (a.  thyreoidea  inferior)  (Fig.  392)  passes  upward,  in 
front  of  the  vertebral  artery  and  Longus  colli  muscle;  then  turns  inward  behind  the 
sheath  of  the  common  carotid  artery  and  internal  jugular  vein,  and  also  behind 
the  sympathetic  nerve,  the  middle  cervical  ganglion  resting  upon  the  vessel,  and 
reaching  the  lower  border  of  the  lateral  lobe  of  the  thyroid  gland  it  divides  into 
two  branches,  which  supply  the  posterior  and  imder  part  of  the  organ,  and  anasto- 
mose in  its  substance  with  the  superior  thyroid  and  with  the  corresponding  artery  ^ 
of  the  opposite  side.  (See  page  602.)  The  recurrent  laryngeal  nerve  passes  upward,  j  > 
generally  behind  but  occasionally  in  front  of  the  artery.    Its  branches  are:  n)^ 

Inferior  I^aryngeal.  Gi^sophageal. 

Tracheal.  Ascending  Cervical. 

Muscular. 

The  inferior  larjmgeal  branch  (a.  laryngea  inferior)  ascends  upon  the  trachea 
to  the  back  part  of  the  larynx,  in  company  with  the  recurrent  laryngeal  nerve, 
and  supplies  the  muscles  and  mucous  membrane  of  this  part,  anastomosing  with 
the  laryngeal  branch  from  the  superior  thyroid  artery  and  with  the  inferior  laryn- 
geal branch  from  the  opposite  side.  The  tracheal  branches  {rami  tracheales)  are 
distributed  upon  the  trachea,  anastomosing  below  with  the  bronchial  arteries. 
The  (esophageal  branches  {rami  oesophagei)  are  distributed  to  the  oesophagus, 
and  anastomose  with  the  oesophageal  branches  of  the  aorta.  The  ascending 
cervical  (a.  cervicalis  ascendens)  is  a  small  branch  which  arises  from  the  inferior 
thyroid  just  where  that  vessel  is  passing  behind  the  common  carotid  artery,  and 
runs  up  on  the  anterior  tubercles  of  the  transverse  processes  of  the  cervical 
vertebrae  in  the  interval  between  the  Scalenus  anticus  and  Rectus  capitis  anticus 
major  muscles.  It  gives  muscular  branches  {rami  musculares)  to  the  muscles  of 
the  neck,  which  anastomose  with  branches  of  the  vertebral,  and  sends  one  or  two 
branches  {rami  spinales)  into  the  spinal  canal  through  the  intervertebral  foramina 
to  be  distributed  to  the  spinal  cord  and  its  membranes,  and  to  the  bodies  of  the 
vertebra?  in  the  same  manner  as  the  lateral  spinal  branches  from  the  vertebral. 
It  anastomoses  with  the  ascending  pharyngeal  and  occipital  arteries.  The  mus- 
cular branches  supply  the  depressors  of  the  hyoid  bone,  the  Longus  colli,  the 
Scalenus  anticus,  and  the  Inferior  constrictor  of  the  pharynx.  One  of  the  mus- 
cular branches  passes  between  the  transverse  processes  of  the  fourth  and  fifth 
cervical  vertebrae  and  reaches  the  deep  muscles  of  the  neck.  It  is  called  the 
ramus  profundus. 

Surgical  Anatomy. — The  inferior  thyroid  artery  has  been  tied,  in  conjunction  with  the 
superior  thyroid,  in  cases  of  bronchocele.  An  incision  is  made  along  the  anterior  border  of  the 
Sterno-mastoid  down  to  the  clavicle.  After  the  deep  fascia  has  been  divided,  the  Sterno-mas- 
toid  and  carotid  vessels  are  drawn  outward  and  the  carotid  tubercle  (C hassaignac' s  tubercle) 
sought  for.  The  vessel  will  be  found  just  below  this  tubercle,  between  the  carotid  sheath  on  the 
outer  side  of  the  trachea  and  oesophagus  on  the  inner  side.  In  passing  the  ligature  great  care . 
must  be  exercised  to  avoid  including  the  recurrent  laryngeal  nerve,  which  is  occasionally  found 
^crossing  in  front  of  the  vessel.  Before  extirpating  a  goitrous  lobe  of  the  thyroid  the  superior 
and  inferior  thyroid"  arteries  ot'  the  diseased  side  are  to  be  ligated. 

The  Suprascapular  or  Transversalis  Humeri  Artery  (a.  transversa  scapulce)  (Figs.  392 
and  409),  smaller  than  the  tranversalis  colli,  passes  obliquely  from  within  outward, 
across  the  root  of  the  neck.  It  at  first  passes  downward  and  outward  across  the 
Scalenus  anticus  muscle  and  phrenic  nerve,  being  covered  by  the  Sterno-mastoid; 
it  then  crosses  the  subclavian  artery  and  the  cords  of  the  brachial  plexus,  and  runs 
outward,  behind  and  parallel  with  the  clavicle  and  Subclavius  muscle,  and  beneath 
the  posterior  belly  of  the  Omo-hyoid,  to  the  superior  border  of  the  scapula,  where 
it  passes  over  the  transverse  ligament  of  the  scapula,  which  separates  it  froni  the 
suprascapular  nerve,  and  reaches  the  supraspinous  fossa.  In  this  situation  it  lies 
close  to  the  bone,  and  ramifies  between  it  and  the  Supraspinatus  muscle,  to  which  it 

41 


642 


THE   BLOOD -VASCULAR    SYSTEM 


supplies  branches.  It  then  passes  downward  behind  the  neck  of  the  scapula,  to 
reach  the  infraspinous  fossa,  where  it  anastomoses  with  the  dorsalis  scapuhe  branch 
of  the  subscapular  artery  and  branches  of  the  posterior  scapular  arteries.  Besides 
distributing  branches  to  the  Sterno-mastoid,  Subclavius,  and  neighboring  muscles, 
it  gives  off  a  suprasternal  branch,  which  crosses  over  the  sternal  end  of  the  clavicle  to 
the  skin  of  the  upper  part  of  the  chest;  and  a  supra-acromial  branch  {ramus  acro- 
mialis),  which,  piercing  the  Trapezius  muscle,  supplies  the  skin  over  the  acromion, 
anastomosing  with  the  acromial  thoracic  artery.  As  the  artery  passes  over  the  trans- 
verse ligament  of  the  scapula,  a  V)ranch  descends  into  the  subscapular  fossa, 
ramifies  beneath  the  subscapular  muscle,  and  anastomoses  with  the  posterior  and 
subscapular  arteries.  The  suprascapular  artery  also  sends  branches  to  the 
acromio-clavicular  and  shoulder  joints,  and  a  nutrient  artery  to  the  clavicle. 


Posterior  scapular. 


Suprascapular.  Acromial  branch 

of  Thoracico-acromialis. 
I 


Anterior 
circumfiex. 


Fig.  409. — The  scapular  and  circumflex  arteries. 


The  Transverse  Cervical  or  Transversalis  Colli  Artery  (a.  transversa  colli)  (Fig.  392) 
passes  transversely  outward,  across  the  upper  part  of  the  subclavian  triangle,  to 
the  anterior  margin  of  the  Trapezius  muscle,  beneath  which  it  divides  into  two 
branches,  the  superficial  cervical  and  the  posterior  scapular.  In  its  passage  across 
the  neck  it  crosses  in  front  of  the  phrenic  nerve,  Scaleni  muscles,  and  the  brachial 
plexus,  between  the  divisions  of  which  it  sometimes  passes,  and  is  covered  by  the 
Platysma,  Sterno-mastoid,  Omo-hyoid,  and  Trapezius  muscles.  The  superficial 
cervical  {ramus  ascendens)  ascends  beneath  the  anterior  margin  of  the  Trapezius, 
distributing  branches  to  it  and  to  the  neighboring  muscles  and  glands  in  the  neck, 
and  anastomosing  with  the  superficial  branch  of  the  arteria  princeps  cervicis.  The 
posterior  scapular  {ramus  descendens)  (Fig.  409)  passes  beneath  the  Levator  anguli 
scapulae  muscle  to  the  superior  angle  of  the  scapula,  and  then  descends  along  the 
posterior  border  of  that  bone  as  far  as  the  inferior  angle.  In  its  course  it  is 
covered  by  the  Rhomboid  muscles,  supplying  them  and  the  Latissimus  dorsi  and 
Trapezius,  and  anastomosing  with  the  suprascapular  and  subscapular  arteries, 
and  with  the  posterior  branches  of  some  of  the  intercostal  arteries. 

Peculiarities. — The  superficial  cervical  frequently  arises  as  a  separate  branch  from  the  thyroid 
axis;  and  the  posterior  scapular,  from  the  third,  more  rarely  from  the  second,  part  of  the  sub- 
clavian. 


THE  SUBCLAVIAN  ARTERY 


643 


The  Internal  Mammary  (a.  mammaria  interna)   (Fig.  410)  arises  from  the 
under  surface  of  the  first  portion  of  the  subclavian  artery,  opposite  the  thyroid 


Scalenus 
anticus 


Thyroid  axis. 

Common  carotid. 

Innominate. 

■Internal  mam- 
mary. 


Anterior  intercostal 
branches. 


Perforating 
branches. 


Musculo- 
phrenic 


Superior  epi- 
gastric. 


Fig.   410. — The  internal  mammary  artery  and  its  branches. 


axis.  It  passes  downward  and  inward  behind  the  costal  cartilage  of  the  first  rib 
to  the  inner  surface  of  the  anterior  wall  of  the  chest,  resting  against  the  costal 
cartilages  about  half  an  inch  from  the  margin  of  the  sternum;  and,  at  the  interval 


644  THE   BLOOD -VASCULAR   SYSTEM 

between  the  sixth  and  seventh  cartilages,  divides  into  two  branches,  the  musculo- 
phrenic and  superior  epigastric. 

Relations. — At  its  origin  it  is  covered  by  the  internal  jugular  and  subclavian 
veins,  and  as  it  enters  the  thorax  is  crossed  from  without  inward  by  the  phrenic 
nerve,  and  then  passes  forward  close  to  the  outer  side  of  the  innominate  vein.  In 
the  upper  part  of  the  thorax  it  lips  behind  the  costal  cartilages  and  Internal  inter- 
costal muscles,  and  is  crossed  by  the  terminations  of  the  upper  six  intercostal 
nerves.  At  first  it  lies  upon  the  pleura,  but  at  the  lower  part  of  the  thorax  the 
Triangularis  sterni  separates  the  artery  from  this  membrane.  It  has  two  venae 
comites;  these  unite  into  a  single  vein,  which  joins  the  innominate  vein  of  its  own 
side.  t 

Branches. — The  branches  of  the  internal  mammary  are — 

Comes  Nervi  Phrenici  (Superior  Phrenic).  Anterior  Intercostal. 

Mediastinal.  Perforating. 

Pericardiac.  Musculo-phrenic. 

Sternal.  Superior  Epigastric. 

The  Comes  Nervi  Phrenici  or  Superior  Phrenic  (a.  pericardiaco'phrenica)  is  a  long 
slender  branch  which  accompanies  the  phrenic  nerve,  between  the  pleura  and 
pericardium,  to  the  Diaphragm.  It  gives  branches  to  the  pericardium  and  is 
distributed  upon  the  Diaphragm,  anastomosing  with  the  other  phrenic  branches 
from  the  internal  mammary  and  with  phrenic  branches  of  the  abdominal  aorta. 

The  Mediastinal  Branches  {aa.  mediastinales  anteriores)  are  small  vessels 
which  are  distributed  to  the  areolar  tissue  and  lymphatic  glands  in  the  anterior 
mediastinum  and  to  the  remains  of  the  thymus  gland. 

The  Pericardiac  Branches  supply  the  upper  part  of  the  anterior  surface  of  the 
pericardium,  the  lower  part  receiving  branches  from  the  musculo-phrenic  artery. 

The  Sternal  Branches  {raTni  sternales)  are  distributed  to  the  Triangularis  sterni 
and  to  the  posterior  surface  of  the  sternum. 

The  mediastinal,  pericardiac,  and  sternal  branches,  together  with  some  twigs 
from  the  comes  nervi  phrenici,  anastomose  with  branches  from  the  intercostal  and 
bronchial  arteries,  and  form  a  minute  plexus  beneath  the  pleura,  which  has  been 
named  by  Turner  the  subpleural  mediastinal  plexus. 

The  Anterior  Intercostal  Arteries  {rami  intercostales)  supply  the  five  or  six  upper 
intercostal  spaces.  The  branch  corresponding  to  each  space  soon  divides  into 
two,  or  the  two  branches  may  come  off  separately  from  the  parent  trunk.  The 
small  vessels  pass  outward  in  the  intercostal  spaces,  one,  the  larger,  lying  near 
the  lower  margin  of  the  rib  above,  and  the  other,  the  smaller,  near  the  upper 
margin  of  the  rib  below,  and  anastomose  with  the  intercostal  arteries  from  the 
aorta.  They  are  at  first  situated  between  the  pleura  and  the  Internal  intercostal 
muscles,  and  then  between  the  Internal  and  External  intercostal  muscles.  They 
supply  the  Intercostal  muscles,  and,  by  branches  which  perforate  the  External 
intercostal  muscle,  reach  the  Pectoral  muscles  and  the  mammary  gland. 

The  Perforating  or  Anterior  Perforating  Arteries  {rami  perforantes)  correspond 
to  the  five  or  six  upper  intercostal  spaces.  They  arise  trom  the  internal  mam- 
mary, pass  forward  through  the  intercostal  spaces,  and,  curving  outward,  supply 
the  Pectoralis  major  and  the  integument.  Those  which  correspond  to  the  second, 
third,  and  fourth  spaces  are  distributed  to  the  mammary  gland.  In  females, 
during  lactation,  these  branches  are  of  large  size. 

The  Musculo-phrenic  Artery  (a.  musculophrenica)  is  directed  obliquely  down- 
ward and  outward,  behind  the  cartilages  of  the  false  ribs,  perforating  the  Dia- 
phragm at  the  eighth  or  ninth  rib,  and  terminating,  considerably  reduced  in  size, 
opposite  the  last  intercostal  space.  It  gives  off  anterior  intercostal  arteries  to 
each  of  the  intercostal  spaces  across  which  it  passes;  these  diminish  in  size  as  the 


SURGICAL   ANATOMY   OF    THE  AXILLA  645 

spaces  decrease  in  length,  and  are  distributed  in  a  manner  precisely  similar  to 
the  anterior  intercostals  from  the  internal  mammary.  The  musculo-phrenic  also 
gives  branches  to  the  lower  part  of  the  pericardium,  and  others  which  run  back- 
ward to  the  Diaphragm  and  downward  to  the  abdominal  muscles. 

The  Superior  Epigastric  (a.  epigastrica  superior)  continues  in  the  original  direc- 
tion of  the  internal  mammary;  it  descends  through  the  cellular  interval  between 
the  Costal  and  sternal  attachments  of  the  Diaphragm,  and  enters  the  sheath  of  the 
Rectus  abdominis  muscle,  at  first  lying  behind  the  muscle,  and  then  perforating 
it  and  supplying  it,  and  anastomosing  with  the  deep  epigastric  artery  from  the 
external  iliac.  Some  branches  perforate  the  sheath  of  the  Rectus,  and  supply  the 
muscles  of  the  ab<]omen  and  the  integument,  and  a  small  branch,  which  passes 
inward  upon  the  side  of  the  ensiform  appendix,  anastomoses  in  front  of  that 
cartilage  with  the  superior  epigastric  artery  of  the  opposite  side.  It  also  gives 
some  twigs  to  the  Diaphragm,  while  from  the  artery  of  the  right  side  small 
branches  extend  into  the  falciform  ligament  of  the  liver  and  anastomose  with 
the  hepatic  artery. 

Surgical  Anatomy. — The  course  of  the  internal  mammary  artery  may  be  defined  by  draw- 
ing a  hne  across  the  six  upper  intercostal  spaces  half  an  inch  from  and  parallel  with  the  sternum. 
The  position  of  the  vessel  must  be  remembered,  as  it  is  liable  to  be  wounded  in  stabs  of  the 
chest-wall.    It  is  most  easily  reached  by  a  transverse  incision  in  the  second  intercostal  space. 

The  Superior  Intercostal  (truncus  costocervicalis)(Figs.  399  and  416)  arises  from 
the  upper  and  back  part  of  the  subclavian  artery,  behind  the  Scalenus  anticus  mus- 
cle on  the  right  side  and  to  the  inner  side  of  that  muscle  on  the  left  side.  Passing 
backward,  it  gives  off  the  deep  cervical  branch,  and  then  descends  behind  the 
pleura  in  front  of  the  necks  of  the  first  two  ribs,  and  inosculates  with  the  first 
aortic  intercostal.  As  it  crosses  the  neck  of  the  first  rib  it  lies  to  the  inner  side 
of  the  anterior  division  of  the  first  dorsal  nerve  and  to  the  outer  side  of  the  first 
thoracic  ganglion  of  the  sympathetic.  In  the  first  intercostal  space  it  gives  off  a 
branch  which  is  distributed  in  a  manner  similar  to  the  distribution  of  the  aortic 
intercostals.  The  branch  for  the  second  intercostal  space  usually  joins  with  one 
from  the  highest  aortic  intercostal.  Each  intercostal  gives  off  a  branch  to  the 
posterior  spinal  muscles,  and  a  small  branch  which  passes  through  the  corre- 
sponding intervertebral  foramen  to  the  spinal  cord  and  its  membranes. 

The  Deep  Cervical  Branch  (a.  cervicalis  profunda)  arises,  in  most  cases,  from 
the  superior  intercostal,  and  is  analogous  to  the  posterior  branch  of  an  aortic 
intercostal  artery;  occasionally  it  arises  as  a  separate  branch  from  the  sub- 
clavian artery.  Passing  backward,  above  the  eighth  cervical  nerve  and  between 
the  transverse  process  of  the  seventh  cervical  vertebra  and  the  first  rib,  it  runs 
up  the  back  part  of  the  neck,  between  the  Complexus  and  Semispinalis  colli 
muscles,  as  high  as  the  axis  vertebra,  supplying  these  and  adjacent  muscles,  and 
anastomosing  with  the  deep  branch  of  the  arteria  princeps  cervicis  of  the  occipital, 
and  with  branches  which  pass  outward  from  the  vertebral.  It  gives  off  a  special 
branch  which  enters  the  spinal  canal  through  the  intervertebral  foramen  between 
the  seventh  cervical  and  first  dorsal  vertebrae. 


SURGICAL  ANATOMY  OF  THE  AXILLA. 

The  axilla  is  a  pyramidal  space,  situated  between  the  upper  and  lateral  part 
of  the  chest  and  the  inner  side  of  the  arm. 

Boundaries. — Its  apex,  which  is  directed  upward  toward  the  root  of  the  neck, 
corresponds  to  the  interval  between  the  first  rib,  the  upper  edge  of  the  scapula, 
and  the  clavicle,  through  which  the  axillary  vessels,  the  brachial  plexus  of  nerves, 
and  the  long  thoracic  nerve  pass.    This  interval  is  the  cervico -axillary  passage. 


646  THE    BLOOD -VASCULAR    SYSTEM 

The  base,  directed  downward,  is  formed  by  the  integument  and  a  thick  layer  of 
fascia,  the  axillary  fascia  (fascia  axillaris)  (Fig.  313),  extending  between  the  lower 
border  of  the  Pectoralis  major  in  front  and  the  lower  border  of  the  Latissimus 
dorsi  behind  (page  463).  The  axillary  fascia  is  perforated  at  several  points. 
The  large  central  opening  is  called  the  foramen  of  Langer.  The  inner  margin  of 
the  foramen  of  Langer  is  dense  and  constitutes  a  part  of  the  axillary  arch,. 
which  is  a  fibro-muscular  slip  derived  from  the  latissimus  dorsi.  The  axilla 
is  broad  internally  at  the  chest,  but  narrow  and  pointed  externally  at  the 
arm.  The  anterior  boundary  is  formed  by  the  Pectoralis  major  and  minor  mus- 
cles, the  former  covering  the  whole  of  the  anterior  wall  of  the  axilla,  the  latter 
covering  only  its  central  part,  the  costo-coracoid  membrane,  the  clavicle,  and  the 
Subclavius  muscle.  The  posterior  boundary,  which  extends  somewhat  lower 
than  the  anterior,  is  formed  by  the  Subscapularis  above,  the  Teres  major  and 
Latissimus  dorsi  below.  On  the  inner  side  are  the  first  four  ribs  with  their 
corresponding  Intercostal  muscles,  and  part  of  the  Serratus  magnus.  On 
the  outer  side,  where  the  anterior  and  posterior  boundaries  converge,  the  space 
is  narrow,  and  bounded  by  the  humerus,  the  Coraco-brachialis  and  Biceps 
muscles. 

Contents.— This  space  contains  the  axillary  vessels  and  brachial  plexus  of 
nerves,  with  their  branches,  some  branches  of  the  intercostal  nerves,  and  a  large 
number  of  lymphatic  glands,  all  connected  together  by  a  quantity  of  fat  and  loose 
areolar  tissue. 

Position  of  the  Contents. — The  axillary  artery  and  vein,  with  the  brachial  plexus 
of  nerves,  extend  obliquely  along  the  outer  boimdary  of  the  axillary  space,  from 
its  apex  to  its  base,  and  are  placed  much  nearer  the  anterior  than  the  posterior  wall, 
the  vein  lying  to  the  inner  or  thoracic  side  of  the  artery  and  partially  concealing 
it.  At  the  forepart  of  the  axillary  space,  in  contact  with  the  Pectoral  muscles,  and 
along  the  anterior  margin  are  the  thoracic  branches  of  the  axillary  artery,  and 
along  the  lower  margin  of  the  Pectoralis  minor  the  long  thoracic  artery  extends 
to  the  side  of  the  chest.  At  the  back  part,  in  contact  with  the  lower  margin  of 
the  Subscapularis  muscle,  are  the  subscapular  vessels  and  nerves;  winding  around 
the  outer  border  of  this  muscle  is  the  dorsalis  scapulae  artery  and  veins;  and,  close 
to  the  neck  of  the  humerus,  the  posterior  circumflex  vessels  and  the  circumflex 
nerve  are  seen  curving  backward  to  the  shoulder. 

Along  the  inner  or  thoracic  side  no  vessel  of  any  importance  exists,  the  upper 
part  of  the  space  being  crossed  merely  by  a  few  small  branches  from  the  superior 
thoracic  artery.  There  are  some  important  nerves,  however,  in  this  situation — 
viz.,  the  posterior  thoracic  or  external  respiratory  nerve,  descending  on  the  sur- 
face of  the  Serratus  magnus,  to  which  it  is  distributed;  and  perforating  the  upper 
and  anterior  part  of  this  wall,  the  intercosto-humeral  nerve  or  nerves,  passing 
across  the  axilla  to  the  inner  side  of  the  arm. 

The  cavity  of  the  axilla  is  filled  by  a  quantity  of  loose  areolar  tissue  and  a  large 
number  of  small  arteries  and  veins,  all  of  which  are,  however,  of  inconsiderable 
size,  and  numerous  lymphatic  glands,  the  position  and  arrangement  of  which  are 
described  on  a  subsequent  page. 

Surgical  Anatomy. — The  axilla  is  a  space  of  considerable  surgical  importance.  It  trans- 
mits the  large  vessels  and  nerves  to  the  upper  extremity,  and  these  may  be  the  seat  of  injury  or 
disease:  it  contains  numerous  lymphatic  glands  which  may  require  removal  when  diseased;  in  it 
is  a  quantity  of  loose  connective  and  adipose  tissue  which  may  be  readily  infiltrated  with  blood 
or  pus.  The  axilla  may  be  the  seat  of  rapidly  growing  tumors.  Moreover,  it  is  covered  at  its 
base  by  thin  skin,  largely  supplied  with  sebaceous  and  sweat  glands,  which  is  frequently  the 
seat  of  small  cutaneous  abscesses  and  boils,  and  of  eruptions  due  to  irritation. 

In  suppuration  in  the  axilla  the  arrangement  of  the  fascije  plays  a  very  important  part  in  the 
direction  which  the  pus  takes.  As  described  on  page  464,  the  costo-coracoid  membrane,  after 
covering  in  the  space  between  the  clavicle  and  the  upper  border  of  the  Pectoralis  minor,  splits 


THE   AXILLARY   ARTERY 


647 


to  enclose  this  muscle,  and,  reblending  at  its  lower  border,  becomes  incorporated  with  the  axillary 
fascia  at  the  anterior  fold  of  the  axilla.  This  is  known  as  the  clavi-pectoral  fascia.  Suppura- 
tion may  take  place  either  superficial  to  or  beneath  this  layer  of  fascia;  that  is,  either  between 
the  Pectorals  or  below  the  Pectoralis  minor:  in  the  former  case,  the  pus  would  point  either  at  the 
anterior  border  of  the  axillary  fold  or  in  the  groove  between  the  Deltoid  and  the  Pectoralis  major; 
in  the  latter,  the  pus  would  have  a  tendency  to  surround  the  vessels  and  nerves  and  ascend  into 
the  neck,  that  being  the  direction  in  which  there  is  least  resistance.  Its  progress  toward  the 
skin  is  prevented  by  the  axillary  fascia;  its  progress  backward,  by  the  Serratus  magnus;  forward, 
by  the  clavi-pectoral  fascia;  inward,  by  the  wall  of  the  thorax;  and  outward,  by  the  upper  limb. 
The  pus  in  these  cases,  after  extending  into  the  neck,  has  been  known  to  spread  through  the 
superior  opening  of  the  thorax  into  the  mediastinum. 

In  opening  an  axillary  abscess  the  knife  should  be  entered  in  the  floor  of  the  axilla,  midway 
between  the  anterior  and  posterior  margins  and  near  the  thoracic  side  of  the  space.  It  is  well 
to  use  a  director  and  dressing  forceps  after  an  incision  has  been  made  through  the  skin  and  fascia 
in  the  manner  directed  by  the  late  Mr.  Hilton. 

The  student  should  attentively  consider  the  relation  of  the  vessels  and  nerves  in  the  several 
parts  of  the  axilla,  for  it  is  the  universal  plan,  at  the  present  day,  to  remove  the  glands  from 
the  axilla  in  operating  for  cancer  of  the  breast.  In  performing  such  an  operation  it  will  be 
necessary  to  proceed  with  much  caution  in  the  direction  of  the  outer  wall  and  apex  of  the  space, 


Anterior 
circumjlex. 


Fig.  411. — The  axillary  artery  and  its  branches. 


as  here  the  axillary  vessels  will  be  in  danger  of  being  wounded.  Toward  the  posterior  wall  it 
will  be  necessary  to  avoid  the  subscapular,  dorsalis  scapulae,  and  posterior  circumflex  vessels. 
Along  the  anterior  wall  it  will  be  necessary  to  avoid  the  thoracic  branches.  In  clearing  out  the 
axilla  the  axillary  vein  should  be  first  defined  and  cleared  up  to  the  apex  of  the  axilla. 
When  the  apex  of  the  space  is  reached,  all  fat  and  glands  must  be  carefully  removed  and  the 
whole  axilla  cleared  by  separating  the  tissues  along  the  inner  and  posterior  walls,  so  that  when 
the  proceeding  is  completed,  the  axilla  is  cleared  of  all  its  contents  except  the  main  vessels  and 


THE  AXILLARY  ARTERY  (A.  AXILLARIS)  (Fig.  411). 

The  axillary  artery,  the  continuation  of    the  subclavian,  commences   at  the 
outer  border  of  the  first  rib,  and  terminates  at  the  lower  border  of  the  tendon 


648  THE    BLOOD -VASCULAB    SYSTEM 

of  the  Teres  major  muscle,  where  it  takes  the  name  of  brachial.  Its  direction 
varies  with  the  position  of  the  limb:  when  the  arm  lies  by  the  side  of  the 
chest,  the  vessel  forms  a  gentle  curve,  the  convexity  being  upward  and  outward; 
when  the  arm  is  directed  at  right  angles  with  the  trunk,  the  vessel  is  nearly 
straight;  and  when  the  arm  is  elevated  still  higher,  the  arteries  describe  a  curve 
the  concavity  of  which  is  directed  upward.  At  its  commencement  the  artery  is 
very  deeply  situated,  but  near  its  termination  it  is  superficial,  being  covered  only 
by  the  skin  and  fascia.  The  description  of  the  relations  of  this  vessel  is  facili- 
tated by  its  division  into  three  portions,  the  first  portion  being  above  the 
Pectoralis  minor;  the  second  portion  behind;  and  the  third  below  that  muscle. 

Relations. — The  first  portion  of  the  axillary  artery  is  in  relation,  in  front,  with 
the  clavicular  portion  of  the  Pectoralis  major,  the  costo-coracoid  membrane,  the 
external  anterior  thoracic  nerve,  and  the  acromio-thoracic  and  cephalic  veins; 
behind,  with  the  first  intercostal  space,  the  corresponding  Intercostal  muscle, 
the  second  and  a  portion  of  the  third  digitation  of  the  Serratus  magnus,  and  the 
posterior  thoracic  and  internal  anterior  thoracic  nerves;  on  its  outer  side,  with  the 
brachial  plexus,  from  which  it  is  separated  by  a  little  cellular  interval;  on  its  inner 
or  thoracic  side,  with  the  axillary  vein,  which  overlaps  the  artery. 

Relations  of  the  First  Portion  of  the  Axillary  Artery. 

In  front. 
Pectoralis  major. 
Costo-coracoid  membrane. 
External  anterior  thoracic  nerve. 
Acromio-thoracic  and  cephalic  veins. 


Outer  side.  I      Axillary     \  Inner  side. 

Brachial  plexus.  I  First  portion,  j  Axillary  vein. 

Behind. 
First  Intercostal  space  and  Intercostal  muscle. 
Second  and  third  digitations  of  Serratus  magnus. 
Posterior  thoracic  and  Internal  anterior  thoracic  nerves. 

The  second  portion  of  the  axillary  artery  lies  beyond  the  Pectoralis  minor.  It 
is  covered,  in  front,  by  the  Pectoralis  major  and  minor  muscles;  behind,  it  is 
separated  from  the  Subscapularis  by  a  cellular  interval;  on  the  inner  side  is  the 
axillary  vein,  separated  from  the  artery  by  the  inner  cord  of  the  plexus  and  the 
internal  anterior  thoracic  nerve.  The  brachial  plexus  of  nerves  surrounds  the 
artery  on  three  sides,  and  separates  it  from  direct  contact  with  the  vein  and 
adjacent  muscles. 

Relations  of  the  Second  Portion  of  the  Axillary  Artery. 

In  front. 
Pectoralis  major  and  minor. 

Outer  side.  /  X  Inner  side. 

Outer  cord  of  plexus.  [       Arte*/''      )  Axillary  vein. 

Inner  cord  of  plexus. 

Internal  anterior  thoracic  nerve. 

Behind. 
Subscapularis. 
Posterior  cord  of  plexus. 


THE   AXILLARY  ABTEBY  649 

The  third  portion  of  the  axillary  artery  lies  below  the  Pectoralis  minor.  It  is 
in  relation,  in  front,  with  the  lower  part  of  the  Pectoralis  major  above,  being 
covered  only  by  the  integument  and  fascia  below,  where  it  is  crossed  by  the  inner 
head  of  the  median  nerve;  behind,  with  the  lower  part  of  the  Subscapularis  and 
the  tendons  of  the  Latissimus  dorsi  and  Teres  major;  on  its  outer  side,  with  the 
Coraco-brachialis;  on  its  inner  or  thoracic  side,  with  the  axillary  vein.  The  nerves 
of  the  brachial  plexus  bear  the  following  relation  to  the  artery  in  this  part  of  its 
course:  on  the  outer  side  is  the  median  nerve,  and  the  musculo-cutaneous  for  a 
short  distance;  on  the  inner  side,  the  ulnar  nerve  (between  the  vein  and  artery) 
and  the  lesser  internal  cutaneous  nerve  (to  the  inner  side  of  the  vein);  in  front 
is  the  internal  cutaneous  nerve,  and  behind,  the  musculo-spiral  and  circumflex,  the 
latter  extending  only  to  the  lower  border  of  the  Subscapularis  muscle. 

Relations  of  ihe  Third  Portion  of  the  Axillary  Artery. 

In  front. 
Integument  and  fascia. 
Pectoralis  major. 
Inner  head  of  median  nerve. 
Internal  cutaneous  nerve. 

Older  side,  /^  \  Inner  side. 

Coraco-brachialis.  [      "A^rtery^      |  Ulnar  nerve. 

Median  nerve.  I  Third  porticm.  y  Axillary  vein. 

Musculo-cutaneous  nerve.  \  /  Lesser  internal  cutaneous  nerve. 

Behind. 
Subscapularis. 

Tendons  of  Latissimus  dorsi  and  Teres  major. 
Musculo-spiral  and  circumflex  nerves. 

Peculiarities. — The  axillary  artery,  in  about  one  case  out  of  every  ten,  gives  off  a  large 
branch,  which  forms  either  one  of  the  arteries  of  the  forearm  or  a  large  muscular  trunk.  In  the 
first  set  of  cases  this  artery  is  most  frequently  the  radial  (1  in  33),  sometimes  the  ulnar  (1  in  72), 
and,  very  rarely,  the  interosseous  (1  in  506).  In  the  second  set  of  cases  the  trunk  has  been 
found  to  give  origin  to  the  subscapular,  circumflex,  and  profunda  arteries  of  the  arm.  Some- 
times only  one  of  the  circumflex,  or  one  of  the  profunda  arteries,  arose  from  the  trunk.  In 
these  cases  the  brachial  plexus  surrounded  the  trunk  of  the  branches  and  not  the  main  vessel. 

Surface  Marking. — The  course  of  the  axillary  artery  may  be  marked  out  by  raising  the 
arm  to  a  right  angle  with  the  body  and  drawing  a  line  from  the  middle  of  the  clavicle  to  the 
point  where  the  tendon  of  the  Pectoralis  major  crosses  the  prominence  caused  by  the  Coraco- 
brachialis  as  it  emerges  from  under  cover  of  the  anterior  fold  of  the  axilla.  The  third  portion 
of  the  artery  can  be  felt  pulsating  beneath  the  skin  and  fascia,  at  the  junction  of  the  anterior 
with  the  middle  third  of  the  space  between  the  anterior  and  posterior  folds  of  the  axilla,  close  to 
the  inner  border  of  the  Coraco-brachialis  muscle. 

Surgical  Anatomy. — The  student,  having  carefully  examined  the  relations  of  the  axillary 
artery  in  its  various  parts,  should  now  consider  in  what  situation  compression  of  this  vessel 
may  be  most  easily  effected,  and  the  best  position  for  the  application  of  a  ligature  to  it  when 
necessary. 

Compression  of  the  vessel  may  be  required  in  the  removal  of  tumors  or  in  amputation  of 
the  upper  part  of  the  arm ;  and  the  only  situation  in  which  this  can  be  effectually  made  is  in  the 
lower  part  of  its  course;  by  pressing  on  it  in  this  situation  from  within  outward  against  the 
humerus  the  circulation  may  be  effectually  arrested. 

The  axillary  artery  is  perhaps  more  frequently  lacerated  than  any  other  artery  in  the  body, 
with  the  exception  of  the  popliteal,  by  violent  movements  of  the  extremity,  especially  in  those 
cases  where  its  coats  are  diseased.  It  has  occasionally  been  ruptured  in  attempts  to  reduce  old 
dislocations  of  the  shoulder-joint.  This  accident  is  most  likely  to  occur  during  the  preliminary 
breaking  down  of  adhesions,  in  consequence  of  the  artery  having  become  fixed  to  the  capsule 
of  the  joint.  Aneurism  of  tfie  axillary  artery  is  of  frequent  occurrence,  a  large  percentage  of 
the  cases  being  traumatic  in  their  origin,  due  to  the  violence  to  which  the  vessel  is  exposed  in 
the  varied,  extensive,  and  often  violent  movements  of  the  limb. 

The  application  of  a  ligature  to  the  axillary  artery  may  be  required  in  cases  of 
aneurism  of  the  upper  part  of  the  brachial  or  as  a  distal  operation  for  aneurism  of  the  sub- 


650  'J'HE  BLOOD -VASCULAR   JSYSTUIf 

clavian;  and  there  are  only  two  situations  in  which  the  vessel  can  be  secured — viz.,  in  the  first 
and  in  the  third  parts  of  its  course;  for  the  axillary  artery  at  its  central  part  is  so  deeply  seated, 
and,  at  the  same  time,  so  closely  surrounded  with  large  nerve  trunks,  that  the  application  of  a 
ligature  to  it  in  that  situation  would  be  almost  impracticable. 

In  the  third  part  of  its  course  the  operation  is  most  simple,  and  may  be  performed  in  th- 
following  manner:  The  patient  being  placed  on  a  bed  and  the  arm  separated  from  the  side,  with 
the  hand  supinated,  an  incision  about  two  inches  in  length  is  made  through  the  integument 
forming  the  floor  of  the  axilla,  the  cut  being  a  little  nearer  to  the  anterior  than  the  posterior 
fold  of  the  axilla.  After  carefully  dissecting  through  the  areolar  tissue  and  fascia,  the  median 
nerve  and  axillary  vein  are  exposed;  the  former  having  been  displaced  to  the  outer  and  the 
latter  to  the  inner  side  of  the  arm,  the  elbow  being  at  the  same  time  bent,  so  as  to  relax  the 
structures  and  facilitate  their  separation,  the  ligature  may  be  passed  round  the  artery  from  the 
ulnar  to  the  radial  side. 

This  portion  of  the  artery  is  occasionally  crossed  by  a  muscular  slip,  the  axillary  arch,  derived 
from  the  Latissimus  dorsi,  which  may  mislead  the  surgeon  during  an  operation.  The  occasional 
existence  of  this  muscular  fasciculus  was  spoken  of  in  the  description  of  the  muscles.  It  may 
easily  be  recognized  by  the  transverse  direction  of  its  fibres. 

The  first  portion  of  the  axillary  artery  may  be  tied  in  cases  of  aneurism  encroaching  so  far 
upward  that  a  ligature  cannot  be  applied  in  the  lower  part  of  its  course.  Notwithstanding  that 
this  operation 'has  been  performed  in  some  few  cases,  and  with  success,  its  performance  is  at- 
tended with  much  difficulty  and  danger.  The  student  will  remark  that  in  this  situation  it  would 
be  necessary  to  divide  a  thick  muscle,  and,  after  incising  the  costo-coracoid  membrane,  the 
artery  would  be  exposed  at  the  bottom  of  a  more  or  less  deep  space,  with  the  cephalic  and  axil- 
lary veins  in  such  relation  with  it  as  must  render  the  application  of  a  ligature  to  this  part  of 
the  vessel  particularly  hazardous.  Under  such  circumstances  it  is  an  easier,  and  at  the  same 
time  more  advisable,  operation  to  tie  the  subclavian  artery  in  the  third  part  of  its  course. 

The  vessel  in  the  first  part  of  its  course  can  best  be  secured  through  a  curved  incision  the 
convexity  of  which  is  downward.  This  incision  passes  from  a  point  half  an  inch  external  to 
the  sterno-clavicular  joint  to  a  point  half  an  inch  internal  to  the  coracoid  process.  The  limb 
is  to  be  well  abducted  and  the  head  inclined  to  the  opposite  side,  and  this  incision  is  carried 
through  the  superficial  structures,  care  being  taken  to  avoid  the  cephalic  vein  at  the  outer  angle 
of  the  incision.  The  clavicular  origin  of  the  Pectoralis  major  is  then  divided  in  the  whole 
extent  of  the  wound.  The  arm  is  now  to  be  brought  to  the  side,  and  the  upper  edge  of  the 
Pectoralis  minor  defined  and  drawn  downward.  The  costo-coracoid  membrane  is  to  be  care- 
fully divided  close  to  the  coracoid  process,  and  the  axillary  sheath  exposed;  this  is  to  be  opened 
with  especial  care  on  account  of  the  vein  overlapping  the  artery.  The  needle  should  be  passed 
from  below,  so  as  to  avoid  wounding  the  vein. 

In  a  case  of  wound  of  the  vessal  the  general  practice  of  cutting  down  upon  and  tying  it  above 
and  below  the  wounded  point  should  be  adopted  in  all  cases. 

Collateral  Circulation  after  Ligature  of  the  Axillary  Artery.— If  the  artery  be  tied 
above  the  origin  of  the  acromial  thoracic,  the  collateral  circulation  will  be  carried  on  by  the  same 
branches  as  after  the  ligature  of  the  subclavian;  if  at  a  lower  point,  between  the  acromial  thoracic 
and  subscapular  arteries,  the  latter  vessel,  by  its  free  anastomoses  with  the  other  scapular  arteries, 
branches  of  the  subclavian,  will  become  the  chief  agent  in  carrying  on  the  circulation,  to  which 
the  long  thoracic,  if  it  be  below  the  ligature,  will  materially  contribute  by  its  anastomoses  with 
the  intercostal  and  internal  mammary  arteries.  If  the  point  included  in  the  ligature  be  below 
the  origin  of  the  subscapular  artery,  it  will  most  probably  also  be  below  the  origins  of  the  cir- 
cumflex arteries.  The  chief  agents  in  restoring  the  circulation  will  then  be  the  subscapular  and 
the  two  circumflex  arteries  anastomosing  with  the  superior  profunda  from  the  brachial,  which 
will  be  afterward  referred  to  as  performing  the  same  office  after  ligation  of  the  brachial.  The 
cases  in  which  the  operation  has  been  performed  are  few  in  number,  and  no  published  account 
of  dissections  of  the  collateral  circulation  appears  to  exist. 

Branches. — The  branches  of  the  axillary  artery  are — 


From  first  part  <  '^P^^^^^    rrii*^^^^^^'  From  second  part  \  \  ?"^r 

'         ^        [  Acromial    1  horacic.  ^       ( Alar 


Thoracic. 
Thoracic. 
(  Subscapular. 
From  third  part  <  Posterior  Circumflex. 
'  Anterior  Circumflex. 


The  Superior  Thoracic  (a.  thoracalis  suprema)  is  a  small  artery  which  arises 
from  the  axillary  separately  or  by  a  common  trunk  with  the  acromial  thoracic. 
Running  forward  and  inward  along  the  upper  border  of  the  Pectoralis  minor,  it 


THE    AXILLARY  ABTEBY  651 

passes  between  it  and  the  Pectoralis  major  to  the  side  of  the  chest.  It  supplies 
these  muscles  and  the  parietes  of  the  thorax,  anastomosing  with  the  internal  mam- 
mary and  intercostal  arteries. 

The  Acromial  Thoracic  or  the  Thoracic  Axis  (a.  thoracoacromialis)  is  a 
short  trunk  which  arises  from  the  forepart  of  the  axillary  artery,  its  origin  being 
generally  overlapped  by  the  upper  edge  of  the  Pectoralis  minor.  Projecting 
forward  to  the  upper  border  of  the  Pectoralis  minor,  it  divides  into  four  sets  of 
branches — thoracic,  acromial,  descending,  and  clavicular. 

The  Thoracic  Branches  {rami  pedorales),  two  or  three  in  number,  are  distributed 
to  the  Serratus  magnus  and  Pectoral  muscles,  anastomosing  with  the  intercostal 
branches  of  the  internal  mammary. 

The  Acromial  Branch  (ramus  acromialis)  is  directed  outward  toward  the  acro- 
mion, supplying  the  Deltoid  muscle,  and  anastomosing,  on  the  surface  of  the 
acromion,  with  the  suprascapular  and  posterior  circumflex  arteries. 

The  Descending  or  Humeral  Branch  (ramus  deltoideu^)  passes  in  the  space  between 
the  Pectoralis  major  and  Deltoid,  in  the  same  groove  as  the  cephalic  vein,  and 
supplies  both  muscles. 

The  Clavicular  Branch  (ramu^  clavicularis) ,  which  is  very  small,  passes  upward 
to  the  Subclavius  muscle. 

The  Long  Thoracic  or  the  External  Mammary  (a.  thoracalis  lateralis)  passes 
downward  and  inward  along  the  lower  border  of  the  Pectoralis  minor  to  the  side 
of  the  chest,  supplying  the  Serratus  magnus,  the  Pectoral  muscles,  and  mammary 
gland,  and  sending  branches  across  the  axilla  to  the  axillary  glands  and  Sub- 
scapularis;  it  anastomoses  with  the  internal  mammary  and  intercostal  arteries. 

The  Alar  Thoracic  is  a  small  branch  which  supplies  the  glands  and  areolar 
tissue  of  the  axilla.  Its  place  is  frequently  supplied  by  branches  from  some  of  the 
other  thoracic  arteries. 

The  Subscapular  (a.  subscapularis) ,  the  largest  branch  of  the  axillary  artery, 
arises  opposite  the  lower  border  of  the  Subscapularis  muscle,  and  passes  downward 
and  backward  along  its  lower  margin  to  the  inferior  angle  of  the  scapula,  where  it 
anastomoses  with  the  long  thoracic  and  intercostal  arteries  and  with  the  posterior 
scapular,  a  branch  of  the  trans versalis  colli,  from  the  thyroid  axis  of  the  sub- 
clavian. About  an  inch  and  a  half  from  its  origin  it  gives  off  a  large  branch,  the 
dorsalis  scapulae,  and  terminates  by  supplying  branches  to  the  muscles  in  the 
neighborhood. 

The  Dorsalis  Scapulae  (a.  circumflexa  scapulce)  is  given  off  from  the  subscapular 
about  an  inch  and  a  half  from  its  origin,  and  is  generally  larger  than  the  continua- 
tion of  the  vessel.  It  curves  round  the  axillary  border  of  the  scapula,  leaving  the 
axilla  through  the  space  between  the  Teres  minor  above,  the  Teres  major  below, 
and  the  long  head  of  the  Triceps  externally  (Fig.  409),  and  enters  the  infraspinous 
fossa  by  passing  under  cover  of  the  Teres  minor,  where  it  anastomoses  with  the 
posterior  scapular  and  suprascapular  arteries.  In  its  course  it  gives  off  two  sets 
of  branches :  one  enters  the  subscapular  fossa  beneath  the  Subscapularis,  which  it 
supplies,  anastomosing  with  the  posterior  scapular  and  suprascapular  arteries; 
the  other  is  continued  along  the  axillary  border  of  the  scapula,  between  the  Teres 
major  and  minor,  and,  at  the  dorsal  surface  of  the  inferior  angle  of  the  bone,  anas- 
tomoses with  the  posterior  scapular.  In  addition  to  these,  small  branches  are 
distributed  to  the  back  part  of  the  Deltoid  muscle  and  the  long  head  of  the 
Triceps,  anastomosing  with  an  ascending  branch  of  the  superior  profunda  of  the 
brachial. 

The  Circumflex  Arteries  wind  round  the  surgical  neck  of  the  humerus.  The 
posterior  circumflex  (a.  circumflexa  humeri  posterior)  (Fig.  409),  the  larger  of  the 
two,  arises  from  the  back  part  of  the  axillary  opposite  the  lower  border  of  the 
Subscapularis  muscle,  and,  passing  backward  with  the  circumflex  veins  and  nerve 


652 


THE   BLOOD -VASCULAB    SYSTEM 


through  the  quadrangular  space  bounded  by  the  Teres  major  and  minor,  the 
scapular  head  of  the  Triceps  and  the  humerus,  winds  round  the  neck  of  that  bone 
and  is  distributed  to  the  Deltoid  muscle  and  shoulder-joint,  anastomosing  with  the 
anterior  circumflex  and  acromial  thoracic  arteries,  and  with  the  superior  profunda 
branch  of  the  brachial  artery.  The  anterior  circumflex  {a.  circumflexa  humeri  ante- 
rior) (Figs.  409  and  411),  considerably  smaller  than  the  preceding,  arises  nearly 
opposite  that  vessel  from  the  outer  side  of  the  axillary  artery.  It  passes  horizon- 
tally outward  beneath  the  Coraco-brachialis  and  short  head  of  the  Biceps,  lying 

upon  the  forepart  of  the  neck  of  the 
humerus,  and,  on  reaching  the  bicipital 
groove,  gives  off  an  ascending  branch 
which  passes  upward  along  the  groove 
to  supply  the  head  of  the  bone  and  the 
shoulder-joint.  The  trunk  of  the  vessel 
is  then  continued  outward  beneath  the 
Deltoid,  which  it  suppHes,  and  anasto- 
moses with  the  posterior  circumflex 
artery. 


THE    BRACHIAL    ARTERY    (A. 

OHIALIS)  (Fig.  412). 


BRA- 


The  brachial  artery  (a.  brachialis) 
commences  at  the  lower  margin  of  the 
tendon  of  the  Teres  major,  and,  passing 
down  the  inner  and  anterior  aspect  of 
the  arm,  terminates  about  half  an  inch 
below  the  bend  of  the  elbow,  where  it 
divides  into  the  radial  and  ulnar  arteries. 
At  first  the  brachial  artery  lies  internal 
to  the  humerus ;  but  as  it  passes  down 
the  arm  it  gradually  gets  in  front  of 
the  bone,  and  at  the  bend  of  the  elbow 
it  lies  midway  between  the  two  condyles. 
Relations. — This  artery  is  superficial 
throughout  its  entire  extent,  being  cov- 
ered, in  front,  by  the  integument,  the 
superficial  and  deep  fasciae;  the  bicipital 
fascia  separates  it  opposite  the  elbow 
from  the  median  basilic  vein ;  the  median 
nerve  crosses  it  at  its  middle;  behind,  it 
is  separated  from  the  long  head  of  the 
Triceps  by  the  musculo-spiral  nerve  and 
superior  profunda  artery.  It  then  lies 
upon  the  inner  head  of  the  Triceps,  next 
upon  the  insertion  of  the  Coraco-bra- 
chialis, and  lastly  on  the  Brachialis  an- 
ticus;  by  its  outer  side,  it  is  in  relation  with  the  commencement  of  the  median 
nerve  and  the  Coraco-brachialis  and  Biceps  muscles,  which  overlap  the  artery 
to  a  considerable  extent;  by  its  inner  side,  its  upper  half  is  in  relation  with  the 
internal  cutaneous  and  ulnar  nerves,  its  lower  half  with  the  median  nerve.  The 
basihc  vein  lies  on  the  inner  side  of  the  artery,  but  is  separated  from  it  in  the 
lower  part  of  the  arm  by  the  deep  fascia.     The  brachial  artery  is  accompanied  by 


Fig.  412. — The  brachial  artery. 


SURGICAL   ANATOMY   OF    THE  BEND    OF    THE  ELBOW    653 

two  venae  comites,  which  he  in  close  contact  with,  the  artery,  being  connected 
together  at  intervals  by  short  transverse  communicating  branches. 

Plan  of  the  Relations  of  the  Brachial  Artery. 

In  front. 

Integument  and  fasciae. 

Bicipital  fascia,  median  basilic  vein. 

Median  nerve. 

Overlapped  by  Coraco-brachialis  and  Biceps. 

Outer  side.  /  \  Inner  side. 

Median  nerve  (above).  I  Brachial      \  Internal  cutaneous  and  Ulnar  nerves. 

Coraco-brachialis.  I  Artery.       i  jvie^jian  nerve  (below). 

Biceps.  \  /  Basilic  vein. 

Behind. 

Triceps  (long  and  inner  heads). 
Musculo-spiral  nerve. 
Superior  profunda  artery. 
Coraco-brachialis. 
Brachialis  anticus. 

SURGICAL  ANATOMY  OF  THE  BEND  OF  THE  ELBOW. 

At  the  bend  of  the  elbow  the  brachial  artery  sinks  deeply  into  a  triangular  inter- 
val, the  antecubital  space,  the  base  of  which  is  directed  upward,  and  may  be  repre- 
sented by  a  line  connecting  the  two  condyles  of  the  humerus;  the  sides  are  bounded, 
externally,  by  the  inner  edge  of  the  Supinator  longus;  internally,  by  the  outer  mar- 
gin of  the  Pronator  radii  teres;  its  floor  is  formed  by  the  Brachialis  anticus  and 
Supinator  brevis.  This  space  contains  the  brachial  artery  with  its  accompanying 
veins,  the  radial  and  ulnar  arteries,  the  median  and  musculo-spiral  nerves,  and  the 
tendon  of  the  Biceps.  The  brachial  artery  occupies  the  middle  line  of  this  space,  and 
divides  opposite  the  neck  of  the  radius  into  the  radial  and  ulnar  arteries;  it  is 
covered,  in  front,  by  the  integument,  the  superficial  fascia,  and  the  median  basilic 
vein,  the  vein  being  separated  from  direct  contact  with  the  artery  by  the  bicipital 
fascia.  Behind,  it  lies  on  the  Brachialis  anticus,  which  separates  it  from  the 
elbow-joint.  The  median  nerve  lies  on  the  inner  side  of  the  artery,  close  to  it 
above,  but  separated  from  it  below  by  the  coronoid  origin  of  the  Pronator  radii 
teres.  The  tendon  of  the  Biceps  lies  to  the  outer  side  of  the  space,  and  the  mus- 
culo-spiral nerve  still  more  externally,  situated  upon  the  Supinator  brevis  and 
partly  concealed  by  the  Supinator  longus. 

Peculiarities  of  the  Brachial  Artery  as  Regards  its  Course. — The  brachial  artery,  accom- 
panied by  the  median  nerve,  may  leave  the  inner  border  of  the  Biceps  and  descend  toward  the 
inner  condyle  of  the  humerus,  where  it  usually  curves  round  a  prominence  of  bone,  the  supra- 
condylar process.  From  this  process,  in  most  subjects,  a  fibrous  arch  is  thrown  over  the 
artery.  The  vessel  then  inclines  outward,  beneath  or  through  the  substance  of  the  Pronator 
radii  teres  muscle,  to  the  bend  of  the  elbow.  The  variation  bears  considerable  analogy  to  the 
normal  condition  of  the  artery  in  some  of  the  carnivora:  it  has  been  referred  to  in  the  descrip- 
tion of  the  humerus  (page  180). 

As  Regards  its  Division. — Occasionally,  the  artery  is  divided  for  a  short  distance  at  its  upper 
part  into  two  trunks,  which  are  united  above  and  below.  A  similar  peculiarity  occurs  in  the  main 
vessel  of  the  lower  limb. 

The  point  of  bifurcation  may  be  above  or  below  the  usual  point,  the  former  condition  being 
by  far  the  more  frequent.  Out  of  481  examinations  recorded  by  Mr.  Quain,  some  made  on  the 
right  and  some  on  the  left  side  of  the  body,  in  386  the  artery  bifurcated  in  its  normal  position. 
In  one  case  only  was  the  place  of  division  lower  than  usual,  being  two  or  three  inches  below  the 
elbow-joint.  "In  94  cases  out  of  481,  or  about  1  in  5J,  there  were  two  arteries  instead  of  one 
in  some  part  or  in  the  whole  of  the  arm." 


654  THE   BLOOD -VASCULAR    SYSTEM 

There  appears,  however,  to  be  no  correspondence  between  the  arteries  of  the  two  arms  with 
respect  to  their  irregular  division;  for  in  61  bodies  it  occurred  on  one  side  only  in  43;  on  both 
sides,  in  different  positions,  in  13;  on  both  sides,  in  the  same  position,  in  5. 

The  point  of  bifurcation  takes  place  at  different  parts  of  the  arm,  being  most  frequent  in 
the  upper  part,  less  so  in  the  lower  part,  and  least  so  in  the  middle,  the  most  usual  point  for 
the  application  of  a  ligature;  under  any  of  these  circumstances  two  large  arteries  would  be  found 
in  the  arm  instead  of  one.  The  most  frequent  (in  three  out  of  four)  of  these  peculiarities  is 
the  high  origin  of  the  radial.  That  artery  often  arises  from  the  inner  side  of  the  brachial, 
and  runs  parallel  with  the  main  trunk  to  the  elbow,  where  it  crosses  it,  lying  beneath  the  fascia; 
or  it  may  perforate  the  fascia  and  pass  over  the  artery  immediately  beneath  the  integument. 

The  ulnar  sometimes  arises  from  the  brachial  high  up,  and  accompanies  that  vessel  to  the 
lower  part  of  the  arm,  and  descends  toward  the  inner  condyle.  In  the  forearm  it  generally  lies 
beneath  the  deep  fascia,  superficial  to  the  flexor  muscles;  occasionally  between  the  integument 
and  deep  fascia,  and  very  rarely  beneath  the  flexor  muscles. 

The  interosseous  artery  sometimes  arises  from  the  upper  part  of  the  brachial  or  axillary;  as 
it  passes  down  the  arm  it  lies  behind  the  main  trunk,  and  at  the  bend  of  the  elbow  regains  its 
.usual  position. 

In  some  cases  of  high  origin  of  the  radial  the  remaining  trunk  (ulnar  interosseous)  occa- 
sionally passes,  together  with  the  median  nerve,  along  the  inner  margin  of  the  arm  to  the  inner 
condyle,  and  then  passing  from  within  outward,  beneath  or  through  the  Pronator  radii  teres, 
regains  its  usual  position  at  the  bend  of  the  elbow. 

Occasionally  the  two  arteries  representing  the  brachial  are  connected  at  the  bend  of  the  elbow 
by  a  short  transverse  branch,  and  are  even  sometimes  reunited. 

Sometimes,  long  slender  vessels,  vasa  aberrantia,  connect  the  brachial  or  axillary  arteries 
with  one  of  the  arteries  of  the  forearm  or  a  branch  from  them.  These  vessels  usually  join  the 
radial. 

Varieties  in  Muscular  Relations.' — The  brachial  artery  is  occasionally  concealed  in  some 
part  of  its  course  by  muscular  or  tendinous  slips  derived  from  the  Coraco-brachialis,  Biceps, 
Brachialis  anticus,  and  Pronator  radii  teres  muscles. 

Surface  Marking. — The  direction  of  the  brachial  artery  is  marked  by  a  line  drawn  along 
the  inner  edge  of  the  Biceps  from  the  junction  of  the  anterior  and  middle  thirds  of  the  axillary 
outlet  to  the  middle  of  the  front  of  the  elbow-joint. 

Surgical  Anatomy. — Compression  of  the  brachial  artery  is  required  in  cases  of  amputation 
and  some  other  operations  in  the  arm  and  forearm ;  and  it  will  be  observed  that  it  may  be  effected 
in  almost  any  part  of  the  course  of  the  artery.  If  pressure  is  made  in  the  upper  part  of  the 
limb,  it  should  be  directed  from  within  outward;  and  if  in  the  lower  part,  from  before  backward, 
as  the  artery  lies  on  the  inner  side  of  the  humerus  above  and  in  front  of  the  humerus  below. 
The  most  favorable  situation  is  about  the  middle  of  the  arm,  where  it  lies  on  the  tendon  of  the 
Coraco-brachialis  on  the  inner  flat  side  of  the  humerus. 

The  application  of  a  ligature  to  the  brachial  artery  may  be  required  in  case  of  wound  of 
the  vessel  and  in  some  cases  of  wound  of  the  palmar  arch.  It  is  also  sometimes  necessary  in 
cases  of  aneurism  of  the  brachial,  the  radial,  ulnar,  or  interosseous  arteries.  The  artery  may 
be  secured  in  any  part  of  its  course.  The  chief  guides  in  determining  its  position  are  the  sur- 
face markings  produced  by  the  inner  margin  of  the  Coraco-brachialis  and  Biceps,  the  known 
course  of  the  vessel,  and  its  pulsation,  which  should  be  carefully  felt  for  before  any  operation  is 
performed,  as  the  vessel  occasionally  deviates  from  its  usual  position  in  the  arm.  In  whatever 
situation  the  operation  is  performed,  great  care  is  necessary,  on  account  of  the  extreme  thinness 
of  the  parts  covering  the  artery  and  the  intimate  connection  which  the  vessel  has  throughout  its 
whole  course  with  important  nerves  and  veins.  Sometimes  a  thin  layer  of  muscular  fibre  is 
met  with  concealing  the  artery ;  if  such  is  the  case,  it  must  be  cut  across  in  order  to  expose  the 
vessel. 

In  the  upper  third  of  the  arm  the  artery  may  be  exposed  in  the  following  manner:  The 
patient  being  placed  supine  upon  a  table,  the  affected  limb  should  be  raised  from  the  side  and 
the  hand  supinated.  An  incision  about  two  inches  in  length  should  be  made  on  the  inner 
side  of  the  Coraco-brachialis  muscle,  and  the  subjacent  fascia  cautiously  divided,  so  as  to  avoid 
wounding  the  internal  cutaneous  nerve  or  basilic  vein,  which  sometimes  runs  on  the  surface  of 
the  artery  as  high  as  the  axillary.  The  fascia  having  been  divided,  it  should  be  remembered  that 
the  ulnar  and  internal  cutaneous  nerves  lie  on  the  inner  side  of  the  artery,  the  median  on  the 
outer  side,  the  latter  nerve  being  occasionally  superficial  to  the  artery  in  this  situation,  and  that 
the  venje  comites  are  also  in  relation  with  the  vessel,  one  on  either  side.  These  being  carefully 
separated,  the  aneurism  needle  should  be  passed  round  the  artery  from  the  inner  to  the  outer 
side. 

If  two  arteries  are  present  in  the  arm  in  consequence  of  a  high  division,  they  are  usually 
placed  side  by  side:  and  if  they  are  exposed  in  an  operation,  the  surgeon  should  endeavor  to 

1  See  Struther's  Anatomical  and  Physiological  Observations. 


BRANCHES    OF    THE   BRACHIAL    ARTERY  655 

ascertain,  by  alternately  pressing  on  each  vessel,  which  of  the  two  communicates  with  the  wound 
or  aneurism,  when  a  ligature  may  be  applied  accordingly;  or  if  pulsation  or  hemorrhage  ceases 
only  when  both  vessels  are  compressed,  both  vessels  may  be  tied,  as  it  may  be  concluded  that 
the  two  communicate  above  the  seat  of  disease  or  are  reunited. 

It  should  also  be  remembered  that  two  arteries  may  be  present  in  the  arm  in  a  case  of  high 
division,  and  that  one  of  these  may  be  found  along  the  inner  intermuscular  septum,  in  a  line 
toward  the  inner  condyle  of  the  humerus,  or  in  the  usual  position  of  the  brachial,  but  deeply 
placed  beneath  the  common  trunk:  a  knowledge  of  these  facts  will  suggest  the  precautions 
necessary  in  every  case,  and  indicate  the  measures  to  be  adopted  when  anomalies  are  met  with. 

In  the  middle  of  the  arm  the  brachial  artery  may  be  exposed  by  making  an  incision  along 
the  inner  margin  of  the  Biceps  muscle.  The  forearm  being  bent  so  as  to  relax  the  muscle,  it 
should  be  drawn  slightly  aside,  and,  the  fascia  being  carefully  divided,  the  median  nerve  will  be 
exposed  lying  upon  the  artery  (sometimes  beneath);  this  being  drawn  inward  and  the  muscle 
outward,  the  artery  should  be  separated  from  its  accompanying  veins  and  secured.  In  this 
situation  the  inferior  profunda  may  be  mistaken  for  the  main  trunk,  especially  if  enlarged,  from 
the  collateral  circulation  having  become  established;  this  may  be  avoided  by  directing  the 
incision  externally  toward  the  Biceps,  rather  than  inward  or  backward  toward  the  Triceps. 

The  lower  part  of  the  brachial  artery  is  of  interest  in  a  surgical  point  of  view,  on  account 
of  the  relation  which  it  bears  to  the  veins  most  commonly  opened  in  venesection.  Of  these 
vessels,  the  median  basilic  is  the  largest  and  most  prominent,  and,  consequently,  the  one  usually 
selected  for  the  operation.  It  should  be  remembered  that  this  vein  runs  parallel  with  the 
brachial  artery,  from  which  it  is  separated  by  the  bicipital  fascia,  and  that  care  should  be  taken 
in  opening  the  vein  not  to  carry  the  incision  too  deeply,  so  as  to  endanger  the  artery. 

Collateral  Circulation. — After  the  application  of  a  ligature  to  the  brachial  artery  in  the 
upper  third  of  the  arm,  the  circulation  is  carried  on  by  branches  from  the  circumflex  and  sub- 
scapular arteries,  anastomosing  with  ascending  branches  from  the  superior  profunda.  If  the 
brachial  is  tied  helow  the  origin  of  the  profunda  arteries,  the  circulation  is  maintained  by  the 
branches  of  the  profundse,  anastomosing  with  the  recurrent  radial,  ulnar,  and  interosseous 
arteries.  In  two  cases  described  by  Mr.  South,'  in  which  the  brachial  artery  had  been  tied  some 
time  previously,  in  one  "a  long  portion  of  the  artery  had  been  obliterated,  and  sets  of  vessels 
are  descending  on  either  side  from  above  the  obliteration,  to  be  received  into  others  which  ascend 
in  a  similar  manner  from  below  it.  In  the  other  the  obliteration  is  less  extensive,  and  a  single 
curved  artery  about  as  bi^  as  a  crow-quill  passes  from  the  upper  to  the  lower  open  part  of  the 
artery." 

Branches. — The  branches  of  the  brachial  artery  are — the 

Superior  Profunda.  Inferior  Profunda. 

Nutrient.  Anastomotica  Magna. 

Muscular. 

The  Superior  Profunda  Artery  (a.  profunda  hrachii)  arises  from  the  inner  and 
back  part  of  the  brachial,  just  below  the  lower  border  of  the  Teres  major,  and 
passes  backward  to  the  interval  between  the  outer  and  inner  heads  of  the  Triceps 
muscle;  accompanied  by  the  musculo-spiral  nerve  it  winds  around  the  back  part  of 
the  shaft  of  the  humerus  in  the  spiral  groove,  between  the  outer  head  of  the  Triceps 
and  the  bone,  to  the  outer  side  of  the  humerus,  where  it  reaches  the  external  inter- 
muscular septum  and  divides  into  two  terminal  branches.  One  of  these  pierces 
the  external  intermuscular  septum,  and  descends,  in  company  with  the  musculo- 
spiral  nerve,  to  the  space  between  the  Brachialis  anticus  and  Supinator  longus, 
where  it  anastomoses  with  the  recurrent  branch  of  the  radial  artery;  while  the 
other,  much  the  larger  of  the  two,  descends  along  the  back  of  the  external  inter- 
muscular septum  to  the  back  of  the  elbow-joint,  where  it  anastomoses  with  the 
posterior  interosseous  recurrent,  and  across  the  back  of  the  humerus  with  the  pos- 
terior ulnar  recurrent,  the  anastomotica  magna,  and  inferior  profunda  (Fig.  415). 
The  superior  profunda  supplies  the  Triceps  muscle  and  gives  off  a  nutrient  artery 
which  enters  the  bone  at  the  upper  end  of  the  musculo-spiral  groove.  Near  its 
commencement  it  sends  off  a  branch  which  passes  upward  between  the  external 
and  long  heads  of  the  Triceps  muscle  to  anastomose  with  the  posterior  circumflex 

'  Chelius's  Surgery,  vol.  ii.  p.  254.  See  also  White'."?  engravings,  referred  to  by  Mr.  South,  of  the  anastomos- 
ing branches  after  ligature  of  the  brachial,  in  White's  Cases  in  Surgery.  Porta  also  gives  a  case  (with  drawings) 
of  the  circulation  after  ligature  of  both  brachial  and  radial  (Alterazioni  Patoligiche  delle  Arterie). — Ed.  of  15th 
English  edition. 


656 


THE   BLOOD -VASCULAR    SYSTEM 


Radial  recurrent.-^ 

$\l 

X 

o 

J 

c 

e 

f 

' 

< 

z 

'i*'l 

III 

artery,  and,  while  in  the  groove,  a  small  branch  which  accompanies  a  branch  of 
the  musculo-spiral  nerve  through  the  substance  of  the  Triceps  muscle  and  ends 

in   the  Anconeus   below  the   outer 
condyle  of  the  humerus. 

The  Nutrient  Artery  (a.  nutricia 
humeri)  of  the  shaft  of  the  humerus 
arises  from  the  brachial,  about  the 
middle  of  the  arm.  Passing  down- 
ward it  enters  the  nutrient  canal  of 
that  bone  near  the  insertion  of  the 
Coraco-brachialis  muscle. 

The  Inferior  Profunda  (a.  col- 
lateralis  ulnar  is  superior),  of  small 
size,  arises  from  the  brachial,  a  little 
below  the  middle  of  the  arm;  pierc- 
ing the  internal  intermuscular  sep- 
tum, it  descends  on  the  surface  of 
the  inner  head  of  the  Triceps  mus- 
cle to  the  space  between  the  inner 
condyle  and  olecranon,  accompanied 
by  the  ulnar  nerve,  and  terminates 
by  anastomosing  with  the  posterior 
ulnar  recurrent  and  anastomotica 
magna.  It  sometimes  supplies  a 
branch  to  the  front  of  the  internal 
condyle,  which  anastomoses  with 
the  anterior  ulnar  recurrent. 

The  Anastomotica  Magna  (a. 
collateralis  ulnaris  inferior)  arises 
from  the  brachial  about  two  inches 
above  the  elbow-joint.  It  passes 
transversely  inward  upon  the  Bra- 
chialis  anticus,  and,  piercing  the 
internal  intermuscular  septum,winds 
round  the  back  of  the  humerus  be- 
tween the  Triceps  and  the  bone, 
forming  an  arch  above  the  olecranon 
fossa  by  its  junction  with  the  poste- 
rior articular  branch  of  the  superior 
profunda.  As  this  vessel  lies  on  the 
Brachialis  anticus,  branches  ascend 
to  join  the  inferior  profunda,  and 
others  descend  in  front  of  the  inner 
condyle  to  anastomose  with  the  an- 
terior ulnar  recurrent.  Behind  the 
internal  condyle  an  offset  is  given 
off  which  anastomoses  with  the  infe- 
rior profunda  and  posterior  ulnar 
recurrent  arteries  and  supplies  the 
Triceps. 

The  Muscular  (rami  muscidares) 
are  three  or  four  large  branches, 
which  are  distributed  to  the  muscles  in  the  course  of  the  artery.  They  supply 
the  Coraco-brachialis,  Biceps,  and  Brachialis  anticus  muscles. 


Deep  branch 
of  ulnar. 


Superficialis  volse 


Fig.  413. — The  radial  and  ulnar  arteries. 


THE   BADIAL    ABTEBY  657 

The  Anastomosis  around  the  Elbow-joint  (Fig.  415). — The  vessels  engaged 
in  this  anastomosis  may  be  conveniently  divided  into  those  situated  in  front  and 
behind  the  internal  and  external  condyles.  The  branches  anastomosing  in  front 
of  the  internal  condyle  are  the  anastomotica  magna,  the  anterior  ulnar  recurrent, 
and  the  anterior  terminal  branch  of  the  inferior  profunda.  Those  behind  the  in- 
ternal condyle  are  the  anastomotica  magna,  the  posterior  ulnar  recurrent,  and  the 
posterior  terminal  branch  of  the  inferior  profunda.  The  branches  anastomosing 
in  front  of  the  external  condyle  are  the  radial  recurrent  and  the  anterior  terminal 
branch  of  the  superior  profunda.  Those  behind  the  external  condyle  (perhaps 
more  properly  described  as  being  situated  between  the  external  condyle  and  the 
olecranon)  are  the  anastomotica  magna,  the  interosseous  recurrent,and  the  posterior 
terminal  branch  of  the  superior  profimda.  There  is  also  a  large  arch  of  anasto- 
mosis above  the  olecranon,  formed  by  the  interosseous  recurrent,  joining  with  the 
anastomotica  magna  and  posterior  ulnar  recurrent. 

From  this  description  it  will  be  observed  that  the  anastomotica  magna  is  the 
vessel  most  engaged,  the  only  part  of  the  anastomosis  in  which  it  is  not  employed 
being  that  in  front  of  the  external  condyle. 

The  Radial  Artery  (A.  Radialis)  (Figs.  413,  414). 

The  radial  artery  appears,  from  its  direction,  to  be  the  continuation  of  the 
brachial,  but  in  size  it  is  smaller  than  the  ulnar.  It  commences  at  the  bifurcation  of 
the  brachial,  just  below  the  bend  of  the  elbow,  and  passes  alongthe  radial  side  of  the 
forearm  to  the  wrist;  it  then  winds  backward,  round  the  outer  side  of  the  carpus, 
beneath  the  extensor  tendons  of  the  thumb,  to  the  upper  end  of  the  space  between 
the  metacarpal  bones  of  the  thumb  and  index  finger,  and  finally  passes  forward, 
between  the  two  heads  of  the  First  dorsal  interosseous  muscle,  into  the  palm  of  the 
hand,  where  it  crosses  the  metacarpal  bones  to  the  ulnar  border  of  the  hand,  to  form 
the  deep  palmar  axch.  At  its  termination  it  inosculates  with  the  deep  branch  of  the 
ulnar  artery.  The  relations  of  this  vessel  may  thus  be  conveniently  divided  into 
three  parts — viz.,  in  the  forearm,  at  the  back  of  the  wrist,  and  in  the  hand. 

Relations. — In  the  forearm  this  vessel  extends  from  opposite  the  neck  of  the 
radius  to  the  forepart  of  the  styloid  process,  being  placed  to  the  inner  side  of  the 
shaft  of  the  bone  above  and  in  front  of  it  below.  It  is  overlapped  in  the  upper 
part  of  its  course  by  the  fleshy  belly  of  the  Supinator  longus  muscle;  throughout 
the  rest  of  its  course  it  is  superficial,  being  covered  by  the  integument,  the  super- 
ficial and  deep  fasciae.  In  its  course  downward  it  lies  upon  the  tendon  of  the 
Biceps,  the  Supinator  brevis,  the  Pronator  radii  teres,  the  radial  origin  of  the 
Flexor  sublimis  digitorum,  the  Flexor  longus  pollicis,  the  Pronator  quadratus,  and 
the  lower  extremity  of  the  radius.  In  the  upper  third  of  its  course  it  lies  between 
the  Supinator  longus  and  the  Pronator  radii  teres;  in  the  lower  two-thirds,  between 
the  tendons  of  the  Supinator  longus  and  the  Flexor  carpi  radialis.  The  radial 
nerve  lies  close  to  the  outer  side  of  the  artery  in  the  middle  third  of  its  course, 
and  some  filaments  of  the  musculo-cutaneous  nerve,  after  piercing  the  deep  fascia, 
run  along  the  lower  part  of  the  artery  as  it  winds  round  the  wrist.  The  vessel  is 
accompanied  by  venje  comites  throughout  its  whole  course. 

Plan  of  the  Relations  of  the  Radial  Artery  in  the  Forearm. 

In  front. 
Skin,  superficial  and  deep  fasciae. 
Supinator  longus. 

Inner  side.  f     Radial      \  Outer  side. 

Pronator  radii  teres.  I     Foreara"     )  Supinator  longus. 

Flexor  carpi  radialis.  V  /  Radial  nerve  (middle  third). 


658  THE   BLOOD -VASCULAR   SYSTEM 

Behind. 
Tendon  of  Biceps. 
Supinator  brevis. 
Pronator  radii  teres. 
Flexor  sublimis  digitorum. 
Flexor  longus  pollicis. 
Pronator  quadratus. 
Radiias. 

At  the  wrist,  as  it  winds  round  the  outer  side  of  the  carpus  from  the  styloid 
process  to  the  first  interosseous  space,  it  Hes  upon  the  external  lateral  ligament, 
and  then  upon  the  scaphoid  bone  and  trapezium,  being  covered  by  the  extensor 
tendons  of  the  thumb,  subcutaneous  veins,  some  filaments  of  the  radial  nerve,  and 
the  integument.  It  is  accompanied  by  two  veins  and  a  filament  of  the  musculo- 
cutaneous nerve. 

In  the  hand  it  passes  from  the  upper  end  of  the  first  interosseous  space, 
between  the  heads  of  the  Abductor  indicis  or  First  dorsal  interosseous  muscle, 
transversely  across  the  palm,  to  the  base  of  the  metacarpal  bone  of  the  little 
finger,  where  it  inosculates  with  the  communicating  branch  from  the  ulnar  artery, 
forming  the  deep  palmax  arch. 

The  Deep  Palmar  Arch  {arcus  volaris  profundus)  (Fig.  414). — It  lies  upon  the 
carpal  extremities  of  the  metacarpal  bones  and  the  Interossei  muscles,  being 
covered  by  the  Adductor  obliquus  pollicis,  the  flexor  tendons  of  the  fingers,  the 
Lumbricales,  the  Opponens,  and  Flexor  brevis  minimi  digiti.  Alongside  of  it  is 
the  deep  branch  of  the  ulnar  nerve,  but  running  in  the  opposite  direction;  that 
is  to  say,  from  within  outward.  The  branches  of  the  deep  palmar  arch  are  the 
palmar  interosseous,  perforating  and  palmar  recurrent  vessels  (page  660) . 

Peculiarities. — The  origin  of  the  radial  artery,  according  to  Quain,  is,  in  nearly  one  case 
in  eight,  higher  than  usual ;  more  frequently  arising  from  the  axillary  or  upper  part  of  the  brachial 
than  from  the  lower  part  of  this  vessel.  The  variations  in  the  position  of  this  vessel  in  the  arm 
and  at  the  bend  of  the  elbow  have  been  already  mentioned.  In  the  forearm  it  deviates  less  fre- 
quently from  its  position  than  the  ulnar.  It  has  been  found  lying  over  the  fascia  instead  of 
beneath  it.  It  has  also  been  observed  on  the  surface  of  the  Supinator  longus,  instead  of  under 
its  inner  border;  and  in  turning  round  the  wrist  it  has  been  seen  lying  over,  instead  of  beneath, 
the  extensor  tendons  of  the  thumb. 

Surface  Marking. — The  position  of  the  radial  artery  in  the  forearm  is  represented  by  a  line 
drawn  from  the  outer  border  of  the  tendon  of  the  Biceps  in  the  centre  of  the  hollow  in  front 
of  the  elbow-joint  with  a  straight  course  to  the  inner  side  of  the  forepart  of  the  styloid  process 
of  the  radius. 

Surgical  Anatomy. — The  radial  artery  is  much  exposed  to  injury  in  its  lower  third,  and  is 
frequently  wounded  by  the  hand  being  driven  through  a  pane  of  glass,  by  the  slipping  of  a 
knife  or  chisel  held  in  the  other  hand,  and  similar  accidents.  The  injury  is  often  followed  by 
a  traumatic  aneurism,  for  which  the  operation  of  extirpating  or  laying  open  the  sac  after  securing 
the  vessel  above  and  below  is  required. 

The  operation  of  tying  the  radial  artery  is  required  in  cases  of  wounds  either  of  its  trunk  or 
of  some  of  its  branches,  or  for  aneurism ;  and  it  will  be  observed  that  the  vessel  may  be  exposed 
in  any  part  of  its  course  through  the  forearm  without  the  division  of  any  muscular  fibres.  The 
operation  in  the  middle  or  inferior  third  of  the  forearm  is  easily  performed,  but  in  the  upper 
third,  near  the  elbow,  it  is  attended  with  some  difficulty,  from  the  greater  depth  of  the  vessel 
and  from  its  being  overlapped  by  the  Supinator  longus  muscle. 

To  tie  the  artery  in  the  upper  third  an  incision  three  inches  in  length  should  be  made  through 
the  integument,  in  a  line  drawn  from  the  centre  of  the  bend  of  the  elbow  to  the  front  of  the 
styloid  process  of  the  radius,  avoiding  the  branches  of  the  median  vein;  the  fascia  of  the  arm 
being  divided  and  the  Supinator  longus  drawn  a  little  outward,  the  artery  will  be  exposed.  The 
venae  comites  should  be  carefully  separated  from  the  vessel,  and  the  ligature  passed  from  the 
radial  to  the  ulnar  side. 

In  the  middle  third  of  the  forearm  the  artery  may  be  exposed  by  making  an  incision  of  similar 
length  on  the  inner  margin  of  the  Supinator  longus.  In  this  situation  the  radial  nerve  lies  in  close 
relation  with  the  outer  side  of  the  artery,  and  should,  as  well  as  the  veins,  be  carefully  avoided. 

In  the  lower  third  the  artery  is  easily  secured  by  dividing  the  integument  and  fascia  in  the 
interval  between  the  tendons  of  the  Supinator  longus  and  Flexor  carpi  radialis  muscles. 


THE   RADIAL    ABTEBY  659 

Branches  (Figs.  413,  414,  and  415). — The  branches  of  the  radial  artery  may 
be  divided  into  three  groups,  corresponding  with  the  three  regions  in  which  the 
vessel  is  situated. 


In  the 
Forearm 


Radial  Recurrent 

Muscular.  w  '  i  i 

Anterior  Radial  Carpal  ^^ 

Superficialis  Vola? 


Posterior  Radial  Carpal. 
Metacarpal. 
Dorsales  Pollicis. 
Dorsalis  Indicis. 


Hand 


Princeps  Pollicis. 
Radialis  Indicis. 
Perforating. 
Palmar  Interosseous. 
Palmar  Recurrent. 


The  Radial  Recurrent  (a.  recurrens  radialis)  (Fig.  414)  is  given  off  imme- 
diately below  the  elbow.  It  ascends  between  the  branches  of  the  musculo-spiral 
nerve  lying  on  the  Supinator  brevis,  and  then  between  the  Supinator  longus  and 
Brachialis  anticus,  supplying  these  muscles  and  the  elbow-joint,  and  anastomosing 
with  the  terminal  branches  of  the  superior  profunda. 

The  Muscular  Branches  {rami  musculares)  are  distributed  to  the  muscles  on 
the  radial  side  of  the  forearm. 

The  Anterior  Radial  Carpal  {ramus  carpeus  volaris)  (Fig.  414)  is  a  small 
vessel  which  arises  from  the  radial  artery  near  the  lower  border  of  the  Pronator 
quadratus,  and,  running  inward  in  front  of  the  radius,  anastomoses  with  the  ante- 
rior carpal  branch  of  the  ulnar  artery.  In  this  way  an  arterial  anastomosis,  the 
anterior  carpal  arch  (rete  carpi  volare),  is  formed  in  front  of  the  wrist;  it  is  joined 
by  branches  from  the  anterior  interosseous  above,  and  by  recurrent  branches  from 
the  deep  palmar  arch  below,  and  gives  off  branches  which  descend  to  supply  the 
articulations  of  the  wrist  and  carpus. 

The  Superficiahs  Volae  {ramus  volaris  superficialis)  (Fig.  414)  arises  from  the 
radial  artery,  just  where  this  vessel  is  about  to  wind  round  the  wrist.  Running 
forward,  it  passes  between,  occasionally  over,  the  muscles  of  the  thumb,  which  it 
supplies,  and  sometimes  anastomoses  with  the  palmar  portion  of  the  ulnar  artery, 
completing  the  superficial  palmar  arch.  This  vessel  varies  considerably  in  size: 
usually  it  is  very  small,  and  terminates  in  the  muscles  of  the  thumb;  sometimes 
it  is  as  large  as  the  continuation  of  the  radial. 

The  Posterior  Radial  Carpal  {ramus  carpeus  dorsalis)  (Fig.  415)  is  a  small 
vessel  which  arises  from  the  radial  artery  beneath  the  extensor  tendons  of  the 
thumb;  crossing  the  carpus  transversely  to  the  inner  border  of  the  hand,  it 
anastomoses  with  the  posterior  carpal  branch  of  the  ulnar,  forming  the  posterior 
carpal  arch  {rete  carpi  dorsale),  which  is  joined  by  the  termination  of  the  anterior 
interosseous  artery.  From  this  arch  are  given  off  descending  branches,  the 
dorsal  interosseous  arteries  {aa.  metacarpea;  dorsales)  for  the  second,  third,  and 
fourth  interosseous  spaces,  which  run  forward  on  the  Second,  Third,  and 
Fourth  dorsal  interossei  muscles,  and  divide  into  dorsal  digital  branches  {aa. 
digital es  dorsales),  which  supply  the  adjacent  sides  of  the  index,  middle,  ring, 
and  little  fingers  respectively,  communicating  with  the  digital  arteries  of  the 
superficial  palmar  arch.  The  dorsal  interosseous  arteries  anastomose  with  the 
perforating  branches  from  the  deep  palmar  arch  {rami  per  for  antes) . 

The  Dorsales  Pollicis  (Fig.  415)  are  two  vessels  which  run  along  the  sides  of 
the  dorsal  aspect  of  the  thumb.  They  arise  separately,  or  occasionally  by  a 
common  trunk,  near  the  base  of  the  first  metacarpal  bone. 

The  Dorsalis  Indicis  (Fig.  415),  also  a  small  branch,  runs  along  the  radial  side 
of  the  back  of  the  index  finger,  sending  a  few  branches  to  the  Abductor  indicis. 


660 


THE   BLOOD -VASCULAR    SYSTEM 


Anastomotica, 
magna. 


Radial   , 
recurrent. 


Posterior 
interosseous. 


Anterior  ulnar 
recurrent. 

Posterior  ulnar 
recurrent. 


The  Princeps  PoUicis  (a.  princeps  pollicis)  (Fig.  A\^) arises  from  the  radial  just  as 
it  turns  inward  to  the  deep  part  of  the  hand;  it  descends  between  the  Abductor  incHcis 

and  Adductor  obhquu  ponicis,then 
between  the  Adductor  transversus 
poUicis  and  Adductor  obUquus 
pollicis,  along  the  ulnar  side  of  the 
metacarpal  bone  of  the  thumb,  to 
the  base  of  the  first  phalanx,  where 
it  divides  into  two  branches,  which 
run  along  the  sides  of  the  palmar 
aspect  of  the  thumb,  and  form  an 
arch  on  the  palmar  surface  of  the 
last  phalanx,  from  which  branches 
are  distributed  to  the  integument 
and  pulp  of  the  thumb. 

The  Radialis  Indicis  (a.  volaris 
indicis  radialis)  (Fig.  414)  arises 
close  to  the  preceding,  descends 
between  the  Abductor  indicis  and 
Adductor  transversus  pollicis,  and 
runs  along  the  radial  side  of  the 
index  finger  to  its  extremity,  where 
it  anastomoses  with  the  collateral 
digital  artery  from  the  superficial 
palmar  arch.  At  the  lower  border 
of  the  Adductor  transversus  pollicis 
this  vessel  anastomoses  with  the 
princeps  pollicis,  and  gives  a  com- 
municating branch  to  th^  super- 
ficial palmar  arch. 

The  Perforating  Arteries  {rami 
perforantes)  (Fig.  414),  three  in 
number,  pass  backward  from  the 
deep  palmar  arch  between  the 
heads  of  the  last  three  Dorsal  inter- 
ossei  muscles,  to  inosculate  with 
the  dorsal  interosseous  arteries. 

The  Palmar  Interosseous  (aa. 

metacarpecB  volar  es)  (Fig.  414),  three 

or  four  in  number,  arise  from  the 

convexity  of  the  deep  palmar  arch; 

they  run  forward  upon  the  Inter- 

ossei  muscles,and  anastomose  at  the 

clefts  of  the  fingers  with  the  digital 

branches  of   the   superficial    arch. 

The  Palmar  Recurrent  Branches  arise  from  the  concavity  of  the  deep  palmar 

arch.    They  pass  upward  in  front  of  the  wrist,  supplying  the  carpal  articulations 

and  anastomosing  with  the  anterior  carpal  arch. 


MiisciUar. 


Anterior  carpal. 
Superficialis  volse. 


Muscular. 


Anterior  carpal. 


Deep  branch  of 
jdnar. 


Fig.  414. — Ulnar  and  radial  arteries.     Deep  view. 


The  Ulnar  Artery  (A.  Uhiaris)  (Figs.  413,  414). 


The  ulnar  artery,  the  larger  of   the   two   terminal   branches  of  the  brachial, 
commences  a  little   below  the  bend  of  the  elbow,   and  crosses  obliquely  the 


THE    ULNAR    ARTERY  661 

inner  side  of  the  forearm  to  the  commencement  of  its  lower  half;  it  then 
runs  along  its  ulnar  border  to  the  wrist,  crosses  the  annular  ligament  on  the 
radial  side  of  the  pisiform  bone,  and  immediately  beyond  this  bone  divides  into 
two  branches  which  enter  into  the  formation  of  the  superficial  and  deep  palmar 
arches. 

Relations.  In  the  Foreaxm. — In  its  upper  half  it  is  deeply  seated,  being  cov- 
ered by  all  the  superficial  Flexor  muscles,  excepting  the  Flexor  carpi  ulnaris;  the 
median  nerve  is  in  relation  with  the  inner  side  of  the  artery  for  about  an  inch  and 
then  crosses  the  vessel,  being  separated  from  it  by  the  deep  head  of  the  Pronator 
radii  teres;  it  lies  upon  the  Brachialis  anticus  and  Flexor  profundus  digitorum 
muscles.  In  the  lower  half  of  the  forearm  it  lies  upon  the  Flexor  profundus,  being 
covered  by  the  integument,  the  superficial  and  deep  fasciae,  and  is  placed  between 
the  Flexor  carpi  ulnaris  and  Flexor  sublimis  digitorum  muscles.  It  is  accompanied 
by  two  venae  comites;  the  ulnar  nerve  lies  on  its  inner  side  for  the  lower  two- 
thirds  of  its  extent,  and  a  small  branch  from  the  nerve  descends  on  the  lower  part 
of  the  vessel  to  the  palm  of  the  hand. 

Plan  of  Relations  of  the  Ulnar  Artery  in  the  Forearm. 

In  front. 
Superficial  layer  of  flexor  muscles. )  yj  ,    ,. 

Median  nerve.  )      "" 

Superficial  and  deep  fasciae.  Lower  half. 

Inner  side.  I       Ulnar       \  Outer  side. 

Artery  in  ,,..,.. 

Flexor  carpi  ulnaris.  \     Forearm,     y  Flexor  sublmus  digitorum. 

Ulnar  nerve  (lower  two-thirds).       \  / 

Behind. 
Brachialis  anticus. 
Flexor  profundus  digitorum. 

At  the  wrist  (Fig.  413)  the  ulnar  artery  is  covered  by  the  integument  and  fascia, 
and  lies  upon  the  anterior  annular  ligament.  On  its  inner  side  is  the  pisiform  bone. 
The  ulnar  nerve  lies  at  the  inner  side,  and  somewhat  behind  the  artery;  here  the 
nerve  and  artery  are  crossed  by  a  band  of  fibres,  which  extends  from  the  pisiform 
bone  to  the  anterior  annular  ligament. 

Peculiarities. — The  ulnar  artery  has  been  found  to  vary  in  its  origin  nearly  in  the  propor- 
tion of  one  in  thirteen  cases,  in  one  case  arising  lower  than  usual,  about  two  or  three  inches 
below  the  elbow,  and  in  all  other  cases  much  higher,  the  brachial  being  a  more  frequent  source 
or  origin  than  the  axillary. 

Variations  in  the  position  of  this  vessel  are  more  frequent  than  in  the  radial.  When  its  origin 
is  normal  the  course  of  the  vessel  is  rarely  changed.  When  it  arises  high  up  it  is  almost  invaria- 
bly superficial  to  the  Flexor  muscles  in  the  forearm,  lying  commonly  beneath  the  fascia,  more 
rarely  between  the  fascia  and  integument.  In  a  few  cases  its  position  was  subcutaneous  in  the 
upper  part  of  the  forearm,  subaponeurotic  in  the  lower  part. 

Surface  Marking.— On  account  of  the  curved  direction  of  the  ulnar  artery  the  line  on  the 
surface  of  the  body  which  indicates  its  course  is  somewhat  complicated.  First,  draw  a  line  from 
the  front  of  the  internal  condyle  of  the  humerus  to  the  radial  side  of  the  pisiform  bone;  the 
lower  two-thirds  of  this  line  represents  the  course  of  the  middle  and  lower  third  of  the  ulnar 
artery.  Secondly,  draw  a  line  from  the  centre  of  the  antecubital  space  to  the  junction  of  the 
upper  and  middle  third  of  the  first  line;  this  represents  the  course  of  the  upper  third  of  the 
artery. 

Surgical  Anatomy.— The  application  of  a  ligature  to  this  vessel  is  required  in  cases  of  wound 
of  the  artery  or  of  its  branches,  or  in  consequence  of  aneurism.  In  the  upper  half  of  the  fore- 
arm the  artery  is  deeply  seated  beneath  the  superficial  flexor  muscles,  and  the  application  of  a 
ligature  in  this  situation  is  attended  with  some  difficulty.  An  incision  is  to  be  made  in  the 
course  of  a  line  drawn  from  the  front  of  the  internal  condyle  of  the  humerus  to  the  outer  side 


662  THE  BLOOD    VASCULAR   SYSTEM 

of  the  pisiform  bone,  so  that  the  centre  of  the  incision  is  three  fingers'  breadth  below  the  internal 
condyle.  The  skin  and  superficial  fascia  having  been  divided  and  the  deep  fascia  exposed, 
the  white  line  which  separates  the  Flexor  carpi  ulnaris  from  the  other  flexor  muscles  is  to  be 
sought  for,  and  the  fascia  incised  in  this  line.  The  Flexor  carpi  ulnaris  is  now  to  be  carefully 
separated  from  the  other  muscles,  when  the  ulnar  nerve  will  be  exposed,  and  must  be  drawn 
aside.  Some  little  distance  below  the  nerve  the  artery  will  be  found  accompanied  by  its  venae 
comites,  and  it  may  be  ligatured  by  passing  the  needle  from  within  outward.  In  the  middle  and 
lower  third  of  the  forearm  this  vessel  may  be  easily  secured  by  making  an  incision  on  the  radial 
side  of  the  tendon  of  the  Flexor  carpi  ulnaris:  the  deep  fascia  being  divided,  and  the  Flexor 
carpi  ulnaris  and  its  companion  muscle,  the  Flexor  sublimis,  being  separated  from  each  other, 
the  vessel  will  be  exposed,  accompanied  by  its  venae  comites,  the  ulnar  nerve  lying  on  its  inner 
side.  The  veins  being  separated  from  the  artery,  the  ligature  should  be  passed  from  the  ulnar 
to  the  radial  side,  taking  care  to  avoid  the  ulnar  nerve. 

Branches  (Figs.  413,  414,  and  415). — The  branches  of  the  ulnar  artery  may 
be  arranged  in  the  following  groups: 


Forearm 

Wrist 
Hand 


Anterior  Ulnar  Recurrent. 

Posterior  Ulnar  Recurrent. 

T  .  I  Anterior  Interosseous. 

Interosseous       {  -n     .    •      x  ^ 

(  rosterior  Interosseous. 

Muscular. 

Anterior  Carpal. 

Posterior  Carpal. 

Deep  Palmar  or  Communicating. 

.  Superficial  Palmar  Arch. 


The  Anterior  Ulnar  Recurrent  (a.  recurrentes  ulnaris  anterior)  (Fig.  414) 
arises  immediately  below  the  elbow-joint,  passes  upward  and  inward  between  the 
Brachialis  anticus  and  Pronator  radii  teres,  supplies  twigs  to  those  muscles,  and, 
in  front,  of  the  inner  condyle  anastomoses  with  the  anastomotica  magna  and 
inferior  profunda. 

The  Posterior  Ulnar  Recurrent  (a.  recurrentes  ulnaris  posterior)  (Figs.  414  and 
415)  is  much  larger,  and  arises  somewhat  lower  than  the  preceding.  It  passes 
backward  and  inward,  beneath  the  Flexor  sublimis,  and  ascends  behind  the  inner 
condyle  of  the  humerus.  In  the  interval  between  this  process  and  the  olecranon 
it  lies  beneath  the  Flexor  carpi  ulnaris,  and  ascending  between  the  heads  of  that 
muscle,  in  relation  with  the  ulnar  nerve;  it  supplies  the  neighboring  muscles  and 
joint,  and  anastomoses  with  the  inferior  profunda,  anastomotica  magna,  and 
interosseous  recurrent  arteries. 

The  Interosseous  Artery  (a.  interossea  communis)  (Fig.  414)  is  a  short  trunk 
about  half  an  inch  in  length,  and  of  considerable  size,  which  arises  immediately, 
below  the  tuberosity  of  the  radius,  and,  passing  backward  to  the  upper  border  ol 
the  interosseous  membrane,  divides  into  two  branches,  the  anterior  and  posterioi 
interosseous. 

The  Anterior  Interosseous  (a.  interossea  volaris)  (Fig.  414)  passes  down  the  fore- 
arm on  the  anterior  surface  of  the  interosseous  membrane,  to  which  it  is  connected 
by  a  thin  aponeurotic  arch.  It  is  accompanied  by  the  interosseous  branch  of  the 
median  nerve,  and  overlapped  by  the  contiguous  margins  of  the  Flexor  profundus 
digitorum  and  Flexor  longus  pollicis  muscles,  giving  off  in  this  situation  muscular 
branches  and  the  nutrient  arteries  of  the  radius  and  ulna.  At  the  upper  border 
of  the  Pronator  quadratus  a  branch,  anterior  communicating  artery,  descends 
beneath  the  muscle  to  anastomose  in  front  of  the  carpus  with  the  anterior  carpal 
arch.  The  continuation  of  the  artery  passes  behind  the  Pronator  quadratus,  and, 
piercing  the  interosseous  membrane,  reaches  the  back  of  the  forearm,  and  anasto- 
moses with  the  posterior  interosseous  artery  (Fig.  415).  It  then  descends  to  the 
back  of  the  wrist  to  join  the  posterior  carpal  arch.    The  anterior  interosseous  gives 


THE    ULNAR   ARTERY 


663 


off  a  long,  slender  branch,  the  median  artery  or  artery  comes  nervi  mediana 
(a.  mediana),  which  accompanies  the  median  nerve  and  gives  offsets  to  its  sub- 
stance.    This  artery  is  some- 


_  Descending  branch  from 
superior  profunda. 


Anastomotica 
magna. 


Posterior  ulnar 
recurrent. 


Posterior  interosseous. 


times  much  enlarged,  and  ac- 
companies the  nerve  into  the 
palm  of  the  hand. 

The  Posterior  Interosseous 
Artery  (a.  interossea  dorsalis) 
(Figs.  414  and  415)  passes 
backward  through  the  inter- 
val between  the  oblique  liga- 
ment and  the  upper  border  of 
the  interosseous  membrane. 
It  appears  between  the  con- 
tiguous borders  of  the  Supina- 
tor brevis  and  the  Extensor 
ossis  metacarpi  poUicis,  and 
runs  down  the  back  part  of 
the  forearm,  between  the  su- 
perficial and  deep  layer  of 
jnuscles,  to  both  of  which  it 
distributes  branches.  At  the 
lower  part  of  the  forearm  it 
anastomoses  with  the  termina- 
tion of  the  anterior  interosse- 
ous artery.  Then,  continuing 
its  course  over  the  head  of 
the  ulna,  it  joins  the  posterior 
carpal  branch  of  the  ulnar 
artery.  This  artery  gives  off, 
near  its  origin,  the  interosseous 
recurrent  branch. 

The  interosseous  recurrent 
artery  (a.  interossea  recurrens) 
(Fig.415)is  a  large  vessel  which 
ascends  to  the  interval  between 
the  external  condyle  and  olec- 
ranon, on  or  through  the  fibres 
of  the  Supinator  brevis,  but 
beneath  the  Anconeus,  anas- 
tomosing with  a  branch  from 
the  superior  profunda,  and 
with  the  posterior  ulnar  recur- 
rent and  anastomotica  magna. 

The  Muscular  Branches 
{rami  musculares)  are  distri- 
buted to  the  muscles  along 
the  ulnar  side  of  the  forearm. 

The  Anterior  Carpal  {ramus  carpeus  volaris)  (Fig.  414)  is  a  small  vessel 
which  crosses  the  front  of  the  carpus  beneath  the  tendons  of  the  Flexor  pro- 
fundus, and  inosculates  with  a  corresponding  branch  of  the  radial  artery. 

The  Posterior  Carpal  {ramus  carpem  dorsalis)  (Fig.  415)  arises  immediately 
above  the  pisiform  bone,  and  winds  backward  beneath  the  tendon  of  the  Flexor 
carpi  ulnaris :  it  passes  across  the  dorsal  surface  of  the  carpus  beneath  the  extensor 


Posterior  carpal 

(ulnar). 


Termination  of  an- 
terior interosseous. 


Posterior  carpal 

{radial). 

Radial. 

Dorsalis  pollicis. 
salis  indicis. 


Fig.  415. — Arteries  of  the  back  of  the  forearm  and.hand. 


664  THE  BLOOD -VASCULAR   SYSTE3I 

tendons,  anastomosing  with  a  corresponding  branch  of  the  radial  artery,  and 
forming  the  posterior  carpal  arch  {rete  carpi  dor  sale)  (Fig.  415).  Immediately  after 
its  origin  it  gives  off  a  small  branch  which  runs  along  the  ulnar  side  of  the  meta- 
carpal bone  of  the  little  finger,  forming  one  of  the  metacarpal  arteries,  and  supplies 
the  ulnar  side  of  the  dorsal  surface  of  the  Uttle  finger. 

The  Deep  or  Communicating  Branch  to  the  Deep  Palmar  Arch  {ramus 
volaris  ^profundus)  (Fig.  414)  passes  deeply  inward  between  the  Abductor  minimi 
digiti  and  Flexor  brevis  minimi  digiti,  near  their  origins;  it  anastomoses  with  the 
termination  of  the  radial  artery,  completing  the  deep  palmar  arch. 

The  continuation  of  the  trunk  of  the  ulnar  artery  in  the  hand  forms  the  greater 
part  of  the  superficial  palmar  arch. 

The  Superficial  Palmar  Arch  (arcus  volaris  superficialis)  (Fig.  413)  is  formed 
by  the  ulnar  artery  in  the  hand,  and  is  completed  on  the  outer  side  by  this  vessel 
anastomosing  with  a  branch  from  the  radialis  indicis,  though  sometimes  the  arch 
is  completed  by  the  ulnar  anastomosing  with  the  superficialis  volte  or  the  princeps 
pollicis  of  the  radial  artery.  The  arch  passes  across  the  palm,  describing  a  curve, 
with  its  convexity  forward,  to  the  space  between  the  ball  of  the  thumb  and  the 
index  finger,  where  the  above-mentioned  anastomosis  takes  place. 

Relations. — The  superficial  palmar  arch  is  covered  by  the  skin,  the  Palmaris 
brevis,  and  the  palmar  fascia.  It  lies  upon  the  annular  ligament,  the  Flexor 
brevis  of  the  little  finger,  the  tendons  of  the  superficial  flexor  of  the  fingers,  and 
the  divisions  of  the  median  and  ulnar  nerves. 

Plan  of  the  Relations  of  the  Superficial  Palmar  Arch. 

In  front. 
Skin. 

Palmaris  brevis. 
Palmar  fascia. 


Behind. 
Annular  ligament. 
Flexor  brevis  of  little  finger. 
Superficial  flexor  tendons. 
Divisions  of  median  and  ulnar  nerves. 

Branches. — The  branches  of  the  Superficial  Palmar  Arch  are  the 

Digital. 

The  Digital  Branches  (aa.  digitales  volares  communes)  (Fig.  413),  four  in  number, 
are  given  off  from  the  convexity  of  the  superficial  palmar  arch.  They  supply  the 
ulnar  side  of  the  little  finger  and  the  adjoining  sides  of  the  little,  ring,  middle,  and 
index  fingers,  the  radial  side  of  the  index  finger  and  thumb  being  supplied  from 
the  radial  artery.  The  digital  arteries  at  first  lie  superficial  to  the  flexor  tendons, 
but  as  they  pass  forward  with  the  digital  nerves  to  the  clefts  between  the  fingers 
they  lie  between  them,  and  are  there  joined  by  the  interosseous  branches  from  the 
deep  palmar  arch.  The  digital  arteries  on  the  sides  of  the  fingers  lie  beneath  the 
digital  nerves ;  and  about  the  middle  of  the  last  phalanx  the  two  branches  for  each 
finger  form  an  arch,  from  the  convexity  of  which  branches  pass  to  supply  the 
pulp  of  the  finger. 


THE    THORACIC  AORTA  665 

Surface  Marking. — The  superficial  palmar  arch  is  represented  by  a  curved  line,  starting 
from  the  outer  side  of  the  pisiform  bone  and  carried  downward  as  far  as  the  middle  third  of 
the  palm,  and  then  curved  outward  on  a  level  with  the  upper  end  of  the  cleft  between  the  thumb 
and  index  finger.  The  deep  palmar  arch  is  situated  about  half  an  inch  nearer  to  the  carpus. 

Surgical  Anatomy. — Wounds  of  the  palmar  arches  are  of  special  interest,  and  are  always 
difficult  to  deal  with.  When  the  superficial  arch  is  wounded  it  is  generally  possible,  by  enlarging 
the  wound  if  necessary,  to  secure  the  vessel  and  tie  it;  or  in  cases  where  it  is  found  impossible  to 
encircle  the  vessel  with  a  ligature,  a  pair  of  haemostatic  forceps  may  be  applied  and  left  on  for 
twenty-four  or  forty-eight  hours.  Wounds  of  the  deep  arch  are  not  so  easily  dealt  with.  It  may 
be  possible  to  secure  the  vessel  by  ligature  or  by  forcipressure  forceps,  which  may  be  left  on; 
or,  failing  in  this,  the  wound  may  be  carefully  plugged  with  gauze  and  an  outside  dressing  care- 
fully bandaged  on.  The  plug  should  be  allowed  to  remain  untouched  for  three  or  four  days. 
In  wounds  of  the  deep  palmar  arch  a  ligature  may  be  applied  to  the  bleeding  points  from  the 
dorsum  of  the  hand  by  resection  of  the  upper  part  of  the  third  metacarpal  bone.  It  is  useless 
in  these  cases  to  ligate  one  of  the  arteries  of  the  forearm  alone,  and  indeed  simultaneous  liga- 
tion of  both  radial  and  ulnar  arteries  above  the  wrist  is  often  unsuccessful,  on  account  of  the 
anastomosis  carried  on  by  the  carpal  arches.  Therefore,  if  unable  to  ligate  the  divided  ends 
of  the  arch,  upon  the  failure  of  pressure  to  arrest  hemorrhage,  it  is  expedient  to  apply  a  ligature 
to  the  brachial  artery. 

ARTERIES  OF  THE  TRUNK. 
THE  DESCENDING  AORTA  (Figs.  416,  417). 

The  descending  aorta  is  divided  into  two  portions,  the  thoracic  and  abdominal, 
in  correspondence  with  the  two  great  cavities  of  the  trunk  in  which  it  is  situated. 

The  Thoracic  Aorta  (Aorta  Thoracalis)  (Fig.  416). 

The  thoracic  aorta  commences  at  the  lower  border  of  the  fourth  dorsal 
vertebra,  on  the  left  side,  and  terminates  at  the  aortic  opening  in  the  Diaphragm, 
in  front  of  the  lower  border  of  the  last  dorsal  vertebra.  At  its  commencement  it 
is  situated  on  the  left  side  of  the  spine;  it  approaches  the  median  line  as  it 
descends,  and  at  its  termination  lies  directly  in  front  of  the  spinal  column.  The 
direction  of  this  vessel  being  influenced  by  the  spine,  upon  which  it  rests,  it 
describes  a  curve  which  is  concave  forward  in  the  dorsal  region.  As  the  branches 
given  off  from  it  are  small,  the  diminution  in  the  size  of  the  vessel  is  inconsider- 
able.   It  is  contained  in  the  back  part  of  the  posterior  mediastinum. 

Relations. — It  is  in  relation,  in  front,  from  above  downward,  with  the  root  of 
the  left  lung,  the  pericardium,  the  cesophagus,  and  the  Diaphragm:  behind,  with 
the  vertebral  column  and  the  vense  azygos  minor;  on  the  right  side,  with  the  vena 
azygos  major  and  thoracic  duct;  on  the  lejt  side,  with  the  left  pleura  and  lung. 
The  oesophagus,  with  its  accompanying  nerves,  lies  on  the  right  side  of  the  aorta 
above;  but  at  the  lower  part  of  the  thorax  it  gets  in  front  of  the  aorta,  and  close 
to  the  Diaphragm  is  situated  to  its  left  side. 

Plan  of  the  Relations  of  the  Thoracic  Aorta. 

In  front. 
Root  of  left  lung. 


Pericardium. 

(Esophagus. 
Diaphragm. 

Right  side. 

y^'        ^ 

Left  side. 

(Esophagus  (above). 
Vena  azygos  major. 
Thoracic  duct. 

1        Thoracic       \ 
1          Aorta.          1 

Behind. 

Pleura. 
Left  lung. 
(Esophagus  (below) 

Vertebral  column. 

Superior 

and  inferior  azygos  minor 

veins. 

666  THE  BLOOD-VASCULAB    SYSTEM 

The  aorta  is  occasionally  found  to  be  obliterated  at  a  particular  spot — viz.,  at  the  junction  of 
the  arch  with  the  thoracic  aorta  just  below  the  ductus  arteriosus.  Whether  this  is  the  result  of 
disease  or  of  congenital  malformation  is  immaterial  to  our  present  purpose;  it  affords  an  interest- 
ing opportunity  of  observing  the  resources  of  the  collateral  circulation.  The  course  of  the  anas- 
tomosing vessels,  by  which  the  blood  is  brought  from  the  upper  to  the  lower  part  of  the  artery, 
will  be  found  well  described  in  an  account  of  two  cases  in  the  Pathological  Transactions,  vols.  viii. 
and  X.  In  the  former  (p.  162)  Mr.  Sydney  Jones  thus  sums  up  the  detailed  description  of  the 
anastomosing  vessels:  "The  principal  communications  by  which  the  circulation  was  carried  on, 
were — Firstly,  the  internal  mammary,  anastomosing  with  the  intercostal  arteries,  with  the  phrenic 
of  the  abdominal  aorta  by  means  of  the  musculo-phrenic  and  comes  nervi  phrenici,  and  largely 
with  the  deep  epigastric.  Secondly,  the  superior  intercostal,  anastomosing  anteriorly  by  means 
of  a  large  branch  with  the  first  aortic  intercostal,  and  posteriorly  with  the  posterior  branch  of  the 
same  artery.  Thirdly,  the  inferior  thyroid,  by  means  of  a  branch  about  the  size  of  an  ordinary 
radial,  formed  a  communication  with  the  first  aortic  intercostal.  Fourthly,  the  transversalis  colli, 
by  means  of  very  large  communications  with  the  posterior  branches  of  the  intercostals.  Fifthly, 
the  branches  (of  the  subclavian  and  axillary)  going  to  the  side  of  the  chest  were  large,  and  anas- 
tomosed freely  with  the  lateral  branches  of  the  intercostals."  In  the  second  case  also  (vol.  x. 
p.  97)  Mr.  Wood  describes  the  anastomoses  in  a  somewhat  similar  manner,  adding  the  remark 
that  "the  blood  which  was  brought  into  the  aorta  through  the  anastomoses  of  the  intercostal 
arteries  appeared  to  be  expended  principally  in  supplying  the  abdomen  and  pelvis,  while  the 
supply  to  the  lower  extremities  had  passed  through  the  internal  mammary  and  epigastrics." 

Surgical  Anatomy. — The  student  should  now  consider  the  effects  likely  to  be  produced  by 
aneurism  of  the  thoracic  aorta,  a  disease  of  common  occurrence.  When  we  consider  the  great 
depth  of  the  vessel  from  the  surface  and  the  number  of  important  structures  which  surround  it 
on  every  side,  it  may  easily  be  conceived  what  a  variety  of  obscure  symptoms  may  arise  from  dis- 
ease of  this  part  of  the  arterial  system,  and  how  they  may  be  liable  to  be  mistaken  for  those  of 
other  affections.  Aneurism  of  the  thoracic  aorta  most  usually  extends  backward  along  the  left 
side  of  the  spine,  producing  absorption  of  the  bodies  of  the  vertebrae,  with  curvature  of  the  spine; 
whilst  the  irritation  or  pressure  on  the  cord  will  give  rise  to  pain,  either  in  the  chest,  back,  or 
loins,  with  radiating  pain  in  the  left  upper  intercostal  spaces,  from  pressure  on  the  intercostal 
nerves;  at  the  same  time  the  tumor  may  project  backward  on  each  side  of  the  spine,  beneath  the 
integument,  as  a  pulsating  swelling,  simulating  abscess  connected  with  diseased  bone,  or  it  may 
displace  the  oesophagus  and  compress  the  lung  on  one  or  the  other  side.  If  the  tumor  extend 
forward,  it  may  press  upon  and  displace  the  heart,  giving  rise  to  palpitation  and  other  symptoms 
of  disease  of  that  organ;  or  it  may  displace,  or  even  compress,  the  oesophagus,  causing  pain  and 
difficulty  of  swallowing,  as  in  stricture  of  that  tube;  and  ultimately  even  open  into  it  by  ulcera- 
tion, producing  fatal  hemorrhage.  If  the  disease  extends  to  the  right  side,  it  may  press  upon 
the  thoracic  duct;  or  it  may  burst  into  the  pleural  cavity  or  into  the  trachea  or  lung;  and,  lastly, 
it  may  open  into  the  posterior  mediastinum. 

Branches. — Branches  of  the  thoracic  aorta  supply  the  thoracic  viscera. 
They  are  known  as  rami  viscerales.  The  rami  viscerales  are  the  bronchial,  oesoph- 
ageal, pericardial,  and  mediastinal  arteries.  Other  branches  of  the  thoracic  aorta 
supply  the  walls  of  the  chest.  They  are  known  as  rami  parietales  or  intercostal  arteries. 

The  Bronchial  Arteries  (aa.  hronchiales)  are  the  nutrient  vessels  of  the  lungs, 
and  vary  in  number,  size,  and  origin.  That  of  the  right  side  arises  from  the  first 
aortic  intercostal,  or  by  a  common  trunk  with  the  left  bronchial  from  the  front  of 
the  thoracic  aorta.  Those  of  the  left  side,  usually  two  in  number,  arise  from  the 
thoracic  aorta,  one  a  little  lower  than  the  other.  Each  vessel  is  directed  to  the 
back  part  of  the  corresponding  bronchus  along  which  it  runs,  dividing  and  sub- 
dividing along  the  bronchial  tube,  supplying  them,  the  cellular  tissue  of  the  lungs, 
the  bronchial  glands,  and  the  oesophagus. 

The  (Esophageal  Arteries  {aa.  oesophagece),  usually  four  or  five  in  number, 
arise  from  the  front  of  the  aorta,  and  pass  obliquely  downward  to  the  oesophagus, 
forming  a  chain  of  anastomoses  along  that  tube,  anastomosing  with  the  oesoph- 
ageal branches  of  the  inferior  thyroid  arteries  above,  and  with  ascending  branches 
from  the  phrenic  and  gastric  arteries  below. 

The  Pericardiac  (rami  pericardiaci)  are  a  few  small  vessels,  irregular  in  their 
origin,  distributed  to  the  pericardium. 

The  Posterior  Mediastinal  Arteries  (rami  mediastinales)  are  numerous 
small  vessels  which  supply  the  glands  and  loose  areolar  tissue  in  the  mediastinum. 


THE    THORACIC  AORTA 


667 


The  lower  mediastinal  branches  are  known  as  the  superior  phrenic  arteries  {aa. 
phrenicoB  superiores),  and  are  distributed  to  the  posterior  portion  of  the  Diaphragm. 
The  Intercostal  Arteries  (aa.  intercostales)  (Fig.  416)  arise  from  the  back  of  the 
aorta.  The  aortic  intercostals  are  usually  nine  in  number  on  each  side,  the  two 
superior  intercostal  spaces  being  supplied 
by  the  superior  intercostal,  a  branch  of  the 
subclavian.  The  second  space  usually 
receives  a  considerable  branch  from  the 
first  aortic  intercostal,  which  joins  with 
the  branch  from  the  superior  intercostal 
of  the  subclavian.  The  branch  which  runs 
along  the  lower  border  of  the  last  rib  is 
named  the  subcostal  artery.  The  right 
intercostals  are  longer  than  the  left,  on 
account  of  the  position  of  the  aorta  on  th( 
left  side  of  the  spine:  they  pass  outward, 
across  the  bodies  of  the  vertebrae,  to  the 
intercostal  spaces,  being  covered  by  the 
pleura,  the  oesophagus,  thoracic  duct, 
sympathetic  nerve,  and  the  vena  azygos 
major;  the  left,  passing  outward,  are 
crossed  by  the  sympathetic;  the  upper  two 
are  also  crossed  by  the  superior  inter- 
costal vein,  the  lower  by  the  azygos  minor 
veins.  In  each  intercostal  space  the  artery 
passes  outward,  the  External  intercostal 
muscle  being  behind,  the  pleura  and  a  thin 
fascia  being  in  front.  It  then  passes  be- 
tween the  two  layers  of  Intercostal  mus- 
cles, and,  having  ascended  obliquely  to 
the  lower  border  of  the  rib  above  it,  is 
continued  forward  in  the  groove  on  its 
lower  border  and  anastomoses  with  the 
anterior  intercostal  branches  of  the  in- 
ternal mammary.  The  first  aortic  inter- 
costal anastomoses  with  the  superior  in- 
tercostal branch  of  the  subclavian,  and 
the  last  three  intercostals  pass  between 
the  abdominal  muscles,  inosculating  with  the  epigastric  in  front  and  with  the 
phrenic  and  lumbar  arteries.  Each  intercostal  artery  is  accompanied  by  a  vein  and 
nerve,  the  former  being  above,  and  the  latter  below,  except  in  the  upper  inter- 
costal spaces,  where  the  nerve  is  at  first  above  the  artery.  The  arteries  are  pro- 
tected from  pressure  during  the  action  of  the  Intercostal  muscles  by  fibrous  arches 
thrown  across,  and  attached  by  each  extremity  to  the  bone.  The  lower  intercostal 
arteries  are  continued  anteriorly  from  the  intercostal  spaces  into  the  abdominal 
wall,  except  the  subcostal,  which  lies  throughout  its  whole  course  in  the  abdominal 
wall,  since  it  is  placed  below  the  last  rib.  They  pass  behind  the  costal  cartilages 
between  the  Internal  oblique  and  Transversalis  muscle  to  the  sheath  of  the  Rectus, 
where  they  anastomose  with  the  internal  mammary  and  the  deep  epigastric 
arteries.  Behind,  the  subcostal  artery  anastomoses  with  the  first  lumbar  artery. 
Branches. — Each  intercostal  artery  gives  off  numerous  muscular  branches  {rami 
musculares). 

Lateral  cutaneous.  Muscular. 

Posterior  or  dorsal  branch.  Collateral  intercostal. 


Fig.  416. — Thoracic  aorta.     (Testut.) 


66S  THE  BLOOD -VASCULAR    SYSTEM 

Lateral  Cutaneous  Branches  {rami  cutanei  laterales)  come  off  from  each  intercostal 
and  take  a  similar  course  to  that  of  the  lateral  cutaneous  branch  of  the  intercostal 
nerve.  These  arteries  are  distributed  to  the  walls  of  the  chest  and  to  the  mammary 
gland  {rami  mammarii  laterales). 

Small  branches  pass  to  the  mammary  gland  through  the  fourth,  fifth,  and  sixth 
interspaces  {rami  mammarii  medialis),  and  to  the  skin  to  the  inner  side  of  the 
nipple  {rami  cutanei  arteriores). 

The  portion  of  the  artery  considered  here  as  the  prolongation  of  the  main  trunk 
is  called  by  Spalteholz  and  others  the  anterior  branch  {ramus  anterior). 

The  Posterior  or  Dorsal  Branch  {ramus  posterior)  of  each  intercostal  artery  passes 
backward  to  the  inner  side  of  the  anterior  costo-transverse  ligament,  and  divides 
into  an  external  branch  {ramus  cutaneus  lateralis),  and  an  internal  branch  {ramus 
cutaneus  medialis),  which  are  distributed  to  the  muscles  and  integument  of  the 
back.  Muscular  branches  {rami  musculares)  are  given  off  by  the  dorsal  branch  soon 
after  its  origin.  A  spinal  branch  {ramus  spinalis)  comes  off  from  the  dorsal 
branch  of  the  intercostal.  It  traverses  the  vertebral  arches  and  enters  the  spinal 
canal  through  the  intervertebral  foramen,  is  distributed  to  the  spinal  cord  and 
its  membranes,  and  to  the  bodies  of  the  vertebra?  in  the  same  manner  as  the 
lateral  spinal  branches  from  the  vertebral.  It  gives  off  three  branches,  the 
neural,  which  accompanies  the  spinal  nerve-roots,  and  is  distributed  to  the  mem- 
branes of  the  spinal  cord.  The  post-central  branch  divides  into  ascending  and 
descending  branches,  which,  anastomosing  with  similar  branches  above  and 
below,  form  a  series  of  vertical  arches  in  the  back  of  the  bodies  of  the  verte- 
brae.^ The  prelaminar  branch  is  distributed  to  "the  posterior  wall  of  the  spinal 
canal."^ 

The  Collateral  Intercostal  Branch  comes  off  from  the  intercostal  artery  near  the 
angle  of  the  rib,  and  descends  to  the  upper  border  of  the  rib  below,  along  which 
it  courses  to  anastomose  with  the  anterior  intercostal  branch  of  the  internal 
mammary  or  its  branch,  the  musculo-phrenic. 

The  two  lower  intercostals  on  each  side  have  not  constant  collateral  branches. 
Even  when  present  they  are  of  small  size  and  end  in  the  wall  of  the  abdomen. 
Each  collateral  intercostal  branch  gives  off  muscular  branches. 

Surgical  Anatomy. — The  position  of  the  intercostal  vessels  should  be  borne  in  mind  in 
performing  the  operation  of  paracentesis  thoracis.  The  puncture  should  never  be  made  nearer 
the  middle  line  posteriorly  than  the  angle  of  the  rib,  as  the  artery  crosses  the  space  internal  to 
this  point.  In  the  lateral  portion  of  the  chest,  where  the  puncture  is  usually  made,  the  artery 
lies  at  the  upper  part  of  the  intercostal  space,  and  therefore  the  puncture  should  be  made  just 
above  the  upper  border  of  the  rib  forming  the  lower  boundary  of  the  space. 

The  Abdominal  Aorta  (Aorta  Abdominalis)  (Fig.  417). 

The  abdominal  aorta  commences  at  the  aortic  opening  of  the  Diaphragm,  in 
front  of  the  lower  border  of  the  body  of  the  last  dorsal  vertebra,  and,  descending  a 
little  to  the  left  side  of  the  vertebral  column,  terminates  on  the  body  of  the  fourth 
lumbar  vertebra,  commonly  a  little  to  the  left  of  the  middle  line,^  where  it 
divides  into  the  two  common  iliac  arteries.  It  diminishes  rapidly  in  size,  in 
consequence  of  the  many  large  branches  which  it  gives  off.  As  it  lies  upon  the 
bodies  of  the  vertebrae,  the  curve  which  it  describes  is  convex  forward,  the 
greatest  convexity  corresponding  to  the  third  lumbar  vertebra,  which  is  a  little 
above  and  to  the  left  side  of  the  umbilicus. 

'  Cunningham's  Text-book  of  Anatomy.  .     °  Ibid-    . 

^  Lord  Lister,  having  accurately  examined  30  bodies  in  order  to  ascertain  the  exact  point  of  termmation  of 
this  vessel,  found  it  "  either  absolutely,  or  almost  absolutely,  mesial  in  15,  while  in  13  it  deviated  more  or  less. 
totheleft,andin2  was  slightly  to  the  right"  (System  of  Surgery,  edited  by  T.Holmes,  2d  ed.,  vol.  v.  p.  652). 
— Ed.  of  15th  English  edition. 


THE   ABDOMINAL    AORTA 


669 


Relations.— It  is  covered,  in  front,  by  the  lesser  omentum  and  stomach  behind 
which  are  the  branches  of  the  cochac  axis  and  the  solar  plexus;  below  these  by 
the  splenic  vein,  the  pancreas,  the  left  renal  vein,  the  transverse  portion  ot  he 
duodenum,  the  mesentery,  and  aortic  plexus.  Behind,  it  is  separated  from  the 
lumbar  vertebra  and  intervening  disks  by  the  anterior  common  ligament  and  lett 


Fig.  417. — The  abdominal  aorta  and  its  branches. 


lumbar  veins.  On  the  right  side  it  is  in  relation  with  the  inferior  vena  cava  (the 
right  crus  of  the  Diaphragm  being  interposed  above),  the  vena  azygos  major, 
thoracic  duct,  and  right  semilunar  ganglion;  on  the  left  side,  with  the  sympathetic 
nerve  and  left  semilunar  ganglion. 


670 


THE    BLOOD -VASCULAR    SYSTEM 
Plan  of  the  Relations  of  the  Abdominal  Aorta. 

In  front. 
Lesser  omentum  and  stomach. 
Branches  of  the  coeliac  axis  and  solar  plexus. 
Splenic  vein. 
Pancreas. 
Left  renal  vein. 
Transverse  duodenum. 
Mesentery. 
Aortic  plexus. 
Right  side. 
Right  crus  of  Diaphragm.  /  \  Left  side 


Inferior  vena  cava.  .  "*  Aom"*'    '  Sympathetic  nerve. 

Vena  azygos  major.  \  '      /  Left  semilunar  ganglion. 

Thoracic  duct. 
Right  semilunar  ganglion. 

Behind. 

Left  lumbar  veins. 

Vertebral  column. 

Surface  Marking. — In  order  to  map  out  the  abdominal  aorta  on  the  surface  of  the  abdomen, 
a  line  must  be  drawn  from  the  middle  line  of  the  body,  on  a  level  with  the  distal  extremity  of 
the  seventh  costal  cartilage,  downward  and  slightly  to  the  left,  so  that  it  just  skirts  the  umbilicus, 
to  a  zone  drawn  round  the  body  opposite  the  highest  point  of  the  crest  of  the  ilium.  This 
point  is  generally  half  an  inch  below  and  to  the  left  of  the  umbilicus,  but  as  the  position  of  this 
structure  varies  with  the  obesity  of  the  individual,  it  is  not  a  reliable  landmark  as  to  the  situation 
of  the  bifurcation  of  the  aorta. 

Surgical  Anatomy. — Aneurisms  of  the  abdominal  aorta  near  the  coeliac  axis  communicate 
in  nearly  equal  proportion  with  the  anterior  and  posterior  parts  of  the  artery. 

When  an  aneurismal  sac  is  connected  with  the  back  part  of  the  abdominal  aorta,  it  usually 
produces  absorption  of  the  bodies  of  the  vertebrae,  and  forms  a  pulsating  tumor  that  presents 
itself  in  the  left  hypochondriac  or  epigastric  regions,  and  is  accompanied  by  symptoms  of  dis- 
turbance in  the  alimentary  canal.  Pain  is  invariably  present,  and  is  usually  of  two  kinds — a 
fixed  and  constant  pain  in  the  back,  caused  by  the  tumor  pressing  on  or  displacing  the  branches 
of  the  solar  plexus  and  splanchnic  nerves;  and  a  sharp  lancinating  pain,  radiating  along  those 
branches  of  the  lumbar  nerves  which  are  pressed  on  by  the  tumor;  hence  the  pain  in  the  loins, 
the  testes,  the  hypogastrium,  and  in  the  lower  limb  (usually  of  the  left  side).  This  form  of 
aneurism  usually  bursts  into  the  peritoneal  cavity  or  behind  the  peritoneum  in  the  left  hypo- 
chondriac region;  or  it  may  form  a  large  aneurismal  sac,  extending  down  as  low  as  Poupart's 
ligament;  hemorrhage  in  these  cases  being  generally  very  extensive,  but  slowly  produced,  and 
not  rapidly  fatal. 

When  an  aneurismal  sac  is  connected  with  the  front  of  the  aorta  near  the  coeliac  axis  it 
forms  a  pulsating  tumor  in  the  left  hypochondriac  or  epigastric  regions,  usually  attended  with 
symptoms  of  disturbance  of  the  alimentary  canal,  as  sickness,  dyspepsia,  or  constipation,  and 
is  accompanied  by  pain,  which  is  constant,  but  nearly  always  fixed  in  the  loins,  epigastrium,  or 
some  part  of  the  abdomen;  the  radiating  pain  being  rare,  as  the  lumbar  nerves  are  seldom 
implicated.  This  form  of  aneurism  may  burst  into  the  peritoneal  cavity  or  behind  the  peri- 
toneum, between  the  layers  of  the  mesentery,  or,  more  rarely,  into  the  duodenum;  it  seldom 
extends  backward  so  as  to  affect  the  spine. 

The  abdominal  aorta  has  been  tied  15  times,  and  although  none  of  the  patients  permanently 
recovered,  still,  as  Prof.  Keen's  lived  48  days,  the  possibility  of  the  re-establishment  of  the 
circulation  is  proved.  In  the  lower  animals  this  artery  has  been  often  successfully  tied.  The 
vessel  may  be  reached  in  several  ways.  In  the  original  operation,  performed  by  Sir  A.  Cooper, 
in  1817,  an  incision  was  made  in  the  linea  alba,  the  peritoneum  opened  in  front,  the  finger 
carried  down  amongst  the  intestines  toward  the  spine,  the  peritoneum  again  opened  behind  by 
scratching  through  the  mesentery,  and  the  vessel  thus  reached.  Or  either  of  the  operations 
described  below  for  securing  the  common  iliac  artery  may,  by  extending  the  dissection  a  suf- 
ficient distance  upward,  be  made  use  of  to  expose  the  aorta.  The  chief  difficulty  in  the 
dead  subject  consists  in  isolating  the  artery  in  consequence  of  its  great  depth;  but  in  the 
living  subject  the  embarrassment  resulting  from  the  proximity  of  the  aneurismal  tumor,  and 
the  great  probability  of  disease  in  the  vessel  itself,  add  to  the  dangers  and  difficulties  of  this 
formidable  operation  so  greatly  that  it  is  very  doubtful  whether  it  ought  ever  to  be  performed. 

The  collateral  circulation  would  be  carried  on  by  the  anastomosis  between  the  internal  mam- 


THE  ABDOMINAL   AORTA  671 

mary  and  the  deep  epigastric;  by  the  free  communication  between  the  superior  and  inferior 
mesenteries  if  the  Hgature  were  placed  above  the  latter  vessel;  or  by  the  anastomosis  between 
the  inferior  mesenteric  and  the  internal  pudic  when  (as  is  more  common)  the  point  of  ligature  is 
below  the  origin  of  the  inferior  mesenteric;  and  possibly  by  the  anastomoses  of  the  lumbar 
arteries  with  the  branches  of  the  internal  iliac. 

During  an  amputation  at  the  hip  the  circulation  through  the  abdominal  aorta  may  be  com- 
manded \>^  an  assistant,  who  throws  the  entire  weight  of  his  body  upon  his  rigidly  extended 
forearm,  the  fist  of  which  lies  directly  upon  the  patient's  aorta  (Macewen's  method).  The 
abdominal  tourniquet  is  no  longer  used,  as  modern  methods  enable  the  surgeon  to  do  a  prac- 
tically bloodless  hi{>joint  amputation  (Wyeth's  method,  Senn's  method,  McBurney's  method). 

Branches  (Fig.  417). — The  branches  of  the  abdominal  aorta  are — the 

Phrenic  f  ^^^*^^^-  Superior  Mesenteric.  Ovarian  in  female. 

Coehac  Axisi  Hepatic.  Suprarenal.  Inferior  Mesenteric. 

( Splenic.  Renal.  Lumbar. 

Spermatic  in  male.  Sacra  Media. 

Branches. — ^The  branches  of  the  abdominal  aorta  may  be  divided  into  two 
sets:  1.  Those  supplying  the  viscera  (rami  vicerales).  2.  Those  distributed  to 
the  walls  of  the  abdomen  {rami  parietales). 

Visceral  Branches.  Parietal  Branches. 

(  Gastric. 
Cceliac  Axiss  Hepatic.  Inferior  Phrenic. 

I  Splenic.  I^umbar. 

Superior  Mesenteric.  Sacra  Media. 

Inferior  Mesenteric. 
Suprarenal. 
Renal. 
Spermatic  or  Ovarian. 

To  expose  the  coeliac  axis  raise  the  liver,  draw  down  the  stomach,  and  then  tear  through  the 
layers  of  the  lesser  omentum. 

The  Coeliac  Axis  or  Artery  (a.  cceliacd)  (Figs.  417,  418,  and  419). — The  coeHae 
axis  is  a  short  thick  trunk,  about  half  an  inch  in  length,  which  arises  from  the 
aorta,  close  to  the  margin  of  the  opening  in  the  Diaphragm,  behind  the  posterior 
parietal  peritoneum,  above  the  pancreas,  and  below  the  twelfth  dorsal  vertebra, 
and,  passing  nearly  horizontally  forward  (in  the  erect  posture),  divides  into  three 
large  branches,  the  gastric,  hepatic,  and  splenic,  occasionally  giving  off  one  of  the 
phrenic  arteries. 

Relations. — It  is  covered  by  the  lesser  omentum.  On  the  right  side  it  is  in 
relation  with  the  right  semilunar  ganglion  and  the  lobus  Spigelii;  on  the  lejt  side, 
with  the  left  semilunar  ganglion  and  cardiac  end  of  the  stomach.  Below,  it  rests 
upon  the  upper  border  of  the  pancreas. 

The  Gastric  or  Coronary  Artery  (a.  gastrica  sinistra)  (Figs.  418  and  419),  the  small- 
est of  the  three  branches  of  the  coeliac  axis,  passes  upward  and  to  the  left  side, 
behind  the  peritoneum  of  the  lesser  peritoneal  cavity,  raising  this  portion  of  the 
peritoneum  into  a  fold,  known  as  the  left  or  secondary  pancreatico -gastric  fold.  It 
continues  this  course  until  it  nearly  reaches  the  lesser  curvature  of  the  stomach  just 
below  the  cardia.  It  then  turns  to  the  front  and  curves  forward  to  the  cardiac 
orifice  of  the  stomach,  distributing  branches  to  the  oesophagus  which  anastomose 
with  the  aortic  oesophageal  arteries;  others  supply  the  cardiac  end  of  the  stomach, 
inosculating  with  branches  of  the  splenic  artery;  it  then  passes  from  left  to 
right,  along  and  upon  the  lesser  curvature  of  the  stomach  and  beneath  the 
peritoneum  to  the  pylorus,  lying  in  its  course  between  the  layers  of  the  lesser 
omentum,  and  sometimes  dividing  into  two  vessels,  which  run  along  each  side 


672 


THE  BLOOD -VASCULAR   SYSTEM 


of  the  lesser  curvature.  One  vascular  arch  gives  branches  to  the  anterior  wall 
of  the  stomach  and  the  other  to  the  posterior  wall  (Fig.  886),  and  both  give 
them  to  the  lesser  omentum  or  the  single  artery  gives  branches  to  both  sur- 
faces of  the  organ  and  to  the  lesser  omentum:  at  its  termination  it  anastomoses 
with  the  pyloric  branch  or  the  two  pyloric  branches  of  the  hepatic.  It  gives  off 
gastric  branches  to  both  the  anterior  and  posterior  surfaces  of  the  stomach, 
branches  to  the  lesser  omentum,  a  small  hepatic  branch,  to  the  left  lobe  of  the  liver 
and  oesophageal  branches  {rami  cesophagei)  which  anastomose  with  oesophageal 
branches  from  the  thoracic  aorta  and  the  inferior  phrenic. 


Oysti^  artery. 


Fig.  418. — The  ccsliac  axis  and  its  branches,  the  liver  having  been  raised  and  the  lesser  omentum  removed. 


The  Hepatic  Artery  (a.  hepatica)  (Figs.  418  and  419)  in  the  adult  is  intermediate 
in  size  between  the  gastric  and  splenic ;  in  the  foetus  it  is  the  largest  of  the  three 
branches  of  the  coeliac  axis.  It  is  first  directed  forward  and  to  the  right,  in  the 
right  pancreatico-gastric  fold,  to  the  upper  margin  of  the  pyloric  end  of  the 
stomach,  forming  the  lower  boundary  of  the  foramen  of  Winslow.  It  then  passes 
upward  between  the  layers  of  the  lesser  omentum,  and  in  front  of  the  foramen  of 
Winslow,  to  the  transverse  fissure  of  the  liver,  where  it  divides  into  two  branches, 
right  and  left,  which  supply  the  corresponding  lobes  of  that  organ,  accompanying 
the  ramifications  of  the  vena  portae  and  hepatic  duct.  The  hepatic  artery,  in 
its  course  along  the  right  border  of  the  lesser  omentum,  is  in  relation  with  the 
ductus  communis  choledochus  and  portal  veins,  the  duct  lying  to  the  right  of 
the  artery  and  the  vena  portse  behind. 


THE   ABD03£INAL    AOBTA 


673 


Its  branches  (Figs.  418  and  419)  are — the 

Pyloric. 

r^     ,       1      ,       ,.         i  Gastro-epiploica  Dextra. 
(jrastro-duodenalis       i  o  4.-      j     j       to 

(  rancreatico-duodenalis  bupenor 

Cystic. 

The  pyloric  or  superior  pyloric  branch  (a.  gastrica  dextra)  arises  from  the 
hepatic,  above  the  pylorus,  descends  between  the  layers  of  the  lesser  omentum 
to  the  pyloric  end  of  the  stomach,  and  passes  from  right  to  left  along  its  lesser  cur- 
vature, supplying  it  with  branches  and  inosculating  with  the  gastric  branches  of 
the  coronary  artery.  The  vessel  often  divides  into  two  vascular  arches  to  anas- 
tomose with  two  vascular  arches  from  the  gastric. 


jucHfis 


to       Great       Omentum. 


Fig.  419. — The  coeliac  axis  and  its  branches,  the  stomach  having  been  raised  and  the  transverse  mesocolon 
removed  (semi-diagrammatic). 

The  gastro-duodenalis  (Fig.  419)  is  a  short  but  large  branch,  which  descends 
near  the  pylorus,  behind  the  first  portion  of  the  duodenum,  and  divides  at  the 
lower  border  of  this  viscus  into  two  branches,  the  gastro-epiploica  dextra  and  the 
pancreatico-duodenalis  superior.  Previous  to  its  division,  it  gives  off  two  or  three 
small  inferior  pyloric  branches,  to  the  pyloric  end  of  the  stomach  and  pancreas. 

The  gastro-epiploica  dextra  runs  from  right  to  left  along  but  distinctly  below 
the  greater  curvature  of  the  stomach,  between  the  layers  of  the  great  omentum, 
anastomosing  about  the  middle  of  the  lower  border  of  the  stomach  with  the  gastro- 
epiploica  sinistra  from  the  splenic  artery.    This  vessel  gives  off  numerous  branches, 

43 


674  THE    BLOOD -VASCULAR   SYSTEM 

some  of  which  ascend  to  supply  both  surfaces  of  the  stomach,  whilst  others 
descend  to  supply  the  great  omentum  {rami  epiploici). 

The  pancreatico-duodenalis  superior  descends  between  the  contiguous  margins 
of  the  duodenum  and  pancreas.  It  supplies  the  head  of  the  pancreas  by  means 
of  the  rami  pancreatica,  and  the  duodenum  by  means  of  the  rami  duodenalis, 
and  anastomoses  with  the  inferior  pancreatico-duodenal  branch  of  the  superior 
mesenteric  artery  and  with  the  pancreatic  branches  of  the  splenic. 

The  cystic  artery  (a,  cystica)  (Fig,  418),  usually  a  branch  of  the  right  hepatic, 
passes  downward  and  forward  along  the  cystic  duct  to  the  gall-bladder,  and 
divides  into  two  branches,  one  of  which  ramifies  on  its  free  surface  beneath 
the  peritoneum,  the  other  between  the  gall-bladder  and  the  substance  of  the 
liver. 

The  Splenic  Artery  (a.  lienalis)  (Figs.  418  and  419),  in  the  adult,  is  the  largest  of 
the  three  branches  of  the  coeliac  axis,  and  is  remarkable  for  the  extreme  tortuosity 
of  its  course.  It  passes  horizontally  to  the  left  side,  behind  the  peritoneum  and 
along  the  upper  border  of  the  pancreas,  accompanied  by  the  splenic  vein,  which  lies 
below  it,  and  on  arriving  near  the  spleen  divides  into  branches,  some  of  which 
enter  the  hilum  of  that  organ  to  be  distributed  to  its  structure,  whilst  others  are 
distributed  to  the  pancreas  and  great  end  of  the  stomach.    Its  branches  are — the 

Pancreaticse  Parvse.  Gastric  (Vasa  Brevia). 

Pancreatica  Magna.  Gastro-epiploica  Sinistra. 

Rami  Lienalis. 

The  pancreatic  branches  {rami  pancreatici)  are  numerous  small  branches 
derived  from  the  splenic  as  it  runs  behind  the  upper  border  of  the  pancreas, 
supplying  its  middle  and  left  parts.  One  of  these,  larger  than  the  rest,  is  given 
off  from  the  splenic  near  the  left  extremity  of  the  pancreas;  it  runs  from  left 
to  right  near  the  posterior  surface  of  the  gland,  following  the  course  of  the  pan- 
creatic duct,  and  is  called  the  pancreatica  magna.  The  others  are  called  the 
pancreaticoB  parvcB.  These  vessels  anastomose  with  the  pancreatic  branches  of  the 
pancreatico-duodenal  arteries,  derived  from  the  hepatic  on  the  one  hand  and 
superior  mesenteric  on  the  other. 

The  gastric  branches  or  vasa  brevia  {aa.  gastriccB  breves)  consists  of  from  five  to 
seven  small  branches,  which  arise  either  from  the  termination  of  the  splenic 
artery  or  from  its  terminal  branches,  and,  passing  from  left  to  right,  between 
the  layers  of  the  gastro-splenic  omentum,  are  distributed  to  the  great  curvature 
of  the  stomach,  anastomosing  with  branches  of  the  gastric  and  gastro-epiploica 
sinistra  arteries. 

The  gastro-epiploica  sinistra,  the  largest  branch  of  the  splenic,  runs  from  left 
to  right  along  but  distinctly  below  the  great  curvature  of  the  stomach,  between 
the  layers  of  the  great  omentum,  and  anastomoses  with  the  gastro-epiploica 
dextra.  In  its  course  it  distributes  several  branches  to  the  stomach,  which 
ascend  upon  both  surfaces;  others  descend  to  supply  the  omentum. 

The  rami  lienales  leave  the  splenic  artery  in  the  hilum  and  pass  into  the  spleen. 

Surgical  Anatomy. — The  operation  of  pyloredomy  can  be  made  an  almost  bloodless  pro- 
cedure by  tying  the  gastric,  the  pyloric,  and  the  right  and  left  gastro-epiploic  arteries.  "The 
gastric  is  doubly  tied  about  one  inch  below  the  cardiac  orifice  at  a  point  where  it  joins  the  lesser 
curvature  and  is  divided  between  the  ligatures.  The  superior  pyloric  is  doubly  tied  and  divided. 
The  fingers  are  passed  beneath  the  pylorus,  raising  the  gastro-colic  omentum  from  the  trans- 
verse mesocolon,  and  in  this  way  safe  ligation  behind  the  pylorus  of  the  right  gastro-epiploic 
artery,  or  in  most  cases  its  parent  vessel,  the  gastro-duodenal,  is  secured.  The  left  gastro- 
epiploic is  now  tied  at  an  appropriate  point,  and  the  necessary  amount  of  gastro-colic  omentum 
doubly  tied  and  cut."' 

*  William  J.  Mayo.    Annals  of  Surgery,  March,  1904. 


THE   ABDOMINAL   AORTA  675 

The  Superior  Mesenteric  Artery  (a.  mesenterica  superior)  (Figs.  417  and  420). 
— The  superior  mesenteric  artery  supplies  the  whole  length  of  the  small  intestine, 
except  the  first  part  of  the  duodenum ;  it  also  supplies  the  ctecum  and  the  ascending 
and  transverse  colon ;  it  is  a  vessel  of  large  size,  arising  from  the  forepart  of  the 
aorta  about  a  quarter  of  an  inch  below  the  coeliac  axis ;  being  covered  at  its  origin 
by  the  splenic  vein  and  pancreas.  It  passes  forward,  between  the  pancreas  and  the 
transverse  portion  of  the  duodenum,  crosses  in  front  of  this  portion  of  the  intes- 
tine, and  descends  between  the  layers  of  the  mesentery  to  the  right  iliac  fossa, 
where,  considerably  diminished  in  size,  it  anastomoses  with  one  of  its  own  branches 
— viz.,  the  ileo-colic.  In  its  course  it  forms  an  arch,  the  convexity  of  which  is 
directed  forward  and  downward  to  the  left  side,  the  concavity  backward  and 
upward  to  the  right.  It  is  accompanied  by  the  superior  mesenteric  vein,  and  is 
surrounded  by  the  superior  mesenteric  plexus  of  nerves. 

In  order  to  expose  the  superior  mesenteric  artery  raise  the  great  omentum  and  transverse 
colon,  draw  down  the  small  intestines,  and  cut  through  the  peritoneum  where  the  transverse 
mesocolon  and  mesentery  join;  the  artery  will  then  be  exposed  just  as  it  issues  from  beneath 
the  lower  border  of  the  pancreas 

Branches. — Its  branches  are — the 

Inferior  Pancreatico-duodenal.  Ileo-colic. 

Vasa  Intestini  Tenuis.  Right  Colic. 

Middle  Colic. 

The  Inferior  Pancreatico-duodenal  (a.  pancreaticoduodei talis  inferior)  is  given 
off  from  the  superior  mesenteric,  or  from  its  first  intestinal  branch  behind  the 
pancreas.  It  courses  to  the  right  between  the  head  of  the  pancreas  and  duodenum, 
and  then  ascends  to  anastomose  with  the  superior  pancreatico-duodenal  artery. 
It  distributes  branches  to  the  head  of  the  pancreas  and  to  the  transverse  and 
descending  portions  of  the  duodenum. 

The  Vasa  Intestini  Tenuis  (aa.  intestinales)  arise  from  the  convex  side  of  the 
superior  mesenteric  artery.  They  are  usually  from  twelve  to  fifteen  in  number, 
and  are  distributed  to  the  jejunum  {aa.  jejunales)  and  ileum  {aa.  ilece).  They 
run  parallel  with  one  another  between  the  layers  of  the  mesentery,  each  vessel 
dividing  into  two  branches,  which  unite  with  similar  branches  on  each  side, 
forming  a  series  of  arches  the  convexities  of  which  are  directed  toward  the 
intestine.  From  this  first  set  of  arches  branches  arise,  which  again  unite  with 
similar  branches  from  either  side,  and  thus  a  second  series  of  arches  is  formed; 
and  from  these  latter,  a  third  and  a  fourth,  or  even  a  fifth,  series  of  arches  is 
constituted,  diminishing  in  size  the  nearer  they  approach  the  intestine.  From 
the  terminal  arches  numerous  small  straight  vessels  arise  which  encircle  the 
intestine,  upon  which  they  are  distributed,  ramifying  between  its  coats.  Through- 
out their  course  small  branches  are  given  off  to  the  glands  and  other  structures 
between  the  layers  of  the  mesentery.  (See  the  description  of  the  vascular  loops 
in  the  section  upon  the  Intestines.  The  form  and  arrangement  of  the  loops 
have  been  studied  by  Monks,  of  Boston.) 

The  Ileo-colic  Artery  (a.  ileocolica)  is  the  lowest  branch  given  off  from  the 
concavity  of  the  superior  mesenteric  artery.  It  descends  between  the  layers  of 
the  mesentery  to  the  right  iliac  fossa,  where  it  divides  into  two  branches.  Of 
these,  the  inferior  division  inosculates  with  the  termination  of  the  superior  mesen- 
teric artery,  forming  with  it  an  arch,  from  the  convexity  of  which  branches 
proceed  to  supply  the  termination  of  the  ileum,  the  ctecum,  the  vermiform 
appendix,  and  the  ileo-cfecal  valve.  The  superior  division  inosculates  with 
the  colica  dextra  and  supplies  the  commencement  of  the  colon. 

The  Right  Colic  Artery  (a.  colica  dextra)  arises  from  about  the  middle  of  the 
concavity  of  the  superior  mesenteric  artery,  and,  passing  behind  the  peritoneum 


676 


THE  BLOOD -VASCULAR   SYSTEM 


to  the  middle  of  the  ascending  colon,  divides  into  two  branches — a  descending 
branch,  which  inosculates  with  the  ileo-colic,  and  an  ascending  branch,  which 
anastomoses  with  the  colica  media.  These  branches  form  arches,  from  the 
convexity  of  which  vessels  are  distributed  to  the  ascending  colon.  The  branches 
of  this  vessel  are  covered  with  peritoneum  only  on  their  anterior  aspect. 

The  Middle  Colic  Artery  (a.  colica  media)  arises  from  the  upper  part  of  the 
concavity  of  the  superior  mesenteric,  and,  passing  forward  between  the  layers 
of  the  transverse  mesocolon,  divides  into  two  branches,  the  one  on  the  right 
side  inosculating  with  the  colica  dextra;  that  on  the  left  side,  with  the  colica 
sinistra,  a  branch  of  the  inferior  mesenteric.  From  the  arches  formed  by  their 
inosculation  branches  are  distributed  to  the  transverse  colon.  The  branches 
of  this  vessel  lie  between  the  two  layers  of  the  transverse  mesocolon. 


Fig.  420. — The  superior  mesenteric  artery  and  its  branches. 

Blood-supply  of  the  Right  Iliac  Fossa.— The  descending  branch  of  the  right  colic  artery  by 
anastomosing  with  the  ascending  branch  of  the  ileo-coHc  artery  forms  a  vascular  loop.  The 
union  of  the  descending  branch  of  the  ileo-coUc  artery  with  the  terminal  vessel  of  the  superior 
mesenteric  artery  forms  another  vascular  loop.  These  two  loops  give  off  secondary  loops,  and 
from  the  secondary  loops  come  the  vessels  which  supply  the  appendix,  the  caecum,  and  the 
lower  end  of  the  ileum.  The  branch  which  goes  to  the  appendix  is  called  the  appendicular 
artery  (a.  appendicularis).  If  there  is  a  distinct  meso-appendix  the  artery  passes  along  its 
unattached  edge.     If  there  is  a  rudimentary  meso-appendix  or  no  meso-appendix  the  artery 


THE   ABDOMINAL    AORTA 


677 


usually  lies  upon  the  appendix  from  base  to  tip  beneath  the  peritoneal  covering.  In  females 
the  appendix  may  receive  an  additional  vessel  from  the  ovarian,  which  vessel  lies  in  the 
appendiculo-ovarian  ligament. 

The  Inferior  Mesenteric  Artery  (a.  mesenterica  inferior)  (Figs.  417  and  421). — 
The  inferior  mesenteric  artery  supplies  the  descending  colon,  the  sigmoid  flexure 
of  the  colon  and  the  greater  part  of  the  rectum.  It  is  smaller  than  the  superior 
mesenteric,  and  arises  from  the  left  side  of  the  aorta,  between  one  and  two  inches 
above  the  division  of  that  vessel  into  the  common  iliacs.  It  passes  downward 
to  the  left  iliac  fossa,  and  then  descends  between  the  layers  of  the  mesorectum, 


Middle  hxmorrhoidai, 
Inferior  hsemorrhoiddl, 


Fig.  421. — The  inferior  mesenteric  and  its  branches. 


into  the  pelvis,  under  the  name  of  the  superior  hsemorrhoidal  artery.  It  lies  at  first 
in  close  relation  with  the  left  side  of  the  aorta,  and  then  passes  as  the  superior 
haemorrhoidal  in  front  of  the  left  common  iliac  artery. 

In  order  to  expose  the  inferior  mesenteric  artery  draw  the  small  intestines  and  mesentery  over 
to  the  right  side  of  the  abdomen,  raise  the  transverse  colon  toward  the  thorax,  and  divide  the 
peritoneum  covering  the  front  of  the  aorta. 


Branches. — Its  branches  are — the 

Left  Colic. 

Superior  Hsemorrhoidal. 


Sigmoid. 


678 


THE    BLOOD -VASCULAR    SYSTEM 


The  Left  Colic  Artery  {a.  colica  sinistra)  passes  behind  the  peritoneum,  in 
front  of  the  left  kidney,  to  reach  the  descending  colon,  and  divides  into  two 
branches — an  ascending  branch,  which  inosculates  with  the  colica  media;  and 
a  descending  branch,  which  anastomoses  with  the  sigmoid  artery.  From  the 
arches  formed  by  these  inosculations  branches  are  distributed  to  the  descending 
colon. 

The  Sigmoid  Arteries  (aa.  sigmoideae). — As  a  rule  there  are  two  of  these  vessels, 
but  may  be  three.  They  run  obliquely  downward  across  the  Psoas  muscle  to  the 
sigmoid  flexure  of  the  colon,  and  divide  into  branches  which  supply  that  part  of 
the  intestine,  anastomosing  above  with  the  left  colic,  and  below  with  the  superior 
hsemorrhoidal  artery. 

The  Superior  Hsemorrhoidal  Artery  (a.  hcemorrhoidalis  superior)  (Figs.  421  and 
424) ,  the  continuation  of  the  inferior  mesenteric,  descends  into  the  pelvis  between 
the  layers  of  the  mesorectum,  crossing,  in  its  course,  the  ureter  and  left  common 
iliac  vessels.  Opposite  the  middle  of  the  sacrum  it  divides  into  two  branches, 
which  descend  one  on  each  side  of  the  rectum,  and  about  five  inches  from  the 
anus  break  up  into  several  small  branches,  which  pierce  the  muscular  coat  of  the 
bowel  and  run  downward,  as  straight  vessels,  placed  at  regular  intervals  from 
each  other  in  the  wall  of  the  gut  between  its  muscular  and  mucous  coat,  to  the 
level  of  the  internal  sphincter;  here  they  form  a  series  of  loops  around  the  lower 
end  of  the  rectum,  and  communicate  with  the  middle  hemorrhoidal  arteries  which 
are  branches  of  the  internal  iliac  and  with  the  inferior  hsemorrhoidal  branches 
of  the  internal  pudic. 


Fig.  422. — Corrosion  anatomy.     Hyrtl's  exsanguinated  renal  zone.     (Byron  Robinson.) 

The  Suprarenal  Artery  (a.  suprarenalis  media)  (Fig.  417). — A  suprarenal  or 
capsular  artery  arises,  one  on  each  side  of  the  aorta,  opposite  the  superior  mesenteric 
artery.  It  is  a  small  vessel  which  passes  obliquely  upward  and, out  ward,  over 
the  crura  of  the  Diaphragm,  to  the  under  surface  of  the  suprarenal  capsule,  to 
which  it  is  distributed,  anastomosing  with  capsular  branches  from  the  phrenic 
and  renal  arteries.  In  the  adult  these  arteries  are  of  small  size;  in  the  foetus 
they  are  as  large  as  the  renal  arteries. 

The  Renal  Arteries  (aa.  renales)  (Fig.  417). — The  renal  arteries  are  two 
large  trunks  which  arise  from  the  sides  of  the  aorta  immediately  below  the  superior 


THE  ABDOMINAL   AOBTA 


679 


mesenteric  artery.  Each  is  directed  outward  across  the  crus  of  the  Diaphragm, 
so  as  to  form  nearly  a  right  angle  with  the  aorta.  The  right  is  longer  than  the 
left,  on  account  of  the  position  of  the  aorta;  it  passes  behind  the  inferior  vena 
cava.  The  left  is  somewhat  higher  than  the  right.  Before  reaching  the  hilum 
of  the  kidney,  each  artery  usually  divides  into  four  branches.  Two  of  these  vessels 
enter  the  anterior  portion  and  two  the  posterior  portion  of  the  kidney.  There 
may  be  but  one  renal  artery;  there  may  be  two,  three,  four,  or  five  branches.  The 
greater  number  of  the  branches  generally  lie  between  the  renal  vein  and  ureter,  the 
vein  being  in  front  of  the  arteries,  the  ureter  behind.  The  anterior  branches  supply 
three-fourths  of  the  kidney,  the  posterior  supply  one-fourth.  Each  vessel  gives 
off  a  small  branch  to  the  suprarenal  capsule  (a.  swprarenalis  inferior)  and  branches 
to  the  ureter,  ureteral  branches,  and  to  the  surrounding  cellular  tissue  and  muscles, 
perirenal  branches.  Hyrtl,  in  1870,  pointed  out  that  the  renal  artery  gives  off  a 
branch  which  divides  and  supplies  the  dorsal  or  posterior  portion  of  the  kidney  and 


Fig.  423. — Corrosion  anatomy.     The  renal  vascular  blades  opened  like  a  book.     (Byron  Robinson.) 

its  pelvis,  and  a  branch  which  divides  and  supplies  the  ventral  or  anterior  portion 
of  the  kidney  and  its  pelvis.  The  two  circulations  are  distinct  and  do  not  anas- 
tomose even  at  the  periphery.  Between  these  two  sets  of  vessels  is  a  bloodless  zone 
called  by  Byron  Robinson  the  exsanguinated  renal  zone  of  Hyrtl,  which  does  not  cor- 
respond to  the  median  line,  but  is  "one-half  inch  dorsal  to  the  lateral  longitudinal 
renal  border."^  The  ventral  or  anterior  segment  is  much  the  larger.  In  very  rare 
instances  the  bloodless  zone  corresponds  to  the  median  line  (Kiimmel) .  An  incision 
of  the  middle  third  of  the  kidney  exactly  at  the  junction  of  the  two  segments  does 
not  divide  vessels.  As  the  incision  approaches  either  pole  there  is  danger  of  cutting 
a  branch  (Schede).  Frequently  there  is  a  second  renal  artery,  which  is  given  off 
from  the  abdominal  aorta  either  above  or  below  the  renal  artery  proper,  the  former 
being  the  more  common  position.  Instead  of  entering  the  kidney  at  the  hilum, 
an  accessory  renal  artery  usually  pierces  the  upper  or  the  lower  part  of  the  gland. 
The  Spermatic  Arteries  (aa.  spermaticoB  internee)  (Fig.  417). — The  internal 
spermatic  arteries  are  distributed  to  the  testes.    They  are  two  slender  vessels  of 

1  Byron  Robinson.     The  Circulation  of  the  Kidney,  American  Journal  of  Surgery. 


680  THE    BLOOD -VASCULAR   SYSTEM 

considerable  length,  which  arise  from  the  front  of  the  aorta  a  little  below  the  renal 
arteries.  Each  artery  passes  obliquely  outward  and  downward  behind  the  peri- 
toneum, resting  on  the  Psoas  muscle,  the  right  spermatic  lying  in  front  of  the 
inferior  vena  cava,  the  left  behind  the  sigmoid  flexure  of  the  colon.  It  then  crosses 
obliquely  over  the  ureter  (to  which  it  sends  a  few  branches)  and  the  lower  part 
of  the  external  iliac  artery  to  reach  the  internal  abdominal  ring,  through  which 
it  passes,  and  accompanies  the  other  constituents  of  the  spermatic  cord  along 
the  inguinal  canal  to  the  scrotum,  where  it  becomes  tortuous  and  is  prolonged 
as  the  testicular  artery,  which  accompanies  the  vas  deferens,  anastomosing  with 
the  artery  of  the  vas  deferens  and  is  distributed  to  the  epididymis,  the  back  part 
of  the  tunica  albuginea,  and  the  substance  of  the  testes.  The  spermatic  artery 
in  the  inguinal  canal  gives  off  cremasteric  branches  to  supply  the  Cremaster  muscle. 
In  the  canal  and  scrotum  the  artery  lies  behind  the  pampiniform  plexus  and  in 
front  of  the  vas  deferens. 

The  Ovarian  Arteries  {aa.  ovaricce). — The  ovarian  arteries  (Fig.  425)  are 
the  corresponding  arteries  in  the  female  to  the  spermatic  in  the  male.  They 
supply  the  ovaries,  are  shorter  than  the  spermatic,  and  do  not  pass  out  of 
the  abdominal  cavity.  The  origin  and  course  of  the  first  part  of  the  artery  are  the 
same  as  the  spermatic  in  the  male,  but  on  arriving  at  the  margin  of  the  pelvis  the 
ovarian  artery  passes  inward,  between  the  two  layers  of  the  broad  ligament  of  the 
uterus,  to  be  distributed  to  the  ovary,  ovarian  branches.  Branches  go  to  the  Fallopian 
tube, tubal  branches, the  ureter,  ureteral  branches,  and  the  broad  ligament,  ligamentous 
branches.  A  branch  passes  on  to  the  side  of  the  uterus  and  anastomoses  with  the 
uterine  arteries,  uterine  branch.  Other  offsets  are  continued  along  the  round 
ligament  through  the  inguinal  canal,  to  the  integument  of  the  labium  and  groin. 

At  an  early  period  of  foetal  life,  when  the  testes  or  ovaries  lie  by  the  side  of 
the  spine  below  the  kidneys,  the  spermatic  or  ovarian  arteries  are  short;  but  as 
these  organs  descend  from  the  abdomen  into  the  scrotum  or  pelvis,  the  arteries 
become  gradually  lengthened. 

The  Inferior  Phrenic  Arteries  (aa.  phrenicoB  inferiores)  (Fig.  417). — ^The  inferior 
phrenic  arteries  are  two  small  vessels  which  present  much  variety  in  their  origin. 
They  may  arise  separately  from  the  front  of  the  aorta,  immediately  above  the 
coeliac  axis,  or  by  a  common  trunk,  which  may  spring  either  from  the  aorta  or 
from  the  coeliac  axis.  Sometimes  one  is  derived  from  the  aorta,  and  the  other 
from  one  of  the  renal  arteries.  In  only  one  out  of  thirty-six  cases  examined  did 
these  arteries  arise  as  two  separate  vessels  from  the  aorta.  They  diverge  from 
one  another  across  the  crura  of  the  Diaphragm,  and  then  pass  obliquely  upward 
and  outward  upon  the  under  surface  of  the  Diaphragm.  The  left  phrenic  passes 
behind  the  oesophagus  and  runs  forward  on  the  left  side  of  the  oesophageal 
opening.  The  right  phrenic  passes  behind  the  inferior  vena  cava,  and  ascends 
along  the  right  side  of  the  aperture  for  transmitting  that  vein.  Near  the  back 
part  of  the  central  tendon  each  vessel  divides  into  two  branches.  The  internal 
branch  runs  forward  to  the  front  of  the  thorax,  supplying  the  Diaphragm  and 
anastomosing  with  its  fellow  of  the  opposite  side,  and  with  the  musculo-phrenic 
and  comes  nervi  phrenici  branches  of  the  internal  mammary.  The  external  branch 
passes  toward  the  side  of  the  thorax  and  inosculates  with  the  intercostal  arteries. 
The  internal  branch  of  the  right  phrenic  gives  off  a  few  vessels  to  the  inferior 
vena  cava,  and  the  left  one  some  branches  to  the  oesophagus.  Each  vessel  also 
sends  capsular  branches  (rami  suprarenales  superior)  to  the  suprarenal  capsule 
of  its  own  side.  The  spleen  on  the  left  side  and  the  liver  on  the  right  also 
receive  a  few  branches  from  these  vessels. 

The  Lumbar  Arteries  (aa.  lumhales). — The  lumbar  arteries  are  analogous  to 
the  intercostals.  They  are  usually  four  in  number  on  each  side,  and  arise  from 
the  back  part  of  the  aorta,  nearly  at  right  angles  with  that  vessel.     They  pass 


THE    COMMON  ILIAC   ARTERIES  681 

outward  and  backward,  around  the  sides  of  the  bodies  of  the  lumbar  vertebrae, 
behind  the  sympathetic  nerve  and  the  Psoas  magnus  muscle,  those  on  the  right 
side  being  covered  by  the  inferior  vena  cava,  and  the  two  upper  ones  on  each  side 
by  the  crura  of  the  Diaphragm.  In  the  interval  between  the  transverse  processes 
of  the  vertebrae  each  artery  gives  off  a  dorsal  branch. 

After  the  formation  of  the  dorsal  branch  the  artery  passes  outward,  having 
a  variable  relation  to  the  Quadratus  lumborum  muscle.  Most  frequently  the 
first  lumbar  passes  in  front  of  the  muscle  and  the  others  behind  it;  sometimes 
the  order  is  reversed  and  the  lowest  lumbar  passes  in  front  of  the  muscle.  At 
the  outer  border  of  the  Quadratus  they  are  continued  between  the  abdominal 
muscles,  anastomose  with  branches  of  the  epigastric  and  internal  mammary 
in  front,  the  intercostals  above,  and  branches  of  the  ilio-lumbar  and  circumflex 
iliac  below.  The  lumbar  arteries  are  also  distributed  to  the  skin  of  the  sides  of 
the  abdomen. 

The  Dorsal  Branch  {ramus  dorsalis)  gives  off,  immediately  after  its  origin,  a 
spinal  branch,  which  enters  the  spinal  canal.  The  dorsal  branch  then  continues 
its  course  backward  between  the  transverse  processes,  and  is  distributed  to  the 
muscles  and  integument  of  the  back,  anastomosing  with  similar  branches  of  the 
adjacent  lumbar  arteries  and  with  the  posterior  branches  of  the  intercostal 
arteries. 

The  Spinal  Branch  (ramus  spinalis)  enters  the  spinal  canal  through  the  inter- 
vertebral foramen,  to  be  distributed  to  the  spinal  cord  and  its  membranes  and 
to  the  bodies  of  the  vertebrae  in  the  same  manner  as  the  lateral  spinal  branches 
from  the  vertebral  (see  page  638). 

The  Middle  Sacral  Artery  (a.  sacralis  media)  (Fig.  424). — The  middle  sacral 
artery  is  a  small  vessel,  which  arises  from  the  back  part  of  the  aorta  just  at  its  bifur- 
cation. It  descends  upon  the  last  lumbar  vertebra,  and  along  the  middle  line  of  the 
front  of  the  sacrum,  to  the  upper  part  of  the  coccyx,  where  it  anastomoses  with 
the  lateral  sacral  arteries,  and  terminates  in  a  minute  branch,  which  runs  down 
to  the  situation  of  the  body  described  as  Luschka's  gland.  It  gives  off  on  each 
side  opposite  the  body  of  the  fifth  lumbar  vertebra  a  branch  known  as  the  a. 
lumbalis  ima.  From  the  middle  sacral  artery  branches  arise  which  run  through 
the  mesorectum  to  supply  the  posterior  surface  of  the  rectum.  Other  branches 
are  given  off  on  each  side,  which  anastomose  with  the  lateral  sacral  arteries, 
and  send  off  small  offsets  which  enter  the  anterior  sacral  foramina. 

The  artery  is  the  representative  of  the  caudal  prolongation  of  the  aorta  of 
animals,  and  its  lateral  branches  correspond  to  the  intercostal  and  lumbar  arteries 
in  the  dorsal  and  lumbar  regions. 


THE  COMMON  ILIAC  ARTERIES  (AA.  ILIAC^   COMMUNES)  (Figs.  417,  424). 

The  abdominal  aorta  divides  into  the  two  common  iliac  arteries.  The  bifurca- 
tion usually  takes  place  on  the  left  side  of  the  body  of  the  fourth  lumbar  ver- 
tebra. The  common  iliac  arteries  are  about  two  inches  in  length;  diverging 
from  the  termination  of  the  aorta,  they  pass  downward  and  outward  to  the  margin 
of  the  pelvis,  each  divides  opposite  the  intervertebral  substance,  between  the  last 
lumbar  vertebra  and  the  sacrum,  into  two  branches,  the  internal  and  external 
iliac  arteries,  the  latter  supplying  the  lower  extremity;  the  former,  the  viscera  and 
parietes  of  the  pelvis. 

The  right  common  iliac  is  somewhat  longer  than  the  left,  and  passes  more 
obliquely  across  the  body  of  the  last  lumbar  vertebra.  In  front  of  it  are  the 
peritoneum,  the  small  intestines,  branches  of  the  sympathetic  nerve,  and,  at  its 
point  of  division,  the  ureter.    Behind,  it  is  separated  from  the  fourth  and  fifth 


682 


THE  BLOOD- VASCULAR    SYSTEM 


lumbar  vertebrae,  with  the  intervening  intervertebral  disk,  by  the  two  common 
iliac  veins.  On  its  outer  side,  it  is  in  relation  with  the  inferior  vena  cava  and 
the  right  common  iliac  vein,  above,  and  the  Psoas  magnus  muscle  below. 

The  left  common  iliac  is  in  relation,  in  jront,  with  the  peritoneum,  branches 
of  the  sympathetic  nerve,  and  the  superior  hiemorrhoidal  artery;  and  is  crossed 
at  its  point  of  bifurcation  by  the  ureter.  It  rests  on  the  bodies  of  the  fourth  and 
fifth  lumbar  vertebrae,  with  the  intervening  intervertebral  disk.  The  left  common 
iliac  vein  lies  partly  on  the  inner  side,  and  partly  beneath  the  artery;  on  its  outer 
side,  the  artery  is  in  relation  with  the  Psoas  magnus  muscle. 

Plan  of  the  Relations  of  the  Common  Iliac  Arteries. 


In  front. 
Peritoneum. 
Small  intestines. 
Sympathetic  nerves. 
Ureter. 

Outer  side. 
Vena  cava. 
Right  common . 

iliac  vein. 
Psoas  muscle. 

Behind. 
Fourth  and  fifth  lumbar  vertebrae. 
Right  and  left  common  iliac  veins. 


Inner  side. 

Left  common 

iliac  vein. 


In  front. 
Peritoneum. 
Sympathetic  nerves. 
Superior  hsemorrhoidal  artery. 
Ureter. 


Outer  side. 


Psoas  magnus 
muscle. 


Behind. 

Fourth  and  fifth  lumbar  vertebrae. 
Left  common  iliac  vein. 


Branches. — The  common  iliac  arteries  give  off  small  branches  to  the  perito- 
neum. Psoas  magnus,  ureters,  and  the  surrounding  cellular  tissue,  and  occasionally 
give  origin  to  the  ilio-lumbar  or  renal  arteries. 

Peculiaxities. — The  point  of  origin  varies  according  to  the  bifurcation  of  the  aorta.  In 
three-fourths  of  a  large  number  of  cases  the  aorta  bifurcated  either  upon  the  fourth  lumbar 
vertebra  or  upon  the  intervertebral  disk  between  it  and  the  fifth,  the  bifurcation  being,  in  one 
case  out  of  nine  below,  and  in  one  out  of  eleven  above,  this  point.  In  ten  out  of  every  thirteen 
cases  the  vessel  bifurcated  within  half  an  inch  above  or  below  the  level  of  the  crest  of  the  ilium, 
more  frequently  below  than  above. 

The  point  of  division  is  subject  to  great  variety.  In  two-thirds  of  a  large  number  of  cases 
it  was  between  the  last  lumbar  vertebra  and  the  upper  border  of  the  sacrum,  being  above  that 
point  in  one  case  out  of  eight  and  below  it  in  one  case  out  of  six.  The  left  common  iliac  artery 
divides  lower  down  more  frequently  than  the  right. 

The  relative  length,  also,  of  the  two  common  iliac  arteries  varies.  The  right  common  iliac 
was  the  longer  in  sixty-three  cases,  the  left  in  fifty-two,  whilst  they  were  both  equal  in  fifty- 
three.  The  length  of  the  arteries  varied  in  five-sevenths  of  the  cases  examined  from  an  inch 
and  a  half  to  three  inches;  in  about  half  of  the  remaining  cases  the  artery  was  longer  and  in 
the  other  half  shorter,  the  minimum  length  being  less  than  half  an  inch,  the  maximum  four 
and  a  half  inches.  In  two  instances  the  right  common  iliac  has  been  found  wanting,  the  external 
and  internal  iliacs  arising  directly  from  the  aorta. 

Surface  Marking. — Draw  a  zone  around  the  body  opposite  the  highest  part  of  the  crest  of 
the  ilium;  in  this  line  take  a  point  half  an  inch  to  the  left  of  the  middle  line.  From  this  draw 
two  lines  to  points  midway  between  the  anterior  superior  spines  of  the  ilium  and  the  symphysis 
pubis.  These  two  diverging  lines  will  represent  the  course  of  the  common  and  external  iliac 
arteries.  Draw  a  second  zone  round  the  body  corresponding  to  the  level  of  the  anterior  superior 
spines  of  the  ilium:  the  portion  of  the  diverging  lines  between  the  two  zones  will  represent  the 
course  of  the  common  iliac  artery;  the  portion  below  the  lower  zone,  that  of  the  external  iliac 
artery. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  common  iliac  artery  may  be 
required  on  account  of  aneurism  or  hemorrhage  implicating  the  external  or  internal  iliacs. 
Now  that  the  surgeon  no  longer  dreads  opening  the  peritoneal  cavity,  there  can  be  no  question 
that  the  easiest  and  best  method  of  tying  the  artery  is  by  a  transperitoneal  route.  The  abdomen 
is  opened  by  an  incision  in  either  the  semilunar  line  or  the  linea  alba;  the  intestines  are  drawn 
to  one  side  and  the  peritoneum  covering  the  artery  divided.  The  sheath  is  then  opened,  and 
the  needle  passed  from  within  outward.     On  the  right  side  great  care  must  be  exercised  in 


THE  INTERNAL    ILIAC  ARTERY  683 

passing  the  needle,  since  both  the  common  iliac  veins  lie  behind  the  artery.  After  the  vessel 
has  been  tied  the  incision  in  the  peritoneum  over  the  artery  should  be  sutured.  Formerly  there 
were  two  different  methods  by  which  the  common  iliac  artery  was  tied  without  opening  the 
peritoneal  cavity:  1,  an  anterior  or  iliac  incision,  by  which  the  vessel  is  approached  more  directly 
from  the  front;  and  2,  a  posterior  abdominal  or  lumbar  incision,  by  which  the  vessel  is  reached 
from  behind.  If  the  surgeon  select  the  iliac  region,  a  curved  incision,  from  five  to  eight  inches 
in  length,  according  to  the  amount  of  fat,  is  made,  commencing  just  outside  the  middle  of 
Poupart's  ligament  and  a  finger's  breadth  above  it,  and  carried  outward  toward  the  anterior 
superior  iliac  spine,  then  upward  toward  the  ribs,  and  finally  curving  inward  toward  the  umbili- 
cus. The  abdominal  muscles  and  transversalis  fascia  are  divided,  and  the  peritoneum  raised 
upward  and  inward  until  the  Psoas  is  reached.  The  artery  will  be  found  on  the  inner  side  of 
this  muscle,  and  is  to  be  cleared  with  a  director,  especial  care  being  taken  on  the  right  side,  as 
here  the  common  iliac  veins  lie  behind  the  artery.  The  aneurism  needle  is  to  be  passed  from 
within  outward.  But  if  the  aneurismal  tumor  should  extend  high  up  in  the  abdomen,  along 
the  external  iliac,  it  is  better  to  select  the  posterior  or  lumbar  route,  making  an  incision  partly  in 
the  abdomen,  partly  in  the  loin.  The  incision  is  commenced  at  the  anterior  extremity  of  the 
last  rib,  proceeding  directly  downward  to  the  ilium;  it  is  then  curved  forward  along  the  crest  of 
the  ilium  and  a  little  above  it  to  the  anterior  superior  spine  of  that  bone.  The  abdominal  mus- 
cles having  been  cautiously  divided  in  succession,  the  transversalis  fascia  must  be  carefully  cut 
through,  and  the  peritoneum,  together  with  the  ureter,  separated  from  the  artery  and  pushed 
aside;  the  sacro-iliac  articulation  must  then  be  felt  for,  and  upon  it  the  vessel  will  be  felt  pulsat- 
ing, and  may  be  fully  exposed  in  close  connection  with  the  accompanying  vein.  On  the  right 
side  both  common  iliac  veins,  as  well  as  the  inferior  vena  cava,  are  in  close  connection  with  the 
artery,  and  must  be  carefully  avoided.  On  the  left  side  the  vein  usually  lies  on  the  inner  side 
and  behind  the  artery;  but  it  occasionally  happens  that  the  two  common  iliac  veins  are  joined  on 
the  left  instead  of  the  right  side,  which  would  add  much  to  the  difficulty  of  an  operation  in  such 
a  case.  The  common  iliac  artery  may  be  so  short  that  danger  may  be  apprehended  from  sec- 
ondary hemorrhage  if  a  ligature  is  applied  to  it.  It  would  be  preferable,  in  such  a  case,  to  tie 
both  the  external  and  internal  iliacs  near  their  origin. 

Collateral  Circulation. — The  principal  agents  in  carrying  on  the  collateral  circulation  after 
the  ai)plication  of  a  ligature  to  the  common  iliac  are— the  anastomoses  of  the  hsemorrhoidal 
branches  of  the  internal  iliac  with  the  superior  hsemorrhoidal  from  the  inferior  mesenteric;  the 
anastomoses  of  the  uterine  and  ovarian  arteries  and  of  the  vesical  arteries  of  opposite  sides;  of 
the  lateral  sacral  with  the  middle  sacral  artery;  of  the  epigastric  with  the  internal  mammary, 
inferior  intercostal,  and  lumbar  arteries;  of  the  circumflex  iliac  with  the  lumbar  arteries;  of  the 
ilio-lumbar  with  the  last  lumbar  artery;  of  the  obturator  artery,  by  means  of  its  pubic  branch, 
with  the  vessel  of  the  opposite  side  and  with  the  deep  epigastric. 

Compression  of  the  Common  Iliac  Arteries. — The  common  iliac  arteries  may  be  com- 
pressed by  Davy's  lever.  The  instrument  consists  of  a  gum-elastic  tube  about  two  feet  long, 
in  which  fits  a  round  wooden  "lever"  considerably  longer  than  the  tube.  A  small  quantity 
of  olive  oil  having  been  injected  into  the  rectum,  the  gum-elastic  tube,  softened  in  hot  water, 
is  passed  into  the  bowel  sufficiently  far  to  permit  its  pressing  upon  the  common  iliac  artery 
as  it  lies  in  the  groove  between  the  last  lumbar  vertebra  and  the  Psoas  muscle.  The  wooden 
lever  is  then  inserted  into  the  tube,  and  the  projecting  end  carried  toward  the  opposite  thigh 
and  raised,  when  it  acts  as  a  lever  of  the  first  order,  the  anus  being  the  fulcrum.  In  cases  where 
the  mesorectum  is  abnormally  short  it  may  be  impossible,  without  unjustifiable  force,  to  com- 
press the  artery  on  the  right  side.  In  amputation  of  the  hip-joint  the  common  iliac  can  be 
compressed  inost  certainly  and  safely  by  opening  the  abdomen  and  compressing  the  vessel  by 
means  of  the  fingers  against  the  Psoas  muscle  (McBurney's  method). 

The  Internal  Iliac  Artery  (Figs.  417,  424). 

The  internal  iliac  or  hypogastric  artery  (a.  hypogastrica)  supplies  the  walls  and 
viscera  of  the  pelvis,  the  generative  organs,  and  inner  side  of  the  thigh.  It  is 
a  short  thick  vessel,  smaller  in  the  adult  than  the  external  iliac,  and  about  an 
inch  and  a  half  in  length.  It  arises  at  the  point  of  bifurcation  of  the  common 
iliac,  and,  passing  downward  to  the  upper  margin  of  the  great  sacro-sciatic 
foramen,  divides  into  two  large  trunks,  an  anterior  and  posterior;  from  its  anterior 
division  a  partially  obliterated  cord,  a  part  of  the  foetal  hypogastric  artery,  extends 
forward  to  the  bladder. 

Relations. — In  front,  with  the  ureter,  which  is  between  the  artery  and  the 
peritoneum.  Behind,  with  the  internal  iliac  vein,  the  lumbo-sacral  cord,  and 
Pyriformis  muscle.   By  its  outer  side,  near  its  origin,  with  the  Psoas  magnus  muscle. 


684 


THE   BLOOD -VASCULAR   SYSTEM 


Plan  of  the  Relations  of  the  Internal  Iliac  Artery, 

In  front. 
Peritoneum. 
Ureter. 


Outer  side. 
Psoas  magnus. 


Behind. 
Internal  iliac  vein. 
Lumbo-sacral  cord. 
Pyriformis  muscle. 


lumbar. 


Gluteal. 


Fig.  424. — Arteries  of  the  pelvis. 

In  the  foetus  the  hypogastric  artery  is  twice  as  large  as  the  external  iUac,  and 
appears  to  be  the  continuation  of  the  common  iUac.  Instead  of  dipping  into 
the  pelvis,  it  passes  forward  to  the  bladder,  and  ascends  along  the  sides  of  that 
viscus  to  its  summit,  to  which  it  gives  branches;  it  then  passes  upward  along  the 
back  part  of  the  anterior  wall  of  the  abdomen  to  the  umbilicus,  converging 
toward  its  fellow  of  the  opposite  side.      Having  passed  through  the  umbilical 


THE   INTERNAL    ILIAC  ARTERY  685 

opening,  the  two  arteries  twine  round  the  umbilical  vein  in  the  umbilical  cord, 
and  ultimately  ramify  in  the  placenta.  The  portion  of  the  vessel  within  the 
abdomen  is  called  the  hypogastric  axtery;  the  portion  external  to  that  cavity,  the 
umbilical  artery. 

At  l)irth,  when  the  placental  circulation  ceases,  the  upper  portion  of  the  hypo- 
gastric artery,  extending  from  the  summit  of  the  bladder  to  the  umbilicus,  con- 
tracts, and  ultimately  dwindles  to  a  solid  fibrous  cord;  but  the  lower  portion, 
extending  from  its  origin  (in  what  is  now  the  internal  iliac  artery)  for  about  an 
inch  and  a  half  to  the  wall  of  the  bladder,  and  thence  to  the  summit  of  that  organ, 
is  not  totally  impervious,  though  it  V)ecomes  considerably  reduced  in  size,  and 
serves  to  convey  blood  to  the  bladder  under  the  name  of  the  superior  vesical 
artery. 

Peculiarities  as  Regards  Length. — In  two-thirds  of  a  large  number  of  cases  the  length  of 
the  internal  iliac  varied  between  an  inch  and  an  inch  and  a  half;  in  the  remaining  third  it  was 
more  frequently  longer  than  shorter,  the  maximum  length  being  three  inches,  the  minimum 
half  an  inch. 

The  lengths  of  the  common  and  internal  iliac  arteries  bear  an  inverse  proportion  to  each 
other,  the  internal  iliac  artery  being  long  when  the  common  iliac  is  short,  and  vice  versa. 

As  Regards  its  Place  of  Division. — The  place  of  division  of  the  internal  iliac  varies 
between  the  upper  margin  of  the  sacrum  and  the  upper  border  of  the  sacro-sciatic  foramen. 

The  arteries  of  the  two  sides  in  a  series  of  cases  often  differed  in  length,  but  neither  seemed 
constantly  to  exceed  the  other. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  internal  iliac  artery  may  be 
required  in  cases  of  aneurism  or  hemorrhage  affecting  one  of  its  branches.  The  vessel  may  be 
secured  by  making  an  incision  through  the  abdominal  parietes  in  the  iliac  region  in  a  direction 
and  to  an  extent  similar  to  that  for  securing  the  common  iliac;  the  transversalis  fascia  having 
been  cautiously  divided,  and  the  peritoneum  pushed  inward  from  the  iliac  fossa  toward  the 
pelvis,  the  finger  may  feel  the  pulsation  of  the  external  iliac  at  the  bottom  of  the  wound,  and  by 
tracing  this  vessel  upward  the  internal  iliac  is  arrived  at,  opposite  the  sacro-iliac  articulation.  It 
should  be  remembered  that  the  vein  lies  behind  and  on  the  right  side,  a  little  external  to  the 
artery,  and  in  close  contact  with  it;  the  ureter  and  peritoneum,  which  lie  in  front,  must  also  be 
avoided.  The  degree  of  facility  in  applying  a  ligature  to  this  vessel  will  mainly  depend  upon 
the  length  of  the  vessel.  It  has  been  seen  that  in  the  great  majority  of  the  cases  examined  the 
artery  was  short,  varying  from  an  inch  to  an  inch  and  a  half;  m  these  cases  the  artery  is  deeply 
seated  in  the  pelvis;  when,  on  the  contrary,  the  vessel  is  longer,  it  is  found  partly  above  that 
cavity.  If  the  artery  is  very  short,  as  occasionally  happens,  it  would  be  preferable  to  apply  a 
ligature  to  the  common  iliac  or  to  both  the  external  and  internal  iliacs  at  their  origin. 

A  better  method  of  tying  the  internal  iliac  artery  is  by  an  abdominal  section  in  the  median 
line  and  reaching  the  vessel  through  the  peritoneal  cavity.  This  plan  has  been  advocated  by 
Dennis,  of  New  York,  on  the  following  grounds:  (1)  It  in  no  way  increases  the  danger  of  the 
operation ;  (2)  it  prevents  a  series  of  accidents  which  have  occurred  during  ligature  of  the  artery 
by  the  older  methods;  (3)  it  enables  the  surgeon  to  ascertain  the  exact  extent  of  disease  in  the 
main  arterial  trunk,  and  select  his  spot  for  the  application  of  the  ligature;  and  (4)  it  occupies 
much  less  time. 

Collateral  Circulation. — In  Professor  Owen's  dissection  of  a  case  in  which  the  internal 
iliac  artery  had  been  tied  by  Stevens  ten  years  before  death  for  aneurism  of  the  sciatic  artery, 
the  internal  iliac  was  found  impervious  for  about  an  inch  above  the  point  where  the  ligature  had 
been  applied,  but  the  obliteration  did  not  extend  to  the  origin  of  the  external  iliac,  as  the  ilio- 
lumbar artery  arose  just  above  this  point.  Below  the  point  of  obliteration  the  artery  resumed 
its  natural  diameter,  and  continued  so  for  half  an  inch,  the  obturator,  lateral  sacral,  and  gluteal 
arising  in  succession  from  the  latter  portion.  The  obturator  artery  was  entirely  obliterated. 
The  lateral  sacral  artery  was  as  large  as  a  crow's  quill,  and  had  a  very  free  anastomosis  with  the 
artery  of  the  opposite  side  and  with  the  middle  sacral  artery.  The  sciatic  artery  was  entirely 
obliterated  as  far  as  its  point  of  connection  with  the  aneurismal  tumor,  but  on  the  distal  side  of 
the  sac  it  was  continued  down  along  the  back  of  the  thigh  nearly  as  large  in  size  as  the  femoral, 
being  pervious  about  an  inch  below  the  sac  by  receiving  an  anastomosing  vessel  from  the  pro- 
funda.* The  circulation  was  carried  on  by  the  anastomoses  of  the  uterine  and  ovarian  arteries; 
of  the  opposite  vesical  arteries;  of  the  hemorrhoidal  branches  of  the  internal  iliac  with  those 
from  the  inferior  mesenteric;  of  the  obturator  artery,  by  means  of  its  pubic  branch,  with  the 
vessel  of  the  opposite  side  and  with  the  epigastric  and  internal  circumflex;  of  the  circumflex 

'  Medico-Chirurgical  Transactions,  vol.  xvi.  '' 


686 


THE    BLOOD -VASCULAR    SYSTEM 


From  the  Posterior  Trunk. 
Ilio-lumbar. 
Lateral  Sacral. 
Gluteal. 


and  perforating  branches  of  the  profunda  femoris  with  the  sciatic;  of  the  gluteal  with  the  poste- 
rior branches  of  the  sacral  arteries;  of  the  ilio-lumbar  with  the  last  lumbar;  of  the  lateral  sacral 
with  the  middle  sacral;  and  of  the  circumflex  iliac  with  the  ilio-lumbar  and  gluteal. 

Branches  (Fig.  424). — The  branches  of  the  internal  iliac  are; 

From  the  Anterior  Trunk. 

Superior  Vesical. 

Middle  Vesical. 

Inferior  Vesical. 

Middle  Hsemorrhoidal. 

Obturator. 

Internal  Pudic. 

Sciatic. 

r     ,       if  Uterine. 
In  female  <  ^j     .     , 
'  (  Vaginal. 

The  Superior  Vesical  (a.  vesicalis  superior)  (Fig.  424)  is  that  part  of  the  foetal 
hypogastric  artery,  which  remains  pervious  after  birth.  It  extends  to  the  side  of 
the  bladder,  distributing  numerous  branches  to  the  apex  and  body  of  the  organ. 
From  one  of  these  a  slender  vessel  is  derived  which  accompanies  the  vas  deferens 
in  its  course  to  the  testis,  where  it  anastomoses  with  the  spermatic  artery.  This  is 
the  axtery  of  the  vas  deferens.    Other  branches  supply  the  ureter. 


Branches  to  fundus. 


Branches  to  tube. 


Vaginal  arteries. 
Fig.  425. — The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind. 


(After  Hyrtl.) 


The  Middle  Vesical  (a.  vesicalis  medialis)  (Fig.  424),  usually  a  branch  of  the 
superior,  is  distributed  to  the  base  of  the  bladder  and  under  surface  of  the  vesiculse 
seminales. 

The  Inferior  Vesical  (a.  vesicalis  inferior)  (Fig.  424)  arises  from  the  anterior 
division  of  the  internal  iliac,  frequently  in  common  with  the  middle  hemorrhoidal, 
and  is  distributed  to  the  base  of  the  bladder,  the  prostate  gland,  and  vesiculse 


THE   INTERNAL    ILIAC  ARTERY 


687 


seminales.  The  branches  distributed  to  the  prostate  communicate  with  the 
corresponding  vessel  of  the  opposite  side. 

The  Middle  Hsemorrhoidal  Artery  (a.  hoBmorrhoidalis  media)  (Fig.  424) 
usually  arises  together  with  the  preceding  vessel.  It  supplies  the  anus  and 
parts  outside  the  rectum,  anastomosing  with  the  other  hemorrhoidal  arteries. 

The  Uterine  Artery  (a.  uterina)  (Fig.  425)  passes  inward  from  the  anterior 
trunk  of  the  internal  iliac  to  the  neck  of  the  uterus.  Ascending  in  a  tortuous  course 
on  the  side  of  this  viscus,  between  the  layers  of  the  broad  ligament,  it  distributes 
branches  to  its  substance  and  to  the  round  ligament  and  the  Fallopian  tube  (ramus 
tubarius),  anastomosing,  near  its  termination,  with  the  ovarian  artery.  It  gives  a 
branch  to  the  ovary  {ramus  ovarii),  which  anastomoses  with  a  branch  from  the 
ovarian  branches  to  the  cervix  uteri  (cervico-uieri) ,  and  a  branch  which  descends 


Fig.  426. — The  utero-ovarian  artery  forming  the  circle  described  by  Byron  Robinson. 

on  the  vagina  (cervico-vaginal) ,  and,  joining  with  branches  from  the  vaginal 
arteries,  form  a  median  longitudinal  vessel  both  in  front  and  behind;  these 
descend  on  the  anterior  and  posterior  surfaces  of  the  vagina,  and  are  named 
the  azygos  arteries  of  the  vagina. 

The  Vaginal  Artery  (a.  vaginalis)  (Fig.  426)  is  analogous  to  the  inferior  vesical 
in  the  male;  it  descends  upon  the  vagina,  supplying  its  mucous  membrane,  and 
sending  branches  to  the  neck  of  the  bladder  and  contiguous  part  of  the  rectum. 
There  may  be  several  vaginal  arteries.  The  vaginal  artery  assists  in  forming  the 
azygos  arteries  of  the  vagina,  which  are  anterior  and  posterior  vessels,  running 
longitudinally,  and  due  to  anastomoses  of  the  branches  of  the  vaginal  from  each 
side  and  the  cervico-vaginal  artery. 

Luschka,  Hyrtl,  Waldeyer,  Byron  Robinson,  and  others,  instead  of  describing 
the  ovarian  and  uterine  arteries  as  two  distinct  vessels,  regard  them  as  constituting 


688  THE   BLOOD -VASCULAR    SYSTEM 

the  chief  parts  of  one  vessel,  the  axteria  uterina  ovarica.  What  has  been  called  "  the 
circle  of  Byron  Robinson"  is  composed  of  a  spiral  segment  (the  arteria  uterina 
ovarica),  with  a  portion  of  the  abdominal  aorta,  common  iliacs,  and  internal  iliacs 
(Fig.  426). 

Byron  Robinson*  has  made  a  careful  study  of  this  vascular  circle;  he  shows 
that  it  is  of  great  importance  in  certain  surgical  procedures,  and  that  its  remark- 
able "capacity  for  extension"  saves  it  from  damage  when  the  uterus  is  enormously 
distended  by  pregnancy,  or  when  it  is  "drawn  through  the  pudendum  with  trac- 
tion forceps  for  palpation,  inspection,  or  repair." 

The  author  just  quoted  says  further  that  the  utero-ovarian  artery  has  three 
origins,  because  it  develops  from  the  Wolffian  body:  The  ovarian  segment  arises 
from  the  abdominal  aorta.  The  uterine  segment  arises  from  the  anterior  branch 
of  the  internal  iliac  artery.  The  artery  of  the  round  ligament  arises  from  the  deep 
epigastric.  The  arteria  uterina  ovarica  artery  secures  nutrition  to  the  uterus  by 
bringing  blood  from  three  sources.  It  is  spiral  throughout  its  entire  course,  in 
certain  parts  is  convoluted  or  looped,  and  it  is  accompanied  by  the  pampiniform 
plexus  of  veins. 

The  three  origins  of  this  vessel  are  freely  united  by  anastomoses,  and  rami 
laterales  are  given  off,  which  unite  the  bilateral  vessels  in  the  median  line.  Robin- 
son describes  three  bifurcations  of  the  utero-ovarian  artery.  The  distal  bifurcation, 
which  is  "about  midway  between  the  uterus  and  the  pelvic  wall,"  and  forms  an 
acute  angle  with  the  main  vessel.  This  bifurcation  indicates  the  point  of  division 
of  the  external  from  the  internal  genitals.  The  cervico-vaginal  artery  supplies  the 
external  genitals.  The  proximal  bifurcation  marks  the  situation  of  the  ovary.  The 
artery  bifurcaies  at  an  acute  angle  into  two  branches  to  supply  the  ovary  and 
Fallopian  tube.  The  middle  bifurcation  consists  of  (1)  the  division  of  the  uterine 
segment  at  the  angle  formed  by  the  uterus  and  oviduct  ("forming  the  ramus  ovi- 
ductus  and  ramus  ovarii")  and  (2)  "the  bifurcation  of  the  ramus  oviductus  form- 
ing the  ramus  oviductus  and  the  ramus  ligamenti  teretis,  or  the  segment  of  the 
round  ligament."^  The  relations  of  the  utero-ovarian  artery  and  the  ureter  are 
shown  in  Fig.  426. 

Surgical  Anatomy. — As  pointed  out  by  Byron  Robinson,  the  source  of  bleeding  after  vaginal 
hysterectomy  is  usually  the  torn  and  undamped  cervico-vaginal  artery. 

As  previously  pointed  out,  the  spiral  and  convoluted  shape  of  the  utero-ovarian  artery  allows 
the  uterus,  ovary,  and  tube  to  be  drawn  into  the  vagina  without  injury  to  the  vessels.  Bryon 
Robinson  points  out  that  in  vaginal  hysterectomy  the  genital  circle  is  not  divided  and  only  the 
rami  laterales  which  go  to  the  uterus  are  cut,  the  ovaries  retaining  a  normal  blood-supply  and 
continuing  to  functionate. 

The  Obturator  Artery  (a.  obturatoria)  (Fig.  424)  usually  arises  from  the  anterior 
trunk  of  the  internal  iliac;  frequently  from  the  posterior.  It  passes  forward,  below 
the  brim  of  the  pelvis,  to  the  upper  part  of  the  obturator  foramen,  accompanied  by 
the  obturator  nerve  and  vein,  and,  escaping  from  the  pelvic  cavity  through  a  short 
canal  formed  by  a  groove  on  the  under  surface  of  the  ascending  ramus  of  the  os 
pubis  and  the  arched  border  of  the  obturator  membrane,  it  divides  into  an  internal 
and  external  branch.  In  the  pelvic  cavity  this  vessel  lies  upon  the  pelvic  fascia, 
beneath  the  peritoneum,  and  a  little  below  the  obturator  nerve. 

Branches. — Within  the  pelvis,  the  obturator  artery  gives  off  an  iliac  branch 
{ramus  iliacus)  to  the  iliac  fossa,  which  supplies  the  bone  and  the  Iliacus  muscle, 
and  anastomoses  with  the  ilio-lumbar  artery;  a  vesical  branch  (ramus  vesicalis), 
which  runs  backward  to  supply  the  bladder;  and  a  pubic  branch  [ramus  pubicus), 
which  is  given  off  from  the  vessel  just  before  it  leaves  the  pelvic  cavity.  This 
branch  ascends  upon  the  back  of  the  os  pubis,  communicating  with  offsets  from 

'  The  Utero-ovarian  Artery.  2  Byron  Robinson.    The  Utero-ovarian  Artery. 


THE   INTERNAL   ILIAC  ABTEBY  689 

the  deep  epigastric  artery  and  with  the  corresponding  vessel  of  the  opposite 
side.  It  is  placed  on  the  inner  side  of  the  femoral  ring.  External  to  the  pelvis, 
the  obturator  artery  divides  into  an  internal  and  an  external  branch,  which  are 
deeply  situated  beneath  the  Obturator  externus  muscle. 

The  Internal  Branch  {ramus  anterior)  curves  downward  along  the  inner  margin 
of  the  obturator  foramen,  lying  beneath  the  Obturator  externus  muscle;  it  dis- 
tributes branches  to  the  Obturator  externus,  Pectineus,  Adductors,  and  Gracilis, 
and  anastomoses  with  the  external  branch  and  with  the  internal  circumflex  artery. 

The  External  Branch  {ramus  'posterior)  curves  round  the  outer  margin  of  'the 
obturator  foramen,  also  lying  beneath  the  Obturator  externus  muscle,  to  the  space 
between  the  Gemellus  inferior  and  Quadratus  femoris,  where  it  divides  into  two 
branches:  one,  smaller,  courses  inward  around  the  lower  margin  of  the  foramen 
and  anastomoses  with  the  internal  branch  and  with  the  internal  circumflex;  the 
other  inclines  outward  in  the  groove  below  the  acetabulum  {a.  acetabulis) ,  and 
supplies  the  muscles  attached  to  the  tuberosity  of  the  ischium  and  anastomoses 
with  the  sciatic  artery.  It  sends  a  branch  to  the  hip-joint  through  the  cotyloid 
notch,  which  ramifies  on  the  round  ligament  as  far  as  the  head  of  the  femur. 

Peculiarities  (Fig.  427). — In  two  out  of  every  three  cases  the  obturator  arises  from  the 
internal  iliac ;  in  one  case  in  three  and  a  half  from  the  epigastric ;  and  in  about  one  in  seventy- 
two  cases  by  two  roots  from  both  vessels.  It  arises  in  about  the  same  proportion  from  the 
external  iliac  artery.  The  origin  of  the  obturator  from  the  epigastric  is  not  commonly  found 
on  both  sides  of  the  same  body. 


Fig.  427. — Variations  in  origin  and  course  of  the  obturator  artery. 

When  the  obturator  artery  arises  at  the  front  of  the  pelvis  from  the  epigastric,  it  descends 
almost  vertically  to  the  upper  part  of  the  obturator  foramen.  The  artery  in  this  course  usually 
lies  in  contact  with  the  external  iliac  vein  and  on  the  outer  side  of  the  femoral  ring  (Fig.  427,  A); 
in  such  cases  it  would  not  be  endangered  in  the  operation  for  femoral  hernia.  Occasionally, 
however,  it  curves  inward  along  the  free  margin  of  Gimbernat's  ligament  (Fig.  427,  B),  and 
under  such  circumstances  would  almost  completely  encircle  the  neck  of  a  hernial  sac  (supposing 
a  hernia  to  exist  in  such  a  case),  and  would  be  in  great  danger  of  being  wounded  if  an  operation 
was  performed. 

The  Internal  Pudic  Artery  (a.  pudenda  interna)  (Figs.  424,  428,  and  429)  is  the 
smaller  of  the  two  terminal  branches  of  the  anterior  trunk  of  the  internal  iliac, 
and  supplies  the  external  organs  of  generation.  Though  the  course  of  the  artery 
is  the  same  in  the  two  sexes,  the  vessel  is  much  smaller  in  the  female  than  in  the 
male,  and  the  distribution  of  its  branches  somewhat  dift'erent.  The  description  of 
its  arrangement  in  the  male  will  first  be  given,  and  subsequently  the  differences 
which  it  presents  in  the  female  will  be  mentioned. 

The  Internal  Pudic  Artery  in  the  Male  passes  downward  and  outward  to  the 
lower  border  of  the  great  sacro-sciatic  foramen,  and  emerges  from  the  pelvis 
between  the  Pyriformis  and  Coccygeus  muscles:  it  then  crosses  the  spine  of  the 
ischium  and  re-enters  the  pelvis  through  the  lesser  sacro-sciatic  foramen.  The 
artery  now  crosses  the  Obturator  internus  muscle  along  the  outer  wall  of  the  ischio- 
rectal fossa,  being  situated  about  an  inch  and  a  half  above  the  lower  margin  of  the 
ischial  tuberosity.     It  is  here  contained  in  a  sheath  of  the  obturator  fascia,  and 

44 


690  THE   BLOOD -VASCULAR   SYSTEM 

gradually  approaches  the  margin  of  the  ramus  of  the  ischium,  along  which  it  passes 
forward  and  upward,  pierces  the  base  of  the  superficial  layer  of  the  triangular 
ligament  of  the  urethra,  and  runs  forward  along  the  inner  margin  of  the  ramus  of 
the  OS  pubis,  and  divides  into  its  two  terminal  branches,  the  dorsal  artery  of  the 
penis  and  the  artery  of  the  corpus  cavemosum. 

Relations. — In  the  first  part  of  its  course,  within  the  pelvis,  it  lies  in  front  of 
the  Pyriformis  muscle  and  sacral  plexus  of  nerves,  and  the  sciatic  artery,  and 
on  the  outer  side  of  the  rectum  (on  the  left  side).  As  it  crosses  the  spine  of  the 
ischium  it  is  covered  by  the  Gluteus  maximus  and  overlapped  by  the  great  sacro- 
sciatic  ligament.  Here  the  obturator  nerve  lies  to  the  inner  side  and  the  nerve 
to  the  Obturator  internus  to  the  outer  side  of  the  vessel.  In  the  pelvis  it  lies  on 
the  outer  side  of  the  ischio-rectal  fossa,  upon  the  surface  of  the  Obturator  internus 
muscle,  contained  in  a  fibrous  canal,  the  canal  of  Alcock,  formed  by  the  splitting  of 
the  obturator  fascia.    It  is  accompanied  by  the  pudic  veins  and  the  pudic  nerve. 

Peculiarities.— The  internal  pudic  is  sometimes  smaller  than  usual,  or  fails  to  give  off  one 
or  two  of  its  usual  branches;  in  such  cases  the  deficiency  is  supplied  by  branches  derived  from 
an  additional  vessel,  the  accessory  pudic,  which  generally  arises  from  the  internal  pudic  artery 
before  its  exit  from  the  great  sacro-sciatic  foramen.  It  passes  forward  along  the  lower  part  of 
the  bladder  and  across  the  side  of  the  prosta^'^  gland  to  the  root  of  the  penis,  where  it  perforates 
the  triangular  ligament  and  gives  off  the  branches  usually  derived  from  the  pudic  artery.  The 
•deficiency  most  frequently  met  with  is  that  in  which  the  internal  pudic  ends  as  the  artery  of  the 
bulb,  the  artery  of  the  corpus  cavemosum  and  arteria  dorsalis  penis  being  derived  from  the 
accessory  pudic.  Or  the  pudic  may  terminate  as  the  superficial  perineal,  the  artery  of  the  bulb 
being  derived,  with  the  other  two  branches,  from  the  accessory  vessel.  Occasionally  the  acces- 
sory pudic  artery  is  derived  from  one  of  the  other  branches  of  the  internal  iliac,  most  frequently 
the  inferior  vesical  or  the  obturator. 

Surgical  Anatomy.— The  relation  of  the  accessory  pudic  to  the  prostate  gland  and  urethra 
is  of  the  greatest  interest  in  a  surgical  point  of  view,  as  this  vessel  is  in  danger  of  being  wounded 
in  the  operation  of  lateral  lithotomy.  The  student  should  also  study  the  position  of  the  internal 
pudic  artery  and  its  branches,  when  running  a  normal  course  with  regard  to  the  same  operation. 
The  superficial  and  the  transverse  perineal  arteries  are,  of  necessity,  divided  in  this  operation, 
but  the  hemorrhage  from  these  vessels  is  seldom  excessive;  should  a  ligature  be  required,  it 
can  readily  be  applied  on  account  of  their  superficial  position.  The  artery  of  the  bulb  may 
be  divided  if  the  incision  be  carried  too  far  forward,  and  injury  of  this  vessel  may  be  attended 
with  serious  or  even  fatal  consequences.  The  main  trunk  of  the  internal  pudic  artery  may  be 
wounded  if  the  incision  be  carried  too  far  outward;  but,  being  bound  down  by  the  strong  obtura- 
tor fascia  and  under  cover  of  the  ramus  of  the  ischium,  the  accident  is  not  very  likely  to  occur 
unless  the  vessel  runs  an  anomalous  course. 

Branches. — ^The  branches  of  the  internal  pudic  artery  are — the 

Muscular.  Transverse  Perineal. 

Inferior  H hemorrhoidal.  Artery  of  the  Bulb. 

Superficial  Perineal.  Artery  of  the  Corpus  Cavemosum. 

Dorsal  Artery  of  the  Penis. 

The  Muscular  Branches  consist  of  two  sets — one  given  off  in  the  pelvis,  the 
•other  as  the  vessel  crosses  the  ischial  spine.  The  former  are  several  small  offsets 
which  supply  the  Levator  ani,  the  Obturator  internus,  the  Pyriformis,  and  the 
Coccygeus  muscles.  The  branches  given  off  outside  the  pelvis  are  distributed  to 
the  adjacent  part  of  the  Gluteus  maximus  and  External  rotator  muscles.  They 
anastomose  with  branches  of  the  sciatic  artery. 

The  Inferior  H hemorrhoidal  Artery  (a.  hcemorrhoidalis  inferior)  arises  from 
the  internal  pudic  as  it  passes  above  the  tuberosity  of  the  ischium.  Crossing  the 
ischio-rectal  fossa  it  is  distributed  by  two  or  three  terminal  branches  to  the 
muscles  and  integument  of  the  anal  region.  Instead  of  one  inferior  hemor- 
rhoidal artery  two  or  three  small  vessels  may  arise  from  the  internal  pudic. 

The  Superficial  Perineal  Artery  (a.  perinei)(Fig.  428)  supplies  the  scrotum  and  the 
muscles  and  integument  of  the  perinseum.   It  arises  from  the  internal  pudic  in  front 


THE  INTERNAL    ILIAC  ARTERY 


691 


of  the  preceding  branches,  and  turns  upward,  crossing  either  over  or  under  the 
Transversus  perinei  superficiaUs  muscle,  and  runs  forward,  parallel  to  the  pubic 
arch,  in  the  interspace  between  the  Accelerator  urinse  and  Erector  penis  muscles, 
both  of  which  it  supplies,  and  is  finally  distributed  to  the  skin  and  dartos  of  the 
scrotum.  In  its  passage  through  the  perinseum  it  lies  beneath  the  superficial 
perineal  fascia. 

The  Transverse  Perineal  Artery  is  a  small  branch  which  arises  either  from  the 
internal  pudic  or  from  the  superficial  perineal  artery  as  it  crosses  the  Transversus 
perinaei  muscle.  It  runs  transversely  inward  along  the  cutaneous  surface  of  the 
Transversus  perinei  superficialis  muscle,  which  it  supplies,  as  well  as  the  structures 
between  the  anus  and  bulb  of  the  urethra,  and  anastomoses  with 'the  like  vessel 
of  the  opposite  side. 


Transversus  perinei 
superficialis. 


GREAT  SACRO- 
SCIATIC   LIGAMENT 


Superficial  perineal  artery. 
Superficial  perineal  nerve. 
Internal  pudic  nerve. 
Internal  pudic  artery. 


Fig.  428. — The  superficial  muscles  and  vessels  of  the  perinaeum. 

The  Artery  of  the  Bulb  (a.  bulbi  urethrce)  is  a  large  but  very  short  vessel  which 
arises  from  the  internal  pudic  between  the  two  layers  of  the  triangular  ligament, 
and,  passing  nearly  transversely  inward,  between  the  fibres  of  the  Compre  sor 
urethrse  muscle,  it  pierces  the  bulb  of  the  urethra,  which  it  supplies,  and  con- 
tinues anteriorly  in  the  corpus  spongiosum  to  the  glans  and  anastomoses  with  its 
fellow  of  the  opposite  side.  It  gives  off  a  small  branch  which  descends  to  supply 
Cowper's  gland. 

Surgical  Anatomy. — Thi.s  artery  is  of  considerable  importance  in  a  surgical  point  of  view, 
as  it  is  in  dan2;er  of  being  wounded  in  the  median  or  the  lateral  operation  of  lithotomy— an 
accident  usually  attended  in  the  adult  with  alarming  hemorrhage.  The  vessel  is  sometimes 
very  small,  occasionally  wanting,  or  even  double.  It  sometimes  arises  from  the  internal  pudic 
earlier  than  usual,  and  cros.ses  the  perinaeum  to  reach  the  back  part  of  the  bulb.  In  such  a  case 
the  ve.s.sel  could  hardly  fail  to  be  wounded  in  the  performance  of  the  lateral  operation  of  lith- 
otomy. If,  on  the  contrary,  it  should  arise  from  an  accessory  pudic,  it  lies  more  forward  than 
usual  and  is  out  of  danger  in  the  operation. 

The  Artery  of  the  Corpus  Cavemosum  (a.  profunda  penis),  one  of  the  terminal 
branches  of  the  internal  pudic,  arises  from  that  vessel  while  it  is  situated  between 


692 


THE   BLOOD -VASCULAR    SYSTEM 


the  two  layers  of  the  triangular  ligament;  it  pierces  the  superficial  layer,  and, 
entering  the  crus  penis  obliquely,  it  runs  forward  in  the  centre  of  the  corpus 
cavernosum,  to  which  its  branches  are  distributed. 

The  Dorsal  Artery  of  the  Penis  (a.  dorsalis  penis)  ascends  between  the  crus  and 
pubic  symphysis,  and,  piercing  the  triangular  ligament,  passes  between  the  two 

layers  of  the  suspensory  ligament 
of  the  penis,  and  runs  forward 
on  the  dorsum  of  the  penis  to  the 
glans,  where  it  divides  into  two 
branches  which  supply  the  glans 
and  prepuce.  On  the  dorsum 
of  the  penis  it  lies  immediately 
beneath  the  integument,  parallel 
with  the  dorsal  vein  and  the 
corresponding  artery  of  the  op- 
posite side.  It  supplies  the  in- 
tegument and  fibrous  sheath  of 
the  corpus  cavernosum,  sending 
branches  through  the  sheath  to 
anastomose  with  the  preceding 
vessel. 

The  Internal  Pudic  Artery  in 
the  Female  is  smaller  than  in  the 
male.  Its  origin  and  course  are 
similar,  and  there  is  consider- 
able analogy  in  the  distribution 
of  its  branches.  The  superficial 
perineal  artery  supplies  the  labia 
pudendi;  the  artery  of  the  bulb 
supplies  the  bulbi  vestibuli  and 
the  erectile  tissue  of  the  vagina; 
the  artery  of  the  corpus  cav- 
ernosum (a.  profunda  clitoridis) 
supplies  the  cavernous  body  of 
the  clitoris;  and  the  arteria 
dorsalis  clitoridis  supplies  the 
dorsum  of  that  organ,  and  ter- 
minates in  the  glans  and  in  the 
membranous  fold  corresponding 
to  the  prepuce  of  the  male. 

The  Sciatic  Artery  (a.  glutoea 
inferior)  (Fig.  429),  the  larger  of 
the  two  terminal  branches  of  the 
anterior  trunk  of  the  internal 
iliac,  is  distributed  to  the  mus- 
cles at  the  back  of  the  pelvis. 
It  passes  down  to  the  lower  part 
of  the  great  sacro-sciatic  fora- 
men behind  the  internal  pudic  artery,  resting  on  the  sacral  plexus  of  nerves  and 
Pyriformis  muscle,  and  escapes  from  the  pelvis  through  this  foramen  between  the 
Pyriformis  and  Coccygeus.  It  then  descends  in  the  interval  between  the  tro- 
chanter major  and  tuberosity  of  the  ischium,  accompanied  by  the  sciatic  nerves, 
and  covered  by  the  Gluteus  maximus,  and  is  continued  down  the  back  of  the  thigh 
supplying  the  skin,  and  anastomosing  with  branches  of  the  perforating  arteries. 


Superior  internal 
articular. 


Fig.  429.- 


Termination 
of  internal 
circumflex. 


Superior 
perforating 


Middle 
perforating. 

Inferior 
perforating. 


Termination  of 
profunda. 


Superior  muscular. 


Superior  external 
articular. 


Inferior  muscular. 


The  arteries  of  the  gluteal  and  posterior  femoral 
regions. 


THE   INTERNAL    ILIAC    ABTEBY  693 

Within  the  'pelvis  it  distributes  branches  to  the  Pyriformis,  Coccygeus,  and 
Levator  ani  muscles;  some  hemorrhoidal  branches,  which  supply  the  rectum,  and 
occasionally  take  the  place  of  the  middle  hemorrhoidal  artery;  and  vesical 
branches  to  the  base  anfl  neck  of  the  bladder,  vesiculse  seminales,  and  prostate 
gland.    External  to  the  pelvis  it  gives  off  the  following  branches : 

Coccygeal.  Muscular. 

Inferior  Gluteal.  Anastomotic. 

Comes  Nervi  Ischiadici.  Articular. 

The  Coccygeal  Branch  runs  inward,  pierces  the  great  sacro-sciatic  ligament,  and 
supplies  the  Gluteus  maximus,  the  integument,  and  other  structures  on  the  back 
of  the  coccyx. 

The  Inferior  Gluteal  Branches,  three  or  four  in  number,  supply  the  Gluteus 
maximus  muscle,  anastomosing  with  the  gluteal  artery  in  the  substance  of  the 
muscle. 

The  Comes  Nervi  Ischiadici  (a.  comitans  n.  ischiadici)  is  a  long,  slender  vessel 
which  accompanies  the  great  sciatic  nerve  for  a  short  distance;  it  then  penetrates 
it  and  runs  in  its  substance  to  the  lower  part  of  the  thigh. 

The  Muscular  Branches  supply  the  Gluteus  maximus,  anastomosing  with  the 
gluteal  artery  in  the  substance  of  the  muscle;  the  external  rotators,  anastomosing 
with  the  internal  pudic  artery;  and  the  muscles  attached  to  the  tuberosity  of  the 
ischium,  anastomosing  with  the  external  branch  of  the  obturator  and  the  internal 
circumflex  arteries. 

The  Anastomotic  Artery  is  directed  downward  across  the  external  rotators  and 
assists  in  forming  the  so-called  crucial  anastomosis  by  anastomosing  with  the 
superior  perforating  and  the  internal  and  external  circumflex  arteries. 

The  Articular  Branch,  generally  derived  from  the  anastomotic,  is  distributed  to 
the  capsule  of  the  hip-joint. 

The  Ilio-lumbar  Artery  (a.  ilio  lumbalis),  given  off  from  the  posterior  trunk 
of  the  internal  iliac,  turns  upward  and  outward  between  the  obturator  nerve  and 
lumbo-sacral  cord,  to  the  inner  margin  of  the  Psoas  muscle,  behind  which  it  divides 
into  a  lumbar  and  an  iliac  branch. 

The  Lumbar  Branch  {ramus  lumbalis)  supplies  the  Psoas  and  Quadratus  lum- 
borinn  muscles,  anastomosing  with  the  last  lumbar  artery,  and  sends  a  small 
spinal  branch  (ramus  spinalis)  through  the  intervertebral  foramen,  between  the  last 
lumbar  vertebra  and  the  sacrum,  into  the  spinal  canal,  to  supply  the  cauda  equina. 

The  Iliac  Branch  (ramus  iliacus)  descends  to  supply  the  Iliacus  muscle;  some 
offsets,  running  between  the  muscle  and  the  bone,  anastomose  with  the  iliac  branch 
of  the  obturator;  one  of  these  enters  an  oblique  canal  to  supply  the  diploe,  whilst 
others  run  along  the  crest  of  the  ilium,  distributing  branches  to  the  Gluteal  and 
Abdominal  muscles,  and  anastomose  in  their  course  with  the  gluteal,  circumflex 
iliac,  and  external  circumflex  arteries. 

The  Lateral  Sacral  Artery  (a.  sacralis  lateralis)  (Fig.  424)  runs  downward. 
It  may  be  single,  but  usually  there  are  two  on  each  side,  the  superior  and  inferior 
divisions. 

The  Superior  Division,  which  is  of  large  size,  passes  inward,  and,  after  anastomos- 
ing with  branches  from  the  middle  sacral,  enters  the  first  or  second  anterior  sacral 
foramen,  gives  spinal  branches  (rami  spinalis)  to  the  contents  of  the  sacral  canal, 
and,  escaping  by  the  corresponding  posterior  sacral  foramen,  supplies  the  skin 
and  muscles  on  the  dorsum  of  the  sacrum,  anastomosing  with  the  gluteal. 

The  Inferior  Division  passes  obliquely  across  the  front  of  the  Pyriformis  muscle 
and  sacral  nerves  to  the  inner  side  of  the  anterior  sacral  foramina,  descends  on  the 
front  of  the  sacrum,  and  anastomoses  over  the  coccyx  with  the  middle  sacral  and 
opposite  lateral  sacral  arteries.     In  its  course  it  gives  off  spinal  branches  which 


694  THE  BLOOD -VASCULAR    SYSTEM 

enter  the  anterior  sacral  foramina  {rami  spinalcs) ;  these,  after  supplying  the  con- 
tents of  the  sacral  canal,  escape  by  the  posterior  sacral  foramina,  and  are  dis- 
tributed to  the  muscles  and  skin  on  the  dorsal  surface  of  the  sacrum,  anastomosing 
with  the  gluteal. 

The  Gluteal  Artery  (a.  glutoea  superior)  (Fig.  429)  is  the  largest  branch  of 
the  internal  iliac,  and  appears  to  be  the  continuation  of  the  posterior  division  of 
that  vessel.  It  is  a  short  thick  trunk,  which  passes  out  of  the  pelvis  above  the 
upper  border  of  the  Pyriformis  muscle,  and  immediately  divides  into  a  superficial 
and  deep  branch.  Within  the  pelvis  it  gives  off  a  few  muscular  branches  to  the 
Iliacus,  Pyriformis,  and  Obturator  internus,  and,  just  previous  to  emerging  from 
that  cavity,  a  nutrient  artery,  which  enters  the  ilium. 

The  Superficial  Branch  passes  beneath  the  Gluteus  maximus  and  divides  into 
numerous  branches,  some  of  which  supply  that  muscle,  whilst  others  perforate  its 
tendinous  origin,  and  supply  the  integument  covering  the  posterior  surface  of  the 
sacrum,  anastomosing  with  the  posterior  branches  of  the  sacral  arteries. 

The  Deep  Branch  runs  between  the  Gluteus  medius  and  minimus,  and  sub- 
divides into  two.  Of  these,  the  superior  division  (ramus  superior),  continuing  the 
original  course  of  the  vessel,  passes  along  the  upper  border  of  the  Gluteus  minimus 
to  the  anterior  superior  spine  of  the  ilium,  anastomosing  with  the  circumflex  iliac 
and  ascending  branches  of  the  external  circumflex  artery.  The  inferior  division 
{ramus  inferior)  crosses  the  Gluteus  minimus  obliquely  to  the  trochanter  major, 
distributing  branches  to  the  Glutei  muscles,  and  inosculates  with  the  external 
circumflex  artery.  Some  branches  piece  the  Gluteus  minimus  to  supply  the  hip- 
joint. 

Surface  Marking. — The  position  of  the  three  main  branches  of  the  internal  iliac,  the 
sciatic,  internal  pudic,  and  gluteal,  which  may  occasionally  be  the  object  of  surgical  interference, 
is  indicated  on  the  surface  in  the  following  way:  A  line  is  to  be  drawn  from  the  posterior  supe- 
rior iliac  spine  to  the  posterior  superior  angle  of  the  great  trochanter,  with  the  limb  slightly 
flexed  and  rotated  inward:  the  point  of  emergence  of  the  gluteal  artery  from  the  upper  part  of 
the  sciatic  notch  will  correspond  with  the  junction  of  the  upper  with  the  middle  third  of  this 
line.  A  second  line  is  to  be  drawn  from  the  same  point  to  the  outer  part  of  the  tuberosity  of 
the  ischium;  the  junction  of  the  lower  with  the  middle  third  marks  the  point  of  emergence  of 
the  sciatic  and  pudic  arteries  from  the  great  sciatic  notch. 

Surgical  Anatomy. — Any  of  these  three  vessels  may  require  ligating  for  a  wound  or  for 
aneurism,  which  is  generally  traumatic.  The  gluteal  artery  is  ligated  by  turning  the  patient 
two-thirds  over  on  his  face  and  making  an  incision  from  the  posterior  superior  spine  of  the  ilium 
to  the  upper  and  posterior  angle  of  the  great  trochanter.  This  must  expose  the  Gluteus  maxi- 
mus muscle,  and  its  fibres  are  to  be  separated  through  the  whole  thickness  of  the  muscle  and 
pulled  apart  with  retractors.  The  contiguous  margins  of  the  gluteus  medius  and  Pyriformis 
are  now  to  be  separated  from  each  other,  and  the  artery  will  be  exposed  emerging  from  the 
sciatic  notch.  In  ligation  of  the  sciatic  artery,  the  incision  should  be  made  parallel  with  that 
for  ligation  of  the  gluteal,  but  one  inch  and  a  half  lower  down.  After  the  fibres  of  the  Gluteus 
maximus  have  been  separated,  the  vessel  is  to  be  sought  for  at  the  lower  border  of  the  Pyri- 
formis; the  great  sciatic  nerve,  which  lies  just  above  it,  forming  the  chief  guide  to  the  artery. 
The  internal  pudic  can  be  reached  through  the  incision  used  to  reach  the  sciatic. 

The  External  Iliac  Artery  (A.  Iliaca  Externa)  (Fig.  424). 

The  external  iliac  artery  is  larger  in  the  adult  than  is  the  internal  iliac.  It 
passes  obliquely  downward  and  outward  along  the  inner  border  of  the  Psoas, 
muscle,  from  the  bifurcation  of  the  common  iliac  to  Poupart's  ligament,  where 
it  enters  the  thigh  and  becomes  the  femoral  artery. 

Relations. — In  front,  with  the  peritoneum,  subperitoneal  areolar  tissue  or  Aber- 
nethy's  fascia,  the  termination  of  the  ileum  on  the  right  side,  and  the  sigmoid  flexure 
on  the  left,  and  a  thin  layer  of  fascia  derived  from  the  iliac  fascia,  which  surrounds 
the  artery  and  vein.  At  its  origin  it  is  occasionally  crossed  by  the  ureter.  The 
spermatic  vessels  descend  for  some  distance  upon  it  near  its  termination,  and  it  is 


THE  EXTERNAL    ILIAC  ARTERY  695 

crossed  in  this  situation  by  the  genital  branch  of  the  genito-crural  nerve  and  the  deep 
circumflex  ihac  vein;  the  vas deferens  curves  down  along  its  inner  side.  Behind, 
it  is  in  relation  with  the  external  iliac  vein,  which,  at  Poupart's  ligament,  lies  at 
its  inner  side;  on  the  left  side  the  vein  is  altogether  internal  to  the  artery.  Exter- 
nally, it  rests  against  the  Psoas  muscle,  from  which  it  is  separated  by  the  iliac 
fascia.  The  artery  rests  upon  this  muscle,  near  Poupart's  ligament.  Numerous 
lymphatic  vessels  and  glands  are  found  lying  on  the  front  and  inner  side  of  the 
vessel. 

Plan  of  the  Relations  of  the  External  Iliac  Artery. 

In  front. 
Peritoneum,  intestines,  and  fascia. 
Near  [Lymphatic  vessels  and  glands. 

Poupart's  Spermatic  vessels. 

Ligament  I  Genito-crural  nerve  (genital  branch). 

°  *  [Deep  circumflex  iliac  vein. 

Outer  side.  /  \  Inner  side. 

Psoas  magnus.  ^'iHar'!'*'  External  iliac  vein  and  vas  deferens 

Iliac  fascia.  \  J  near  Poupart's  ligament. 

Behind. 
External  iliac  vein. 
Psoas  magnus. 

Surface  Marking. — The  surface  line  indicating  the  course  of  the  external  iliac  artery  has 
been  already  given  (see  page  682). 

Surgical  Anatomy, — The  application  of  a  ligature  to  the  external  iliac  may  be  required  in 
cases  of  aneurism  of  the  femoral  artery  or  for  a  wound  of  the  artery.  This  vessel  may  be 
secured  in  any  part  of  its  course,  excepting  near  its  upper  end,  which  is  to  be  avoided  on  account 
of  the  proximity  of  the  great  stream  of  blood  in  the  internal  iliac,  and  near  its  lower  end,  which 
should  also  be  avoided,  on  account  of  the  proximity  of  the  deep  epigastric  and  circumflex  iliac 
vessels.  The  patient  having  been  placed  in  the  supine  position,  an  incision  should  be  made, 
commencing  below  at  a  point  about  three-quarters  of  an  inch  above  Poupart's  ligament,  and 
a  little  external  to  its  middle,  and  running  upward  and  outward,  parallel  to  Poupart's  ligament, 
to  a  point  one  inch  internal  and  one  inch  above  the  anterior  superior  spine  of  the  ilium.  When 
the  artery  is  deeply  seated  more  room  will  be  required,  and  may  be  obtained  by  curving  the 
incision  from  the  point  last  named  inward  toward  the  umbilicus  for  a  short  distance.  Another 
mode  of  ligating  the  vessel  is  the  plan  advocated  by  Sir  Astley  Cooper,  by  making  an  incision 
close  to  Poupart's  ligament  from  about  half  an  inch  outside  of  the  external  abdominal  ring  to 
one  inch  internal  to  the  anterior  superior  spine  of  the  ilium.  This  incision,  being  made  in  the 
course  of  the  fibres  of  the  aponeurosis  of  the  external  oblique,  is  less  likely  to  be  followed  by  a 
ventral  hernia,  but  there  is  danger  of  wounding  the  epigastric  artery,  and  only  the  lower  end 
of  the  vessel  can  be  ligated.  Abernethy,  who  first  tied  this  artery,  made  his  incision  in  the 
course  of  the  vessel.  The  abdominal  muscles  and  transversalis  fascia  having  been  cautiously 
divided,  the  peritoneum  should  be  separated  from  the  iliac  fossa  and  raised  toward  the  pelvis; 
and  on  introducing  the  finger  to  the  bottom  of  the  wound,  the  artery  may  be  felt  pulsating  along 
the  inner  border  of  the  Psoas  muscle.  The  external  iliac  vein  is  generally  found  on  the  inner 
side  of  the  artery,  and  must  be  cautiously  separated  from  it  by  the  finger-nail  or  handle  of  the 
knife,  and  the  aneurism  needle  should  be  introduced  on  the  inner  side,  between  the  artery  and 
the  vein. 

Ligation  of  the  external  iliac  artery  has  recently  been  performed  by  a  transperitoneal  method. 
An  incision  four  inches  in  length  is  made  in  the  semilunar  line,  commencing  about  an  inch 
below  the  umbilicus  and  carried  through  the  abdominal  wall  into  the  peritoneal  cavity.  The 
intestines  are  then  pushed  upward  and  held  out  of  the  way  by  a  broad  abdominal  retractor,  and 
an  incision  is  made  through  the  peritoneum  at  the  margin  of  the  pelvis  in  the  course  of  the  artery, 
and  the  vessel  is  secured  in  any  part  of  its  course  which  may  seem  desirable  to  the  operator.  The 
advantages  of  this  operation  appear  to  be  that  if  it  is  found  necessary,  the  common  iliac  artery 
can  be  ligated  instead  of  the  external  iliac  without  extension  or  modification  of  the  incision; 
and  secondly,  that  the  vessel  can  be  ligated  without  in  any  way  interfering  with  the  coverings 
of  the  sac  of  an  aneurism.  Possibly  a  disadvantage  may  exist  in  the  greater  risk  of  hernia  after 
this  method. 


k 


696  THE  BLOOD -VASCULAR   SYSTEM 

Collateral  Circulation. — The  principal  anastomoses  in  carrying  on  the  collateral  circulation, 
after  the  application  of  a  ligature  to  the  external  iliac,  are — the  ilio-lumbar  with  the  circumflex 
iliac;  the  gluteal  with  the  external  circumflex;  the  obturator  with  the  internal  circumflex;  the 
sciatic  with  the  superior  perforating  and  circumflex  branches  of  the  profunda  artery;  and  the 
internal  pudic  with  the  external  pudic.  When  the  obturator  arises  from  the  epigastric  it  is 
supplied  with  blood  by  branches,  either  from  the  internal  iliac,  the  lateral  sacral,  or  the  internal 
pudic.  The  epigastric  receives  its  supply  from  the  internal  mammary  and  inferior  intercostal 
arteries,  and  from  the  internal  iliac  by  the  anastomoses  of  its  branches  with  the  obturator. 

In  the  dissection  of  a  limb  eighteen  years  after  the  successful  ligature  of  the  external  iliac 
artery  by  Sir  A.  Cooper,  the  report  of  which  is  to  be  found  in  Guys  Hospital  Reports,  vol. 
i.  p.  50,  the  anastomosing  branches  are  described  in  three  sets:  An  anterior  set. — 1,  a  very 
large  branch  from  the  ilio-lumbar  artery  to  the  circumflex  iliac;  2,  another  branch  from  the 
ilio-lumbar,  joined  by  one  from  the  obturator,  and  breaking  up  into  numerous  tortuous  branches 
to  anastomose  with  the  external  circumflex;  3,  two  other  branches  from  the  obturator,  which 
passed  over  the  brim  of  the  pelvis,  communicated  with  the  epigastric,  and  then  broke  up  into  a 
plexus  to  anastomose  with  the  internal  circumflex.  An  internal  set. — Branches  given  off  from 
the  obturator,  after  quitting  the  pelvis,  which  ramified  among  the  adductor  muscles  on  the 
inner  side  of  the  hip-joint,  and  joined  most  freely  with  branches  of  the  internal  circumflex. 
A  posterior  set. — 1,  three  large  branches  from  the  gluteal  to  the  external  circumflex;  2,  several 
branches  from  the  sciatic  around  the  great  sciatic  notch  to  the  internal  and  external  circumflex, 
and  the  perforating  branches  of  the  profunda. 

Branches. — Besides  several  small  branches  to  the  Psoas  muscle  and  the  neigh- 
boring lymphatic  glands,  the  external  iliac  gives  off  two  branches  of  considerable 
size — the  deep  epigastric  and  deep  circumflex  iliac  arteries. 

The  Internal  or  Deep  Epigastric  Artery  (a.  epigastrica  inferior)  (Fig.  424) 
arises  from  the  external  iliac  a  few  lines  above  Poupart's  ligament.  It  at  first 
descends  to  reach  this  ligament,  and  then  ascends  obliquely  along  the  inner  margin 
of  the  internal  abdominal  ring,  lying  between  the  transversalis  fascia  and  peri- 
toneum, and,  continuing  its  course  upward,  it  pierces  the  transversalis  fascia,  and 
passing  over  the  semilunar  fold  of  Douglas,  enters  the  sheath  of  the  Rectus  muscle. 
It  then  ascends  on  the  posterior  surface  of  the  muscle,  and  finally  divides  into 
numerous  branches  which  anastomose,  above  the  umbilicus,  with  the  superior 
epigastric  branch  of  the  internal  mammary  and  with  the  inferior  intercostal  arteries 
(Fig.  410).  The  deep  epigastric  artery  bears  a  very  important  relation  to  the 
internal  abdominal  ring  as  it  passes  obliquely  upward  and  inward  from  its  origin 
from  the  external  iliac.  In  this  part  of  its  course  it  lies  along  the  lower  and  inner 
margin  of  the  ring  and  beneath  the  commencement  of  the  spermatic  cord.  As 
it  passes  to  the  inner  side  of  the  internal  abdominal  ring  it  is  crossed  by  the  vas 
deferens  in  the  male  and  the  round  ligament  in  the  female. 

Branches. — The  branches  of  this  vessel  are  the  following:  The  cremasteric 
(a.  spermatica  externa  in  the  male,  a.  ligamenti  teretis  uteri  in  the  female),  which 
accompanies  the  spermatic  cord,  and  supplies  the  Cremaster  muscle  and  other 
coverings  of  the  cord,  anastomosing  with  the  spermatic  artery  in  the  male, 
and  which  accompanies  the  round  ligament  in  the  female;  a  pubic  branch 
{ramus  pvbicus),  which  runs  along  Poupart's  ligament,  and  then  descends  behind 
the  OS  pubis  to  the  inner  side  of  the  femoral  ring,  and  anastomoses  with  offsets 
from  the  obturator  artery;  muscular  branches,  some  of  which  are  distributed  to  the 
abdominal  muscles  and  peritoneum,  anastomosing  with  the  lumbar  and  circum- 
flex iliac  arteries;  cutaneous  branches  perforate  the  tendon  of  the  External  oblique, 
and  supply  the  integument,  anastomosing  with  branches  of  the  superficial  epi- 
gastric. 

Peculiarities. — The  origin  of  the  deep  epigastric  may  take  place  from  any  part  of  the 
external  iliac  between  Poupart's  ligament  and  two  inches  and  a  half  above  it,  or  it  may  arise 
below  this  ligament,  from  the  common  femoral  or  from  the  deep  femoral. 

Union  with  Branches. — It  frequently  arises  from  the  external  iliac  by  a  common  trunk 
with  the  obturator.  Sometimes  the  epigastric  arises  from  the  obturator,  the  latter  vessel  being 
furnished  by  the  internal  iliac,  or  the  epigastric  may  be  formed  by  two  branches,  one  derived 
from  the  external  iliac,  the  other  from  the  internal  iliac. 


THE   FEMORAL    ABTEBY  697 

Surgical  Anatomy. — The  deep  epigastric  artery  follows  a  line  drawn  from  the  middle  of 
Poupart's  ligament  toward  the  umbilicus;  but  shortly  after  this  line  crosses  the  linea  semilunaris 
the  direction  changes,  and  the  course  of  the  vessel  is  directly  upward  in  the  line  of  junction  of 
the  inner  third  with  the  outer  two-thirds  of  the  Rectus  muscle.  It  has  important  surgical  rela- 
tions, in  addition  to  the  fact  that  it  is  one  of  the  principal  means,  through  its  anastomosis  with 
the  internal  mammary,  in  establishing  the  collateral  circulation  after  ligature  of  either  the  com- 
mon or  external  iliac  arteries.  It  lies  close  to  the  internal  abdominal  ring,  and  is  therefore 
internal  to  an  oblique  inguinal  hernia,  but  external  to  a  direct  inguinal  hernia,  as  the  hernia 
emerges  from  the  abdomen.  It  forms  the  outer  boundary  of  Hesselbach's  triangle.  It  is  in 
close  relationship  with  the  spermatic  cord,  which  lies  in  front  of  it  in  the  inguinal  canal, 
separated  only  by  the  transversalis  fascia.     The  vas  deferens  hooks  round  its  outer  side. 

The  Deep  Circumflex  Hiac  Artery  (a.  circumflexa  ilium  profunda)  (Fig.  424) 
-arises  from  the  outer  side  of  the  external  iUac  nearly  opposite  the  epigastric  artery. 
It  ascends  obliquely  outward  behind  Poupart's  ligament,  contained  in  a  fibrous 
sheath  formed  by  the  junction  of  the  transversalis  and  iliac  fasciae,  to  the  anterior 
superior  spinous  process  of  the  ilium.  It  then  runs  along  the  inner  surface  of  the 
crest  of  the  ilium  to  about  its  middle,  where  it  pierces  the  Transversalis,  and 
runs  backward  between  that  muscle  and  the  Internal  oblique,  to  anastomose  with 
the  ilio-lumbar  and  gluteal  arteries.  Opposite  the  anterior  superior  spine  of  the 
ilium  it  gives  off  a  large  branch  which  ascends  between  the  Internal  oblique  and 
Transversalis  muscles,  supplying  them,  and  anastomosing  with  the  lumbar  and 
epigastric  arteries.    It  also  gives  off  cutaneous  branches. 


ARTERIES  OF  THE  LOWER  EXTREMITY. 

The  artery  which  supplies  the  greater  part  of  the  lower  extremity  is  the  direct 
continuation  of  the  external  iliac.  It  continues  as  a  single  trunk  from  Poupart's 
ligament  to  the  lower  border  of  the  Popliteus  muscle,  and  here  divides  into  two 
branches,  the  anterior  and  posterior  tibial,  an  arrangement  exactly  similar  to  what 
occurs  in  the  upper  limb.  For  convenience  of  description,  the  upper  part  of  the 
main  trunk  is  named  femoral,  the  lower  part,  popliteal. 


THE  FEMORAL  ARTERY  (A.  FEMORALIS)  (Figs.  430,  431,  432). 

The  femoral  artery  commences  immediately  behind  Poupart's  ligament, 
midway  between  the  anterior  superior  spine  of  the  ilium  and  the  symphysis 
pubis,  and,  passing  down  the  forepart  and  inner  side  of  the  thigh,  terminates 
at  the  opening  in  the  Adductor  magnus,  at  the  junction  of  the  middle  with  the 
lower  third  of  the  thigh,  where  it  becomes  the  popliteal  artery.  The  vessel,  at 
the  upper  part  of  the  thigh,  lies  in  front  of  the  hip-joint,  just  on  a  line  with  the 
innermost  part  of  the  head  of  the  femur;  in  the  lower  part  of  its  course  it  is  in  close 
relation  with  the  inner  side  of  the  shaft  of  the  bone,  and  between  these  two  parts 
the  vessel  is  some  distance  from  the  bone.  In  the  upper  third  of  the  thigh  it  is 
contained  in  a  triangular  space  called  Scarpa's  triangle.  In  the  middle  third  of  the 
thigh  it  is  contained  in  an  aponeurotic  canal  called  Hunter's  canal. 

Scarpa's  Triangle  (trigonum  femorale). — Scarpa's  triangle  corresponds  to  the 
depression  seen  immediately  below  the  fold  of  the  groin.  It  is  a  triangular  space, 
the  apex  of  which  is  directed  downward,  and  the  sides  formed  externally  by  the 
Sartorius,  internally  by  the  inner  margin  of  the  Adductor  longus,  and  above  by 
Poupart's  ligament.  The  floor  of  the  space  is  formed  from  without  inward  by  the 
Iliacus,  Psoas,  Pectineus  (in  some  cases  a  small  part  of  the  Adductor  brevis),  and 
the  Adductor  longus  muscles ;  and  it  is  divided  into  two  nearly  equal  parts  by  the 
femoral  vessels,  which  extend  from  the  middle  of  its  base  to  its  apex,  the  artery 


698 


THE   BLOOD -VASCULAR    SYSTEM 


giving  off  in  this  situation  its  superficial  and  profunda  branches,  the  vein  receiving 
the  deep  femoral  and  internal  saphenous.  On  the  outer  side  of  the  femoral  artery 
is  the  anterior  crural  nerve  dividing  into  its  branches.  In  the  outer  corner  of  the 
space  is  the  external  cutaneous  nerve.  Within  the  sheath  of  the  artery,  and  lying 
upon  the  outer  side  of  the  vessel,  is  the  crural  branch  of  the  genito-crural  nerve. 
At  the  base  of  the  triangle  the  vein  is  to  the  inner  side  of  the  artery;  at  the  apex 
of  the  triangle  it  is  passing  behind  the  artery.  Besides  the  vessels  and  nerves, 
this  space  contains  some  fat  and  lymphatics. 


SUPERFICIAL 
EPIGASTRIC 

SUPERFICIAL  CIR- 
CUMFLEX ILIAC 

COMMON 
FEMORAL 


EXTERNAL 
CIRCUMFLEX 

DESCENDING 
RAMUS  OF 
EXTERNAL 

CIRCUMFLEX 


SUPERFICIAL 

EXTERNAL 

PUDIC 


SUPERIOR  EXTER- 
NAL ARTICULAR 
BRANCH  OF 
POPLITEAL 


DEEP 

EXTERNAL 

PUDIC 

INTERNAL 

CIRCUMFLEX 


ANASTOMOTICA 
MAGNA 


SUPERIOR   INTERNAL 
ARTICULAR 
BRANCH   OF 
POPLITEAL 


Fig.  430. — Scheme  of  the  femoral  artery.     (Poirier  and  Charpy.) 


Hunter's  Canal  or  the  Adductor  Canal  (canalis  addvdorius  [Hunteri]). — 
This  is  the  aponeurotic  space  in  the  middle  third  of  the  thigh,  extending  from 
the  apex  of  Scarpa's  triangle  to  the  femoral  opening  in  the  Adductor  magnus 
muscle.  It  is  bounded,  externally,  by  the  Vastus  internus;  internally  by  the 
Adductors  longus  and  magnus  muscles;  and  is  covered  in  by  a  strong  apon- 
eurosis which  extends  transversely  from  the  Vastus  internus  across  the  femoral 


THE    COMMON  FEMORAL    ARTERY 


699 


Scrotum. 


vessels  to  the  Adductor  longus  and  magnus;  lying  on  which  aponeurosis  is  the 
Sartorius  muscle.  It  contains  the  femoral  artery  and  vein  enclosed  in  their  own 
sheath  of  areolar  tissue,  the  vein  being  behind  and  on  the  outer  side  of  the  artery, 
and  the  internal  or  long  saphenous 
nerve  lying  at  first  on  the  outer  side 
and  then  in  front  of  the  vessels. 

For  convenience  of  description, 
and  also  in  reference  to  its  surgi- 
cal anatomy,  the  femoral  artery  is 
divided  into  a  short  trunk,  about 
an  inch  and  a  half  or  two  inches 
long,  which  is  known  as  the  com- 
mon femoral  artery,  while  the  re- 
mainder of  the  vessel  is  termed 
the  superficial  femoral  artery,  to 
distinguish  it  from  the  deep  femoral 
(profunda  femoris),  a  large  branch 
given  off  from  the  common  femoral 
at  its  termination,  and  which, 
by  its  derivation,  from  the  parent 
trunk,  marks  the  commencement 
of  the  superficial  femoral  artery. 


The  Common  Femoral  Artery 

(Figs.  430,  431,  432). 

The  common  femoral  artery  is 
very  superficial,  being  covered  by 
the  skin  and  superficial  fascia, 
superficial  inguinal  lymphatic 
glands,  the  iliac  portion  of  the 
fascia  lata,  and  the  prolongation 
downward  of  the  transversalis 
fascia,  which  forms  the  anterior 
part  of  the  sheath  of  the  vessels. 
It  has  in  front  of  it  filaments  from 
the  crural  branch  of  the  genito- 
crural  nerve,  the  superficial  cir- 
cumflex iliac  vein,  and  occasionally 
the  superficial  epigastric  vein.  It 
rests  on  the  inner  margin  of  the 
Psoas  muscle,  which  separates  it 
from  the  capsular  ligament  of  the 
hip-joint,  and  a  little  lower  on  the 
Pectineus  muscle  ;  and  crossing 
behind  it  is  the  branch  to  the 
Pectineus  from  the  anterior  crural 
nerve.  Separating  the  artery  from 
the  Pectineus  muscles  is  the  pubic  portion  of  the  fascia  lata  and  the  prolongation 
from  the  fascia  covering  the  Iliacus  muscle,  which  forms  the  posterior  layer  of  the 
sheath  of  the  vessels.  The  anterior  crural  nerve  lies  about  half  an  inch  to  the 
outer  side  of  the  common  femoral  artery,  being  separated  from  the  artery  by  a 
small  part  of  the  Psoas  muscle.  To  the  inner  side  of  the  artery  is  the  femoral  vein, 
between  the  margins  of  the  Pectineus  and  Psoas  muscles.    The  two  vessels  are 


Long  saphenous 

nerve. 

Anastomotica 
magna. 


Superior  external 
articular. 


Inferior  internal 
articular 


Anterior  tibial 
recurrent. 


Anastomotica 

magna. 
Superior  internal 

articular. 


Inferior  internal 
articular. 


Fig.  431. — The  femoral  artery. 


700 


THE   BLOOD  -  VASCULAR   SYSTEM 


enclosed  in  a  strong  fibrous  sheath  formed  by  the  proper  sheath  of  the  vessels, 
strengthened  by  fascia  (see  page  509) ;  the  artery  and  vein  are  separated,  however, 
from  one  another  by  a  thin  fibrous  partition. 

Plan  of  the  Relations  of  the  Common  Femoral  Artery. 

In  front. 
Skin  and  superficial  fascia. 
Superficial  inguinal  glands. 
Iliac  portion  of  fascia  lata. 
Prolongation  of  transversalis  fascia. 
Crural  branch  of  genito-crural  nerve. 
Superficial  circumflex  iliac  vein. 
Superficial  epigastric  vein. 


Inner  side. 
Femoral  vein. 


Outer  side. 
Small  part  of  Psoas  muscle, 
separating  the  artery  from  the 
anterior  crural  nerve. 


Behind. 
Prolongation  of  fascia  covering  the  Iliacus  muscle. 
Pubic  portion  of  fascia  lata. 
Nerve  to  Pectineus. 
Psoas  muscle. 
Pectineus  muscle. 
Capsule  of  hip-joint. 

The  Superficial  Femoral  Artery  (Figs.  430,  431,  432). 

The  superficial  femoral  artery  is  only  superficial  where  it  lies  in  Scarpa's  tri- 
angle. Here  it  is  covered  by  the  skin,  superficial  and  deep  fascia,  and  crossed 
by  the  internal  cutaneous  branch  of  the  anterior  crural  nerve.  In  Hunter's  canal 
it  is  more  deeply  seated,  being  covered  by  the  integument,  the  superficial  and 
deep  fascia,  the  Sartorius  and  the  aponeurotic  covering  of  Hunter's  canal.  The 
internal  saphenous  nerve  crosses  the  artery  from  without  inward.  Behind,  the 
artery  lies  at  its  upper  part  on  the  femoral  vein  and  the  profunda  artery  and 
vein,  which  separate  it  from  the  Pectineus  muscle,  and  lower  down  on  the  Adduc- 
tor longus  and  Adductor  magnus  muscles.  To  the  outer  side  is  the  long  saphenous 
nerve  and  the  nerve  to  the  Vastus  internus,  the  Vastus  internus  muscle,  and, 
at  its  lower  part,  the  femoral  vein.  To  the  inner  side  is  the  Adductor  longus 
above  and  the  Adductor  magnus  and  Sartorius  below. 

Plan  of  the  Relations  of  the  Superficial  Femoral  Artery. 

In  front. 
Skin,  superficial  and  deep  fasciae. 
Internal  cutaneous  nerve. 
Sartorius. 

Aponeurotic  covering  of  Hunter's  canal. 
Internal  saphenous  nerve. 

Outer  side. 

Long  saphenous  nerve. 

Nerve  to  vastus  internus. 

Vastus  internus. 

Femoral  vein  (below). 

Behind. 
Femoral  vein. 
Profunda  artery  and  vein. 
Pectineus  muscle. 
Adductor  longus. 
Adductor  magnus. 


Inner  side. 
Adductor  longus. 
Adductor  magnus. 
Sartorius. 


THE   SUPERFICIAL    FEMORAL    ARTERY  701 

The  femoral  vein,  at  Poupart's  ligament,  lies  close  to  the  inner  side  of  the  artery, 
separated  from  it  by  a  thin  fibrous  partition;  but  lower  down  it  is  behind  it,  and 
then  to  its  outer  side. 

The  internal  saphenous  nerve  is  situated  on  the  outer  side  of  the  artery,  in  the 
middle  third  of  the  thigh,  beneath  the  aponeurotic  covering  of  Hunter's  canal,  but 
not  usually  within  the  sheath  of  the  vessels.  The  internal  cutaneous  nerve  passes 
obliquely  across  the  upper  part  of  the  sheath  of  the  femoral  artery. 

Peculiarities.  Double  Femoral  Reunited. — Several  cases  are  recorded  in  which  the  femoral 
artery  divided  into  two  trunks  below  the  origin  of  the  profunda,  and  became  reunited  near  the 
opening  of  the  Adductor  magnus  so  as  to  form  a  single  popliteal  artery.  One  of  them  occurred 
in  a  patient  operated  upon  for  popliteal  aneurism. 

Change  of  Position. — A  few  cases  have  been  recorded  in  which  the  femoral  artery  was 
situated  at  the  back  of  the  thigh,  the  vessel  being  continuous  above  with  the  internal  iliac,  escap- 
ing from  the  pelvis  through  the  great  sacro-sciatic  foramen,  and  accompanying  the  great  sciatic 
nerve  to  the  pophteal  space,  where  its  division  occurred  in  the  usual  manner.  The  external 
iliac  in  these  cases  was  small,  and  terminated  in  the  profunda. 

Position  of  the  Vein. — The  femoral  vein  is  occasionally  placed  along  the  inner  side  of  the 
artery,  throughout  the  entire  extent  of  Scarpa's  triangle,  or  it  may  be  slit  so  that  a  large  vein  is 
placed  on  each  side  of  the  artery  for  a  greater  or  less  extent. 

Origin  of  the  Profunda. — This  vessel  occasionally  arises  from  the  inner  side,  and,  more 
rarely,  from  the  back  of  the  common  trunk;  but  the  more  important  peculiarity,  in  a  surgical 
point  of  view,  is  that  which  relates  to  the  height  at  which  the  vessel  arises  from  the  femoral.  In 
three-fourths  of  a  large  number  of  cases  it  arose  between  one  or  two  inches  below  Poupart's 
ligament;  in  a  few  cases  the  distance  was  less  than  an  inch;  more  rarely,  opposite  the  ligament; 
and  in  one  case,  above  Poupart's  ligament,  from  the  external  iliac.  Occasionally,  the  distance 
between  the  origin  of  the  vessel  and  Poupart's  ligament  exceeds  two  inches,  and  m  one  case  it 
was  found  to  be  as  much  as  four  inches. 

Surface  Marking. — The  upper  two-thirds  of  a  line  drawn  from  a  point  midway  between 
the  anterior  superior  spine  of  the  ilium  and  the  symphysis  pubis  to  the  adductor  tubercle  on 
the  inner  condyle  of  the  femur,  with  the  thigh  abducted  and  rotated  outward,  will  indicate  the 
course  of  the  femoral  artery. 

Surgical  Anatomy. — Com-pression  of  the  femoral  artery,  which  is  constantly  requisite  in 
amputations  and  other  operations  on  the  lower  limbs,  and  also  for  the  cure  of  popliteal  aneurisms, 
is  most  effectually  made  immediately  below  Poupart's  ligament.  In  this  situation  the  artery  is 
very  superficial,  and  is  merely  separated  from  the  ascending  ramus  of  the  os  pubis  by  the  Psoas 
muscle;  so  that  the  surgeon,  by  means  of  his  thumb  or  a  compressor,  may  effectually  control  the 
circulation  through  it.  This  vessel  may  also  be  compressed  in  the  middle  third  of  the  thigh  by 
placing  a  compress  over  the  artery,  beneath  the  tourniquet,  and  directing  the  pressure  from 
within  outward,  so  as  to  compress  the  vessel  against  the  inner  side  of  the  shaft  of  the  femur. 

The  application  of  a  ligature  to  the  femoral  artery  may  be  required  in  the  cases  of  wound 
or  aneurism  of  the  arteries  of  the  leg,  of  the  popliteal  or  femoral  ;^  and  the  vessel  may  be  exposed 
and  tied  in  any  part  of  its  course.  The  great  depth  of  this  vessel  at  its  lower  part,  its  close  con- 
nection with  important  structures,  and  the  density  of  its  sheath  render  the  operation  in  this 
situation  one  of  much  greater  difficulty  than  the  application  of  a  ligature  at  its  upper  part, 
where  it  is  more  superficial. 

Ligature  of  the  common  femoral  artery  is  usually  considered  unsafe,  on  account  of  the  con- 
nection of  large  branches  with  it — viz.,  the  deep  epigastric  and  the  deep  circumflex  iliac  arising 
just  above  Poupart's  ligament;  on  account  of  the  number  of  small  branches  which  arise  from 
it  in  its  short  course;  and  on  account  of  the  uncertainty  of  the  origin  of  the  profunda  femoris, 
which,  if  it  arise  high  up,  would  be  too  close  to  the  ligature  for  the  formation  of  a  firm  coagu- 
lum.  The  profunda  sometimes  arises  higher  than  the  point  above  mentioned,  and  rarely  between 
two  or  three  inches  (in  one  case  four)  below  Poupart's  ligament.  It  would  appear,  then,  that 
the  most  favorable  situation  for  the  application  of  a  ligature  to  the  femoral  is  on  the  superficial 
femoral  at  the  apex  of  Scarpa's  triangle.  In  order  to  expose  the  artery  in  this  situation,  an  inci- 
sion between  three  and  four  inches  long  should  be  made  in  the  course  of  the  vessel,  the  patient 
lying  in  the  recumbent  position,  with  the  limb  slightly  flexed  and  abducted,  and  rotated  outward. 
A  large  vein  is  frequently  met  with,  passing  in  the  course  of  the  artery  to  join  the  internal  saphe- 
nous vein;  this  must  be  avoided,  and  the  fascia  lata  having  been  cautiously  divided  and  the 
Sartorius  exposed,  that  muscle  must  be  drawn  outward  in  order  to  expose  fully  the  sheath  of 
the  vessels.  The  finger  being  introduced  into  the  wound  and  the  pulsation  of  the  artery  felt, 
the  sheath  should  be  opened  on  the  outer  side  of  the  vessel  to  a  sufficient  extent  to  allow  of  the 

1  Ligation  of  the  femoral  artery  has  been  also  recommended  and  performed  for  elephantiasis  of  the  leg  and 
acute  inflammation  of  the  knee-joint  (Maunder,  Clin.  Soc.  Trans.,  vol.  ii.  p.  37). — Ed.  of  15th  English  edition. 


702  THE  BLOOD -VASCULAR  SYSTEM 

introduction  of  the  ligature,  but  no  farther;  otherwise  the  nutrition  of  the  coats  of  the  vessel 
naay  be  interfered  with,  or  muscular  branches  which  arise  from  the  vessel  at  irregular  intervals 
may  be  divided.  In  this  part  of  the  operation  the  long  saphenous  nerve  and  the  nerve  to  the 
Vastus  internus,  which  is  in  close  relation  with  the  sheath,  should  be  avoided.  The  aneurism 
needle  must  be  carefully  introduced  and  kept  close  to  the  artery,  to  avoid  the  femoral  vein,  which 
lies  behind  the  vessel  in  this  part  of  its  course. 

To  expose  the  artery  in  Hunter's  canal,  an  incision  should  be  made  between  three  and  four 
inches  in  length,  a  finger's  breadth  internal  to  the  line  of  the  artery,  in  the  middle  of  the  thigh 
— i.  e.,  midway  between  the  groin  and  the  knee.  The  integument  is  first  divided.  The  fascia 
lata  having  been  divided,  and  the  outer  border  of  the  Sartorius  muscle  exposed,  it  should  be 
drawn  inward,  when  the  strong  fascia  which  is  stretched  across  from  the  Adductors  to  the  Vastus 
internus  will  be  exposed,  and  must  be  freely  divided;  the  sheath  of  the  vessels  is  now  seen, 
and  must  be  opened,  and  the  artery  secured  by  passing  the  aneurism  needle  between  the  vein 
and  artery  in  the  direction  from  without  inward.  The  femoral  vein  in  this  situation  lies  on  the 
outer  side  of  the  artery  and  the  long  saphenous  nerve  on  the  anterior  and  outer  side  of  the 
artery. 

It  has  been  seen  that  the  femoral  artery  occasionally  divides  into  two  trunks  below  the  origin 
of  the  profunda.  If  in  the  operation  for  tying  the  femoral  two  vessels  are  met  with,  the  surgeon 
should  alternately  compress  each,  in  order  to  ascertain  which  vessel  is  connected  with  the 
aneurismal  tumor  or  with  the  bleeding  from  the  wound,  and  that  one  only  should  be  tied  which 
controls  the  pulsation  or  hemorrhage.  If,  however,  it  is  necessary  to  compress  both  vessels 
before  the  circulation  in  the  tumor  is  controlled,  both  should  be  tied,  as  it  would  be  probable  that 
they  became  reunited,  as  in  the  instances  referred  to  above. 

In  wounds  of  the  femoral  artery  the  question  of  the  mode  of  treatment  is  of  considerable 
importance.  If  the  wound  in  the  superficial  structures  is  a  large  one,  the  injured  vessel  must 
be  exposed  and  tied;  but  if  the  wound  is  a  punctured  one  and  the  bleeding  has  ceased,  the  ques- 
tion will  arise  whether  to  cut  down  upon  the  artery  or  to  trust  to  pressure.  Mr.  Cripps'  advises 
that  if  the  wound  is  in  the  "upper  part  of  the  thigh — that  is  to  say,  in  a  position  where  the 
femoral  artery  is  comparatively  superficial — the  surgeon  may  enlarge  the  opening  with  a  good 
prospect  of  finding  the  wounded  vessel  without  an  extensive  or  prolonged  operation,  if  the 
wound  be  in  the  lower  half  of  the  thigh,  owing  to  the  greater  depth  of  the  artery  and  the  possi- 
bility of  its  being  the  popliteal  that  is  wounded,  the  search  is  rendered  a  far  more  severe  and 
hazardous  operation,  and  it  should  not  be  undertaken  until  a  thorough  trial  of  pressure  has 
proved  ineffectual." 

Great  care  and  attention  are  necessary  for  the  successful  application  of  pressure.  The  limb 
should  be  carefully  bandaged  from  the  foot  upward  to  the  wound,  which  is  not  covered,  and  then 
onward  to  the  groin.  The  wound  is  then  dusted  with  iodoform  or  boracic  powder  and  a  conical 
pad  applied  over  the  wound.  Rollers  the  thickness  of  the  index  finger  are  then  placed  along 
the  course  of  the  vessel  above  and  below  the  wound,  and  the  whole  carefully  bandaged  to  a  back 
splint  with  a  foot-piece. 

Collateral  Circulation. — ^When  the  common  femoral  is  tied  the  main  channels  for  carrying 
on  the  circulation  are  the  anastomoses  of  the  gluteal  and  circumflex  iliac  arteries  above  with  the 
external  circumflex  below;  of  the  obturator  and  sciatic  above  with  the  internal  circumflex  below; 
and  of  the  comes  nervi  ischiadici  with  the  arteries  in  the  ham. 

The  principal  agents  in  carrying  on  the  collateral  circulation  after  ligature  of  the  superficial 
femoral  artery  are,  according  to  Sir  A.  Cooper,  as  follows: 

"  The  arteria  profunda  formed  the  new  channel  for  the  blood.  The  first  artery  sent  off 
passed  down  close  to  the  back  of  the  thigh-bone,  and  entered  the  two  superior  articular  branches 
of  the  popliteal  artery. 

"The  second  new  large  vessel,  arising  from  the  profunda  at  the  same  part  with  the  former, 
passed  down  by  the  inner  side  of  the  Biceps  muscle  to  a  branch  of  the  popliteal  which  was  dis- 
tributed to  the  Gastrocnemius  muscle;  whilst  a  third  artery,  dividing  into  several  branches, 
passed  down  with  the  sciatic  nerve  behind  the  knee-joint,  and  some  of  its  branches  united  them- 
selves with  the  inferior  articular  arteries  of  the  popliteal,  with  some  recurrent  branches  of  those 
arteries,  with  arteries  passing  to  the  Gastrocnemii,  and,  lastly,  with  the  origin  of  the  anterior 
and  posterior  tibial  arteries. 

"It  appears,  then,  that  it  is  those  branches  of  the  profunda  which  accompany  the  sciatic 
nerve  that  are  the  principal  supporters  of  the  new  circulation."^ 

In  Porta's  work'  (tab.  xii.,  xiii.)  is  a  good  representation  of  the  collateral  circulation  after 
the  ligature  of  the  femoral  artery.  The  patient  had  survived  the  operation  three  years.  The 
lower  part  of  the  artery  is  at  least  as  large  as  the  upper;  about  two  inches  of  the  vessel  appear 
to  have  been  obliterated.  The  external  and  internal  circumflex  arteries  are  seen  anastomosing 
by  a  great  number  of  branches  with  the  lower  branches  of  the  femoral  (muscular  and  anasto- 

'   Heath's  Dictionary  of  Practical  Surgery,  vol.  i.  p.  525.  -  Med.-Chir.  Trans.,  vol.  ii.,  18H. 

8  Alterazioni  patologiche  delle  Arterie. 


THE  SUPERFICIAL    FEMORAL    ARTERY 


703 


motica  magna)  and  with  the  articular  branches  of  the  pophteal.  The  branches  from  the  external 
circumflex  are  extremely  large  and  numerous.  One  very  distinct  anastomosis  can  be  traced 
between  this  artery  on  the  outside  and  the  anastomotica  magna  on  the  inside  through  the  inter- 
vention of  the  superior  external  articular  artery,  with  which  they  both  anastomose;  and  blood 
reaches  even  the  anterior  tibial  recurrent  from  the  external  circumflex  by  means  of  anastomosis 
with  the  same  external  articular  artery.  The  perforating  branches  of  the  profunda  are  also 
seen  bringing  blood  round  the  obliterated  portion  of  the  artery  into  long  branches  (muscular) 


External  iliac  artery. 

Deep  epiiv'^tric  artery. 
^  I'    'III tic  void. 


Superior 

circumfle.t' 

iliac  artery 


Common  femoral.  ■ 


Profniula  . 
femoris. 

External  cir-   I'.lS 
cumflex. 


l^nperficial 
^  J  femoral. 


I-  Opening  in 
adductor 
magnus. 


Fig.  432.- 


-  Femoral  artery  and  its  branches.     (From  a  preparation  in  the  Museum  of  the  Royal  College  of 
Surgeons  of  England.) 


which  have  been  given  off  just  below  that  portion.  The  termination  of  the  profunda  itself 
anastomoses  most  freely  with  the  superior  external  articular.  A  long  branch  of  anastomosis 
is  also  traced  down  from  the  internal  iliac  by  means  of  the  comes  nervi  ischiadici  of  the  sciatic, 
which  anastomoses  on  the  popliteal  nerves  with  branches  from  the  popliteal  and  posterior  tibial 
arteries.  In  this  case  the  anastomosis  had  been  too  free,  since  the  pulsation  and  growth  of  the 
aneurism  recurred,  and  the  patient  died  after  ligature  of  the  external  iliac. 

There  is  an  interesting  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  a 
limb  on  which  John  Hunter  had  tied  the  femoral  artery  fifty  years  before  the  patient's  death. 


k 


704  '^HE  BLOOD -VASCULAR   SYSTEM 

The  whole  of  the  superficial  femoral  and  popliteal  artery  seems  to  have  been  obliterated.  The 
anastomosis  by  means  of  the  comes  nervi  ischiadici,  which  is  shown  in  Porta's  plate,  is  distinctly 
seen:  the  external  circumflex  and  the  termmation  of  the  profunda  artery  seem  to  have  been  the 
chief  channels  of  anastomoses;  but  the  injection  has  not  been  a  very  successful  one. 

Branches  (Figs.  430,  431,  and  432). — The  branches  of  the  femoral  artery 
are — the 

Superficial  Epigastric.  (  External  Circumflex. 

Superficial  Circumflex  Ihac.  Profunda  Femoris  \  Internal  Circumflex. 

Superficial  External  Pudic.  (  Three  Perforating. 

Deep  External  Pudic.  Muscular. 

Anastomotica  Magna. 

The  Superficial  Epiglistric  (a.  epigastrica  swperficiaUs)  arises  from  the  fem- 
oral about  half  an  inch  below  Poupart's  ligament,  and,  passing  through  the 
saphenous  opening  in  the  fascia  lata,  ascends  on  the  abdomen,  in  the  superficial 
fascia  covering  the  External  oblique  muscle,  nearly  as  high  as  the  umbilicus.  It 
distributes  branches  to  the  superficial  inguinal  glands,  the  superficial  fascia,  and 
the  integument,  anastomosing  with  branches  of  the  deep  epigastric. 

The  Superficial  Circumflex  Iliac  (a.  circumflexa  ilium  super ficialis),  the 
smallest  of  the  cutaneous  branches,  arises  close  to  the  preceding,  and,  piercing  the 
fascia  lata,  runs  outward,  parallel  with  Poupart's  ligament,  as  far  as  the  crest  of 
the  ilium,  dividing  into  branches  which  supply  the  integument  of  the  groin,  the 
superficial  fascia,  and  the  superficial  inguinal  lymphatic  glands,  anastomosing 
with  the  deep  circumflex  iliac  and  with  the  gluteal  and  external  circumflex 
arteries. 

The  Superficial  External  Pudic  or  the  Superior  Superficial  External  Pudic 
(a.  pudenda  externa  superficialis)  arises  from  the  inner  side  of  the  femoral  artery, 
close  to  the  preceding  vessels,  and,  after  passing  through  the  saphenous  opening, 
courses  inward,  across  the  spermatic  cord  or  round  ligament,  to  be  distributed  to 
the  integument  on  the  lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the 
male,  and  the  labium  in  the  female,  anastomosing  with  branches  of  the  internal 
pudic. 

The  Deep  External  Pudic  or  the  Deep  Superficial  External  Pudic  (a.  pudenda 
externa  profunda),  more  deeply  seated  than  the  preceding,  passes  inward  across 
the  Pectineus  and  Adductor  longus  muscles,  covered  by  the  fascia  lata,  which  it 
pierces  at  the  inner  border  of  the  thigh,  its  branches  being  distributed,  in  the  male, 
to  the  integument  of  the  scrotum  and  perimeum;  and  in  the  female  to  the  labium, 
anastomosing  with  branches  of  the  superficial  perineal  artery. 

The  Deep  Femoral  or  the  Profunda  Femoris  (a.  profunda  femoris)  (Figs.  430, 
431,  and  432)  nearly  equals  the  size  of  the  superficial  femoral.  It  arises  from  the 
outer  and  back  part  of  the  femoral  artery,  from  one  to  two  inches  below  Poupart's 
ligament.  It  at  first  lies  on  the  outer  side  of  the  superficial  femoral,  and  then 
passes  behind  it  and  the  femoral  vein  to  the  inner  side  of  the  femur,  and,  passing 
downward  beneath  the  Adductor  longus,  terminates  at  the  lower  third  of  the  thigh 
in  a  small  branch  which  pierces  the  Adductor  magnus  (and  from  this  circum- 
stance is  sometimes  called  the  fourth  perforating  artery),  and  is  distributed  to  the 
flexor  muscles  on  the  back  of  the  thigh,  anastomosing  with  branches  of  the 
popliteal  and  inferior  perforating  arteries. 

Relations. — Behind,  it  lies  first  upon  the  Iliacus,  and  then  on  the  Pectineus, 
Adductor  brevis,  and  Adductor  magnus  muscles.  In  front,  it  is  separated  from 
the  superficial  femoral  artery,  above  by  the  femoral  and  profunda  veins,  and 
below  by  the  Adductor  longus.  On  its  outer  side  the  origin  of  the  Vastus  internus 
seoarates  it  from  the  femur. 


THE   SUPERFICIAL    FEMORAL    ARTERY  705 

Plan  of  the  Relations  of  the  Profunda  Artery. 

In  front. 
Superficial  femoral  artery. 
Femoral  and  profunda  veins. 
Adductor  longus. 


Outer  side. 
Vastus  internus. 


Behind.  , 
Iliacus. 
Pectineus. 
Adductor  brevis. 
Adductor  magnus. 

Branches. — The  profunda  gives  off  the  following  named  branches: 

Muscular.  Internal  circumflex. 

External  circumflex.  Four  perforating. 

Muscular  Branches  are  given  off  in  Scarpa's  triangle,  and  also  from  the  vessel  as 
it  lies  between  the  Adductor  muscles. 

The  External  Circumflex  Artery  (a.  circumflexa  femoris  lateralis)  supplies  the 
muscles  on  the  front  of  the  thigh.  It  arises  from  the  outer  side  of  the  profunda, 
passes  horizontally  outward,  between  the  divisions  of  the  anterior  crural  nerve  and 
behind  the  Sartorius  and  Rectus  muscles,  and  divides  into  three  sets  of  branches — 
ascending,  transverse,  and  descending. 

The  ascending  branch  (ramus  ascendens)  passes  upward,  beneath  the  Tensor 
fasciae  femoris  muscle,  to  the  outer  side  of  the  hip,  anastomosing  with  the  terminal 
branches  of  the  gluteal  and  deep  circumflex  iliac  arteries.  It  sends  out  muscular 
branches.  The  descending  branch  {ramus  descendens)  passes  downward,  behind 
the  Rectus,  upon  the  Vasti  muscles,  to  which  its  branches  are  distributed,  one 
or  two  passing  beneath  the  Vastus  externus  as  far  as  the  knee,  anastomosing  with 
the  superior  articular  branches  of  the  popHteal  artery.  These  are  accompanied  by 
the  branch  of  the  anterior  crural  nerve  to  the  Vastus  externus.  The  transverse 
branch,  the  smallest,  passes  outward  over  the  Crureus,  pierces  the  Vastus  externus, 
and  winds  round  the  femur  to  its  back  part,  just  below  the  great  trochanter, 
anastomosing  at  the  back  of  the  thigh  with  the  internal  circumflex,  sciatic,  and 
superior  perforating  arteries. 

The  Internal  Circumflex  Artery  (a.  circumflexa  femoris  medialis),  smaller  than 
the  external,  arises  from  the  inner  and  back  part  of  the  profunda,  and  winds 
round  the  inner  side  of  the  femur,  between  the  Pectineus  and  Psoas  muscles.  On 
reaching  the  upper  border  of  the  Adductor  brevis  it  gives  off  two  muscular  branches, 
one  of  which  passes  inward  to  be  distributed  to  the  Adductor  muscles,  the  Gracilis, 
and  Obturator  externus,  anastomosing  with  the  obturator  artery;  the  other 
descends,  and  passes  beneath  the  x\dductor  brevis,  to  supply  it  and  the  great 
Adductor;  while  the  continuation  of  the  vessel  passes  backward  and  divides  into 
an  ascending  and  a  transverse  branch  (Fig.  348).  The  ascending  branch  {ramus 
profundus)  passes  obliquely  upward  upon  the  tendon  of  the  Obturator  externus 
and  under  cover  of  the  Quadratus  femoris  toward  the  digital  fossa,  where  it 
anastomoses  with  twigs  from  the  gluteal  and  sciatic  arteries.  The  transverse 
branch  (ramus  super ficialis),  larger  than  the  ascending,  appears  between  the 
<5uadratus  femoris  and  upper  border  of  the  Adductor  magnus,  anastomosing  with 
the  sciatic,  external  circumflex,  and  superior  perforating  arteries,  the  crucial  anas- 

45 


706 


THE   BLOOD -VASCULAR   SYSTEM 


tomosis.  Opposite  the  hip-joint  the  artery  gives  off  an  articular  vessel  (ramus 
acetahuli),  which  enters  the  joint  beneath  the  transverse  Hgament;  and,  after  sup- 
plying the  adipose  tissue,  passes  along  the  round  ligament  to  the  head  of  the  bone. 
The  Perforating  Arteries  (Figs.  429,  430,  and  431),  usually  three  in  number,  are 
so  called  from  their  perforating  the  tendon  of  the  Adductor  magnus  muscle  to 


Internal 
saphenous^ 
vein. 


'--Femoral 
artery. 


Fig.  433.- 


-Side  view  of  the  popliteal  artery.     (From  a  preparation  in  the  Museum  of  the  Royal  College  of 

Surgeans  of  England.) 


reach  the  back  of  the  thigh.  They  pass  backward  close  to  the  linea  aspera  of  the 
femur,  under  cover  of  small  tendinous  arches  in  the  Adductor  magnus.  The 
first  is  given  off  above  the  Adductor  brevis,  the  second  in  front  of  that  muscle, 
and  the  third  immediately  below  it. 

The  first  perforating  artery  (a.  perforans  prima)  passes  backward  between  the 
Pectineus  and  Adductor  brevis  (sometimes  perforates  the  latter);  it  then  pierces 


THE  POPLITEAL  SPACE  707 

the  Adductor  magnus  close  to  the  Hnea  aspera.  It  gives  off  branches  which  supply 
the  Adductor  brevis,  the  Adductor  magnus,  the  Biceps,  and  Gluteus  maximus 
muscles,  and  anastomoses  with  the  sciatic,  internal  and  external  circumflex,  and 
middle  perforating  arteries.  The  second  perforating  artery  (a.  perforans  secunda), 
larger  than  the  first,  pierces  the  tendons  of  the  Adductor  brevis  and  Adductor 
magnus  muscles,  and  divides  into  ascending  and  descending  branches,  which 
supply  the  flexor  muscles  of  the  thigh,  anastomosing  with  the  first  and  third 
perforating  arteries.  The  second  artery  frequently  arises  in  common  with  the  first. 
The  nutrient  artery  of  the  femur  is  usually  given  off  from  this  branch.  The  third 
perforating  artery  (a.  perforans  tertia)  is  given  off  below  the  Adductor  brevis;  it 
pierces  the  Adductor  magnus,  and  divides  into  branches  which  supply  the  flexor 
muscles  of  the  thigh ;  anastomosing  above  with  the  higher  perforating  arteries,  and 
below  with  the  terminal  branches  of  the  profunda  and  the  muscular  branches  of 
the  popliteal.  A  fourth  perforating  artery  is  represented  by  the  termination  of  the 
profunda  femoris  artery. 

The  nutritive  artery  of  the  femur  (a.  nutricia  femoris),  if  single,  comes  from  the 
second  perforating  artery;  if  double,  from  the  first  and  third  perforating  arteries. 
If  double,  one  vessel  is  called  superior  and  the  other  inferior. 

Muscular  Branches  (rami  musculares)  are  given  off  from  the  superficial  femoral 
throughout  its  entire  course.  They  vary  from  two  to  seven  in  number,  and  supply 
chiefly  the  Sartorius  and  Vastus  internus. 

The  Anastomotica  Magna  (a.  genu  swprema)  (Figs.  430,431,  and  433)  arises 
from  the  femoral  artery  just  before  it  passes  through  the  tendiVious  opening  in  the 
Adductor  magnus  muscle,  and  immediately  divides  into  a  superficial  and  deep  branch. 

The  Superficial  Branch  {ramus  saphenous)  pierces  the  aponeurotic  covering  of 
Hunter's  canal,  and  accompanies  the  long  saphenous  nerve  to  the  inner  side  of  the 
thigh.  It  passes  between  the  Sartorius  and  Gracilis  muscles,  and,  piercing  the  fascia 
lata,  is  distributed  to  the  integument  of  the  upper  and  inner  part  of  the  leg,  anasto- 
mosing with  the  inferior  internal  articular  artery. 

The  Deep  Branch  (ramus  musculoarticularis)  descends  in  the  substance  of  the 
Vastus  internus,  lying  in  front  of  the  tendon  of  the  Adductor  magnus,  to  the  inner 
side  of  the  knee,  where  it  anastomoses  with  the  superior  internal  articular  artery 
and  the  anterior  recurrent  branch  of  the  anterior  tibial.  A  branch  from  this  vessel 
crosses  outward  above  the  articular  surface  of  the  femur,  forming  an  anastomotic 
arch  with  the  superior  external  articular  artery,  and  supplies  branches  to  the 
knee-joint. 

THE  POPLITEAL  ARTERY  (A.  POPLITEA)  (Figs.  429,  430,  433). 

The  popliteal  artery  commences  at  the  termination  of  the  femoral  at  the 
opening  in  the  Adductor  magnus,  and,  passing  obliquely  downward  and  out- 
ward behind  the  knee-joint  to  the  lower  border  of  the  Popliteus  muscle  divides 
into  the  anterior  and  posterior  tibial  arteries.  A  portion  of  the  artery  lies  in  the 
popliteal  space;  but  above  and  below,  to  a  considerable  extent,  it  is  covered 
by  the  muscles  which  form  the  boundaries  of  the  space,  and  is  therefore  beyond 
the  confines  of  the  hollow. 

The  Popliteal  Space  (Fig.  434). 

Dissection. — A  vertical  incision  about  eight  inches  in  length  should  be  made  along  the  back 
part  of  the  knee-joint,  connected  above  and  below  by  a  transverse  incision  from  the  inner  to  the 
outer  side  of  the  Hmb.  The  flaps  of  integument  included  between  these  incisions  should  be 
reflected  in  the  direction  shown  in  Fig.  345,  page  522. 

Boundaries. — The  popliteal  space,  or  the  ham,  is  a  lozenge-shaped  space, 
widest  at  the  back  part  of  the  knee-joint,  and  deepest  above  the  articular  end  of 


708 


THE   BLOOD -VASCULAR    SYSTEM 


the  femur.  It  is  bounded  externally,  above  the  joint,  by  the  Biceps,  and  below 
the  joint  by  the  Plantaris  and  external  head  of  the  Gastrocnemius.  Internally, 
above  the  joint,  by  the  Semimembranosus,  Semitendinosus,  Gracilis,  and  Sartorius; 

below  the  joint,  by  the  inner  head   of  the 
Gastrocnemius. 

Above,  it  is  limited  by  the  apposition  of  the 
inner  and  outer  hamstring  muscles ;  below,  by 
the  junction  of  the  two  heads  of  the  Gastroc- 
nemius. The  floor  is  formed  by  the  lower 
part  of  the  posterior  surface  of  the  shaft  of 
the  femur,  the  posterior  ligament  of  the  knee- 
joint,  the  upper  end  of  the  tibia,  and  the 
fascia  covering  the  Popliteus  muscle,  and  the 
-Sural  arteries  space  is  covered  in  by  the  fascia  lata. 

Contents. — It  contains  the  popliteal  vessels 
and  their  branches,  together  with  the  termina- 
tion of  the  external  saphenous  vein,  the  in- 
ternal and  external  popliteal  nerves  and  some 
of  their  branches,  the  lower  extremity  of  the 
small  sciatic  nerve,  the  articular  branch  from 
the  obturator  nerve,  a  few  small  lymphatic 
glands,  and  a  considerable  quantity  of  loose 
adipose  tissue. 

Position  of  Contained  Parts. — The  in- 
ternal popliteal  nerve  descends  in  the  middle 
line  of  the  space  lying  superficial  and  cross- 
ing the  artery  from  without  inward.  The 
external  popliteal  nerve  descends  on  the  outer 
side  of  the  upper  part  of  the  space,  lying 
close  to  the  tendon  of  the  Biceps  muscle. 
More  deeply  at  the  bottom  of  the  space  are 
the  popliteal  vessels,  the  vein  lying  superficial 
to  the  artery,  to  which  it  is  closely  united  by 
dense  areolar  tissue  ;  it  is  a  thick-walled 
vessel,  and  lies  at  first  to  the  outer  side  of  the 
artery,  and  then  crosses  it  to  gain  the  inner 
side  below;  sometimes  the  vein  is  double,  the 
artery  lying  between  the  two  venae  comites, 
which  are  usually  connected  by  short  trans- 
verse branches.  INIore  deeply  and,  at  its 
upper  part,  close  to  the  surface  of  the  bone 
is  the  popliteal  artery,  and  passing  off  from 
it  at  right  angles  are  its  articular  branches. 
The  articular  branch  from  the  obturator 
nerve  descends  upon  the  popliteal  artery  to 
supply  the  knee,  and  occasionally  there  is 
found  deep  in  the  space  an  articular  filament 
from  the  great  sciatic  nerve. 

The  popliteal  lymphatic  glands,  four  or 
five  in  number,  are  found  surrounding  the 
artery  ;  one  usually  lies  superficial  to  the 
vessel  ;  another  is  situated  between  it  and 
the  bone,  and  the  rest  are  placed  on  either 

-The  popliteal,  posterior  tibial,  and      oirlp  nf  it 
peroneal  arteries.  blue  Ol    11. 


-Anterior  peroneal. 


434.- 


THE  POPLITEAL  SPACE  709 

The  Popliteal  Artery,  in  its  course  downward  from  the  aperture  in  the  Adductor 
magnus  to  the  lower  border  of  the  PopHteus  muscle,  rests  first  on  the  inner  surface 
of  the  femur,  and  is  then  separated  by  a  Httle  fat  from  the  hollowed  popliteal 
surface  of  the  bone;  in  the  middle  of  its  course  it  rests  on  the  posterior  ligament 
of  the  knee-joint,  and  below  on  the  fascia  covering  the  Popliteus  muscle.  Super- 
ficially, it  is  covered  above  by  the  Semimembranosus;  in  the  middle  of  its  course, 
by  a  quantity  of  fat,  which  separates  it  from  the  deep  fascia  and  integument;  and 
below  it  is  overlapped  by  the  Gastrocnemius,  Plantaris,  and  Soleus  muscles,  the 
popliteal  vein,  and  the  internal  popliteal  nerve.  The  popliteal  vein,  which  is 
intimately  attached  to  the  artery,  lies  superficial  and  external  to  it  above;  it  then 
crosses  it  and  lies  to  its  inner  side.  The  internal  popliteal  nerve  is  still  more 
superficial  and  external  above,  but  below  the  joint  it  crosses  the  artery  and  lies 
on  its  inner  side.  Laterally,  the  artery  is  bounded  by  the  muscles  which  are 
situated  on  either  side  of  the  popliteal  space. 

Plan  of  the  Relations  of  the  Popliteal  Artery. 

In  front. 
Femur. 

Ligamentum  posticum. 
Popliteus. 
Inner  side  /^^       ^  Outer  side. 

Semimembranosus.  /  \  oiceps. 

Internal  condyle  (      P^P'^'-ai      ]  Outer  condyle. 

Gastrocnemius  (inner  head).  V  ''"     /  Gastrocnemius  (outer  head). 

\  /  rlantaris. 

Behind. 
Semimembranosus. 
Fascia. 

Popliteal  vein. 
Internal  popliteal  nerve. 
Gastrocnemius. 
Plantaris. 
Soleus. 

Peculiarities  in  Point  of  Division.— Occasionally  the  popliteal  artery  divides  prematurely 
into  its  terminal  branches;  this  unusual  division  occurs  most  frequently  opposite  the  knee-joint. 
The  anterior  tibial  under  these  circumstances  may  pass  in  front  of  the  Popliteus  muscle. 

Unusual  Branches. — The  artery  sometimes  divides  into  the  anterior  tibial  and  peroneal,  the 
posterior  tibial  being  wanting  or  very  small.  Occasionally  the  popliteal  is  found  to  divide  into 
three  branches,  the  anterior  and  posterior  tibial  and  peroneal. 

Surface  Marking. — The  course  of  the  upper  part  of  the  popliteal  artery  is  indicated  by 
a  line  drawn  from  the  outer  border  of  the  Semimembranosus  muscle  at  the  junction  of  the 
middle  and  lower  third  of  the  thigh  obliquely  downward  to  the  middle  of  the  popliteal  space, 
exactly  behind  the  knee-joint.  From  this  point  it  passes  vertically  downward  to  the  level  of  a 
line  drawn  through  the  lower  part  of  the  tubercle  of  the  tibia. 

Surgical  Anatomy.— The  popliteal  artery  is  not  infrequently  the  seat  of  injury.  It  may  be 
torn  l)y  direct  violence,  as  by  the  passage  of  a  cart-wheel  over  the  knee  or  by  hyper-extension  of 
the  knee;  and  in  the  dead  body,  at  all  events,  the  middle  and  internal  coats  may  be  ruptured  by 
extreme  flexion.  It  may  also  be  lacerated  by  fracture  of  the  lower  part  of  the  shaft  of  the 
femur  or  by  antero-posterior  dislocation  of  the  knee-joint.  It  has  been  torn  in  breaking  down 
adhesions  in  cases  of  fibrous  ankylosis  of  the  knee,  and  is  in  danger  of  being  wounded,  and  in 
fact  has  been  wounded,  in  performing  Macewen's  operation  of  osteotomy  of  the  lower  end  of  the 
femur  for  genu  valgum.  In  addition,  Spencer  records  a  case  in  which  the  popliteal  artery  was 
wounded  from  in  front  by  a  stab  just  below  the  knee,  the  knife  passing  through  the  interosseous 
space.  The  popliteal  artery  is  more  frequently  the  seat  of  aneurism  than  is  any  other  artery 
in  the  body,  with  the  exception  of  the  thoracic  aorta.  This  is  due  no  doubt,  in  a  great  measure, 
to  the  amount  of  movement  to  which  it  is  subjected,  and  to  the  fact  that  it  is  supported  by  loose 
and  lax  tissue  only,  and  not  by  muscles,  as  is  the  case  with  most  arteries. 

Ligature  of  the  popliteal  artery  is  required  in  cases  of  wound  of  that  vessel,  but  for  aneurism 
of  the  posterior  tibial  it  is  preferable  to  tie  the  superficial  femoral.  The  popliteal  may  be  tied 
in  the  upper  or  lower  part  of  its  course;  but  in  the  middle  of  the  ham  the  operation  is  attended 


710  THE   BLOOD -VASCULAR   SYSTEM 

with  considerable  difficulty,  from  the  great  depth  of  the  artery  and  from  the  extreme  degree  of 
tension  of  the  lateral  boundaries  of  the  space. 

In  order  to  expose  the  vessel  in  the  upper  part  of  its  course,  the  patient  should  be  placed 
in  the  supine  position,  with  the  knee  flexed  and  the  thigh  rotated  outward,  so  that  it  rests  on 
its  outer  surface;  an  incision  three  inches  in  length,  beginning  at  the  junction  of  the  middle 
and  lower  third  of  the  thigh,  is  to  be  made  parallel  to  and  immediately  behind  the  tendon  of 
the  Adductor  magnus,  and  the  skin,  superficial  and  deep  fascia  divided.  The  tendon  of  the 
muscle  is  thus  exposed,  and  is  to  be  drawn  forward  and  the  hamstring  tendons  backward.  A 
quantity  of  fatty  tissue  will  now  be  opened  up,  in  which  the  artery  will  be  felt  pulsating.  This 
is  to  be  separated  with  the  point  of  a  director  until  the  artery  is  exposed.  The  vein  and  nerve 
will  not  be  seen,  as  they  lie  to  the  outer  side  of  the  artery.  The  sheath  is  to  be  opened  and 
the  aneurism  needle  passed  from  before  backward,  keeping  its  point  close  to  the  artery  for  fear 
of  injuring  the  vein.  The  only  structure  to  avoid  is  the  long  saphenous  vein  in  the  superficial 
incision.  The  upper  part  of  the  popliteal  artery  may  also  be  tied  by  an  incision  on  the  back  of 
the  limb,  along  the  outer  margin  of  the  Semimembranosus,  but  the  operation  is  a  more  difficult 
one,  as  the  internal  popliteal  nerve  and  the  popliteal  vein  are  first  exposed,  and  great  care  has 
to  be  exercised  in  separating  them  from  the  artery. 

To  expose  the  vessel  in  the  lower  part  of  its  course,  where  the  artery  lies  between  the  two 
heads  of  the  Gastrocnemius,  the  patient  should  be  placed  in  the  prone  position  with  the  limb 
extended.  An  incision  should  then  be  made  through  the  integument  in  the  middle  line,  com- 
mencing opposite  the  bend  of  the  knee-joint,  care  being  taken  to  avoid  the  external  saphenous 
vein  and  nerve.  After  dividing  the  deep  fascia  and  separating  some  dense  cellular  membrane, 
the  artery,  vein,  and  nerve  will  be  exposed,  descending  between  the  two  heads  of  the  Gastrocne- 
mius. Some  muscular  branches  of  the  popliteal  should  be  avoided  if  possible,  or,  if  divided, 
tied  immediately.  The  leg  being  now  flexed,  in  order  the  more  effectually  to  separate  the  two 
heads  of  the  Gastrocnemius,  the  nerve  should  be  drawn  inward  and  the  vein  outward,  and  the 
aneurism  needle  passed  between  the  artery  and  vein  from  without  inward. 

Branches. — The  branches  of  the  popliteal  artery  are — the 

^        ,      f  Superior.  Superior  External  Articular. 

\  Inferior  or  Sural.  Azygos  Articular. 

Cutaneous.  Inferior  Internal  Articular. 

Superior  Internal  Articular.  Inferior  External  Articular. 

The  Superior  Muscular  Branches,  two  or  three  in  number,  arise  from  the 
upper  part  of  the  popliteal  artery,  and  are  distributed  to  the  lower  part  of  the 
Adductor  magnus  and  flexor  muscles  of  the  thigh,  anastomosing  with  the  fourth 
perforating  branch  of  the  profunda. 

The  Inferior  Muscular  {aa.  surales)  are  two  large  branches  which  are  dis- 
tributed to  the  two  heads  of  the  Gastrocnemius  and  to  the  Plantaris  muscle.  They 
arise  from  the  popliteal  artery  opposite  the  knee-joint. 

The  Cutaneous  Branches  arise  separately  from  the  popliteal  artery  or  from 
some  of  its  branches;  they  descend  between  the  two  heads  of  the  Gastrocnemius 
muscle,  and,  piercing  the  deep  fascia,  are  distributed  to  the  integument  of  the 
calf.  One  branch  usually  accompanies  the  short,  or  external,  saphenous  vein, 
the  superficial  sural  artery. 

The  Superior  Articular  Arteries,  two  in  number,  arise  one  on  each  side  of  the 
popliteal,  and  wind  round  the  femur  immediately  above  its  condyles  to  the  front 
of  the  knee-joint.  The  internal  branch  (a.  genu  superior  medialis)  winds  inward 
beneath  the  hamstring  muscles,  to  which  it  supplies  branches,  above  the  inner 
head,  of  the  Gastrocnemius,  and,  passing  beneath  the  tendon  of  the  Adductor 
magnus,  divides  into  two  branches,  one  of  which  supplies  the  Vastus  internus, 
inosculating  with  the  anastomotica  magna  and  inferior  internal  articular;  the  other 
ramifies  close  to  the  surface  of  the  femur,  supplying  it  and  the  knee-joint,  and  an- 
astomosing with  the  superior  external  articular  artery.  This  branch  is  frequently 
of  small  size,  a  condition  which  is  associated  with  an  increase  in  the  size  of  the  an- 
astomotica magna.  The  external  branch  (a.  genu  superior  lateralis)  passes  above 
the  outer  condyle,  beneath  the  tendon  of  the  Biceps,  and  divides  into  a  superficial 
and  deep  branch:  the  superficial  branch  supplies  the  Vastus  externus,  and  anasto- 


i 


» 


TMU   ANTERIOR    TIBIAL    ARTERY  711 

moses  with  the  descending  branch  of  the  external  circumflex  and  the  inferior  exter- 
nal articular  arteries;  the  deep  branch  supplies  the  lower  part  of  the  femur  and 
knee-joint,  and  forms  an  anastomotic  arch  across  the  bone  with  the  anastomotica 
magna  and  the  inferior  internal  articular  arteries. 

The  Azygos  Articular  (a.  genu  media)  is  a  small  branch  arising  from  the  pop- 
liteal artery  opposite  the  bend  of  the  knee-joint.  It  pierces  the  posterior  ligament, 
and  supplies  the  ligaments  and  synovial  membrane  in  the  interior  of  the  articu- 
lation. 

The  Inferior  Articular  Arteries,  two  in  number,  arise  from  the  popliteal 
beneath  the  Gastrocnemius,  and  wind  round  the  head  of  the  tibia  below  the  joint. 
The  internal  branch  (a.  genu  inferior  medialis)  first  descends  along  the  upper  mar- 
gin of  the  Popliteus  muscle,  to  which  it  gives  branches;  it  then  passes  below  the 
inner  tuberosity,  beneath  the  internal  lateral  ligament,  at  the  anterior  border  of 
which  it  ascends  to  the  front  and  inner  side  of  the  joint,  to  supply  the  head  of  the 
tibia  and  the  articulation  of  the  knee,  anastomosing  with  the  inferior  external 
articular  and  superior  internal  articular  arteries.  The  external  branch  (a.  genu 
inferior  lateralis)  passes  outward  above  the  head  of  the  fibula,  to  the  front  of  the 
knee-joint,  passing  in  its  course  beneath  the  outer  head  of  the  Gastrocnemius,  the 
external  lateral  ligament,  and  the  tendon  of  the  Biceps  muscle,  and  divides  into 
branches  which  anastomose  with  the  inferior  internal  articular  artery,  the  superior 
external  articular  artery,  and  the  anterior  recurrent  branch  of  the  anterior  tibial. 

Circumpatellar  Anastomosis. — Around  and  above  the  patella,  and  on  the  con- 
tiguous ends  of  the  femur  and  tibia,  is  a  large  network  of  vessels,  forming  a  super- 
ficial and  a  deep  plexus.  The  superficial  plexus  is  situated  between  the  fascia  and 
skin  round  about  the  patella;  the  deep  plexus,  which  forms  a  close  network  of 
vessels,  lies  on  the  surface  of  the  lower  end  of  the  femur  and  upper  end  of  the 
tibia  around  their  articular  surfaces,  and  sends  numerous  offsets  into  the  interior 
of  the  joint.  The  arteries  from  which  this  plexus  is  formed  are  the  two  internal  and 
two  external  articular  branches  of  the  popliteal,  the  anastomotica  magna,  the  ter- 
minal branch  of  the  profunda,  the  descending  branch  from  the  external  circumflex 
and  the  anterior  recurrent  branch  of  the  anterior  tibial. 

The  Anterior  Tibial  Artery  (A.  Tibialis  Anterior)   (Fig.  435). 

The  anterior  tibial  artery  commences  at  the  bifurcation  of  the  popliteal  at 
the  lower  border  of  the  Popliteus  muscle,  passes  forward  between  the  two 
heads  of  the  Tibialis  posticus,  and  through  the  large  oval  aperture  above  the 
upper  border  of  the  interosseous  membrane  to  the  deep  part  of  the  front  of  the 
leg;  it  here  lies  close  to  the  inner  side  of  the  neck  of  the  fibula;  it  then  descends  on 
the  anterior  surface  of  the  interosseous  membrane,  gradually  approaching  the 
tibia;  and  at  the  lower  part  of  the  leg  lies  on  this  bone,  and  then  on  the  anterior 
ligament  of  the  ankle  to  the  bend  of  the  ankle-joint,  where  it  lies  more  superficially, 
and  becomes  the  dorsalis  pedis. 

Relations. — In  the  upper  two-thirds  of  its  extent  it  rests  upon  the  interosseous 
membrane,  to  which  it  is  connected  by  delicate  fibrous  arches  thrown  across  it; 
in  the  lower  third,  upon  the  front  of  the  tibia  and  the  anterior  ligament  of  the 
ankle-joint.  In  the  upper  third  of  its  course  it  lies  between  the  Tibialis  anticus 
and  Extensor  longus  digitorum;  in  the  middle  third,  between  the  Tibialis  anticus 
and  Extensor  proprius  hallucis.  At  the  bend  of  the  ankle  it  is  crossed  by  the 
tendon  of  the  Extensor  proprius  hallucis,  and  lies  between  it  and  the  innermost 
tendon  of  the  Extensor  longus  digitorum.  It  is  covered,  in  the  upper  two- 
thirds  of  its  course,  by  the  muscles  which  lie  on  either  side  of  it  and  by  the 
deep  fascia  ;  in  the  lower  third,  by  the  integument,  anterior  annular  ligament, 
and  fascia. 


712  THE  BLOOD -VASCULAR    SYSTEM 

The  anterior  tibial  artery  is  accompanied  by  two  veins,  venae  comites,  which 
lie  one  on  each  side  of  the  artery;  the  anterior  tibial  nerve,  coursing  round  the 
outer  side  of  the  neck  of  the  fibula,  comes  into  relation  with  the  outer  side  of  the 
artery  shortly  after  it  has  passed  through  the  opening  in  the  interosseous  mem- 
brane; about  the  middle  of  the  leg  it  is  placed  superficial  to  it;  at  the  lower  part 
of  the  artery  the  nerve  is  generally  again  on  the  outer  side. 

Plan  of  the  Relations  of  the  Anterior  Tibial  Artery. 

In  front. 

Integument,  superficial  and  deep  fasciae. 

Anterior  tibial  nerve. 

Tibialis  anticus  (overlaps  it  in  the  upper  part  of  the  leg). 

Extensor  longus  digitorum  I     .        ,       .     i-p,ux|  n 

Extensor  proprius  hallucis  )    ^  "         o     JJ- 

Anterior  annular  ligament. 

Inner  side.  /  \  Outer  side. 

Tibialis  anticus.  [      Anterior     \  Anterior  tibial  nerve. 

Extensor  proprius  hallucis  i       Tibial.        I  Extensor  longus  digitorum. 

(crosses  it  at  its   lower  V  /  Extensor  proprius  hallucis. 

part).  -~ -^ 

Behind. 

Interosseous  membrane. 

Tibia. 

Anterior  ligament  of  ankle-joint. 

Peculiaxities  in  Size. — ^This  vessel  may  be  very  small,  may  be  deficient  to  a  greater  or  less 
extent,  or  may  be  entirely  vi^anting,  its  place  being  supplied  by  perforating  branches  from  the 
posterior  tibial  or  by  the  anterior  division  of  the  peroneal  artery. 

Course. — The  artery  occasionally  deviates  in  its  course  toward  the  fibular  side  of  the  leg, 
regaining  its  usual  position  beneath  the  annular  ligament  at  the  front  of  the  ankle.  In  two 
instances  the  vessel  has  been  found  to  approach  the  surface  in  the  middle  of  the  leg,  being  covered 
merely  by  the  integument  and  fascia  below  that  point. 

Surface  Marking. — Draw  a  line  from  the  inner  side  of  the  head  of  the  fibula  to  midway 
between  the  two  malleoli.  In  this  line  take  a  point  one  inch  and  a  quarter  below  the  head  of 
the  fibula,  and  the  portion  of  the  line  below  this  point  will  mark  the  course  of  the  artery. 

Surgical  Anatomy.— The  anterior  tibial  artery  may  be  tied  in  the  upper  or  lower  part  of 
the  leg.  In  the  upper  part  the  operation  is  attended  with  great  difficulty,  on  account  of  the 
depth  of  the  vessel  from  the  surface.  An  incision,  about  four  inches  in  length,  should  be  made 
through  the  integument,  midway  between  the  spine  of  the  tibia  and  the  outer  margin  of  the 
fibula,  and  the  deep  fascia  exposed.  The  wound  must  now  be  carefully  dried,  its  edges  retracted, 
and  the  white  line  separating  the  Tibialis  anticus  from  the  Extensor  longus  digitorum  sought 
for.  When  this  has  been  clearly  defined,  the  deep  fascia  is  to  be  divided  in  this  line,  and  the 
Tibialis  anticus  separated  from  adjacent  muscles  with  the  handle  of  the  scalpel  or  a  director  until 
the  interosseous  membrane  is  reached.  The  foot  is  to  be  flexed  in  order  to  relax  the  muscles,  and 
upon  drawing  them  apart  the  artery  will  be  found  lying  on  the  interosseous  membrane  with  the 
nerve  on  its  outer  side  or  on  the  top  of  the  artery.  The  nerve  should  be  drawn  outward,  and 
the  venae  comites  separated  from  the  artery  and  the  needle  passed  round  it. 

To  tie  the  vessel  in  the  lower  third  of  the  leg  above  the  ankle-joint  an  incision  about  three 
inches  in  length  should  be  made  through  the  integument  between  the  tendons  of  the  Tibialis 
anticus  and  Extensor  proprius  hallucis  muscles,  the  deep  fascia  being  divided  to  the  same  extent. 
The  tendon  on  either  side  should  be  held  aside,  when  the  vessel  will  be  seen  lying  upon  the 
tibia,  with  the  nerve  on  the  outer  side  and  one  of  the  venae  comites  on  either  side. 

Branches. — The  branches  of  the  anterior  tibial  artery  are — the 

Posterior  Recurrent  Tibial.  Muscular. 

Superior  Fibular.  Internal  Malleolar. 

Anterior  Recurrent  Tibial.  External  Malleolar. 


THE  ANTERIOR    TIBIAL    ARTERY 


713 


Inferior  xnierndl 
articular. 


The  Posterior  Recurrent  Tibial 

(a.  recurrens  tibialis  posterior)  is  not 
a  constant  branch,  and  is  given  off 
from  the  anterior  tibial  before  that 
vessel  passes  through  the  interosse- 
ous space.  It  ascends  beneath  the 
Popliteus  muscle,  which  it  supplies, 
and  anastomoses  with  the  lower 
articular  branches  of  the  popliteal 
artery,  giving  off  an  offset  to  the 
superior  tibio-fibular  joint. 

The  Superior  Fibular  is  some- 
times given  off  from  the  anterior 
tibial,  sometimes  from  the  posterior 
tibial.  It  passes  outward,  round 
the  neck  of  the  fibula,  through  the 
Soleus,  which  it  supplies,  and  ends 
in  the  substance  of  the  Peroneus 
longus  muscle. 

The  Anterior  Recurrent  Tibial 
(a.  recurrens  tibialis  anterior)  arises 
from  the  anterior  tibial  as  soon  as 
that  vessel  has  passed  through  the 
interosseous  space;  it  ascends  in  the 
Tibialis  anticus  muscle,  and  ramifies 
on  the  front  and  sides  of  the  knee- 
joint,  anastomosing  with  the  artic- 
ular branches  of  the  popliteal,  with 
the  anastomotica  magna,  and  the 
external  articular  branches  of  the 
popliteal,  assisting  in  the  formation 
of  the  circumpatellar  plexus. 

The  Muscular  Branches  are 
numerous  ;  they  are  distributed  to 
the  muscles  which  lie  on  each  side 
of  the  vessel,  some  cutaneous  branches 
piercing  the  deep  fascia  to  supply 
the  integument,  others  passing 
through  the  interosseous  membrane, 
and  anastomosing  with  branches 
of  the  posterior  tibial  and  peroneal 
arteries. 

The  Malleolar   Arteries    supply 

the  ankle-joint.     The  internal  branch 

(a.     malleolaris     anterior     medialis) 

arises  about   two    inches    above  the 

articulation,  and  passes  beneath  the 

tendons   of    the    Extensor    proprius 

hallucis   and   Tibialis  anticus  to  the 

inner  ankle,  upon  which  it  ramifies, 

'~1  anastomosing  with  branches  of   the 

/  posterior  tibial  and  internal  plantar  arteries  and  with  the   internal  calcanean 

V^from  the  posterior  tibial.     The  external  branch  (a.  malleolaris  anterior  lateralis) 

passes   beneath  the  tendons  of  the  Extensor  longus   digitorum   and  Peroneus 


Communicating. 


Fig.  435. — Surgical  anatomy  of  the  anterior  tibial 
and  dorsalis  pedis  arteries. 


714 


THE  BLOOD -VASCULAR  SYSTEM 


tertius,  and  supplies  the  outer  ankle,  anastomosing  with  the  anterior  peroneal 
artery  and  with  ascending  branches  from  the  tarsal  branch  of  the  dorsalis 
pedis. 

The  Dorsalis  Pedis  Artery  (A.  Dorsalis  Pedis)  (Figs.  435,  436). 

The  dorsalis  pedis,  the  continuation  of  the  anterior  tibial,  passes  forward  from 
the  bend  of  the  ankle  along  the  tibial  side  of  the  foot  to  the  back  part  of  the  first 
intermetatarsal  space,  where  it  divides  into  two  branches,  the  dorsalis  hallucis  and 
communicating. 


ANTERIOR 

PERONEAL' 

ARTERY 


EXTERNAL 

MALLEOLAR 

ARTERY 


METATARSAL 
ARTERY 


DORSAL 
INTEROSSEOUS 


INTERNAL 

MALLEOLAR 

ARTERY 


DORSALIS  PEDIS 
ARTERY 


COMMUNICATING 
ARTERY 

DORSALIS 
HALLUCIS 
ARTERY 


Fig.  436. — Diagram  of  the  arteries  of  the  dorsal  surface  of  the  foot.     (Poirier  and  Charpy.) 


Relations. — ^This  vessel,  in  its  course  forward,  rests  upon  the  astragalus,  navic- 
ular, and  middle  cuneiform  bones  and  the  ligaments  connecting  them,  being  cov- 
ered by  the  integument  and  fascia,  anterior  annular  ligament,  and  crossed  near 
its  termination  by  the  innermost  tendon  of  the  Extensor  brevis  digitorum.  On 
its  tibial  side  is  the  tendon  of  the  Extensor  proprius  hallucis;  on  its  fibular  side, 
the  innermost  tendon  of  the  Extensor  longus  digitorum,  and  the  termination  of 
the  anterior  tibial  nerve.    It  is  accompanied  by  two  veins. 


THE    DOBSALIS  PEDIS  ABTEJRY  715 

Plan  of  the  Relations  of  the  Dorsalis  Pedis  Artery. 

In  front. 
Integument  and  fascia. 
Anterior  annular  ligament. 
Innermost  tendon  of  Extensor  brevis  digitorum. 

Tibial  side.  I  \  Fibular  side. 

Extensor  proprius  hallucis.  I        pedis.       )  Extensor  longus  digitorum. 

\  /  Anterior  tibial  nerve. 

Behind. 
Astragalus. 
Navicular. 
Middle  cuneiform. 
And  their  ligaments. 

Peculiarities  in  Size. — The  dorsal  artery  of  the  foot  may  be  larger  than  usual,  to  compen- 
sate for  a  deficient  plantar  artery;  or  it  may  be  deficient  in  its  terminal  branches  to  the  toes, 
which  are  then  derived  from  the  internal  plantar;  or  its  place  may  be  supplied  altogether  by  a 
large  anterior  peroneal  artery. 

Position. — This  artery  frequently  curves  outward,  lying  external  to  the  line  between  the 
middle  of  the  ankle  and  the  back  part  of  the  first  interosseous  space. 

Surface  Marking. — The  dorsalis  pedis  artery  is  indicated  on  the  surface  of  the  dorsum  of 
the  foot  by  a  line  drawn  from  the  centre  of  the  space  between  the  two  malleoli  to  the  back  of  the 
first  intermetatarsal  space. 

Surgical  Anatomy. — This  artery  may  be  tied,  by  making  an  incision  through  the  integu- 
ment between  two  and  three  inches  in  length,  on  the  fibular  side  of  the  tendon  of  the  Extensor 
proprius  hallucis,  in  the  interval  between  it  and  the  inner  border  of  the  short  Extensor  muscle. 
The  incision  should  not  extend  farther  forward  than  the  back  part  of  the  first  intermetatarsal 
space,  as  the  artery  divides  in  that  situation.  The  deep  fascia  being  divided  to  the  same  extent, 
the  artery  will  be  exposed,  the  nerve  lying  upon  its  outer  side. 

Branches. — The  branches  of  the  dorsalis  pedis  are — the 

Cutaneous.  Metatarsal — Interosseous. 

Tarsal.  Dorsalis  Hallucis. 

Communicating. 

Cutaneous  Branches  go  to  the  skin  of  the  dorsum  and  inner  surface  of  the 
foot. 

The  Tarsal  Artery  (a.  tarsea  lateralis)  arises  from  the  dorsalis  pedis,  as  that 
vessel  crosses  the  navicular  bone;  it  passes  in  an  arched  direction  outward,  lying 
upon  the  tarsal  bones,  and  covered  by  the  Extensor  brevis  digitorum;  it  supplies 
that  muscle  and  the  articulations  of  the  tarsus,  and  anastomoses  with  branches 
from  the  metatarsal,  external  malleolar,  peroneal,  and  external  plantar  arteries. 

The  Metatarsal  (a.  arcuata)  arises  a  little  anterior  to  the  preceding;  it  passes 
outward  to  the  outer  part  of  the  foot,  over  the  bases  of  the  metatarsal  bones, 
beneath  the  tendons  of  the  short  Extensor,  its  direction  being  influenced  by  its 
point  of  origin;  and  it  anastomoses  with  the  tarsal  and  external  plantar  arteries. 
This  vessel  gives  off  three  branches,  the  dorsal  interosseous  arteries  {aa.  meta- 
tarsece  dorsales),  which  pass  forward  upon  the  three  outer  Dorsal  interossei  mus- 
cles, and,  in  the  clefts  between  the  toes,  divide  into  two  dorsal  collateral  branches 
for  the  adjoining  toes  {aa.  digitales  dorsales).  At  the  back  part  of  each  inter- 
osseous space  these  vessels  receive  the  posterior  perforating  branches  from  the 
plantar  arch,  and  at  the  forepart  of  each  interosseous  space  they  are  joined  by 
the  anterior  perforating  branches  from  the  digital  arteries.  The  outermost 
interosseous  artery  gives  off  a  branch  which  supplies  the  outer  side  of  the  little 
toe. 


716  THE  BLOOD -VASCULAR   SYSTEM 

The  Dorsalis  Hallucis  or  the  First  Dorsal  Interosseous  (a.  dorsalis  hallucis)  is  one 
of  the  terminal  branches  of  the  dorsalis  pedis.  It  runs  forward  along  the  outer 
border  of  the  first  metatarsal  bone,  and  at  the  cleft  between  the  first  and  second 
toes  divides  into  two  branches,  one  of  which  passes  inward,  beneath  the  tendon  of 
the  Extensor  proprius  hallucis,  and  is  distributed  to  the  inner  border  of  the  great 
toe;  the  outer  branch  bifurcates,  to  supply  the  adjoining  sides  of  the  great  and 
second  toes. 

The  Communicating  Artery  {ramus  plantaris  profwidus),  the  other  terminal 
branch  of  the  dorsalis  pedis,  dips  down  into  the  sole  of  the  foot,  between  the  two 
heads  of  the  First  dorsal  interosseous  muscle,  and  inosculates  with  the  termina- 
tion of  the  external  plantar  artery,  to  complete  the  plantar  arch.  It  here  gives 
off  its  plantar  digital  branch,  which  is  named  the  arteria  magna  hallucis,  or  the 
princeps  hallucis.  This  artery  passes  forward  along  the  first  interosseous  space, 
and,  after  sending  a  branch  along  the  inner  side  of  the  great  toe,  bifurcates  for 
the  supply  of  the  adjacent  sides  of  the  great  and  second  toes. 

The  Posterior  Tibial  Artery  (A.  Tibialis  Posterior)  (Fig.  434). 

The  posterior  tibial  is  an  artery  of  large  size,  which  extends  obliquely  down- 
ward from  the  lower  border  of  the  Popliteus  muscle,  along  the  tibial  side  of  the 
leg,  to  the  fossa  between  the  inner  ankle  and  the  heel,  where  it  divides  beneath 
the  origin  of  the  Abductor  hallucis,  on  a  level  with  a  line  drawn  from  the  point 
of  the  internal  malleolus  to  the  centre  of  the  convexity  of  the  heel,  into  the 
internal  and  external  plantar  arteries.  At  its  origin  it  lies  opposite  the  interval 
between  the  tibia  and  fibula;  as  it  descends,  it  approaches  the  inner  side  of 
the  leg,  lying  behind  the  tibia,  and,  in  the  lower  part  of  its  course,  is  situated 
midway  between  the  inner  malleolus  and  the  tuberosity  of  the  os  calcis. 

Relations. — It  lies  successively  upon  the  Tibialis  posticus,  the  Flexor  longus 
digitorum,  the  tibia,  and  the  back  part  of  the  ankle-joint.  It  is  covered  by  the 
deep  transverse  fascia,  which  separates  it  above  from  the  Gastrocnemius  and 
Soleus  muscles:  at  its  termination  it  is  covered  by  the  Abductor  hallucis  muscle. 
In  the  lower  third,  where  it  is  more  superficial,  it  is  covered  only  by  the  integu- 
ment and  fascia,  and  runs  parallel  with  the  inner  border  of  the  tendo  Achillis. 
It  is  accompanied  by  two  veins  and  by  the  posterior  tibial  nerve,  which  lies  at 
first  to  the  inner  side  of  the  artery,  but  soon  crosses  it,  and  is,  in  the  greater  part 
of  its  course,  on  its  outer  side. 

Plan  of  the  Relations  of  the  Posterior  Tibial  Artery. 

In  front. 
Tibialis  posticus. 
Flexor  longus  digitorum. 
Tibia. 
Ankle-joint. 
Inner  side.  Outer  side. 

Posterior  tibial  nerve,  Posterior  tibial  nerve, 

upper  third.  lower  two-thirds. 

Behind. 
Integument  and  fascia. 
Gastrocnemius. 
Soleus. 

Deep  transverse  fascia. 
Posterior  tibial  nerve. 
Abductor  hallucis. 

Behind  the  inner  ankle  the  tendons  and  blood-vessels  are  arranged,  under 
cover  of  the  internal  annular  ligament,  in  the  following  order,  from  within  out- 


THE  POSTERIOR    TIBIAL    ARTERY  'JYJ 

ward:  First,  the  tendons  of  the  Tibiahs  posticus  and  Flexor  longus  digitorum, 
lying  in  the  same  groove,  behind  the  inner  malleolus,  the  former  being  the  most 
internal.  External  to  these  is  the  posterior  tibial  artery,  having  a  vein  on  either 
side:  and,  still  more  externally,  the  posterior  tibial  nerve.  About  half  an  inch 
nearer  the  heel  is  the  tendon  of  the  Flexor  longus  hallucis. 

Peculiarities  in  Size. — The  posterior  tibial  is  not  unfrequently  smaller  than  usual,  or  absent, 
its  place  being  suppHed  by  a  large  peroneal  artery  which  passes  inward  at  the  lower  end  of  the 
tibia,  and  either  joins  the  small  tibial  artery  or  continues  alone  to  the  sole  of  the  foot. 

Surface  Marking. — The  course  of  the  posterior  tibial  artery  is  indicated  by  a  line  drawn  from 
a  point  one  inch  below  the  centre  of  the  popliteal  space  to  midway  between  the  tip  of  the 
internal  malleolus  and  the  centre  of  the  convexity  of  the  heel. 

Surgical  Anatomy. — The  application  of  a  ligature  to  the  posterior  tibial  may  be  required 
in  cases  of  wound  of  the  sole  of  the  foot  attended  with  great  hemorrhage,  when  the  vessel 
should  be  tied  at  the  inner  anlvle.  In  cases  of  wound  of  the  posterior  tibial  it  will  be  necessary 
to  enlarge  the  opening  so  as  to  expose  the  vessel  at  the  wounded  point,  excepting  where  the 
vessel  is  injured  by  a  punctured  wound  from  the  front  of  the  leg.  In  cases  of  aneurism  from 
wound  of  the  artery  low  down,  the  vessel  should  be  tied  in  the  middle  of  the  leg.  But  in  aneurism 
of  the  posterior  tibial  high  up  it  would  be  better  to  tie  the  femoral  artery. 

To  tie  the  posterior  tibial  artery  at  the  ankle,  a  semilunar  incision,  convex  backward,  should 
be  made  through  the  integument,  about  two  inches  and  a  half  in  length,  midway  between  the 
heel  and  the  inner  ankle  or  a  little  nearer  the  latter.  The  subcutaneous  cellular  tissue  having  been 
divided,  a  strong  and  dense  fascia,  the  internal  annular  ligament,  is  exposed.  This  ligament  is 
continuous  above  with  the  deep  fascia  of  the  leg,  covers  the  vessels  and  nerves,  and  is  intimately 
adherent  to  the  sheaths  of  the  tendons.  This  having  been  cautiously  divided  upon  a  director, 
the  sheath  of  the  vessels  is  exposed,  and,  being  opened,  the  artery  is  seen  with  one  of  the  venae 
comites  on  each  side.  The  aneurism  needle  should  be  passed  round  the  vessel  from  the  heel 
toward  the  ankle,  in  order  to  avoid  the  posterior  tibial  nerve,  care  being  at  the  same  time  taken 
not  to  include  the  vente  comites. 

The  vessel  may  also  be  tied  in  the  lower  third  of  the  leg  by  making  an  incision,  about  three 
inches  in  length,  parallel  with  the  inner  margin  of  the  tendo  Achillis.  The  internal  saphenous 
vein  being  carefully  avoided,  the  Iwo  layers  of  fascia  must  be  divided  upon  a  director,  when  the 
artery  is  exposed  along  the  outer  margin  of  the  Flexor  longus  digitorum,  with  one  of  its  vense 
comites  on  either  side  and  the  nerve  lying  external  to  it. 

To  tie  the  posterior  tibial  in  the  middle  of  the  leg  is  a  very  difficult  operation,  on  account  of 
the  great  depth  of  the  vessel  from  the  surface.  The  patient  being  placed  in  the  recumbent  posi- 
tion, the  injured  limb  should  rest  on  its  outer  side,  the  knee  being  partially  bent  and  the  foot 
extended,  so  as  to  relax  the  muscles  of  the  calf.  An  incision  about  four  inches  in  length  should 
then  be  made  through  the  integument  a  finger's  breadth  behind  the  inner  margin  of  the  tibia, 
taking  care  to  avoid  the  internal  saphenous  vein.  The  deep  fascia  having  been  divided,  the 
margin  of  the  Gastrocnemius  is  exposed,  and  must  be  drawn  aside,  and  the  tibial  attachment  of 
the  Soleus  divided,  a  director  being  previously  passed  beneath  it.  The  artery  may  now  be 
felt  pulsating  beneath  the  deep  fascia  about  an  inch  from  the  margin  of  the  tibia.  The  fascia 
having  been  divided,  and  the  limb  placed  in  such  a  position  as  to  relax  the  muscles  of  the  calf 
as  much  as  possible,  the  veins  should  be  separated  from  the  artery,  and  the  aneurism  needle 
passed  round  the  vessel  from  without  inward,  so  as  to  avoid  wounding  the  posterior  tibial  nerve. 

Branches. — The  branches  of  the  posterior  tibial  artery  are — the 

Peroneal.  Cutaneous. 

Nutrient.  Communicating. 

Muscular.  Internal  Calcanean. 

Malleolar  cutaneous. 

The  Peroneal  Artery  (a.  peroncBo)  (Fig.  434)  lies,  deeply  seated,  along  the  back 
part  of  the  fibular  side  of  the  leg.  It  arises  from  the  posterior  tibial  about  an  inch 
below  the  lower  border  of  the  Popliteus  muscle,  passes  obliquely  outward  to  the 
fibula,  and  then  descends  along  the  inner  border  of  that  bone,  contained  in  a 
fibrous  canal  between  the  Tibialis  posticus  and  the  Flexor  longus  hallucis,  or  in 
the  substance  of  the  latter  muscle  to  the  lower  third  of  the  leg,  where  it  gives  off 
the  anterior  peroneal.  It  then  passes  across  the  articulation  between  the  tibia  and 
fibula  to  the  outer  side  of  the  os  calcis,  where  it  gives  off  its  terminal  branches,  the 
external  calcanean. 


718  THE  BLOOD -VASCULAR   SYSTEM 

Relations.— This  vessel  rests  at  first  upon  the  TibiaHs  posticus,  and  then,  for 
the  greater  part  of  its  course,  in  a  fibrous  canal  between  the  origins  of  the  Flexor 
longus  hallucis  and  Tibialis  posticus,  covered  or  surrounded  by  the  fibres  of  the 
Flexor  longus  hallucis.  It  is  covered,  in  the  upper  part  of  its  course,  by  the  Soleus 
and  deep  transverse  fascia;  helow,  by  the  Flexor  longus  hallucis. 

Plan  of  the  Relations  of  the  Peroneal  Artery. 

In  front. 

Tibialis  posticus. 
Flexor  longus  hallucis. 

Outer  side.  f  \  Jnn^r  side. 

Fibula.  I      ^»*T"!f^      I  Flexor  longus  hallucis. 

Flexor  longus  hallucis. 

Behind. 
Soleus. 

Deep  transverse  fascia. 
Flexor  longus  hallucis. 

Peculiarities  in  Origin. — The  peroneal  artery  may  arise  three  inches  below  the  Popliteus, 
or  from  the  posterior  tibial  high  up,  or  even  from  the  popliteal. 

Its  size  is  more  frequently  increased  than  diminished ;  and  then  it  either  reinforces  the  poste- 
rior tibial  by  its  junction  with  it,  or  altogether  takes  the  place  of  the  posterior  tibial  in  the  lower 
part  of  the  leg  and  foot,  the  latter  vessel  only  existing  as  a  short  muscular  branch.  In  those 
rare  cases  where  the  peroneal  artery  is  smaller  than  usual  a  branch  from  the  posterior  tibial 
supplies  its  place,  and  a  branch  from  the  anterior  tibial  compensates  for  the  diminished  anterior 
peroneal  artery.     In  one  case  the  peroneal  artery  has  been  found  entirely  wanting. 

The  anterior  peroneal  is  sometimes  enlarged,  and  takes  the  place  of  the  dorsal  artery  of  the 
foot. 

Branches. — ^The  branches  of  the  peroneal  are — the 

Muscular.  Communicating. 

Nutrient.  Posterior  Peroneal. 

Anterior  Peroneal.  External  Calcanean. 

Muscular  Branches. — The  peroneal  artery  in  its  course  gives  off  branches  to  the 
Soleus,  Tibialis  posticus.  Flexor  longus  hallucis,  and  Peronei  muscles. 

The  Nutrient  Artery  (a.  nutritia  fibulcB)  supplies  the  fibula. 

The  Anterior  Peroneal  (ramus  perforans)  (Fig.  436)  pierces  the  interosseous 
membrane,  about  two  inches  above  the  outer  malleolus,  to  reach  the  forepart  of 
the  leg,  and,  passing  down  beneath  the  Peroneus  tertius  to  the  outer  ankle,  ramifies 
on  the  front  and  outer  side  of  the  tarsus,  anastomosing  with  the  external  malleolar 
and  tarsal  arteries. 

The  Communicating  (ramus  communicans)  is  given  off  from  the  peroneal  about 
an  inch  from  its  lower  end,  and,  passing  inward,  joins  the  communicating  branch 
of  the  posterior  tibial. 

The  Posterior  Peroneal  passes  down  behind  the  outer  ankle  to  the  back  of  the 
external  malleolus,  to  terminate  in  branches  which  ramify  on  the  outer  surface 
and  back  of  the  os  calcis. 

External  Calcanean  (ramus  calcaneus  lateralis)  are  the  terminal  branches  of  the 
peroneal  artery;  they  pass  to  the  outer  side  of  the  heel,  and  communicate  with  the 
external  malleolar,  and,  on  the  back  of  the  heel,  with  the  internal  calcanean 
arteries. 

Cutaneous  Branches  come  from  the  posterior  tibial  and  supply  the  skin  of 
the  inner  side  and  back  of  the  leg. 


THE   POSTERIOR    TIBIAL    ARTERY 


719 


The  Nutrient  Artery  of  the  tibia  (a.  nutricia  tibioe)  arises  from  the  posterior 
tibial  near  its  origin,  and,  after  supplying  a  few  muscular  branches,  enters  the 
nutrient  canal  of  that  bone,  which  it  traverses  obliquely  from  above  downward. 
This  is  the  largest  nutrient  artery  of  bone  in  the  body. 

The  Muscular  Branches  of  the  posterior  tibial  are  distributed  to  the  Soleus  and 
deep  muscles  along  the  back  of  the  leg. 

The  Communicating  Branch  (ramus  communicafis),  to  join  a  similar  branch 
of  the  peroneal,  runs  transversely  across  the  back  of  the  tibia,  about  two  inches 
above  its  lower  end,  passing  beneath  the  Flexor  longus  hallucis. 

The  Malleolar  or  Internal  Malleolar  (a.  malleolaris  posterior  medialis)  lies 
upon  the  tibia,  sends  branches  over  the  inner  ankle,  and  anastomoses  with  the 
inner  malleolar  branch  of  the  anterior  tibial. 

The  Internal  Galcanean  (rami  calcanei  mediates)  are  several  large  arteries 
which  arise  from  the  posterior  tibial  just  before  its  division:  they  are  distributed 


Communicating 

branch  of 
dorsalis  pedis. 
Its  digital 
branches. 


Fig.  437. — The  plantar  arteries.     Superficial  view. 


Fig.  438. — The  plantar  artenes.     Deep  view. 


to  the  fat  and  integument  behind  the  tendo  Achillis  and  about  the  heel,  and  to  the 
muscles  on  the  inner  side  of  the  sole,  anastomosing  with  the  peroneal  and  internal 
malleolar,  and,  on  the  back  of  the  heel,  with  the  external  calcanean  arteries. 

The  Internal  Plantar  Artery  (a.  plantaris  medialis)  (Figs.  437  and  438),  much 
smaller  than  the  external,  passes  forward  along  the  inner  side  of  the  foot.  It  is 
at  first  situated  above^  the  Abductor  hallucis,  and  then  between  it  and  the  Flexor 
brevis  digitorum,  both  of  which  it  supplies.  At  the  base  of  the  first  metatarsal 
bone,  where  it  has  become  much  diminished  in  size,  it  passes  along  the  inner  border 
of  the  great  toe,  inosculating  with  its  digital  branch.  Small  superficial  digital 
branches  accompany  the  digital  branches  of  the  internal  plantar  nerve  and  join 
the  plantar  digital  arteries  of  the  three  inner  spaces.  In  addition,  this  vessel  gives 
off  numerous  cutaneous  branches. 

'  Thi.s  refers  to  the  erect  position  of  the  body.     In  the  ordinary  position  for  dissection  the  artery  is  deeper 
than  the  muscle. 


720  •  THE   BLOOD -VASCULAR   SYSTEM 

The  External  Plantar  Artery  (a.  plantaris  lateralis)  (Figs.  437  and  438),  much 
larger  than  the  internal,  passes  obliquely  outward  and  forward  to  the  base  of  the 
fifth  metatarsal  bone.  It  then  turns  obliquely  inward  to  the  interval  between 
the  bases  of  the  first  and  second  metatarsal  bones,  where  it  anastomoses  with 
the  communicating  branch  from  the  dorsalis  pedis  artery,  thus  completing  the 
plantax  axch  (arcus  plantaris)  (Fig.  438).  As  this  artery  passes  outward,  it  is  first 
placed  between  the  os  calcis  and  Abductor  hallucis,  and  then  between  the  Flexor 
brevis  digitorum  and  Flexor  accessorius,  and  as  it  passes  forward  to  the  base  of 
the  little  toe  it  lies  more  superficially  between  the  Flexor  brevis  digitorum  and 
Abductor  minimi  digiti,  covered  by  the  deep  fascia  and  integument.  The  remain- 
ing portion  of  the  vessel  is  deeply  situated :  it  extends  from  the  base  of  the  meta- 
tarsal bone  of  the  little  toe  to  the  back  part  of  the  first  interosseous  space,  and 
forms  the  plantar  arch;  it  is  convex  forward,  lies  upon  the  Interossei  muscles 
opposite  the  tarsal  ends  of  the  metatarsal  bones,  and  is  covered  by  the  Adductor 
obliquus  hallucis,  the  flexor  tendons  of  the  toes,  and  the  Lumbricales. 

Surface  Marking. — The  course  of  the  internal  plantar  artery  is  represented  by  a  line 
drawn  from  the  mid-point  between  the  tip  of  the  internal  malleolus  and  the  centre  of  the  con- 
vexity of  the  heel  to  the  middle  of  the  under  surface  of  the  great  toe;  the  external  plantar  by 
a  line  from  the  same  point  to  within  a  finger's  breadth  of  the  tuberosity  of  the  fifth  metatarsal 
bone.  The  plantar  arch  is  indicated  by  a  line  drawn  from  this  point — i.  e.,  a  finger's  breadth 
internal  to  the  tuberosity  of  the  fifth  metatarsal  bone  transversely  across  the  foot  to  the  back  of 
the  first  interosseous  space. 

Surgical  Anatomy.^Wounds  of  the  plantar  arch  are  always  serious,  on  account  of  the 
depth  of  the  vessel  and  the  important  structures  which  must  be  interfered  with  in  an  attempt 
to  ligate  it.  They  must  be  treated  on  similar  lines  to  those  of  wounds  of  the  palmar  arches 
(see  page  665).  Delorme  has  shown  that  the  plantar  arch  may  be  ligated  from  the  dorsum  of  the 
foot  in  almost  any  part  of  its  course  by  removing  a  portion  of  one  of  the  three  middle  metatarsal 
bones. 

Branches. — The  plantar  arch,  besides  distributing  numerous  branches  to  the 
muscles,  integument,  and  fasciae  in  the  sole,  gives  off  the  following  branches: 

Posterior  Perforating.  Digital. 

The  Posterior  Perforating  {rami  perforantes  posteriores)  are  three  small  branches 
which  ascend  through  the  back  part  of  the  three  outer  interosseous  spaces,  between 
the  heads  of  the  Dorsal  interossei  muscles,  and  anastomoses  with  the  interosseous 
branches  from  the  metatarsal  artery. 

The  Digital  Branches  (aa.  metatarsece  plantares)  are  four  in  number,  and  supply 
the  three  outer  toes  and  half  the  second  toe.  It  will  be  remembered  that  the 
arteria  princeps  hallucis  is  the  plantar  digital  branch  of  the  communicating 
arms  in  the  first  interosseous  space  and  supplies  the  adjacent  sides  of  the  great 
and  little  toes.  The  first  digital  branch  of  the  plantar  arch  passes  outward 
from  the  outer  side  of  the  plantar  arch,  and  is  distributed  to  the  outer  side  of  the 
little  toe,  passing  in  its  course  beneath  the  Abductor  and  short  Flexor  muscles. 
The  second,  third,  and  fourth  run  forward  along  the  interosseous  spaces,  and  on 
arriving  at  the  clefts  between  the  toes  divides  into  collateral  digital  branches  {aa. 
digitales  plantares),  which  supply  the  adjacent  sides  of  the  three  outer  toes  and 
the  outer  side  of  the  sscond.  At  the  bifurcation  of  the  toes  each  digital  artery 
sends  upward,  through  the  forepart  of  the  corresponding  interosseous  space,  a 
small  branch  which  inosculates  with  the  interosseous  branches  of  the  metatarsal 
artery.     These  are  the  anterior  perforating  branches  {rami  perforantes  anteriores). 

From  the  arrangement  already  described  of  the  distribution  of  the  vessels  to 
the  toes  it  will  be  seen  that  both  sides  of  the  three  outer  toes  and  the  outer  side 
of  the  second  toe  are  supplied  by  branches  from  the  plantar  arch ;  both  sides  of 
the  great  toe  and  the  inner  side  of  the  second  are  supplied  by  the  communicating 
branch  of  the  dorsalis  pedis. 


THE  VEINS. 


The  Veins  are  the  vessels  which  serve  to  return  the  blood  from  the  capillaries 
of  the  different  parts  of  the  body  to  the  heart.  They  consist  of  two  distinct  sets 
of  vessels,  the  pulmonary  and  systemic  veins,  and  an  appendage  to  the  systemic, 
the  portal  system. 

The  Pulmonary  Veins  are  concerned  in  the  circulation  in  the  lungs.  Unlike 
other  vessels  of  this  kind,  they  contain  arterial  blood,  which  they  return  from  the 
lungs  to  the  left  auricle  of  the  heart.    The  pulmonary  veins  are  four  in  number. 


i; 


Fig.  439.— Valves  of  a  vein.  In  the  lower  part 
of  the  figure  is  seen  the  parietal  valves;  the  upper 
part  .shows  the  mouth  of  a  vein  guarded  by  a  valve. 
(Poirier  and  Charpy.) 


Fig.  440. — Collateral  anastomosis  of  veins.  The  arrows 
indicate  the  direction  of  the  flow  of  blood  (schematic). 
(Poirier  and  Charpy.) 


The  Systemic  Veins  are  concerned  in  the  general  circulation;  they  return  the 
venous  blood  from  the  body  generally  to  the  right  auricle  of  the  heart.  The  .sys- 
temic veins  are  the  superior  vena  cava,  the  inferior  vena  cava,  and  the  coronary 
sinus. 

The  Portal  Vein  constitutes  the  portal  system.  The  portal  system  is  in  reality 
an  appendage  to  the  systemic  venous  system.  It  is  confined  to  the  abdominal 
cavity,  returning  the  venous  blood  from  the  viscera  of  digestion,  and  carrying  it 
to  the  liver  by  a  single  trunk  of  large  size,  the  portal  vein  or  vena  portae.  This 
vessel  ramifies  in  the  substance  of  the  liver  and  breaks  up  into  a  minute  network 

46  ( 721  ) 


722 


THE   BLOOD -VASCULAR    SYSTEM 


of  capillaries.     These  capillaries  then  re-collect  to  form  the  hepatic  veins,  by 
which  the  blood  is  conveyed  to  the  inferior  vena  cava. 

The  veins,  like  the  arteries,  are  found  in  nearly  every  tissue  of  the  body.  They 
commence  by  minute  plexuses  which  receive  the  blood  from  the  capillaries.  The 
branches  which  have  their  commencement  in  these  plexuses  unite  together 
into  trunks,  and  these,  in  their  passage  toward  the  heart,  constantly  increase  in 
size  as  they  receive  tributaries  or  join  other  veins.  The  veins  are  larger  and 
altogether  more  numerous  than  the  arteries;  hence  the  entire  capacity  of  the 
venous  system  is  much  greater  than  that  of  the  arterial,  the  pulmonary  veins 
excepted,  which  only  slightly  exceed  in  capacity  the  pulmonary  arteries.  From 
the  combined  area  of  the  smaller  venous  branches  being  greater  than  the  main 
trunks,  it  results  that  the  venous  system  represents  a  cone,  the  summit  of  which 
corresponds  to  the  heart,  its  base  to  the  circumference  of  the  body.  In  form  the 
veins  are  perfectly  cylindrical,  like  the  arteries,  their  walls  being  collapsed  when 
empty,  and  the  uniformity  of  their  surface  being  interrupted  at  intervals  by  slight 
constrictions,  which  indicate  the  existence  of  valves  in  their  interior  (Fig.  439). 
They  usually  retain,  however,  about  the  same  calibre  as  long  as  they  receive  no 
branches,  but  not  so  uniformly  as  do  the  arteries. 

The  veins  communicate  very  freely  with  one  another  (Fig.  441),  especially  in 
certain  regions  of  the  body,  and  this  communication  exists  between  the  larger 

trunks  as  well  as  between  the  smaller 
branches.  Thus,  in  the  cavity  of  the 
cranium  and  between  the  veins  of  the 
neck,  where  obstruction  would  be  at- 
tended with  imminent  danger  to  the 
cerebral  venous  system,  we  find  that 
the  sinuses  and  larger  veins  have  large 
and  very  frequent  anastomoses  (Fig. 
440).  The  same  free  communication 
exists  between  the  veins  throughout 
the  whole  extent  of  the  spinal  canal, 
and  between  the  veins  composing  the 
various  venous  plexuses  in  the  abdo- 
men and  pelvis,  as  the  spermatic, 
uterine,  vesical,  and  prostatic. 

Veins    have    thinner    walls     than 

arteries,  the  difference  in   thickness 

being   due  to  the  small   amount  of 

elastic  and    muscular  tissues   which 

the  veins  contain.    The  superficial  veins  usually  have  thicker  coats  than  the  deep 

veins,  and  the  veins  of  the  lower  limb  are  thicker  than  those  of  the  upper. 

Histology  of  the  Veins.^ — As  previously  stated,  capillaries  enter  into  venules 
or  precapillary  veins.  The  venules  empty  into  larger  veins.  Vein  walls  are  much 
thinner  than  arterial  walls.  A  vein  has  a  much  thinner  media  and  much  less 
elastic  tissue  than  an  artery,  and  a  very  strongly  developed  adventitia.  The 
intima  is  a  connective-tissue  layer  containing  a  small  number  of  elastic  fibres 
and  lined  with  endothelium.  The  media  contains  some  circular  muscle  fibres 
and  some  fine  elastic  fibres.  In  some  veins  the  media  is  thoroughly  well  devel- 
oped (veins  of  the  lower  extremities),  in  others  it  is  practically  absent  (veins  of 
the  retina,  of  the  pia  mater,  of  bone,  the  superior  vena  cava).  The  adventitia 
IS  dense  and  strong,  and  is  composed  of  connective-tissue  elastic  fibres  and 
non-striated  muscle  fibres  placed  longitudinally.  Fig.  442  shows  a  transverse  sec- 
tion of  part  of  the  wall  of  a  vein.  The  vein  valves  (Fig.  439)  are  composed 
of  intima  and  contain  elastic  fibres.     The  large  veins  and  the  veins  of  medium 


Fig.  441. — The  venous  circle  of  Braune  (schematic). 
The  arrows  indicate  the  direction  of  the  blood  current. 
(Poirier  and  Charpy.) 


THE   PULMONARY    VEINS  723 

size  possess  vasa  vasorum,  in  the  adventitia  and  to  some  extent  in  the  media. 
The  walls  of  veins  contain  vasomotor  nerves.  "  Small  blood-vessels  are  often 
surrounded  by  lymph  capillaries  and  sometimes  by  endothelium-lined  spaces 
which  are  in  communication  with  the  lymphatic  system.  These  are  called  peri- 
vascular lymph  spaces."* 

The  systemic  veins  are  subdivided  into  three  sets:  superficial,  deep,  and  sinuses. 

The  Superficial  or  Cutaneous  Veins  are  found  between  the  layers  of  the  super- 
ficial fascia,  immediately  beneath  the  integument;  they  return  the  blood  from 
these  structures,  and  communicate  with  the  deep  veins  by  perforating  the  deep 
fascia. 

Endothelial  and 
y  subendothelial 
^^^-^    •  layers. 

^B!Wte'-v-,  ^./^t^SSa^ Elastic  layer. 

ifll^f '"""     ~      ''■''""    " '■^^gBaBBmA\ — Middle  coat. 


-Outer  coat. 


Fig.  442. — Transverse  section  of  part  of  the  wall  of  one  of  the  posterior  tibial  veins.     (After  Schafer.) 

The  Deep  Veins  accompany  the  arteries,  and  are  usually  enclosed  in  the  same 
sheath  with  those  vessels.  With  the  smaller  arteries — as  the  radial,  ulnar,  brachial, 
tibial,  and  peroneal — they  exist  generally  in  pairs,  one  lying  on  each  side  of  the 
vessel,  and  are  called  venae  comites.  The  larger  arteries — as  the  axillary,  sub- 
clavian, popliteal,  and  femoral — have  usually  only  one  accompanying  vein.  In 
certain  organs  of  the  body,  however,  the  deep  veins  do  not  accompany  the 
arteries;  for  instance,  the  veins  in  the  skull  and  spinal  canal,  the  hepatic  veins  in 
the  liver,  and  the  larger  veins  returning  blood  from  the  osseous  tissue. 

Sinuses  are  venous  channels  which,  in  their  structure  and  mode  of  distribution, 
differ  altogether  from  the  veins.  They  are  found  only  in  the  interior  of  the  skull, 
and  consist  of  channels  formed  by  a  separation  of  the  two  layers  of  the  dura  mater, 
their  outer  coat  consisting  of  fibrous  tissue,  their  inner  of  an  endothelial  layer 
continuous  with  the  lining  membrane  of  the  veins. 


THE  PULMONARY  VEINS  (V.  PULMONALES)  (Fig.  443). 

The  pulmonary  veins  return  the  arterial  blood  from  the  lungs  to  the  left  auricle 
of  the  heart.  They  are  four  in  number,  two  for  each  lung.  The  pulmonary  veins 
differ  from  other  veins  in  several  respects:  1.  They  carry  arterial  instead  of 
venous  blood.  2.  They  are  destitute  of  valves.  3.  They  are  only  slightly  larger 
than  the  arteries  they  accompany.  4.  They  accompany  those  vessels  singly. 
They  commence  in  a  capillary  network  upon  the  walls  of  the  air-cells,  where  they 
are  continuous  with  the  capillary  ramifications  of  the  pulmonary  artery,  and, 
uniting  together,  form  one  vessel  for  each  lobule.  These  vessels,  uniting  suc- 
cessively, form  a  single  trunk  for  each  lobe,  three  for  the  right  and  two  for  the 
left  lung.  The  vein  from  the  middle  lobe  of  the  right  lung  generally  unites  with 
that  from  the  upper  lobe,  forming  two  trunks  on  each  side,  which  open  separately 
into  the  left  auricle.     Occasionally  they  remain  separate;  there  are  then  three 

*  Histology  and  Microscopic  Anatomy.    By  Szymonowicz  and  MacCallum. 


724 


THE   BLOOD -VASCULAR   SYSTEM 


veins  on  the  right  side.    Not  unfrequently  the  two  left  pulmonary  veins  terminate 
by  a  common  opening. 

^  Within  the  lung,  the  branches  of  the  pulmonary  artery  are  in  front,  the  veins 
behind,  and  the  bronchi  between  the  two. 

At  the  root  of  the  lung,  the  veins  are  in  front,  the  artery  in  the  middle,  and  the 
bronchus  behind. 


ENTRANCE   OF 
— VENA     AZVGOS 
BRANCH    OF   PUL- 
MONARY  ARTERY 


Fig.  443. — Pulmonary  veins,  seen  in  a  dorsal  view  of  the  heart  and  lungs.  The  left  lung  is  pulled  to  the 
left,  and  the  right  lung  has  been  partly  cut  away  to  show  the  ramifications  of  the  air-tubes  and  blood-vessels. 
(Testut.) 

Within  the  pericardium,  their  anterior  surface  is  invested  by  the  serous  layer 
of  this  membrane.  The  right  pulmonary  veins  pass  behind  the  right  auricle  and 
ascending  aorta  and  superior  vena  cava;  the  left  pass  in  front  of  the  thoracic 
aorta  with  the  left  pulmonary  artery. 


THE  SYSTEMIC  VEINS. 

The  systemic  veins  may  be  arranged  into  three  groups:  1.  Those  of  the  head 
and  neck,  upper  extremity,  and  thorax,  which  terminate  in  the  superior  vena  cava. 
2.  Those  of  the  lower  extremity,  abdomen,  and  pelvis,  which  terminate  in  the 
inferior  vena  cava.  3.  The  cardiac  veins,  which  open  directly  into  the  right  auricle 
of  the  heart. 

VEINS  OF  THE  HEAD  AND  NECK. 


The  veins  of  the  head  and  neck  may  be  subdivided  into  three  groups:  1.  The 
veins  of  the  exterior  of  the  head  and  face.  2.  The  veins  of  the  neck.  3.  The  veins 
of  the  diplo'e  and  interior  of  the  cranium. 


VEINS    OF    THE  EXTERIOR    OF    THE    HEAD    AND    FACE     725 

Veins  of  the  Exterior  of  the  Head  and  Face  (Fig.  444). 
The  veins  of  the  exterior  of  the  head  and  face  are — the 


Frontal. 
Supraorbital. 
Angular. 
Facial. 


Temporal. 
Internal  Maxillary. 
Tempo  ro-m  axillary. 
Posterior  Auricular. 


Occipital. 


The  Frontal  Vein  {v.  frontalis)  commences  on  the  anterior  part  of  the  skull  by 
a  venous  plexus  which  communicates  with  the  anterior  tributaries  of  the  temporal 
vein.    The  veins  converge  to  form  a  single  trunk,  which  runs  downward  near  the 


Frontal 
Communicating 
branch  with 
hthalmic  vein. 
Angular. 


Interior 
facial. 


Comm,on 
facial 
ngual. 
yngeai. 


Fig.  444. — Veins  of  the  head  and  neck. 


middle  line  of  the  forehead  parallel  with  the  vein  of  the  opposite  side,  and  unites 
with  it  at  the  root  of  the  nose  by  a  transverse  branch  called  the  nasal  arch  (v.  naso- 
frontalis).    Occasionally  the    frontal  veins  join  to  form    a  single   trunk,  which 


726  THE  BLOOD -VASCULAR    SYSTEM 

bifurcates  at  the  root  of  the  nose  into  the  two  angular  veins.  At  the  root  of 
the  nose  the  veins  diverge  and  join  the  supraorbital  vein,  at  the  inner  angle  of 
the  orbit,  to  form  the  angular  vein. 

The  Supraorbital  Vein  {v.  swpraorhitalis)  commences  on  the  forehead,  com- 
municating with  the  anterior  temporal  vein,  and  runs  downward  and  inward, 
superficial  to  the  Occipito-frontalis  muscle,  receiving  tributaries  from  the  neigh- 
boring structures,  and  from  the  frontal  vein  of  the  diploe,  and  joins  the  frontal 
vein  at  the  inner  angle  of  the  orbit  to  form  the  angular  vein. 

The  Angular  Vein  {v.  angularis),  formed  by  the  junction  of  the  frontal  and 
supraorbital  veins,  runs  obliquely  downward  and  outward  on  the  side  of  the  root 
of  the  nose,  and  receives  the  veins  of  the  ala  nasi  on  its  inner  side  and  the  superior 
palpebral  veins  on  its  outer  side;  it  moreover  communicates  with  the  ophthalmic 
vein,  thus  establishing  an  important  anastomosis  between  this  vessel  and  the 
cavernous  sinus.  Some  small  veins  from  the  dorsum  of  the  nose  terminate  in  the 
nasal  arch. 

The  Anterior  Facial  Vein  {v.  facialis  anterior)  commences  at  the  side  of  the 
root  of  the  nose,  being  a  direct  continuation  of  the  angular  vein,  which  is  itself 
formed  by  the  union  of  the  frontal  vein  and  the  supraorbital  vein.  It  lies  behind 
and  follows  a  less  tortuous  course  than  the  facial  artery.  It  passes  obliquely 
downward  and  outward,  beneath  the  Zygomaticus  major  and  minor  muscles, 
descends  along  the  anterior  border  of  the  Masseter,  crosses  over  the  body  of  the 
lower  jaw,  with  the  facial  artery  to  beneath  the  angle,  and  unites  with  the  anterior 
division  of  the  temporo-maxillary  vein  {v.  facialis  posterior)  to  form  the  common 
facial  vein. 

The  Common  Facial  Vein  (v.  facialis  communis)  is  formed  by  the  union  of  the 
anterior  facial  and  the  anterior  division  of  the  temporo-maxillary  vein,  just  beneath 
the  angle  of  the  mandible.  The  vein  is  covered  by  the  Platysma  myoid  muscle, 
runs  downward  and  backward  beneath  the  Sterno-cleido-mastoid  muscle,  crosses 
the  external  carotid  artery,  and  empties  into  the  internal  jugular  vein  at  the  level 
of  the  hyoid  line.  It  receives  a  large  branch  at  the  anterior  border  of  the  Sterno- 
cleido-mastoid  muscle,  which  comes  from  the  anterior  jugular  vein  in  the  supra- 
sternal fossa. 

Tributaries  of  the  Anterior  and  Common  Facial  Veins. — The  anterior  facial  vein 
receives,  near  the  angle  of  the  mouth,  communicating  tributaries  of  considerable 
size,  the  deep  facial  or  anterior  internal  maxillary  vein,  from  the  pterygoid 
plexus.  It  is  also  joined  by  the  inferior  palpebral,  the  superior  and  inferior 
labial  veins,  the  buccal  veins  from  the  cheek,  and  the  masseteric  veins.  The 
common  facial  vein  receives  the  submental;  the  inferior  palatine,  which  returns 
the  blood  from  the  plexus  round  the  tonsil  and  soft  palate;  the  submaxillary 
vein,  which  commences  in  the  submaxillary  gland;  and,  generally,  the  ranine 
vein. 

Surgical  Anatomy. — There  are  some  points  about  the  facial  vein  which  render  it  of  great 
importance  in  surgery.  It  is  not  so  flaccid  as  are  most  superficial  veins,  and,  in  consequence  of 
this,  remains  more  patent  when  divided.  It  has,  moreover,  no  valves.  It  communicates  freely 
with  the  intracranial  circulation,  not  only  at  its  commencement  by  its  tributaries,  the  angular 
and  supraorbital  veins,  communicating  with  the  ophthalmic  vein,  a  tributary  of  the  cavernous 
sinus,  but  also  by  its  deep  branch,  which  communicates  through  the  pterygoid  plexus  with  the 
cavernous  sinus  by  branches  which  pass  through  the  foramen  ovale  and  foramen  lacerum 
medium.  These  facts  have  an  important  bearing  upon  the  surgery  of  some  diseases  of  the 
face,  for  on  account  of  its  patency  the  facial  vein  favors  septic  absorption,  and  therefore  any 
phlegmonous  inflammation  of  the  face  following  a  poisoned  wound  is  liable  to  set  up  thrombosis 
in  the  facial  vein,  and  detached  portions  of  the  clot  may  give  rise  to  purulent  foci  in  other 
parts  of  the  body.  And  on  account  of  its  communications  with  the  cerebral  sinuses  these 
thrombi  are  apt  to  extend  upward  into  them  and  so  induce  a  fatal  issue. 


VEINS    OF    THE    EXTERIOR    OF    THE    HEAD    AND    FACE     727 

The  Superficial  Temporal  Vein  {w.  temporales  superficiales)  commences  by  a 
minute  plexus  on  the  side  and  vertex  of  the  skull,  which  communicates  with  the 
frontal  and  supraorbital  veins  in  front,  the  corresponding  vein  of  the  opposite 
side,  and  the  posterior  auricular  and  occipital  veins  behind.  From  this  network 
anterior  and  posterior  branches  are  formed  which  unite  above  the  zygoma,  form- 
ing the  trunk  of  the  vein.  The  trunk  is  joined  in  this  situation  by  a  large  vein, 
the  middle  temporal  (v.  temporalis  media),  which  receives  blood  from  the  sub- 
stance of  the  Temporal  muscle  and  pierces  the  fascia  at  the  upper  border  of 
the  zygoma.  The  junction  of  the  superficial  temporal  and  the  middle  temporal 
veins  forms  the  common  temporal  vein  (v.  temporalis  communis),  which  descends 
between  the  external  auditory  meatus  and  the  condyle  of  the  jaw,  enters  the 
substance  of  the  parotid  gland,  and  unites  with  the  internal  maxillary  vein  to  form 
the  temporo-maxillary  vein. 

Tributaries. — The  common  temporal  vein  receives  in  its  course  some  parotid 
veins,  an  articular  branch  from  the  articulation  of  the  jaw,  anterior  auricular  veins 
from  the  external  ear,  and  a  vein  of  large  size,  the  transverse  facial  (v.  transversa 
faciei),  from  the  side  of  the  face.  The  middle  temporal  vein,  previous  to  its  junc- 
tion with  the  temporal  vein,  receives  a  branch,  the  orbital  vein  (v.  orhitalis),  which 
is  formed  by  some  external  palpebral  branches,  and  passes  backward  between 
the  layers  of  the  temporal  fascia. 

The  Pterygoid  Plexus  (plexus  pterygoideus)  and  the  Internal  Maxillary 
Vein. — The  internal  maxillary  vein  is  a  vessel  of  considerable  size,  receiving 
branches  which  correspond  with  those  of  the  internal  maxillary  artery.  Thus  it 
receives  the  two  middle  meningeal  veins,  the  deep  temporal,  the  pterygoid,  mas- 
seteric, buccal,  and  alveolar  veins,  some  palatine  veins,  the  spheno-palatine  and  the 
inferior  dental  veins.  The  deep  temporal  veins  {vv.  temporales  profundce)  come  to 
the  pterygoid  plexus  from  the  temporal  muscle.  These  branches  form  a  large 
plexus,  the  pterygoid  plexus,  which  is  placed  between  the  Temporal  and  External 
pterygoid  and  partly  between  the  Pterygoid  muscles.  This  plexus  is  a  tributary 
of  the  internal  maxillary  vein,  and  communicates  very  freely  with  the  facial  vein 
and  with  the  cavernous  sinus  by  branches  through  the  foramen  Vesalii,  foramen 
ovale,  and  foramen  lacerum  medium,  at  the  base  of  the  skull.  The  trunk  of 
the  internal  maxillary  vein  comes  from  the  plexus,  then  passes  backward  behind 
the  neck  of  the  lower  jaw,  and  unites  with  the  temporal  vein,  forming  the 
temporo-maxillary  vein. 

The  Temporo-maxillary  Vein  (v.  facialis  posterior),  formed  by  the  union  of 
the  superficial  temporal  and  internal  maxillary  veins,  descends  in  the  substance  of 
the  parotid  gland  on  the  outer  surface  of  the  external  carotid  artery,  between  the 
ramus  of  the  jaw  and  the  Sterno-mastoid  muscle,  and  divides  into  two  branches, 
an  anterior,  which  passes  inward  to  join  the  facial  vein,  and  a  posterior,  which 
is  joined  by  the  posterior  auricular  vein  and  becomes  the  external  jugular. 

The  Posterior  Auricular  Vein  (v.  auricularis  posterior)  commences  upon  the 
side  of  the  head  by  a  plexus  which  communicates  with  the  tributaries  of  the  tem- 
poral and  occipital  veins.  The  vein  descends  behind  the  external  ear  and  joins 
the  posterior  division  of  the  temporo-maxillary  vein,  forming  the  external  jugular. 
This  vessel  receives  the  stylo-mastoid  vein  and  some  tributaries  from  the  back 
part  of  the  external  ear. 

The  Occipital  Vein  (v.  occipitalis)  commences  at  the  back  part  of  the  vertex 
of  the  skull  by  a  plexus  in  a  similar  manner  to  the  other  veins.  From  the  plexus 
comes  one  or  two  veins,  which  follow  the  course  of  the  occipital  artery,  passing 
deeply  beneath  the  muscles  of  the  back  part  of  the  neck,  and  terminating  in  the 
suboccipital  triangle  by  becoming  continuous  with  the  posterior  vertebral  vein. 
Sometimes  they  are  more  superficial,  and  in  this  case  they  are  tributaries  of  the 


k 


728  THE  BLOOD -VASCULAR   SYSTEM 

external  jugular  vein.  As  the  outermost  occipital  vein  passes  across  the  mastoid 
portion  of  the  temporal  bone,  it  receives  the  mastoid  vein,  which  thus  establishes 
a  communication  with  the  lateral  sinus. 


The  Veins  of  the  Neck  (Fig.  444). 

The  veins  of  the  neck,  which  return  the  blood  from  the  head  and  face,  are — the 

External  Jugular.  Anterior  Jugular. 

Posterior  External  Jugular.    •  Internal  Jugular. 

Vertebral. 

The  External  Jugular  Vein  {v.  jugularis  externa)  receives  the  greater  part 
of  the  blood  from  the  exterior  of  the  cranium  and  deep  parts  of  the  face,  being 
formed  by  the  junction  of  the  posterior  division  of  the  temporo-maxillary  and 
the  posterior  auricular  veins.  It  commences  in  the  substance  of  the  parotid  gland, 
on  a  level  with  the  angle  of  the  lower  jaw,  and  runs  perpendicularly  down  the  neck 
in  the  direction  of  a  line  drawn  from  the  angle  of  the  jaw  to  the  middle  of  the 
clavicle.  In  its  course  it  crosses  the  Sterno-mastoid  muscle,  and  runs  parallel  with 
its  posterior  border  as  far  as  its  attachment  to  the  clavicle,  where  it  perforates  the 
deep  fascia,  and  terminates  in  the  subclavian  vein,  on  the  outer  side  of,  or  in  front 
of,  the  Scalenus  anticus  muscle.  In  the  neck  it  is  separated  from  the  Sterno- 
mastoid  by  the  investing  layer  of  the  deep  cervical  fascia,  and  is  covered  by  the 
Platysma,  the  superficial  fascia,  and  the  integument.  This  vein  is  crossed  about 
its  middle  by  the  superficialis  colli  nerve,  and  throughout  the  upper  half  of  its 
course  is  accompanied  by  the  auricularis  magnus  nerve.  The  external  jugular  vein 
varies  in  size,  bearing  an  inverse  proportion  to  that  of  the  other  veins  of  the  neck; 
it  is  occasionally  double.  It  is  provided  with  two  pairs  of  valves,  the  lower  pair 
being  placed  at  its  entrance  into  the  subclavian  vein,  the  upper  pair  in  most  cases 
about  an  inch  and  a  half  above  the  clavicle.  The  portion  of  vein  between  the  two 
sets  of  valves  is  often  dilated,  and  is  termed  the  sinus.  These  valves  do  not  prevent 
the  regurgitation  of  the  blood  or  the  passage  of  injection  from  below  upward.^ 

Tributaries. — ^This  vein  receives  the  occipital  occasionally,  the  posterior  external 
jugular,  and,  near  its  termination,  the  suprascapular  and  transverse  cervical  veins. 
It  communicates  with  the  anterior  jugular,  and,  in  the  substance  of  the  parotid, 
receives  a  large  branch  of  communication  from  the  internal  jugular. 

The  Posterior  External  Jugular  Vein  {v.  jugularis  'posterior)  commences  in 
the  occipital  region,  and  returns  the  blood  from  the  integument  and  superficial 
muscles  in  the  upper  and  back  part  of  the  neck,  lying  between  the  Splenius  and 
Trapezius  muscles.  It  runs  down  the  back  part  of  the  neck,  and  opens  into  the 
external  jugular  just  below  the  middle  of  its  course. 

The  Anterior  Jugular  Vein  (^».  jugularis  anterior)  commences  near  the 
hyoid  bone  from  the  convergence  of  the  inferior  coronary,  the  submental  and  the 
mental  veins,  and  communicating  branches.  It  passes  down  between  the  median 
line  and  the  anterior  border  of  the  Sterno-mastoid,  and  at  the  lower  part  of  the 
neck  passes  beneath  that  muscle  to  open  into  the  termination  of  the  external 
jugular  or  into  the  subclavian  vein  (Fig.  465).  This  vein  varies  considerably  in 
size,  bearing  almost  always  an  inverse  proportion  to  the  external  jugular.  Most 
frequently  there  are  two  anterior  jugulars,  a  right  and  left,  but  occasionally  only 
one.  This  vein  receives  some  laryngeal  veins,  and  occasionally  a  small  thyroid 
vein.     Just  above  the  sternum  the  two  anterior  jugular  veins  communicate  by  a 

1  The  student  may  refer  to  an  interesting  paper  by  Dr.  Struthers,  "  On  Jugular  Venesection  in  Asphyxia. 
Anatomically  and  Experimentally  Considered,  including  the  Demonstration  of  Valves  in  the  Veins  of  the  Neck," 
in  the  Edinburgh  Medical  Journal  for  November,  1856.— Ed.  of  15th  English  edition. 


THE    VEINS    OF   THE  NECK 


729 


transverse  trunk,  which  receives  tributaries  from  the  inferior  thyroid  veins.  It 
also  communicates  with  the  internal  jugular.  There  are  no  valves  in  this  vein. 
The  Internal  Jugular  Vein  {v.  jugularis  interna)  collects  the  blood  from 
the  interior  of  the  cranium,  from  the  superficial  parts  of  the  face,  and  from  the 
neck.  It  commences  just  external  to  the  jugular  foramen,  at  the  base  of  the  skull, 
being  formed  by  the  coalescence  of  the  lateral  and  inferior  petrosal  sinuses  (Fig. 
458).  At  its  origin  it  is  somewhat  dilated,  and  this  dilatation  is  called  the  sinus 
or  gulf  of  the  internal  jugular  vein  (bulbus  v.  jugularis  superior).  It  runs  down  the 
side  of  the  neck  in  a  vertical  direction,  lying  at  first  on  the  outer  side  of  the  internal 
carotid  artery,  and  then  on  the  outer  side  of  the  common  carotid  artery,  and  at 
the  root  of  the  neck  unites  with  the  subclavian  vein  to  form  the  innominate  vein. 
Just  before  its  termination  it  is  distinctly  dilated  {bulhus  v.  jugularis  inferior).   The 


DORSALIS 
LINGU/C   ARTERY 
LINGUAL  VEIN 
VEINS  OF 
DORSUM  OF— -^ 


HYPOGLOSSAL   NERVE 

Fig.  445. — Veins  of  the  tongue 


(Testut,  modified  from  Hirschfeld.) 


internal  jugular  vein,  at  its  commencement,  lies  upon  the  Rectus  capitis  lateralis, 
and  behind  the  internal  carotid  artery  and  the  nerves  passing  through  the  jugular 
foramen;  lower  down,  the  vein  and  artery  lie  upon  the  same  plane,  the  glosso- 
pharyngeal and  hypoglossal  nerves  passing  forward  between  them ;  the  pneumo- 
gastric  descends  between  and  behind  them  in  the  same  sheath,  and  the  spinal 
accessory  passes  obliquely  outward,  behind  or  in  front  of,  the  vein.  At  the  root  of 
the  neck  the  vein  of  the  right  side  is  placed  at  a  little  distance  from  the  artery;  on 
the  left  side  it  usually  lies  over  the  artery  at  its  lower  part.  The  right  internal 
jugular  vein  crosses  the  first  part  of  the  subclavian  artery.  The  internal  jugular 
vein  is  of  considerable  size,  but  varies  in  different  individuals,  the  left  one  being 
usually  the  smaller.  It  is  provided  with  a  pair  of  valves,  which  are  placed  at  its 
point  of  termination  or  from  half  to  three-quarters  of  an  inch  above  it. 

Tributaries. — This  vein  receives  in  its  course  the  facial,  lingual,  pharyngeal, 
superior,  and  middle  thyroid  veins.  A  branch  from  the  cochlea  opens  into  the 
sinus  of  the  internal  jugular  vein.  A  venous  plexus  from  the  lateral  sinus  (plexus 
venosus  caroticus  internus)  surrounds  the  internal  carotid  artery  in  the  carotid 
canal  and  empties  into  the  internal  jugular  vein.  At  its  point  of  junction  with  the 
common  facial  vein  it  becomes  increased  in  size.     (See  Facial  Veins,  p.  726.) 

The  Lingual  Veins  {vv.  linguale)  (Fig.  445)  commence  on  the  dorsum,  sides,  and 
under  surface  of  the  tongue,  and,  passing  backward,  following  the  course  of  the 
lingual  artery  and  its  branches,  terminate  in  the  internal  jugular.  Sometimes  the 
ranine  vein,  which  is  a  branch  of  considerable  size  commencing  below  the  tip  of  the 


730 


THE  BLOOD -VASCULAR   SYSTEM 


tongue,  joins  the  lingual.  Generally,  however,  it  passes  backward,  crosses  the 
Hyo-glossus  muscle  in  company  with  the  hypoglossal  nerve,  and  joins  the  internal 
jugular.  The  lingual  vein  receives  the  subhngual  vein  and  the  dorsalis  lingute  veins. 
The  Phax3mgeal  Veins  (vv.  pharyngeir)  vary  in  number.  They  commence  in  a 
minute  plexus,  the  pharyngeal  plexus  (plexus  pharyngeus),  at  the  back  part  and 
sides  of  the  pharynx,  and,  after  receiving  meningeal  tributaries,  the  meningeal 
veins  {vv.  meningea),  the  Vidian  veins  {vv.  canalis  pterygoidei),  and  the  spheno- 
palatine veins,  terminate  in  the  internal  jugular.  They  occasionally  open  into  the 
facial,  lingual,  or  superior  thyroid  vein. 


Fig.  446. 


SUBCLAVIAN 

-The  veins  of  the  neck,  viewed  from  in  front. 


(Spalteholz.) 


The  Superior  Th3n:oid  Vein  {v.  thyreoidea  superioris)  (Fig.  446)  commences  in  the 
substance  and  on  the  surface  of  the  thyroid  gland  by  tributaries  corresponding 
with  the  branches  of  the  superior  thyroid  artery,  and  terminates  in  the  upper 
part  of  the  internal  jugular  vein.  It  receives  the  superior  laryngeal  and  crico- 
thyroid veins.  Some  anatomists  teach  that  there  are  two  superior  thyroid  veins 
on  each  side,  the  upper  vein  being  the  one  just  considered,  the  lower  vein  being 
the  one  usually  pointed  out  as  the  middle  thyroid. 

The  Middle  Thyroid  Vein  (Fig.  448)  collects  the  blood  from  the  lower  part  of  the 
lateral  lobe  of  the  thyroid  gland,  and,  being  joined  by  some  veins  from  the  larynx 
and  trachea,  terminates  in  the  lower  part  of  the  internal  jugular  vein.    Often  in 


THE    VEINS    OF    THE   NECK 


731 


place  of  the  middle  thyroid  vein  there  are  two  veins,  the  superior  and  inferior 
accessory  thyroid.    These  veins  pass  into  the  internal  jugular. 


SUPERtOR 

THYROID 

ARTERY 


INFERrOR 

THYROID 

VEIN 


Fig.  447. — Diagram  showing  common  arrangement  of  thyroid  veins.     (Kocher.) 


INFERIOR 
THYROID 
VEIN 


Fig.  448.— The  fascia  and  middle  thyroid  veins.     The  veins  here  designate^~TBeTnferior  thyroid  are  called  by 
Kocher  the  thyreoidea  ima.     (Poirier  and  Charpy.) 

Veins  of  the  Thyroid  Gland^  (Fig.  447) . — On  the  surface  qf  the  thyroid  glands 
the  veins  form  a  plexus  between  the  capsule  and  the  gland.     A  number  of  veins 


'  See  Kocher's  description  in  Langenbeck's  Arch.  f.  klin.  Chir.,  vol.  xxix.,  and  James  Berry's  description  in  his 
treatise  on  Diseases  of  the  Thyroid  Gland. 


732  THE  BLOOD -VASCULAR    SYSTEM 

penetrate  the  capsule  and  pass  into  adjacent  trunks.  The  most  important  veins 
coming  from  the  gland  are  the  superior,  middle,  and  inferior  thyroids  (or  instead 
of  the  middle  thyroid  the  superior  and  inferior  accessory  thyroid)  and  the 
thyreoidea  ima. 

The  superior  thyroid  vein  emerges  from  the  summit  of  the  superior  horn  of  the 
gland,  runs  along  by  the  superior  thyroid  artery,  and  terminates  in  the  internal 
jugular  vein.  A  large  branch  which  passes  along  the  inner  margin  of  the  upper 
horn  and  across  the  upper  surface  of  the  isthmus  joins  the  superior  thyroid  veins 
of  each  side.  The  middle  thyroid  vein  when  present  emerges  from  the  side  of  the 
gland  and  empties  into  the  internal  jugular.  This  single  vein  may  be  replaced  by 
two  veins,  the  superior  and  inferior  accessory  thyroid  veins.  The  superior  vein 
emerges  from  the  outer  surface  of  the  upper  horn  somewhat  below  the  apex.  The 
inferior  vein  comes  from  the  posterior  and  inferior  portion  of  the  gland.  Both 
empty  into  the  internal  jugular.  The  lower  surface  of  the  isthmus  and  the  inner 
side  of  each  inferior  horn  is  drained  by  two  veins.  Each  vein  is  called  the  thy- 
reoidea ima  (Kocher).  The  left  vein  empties  into  the  left  innominate  vein.  The 
right  vein  empties  into  either  the  right  or  left  innominate  vein.  These  veins  may 
be  very  small,  may  be  absent,  or  may  join  and  form  one  vein  which  empties  into 
the  left  innominate.  An  inferior  thyroid  is  often  also  present.  It  comes  from  the 
outer  portion  of  the  inferior  horn  of  the  gland  and  empties  into  the  innominate  vein. 

The  facial  and  occipital  veins  have  been  described  on  pages  726  and  727. 

Surgical  Anatomy. — The  internal  jugular  vein  occasionally  requires  ligature  in  eases  of  septic 
thrombosis  of  the  lateral  sinus  from  suppuration  in  the  middle  ear.  This  is  done  in  order  to 
prevent  septic  emboli  being  carried  into  the  general  circulation.  This  operation  has  been 
performed  in  a  number  of  cases,  with  satisfactory  results.  The  cases  are  generally  those  of 
chronic  disease  of  the  middle  ear,  with  discharge  of  pus  which  perhaps  has  existed  for  many 
years.  The  patient  is  seized  with  acute  septic  inflammation,  spreading  to  the  mastoid  cells, 
and,  consequent  on  this,  septic  thrombosis  of  the  lateral  sinus  extending  to  the  internal  jugular 
vein.  Such  cases  are  always  extremely  grave,  for  there  is  danger  that  a  portion  of  the  septic 
clot  will  be  detached  and  cause  septic  embolism  in  the  thoracic  viscera.  If  thrombo-phlebitis 
of  the  sinus  is  suspected  the  mastoid  should  be  opened  and  cleansed  and  the  sinus  should  be  at 
once  exposed  and  explored.  If  the  sinus  is  found  to  be  thrombosed  the  surgeon  should  at 
once  proceed  to  ligate  the  internal  jugular  vein,  by  an  incision  along  the  anterior  border  of  the 
sterno-mastoid,  the  centre  of  which  is  on  a  level  with  the  greater  cornu  of  the  hyoid  bone.  The 
vein  should  be  ligated  in  two  places  and  divided  between.  After  the  vessel  has  been  secured 
and  divided  the  lateral  sinus  is  to  be  thoroughly  cleared  out,  and,  by  removing  the  ligature  from 
the  upper  end  of  the  divided  vein,  all  septic  clots  may  be  removed  by  syringing  from  the  sinus 
through  the  vein.  If  hemorrhage  occurs  from  the  distal  end  of  the  sinus,  it  can  be  arrested  by 
careful  plugging  with  antiseptic  gauze. 

The  thyroid  veins  are  small  vessels  when  the  gland  is  of  normal  size,  but  become  enormous 
when  the  gland  is  much  enlarged. 

In  the  operation  of  thyroidectomrj  the  veins  as  well  as  the  arteries  are  ligated  before  the  gland, 
or  rather  before  one  lobe  of  it  is  extirpated. 

The  Vertebral  Vein  {v.  vertebralis)  (Fig.  449)  commences  by  numerous  small 
veins  from  the  intraspinal  venous  plexuses  (plexus  venosi  vertebrates);  these  pass 
outward  and  enter  the  foramen  in  the  transverse  process  of  the  atlas,  and  descend, 
forming  a  dense  plexus  around  the  vertebral  artery  in  the  canal  formed  by  the 
foramina  in  the  transverse  processes  of  the  cervical  vertebrje.  The  vessels  of  this 
plexus  unite  at  the  lower  part  of  the  neck  into  two  main  trunks,  one  of  which 
emerges  from  the  foramen  in  the  transverse  process  of  the  sixth  cervical  vertebra, 
and  the  other  through  that  of  the  seventh.  Uniting,  these  two  trunks  form  a 
single  vessel  which  terminates  at  the  root  of  the  neck  in  the  back  part  of  the 
innominate  vein  near  its  origin,  its  mouth  being  guarded  by  a  pair  of  valves. 
On  the  right  side  it  crosses  the  first  part  of  the  subclavian  artery. 

Tributaries. — ^The  vertebral  vein  receives  in  its  course  a  vein  from  the  inside 
of  the  skull  through  the  posterior  condyloid  foramen.     It  anastomoses  with  the 


THE     VEINS    OF    THE    DIPLOE 


733 


occipital  vein  and  receives  muscular  veins  from  the  muscles  in  the  prevertebral 
region;  dorsi-spinal  veins,  from  the  back  part  of  the  cervical  portion  of  the  spine; 
meningo-rachidian  veins,  from  the  interior  of  the  spinal  canal;  the  anterior  and 
posterior  vertebral  veins ;  and  close  to  its  termination  it  is  joined  by  a  small  vein 
from  the  first  intercostal  space  which  accompanies  the  superior  intercostal  artery. 
The  Anterior  Vertebral  or  Anterior  Deep  Cervical  Vein  commences  in  a  plexus 
around  the  transverse  processes  of  the  upper  cervical  vertebrae,  descends  in  com- 
pany with  the  ascending  cervical  artery  between  the  Scalenus  anticus  and  Rectus 
capitis  anticus  major  muscles,  and  opens  into  the  vertebral  vein  just  before  its 
termination. 


VERTEBRAL- 


POSTERIOR 

DEEP 

CERVICAL 


POSTERIOR 

EXTERNAL 

JUGULAR 


VERTEBRAL 


ASCENDING 
CERVICAL 


Fig.  449. — The  vertebral  vein.     (Poirier  and  Charpy.) 


The  Posterior  Vertebral  or  Posterior  Deep  Cervical  Vein  {v.  cervicalis  profunda) 
(Fig.  449)  accompanies  the  profunda  cervicis  artery,  lying  between  the  Com- 
plexus  and  Semispinalis  colli.  It  commences  in  the  suboccipital  region  by  com- 
municating branches  from  the  occipital  vein  and  tributaries  from  the  deep  muscles 
at  the  back  of  the  neck.  It  receives  tributaries  from  the  plexuses  around  the  spinous 
processes  of  the  cervical  vertebrae,  and  terminates  in  the  lower  end  of  the  vertebral 
vein. 

The  Veins  of  the  Diploe  (Vense  Diploicae)  (Fig.  450). 

The  diploe  of  the  cranial  bones  is  channelled  in  the  adult  by  a  number  of 
tortuous  canals,  the  diploic  canals  or  canals  of  Breschet  (canales  diploid  [Brescheti]) , 
which  are  lined  by  a  more  or  less  complete  layer  of  compact  tissue.  The  veins 
they  contain  are  large  and  capacious,  their  walls  being  thin,  and  formed  only  of 
endothelium  resting  upon  a  layer  of  elastic  tissue,  and  they  present  at  irregular 
intervals  pouch -like  dilatations,  or  culs-de-sac,  which  serve  as  reservoirs  for  the 
blood.  These  are  the  veins  of  the  diploe ;  they  can  only  be  displayed  by  removing 
the  outer  table  of  the  skull. 

In  adult  life,  as  long  as  the  cranial  bones  are  distinct  and  separable,  these 
veins  are  confined  to  the  particular  bones;  but  in  old  age,  when  the  sutures  are 


734 


THE   BLOOD -VASCULAB    SYSTEM 


united,  they  communicate  with  each  other  and  increase  in  size.  These  vessels 
communicate,  in  the  interior  of  the  cranium,  with  the  meningeal  veins  and  with 
the  sinuses  of  the  dura  mater,  and  on  the  exterior  of  the  skull  with  the  veins  of 
the  pericranium.  They  are  divided  into  the  frontal  diploic  vein  {v.  diploica  fron- 
talis), which  opens  into  the  supraorbital  vein  by  an  aperture  in  the  supraorbital 
notch  and  into  the  superior  longitudinal  sinus;  the  anterior  temporal  diploic  vein 
(v.  diploica  temporalis  anterior),  which  is  confined  chiefly  to  the  frontal  bone, 
communicates  with  the  spheno-parietal  sinus  and,  after  escaping  by  an  aperture 
in  the  great  wing  of  the  sphenoid,  opens  into  one  of  the  deep  temporal  veins;  the 
posterior  temporal,  or  external  parietal  diploic  vein  (v.  diploica  temporalis  posterior), 
is  between  the  emissarium  parietale  and  the  emissarium  mastoideum;  and  the 
occipital  diploic  vein  {v.  diploica  occipitalis),  the  largest  of  the  four,  which  is 
confined  to  the  occipital  bone,  and  opens  into  the  emissarium  occipitale. 


Fig.  450. — Veins  of  the  diploe  as  displayed  by  the  removal  of  the  outer  table  of  the  skull. 


The  Emissary  Veins  are  considered  on  page  743. 

The  Meningeal  Veins  (vv.  meningeoe). — They  are  numerous  in  the  dura  mater, 
are  without  valves,  anastomose  freely  with  each  other,  do  not  increase  in  size  as 
they  reach  the  sinus  which  receives  them,  and  bear  no  regular  relation  to  the 
meningeal  arteries.  The  middle  meningeal  artery  has  two  vense  comites.  The 
other  meningeal  arteries  usually  have  two  apiece,  but  may  have  but  one.  The 
middle  meningeal  veins  {vv.  meningece  medics)  accompany  the  middle  meningeal 
artery,  are  united  to  the  spheno-parietal  sinus,  pass  through  the  foramen  spino- 
sum,  and  join  the  pterygoid  plexus.  The  other  meningeal  veins  empty  into  the 
superior  longitudinal  sinus  and  communicate  with  the  plexus  of  the  foramen 
ovale. 

The  Cerebral  Veins  (Venae  Cerebri). 

The  cerebral  veins  are  remarkable  for  the  absence  of  valves  and  for  the  extreme 
thinness  of  their  coats.  The  coats  are  thin  because  they  contain  no  muscular 
tissue.  The  cerebral  veins  may  be  divided  into  two  sets:  the  superficial  veins, 
which  are  placed  on  the  surface,  and  the  deep  veins,  which  occupy  the  interior  of 
the  organ.    The  veins  of  the  brain  do  not  accompany  associated  arteries. 


THE    CEREBRAL     VEINS  735 

The  Superficial  or  Cortical  Cerebral  Veins  {venoe  cerebri  externce)  (Fig.  546) 
ramify  upon  the  surface  of  the  brain,  being  lodged  in  the  sulci  between  the  con- 
volutions, a  few  running  across  the  convolutions.  They  receive  branches  from  the 
substance  of  the  brain  and  terminate  in  the  sinuses.  They  are  named,  from  the 
position  they  occupy,  superior,  median,  and  inferior  cerebral  veins. 

The  Superior  Cerebral  Veins  (yy.  cerebri  super iores),  eight  to  twelve  in  number 
on  each  side,  return  the  blood  from  the  convolutions  on  the  superior  surface  of  the 
hemisphere;  they  pass  forward  and  inward  toward  the  great  longitudinal  fissure, 
where  they  receive  the  median  cerebral  veins ;  near  their  termination  they  become 
invested  with  a  tubular  sheath  of  the  arachnoid  membrane,  and  open  into  the 
superior  longitudinal  sinus  in  the  opposite  direction  to  the  course  of  the  current  of 
the  blood. 

The  Median  Cerebral  Veins  (v.  cerebri  mediana)  return  the  blood  from  the  con- 
volutions of  the  mesial  surface  of  the  corresponding  hemisphere;  they  open  into 
the  superior  cerebral  veins,  or  occasionally  into  the  inferior  longitudinal  sinus. 

The  Inferior  Cerebral  Veins  {vv.  cerebri  inferiores)  ramify  on  the  lower  part  of  the 
outer  surface  and  on  the  under  surface  of  the  cerebral  hemisphere.  Some,  collecting 
tributaries  from  the  under  surface  of  the  anterior  lobes  of  the  brain,  terminate  in 
the  cavernous  sinus.  One  vein  of  large  size,  the  middle  cerebral  or  superficial 
Sylvian  vein  (v.  cerebri  media),  commences  on  the  under  surface  of  the  temporal 
lobe,  and,  running  along  a  portion  of  the  fissure  of  Sylvius,  opens  into  the  cav- 
ernous sinus.  The  great  anastomotic  vein  of  Trolard  or  the  superficial  communi- 
cating vein  establishes  a  union  between  the  sinuses  of  the  vertex  and  those  of  the 
base  of  the  brain.  It  comes  from  one  of  the  superior  cerebral  veins,  passes  down- 
ward into  the  fissure  of  Sylvius,  and,  by  means  of  the  middle  cerebral  vein,  effects  a 
communication  with  the  cavernous  sinus.  The  posterior  anastomotic  vein  connects 
the  middle  cerebral  vein  with  the  lateral  sinus.  Other  veins  commence  on  the 
under  surface  of  the  base  of  the  brain,  and  unite  to  form  from  three  to  five  veins, 
which  open  into  the  superior  petrosal  and  lateral  sinuses  from  before  backward. 

The  Deep  Cerebral,  Central,  or  Ventricular  Veins,  Veins  of  Galen  (venoe 
Galeni,  vv.  cerebri  internoe)  (Fig.  548),  are  two  in  number.  Each  is  formed  by 
the  union  of  two  veins,  the  vena  corporis  striati,  and  the  choroid  vein,  on  either  side. 
The  deep  cerebral  veins  run  backward,  parallel  with  one  another,  between  the 
layers  of  the  velum  interpositum,  and  in  the  region  of  the  pineal  body  unite 
to  form  one  vein,  the  vena  magna  Galeni  {v.  cerebri  magna),  which  passes  out 
of  the  brain  at  the  great  transverse  fissure,  between  the  posterior  extremity,  or 
splenium,  of  the  corpus  callosum  and  the  tubercula  quadrigemina,  to  enter  the 
straight  sinus.  The  two  deep  cerebral  veins  receive  branches  from  the  callosal 
region,  from  a  portion  of  the  occipital  lobe,  and  just  before  their  union  each  vein 
receives  the  basilar  vein.  The  vena  magna  Galeni  receives  the  vermian  vein  from 
the  superficial  cerebellar  veins. 

The  Vena  Corporis  Striati  on  each  side  commences  in  the  groove  between  the 
corpus  striatum  and  thalamus  opticus,  receives  numerous  veins  from  both  of  these 
parts,  and  unites  behind  the  anterior  pillar  of  the  fornix  with  the  choroid  vein  to 
form  one  of  the  deep  cerebral  veins. 

The  Choroid  Vein  {v.  choroidea)  originates  in  the  extreme  end  of  the  middle 
cornu  of  the  lateral  ventricle  and  runs  along  the  whole  length  of  the  outer  border  of 
the  choroid  plexus,  receiving  veins  from  the  hippocampus  major,  the  fornix,  and 
corpus  callosum,  and  unites,  at  the  anterior  extremity  of  the  choroid  plexus,  with 
the  vein  of  the  corpus  striatum  to  form  the  deep  cerebral  vein  of  that  side. 

The  Basilar  Vein  (v.  basalis)  commences  at  the  anterior  perforated  space  at  the 
base  of  the  brain  by  the  union  of  a  small  anterior  cerebral  vein,  which  courses 
backward  between  the  anterior  lobes  of  the  cerebrum,  with  the  deep  Sylvian  vein, 
which  descends  through  the  lower  part  of  the  Sylvian  fissure  and  receives  veins  from 


736  THE  BLOOD -VASCULAR    SYSTEM 

the  island  of  Reil.  It  passes  backward  over  the  crus  cerebri,  receiving  the  inferior 
striate  vein  from  the  corpus  striatum,  interpeduncular  veins  from  the  interpedun- 
cular space,  ventricular  veins  from  the  middle  cornu  of  the  lateral  ventricles,  and 
tributaries  from  the  uncinate  convolution,  and  enters  the  vein  of  Galen  just 
before  its  junction  with  the  vein  of  the  opposite  side. 

The  Superficial  Cerebellar  Veins  (Fig.  546)  occupy  the  surface  of  the  cere- 
bellum, and  are  disposed  in  two  sets,  superior  and  inferior. 

The  Superior  Superficial  Cerebellar  Veins  {vv.  cerebelli  swperiores)  pass  partly 
forward  and  inward,  across  the  superior  vermiform  process,  to  terminate  in  lateral 
branches  which  pass  partly  to  the  straight  sinus  and  partly  outward  to  the  lateral 
and  superior  petrosal  sinuses. 

The  Inferior  Superficial  Cerebellar  Veins  {vv.  cerebelli  inferiores),  of  large  size, 
terminate  in  the  lateral,  inferior  petrosal,  and  occipital  sinuses. 

The  Deep  Cerebellar  Veins  bring  blood  from  the  interior  of  the  cerebellum 
to  the  superficial  veins. 

Veins  of  the  Pons  Varolii. — Veins  come  from  the  depth  of  the  pons,  the  deep 
veins,  and  empty  into  a  plexus  of  superficial  veins.  From  this  superficial  venous 
plexus  a  superior  vein  passes  to  the  basilar  vein,  and  an  inferior  vein  either  into  a 
cerebellar  vein  or  into  the  superior  petrosal  sinus. 

Veins  of  the  Medulla  Oblongata. — Veins  pass  from  the  depth  of  the  medulla  and 
end  in  a  plexus  on  the  surface.  From  this  plexus  comes  an  anterior  median 
vein,  which  is  a  prolongation  of  a  like  vein  of  the  spinal  cord — a  posterior  median 
vein  corresponding  to  a  like  vein  of  the  cord — and  small  branches  which  pass 
with  the  roots  of  the  ninth,  tenth,  eleventh,  and  twelfth  cranial  nerves,  and  empty 
into  the  occipital  and  the  inferior  petrosal  sinuses. 

The  perivascular  lymph-spaces  are  especially  found  in  connection  with  the  vessels  of  the  brain. 
These  vessels  are  enclosed  in  a  sheath,  which  acts  as  a  lymphatic  channel,  through  which  the 
lymph  is  carried  to  the  subarachnoid  and  subdural  spaces,  from  which  it  is  returned  into  the 
general  circulation. 

The  Sinuses  of  the  Dura  Mater  (Sinus  Diirae  Matris)(Figs.451, 452 ,453,456,457) 
Ophthalmic  Veins  and  Emissary  Veins. 

The  sinuses  of  the  dura  mater  are  venous  channels,  analogous  to  the  veins. 
The  outer  coat  of  a  sinus  is  formed  by  the  dura  mater;  the  inner  coat,  by  a 
continuation  of  the  lining  membrane  of  the  veins.  The  thick  walls  of  a  sinus 
resist  intracranial  pressure.^  They  are  divided  into  two  sets:  (1)  those  situated 
at  the  upper  and  back  part  of  the  skull;  (2)  those  at  the  base  of  the  skull.  The 
former  are — the 

Superior  Longitudinal  Sinus.  Straight  Sinus. 

Inferior  Longitudinal  Sinus.  Lateral  Sinuses. 

Occipital  Sinus. 

The  Superior  Longitudinal  Sinus  (sinus  sagittalis  superior)  (Figs.  451,  452, 
and  453)  occupies  the  attached  margin  of  the  falx  cerebri.  Commencing  at  the 
foramen  caecum,  through  which,  in  the  child,  it  constantly  communicates  by  a 
small  branch  with  the  veins  of  the  nasal  fossse,  it  runs  from  before  backward, 
grooving  the  inner  surface  of  the  frontal,  the  adjacent  margins  of  the  two  parietal, 
and  the  superior  division  of  the  crucial  ridge  of  the  occipital  bone,  and  terminates 
by  opening  into  the  torcular  Herophili.  The  sinus  is  triangular  on  transverse 
section,  is  narrow  in  front,  and  gradually  increases  in  size  as  it  passes  backward. 
On  examining  its  inner  surface  it  presents  the  internal  openings  of  the  superior 
cerebral  veins,  which  run,  for  the  most  part,  from  behind  forward,  and  open 

1  A.  W.  Hughes. 


THE   SINUSES    OF    THE    DUB  A    MATER 


737 


chiefly  at  the  back  part  of  the  sinus,  their  orifices  being  concealed  by  fibrous 
folds;  numerous  fibrous  bands,  chordae  Willisii  (Fig.  453),  are  also  seen  extend- 
ing transversely  across  the  inferior  angle  of  the  sinus;  and  some  small,  white, 
projecting  bodies,  the  glandulse  Pacchioni  (granulationes  arachnoidales) .  This 
sinus  communicates  by  numerous  small  apertures  with  spaces  in  the  dura 
mater   known    as    lacunae    laterales    or    parasinoidal    spaces    (Fig.    453).      The 


SUPERIOR 

LONGITUDINAL 

SINUS 


STRAIGHT 
SINUS 


_. LATERAL 
SINUS 


Fig.  451. 


-Coronal  section  of  the  skull  to  show  tne  situations  and  shapes  of  the  chief  sinuses. 
(Poirier  and  Charpy.) 


Pacchionian  bodies  project  into  these  spaces.  This  sinus  receives  the  superior 
cerebral  veins,  numerous  veins  from  the  diploe  and  dura  mater,  the  outlets  of  the 
parasinoidal  spaces,  and,  at  the  posterior  extremity  of  the  sagittal  suture,  veins 
from  the  pericranium,  which  pass  through  the  parietal  foramina.  In  children  a 
twig  from  the  longitudinal  sinus  passes  through  the  foramen  csecum  and  into 
the  nose. 


Torcular  herophili. 


Foramen  csccum. 


Fig.  452. — Vertical  section  of  the  skull,  showing  the  sinuses  of  the  dura  mater. 


The  Torcular  Herophili  or  the  confluence  of  the  sinuses  (Figs.  452  and  456)  is  the 
dilated  extremity  of  the  superior  longitudinal  sinus.    It  is  of  irregular  form,  and 

47 


738 


THE    BLOOD -VASCULAR    SYSTEM 


is  lodged  on  one  side  (generally  the  right)  of  the  internal  occipital  protuberance. 
From  it  the  lateral  sinus  of  the  side  to  which  it  is  deflected  is  derived.  It  receives 
also  the  blood  from  the  occipital  sinus. 

The  Inferior  Longitudinal  Sinus  (sinus  sagittalis  inferior)  (Fig.  452),  more 
correctly  described  as  the  inferior  longitudinal  vein,  is  contained  in  the  posterior 
part  of  the  free  margin  of  the  falx  cerebri.  It  is  of  a  cylindrical  form,  increases 
in  size  as  it  passes  backward,  and  terminates  in  the  straight  sinus.  It  receives 
several  veins  from  the  falx  cerebri,  and  occasionally  a  few  from  the  mesial  surface 
of  the  hemispheres. 

The  Straight  Sinus  (sinus  rectus)  (Figs.  451  and  452)  is  situated  at  the  line  of 
junction  of  the  falx  cerebri  with  the  tentorium.  It  is  triangular  in  form,  increases 
in  size  as  it  proceeds  backward,  and  runs  obliquely  downward  and  backward  from 


MENINGEAL 
VEIN 


SUPERIOR 

LONGITUDINAL 

SINUS 


\  PARASI- 

NOIDAL 
SINUS 


PARASINOIDAL 
SINUS 


Fig.  453. — ^Superior  longitudinal  sinus  seen  from  above  after  removal  of  the  skull-cap.  The  chorda  Willisii 
are  clearly  visible.  The  para-sinoidal  sinuses  are  also  well  shown.  Probes  passing  from  the  latter  to  the 
longitudinal  sinus  show  that  they  communicate.     (Poirier  and  Charpy.) 


the  termination  of  the  inferior  longitudinal  sinus  to  the  lateral  sinus  of  the  oppo- 
site side  to  that  into  which  the  superior  longitudinal  sinus  is  prolonged.  It  com- 
municates by  a  cross-branch  with  the  torcular  Herophili.  Besides  the  inferior 
longitudinal  sinus,  it  receives  the  vena  magna  Galeni  and  the  superior  cerebellar 
veins.  A  few  transverse  bands  cross  its  interior.  This  sinus  is  usually  considered 
to  be  formed  by  the  union  of  the  great  vein  of  Galen  and  the  inferior  longitudinal 
sinus. 

The  Lateral  Sinus  (sinus  transversus)  (Figs.  451,  452,  456,  and  457)  is  of 
large  size.  There  are  two  lateral  sinuses  situated  in  the  attached  margin  of 
the  tentorium   cerebelli   throughout  most  of   its   extent.     They  commence  at 


THE   SINUSES    OF    THE   DUBA    MATER  739 

the  internal  occipital  protuberance,  one,  generally  the  right,  being  the  direct 
continuation  of  the  superior  longitudinal  sinus,  the  other  of  the  straight  sinus. 
Each  passes  outward  and  forward,  describing  a  slight  curve  with  its  convexity 
upward,  to  the  base  of  the  petrous  portion  of  the  temporal  bone,  then,  leaving 
the  tentorium,  curves  downward  and  inward  to  reach  the  jugular  foramen, 
where  it  terminates  in  the  internal  jugular  vein.  It  rests,  in  its  course,  upon 
the  inner  surface  of  the  occipital,  the  posterior  inferior  angle  of  the  parietal, 
and  the  mastoid  portion  of  the  temporal  bone,  and  on  the  occipital  again,  at 
the  jugular  process,  just  before  its  termination.  The  portion  of  the  sinus  rest- 
ing on  the  mastoid  process  of  the  temporal  and  the  jugular  process  of  the 
occipital  bone  is  not  covered  by  the  tentorium  and  is  often  called  the  sigmoid 
sinus  because  of  its  shape,  which  resembles  the  letter  S.  These  sinuses  are  fre- 
quently of  unequal  size,  that  formed  by  the  superior  longitudinal  sinus  being 
the  larger,  and  they  increase  in  size  as  they  proceed  from  behind  forward.  The 
horizontal  portion  is  of  a  triangular  form,  the  curved  portion  semicylindrical. 
Their  inner  surface  is  smooth,  and  not  crossed  by  the  fibrous  bands  found  in  the 
other  sinuses.  The  lateral  sinuses  receive  the  blood  from  the  superior  petrosal 
sinuses  at  the  base  of  the  petrous  portion  of  the  temporal  bone,  and  they  unite 
with  the  inferior  petrosal  sinus,  just  external  to  the  jugular  foramen,  to  form  the 
internal  jugular  vein  (Fig.  457).  They  communicate  with  the  veins  of  the 
pericranium  by  means  of  the  mastoid  and  posterior  condyloid  veins,  and  they 
receive  some  of  the  inferior  cerebral  and  inferior  cerebellar  veins,  some  veins 
from  the  diploe,  and  often  veins  from  the  internal  ear  {w.  auditivcB  internae), 
which  come  out  of  the  internal  auditory  meatus.  The  petro-squamous  sinus,  when 
present,  runs  backward  along  the  junction  of  the  petrous  and  squamous  portions 
of  the  temporal  bone,  and  opens  into  the  lateral  sinus. 

Surgical  Anatomy. — The  lateral  sinus  may,  as  a  result  of  middle-ear  disease,  be  attacked  by 
suppurative  inflammation,  which  leads  to  blocking  {septic  thrombo-phlebitis) .  In  such  a  case 
the  surgeon  will  be  obliged  to  open  the  sinus  to  remove  infected  clot  and  tie  the  internal  jugular 
vein  to  intercept  thrombi.  The  lines  overlying  the  sinus  is  as  follows:  Draw  a  line  horizontally 
outward  from  the  occipital  protuberance  to  a  point  one  inch  posterior  to  a  vertical  line  drawn 
through  the  external  auditory  meatus  and  from  this  point  drop  a  second  line  to  the  mastoid 
process. 

The  Occipital  Sinus  (sinus  occipitalis)  (Fig.  452)  is  the  smallest  of  the  cranial 
sinuses.  There  is  often  but  a  single  occipital  sinus,  but  occasionally  there  are 
two.  It  is  situated  in  the  attached  margin  of  the  falx  cerebelli.  It  commences 
by  several  small  veins  around  the  margin  of  the  foramen  magnum,  one  of  which 
joins  the  termination  of  the  lateral  sinus;  it  communicates  with  the  posterior 
spinal  veins  and  terminates  in  the  torcular  Herophili. 

The  sinuses  at  the  base  of  the  skull  are — the 

Cavernous  Sinuses.  Superior  Petrosal  Sinuses. 

Spheno-parietal  Sinuses.  Inferior  Petrosal  Sinuses. 

Circular  Sinus.  Transverse  Sinus. 

The  Cavernous  Sinus  (sinus  cavernosu^)  (Figs.  456  and  457)  is  named  from 
presenting  a  reticulated  structure,  due  to  being  traversed  by  numerous  interlacing 
filaments  (Fig.  454).  There  are  two  cavernous  sinuses,  of  irregular  form,  larger 
behind  than  in  front,  and  placed  one  on  each  side  of  the  sella  turcica,  extending 
from  the  sphenoidal  fissure  to  the  apex  of  the  petrous  portion  of  the  temporal  bone. 
Each  receives  anteriorly  the  ophthalmic  vein  through  the  sphenoidal  fissure,  and 
opens  behind  into  the  petrosal  sinuses.  On  the  inner  wall  of  each  sinus  is  found 
the  internal  carotid  artery,  accompanied  by  filaments  of  the  carotid  plexus  and 
by  the  sixth  nerve;  and  on  its  outer  wall,  the  third,  fourth,  and  ophthalmic  division 


740 


THE  BLOOD -VASCULAR   SYSTEM 


of  the  fifth  nerve  (Fig.  454) .  These  parts  are  separated  from  the  blood  flowing 
along  the  sinus  by  the  lining  membrane,  which  is  continuous  with  the  inner  coat 
of  the  veins.  The  cavernous  sinuses  receive  some  of  the  cerebral  veins,  and  also 
the  spheno-parietal  sinuses.  They  communicate  with  the  lateral  sinuses  by 
means  of  the  superior  and  inferior  petrosal  sinuses,  and  with  the  facial  veins 
through  the  ophthalmic  veins.  They  also  communicate  with  each  other  by  means 
of  the  circular  sinus. 


TRANSVERSE 
SINUS 


CAVERNOUS 

ilNUS 


THIRD 
NERVE 


OPHTHALMIC 
DIVISION  OF 
FIFTH   NERVE 

SUPERIOR  MAXIL 
LARY   DIVISION 
OF  FIFTH   NERVE 


Fig.  454. — Frontal  section  through  the  right  ca\ernoui5  sinus      (Spalteholz.) 


Surgical  Anatomy. — An  arterio-venous  communication  may  be  established  between  the 
cavernous  sinus  and  the  carotid  artery,  as  it  lies  in  it,  giving  rise  to  a  'pulsating  tumor  in  the 
orbit.  Such  a  communication  may  be  the  resuH  of  injury,  such  as  a  bullet  wound,  a  stab,  or 
a  blow  or  fall  sufficiently  severe  to  cause  a  fracture  of  the  base  of  the  skull  in  this  situation, 
or  it  may  occur  from  the  rupture  of  an  aneurism  or  a  diseased  condition  of  the  internal 
carotid  artery.  The  disease  begins  with  sudden  noise  and  pain  in  the  head,  followed  by 
exophthalmos,  swelling  and  congestion  of  the  lids  and  conjunctivae.  A  pulsating  tumor 
develops  at  the  margin  of  the  orbit,  with  thrill  and  the  characteristic  bruit;  accompanying 
these  symptoms  there  may  be  impairment  of  sight,  paralysis  of  the  iris  and  orbital  muscles, 
and  pain  of  varying  intensity.  In  some  cases  the  opposite  orbit  becomes  affected  by  the  passage 
of  the  arterial  blood  into  the  opposite  sinus  by  means  of  the  circular  sinus.  Or  the  arterial 
blood  may  find  its  way  through  the  emissary  veins  into  the  pterygoid  plexus,  and  thence  into  the 
veins  of  the  face.  Pulsating  tumors  of  the  orbit  may  also  be  due  to  traumatic  aneuri.sm  of 
one  of  the  orbital  arteries,  and  symptoms  resembling  those  of  pulsating  tumor  may  be  produced 
by  pressure  on  the  ophthalmic  vein,  as  it  enters  the  sinus,  by  an  aneurism  of  the  internal 
carotid  artery. 

The  Spheno-parietal  Sinus  or  Sinus  Alse  Parvae  {sinus  sphenoparietalis).— 
Each  of  these  sinuses  is  lodged  in  the  dura  mater  on  the  imder  surface  of  the 
lesser  wing  of  the  sphenoid  bone.  It  takes  origin  from  one  of  the  middle  menin- 
geal veins,  usually  receives  blood  from  the  diploe  of  the  skull,  passes  inward,  and 
ends  in  the  anterior  part  of  the  cavernous  sinus. 

The  Ophthalmic  Veins  are  two  in  number,  superior  and  inferior. 

The  superior  ophthalmic  vein  (v.  ophthalmica  superior)  (Fig.  455)  begins  as  the 
naso-frontal  vein  (v.  nasofrontalis) ,  at  the  inner  angle  of  the  orbit,  which  communi- 
cates with  the  angular  vein.  It  joins  the  angular  vein  with  the  cavernous  sinus; 
it  pursues  the  same  course  as  the  ophthalmic  artery,  and  receives  tributaries  corre- 
sponding to  the  branches  derived  from  that  vessel.  Forming  a  short  single  trunk, 
it  passes  through  the  inner  extremity  of  the  sphenoidal  fissure,  and  terminates  in 
the  cavernous  sinus.  It  anastomoses  with  the  inferior  ophthalmic  vein  and  receives 
lachrymal,  anterior,  and  posterior  ethmoidal  and  muscular  branches,  and  veins 
of  the  eyelids  and  of  the  bulbus  oculi. 


THE  SINUSES    OF   THE  DURA    MATEB 


741 


The  inferior  ophthalmic  vein  {v.  ophthalmica  inferior)  (Fig.  455)  arises  in  the  veins 
of  the  eyelids  and  lachrymal  sac,  receives  the  veins  from  the  floor  of  the  orbit,  and 


CAVERNOUS 
SINUS 


INFERIOR 
OPHTHALMIC 


Fig.  455  — Veins  of  the  orbit.      (Poirier  and  Charpy.) 


from  the  portion  of  the  nasal  fossa  supplied  by  the  anterior  and  posterior  ethmoidal 
arteries.  It  either  passes  out  of  the  orbit  through  the  spheno-m axillary  fissure  to 
join  the  pterygoid  plexus  of  veins,  or  else,  passing  backward  through  the  sphenoidal 


Opening  of  mastoid 
vein. 


'  Torcular  Herophili. 
Fig.  456.— The  sinuses  at  the  base  of  the  skull. 


fissure,  it  enters  the  cavernous  sinus,  either  by  a  separate  opening,  or,  more  fre- 
quently, in  common  with  the  superior  ophthalmic  vein.     It  receives  muscular 


742 


THE    BLOOD -VASCULAR    SYSTEM 


branches  and  veins  of   the  bulbus    ocuh,  and   anastomoses  with   the  superior 
ophthalmic  vein. 

The  Circular  Sinus  (sinus  circularis)  (Figs.  454  and  456)  is  formed  by  two 
transverse  vessels,  the  anterior  and  posterior  intercavernous  sinuses  {sinus  inter- 
cavernous anterior  and  sinu^  intercavernous  posterior),  which  connect  together  the 
two  cavernous  sinuses ;  the  one  passing  in  front  and  the  other  behind  the  pituitary 
body,  and  thus  forming  with  the  cavernous  sinuses  a  venous  circle  around  that 
body.  The  anterior  one  is  usually  the  larger  of  the  two,  and  one  or  other  is  occa- 
sionally found  to  be  absent. 

•'  Falx  cerebri 


Optic  nerve 
Int.  carotid  artery 

Motor  oculi  nerve 


Inferior 
petrosal  sinus 


Dorsum  sellse 


9th,  10th,  and  11th 
cranial  nerves 


Lateral  sinus 
Fig.  457. — Relation  of  nerves  to  sinuses  in  jugular  foramen.     (Henle.) 

The  Superior  Petrosal  Sinus  (sinv^  petrosus  superior)  (Figs.  452  and  456) 
is  situated  along  the  superior  border  of  the  petrous  portion  of  the  temporal 
bone,  in  the  front  part  of  the  attached  margin  of  the  tentorium.  It  is  small 
and  narrow,  and  connects  together  the  cavernous  and  lateral  sinuses  at  each  side. 
It  receives  some  cerebellar  and  inferior  cerebral  veins,  and  usually  veins  from  the 
tympanic  cavity  (vv.  auditivoB  internee). 

The  Inferior  Petrosal  Sinus  {sinus  petrosus  inferior)  (Figs.  452  and  456)  is 
situated  in  the  groove  formed  by  the  junction  of  the  posterior  border  of  the 
petrous  portion  of  the  temporal  with  the  basilar  process  of  the  occipital  bone. 
It  commences  in  front  at  the  termination  of  the  cavernous  sinus,  and  behind  joins 
the  lateral  sinus  after  it  has  passed  through  the  jugular  foramen;  the  junction  of 
these  two  sinuses  forming  the  commencement  of  the  internal  jugular  vein.  The 
inferior  petrosal  sinus  receives  a  vein  from  the  internal  ear  and  also  veins  from 
the  medulla,  pons,  and  under  surface  of  the  cerebellum. 

The  junction  of  the  two  sinuses  takes  place  at  the  lower  border  of,  or  just 
external  to,  the  jugular  foramen.    The  exact  relation  of  the  parts  to  one  another 


THE  SINUSES    OF    THE  DURA    MATER  743 

in  the  foramen  is  as  follows:  The  inferior  petrosal  sinus  is  in  front,  with  the 
meningeal  branch  of  the  ascending  pharyngeal  artery,  and  is  directed  obliquely 
downward  and  backward;  the  lateral  sinus  is  situated  at  the  back  part  of  the 
foramen  with  a  meningeal  branch  of  the  occipital  artery,  and  between  the  two  are 
the  glosso-pharyngeal,  pneumogastric,  and  spinal  accessory  nerves  (Fig.  457). 
These  three  sets  of  structures  are  divided  from  each  other  by  two  processes  of 
fibrous  tissue.  The  junction  of  the  sinuses  takes  place  superficial  to  the  nerves, 
so  that  these  latter  lie  a  little  internal  to  the  venous  channels  in  the  foramen  (see 
Fig.  457).    These  sinuses  are  semicylindrical  in  form. 

The  Transverse  or  Basilar  Sinus  {plexus  hasilaris)  (Figs.  456  and  457)  con- 
sists of  several  interlacing  veins  between  the  layers  of  the  dura  mater  over  the 
basilar  process  of  the  occipital  bone,  which  serve  to  connect  the  two  inferior 
petrosal  sinuses.     With  them  the  anterior  spinal  veins  communicate. 

Emissary  Veins  (emissaria) . — The  emissary  veins  are  vessels  which  pass 
through  apertures  in  the  cranial  wall  and  establish  communications  between  the 
sinuses  inside  the  skull  and  the  diploic  veins  in  the  diploe,  and  the  veins  external 
to  the  skull.  Some  of  these  are  always  present,  others  only  occasionally  so. 
They  vary  much  in  size  in  different  individuals.  The  principal  emissary  veins 
are  the  following:  1.  A  vein,  almost  always  present,  which  passes  through  the 
mastoid  foramen  (emissarium  masioideum)  and  connects  the  lateral  sinus  with 
the  posterior  auricular  or  with  an  occipital  vein.  2.  A  constant  vein  which 
passes  through  the  parietal  foramen  {emissarium  parietale)  and  connects  the 
superior  longitudinal  sinus  with  the  veins  of  the  scalp.  3.  A  plexus  of  minute  veins 
which  pass  through  the  anterior  condyloid  foramen  {emissarium  condyloideum) 
and  connect  the  occipital  sinus  with  the  vertebral  vein  and  deep  veins  of  the  neck. 
4.  An  inconstant  vein  which  passes  through  the  posterior  condyloid  foramen  and 
connects  the  lateral  sinus  with  the  deep  veins  of  the  neck.  5.  One  or  two  veins 
of  considerable  size  which  pass  through  the  foramen  ovale  and  connect  the  cav- 
ernous sinus  with  the  pterygoid  and  pharyngeal  plexuses.  6.  Two  or  three  small 
veins  which  pass  through  the  foramen  lacerum  medium  and  connect  the  cavernous 
sinus  with  the  pterygoid  and  pharyngeal  plexuses.  7.  There  is  sometimes  a  small 
vein  connecting  the  same  parts  and  passing  through  the  inconstant  foramen  of 
Vesalius  at  the  root  of  the  pterygoid  process  of  the  sphenoid  bone.  8.  A  plexus  of 
veins  passing  through  the  carotid  canal  and  connecting  the  cavernous  sinus  with 
the  internal  jugular  vein.  9.  A  small  vein  {emissarium  occipitale)  usually  con- 
nects the  occipital  vein  with  the  lateral  sinus  or  the  torcular  Herophili  and  the 
occipital  diploic  vein. 

Surgical  Anatomy. — These  emissary  veins  are  of  great  importance  in  surgery.  In  addition 
to  them  there  are,  however,  other  communications  between  the  intra-  and  extra-cranial  circula- 
tion, as,  for  instance,  the  communication  of  the  angular  and  supra-orbital  veins  with  the  ophthal- 
mic vein  at  the  inner  angle  of  the  orbit,  and  the  communication  of  the  veins  of  the  scalp  with 
the  diploic  veins.  Through  these  communications  inflammatory  processes  commencing  on  the 
outside  of  the  skull  may  travel  inward,  leading  to  osteo-phlebitis  of  the  diploe  and  inflammation 
of  the  membranes  of  the  brain.  To  this  in  former  days  was  to  be  attributed  one  of  the  principal 
dangers  of  scalp  wounds  and  other  injuries  of  the  scalp. 

By  means  of  these  emissary  veins  blood  may  be  abstracted  almost  directly  from  the  intra- 
cranial circulation.  For  instance,  leeches  applied  behind  the  ear  abstract  blood  almost  directly 
from  the  lateral  sinus  by  means  of  the  vein  passing  through  the  mastoid  foramen.  Again, 
epistaxis  in  children  will  frequently  relieve  severe  headache,  the  blood  which  flows  from  the  nose 
being  derived  from  the  longitudinal  sinus  by  means  of  the  vein  which  passes  through  the  foramen 
caecum,  which  is  another  communication  between  the  intracranial  and  extracranial  circulation 
constantly  found  in  children. 


744  THE  BLOOD -VASCULAR    SYSTEM 

VEINS  OF  THE  UPPER  EXTREMITY  AND  THORAX. 

The  veins  of  the  Upper  Extremity  are  divided  into  two  sets,  superficial  and 
deep. 

The  Superficial  Veins  are  placed  immediately  beneath  the  integument  between 
the  layers  of  superficial  fascia.  * 


Fig.  458. — The  veins  on  the  dorsum  of  the  hand.     (Bourgery.) 

The  Deep  Veins  accompany  the  arteries,  and  constitute  the  venae  comites  of 
those  vessels. 

Both  sets  of  vessels  are  provided  with  valves,  which  are  more  numerous  in  the 
deep  than  in  the  superficial  veins. 


THE  SUPERFICIAL     VEINS    OF    THE    UPPER    EXTREMITY    745 

The  Superficial  Veins  of  the  Upper  Extremity  (Fig.  459). 

The  superficial  veins  of  the  upper  extremity  are — the 

Superficial  Veins  of  the  Hand.  Median. 

Anterior  Ulnar.  Median  Cephalic. 

Posterior  Ulnar.  Median  Basilic. 

Common  Ulnar.  Basilic. 

Radial.  Cephalic. 

The  Superficial  Veins  of  the  Hand  and  Fingers  (Figs.  458  and  459)  are 
principally  situated  on  the  dorsal  surface.  These  dorsal  veins  begin  in  each  finger 
as  a  venous  plexus,  in  which  are  distinct  veins  running  in  a  longitudinal  direction, 
and  called  dorsal  digital  veins  {vv.  digitales  dorsales  propria^).  The  dorsal  digital 
veins  terminate  over  the  first  phalanges,  in  the  venous  arches  of  the  fingers  {arcus 
venosi  digitales).  From  these  arches  take  origin  the  four  dorsal  interosseous  or 
the  interdigital  veins  (vv.  metacarpecB  dorsales).  These  veins  form  the  dorsal  venous 
plexus  of  the  hand  (rete  venosum  dor  sale  manus).  This  plexus  lies  in  a  line  w^ith  the 
lower  ends  of  the  shafts  of  the  metacarpal  bones.  It  receives  the  dorsal  inter- 
osseous veins,  the  radial  digital  vein  of  the  index  finger,  and  numerous  superficial 
veins  from  the  back  of  the  hand.  It  gives  origin  to  the  superficial  radial  vein  and 
the  posterior  ulnar  vein.  The  superficial  veins  of  the  palmar  surface  are  of  less 
diameter  than  the  dorsal  veins.  They  arise  from  each  of  the  phalanges  by  a 
plexus  {vv.  digitales  volares  propria;).  Vessels  at  the  edges  of  the  fingers  take  most 
of  the  blood  to  the  dorsal  veins.  There  are  also  veins  in  the  finger  webs  (vv.  inter- 
capitulares) ,  which  take  blood  from  the  palm  to  the  dorsum.  A  superficial  plexus, 
the  palmar  plexus,  lies  upon  the  palmar  fascia,  the  fascia  of  the  thenar  eminence, 
and  the  fascia  of  the  hypothenar  eminence. 

The  Anterior  Ulnar  Vein  (v.  ulnaris  anterior)  (Fig.  459)  commences  on  the 
anterior  surface  of  the  ulnar  side  of  the  hand  and  wrist,  and  ascends  along  the 
anterior  surface  of  the  ulnar  side  of  the  forearm  to  the  bend  of  the  elbow,  where 
it  joins  with  the  posterior  ulnar  vein  to  form  the  common  ulnar.  Occasionally  it 
opens  separately  into  the  median  basilic  vein.  It  communicates  with  branches 
of  the  median  vein  in  front  and  with  the  posterior  ulnar  behind. 

The  Posterior  or  Dorsal  Ulnar  Vein  (v.  ulnaris  posterior)  (Fig.  458)  commences 
on  the  posterior  surface  of  the  ulnar  side  of  the  wrist.  It  runs  on  the  posterior 
surface  of  the  ulnar  side  of  the  forearm,  and  just  below  the  elbow  unites  with 
the  anterior  ulnar  vein  to  form  the  common  ulnar,  or  else  joins  the  median 
basilic  and  helps  to  form  the  basilic.  It  communicates  with  the  deep  veins 
of  the  palm  by  a  branch  which  emerges  from  beneath  the  Abductor  minimi  digiti 
muscle. 

The  Common  Ulnar  Vein  (v.  ulnaris  communis)  (Fig.  459)  is  a  short  trunk 
which  is  not  constant.  When  it  exists  it  is  formed  by  the  junction  of  the  two 
preceding  veins,  and,  passing  upward  and  outward,  joins  the  median  basilic  to 
form  the  basilic  vein.  When  it  does  not  exist  the  anterior  and  posterior  ulnar 
veins  open  separately  into  the  median  basilic  vein. 

The  Radial  Vein  (1;.  radiaUs)  (Figs.  459  and  460)  commences  upon  the  dorsal 
surface  of  the  wrist,  communicating  with  the  deep  veins  of  the  palm  by  a  branch 
which  passes  through  the  first  interosseous  space.  The  radial  vein  soon  forms  a 
large  vessel,  which  ascends  along  the  radial  side  of  the  forearm  and  receives 
numerous  veins  from  both  its  surfaces.  At  the  bend  of  the  elbow  it  unites  with 
the  median  cephalic  to  form  the  cephalic  vein.  Spalteholz  considers  the  ulnar 
vein  as  a  portion  of  the  basilic  and  the  radial  vein  a  portion  of  the  cephalic. 

The  Median  Vein  (v.  mediana  cubiti)  (Fig.  459)  ascends  on  the  front  of  the 
forearm,  and  communicates  with  the  anterior  ulnar  and  radial  veins.    At  the  bend 


746 


THE   BLOOD -VASCULAR    SYSTEM 


Median  cephalic. 


External 
cutaneous  nerve. 


r  Internal 
<  cutaneous 
(     nerve. 
Median 
basilic. 


'Common 
ulnar. 


Fig.  459. — The  superficial  veins  of  the  flexor  aspect 
of  the  upper  extremity. 


of  the  elbow  it  receives  a  branch  of 
communication  from  the  deep  veins, 
the  deep  median  vein,  and  di\ides  into 
two  branches,  the  median  cephalic  and 
median  basilic,  which  diverge  from  each 
other  as  they  ascend. 

The  Median  Cephalic  (v.  mediana 
cephalica)  (Fig.  459) ,  usually  the  smaller 
of  the  two,  passes  outward  in  the  groove 
between  the  Supinator  longus  and  Bi- 
ceps muscles,  and  joins  with  the  radial 
to  form  the  cephalic  vein.  The  branches 
of  the  external  cutaneous  nerve  pass 
beneath  this  vessel. 

The  Median  Basilic  Vein  (v.  mediana 
basilica)  (Fig.  459)  passes  obliquely  in- 
ward, in  the  groove  between  the  Biceps 
and  Pronator  radii  teres  muscles,  and 
joins  the  common  ulnar  to  form  the 
basilic.  This  vein  passes  in  front  of 
the  brachial  artery,  from  which  it  is 
separated  by  a  fibrous  expansion,  the 
bicipital  fascia,  which  is  given  off  from 
the  tendon  of  the  Biceps  to  the  fascia 
covering  the  Flexor  muscles  of  the  fore- 
arm. Filaments  of  the  internal  cuta- 
neous nerve  pass  in  front  as  well  as 
behind  this  vessel.^ 

Venesection  is  usually  performed  at  the 
bend  of  the  elbow,  and  as  a  matter  of  practice 
the  largest  vein  in  this  situation  is  commonly 
selected.  This  is  usually  the  median  basilic, 
and  there  are  anatomical  advantages  and  dis- 
advantages in  selecting  this  vein.  The  advan- 
tages are,  that  in  addition  to  its  being  the 
largest,  and  therefore  yielding  a  greater  supply 
of  blood,  it  is  the  least  movable  and  can  be 
easily  steadied  on  the  bicipital  fascia  on  which 
it  rests.  The  disadvantages  are,  that  it  is  in 
close  relationship  with  the  brachial  artery,^ 
separated  only  by  the  bicipital  fascia;  and 
formerly,  when  venesection  was  frequently 
practised,  arterio-venous  aneurism  was  no 
uncommon  result  of  this  practice.  Another 
disadvantage  is,  that  the  median  basilic  is 
crossed  by  some  of  the  branches  of  the  internal 
cutaneous  nerve,  and  these  may  be  divided 
in  the  operation,  giving  rise  to  "  traumatic 
neuralgia  of  extreme  intensity"   (Tillaux). 

The  Basilic  Vein  (v.  basilica)  (Figs» 
460  and  462)  is  of  considerable  size  and 
is  formed  by  the  coalescence  of  the 
common  ulnar  vein   with  the  median 


Cruveilhier  says:  "Numerous  varieties  are  observed  in  the  disposition  of  the  veins  of  the  elbow;  some- 
"Jnes  the  comrnon  median  vein  is  wanting;  but  in  those  cases  its  two  branches  are  furnished  by  the  radial  vein, 
and  the  cephalic  is  almost  always  in  a  rudimentary  condition.  In  other  cases  only  two  veins  are  found  at  the 
bend  of  the  elbow,  the  radial  and  ulnar,  which  are  continuous,  without  any  demarcation,  with  the  cephalic  and 
basihc."— Ed.  of  15th  Engli.sh  edition. 


THE   DEEP    VEINS    OF    THE    UPPER    EXTREMITY  747 

basilic.  It  passes  upward  along  the  inner  side  of  the  Biceps  muscle  and  pierces 
ihe  deep  fascia  a  little  below  the  middle  of  the  arm.  The  opening  in  the  fascia 
is  known  as  the  semilunar  hiatus  (hiatus  semilunaris).  The  vein  ascends  in  the 
course  of  the  brachial  artery  to  the  lower  border  of  the  tendons  of  the  Latissimus 
dorsi  and  Teres  major  muscles,  and  is  continued  onward  as  the  axillary  vein. 

The  Cephalic  Vein  (v.  cephalica)  (Fig.  459)  is  formed  by  the  union  of  the 
median  cephalic  and  the  radial  veins.  It  courses  along  the  outer  border  of  the 
Biceps  muscle,  lying  in  the  same  groove  with  the  upper  external  cutaneous  branch 
of  the  musculo-spiral  nerve,  to  the  upper  third  of  the  arm;  it  then  passes  in  the 
interval  between  the  Pectoralis  major  and  Deltoid  muscles,  lying  in  the  same 
groove  with  the  descending  or  humeral  branch  of  the  acromial-thoracic  artery. 
It  pierces  the  costo-coracoid  membrane,  and,  crossing  the  axillary  artery,  ter- 
minates in  the  axillary  vein  just  below  the  clavicle.  This  vein  is  occasionally 
connected  with  the  external  jugular  or  subclavian  by  a  branch  which  passes 
from  it  upward  in  front  of  the  clavicle. 

The  Deep  Veins  of  the  Upper  Extremity  (Fig.  460). 

The  deep  veins  of  the  upper  extremity  follow  the  course  of  the  arteries,  forming 
their  venae  comites  or  companion  veins.  Usually  there  is  one  vein  lying  on  each 
side  of  the  corresponding  artery,  and  they  are  connected  at  intervals  by  short 
transverse  branches. 

There  are  two  digital  veins  accompanying  each  artery  along  the  sides  of  the 
fingers:  these,  uniting  at  their  base,  pass  along  the  interosseous  spaces  in  the 
palm,  and  terminate  in  the  two  venai  comites  which  accompany  the  superficial 
palmar  arch.  Branches  from  these  vessels  on  the  radial  side  of  the  hand  accom- 
pany the  superficialis  volae,  and  on  the  ulnar  side  terminate  in  the  deep  ulnar 
veins  (Fig.  460) .  The  deep  ulnar  veins,  as  they  pass  in  front  of  the  wrist,  com- 
municate with  the  interosseous  and  superficial  veins,  and  at  the  elbow  unite  with 
the  deep  radial  veins  to  form  the  vena  comites  of  the  brachial  artery.  The  venae 
comites  of  the  brachial  communicate  by  numerous  transverse  branches,  which 
cross  over  or  under  the  artery. 

The  Interosseous  Veins  (Fig.  460)  accompany  the  anterior  and  posterior 
interosseous  arteries.  The  anterior  interosseous  veins  commence  in  front  of  the 
wrist,  where  they  communicate  with  the  deep  radial  and  ulnar  veins;  at  the  upper 
part  of  the  forearm  they  receive  the  posterior  interosseous  veins,  and  terminate  in 
the  vense  comites  of  the  ulnar  artery. 

The  Deep  Pahnar  Veins  accompany  the  deep  palmar  arch,  being  formed  by 
tributaries  which  accompany  the  ramifications  of  that  vessel.  At  the  wrist  they 
receive  a  dorsal  and  a  palmar  tributary  from  the  thumb.  The  deep  palmar  veins 
communicate  with  the  deep  ulnar  veins  at  the  inner  side  of  the  hand,  and  on  the 
outer  side  terminate  in  the  deep  radial  veins  (Fig.  460),  which  are  the  vense 
comites  of  the  radial  artery.  Accompanying  the  radial  artery  the  deep  radial 
veins  terminate  in  the  vena?  comites  of  the  brachial  artery. 

The  Brachial  Veins  (w.  brachiales)  (Fig.  460)  are  placed  one  on  each  side  of 
the  brachial  artery,  receiving  tributaries  corresponding  with  the  branches  given  off 
from  that  vessel;  at  the  lower  margin  of  the  Subscapularis  muscle  they  join  the 
axillary  vein. 

These  deep  veins  have  numerous  anastomoses,  not  only  with  each  other,  but 
also  with  the  superficial  veins.  One  of  the  brachial  veins  empties  into  the 
axillary,  the  other,  usually  the  smaller,  generally  unites  with  the  basilic. 

The  Axillary  Vein  (v.  axillaris)  (Fig.  461)  is  of  large  size,  and  may  be  regarded 
as  the  continuation  upward  of  the  basilic  vein,  or  as  formed  by  the  fusion  of  a 
brachial  vein  with  the  basilic  vein.  If  the  first  view  is  accepted  a  brachial  vein 
is  described  as  one  of  the  tributaries  of  the  axillary  vein.    The  axillary  vein  com- 


748 


THE   BLOOD-VASGULAB   SYSTEM 


mences  at  the  lower  border  of  the  tendons  of  the  Teres  major  and  I^atissimus  dorsi 
muscles,  increases  in  size  as  it  ascends,  by  receiving  tributaries  corresponding  with 
the  branches  of  the  axillary  artery,  and  terminates  immediately  beneath  the  clavicle 
at  the  outer  border  of  the  first  rib,  where  it  becomes  the  subclavian  vein.  This 
vessel  is  covered  in  front  by  the  Pectoral  muscles  and  costocoracoid  membrane, 
and  Ues  on  the  thoracic  side  of  the  axillary  artery,  which  it  partially  overlaps.  It 
receives  the  brachial  veins,  the  vense  comites  of  the  axillary  artery  except  the  cir- 
cumflex veins;  and  near  its  termination  the  cephalic  vein.  This  vein  is  provided 
with  a  pair  of  valves  opposite  the  lower  border  of  the  Subscapularis  muscle;  valves 
are  also  found  at  the  termination  of  the  cephalic  and  subscapular  veins.  The 
circumflex  veins  end  in  the  subscapular  or  one  of  the  brachial  veins. 

The  Long  Thoracic  Branch  {v.  thoracalis  lateralis)  (Fig.  462)  receives  the  thoracico- 
epigastric  vein  {v.  thoracoepigastrica),  which  comes  all  the  way  from  the  superficial 
epigastric  or  from  the  femoral  vein. 

The  Costo-axillary  Veins  {w.  costoaxillares)  (Fig.  462)  come  from  the  first  six 
intercostal  spaces  and  bring  blood  from  the  intercostal  veins  to  the  axillary. 


INTEROSSEOUS 
VEINS 


ULNAR  DEEP 
VEINS 


VEN>E  COMITES 
OF    BRACHIAL 
ARTERY 


ANASTOMOSIS 
OF  RADIAL 
AND  ULNAR 


RADIAL  DEEP 
VEINS 


Fig.  460. — The  deep  veins  of  the  upper  extremity.     (Bourgery.) 


Surgical  Anatomy. — There  are  several  points  of  surgical  interest  in  connection  with  the 
axillary  vein.  Being  more  superficial,  larger,  and  slightly  overlapping  the  axillary  artery,  it  is 
more  liable  to  be  wounded  in  the  operation  of  extirpation  of  the  axillary  glands,  especially  as 
these  glands,  when  diseased,  are  apt  to  become  adherent  to  the  vessel.  When  wounded  there 
is  always  danger  of  air  being  drawn  into  its  interior,  and  death  resulting.  This  is  due  not  only 
to  the  fact  that  it  is  near  the  thorax,  and  therefore  liable  to  be  influenced  by  the  respiratory 
movements,  but  also  because  it  is  adherent  by  its  anterior  surface  to  the  costo-coracoid  membrane, 
and  therefore  if  wounded  is  likely  to  remain  patulous  and  favor  the  chance  of  air  being  sucked 
in.  This  adhesion  of  the  vein  to  the  fascia  prevents  its  collapsing,  and  therefore  favors  the 
furious  bleeding  which  takes  place  in  these  cases. 


THE   DEEP     VEINS    OF    THE    UPPER    EXTREMITY 


749 


To  avoid  wounding  the  axillary  vein  in  the  extirpation  of  glands  from  the  axilla  no  undue 
force  should  be  used  in  isolating  the  glands.  If  the  vein  is  found  to  be  so  embedded  in  the 
malignant  deposit  that  the  latter  cannot  be  removed  without  taking  away  a  part  of  the  vein, 
this  must  be  done,  the  vessel  having  been  first  ligated  above  and  below. 


AXILLARY 
ARTERY 
MUSCULO- 
CUTANEUS   NERVC 
MEDIAN   NERVE 


LONG  THORACIC 

Fig.  461. — The  veins  of  the  right  axilla,  viewed  from  in  front.     (Spalteholz.) 


PECTORALIS 

MAJOR 

MUSCLE 


SUBCLAVIUS 
MUSCLE 


The  Subclavian  Vein  {v.  suhdavia)  (Figs.  421  and  446),  the  continuation  of  the 
axillary,  extends  from  the  outer  border  of  the  first  rib  to  the  inner  end  of  the  clavicle, 
where  it  unites  with  the  internal  jugular  to  form  the.  innominate  vein.  It  is  in 
relation,  in  jront,  with  the  clavicle  and  Subclavius  muscle;  behind  and  above,  with 
the  subclavian  artery,  from  which  it 
is  separated  internally  by  the  Scal- 
enus anticus  muscle  and  phrenic 
nerve.  Below,  it  rests  in  a  depres- 
sioTi  on  the  first  rib  and  upon  the 
pleura.  Above,  it  is  covered  by  the 
cervical  fascia  and  integument. 

An  expansion  of  the  aponeurosis 
of  the  Subclavius  muscle  lies  upon 
the  vein  (Fig.  462). 

The  subclavian  vein  occasionally 
rises  in  the  neck  to  a  level  with  the 
third  part  of  the  subclavian  artery,  and  in  two  instances  has  been  seen  passing 
with  this  vessel  behind  the  Scalenus  anticus.  This  vessel  is  usually  provided 
with  valves  about  an  inch  from  its  termination  in  the  innominate,  just  external 
to  the  entrance  of  the  external  jugular  vein. 

Tributaries.^ — It  receives  the  external  and  anterior  jugular  veins  and  a  small 
branch  from  the  cephalic,  outside  the  Scalenus,  and  on  the  inner  side  of  that 
muscle  the  internal  jugular  vein.     At  the  angle  of  junction  with  the  internal 


Fig.  462. — The  aponeurotic  expansion  of  the  Subclavius 
muscle  over  the  subclavian  vein.      (Poirier  and  Charpy.) 


750 


THE   BLOOD -VASCULAB    SYSTEM 


jugular  the  left  subclavian  vein  receives  the  thoracic  duct  (Fig.  463),  while  the 
right  subclavian  vein  receives  the  right  lymphatic  duct. 

The  Innominata  or  Brachio-cephalic  Veins  {w.  anonymcB)  (Fig.  464)  are 
two  large  trunks,  placed  one  on  each  side  of  the  root  of  the  neck,  and  formed  by 
the  union  of  the  internal  jugular  and  subclavian  veins  of  the  corresponding  side. 

The  Right  Innominate  Vein  (v.  anonyma  dextra)  is  a  short  vessel,  an  inch 
in  length,  which  commences  at  the  inner  end  of  the  clavicle,  and,  passing  almost 
vertically  downward,  joins  with  the  left  innominate  vein  just  below  the  cartilage 
of  the  first  rib,  close  to  the  right  border  of  the  sternum,  to  form  the  superior  vena 
cava.  It  lies  superficial  and  external  to  the  innominate  artery;  on  its  right  side 
is  the  phrenic  nerve,  and  the  pleura  is  here  interposed  between  it  and  the  apex  of 
the  lung.  This  vein,  at  the  angle  of  junction  of  the  internal  jugular  with  the  sub- 
clavian, receives  the  right  vertebral  vein,  and,  lower  down,  the  right  internal 
mammary,  right  inferior  thyroid,  and  sometimes  the  right  thyroidea  ima  and  the 
right  superior  intercostal  veins. 

The  Left  Innominate  Vein  {v.  anonyma  sinistra),  about  two  and  a  half 
inches  in  length,  and  larger  than  the  right,  passes  from  left  to  right  across  the 
upper  and  front  part  of  the  chest,  at  the  same  time  inclining  downward,  and  unites 


LONGUS  COLLI   MUSCLE 

COMMON  CAROTrO 

ARTERY 

LEFT  PNEUMOGASTRIC 

NERVE 

VERTEBRAL  ARTERY 

VERTEBRAL  VEIN 

THORACIC  DUCT 

INTERNAL  JUGULAR 

VEIN 

EXTERNAL  JUGULAR 

VEIN 

ANTERIOR  JUGULAR 

VEIN 

SUBCLAVIAN 

VEIN 


Fig.  463. — The  bend  of  the  thoracic  duct  at  its  termination  in  the  subclavian  vein.      (Poirier  and  Charpy.) 


with  the  right  innominate  vein  to  form  the  superior  vena  cava.  It  is  in  relation, 
in  jront,  with  the  first  piece  of  the  sternum,  from  which  it  is  separated  by  the 
Sterno-hyoid  and  Sterno-thyroid  muscles,  the  thymus  gland  or  its  remains,  and  some 
loose  areolar  tissue.  Behind,  it  lies  across  the  roots  of  the  three  large  arteries 
arising  from  the  arch  of  the  aorta.  This  vessel  is  joined  by  the  left  vertebral, 
left  internal  mammary,  left  inferior  thyroid,  left  thyroidea  ima,  and  the  left 
superior  intercostal  veins,  and  occasionally  some  thymic  and  pericardiac  veins, 
and  the  right  thyroidea  ima.    There  are  no  valves  in  the  innominate  veins. 

Peculiarities. — Sometimes  the  innominate  veins  open  separately  into  the  right  auricle;  in  such 
cases  the  right  vein  takes  the  ordinary  course  of  the  superior  vena  cava;  but  the  left  vein — the  left 
superior  vena  cava,  as  it  is  termed — after  communicating  by  a  small  branch  with  the  right  one, 
passes  in  front  of  the  root  of  the  left  lung,  and,  turning  to  the  back  of  the  heart,  receives  the 
cardiac  veins,  and  terminates  in  the  back  of  the  right  auricle.  This  occasional  condition  in  the 
adult  is  due  to  the  persistence  of  the  early  foetal  condition,  and  is  the  normal  state  of  things  in 
birds  and  some  mammalia. 

The  Internal  Mammary  Vein  {v.  mammaria  interna)  corresponds  to  the  internal 
mammary  artery,  follows  the  course  of  that  vessel,  and  receives  branches  corre- 
sponding with  those  derived  from  it.  There  are  two  internal  mammary  veins  in  the 
region  of  the  Triangularis  sterni  muscle,  but  above  this  point  the  vein  is  single.  The 
double  vein  is  formed  by  the  union  of  the  vense  comites  of  the  superior  epigastric 


THE   DEEP     VEINS    OF    THE    UPPER    EXTREMITY 


751 


Superior  thyroid. 


Middle  thyroid. 


—  External  jugular. 


artery  (vv.  epigastricoe  superiores)  and  the  venae  comites  of  the  musculo-phrenic 

artery  (vv.  musculophrenicce) .    It  receives  the  twelve  anterior  intercostal  veins  from 

the  upper  six  intercostal  spaces  of  the  corresponding  side — six  anterior  perforating 

veins    {rami    per]  or  antes) — 

veins  from  the  surface  of  the  i^.^^Antertor  jugxdar. 

sternum    {rami  sternales)  — 

muscular  veins,  and  vessels 

from  the  mediastinum   and 

pleura.     The  two  veins   of 

each  side  unite  into  a  single 

trunk,  at  the  upper  margin 

of    the    triangularis     sterni 

muscle,  which  terminates  in 

the  innominate  vein. 

The  Vertebral  Vein  (see 
p.  732). 

Thelnferior  Thyroid  Veins 
{vv.  thyreoideoe  inferiores) 
(Fig.  464),  two,  frequently 
three  or  four,  in  number, 
arise  in  the  venous  plexus 
on  the  thyroid  body  {plexus 
ihyreoideus  impar),  commu- 
nicating with  the  middle 
and  superior  thyroid  veins. 
(See  Kocher's  views,  pages 
731  and  732.)  Kocher  states 
that  two  thyroidea  ima  veins 
are  present,  and  that  inferior 
thyroid  veins  may  also  be 
present.  The  veins  from  the 
lower  portion  of  the  gland 
form  a  plexus  in  front  of  the 
trachea,  behind  the  Sterno- 
thyroid muscles.  From  this 
plexus  a  left  vein  descends 
and  joins  the  left  innomi- 
nate trunk,  and  a  right  vein 
passes  obliquely  downward 
and  outward  across  the  in- 
nominate artery  to  open  into 
the  right  innominate  vein, 
just  at  its  junction  with  the 
superior  vena  cava.  The  thy- 
roidea ima  vein  {v.  thyreoidca 
ima)  passes  downward  in 
front  of  the  trachea  and  ter- 
minates in  the  left  innominate 
vein.  These  veins  receive 
tributaries  from  the  tracheal 
y%v[iz{vv.tracheales),irou\  the 
oesophageal  veins  {vv.  cesopha- 
c)e(jc),  from  the  inferior  laryn- 
geal y6ili(v .larunaea inferior)  ■^'"'  ^^^' — '^^^  vense  cavae  and  azygos  veins,  with  their  formative 


752  THE  BLOOD -VASCULAR   SYSTEM 

The  Intercostal  Veins  {w.  intercostales)  are  divided  into  anterior  and  posterior 
intercostals. 

The  Anterior  Intercostal  Veins  are  tributaries  of  the  internal  mammary  or  the 
musculo-phrenic  veins  (p.  731). 

The  Posterior  Intercostal  Veins  (Fig.  464)  number  eleven  on  each  side,  there 
being  one  vein  in  each  intercostal  space.  Each  vein  lies  in  the  groove  at  the 
lower  margin  of  the  rib  above  the  corresponding  intercostal  artery.  On  the  right 
side  the  first  posterior  intercostal  vein  crosses  the  neck  of  the  first  rib  anteriorly 
and  opens  into  the  vertebral  vein  or  the  innominate  vein.  The  first  posterior 
intercostal  of  the  left  side  follows  a  like  course,  and  empties  into  the  vertebral 
or  innominate  vein.  The  posterior  intercostals  of  the  right  side,  from  the  fifth 
to  the  eleventh,  inclusive,  open  individually  into  the  vena  azygos  major.  The 
left  upper  azygos  vein  receives  the  fifth,  sixth,  seventh,  and  eighth  posterior 
intercostals  of  the  left  side.  The  left  lower  azygos  vein  receives  the  ninth,  tenth, 
and  eleventh  left  posterior  intercostals. 

The  Right  Superior  Intercostal  Vein  {v.  intercostalis  suprema  dextra)  is  formed 
by  the  vmion  of  the  second,  third,  and  fourth  right  posterior  intercostals.  It 
passes  downward  and  inward  and  opens  into  the  vena  azygos  major. 

The  Left  Superior  Intercostal  Vein  {v.  intercostalis  suprema  sinister)  runs  across 
the  transverse  aorta  and  opens  into  the  left  innominate  vein.  It  usually  receives 
the  left  bronchial  and  left  superior  phrenic  vein,  and  communicates  below  with 
the  vena  azygos  minor  superior.  Each  posterior  intercostal  vein  obtains  branches 
from  the  ribs  and  muscles  and  also  a  dorsal  branch,  which  receives  blood  from  the 
muscles  of  the  back,  from  in  front  of  the  vertebral  bodies,  from  back  of  the  ver- 
tebral arches,  and  from  the  spinal  canal  by  way  of  a  vein  which  passes  through 
the  intervertebral  foramen. 

The  Superior  Vena  Cava  (v.  cava  superior)  (Fig.  464)  receives  the  blood 
which  is  conveyed  to  the  heart  from  the  whole  of  the  upper  half  of  the  body. 
It  is  a  short  trunk,  varying  from  two  inches  and  a  half  to  three  inches  in  length, 
formed  by  the  junction  of  the  two  innominate  veins.  It  commences  immediately 
below  the  cartilage  of  the  first  rib  close  to  the  sternum  on  the  right  side,  and, 
descending  vertically,  enters  the  pericardium  about  an  inch  and  a  half  above  the 
heart,  and  terminates  in  the  upper  part  of  the  right  auricle  opposite  the  upper 
border  of  the  third  right  costal  cartilage.  In  its  course  it  describes  a  slight  curve, 
the  convexity  of  which  is  turned  to  the  right  side. 

Relations. — In  front,  with  the  pericardium  and  process  of  cervical  fascia  which 
is  continuous  with  it:  this  separates  it  from  the  thymus  gland  and  from  the  ster- 
num; behind,  with  the  root  of  the  right  lung;  on  its  right  side,  with  the  phrenic 
nerve  and  right  pleura;  on  its  left  side,  with  the  commencement  of  the  innominate 
artery  and  ascending  part  of  the  aorta.  The  portion  contained  within  tlie  peri- 
cardium is  covered  by  the  serous  layer  of  that  membrane  in  its  anterior  three- 
fourths.  It  receives  the  vena  azygos  major  just  before  it  enters  the  pericardium, 
and  several  small  veins  from  the  pericardium  and  parts  in  the  mediastinum.  The 
superior  vena  cava  has  no  valves. 

The  Azygos  Veins  connect  together  the  superior  and  inferior  venoe  cavse, 
taking  the  place  of  those  vessels  in  that  part  of  the  chest  occupied  by  the  heart. 

The  Larger  or  Right  Azygos  Vein  or  the  Vena  Azygos  Major  (v.  azygos)  (Fig.  464) 
commences  opposite  the  first  or  second  lumbar  vertebra  by  a  branch  from  the  right 
lumbar  veins,  called  the  right  ascending  lumbar  vein  (v.  lumbalis  ascendens  dextra) ; 
sometimes  by  a  branch  from  the  right  renal  vein  or  from  the  inferior  vena  cava.  It 
enters  the  thorax  through  the  aortic  opening  in  the  Diaphragm,  and  passes  along 
the  right  side  of  the  vertebral  column  to  the  fourth  dorsal  vertebra,  where  it 
arches  forward  over  the  root  of  the  right  lung,  and  terminates  in  the  superior  vena 
cava  just  before  that  vessel  enters  the  pericardium.     Whilst  passing  through  the 


THE   SPINAL    VEINS  753 

aortic  opening  of  the  Diaphragm  it  lies  with  the  thoracic  duct  on  the  right  side 
of  the  aorta,  and  in  the  thorax  it  Hes  upon  the  intercostal  arteries  on  the  right 
side  of  the  aorta  and  thoracic  duct,  and  is  partly  covered  by  pleura. 

Tributaries. — It  receives  the  lower  ten  posterior  intercostal  veins  of  the  right  side, 
the  upper  two  or  three  of  these  opening  first  of  all  into  the  right  superior  intercostal 
vein.  It  receives  the  azygos  minor  veins,  several  oesophageal,  mediastinal,  and 
pericardial  veins;  near  its  termination,  the  right  bronchial  vein;  and  generally 
the  right  superior  intercostal  vein.  A  few  imperfect  valves  are  found  in  this  vein; 
but  its  tributaries  are  provided  with  complete  valves. 

The  intercostal  veins  on  the  left  side,  below  the  three  upper  intercostal  spaces, 
usually  form  two  trunks,  named  the  left  lower  and  the  left  upper  azygos  veins. 

The  Left  Lower  or  Smaller  Azygos  Vein  or  the  Vena  Azygos  Minor  {v.  hemiazygos) 
(Fig.  464)  commences  in  the  lumbar  region  by  a  branch  from  one  of  the  lumbar 
veins,  ascending  lumbar  (v.  lumhalis  ascendens),  or  from  the  left  renal.  It  passes 
into  the  thorax  through  the  left  crus  of  the  Diaphragm,  and,  descending  on  the 
left  side  of  the  spine  as  high  as  the  ninth  dorsal  vertebra,  passes  across  the 
column,  behind  the  aorta  and  thoracic  duct,  to  terminate  in  the  right  azygos  vein. 
It  receives  the  four  or  five  lower  intercostal  veins  of  the  left  side,  and  some 
oesophageal  and  mediastinal  veins. 

The  Left  Upper  Azygos  Vein  {v.  hemiazygos  accessoria)  varies  inversely  with  the 
size  of  the  left  superior  intercostal.  It  receives  veins  from  the  intercostal  spaces 
between  the  left  superior  intercostal  vein  and  highest  tributary  of  the  left  lower 
azygos.  They  are  usually  three  or  four  in  number,  usually  the  fourth,  fifth,  sixth, 
and  seventh  left  posterior  intercostal  veins.  They  join  to  form  a  trunk  which  ends 
in  the  right  azygos  vein  or  in  the  left  lower  azygos.  It  sometimes  receives  the  left 
bronchial  vein.  When  this  vein  is  small  or  altogether  wanting,  the  left  superior 
intercostal  vein  will  extend  as  low  as  the  fifth  or  sixth  intercostal  space. 

Surgical  Anatomy.  — In  obstruction  of  the  inferior  vena  cava  the  azygos  veins  are  one  of  the 
principal  means  l)y  which  the  venous  circulation  is  carried  on,  connecting  as  they  do  the  superior 
and  inferior  venae  cavse,  and  communicating  with  the  common  iliac  veins  by  the  ascending  lum- 
bar veins,  and  with  many  of  the  tributaries  of  the  inferior  vena  cava. 

The  Bronchial  Veins  (vv.  hronchiales)  return  the  blood  from  the  substance  of 
the  lungs,  except  from  the  smaller  bronchial  tubes  and  alveola.  The  blood  from 
them  is  received  by  the  pulmonary  veins.  The  bronchial  vein  of  the  right  side 
opens  into  the  vena  azygos  major  near  its  termination.  The  bronchial  vein  of 
the  left  side  opens  into  the  left  superior  intercostal  vein  or  the  left  upper  azygos 
vein.  The  bronchial  veins  are  joined  by  veins  from  the  trachea  and  medias- 
tinum. 

The  Spinal  Veins. 

The  numerous  venous  plexuses  placed  upon  and  within  the  spine  may  be 
arranged  into  four  sets: 

1.  Those  placed  on  the  exterior  of  the  spinal  column,  the  dorsi-spinal  veins. 

2.  Those  situated  in  the  interior  of  the  spinal  canal,  between  the  vertebrae  and 
the  theca  vertebralis,  meningo-rachidian  veins. 

3.  The  veins  of  the  bodies  of  the  vertebra%  venae  basis  vertebrarum. 

4.  The  veins  of  the  spinal  cord,  medulli-spinal  veins. 

1.  The  Dorsi-spinal  Veins  {plexus  vcnosi  vertebrates  externi)  commence  by 
small  branches  which  receive  their  blood  from  the  integument  of  the  back  of  the 
spine  and  from  the  muscles  in  the  vertebral  grooves.  They  constitute  two  plexuses : 
an  anterior  plexus  (plexus  venosi  verfebrales  anteriores)  upon  the  vertebral  bodies 
and  a  posterior  plexus  (plexus  venosi  vertehrales  posteriores) ,  which  surrounds  the 
spinous  processes,  the  laminae,  and  the  transverse  and  articular  processes   of 

48 


754 


THE    BLOOD    VASCULAR    SYSTEM 


all  the  vertebrse.  At  the  bases  of  the  transverse  processes  they  communicate,  by 
means  of  ascending  and  descending  branches,  with  the  veins  surrounding  the 
contiguous  vertebrae,  and  they  join  v^ith  the  veins  in  the  spinal  canal  by  branches 
which  perforate  the  ligamenta  subflava.  Other  branches  pass  obliquely  forward, 
between  the  transverse  processes,  and  communicate  with  the  intraspinal  veins 
through  the  intervertebral  foramina  {vv.  intervertehrales).  The  dorsi-spinal  veins 
terminate  by  joining  the  vertebral  veins  in  the  neck,  the  intercostal  veins  in  the 
thorax,  and  the  lumbar  and  sacral  veins  in  the  loins  and  pelvis. 


The  dorsi-spinal  veins. 


Fig.  465. — Transverse  section  of  a  dorsal  vertebra,  showing  the  spinal  veins. 

2.  The  MeningO-rachidian  Veins  (plexus  venosi  vertebrates  interni). — The 
principal  veins  contained  in  the  spinal  canal  are  situated  between  the  theca  verte- 
bralis  and  the  vertebrae.  They  consist  of  two  longitudinal  plexuses,  one  of  which 
runs  along  the  posterior  surface  of  the  bodies  of  the  vertebra;,  anterior  longitudinal 
spinal  veins.  The  other  plexus,  posterior  longitudinal  spinal  veins,  is  placed  on  the 
inner  or  anterior  surface  of  the  laminae  of  the  vertebrae. 


Fig.  466. — Vertical  section  of  two  dorsal  vertebrae,  showing  the  spinal  veins. 


The  Anterior  Longitudinal  Spinal  Veins  (sinus  vertehrales  longitudmales)  consist 
of  two  large,  tortuous  veins  which  extend  along  the  whole  length  of  the  vertebral 
column,  from  the  foramen  magnum,  where  they  communicate  by  a  venous  ring 
around  that  opening,  to  the  base  of  the  coccyx,  being  placed  one  on  each  side  of 
the  posterior  surface  of  the  bodies  of  the  vertebrae  along  the  margin  of  the  posterior 
common  ligament.    These  veins  communicate  together  opposite  each  vertebra  by 


VEINS    OF  LOWER    EXTREMITY,    ABDOMEN   AND    PELVIS     755 

transverse  trunks  which  pass  beneath  the  Hgament.  Each  transverse  trunk 
receives  the  large  vena  basis  vertebrae  {v.  hasivertehralis)  from  the  interior  of  the 
body  of  the  vertebra.  The  anterior  longitudinal  spinal  veins  are  least  developed 
in  the  cervical  and  sacral  regions.  They  are  not  of  uniform  size  throughout, 
being  alternately  enlarged  and  constricted.  At  the  intervertebral  foramina  they 
communicate  with  the  dorsi-spinal  veins,  and  with  the  vertebral  veins  in  the  neck, 
with  the  intercostal  veins  in  the  dorsal  region,  and  with  the  lumbar  and  sacral 
veins  in  the  corresponding  regions. 

The  Posterior  Longitudinal  Spinal  Veins,  smaller  than  the  anterior,  are  situated 
one  on  each  side,  between  the  inner  surface  of  the  laminae  and  the  theca  verte- 
bralis.  They  communicate  (like  the  anterior)  opposite  each  vertebra  by  trans- 
verse trunks,  and  with  the  anterior  longitudinal  veins  by  lateral  transverse  branches 
which  pass  from  behind  forward.  The  posterior  longitudinal  veins,  by  branches 
which  perforate  the  ligamenta  subflava,  join  with  the  dorsi-spinal  veins.  From 
them  branches  are  given  off  which  pass  through  the  intervertebral  foramina  and 
join  the  vertebral,  intercostal,  lumbar,  and  sacral  veins.  The  anterior  and  pos- 
terior longitudinal  spinal  veins  join  by  numerous  branches  and  really  constitute 
one  plexus,  the  plexus  venosi  vertebrales  interni. 

The  Intervertebral  Veins  {vv.  intervertehrales)  accompany  the  spinal  nerves 
in  the  intervertebral  foramina,  receive  veins  from  the  spinal  cord,  and  join  the 
meningo-rachidian  and  the  dorsi-spinal  veins. 

3.  The  Veins  of  the  Bodies  of  the  Vertebrae  or  the  Venae  Basis  Vertebramm 
{w.  hasivertehrales)  emerge  from  the  foramen  on  the  posterior  surface  of  each 
vertebra  and  join  the  transverse  trunk  connecting  the  anterior  longitudinal  spinal 
veins.  They  are  contained  in  large,  tortuous  channels  in  the  substance  of  the 
bones,  similar  in  every  respect  to  those  found  in  the  diploe  of  the  cranial  bones. 
These  canals  lie  parallel  to  the  upper  and  lower  surface  of  the  bones.  They  com' 
mence  by  small  openings  on  the  front  and  sides  of  the  bodies  of  the  vertebrae, 
through  which  communicating  branches  from  the  veins  external  to  the  bone  pass 
into  its  substance,  and  converge  to  the  principal  canal,  which  is  sometimes  double 
toward  its  posterior  part.  They  open  into  the  corresponding  transverse  branch  unit- 
ing the  anterior  longitudinal  veins.    They  become  greatly  developed  in  advanced  age. 

4.  The  Veins  of  the  Spinal  Cord  or  the  Medulli-spinal  Veins  {w.  syinales) 
emerge  from  the  cord  substance  and  enter  the  pia  mater  plexus.  The  pia  mater 
plexus  is  a  minute,  tortuous,  venous  plexus  which  covers  the  entire  surface  of  the 
cord,  being  situated  between  the  pia  mater  and  arachnoid,  "  In  this  plexus  there 
are  six  longitudinal  channels — one  antero-median,  along  the  anterior  fissure — 
two  antero-lateral,  immediately  behind  the  anterior  nerve  roots — two  postero- 
lateral, immediately  behind  the  posterior  nerve  roots — and  one  postero-median, 
over  the  postero-septum."^  These  vessels  are  largest  in  the  lumbar  region. 
Near  the  base  of  the  skull  they  unite  and  form  two  or  three  small  trunks,  which 
communicate  with  the  vertebral  veins,  and  terminate  in  the  inferior  cerebellar 
veins  or  in  the  inferior  petrosal  sinuses.  Each  of  the  spinal  nerves  is  accompanied 
by  a  branch  as  far  as  the  intervertebral  foramina,  where  it  joins  the  other  veins 
from  the  spinal  canal. 

There  are  no  valves  in  the  spinal  veins, 

VEINS    OF    THE    LOWER    EXTREMITY,    ABDOMEN,    AND    PELVIS 

(Figs.  467,  468). 

The  Veins  of  the  I>ower  Extremity  are  subdivided,  like  those  of  the  upper, 
into  two  sets,  superficial  and  deep,  the  superficial  veins  being  placed  beneath  the 

'  D.  J.  Cunningham.     A  Text-book  of  Anatomy. 


756  THE  BLOOD -VASCULAR    SYSTEM 

integument,  between  the  two  layers  of  superficial  fascia,  the  deep  veins  accom- 
panying the  arteries,  and  forming  the  venae  comites  of  those  vessels.  Both  sets 
of  veins  are  provided  with  valves,  which  are  more  numerous  in  the  deep  than  in 
the  superficial  set.  These  valves  are  also  more  numerous  in  the  lower  than  in 
the  upper  limb. 

The  Superficial  Veins  of  the  Lower  Extremity. 

The  Superficial  Veins  of  the  Foot. — On  the  sole  of  the  foot  there  is  a  sub- 
cutaneous venous  plexus  {rete  venosum  plantare  cutaneum),  from  which  some 
branches  go  to  the  deep  veins,  but  most  of  the  branches  pass  around  the  margins 
to  the  dorsum  of  the  foot.  There  is  a  transverse  venous  arch  at  the  root  of  the 
toes  which  receives  plantar  vessels  from  the  toes  and  sends  branches  between  the 
toes  (vv.  intercapitulares)  to  the  venous  arch  of  the  dorsum.  On  the  dorsum  of  each 
toe  the  veins  gather  into  two  vessels,  known  as  the  dorsal  digital  veins  {vv.  digitales 
pedis  dorsales).  The  dorsal  digital  veins  from  the  opposed  margins  of  two  toes 
unite  to  form  a  dorsal  interdigital  vein.  There  are  four  dorsal  interdigital  veins 
{vv.  digitales  communes  pedis),  and  they  pass  into  the  venous  arch  of  the  dorsum. 
The  dorsal  digital  vein,  from  the  inner  surface  of  the  great  toe,  passes  directly 
into  the  internal  saphenous  vein,  and  the  dorsal  digital  vein,  from  the  outer 
surface  of  the  little  toe,  passes  directly  into  the  external  saphenous  vein. 

On  the  dorsum  of  the  foot  is  a  venous  arch  {arcus  venosus  dorsalis  pedis 
[cutaneus]),  situated  in  the  superficial  structures  over  the  anterior  extremities  of 
the  metatarsal  bones.  It  has  its  convexity  directed  forward,  and  receives  digital 
tributaries  from  the  upper  surface  of  the  toes;  at  its  concavity  it  is  joined  by 
numerous  small  veins  which  form  a  plexus  on  the  dorsum  of  the  foot  {rete 
venosum  dorsale  pedis  cutaneum).  The  arch  terminates  internally  in  the  long 
saphenous,  externally  in  the  short  saphenous  vein. 

The  chief  superficial  veins  of  the  lower  extremity  are  the  internal  or  long  saphenous 
and  the  external  or  short  saphenous. 

The  Internal  or  Long  Saphenous  Vein  {v.  saphena  magna)  (Figs.  467  and  470) 
commences  at  the  inner  side  of  the  arch  on  the  dorsum  of  the  foot ;  it  ascends  in  front 
of  the  inner  malleolus  and  along  the  inner  side  of  the  leg,  behind  the  inner  margin 
of  the  tibia,  accompanied  by  the  internal  saphenous  nerve.  At  the  knee  it  passes 
backward  behind  the  inner  condyle  of  the  femur,  ascends  along  the  inside  of  the 
thigh,  and,  passing  through  the  saphenous  opening  in  the  fascia  lata,  terminates 
in  the  femoral  vein  about  an  inch  and  a  half  below  Poupart's  ligament.  This  vein 
receives  in  its  course  cutaneous  tributaries  from  the  leg  and  thigh,  and  at  the 
saphenous  opening  receives  the  superficial  epigastric,  superficial  circumflex  iliac, 
and  external  pudic  veins.  The  veins  from  the  inner  and  back  part  of  the  thigh 
frequently  unite  to  form  a  large  vessel,  which  enters  the  main  trunk  near  the 
saphenous  opening;  and  sometimes  those  on  the  outer  side  of  the  thigh  join  to  form 
another  large  vessel;  so  that  occasionally  three  large  veins  are  seen  converging  from 
different  parts  of  the  thigh  toward  the  saphenous  opening.  The  internal  saphenous 
vein  communicates  in  the  foot  with  the  internal  plantar  vein;  in  the  leg,  with  the 
posterior  tibial  veins  by  branches  which  perforate  the  tibial  origin  of  the  Soleus 
muscle,  and  also  with  the  anterior  tibial  veins;  at  the  knee,  with  the  articular 
veins;  in  the  thigh,  with  the  femoral  vein  by  one  or  more  branches.  The  valves 
in  this  vein  vary  from  two  to  six  in  number;  they  are  more  numerous  in  the  thigh 
than  in  the  leg. 

The  External  or  Short  Saphenous  Vein  {v.  saphena  parva)  (Fig.  468)  com- 
mences at  the  outer  side  of  the  arch  on  the  dorsum  of  the  foot ;  it  ascends  behind  the 
outer  malleolus,  and  along  the  outer  border  of  the  tendo  Achillis,  across  which  it 
passes  at  an  acute  angle  to  reach  the  middle  line  of  the  posterior  aspect  of  the  leg. 


I 


THE   SUPERFICIAL     VEINS    OF    THE   LOWER    EXTREMITY    757 

Passing  directly  upward,  it  perforates  the  deep  fascia  in  the  lower  part  of  the 
popHteal  space,  and  terminates  in  the  popUteal  vein,  between  the  heads  of  the 


vV 


F^^: 


m 


I  mh 


Fig.  468. — External  or  short  saphenous  vein. 

Gastrocnemius  muscle/  It  receives  numerous  large 
tributaries  from  the  back  part  of  the  leg,  and  com- 
municates with  the  deep  veins  on  the  dorsum  of  the 
foot  and  behind  the  outer  malleolus.  Before  it  per- 
forates the  deep  fascia  it  gives  off  a  communicating 
branch,  which  passes  upward  and  inward  to  join  the 
internal  saphenous  vein.  This  vein  has  a  variable 
number  of  valves,  from  three  to  nine  (Gay),  one  of 
which  is  always  found  near  its  termination  in  the 
popliteal  vein.  The  external  saphenous  nerve  lies 
close  beside  this  vein. 

Surgical  Anatomy.— The  saphenous  veins  are  of  consider- 
^        .  able  surgical  importance,  since  a  varicose  condition  of  these 

saphtn^ouTvei'n  andTts  branch'eT^    vessels  is  more  frequently  met  with  than  of  those  in  other  parts 

'  Mr.  Gay  calls  attention  to  the  fact  that  the  external  saphenous  vein  often  (he  says  invariably)  penetrates 
the  fascia  at  or  about  the  point  where  the  tendon  of  the  Gastrocnemius  commences,  and  runs  below  the  fascia 
in  the  rest  of  its  course,  or  sometimes  among  the  muscular  fibres,  to  join  the  popliteal  vein.  (See  Gay  on  Vari- 
cose Disease  of  the  Lower  Extremities,  p.  24,  where  there  is  also  a  careful  and  elaborate  description  of  the 
branches  of  the  saphena  veins.) — Ed.  of  15th  English  edition. 


758 


THE   BLOOD -VASCULAB    SYSTEM 


of  the  body,  except  perhaps  the  spermatic  and  hemorrhoidal  veins.  The  course  of  the  internal 
saphenous  is  in  front  of  the  tip  of  the  inner  malleolus,  over  the  subcutaneous  surface  of  the  lower 
end  of  the  tibia,  and  then  along  the  internal  border  of  this  bone  to  the  back  part  of  the  internal 
condyle  of  the  femur,  whence  it  follows  the  course  of  the  Sartorius  muscle,  and  is  represented  on 
the  surface  by  a  line  drawn  from  the  posterior  border  of  the  Sartorius  on  a  level  with  the  internal 
condyle  to  the  saphenous  opening.  The  external  saphenous  lies  behind  the  external  malleolus, 
and  from  this  follows  the  middle  line  of  the  calf  to  just  below  the  ham.  It  is  not  generally  so 
apparent  beneath  the  skin  as  the  internal  saphenous.  Both  these  veins  in  the  leg  are  accom- 
panied by  nerves,  the  internal  saphenous  being  joined  by  its  companion  nerve  just  below  the 
level  of  the  knee-joint.  No  doubt  much  of  the  pain  of  varicose  veins  in  the  leg  is  due  to  this 
fact. 

The  Deep  Veins  of  the  Lower  Extremity. 

The  deep  veins  of  the  lower  extremity  accompany  the  arteries  and  their  branches 
and  are  called  the  venae  comites  of  those  vessels.    The  vense  comites  in  the  lower 

extremity  pass  into  one  trunk,  the  popliteal  vein, 
whereas  in  the  upper  extremity  the  vena?  comites  con- 
tinue with  the  artery  to  the  axilla. 

The  Deep  Veins  of  the  Foot.— The  plantar  digital 
veins  {vv.  digitales  'plantar es)  form  the  plantar  metatarsal 
veins  {vv.  metatarsew  plantares),  which  communicate 
with  the  veins  of  the  dorsum  of  the  foot  by  perfor- 
ating veins  and  also  communicate  with  the  deep  venous 
arch  of  the  sole  of  the  foot  (arcus  venosus  plantaris  pro- 
fundus). The  plantar  arch  gives  off  lateral  or  external 
plantar  veins,  which  unite  with  median  or  internal  plantar 
veins  to  form  the  posterior  tibial  veins.  On  the  dorsum 
of  the  foot  the  deep  veins  begin  as  the  dorsal  metatarsal 
veins  (vv.  metatarsece  dor  sales  pedis),  which  form  the 
vense  comites  of  the  dorsalis  pedis  artery. 

The  Posterior  Tibial  Veins  {w.  tihiales  posteriores) 
accompany  the  posterior  tibial  artery  and  are  joined 
by  the  peroneal  veins. 

The  Anterior  Tibial  Veins  (vv.  tihiales  anteriores) 
are  formed  by  a  continuation  upward  of  the  vense 
comites  of  the  dorsalis  pedis  artery.  They  pass  be- 
tween the  tibia  and  fibula,  through  the  large  oval  aper- 
ture above  the  interosseous  membrane,  and  form,  by 
their  junction  with  the  posterior  tibial,  the  popliteal 
vein. 

The  valves  in  the  deep  veins  are  very  numerous. 
The  Popliteal  Vein  (v.  poplitea)  (Fig.  469)  is  formed 
by  the  junction  of  the  anterior  and  posterior  tibial 
veins;  it  ascends  through  the  popliteal  space  to  the 
aperture  in  the  Adductor  magnus,  where  it  becomes  the  femoral  vein.  In  the 
lower  part  of  its  course  it  is  placed  internal  to  the  artery;  between  the  heads  of 
the  Gastrocnemius  it  is  superficial  to  that  vessel;  but  above  the  knee-joint  it  is 
close  to  the  outer  side  of  the  artery.  It  receives  the  sural  veins  from  the  Gastroc- 
nemius muscle,  the  articular  veins,  and  the  external  saphenous  vein.  The  valves 
in  this  vein  are  usually  four  in  number. 

The  Femoral  Vein  (v.  femoralis)  (Figs.  470  and  471)  accompanies  the  femoral 
artery  through  the  upper  two-thirds  of  the  thigh.  In  the  lower  part  of  its  course 
it  lies  external  to  the  artery;  higher  up  it  is  behind  it;  and  at  Poupart's  ligament 
it  lies  to  its  inner  side  and  on  the  same  plane.  It  receives  numerous  muscular 
tributaries,  and  about  an  inch  and  a  half  below  Poupart's  ligament  it  is  joined  by 


Fig.  469.— The  popliteal  vein. 
(Poirier  and  Charpy.) 


THE    DEEP     VEINS    OF    THE    LOWER    EXTREMITY 


759 


the  profunda  femoris  {v.  profunda  femoris);  near  its  termination  it  is  joined  by 
the  internal  saphenous  vein.  The  valves  in  this  vein  are  four  or  five  in  number. 
The  External  Iliac  Vein  (v.  iliaca  externa)  (Figs.  464,  471,  and  473)  commences 
at  the  termination  of  the  femoral,  beneath  the  crural  arch,  and,  passing  upward 
along  the  brim  of  the  pelvis,  terminates  opposite  the  sacro-iliac  synchondrosis  by 
uniting  with  the  internal  iliac  to  form  the  common  iliac  vein.  On  the  right  side  it 
lies  at  first  along  the  inner  side  of  the  external  iliac  artery,  but  as  it  passes  upward 
gradually  inclines  behind  it.  On  the  left  side  it  lies  altogether  on  the  inner  side 
of  the  artery.     It  receives,  immediately  above  Poupart's  ligament,  the  deep  epi- 


UMBILICUS 


SUPERFICIAL 
EPIGASTRIC 


SUPERFICIAL 

INTERNAL 

CIRCUMFLEX 


SUPERFICIAL 

EXTERNAL 

CIRCUMFLEX 


Fig.  470. — The  femoral  vein  and  its  tributaries.      (Poirier  and  Charpy.) 


gastric  and  deep  circumflex  iliac  veins  and  a  small  pubic  vein,  corresponding  to 
the  pubic  branch  of  the  obturator  artery.  According  to  Friedreich,  it  frequently 
contains  one  and  sometimes  two  valves. 

The  Deep  Epigastric  Vein  (v.  epigastrica  inferior)  (Fig.  471). — Two  veins 
accompany  the  deep  epigastric  artery;  they  usually  unite  into  a  single  trunk 
before  their  termination  in  the  external  iliac  vein. 

The  Deep  Circumflex  Hiac  Vein  (v.  circumflexa  ilium  profunda)  (Fig.  471). — 
Two  veins  accompany  the  deep  circumflex  iliac  artery.  These  unite  into  a  single 
trunk  which  crosses  the  external  iliac  artery  just  above  Poupart's  ligament  and 
terminates  in  the  external  iliac  vein. 


760 


THE  BLOOD -VASCULAR    SYSTEM 


The  Hypogastric  or  Internal  Iliac  Vein  {v.  iliaca  interna  or  v.  hypogastrica) 
(Figs.  464, 471,  and  473)  is  formed  by  the  veins  corresponding  to  all  the  branches 
of  the  internal  iliac  artery  except  the  umbilical  branch.  It  receives  the  blood 
from  the  exterior  of  the  pelvis  by  the  gluteal,  sciatic,  internal  pudic,  and  obturator 
veins,  and  from  the  organs  in  the  cavity  of  the  pelvis  by  the  middle  hemor- 
rhoidal veins,  the  superior  vesical  plexus  and  the  prostatico-vesical  plexus  in  the 
male,  and  the  superior  vesical,  inferior  vesical,  uterine  and  vaginal  plexuses  in 
the  female.  The  vessels  forming  these  plexuses  are  remarkable  for  their  large  size, 
their  frequent  anastomoses,  and  the  number  of  valves  which  they  contain.  The 
internal  iliac  vein  lies  at  first  on  the  inner  side,  and  then  behind  the  internal  iliac 
artery,  and  terminates  opposite  the  sacro-iliac  articulation  by  uniting  with  the 
external  iliac  to  form  the  common  iliac  vein.    This  vessel  has  no  valves. 

The  Internal  Pudic  Veins  (vv.  pudendce  intern(F)(Fig.  471)  have  the  same  course  as 
the  internal  pudic  artery.  They  receive  tributaries  corresponding  to  the  branches 
of  the  artery,  except  the  tributary  corresponding  to  the  dorsal  artery  of  the 
penis ;  that  is,  the  deep  dorsal  vein  of  the  penis,  which  opens  into  the  prostatico- 
vesical  plexus. 


CIRCUMFLEX 
ILIAC 


DEEP 
EPIGASTRIC 


LATERAL 
SACRAL 


MID 
SACRAL 


Fig.  471. — The  iliac  veins.     (Poirier  and  Charpy.) 


The  Inferior  or  External  Haemorrhoidal  Veins  (Figs.  472  and  473)  collect  blood 
from  the  anus.  They  pass  outward  over  the  External  sphincter  muscle,  unite  with 
numerous  subcutaneous  veins,  and  form  larger  vessels  which  join  the  internal 
pudic  veins. 

The  Middle  Haemorrhoidal  Veins  (Figs.  472  and  473)  help  to  form  the  hemor- 
rhoidal plexus,  perforate  the  rectal  wall,  and  empty  into  the  internal  iliac  vein. 
These  veins,  by  their  anastomoses  in  the  hemorrhoidal  plexus,  establish  a 
communication  between  the  portal  and  systemic  venous  systems. 

The  Lateral  Sacral  Veins  (vv.  sacrales  latcrales)  (Fig.  471)  accompany  the  lateral 
sacral  arteries  and  terminate  in  the  internal  iliac  vein. 


THE   DEEP    VEINS    OF    THE  LOWER    EXTREMITY 


761 


Surgical  Anatomy. — The  veins  of  the  hemorrhoidal  plexus  are  apt  to  become  dilated  and 
varicose,  and  form  piles,  hemorrhoids.  This  is  due  to  several  anatomical  reasons:  the  vessels  are 
contained  in  very  loose,  or  connective  tissue,  so  that  they  obtain  less  support  from  surrounding 
structures  than  most  other  veins,  and  are  less  capable  of  resisting  increased  blood  pressure: 
the  condition  is  favored  by  gravitation,  being  influenced  by  the  erect  posture,  either  sitting  or 
standing,  and  by  the  fact  that  the  superior  hemorrhoidal  and  portal  veins  have  no  valves.  The 
veins  pass  through  muscular  tissue  and  are  liable  to  be  compressed  by  its  contraction,  especially 
during  the  act  of  defecation,  and  they  are  affected  by  every  form  of  portal  obstruction. 

The  Obturator  Vein  {v.  ohturatorke)  (Figs,  471  and  473)  follows  the  course  of 
the  obturator  artery,  lying  below  the  artery  as  it  passes  over  the  side  of  the 
pelvis;  this  vein  empties  into  the  front  part  of  the  internal  iliac  vein. 

The  Sciatic  Veins  are  two  in  number;  they  accompany  the  sciatic  artery  in 
the  upper  part  of  the  back  of  the  thigh,  and  just  before  their  termination  in  the 
internal  iliac  the  two  veins  unite. 

The  Gluteal  Veins  {w.  glutea)  are  usually  two  in  number,  and  return  to  the 
internal  iliac  vein  the  blood  that  has  been  distributed  by  the  gluteal  artery  and 
its  branches. 


MIDDLE 
HCMORRHOiDAL' 


Fig.  472. — Scheme  of  the  anastomosis  of  the  veins  of  the  rectum.     (Poirier  and  Charpy.) 

The  Superior  Vesical  Plexus  (Fig.  473)  is  placed  upon  the  fundus  and 
lateral  aspects  of  the  bladder  on  the  external  aspect  of  the  muscular  coat.  It 
receives  vessels  from  the  mucous  membrane  and  from  the  muscular  walls.  It 
empties  into  the  internal  pudic  vein:  in  the  male  it  communicates  with  the 
prostatico-vesical  plexus,  and  in  the  female  with  the  inferior  vesical  plexus. 

The  Prostatic  or  the  Prostatico-vesical  Plexus  (Fig.  473)  surrounds  the 
prostate  gland  and  the  neck  of  the  bladder.  It  is  contained  between  the  recto- 
vesical fascia  which  surrounds  the  base  and  sides  of  the  gland  and  the  true  capsule 
of  the  glaijd.  It  communicates  with  the  superior  vesical  plexus  behind  and 
above,  and  receives  the  deep  dorsal  vein  of  the  penis,  which  enters  the  pelvis 
between  the  subpubic  and  triangular  ligaments.  This  plexus  receives  veins  from 
the  seminal  vesicles  and  vasa  deferentia.    On  each  side  one  or  more  vessels  pass 


762 


THE   BLOOD -VASCULAR    SYSTEM 


from  the  prostatico-vesical  plexus  to  the  internal  iliac  vein.  The  veins  composing 
the  prostatic  plexus  are  very  liable  to  become  varicose,  and  often  contain  hard, 
earthy  concretions  called  phleboliths. 

The  Inferior  Vesical  Plexus  exists  only  in  the  female,  and  corresponds  to  the 
prostatico-vesical  plexus  in  the  male,  and  surrounds  the  neck  of  the  bladder  and 
the  upper  portion  of  the  urethra.  It  receives  the  dorsal  vein  of  the  clitoris  and 
sends  efferents  to  the  internal  iliac  vein. 


THIRD  LUMBAR 


SUPERIOR 
HEMORRHOIDAL 


DEEP 

CIRCUMFLEX 

ILIAC 


OBTURATOR 


PROSTATIC 
PLEXUS 


HEMORRHOIDAL 
PLEXUS 


MIDDLE 
HEMORRHOIDAL 


INFERIOR 
HEMORRHOIDAL 


DORSAL 
OF  PEN 


VESICAL   PLEXUS  INTERNAL   PUDIC 

Fig.  473. — The  veins  of  the  male  pelvis,  right  half,  viewed  from  the  left.     The  psoas  mu-scle  has  been  removed 
and  the  rectum  drawn  down  somewhat  to  the  side.      (Spalteholz.) 

Surgical  Anatomy. — The  prostatico-vesical  plexus  is  wounded  in  the  lateral  operation  of 
lithotomy,  and  it  is  through  it  that  septic  matter  finds  its  way  into  the  general  circulation  after 
this  operation.  In  enucleating  the  prostate  the  gland  is  shelled  out  from  its  capsule  of  recto- 
vesical fascia.     The  veins  of  the  plexus  remain  attached  to  the  sheath. 

The  Dorsal  Veins  of  the  Penis.— The  Superficial  Dorsal  Vein  of  the  Penis  (Fig. 
474)  receives  blood  from  the  prepuce  and  runs  backward  beneath  the  skin,  and 
divides  into  two  branches  which  terminate  in  the  superficial  external  pudic  vein. 

The  Deep  Dorsal  Vein  of  the  Penis  {v.  dorsalis  'penis)  (Figs.  473  and  474)  is  a  vessel 
of  large  size  which  returns  the  blood  from  the  body  of  that  organ.    At  first  it  con- 


THE   DEEP     VEINS    OF    THE   LOWER   EXTREMITY 


763 


SUPERFICIAL  DOR- 
SAL VEIN 
DORSAL  ARTERY   i  .DEEP  DORSAL  VEIN 

CORPUS  cavernosum',        ■ 

^i        ,__ 

AREOLAR 
TISSUE 

CAVERNOUS, 
ARTERY 


sists  of  two  branches,  which  are  contained  in  the  groove  on  the  dorsum  of  the  penis, 
and  it  receives  numerous  superficial  veins  and  veins  from  the  glans  penis  and  the 
corpus  spongiosum.  These  vessels  unite  into  a  single  trunk,  which  passes  between 
the  two  parts  of  the  suspensory  ligament  of  the  penis,  and  through  an  aperture 
between  the  subpubic  ligament  and 
the  apex  of  the  triangular  ligament, 
and  divides  into  two  branches,  which 
enter  the  prostatico-vesical  plexus. 
The  dorsal  vein  of  the  clitoris  corre- 
sponds in  woman  to  the  dorsal  vein 
of  the  penis  in  man,  and  runs  into 
the  inferior  vesical  plexus. 

The  Vaginal  Plexuses  and  Veins 
(Fig.  475). — The  vaginal  plexuses  are 
placed  at  the  sides  of  the  vagina,  being 
especially  developed  at  the  orifice  of 
the  canal.  They  receive  vessels  from 
the  vaginal  walls.  The  plexuses 
communicate  with  the  uterine  plexus  above,  with  the  bulbar  veins 'below,  with 
the  inferior  vesical  plexus  in  front  and  with  the  hemorrhoidal  plexus  behind. 
From  the  upper  part  of  each  vaginal  plexus  comes  a  vaginal  vein  which  passes 
to  the  internal  iliac. 

The  Uterine  Plexuses  (Fig.  475)  are  situated  along  the  sides  and  superior  angles 
of  the  uterus,  between  the  layers  of  the  broad  ligament.  They  receive  the  veins 
from  the  uterus,  which  veins  are  without  valves.     During  pregnancy  these  veins 


URETHRA 


BULBO-CAVERNOUS    ARTERY/ 

—  ANTERIOR    BRANCH  '\ 

CORPUS 
SPONGIOSUM 

Fig.  474. — The  penis  in  transverse  section,  showing  the 
blood-vessels.      (Testut.) 


FALLOPIAN 


UTERINE 

VEINS 


VAGINAL  VENOUS   PLEXUS 


UTERINE   ARTERY 


SUPERIOR    VAGINAL 
ARTERIES 


OS    UTERI        VAGINA   CUT   OPEN    BEHIND 

Fig.  475. — Vessels  of  the  uterus  and  its  appendages,  rear  view.     (Testut.) 


become  large  venous  canals  known  as  the  uterine  sinuses,  and  bring  blood  from  the 
substance  of  the  placenta.  These  veins  join  the  ovarian  above  and  the  vaginal 
below,  and  anastomose  with  each  other.     They  are  not  tortuous  like  the  artery. 

The  Uterine  Veins  {vv.  uterinoe)  (Fig.  475)  arise  from  the  lower  part  of  the 
plexus,  and  there  are  usually  two  veins  on  each  side  and  they  are  without  valves. 
These  veins  for  the  first  portion  of  their  course  are  placsd  in  the  base  and  inner 
portion  of  the  broad  ligament;  they  then  pass  back  with  the  uterine  artery  in  a 
peritoneal  fold  between  the  back  of  the  broad  ligament  and  the  recto-uterine 
fold  (Cunningham) ;  they  then  pass  upward  and  enter  the  internal  iliac  vein. 


764  '^'HE   BLOOD -VASCULAR    SYSTEM 

The  Common  Iliac  Vein  {v.  iliaca  communis)  (Figs.  464,  471,  and  473)  on 
each  side  is  formed  by  the  union  of  the  external  and  internal  iliac  veins  in 
front  of  the  sacro-iliac  articulation :  passing  obliquely  upward  toward  the  right 
side,  each  vein  terminates  upon  the  intervertebral  substance  between  the  fourth 
and  fifth  lumbar  vertebrae,  where  the  veins  of  the  two  sides  unite  at  an  acute 
angle  to  form  the  inferior  vena  cava.  The  right  common  iliac  {v.  iliaca  communis 
dextra)  is  shorter  than  the  left,  nearly  vertical  in  its  direction,  and  ascends  behind 
and  then  to  the  outer  side  of  its  corresponding  artery.  The  left  common  iliac 
{v.  iliaca  communis  sinistra),  longer  and  more  obUque  in  its  course,  is  at  first 
situated  on  the  inner  side  of  the  corresponding  artery,  and  then  behind  the  right 
common  iliac.  Each  common  iliac  receives  the  ilio-lumbar,  and  sometimes  the 
lateral  sacral,  veins.  The  left  receives,  in  addition,  the  middle  sacral  vein.  No 
valves  are  found  in  these  veins. 

The  Middle  Sacral  Veins  (Figs.  471  and  472)  accompany  the  corresponding 
artery  along  the  front  of  the  sacrum,  and  join  to  form  a  single  vein  (v.  sacralis 
media),  which  terminates  in  the  left  common  iliac  vein;  occasionally  in  the  angle 
of  junction  of  the  two  iliac  veins.  The  middle  sacral  veins  communicate  with 
the  inferior  hemorrhoidal. 

The  Ilio-lumbar  Veins  (t'v.  iliolumhales)  receive  branches  from  the  iliac  fossae, 
spinal  muscles,  and  spinal  canal.  One  vein  on  each  side  runs  with  the  artery, 
passes  posterior  to  the  psoas  muscle,  and  joins  the  common  iliac  vein. 

Peculiarities. — The  left  common  iliac  vein,  instead  of  joining  with  the  right  in  its  usual 
position,  occasionally  ascends  on  the  left  side  of  the  aorta  as  high  as  the  kidney,  where,  after 
receiving  the  left  renal  vein,  it  crosses  over  the  aorta,  and  then  joins  with  the  right  vein  to  form 
the  vena  cava.  In  these  cases  the  two  common  iliacs  are  connected  by  a  small  communicating 
branch  at  the  spot  where  they  are  usually  united.^ 

The  Ascending  or  Inferior  Vena  Cava  {v.  cava  inferior)  (Figs.  464  and  471) 
returns  to  the  heart  the  blood  from  all  the  parts  below  the  Diaphragm.  It  is 
formed  by  the  junction  of  the  two  common  iliac  veins  on  the  right  side  of  the 
intervertebral  substance  between  the  fourth  and  fifth  lumbar  vertebrae.  It  passes 
upward  along  the  front  of  the  spine  on  the  right  side  of  the  aorta,  and,  having  reached 
the  under  surface  of  the  liver,  is  contained  in  a  groove  on  its  posterior  surface.  It 
then  perforates  the  central  tendon  of  the  Diaphragm,  enters  the  pericardium, 
where  it  is  covered  for  a  very  short  distance  by  the  serous  layer  of  the  pericardium, 
and  terminates  in  the  lower  and  back  part  of  the  right  auricle.  At  its  termination 
in  the  auricle  it  is  provided  with  a  valve,  the  Eustachian  valve  (valvida  v.  cavas 
[inferioris  Eustachii]) ,  which  is  of  large  size  during  foetal  life. 

Relations. — In  front,  from  below  upward,  with  the  mesentery,  right  spermatic 
artery,  transverse  portion  of  the  duodenum,  the  pancreas,  portal  vein,  and  the 
posterior  surface  of  the  liver,  which,  in  most  cases,  partly  and  occasionally  com- 
pletely surrounds  it;  behind,  with  the  vertebral  column,  the  right  crus  of  the 
Diaphragm,  the  right  renal  and  lumbar  arteries,  and  the  right  semilunar  ganglion; 
on  the  left  side,  with  the  aorta. 

Peculiarities.  In  Position. — This  vessel  is  sometimes  placed  on  the  left  side  of  the  aorta, 
as  high  as  the  left  renal  veins,  after  receiving  which  it  crosses  over  to  its  usual  position  on  the 
right  side;  or  it  may  be  placed  akogether  on  the  left  side  of  the  aorta,  as  far  upward  as  its  ter- 
mination in  the  heart:  in  such  cases  the  abdominal  and  thoracic  viscera,  together  with  the  great 
vessels,  are  all  transposed. 

Point  of  Termination. — Occasionally  the  inferior  vena  cava  joins  the  right  azygos  vein, 
which  is  then  of  large  size.  In  such  cases  the  superior  cava  receives  the  whole  of  the  blood 
from  the  body  before  transmitting  it  to  the  right  auricle,  except  the  blood  from  the  hepatic  veins, 
which  passes  directly  into  the  right  auricle. 

*  See  two  cases  which  have  been  described  by  Mr.  Walsham  in  the  St.  Bartholomew's  Hospital  Reports, 
vols.  xvi.  and  xvii. — Ed.  of  15th  English  edition. 


THE  DEEP    VEINS    OE    THE  LOWER    EXTREMITY  765 

Tributaries. — It  receives  in  its  course  the  following  veins: 

Lumbar.  Suprarenal. 

Right  Spermatic.  Phrenic. 

Renal.  Hepatic. 

The  Lmnbax  Veins  {vv.  lumbales),  four  in  number  on  each  side,  collect  the 
blood  by  dorsal  tributaries  from  the  muscles  and  integument  of  the  loins  and  by 
abdominal  tributaries  from  the  walls  of  the  abdomen,  where  they  communicate 
with  the  epigastric  veins.  At  the  spine  they  receive  veins  from  the  spinal  plexuses, 
and  then  pass  forward,  round  the  sides  of  the  bodies  of  the  vertebrae  beneath  the 


Fig.  476. — Spermatic  veins.     (Testut.) 

Psoas  magnus  muscle,  and  terminate  at  the  back  part  of  the  inferior  cava.  The 
left  lumbar  veins  are  longer  than  the  right,  and  pass  behind  the  aorta.  The  lumbar 
veins  of  a  side  are  connected  together  by  a  longitudinal  vein  which  passes  in  front 
of  the  transverse  processes  of  the  lumbar  vertebrae,  and  is  called  the  ascending 
lumbar  vein  (v.  lumhalis  ascendens)  (Fig.  464) .  It  forms  the  most  frequent  origin 
of  the  corresponding  vena  azygos,  and  serves  to  connect  the  common  iliac,  ilio- 
lumbar, lumbar,  and  azygos  veins  of  the  corresponding  side  of  the  body. 

The  Spermatic  Veins  {vv.  spermatic(E)  (F\g.  476)  emerge  from  the  back  of  the  testis, 
and  receive  tributaries  from  the  epididymis;  they  unite  and  form  a  convoluted 
plexus  called  the  spermatic  plexus  {plexus  pampiniformis),  which  forms  the  chief 


766 


THE   BLOOD -VASCULAR   SYSTEM 


mass  of  the  cord :  the  vessels  composing  this  plexus  are  very  numerous,  and  ascend 
along  the  cord  in  front  of  the  vas  deferens;  below  the  external  abdominal  ring  they 
unite  to  form  three  or  four  veins,  which  pass  along  the  inguinal  canal,  and,  enter- 
ing the  abdomen  through  the  internal  abdominal  ring,  coalesce  to  form  two  veins, 
which  ascend  on  the  Psoas  muscle  behind  the  peritoneum,  lying  one  on  each  side 
of  the  spermatic  artery,  and  unite  to  form  a  single  vein,  which  opens  on  the  right 
side  into  the  inferior  vena  cava  at  an  acute  angle;  on  the  left  side  into  the  left  renal 
vein  at  a  right  angle  (Fig.  477).    The  termination  of  the  left  spermatic  vein 


SPERtMATIC  VEIN- 
LEFT  SIDE 


SPERMATIC  VEIN— _ 
RIGHT  SIDE 


Fig.  477. — Terminations  of  the  right  and  left  spermatic  veins.     (Poirier  and  Charpy.) 

is  called  the  emulgent  vein.  Professor  John  H.  Brinton  pointed  out  that  a 
valve  is  usually  absent  in  the  emulgent  vein  (Fig.  478),  but  regularly  present  in 
the  right  spermatic  vein.^  The  left  spermatic  vein  passes  behind  the  sigmoid 
flexure  of  the  colon,  and  is  thus  exposed  to  pressure  from  the  contents  of  that 
bowel. 

Surgical  Anatomy. — The  spermatic  veins  are  very  frequently  varicose,  constituting  the  dis- 
ease known  as  varicocele.  Though  it  is  quite  possible  that  the  originating  cause  of  this  affection 
may  be  a  congenital  abnormaUty  either  in  the  size  or  number  of  the  veins  of  the  pampiniform 
plexus,  still  it  must  be  admitted  that  there  are  many  anatomical  reasons  why  these  veins  should 
become  varicose — viz.,  the  imperfect  support  afforded  to  them  by  the  loose  tissue  of  the  scrotum; 
their  great  length;  their  vertical  course;  their  dependent  position;  their  plexiform  arrangement 
in  the  scrotum,  with  their  termination  in  one  small  vein  in  the  abdomen ;  their  few  and  imperfect 
valves;  and  the  fact  that  they  may  be  subjected  to  pressure  in  their  passage  through  the  abdominal 
wall.  The  left  veins  more  often  become  varicose  than  the  right  veins,  probably,  as  Brinton  sug- 
gests, because  the  right  spermatic  vein  practically  always  has  a  valve  and  opens  into  the  vena 
cava  at  an  acute  angle,  whereas  the  left  spermatic  vein  is  not  unusually  destitute  of  a  valve  at 
its  opening  and  passes  into  the  left  renal  vein  at  a  right  angle. 

The  Ovarian  Veins  {vv.  ovaricoe)  (Fig.  475)  are  analogous  to  the  spermatic  in  the 
male;  they  form  a  plexus  near  the  ovary  in  the  broad  ligament  and  about  the  Fallo- 
pian tube,  communicating  with  the  uterine  plexus.  They  terminate  in  the  same  way 
as  the  spermatic  veins  in  the  male.  Valves  are  occasionally  found  in  these  veins. 
These  vessels,  like  the  uterine  veins,  become  much  enlarged  during  pregnancy. 

1  See  John  H.  Brinton  in  the  American  Journal  of  the  Medical  Sciences,  and  also  Handbuch  der  Topographi- 
schen  Anatomic, von  Joseph  Hyrtl.  Rivington  maintains  that  a  valve  is  usually  found  at  the  orifices  of  both  the 
right  and  left  spermatic  veins.  When  no  valves  exist  at  the  opening  of  the  left  spermatic  vein  into  the  left  renal 
vein,  valves  are  generally  present  in  the  left  renal  vein  within  a  quarter  of  an  inch  from  the  orifice  of  the 
spermatic  vein.     (Journal  of  Anatomy  and  Physiology,  vol.  vii.  p.  163). — Ed.  of  15th  English  edition. 


THE    DEEP  VEINS    OF    THE   LOWER    EXTREMITY 


767 


The  Renal  Veins  {vv.  renales)  (Fig.  465)  are  of  large  size,  and  are  placed  in  front 
of  the  renal  arteries.^  The  left  is  longer  than  the  right,  and  passes  in  front  of  the 
aorta,  just  below  the  origin  of  the  superior  mesenteric  artery.  It  receives  the  left 
spermatic,  the  left  inferior,  and,  generally,  the  left  suprarenal  veins.  It  opens  into 
the  vena  cava  a  little  higher  than  the  right.  The  utero-venous  triangle  of  Byron 
Robinson  is  formed  by  the  ureter,  the  renal  veins,  and  the  ovarian  veins. 

The  Suprarenal  Veins  (vv.  swprarenales)  (Fig.  464)  are  two  in  number:  that  on 
the  right  side  terminates  in  the  vena  cava;  that  on  the  left  side,  in  the  left  renal 
or  in  the  left  phrenic  vein. 

The  Phrenic  Veins  {vv.  phrenicce)  follow  the  course  of  the  phrenic  arteries. 
The  two  superior  phrenic  veins  (vv.  phrenicoB  superior es) ,  of  small  size,  accom- 
pany the  phrenic  nerve  and  comes  nervi  phrenici  artery,  and  join  the  internal 
mammary  vein.  The  two  inferior  phrenic  veins  {vv.  phrenicoe  inferiores)  follow 
the  course  of  the  phrenic  arteries,  and  terminate,  the  right  in  the  inferior  vena 
cava,  the  left  in  the  left  renal  vein. 


Fig.  478. — Dis.section  of  the  vena  cava,  emulgent-  and  spermatic  veins,  showing  the  right  spermatic  valve 
and  its  accompanying  sinus,  c,  vena  cava;  e,  emulgent  vein;  r,  right  spermatic  vein;  /,  left  spermatic  vein; 
a.  aperture  by  which  the  right  spermatic  vein  empties  into  the  vena  cava;  v,  right  spermatic  valve;  s,  sinus 
across  which  the  valve  is  stretched;  /,  termination  of  the  left  spermatic  vein  in  the  emulgent  vein.  (John  H. 
Brinton.) 

The  Hepatic  Veins  {vv.  hepaticce)  commence  in  the  substance  of  the  liver,  in 
the  capillary  terminations  of  the  portal  vein  and  hepatic  artery,  intralobular  veins: 
these  tributaries,  gradually  uniting  into  sublobular  veins;  usually  form  three  large 
hepatic  veins,  which  converge  toward  the  posterior  surface  of  the  liver  and  open 
into  the  inferior  vena  cava,  whilst  that  vessel  is  situated  in  the  groove  at  the  back 
part  of  this  organ.      Of  these  three  veins,  one  from  the  right  and  another  from 

1  The  student  may  observe  that  all  veins  above  the  Diaphragm,  which  do  not  lie  on  the  same  plane  as  the 
arteries  which  they  accompany,  lie  in  front  of  them,  and  that  all  veins  below  the  Diaphragm,  which  do  not 
lie  on  the  same  plane  as  the  arteries  which  they  accompany,  lie  behind  them,  except  the  renal  and  profunda 
femoris  vein. —  En.  of  15th  English  edition. 


768  THE  BLOOD -VASCULAR  SYSTEM 

the  left  lobe  open  obliquely  into  the  inferior  vena  cava,  that  from  the  middle  of 
the  organ  and  lobulus  Spigelii  having  a  straight  course.  The  hepatic  veins  run 
singly,  and  are  in  direct  contact  with  the  hepatic  tissue.  They  are  destitute  of 
valves. 

The  Portal  System  of  Veins  (Fig.  479). 

The  portal  venous  system  is  composed  of  four  large  veins  which  collect  the  venous 
blood  from  the  viscera  of  digestion  (stomach,  intestine,  and  pancreas)  and  from 
the  spleen.  The  trunk  formed  by  their  union,  the  Portal  Vein  {vena  portce), 
enters  the  liver  and  ramifies  throughout  its  substance  after  the  manner  of  an 
artery  and  ends  in  capillaries,  from  which  the  blood  is  collected  into  the  hepatic 
veins,  which  terminate  in  the  inferior  vena  cava.  The  branches  of  this  vein  are 
in  all  cases  single,  and  destitute  of  valves. 

The  veins  forming  the  portal  system  are — the 

Superior  Mesenteric.  Inferior  Mesenteric. 

Splenic.  Gastric. 

Cystic. 

The  Superior  Mesenteric  Vein  (v.  mesenterica  superior)  (Fig.  479)  returns  the 
blood  from  the  small  intestines  and  from  the  caecum  and  ascending  and  transverse 
portions  of  the  colon,  corresponding  with  the  distribution  of  the  branches  of  the 
superior  mesenteric  artery.  The  large  trunk  formed  by  the  union  of  these  branches 
ascends  along  the  right  side  and  in  front  of  the  corresponding  artery,  passes  in  front 
of  the  transverse  portion  of  the  duodenum,  and  unites,  behind  the  upper  border 
of  the  pancreas,  with  the  splenic  vein  to  form  the  vena  portse.  It  receives  the 
right  gastro-epiploic  vein.  The  appendicular  vein  is  a  tributary  of  the  superior 
mesenteric  vein. 

The  Splenic  Vein  (v.  lienalis)  (Fig.  479)  commences  by  five  or  six  large  branches 
which  return  the  blood  from  the  substance  of  the  spleen.  These,  uniting,  form  a 
single  vessel,  which  passes  from  left  to  right,  grooving  the  upper  and  back  part  of 
the  pancreas  below  the  artery,  and  terminates  at  its  greater  end  by  uniting  at  a 
right  angle  with  the  superior  mesenteric  to  form  the  vena  portse.  The  splenic  vein 
is  of  large  size,  and  not  tortuous  like  the  artery.  It  receives  the  vasa  brevia  from 
the  left  extremity  of  the  stomach,  the  left  gastro-epiploic  vein,  pancreatic  branches 
from  the  pancreas,  the  pancreatico-duodenal  vein,  and  the  inferior  mesenteric  vein. 

The  Inferior  Mesenteric  Vein  {v.  mesenterica  inferior)  (Fig.  479)  returns  the 
blood  from  the  rectum,  sigmoid  flexure,  and  descending  colon,  corresponding  with 
the  ramifications  of  the  branches  of  the  inferior  mesenteric  artery.  It  lies  to  the  left 
of  the  artery,  and  ascends  beneath  the  peritoneum  in  the  lumbar  region ;  it  passes 
behind  the  transverse  portion  of  the  duodenum  and  pancreas,  and  terminates 
in  the  splenic  vein.  Its  hemorrhoidal  branches,  the  superior  haemorrhoidal  veins, 
inosculate  with  the  middle  hemorrhoidal  branches  of  the  internal  iliac,  and  thus 
establish  a  communication  between  the  portal  and  the  general  venous  system.^ 

The  Gastric  Veins  (vv.  gastricce)  (Fig.  479)  ai-e  two  in  number:  one,  a  small  vein, 
corresponds  to  the  pyloric  branch  of  the  hepatic  artery;  the  other,  considerably 
larger,  corresponds  to  the  gastric  artery.  The  former,  the  pyloric  vein  (v.  pylorica), 
runs  along  the  lesser  curvature  of  the  stomach  toward  the  pyloric  end,  receives 
branches  from  the  pylorus  and  duodenum,  and  ends  in  the  vena  portse.  The 
latter,  the  gastric  or  coronary  vein  (v.  coronaria  veniriculi),  begins  near  the  pylorus, 

1  Besides  this  anastomosis  between  the  portal  vein  and  the  branches  of  the  vena  cava,  other  anastomoses 
between  the  portal  and  systemic  veins  are  formed  by  the  communication  between  the  gastric  veins  and  the 
oesophageal  veins,  which  empty  themselves  into  the  vena  azygos  minor;  between  the  left  renal  vein  and  the 
vems  of  the  intestines,  especially  of  the  colon  and  duodenum;  between  the  veins  of  the  round  ligament  of  the 
liver  and  the  portal  veins;  and  between  the  superficial  branches  of  the  portal  veins  of  the  liver  and  the  phrenic 
yems,  as  pointed  out  by  Mr.  Kiernan.  (See  Physiological  Anatomy,  by  Todd  and  Bowman,  1859,  vol.  ii.  p. 
348).— Ed.  of  15th  English  edition. 


THE    PORTAL    SYSTEM    OF    VEINS 


769 


runs  along  the  lesser  curvature  of  the  stomach  toward  the  oesophageal  opening 
in  the  diaphragm,  and  then  passes  across  the  front  of  the  spine  from  left  to  right 
to  end  in  the  vena  portse,  at  a  point  a  little  above  the  junction  of  the  pyloric  vein. 
The  Cystic  Vein  {v.  cystica)  (Fig.  479) . — The  vena  portae  generally  receives  the 
cystic  vein,  although  that  vessel  sometimes  terminates  in  the  right  branch  of  the 
vena  portae. 


Fig.  479. — Portal  vein  and  its  branches. 


Note.  In  this  diagram  the  right  gastro-epiploic  vein  opens  into  the  splenic  vein;  generally 
It  empties  itself  into  the  superior  mesenteric,  close  to  its  termination. 

The  Portal  Vein  {vena  'porta:)  (Fig.  479)  is  formed  by  the  junction  of  the  superior 
mesenteric  and  splenic  veins,  their  union  taking  place  in  front  of  the  vena  cava  and 
behind  the  upper  border  of  the  head  of  the  pancreas.  Passing  upward  through 
the  right  border  of  the  lesser  omentum  to  the  under  surface  of  the  liver,  it  enters 
the  transverse  fissure,  where  it  is  somewhat  enlarged,  forming  the  sinus  of  the 
portal  vein,  and  divides  into  two  branches  which  accompany  the  ramifications  of 
the  hepatic  artery  and  hepatic  duct  throughout  the  substance  of  the  liver.     Of 

49 


770 


THE   BLOOD -VASCULAR    SYSTEM 


these  two  branches,  the  right  is  the  larger,  but  the  shorter,  of  the  two.  The  portal 
vein  is  about  three  or  four  inches  in  length,  and,  whilst  contained  in  the  lesser 
omentum,  lies  behind  and  between  the  common  bile-duct  and  the  hepatic  artery, 
the  former  being  to  the  right,  the  latter  to  the  left.  These  structures  are  accom- 
panied by  filaments  of  the  hepatic  plexus  of  nerves  and  numerous  lymphatics, 
and  are  surrounded  by  a  quantity  of  loose  areolar  tissue,  the  capsule  of  Glisson. 

The  portal  vein  divides,  in  the  substance  of  the  liver,  like  an  artery,  and  its 
minute  ramifications  end  in  capillaries,  from  which  the  blood  is  carried  to  the 
inferior  vena  cava  by  the  hepatic  veins;  these  veins  also  collect  the  blood  which 
has  been  brought  to  the  liver  by  the  hepatic  artery.  It  will  therefore  be  seen 
that  the  blood  which  is  carried  to  the  liver  by  the  portal  vein  passes  through  two 
sets  of  capillary  vessels — viz. :  (1)  the  capillaries  in  the  stomach,  intestine,  pancreas, 
and  spleen,  and  (2)  the  capillaries  of  the  portal  vein  in  the  liver. 


THE  CARDIAC  VEINS  (Fig.  480). 
The  veins  which  return  the  blood  from  the  substance  of  the  heart  are — the 


Great  Cardiac  Vein. 
Posterior  Cardiac  Vein. 
Left  Cardiac  Veins. 


Anterior  Cardiac  Veins. 
Right  or  Small  Coronary  Vein. 
Coronary  Sinus. 
Vense  Thebesii. 


The  Great  Cardiac  or  Left  Coronary  Vein  {v.  cordis  magna)  is  a  vessel  of 
considerable  size,  which  commences  at  the  apex  of  the  heart,  and  ascenrls  along 
the  anterior  interventricular  groove  to  the  base  of  the  ventricles.     It  then  curves 


PULMONARY 
VEINS. 
LEFT   AURICULAR, 
APPENDIX 

RIGHT  CORONARY  ARTERY      

AURICULAR- VENTRICULAR. 
GROOVE 

CORONARY. 
SINUS 


LEFT 
VENTRICLE 


VENA    AZYGOS 
MAJOR 


PULMONARY 

VEINS 
LEFT 

AURICLE 


POSTERIOR  CARDIAC 
VEIN 

POSTERIOR 
INTERVENTRIO 
ULAR  GROOVE 


'BIGHT 
VENTRICLE 


RIGHT  CORONARY 
ARTERY DESCEND- 
ING   BRANCH 


Fig.  480. — Cardiac  veins,  dorsal  view.      (Testut.) 


to  the  left  side,  around  the  auriculo-ventricular  groove,  between  the  left  auricle 
and  ventricle,  to  the  back  part  of  the  heart,  and  opens  into  the  left  extremity 
of  the  coronary  sinus,  its  aperture  being  guarded  by  two  valves.     It  receives,  in 


THE    CARDIAC    VEINS  771 

its  course,  tributaries  from  both  ventricles,  but  especially  from  the  left,  and  also 
from  the  left  auricle;  one  of  these  ascending  along  the  thick  margin  of  the  left 
ventricle  is  of  considerable  size,  and  is  called  the  left  marginal  vein.  The  vessels 
joining  the  great  cardiac  vein  are  provided  with  valves. 

The  Posterior  or  Middle  Cardiac  Vein  (v.  cordis  media)  commences  by  small 
tributaries,  at  the  apex  of  the  heart,  communicating  with  those  of  the  preceding. 
It  ascends  along  the  posterior  interventricular  groove  to  the  base  of  the  heart, 
and  terminates  in  the  coronary  sinus,  its  orifice  being  guarded  by  a  valve.  It 
receives  veins  from  the  posterior  surface  of  both  ventricles. 

The  Left  Cardiac  Vein  {v.  'posterior  ventriculi  sinistri)  receives  three  or  four 
small  vessels,  which  collect  the  blood  from  the  posterior  surface  of  the  left  ven- 
tricle.    It  opens  into  the  lower  border  of  the  coronary  sinus. 

The  Anterior  Cardiac  Veins  {w.  cordis  anteriores)  are  three  or  four  small 
vessels,  which  collect  the  blood  from  the  anterior  surface  of  the  right  ventricle. 
One  of  these,  the  vein  of  Galen,  larger  than  the  rest,  runs  along  the  right  border 
of  the  heart.    They  open  separately  into  the  lower  part  of  the  right  auricle. 

The  Right  Cardiac  or  Small  Coronary  Vein  {v.  cordis  parva)  runs  along  the 
groove  between  the  right  auricle  and  ventricle,  to  open  into  the  right  extremity  of 
the  coronary  sinus.  It  receives  blood  from  the  back  part  of  the  right  auricle  and 
ventricle. 

The  Coronary  Sinus  (sinus  coronarius)  is  that  portion  of  the  anterior  or  great 
cardiac  vein  which  is  situated  in  the  posterior  part  of  the  left  auriculo-ventricular 
groove.  It  is  about  an  inch  in  length,  presents  a  considerable  dilatation,  and  is 
covered  by  the  muscular  fibres  of  the  left  auricle.  It  receives  most  of  the  veins  of 
the  heart.  Besides  those  mentioned  it  receives  the  oblique  vein  of  Marshall  {v.  obliqua 
atrii  sinistri)  from  the  back  part  of  the  left  auricle,  the  remnant  of  the  obliterated 
left  Cuvierian  duct  of  the  foetus,  described  by  Mr.  Marshall.  The  great  coronary 
sinus  terminates  in  the  right  auricle,  between  the  inferior  vena  cava  and  the 
auriculo-ventricular  aperture,  its  orifice  being  guarded  by  a  semilunar  fold  of  the 
lining  membrane  of  the  heart,  the  Thebesian  valve.  All  the  veins  joining  this 
vessel,  excepting  the  oblique  vein  above  mentioned,  are  provided  with  valves. 

The  Venae  Thebesii  (vence  cordis  minimcE)  are  numerous  minute  veins,  which 
return  the  blood  directly  from  the  muscular  substance,  without  entering  the  venous 
current.  They  open  by  minute  orifices,  foramina  Thebesii  (foramina  venarum 
minamarum),  chiefly  on  the  inner  surface  of  the  right  auricle. 


THE    LYMPHATIC   SYSTEM. 


Lymph  is  obtained  from  the  blood-plasma.  From  lymph  the  body  cells 
obtain  food,  into  lymph  they  discharge  their  waste  materials,  and  there  is  a 
distinct  lymphatic  circulation,  the  constituents  of  the  plasma  passing  into  the 
perivascular  lymph-spaces  and  returning  to  the  heart  by  way  of  the  lymphatics 
and  certain  veins. 

The  lymphatic  system  consists  of  lymphatic  glands— large  lymph-vessels,  small 
lymph- vessels  (lymphatic  capillaries),  the  perivascular  lymph-spaces,  the  lymph 
canalicular  system,  and  the  body  cavities.  To  this  system  also  belong  the  lacteal  or 
chyliferous  vessels.  The  lacteals  are  the  lymphatic  vessels  of  the  small  intestine,, 
and  differ  in  no  respect  from  the  lymphatics  generally,  excepting  that  during  the 
process  of  digestion  they  contain  a  milk-white  fluid,  the  chyle,  which  passes  into 
the  blood  through  the  thoracic  duct. 

The  lymph  canalicular  system  is  the  system  of  spaces  in  areolar  connective 
tissue.  The  spaces  are  called  lymph-spaces.  In  these  spaces  lie  the  cells  of  the 
tissue.  The  larger  spaces  are  lined  with  endothelium,  the  smaller  spaces  are  not 
lined -with  endothelium;  they  form  connections  with  each  other  by  anastomotic 
channels  and  constitute  a  system  of  spaces  and  channels  which  probably  join 
the  lymphatic  capillaries. 

The  perivascular  lymph-spaces  are  found  around  certain  blood-vessels.  Each 
space  is  lined  with  endothelium,  and  is  joined  to  other  spaces  by  trabecuhe  of  con- 
nective tissue.  The  spaces  form  a  system  which  joins  the  lymphatic  capillaries. 
Perivascular  lymph-spaces  have  been  demonstrated  in  the  Haversian  canals  and 
in  the  subdural  space  of  the  pia  mater. 

The  pleural,  pericardial,  peritoneal,  and  S3movial  cavities  belong  to  the  lymphatic 
system.  These  cavities  are  lined  by  endothelial  cells.  Beneath  the  layer  of  lining 
cells  are  lymph-spaces  or  lymph-vessels,  which  communicate  with  the  body  cavity 
by  means  of  numerous  openings  in  the  lining  membrane.  These  openings  are 
called  stomata. 

Lymph-capillaries  are  larger  than  blood-capillaries,  but  the  diameter  of  a  lymph- 
capillary  is  different  at  different  points,  at  some  places  being  much  larger  than 
at  others.  Lymph-capillaries  are  formed  of  flattened  endothelial  cells.  In  some 
situations  networks  of  lymphatic  capillaries  surround  the  blood-vessels.  The 
lymph- vessels  are  called  the  lymphatics. 

The  lymphatics  have  derived  their  name  from  the  appearance  of  the  fluid  con- 
tained in  their  interior  (lympha,  water).  They  are  also  called  absorbents,  from  the 
property  they  possess  of  absorbing  certain  materials  from  the  tissues  and  con- 
veying them  into  the  circulation.  Larger  lymphatics  are  called  trunks  and  the 
largest  are  called  ducts. 

The  lymphatics  are  exceedingly  delicate  vessels,  the  coats  of  which  are  so 
transparent  that  the  fluid  they  contain  is  readily  seen  through  them,  and  they 
appear  milky-white;  hence  the  name  Asellius  gave  them  of  lacteal  veins.  They 
retain  a  nearly  uniform  size,  and  may  be  cylindrical  in  shape,  but  usually  are  inter- 
rupted at  intervals  by  constrictions  which  give  them  a  knotted,  beaded,  or  sac- 
like appearance.  These  constrictions  are  due  to  the  presence  of  valves  in  the 
interior  of  the  vessel.  Lymphatic  vessels  do  not  invariably  contain  valves.  Valves 
(772) 


J 


THE    LYMPHATIC  SYSTEM  773 

are  absent  at  the  starting  points  of  lymphatics,  are  absent  in  lymphatic  capillaries, 
are  not  numerous  in  the  largest  ducts  (thoracic  duct),  and  are  seldom  found  in  vis- 
ceral lymphatics.  The  valves  are  not  found  in  fixed  situations  and  vary  in  number. 
Between  the  ends  of  the  fingers  and  the  axillary  glands  Sappey  counted  from  sixty 
to  eighty.  "  They  are  arranged  in  pairs  and  resemble  the  aortic  semilunar  valves."^ 
The  lymphatic  capillaries  are  composed  purely  of  endothelium,  but  the  collecting 
trunks  possess  not  only  an  endothelial  inner  coat,  but  an  investing  elasto-muscular 
coat.  Vessels  in  the  subcutaneous  connective  tissue  are  devoid  of  muscle.  Lymph- 
atics have  been  found  in  nearly  every  texture  and  organ  of  the  body  v^hich  contains 
blood-vessels.  Such  non-vascular  structures  as  cartilage,  the  nails,  cuticle,  and 
hair  have  none,  but  with  these  exceptions  it  is  probable  that  eventually  all  parts 
will  be  found  to  be  permeated  by  these  vessels. 

A  larger  lymphatic  vessel  is  composed  of  three  coats.  The  inner  coat  is 
composed  of  elastic  tissue  hned  with  endothelium.  The  middle  coat  is  com- 
posed of  elastic  and  muscular  fibres.  The  external  coat  is  composed  of  connec- 
tive tissue  intermixed  with  smooth  muscular  fibres  longitudinally  or  obliquely 
placed. 

The  thoracic  duct  possesses  a  subendothelial  layer  of  connective  tissue  like  that 
found  in  the  arteries,  and  in  the  middle  coat  there  is  a  longitudinal  layer  of 
connective  tissue.  The  wall  of  a  smaller  lymphatic  contains  no  elastic  and  no 
muscular  tissue,  and  consists  merely  of  connective  tissue  lined  with  endothelium. 

The  lymphatics  are  arranged  in  superficial  and  deep  sets.  The  superficial  lym- 
phatics, on  the  surface  of  the  body,  are  placed  immediately  beneath  the  integument, 
accompanying  the  superficial  veins;  they  join  the  deep  lymphatics  in  certain  situa- 
tions by  perforating  the  deep  fascia.  In  the  interior  of  the  body  the  lymphatics 
lie  in  the  submucous  areolar  tissue  throughout  the  whole  length  of  the  gastro- 
pulmonary  and  genito-urinary  tracts,  and  in  the  subserous  tissue  of  the  thoracic 
and  abdominal  cavities.  In  the  cranial  cavity  the  perivascular  sheaths  are  lymph- 
spaces.  A  plexiform  network  of  minute,  closed,  capillary  lymphatics  may  be  found 
interspersed  among  the  proper  elements  and  blood-vessels  of  the  several  tissues,  the 
vessels  composing  which,  as  well  as  the  meshes  between  them,  are  much  larger  than 
those  of  the  capillary  blood-vessel  plexus.  From  these  networks  small  collecting 
vessels  emerge,  pass  to  a  neighboring  gland,  and  divide  into  a  capillary  network 
in  the  gland.  Numerous  small  vessels  emerge  from  the  gland,  which  unite  into 
one  lymphatic  vessel,  which  joins  a  larger  lymphatic  trunk,  which  empties  into 
a  branch  of  the  superior  vena  cava.  The  deep  lymphatics,  fewer  in  number  and 
larger  than  the  superficial,  accompany  the  deep  blood-vessels.  Their  mode  of 
origin  is  probably  similar  to  that  of  the  superficial  vessels.  The  lymphatics  of 
any  part  or  organ  exceed  the  veins  in  number  and  in  capacity,  but  in  size  they 
are  much  smaller.  Their  anastomoses  also,  especially  those  of  the  large  trunks, 
are  more  frequent,  and  are  effected  by  vessels  equal  in  diameter  to  those  which 
they  connect.  The  continuous  trunks  retain  the  same  diameter  throughout.  As 
the  lymphatic  vessels  approach  their  point  of  discharge  their  number  diminishes, 
but  the  calibre  of  the  remainder  does  not  increase  in  proportion. 

The  gaps  in  the  connective  tissue,  the  larger  of  which  are  lined  with  endothelium, 
the  smaller  of  which  are  devoid  of  endothelial  lining,  and  all  of  which  communicate 
with  the  lymphatic  capillaries,  are  known  as  lymphatic  spaces.  It  is  asserted  by 
some,  but  is  not  proved,  that  the  spaces  are  continuous  with  the  lymph-capillaries. 
Some  hold  that  lymph  gets  from  the  spaces  into  the  capillaries  by  means  of  open- 
ings in  intervening  tissue.  The  perivascular  spaces,  the  serous  cavities,  and  the 
ventricles  of  the  brain  resemble  in  function  lymphatic  structures. 

>  Treatise  on  Anatomy.  By  P.  Poirier  and  A.  Charpy.  Article  on  the  Lymphatics.  By  G.  Delamare,  P.  Poirier, 
and  B.  Cun6o. 


774 


THE   LYMPHATIC  SYSTEM 


The  lymphatic  or  absorbent  glands  (iymphoglandulae) ,  named  also  conglobate 
glands  and  lymph-nodes,  are  small,  solid,  glandular  bodies  situated  in  the  course  of 
the  lymphatic  and  lacteal  vessels.  They  vary  from  microscopic  dimensions  to  the 
size  of  an  olive,  and  their  color,  on  section,  is  of  a  pinkish-gray  tint,  excepting  the 
bronchial  glands,  which  in  the  adult  are  mottled  with  black,  the  hepatic  glands, 
which  are  yellow,  and  the  splenic  glands,  which  are  brown.  Each  gland  has 
a  layer  or  capsule  of  cellular  tissue  investing  it,  from  which  prolongations  dip 
into  its  substance,  forming  partitions.      The  lymphatic  and  lacteal  vessels  pass 

through  these  glands  in  their  passage  to  the  lymph- 
atic ducts.  A  lymphatic  or  lacteal  vessel,  previous  to 
entering  a  gland,  divides  into  several  small  branches, 
which  are  named  afferent  vessels  {vasa  afferentia). 
As  they  enter  the  gland,  the  external  coat  of  each 
becomes  continuous  with  the  capsule  of  the  gland, 
and  the  vessels  becoming  much  thinned,  and  consist- 
ing only  of  their  internal  or  endothelial  coat,  pass 
into  the  gland,  and  branch  out  upon  and  in  the  tissue 
of  the  capsule,  these  branches  opening  into  the  lymph- 
sinuses  of  the  gland.  There  is  an  extensive  sinus 
beneath  the  capsule;  from  this  subcapsular  sinus 
numerous  branches  run  inward  to  a  central  sinus. 
From  both  sinuses  fine  branches  proceed  to  form  a 
plexus,  the  vessels  of  which  unite  to  form  a  single 
efferent  vessel  (vas  efferens),  which,  on  emerging 
from  the  gland,  is  again  invested  with  an  external 
coat  from  the  gland  capsule.  The  lymph-glands  are 
filters  through  which  lymph  and  chyle  flow.  Car- 
cinoma cells  are  caught  in  them,  and  the  dissemina- 
tion of  the  disease  is  retarded.  In  the  glands  are 
masses  of  newly  formed  leukocytes  which  attack  any 
bacteria  in  the  lymph  or  chyle. 

The  size  of  the  lymphatic  glands  decreases  as  age 
advances,  and  in  very  old  individuals  many  glands 
actually  disappear.  It  is  impossible  to  estimate  the 
number  of  macroscopic  glands.  Sappey  estimated  the  number  to  be  from  600  to 
700.  Glands  are  embedded  in  fat  and  are  distinctly  movable.  Some  of  them  are 
superficial  (above  the  deep  fascia);  others  are  deep  (below  the  deep  fascia). 
Occasionally  a  gland  exists  alone,  but,  as  a  rule,  they  are  assembled  in  com- 
munities or  chains  of  from  eight  to  twelve,  or  even  more.  They  are  usually 
arranged  around  vessels,  and  often  are  upon  vessels.  The  glands  have  a  plen- 
tiful blood-supply,  and  contain  not  only  vascular  nerves,  but  definite  nerve- 
plexuses.  Besides  the  glands,  the  body  contains  numerous  lymphoid  areas, 
which,  in  structure  and  function,  are  allied  to  lymph-glands  (tonsils,  Peyer's 
patches,  etc.). 

Surgical  Anatomy. — In  an  operation  for  cancer  it  is  not  sufficient  to  cut  wide  of  the  growth 
and  remove  it;  it  is  imperatively  necessary  to  remove  the  lymphatic  glands  which  receive  lymph 
from  the  diseased  area,  and  also,  when  possible,  the  lymphatic  vessels  between  the  cancer  and 
the  glands.  Glands  are  diseased  very  early  in  cancer,  long  before  they  are  palpably  enlarged, 
and  are  usually  infected  by  emboU  of  cancer  cells.  The  rule  is  in  any  cancer,  however  recent, 
to  regard  the  associated  glands  as  diseased,  whether  enlarged  or  not,  and  to  thoroughly  remove 
them,  if  possible,  in  one  piece,  with  the  intervening  lymph-vessels  and  the  area  of  primary 
malignant  growth. 


P^iG.  481. — A  lymph-node  with  its 
afferent  and  effeient  vessels.  (Tes- 
tut.) 


THE  THORACIC  AND  BIGHT  LYMPHATIC  DUCT 


lib 


Intercostal 
glands. 


THE  THORACIC  DUCT  AND  THE  RIGHT  LYMPHATIC  DUCT. 

The  thoracic  tkict  or  the  left  lymphatic  duct  (ductus  thoracicus)  (Figs.  482  and 
483)  conveys  the  great  mass  of  lymph  and  chyle  into  the  blood.  It  is  the  common 
trunk  of  all  the  lymphatic  vessels 

of  the  body  below  the  Diaphragm,  i=:  .iiiil — li  ^" 

and  usually,  but  not  always,  also 
receives  the  lymph  from  the  left 
side  of  the  body  above  the  Dia- 
phragm. It  does  not  drain  the 
right  side  of  the  head  and  neck, 
the  right  upper  extremity,  the  right 
lung,  right  side  of  the  heart,  and  the 
convex  surface  of  the  liver.  It  partly 
drains  the  right  chest  wall.  It  varies 
in  length  from  fifteen  to  eighteen 
inches  in  the  adult,  and  extends  from 
the  second  lumbar  vertebra  to  the 
root  of  the  neck.  It  commences  in  the 
abdomen  by  a  triangular  dilatation, 
the  receptaculum  chyli  or  the  reser- 
voir or  cistern  of  Pecquet  (cisterna 
chyli),  which  is  situated  upon  the 
front  of  the  bodies  of  the  first  and 
of  the  second  lumbar  vertebra*,  to 
the  right  side  and  behind  the  aorta, 
by  the  side  of  the  right  crus  of  the 
Diaphragm.  The  receptaculum  is 
absent  in  some  individuals.  The 
thoracic  duct  ascends  into  the  thorax 
through  the  aortic  opening  in  the 
Diaphragm,  lying  to  the  right  of 
the  aorta,  and  is  placed  in  the  pos- 
terior mediastinum  in  front  of  the 
vertebral  column,  lying  between 
the  aorta  and  vena  azygos  major. 
Opposite  the  fourth  dorsal  vertebra 
it  inclines  toward  the  left  side,  and 
ascends  behind  the  arch  of  the  aorta 
on  the  left  side  of  the  oesophagus, 
and  behind  the  first  portion  of  the 
left  subclavian  artery,  to  the  upper 
orifice  of  the  thorax.  Opposite  the 
seventh  cervical  vertebra  it  turns 
outward  and  then  curves  downward 
over  the  subclavian  artery  and  in 
front  of  the  Scalenus  anticus  mus- 
cle, so  as  to  form  an  arch,  and  ter- 
minates in  the  left  subclavian  vein 
at  its  angle  of  junction  with  the  left 
internal  jugular  vein.  It  usually 
opens  at  the  apex  of  the  angle  in  the  superior  and  outer  surface,  but  may  open 
on  the  posterior  surface.     Sometimes  it  terminates  by  two  branches.     Figs.  482 


Fig.  482. — The  thoracic  and  right  lymphatic  ducts. 


776 


THE    LYMPHATIC  SYSTEM 


and  485  show  the  termination  of  the  thoracic  duct.  The  thoracic  duct,  at 
its  commencement,  is  about  equal  in  diameter  to  that  of  a  goose-quill,  dimin- 
ishes considerably  in  its  calibre  in  the  middle  of  the  thorax,  and  is  again 
dilated  just  before  its  termination,  the  ampulla.      It  is  generally  flexuous  in  its 


SUPERIOR  INTER- 
COSTAL VEIN 
MEDIASTINAL  LYM- 
PHATIC VESSEL 


SCALENUS  ANTICU8 
MUSCLE 

SUBCLAVIAN 
ARTERY 


SUPERIOR 

INTERCOSTAL 

VEIN 


BRONCHIAL 
LYMPHATIC 
VESSEL 


VENA  AZYGOS 

MINOR 

SUPERIOR 


VENA  AZYGOS 
MAJOR 


DESCENDING 
THORACIC  LYM- 
PHATIC TRUNK 


RECEPTACULUM 
CHYLI 


VENA  AZYGOS 
MINOR  INFERIOR 


—  OESOPHAGUS 

DESCENDING  THORACIC 
LYMPHATIC  TRUNK 

INFERIOR 
PHRENIC  ARTERY 
SUPRARENAL 
BODY 

COELIAC  AXIS 

SUPERIOR 
MESENTERIC 
COMMON   INTESTINAL 
LYMPHATIC  TRUNK 

RENAL  ARTERY 


LUMBAR 
VEINS 


COMMON   LUMBAR 
LYMPHATIC  TRUNK 


Fig.  483. -^Thoracic  duct  and  its  tributaries.      (Cunningham.) 

course,  the  older  the  person  the  greater  the  flexuosity,  and  it  is  constricted  at  inter- 
vals so  as  to  present  a  varicose  appearance.  The  thoracic  duct  not  infrequently 
divides  in  the  middle  of  its  course  into  two  branches  of  unequal  size,  which 
soon  reunite,  or  divides  into  several  branches,  which  form  a  plexiform  interlace- 
ment.   It  occasionally  divides,  at  its  upper  part,  into  two  branches,  of  which  the 


THE    THORACIC    AND    BIGHT  LYMPHATIC  DUCT 


111 


one  on  the  left  side  terminates  in  the  usual  manner,  while  that  on  the  right  opens 
into  the  right  subclavian  vein,  in  connection  with  the  right  lymphatic  duct.  The 
thoracic  duct  has  several  valves  throughout  its  whole  course,  but  they  are  more 
numerous  in  the  upper  than  in  the  lower  part,  and  the  lower  valves  are  not  com- 
petent; at  its  termination  it  is  provided  with  a  pair  of  competent  valves,  the  free 
borders  of  which  are  turned  toward  the  vein,  so  as  to  prevent  the  passage  of 
venous  blood  into  the  duct. 

The  common  intestinal  trunk  (truncus  intestinalis)  (Figs,  483,  484,  and  511) 
empties  into  the  receptaculum  and  brings  lymph  from  the  small  intestine  (lacteals), 
the  stomach,  the  pancreas,  and  the  spleen. 

Radicals  of  Origin  and  Tributaries. — In  most  individuals  the  juxta-aortic 
glands  which  are  placed  on  each  side  of  the  aorta  send  a  vessel  upward  and 
inward,  which  unite  to  form  the  thoracic  duct.  The  right  vessel  is  known  as 
the  truncus  lymphaticus  lumbalis  dextra.  The  left  vessel  is  known  as  the  truncus 
lymphaticus  lumbalis  sinistra.  A  vessel  from  the  glands  in  front  of  (pre-aortic) 
and  back  (retro-aortic)  of  the  aorta  empties  into  each  of  the  above-named  vessels. 
In  some  cases  a  large  vessel  forms  from  the  glands  in  front  of  the  aorta  and  helps 
form  the  duct.  The  receptaculum  chyli  receives  the  common  intestinal  lymphatic 
trunk,  which  conveys  lymph  from  the  small  intestine,  stomach,  spleen,  pancreas, 
and  a  portion  of  the  liver. 


Fig.  484.— Modes  of  origin  of  the  thoracic  duct,  o,  thoracic  duct;  a',  receptaculum  chyh;  b,  common 
trunk  of  the  eflerents  of  the  right  juxta-aortic  glands;  c,  common  trunk  of  the  efferents  of  the  left  juxta- 
aortic  glands;  d,  one  of  these  efferents  passing  through  the  left  pillar  of  the  diaphragm;  e,  right  juxta-aortic 
gland;  f.  left  juxta-aortic  gland;  h,  retro-aortic  gland;  i,  common  trunk  of  the  pre-aortic  glands  (truncus 
mtestinalis);  j,  collecting  trunks  of  the  interco.stal  lymphatics,  which  reach  the  receptaculum  chyh  by  takmg 
the  downward  course.      (Poirier  and  Charpy.) 

The  branches  of  the  left  lymphatic  duct  are  (Fig.  483) :  1.  A  descending  trunk, 
which  collects  lymph  from  the  posterior  intercostal  glands  of  the  seven  lower 
intercostal  spaces.  2.  A  trunk  is  formed  by  vessels  coming  from  the  superior  juxta- 
aortic  glands  beneath  the  Diaphragm.  3.  The  lymphatic  vessels  form  the  upper 
five  intercostal  spaces.  4.  The  lymphatic  vessels  form  the  posterior  mediastinal 
glands  and  retrosternal  glands.  5.  The  left  jugular  trunk  (truncus  jugularis), 
although  this  may  open  directly  into  the  junction  of  the  subclavian  and  internal 
jugular  veins.  6.  In  rare  cases  the  thoracic  duct  receives  near  its  termination 
the  left  subclavian  trunk  (truncus  suhclavius)  and  a  broncho-mediastinal  trunk. 
As  a  rule,  however,  the  two  last-mentioned  trunks  empty  into  the  jugulo-subclavian 
junction  separately  or  as  one  duct. 

The  thoracic  duct  receives  the  lymph  from  the  extremities,  the  deep  portion 
of  the  abdominal  wall  and  of  the  pelvic  waJl,  the  pelvic  viscera,  the  kidneys  and 
suprarenal  capsules,  the  large  intestine,  the  small  intestine,  the  walls  of  the 
thoracic  cavity,  the  under  surface  and  anterior  portion  of  the  liver,  th^  stomach. 


778 


THE    LYMPHATIC   SYSTEM 


the  spleen,  the  pancreas,  the  sternal  and  intercostal  glands,  the  left  lung,  left 
side  of  the  heart,  trachea,  and  oesophagus,  and  often,  just  before  its  termination, 
the  lymphatics  of  the  left  side  of  the  head  and  neck,  and  of  the  left  upper 
extremity. 

Structure. — ^The  thoracic  duct  is  composed  of  three  coats,  which  differ  in  some 
respects  from  those  of  the  lymphatic  vessels.  The  internal  coat  consists  of  a  single 
layer  of  flattened  endothelial  cells;  of  a  subendothelial  layer,  similar  to  that  found 
in  the  arteries;  and  an  elastic  fibrous  coat,  the  fibres  of  which  run  in  a  longitudinal 
direction.     Each  endothelial  cell  is  shaped  like  a  lance-head  and  has  serrated 


LONGUS  COLLI   MUSCLE 

COMMON   CAROTID 

ARTERY 

LEFT   PNEUMOGASTRIC 

NERVE 

VERTEBRAL  ARTERY 

VERTEBRAL  VEIN 

THORACIC  DUCT 

INTERNAL  JUGULAR 

VEIN 

EXTERNAL  JUGULAR 

VEIN 

ANTERIOR  JUGULAR 

VEIN 

SUBCLAVIAN 

VEIN 


Fig.  485. — The  bend  of  the  thoracic  duct  at  its  termination  in  the  .subclavian  vein.     (Poirier  and  Charpy.) 

borders.  The  middle  coat  consists  of  a  longitudinal  layer  of  white  connective 
tissue  with  elastic  fibres,  external  to  which  are  several  laminae  of  muscular 
tissue,  the  fibres  of  which  are  for  the  most  part  disposed  transversely,  but  some 
are  oblique  or  longitudinal.  The  muscular  fibres  are  intermixed  with  elastic 
fibres.  The  external  coat  is  composed  of  areolar  tissue,  with  elastic  fibres  and 
isolated  fasciculi  of  muscular  fibres. 


The  Right  Lymphatic  Duct  (Ductus  Lymphaticus  Dexter) 

(Figs.  482,  486,  487,  511). 

A  right  lymphatic  duct  is  frequently  present.     It  is  a  short  trunk,  about  half  an 
inch  in  length  and  a  line  or  a  line  and  a  half  in  diameter.    It  is  formed  by  the  union 


Fig.  486. — Terminal  collecting  trunks  of  the  right  half  of  the  supra-diaphragmatic  portion  of  the  body,  o, 
jugular  trunk;  6,  subclavian  trunk;  c,  broncho-mediastinal  trunk;  rf,  right  lymphatic  trunk;  e,  gland  of  the 
internal  mammary  chain;  /,  gland  of  the  deep  cervical  chain.      (Poirier  and  Charpy.) 

of  the  right  jugular,  right  broncho-mediastinal,  and  right  subclavian  trunks. 
Often  on  the  right  side  the  jugular,  subclavian,  and  broncho-mediastinal  trunks 


LYMPHATICS  OF   THE  CRANIAL    REGION,   FACE  AND   NECK    779 

are  double.  Usually  they  open  into  the  junction  of  the  internal  jugular  and 
subclavian  veins  separately.  Sometimes^  they  unite  and  open  by  one  duct,  and 
that  is  the  right  lymphatic  duct.  The  orifice  of  the  right  lymphatic  duct  is 
guarded  by  tvi^o  semilunar  valves,  which  prevent  the  passage  of  venous  blood 
into  the  duct. 

Tributaries. — The  right  lymphatic  duct,  if  present,  receives  lymph  from  the 
right  side  of  the  head  and  neck,  the  right  upper  extremity,  the  right  side  of 
the  thorax,  the  right  lung,  and  the  right  side  of  the  heart,  and  from  part  of  the 
convex  surface  of  the  liver. 


LYMPHATICS  OF  THE  CRANIAL  REGION,  FACE,  AND  NECK. 

It  is  customary  to   divide  the  lymphatics  of   this  region  into  intracranial  and 
extracranial  lymphatics.      The  statement  is  made  by  Poirier  and  Cun^o^  that  the 


Fig.  487. —  1  lie  lyinpiiancs  oi  t lie  neau  and  neck.      (Sappey.) 

brain  and  its  membranes  are  without  lymphatics.  They  state  that  there  are 
spaces  in  the  nervous  centres  comparable  to  lymphatic  channels,  but  which  are 
not  truly  lymphatic  vessels  and  which  are  regarded  by  most  as  independent  of  the 
lymphatic  system.  Other  writers^  believe  that  there  are  cerebral  and  meningeal 
lymphatic  vessels.  It  is  highly  probable  that  the  perivascular  spaces  around  the 
cerebral  arteries  are  the  beginning  of  a  cerebral  lymph  system,  antl  that  these  peri- 


'  Article  on  the  Lymphatics  in  the  Treatise  on  Human  Anatomy. 
2  Cunningham's  Text-book  of  Anatomy. 


By  Poirier  and  Charpy. 


780 


THE    LYMPHATIC  SYSTEM 


vascular  lymph-channels  pass  out  of  the  cranium  with  the  arteries  and  the  internal 
jugular  vein  and  terminate  in  the  superior  deep  cervical  glands.  It  is  also  probable 
that  lymph-spaces  surround  the  meningeal  blood-vessels  and  terminate  in  the 
superior  deep  cervical  and  the  internal  maxillary  glands. 

The  extracranial  lymphatics  are  divided  into  superficial  and  deep,  and  the  two 
systems  freely  communicate.  All  of  these  vessels  run  into  glands  about  the 
head  and  neck.  The  superficial  lymphatics  take  origin  in  the  subcutaneous 
tissue  and  superficial  muscles.  The  deep  vessels  arise  in  the  orbit,  mouth,  nose, 
pharynx,  oesophagus,  tongue,  larynx,  and  the  muscular,  ligamentous,  and  osseous 
structures. 

The  Lymphatic  Glands  of  the  Head  and  Face. 

The  lymphatic  glands  of  the  head  and  face  are  as  follows: 

1.  The  Occipital. 

2.  The  Posterior  Auricular. 

3.  The  Parotid  and  Subparotid. 

4.  The  Internal  Maxillary. 

5.  The  Facial. 

The  Occipital  or  Suboccipital  Glands  (lymphoglandulae  occipitales)  (Figs. 
488  and  49.3) . — There  are  only  two  or  three  of  these  glands  on  each  side.  They 
are  situated  beneath  the  deep  fascia,  a  little  in  front  of  the  anterior  edge  of  the 


MASTOID 
OCCIPITAL 


FACIAL 

SUBMAXILLARY 
SUBMENTAL 


Fig.  488.— General  arrangement  of  the  lymphatic  gland  groups  of  the  head  and  neck.     (Poirier  and  Charpy.) 


Trapezius  muscle,  near  to  but  seldom  upon  the  insertion  of  the  Complexus 
rnuscle.  They  receive  lymph  from  the  occipital  region  of  the  scalp  and  from 
them  it  is  sent  to  the  upper  deep  cervical  glands. 

The  Posterior  Auricular  Retro-auricular  or  Mastoid  Glands  (lymphoglandulae 
aunculares  posteriores)  (Figs.  488, 492,  and  493).— There  are  two  of  these  on  each 
side.  They  are  situated  just  beneath  the  lower  margin  of  the  Retrahens  aurem 
muscle.     They  receive  lymph  from  the  parietal  lymph- vessels,  "from  the  internal 


THE  LYMPHATIC    GLANDS   OF   THE  HEAD   AND   FACE    781 

surface  of  the  auricle,  with  the  exception  of  the  lobule,  and  from  the  posterior 
surface  of  the  external  auditory  meatus."^  The  lymph-vessels  from  these  glands 
empty  into  the  upper  deep  cervical  glands. 


GLANDS   OF 
EXTERNAL  JUGULAR i 
CHAIN 


SUBMAXILLARY 


GLAND  OF 
INTERNAL  JUGULAR 
CHAIN 


Fig.  489. — The  lymphatics  of  the  neck.     (Kiittner.) 


The  Parotid  Lymph-glands  {lymphoglandulae  auriculares  anteriores)  (Figs. 
488,  489,  and  493)  are  divided  into  two  groups,  the  superficial  and  the  deep. 

The  Superficial  Paxotid  or  Pre-auricular  Lymph-glands. — The  superficial  parotid 
lymph-glands  are  not  the  subcutaneous  lymph-glands  occasionally  but  very  rarely 


SUBORBITAL 
GLAND  OF  NASO« 
GENIAL  GROOVE 
BUCCINATOR 

(posterior  mass) 

BUCCINATOR 

(middle  mass) 


SUPRAMAXILLARY 
INFRAMAXILLARV 


Fig.  490. — Facial  glands.     (Poirier  and  Charpy.) 


found  in  this  region,  and  which  have  been  described  by  Richet,  but  are  lymph- 
nodes  situated  between  the  parotid  fascia  and  the  parotid  salivary  gland.  There 
may  be  three  glands,  two  glands,  or  only  one  gland. 


'  The  Lymphatics.    By  G.  Delamare,  P.  Poirier,  and  B.  Cun#o. 
Cecil  H.  Leaf. 


English  edition,  translated  and  edited  by 


782  THE   LYMPHATIC  SYSTEM 

The  Deep  Parotid  Lymph-glands. — The  deep  parotid  lymph-glands  are  situated 
within  the  parotid  salivary  gland.  There  are  from  fifteen  to  twenty  of  the  deep  glands. 
The  parotid  glands  receive  lymph  from  the  eyelids,  eyebrows,  the  root  of  the  nose, 
upper  portion  of  the  cheek,  frontal  portion  of  the  scalp,  temporal  portion  of  the 
scalp,  from  the  outer  surface  of  the  pinna,  from  the  external  auditory  meatus, 
from  the  tympanum,  and  possibly  from  the  mucous  membrane  of  the  nose,  the 
posterior  alveolar  region  of  the  superior  maxillary  bone,  and  the  soft  palate. 
Lymphatics  pass  from  the  superficial  parotid  glands  into  the  superficial  cervical 
and  the  upper  deep  cervical  glands.  Lymphatics  pass  from  the  deep  parotid 
glands  into  the  upper  deep  cervical  glands. 

The  Subparotid  Glands  (lymphoglandulae  parotidae). — The  subparotid  glands 
lie  between  the  parotid  salivary  gland  and  the  pharynx,  and  they  are  close  to  the 
internal  carotid  artery  and  the  internal  jugular  vein.  They  receive  lymph  from 
the  nasal  fossfe,  naso-pharynx,  and  Eustachian  tube,  and  send  vessels  to  the  upper 
deep  cervical  glands. 

The  Internal  Maxillary  or  Zygomatic  Glands  (lymphoglandulae  jaciales  pro- 
f undue)  (Fig.  493). — The  internal  maxillary  glands  lie  in  the  course  of  the  internal 
maxillary  artery  in  the  anterior  pharyngeal  wall.  They  receive  vessels  from  the 
naso-pharynx,  palate,  zygomatic  fossa,  temporal  fossa,  and  orbit.  From  them 
vessels  go  to  the  upper  deep  cervical  glands. 

The  Facial  Glands  or  Genial  Glands  {lymphoglandulae  jaciales)  (Figs.  488, 
489,  and  490). — The  facial  glands  lie  in  three  groups  in  the  course  of  the  lymphatic 
vessels  which  are  passing  to  the  submaxillary  glands.  According  to  Poirier  and 
Cun^o  the  supramaxillary  or  inferior  group  (Fig.  490)  lies  upon  the  outer  surface 
of  the  mandible,  at  the  anterior  margin  of  the  Masseter  muscle,  and  beneath  the 
Platysma  myoides.  There  may  be  only  one  or  two  glands  in  this  group,  but  often 
there  are  ten  or  twelve.  These  glands  lie  about  the  facial  artery  and  vein  and 
are  not  constantly  present.  In  many  cases  a  salivary  gland,  the  inframaxillary 
(Fig.  490),  is  interposed  between  the  supramaxillary  and  submaxillary  glands. 
The  buccinator,  buccal,  or  middle  group  (Figs.  490  and  493)  is  present  in  about 
one-third  of  the  subjects  and  lies  upon  the  outer  surface  of  the  Buccinator  muscle 
external  to  the  buccal  fascia.  Some  of  these  glands  are  situated  in  the  region 
where  Steno's  duct  perforates  the  Buccinator  muscle.  Others  are  beneath  the 
posterior  fibres  of  the  Zygomaticus  major  muscle. 

The  superior  group  of  facial  glands  (Fig.  490)  includes  a  malar  gland,  a  suborbital 
gland,  and  a  gland  in  the  naso-genial  groove.^  An  anterior  gland  is  sometimes 
found,  subcutaneous,  on  the  outer  surface  of  the  Orbicularis  oris  muscle,  the 
commissural  gland. 

The  Lymphatic  Vessels  of  the  Cranial  Region  (Figs.  487,  493). 

The  lymphatic  vessels  of  the  cranial  subcutaneous  tissues  are  divided  into 
anterior,  lateral,  and  posterior.  The  anterior  or  frontal  terminate  in  the  parotid 
lymph-glands.  The  lateral  or  parietal  terminate  in  the  parotid  and  mastoid  lymph- 
glands.  The  posterior  or  occipital  terminate  in  the  sterno-mastoid  and  occipital 
glands. 

The  Lymphatic  Vessels  of  the  Face,  the  Interior  of  the  Nose,  Tongue,  Floor 
of  the  Mouth,  Pharynx,  Larynx,  and  Thyroid  Gland 

(Figs.  487,  489,  490,  491,  492,  494). 

The  lymphatic  vessels  of  the  face  are  more  numerous  than  those  of  the  cranial 
region,  and  commence  over  its  entire  surface.  Those  from  the  frontal  region 
accompany  the  frontal  vessels;  they  then  pass  obliquely  across  the  face,  running 

^  Article  on  the  Lymphatics  in  the  Treatise  on  Human  Anatomy.     By  P.  Poirier  and  B.  Cun6o. 


THE   LYMPHATIC    VESSELS    OF    THE    FACE 


783 


with  the  facial  vein,  pass  through  the  glands  on  the  buccal  surface  of  the  Buccina- 
tor muscle,  and  join  the  submaxillary  lymphatic  glands.  The  submaxillary  lymph 
glands  receive  the  lymphatic  vessels  from  the  lips,  and  are  often  found  enlarged 
in  cases  of  malignant  disease  of  those  parts. 

The  lymphatics  of  the  orbit  and  of  the  temporal  and  zygomatic  fossae  run  with 
the  branches  of  the  internal  maxillary  artery  to  the  maxillary  glands,  and  after- 
ward to  the  deep  cervical  glands. 


VESSELS   FROM 
BASE  OF  TONGUE 


MARGINAL  COL- 
ING  TRUNKS 


PRINCIPAL 
GLANO 


SUBMENTAL 


TRUNKS  OF 
MARGIN 


SUPRA-OMO 
HYOID  GLAND 


Fig.  491. — The  lymphatics  of  thfe  tongue;  anterior  view.     (Poirier  and  Charpy.) 

The  lymphatics  of  the  nose  can  be  injected  from  the  subdural  and  subarachnoid 
spaces.  They  terminate  in  the  retro-pharyngeal  and  suprahyoid  glands.  The 
lymphatics  of  the  tongue  (Fig.  491)  chiefly  accompany  the  ranine  vein  first  to  the 
lingual  glands  and  from  these  to  the  deep  cervical  glands.  The  lymphatics  from 
the  anterior  part  of  the  tongue  and  floor  of  the  mouth  pierce  the  Mylo-hyoid  muscles 
and  so  reach  the  submaxillary  lymph-glands  (p.  1093).  From  the  upper  part  of 
the  pharynx  the  lymphatics  pass  to  the  retro-pharyngeal  glands;  from  the  lower 
part  of  the  phaiynx  to  the  deep  cervical  glands.  From  the  larynx  two  sets  of  vessels 
arise:  an  upper,  piercing  the  thyro-hyoid  membrane  and  joining  the  upper  set 
of  deep  cervical  glands;  and  a  lower,  perforating  the  crico-thyroid  membrane  to 
join  the  lower  set  of  deep  cervical  glands.  The  lymphatics  of  the  thyroid  gland 
accompany  the  superior  and  inferior  thyroid  arteries,  and  open  partly  into  the 
upper  and  partly  into  the  lower  set  of  deep  cervical  glands. 


784 


THE  LYMPHATIC  SYSTEM 


The  Lymphatic  Glands  of  the  Neck. 

The  lymphatic  glands  of  the  neck  are: 

1.  The  Superficial  Cervical,  including  the  external  jugular  and  the  superficial 
anterior  cervical. 

2.  The  Submaxillary. 

3.  The  Submental. 

4.  The  Retro-pharyngeal. 

5.  The  Deep  Cervical,  including  the  anterior  deep  cervical. 

The  Superficial  Cervical  Glands  {lymphoglandulae  cervicales  superficiales) 
(Figs.  492  and  493) . — The  superficial  cervical  glands  are  composed  of  two  groups, 
the  external  jugular  and  the  superficial  anterior  cervical  glands. 

The  External  Jugular  Glands  (Figs.  489  and  492). — The  external  jugular  glands 
are  superficial  to  the   Sterno-cleido-mastoid  muscle.     They  are  four  to  six  in 


LYMPHATIC  VESSELS 
OF  AURICLE 


MASTOID  GLANDS 


STERNO-MASTOID 

GLAND  (external 
group) 

GLAND  OF 

EXTERNAL  JUGULAR 
CHAIN 


STERNO-MASTOID 

GLAND  (internal 
group) 

SUBHYOID  GLAND 


Fig.  492. — Deep  cervical  chain.     (Poirier  and  Charpy.) 

number  and  lie  along  the  external  jugular  vein  upon  the  outer  surface  of  the  deep 
cervical  fascia,  each  gland  occupying  a  depression  in  the  fascia.  The  sterno- 
cleido-mastoid  muscle  is  beneath  them.  They  are  usually  gathered  in  a  group 
a  little  below  the  parotid  gland,  but  sometimes  extend  to  the  middle  of  the  vein. 
They  receive  vessels  from  the  occipital,  the  posterior  auricular,  the  parotid,  and 
the  submaxillary  lymph-glands,  from  the  auricle,  and  from  the  skin  and  subcu- 
taneous structures  of  the  neck.  From  them  lymphatic  vessels  pass  to  the  upper 
deep  cervical  and  to  the  lower  deep  cervical  glands. 

The  Superficial  Anterior  Cervical  Glands. — The  superficial  anterior  cervical  glands 
lie  along  the  anterior  jugular  vein  and  from  them  vessels  pass  to  the  deep  cervical 
glands. 

The  Submaxillary  or  Lateral  Suprahyoid  Glands  (lymphoglandulae  submaxil- 
lares)  (Figs.  488,  489,  and  493), — The  submaxillary  glands  are  in  the  submaxil- 
lary triangle  beneath  the  deep  fascia.  They  number  three  to  six;  are  embedded 
in  the  superficial  surface  of  the  sheath  of  the  submaxillary  gland,  but  are  not  found 
within  the  sheath.  Occasionally  one  or  two  are  found  in  the  deep  portion  of  the 
sheath  toward  the  floor  of  the  mouth.  The  middle  gland  of  Stahr  is  situated  at 
the  point  where  the  submaxillary  group  is  crossed  by  the  facial  artery.  This  is 
the  largest  gland  of  the  group.     The  submaxillary  glands  receive  vessels  from  the 


THE   LYMPHATIC    GLANDS    OF   THE   NECK 


785 


"nose,  the  cheek,  the  upper  Hp,  and  the  external  part  of  the  lower  lip,  almost 
the  whole  of  the  gums,  and  the  anterior  third  of  the  lateral  border  of  the  tongue."^ 
They  also  obtain  lymph  from  the  floor  of  the  mouth  and  from  the  sublingual  and 
submaxillary  salivary  glands.^  They  send  vessels  to  the  jugular  and  to  the  upper 
deep  cervical  glands. 

The  Submental  or  Median  Suprahyoid  Glands  (Figs.  4S8,  491,  and  493).— 
There  are  usually  two  glands  situated  between  the  anterior  bellies  of  the  two 
digastric  muscles  and  upon  the  Mylo-hyoid  muscle.  They  receive  lymph  from  the 
cutaneous  surface  of  the  chin,  from  the  cutaneous  and  mucous  surfaces  of  the 


YGOMATIC 


SUPERFICIAL 
PAROTID 


Fig.  493.— The  lymphatic  glands  and  vessels  of  the  head  and  neck.  The  deep  lymphatics  are  colored  blue 
and  the  superficial  black.  In  each  set  the  afferent  vessels  are  shown  in  continuous  lines;  the  efferent  and  inter- 
glandular  ves.seis  are  represented  by  dotted  lines.      (Cunningham.) 

central  portion  of  the  lower  lip,  from  the  central  portion  of  the  gums,  from  the 
floor  of  the  mouth,  and  from  the  tip  of  the  tongue.  They  send  some  vessels  to 
the  submaxillary  lymph-glands,  and  frequently  a  gland  is  interposed  on  the  anterior 
belly  of  the  Digastric  muscle.  They  send  other  vessels  to  the  upper  deep  cervical 
glands. 

The  Retro-pharyngeal  or  Post-pharyngeal  Glands  (Fig.  494).— The  retro- 
pharyngeal glands  are  placed  between  the  upper  lateral  portion  of  the  posterior 
part  of  the  pharynx  and  the  first  two  cervical  vertebrae.     Leaf  tells  us  that,  as  a 

'  The  Lymphatics.      By  G.  Delamare,  P.  Poirier,  and  B.  Cuneo.     Translated  and  edited  by  Cecil  H.  Leaf. 
^  Cunningham's  Text-book  of  Anatomy. 

50 


786 


THE   LYMPHATIC  SYSTEM 


rule,  there  is  but  one  gland  on  each  side,  though  two  may  be  present.  The  retro- 
pharyngeal glands  lie  upon  the  Rectus  capitis  anticus  major  muscle,  which  sepa- 
rates them  from  the  vertebrae.  They  receive  vessels  from  the  muscles  and  fascia 
in  front  of  the  vertebrse,  from  the  nasal  fossae  and  accessory  cavities,  from  the  naso- 
pharynx and  Eustachian  tube,  and  possibly  from  the  cavity  of  the  tympanum. 
They  send  vessels  to  the  upper  deep  cervical  glands. 

The  Deep  Cervical,  Carotid,  or  Sterno-mastoid  Glands  (hjmphoglandulae 
cervicales  profundae)  (Figs.  488,  489,  491,  492,  493,  and  494).— The  deep  cervical 
glands  are  divided  into  the  upper  deep  cervical  and  the  lower  deep  cervical,  and  are 
associated  with  certain  accessory  glands,  including  the  jugular  and  superficial  anterior 
cervical,  which  have  been  discussed  under  the  head  of  superficial  cervical  glands; 
and  the  anterior  deep  cervical  and  the  recurrent  glands,  which  have  not  yet  been 
studied.  The  deep  cervical  chain  extends  from  the  apex  of  the  mastoid  process 
of  the  temporal  bone  to  the  junction  of  the  internal  jugular  and  subclavian  veins. 


LYMPHATICS 
OF  PHARYNX 


INTERRUPTING 

GLANDULAR 

NODULE 

GLAND  OF 

DEEP  CERVICAL 

CHAIN 

EFFERENT 

VESSEL  OF 

RETRO- PHARYNGEAL 

GLANDS 


Fig.  494. — The  retro-pharyngeal  glands.     (Poirier  and  Charpy.) 


The  Upper  Deep  Cervical  or  Substerno -mastoid  Glands  (lymphoglandulae  cervi- 
cales profundae  superiores). — The  upper  deep  cervical  glands  extend  from  the" 
tip  of  the  mastoid  process  of  the  temporal  bone  to  about  the  region  where  the 
common  carotid  artery  is  crossed  by  the  Omo-hyoid  muscle.  One  group, 
the  external  group,  is  placed  external  and  posterior  to  the  internal  jugular  vein. 
The  glands  are  small  and  numerous,  are  embedded  in  the  fatty  tissue  about  the 
nerves  from  the  deep  cervical  plexus,  and  at  the  posterior  margin  of  the  Sterno- 
cleido-mastoid  muscle  constitute  a  continuous  mass  passing  to  join  the  subclavian 
glands.  Another  group,  known  as  the  internal  group  or  the  internal  jugular 
glands,  lie  directly  upon  or  close  by  the  outer  border  of  the  internal  jugular  vein. 
This  group  forms  a  chain  along  the  internal  jugular  vein,  and  the  glands  are 
of  larger  size  than  those  of  the  external  group.  Some  glands  of  this  group 
are  beneath  the  vein.  The  glands  of  the  internal  jugular  group  communicate 
freely  with  each  other  and  with  the  external  group.  The  external  group  receives 
lymph-vessels  from  the  posterior  auricular,  occipital,  and  external  jugular  glands, 
from  the  occipital  region  of  the  scalp,  from  the  auricle,  and  from  the  skin,  sub- 
cutaneous tissue,  and  muscles  of  the  upper  portion  of  the  neck.*  The  internal 
group  receives  lymph-vessels  from  the  retro-pharyngeal,  parotid,  subparotid,  sub- 


1  The  Lymphatics.     By  G.  Delamare,  P.  Poirier,  and  B.  CunSo.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC    VESSELS    OF    THE   NECK  'J^'J 

maxillary,  and  submental  glands,  the  anterior  cervical  glands  (superficial  and 
deep),  and  the  recurrent  glands,  and  from  the  tongue,  naso-pharynx,  larynx,  soft 
palate,  roof  of  the  mouth,  oesophagus  (cervical  portion),  nasal  fossfe,  trachea 
(cervical  portion),  and  the  thyroid  gland.^  The  external  group  terminates  in 
the  supraclavicular  glands.  The  internal  jugular  group  terminates  in  the 
jugular  trunk,  which,  on  the  right  side,  helps  to  form  the  right  lymphatic  duct 
or  empties  directly  into  the  junction  of  the  internal  jugular  and  subclavian  veins, 
and  on  the  left  side  empties  directly  into  the  venous  junction  or  into  the  thoracic 
duct. 

The  Lower  Deep  Cervical  or  Supraclaviculax  Glands  (lymphoglandulae  cervicales 
projundae  injeriores). — The  lower  deep  cervical  glands  lie  along  the  internal 
jugular  vein  in  the  lower  part  of  its  course.  They  receive  lymph-vessels 
from  the  superficial  cervical  glands,  the  upper  deep  cervical  glands,  the 
axillary  glands,  the  accessory  chain,  the  occipital  region  of  the  scalp,  the  skin  of 
the  neck,  the  lower  prevertebral  muscles,  the  skin  of  the  pectoral  and  mammary 
regions,  and  the  skin  of  the  arm.  The  supraclavicular  glands  send  vessels  which 
unite  with  the  vessels  of  the  upper  deep  glands  to  form  the  jugular  lymphatic 
trunk.  The  jugular  trunk  on  the  right  side  may  empty  directly  into  the  junc- 
tion of  the  internal  jugular  and  subclavian  veins  or  may  unite  with  the  subclavian 
trunk  to  form  the  right  lymphatic  duct.  On  the  left  side  it  may  empty  into  the 
thoracic  duct  or  directly  into  the  venous  junction. 

Accessory  Chains  to  the  Deep  Cervical  Glands. — The  accessory  chains  to  the  deep 
cervical  glands  are:  1.  The  external  jugular  glands  (p.  784).  2.  The  superficial 
anterior  cervical  (p.  784).  3.  The  prelaryngeal  or  infralaryngeal  glands  (Fig.  493) 
between  the  Crico-thyroid  muscles.  They  receive  lymph  from  the  trachea,  larynx, 
and  thyroid  gland,  and  send  vessels  to  the  pretracheal  glands  and  to  the  upper 
deep  cervical  glands.  4.  The  tracheal  or  pretracheal  glands  (Fig.  493)  lie  upon  the 
front  of  the  trachea,  receive  vessels  from  the  trachea,  thyroid  body,  and  prelaryngeal 
glands,  and  send  vessels  to  the  lower  deep  cervical  glands.  Some  anatomists  speak 
of  the  prelaryngeal  and  the  pretracheal  glands  as  the  anterior  deep  cervical  glands. 
5.  The  recurrent  glands  lie  on  the  sides  of  the  oesophagus  and  trachea,  by  the  recur- 
rent laryngeal  nerves.  They  receive  vessels  from  the  larynx,  trachea,  oesophagus, 
and  thyroid  gland,  and  send  vessels  to  the  upper  and  lower  deep  cervical  glands. 

The  Lymphatic  Vessels  of  the  Neck  (Figs.  487,  491,  492,  493). 

The  superficial  and  deep  cervical  lymphatic  vessels  are  continuations  of  those 
already  described  on  the  cranium  and  face.  After  traversing  the  glands  in  those 
regions,  they  pass  through  the  chain  of  glands  which  lie  along  the  sheath  of  the 
carotid  vessels,  being  joined  by  the  lymphatics  from  the  pharynx,  oesophagus, 
larynx,  trachea,  and  thyroid  gland.  At  the  lower  part  of  the  neck,  after  receiving 
some  lymphatics  from  the  thorax,  they  unite  to  form  the  jugular  trunk  (Fig.  486), 
which  often  terminates,  on  the  left  side,  in  the  thoracic  duct,  and  on  the  right  side, 
in  the  right  lymphatic  duct,  but  which  may  on  either  side  open  directly  into  the  vein. 

Surgical  Anatomy. — In  secondary  syphilis  there  is  general  enlargement  of  the  lymphatic 
glands,  and  in  the  posterior  triangle  of  the  neck  the  enlarged  glands  are  distinctly  palpable.  The 
occipital  glands  may  enlarge  because  of  inflammation  or  suppuration  about  the  occipital  region 
of  the  scalp,  and  the  posterior-auricular  glands  enlarge  from  inflammation  or  szippuration  of  the 
temporal  portion  of  the  scalp,  the  external  ear  (except  the  lobule),  and  the  external  auditory  meatus. 
Otorrhxfa  sometimes  causes  them  to  enlarge. 

The  cervical  glands  are  very  frequently  the  seat  of  tuberculous  disease.  This  condition  is 
usually  preceded  by  a  lesion  in  those  parts  from  which  they  receive  their  lymph.  The  lesion  may 
be  tuberculous  or  inflammatory.  If  tuberculous  it  furnishes  bacilli  directly  to  the  lymph.  If 
inflammatory  it  lessens  tissue  resistance  and  opens  the  portals  to  infection.     The  glands  receive 

1  The  Lymphatics.     By  G.  Delamare,  P.  Poirier,  and  B.  Cun6o.     Translated  and  edited  by  Cecil  H.  Leaf. 


788  THE   LYMPHATIC  SYSTEM 

the  lymph  from  the  seat  of  primary  disease  and  become  tuberculous.  It  is  very  desirable,  there- 
fore, for  the  surgeon,  in  dealing  with  these  cases,  to  possess  a  knowledge  of  the  relation  of  the 
respective  groups  of  glands  to  the  periphery.  Some  years  ago  Sir  Frederick  Treves  prepared  a 
table  to  show  to  what  glandular  group  lymph  from  each  region  is  sent.  The  table  is  practically 
as  follows: 

Scalp. — Posterior  part  =  suboccipital  and  mastoid  glands.  Frontal  and  parietal  portions  = 
parotid  glands. 

Lymphatic  vessels  from  the  scalp  also  enter  the  superficial  cervical  set  of  glands. 

Skin  of  face  and  neck  -=  submaxillary,  parotid,  and  superficial  cervical  glands. 

External  ear  =  superficial  cervical  glands. 

Lower  lip  =  submaxillary  and  suprahyoid  glands. 

Buccal  cavity  =^  submaxillary  and  upper  set  of  deep  cervical  glands. 

Gums  of  lower  jaw  =  submaxillary  glands. 

Tongue. — Anterior  portion  =  suprahyoid  and  submaxillary  glands.  Posterior  portion  = 
upper  set  of  deep  cervical  glands. 

Tonsils  and  palate  =  upper  set  of  deep  cervical  glands. 

Pharynx. — Upper  part  =:  parotid  and  retro-pharyngeal  glands.  Lower  part  =  upper  set  of 
deep  cervical  glands. 

Larynx,  orbit,  and  roof  of  mouth  =  upper  set  of  deep  cervical  glands. 

Nasal  fossir  =  retropharyngeal  glands,  upper  set  of  deep  cervical  glands.  Some  lymphatic 
vessels  from  posterior  part  of  the  fossae  enter  the  parotid  glands. 

Treves's  table  indicates  the  glands  usually  involved,  but  the  seat  of  primary  disease  cannot  in- 
variably be  affirmed  from  a  knowledge  of  the  seat  of  glandular  involvement,  because  the  course 
of  the  lymphatic  vessels  is  sometimes  varied  from  that  which  usually  maintains ;  for  instance,  in 
some  cases  lymphatics  from  the  right  side  of  the  tongue  pass  to  glands  in  the  left  side  of  the 
neck. 

Glands  may  enlarge  directly  because  of  primary  inflammation,  injury,  or  tumor,  but  usually 
a  glandular  enlargement  is  secondary  to  a  bacterial  disease  or  to  cancer  involving  the  lymph- 
vessels  which  come  to  the  gland.  The  seat  of  disease  may  be  distant.  Disease  of  the  nasal 
fossae  may  cause  retropharyngeal  abscess  or  enlargement  of  the  submaxillary  glands.  Cancer 
of  the  breast,  stomach,  or  oesophagus  may  be  followed  by  disease  of  the  cervical  glands.  Dis- 
ease of  the  teeth,  tongue,  gums,  floor  of  the  mouth,  and  alveolar  processes  may  cause  enlarge- 
ment of  the  submaxillary  and  other  glands,  and  disease  of  the  tonsil  may  lead  to  enlargement 
of  the  glands  at  the  angle  of  the  jaw. 

The  modern  radical  surgery  of  cancer  depends  on  a  knowledge  of  these  glandular  relations, 
and  consists  in  thoroughly  removing  the  growth  and  also  the  associated  lymphatic  glands,  and, 
when  possible,  the  lymph-vessels  running  from  the  tumor  to  the  glands.  The  lower  deep  cer- 
vical glands  occasionally  enlarge  secondarily  to  malignant  growths  of  the  abdomen  or  medias- 
tinum, but  this  is  not  due  to  a  direct  flow  of  lymph,  as  the  mediastinal  glands  do  not  send  ves- 
sels to  the  supraclavicular  glands.  It  is  due  to  blocking  of  lymphatic  vessels  and  reversal  of 
the  lymph-stream,  so  that  lymph  containing  cancerous  cells  regurgitates. 

A  retropharyngeal  abscess  begins  to  the  side  of  the  pharynx.  It  enlarges  toward  the  centre 
rather  than  from  it,  because  the  constrictions  of  the  pharynx  limit  the  outward  progress  of  the 
pus. 

The  glands  within  the  parotid  salivary  gland  not  unusually  become  tuberculous,  and  the 
surgeon  may  be  led  to  believe  that  the  salivary  gland  is  the  seat  of  primary  disease. 

Sometimes,  though  seldom,  after  the  extensive  removal  of  lymph-glands  the  region  drained 
by  their  tributaries  becomes  the  seat  of  persistent  hard  oedema  {lymph  a'dema).  It  used  to  be 
thought  that  wounds  of  the  thoracic  duct  were  of  necessity  fatal,  but  it  is  now  known  that,  unless 
close  to  the  vein,  they  are  seldon  even  very  dangerous.  It  may  be  possible  to  suture  a  partly 
divided  duct.'  In  an  unsutured  wound  of  the  duct  recovery  follows  if  a  collateral  lymphatic 
circulation  is  established.'^ 

THE  LYMPHATICS  OF  THE  UPPER  EXTREMITY. 

The  Lymphatic  Glands  of  the  Upper  Extremity. 

The  lymphatic  glands  of  the  upper  extremity  are  divided  into  two  sets,  super- 
ficial and  deep. 

Superficial  Lymphatic  Glands  (Figs.  495  and  503).— The  superficial  lymphatic 
glands  of  the  upper  extremity  are  few  in  number  and  small  in  size.     They  lie  in  the 

'  Dudley  P.  Allen's  case.     See  Allen  and  Briggs,  in  American  Medicine.  September  21.  1901. 
^  Harvey  Gushing,  Annals  of  Surgery,  .June,  1898. 


THE   LYMPHATIC    GLANDS    OF   THE    UPPER    EXTREMITY    789 

subcutaneous  tissue.  They  are  not  receiving  depots  of  great  areas,  but  interrupt 
lymphatic  vessels  here  and  there.  The  glands  in  the  axilla  receive  all  of  the 
lymphatic  vessels,  superficial  and  deep.  There  may  be  three  sets  of  superficial 
glands. 

One  set,  the  ante-cubital  glands,  lies  in  front  of  the  elbow.  These  glands  are 
often  absent.  When  these  glands  are  present  they  receive  vessels  from  the  anterior 
portion  of  the  forearm  and  the  middle  of  the  palm.  The  vessels  from  them  pass 
upward  along  the  front  and  iimer  aspect  of  the  arm. 


Axillary  glands, 


Fig.  495. — The  superficial  lymphatics  and  glands  of  the  upper  extremity. 


Another  superficial  gland  lies  above  the  internal  condyle.  It  is  the  supratrochlear 
or  supraepitrochlear  gland  or  group  of  glands.  There  is  usually  but  one  gland,  but 
there  may  be  two  or  more.  It  receives  vessels  from  the  inner  portion  of  the  hand, 
the  three  inner  fingers,  and  the  inner  portion  of  the  forearm,  but,  because  of  free 
anastomoses,  also  may  receive  lymph  from  any  portion  of  the  hand  and  forearm. 
Lymph-vessels  from  the  supratrochlear  gland  pass  up  along  the  basilic  vein  to 
the  axillary  glands. 


790 


THE   LYMPHATIC   SYSTEM 


There  are  sometimes  several  small  glands  by  the  cephalic  vein  in  the  groove 
between  the  Deltoid  and  great  Pectoral  muscles.  These  are  called  infraclavicular 
glands.  The  lymph-tract  from  the  infraclavicular  glands  does  not  terminate  in 
the  axillary  glands,  but  ends  in  the  subclavian  glands. 

The  Deep  Lymphatic  Glands  of  the  Upper  Extremity  or  the  Axillary  Glands 
{lymphoglandulae  axillares)  (Figs.  495,  496,  497,  498,  and  503). — The  chief  deep 
(ylands  are  situated  adjacent  to  the  axillary  vessels.  There  are  also  a  few  small 
glands  along  the  radial,  ulnar,  and  brachial  arteries  which  receive  deep  lymphatics 
from  bones,  muscles,  and  ligaments,  and  send  lymphatics  to  the  axillary  glands. 
The  axillary  glands  number  from  fifteen  to  thirty-five  in  each  axilla.  They  are 
embedded  in  the  axillary  fat  and  receive  the  lymphatic  vessels  from  the  upper 
extremity,  from  the  skin  of  the  upper  portion  of  the  chest,  from  the  Pectoral 
muscles,  and  from  the  mammary  gland.  The  following  division  of  the  axillary 
glands  is  made  by  Poirier,  Cun^o,  and  Delamare:^      1.  An  external  group,  the 


DELTA-PECTORAL      HUMERAL  CHAIN 


Y  LYMPHATIC 
IN  SUB- 
G  LAN  OS 


RY  COL- 
TRUNKS 


THORACIC 
CHAIN 


CUTANEOUS  COLLECTING 

TRUNK   FROM  THE 

THORACIC  WALL 


SUBAREOLAR 
PLEXUS 


Fig.  496. 


CUTANEOUS  COL-  '^  -%jr ■ ^COLLECTING  TRUNKS 

LECTENG  TRUNKS  \  V  PASSI NG  TO  I NTE  RNAL 

MAMMARY  GLANDS 

Axillary  glands  and  lymphatics  of  the  breast. 


humeral  chain,  lying  on  the  inner  surface  of  the  vessels  and  nerves,  particularly  the 
axillary  vein,  to  the  sheath  of  which  they  are  adherent.  Occasionally  one  or  several 
of  these  glands  are  found  beneath  the  vein.  Some  of  the  vessels  from  these  glands 
pass  into  the  central  group  of  lymph-nodes;  others  enter  the  subclavian  glands; 
others  pass  above  the  clavicle  and  terminate  in  glands  situated  in  that  region.  2. 
An  anterior  group,  the  thoracic  chain,  called  also  the  pectoral  glands.  One  mass  of  this 
chain,  the  supero-intemal,  is  situated  in  the  second  or  third  intercostal  space  in 
front  of  the  long  thoracic  artery  and  beneath  the  lower  edge  of  the  great  Pectoral 
muscle.  Another  mass,  the  infero-extemal,  is  situated  in  the  fourth  and  fifth 
intercostal  spaces  along  the  course  of  the  long  thoracic  artery.  The  vessels  from 
this  chain  end  in  the  central  group,  and  some  few  of  them  in  the  subclavian  glands. 
3.  A  posterior  group,  the  scapular  chain,  lying  along  the  dorsalis  scapula?  artery  in  the 
groove  between  the  Teres  major  and  the  Subscapularis  muscles.   They  send  vessels 


'  The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE   LYMPHATIC    GLANDS    OF    THE     UPPER    EXTREMITY    791 

to  the  humeral  and  central  chains.   4.  A  central  group,  the  intermediate  glands,  placed 
near  the  base  of  the  axilla,  between  the  previously  described  chains.    Their  efferent 


Fig.  497. — Lymphatics  of  the  antero-lateral  portion  of  the  thorax.     (Sappey.) 

vessels  end  in  the  subclavian  glands.    The  glands  of  the  central  group  in  many  indi- 
viduals protrude  through  the  opening  in  the  axillary  fascia  known  as  the  foramen 


SUPRA 
CLAVICULAR 


SUBCLAVIAN 


HUMERAL 


SCAPULAR 
CHAIN 


TRAL  GROUP 


RO-INTERNAL 
ION   OF 
ACIC  CHAIN 


O-EXTERNAL 
ON  OF 
CIC  CHAIN 


Fig.  498. — Scheme  of  the  axillary  glands.     The  dotted  line  indicates  the  position  of  the  clavicle. 

(Poirier  and  Charpy.) 

of  Langer  (Fig.  313).     5.  A  subclavian  group,  situated  above  the  upper  margin 
of  the  lesser  Pectoral  muscle.    Most  of  them  are  internal  to  the  axillary  vein, 


792 


THE  LYMPHATIC  SYSTEM 


"  between  this  vein  and  the  first  digitation  of  the  Serratus  magnus."^  The  humeral 
chain  and  the  thoracic  chain  cime  together  and  form  the  subclavian  group  of 
glands  situated  at  the  apex  of  the  axilla.  From  the  axillary  glantis  come  many 
vessels  which,  by  anastomosing,  form  the  infraclavicular  plexus,  they  then  unite 
into  a  trunk,  the  subclavian  trunk,  which  courses  between  the  subclavian  vein  and 
Subclavius  muscle.  On  the  right  side  it  empties  into  the  junction  of  the  internal 
jugular  and  subclavian  vein  or  unites  with  the  jugular  trunk  to  form  the  right 
lymphatic  duct.  On  the  left  side  it  may  empty  into  the  venous  junction  or  into 
the  thoracic  duct. 

The  Lymphatic  Vessels  of  the  Upper  Extremity  (Figs.  495, 496,  497,  498,  499). 

The  lymphatic  vessels  of  the  upper  extremity  are  divided  into  the  superficial 
and  the  deep. 

The  Superficial  Lymphatic  Vessels  of  the  Upper  Extremity. — The  superficial 
vessels  begin  as  plexuses  in  the  skin  and  form  vessels  which  ascend  in  the  sub- 
cutaneous tissue.  These  plexuses  are  particularly  plentiful  in  the  palm  and 
palmar  surface  of  the  digits  (Fig.  499).     On  each  side  of  each  finger  two  lymph- 


FiG.  499. — Superficial  lymphatics  of  the  digits  and  of  the  dorsal  aspect  of  the  hand.      (Cunningham.) 

vessels  are  formed;  they  ascend  toward  the  hand,  cross  the  dorsum,  and  anas- 
tomose frequently  with  each  other.  The  vessels  from  the  dorsum  of  the  hand 
join  the  lymph-vessels  of  the  forearm,  which  ascend  chiefly  along  the  superficial 
veins.  The  lymph-vessels  which  ascend  with  the  superficial  ulnar  vein  pass  into 
the  supratrochlear  gland.  The  vessels  which  accompany  the  median  veins  pass 
into  the  ante-cubital  or  supratrochlear  glands.  Some  of  the  lymph-vessels  on 
the  radial  side  of  the  forearm  run  up  along  the  cephalic  vein.  All  the  other 
lymph-vessels  of  the  upper  extremity  pass  direct  to  the  axillary  glands.  In  the 
forearm  there  are  about  thirty  vessels,  in  the  middle  of  the  arm  there  are  from 
fifteen  to  eighteen  (Sappey). 

The  Deep  Lymphatic  Vessels  of  the  Upper  Extremity.— The  deep  lymph- 
vessels  convey  the  lymph  from  bone,  periosteum,  muscle,  ligament,  etc.  They  pass 
up  the  limb  with  the  chief  vessels,  there  usually  being  two  trunks  to  each  artery. 
In  the  arm  there  are  two  or  three  vessels.  Some  few  vessels  terminate  in  the 
small  glands  along  the  radial,  ulnar,  and  brachial  arteries,  but  most  of  them  pass 
directly  to  the  axillary  glands. 

Surgical  Anatomy. — In  malignant  diseases,  or  other  affections  implicating  the  upper  part  of 
the  back  and  shoulder,  the  front  of  the  chest  and  mamma,  the  upper  part  of  the  front  and  side 
of  the  abdomen,  or  the  hand,  forearm,  or  arm,  the  axillary  glands  are  liable  to  be  found  enlarged. 

In  secondary  syphilis  the  supratrochlear  gland  is  found  to  be  enlarged.  This  gland  is  sub- 
cutaneous and  readily  palpable  when  enlarged.     Normal  axillary  glands  cannot  be  palpated. 

'  The  Lymphatics.     By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE   LYMPHATIC    GLAND.S    OF    THE    LOWER    EXTREMITY     793 

The  axilla  is  a  passage-way  for  structures  between  the  neck  and  the  upper  extremity,  and  puru- 
lent collections  or  tumors  may  extend  from  the  neck  into  the  axilla  or  from  the  axilla  into  the 
neck. 

The  axillary  glands  are  involved  early  in  cases  of  cancer  of  the  mammary  gland,  and  later 
the  lower  deep  cervical  glands  are  involved,  and,  as  Snow  has  pointed  out,  regurgitation  of 
lymph  containing  cancer  cells  leads  to  retrosternal  involvement  and  to  secondary  cancer  of  the 
head  of  the  humerus.  In  operating  for  cancer  of  the  breast,  follow  the  principle  of  Halsted  and 
remove  the  breast,  the  skin  over  it,  the  muscles  and  fascia,  the  lymph-vessels,  and  the  axillary 
glands  in  one  piece.  By  this  plan  thorough  removal  is  possible,  and  as  lymph-vessels  containing 
carcinoma  cells  are  not  cut  across,  the  wound  is  not  grafted  with  malignant  epithelial  cells.  Dis- 
eased axillary  glands  are  apt  to  adhere  to  the  sheath  of  the  vein.  In  removing  cancerous  glands, 
always  excise  the  sheath  of  the  vein. 


THE  LYMPHATICS  OF  THE  LOWER  EXTREMITY. 

The  Ljrmphatic  Glands  of  the  Lower  Extremity. 

Tlie  lymphatic  glands  of  the  lower  extremity  are  divided  into  two  sets,  super- 
ficial and  deep.  The  superficial  are  confined  to  the  inguinal  i-egion,  forming  the 
superficial  inguinal  lymphatic  glands. 

The  Superficial  Inguinal  Lymphatic  Glands  (lymphoglandulae  inguinales 
superfciales)  (Figs.  500,501,  502,  and  503). — The  superficial  inguinal  lymphatic 
glands,  placed  immediately  beneath  the  integument  in  Scarpa's  triangle,  are  of 

SUPERIOR 

EXTERNAL 

GROUP 


SUPERIOR 

INTERNAL 

GROUP 

INFERIOR 

INTERNAL 

GROUP 


EXTERNAL 
GROUP 


Fig.  500. — Superficial  inguinal  glands.     Cribriform  fascia  has  been  removed  so  as  to  expose  the  femoral 

vessels.     (Poirier  and  Charpy.) 

large  size,  and  vary  in  number  from  ten  to  twenty.  It  is  customary  to  divide 
these  glands  into  groups  according  to  the  region  in  which  they  are  found.  The 
following  division  is  suggested  by  Poirier,  Cuneo,  and  Delamare:^  A  horizontal 
line  carried  through  the  saphenous  opening  divides  the  glands  into  two  groups, 
a  superior  group  and  an  inferior  group.  A  vertical  line  through  the  saphenous 
opening  divides  each  of  the  two  groups  into  two  secondary  groups,  an  external  and 
an  internal  group.  We  thus  have  an  external  and  superior  group,  and  internal  and 
superior  group,  an  external  and  inferior  group,  and  an  internal  and  inferior  group. 


1  The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


794 


THE   LYMPHATIC   SYSTEM 


Directly  in  the  saphenous  opening  there  are  often  several  glands  constituting  a 
central  group. 

Leaf  joints  out  that  a  gland  usually  exists  near  the  saphenous  opening,  which 
is  interposed  between  the  superficial  inguinal  and  deep  inguinal  glands.  The 
superior  group  of  glands,  sometimes  called  the  oblique  group,  is  so  placed  that  the 
glands  lie  with  a  certain  regularity  along  and  below  Poupart's  ligament,  the  long 
axis  of  each  gland  corresponding  with  the  direction  of  the  ligament.  It  is  now 
known  that  each  group  of  the  superficial  glands  does  not  receive  with  regularity 
the  lymph  from  and  only  from  a  definite  and  accurately  determined  area.  Hence,  it 
is  not  possible,  as  was  once  taught,  to  determine  with  certainty  the  exact  situation 
of  a  lesion  by  the  group  of  superficial  glands  involved.  The  superficial  inguinal 
glands  receive  vessels  from  the  skin  of  the  lower  extremity,  gluteal  region,  peri- 


FiG.  501. — Glands  of  the  inguinal  region  with  the  afferent  and  efferent  lymphatics.      (Poirier  and  Charpy.) 

neum,  abdominal  wall,  scrotum,  anus,  and  from  the  prepuce  of  the  clitoris  and 
penis.  Occasionally,  though  not  normally,  they  receive  vessels  from  the  glans 
penis  and  glans  clitoris.  The  superficial  glands  send  vessels  to  the  deep  inguinal 
glands  and  to  the  external  iliac  glands,  and  these  vessels  penetrate  the  femoral 
sheath.  The  vessels  which  go  to  the  iliac  glands  ascend  with  the  femoral  vessels. 
Leaf  ^  figures  some  of  the  efferent  vessels  from  these  glands  as  terminating  directly 
in  the  veins  of  this  region. 

Surgical  Anatomy. — The  superficial  inguinal  glands  frequently  become  enlarged  in  diseases 
implicating  the  parts  from  which  their  lymphatics  originate.  Thus,  in  malignant  or  syphilitic 
affections  of  the  prepuce  and  penis,  or  of  the  labia  majora  in  the  female,  in  cancer  scroti,  in 
abscess  in  the  perinseum,  and  in  other  diseases  affecting  the  integument  and  superficial  structures 

1  The  Surgical  Anatomy  of  the  Lymphatic  Glands,  1898. 


THE   LYMPHATIC    GLANDS    OF    THE   LOWER   EXTREMITY    795 


in  those  parts,  or  the  subumbihcal  part  of  the 
abdominal  wall  or  the  gluteal  region,  the  upper 
chain  of  glands  is  almost  invariably  enlarged,  the 
lower  chain  being  implicated  in  diseases  affecting 
the  lower  limb. 

The  Deep  Lymphatic  Glands  of  the 
Lower  Extremity. — The  tleep  glands  are 
the  inguinal,  anterior  tibial,  popliteal,  gluteal, 
and  ischiatic. 

The  Deep  Inguinal  or  Deep  Femoral 
Lymphatic  Glands  (lymphoglandidae  in- 
guinalcs  profundae)  (Fig.  503). — The  deep 
inguinal  lymphatic  glands  are  beneath  the 
deep  fascia.  There  are  only  two  or  three  of 
them,  and  they  lie  to  the  inner  side  of  the 
femoral  vein,  the  upper  gland  being  in  the 
crural  canal  and  projecting  into  the  pelvis. 
It  is  called  the  gland  of  Cloquet  or  the 
gland  of  RosenmuUer.  The  deep  inguinal 
glands  receive  vessels  from  the  superficial 
inguinal  glands,  deep  lymphatics  from 
along  the  femoral  vessels,  and  vessels  from 
the  glans  penis  or  clitoris.  They  send 
vessels  to  the  ilio-pelvic  glands. 

The  Anterior  Tibial  Gland  (lympho- 
glandula  tibialis  anterior)  (Fig.  503).— The 
anterior  tibial  gland  is  not  constant  in  its 
existence.  It  is  generally  found  by  the 
side  of  the  anterior  tibial  artery,  upon  the 
interosseous  membrane  at  the  upper  part 
of  the  leg.  Occasionally,  two  glands  are 
found  in  this  situation.  It  receives  a  deep 
anterior  tibial  lymphatic  trunk  and  sends 
off  a  vessel  to  the  popliteal  glands. 

The  Popliteal  Glands  (lymphoglandidae 
popliteae). — Tlie  popliteal  glands  are  em- 
bedded in  the  cellular  tissue  and  fat  of 
the  popliteal  space  and  about  the  peroneal 
vessels  The  juxta-articular  gland  receives 
lymph-vessels  from  the  knee-joint.  The 
popliteal  glands  send  vessels  to  the  super- 
ficial and  deep  inguinal  glands. 

The  popliteal  glands  are  divided  into 
three  groups  •}  1 .  A  gland  external  to  the 
termination  of  the  external  saphenous 
vein,  the  external  saphenous  gland.  2.  A 
middle  group  of  three  or  four  glands  on 
the  sides  of  the  popliteal  vessels.  The 
inferior  glands  of  this  group  are  the  inter- 
condyloid  glands  of  Leaf.  The  superior 
glands  are  the  supracondyloid  glands  of 
Leaf.    3.  A  gland  adherent  to  the  posterior 


Superficial 
i7iguinal 
glands. 


vm 


'  The  Lymphatics.    By  Poirier,  Cun^o,  and  Delamare. 
Translated  and  edited  by  Cecil  H.  Leaf. 


Fio.  502. — The  superficial  lymphatics  and  glands 
of  the  lower  extremity. 


796 


THE   LYMPHATIC  SYSTEM 


ligament  of  the  knee-joint,  the  juxta-articular  gland  of  Poirier  and  Cun6o.    Tlie  ex- 
ternal saphenous  gland  receives  vessels  which  ascend  along  the  external  saphenous 


INTRACLAVIC 


EXTERNAL  AXILLA 
ANTERIOR  AXILLA 


POSTERIOR  AXILLA 


NFRACLAVICULAR 


PERFICIAL  FEMORAL 
EP   FEMORAL 
ETHRAL 


Fig.  503. — Superficial  lymphatic  vessel.?  of  the  trunk,  and  the  lymphatic  glands  and  vessel.*,  superficial  and 
deep,  of  the  limbs  (diagrammatic).  Afferent  vessels  are  represented  by  continuous  lines;  efferent  and  mter- 
glandular  vessels  by  dotted  lines.     (Cunningham.) 


THE    ILIAC   OB    ILIO -PELVIC    GLANDS  797 

vein.    The  middle  group  receives  vessels  from  the  anterior  tibial  glands  and  deep 
lymphatic  vessels  which  ascend  with  the  posterior  tibial. 

The  Gluteal  and  Ischiatic  Glands. — The  gluteal  and  ischiatic  glands  are  placed, 
the  former  above,  the  latter  below,  the  Pyriformis  muscle,  resting  on  their  corre- 
sponding blood-vessels  as  they  pass  through  the  great  sacro-sciatic  foramen. 

The  Lymphatic  Vessels  of  the  Lower  Extremity  (Figs.  502,  503). 

The  lymphatic  vessels  of  the  lower  extremity,  like  the  veins,  may  be  divided 
into  two  sets,  superficial  and  deep. 

The  Superficial  Lymphatic  Vessels  of  the  Lower  Extremity. — The  superficial 
lymphatic  vessels  are  placed  beneath  the  integument  in  the  superficial  fascia,  and 
are  divisible  into  three  sets:  trunks  which  follow  the  course  of  the  internal 
saphenous  vein,  trunks  which  accompany  the  external  saphenous  vein,  and 
trunks  from  the  <jluteal  region.  1.  Trunks  which  follow  the  course  of  the 
internal  saphenous  vein  arise  from  a  plexus  on  the  dorsum  of  the  foot,  which 
plexus  obtains  lymphatics  from  all  the  toes,  the  sole,  and  both  borders  of  the  foot. 
The  internal  trunks,  three  or  four  in  number,  pass  to  the  superficial  inguinal 
glands.  Theexternal  trunks  run  upward  and  inward  and  end  in  the  internal  trunks. 
2.  The  trunks  which  follow  the  external  saphenous  vein  number  two  or  three,  and 
they  take  origin  from  the  heel  and  from  the  posterior  half  of  the  outer  edge  of 
the  foot.  They  empty  into  the  superficial  inguinal  glands.  3.  The  lymph-trunks 
from  the  gluteal  region  join  vessels  from  the  anus  and  enter  the  superficial 
inguinal  glands. 

The  Deep  Lymphatic  Vessels  of  the  Lower  Extremity.— The  deep  lymphatic 
vessels  of  the  lower  extremity  are  few  in  number  and  accompany  the  deep  blood- 
vessels. In  the  leg  they  consist  of  three  sets,  the  anterior  tibial,  peroneal,  and 
posterior  tibial,  which  accompany  the  corresponding  blood-vessels,  two  or  three 
to  each  artery;  they  ascend  with  the  blood-vessels  and  enter  the  lymphatic  glands 
in  the  popliteal  space;  the  efferent  vessels  from  these  glands  accompany  the  femoral 
vein  and  join  the  deep  inguinal  glands;  from  these  glands  vessels  pass  beneath  Pou- 
part's  ligament  and  communicate  with  the  chain  of  glands  surrounding  the  exter- 
nal iliac  vessels.  The  deep  lymphatic  vessels  of  the  gluteal  and  ischiatic  regions 
follow  the  course  of  the  blood-vessels,  and  join  the  gluteal  and  ischiatic  glands  at 
the  great  sacro-sciatic  foramen. 


THE  LYMPHATICS  OF  THE  PELVIS  AND  ABDOMEN. 

The  lymphatics  of  the  pelvis  and  abdomen  constitute  a  continuous  chain,  but 
for  convenience  of  study  it  is  customary  to  divide  them  into  two  groups,  which 
we  call,  with  Poirier  and  Cuneo,*  the  ilio-pelvic  glands  and  the  abdomino-aortic 
glands;  the  first  group  being  below  and  the  second  above  the  level  of  the  bifurca- 
tion of  the  aorta  into  the  two  common  iliac  arteries. 

The  Iliac  or  Ilio-pelvic  Glands  (Lymphoglandulae  Iliacae)  (Figs.  504,  505). 

The  ilio-pelvic  glands  are  at  the  level  of  the  inlet  of  or  in  the  cavity  of  the 
pelvis.  They  follow  the  course  of  the  blood-vessels  and  are  divisible  into  the 
external  iliac,  the  internal  iliac,  and  the  common  iliac  chains. 

The  External  Hiac  Glands. — The  external  iliac  glands  form  chains  around 
the  external  iliac  vessels.  There  are  three  chains  of  these  glands.  An  external 
chain  of  three  or  four  glands  lies  between  the  artery  and  the  Psoas  muscle. 

'  Treatise  on  Human  Anatomy.  ^'' 


798 


THE   LYMPHATIC  SYSTEM 


The  lowest  gland  of  the  external  chain  is  called  by  Poirier  and  Cun^o  the  external 
retro-crural  gland  (Fig.  504).  A  middle  chain  of  three  glands  lies  upon  the  front 
surface  of  the  external  iliac  vein.  The  lowest  gland  of  this  group  is  called  by 
Poirier  and  Cun^o  the  middle  retro-crural  gland.  An  internal  chain  of  three  or 
four  glands  is  placed  to  the  inner  side  of  the  external  iliac  vein.  The  lowest  gland 
of  this  chain  is  called  the  internal  retro-crural  gland,  and  is  close  to  the  upper  gland 
of  the  deep  inguinal  chain,  the  gland  of  Cloquet.  The  obturator  gland  belongs  to 
the  inner  chain  of  external  iliac  glands.  The  external  iliac  glands  receive  vessels 
from  the  superficial  and  deep  iliac  glands,  from  the  glans  penis  or  glans  clitoris, 


LEFT  JUXTA 


PROMONTORY 


COMMON   ILIAC 

(middle  group) 


EXTERNAL  ILIAC 

(external  chain) 


COMMON  ILIAC 
ZXTERNAL  ILIAI 


EXTERNAL  ILIA( 

(middle  chain) 


OBTURATOR 
NERVE 
OBTURATOR 
ARTERY 


EXTERNAL 
RETROCRURAL 


OBTURATOR 
ARTERY 


OBTURATOR 
GLAND 


Fig.  504. — Ilio-pelvic  glands.      (Poirier  and  Charpy.) 


deep  lymphatics  from  the  umbilicus  and  lower  part  of  the  belly  wall,  vessels  from  the 
superior  portion  of  the  vagina,  the  uterine  neck,  the  prostate  gland,  the  bladder, 
the  membranous  portion  of  the  urethra,  and  the  internal  iliac  glands,  and  the 
obturator  gland  receives  deep  lymph-vessels  from  along  the  course  of  the  obtu- 
rator vessels.  The  external  iliac  glands  send  vessels  direct  to  the  common  iliac 
glands  and  also  lymphatics  to  join  vessels  from  the  internal  iliac  glands  on  their 
way  to  the  common  iliac  group.  The  glands  along  the  deep  epigastric  artery 
and  those  along  the  deep  circumflex  iliac  artery  are  accessory  chains  to  the  main 
group  of  external  iliac  glands. 


THE   ABDOMINO- AORTIC    GLANDS 


799 


The  Internal  Iliac  or  Hypogastric  Glands.— The  internal  iliac  glands  are 
placed  along  the  internal  iliac  artery  and  its  branches.  The  gland  on  the  middle 
hsemorrhoidal  artery  is  called  the  middle  hsemorrhoidal  gland.  The  lateral  sacral 
gland  is  on  the  lateral  sacral  artery.  The  internal  iliac  glands  receive  lymph  from 
the  pelvic  viscera,  perinieum,  and  penile  portion  of  the  urethra,  deep  tissues  of  the 
posterior  portion  of  the  thigh,  and  from  the  buttocks.  They  send  vessels  to  the 
common  iliac  glands  and  also  to  the  external  iliac  g-lands. 

The  Common  Hiac  Glands. — The  common  iliac  glands  are  found  about  the 
common  iliac  artery  and  are  divided  into  an  external  group,  which  lies  upon  the 


INTERPELVIC 
GLUTEAL 


PROMONTORY 


EXTERNAL  ILIAC 

(middle  chain) 


EXTERNAL  ILIAC 

(middle  chain) 

EXTERNAL  ILIAC 

(external  chain) 

RETROCRURAL 

EXTERNAL 

RETROCRURAL- 

INTERNAL 

LYMPHATICS 

OF   BLADDER 

LYMPHATIC    FROM 

CLANS    PENIS 

LYMPHATICS 
OF  BLADDER 


J_HYPOGASTBIC 


HYPOGASTRIC 
SATELLITE  TRUNK 
OF   INTERNAL 
PUDIC  VESSELS 
TRUNK  OF 
MIDDLE  HEMOR- 
RHOIDAL VESSELS 


PROSTATIC  COL- 
LECTING TRUNK 


tETHRAL  COL- 
LECTING TRUNKS 


LYMPHATIC  GLANDULAR    NODULE 
IN    FRONT  OF  SYMPHYSIS 


PROSTATIC  COL- 
LECTING TRUNK 


Fig.  505. — Ilio-pelvic  gland.s  (lateral  view.)     (Poirier  and  Charpy.) 

inner  edge  of  the  Psoas  muscle;  a  middle  group,  behind  the  artery,  and  an  internal 
group,  which  lies  upon  the  front  of  the  body  of  the  fifth  lumbar  vertebra  or  upon 
the  sacro-vertebral  junction.  They  receive  vessels  from  the  external  and  internal 
iliac  glands  and  from  the  pelvic  viscera,  the  vessels  from  the  pelvic  viscera  ascend- 
nig  to  the  promontory  of  the  sacrum  and  containing  perhaps,  here  and  there, 
mterrupting  glands,  known  as  sacral  glands  {lymphoglandulae  sacrales)  (Fig.  511). 
They  also  receive  lymph-vessels  from  the  lumbo-sacral  region.  They  send  vessels 
to  the  aortic  glands.  Some  anatomists  place  the  common  ihac  glands  and  the 
glands  al)out  the  lower  portion  of  the  aorta  and  vena  cava  in  a  group  called  the 
lumbar  glands  {lymphoglandulae  lumhales)  (F\g.  511). 

The  Abdomino-aortic  Glands  (Figs.  484,  511). 

The  abdomino-aortic  glands  are  placed  about  the  abdominal  aorta.    There  are 
twenty-five  or  thirty  of  them.    They  are  divided  by  Poirier,  Cun^o,  and  Delamare^ 


'   The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


800  THE   LYMPHATIC  SYSTEM 

into  the  right  and  left  juxta-aortic  glands,  the  retro-aortic  glands,  and  the  pre-aortic 
glands. 

The  Right  Juxta-aortic  Glands. — The  right  juxta-aortic  glands  are  grouped 
in  front  of  and  behind  the  inferior  vena  cava,  the  posterior  glands  lying  upon  the 
Psoas  muscle  and  the  adjacent  pillar  of  the  Diaphragm.  They  receive  lymph- 
vessels  from  the  right  common  iliac  glands,  from  the  right  testicle  or  the  right 
half  of  the  uterus,  and  the  right  tube,  ovary,  broad  ligament,  the  right  kidney 
and  suprarenal  capsule,  and  also  lymph-vessels  which  pass  along  the  lumbar 
arteries.  They  send  vessels  to  the  pre-aortic  and  the  retro-aortic  glands  and  the 
receptaculum  chyli. 

The  Left  Juxta-aortic  Glands. — The  left  juxta-aortic  glands  lie  by  the  side  of 
the  abdominal  aorta,  upon  the  Psoas  muscle,  and  the  left  pillar  of  the  Diaphragm. 
They  receive  tributaries  from  the  left  side  corresponding  to  those  received  by 
the  glands  of  the  right  side,  and  also  send  out  corresponding  efferent  vessels,  and 
several  additional  vessels  which  pass  through  the  left  pillar  of  the  Diaphragm  and 
empty  into  the  thoracic  duct. 

The  Retro-aortic  Glands. — The  retro-aortic  glands  are  placed  beneath  the 
receptaculum  chyli  and  in  front  of  the  bodies  of  the  fourth  and  fifth  lumbar  ver- 
tebrae. They  receive  lymph-vessels  from  both  juxta-aortic  groups,  and  also  from 
the  pre-aortic  glands,  and  they  send  vessels  to  the  receptaculum  chyli. 

The  Pre-aortic  Glands. — The  pre-aortic  glands  lie  upon  the  front  of  the  aorta, 
and  in  most  subjects  are  divisible  into  three  groups:  an  inferior,  lying  at  the  origin 
of  the  inferior  mesenteric  artery;  a  middle,  at  the  origin  of  the  superior  mesenteric 
artery,  and  a  superior,  about  the  coeliac  axis,  the  coeliac  glands  (lymphoglandulae 
coeliacae).  Glands  which  are  found  along  the  course  of  all  the  branches  of  the 
abdominal  aorta  empty  into  and  belong  to  the  group  of  pre-aortic  glands.  The 
pre-aortic  glands  receive  vessels  from  the  juxta-aortic  glands  and  from  all  the 
glands  along  the  mesenteric  vessels  and  the  coeliac  axis  and  its  branches, 
and  receive  lymph  from  the  stomach,  intestines,  liver,  pancreas,  and  spleen. 
They  anastomose  with  each  other  and  send  vessels  to  the  retro-aortic  glands  and 
to  the  receptaculum  chyli.  Instead  of  the  glands  terminating  in  the  receptaculum 
by  separate  vessels,  the  vessels  may  unite  and  form  a  common  trunk,  the  intes- 
tinal trunk  (truncus  intestinalis) ,  which  runs  along  with  the  common  trunk  from 
the  juxta-aortic  glands,  and  empties  into  the  receptaculum  (Fig.  484). 

1 .  The  Glands  along  the  Mesenteric  Arteries  {lymphoglandulae  mesentericae)  receive 
the  lymph  from  the  colon,  csecum,  appendix,  ileum,  jejunum,  duodenum,  and 
perhaps  also  some  from  the  stomach. 

2.  The  Glands  Connected  with  the  Coeliac  Axis  and  its  Branches. — There  are  three 
groups  of  these  glands:  the  gastric  or  coronary,  the  splenic,  and  the  hepatic  (in- 
cluding those  of  the  bile-ducts). 

The  Gastric  Glands  (lymphoglandulae  gasiricae). — One  group  is  situated  in  the 
gastro-pancreatic  fold;  another  group  is  connected  with  the  lesser  curvature  of  the 
stomach  (Fig.  508) .  Some  of  them  are  in  the  lesser  omentum  close  to  insertion  of 
the  thicker  part  upon  the  stomach,  and  lie  near  the  ascending  branches  of  the  gastric 
artery,  that  is  to  say,  upon  the  vertical  portion  of  the  lesser  curvature.  Others  lie 
within  the  lesser  omentum  and  accompany  the  descending  branches  of  the  gas- 
tric artery,  and  particularly  gather  near  the  point  where  the  gastric  artery  comes 
toward  the  stomach  wall.  The  gastric  glands  receive  lymph  from  most  of  the 
stomach.  They  send  lymph  to  the  upper  group  of  pre-aortic  glands,  the  coeliac 
glands. 

The  Splenic  Glands  {lymphoglandulae  pancreaticolienales) . — ^The  splenic  glands 
accompany  the  splenic  artery  and  lie  upon  the  posterior  surface  of  the  spleen, 
between  the  spleen  and  pancreas.  They  receive  lymph  from  the  fundus  of  the 
stomach,  from  the  spleen,  and  from  the  pancreas,  and  send  it  to  the  coeliac  glands. 


THE  LYMPHATIC   VESSELS  OF  THE  ABDOMEN  AND  PELVIS    801 

The  Hepatic  Glands  (lympJwglatidulae  hepaticae). — These  glands  lie  along  the 
hepatic  artery,  some  on  the  level  of  the  floor  of  the  foramen  of  Winslow,  others  by 
the  left  side  of  the  portal  vein.^  The  authors  previously  quoted  point  out  that  there 
is  a  secondary  chain  of  hepatic  glands  about  the  right  gastro-epiploic  artery,  the 
gastro -epiploic  chain,  and  that  this  comprises  a  subpyloric  group  and  a  retro-pyloric 
group.  The  subpyloric  group  (Fig.  508)  is  placed  in  the  great  omentum  below  the 
pylorus,  and  is  usually  distinctly  separated  from  it.  The  retro-pyloric  group  is  not 
constant.  It  is  placed  along  the  gastro-duodenalis  artery  back  of  the  pylorus. 
There  is  also  a  group  of  glands,  secondary  to  the  hepatic  glands,  to  the  right  of 
or  posterior  to  the  cystic  duct  and  the  common  bile-ducts.  The  hepatic  glands 
proper  receive  lymph  from  the  liver  and  send  it  to  the  coeliac  glands.  The 
subpyloric  glands  receive  lymph  from  the  inferior  portion  of  the  stomach  and 
from  the  superior  portion  of  the  great  omentum.  They  send  lymph  to  the  hepatic 
glands  proper,  the  retro-pyloric  glands,  and  sometimes  also  to  the  glands  about 
the  superior  mesenteric  artery.  The  retro-pyloric  glands  receive  lymph  from  the 
suljpyloric  glands,  from  the  upper  surface  and  from  the  posterior  surface  of 
the  pylorus,  and  from  the  duodenum.  They  send  lymph  to  the  hepatic  glands 
proper  and  sometimes  to  the  glands  along  the  superior  mesenteric  artery.  The 
glands  along  the  gall-ducts  empty  into  the  hepatic  glands  proper. 

The  Lymphatic  Vessels  of  the  Abdomen  and  Pelvis. 

The  lymphatic  vessels  of  the  abdomen  and  pelvis  may  be  divided  into  two  sets, 
superficial  and  deep. 
The  Superficial  Lymphatic  Vessels  of  the  Walls  of  the  Abdomen.— The 

superficial  lymphatic  vessels  of  the  walls  of  the  abdomen  follow  the  course  of  the 
superficial  blood-vessels.  The  superficial  lymphatics  are  derived  from  the  integu- 
ment. Those  of  the  lower  part  of  the  abdomen  below  the  umbilicus  follow  the  course 
of  the  superficial  epigastric  vessels  and  converge  to  the  superior  group  of  the  super- 
ficial inguinal  glands  (Figs.  501  and  503).  Those  from  the  costal  margins  of  the 
abdomen  terminate  in  the  axillary  glands  (Fig.  497).  The  superficial  lymphatics 
from  the  sides  of  the  lumbar  part  of  the  abdominal  wall  wind  aroimd  the  crest  of 
the  ilium,  accompanying  the  superficial  circumflex  iHac  vessels,  to  join  the  super- 
ficial inguinal  glands  (Fig.  501). 

The  Superficial  Lymphatic  Vessels  of  the  Gluteal  Region. — The  superficial  lym- 
phatic vessels  of  the  gluteal  region  turn  horizontally  around  the  outer  side  of  the 
nates,  and  join  the  superficial  inguinal  glands. 

The  Superficial  Lymphatic  Vessels  of  the  Scrotum  and  Perinaeum. — The  superficial 
lymphatic  vessels  of  the  scrotum  and  perinaium  terminate  in  the  superficial  inguinal 
glands. 

The  Superficial  Lymphatic  Vessels  of  the  Penis. — The  superficial  lymphatic  vessels 
of  the  penis  occupy  the  sides  and  dorsum  of  the  organ,  the  latter  receiving  the 
lymphatics  from  the  prepuce ;  they  all  converge  to  the  superficial  inguinal  glands. 
Lymph  vessels  from  the  glans  penis  empty  into  the  deep  inguinal  and  the  external 
iliac  glands. 

In  the  female  the  lymphatic  vessels  of  the  vulva  and  prepuce  of  the  clitoris  pass 
to  the  superficial  inguinal  glands;  those  of  the  glans  of  the  clitoris  pass  to  the 
deep  inguinal  and  the  external  iliac  glands. 

The  Deep  Lymphatic  Vessels  of  the  Abdominal  Wall. — The  deep  lymphatic 
vessels  of  the  abdominal  wall  take  the  course  of  the  principal  blood-vessels,  and 
arise  from  muscular  or  aponeurotic  layers.  One  set  of  lymph-vessels  runs  along 
with  the  deep  epigastric  artery  and  terminates  in  the  external  iliac  glands.  Another 

'  The  Lymphatics.    By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 

51 


g02  THE   LYMPHATIC  SYSTEM 

accompanies  the  deep  circumflex  iliac  artery,  and  also  terminates  in  the  external 
iUac  glands.  Several  lymph-vessels  accompany  the  lumbar  arteries  and  empty 
into  the  juxta-aortic  glands.  A  vessel  accompanies  the  internal  mammary  artery 
and  empties  into  the  internal  mammary  glands.  Lymph-vessels  of  the  parietes  of 
the  pelvis,  which  accompany  the  gluteal,  ischiatic,  and  obturator  vessels,  follow 
the  course  of  the  internal  iliac  artery,  and  ultimately  join  the  external  iUac,  internal 
iUac,  and  common  iliac  glands,  and  the  glands  about  the  lower  portions  of  the  aorta 
and  vena  cava. 

The  Lymphatic  Vessels  of  the  Umbilicus. — The  lymphatics  of  the  umbilicus  are 
divided  into  three  groups:^  The  cutaneous  lymphatics,  which  are  very  superficial, 
and  empty  into  the  superficial  inguinal  glands.  The  lymphatics  of  the  fibrous 
nucleus,  which  pass  through  the  rectus  sheath,  reach  the  deep  epigastric  artery 
and  join  the  deep  lymphatics  which  come  from  the  muscular  and  aponeurotic 
layers  of  the  belly  wall.  The  lymphatics  of  the  aponeurotic  margin  are  in  two  sets: 
An  anterior  set,  some  of  which  penetrate  the  rectus  sheath  and  join  the  lymphatics 
from  the  fibrous  nucleus;  others  of  which  pass  outward,  penetrate  the  external  and 
internal  oblique  muscles,  and  join  the  posterior  lymph-vessels  from  the  aponeu- 
rotic margin.  A  posterior  set,  which  forms  a  collection  of  vessels  on  the  posterior 
aspect  of  the  rectus  sheath,  from  which  several  trunks  emerge.  One  trunk  passes 
outward,  penetrates  the  Transversalis  muscle,  joins  the  anterior  trunk  from  the 
aponeurotic  margin,  and  empties  into  the  external  iliac  glands.^  Other  ducts  run 
along  with  the  deep  epigastric  artery  and  pass  into  the  external  iliac  glands. 
Glands  lie  along  the  lower  portion  of  these  lymph-ducts,  and  are  known  as 
the  superior  epigastric  glands,  and  a  gland  may  exist  in  the  subperitoneal  tissue 
beneath  the  umbihcus. 

The  Lymphatic  Vessels  of  the  Peritoneum. — It  seems  probable  that  the  peritoneal 
cavity  is  a  lymph-sac  and  that  lymphatics  take  origin  from  the  peritoneum  in 
several  ways.  Byron  Robinson^  points  out  three  modes  of  origin:  1.  By  stomata 
between  endothelial  cells.  These  stomata  are  in  direct  communication  with 
lymph-vessels.  2.  By  interstitial  spaces  in  the  subperitoneal  tissue.  3.  By  a 
plexiform  origin  similar  to  interstitial  spaces. 

Surgical  Anatomy. — The  fact  emphasized  by  Byron  Robinson  that  the  peritoneum  is  a  great 
lymph-sac  explains  the  quick  absorption  of  septic  material  and  the  rapid  spread  of  infectious  pro- 
cesses. If  the  exudate  clots  and  blocks  the  lymph-channels,  absorption  is  slow  and  life  may  be 
saved.  If  it  does  not  clot,  absorption  is  rapid  and  death  is  certain.  Whether  it  clots  or  not 
depends  on  the  nature  of  the  bacteria  present.''  Fowler,  impressed  by  the  fact  that  absorption 
takes  place  most  rapidly  from  the  diaphragmatic  region  and  least  rapidly  from  the  pelvic  region, 
advises  placing  the  victim  of  peritonitis  in  bed,  with  his  head  and  body  elevated.* 

The  Lymphatic  Vessels  of  the  Bladder. — No  lymphatics  exist  in  the  mucous  mem- 
brane of  the  bladder,  although  they  do  exist  in  the  mucous  membrane  of  the  pros- 
tate. There  are  some  lymphatics  in  the  bladder  muscle,  and  numerous  lymphatics 
in  the  subperitoneal  tissue.  The  network  of  lymph-vessels  in  the  muscles  is  con- 
nected with  the  network  beneath  the  peritoneum  and  prevesical  fascia,  and  collect- 
ing trunks  come  from  both  the  anterior  and  posterior  surfaces  of  the  bladder. 
The  anterior  collecting  trunks  are  divided  into  two  sets.  One  set  comes  from  the 
inferior  portion  of  the  anterior  surface  and  passes  outward  to  terminate  in  an 
external  iliac  gland  "between  the  external  iUac  vein  and  the  obturator  nerve. "^ 
The  other  set  comes  from  the  superior  and  anterior  vesical  surface,  runs  upward 
and  outward,  and  terminates  in  the  external  ihac  glands.  Each  set  of  vessels 
possesses  interrupting  lymph-nodes,  some  of  which  are  directly  in  front  of  the 
bladder. 

*  The  Lymphatics.     By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 

2  Poirier.  Cun6o,  and  Delamare.  "  The  Peritoneum.  ♦  Byron  Rbbinson.     The  Peritoneum. 

*  George  Ryerson  Fowler,  on  Diffuse  Septic  Peritonitis,  in  the  Medical  Record,  .\pril  14,  1900. 

*  The  Lymphatics.      By  Poirier,  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC   VESSELS  OF  THE  ABDOMEN  AND  PELVIS    803 

The  posterior  collecting  trunks  are  divided  into  four  sets.  The  first  set  comes 
from  the  superior  and  posterior  portion  and  passes  outward,  exhibiting  interrupting 
nodes  in  its  course.  These  trunks  terminate  in  the  external  iliac  glands.  The 
second  set  runs  directly  back  into  the  external  iliac  glands.  The  third  set  comes 
from  the  middle  of  the  posterior  portion  of  the  bladder  and  terminates  in  the 
hypogastric  glands.  The  fourth  set  comes  from  the  vesical  neck,  passes  back 
and  then  ascends  and  terminates  in  the  glands  in  front  of  the  sacral  promontory. 
This  fourth  set  joins  with  the  lymphatics  from  the  prostate  and  seminal  vesicles. 

The  Lymphatic  Vessels  of  the  Prostate  Gland. — These  vessels  form  a  peri-pros- 
tatic  plexus,  which  receives  its  afferents  from  the  gland  structure.  This  plexus  is 
drained  by  four  vessels,  three  of  which  commence  on  the  posterior  surface  of  the 
gland.  Although  these  vessels  begin  on  the  posterior  surface  of  the  prostate,  their 
termination  in  each  case  is  different.  One  passes  on  the  under  surface  of  the 
bladder,  crosses  the  superior  vesical  artery,  runs  outward,  and  ends  in  the  middle 
chain  of  the  external  iliac  group.  Another  passes  upward,  outward,  and  back- 
ward, and  terminates  in  the  hypogastric  group.  A  third  passes  along  the 
floor  of  the  pelvis,  runs  by  the  side  of  the  rectum,  and  ascends  on  the  anterior 
surface  of  the  sacrum  to  terminate  in  the  lateral  sacral  glands  and  in  the  hypo- 
gastric group.  Occasionally  a  fourth  trunk  is  found  on  the  anterior  surface  of 
the  prostate,  which  descends  and  joins  the  vessels  from  the  membranous  urethra 
and  ends  in  the  hypogastric  glands. 

The  Lymphatic  Vessels  of  the  Male  Urethra. — These  vessels  are  divided  into  two 
groups:  First,  those  of  the  penile  portion  of  the  urethra;  second,  those  of  the  bulb 
and  membranous  portion.  The  lymphatics  of  the  prostatic  urethra  belong  to  those 
of  the  prostate  gland.  The  lymph-vessels  of  the  penile  urethra  in  front  of  the 
sulcus  all  run  toward  the  frsenum,  at  which  point  they  bend  backward  to  the  sul- 
cus; here  they  run  to  the  dorsal  surface  of  the  penis  and  terminate  in  the  same  man- 
ner as  the  vessels  from  the  glans.  The  trunks  from  the  remainder  of  the  penile 
urethra  emerge  from  the  inferior  surface,  run  around  the  corpus  cavernosa,  and 
mostly  unite  with  the  vessels  from  the  glans  penis.  One  vessel,  though,  passes  over 
the  symphysis  and  enters  in  the  internal  retro-crural  gland,  whilst  another  passes 
beneath  the  symphysis  and  terminates  with  the  vessels  from  the  bulb  and  mem- 
branous portion  of  the  urethra.  The  lymphatics  of  the  bulb  and  membranous 
portions  end  in  three  trunks,  one  of  which  accompanies  first  the  artery  of  the  bulb 
and  then  the  internal  pudic  artery,  and  ends  in  the  hypogastric  gland  attached  to 
the  pelvic  portion  of  this  artery.  A  second  trunk  runs  behind  the  pubes,  to  end 
in  the  internal  retro-crural  gland.  A  third  trunk  runs  on  the  bladder,  where  it 
joins  with  vessels  from  this  organ,  to  end  in  the  internal  chain  of  external  iliac 
glands. 

The  Lymphatic  Vessels  of  the  Female  Urethra. — The  lymphatics  of  the  female 
urethra  terminate  in  the  same  manner  as  do  the  lymphatics  of  the  bulb  and  mem- 
branous portions  of  the  male  urethra 

The  Lymphatic  Vessels  of  the  Uterus. — These  consist  of  three  sets,  each  of  which 
arises  by  a  network  of  capillaries.  There  is  a  mucous  network,  a  muscular  network, 
and  a  peritoneal  network.  The  vessels  from  these  three  regions  of  origin  are  col- 
lected in  the  subperitoneal  tissue,  from  which  area  the  collecting  trunks  take  origin. 
From  the  cervix,  according  to  Poirier  and  Cun^o,  come  from  five  to  eight  collecting 
trunks,  which  pass  toward  the  sides  of  the  body  of  the  uterus,  forming  on  each 
side,  by  twisting  and  dilatation,  the  juxta-cervical  lymphatic  knot  of  Cun^o.  The 
cervical  connecting  trunks  are  divisible  into  three  groups  on  each  side.  One  group 
is  composed  of  two  vessels,  which  pass  to  the  middle  chain  of  the  external  iliac 
glands  (superior  and  middle  glands).  Another  group  is  composed  of  two  vessels, 
which  enter  the  hypogastric  glands.  A  third  group  is  composed  of  several  vessels, 
some  of  which  enter  the  lateral  sacral  glands,  and  the  balance  of  which  terminate 


804  THE   LYMPHATIC  SYSTE^I 

in  the  glands  of  the  sacral  promontory.  From  the  body  of  the  uterus  come  three 
groups  on  each  side.  One  group  is  composed  of  four  or  five  vessels  which  emerge 
below  the  uterine  cornu,  pass  beneath  the  ovary,  where  they  receive  the  ovarian 
lymphatics,  and  terminate  in  the  juxta-aortic  glands  of  the  same  side.  One 
so-called  accessory  lymphatic  pedicle  terminates  in  the  external  iliac  glands,  the 
other  in  the  inguinal  glands. 

The  Lymphatic  Vessels  of  the  Fallopian  Tube. — The  lymphatics  of  the  Fallopian 
tube  join  with  those  of  the  uterus  and  ovary  and  terminate  in  the  lateral  aortic 
glands. 

The  Lymphatic  Vessels  of  the  Ovary. — The  ovary  is  extremely  rich  in  lymphatics ; 
thev  form  a  plexus  which  is  superficial  to  the  veins.  The  vessels  leading  from  this 
plexus,  four  or  five  in  number,  pass  upward  in  company  with  the  ovarian  vessels 
and  end  in  the  lateral  aortic  glands.  Above  the  fifth  lumbar  vertebra  these  ves- 
sels anastomose  with  the  lymphatics  from  the  fundus  of  the  uterus  and  Fallopian 
tube.  Quite  often  there  is  a  lymph-vessel  which  emerges  from  the  ovary,  passes 
downward  and  outward  and  ends  in  the  middle  chain  of  the  internal  iliac  glands. 

The  Lymphatic  Vessels  of  the  Vagina. — The  lymphatics  of  the  vagina  are  cHvided 
into  those  of  the  mucous  coat  and  those  of  the  muscular  coat;  these  anastomose 
freely  with  each  other  and  terminate  in  a  peri-vaginal  network,  which  is  drained 
by  three  groups  of  trunks.  One  group  drains  the  upper  third  of  the  vagina  and 
passes  to  the  middle  chain  of  the  external  iliac  glands.  A  second  group  is  efl^erent 
to  the  middle  third  of  the  vagina  and  ends  in  the  hypogastric  glands.  A  third 
group  carries  the  lymph  from  the  lower  third  of  the  vagina  to  the  gland  of  the 
promontory. 

The  Lymphatic  Vessels  of  the  Testicle. — The  lymphatic  vessels  of  the  testicle 
consist  of  two  sets,  superficial  and  deep;  the  former  commence  on  the  visceral  sur- 
face of  the  tunica  vaginalis,  the  latter  in  the  epididymis  and  body  of  the  testis. 
They  form  several  large  trunks  which  ascend  with  the  spermatic  cord,  and,  accom- 
panying the  spermatic  vessels  into  the  abdomen,  terminate  in  the  juxta-aortic 
and  sometimes  also  in  the  pre-aortic  glands ;  hence  the  enlargement  of  these  glands 
in  malignant  disease  of  the  testis. 

The  Lymphatic  Vessels  of  the  Vas  Deferens. — These  lymphatics  empty  into  the 
external  iliac  glands. 

The  Lymphatic  Vessels  of  the  Seminal  Vesicles. — A  network  exists  on  the  surface 
of  each  vesicle,  formed  by  a  collection  of  lymph-vessels  from  the  mucous  lining  and 
from  the  muscular  structure  of  the  vesicle.  The  trunks  from  this  network  empty 
into  the  external  and  internal  iliac  glands. 

The  Lymphatic  Vessels  of  the  Kidney,  Ureter,  and  Suprarenal  Capsule. — Their 
courses  and  terminations  differ  on  the  two  sides.  They  take  origin  from  a  super- 
ficial network  just  beneath  the  capsule  of  the  kidney  and  a  deep  network  in  the  in- 
terior of  the  organ.  The  superficial  network  is  connected  to  the  collecting  vessels 
of  the  deep  network  at  the  hilum.  From  the  superficial  network  numerous  ves- 
sels penetrate  the  capsule  of  the  kidney  and  join  the  lymphatics  of  the  fatty  cap- 
sule. According  to  Poirier,  Cuneo,  and  Delamare,^  anterior  and  posterior  trunks 
come  off  from  the  deep  lymphatics  of  the  right  kidney.  The  anterior  trunk 
usually  terminates  in  the  right  juxta-aortic  glands  which  lie  upon  the  vena  cava. 
The  posterior  trunks  terminate  in  the  juxta-aortic  glands  which  lie  behind  the 
vena  cava.  On  the  left  side  all  the  collecting  trunks  terminate  in  the  juxta-aortic 
glands  of  the  left  side  of  the  aorta. 

The  lymphatics  of  the  fatty  capsule  of  the  kidney  communicate  with  the  lym- 
phatics of  the  kidney^  and  both  terminate  in  the  same  glands.  The  lymphatics  of 
the  suprarenal  capsule  terminate  in  the  juxta-aortic  glands  of  the  same  side.    From 

'  The  Lymphatics.    Translated  and  edited  by  Cecil  H.  Leaf. 


THE  LYMPHATIC   VESSELS  OF  THE  ABDOMEN  AND  PELVIS    805 

the  ureter  lymph-vessels  come  off  and  terminate  in  the  juxta-aortic  and  adjacent 
glands. 

The  Lymphatic  Vessels  of  the  Liver. — The  lymphatic  vessels  of  the  liver  are 
divisible  into  two  sets,  superficial  and  deep.  The  former  arise  in  the  lobules  at  the 
periphery  of  the  liver  and  pass  to  the  subperitoneal  connective  tissue  over  the 
entire  organ.  The  latter  arise  from  the  deeper  lobules,  and  emerge  from  the  liver 
along  the  portal  vein  or  the  hepatic  veins. 

According  to  Poirier,  Cuneo,  and  Delamare,*  three  groups  of  superficial  collect- 
ing trunks  arise  from  the  subperitoneal  network.  The  'posterior  trunks  divide 
into  three  groups.  The  single  right  posterior  trunk  terminates  in  a  gland  about  the 
coeliac  axis.  The  middle  posterior  trunks  (five  to  seven  in  number)  pass  through 
the  opening  in  the   Diaphragm.     The   left   posterior   trunks   pass   into  glands 


LEFT   LATERAL 

LIGAMENT 


OBLrTERATED 
UMBILICAL  VEIN 


Fig.  506. — Lymphatics  of  the  inferior  surface  of  the  liver.     (Sappey.) 

about  the  subdiaphragmatic  portion  of  the  oesophagus.  The  anterior  collecting 
trunks  terminate  in  the  lymph-glands  of  the  hilum  of  the  liver.  The  superior 
trunks  ascend.  One  of  these  trunks  or  a  posterior  trunk  passes  with  the  vena  cava 
through  the  Diaphragm  and  terminates  in  glands  about  the  vena  cava.  Another 
trunk,  an  anterior  one,  pas.ses  over  the  anterior  border  of  the  liver,  runs  for  a  time 
wnth  the  round  ligament,  and  terminates  in  the  hepatic  glands.  Numerous  middle 
trunks  ascend  in  the  suspensory  ligament,  unite  beneath  the  Diaphragm  into  a 
short  trunk  of  large  size,  which  passes  through  the  Diaphragm  and  divides  into 
several  smaller  ducts,  which  terminate  in  the  glands  back  of  the  xiphoid  cartilage. 
Trunks  from  the  superficial  lymphatic  network  also  emerge  from  the  inferior 
surface  of  the  liver.  The  posterior  trunks  from  the  right  lobe  reach  the  vena  cava 
and  terminate  in  the  glands  about  the  intra-thoracic  end  of  that  vessel.  The 
middle  and  anterior  trunks  from  the  right  lobe  reach  the  glands  along  the  cystic 
duct.  The  trunks  from  the  left  lobe  terminate  in  the  glands  along  the  hepatic 
artery.  The  trunks  from  the  lobus  Spigelii  reach  the  glands  of  the  hilum  and  the 
glands  about  the  lower  intra-thoracic  portion  of  the  vena  cava.  The  trunks  from 
the  quadrate  lobe  terminate  in  the  glands  of  the  hilum.    The  deep  collecting  trunks 

'  The  Lympliatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


806 


THE   LYMPHATIC  SYSTEM 


are  divisible  into  two  groups.  One  group  descends  along  the  portal  vein,  the  other 
ascends  along  the  hepatic  veins. 

Sappey  pointed  out  that  the  deep  descending  trunks  accompany  the  bile  pass- 
ages and  the  branches  of  the  portal  vein,  several  anastomosing  vessels  accom- 
panying each  branch  of  the  portal  vein.  The  same  authority  affirmed  that  from 
fifteen  to  eighteen  trunks  emerge  from  the  hilum  and  terminate  in  the  adjacent 
glands.  The  dee'p  ascending  trunks  surround  as  a  sheath  the  branches  of  the 
hepatic  vein  (Sappey).  As  they  approach  the  Diaphragm  they  diminish  in  num- 
ber to  five  or  six,  pass  through  the  opening  for  the  vena  cava,  and  terminate  in 
the  glands  about  the  lower  portion  of  the  intra-thoracic  cava. 

The  Lymphatic  Vessels  of  the  Bile-ducts. — The  lymphatics  of  the  bile-ducts  arise 
from  the  mucous  membrane  and  from  within  the  muscular  tissue,  and  terminate 
in  glands  along  the  cystic  and  common  ducts. 

The  Lymphatic  Vessels  of  the  Stomach  (Figs.  507  and  508). — The  lymphatic 
vessels  of  the  stomach  consist  of  two  sets,  superficial  and  deep.  The  superficial 
arise  from  the  outer  (serous)  and  the  middle  (muscular)  coats.  The  deep  arise 
from  the  mucous  membrane  and  form  a  network  in  the  submucous  tissue.  Trunks 
from  the  submucous  network  pass  through  the  muscular  tunic  and  terminate  in 
the  trunks  coming  from  the  sero-muscular  layers.    These  latter,  the  musculo-serous 


CORONARY 
CURRENT 


RIGHT 

OASTRO-EPIPLOIC 

CURRENT 


SPLENIC 
CURRENT 


Fig.  507. — Lymphatic  areas  of  the  stomach.     (Cun6o.) 

collecting  trunks,  are  divided  into  three  groups.  The  first  group  is  composed  of  six 
or  eight  vessels  which  pass  toward  the  lesser  curvature  (Sappey).  There  are  from 
three  to  ten  glands  upon  the  lesser  curvature  along  the  course  of  the  gastric  artery 
which  receive  these  superior  trunks.  Vessels  come  to  these  glands  from  the  cardia, 
from  the  body  of  the  stomach,  and  from  the  pyloric  end.  In  the  lesser  curvature 
the  lymphatic  vessels  lie  in  the  wall  of  the  stomach.  According  to  Cun^o,  two- 
thirds  of  the  stomach  is  drained  by  the  lymph-vessels  of  group  I.  The  second 
group  comprises  the  trunks  from  the  greater  curvature  which  end  in  the  subpyloric 
glands.  The  glands  along  the  greater  curvature  are  some  distance  from  the 
stomach  wall  in  the  pyloric  region,  and  lymph-streams  flow  from  left  to  right,  that 
is,  toward  the  pylorus  and  not  from  it.  These  lymphatics  drain  one-third  of  the 
stomach.  The  first  and  second  groups  send  lymph  eventually  to  the  coeliac 
glands  and  juxta-aortic  glands.  The  third  group  comprises  trunks  which  come 
from  the  fundus  of  the  stomach  and  enter  the  lymphatic  glands  about  the  spleen. 

Surgical  Anatomy. — Mikulicz  pointed  out  the  early  infection  of  the  glands  of  the  lesser  curva- 
ture in  pyloric  cancer,  and  insisted  that  in  operation  for  pyloric  cancer  the  entire  lesser  curvature 
must  be  removed.  Cuneo  showed  us  that  in  pyloric  cancer  the  fundus  and  two-thirds  of  the 
greater  curvature  usually  remain  free  from  disease,  because  the  lymph-current  is  toward  the 
pylorus  and  not  from  it.  Of  course,  if  the  lymphatics  become  blocked,  the  lymph-current  may 
be  reversed  (regurgitation),  and  then  infection  of  these  parts  can  occur.  William  J.  Mayo  has 
noted  the  ''lymphatic  isolation"  of  the  dome  of  the  stomach.    In  operating  for  cancer  of  the 


THE   LYMPHATIC  SYSTEM   OF    THE   INTESTINES 


807 


pylorus,  make  the  section  of  the  stomach  as  directed  by  Hartmann,  that  is,  a  section  which 
removes  all  of  the  lesser  curvature  and  cuts  the  greater  curvature  well  to  the  left  of  the  subpyloric 
glands.  • 

The  Lymphatic  Vessels  of  the  Pancreas.— The  lymphatics  of  the  pancreas  arise 
from  a  network  about  the  pancreatic  lobules.  The  collecting  trunks  anastomose 
freely  on  the  surface  of  the  pancreas.  Some  of  the  trunks  terminate  in  the 
splenic  glands,  which  send  vessels  to  the  coeliac  glands.  Others  terminate  directly 
in  the  coeliac  glands.  The  lymphatics  of  the  head  of  the  pancreas  communicate 
with  the  duodenal  lymphatics  and  the  lymphatics  of  the  lower  end  of  the  com- 
mon duct.    The  pancreatic  and  splenic  lymphatics  probably  communicate. 

The  Lymphatic  Vessels  of  the  Spleen. — The  lymphatics  of  the  spleen  consist  of 
two  sets,  superficial  and  deep;  the  former  are  placed  beneath  its  peritoneal  covering, 
the  latter  in  the  substance  of  the  organ;  they  accompany  the  blood-vessels,  passing 
through  a  series  of  small  glands,  and  pass  into  the  splenic  glands  which  are  placed 
in  the  omentum  between  the  spleen  and  pancreas.  The  gastro-splenic  omentum 
contains  no  glands. 

THE  LYMPHATIC  SYSTEM  OF  THE  INTESTINES. 

The  Lymphatic  Glands  of  the  Small  Intestine  (Fig.  509). — The  lymphatic 
glands  of  the  small  intestine  are  placed  between  the  layers  of  the  mesentery,  and  are 


RIGHT  GASTRO 
EPIPLOIC  ARTCRY 


SUBPYLORIC 
GLAND 


LEFT  PNEUMO- 
GASTRIC  NERVE 


RIGHT  PNEUMO- 
GASTRIC  NERVE 


CORONARY 

VEIN 

GLANDS  OFTHE 

LESSER  CURVATURE 


RIGHT  GASTRO 
EPIPLOIC  VEIN 


Fig.  508. — General  view  of  the  subperitoneal  lymphatic  plexus  of  the  stomach  prepared  by  the  method  of 

Gerota.     (Cun6o.) 


called  mesentery  glands  (lymphoglandulae  mesentericae) .  They  vary  in  number  from 
a  hundred  to  a  hundred  and  fifty,  and  in  size  from  that  of  a  pea  to  that  of  a  small 


808 


THE  LYMPHATIC  SYSTEM 


almond/  These  glands  are  most  numerous  and  largest  above,  the  glands  of  the 
jejunum  being  more  numerous  than  those  of  the  ileum.  This  latter  group  becomes 
enlarged  and  infiltrated  with  deposit  in  cases  of  fever  accompanied  v^ith  ulceration 
of  the  intestines.  The  glands  diminish  in  number  as  we  descend  until  the  ileo- 
csecal  region  is  reached,  when  a  number  of  glands  appear  about  the  ileo-ceecal 
artery.  The  mesenteric  glands  receive  the  lacteals  and  send  out  trunks  to  the 
receptaculum  chyli.  The  chyle  from  the  intestine  passes  through  the  glands  on 
its  way  to  the  thoracic  duct. 

The  glands  may  be  divided  into:  I.  A  group  of  glands  the  members  of  which 
are  chiefly  found  along  the  terminal  vessels  from  the  vascular  loops  of  the  intestinal 
branches  of  the  superior  mesenteric  artery.  Some  glands  of  this  group  are  placed 
upon  "the  anterior  surface  of  the  upper  end  of  the  jejunum."^  II.  A  group  of 
glands  along  the  vascular  loops  of  the  superior  mesenteric  artery.  Most  of  them 
are  between  the  primary  loops.  Some  of  them  are  between  the  secondary  and 
tertiary  loops.  III.  A  group  of  glands  along  the  trunk  of  the  superior  mesenteric 
artery. 


Fig.  509. — Lymphatics  of  the  small  intestine.     (Poirier  and  Charpy.) 

The  L3miphatic  Vessels  of  the  Small  Intestine  (Fig.  509).— The  lymphatic 
vessels  of  the  small  intestine  are  called  lacteals,  from  the  milk-white  fluid  they 
usually  contain.  They  take  origin  in  the  intestinal  villi  and  in  lymphatic  sinuses 
around  the  bases  of  the  solitary  glands.  Lymphatic  plexuses  exist  in  the  submucous 
tissue,  the  muscular  coat,  and  the  subserous  tissue.  The  lymphatic  vessels  pass 
between  the  layers  of  the  mesentery,  enter  the  mesenteric  glands,  and  finally  unite 
to  form  two  or  three  large  trunks  which  terminate  separately  in  the  receptaculum 
chyli;  frequently,  however,  they  first  unite  to  form  a  single  large  trunk,  termed  the 
intestinal  lymphatic  trunk  (Figs.  483,  484,  and  511). 

The  Lymphatic  Glands  of  the  Large  Intestine.— The  lymphatic  glands  of  the 
large  intestine  are  divided  into  the  colic  glands  and  rectal  glands. 

The  Colic  Glands  {lymphoglandulae  coliacae). — The  colic  glands  are  subdivided 
into:  1.  The  ileo-colic  or  ileo-ca^cal  glands  (Fig.  510),  which  he  along  the  course 
of  the  ileo-cohc  artery,  one  or  two  of  the  glands  being  placed  upon  the  anterior 
surface  of  the  caecum.     The  mesoappendix  also  contains  a  gland  which  com- 


'  Leaf  (Surgical  Anatomy  of  the   Lymphatic  Glands)  says  it  is  very  common"  to  find  not  more  than  forty  or 
fifty. 

■•i  The  Surgical  Anatomy  of  the  Lymphatic  Glands.      By  Cecil  H.  Leaf. 


THE   LYMPHATIC  SYSTEM    OF    THE    INTESTINES 


809 


municates  with  glands  in  the  mesocolon,  and  receives  lymph  from  the  appendix 
and,  in  the  female,  from  the  ovary.  2.  Glands  in  the  mesocolon  along  the  right 
colic  artery,  which  receive  lymph  from  the  ascending  colon  and  the  hepatic  flexure. 
3.  Glands  in  the  mesocolon  along  the  middle  colic  artery,  which  receive  lymph 
from  the  hepatic  flexure  and  transverse  colon.  4.  Glands  in  the  mesocolon 
along  the  left  colic  artery,  which  receive  lymph  from  the  descending  colon  and 
sigmoid  flexure.  The  vessels  from  the  colic  glands  pass  to  the  pre-aortic 
glands. 

The  Rectal  Glands. — The  rectal  glands  lie  in  the  mesorectum;  they  receive  lymph 
from  the  anus  antl  rectum  and  it  passes  from  them  to  the  lumbar  and  sacral  glands. 

The  Lymphatic  Vessels  of  the  Large  Intestine.— The  lymphatic  vessels  of  the 
large  intestine  consist  of  three  sets:  those  of  the  caecum,  ascending  and  transverse 


ANTERIOR 
LYMPHATICS 
OF  OECUM 


GLAND  OF 
APPENDIX 


Fig.  510.  — Anterior  view  of  the  lymphatics  of  the  Cffcum  and  appendix.     (Poirier  and  Charpy.) 

colon,  which,  after  passing  through  their  proper  glands,  enter  the  mesenteric 
glands;  those  of  the  descending  colon  and  sigmoid  flexure,  which  pass  to  the  lumbar 
glands,  and  those  of  the  rectum  and  anus,  which  pass  to  the  sacral  and  superficial 
inguinal  glands. 

Lymphatics  of  the  Anus  and  Rectum. — These  vessels  take  origin  from  two 
networks,  one  from  the  skin  and  mucous  membrane  and  the  other  from  the  mus- 
cular coat.  The  lymph-vessels  from  the  skin  at  the  anal  margin  pass  to  the  super- 
ficial inguinal  glands.  Some  vessels  from  the  skin  of  the  anus  ascend  and  reach 
the  submucous  plexus  of  the  rectum,  from  which  region  lymph-vessels  pass  to 
the  rectal  glands,  to  the  glands  along  the  middle  haemorrhoidal  artery,  and  along 
the  inferior  haemorrhoidal  artery,  and  to  a  pelvic  gland  near  the  origin  of  the 
internal  pudic  artery.*  The  vessels  from  the  anal  mucous  membrane  and  from 
the  muscular  wall  of  the  rectum  penetrate  the  muscular  wall  of  the  rectum 
with  the  arteries  and  reach  the  rectal  glands. 


'  The  Lymphatics.     By  Poirier,  Cun<!'o,  and  Delamare.    Translated  and  edited  by  Cecil  H.  Lieaf. 


810  THE   LYMPHATIC  SYSTEM 

THE  LYMPHATICS  OF  THE  THORAX. 

The  thoracic  lymphatics  are  divided  into  the  deep  lymphatics  of  the  chest  wall, 
the  diaphragmatic  lymphatics,  and  the  visceral  lymphatics. 

The  Lymphatic  Glands  of  the  Thoracic  Wall  or  the  Parietal  Lymphatics. 

The  lymphatic  glands  of  the  thoracic  wall  include  the  internal  mammary  and 
intercostal  glands. 

The  Internal  Mammary  Glands. — The  internal  mammary,  retro-sternal,  or 
sternal  glands  form  a  chain  of  five  or  six  glands  on  each  side  of  the  sternum  along 
the  course  of  the  corresponding  internal  mammary  artery,  and  back  of  the  Internal 
intercostal  muscles.  The  glands  are  separated  from  the  pleura  by  cellular  tissue. 
The  internal  mammary  glands  receive  vessels  from  the  diaphragmatic  glands,  the 
abdominal  muscles  above  the  umbilicus,  the  anterior  ends  of  the  intercostal  spaces, 
the  skin  over  the  sternum,  and  the  mammary  gland.  The  vessels  given  off  by 
each  chain  form  a  single  trunk.  On  the  right  side  this  trunk  terminates  at  the 
junction  of  the  internal  jugular  and  subclavian  veins,  unites  with  the  subclavian 
lymph-trunk  to  form  the  right  lymphatic  duct,  or  empties  directly  into  the  sub- 
clavian trunk  (Fig.  486).  On  the  left  side  it  empties  either  at  the  junction  of 
the  subclavian  and  internal  jugular  veins  or  into  the  thoracic  duct. 

The  Intercostal  Glands  (lymphoglandulae  intercostales)  (Fig.  511). — The  inter- 
costal glands  are  small  glands  lying  in  the  intercostal  spaces  along  the  intercostal 
arteries.  In  the  posterior  end  of  each  space  they  are  constantly  found.  These  are 
called  the  posterior  glands,  and  there  are  one,  two,  or  three  in  each  space.  These 
glands  are  opposite  the  neck  of  the  rib  or  over  the  articulation  of  the  rib  with  the 
vertebra.  The  pleura  is  in  front  of  them,  and  they  lie  upon  the  external  inter- 
costal muscles.  In  the  middle  of  the  intercostal  spaces  are  inconstant  glands 
which  are  called  lateral  glands.  They  are  merely  interrupting  nodes  in  the 
trunks  from  the  intercostal  muscles.  The  intercostal  glands  receive  vessels  from 
the  intercostal  muscles  and  pleura.  They  send  vessels  back  toward  the  spine, 
which  unite  with  lymphatics  from  the  back  part  of  the  thorax  and  spinal  canal, 
and  which  pass  down  the  spine  and  terminate  in  the  thoracic  duct. 

The  Diaphragmatic  Ljmiphatics.— The  diaphragmatic  lymph-glands  are  dis- 
tinct and  numerous.  These  glands  are  on  the  convex  surface  of  the  Diaphragm 
and  are  divided  into  an  anterior,  a  middle,  and  a  posterior  group.  They  receive 
vessels  from  the  Diaphragm  and  liver  and  send  vessels  to  the  internal  mammary 
and  posterior  mediastinal  glands.  The  lymph- vessels  of  the  Diaphragm  take 
origin  from  a  capillary  network  contained  in  the  spaces  between  the  muscular 
and  tendinous  fasciculi  of  the  Diaphragm.  Numerous  lymph-vessels  descend 
until  they  reach  the  subperitoneal  tissues  and  then  ascend.  Others  immediately 
ascend  to  beneath  the  pleura.  The  collecting  trunks  are  all  on  the  convex  surface 
of  the  Diaphragm.  The  lymphatic  vessels  of  the  Diaphragm  anastomose  with 
the  lymphatic  vessels  of  the  pleura  and  the  peritoneum.  This  subperitoneal 
network  is  so  extensive  that  absorption  in  this  region  is  extremely  rapid. 
Hence,  after  an  abdominal  operation,  if  salt  solution  has  been  left  in  the  ab- 
domen, it  will  be  very  rapidly  absorbed  if  the  foot  of  the  bed  is  elevated. 
Influenced  by  the  knowledge  that  the  pelvic  peritoneum  absorbs  comparatively 
slowly  and  the  peritoneum  in  the  upper  abdomen  very  rapidly,  and  that  septic 
processes  in  the  upper  abdomen  are  more  rapidly  fatal  than  septic  processes  in 
the  pelvis.  Fowler  was  led  to  recommend  the  elevation  of  the  head  of  the  bed 
after  operations  for  abdominal  infections.  This  posture  causes  poisonous  fluids 
to  gravitate  away  from  the  Diaphragm. 


THE    LYMPHATIC    GLANDS    OF    THE    THORACIC    WALL     811 

The  Visceral  Lymphatics. — The  visceral  lymphatics  include  the  anterior  medi- 
astinal glands,  the  posterior  mediastinal  glands,  and  the  peritracheo-bronchial  glands. 

The  Anterior  Mediastinal  Glands  {lymphoglandulae  mediastinales  anteriores) . — The 
anterior  mediastinal  glands  are  in  the  upper  portion  of  the  anterior  mediastinum, 
a  group  of  six  or  seven  glands  lying  above  and  upon  the  front  of  the  transverse 


MEDIASTINAL 

GLANDS  AND 

VESSELS 


INTERCOSTAL 

GLANDS  AND 

VESSELS 


COMMON   INTE8 
TINAL  TRUNK 

PRE-AORTIC 
GLANDS  AND 
VESSELS 
LUMBAR 

COMMON   INTES- 
TINAL TRUNK 


INTERNAL  ILIAC 
EXTERNAL  ILIAC 


Fig.  511. — Deep  lymphatic  glands  and  vessels  of  the  thorax  and  abdomen  (diagrammatic).    Afferent  vessels  are 
represented  by  continuous  lines,  and  efferent  and  interglandular  vessels  by  dotted  lines.      (Cunningham.) 


portion  of  the  arch  of  the  aorta  and  sending  glandular  chains  toward  the  neck. 
On  the  right  side  these  glands  are  found  between  the  innominate  artery  and  vein 
and  in  front  of  the  vein.  On  the  left  side  they  are  in  front  of  and  behind  the  left 
common  carotid  and  left  subclavian  arteries.  They  receive  lymph  from  the  heart, 
pericardium,  thymus  gland,  and  anterior  mediastinum. 


§12  THE   LYMPHATIC  SYSTEM 

The  Posterior  Mediastinal  Glands  (lymphoglandulae  mediastinales  posteriores) 
(Fig.  511). — The  posterior  mediastinal  glands  are  behind  the  pericardium  and 
in  front  of  the  oesophagus.  Occasionally  one  or  two  are  placed  back  of  the 
oesophagus.  They  receive  vessels  from  the  intercostal  glands,  aortic  glands, 
deep  cervical  glands,  and  pleura,  and  send  vessels  to  the  thoracic  duct. 

The  Peritracheo-bronchial  Glands. — The  peritracheo-bronchial  glands  are  divided 
by  Barety  into  four  groups.  One  group  is  in  the  angle  formed  by  the  junction 
of  the  trachea  and  right  bronchus.  Another  group  is  in  a  corresponding  situation 
on  the  left  side.  Another  group  is  below  the  tracheal  bifurcation.  The  glands  of 
the  fourth  group  are  about  the  points  of  division  of  the  larger  bronchi.  The 
peritracheo-bronchial  glands  receive  lymph-vessels  from  the  lung,  heart,  peri- 
cardium, oesophagus,  trachea,  and  thymus. 

In  infancy  these  glands  present  the  same  appearance  as  the  lymphatic  glands  in  other  situa- 
tions. In  early  adult  life  they  assume  a  brownish  tinge,  and  in  old  age  become  deep  black, 
because  they  arrest  particles  of  carbon  brought  from  the  bronchi.  This  change  is  known  as 
anthracosis,  and  the  darkened  glands  are  usually  sclerotic.  In  fact,  in  old  age  these  glands  often 
lose  all  lymphatic  characters  and  become  fibrous  masses.  These  glands  enlarge  from  infection, 
and  when  very  large  may  compress  the  bronchi,  the  pulmonary  artery,  etc.  They  are  often  the  seat 
of  tuberculous  deposits. 

The  Lsnnphatic  Vessels  of  the  Thoracic  Wall. — The  lymphatic  vessels  of  the 
thoracic  wall  include  the  deep  lymphatic  vessels,  intercostal  and  internal  mammary, 
which  have  been  described,  the  cutaneous  lymphatics,  and  the  lymphatics  of  the 
mammary  gland. 

The  Cutaneous  Lymphatics  (Fig.  497).— The  area  drained  by  these  lymphatics 
is  very  extensive.  It  is  divided  by  Poirier,  Cun^o,  and  Delamare  into  three  regions. 
The  anterior  region  extends  from  over  the  middle  of  the  sternum  to  the  anterior  axil- 
lary line.  The  trunks  pass  to  the  axilla  and  terminate  in  the  thoracic  chain  of  the 
axillary  glands.  From  this  anterior  region  some  accessory  trunks  pass  above  the 
clavicle  and  reach  the  supra-clavicular  glands,  and  trunks  may  arise  to  one  side 
of  the  mid-sternal  line  and  pass  to  the  opposite  axilla.  From  the  lateral  region  the 
trunks  ascend  to  the  thoracic  chain  of  axillary  glands.  This  region  is  between 
the  anterior  and  posterior  axillary  lines.  The  posterior  region  is  back  of  the 
posterior  axillary  line,  and  includes  the  thorax  to  the  mid-line,  and  the  posterior 
portion  of  the  root  of  the  neck.  The  trunks  from  the  posterior  area  empty  into 
the  scapular  group  of  axillary  glands. 

Lymphatics  of  the  Mammary  Gland  (Figs.  496  and  512).— There  are  two  sets 
of  lymphatics  in  this  gland,  the  cutaneous  or  superficial  and  the  glandular  or  deep. 

The  Peripheral  Cutaneous  Lymphatics  of  the  Mammary  Gland. — The  peripheral 
cutaneous  lymphatics  do  not  arise  from  the  nipple.  Their  collecting  trunks  are 
arranged  as  are  other  collecting  trunks  of  the  anterior  portion  of  the  thorax,  and 
end  in  the  thoracic  group  of  axillary  glands  of  the  same  side.  Trunks  arising  from 
the  sternal  margin  of  the  skin  of  the  breast  may  run  to  the  glands  of  the  opposite 
axilla. 

The  Central  Deep  Lymphatics  of  the  Mammary  Gland. — The  central  lymphatics 
form  a  very  extensive  network  in  the  nipple  and  areola,  and  from  this  network 
numerous  vessels  pass  into  a  plexus  beneath  the  areola,  Sappey's  subareolar  plexus; 
most  of  the  trunks  coming  from  the  gland  also  enter  the  subareolar  plexus. 

The  Glandular  Lymphatics  of  the  Mammary  Gland. — The  glandular  lymphatics 
arise  from  spaces  about  the  lobules  and  from  networks  about  the  milk-ducts.  We 
can  distinguish  a  chief  lymphatic  channel  and  three  accessory  channels. 

The  chief  lymphatic  channel  takes  origin  from  collecting  trunks  which  begin 
in  the  spaces  about  the  lobules  and  in  the  lymph-capillaries  about  the  milk-ducts. 
These  collectors  pass  toward  the  nipple  and  terminate  in  the  subareolar  plexus, 
which  plexus  also  receives  the  vessels  from  the  areola  and  nipple.     Two  large 


THE   LYMPHATIC    GLANDS    OF    THE    THORACIC    WALL     813 

trunks  take  origin  from  the  subareolar  plexus :  one  from  its  inner  side,  the  other 
from  its  outer  side.  "The  internal  trunk  runs  at  first  downward  and  then  out- 
ward, turning  round  the  inferior  border  of  the  subareolar  plexus.  It  is  thus 
directed  toward  the  axilla  and  runs  in  the  subcutaneous  cellular  tissue,  along  the 
lower  border  of  the  Pectoralis  major,  which  it  crosses  at  the  level  of  the  third 
rib  to  reach  the  base  of  the  axilla.  This  collecting  trunk  constantly  receives  as 
afferents  one  or  two  fair-sized  trunks  coming  directly  from  the  inferior  portion  of 
the  mammary  gland.  The  external  trunk,  which  is  usually  smaller  than  the  pre- 
ceding, runs  directly  outward  toward  the  axilla.  Before  it  reaches  the  latter  it 
is  augmented  by  a  vessel  coming  from  the  superior  part  of  the  gland.  At  the  base 
of  the  axilla  these  two  collecting  trunks  perforate  the  axillary  aponeurosis  and 
terminate  in  one  or  two  glands,  placed  on  the  inner  wall  of  the  axilla  on  the  third 
digitation  of  the  Serratus  magnus  muscle.  These  glands  (the  principal  regional 
glands  of  the  breast)  may  or  may  not  be  covered  by  the  lower  part  of  the  Pec= 


Fig.  512. — The  vessels  and  lymphatics  of  the  anterior  face  of  the  mammary  glands.     (Sappey.) 

toralis  major  muscle  according  to  the  muscular  development  of  the  subject  (Sur- 
gius)."^  These  glands  constitute  the  supero-internal  mass  of  the  anterior  axillary 
chain.  An  interrupting  gland  is  sometimes  found  in  the  course  of  these  two 
trunks,  the  paxamammaxy  gland. 

The  Accessory  Channels  from  the  Mammary  Gland. — The  accessory  channels  from 
the  mammary  gland,  according  to  Poirier,  Cun^o,  and  Delamare,  are  three.  They 
call  one  the  accessory  axillary  channel.  It  is  not  constant,  and  there  may  be  inter- 
rupting glands  on  its  collectors.  Its  collectors  come  off  from  the  inferior  portion 
of  the  mammary  gland  and  pass  directly  to  the  axillary  glands.  Another  channel 
is  the  subclavian  channel.  Neither  is  it  constant.  It  comes  off  from  the  posterior 
surface  of  the  mammary  gland,  pierces  the  great  Pectoral  muscle,  and  ascends 
between  the  greater  and  lesser  Pectorals  to  reach  the  subclavian  glands.    There 

'  The  Lymphatics.     By  Poirier,  Cun<5o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


814  THE   LYMPHATIC  SYSTEM 

are  usually  interrupting  glands  along  this  channel,  the  retro-pectoral  glands.  The 
subclavian  channel  runs  along  the  superior  thoracic  artery.  They  call  the  third 
accessory  channel  the  internal  mammary  channel.  The  collecting  trunks  arise 
from  the  inner  portion  of  the  mammary  gland  and  pass  along  the  vessels  sent  off 
from  the  internal  mammary  artery  to  the  gland.  They  pierce  the  Pectoral  and 
Intercostal  muscles  and  reach  the  internal  mammary  glands.  This  channel  is 
constant  and  along  it  there  may  be  interrupting  glands. 

Lymphatics  of  the  Great  Pectoral  Muscle. — The  lymphatics  of  the  great  Pectoral 
muscle  end  in  the  subclavian  glands,  the  thoracic  group  of  axillary  glands,  and 
the  internal  mammary  glands. 

Surgical  Anatomy. — A  knowledge  of  the  lymphatics  of  the  breast  and  of  the  glands  into  which 
the  lymphatics  drain  is  of  the  first  importance  to  a  surgeon.  Certain  surgical  deductions  from 
the  anatomy  of  this  region  are  perfectly  obvious — viz. :  1 .  If  the  skin  of  the  mammary  gland  is 
involved  in  carcinoma,  the  thoracic  group  of  axillary  glands  of  the  same  side  is  involved.  If  the 
skin  over  the  sternal  margin  of  the  gland  is  involved,  the  glands  of  the  opposite  axilla  may  be  can- 
cerous, as  from  this  point  lymph-vessels  rise  and  pass  across  the  mid-line.  If  the  skin  of  the 
sternal  margin  is  involved  the  prognosis  is  worse  than  if  it  is  free,  the  opposite  axilla  may  be 
cancerous,  and  the  opposite  breast  may  become  diseased.  2.  When  lymphatic  ducts  become 
blocked  by  cancer  cells  the  lymph  backs  up,  flows  backward  instead  of  in  its  proper  direc- 
tion, and  may  cause  infecton  in  the  most  unsuspected  situations.  For  instance,  a  block  in  the 
cutaneous  lymphatics  of  a  portion  of  the  breast  may  lead  to  infection  of  the  opposite  breast  and 
axilla,  though,  of  course,  it  is  not  so  likely  to  as  is  cancer  of  the  skin  of  the  sternal  margin.  By 
regurgitation  of  lymph  the  head  of  the  humerus  or  the  retro-sternal  structures  may  become  dis- 
eased in  mammary  cancer.  3.  If  the  nipple  or  areola  is  cancerous,  the  entire  gland  is  sure  to  be 
diseased,  as  the  lymphatic  network  of  this  region  empties  into  the  subareolar  plexus,  and  most 
of  the  trunks  coming  from  the  gland  also  enter  this  plexus.  4.  If  the  mammary  gland  is  cancer- 
ous, all  of  the  axillary  glands  are  regarded  as  diseased,  as  the  main  lymphatic  channel  from  the 
breast  reaches  the  glands  on  the  inner  wall  of  the  axilla  upon  the  third  digitation  of  the  Ser- 
ratus  magnus.  Furthermore,  in  many  cases  an  accessory  lymph-channel  comes  off  from  the 
lower  portion  of  the  mammary  gland  and  passes  directly  to  the  axilla.  5.  The  subclavian  glands 
are  to  be  regarded  as  diseased,  because  in  a  certain  proportion  of  cases  (the  exact  proportion 
being  uncertain)  an  accessory  lymph-channel  comes  off  from  the  posterior  surface  of  the  mam- 
mary gland,  passes  through  the  great  Pectoral  muscle  and  ascends  between  the  greater  and 
lesser  Pectorals  to  reach  the  subclavian  glands.  6.  The  element  which  greatly  interferes  with 
the  cure  of  mammary  carcinoma  is  the  existence  of  lymph-channels  which  arise  from  the  inner 
portion  of  the  mammary  gland,  pierce  the  greater  Pectoral  and  Internal  intercostal  muscles,  and 
reach  the  internal  mammary  glands.  Mediastinal  involvement  is  apt  to  be  earlier  in  carcinoma 
of  the  inner  portion  of  the  breast  than  in  carcinoma  of  other  portions,  and  the  prognosis  is  par- 
ticularly bad  in  cancer  of  the  inner  portion  of  the  breast.  What  is  known  as  the  sternal  symptom 
of  Snow  is  bulging  of  the  sternum  due  to  involvement  of  the  thymus  gland.  7.  The  sternal 
portion  of  the  great  Pectoral  and  the  tissue  between  it  and  the  lesser  Pectoral  muscle  are  to  be 
regarded  as  diseased,  because  in  some  cases  an  accessory  lymph-channel  from  the  breast  pene- 
trates the  greater  Pectoral  and  ascends  to  the  subclavian  glands.  This  trunk  has  several  inter- 
rupting or  satellite  glands,  the  retro-pectoral  glands,  in  the  tissue  back  of  the  great  Pectoral 
muscle.  8.  When  the  great  Pectoral  muscle  is  diseased,  cancer  cells  soon  spread  widely  through 
the  sternal  portion  of  the  muscle,  and  this  entire  portion  of  the  muscle  becomes  cancerous.  The 
clavicular  portion  does  not  suffer  early,  but  escapes  until  the  cancer  becomes  extensive,  as  it 
is  anatomically  distinct  from  the  sternal  portion.  If  the  fibres  of  the  great  Pectoral  are  exten- 
sively diseased,  the  thoracic  group  of  axillary  glands,  the  subclavian  glands,  and  possibly  the 
internal  mammary  glands  are  involved.  9.  The  only  operation  in  cancer  of  the  breast  which 
offers  any  real  hope  of  cure  is  one  which  is  done  early  and  is  radical.  10.  It  must  be  done 
early,  because  delay  permits  involvement  of  the  mediastinum,  and  if  the  disease  has  entered 
the  mediastinum  operation  is  hopeless.  If  the  sternum  is  bulged  operation  is  useless,  and 
nothing  short  of  amputation  at  the  shoulder-joint  could  be  of  help  if  the  head  of  the  humerus 
is  enlarged  by  the  disease.  Even  this  radical  procedure  is  of  no  avail,  because  the  mediastinum 
is  certainly  involved  if  the  head  of  the  humerus  is  diseased.  11.  If  the  lymph-glands  above 
the  clavicle  are  extensively  diseased  operation  is  useless,  as  in  such  cases  the  mediastinum  is 
sure  to  be  involved.  12.  A  radical  operation  means  the  removal  of  the  skin  of  the  breast  with 
the  nipple  and  areola,  the  subcutaneous  tissue  of  this  region,  the  entire  breast  the  sternal 
portion  of  the  great  Pectoral  with  its  fascia,  the  retro-pectoral  glands  and  tissue,  all  the  con- 
tents of  the  axilla  except  vessels  and  nerves,  the  glands  and  cellular  tissue  beneath  the  anterior 
margin  of  the  Latissimus  dorsi,  and  the  subclavian  glands.  It  is  probably  always  wisest  to 
open  above  the  clavicle  as  well  as  below  to  facilitate  the  removal  of  glands.    It  is  seldom  necessary 


THE   LYMPHATIC    GLANDS    OF    THE    THORACIC    WALL     815 

to  remove  the  clavicular  portion  of  the  greater  Pectoral.  The  lesser  Pectoral  does  not  require 
removal,  but  it  should  be  taken  away,  because  of  the  added  safety  and  speed  thus  obtained 
in  cleaning  the  great  vessels  and  because  its  retention  does  not  improve  the  functional  result. 
The  surgeon  must  remember  that  the  breast  is  a  much  larger  organ  than  we  used  to  think,  and 
all  of  its  irregular  projections  and  outlying  lobules  must  be  removed  (p.  793).  Formerly, 
surgeons  did  not  completely  remove  the  breast,  but  only  got  rid  of  a  large  portion  of  it. 

The  Pulmonary  Lymphatics. — The  pulmonary  lymphatics  arise  from  net- 
works betw^een  the  lobules,  around  the  bronchi  and  under  the  mucous  membrane. 
The  collecting  trunks  are  in  two  sets,  superficial  and  deep:  the  former  are  placed 
beneath  the  pleura,  forming  a  minute  plexus  which  covers  the  outer  surface  of 
the  lung;  the  latter  accompany  the  blood-vessels  and  run  along  the  bronchi;  they 
both  terminate  at  the  root  of  the  lungs  in  the  tracheo-bronchial  glands. 

The  Pleural  Lymphatics. — The  lymphatics  of  the  pulmonary  pleura  pass  into  the 
superficial  pulmonary  trunks;  those  from  the  costal  pleura  enter  the  intercostal 
trunks;  those  from  the  diaphragmatic  pleura  enter  the  diaphragmatic  trunks,  and 
those  from  the  mediastinal  pleura  enter  the  posterior  mediastinal  glands.^ 

The  Cardiac  Ljnnphatic  Vessels. — The  cardiac  lymphatic  vessels  consist  of 
two  sets,  superficial  and  deep:  the  former  arise  in  the  subpericardial  areolar  tissue  of 
the  surface,  and  the  latter  in  the  subendocardial  tissue.  From  the  network  of  deep 
lymphatics  trunks  pass  to  the  superficial  lymphatics.  The  superficial  lymphatics 
follow  the  course  of  the  coronary  vessels.  Two  trunks  are  formed:  an  anterior, 
which  lies  in  the  anterior  interventricular  furrow,  and  an  inferior,  which  lies  in 
the  inferior  interventricular  furrow.  These  two  trunks  collect  the  lymph  from  the 
ventricles  and  pass  to  the  base  of  the  heart,  where  they  receive  lymph  from  the 
auricles.  The  anterior  or  left  trunk  ascends  between  the  left  auricle  and  the  pul- 
monary artery  on  the  posterior  surface  of  the  artery,  perforates  the  pericardium,  and 
enters  the  glands  about  the  tracheal  bifurcation.  The  right,  posterior  or  inferior 
trunk  ascends  between  the  aorta  and  pulmonary  artery  and  terminates  in  the  same 
group  of  glands  as  the  left  tnmk. 

The  Thymic  Ljnnphatic  Vessels. — The  thymic  lymphatic  vessels  arise  from 
the  under  surface  of  the  thymus  gland,  and  enter  the  anterior  mediastinal,  the 
internal  mammary,  and  the  peritracheo-bronchial  glands. 

The  Lymphatic  Vessels  of  the  CEsophagus. — The  lymphatics  of  the  thoracic 
oesophagus  arise  from  two  networks,  one  beneath  the  mucous  membrane  and  one 
beneath  the  muscular  fasciculi.  The  connecting  trunks  terminate  in  the  peri- 
oesophageal  glands. 

The  Ljrmphatic  Vessels  of  the  Thoracic  Trachea. — The  lymphatics  of  the 
thoracic  trachea  take  origin  from  a  network  in  the  submucous  tissue.  From  this 
a  number  of  collecting  trunks  pass  through  the  trachea  in  the  line  of  junction  of 
the  cartilaginous  with  the  membranous  portion.  They  terminate  the  peritracheo- 
bronchial  glands. 

'  The  Lymphatics.     By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE   NEEVOUS   SYSTEM. 


THE  nervous  system  consists  of  (1)  the  cerebro -spinal  nervous  system  and  (2) 
the  sympathetic  nervous  system. 
1.  The  Cerebro-spinal  Nervous  System  is  composed  of  the  spinal  cord  and 
brain  and  of  nerves  joined  to  the  brain  and  cord.  The  spinal  cord  and  brain 
constitute  the  cerebro-spinal  axis,  or,  as  it  is  also  called,  the  encephalo-spinal  axis, 
the  neuraxis,  or  the  central  nervous  system.  The  nerves  which  join  the  cord  and 
which  join  the  brain  constitute  the  peripheral  nervous  system.  The  term  central 
nervous  system  is  applied  to  structures  contained  altogether  within  the  spinal 
and  cranial  cavities,  but  this  narrow  uc?  is  not  strictly  accurate.  By  far  the  greater 
part  of  the  central  nervous  system  i:  contained  within  those  cavities,  but  any 
centre  of  energy  must  be  regarded  as  a  portion  of  the  central  system,  and  certain 
ganglia  which  are  centres  of  energy  lie  along  certain  nerves  and  really  belong  to 
the  central  nervous  system,  though  they  are  discussed  with  the  peripheral  nerves. 

The  term  peripheral  nervous  system  does  not  mean,  as  it  would  seem  to, 
structures  outside  the  spinal  and  cranial  cavities.  The  chief  part  of  the  peripheral 
system  is  outside  of  the  spinal  and  cerebral  cavities,  but  peripheral  nerves 
"sometimes  run  a  considerable  distance  within  these  cavities."^  The  peripheral 
nerv^ous  syst.^m  is  composed  of  thirty-one  pairs  of  spinal  nerves  and  twelve 
pairs  of  cranial  nerves.  Each  spinal  nerve  is  joined  to  the  spinal  cord  by  two  roots, 
an  anterior  and  a  posterior  root,  and  the  posterior  root  at  one  point  has  an  enlarge- 
ment called  a  spinal  ganglion.  The  fifth  cranial  nerve,  alone  among  cranial  nerves, 
takes  origin  by  two  roots,  as  does  a  spinal  nerve.  Five  of  the  cranial  nerves 
possess  ganglia  similar  to  the  ganglia  on  the  posterior  roots  of  the  spinal  nerves. 
The  cranial  nerves  which  possess  ganglia  are  the  trigeminal  or  fifth,  the  facial  or 
seventh,  the  auditory  or  eighth,  the  glosso-pharyngeal  or  ninth,  and  the  pneumo- 
gastric  or  tenth. 

2.  The  Sympathetic  Nervous  System  consists  of  a  chain  of  ganglia  on  either  side 
of  the  vertebral  column.  The  ganglia  of  each  chain  are  joined  by  cords  of  nervous 
matter.  The  sympathetic  system  contains,  beside  the  gangliated  cords,  numerous 
nerve  plexuses  and  ganglia  in  various  regions.  The  sympathetic  nervous  system 
is  closely  connected  at  many  points  with  the  cerebro-spinal  nervous  system,  and 
the  two  systems  in  all  probability  develop  from  a  common  origin. 

Structure  of  the  Cerebro-spinal  Nervous  System. — The  spinal  cord  and 
brain  contain  gray  matter  and  white  matter.  The  gray  matter  is  vascular  and  is 
composed  chiefly  of  nerve-cells:  the  white  matter  is  less  vascular  and  is  composed 
chiefly  of  nerve-fibres.  Until  recently  it  was  the  custom  to  regard  nerve-cells  and 
nerve-fibres  as  definitely  distinct  elements,  but  we  now  know  that  nerve-fibres  are 
processes  of  nerve-cells.  One  process,  several  processes,  or  many  processes  come 
off  from  nerve-cells.  If  there  is  but  one  process  from  a  cell,  that  process  becomes 
Deiters'  process,  the  axis- cylinder  or  axone  of  a  nerve-fibre.  If  more  than  one 
process  comes  off  from  a  cell,  one  of  the  processes  becomes  an  axone,  and  the 
other  processes  are  known  as  protoplasmic  or  dendritic  processes,  or,  as  His  named 

'  The  Nervous  System  and  its  Diseases.     By  Charles  K.  Mills. 

52.  (817) 


818 


THE   NERVOUS   SYSTEM 


them,  dendrites.  There  are  no  nerve-fibres  unconnected  with  cells.  The  nerve- 
cell,  with  its  axone  and  its  dendrites,  constitutes  what  is  called  a  nerve-unit  or 
neurone.  The  nervous  system  is  said  to  be  composed  of  aggregations  of  multitudes 
of  neurones.    The  term  neurone  was  devised  by  Waldeyer  in  1891. 

Gray,  vesicular,  or  cineritious  substance  is  of  a  dark,  reddish-gray  color  and  of  a 
soft  consistence.  It  is  found  in  the  spinal  cord,  brain,  and  various  ganglia,  in 
some  of  the  nerves  of  special  sense,  and  in  gangliform  enlargements  in  the  course 
of  certain  spinal  nerves.  It  is  composed  of  nerve-cells  and  contains  blood-vessels, 
both  the  cells  and  vessels  being  embedded  in  a  ground  substance  named  by 
Virchow  the  neuroglia.  The  nerve-fibres  and  the  vessels  in  the  white  substance 
are  also  embedded  in  neuroglia.  Neuroglia  consists  of  fibres  and  neuroglia  cells. 
Some  of  the  cells  are  stellate  in  shape  and  their  fine  processes  become  neuroglia- 
fibres,  which  extend  radially  and  unbranched  (Fig.  513  B)  among  the  nerve-cells 
and  fibres,  which  they  aid  in  supporting.  Other  cells  give  off  fibres,  which  branch 
repeatedly  (Fig.  513  A). 


Fici.  513.— Neuroglia-cells  of  brain  shown  by  Golgi's  method.      A.  Cell  with  branched  processes.      B.  Spider- 
cell  with  unbranched  processes.     (After  Andriezen.)     (Copied  from  Schiifer's  Essentials  of  Histology.) 


In  addition  to  these  fibres  there  are  others  which  do  not  appear  to  be  connected 
with  the  neuroglia-cells.  They  start  from  the  lining  ependi/mal  cells,  that  is,  the 
epithelial  cells  lining  the  ventricles  of  the  brain  and  central  canal  of  the  spinal 
cord,  and  pass  through  the  nervous  tissue,  branching  repeatedly,  to  terminate  in 
slight  enlargements  on  the  pia  mater.  Thus,  neuroglia  is  evidently  a  connective 
tissue  in  function,  though  it  is  not  in  development;  it  is  epiblastic  in  origin,  whereas 
all  true  connective  tissues  are  mesoblastic. 

The  white  or  fibrous  tissue  is  composed  of  nerve-fibres,  which,  with  blood- 
vessels, are  embedded  in  neuroglia. 

Nerve-cells  or  the  Cell-bodies  of  the  Neurones  (Figs.  514,  515,  516,  517,  518,  and 
519). — Nerve-cells  constitute  the  essential  element  of  nervous  tissue.  They  are  the 
originators  of  nervous  impulses  and  impressions.  All  nervous  conduction  is  from 
nerve-cell  to  nerve-cell  by  contact  (Mills),  and  the  transmission  of  an  impulse 
from  one  nerve-cell  to  another  may  be  over  a  long  distance.  The  nerve-cells  of 
the  brain  and  cord  differ  in  origin,  development,  and  connections  from  the  nerve- 
cells  of  the  spinal  ganglia.  They  vary  greatly  in  shape  and  size  (Fig.  515). 
Some  are  so  small  that  they  become  visible  only  under  a  microscope  of  high 


STRUCTURE    OF    THE    CEBEBBO- SPINAL    NERVOUS   SYSTEM    819 

power;  some  "almost  come  within  the  range  of  unaided  vision."*  The  largest 
cells  are  found  in  the  anterior  cornua  of  the  spinal  cord,  in  the  vesicular  columns 
of  Clarke,  in  the  large  pyramidal  cell-layer  of  the  cerebral  cortex,  and  the  Purkin- 
jean  cell-layer  of  the  cerebellum.  The  smallest  cells  are  in  the  olfactory  bulbs, 
in  the  substantia  gelatinosa  Rolandi  of  the  cord,  and  in  the  granular  cortical 
layers  of  the  cerebrum  and  cerebellum. 


Fig.  .514. — Nerve-cells  from  the  Gasserian 
Kanglion  of  the  human  subject,  a.  A  globu- 
lar one  with  defined  border,  h.  Its  nucleus, 
c.  Its  nucleolus,  d.  Caudate  cell.  e.  Elon- 
gated cell  with  two  groups  of  pigment-par- 
ticles. /.  Cell  surrounded  by  its  sheath  or 
capsule  of  nucleated  particles,  a.  The  sanrie, 
the  sheath  only  being  in  focus.  Magnified  300 
diameters. 


Axone. 


Fig.  515. — Nerve-cells  from  the  inner  part  of  the 
gray  matter  of  the  convolutions  of  the  human  brain. 
Nerve-cells:  a.  Larger,  b.  Smaller,  c.  Nerve-fibre 
with  axis-cylinder.     Magnified  350  times. 


'heath  of 
cell  body. 

Nucleus. 

Cell  protoplasm. 


Axone. 
Myelin  sheath. 


Fig.  516. — Bipolar  nerve-cells  from  the  spinal  gan- 
glion of  the  pike.      (After  Kiilliker.) 


•>^  A.rnne. 


Fig.  517. — Motor  nerve-cell  from  ventral  horn 
of  spinal  cord  of  rabbit.  The  angular  and  spindle- 
shaped  Nissl  bodies  are  well  shown.  (After 
Nissl.) 


The  Body  of  the  nerve-cell  may  possess  a  limiting  membrane,  as  is  seen  in  the 
cells  of  the  spinal  ganglia  (Fig.  516)  and  sympathetic  ganglia,  and  some  of  the 
cells  of  the  Gasserian  ganglion  (Figs.  514,  /  and  g),  but  may  be  devoid  of  any 
limiting  membrane,  as  is  .seen  in  the  motor  cells  of  the  anterior  cornua  of  the  cord 
(Fig.  517).  All  cell-bodies,  like  all  cell-processes,  show  intracellular  fibrillation, 
and  the  fibrils  of  the  cell-body  are  continuous  with  those  of  the  axone  and  run  in 


'  Text-book  of  Anatomy.     By  Prof.  D.  J.  Cunningham. 


820 


THE   NERVOUS   SYSTEM 


various  directions.  The  cell-body  is  composed  of  protoplasm,  which  contains, 
besides  fibrils,  many  fine  spindle-shaped  granules.  The  granules  stain  deeply 
and  are  called  chromatophile  granules,  Nissl's  bodies,  or  trigoid  bodies  (Fig.  517). 
They  are  probably  nucleo-albumins  (Held).  Most  nerve-cells,  certainly  most  large 
nerve-cells,  possess  considerable  pigmented  material,  a  nucleus,  and  a  nucleolus. 
The  nucleus  (Fig.  514  h)  is,  as  a  rule,  a  large,  well-defined,  round,  vesicular 
body,  often  presenting  an  intranuclear  network.      It  contains  a  nucleolus  (Fig. 

514  c),  which  is  peculiarly  clear  and  bril- 
liant. Figment  granules  (Fig.  514  e), 
when  present,  he  by  the  side  of  the  nu- 
cleus. Masses  of  pigment  are  present 
in  the  cells  of  the  substantia  nigra  and 
locus  caeruleus. 

Nerve-cells  are  divided  for  purposes 
of  study  into  three  groups,  according  to 
the  number  of  their  processes. 

1.  Unipolar  Cells. — The  single  process 
of  such  a  cell,  after  a  short  course,  divides 
in  a  T-shaped  manner.  Unipolar  cells 
are  found  in  the  spinal  ganglia  of  the 
adult  and  among  the  olfactory  cells  of 
mammals. 


Fig.  518. — Pyramidal  cell  from  the  cerebral  cortex 
of  a  mouse.      (After  Ramon  y  Cajal.) 


Fig.  519. — Cell  of  Purkinje  from  the  cerebellum  of 
a  cat.     (After  Ramon  y  Cajal.) 


2.  Bipolar  cells  (Fig.  516)  are  found  in  spinal  ganglion-cells  when  the  cells  are  in 
an  embryonic  condition.  They  are  best  demonstrated  in  the  sympathetic  ganglion- 
cells  of  a  frog.  Sometimes  the  processes  come  off  from  opposite  poles  of  the  cell, 
and  the  cell  then  assumes  a  spindle  shape;  in  others  they  both  emerge  at  the  same 
point.  In  some  cases  where  two  fibres  are  apparently  connected  with  a  cell,  one 
of  the  fibres  is  really  derived  from  an  adjoining  nerve-cell  and  is  passing  to  end 
in  a  ramification  around  the  ganglion-cell,  or,  again,  it  may  be  coiled  spirally 
around  the  nerve-process  which  is  issuing 'from  the  cell. 


I 


STRUCTURE    OF    THE    CEBEBRO- SPINAL    NERVOUS  SYSTEM    821 

3.  Multipolar  cells  (Fig.  517)  are  caudate  or  stellate  in  shape,  and  are  character- 
ized by  their  large  size  and  by  the  tail-hke  processes  which  issue  from  them.  The 
processes  are  of  two  kinds :  one  of  them  is  the  axis-cyhnder  or  axone ;  the  others 
are  the  protoplasmic  processes  or  dendrites. 

The  Axone  (Figs.  515,  516,.  517,  518,  and  519). — ^The  axone  emerges  from  the 
nerve-cell  by  a  slender  stalk;  it  is  smooth  and  free  from  Nissl's  bodies;  it  main- 
tains a  uniform  diameter  for  a  considerable  distance;  it  does  not,  as  a  rule,  divide 
into  branches,  although  it  may  possess  collaterals,  and  it  becomes  the  axis-cylinder 
of  a  nerve-fibre.  Cerebro-spinal  axones,  as  a  rule,  are  medullated,  except  near 
their  terminations.  Sympathetic  axones  are  non-medullated.  Axones  may  be 
extremely  short  or  may  be  several  feet  in  length.  The  fibres  of  the  pyramidal 
tract  are  axones  of  great  length.  Some  short  axones  divide  at  their  terminations 
into  many  branches.  Short  axones  are  called  dendraxones,  and  the  cells  with  den- 
draxones  are  called  the  second  type  of  Golgl  cells.  An  axone  may  remain  throughout 
its  entire  course  in  the  brain  or  cord  or  may  enter  into  a  spinal  or  cerebral  nerve. 
Most  cells  possess  but  one  axone,  and  such  a  neurone  is  called  monoaxonic.  A  cell 
may  possess  two  axones,  the  neurone  being  called  diaxonic,  or  several  axones,  the 
neurone  being  called  polyaxonic.  The  collaterals  are  branches  given  off  from  the 
neurone  at  right  angles  to  it.  Some  axones  have  a  number  of  collaterals;  others 
do  not  have  any.  They  are  present  everywhere  in  the  central  nervous  system 
(Cajal,  Kolliker).  Some  collaterals  are  medullated;  others  are  not.  They 
approach  the  dendrites  of  the  nerve-cells  of  the  neurones.  Each  axone  and  col- 
lateral ends  in  a  button-like  termination  or  end-tuft,  or  in  a  free  arborization,  the 
end-brush.  If  the  termination  is  within  the  brain  or  cord,  it  may  wrap  around 
nerve-cells  or  arborize  about  dendrites.  If  the  axone  emerges  from  the  cerebro- 
spinal axis,  it  terminates  about  muscle-cell  or  some  other  structure.  The  termi- 
nation of  the  axone  or  the  collateral  is  never  continued  into  the  structure  about 
which  it  lies.  It  may  surround  that  tissue;  it  may  touch  it;  it  may  lie  close  against 
it,  but  the  termination  is  free,  and  the  relation  is  simply  one  of  contact  and  not  of 
continuity. 

The  Dendrites. — ^The  dendrites  are  protoplasmic  processes  resembling  in  struc- 
ture and  staining  reactions  the  protoplasm  of  the  body  of  the  cell.  Each  emerges 
by  a  thick  base  (gemmule),  and  divides  into  many  fine  branches,  with  free  ends. 
They  are  not  straight,  are  not  smooth,  and  do  not  maintain  the  same  diameter  for 
a  considerable  distance  as  does  the  axis-cylinder.  A  dendrite  may  branch  at 
any  distance  from  the  body  of  the  cell,  and  the  branches  do  not  join.  The  den- 
drites from  a  single  cell  vary  greatly  in  number,  thickness,  and  length.  Some 
cells  are  devoid  of  dendrites;  some  give  off  a  few;  some  give  off  many.  As  a  rule, 
they  are  non-medullated. 

The  Theory  of  Neurones. — This  theory  maintains  that  the  nervous  system  is  com- 
posed of  a  multitude  of  units  called  neurones.  Each  neurone  consists  of  a  cell  and 
processes.  The  neurones  in  aggregation  form  cell  groups  and  fibre  systems.  The 
connection  of  nerve-cells  with  other  nerve-cells  is  not  by  continuity  of  structure. 
It  is  by  contact  and  not  by  actual  junction;  it  is  physiological  and  not  anatomical. 
"When  fully  developed  in  man,  perhaps  a  very  small  number  of  neurones  are 
united  together  by  concrescence  or  protoplasmic  bridges,  but  their  predominant 
relation  is  certainly  that  of  contact  or  synapsis."^  Process  comes  in  contact  with 
process,  or  process  with  cell.  The  terminal  tufts  of  the  axone  of  a  cortical  motor- 
cell  surround  a  cell  in  the  anterior  horn  of  the  spinal  cord,  and  this  spinal  cell 
sends  out  an  axone,  the  termination  of  which  reaches  a  muscle.  Doubt  has  of 
late  arisen  as  to  the  neurone  theory,  because  of  the  investigations  of  Apathy  and 
others.     Apathy  claims  that  ganglion  cells  join  directly  and  that  the  ultimate 

1  Anatomy  of  the  Brain  and  Nervous  System.     By  Harris  E.  Santee. 


822 


THE  NERVOUS  SYSTEM 


elements  of  the  nervous  system  are  neurofibrils,  which  pass  from  cell  to  celL 
However,  as  stated  by  Szymonowicz/  Apathy's  observations,  even  if  correct,  do 
not  disprove  the  neurone  theory,  but  indicate  that  the  nervous  units  or  neurones 
are  occasionally  connected  by  neurofibrils. 

Nerve-fibres. — Nerve-fibres  serve  to  conduct  nervous  impulses  and  bring  nerve- 
cells  into  relation  with  each  other  and  into  relation  with  other  structures.  Nerves 
are  composed  of  numbers  of  nerve-fibres  bound  into  bundles.  There  are  two  sorts 
of  fibres:  medullated  or  white  and  non-meduUated  or  gray. 

The  Medullated  fibres  form  the  white  part  of  the  brain  and  spinal  cord,  and 
also  the  greater  part  of  the  cerebro-spinal  nerves,  and  gives  to  these  structures 
their  opaque,  white  aspect.  When  perfectly  fresh  they  appear  to  be  homoge- 
neous; but  soon  after  removal  from  the  body  they  present,  when  examined  by 
transmitted  light,  a  double  outline  or  contour,  as  if  consisting  of  two  parts  (Figs. 
520  and  521).  The  central  portion  is  named  the  axis-cylinder  of  PUrkinje  (Fig. 
521);  around  this  is  a  sort  of  sheath  of  fatty  material,  staining  black  with  osmic 


Fig.  520. — White  or  medullated  nerve- 
fibres  showing  the  sinuous  outline  and 
double  contours.     (After  Schafer.) 


Fibrils  of  axis- 
cylinder. 

Neurilemma. 


Segment  of 
Lantermann. 

White  substance 
of  Schwann 
stained  black 
by  osmic  add. 


Fig.  521. — Longitudinal  section  through  a  nerve-fibre- 
from  the  sciatic  nerve  of  a  frog.  X  830.  (After  Buhm  and 
Davidoff.) 


acid,  named  the  white  substance  of  Schwann  (Fig.  521),  which  gives  to  the  fibre 
its  double  contour,  and  the  whole  is  enclosed  in  a  delicate  membrane,  the  neuri- 
lemma, primitive  sheath,  or  nucleated  sheath  of  Schwann  (Fig.  521). 

The  axis-cylinder  is  the  essential  part  of  the  nerve-fibre,  and  is  always  present ; 
the  other  parts,  the  medullary  sheath  and  the  neurilemma,  being  occasionally 
absent,  especially  at  the  origin  and  termination  of  the  nerve-fibre.  It  undergoes 
no  interruption  from  its  origin  in  the  nerve-centre  to  its  peripheral  termination, 
and  must  be  regarded  as  a  direct  prolongation  of  a  nerve-cell.  It  constitutes 
about  one-half  or  one-third  of  the  nerve-tube,  the  whole  substance  being  greater 
in  proportion  in  the  nerves  than  in  the  central  organs.  It  is  perfectly  transparent, 
and  is  therefore  indistinguishable  in  a  perfectly  fresh  and  natural  state  of  the 
nerve.  It  is  made  up  of  exceedingly  fine  fibrils,  which  stain  darkly  with  gold 
chloride  (Fig.  521).  At  its  termination  the  axis-cylinder  of  a  nerve-fibre  may  be 
seen  to  break  up  into  fibrillse,  confirming  the  accepted  view  of  its  structure.  These 
fibrillae  6ave  been  termed  the  primitive  fibrillae  of  Schultze.    The  axis-cylinder  is  said 


'  Text-book  of  Histology  and  Microscopic  Anatomy.    By  Dr.  Ladislaus  Szymonowicz.   Translated  and  edited 
by  John  Bruce  MacCallum,  M.D. 


DEVELOPMENT   OF  NERVE  CELLS   AND    FIBRES  823 

by  some  to  be  enveloped  in  a  special,  reticular  sheath,  which  separates  it  from  the 
white  matter  of  Schwann,  and  is  composed  of  a  substance  called  neurokeratin. 
The  more  common  opinion  is  that  this  network  or  reticulum  is  contained  in  the 
white  matter  of  Schwann,  and  by  some  it  is  believed  to  be  produced  by  the  action 
of  the  reagents  employed  to  demonstrate  it.  The  medullary  sheath  or  white  sub- 
stance of  Schwann  (Fig.  521)  is  regarded  as  being  fatty  matter  in  a  fluid  state,  which 
insulates  and  protects  the  essential  part  of  the  nerve — the  axis-cylinder.  The  white 
matter  varies  in  thickness  to  a  very  considerable  extent,  in  some  nerve-fibres  forming 
a  layer  of  extreme  thinness,  so  as  to  be  scarcely  distinguishable;  in  others  forming 
about  one-half  of  the  nerve-tube.  The  size  of  the  nerve-fibres,  which  varies  from 
^q^qO  to  xToT  of  an  inch,  depends  mainly  upon  the  amount  of  the  white  substance, 
though  the  axis-cylinder  also  varies  in  size  within  certain  limits.  The  white  sub- 
stance of  Schwann  does  not  always  form  a  continuous  sheath  for  the  axis-cylinder, 
but  undergoes  interruptions  in  its  continuity  at  regular  intervals,  giving  to  the 
fibre  the  appearance  of  constriction  at  these  points.  These  constrictions  were  first 
described  by  Ranvier,and  are  known  as  the  nodes  of  Ranvier  (Fig.  522).  The  portion 


Fig.  522. — \  node  of  Ranvier  of  a  medullated  nerve-fibre,  viewed  from_  above,  magnified  about  750  diameters. 
The  medullary  sheath  is  discontinuous  at  the  node,  whereas  the  axi.s-cylinder  passe.s  from  one  segment  into  the 
other.     At  the  node  the  sheath  of  Schwann  appears  thickened.     (Klein  and  Noble  Smith.) 

of  nerve-fibre  between  two  nodes  is  called  an  intemodal  segment.  The  neurilemma 
or  primitive  sheath  is  not  interrupted  at  the  nodes,  but  passes  over  them  as  a  con- 
tinuous membrane.  In  addition  to  these  interruptions  obHque  clefts  may  be  seen 
in  the  medullary  .sheath,  subdividing  it  into  irregular  portions,  which  are  termed 
medullary  segments  or  segments  of  Lantermann  (Fig.  521).  There  is  reason  to 
believe  that  these  clefts  are  artificially  produced  in  the  preparation  of  the  speci- 
mens. Medullated  nerve-fibres,  when  examined,  frequently  present  a  beaded  or 
varicose  appearance;  this  is  due  to  manipulation  and  pressure  causing  the  oily 
matter  to  collect  into  drops,  and  in  consequence  of  the  extreme  delicacy  of  the 
primitive  sheath,  even  slight  pressure  will  cause  the  transudation  of  the  fatty 
matter,  which  collects  as  drops  of  oil  outside  the  membrane.  This  is,  of  course, 
promoted  by  the  action  of  certain  reagents. 

The  neurilemma  or  primitive  sheath,  sometimes  called  the  tubular  membrane  or 
sheath  of  Schwann  (Fig.  521),  presents  the  appearance  of  a  delicate,  structureless 
membrane.  Here  and  there  beneath  it,  and  situated  in  depressions  in  the  white 
matter  of  Schwann,  are  nuclei  surrounded  by  a  small  amount  of  protoplasm. 
The  nuclei  are  oval  and  somewhat  flattened,  and  bear  a  definite  relation  to  the 
nodes  of  Ranvier;  one  nucleus  generally  lying  in  the  centre  of  each  internode. 
The  primitive  sheath  is  not  present  in  all  medullated  nerve-fibres,  being  absent 
in  those  fibres  which  are  found  in  the  brain  and  spinal  cord. 

Non-medullated  Fibres. — Most  of  the  nerves  of  the  sympathetic  system,  and 
some  of  the  cerebro-spinal,  consist  of  another  variety  of  nervous  fibres,  which  are 
called  the  gray  or  gelatinous  nerve- fibres — fibres  of  Remak  (Fig.  523).  These  con- 
sist of  a  central  core  or  axis-cylinder  enclosed  in  a  nucleated  sheath,  which  tends 
to  split  into  fibrillse,  and  is  probably  of  the  nature  of  neurokeratin.  In  external 
appearance  the  gelatinous  nerves  are  semi-transparent  and  gray  or  yellowish- 
gray.  The  individual  fibres  vary  in  size,  generally  averaging  about  half  the  size 
of  the  medullated  fibres. 

Development  of  Nerve-cells  and  Fibres. — The  nerve-cells  are  developed 
from  certain  of  the  cells  which  line  the  neural  canal  and  form  the  neural  crest  of  the 
embryo.    Some  of  these  cells  assume  a  rounded  form  and  are  termed  neuroblasts, 


824 


THE   NERVOUS  SYSTEM 


and  from  each  neuroblast  there  grows  out  a  process,  the  axis-cyhnder  process  or 
axone,  and  subsequently  the  branching  processes  or  dendrons.  The  axis-cylin- 
ders, at  first  naked,  acquire  their  medullary  sheaths,  possibly  by  some  metamor- 
phosis of  their  outer  layer.  The  neurilemma  is  thought  to  be  derived  from 
mesoblastic  cells  which  become  flattened  and  wrapped  around  the  fibre,  the 
cement-substance  at  their  opposed  ends  forming  the  material  which  stains  with 
silver  nitrate  at  the  nodes  of  Ranvier.  Nerve-cells  in  the  sympathetic  and  periph- 
eral ganglia  take  their  origin  from  small  collections  of  neuroblasts,  which  are  split 
off  from  the  rudimentary  spinal  ganglia.  Cells  which  are,  originally,  similar  to 
neuroblasts  seem  to  give  rise  to  neuroglia-cells,  numerous  processes  sprouting  from 
the  cell  to  form  the  neuroglial  fibres. 

Chemical  Composition. — The  amount  of  water  in  nervous  tissue  varies  with 
the  situation.  Thus  in  the  gray  matter  of  the  cerebrum  it  constitutes  about  83  per 
cent.,  in  the  white  matter  from  the 
same  region  about  70  per  cent.,  while 
in  the  peripheral  nerves,  such  as  the 
sciatic,  it  may  fall  to  60  per  cent. 
The  solids  consist  of  proteids  (in 
the  gray  matter  proteids  constitute 
half  the  total  solids),  neurokeratin, 
nuclein,  protagon,  lecithin,  cerebro- 


FiG.  523. — A  small  nervous  branch  from  the 
sympathetic  of  a  mammal,  a.  Two  medullated 
nerve-fibres  among  a  number  of  gray  nerve-fibres,  6. 


Fig.  524. — Transverse  section  through  a  microscopic 
nerve,  representing  a  compound  nerve-bundle,  sur- 
rounded by  perineurium.  Magnified  120  diameters. 
The  medullated  fibres  are  seen  as  circles  with  a  cen- 
tral dot — viz..  medullary  sheath  and  axis-cylinder — in 
transverse  section.  They  are  embedded  in  endoneurium, 
containirig  numerous  nuclei,  which  belong  to  the  con^ 
nective-tissue  cells  of  the  latter,  p.  Perineurium,  con- 
sisting of  lamina;  of  fibrous  connective  tissues,  alter- 
nating with  flattened  nucleated  connective-tissue  cells. 
/.  Lymph-space  between  epineurium  and  surface  of 
nerve-bundle.     (Klein  and  Noble  Smith.) 


sides,  cholesterin,  nitrogenous  extractives,  and  salts,  with  some  gelatin  and  fat 
from  the  adherent  connective  tissue. 

The  nervous  structures  are  divided,  as  before  mentioned,  into  two  great  systems 
— viz.,  the  cerebro-spinal,  comprising  the  spinal  cord  and  brain,  the  nerves  con- 
nected with  these  structures  and  the  ganglia  situated  on  them;  and  the  sympa- 
thetic, consisting  of  a  double  chain  of  ganglia  and  the  nerves  connected  with  thern. 
All  these  structures  require  separate  consideration ;  they  are  composed  of  the  two 
kinds  of  nervous  tissue  above  described,  intermingled  in  various  proportions,  and 
having,  in  some  parts,  a  very  intricate  arrangement. 

The  nerves  are  round  or  flattened  cords,  formed  of  a  number  of  nerve-fibres. 
They  are  connected  at  one  end  with  the  cerebro-spinal  centre  or  with  the  ganglia, 
and  are  distributed  at  the  other  end  to  the  various  textures  of  the  body;  they 
are  subdivided  into  two  great  classes — the  cerebro-spinal,  which  proceed  from  the 
cerebro-spinal  axis,  and  the  S3rmpathetic  or  ganglionic  nerves,  which  proceed  from 
the  ganglia  of  the  sympathetic.     The  cerebro-spinal  nerves  consist  of  numerous 


CHEMICAL    COMPOSITION  825 

nerve-fibres  collected  together  and  enclosed  in  a  membranous  sheath  (Fig.  524). 
A  small  bundle  of  primitive  fibres, enclosed  in  a  tubular  sheath,  is  called  a  funiculus: 
if  the  nerve  is  of  small  size,  it  may  consist  only  of  a  single  funiculus;  but  if  large, 
the  funiculi  are  collected  together  into  larger  bundles  or  fasciculi,  which  are  bound 
together  in  a  common  membranous  investment. 

In  structure  the  common  membranous  investment,  or  sheath  of  the  whole  nerve, 
which  is  called  the  epineurium,  as  well  as  the  septa  given  off  from  it,  and  which 
separate  the  fasciculi,  consists  of  connective  tissue,  composed  of  white  and  yellow 
elastic  fibres,  the  latter  existing  in  great  abundance.  The  tubular  sheath  of  the 
funiculi,  called  the  perineurium,  consists  of  a  fine,  smooth,  transparent  membrane, 
which  may  be  easily  separated,  in  the  form  of  a  tube,  from  the  fibres  it  encloses; 
in  structure  it  consists  of  connective  tissue,  which  has  a  distinctly  lamellar  arrange- 
ment, being  composed  of  several  lamella?,  separated  from  each  other  by  spaces 
containing  lymph.  The  nerve-fibres  are  held  together  and  supported  within  the 
funiculus  by  delicate  connective  tissue  called  the  endoneurium.  It  is  continuous 
with  septa  which  pass  inward  from  the  innermost  layer  of  the  perineurium,  and 
consists  of  a  ground-substance  in  which  are  embedded  fine  bundles  of  fibrous 
connective  tissue  which  run  for  the  most  part  longitudinally.  It  serves  to  support 
the  capillary  vessels,  which  are  arranged  so  as  to  form  a  network  with  elongated 
meshes.  The  cerebro-spinal  nerves  consist  almost  exclusively  of  medullated  nerve- 
fibres  the  non-medullated  existing  in  very  small  proportions. 

The  blood-vessels  supplying  a  nerve  terminate  in  a  minute  capillary  plexus, 
the  vessels  composing  which  pierce  the  perineurium  and  run,  for  the  most  part, 
parallel  with  the  fibres;  they  are  connected  together  by  short,  transverse  vessels, 
forming  narrow,  oblong  meshes,  similar  to  the  capillary  system  of  muscle.  Fine 
non-medullated  nerve-fibres  accompany  these  capillary  vessels,  the  vaso-motor 
fibres,  and  break  up  into  elementary  fibrils,  which  form  a  network  around  the 
vessel.  Horsley  has  also  demonstrated  certain  medullated  fibres  as  running  in  the 
epineurium  and  terminating  in  small  spheroidal  tactile  corpuscles  or  end-bulbs  of 
Krause.  These  nerve-fibres,  which  Marshall  believes  to  be  sensory,  and  which  he 
has  termed  nervi  nervorum,  are  considered  by  him  to  have  an  important  bearing 
upon  certain  neuralgic  pains. 

Nerves,  in  their  course,  subdivide  into  branches,  and  these  frequently  commu- 
nicate with  branches  of  a  neighboring  nerve. 

The  nerve-fibres,  as  far  as  is  at  present  known,  do  not  coalesce,  but  pursue  an 
uninterrupted  course  from  the  centre  to  the  periphery.  In  separating  a  nerve, 
however,  into  its  component  funiculi,  it  may  be  seen  that  they  do  not  pursue  a 
perfectly  insulated  course,  but  occasionally  join  at  a  very  acute  angle  with  other 
funiculi  proceeding  in  the  same  direction;  from  this,  branches  are  given  off,  to 
join  again  in  like  manner  with  other  funiculi.  It  must  be  distinctly  understood, 
however,  that  in  these  communications  the  nerve-fibres  do  not  coalesce,  but  merely 
pass  into  the  sheath  of  the  adjacent  nerve,  become  intermixed  with  its  nerve-fibres, 
and  again  pass  on,  to  become  blended  with  the  nerve-fibres  in  some  adjoining 
funiculus. 

The  communications  which  take  place  between  two  or  more  nerves  form  what 
is  called  a  plexus.  Sometimes  a  plexus  is  formed  by  the  primary  branches  of  the 
trunks  of  the  nerves — as  the  cervical,  brachial,  lumbar,  and  sacral  plexuses — and 
occasionally  by  the  terminal  funiculi,  as  in  the  plexuses  formed  at  the  periphery 
of  the  body.  In  the  formation  of  a  plexus  the  component  nerves  divide,  then 
join,  and  again  subdivide  in  such  a  complex  manner  that  the  individual  funiculi 
become  interlaced  most  intricately;  so  that  each  branch  leaving  a  plexus  may 
contain  filaments  from  each  of  the  primary  nervous  trunks  which  form  it.  In  the 
formation  also  of  smaller  plexuses  at  the  periphery  of  the  body  there  is  a  free 
interchange  of  the  funiculi  and  primitive  fibres.     In  each  case,  however,  the 


826  THE  NERVOUS  SYSTEM 

individual  filaments  remain  separate  and  distinct,  and  do  not  inosculate  with  one 
another. 

It  is  probable  that  through  this  interchange  of  fibres  the  different  branches 

passing  off  from  a  plexus  have  a  more  extensive  connection  with  the  spinal  cord 

than  if  they  each  had  proceeded  to  be  distributed  without  such  connection  with 

lother  nerves.    Consequently  the  parts  supplied  by  these  nerves  have  more  extended 

1  relations  with  the  nervous  centres;  by  this  means,  also,  groups  of  muscles  may  be 

associated  for  combined  action. 

The  sympathetic  nerves  are  constructed  in  the  same  manner  as  the  cerebro- 
spinal nerves,  but  consist  mainly  of  non-medullated  fibres,  collected  into  funiculi, 
and  enclosed  in  a  sheath  of  connective  tissue.  There  is,  however,  in  these  nerves  a 
certain  admixture  of  medullated  fibres  (Fig.  523),  and  the  amount  varies  in  different 
nerves,  and  may  be  known  by  their  color.  Those  branches  of  the  sympathetic 
which  present  a  well-marked  gray  color  are  composed  more  especially  of  gelatinous 
nerve-fibres,  intermixed  with  a  few  medullated  fibres;  while  those  of  a  white 
color  contain  more  of  the  latter  fibres  and  a  few  of  the  former.  Occasionally,  the 
gray  and  white  cords  run  together  in  a  single  nerve,  without  any  intermixture,  as 
in  the  branches  of  communication  between  the  sympathetic  ganglia  and  the  spinal 
nerves,  or  in  the  communicating  cords  between  the  ganglia. 

The  nerve-fibres,  both  of  the  cerebro-spinal  and  sympathetic  system,  convey 
impressions  of  a  twofold  kind.  The  sensory  nerves,  called  also  centripetal  or 
afferent  nerves,  transmit  to  the  nervous  centres  impressions  made  upon  the  periph- 
eral extremities  of  the  nerves,  and  in  this  way  the  mind,  through  the  medium 
of  the  brain,  becomes  conscious  of  external  objects.  The  motor  nerves,  called 
also  centrifugal  or  efferent  nerves,  transmit  impressions  from  the  nervous  centres 
to  the  parts  to  which  the  nerves  are  distributed,  these  impressions  either  exciting 
muscular  contraction,  or  influencing  the  processes  of  nutrition,  growth,  and 
secretion. 

Origin  and  Termination  of  Nerves. — By  the  expression  "the  termination  of 
nerve-fibres"  is  signified  their  connection  with  the  nerve-centres,  and  with  the 
parts  they  supply.  The  former  are  sometimes  called  their  origin,  or  central 
termination;  the  latter  their  peripheral  termination.  The  origin  in  some  cases  is 
single — that  is  to  say,  the  whole  nerve  emerges  from  the  nervous  centre  by  a  single 
root;  in  other  instances  the  nerve  arises  by  two  or  more  roots,  which  come  off 
from  different  parts  of  the  nerve-centre,  sometimes  widely  apart  from  each  other, 
and  it  often  happens,  when  a  nerve  arises  in  this  way  by  two  roots,  that  the 
functions  of  these  two  roots  are  different;  as,  for  example,  in  the  spinal  nerves, 
each  of  which  arises  by  two  roots,  the  anterior  of  which  is  motor  and  the  posterior 
sensory.  The  point  where  the  nerve-root  or  roots  emerge  from  the  nervous  centre 
is  named  the  superficial  or  apparent  origin,  but  the  fibres  of  which  the  nerve  con- 
sists can  be  traced  for  a  certain  distance  into  the  nervous  centre  to  some  portion 
of  the  gray  substance,  which  constitutes  the  deep  or  real  origin  of  the  nerve. 

The  manner  in  which  these  fibres  arise  at  their  deep  origin  varies  with  their 
functions.  The  centrifugal  or  efferent  nerve-fibres  originate  in  the  nerve-cells  of 
the  gray  substance,  the  axis-cylinder  processes  of  these  cells  being  prolonged  to 
form  the  fibres.  In  the  case  of  the  centripetal  or  afferent  nerves  the  fibres  grow 
inward  either  from  nerve-cells  in  the  organs  of  special  sense  (e.  g.,  the  retina) 
or  from  nerve-cells  in  the  ganglia.  Having  entered  the  nerve-centre,  they  branch 
and  send  their  ultimate  twigs  among  the  cells,  without,  however,  uniting  with 
them. 

Peripheral  Terminations  of  Nerves. — Nerve-fibres  terminate  peripherally  in 
various  ways,  and  these  may  be  conveniently  studied  in  the  sensory  and  motor 
nerves,  respectively.  Sensory  nerves  would  appear  to  terminate  either  in  minute 
primitive  fibrillar  or  networks  of  fibrillae;  or  else  in  special  terminal  organs,  which 


ORIGIN  AND    TERMINATION    OF   NERVES 


827 


have  been  termed  peripheral  end-organs,  and  of  which  tliere  are  several  principal 
varieties — viz.,  the  end-bulbs  of  Krause,  the  tactile  corpuscles  of  Wagner,  the  Pacinian 
corpuscles,  and  the  neuro-tendinous  and  neuro-muscular  spindles. 

Termination  in  Fibrillae. — When  a  medullated  nerve-fibre  approaches  its  termi- 
nation, the  white  matter  of  Schwann  suddenly  disappears,  leaving  only  the  axis- 
cylinder,  surrounded  by  the  neurilemma,  and  forming  a  non-medullated  fibre. 
This,  after  a  time,  loses  its  neurilemma,  and  consists  only  of  an  axis-cylinder, 
which  can  be  seen,  in  preparations  stained  with  chloride  of  gold,  to  be  made  up 
of  fine  varicose  fibrils.  Finally,  the  axis-cylinder  breaks  up  into  its  constituent 
primitive  nerve-fibrillje,  which  often  present  regular  varicosities  and  anastomose 
with  one  another,  thus  forming  a  network.  This  network  passes  between  the 
elements  of  the  tissue  to  which  the  nerves  are  distributed,  which  is  always  epithe- 
lial, the  nerve-fibrils  lying  in  the  interstitial  substance  between  the  epithelial  cells, 
and  there  terminating,  though  some  observers  maintain  that  the  actual  termina- 
tions are  within  the  cells.  In  this  way  nerve-fibres  have  been  found  to  terminate 
in  the  epithelium  of  the  skin  and  mucous  membranes,  and  in  the  anterior  epithe- 
lium of  the  cornea. 


Fio.  525. — End-bulb  of  Krause.  o.  Medul- 
lated nerve-fibre.  b.  Capsule  of  corpu.scle. 
(From  Klein's  Elements  of  Histology.) 


Fig.  526.— Tactile  papilla  of  the  hand  treated  with  acetic 
acid.  Magnified  350  time.s.  A.  Side  view  of  a  papilla  of  the 
hand.  a.  Cortical  layer,  h.  Tactile  corpuscle,  with  trans- 
verse nuclei,  c.  Small  nerve  of  the  papilla,  with  neuri- 
lemma, d.  Its  two  nervous  fibres  running  with  spiral 
coils  around  the  tactile  corpuscle,  e.  Apparent  termina- 
tion of  one  of  these  fibres.  B.  A  tactile  papilla  seen  from 
above,  so  as  to  show  its  transverse  section,  a.  Cortical 
layer  h.  Nerve-fibre.  _  c.  Outer  layer  of  the  tactile  body, 
with  nuclei,     d.  Clear  interior  substance. 


The  End-bulbs  of  Krause  (Fig.  525)  are  minute  cylindrical  or  oval  bodies,  con- 
sisting of  a  capsule  formed  by  the  expansion  of  the  connective-tissue  sheath  of  a 
medullated  fibre,  and  containing  a  soft  semifluid  core  in  which  the  termination  of 
the  axis-cylinder  is  situated,  ending  either  as  a  bulbous  extremity,  or  in  a  coiled- 
up  plexiform  mass.  End-bulbs  are  found  in  the  conjunctiva  of  the  eye,  where 
they  are  spheroidal  in  shape  in  man,  but  cylindrical  in  most  other  animals,  in  the 
mucous  membrane  of  the  lips  and  tongue,  and  in  the  epineurium  of  nerve-trunks. 
They  are  also  found  in  the  genital  organs  of  both  sexes,  the  penis  in  the  male, 
and  the  clitoris  in  the  female.  In  this  situation  they  have  a  mulberry-like  appear- 
ance, from  being  constricted  by  connective-tissue  septa  into  from  two  to  six 
knob-like  masses,  and  have  received  the  name  of  genital  corpuscles.  Very  similar 
corpuscles  are  found  in  the  epineurium  of  nerve-trunks.  In  the  synovial  mem- 
brane of  certain  joints  {e.  cj.,  those  of  the  fingers)  rounded  or  oval  end-bulbs  have 
been  found;  these  are  designated  articular  end-bulbs. 

Tactile  Corpuscles,  known  as  Grandry's  corpuscles,  have  been  described  by 
Grandry  as  occurring  in  the  papillae  of  the  beak  and  tongue  of  birds,  and  by 
Merkel  as  occurring  in  the  papillae  and  epithelium  of  the  skin  of  man  and  animals. 


828 


THE   NERVOUS   SYSTEM 


especially  in  those  parts  of  the  skin  devoid  of  hair.  They  consist  of  a  capsule  com- 
posed of  a  very  delicate,  nucleated  membrane,  and  contain  two  or  more  granular, 
somewhat  flattened  cells,  between  which  the  medullated  nerve-fibre,  which  enters 
the  capsule  by  piercing  its  investing  membrane,  is  supposed  to  terminate. 

Meissner's  corpuscles  are  the  tactile  corpuscles  (Fig.  526),  described  by  Wagner 
and  Meissner.  They  are  oval-shaped  bodies,  made  up  of  connective  tissue, 
and  consisting  of  a  capsule,  and  imperfect  membranous  septa,  derived  from  it, 
which  penetrate  its  interior.  The  axis-cylinder  of  the  medullated  fibres  passes 
through  the  capsule,  and  having  entered  the  corpuscle  terminates  in  a  small 
globular  or  pyriform  enlargement,  near  the  inner  surface  of  the  capsule.  These 
tactile  corpuscles  have  been  described  as  occurring  in  the  papillae  of  the  corium 
of  the  skin,  hand,  foot,  front  of  the  forearm,  and  skin  of  the  lips,  and  the  mucous 
membrane  of  the  tip  of  the  tongue,  the  palpebral  conjunctiva,  and  the  skin  of  the 
nipple.  They  are  not  found  in  all  the  papillae,  but  from  their  existence  in  those 
parts  in  which  the  skin  is  highly  sensitive,  it  is  probable  that  they  are  especially 
concerned  in  the  sense  of  touch,  though  their  absence  from  the  papillae  of  other 
tactile  parts  shows  that  they  are  not  essential  to  this  sense.  They  may  be  regarded 
as  end-bulbs. 

Ruffini  has  described  a  special  variety  of  nerve-ending  in  the  subcutaneous 
tissue  of  the  human  finger  (Fig.  527).     These  are  usually  known  as  Ruffini's 


Nerve-fibres. 


Terminal  ramifications 
of  axis-cylinder. 


Fig.  527.— Nerve-ending  of  Ruffini.     (After  A.  Ruffini,  Arch.  ital.  de  Biol.,  Turin,  1894,  t.  xxi.) 

nerve -endings.  They  are  principally  situated  at  the  junction  of  the  corium  with  the 
subcutaneous  tissue;  they  are  oval  in  shape,  and  consist  of  a  strong  connective- 
tissue  sheath,  inside  which  the  nerve-fibre  divides  into  numerous  branches,  which 
show  varicosities  and  end  in  small  free  knobs.  They  resemble  the  corpuscles  of 
Golgi. 

The  Pacinian  Corpuscles  or  Corpuscles  of  Vater  (Fig.  528)  are  found  in  the 
human  subject  chiefly  on  the  nerves  of  the  palm  of  the  hand  and  sole  of  the 
foot  and  in  the  genital  organs  of  both  sexes,  lying  in  the  subcutaneous  tissue; 
but  they  have  also  been  described  as  connected  with  the  nerves  of  the  joints, 
and  in  some  other  situations  in  the  lower  animals,  as  the  mesentery  of  the 
cat  and  along  the  tibia  of  the  rabbit.  Each  of  these  corpuscles  is  attached 
to  and  encloses  the  termination  of  a  single  nerve-fibre.  The  corpuscle  which 
is  perfectly  visible  to  the  naked  eye  (and  which  can  be  most  easily  demon- 
strated in  the  mesentery  of  a  cat)  consists  of  a  number  of  lamellae  or  capsules, 
arranged  more  or  less  concentrically  around  a  central  clear  space,  in  which  the 
nerve-fibre  is  contained.  Each  lamella  is  composed  of  bundles  of  fine  connective- 
tissue  fibres,  and  is  lined  on  its  inner  surface  by  a  single  layer  of  cells.  The  central 
clear  space,  which  is  elongated  or  cylindrical  in  shape,  is  filled  with  a  transparent 
material,  in  the  middle  of  which  is  the  single  medullated  fibre,  which  traverses 
the  space  to  near  its  distal  extremity.  Here  it  terminates  in  a  rounded  knob  or 
end,  sometimes  bifurcating  previously,  in  which  case  each  branch  has  a  similar 


ORIGIN  AND    TERMINATION   OF  NERVES 


829 


arrangement.    Todd  and  Bowman  have  described  minute  arteries  as  entering  by 
the  sides  of  the  nerves  and  forming  capillary  loops  in  the  intercapsular  spaces, 
and    even    penetrating    into    the   central   space. 
Other  authors  describe  the  artery  as  entering  the 
corpuscle  at  the  pole  opposite  to  the  nerve-fibre. 

Herbst  has  described  a  somewhat  similar 
"nerve-ending"  to  the  Pacinian  corpuscle,  as 
being  found  in  the  mucous  membrane  of  the 
tongue  of  the  duck  and  in  some  other  situations. 
It  differs,  however,  from  the  Pacinian  corpuscles 
in  being  smaller,  its  capsules  thinner  and  more 
closely  approximated,  and  especially  in  the  fact 
that  the  axis-cylinder  in  the  central  clear  space  is 
coated  with  a  continuous  row  of  nuclei.  These 
bodies  are  known  as  the  corpuscles  of  Herbst. 

Neuro-tendinous  Spindles. — Hie  nerves  supplying 
tendons  have  a  special  modification  of  the  terminal 
fibres,  especially  numerous  at  the  point  where  the 
tendon  is  becoming  muscular.  The  tendon  bundles 
become  enlarged,  and  the  nerve-fibres — one,  two, 
or  more  in  number — penetrate  between  the  fas- 
ciculi of  the  tendon  and  spread  out  between  the 
fibres  to  end  in  irregular  disks  or  varicosities.  A 
spindle-shaped  body  is  thus  formed,  composed  of 
tendon  bundles  and  nerve-fibres,  which  is  known 
as  the  organ  of  Golgi  (Fig.  529). 

Neuro-muscular  Spindles.  —  In  the  majority  of 
voluntary  muscles  there  have  been  found  special 
end-organs  consisting  of  a  small  bundle  of  pecu- 

,.  ,  r.-,  /•     .       e         if»i  \  1  •        capsular  spaces,  and  one  penetrates  to 

liar  muscular  nbres  (mtraiusal  nbres),  embryonic   the  central  capsule,    t.  The  fibrous  tis- 

,  •  ill  1  •J.^  '  1*1  sue  of  the  stalk  prolonged  from  the  peri- 

in  type,  invented   by  a  capsule  within  which  nerve-     neurium.     n.    Nerve-tube   advancing  to 

fibres,  experimentally  shown  to  be  sensory  in  ^^Vtl?!;^'d''s'?rethinraK^he''^^^^^^^ 
origin,  terminate.  These  neuro-muscular  spindles  tube^cuw^enCfrgrmlnl'*  "  ^""^"^  ^^  * 
vary  in  length  from  ^^  to  ^  of  an  inch  and  have  a 

distinctly  fusiform  appearance.  The  large  medullated  nerve-fibres  passing  to  the 
end-organ  are  from  one  to  three  or  four  in  number;  entering  the  fibrous  capsule 


Fig.  528. — Pacinian  corpuscle,  with  its 
system  of  capsules  and  central  cavity. 
a.  Arterial  twig,  ending  in  capillaries, 
which  form  loops  in  some  of  the  inter- 
capsular 


Organ  of  Golgi,  showing  Tendon  bundles, 

ramification  of  nerve-fibrils. 
Muscular  fibres. 
Fig.  529. — Organ  of  Golgi  (neuro-tendinous  spindle)  from  the  human  tendon  Achillis.      (After  Ciaccio.) 


they  divide  several  times^  and,  losing  their  medulla,  ultimately  end  in  naked  axis- 
cylinders  encircling  the  intrafusal  fibres  by  flattened  expansions,  or  irregular  ovoid 


830 


THE  NERVOUS  SYSTEM 


or  rounded  disks  (Fig.  530).  Neuro-muscular  spindles  have  not  yet  been  demon- 
strated in  the  tongue  or  eye  muscles. 

In  the  organs  of  special  sense  the  nerves  appear  to  terminate  in  cells  which 
belong  to  the  epithelial  class,  and  have  received  the  name  of  sensory  or  nerve- 
epithelium  cells.  This  is  not,  however,  the  real  state  of  the  case;  the  nerve-fibre 
is  in  reality  a  process  from  the  epithelial  cell,  and  terminates  by  branching  around 
a  ganglion-cell.  The  stimulus  carried  by  it  is  continued  onward  by  an  axis- 
cylinder,  derived  from  the  ganglion,  to  the  brain.  These  nerve-epithelium  cells 
must  therefore  be  regarded  as  modified  forms  of  nerve-cells.  They  will  be  more 
particularly  described  in  connection  with  the  description  of  the  organs  of  special 
sense. 

Motor  nerves  are  to  be  traced  either  into  unstriped  or  striped  muscular  fibres. 
In  the  unstriped  or  involuntary  muscles  the  nerves  are  derived   from  the  sympa- 


Dendritic  branchings 


Spirals. 


Spirals.'/ 
Fig.  530. — Middle  third  of  a  terminal  plaque  in  the  muscle  spindle  of  an  adult  cat.     (After  Ruffinl.) 


thetic,  and  are  composed  mainly  of  the  non-medullated  fibres.  Near  their  termi- 
nation they  divide  into  a  number  of  branches,  which  communicate  and  form  an 
intimate  plexus.  At  the  junction  of  the  branches  small  triangular  nuclear  bodies, 
the  ganglion-cells,  are  situated.  From  these  plexuses  minute  branches  are  given 
off,  which  divide  and  break  up  into  the  ultimate  fibrillse  of  which  the  nerve  is  com- 
posed. These  fibrillse  course  between  the  involuntary  muscle-cells,  and,  according 
to  Elischer,  terminate  on  the  surface  of  the  cell,  opposite  the  nucleus,  in  a  minute 
swelling.  Arnold  and  Frankenhiiuser  believed  that  these  ultimate  fibrillse  pene- 
trated the  muscular  cell  and  ended  in  the  nucleus.  More  recent  observation, 
however,  has  tended  to  disprove  this. 

In  the  striped  or  voluntary  muscle  the  nerves  supplying  the  muscular  fibres  are 
derived  from  the  cerebro-spinil  nerves,  and  are  composed  mainly  of  medullated 
fibres.  The  nerve,  after  entering  the  sheath  of  the  muscle,  breaks  up  into  fibres, 
or  bundles  of  fibres,  which  form  plexuses,  and  gradually  divide  until,  as  a  rule, 
a  single  nerve-fibre  enters  a  single  muscular  fibre.  Sometimes,  however,  if  the 
muscular  fibre  is  long,  more  than  one  nerve-fibre  enters  it.  Within  the  muscular 
fibre  the  nerve-fibre  terminates  in  a  special  expansion,  called  by  Kuhne,  who  first 


ORIGIN  AND    TERMINATION    OF   NERVES 


831 


accurately  described  it,  the  motorial  end-plates  (Fig.  531)/  The  nerve-fibre, 
on  approaching  the  muscular  fibre,  suddenly  loses  its  white  matter  of  Schwann, 
which  abruptly  terminates;  the  neurilemma  becomes  continuous  with  the  sarco- 


FiG.  531. — Muscular  fibres  of  Lacerta  mridis  with  the  terminations  of  nerves,  a.  Seen  in  profile,  p  p.  The 
nerve  end-plates,  s  .s.  The  base  of  the  plate,  consisting  of  a  granular  mass  with  nuclei,  b.  The  same  as  seen  in 
looking  at  a  perfectly  fresh  fibre,  the  nervous  ends  being  probably  still  excitable.  (The  forms  of  the  variously 
divided  plate  can  hardly  be  represented  in  a  wood-cut  by  sufficiently  delicate  and  pale  contours  to  reproduce 
correctly  what  is  seen  in  nature.)     c.  The  same  as  seen  two  hours  after  death  from  poisoning  by  curare. 

lemma  of  the  muscle,  and  only  the  axis-cylinder  enters  the  muscular  fibre,  where 
it  immediately  spreads  out,  ramifying  like  the  roots  of  a  tree,  immediately  beneath 
the  sarcolemma,  and  is  embedded  in  a  layer  of  granular  matter,  containing  a 
number  of    clear,   oblong    nuclei,   the 
whole   constituting   an  end-plate  from 
which  the  contractile  wave  of  the  mus- 
cular fibre  is  said  to  start. 

The  Ganglia  may  be  regarded  as  sepa- 
rate small  aggregations  of  nerve-cells, 
connected  with  each  other,  with  the 
cerebro-spinal  axis,  and  with  the  nerves 
in  various  situations.  They  are  found 
on  the  posterior  root  of  each  of  the 
spinal  nerves;  on  the  posterior  or  sensory 
root  of  the  fifth  cranial  nerve;  on  the 
facial  and  auditory  nerves;  and  on  the 
glosso-pharyngeal  and  pneumogastric 
nerves.  They  are  also  found  in  a  con- 
nected series  along  each  side  of  the  ver- 
tebral column,  forming  the  trunk  of  the 
sympathetic;  and  on  the  branches  of 
that  nerve,  generally  in  the  plexuses  or 

at  the   point  of  junction   of  two  or  more  Fig.  532.— Section   through  a  microscopic  ganglion. 


fibres  which  entered  the  ganglion  are  not  represented. 
The  nerve-fibres  are  ordinary  medullated  fibres,  but  the 
details  of  their  structure  are  not  shown,  owing  to  the 
low  magnifying  power.     The  ganglion-cells  are  invested 


• ,  1  1        ,1  • ,  1     1  1  Magnified  300  diameters,      c.  Capsule  of  the  ganglion 

nerves  with  each  other  or  with   branches     n.  Nerve^fibres  pa.s.sing  out  of  the  ganglion.    The  nerve- 

of  the  cerebro-spinal  system.     On  sec- 
tion they  are  seen  to  consist  of  a  reddish- 
gray  substance,    traversed    by  numerous     by  speciaTcapsules    lined  by  afew  nuclei   which  are 
<-'..•'  •'  here  represented  as  il  contained  in  the  capsule.     (Klein 

white  nerve-nbres;  they  vary  consider-  and  Noble  Smith.) 

ably  in  form  and  size;  the  largest  are 

found  in  the  cavity  of  the  abdomen;  the  smallest,  not  visible  to  the  naked  eye, 

exist  in  considerable  numbers  upon  the  nerves  distributed  to  the  difl'erent  viscera. 

'  They  had,  however,  previously  been  noticed,  though  not  accurately  described,  by  Doydre,  who  named  them 
"nerve-hillocks." — Ed.  of  15th  English  edition. 


832  THE  NERVOUS  SYSTEM 

The  ganglia  are  invested  by  a  smooth  and  firm,  closely  adhering  membranous 
envelope,  consisting  of  dense  areolar  tissue;  this  sheath  is  continuous  with  the 
perineurium  of  the  nerves,  and  sends  numerous  processes  into  the  interior  of  the 
ganglion,  which  support  the  blood-vessels  supplying  its  substance. 

In  structure  all  ganglia  are  essentially  similar  (Fig.  532),  consisting  of  the  same 
structural  elements  as  the  other  nervous  centres — viz.,  a  collection  of  nerve-cells 
and  nerve-fibres.  Each  nerve-cell  has  a  nucleated  sheath,  which  is  continuous 
with  the  sheath  of  the  nerve-fibre  with  which  the  cell  is  connected.  The  nerve- 
cells  in  the  ganglia  of  the  spinal  nerves  are  pyriform  in  shape,  and  have  only  one 
process,  the  axis-cylinder  or  axone.  A  short  distance  from  the  cell,  and  while 
still  within  the  ganglion,  this  process  divides  in  a  T-shaped  manner,  one  limb 
of  the  cross-bar  passing  centrally  and  forming  the  central  portion  of  a  sensory 
nerve-fibre;  the  other  limb  passing  peripherally  to  form  the  axis-cylinder  process 
of  the  peripheral  nerve-fibre.  In  the  sympathetic  ganglia  the  nerve-cells  are 
multipolar  and  have  one  axis-cylinder  process  or  axone  and  several  protoplasmic 
processes  or  dendrons.  The  former  of  these  emerges  from  the  ganglion  as  a  non- 
medullated  nerve-fibre.  Similar  cells  are  found  in  the  ganglia  connected  with  the 
fifth  cranial  nerve,  and  these  ganglia  are  therefore  regarded  by  some  as  the  cranial 
portions  of  the  sympathetic  system.  The  nerve-cells  are  disposed  in  the  ganglia 
in  groups  of  varying  size,  and  these  groups  are  separated  from  each  other  by 
bundles  of  nerve-fibres,  some  of  which  traverse  the  ganglia  without  being  con- 
nected with  the  cells. 

THE  CEREBRO-SPINAL  AXIS. 

The  cerebro-spinal  axis  consists  of  the  spinal  cord  and  the  brain  or  encephalon, 
which  are  contained  within  the  skull  and  spinal  canal.  The  spinal  cord  and  its 
coverings  will  be  first  considered,  and  then  the  brain  and  its  membranes. 

THE  SPINAL  CORD  AND  ITS  MEMBRANES. 

Dissection. — To  dissect  the  cord  and  its  membranes  it  will  be  necessary  to  lay  open  the 
whole  length  of  the  spinal  canal.  For  this  purpose  the  muscles  must  be  separated  from  the 
vertebral  grooves,  so  as  to  expose  the  spinous  processes  and  laminie  of  the  vertebrae;  and  the 
latter  must  be  sawed  through  on  each  side,  close  to  the  roots  of  the  transverse  processes,  from 
the  third  or  fourth  cervical  vertebra  above  to  the  sacrum  below.  The  vertebral  arches  having 
been  displaced  by  means  of  a  chisel  and  the  separate  fragments  removed,  the  dura  mater  will  be 
exposed,  covered  by  a  plexus  of  veins  and  a  quantity  of  loose  areolar  tissue,  often  infiltrated  with 
serous  fluid.  The  arches  of  the  upper  vertebrae  are  best  divided  by  means  of  a  strong  pair  of 
cutting  bone-forceps. 

MEMBRANES  OF  THE  CORD. 

The  membranes  which  envelop  the  spinal  cord  are  three  in  number.  The  most 
external  is  the  dura  mater,  a  strong  fibrous  membrane  which  forms  a  loose  sheath 
around  the  cord.  The  most  internal  is  the  pia  mater,  a  cellulo-vascular  membrane 
which  closely  invests  the  entire  surface  of  the  cord.  Between  the  two  is  the  arach- 
noid membrane,  a  non-vascular  membrane  which  envelops  the  cord  and  is  con- 
nected to  the  pia  mater  by  slender  filaments  of  connective  tissue. 

The  Spinal  Dura  Mater  (Dura  Mater  Spinalis)  (Figs.  533,  534,  535,  537). 

I  he  spinal  dura  mater  represents  only  the  meningeal  or  supporting  layer  of 
the  cranial  dura  mater.  The  endocranial  or  endosteal  layer  ceases  at  the  foramen 
magnum  posteriorly,  but  reaches  as  low  as  the  third  cervical  vertebra  in  front; 
below  these  levels  its  place  is  taken  by  the  periosteum.    The  dura  mater  forms  a 


THE   SPINAL    DUB  A    MATEB 


833 


loose  sheath  which  surrounds  the  cord  and  the  cauda  equina,  and  is  loosely  con- 
nected with  the  vertebral  periosteum  and  the  ligaments  by  a  quantity  of  lax 
areolar  tissue  and  a  plexus  of  veins,  the  meningo-rachidian  veins  (plexus  venosi 
vertehrales  interni).  The  space  containing  the  fat  and  veins  is  called  the  epidural 
space  (cavum  epidurale) .  The  situation  of  the  veins  between  the  dura  mater  and  the 
periosteum  of  the  vertebrae  corresponds  therefore  to  that  of  the  cranial  sinuses 
between  the  endocranial  and  supporting  layers.  The  dura  is  attached  to  the 
circumference  of  the  foramen  magnum  and  to  the  axis  and  third  cervical  vertebra; 
it  is  also  fixed  to  the  posterior  common  ligament,  especially  near  the  lower  end  of 
the  spinal  canal,  by  fibrous  slips;  it  extends  below  as  far  as  the  second  or  third 
piece  of  the  sacrum;  here  it  becomes  imper- 
vious, and,  ensheathing  the  filum  terminale, 
constitutes  the  filum  durae  matris  spinalis  (Fig. 
537),  and  descends  to  the  back  of  the  coccyx, 
to  blend  with  the  periosteum.  This  part  of 
the   dura   is   called  the   coccygeal   ligament, 


I 


ANTERIOR 
NERVE  ROOt 


Dili 


Fig.  533. — The  spinal  cord  and  its  membranes. 


Fig.  534— The  dentate  ligament.  The  dura 
mater  has  been  opened  and  turned  back.  The 
anterior  surface  is  seen.     (Hirschfeld.) 


(Fig.  537).  The  dura  mater  is  much  larger  than  is  necessary  for  its  contents, 
and  its  size  is  greater  in  the  cervical  and  lumbar  regions  than  in  the  dorsal. 
Its  inner  surface  is  smooth.  On  each  side  may  be  seen  the  double  openings, 
which  transmit  the  two  roots  of  the  corresponding  spinal  nerve,  the  fibrous  layer 
of  the  dura  mater  being  continued  in  the  form  of  a  tubular  prolongation  on 
them  as  they  pass  through  these  apertures.  These  prolongations  of  the  dura 
mater  are  short  in  the  upper  part  of  the  spine,  but  become  gradually  longer 
below,  forming  a  number  of  tubes  of  fibrous  membrane,  which  enclose  the  sacral 
nerves,  and  are  contained  in  the  spinal  canal. 

The  chief  peculiarities  of  the  dura  mater  of  the  cord,  as  compared  with  that 
investing  the  brain,  are  the  following: 

The  dura  mater  of  the  cord  is  not  closely  adherent  to  the  bones  of  the  spinal 
canal,  and  is  not,  as  is  the  cerebral  dura,  the  internal  periosteum  of  the  vertebrae. 
The  vertebrae  have  an  independent  periosteum. 


834  THE  NERVOUS  SYSTEM 

It  does  not  send  partitions  into  the  fissures  of  the  cord,  as  the  cerebral  dura 
sends  partitions  into  certain  fissures  of  the  brain. 

Its  fibrous  laminfE  do  not  separate  to  form  venous  sinuses,  as  in  the  brain. 

It  contains  no  Pacchionian  bodies. 

Structure. — The  dura  mater  consists  of  white  fibrous  and  elastic  tissue  arranged 
in  bands  or  lamellte,  which,  for  the  most  part,  are  parallel  with  one  another  and 
have  a  longitudinal  arrangement.  Each  surface  is  covered  by  a  layer  of  endothelial 
cells.  It  is  sparingly  supplied  with  vessels,  and  some  few  nerves  have  been  traced 
into  it. 

The  Arachnoid  Membrane  (Arachnoidea  Spinalis)  (Figs.  533,  535). 

The  arachnoid  is  exposed  by  slitting  up  the  dura  mater  and  reflecting  that 
membrane  to  either  side.  It  is  a  thin,  delicate,  tubular  membrane  which  invests 
the  surface  of  the  cord,  and  is  connected  to  the  pia  mater  by  slender  filaments 
of  connective  tissue.  Above,  it  is  continuous  with  the  cerebral  arachnoid;  on 
each  side  it  is  continued  on  the  various  nerves,  so  as  to  form  a  sheath  for  them 
as  they  pass  outward  to  the  intervertebral  foramina.  The  outer  surface  of  the 
arachnoid  is  in  contact  with  the  inner  surface  of  the  dura  mater,  and  the  two 
are,  here  and  there,  joined  together  by  isolated  connective-tissue  trabeculse.  These 
trabecule  are  especially  numerous  on  the  posterior  surface  of  the  cord.  For  the 
most  part,  however,  the  membranes  are  not  connected  together,  and  the  interval 
between  them  is  named  the  subdural  space  (cavum  suhdurale).  The  subdural 
space  contains  a  very  small  amount  of  lymph-like  fluid.  There  is  no  com- 
munication between  the  subdural  space  and  the  subarachnoid  space.  The  sub- 
dural space  is  prolonged  outward  for  a  short  distance  on  each  emerging  nerve 
and  communicates  with  the  lymph  tract  of  the  nerve.  The  inner  surface  of  the 
arachnoid  is  separated  from  the  pia  mater  by  a  considerable  interval,  which  is 
called  the  subarachnoid  or  subarachnoidean  space  {cavum  suharachnoideale) .  The 
space  is  largest  at  the  lower  part  of  the  spinal  canal,  and  encloses  the  mass 
of  nerves  which  form  the  cauda  equina.  Superiorly  it  is  continuous  with  the 
cranial  subarachnoid  space,  and  communicates  with  the  general  ventricular 
cavity  of  the  brain  by  means  of  openings  in.  the  pia  mater,  in  the  roof  of  the 
fourth  ventricle,  foramen  of  Majendie  and  foramina  of  Key  and  Retzius  (p.  852). 
It  contains  an  abundant  serous  secretion,  the  cerebro-spinal  fluid  {liquor  cerebro- 
spinalis).  This  secretion  is  sufficient  in  amount  to  expand  the  arachnoid  mem- 
brane, and  thus  to  distend  completely  the  whole  of  the  space  included  in  the 
dura  mater.  The  subarachnoid  space  is  occupied  by  trabeculae  of  delicate 
endothelial  covered  connective  tissue,  connecting  the  pia  mater  on  the  one 
hand  with  the  arachnoid  membrane  on  the  other.  This  is  named  subarachnoid 
tissue. 

In  addition  to  this  the  space  is  partially  subdivided  by  a  longitudinal  mem- 
branous partition,  the  septum  posticum  or  the  posterior  fenestrated  septum  {septum 
suharachnoideale),  which  serves  to  connect  the  arachnoid  with  the  pia  mater, 
opposite  the  posterior  median  fissure  of  the  spinal  cord.  It  is  a  partition,  but  an 
incomplete  and  cribriform  partition,  consists  of  bundles  of  white  fibrous  tissue 
interlacing  with  each  other,  and  is  coated  with  endothelium.  The  ligamenta 
denticulata,  which  run  from  the  pia  mater  to  the  dura  mater  on  either  side  of 
the  cord,  divide  the  subarachnoid  space  into  an  anterior  and  a  posterior  space 
{cavum  suharachnoideale  anterius  et  posterius),  which  join  like  spaces  in  the  cavity 
of  the  cranium.  The  medulli-spinal  veins  {venae  spinales  externae)  lie  in  the  sub- 
arachnoid space. 

Structure.  —  The  arachnoid  is  a  delicate  membrane  made  up  of  closely 
arranged  interlacing  bundles  of   connective  tissue   in   several    layers.     It  con- 


THE   PI  A    MATER    OF    THE    CORD  835 

tains  many  elastic  fibres,  and    is   covered    on  each   side   by  endothelial  cells. 
The  arachnoid  contains  neither  vessels  or  nerves. 

The  Pia  Mater  of  the  Cord  (Pia  Mater  Spinalis). 

The  pia  mater  of  the  cord  is  exposed  on  the  removal  of  the  arachnoid  (Figs.  533 
and  535).  It  covers  the  entire  surface  of  the  cord,  to  which  it  is  very  intimately 
adherent,  forming  its  neurilemma,  and  sending  a  process  downward  into  its  ante- 
rior fissure.  It  also  forms  a  sheath  for  each  of  the  filaments  of  the  spinal  nerves, 
and  invests  the  nerves  themselves.  A  longitudinal  fibrous  band  extends  along  the 
middle  line  on  its  anterior  surface,  called  by  Haller  the  linea  splendens;  and  a 
somewhat  similar  band,  the  ligamentum  denticulatum,  is  situated  on  each  side. 
At  the  point  where  the  cord  terminates  the  pia  mater  becomes  contracted,  and  is 
continued  down  as  a  long,  slender  filament,  the  filum  terminale  (Fig.  537),  which 
descends  within  the  sheath  of  the  dura  and 

the  arachnoid  and  through  the  centre  of  the  /^  Dura  mater 

mass  of  nerves  forming  the  cauda  equina.    It 

unites  with  the  dura  and  arachnoid  about  the  J^^V  /^'■««*"o»a 

level  of  the  third  sacral  vertebra,  and  as  the  fnt^veT  yit^Ss/    /^^^-  '"""^ 

central  ligament  of  the  spinal  cord,  the  coccygeal  \S<:^J^i^^^^    y^n<.  root 

ligament,  or  the  filum  durae  matris  spinalis  the 
fused  membranes  extend  downward  as  far 
as  the  base  of  the  coccyx,  where  they  blend 
with  the  periosteum.  It  assists  in  maintain- 
ing the  cord  in  its  position  during  the  move- 
ments of  the  trunk.  It  contains  a  little  gray  ^  /xjsv?>4'5»;'i?-v^  i 
nervous  substance,  which  may  be  traced  for  /  ^'^^S'^^*^  ^«««  vertebraiia 

]•    ,  •     ,       .,  ''       .  1   .  Plexus  venosvs 

some  distance  into  its  upper  part,  and  is  ac- 

.     II  II  ,  1  •  i  ■     Fro.  535. — Transverse  section  of  the  spinal  cord 

COmpanied    by  a   small    artery  and    vein.       At  and  its  membranes.     (Gegenbauer.) 

the  upper  part  of  the  cord  the  pia  mater  pre- 
sents a  grayish,  mottled  tint,  which  is  owing  to  yellow  or  brown  pigment-cells 
scattered  among  the  elastic  fibres. 

Structure. — ^The  pia  mater  of  the  cord  is  less  vascular  in  structure,  but  thicker 
and  denser,  than  the  pia  mater  of  the  brain,  with  which  it  is  continuous.  It 
consists  of  two  layers:  an  outer,  resembling  the  arachnoid,  composed  of  bundles 
of  connective-tissue  fibres,  arranged  for  the  most  part  longitudinally;  and  an  inner 
(intima  pia),  consisting  of  stiff  circular  bundles  of  the  same  tissue,  which  present 
peculiar  angular  bends.  It  is  covered  on  both  surfaces  by  a  layer  of  endothelium. 
Between  the  two  layers  are  a  number  of  cleft-like  lymphatic  spaces  which  com- 
municate with  the  subarachnoid  cavity,  and  a  number  of  blood-vessels  which  are 
enclosed  in  a  perivascular  sheath,  derived  from  the  inner  layer  of  the  pia  mater, 
into  which  the  lymphatic  spaces  open.  The  pia  mater  contains  the  anterior  spinal 
artery  and  its  branches,  the  two  posterior  spinal  arteries,  and  numerous  veins 
which  pass  to  the  medulli-spinal  veins.  It  is  also  supplied  with  nerves,  which  are 
derived  in  part  from  the  sympathetic  and  in  part  from  the  cerebro -spinal  nerves. 
These  nerves  supply  the  walls  of  the  blood-vessels  and  enter  the  cord  with  the 
vessels. 

The  Dentate  Ligament  (ligamentum  denticulatum)  (Figs.  533  and  534)  is  a  narrow 
fibrous  band,  situated  on  each  side  of  the  spinal  cord,  throughout  its  entire  length, 
running  from  the  pia  mater  to  the  dura  mater,  and  separating  the  anterior  from  the 
posterior  roots  of  the  spinal  nerves.  It  has  received  its  name  from  the  serrated 
appearance  which  it  presents.  Its  inner  border  is  continuous  with  the  pia  mater 
at  the  side  of  the  cord.  Its  outer  border  presents  a  series  of  triangular,  dentated 
serrations,  the  points  of  which  are  fixed  at  intervals  to  the  dura  mater.     These 


836 


THE   NERVOUS  SYSTEM 


Fio.  536. — Posterior  view  of  the 
spinal  cord  in  situ. 


serrations  are  twenty-one  in  number  on  each  side,  the 
first  being  attached  to  the  dura  mater,  opposite  the 
margin  of  the  foramen  magnum  between  the  vertebral 
artery  and  the  hypoglossal  nerve,  and  the  last  near  the 
lower  end  of  the  cord.  Its  use  is  to  support  the  cord 
in  the  fluid  by  which  it  is  surrounded. 

Surgical  Anatomy. — Evidence  of  value  in  the  diagnosis  of 
meningitis  may  be  obtained  by  the  operation  of  lumbar  puncture, 
that  is,  by  puncturing  the  theca  of  the  cord  and  withdrawing 
some  of  the  cerebro-spinal  fluid,  and  the  operation  is  regarded 
by  some  as  curative,  under  the  supposition  that  the  draining 
away  of  the  cerebro-spinal  fluid  relieves  the  patient  by  diminish- 
ing the  intracranial  pressure.  Lumbar  puncture  may  give  im- 
portant diagnostic  aid  after  a  head  injury  by  disclosing  bloody 
cerebro-spinal  fluid.  The  operation  is  performed  by  inserting  a 
trocar,  of  the  smallest  size,  below  the  level  of  the  fourth  lumbar 
vertebra.  In  an  adult  the  cord  terminates  at  the  lower  border 
of  the  first  lumbar  vertebra,  and  in  a  child  opposite  the  body 
of  the  third  lumbar  vertebra.  The  canal  may  be  punctured 
below  the  fourth  vertebra  without  any  risk  of  injuring  its  con- 
tents. The  point  of  puncture  is  indicated  by  laying  the  child  on 
its  side  and  dropping  a  perpendicular  line  from  the  highest  point 
of  the  crest  of  the  ilium;  this  will  cross  the  upper  border  of  the 
spine  of  the  fourth  lumbar  vertebra.  In  a  child  the  puncture  is 
made  just  below  the  vertebral  spine.  In  adults  one-half  an  inch 
to  one  side  of  the  end  of  the  vertebral  spine.  However  the  pre- 
liminary puncture  is  made,  the  needle  penetrates  the  dura  in  the 
middle  line.  In  entering  the  needle  it  should  be  directed  up- 
ward and  forward  in  a  child;  upward,  forward,  and  slightly 
inward  in  an  adult. 


THE  SPINAL  CORD  (MEDULLA  SPINALIS)  (Fig.  536). 

The  spinal  cord  is  the  cylindrical,  elongated  part  of 
the  cerebro-spinal  axis  which  is  contained  in  the  verte- 
bral canal.  Its  length  is  usually  about  seventeen  or 
eighteen  inches,  and  its  weight,  when  divested  of  its 
membranes  and  nerves,  about  one  ounce  and  a  half, 
its  proportion  to  the  encephalon  being  about  1  to  33. 
It  does  not  nearly  fill  the  canal  in  which  it  is  con- 
tained, its  investing  membranes  being  separated  from 
the  surrounding  walls  by  areolar  tissue  and  a  plexus  of 
veins.  It  occupies,  in  the  adult,  the  upper  two-thirds 
of  the  vertebral  canal,  extending  from  the  upper  border 
of  the  atlas  to  the  lower  border  of  the  body  of  the  first 
lumbar  vertebra,  where  it  terminates  in  a  slender  fila- 
ment of  gray  substance,  which  is  continued  for  some 
distance  into  the  filum  terminale  (Fig.  537).  In  the 
foetus,  before  the  third  month,  it  extends  to  the  bottom 
of  the  sacral  canal,  but  after  this  period  it  gradually 
recedes  from  below,  as  the  growth  of  the  bones  com- 
posing the  canal  is  more  rapid  in  proportion  than  that 
of  the  cord,  so  that  in  the  child  at  birth  the  cord  extends 
as  far  as  the  third  lumbar  vertebra.  Its  position  varies 
also  according  to  the  degree  of  curvature  of  the  spinal 
column,  being  raised  somewhat  in  flexion  of  the  spine. 
The  spinal  cord  is  cylindrical,  being  somewhat  flattened 


THE  SPINAL    COBD 


837 


anteriorly  and  posteriorly  (Fig.  538).  On  examining  its  surface  it  presents  a 
difference  in  its  diameter  in  different  parts,  being  marked  by  two  enlarge- 
ments, an  upper  or  cervical,  and  a  lower  or  lumbar.  The  cervical  enlargement 
{intumescentia  cervicalis)  extends  from  about  the  third  cervical  to  the  first  or 
second  dorsal  vertebra;  its  greatest  diameter  is  in  the  transverse  direction  (13 
mm.),  and  it  corresponds  with  the  origin  of  the  nerves  which  supply  the  upper 
extremities.  The  lumbar  enlargement  {intumescentia  lumbalis)  is  situated  oppo- 
site the  last  two  or  three  dorsal  vertebrte,  and  corresponds  with  the  origin  of 
the  nerves  which  supply  the  lower  extremities.  Below  the  lumbar  enlargement 
the  cord  gradually  tapers  to  form  a  cone,  the  conus  terminalis  {conus  medullaris), 
the  apex  of  which  is  continuous  with  the  filum  terminale. 


FILUM 
TERMINALt 


I 


Fig.  537. — The  filum  terminale.     (Poirier  and  Charpy.) 

Fissures  and  Grooves  (Fig.  538).— It  presents  on  its  anterior  or  ventral  sur- 
face, along  the  middle  line,  a  longitudinal  fissure,  the  anterior  median  or  ventro- 
median  fissm-e,  and  on  its  posterior  or  dorsal  surface  another  fissure,  which  also 
extends  along  the  entire  length  of  the  cord,  the  posterior  median  or  dorso-median 
fissure  or  sulcus.  These  fissures  penetrate  through  the  greater  part  of  the 
thickness  of  the  cord,  and  incompletely  divide  the  cord  into  symmetrical 
halves,  united  in  the  middle  line  by  a  transverse  band  of  nervous  substance, 
the  commissure. 

The  Anterior  Median  or  Ventro-median  Fissure  (fissura  mediana  anterior)  (Fig. 
538). — The  anterior  median  fissure  is  wider,  but  of  less  depth,  than  the  posterior, 
extending  into  the  cord  for  about  one-third  of  its  thickness,  and  is  deepest  at  the 


838 


THE   NERVOUS    SYSTEM 


lower  part  of  the  cord.  It  contains  a  prolongation  from  the  pia  mater,  and  its 
floor  is  formed  by  the  anterior  or  white  commissure,  which  is  perforated  by  numer- 
ous blood-vessels  passing  to  the  centre  of  the  cord. 

The  Posterior  Median  or  Dorso-median  Fissure  or  Sulcus  (sulcus  medianus  pos- 
terior) (Fig.  538). — The  posterior  median  sulcus  is  not  an  actual  fissure,  as  the 
space  between  the  lateral  halves  of  the  posterior  part  of  the  cord  is  crossed  by 
connective  tissue  and  numerous  blood-vessels,  so  that  no  actual  hiatus  exists, 
and  there  is  consequently  no  prolongation  of  the  pia  mater  into  it.  It  extends 
into  the  cord  to  about  one-half  its  width.  The  floor  of  the  posterior  median 
sulcus  is  formed  by  the  posterior  or  gray  commissure. 

Lateral  Fissures. — On  each  side  of  the  posterior  median  fissure,  along  the  line 
of  attachment  of  the  posterior  roots  of  the  nerves,  a  delicate  fissure  may  be  seen, 
leading  down  to  the  gray  matter  which  approaches  the  surface  in  this  situation; 
this  is  called  the  postero-lateral  or  dorso-lateral  sulcus  or  fissure  of  the  spinal  cord 
(sulcus  lateralis  posterior).     On  the  posterior  surface  of  the  spinal  cord,  between 


VENTRAL    AAEDIAN 
FISSURE 

VENTRAL    ROOTS 


VENTRAL   HORN 


LATERAL  HORN 


RETICULAR 
FORMATION 


DORSAL    HORN 


DORSO-LATERAL 
FISSURE 


DORSAL   ROOTS 


'LUMN 

DORSAL    MEDIAN 
FISSURE 

Fig.  538. — Transverse  section  of  the  spinal  cord  at  the  middle  of  the  thoracic  region.    The  neuroglia  septum 
has  been  removed  from  between  the  dorsal  columns.     (Testut,  after  Pierret.) 

the  posterior  median  fissure  and  the  postero-lateral  fissure  on  each  side,  is  a  slight 
longitudinal  furrow,  the  posterior  intermediate  furrow  or  the  posterior  paramedian 
groove  (sulcus  intermedins  posterior),  marking  off  two  slender  tracts,  the  postero- 
median and  postero-lateral  columns.  These  are  most  distinct  in  the  cervical 
region,  but  are  stated  by  Foville  to  exist  throughout  the  whole  length  of  the 
cord.  On  each  side  of  the  anterior  median  fissure  the  anterior  roots  of  the  spinal 
nerves  emerge  from  the  cord,  not  in  one  vertical  line,  but  by  separate  bundles 
which  occupy  an  area  of  some  width.  This  is  called,  by  some  anatomists,  the 
antero-lateral  fissure  of  the  cord  (sulcus  lateralis  anterior),  although  no  actual 
fissure  exists  in  this  situation. 

Columns  of  the  Cord  (funiculi  medtdlae  spinalis)  (Figs.  538  and  539).— Each 
half  of  the  spinal  cord  is  thus  divided  into  four  columns:  an  anterior  column,  a  lateral 
column,  a  posterior  column,  and  a  postero-median  column.  This  division,  however,  is 
very  imperfect,  since  the  limit  between  the  so-called  anterior  and  lateral  columns 
cannot  be  defined  on  account  of  the  bundles  of  the  anterior  roots  being  spread  over 


THE  SPINAL    CORD  839 

a  considerable  area.  It  is  therefore  customary  to  divide  each  half  of  the  spinal  cord 
into  two  columns,  separated  by  the  postero-lateral  sulcus:  (1)  a  small  posterior 
column  (funiculus  posterior),  which  is  bounded  internally  by  the  posterior  median 
fissure,  and  externally  by  the  postero-lateral  sulcus,  and  the  posterior  column  is 
subdivided  by  the  posterior  intermediate  septum  into  an  outer  portion,  the  column 
or  tract  of  Burdach  {fasciculus  cuneatu^) ,  and  an  inner  portion,  the  column  or  tract 
of  GoU  {fasciculus  gracilis)',  (2)  a  large  antero-lateral  column,  which  comprises 
the  rest  of  the  cord.  The  antero-lateral  column  is  divided  arbitrarily  into  the 
lateral  column  (funiculus  lateralis)  and  the  anterior  column  (funiculus  anterior). 

Structure  of  the  Cord  (Fig.  538). — If  a  transverse  section  of  the  spinal  cord 
be  made,  it  will  be  seen  to  consist  of  white  and  gray  nervous  substance.  The 
white  matter  is  situated  externally,  and  constitutes  the  greater  part.  The  gray 
substance  occupies  the  centre,  and  is  so  arranged  as  to  present  on  the  surface  of 
the  section  two  crescentic  masses,  placed  one  in  each  lateral  half  of  the  cord,  united 
together  by  a  transverse  band  of  gray  matter,  the  gray  commissure.  Each  cres- 
centic mass  has  an  anterior  or  ventral  horn  (coluvma  grisea  anterior)  and  a  posterior 
or  dorsal  horn  (columna  grisea  posterior).  The  posterior  horn  is  long  and  narrow,  and 
approaches  the  surface  of  the  postero-lateral  fissure,  near  which  it  presents  a  slight 
enlargement,  the  caput  comu;  from  this  it  tapers  to  form  the  apex  comu  {apex 
columna  grisea  posterior),  which  at  the  surface  of  the  cord  becomes  continuous 
with  some  of  the  fibres  of  the  posterior  roots  of  the  spinal  nerves.  The  constriction 
near  the  gray  commissure  is  called  the  cervix  comu  (cervix  columna  grisea  posterior). 
The  anterior  horn  is  short  and  thick,  and  does  not  quite  reach  the  surface,  but 
extends  toward  the  point  of  attachment  of  the  anterior  roots  of  the  nerves.  Its 
margin  presents  a  dentate  or  stellate  appearance.  What  is  known  as  the  lateral 
horn  (columna  grisea  lateralis)  projects  from  the  outer  aspect  of  the  gray  matter 
nearly  on  the  line  of  the  gray  commissure.  It  is  distinct  in  the  upper  dorsal  region ; 
in  the  cervical  enlargement  it  is  merged  in  the  anterior  horn,  but  it  reappears  in 
the  upper  cervical  region.  In  the  lumbar  region  it  merges  with  the  anterior  horn. 
Owing  to  the  projections  toward  the  surface  of  the  anterior  and  posterior  horns 
of  the  gray  matter,  each  half  of  the  cord  is  divided  by  the  gray  matter,  more  or 
less  completely,  into  three  columns,  anterior,  middle,  and  posterior,  the  anterior 
and  middle  being  joined  to  form  the  antero-lateral  column,  as  the  anterior  horn 
does  not  quite  reach  the  surface. 

The  Commissure  of  the  Spinal  Cord. — The  commissure  of  the  spinal  cord  is  com- 
posed of  white  and  gray  matter,  and  is  therefore  divided  into  the  white  and  gray 
commissure. 

The  Anterior  or  White  Commissure  (commissura  anterior  alba)  is  situated  at  the 
bottom  of  the  anterior  median  fissure,  and  is  formed  of  medullated  nerve-fibres, 
which  pass  between  the  gray  matter  of  the  anterior  horn  and  the  anterior  and 
lateral  white  columns  of  one  side  into  similar  parts  on  the  other  side.  The 
fibres  are  oblique  in  direction;  many  which  enter  at  the  posterior  part  of  the 
commissure  on  the  one  side  leave  it  at  the  anterior  part  of  the  commissure  on  the 
other,  and  vice  versa,  a  decussation  taking  place  in  the  middle  line. 

The  Posterior  or  Gray  Commissure  (commissura  grisea),  which  connects  the  two 
crescentic  masses  of  gray  matter,  is  separated  from  the  bottom  of  the  anterior 
median  fissure  by  the  anterior  white  commissure.  It  consists  of  transverse 
medullated  nerve-fibres,  with  a  considerable  quantity  of  neuroglia  between  them. 
The  fibres  w^hen  they  reach  the  lateral  crescents  diverge :  some  pass  backward  to 
the  posterior  roots;  others  spread  out,  at  various  angles,  into  the  crescent.  The 
portion  of  the  gray  commissure  in  front  of  the  central  canal  is  called  the  anterior 
gray  commissure  (commissura  grisea  anterior) ;  the  portion  behind  the  central  canal 
is  called  the  posterior  gray  commissure  (commissura  grisea  posterior). 

Running  through  the  gray  commissure  of  the  whole  length  of   the  cord  is  a 


840  THE   NERVOUS  SYSTEM 

minute  canal,  which  is  barely  visible  to  the  naked  eye  in  the  human  cord,  but  is 
proportionately  larger  in  some  of  the  lower  vertebrata.  It  is  called  the  central 
canal  (canalis  centralis);  it  opens  above  into  the  fourth  ventricle,  and  terminates 
below  in  a  somewhat  dilated  extremity,  the  inferior  rhomboid  fossa  (fossa  rhom- 
boidea  inferior).  It  is  surrounded  by  an  area  of  neuroglia,  which,  in  the  recent 
state,  has  a  gelatinous  appearance,  and  in  which  there  are  no  nerve-fibres.  This 
is  sometimes  called  the  substantia  gelatinosa  centralis.  When  hardened  in  alcohol 
or  chromic  salts  it  has  a  finely  reticulated  appearance.  The  canal  is  lined  in  the 
foetus  by  columnar  ciliated  epithelium,  but  in  the  adult  the  cilia  have  disappeared, 
and  the  canal  is  filled  with  their  remains. 

The  mode  of  arrangement  of  the  gray  matter,  and  its  amount  in  proportion  to 
the  white,  vary  in  different  parts  of  the  cord.  Thus,  the  posterior  horns  are  long 
and  narrow  in  the  cervical  region;  short  and  narrower  in  the  dorsal;  short,  but 
wider,  in  the  lumbar  region.  In  the  cervical  region  the  crescentic  portions  are 
small,  and  the  white  matter  more  abundant  than  in  any  other  region  of  the  cord. 
In  the  dorsal  region  the  gray  matter  is  least  developed,  the  white  matter  being 
also  small  in  quantity.  In  the  lumbar  region  the  gray  matter  is  more  abundant 
than  in  any  other  region  of  the  cord.  Toward  the  lower  end  of  the  cord  the  white 
matter  gradually  ceases.  The  crescentic  portions  of  the  gray  matter  soon  blend 
into  a  single  mass,  which  forms  the  only  constituent  of  the  extreme  point  of  the 
cord. 

Blood  Supply  of  the  Cord. — Spinal  branches  are  given  off  by  the  vertebral, 
ascending  cervical,  deep  cervical,  intercostal,  lumbar,  lumbar  branches  of  the  ilio- 
lumbar, lateral  and  middle  sacral  arteries.^  Many  of  these  spinal  arteries  give 
branches  to  the  cord  and  the  branches  reach  the  cord  in  the  spinal  nerve-roots 
and  form  three  vascular  chains  in  the  cord.  The  arteries  of  the  cord  are  the 
anterior  spinal  and  the  two  posterior  spinal,  which  take  origin  from  the  vertebral 
arteries  (pp.  638  and  639).  The  anterior  spinal  lies  at  the  surface  of  the  anterior 
median  fissure.  The  posterior  spinal  arteries  descend  on  either  side  of  the  cord 
behind  the  posterior  nerve-roots.  The  central  supply  of  the  cord  is  chiefly  from 
the  anterior  spinal  artery.  It  sends  sulcal  branches  inward  in  the  fissure  toward 
the  cord,  and  branches  of  these  vessels  enter  the  cord.  The  vessels  of  the  cord 
are  terminal  arteries.  The  gray  matter  is  chiefly  supplied  by  the  anterior  spinal, 
partly  by  the  posterior  spinal.  The  white  matter  is  supplied  by  both  vessels.  From 
the  interior  of  the  cord  blood  is  brought  by  fissural  veins  (which  emerge  from  the 
fissures),  root-veins  (which  emerge  with  the  fibres  of  the  anterior  and  posterior 
roots),  and  a  few  veins  which  emerge  from  different  parts  of  the  surface  of  the 
cord.  These  vessels  unite  to  form  the  meduUi-spinal  plexus,  which  is  between  the 
pia  mater  and  the  arachnoid  membrane.     (See  Spinal  Veins.) 

Lymphatics. — There  are  no  lymph-vessels  in  the  cord,  but  l\Tnph  is  collected  by 
perivascular  lymph-spaces  and  by  spaces  about  the  nerve-fibres. 

Minute  Anatomy  of  the  Cord. — The  cord  consists  of  an  outer  part,  composed 
of  medullated  nerve-fibres,  which  is  the  white  substance ;  and  of  a  central  part,  the 
gray  matter,  both  supported  in  a  stroma. 

The  stroma  is  composed  of  connective  tissue,  which  is  derived  from  the  pia  by 
ingrowth,  and  hence  is  of  mesodermic  origin,  and  of  neurogUa. 

The  Neuroglia. — ^The  neuroglia  consists  of  a  homogeneous  transparent  matrix, 
of  a  network  of  very  delicate  fibrillae,  and  of  small  stellate  or  branched  cells,  the 
neuroglia-cells. 

It  takes  origin  from  cells  which  were  derived  from  the  large  columnar  cells  of 
the  wall  of  the  neural  canal,  and  hence  is  of  epithelial  origin. 

„\^  Manual  of  Practical  Anatomy.    By  the  late  Prof.  Alfred  W.  Hughes.     Edited  and  completed  by  Arthur 


THE    SPINAL    COBD 


841 


In  addition  to  forming  a  ground  substance,  in  which  the  nerve-fibres,  nerve- 
cells,  and  blood-vessels  are  embedded,  a  considerable  accumulation  of  neuroglia 
takes  place  in  three  situations:  (1)  on  the  surface  of  the  cord,  beneath  the  pia 
mater;  (2)  around  the  central  canal,  the  substantia  gelatinosa  centralis;  and  (3) 
as  a  cap  over  the  extremity  of  the  posterior  horn,  forming  the  substantia  cinerea 
gelatinosa. 

The  White  Substance  of  the  Cord  (substantia  alba). — The  white  substance  of  the 
cord  is  placed  at  the  periphery  and  in  the  anterior  commissure.  It  consists  of 
medullated  nerve-fibres,  mostly  disposed  longitudinally,  with  blood-vessels  and 
neuroglia,  sustained  by  a  network  of  connective  tissue  from  the  pia.  When  stained 
with  carmine  it  presents  a  very  striking  appearance  on  transverse  section.  It  is 
seen  to  be  studded  all  over  with  minute  dots,  surrounded  by  white  areas.  This 
is  due  to  the  longitudinal  medullated  fibres  seen  on  section.  Each  dot  is  an  axis- 
cylinder,  the  white  area  about  it  is  the  substance  of  Schwann.  Externally,  the 
neuroglia  forms  a  sheath  closely  in- 
vesting the  outer  surface  of  the  cord 
immediately  beneath  the  pia  mater; 
from  it  numerous  septa  pass  in- 
ward and  separate  the  respective 
bundles  of  fibres  and  extend  between 
the  individual  nerve-fibres,  acting 
as  a  supporting  medium,  in  which 
they  are  embedded.  There  are 
transverse,  oblique  or  dorso-ventral 
and  longitudinal  fibres  in  the  white 
substance. 

Transverse  Fibres. — These  fibres 
pass  between  the  longitudinal  tracts 
of  the  cord  and  the  gray  matter. 
They  constitute  the  anterior  or 
white  commissure,  which  joins  the 
anterior  and  lateral  white  columns 
and  the  anterior  gray  horn  of  one  side 
to  like  parts  of  the  opposite  side. 

As  previously  stated,  it  is  in  front 
of  the  gray  commissure,  and  is  the 
floor  of  the  anterior  median  fissure. 
It  contains  four  sets  of  fibres:  (1) 
those  belonging  to  the  direct  pyram- 
idal tract,  (2)  those  belonging  to  the 
antero-lateral  ground  bundle,  (3)  those  belonging  to  the  antero-lateral  ascending 
cerebellar  tract,  (4)  crossed  fibres  to  the  anterior  spinal  nerve-roots.^ 

Oblique  or  Dorso-ventral  Fibres. — These  are  the  anterior  root-fibres  passing  from 
the  anterior  gray  horn  to  the  periphery  of  the  cord  and  the  posterior  root-fibres 
passing  from  the  periphery  of  the  cord  to  the  posterior  gray  horn. 

Longitudinal  Fibres. — They  constitute  the  conducting  tracts  (Fig.  539). 

It  is  impossible  to  trace  the  course  of  the  nerve-fibres  in  their  passage  through 
the  cord;  but  the  investigation  of  pathological  lesions  has  shown  that  the  white 
matter  of  the  cord  consists  of  certain  columns  or  tracts  of  fibres;  for  it  has  been 
found  that  certain  lesions  are  strictly  limited  to  certain  well-determined  parts  of 
the  cord  without  involving  neighboring  regions.  That  these  parts  or  fasciculi 
correspond  to  so  many  distinct  anatomical  systems,  each  endowed  with  special 


Fig.  539. — Columns  of  the  cord. 


'  Santee.    The  Anatomy  of  the  Brain  and  Spinal  Cord. 


I 


842  THE   NERVOUS  SYSTEM 

functions,  seems  abundantly  proved  by  the  researches  of  Flechsig  and  others  on 
the  development  of  the  spinal  cord  during  the  later  periods  of  utero-gestation  and 
in  the  newly  born  infant.  By  these  researches  several  tracts  can  be  traced  along 
the  greater  part  of  the  cord  and  into  or  from  the  encephalon  (Fig.  539).  Thus  ( 1)  in 
the  antero-lateral  column  of  the  cord,  on  either  side  of  the  anterior  median  fissure,  a 
portion  of  the  column  may  be  divided  off  as  the  uncrossed  or  direct  pyramidal  tract 
or  the  fasciculus  of  Turck  (fasciculus  cerebrospinalis  anterior  [ventralis]) .  This  tract 
is  a  continuation  of  the  corresponding  tract  in  the  medulla.  It  is  only  found  in  the 
upper  part  of  the  cord;  it  gradually  diminishes  as  it  is  traced  downward,  and  dis- 
appears about  the  middle  of  the  dorsal  region.  It  consists  of  centrifugal  or  descend- 
ing fibres  which  can  be  traced  downward  from  the  pyramid  of  the  medulla  of  the 
same  side,  and  are  derived  from  the  motor  area  of  the  cerebral  cortex.  The  fibres 
of  this  tract  decussate  in  their  course  down  the  cord,  passing  across  the  middle 
line  through  the  anterior  white  commissure  and  terminating  in  the  anterior  gray 
horn  of  the  opposite  side;  this  explains  the  gradual  diminution  and  eventual  dis- 
appearance of  the  tract.  (2)  In  the  hinder  part  of  the  antero-lateral  column  is  a 
somewhat  triangular  area,  larger  than  the  preceding,  which  is  named  the  crossed 
pyramidal  tract  (fasciculus  cerebrospinalis  lateralis).  In  the  cervical  and  dorsal 
regions  the  crossed  pyramidal  tract  is  overlaid  by  the  direct  cerebellar  tract,  but 
in  the  lumbar  cord  it  is  at  the  surface.  This  also  consists  of  descending  fibres, 
which  are  derived  from  the  pyramid  of  the  medulla  of  the  opposite  side,  and 
which  have  crossed  in  the  decussation  of  the  pyramids.  After  crossing  in  the 
medulla  the  fibres  descend  and  terminate  about  the  cells  in  the  anterior  cornu 
of  the  same  side  as  the  column.  The  fibres  are  derived  from  the  motor  area 
of  the  cerebral  cortex  of  the  opposite  side.  Thus  it  will  be  seen  that  all  the 
fibres  from  the  motor  area,  which  descend  through  the  internal  capsule,  the  crus 
cerebri,  and  the  pons  Varolii  to  the  pyramidal  body  of  the  medulla,  decussate. 
Some  decussate  in  the  lower  part  of  the  medulla,  and  descend  through  it  as  the 
crossed  pyramidal  tract.  Others  do  not  decussate  in  the  medulla  but  descend  as  the 
direct  pyramidal  tract  and  cross  through  the  anterior  commissure  of  the  cord  to  ter- 
minate in  the  anterior  gray  horn  of  the  opposite  side,  where  the  fibres  end  by  forming 
synapses  around  its  cells.  Investigations  render  it  probable  that  the  crossed  pyram- 
idal tract  contains  some  fibres  from  the  main  pyramidal  tract  in  the  medulla,  which 
have  descended  from  the  corresponding  side  of  the  brain  undecussated  and  terminate 
about  the  cells  of  the  gray  cornu  of  the  same  side  of  the  cord.  The  crossed  descending 
tract  of  the  red  nucleus  is  found  within  the  crossed  pyramidal  tract  at  the  junction  of 
its  lateral  and  dorsal  portions.  This  tract  from  the  opposite  red  nucleus  reaches 
the  lumbar  cord  and  ends  in  the  gray  matter.  (3)  The  antero-lateral  tract  is  an 
extensive  crescent-shaped  strand  which  skirts  the  circumference  of  the  anterior 
three-quarters  of  the  antero-lateral  colunm  of  the  cord.  Behind,  where  it  is 
thickest,  it  lies  in  the  angle  formed  by  the  direct  cerebellar  and  crossed  pyramidal 
tracts,  becoming  narrower  as  it  passes  forward  toward  the  direct  pyramidal  tract. 
It  contains  two  sets  of  fibres,  centripetal  or  ascending,  and  centrifugal  or  descend- 
ing, and  hence  is  divided  into  two  tracts,  the  antero-lateral  ascending  and  the 
antero-lateral  descending  cerebellar  tracts,  (a)  The  antero-lateral  ascending  cerebellar 
tract  or  the  column  of  Gowers  (fasciculus  anterolateralis  superficialis  ascendens) 
is  chiefly  in  the  posterior  part  of  the  antero-lateral  tract,  although  some  of  its 
fibres  mingle  with  the  descending  tract.  The  axones  which  compose  this  tract 
arise  from  cells  in  the  central  gray  matter  and  the  gray  matter  of  the  base  of  the 
anterior  horn,  chiefly  from  the  opposite  side  of  the  cord  (Santee),  most  of  the 
fibres  crossing  soon  after  their  beginning  by  way  of  the  anterior  commissure.  The 
fibres  of  the  column  of  Gowers  pass  through  the  dorsal  portion  of  the  lateral  region 
of  the  medulla  (sending  nerve  fibres  to  the  lateral  nucleus)  and  the  formatio  reticu- 
laris of  the  pons,  turn  backward  over  the  superior  peduncle  of  the  cerebellum,  and 


THE  SPINAL    CORD  843 

pass  into  the  superior  vermis  through  the  valve  of  Yieussens  (San tee,  from  Hoche). 
Between  the  ascending  and  descending  tracts  is  the  olivary  bundle  of  the  cord  or  the 
triangular  tract  of  Helwig  (tractus  triangularis  [Helwigi]) .  It  arises  in  the  lumbar  cord 
and  terminates  in  the  olive  of  the  medulla,  (b)  The  antero-lateral  descending  cere- 
bellar tract  or  the  column  of  Marchi  and  Lowenthal  (Jasciculus  anterolateralis  super- 
ficialis  descendens)  is  situated  chiefly  in  the  anterior  portion  of  the  antero-lateral 
tract,  but  some  of  its  fibres  are  scattered  among  the  fibres  of  Gowers'  column.  The 
axones  of  the  descending  tract  are  derived  from  Purkinjean  cells  in  the  cerebellar 
cortex.  The  fibres  pass  through  the  inferior  peduncle  of  the  cerebellum  and  the 
lateral  region  of  the  medulla  and  terminate  in  the  anterior  gray  horn.  (4)  The 
direct  cerebellar  or  dorso-lateral  cerebellar  tract  (fasciculus  cerebellospinalis)  is  situ- 
ated at  the  circumference  of  the  cord  behind  the  preceding  and  external  to  the 
crossed  pyramidal  tract,  occupying  a  narrow  area  which  extends  backward  as  far 
as  the  postero-lateral  fissure  or  nearly  so.  It  commences  at  the  upper  level  of  the 
lumbar  cord.  Below  this  level  it  is  absent,  and  where  it  is  absent  the  crossed  pyram- 
idal tract  reaches  the  surface.  As  the  direct  cerebellar  tract  ascends  it  increases  in 
size.  It  passes  through  the  restiform  body  of  the  medulla  and  terminates  in  the 
superior  vermis  of  the  cerebellum.  Its  fibres  are  derived  from  the  cells  of  the 
posterior  vesicular  column  of  Clarke  in  the  gray  matter  of  the  cord.  (5)  Close  to 
the  point  where  the  posterior  roots  enter  the  cord,  in  the  antero-lateral  column,  is 
a  small  collection  of  fibres,  which  is  known  as  the  marginal  tract  of  Spitzka  and 
Lissauer  (fasciculus  marginalis) ;  it  is  formed  by  some  of  the  outer  fibres  of  the 
posterior  roots  which  run  upward  in  the  tract  for  a  short  distance,  and  end  about 
the  cell-bodies  of  the  substantia  gelatinosa  (Santee).  (6)  The  rest  of  the  antero- 
lateral column  of  the  spinal  cord  is  occupied  by  the  antero-lateral  ground  bundle 
(fasciculus  proprius  anterolateralis).  It  surrounds  the  anterior  cornu  and  sepa- 
rates the  antero-lateral  tract  and  the  crossed  pyramidal  tract  from  the  gray  matter 
of  the  cord.  Nowhere  does  it  reach  the  surface  of  the  cord,  but  at  one  place  it  very 
closely  approaches  it.  The  direct  pyramidal  tract  separates  it  from  the  antero- 
median fissure.  The  fibres  are  very  short  and  are  commissural  and  associative. 
The  portion  of  the  ground  bundle  in  the  anterior  column  is  chiefly  coinmissural, 
its  fibres  passing  between  the  anterior  cornua.  The  portion  in  the  lateral  column 
is  chiefly  for  association,  its  fibres  joining  different  areas  of  the  cord  on  the  same 
side.  It  consists  of  (a)  longitudinal  fibres.  A  posterior  longitudinal  bundle  (fas- 
ciculus longitudinalis  medialis) ,vfh\Qh.  ascends  to  reach  the  motor  nuclei  of  cranial 
nerves  and  the  subthalamic  region.  An  anterior  longitudinal  bundle  (fasciculus 
veniralis)  passes  from  the  superior  corpus  quadrigeminum  to  the  cilio-spinal  and 
other  centres  (Santee).  Longitudinal  commissural  fibres,  which  unite  the  groups 
of  cells  in  the  gray  matter  with  one  another;  (b)  of  fibres  which  pass  across  the 
anterior  commissure  from  the  gray  matter  of  the  opposite  side;  and  (c)  horizontal 
fibres  belonging  to  the  anterior  roots  of  the  nerves,  which  pass  through  it  before 
leaving  the  cord.  In  the  posterior  column  of  the  cord  there  are  two  definite  tracts. 
They  are  marked  off  fr6m  each  other  by  the  posterior  intermediate  furrow  on  the 
surface  of  the  cord.  The  part  which  has  been  described  previously  as  the  posterior 
median  column  pretty  nearly  corresponds  to  the  one  tract,  the  tract  of  GoU,  and 
the  remainder  of  the  posterior  column  corresponds  to  the  other,  the  tract  of  Bur- 
dach.  (7)  The  postero-median  tract  or  tract  of  GoU  (fasciculus  gracilis)  increases 
as  it  ascends,  and  consists  of  long,  but  small,  fibres  derived  from  the  posterior 
roots  of  the  spinal  nerves,  which  ascend  to  the  medulla  oblongata,  the  fascic- 
ulus gracilis  of  the  medulla,  and  end  in  the  nucleus  gracilis.  Some  fibres  leave 
the  tract  and  end  in  the  gray  matter  of  the  cord.  A  few  fibres  pass  to  the 
thalamus  and  a  few  to  the  cerebellum.  (8)  The  postero-lateral  tract  or  the  tract 
of  Burdach  (fasciculus  cuneatus)  consists  of  shorter,  but  larger,  fibres  than  the 
preceding;  they  are  derived  from  the  posterior  roots  and  from  cells  in  the  gray 


844  THE  NERVOUS  SYSTEM 

matter  of  the  cord;  some  ascend  only  for  a  short  distance  in  the  tract  and  then 
enter  the  gray  matter  and  come  into  close  relationship  with  the  cells  of  the  pos- 
terior vesicular  column  of  Clarke;  others  incline  toward  the  mesial  plane,  and, 
entering  Goll's  column,  can  be  traced  as  far  as  the  medulla.  The  tract  of  Burdach 
becomes  in  the  medulla  the  fasciculus  cuneatus  and  the  fasciculus  of  Rolando. 
Some  of  its  fibres  continue  along  the  interolivary  fillet,  others  along  the  arciform 
fibres,  and  some  terminate  in  the  gray  matter  of  the  cord  (Santee).  In  the  cervical 
and  upper  dorsal  regions  there  is  contained  in  the  substance  of  Burdach's  column 
a  small  strand  of  fibres,  called  the  descending  comma  tract.  It  presents,  on  trans- 
verse section,  the  appearance  of  a  comma,  the  blunt  extremity  of  which  is  directed 
forward.  The  fibres  forming  it  probably  represent  in  part  descending  portions  of 
the  dorsal  nerve-roots,  together  with  descending  commissural  fibres  within  the 
cord  itself. 

What  is  known  as  the  comu  commissural  tract  is  in  the  lumbar  and  lower  dorsal 
regions,  between  the  posterior  cornu  and  the  gray  commissure.  The  septo- 
marginal tract  is  only  found  in  a  portion  of  the  lumbar  cord.  It  is  between  the 
septum  and  the  dorsal  surface  of  the  cord  (Santee). 

Functions  of  the  Various  Tracts  in  the  Cord. — 1.  The  direct  pyramidal 
tract  is  motor,  and  conveys  impulses  chiefly  to  the  arms  and  trunk.  It  conducts 
motor  impulses  from  the  cerebral  cortex  of  one  side,  along  the  spinal  cord  of  the 
same  side,  and  to  the  multipolar  nerve-cells  of  the  anterior  horn  of  the  opposite 
side  of  the  cord.  A  given  muscular  region  is  supplied  chiefly  by  the  crossed 
pyramidal  tract  of  the  corresponding  side  of  the  cord  and  partly  by  the  direct 
pyramidal  tract  of  the  opposite  side  of  the  cord,  but  both  tracts  are  innervated 
by  the  same  brain  area.  It  is  further  to  be  remembered  that  there  are  prob- 
ably direct  or  uncrossed  fibres  in  the  crossed  pyramidal  tracts  of  the  cord  which 
convey  motor  impulse  from  the  cortex  to  muscles  of  the  same  side. 

2.  The  crossed  pyramidal  tract  conveys  motor  impulses  and  impulses  which 
control  reflex  movements.  It  descends  from  the  cortex,  decussates  in  the  lower 
part  of  the  medulla,  and  descends  in  the  cord  on  the  side  opposite  to  the  brain  area 
from  which  it  arose.  It  supplies  muscles  on  the  same  side  of  the  body  as  the  tract 
is  of  the  cord.  This  tract  also  contains  a  few  uncrossed  fibres  from  the  same  side 
of  the  brain.  Hence  the  muscles  of  one  side  receive  their  chief  innervation  from 
the  opposite  side  of  the  brain  by  way  of  the  crossed  and  the  direct  pyramidal  tracts, 
but  receive  some  slight  innervation  from  the  same  side  of  the  brain  by  way  of  the 
direct  fibres  in  the  crossed  pyramidal  tract.  Gowers^  says:  "There  is  abundant 
evidence  that  each  hemisphere  of  the  brain  is  connected  with  both  legs,  although 
chiefly  with  that  of  the  opposite  side.  There  is  also  a  similar  and  even  more 
equal  connection  with  the  trunk  muscles,  and  a  slighter  connection  with  certain 
muscles  of  the  arm.  Such  muscles  invariably  regain  some  power  on  the  paralyzed 
side,  even  with  a  complete  interruption  to  the  motor  path,  and  they  are  weakened 
on  the  unparalyzed  side." 

3.  The  antero-lateral  descending  cerebellar  tract  is  a  ''segment  of  an  indirect 
motor  path"  (Santee).  The  antero-lateral  ascending  cerebellar  tract  conveys 
impressions  of  temperature  and  pain. 

4.  The  direct  cerebellar  tract  conveys  impressions  of  equilibrium,  particularly 
from  the  viscera. 

5.  The  antero-lateral  ground  bundle  is  associative  between  the  anterior  cornua 
and  is  commissural  between  different  segments  of  the  cord.  These  commissural 
and  associative  connections  are  of  great  importance,  for  if  the  regular  route  of 
nervous  conduction  is  interrupted  they  may  serve  to  convey  the  nerve  current 
around  the  block. 

'  Diseases  of  the  Nervous  System. 


THE   SPINAL    CORD  845 

6.  The  marginal  tract  of  Spitzka  and  Lissauer  is  composed  of  ascending  fibres 
from  the  posterior  nerve-roots. 

7.  The  postero-lateral  tract  conveys  impressions  of  common  sensation. 

8.  The  postero-median  tract  conveys  impressions  of  muscular  sense. 

The  Gray  Substance  of  the  Cord  {substantia  grisea). — The  gray  substance  of  the 
cord  occupies  its  central  part  in  the  shape  of  two  crescentic  horns,  joined  together 
by  the  gray  commissure.  Each  of  these  crescents  has  an  anterior  or  ventral  and 
a  posterior  or  dorsal  comu. 

The  Posterior  or  Dorsal  Horn  (columna  grisea  posterior)  consists  of  a  slightly  nar- 
rowed portion,  at  its  base,  where  it  is  connected  with  the  rest  of  the  gray  substance 
— this  is,  the  cervix  comu;  from  this  it  gradually  expands  into  the  main  part  of  the 
horn,  the  caput  comu,  and  tapers  to  form  the  apex  comu;  around  its  extremity  is  a 
lamina  or  layer  of  gelatinous  material,  which  covers  the  head  like  a  cap,  and 
from  this  it  tapers  almost  to  a  point,  which  approaches  the  surface  of  the  cord  at 
the  postero-lateral  groove. 

The  gelatinous  substance  is  a  peculiar  accumulation  of  neuroglia  (Klein) 
similar  to  that  found  around  the  central  canal,  and  has  been  named  by  Rolando 
the  substantia  cinerea  gelatinosa.  It  probably  takes  its  origin  from  the  columnar 
cells  which  line  the  posterior  part  of  the  embryonic  spinal  canal. 

The  Anterior  or  Ventral  Hom  of  the  Gray  Substance  (columna  grisea  anterior)  in 
the  cervical  and  lumbar  swellings,  where  it  gives  origin  to  the  motor  nerves  of  the 
extremities,  is  much  larger  than  in  any  other  region,  and  contains  several  distinct 
groups  of  large  and  variously  shaped  cells. 

In  addition  to  this,  a  lateral  horn  (columna  grisea  lateralis)  is  found  projecting 
outward  from  the  lateral  region  of  the  gray  matter  on  a  level  with  the  gray  com- 
missure in  the  upper  part  of  the  dorsal  region  of  the  cord;  in  the  cervical  and 
lumbar  regions  this  lateral  horn  blends  with  the  anterior  horn,  which  thus  becomes 
broad  and  expanded.  From  the  concavity  of  the  crescent,  between  the  anterior 
and  posterior  horns,  processes  of  gray  matter  extend  into  the  white  substance, 
where  they  divide  and  anastomose  to  form  a  network,  termed  the  formatio  reticu- 
laris. 

The  gray  commissure  contains  the  central  canal  (canalis  centralis),  and  is  situated 
behind  the  white  commissure,  which  separates  it  from  the  bottom  of  the  anterior 
median  fissure. 

The  gray  substance  of  the  cord  is  composed  of — (1)  the  substantia  gelatinosa, 
which  envelops  the  head  of  the  posterior  horn  and  which  encircles  the  central  canal 
of  the  cord;  (2)  the  substantia  spongiosa,  which  forms  the  crescentic  horns  (except 
the  heads  of  the  posterior  horns  and  the  envelope  of  the  central  canal).  Further, 
it  may  be  stated  that  the  gray  matter  consists  of  nerve-fibres  of  variable  but 
smaller  average  diameter  than  those  of  the  white  column;  (3)  nerve-cells  of  various 
shapes  and  sizes,  with  from  two  to  eight  processes;  (4)  blood-vessels  and  con- 
nective tissue. 

The  nerve- fibres  of  the  gray  matter  of  the  posterior  horn  are  for  the  most  part 
composed  of  a  dense  interlacement  of  minute  fibrils,  intermingled  with  nerves 
of  a  larger  size.  This  interlacement  is  formed  partly  by  the  axones  and  dendrites 
of  the  cells  of  the  gray  matter,  and  partly  by  fibres  which  enter  the  gray  matter 
and  which  come  from  various  sources. 

The  nerve-cells  of  the  gray  matter  are  collected  into  groups  as  seen  on  trans- 
verse section,  but  they  really  form  columns  of  cells  placed  longitudinally;  or  else 
they  are  found  scattered  throughout  the  whole  of  the  gray  matter. 

In  the  anterior  horn  the  cells  consist  of  two  chief  groups;  one  medial,  the  more 
constant,  near  the  anterior  column;  the  other  lateral,  near  the  lateral  column. 
The  axones  of  these  cells  constitute  the  bulk  of  the  anterior  roots  of  the  spinal 
nerves.    The  spinal  nerves  obtain  axones  from  the  entire  lateral  gray  column  and 


k 


846 


THE   NERVOUS  SYSTEM 


from  part  of  the  medial  gray  column  of  the  same  side,  and  also  from  the  gray 
matter  of  the  medial  column  of  the  opposite  side  by  way  of  the  white  commissure. 
The  nerve-fibres  from  these  cells  are  distributed  to  the  muscles  of  the  trunk  and 
extremities.  A  second  lateral  group  is  present  in  the  cervical  and  lumbar  enlarge- 
ments. In  the  centre  of  the  gray  crescent  (substantia  intermedia  grisea)  the  cells 
are  collected  into  three  groups  or  columns.  The  intermedio-lateral  column  runs 
throughout  the  length  of  the  cord,  but  is  most  distinct  in  the  thoracic  region.  Its 
cells  are  in  relation  with  fibres  from  the  posterior  nerve-roots  and  send  off  axones 
to  the  anterior  nerve-roots.  It  is  believed  by  Morris  and  others  that  these  fibres  are 
sympathetic  and  pass  to  glands  and  blood-vessels.  Other  axones  enter  the  antero- 
lateral ascending  cerebellar  tract  (San tee).  The  middle  column  is  most  distinct  in  the 
cervical  cord.  It  certainly  receives  fibres  from  the  posterior  roots,  and  possibly 
sends  fibres  to  the  antero-lateral  ascending  cerebellar  tract.  At  the  base  of  the  pos- 
terior horn  on  its  inner  side,  adjoining  the  gray  commissure,  is  a  group  of  nerve- 
cells,  called  Clarke's  posterior  or  dorsal  column  or  Clarke's  vesicular  column  {nucleus 
dorsalis) ,  which  extends  from  the 
eighth  cervical  to  the  second  lum- 
bar nerve.  In  the  cervical  and 
lumbar  cord  the  nuclei  of  Stilling 
are  its  representatives,  and  in  the 
medulla  the  accessory  cuneate  nu- 
cleus represents  it.   This  column 


Fig.  540. 


-Formation  of  a  spinal  nerve. 
(Testut.) 


Fig.  541. — Dorsal  roots  entering  cord  and  dividing  into  ascend- 
ing and  descending  branches,  a.  Stem-iibre.  b,  b.  Ascending  and 
descending  limbs  of  bifurcation,  c.  Collateral  arising  from  stem- 
fibre.     (Van  Gehuchten.) 


is  in  relation  with  the  fibres  of  the  posterior  nerve-roots,  and  the  axones  from 
the  cells  of  the  column  compose  the  direct  cerebellar  tract,  and  some,  which  are 
sympathetic,  enter  the  anterior  roots  of  the  spinal  nerves.  In  the  posterior  cornu 
are  many  cells  not  definitely  arranged,  but  groups  which  are  named  peripheral, 
central,  and  basal.  The  axones  of  the  cells  of  the  posterior  cornu  enter  the 
ground  bundles,  the  column  of  Burdach,  the  anterior  cornu  of  the  same  side,  and 
the  anterior  and  posterior  cornua  of  the  opposite  side.  Many  fibres  of  the  poste- 
rior roots  are  in  relation  with  the  cells  of  the  posterior  cornu. 

At  the  junction  of  the  anterior  and  posterior  cornua,  in  the  outer  portion  of  the- 
gray  matter,  is  a  third  group  of  cells,  the  lateral  cell  column;  this  is  best  seen  in 
the  dorsal  region.    In  certain  regions  of  the  cord  these  cells  extend  in  among 
the  fibres  of  the  white  matter  of  the  lateral  column,  and  give  rise  to  the  lateral 
horn. 


THE  DURA    MATER    OF   THE  BRAIN  847 

In  addition  to  these  groups  a  few  large  scattered  cells  are  found  in  the  posterior 
horn  and  in  the  substantia  gelatinosa  of  Rolando. 

Origin  of  the  Spinal  Nerves  (Figs.  538  and  540). — The  roots  of  the  spinal  nerves 
are  attached  to  the  surface  of  the  cord,  opposite  the  horns  of  gray  matter. 

A  Posterior  Nerve-root  enters  the  cord  in  two  bundles,  medial  and  lateral.  The 
medial  strand  consists  of  coarse  fibres  which  enter  the  outer  part  of  the  column  of 
Burdach.  The  lateral  strand  is  sometimes  divided  into  a  middle  and  an  external 
bundle.  The  former  contains  large  fibres,  and  passes  through  the  gelatinous  sub- 
stance of  Rolando  into  the  posterior  horn.  The  external  bundle  consists  of  fine 
fibres  which  assume  a  longitudinal  direction  in  the  Spitzka-Ivissauer  tract.  All  the 
posterior  root-fibres  divide  into  ascending  and  descending  branches  on  entering  the 
cord,  and  these  in  their  turn  give  off  collaterals  (Fig.  541).  The  fibres  and  their 
collaterals  terminate  by  forming  arborescences,  some  around  the  cells  in  the 
posterior  horn,  and  others  around  the  cells  of  Clarke's  column,  while  the  long 
ascending  branches  pass  up  in  the  columns  of  GoU  and  Burdach,  and  end  by 
arborizing  around  the  cells  in  the  gracile  and  cimeate  nuclei.  Some  of  the  fibres, 
however,  pass  to  the  gray  matter  of  the  opposite  horn,  and  others  to  the  anterior 
horn  of  the  same  side  of  the  cord. 

Anterior  Nerve-roots. — The  majority  of  the  fibres  of  the  anterior  nerve-roots  are 
the  continuations  outward  of  the  axones  of  the  large  or  small  multipolar  cells  in  the 
anterior  horn  of  gray  matter.  Some,  however,  appear  to  pass  across  in  the  anterior 
a  white  commissure  to  the  cells  in  the  anterior  horn  of  the  opposite  side,  while  others 
extend  backward  to  the  posterior  horn  and  outward  to  the  lateral  column  of  the 
same  side. 

THE  MENINGES  OR  MENINGEAL  MEMBRANES  OF  THE  BRAIN 
(MENINGES  ENOEPHALI). 

Dissection. — To  examine  the  brain  with  its  membranes,  the  skull-cap  must  be  removed. 
In  order  to  effect  this,  saw  through  the  external  table,  the  section  commencing,  in  front,  about 
an  inch  above  the  margin  of  the  orbit,  and  extending,  behind,  to  a  Httle  above  the  level  with 
the  occipital  protuberance.  Then  break  the  internal  table  with  the  chisel  and  hammer,  to  avoid 
injuring  the  investing  membranes  or  brain;  loosen  and  forcibly  detach  the  skull-cap,  when  the 
dura  mater  will  be  exposed.  The  adhesion  between  the  bone  and  the  dura  mater  is  very 
intimate,  and  much  more  so  in  the  young  subject  than  in  the  adult. 

The  membranes  of  the  brain  are  from  without  inward :  the  dura  mater,  arachnoid 
membrane,  and  the  pia  mater. 

The  Dura  Mater  of  the  Brain  (Dura  Mater  Encephali)  (Figs.  543,544,545,547). 

The  dura  mater  of  the  brain  is  a  thick  and  dense  inelastic  fibrous  membrane 
which  lines  the  interior  of  the  skull.  It  is  a  covering  for  the  brain  and  is  also 
the  internal  periosteum.  Its  outer  surface  is  rough  and  fibrillated,  and  adheres 
closely  to  the  inner  surface  of  the  bones  by  fibrous  processes  and  blood-vessels. 
The  adhesion  is  most  marked  on  bony  projections,  opposite  the  sutures  and  at 
the  base  of  the  skull.  Except  at  the  sutures  the  adhesions  are  not  dense,  and 
between  the  fibrous  processes  which  pass  to  the  bone  are  spaces  which  are 
thought  to  be  lymph-spaces,  and  are  called  epidural  spaces.  At  these  points 
the  outer  surface  of  the  dura  is  covered  with  endothelium.  Fibrous  tissue 
passes  through  the  open  sutures  and  joins  the  outer  layer  of  the  dura  to  the 
external  periosteum.  It  is  known  as  the  sutural  membrane.  The  inner  sur- 
face of  the  dura  limits  the  subdural  space.  It  is  smooth  and  lined  by  a  layer  of 
endothelium.  The  dura  mater  sends  four  processes  inward,  into  the  cavity  of 
the  skull,  for  the  support  and  protection  of  the  different  parts  of  the  brain,  and  is 
prolonged  to  the  outer  surface  of  the  skull  through  the  various  foramina  which 


848  THE  NERVOUS  SYSTEM 

exist  at  the  base,  and  thus  becomes  continuous  with  the  pericranium;  its  fibrous 
layer  forms  sheaths  for  the  nerves  which  pass  through  these  apertures.  At  the 
base  of  the  skull  it  sends  a  fibrous  prolongation  into  the  foramen  ciecum ;  it  sends 
a  series  of  tubular  prolongations  around  the  filaments  of  the  olfactory  nerves  as 
they  pass  through  the  cribriform  plate,  and  also  around  the  nasal  nerve  as  it  passes 
through  the  nasal  slit;  a  prolongation  is  also  continued  through  the  sphenoidal 
fissure  into  the  orbit,  and  another  is  continued  into  the  same  cavity  through  the 
optic  foramen,  forming  a  sheath  for  the  optic  nerve,  which  is  continued  as  far  as  the 
eyeball.  In  the  posterior  fossa  it  sends  a  process  into  the  internal  auditory  meatus, 
ensheathing  the  facial  and  auditory  nerves;  another  through  the  jugular  foramen, 
forming  a  sheath  for  the  structures  which  pass  through  this  opening;  and  a  third 
through  the  anterior  condyloid  foramen.  Around  the  margin  of  the  foramen  mag- 
num it  is  closely  adherent  to  the  bone,  and  is  continuous  with  the  dura  mater  lining 
the  spinal  canal.  The  cavity  or  cave  of  Meckel  (cavum  Meckeli)  (Fig.  545)  is  an 
osteo-fibrous  recess  near  the  apex  of  the  petrous  portion  of  the  temporal  bone, 
formed  by  folding  of  the  dura  mater  in  a  bony  depression.  It  contains  the  Gas- 
serian  ganglion.  In  certain  situations,  as  already  mentioned  (p.  736),  the  fibrous 
layers  of  this  membrane  separate  to  form  sinuses  for  the  passage  of  venous  blood. 
Upon  the  outer  surface  of  the  dura  mater,  in  the  situation  of  the  longitudinal  sinus, 
may  be  seen  numerous  small,  whitish  bodies,  the  glandulae  Pacchioni  (p.  854). 

Structure  (Fig.  542). — The  dura  mater  consists  of  white  fibrous  tissue  with 
connective-tissue  cells  and  elastic  fibres  arranged  in  flattened  laminae,  which  are 
imperfectly  separated  by  lacunar  spaces  and  blood-vessels  into  two  layers, 
endosteal  and  meningeal.    The  endosteal  layer  is  the  internal  periosteum  for  the 


ENDOSTEAL 
LAYER 
MENINGEAL 
LAYER 

ENDOTHELIAL 
LINING 


Fig.  542. — The  structure  of  the  dura  mater.     Section  through  the  cranial  vault  of  a  child,  slightly  enlarged. 

(Poirier  and  Charpy.) 

cranial  bones  and  contains  the  blood-vessels  for  their  supply.  At  the  margin 
of  the  foramen  magnum  it  becomes  continuous  with  the  periosteum  lining  the 
spinal  canal.  The  meningeal  or  supporting  layer  is  lined  on  its  inner  surface  by  a 
layer  of  nucleated  endothelium,  similar  to  that  found  on  serous  membranes; 
these  cells  were  formerly  regarded  as  belonging  to  the  arachnoid  membrane. 
By  its  reduplication  the  meningeal  layer  forms  the  falx  cerebri,  the  tentorium 
and  falx  cerebelli,  and  the  diaphragma  sellae.  The  two  layers  are  connected  by 
fibres  which  intersect  each  other  obliquely. 

The  Arteries  of  the  Dura  Mater  (see  section  on  Arteries). — Its  arteries  are  very 
numerous,  but  are  chiefly  distributed  to  the  bones.  Those  found  in  the  anterior 
fossa  are  tlie  anterior  meningeal  branches  of  the  anterior  and  posterior  ethmoidal 
and  internal  carotid,  and  a  branch  from  the  middle  meningeal.  In  the  middle 
fossa  are  the  middle  and  small  meningeal  branches  of  the  internal  maxillary,  a 
branch  from  the  ascending  pharyngeal,  which  enters  the  skull  through  the 
foramen  lacerum  medium  basis  cranii,  branches  from  the  internal  carotid,  and 
a  recurrent  branch  from  the  lachrymal.  In  the  posterior  fossa  are  meningeal 
branches  from  the  occipital,  one  of  which  enters  the  skull  through  the  jugular 
foramen,  and  the  other  through  the  mastoid  foramen;  the  posterior  meningeal, 


THE   DUBA    MATER    OF    THE   BRAIN 


849 


from  the  vertebral;  occasionally  meningeal  branches  from  the  ascending  pharjm- 
geal,  which  enter  the  skull,  one  at  the  jugular  foramen,  the  other  at  the  anterior 
condyloid  foramen,  and  a  branch  from  the  middle  meningeal. 

The  Veins  of  the  Dura  Mater. — The  veins  which  return  the  blood  from  the  dura 
mater  (see  p.  734) ,  and  partly  from  the  bones,  anastomose  with  the  diploic  veins 
(see  p.  733).  These  vessels  terminate  in  the  various  sinuses,  with  the  exception 
of  two  which  accompany  the  middle  meningeal  artery,  and  pass  out  of  the  skull 
at  the  foramen  spinosum  to  join  the  internal  maxillary  vein ;  above,  the  meningeal 
veins  communicate  with  the  superior  longitudinal  sinus.  The  sinuses  are  con- 
sidered on  pages  736  to  743  inclusive.  On  either  side  of  the  superior  longitu- 
dinal sinus,  especially  near  its  middle,  and  also  near  the  lateral  and  straight 
sinuses,  are  numerous  spaces  in  the  dura  mater  which  communicate  with  the 
sinus,  either  by  a  small  opening  or  a  distinct  venous  channel.  These  spaces  are 
the  parasinoidal  sinuses  {lacunae  laterales)  (Fig.  453).  Many  of  the  meningeal 
veins  do  not  open  directly  into  the  sinuses,  but  indirectly  through  the  parasinoidal 
sinuses.  These  venous  lacunae  are  often  invaginated  by  Pacchionian  bodies,  and 
they  communicate  with  the  underlying  cerebral  veins,  and  also  with  the  diploic 
and  emissary  veins. 

The  Lymphatics  of  the  Dura  Mater. — The  existence  of  lymphatic  vessels  is  not 
proved.  Some  anatomists  claim  to  have  injected  such  vessels  along  the  middle 
meningeal  arteries  (Mascagni,  Arnold).     Perivascular  lymph-spaces  do  exist. 

The  Nerves  of  the  Dura  Mater. — The  nerves  of  the  dura  mater  are  filaments  from 
the  fourth,  the  ophthalmic  division  of  the  fifth,  the  Gasserian  ganglion,  the  pneumo- 
gastric,  the  hypoglossal,  and  the  sympathetic. 

Processes  of  the  Dura  Mater  (processus  durae  matris). — The  processes  of  the 
dura  mater,  sent  inward  into  the  cavity  of  the  skull,  are  four  in  number:  the  falx 
cerebri,  the  tentorium  cerebelli,  the  falx  cerebelli,  and  the  diaphragma  sellae. 


SUPERIOR  LONGI- 
TUDINAL SINUS 


TENTORIUM 
CEREBELLI 


FALX  CEREBELLI 


Fic.  543. — Crucial  prolongation  of  the  dura  mater.     Frontal  section  passing  through  the  tentorium  cerebelli. 
The  torcular  Herophili  is  seen  in  the  centre.     (Poirier  and  Charpy.) 


The  Falx  Cerebri  (Figs.  543  and  545). — The  falx  cerebri,  so  named  from  its 
sickle-like  form,  is  a  strong  arched  process  of  the  dura  mater,  which  descends 
vertically  in  the  longitudinal  fissure  between  the  two  hemispheres  of  the  brain. 
It  is  narrow  in  front,  where  it  is  attached  to  the  crista  galli  of  the  ethmoid  bone, 
and  broad  behind,  where  it  is  connected  with  the  upper  surface  of  the  tentorium. 
Its  upper  margin  is  convex,  and  attached  to  the  inner  surface  of  the  skull,  in  the 

54 


850 


THE   NERVOUS  SYSTEM 


middle  line,  as  far  back  as  the  internal  occipital  protuberance;  it  contains  the 
superior  or  great  longitudinal  sinus  {sinus  sagittalis  superior).  Its  lower  margin 
is  free,  concave,  and  presents  a  sharp  curved  edge,  which  contains  the  inferior 
longitudinal  sinus  (sinus  sagittalis  inferior).  The  straight  sinus  (sinus  rectus)  is 
formed  by  the  attachment  of  the  falx  cerebri  to  the  tentorium  cerebelli. 

The  Tentorium  Cerebelli  (Figs.  543,  544,  and  545). — The  tentorium  cerebelli  is 
an  arched  lamina  of  dura  mater,  elevated  in  the  middle  and  inclining  downward 


DIAPHRAGMA  SELLAE 


ANTERIOR 

CLINOID 

PROCESS 


INCISURA 
TENTORII 


TENTORIUM 
CEREBELLI 


Fig.  544. — The  tentorium  cerebelli.     (Poirier  and  Charpy.) 


toward  the  circumference.  It  covers  the  upper  surface  of  the  cerebellum,  and 
supports  the  occipital  lobes  of  the  brain,  and  prevents  them  pressing  upon  the 
cerebellum.  It  is  attached,  behind,  by  its  convex  border  to  the  transverse  ridges 
upon  the  inner  surface  of  the  occipital  bone,  and  there  encloses  on  each  side  the 
lateral  sinus  (sinus  transversus) ;  in  front,  to  the  superior  margin  of  the  petrous 
portion  of  the  temporal  bone  on  either  side,  enclosing  the  superior  petrosal 
sinus  (sinus  petrosus  superior);  and  at  the  apex  of  this  bone  the  free  or  internal 
border  and  the  attached  or  external  border  meet,  and,  crossing  one  another,  are 
continued  forward,  to  be  attached  to  the  anterior  and  posterior  clinoid  processes 
respectively.  Along  the  middle  line  of  its  upper  surface  the  posterior  border 
of  the  falx  cerebri  is  attached,  the  straight  sinus  being  placed  at  their  point  of 
junction.  Its  anterior  border  is  free  and  concave,  and  with  the  dorsum  sellae 
forms  a  large  oval  opening.  This  opening  is  called  the  incisura  tentorii  and 
transmits  the  mesencephalon. 

The  Falx  Cerebelli  (Fig.  543) . — The  falx  cerebelli  is  a  small  triangular  process 
of  dura  mater  received  into  the  indentation  between  the  two  lateral  lobes  of  the 
cerebellum  behind.    Its  base  is  attached,  above,  to  the  under  and  back  part  of 


THE  ARACHNOID   MEMBRANE 


851 


the  tentorium;  its  posterior  margin,  to  the  lower  division  of  the  vertical  crest  on 
the  inner  surface  of  the  occipital  bone.  As  it  descends  it  sometimes  divides  into 
two  smaller  folds,  which  are  lost  on  the  sides  of  the  foramen  magnum. 

The  Diaphragma  Sellae  (Fig.  544), — The  diaphragma  sellae  is  a  horizontal  process 
formed  by  a  reduplication  of  the  meningeal  layer  of  the  dura  mater.  It  forms 
a  small  circular  fold,  which  constitutes  a  roof  for  the  sella  turcica.    This  almost 


Fio.  545. — Falx  cerebri  and  tentorium,  left  lateral  view.     (Testut.) 

completely  covers  the  pituitary  body,  presenting  merely  a  small  central  opening 
(foramen  diaphragmatis  sellae)  for  the  infundibulum  to  pass  through. 


The  Arachnoid  Membrane  (Arachnoidea  Encephaii)  (Fig.  546). 

The  term  arachnoid  is  from  the  Greek  aftdj^uT^  £^ooc,  like  a  spider's  web,  so 
named  for  its  extreme  thinness.  The  cranial  arachnoid  is  a  delicate  membrane 
which  envelops  the  brain,  lying  between  the  pia  mater  internally  and  the  dura 
mater  externally;  from  this  latter  membrane  it  is  separated  by  a  very  fine  slit  or 
space,  the  subdural  space  (cavum  suhdurale).  The  subdural  space  contains  a  very 
minute  quantity  of  fluid  of  the  nature  of  lymph.  This  fluid  obtains  exit  by  way 
of  the  parasinoidal  sinuses.  The  subdural  space  is  prolonged  upon  emerging 
nerves  and  joins  the  lymph  spaces  of  the  nerves.  The  subdural  space  does  not 
communicate  with  the  subarachnoid  space. 

The  arachnoid  invests  the  brain  loosely,  being  separated  from  direct  contact 
with  the  cerebral  substance  by  the  pia  mater,  and  a  quantity  of  loose  areolar 
tissue,  the  subarachnoidean  areolar  tissue.  On  the  upper  surface  of  the  cere- 
brum the  arachnoid  is  thin  and  transparent,  and  may  be  easily  demonstrated  by 


852 


THE  NERVOUS  SYSTEM 


injecting  a  stream  of  air  beneath  it  by  means  of  a  blowpipe;  it  passes  over  the 
convolutions  without  dipping  down  into  the  sulci  between  them,  but  does  pass 
into  the  Sylvian  and  great  longitudinal  fissures  and  is  prolonged  upon  the  nerves 
as  a  sheath.  At  the  base  of  the  brain  the  arachnoid  is  thicker,  and  slightly 
opaque  toward  the  central  part;  it  covers  the  orbital  surface  of  the  anterior 
lobes,  and  extends  across  between  the  two  temporal  lobes  so  as  to  leave  a  con- 
siderable interval  between  it  and  the  brain,  the  cistema  basalis. 

The  Subarachnoid  Space  (cavum  subarachnoideale)  (Fig.  547). — The  subarach- 
noid space  is  the  interval  between  the  arachnoid  and  pia  mater.    It  is  not  only  on 


OLFACTORY 
NERVE 


VERTEBRAL 
ARTERY 


SPIN/ 
ARACHNOID 

Fig.  546. — The  arachnoid  upon  the  base  of  the  brain.     On  the  right  the  arachnoid  ha.s  been  partly  removed 
to  show  the  cerebrum  and  cerebellum  with  their  superficial  veins.     (Poirier  and  Charpy.) 


the  surface,  but  dips  between  the  convolutions.  It  is  not,  properly  speaking, 
a  space,  for  it  is  occupied  everywhere  by  a  spongy  tissue  consisting  of  trabeculse 
of  delicate  connective  tissue  covered  with  endothelium,  which  pass  from  the  pia 
mater  to  the  arachnoid,  and  in  the  meshes  of  which  the  subarachnoid  fluid  is  con- 
tained. This  so-called  space  is  small  on  the  surface  of  the  hemispheres;  but  at 
the  base  of  the  brain  the  subarachnoid  tissue  is  less  abundant  and  its  meshes 
larger. 

In  certain  regions  the  arachnoid  and  pia  are  farther  apart  than  was  previously 
.ndicated,  and  these  spaces  are  called  subarachnoid  cisternae  (cisternae  subarach- 
noidalis).  The  largest  space  is  the  continuation  of  the  posterior  part  of  the  sub- 
arachnoid space  of  the  spinal  cord.     It  is  called  the  posterior  subarachnoid  space 


THE  ARACHNOID  MEMBRANE  853 

or  cistema  magna  (cisterna  cerehellomedullaris).  It  is  a  space  formed  by  the 
arachnoid  passing  across  the  back  and  under  portions  of  the  medulla  and  cere- 
bellum. It  communicates  with  the  fourth  ventricle  by  three  foramina.  The 
largest  opening  is  the  foramen  of  Majendie  (apertura  medialis  veniriculi  quarti). 
It  is  in  the  middle  line  of  the  tela  choroidea  inferior.  At  the  end  of  each  recessus 
lateralis  of  the  fourth  ventricle  there  is  also  an  opening,  and  each  opening  is 
called  the  foramen  of  Key  and  Retzius  (apertura  lauralis  ventriculi  quarti). 
The  cistema  pontis  is  the  continuation  upward  of  the  anterior  part  of  the  sub- 
arachnoid space  of  the  cord.  About  the  medulla  it  is  continuous  with  the 
cisterna  magna,  so  this  important  nerve  centre  is  surrounded  by  a  large  sub- 
arachnoid space.  The  cistema  basalis  (cisterna  interpeduncularis)  is  formed 
by  the  arachnoid  extending  between  the  two  temporal  lobes,  and  it  contains  the 
arteries  forming  the  circle  of  Willis.  The  anterior  subarachnoid  space  (cisterna 
pontis,  interpeduncularis  et  chiasmatis)  includes  the  cisterna  pontis,  the  cisterna 
basalis  and  the  cisterna  of  the  chiasm.  There  is  a  cisterna  between  the  inferior 
edge  of  the  falx  cerebri  and  the  superior  surface  of  the  corpus  callosum  which 
contains  the  anterior  cerebral  arteries,  a  cisterna  in  the  fissure  of  Sylvius  which 
contains  the  anterior  cerebral  artery,  and  a  cisterna  between  the  corpora  quad- 
rigemina  which  contains  the  vena  magna  Galeni. 

It  is  stated  by  Merkel  that  the  lateral  ventricles  also  communicate  with  the 
subarachnoid  space  at  the  apices  of  their  descending  horns. 


=ARACHNOID 
-PIA  MATER 


CONVOLUTION 
OF  BRAIN 


Fig.  547. — The  subarachnoid  space.     (Schematic.)     (Poirier  and  Charpy.) 

The  cerebro-spinal  fluid  (liquor  cerebrospinalis)  fills  the  subarachnoid  space.  It 
IS  a  clear,  limpid  fluid,  having  a  saltish  taste  and  a  slightly  alkaUne  reaction. 
According  to  I^assaigne,  it  consists  of  98.5  parts  of  water,  the  remaining  1.5  per 
cent,  being  solid  matters,  animal  and  saline.  It  varies  in  quantity,  being  most 
abundant  in  old  persons,  and  is  quickly  reproduced.  Its  chief  use  is  probably 
to  afford  mechanical  protection  to  the  nervous  centres,  and  to  prevent  the  effects 
of  concussions  communicated  from  without. 

Structure. — The  arachnoid  consists  of  bundles  of  connective  tissue,  the  fine 
fibres  of  which  form  one  layer  and  cross  each  other  in  every  direction.  At  the 
level  of  the  large  fissures,  and  especially  around  the  circle  of  Willis,  it  is  reinforced 
by  thick  fibrous  tissue.  Both  surfaces  are  covered  with  endothelium.  There  are 
no  blood-vessels  in  the  arachnoid;  the  vessels  which  appear  to  be  in  it  are  really 
in  the  pia.  There  is  no  positive  proof  that  nerves  are  present  in  the  arachnoid. 
It  is  true  that  Bochdalek  and  I>uschka  long  ago  described  arachnoid  nerves,  but 
these  observations  have  never  been  corroborated. 


g54  THE  NERVOUS  SYSTEM 

Glandulae  Pacchioni,  Luschka's  Villi  or  the  Arachnoid  Villi  (Granulationes 

Arachnoideales). 

The  glandulae  Pacchioni  are  numerous  small  whitish  or  purplish  projections, 
usually  collected  into  clusters  of  variable  size,  which  are  found  in  the  following 
situations:  1.  Upon  the  outer  surface  of  the  dura  mater,  in  the  vicinity  of  the 
superior  longitudinal  sinus,  being  received  into  little  depressions  on  the  inner 
surface  of  the  calvarium.  2.  On  the  inner  surface  of  the  dura  mater.  3.  In  the 
superior  longitudinal  sinus  and  the  other  sinuses.  4.  On  the  pia  mater,  near 
the  margin  of  the  hemispheres. 

A  hasty  examination  would  lead  us  to  suppose  that  these  bodies  spring  from 
the  dura,  but,  as  a  matter  of  fact,  they  originate  from  the  arachnoid.  They  are 
not  glandular  in  structure,  but  are  simply  enlarged  normal  villi  of  the  arachnoid. 
In  their  growth  they  appear  to  perforate  the  dura  mater,  and  when  a  group  of 
villi  is  of  large  size  it  causes  absorption  of  the  })one,  and  comes  to  be  lodged  in  a 
pit  or  depression  (foveola  granularis  [Pacchioni])  on  the  inner  table  of  the  skull. 
Their  manner  of  growth  is  as  follows :  at  an  early  period  they  project  through 
minute  holes  in  the  inner  layer  of  the  dura  mater,  which  open  into  large  venous 
spaces  situated  in  the  tissues  of  the  membrane,  on  either  side  of  the  longitudinal 
sinus  and  communicating  with  it.  In  their  onward  growth  the  villi  push  the  outer 
layer  of  the  dura  mater  before  them,  and  this  forms  over  them  a  delicate  mem- 
branous sheath.  In  structure  they  consist  of  spongy  trabecular  tissue,  covered 
over  by  a  membrane,  which  is  continuous  with  the  arachnoid.  The  space  between 
these  two  coverings,  derived  from  the  dura  mater  and  arachnoid  respectively, 
corresponds  to  and  is  continuous  with  the  subdural  space.  The  spongy  tissue  of 
which  they  are  composed  is  continuous  with  the .  trabecular  tissue  of  the  sub- 
arachnoid space;  so  that  fluid  injected  into  the  subarachnoid  space  finds  its 
way  into  the  Pacchionian  bodies,  and  through  their  coverings  filters  into  the 
superior  longitudinal  sinus.  They  are  supposed  to  be  a  means  of  getting  rid  of 
an  excess  of  cerebro-spinal  fluid,  when  its  quantity  is  increased  above  normal. 
Another  means  of  getting  rid  of  cerebro-spinal  fluid  is  absorption  by  the  lymph- 
spaces  of  the  cranial  nerves,  which  possess  sheaths  of  arachnoid  up  to  the  points 
at  which  they  emerge  from  the  skull. 

These  bodies  are  not  found  in  infancy,  and  very  rarely  until  the  third  year. 
They  are  usually  found  after  the  tenth  year;  and  from  this  period  they  increase 
in  number  as  age  advances.    Occasionally  they  are  wanting. 

The  Pia  Mater  of  the  Brain  (Pia  Mater  Encephali)  (Figs.  547,  548). 

The  pia  mater  of  the  brain  is  a  vascular  membrane,  and  derives  its  blood  from 
the  Internal  carotid  and  vertebral  arteries.  It  consists  of  a  minute  plexus  of  blood- 
vessels, held  together  by  an  extremely  fine  areolar  tissue.  It  invests  the  entire 
surface  of  the  brain,  dipping  down  between  the  convolutions  and  laminje,  and 
is  prolonged  into  the  interior,  forming  the  velum  interpositum  and  the  choroid 
plexuses  of  the  lateral  and  fourth  ventricles. 

The  Velum  Interpositum  or  the  Tela  Chorioidea  Superior  (tela  chorioidea 
ventriculi  tertii)  (Fig.  548). — The  velum  interpositum  is  the  prolongation  of  the 
pia  mater  into  the  interior  of  the  brain  through  the  middle  of  the  transverse 
fissure.  It  is  a  double  triangular  vascular  fokl,  lies  between  the  body  of  the 
fornix  above  and  the  optic  thalami  and  the  epithelial  roof  of  the  third  ventricle 
below,  and  passes  forward  to  the  foramen  of  Monro.  At  each  edge  of  the 
velum  interpositum  is  the  choroid  plexus  (plexus  chorioideus  ventriculi  lateralis) 
of  the  corresponding  lateral  ventricle.     In  front  the  two  plexuses  join  behind 


THE  PIA    MATER    OF    THE    BRAIN 


855 


ANTERIOR  PILLAR 
OF  FORNIX 


CAUDATE 
NUCLEUS 


VEINS  OF 
GALEN 


VENA  MAGNA 
OALENI 

Fig.  548. — Velum  interpositum.     (Poirier  and  Charpy.) 


:rior 
municating 

RY 

RNAL 
OTID 


EXTERNAL 

GENICULATE 

BODY 

INTERNAL 

6ENICULATE 

BODY 

PULVINAR 

MIDDLE  CORNU 
OF  LATERAL 
VENTRICLE 


ERIOR 
MUNICATING 
RY 
BASILAR 
ARTERY 

POSTERIOR 

CEREBRAL 

ARTERY 


RA 
IGEMINA 


Fig.  549. — The  anterior  cerebral  and  choroid  arteries.     (Spalteholz.) 


856 


THE   NERVOUS  SYSTEM 


the  foramen  of  Monro,  and  at  the  point  of  junction  two  lesser  choroid  plexuses 
pass  back  along  the  under  surface  of  the  velum  to  the  third  ventricle,  the  median 
plexus  {plexus  chorioideus  ventriculi  tertii).  The  veins  of  Galen  or  the  deep 
cerebral  veins  (p.  735)  are  two  veins  which  lie  on  either  side  of  the  middle  of  the 
velum  interpositum  and  pass  back.  Each  vein  of  Galen  is  formed  by  the  union 
of  the  vein  from  the  corpus  striatum  and  the  choroid  vein  from  the  choroid 
plexus.  The  two  veins  of  Galen  unite  and  form  the  vena  magna  Galeni,  which 
empties  into  the  straight  sinus. 

The  pia  mater  of  the  surfaces  of  the  hemispheres,  where  it  covers  the  gray 
matter  of  the  convolutions,  is  very  vascular,  and  gives  off  from  its  inner  surface 
a  multitude  of  minute  vessels,  which  extend  perpendicularly  for  some  distance 
into  the  cerebral  substance.  At  the  base  of  the  brain,  in  the  situation  of  the 
anterior  and  posterior  perforated  spaces,  a  number  of  long  straight  vessels  are 
given  off,  which  pass  through  the  white  matter  to  reach  the  gray  substance  in  the 


CALLOSO-MARGINAL 
FISSURE 


PARIETO-OCCIPITAL 
ULCUS 


ANTERIOR   CERE 
BRAL  ARTERY 

OPTIC 
NERVE 


CALCARINE 
FISSURE 


ANTERIOR  COM- 
MUNICATING ARTERY 

INTERNAL  POSTERIOR  POSTERIOR 

CAROTID  COMMUNICATING  CEREBRAL 
ARTERY  ARTERY  ARTERY 

Fig.  550. — The  arteries  of  the  medial  surface  of  the  right  cerebral  hemisphere.     (Spalteholz.) 

interior.  On  the  cerebellum  the  membrane  is  more  delicate,  and  the  vessels  from 
its  inner  surface  are  shorter.  The  pia  mater  of  the  spinal  cord  is  thicker,  firmer, 
and  less  vascular  than  that  of  the  brain,  and  as  it  is  traced  upward  over  the 
medulla  it  is  seen  to  preserve  these  characters.  At  the  upper  border  of  the  medulla 
it  is  prolonged  over  the  lower  half  of  the  fourth  ventricle,  forming  a  covering  for 
it  called  the  tela  chorioidea  inferior  {tela  chorioidea  ventriculi  quarti),  before  it  is 
reflected  on  to  the  under  surface  of  the  cerebellum,  and  which  carries  the  choroid 
plexus  of  the  fourth  ventricle  {plexus  chorioideus  ventriculi  quarti). 

The  arteries  of  the  pia  mater  (see  pp.  626,  627,  and  628)  (Figs.  549  and  550) 
are  the  anterior  cerebrals,  middle  cerebrals,  posterior  cerebrals,  anterior  choroids, 
posterior  choroids,  the  superior  cerebellars,  and  the  anterior  and  posterior  inferior 
cerebellars.  (The  vessels  of  the  cerebral  ganglionic  system  and  of  the  cortical 
arterial  system  are  considered  on  pp.  630  and  631.) 

The  veins  of  the  pia  mater  (see  pp.  734,  735,  and  736)  are  the  basilar  vein, 
the  veins  of  Galen  (Fig.  548),  the  veins  constituting  the  choroid  plexuses  of  the 


THE   BRAIN  857 

third  ventricle,  the  lateral  ventricles,  and  the  fourth  ventricle;  the  cerebral  veins 
(Fig.  546)  and  the  cerebellar  veins  (Fig.  540). 

The  nerves  of  the  pia  mater  accompany  the  branches  of  the  arteries  and  are 
derived  from  the  sympathetic  and  from  the  third,  fifth,  sixth,  seventh,  ninth,  tenth, 
and  eleventh  cranial  nerves. 

According  to  Fohmann,  Arnold,  and  Mascagni,  this  membrane  contains  numer- 
ous lymphatic  vessels,  but  the  question  is  uncertain. 


THE  BRAIN  (ENCEPHALON) . 

The  encephalon  or  brain  is  that  portion  of  the  cerebro-spinal  axis  which  is 
contained  in  the  cavity  of  the  cranium. 

The  Development  of  the  Brain. — The  nervous  system  (brain,  ganglia,  spinal 
cord,  and  nerves)  is  derived  from  the  ectoderm  (the  epiblastic  layer  of  the  blasto- 
dermic vesicle).  This,  it  will  l)e  remembered,  is  an  epithelial  layer,  and  nervous 
structure  is  composed  of  epithelial  cells  variously  modified.  The  embryonal  area 
of  the  surface  of  the  developing  germ  is  a  white  spot,  which  at  first  is  round,  but 
becomes  pear-shaped  and  develops  a  transverse  ridge,  the  terminal  ridge,  on  its 
posterior  margin.  From  the  embryonal  layer,  and  from  this  alone,  the  new  indi- 
vidual is  developed. 

About  the  twelfth  or  the  thirteenth  day  of  the  development  of  the  human 
embryo,  cell-proliferation  occurs  at  a  certain  portion  of  the  under  surface  of  the 
ectoderm.  This  proliferation  gives  rise  to  a  white,  longitudinal  streak  in  the 
embryonal  area,  known  as  the  primitive  streak  or  axis  plate.  The  head  process  of 
the  primitive  streak  appears  somewhat  later,  and  is  situated  directly  in  front 
of  the  anterior  end  of  the  streak. 

At  the  anterior  end  of  the  primitive  streak  is  a  group  of  epiblastic  cells  known 
as  Hensen's  node.  The  epiblastic  cells  of  the  head-process  of  the  primitive  streak 
enlarge  and  become  columnar,  and  the  cells  at  each  side  of  the  streak  become 
flat  (Heisler).  Thus  is  formed  from  the  ectoderm  the  medullary  plates;  and  the 
turning  up  of  the  edge  of  the  medullary  plates  forms  the*  spinal  or  medullary 
furrow  or  groove.  As  the  curling  up  of  the  edges  of  the  medullary  plates  continues 
the  groove  deepens,  finally  becoming  a  tube  known  as  the  medullary  or  neural  tube 
or  canal. 

The  neural  tube  lies  beneath  the  ectoderm;  is  finally  separated  from  it;  runs 
from  one  end  of  the  body  to  the  other;  forms  the  primitive  nervous  system,  and 
gives  origin  to  the  entire  nervous  system.  The  constricted  portion  between  the 
hind-brain  and  the  mid-brain  is  known  as  the  isthmus  rhombencephali. 

It  is  thus  seen  that  the  medullary  or  neural  groove  is  converted  into  a  canal, 
the  neural  canal.  Its  cephalic  end  dilates  into  a  sac,  from  which  the  brain  is 
developed,  and  the  remainder  forms  the  spinal  cord.  In  consequence  of  the  curve 
that  the  cephalic  portion  of  the  embryo  undergoes,  a  marked  bend  in  the  canal 
takes  place  forward,  so  that  the  plane  of  the  ventricles  is  placed  almost  at  a  right 
angle  with  the  long  axis  of  the  central  canal  of  the  cord.  The  rudimentary  brain 
consists  of  a  hollow  sac — the  rudimentary  corrl  of  a  hollow  canal.  The  sac  and 
the  canal  communicate  freely  with  each  other. 

The  sac  elongates,  and  in  it  appear  two  constrictions,  which  partially  divide  it 
into  three  portions,  namely,  the  anterior,  middle,  and  posterior  primitive  cerebral 
vesicles,  or  the  fore-brain  (prosencephalon),  the  mid-brain  {mesencephalon),  and  the 
hind-brain  {rhombencephalon)  (Fig.  551).  Subsequently  the  anterior  and  the  pos- 
terior vesicles  become  constricted,  each  into  two,  while  the  middle  remains 
undivided  (Figs.  553  and  554).  It  will  thus  be  seen  that  at  the  anterior 
extremity  of  the  medullary  canal  there  are  five  dilatations,  separated  from' each 


858 


THE  NERVOUS  SYSTEM 


other  by  constrictions,  through  which,  however,  they  freely  communicate  with 
one  another.  These  five  vesicles  are  the  fundamental  or  primitive  divisions  of 
the  adult  brain.  They  are  named,  from  before  backward,  the  fore-brain  (pros- 
encephalon), the  inter-brain  (thalamencephalon,  formed  from  the  prosencephalon), 
the  mid-brain  (mesencephalon),  the  upper  portion  of  the  hind-brain  (metencephalon). 


-  -Head  fold  of  amnion. 

Forebraiii. 

—  Optic  vesicle. 


M^hrain.--'^-''~- 


Eindbrain.- 


Auditory  vesicle.  - 


Medullary  ridge.  —-,4*- 


Remains  of  primitive— t 
streak. 


Heart. 


(tmphalo-mesenterie  vem. 

I  Protorertebrx  or 

)      mesoblastic  somites. 


-9— -Sinus  rhomboidalis. 


Fig.  551. 


-Chick  embryo  of  thirty-three  hours'  incubation,  \  iewed  from  the  dorsal  a.spect. 
(From  Duval's  Atlas  d'Embryologie.) 


X  30. 


and  the  lower  portion  of  the  hind-brain  (myelencephalon).  The  constricted  por- 
tion between  the  hind-brain  and  the  mid-brain  is  known  as  the  isthmus  rhomb- 
encephali. 

These  five  vesicles  are  at  first  fairly  uniform  in  size  and  in  shape,  but  they  soon 
begin  to  grow  at  different  rates  and  to  assume  different  forms.  The  changes  are 
most  marked  in  the  first  vesicle. 


THE   BRAIN 


859 


The  first  secondary  vesicle  sends  out  two  hollow  protrusions,  one  on  each  side, 
from  the  forepart  of  its  lateral  surface.  These  grow  rapidly,  spread  out,  and 
extend  forward,  laterally,  and  backward,  over  the  sides  of  the  first  and  second 
ventricles,  forming  large  cavities,  which  become  the  lateral  ventricles  (Fig.  552,  G). 
From  each  protrusion  three  prolongations  take  place:  one  forward  and  out- 
ward; the  second  backward  and  inward,  and  the 
third  at  first  backward,  outward,  and  downward, 
and  then  forward  and  inward.  These  prolonga- 
tions form  the  horns  of  the  lateral  ventricles,  and 
they  far  exceed  in  size  the  original  vesicle  from 
which  they  have  taken  origin,  which  does  not 
increase  to  any  great  extent,  but  remains  as  the 
anterior  part  of  the  third  ventricle.  The  com- 
munication between  it  and  the  future  lateral  ven- 
tricle persists  as  the  foramen  of  Monro  (Fig.  552). 

The  second  vesicle  or  thalamencephalon  be- 
comes elongated  from  before  backward  and  com- 
pressed laterally,  so  as  to  form  the  greater  part 
of  the  third  ventricle  (Fig.  552,  J?).  From  each 
side  of  that  part  of  the  fore-brain,  which  ulti- 
mately becomes  the  lateral  ventricle,  is  budded 
off  a  hollow  projection,  the  primary  optic  vesicle, 
that  is  developed  eventually  into  the  optic  nerve 
and  the  retina.    It  will  be  considered  later. 

The  constriction  between  the  first  and  the 
second  vesicle  disappears,  so  as  to  throw  the 
whole  cavity  of  the  future  third  ventricle,  formed 
by  the  remains  of  the  first  ventricle  and  the  whole 
of  the  second  vesicle,  into  one. 

The  third  vesicle  or  mesencephalon  forms  a 
very  insignificant  part  of  the  brain  of  the  adult. 
It  constitutes  a  stem  of  junction  between  the 
parts  that  take  origin  from  the  rhombencephalon 
and  those  that  arise  from  the  prosencephalon. 
The  wall  of  the  mesencephalon  is  completely 
converted  into  nerve-tissue,  and  forms  the  corpora 
quadrigemina,  the  two  crm-a  cerebri,  and  the  aque- 
duct of  Sylvius,  which  join  the  third  ventricle  with 
the  fourth. 

The  metencephalon  gives  origin  to  the  cere- 
bellum and  the  pons  Varolii.  The  cerebellum 
takes  origin  from  a  thickening  of  the  superior 

wall  of  the  vesicle,  while  the  pons  takes  origin  from  a  thickening  of  the  lateral 
and  inferior  walls  of  the  vesicle. 

The  myelencephalon  gives  origin  to  the  bulb  or  medulla  oblongata,  chiefly  by  a 
thickening  of  the  lateral  walls  of  the  vesicle.  The  original  hind-brain  remains  in 
the  brain  of  the  adult  as  the  fourth  ventricle. 

As  already  stated ,  these  vesicles  do  not  remain  in  the  same  plane.  The  formation 
of  certain  definite  flexures  alters  the  position  of  the  vesicles  with  regard  to  one  another 
(Fig.  554).  The  cephalic  flexure  is  opposite  the  base  of  the  mid-brain,  which 
becomes  sharply  bent  upon  itself  over  the  end  of  the  notochord.  This  bending 
causes  the  mid-brain  to  become  the  most  prominent  part  of  the  encephalon  on  the 
convexity  of  the  curve.  The  pontine  or  pontal  flexure  is  a  curve  in  the  hind-brain, 
in  the  opposite  direction  to  that  of  the  cephalic  flexure.     At  the  junction  of  the 


\J 


Fig.  552. 


Plan  showing  the  mode  of 
formation  of  the  ventricles  of  the  brain 
and  the  central  canal  of  the  spinal  cord. 
A.  Prosencephalon.  B.  Thalamenceph- 
alon. C.  Mesencephalon.  D.  Metenceph- 
alon. E.  Myelencephalon.  F.  Central  canal 
of  cord.  G.  Lateral  ventricle.  H.  Fora- 
men of  Monro.     (After  Gerrish.) 


860 


THE   NERVOUS  SYSTEM 


hind-brain  with  the  spinal  cord  is  the  cervical  or  nuchal  flexure.  In  the  develop- 
ment of  the  brain  the  cephalic  flexure  remains  permanent,  but  the  other  two 
flexures  completely  disappear. 

The  manner  in  which  the  different  parts  of  the  encephalon  are  formed  from 
the  walls  of  this  greatly  altered  medullary  canal  will  now  be  considered,  it  being 
remembered  that  the  ventricles  are  developed,  as  previously  described,  from  the 
five  secondary  vesicles. 

The  first  vesicle,  or  prosencephalon,  sends  out  two  hollow  protrusions,  which 
spread  rapidly,  and  in  the  walls  of  these  nervous  matter  is  developed,  which  con- 
stitutes the  cerebral  hemispheres  (Fig.  554,  H),  the  cavities  remaining  as  the 
lateral  ventricles.  As  these  hemispheres  extend  they  grow  forward  in  front  of 
the  anterior  extremity  of  the  primitive  brain,  and  lie  side  by  side,  separated  by  the 
longitudinal  fissure;  they  also  grow  upward,  and  again  lying  side  by  side  are 
separated  by  another  portion  of  the  same  fissure,  containing  a  thin  layer  of  meso- 
blast,  which  forms  the  falx  cerebri;  behind  and  laterally  they  overlap  the  roof 
and  sides  of  the  other  cerebral  vesicles,  so  that  by  the  seventh  month  they  project 


Fig.  553. — Vertical  section  of  the  head  in  early  embryos  of  the  rabbit.  Magnified.  A.  From  an  embryo  five 
millimetres  long.  13.  From  an  embryo  six  millimetres  long.  C.  Vertical  section  of  the  anterior  end  of  the 
notochord  and  pituitary  body,  etc.,  from  an  embryo  sixteen  millimetres  long.  In  A,  the  faucial  opening  is  still 
closed.  In  B,  it  is  formed,  c.  Anterior  cerebral  vesicle,  inc.  Mesocerebrum.  mo.  Medulla  oblongata,  co. 
Corneous  layer,  to.  Medullary  layer,  if  Tnfundibulum.  owi.  _  Amnion,  spe.  Spheno^ethmoidal,  6c,  central 
(dorsum  sellae),  and  sp.o,  spheno-occipital  parts  of  the  basis-cranii.  h.  Heart.  /.  Anterior  extremity  of  primi- 
tive alimentary  canal  and  opening  (later)  of  the  fauces,  i.  Cephalic  portion  of  primitive  intestine,  tha.  Thalamus. 
p'.  Closed  opening  or  the  involuted  part  of  the  pituitary  body  (jpy)  ch.  Notochord.  ph.  Pharynx.  (From 
Mihalkovics.) 


behind  them  In  the  floor  of  each  of  these  hemispheres  there  occurs  a  local 
thickening,  which  forms  the  corpus  striatum,  which  is  continuous  behind  with  the 
optic  thalamus  presently  to  be  described  The  surface  of  the  hemisphere  is  at 
first  smooth,  but  about  the  fifth  month  a  sulcus  or  groove  appears  in  either  hemi- 
sphere just  external  to  the  corpus  striatum;  this  is  the  fissure  of  Sylvius:  subse- 
quently other  fissures  appear  on  the  surface,  three  of  which  are  of  sufficient  depth 
to  cause  a  projection  into  the  lateral  ventricle.  These  are  the  hippocampal  fissure, 
corresponding  to  the  hippocampus  major  of  the  lateral  ventricle,  the  collateral 
fissure,  corresponding  with  the  bend  of  the  posterior  horn  of  the  ventricle;  and 
the  calcarine  fissure,  corresponding  with  the  projection  of  the  calcar  avis. 

The  remainder  of  the  first  vesicie  and  the  second,  as  we  have  seen,  form  the 
third  ventricle,  in  its  normal  wails  a  thickening  takes  place,  which  forms  the 
optic  thalamus.  From  the  floor  of  this  ventricle  a  hollow  protrusion  passes  down- 
ward, and  is  intimately  connected  with  a  diverticulum  from  the  stomodaeum,  to 
form  part  of  the  pituitary  body  {hypophysis  cerebri)  (Figs  553,  554,  and  555).  The 
greater  part  of  the  roof  of  the  third  ventricle  is  very  thin,  and  with  the  pia  mater 


THE   BBAIN 


861 


NK. 


Fig.  554. — Profile  views  of  the  brain  of  human  embryos  at  three  several  stages,  reconstructed  from  sections. 
(Copied  from  Quain's  Anatomy.)  A.  Brain  of  an  embryo  vif  about  fifteen  days,  magnified  35  diameters.  _  B. 
I5rain  of  an  embryo  about  three  and  a  half  weeks  old.  The  optic  vesicle  has  been  cut  away.  C.  Brain  of 
an  embryo  about  seven  and  a  half  weeks  old.  The  optic  stalk  is  cut  through.  A.  Optic  vesicle.  H.  Vesicle  of 
cerebral  hemisphere,  first  secondary  vesicle.  Z.  Thalamencephalon,  second  secondary  vesicle.  M.  Mid-brain. 
J.  Isthmus  between  mid-brain  and  hind-brain.  Hh.  Fourth  secondary  vesicle.  A'.  Fifth  .secondary  vesicle.  Ob. 
Otic  vesicle.  Rf.  Fourth  ventricle.  NK.  Neck  curvature.  Br.  Pons  curvature.  Pm.  Mammillary  process. 
TV.  Infundibulum.  Hp.  (in  B).  Outline  of  hypophysis-fold  of  buccal  epiblast.  Kl.  Olfactory  fold.  In  C  the 
basilar  artery  is  represented  along  its  whole  course.     (His.) 


862 


THE    NERVOUS  SYSTE3£ 


forms  the  velum  interpositum ;  from  its  posterior  part  an  outgrowth  of  cells  forms 
the  pineal  body  {epiphysis  cerebri).  Where  the  cerebral  hemispheres  are  not 
separated  in  the  middle  line  by  the  falx,  in  front  and  for  some  distance  backward 
over  the  roof  of  the  third  ventricle  their  mesial  surfaces  come  in  contact,  and  to  a 
certain  extent  fuse  together,  leaving,  however,  a  small  portion  where  no  union 
takes  place,  and  thus  a  slit-like  cavity  is  left;  this  is  termed  the  fifth  ventricle,' 
though  it  will  be  at  once  seen  that  its  development  is  quite  different  from  that 
of  the  other  ventricles.  Its  lateral  walls  form  the  septum  lucidum.  The  roof  of 
this  cavity  becomes  thickened,  and  nerve-fibres  pass  across  from  the  one  hemi- 
sphere to  the  other  to  form  the  corpus  callosum,  while  in  its  floor  longitudinal  fibres 
are  developed  to  form  the  fornix. 

The  third  vesicle,  the  cavity  of  which  forms  the  iter  a  tertio  ad  quartum  ven- 
triculum,  develops  in  its  roof  four  well-marked  thickenings,  which  together  form 


Optic  thalamus. 
Foramen  of  Monro 


Posterior  commissure. 
Pineal  body. 

Cms  cerebri. 

Aqueduct  of  Sylvius. 


Corpora  quadrigemina. 

1  Cerebellum. 


'~IV.  Ventncle. 


Cerebral  hemisphere. 


Olfactory  lobe  or  1 1  , 
rhinencephalon.  1 1  '         | 
Lamina  cinerea.  [    \        | 
Optic  nerve,  j       ' 
Optic  commissure.      i 
Pituitary  body, 
Infundibulum. 


Corpus 
albicans. 


Spinal  cord. 


Fig.  555, — Median  section  of  brain  of  human  foetus  during  the  third  month.      (After  His.) 

the  corpora  quadrigemina,  while  its  lateral  regions  become  thickened  to  form  the 
crura  cerebri  (Fig.  555). 

The  dorsal  surface  of  the  fourth  vesicle  forms  the  covering  of  the  fourth  ventricle, 
and  in  it  a  thickening  occurs  which  is  developed  into  the  cerebellum;  its  ventral 
and  lateral  regions  form  the  pons  (Fig.  555). 

In  the  fifth  vesicle  the  lateral  parts  increase  and  grow  downward  on  each  side 
toward  the  middle  line,  forming  the  medulla,  while  the  dorsal  surface  assists  in 
forming  the  roof  of  the  fourth  ventricle. 

On  making  a  transverse  section  of  the  lower  part  of  the  fourth  ventricle,  the 
alar  and  basal  laminae,  already  referred  to  as  being  present  in  the  cord, are  readily 
recognized,  while  the  thin  roof-plate  is  seen  to  be  greatly  expanded  laterally. 
The  dorsal  part  of  the  alar  lamina  becomes  folded  outward  and  downward,  form- 


THE   BRAIN 


863 


ing  what  is  termed  the  rhomboid  lip  (Fig.  556).  This  is  at  first  separated  by  a 
groove  from  the  lateral  aspect  of  the  alar  lamina,  but  ultimately  fuses  with  it.  As 
the  central  canal  of  the  cord  opens  out  to  form  the  fourth  ventricle,  the  alar  and 
basal  laminae  come  to  occupy  the  floor  of  the  ventricle — the  basal  lamina  lying 
nearest  the  mesial  plane. 


■l...Rhomho%d, 
--^yy         lip. 


Tractus 
solitarius. 


I'agua  nerve. 


Raphe.  \ 

Fig.  556. — Transverse  section  of  medulla  oblongata  of  human  embryo.     (After  His.) 


/jwglossal 
nerve. 


The  Communications  of  the  Parts  of  the  Brain. — In  the  posterior  fossa  of  the 
cranium  lies  the  medulla  oblongata,  the  pons  Varolii,  and  the  cerebellum,  and 
between  these  structures  and  the  cerebrum  is  the  tentorium  cerebelli.  The  pons, 
medulla,  and  cerebellum  surroimd  the  fourth  ventricle.  The  greater  portion  of 
the  fibres  of  the  medulla  are  continued  into  the  pons,  but  some  fibres  from  the 
dorsal  aspect  of  the  medulla  (the  restiform  bodies)  pass  into  the  cerebellum  and 


Mesencephalon 

Superior  cerebellar  peduncle 

Middle  cerebellar  peduncle 
Inferior  cerebellar  peduncle 


Fig.  557.— Scheme  showing  the  connection.s  of  the  several  parts  of  the  brain.      (Cunningham.) 

become  the  inferior  cerebellar  peduncles  (Fig.  557).  On  each  side  of  the  pons  a 
thick  strand  of  transverse  fibres  passes  to  the  cerebellum.  These  strands  are  the 
middle  cerebellar  pedimcles  (Fig.  557). 

The  cerebral  hemispheres  are  joined  together  by  the  corpus  callosum,  a  com- 
missure lying  within  the  depths  of  the  great  longitudinal  fissure.  Between  and 
beneath  the  cerebral  hemispheres  is  the  inter -brain  (thalamencephalon) ,  composed 
chiefly  of  the  optic  thalami.     In  the  interior  of  each  hemisphere  is  a  space  called 


864  THE  NERVOUS   SYSTEM 

the  lateral  ventricle.  Between  the  optic  thalami  is  the  third  ventricle.  The  foramen 
of  Monro  connects  the  third  ventricle  with  the  lateral  ventricles. 

The  mid-brain  connects  the  cerebrum  with  the  pons,  medulla,  and  cerebellum. 
It  is  composed  of  the  crura  cerebri,  which  join  together  the  pons  and  the  cere- 
brum; the  corpora  quadrigemina,  and  the  superior  cerebellar  peduncles  (Fig.  557), 
which  connect  together  the  cerebrum  and  the  cerebellum.  In  the  mid-brain  the 
aqueduct  of  Sylvius  joins  the  third  ventricle  and  the  fourth  ventricle. 

General  Considerations  and  Divisions. — For  the  purposes  of  description  the 
brain  may  be  divided  into  five  parts,  as  follows:  (1)  the  two  cerebral  hemispheres; 
(2)  the  inter-brain  (thalamencephalon) ;  (3)  the  mid-brain  (mesencep^talan) ;  the  hind- 
brain  (rhombencephalon) ,  which  includes  (4)  the  pons  Varolii  and  cerebellum ;  and 
(5)  the  medulla  oblongata.  If  the  student  will  refer  to  the  section  on  the  Development 
of  the  Brain  he  will  find  that  these  five  portions  correspond  fairly  accurately  to 
the  five  secondary  cerebral  vesicles,  of  which  the  brain  at  an  early  period  of  em- 
bryonal life  consisted ;  the  prosencephalon,  or  first  vesicle,  by  means  of  a  protrusion 
from  its  front  part  on  either  side,  forms  the  cerebral  hemispheres  and  the  lateral 
ventricles;  the  remainder  of  the  prosencephalon,  together  with  the  ^econc?  vesicle, 
the  thalamencephalon,  form  the  inter-brain  and  third  ventricle;  the  third  vesicle, 
the  mesencephalon,  forms  the  mid-brain,  or  that  portion  which  connects  the  inter- 
brain  and  hemispheres  above  with  the  pons  Varolii  below,  and  the  cavity  of  the 
vesicle  forms  the  aqueduct  of  Sylvius,  or  iter  a  tertio  ad  quartum  ventriculum ;  the 
fourth  vesicle,  the  metencephalon,  becomes  the  future  pons  Varolii  and  cerebellum, 
and  its  cavity  forms  the  upper  half  of  the  fourth  ventricle;  and,  finally,  the  fifth 
vesicle,  the  myelencephalon,  develops  into  the  medulla  oblongata,  and  its  cavity 
forms  the  lower  half  of  the  fourth  ventricle.  It  will  thus  be  seen  that  the  five 
divisions  of  the  encephalon  mentioned  above  correspond  to  the  five  secondary  cere- 
bral vesicles,  with  the  exception  of  the  first  two,  which  together  form  the  cerebral 
hemispheres  and  the  inter-brain.  In  consequence  of  this  these  two  portions  of 
the  brain  are  sometimes  grouped  together  as  the  cerebrum. 

I.  The  Hemispheres  of  tjie  Cerebrum  (Hemisphaeria  Cerebri). 

General  Considerations. — The  two  hemispheres  constitute  the  largest  portion 
of  the  encephalon,  and,  together  with  the  parts  derived  from  the  inter-brain 
(thalamencephalon)  form  what  is  called  by  some  writers  the  fore-brain  (pros- 
encephalon). They  occupy  the  whole  of  the  vault  of  the  skull,  and  consist  of  a 
central  cavity,  in  either  hemisphere,  surrounded  by  exceedingly  thick  and  con- 
voluted walls  of  nervous  tissue.  The  under  surface  or  base  of  the  cerebrum  is 
of  an  irregular  form,  resting  in  front  on  the  anterior  and  middle  fossae  of  the 
skull  and  behind  upon  the  tentorium  cerebelli.  The  upper  surface  is  of  an 
ovoid  form,  broader  behind  than  in  front  and  convex  in  general  outline.  The 
frontal  pole  (polus  frontalis)  is  the  most  prominent  portion  of  the  anterior  end 
of  the  hemisphere.  The  most  prominent  portion  of  the  posterior  end  is  the 
occipital  pole  (polus  occipitalis).  The  most  prominent  part  of  the  temporal 
lobe  below  the  fissure  of  Sylvius  is  the  temporal  pole  (polus  temporalis).  The 
upper  surface  is  divided  into  two  lateral  halves  or  hemispheres,  the  right  and 
left,  by  the  great  longitudinal  fissure  (fissura  longitudinalis  cerebri),  which  extends 
throughout  the  entire  length  of  the  cerebrum  in  the  middle  line,  reaching  down 
to  the  base  of  the  brain  in  front  and  behind,  but  interrupted  in  the  middle 
by  a  broad  transverse  commissure  of  white  matter,  the  corpus  callosum,  which 
connects  the  two  hemispheres  together. 

The  Constituent  Parts  of  the  Hemisphere. — The  hemisphere  is  composed 
of  three  distinct  parts:  the  brain-mantle  (pallium),  the  chief  mass  of  the  hemi- 
sphere;   the  olfactory  brain  or  lobe  (rhinencephalon) ,  composed  of  the  olfactory 


THE    HEMISPHERES    OF   THE    CEREBRUM  865 

bulb,  anterior  perforated  space,  a  portion  of  the  uncinate  gyrus,  the  hippocampus, 
the  septum  hicidum,  etc.,  and  the  corpus  striatum. 

The  Surface  of  the  Cerebrum. — Each  hemisphere  presents  an  outer  convex 
surface  (fades  convexa  cerebri),  fiUing  the  concavity  of  the  corresponding  half  of 
the  vault  of  the  cranium;  an  inner,  flattened  surface  {fades  medialis  cerebri),  which 
is  vertical  and  directed  toward  the  corresponding  surface  of  the  opposite  hemi- 
sphere (the  two  inner  surfaces  forming  the  sides  of  the  longitudinal  fissure) ;  and  an 
under  surface  or  base  {basis  cerebri),  of  irregular  form,  which  rests  in  front  on  the 
anterior  and  middle  fossae  of  the  base  of  the  skull,  and  behind  upon  the  tentorium 
cerebelli.  The  hemispheres  are  composed  of  an  outer  stratum  of  gray  matter  {sub- 
stantia grisea),  called  the  cortical  substance  or  the  cerebral  cortex,  and  in  the  inte- 
rior of  a  mass  of  white  matter  (substantia  alba)  called  the  medullary  centre.  The 
cortex  is  thrown  into  a  number  of  creases  or  infoldings,  which  are  termed 
fissures  and  sulci  (sulci  cerebri),  and  these  separate  the  surface  into  a  number 
of  irregular  eminences,  named  convolutions  or  gyri  (gyri  cerebri). 

The  infoldings  or  creases  are  of  two  kinds,  complete  fissures  and  incomplete 
fissures  or  sulci.  The  complete  fissures  (fissurae)  are  of  large  size,  and  appear 
early  in  foetal  life;  they  are  few  in  number,  nearly  constant  in  their  arrangement, 
and  are  produced  by  infoldings  of  the  entire  thickness  of  the  wall  of  the  cerebrum, 
producing  corresponding  elevations  in  the  interior  of  the  ventricle,  and  hence  are 
termed  complete  fissures.  They  comprise  (a)  the  hippocampal  or  dentate  fissure; 
(b)  the  anterior  part  of  the  calcarine  fissure;  (c)  the  collateral  fissure.  The  sulci  are 
vastly  more  numerous  than  the  complete  fissures;  they  are  superficial  depressions 
of  the  gray  matter,  which  is  folded  inward  and  only  indents  the  central  white 
substance.  They  produce  no  corresponding  elevations  in  the  interior  of  the 
ventricle,  and  are  therefore  spoken  of  as  incomplete  fissures.  They  are  fairly  con- 
stant in  their  arrangement,  and  have  received  names  indicative  of  their  position 
and  direction,  but  at  the  same  time  vary,  within  certain  limits,  in  different  indi- 
viduals. They  are  similar,  without  being  absolutely  identical,  on  the  two  sides  of 
the  brain.  It  therefore  follows  that  the  gyri  or  convolutions  (gyri  cerebri)  which 
lie  between  these  sulci  are  fairly  constant  in  their  general  arrangement.  The 
gyri  upon  the  surface  are  called  superficial  gyri.  Within  the  sulci,  adjacent  super- 
ficial gyri  are  joined  by  deep  gjrri  (gyri  profundi).  Short  gyri,  superficial  or  deep 
which  connect  two  gyri  of  greater  length  are  called  annectant  or  transitional 
gyri  (gyri  transitivi). 

The  number  and  extent  of  the  convolutions,  as  well  as  the  depth  of  the  inter- 
vening sulci,  appear  to  bear  a  close  relation  to  the  intellectual  power  of  the  indi- 
vidual, as  is  shown  in  their  increasing  complexity  of  arrangement  as  one  ascends 
from  the  lowest  mammalia  up  to  man,  where  they  present  a  most  complex  arrange- 
ment. Again,  in  the  child,  at  birth,  before  the  intellectual  faculties  are  exercised, 
the  convolutions  are  simpler,  and  the  sulci  between  them  shallower,  than  in  the 
adult.  In  old  age,  when  the  mental  faculties  have  diminished  in  activity,  the 
gyri  and  sulci  become  less  prominently  marked.  By  their  arrangement  the  con- 
volutions are  adapted  to  increase  the  amoimt  of  gray  matter  without  occupying 
much  additional  space,  while  they  also  afford  a  greater  extent  of  surface  for  the 
termination  of  white  fibres  in  gray  matter. 

It  will  be  convenient  in  the  first  instance  to  describe  the  fissure  which  sepa- 
rates the  two  hemispheres  from  each  other,  and  those  which  divide  each  hemisphere 
into  its  larger  divisions. 

Fissures  and  Sulci  of  the  Outer  Surface  of  the  Hemispheres.  The  Longitu- 
dinal Fissure  (fssura  Inngitudinalis  cerebri)  (Fig.  560). — This  great  fissure  separates 
the  cerebrum  into  two  hemispheres,  and  reaches  from  the  front  to  the  back  of  the 
organ ;  it  contains  a  vertical  process  of  the  dura  mater,  the  falx  cerebri  (p.  849).  In 
front  and  behind  the  longitudinal  fissure  extends  from  the  top  (dorsal  surface)  to 

55 


866 


THE  NERVOUS  SYSTEM 


the  bottom  (ventral  surface)  of  the  cerebrum,  and  completely  separates  the  two 
hemispheres,  but  its  middle  portion  only  separates  the  hemispheres  for  about 
half  their  vertical  extent,  the  floor  of  this  part  of  the  fissure  being  formed  by  the 
great  central  white  commissure,  the  corpus  callosum  (Figs.  567  and  571),  which 
connects  the  two  hemispheres  together. 

The  remaining  fissures  are  situated  in  one  or  other  of  the  two  hemispheres,  with 
the  exception  of  the  transverse  fissure,  one-half  of  which  is  contained  in  each 
hemisphere. 

Sylvian  Fissure  (fissura  cerebri  lateralis  [Sylvii])  (Figs.  558,  561,  565,  and  570). 
— This  fissure  is  a  well-marked  cleft  on  the  base  and  side  of  the  hemisphere. 
Starting  at  the  base  of  the  brain  in  a  depression,  the  vallecula  Sylvii,  in  which  is 
situated  the  anterior  perforated  space  (Fig.  570).  The  fissure  passes  outward 
between  the  frontal  and  temporal  lobes,  along  the  lesser  wing  of  the  sphenoid 


Parieto- 
occipital 
Sulcus. 


Fig.  558. — Chief  fissures  and  lobes  on  the  external  surface  of  the  cerebral  hemispheres. 

bone  to  the  external  surface  of  the  hemisphere.  The  point  at  which  it  reaches 
the  external  surface  is  called  the  Sylvian  point.  It  here  gives  off  a  short  anterior 
horizontal  limb  (ramus  anterior  horizontalis) ,  which  passes  forward,  and  a  short 
ascending  or  vertical  limb  (ramus  anterior  ascendens),  which  passes  upward  into 
the  inferior  frontal  convolution.  It  also  gives  off  the  posterior  horizontal  limb 
(ramus  posterior),  which  is  the  most  distinct  of  the  three  branches.  The  posterior 
horizontal  limb  lies  under  the  middle  third  of  the  lateral  surface  of  the  hemisphere 
and  above  the  temporal  lobe.  It  passes  backward  and  slightly  upward  for  about 
two  and  a  half  inches  and  terminates  by  an  upward  inflexion  in  the  parietal  lobe, 
which  is  called  the  ascending  terminal  portion.  The  anterior  horizontal  and  the 
vertical  limbs  are  separated  by  the  frontal  operculum  (pars  triangularis) , which  is  the 
foot  of  the  inferior  frontal  convolution.  A  portion  of  the  same  convolution  below 
the  anterior  limb  is  called  the  orbital  operculum  (pars  orbitaUs) .  Between  the  vertical 
and  posterior  horizontal  limbs  is  the  fronto -parietal  operculum  (pars  opercularis). 


THE   HEMISPHERES    OF    THE    CEREBRUM 


867 


Limiting  Sulcus  of  Rell  {sulcus  circularis  Reili)  (Fig.  566). — If  the  lips  of  the 
posterior  liorizontal  Hmb  of  the  Sylvian  fissure  are  widely  separated,  the  island  of 
Reil  (insula)  (Figs.  566  and  568)  is  seen*  in  the  depths,  surrounded  by  the  limiting 
sulcus.  The  upper  or  external  portion  of  the  sulcus  separates  the  island  from 
the  parietal  and  frontal  lobes,  the  lower  or  posterior  portion  from  the  temporal 
lobe,  and  the  anterior  portion  from  the  frontal  lobe. 

The  Central  Sulcus  of  Rolando  or  the  Fissure  of  Rolando  (sulcus  centralis 
[Rolandi])  (Figs.  558,  559,  561,  565,  and  574). — The  fissure  of  Rolando  is  situ- 
ated about  the  middle  of  the  outer  surface  of  the  hemisphere,  and,  coursing 
obliquely  downward  and  forward,  divides  the  surface  of  the  hemisphere  into 
approximately  equal  parts.  It  is  between  the  frontal  and  parietal  lobes.  It  com- 
mences as  a  rule  on  the  mesial  surface  of  the  longitudinal  fissure,  runs  forward 
a  short  distance,  and  ascends  to  the  superior  mesial  border,  which  it  reaches  a 
little  behind  its  mid-point,  that  is  at  a  point  half  an  inch  behind  the  middle  of  a 
line  drawn  from  the  nasal  eminence  to  the  external  occipital  protuberance.  It 
then  runs  sinuously  downward  and  forward,  to  terminate  a  little  above  the  hori- 


INTERLOCKING 
'GYRI 


ASCENDING 

FRONTAL 

CONVOLUTION 


Fig.  559.- 


-Sulcus  of  Rolando  fully  opened  up,  so  as  to  exhibit  the  interlocking  gyri  and  deep  annectant 
gyrus  behind  it.     (Cunningham.) 


zontal  limb  of  the  fissure  of  Sylvius,  and  about  half  an  inch  behind  the  ascend- 
ing limb  of  the  same  fissure.  The  angle  made  by  the  fissure  of  Rolando  and  the 
mesial  plane  is  known  as  the  Rolandic  angle,  and  it  varies  in  the  adult  between 
69  degrees  and  74  degrees  (Cunningham).  It  forms  two  chief  curves:  the  upper 
or  superior  curve  or  genu  is  concave  forward  and  upward,  while  the  lower  or 
inferior  curve  or  genu  has  its  concavity  directed  backward.  If  the  lips  of  the 
Rolandic  fissure  are  opened,  we  will  see  in  the  depths  frontal  gyri  interlocked 
with  parietal  gyri  (Fig.  559).  Two  of  these  gyri  are  often  fused,  and  this  fused 
gyrus  is  named  the  deep  annectant  gyrus  (Fig.  559) . 

The  Parieto-occipital  Sulcus  (sulcus  occipitoparietalis)  (Figs.  558,  562,  564,  and 
565). — The  parieto-occipital  sulcus  is  only  seen  to  a  slight  extent  on  the  outer 
surface  of  the  hemisphere,  being  situated  for  the  most  part  on  its  mesial  aspect. 
The  portion  on  the  outer  surface  is  called  the  external  parieto-occipital  sulcus, 
to  distinguish  it  from  the  part  continued  on  to  the  internal  surface,  which  is 
termed  the  internal  parieto-occipital  sulcus.  The  external  parieto-occipital  sulcus 
commences  about  midway  between  the  posterior  extremity  or  occipital  pole  of 
the  brain  and  the  central  sulcus  of  Rolando,  and  runs  downward  and  outward  for 
about  half  an  inch,  and  is  ended  by  an  arch-shaped  convolution  (arcus  parieto- 


868 


THE  NERVOUS  SYSTE3I 


occipitalis).  The  internal  parieto-occipital  sulcus  is  vertical  in  direction,  is  very 
distinct,  and  passes  into  the  calcarine  fissure.  When  its  lips  are  fully  separated, 
deep  annectant  gyri  come  into  view. 

Besides  the  three  fissures  which  have  been  discussed,  the  following  must  be 
mentioned  (the  situation  of  each  is  shown  in  Fig.  561).  On  the  outer  surface 
of  the  hemisphere  there  are  the  three  frontal  sulci,  the  sulcus  frontalis  superior, 
medius,  and  inferior.  The  sulcus  paxamedialis,  the  superior  and  inferior  precentral 
sulci,  sulcus  diagonalis,  the  superior  and  inferior  temporal  sulci,  tiie  superior  and 
inferior  post-central  sulci,  the  ramus  occipitalis,  the  sulcus   occipitalis  transversus, 


OCCIPITAL 
POLE 


LONGITUDINAL 
FISSURE 


FRONTAL  LONGITUDINAL 

POLE         FISSURE 
Fig.  560. — The  cerebral  hemispheres  \ievviKl  from  above. 


fSpalteholz.) 


the  ramus  horizontalis,  the  callo  so -marginal  sulcus,  the  inferior  transverse  furrow 
(Fig.  561).  The  sulcus  interparietalis  (of  Turner)  is  a  group  of  four  sulci:  the 
sulcus  post-centralis  inferior,  the  sulcus  post-centralis  superior,  the  ramus  horizontalis, 
and  the  ramus  occipitalis.  The  first  two  are  usually  joined;  the  last  two  remain 
distinct  and  separate.  When  the  lips  of  the  intraparietal  sulcus  are  widely 
opened,  deep  annectant  gyri  come  into  view. 

The  fissures  of  Sylvius,  of  Rolando,  and  the  parieto-occipital  sulcus  divide 
the  external  surface  of  tlie  hemisphere  into  four  lobes:  the  frontal,  the  parietal,  the 
occipital,  and  the  temporal  lobes.  To  these  must  be  added  (1)  the  central  lobe  or 
island  of  Reil,  which  is  situated  deeply  in  the  Sylvian  fissure,  and  (2)  the  olfactory 


I 


THE   HEMISPHERES    OF    THE    CEREBRUM 


869 


lobe,  which  is  found  at  the  base  of  the  brain  and  was  formerly  described  under  the 
name  of  the  olfactory  nerve. 

The  Lobes  on  the  External  Surface. — The  lobes  on  the  external  surface  have 
received  their  names  from  the  bones  of  the  skull  with  which  they  are  most  nearly 
in  relation,  but  it  must  be  borne  in  mind  that  they  do  not  correspond  in  shape  or 
limit  with  the  bone  after  which  they  are  named.  The  division  is,  moreover,  to  a 
certain  extent  artificial,  as  will  be  seen  from  the  following  description.  If  a  line 
is  drawn  in  continuation  of  the  external  oarieto-occipital  sulcus  downward  and 
outward  to  the  lower  border  of  the  hemisphere,  it  will  impinge  on  a  slight  notch, 
the  pre-occipital  notch,  and  if  a  second  line  is  prolonged  backward  from  the  hori- 
zontal part  of  the  fissure  of  Sylvius  to  join  the  first  line,  the  division  of  the  outer 
surface  of  the  hemisphere  into  four  lobes  will  be  accomplished  (Fig.  558).  The 
portion  in  front  of  the  central  sulcus  of  Rolando  is  the  frontal  lobe ;  that  behind  the 
central  sulcus  of  Rolando  and  above  the  fissure  of  Sylvius  is  the  parietal  lobe;  the 


Fig.  561.- — Gyri  and  sulci  on  the  outer  surface  of  the  cerebral  hemisphere,  f',  sulcus  frontalis  superior; 
/^,  sulcus  frontalis  inferior;  i.m.,  sulcus  frontalis  medius;  p.m..  sulcus  paramedialis;  A,  pars  basilaris;  B,  pars 
triangularis;  C,  pars  orbitalis;  <S,  Sylvian  fissure;  s',  anterior  horizontal  limb  (Sylvian  fi.ssure);  s',  ascending 
limb  (Sylvian  fissure);  s^,  posterior  horizontal  limb  (Sylvian  fissure);  p.c.i.,  inferior  precentral  sulcus;  p.c.s., 
superior  precentral  sulcus;  r,  fissure  of  Rolando;  g.s..  superior  genu;  q.i.,  inferior  genu;  d,  sulcus  diagonalis; 
<',  superior  temporal  sulcus  (parallel);  <-,  inferior  temporal  sulcus;  pi.  inferior  post-central  sulcus;  ;>-,  superior 
post-central  sulcus;  p-',  ramus  horizontalis;  p*,  ramus  occipitalis;  s.o.t.,  sulcus  occipitalis  transversus;  cm., 
calloso-marginal  sulcus;  c.l.r.,  inferior  transverse  furrow.     (Cunningham). 

portion  behind  the  parieto-occipital  sulcus  and  its  imaginary  line  of  continuation 
to  the  pre-occipital  notch  is  the  occipital  lobe;  and  the  part  below  the  fissure  of 
Sylvius  and  in  front  of  the  occipital  lobe  is  the  temporal  lobe. 

The  Fissures,  Sulci,  and  Lobes  of  the  Mesial  and  Tentorial  Surfaces.— The 
mesial  surface  of  the  cerebrum  can  only  be  fully  viewed  by  dividing  the  corpus 
callosum  and  the  structures  beneath  it  longitudinally  in  the  middle  line;  in  order 
to  expose  the  tentorial  surface,  the  pons  Varolii,  cerebellum,  and  medulla  must 
be  removed,  by  division  of  the  crus  cerebri  on  either  side.  The  diagram  (Fig.  562) 
and  the  section  (Fig.  564)  show  these  fissures  and  sulci.  The  parts  in  the  centre, 
below  the  corpus  callosum,  belong  to  the  interior  of  the  brain,  and  will  be  disre- 
garded for  the  present,  while  the  lobes  and  fissures  of  the  remaining  portion  of  the 
hemisphere  are  considered.  The  fissures  and  sulci  are  ten  in  number  on  each  side, 
m  addition  to  a  small  part  of  the  fissure  of  Sylvius,  the  commencement  of  which 
is  seen  separating  the  frontal  and  temporal  lobes  and  the  beginning  and  end  of 
the  great  longitudinal  fissure.     These  fissures  and  sulci  are  named  the  olfactory 


870 


THE   NERVOUS  SYSTEM 


sulci,  the  orbital  sulci,  the  inferior  and  middle  temporal  sulci,  the  occipito -temporal 
sulci,  the  calloso-marginal  and  the  internal  parieto-occipital  sulci,  the  calcarine,  the 
collateral,  and  the  dentate  or  hippocampal  fissures. 

The  Olfactory  Sulcus  (sulcus  olfadorius)  (Figs.  563  and  566) . — The  olfactory 
sulcus  is  a  straight  furrow  which  lodges  the  olfactory  tract  and  bulb. 

The  Orbital  Sulcus  (sulcus  orbitalis)  (Figs.  563  and  566) . — The  orbital  sulcus  is 
usually  shaped  somewhat  like  the  letter  H,  and  is  then  composed  of  an  external 
limb  (sulcus  orbitalis  externus),  an  internal  limb  (sulcus  orbitalis  internus),  and 
a  transverse  portion  (sulcus  orbitalis  transversus).  The  parts  of  the  orbital  sulcus 
are  often  complicated  and  irregular,  and  are  sulci  rather  than  parts  of  a  sulcus. 

The  Inferior  Temporal  Sulcus  (sulcus  temporalis  inferior). — The  inferior  temporal 
sulcus  is  shown  in  Fig.  563. 

The  Occipito-temporal  Sulcus  (Fig.  563). — The  occipito-temporal  sulcus  is  in 
the  tentorial  base  of  the  occipital  lobe.  It  is  external  to  the  collateral  fissure,  is 
not  limited  purely  to  the  temporal  lobe,  and  bounds  the  occipito-temporal  gyrus 
externally.    It  often  consists  of  two  or  more  portions. 


Fig.  562. — The  gyri  and  sulci  on  the  mesial  asjiect  of  the  cerebral  hemisphere:     r,  fissure  of  Rolando; 
r.o.,  rostral  sulcus;  i.t.,  incisura  temporalis.      (Cunningham.) 

The  Calloso-marginal  Sulcus  (sulcus  cingulus)  (Figs.  562,  564,  and  567). — The 
calloso-marginal  sulcus  commences  below  the  anterior  extremity  of  the  corpus 
callosum;  it  at  first  runs  forward  and  upward,  parallel  with  the  rostrum  of 
the  corpus  callosum,  and,  winding  round  in  front  of  the  genu  of  that  body,  it 
continues  from  before  backward,  between  the  upper  margin  of  the  hemisphere 
and  the  convolution  of  the  corpus  callosum,  to  about  midway  between  the  ante- 
rior and  posterior  extremities  of  the  brain,  where  it  ascends  to  reach  the  upper 
margin  of  the  hemisphere,  a  short  distance  behind  the  superior  extremity  of  the 
fissure  of  Rolando. 

The  Internal  Parieto-occipital  Sulcus  (sulcus  parietooccipitalis)  (Figs.  562,  564, 
and  567) . — The  internal  parieto-occipital  sulcus  extends  in  an  oblique  direction 
downward  and  forward  to  join  the  calcarine  fissure,  on  a  level  with  the  hinder 
end  of  the  corpus  callosum. 

The  Calcarine  Fissure  (fissura  calcarina)  (Figs.  562,  564,  and  567). — The  cal- 
carine fissure  commences,  usually  by  two  branches,  close  to  the  posterior  extremity 
of  the  hemisphere.  These  soon  unite,  and  the  fissure  runs  nearly  horizontally  for- 
ward, and  is  joined  by  the  parieto-occipital  fissure,  and  continues  as  far  as  the 


THE   HEMISPHERES    OF    THE    CEREBRUM 


871 


posterior  extremity  of  the  corpus  callosum,  a  little  below  the  level  of  which  it 
terminates  in  the  limbic  lobe.  Its  anterior  part  causes  the  prominence  in  the 
interior  of  the  brain  known  as  the  hippocampus  minor  or  calcar  avis. 

The  Collateral  Fissure  {fissura  collateralis)  (Figs.  562,  563,  564,  and  567). — The 
collateral  fissure  is  situated  on  the  tentorial  surface,  below  and  external  to  the 
preceding,  being  separated  from  it  by  the  subcollateral  or  uncinate  gyrus.  It  runs 
forward,  from  the  posterior  extremity  of  the  brain,  nearly  as  far  as  the  tip  of  the 
temporal  lobe.  It  lies  below  the  posterior  and  descending  horns  of  the  lateral 
ventricle,  and  its  middle  part  causes  the  prominence  in  the  interior  of  the  brain 
known  as  the  eminentia  collateralis. 

The  Dentate  or  Hippocampal  Fissure  (fissura  hippocampi)  (Figs.  563,  564,  and 
567). — The  dentate  or   hippocampal    fissure    commences    immediately  behind 


Fig.  563. — Gyri  and  sulci  on  the  tentorial  and  orbital  aspects  of  the  cerebral  hemisphere.     (Cunningham.) 

the  posterior  extremity  of  the  corpus  callosum,  and  runs  forward  to  terminate 
at  the  recurved  part  of  the  hippocampal  gyrus.  It  causes  the  prominence  of  the 
hippocampus  major  in  the  descending  horn  of  the  lateral  ventricle. 

In  addition  to  these  fissures,  which  are  constant,  there  is  frequently  an  irregular 
broken  fissure,  which  is  sometimes  an  independent  sulcus,  but  which  often  appears 
to  be  a  continuation  backward  of  the  posterior  part  of  the  calloso-marginal 
fissure,  before  it  ascends  to  reach  the  upper  edge  of  the  hemisphere.  This 
has  been  termed  the  post-limbic  fissure  (Fig.  562) .  The  fissures  of  the  internal 
and  tentorial  surfaces  map  off  portions  of  the  hemisphere,  which  form  parts 
of  the  lobes  found  on  the  external  surfaces.  That  portion  which  lies  in  front  and 
above  the  calloso-marginal  fissure  belongs  almost  entirely  to  the  frontal  lobe;  its 
posterior  extremity,  which  extends  for  a  short  distance  behind  the  upper  end  of  the 


872 


THE   NERVOUS    SYSTEM 


fissure  of  Rolando,  forms  a  small  part  of  the  parietal  lobe;  that  portion  which  lies 
above  the  internal  parieto-occipital  fissure  and  behind  the  calloso-marginal  fissure 
forms  apart  of  the  parietal  lobe;  that  between  the  parieto-occipital  fissure  above 
and  the  calcarine  fissure  below  is  a  portion  of  the  occipital  lobe;  and  all  the  region 
below  the  calcarine  fissure  behind  and  the  collateral  fissure  in  front  belongs  to 
the  temporal  lobe.  The  remainder  of  the  mesial  and  tentorial  surfaces  of  the 
hemisphere  constitute  what  Broca  termed  the  limbic  lobe,  which  is  subsequently 
referred  to  (p.  878). 

The  surface  of  the  hemisphere  has  thus  been  divided  by  large  sulci  and 
fissures  into  its  different  parts — viz.,  the  frontal,  the  parietal,  the  occipital,  the 
temporal,  the  limbic,  the  olfactory  lobes,  and  the  island  of  Reil.  Each  of  these 
lobes  is  further  subdivided  into  convolutions  or  gyri  by  smaller  fissures,  which, 
though  less  constant  in  their  arrangement  than  the  larger  fissures,  have  a  fairly 
definite  course. 

1.  The  Frontal  Lobe  (lohus  frontalis)  (Figs.  558, 561, 562, 563, 564, 565,  and  566). 
— It  is  the  largest  of  the  lobes  of  the  cerebrum.    Its  outer  surface  is  bounded  behind 


Fig.  564. — Fissures  and  lobes  on  the  internal  surface  of  the  cerebral  hemispheres. 


by  the  central  sulcus  of  Rolando  and  below  by  the  posterior  horizontal  limb  of 
the  fissure  of  Sylvius.  On  the  orbital  surface  the  fissure  of  Sylvius  bounds  it 
posteriorly.    On  the  mesial  surface  it  is  bounded  by  the  calloso-marginal  sulcus. 

External  Surface. — On  its  external  surface  the  frontal  lobe  presents  three  sulci 
and  four  gyri  or  convolutions.  The  sulci  are  the  precentral,  the  superior  frontal, 
and  the  inferior  frontal. 

The  Precentral  Sulcus  (sulcus  'praecentralis)  is  divided  into  two  parts:  The 
inferior  precentral  sulcus  (sulcus  praecentralis  inferior)  is  composed  of  two  parts 
(Figs.  561  and  565):  one  part  (the  vertical)  is  placed  before  the  Rolandic  fissure; 
the  other  part  (the  horizontal)  passes  upward  and  to  the  front  into  the  middle 
frontal  convolution.  The  superior  precentral  sulcus  (sulcus  praecentralis  superior) 
is  vertical  in  direction  and  is  placed  in  front  of  the  upper  part  of  the  Rolandic 
fissure.    The  other  frontal  sulci  are  shown  in  the  diagrams. 

The  ascending  frontal  convolution  or  praecentral  g3mis  (gyrus  centralis  anterior  or 
gyrus  frontalis  ascendens)  (Figs.  561  and  565),  one  of  the  chief  motor  areas  of  the 


THE   HEMISPHERES    OF   THE    CEREBRUM 


873 


cortex,  is  a  simple  convolution,  and  is  limited  in  front  by  the  precentral  sulcus  and 
behind  by  the  fissure  of  Rolando.  It  extends  from  the  upper  margin  of  the  hemi- 
sphere above  to  a  little  behind  the  bifurcation  of  the  fissure  of  Sylvius  below.  From 
it  two  sulci,  the  superior  and  inferior  frontal  sulci  [sulcus  frontalis  superior  and  sulcus 
frontalis  inferior),  run  forward  and  downward,  and  divide  the  remainder  of  the 
outer  surface  of  the  lobe  into  three  parallel  principal  convolutions,  named  respect- 
ively the  superior,  middle,  and  inferior  frontal  convolutions  (Figs.  561  and  565). 

The  superior  or  first  frontal  convolution  (gyrus  frontalis  superior)  (Figs.  561  and 
565)  is  situated  between  the  margin  of  the  longitudinal  fissure  and  the  superior 
frontal  sulcus.  It  extends  above  on  to  the  inner  aspect  of  the  hemisphere,  forming 
the  greater  part  of  the  marginal  convolution  (Figs.  562,  564,  and  567),  and  in  front 
on  to  the  orbital  surface,  forming  the  internal  orbital  convolution  (Figs.  563  and 

End  of  calloso- 
marginal  fissure. 


Ascending  fissure 
of  Sylvius. 

Fissure 
of  Sylvius 


^^P0R^\. 


Fig.  565. — Convolutions  and  sulci  on  the  external  surface  of  the  cerebral  hemisphere. 


566).  It  is  usually  more  or  less  completely  subdivided  into  two  (pars  superior 
and  pars  inferior)  by  several  depressions  of  trivial  length,  the  aggregation  being 
called  by  Cunningham  the  sulcus  paramedians.  It  is  frequently  interrupted  and 
broken  into  several  parts  by  bridging  convolutions. 

The  second  or  middle  frontal  convolution  (gyrus  frontalis  medius)  (Figs.  561  and 
565)  is  situated  between  the  superior  and  inferior  frontal  sulci,  and  extends  from 
the  precentral  sulcus  on  to  the  orbital  surface  of  the  lobe,  where  it  forms  the 
anterior  orbital  convolution  (Figs.  563  and  566).  The  middle  frontal  convolution 
is  frequently  subdivided  into  two  (pars  superior  and  pars  inferior)  by  a  sagittally 
directed  sulcus,  the  sulcus  frontalis  medius  of  Eberstaller. 

The  third  or  inferior  frontal  convolution  (gijrus  frontalis  inferior)  (Figs.  561  and  565) 
is  situated  below  the  inferior  frontal  sulcus,  and  extends  forward  from  the  lower  part 
of  the  precentral  sulcus,  on  to  the  under  surface  of  the  lobe,  where  it  forms  the  pos- 


874 


THE  NERVOUS   SYSTEM 


terior  orbital  convolutions  (Figs.  563  and  566).  The  inferior  frontal  convolution  is 
subdivided  by  the  anterior  and  ascending  limbs  of  the  fissure  of  wSylvius  into  three 
parts — viz. :  (1)  anterior  part  or  the  orbital  operculum  {jyars  orhitalis),  below  the  ante- 
rior limb  of  the  fissure  of  Sylvius;  (2)  middle  part  or  "cap"  of  Broca  or  the  frontal 
operculum  {'pars  triangularis) ,  between  the  anterior  horizontal  and  the  vertical  limbs 
of  the  fissure  of  Sylvius;  and  (3)  posterior  part  or  the  fronto- parietal  operculum  (pars 
hasilaris) ,  behind  the  posterior  horizontal  and  vertical  limbs  of  the  fissure  of  Sylvius. 
In  the  basilar  part  is  the  sulcus  diagonalis  (d  in  Fig.  561).  The  left  inferior  frontal 
convolution  is,  as  a  rule,  more  highly  developed  than  the  right,  and  is  named  the 
convolution  of  Broca,  from  the  fact  that  in  1861  Broca  declared  that  it  was  the  centre 
for  speech.  It  is  now  known  that  the  region  of  speech  comprises  the  posterior  part 
of  the  inferior  frontal  convolution  and  the  fronto-parietal  operculum. 


GYRUS 
RECTUS 


ANTERIOR 

PERFORATED 

SPACE 


Fig.  566. — Convolutions  and  sulci  on  the  under  surface  of  the  anterior  lobe. 


Under  Surface  (Figs.  563  and  566).— The  under  surface  of  the  frontal  lobe  rests 
on  the  orbital  plate  of  the  frontal  bone,  and  is  sometimes  named  the  orbital  lobe. 
It  is  divided  into  three  convolutions  by  a  well-marked  sulcus,  the  orbital  or 
tri-radiate  sulcus  (sulci  orhitales).  These  convolutions  are  named,  from  their 
position,  the  internal,  anterior,  and  posterior  orbital  convolutions,  and  are  the  con- 
tinuations respectively  of  the  superior,  middle,  and  inferior  frontal  convolutions 
of  the  external  surface.  The  internal  orbital  convolution  presents  a  well-marked 
antero-posterior  groove  or  sulcus,  the  olfactory  sulcus  {sulcus  olfactorius),  for 
the  olfactory  bulb  and  tract;  and  the  portion  internal  to  this  is  named  the  gyrus 
rectus,  and  is  continuous  with  the  marginal  gyrus,  presently  to  be  described. 

Mesial  or  Internal  Surface  (Figs.  562  and  567).— The  mesial  or  internal  surface 
of  the  frontal  lobe  is  occupied  by  a  single  curved  convolution,  which  from  its 


THE    HEMISPHERES    OF    THE    CEREBRUM 


875 


situation  is  termed  the  maxginal  gyrus  (gyrus  marginalis).  It  commences  in  front 
of  the  anterior  perforated  space,  runs  along  the  margin  of  the  longitudinal  fissure 
on  the  mesial  surface  of  the  orbital  lobe,  where  it  is  continuous  with  the  internal 
orbital  convolution;  it  then  ascends,  and  runs  backward  to  the  point  where  the 
calloso-marginal  fissure  turns  upward  to  reach  the  superior  border  of  the  hemi- 
sphere. An  oval  portion  at  the  posterior  part  of  this  convolution  is  sometimes 
marked  off  by  a  vertical  fissure,  and  is  distinguished  as  the  paracentral  lobule 
(lobulus  paracentralis) ,  because  it  is  continuous  with  the  convolutions  in  front  and 
behind  the  central  fissure  or  fissure  of  Rolando.  In  the  anterior  portion  of  the 
marginal  gyrus  are  two  sulci  named  the  sulci  rostrales. 

2.  The  Parietal  Lobe  (lobus  pariefalis)  (Figs. 558,561,562,564, 565,  and  567).— 
This  lobe  includes  a  considerable  portion  of  the  surface   of  the   hemisphere. 


Fig.  567. — Convolutions  and  sulci  on  the  internal  surface  of  the  cerebral  hemispheres. 

and  it  also  occupies  the  portion  of  the  mesial  surface  known  as  the  quadrate 
lobule  or  cuneus.  It  is  bounded  in  front  by  the  central  sulcus  of  Rolando, 
Posteriorly  it  is  partly  separated  from  the  occipital  lobe  by  the  external  parieto- 
occipital sulcus.  Below  it  is  partly  limited  by  the  posterior  horizontal  limb  of  the 
fissure  of  Sylvius. 

External  Surface. — On  its  external  surface  the  parietal  lobe  presents  for  examina- 
tion one  sulcus  (which  is  divided  into  four  parts)  and  three  convolutions. 

The  Intraparietal  Sulcus  of  Turner  (sulcus  intraparietalis)  (Figs.  561  and  565), 
according  to  Prof.  Cunningham,  is  a  group  of  four  sulci — viz.,  the  superior  post- 
central sulcus  (sulcus  postcentralis  superior),  the  inferior  post-central  sulcus  (sulcus 
postcentralis  inferior),  the  horizontal  ramus  (ramus  horizontalis) ,  and  the  occipital 
ramus  (ramus  occipitalis).  The  first  named  lies  back  of  the  upper  portion  of  the 
central  sulcus  of  Rolando;  the  second  lies  back  of  the  lower  portion  of  the  same 
sulcus.  In  front  of  the  post-central  sulci  is  the  ascending  parietal  (post-central) 
convolution  (gyrus  centralis  posterior).  The  superior  and  inferior  post-central  sulci 
are  usually  continuous.  The  upper  end  of  the  inferior  post-central  sulcus  is  pro- 
longed upward  and  backward  as  the  ramus  horizontalis  between  the  superior 
and  inferior  parietal  gyri.  The  ramus  occipitalis  may  or  may  not  be  joined  to  the 
ramus  horizontalis.     It  is  the  external  boundary  of  the  arcus  parieto-occipitalis. 


876  THE  NERVOUS  SYSTEM 

The  ascending  parietal  convolution  or  the  post-central  g3rras  {gyrus  ascendens  parte- 
talis  or  gyrus  posicentralis)  (Figs.  561  and  565)  is  usually  regarded  as  one  of  the 
chief  motor  areas  of  the  cortex,  although  Mills,  Sherrington  and  others  are  of  the 
opinion  that  the  motor  areas  are  all  in  front  of  the  central  sulcus  of  Roland.  The 
ascending  parietal  convolution  is  bounded  in  front  by  the  central  sulcusof  Rolando, 
behind  by  the  superior  and  inferior  post-central  sulci.  It  extends  from  the  great  lon- 
gitudinal fissure  above  to  the  posterior  horizontal  limbof  the  fissureof  Sylvius  below. 
It  lies  parallel  with  the  ascending  frontal  convolution,  with  which  it  is  connected 
below,  and  also,  sometimes,  above  the  termination  of  the  central  sulcus  of  Rolando. 

The  superior  parietal  convolution  (lobulus  parietalis  superior)  (Figs.  561  and  565), 
still  regarded  by  some  as  a  part  of  the  motor  area  of  the  cortex,  is  bounded  in  front 
by  the  superior  post-central  sulcus,  which  lies  between  it  and  the  previous  convolu- 
tion, but  with  which  it  is  usually  connected  above  the  upper  extremity  of  the  sulcus; 
behind,  it  is  joined  to  the  occipital  lobe  by  a  narrow  convolution,  the  first  annectant 
gyrus  {arcus  parietooccipitalis) ;  below,  it  is  separated  from  the  inferior  parietal  con- 
volution by  the  horizontal  portion  of  the  intraparietal  sulcus;  and  above,  it  is 
continuous  on  the  inner  surface  of  the  hemisphere  with  the  quadrate  lobe. 

The  inferior  parietal  convolution  (lobulus  parietalis  inferior)  (Figs.  561  and  565)  is 
that  portion  of  the  parietal  lobe  which  is  situated  between  the  ascending  portion  of 
the  intraparietal  sulcus  in  front,  the  horizontal  portion  of  the  same  sulcus  above,  the 
horizontal  limb  of  the  fissure  of  Sylvius  below,  and  the  posterior  boundary  of  the 
parietal  lobe  behind.  It  is  divided  into  three  convolutions:  the  supramarginal,  the 
angular,  and  the  post-parietal.  One,  the  supramarginal  convolution  {gyrus  supra- 
marginalis),  lies  behind  the  ascending  part  of  the  intraparietal  sulcus  and  above  the 
horizontal  limb  of  the  fissure  of  Sylvius,  over  the  extremity  of  which  it  arches.  It  is 
connected  in  front  with  the  ascending  parietal  convolution  below  the  intraparietal 
sulcus,  and  behind  with  the  first  or  superior  temporal  convolution  around  the  pos- 
terior extremity  of  the  fissure  of  Sylvius  (Fig.  561) .  The  angular  convolution  or  the 
angular  gyrus  {gyrus  angularis)  is  united  anteriorly  with  the  foregoing,  while  pos- 
teriorly it  is  continuous  with  the  middle  or  second  temporal  convolution  by  a  process 
which  curves  around  the  superior  temporal  or  parallel  sulcus  (Fig.  561).  The 
post-parietal  convolution  or  the  second  annectant  gyrus  passes  around  the  posterior 
end  of  the  middle  temporal  convolution  and  into  the  inferior  temporal  convolu- 
tion.    It  joins  the  inferior  parietal  convolution  to  the  occipital  lobe. 

The  Internal  or  Mesial  Surface  (Figs.  562  and  564) . — The  internal  or  mesial  surface 
of  the  parietal  lobe  is  continuous  with  the  external  surface  over  the  upper  edge  of 
the  hemisphere.  It  is  of  small  size,  and  forms  one  square-shaped  convolution, 
which  from  its  shape  is  termed  the  quadrate  lobe.  From  its  situation  above  the 
cuneate  lobe  it  is  named  the  precuneus  (praecuneus).  The  post-limbic  sulcus  imper- 
fectly separates  the  precuneus  from  the  limbic  lobe. 

3.  The  Occipital  Lobe  {lohus  occipitalis)  (Figs.  558,  561,  5()2,  563,  564,  565, 
and  567). — The  occipital  lobe  is  indefinitely  separated  from  the  temporal  and 
parietal  lobes.  It  is  defined  by  Cunningham  as  the  portion  of  "the  hemisphere 
which  encloses  the  posterior  horn  of  the  lateral  ventricle."  In  form  it  is  pyram- 
idal, and  it  possesses  an  apex,  the  occipital  pole  {polus  occipitalis),  and  three 
surfaces.  The  inferior  surface  is  directly  continuous  with  the  temporal  and 
limbic  lobes.  On  the  outer  surface  the  external  parieto-occipital  fissure  partly 
separates  it  from  the  parietal  lobe.  On  the  mesial  surface  the  internal 
parieto-occipital  fissure  separates  it  from  the  precuneus. 

External  Surface  (Figs.  561  and  565) . — The  occipital  lobe  is  divided  on  its  external 
surface  into  three  convolutions  by  two  indistinct  sulci,  the  superior  and  middle  occip- 
ital sulci  {sulcus  occipitalis  transversus  and  sulcus  occipitalis  lateralis).  They  are 
directed  backward  across  the  lobe,  being  frequently  small  and  ill  marked ;  the  supe- 
rior is  sometimes  continuous  with  the  horizontal  portion  of  the  intraparietal  sulcus. 


THE   HEMISPHERES    OF    THE    CEREBRUM  877 

The  superior  occipital  convolution  {gyrus  occipitalis  superior)  is  situated  above 
the  superior  sulcus,  and  is  connected  to  the  superior  parietal  convolution  by  the 
first  annectant  gyrus. 

The  middle  occipital  convolution  (gyrus  occipitalis  medius)  is  situated  between 
the  superior  and  middle  occipital  sulci,  and  is  connected  to  the  angular  convolution 
by  the  second  annectant  gyrus,  and  to  the  middle  temporal  convolution  by  the 
third  annectant  gyrus. 

The  inferior  occipital  convolution  {gyrus  occipitalis  inferior)  is  situated  below  the 
middle  occipital  sulcus,  and  is  sometimes  separated  from  the  external  occipito- 
temporal convolution  on  the  under  surface  of  the  hemisphere  by  an  inconstant 
sulcus,  the  inferior  occipital  sulcus  (sulcus  occipitalis  inferior).  The  inferior  occipi- 
tal convolution  is  connected  to  the  inferior  temporal  convolution  by  the  fourth 
annectant  gyrus. 

Internal  or  Mesial  Surface  (Figs.  562,  564,  and  567).— The  internal  or  mesial  sur- 
face of  the  occipital  lobe  presents  a  triangular  convolution,  which  is  known  as  the 
cuneate  lobule  {cimeus).  I  is  situated  between  the  internal  parieto-occipital  sulcus 
and  the  calcarine  fissure,  which,  as  already  mentioned,  meet  some  distance  behind 
the  posterior  extremity  of  the  corpus  callosum. 

The  lingual  gyrus  or  subcalcarine  convolution  {gyrus  lingualis)  is  between  the 
calcarine  and  collateral  fissures,  and  runs  forward  into  the  hippocampal  portion 
of  the  limbic  lobe.  A  portion  of  the  gyrus  lingualis  is  on  the  mesial  aspect  and 
a  portion  on  the  inferior  aspect  of  the  occipital  lobe  (Fig.  563) . 

Inferior  Surface  (Fig.  563). — The  inferior  or  tentorial  surface  of  the  occipital  lobe 
possesses  one  convolution,  the  occipito -temporal  gyrus,  which  is  continuous  wath 
the  temporal  lobe  and  the  limbic  lobe  (p.  878),  and  is  bounded  externally  by  the 
occipito-temporal  sulcus. 

The  centre  for  visual  memory  is  in  the  external  surface  of  the  occipital  lobe 
and  the  angular  gyrus. 

4.  The  Temporal  Lobe  (lobus  temporalis)  (Figs.  558,  561,  562,  563,  564,  565, 
and  567). — The  temporal  lobe  is  sometimes  called  the  temporo-sphenoidal  lobe. 
This  lobe  lies  behind  the  junction  point  and  below  the  posterior  horizontal  limb 
of  the  Sylvian  fissure.  On  its  inferior  (tentorial)  surface  the  collateral  fissure 
separates  it  from  the  hippocampal  portion  of  the  limbic  lobe.  The  apex  of  the 
temporal  lobe  projects  in  front  of  the  Sylvian  junction.  The  lobe  presents  an 
outer  and  an  inferior  surface. 

Outer  Surface  (Figs.  561  and  565). — The  outer  surface  is  subdivided  by  two 
sulci,  named  respectively  the  first  and  second  temporal  sulci. 

The  First  Temporal  Sulcus  (sulcus  temporalis  superior)  is  well  marked,  and  runs 
from  before  backward  through  the  temporal  lobe  parallel  with,  but  some  little 
distance  below,  the  posterior  horizontal  limb  of  the  fissure  of  Sylvius;  hence  it 
is  often  termed  the  parallel  sulcus. 

The  Second  Temporal  Sulcus  (sulcus  temporalis  medius)  takes  the  same  direction 
as  the  first,  but  is  situated  at  a  lower  level,  and  is  often  interrupted  by  one  or  more 
bridging  convolutions.  These  two  sulci  subdivide  this  surface  of  the  temporal  lobe 
into  three  convolutions. 

The  first  or  superior  temporal  convolution  (gyrus  temporalis  superior)  is  situated 
between  the  posterior  horizontal  limb  of  the  fissure  of  Sylvius  and  the  first  tem- 
poral sulcus,  and  is  continuous  behind  with  the  supramarginal  convolution. 

The  second  or  middle  temporal  convolution  (gyrus  temporalis  medius)  lies  between 
the  first  and  second  temporal  sulci,  and  is  continued  behind  into  the  angular  and 
middle  occipital  convolutions. 

The  third  or  inferior  temporal  convolution  (gyrus  temporalis  inferior)  is  placed 
below  the  second  temporal  sulcus;  it  is  connected  posteriorly  with  the  inferior 
occipital  convolution,  and  is  also  prolonged  on  to  the  under  or  tentorial  surface 


878 


THE  NEBVOUS  SYSTEM 


of  the  temporal  lobe  (Fig.  563),  where  it  is  limited  internally  by  the  third  tem- 
poral sulcus,  about  to  be  described. 

Inferior  Surface  (Fig.  563). — The  inferior  or  tentorial  surface  presents  two 
fissures — viz.,  the  third  temporal  sulcus  and  the  collateral  fissure — the  latter  fissure 
has  already  been  described  (p.  871). 

The  Third  Temporal  Sulcus  {sulcus  temporalis  in]erior)  extends  from  near  the 
occipital  pole  behind  to  near  the  anterior  extremity  of  the  temporal  lobe  in  front, 
but  is,  however,  frequently  subdivided  by  bridging  gyri. 

The  convolution  on  the  inferior  surface  is  the  fourth  temporal  or  subcollateral 
or  the  occipito-temporal  convolution.  It  is  situated  between  the  third  temporal 
sulcus  and  the  collateral  fissure. 

5.  The  Central  Lobe  or  Island  of  Reil  (Insula)  (Figs.  566,  568,  576,  and  577). 
— The  central  lobe  or  island  of  Reil  lies  deeply  in  the  Sylvian  fissure,  and  can  only 
be  seen  when  the  lips  of  that  fissure  are  widely  separated,  since  it  is  overlapped 
and  hidden  by  the  convolutions  which  bound  the  fissure.  These  convolutions  are 
termed  the  opercula  of  the  insula  (opercula  insulae)  (operculum,  a  lid) ;  they  are 
separated  from  each  other  by  the  three  limbs  of  the  Sylvian  fissure,  and  are 
named  the  orbital,  frontal,  fronto-parietal,  and  temporal  opercula  (p.  866).  The  insula 


Fig.  568. — The  island  of  Reil.     Left  side.     The  overlapping  parts  of  the  hemisphere  have  been  removed. 
1,  2,  3.  Gyri  breves.     4,  5.  Gyrus  longus,  bifurcated  at  its  upper  extremity.     (Dalton.) 

is  almost  surrounded  by  a  deep  limiting  sulcus,  the  limiting  sulcus  of  Reil  (sulcus 
circularis  Reili)  (Fig.  566  and  p.  867) ,  which  separates  it  from  the  frontal,  parietal, 
and  temporal  lobes.  When  the  opercula  have  been  removed,  the  insula  presents  the 
form  of  a  triangular  eminence;  its  apex  is  directed  downward  and  inward  toward 
the  anterior  perforated  space,  and  is  continuous  in  front  with  the  posterior 
orbital  convolution.  At  the  apex  of  the  insula  the  limiting  sulcus  does  not  exist, 
and  the  gray  matter  passes  into  the  anterior  perforated  space.  This  point  is 
called  the  limen  insulae.  The  insula  is  continuous  behind  with  the  hippocampal 
convolution.  It  is  divided  into  a  pre-central  and  a  post-central  lobe  by  the  sulcus 
centralis,  which  runs  backward  and  upward  from  the  apex  of  the  insula.  The  pre- 
central  lobe  is  further  subdivided  by  shallow  sulci  into  three  or  four  short  con- 
volutions, the  gjii  breves  insulae,  while  the  post-central  lobe  is  named  the  gjTV& 
longus  insulae,  and  is  often  bifurcated  at  its  upper  extremity.  The  gray  matter  of 
the  insula  is  continuous  with  that  of  the  different  opercula,  while  its  mesial  surface 
corresponds  with  the  external  surface  of  lenticular  nucleus  of  the  corpus  striatum, 
from  which  it  is  separated  by  the  external  capsule  and  claustrum. 

6.  Limbic  Lobe  (Figs.  564  and  569) . — ^The  term  limbic  lobe  or  grande  lobe 
limhyjue  was  introduced  by  Broca  in  1878,  and  under  it  he  included  two  convolu- 
tions— viz.,  the  callosal  and  hippocampal  convolutions,  which  together  arch  around 


THE   HEMISPHERES    OF    THE   CEREBRUM  879 

the  corpus  callosum  and  the  hippocampal  fissure.  These  he  separated  on  the 
morphological  ground  that  they  are  well  developed  in  animals  possessing  a  keen 
sense  of  smell  (osmatic  animals),  such  as  the  dog  and  fox.  To  the  lobe  thus  de- 
fined the  following  parts  must  be  added — viz.,  the  laminae  of  the  septum  lucidum, 
together  with  the  fornix  and  its  fimbriae,  which  may  be  regarded  as  forming  an 
inner  or  deep  arch;  the  peduncles  and 
longitudinal  striae  of  the  corpus  cal-  ^loIe*^  *  a''i,"h°'' 

losum,  together  with  the  gyrus  den-  1      ;| 

tatus,  which  form  a  middle  arch,  while       /     i  ^~^^\l 

the  outer  arch   is  constituted  by  the      /      ...-•■ •-..     ^N^^ 

callosal  and  hippocampal  convolutions;    /       P  N.    \ 

the  first  two  arches  are  separated  from    I        !  \    \ 

each  other  by  the  corpus  callosum.  \        \  \    \  

Convolutions  of  the  Limbic  Lobe.—     \        "'"; ■^- .:::^^:r~2r^^l 

(1)    The    callosal    convolution    {gyrus        ^---_L,_ — - — "^    ^^^ctLry 

jornicatiis  or  qyrus  cinquli)  (Figs.  562  •  "-obe 

'         ,      _„_.     .  -'■^  ,         ^  1  1  INFERIOR  PEDUNCLE 

and  5o7)  is  an  arch-shaped  convolu-  arch 

tion,      lying     in     close     relation     to    the        Fig.  569.-Scheme  of  ^the^Umbic  lobe.     (Poirierand 

superficial  surface  of  the  corpus  cal- 
losum, from  which  it  is  separated  by  a  slit-like  sulcus,  the  callosal  sulcus  (sulcus 
corporis  callosi).  It  commences  below  the  rostrum  of  the  corpus  callosum.  The  inner 
root  of  the  olfactory  tract  enters  the  beginning  of  the  convolution.  The  callosal  con- 
volution curves  around  in  front  of  the  genu,  extends  along  the  upper  surface  of  the 
body,  and  finally  turns  downward  behind  the  splenium,  where  it  becomes  narrow 
because  the  calcarine  fissure  cuts  it.  The  narrow  portion  is  the  isthmus  (isthmus 
gijri  fornicati).  The  isthmus  connects  the  callosal  convolution  with  the  gyrus  hippo- 
campi. The  callosal  convolution  is  separated  from  the  marginal  convolution  by  the 
calloso-marginal  sulcus,  from  the  precuneus  by  the  post-limbic  sulcus,  and  from  the 
lingual  gyrus  by  the  anterior  portion  of  the  calcarine  fissure. 

(2)  The  hippocampal  convolution  (gyrus  hippocampi)  (Figs.  562  and  563)  is 
bounded  above  by  the  hippocampal  or  dentate  fissure,  and  below  by  the  anterior 
part  of  the  collateral  fissure.  Behind,  it  is  continuous  superiorly,  through  the 
isthmus, with  the  callosal  convolution,  and  inferiorly  with  the  subcalcarine  or  lingual 
convolution.  Its  anterior  extremity  is  recurved  in  the  form  of  a  hook,  and  is  named 
the  uncinate  convolution  or  uncus  (Fig.  567) .  Running  in  the  substance  of  the  callosal 
and  hippocampal  convolutions,  and  connecting  them  together,  is  a  tract  of  arched 
fibres,  named  the  fillet  of  the  gyrus  fomicatus  or  the  cingulum.  The  outer  root  of  the 
olfactory  tract  passes  into  the  anterior  extremity  of  the  hippocampal  convolution, 
and  the  inner  root  into  the  commencement  of  the  callosal  convolution,  so  that  these 
two  convolutions,  with  the  addition  of  the  olfactory  tract,  present  a  racquet-like 
appearance — the  olfactory  tract  constituting  the  handle  and  the  two  convolutions 
the  circumference  of  the  blade. 

(3)  The  dentate  convolution  (gyrus  dentatus)  (Figs.  562  and  581) ,  also  called  the 
dentate  fascia  (fascia  dentata  hippocampi) .  It  is  situated  above  the  gyrus  hippo- 
campi, from  which  it  is  separated  by  the  hippocampal  or  dentate  fissure  (fissura 
hippocampi)  (Figs.  562,  564,  and  567).  The  dentate  convolution  is  covered  by  the 
fimbria,  a  prolongation  of  the  posterior  pillar  of  the  fornix,  and  is  a  narrow,  elon- 
gated convolution,  the  free  surface  of  which  presents  a  notched  or  toothed  appear- 
ance, hence  its  name.  Posteriorly  it  is  prolonged  as  a  delicate  lamina,  the  fasciola 
cinerea,  around  the  splenium  of  the  corpus  callosum,  and  becomes  continuous  on 
the  upper  surface  of  that  body  with  its  mesial  and  lateral  longitudinal  striae. 
Anteriorly  it  is  prolonged  into  the  notch  produced  by  the  recurving  of  the  uncus, 
where  it  forms  a  sharp  curve;  from  here  it  can  be  traced  as  a  delicate  band,  the 
band  of  Giacomini,  over  the  uncus,  on  the  outer  surface  of  which  it  is  lost. 


880 


THE  NERVOUS   SYSTEM 


The  remaining  structures  which  contribute  to  the  formation  of  the  Hmbic  lobe 
will  be  subsequently  described. 

7.  The  Olfactory  Lobe  or  Rhinencephalon  {lohus  oljactorius)  (Figs.  555  and 
569). — The  olfactory  lobe  is  situated  on  the  under  surface  of  the  frontal  lobe.  It  is 
rudimentary  in  man  and  some  other  mammals,  but  in  vertebrates  generally  it  is  well 
developed,  and  consists  of  a  distinct  extension  of  the  cerebral  hemisphere,  enclosing 
a  portion  of  the  anterior  horn  of  the  lateral  ventricle.  In  man  it  is  long  and  slender, 
and  may  be  described  as  consisting  of  two  parts,  the  anterior  and  posterior  olfactory 
lobules. 

The  Anterior  Olfactory  Lobule. — The  anterior  olfactory  lobule  is  made  up  of: 
(1)  the  olfactory  bulb;  (2)  the  olfactory  tract;  (3)  the  trigonum  olf actorium ;  (4)  the 
area  of  Broca. 


OLFACTORY 
BULB 
, GENU    OF 
"CALLOSUM 


SYLVIAN 
FISSURE 

ANTERIOR    PEH- 
,      FORATED    SPACE 
k   ..INFUNDI- 
BULUM 


..POSTERIOR  PER- 
FORATED SPACE 
CRUS   CEREBRI 


MIDDLE    CEREBEL- 
LAR   PEDUNCLE 


OBLONGATA 


'-  —CEREBELLUM 


Fig.  570. — Under  surface  of  the  brain,  showing  the  superficial  origins  of  the  cranial  nerves, 
numerals  indicate  the  nerves.     (Testut.) 


The  Roman 


(1)  The  Olfactory  Bulb  (bulbus  olfactorius)  (Fig.  570)  is  an  oval  mass  of  reddish- 
gray  color,  which  rests  on  the  cribriform  plate  of  the  ethmoid  bone  below  and 
the  olfactory  sulcus  of  the  orbital  surface  of  the  frontal  lobe  above.  It  forms 
the  anterior  expanded  extremity  of  the  olfactory  tract.  Its  under  surface  receives 
the  olfactory  nerves,  which  pass  upward  through  the  cribriform  plate  from  the 
olfactory  region  of  the  nose.     Its  minute  structure  will  be  subsequently  described. 

(2)  The  Olfactory  Tract  (tractus  olfactorius)  (Fig.  570),  often  called  the  olfactory 
nerve  or  first  cranial  nerve,  is  a  band  of  white  matter,  triangular  on  section,  the 
apex  being  directed  upward.  It  lies  in  the  olfactory  sulcus  on  the  under  surface 
of  the  frontal  lobe.    Traced  backward,  it  is  seen  to  divide  into  two  roots,  an  outer 


THE   HEMISPHERES    OF   THE    CEREBRUM  881 

and  an  inner.  Some  have  called  the  olfactory  tubercle  a  middle  root.  The  outer 
root  passes  across  the  outer  part  of  the  anterior  perforated  space  to  the  nucleus 
amygdalae  and  the  anterior  part  of  the  gyms  hippocampi.  The  inner  root  turns 
sharply  inward,  and  ends  partly  in  Broca's  area  and  partly  in  the  callosal  convolu- 
tion; in  other  words,  the  inner  root  is  continuous  with  one  extremity  and  the  outer 
root  with  the  other  extremity  of  the  limbic  lobe  (Fig.  569). 

(3)  The  Trigonum  Olfactorium  or  Olfactory  Tubercle  is  situated  between  the 
diverging  roots  of  the  olfactory  tract,  and  is  sometimes  described  at  the  middle  or 
gray  root  of  the  tract.  It  is  part  of  an  area  of  gray  matter,  which  forms  the  base 
of  the  anterior  olfactory  lobule;  another  portion  of  it  is  termed  (4)  the  area  of 
Broca  (area  par olf actor ia),  the  portion  of  gray  matter  between  the  internal  root 
and  the  peduncle  of  the  corpus  callosum;  and  a  third  portion,  of  no  special  sig- 
nificance, is  situated  external  to  the  outer  root  of  the  olfactory  tract.  This  area  of 
gray  matter  is  bounded  internally  and  posteriorly  by  a  sulcus,  the  fissura  prima 
(sidcus  par  olf  actor  ius  posterior) , which  separates  it  from  the  peduncle  of  the  corpus 
callosum  and  from  the  posterior  olfactory  lobule.  The  area  of  Broca  is  continuous 
with  the  gyrus  fornicatus,  and  receives  fibres  from  the  inner  or  mesial  root. 

The  Posterior  Olfactory  Lobule. — The  posterior  olfactory  lobule  corresponds  to 
the  portion  of  the  hemisphere  called  the  anterior  perforated  space  (locus  perforatum 
anticus  or  substantia  perforata  anterior)  (Figs.  566  and  570).  It  is  marked  off  from 
the  anterior  lobule  by  the  sulcus  parolfactorius  posterior,  and  is  situated  at  the  com- 
mencement of  the  fissure  of  Sylvius.  Internally,  it  is  bounded  by  the  peduncle  of 
the  corpus  callosum,  and  is  continuous  with  the  lamina  cinerea.  Posteriorly  it  is 
bounded  by  the  optic  tract,  and  it  is  partially  concealed  by  the  temporal  lobe  which 
overlaps  it.  It  has  received  the  name  of  anterior  perforated  space  from  its  being 
perforated  by  numerous  openings,  which  transmit  blood-vessels  to  the  interior  of 
the  brain,  and  it  coi'responds  to  the  under  surface  of  the  lenticular  nucleus. 

Under  Surface  or  Base  of  the  Encephalon  (fades  hasalis  encephali)  (Fig. 
570). — Having  considered  the  surface  of  the  hemispheres,  the  student  should 
direct  his  attention  to  the  base  of  the  brain,  before  commencing  the  study  of  the 
component  parts  which  make  up  the  two  hemispheres. 

The  base  of  the  brain  presents  for  examination  the  under  surfaces  of  the  frontal 
and  temporal  lobes;  the  structures  contained  in  the  interpeduncular  space,  with 
the  crura  cerebri  or  cerebral  peduncles;  the  under  surfaces  of  the  pons  Varolii, 
cerebellum,  and  medulla  oblongata;  and  the  superficial  origins  of  the  cranial 
nerves. 

The  various  objects  exposed  to  view  (with  the  exception  of  the  superficial 
origins  of  the  cranial  nerves,  which  will  be  considered  in  another  section),  in  the 
middle  line  and  on  either  side  of  the  middle  line,  are  here  arranged  in  the  order 
they  are  met  with  from  before  backward. 

In  the  Middle  Line.  On  Each  Side  of  the  Middle  Line. 

Longitudinal  fissure.  Frontal  lobe. 

Rostrum  and  peduncles  of  Olfactory  lobe. 

corpus  callosum.  The  anterior  perforated  space. 

Lamina  cinerea.  Fissure  of  Sylvius. 

Optic  commissure.  Optic  tracts. 

Tuber  cinereum.  Crura  cerebri. 

Tnfundibulum.  Temporal  lobe. 

Pituitary  body.  .  Hemisphere  of  cerebellum. 

Corpora  albicantia. 
Posterior  perforated  space. 
Pons  Varolii. 
Medulla  oblongata. 

56 


882  'J'HE  NERVOUS  SYSTEM 

The  Longitudinal  Fissure  (fissura  longitudinal  is  cerebri)  (p.  865). — The  longi- 
tudinal fissure  partially  separates  the  two  hemispheres  from  each  other.  It 
divides  completely  the  anterior  portions  of  the  two  frontal  lobes;  and  on  raising 
the  cerebellum  and  pons  it  will  be  seen  to  separate  completely  the  two  occipital 
lobes;  of  these  two  portions  of  the  longitudinal  fissure,  that  which  separates  the 
occipital  lobes  is  the  longer.  The  intermediate  part  of  the  fissure  is  filled  up  by  the 
great  transverse  band  of  white  matter,  the  corpus  callosum.  In  the  fissure  between 
the  two  frontal  lobes  the  anterior  cerebral  arteries  ascend  on  the  corpus  callosum. 

The  Corpus  Callosum. — The  corpus  callosum,  the  transverse  commissure  which 
joins  the  two  cerebral  hemispheres,  is  described  on  p.  886.  It  terminates  at  the 
base  of  the  brain  by  a  concave  margin,  which  is  connected  with  the  tu})er  cinereum 
through  the  intervention  of  a  thin  layer  of  gray  substance,  the  lamina  cinerea.  This 
may  be  exposed  by  gently  raising  and  drawing  back  the  optic  commissure.  A 
white  band  may  be  observed  on  each  side,  passing  backward  from  the  under  sur- 
face of  the  corpus  callosum,  across  the  posterior  margin  of  the  anterior  perforated 
space  to  the  hippocampal  gyrus,  where  it  meets  the  corres}X)nding  outer  root 
of  the  olfactory  tract;  this  band  is  called  the  peduncle  of  the  corpus  callosum  or  the 
gyrus  subcallosus  (pedunculus  corporis  callosi).  The  band  may  be  traced  upward 
around  the  genu  to  become  continuous  with  the  striae  longitudinales  on  its  upper 
surface.  Laterally,  this  portion  of  the  corpus  callosum  extends  into  the  frontal 
lobe. 

The  Lamina  Cinerea. — The  lamina  cinerea  is  a  thin  layer  of  gray  substance, 
extending  upward  in  the  anterior  portion  of  the  great  longitudinal  fissure  from  the 
optic  commissure  to  join  the  rostrum  of  the  corpus  callosum.  It  is  continuous  on 
each  side  with  the  gray  matter  of  the  anterior  perforated  space,  and  forms  the 
anterior  part  of  the  inferior  boundary  of  the  third  ventricle.  The  portion  of  the 
lamina  cinerea  which  is  turned  upward  is  called  the  lamina  terminalis. 

The  Optic  Commissure  or  Optic  Chiasma  (chiasmaopticum) . — The  optic  commissure 
is  situated  in  the  middle  line,  immediately  in  front  of  the  tuber  cinereum  and  below 
the  lamina  cinerea;  that  is  to  say,  the  commissure  is  superficial  to  the  lamina  in 
the  order  of  dissection  when  the  base  is  uppermost.  It  is  the  point  of  junction 
between  the  two  optic  tracts,  and  will  be  described  with  the  cranial  nerves.  Imme- 
diately behind  the  diverging  optic  tracts,  and  between  them  and  the  pedimcles 
of  the  cerebrum  (crura  cerebri  or  pedunculi  cerebri),  is  a  lozenge-shaped  interval, 
the  interpeduncular  space  {fossa  interpeduncularis  [Tarini]).  The  posterior  recess 
(recessus  posterior)  of  this  space  passes  for  a  little  way  underneath  the  anterior 
margin  of  the  pons;  the  anterior  recess  (recessus  anterior)  passes  between  the 
corpora  albicantia.  The  floor  of  the  interpeduncular  space  is  the  substantia 
perforata  posterior,  and  in  the  space  are  found  the  following  parts:  the  tuber 
cinereum,  infundibulum,  pituitary  body,  corpora  albicantia,  and  the  posterior 
perforated  space. 

The  Tuber  Cinereum. — The  tuber  cinereum  is  an  eminence  of  gray  matter, 
situated  between  the  optic  tracts,  and  extending  from  the  corpora  albicantia  to  the 
optic  commissure,  to  which  it  is  attached;  it  is  connected  with  the  surrounding 
parts  of  the  cerebrum,  forms  part  of  the  floor  of  the  third  ventricle,  and  is  con- 
tinuous with  the  gray  substance  in  that  cavity.  From  the  middle  of  its  under  sur- 
face a  conical  tubular  process  of  gray  matter,  about  two  lines  in  length,  is  con- 
tinued downward  and  forward  to  be  attached  to  the  posterior  lobe  of  the  pituitary 
body.  This  is  the  infundibulum,  and  its  canal,  which  is  funnel-shaped,  com- 
municates with  the  third  ventricle. 

The  Pituitary  Body  (hypophijsis  cerebri). — The  pituitary  body  is  a  small,  reddish- 
gray,  vascular  mass,  weighing  from  five  to  ten  grains,  and  of  an  oval  form,  situated 
in  the  sella  turcica,  where  it  is  retained  by  a  process  of  dura  mater,  named  the 
diaphragma  sellae  (Fig.  544).    This  process  of  the  dura  covers  in  the  sella  turcica, 


THE    HEMISPHEBES    OF    THE    CEREBRUM  883 

and  has  a  small  hole  in  its  centre  through  which  the  infundibulum  passes,  the 
foramen  diaphragmatis  sellae  (Fig.  544). 

Structure. — The  pituitary  body  is  very  vascular,  and  consists  of  two  lobes, 
separated  from  one  another  by  a  fibrous  lamina.  Of  these,  the  anterior  and  the 
larger  is  of  an  oblong  form,  and  somewhat  concave  behind,  where  it  receives 
the  posterior  lobe,  which  is  round.  The  two  lobes  differ  both  in  development 
and  structure.  The  anterior  lobe,  of  a  dark,  reddish-brown  color,  is  developed 
from  the  epiblast  of  the  buccal  cavity,  and  resembles  to  a  considerable  extent,  in 
microscopic  structure,  the  thyroid  body.  It  consists  of  a  number  of  isolated 
vesicles  and  slightly  convoluted  tubules,  lined  by  epithelium  and  united  together 
by  a  very  vascular  connective  tissue.  The  epithelium  is  columnar  and  occasion- 
ally ciliated.  The  alveoli  sometimes  contain  a  colloid  material,  similar  to  that 
found  in  the  thyroid  body,  and  their  walls  are  surrounded  by  a  close  network  of 
lymphatic  and  capillary  blood-vessels.  The  posterior  lobe  is  developed  as  an 
outgrowth  from  the  embryonic  brain,  and  during  foetal  life  contains  a  cavity 
which  communicates  through  the  infundibulum  with  the  cavity  of  the  third 
ventricle.  In  the  adult  it  becomes  firmer  and  more  solid,  and  consists  of  a 
sponge-like  connective  tissue  arranged  in  the  form  of  reticulating  bundles, 
between  which  are  branched  cells,  some  of  them  containing  pigment.  In  the 
lower  animals  the  two  lobes  are  quite  distinct,  and  it  is  only  in  the  mammalia 
that  they  become  fused  together.  The  pituitary  body  is  believed  to  be  a  ductless 
gland,  which  furnishes  an  internal  secretion.  In  many  cases  of  acromegaly  the 
gland  is  enlarged  or  otherwise  diseased. 

The  Corpora  Albicantia  or  Corpora  Mamillaria. — The  corpora  albicantia  or  mam- 
illaria  are  two  small,  round,  white  masses,  each  about  the  size  of  a  pea,  placed 
side  by  side  immediately  behind  the  tuber  cinereum,  and  connected  with  each 
other  across  the  mesial  plane.  They  are  mainly  formed  by  the  anterior  crura  or 
pillars  of  the  fornix,  which,  after  descending  to  the  base  of  the  brain,  are 
twisted  upon  themselves  to  form  loops,  and  constitute  the  white  covering  of  the 
corpora  albicantia.  A  second  fasciculus,  the  bundle  of  Vicq  d'Az3n:  (fasciculus 
ihalamomamillaris)  (Figs.  574  and  586),  converges  from  the  optic  thalamus,  and 
enters  the  anterior  part  of  each  body  on  its  dorso-mesial  surface.  The  corpora 
albicantia  are  composed  externally  of  white  substance,  and  internally  of  gray 
matter;  the  nerve-cells  of  the  gray  matter  are  arranged  in  two  sets,  inner  and 
outer,  the  cells  of  the  former  set  being  the  smaller.  Each  corpus  is  connected 
to  the  tegmentum  by  a  small  bundle  of  fibres,  the  peduncle  of  the  mamillary 
body  (pedunculus  corporis  mamillaris  (Fig.  586).'  At  an  early  period  of  foetal 
life  the  corpora  albicantia  are  blended  together  into  one  large  mass,  but  become 
separated  about  the  seventh  nionth.  In  most  vertebrates  there  is  only  one  median 
corpus  albicans. 

The  Posterior  Perforated  Space  or  Lamina  or  the  Pons  Tarini  (locu^  perforatum 
posticus,  substantia  perforata  posterior). — The  posterior  perforated  space  cor- 
responds to  a  whitish-gray  fossa  placed  between  the  corpora  albicantia  in  front, 
the  pons  Varolii  behind,  and  the  crus  cerebri  on  either  side.  It  is  in  reality  a 
visible  portion  of  the  substantia  nigra  and  forms  the  floor  of  the  interpeduncular 
fossa.  It  forms  the  posterior  part  of  the  floor  of  the  third  ventricle,  and  is  per- 
forated by  numerous  small  orifices  for  the  passage  of  the  postero-median  ganglionic 
branches  of  the  posterior  cerebral  and  posterior  communicating  arteries.  Slender 
white  bands  are  observed  in  some  subjects  coming  from  the  gray  matter  of  the 
posterior  perforated  space,  passing  around  the  crura  cerebri,  and  entering  into  the 
pons  Varolii.    The  bands  bear  the  name  of  the  taenia  pontis. 

The  Pons  Varolii  (p.  922). — The  pons  Varolii  is  situated  immediately  behind  the 
two  crura  of  the  cerebrum.  It  consists  of  a  broad  band  of  white  fibres,  which  pass 
transversely  from  one  cerebellar  hemisphere  to  the  other;  the  band  becoming 


884 


THE   NERVOUS    SYSTEM 


narrower  as  it  enters  the  cerebellum.  In  the  middle  line  on  its  under  surface  a 
narrow  groove  runs  from  before  backward  and  accommodates  the  basilar  aitery. 

The  Medulla  Oblongata,  Medulla  Spinalis  or  Bulb  (p.  938). — The  medulla  oblongata 
emerges  from  the  posterior  border  of  the  pons  Varolii;  it  is  pyramidal  in  form,  and 
is  continuous  below  with  the  cervical  portion  of  the  spinal  cord.  It  is  marked  on 
its  ventral  surface  by  a  median  fissure,  continuous  below  with  the  anterior  median 
fissure  of  the  cord,  and  on  either  side  by  secondary  fissures  and  columns,  which 
will  be  described  in  the  sequel. 

The  Frontal  Lobe. — The  under  surface  of  the  frontal  lobe,  sometimes  named 
the  orbital  lobe,  is  seen  on  the  anterior  part  of  the  base  of  the  brain  on  either  side 
of  the  median  line.    It  has  already  been  described  (p.  874). 

The  Olfactory  Lobe   (p.  880). 

The  Anterior  Perforated  Space  (p.  881). 

The  Fissure  of  Sylvius  (fissura  lateralis  cerebri). — The  fissure  of  Sylvius  at  the 
base  of  the  brain  separates  the  frontal  from  the  temporal  lobe,  and  lodges  the 
middle  cerebral  artery.    It  has  also  been  described  (p.  866). 


Fig.  671. — Section  of  the  brain.     Made  on  a  level  with  the  corpus  callosum. 


The  Optic  Tracts. — The  optic  tracts  are  well-marked,  flattened  bands  of  fibres, 
which  run  obliquely  across  the  crus  cerebri  on  either  side,  and  unite  anteriorly  to 
form  the  optic  commissure.  They  will  be  described  in  connection  with  the  cranial 
nerves. 

The  Crura  Cerebri  or  the  Peduncles  of  the  Cerebrum  (pedunculi  cerebri)  (p.  906). — 
The  crura  cerebri  are  two  thick  cylindrical  bundles  of  white  matter,  which  appear 


1 


THE   HEMISPHERES    OF    THE    CEREBRUM  8S5 

in  front  of  the  anterior  border  of  the  pons,  and  diverge  as  they  pass  forv/ard  and 
outward  to  enter  the  under  surface  of  each  hemisphere.  They  compose  the  chief 
portion  of  the  mesencephalon.  Each  crus  is  about  three-quarters  of  an  inch  in 
length,  and  is  about  the  same  in  breadth  anteriorly,  but  somewhat  less  posteriorly. 
They  are  marked  upon  their  surface  with  longitudinal  striae,  and  each  is  crossed, 
just  before  entering  the  hemisphere,  by  the  fourth  nerve  and  the  optic  tract,  the 
latter  of  which  is  adherent  by  its  upper  surface  to  the  peduncle.  Each  crus  is 
composed  of  two  parts,  a  superior  or  dorsal  part,  and  an  inferior,  ventral,  or  pedal  part. 
The  dorsal  part  is  known  as  the  tegmentum  of  the  crus  cerebri  {tegmentum) ,  the  fibres 
(p.  90S)  of  which  pass  up  into  the  region  beneath  the  optic  thalamus,  a  region  known 
as  the  subthalamic  tegmental  region.  The  ventral  portion  is  known  as  the  crusta 
(basis  pedunculi),  the  fibres  of  which  (p.  907)  pass  up  external  to  the  optic  thala- 
mus and  into  the  internal  capsule.  On  the  surface  of  the  crus  are  two  grooves 
which  mark  the  separation  between  the  tegmentum  and  the  crusta.  One  groove 
is  on  the  inner  (mesial)  surface;  it  is  called  the  sulcus  nervi  oculo-motorii,  and 
from  it  comes  the  third  or  motor  oculi  nerve.  The  other  groove  on  the  outer 
(lateral)  surface  is  called  the  sulcus  lateralis  mesencephali.  It  passes  down  into  the 
interval  between  the  superior  and  middle  cerebellar  peduncles.  From  the  outer 
surface  of  the  tegmentum  some  slender  fibres,  called  the  lateral  fillet  (lemniscus 
lateralis) ,  pass  to  the  inferior  quadrigeminal  body.  If  a  transverse  section  of  the 
crus  is  made,  the  substantia  nigra  is  seen  between  the  tegmentum  and  the  crusta. 
It  is  a  band  of  pigmented  gray  matter  which  begins  somewhat  below  the 
upper  margin  of  the  pons  and  ascends  into  the  subthalamic  area. 

The  Temporal  Lobe  (Fig.  878). — The  under  surface  of  the  temporal  lobe  is 
visil)le  at  the  base  of  the  brain,  on  either  side  of  the  crura  and  the  structures  con- 
tained in  the  interpeduncular  space.  It  is  separated  anteriorly  from  the  frontal 
lobe  by  the  fissure  of  Sylvius,  and  behind  is  limited  by  the  anterior  border  of 
the  lateral  hemispheres  of  the  cerebellum.  The  fissures  and  lobes  on  its  surface 
have  already  been  described  (p.  877). 

The  Hemispheres  of  the  Cerebellum  (hemisphaeria  cerehelli)  (p.  929). — The 
hemispheres  of  the  cerebellum  are  situated  on  either  side  of  the  middle  line, 
and  cover  the  occipital  lobes  of  the  cerebrum,  when  viewed  from  the  base. 
The  cerebellum  differs  much  in  appearance  from  the  rest  of  the  encephalon, 
being  of  a  darker  color,  while  its  convolutions  are  smaller  and  narrower,  are 
arranged  like  the  leaves  of  a  book,  and  hence  are  called  folia. 

General  Arrangement  of  the  Parts  Composing  the  Cerebrum. — Each  hemi- 
sphere, as  already  stated,  consists  of  a  central  cavity,  the  lateral  ventricle,  surrounded 
by  thick  and  convoluted  walls  of  nervous  tissue. 

Interior  of  the  Cerebrum. — If  the  upper  part  of  either  hemisphere  is  removed 
with  a  knife,  about  half  an  inch  above  the  level  of  the  corpus  callosum,  its  internal 
white  matter  will  be  exposed.  It  is  an  oval-shaped  centre,  of  white  substance, 
surrounded  on  all  sides  by  a  narrow  convoluted  margin  of  gray  matter,  which 
presents  an  equal  thickness  in  nearly  every  part.  This  white  central  mass  has 
been  called  the  centrum  ovale  minus.  Its  surface  is  studded  with  numerous  minute 
red  dots  (puncta  vasculosa),  produced  by  the  escape  of  blood  from  divided  blood- 
vessels. In  inflammation  or  great  congestion  of  the  brain  these  are  very  numerous 
and  of  a  dark  color.  If  the  remaining  portion  of  one  hemisphere  is  slightly  sepa- 
rated from  the  other,  a  broad  band  of  white  substance  will  be  observed,  connect- 
ing them  at  the  bottom  of  the  longitudinal  fissure;  this  is  the  corpus  callosum.  The 
margins  of  the  hemispheres  which  overlap  this  portion  of  the  brain  are  called  the 
labii  cerebri.  Each  labium  is  part  of  the  callosal  convolution  already  described; 
and  the  space  between  it  and  the  upper  surface  of  the  corpus  callosum  is  termed 
the  callosal  sulcus  (sulcus  corporis  callosi)  (Figs.  562  and  567).  The  hemispheres 
should  now  be  sliced  off  to  a  level  with  the  upper  surface  of  the  corpus  callosum, 


886 


THE   NERVOUS   SYSTEM 


when  the  white  substance  of  that  structure  will  be  seen  connecting  the  two 
hemispheres.  The  large  expanse  of  medullary  matter  now  exposed,  surrounded 
by  the  convoluted  margin  of  gray  substance,  is  called  the  centrum  ovale  majus 
of  Vieussens  (Fig.  571). 

The  Corpus  Callosum  (Figs.  571,  574,  and  586). — The  corpus  callosum  is  a  thick 
stratum  of  transversely  directed  nerve-fibres,  by  which  probably  almost  every 
part  of  one  hemisphere  is  connected  with  the  corresponding  part  of  the  other  hemi- 
sphere (Figs.  572  and  573).  It  connects  not  only  corresponding  but  also  non- 
corresponding  portions  of  the  cortices.  The  fibres  of  this  body,  when  they  pass 
from  it  into  the  hemispheres  radiate  in  various  directions  (radiatio  corporis  callosi) 
between  the  fibres  of  the  corona  radiata,  to  terminate  in  the  gray  matter  of  the 
periphery.  According  to  Cajal  the  termination  is  in  the  layer  of  small  pyramidal 
cells  of  the  cortex.  The  corpus  callosum  thus  connects  the  two  hemispheres  of 
the  brain,  forming  their  great  transverse  commissure,  and  at  the  same  time  roofs 
in  the  lateral  ventricles  (Fig.  575).    The  best  conception  of  its  size  and  form  is 


Fig.  572. — Diagram  of  coronal  section  of  cerebrum  to 
show  course  of  fibres  of  callosum.    (Testut.") 


Fig.  573. — Diagram  of  lioiizoutal  section  of  cerehnim 
to  show  course  of  fibres  of  callosum.     (Testut . ) 


obtained  by  making  an  anterior  posterior  vertical  section  through  the  centre  of 
the  brain  (Figs.  574  and  586) .  It  is  then  seen  to  be  a  long,  thick,  irregularly 
flattened  arch,  body  of  the  corpus  callosum  {truncus  corporis  callosi);  in  front  taking 
a  sharp  bend,  the  genu  {genu  corporis  callosi)  (Fig.  577) ,  and  dipping  downward 
and  backward  to  the  base  of  the  brain  by  a  reflected  portion,  the  beak  or  rostrum 
{rostrum  corporis  callosi),  which  is  connected  with  the  lamina  cinerea;  behind  it 
terminates  by  a  rounded  end,  which  is  folded  over  and  is  named  the  splenium 
{splenium  corporis  callosi)  (Fig.  577) .  The  corpus  callosum  is  about  four  inches 
in  length,  and  extends  to  within  an  inch  and  a  half  of  the  anterior  and  two 
inches  and  a  half  of  the  posterior  extremity  of  the  cerebrum.  It  is  somewhat 
broader  behind  than  in  front,  and  is  thicker  at  either  end  than  in  its  central 
part.  The  reflected  anterior  portion  of  the  corpus  callosum  is  called  the  beak 
or  rostrum;  it  becomes  gradually  thinner  as  it  descends,  and  is  attached  by 
its  lateral  margins  to  the  frontal  lobes.  At  its  termination,  in  addition  to 
joining  the  lamina  cinerea,  the  corpus  callosum  gives  off  on  each  side  a  band 
of  white  substance,  the  peduncle  of  the  corpus  callosum  {gyrus  suhcallosus  or 
pedunculus  corporis  callosi),  already  described  fp.  882). 

Posteriorly,  the  corpus  callosum  forms  a  thick  rounded  fold,  called  the  pad  or 
splenium,  which  is  free  for  a  little  distance  as  it  curves  forward,  and  is  then  con- 
tinuous by  its  under  surface  with  the  fornix.  The  splenium  overlaps  the  mesen- 
cephalon, but  is  separated  from  it  by  the  pia  mater,  which  is  prolonged  forward  to 


THE    HEMISPHERES    GF    THE    CEREBRUM 


887 


form  the  velum  interpositum  (Fig.  548) .  On  the  upper  surface  of  the  corpus  cal- 
losum  the  structure  is  very  apparent,  the  fibres  being  collected  into  coarse  transverse 
bundles  (Fig.  571).  Along  the  middle  line  is  a  longitudinal  depression,  the  so-caMed 
raphe,  bounded  laterally  on  each  side  by  two  or  more  slightly  elevated  longitudinal 
bands  (Fig.  571).  The  internal  band  on  each  side  is  called  the  stria  longitudinalis 
medialis  or  nerve  of  Lancisi.  The  external  band  is  the  stria  longitudinalis  lateralis  or 
taenia  tectae.  The  external  band  is  beneath  the  convolution  of  the  corpus  callosum. 
There  is  an  attenuated  sheet  of  gray  matter  with  the  external  and  internal  striae,  and 
it,  with  the  striae,  constitutes  the  so-called  gyms  supra-callosus  (pp.  882  and  886). 
On  each  side  of  the  middle  line  the  under  surface  of  the  corpus  callosum  forms  the 
roof  of  the  lateral  ventricle,  while  in  the  mesial  plane  it  is  continuous  behind  with 
the  fornix,  being  separated  from  it  in  front  by  the  septum  lucidum,  which  forms 


Fig.  574. — Vertical  median  section  of  the  encephalon.  showing  the  parts  of  the  middle  line. 


1.  Convolution  of  the  corpus  callosum.  Above  it  is 
the  calloso-marginal  fi.ssure. 

2.  Fissure  of  Rolando. 

3.  The  parieto-occipital  fissure. 

4.  4,  point  to  the  calcarine  fissure,  which  is  just 
above  the  numbers.  Between  2  and  3  are  the  convo- 
lutions of  the  quadrate  lobe.  Between  3  and  4  is  the 
cuneate  lobe. 

5.  The  corpus  callosum. 

6.  The  septum  lucidum. 

7.  The  fornix. 

8.  Anterior  crus  of  the  fornix,  descending  to  the 
base  of  the  brain,  and  turning  on  itself  to  form  the 
corpus  albicans.  The  bundle  of  Vicq  d'Azyr  is  indi- 
cated by  a  dotted  line. 


9.  The  optic  thalamus.  Behind  the  anterior  crus  of 
the  fornix  a  shaded  part  indicates  the  foramen  of 
Monro;  in  front  of  the  number  an  oval  mark  shows 
the  position  of  the  gray  or  middle  commissure. 

10.  The  velum  interpositum. 

11.  The  pineal  gland. 

12.  The  corpora  quadrigemina. 

13.  The  crus  cerebri. 

14.  The  valve  of  Vieussens  (to  right  of  the  number). 

15.  The  pons  Varolii. 

16.  The  third  nerve. 

17.  The  pituitary  body. 

18.  The  optic  nerve. 

19  points  to  the  anterior  commissure,  indicated  by 
the  oval  outline  behind  the  number. 


a  vertical  partition  between  the  two  ventricles  (Figs.  574  and  586).  On  each 
side  the  fibres  of  the  corpus  callosum  extend  into  the  substance  of  the  hemispheres, 
connecting  them  together.  The  greater  thickness  of  the  two  extremities  of  this 
commissure  is  explained  by  the  fact  that  the  fibres  from  the  anterior  and  posterior 
parts  of  each  hemisphere  cannot  pass  directly  across,  but  have  to  take  a  curved 
direction.  The  part  of  the  corpus  callosum  which  curves  forward  on  each  side 
from  the  genu  into  the  frontal  lobe  and  covers  the  front  part  of  the  anterior  cornu 
of  the  lateral  ventricle  is  called  the  forceps  anterior  or  forceps  minor.  The  part  which 


THE  NERVOUS  SYSTEM 

curves  backward  from  each  side  of  the  splenium  into  the  occipital  lobe  is  known 
as  the  forceps  posterior  or  forceps  major.  Between  these  two  parts  on  each  side  is 
a  collection  of  fibres,  which  cover  in  the  body  of  the  lateral  ventricle.  These 
constitute  the  tapetum  or  mat.  The  tapetum  helps  to  form  the  roof  and  outer  wall 
of  the  posterior  horn  of  the  lateral  ventricle  and  the  outer  wall  of  the  posterior 
portion  of  the  descending  horn  of  the  ventricle.  These  fibres  were  formerly 
regarded  as  fibres  of  the  callosum,  but  in  reality  are  the  fibres  of  the  fasciculus 
occipito-frontalis  which  diverge  posteriorly.  The  corpus  callosum  contains  a  few 
projection  fibres,  but  is  chiefly  composed  of  association  fibres  and  branches 
from  both  association  and  projection  fibres. 

An  incision  should  now  be  made  through  the  corpus  callosum,  on  either  side  of  the  raph^, 
when  two  large  irregular  cavities  will  be  exposed,  which  extend  through  a  great  part  of  the 
length  of  each  hemisphere.     These  are  the  lateral  ventricles. 

The  Lateral  Ventricle  (ventriculus  lateralis)  (Fig,  575). — The  lateral  ventricle  is  an 
irregular  cavity  situated  in  the  lower  and  inner  parts  of  the  cerebral  hemisphere. 


Fig.  575. — The  lateral  ventricles  of  the  brain. 

There  are  two  lateral  ventricles,  one  being  placed  on  either  side  of  the  middle  fine. 
They  are  separated  from  each  other  by  a  mesial  vertical  partition,  the  septum  lucidum 
(Figs.  574  and  586),  but  communicate  with  the  third  ventricle  and  indirectly  with 
each  other  through  the  foramen  of  Monro  (Figs.  548,  574,  and  575) .  They  are  lined 
by  a  thin,  diaphanous  membrane,  the  ependyma,  which  is  neuroglia  covered  by 
ciliated  epithelium.  The  layer  of  neuroglia  is  absent  over  the  optic  thalamus  and 
the  choroid  plexus.     The  lateral  ventricles  communicate  with  each  other  and  with 


THE  HEMISPHEBES    OF    THE    CEREBRUM  889 

the  third  ventricle,  and  are  moistened  by  the  cerebro-spinal  fluid,  which,  even  in 
health,  may  be  secreted  in  considerable  amount.  Each  lateral  ventricle  consists  of 
a  central  cavity  or  body  and  three  prolongations  from  it,  termed  comua.  The 
anterior  ^:ovn\l  cnvxes,  forward  and  outward  into  the  frontal  lobe;  the  posterior 
backward  and  inward  into  the  occipital  lobe;  and  the  middle  descends  into  the 
temporal  lobe. 

The  Septum  Lucidum  (septum  pellucidum)  (Figs.  574,  586,  and  587)  is  composed 
of  two  thin,  vertical  laminae,  which  lie  in  the  median  line  with  their  mesial  sur- 
faces almost  in  contact.  These  sheets  are  triangular  and  can  be  separated,  and 
the  cavity  thus  shown  is  called  the  fifth  ventricle  (cavum  septi  pellucidi)  (Fig.  575). 
It  contains  a  little  fluid,  but  does  not  communicate  with  the  general  ventricular 
cavity.  Each  lamina  of  the  septum  lucidum  bears  the  name  of  the  lamina  septi 
pellucidi.  The  front  part  of  the  septum  lucidum  lies  behind  the  genu  of  the  corpus 
callosum,  and  below  it  passes  toward  the  base  of  the  brain  between  the  fornix  and 
the  posterior  margin  of  the  rostrum,  to  terminate  in  the  subcallosal  gyrus.  Pos- 
teriorly, the  septum  lucidum  passes  back  between  the  fornix  and  the  body  of  the 
corpus  callosum,  being  attached  to  each  structure. 

The  Central  Cavity  or  Body  of  the  lateral  ventricle  (ventriculus  lateralis  [pars 
centralis])  (Fig.  575)  is  situated  in  the  lower  part  of  the  parietal  lobe.  It  is  an 
irregularly  curved  cavity,  triangular  in  shape  on  transverse  section,  and  presents 
a  roof,  a  floor,  an  inner  wall,  and  an  outer  wall.  Its  roof  is  formed  by  the  under 
surface  of  the  corpus  callosum;  its  mesial  wall  is  the  septum  lucidum,  which  sepa- 
rates it  from  the  opposite  ventricle  and  connects  the  under  surface  of  the  corpus 
callosum  with  the  fornix;  its  external  wall  is  the  internal  capsule;  its  floor  is  formed 
by  the  following  parts,  enumerated  in  their  order  of  position,  from  before  back- 
ward ;  the  caudate  nucleus  of  the  corpus  striatum,  taenia  semicircularis,  the  epithe- 
lial covered  optic  thalamus,  the  epithelial  covered  choroid  plexus,  the  superior 
surface  of  the  body  of  the  fornix  and  part  of  its  posterior  pillar. 

The  Anterior  Comu  or  Frontal  Horn  (cornu  anterius)  (Fig.  575)  passes  forward  and 
outward,  with  a  slight  inclination  downward,  from  the  foramen  of  Monro  into  the 
frontal  lobe,  curving  round  the  anterior  extremity  of  the  caudate  nucleus.  Its  roof 
is  the  forceps  minor  of  the  corpus  callosum,  and  its  floor  the  upper  surface  of 
the  reflected  portion  of  the  corpus  callosum,  the  rostrum.  It  is  bounded  mesially 
by  the  anterior  portion  of  the  septum  lucidum,  and  externally  by  the  head  of 
the  caudate  nucleus  of  the  corpus  striatum.  Its  apex  reaches  the  posterior  surface 
of  the  genu  of  the  corpus  callosum. 

The  Foramen  of  Monro  (foramen  interventriculare)  (Figs.  548,  574,  575,  and  587) 
extends  from  the  anterior  and  superior  extremity  of  the  third  ventricle  and  the  point 
of  junction  of  the  anterior  horn  with  the  central  cavity  of  the  lateral  ventricle.  It 
lies  between  the  anterior  pillar  of  the  fornix  and  the  anterior  margin  of  the  optic 
thalamus    This  foramen  connects  the  third  ventricle  with  the  two  lateral  ventricles. 

The  Posterior  Comu  or  Occipital  Horn  (cornu  posterius)  (Fig.  575)  curves  backward 
into  the  substance  of  the  occipital  lobe,  its  direction  being  backward  and  outward, 
and  then  inward ;  itsconcavity  is  therefore  directed  inward.  Its  roof  is  formed  by  the 
tapetum  of  the  corpus  callosum  passing  to  the  temporal  and  occipital  lobes,  which 
also  helps  to  bound  this  horn  externally.  On  its  mesial  wall  is  seen  a  longitudinal 
eminence,  which  is  in  an  involution  of  the  ventricular  wall  produced  by  the 
calcarine  sulcus;  this  is  called  the  hippocampus  minor  (calcaravis).  Just  above  this 
the  forceps  major  of  the  splenium,  sweeping  around  to  enter  the  occipital  lobe, 
causes  another  projection,  which  is  known  as  the  bulb  of  the  posterior  horn  (bulbus 
cornu  posterius).  The  hippocampus  minor  and  bulb  of  the  posterior  horn  are 
extremely  variable  in  their  degree  of  development,  being  in  some  cases  ill  defined, 
while  in  others  they  are  unusually  prominent.  The  balance  of  the  posterior  horn 
is  bounded  by  the  white  substance  of  the  occipital  lobe. 


890 


THE   NERVOUS  SYSTEM 


Between  the  middle  and  posterior  cornu  is  a  triangular  area,  called  the  txigonum 
ventriculi  (see  Descending  Horn). 

The  Middle  or  Descending  Cornu  or  Temporal  Horn  {cornu  injerius)  (Figs.  575,  581, 
and  583),  the  largest  of  the  three  traverses  the  temporal  lobe  of  the  brain,  forming  in 
its  course  a  remarkable  curve  around  the  back  of  the  optic  thalamus.  It  passes  at 
first  backward,  outward,  and  downward,  and  then  curves  around  the  crus  cerebri, 
forward  and  inward,  to  within  an  inch  of  the  apex  of  the  temporal  lobe,  its  direction 
being  fairly  well  indicated  on  the  surface  of  the  brain  by  that  of  the  parallel  sulcus. 
Its  antero-extemal  boundary  or  roof  is  formed  by  the  under  surface  of  the  tapetum  of 
the  corpus  callosum,  the  pulvinar  of  the  optic  thalamus,  and  the  inferior  layer  of  the 
internal  capsule.  The  tail  of  the  nucleus  caudatus  of  the  corpus  striatum  and  the 
taenia  semicircularis  are  also  prolonged  into  it,  and  extend  forward  in  the  roof  of 
the  descending  horn  to  its  extremity,  where  they  end  in  a  mass  of  gray  matter,  the 
amygdaloid  nucleus  {nucleus  amygdalae);  this  nucleus  is  merely  a  localized  thick- 
ening of  the  adjacent  gray  cortex.  The  posterior  boundary  or  floor  of  the  lateral 
ventricle  presents  for  examination  the  following  parts:  the  hippocampus  major 
{hippocampus),  pes  hippocampi  (digitationes  hippocampi),  eminentia  collateralis 
or  pes  accessorius,  corpus  fimbriatum  (fimbria  hippocampi),  prolonged  from  the 
posterior  pillar  of  the  fornix,  and  the  choroid  plexus.  Along  the  medial  aspect  of 
the  descending  cornu  there  is  a  cleft-like  opening,  the  choroid  fissure,  which  is 

the  lower  part  of  the  trans- 
verse fissure,  through  which 
the  choroid  plexus  of  the  pi  a 
mater  is  invaginated  into  the 
ventricle,  but  covered  by  the 
epithelium  of  the  ependyma, 
which  is  pushed  in  before  it. 
Upon  the  inner  wall  are  also 
noted  the  epithelial  covering, 
the  pulvinar,  and  the  dentate 
convolution  or  fascia  (fascia 
dentata  hippocampi)  (Figs.  562 
and  581) ,  which  is  the  irregu- 
lar and  free  cortical  margin. 

The  Corpus  Striatum  (Figs. 
575,576,  577,  580,  and  584), 
the  basal  ganglion  of  the  hemi- 
sphere, has  received  its  name 
from  the  striped  appearance 
which  its  section  presents, 
in  consequence  of  diverging 
white  fibres  being  mixed  with 
the  gray  matter  which  forms 
the  greater  part  of  its  sub- 
stance. It  is  situated  to  the 
front  and  to  the  outside  of  the 
optic  thalamus.  The  corpus 
striatum  measures  about  two 
inches  in  its  antero-posterior 
diameter  and  one  and  a  quarter  inches  transversely.^  The  larger  portion  of  this  body 
is  embedded  in  the  white  substance  of  the  hemisphere,  and  is  therefore  external 
to  the  ventricle.     It  is  termed  the  extra-ventricular  portion  or  the  lenticular  nucleus 


CLAUS 
TRUM 


ANTERIOR    PILLARS 
OF    FORNIX 


POSTERIOR    PILLAR 
OF   FORNIX 


Fig.  576. — Horizontal  section  of  Icn   iicniisphere  through  the  basal 
ganglia,  viewed  from  above.     C.N.,  caudate  nucleus.      (Testut.) 


'  Anatomy  of  the  Brain  and  Spinal  Cord.     By  Harris  E.  Santee. 


THE   HEMISPHERES    OF    THE    CEREBRUM 


891 


(nucleus  lent  if  or  mis);  a  part,  however,  is  visible  in  the  ventricle  and  its  anterior 
cornu;  this  is  the  intra-ventriculax  portion  or  the  caudate  nucleus  (nucleus  caudatus). 
These  two  portions  are  separated  by  the  internal  capsule. 

The  caudate  nucleus  (nucleus  caudatus)  (P^igs.  576,  577, 579,  and  580)  is  a  pear- 
shaped,  highly  arched  mass  of  gray  matter;  its  broad  anterior  extremity,  the  bulb 
or  head  {caput  nuclei  caudati),  is  directed  forward  into  the  forepart  of  the  body 
and  anterior  cornu  of  the  lateral  ventricle;  its  narrow  posterior  end,  the  tail  or 
surcingle  [cauda  nuclei  caudati),  is  directed  outward  and  backward  on  the  floor 
of  the  body  of  the  lateral  ventricle  and  on  the  outer  side  of  the  optic  thalamus, 
from  which  structure  it  is  separated  by  the  taenia  semicircularis  (Fig.  577) ;  it 
is  continued  downward  into  the  descending  cornu  of  the  lateral  ventricle  and 


Fig.  577. — Middle  part  of  a  horizontal  section  through  the  cerebrum  at  the  level  of  the  dotted  line  in  the 
small  figure  in  one  hemisphere.      (From  Ellis,  after  Dalton.) 

is  continued  forward  in  the  roof  to  terminate  in  the  amygdaloid  nucleus,  a  collec- 
tion of  gray  matter  in  the  apex  of  the  temporal  lobe.  It  is  covered  by  the  lining 
of  the  ventricle,  and  crossed  by  some  veins  of  considerable  size.  It  is  separated 
from  the  extra-ventricular  portion,  in  the  greater  part  of  its  extent,  by  a  lamina 
of  white  matter  which  is  called  the  internal  capsule,  but  the  two  portions  of  the 
corpus  striatum  are  united  in  front. 

The  lenticular  nucleus  (nucleus  lentiformis)  (Figs.  576,  577,  579,  and  580)  is  a 
mass  of  gray  matter  which  lies  external  to  the  caudate  nucleus  and  the  thalamus, 
and  is  only  seen  in  sections  of  the  hemisphere.  The  laminae  of  the  internal  capsule 
separate  it  from  the  ventricle.  If  a  coronal  section  is  made  through  the  anterior 
portion  of  the  lenticular  nucleus,  it  is  seen  to  be  continuous  below  with  the  head  of 
the  caudate  nucleus  (Fig.  578) .     Above  strands  of  gray  matter  join  the  two  nuclei. 


892 


THE   NERVOUS  SYSTEM 


and  these  bands  pass  through  the  anterior  part  of  the  white  internal  capsule  and' 
give  it  a  striated  appearance;  hence  the  term  corpus  striatum,  which  is  applied  to 
the  mass  of  which  the  two  nuclei  are  parts.  When  divided  horizontally,  it  pre- 
sents, to  some  extent,  the  appearance  of  a  biconvex  lens,  while  a  vertical  trans- 
verse section  of  it  gives  a  somewhat  triangular  outline.  It  does  not  extend  as  far 
forward  or  backward  as  the  nucleus  caudatus.  It  is  bounded  externally  by  a 
lamina  of  white  matter  called  the  external  capsule  {capsula  externa)  (Figs.  576, 
577,  578,  and  579) ,  on  the  outer  surface  of  which  is  a  thin  layer  of  gray  matter 
termed  the  bulwark  or  claustrum  (Figs.  576,  577,  578,  and  579) .  The  claustrum 
presents  ridges  and  furrows  on  its  outer  surface,  corresponding  to  the  convolu- 
tions and  sulci  of  the  island  of  Reil,  from  which  it  is  separated  by  a  thin  white 
lamina  (Figs.  576,  577,  and  578). 

Upon  making  a  transverse  vertical  section  through  the  middle  of  the  lenticular 
nucleus,  it  is  seen  to  present  two  white  lines,  external  and  internal  medullary 
laminae  {laminae  medullare  externa  et  interna)  (Fig.  579) ,  parallel  with  its  lateral 
border,  which  divide  it  into  three  zones,  of  which  the  outer  and  largest  is  of  a 
reddish  color,  and  is  known  as  the  putamen,  while  the  two  inner  are  paler  and  of  a 
yellowish  tintj  and  constitute  the  globus  pallidus  (Figs.  578  and  579) .  All  three 
zones  are  marked  by  fine  radiating  white  fibres,  which  are  most  distinct  in  the 
putamen.  The  gray  matter  of  the  corpus  striatum  is  traversed  by  nerve-fibres, 
some  of  which  are  believed  to  originate  in  it.  The  cells  of  the  corpus  striatum 
are  multipolar,  both  large  and  small;  those  of  the  lenticular  nucleus  containing 
yellow  pigment. 

The  internal  capsule  (capsula  interna)  (Figs.  576,  577,  578,  579,  and  580)  is 
formed  by  fibres  of  the  crusta  of  the  crus  cerebri,  supplemented  by  fibres  derived 
from  the  corpus  striatum  and  optic  thalamus  on  each  side.  Sagittal  section  ex- 
hibits a  superior  lamina  and  an  inferior  lamina,  continuous  with  each  other  behind, 
but  separated  in  front  by  the  Sylvian  fissure.  The  inferior  lamina  is  thin  and 
its  fibres  terminate  in  the  parietal  and  temporal  lobes.  The  superior  lamina 
is  thick,  contains  most  of  the  crusta,  and  the  term  internal  capsule  as  usually 
employed  is  synonymous  with  it.  In  horizontal  section  (Figs.  576,  577,  578, 
and  579)  the  internal  capsule  is  seen  to  be  somewhat  abruptly  curved,  with  its 
convexity  inward;  the  prominence  of  the  curve  is  called  the  knee  or  genu  of  the 
internal  capsule  (genu  capsule  internal)  (Fig.  578) ,  and  projects  between  the  cau- 
date nucleus  and  the  optic  thalamus.  The  portion  in  front  of  the  genu  is  termed 
the  frontal  portion,  the  anterior  limb  or  the  lenticulo -striate  division  (pars  frontalis 
capsulae  internae),  and  separates  the  lenticular  from  the  caudate  nucleus;  the  por- 
tion behind  the  genu  is  the  occipital  portion,  the  posterior  limb  or  the  lenticulo -optic 
division  (pars  occipitalis  capsulae  internae),  and  separates  the  lenticular  nucleus 
from  the  optic  thalamus. 

Fibres  of  the  Internal  Capsule  (Figs.  578  and  579).  Inferior  Lamina. — The 
fibres  of  the  inferior  lamina  of  the  internal  capsule  pass  externally  under  the  len- 
ticular nucleus,  over  the  amygdala  and  descending  horn  of  the  lateral  ventricle, 
and  reach  the  parietal  lobe  and  the  temporal  lobe.  The  motor  fibres  constitute 
a  portion  of  the  motor  tempore -pontal  tract  which  extend  from  the  temporal  cortex 
to  the  nucleus  pontis.  The  sensory  fibres  consist  of  a  portion  of  the  acustic  radia- 
tion, which  passes  from  the  corpus  geniculata  interna  to  the  auditory  cortex  in  the 
temporal  lobe,  and  ansa  peduncularis,  a  tract  of  common  sensation  which  passes 
from  the  optic  thalamus  to  the  sensory  region  of  the  cortex.  Some  of  the  fibres 
of  the  median  fillet  join  the  ansa  peduncularis  and  pass  through  the  inferior  lamina. 

Superior  Lamina. — This  portion  is  often  spoken  of  as  though  it  were  the  entire 
internal  capsule.  It  contains  the  greater  part  of  the  crusta  and  enters  the 
corona  radiata.  The  pyramidal  tract  is  in  the  knee  of  the  internal  capsule.  Its 
fibres  come  from  the  cortical  region  about  the  central  sulcus  of  Rolando  and 


THE   HE3IISPHEIIES    OF    THE    CEREBRUM 


893 


pass  through  the  knee  of  the  internal  capsiile;  most  of  them,  by  way  of  the 
middle  of  the  crusta,  to  reach  the  spinal  cord  (p.  907) ;  some  of  them  end  in  the 
pons  and  medulla.  The  anterior  segment  of  the  superior  lamina  of  the  internal 
capsule  contains  motor  fibres  which  come  from  the  prefrontal  region  of  the 
cortex  and  pass  by  way  of  the  inner  one-fifth  of  the  crusta  to  the  nucleus  pontis 


B.  Kn. 


Hypoglossus 


r.  lie. 

Audifory 

tract 


Fig.  578. — Horizontal  section  through  the  right  hemisphere.  B.  kn,  knee  of  corpus  callosum;  Vh,  anterior 
horn  of  lateral  ventricle;  Fg,  inferior  part  of  third  frontal  convolution;  /.  stric,  lenticulo-striate  division  of  in- 
ternal capsule;  Knie.  ic,  knee  of  internal  capsule;  I.  optic,  lenticulo-optic  division  of  internal  capsule;  Th,  optic 
thalamus;  ./,  i.sland  of  Reil;  cl,  claustrum;  Operc,  operculum;  T\,  first  temporal  convolution;  r.  lie,  retrolenticular 
region  of  internal  capsule;  C.A.,  hippocampus  major;  cnlc,  calcarine  fissure;  Hh,  posterior  horn  of  lateral  ventricle; 
8S,  optic  radiation  of  Gratiolet;  T«,  second  temporal  convolution;  Facialis,  position  in  capsule  of  motor  tract 
to  the  face;  Hypofjlossus,  position  of  tract  to  the  tongue;  Arm,  position  of  tract  to  the  arm;  Bein,  position  of 
tract  to  the  leg;  iS.fi.,  sensory  fibres;  S,  visual  tract;  A,  auditory  tract.     (M.  Allen  Starr,  after  von  Monakow.) 

and  nuclei  of  cranial  nerves.  These  fibres  constitute  the  fronto-pontal  tract 
(tractus  cerebrocorticofrontalis  fontalis).  In  the  posterior  segment  of  the  supe- 
rior lamina  of  the  internal  capsule  is  a  part  of  the  tract  from  the  temporal 
cortex  to  the  nucleus  pontis  and  the  nuclei  of  cranial  motor  nerves,  the  balance 


894 


THE   NEBVOUS  SYSTEM 


of  which  tract  is  in  the  inferior  lamina.  This  path  occupies  the  outer  one-fifth 
of  the  crusta,  and  is  the  temporo-pontal  tract  (tractus  cerebrocorticopontalis  tem- 
poralis). 

The  sensory  fibres  include  common  sensory  fibres  and  fibres  of  special  sense. 
Fibres  of  common  sensation  exist  in  both  the  anterior  and  posterior  segments, 
and  these  fibres  pass  from  the  optic  thalamus  to  the  sensory  region  of  the  cortex, 
and  are  known  as  the  cortical  fillet.  The  fibres  of  special  sense  are  found  where 
the  superior  lamina  joins  the  inferior  lamina. 

The  optic  radiations  of  Gratiolet  (radiatio  occipitothalamica  [Grafioleti])  are  in 
the  portion  back  of  the  lenticular  nucleus,  and  pass  from  the  optic  thalamus 
and  corpus  geniculatum  externum  to  the  cuneus. 

The  auditory  radiations  (radiatio  temporothalamica)  are  also  back  of  the  len- 
ticular nucleus  and  pass  from  the  corpus  geniculatum  externum  to  the  temporal 
cortex. 

Numerous  fibres  of  the  internal  capsule  give  off  collaterals  which  reach  the 
opposite  hemisphere  by  way  of  the  corpus  callosum,  none  of  them  reaching  the 
cortex. 

Note. — The  above  description  of  the  fibres  of  the  internal  capsule  is  largely  taken  from 
the  Anatomy  of  the  Brain  and  Cord,  by  Harris  E.  Santee,  M.D. 

As  the  fibres  of  the  internal  capsule  ascend  to  reach  the  various  convolutions 
of  the  cerebral  hemisphere  they  spread  out  like  an  open  fan.  This  expansion 
is  the  corona  radiata.  The  constituent  parts  and  fibre-groups  of  the  internal 
capsule  are  shown  in  Figs.  578  and  579. 

The  external  capsule  (capsula  externa)  (Figs.  576,  577, 578  and  579)  is  a  lamina 
of  white  matter,  situated  on  the  outer  side  of  the  lenticular  nucleus,  between  it 

and  the  claustrum,  and  is  continuous 
with  the  internal  capsule  in  front 
of  and  behind  the  putamen.  It  is 
made  up  of  fibres  derived  partly  from 
the  anterior  white  commissure  (Fig. 
580)  and  partly  from  the  subthalamic 
region. 

The  Claustrum  (Figs.  576,  577,  578, 
and  579)  is  a  thin  layer  of  gray  mat- 
ter, situated  on  the  outer  surface  of 
the  external  capsu'le.  On  transverse 
section  it  is  seen  to  be  triangular, 
with  its  apex  directed  upward  and  its 
base  downward.  Its  inner  surface, 
which  is  contiguous  to  the  external 
capsule,  is  smooth,  but  its  outer  sur- 
face presents  ridges  and  furrows 
which  correspond  with  the  convolutions  and  sulci  of  the  island  of  Reil,  with 
which  it  is  in  close  relationship.  The  claustrum  is  regarded  as  a  detached  por- 
tion of  the  gray  matter  of  the  island  of  Reil,  from  which  it  is  separated  by  a 
layer  of  white  fibres,  the  band  of  Baillarger  (capsula  extrema)  (Figs.  576  and  577). 
The  cells  of  the  claustrum  are  small  and  spindle-shaped,  and  contain  yellow 
pigment ;  they  are  similar  to  those  found  in  the  deepest  layer  of  the  cortex. 

The  Taenia  Semicircularis  (stria  terminalis)  (Figs.  575,  577,  and  584)  is  a  narrow, 
whitish  band  of  medullary  substance,  situated  in  the  depression  between  the  cau- 
date nucleus  and  the  optic  thalamus.  Anteriorly  its  fibres  are  partly  continued  into 
the  anterior  pillar  of  the  fornix;  some,  however,  pass  over  the  anterior  commissure 
to  the  gray  matter  between  the  caudate  nucleus  and  septum  lucidum,  while 


Fio.  579. — Scheme  of  the  internal  capsule.     (Jakob.) 


THE   HEMISPHERES    OF    THE    CEREBRUM  895 

others  penetrate  the  caudate  nucleus.  Posteriorly  it  is  continued  into  the  roof  of  the 
middle  or  descending  horn  of  the  lateral  ventricle,  at  the  extremity  of  which  it  enters 
the  amygdaloid  nucleus,  an  oval  mass  of  gray  matter,  situated  in  the  roof  of  the 
lower  extremity  of  the  descending  horn.  Like  the  corpus  striatum,  it  is  formed 
by  a  localized  thickening  of  the  gray  matter  of  the  cortex  cerebri.  Superficial  to  it 
is  a  large  vein,  vena  corporis  striati,  which  receives  numerous  small  veins  from  the 
surface  of  the  corpus  striatum  and  optic  thalamus;  it  unites  with  the  choroid 
vein  to  form  the  vein  of  Galen  (p.  856).  On  the  surface  of  the  vein  of  the 
corpus  striatum  is  a  narrow  band  of  white  fibres,  named  the  lamina  cornea. 
The  remains  of  the  corpus  callosum  should  now  be  removed  in  order  to  ex{X)se  the  fornix. 

The  Fornix  (Figs.  574,  575,  576,  577,  580,  582,  583,  586,  and  587).— The  fornix 
is  a  longitudinal,  arch-shaped  lamella  of  white  matter,  situated  beneath  the 
corpus  callosum,  with  which  it  is  continuous  behind,  but  from  which  it  is  sep- 
arated in  front  by  the  septum  lucidum.  It  may  be  described  as  consisting  of 
two  symmetrical  halves,  one  for  either  hemisphere.  The  two  portions  are  not 
united  to  each  other  in  front  and  behind,  but  their  central  parts  are  joined  together 
in  the  middle  line.  The  two  anterior,  separated  parts  are  called  the  anterior 
pillars;  the  intermediate  united  portions  constitute  the  body  of  the  fornix;  and 
the  posterior  parts,  which  are  also  separated  from  each  other,  are  called  the 
posterior  pillars. 

The  Body  of  the  Fornix  (corpiis  Jomicis)  is  triangular,  narrow  in  front,  broad 
behind.  Its  upper  surface  is  connected,  in  the  median  line,  to  the  septum  lucidum 
in  front,  and  the  corpus  callosum  behind;  laterally  this  surface  forms  part  of  the 
floor  of  each  lateral  ventricle.  Its  under  surface  rests  upon  the  velum  interpositum, 
which  separates  it  from  the  third  ventricle  and  the  inner  portion  of  the  upper 
surface  of  the  optic  thalami.  Its  outer  edge,  on  each  side,  is  free,  and  is  connected 
with  the  choroid  plexuses. 

The  Anterior  Pillars  of  the  Fornix  (columnae  fornicis)  arch  downward  toward 
the  base  of  the  brain  and  are  separated  from  each  other  by  a  narrow  interval. 
They  are  composed  of  white  fibres,  which  descend  immediately  behind  the 
anterior  commissure,  where  each  anterior  pillar  passes  through  the  inner  part  of 
the  optic  thalamus  of  that  side.  At  the  base  of  the  brain  each  pillar  becomes 
twisted  upon  itself  to  form  a  loop,  somewhat  resembling  the  figure  8.  The  lowest 
part  of  the  loop  constitutes  the  white  matter  of  the  corresponding  corpus  albicans, 
from  which  the  fibres  can  apparently  be  traced  upward  and  backward,  as  the  bundle 
of  Vicq  d'Azyr,  into  the  substance  of  the  corresponding  optic  thalamus  (Figs.  574 
and  586).  It  must  be  stated,  however,  that  there  is  probably  no  direct  continuity 
between  this  bundle  and  the  anterior  pillar  of  the  fornix — the  latter  possibly  ending 
in  the  gray  matter  of  the  corpus  albicans.  The  anterior  pillars  of  the  fornix  are 
joined  in  their  course  by  the  peduncles  of  the  pineal  gland  and  the  superficial  fibres 
of  the  taenia  semicircularis,  and  receive  fibres  from  the  septum  lucidum.  Zucker- 
kandl  describes  an  olfactory  fasciculus,  which  becomes  detached  from  the  main 
portion  of  the  anterior  pillar  of  the  fornix,  and  passes  downward,  in  front  of  the 
anterior  commissure,  to  the  base  of  the  brain,  where  it  divides  into  two  bundles, 
one  joining  the  inner  root  of  the  olfactory  tract;  the  other,  the  peduncle  of  the 
corpus  callosum,  and  through  it  reaching  the  hippocampal  convolution. 

Between  the  anterior  pillars  of  the  fornix  and  the  anterior  extremity  of  the 
optic  thalamus  an  oval  aperture  is  seen  on  each  side;  this  is  the  foramen  of  Monro 
{foramen  interventriculare)  (Figs.  548,  574,  575,  and  587).  The  two  openings 
descend  toward  the  middle  line,  and  lead  into  the  upper  part  of  the  third  ven- 
tricle. Through  this  foramen  the  lateral  ventricles  communicate  with  the  third 
ventricle,  and  consequently  with  each  other;  through  it  also  the  two  choroid  plex- 
uses become  joined  with  each  other  across  the  middle  line.    The  boundaries  of  the 


896 


THE  NERVOUS  SYSTEM 


opening  are,  above  and  in  front,  the  anterior  pillars  of  the  fornix;  behind,  the 
anterior  extremity  of  the  optic  thalamus. 

The  Posterior  Pillars  of  the  Fornix  (crura  fornicis)  are  the  backward  prolongations 
of  the  two  halves  of  the  body  of  the  fornix.  They  are  flattened  bands,  and,  at  their 
commencement,  are  intimately  connected  by  their  upper  surfaces  with  the  corpus 
callosum.  Diverging  from  one  another,  each  curves  round  the  posterior  extremity 
of  the  optic  thalamus,  and  then  passes  downward  and  forward  into  the  descending 
horn  of  the  lateral  ventricle.  Here  it  lies  along  the  concavity  of  the  hippocampus 
major,  on  the  surface  of  which  some  of  its  fibres  are  spread  out,  the  alveus,  while 
the  remainder  are  continued,  as  the  fimbria,  the  corpus  fimbriatum,  the  taenia 
fornicis  or  the  taenia  hippocampi  (for  it  bears  these  different  names)  (Figs.  562, 
575,  577,  and  583),  into  the  hook  or  uncus  of  the  hippocampal  convolution.  Upon 
examining  the  under  surface  of  the  fornix,  between  its  diverging  posterior  pillars, 
a  triangular  portion  of  the  under  surface  of  the  corpus  callosum  may  be  seen. 
On  it  are  a  number  of  curved  or  oblique  lines  passing  between  the  two  pillars 
of  the  fornix.  This  portion  has  been  termed  the  lyra  or  psalterium  (Fig.  583) , 
from  the  fancied  resemblance  it  bears  to  a  harp.  It  is  also  called  the  commissura 
hippocampi.  In  some  cases  there  is  a  small  space  intervening  between  the  lyra 
and  the  under  surface  of  the  corpus  callosum  known  as  Verga's  ventricle. 

The  Anterior  Commissure  of  the  Cerebrum  (commissura  anterior  cerebri)  (Figs.  580, 
584,  and  587) . — The  anterior  commissure  of  the  cerebrum  is  a  bundle  of  white  fibres, 

in  the  anterior  wall  of  the  third  ven- 
tricle, placed  in  front  of  the  ante- 
rior pillars  of  the  fornix,  behind  the 
rostrum  of  the  corpus  callosum, 
and  resting  upon  the  lamina  ter- 
minalis.  The  anterior  commissure 
connects  the  two  hemispheres,  and 
in  vertebrates  possessing  a  corpus 
callosum  is  an  extremely  import- 
ant structure.  On  transverse  sec- 
tion it  is  oval  in  shape,  its  largest 
diameter  being  vertical  in  direction 
and  measuring  about  one-fifth  of 
an  inch.  Its  fibres  pass  backward 
and  downward  through  the  globus 
pallidus  and  below  the  putamen 
on  each  side,  from  which  point 
most  of  the  fibres  radiate  to  the 
cortex,  but  some  go  to  the  external 
capsule.  The  fibres  of  the  an- 
terior commissure  are  divisible  into  two  groups:  1.  An  anterior  group  (-pars  ante- 
rior or  pars  olfactoria),  the  fibres  of  which  join  the  limbic  lobes  and  connect  each 
limbic  lobe  to  the  olfactory  tract  of  the  opposite  side.  The  fact  that  the  pais 
anterior  contains  fibres  from  the  olfactory  tract  of  the  opposite  side  may  serve  to 
explain  the  condition  of  crossed  anosmia,  e.  g.,  where  there  is  a  lesion  in  one 
temporal  lobe  with  a  loss  of  smell  in  the  olfactory  area  of  the  opposite  side  of  the 
nose.  2.  A  posterior  group  (pars  posterior  or  pars  occipitotemporalis) ,  the  fibres 
of  which  pass  to  the  cortex  of  the  temporal  lobe  and  of  the  lower  part  of  the 
occipital  lobe. 

The  Septum  Lucidum  (septum  pellucidum)  (Figs.  574,586,  and  587)  .—The  septum 
lucidum  is  a  thin,  double,  vertically  placed  partition,  which  forms  the  internal 
bpundary  of  the  body  and  anterior  horn  of  the  lateral  ventricle.  It  consists  of  two 
distinct  laminae,  separated  in  part  of  their  extent  by  a  narrow  chink  or  interval, 


ANTERIOR    PILLARS 
OF    FORNIX 


Fio.  580. — Anterior  commissure,  left  half,  viewed  from  above. 
(Testut.) 


THE    HEMISPHERES    OF    THE    CEREBRUM 


897 


called  the  fifth  ventricle.  It  is  a  thin,  semitransparent  septum,  attached,  above, 
to  the  under  surface  of  the  corpus  callosum ;  in  front  to  the  reflected  portion  of  the 
corpus  callosum;  below  it  passes  between  the  fornix  and  the  posterior  margin  of 
the  rostrum  to  terminate  in  the  sub-callosal  gyrus;  posteriorly  it  is  between  the 
fornix  and  body  of  the  corpus  callosum,  being  attached  to  each.  It  is  triangular 
in  form,  broad  in  front  and  narrow  behind;  its  inferior  angle  corresponds  with 
the  upper  part  of  the  anterior  commissure.  The  outer  surface  of  each  lamina  is 
directed  toward  the  lateral  ventricle,  and  is  covered  by  the  ependyma  of  that 
cavity,  while  its  medial  surface  bounds  the  cavity  of  the  fifth  ventricle  (p.  889). 
Fifth  Ventricle  {cavum  septi  pellucidi). — The  fifth  ventricle  was  originally  a  part 
of  the  great  longitudinal  fissure,  which  was  shut  off  by  the  union  of  the  hemi- 
spheres in  the  formation  of  the  corpus  callosum  above  and  the  fornix  below. 
Each  half  of  the  septum  is  therefore  formed  by  the  medial  wall  of  the  hemisphere, 
and  consists  of  an  internal  layer  of  gray  matter,  derived  from  the  gray  matter  of 
the  cortex,  and  an  external  layer  of  white  substance  continuous  with  the  white 
matter  of  the  cerebral  hemispheres.  The  fifth  ventricle  differs  from  the  other 
ventricles  of  the  brain,  inasmuch  as  it  is  not  developed  from  the  cavity  of  the  cere- 


Eminentia  ) 
collateralis.  j 


Hippocampus 
major. 

Gray  matter 

of  the 
hippocampus. 


r  Fascia 

\  dentata. 

f  Uncinate 

I  convolution. 
Uncinate 
process  or 
uncus. 


Fig.  581. — Transverse  section  of  the  middle  horn  of  the  lateral  ventricle. 

Mr.  F.  A.  Barton.) 


(From  a  drawing  by 


bral  vesicles,  it  is  not  lined  by  ciliated  epithelium  but  by  altered  pia  mater,  and 
it  does  not  communicate  with  the  general  ventricular  cavity;  further,  tlie  fluid 
it  contains  is  not  cerebro-spinal  fluid  but  is  of  the  nature  of  lymph. 

The  structures  on  the  floor  of  the  descending  horn  of  the  lateral  ventricle  will 
now  be  described. 

The  Hippocampus  Major  or  Comu  Ammonis  (Figs.  581  and  583)  is  a  white  emi- 
nence, about  two  inches  in  length,  of  a  curved  elongated  form,  extending  through- 
out the  entire  length  of  the  floor  of  the  descending  horn  of  the  lateral  ventricle. 
At  its  lower  extremity  it  becomes  enlarged,  and  presenting  two  or  three  rounded 
elevations  with  intervening  depressions,  it  resembles  the  paw  of  an  animal,  and 
is  called  the  pes  hippocampi  (digitationes  hippocampi)  (Fig.  583) .  If  a  transverse 
section  is  made  through  the  hippocampus  major,  it  will  be  seen  that  this  eminence 
is  produced  by  the  folding  of  the  cortex  of  the  brain  to  form  the  dentate  or  hippo- 
campal  sulcus  (Figs.  562,  563,  564,  and  567).  The  dentate  fissure  is  separated 
from  the  choroid  fissure  by  the  dentate  gyrus  or  dentate  fascia  (fascia  dentata) 
(Figs.  562  and  581) .  The  hippocampal  gyrus  and  the  fifth  temporal  gyrus  together 
constitute  the  uncinate  convolution  (Figs.  567  and  581) .     The  uncus  (Fig.  581)  is  the 

57 


898 


THE    NERVOUS   SYSTEM 


hook-like  anterior  extremity  of  the  hippocampal  or  uncinate  gyrus.  To  the  outer 
side  and  parallel  with  the  hippocampus  major  an  elongated  eminence,  the 
eminentia  collateralis,  is  frequently  recognized  (Fig.  581).  It  corresponds  with 
the  middle  part  of  the  collateral  fissure,  and  its  size  depends  on  the  direction  and 
depth  of  this  fissure.  The  main  mass  of  the  hippocampus  major  consists  of  gray 
matter,  but  on  its  ventricular  surface  is  a  thin  layer  of  white  matter,  known  as 
the  alveus,  which  is  continuous  with  the  corpus  fimbriatum  of  the  fornix  and 
is  covered  by  the  ependyma  of  the  ventricle.  Dr.  J.  G.  Macarthy,  of  McGill 
University,  Montreal,  has  shown^  that,  if  the  alveus  and  superficial  strata  of  gray 
matter  be  reflected  from  the  surface  of  the  hippocampus  by  an  incision  carried 
along  its  convexity,  the  "core"  of  the  hippocampus,  as  he  terms  it,  presents  in 
many  cases  a  corrugated  or  crimped  appearance. 

The  Corpus  Fimbriatum,  Taenia  Fomicis,  or  Fimbria  {taenia  hippocampi  or  taenia 
fimbriae)  (Figs.  562,  575,  577,  and  583)  has  already  been  mentioned  as  a  part  of  the 
posterior  pillar  of  the  fornix.  It  consists  of  a  narrow  white  band,  which  is  placed 
immediately  below  the  choroid  plexus,  and  is  attached  by  its  deep  surface  to  the 


_  Fornix 

Optic  thalamus 
Corpora  quadrigemina 


FiQ.  682. — Diagram  showing  the  mode  of  formation  of  the  velum  interpositum. 

white  matter  or  alveus  of  the  hippocampus  major  as  it  courses  through  the  descend- 
ing cornu  of  the  lateral  ventricle.  It  can  be  traced  as  far  as  the  uncus  or  hook  of 
the  hippocampal  gyrus.  Its  inner  margin  is  free,  and  rests  upon  the  dentate  fascia, 
from  which  it  is  separated  by  a  slit-like  fissure,  the  fimbrio-dentate  fissure.  The 
groove  between  the  fimbria  and  tHe  hippocampal  convolution  is  the  defile  of  the 
dentate  fissure.  Its  outer  margin  is  attenuated  and  irregular,  and  forms  the  line 
along  which  the  ependyma  is  reflected  over  the  choroid  plexus  as  the  latter  is 
invaginated  through  the  inferior  part  of  the  transverse  fissure.  When  the  choroid 
plexus  is  pulled  away  it  carries  the  ependyma  with  it,  and  the  descending  horn 
opens  on  to  the  surface  of  the  brain  through  the  transverse  fissure.  If  now 
the  inner  border  of  the  corpus  fimbriatum  be  raised,  a  notched  band  of  gray 
matter,  which  is  a  free  border  of  cortex,  and  is  called  the  dentate  fascia  (fascia 
dentata  hippocampi)  (Figs.  562  and  581),  will  be  exposed;  this  has  already  been 
described  as  forming  part  of  the  limbic  lobe  (p.  879). 


'  Journal  of  Anat.  and  Phys.,  1899,  vol.  xxiii. 


THE    HEMISPHERES    OF    THE    CEREBRUM 


899 


The  Choroid  Plexus  {plexus  chorioideus)  (Figs.  548,  575,  and  583)  is  a  highly 
vascular,  fringe-like  structure,  which  is  situated  partly  in  the  body  and  partly  in 
the  descending  cornu  of  the  lateral  ventricle,  It  will  be  desirable  to  consider  these 
two  portions  separately,  in  order  to  get  a  just  conception  of  how  they  are  formed. 

The  portion  in  the  body  of  the  ventricle  is  the  vascular,  fringed  border  of  a 
triangular  fold  of  pia  mater,  the  velum  interpositum  {tela  chorioidea  superior  or  tela 
chorioidea  ventriculi  tertii),  which  lies  on  the  under  surface  of  the  fornix  and  forms 
the  roof  of  the  third  ventricle.  The  developing  brain  vesicles  are  covered  by  pia 
mater.  As  the  prolongation  from  the  first  vesicle,  which  is  to  form  the  cerebral 
hemispheres,  increases  in  size,  it  grows  backward  and  downward  and  covers  the 
other  vesicles,  with  the  result  that  the  pia  mater  covering  the  hemisphere  comes  in 


Fig.  583. — The  fornix,  velum  interpositum,  and  middle  or  descending  cornu  of  the  lateral  ventricle. 


contact  with  that  covering  the  upper  surface  of  the  second  vesicle.  Portions  of  the 
two  layers  which  are  in  contact  form  the  velum  interpositum.  Immediately  above  is 
the  body  of  the  fornix,  which  is  formed  by  the  fusion  of  the  cerebral  hemispheres  in 
the  middle  line,  and  below  is  the  cavity  of  the  second  vesicle  (the  third  ventricle), 
with  the  optic  thalamus  on  either  side.  Just  beyond  the  free  lateral  border  of  the 
fornix,  between  it  and  the  taenia  semicircularis,  is  a  portion  of  the  first  cerebral 
vesicle,  which  is  not  developed  into  nervous  matter,  but  is  made  up  only  of  epen- 
dyma  covered  by  pia  mater.  The  vessels  of  this  portion  of  the  highly  vascular  pia 
mater  become  dilated  and  prolonged,  and  grow  into  the  ventricle,  pushing  the 


900  THE  NEBVOUS  SYSTEM 

ependyma  before  them,  and  forming  an  irregular  congeries  of  vessels,  apparendy 
encroaching  on  the  cavity  of  the  lateral  ventricle,  but  in  reality  being  external  to  it, 
because  they  are  separated  from  it  by  the  lining  membrane  of  the  cavity,  the 
ependyma.    This  vascular  structure  is  the  choroid  plexus  of  the  body  of  the  ventricle. 

The  part  of  the  choroid  plexus  seen  in  the  descending  cornu  is  formed  in 
exactly  the  same  way — viz.,  by  an  ingrowth  of  the  vessels  of  the  pia  mater  into  the 
cavity,  pushing  the  ependyma  before  it,  at  a  part  of  the  wall  of  the  horn  where 
there  is  a  similar  absence  of  nervous  tissue  and  where  it  consists  simply  of  pia 
mater  and  ependyma  in  close  contact.  This  portion  lies  between  the  corpus  fim- 
briatum  in  the  floor  and  the  taenia  semicircularis  in  the  roof  of  the  descending 
horn.  This  area,  destitute  of  nervous  matter,  is  continuous  with  the  area  in  the 
body  of  the  ventricle,  from  which  the  choroid  plexus  of  this  region  originated,  and 
in  it  the  vessels  of  its  pia  mater  increase,  and,  invaginating  the  ependyma,  appear 
in  the  descending  horn  as  its  choroid  plexus.  In  the  body  of  the  ventricle  the 
choroid  plexus  is  really  the  vascular  fringed  margin  of  the  velum ;  beyond  the  pos- 
terior margin  of  the  velum  the  plexus  of  the  descending  horn  is  continuous  with 
the  pia  mater  on  the  surface  of  the  gyrus  hippocampi;  the  two  portions  of  the 
plexus  are,  however,  directly  continuous  with  each  other,  and  constitute  the 
choroid  plexus  of  the  lateral  ventricle  (plexus  chorioideus  ventriculi  lateralis).  The 
gap  or  cleft  through  which  the  invagination  of  the  pia  mater  takes  place  is  called 
the  choroid  fissure. 

In  front  the  choroid  plexus  of  the  lateral  ventricle  is  small  and  tapering,  and 
communicates  with  the  plexus  of  the  opposite  side  through  the  foramen  of  Monro. 
In  structure  it  consists  of  minute  and  highly  vascular  villous  processes,  contain- 
ing an  afferent  and  efferent  vessel,  and  covered  by  a  single  layer  of  flattened  epi- 
thelium, the  cells  of  which  often  contain  yellowish  fat  molecules.  The  anterior 
choroidal  artery  is  derived  from  the  internal  carotid,  and  enters  the  ventricle  at  the 
extremity  of  the  descending  cornu,  and,  after  ramifying  in  the  plexus,  sends 
branches  into  the  adjacent  parts  of  the  brain.  The  posterior  choroidal  arteries, 
one  or  two  in  number  on  each  side,  are  derived  from  the  posterior  cerebral  artery, 
and  reach  the  plexus  by  passing  forward  under  the  splenium  of  the  corpus  cal- 
losum.  The  veins  of  the  choroid  plexus  unite  to  form  a  prominent  vein,  the  choroid 
vein,  which  courses  from  behind  forward  to  the  foramen  of  ]\Ionro.  On  each 
side  of  the  foramen  of  Monro  a  deep  cerebral  vein  or  vein  of  Galen  is  formed  by 
the  union  of  the  choroid  vein  and  the  vein  of  the  corpus  striatum.  The  veins  of 
Galen  pass  back  in  the  velum  interpositum,  unite  to  form  the  common  vein  of 
Galen  or  the  vena  magna  Galeni  (v.  cerebri  magna),  which  empties  into  the  straight 
sinus  (p.  735). 

The  Transverse  Fissure  or  Fissure  of  Bichat  (fissura  cerebri  transversa) ,  separates 
the  cerebrum  from  the  cerebellum.  This  fissure  passes  forward  and  ends  in  the 
cerebrum  as  the  lateral  part  of  the  transverse  fissure  or  the  choroid  fissure  (fissura 
chorioidea).  The  posterior  part  of  the  transverse  fissure  is  occupied  by  the 
tentorium.  Posteriorly  the  transverse  fissure  has  above  it  the  mass  of  the 
cerebral  hemisphere  and  below  it  the  upper  surface  of  the  cerebellum,  the  cor- 
pora quadrigemina,  and  the  pineal  gland.  The  transverse  fissure  is  a  complete 
fissure,  but  it  is  filled  by  the  invagination  of  the  pia  mater,  forming  laterally 
the  velum  interpositum  and  the  choroid  plexuses,  which  invagination  is  covered 
by  the  fining  of  the  ventricular  cavities.  If  this  involution  of  pia  mater  is  pulled 
out,  the  ventricular  lining  will  necessarily  be  torn  away  with  it,  and  a  cleft-like 
space  will  be  left  on  either  side,  extending  from  the  foramen  of  Monro  to  the 
bottom  of  the  descending  horn  of  the  lateral  ventricle.  The  upper  part  of  the 
cleft,  that  is  to  say,  the  part  nearest  the  foramen  of  Monro,  is  between  the  lateral 
border  of  the  body  of  the  fornix  and  the  optic  thalamus;  below  this,  at  the  com- 
mencement of  the  middle  horn,  it  is  between  the  commencing  corpus  fimbriatum 


THE   INTEB-BBAIN  901 

of  the  fornix  and  the  pulvinar  of  the  optic  thalamus;  and  lower  still,  in  the 
descending  horn,  between  the  corpus  fimbriatum  on  the  floor  and  the  taenia 
semicircularis  in  the  roof  of  the  cornu.  The  course  of  the  choroid  fissure  from 
the  foramen  of  Monro  is  backward,  downward,  and  forward,  to  near  the  apex 
of  the  temporal  lobe.  The  choroid  fissures  of  the  two  sides  are  continuous 
between  the  fornix  and  the  roof  of  the  third  ventricle. 

The  Velum  Interpositum^or  Tela  Chorio idea  Superior  (te/a  c^onoitim -yenincM/i 
tertii)  (Fig.  548)  is  a  vascular  membrane,  and  is  a  prolongation  of  the  pia  mater 
into  the  interior  of  the  brain  through  the  middle  part  of  the  transverse  fissure. 
It  is  of  a  triangular  form,  and  separates  the  under  surface  of  the  body  and  pos- 
terior pillars  of  the  fornix  from  the  cavity  of  the  third  ventricle.  Laterally  it  covers 
the  inner  part  of  the  upper  surface  of  the  optic  thalamus.  Its  posterior  border  or 
base  lies  beneath  the  splenium  of  the  corpus  callosum  above,  and  the  optic  thala- 
mus, the  corpora  quadrigemina,  and  pineal  body  below.  The  upper  layer  of  the 
base  is  continuous  with  the  pia  mater  of  the  occipital  lobe,  and  the  lower  layer  of 
the  base  is  continuous  with  the  pia  mater  of  the  dorsal  aspect  of  the  cerebellum 
and  mid-brain.  Its  anterior  extremity  or  a'pex  ends  just  behind  the  anterior  com- 
missure, where  it  receives  the  anterior  extremities  of  the  choroid  plexuses,  which 
are  here  vmited  through  the  foramen  of  Monro,  and  are  then  prolonged  back- 
ward on  the  under  surface  of  the  velum  as  the  choroid  plexus  of  the  third 
ventricle  (plexus  chorioideus  ventriculi  tertii).  The  inferior  layer  of  the  velum  which 
carries  the  choroid  plexus  of  the  third  ventricle  is  called  the  superior  choroid  tela 
(tela  chorioidea  ventriculi  tertii).  The  external  portion  of  the  inferior  layer  of  the 
velum  interpositum  covers  the  inner  half  of  the  superior  surface  of  the  optic 
thalamus.  In  front  the  plexuses  of  the  third  ventricle  lie  close  to  the  middle  line, 
but  diverge  from  each  other  behind.  Each  lateral  margin  of  the  velum  inter- 
])ositum  constitutes  the  choroid  plexus  of  the  corresponding  lateral  ventricle.  It 
is  supplied  by  the  anterior  and  posterior  choroidal  arteries,  already  described. 
The  veins  of  the  velum  interpositum,  the  venae  Galeni  (vv.  cerebri  internae),  two 
in  number,  riin  between  its  layers,  each  being  formed  by  the  union  of  the  vein 
of  the  corpus  striatum  (v.  corporis  striata)  with  the  choroid  vein  (v.  chorioidea).  The 
venae  Galeni  unite  posteriorly  into  a  single  trunk,  the  vena  magna  Galeni  or  the 
common  vein  of  Galen  (v.  cerebri  magna),  which  terminates  in  the  straight  sinus 
(Fig.  548).  The  portion  of  the  pia  mater  prolonged  over  the  lower  half  of  the 
fourth  ventricle  is  known  as  the  tela  chorioidea  inferior  quarti.  It  carries  the 
choroid  plexus  of  the  fourth  ventricle  (plexus  chorioideus  ventriculi  quarti.) 


II.  The  Inter-brain  (Thalamencephalon). 

The  inter-brain  is  the  region  of  the  third  ventricle,  and  comprises  the  parts 
developed  from  the  second  cerebral  vesicle,  together  with  parts  from  that  portion  of 
the  first  vesicle  which  is  not  concerned  in  the  formation  of  the  cerebral  hemispheres. 

The  inter-brain  is  connected  above  and  in  front  with  the  cerebral  hemispheres; 
behind,  with  the  raid-brain  or  mesencephalon.  On  its  upper  surface  it  is  entirely 
concealed  from  view,  as  it  is  covered  by  those  portions  of  the  internal  surfaces  of 
the  cerebral  hemispheres  which  have  fused  together  to  form  the  corpus  callosum 
and  the  fornix,  and  is  separated  from  the  latter  by  the  two  layers  of  pia  mater 
which  form  the  velum  interpositum.  Inferiorly  it  reaches  the  base  of  the  brain, 
forming  the  structures  contained  in  the  interpeduncular  space. 

The  Third  Ventricle  (ventriculus  tertius)  (Fig.  584). — The  third  ventricle  is 
the  cavity  of  the  inter-brain;  it  is  in  the  mid-line,  is  at  a  lower  level  than  the  lateral 
ventricles;  and  the  epithelial  layer  of  the  ependyma  from  the  lateral  ventricles 
is  prolonged  into  the  third  ventricle  through  the  foramen  of  Monro.    The  third  ven- 


902 


THE   NERVOUS    SYSTEM 


tricle  contains  cerebro-spinal  fluid.  It  is  a  narrow  median  crevice  between  the  two 
optic  thalami,  which  constitute  the  side  walls  of  the  inter-brain.  It  is  "about  an 
inch  in  length  from  before  backward  and  one-quarter  of  an  inch  broad  at  its 
widest  part."^  Its  roof  is  formed  by  the  velum  interpositum,  from  which  is  sus- 
pended the  choroid  plexus  of  the  third  ventricle.  Its  floor,  somewhat  oblique  in 
its  direction,  is  formed,  from  before  backward,  by  the  tuber  cinereum,  with  its 
infundibulum  and  pituitary  body;  the  corpora  albicaijtia;  the  posterior  perforated 
space;  and  the  tegmenta  of  the  crura  cerebri.  Its  sides  are  formed  by  the  optic 
thalami,  and  are  limited  above  by  a  delicate  band  of  white  fibres,  the  pineal  stria 
{stria  medullaris  thalami),  which  runs  along  the  junction  of  the  mesial  and  upper 


Fio.  684. — ^The  third  and  fourth  ventricles.    An  arrow  has  been  placed  in  the  position  of  the  foramen  of  Monro. 

surfaces  of  the  optic  thalamus  to  join  the  anterior  pillars  of  the  fornix.  Its  sides 
are  somewhat  convex,  so  that  in  the  middle  of  the  ventricle  the  two  lateral  walls 
are  almost  in  contact,  and  are  here  united  across  the  middle  line  by  a  band  of  gray 
nervous  matter,  the  middle,  gray,  or  soft  commissure  (Fig.  584).  The  ventricle  is 
bounded  in  front  by  the  anterior  pillars  of  the  fornix  and  the  lamina  cinerea;  behind 
by  the  pineal  gland,  the  posterior  commissure,  and  the  upper  end  of  the  aqueduct 
of  Sylvius,  the  iter  a  tertio  ad  quartum  ventriculum.  The  cavity  is  much  deeper  in 
front  than  behind,  and  presents  a  recess  at  its  anterior  part,  which  lies  over  the  optic 
commissure  and  is,  therefore,  termed  the  optic  recess  (recessus  opticus).  Behind 
and  below  this  is  the  conical  depression  of  the  infundibulum  (Fig.  587),  passing 


'  Anatomy  of  the  Brain  and  Spinal  Cord.     By  Harris  E.  Santee. 


THE  INTER-BBAIN  903 

downward  and  forward  to  the  pituitary  body.  At  its  posterior  extremity  the 
cavity  forms  another  and  smaller  recess,  which  extends  into  the  stalk  of  the 
pineal  gland,  and  is  termed  the  pineal  recess  (recessus  pinealis).  The  anterior 
part  of  the  third  ventricle  is  called  the  aula.  At  the  upper  and  anterior  part  of 
the  third  ventricle,  immediately  behind  the  anterior  pillars  of  the  fornix  and  in 
front  of  the  optic  thalamus,  is  an  opening,  the  foramen  of  Monro  {foramen  inter- 
ventriculare  [Monroi\),  by  which  this  ventricle  communicates  with  the  lateral 
ventricle  on  either  side  (Figs.  548,  574,  575,  and  587).  The  foramen  of  Monro 
opens  into  each  lateral  ventricle  at  the  point  of  junction  of  the  anterior  horn  and 
the  body  of  the  ventricle.  It  lies  between  the  anterior  pillar  of  the  fornix  and  the 
anterior  margin  of  the  optic  thalamus  and  ends  by  opening  into  the  anterior  and 
superior  extremity  of  the  third  ventricle.  Running  back  from  the  foramen  of 
Monro  toward  the  aqueduct  of  Sylvius  is  a  furrow  called  the  sulcus  of  Monro 
(sulcus  hypothalamicus  [Monroi]).  At  the  posterior  part  of  the  floor  of  the  third 
ventricle,  beneath  the  posterior  commissure,  is  the  opening  of  the  aqueduct  of 
Sylvius  or  iter  a  tertio  ad  quartum  ventriculum  (Fig.  587) ,  the  channel  which  joins 
the  third  and  fourth  ventricles  (p.  912).  The  roof  of  the  cavity  of  the  third  ventricle 
is  limited  in  front  and  behind  by  transverse  bands  of  white  matter,  known 
respectively  as  the  anterior  and  posterior  commissures.  The  former  has  already 
been  described  in  connection  with  the  corpus  striatum  (p.  896). 

The  Middle,  Gray,  or  Soft  Commissure  (massa  intermedia  or  commissura  mollis) 
(Fig.  584). — The  middle,  gray,  or  soft  commissure  consists  almost  entirely  of 
gray  matter.  It  connects  the  two  optic  thalami,  and  is  continuous  with  the 
gray  matter  lining  the  anterior  part  of  the  third  ventricle.  It  is  frequently 
broken  in  examining  the  brain,  and  might  then  be  supposed  to  be  wanting;  it  is 
sometimes  double. 

The  Posterior  Commissure  (commissura  posterior)  (Figs.  584  and  587. — The  poste- 
rior commissure  is  a  rounded  band  of  white  fibres,  which  stretches  across  from  one 
optic  thalamus  to  the  other,  overlying  the  upper  end  of  the  aqueduct  of  Sylvius. 
It  is  usually  described  as  belonging  to  the  inter-brain,  but  would  appear  to 
belong  in  part  to  the  mid-brain,  since  some  of  its  fibres  are  commissural  and 
connect  the  anterior  corpora  quadrigemina  to  the  fillet  of  the  opposite  side  (see 
below).  In  addition  there  are  other  decussating  fibres,  which  come  from  the 
tegmentum  of  the  crus  cerebri  on  one  side  and  decussate  with  those  of  the 
opposite  side  in  the  posterior  commissure,  and  passing  through  the  optic 
thalamus  reach  the  cerebral  hemispheres.  Fibres  have  also  been  described  as 
taking  their  origin  in  the  pineal  body  and  ganglion  habenulae,  and  passing  across 
to  the  posterior  longitudinal  bundle  and  oculomotor  nucleus  of  the  opposite  side; 
these  fibres  occupy  the  ventral  part  of  the  commissure,  and  receive  their  myelin 
sheath  before  those  in  its  dorsal  part.  But  to  a  certain  extent  the  posterior  com- 
missure belongs  to  the  inter-brain,  since  it  contains  fibres  which  serve  as  com- 
missural fibres  between  the  two  optic  thalami. 

The  Optic  Thalamus  (thalamus)  (Figs.  576,577,  578,  579,  580,  582,  and  584). 
— ^The  optic  thalami  are  two  large  oblong  masses,  situated  on  either  side  of  the  third 
ventricle,  and  lying  between  the  diverging  portions  of  the  corpora  striata.  They  are 
composed  mainly  of  gray  matter,  but  the  free  surface  of  each  is  coated  with  a  thin 
layer  of  white  nervous  tissue,  the  stratum  zonale.  They  present  outer  and  under 
surfaces,  which  are  not  free,  but  are  blended  with  contiguous  parts  of  the  brain, 
and  upper,  inner,  and  posterior  surfaces,  which  are  free.  The  anterior  extremity 
is  narrow,  and  forms  the  posterior  boundary  of  the  foramen  of  Monro.  The  outer 
surface  is  in  contact  with  the  posterior  limb  of  the  internal  capsule,  which  sepa- 
rates it  from  the  lenticular  nuclues.  The  inferior  surface  rests  upon  and  is  con- 
tinuous with  the  tegmentum  of  the  crus  cerebri.  Its  upper  surface  is  free,  and 
is  separated  from  the  caudate  nucleus  by  a  furrow  which  lodges  the  vein  of  the 


904  THE  NERVOUS  SYSTEM 

corpus  striatum,  and  the  taenia  semicircularis.  It  is  divided  into  an  outer  and  an 
inner  part  by  a  groove  which  runs  from  behind,  forward,  and  inward.  The  outer 
part  forms  a  portion  of  the  floor  of  the  lateral  ventricle,  and  is  covered  by  the 
ependyma  of  that  cavity;  it  terminates  in  front  in  a  tubercle,  the  anterior  tubercle 
of  the  optic  thalamus  (tuberculum  anterius  thalami).  The  inner  part  is  covered  by 
the  velum  interpositum,  which  separates  it  from  the  fornix,  and  is  excluded  from 
both  the  lateral  and  third  ventricles  by  the  reflection  of  the  lining  of  these  cavities, 
and  is  therefore  destitute  of  an  ependymal  covering. 

The  internal  surface  forms  the  lateral  wall  of  the  third  ventricle,  and  running 
along  its  upper  border  is  the  peduncle  of  the  pineal  gland,  from  which  the  ependyma 
of  the  third  ventricle  is  reflected  on  to  the  under  surface  of  the  velum  interpositum. 
The  shelf-like  edge  of  the  ependyma  separates  the  superior  from  the  internal 
surface  of  the  thalamus.  The  edge  is  called  the  taenia  thalami,  and  close  to  it  is  a 
narrowband  of  longitudinal  fibres  called  the  pineal  striae  (striae  medullaris  thalami). 
The  taenia  thalami  and  the  pineal  striae  pass  backward  and  then  inward  into  the 
stalk  of  the  pineal  gland.  The  portion  of  the  taenia  which  turns  inward  has  pos- 
terior to  it  a  small  triangular  depression  called  the  trigone  of  the  habenula  {trigonum 
hahenulae).  This  depression  is  just  in  front  of  the  superior  quadrigeminal  body. 
Passing  in  a  medial  direction  from  the  trigonum  habenulae  is  a  collection  of 
white  fibres,  the  habenula.  The  fibres  of  the  anterior  portion  of  this  band  are 
continuous  with  those  of  the  opposite  side,  and  constitute  the  commissure  of  the 
habenula  (commmwra  hahenularmn).  The  fibres  of  the  posterior  portion  consti- 
tute the  peduncle  of  the  pineal  gland  (p.  906).  The  posterior  surface  projects 
beyond  the  level  of  the  corpora  quadrigemina,  and  forms  a  well-marked  rounded 
prominence,  the  posterior  tubercle  or  pulvinar.  The  pulvinar  is  continued  exter- 
nally into  a  second  eminence,  the  external  geniculate  body  {corpus  geniculatum 
laterale),  which  is  placed  above  and  to  the  outer  side  of  the  internal  geniculate  body 
(corpus  geniculatum  mediale),  and  from  which  it  is  separated  by  the  superior 
brachiimi,  one  of  the  roots  of  the  optic  tract. 

The  optic  or  free  upper  surface  of  the  thalamus  is  covered  by  white  fibres  derived, 
in  part,  at  least,  from  the  optic  tract  and  radiation.  The  thalamus  is  formed  chiefly 
of  gray  matter,  which  is  arranged  in  three  masses  partially  separated  from  each 
other  by  white  matter  called  the  internal  medullary  lamina  (lamina  medullaris 
interna),  which  is  named  internal  in  contradistinction  to  a  second  or  external 
medullary  lamina  (lamina  medullaris  externa),  which  coats  the  outer  surface  of  the 
thalamus  and  lies  between  it  and  the  internal  capsule.  These  masses  of  gray 
matter  are  the  nuclei  of  the  optic  thalamus.  Twenty  nuclei  have  been  described 
(Nissl).     The  chief  nuclei  are  the  following: 

1.  The  External  or  Lateral  Nucleus  (nucleus  lateralis  thalami). — The  external  or 
lateral  nucleus,  the  largest  of  the  nuclei,  between  the  external  and  internal  medul- 
lary laminae  and  extending  the  entire  length  of  the  thalamus,  including,  as  Prof. 
Cunningham  points  out,  the  entire  pulvinar,  most  of  the  tegmental  fibres,  and  one- 
fifth  of  the  optic  fibres,  terminate  in  this  nucleus,  and  from  it  originate  the  fibres 
of  the  thalamic  radiation. 

2.  The  Middle  or  Internal  Nucleus  (nucleus  medialis  thalami). — The  middle  or 
internal  nucleus  is  separated  by  the  internal  medullary  lamina  from  the  other  gray 
nuclei  of  the  same  side.  It  joins  the  middle  nucleus  of  the  opposite  thalamus  by 
means  of  the  middle  commissure. 

3.  The  Anterior  Nucleus  (nucleus  anterior  thalami). — The  anterior  nucleus  is  in 
the  anterior  tubercle,  and  in  it  terminate  the  fibres  of  the  bundle  of  Vicq  d'Azyr 
which  come  from  the  corpus  mamillare  (Fig.  586). 

In  the  substance  of  the  thalamus  are  two  other  distinct  nuclei,  (4)  the  central 
nucleus  of  Luys  and  (5)  the  nucleus  arcuatus.  The  nucleus  or  ganglion  of  the  habenula 
lies  in  the  trigonum  habenulae. 


THE  INTER- BBAIN  905 

Connections  of  the  Optic  Thalamus  (Figs.  586,  589,  and  590). — The  optic  thalamus 
is  a  ganglion  interposed  between  the  sensory  tracts  in  the  tegmentum  and  the  cere- 
bral cortex,  being  connected  also  with  the  optic  tract.  In  this  ganglion  or  in  the 
adjacent  ganglia  of  the  subthalamic  region,  "  almost  every  impulse  of  general  sen- 
sation, on  its  journey  to  the  cerebral  cortex,  is  transferred  to  a  higher  neurone."^ 
The  crusta  of  the  crus  cerebri  is  external  to  the  optic  thalamus  and  passes  into 
the  internal  capsule.  The  tegmental  fibres  of  the  crus  (Fig.  586)  pass  to  the  under 
surface  of  the  thalamus,  and  the  forward  prolongation  of  the  tegmentum  which 
becomes  continuous  with  the  under  surface  of  the  thalamus  is  called  the  sub- 
thalamic region,  and  most  of  the  longitudinal  fibres  enter  this  ganglion,  some  of 
them  terminating  in  it,  some  of  them  traversing  it  and  entering  the  internal 
capsule.  The  internal  capsule  (Figs.  578,  589,  and  590)  is  composed  of  fibres  going 
to  and  coming  from  the  cerebral  cortex.  Most  of  these  fibres  are  descending  and 
form  the  crus  cerebri.  From  all  over  the  external  surface  of  the  optic  thalamus 
fibres  emerge,  pass  into  the  internal  capsule,  and  from  there  go  to  the  cerebral 
cortex.     These  fibres  constitute  the  thalamic  radiation. 

The  nuclei  of  the  thalamus  have  been  described  (p.  904).  The  white  matter 
receives  the  fibres  of  the  tegmentum  and  fillet,  the  majority  of  which  enter  the 
lateral  nucleus;  it  receives  fibres  (axones)  from  the  entire  cerebral  cortex  and 
sends  fibres  to  the  cortical  special  sense  areas  of  sight,  hearing,  and  smell  and 
to  the  area  of  general  sensation)  the  somaesthetic  area). 

The  following  groups  of  fibres  of  white  matter  are  found  in  the  thalamus:  1. 
The  anterior  pillar  of  the  fornix,  which  passes  through  the  inner  part  of  the  optic 
thalamus  on  its  way  to  the  corpus  mamillare,  and  the  bundle  of  Vicq  d'Azyr, 
(fasciculus  thalavwmamillaris)  (Fig.  586),  which  arises  in  the  corpus  mamil- 
lare and  ascends  to  the  anterior  gray  nucleus.  2.  Two  bundles  of  fibres  emerging 
from  the  external  surface  of  the.  thalamus.  The  superior  bundle  {ansa  lenticu- 
laris)  arises  largely  in  the  lateral  nucleus,  passes  through  the  internal  capsule  and 
the  lenticular  nucleus;  it  then  enters  the  external  capsule,  and  passes  to  the 
insula,  the  paracentral  lobule,  the  superior  frontal  convolution,  and  "the  entire 
limbic  lobe  "^  (Fig.  589).  The  inferior  bundle  (ansa  peduncularis)  arises  in  the 
lateral  nucleus,  passes  through  the  internal  capsule  below  the  lenticular  nucleus, 
"enters  into  both  the  medullary  laminae  of  that  nucleus  and  the  external  capsule. 
It  ends  chiefly  in  the  cortex  of  the  ascending  frontal  and  ascending  parietal 
convolutions"^  (Fig.  589).  These  fibres  constitute  the  ventral  or  inferior  stalk 
of  the  thalamic  radiation.  8.  The  anterior  stalk  of  the  thalamic  radiation  (Figs.  588 
and  500)  arises  in  the  lateral  nucleus,  passes  to  the  frontal  portion  of  the 
internal  capsule,  and  reaches  the  inferior  and  middle  frontal  convolutions, 
the  anterior  portion  of  the  superior  frontal  convolution,  and  the  middle  of  the 
gyrus  fornicatus  (Santee),  The  anterior  stalk  of  the  thalamic  radiation,  plus 
the  ansa  lenticularis  and  the  ansa  peduncularis,  constitutes  the  cortical  fillet  or 
the  three  systems  of  Flechsig  (p.  915).  4.  The  posterior  stalk  of  the  thalamic 
radiation  (Fig.  590)  is  called  the  optic  radiation  (radiatio  occipitothalamica). 
The  afferent  part  arises  in  the  pulvinar  and  the  external  geniculate  body,  passes 
through  the  internal  capsule,  and  terminates  in  the  occipital  cortex.  The 
efferent  portion  terminates  in  the  superior  quadrigeminal  body.  5.  The  acoustic 
radiation  (Fig.  590)  arises  about  the  internal  geniculate  body,  passes  through  the 
internal  capsule,  and  reaches  the  auditory  region  in  the  temporal  cortex. 

The  Pineal  Body,  Epiphysis  Cerebri,  Conarium,  or  Pineal  Gland  (corpus 
pineale)  (Figs.  584  and  587). — The  pineal  body  or  gland,  so  named  from 
its  peculiar  shape  (pinus,  a  fir-cone),  is  a  small  reddish-gray  body,  conical  in 
shape  (hence  its  synonym,  conarium),  placed  immediately  above  and  behind  the 

^  Anatomy  of  the  Brain  and  Spinal  Cord.     By  Harris  E.  Santee.  -  Ibid.  •  Il)id. 


906  THE    NERVOUS   SYSTEM 

posterior  commissure  and  between  the  anterior  corpora  quadrigemina,  on  which 
it  rests.  It  is  covered  by  the  velum  interpositum,  which  intervenes  between  it 
and  the  splenium  of  the  corpus  callosum.  It  is  an  upgrowth  from  the  second 
cerebral  vesicle  (hence  the  name  epiphysis),  and  is  at  first  hollow,  but  soon 
becomes  solid  and  loses  its  connection  with  the  ventricular  cavity.  It  is 
retained  in  its  position  by  a  duplicature  of  pia  mater,  derived  from  the  under 
surface  of  the  velum  interpositum,  which  almost  completely  invests  it.  The 
pineal  gland  is  about  four  lines  in  length  and  from  two  to  three  in  width  at 
its  base,  and  is  said  to  be  larger  in  the  child  than  in  the  adult,  and  in  the 
female  than  in  the  male.  It  is  attached  on  either  side  by  a  flattened  stalk 
or  peduncle  of  white  matter,  the  pedunculus  conaxii  (habenula).  This  stalk 
consists  of  two  laminae,  upper  and  lower,  separated  by  a  little  recess,  the 
pineal  recess  (recessus  pinealis).  The  lower  lamina  is  prolonged  into  the  pos- 
terior commissure.  The  upper  divides  into  two  strands,  the  peduncles  of  the 
pineal  gland  (striae  pinealis) ;  these  extend  on  either  side  along  the  optic  thalamus 
at  the  junction  of  its  mesial  and  upper  surfaces  to  the  anterior  pillars  of  the 
fornix,  with  which  they  blend.  The  two  stalks  join  together  at  their  posterior 
extremity,  in  front  of  the  pineal  gland,  forming  a  sort  of  festoon,  and  the  base  of 
the  gland  is  connected  to  their  posterior  margin  at  the  point  of  junction. 

Structure. — ^The  pineal  gland  consists  of  a  number  of  follicles,  lined  by  epithe- 
lium, and  connected  together  by  ingrowths  of  connective  tissue.  The  follicles  con- 
tain a  transparent  viscid  fluid  and  a  quantity  of  sabulous  matter  named  brain  sand 
(acervulus  cerebri),  composed  of  phosphate  and  carbonate  of  lime,  phosphate  of 
magnesia  and  ammonia,  with  a  little  animal  matter.  These  concretions  are  almost 
constant  in  their  existence,  and  are  present  at  all  periods  of  life.  They  are  found 
upon  the  surface  of  the  pineal  body  and  occasionally  upon  its  peduncles. 

Morphologically  the  pineal  gland  is  regarded  as  the  homologue  of  the  structure 
termed  the  pineal  eye  of  the  lizards.  In  these  reptiles  the  epiphysis  cerebri  is 
attached  by  an  elongated  stalk  and  projects  through  the  parietal  foramen.  Its 
extremity  lies  immediately  under  the  epidermis,  and  on  microscopic  examination 
presents,  in  a  rudimentary  fashion,  structures  similar  to  those  found  in  the  eyeball. 

III.  The  Mid-brain  (Mesencephalon)  (Figs.  557,  584,  585,  587). 

The  mid-brain  is  the  short  and  constricted  portion  of  the  brain  which  lies  in 
the  opening  of  the  tentorium  cerebelli  (incisura  tentorii)  and  which  connects  the 
pons  Varolii  with  the  inter-brain  and  hemispheres,  and  hence  it  is  frequently 
called  the  isthmus  cerebri  (isthmus  rhombencephali) .  It  is  developed  from  the 
third  cerebral  vesicle,  the  cavity  of  which  becomes  the  aqueduct  of  Sylvius. 
It  comprises  the  crura  cerebri,  the  corpora  quadrigemina,  the  geniculate  bodies, 
and  the  Sylvian  aqueduct.  Its  direction  is  from  before  backward  and  down- 
ward. In  front  and  above  it  is  continuous  with  the  inter-brain;  below  with 
the  pons.  Its  two  surfaces  are  ventral  and  dorsal.  They  are  free,  but  concealed: 
the  ventral  surface  by  the  apices  of  the  temporal  lobes  which  overlap  it;  the  dorsal, 
by  the  overhanging  cerebral  hemispheres.  The  ventral  surface,  when  exposed  by 
drawing  aside  the  temporal  lobes,  is  seen  to  consist  of  two  cylindrical  bundles  of 
white  matter  which  emerge  from  the  pons  and  diverge  as  they  pass  forward  and  out- 
ward to  enter  the  inner  and  under  part  of  either  hemisphere.  They  are  the  cerebral 
peduncles  (crura  cerebri),  and  between  them  is  a  triangular  area,  already  described 
as  part  of  the  interpeduncular  space  (fossa  inter peduncularis)  (see  pp.  884  and  885) ; 
near  the  point  of  divergence  of  the  crura  the  roots  of  the  third  nerve  are  seen  to 
emerge  in  several  bundles  from  a  groove,  the  sulcus  oculomotorius  (sulcus  nervi 
oculomotorii)  (Fig.  570) .  The  dorsal  surface  (Fig.  584)  is  not  visible  until  a  con- 
siderable portion  of  the  cerebral  hemispheres  and  other  overlying  structures  have 


I 


THE    MIDBRAIN 


907 


C.  Quadrigemina. 
Aqueduct. 


Interpeduncular  space. 


Fig.  585. — Transverse  section  of  the 
mid-brain. 


been  removed.  It  then  presents  four  rounded  eminences  placed  in  pairs,  two  in 
front  and  two  behind,  and  separated  from  one  another  by  crucial  depression. 
These  are  termed  the  corpora  quadrigemina  (tubercula  quadrigemina)  (Figs.  584  and 
585).  The  ventral  and  dorsal  surfaces  meet  on  the  side  of  the  mid-brain,  and 
are  separated  from  each  other  by  a  furrow,  the  lateral  groove  (sulcus  lateralis 
mesencephali) ,  which  runs  from  below  upward  and  forward  (Fig.  585). 

If  a  cross-section  be  made  through  the  mesencephalon  (Fig.  585),  it  will  be  seen 
that  each  lateral  half  is  divided  into  two  unequal  portions  by  a  lamina  of  deeply 
pigmented  gray  matter,  named  the  substantia  nigra.  The  postero-superior  portion 
of  the  crus  is  named  the  tegmentum,  and  the  antero-inferior  the  crusta  or  pes.  The 
substantia  nigra  is  curved  on  section  with  its  concavity  upward,  and  extends  from 
the  lateral  groove  externally  to  the  oculomotor 
sulcus  internally.  The  two  crustae  are  in  con- 
tact in  front  of  the  pons,  from  which  point  they 
diverge  from  one  another,  but  the  two  halves  of 
the  tegmentum  are  joined  to  each  other  in  the 
mesial  plane  by  a  prolongation  forward  of  the 
raphe  or  median  septum  of  the  pons.  Laterally' 
the  tegmenta  are  free,  but  dorsally  they  blend 
with  the  corpora  quadrigemina. 

Crusta  or  Pes  (basis  pedunculi)  (Fig.  585) . — 
The  crusta  is  known  as  the  pes  of  the  crus 
cerebri.  The  crustae  are  two  in  number,  are 
semilunar  on  section,  and  are  separated  by  the 
interpeduncular  space  (Fig.  570) .  From  the  front 

of  the  pons  each  crusta  passes  upward,  forward,  and  outward,  enters  the  cerebrum 
to  the  outer  side  of  the  thalamus,  and  its  fibres  enter  and  spread  out  in  the  internal 
capsule  (Figs.  589  and  590) .  The  great  bulk  of  the  fibres  are  limited  to  the  superior 
lamina  of  the  capsule.  The  deep  portion  of  the  crusta  contains  the  intermediate 
bundle  or  tract  (Fig.  590),  the  fibres  of  which  rise  in  the  corpus  striatum  and 
terminate  in  motor  cranial  nuclei  and  the  nucleus  pontis,  and  from  this  nucleus 
fibres  pass  by  way  of  the  middle  peduncle  of  the  cerebellum  to  the  cortex  of  the 
opposite  cerebellar  hemisphere. 

The  superficial  portion  of  the  crusta  contains  three  sets  of  fibres  (Figs.  589 
and  590):  1.  The  outer  one-fifth  is  composed,  according  to  Dejerine,  of  fibres 
which  take  origin  in  the  cortex  of  the  superior,  middle,  and  inferior  temporal 
convolutions,  the  cerebro-cortico-pontal  tract  (tractus  cerebrocorticopontalis  tem- 
poralis). They  pass  through  the  inferior  lamina  of  the  internal  capsule  and 
through  a  portion  of  the  superior  lamina,  and  mostly  terminate  in  the  nucleus 
pontis.  Some  few  of  these  fibres  terminate  in  the  motor  nuclei  of  the  cranial 
nerves.^  2.  The  middle  three-fifths,  which  is  largely  composed  of  motor  fibres, 
is  known  as  the  pyramidal  tract  (fasciculus  longitudinalis  pyramidalis).  These 
fibres  take  origin  in  the  cells  of  the  Rolandic  area  of  the  cortex,  converge  to 
the  internal  capsule,  and  pass  down  through  its  genu  and  through  the  ante- 
rior two-thirds  of  its  posterior  limb  to  the  crusta,  from  which  they  are  pro- 
longed as  longitudinal  fibres  through  the  ventral  portion  of  the  pons  and  as 
the  pyramid  through  the  medulla.  Below  the  medulla  they  pass  into  the  direct 
and  crossed  pyramidal  tracts  of  the  spinal  cord.  The  median  portion  of  the 
pyramidal  tract  occupies  the  genu  of  the  internal  capsule  and  passes  to  the 
muscles  of  the  face  and  the  muscles  of  speech.  The  fibres  which  pass  to  the  arm 
muscles,  in  the  crusta,  are  posterior  and  external  to  the  fibres  which  go  to  the  face. 
Behind  and  external  to  the  arm  fibres  are  the  fibres  to  the  muscles  of  the  trunk 


'  Spitzka;  Santee. 


908  THE  NERVOUS  SYSTEM 

and  leg.  A  few  fibres  from  the  cerebellum  are  placed  among  the  pyramidal  fibres. 
These  fibres  reached  the  pons  by  way  of  the  middle  cerebellar  peduncle,  ascend 
from  the  pons  with  the  longitudinal  fibres,  and  reach  the  crusta.  3.  The  inner 
one-fifth  of  the  crusta  is  formed  by  the  fibres  of  the  median  fillet  {lemniscus 
medialis)  and  motor  fibres  coming  from  the  cortex  in  front  of  the  Rolandic  fissure 
(from  the  prefrontal  lobe).  This  tract  from  the  prefrontal  lobe  descends  through 
the  anterior  limb  of  the  internal  capsule  and  through  the  crusta  and  reaches  the 
nucleus  pontis,  from  which  point  it  is  connected  by  fibres  with  the  cerebellar 
hemisphere  of  the  opposite  side.  It  is  called  the  frontal  cerebro-cortico-pontal  tract 
(tractus  cerebrocorticopontalis  frontalis).  The  median  fillet  is  composed  of  central 
sensory  fibres  from  the  spinal  nerves  and  all  the  cranial  nerves,  except  the 
cochlear  branch  of  the  auditory  (Santee).  It  arises  from  the  fillet,  and  at  the 
lower  part  of  the  crusta  is  situated  at  the  mesial  border.  As  it  ascends  it  courses 
obliquely  outward  to  meet  the  lateral  border  of  the  pyramidal  tract.  It  enters 
the  sub-thalamic  region,  and  ends  in  the  lateral  nucleus  of  the  optic  thalamus. 
Some  of  the  fibres  of  this  tract  reach  the  cortex  by  joining  the  ansa  peduncularis 
and  the  ansa  lenticularis. 

The  Tegmentum  (Fig.  585). — The  tegmentum  (the  cover)  is  that  portion  of  the 
mid-brain  which  is  superior  to  the  substantia  nigra  and  covers  the  two  crustae 
and  the  substantia  nigra.  Its  ventral  surface  is  placed  within  the  concave  sur- 
face of  the  substantia  nigra.  The  internal  geniculate  bodies  and  the  corpora 
quadrigemina  are  upon  its  dorsal  surface.  The  anterior  extremity  of  the 
tegmentum  enters  the  optic  thalami,  and  the  posterior  extremity  is  continued 
into  the  pons.  The  tegmentum  contains  the  aqueduct  of  Sylvius  (p.  912  and 
Figs.  585  and  587). 

Fibres  of  the  Tegmentum  (Fig.  590). — The  pontine  formatio  reticularis,  the  gray 
matter  of  the  floor  of  the  fourth  ventricle,  and  the  longitudinal  fibres  of  the  dorsal 
portion  of  the  pons  are  continued  and  compose  the  tegmentum,  which  structure 
has  upon  its  dorsal  aspect  the  geniculate  and  quadrigeminal  ganglia.  Each  half 
of  the  tegmentum  consists  of  strands  of  longitudinal  white  fibres  separated  from 
each  other  by  transversely  arched  fibres.  There  is  also  a  considerable  quantity  of 
gray  matter.  The  peculiarly  reticulated  structure  formed  by  the  gray  and  white 
matter  is  named  the  formatio  reticularis,  and  is  similar  to  the  structure  met  with  in 
the  pons  and  medulla,  with  which  it  is  continuous. 

The  Red  Nucleus  of  the  Tegmentum  (nucleus  tegmenti)  (Fig.  589) . — ^The  red  nucleus 
of  the  tegmentum  is  a  tract  of  gray  matter  situated  partly  in  the  tegmentum  and 
partly  in  the  subthalamic  tegmental  region  on  either  side  of  the  middle  line.  It  is 
composed  of  numerous  large  cells  which  are  deeply  pigmented.  It  is  pierced  by 
the  fibres  of  the  third  nerve.  The  red  nucleus  sends  fibres  to  the  corpus  dentatum 
by  means  of  the  opposite  superior  peduncles  of  the  cerebellum,  and  also  gives 
off  the  crossed  descending  tract.  The  nucleus  of  Luys  (nucleus  hypothalamicus) 
is  above  and  external  to  the  red  nucleus  and  between  it  and  the  crusta.  It 
receives  fibres  from  the  median  fillet  and  from  the  corpus  striatum,  and  is  con- 
nected by  fibres  to  the  lamina  cinerea  and  tuber  cinereum,  which  are  known  as 
the  commissure  of  Meynert  (Santee). 

The  longitudinal  fibres  in  some  parts  of  the  tegmentum  are  arranged  in  six 
fairly  well-defined  tracts,  which  are  described  as  follows  by  Harris  E.  Santee  in 
the  Anatomy  of  the  Brain  and  Spinal  Cord: 

1.  The  Posterior  Longitudinal  Bundle  (fasciculus  longitudinalis  medialis)  (Fig. 
586)  is  in  large  part  an  associated  tract.  It  lies  by  the  side  of  the  raphe  just  below 
the  aqueduct.  These  fibres  ascend  from  the  gray  substance  of  the  anterior  cornu 
of  the  spinal  cord.  In  the  anterior  column  of  the  cord  they  probably  form  short 
longitudinal  commissures  between  different  segments  of  the  cord.  They  ascend 
through  the  pyramid  of  the  medulla,  form  the  posterior  longitudinal  bundle  of  the 


THE  MID   BRAIN 


909 


pons,  and  enter  the  tegmentum.  The  posterior  longitudinal  bundle,  while  travers- 
ing the  pons,  receives  fibres  from  the  cerebellum,  and  in  the  pons  and  medulla 
receives  fibres  from  the  sensory  nuclei  of  cranial  nerves.  "It  carries  motor  fibres 
from  the  sixth  to  the  third  nerve;  also  descending  motor  fibres  from  the  nucleus 
of  the  motor  oculi  to  the  genu  of  the  seventh  or  facial  nerve."  Soon  after  entering 
the  tegmentum  the  posterior  longitudinal  bundle  decussates  across  the  raph€  with 
the  bundle  of  the  opposite  side.  This  constitutes  the  lower  decussation,  and  the 
decussated  fibres  pass  to  the  nuclei  of  the  third,  fourth,  and  other  cranial  nerves. 
The  undecussated  fibres  ascend,  and  in  the  posterior  commissure  decussate.  This 
is  known  as  the  upper  decussation,  and  the  fibres  enter  "the  pineal  body  and 
stratum  dorsale  of  the  hypothalamic  region." 


Fig.  586.— The  short  tracts  in  the  brain-stem  and  inter-brain.  Sagittal  section  through  the  middle  of  the 
brain-.st em :  mf,  infundibulum;  c.  mam,  corpus  mamillare;  jasc.  Vic,  bundles  of  Vicq  d'Azyr;  /.  teg,  tegmental 
bundle;  perf.  m,  peduncle  of  corpus  mamillare; /asc.  rt,  fasciculus  retroflexus;  jasc.  I.  in/,  posterior  longitudinal 
bundle;  II,  III,  VI,  XII.  corresponding  cranial  nerves;  c,  pineal  gland.     (Jakob.) 

2.  The  Anterior  Longitudinal  Bundle  is  composed  of  fibres  which  pass  from  the 
superior  quadrigeminal  body  to  the  ciliary  centre  (dilator  fibres  of  the  pupil)  and 
other  centres  in  the  spinal  cord. 

3.  The  Fillet  or  Lemniscus  is  "a  segment  in  the  direct  sensory  tract.  It 
carries  spinal  and  cranial  impulses  to  the  corpora  quadrigemina  and  optic 
thalamus."  It  takes  its  chief  origin  from  the  medulla,  and  passes  through  the 
formatio  reticularis  of  the  pons  to  the  ventral  portion  of  the  tegmentum,  where  it 
divides  into  two  portions,  the  interolivary  fillet  and  the  lateral  fillet. 

The  interolivary  fillet  (lemniscus  interolivaris)  arises  from  the  opposite  side  of 
the  medulla  oblongata  (from  the  nucleus  gracilis  and  nucleus  cuneatus),  decus- 
sates with  the  sensory  fibres,  and  terminates  in  the  lateral  nucleus  of  the  thalamus. 
A  bundle  of  fibres  come  off  from  the  interolivary  fillet  soon  after  its  origin  and 


910  THE   NERVOUS    SYSTEM 

passes  to  the  superior  quadrigeminal  bodies.  This  bundle  is  the  upper  or  superior 
fillet  {lemniscus  superior).  The  interoHvary  bundle  after  giving  off  the  superior 
fillet  is  known  as  the  median  or  mesial  fillet  (lemniscus  medialis  or  mesiqjtis).  It 
ascends,  turns  toward  the  ventral  surface  of  the  tegmentum,  passes  through  the 
substantia  nigra,  and  along  the  inner  one-fifth  of  the  crusta  to  the  thalamus,  and 
from  the  thalamus  connection  with  the  cortex  is  established  by  the  ansa  lenticularis 
and  the  ansa  peduncularis. 

The  lower  or  lateral  fillet  {lemniscus  lateralis)  arises  almost  entirely  from  the 
cochlear  nuclei,  and  mostly  from  the  opposite  nucleus.  It  is  situated  in  the  ventral 
part  of  the  tegmentum,  through  which  it  passes  obliquely  and  emerges  at  its  side, 
and  after  crossing  the  superior  peduncle  of  the  cerebellum,  passes  to  the  inferior 
quadrigeminal  bodies.  It  is  reinforced  by  some  fibres  from  the  superior  medullary 
velum.  It  is  a  path  in  the  conduction  of  auditory  impressions.  These  impressions 
pass  from  the  auditory  nerve  to  the  lateral  fillet,  from  this  to  the  inferior  brachium, 
and  then  to  the  cortex  by  the  acoustic  radiation  (Fig.  590). 

4.  The  Superior  Peduncle  of  the  Cerebellum  (brachium  conjunctivum)  (Figs.  590 
and  599)  ascends  from  the  dorsal  surface  of  the  pons.  It  is  connected  to  its  fellow 
peduncle  by  a  band  of  white  matter  called  the  valve  of  Vieussens  {velum  medullare 
anterius)  (Fig.  584).  The  fibres  of  the  superior  peduncles  of  the  cerebellum  pass 
beneath  the  quadrigeminal  bodies,  and  to  a  large  extent  decussate  across  the  raphd 
and  below  the  Sylvian  aqueduct.  It  is  thus  evident  that  the  fibres  from  one-half 
of  the  cerebellum  pass  largely  to  the  opposite  half  of  the  cerebrum.  The  numerous 
crossed  and  the  few  uncrossed  fibres  pass  forward,  enclosing  the  red  nucleus  (in 
which  structure  many  of  the  fibres  terminate  and  from  which  structure  it  obtains 
some  fibres),  and  passes  to  the  "stratum  dorsale  of  the  hypothalamic  region." 

5.  The  Olivary  Fasciculus  (fasciculus  tegmenti  centralis)  (Fig.  589)  arises  from 
the  inferior  olivary  nucleus  of  the  medulla,  ascends  through  the  medulla  and 
pons  to  the  tegmentum,  passes  through  the  decussation  of  the  superior  peduncles 
of  the  cerebellum,  and  ascends  to  the  outer  side  of  the  posterior  longitudinal 
bundle  of  tegmental  fibres,  to  end  in  the  lenticular  nucleus. 

6.  The  Crossed  Descending  Tract  arises  in  the  red  nucleus  (Fig.  589) ,  decussates 
with  the  opposite  tract,  enters  the  lateral  fillet,  reaches  the  medulla,  where  it 
"mingles  with  the  antero-lateral  ascending  cerebellar  tract,"  and  passes  into  the 
pyramidal  tract  of  the  cord,  to  end  in  "the  lateral  horn  and  centre  of  the  gray 
crescent. "  The  nucleus  of  Luys  (Fig.  589)  is  the  anterior  termination  of  the 
substantia  nigra. 

The  Substantia  Nigra  (Figs.  585  and  589).— This,  as  already  stated,  constitutes 
the  central  portion  of  the  mid-brain.  It  is  a  layer  of  deeply  pigmented  gray  matter, 
which  separates  the  crusta  below  from  the  tegm.entum  above.  It  can  be  seen  at 
the  base  of  the  brain  between  the  crustae.  In  this  region  it  is  known  as  the  posterior 
perforated  lamina  (substantia  perforata  posterior)  (Fig.  570) .  In  each  lateral  sulcus 
the  edge  of  the  substantia  nigra  reaches  the  surface  (Fig.  585) .  The  substantia 
nigra  extends  from  the  pons  behind  to  the  corpora  albicantia  and  nucleus  of  Luys 
in  front.  It  is  thicker  internally  than  externally,  where  it  is  partially  divided  up 
by  the  mesial  fillet  passing  from  the  tegmentum  to  the  crusta.  It  is  traversed 
at  its  inner  part  by  some  of  the  fibres  of  origin  of  the  third  cranial  nerve,  which 
emerge  from  the  motor  oculi  groove.  The  cells  are  small  and  multipolar,  and  are 
characterized  by  containing  a  large  amount  of  dark  pigment  granules. 

The  Interpeduncular  Ganglion  (ganglion  interpedunculare)  is  just  in  front  of  the 
pons  in  the  median  line.  Some  fibres  (the  fasciculus  retroflexus)  (Fig.  586)  join 
this  ganglion  to  the  nucleus  habenulae  of  the  thalamus  (Forel,  Santee).  In 
each  half  of  the  substantia  nigra,  laterally  and  anteriorly,  is  a  nucleus  known  as 
the  nucleus  of  Luys  (nucleus  hypothalamicus)  (Fig.  589).  The  zona  incerta  sepa- 
rates the  nucleus  of  Luys  from  the  red  nucleus  of  the  tegmentum. 


THE  MID~BBAIN  911 

The  Corpora  or  Tubercula  Quadrigemina  (Figs.  574, 584,  585, 586,  and  587). — 
The  corpora  or  tubercula  quadrigemina  are  four  rounded  eminences  placed  in  pairs, 
two  in  front  and  two  behind,  and  separated  from  one  another  by  the  crucial  groove 
or  depression.  They  are  situated  on  the  dorsal  surface  of  the  mid-brain,  imme- 
diately behind  the  third  ventricle  and  posterior  commissure,  and  beneath  the 
splenium  of  the  corpus  callosum.  The  anterior  or  upper  pair  (colliculi  superiores), 
called  the  nates,  are  the  larger.  They  are  oval,  their  long  diameter  being  directed 
forward  and  outward,  and  are  of  a  gray  color.  The  posterior  or  lower  pair  (col- 
liculi injeriores),  called  the  testes,  are  hemispherical  in  form,  and  lighter  in  color 
than  the  preceding.  From  the  outer  side  of  each  of  these  eminences  a  prominent 
white  band,  termed  the  brachium,  is  continued  forward  and  outward.  The  band 
from  the  nates  [brachium  quadrigeminum  super ius)  passes  obliquely  outward 
between  the  pulvinar  and  the  inner. geniculate  bodies  into  the  external  geniculate 
body.  The  band  from  the  testes  {brachium  quadrigeminum  inferius)  loses  itself 
beneath  an  oval  prominence  on  the  side  of  the  quadrigeminal  body.  This  promi- 
nence is  calledthe  internal  geniculate  body.  The  corpora  quadrigemina  are  larger  in 
the  lower  animals  than  in  man.  In  fishes,  reptiles,  and  birds  they  are  hollow,  and 
only  two  in  number  (corpora  bigemina) ;  they  represent  the  anterior  quadrigeminals 
of  mammals.  In  these  lower  animals  the  corpora  bigemina  are  frequently  termed 
the  optic  lobes,  because  of  their  connection  with  the  optic  tracts.  In  the  mammalia 
the  corpora  are  four  in  number,  and  solid.  In  the  human  foetus  all  four  bodies 
are  differentiated  by  the  fifth  month,  and  form  at  this  time  a  considerable  propor- 
tion of  the  brain.  In  man  the  anterior  quadrigeminal  bodies  are  sometimes  called 
the  optic  lobes  and  the  posterior  bodies  the  auditory  lobes. 

Structure, — The  corpora  quadrigemina  are  composed  of  white  matter  externally, 
and  gray  matter  within.  The  posterior  pair  consist  almost  entirely  of  gray  matter, 
covered  over  by  a  very  thin  stratum  of  white  substance.  Beneath  the  gray  matter 
is  a  thin  layer  of  white  fibres,  forming  a  part  of  the  lower  fillet.  This  separates 
the  gray  matter  of  the  posterior  corpora  quadrigemina  from  the  central  gray 
matter  of  the  aqueduct.  The  anterior  pair  are  covered  superficially  by  a  thin 
stratum  of  white  matter.  The  stratum  zonale,  the  fibres  of  which  are  fine  and 
arranged  transversely.  Beneath  this  is  the  stratum  cinereum,  a  layer  of  gray 
matter  which  resembles  a  cup,  semilunar  in  shape,  thicker  in  the  centre,  and 
thinning  off  toward  the  margins,  and  consisting  of  numerous  multipolar  cells,  for 
the  most  part  of  small  size,  embedded  in  a  fine  network  of  nerve-fibres.  Below 
this  again  is  the  stratum  opticum  or  upper  gray-white  layer,  characterized  by  the 
large  amount  of  fine  nerve-fibres  which  intersect  the  gray  matter.  These  fibres 
vary  in  size  in  different  parts  of  the  layer,  but  have  for  the  most  part  a  longitudinal 
direction.  The  nerve-cells  between  the  fibres  are  larger,  and  send  their  axis- 
cylinder  processes  into  the  next  stratum.  Finally  there  is  the  stratum  lemnisci, 
or  deep  gray-white  layer,  which  separates  the  rest  of  the  quadrigeminal  body  from 
the  gray  matter  around  the  aqueduct.  It  consists  of  fibres  partly  derived  from 
the  upper  fillet  and  partly  from  the  cells  of  the  preceding  layer.  Interspersed 
among  these  fibres  are  nerve-cells  of  large  size. 

The  anterior  quadrigeminal  body  contains  an  anterior  layer  of  longitudinal 
fibres,  which  takes  origin  in  close  relation  to  the  optic  fibres  and  ends  in  the  ciliary 
centre  of  the  spinal  cord.  In  the  posterior  quadrigeminal  body  the  white  fibres 
are  continuous  posteriorly  with  the  lateral  fillet,  and  are  continuous  laterally  with 
the  brachium.  The  anterior  quadrigeminal  bodies  "associate  optic  fibres  with 
the  nuclei  of  the  third,  fourth,  and  sixth  cranial  nerves  and  with  the  cilio-spinal 
centre  in  the  cervical  cord"  (Santee).  The  posterior  bodies  constitute  "a  way- 
station  in  the  auditory  conduction  path"  (Santee)  (Fig.  590). 

The  Corpora  Geniculata. — The  corpora  geniculata  are  two  small,  oblong 
masses  on  each  side,  situated  behind  and  beneath  the  posterior  end  of  the  optic 


912 


THE   NERVOUS   SYSTEM 


thalamus,  and  named,  from  their  position,  external  and  internal  geniculate  bodies. 
These  two  bodies  are  separated  from  each  other  by  the  brachium  anterius  of  the 
anterior  quadrigeminal  body.  It  is  convenient  and  customary  to  describe  these 
two  bodies  together,  but  the  student  should  bear  in  mind  that  the  corpus  genic- 
ulatum  externum  belongs  in  reality  to  the  optic  thalamus;  the  corpus  geniculatum 
internum,  which  is  part  of  the  tegmentum,  alone  belonging  to  the  mid-brain. 

The  External  Geniculate  Body  (corpus  geniculatum  laterale)  (Fig.  613). — The 
external  geniculate  body  is  of  a  dark  color,  and  presents  a  laminated  arrangement, 
consisting  of  alternate  layers  of  gray  and  white  matter.  Its  cells  are  large,  multi- 
polar, and  pigmented;  their  processes  are  intimately  related  with  the  visual  area 
in  the  cerebral  cortex  of  the  occipital  region  (Fig.  590).  It  is  believed  that  the 
intercellular  gray  matter  of  these  bodies  is  composed,  to  a  considerable  extent,  of 
the  terminations  of  the  optic  nerve,  which  form  synapses  around  the  cells.  About 
80  per  cent,  of  the  optic  fibres  enter  the  external  geniculate  body  (von  Monokow, 
Santee).    It  is,  in  fact,  the  termination  of  the  outer  root  of  the  optic  tract. 

The  Internal  Geniculate  Body  {corpus  geniculatum  mediale)  (Fig.  613) . — The  inter- 
nal geniculate  body  is  the  termination  of  the  inner  root  of  the  optic  tract.     It  seems 


MEN 
ONRO 
RIOR 
MISSURE 


OPTIC    NERVC 
DIBULUM 


Fig.  587. — Median  section  through  the  third  and  fourth  ventricles,  left  half.  M.C.,  middle  commissure.    (Testut.) 

to  receive  some  of  the  fibres  of  the  optic  tract  and  is  "a  way-station  in  the  auditory 
tract"  (Santee).  It  is  smaller  in  size  and  lighter  in  color  than  the  external  genicu- 
late body,  and  does  not  present  a  laminated  arrangement.  It  receives  the  pos- 
terior brachium  from  the  inferior  quadrigeminal  body.  The  internal  geniculate 
bodies  are  connected  with  each  other  through  the  optic  commissure  by  a  band 
of  intercerebral  fibres  of  the  optic  tract  named  Gudden's  commissure.  The  anterior 
quadrigeminal  body,  the  pulvinar,  and  the  external  geniculate  body  are  intimately 
concerned  with  vision.  They  constitute  the  lower  cerebral  centre  for  the  optic 
nerve-fibres  which  end  in  them.  Extirpation  of  the  eyes  in  newly  born  animals 
entails  an  arrest  of  their  development,  but  has  no  effect  on  the  posterior  quadri- 
geminal body  or  the  internal  geniculate  body.  These  latter  also  are  well  developed 
in  the  mole,  in  which  animal  the  superior  quadrigeminal  body  is  rudimentary. 

The  Aqueduct  of  Sylvius  or  Iter  a  Tertio  ad  Quartum  Ventriculum  (aquae- 
ductus  cerebri)  (Figs.  574,  584,  585,  and  587).^This  is  a  narrow  canal,  about 


THE   MID -BRAIN  913 

half  an  inch  in  length  and  from  one-sixteenth  to  one-eighth  of  an  inch  in  height, 
situated  between  the  corpora  quadrigemina  and  the  tegmentum,  and  connecting 
the  third  with  the  fourth  ventricle.  Its  shape  on  transverse  section  varies,  being 
T-shaped  below,  triangular  above,  and  oval  about  the  middle  of  its  course.  It 
is  lined  by  columnar  ciliated  epithelium,  and  is  surrounded  by  a  layer  of  gray 
matter,  called  the  central  gray  matter  of  the  aqueduct,  which  is  continuous  with 
the  gray  matter  of  the  third  and  fourth  ventricles.  This  gray  matter  is  sepa- 
ratetl  above  from  that  of  the  corpora  quadrigemina  by  the  stratum  lemnisci; 
below  the  central  gray  matter  lie  the  posterior  longitudinal  bundle  and  the 
formatio  reticularis  of  the  tegmentum.  The  central  gray  matter  is  more  abun- 
dant below  the  canal  than  above  it.  In  the  gray  matter  are  certain  defined  groups 
of  cells,  which  are  the  nuclei  of  the  third  and  fourth  cranial  nerves. 

Subthalamic  Region. — One  other  structure,  to  which  allusion  has  already 
been  made,  recjuires  mention  in  this  connection;  it  is  the  subthalamic  region.  It  is 
a  prolongation  forward  of  the  tegmentum  of  the  crus  cerebri,  which  becomes  con- 
tinuous with  the  lower  surface  of  the  optic  thalamus.  Toward  the  anterior  part 
of  the  crus  cerebri  the  tegmentum  becomes  thinned  out,  and  is  blended  with  the 
superjacent  portion  of  the  optic  thalamus.  To  this  region,  the  name  subthalamic 
tegmental  region  has  been  given.  In  front  it  is  lost  at  the  base  of  the  brain  in 
the  gray  matter  of  the  anterior  perforated  space,  and  is  continuous  with  the  gray 
matter  of  the  floor  of  the  third  ventricle.  The  subthalamic  tegmental  region  con- 
tains a  forward  prolongation  of  the  red  nucleus,  and  consists  from  above  down- 
ward of  three  layers:  (1)  stratum  dorsale,  which  is  directly  applied  to  the  under 
surface  of  the  optic  thalamus,  and  consists  of  fine  longitudinal  fibres;  (2)  the  zona 
incerta,  a  continuation  forward  of  the  formatio  reticularis  of  the  tegmentum ;  and 
(3)  the  corpus  subthalamicum  or  the  nucleus  of  Luys  (nucleus  of  Luys  or  nucleus 
hypothalamic  us),  a  mass  of  gray  matter  which  on  section  presents  a  lenticular 
shape,  and  is  the  termination  of  the  substantia  nigra. 

Structure  of  the  Cerebrum. — The  cerebrum,  like  the  other  parts  of  the  great 
nerve  centre,  is  composed  of  gray  and  white  matter.  In  order  to  give  some  general 
idea  of  its  construction,  at  all  events  in  part,  it  may  be  compared,  for  the  sake  of 
illustration,  to  a  tree,  the  trunk  of  which  divides  into  two  main  divisions,  and 
these  break  up  into  smaller  branches,  which  finally  end  in  twigs,  to  which  are 
attached  the  leaves,  forming  an  investment  to  the  branches  and  covering  the  whole 
tree.  The  trunk  is  represented  by  the  medulla  oblongata  as  it  passes  through  the 
foramen  magnum;  the  two  main  divisions  by  the  crura  cerebri,  which  break  up 
into  smaller  branches;  these  diverge  from  each  other,  divide  and  subdivide, 
until  they  reach  the  surface  of  the  hemispheres,  where  they  terminate  in  single 
nerve-fibres,  which  are  continuous  with  the  basal  axial  cylinder  processes  of  the 
nerve-cells,  the  representatives  of  the  leaves.  These  cells  are  arranged  on  the 
surface,  covering  the  hemispheres  like  a  cap,  and  constitute  the  cerebral  cortex. 
But  here  the  analogy  ends,  for  in  the  cerebrum  there  are,  in  addition  to  this 
cortex,  other  masses  of  gray  matter  situated  in  the  middle  of  the  brain;  and 
other  white  fibres  besides  the  diverging  ones  that  have  been  mentioned,  and  which 
serve  either  to  connect  the  two  cerebral  hemispheres,  or  to  unite  different  structures 
in  the  same  hemisphere. 

The  White  Matter  of  the  Cerebrum. — The  white  matter  of  the  cerebrum  con- 
sists of  medullated  fibres,  varying  in  size  and  arranged  in  bundles,  separated 
by  neuroglia.  They  may  be  divided  into  three  distinct  systems,  according  to 
the  course  they  take.  1.  Projection  or  peduncular  fibres  (Figs.  588,  589,  and  590), 
which  connect  the  hemisphere  with  the  medulla  oblongata  and  corfl.  2.  Trans- 
verse or  commissural  fibres  (C.C.  in  Fig.  588),  which  unite  together  the  two 
hemispheres.  3.  Association  fibres  (Figs.  591  and  592) ,  which  connect  different 
structures  in  the  same  hemisphere.     Many  of  the  association  fibres  are  collateral 

58 


914 


THE   NEBVOUS   SYSTEM 


branches  of  the  projection  fibres,  but  others  are  the   axones  of  independent 
cells. 

1.  The  Projection  or  Peduncular  Fibres  (Figs.  588,  589,  and  590)  are  either  cen- 
trifugal (motor)  or  centripetal  (sensory),  and  they  connect  the  cerebral  cortex  with 
every  portion  of  the  body,  and  either  project  impulses  from  the  cortex  to  every  por- 
tion of  the  body  or  bring  impressions  from  all  parts  to  the  cortex.    The  basal  ganglia 

intercept  many  projection  fibres, 
especially  centripetal  fibres.  The 
projection  fibres  are  composed  first 
of  the  "medullated  axis-cylinders 
of  the  large  and  medium-sized  pyr- 
amids and  a  few  of  the  polymor- 
phous neurones  in  the  cerebral  cor- 
tex; and  second,  of  medullated  ax- 
ones of  neurones  whose  centres  are 
situated  in  masses  of  gray  matter 
below  the  cerebral  cortex."*  These 
fibres  form  in  the  hemisphere  the 
corona  radiata  and  the  internal 
capsule,  and  in  the  mid-brain  the 
crus.  The  fibres  of  the  crus  are 
arranged  in  two  strata,  the  ventral 
or  superficial  stratum  or  crusta  and 
the  dorsal  or  deep  stratum  or  teg- 
mentum. Between  the  two  strata 
is  the  substantia  nigra. 

The  Centrifugal  or  Motor 
Projection    Fibres. — Most    of 

•  ^^^'-  588.— Section  through  the  frontal  lobe,  showing  the  be-  ^hc   lliotor   fibres    are    iucludcd    in 
ginning  of   the  most  anterior   bundles  of   the  corona  radiata, 

•which  contain  the  first  fibres  of  the  pyramidal  tract  (R).    C.  C,  -{^iQ  crUSta.       Thc  deep   DOl'tlOn  of 
corpus  callosum;  C.  V.,  centrum  semiovale  Vieussenii;  C.  A.,  .    '  .  ^    -^  , 

anterior  limb  of  the  internal  capsule;  ^^ /.,  inferior  frontal  con-  the  Cn*5  IS  COmpOSCd  01   the  mter- 
volution  (base  of  the  third  frontal  convolution — motor  speech  ,.    .       ,         ,.  .        ^    /        r\n'y\ 

centre).    (Jakob.)  mediate  bundle   or  tract  (p.  907), 

and  the  superficial  portion  of  the 
crus  is  composed  of  three  sets  of  fibres  (p.  907):  1.  The  temporal  cerebro-cortico- 
pontal  tract  (tractus  cerehrocortico'pontalis  temporalis),  occupying  the  outer  one- 
fifth  of  the  crus.  2.  The  pyramidal  tract  (fasciculus  longitudinalis  'pyramidalis) , 
occupying  the  middle  three-fifths  of  the  crus.  These  fibres  pass  to  the  pyramid 
of  the  medulla  and  to  the  direct  and  crossed  pyramidal  tracts  of  the  spinal 
cord  A  few  fibres  from  the  cerebellum  are  placed  among  the  pyramidal  fibres. 
They  reach  the  pons  by  way  of  the  middle  cerebellar  peduncle,  ascend  from  the 
pons  with  the  longitudinal  fibres,  and  reach  the  crusta.  3.  The  inner  one- 
fifth  of  the  crusta  is  formed  by  the  median  fillet  and  motor  fibres  coming  from 
the  cortex  in  front  of  the  Rolandic  fissure.  The  tegmentum  contains  some  few 
motor  fibres  arranged  in  several  bundles — viz.,  the  anterior  longitudinal  bundle, 
a  portion  of  the  superior  peduncle  of  the  cerebellum :  the  descending  or  motor 
root  of  the  fifth  nerve,  the  crossed  descending  tract  from  the  red  nucleus.  To 
these  previously  mentioned  motor  fibres  in  the  tegmentum,  San  tee  adds  "certain 
fibres  in  the  formatio  reticularis."^ 

The  Centripetal  or  Sensory  Projection  Fibres. — In  the  tegmentum  are 
the  sensory  fibres,  some  of  the  fibres  of  the  formatio  reticularis,  some  of  the  fibres 
of  the  posterior  longitudinal  bundle,  the  fillets,  most  of  the  fibres  of  the  superior 
cerebellar  peduncle,  the  outer  root  of  the  optic  tract,  and  the  olivary  fasciculus. 
Nearly  all  of  the  bundles  terminate  in  the  basal  ganglia,  "but  the  paths  of  con- 


'  Anatomy  of  the  Brain  and  Spinal  Cord.     By  Harris  E.  Santee. 


«  Ibid. 


THE   MID -BRAIN 


915 


duction  are  continued  through  the  internal  capsule"  (Santee).     In  the  internal 
capsule  the  sensory  projection  fibres  comprise  the  three  systems  of  Flechsig  (the 
cortical  fillet),  the    optic   radiation, 
and  the  acoustic  radiation. 

The  Three  Systems  of  Flech- 
sig.— The  chief  origin  of  the  three 
systems  of  Flechsig  is  in  the  lateral 
nucleus  of  the  thalamus.  The  first 
system  of  Flechsig  is  composed  of 
fibres  of  common  sensation  and  is 
called  the  ansa  peduncularis.  It 
passes  from  the  thalamus  to  the 
cortex  of  the  ascending  frontal  and 
parietal  convolutions.  The  fibres  of 
this  first  system  are  in  the  inferior 
lamina  of  the  internal  capsule,  and 
are  posterior  to  the  pyramidal  tract. 
Some  fibres  of  the  ansa  peduncularis 
pass  through  the  lenticular  nucleus, 
others  pass  through  the  external 
capsule,  but  all  of  them  terminate 
as  do  those  in  the  internal  capsule, 
in  the  cortex.  The  second  system  of 
Flechsig  is  called  the  ansa  lenticularis. 
Its  fibres  convey  impressions  of  com- 
mon sensation.  It  arises  from  the 
thalamus  at  a  higher  level  than  the 
ansa  peduncularis,  and  in  the  in- 
ternal capsule  its  fibres  are  among 
the  pyramidal  fibres.  It  terminates 
in  the  cortex  about  the  central  con- 
volution, the  superior  frontal  con- 
volution, the  paracentral  lobule,  and 
the  limbic  lobe.  Some  fibres  pass 
through  the  internal  capsule  to  the 
lenticular  nucleus  and  aid  in  form- 
ing the  external  capsule.  The  third  FPyc-- 
system  of  Flechsig  is  the  anterior 
stalk  of  the  thalamic  radiation.     It 

arises  ni  the  thalamus,  passes  to  the  Fig.  589.— Scheme  of  the  projection  fibres  of  the  cerebral 

frontal   nnrtinn   nf    tlio  infernal    r.Qt-.  cortex.      Cc.   Corpus   callosum.      Cr.  Internal   capsule,   into 

lionidl   portion   or    me  internal   cap-  ^hich  fibres  pa.ss  from  the  cortex  above  the  Sylvian  fissure. 

Sule,  and   reaches  the   inferior,  mid-  ^S{  Caudate  nucleus.     NL    Lenticular  nucleus.      Th.  Optic 

.                                     .                     .jiv,i.vi,  liiiM  thalamus,  m  which  many  fibres  from  all  parts  of  the  cortex 

die,    and    superior    frontal    COnVolu-  ^^^-     Cip.  Posterior  divi.sion  of  the  internal  cap.sule  (the  sen- 

.                  ,    ,    ^                (•         •                    m(i  sory  tract)-     Ci»l.  Sublenticular  part  of  the  internal  capsule, 

tlOIlS  and  the  gyrus  forniCatUS.     The  containing  fibres  of  auditory  tract  and  fibres  to  the  thalamus 

.1  •     1             ,              ,  from  the  cortex  below  the  Sylvian  fissure.     Ch.  Luys's  body. 

tnircl    system   also   conveys  common  NR.  Red  nucleus  of    tegmentum.      Ln.    Locus  niger.      YP. 

oo,Tc/-.T.-ir  It-t.               *  Tract  from  capsule  to  pons.     Po.  Pons.      NP.  Gray  matter 

bensor\    impressions.  of  pons.    Oi.  OUve.     Py.  Pyramidal  tract  in  medulla,  passing 

TVip  f>nti/»  ra/li'Q+iftn  (Ti  ir,  "C.'r,    KO^^  *<3    PPyd.   anterior   median   column   of    cord,  and  to  FPyc, 

i  ne  optic  raaiatlOn  [U  in  l^lg.  59U)  lateral  column  of  cord  of  opposite  side,  and  to  fPyh,  lateral 

takes  oricrin    in   tlif»  nnlvintir  nf    +]io  column  of  cord  of  same  side.     fi.  Medulla.      (Dejerine,  Anat- 

idKtt,  origin    in  tne  pUiVinar  Ot    tne  omie  des  Centres  Nerveux,  vol.  ii.  p.  2.) 

thalamus  and  in  the  external  corpus 

geniculatum.    The  fibres  pass  back  of  the  lenticular  nucleus  and  reach  the  cortex 

of  the  cuneate  lobe,  in  which  region  the  corresponding  half  of  each  retina  is 

represented. 

The  acoustic  radiation  (D  in  Fig.  590)  with   the  inferior  brachium  from  the 
inferior  quadrigeminal  body,  according  to  Barker,  constitute  the  continuation  of 


916 


THE   NERVOUS  SYSTEM 


the  auditory  path  "from  the  end  of  the  lateral  fillet,  in  the  inferior  qiiadrigeminal 
body,  to  the  internal  geniculate  body,  and  then,  through  the  retro-lenticular  part  of 
the  internal  capsule,  to  the  transverse  temporal  gyri  and  the  third  and  fourth 
fifths  of  the  superior  temporal  convolution."* 

2.  The  Transverse  or  Commissural  Fibres  (Figs.  572,  573,  and  C.C.  in  Fig.  588) 
connect  the  two  hemispheres.  They  include:  (a)  the  transverse  fibres  of  the 
corpus  callosum  (p.  886) ;  (6)  the  anterior  commissure  (p.  896) ;  (c)  the  posterior 
commissure  (p.  903),  and  have  already  been  described. 


Fig.  590. — The  projection  tracts  joining  the  cortex  with  lower  nerve  centres.  Sagittal  section,  showing  the 
arrangements  of  tracts  in  the  internal  capsule.  A,  tract  from  the  frontal  lobe  to  the  anterior  half  of  the  capsule, 
thence  in  part  to  the  optic  thalamus,  A-,  and  in  part  to  the  pons,  and  thus  to  the  cerebellar  hemisphere  of  the 
oppcsite  side;  B,  motor  tract  from  the  central  convolutions  to  the  facial  nucleus  in  the  pons  and  to  the  spinal 
cord;  C,  sensory  tract  from  posterior  columns  of  the  cord,  through  the  posterior  part  of  the  medulla,  pons,  cru.s, 
and  capsule  to  the  parietal  lobe;  D,  visual  tract  from  the  optic  thalamus  (OT)  to  the  occipital  lobe;  E,  auditory 
tract  from  the  int.  geniculate  body  (to  which  a  tract  passes  from  the  VIII .  N .  nucleus)  to  the  temporal  lobe; 
F,  superior  cerebellar  peduncle;  G,  middle  cerebellar  peduncle;  H,  inferior  cerebellar  peduncle;  CN,  caudate 
nucleus;  CQ,  corpora  quadrigemina.     The  numerals  refer  to  the  cranial  nerves.      (Starr.) 

3.  The  Association  Fibres  (Figs.  591  and  592)  connect  different  structures  in  the 
same  hemispheres,  and  are  in  or  near  to  the  cortex.  They  take  origin  from  the 
small  pyramidal  and  polymorphous  cells  of  the  deep  layer  of  the  cortex.  Their 
direction  is  parallel  to  the  surface  of  the  hemisphere,  and  in  their  course  they 
cross  the  projection  and  commissural  fibres.  They  are  of  two  kinds:  (1)  those 
which  unite  adjacent  convolutions,  short  association  fibres;  (2)  those  which  pass 
between  more  distant  parts  in  the  same  hemisphere,  long  association  fibres. 

The  short  association  fibres  are  situated  immediately  beneath  the  gray  substance  i 
of  the  cortex  of  the  hemispheres,  and  connect  together  adjacent  convolutions. 
They  constitute  subcortical  tracts  and  are  divided  into  arcuate  fibres  and  tangen- 
tial fibres.    Some  of  these  fibres  connect  the  "visual  sensory  area  with  the  visual 
memory  area,  and  the  auditory  sensory  with  the  auditory  memory  area."^ 

The  long  association  fibres  associate  cerebral  centres  which  are  far  apart.    They  j 
are  gathered  into  bundles  and  dip  down  deep  into  the  centrum  ovale.     Theyi 


'  Anatomy  of  the  Brain  and  Spinal  Cord,  by  Harris  E.  Santee 


2  Ibid. 


THE   MID -BRAIN 


917 


include  the  following:  (a)  the  uncinate  fasciculus;  (6)  the  cingulum;  (c)  the  superior 
longitudinal  fasciculus;  {d)  the  inferior  longitudinal  fasciculus;  (e)  the  perpendicular 
fasciculus;  (/)  the  fornix;  {g)  the  occipito-frontal  fasciculus. 


Loee 
Fig.  591. — Diagram  showing  association-fibres  of  the  hemisphere.     (Testut.) 

(a)  The  Uncinate  Fasciculus  (fasciculus  uncinatus)  (Fig.  592) . — The  unci- 
nate fasciculus  passes  across  the  bottom  of  the  Sylvian  fissure  and  connects  the 


Fio.  592. — The  long  association  fibres.^  A  shows  the  bundles  contained  in  the  lateral  white  substance  of  the 
hemispheres;  B,  those  in  the  mesial  white  matter.  At  the  upper  border  a  few  short  association  bundles  are 
shown  diagrammatically.      (Jakob.) 

uncinate  convolution  with  the  orbital  portion  of  the  frontal  lobe.  Barker  points 
out  that  this  fasciculus  joins  the  third  frontal,  internal  orbital,  and  posterior 
orbital  convolutions  with  the  limbic  lobe. 


918  THE  NERVOUS  SYSTEM 

(b)  The  Cingulum  or  the  Fillet  of  the  Gyrus  Fornicatus  (Fig.  592)  is 
a  band  of  white  matter  which  encircles  the  hemisphere  in  an  antero-posterior 
direction,  lying  in  the  substance  of  the  convolution  of  the  corpus  callosum. 
Commencing  in  front  at  the  anterior  perforated  space,  it  passes  forward  and 
upward  parallel  with  the  rostrum,  wind  around  the  genu,  runs  in  the  convolu- 
tion from  before  backward,  immediately  above  the  corpus  callosum,  turns  around 
its  posterior  extremity,  and  passes  into  the  Hippocampus  major,  through  which 
it  courses  to  its  anterior  extremity.  According  to  Beem  there  are  three  sets  of 
fibres  in  the  cingulum.  The  anterior  fibres  join  the  internal  olfactory  root  and 
the  anterior  perforated  lamina  with  the  front  of  the  frontal  lobe.  The  horizontal 
fibres  join  the  gyrus  fornicatus  with  the  frontal  lobe.  The  posterior  fibres  join 
the  fusiform  convolution  (the  fourth  temporal)  with  the  hippocampal  convolution 
and  the  temporal  lobe.^ 

(c)  The  Superior  Longitudinal  Fasciculus  {jasciculus  longitudinalis  supe- 
rior) (Fig.  592). — The  superior  longitudinal  fasciculus  is  beneath  the  convex 
surface  of  the  hemisphere.  It  joins  the  frontal  cortex  with  the  parietal  and  tem- 
poral cortex  and  brings  into  relation  the  motor  speech  centres  and  the  centres  of 
auditory  and  visual  memories. 

(d)  The  Inferior  Longitudinal  Fasciculus  (fasciculus  longitudinalis  infe- 
rior) (Fig.  592). — The  inferior  longitudinal  fasciculus  associates  the  centres  of 
auditory  and  visual  memory.  It  is  a  collection  of  fibres  which  connects  the 
temporal  and  occipital  lobes,  running  along  the  outer  wall  of  the  descending 
and  posterior  cornua  of  the  lateral  ventricle. 

(e)  The  Perpendicular  Fasciculus  or  Fasciculus  Rectus  (Fig.  592) . — 
The  perpendicular  fasciculus  runs  vertically  in  front  of  the  occipital  lobe,  and 
connects  the  inferior  parietal  lobule  with  the  second  and  third  temporal  convolu- 
tions, and  also  connects  the  superior  occipital  convolution  with  the  inferior  occipital 
and  the  fourth  temporal  convolutions. 

(/)  The  Fornix  (corpus  fornicis)  (Fig.  586) . — The  fornix  by  its  anterior  pillar  is 
connected  with  the  corpus  albicans  and  by  means  of  the  bundle  of  Vicq  d'Azyr 
with  the  optic  thalamus.  Most  of  the  posterior  pillar  ends  in  the  hippocampus 
major,  but  some  of  the  fibres  (the  corpus  fimbriatum)  go  to  the  uncinate  con- 
volution. Through  the  fibres  of  the  lyra  it  probably  also  unites  the  opposite 
hippocampal  convolutions. 

{g)  The  Occipito-frontal  Fasciculus  of  Forel  {fasciculus  occipitofron- 
talis)  (Fig.  592). — The  occipito-frontal  fasciculus  is  placed  between  the  cingulum 
and  the  superior  longitudinal  fasciculus.  It  connects  the  frontal  cortex  with  the 
occipital  cortex.    Some  regard  it  as  a  part  of  the  corpus  callosum. 

The  Gray  Matter  of  the  Cerebrum. — The  gray  matter  of  the  cerebrum,  in 
accordance  with  its  situation,  is  disposed  in  three  great  groups:  (1)  The  gray 
matter  of  the  cerebral  cortex  or  cortical  gray  matter.  (2)  The  gray  matter  of  the 
ganglia  or  ganglionar  gray  matter.      (3)  The  central  or  ventricular  gray  matter. 

The  Gray  Matter  of  the  Cortex. — ^The  cortex,  bark  or  envelope  of  the  cerebrum, 
is  a  thin  layer  of  gray  matter  on  the  surface,  which  encompasses  the  white  matter 
of  the  hemispheres  {centrum  ovale).  The  cortex  has  been  mapped  out  into  definite 
areas  and  centres,  each  of  which  is  connected  with  a  well-defined  function 
(p.  952). 

On  examining  a  section  through  one  of  the  convolutions  of  the  Rolandic  area 
with  a  lens,  it  is  seen  to  consist  of  alternating  white  and  gray  layers  thus  disposed 
from  the  surface  inward:  (1)  a  thin  layer  of  white  substance;  (2)  a  layer  of  gray 
substance;  (3)  a  second  layer  of  white  substance  (outer  band  of  Baillarger  or 
band  of  Gennari);  (4)  a  second  gray  layer;  (5)  a  third  white  layer  (inner  band  of 

'  Anatomy  of  the  Brain  and  Nervous  System.    By  Harris  E.  Santee. 


THE  MID- BRAIN 


919 


Molectilar  layer 


Layer  of  small 

pyramidal  cells. 


Baillarger) ;  (C)  a  third  gray  layer,  which  rests  on  the  medullary  substance  of  the 
convolution. 

The  cortex  is  made  up  of  nerve-cells  which  vary  in  size  and  shape,  and  of  nerve- 
fibres,  some  of  which  are  medullated,  but  most  of  which  are  non-medullated, 
embedded  in  a  matrix  of  neuroglia. 

The  nerve-cells  in  a  typical  section  of  the  cortex  are  arranged  in  five  layers  (Fig. 
593);  named  from  the  surface  inward  as  follows:  (1)  the  molecular  layer;  (2)  the  layer 
of  small  pyramidal  cells;  (3)  the  layer  of  large  pyramidal  cells;  (4)  the  layer  of  poly- 
morphous cells;  (5)  the  layer  of  fusiform  cell-bodies  (Santee)  (not  shown  in  Fig.  593). 

The  Molecular,  the  Superficial  or  the  Neuroglia  I^ayer. — This  layer 
is  immediately  adjacent  to  the  pia  mater.  Neuroglia  constitutes  the  greatest 
amount  of  the  superficial  layer; 
hence  its  other  name  of  neuroglia 
layer.  In  this  layer  the  cells  are 
irregular  and  are  known  as  the  neu- 
rones of  Cajal.  The  cells  are  polyg- 
onal, triangular,  and  fusiform  in 
shape,  and  are  associative  in  func- 
tion. Each  polygonal  cell  gives  off 
some  four  or  five  dendrites,  while 
its  axones  may  arise  directly  from 
the  cell  or  from  one  of  its  dendrites. 
The  axones  and  dendrites  of  these 
cells  ramify  in  the  molecular  layer. 
Each  triangular  cell  gives  off  two  or 
three  dendrites,  from  one  of  which 
the  axone  arises,  the  dendrites  and 
the  axone  ramifying  in  the  molec- 
ular layer.  The  fusiform  cells  are 
placed  with  their  long  axes  parallel 
to  the  surface  and  are  mostlybipolar, 
each  pole  being  prolonged  into  a 
dendrite,  which  runs  horizontally  for 
some  distance  and  furnishes  ascend- 
ing branches.  Their  axones,  two  or 
three  in  number,  arise  from  the  den- 
drites, and,  like  them,  take  a  hori- 
zontal course,  giving  off  numerous 
ascending  collaterals.  The  distri- 
bution of  the  axones  and  dendrites 
of  all  three  sets  of  cells  is  limited  to 
the  molecular  layer. 

Besides  the  neuroglia,  the  cells, 
and  the  gray  fibres,  this  layer  contains  medullated  nerve-fibres  arranged  in  a 
network  and  constituting  the  superficial  white  layer. 

The  Layer  of  Small  and  the  Layer  of  Large  Pyramidal  Cells. — The 
cells  in  the  second  and  third  layers  may  be  studied  together,  since,  with  the  excep- 
tion of  the  difference  in  size  and  the  more  superficial  position  of  the  smaller  cells, 
they  resemble  each  other.  The  body  of  each  cell  is  pyramidal  in  shape,  its  base 
being  directed  to  the  deeper  parts  and  its  apex  toward  the  surface.  It  contains 
granular  pigment,  and  stains  deeply  with  ordinary  reagents.  The  nucleus  is 
nucleolated,  of  large  size,  and  round  or  oval  in  shape.  The  base  of  the  cell  gives 
off  the  axone,  and  this  passes  into  the  central  white  substance,  giving  off  collaterals 
in  its  course,  and  is  distributed  as  a  projection,  commissural,  or  association  fibre. 


Layer  of  large 
pyramidal  cells. 


Polymorphous 
layer. 


White  medullary 

substance. 


Fig.  593. — The  four  layers  of  cells  in  the  cerebral  cortex. 
Modified  from  Testut.     (After  Cajal.) 


920  THE    NERVOUS  SYSTEM 

Both  the  apical  and  basal  parts  of  the  cell  give  off  dendrites.  The  apical  dendrite 
is  directed  toward  the  surface,  and  ends  in  the  molecular  layer  by  dividing  into 
numerous  branches,  all  of  which  may  be  seen,  when  prepared  by  the  silver  or 
methylene-blue  method,  to  be  studded  with  projecting  bristle-like  processes.  The 
larger  pyramidal  cells,  especially  in  the  Rolandic  area,  may  exceed  50//  in  length 
and  40//  in  breadth,  and  are  termed  giant  cells.  The  chief  function  of  the  small 
pyramids  is  commissural  and  associative.  The  chief  function  of  the  large  pyramids 
is  motor,  but  they  have  also  commissural  and  associative  functions. 

Layer  of  Polymorphous  Cells. — The  cells  in  this  layer,  as  their  name  implies, 
are  very  irregular  in  contour,  the  commonest  varieties  being  of  a  spindle,  star, 
oval,  or  triangular  shape.  Their  dendrites  are  directed  outward,  toward,  but  do 
not  reach,  the  molecular  layer;  their  axones  pass  into  the  subjacent  white  matter. 
From  this  layer  come  commissural  fibres,  long  association  fibres,  and  some  pro- 
jection fibres. 

There  are  two  other  kinds  of  cells  in  the  cerebral  cortex,  but  their  axones  pass 
in  a  direction  opposite  to  that  of  the  pyramidal  and  polymorphous  cells,  among 
which  they  lie.  They  are:  (a)  the  cells  of  Golgi,  the  axones  of  which  do  not 
become  medullated,  but  divide  immediately  after  their  origin  into  a  large  number 
of  branches,  which  are  directed  toward  the  surface  of  the  cortex;  {h)  the  cells  of 
Martinotti,  which  are  chiefly  found  in  the  polymorphous  layer.  Their  dendrites 
are  short,  and  may  have  an  ascending  or  descending  course,  while  their  axones 
pass  out  into  the  molecular  layer  and  form  an  extensive  horizontal  arborization. 

Layer  of  Fusiform  Cell-bodies. — It  receives  the  name  of  the  claustral 
formation,  because  it  is  formed  like  the  claustrum.  This  layer  is  not  sharply 
defined  from  the  white  matter  beneath;  the  change  from  one  to  the  other  is  gradual. 
The  long  axes  of  most  of  the  cells  are  perpendicular  to  the  surface  of  the  hemi- 
sphere, but  beneath  the  fissures  they  are  parallel  to  the  surface  (San tee).  "The 
commissural  and  long  association  fibres  belong,  for  the  most  part,  to  the  fusi- 
form and  polymorphous  neurones."^ 

Nerve-fibres. — These  fill  up  a  large  part  of  the  intervals  between  the  cells.  Some 
of  these  fibres  form  fascicului;  some  are  isolated,  and  others  are  arranged  in 
plexuses.  They  may  be  medullated  or  non-medullated — the  latter  comprising 
the  axones  of  the  smallest  pyramidal  cells  and  the  cells  of  Golgi.  In  their  direction 
the  fibres  may  be  either  transverse,  the  transverse  tangential  or  horizontal  fibres, 
or  vertical,  the  vertical  or  radial  fibres.  The  transverse  fibres  run  parallel  to  the 
surface  of  the  hemisphere,  intersecting  the  vertical  fibres  at  a  right  angle.  They 
consist  of  several  strata,  of  which  the  following  are  the  most  important:  (1)  a 
stratum  of  white  fibres  covering  the  superficial  aspect  of  the  molecular  layer;  (2) 
the  band  of  Bechterew,  found  in  certain  parts  of  the  superficial  portion  of  the 
layer  of  the  smaller  pyramidal  cells;  (3)  the  external  or  outer  band  of  Baillarger 
or  ths  band  of  Gennari,  which  runs  through  the  layer  of  large  pyramidal  cells; 
(4)  the  internal  band  of  Baillarger,  which  intervenes  between  the  layer  of  large 
pyramidal  cells  and  the  polymorphous  layer.  According  to  Cajal,  the  transverse 
fibres  consist  of  (a)  the  collaterals  of  the  pyramidal  and  polymorphous  cells  and 
of  the  cells  of  Martinotti;  (6)  the  arborizations  of  the  axones  of  Golgi's  cells; 
(c)  the  collaterals  and  terminal  arborizations  of  the  projection,  commissural, 
or  association  fibres.  The  vertical  fibres. — Some  of  these— viz.,  the  axones  of  the 
pyramidal  and  polymorphous  cells — ^are  directed  toward  the  central  white  matter, 
while  others,  the  terminations  of  the  commissural,  projection,  or  association  fibres, 
pass  outward  to  end  in  the  cortex.  The  axones  of  the  cells  of  Martinotti  are  also 
ascending  fibres. 

In  certain  parts  of  the  cortex  this  typical  structure  is  departed  from.    The  chief 

'  Anatomy  of  the  Brain  and  Spinal  Cord.     By  Harris  E.  Santee. 


THE  MIB-BBAIN  921 

of  these  regions  are:  (1)  the  occipital  lobe,  (2)  the  hippocampus  major,  (3)  the 
dentate  convolution,  and  (4)  the  olfactory  bulb. 

Special  Tjrpes  of  Gray  Matter.  1.  The  Occipital  Lobe. — In  the  cuneiis  and 
the  calcarine  fissure  of  the  occipital  lobe,  Cajal  has  recently  described  as  many  as 
nine  layers.  Here  the  inner  band  of  Baillarger  is  absent;  the  outer  band  of  Bail- 
larger  or  band  of  Gennari  is,  on  the  other  hand,  of  considerable  thickness.  If  a 
section  be  examined  microscopically,  an  additional  layer  is  seen  to  be  interpolated 
between  the  molecular  layer  and  the  layer  of  small  pyramidal  cells.  This  extra 
layer  consists  of  two  or  three  strata  of  fusiform  cells,  the  long  axes  of  which  are  at 
right  angles  to  the  surface.  Each  cell  gives  off  two  dendrites,  external  and  internal, 
from  the  latter  of  which  the  axone  arises  and  passes  into  the  white  central  sub- 
stance. In  the  layer  of  small  pyramidal  cells,  fusiform  cells,  identical  with  the 
above,  are  seen,  as  well  as  ovoid  or  star-like  cells  with  ascending  axones,  the  cells 
of  Martinotti.  This  area  of  the  cortex  forms  the  visual  centre,  and  it  has  been 
shown  by  Dr.  J.  S.  Bolton*  that  in  old-standing  cases  of  optic  atrophy  the  thick- 
ness of  Gennari's  band  is  reduced  by  nearly  50  per  cent. 

2.  The  Hippocampus  Major. — In  the  hippocampus  major  the  molecular  layer  is 
very  thick  and  contains  a  large  number  of  Golgi  cells.  It  has  been  divided  into 
three  strata:  (a)  S.  convolutum  or  S.  granulosum,  containing  many  tangential 
fibres;  (6)  S.  lacunosum,  presenting  numerous  lymphatic  or  vascular  spaces;  (c) 
S.  radiatum,  exhibiting  a  rich  plexus  of  fibrils.  The  two  layers  of  pyramidal  cells 
are  condensed  into  one,  and  the  cells  are  mostly  of  large  size.  The  axones  of  the 
cells  in  the  polymorphous  layer  may  run  in  an  ascending,  descending,  or  horizontal 
direction.  Between  the  polymorphous  layer  and  the  ventricular  ependyma  is  the 
white  substance  of  the  alveus. 

3.  The  Dentate  Convolution. — In  the  rudimentary  dentate  convolution  the  molec- 
ular layer  contains  some  pyramidal  cells,  while  the  layer  of  pyramidal  cells  is 
almost  entirely  represented  by  small  ovoid  cells. 

4/  The  Olfactory  Bulb. — In  many  of  the  lower  animals  this  contains  a  cavity 
which  communicates  through  the  hollow  olfactory  stalk  with  the  cavity  of  the 
lateral  ventricle.  In  man  the  original  cavity  is  filled  up  by  neuroglia  and  its 
wall  becomes  thickened,  but  much  more  so  on  its  ventral  than  on  its  dorsal  aspect. 
Its  dorsal  part  contains  a  small  amount  of  gray  and  white  matter,  but  it  is  scanty 
and  ill  defined.  A  section  through  the  ventral  part  shows  it  to  consist  of  the 
following  layers  from  without  inward.  (1)  A  layer  of  olfactory  nerve-fibres,  which 
are  the  non-medullated  axones  prolonged  from  the  olfactory  cells  of  the  nose,  and 
which  reach  the  bulb  by  passing  through  the  cribriform  plate  of  the  ethmoid  bone. 
At  first  they  cover  the  bulb,  and  then  penetrate  it  to  end  by  forming  synapses 
with  the  dendrites  of  the  mitral  cells,  presently  to  be  described.  (2)  Glomerular 
layer  {stratum  glomerulosum). — This  contains  numerous  spheroidal  reticulated 
enlargements,  termed  glomeruli,  which  are  produced  by  the  branching  and  arbor- 
ization of  the  processes  of  the  olfactory  nerve-fibres  with  the  descending  dendrites 
of  the  mitral  cells.  (3)  Molecular  layer. — ^This  layer  is  formed  of  a  matrix  of 
neuroglia,  embedded  in  which  are  the  mitral  cells.  These  cells  are  pyramidal  in 
shape,  and  the  basal  part  of  each  gives  off  a  thick  dendrite  which  descends  into 
the  glomerular  layer,  where  it  arborizes  as  indicated  above,  and  others  which 
interlace  with  similar  dendrites  of  neighboring  mitral  cells.  The  axones  pass 
through  the  next  layer  into  the  white  matter  of  the  bulb,  from  which,  after  becom- 
ing bent  on  themselves  at  a  right  angle,  they  are  continued  into  the  olfactory  tract. 
(4)  N erve-fihre  layer. — This  lies  next  the  central  core  of  neuroglia,  and  its  fibres 
consist  of  the  axones  or  afferent  processes  of  the  mitral  cells  which  are  passing  to 
the  brain;  some  efferent  fibres  are,  however,  also  present,  and  terminate  in  the 

^  Phil.  Trans,  of  Royal  Society,  Series  B,  vol.  exciii.  p.  165. 


922  ^'HE   NERVOUS  SYSTEM 

molecular  layer,  but  nothing  is  known  as  to  their  exact  origin.  It  is  to  be  remem- 
bered that  the  olfactory  path  is  uncrossed  or  almost  completely  uncrossed. 

The  Gray  Matter  of  the  Ganglia  or  the  Ganglionar  Gray  Matter. — These  ganglia 
have  been  previously  described.  They  are  as  follows:  The  corpus  striatum,  the 
optic  thalamus,  the  external  geniculate  body,  the  internal  geniculate  body,  the 
nucleus  of  Luys,  the  red  nucleus  of  the  tegmentum,  the  anterior  quadrigeminal 
body,  the  posterior  quadrigeminal  body,  the  substantia  nigra,  and  the  inter- 
peduncular ganglion. 

The  €entral  or  Ventricular  Gray  Matter. — This  includes  the  lamina  cinerea,  the 
tuber  cinereum,  the  middle  commissure,  the  nuclei  of  the  third  and  fourth 
cranial  nerves,  and  the  gray  matter  about  the  aqueduct  of  Sylvius. 

IV.  The  Hind-brain  (Rhombencephalon). 

From  the  hind-brain  or  rhombencephalon,  as  previously  stated,  come  two  vesi- 
cles, the  metencephalon,  or  upper  portion  of  the  hind-brain  or  the  hind-brain  proper, 
and  the  myelencephalon,  or  lower  portion  of  the  hind-brain.  From  the  metence- 
phalon come  the  pons  and  the  cerebellum.  From  the  myelencephalon  comes  the 
medulla  oblongata.  The  original  hind-brain  remains  in  the  brain  of  the  adult 
as  the  fourth  ventricle. 

Pons  Varolii  (Figs.  557,  599,  and  693). — The  pons  Varolii  is  the  bond  of  union 
between  the  various  segments  of  the  encephalon,  connecting  the  cerebrum  above, 
the  medulla  oblongata  below,  and  the  cerebellum  behind.  It  lies  upon  a  portion 
of  the  clivus,  the  groove  of  bone  between  the  foramen  magnum  and  the  dorsum 
sellae,  and  is  situated  above  the  medulla  oblongata,  below  the  crura  cerebri,  and 
between  the  hemispheres  of  the  cerebellum.  It  is  about  an  inch  in  length,  an 
inch  in  thickness,  and  an  inch  and  a  half  in  width.  It  presents  four  surfaces:  the 
superior  surface,  which  is  attached,  by  direct  continuation  of  fibres,  to  the  mid- 
brain; the  inferior  surface,  which  is  continuous  with  the  medulla  oblongata;-  the 
anterior  or  ventral  and  the  posterior  or  dorsal  surfaces  are  free. 

The  Anterior  or  Ventral  Surface,  the  Tuber  Annulare  or  Base  {^ars  hasilaris  pontis)^ 
is  very  prominent,  markedly  convex  from  side  to  side,  but  less  so  from  before  back- 
ward. It  consists  of  transverse  white  fibres  (Fig.  594) ,  which  arch  like  a  bridge 
across  the  middle  line,  and  on  either  side  are  gathered  together  into  a  compact  mass, 
forming  the  middle  peduncle  of  the  cerebellum  (Fig.  599).  Above  and  below  it 
presents  a  well-defined  border;  below,  its  transverse  fibres  slightly  overlap  the 
pyramidal  bodies  of  the  medulla,  which  disappear  into  its  substance;  above,  the 
transverse  fibres  slightly  overlap  the  crura  cerebri  which  emerge  from  it.  This 
surface  rests  upon  the  clivus  of  the  sphenoid  bone,  and  presents  in  the  middle 
line  a  longitudinal  groove  (sulcus  hasilaris)  (Fig.  603),  wider  in  front  than  behind, 
in  which  rests  the  basilar  artery.  Slightly  in  advance  of  the  middle  of  the  ventral 
surface  of  the  pons  and  at  the  margin  the  two  roots  of  the  fifth  nerve  emerge. 

The  Posterior  or  Dorsal  Surface  (jpars  dorsalis  pontis). — The  posterior  or  dorsal 
surface  of  the  pons  is  free,  but  is  concealed  from  view  by  the  cerebellum.  It  forms 
the  upper  part  of  the  floor  of  the  fourth  ventricle,  and  will  be  described  with  this 
cavity  (Fig.  604  and  p.  942). 

Structure. — Transverse  sections  of  the  pons  Varolii  show  that  it  consists  of  two 
parts,  which  differ  in  appearance  and  structure  from  each  other:  the  anterior  or 
ventral  portion  (Fig.  594)  consists  for  the  most  part  of  fibres  arranged  in  transverse 
and  longitudinal  bundles  with  a  small  amount  of  gray  matter;  the  posterior  or  dorsal 
portion  is  chiefly  constituted  by  a  continuation  upward  of  the  reticular  formation 
of  the  gray  matter  of  the  medulla,  and  is  called  the  tegmental  portion,  as  most 
of  its  constituents  are  continued  into  the  tegmentum  of  the  crus  cerebri.  It  is 
subdivided  into  lateral  halves  by  a  median  raphe  continuous  with  that  of  the 


THE   IIEXB-BHAIJV 


923 


medulla,  but  the  raphe  does  not  extend  into  the  ventral  half  of  the  pons,  behig 
here  obliterated  by  the  transverse  fibres. 

Transverse  Fibres  of  the  Pons. — The  transverse  fibres  are  placed  in  the  ventral 
portion  of  the  pons.     These  are  disposed  in  three  sets: 

1 .  The  Superficial  or  Ventral  Transverse  Fibres  (fihrae  pontis  superficiales)  (Fig. 
594)  constitute  a  rather  thin  layer  on  the  ventral  surface  of  the  pons.  This  thin 
white  layer  is  called  the  tuber  annulare. 

2.  The  Middle  or  Deep  Transverse  Fibres  are  placed  dorsally  or  above  the 
superficial  transverse  fibres,  and  form  a  thick  layer,  with  much  gray  matter 
between  them.  These  collections  of  gray  matter  are  named  the  nuclei  pontis.  In 
this  layer  of  transverse  fibres  are  longitudinal  fibres  coming  from  the  middle 
three-fifths  of  the  crustae  and  passing  to  the  pyramids  of  the  medulla  and  also 


Fig.  594.  — Superficial  dissection  of  the  medulla  oblongata  and  pons.     (Ellis.) 

fibres  of  the  fronto-pontal,  intermediate,  and  temporo-frontal  tracts  (Santee). 
The  middle  cerebellar  peduncles  (brachia  pontis)  (Fig.  599)  are  formed  by  the 
superficial  and  middle  transverse  fibres. 

3.  The  Dorsal  Transverse  or  Dorsal  Deep  Transverse  Fibres  lie  dorsally  to  the 
middle  transverse  fibres  and  the  pyramidal  fibres  between  them  and  the  formatio 
reticularis.  These  fibres  are  collected  into  a  distinct  bundle  which  is  most  defi- 
nite in  the  posterior  portion  of  the  pons  and  in  which  region  it  is  named  the  trape- 
zium (corpus  trapezoideum) ,  because  of  its  shape.  The  trapezium  is  the  mark  of 
the  boundary  between  the  dorsal  and  ventral  surfaces.  The  chief  origin  of  the 
trapezium  is  from  the  cochlear  nerve  nuclei;  they  decussate  and  pass  by  the 
lateral  fillet  to  the  inferior  quadrigeminal  body.  Santee  points  out  that  the  trape- 
zium and  lateral  fillet  are  part  of  the  auditory  conduction  path. 

Longitudinal  Fibres  of  the  Pons. — These  are  found  in  both  the  ventral  and  dorsal 
portions.    There  are  three  sets: 


924  THE  NERVOUS  SYSTEM 

The  Ventral  Longitudinal  or  Ventral  Deep  Longitudinal  Fibres  (Fig.  594)  are  chiefly 
the  continuation  of  the  pyramidal  fibres  of  the  crustae  which  reach  the  pyramids 
of  the  medulla.  They  form  a  thick  bundle.  Among  these  fibres  are  some  from 
the  opposite  cerebellar  peduncles  and  the  nuclei  pontis.  During  the  descent  of 
the  pyramidal  tract  it  grows  constantly  smaller,  because  it  loses  here  and  there 
fibres  which  pass  to  motor  cranial-nerve  nuclei.  The  pressure  of  the  thick  bundle 
of  pyramidal  fibres  causes  a  bulging  of  the  superficial  transverse  fibres  on  the 
ventral  surface  of  the  pons  and  the  formation  of  the  mesial  groove  between  them. 

The  Middle  Longitudinal  or  Dorsal  Deep  Longitudinal  Fibres  are  placed  in  the 
floor  of  the  fourth  ventricle  in  the  'pontine  formatio  reticularis,  which  is  continuous 
with  the  formatio  reticularis  of  the  medulla  oblongata.  The  pontine  formatio 
reticularis  is  a  network  of  these  longitudinal  fibres  with  some  oblique  fibres,  the 
network  containing  gray  matter.  Some  of  the  gray  matter  of  the  formatio  retic- 
ularis forms  the  nuclei  of  certain  cranial  nerves;  the  rest  of  it  forms  the  nuclei 
of  the  formatio  reticularis.  Santee  describes  six  bundles  of  longitudinal  fibres  in 
the  formatio  reticularis :  1 .  The  fillet  (lemniscus) ,  consisting  of  the  lateral,  the  median, 
and  the  superior  fillet  {lemniscus  lateralis,  lemniscus  medialis,  lemniscus  superior), 
passing  to  and  through  the  tegmentum  to  the  thalamus  and  the  two  quadri- 
geminal  bodies.  2.  The  posterior  longitudinal  bundle  (fascic^dus  longitudinalis 
medialis)  contains  both  ascending  and  descending  fibres;  most  of  the  fibres  do 
not  decussate  but  reach  the  anterior  column  of  the  same  side  of  the  cord. 
Some  of  its  fibres  decussate  through  the  pons,  medulla,  and  mid-brain. 
According  to  Santee,  it  receives  ascending  fibres  from  the  gray  matter  of  the 
anterior  cornu  of  the  spinal  cord,  from  the  sensory  nuclei  of  cranial  nerves,  and 
through  the  middle  peduncle  from  the  cerebellum.  It  terminates  in  the  sub- 
thalamic region.  The  fibres  decussate  across  the  posterior  commissure.  In  this 
bundle  are  motor  fibres  passing  from  the  sixth  to  the  third  nerves  and  from  the 
third  to  the  seventh.  3.  The  anterior  longitudinal  bundle  {fasciculus  ventralis) 
passes  from  the  superior  quadrigeminal  body  to  the  gray  matter  of  the  anterior 
cornu  of  the  cervical  cord.  "It  is  the  pupillo-dilator  tract. "^  4.  The  olivary 
bundle  or  the  central  tegmental  tract  (fascicidus  tegmenti  centralis)  arises  from 
the  inferior  olivary  nucleus  of  the  medulla,  ascends  to  the  lenticular  nucleus, 
from  which  situation  some  of  the  fibres  pass  to  the  cortex.  5.  The  crossed  descend- 
ing tract  from  the  red  nucleus.  It  arises  in  the  red  nucleus  of  the  tegmentum, 
soon  crosses  the  raph^,  and,  as  Barker  points  out,  reaches  the  lumbar  region  of 
the  cord.  In  the  pons  the  fibres  are  in  the  lateral  fillet.  6.  The  ascending  or  infe- 
rior sensory  root  of  the  fifth  nerve  {tractus  spinalis  nervi  trigemini)  arises  near  the 
Rolandic  tubercle  in  the  medulla  and  effects  a  junction  with  the  superior  root 
ventrally  to  the  superior  peduncles  of  the  cerebellum. 

The  Dorsal  Longitudinal  or  Superficial  Longitudinal  Fibres  constitute  the  roof 
of  the  superior  portion  of  the  fourth  ventricle,  and  form  the  superior  peduncles 
of  the  cerebellum  (p.  932)  and  the  valve  of  Vieussens  (p.  933). 

Gray  Matter  of  the  Pons. — The  nuclei  pontis  constitute  a  portion  of  it,  th«»  gray 
matter  of  the  formatio  recticularis  the  balance. 

The  Nuclei  Pontis,  which  have  been  previously  referred  to,  are  collections  of 
gray  matter  .on  each  side  of  the  pons,  between  the  fibres  of  the  middle  transverse 
bundle  and  of  the  ventral  longitudinal  bundle  of  the  pons.  The  nucleus  pontis 
of  each  side  receives  fibres  from  the  crusta — viz.,  the  intermediate  bundle,  the  frontal 
cerebro-cortico-pontal  tract  (p.  893),  and  the  temporal  cerebro-cortico-ponval  tract 
(p.  894),  and  also  receives  fibres  from  the  middle  peduncle  of  the  cericbellum 
(p.  934) .  It  sends  fibres  by  the  middle  peduncle  to  the  opposite  cerebellar  hemi- 
sphere.   The  nuclei  pontis  contain  numerous  multipolar  ganglion  cells. 

'  Anatomy  of  the  Brain  and  Spinal  Cord.    By  Harris  E.  Santee. 


THE  HIND-BRAIN  925 

The  Gray  Matter  of  the  Pontine  or  Formatio  Reticularis  forms  the  superior 
olivary  nucleus,  the  nuclei  of  the  trapezium,  numerous  nuclei  of  the  formatio  reticu- 
laris, and  nuclei  of  certain  cranial  nerves.  The  portion  of  the  formatio  reticularis 
between  the  roots  of  the  sixth  pair  of  cranial  nerves  is  called  the  formatio  reticularis 
alba;  the  portion  between  the  roots  of  the  sixth  and  seventh  nerves  is  called  the 
formatio  reticularis  grisea. 

The  Superior  Olivary  Nucleus  (nucleus  olivaris  superior)  is  upon  the  dorsal  surface 
of  the  outer  part  of  that  collection  of  fibres  known  as  the  trapezium.  It  is  not  large 
enough  to  be  visible  to  the  naked  eye  and  contains  very  small  nerve-cells.  It  is  a 
part  of  the  auditory  pathway,  and  its  fibres  enter  the  accessory  auditory  nucleus 
of  the  opposite  sitle.  The  nuclei  of  the  trapezium  are  in  the  auditory  pathway. 
There  are  numerous  other  nuclei  in  the  formatio  reticularis  (nuclei  of  the  formatio 
reticularis,  or  the  nucleus  magnocellularis  diffusus  of  Koelliker).  The  cells  of 
these  nuclei  are  large  and  multipolar,  and  their  axones  cross  to  the  opposite  side 
of  the  pons.  They  receive  fibres  from  cranial-nerve  nuclei  and  axones  from  the 
cells  of  the  folium  of  the  cerebellum  which  are  called  cells  of  Purkinje.  These 
nuclei  are  probably  connected  with  various  pontine  tracts. 

The  Nuclei  of  the  Fifth  Nerve  (Fig.  613)  in  the  pons  are  two  in  number,  one  for 
the  motor  root  and  the  other  for  the  sensory.  The  motor  nucleus  is  situated  in  the 
higher  portion  of  the  pons,  close  under  the  dorsal  surface  and  along  the  line  of  the 
lateral  margin  of  the  fourth  ventricle.  The  sensory  nucleus  lies  external  to  the  motor 
one,  beneath  the  superior  peduncle  of  the  cerebellum,  which  forms  the  lateral 
boundary  of  the  upper  half  of  the  fourth  ventricle.  Some  of  the  fibres  from  these 
nuclei  pass  to  the  raphe  of  the  pons,  and  thence  probably  to  the  higher  parts  of  the 
brain ;  the  rest  form  the  nerve-roots  of  the  motor  and  sensory  parts  of  the  fifth 
nerve  respectively.  They  pass  through  the  pons  to  emerge  on  its  ventral  surface 
at  its  lateral  and  constricted  portion,  nearer  its  superior  than  its  inferior  margin. 
It  must  be  mentioned  that  the  whole  of  the  roots  of  the  fifth  nerve  are  not  formed 
from  these  nuclei.  The  sensory  root  is  partly  formed  by  a  long  tract  of  fibres, 
known  as  the  ascending  root,  which  can  be  traced  through  the  pons  to  the  nucleus 
of  Rolando  in  the  medulla.  The  motor  root,  in  like  manner,  is  partly  formed  by 
a  long  tract  of  fibres,  which  passes  downward  from  the  gray  matter  in  the  floor 
of  the  fourth  ventricle  and  the  floor  of  the  Sylvian  aqueduct  and  which  is  termed 
the  descending  root. 

The  Nucleus  of  the  Sixth  Nerve  (Fig.  613)  is  situated  beneath  the  floor  of  the  fourth 
ventricle,  on  either  side  of  the  middle  line.  It  lies  close  to  the  root  of  the  facial  nerve, 
immediately  to  be  described,  being  a  little  external  to  and  beneath  it,  and  corre- 
sponds to  the  upper  half  of  the  fasciculus  teres  of  the  floor  of  the  fourth  ventricle 
(Fig.  606).  The  fibres  pass  through  the  substance  of  the  pons,  and  emerge  at  the 
lower  margin  of  this  structure,  between  it  and  the  upper  end  of  the  medulla. 

The  Nucleus  of  the  Facial  Nerve  (nucleus  n.  facialis)  (Fig.613)  is  of  elongated  form, 
and  is  situated  deeply  in  the  reticular  formation  below  the  superior  fovea  of  the  floor 
of  the  fourth  ventricle.  The  roots  of  the  nerve  derived  from  it  pursue  a  remarkably 
tortuous  course  in  the  substance  of  the  pons.  At  first  they  pass  backward  and 
inward  till  they  reach  the  floor  of  the  fourth  ventricle,  close  to  the  median  groove, 
where  they  are  collected  into  a  rounded  bundle.  This  passes  upward  and  for- 
ward, producing  an  elevation  (fasciculus  teres)  in  the  floor  of  the  ventricle,  and 
then  takes  a  sharp  bend  and  arches  outward  through  the  substance  of  the  pons 
to  emerge  at  its  lower  border  in  the  interval  between  the  olivary  and  restiform 
bodies  of  the  medulla.  The  pars  intermedia  of  Wrisberg  takes  origin  from  the 
floor  of  the  fourth  ventricle  beneath  the  inferior  fovea. 

The  Nuclei  of  the  Auditory  Nerve  (nuclei  n.  acu^tici)  (Fig.  613)  are  two  in  number, 
dorsal  and  ventral.  The  origin  of  the  dorsal  or  vestibular  root  is  from  a  nucleus  situ- 
ated in  the  medulla,  but  prolonged  upward  into  the  pons,  where  it  lies  beneath  the 


926  THE   NERVOUS  SYSTEM 

upper  half  of  the  floor  of  the  fourth  ventricle  {nuclei  n.  vestibularis) .  The  dorsal 
root  also  takes  origin  from  the  cerebellum  (from  the  nucleus  fastigii  and  the 
nucleus  globosus).  iVccording  to  Golgi,  the  vestibular  root  is  also  in  connection 
with  the  nucleus  of  Deiters  and  the  nucleus  of  Bechterew.  The  ventral  or 
cochlear  root  arises  from  the  ventral  or  accessory  nucleus  (nuclei  n.  cochlearis) 
which  is  also  partly  contained  in  the  medulla  and  partly  in  the  pons.  In  the 
medulla  it  is  situated  on  the  antero-external  surface  of  the  restiform  body, 
lying  between  the  vestibular  and  cochlear  divisions  of  the  auditory  nerve,  the 
latter  being  to  its  outer  side.  In  the  pons  it  is  seen  to  lie  beyond  the  boundary  of 
the  fourth  ventricle  on  the  outer  and  ventral  aspect  of  the  restiform  body.  A  third 
nucleus,  nucleus  of  Deiters,  is  sometimes  termed  the  outer  nucleus  of  the  auditory 
nerve.  It  is  situated  below  the  outer  angle  of  the  fourth  ventricle,  and  contains 
multipolar  nerve-cells  of  large  size.  The  outer  portion  of  the  nucleus  of  Deiters 
is  called  Bechterew's  nucleus.  The  root  of  the  auditory  nerve  consists  of  two 
portions,  lateral  and  mesial,  which  pass,  one  to  the  outer  and  the  other  to  the 
inner  side  of  the  restiform  body,  those  from  the  lateral  part  arising  mainly  from 
the  ventral  nucleus,  those  from  the  mesial  part  arising  from  the  dorsal  auditory 
nucleus.  They  emerge  at  the  lower  border  of  the  pons,  in  the  groove  between 
the  olivary  and  restiform  bodies. 

The  Cerebellum  or  Little  Brain  (Figs.  557,  595,  596,  597,  598,  and  599).— 
The  cerebellum  is  contained  in  the  inferior  occipital  fossse,  and  is  situated  beneath 
the  occipital  lobes  of  the  cerebrum,  from  which  it  is  separated  by  the  tentorium 
cerebelli.  In  form  it  is  oblong  and  flattened  from  above  downward,  its  great 
diameter  being  from  side  to  side.  It  measures  from  three  and  a  half  to  four  inches 
transversely,  two  to  two  and  a  half  inches  from  before  backward,  and  is  about 
two  inches  thick  in  the  centre,  and  about  six  lines  thick  at  the  circumference. 
It  consists  of  gray  and  white  matter:  the  former,  darker  than  that  of  the  cere- 
brum, occupies  the  surface  (substantia  corticalis),  and  masses  of  it  are  also 
found  in  the  interior.  The  white  matter  is  in  the  interior  (corpus  medullare). 
The  surface  of  the  cerebellum  is  not  convoluted  like  that  of  the  cerebrum,  but 
is  traversed  by  numerous  curved  furrows  or  sulci,  which  vary  in  depth  at  dif- 
ferent parts,  and  separate  the  laminae  of  which  it  is  composed. 

Lobes  of  the  Cerebellum. — The  cerebellum  consists  of  three  parts  or  lobes,  a 
median  and  two  lateral.  They  are  all  continuous  with  each  other,  and  are  sub- 
stantially the  same  in  structure.  The  median  portion  is  called  the  worm  or  vermi- 
form process  (vermis),  from  the  annulated  appearance  which  it  presents,  owing  to 
transverse  ridges  and  furrows  upon  it.  On  the  upper  surface  of  the  cerebellum, 
the  worm  is  only  slightly  elevated  above  the  level  of  the  lateral  portions,  but  on  the 
under  surface  it  is  sunk  almost  out  of  sight  in  a  deep  depression,  which  is  called 
the  valley  or  vallecula  (vallecula  cerebelli).  The  lateral  parts  of  the  cerebellum  are 
called  hemispheres  (hemisphaeria  cerebelli) ;  they  attain  a  considerable  size,  overlap- 
ping and  obscuring  the  inferior  part  of  the  worm.  Below  and  behind  they  are 
separated  by  a  deep  notch,  the  posterior  cerebellar  notch  or  the  incisura  marsupialis 
(incisura  cerebelli  posterior),  and  in  front  by  a  broader,  shallower  notch,  the  anterior 
cerebellar  notch  or  the  incisura  semilunaris  (incisura  cerebelli  anterior).  The  anterior 
notch  lies  close  to  the  pons  and  upper  part  of  the  medulla,  and  its  upper  edge  encir- 
cles the  posterior  corpora  quadrigemina.  The  posterior  notch  is  free,  and  contains, 
in  the  recent  state,  the  upper  part  of  the  falx  cerebelli.  The  sides  of  the  notches  are 
formed  by  the  margins  of  the  hemispheres,  while  the  bottom  of  the  notches  is 
formed  by  the  anterior  and  posterior  extremities  of  the  worm  respectively.  The 
cerebellum  is  characterized  by  its  laminated  or  foliated  appearance ;  it  is  everywhere 
marked  by  deep,  transverse,  somewhat  curved  fissures,  which  lie  close  together, 
and  extend  for  a  considerable  depth  into  the  substance  of  the  cerebellum,  dividing 
it  nito  a  senes  of  layers  or  leaves.     Upon  making  sections  across  the  laminae 


THE   HIND -BRAIN 


92: 


it  will  be  seen  that  the  folia,  though  differing  in  appearance  from  the  convolu- 
tions of  the  cerebrum,  are  homologous  with  them,  inasmuch  as  they  consist  of  a 
central  white  substance,  with  a  covering  or  cortex  of  gray  matter. 

The  largest  and  deepest  fissure  is  the  great  horizontal  fissure  (sulcus  horizontalis 
cerehelli)  (Figs.  595  and  596).  It  commences  in  front  at  the  pons,  and  passes  hori- 
zontally around  the  free  margin  of  the  hemisphere  to  the  middle  line  behind,  and 
divides  the  cerebellum  into  an  upper  and  lower  portion.  Several  secondary  but 
deep  fissures  separate  thecerebelhun  into  lobes,  and  these  are  further  subdivided  by 
shallower  sulci,  which  separate  the  individual  folia  or  laminae  from  each  other. 

When  the  cerebellum  is  removed  from  the  pons  and  medulla,  the  transverse 
fissure  (fissura  transversa  cerehelli)  is  seen  upon  its  anterior  margin.  This  fissure 
is  between  the  superior  and  inferior  medullary  laminae. 

The  white  matter  in  the  interior  of  the  cerebellum  is  known  as  the  medullary 
body  (corpus  medullare) .  About  the  middle  it  divides  into  a  superior  and  an  inferior 
lamina  (Laminae  medullares) .  These  laminae  help  to  form  the  fourth  ventricle. 
The  superior  lamina  is  composed  of  the  superior  medullary  velum  and  the 
peduncles  of  the  cerebellum.  The  inferior  lamina  constitutes  the  inferior 
medullary  velum. 

The  cerebellum  is  connected  to  the  cerebrum,  pons,  and  medulla  by  three  pairs 
of  peduncles,  which  will  be  described  in  the  sequel;  a  superior  pair  connect  it 
with  the  cerebrum;  a  middle  pair,  with  the  pons;  and  an  inferior  pair,  with  the 
medulla. 


Ala  lohuli  centralis.     Post-central        Pre-clival  fissure. 
Lohnlus  centralis. 


Great 
liorisontal 

Jissnre 


clival  fissure. 


Fig  595. — Upper  surface  of  the  cerebellum.     (Schafer.) 

The  Upper  Surface  of  the  Cerebellum  (fades  cerehelli  superior)  (Fig.  595). — The 
superior  surface  of  the  cerebellum  is  somewhat  elevated  in  the  middle  line  and 
sloped  toward  its  circumference,  its  hemispheres  being  connected  together  by  an 
elevated  median  portion  or  lobe,  the  superior  vermis  or  superior  vermiform  process 
(vermis  superior  cerehelli).  The  front  of  the  superior  vermis  is  elevated,  and  the 
highest  point  is  called  the  monticulus  cerehelli.  The  surface  is  traversed  by  four 
curved  fissures,  which  are  named  from  their  situation,  in  front  or  behind  two 
prominent  lobes  of  the  worm,  the  central  lobe  and  the  clivus:  (1)  the  pre-central 
fissure  (sulcus  praecentralis  cerehelli) ;  (2)  the  post-central  fissure  (sulcus  postcentralis) ; 
(3)  the  pre-clival  fissure,  and  (4)  the  post-clival  fissure.  These  four  fissures  divide 
the  entire  upper  surface  of  the  cerebellum  into  five  lobes,  but  the  portion  of  the 
lobe  in  the  worm  has  received  a  different  name  from  that  in  the  hemisphere, 
though  the  two  are  continuous  with  each  other.  The  five  lobes  in  the  worm  are 
named  from  before  backward :  (1)  the  lingula,  (2)  the  central  lobule,  (3)  the  culmen 
monticuli,  (4)  the  clivus  monticuli,  and  (5)  the  folium  cacuminis  (folium  vermis). 


928  THE  NERVOUS  SYSTEM 

The  five  lobes  in  the  hemispheres  are  named  from  before  backward:  (1)  the 
fraenulum,  (2)  the  ala  lobuli  centralis,  (3)  anterior  crescentic,  (4)  posterior  crescentic, 
and  (5)  posterior  superior.  The  arrangement  of  these  fissures  and  lol)ules  will  be 
understood  by  reference  to  the  accompanying  schematic  arrangement,  in  which 
the  lobules  are  named  in  order  from  before  backward  with  the  fissures  which 
separate  them: 

Worm.  Hemisphere. 

Lingula.  Fraenulum. 

Pre-central  Fissure. 
Lobulus  centralis.  Ala  lobuli  centralis. 

Post-central  Fissure. 
Culmen  monticuli.  Anterior  crescentic  lobe. 

Pre-clival  Fissure. 
Clivus  monticuli.  Posterior  crescentic  lobe. 

Post-clival  Fissure. 
Folium  cacuminis.  Posterior  superior  lobe. 

The  Lingula  (lingula  cerebelli)  (Fig.  598)  is  a  tongue-shaped  process  of  the  vermis^ 
which  lies  in  the  anterior  cerebellar  notch  in  front  of  the  lobulus  centralis,  and  is 
partially  or  completely  concealed  by  it.  It  is  in  relation,  in  front,  with  the  valve  of 
Vieussens,  on  the  dorsal  surface  of  which  it  rests  and  with  which  it  is  connected ; 
its  white  matter  being  continuous  with  that  of  the  valve.  At  either  side  the 
lingula  gradually  shades  off,  and  is  prolonged  only  for  a  short  distance  into  the 
hemispheres,  where  it  forms  the  fraenulum  {vinculum  lingulae  cerebelli).  This  does 
not  stretch  beyond  the  superior  peduncle  of  the  cerebellum  over  which  it  lies. 

The  Central  Lobe  and  Alae  {lobulus  centralis). — The  lobusor  lobulus  centralis  is 
a  small  square  lobe,  situated  in  the  anterior  notch.  It  overlaps  the  lingula  and  is 
in  turn  partially  concealed  l)y  the  culmen  monticuli.  I^aterally  the  lobulus  cen- 
tralis extends  along  the  upper  and  anterior  part  of  each  hemisphere,  where  it 
forms  a  wing-like  prolongation,  the  ala  lobuli  centralis. 

The  Culmen  Monticuli  Cerebelli  is  much  larger  than  the  two  lobes  just  described, 
and  constitutes,  with  the  succeeding  lobe,  the  clivus,  the  bulk  of  the  upper  worm. 
In  front  it  partially  overlaps  and  obscures  the  lobulus  centralis,  and  l)ehind  it  is 
separated  from  the  clivus  by  the  pre-clival  fissure.  It  forms  the  most  prominent 
part  of  the  upper  worm,  and  is  marked  on  its  surface  by  three  or  four  secondary 
fissures,  dividing  it  up  into  smaller  lobules.  Laterally  it  is  continuous  with  the 
anterior  crescentic  lobe  of  the  hemisphere  {-pars  anterior  lobuli  quadrangularis), 
which  is  distinctly  differentiated  from  the  posterior  crescentic  lobe  by  the  pre- 
clival  fissure,  though  the  two  were  formerly  classed  together  as  the  quadrate  lobe 
of  the  lateral  hemisphere. 

The  Clivus  Monticuli  (declive  monticuli  cerebelli)  is  of  considerable  size,  and,  as 
stated  above,  forms  with  the  culmen  the  major  part  of  the  superior  worm.  It  con- 
sists of  a  group  of  laminae,  which  in  front  are  separated  from  the  culmen  by  the 
pre-clival  fissure  and  behind  appear  to  be  almost  continuous  with  the  folium 
cacuminis,  especially  in  the  median  line;  but  it  will  be  found,  on  careful  examina- 
tion, to  be  separated  from  it  by  a  well-defined  fissure,  the  post-clival  fissure.  I^ater- 
ally  this  lobe  is  continued  into  the  hemispheres  as  the  posterior  crescentic  lobe 
(pars  posterior  lobuli  quadrangularis),  which  is  somewhat  semilunar  in  shape,  and, 
with  the  anterior  crescentic  lobe,  constitutes  the  greater  part  of  the  upper  surface 
of  the  hemispheres. 


THE    HIND- BRAIN 


929 


The  Folium  Cacuminis  {folium  vermis)  is  a  short  and  narrow,  concealed  band 
at  the  posterior  extremity  of  the  worm,  consisting  apparently  of  a  single  folium, 
but  in  reality  marked  on  its  upper  and  under  surfaces  by  secondary  fissures. 
Laterally  it  expands  in  either  hemisphere  into  a  considerable  lobe,  which  is  semi- 
lunar in  shape,  and  is  situated  at  the  postero-superior  part  of  the  hemisphere  and 


Post- nodular  fissure. 


Fhcculus. 


Pre- 

pyramidal 

fissure. 


Great 

orizontal 
ssure. 


pyram 
fissure. 


Fig.  596. — Under  surface  of  the  cerebellum.     (Schafer.) 


is  bounded  below  by  the  great  horizontal  fissure.  It  is  named  the  posterior  superior 
lobe  {lobulus  semilunaris  superior),  and  occupies  the  posterior  third  of  the  upper 
surface  of  the  hemisphere,  forming  its  rounded  postero-lateral  border. 

The  Under  Surface  of  the  Cerebellum  (fades  cerehelli  inferior)  (Figs.  596  and  597). 
— The  under  surface  of  the  cerebellum  presents  in  the  middle  line  the  inferior  vermis 


Fig.  597. — Diagram  showing  fissures  on  under  surface  of  the  cerebellum.    F.  Flocculus.    N.  Nodule. 
Py.  Pyramid.     Am.  Amygdala.     Bivent.  Biventral  lobe. 


V.  Uvula. 


or  inferior  vermiform  process  (vermis  inferior  cerehelli),  buried  in  the  vallecula, 
and  separated  from  the  hemispheres  by  lateral  grooves.  Here,  as  on  the  upper 
surface,  there  are  deep  fissures,  dividing  it  into  separate  segments  or  lobes,  but 
the  arrangement  is  more  complicated,  and  the  relation  of  the  segments  of  the 
worm  to  those  of  the  hemisphere  is  less  clearly  marked.    The  fissures  are  three 

59 


930  THE  NERVOUS  SYSTEM 

in  number,  but  are  not  so  regularly  disposed  as  those  on  the  upper  surface  (Fig. 
597).  They  are  named,  from  their  relation  to  the  pyramid  and  nodule,  two  of 
the  lobes  on  the  under  surface  of  the  worm:  (1)  post-nodular,  (2)  pre-pyramidal, 
and  (3)  post-pyramidal  fissures.  The  part  of  the  worm  in  front  of  the  post-nodular 
fissure  is  termed  the  nodule  {nodulus  vermis),  and  the  lobule  in  the  hemisphere 
corresponding  with  this  is  the  flocculus.  The  next  lobe  is  situated  between  the 
post-nodular  and  pre-pyramidal  fissures.  In  the  vermiform  process  it  is  known 
as  the  uvula,  and  its  lateral  expansion  in  the  hemisphere  is  named  the  amygdala 
or  tonsil.  The  lobule  of  the  worm  between  the  pre-  and  post-pyramidal  fissures 
is  the  pyramid,  and  its  corresponding  part  in  the  hemisphere  is  the  biventral  or 
digastric  lobe.  Finally,  behind  the  post-pyramidal  fissure  in  the  worm  i^  a  small 
lobe,  the  tuber  valvulae  or  tuber  posticum ;  this,  in  the  hemispheres,  expands  into  a 
large  lobe,  which  occupies  at  least  two-thirds  of  the  inferior  surface  of  the  cere- 
bellum, and  is  subdivided  into  two  by  a  secondary  fissure,  named  the  post-gracile 
fissure.  The  anterior  of  the  two  subdivisions  is  named  the  slender  lobe;  and  the 
posterior,  the  inferior  semilunar  or  posterior  inferior  lobe.  These  fissures  and  lobes 
are  here  arranged,  from  before  backward,  in  a  schematic  form: 

Worm.  Hemisphere. 

Nodule.  Flocculus. 

Post-nodular  Fissure. 
Uvula.  Amygdala. 

Pre-pyramidal  Fissure. 
Pyramid.  Biventral  lobe. 

Post-pyramidal  Fissure. 

r  Slender  lobe. 
Tuber  valvulae  s  Post-gracile  Fissure. 

(.Inferior  semilunar  lobe. 

The  Fissures  of  the  Under  Surfaces  of  the  Cerebellum. — The  chief  fissures  of  the 
under  surface,  as  stated  above,  are  three  in  number,  and  are  not  so  regularly  dis- 
posed as  on  the  upper  surface. 

(1)  The  Post-nodular  Fissure  in  the  worm  courses  transversely  across  it,  separat- 
ing the  nodule  in  front  from  the  uvula  behind.  When  it  reaches  the  hemispheres 
it  passes  in  front  of  the  amygdala,  and  then  crosses  between  the  flocculus  in  front 
and  the  biventral  lobe  behind,  and  joins  the  anterior  end  of  the  great  horizontal 
fissure. 

(2)  The  Pre-pyramidal  Fissure  crosses  the  worm  between  the  uvula  in  front  and 
the  pyramid  behind,  then  curves  laterally  behind  the  amygdala,  and  passes  forward 
along  the  outer  border  of  this  lobe,  between  it  and  the  biventral  lobe,  to  join  the 
post-nodular  sulcus. 

(3)  The  Post-pyramidal  Fissure  passes  across  the  worm  behind  the  pyramid  and 
in  front  of  the  tuber  valvulae,  and  in  the  hemispheres  courses  behind  the  amygdala 
and  biventral  lobes,  and  then  along  the  outer  border  of  the  biventral  lobe  to  the 
post-nodular  sulcus.  It  cuts  off  at  least  two-thirds  of  the  inferior  surface  of  the 
hemisphere.  From  it  a  secondary  sulcus  springs,  and,  coursing  forward  and 
outward,  divides  this  surface  into  two  parts  and  falls  into  the  great  horizontal 
fissure.    This  sulcus  is  termed  the  post-gracile  fissure. 

The  Lobes  of  the  Inferior  Surface  of  the  Cerebellum. — The  Nodule  (nodulus  vermis) 
is  a  distinct  prominence,  forming  the  anterior  extremity  of  the  inferior  worm.  It 
projects  into  the  roof  of  the  fourth  ventricle,  and  can  only  be  distinctly  seen  after 
the  cerebellum  has  been  separated  from  the  medulla  and  pons.    On  each  side  of 


THE   HIND- BRAIN  931 

the  nodule  is  a  thin  layer  of  white  substance,  named  the  inferior  meduUaxy  velum. 
It  is  semilunar  in  form,  its  convex  border  being  continuous  with  the  middle 
peduncle  of  the  cerebellum;  it  extends  on  either  side  as  far  as  the  flocculus, 
which  it  connects  with  the  nodule. 

The  flocculus  {flocculi  secondarii)  is  a  prominent,  irregular  lobule,  situated 
just  in  front  of  the  biventral  lobe,  between  it  and  the  middle  peduncle  of  the 
cerebellum.  It  takes  origin  from  a  fold  of  gray  matter  in  the  inferior  medullary 
velum,  which  is  anterior  to  the  tonsil.  This  fold  is  called  the  peduncle  of  the 
flocculus  {peduncidus  flocculi).  Externally  the  gray  fold  enlarges  and  the  enlarge- 
ment is  the  flocculus.     It  is  subdivided  into  a  few  small  laminae. 

The  Uvula  (uvula  vermis)  occupies  a  considerable  portion  of  the  inferior  worm ; 
it  is  separated  on  either  side  from  the  amygdala  by  a  deep  groove,  the  sulcus  val- 
leculae,  at  the  bottom  of  which  it  is  connected  to  the  amygdala  by  a  commissure 
of  gray  matter,  indented  on  its  surface,  and  called  the  furrowed  band.  The  uvula 
is  marked  on  its  surface  by  three  or  four  transverse  fissures. 

The  Tonsil  or  Amygdala  {tonsilla  cerehelli)  is  a  rounded  mass  in  the  lateral 
hemisphere.  There  are  two  tonsils,  one  in  each  lateral  hemisphere.  Each  lies 
in  a  deep  fossa' between  the  uvula  and  the  biventral  lobe;  this  fossa  is  known  by 
the  name  of  the  bird's  nest  {nidus  avis). 

The  P3nramid  Lobe  {pyramis  vermis)  is  a  conical  projection,  forming  the  largest 
prominence  of  the  lower  worm.  It  is  separated  from  the  hemispheres  by  the  sulcus 
valleculae,  across  which  it  is  connected  to  the  biventral  lobe  by  an  indistinct  band 
of  gray  matter,  analogous  to  the  furrowed  band  already  described. 

The  Biventral  Lobe  or  Digastric  Lobule  (lobulus  hiventer)  is  triangular  in  shape, 
with  the  apex  pointing  inward  and  backward  to  become  joined  by  the  connecting 
band  to  the  pyramid.  The  external  border  is  separated  from  the  slender  lobe  by 
the  post-pyramidal  fissure.  The  base  is  directed  forward,  and  is  on  a  line  with  the 
anterior  border  of  the  amygdala,  and  is  separated  from  the  flocculus  by  the  post- 
nodular  fissure. 

The  Tuber  Valvulae  or  Tuber  Posticum  {tuber  vermis)  is  the  posterior  division  of 
the  inferior  worm.  It  is  of  small  size,  and  laterally  spreads  out  into  the  large  poste- 
rior inferior  lobes  of  the  hemispheres.  These  lobes,  which,  as  stated  above,  com- 
prise at  least  two-thirds  of  the  inferior  surface  of  the  hemisphere,  are  divided  into 
two  by  the  post-gracile  fissure.  The  anterior  lobe  is  named  the  slender  lobe,  and 
the  posterior,  the  inferior  semilunar  lobe  {lobulus  semilunaris  inferior).  Both  these 
lobes  show  a  tendency  to  subdivision  into  two;  that  of  the  slender  lobe  is  well 
marked,  and  its  subdivisions  are  sometimes  described  as  distinct  lobes  and  named 
the  anterior  and  posterior  slender  lobes,  the  fissure  between  them  being  termed  the 
intra-gracile  fissure. 

The  Internal  Structm-e  of  the  Cerebellum. — The  cerebellum  consists  of  white  and 
gray  matter. 

The  White  Matter. — If  a  sagittal  section  (Fig.  598)  is  made  through  either 
hemisphere  of  the  cerebellum,  the  interior  will  be  found  to  consist  of  a  central 
stem  of  white  matter,  the  medullary  body  (corpus  medullare),  which  contains  in  its 
interior  a  gray  mass,  the  corpus  dentatimi  (nucleus  dentatus).  It  is  a  fold  of  gray 
matter  thrown  into  corrugations  and  surrounding  a  centre  of  white  matter.  From 
the  surface  of  this  central  stem  a  series  of  plates  of  medullary  matter  are  de- 
tached, which,  covered  with  gray  matter,  form  the  laminae.  In  consequence  of 
the  main  branches  from  the  central  stem  dividing  and  subdividing,  the  section 
presents  a  characteristic  appearance,  which  is  named  the  arbor  vitae  cerebelli.  If 
a  vertical  section  is  made  in  the  median  plane  of  the  cerebellum  it  will  be  found 
that  the  central  stem  divides  into  two  main  branches,  which,  from  their  direction, 
may  be  named  respectively  the  vertical  and  the  horizontal  branch.  The  vertical 
branch  passes  upward  to  the  culmen,  where  it  subdivides  freely,  some  of  its  ramifi- 


932 


THE   NERVOUS   SYSTEM 


cations  passing  forward  and  upward  to  the  central  lobe.  The  horizontal  branch 
passes  backward  to  the  folium  cacuminis,  considerably  diminished  in  size  in 
consequence  of  having  given  off  large  secondary  branches :  one,  from  its  upper 
surface,  ascends  to  the  clivus;  the  others  descend,  and  enter  the  lobes  in  the 
inferior  vermiform  process,  the  tuber  valvulae,  the  pyramid,  the  uvula,  and  the 
nodule.  In  the  interior  of  the  worm  is  white  matter  called  the  corpus  trapezoides. 
It  is  not  necessary  to  describe  in  detail  the  various  divisions  of  the  white  matter, 
as  they  correspond  to  the  lobes  on  the  surface. 


Anterior 

crescenUc  lobe. 


Ala  lohnli  centralis. 


Lingula. 


Superior  peduncles 
of  cerebellum. 


Great 
horizontal    ^ 
fissure.         '"''^>' 


Slender  lobe. 


Amygdala. 


Nodule.    Fourth  ventricle. 


Fig.  598. — Sagittal  section  of  the  cerebellum,  near  the  point  of  junction  of  the  worm  with  the  hemisphere. 

(Schiifer.) 

The  white  matter  of  the  cerebellum  includes  three  systems  of  fibres:  (1) 
projection  or  peduncular  fibres,  which  are  directly  continuous  with  those  of  the 
peduncles  of  the  cerebellum ;  (2)  the  fibres  proper  {fibrae  p-opriae)  of  the  cere- 
bellum itself. 

Projection  or  Peduncular  Fibres. — The  medullary  body,  as  it  emerges  from  the 
anterior  cerebellar  notch,  is  composed  of  projection  fibres.  These  fibres  are 
continuous  with  the  branches  of  the  medullary  body  and  constitute  the  arbor 
vitae.  The  medullary  body  divides  into  a  superior  lamina  and  an  inferior  lamina, 
and  it  also  forms  a  portion  of  the  fourth  ventricle.  The  inferior  lamina  is  the 
inferior  medullary  velum,  and  its  fibres  reach  the  nodule  and  each  flocculus. 
The  superior  lamina  forms  the  superior  medullary  velum  and  the  cerebellar 
peduncles. 

The  Peduncles  of  the  Cerebellum  (Figs.  599  and  600). — From  the  anterior  part 
of  each  hemisphere  arise  three  large  processes  or  peduncles — superior,  middle, 
and  inferior  peduncles — by  which  the  cerebellum  is  connected  with  the  rest  of 
the  encephalon. 

The  Superior  Cerebellar  Peduncles  or  Crura  ad  Cerebrum  (hrachia  conjunctiva 
cerebelli)  form  the  upper  lateral  boundaries  of  the  floor  of  the  fourth  ventricle. 
As  they  extend  forward  and  upward  they  converge  on  the  dorsal  aspect  of  the 
ventricle,  and  thus  assist  in  roofing  it  in.  They  may  be  traced  as  far  as  the  corpora 
quadrigemina,  under  which  they  pass.    They  enter  the  upper  and  mesial  part  of 


THE   HIND -BRAIN 


933 


the  medullary  substance  of  the  hemispheres,  beneath  the  ala  lobuli  centralis  and 
the  fraenulum,  and  pass  to  a  great  extent  into  the  interior  of  the  corpus  dentatum, 
though  some  of  their  fibres  wind  around  it  and  reach  the  gray  cortical  matter, 
especially  of  the  inferior  surface. 

There  are  both  afferent  and  efferent  fibres  in  the  superior  peduncle,  and  the 
fibres  are  in  two  bundles  (Fig.  600) .  The  fibres  to  the  cerebrum  are  axones  of  cells, 
most  of  which  are  situated  in  the  corpus  dentatum,  but  some  of  the  fibres  to  the 
cerebrum  come  from  the  Purkinje  cells  of  the  cerebellar  cortex,  and  probably 
also  a  few  come  from  the  smaller  nuclei  in  the  central  white  substance.  The 
majority  of  the  fibres  decussate  below  the  corpora  quadrigemina,  and  pass  to 
the  opposite  red  nucleus  of  the  tegmentum,  from  which  a  relay  is  prolonged 
through  the  optic  thalamus  to  the  cerebral  cortex.  The  fibres  of  the  second  group 
take  origin  in  the  opposite  red  nucleus  and  end  in  the  corpus  dentatum  (Santee). 


Fig.  599. — The  peduncles  of  the  cerebellum.  On  the  left  the  three  peduncles  have  been  cut  at  their  entrance 
into  the  cerebellum;  on  the  right  side  they  are  shown  penetrating  the  cerebellar  hemisphere.  (Poirier  and 
Charpy.) 


The  Valve  of  Vieussens  or  Superior  Medullary  Velum  (velum  medullare 
anierius)  (Figs.  574,  584,604,  and  606). — Stretched  across  from  one  superior  cere- 
bellar peduncle  to  the  other  is  a  thin,  transparent  lamina  of  white  matter,  the 
valv«  of  Vieussens;  on  to  the  dorsal  surface  of  its  lower  half  the  folia  of  the  lingula 
are  prolonged.  It  helps  to  form  with  the  superior  peduncles  the  roof  of  the  upper 
part  of  the  fourth  ventricle,  and  is  continuous  with  the  central  white  stem  of  the 
cerebellum.  It  is  narrow  above,  where  it  passes  beneath  the  corpora  quadri- 
gemina, and  broader  below,  at  its  connection  with  the  white  substance  of  the 
superior  worm  of  the  cerebellum.  A  slightly  elevated  ridge  descends  upon  the 
upper  part  of  the  valve  from  between  the  lower  corpora  quadrigemina,  and  on 
either  side  of  this  may  be  seen  the  fourth  nerve.  The  majority  of  the  fibres  of 
the  superior  medullary  velum  are  chiefly  longitudinal  fibres,  passing  between  the 
cerebrum  and  the  worm  of  the  cerebellum.  What  is  known  as  the  antero-lateral 
ascending  cerebellar  tract  of  Gowers  is  said  by  Hoche  to  pass  to  the  worm  by  way  of 


934 


THE  NERVOUS  SYSTEM 


the  superior  velum.    The  velum  also  contains  some  commissural  fibres  and  decus- 
sating fibres  of  the  roots  of  the  fourth  nerves. 

The  Middle  Peduncles  or  Crura  ad  Posterior  (brachia  pontis)  are  the  largest 
of  the  three  pairs.  They  consist  of  a  mass  of  curved  fibres,  which,  as  already 
described,  pass  to  the  pons  and  fovea,  comprises  most  of  the  transverse  fibres  of 
the  pons.  These  tracts  are  both  afferent  and  efferent,  and  the  middle  peduncle 
emerges  from  the  cerebellum  at  the  anterior  notch,  between  the  margins  of  the 
great  horizontal  fissure.    The  fibres  of  the  middle  peduncle  (Fig.  600)  rise  from 


Fig.  600. — Diagram  showing  the  origin  and  course  of  the  fibres  of  the  peduncles  of  the  cerebellum. 

(Edinger.) 

all  portions  of  the  cortex  of  the  cerebellum.  In  the  peduncle  the  fibres  effect  a 
crossing,  so  that  fibres  from  the  anterior  part  of  the  hemisphere  pass  to  the 
posterior  part  of  the  pons,  and  fibres  from  the  posterior  portion  of  the  hemisphere 
pass  to  the  anterior  portion  of  the  pons.  The  fibres  approach  the  median  line 
and  terminate  on  both  sides  of  the  raph^  in  the  nuclei  pontis  and  the  nuclei  of 
the  formatio  reticularis  (Cajal).  The  balance  of  the  fibres  are  "axones  of  cell- 
bodies,  situated  mainly  in  the  opposite  nucleus  pontis."^  These  fibres  "form  a 
segment  in  the  indirect  motor  paths  contained  above  the  pons,  in  the  medial 


Anatomy  of  the  Brain  and  Spinal  Cord.     By  Harris  E.  Santee. 


THE  HIND-BRAIN 


935 


and  lateral  fifths,  and  the  intermediate  bundle  of  the  crusta.  Collaterals  from 
both  groups  of  fibres  ascend  and  descend  in  the  pons.  They  run  upward  with 
both  crustae,  but  chiefly  with  the  opposite  one;  and  they  accompany  the  fillet 
and  posterior  longitudfnal  bundle  of  the  same  side  to  the  nuclei  of  the  third, 
fourth,  and  sixth  cranial  nerves."^ 

The  Inferior  Peduncles  or  Crura  ad  Medullam  {corpora  restiformia)  connect  the 
cerebellum  with  the  medulla  oblongata.  The  fibres  (Fig.  600)  are  both  afferent 
and  efferent  and  begin  in  the  gray  cortex  of  the  upper  surface  of  the  cerebellar 
hemispheres  and  the  worm.  They  descend  in  a  direction  downward  and  inward, 
from  part  of  the  lateral  walls  of  the  fourth  ventricle,  reach  the  medulla,  and 
become  the  restiform  bodies,  which  will  be  subsequently  described  (p.  941) .  The 
following  are  the  chief  sets  of  fibres  in  the  inferior  peduncles:  1.  The  direct 
cerebellar  tract,  which  takes  origin  in  Clarke's  column  of  the  spinal  cord  and 
terminates  in  the  superior  worm  of  the  cerebellum.  2.  The  external  arciform 
fibres,  which  rise  in  the  gracile  and  cuneate  nuclei  of  the  medulla  and  terminate 
in  the  vermis  superior.  The  posterior  or  uncrossed  fibres  terminate  on  the  same 
side,  the  anterior  or  crossed  fibres  on  the  opposite  side.  3.  The  acustico-cerebellar 
tract.  These  fibres  originate  from  the  nucleus  of  the  auditory  nerve  in  the  floor  of 
the  fourth  ventricle,  and  terminate  in  the  opposite  nucleus  fastigii  and  nucleus 
globosus  of  the  cerebellum.  4.  Fibres  which  pass  between  the  lateral  nucleus  of 
the  medulla  oblongata  and  the  corresponding  side  of  the  cerebellar  cortex.    5.  The 


Punctated 

molecular 

layer. 


Fig.  601. — Diagrammatic  representation  of  the  cells  of  the  cerebellum.     A.  Molecular  layer, 
layer.     C.  White  matter.     (Modified  from  Foster's  Physiology.) 


B.  Nuclear 


descending  cerebellar  tract,  which  originates  in  the  cerebellar  cortex  and  which 
passes  down  by  way  of  the  restiform  body  of  the  medulla  and  the  antero-lateral 
column  of  the  spinal  cord  and  reaches  the  anterior  gray  horn  of  the  cord.  6.  The 
internal  arciform  fibres,  which  pass  between  the  cerebellar  cortex  and  the  opposite 
olivary  body  of  the  medulla  (the  cerebello -olivary  tract).  Santee  emphasizes  the 
fact  that  most  of  the  fibres  which  emerge  from  the  cerebellum  in  the  middle  and 
inferior  peduncles  are  "axones  of  Purkinje's  cells;  they  connect  the  cerebellum 
with  the  motor  nuclei  of  cranial  and  spinal  nerves."^ 


1  Anatomy  of  the  Brain  and  Spinal  Cord.     By  Harris  E.  Santee. 


2  Ibid. 


936  THE  NERVOUS  SYSTEM 

The  Fibres  Proper  of  the  Cerebellum. — The  fibrae  propriae  of  the  cerebellum  are 
of  two  kinds:  (1)  commissural  fibres,  which  cross  the  middle  line  to  connect  the 
opposite  halves  of  the  cerebellum,  some  at  the  anterior  part  and  others  at  the 
posterior  part  of  the  vermiform  process;  (2)  association  fibres,  which  are  antero- 
posterior fibres  connecting  adjacent  laminae  with  each  other. 

The  Gray  Matter  of  the  Cerebellum. — The  gray  matter  of  the  cerebellum  is  found 
in  two  situations:  (1)  on  the  surface,  forming  the  cortex;  (2)  as  independent  masses 
in  the  interior. 

1.  The  Cortex  of  the  Cerebellum  (substantia  corticalis)  presents  a  characteristic 
foliated  appearance,  due  to  the  series  of  laminae  which  are  given  off  from  the 
central  white  matter;  these  in  their  turn  give  off  secondary  laminae,  which  are 
covered  with  gray  matter.  This  arrangement  gives  to  the  cut  surface  of  the  organ 
a  foliated  appearance  (Fig.  598).  Externally,  the  cortex  is  covered  by  pia  matter; 
internally,  is  the  medullary  centre,  consisting  mainly  of  nerve-fibres. 

Microscopic  Appearance  of  the  Cortex  (Figs.  601  and  602). — The  cortex 
presents  a  remarkable  structure,  consisting  of  two  distinct  layers — viz.,  an  external 
or  superficial  molecular  layer,  and  an  internal,  deep,  nuclear,  rust-colored,  or  granular 
layer.  Between  the  two  layers  is  an  incomplete  stratum  of  the  characteristic  cells 
of  the  cerebellum,  the  corpuscles  of  Purkinje. 

The  external,  superficial  gray  or  molecular  layer  (Figs.  601  and  602)  consists  of 
fibres  and  cells.  The  nerve-fibres  are  delicate  fibrillae,  and  are  derived  from  the  fol- 
lowing sources:  (a)  the  dendrites  and  axone  collaterals  of  Purkinje's  cells;  {b) fibres 
from  cells  in  the  granular  layer;  (c)  fibres  from  the  central  white  substance  of  the 
cerebellum;  (c^)  fibres  derived  from  cells  in  the  molecular  layer  itself.  In  addition 
to  these  are  other  fibres,  which  have  a  vertical  direction.  These  are  the  processes 
of  large  glia-cells,  situated  in  the  granular  layer.  They  pass  outward  to  the 
periphery  of  the  gray  matter,  where  they  expand  into  little  conical  enlargements, 
which  form  a  sort  of  limiting  membrane  beneath  the  pia  mater,  analogous  to  the 
membrana  limitans  interna  in  the  retina,  formed  by  the  fibres  of  Miiller. 

The  cells  of  the  molecular  layer  are  small,  and  are  arranged  in  two  strata,  an 
outer  and  an  inner.  They  all  possess  branching  axis-cylinder  processes;  those  of 
the  inner  layer  run  for  some  distance  horizontally,  i.  e.,  parallel  with  the  surface  of 
the  folia,  giving  off  at  intervals  collaterals,  which  pass  in  a  vertical  direction 
toward  the  cell-bodies  of  Purkinje's  corpuscles,  around  which  they  become  enlarged 
and  ramify  like  a  basket.  Hence  these  cells  of  the  inner  portion  of  the  external 
layer  are  named  basket-cells  (Fig.  601). 

The  cells  or  corpuscles  of  Purkinje  (Fig.  602)  are  flask-shaped  cells,  situated  at  the 
junction  of  the  molecular  and  granular  layers,  their  bases  resting  against  the  latter. 
From  the  bottom  of  each  flask  one  axis-cylinder  process  arises ;  this  passes  through 
the  granular  layer,  and,  becoming  medullated,  is  continued  as  a  nerve-fibre  in 
the  medullary  substance  beneath.  This  axone  gives  off  fine  collaterals  as  it 
passes  through  the  granular  layer,  some  of  which  run  back  into  the  molecular 
layer.  From  the  neck  of  the  flask  numerous  dendrites  are  given  off,  which  branch 
in  an  antler-like  manner  in  the  molecular  layer  and  terminate  in  free  extremities. 

The  internal,  rust-colored,  nuclear  or  granular  layer  (Figs.  601  and  602)  is  charac- 
terized by  containing  numerous  small  nerve-cells  or  granules  of  a  reddish-brown 
color,  together  with  many  nerve-fibrils.  Most  of  the  cells  are  nearly  spherical  and 
provided  with  short  dendrites,  which  spread  out  in  a  spider-like  manner  in  the  gran- 
ular layer.  Their  axones  pass  outward  into  the  molecular  layer,  and,  bifurcating 
at  right  angles,  run  horizontally  for  some  distance.  In  the  outer  part  of  the  gran- 
ular layer  are  also  to  be  observed  some  larger  cells,  of  the  type  termed  Golgi  cells 
(Fig.  601).  Their  axones  undergo  frequent  division  as  soon  as  they  leave  the 
nerve-cells,  and  pass  into  the  granular  layer,  while  their  dendrites  ramify  chiefly 
in  the  molecular  layer. 


THE    HIND-BMAIN 


937 


Finally,  in  the  gray  matter  of  the  cerebellar  cortex  fibres  are  to  be  seen  which 
come  from  the  white  centre  and  penetrate  the  cortex.  The  cell  origin  of  these 
fibres  is  unknown,  though  it  is  believed  that  it  is  probably  in  the  gray  matter  of 
the  spinal  cord.  Some  of  these  fibres  end  in  the  granular  layer,  by  dividing  into 
numerous  branches,  on  which  are  to  be  seen  peculiar  moss-like  appendages;  hence 
they  have  been  termed  by  Ramon  y  Cajal  the  moss  fibres  (Fig.  601) ;  they  form 
an  arborescence  around  the  cells  of  the  granular  layer.  Other  fibres  derived 
from  the  medullary  centre  can  be  traced  into  the  molecular  layer,  where  their 
branches  cling  around  the  dendrites  of  Purkinje's  cells,  and  hence  they  have  been 
named  the  clinging  or  tendril  fibres  (Fig.  601). 


External  gray  or 
cellular  layer. 


Corpuscles  of  PurMnje. 


Intei-nal  or  rust- 
colored  layer. 


—  White  substance. 

Fig.  602. — Vertical  section  through  the  gray  matter  of  the  human  cerebellum.    Magnified  about  100  diameters. 

(Klein  and  Noble  Smith.) 


2.  The  Independent  Centres  of  Gray  Matter  in  the  Cerebellum  are  four  in  number 
on  each  side:  one  is  of  large  size,  and  is  known  as  the  corpus  dentatum;  the  other 
three,  much  smaller,  are  situated  near  the  middle  of  the  cerebellum,  and  are  known 
as  the  nucleus  emboliformis,  nucleus  globosus,  and  nucleus  fastigii. 

The  corpus  dentatum  or  ganglion  of  the  cerebellum  {nucleus  dentatus)  is  a  gray 
nucleus  situated  a  little  to  the  inner  side  of  the  centre  of  the  stem  of  the  white 
matter  of  the  hemisphere.  It  consists  of  an  irregularly  folded  lamina  of  a  grayish- 
yellow  color,  containing  white  fibres,  and  presenting  on  its  antero-internal  aspect 
an  opening,  the  hilum  {hilus  nuclei  dentati),  from  which  most  of  the  fibres  of  the 


938 


THE   NERVOUS  SYSTEM 


superior  cerebellar  peduncle  emerge.  The  nucleus  emboliformis  is  a  mass  of  gray 
matter  placed  immediately  to  the  inner  side  of  the  corpus  dentatum,  and  partly 
covering  its  hilum.  The  nucleus  globosus  is  an  elongated  mass  of  gray  matter, 
directed  antero-posteriorly,  and  placed  to  the  inner  side  of  the  preceding.  The 
nucleus  fastigii  is  somewhat  larger  than  the  other  two,  and  is  situated  close  to  the 
middle  line  at  the  anterior  end  of  the  superior  vermiform  process,  and  immediately 
over  the  roof  of  the  fourth  ventricle,  from  which  it  is  separated  by  a  thin  layer 
of  white  matter.    It  is  known  as  the  roof  nucleus  of  Stilling. 

Weight  of  the  Cerebellum. — Its  average  weight  in  the  male  is  about  5  oz.,  4  drs. 
It  attains  its  maximum  weight  between  the  twenty-fifth  and  fortieth  years,  its 
increase  in  weight  after  the  fourteenth  year  being  relatively  greater  in  the  female 
than  in  the  male.  The  proportion  between  the  cerebellum  and  cerebrum  is,  in  the 
male,  as  1  to  83-,  and  in  the  female  as  1  to  8.  In  the  infant  the  cerebellum  is 
proportionately  much  smaller  than  in  the  adult,  the  relation  between  it  and  the 
cerebrum  being,  according  to  Chaussier,  between  1  to  13,  and  1  to  26;  by  Cruveil- 
hier,  the  proportion  was  found  to  be  1  to  20. 


Middle 
peduncle  of 
cerebellum. 


V.  The  Medulla  Oblongata  (Myelencephaion)  (Figs.  557,  594,  603, 604). 

The  medulla  oblongata,  known  also  as  the  spinal  bulb,  is  the  lowest  division  of 
the  encephalon,  and  is  continuous  with  the  spinal  cord.  It  is,  in  fact,  the  intra- 
cranial portion  of  the  spinal  cord.  It  is  developed  from  the  fifth  cerebral  vesicle, 
the  cavity  of  which  forms  the  lower  half  of  the  fourth  ventricle.  It  extends  from 
the  lower  margin  of  the  pons  Varolii  to  a  plane  passing  transversely  just  below 
the  decussation  of  the  pyramids,  at  which  level  the  spinal  cord  commences.  This 
plane  corresponds  to  the  lower  margin  of  the  foramen  magnum.    The  upper  limit 

of  the  medulla  is  marked  off  from  the  pons 
Varolii  on  its  ventral  aspect  by  the  abrupt 
lower  margin  of  the  latter. 

The  medulla  oblongata  is  directed  from 
above  obliquely  downward  and  backward; 
its  ventral  surface  rests  on  the  basilar  groove 
of  the  occipital  bone,  while  its  dorsal  surface 
is  received  into  the  fossa  between  the  hemi- 
spheres of  the  cerebellum,  and  forms  the 
lower  part  of  the  floor  of  the  fourth  ventricle. 
It  is  pyramidal  in  shape,  its  broad  extremity 
directed  upward,  its  lower  end  being  narrow 
at  its  point  of  connection  with  the  cord.  It 
measures  an  inch  in  length,  three-quarters 
of  an  inch  in  breadth  at  its  widest  part,  and 
half  an  inch  in  thickness.  Its  surface  is 
marked,  in  the  median  line,  in  front  and  be- 
hind, by  an  anterior  and  a  posterior  median 
fissure  (fissura  mediana  anterior  and  fissura 
mediana  posterior),  which  are  continuous  with  similar  fissures  on  the  anterior  and 
posterior  surfaces  of  the  cord,  but  neither  one  of  them  extends  the  entire  length 
of  the  bulb.  The  anterior  fissure  contains  a  fold  of  pia  mater,  and  terminates  just 
below  the  pons  in  a  cul-de-sac,  the  foramen  caecum  of  Vicq  d'Azyr.  It  is  interrupted 
at  its  lower  part  by  some  bundles  of  fibres,  which  cross  obliquely  from  one  side  to 
the  other,  forming  the  decussation  of  the  p3n:amids  (decussatio  'pyramidum)  (Figs. 
594  and  605) .  The  posterior  fissure  is  a  deep  but  narrow  fissure,  continued  upward 
to  about  the  middle  of  the  medulla.  As  it  ascends  its  depth  diminishes,  and  about 
the  middle  of  the  posterior  surface  of  the  medulla  the  central  canal  of  the  cord 


Fig.  603. — Medulla  oblongata  and  pons  Varolii. 
Anterior  surface. 


THE   MEDULLA    OBLONGATA  939 

opens,  and  the  lips  of  the  shallow  posterior  fissure  diverge  and  bound  the  triangular 
opening,  which  is  the  lower  portion  of  the  floor  of  the  fourth  ventricle  (Figs.  604 
and  606).  As  the  lower  half  of  the  medulla  contains  the  central  canal  of  the  cord, 
it  is  called  the  closed  portion;  the  upper  half  of  the  medulla  is  above  the  opening 
of  the  central  canal  and  is  called  the  open  portion. 

These  two  fissures  divide  the  medulla  into  two  symmetrical  halves,  each  half 
presenting  elongated  eminences,  which  are  continuous  with  the  columns  of  the  cord. 
By  taking  the  lines  along  which  some  of  the  cranial  nerves  emerge  from  the 
medulla  as  landmarks,  the  surface  of  this  portion  of  the  nervous  system  may  be 
divided  into  three  columns,  in  the  same  way  as  the  spinal  cord  is  divided  into  three 
columns  by  the  lines  corresponding  to  the  points  of  exit  of  the  anterior  and  poste- 
rior roots  of  the  spinal  nerves.  The  hjrpoglossal  nerve-roots  arise  from  a  furrow 
on  the  antero-lateral  surface  of  the  medulla,  which  is  known  as  the  antero-lateral 
furrow,  or  the  ventro-lateral  groove  {sulcus  lateralis  anterior).  There  is  no  furrow 
on  the  cord  corresponding  with  this  medullary  furrow.  The  roots  of  the  glosso- 
pharyngeal and  pnemnogastric  nerves  and  the  accessory  root  of  the  spinal  accessory 
nerve  lie  in  a  furrow  upon  the  postero-lateral  surface  of  the  medulla.  This  furrow 
is  called  the  postero-lateral  furrow  or  dorso-lateral  groove  (sulcus  lateralis  posterior). 
This  groove  is  the  continuation  of  the  postero-lateral  fissure  of  the  cord.  It  is  not 
straight,  but  turns  forward  as  it  ascends.  At  the  termination  of  this  groove  ante- 
riorly the  seventh  and  eighth  cranial  nerves  emerge.  At  the  lower  portion  of  the 
medulla  the  groove  ceases  for  a  short  distance  as  the  direct  cerebellar  tract  passes 
from  the  lateral  to  the  posterior  surface  of  the  bulb.  The  anterior  column  com- 
prises that  portion  which  is  situated  between  the  anterior  median  fissure  and  the 
antero-lateral  furrow;  this  column  is  called  the  anterior  pyramid  or  simply  the 
pyramid  (Fig.  603).  The  lateral  column  comprises  that  portion  which  is  situated 
between  the  antero-lateral  and  the  postero-lateral  furrows.  In  the  lower  part 
of  the  medulla  this  column  is  single,  and  is  called  the  lateral  tract;  but  in  the 
upper  part  an  oval -shaped  body  comes  forward  between  it  and  the  pyramid,  and 
pushes  aside  the  lateral  tract.  This  is  called  the  olivary  body  (Fig.  603)  The 
posterior  column  (Fig.  604)  comprises  that  portion  which  is  situated  between  the 
postero-lateral  furrow  and  the  posterior  median  fissure.  It  is  marked  by  slight 
furrows  dividing  it  into  smaller  columns,  and  these  in  the  lower  part  of  the 
medulla  are  named,  from  without  inward,  the  fasciculus  of  Rolando,  the  fasciculus 
cuneatus  and  the  fasciculus  gracilis;  in  the  upper  part  of  the  medulla,  the  fasciculus 
of  Rolando  and  the  fasciculus  cuneatus  appear  to  become  fused  together  and  seem 
to  form  the  single  body,  called  the  restiform  body  (Fig.  604).  As  a  matter  of  fact 
the  restiform  body  is  not  so  formed  (p.  941) . 

The  Pyramid  (pyramis  medullae  oblongatae)  (Figs.  594  and  603). — The 
pyramid  is  a  pyramidal  bundle  of  white  matter.  A  pyramid  is  placed  one 
on  either  side  of  the  anterior  median  fissure,  and  separated  from  the  olivary 
body  by  a  slight  depression,  from  which  the  roots  of  the  hypoglossal  nerve 
emerge  (antero-lateral  furrow).  At  the  lower  border  of  the  pons  these  bodies 
are  somewhat  constricted  and  are  here  crossed  by  a  band  of  arched  fibres, 
the  ponticulus  of  Arnold;  below  this  they  become  enlarged,  and  then  taper  as 
they  descend  to  their  lower  extremity.  The  fibres  of  which  compose  these 
pyramids  may  be  arranged  in  two  bundles:  an  outer,  continuous  below  with 
the  direct  or  uncrossed  pyramidal  tract  of  the  anterior  column  of  the  same 
side  of  the  spinal  cord,  and  an  inner,  continuous  with  the  crossed  pjnramidal  tract 
of  the  lateral  column  of  the  opposite  side  of  the  cord  (Fig.  605).  As  will  be 
subsequently  mentioned,  the  direct  pyramidal  tract  in  the  cord  lies  next  to  the 
anterior  median  fissure,  but  as  the  crossed  pyramidal  tract  of  the  cord  ascends  to 
the  medulla  it  decussates  with  its  fellow  of  the  opposite  side  across  the  anterior 
median  fissure,  and  so  displaces  laterally  the  direct  pyramidal  tract,  and  ascends, 


940 


THE   NERVOUS  SYSTE3f 


after  decussation,  through  the  medulla  to  its  inner  or  mesial  side.  This  decussa- 
tion is  usually  spoken  of  as  the  decussation  of  the  pyramids  (Figs.  594  and  605), 
but  it  must  be  borne  in  mind  that  it  is  only  a  portion  of  the  fibres  of  the 
pyramid  (90  percent,  of  them)  which  decussate ;  namely,  those  derived  from  the 
crossed  pyramidal  tract  of  the  cord;  the  outermost  fibres,  derived  from  the  anterior 
column  of  the  cord,  do  not  decussate.  Each  pyramid  enters  the  substance  of  the 
pons  in  one  bundle,  and  maybe  traced  through  it,  after  breaking  up  into  several 
smaller  fasciculi,  into  the  corresponding  crus  cerebri. 


PONS  _,, 


!*ife!3 


Restiform  body, 

Clava. 

Cuneate  tubercle. 


LONGITUDINAL 
■COMMISSURAL 


VENTRAL  PLANE 
OF  OBLONGATA 
MIDDLE  PLANE 
OF  OBLONGATA 
DORSAL  PLANE 
OF   OBLONGATA 


Fig.  604.- 


-Posterior  surface  of  the  medulla 
oblongata. 


Fig.  605. — Diagram  to  show  the  crossing  of  the  pyramids 
(red)  and  of  the  lemniscus  (blue).     (Testut.) 


The  Lateral  Column  or  Lateral  Area. — The  lateral  column  or  area  is 
between  the  antero-lateral  and  postero-lateral  furrows.  In  the  lower  part  of 
the  medulla  it  is  of  the  same  width  as  the  lateral  column  of  the  cord,  and 
appears  on  the  surface  to  be  a  direct  continuation  of  it.  As  a  matter  of  fact  it  is 
only  a  part  of  the  lateral  column  of  the  spinal  cord  which  is  continued  upward  into 
this  column;  for  the  crossed  pyramidal  tract  passes  into  the  pyramid  of  the  oppo- 
site side,  and  the  direct  cerebellar  tract  of  the  lateral  column  of  the  cord  passes  into 
the  restiform  body.  The  rest  of  the  lateral  column  of  the  cord,  that  is  to  say,  the 
antero-lateral  ground  bundle  (fasciculus  proprius  anterolateralis)  and  the  antero- 
lateral cerebellar  tract    (fasciculus  anterolateralis   super ficialis) ,    can    be    traced 


THE  MEDULLA     OBLONGATA  •       941 

upward  into  this  area.  In  the  upper  part  of  the  medulla,  the  lateral  tract,  on 
account  of  the  interpolation  of  the  olivary  body,  becomes  almost  concealed  by 
this  body. 

The  Oiive,  Olivary  Body  or  Olivary  Eminence  {oliva)  (Figs.  586,  589,  and  603). 
— The  olivary  body  or  eminence  is  a  prominent  oval  mass,  bulging  from  the 
upper  part  of  the  lateral  column  of  the  medulla.  It  is  situated  on  the  outer  side 
of  the  pyramid,  from  which  it  is  separated  by  the  slight  groove,  along  which 
the  fibres  of  the  hypoglossal  nerve  emerge.  It  is  separated  externally  from  the 
restiform  body  by  a  longitudinal,  narrow  band  of  fibres,  prolonged  upward  from 
the  lateral  tract,  and  by  the  groove,  from  which  the  glosso-pharyngeal,  pneu- 
mogastric,  and  spinal  accessory  nerves  arise.  It  is  equal  in  breadth  to  the 
pyramid;  it  is  broader  above  than  below,  and  is  about  half  an  inch  in  length, 
being  separated  above  from  the  pons  Varolii  by  a  slight  depression,  in  which  a 
band  of  arched  fibres  is  sometimes  to  be  seen.  Numerous  white  fibres,  superficial 
or  external  arciform  or  arcuate  fibres  (Fig.  607) ,  are  seen  winding  across  the  lower 
half  of  the  pyramid  and  the  olivary  body  to  enter  the  restiform  body.  The 
olivary  body  is  formed  by  the  olivary  nucleus  of  the  medulla  (Fig.  607),  a  lamina 
of  gray  matter,  the  surface  of  which  is  covered  by  a  very  thin  layer  of  white 
matter. 

The  Funiculus  or  Fasciculus  of  Rolando  {fasciculus  lateralis)  (Fig.  604). — The 
fasciculus  of  Rolando  is  a  longitudinal  prominence  on  the  outer  side  of  the  lateral 
tract.  It  begins  at  the  lower  end  of  the  medulla  by  a  tapering  extremity,  and  has, 
apparently,  no  corresponding  column  in  the  cord.  It  gradually  enlarges  as  it 
ascends,  and  forms,  at  a  level  with  the  lower  border  of  the  olivary  body,  a  consid- 
erable prominence,  known  as  the  tubercle  of  Rolando  (tuberculum  Rolandi)  (Fig. 
607).  This  is  caused  by  the  substantia  gelatinosa  of  Rolando  of  the  cord  gradually 
finding  its  way  to  the  surface,  so  as  to  form  a  prominence  there.  About  half  an 
inch  below  the  pons  the  fasciculus  of  Rolando  appears  to  blend  with  the  fasciculus 
cuneatus.  In  front,  it  is  separated  from  the  lateral  tract  by  a  distinct  groove,  the 
continuation  upward  of  the  postero-lateral  groove  of  the  cord;  behind,  the 
separation  from  the  fasciculus  cuneatus  is  much  less  distinct. 

The  Wedge-shaped  or  Guneate  Funiculus  or  the  Fasciculus  Cuneatus  (Fig. 
604)  is  the  direct  continuation  upward  of  the  postero-lateral  column  (tract  of 
Burdach)  of  the  cord.  It  is  situated  between  the  fasciculus  of  Rolando  and  the  fas- 
ciculus gracilis.  It  enlarges  as  it  ascends,  and  forms,  opposite  the  lower  extremity 
of  the  fourth  ventricle,  a  slight  eminence  or  enlargement,  the  cuneate  tubercle 
(tuberculum  cuneatum)  (Fig.  604),  which  is  marked  only  in  children.  Above  this 
point  it  disappears  from  the  surface. 

The  Slender  Funiculus  or  the  Fasciculus  Gracilis  (Fig.  604)  is  the  direct 
continuation  upward  of  the  postero-median  column  of  the  cord  (tract  of  Goll).  It 
is  a  narrow  white  band,  placed  parallel  to  and  along  the  side  of  the  posterior 
median  fissure.  It  is  separated  from  the  fasciculus  cuneatus  by  a  slight  groove, 
continuous  with  that  on  the  surface  of  the  cord,  which  marks  off  the  postero- 
median column.  At  first  the  fasciculi  of  the  two  sides  lie  in  close  contact  on 
either  side  of  the  posterior  median  fissure.  Opposite  the  apex  of  the  fourth 
ventricle  each  presents  an  enlargement,  the  clava  (Fig.  604) ;  they  then  diverge 
and  form  the  lateral  boundaries  of  the  lower  part  of  the  fourth  ventricle,  and 
gradually  tapering  off  become  no  longer  traceable.  The  surface  prominence 
of  the  fasciculus  gracilis  is  formed  by  the  gray  nucleus  beneath.  This  nucleus 
is  known  as  the  nucleus  fasciculi  gracilis. 

The  Restiform  Body  (corpus  restijorme)  (Fig.  604). — The  upper  part 
of  the  posterior  area  of  the  medulla  is  occupied  by  the  restiform  body.  It 
appears,  at  first  sight,  as  if  this  body  were  the  direct  continuation  upward  of 
the  fasciculus  cuneatus  and   the  fasciculus  of   Rolando,  and  it  was  formerly 


942  THE  NERVOUS  SYSTEM 

described  as  such.  This,  however,  is  not  so,  for  the  restiform  body  is  largely 
formed  by  a  set  of  fibres,  the  superficial  or  external  arcifonn  or  arcuate  fibres 
(Fig.  607),  which  issue  from  the  anterior  median  fissure  and  will  presently  be 
described.  They  pass  laterally  over  the  pyramid  and  olive,  and  assist  in  form- 
ing the  restiform  body.  There  is  also  a  narrow  strand  of  fibres,  derived  from 
the  lateral  column  of  the  cord,  the  direct  cerebellar  tract  (fasciculus  cerebello- 
spinalis),  which  joins  the  above-mentioned  arcuate  fibres.  These  two  sets  of 
fibres,  reinforced  by  the  internal  arcuate  fibres  from  the  opposite  side  of  the 
medulla,  form  the  restiform  body. 

The  restiform  bodies  are  the  largest  prominences  of  the  medulla,  and  are 
placed  between  the  lateral  tracts  in  front  and  the  fasciculus  cuneatus  behind,  from 
both  of  which  they  are  separated  by  slight  grooves.  As  they  ascend  they  diverge 
from  each  other,  assist  in  forming  the  lower  part  of  the  lateral  boundaries  of  the 
fourth  ventricle,  and  then  enter  the  corresponding  hemisphere  of  the  cerebellum, 
forming  its  inferior  peduncles. 

The  Posterior  Surface  of  the  Medulla  Oblongata  (fades  posterius)  (Fig. 
604) . — The  posterior  surface  of  the  medulla  oblongata  forms  part  of  the  floor  of 
the  fourth  ventricle  (Fig.  606).  This  portion  is  of  a  triangular  form,  bounded 
on  each  side  by  the  diverging  fasciculi  graciles  and  cuneati  and  restiform  bodies. 
The  divergence  of  these  two  fasciculi  and  of  the  restiform  bodies,  together  with  the 
opening  out  of  the  posterior  fissure  and  central  canal  of  the  spinal  cord,  displays 
in  the  floor  of  the  ventricle  the  gray  matter  of  the  medulla,  which  is  continuous 
below  with  the  gray  matter  of  the  cord.  In  the  middle  line  is  seen  a  longitudinal 
furrow,  which  divides  this  part  of  the  ventricle  into  right  and  left  halves,  and  is 
continuous  below  with  the  central  canal  of  the  cord. 

The  Arciform  or  Arcuate  Fibres  (Fig.  607) . — The  arciform  or  arcuate  fibres,  which 
have  been  mentioned  as  forming  part  of  the  restiform  body,  are  found  in  the  upper 
half  of  the  medulla,  crossing  its  surface  and  also  traversing  its  substance.  They 
are  divided  for  purposes  of  description  into  two  sets — external  and  internal.  The 
external  or  superficial  arciform  or  arcuate  fibres  (fibrae  arcuatae  externae)  have  already 
been  alluded  to  as  crossing  the  pyramid  and  olivary  body  on  each  side.  They 
emerge  from  the  anterior  median  fissure,  and  if  traced  into  it  are  found  to  enter 
the  raph^  and  cross  to  the  opposite  side,  after  which  their  further  course  is  a  matter 
of  some  doubt.  After  emerging  from  the  anterior  median  fissure  they  cross  the 
pyramid  and  olivary  body,  often  concealing  from  view  the  upper  part  of  the 
cuneate  and  Rolandic  fasciculi,  and  enter  the  restiform  body.  Kb  they  cross  the 
olivary  body  they  are  reinforced  by  some  of  the  internal  arciform  fibres,  which 
come  to  the  surface  on  the  inner  side  of,  or  through,  this  structure.  The  internal 
arciform  or  arcuate  fibres  (fibrae  arcuatae  internae)  are  described  with  the  microscopic 
anatomy  of  the  medulla. 

It  is  advisable,  at  this  stage,  to  take  up  the  consideration  of  the  cavity  of  the 
fourth  ventricle,  an  acquaintance  with  which  will  render  the  description  of  the 
internal  structure  of  the  medulla  oblongata  more  intelligible. 

The  Fourth  Ventricle  (Ventriculus  Quartus)  (Fig.  606). 

The  fourth  ventricle  is  the  cavity  common  to  the  metencephalon,  and  the  myel- 
encephalon  is  in  the  pons  and  medulla  oblongata  and  is  anterior  or  ventral  to  the 
cerebellimi.  It  is  lozenge-  or  diamond-shaped ;  that  is  to  say,  it  is  composed  of  two 
triangles,  with  their  bases  in  contact.  The  sides  of  the  lower  triangle  are  formed 
by  the  divergence  of  the  fasciculi  graciles,  fasciculi  cuneati,  and  restiform  bodies 
of  the  medulla  on  either  side.  As  these  columns  pass  upward  in  the  medulla  they 
turn  outward  from  the  median  line,  and,  diverging  from  each  other,  form  the 
lateral  boundaries  of  the  lower  half  of  the  fourth  ventricle.    In  like  manner  the 


THE  FOURTH    VENTRICLE  943 

sides  of  the  upper  triangle  are  formed  by  the  convergence  of  the  superior  peduncles 
of  the  cerebellum.  These  peduncles  are  separated  below  by  a  somewhat  wide 
interval,  but  as  they  pass  upward  and  forward  toward  the  corpora  quadrigemina 
they  gradually  converge  and  ultimately  come  into  contact  with  each  other.  This 
cavity  is  therefore  bounded  laterally  on  each  side  by  the  superior  peduncle  of  the 
cerebellum  in  its  upper  half,  and  by  the  fasciculus  gracilis,  the  fasciculus  cuneatus, 
and  the  restiform  body  in  its  lower  half.  It  presents  four  angles.  The  upper 
angle  reaches  as  high  as  the  upper  border  of  the  pons,  and  corresponds  with  the 
lower  opening  of  the  aqueduct  of  Sylvius,  by  which  this  ventricle  communicates 
with  the  third  ventricle  (Fig.  587).  The  lower  angle  is  on  a  level  with  the  lower 
border  of  the  olivary  body,  and  is  continuous  with  the  central  canal  of  the  spinal 
cord.  From  the  resemblance  that  it  bears  to  the  point  of  a  writing  pen  it  has  been 
named  the  calamus  scriptorius.  Its  lateral  angles  extend  for  some  distance  between 
the  medulla  and  the  cerebellum,  each  forming  a  pointed  lateral  recess. 

The  Roof  or  Posterior  Wall  of  the  Fourth  Ventricle.— The  roof  of  the  fourth 
ventricle  is  formed  from  above  downward  by  the  following  structures:  a  part  of 
the  superior  peduncles  of  the  cerebellum,  the  anterior  or  superior  medullary  velum, 
the  posterior  or  inferior  medullary  velum,  the  tela  chorioidea  inferior,  the  obex,  and 
the  lingula.  The  superior  half  of  the  roof  meets  the  inferior  half  at  an  acute  angle 
to  form  the  tent  of  the  fourth  ventricle  (fastigium). 

The  Superior  Peduncles  of  the  Cerebellum  {brachia  conjunctiva  cerebelli)  (Figs. 
557,  598,  599,  604,  and  606). — The  superior  peduncles  of  the  cerebellum,  when 
they  emerge  from  the  medullary  substance  of  its  hemispheres,  pass  upward  and 
forward,  forming  the  lateral  boundaries  of  the  upper  half  of  the  fourth  ventricle, 
but,  converging  as  they  approach  the  corpora  quadrigemina,  the  mesial  portions 
of  the  peduncles  form  a  part  of  the  roof  of  the  cavity,  in  consequence  of  the  ven- 
tricle extending  to  a  slight  extent  underneath  the  peduncles. 

The  Anterior  or  Superior  Medullary  Velum  (Valve  of  Vieussens)  (velum  medullare 
anterius)  (Figs.  584,  596,  605,  and  606). — In  the  angular  interval  left  between  the 
two  superior  peduncles  is  a  thin  lamina  of  white  matter,  continuous  with  the  white 
centre  of  the  cerebellum,  which  bridges  across  from  one  peduncle  to  the  other, 
and  so  completes  the  roof  of  the  superior  part  of  the  ventricle.  This  is  the  superior 
medullary  velum  or  valve  of  Vieussens.  Its  dorsal  surface  is  covered  by  the  folia 
of  the  lingula,  already  described  (p.  928). 

The  Posterior  or  Inferior  Medullary  Velum  {velum  medullare  posterius). — The  pos- 
terior or  inferior  medullary  velum  is  a  thin  layer  of  white  substance,  prolonged 
from  the  white  centre  of  the  medulla  on  either  side  of  the  nodule,  which  assists  in 
forming  a  part  of  the  roof  of  the  fourth  ventricle,  stretching  over  it  toward  its 
lateral  angles.  It  is  continuous  with  the  white  substance  of  the  cerebellum  by 
its  convex  edge,  while  its  thin  concave  margin  is  apparently  free.  In  reality, 
however,  it  is  continuous  with  the  epithelium  of  the  ventricle,  which  is  prolonged 
downward  from  the  velum  to  the  edge  of  the  lingula. 

The  Tela  Chorioidea  Inferior  (tela  chorioidea  ventriculi  quarti) . — The  tela  chorioidea 
inferior  is  a  layer  of  pia  mater  which  covers  in  the  lower  part  of  the  fourth  ventricle 
below  the  inferior  medullary  velum.  Superiorly  it  is  reflected  on  to  the  under 
surface  of  the  cerebellum,  while  inferiorly  it  is  continued  on  to  the  restiform  bodies 
and  lower  part  of  the  medulla.  This  part  of  the  roof  of  the  ventricle  contains  no 
nervous  matter,  but  consists  merely  of  the  ventricular  epithelium  covered  by  pia 
mater.  The  tela  chorioidea  inferior,  like  the  velum  interpositum  or  tela  chorioidea 
superior  (p.  855),  really  consists  of  two  layers,  which  become  more  or  less  adherent, 
viz.,  that  covering  the  under  surface  of  the  cerebellum  and  that  covering  the  epithe- 
lium. It  also  possesses  on  each  side  a  choroid  plexus  (plexus  chorioideus  ventriculi 
^war/i),  which  projects  into  the  ventricular  cavity  invaginating before  it  the  epithelial 
lining.    Each  plexus  consists  of  a  vertical  portion  which  extends  forward,  near  the 


944 


THE  NERVOUS  SYSTEM 


middle  line,  from  the  foramen  of  Majendie,  and  of  a  transverse  fart,  which  passes 
outward  into  the  lateral  recess  of  the  ventricle  as  far  as  the  foramina  of  Key  and 
Retzius.  The  two  plexuses  present  the  form  of  a  T,  the  vertical  limb  of  which  is, 
however,  double,  ||  .  The  tela  does  not  form  a  complete  membrane,  for  in  it 
there  are  three  openings:  one  in  the  middle  line  at  the  inferior  angle  of  the  ven- 
tricle, just  above  the  position  of  the  opening  of  the  central  canal  of  the  cord;  this 
is  the  foramen  of  Majendie  (apertura  medialis  ventriculi  quarti) ;  the  other  two  are 
at  the  right  and  left  extremities  of  the  lateral  recesses  of  the  ventricle,  and  each  is 
named  the  foramen  of  Key  and  Retzius  {apertura  lateralis  ventriculi  quarti)  (see 
pp.  852  and  853).  Through  these  foramina  the  ventricles  of  the  brain  commu- 
nicate with  the  subarachnoid  space. 

The  Obex. — The  obex  is  a  thin,  triangular  lamina  of  gray  matter,  continuous 
below  with  the  anterior  gray  commissure  of  the  cord,  which  fills  in  the  angle 
between  the  two  diverging  fasciculi  graciles  for  a  short  distance. 

The  Ligula. — The  ligula  {taenia  ventriculi  quarti)  are  narrow  bands  of  white 
matter,  which  project  from  the  internal  border  of  the  funiculi  graciles.  They  at 
first  run  upward  and  forward,  and  then  turn  outward  over  the  restiform  bodies, 
as  far  as  the  lateral  recesses  of  the  ventricle.  Their  inner  borders  are  continuous 
with  the  epithelial  roof  of  the  ventricle. 

The  Floor  or  Anterior  Wall  of  the  Fourth  Ventricle  (jossa  rhomboidea) 
(Figs.  599,  604,  and  606). — The  floor  of  the  fourth  ventricle  is  rhomboidal  in  shape, 


Corpora  qiiadrigemina. 


(Superior  peduncle 
of  cerebellum. 


Locus  cseruleus. 
Fovea  superior. 


I^gonum  hypogloasi, 

Ala  cinerea 


Valve  of  Vieussens, 

Fasciculus  teres. 

Conductor  sonorus. 
Strix  acusticse. 

Tr'igonum  acustici. 
Clava. 

Tuberculiim  cuneaium. 
Lateral  column. 


Fig.  606. — Floor  of  the  fourth  ventricle.     Diagrammatic. 


and  is  traversed  by  a  vertical  median  fissure  {sidcus  longitudinalis  fossae  rhom- 
boideae),  which  below  is  continuous  with  the  central  canal  of  the  spinal  cord.  At 
the  junction  of  the  fourth  ventricle  with  the  central  canal  of  the  cord  is  a  dilata- 
tion or  ampulla  called  the  ventricle  of  Arantius.  At  the  widest  part  of  the  fourth 
ventricle,  opposite  the  level  of  the  lateral  recesses,  it  is  marked  by  some  trans- 
verse white  lines,  the  striae  medullares  or  striae  acusticae.  These  consist  of  white 
fibres,  which  emerge  from  the  longitudinal  sulcus,  and  pass  outAvard  across  the 
floor  of  the  ventricle.  Most  of  the  striae  acusticae  take  origin  from  cochlear 
nucleus,  but  some  arise  from  the  cochlear  root.     Most  of  them  pass  to  the  trape- 


INTERNAL    STBUCTUBE    OF    THE   MEDULLA    OBLONGATA     945 

zium  and  lateral  fillet  of  the  opposite  side,  but  some  become  external  arciform 
fibres  (Koelliker).  These  striae  divide  the  floor  of  the  ventricle  into  two  triangles, 
inferior  and  superior. 

The  Inferior  Triangle  (Fig.  606). — The  inferior  triangle,  or  lower  or  posterior 
half  of  the  floor,  presents  above  an  angular  groove,  the  fovea  inferior,  the  apex  of 
which  is  at  the  striae,  while  the  two  limbs  diverge  below,  and  form  the  sides  of  a 
triangular  dark  area,  termed  the  ala  cinerea,  which  becomes  elevated  into  a  promi- 
nence below  (eminentia  cinerea).  This  area  corresponds  with  the  nuclei  of  the 
vagus  and  glosso-pharyngeal  nerves,  and  is  therefore  termed  the  trigonum  vagi. 
A  second  triangular  area  lies  between  the  inner  limb  of  the  fovea  and  the  median 
sulcus ;  its  base  is  directed  upward,  and  limited  by  the  striae  medullaris.  It  is 
termed  the  trigonum  n.  hypoglossi,  because  it  corresponds  in  position  to  the  tract  of 
nerve-cells  from  which  the  hypoglossal  nerve  takes  origin.  A  third  triangular  area 
to  the  outer  side  of  the  fovea  inferior  is  named  the  trigonum  acustici  (area  acuMica). 
It  lies  between  the  groove  forming  the  outer  boundary  of  the  fovea  inferior  and 
the  lateral  wall  of  the  ventricle,  and,  like  the  trigonum  hypoglossi,  has  its  base 
directed  upward.  Here  it  is  continuous  with  a  prominence,  the  tuberculum  acusti- 
cum,  which  extenfls  into  the  anterior  part  of  the  floor  of  the  ventricle. 

The  Superior  Triangle  (Fig.  606) . — The  superior  triangle  or  upper  or  anterior 
half  of  the  floor  of  the  fourth  ventricle,  i.  e.,  the  part  above  the  striae  medullaris, 
presents  in  the  middle  line  the  continuation  of  the  median  longitudinal  sulcus. 
On  either  side  of  this  is  a  spindle-shaped  longitudinal  eminence,  prominent  in  its 
centre,  but  less  so  above  and  below.  This  is  the  eminentia  teres  or  fasciculus 
teres  (colliculus  facialis),  and  is  produced  by  an  underlying  bundle  of  white  fibres, 
the  fasciculus  teres  (eminentia  medialis),  formed,  in  part  at  all  events,  by  the  fibres 
of  the  facial  nerve.  Immediately  above  and  to  the  outer  side  of  the  eminentia 
teres  is  an  angular  depression,  the  fovea  superior;  this  is  sometimes  crossed  by 
a  whitish  band  of  fibres,  the  conductor  sonorus,  which  is  connected  below  with 
the  striae  meduUares  of  the  same  side.  Above  the  fovea  is  a  bluish  depressed 
area,  the  locus  caeruleus.  Its  color  is  due  to  some  pigmented  nerve-cells,  showing 
through  the  white  covering  of  the  floor.  These  pigmented  cells  are  named  the 
substantia  ferruginea,  and  in  them  one  of  the  roots  of  the  fifth  nerve  terminates. 

The  Lining  Membrane. — The  lining  membrane  of  the  fourth  ventricle  is  con- 
tinuous above  with  that  of  the  third  ventricle,  through  the  aqueduct  of  Sylvius 
(p.  912),  and  below  with  that  of  the  central  canal  of  the  spinal  cord.  The  cavity 
of  the  ventricle  communicates  below  with  the  subarachnoidean  space  by  means 
of  the  foramen  of  Majendie  and  the  foramina  of  Key  and  Retzius,  already 
described. 

The  Internal  Structure  of  the  Medulla  Oblongata  (Figs.  607,  608,  609, 610,  611,  612). 

If  the  cranial  nerves  emerging  from  the  medulla  are  traced  into  its  substance, 
it  will  be  seen  that  they  divide  each  half  of  the  bulb  into  three  wedge-shaped  areas, 
which  are  named  the  anterior,  lateral,  and  posterior  areas  of  the  medulla,  and  each 
of  which  corresponds  to  one  of  the  subdivisions  already  described  on  the  surface 
of  this  portion  of  the  encephalon. 

The  Anterior  Area. — The  anterior  area  comprises  that  portion  which  is  situ- 
ated between  the  anterior  median  fissure  and  the  fibres  of  superficial  origin  of  the 
hypoglossal  nerve.     On  the  surface  of  the  medulla  this  area  corresponds  to  the 
pyramid  (Fig.  607). 

The  Lateral  Area. — The  lateral  area  is  situated  between  the  fibres  of  super- 
ficial origin  of  the  hypoglossal  nerve  on  the  one  hand,  and  the  fibres  of  superficial 
origin  of  the  glosso-pharyngeal  pneumogastric  and  spinal  accessory  nerves  on  the 
other.    On  the  surface  of  the  medulla,  in  its  lower  part,  this  area  is  single,  and  is 

60 


946 


THE  NERVOUS  SYSTEM 


called  the  lateral  tract;  but  in  the  upper  part  an  oval-shaped  body,  the  olivary 
body,  comes  forward  between  it  and  the  pyramid,  pushing  aside  the  lateral  tract 
(Fig.  607). 

The  Posterior  Area. — The  posterior  area  comprises  that  portion  which  is  situ- 
ated between  the  fibres  of  superficial  origin  of  the  glosso-pharyngeal,  pneumogas- 
tric,  and  spinal  accessory  nerves,  and  the  posterior  median  fissure.  On  the  surface 
of  the  medulla  this  area  is  marked  by  slight  furrows,  splitting  it  up  into  smaller 
columns;  those  in  the  lower  part  of  the  medulla  are  named,  from  without  inward, 
the  fasciculus  of  Rolando,  the  fasciculus  cuneatus,  and  the  fasciculus  gracilis;  in 
the  upper  part  of  the  medulla  they  are  replaced  by  the  restiform  body.  Finally, 
the  halves  of  the  medulla  are  separated  from  each  other  by  a  median  septum  or 
raph^  (Fig.  607). 

Vagus  nuclei.         ^'ff"'"'       Z"'"''^''^''' ^^'^'^• 
Nucleus  of^ypooiossal     /\      ,-J_         /      Nucleus  gracilis, 
fasciculus  teres,    nucleus. 

'        '      '      ■''«*'■     ~^^  "^        Nucleus  cuneatus. 


Nucleus  ambig. 

Raphe- 
Formatio  reticularis 


Continuation  of  antero- 
lateral ground-bundle 


AccessoiT/  olivary  nuclei 


Gorpus  restiforme. 

Nucleus  or 
tubercle  of 
Rolando. 
-Ascending  root  of 
fifth  nerve. 


Vagus  root. 

-Arciform  fibres. 
■^Nucleus  lateralis. 


ivary  nucleus. 

Hyi'oglossal  nerve. 
Nucleus  of  ext.  arc.  fibres. 
"External  arciform  fibres. 
Anterior  median  fitssurc 

Fig.  607. — Section  of  the  medulla  oblongata  at  about  the  middle  of  the  olivary  body. 


(Schwalbe.) 


Each  of  these  three  areas  is  made  up  of  gray  and  white  matter.  The  gray 
matter  is  derived  for  the  most  part  from  that  of  the  cord.  In  like  manner  the 
white  matter  is  partly  made  up  of  longitudinal  fibres  continuous  with  those  of 
the  cord,  and  partly  of  transverse  fibres  which  intersect  them. 

In  order  to  understand  the  internal  structure  of  the  medulla,  it  is  necessary  to 
describe  the  appearances  as  they  are  seen  in  the  upper  and  lower  portions  of  the 
medulla,  since  they  differ  considerably  in  these  two  parts. 

The  Lower  Part  of  the  Medulla  (Figs.  608  and  609).— The  first  change 
in  the  internal  structure  is  caused  by  the  passage  of  the  fibres  of  the  crossed 
pyramidal  tract  obliquely  through  the  gray  matter  of  the  anterior  horn.  As 
stated  above,  the  pyramid  is  composed  of  fibres  derived  from  the  direct 
pyramidal  tract  of  the  anterior  column  of  the  cord  of  the  same  side,  and 
from  the  crossed  pyramidal  tract  of  the  lateral  column  of  the  opposite  half 
of  the  cord.  Those  fibres  which  are  derived  from  the  direct  pyramidal  tract 
and  which  in  the  cord  lie  close  to  the  median  fissure  are  in  the  medulla 
placed  to  the  outer  side  of  the  pyramid,  being  pushed  aside,  as  it  were,  by 
the  interpolation  of  the  fibres  derived  from  the  crossed  pyramidal  tract,  which 


INTERNAL    STRUCTURE    OF    THE  MEDULLA    OBLONGATA     947 

are  much  more  numerous.  The  crossed  pyramidal  fibres  ascend  from  the  lat- 
eral column  of  the  spinal  cord,  and,  passing  through  the  anterior  gray  cornu 
and  across  the  middle  line,  form  the  inner  part  of  the  pyramid.  In  consequence 
of  this  passage  of  white  fibres  through  its  substance  the  anterior  gray  cornu 
is  broken  up  into  a  coarse  network,  while  one  portion  of  it,  the  caput  cornu,  is 
entirely  separated  from  the  rest;  only  the  base  of  the  cornu  remains  intact,  close 
to  the  ventrolateral  aspect  of  the  central  canal.  The  caput  cornu,  thus  separated, 
is  displaced  laterally,  and  comes  to  lie  close  to  the  caput  cornu  posterioris,  which 


DOnSO-MEOIAN 
FISSURE 


DORSO-LATEHAU 
COLUMN 


DORSO-MEDIAN 
FISSURE 


CROSSED    PYRAM- 
IDAL TRACT 


VENTRAL^' 
ROOTS 

VENTRAL    MEDIAN 
FISSURE 

Fig.  608. — Transverse  section  of  the  oblongata  at  its 
lower  end.   (Testut.) 


MOTOR 
ROOTS 

VENTRO-MEDIAN 
FISSURE 

Fig.  609. — Transverse  section  of  the  oblon- 
gata at  the  decussation  of  the  pyramids. 
(Testut,  after  Duval.) 


has  also  shifted  its  position.  In  consequence  of  this  breaking  up  of  the  greater 
part  of  the  anterior  gray  cornu  by  white  fibres  a  coarse  network  is  formed  in  the 
anterior  and  lateral  areas  of  the  medulla,  which  is  named  the  formatio  reticularis 
(Fig.  607). 

The  posterior  cornu  also  undergoes  somewhat  similar  changes.  It  becomes 
subdivided  by  the  passage  through  it  of  the  sensory  fibres  of  the  columns  of  Goll 
and  Burdach.  These  pass  across  to  the  opposite  anterior  area  of  the  medulla, 
where  they  are  seen  to  lie  immediately  on  the  dorsal  aspect  of  the  pyramids.    In 


NUCLEUS 

QRACILIS 

^MEATUS  j        DORSOMEOiAn 


-HEAD  OF  DORSAL  HORN 
BASE  OF  VENTRAL  HORN 
EAD    OF   VENTRAL    HORN 


Fio.  610. — Transverse  section  of  the  oblongata  at  the  crossing  of  the  fillets.     (Testut.) 


their  passage  through  the  posterior  horns  of  gray  matter  the  latter  become  sub- 
divided, in  a  manner  somewhat  similar  to  what  has  been  seen  to  occur  in  the 
anterior  horns.  This  crossing  of  the  sensory  fibres  is  termed  the  superior  pyram- 
idal or  sensory  decussation  (Fig.  605).  The  caput  cornu  is  displaced  outward,  so 
as  almost  to  reach  the  surface,  where  it  forms  a  projection,  the  fasciculus  of  Rolando, 
which  enlarges  above  into  a  distinct  prominence,  the  tubercle  of  Rolando  (Fig.  607). 
Above  the  level  of  the  tubercle  of  Rolando  the  caput  cornu  is  separated  from 


948 


THE  NERVOUS  /SYSTEM 


the  surface  by  a  band  of  fibres  termed  the  ascending  root  of  the  fifth  nerve  (tradus 
spinalis  n.  trigemini)  and  by  the  external  arcuate  fibres  (Fig.  607).  The  neck 
of  the  cornu  becomes  broken  up  into  a  reticular  formation  by  the  decussation  of 
the  columns  of  GoU  and  Burdach,  and  by  this  means  the  caput  is  separated  from 
the  rest  of  the  gray  matter.  The  base  of  the  cornu  increases  in  size,  and,  as  the 
central  canal  expands  into  the  fourth  ventricle,  becomes  pushed  outward,  and 
portions  of  it  extend  into  the  fasciculus  graciles  and  cuneati,  and  produce  exter- 
nally the  eminences  of  the  clava  and  cuneate  tubercle.  A  third  portion  of  the 
base  becomes  separated  from  the  rest,  and  is  placed  outside  the  nucleus  of  the 
fasciculus  cuneatus.  This  is  called  the  accessory  cuneate  nucleus,  and  is  supposed 
to  be  a  continuation  upward  of  Clarke's  vesicular  column  of  the  cord. 

The  Upper  Part  of  the  Medulla  (Figs.  607,611,  and  612).— The  upper  part 
of  the  medulla  comprises  the  portion  which  enters  into  the  formation  of  the 


FLOOR   OF   FOURTH   VENTRICLE 


NUCLEUS    GRACILIS 

NUCLEUS    CUNEATUS 

BASE    OF   VENTRAL   HORN 
ROOT   OF  TRIFACIAL   CAPPING 
HEAD   OF    DORSAL    HORN 

VAGUS    NERVE 

HEAD   OF  VENTRAL   HORN 


HYPOGLOSSAL   NERVE 


LEIMNISCUS  VENTRAL   PYRAMID 

Fig.  611. — Transverse  section  of  the  oblongata  at  the  lower  end  of  the  olives.     The  roof  of  the  fourth 
ventricle  is  not  represented.      (Testut,  after  Duval.) 


floor  of  the  fourth  ventricle,  where,  in  fact,  the  upper  end  of  the  central  canal 
has  opened  out  into  this  cavity.  In  this  region  the  formatio  reticularis  is  con- 
fined chiefly  to  the  anterior  and  lateral  areas.  In  the  ventral  portion  of  the  pos- 
terior area  there  is  only  a  small  amount  of  reticular  formation,  but  in  addition  to 
this  there  are  individual  masses  of  cells  scattered  among  the  longitudinal  fibres. 


HYPOGLOSSAL 
r«..™  NUCLEUS 

qqB  of_foubth  ventbicle 


SENSORY  NUCLEUS 


NUCLEUS   CUNEATUS 

HEAD    OF    DORSAL    HORN 
ROOT   OF  TRIFACIAL    NERVE 

MOTOR    NUCLEUS    OF    MIXED 

NERVES 

ACCESSORY  HYPOGLOSSAL 

NUCLEUS 

OLIVE 


HYPOGLOSSAL  NERVE 


LEMNISCUS       VENTROMEDI 
FISSURE 


ARCIFORM 
NUCLEUS 

Fig.  612. — Transverse  section  of  the  oblongata  at  the  middle  of  the  olives.     The  roof  ol  the  fourth  ventricle 
is  not  represented.      (Testut,  after  Duval.) 

The  Formatio    Reticularis  (Fig.  607). — The  formatio  reticularis  is  a  network 
of  white   matter  in   the   deep  portion  of  the  medulla,  the  network  containing 


INTERNAL    STBUCTUBE   OF   THE   MEDULLA    OBLONGATA      949 

gray  matter.  It  is  situated  behind  the  pyramid  and  ohvary  body,  extending 
laterally  as  far  as  the  restiform  bodies,  and  dorsally  to  within  a  short  distance 
of  the  floor  of  the  fourth  ventricle.  It  presents  a  peculiar  reticulated  appear- 
ance, from  which  it  derives  its  name,  and  which  is  due  to  the  intersection  of 
bundles  of  fibres  running  at  right  angles  to  each  other,  some  being  longitudinal, 
others  transverse.  The  formatio  reticularis  presents  a  different  appearance  in 
the  anterior  area  from  what  it  does  in  the  lateral  area.  In  the  former  there  is 
almost  an  entire  absence  of  nerve-cells  in  the  reticulated  network,  and  hence  it 
is  known  as  the  formatio  reticularis  alba;  whereas,  in  the  lateral  area,  the  nerve- 
cells  are  numerous,  and,  as  a  consequence,  this  part  is  known  as  the  formatio 
reticularis  grisea.  In  the  substance  of  the  formatio  reticularis  is  a  small  nucleus 
of  gray  matter.  It  is  situated  near  the  dorsal  aspect  of  the  hilum  of  the  olivary 
nucleus,  and  has  been  named  the  inferior  central  nucleus.  The  formatio  reticu- 
laris contains  both  longitudinal  and  transverse  fibres.  In  the  anterior  area 
the  longitudinal  fibres  may  be  arranged  in  two  well-defined  sets:  (1)  One  set 
lies  immediately  behind  the  pyramid,  and  is  named  the  interolivary  fillet  or 
lemniscus  {lemniscus  interolivaris)  (Fig.  610).  The  fibres  of  the  fillet  are  chiefly 
derived  from  the  cells  of  the  gracile  and  cuneate  nuclei  (Fig.  607),  and  may 
therefore  be  regarded  as  relay  fibres  of  the  columns  of  Goll  and  Burdach  of 
the  spinal  cord,  which  terminate  in  synapses  around  the  cells  of  the  gracile  and 
cuneate  nuclei.  They  are  prolonged  inward  and  forward  across  the  middle  line 
forming  the  superior  pyramidal  or  sensory  decussation  or  the  decussation  of  the 
fillet  (Fig.  605).  (2)  The  other  set  is  continuous  from  the  antero-lateral  ground 
bundle  of  the  cord,  and  a  portion  of  these  fibres  forms  the  posterior  longitu- 
dinal bundle  {fasciculus  longitudinalis  medialis),  already  referred  to  (p.  908). 
Both  these  sets  of  fibres  are  continued  upward  into  the  pons  and  mid-brain. 
The  longitudinal  fibres  of  the  reticular  formation  in  the  lateral  area  are  not 
arranged  in  distinct  bundles.  They  are  derived  from  the  lateral  column  of  the 
cord,  after  the  crossed  pyramidal  tract  has  passed  over  to  the  opposite  side. 
The  longitudinal  fibres  of  the  posterior  area  are  merely  indeterminate  fibres  of 
the  formatio  reticularis,  with  the  exception  of  two  distinct  bundles,  which  may 
be  regarded  as  ascending  roots  of  the  fifth  nerve  (Fig.  607)  and  vago-glosso- 
pharyngeal  nerves;  the  latter  is  termed  the  fasciculus  solitarius  (Fig.  607). 

The  Transverse  Fibres  of  the  reticular  formation  are  the  arched  or  arcuate  fibres. 
The  external  arciform  or  arcuate  fibres  have  already  been  described.  The  internal  arci- 
form  or  arcuate  fibres  (fihrae  arcuatae  internae)  are  more  numerous  than  the  super- 
ficial set;  they  traverse  nearly  the  whole  area  of  the  upper  half  of  the  medulla,  except 
the  pyramid.  They  pass  from  the  raphe;  some  become  superficial  and  join  the 
external  arciform  fibres,  while  others  remain  deep  and  pass  to  the  olivary  body,  the 
restiform  body,  and  to  the  nuclei  of  the  fasciculus  cuneatus  and  fasciculus  gracilis. 

Independent  Nuclei  (Fig.  613). — In  the  upper  part  of  the  medulla  are  several 
independent  nuclei  of  gray  matter,  which  may  be  divided  into  two  sets:  (1)  those 
which  are  traceable  from  the  gray  matter  of  the  spinal  cord,  and  (2)  those  which 
are  not  represented  in  the  cord.  The  former  are  the  hypoglossal  nucleus,  the 
nucleus  of  the  fasciculus  teres,  and  those  of  the  auditory,  glosso-pharyngeal,  vagus, 
and  spinal  accessory  nerves.  The  latter  are  the  nucleus  of  the  olivary  body  and 
the  accessory  olivary  nuclei.  In  addition  to  these,  small  collections  of  gray  matter 
are  to  be  found  in  the  median  septum  or  raphe. 

The  Hypoglossal  Nucleus  (Figs.  607,  612,  and  613).— The  base  of  the  anterior 
horn,  which  in  the  lower  part  of  the  medulla  was  situated  on  the  ventro-lateral 
aspect  of  the  central  canal,  now  approaches  the  floor  of  the  ventricle,  where  it 
lies  close  to  the  median  sulcus  under  the  fasciculus  teres.  In  it  is  a  column  of 
large  nerve-cells,  from  which  the  roots  of  the  hypoglossal  nerve  are  derived.  It 
is  accordingly  designated  the  hypoglossal  nucleus. 


950 


THE   NERVOUS  SYSTEM 


The  Auditory  Nuclei  (Fig.  613). — Toward  the  upper  part  of  the  medulla,  a  con- 
siderable tract  of  gray  matter  may  be  found  lying  immediately  beneath  that  por- 
tion of  the  floor  of  the  fourth  ventricle  which  is  known  as  the  trigonum  acustici. 
This  is  the  dorsal  or  inner  auditory  nucleus,  and  it  lies  just  external  to  the  vago- 
glosso-pharyngeal  nucleus.  In  addition  to  this  there  is  a  small  collection  of 
nerve-cells  on  the  ventral  surface  of  the  restiform  body,  between  the  two  roots 
of  the  auditory  nerve,  which  is  known  as  the  accessory  or  ventral  auditory  nucleus. 
On  the  outer  side  of  the  restiform  body  is  a  mass  of  cells  associated  with  the 
cochlear  root  of  the  auditory  nerve.  This  mass  is  termed  the  lateral  acoustic 
tubercle  or  ganglion  radicis  cochlearis. 

Nuclei  of  the  Glosso-pharjmgeal  and  Vagus  Nerves  (Fig.  613). — These  are  two  in 
number,  principal  and  accessory.  The  principal  nucleus  of  the  two  nerves  lies  beneath 
that  portion  of  the  floor  of  the  fourth  ventricle  which  is  known  as  the  ala  cinerea 


INTERNAL 
GENICULATE 

BODY       PULVINAR 


SUPERIOR 

QUADRIGEMINAL 

BODY 


NUCLEUS 
OF  FOURTH 


INTERNAL  ROOT 

OF  OPTIC  TRACT 

OPTIC 

TRACT 

EXTERNAL 

GENICULATE 

BODY 

EXTERNAL  ROOT 

OF  OPTIC  tract" 


SENSORY  NUCLEUS. 
OF  FIFTH 
SENSORY    PORTION 
OF  FIFTH 
SUPERIOR   NUCLEUS 
OF  VESTIBULAR 
INNER  NUCLEUS 
OF  VESTIBULAR 
OUTER    NUCLEUS 
OF  VESTIBULAR' 
VENTRAL    NUCLEUS 
OF  COCHLEAR 
COCHLEAR 
ROOT 


DESCENDING  ROOT 
AND  NUCLEUS  OF 
DESCENDING  ROOT 
OF    FIFTH 

MOTOR    ROOT 
/   OF  FIFTH 


GASSERIAN 
GANGLION 

SENSORY   PORTION        I 
MOTOR   PORTION  J 

EMERGING   PORTION   1 
INNER   PORTION  J 

NUCLEUS  OF  SIXTH 
PARS  PRIMA  RADICIS 
N.   FACIALIS 


NUCLEUS 
OF  SEVENTH 
SEVENTH 


ROOT  OF 
SEVENTH 


VESTIBULAR 
ROOT 


TENTH 

DORSAL  NUCLEUS 
OF  COCHLEAR 

SPINAL  ROOT 
OF  FIFTH 
SPINAL  NUCLEUS' 
OF  VESTIBULAR 

NUCLEUS  OF  ALA 
CINEREA  AND 
TRACTUS  SOLITARIUS 
COMMISSURAL  GANGLI'C 

OF  ALA  CINEREA' 

Fig.  613. — The  nuclei  of  the  origin  of  the  motor  and  primary  terminal  nuclei  of  sensory  cerebral  nerves, 
schematically  represented  in  a  supposedly  transparent  brain  stem,  viewed  from  behind.  Nuclei  and  roots  of 
motor  nerves,  red;  of  sensory,  reddish- violet ;  of  the  cochlear  nerve,  yellow;  and  of  the  optic  nerve,  bluish-violet. 
X  2.     (Held.) 

and  fovea  inferior.  They  form  an  oblong  mass  of  gray  matter,  above  the  nucleus 
of  the  spinal  accessory  and  lateral  to  the  hypoglossal  nucleus.  The  accessory  nuclei 
are  situated  in  the  reticular  formation  of  the  posterior  area,  some  distance  from 
the  floor  of  the  fourth  ventricle.  They  consist  of  a  pear-shaped  mass  of  cells, 
which  is  connected  with  the  rest  of  the  gray  matter  by  a  sort  of  stalk  or  peduncle, 
and  was  formerly  known  as  the  nucleus  ambiguus  (Fig.  607). 

Nucleus  of  the  Spinal  Accessory  Nerve  (Fig.  613). — This  nucleus  consists  of  a 
group  of  cells,  which  is  situated  partly  in  the  lower  part  of  the  medulla  at  the 
base  of  the  posterior  horn  and  close  to  the  central  canal.    It  extends  upward. 


INTERNAL   STRUCTURE   OF   THE  MEDULLA    OBLONGATA     951 

lying  beneath  the  lower  part  of  the  floor  of  the  fourth  ventricle  and  on  the  outer 
side  of  the  hypoglossal  nucleus. 

The  Nucleus  of  the  Olivary  Body  (nucleus  olivaris  inferior)  (Fig.  607). — When 
the  olivary  body  is  cut  across,  it  is  seen  to  be  covered  externally  by  white  fibres, 
and  internally  to  consist  of  a  gray  layer.  The  fibres  which  invest  the  nucleus  are 
derived  from  the  antero-lateral  ground  bundle.  The  gray  layer  is  the  nucleus  of 
the  olivaxy  body,  or,  as  it  is  sometimes  called,  the  corpus  dentatum  of  the  olive.  It  is 
composed  of  a  thin,  wavy  lamina,  which  is  arranged  in  the  form  of  a  hollow  capsule, 
open  at  its  upper  and  inner  part,  and  presenting  a  zigzag  or  dentated  outline. 
Microscopically  examined,  the  olivary  nucleus  is  seen  to  consist  of  small,  rounded, 
yellowish  nerve-cells  embedded  in  a  matrix  of  neuroglia  and  fine  nerve-fibres. 
White  fibres,  which  can  be  traced  from  the  raphe,  and  are  probably  derived 
from  the  opposite  olive,  enter  the  interior  of  the  capsule  by  the  aperture  at  its  upper 
or  inner  part,  these  fibres  constituting  the  olivary  peduncle.  The  olivary  peduncle 
is  the  lower  portion  of  the  cerebello -olivary  tract  (fibrae  cerebelloolivares) .  This 
tract  connects  the  cerebellar  hemisphere  with  the  opposite  olivary  nucleus. 

The  fibres  of  the  olivary  peduncle  as  they  enter  the  olivary  body  diverge  and 
some  are  lost  in  the  gray  matter  of  the  olivary  nucleus;  others  pass  through  it,  and 
of  these  some  turn  backward  to  join  the  restiform  body,  and  pass  to  the  cerebellum 
as  internal  arcuate  fibres;  while  others  pierce  the  white  matter  of  the  olivary  body 
and,  reaching  the  surface,  are  continued  to  the  restiform  body  as  external  arcuate 
fibres.  The  nucleus  receives  the  olivary  bundle  of  the  spinal  cord,  the  group  of 
fibres  called  the  triangular  tract  of  Helwig.  The  central  tegmental  tract  arises 
in  the  olivary  nucleus  and  passes  to  the  lenticular  nucleus.  The  olivary 
nucleus  receives  another  descending  tract  besides  the  cerebello-olivary,  namely, 
the  vestibule -olivary  (Santee).  From  the  nucleus  fibres  pass  by  way  of  the  lateral 
column  to  the  anterior  cornu  of  the  same  side  of  the  spinal  cord.  Removal  of 
one  cerebellar  hemisphere  is  followed  by  atrophy  of  the  opposite  olivary  nucleus. 
Accessory  Olivary  Nuclei  (Fig.  607) . — Two  small  isolated  masses  of  gray  matter 
are  to  be  found,  one  on  the  mesial  and  the  other  on  the  dorsal  aspect  of  the  corpus 
dentatum.  These  are  the  medial  or  internal  accessory  olivary  nucleus  (nucleus 
olivaris  accessorius  medialis)  and  the  external  or  lateral  accessory  olivary  nucleus 
{nucleus  olivaris  accessorius  dorsalis).  They  are  connected  with  the  restiform 
body  by  some  of  the  internal  arcuate  fibres.  The  fibres  of  the  hypoglossal 
nerve,  as  they  traverse  the  bulb,  pass  between  the  medial  accessory  nucleus  and 
the  chief  olivary  nucleus. 

The  Raphe  (Fig.  607). — The  raphd  is  situated  in  the  middle  line  of  the  medulla, 
above  the  decussation  of  the  pyramids.  It  consists  of  nerve-fibres  intermingled 
with  nerve-cells.  The  fibres  have  different  directions,  which  can  only  be  seen  in 
suitable  microscopic  sections,  thus:  1.  Some  are  antero-posterior ;  these  in  front 
are  continuous  with  the  superficial  arciform  fibres.  2.  Some  are  longitudinal; 
these  are  derived  from  the  arciform  fibres,  which  on  entering  the  raph^  change 
their  direction  and  become  longitudinal.  3.  Some  are  oblique;  these  are  continu- 
ous with  the  deep  arciform  fibres  which  pass  from  the  raph^. 

The  nerve-cells  of  the  raphe  are  multipolar;  some  are  connected  with  the 
antero-posterior  fibres,  others  with  the  superficial  arcuate  fibres. 

Weight  of  the  Encephalon. — ^The  average  weight  of  the  brain  in  the  adult  male 
is  49 J  oz.,  or  a  little  more  than  3  lbs.  avoirdupois;  that  of  the  female  44  oz.;  the 
average  difference  between  the  two  being  from  5  to  6  oz.  The  prevailing  weight 
of  the  brain  in  the  male  ranges  between  46  oz.  and  53  oz.,  and  in  the  female 
between  41  oz.  and  47  oz.  In  the  male  the  maximum  weight  out  of  278  cases  was 
65  oz.,  and  the  minimum  weight  34  oz.  The  maximum  weight  of  the  adult  female 
brain  out  of  191  cases  was  56  oz.,  and  the  minimum  weight  31  oz.  According  to 
Luschka,  the  average  weight  of  a  man's  brain  is  1424  grammes  (about  45  oz.). 


952  THE  NERVOUS  SYSTEM 

of  a  woman's  1272  grammes  (about  41  oz.),  and,  according  to  Krause,  1570 
grammes  (about  48|  oz.)  for  the  male  and  1350  (about  43  oz.)  for  the  female.  It 
appears  that  the  weight  of  the  brain  increases  rapidly  up  to  the  seventh  year,  more 
slowly  to  between  sixteen  and  twenty,  and  still  more  slowly  to  between  thirty  and 
forty,  when  it  reaches  its  maximum.  Beyond  this  period,  as  age  advances  and  the 
mental  faculties  decline,  the  brain  diminishes  slowly  in  weight,  about  an  ounce 
for  each  subsequent  decennial  period.  These  results  apply  alike  to  both  sexes. 
Marshall  concluded  that  if  woman  is  judged  by  her  height  only,  she  has  a  smaller 
amount  of  cerebral  matter  than  has  man;  if  she  is  judged  by  her  weight  alone,  she 
has  more;  but  if  both  sexes  are  gauged  by  both  standards,  their  "cerebral  endow- 
ment is  seen  to  be  practically  equal.  "^ 

The  size  pf  the  brain  was  formerly  said  to  bear  a  general  relation  to  the  intel- 
lectual capacity  of  the  individual.  Cuvier's  brain  weighed  rather  more  than  64 
oz.,  that  of  Daniel  Webster  63f  oz.,  that  of  Dr.  Abercrombie  63  oz.  On  the 
other  hand,  the  brain  of  an  idiot  seldom  weighs  more  than  23  oz.  But  these 
facts  are  by  no  means  conclusive,  and  it  is  well  known  that  these  weights  have  been 
equalled  by  the  brains  of  persons  who  never  displayed  any  remarkable  intellect. 
Dr.  Haldennan,  of  Cincinnati,  has  recorded  the  case  of  a  mulatto,  aged  forty-five, 
whose  brain  weighed  68|  oz.;  he  had  been  a  slave,  and  was  never  regarded  as 
particularly  intelligent;  he  was  illiterate,  but  is  said  to  have  been  reserved,  medi- 
tative, and  economical.  Dr.  James  Morris  recorded  the  case  of  a  bricklayer,  who 
could  not  read  or  write,  whose  brain  weighed  67  oz.  Dr.  Ensor,  district  medical 
officer  at  Port  Elizabeth,  reports  that  the  brain  of  Carey,  the  Irish  informer, 
weighed  61  oz.  In  not  a  few  instances  the  brains  of  very  able  men  have  been  of 
average  weight  or  of  less  than  average  weight.  The  brain  of  Samuel  D.  Gross, 
the  surgeon,  weighed  48  oz.,  the  brain  of  Gambetta,  the  statesman,  40^  oz.,  the 
brain  of  Walt  Whitman,  the  poet,  43.3  oz,,  the  brain  of  Hughes  Bennett,  the 
physician,  47  oz.,  the  brain  of  Joseph  Leidy,  the  naturalist  and  anatomist,  49.9  oz., 
and  the  brain  of  Dollinger,  the  physiologist,  42.6  oz.  M.  Nikiforoff  has  published 
an  article  in  the  Novosti  on  the  subject  of  the  weight  of  brains.  According  to 
him,  the  weight  of  the  brain  has  no  influence  whatever  on  the  mental  faculties. 
It  ought  to  be  remembered  that  the  significance  of  the  weight  of  the  brain  should 
depend  upon  the  proportion  it  bears  to  the  dimensions  of  the  whole  body  and  to 
the  age  of  the  individual.  There  seems  to  be  a  relation  between  the  weight  of  the 
brain  and  the  body  weight  and  stature.  Quain  gives  the  ratio  between  the 
brain  weight  and  body  weight  as  1  to  41  in  healthy  individuals,  but  this  propor- 
tion is  by  no  meaiis  fixed  and  seems  to  vary  widely  in  either  direction.  As  the 
stature  increases  the  brain  weight  increases,  but,  as  Mills  says,^  "taller  persons 
have  relatively  less  brain  matter  than  shorter  ones,  although  absolutely  they  have 
more."  The  significance  of  the  weight  of  the  brain  also  depends  upon  the  cause 
of  death,  for  long  illness  or  old  age  wastes  the  brain.  To  define  the  real 
degree  of  development  of  the  brain,  it  is  therefore  necessary  to  have  a  knowl- 
edge of  the  condition  of  the  whole  body,  and,  as  this  is  usually  lacking,  the  mere 
record  of  weight  possesses  little  significance.  As  Mills  says:^  "Apparently  there 
is  no  invariable  nor  necessary  relation  between  mere  brain  weight  and  the 
degree  of  individual  intelligence;  but  high  brain  weights  occur  in  larger  propor- 
tions among  civilized  than  among  uncivilized  races."  Furthermore,  it  is  to  be 
remembered  that  a  heavy  brain  may  be  a  diseased  brain.  For  instance,  Byron's 
brain  weighed  nearly  64  oz.  and  showed  evidences  of  disease. 

The  human  brain  is  heavier  than  the  brain  of  any  of  the  lower  animals,  except- 
ing the  elephant  and  whale.  The  brain  of  the  former  weighs  from  eight  to  ten 
pounds;  and  that  of  a  whale,  in  a  specimen  seventy-five  feet  long,  weighed  rather 
more  than  five  pounds. 

'  The  Nervous  System  and  its  Diseases.     By  Prof.  Charles  K.  Mills.  2  Jbid.  3  Jbid. 


CEREBRAL    LOCALIZATION  AND     TOPOGRAPHY 


953 


CEREBRAL  LOCALIZATION  AND  TOPOGRAPHY. 


The  cortex  of  the  brain  is  highly  speciaHzed,  and  different  regions  represent  special  functions. 
In  it  are  represented  "the  numerous  manifestations  associated  with  consciousness;"  in  it  mem- 
ories are  stored  up;  and  "in  it  occur  the  last  and  highest  bodily  processes  concerned  with  sensa- 
tions received  from  without,  and  with  the  setting  free  of  impulses  which  are  projected  to  lower 
centres  and  to  the  outside  world."'  A  centre  is  an  aggregation  of  nerve-cells  and  fibres,  which 
"aggregation  represents  physiologically  some  action"  (Mills).  Physiological  and  pathological 
researches  and  surgical  operations  have  proved  that  the  surface  of  the  brain  may  be  mapped  out 
into  series  of  definite  centres,  each  one  of  which  is  intimately  connected  with  some  well-defined 
function.  A  group  of  centres  is  known  as  a  zone,  an  area,  or  a  region.  As  Hughlings  Jackson 
says,  the  study  of  centres  is  an  investigation  into  the  anatomical  "substrata"  of  visual,  motor, 
tactile,  and  other  ideas;  of  "the  parts  which  represent  impressions  of  sight,  of  touch,  of  move- 
ment, and  other  functions"  (Mills).  Certain  cortical  centres  are  known  as  moior  cewirfs.  Stimu- 
lation of  these  centres  causes  movement.    Destruction  of  these  centres  renders  movement  impos- 


FiG.  614. — Drawing  to  illustrate  cranio-,  (■itl)ral  topography.     (Taken  from  a  cast  in  the  Museum  of  the  Royal 
College  of  Surgeon.s  of  I'^ngiand,  prepared  by  Professor  Cunningham.) 

sible.  The  centres  are  associated  with  contraction  of  muscular  groups  producing  special  move- 
ments not  with  the  contraction  of  individual  muscles.  They  represent  movements  rather  than 
muscles.  These  centres  are  found  particularly  around  the  fissure  of  Rolando  and  on  the  mesial 
surface  of  the  hemisphere,  and  they  are  associated  with  movements  of  the  extremities  of  the 
opposite  side  of  the  body,  and  movements  of  the  face,  mouth,  and  tongue.  Mills,  von  Monakow, 
and  Sherrington  are  of  the  opinion  that  the  motor  areas  are  entirely  in  front  of  the  fissure  of 
Rolando  (Figs.  61 5  and  61 6).  This  view  is  highly  probable,  but  is  not  absolutely  proved.  Other 
observers  hold  that  the  motor  areas  occupy  the  entire  ascending  frontal  and  ascending  parietal  con- 
volutions, extend  a  little  way  forward  into  the  third  frontal  convolution  and  backward  into  the 
superior  parietal  convolution.  The  motor  areas  certainly  extend  on  to  the  mesial  surface  in  the 
paracentral  lobule  and  pass  perhaps  into  the  marginal  convolution.  On  the  convexity  of  the  hemi- 

'  The  Nervous  System  and  its  Diseases.     By  Prof.  Charles  K.  Mills. 


954 


THE  NERVOUS  SYSTEM 


sphere  the  highest  centre  is  the  leg  area.  Below  this,  in  the  order  named,  are  the  centres  for  the  arm, 
face,  lips,  tongue,  larynx,  and  pharynx.  On  the  mesial  surface  from  before  backward  are  areas  for 
the  head,  shoulder,  trunk,  hip,  knee,  leg,  and  foot.  The  centres  for  head  and  eye  movements  are 
in  front  of  the  arm  centre.  In  a  large  motor  area  there  are  certain  smaller  areas.  For  instance, 
the  area  for  the  lower  extremity  contains  separate  centres,  representing  movements  of  the  hip, 
knee,  leg,  foot,  and  toes. 

The  arm  centre  contains  centres  for  movements  of  the  shoulder,  arm,  wrist,  thumb,  and 
fingers.     The  face  centre  contains  centres  for  movements  of  the  upper  face,  the  lower  face,  the 


CONCRLTE  CONCEPT 

Fig.  615. — Side  view  of  human  brain,  showing  localization  of  functions.      (Charles  K.  Mills.) 

lips,  and  tongue.  The  somcesthetic  area  or  the  area  of  general  sensation  is  not  certainly  marked 
out.  Those  who  believe  that  the  motor  area  is  both  front  and  back  of  the  Rolandic  fissure 
maintain  that  the  area  of  general  sensation  largely  corresponds  to  the  motor  area,  but  is  of 
greater  extent  as  it  enters  into  the  limbic  lobe.  Mills  places  it  back  of  the  fissure  of  Rolando 
in  the  convexity  and  also  on  the  mesial  surface  of  the  hemisphere. 


Fig.  616. — View  of  the  mesial  surface  of  human  brain,  showing  localization  of  functions.     (Charles  K.  Mills.) 

The  cortical  centres  are  shown  in  Figs.  617  and  618.  This  is  not  the  place,  nor  can  space 
be  given,  to  describe  the.se  localities. 

Cranio-cerebral  Topography.— The  position  of  the  principal  fissures  and  convolutions  of  the 
cerebrum  and  their  relation  to  the  outer  surface  of  the  scalp  (Fig.  614)  have  been  the  subject  of 


CEREBRAL  LOCALIZATION  AND    TOPOGRAPHY 


955 


much  investigation,  and  many  systems  have  been  devised  by  which  one  may  localize  these  parts 
from  an  explanation  of  the  external  surface  of  the  head. 

These  plans  can  only  be  regarded  as  approximately  correct  for  several  reasons;  in  the  first 
place,  because  the  relations  of  the  convolutions  and  sulci  to  the  surface  are  found  to  be  very 
variable  in  different  individuals;  secondly,  because  the  surface  area  of  the  scalp  is  greater  than 
the  surface  area  of  the  brain,  so  that  lines  drawn  on  the  one  cannot  correspond  exactly  to  sulci 
or  convolutions  on  the  other;  and  thirdly,  because  the  sulci  and  convolutions  in  two  individuals 
are  never  precisely  alike.  Nevertheless,  the  principal  fissures  and  convolutions  can  be  mapped 
out  with  sufficient  accuracy  for  all  practical  purposes,  so  that  any  particular  convolution  can  be 
generally  exposed  by  removing  with  the  trephine  a  certain  portion  of  the  skull's  area. 


Fig.  617.- 


-The  localization  of  variou.s  centres  on  the  outer  surface  of  the  left  side  of  the  human  brain. 
(American  Text-book  of  Surgery.) 


The  various  landmarks  on  the  outside  of  the  skull,  which  can  be  easily  felt,  and  which  serve 
as  indications  of  the  position  of  the  parts  beneath,  have  been  already  referred  to  (see  page  149), 
and  the  relation  of  the  fissures  and  convolutions  to  these  landmarks  is  as  follows: 

Longitudinal  Fissure  (Fig.  619). — This  corresponds  to  a  line  drawn  from  the  glabella  at 
the  root  of  the  nose  to  the  external  occipital  protuberance. 

The  Fissure  of  Sylvius  (Fig.  619).— The  position  of  the  fissure  of  Sylvius  and  its  posterior 
horizontal  limb  is  marked  by  a  line  starting  from  a  point  one  inch  and  a  quarter  horizontally 
behind  the  external  angular  process  of  the  frontal  bone  to  a  point  three-quarters  of  an  inch  below 


Fig.  618. 


-The  localization  of  various  centres  on  the  median  surface  of  the  human  brain. 
(American  Text-book  of  Surgery.) 


L 


the  most  prominent  point  of  the  parietal  eminence.  The  first  three-quarters  of  an  inch  will  rep- 
resent the  main  fissure,  the  remainder  the  horizontal  limb.  The  bifurcation  of  the  fissure  is 
therefore  two  inches  behind  and  about  a  quarter  of  an  inch  above  the  level  of  the  external  angu- 
lar process.  The  ascending  limb  of  the  fissure  passes  upward  from  this  point  parallel  to,  and 
immediately  behind,  the  coronal  suture. 

The  Transverse  Fissure  or  Fissure  of  Bichat.— This  is  between  the  cerebrum  and  cerebellum 
and  corresponds  to  a  line  drawn  from  the  inion  to  the  external  auditory  meatus  (the  line  B  C  in 
Fig.  619). 


956 


THE  NERVOUS   SYSTEM 


Fissure  of  Rolando. — To  find  the  upper  end  of  the  fissure  of  Rolando,  a  measurement  should 
be  taken  from  the  glabella  to  the  external  occipital  protuberance.  The  position  of  the  top 
of  the  sulcus  will  be,  measuring  from  in  front,  55.6  per  cent,  of  the  whole  distance  from  the 
glabella  to  the  external  occipital  protuberance.  Professor  Thane  adopts  a  somewhat  simpler 
method.  He  divides  the  distance  from  the  glabella  to  the  external  occipital  protuberance  over 
the  top  of  the  head  into  two  equal  parts,  and,  having  thus  defined  the  middle  point  of  the  vertex, 
he  takes  half  an  inch  behind  it  as  the  top  of  the  sulcus.  This  is  not  quite  so  accurate  as  the 
former  method,  but  it  is  sufficiently  so  for  all  practical  purposes,  and  on  account  of  its  simplicity 
is  very  generally  adopted.  From  this  point  the  fissure  runs  downward  and  forward  for  3f  inches, 
its  axis  making  an  angle  of  67°  with  the  middle  line.  Cunningham  states  that  this  angle  more 
nearly  averages  71.5°.  In  order  to  mark  this  groove,  two  strips  of  metal  may  be  employed — 
one,  the  shorter,  being  fixed  to  the  middle  of  the  other  at  the  angle  mentioned.  If  the  longer 
strip  is  now  placed  along  the  sagittal  suture  so  that  the  junction  of-  the  two  strips  is  over  the 
point  corresponding  to  the  top  of  the  furrow,  the  shorter,  oblique  strip  will  indicate  the  direction 
and  3f  inches  will  mark  the  length  of  the  furrow.  Dr.  Wilson  has  devised  an  instrument,  called 
a  cyrtometer,  which  combines  the  scale  of  measurements  for  localizing  the  fissure  with  data  for 
representing  its  length  and  direction. '     Professor  Thane  gives  the  lower  end  of  the  furrow  as 


Fig.  619. — Relations  of  the  principal  fissures  and  convolutions  of  the  cerebrum  to  the  outer  surface  of  the 

scalp.     (Reid.) 

"close  to  the  posterior  limb,  and  about  half  an  inch  behind  the  bifurcation  of  the  fissure  of 
Sylvius."  So  that,  according  to  this  anatomist,  a  line  drawn  from  a  point  half  an  inch  behind 
the  mid-point  between  the  glabella  and  external  occipital  protuberance  to  this  spot  would  mark 
out  the  fissure  of  Rolando.  Dr.  Reid  adopts  a  different  method  (Fig.  619).  He  first  indicates 
on  the  surface  the  longitudinal  fissure  and  the  horizontal  limb  of  the  fissure  of  Sylvius  (as  above). 
He  then  draws  two  perpendicular  lines  from  his  "base-line"  (that  is,  a  line  from  the  lowest 
part  of  the  infraorbital  margin  through  the  middle  of  the  external  auditory  meatus  to  the  back 
of  the  head)  to  the  top  of  the  cranium,  one  (Z)  E,  Fig.  619)  from  the  depression  in  front  of  the 
e:;?ternal  auditory  meatus,  and  the  other  (  F  G,  Fig.  619)  from  the  posterior  border  of  the  mastoid 
process  at  its  root.  He  has  thus  described  on  the  surface  of  the  head  a  four-sided  figure  (F  D  G  E, 
Fig.  619),  and  a  diagonal  line  from  the  posterior  superior  angle  to  the  anterior  perpendicular 
line  where  it  is  crossed  by  the  fissure  of  Sylvius  will  represent  the  furrow. 

The  ParietO-OCCipital  Fissure  on  the  upper  surface  of  the  cerebrum  runs  outward  at  right 
angles  to  the  great  longitudinal  fissure  for  about  an  inch,  from  a  point  one-fifth  of  an  inch  in 
front  of  the  lambda  (posterior  fontanelle).  Reid  states  that  if  the  horizontal  limb  of  the  fissure 
of  Sylvius  be  continued  onward  to  the  sagittal  suture,  the  last  inch  of  this  line  will  indicate  the 
position  of  the  sulcus  (Fig.  619). 

'  Lancet,  1888,  vol.  i.  p.  408. 


CEREBRAL  LOCALIZATION  AND   TOPOGRAPHY 


957 


The  Pre-central  Sulcus  begins  four-fifths  of  an  inch  in  front  of  the  middle  of  the  fissure  of 
Rolando,  and  extends  nearly,  but  not  quite,  to  the  horizontal  limb  of  the  fissure  of  Sylvius. 

The  Superior  Frontal  Fissure  runs  backward  from  the  supraorbital  notch,  parallel  with  the 
line  of  the  longitudinal  fissure  to  two-fifths  of  an  inch  in  front  of  the  line  indicating  the  position 
of  the  fissure  of  Rolando. 

The  Inferior  Frontal  Fissure  follows  the  course  of  the  superior  temporal  ridge  on  the  frontal 
bone. 

The  Intraparietal  Fissure  begins  on  a  level  with  the  junction  of  the  middle  and  lower  third 
of  the  fissure  of  Rolando,  on  a  line  carried  across  the  head  from  the  back  of  the  root  of  one 
auricle  to  that  of  the  other.  After  passing  upward  it  curves  backward,  lying  parallel  to  the 
longitudinal  fissure,  midway  between  it  and  the  parietal  eminence;  it  then  curves  downward  to 
end  midway  between  the  posterior  fontanelle  and  the  parietal  eminence. 


^ 

1 

jR, 

S 

Supra  orbital  line 
(Superior  HorizontaD  K 

/a 

B 

K' 

Orhital-anricular  line 
( Base  line ) 

Z       A  M 

Fig.  620. — Kronlein's  method  for  determining  the  situations  of  certain  fissures  of  the  brain. 


Kronlein's  method  for  determining  the  situations  of  certain  fissures  of  the  brain  is  very  useful 
and  easy  of  application(Fig.  620).  It  is  as  follows:  (1)  The  base  line,  Z  If ,  is  a  horizontal  line  run- 
ning at  the  level  of  the  lower  border  of  the  orbit  and  the  upper  border  of  the  external  auditory 
meatus.  (2)  Another  horizontal  line,  K  K' ,  is  drawn  parallel  to  Z  M.  The  second  horizontal  line 
is  on  a  level  with  the  supraorbital  ridge.  (3)  A  vertical  line,  Z  K,  is  erected  from  Z  M  at  the 
middle  of  the  zygoma  and  is  carried  to  the  line,  K  K'.  (4)  Another  vertical  line,  A  R,  is  erected 
from  the  base-line  at  the  level  of  the  articulation  of  the  mandible  and  is  carried  to  R.  (5)  A  third 
vertical  line,  M  P,  is  erected  from  the  base-line  at  the  posterior  border  of  the  mastoid  process 
and  is  carried  to  the  middle  line  of  the  skull,  which  is  marked  P.     (6)  A  line  is  drawn  from 


958  THE  NERVOUS   SYSTEM 

K  to  P.  The  portion  of  this  Hne  between  R  and  P'  corresponds  to  the  fissure  of  Rolando.  (7) 
The  angle  P  K  K'  is  bisected  by  the  line  A'  S.  K  S  corrssponds  to  the  fissure  of  Sylvius  from 
its  bifurcation  to  its  termination  posteriorly,  and  K  is  directly  over  the  bifurcation.  To  reach 
the  anterior  branch  of  the  middle  meningeal,  apply  the  trephine  at  A';  to  reach  the  posterior 
branch,  apply  it  at  K'.  In  abscess  of  the  temporo-sphenoidal  lobe  the  trephine  should  be  applied, 
according  to  von  Bergmann,  in  the  region  Aa  K'  M. 


THE  NERVE-PATHS. 

The  anatomy  of  the  various  parts  of  the  central  nervous  system  having  been 
described,  a  short  account  will  now  be  given  of  the  course  taken  by  its  more  impor- 
tant nerve-paths,  and  of  the  direction  in  which  impulses  pass  along  them.  Before 
doing  so,  however,  it  is  necessary  to  refer  to  the  methods  employed  in  elucidating 
this  complex  subject.  All  nerve-fibres  may  be  regarded  as  outgrowths  from  nerve- 
cells,  and  it  is  found  that  if  a  nerve-fibre  be  cut,  the  portion  of  it  which  is  severed 
from  the  cell  undergoes  degeneration  and  becomes  atrophied.  Until  recent  years 
it  was  believed  that  the  cell  itself  showed  no  change  under  such  circumstances. 
This,  however,  is  not  the  case,  for  if  a  nerve,  the  sciatic,  for  instance,  be  divided  in 
an  animal,  and  after  an  interval  of  some  weeks  the  animal  be  injected  with  methy- 
lene blue  and  killed,  it  will  be  seen,  on  examining  sections  of  the  lumbar  region 
of  the  spinal  cord,  that  the  cells  are  stained  imperfectly  or  not  at  all,  owing  to  a 
diminution,  or,  it  may  be,  an  entire  disappearance  of  the  chromatin,  a  substance 
which,  in  a  normal  cell,  shows  marked  affinity  for  staining  reagents.  Further,  the 
body  of  the  cell  is  swollen,  the  nucleus  displayed  toward  the  periphery,  and  the 
part  of  the  axone  still  attached  to  the  altered  cell  is  diminished  in  size  and  some- 
what atrophied.  Under  favorable  conditions  the  cell  is  capable  of  reassuming  its 
normal  appearance  and  the  axone  may  commence  to  grow.  This  method  of  study  by 
injection  of  methylene  blue  is  of  great  value  in  determining  the  origin  of  nerve-fibres 
from  their  cells.  Again,  electrical  stimulation  of  certain  localized  areas  of  the  brain 
or  of  the  tracts  arising  from  them  is  followed  by  the  contraction  of  the  muscles  of 
the  body.  The  cortical  centres  of  the  motor  tracts  are  situated  in  the  convolutions 
adjacent  to  the  fissure  of  Rolando  (page  953).  When  the  stimulus  is  applied  to  one 
part  of  the  motor  area  the  muscles  of  one  limb  of  the  opposite  contract,  while  other 
portions  control  the  movements  of  the  other  limb  of  the  opposite  side,  etc.  Destruc- 
tion of  these  paHs  entails  loss  of  function,  paralysis  of  muscles,  and  degeneration 
of  the  tracts  below  the  seat  of  injury.  During  life  injury  and  disease  may  give 
rise  to  symptoms  resembling  either  the  effects  of  stimulation  or  those  of  destruc- 
tion; and  after  death  the  tracts,  or  the  centres  of  the  tracts,  are  seen  to  be 
degenerated  or  otherwise  altered.  It  was  long  believed  by  all  and  is  still  main- 
tained by  many  that  the  motor  area  includes  the  ascending  parietal,  ascending 
frontal,  and  superior  parietal  convolutions.  Mills,  von  Monakow,  Sherrington  and 
other  high  authorities  now  teach  that  the  motor  region  is  entirely  in  front  of  the 
central  fissure,  with  the  possible  exception  that  the  gyral  mass  between  the  foot 
of  the  fissure  of  Rolando  and  the  Sylvian  fissure,  and  extending  a  little  back  of  the 
line  of  the  central  fissure,  which  may  be  included  in  the  area  for  the  face  (Charles 
K.  Mills)  (Figs.  615  and  616).  The  motor  areas  are  separated  from  each  other 
and  do  not  overlap,  but  probably  interdigitate  (Mills).  The  same  is  true  of  the 
areas  for  cutaneous  sensibility.  By  observing  the  development  of  the  nervous  sys- 
tem during  the  growth  of  the  embryo,  the  fact  is  disclosed  that  all  axis-cylinders 
do  not  acquire  a  medullary  sheath  at  one  and  the  same  time.  Speaking  generally, 
it  may  be  said  that  afferent  fibres  become  medullated  before  efferent,  and  that  in 
the  case  of  the  latter  myelination  occurs  earlier  in  the  brain  than  in  the  cord. 
By  watching  the  effects  of  these  different  processes  the  functions  of  a  considerable 
part  of  the  brain  and  of  the  nerves  leading  from  or  to  it  have  been  determined. 


THE   NERVE- PATHS 


959 


The  Motor,  Efferent,  or  Descending  Tract  (Figs.  621,  622,  and  623).— The 
constituent  fibres  of  this  tract  are  the  axis-cyhnder  processes  of  cells  situated 
in  the  cortex  of  the  convolutions  about  and  probably  solely  in  front  of  the 
fissure  of  Rolando,     At  first  they  are  somewhat  widely  diffused,  but  as  they 


N  motor 


Fig.  621. — Scheme  of  the  motor  pathway:     c.  Fig.  622. — Scheme   i~howing   the   course  of  the 

central,  p,  peripheral,  neurone;  d,  decussation:  m,  pyramidal  tract.     /,  in  the  cerebrum  and  crus;  //, 

muscle.     (Jakob.)  m  the  pons;  ///,  in  the  medulla  oblongata;  /F,  de- 

cussation of  the   pyramids;  V ,  in  the  cervical  en- 
largement; y/,  in  the  lumbar  enlargement.  (Jakob.) 

descend  through  the  corona  radiata  they  gradually  approach  each  other  and 
pass  between  the  lenticular  nucleus  and  optic  thalamus  in  the  genu  and 
anterior  two-thirds  of  the  posterior  limb  of  the  internal  capsule.  Proceeding 
downward  they  next  occupy  the  middle  three-fifths  of  the  pes  or  crusta  of  the 
crus  cerebri,  and  enter  the  pons  Varolii,  where  the 
transverse  fibres  of  this  body  not  only  conceal  them, 
but  divide  them  up  into  irregular  bundles.  Eventu- 
ally they  reach  the  medulla,  and  here  the  motor 
tracts  form  the  anterior  pyramids  which  lie  one  on 
each  side  of  the  median  fissure.  The  transit  of  the 
fibres  from  the  medulla  is  effected  by  two  paths. 
The  fibres  nearest  to  the  anterior  median  fissure 
cross  the  middle  line,  forming  the  decussation  of 
the  pyramids  (Figs.  594,  605,  609,  621,  622,  and  623), 
and  flescend  in  the  opposite  side  of  the  cord  as  the 
indirect  or  crossed  pyramidal  tract  (Figs.  605  and  623). 
Throughout  the  length  of  the  spinal  cord  fibres 
from  this  column  pass  into  the  gray  matter,  to  ter- 
minate by  ramifying  around  the  cells  of  the  ante- 
rior horn.    The  more  laterally  placed  portion  of  the 

motor  tract  does  not  decussate  in  the  medulla,  but  positTon"of"thepTrarSdaiTract.'*  Py, 
descends  as  the  direct  or  microssed  pyramidal  tract  ^xif!^c^u^''^^tlTVa^ih^^yI^to 
(Fig.  605) ;  these  fibres,  however,  end  in  the  anterior  (jlkob"^"'"'"'^'"^  "^"""^^  "^'■''^'* 
gray  horn  of  the  opposite  side  of  the  spinal  cord  by 

passing  across  in  the  anterior  white  commissure.  1.  Motor  SiwA  inhihiiing  influ- 
ences which  reach  the  spinal  nerves  arise  in  the  upper  three-fourths  of  the  motor 
area  in  front  of  the  Rolandic  fissure,  pass  along  the  fibres  of  the  corona  radiata 


Fig.  623. — Scheme    showing    the 


960  THE   NERVOUS  SYSTEM 

and  of  the  anterior  two-thirds  of  the  posterior  hmb  of  the  internal  capsule,  the 
middle  three-fifths  of  the  crusta,  the  anterior  or  ventral  pontine  fibres,  and  the 
medullary  pyramids.  From  this  point  they  may  pass  along  either  the  crossed  or  the 
uncrossed  pyramidal  tract  to  reach  the  gray  horn  of  the  opposite  side  of  the  spinal 
cord.  "By  the  former  route  the  impulses  cross  over  in  the  medulla,  through  the 
decussation  of  the  pyramids,  and  descend  in  the  lateral  column  of  the  spinal  cord ; 
but  by  the  uncrossed  route  they  descend  in  the  anterior  column  of  the  cord  and 
decussate  in  succession  through  the  white  commissure.  Impulses  by  either  route 
finally  reach  the  anterior  gray  cornu  of  the  spinal  cord,  and,  with  the  exception  of  a 
small  percentage  of  them,  they  reach  the  cornu  opposite  to  their  Rolandic  origin. 
The  few  undecussated  fibres  in  the  crossed  pyramidal  tract  conduct  uncrossed 
impulses  to  the  anterior  cornu  of  the  same  side."^  2.  Motor  and  inhibiting  influ- 
ences which  reach  the  cranial  nerves  arise  in  the  lower  portion  of  the  motor 
area,  pass  through  the  corona  radiata  and  posterior  two-thirds  of  the  internal 
capsule,  but  deviate  from  the  pyramidal  tract  before  reaching  the  medulla,  and 
pass  to  the  nuclei  of  cranial  nerves  (Fig.  623).  On  the  same  side  fibres  pass  to 
the  nuclei  of  the  fourth  nerve,  but  the  balance  of  the  fibres  cross  and  pass  to 
nuclei  on  the  opposite  side — viz.,  the  nuclei  of  the  third,  fifth,  sixth,  seventh, 
ninth,  tenth,  eleventh,  and  twelfth  cranial  nerves. 

The  Oerebro-cortico-pontal  Paths. — These  paths  pass  through  the  cerebellum. 
Impulses  from  the  prefrontal  region  pass  along  the  corona  radiata,  through  the 
anterior  limb  of  the  internal  capsule  and  the  inner  portion  of  the  crusta.  Impulses 
from  the  temporal  region  pass  along  the  corona  radiata,  through  the  poste- 
rior limb  of  the  internal  capsule  and  the  outer  portion  of  the  crusta.  The  nucleus 
pontis  and  cranial  nerve  nuclei  of  the  same  side  receive  the  impulses  from  both  the 
frontal  and  the  temporal  paths,  and  from  these  depots  the  impulses  are  sent  to 
cranial  nerves  or  to  spinal  nerves.  To  cranial  nerves  they  are  sent  direct  from 
the  synapses  about  the  nuclei.  In  order  to  reach  spinal  nerves  they  pass  to  the 
cerebellar  cortex  by  means  of  the  middle  peduncle  of  the  cerebellum.  From  the 
cerebellar  cortex  the  impulses  pass  through  the  inferior  peduncles  of  the  cerebellum 
and  the  lateral  region  of  the  medulla  to  reach  the  anterior  gray  horn  (by  way  of 
the  antero-lateral  descending  cerebellar  tract). 

The  Intermediate  Crusta  Path  (by  Way  of  the  Intermediate  Bmidle). — Some 
impulses  which  arise  in  the  cerebral  cortex  pass  to  the  corpus  striatum,  then  to  the 
nucleus  pontis  of  the  same  side  (chiefly),  then  byway  of  the  middle  peduncle  of 
the  cerebellum  to  the  cerebellar  cortex,  and  then  along  the  antero-lateral  descend- 
ing cerebellar  tract. 

The  Red  Nucleus  Path. — Impulses  from  the  cerebral  cortex  may  reach  the  red 
nucleus  by  way  of  the  optic  thalamus  (direct  route)  and  by  way  of  the  corpus 
striatum  (indirect  route). 

Impulses  which  reach  the  red  nucleus  by  the  direct  route  travel  along  the 
crossed  descending  tract  of  the  red  nucleus  to  the  centre  of  the  gray  matter  in  the 
crescent  of  the  opposite  side  of  the  cord.  Impulses  which  reach  the  red  nucleus 
by  the  indirect  route  pass  to  the  cerebellar  cortex  of  the  opposite  side  and  from 
the  cortex  along  the  descending  cerebellar  tract. 

Short  Fibre  Paths  (chiefly  in  the  formatio  reticularis). — Santee  presents  a  concise 
explanation  of  the  course  of  impulses  along  these  paths.^  He  describes  five  paths: 
1.  Impulses  having  reached  the  ganglia  of  the  cerebrum  and  mesencephalon, 
pass  along  the  formatio  reticularis  and  reach  the  antero-lateral  ground  bundle 
of  the  spinal  cord  to  ultimately  reach  the  spinal  nerves.  Impulses  leaving  the 
formatio  reticularis  may  reach  motor  cranial  nerve  nuclei.  2.  Impulses  may 
pass  from  the  formatio  in  the  pons  and  by  way  of  the  middle  cerebellar  peduncle 

1  Anatomy  of  the  Brain  and  Spinal  Cord.    By  Harris  E.  Santee.  ^  Ibid. 


THE  NEBVE- PATHS 


961 


reach  the  cerebellar  cortex.  3.  Impulses  which  reach  the  cerebellar  cortex  may 
reach  the  antero-lateral  ground  bundle  of  the  opposite  side  of  the  cord.  4.  From 
the  third  cranial  nerve  nucleus  fibres  pass  to  the  seventh  nerve,  and  impulses  come 
from  the  third  nerve  and  are  sent  to  the  Occipito-fontalis,  Corrugator  supercilii,  and 
Orbicularis  palpebrarum  muscles.  5.  Fibres  pass  from  the  nucleus  of  the  sixth 
cranial  nerve  to  the  nucleus  of  the  opposite  third  nerve,  and  impulses  pass  from 
the  nucleus  of  the  sixth  nerve  of  one  side  to  the  Internal  rectus  muscle  of  the 
opposite  side. 

The  Sensory,  Afferent,  or  Ascending  Tract  (Figs.  624,  625,  and  626).  Path 
by  the  Columns  of  GoU  and  Burdach. — The  course  taken  by  those  fibres  of  the 
posterior  nerve-roots  which  ascend  has  been 
arrived  at  by  dividing  the  nerve-roots  between 
their  ganglia  and  their  entrance  into  the 
spinal  cord  and  subsequently  examining  the 
degenerated  areas.  It  has  been  found  that 
the  fibres  pursue  an  oblique  course,  being 
situated  at  first  in  the  outer  part  of  Bur- 
dach's  column;  higher  up   they  occupy  the 


N.  sens. 


Fig.  624. — Scheme  of  the  sensory  pathway:  c,  central,  p,  peripheral,  neurone;  g,  intervertebral  ganglion 
cell;  b,  short,,  I,  long,  tract;  d,  decussation.     (.Jakob.) 

Fig.  625. — Scheme  showing  the  course  of  the  sensory  pathway:  /,  in  the  cerebrum  and  cerebral  pedun- 
cles; //,  pons  and  cerebellum;  ///,  medulla  oblongata;  IV,  upper  portion  of  cervical  cord;  V,  middle  portion  of 
cervical  cord;  VI,  lumbar  cord;  a,  fibres  from  the  antero-lateral  columns  and  fillet;  b,  fibres  in  the  posterior 
columns;  c,  fibres  from  the  cerebellum  and  lateral  columns.      (.Jakob.) 

Fip.  626. — Scheme  of  the  sensory  pathway.  Peripheral  neurone  (dotted  line):  1,  2,  3,  short,  4,  long,  tracts. 
The  "  switching  stations  "  are  indicated  by  smaller  circles.  Central  neurone  (broken  line):  /,  columns  of  Clarke 
(direct  cerebellar  tract);  //,  interrupted,  ///.  long,  antero-lateral  tracts;  H,  nuclei  of  posterior  column  (f.  gra- 
cilis and  f.  cuneatus);  SIV,  decussatio  lemnisci.      (.Jakob.) 


middle  of  this  column,  being  displaced  inward  by  the  accession  of  other  entering 
fibres,  while  still  higher  they  enter  and  are  continued  upward  in  the  column  of 
Goll.  The  upper  cervical  fibres  do  not  reach  the  column  of  Goll,  but  are 
entirely  confined  to  that  of  Burdach:  The  degeneration  method  proves  that  the 
localization  of  these  fibres  is  very  precise:  the  sacral  nerves  lying  to  the  inner 
side  of  GoU's  column  and  near  its  periphery;  the  lumbar  nerves  to  their  outer 
side;  the  dorsal  nerves  still  more  laterally;  while  the  cervical  nerves  are  con- 
fined to  the  outer  part  of  Burdach's  column. 

61 


962 


THE   NERVOUS   SYSTEM 


On  reaching  the  medulla  these  ascending  fibres  end  by  arborizing  around  the 
cells  in  the  gracile  and  cuneate  nuclei,  and  the  further  upward  course  of  the  tract 
is  effected  by  the  axis-cylinder  processes  of  these  cells.  There  are  two  paths  from 
this  region,  the  direct  and  the  indirect.  The  fibres  of  the  direct  path  decussate  in 
the  medulla,  dorsal  to  the  crossing  of  the  motor  tract,  in  what  is  termed  the  superior 
pyramidal  decussation,  the  sensory  decussation,  or  the  decussation  of  the  fillet(Figs.  605, 
610,  624,  and  626),  terms  which  are  synonymous.  Having  crossed  the  middle  line 
they  ascend  through  the  pons  and  tegmentum  of  the  crus  cerebri,  and,  reaching  the 
ventral  surface  of  the  optic  thalamus,  from  which  they  pass  by  the  three  systems  of 
Flechsig  to  the  cortex.  The  impulses  ascending  from  the  optic  thalamus  pass  to  the 
cortex  through  the  internal  capsule  and  corona  radiata.  Impulses  which  take  the  indi- 
rect path  leave  the  medulla,  pass  to  the  cortex  of  the  superior  worm  of  the  cerebellum, 


Vt    ^ly"  \C)    ,>-,'vN  J* 


I.  Sacral 


Fig.  627. 


-Cutaneous  areas  corresponding  to  the  sensory  segments  of  the  spinal  cord. 
B,  posterior  surface.     (After  Sticker.) 


A ,  anterior  surface. 


and  then  through  the  superior  peduncle  to  the  optic  thalamus  and  the  red  nucleus 
of  the  opposite  side.  These  fibres  also  reach  the  cortex  by  means  of  the  systems 
of  Flechsig.  The  fibres  of  the  sensory  path  are  arranged  as  follows  in  the  internal 
capsule :  those  which  go  to  the  fronto-parietal  cortex  being  situated  in  the  extreme 
front  part  of  the  anterior  limb  of  the  internal  capsule,  while  in  the  hinder  extremity 
of  the  posterior  limb  other  fibres  pass  to  their  distribution  in  the  temporal  and 
occipital  cortex. 

Path  of  Cranial  Nerves  and  Medial  Fillet. — Common  senisory  impulses  passing 
along  the  fifth,  the  vestibular  portion  of  the  eighth,  the  ninth,  and  the  tenth 
nerves  are  conveyed  by  the  medial  fillet  to  the  ventral  portion  of  the  opposite 
optic  thalamus,  and  from  this  region  they  are  taken  to  the  cortex  by  the  systems 
of  Flechsig. 


THE  NERVE-PATHS  963 

Paths  by  the  Direct  Cerebellar  Tract.— The  direct  cerebellar  tract  begins  about 
the  level  of  the  second  lumbar  vertebra,  and  is  the  continuation  upward  of  the 
axis-cylinders  of  Clarke's  column.  At  the  upper  end  of  the  cord  it  passes  into  the 
restiform  body  and  through  this  reaches  the  cortex  of  the  superior  vermis  of 
the  cerebellum.  This  tract  seems  to  lose  some  of  its  fibres  in  the  cord,  since  the 
area  of  degeneration  resulting  from  a  section  of  the  lower  part  of  the  cord  dimin- 
ishes from  below  upward;  only  some  of  its  fibres  therefore  pass  directly  to  the 
cerebellum.  On  the  other  hand,  the  tract  is  reinforced  by  an  accession  of  fibres 
from  the  cord  itself,  so  that  its  transverse  area  is  greater  above  than  below.  Im- 
pulses of  equilibrium  pass  from  the  posterior  roots  of  the  spinal  nerves  and 
ascend  along  the  direct  cerebellar  tract,  chiefly  to  the  cerebellar  cortex  of  the  same 
side,  partly  to  the  cerebellar  cortex  of  the  opposite  side.  From  the  cerebellar 
cortex  they  pass  to  the  cerebral  cortex  by  the  route  previously  referred  to. 

The  Path  by  the  Antero-lateral  Ascending  Cerebellar  Tract. — Ordinary  sensory  and 
thermic  impulses  ascend  along  this  tract  to  the  cerebellar  cortex  of  the  opposite 
side  (the  superior  worm)  and  partly  to  the  optic  thalamus  and  parietal  cortex. 

Short  Fibre  Paths. — According  to  Santee  there  are  three  of  these  paths:  1.  One 
path  is  in  the  antero-lateral  ground  bundle  and  formatio  reticularis.  It  conveys 
sensory  impressions  from  the  gray  matter  of  the  cord  or  from  pontine  and  medul- 
lary nuclei  which  receive  fibres  of  common  sensation  from  cranial  nerves  to  the 
opposite  optic  thalamus.  2.  Another  path  takes  impulses  from  the  formatio 
reticularis  to  the  cerebellar  cortex  and  then  to  the  red  nucleus  and  optic  thalamus. 
3.  Impulses  may  leave  the  antero-lateral  ascending  cerebellar  tract  along  fibres 
which  diverge  in  the  medulla.  These  impulses  reach  the  lateral  nucleus,  pass  to 
the  cerebellar  cortex,  and  finally  attain  the  cerebral  cortex.^ 

Paths  of  Special  Sensations. — (See  the  section  on  Cranial  Nerves.) 

Reflex  Paths. — Reflex  paths  are  almost  infinite  in  number  and  only  a  few  can 
be  set  forth.  A  spinal  reflex  action  is  produced  as  follows:  A  stimulus  im- 
parted to  a  sensory  nerve  ending  is  conveyed  up  the  nerve  to  a  centre  or  several 
centres  in  the  spinal  gray  matter,  from  which  it  is  transferred  to  a  motor  nerve, 
and  by  this  to  a  muscle  which  responds  to  the  stimulus  by  movement.  Such  a 
path  is  called  a  reflex  arc. 

Spinal  Reflexes  (Fig.  628)  may  be  very  simple  or  somewhat  complicated.  In 
the  simple  spinal  reflex  the  cause  of  the  stimulus  is  as  indicated  above.  Among 
these  simple  spinal  reflexes  are  the  patellar  reflex,  the  reflex  withdrawal  of  a  part 
when  irritated,  and  the  skin  reflexes. 

In  a  more  complicated  spinal  reflex  the  "impulses  traverse  at  least  three  neu- 
rones" (Santee).  The  more  complicated  reflexes  are  those  of  "defecation,  mic- 
turition, parturition,  vasomotor  reflexes,  cardio-accelerator  reflexes,  etc."  (Santee). 

A  Cranial  Reflex  travels  up  a  sensory  cranial  nerve  and  is  transferred  to  a  motor 
cranial  nerve.  Among  these  impulses  are  "watering"  of  the  mouth  on  smelling  a 
savory  dish,  the  facial  muscular  contraction  due  to  pain  in  the  fifth  nerve,  cough- 
ing, sneezing,  vomiting,  and  swallowing. 

Spinal  Cranial  Reflexes  are  due  to  the  ascent  of  impulses  in  the  cord  by  way  of 
the  posterior  longitudinal  bundle  or  by  Burdach's  column,  which  impulses  reach 
the  nuclei  of  cranial  motor  nerves.  "Thus  is  brought  about  the  movement  of  the 
eyes  toward  the  source  of  impulse,  a  change  of  facial  expression  to  agree  with 
the  painful  or  pleasing  character  of  the  impulses,  etc."^  Cranial  spinal  reflexes 
are  produced  by  impulses  from  cranial  sensory  nerves  being  transferred  to  spinal 
motor  fibres.  An  example  of  one  of  these  reflexes  is  the  starting  on  hearing  a 
sudden  loud  sound.  Among  these  numerous  reflexes  are  the  respiratory,  auditory, 
and  pupillary. 

'  Anatomy  of  the  Brain  and  Spinal  Cord.     By  Harris  E.  Santee.  *  I^id. 


964 


THE   NERVOUS   SYSTEM 


Cutaneous  Areas  Corresponding  to  the  Sensory  Segments  of  the  Spinal  Cord. — These 
are  shown  in  Figs.  627  and  628. 

Muscular  Supply  from  Motor  Segments  of  the  Cord. — This  is  shown  in  Fig.  628. 


LOCATION   OF    THE    SEGMENTS    FOR 
SENSIBILITY.  MOTILITY 

Smell 


Ihalcam 


aight  j ; 

PhnUal  region  • 

Bye- 

Face  I 

Tongue [ 

Taste 

Hearing  • 

Pharynx  • 

Larynx 
£sophagus 

Thoracic  and  abdominal  • 
viscera 
Occipital  region  • 

Front  of  neck 
Back  of  neck 
Shoulder  . 

(Musculo- 
spiral  n. 
Median  n. 
Ulnar  n. 


:z 


j^ 


.jHf.^ 


Nipple  ' 

Thorax 


Epigastrium  • 

Spigattrie  reflex 

Abdomen  • 
Navel 

Inferior  abdominal  reflex  ■ 


Gluteal  region  • 

Inguinal  region 

Sips 

'  Anterior  ' 


Thigh 


Legi 


Median     

External   ..  . 

.  Posterior 

j  Internal  — 

(  External  — 

Foot,^ 

Scrotum,  penis,  etc.  — 

Bladder,  rectum  w. 

Anvx — 


,  Sphincter  iridis 

"  Ciliaris 

n  Rectus  int.,  levator  palpehr.  sup. 

Rectus  inf.  and  sup. 
'  Obi.  infer. 

•  Obi.  super. 

'  Masseter,  temporal,  pterygoids 

•  Rectus  extern. 

.  Occipitofront.,  orbicularis  oculi  (upper  facial) 
^Muscles  of  expression  {lower  facial) 
'  Palatal  and  pharyngeal  muscle* 
'  Muscles  of  the  larynx 
'  Muscles  of  the  tongue 

"  Sternocleidomastoid 

•  Deep  muscles  of  the  neck 

•  Scaleni 

Trapezius,  serratus  anticut 

•  Diaphragm 

'  Delt.,  biceps,  pectoral,  maj.  {clavic.  piyrtion)  }  ^ 
'  Brachial,  antic,  supinator  longus  >  3 

"^Triceps,  latvi.dorsi,pect.maj.  {costal    "     )J* 
'  Extensores  carpi  et  digitorum^ 

•  Flexores  carpi  et  digitorum    j     '"'*'•''''' 
■  Interossei,  lumbrical.e8  "J 

C  Band, 
'  Thenar,  hypothenar    ) 


Intereottali 
Muscles  of  the  back 
Abdomirud  mutclte 


-•-•  Iliopsoas    "i 
— —  Sartorius    I 
■^Adductors  r  ^*''* 
"Abductors  J 

'  Quadriceps  ^ 

» Flexors        fl^ 

-  Extensors    y 

'Peronei 

.  Flexors,  extenaort  of  the  foot  and  toes 

.  Glutei  (?) 

•  Perineal  > 
•-«.  Vesical    >  Muscidature 

.Rectal     S 


Fig.  628. — Explanation  of  abbreviations:  tr.  oil.,  olfactory  tract;  c.  g.  I.,  lateral  geniculate  body;  p,  r,  cr.  A, 
indicate  approximately  the  location  of  the  reflex  centres  for  the  pupillary  (p),  the  respiratory  (r),  cremasteric  (cr), 
patellar  (pat),  and  tendo  Achillis  (.4)  reflexes.  The  vesical  centre  lies  in  the  third  and  fourth  sacral  segments; 
the  anal  centre  in  the  fourth  and  fifth  (represented  by  circlesK  the  centres  for  erection,  ejaculation,  labor 
pains  (?)  are  probably  also  situated  in  this  region.  In  reality,  the  divisions  between  the  various  segments  are, 
of  course,  not  so  sharp  as  they  are  shown  in  the  diagram,  so  that  a  given  muscle  or  cutaneous  region  derives 
some  of  its  controlling  nerve-roots  from  the  segments  lying  immediately  above  and  below  the  principal  segment. 
The  sensory  segment  for  any  given  regioa  is  regularly  somewhat  higher  than  the  corresponding  motor  segment. 
(Jakob.) 


THE  SPINAL  NERVES  (NERVI  SPINALES). 


The  spinal  nerves  are  so  called  because  they  take  their  origin  from  the  spinal 
cord,  and  are  transmitted  through  the  intervertebral  foramina  on  either  side  of  the 
spinal  column.    There  are  thirty-one  pairs  of  spinal  nerves,  which  are  arranged 


THE    ROOTS    OF    THE   SPINAL    NERVES 


965 


into  the  following  groups,  corresponding  to  the  region  of  the  spine  through  which 
they  pass: 

Cervical    .......       8  pairs. 


Thoracic  or  Dorsal 
Lumbar   . 
Sacral 
Coccygeal 


12 
5 
5 
1 


It  will  be  observed  that  each  group  of  nerves  corresponds  in  number  with  the 
vertebrae  in  that  region,  except  the  cervical  and  coccygeal.  Sometimes  there  is  no 
thirty-first  pair.  Occasionally  below  the  thirty-first  pair  there  may  be  one  or  even 
two  filamentous  pairs  which  do  not  pass  out  of  the  spinal  canal. 

Each  spinal  nerve  arises  by  two  roots,  an  anterior  or  motor  root  and  a  posterior 
or  sensory  root,  the  latter  being  distinguished  by  a  ganglion,  termed  the  spinal 
ganglion. 


DORSA 
NERVE 
ROOTS 


LIGAMENTUM 
,DENTICULATUM 
DURA 
PENED 


SPINAL  NERVE 
IN  ITS  PIAL 
SHEATH 


The  Roots  of  the  Spinal  Nerves  (Figs.  538,  540,  541,  629,  630,  631). 

The  Anterior  or  Ventral   Root  {radix  anterior). — The  superficial    origin  is 
from  the  antero-lateral  columns  of  the  cord,  corresponding  to  the  situation  of  the 
anterior  cornu  of  gray  matter.    Each  root 
is  composed  of   from  four  to  eight  fila- 
ments (fila  radicularia). 

The  deep  origin  can  be  traced  through 
the  antero-lateral  column;  the  roots,  after 
penetrating  horizontally  through  the  lon- 
gitudinal fibres  of  this  tract,  enter  the  gray 
substance,  where  their  fibrils  diverge  in 
several  directions:  some  passing  inward, 
are  continued  across  the  anterior  com- 
missure in  front  of  the  central  canal,  to 
become  continuous  with  the  axis-cylinder 
processes  of  the  large  cells  of  the  anterior 
cornu  of  the  opposite  side;  others  termi- 
nate in  the  mesial  group  of  cells  of  the 
anterior  column  of  the  same  side;  other 
fibrils  pass  outward,  to  become  continuous 
with  the  axis-cylinder  processes  of  the 
group  of  cells  in  the  lateral  part  of  the 
anterior  column. 

The  Posterior  or  Dorsal  Root  {radix 
posterior). — The  superficial  origin  is  by 
filaments  (fila  radicularia),  from  the  pos- 
tero-lateral  fissure  of  the  cord.  The  real 
origin  of  these  fibres  is  from  the  nerve- 
cells  in  the  posterior  root  ganglion,  from 
which  they  can  be  traced  into  the  cord 
in  two  main  bundles,  the  course  of  which 
has  already  been  studied  (p.  847). 

The  anterior  roots  are  smaller  than  the 
posterior,  devoid   of    ganglionic    enlargement,  and  their  component   fibrils   are 
collected  into  two  bundles  near  the  intervertebral  foramina. 

The  posterior  roots  of  the  nerves  are  larger,  but  the  individual  filaments  are 
finer  and  more  delicate  than  those  of  the  anterior.    As  their  component  fibrils 


LIGAMENTUM 
DENTICULATUM 
VENTRAL  ROOTS 


SPINAL   NERVE 
IN   ITS    SHEATH 


Fig.  629. — A  portion  of  the  spinal  cord,  showing 
its  right  lateral  surface.  The  dura  is  opened  and 
arranged  to  show  the  nerve  roots.      (Testut.) 


b 


966 


THE    NERVOUS   SYSTEM 


pass  outward  toward  the  aperture  in  the  dura  mater,  they  coalesce  into  two 
bundles,  receive  a  tubular  sheath  from  that  membrane,  and  enter  the  ganglion 
(Figs.  629,  630,  and  631)  which  is  developed  upon  each  root. 

The  posterior  root  of  the  first  cervical  nerve  forms  an  exception  to  these  char- 
acters. It  is  smaller  than  the  anterior,  has  occasionally  no  ganglion  developed 
upon  it,  and  when  the  ganglion  exists,  it  is  often  situated  within  the  dura  mater. 
The  first  cervical  may  have  a  rudimentary  posterior  root  or  no  posterior  root. 


NTERNAL  BRANCH 

EXTERNAL  BRANCH 


POSTERIOR  PRIMARY 
DIVISION 


^ANTERIOR  PRIMARY 
DIVISION 


RAMUS  COMMUNICANS 


Fig.  630. — Plan  of  the  constitution  of  a  spinal  nerve.     (W.  Xeiller,  in  Gerrish's  Text -book  of  Anatomy.) 

Within  the  spinal  canal  the  nerve-roots  are  separated  from  each  other  by  the 
ligamentum  denticulatum  (Fig.  629).  In  the  cervical  region  the  spinal  portion 
of  the  spinal  accessory  nerve  separates  the  roots.  Each  root  obtains  a  covering 
of  pia  mater,  which  becomes  continuous  with  the  neurilemma;  "  the  arachnoid 
invests  each  root  as  far  as  the  point  where  it  meets  with  the  dura  mater;  the  two 
roots,  after  piercing  the  dura  separately,  are  enclosed  by  it  in  a  single  tubular 
sheath,  in  which  is  included  the  spinal  ganglion  of  the  dorsal  root."* 


Neuraxis  of  Peripheral 
Sensory  Neurone 


Nerve  Trunk 


Spinal  Ganglion 

Dendrite  of 

Peripheral  Sensory 

Neurone 


Neuraxis  of 
Sympathetic  Neurone 


'Neuraxis  of  Peripheral  Motor  Neurone 


f -Sympathetic  Ganglion 

\ 


Fig.  631. — Diagram  to  show  the  composition  of  a  peripheral  nerve-trunk.     (Bohm  and  Davidoff.) 

The  Ganglia  of  the  Spinal  Nerves  (Ganglia  Spinales)  (Figs.  629,  630,  631). 

A  ganglion  is  developed  upon  the  posterior  root  of  each  of  the  spinal  nerves. 
The  ganglion  upon  the  posterior  root  of  the  first  cervical  nerve  may  be  rudimentary 
or  absent.  These  ganglia  are  of  an  oval  form  and  of  a  reddish  color;  they  bear 
a  proportion  in  size  to  the  nerves  upon  which  they  are  formed,  and  are  placed 
in  the  intervertebral  foramina,  external  to  the  point  where  the  nerves  perforate 


1  Cunningham's  Text-book  of  Anatomy. 


POINTS    OF   EMERGENCE    OF    THE   SPINAL    NERVES        967 

the  dura  mater.  Each  gangHon  is  bifid  internally,  where  it  is  joined  by  the 
two  bundles  of  the  posterior  root,  the  two  portions  being  united  into  a  single 
mass  externally.  The  ganglia  upon  the  first  and  second  cervical  nerves  form  an 
exception  to  these  characters,  being  placed  on  the  arches  of  the  vertebrae  over 
which  the  nerves  pass.  The  ganglia  of  the  sacral  nerves  are  placed  within  the 
spinal  canal;  and  that  on  the  coccygeal  nerve,  also  in  the  canal,  is  situated  at 
some  distance  from  the  origin  of  the  posterior  root. 

The  ganglion  in  an  embryo  is  composed  of  bipolar  nerve-cells.  In  an  adult 
the  bipolar  nerve-cells  by  fusion  of  their  two  poles  form  unipolar  nerve-cells.  The 
process  of  each  unipolar  cell  divides  into  two  a  short  distance  from  the  cell.  One 
of  the  processes  from  each  cell  passes  to  the  spinal  cord,  and  the  other  passes 
into  the  spinal  nerve.  On  the  dorsal  roots  of  the  lumbar  and  sacral  nerves, 
between  the  spinal  ganglia  and  the  cord,  small  cellular  masses  occasionally  exist. 
They  are  called  accessory  spinal  ganglia  {ganglia  aberrantia). 

Distribution  of  the  Spinal  Nerves. 

Immediately  beyond  the  ganglion  the  two  roots  coalesce,  their  fibres  inter- 
mingle, and  the  trunk  thus  formed  constitutes  the  spinal  nerve;  it  passes  out 
of  the  intervertebral  foramen,  and  divides  into  a  posterior  primary  division  for 
the  supply  of  the  posterior  part  of  the  body,  and  an  anterior  primary  division 
for  the  supply  of  the  anterior  part  of  the  body  (Fig.  630).  Each  division  contains 
fibres  from  both  roots. 

Before  dividing,  each  spinal  nerve  gives  off  a  small  recurrent  or  meningeal 
branch  (ramus  meningeus)  (Fig.  630),  which  is  joined  by  a  filament  from  the 
communicating  branch  of  the  sympathetic  (ramus  communicans)  (Fig.  630),  which 
connects  the  ganglion  with  the  anterior  division.  The  meningeal  branches  unite 
and  form  one  nerve,  which  passes  inward  through  the  intervertebral  foramen  and 
supplies  the  dura  mater,  sending  branches  to  the  vertebrae  and  vertebral  ligaments. 

The  Posterior  Primary  Divisions  (rami  posteriores)  (Fig.  630). — ^The  posterior  pri- 
mary divisions  of  the  spinal  nerves  are  generally  smaller  than  the  anterior;  they  arise 
from  the  trunk  resulting  from  the  union  of  the  roots,  in  the  intervertebral  foramina; 
and,  passing  backward,  divide  into  internal  and  external  branches,  which  are  dis- 
tributed to  the  muscles  and  integument  behind  the  spine.  The  posterior  primary 
divisions  of  the  spinal  nerves  form  two  small  plexuses,  the  posterior  cervical  plexus 
and  the  posterior  sacral  plexus.  The  first  cervical,  the  fourth  and  fifth  sacral,  and 
the  coccygeal  nerves  do  not  divide  into  external  and  internal  branches. 

The  Anterior  Primary  Divisions  (rami  anteriores)  (Fig.  630). — The  anterior 
primary  divisions  of  the  spinal  nerves  supply  the  parts  of  the  body  in  front  of 
the  spine,  including  the  limbs.  They  are  for  the  most  part  larger  than  the 
posterior  primary  divisions.  Each  division,  soon  after  its  origin,  receives  a  slen- 
der filament  from  the  sympathetic,  which  is  called  the  gray  ramus  communi- 
cans. In  the  dorsal  region  the  anterior  primary  divisions  of  the  spinal  nerves 
are  quite  separate  from  each  other,  and  are  uniform  in  their  distribution ;  but  in  the 
cervical,  lumbar,  and  sacral  regions  they  form  intricate  plexuses  previous  to  their 
distribution.  The  anterior  primary  divisions  of  certain  dorsal,  lumbar,  and  sacral 
nerves  give  off  a  delicate  collection  of  nerve  filaments  to  the  sympathetic  cord. 
These  are  called  the  white  rami  communicantes  or  the  visceral  branches  of  the  spinal 
nerves. 

Points  of  Emergence  of  the  Spinal  Nerves. 

The  roots  of  the  spinal  nerves  from  their  origin  in  the  cord  run  obliquely 
downward  to  their  point  of  exit  from  the  intervertebral  foramina,  the  amount  of 
obliquity  varying  in  different  regions  of  the  spine,  and  being  greater  in  the  lower 


968 


THE   NERVOUS  SYSTEM 


than  the  upper  part.  The  level  of  their  emergence  from  the  cord  is  within  certain 
limits  variable,  and  of  course  does  not  correspond  to  the  point  of  emergence  of 
the  nerve  from  the  intervertebral  foramina. 

The  following  table,  from  Macalister,  shows  as  accurately  as  can  be  shown  the 
relation  of  these  points  of  origin  from  the  spinal  cord  to  the  bodies  and  spinous 
processes  of  the  vertebrae: 


Level  of  body  of 

No.  of  nerve. 

Level  of  tip  of 
spine  of 

Level  of  body  of 

No.  of  nerve. 

Level  of  tip  of 
spine  of 

C.  1 

C.  1 

D.    8 

9 

7  d. 

M 

2 

9 

10 

8  d. 

3 

i'c. 

10 

11 

9  d. 

3 

4 

2  c. 

12 

10  d. 

4 

5 

3  c. 

i'i 

L.  1 

11  d. 

5 

6 

4  c. 

f 

2 

6 

7 
8 

5  c. 

6  c. 

'1 

3 
4 

12  d. 

7 

D.  1 

7  c. 

r 

5 

■      ■ 

D.  1 

2 

1  d. 

1 

S.  1 

2 

3 

L.     1-1 

2 

3 

4 

2'd. 

3 

4 

5 

3  d. 

4 

1  L. 

5 

6 

4  d. 

5 

6 

7 

5  d. 

C.  1 

7 

8 

6  d. 

L.  '"2 

THE  CERVICAL  NERVES  (NN.  CERVICALES). 

The  Roots  of  the  Cervical  Nerves. 

The  roots  of  the  cervical  nerves  increase  in  size  from  the  first  to  the  fifth,  and 
then  remain  the  same  size  to  the  eighth.  The  posterior  roots  bear  a  proportion 
to  the  anterior  as  3  to  1,  which  is  much  greater  than  in  any  other  region,  the 
individual  filaments  being  also  much  larger  than  those  of  the  anterior  roots.  The 
posterior  root  of  the  first  cervical  is  an  exception  to  this  rule;  it  is  smaller  than 
the  anterior  root.  In  direction  the  roots  of  the  cervical  are  less  oblique  than 
those  of  the  other  spinal  nerves.  The  first  cervical  nerve  is  directed  a  little  upward 
and  outward;  the  second  is  horizontal;  the  others  are  directed  obliquely  down- 
ward and  outward,  the  lowest  being  the  most  oblique,  and  consequently  longer 
than  the  upper,  the  distance  between  their  place  of  origin  and  their  point  of  exit 
from  the  spinal  canal  never  exceeding  the  depth  of  one  vertebra. 

The  First  Cervical  or  Suboccipital  Nerve  (w.  suboccipitalis)  (Fig.  632).— The 
posterior  root  may  be  rudimentary  or  absent.  The  trunk  of  the  first  cervical 
nerve  leaves  the  spinal  canal  between  the  occipital  bone  and  the  posterior  arch 
of  the  atlas  (Figs.  16  and  202). 

The  Trunk  of  the  Second  Cervical  Nerve  leaves  the  spinal  canal  between  the 
posterior  arch  of  the  atlas  and  the  lamina  of  the  axis;  and  the  Eighth  (the  last), 
between  the  last  cervical  and  first  dorsal  vertebrae. 

Each  nerve,  at  its  exit  from  the  intervertebral  foramen,  divides  into  a  posterior 
and  an  anterior  division.  The  anterior  divisions  of  the  four  upper  cervical  nerves 
form  the  cervical  plexus.  The  anterior  divisions  of  the  four  lower  cervical  nerves, 
together  with  the  first  dorsal,  form  the  brachial  plexus. 


The  Posterior  or  Dorsal  Divisions  of  the  Cervical  Nerves  (Rami  Posteriores) 

(Fig.  633). 

The  Posterior  Division  of  the  First  Cervical  Nerve  (Figs.  632  and  633)  differs 
from  the  posterior  divisions  of  the  other  cervical  nerves  in  not  dividing  into  an 
internal  and  external  branch.  It  is  larger  than  the  anterior  division,  and  escapes 
from  the  spinal  canal  between  the  occipital  bone  and  the  posterior  arch  of  the  atlas, 


POSTERIOR    OR   DORSAL  DIVISIONS  OF  CERVICAL  NERVES    969 

lying  beneath  the  vertebral  artery.  It  enters  the  suboccipital  triangle  formed  by 
the  Rectus  capitis  posticus  major,  the  Obliquus  superior  and  Obliquus  inferior, 
and,  by  muscular  branches,  supphes  the  Recti  and  Obliqui  muscles,  and  the 
Complexus.  From  the  branch  which  supplies  the  Inferior  oblique  a  communi- 
cating filament  is  given  off  which  joins  the  second  cervical  nerve.  This  nerve 
also  occasionally  gives  off  a  cutaneous  filament,  which  accompanies  the  occipital 
artery  and  communicates  with  the  occipitalis  major  and  minor  nerves. 

The  Posterior  Division  of  the  Second  Cervical  Nerve  is  three  or  four  times  greater 
in  diameter  than  the  anterior  division,  and  the  largest  of  all  the  posterior 
cervical  divisions.  It  emerges  from  the  spinal  canal  between  the  posterior  arch 
of  the  atlas  and  lamina  of  the  axis,  below  the  Inferior  oblique.  It  supplies  a  twig 
to  this  muscle,  and  receives  a  communicating  filament  from  the  first  cervical. 
It  then  divides  into  an  internal  and  an  external  branch. 

The  internal  branch,  called,  from  its  size  and  distribution,  the  great  occipital  nerve 
(occipitalis  major)  (Figs.  632  and  633),  ascends  obliquely  inward  between  the 
Obliquus  inferior  and  Complexus,  and  pierces  the  latter  muscle  and  the  Trapezius 


GREAT   OCCIPI- 
TAL   NERVE 


RECTUS    CAPITIS 
LATERALIS 

ANTERIOR    PRIMARY   DIV1-. 
SION   OF    FIRST   CERVICAL 


POSTERIOR  PRIMARY   DIVI 
SION  OF  FIRST  CERVICAL 


OBLIQUUS 
SUPERIOR 

BRANCH   TO  COMPLEXUS — OUT 

VERTEBRAL   ARTERY 

POSTERIOR  PRIMARY  DIVI- 
SION OF  FIRST  CERVICAL 
ANASTOMOTIC  BRANCH 

ANASTOMOTIC 
THIRD   CERVICAL 


BLIQUUS 
NFERIOR 


Fig.  632. — Dorsal  primary  divisions  of  the  upper  three  cervical  nerves.     (Testut.) 


near  their  attachments  to  the  cranium.  It  is  now  joined  by  a  filament  from  the 
posterior  division  of  the  third  cervical  nerve,  the  anastomotic,  and,  ascending  on 
the  back  part  of  the  head  with  the  occipital  artery,  divides  into  two  branches, 
which  supply  the  integument  of  the  scalp  as  far  forward  as  the  vertex,  com- 
municating with  the  occipitalis  minor.  It  gives  off  an  auricular  branch  to  the 
back  part  of  the  ear  and  muscular  branches  to  the  Complexus. 

The  external  branch  is  often  joined  by  the  external  branch  of  the  posterior 
division  of  the  third  cervical  nerve,  and  supplies  the  Splenius,  Trachelo-mastoid, 
and  Complexus 

The  Posterior  Division  of  the  Third  Cervical  Nerve  (Figs.  632  and  633)  is  smaller 
than  the  preceding,  but  larger  than  the  fourth;  it  differs  from  the  posterior 
divisions  of  the  remaining  cervical  nerves  in  its  supplying  an  additional  filament, 
the  third  occipital  nerve,  to  the  integument  of  the  occiput.  The  posterior  division 
of  the  third  nerve,  like  the  others,  divides  into  an  internal  and  external  branch. 

The  internal  or  cutaneous  branch  passes  between  the  Complexus  and  Semi- 
spinalis,  and,  piercing  the  Splenius  and  Trapezius,  supplies  the  skin  over  the 
latter  muscle. 


970 


THE   NERVOUS   SYSTEM 


The  external  branch  joins  with  that  of  the  posterior  division  of  the  second  to 
supply  the  Splenius,  Trachelo-mastoid,  and  Complexus. 

The  third  or  least  occipital  nerve  {n.  occipitalis  minimus  or  n.  occipitalis  icriius) 
(Fig.  632)  arises  from  the  internal  or  cutaneous  branch  of  the  posterior  division  of 
the  third  cervical  nerve,  beneath  the  Trapezius;  it  then  pierces  that  muscle,  and 
supplies  the  skin  on  the  lower  and  back  part  of  the  head.  It  lies  to  the  inner  side 
of  the  occipitalis  major,  with  which  it  is  connected. 


SA:in>  over* 


Fig.  633. — Posterior  divisions  of  the  upper  cervical  nerves. 

The  posterior  division  of  the  suboccipital  nerve  and  the  internal  branches  of 
the  posterior  divisions  of  the  second  and  third  cervical  nerves  are  occasionally 
joined  beneath  the  Complexus  by  communicating  branches.  This  communication 
is  described  by  Cruveilhier  as  the  posterior  cervical  plexus. 

The  Posterior  Divisions  of  the  Fourth,  Fifth,  Sixth,  Seventh,  and  Eighth  Cervical 
Nerves  pass  backward,  and  divide,  behind  the  Intertransversales  muscles,  into 
internal  and  external  branches. 

The  internal  branches,  the  larger,  are  distributed  differently  in  the  upper  and 
lower  part  of  the  neck.     T^hose  derived   from  the  fourth  and   fifth  nerves   pass 


THE   ANTERIOR    DIVISIONS    OF    THE    CERVICAL   NERVES    97 1 

between  the  Complexus  and  Semispinalis  muscles,  and,  having  reached  the  spin- 
ous processes,  perforate  the  aponeurosis  of  the  Splenius  and  Trapezius,  and  are 
continued  outward  to  the  integument  over  the  Trapezius,  whilst  those  derived 
from  the  three  lowest  cervical  nervies  are  the  smallest,  and  are  placed  beneath 
the  Semispinalis  colli,  which  they  supply,  and  then  pass  into  the  Interspinalis, 
Multifidus  spinae,  and  Complexus,  and  send  twigs  through  this  latter  muscle  to 
supply  the  integument  near  the  spinous  processes  (Hirschfeld). 

The  external  branches  supply  the  muscles  at  the  side  of  the  neck — viz.,  the 
Cervicalis  ascendens,  Transversalis  colli,  and  Trachelo-mastoid. 

The  Anterior  Divisions  of  the  Cervical  Nerves  (Rami  Anteriores). 

The  Anterior  Division  of  the  First  Cervical  Nerve  (Fig.  635)  is  of  small  size. 
It  escapes  from  the  spinal  canal  through  a  groove  upon  the  posterior  arch  of  the 
atlas.  In  this  groove  it  lies  beneath  the  vertebral  artery,  to  the  inner  side  of  the 
Rectus  capitis  lateralis.  As  it  crosses  the  foramen  in  the  transverse  process  of 
the  atlas  it  receives  a  filament  from  the  sympathetic.  It  then  descends  in  front 
of  the  transverse  process,  to  communicate  with  an  ascending  branch  from  the 
second  cervical  nerve. 

Communicating  filaments  from  the  loop  between  this  nerve  and  the  second 
cervical  nerve  join  the  pneumogastric,  the  hypoglossal,  and  sympathetic,  and 
some  branches  are  distributed  to  the  Rectus  lateralis  and  the  two  Anterior  recti. 
The  fibres  which  communicate  with  the  hypoglossal  simply  pass  through  the 
latter  nerve  to  become  for  the  most  part  the  descendens  h3rpoglossi.  According 
to  Valentin,  the  anterior  division  of  the  suboccipital  nerve  distributes  filaments 
to  the  occipito-atlantal  articulation  and  to  the  mastoid  process  of  the  temporal 
bone. 

The  Anterior  Division  of  the  Second  Cervical  Nerve  (Fig.  635)  escapes  from  the 
spinal  canal,  between  the  posterior  arch  of  the  atlas  and  the  lamina  of  the  axis,  and, 
passing  forward  on  the  outer  side  of  the  vertebral  artery,  divides  in  front  of  the 
Intertransverse  muscle  into  an  ascending  branch,  which  joins  the  first  cervical;  and 
one  or  two  descending  branches,  which  join  the  third  cervical.  It  gives  off  the 
small  occipital;  a  branch  to  assist  in  forming  the  great  auricular;  another  to  assist 
in  forming  the  superficial  cervical;  one  of  the  communicantes  h3rpoglossi,  and  a 
filament  to  the  Sterno-mastoid,  which  communicates  in  the  substance  of  the 
muscle  with  the  spinal  accessory. 

The  Anterior  Division  of  the  Third  Cervical  Nerve  (Fig.  635)  is  double  the  size  of 
the  preceding.  At  its  exit  from  the  intervertebral  foramen  it  passes  downward  and 
outward  beneath  the  Sterno-mastoid  muscle,  and  divides  into  two  branches.  The 
ascending  branch  joins  the  anterior  division  of  the  second  cervical;  the  descending 
branch  passes  down  in  front  of  the  Scalenus  anticus  muscle  and  communicates 
with  the  fourth  cervical.  It  gives  off  the  larger  part  of  the  great  auricular  and 
superficial  cervical  nerves;  one  of  the  communicantes  h3rpoglossi;  a  branch  to  the 
supraclavicular  nerves;  a  filament  to  assist  in  forming  the  phrenic;  and  muscular 
branches  to  the  Levator  anguli  scapulae  and  Trapezius;  this  latter  nerve  com- 
municates beneath  the  muscle  with  the  spinal  accessory.  Sometimes  the  nerve 
to  the  Scalenus  medius  is  derived  from  this  source. 

The  Anterior  Division  of  the  Fourth  Cervical  Nerve  (Fig.  635)  is  of  the  same  size  as 
the  preceding.  It  receives  a  branch  from  the  third,  sends  a  communicating  branch 
to  the  fifth  cervical,  and,  passing  downward  and  outward,  divides  into  numerous 
filaments,  which  cross  the  posterior  triangle  of  the  neck,  forming  the  supraclavicular 
nerves.  It  gives  a  branch  to  the  phrenic  nerve,  while  it  is  contained  in  the  inter- 
transverse space,  and  sometimes  a  branch  to  the  Scalenus  medius  muscle.  It  also 
gives  a  branch  to  the  Levator  anguli  scapulae  and  to  the  Trapezius,  which  unites 


972 


THE  NERVOUS  SYSTEM 


with  the  branch  given  off  from  the  third  nerve,  and  communicates  beneath  the 
muscle  with  the  spinal  accessory. 

The  Anterior  Divisions  of  the  Fifth,  Sixth,  Seventh,  and  Eighth  Cervical  Nerves  are 
remarkable  for  their  size.  They  are  much  larger  than  the  preceding  nerves,  and 
are  all  of  equal  dimensions.    They  assist  in  the  formation  of  the  brachial  plexus. 

The  Cervical  Plexus  (Plexus  Cervicalis)  (Figs.  634  and  635). 

The  cervical  plexus  is  formed  by  the  anterior  divisions  of  the  four  upper 
cervical  nerves.  It  is  situated  opposite  the  four  upper  cervical  vertebrae,  rest- 
ing upon  the  Levator  anguli  scapulae  and  Scalenus  medius  muscles,  and  covered 
in  by  the  Stern o-mastoid. 

Its  branches  may  be  divided  into  two  groups,  superficial  and  deep,  which  may 
be  thus  arranged: 

{Occipitalis  minor. 
Auricularis  magnus. 
Superficialis  colli. 


Superficial 


Deep 


Descending 


Internal 


External 


1  Suprasternal. 
Supraclavicular. 
Supra-acromial. 
Communicating. 
Muscular. 

Communicantes  hypoglossi. 
Phrenic. 
Communicating. 
Muscular. 


The  Superficial  Branches  of  the  Cervical  Plexus.     The  Small  Occipital  Nerve 

(n.  occipitalis  minor)  (Fig.  634), — The  small  occipital  nerve  arises  from  the  second 
cervical  nerve,  sometimes  also  from  the  third ;  it  curves  round  the  posterior  border 
of  the  Sterno-mastoid,  and  ascends,  running  parallel  to  the  posterior  border  of  the 
muscle,  to  the  back  part  of  the  side  of  the  head.  Near  the  cranium  it  perforates 
the  deep  fascia,  and  is  continued  upward  along  the  side  of  the  head  behind  the 
ear,  supplying  the  integument,  and  communicating  with  the  occipitalis  major,  the 
auricularis  magnus,  and  with  the  posterior  auricular  branch  of  the  facial. 

This  nerve  gives  off  an  auricular  branch,  which  supplies  the  integument  of  the 
upper  and  back  part  of  the  auricle,  communicating  with  the  mastoid  branch 
of  the  auricularis  magnus.  The  auricular  branch  is  occasionally  derived  from 
the  great  occipital  nerve.  The  occipitalis  minor  varies  in  size;  it  is  occasionally 
double. 

The  Great  Auricular  Nerve  (n.  auricularis  magnus)  (Fig.  634). — The  great 
auricular  nerve  is  the  largest  of  the  ascending  branches.  It  arises  from  the 
second  and  third  cervical  nerves,  winds  around  the  posterior  border  of  the  Sterno- 
mastoid,  and,  after  perforating  the  deep  fascia,  ascends  upon  that  muscle  beneath 
the  Platysma  to  the  parotid  gland,  where  it  divides  into  facial,  auricular,  and 
mastoid  branches. 

The  Facial  Branches  pass  across  the  parotid,  and  are  distributed  to  the  integ- 
ument of  the  face  over  the  parotid  gland;  others  penetrate  the  substance  of  the 
gland  and  communicate  with  the  facial  nerve. 

The  Auricular  Branches  ascend  to  supply  the  integument  of  the  back  of  the 
pinna,  except  at  its  upper  part,  communicating  with  the  auricular  branches  of 
the  facial  and  pneumogastric  nerves.  A  filament  pierces  the  pinna  to  reach  its 
outer  surface,  where  it  is  distributed  to  the  lobule  and  lower  part  of  the  concha. 


THE    CERVICAL   PLEXUS 


973 


The  Mastoid  Branch  communicates  with  the  occipitaUs  minor  and  the  posterior 
auricular  branch  of  the  facial,  and  is  distributed  to  the  integument  behind  the 


ear. 


The  Superficial  Cervical  Nerve  or  the  Superficialis  Colli  {n.  cutaneus  colli)  (Fig. 
634). — The  superficial  cervical  nerve  or  the  superficialis  coUi  arises  from  the 
second  and  third  cervical  nerves,  turns  around  the  posterior  border  of  the  Sterno- 


POSTERIOR 
AURICULAR 
NERVE 


GREAT 

OCCIPITAL 

GREAT 
AURICULAR 

(posterior  branch 

SMALL 
OCCIPITAL 

THIRD 
OCCIPITAL 

GREAT 
AURICULAR 

(anierior  branches) 


BRANCHES  TO 

TRAPEZIUS 

SUPRACLAVICULAR 

NERVES 

(acromial 
branches; 


BRANCHES 
OF  FACIAL 
NERVE 


SUPRACLAVrCULAR 


NERVES  (Sternal 
branches) 


Fig.  634.- 


SUPRACLAVICULAH 

NERVES  (clavicular 
branches) 

-The  cutaneous  branche.s  of  the  right  cervical  plexus,  viewed  from  the  right.    The  Platysma 
has  been  partly  removed.      (Spalteholz  ) 


I 


mastoid  about  its  middle,  and,  passing  obliquely  forward  beneath  the  external 
jugular  vein  to  the  anterior  border  of  the  muscle,  perforates  the  deep  cervical 
fascia,  and  divides  beneath  the  Platysma  into  two  branches,  which  are  distributed 
to  the  antero-lateral  parts  of  the  neck. 

The  Ascending  Sranch  or  Branches  {rami  swperiores)  gives  a  filament  which 
accompanies  the  external  jugular  vein;  it  then  passes  upward  to  the  sub- 
maxillary region,  and  divides  into  branches,  some  of  which  form  a  plexus  with 
the  cervical  branches  of  the  facial   nerve  beneath  the  Platysma;  others  pierce 


974  THE  NERVOUS  SYSTEM 

that  muscle  and  are  distributed  to  the  integument  of  the  upper  half  of  the  neck, 
at  its  forepart,  as  high  as  the  chin. 

The  Descending  Branches  {rami  inferior es),  usually  represented  by  two  or  more 
filaments,  pierce  the  Platysma,  and  are  distributed  to  the  integument  of  the  side 
and  front  of  the  neck,  as  low  as  the  sternum. 

The  Descending  or  Supraclavicular  Branches  {nn.  swpraclaviculares)  (Fig.  634). — 
The  descending  or  supraclavicular  branches  arise  from  the  third  and  fourth 
cervical  nerves;  emerging  beneath  the  posterior  border  of  the  Sterno-mastoid,  they 
descend  in  the  posterior  triangle  of  the  neck  beneath  the  Platysma  and  deep 
cervical  fascia.  Near  the  clavicle  they  perforate  the  fascia  and  Platysma  to 
become  cutaneous,  and  are  arranged,  according  to  their  position,  into  three 
groups. 

The  Inner  or  Suprasternal  Branches  {nn.  swpraclaviculares  anteriores)  cross 
obliquely  over  the  external  jugular  vein  and  the  clavicular  and  sternal  attach- 
ments of  the  Sterno-mastoid  muscle,  and  supply  the  integument  as  far  as  the 
median  line.    They  furnish  one  or  two  filaments  to  the  sterno-clavicular  joint. 

The  Middle  or  Supraclavicular  Branches  {nn.  swpraclaviculares  medii)  cross  the 
clavicle,  and  supply  the  integument  over  the  Pectoral  and  Deltoid  muscles,  com- 
municating with  the  cutaneous  branches  of  the  upper  intercostal  nerves. 

The  External  or  Supra-acromial  Branches  {nn.  supraclaviculares  posteriores)  pass 
obliquely  across  the  outer  surface  of  the  Trapezius  and  the  acromion,  and  supply 
the  integument  of  the  upper  and  back  part  of  the  shoulder. 

The  Deep  Branches  of  the  Cervical  Plexus  (Fig.  635).  Internal  Series. 
The  Communicating  Branches. — The  communicating  branches  consist  of  several 
filaments  which  pass  from  the  loop  between  the  first  and  second  cervical  nerves 
in  front  of  the  atlas  to  the  pneumogastric,  hypoglossal,  and  sympathetic;  of 
branches  from  all  four  cervical  nerves  to  the  superior  cervical  ganglion  of  the 
sympathetic,  together  with  a  branch  from  the  fourth  to  the  fifth  cervical. 

Muscular  Branches. — Muscular  branches  supply  the  Anterior  recti  and  Rectus 
lateralis  muscles;  they  proceed  from  the  first  cervical  nerve,  and  from  the  loop 
formed  between  it  and  the  second. 

The  Gommunicantes  H3rpoglossi  (Fig.  635). — The  communicantes  hypoglossi 
consist  usually  of  two  filaments,  one  being  derived  from  the  second  and  the  other 
from  the  third  cervical.  These  filaments  pass  downward  on  the  outer  side  of  the 
internal  jugular  vein,  cross  in  front  of  the  vein  a  little  below  the  middle  of  the 
neck,  and  form  a  loop  with  the  descendens  hypoglossi  in  front  of  the  sheath  of 
the  carotid  vessels.  Occasionally,  the  junction  of  these  nerves. takes  place  within 
the  sheath. 

The  Phrenic  or  the  Internal  Respiratory  Nerve  of  Bell  {n.  phrenicus)  (Figs.  635  and 
636) . — ^The  phrenic  or  the  internal  respiratory  nerve  of  Bell  arises  chiefly  from  the 
fourth  cervical  nerve,  with  a  few  filaments  from  the  third  and  a  communicating 
branch  from  the  fifth.  It  descends  to  the  root  of  the  neck,  running  obliquely 
across  the  front  of  the  Scalenus  anticus  muscle,  and  beneath  the  Sterno-mastoid 
muscle,  the  posterior  belly  of  the  Omohyoid  muscle,  and  the  Transversalis  colli 
and  suprascapular  vessels.  It  next  passes  over  the  first  part  of  the  subclavian 
artery,  between  it  and  the  subclavian  vein,  and,  as  it  enters  the  chest,  crosses  the 
internal  mammary  artery  near  its  origin.  Within  the  chest  it  descends  nearly 
vertically  in  front  of  the  root  of  the  lung  and  by  the  side  of  the  pericardium, 
between  it  and  the  mediastinal  portion  of  the  pleura,  to  the  Diaphragm,  where 
it  divides  into  branches,  some  few  of  which  are  distributed  to  its  thoracic  surface, 
but  most  of  which  separately  pierce  that  muscle  and  are  distributed  to  its  under 
surface  {rami  phrenicoahdominales) . 

The  two  phrenic  nerves  differ  in  their  length,  and  also  in  their  relations  at  the 
upper  part  of  the  thorax. 


THE    CERVICAL    PLEXUS 


975 


The  right  phrenic  nerve  is  situated  more  deeply,  and  is  shorter  and  more 
vertical  in  direction  than  the  left;  it  lies  on  the  outer  side  of  the  right  vena 
innominata  and  superior  vena  cava. 

The  left  phrenic  nerve  is  rather  longer  than  the  right,  from  the  inclination  of 
the  heart  to  the  left  side,  and  from  the  Diaphragm  being  lower  on  this  than  on  the 
opposite  side.  It  enters  the  thorax  behind  the  left  innominate  vein,  and  crosses 
in  front  of  the  vagus  and  the  arch  of  the  aorta  and  the  root  of  the  lung.  In  the 
thorax  each  phrenic  nerve  is  accompanied  by  a  branch  of  the  internal  mammary 
artery,  the  comes  nervi  phrenici. 


Recti  Cap.  Lat. 


\Rect.  Ant.  Major 
iReci.  Ant.  Minor 


'  To  Sympathetic 

3  To  Hypoglossal 
iTo  Vagiix 

— JTo  Scalp  and  Occipito  Frontalis 


irr 


Fig.  635. — Plan  of  the  cervical  plexus. 


Each  nerve  supplies  filaments  to  the  Diaphragm,  pericardium,  and  pleura, 
and  near  the  chest  is  joined  by  a  filament  from  the  sympathetic,  and,  occasion- 
ally, by  one  from  the  union  of  the  descendens  hypoglossi  with  the  spinal  nerves; 
this  filament  is  found,  according  to  Swan,  only  on  the  left  side.  The  phrenic  fre- 
quently receives  a  filament  from  the  nerve  to  the  Subclavian  muscle.  Branches 
have  been  described  as  passing  to  the  peritoneum. 

From  the  right  nerve  one  or  two  filaments  pass  to  join  in  a  small  ganglion  with 
phrenic  branches  of  the  solar  plexus;  and  branches  from  this  ganglion  are 
distributed  to  the  hepatic  plexus,  the  suprarenal  capsule,  and  inferior  vena 
cava. 

From  the  left  nerve  filaments  pass  to  join  the  phrenic  plexus  of  the  sympathetic, 
but  without  any  ganglionic  enlargement. 


976 


THE  NERVOUS  SYSTEM 


Surgical  Anatomy. — Irritation  of  the  phrenic  nerve  causes  hiccough  and  persistent  cough. 
Bilateral  paralysis  of  the  phrenic  causes  death  from  paralysis  of  the  Diaphragm.  This  form  of 
death  is  seen  by  the  surgeon  in  fracture-dislocation  of  the  third  cervical  vertebra.  Division  of 
the  phrenic  on  one  side  is  not  fatal,  and  is  occasionally  practised  by  the  surgeon  in  removing 
a  tumor  of  the  neck.  In  Hearn's  and  Franklin's  cases  of  removal  of  the  pneumogastric,  the 
phrenic  was  also  divided.  Unilateral  division  of  the  phrenic  nerve  causes  paralysis  of  the  corre- 
sponding half  of  the  Diaphragm,  which  is  difficult  of  recognition,  because,  as  Gowers  points  out, 
the  patient  can  still  take  deep  inspirations,  the  thoracic  muscles  not  being  paralyzed. 


ANTERIOR   PRIMARY 

DIVISION   OF 

FOURTH  CERVICAL 


BRACHIAL 
PLEXUS 


PNEUMOGASTRIC 


PHRENIC 

INFERIOR 
CERVICAL 
GANGLION 
INFERIOR 
LARYNGEAL 


PNEUMOGASTRIO 


rCRICARDIA 
BRANCH 


NERVE  TO 

SUBCLAVIUS 

MUSCLE 

COMMUNICATING 

BRANCH    FROM 
BRACHIAL  PLEXUS 

THORACIC  CARDIAC 
BRANCH  OF 
PNEUMOGASTRIC 
NFERIOR 
RYNGEAL 

ANTERIOR 
PULMONARY 

ANTERIOR 

PULMONARY 

PLEXUS 


RAMIFICATIONS 
OF  PHRENIC 


Fig.  636. — The  phrenic  nerve  and  its  relations  with  the  vagus  nerve.     (Toldt.) 


The  Deep  Branches  of  the  Cervical  Plexus.  External  Series.  Communicating 
Branches. — The  deep  branches  of  the  external  series  of  the  cervical  plexus  com- 
municate with  the  spinal  accessory  nerve,  in  the  substance  of  the  Sterno-mastoid 
muscle,  in  the  posterior  triangle,  and  beneath  the  Trapezius. 

Muscular  Branches. — Muscular  branches  are  distributed  to  the  Sterno-mastoid, 
Trapezius,  Levator  anguli  scapulae,  and  Scalenus  medius. 

The  branch  for  the  Sterno-mastoid  is  derived  from  the  second  cervical;  the 
Trapezius  and  Levator  anguli  scapulae  receive  branches  from  the  third  and  fourth. 


THE  BRACHIAL    PLEXUS 


977 


The  Scalenus  medius  is  derived  sometimes  from  the  third,  sometimes  the  fourth, 
and  occasionally  from  both  nerves. 

Surgical  Anatomy.— The  cervical  plexus  may  be  damaged  by  wounds  or  contusions,  which 
may  or  may  not  be  associated  with  fracture  of  the  clavicle.  Paralysis  ensues,  the  extent  depend- 
ing on  the  degree  of  damage.  After  a  contusion  the  paralysis  is  apt  to  be  temporary  and  to 
be  followed  by  pain  and  muscular  spasm  in  the  arm.  Paralysis  of  the  arm  due  to  plexus  injury 
may  be  partial  or  com))lete.  In  some  cases  there  is  complete  motor  palsy  and  partial  sensory 
palsy,  the  sensory  impulses  passing  along  undamaged  collaterals.  In  certain  spasmodic  diffi- 
culties the  surgeon  occasionally  stretches  the  cervical  plexus.  It  is  reached  by  an  incision  at  the 
posterior  margin  of  the  Sterno-cleido-mastoid  muscle.  This  incision  begins  two  inches  below 
the  level  of  the  tip  of  the  mastoid  and  is  carried  downward  for  three  inches. 

The  Brachial  Plexus  (Plexus  Brachialis)  (Figs.  637,  638,  639). 

The  brachial  plexus  is  formed  by  the  union  of  the  anterior  divisions  of  the 
four  lower  cervical  and  the  greater  part  of  the  first  dorsal  nerves,  receiving  usually 


ANTERIOR 
DIVISION   OF 
FOURTH  CERVICAL' 

DORSALIS- 
SCAPULiE 


DESCENDING 
BRANCH   OF 
HYPOGLOSSAL 

ANSA 
HYPOGLOSSI 


SUPRASCAPULAR 


^L^q 


O.  l''D« 


ICTORALISi 


FtG.  637. — The  right  brachial  plexus  with  its  short  branches,  viewed  from  in  front.  The  sterno-cleido-mastoid 
and  trapezius  muscles  have  been  completely,  the  omohyoid  and  subclavian  have  been  partially,  removed;  a  piece 
has  been  sawed  out  of  the  clavicle;  the  pectoralis  muscles  have  been  incised  and  reflected.     (Spalteholz.) 

a  fasciculus  from  the  fourth  cervical  nerve,  and  frequently  one  from  the  second 
dorsal  nerve.  It  extends  from  the  lower  part  of  the  side  of  the  neck  to  the  axilla. 
It  is  very  broad,  and  presents  little  of  a  plexiform  arrangement  at  its  commence- 
ment. It  is  narrow  opposite  the  clavicle,  becomes  broad  and  forms  a  more  dense 
interlacement  in  the  axilla,  and  divides  opposite  the  coracoid  process  into  numer- 
ous branches  for  the  supply  of  the  upper  limb.  The  nerves  which  form  the  plexus 
are  all  similar  in  size,  and  their  mode  of  communication  is  subject  to  considerable 
variation,  so  that  no  one  plan  can  be  given  as  applying  to  every  case.  The  follow- 
ing appears,  however,  to  be  the  most  constant  arrangement:  above  the  clavicle 

62 


978 


THE  NERVOUS  SYSTEM 


MUSCULOCUTANEOUS 
NERVE 


INTERCOSTC-HUMERAL 
NERVES 


LESSER   INTERNAL 
CUTANEOUS  NERVES 


LONG  SUBSCAPULA 
NERVE 


SUBSCAPULAR 
NERVES 


LATERAL  CUTA- 
NEOUS  BRANCH 
OF   FOURTH 
INTERCOSTAL 


LATERAL  CUTANEOUS 

BRANCH  OF 

THIRD  INTERCOSTAL 


LONG  THORACIC 
NERVE 


Fig  638  —The  riirht  brachial  plexus  (infraclavicular  portion)  in  the  axilliary  fossa,  viewed  from  below  and  in 
tfront. '  The  Pectoralis  major  and  minor  muscles  have  been  in  large  part  removed;  their  attachments  have  been 
reflected.     (Spalteholz.) 


"VCervical 


Bkomboid 

Subclavian 


O.  tetth  Phrenic 

VII  Oe,rvical 

Sranches  to  Longua  1/  — ^i^* 

Colli  and  Scateni 


Anterior  division 
of  Middle.  Trunk 


J.  Dorsal 


Suprascapular 

Upper  Trunk 

Middle  Trunk 

Anterior  division  of  Upper  Trunk 

External  Anterior  Thoracic 
Posterior  division  of  Upper  Trunk 
Upper  Sub-scapular 
Middle  and  Lower 
Sub-scapular 

Circumflex 


Lower  Trunk 


J^)8terior  division  of  Middle  Trunk 


Posterior  Thoracic' 
Anterior  division  of  Lower  Trunk 

Posterior  division  of  Lower  Trunk 

Internal  Anterior  Thoracic 

Lesser  Internal  Cutaneous 

Internal  Cutaneous 


Musculo-cutaneous 


Muaculo-spiral 
Fig.  639. — Plan  of  the  brachial  plexus. 


THE   BRACHIAL    PLEXUS 


979 


{'pars  supraclavicular  is)  the  fifth  and  sixth  cervical  unite  together  soon  after  their 
exit  from  the  intervertebral  foramina  to  form  a  common  trunk.  The  eighth  cer- 
vical and  first  dorsal  also  unite  to  form  one  trunk.  So  that  the  nerves  forming 
the  plexus,  as  they  lie  on  the  Scalenus  medius  external  to  the  outer  border  of  the 


Fig.  640. — Cutaneous  nerves  of  right  upper 
extremity.     Anterior  view. 


Fig.  641. — Cutaneous  nerves  of  right  upper 
extremity.      Posterior  view. 


Scalenus  anticus  muscle,  are  blended  into  three  trunks — an  upper  one,  formed 
by  the  junction  of  the  fifth  and  sixth  cervical  nerves;  a  middle  one,  consisting 
of  the  seventh  cervical  nerve;  and  a  lower  one,  formed  by  the  junction  of  the 
eighth  cervical  and  first  dorsal  nerves.  As  they  pass  beneath  the  clavicle,  to 
compose  the  infraclavicular  part  of  the  plexus  (pars  infraclavicularis),  each  of 


980 


THE   NEBVOU8   SYSTEM 


these  three  trunks  divides  into  two  branches,  an  anterior  and  a  posterior.^     The 
anterior  divisions  of  the  upper  and  middle  trunks  then  unite  to  form  a  common 

cord,  which  is  situated  on  the 
outer  side  of  the  middle  part 
of  the  axillary  artery,  and  is 
called  the  outer  cord  of  the 
brachial  plexus  (fasciculus  lat- 
eralis) .  The  anterior  division 
of  the  lower  trunk  passes 
down  on  the  inner  side  of  the 
axillary  artery  in  the  middle 
of  the  axilla,  and  forms  the 
inner  cord  of  the  brachial  plexus 
{fasciculus  medialis) .  The 
posterior  divisions  of  all  three 
trunks  unite  to  form  the  pos- 
terior cord  of  the  brachial  plexus 
(fasciculus  posterior),  which  is 
situated  behind  the  second 
portion  of  the  axillary  artery. 
From  this  posterior  cord  are 
given  off  the  two  lower  sub- 
scapular nerves,  the  upper 
subscapular  nerve  being  given 
off  from  the  posterior  division 
of  the  upper  trunk  prior  to  its 
junction  with  the  posterior 
division  of  the  lower  and  mid- 
dle trunks.  The  posterior  cord 
divides  into  the  circumflex 
and  musculo-spiral  nerves. 

The  brachial  plexus  com- 
municates with  the  cervical 
plexus  by  a  branch  from  the 
fourth  to  the  fifth  cervical 
nerve,  and  with  the  phrenic 
nerve  by  a  branch  from  the 
fifth  cervical,  which  joins  that 
nerve  on  the  Anterior  scalenus 
muscle;  the  fifth  and  sixth 
cervical  nerves  are  joined  by 
filaments  to  the  middle  cervical 
ganglion  of  the  sympathetic, 
the  seventh  and  eighth  cervical 
to  its  inferior  ganglion,  and  the 
first  dorsal  nerve  to  its  first 
thoracic  ganglion.  Close  to 
their  exit  from  the  interverte- 
bral foramina  the  nerves  give 
off  the  filaments  to  the  ganglia. 
Relations. — In  the  neck,  the  brachial  plexus  lies  in  the  posterior  triangle,  being 
covered  by  the  skin,  Platysma,  and  deep  fascia;  it  is  crossed  by  the  posterior  belly 


Fig.  642. — Cutaneous  nerves  of  the  upper  limb,  ventral  aspect. 
(W.  Keiller,  in  Gerrish's  Text-book  of  Anatomy.) 


'_  The  posterior  division  of  the  lower  trunk  is  very  much  smaller  than  the  others,  and  is  frequently  derived 
entirely  from  the  eighth  cervical  nerve. — En.  of  15th  English  edition. 


I 


THE   BRACHIAL    PLEXUS 


981 


of  the  Omo-hyoid  muscle  and  by  the  transversahs  colH  artery.    When  the  posterior 

scapular  artery  arises  from  the  third  part  of  the  subclavian  it  usually  passes  between 

the  roots  of  the  plexus.    The  plexus  lies  at  first  between  the  Anterior  and  Middle 

scaleni     muscles,     and     then 

above  and  to  the  outer  side 

of  the  subclavian   artery;    it 

next  passes  behind  the  clavicle 

and  Subclavius  muscle,  lying 

upon  the  first  serration  of  the 

Serratus    magnus,    and    the 

Subscapularis  muscles.    It  is 

in  close  relation  with  the  apex 

of  the  lung  (Luschka).    In  the 

axilla  it  is  placed  on  the  outer 

side  of  the  first  portion  of  the 

axillary  artery;    it  surrounds 

the  artery  in  the  second  part 

of  its  course,  one  cord  lying 

upon   the   outer  side  of  that 

vessel,  one  on  the  inner  side, 

and  one  behind  it,  and  at  the 

lower  part  of  the  axillary  space 

gives  off  its  terminal  branches 

to  the  upper  extremity. 

Branches. — The  branches 
of  the  brachial  plexus  are 
arranged  in  two  groups — viz., 
those  given  off  above  the 
clavicle,  and  those  below  the 
clavicle. 

Branches  above  the  Clavicle 
(Figs.  637  and  639).— The 
branches  above  the  clavicle, 
from  the  jpars  swpraclavicu- 
laris,  are — the 

Communicating. 
Muscular. 
Posterior  thoracic. 
Suprascapular. 

The  Communicating    Branch 

(Figs.  636  and  639).— The 
commvmicating  branch  with 
the  phrenic  is  derived  from  the 
fifth  cervical  nerve  or  from 
the  loop  between  the  fifth  and 
sixth;  it  joins  the  phrenic  on 
the  Anterior  scalenus  muscle. 
The  communications  with  the 
sympathetic  have  already  been 
referred  to. 

The  Muscular  Branches  {rami  musculares). — The  muscular  branches  supply  the 
Longus  colli,  Scaleni,  Rhomboidei,  and  Subclavius  muscles.  Those  for  the 
I^ongus  colli  and  Scaleni  arise  from  the  four  lower  cervical  nerves  at  their  exit 


Fig.  643. — Cutaneous  nerve  of  the  upper  limb,  dorsal  aspect. 
(W.  Keiller,  in  Gerrish's  Text-book  of  Anatomy.) 


982 


THE  NERVOUS  SYSTEM 


from  the  intervertebral  foramina.    The  Rhomboid  branch  is  called  the  posterior 
scapular  nerve  (n.  dorsalis  scapulae)  (Figs.  637  and   639),  arises  from  the  fifth 


External  anterior  thoracic. 

Internal  anterior  thoracic. 

Musculo  -  cutaneom. 


Median. 


Musculo-spiral. 
Posterior 

interosseous. 


Anterior 
interosseous. 


Fig.  644. — Nerves  of  the  left  upper  extremity. 


THE  BRACHIAL    PLEXUS  983 

cervical,  pierces  the  Scalenus  medius,  and  passes  beneath  the  Levator  anguli 
scapulae,  which  it  occasionally  supplies,  to  the  Rhomboid  muscles.  The  nerve  to 
the  Subclavius  {n.  suhclavius)  is  a  small  filament  which  arises  from  the  fifth  cervical 
at  its  point  of  junction  with  the  sixth  nerve;  it  descends  in  front  of  the  third 
part  of  the  subclavian  artery  to  the  Subclavius  muscle,  and  is  usually  connected 
by  a  filament  with  the  phrenic  nerve. 

The  Posterior  Thoracic,  the  Long  Thoracic,  or  the  External  Respiratory  Nerve  of  Bell 
(n.thoracalis  longus)  (Figs.  637,  638,  639,  and  644). — The  posterior  thoracic,  the 
long  thoracic,  or  the  external  respiratory  nerve  of  Bell  supplies  the  Serratus 
magnus  muscle,  and  is  remarkable  for  the  length  of  its  course.  It  sometimes 
arises  by  two  roots  from  the  fifth  and  sixth  cervical  nerves  immediately  after 
their  exit  from  the  intervertebral  foramina,  but  generally  by  three  roots  from 
the  fifth,  sixth,  and  seventh  nerves.  These  unite  in  the  substance  of  the  Middle 
scalenus  muscle,  and,  after  emerging  from  it,  the  nerve  passes  down  behind  the 
brachial  plexus  and  the  axillary  vessels,  resting  on  the  outer  surface  of  the  Serratus 
magnus.  It  extends  along  the  side  of  the  chest  to  the  lower  border  of  that  muscle, 
supplying  filaments  to  each  of  the  muscular  digitations. 

The  Suprascapular  Nerve  (n.  suprascapularis)  (Figs.  637,  639,  and  645). — The 
suprascapular  nerve  arises  from  the  cord  formed  by  the  fifth  and  sixth  cervical 
nerves;  passing  obliquely  outward  beneath  the  Trapezius  and  the  Omo-hyoid,  it 
enters  the  supraspinous  fossa  below  the  transverse  or  suprascapular  ligament,, 
and,  passing  beneath  the  Supraspinatiis  muscle,  curves  around  the  external  border 
of  the  spine  of  the  scapula  to  the  infraspinous  fossa.  In  the  supraspinous  fossa 
it  gives  of?  two  branches  to  the  Supraspinatus  muscle,  and  an  articular  fila- 
ment to  the  shoulder-joint;  and  in  the  infraspinous  fossa  it  gives  ofY  two  branches 
to  the  Infraspinatus  muscle,  besides  some  filaments  to  the  shoulder-joint  and 
scapula 

Branches  below  the  Clavicle  (Figs.  638  and  639). — The  branches  below  the 
clavicle,  that  is,  the  branches  from  the  pars  suhclavicularis  of  the  brachial 
plexus,  are  derived  from  the  three  cords  of  the  brachial  plexus,  in  the  following 
manner: 

From  the  Outer  Cord. — From  the  outer  cord  arise  the  external  anterior  thoracic 
nerve,  the  musculo-cutaneous,  and  the  outer  head  of  the  median. 

From  the  Inner  Cord. — From  the  inner  cord  arise  the  internal  anterior  thoracic 
nerve,  the  internal  cutaneous,  the  lesser  internal  cutaneous  (nerve  of  Wrisberg), 
the  ulnar,  and  inner  head  of  the  median. 

From  the  Posterior  Cord. — From  the  posterior  cord  arise  two  of  the  three  sub- 
scapular nerves,  the  third  taking  origin  from  the  posterior  division  of  the  trunk 
formed  by  the  fifth  and  sixth  cervical  nerves;  the  cord  then  divides  into  the 
musculo-spiral  and  circumflex  nerves. 

These  branches  from  below  the  clavicle  may  be  arranged  according  to  the 
parts  they  supply: 

To  the  chest  .  .  .  .         Anterior  thoracic. 

„-      ,       ,      ,  ,  (Subscapular. 

To  the  shoulder     .  .  .  -in-  a 

(Circumflex. 


To  the  arm,  forearm,  and  hand 


Musculo-cutaneous. 

Internal  cutaneous. 

Lesser  internal  cutaneous. 

Median. 

Ulnar. 

Musculo-spiral. 


984  THE  NERVOUS  SYSTEM 

The  fasciculi  of  which  these  nerves  are  composed  may  be  traced  through  the 
plexus  to  the  spinal  nerves  from  which  they  originate.    They  are  as  follows: 

External  anterior  thoracic  from  5th,  6th,  and  7th  cervical. 
Internal  anterior  thoracic      "      8th  cervical  and  1st  dorsal. 
Subscapular  "       5th,  6th,  7th,  and  8th  cervical. 

Circumflex  "       5th  and  6th  cervical. 

Musculo-cutaneous  "       5th  and  6th  cervical. 

Internal  cutaneous  "       8th  cervical  and  1st  dorsal. 

Lesser  internal  cutaneous      "       1st  dorsal. 

Median  "       6th,  7th,  and  8th  cervical,  and  1st  dorsal. 

Ulnar  "       8th  cervical  and  1st  dorsal. 

Musculo-spiral  "       6th,  7th,  and  8th  cervical,  sometimes  also 

from  the  5th. 

The  Anterior  Thoracic  Nerves  {nn.  thoracales  anteriores)  (Figs.  637,  638,  and  639). 
— The  anterior  thoracic  nerves,  two  in  number,  supply  the  Pectoral  muscles. 

The  External  or  Superficial  Anterior  Thoracic  Nerve  (Figs.  637  and  644)  ,the  larger 
of  the  two,  arises  from  the  outer  cord  of  the  brachial  plexus,  through  which  its 
fibres  may  be  traced  to  the  fifth,  sixth,  and  seventh  cervical  nerves.  It  passes 
inward,  across  the  axillary  artery  and  vein,  pierces  the  costo-coracoid  membrane, 
and  is  distributed  to  the  under  surface  of  the  Pectoralis  major  muscle.  It  sends 
down  a  communicating  filament  to  join  the  internal  anterior  thoracic  nerve,  and 
this  communicating  filament  forms  a  loop  around  the  inner  side  of  the  axillary 
artery. 

The  Internal  or  Deep  Anterior  Thoracic  Nerve  arises  fi-om  the  inner  cord,  and 
through  it  from  the  eighth  cervical  and  first  dorsal  nerves.  It  passes  behind 
the  first  part  of  the  axillary  artery,  then  curves  forward  between  the  axillary 
artery  and  vein,  and  joins  with  the  filament  from  the  anterior  nerve.  It  then 
passes  to  the  under  surface  of  the  Pectoralis  minor  muscle,  where  it  divides  into 
a  number  of  branches,  which  supply  the  muscle  on  its  under  surface.  Some 
two  or  three  branches  pass  through  the  muscle  and  reach  the  Pectoralis  major. 

The  Subscapular  Nerves  {nn.  svbscapulares)  (Figs.  638  and  639). — The  sub- 
scapular nerves  arise  from  the  posterior  cord  of  the  plexus.  There  are  three 
subscapular  nerves,  and  they  supply  the  Subscapularis,  Teres  major,  and  Latis- 
siraus  dorsi  muscles,  and  give  filaments  to  the  shoulder-joint.  The  fasciculi  of 
which  they  are  composed  may  be  traced  to  the  fifth,  sixth,  seventh,  and  eighth 
cervical  nerves. 

The  First,  Short  or  Upper  Subscapular  Nerve,  the  smallest,  arises  from  the  pos- 
terior division  of  the  upper  trunk  of  origin  of  the  brachial  plexus,  and  enters 
the  upper  part  of  the  Subscapularis  muscle ;  this  nerve  is  frequently  represented 
by  two  branches. 

The  Second  or  Lower  Subscapular  Nerve  arises  from  the  posterior  end  of  the 
brachial  plexus,  enters  the  axillary  border  of  the  Subscapularis  and  terminates  in 
the  Teres  major.     The  latter  muscle  is  sometimes  supplied  by  a  separate  branch. 

The  Third,  Middle  or  Long  Subscapular  Nerve  (n.  thoracodorsalis)  (Fig.  638) ,  the 
largest  of  the  three,  arises  from  the  posterior  end  of  the  brachial  plexus  and  follows 
the  course  of  the  subscapular  artery,  along  the  posterior  wall  of  the  axilla  to  the 
Latissimus  dorsi  muscle,  through  which  it  may  be  traced  as  far  as  its  lower  border. 

The  Circumflex  Nerve  (n.  axillaris)  (Figs.  639  and  645). — The  circumflex  nerve 
supplies  some  of  the  muscles,  the  shoulder-joint,  and  the  integument  of  the  shoulder 
(Figs.  640  and  641) ,  It  arises  from  the  posterior  cord  of  the  brachial  plexus,  in 
common  with  the  musculo-spiral  nerve,  and  its  fibres  may  be  traced  through  the 
posterior  cord  to  the  fifth  and  sixth  cervical  nerves.  It  is  at  first  placed  behind  the 
axillary  artery,  between  it  and  the  Subscapularis  muscle,  and  passes  downward 


THE   BRACHIAL    PLEXUS  985 

and  outward  to  the  lower  border  of  that  muscle.  It  then  winds  backward  in  com- 
pany with  the  posterior  circumflex  artery,  through  a  quadrilateral  space  bounded 
above  by  the  Teres  minor  muscle,  below  by  the  Teres  major  muscle,  internally 
by  the  long  head  of  the  Triceps  muscle,  and  externally  by  the  neck  of  the  humerus. 
The  nerve  then  divides  into  two  branches. 

The  Upper  Branch  (Fig.  645)  winds  backward  around  the  surgical  neck  of  the 
humerus,  beneath  the  Deltoid,  with  the  posterior  circumflex  vessels,  as  far  as  the 
a.nterior  border  of  that  muscle,  supplying  it,  and  giving  off  cutaneous  branches, 
which  pierce  the  muscle  and  ramify  in  the  integument  covering  its  lower  part 
(Fig.  642). 

The  Lower  Branch  (Fig.  645),  at  its  origin,  distributes  filaments  to  the  Teres 
minor  and  back  part  of  the  Deltoid  muscles.  Upon  the  filaments  to  the  former 
muscle  an  oval  enlargement  usually  exists.  The  nerve  then  pierces  the  deep 
fascia,  and  supplies  the  integument  over  the  lower  two-thirds  of  the  posterior 
surface  of  the  Deltoid  (n.  cutaneus  brachii  lateralis),  as  well  as  that  covering 
the  long  head  of  the  Triceps  (caput  longum  n.  tricipitis  brachii)  (Fig.  643). 

The  circumflex  nerve,  before  its  division,  gives  off  an  articular  filament,  which 
enters  the  shoulder-joint  below  the  Subscapularis  muscle. 

The  Musculo-cutaneous  or  the  External  Cutaneous  Nerve  or  the  Perforating  Nerve 
of  Casserius*  (n.  musculocutayieus)  (Figs.  638,  639,  and  644). — ^The  musculo- 
cutaneous, or  the  external  cutaneous  nerve,  supplies  some  of  the  muscles  of  the 
arm  and  the  integument  of  the  forearm.  It  arises  from  the  outer  cord  of  the 
brachial  plexus,  opposite  the  lower  border  of  the  Pectoralis  minor  muscle, 
receiving  filaments  from  the  fifth,  sixth,  and  seventh  cervical  nerves.  It  per- 
forates the  Coraco-brachialis  muscle  (Fig.  644) ,  passes  obliquely  between  the  Biceps 
and  Brachialis  anticus  muscles  to  the  outer  side  of  the  arm,  and,  a  little  above 
the  elbow,  winds  around  the  outer  border  of  the  tendon  of  the  Biceps,  and,  per- 
forating the  deep  fascia,  becomes  cutaneous  (Fig.  640) .  This  nerve,  in  its  course 
through  the  arm,  supplies  the  Coraco-brachialis,  Biceps,  and  the  greater  part 
of  the  Brachialis  anticus  muscles.  The  branch  to  the  Coraco-brachialis  is  given 
off  from  the  nerve  close  to  its  origin,  and  in  some  instances,  as  a  separate  fila- 
ment from  the  outer  cord  of  the  plexus.  The  branches  to  the  Biceps  and 
Brachialis  anticus  are  given  off  after  the  nerve  has  pierced  the  Coraco-brachialis. 
The  nerve  also  sends  a  small  branch  to  the  humerus,  which  enters  the  nutrient 
foramen  with  the  accompanying  artery,  and  a  filament,  from  the  branch  supplying 
the  Brachialis  anticus,  goes  to  the  elbow-joint.  The  musculo-cutaneous  furnishes 
the  chief  nerve  supply  to  this  joint. 

The  Cutaneous  Portion  of  the  Musculo-cutaneous  Nerve  (n.  cutaneiis  antibrachii 
lateralis)  passes  behind  the  median  cephalic  vein,  and  divides,  opposite  the 
elbow-joint,  into  an  anterior  and  a  posterior  branch. 

The  anterior  branch  descends  along  the  radial  border  of  the  forearm  to  the 
wrist,  and  supplies  the  integument  over  the  outer  half  of  the  anterior  surface.  At 
the  wrist-joint  it  is  placed  in  front  of  the  radial  artery,  and  some  filaments,  piercing 
the  deep  fascia,  accompany  that  vessel  to  the  back  of  the  wrist,  supplying  the 
carpus.  The  nerve  then  passes  downward  to  the  ball  of  the  thumb,  where  it 
terminates  in  cutaneous  filaments.  It  communicates  with  a  branch  from  the  radial 
nerve  and  with  the  palmar  cutaneous  branch  of  the  median. 

The  posterior  branch  passes  downward  along  the  back  part  of  the  radial  side 
of  the  forearm  to  the  wrist.  It  supplies  the  integument  of  the  lower  third  of  the 
forearm,  communicating  with  the  radial  nerve  and  the  external  cutaneous  branch 
of  the  musculo-spiral.  The  cutaneous  areas  supplied  by  the  musculo-cutaneous 
nerve  are  indicated  in  Figs.  642  and  643. 

The  musculo-cutaneous  nerve  presents  frequent  irregularities.    It  may  adhere 

1  See  foot-note,  page  1027. 


986  THE  NERVOUS   SYSTEM 

for  some  distance  to  the  median  and  then  pass  outward,  beneath  the  Biceps, 
instead  of  through  the  Coraco-brachiaUs.  Frequently  some  of  the  fibres  of  the 
median  run  for  some  distance  in  the  musculo-cutaneous  and  then  leave  it  to  join 
their  proper  trunk.  Less  frequently  the  reverse  is  the  case,  and  the  median  sends 
a  branch  to  join  the  musculo-cutaneous.  Instead  of  piercing  the  Coraco-brachialis 
muscle  the  nerve  may  pass  under  it  or  through  the  Biceps.  Occasionally  it  gives  a 
filament  to  the  Pronator  radii  teres  muscle,  and  it  has  been  seen  to  supply  the 
back  of  the  thumb  when  the  radial  nerve  was  absent. 

The  Internal  Cutaneous  Nerve  (w.  cutaneus  antihrachii  medialis)  (Figs.  638,  639, 
and  644). — ^The  internal  cutaneous  nerve  is  one  of  the  smallest  branches  of 
the  brachial  plexus.  It  arises  from  the  inner  cord  in  common  with  the  ulnar 
nerve  and  internal  head  of  the  median  nerve,  and,  at  its  commencement,  is 
placed  on  the  inner  side  of  the  axillary  artery,  and  afterward  of  the  brachial 
artery.  It  derives  its  fibres  from  the  eighth  cervical  and  first  dorsal  nerves. 
It  passes  down  the  inner  side  of  the  arm,  pierces  the  deep  fascia  with  the 
basilic  vein,  about  the  middle  of  the  limb,  and,  becoming  cutaneous,  divides  into 
two  branches,  anterior  and  posterior. 

This  nerve  gives  off,  near  the  axilla,  a  cutaneous  filament,  which  pierces  the  fascia 
and  supplies  the  integument  covering  the  Biceps  muscle  nearly  as  far  as  the  elbow. 
This  filament  lies  a  little  external  to  the  common  trunk,  from  which  it  arises. 

The  anterior  branch,  the  larger  of  the  two,  passes  usually  in  front  of,  but  occa- 
sionally behind,  the  median  basilic  vein.  It  then  descends  on  the  anterior  surface 
of  the  ulnar  side  of  the  forearm,  distributing  filaments  to  the  integument  as  far 
as  the  wrist,  and  communicating  with  a  cutaneous  branch  of  the  ulnar  nerve 
(Fig.  640). 

The  posterior  branch  passes  obliquely  downward  on  the  inner  side  of  the  basilic 
vein,  passes  in  front  of,  or  over,  the  internal  condyle  of  the  humerus  to  the  back 
of  the  forearm,  and  descends  on  the  posterior  surface  of  its  ulnar  side  ae  far  as 
the  wrist,  distributing  filaments  to  the  integument  (Fig.  641) .  It  communicates, 
above  the  elbow,  with  the  lesser  internal  cutaneous  nerve,  and  above  the  wrist 
with  the  dorsal  cutaneous  branch  of  the  ulnar  nerve  (Swan).  The  cutaneous  areas 
supplied  by  the  internal  cutaneous  nerve  are  indicated  in  Figs.  642  and  643. 

The  Lesser  Internal  Cutaneous  Nerve  or  the  Nerve  of  Wrisberg  (n.  cutaneus 
brachii  medialis)  (Figs.  638,  639,  and  644). — The  lesser  internal  cutaneous  nerve 
is  distributed  to  the  integument  on  the  inner  side  of  the  arm.  It  is  the  smallest  of 
the  branches  of  the  brachial  plexus,  and,  arising  from  the  inner  cord,  receives 
its  fibres  from  the  first  dorsal  nerve.  It  passes  through  the  axillary  space,  at  first 
lying  behind,  and  then  on  the  inner  side  of,  the  axillary  vein,  and  communicates 
with  the  intercosto-humeral  nerve.  It  descends  along  the  inner  side  of  the  brachial 
artery  to  the  middle  of  the  arm,  where  it  pierces  the  deep  fascia,  and  is  distributed 
to  the  integument  of  the  back  part  of  the  lower  third  of  the  arm,  extending  as  far 
as  the  elbow  (Figs.  640,  641,  and  642) ,  where  some  filaments  are  lost  in  the  integu- 
ment in  front  of  the  inner  condyle,  and  others  over  the  olecranon.  It  commu- 
nicates with  the  posterior  branch  of  the  internal  cutaneous  nerve. 

In  some  cases  the  nerve  of  Wrisberg  and  the  intercosto-humeral  nerve  are 
connected  by  two  or  three  filaments  which  form  a  plexus  at  the  back  part  of 
the  axilla.  In  other  cases  the  intercosto-humeral  is  of  large  size,  and  takes  the 
place  of  the  nerve  of  Wrisberg,  receiving  merely  a  filament  of  communication  from 
the  brachial  plexus,  which  filament  represents  the  latter  nerve.  In  other  cases 
this  filament  is  wanting,  the  place  of  the  nerve  of  Wrisberg  being  supplied 
entirely  by  the  intercosto-humeral. 

The  Median  Nerve  (n. medianus)  (Figs.  638, 639,  and644).— The  median  nerve  has 
received  its  name  from  the  course  it  takes  along  the  middle  of  the  arm  and  forearm 
to  the  hand,  lying  between  the  ulnar  and  musculo-spiral  nerves,  and  the  ulnar  and 


THE    BRACHIAL    PLEXUS  987 

the  radial  nerves.  It  arises  by  two  roots,  one  from  the  outer,  and  one  from  the  inner, 
cord  of  the  brachial  plexus;  these  embrace  the  lower  part  of  the  axillary  artery, 
uniting  either  in  front  or  on  the  outer  side  of  that  vessel.  The  median  nerve 
receives  filaments  from  the  sixth,  seventh,  and  eighth  cervical  and  the  first 
dorsal  nerves.  As  it  descends  through  the  arm,  it  lies  at  first  on  the  outer  side 
of  the  brachial  artery,  crosses  that  vessel  in  the  middle  of  its  course,  usually  in 
front,  but  occasionally  behind  it,  and  lies  on  its  inner  side  to  the  bend  of  the 
elbow,  where  it  is  placed  beneath  the  bicipital  fascia,  and  is  separated  from  the 
elbow-joint  by  the  Brachialis  anticus  muscle.  In  the  forearm  it  passes  between 
the  two  heads  of  the  Pronor  radii  teres  muscle,  and  descends  beneath  the  Flexor 
sublimis  muscle,  lying  on  the  Flexor  profundus  muscle,  to  within  two  inches 
above  the  annular  ligament,  where  it  becomes  more  superficial,  lying  between  the 
tendons  of  the  Flexor  sublimis  and  Flexor  carpi  radialis  muscles,  beneath,  and 
rather  to  the  radial  side  or  under  the  tendon  of  the  Palmaris  longus,  covered  by 
the  integument  and  fascia.  It  then  passes  through  the  carpal  canal  (canalis  carpi) 
beneath  the  annular  ligament  into  the  hand.  In  its  course  through  the  forearm 
it  is  accompanied  by  a  branch  of  the  anterior  interosseous  artery. 

Branches. — With  the  exception  of  the  nerve  to  the  Pronator  radii  teres  muscle, 
which  sometimes  arises  above  the  elbow-joint,  and  filaments  to  the  elbow-joint, 
the  median  nerve  gives  off  no  branches  in  the  arm.  In  the  forearm  its  branches 
are  muscular,  anterior  interosseous,  and  palmar  cutaneous,  and,  according  to 
Riidinger  and  Macalister,  two  articular  twigs  to  the  elbow-joint. 

The  Muscular  Branches  (rami  muscular es)  supply  all  the  superficial  muscles  on 
the  front  of  the  forearm  except  the  Flexor  carpi  ulnar.is.  These  branches  are 
derived  from  the  nerve  near  the  elbow. 

The  Anterior  Interosseous  (n.  interosseus  [antibrachii]  volaris)  (Fig.  644)  supplies 
the  deep  muscles  on  the  front  of  the  forearm,  except  the  inner  half  of  the  Flexor 
profuntlus  digitorum.  It  accompanies  the  anterior  interosseous  artery  along  the 
interosseous  membrane,  in  the  interval  between  the  Flexor  longus  pollicis  and 
Flexor  profundus  digitorum  muscles,  both  of  which  it  supplies,  and  terminates 
below  in  the  Pronator  quadratus  muscle  sending  filaments  to  the  inferior  radio- 
ulnar articulation  and  the  wrist-joint. 

The  Palmar  Cutaneous  Branch  (ramu^  cutaneus  palmaris  n.  mediani)  arises  from 
the  median  nerve  at  the  lower  part  of  the  forearm.  It  pierces  the  fascia  above 
the  annular  ligament,  and,  descending  over  that  ligament,  divides  into  two 
branches;  of  which  the  outer  branch  supplies  the  skin  over  the  ball  of  the  thumb, 
and  communicates  with  the  anterior  cutaneous  branch  of  the  musculo-cutaneous 
nerve;  and  the  inner  branch  supplies  the  integument  of  the  palm  of  the  hand, 
communicating  with  the  cutaneous  branch  of  the  ulnar. 

In  the  palm  of  the  hand  the  median  nerve  is  covered  by  the  integument  and 
palmar  fascia  and  is  crossed  by  the  superficial  palmar  arch.  It  rests  upon  the 
tendons  of  the  flexor  muscles.  In  this  situation  it  becomes  enlarged,  somewhat 
flattened,  of  a  reddish  color,  and  divides  into  two  branches.  Of  these,  the  external 
branch  supplies  a  muscular  branch  to  some  of  the  muscles  of  the  thumb  and 
digital  branches  to  the  thumb  and  index  finger;  the  internal  branch  supplies  digital 
branches  to  the  contiguous  sides  of  the  index  and  middle  and  of  the  middle  and 
ring  fingers.  The  digital  branches,  before  they  subdivide,  are  called  common 
palmar  digital  branches  of  the  median  nerve  {nn.  digitales  volares  communes). 

The  branch  to  the  muscles  of  the  thumb  (ramus  muscularis)  is  a  short  nerve  which 
divides  to  supply  the  Abductor,  Opponens,  and  the  superficial  head  of  the  Flexor 
brevis  pollicis  muscles,  the  remaining  muscles  of  this  group  being  supplied  by 
the  ulnar  nerve. 

The  Collateral  Palmar  Digital  or  the  Digital  Branches  (nn.  digitales  volares  proprii) 
are  five  in  number.    The  first  and  second  pass  along  the  borders  of  the  thumb. 


988  THE    NERVOUS  SYSTEM 

the  external  branch  communicating  with  branches  of  the  radial  nerve.  The  third 
passes  along  the  radial  side  of  the  index  finger,  and  supplies  the  First  lumbricalis 
muscle.  The  fourth  subdivides  to  supply  the  adjacent  sides  of  the  index  and 
middle  fingers,  and  sends  a  branch  to  the  Second  lumbricalis  muscle.  The  fifth 
supplies  the  adjacent  sides  of  the  middle  and  ring  fingers,  and  communicates  with 
a  branch  from  the  ulnar  nerve. 

Each  digital  nerve,  opposite  the  base  of  the  first  phalanx,  gives  off  a  dorsal 
branch,  which  joins  the  dorsal  digital  nerve  from  the  radial  nerve  and  runs  along 
the  side  of  the  dorsum  of  the  finger,  to  end  in  the  integument  over  the  last  phalanx. 
At  the  end  of  the  finger  the  digital  nerve  divides  into  a  palmar  and  a  dorsal  branch, 
the  former  of  which  supplies  the  extremity  of  the  finger,  and  the  latter  ramifies 
around  and  beneath  the  nail.  The  digital  nerves,  as  they  run  along  the  fingers,  are 
placed  superficial  to  the  digital  arteries.  The  cutaneous  areas  supplied  by  the 
median  nerve  are  shown  in  Figs.  642  and  643. 

The  Ulnar  Nerve  {n.  ulnaris)  (Figs.  638,  639,  and  644). — The  ulnar  nerve  is 
placed  along  the  inner  or  ulnar  side  of  the  upper  limb,  and  is  distributed  to  the 
muscles  and  integument  of  the  forearm  and  hand.  It  is  smaller  than  the  median, 
behind  which  it  is  placed,  diverging  from  it  in  its  course  down  the  arm.  It  arises 
from  the  inner  cord  of  the  brachial  plexus,  in  common  with  the  inner  head  of  the 
median  and  the  internal  cutaneous  nerve,  and  derives  its  fibres  from  the  eighth 
cervical  and  first  dorsal  nerves.  At  its  commencement  it  lies  to  the  inner  side  of 
the  axillary  artery,  and  holds  the  same  relation  with  the  brachial  artery  to  the 
middle  of  the  arm.  From  this  point  it  runs  obliquely  across  the  internal  head 
of  the  Triceps,  pierces  the  internal  intermuscular  septum,  and  descends  to  the 
groove  between  the  internal  condyle  and  the  olecranon,  accompanied  by  the  in- 
ferior profunda  artery.  At  the  elbow  it  rests  upon  the  back  of  the  inner  condyle, 
and  passes  into  the  forearm  between  the  two  heads  of  the  Flexor  carpi  ulnaris 
muscle.  In  the  forearm  it  descends  in  a  perfectly  straight  course  along  th«  ulnar 
side  of  the  extremity,  lying  upon  the  Flexor  profundus  digitorum  muscle,  its 
upper  half  being  covered  by  the  Flexor  carpi  ulnaris  muscle,  its  lower  half  lying 
on  the  outer  side  of  the  muscle,  being  covered  by  the  integument  and  fascia. 
The  ulnar  artery,  in  the  upper  third  of  its  course,  is  separated  from  the  ulnar 
nerve  by  a  considerable  interval,  but  in  the  rest  of  its  extent  the  nerve  lies  to 
its  inner  side.  At  the  wrist  the  ulnar  nerve  crosses  the  annular  ligament  on  the 
outer  side  of  the  pisiform  bone,  to  the  inner  side  of  and  a  little  behind  the  ulnar 
artery,  and  immediately  beyond  this  bone  divides  into  two  branches,  the 
superficial  and  the  deep  palmar. 

Branches. — The  branches  of  the  ulnar  nerve  are — 
Articular. 

In  the  forearm   J  Muscular.  j^  ^^^  ^^^^    rSuperficial  palmar. 

Cutaneous.  (Deep  palmar. 

.  Dorsal  cutaneous. 

The  Articular  Branches  distributed  to  the  elbow-joint  consist  of  several  small 
filaments.  They  arise  from  the  nerve  as  it  lies  in  the  groove  between  the  inner 
condyle  of  the  humerus  and  the  olecranon  process  of  the  ulnar. 

The  Muscular  Branches  {rami  musculares)  are  two  in  number — one  supplying 
the  Flexor  carpi  ulnaris;  the  other,  the  inner  half  of  the  Flexor  profundus  digi- 
torum.    They  arise  from  the  trunk  of  the  nerve  near  the  elbow. 

The  Cutaneous  Branch  arises  from  the  ulnar  nerve  about  the  middle  of  the  fore- 
arm, and  divides  into  two  branches. 

One  branch  (frequently  absent)  pierces  the  deep  fascia  near  the  wrist,  and  is 
distributed  to  the  integument,  communicating  with  a  branch  of  the  internal 
cutaneous  nerve. 

The  second  branch,  the  palmar  cutaneous  {ramus  cutaneus  palmaris)  lies  on  the 


THE   BRACHIAL    PLEXUS  989 

ulnar  artery,  which  it  accompanies  to  the  hand,  some  filaments  entwining  around 
the  vessel;  it  ends  in  the  integument  of  the  palm,  communicating  with  branches 
of  the  median  nerve. 

The  Dorsal  Cutaneous  Branch  {ramus  dorsalis  manus)  arises  about  two  inches 
above  the  wrist;  it  passes  backward  beneath  the  Flexor  carpi  ulnaris  muscle, 
perforates  the  deep  fascia,  and,  running  along  the  ulnar  side  of  the  back  of  the 
wrist  and  hand,  divides  into  branches  (nn.  digitales  dorsales) ;  one  of  these  sup- 
plies the  inner  side  of  the  little  finger;  a  second  supplies  the  adjacent  sides  of 
the  little  and  ring  fingers;  a  third  joins  the  branch  of  the  radial  nerve  which 
supplies  the  adjoining  sides  of  the  middle  and  ring  fingers,  and  assists  in  sup- 
plying these  parts;  a  fourth  is  distributed  to  the  metacarpal  region  of  the  hand, 
communicating  with  a  branch  of  the  radial  nerve. 

On  the  little  finger  the  dorsal  digital  branches  extend  only  as  far  as  the  base 
of  the  terminal  phalanx,  and  on  the  ring  finger  as  far  as  the  base  of  the  second 
phalanx;  the  more  distal  parts  of  these  digits  are  supplied  by  dorsal  branches 
derived  from  the  palmar  digital  branches  of  the  ulnar. 

The  Superficial  Palmar  Branch  [ramus  superficialis  n.  ulnaris)  supplies  the 
Palmaris  brevis  and  the  integument  on  the  inner  side  of  the  hand,  and  terminates 
in  two  digital  branches,  which  are  distributed,  one  to  the  ulnar  side  of  the  little 
finger,  the  other  to  the  adjoining  sides  of  the  little  and  ring  fingers,  the  latter 
communicating  with  a  branch  from  the  median.  The  digital  branches  are  dis- 
tributed to  the  fingers  in  the  same  manner  as  the  digital  branches  of  the  median. 

The  Deep  Palmar  Branch  (ramus  jyrojundus  n.  ulnaris),  accompanied  by  the 
deep  branch  of  the  ulnar  artery,  passes  between  the  Abductor  and  Flexor  brevis 
minimi  digiti  muscles;  it  then  perforates  the  Opponens  minimi  digit!  and  follows 
the  course  of  the  deep  palmar  arch  beneath  the  flexor  tendons.  At  its  origin  it 
supplies  the  muscles  of  the  little  finger.  As  it  crosses  the  deep  part  of  the  hand 
it  sends  two  branches  to  each  interosseous  space,  one  for  the  Dorsal  and  one  for 
the  Palmar  interosseous  muscle,  the  branches  to  the  Second  and  Third  palmar 
interossei  supplying  filaments  to  the  two  inner  Lumbrical  muscles.  At  its  ter- 
mination between  the  thumb  and  index  finger,  it  supplies  the  Adductores  trans- 
versus  et  obliquus  pollicis  and  the  inner  head  of  the  Flexor  brevis  pollicis.  It  also 
sends  articular  filaments  to  the  wrist-joint,  and  to  the  bones  and  joints  of  the  hand. 

It  will  be  remembered  that  the  inner  part  of  the  Flexor  profundus  digitorum 
muscle  is  supplied  by  the  ulnar  nerve;  the  two  inner  Lumbricales,  which  are 
connected  with  the  tendons  of  this  part  of  the  muscle,  are  therefore  supplied  by 
the  same  nerve.  The  outer  part  of  the  Flexor  profundus  is  supplied  by  the 
median  nerve;  the  two  outer  Lumbricales,  which  are  connected  with  the  tendons 
of  this  part  of  the  muscles,  are  therefore  supplied  by  the  same  nerve.  Brooks 
states  that  in  twelve  instances  out  of  twenty-one  he  found  that  the  third  lum- 
brical received  a  twig  from  the  median  nerve,  in  addition  to  its  branch  from  the 
ulnar.  The  palmar  branches  of  the  ulnar  which  go  to  the  fingers  are  called  by 
Toldt  before  division  common  palmar  digital  branches,  and  after  division  collateral 
palmar  digital  branches.  The  cutaneous  areas  supplied  by  the  ulnar  nerve  are 
shown  in  Figs.  642  and  643. 

The  Musculo-spiral  Nerve  {n.  radialis)  (Figs.  639,  644,  and  645). — The  musculo- 
spiral  nerve,  the  largest  branch  of  the  brachial  plexus,  supplies  the  muscles  of  the 
back  part  of  the  arm  and  forearm,  and  the  integument  of  the  same  parts,  as  well  as 
that  of  the  back  of  tlie  hand  (Figs.  642  and  643) .  It  arises  from  the  posterior  cord  of 
the  brachial  plexus,  of  which  it  maybe  regarded  as  the  continuation.  It  receives  fila- 
ments from  the  sixth,  seventh,  and  eighth,  and  sometimes  also  from  the  fifth  cervical 
nerves.  At  its  commencement  it  is  placed  behind  the  axillary  artery  and  the  upper 
part  of  the  brachial  artery,  passing  down  in  front  of  the  tendons  of  the  Latissimus 
dorsi  and  Teres  major  muscles.    It  winds  around  the  humerus  in  the  musculo-spiral 


990 


THE  NERVOUS  SYSTEM 


SuprascapuCar. 


Circumflex. 


groove  with  the  superior  profunda  artery,  passing  from  the  inner  to  the  outer  side 
of  the  bone,  between  the  internal  and  external  heads  of  the  Triceps  muscle  (Fig. 
645).     It  pierces  the  external  intermuscular  septum,  and  descends  between  the 

Brachialis  anticus  and  Supi- 
nator longus  muscles  to  the 
front  of  the  external  condyle 
of  the  humerus,  where  it  sends 
filaments  to  the  elbow-joint 
and  divides  into  the  radial  and 
posterior  interosseous  nerves. 

Branches. — The  branches  of 
the  musculo-spiral  nerve  are — 
Muscular. 
Cutaneous. 
Radial. 

Posterior  interosseous. 
The  Muscular  Branches  (rami 
muscular es  n.  radialis)  are  di- 
vided into  internal,  posterior, 
and  external;  they  supply  the 
Triceps,  Anconeus,  Supinator 
longus.  Extensor  carpi  radialis 
longior,  and  Brachialis  anticus 
muscles.  These  branches  are 
derived  from  the  nerve  at  the 
inner  side,  back  part,  and  outer 
side  of  the  arm. 

The  internal  muscular  branches 
supply  the  inner  and  middle 
heads  of  the  Triceps  muscle. 
That  to  the  inner  head  of  the 
Triceps  is  a  long,  slender  fila- 
ment which  lies  close  to  the 
ulnar  nerve,  as  far  as  the  lower 
third  of  the  arm,  and  is  there- 
fore frequently  spoken  of  as  the 
ulnar  collateral  branch. 

The  posterior  muscular  branch, 
of  large  size,  arises  from  the 
nerve  in  the  groove  between  the 
Triceps  muscle   and    the    hu- 
merus. It  divides  into  branches 
which  supply  the  outer  and  in- 
ner heads  of  the  Triceps  and 
the   Anconeus   muscles.     The 
branch  for  the  latter  muscle  is 
a  long,  slender  filament  which 
descends   in   the  substance  of 
the  Triceps  to  the  Anconeus. 
The  external  muscular  branches  supply  the  Supinator  longus.  Extensor  carpi 
radialis  longior,  and  (usually)  the  outer  part  of  the  Brachialis  anticus  muscles. 
The  Cutaneous  Branches  are  three  in  number,  one  internal  and  two  external. 
The  internal  cutaneous  branch  (n.  cutaneus  hrachii  posterior)  arises  in  the  axil- 
lary space  with  the  inner  muscular  branch.    It  is  of  small  size,  and  passes  through 


Fig.  645. — The  suprascapular,  circumflex,  and  musculo-spiral 
nerves. 


THE   BRACHIAL    PLEXUS  991 

the  axilla  to  the  inner  side  of  the  arm,  supplying  the  integument  on  its  posterior 
aspect  nearly  as  far  as  the  olecranon.  In  its  course  it  crosses  beneath  the  inter- 
costo-humeral  nerve,  with  which  it  communicates. 

The  external  cutaneous  branch  {n.  cutaneus  antibrachii  dorsalis)  divides  into  two 
branches,  and  each  one  perforates  the  outer  head  of  the  Triceps  muscle  at  its 
attachment  to  the  humerus.  The  upper  and  smaller  one  passes  to  the  front  of  the 
elbow,  lying  close  to  the  cephalic  vein,  and  supplies  the  integument  of  the  lower  half 
of  the  arm  on  its  anterior  aspect.  The  lower  branch  pierces  the  deep  fascia  below 
the  insertion  of  the  Deltoid  muscle,  and  passes  down  along  the  outer  side  of  the 
arm  and  elbow,  and  then  along  the  back  part  of  the  radial  side  of  the  forearm  to 
the  wrist,  supplying  the  integument  in  its  course,  and  joining,  near  its  termination, 
with  the  posterior  cutaneous  branch  of  the  musculo-cutaneous  nerve. 

The  Radial  Nerve  (ramus  superficialis  n.  radialis)  (Fig.  644) ,  passes  along  the  front 
of  the  radial  side  of  the  forearm  to  the  commencement  of  its  lower  third.  It  lies  at 
first  a  little  to  the  outer  side  of  the  radial  artery,  concealed  beneath  the  Supinator 
longus  muscle.  In  the  middle  third  of  the  forearm  it  lies  beneath  the  same 
muscle,  in  close  relation  with  the  outer  side  of  the  artery.  It  leaves  the  artery 
about  three  inches  above  the  wrist,  passes  beneath  the  tendon  of  the  Supinator 
longus  muscle,  and,  piercing  the  deep  fascia  at  the  outer  border  of  the  forearm, 
divides  into  two  branches. 

The  external  branch,  the  smaller  of  the  two,  supplies  the  integument  of  the 
radial  side  and  ball  of  the  thumb,  joining  with  the  anterior  branch  of  the  musculo- 
cutaneous nerve. 

The  internal  branch  communicates,  above  the  wrist,  with  the  posterior  cuta- 
neous branch  from  the  musculo-cutaneous,  and  on  the  back  of  the  hand  forms  an 
arch  with  the  dorsal  cutaneous  branch  of  the  ulnar  nerve.  It  then  divides  into 
four  digital  nerves  (nn.  digitales  dorsales),  which  are  distributed  as  follows:  The 
first  supplies  the  ulnar  side  of  the  thumb;  the  second,  the  radial  side  of  the  index 
finger;  the  third,  the  adjoining  sides  of  the  index  and  middle  fingers;  and  the 
fourth,  the  adjacent  borders  of  the  middle  and  ring  fingers.^  The  latter  nerve 
communicates  with  a  filament  from  the  dorsal  branch  of  the  ulnar  nerve. 

The  Posterior  Interosseous  Nerve  {ramus  'profundus  n.  radialis)  (Figs.  644  and 
645) . — ^The  posterior  interosseous  nerve  winds  to  the  back  of  the  forearm  around 
the  outer  side  of  the  radius,  passes  between  the  two  planes  of  fibres  of  the  Supinator 
brevis  muscle,  and  is  prolonged  downward  between  the  superficial  and  deep  layer 
of  muscles,  to  the  middle  of  the  forearm.  Considerably  diminished  in  size,  it 
descends  on  the  interosseous  membrane,  beneath  the  Extensor  longus  pollicis 
muscle,  to  the  back  of  the  carpus,  where  it  presents  a  gangliform  enlargement 
from  which  filaments  are  distributed  to  the  inferior  radio-ulnar  articulation,  to 
the  wrist -joint,  and  to  the  ligaments  and  articulations  of  the  carpus.  It  supplies  all 
the  muscles  of  the  radial  and  posterior  brachial  regions,  excepting  the  Anconeus, 
Supinator  longus,  and  Extensor  carpi  radialis  longior. 

Surgical  Anatomy, — The  brachial  plexus  may  be  ruptured  by  traction  on  the  limb,  leading 
to  complete  paralysis.  Bristow'*  has  reported  three  cases  of  avulsion  of  the  plexus  and  has 
described  twenty-four  cases.  In  these  cases  it  is  generally  believed  that  the  lesion  is  rather  a 
tearing  away  of  the  nerves  from  the  spinal  cord  than  a  solution  of  continuity  of  the  nerve-fibres 
themselves.  In  a  case  operated  upon  by  Bristow  it  was  found  that  the  plexus  had  given  way 
where  the  four  cervical  nerves  and  the  first  dorsal  nerve  unite  to  form  three  trunks.  In  supraclavic- 
ular division  of  the  brachial  plexus,  not  only  will  there  be  motor  and  sensory  paralysis  in  the  limb, 
but  the  Serratus  magnus  muscle  will  probably  be  paralyzed,  because  of  injury  to  the  posterior 
thoracic  nerve.  In  the  axilla  any  of  the  nerves  forming  the  brachial  plexus  may  be  injured  by  a 
wound  of  this  part,  the  median  being  the  one  which  is  most  frequently  damaged  from  its  exposed 

'  According  to  Hutchinson,  the  digital  nerve  to  the  thumb  reaches  only  as  high  as  the  root  of  the  nail;  the 
one  to  the  forefinger  as  high  as  the  middle  of  the  second  phalanx,  and  the  one  to  the  middle  and  ring  fingers  not 
higher  than  the  first  phalangeal  joint  (London  Hospital  Gazette,  vol.  iii.  p.  319). — Ed.  of  15th  English  edition. 

^  Annals  of  Surgery,  September,  1902. 


992 


THE   NERVOUS   SYSTEM 


position.  The  musculo-spiral,  on  account  of  its  sheltered  and  deep  position,  is  least  often 
wounded.  The  brachial  plexus  in  the  axilla  is  often  damaged  from  the  pressure  of  a  crutch,  pro- 
ducing the  condition  known  as  crutch  paralysis.  In  these  cases  the  musculo-spiral  is  the  nerve  most 
frequently  implicated;   the  ulnar  nerve  being  the  one  that  appears  to  suffer  next  in  frequency. 

The  circumflex  nerve  is  of  particular  surgical  interest.  On  account  of  its  course  around  the 
surgical  neck  of  the  humerus,  it  is  liable  to  be  torn  in  fractures  of  this  part  of  the  bone,  and 
in  dislocations  of  the  shoulder-foint,  leading  to  paralysis  of  the  deltoid,  and,  according  to  Erb, 
inflammation  of  the  shoulder-joint  is  liable  to  be  followed  by  a  neuritis  of  this  nerve  from  extension 
of  the  inflammation  to  it. 

Mr.  Hilton  takes  the  circumflex  nerve  as  an  illustration  of  a  law  which  he  lays  down,  that 
"the  same  trunks  of  nerves  whose  branches  supply  the  groups  of  muscles  moving  a  joint  furnish 
also  a  distribution  of  nerves  to  the  skin  over  the  insertions  of  the  same  muscles,  and  the  interior 
of  the  joint  receives  its  nerves  from  the  same  source."  In  this  way  he  explains  the  fact  that  an 
inflamed  joint  becomes  rigid,  because  the  same  nerves  which  supply  the  interior  of  the  joint 
supply  the  muscles  which  move  that  joint. 

The  median  nerve  is  liable  to  injury  in  wounds  of  the  forearm.  When  paralyzed,  there  is 
loss  of  flexion  of  the  second  phalanges  of  all  the  fingers  and  of  the  terminal  phalanges  of  the 
index  and  middle  fingers.  Flexion  of  the  terminal  phalanges  of  the  ring  and  middle  fingers  can 
still  be  effected  by  that  portion  of  the  Flexor  profundus  digitorum  which  is  supplied  by  the  ulnar 
nerve.  There  is  power  to  flex  the  proximal  phalanges  through  the  Interossei.  The  thumb 
cannot  be  flexed  or  opposed,  and  is  maintained  in  a  position  of  extension  and  adduction.  All 
power  of  pronation  is  lost.  The  wrist  can  be  flexed,  if  the  hand  is  first  adducted,  by  the  action 
of  the  Flexor  carpi  ulnaris.  There  is  loss  or  impairment  of  sensation  on  the  palmar  surface 
of  the  thumb,  index,  middle,  and  outer  half  of  the  ring  fingers,  and  on  the  dorsal  surface  of  the 
same  fingers  over  the  last  two  phalanges;  except  in  the  thumb,  where  the  loss  of  sensation  is 
limited  to  the  back  of  the  last  phalanx.  In  order  to  expose  the  median  nerve  for  the  purpose 
of  stretching  it  an  incision  should  be  made  along  the  radial  side  of  the  tendon  of  the  Palmaris 
longus  muscle,  which  serves  as  a  guide  to  the  nerve. 

The  ulnar  nerve  is  liable  to  be  injured  in  wounds  of  the  forearm.  When  paralyzed,  there 
is  loss  of  power  of  flexion  in  the  ring  and  little  fingers;  there  is  impaired  power  of  ulnar 
flexion  and  adduction  of  the  hand;  there  is  inability  to  spread  out  the  fingers  from  paralysis  of 
the  Interossei;  and  there  is  inability  to  adduct  the  thumb.  The  fingers  cannot  be  flexed  at  the 
first  joints,  and  cannot  be  extended  at  the  other  joints.  A  claw-hand  develops,  the  first  pha- 
langes being  overextended  and  the  others  flexed.  Sensation  is  lost  or  impaired  in  the  skin  of  the 
ulnar  side  of  the  hand  anteriorly  and  posteriorly,  involving  the  little  finger,  the  ring  finger,  and 
the  ulnar  half  of  the  middle  finger  posteriorly,  and  anteriorly  involving  the  little  finger  and  the 
ulnar  half  of  the  ring  finger.  In  order  to  expose  the  nerve  in  the  lower  part  of  the  forearm, 
an  incision  should  be  made  along  the  outer  border  of  the  tendon  of  the  Flexor  carpi  ulnaris,  and 
the  nerve  will  be  found  lying  on  the  ulnar  side  of  the  ulnar  artery. 

The  musculo-spiral  nerve  is  probably  more  frequently  injured  than  any  other  nerve  of  the 
upper  extremity.  In  consequence  of  its  close  relationship  to  the  humerus  as  it  lies  in  the 
musculo-spiral  groove,  it  is  frequently  torn  or  injured  in  fractures  of  this  bone,  or  subsequently 
involved  in  the  callus  that  may  be  thrown  out  around  a  fracture,  and  thus  pressed  upon  and  its 
functions  interfered  with.  It  is  also  liable  to  be  squeezed  against  the  Vjone  by  kicks  or  blows  and 
it  may  be  divided  by  wounds  of  the  arm.  When  paralyzed,  the  hand  is  flexed  at  the  wrist 
and  lies  flaccid.  This  condition  is  known  as  drop-wrist.  The  fingers  are  also  flexed,  and  on 
an  attempt  being  made  to  extend  them  the  last  two  phalanges  only  will  be  extended  through  the 
action  of  the  Interossei,  the  first  phalanges  remaining  flexed.  There  is  no  power  of  extending 
the  wrist.  Supination  is  completely  lost  when  the  forearm  is  extended  on  the  arm,  but  is 
possible  to  a  certain  extent  if  the  forearm  is  flexed  so  as  to  allow  of  the  action  of  the  Biceps. 
The  power  of  extension  of  the  forearm  is  lost  on  account  of  paralysis  of  the  Triceps.  liOss  of 
sensation  may  be  considerable  or  slight.  Its  area  is  shown  in  Fig.  643.  The  best  position  in 
which  to  expose  the  nerve  for  the  purpose  of  stretching  is  to  make  an  incision  along  the  inner  border 
of  the  Supinator  longus  muscle,  just  above  the  level  of  the  elbow-joint.  The  skin  and  superficial 
structures  are  to  be  divided  and  the  deep  fascia  exposed.  The  white  line  in  this  structure  indicat- 
ing the  border  of  the  muscle  is  to  be  defined,  and  the  deep  fascia  divided  in  this  line.  By  now  raising 
the  Supinator  longus  the  nerve  will  be  found  lying  beneath  it,  on  the  Brachialis  anticus  muscle. 

Post-anoEsthetic  paralysis.  When  a  person  emerges  from  the  influence  of  a  general  anesthetic 
palsy  of  the  arm  may  be  found  to  exist.  The  brachial  plexus  may  have  been  compressed  during 
the  operation  by  drawing  the  arm  strongly  from  the  body  or  elevating  it  by  the  side  of  the 
head.     In  such  a  case  the  plexus  was  compressed  by  the  head  of  the  humerus  (Braun). 

The  median  nerve  is  stretched  when  the  arm  is  rotated  externally  and  drawn  backward  and 
outward.  The  ulnar  nerve  is  stretched  when  the  forearm  is  flexed  and  supinated  (Braun). 
Garrigues  believes  that  in  most  cases  of  post-anjesthetic  paralysis  the  brachial  plexus  was  squeezed 
between  the  collar  bone  and  the  first  rib  by  the  head  of  the  patient  being  drawn  to  the  opposite 
side  or  being  allowed  to  fall  back. 


ANTERIOR   DIVISIONS    OF  THORACIC   OR   DORSAL   NERVES    993 

THE   THORACIC   OR   DORSAL   NERVES    (NN.   THORACALES.) 

The  thoracic  or  dorsal  nerves  are  twelve  in  number  on  each  side.  The  first 
appears  between  the  first  and  second  dorsal  vertebrae,  and  the  last  between  the 
last  dorsal  and  first  lumbar. 

The  Roots  of  the  Thoracic  or  Dorsal  Nerves. 

The  roots  of  the  thoracic  or  dorsal  nerves  are  of  small  size,  and  vary  but  slightly 
from  the  second  to  the  last.  Both  roots  are  very  slender,  the  posterior  roots 
slightly  exceeding  the  anterior  in  thickness.  They  gradually  increase  in  length 
from  above  downward,  and  in  the  lower  part  of  the  dorsal  region  pass  down  in 
contact  with  the  spinal  cord  for  a  distance  equal  to  the  height  of  at  least  two  ver- 
tebrae, before  they  emerge  from  the  spinal  canal.  They  then  join  in  the  inter- 
vertebral foramen,  and  at  their  exit  divide  into  two  primary  divisions,  a  posterior 
(dorsal)  and  an  anterior  (intercostal). 

The  Posterior  Divisions  of  the  Thoracic  or  Dorsal  Nerves  (Rami  Posteriores) 

(Fig.  646). 

The  posterior  divisions  of  the  thoracic  or  dorsal  nerves  are  smaller  than  the 
anterior,  pass  backward  between  the  transverse  processes,  and  divide  into  interna! 
and  external  branches. 

Each  internal  branch  is  called  a  ramus  medialis ;  each  external  branch  is  called 
a  ramus  lateralis. 

The  Internal  Branches. — The  internal  branches  of  the  six  upper  nerves  pass 
inward  between  the  Semispinalis  dorsi  and  INIultifidus  spinae  muscles,  which  they 
supply,  and  then,  piercing  the  origins  of  the  Rhomboidei  and  Trapezius  muscles, 
become  cutaneous  by  the  side  of  the  spinous  processes  and  ramify  in  the  integu- 
ment. The  internal  branches  of  the  six  lower  nerves  are  distributed  to  the 
Multififlus  spinae,  without  giving  off  any  cutaneous  filaments. 

The  External  Branches. — The  external  branches  increase  in  size  from  above 
downward.  They  pass  through  the  Longissimus  dorsi  muscle  to  the  cellular 
interval  between  it  and  the  Iliocostalis  muscle,  and  supply  those  muscles,  as  well 
as  their  continuations  upward  to  the  head,  and  also  the  Ijcvatores  costarum 
muscles;  the  five  or  six  lower  nerves  also  give  off  cutaneous  filaments,  which  pierce 
the  Serratus  posticus  inferior  and  Latissimus  dorsi  muscles  in  a  line  with  the 
angles  of  the  ribs,  and  then  ramify  in  the  integument. 

The  Cutaneous  Branches.— The  cutaneous  branches  of  the  posterior  primary 
divisions  of  the  dorsal  nerves  are  twelve  in  number.  From  each  ramus  medialis 
of  the  upper  six  nerves  comes  a  ramies  cutaneus  medialis,  and  from  each  ramus 
lateralis  of  the  lower  six  nerves  comes  a  ramus  cutaneus  lateralis.  The  six  upper 
cutaneous  nerves  are  derived  from  the  internal  branches  of  the  posterior  divisions 
of  the  dorsal  nerves.  They  pierce  the  origins  of  the  Rhomboidei  and  Trapezius 
muscles,  and  become  cutaneous  by  the  side  of  the  spinous  processes,  and  then 
ramify  in  the  integument.  They  are  frequently  furnished  with  gangliform  enlarge- 
ments. The  six  lower  cutaneous  nerves  are  derived  from  the  external  branches 
of  the  posterior  divisions  of  the  dorsal  nerves.  They  pierce  the  Serratus  posticus 
inferior  and  Latissimus  dorsi  mugcles  in  a  line  with  the  angles  of  the  ribs,  and 
then  ramify  in  the  integument. 

The  Anterior  Divisions  of  the  Thoracic  or  Dorsal  Nerves  or  the  Intercostal 

Nerves  (Rami  Anteriores). 

The  anterior  divisions  of  the  dorsal  nerves  or  the  intercostal  nerves  {nn.  inter- 
costales)   are  twelve  in  number  on  each   side.     They  are,  for  the  most  part, 

63 


994 


THE   NERVOUS   SYSTEM 


distributed  to  the  parietes  of  the   thorax  and  abdomen,  separately  from  each 
other,  without  being  joined  in  a  plexus;    in  which  respect  they  differ  from  the 


Fig.  646. — Superficial  and  deep  distribution  of  the  posterior  divisions  of  the  spinal  nerves.  (After  Hirschfeld 
and  Leveill6.)  On  the  left  side  the  cutaneous  branches  are  represented  lying  on  the  sunerficial  layer  of  muscles. 
On  the  right  side  the  superficial  muscles  have  been  removed,  the  Splenius  capitis  and  Complexus  divided  in  the 
neck,  and  the  Erector  spinae  divided  and  partly  removed  in  the  back,  so  as  to  expose  the  posterior  divisions  of 
the  spinal  nerves  near  their  origin,  a  a.  Lesser  occipital  nerve  from  the  cervical  plexus.  1.  External  muscular 
branches  of  the  first  cervical  nerve,  and  union  by  a  loop  with  the  second.  2,  placed  on  the  Rectus  capitis 
posticus  major  muscle,  marks  the  great  occipital  nerve,  passing  round  the  short  muscles  and  piercing  the  Com- 
plexus :  the  external  branch  is  seen  to  the  outside.  3.  External  branch  from  the  posterior  division  of  the  third 
nerve.  3'.  Its  internal  branch,  sometimes  called  the  third  occipital.  4'  to  8'.  The  internal  branches  of  the 
several  corresponding  nerves  on  the  left  side.  The  external  branches  of  these  nerves,  proceeding  to  muscles, 
are  displayed  on  the  right  .side,  d  1  to  rf  6,  and  thence  to  d  12.  External  muscular  branches  of  the  posterior 
divisions  of  the  twelve  dorsal  nerves  on  the  right  side,  i^  1'  to  d  6'.  The  internal  cutaneous  branches  of  the  six 
upper  dorsal  nerves  on  the  left  side,  d  7'  to  d  12'.  Cutaneous  twigs  from  the  external  branches  of  the  six  lower 
dorsal  nerves.  1 1.  External  branches  from  the  posterior  divisions  of  several  lumbar  nerves  on  the  right  side, 
piercing  the  muscles,  the  lower  descending  over  the  gluteal  region  V  I'.  The  same,  more  superficially,  on  the 
left  side,  8  8.  The  issue  and  union  by  loops  of  the  posterior  divisions  of  four  sacral  nerves  on  the  right  side 
«  s'.  Some  of  those  distributed  to  the  skin  on  the  left  side. 


ANTERIOR  DIVISIONS   OF   THORACIC  OR  DORSAL  NERVES    995 

other  spinal  nerves.  Each  nerve  is  connected  with  the  adjoining  ganglion  of  the 
sjrmpathetic  by  one  or  two  filaments  {ramus  communicans) .  The  intercostal  nerves 
may  be  divided  into  two  sets,  from  the  difference  they  present  in  their  distribution. 
The  six  upper,  with  the  exception  of  the  first  and  the  intercosto-humeral  branch 
of  the  second,  are  limited  in  their  distribution  to  the  parietes  of  the  chest.  The 
six  lower  supply  the  parietes  of  the  chest  and  abdomen,  the  last  one  sending  a 
cutaneous  filament  to  the  buttock. 

The  Anterior  Division  of  the  First  Thoracic  or  First  Dorsal  Nerve. — 
The  anterior  division  of  the  first  dorsal  nerve  divides  into  two  branches:  one,  the 
larger,  leaves  the  thorax  in  front  of  the  neck  of  the  first  rib,  and  enters  into  the 
formation  of  the  brachial  plexus ;  the  other  and  smaller  branch  runs  along  the  first 
intercostal  space,  forming  the  first  intercostal  nerve  (n.  intercostalis  I),  giving  off 
muscular  branches,  and  terminates  on  the  front  of  the  chest  by  forming  the  first 
anterior  cutaneous  nerve  (ramus  cutaneus  anterior  n.  intercostalis  I)  of  the  thorax. 
Occasionally  this  anterior  cutaneous  branch  is  wanting.  The  first  intercostal 
nerve,  as  a  rule,  gives  off  no  lateral  cutaneous  branch,  but  sometimes  a  small 
branch  is  given  off  which  communicates  with  the  intercosto-humeral.  It  frequently 
receives  a  connecting  twig  from  the  second  dorsal  nerve,  which  passes  upward 
over  the  neck  of  the  second  rib. 

The  Anterior  Divisions  of  the  Upper  Thoracic  or  Dorsal  Nerves  (nn. 
intercostales)  (Fig.  646). — ^The  anterior  divisions  of  the  second,  third,  fourth,  fifth, 
and  sixth  dorsal  nerves  and  the  small  branch  from  the  first  dorsal  are  confined  to 
the  parietes  of  the  thorax,  and  are  named  upper  or  pectoral  intercostal  nerves. 
They  pass  forward  in  the  intercostal  spaces  with  the  intercostal  vessels,  being 
situated  below  them.  At  the  back  of  the  chest  they  lie  between  the  pleura  and 
the  External  intercostal  muscle,  but  are  soon  placed  between  the  two  planes  cf 
Intercostal  muscles  as  far  as  the  middle  of  the  rib.  They  then  enter  the  sub- 
stance of  the  Internal  intercostal  muscles,  and,  running  amidst  their  fibres  as  far 
as  the  costal  cartilages,  they  gain  the  inner  surface  of  the  muscles  and  lie 
between  them  and  the  pleura.  Near  the  sternum,  they  cross  in  front  of  the  internal 
mammary  artery  and  Triangularis  sterni  muscle,  pierce  the  Internal  intercostal 
muscles,  the  anterior  intercostal  membrane,  and  Pectoralis  major  muscle,  and 
supply  the  integument  of  the  front  of  the  chest  and  over  the  mammary  gland, 
forming  the  anterior  cutaneous  nerves  of  the  thorax;  the  branch  from  the  second 
nerve  is  joined  with  the  supraclavicular  nerves  of  the  cervical  plexus. 

Branches. — Numerous  slender  muscular  filaments  (rami  musculares)  supply  the 
Intercostals,  the  Infracostales,  the  Levatores  costarum,  Serratus  posticus  superior, 
and  Triangularis  sterni  muscles.  Some  of  these  branches,  at  the  front  of  the  chest, 
cross  the  costal  cartilages  from  one  to  another  intercostal  space. 

Lateral  Cutaneous  Nerves  of  the  Thorax  (rami  cutanei  laterales  [j)ectorales\j  (Fig. 
638). — These  are  derived  from  the  intercostal  nerves,  midway  between  the  vertebrae 
and  sternum;  they  pierce  the  External  intercostal  and  Serratus  magnus  muscles, 
and  divide  into  two  branches,  anterior  and  posterior. 

The  Anterior  Branches  (rami  anteriores)  are  reflected  forward  to  the  side  and  the 
forepart  of  the  chest,  supplying  the  integument  of  the  chest  and  mamma;  those 
of  the  fifth  and  sixth  nerves  supply  the  upper  digitations  of  the  External  oblique 
muscle. 

The  Posterior  Branches  (rami  posteriores)  are  reflected  backward  to  supply  the 
integument  over  the  scapula  and  over  the  lyatissimus  dorsi  muscle. 

The  Lateral  Cutaneous  Branch  of  the  Second  Intercostal  Nerve  (n.  intercosto- 
brachialis)  is  of  large  size,  and  does  not  divide,  like  the  other  nerves,  into  an 
anterior  and  posterior  branch.  It  may  unite  with  a  branch  of  the  third  intercostal. 
The  single  nerve  or  the  unitefl  nerve  is  named,  from  its  origin  and  distribution,  the 
intercosto-humeral  nerve  (Figs.  638  and  644).     It  pierces  the  External  intercostal 


996  THE   NERVOUS   SYSTEM 

muscle,  crosses  the  axilla  to  the  inner  side  of  the  arm,  and  joins  with  a  filament  from 
the  nerve  of  Wrisberg.  It  then  pierces  the  fascia,  and  supplies  the  skin  of  the  upper 
half  of  the  inner  and  back  part  of  the  arm  (Figs.  642  and  643),  communicating 
with  the  internal  cutaneous  branch  of  the  musculo-spiral  nerve.  The  size  of  this 
nerve  is  in  inverse  proportion  to  the  size  of  the  other  cutaneous  nerves,  especially 
the  nerve  of  Wrisberg.  A  second  intercosto-humeral  nerve  is  frequently  given  off 
from  the  third  intercostal.  It  supplies  filaments  to  the  armpit  and  inner  side  of 
the  arm.     It  may  or  may  not  send  a  branch  to  the  intercosto-humeral. 

The  Anterior  Divisions  of  the  Lower  Thoracic  or  Dorsal  Nerves. — The 
anterior  divisions  of  the  seventh,  eighth,  ninth,  tenth,  and  eleventh  dorsal  nerves 
are  continued  anteriorly  from  the  intercostal  spaces  into  the  abdominal  wall,  and 
the  twelfth  dorsal  is  continued  throughout  its  whole  course  in  the  abdominal  wall, 
since  it  is  placed  below  the  last  rib;  hence  these  nerves  are  named  lower  or  abdom- 
inal intercostal  nerves.  They  have  (with  the  exception  of  the  last)  the  same  arrange- 
ment as  the  upper  ones  as  far  as  the  anterior  extremities  of  the  intercostal  spaces, 
where  they  pass  behind  the  costal  cartilages,  and  between  the  Internal  oblique  and 
Transversalis  muscles,  to  the  sheath  of  the  Rectus,  which  they  perforate.  They 
supply  the  Rectus  muscle,  and  terminate  in  branches  which  become  subcutaneous 
near  the  linea  alba.  These  branches  are  named  the  anterior  cutaneous  nerves  of 
the  abdomen.  They  are  directed  outward  as  far  as  the  lateral  cutaneous  nerves, 
supplying  the  integument  of  the  front  of  the  belly.  The  lower  intercostal  nerves 
supply  the  Intercostals,  Serratus  posticus  inferior,  and  Abdominal  muscles,  and, 
about  the  middle  of  their  course,  give  off  lateral  cutaneous  branches  which  pierce 
the  External  intercostal  and  External  oblique  muscles,  in  the  same  line  as  the 
lateral  cutaneous  nerves  of  the  thorax,  and  divide  into  anterior  and  posterior 
branches,  which  are  distributed  to  the  integument  of  the  abdomen  and  back;  the 
anterior  branches  supply  the  digitations  of  the  External  oblique  muscle  and  extend 
downward  and  forward  nearly  as  far  as  the  margin  of  the  Rectus  muscle;  the 
posterior  branches  pass  backward  to  supply  the  skin  over  the  Latissimus  dorsi 
muscle. 

The  Last  Thoracic  or  Dorsal  Nerve. — The  last  dorsal  is  larger  than  the  other 
dorsal  nerves.  Its  anterior  division  runs  along  the  lower  border  of  the  last  rib, 
and  passes  under  the  external  arcuate  ligament  of  the  Diaphragm.  It  then  runs 
in  front  of  the  Quadratus  lumborum  muscle,  perforates  the  Transversalis  muscle, 
and  passes  forward  between  it  and  the  Internal  oblique  muscle,  to  be  distributed 
in  the  same  manner  as  the  lower  intercostal  nerves.  It  communicates  with  the 
ilio-hypogastric  branch  of  the  lumbar  plexus,  and  is  frequently  connected  with 
the  first  lumbar  nerve  by  a  slender  branch,  the  dorsi-lumbar  nerve,  which  descends 
in  the  substance  of  the  Quadratus  lumborum  muscle.  It  gives  a  branch  to  the 
Pyramidalis  muscle. 

The  Cutaneous  Branches. — ^There  are  two  cutaneous  branches,  an  anterior  and 
a  lateral. 

The  Anterior  Cutaneous  Branch  is  a  terminal  branch  and  is  a  direct  prolongation 
from  the  intercostal.  It  supplies  an  area  of  skin  of  the  abdominal  wall  between 
the  umbilicus  and  pubis. 

The  Lateral  Cutaneous  Branch  {ramu^s  cutaneus  lateralis  [abdominalis]  inter- 
costalis  XII)  is  remarkable  for  its  large  size;  it  perforates  the  Internal  and  Exter- 
nal oblique  muscles,  passes  downward  over  the  crest  of  the  ilium  in  front  of  the 
iliac  branch  of  the  ilio-hypogastric,  and  is  distributed  to  the  integument  of  the 
front  part  of  the  gluteal  region,  some  of  its  filaments  extending  as  low  down  as 
the  trochanter  major.  It  does  not  divide  into  an  anterior  and  a  posterior  branch, 
like  the  other  lateral  cutaneous  branches  of  the  intercostal  nerves. 

Surgical  Anatomy. — The  lower  seven  intercostal  nerves  and  the  ilio-hypogastric  from  the 
first  lumbar  nerve  supply  the  skin  of  the  abdominal  wall.    They  run  downward  and  inward  j 


I 


POSTERIOR    DIVISIONS    OF    THE   LUMBAR    NERVES         997 

fairly  equidistant  from  each  other.  The  sixth  and  seventh  supply  the  skin  over  the  "pit  of  the 
stomach;"  the  eighth  corresponds  to  about  the  position  of  the  middle  linea  transversa;  the 
tenth  to  the  umbilicus;  and  the  ilio-hypogastric  supplies  the  skin  over  the  pubes  and  external 
abdominal  ring.  There  are  several  points  of  surgical  significance  about  the  distribution  of  these 
nerves,  and  it  is  important  to  remember  their  origin  and  course,  for  in  many  diseases  affecting 
the  nerve-trunks  at  or  near  their  origin  the  pain  is  referred  to  their  peripheral  terminations.  Thus 
in  Pott's  disease  of  the  spine  children  will  often  be  brought  to  the  surgeon  suffering  from  pain 
in  the  belly.  This  is  due  to  the  fact  that  the  nerves  are  irritated  at  the  seat  of  disease  as  they 
issue  from  the  spinal  canal.  When  the  irritation  is  confined  to  a  single  pair  of  nerves,  the  sen- 
sation complained  of  is  often  a  feeling  of  constriction,  as  if  a  cord  were  tied  around  the  abdomen; 
and  in  these  cases  the  situation  of  the  sense  of  constriction  may  serve  to  localize  the  disease  in 
the  spinal  column.  In  other  cases,  where  the  bone  disease  is  more  extensive  and  two  or  more 
nerves  are  involved,  a  more  diffused  pain  in  the  abdomen  is  complained  of.  A  similar  conditon 
is  sometimes  present  in  affections  of  the  cord  itself,  as  in  tabes  dorsalis. 

Again,  it  must  be  borne  in  mind  that  the  same  nerves  which  supply  the  skin  of  the  abdomen 
supply  also  the  muscles  which  constitute  the  greater  part  of  the  abdominal  wall.  Hence,  it  follows 
that  any  irritation  applied  to  the  peripheral  terminations  of  the  cutaneous  branches  in  the 
skin  of  the  abdomen  is  immediately  followed  by  reflex  contraction  of  the  abdominal  muscles. 
A  good  practical  illustration  of  this  may  sometimes  be  seen  in  watching  two  surgeons  examine 
the  abdomen  of  the  same  patient.  One,  whose  hand  is  cold,  causes  the  muscles  of  the  abdom- 
inal wall  to  at  once  contract  and  the  belly  to  become  rigid,  and  thus  not  nearly  so  suitable 
for  examination;  the  other,  who  has  taken  the  precaution  to  warm  his  hand,  examines  the 
abdomen  without  exciting  any  reflex  contraction.  The  supply  of  both  muscles  and  skin  from 
the  same  source  is  of  importance  in  protecting  the  abdominal  viscera  from  injury.  A  blow 
on  the  abdomen,  even  of  a  severe  character,  will  do  no  injury  to  the  viscera  if  the  muscles  are 
in  a  condition  of  firm  contraction;  whereas  in  cases  where  the  muscles  have  been  taken  unawares, 
and  the  blow  has  been  struck  while  they  were  in  a  state  of  rest,  an  injury  insufficient  to  produce 
any  lesion  of  the  abdominal  wall  has  been  attended  with  rupture  of  some  of  the  abdominal  con- 
tents. The  importance,  therefore,  of  immediate  reflex  contraction  upon  the  receipt  of  an  injury 
cannot  be  overestimated,  and  the  intimate  association  of  the  cutaneous  and  muscular  fibres  in 
the  same  nerve  produces  a  much  more  immediate  response  on  the  part  of  the  muscles  to  any 
peripheral  stimulation  of  the  cutaneous  filaments  than  would  be  the  case  if  the  two  sets  of  fibres 
were  derived  from  independent  sources. 

Again,  the  nerves  supplying  the  abdominal  muscles  and  skin  are  derive'd  from  the  lower  inter- 
costal nerves  and  are  intimately  connected  with  the  sympathetic  supplying  the  abdominal  viscera 
through  the  lower  thoracic  ganglia  from  which  the  splanchnic  nerves  are  derived.  In  conse- 
quence of  this,  in  rupture  of  the  abdominal  viscera  and  in  acute  peritonitis  the  muscles  of  the 
belly-wall  become  firmly  contracted,  and  thus  as  far  as  possible  preserve  the  abdominal  contents 
in  a  condition  of  rest. 

THE  LUMBAR  NERVES  (NN.  LUMBALES). 

The  lumbar  nerves  are  five  in  number  on  each  side.  The  first  lumbar  nerve 
appears  l)etween  the  first  and  second  lumbar  vertebrae,  and  the  last  between  the 
last  lumbar  vertebra  and  the  base  of  the  sacrum. 

The  Roots  of  the  Lumbar  Nerves. 

The  roots  of  the  lumbar  nerves  are  the  largest,  and  their  filaments  the  most 
numerous,  of  all  the  spinal  nerves,  and  they  are  closely  aggregated  together  upon 
the  lower  end  of  the  cord.  The  anterior  roots  are  the  smaller,  but  there  is  not  the 
same  disproportion  between  them  and  the  posterior  roots  as  in  the  cervical  nerves. 
The  roots  of  these  nerves  have  a  vertical  direction,  and  are  of  considerable  length, 
more  especially  the  lower  ones,  since  the  spinal  cord  does  not  extend  beyond  the 
first  lumbar  vertebra.  The  roots  become  joined  in  the  intervertebral  foramina,  and 
the  nerves  so  formed  divide  at  their  exit  into  two  divisions,  posterior  and  anterior. 

The  Posterior  Divisions  of  the  Lumbar  Nerves  (Rami  Posteriores)  (Fig.  646). 

The  posterior  divisions  of  the  lumbar  nerves  diminish  in  size  from  above  down- 
ward; they  pass  backward  between  the  transverse  processes,  and  divide  into 
internal  and  external  branches. 


998 


THE  NERVOUS  SYSTEM 


The  Internal  Branches  {rami  mediales). — The  internal  branches,  the  smaller, 
pass  inward  close  to  the  articular  processes  of  the  vertebrae,  and  supply  the 
Multifidus  spinae  and  Interspinales  muscles. 

The  External  Branches  {rami  laterales). — ^The  external  branches  supply  the 
Erector  spinae  and  Intertransverse  muscles.  From  the  three  upper  branches 
cutaneous  nerves  are  derived  M^hich  pierce  the  aponeurosis  of  the  Latissimus  dorsi 
muscle  and  descend  over  the  back  part  of  the  crest  of  the  ilium,  to  be  distributed 
to  the  integument  of  the  gluteal  region,  some  of  the  filaments  passing  as  far  as  the 
trochanter  major  (Fig.  652). 

The  posterior  division  of  the  fifth  lumbar  nerve  usually  sends  a  branch  which 
forms  a  loop  with  the  posterior  division  of  the  first  sacral  nerve. 

The  Anterior  Divisions  of  the  Lumbar  Nerves  (Rami  Anteriores). 

The  anterior  divisions  of  the  lumbar  nerves  increase  in  size  from  above  down- 
ward. At  their  origin  they  communicate  with  the  lumbax  ganglia  of  the  sym- 
pathetic by  long,  slender  filaments,  which  accompany  the  lumbar  arteries  around 
the  sides  of  the  bodies  of  the  vertebrae,  beneath  the  Psoas  muscle.  The  nerves  pass 
obliquely  outward  behind  the  Psoas  magnus  or  between  its  fasciculi,  distributing 
filaments  to  it  and  the  Quadratus  lumborum.  The  anterior  divisions  of  the  five 
lumbar,  five  sacral,  and  first  coccygeal  nerve  constitute  the  lumbo-sacral  plexus 
{plexus  lumhosacralis).  This  is  subdivided  into  the  lumbar  plexus,  the  sacral 
plexus,  and  the  pudendal  plexus.  The  anterior  divisions  of  the  four  upper  nerves 
are  connected  together  in  this  situation  by  anastomotic  loops,  and  form  the  lumbar 
plexus.  The  anterior  division  of  the  fifth  lumbar,  joined  with  a  branch  from  the 
fourth,  descends  across  the  base  of  the  sacrum  to  join  the  anterior  division  of  the 
first  sacral  nerve  and  assist  in  the  formation  of  the  sacral  plexus.  The  cord  result- 
ing from  the  union-  of  the  fifth  lumbar  and  the  branch  from  the  fourth  is  called 
the  lumbo-sacral  cord  {truncus  lumhosacralis)  (Figs.  648  and  655) . 

The  Lumbar  Plexus  (Plexus  Lumbalis)  (Figs.  647,  648). 

The  lumbar  plexus  is  formed  by  the  loops  of  communication  between  the  ante- 
rior divisions  of  the  four  upper  lumbar  nerves.  The  plexus  is  narrow  above,  and 
often  connected  with  the  last  dorsal  nerve  by  a  slender  branch,  the  dorsi-lumbar 
nerve.  The  plexus  is  broad  below,  where  it  is  joined  to  the  sacral  plexus  by  the 
lumbo-sacral  cord.  The  lumbar  plexus  is  situated  in  the  substance  of  the  Psoas 
muscle  near  its  posterior  part,  in  front  of  the  transverse  processes  of  the  lumbar 
vertebrae. 

The  mode  in  which  the  plexus  is  arranged  varies  in  different  subjects.  It  differs 
from  the  brachial  plexus  in  not  forming  an  intricate  interlacement,  but  the  several 
nerves  of  distribution  arise  from  one  or  more  of  the  spinal  nerves  in  the  following 
manner:  The  first  lumbar  nerve  receives  a  branch  from  the  last  dorsal,  and  gives 
off  a  larger  branch,  which  subdivides  into  the  ilio-hypogastric  and  ilio-inguinal 
nerves;  the  first  lumbar  also  gives  off  a  communicating  branch  which  passes  down 
to  the  second  lumbar  nerve,  and  a  third  branch  which  unites  with  a  branch  of  the 
second  lumbar,  to  form  the  genito-crural  nerve.  The  second,  third,  and  fourth 
lumbar  nerves  divide  into  anterior  and  posterior  divisions.  The  anterior  division 
of  the  second  divides  into  two  branches,  one  of  which  joins  with  the  above- 
mentioned  branch  of  the  first  nerve  to  form  the  genito-crural;  the  other  unites 
with  the  anterior  division  of  the  third  nerve,  and  a  part  of  the  anterior  division 
of  the  fourth  nerve  to  form  the  obturator  nerve.  The  remainder  of  the  anterior 
division  of  the  fourth  nerve  passes  down  to  communicate  with  the  fifth  lumbar 
nerve.    The  posterior  divisions  of  the  second  and  third  nerves  divide  into  two 


THE   LUMBAR    PLEXUS 


999 


C.  with  nthl 


branches,  a  smaller  branch  from  each  uniting  to  form  the  external  cutaneous  nerve, 
and  a  larger  branch  from  each,  which  join  with  the  whole  of  the  posterior  division 
of  the  fourth  lumbar  nerve  to  form  the  anterior  crural.  The  accessory  obturator, 
when  it  exists,  is  formed  by  the  union  of  two  small  branches  given  off  from  the 
third  and  fourth  nerves. 

From  this  arrangement  it  follows  that  the  ilio-hypogastric  and  ilio-inguinal 
are  derived  entirely  from  the  first  lumbar  nerve;  the  genito-crural  from  the  first 
and  second  nerves;  the  external  cutaneous  from  the  second  and  third;  the  anterior 
crural  and  obturator  by  fibres  derived  from  the  second,  third,  and  fourth;  and  the 
accessory  obturator,  when  it  exists,  from  the  third  and  fourth. 

Branches  (Figs.  647  and  648). — The  branches  of  the  lumbar  plexus  are — the 

Ilio-hypogastric.  Obturator. 

Ilio-inguinal.  Accessory  obturator. 

Genito-crural.  Anterior  crural. 
External  cutaneous. 

The  Ilio-h3rpogastric  Nerve  (n.  iliohypogastricus)  (Figs.  647  and  648). — The 
ilio-hypogastric  nerve  arises  from  the  first  lumbar  nerve.  It  emerges  from  the 
outer  border  of  the  Psoas  muscle  at  its 
upper  part,  and  crosses  obliquely  in  front 
of  the  Quadratus  lumborum  to  the  crest 
of  the  ilium.  It  then  perforates  the  Trans- 
versalis  muscle  at  its  posterior  part  near  the 
crest  of  the  ilium.  It  gives  off  muscular 
branches  {rami  musculares)  to  the  abdom- 
inal wall,  and  divides  between  the  trans- 
versalis  and  the  Internal  oblique  into  two 
cutaneous  branches,  iliac  and  hypogastric. 

The  Iliac  Branch  (ramus  cutaneus  lateralis) 
pierces  the  Internal  and  External  oblique 
muscles  immediately  above  the  crest  of  the 
ilium,  and  is  distributed  to  the  integument 
of  the  gluteal  region,  behind  the  lateral 
cutaneous  branch  of  the  last  dorsal  nerve 
(Figs.  652  and  656).  The  size  of  this  nerve 
bears  an  inverse  proportion  to  that  of  the 
cutaneous  branch  of  the  last  dorsal  nerve. 

The  Hypogastric  Branch  (ramus  cutaneus 
anterior)  (Fig.  649)  continues  onward  be- 
tween the  Internal  oblique  and  Trans- 
versalis  muscles.  It  then  pierces  the  In- 
ternal oblique,  and  becomes  cutaneous  by 
perforating  the  aponeurosis  of  the  External 
oblique,  about  an  inch  above  and  a  little  to 
the  outer  side  of  the  external  abdominal 
ring,  and  is  distributed  to  the  integument  of  the  hypogastric  region.  The  ilio- 
hypogastric nerve  communicates  with  the  last  dorsal  and  ilio-inguinal  nerves. 

The  Ilio-inguinal  Nerve  (n.  ilioinguinalis)  (Figs.  647,  648,  and  649). — The  ilio- 
inguinal nerve,  smaller  than  the  preceding,  arises  with  it  from  the  first  lumbar 
nerve.  It  emerges  from  the  outer  border  of  the  Psoas  muscle  just  below  the  ilio- 
hypogastric nerve,  and,  passing  obliquely  across  the  Quadratus  lumborum  and 
Iliacus  muscles,  perforates  the  Transversalis  near  the  forepart  of  the  crest  of  the 
ilium,  and  communicates  with  the  ilio-hypogastric  nerve  between  that  muscle 
and  the  Internal  oblique.     The  nerve  then  pierces  the  Internal  oblique,  distribu- 


FiG.  647. — Plan  of  the  lumbar  plexus. 


1000 


THE  NERVOUS  SYSTEM 


ting  muscular  branches  {rami  musculares)  to  it,  and,  accompanying  the  spermatic 
cord  through  the  external  abdominal  ring,  is  distributed  to  the  integument  of  the 
upper  and  inner  part  of  the  thigh,  and  to  the  scrotum  in  the  male  (nn.  scrotales 
anteriores)  (Fig.  651) ,  and  to  the  labium  majus  in  the  female  (nn.  labiales  anteriores). 
The  size  of  this  nerve  is  in  inverse  proportion  to  that  of  the  ilio-hypogastric. 
Occasionally  it  is  very  small,  and  ends  by  joining  the  ilio-hypogastric;  in  such 
cases  a  branch  from  the  ilio-hypogastric  takes  the  place  of  the  ilio-inguinal,  or 
the  ilio-inguinal  nerve  may  be  altogether  absent. 

The  Genito-crural  Nerve   (?i.   genitofemoralis)  (Figs.  647  and  648)  arises   from 
the  first  and  second  lumbar  nerves.     It  passes  obliquely  through  the  substance 


Fig.  648. — The  lumbar  plexus  and  its  branches. 

of  the  Psoas  muscle,  and  emerges  from  its  inner  border  at  a  level  corresponding 
to  the  intervertebral  substance  between  the  third  and  fourth  lumbar  vertebrae; 
it  then  descends  on  the  surface  of  the  Psoas  muscle,  under  cover  of  the  peri- 
toneum, and  divides  into  a  genital  and  a  crural  branch. 

The  Genital  Branch  (n.  spermaticus  externus)  passes  outward  on  the  Psoas 
raagnus,  and  pierces  the  fascia  transversalis,  or  passes  through  the  internal  abdom- 
inal ring;  in  the  male  it  then  descends  along  the  back  part  of  the  spermatic  cord  to 
the  scrotum,  and  supplies  the  Cremaster  muscle.  In  the  female  it  accompanies 
the  round  ligament,  and  is  lost  upon  it. 

The  Crural  Branch  (n.  lumhoinguinalis)  (Fig.  649)  descends  on  the  external  iliac 
artery,  sending  a  few  filaments  around  it,  and,  passing  beneath  Poupart's  ligament 


THE   LUMBAR   PLEXUS 


1001 


V 


^  ^\^      ^/'oiju'l- 


A 


External 
saphe7ious. 


External      ))) 
cutaneous. 


Anterior  crural. 


-Anterior  tibial. 


.Anterior  division 
of  obturator. 
Internal 
cutaneotis. 


Internal 
'saphenous. 


Fig.  649.— Cutaneous  nerves  of  lower 
extremity.     Front  view. 


Fig.  650. — Nerves  of  the  lower  extremity. 
Front  view. 


1002 


THE  NERVOUS  SYSTEM 


to  the  thigh,  enters  the  sheath  of  the  femoral  vessels,  lying  superficial  and  a  little 
external  to  the  femoral  artery.  It  pierces  the  anterior  layer  of  the  sheath  of  the 
vessels,  and,  becoming  superficial  by  passing  through  the  fascia  lata,  it  supplies  the 
skin  of  the  anterior  aspect  of  the  thigh  as  far  as  midway  between  the  pelvis  and 


DORSAL    DIVI- 
SIONS   OF 
SACRAL 
NERVES  , 

PERFORATING 
CUTANEOUS 
OF    FOURTH 
SACRAL 


. :»  :h| 


EXTERNAL   SAPHENOUS    I.  II.  S.. 
ANTERIOR   TIBIAL   IV.  V.   L.   I.  S. 
EXTERNAL    PLANTAR- 
INTERNAL    PLANTAR    IV.  V.   L.- 


FiG.  651. — Areas  of  distribution  of  the  cutaneous 
nerves  of  the  front  of  the  lower  limb.  (W.  Keiller, 
after  Testut,  in  Gerrish's  Text-book  of  Anatomy.) 


MUSCULOCUTANEOUS 
V.  V.    L.   I.  S. 


INTERNAL 

CALCANEAN 

I.   M.  S. 


Fig.  652. — Areas  of  distribution  of  the  cutane- 
ous nerves  of  the  back  of  the  lower  limb.  (W. 
Keiller,  after  Testut,  in  Gerrish's  Text-book  of 
Anatomy.) 


knee  (Fig.  651) .     On  the  front  of  the  thigh  it  communicates  with  the  outer  branch 
of  the  middle  cutaneous  nerve,  derived  from  the  anterior  crural. 

A  few  filaments  from  this  nerve  may  be  traced  on  to  the  femoral  artery;  they 
are  derived  from  the  nerve  as  it  passes  beneath  Poupart's  ligament. 


THE  LUMBAR   PLEXUS  1003 

The  External  Cutaneous  Nerve  (n.  cutaneus  femoris  lateralis)  (Figs.  647,  648, 
649,  and  650). — The  external  cutaneous  nerve  arises  from  the  second  and  third 
lumbar  nerves.  It  emerges  from  the  outer  border  of  the  Psoas  muscle  about  its 
middle,  and  crosses  the  Iliacus  muscle  obliquely,  toward  the  anterior  superior 
spine  of  the  ilium.  It  then  passes  under  Poupart's  ligament  and  over  the  Sartorius 
muscle  into  the  thigh,  where  it  divides  into  two  branches,  anterior  and  posterior. 

The  Anterior  Branch  descends  in  an  aponeurotic  canal  formed  in  the  fascia  lata, 
becomes  superficial  about  four  inches  below  Poupart's  hgament,  and  divides  into 
branches  which  are  distributed  to  the  integument  along  the  anterior  and  outer 
part  of  the  thigh,  as  far  down  as  the  knee  (Fig.  651) .  This  nerve  occasionally  com- 
municates with  a  branch  of  the  long  saphenous  nerve  in  front  of  the  knee-joint. 

The  Posterior  Branch  pierces  the  fascia  lata,  and  subdivides  into  branches  which 
pass  backward  across  the  outer  and  posterior  surface  of  the  thigh,  supplying  the 
integument  from  the  crest  of  the  ilium  as  far  as  the  middle  of  the  thigh  (Fig.  652). 

The  Obturator  Nerve  (n.  ohturatoriiis)  (Figs.  647,  648,  and  650).— The  obturator 
nerve  supphes  the  Obturator  externus  and  Adductor  muscles  of  the  thigh,  the 
articulations  of  the  hip  and  knee,  and  occasionally  the  integument  of  the  thigh 
and  leg.  It  arises  by  three  branches — from  the  second,  the  third,  and  the  fourth 
lumbar  nerves.  Of  these,  the  branch  from  the  third  is  the  largest,  while  that 
from  the  second  is  often  very  small.  It  descends  through  the  inner  fibres  of  the 
Psoas  muscle,  and  emerges  from  its  inner  border  near  the  brim  of  the  pelvis;  it  then 
runs  along  the  lateral  wall  of  the  pelvis,  above  the  obturator  vessels,  to  the  upper 
part  of  the  obturator  foramen,  where  it  enters  the  thigh,  and  divides  into  an 
anterior  and  a  posterior  branch,  separated  by  some  of  the  fibres  of  the  Obturator 
externus  muscle,  and  lower  down  by  the  Adductor  brevis  muscle. 

The  Anterior  Branch  (ramus  anterior)  (Fig.  650)  passes  down  in  front  of  the 
Adductor  brevis,  being  covered  by  the  Pectineus  and  Adductor  longus,  and  at  the 
lower  border  of  the  latter  muscle  communicates  with  the  internal  cutaneous  and 
internal  saphenous  nerves,  forming  a  kind  of  plexus.  It  then  descends  upon  the 
femoral  artery,  upon  which  it  is  finally  distributed.  The  nerve,  near  the  obturator 
foramen,  gives  off  an  articular  branch  to  the  hip-joint.  Behind  the  Pectineus  it 
distributes  muscular  branches  to  the  Adductor  longus  and  Gracilis,  and  usually 
to  the  Adductor  brevis,  and  in  rare  cases  to  the  Pectineus,  and  receives  a  com- 
municating branch  from  the  accessory  obturator  nerve. 

Occasionally  the  communicating  branch  to  the  internal  cutaneous  and  internal 
saphenous  nerves  is  continued  down,  as  a  cutaneous  branch  (ramus  cutaneus),  to  the 
thigh  and  leg.  When  this  is  so,  this  occasional  cutaneous  branch  emerges  from 
beneath  the  lower  border  of  the  Adductor  longus,  descends  along  the  posterior 
margin  of  the  Sartorius  to  the  inner  side  of  the  knee,  where  it  pierces  the  deep 
fascia,  communicates  with  the  long  saphenous  nerve,  and  is  distributed  to  the 
integument  of  the  inner  side  of  the  leg  as  low  down  as  its  middle.  When  this 
communicating  branch  is  small  its  place  is  supplied  by  the  internal  cutaneous 
nerve. 

The  Posterior  Branch  (ramu^  posterior)  pierces  the  Obturator  externus,  sending 
branches  to  supply  it,  and  passes  behind  the  Adductor  brevis  on  the  front  of  the 
Adductor  magnus,  where  it  divides  into  numerous  muscular  branches,  which 
supply  the  Adductor  magnus,  and  the  Adductor  brevis  when  the  latter  does  not 
receive  a  branch  from  the  anterior  division  of  the  nerve.  One  of  the  branches 
gives  oft'  a  filament  to  the  knee-joint. 

The  Articular  Branch  for  the  Knee-joint  is  sometimes  absent;  it  perforates  the 
lower  part  of  the  Adductor  magnus,  and  enters  the  popliteal  space;  it  then  descends 
upon  the  popliteal  artery,  as  far  as  the  back  part  of  the  knee-joint,  where  it  per- 
forates the  posterior  ligament,  and  is  distributed  to  the  synovial  membrane.  It 
gives  filaments  to  the  popliteal  artery  in  its  course. 


1004  THE    NERVOUS  SYSTEM 

The  Accessory  Obturator  Nerve  or  the  Accessory  Anterior  Crural  Nerve  of  Winslow 
{n.  ohturatorius  accessorius  (Fig.  648). — The  accessory  obturator  nerve  is  not  con- 
stantly present.  It  is  of  small  size,  and  arises  by  separate  filaments  from  the 
third  and  fourth  lumbar  nerves.  It  descends  along  the  inner  border  of  the  Psoas 
muscle,  crosses  the  ascending  ramus  of  the  os  pubis,  and  passes  under  the  outer 
border  of  the  Pectineus  muscle,  where  it  divides  into  numerous  branches.  One 
of  these  supplies  the  Pectineus,  penetrating  its  under  surface;  another  is  dis- 
tributed to  the  hip-joint;  while  a  third  communicates  with  the  anterior  branch  of 
the  obturator  nerve.  When  this  nerve  is  absent  the  hip-joint  receives  two  branches 
from  the  obturator  nerve.  Occasionally  the  articular  branch  is  very  small,  and 
becomes  lost  in  the  capsule  of  the  hip-joint. 

The  Anterior  Crural  Nerve  (n.  femoralis)  (Figs.  647,  648,  and  650). — The  anterior 
crural  nerve  is  the  largest  branch  of  the  lumbar  plexus.  It  supplies  muscular 
branches  to  the  Iliacus,  Pectineus,  and  all  the  muscles  on  the  front  of  the  thigh, 
excepting  the  Tensor  fasciae  femoris;  cutaneous  filaments  to  the  front  and  inner 
side  of  the  thigh,  and  to  the  leg  and  foot  (Figs.  651  and  652) ;  and  articular 
branches  to  the  hip  and  knee.  It  arises  from  the  second,  third,  and  fourth 
lumbar  nerves.  It  descends  through  the  fibres  of  the  Psoas  muscle,  emerging 
from  muscle  at  the  lower  part  of  its  outer  border,  and  passes  down  between  it 
and  the  Iliacus  muscle,  and  beneath  Poupart's  ligament,  into  the  thigh,  where 
it  becomes  somewhat  flattened,  and  divides  into  an  anterior  and  a  posterior  part. 
Under  Poupart's  ligament  it  is  separated  from  the  femoral  artery  by  a  portion  of 
the  Psoas  muscle,  and  lies  beneath  the  iliac  fascia. 

Within  the  abdomen  the  anterior  crural  nerve  gives  off  from  its  outer  side  some 
small  muscular  branches  to  the  Iliacus,  and  a  branch  to  the  femoral  artery  which 
is  distributed  upon  the  upper  part  of  that  vessel.  The  origin  of  this  branch  varies; 
it  occasionally  arises  higher  than  usual,  or  it  may  arise  lower  down  in  the  thigh. 

External  to  the  pelvis  the  following  branches  are  given  off: 

From  the  Anterior  Division.  From  the  Posterior  Division. 
jNIiddle  cutaneous.  I^ong  saphenous. 

Internal  cutaneous.  Muscular. 

Muscular.  Articular. 

The  middle  and  internal  cutaneous  branches  of  the  anterior  crural  nerve  are 
the  rami  cutanei  anteriores  n.  femoralis  of  the  new  nomenclature. 

The  Middle  Cutaneous  Nerve  (Figs.  649  and  650)  pierces  the  fascia  lata  (generally 
the  Sartorius  muscle  also)  about  three  inches  below  Poupart's  ligament,  and 
divides  into  two  branches  (Fig.  649) ,  which  descend  in  immediate  proximity  along 
the  forepart  of  the  thigh,  to  supply  the  integument  as  low  as  the  front  of  the  knee 
(Fig.  651),  where  it  communicates  with  the  internal  cutaneous  nerve  and  the 
patellar  branch  of  the  internal  saphenous  nerve,  to  form  the  patellar  plexus.  In 
the  upper  part  of  the  thigh  the  outer  division  of  the  middle  cutaneous  nerve  com- 
municates with  the  crural  branch  of  the  genito-crural  nerve. 

The  Internal  Cutaneous  Nerve  (Fig.  649)  passes  obliquely  across  the  upper  part 
of  the  sheath  of  the  femoral  artery,  and  divides  in  front  or  at  the  inner  side  of  that 
vessel  into  two  branches,  anterior  and  posterior  or  internal. 

The  anterior  branch  runs  downward  on  the  Sartorius,  perforates  the  fascia  lata 
at  the  lower  third  of  the  thigh,  and  divides  into  two  branches,  one  of  which  sup- 
plies the  integument  as  low  dowji  as  the  inner  side  of  the  knee;  the  other  crosses 
to  the  outer  side  of  the  patella,  communicating  in  its  course  with  the  nervus 
cutaneus  patellae,  a  branch  of  the  internal  saphenous  nerve. 

The  posterior  or  internal  branch  descends  along  the  inner  border  of  the  Sartorius 
muscle  to  the  knee,  where  it  pierces  the  fascia  lata,  communicates  with  the  long 
saphenous  nerve,  and  gives  off  several  cutaneous  branches.     The  nerve  then 


THE    LUMBAR    PLEXUS  1C05 

passes  down  the  inner  side  of  the  leg,  to  the  integument  of  which  it  is  distributed. 
This  nerve,  beneath  the  fascia  lata,  at  the  lower  border  of  the  Adductor  longus, 
joins  in  a  plexiform  network  by  uniting  with  branches  of  the  long  saphenous  and 
obturator  nerves  (Fig.  650).  VYhen  the  communicating  branch  from  the  obturator 
nerve  is  large  and  continued  to  the  integument  of  the  leg,  the  inner  branch  of  the 
internal  cutaneous  is  small  and  terminates  at  the  plexus,  occasionally  giving  off 
a  few  cutaneous  filaments. 

The  internal  cutaneous  nerve,  before  dividing,  gives  off  a  few  filaments,  which 
pierce  the  fascia  lata,  to  supply  the  integument  of  the  inner  side  of  the  thigh  (Figs. 
651  and  652).  One  of  these  filaments  passes  through  the  saphenous  opening; 
a  second  becomes  subcutaneous  about  the  middle  of  the  thigh  (Fig.  649) ;  and  a 
third  pierces  the  fascia  at  its  lower  third  (Fig.  649). 

The  Muscular  Branches  of  the  Anterior  Division  {rami  musculares). — ^The  nerve 
to  the  Pectineus  is  often  duplicated ;  it  arises  from  the  anterior  crural  immediately 
below  Poupart's  ligament,  and  passes  inward  behind  the  femoral  sheath  to  enter 
the  anterior  surface  of  the  muscle.  The  nerve  to  the  Sartorius  arises  in  common 
with  the  middle  cutaneous. 

The  Long  or  Internal  Saphenous  Nerve  (n.  saphenus)  (Figs.  649  and  650)  is 
the  largest  of  the  cutaneous  branches  of  the  anterior  crural.  It  approaches  the 
femoral  artery  where  this  vessel  passes  beneath  the  Sartorius,  and  lies  in  front  of  it, 
beneath  the  aponeurotic  covering  of  Hunter's  canal,  as  far  as  the  opening  in  the 
lower  part  of  the  Abductor  magnus.  It  then  leaves  the  artery,  and  descends 
vertically  along  the  inner  side  of  the  knee,  beneath  the  Sartorius  muscle,  pierces 
the  fascia  lata  opposite  the  interval  between  the  tendons  of  the  Sartorius  and 
Gracilis  muscles,  and  becomes  subcutaneous.  The  nerve  then  passes  along  the 
inner  side  of  the  leg  (Fig.  649),  accompanied  by  the  internal  saphenous  vein, 
descends  behind  the  internal  border  of  the  tibia,  and,  at  the  lower  third  of  the  leg 
divides  into  two  branches:  one  continues  its  course  along  the  margin  of  the  tibia, 
terminating  at  the  inner  ankle;  the  other  passes  in  front  of  the  ankle,  and  is 
distributed  to  the  integument  along  the  inner  side  of  the  foot,  as  far  as  the  great 
toe,  communicating  with  the  internal  branch  of  the  musculo-cutaneous  nerve. 

The  long  saphenous  nerve  about  the  middle  of  the  thigh  gives  off  a  communicating 
branch  which  joins  the  plexus  formed  by  the  obturator  and  internal  cutaneous 
nerves. 

At  the  inner  side  of  the  knee  it  gives  off  a  large  patellar  branch,  the  nervus 
cutaneus  patellae  (ramus  infrapatellaris) ,  which  pierces  the  Sartorius  and  fascia 
lata,  and  is  distributed  to  the  integument  in  front  of  the  patella.  This  nerve  com- 
municates above  the  knee  with  the  anterior  branch  of  the  internal  cutaneous  and 
with  the  middle  cutaneous;  below  the  knee,  with  other  branches  of  the  long 
saphenous;  and  on  the  outer  side  of  the  joint,  with  branches  of  the  external  cuta- 
neous nerve,  forming  a  plexiform  network,  the  patella  plexus  (plexus  patellae). 
The  cutaneous  nerve  of  the  patella  is  occasionally  small,  and  terminates  by  join- 
ing the  internal  cutaneous,  which  supplies  its  place  in  front  of  the  knee. 

Below  the  knee  the  branches  of  the  long  saphenous  nerves  are  distributed  to 
the  integument  of  the  front  and  inner  side  of  the  leg  (Figs.  651  and  652),  com- 
municating with  the  cutaneous  branches  from  the  internal  cutaneous  or  from  the 
obturator  nerve.      The  nerve  also  sends  filaments  to  the  ankle-joint. 

The  Muscular  Branches  of  the  Posterior  Division. — The  muscular  branches  of  the 
posterior  division  supply  the  four  parts  of  the  Quadriceps  extensor  muscle. 

The  branch  to  the  Rectus  muscle  enters  its  under  sui-face  high  up,  sending  off  a 
small  filament  to  the  hip-joint. 

The  branch  to  the  Vastus  extemus  muscle,  of  large  size,  follows  the  course  of 
the  descending  branch  of  the  external  circumflex  artery  to  the  lower  part  of  the 
muscle.     It  gives  off  an  articular  filament  to  the  knee-joint. 


1006  THE    I^EBVOUS  SYSTEM 

The  branch  to  the  Vastus  internus  muscle  is  a  long  branch  which  runs  down  on 
the  outer  side  of  the  femoral  vessels  in  company  with  the  internal  saphenous 
nerve  for  its  upper  part.  It  enters  the  muscle  about  its  middle,  and  gives  off  a 
filament  which  can  usually  be  traced  downward  on  the  surface  of  the  muscle  to 
the  knee-joint. 

The  branch  to  the  Crureus  muscle  enters  the  muscle  on  its  anterior  surface 
about  the  middle  of  the  thigh,  and  sends  a  filament  through  the  muscle  to  the 
Subcrureus  and  the  knee-joint. 

The  articular  branch  to  the  hip-joint  is  derived  from  the  nerve  to  the  Rectus 
muscle. 

The  articular  branches  to  the  knee-joint  are  three  in  number.  One,  a  long,  slender 
filament,  is  derived  from  the  nerve  to  the  Vastus  externus  muscle;  it  penetrates  the 
capsular  ligament  of  the  joint  on  its  anterior  aspect.  Another  is  derived  from 
the  nerve  to  the  Vastus  internus  muscle.  It  can  usually  be  traced  downward 
on  the  surface  of  this  muscle  to  near  the  joint;  it  then  penetrates  the  muscle 
and  accompanies  the  deep  branch  of  the  anastomotica  magna  artery,  pierces  the 
capsular  ligament  of  the  joint  on  its  inner  side,  and  supplies  the  synovial 
membrane.    The  third  branch  is  derived  from  the  nerve  to  the  Crureus. 


THE  SACRAL  AND  COCCYGEAL  NERVES  (NN.  SACRALES  ET  COCCYGEUS). 

The  sacral  nerves  are  five  in  number  on  each  side.  The  four  upper  ones  pass 
from  the  sacral  canal  through  the  sacral  foramina;  the  fifth  through  the  foramen 
between  the  sacrum  and  coccyx. 

The  Roots  of  the  Upper  Sacral  Nerves. 

The  roots  of  the  upper  sacral  nerves  are  the  largest  of  all  the  spinal  nerves; 
while  those  of  the  lowest  sacral  and  the  coccygeal  nerve  are  the  smallest.  They  are 
longer  than  those  of  any  of  the  other  spinal  nerves,  on  account  of  the  spinal  cord 
not  extending  beyond  the  first  lumbar  vertebra.  From  their  great  length,  and  the 
appearance  they  present  in  connection  with  their  attachment  to  the  spinal  cord, 
the  roots  of  origin  of  these  nerves  are  called  collectively  the  cauda  equina. 

Each  sacral  and  coccygeal  nerve  separates  into  two  divisions,  posterior  and 
.anterior. 

The  Posterior  Divisions  of  the  Sacral  Nerves  (Rami  Posteriores)  (Fig.  653). 

The  posterior  divisions  of  the  sacral  nerves  are  small,  diminish  in  size  from 
.above  downward,  and  emerge,  except  the  last,  from  the  sacral  canal  by  the  posterior 
•sacral  foramina. 

The  Upper  Sacral  Nerves. — Each  of  the  three  upper  ones  is  covered,  at  its 
exit  from  the  sacral  canal,  by  the  Multifidus  spinae  muscle,  and  divides  into  an 
internal  branch  (ramus  medialis)  and  an  external  branch  {ramus  lateralis). 

The  Internal  Branches. — The  internal  branches  are  small,  and  supply  the  Mul- 
tifidus  spinae  muscle. 

The  External  Branches. — The  external  branches  join  with  one  another,  and  with 
the  last  lumbar  and  fourth  sacral  nerves,  in  the  form  of  loops  on  the  posterior 
surface  of  the  sacrum,  constituting  the  posterior  sacral  plexus.  From  these  loops 
branches  pass  to  the  outer  surface  of  the  great  sacro-sciatic  ligament,  where  they 
form  a  second  series  of  loops  beneath  the  Gluteus  maximus  muscle.  Cutaneous 
branches  from  this  second  series  of  loops,  usually  two  or  three  in  number,  pierce 
the  Gluteus  maximus  muscle  along  a  line  drawn  from  the  posterior  superior  spine 


THE   ANTERIOR    DIVISIONS    OF    THE   SACRAL    NERVES     1007 

of  the  ilium  to  the  tip  of  the  coccyx.     They  supply  the  integument  over  the 
posterior  part  of  the  gluteal  region  (Fig.  652). 

The  Lower  Sacral  Nerves. — The  posterior  divisions  of  the  two  lower  sacral 
nerves  are  situated  below  the  Multifidus  spinae  muscle.  They  are  of  small  size, 
and  do  not  divide  into  internal  and  external  branches,  but  join  with  each  other, 


Fig.  653  — The  posterior  sacral  nerves. 

and  with  the  posterior  division  of  the  coccygeal  nerve  to  form  the  posterior  sacro- 
coccygeal nerve,  which  passes  through  the  sacro-sciatic  ligament,  and  forms  loops 
on  the  back  of  the  sacrum,  filaments  from  which  supply  the  Extensor  coccygeus 
and  the  integument  over  the  coccyx  (Fig.  652). 

The  Anterior  Divisions  of  the  Sacral  Nerves  (Rami  Anteriores)  (Fig.  655). 

The  anterior  divisions  of  the  sacral  nerves  diminish  in  size  from  above  down- 
ward. The  four  upper  ones  emerge  from  the  anterior  sacral  foramina;  the  ante- 
rior division  of  the  fifth,  after  emerging  from  the  spinal  canal  through  its  terminal 
opening,  curves  forward  between  the  sacrum  and  the  coccyx.  All  the  anterior  sacral 
nerves  at  their  exit  from  the  sacral  foramina  communicate  with  the  sacral  ganglia  of 
the  sympathetic.  The  first  nerve  (Fig.  654) ,  of  large  size,  unites  with  the  lumbo-sacral 
cord  (trtmcus  lumbosacralis) ,  formed  by  the  fifth  lumbar,  and  a  branch  from  the 
fourth  lumliar  (n.  furcalis).  The  second  (Fig.  654),  equal  in  size  to  the  preceding, 
and  the  third  (n.  higeminus)  (Fig.  654),  about  one-fourth  the  size  of  the  second, 
unite  with  this  trunk,  and  form,  with  a  small  fasciculus  from  the  fourth,  the  sacral 
plexus,  a  visceral  branch  being  given  off  from  the  third  nerve  to  the  bladder 
(Fig.  655). 

The  Fourth  Anterior  Sacral  Nerve  sends  a  branch  to  join  the  sacral  plexus.  The 
remaining  portion  of  the  nerve  divides  into  visceral  and  muscular  branches,  and  a 
communicating  filament  descends  to  join  the  fifth  sacral  nerve. 


1008 


THE   NERVOUS   SYSTEM 


The  visceral  branches  are  distributed  to  the  viscera  of  the  pelvis,  communicating 
with  the  sympathetic  nerve.  These  branches  ascend  upon  the  rectum  and  bladder, 
and  in  the  female  upon  the  vagina,  communicating  with  branches  of  the  sym- 
pathetic from  the  pelvic  plexus.  The  visceral  branches  of  the  third  and  fourth 
sacral  do  not  join  the  gangliated  cord. 

The  muscular  branches  are  distributed  to  the  Levator  ani,  Coccygeus,  and 
Sphincter  ani.  The  branch  to  the  Sphincter  ani  pierces  the  levator  ani,  so  as  to 
reach  the  ischio-rectal  fossa,  where  it  is  found  lying  in  front  of  the  coccyx.  Cuta- 
neous filaments  arise  from  the  latter  branch,  which  supply  the  integument  between 
the  anus  and  coccyx.    Another  cutaneous  branch  is  frequently  given  off  from  this 


Femoral  m  tei  y 


Coccygeal. 
^Br.  to'      I       Br.  to 

LEVATOR  ANI.    SPHINCTER  ANI. 

Fig.  664. — Side  view  of  pelvis,  showing  sacral  nerves. 


nerve,  though  sometimes  from  the  pudic  (Schwalbe).  It  perforates  the  great 
sacro-sciatic  ligament,  and,  winding  around  the  lower  border  of  the  Gluteus 
maximus,  supplies  the  skin  over  the  lower  and  inner  part  of  this  muscle. 

The  Fifth  Anterior  Sacral  Nerve,  after  passing  from  the  lower  end  of  the  sacral 
canal,  curves  forward  through  the  fifth  sacral  foramen,  formed  between  the  lower 
part  of  the  sacrum  and  the  transverse  process  of  the  first  piece  of  the  coccyx.  It 
pierces  the  Coccygeus  muscle,  and  descends  upon  its  anterior  surface  to  near  the 
tip  of  the  coccyx,  where  it  again  perforates  the  muscle,  to  be  distributed  to  the 
integument  over  the  back  part  and  side  of  the  coccyx.  This  nerve  communicates 
above  with  the  fourth  sacral  and  below  with  the  coccygeal  nerve,  and  supplies  the 
Coccygeus  muscle. 

The  Posterior  Division  of  the  Coccygeal  Nerve. 

The  coccygeal  nerve  divides  into  its  anterior  and  posterior  divisions  in  the 
spinal  canal.     The  posterior  division  is  the  smaller.     It  does  not  divide,  but 


THE  SACRAL    OB    SCIATIC  PLEXUS 


1009 


receives,  as  already  mentioned,  a  communicating  branch  from  the  last  sacral, 
and  is  lost  in  the  integument  over  the  back  of  the  coccyx. 

The  Anterior  Division  of  the  Coccygeal  Nerve. 

The  anterior.division  of  the  coccygeal  nerve  is  a  delicate  filament  which  escapes 
at  the  termination  of  the  sacral  canal;  it  passes  downward  behind  the  rudimentary 
transverse  process  of  the  first  piece  of  the  coccyx,  and  curves  forward  through 
the  notch  between  the  first  and  second  pieces,  piercing  the  Coccygeus  muscle,  and 
descending  on  its  anterior  surface  to  near  the  tip  of  the  coccyx,  where  it  again 
pierces  the  muscle,  to  be  distributed  to  the  integument  over  the  back  part  and  side 
of  the  coccyx.  It  is  joined  by  a  branch  from  the  fifth  anterior  sacral  as  it  descends 
on  the  surface  of  the  Coccygeus  muscle. 

The  Pudendal  Plexus  (plexus  pudendus). — The  pudendal  plexus  is  formed  by 
fibres  obtained  from  the  anterior  divisions  of  the  first  three  sacral  nerves  and  by 
the  anterior  divisions  of  the  two  lower  sacral  nerves  and  the  coccygeal  nerve.  It 
is,  so  to  speak,  interpolated  in  the  sacral  plexus  and  is  considered  as  a  portion  of  it. 

The  Sacral  or  Sciatic  Plexus  (Plexus  Sacralis)  and  the  Pudic  or  Pudendal 
Plexus  (Plexus  Pudendalis)  (Fig.  655). 

The  sacral  plexus  is  formed  by  the  lum bo-sacral  cord,  the  anterior  divisions 
of  the  three  upper  sacral  nerves  and  a  branch  from  the  fourth.  The  pudic  or 
pudendal  plexus  is  considered  with  the  sacral  plexus.     It  is  usually  composed  of 

/      FOURTH  LUMBAR 


FIFTH  LUMBAR 


RST  SACRAL 


SECOND  SACRAL 


THIRD  SACRAL 


FOURTH  SACRAL 


FIFTH  SACRAL 
'^/■'  '/hr'-'ft — N.TO  COCCYQEUS 


-T^    vi8oeraDv'>'-;^.' COCCYGEAL 


Fig.  656.- -Plan  of  sacral  plexus  with  the  pudendal  plexus.     (Gerrish.) 

the  anterior  divisions  of  the  second,  third,  fourth,  and  fifth  sacral  nerves  and  the 
coccygeal  nerve.  It  is  irregular  in  composition.  Prof.  Cunningham  says:  "There 
is  no  distinct  point  of  separation  between  the  two  plexuses.  On  the  contrary,  there 
is  considerable  overlapping,  so  that  two  and  sometimes  three  of  the  principal  nerves 
derived  from  the  pudendal  plexus  have  their  origin  in  common  with  nerves  of  the 

64 


1010  THE   NERVOUS   SYSTEM 

sacral  plexus."  The  nerves  of  these  two  plexuses  proceed  in  different  directions: 
the  upper  ones  obliquely  downward  and  outward,  the  lower  ones  nearly  horizontally 
outward,  and  they  all  unite  into  two  cords;  an  upper  and  larger  cord,  which  is  formed 
by  the  lumbo-sacral  cord  with  the  first,  second,  and  the  greater  part  of  the  third 
sacral  nerves;  and  a  lower  and  smaller  cord,  formed  by  the  remainder  of  the  third, 
with  a  portion  of  the  fourth  sacral  nerve.  The  upper  cord  is  prolonged  into  the 
great  sciatic  nerve  and  the  lower  into  the  pudic.  Frequently  a  small  filament  is 
given  off  from  the  second  sacral  nerve  to  join  the  lower  cord. 

Each  of  the  nerves  which  form  the  plexus  joins  the  sympathetic  by  gray  rami 
communicantes.  White  rami  communicantes  join  the  third  sacral  and  sometimes 
also  the  second  and  fourth  sacrals  to  the  s^nnpathetic. 

The  sacro-pudendal  plexus  is  triangular  in  form,  its  base  corresponding  with 
the  exit  of  the  nerves  from  the  sacrum,  its  apex  with  the  lower  part  of  the  great 
sacro-sciatic  foramen.  It  rests  upon  the  anterior  surface  of  the  Pyriformis,  and  is 
covered  in  front  by  the  pelvic  fascia,  which  separates  it  from  the  sciatic  and  pudic 
branches  of  the  internal  iliac  artery  and  from  the  viscera  of  the  pelvis.  The  sacral 
plexus  proper  sends  branches  to  the  lower  extremity;  the  pudendal  plexus  proper 
is  largely  limited  to  supplying  the  perineum. 

Branches. — The  branches  of  the  sacro-pudendal  plexus  are  divided  into  col- 
lateral and  terminal  branches. 

Muscular. 


Collateral  branches 


Terminal  branches 


Superior  gluteal. 

Inferior  gluteal. 

Small  sciatic 

Perforating  cutaneous. 
]  Pudic. 
1  Great  sciatic. 


The  Muscular  Branches  {rami  musculares). — The  muscular  branches  supply  the 
Pyriformis,  Obturator  internus,  the  two  Gemelli,  and  the  Quadratus  femoris. 
The  branch  to  the  Pyriformis  muscle  arises  from  the  upper  two  sacral  nerves 
before  they  enter  the  plexus;  the  branch  to  the  Obturator  internus  muscle  arises 
at  the  jimction  of  the  lumbo-sacral  and  first  sacral  nerves;  it  passes  out  of  the 
pelvis  through  the  great  sacro-sciatic  foramen  below  the  Pyriformis,  crosses  the 
spine  of  the  ischium,  and  re-enters  the  pelvis  through  the  lesser  sacro-sciatic 
foramen  to  enter  the  inner  surface  of  the  Obturator  internus;  the  branch  to  the 
Gemellus  superior  muscle  arises  in  common  with  the  nerve  to  the  Obturator 
internus  muscle;  it  enters  the  muscle  at  the  upper  part  of  its  posterior  surface; 
the  small  branch  to  the  Gemellus  inferior  and  Quadratus  femoris  muscles  also 
arises  from  the  upper  part  of  the  plexus;  it  passes  through  the  great  sacro-sciatic 
foramen  below  the  Pyriformis,  and  courses  down  beneath  the  great  sciatic  nerve, 
the  Gemelli  and  tendon  of  the  Obturator  internus,  supplies  the  muscles  on  their 
deep  or  anterior  surface  and  gives  off  an  articular  branch  to  the  hip-joint.  A  second 
articular  branch  is  occasionally  derived  from  the  upper  part  of  the  sacral  plexus. 

The  Superior  Gluteal  Nerve  {n.  glutaeus  superior)  (Figs.  655  and  657). — The 
superior  gluteal  nerve  arises  from  the  back  part  of  the  lumbo-sacral  cord,  with 
some  filaments  from  the  first  sacral  nerve;  it  passes  from  the  pelvis  through  the 
great  sacro-sciatic  foramen  above  the  Pyriformis  muscle,  accompanied  by  the 
gluteal  vessels,  and  divides  into  a  superior  and  an  inferior  branch. 

The  Superior  Branch  follows  the  line  of  origin  of  the  Gluteus  minimus,  and 
supplies  the  Gluteus  medius  muscle. 

The  Inferior  Branch  crosses  obliquely  between  the  Gluteus  minimus  and  medius, 
distributing  filaments  to  both  these  muscles,  and  terminates  in  the  Tensor  fasciae 
femoris  muscle,  extending  nearly  to  its  lower  end. 


THE  SACRAL    OB    SCIATIC  PLEXUS  1011 

The  Inferior  Gluteal  Nerve  {n.  glutaeus  inferior)  (Fig.  655).— The  inferior  gluteal 
nerve  arises  from  the  lumbo-sacral  cord  and  first  and  second  sacral  nerves,  and  is 
intimately  connected  with  the  small  sciatic  at  its  origin.  It  passes  out  of  the  pelvis 
through  the  great  sciatic  notch,  beneath  the  Pyriformis  muscle,  and,  dividing  into 
a  number  of  branches,  enters  the  Gluteus  maxiraus  muscle  on  its  under  surface. 

The  Small  Sciatic  Nerve  (n.  cutanetis  femoris  posterior)  (Figs.  655,  656,  and  657). 
— The  small  sciatic  nerve  supplies  the  integument  of  the  perineum  and  back  part 
of  the  thigh  and  leg.  It  is  usually  formed  by  the  union  of  two  branches,  which 
arise  from  the  second  and  third  nerves  of  the  sacral  plexus.  It  issues  from  the 
pelvis  through  the  great  sacro-sciatic  foramen  below  the  Pyriformis  muscle, 
descends  beneath  the  Gluteus  maximus  with  the  sciatic  artery,  and  at  the 
lower  border  of  that  muscle  passes  along  the  back  part  of  the  thigh,  beneath  the 
fascia  lata  and  over  the  long  head  of  the  Biceps,  to  the  lower  part  of  the  popliteal 
region,  where  it  pierces  the  fascia  and  becomes  cutaneous.  It  then  accompanies 
the  external  saphenous  vein  to  about  the  middle  of  the  leg,  its  terminal  filaments 
communicating  with  the  external  saphenous  nerve. 

The  Branches  of  the  small  sciatic  nerve  are  all  cutaneous,  and  are  grouped  as 
follows:  gluteal,  perineal,  and  femoral. 

The  Gluteal  Cutaneous  Branches  {nn.  clunium  injeriores  [laterales\)  consist  of  two 
or  thiee  ascending  filaments,  which  turn  upward  around  the  lower  border  of  the 
Gluteus  maximus  to  supply  the  integument  covering  the  lower  and  outer  part 
of  that  muscle  (Fig.  652). 

The  Perineal  Cutaneous  Branches  {rami  perineales)  are  distributed  to  the  skin 
at  the  upper  and  inner  side  of  the  thigh,  on  its  posterior  aspect.  One  branch, 
longer  than  the  rest,  the  inferior  pudendal  or  long  scrotal  nerve  (Fig.  657),  curves 
forward  below  the  tuber  ischii,  pierces  the  fascia  lata,  and  passes  forward  beneath 
the  superficial  fascia  of  the  perineum  to  be  distributed  to  the  integument  of  the 
scrotum  in  the  male  (Fig.  652)  and  the  labium  in  the  female,  communicating  with 
the  supcficial  perineal  and  inferior  hemorrhoidal  nerves. 

The  Femoral  Cutaneous  Branches  are  numerous  descending  filaments,  derived 
from  both  sides  of  the  nerves,  which  are  distributed  to  the  back,  inner,  and  outer 
sides  of  the  thigh,  to  the  skin  covering  the  popliteal  space,  and  to  the  upper  part 
of  the  leg  (Fig.  652). 

The  Perforating  Cutaneous  Nerve  (n.  clunium  inferior  medialis)  (Fig.  655). — The 
perforating  cutaneous  nerve  usually  arises  from  the  second  and  third  sacral 
nerves,  and  is  of  small  size.  It  is  continued  backward  through  the  great  sacro- 
sciatic  ligament,  and,  winding  around  the  lower  border  of  the  Gluteus  maximus, 
supplies  the  integument  covering  the  inner  and  lower  part  of  that  muscle. 

The  Pudic  Nerve  (n.  pudendus)  (Figs.  655  and  657). — ^The  pudic  nerve  is  the 
direct  continuation  of  the  lower  cord  of  the  sacral  plexus,  and  derives  its  fibres 
from  the  third  and  fourth  sacral  nerves,  and  frequently  from  the  second  also. 
It  leaves  the  pelvis  through  the  great  sacro-sciatic  foramen,  below  the  Pyriformis. 
It  then  crosses  the  spine  of  the  ischium,  and  re-enters  the  pelvis  through  the 
lesser  sacro-sciatic  foramen.  It  accompanies  the  pudic  vessels  upward  and  for- 
ward along  the  outer  wall  of  the  ischio-rectal  fossa,  being  contained  in  a  sheath 
of  the  obturator  fascia,  termed  Alcock's  canal,  and  divides  into  two  terminal 
branches,  the  perineal  nerve  and  the  dorsal  nerve  of  the  penis  or  clitoris.  Before 
its  division  it  gives  oft"  the  inferior  hemorrhoidal  nerve. 

The  Inferior  Haemorrhoidal  Nerve  (n.  haemorrhoidalis  inferior)  is  occasionally 
derived  separately  from  the  sacral  plexus.  It  passes  across  the  ischio-rectal  fossa, 
with  its  accompanying  vessels,  toward  the  lower  end  of  the  rectum,  and  is  dis- 
tributed to  the  Sphincter  ani  externus  and  to  the  integument  around  the  anus. 
Branches  of  this  nerve  communicate  with  the  inferior  pudendal  and  superficial 
perineal  nerves  at  the  forepart  of  the  perineum. 


1012 


THE  NERVOUS  SYSTEM 


*y. 


/■I 

Superior         f  _<^ 
gluteal.         V^ 

Pudic.^  .^, 

Nerve  to 

obturator  internus.   a. 


^M  sciatic 


Fig.  656. — Cutaneous  nerves  of  lower 
extremity.     Posterior  view. 


External 

popliteal,  or 

peroneal. 


Communicant 
ptronei. 


Fig.  657. 


-Nerves  of  the  lower  extremity.* 
Posterior  view. 


'  N.  B. — In  this  diaKram  the  external  saphenous  and  communicans  peronei  are  not  in  their  normal  position. 
They  have  been  displaced  by  the  removal  of  the  superficial  muscles. 


THE  SACBAL    OR  SCIATIC  PLEXUS  1013 

The  Perineal  Nerve  (w.  perinei),  the  inferior  and  larger  of  the  two  terminal 
branches  of  the  pudic,  is  situated  below  the  pudic  artery.  It  accompanies  the 
superficial  perineal  artery  in  the  perineum,  dividing  into  cutaneous  and  muscular 
branches. 

The  cutaneous  branches  (superficial  perineal)  are  two  in  number,  posterior  and 
anterior.  The  posterior  or  external  branch  pierces  the  base  of  the  triangular  liga- 
ment of  the  urethra,  and  passes  forward  along  the  outer  side  of  the  urethral 
triangle  in  company  with  the  superficial  perineal  artery;  it  is  distributed  to  the 
skin  of  the  scrotum  (nn.  scrotales  posteriores) .  It  communicates  with  the  inferior 
haemorrhoidal,  the  inferior  pudendal,  and  the  other  superficial  perineal  nerve. 
The  anterior  or  internal  branch  also  pierces  the  base  of  the  triangular  ligament,  and 
passes  forward  nearer  to  the  middle  line,  to  be  distributed  to  the  inner  and  back 
part  of  the  scrotinn.    Both  these  nerves  supply  the  labia  majora  in  the  female. 

The  muscular  branches  are  distributed  to  the  Transversus  perinaei.  Accelerator 
urinae.  Erector  penis,  and  Compressor  urethrae.  A  distant  branch  is  given  off 
from  the  nerve  to  the  Accelerator  urinae,  which  pierces  this  muscle,  and  supplies 
the  corpus  spongiosum,  ending  in  the  mucous  membrane  of  the  urethra.  This 
is  the  nerve  to  the  bulb. 

The  Dorsal  Nerve  of  the  Penis  {n.  dorsalis  penis)  is  the  deepest  division  of  the 
pudic  nerve;  it  accompanies  the  pudic  artery  along  the  ramus  of  the  ischium;  it 
then  runs  forward  along  the  inner  margin  of  the  ramus  of  the  os  pubis,  between 
the  superficial  and  deep  layers  of  the  triangular  ligament.  Piercing  the  superficial 
layer  it  gives  a  branch  to  the  corpus  cavernosum,  and  passes  forward,  in  company 
with  the  dorsal  artery  of  the  penis,  between  the  layers  of  the  suspensory  ligament, 
on  to  the  dorsum  of  the  penis,  along  which  it  is  carried  as  far  as  the  glans,  to  which 
it  is  distributed. 

In  the  female  the  dorsal  nerve  is  very  small,  and  supplies  the  clitoris  (n.  dorsalis 
clitoridis). 

The  Great  Sciatic  Nerve  (/?.  ischiadicus)  (Figs.  655  and  657). — ^The  great  sciatic 
nerve  supplies  nearly  the  whole  of  the  integument  of  the  leg,  the  muscles  of  the 
back  of  the  thigh,  and  those  of  the  leg  and  foot.  It  is  the  largest  nervous  cord  in  the 
body,  measuring  three-quarters  of  an  inch  in  breadth,  and  is  the  direct  continuation 
of  the  upper  division  of  the  sacral  plexus.  It  passes  out  of  the  pelvis  through  the 
great  sacro-sciatic  foramen,  below  the  Pyriformis  muscle.  It  descends  between 
the  trochanter  major  and  tuberosity  of  the  ischium,  along  the  back  part  of  the 
thigh,  to  about  its  lower  third,  where  it  divides  into  two  large  branches,  the  internal 
and  external  popliteal  nerves  (Fig.  657). 

This  division  may  take  place  at  any  point  between  the  sacral  plexus  and  the 
lower  third  of  the  thigh.  When  the  division  occurs  at  the  plexus,  the  two  nerves 
descend  together  side  by  side;  or  they  may  be  separated,  at  their  commencement, 
by  the  interposition  of  part  or  the  whole  of  the  Pyriformis  muscle.  As  the  nerve 
descends  along  the  back  of  the  thigh,  it  rests  upon  the  posterior  surface  of  the 
ischium,  the  nerve  of  the  Quadratus  femoris,  and  the  External  rotator  muscles,  in 
company  with  the  small  sciatic  nerve  and  artery,  being  covered  by  the  Gluteus 
maxim  us;  lower  down,  it  lies  upon  the  Adductor  magnus,  and  is  covered  by  the 
long  head  of  the  Biceps.  The  great  sciatic  even  when  apparently  a  single  nerve 
is  really  two  nerves  appearing  as  one. 

Branches. — The  branches  of  the  nerve,  before  its  division,  are  articular  and  muscular. 

The  Articular  Branches  {rami  articulares)  arise  from  the  upper  part  of  the  nerve ; 
they  supply  the  hip-joint,  perforating  the  posterior  part  of  its  fibrous  capsule. 
These  branches  are  sometimes  derived  from  the  sacral  plexus. 

The  Muscular  Branches  {rami  musculares)  are  distributed  to  the  flexors  of  the  leg — 
viz.,  the  Biceps,  Semitendinosus,  and  Semimembranosus,  and  a  branch  goes  to  the 
Adductor  magnus.    These  branches  are  given  off  beneath  the  Biceps  muscle. 


1014  THE   NERVOUS  SYSTEM 

The  Internal  Popliteal  or  Tibial  Nerve  (n.  tibialis)  (Figs.  655  and  657),  in  reality, 
arises  from  the  fourth  and  fifth  lumbar  nerves  and  the  first  three  sacral  nerves,  and 
becomes  a  part  of  the  trunk  of  the  great  sciatic  in  the  buttock,  to  emerge  from  it 
again  at  the  bifurcation  of  the  sciatic.  It  is  the  larger  of  the  two  terminal  branches 
of  the  great  sciatic,  descends  along  the  back  part  of  the  thigh,  through  the  middle  of 
the  popliteal  space,  to  the  lower  part  of  the  Popliteus  muscle,  where  it  passes  with 
the  artery  beneath  the  arch  of  the  Soleus  and  becomes  the  posterior  tibial.  It  is  over- 
lapped by  the  hamstring  muscles  above,  and  then  becomes  more  superficial,  and 
lies  to  the  outer  side  of,  and  some  distance  from,  the  popliteal  vessels;  opposite 
the  knee-joint  it  is  in  close  relation  with  the  vessels,  and  crosses  to  the  inner  side  of 
the  artery.    Below,  it  is  overlapped  by  the  Gastrocnemius  muscle. 

The  branches  of  this  nerve  are — articular,  muscular,  and  a  cutaneous  branch,  the 
communicating  tibial  nerve. 

The  articular  branches  (rami  articulares),  usually  three  in  number,  supply  the 
knee-joint;  two  of  these  branches  accompany  the  superior  and  inferior  internal 
articular  arteries,  and  a  third,  the  azygos  articular  artery. 

The  muscular  branches  {rami  musculares) ,  four  or  five  in  number,  arise  from  the 
nerve  as  it  lies  between  the  two  heads  of  the  Gastrocnemius  muscle;  they  supply 
that  muscle,  and  the  Plantaris,  Soleus,  and  Popliteus.  The  filaments  which 
supply  the  Popliteus  turn  around  its  lower  border  and  are  distributed  to  its  deep 
surface. 

The  tibial  communicating  nerve  (n.  cutaneus  surae  medialis)  is  the  cutaneous 
branch.  It  descends  between  the  two  heads  of  the  Gastrocnemius  muscle,  and 
about  the  middle  of  the  back  of  the  leg  pierces  the  deep  fascia,  and  joins  the 
peroneal  or  fibular  communicating  nerve  (ramus  anastomoticus  peronaeus)  from  the 
external  popliteal  nerve  to  form  the  external  or  short  saphenous  (n.  surahs)  (Fig. 
657).  The  external  saphenous  nerve,  formed  by  the  communicating  branches  of 
the  internal  and  external  popliteal  nerves,  passes  downward  and  outward  near 
the  outer  margin  of  the  tendo  Achillis,  lying  close  to  the  external  saphenous  vein, 
to  the  interval  between  the  external  malleolus  and  the  os  calcis.  It  divides  in 
two  branches,  the  posteror  of  which  breaks  up  into  external  calcaneal  branches 
(rami  calcanei  laterales).  The  anterior  branch  (n.  cutaneus  dorsalis  lateralis)  winds 
around  the  outer  malleolus,  and  is  distributed  to  the  integument  along  the  outer 
side  of  the  foot  and  little  toe,  communicating  on  the  dorsum  of  the  foot  with  the 
musculo-cutaneous  nerve.  In  the  leg  its  branches  communicate  with  those  of  the 
small  sciatic.  The  cutaneous  area  supplied  by  the  external  saphenous  nerve  is 
indicated  in  Figs.  651,  652,  and  659. 

The  Posterior  Tibial  Nerve  (Fig.  657)  is  the  terminal  portion  of  the  internal 
popliteal  nerve.  It  commences  at  the  lower  border  of  the  Popliteus  muscle,  and 
passes  along  the  back  part  of  the  leg  with  the  posterior  tibial  vessels  to  the  interval 
between  the  inner  malleolus  and  the  heel,  where  it  divides  into  the  external  and 
internal  plantar  nerves.  It  lies  upon  the  deep  muscles  of  the  leg,  and  is  covered  in 
the  upper  part  by  the  muscles  of  the  calf,  lower  down  by  the  skin  and  fascia.  In 
the  upper  part  of  its  course  it  lies  to  the  inner  side  of  the  posterior  tibial  artery,  but 
it  soon  crosses  that  vessel,  and  lies  to  its  outer  side  as  far  as  the  ankle.  In  the  lower 
third  of  the  leg  it  is  placed  parallel  with  the  inner  margin  of  the  tendo  Achillis. 

The  branches  of  the  posterior  tibial  nerve  are  muscular,  internal  calcaneal  or 
calcaneo-plantar,  and  articular. 

The  muscular  branches  {rami  musculares)  arise  either  separately  or  by  a  common 
trunk  from  the  upper  part  of  the  nerve.  They  supply  the  Soleus,  Tibialis  posticus, 
Flexor  longus  digitorum,  and  Flexor  longus  hallucis  muscles;  the  branch  to  the 
latter  muscle  accompanying  the  peroneal  artery.  The  branch  to  the  Soleus  enters 
its  deep  surface,  while  the  branch  which  this  muscle  receives  from  the  internal 
popliteal  enters  its  superficial  aspect. 


THE  SACRAL    OB   SCIATIC  PLEXUS 


1015 


The  internal  calcaneal  or  calcaneo-plantar  branches  {rami  calcanei  mediales)  per- 
forate the  internal  annular  ligament,  and  supply  the  integument  of  the  heel  and 
inner  side  of  the  foot  (Fig.  059). 

The  articular  branch  (ramus  articularis  ad  articulationem  talocruralem)  is  given 
off  just  above  the  bifurcation  of  the  nerve  and  supplies  the  ankle-joint. 

The  Internal  Plantar  Nerve  (^i.  'plantaris  medialis)  (Fig.  658),  the  larger  of  the 
two  terminal  branches  of  the  posterior  tibial,  accompanies  the  internal  plantar 
artery  along  the  inner  side  of  the  foot.  From  its  origin  at  the  inner  ankle  it  passes 
beneath  the  Abductor  hallucis,  and  divides  into  the  common  plantar  digital  nerves 
{nn.  digitales  plantares  communes),  which  pass  forward  between  the  Abductor 
hallucis  and  the  Flexor  brevis  digitorum,  divides  opposite  the  bases  of  the  meta- 
tarsal bones  into  four  collateral  plantar  digital  branches,  and  communicates  with  the 
external  plantar  nerve. 

In  its  course  the  internal  plantar  nerve  gives  off  cutaneous  branches,  which  pierce 
the  plantar  fascia  and  supply  the  integument  of  the  sole  of  the  foot  (Fig.  659) ;  muscu- 
lar branches,  which  supply  the  Abductor  hallucis 
and  Flexor  brevis  digitorum;  articular  branches, 
to  the  articulations  of  the  tarsus  and  meta- 
tarsus; and  four  collateral  plantar  digital  branches 
(nn.  digitales  plantares  proprii) .  The  th ree  outer 
branches  pass  between  the  divisions  of  the 
plantar  fascia  in  the  clefts  between  the  toes ;  the 
first  (innermost)  branch  becomes  cutaneous 
farther    back  between   the  Adductor   hallucis 


Deep 
branch. 


Internal 
plantar.' 


Exteiiml 
plantar. 


Fig.  658. — The  plantar  nerves. 


Fig.  659.— Areas  of  distribution  of  the  cutaneous  nerves  of  the 
sole.    (W.  Keiller,  in  Gerrish's  Text-book  of  Anatomy.) 


and  Flexor  brevis  digitorum.  They  are  distributed  in  the  following  manner: 
The  first  supplies  the  inner  border  of  the  great  toe,  and  sends  a  filament  to  the 
Flexor  brevis  hallucis  muscle;  the  second  bifurcates,  to  supply  the  adjacent  sides 
of  the  great  and  second  toes,  sending  a  filament  to  the  First  lumbrical  muscle;  the 
third  supplies  the  adjacent  sides  of  the  second  and  third  toes;  the  fourth  supplies 
the  corresponding  sides  of  the  third  and  fourth  toes,  and  receives  a  communicating 
branch  from  the  external  plantar  nerve  (Fig.  659).  Each  digital  nerve  gives  off 
cutaneous  and  articular  filaments;  and  opposite  the  last  phalanx  sends  a  dorsal 
branch,  which  supplies  the  structures  around  the  nail,  the  continuation  of  the  nerve 


1016  THE  NERVOUS  SYSTEM 

being  distributed  to  the  ball  of  the  toe.  It  will  be  observed  that  the  distribution 
of  these  branches  is  precisely  similar  to  that  of  the  median  nerve  in  the  hand. 

The  External  Plantar  Nerve  {n.  plantaris  lateralis)  (Fig.  658) ,  the  smaller  of  the 
two,  completes  the  nervous  supply  to  the  structures  of  the  sole  of  the  foot  (Fig.  659) , 
being  distributed  to  the  little  toe,  and  one-half  of  the  fourth,  as  well  as  to  most  of  the 
deep  muscles,  its  distribution  being  similar  to  that  of  the  ulnar  in  the  hand.  It 
passes  obliquely  forward  with  the  external  plantar  artery  to  the  outer  side  of  the 
foot,  lying  between  the  Flexor  brevis  digitorum  and  Flexor  accessorius,  and  in 
the  interval  between  the  former  muscle  and  Abductor  minimi  digiti  divides  into  a 
superficial  and  a  deep  branch.  Before  its  division  it  supplies  the  Flexor  accessorius 
and  Abductor  minimi  digiti. 

The  superficial  branch  (ramus  superficialis)  separates  into  two  digital  nerves. 
Before  division  they  are  called  common  plantar  digital  nerves  (nn.  digitales  plantares 
communes),  after  division  the  collateral  plantar  digital  nerves  (nn.  digitales  plantares 
proprii) :  one,  the  external  branch,  the  smaller  of  the  two,  supphes  the  outer  side  of 
the  little  toe,  the  Flexor  brevis  minimi  digiti,  and  the  two  Interosseous  muscles 
of  the  fourth  metatarsal  space;  the  other  and  larger  digital  branch  supplies  the 
adjoining  sides  of  the  fourth  and  fifth  toes,  and  communicates  with,  the  internal 
plantar  nerve. 

The  deep  or  muscular  branch  (ramus  profundus)  accompanies  the  external 
plantar  artery  into  the  deep  part  of  the  sole  of  the  foot,  beneath  the  tendons  of 
the  Flexor  muscles  and  Adductor  obhquus  hallucis,  and  supplies  all  the  Interossei 
(except  those  in  the  fourth  metatarsal  space),  the  three  outer  Lumbricales,  the 
Adductor  obhquus  hallucis,  and  the  Adductor  transversus  hallucis. 

The  External  Popliteal  or  Peroneal  Nerve  (n.  peronaeus  communis)  (Figs.  655  and 
657)  in  reality  arises  from  the  fourth  and  fifth  lumbar  and  the  first  and  second 
sacral  nerves.  It  is  about  one-half  the  size  of  the  internal  popliteal,  descends 
obliquely  along  the  outer  sides  of  the  popliteal  space  to  the  head  of  the  fibula,  close 
to  the  inner  margin  of  the  Biceps  muscle.  It  is  easily  felt  beneath  the  skin  behind 
the  head  of  the  fibula  at  the  inner  side  of  the  tendon  of  the  Biceps.  It  passes 
between  the  tendon  of  the  Biceps  and  outer  head  of  the  Gastrocnemius  muscle, 
winds  around  the  neck  of  the  fibula,  between  the  Peroneus  longus  and  the  bone, 
and  divides  beneath  the  muscle  into  the  anterior  tibial  and  musculo-cutaneous  nerves. 

The  branches  of  the  peroneal  nerve,  previous  to  its  division,  are  articular  and 
cutaneous. 

The  articular  branches  (rami  articulares)  are  three  in  number:  two  of  these 
accompany  the  superior  and  inferior  external  articular  arteries  to  the  outer  side 
of  the  knee.  The  upper  one  occasionally  arises  from  the  great  sciatic  nerve  before 
its  bifurcation.  The  third  (recurrent)  articular  nerve  is  given  off  at  the  point  of 
division  of  the  peroneal  nerve;  it  ascends  with  the  anterior  recurrent  tibial  artery 
through  the  Tibialis  anticus  muscle  to  the  front  of  the  knee,  which  it  supplies. 

The  Sural  or  Lateral  Cutaneous  Branch  (n,  cutaneu^  surae  lateralis). — There  may 
be  two  or  three  of  these  branches.  They  supply  the  integument  along  the  back 
part  and  outer  side  of  the  leg  (Fig.  652).  The  largest  cutaneous  branch  of  the 
peroneal  is  the  peroneal  communicating  (ramus  anastomoticus  peronaeus  or  commu- 
nicans  fibularis),  arises  near  the  head  of  the  fibula,  crosses  the  external  head  of 
the  Gastrocnemius  to  the  middle  of  the  leg,  and  joins  with  the  communicans  tibialis 
to  form  the  external  saphenous.  This  nerve  occasionally  exists  as  a  separate  branch, 
which  is  continued  as  far  down  as  the  heel. 

The  Anterior  Tibial  Nerve  (n.  peronaeus  profundus)  (Fig.  650)  commences  at  the 
bifurcation  of  the  peroneal  nerve,  between  the  fibula  and  upper  part  of  the  Pero- 
neus longus  muscle,  passes  obliqiiely  forward  beneath  the  Extensor  longus  digi- 
torum muscle  to  the  forepart  of  the  interosseous  membrane,  and  gets  into  relation 
with  the  anterior  tibial  artery  above  the  middle  of  the  leg;  it  then  descends  with 


THE   SACBAL    OB    SCIATIC  PLEXUS  1017 

the  artery  to  the  front  of  the  ankle-joint,  where  it  divides  into  an  external  and  an 
internal  branch.  This  nerve  Hes  at  first  on  the  outer  side  of  the  anterior  tibial  artery, 
then  in  front  of  it,  and  again  at  its  outer  side  at  the  ankle-joint. 

The  branches  of  the  anterior  tibial  nerve  in  its  course  through  the  leg  are  tlie 
muscular  branches  {rami  musculares)  to  the  Tibialis  anticus,  Extensor  longus  digi- 
torum,  Peronaeus  tertius,  and  Extensor  proprius  hallucis  muscles,  and  an  articular 
branch  to  the  ankle-joint. 

The  external  or  tarsal  branch  of  the  anterior  tibial  passes  outward  across  the 
tarsus,  beneath  the  Extensor  brevis  digitorum,  and,  having  become  enlarged, 
like  the  posterior  interosseous  nerve  at  the  wrist,  supplies  the  Extensor  brevis 
digitorum  muscle.  From  the  enlargement  three  minute  interosseous  branches  are 
given  off  which  supply  the  tarsal  joints  and  the  metatarso-phalangeal  joints  of  the 
second,  third,  and  fourth  toes.  The  first  of  these  sends  a  filament  to  the  second 
dorsal  interosseous  muscle. 

The  internal  branch,  the  continuation  of  the  nerve,  accompanies  the  dorsalis 
pedis  artery  along  the  inner  side  of  the  dorsum  of  the  foot,  and  at  the  first  inter- 
osseous space  divides  into  two  dorsal  digital  branches  (nn.  digitales  dorsales  hallucis 
lateralis  et  digiti  secundi  medialis),  which  supply  the  adjacent  sides  of  the  great 
and  second  toes  (Fig.  651),  communicating  with  the  internal  branch  of  the  musculo- 
cutaneous nerve.  Before  it  divides  it  gives  off  an  interosseous  branch  to  the  first 
space,  which  supplies  the  metatarso-phalangeal  joint  of  the  great  toe  and  sends  a 
filament  to  the  First  dorsal  interosseous  muscle. 

The  Musculo-cutaneous  Nerve  (n.  peronaeus  superficialis)  (Fig.  650)  supplies  the 
muscles  on  the  fibular  side  of  the  leg  and  the  integument  of  the  dorsum  of  the  foot 
(Fig.  651) .  It  passes  forward  between  the  Peronei  muscles  and  the  Extensor  longus 
digitorum,  pierces  the  deep  fascia  at  the  lower  third  of  the  leg  on  its  front  and  outer 
side,  and  divides  into  two  branches.  This  nerve  in  its  course  between  the  muscles 
gives  off  muscular  branches  (rami  musculares)  to  the  Peroneus  longus  and  brevis, 
and  cutaneous  filaments  to  the  integument  of  the  lower  part  of  the  leg  (Fig.  651). 

The  internal  branch  (n.  cidaneu^  dorsalis  medialis)  of  the  musculo-cutaneous 
nerve  passes  in  front  of  the  ankle-joint,  and  divides  into  two  dorsal  digital  branches 
(nn.  digitales  dorsales  pedis),  one  of  which  supplies  the  inner  side  of  the  great  toe, 
the  other  the  adjacent  sides  of  the  second  and  third  toes.  It  also  supplies  the 
integument  of  the  inner  ankle  and  inner  side  of  the  foot,  communicating  with 
the  internal  saphenous  nerve,  and  joining  with  the  anterior  tibial  nerve,  between  the 
great  and  second  toes. 

The  external  branch  (n.  cutaneus  dorsalis  intermedius) ,  the  smaller,  passes  along 
the  outer  side  of  the  dorsum  of  the  foot,  and  divides  into  two  dorsal  digital  branches, 
the  inner  being  distributed  to  the  contiguous  sides  of  the  third  and  fourth  toes, 
the  outer  to  the  opposed  sides  of  the  fourth  and  fifth  toes.  It  also  supplies  the 
integument  of  the  outer  ankle  and  outer  side  of  the  foot,  communicating  with  the 
short  saphenous  nerve. 

The  branches  of  the  musculo-cutaneous  nerve  supply  all  the  toes  excepting 
the  outer  side  of  the  little  toe,  which  is  supplied  by  the  external  saphenous  nerve. 
The  adjoining  sides  of  the  great  toe  or  second  toe  are  also  supplied  by  the 
internal  branch  of  the  anterior  tibial.  It  frequently  happens  that  some  of  the 
outer  branches  of  the  musculo-cutaneous  are  absent,  their  place  being  then  taken 
by  branches  of  the  external  saphenous  nerve. 

Surgical  Anatomy. — The  lumbar  plexus  passes  through  the  Psoas  muscle,  and,  therefore, 
in  psoaa  abscess  any  or  all  of  its  branches  may  be  irritated,  causing  severe  pain  in  the  parts  to 
which  the  irritated  nerves  are  distributed.  The  genifo-crural  nerve  is  the  one  which  is  most 
frequently  implicated.  This  nerve  is  also  of  importance,  as  it  is  concerned  in  one  of  the 
reflexes  employed  in  the  investigation  of  diseases  of  the  spine.  If  the  skin  over  the  inner 
side  of  the  thigh  just  below  Poupart's  ligament,  the  part  supplied  by  the  crural  branch  of  the 
genito-crural  nerve,  be  gently  tickled  in  a  male  child,  the  testicle  will  be  noticed  to  be  drawn 


1018  THE  NERVOUS   SYSTEM 

upward  through  the  action  of  the  Cremaster  muscle,  which  is  supplied  by  the  genital  branch  of 
the  same  nerve.  The  same  result  may  sometimes  be  noticed  in  adults,  and  can  almost  always  l)e 
produced  by  severe  stimulation.  This  reflex,  when  present,  shows  that  the  portion  of  the  cord 
from  which  the  first  and  second  lumbar  nerves  are  derived  is  in  a  normal  condition. 

The  anterior  crural  nerve  is  in  danger  of  being  injured  in  fractures  of  the  true  pelvis,  since 
the  fracture  most  commonly  takes  place  through  the  ascending  ramus  of  the  os  pubis,  at  or 
near  the  point  where  this  nerve  crosses  the  bone.  It  is  also  liable  to  be  injured  in  fractures 
and  dislocations  of  the  femur,  and  is  likely  to  be  pressed  upon,  and  its  functions  impaired, 
in  some  tumors  growing  in  the  pelvis.  Moreover,  on  account  of  its  superficial  position,  it  is 
exposed  to  injury  in  wounds  and  stabs  in  the  groin.  When  this  nerve  is  paralyzed,  the  patient 
is  unable  to  flex  his  hip  completely,  on  account  of  the  loss  of  motion  in  the  Iliacus;  or  to  extend 
the  knee  on  the  thigh,  on  account  of  paralysis  of  the  Quadriceps  extensor  cruris;  there  are  com- 
plete paralysis  of  the  Sartorius  and  partial  paralysis  of  the  Pectineus.  There  is  loss  of  sensation 
down  the  front  and  inner  side  of  the  thigh,  except  in  that  part  supplied  by  the  crural  branch  of 
the  genito-crural  nerve,  and  by  the  ilio-inguinal  nerve.  There  is  also  loss  of  sensation  down 
the  inner  side  of  the  leg  and  foot  as  far  as  the  ball  of  the  great  toe. 

The  obturator  nerve  is  of  special  surgical  interest.  It  is  rarely  paralyzed  alone,  but  occasionally 
is  paralyzed  in  association  with  the  anterior  crural.  The  principal  interest  attached  to  it  is  in 
connection  with  its  supply  to  the  knee;  pain  in  the  knee  being  symptomatic  of  many  diseases 
in  which  the  trunk  of  this  nerve,  or  one  of  its  branches,  is  irritated.  Thus  it  is  well  known  that 
in  the  earlier  stages  of  hip-joint  disease  the  patient  does  not  complain  of  pain  in  that  articulation, 
but  on  the  inner  side  of  the  knee,  or  in  the  knee-joint  itself,  both  these  articulations  being  sup- 
plied by  the  obturator  nerve,  the  final  distribution  of  the  nerve  being  to  the  knee-joint.  Again, 
the  same  thing  occurs  in  sacro-iliac  disease:  pain  is  complained  of  in  the  knee-joint  or  on  its 
inner  side.  The  obturator  nerve  is  in  close  relationship  with  the  sacro-iliac  articulation,  passing 
over  it,  and,  according  to  some  anatomists,  distributing  filaments  to  it.  Again,  in  cancer  of 
the  sigmoid  flexure,  and  even  in  cases  where  masses  of  hardened  faeces  are  impacted  in  this 
portion  of  the  gut,  pain  is  complained  of  in  the  knee.  Thfe  left  obturator  nerve  lies  beneath  the 
sigmoid  flexure,  and  is  readily  pressed  upon  and  irritated  when  disease  exists  in  this  part  of  the 
intestine.  Finally,  pain  in  the  knee  forms  an  important  diagnostic  sign  in  obturator  hernia. 
The  hernial  protrusion  as  it  passes  out  through  the  opening  in  the  obturator  membrane  presses 
upon  the  nerve  and  causes  pain  in  the  parts  supplied  by  its  peripheial  filaments.  When  the 
obturator  nerve  is  paralyzed,  the  patient  is  unable  to  press  his  knees  together  or  to  cross  one 
leg  over  the  other,  on  account  of  paralysis  of  the  Adductor  muscles.  Rotation  outward  of  the 
thigh  is  impaired  from  paralysis  of  the  Obturator  externus.  Sometimes  there  is  loss  of  sensation 
in  the  upper  half  of  the  inner  side  of  the  thigh. 

The  great  sciatic  nerve  is  liable  to  be  pressed  upon  by  various  pelvic  tumors,  giving  rise  to 
pain  along  its  trunk,  to  which  the  term  sciatica  is  applied.  Tumors  growing  from  the  pelvic 
viscera,  or  bones,  aneurisms  of  some  of  the  branches  of  the  internal  iliac  artery,  calculus  in  the 
bladder  when  of  large  size,  accumulation  of  fajces  in  the  rectum,  may  all  cause  pressure  on  the 
nerve  inside  the  pelvis,  and  give  rise  to  sciatica.  Outside  the  pelvis  exposure  to  cold,  violent 
movements  of  the  hip-joint,  exostoses  or  other  tumors  growing  from  the  margin  of  the  sacro- 
sciatic  foramen,  may  also  give  rise  to  the  same  condition.  When  paralyzed  there  is  loss  of 
motion  in  all  the  muscles  below  the  knee,  and  loss  of  sensation  in  the  same  situation,  except  the 
upper  half  of  the  back  of  the  leg,  supplied  by  the  small  sciatic  and  the  upper  half  of  the  inner 
side  of  the  leg,  when  the  communicating  branch  of  the  obturator  is  large. 

The  sciatic  nerve  has  been  frequently  cut  down  upon  and  stretched,  or  has  been  acupunctured 
for  the  relief  of  sciatica.  The  nerve  has  also  been  stretched  in  cases  of  locomotor  ataxia,  the 
anaesthesia  of  leprosy,  etc.  In  order  to  define  it  on  the  surface,  a  point  is  taken  at  the  junction 
of  the  middle  and  lower  third  of  a  line  stretching  from  the  posterior  superior  spine  of  the  ilium 
to  the  outer  part  of  the  tuber  ischii,  and  a  line  is  drawn  from  this  point  to  the  middle  of  the  upper 
part  of  the  popliteal  space.  The  line  must  be  slightly  curved  with  its  convexity  outward,  and  as 
it  passes  downward  to  the  lower  border  of  the  Gluteus  maximus  is  slightly  nearer  the  tuberosity 
of  the  ischium  than  to  the  great  trochanter,  as  it  crosses  a  line  drawn  between  these  two  points. 
The  operation  of  stretching  the  sciatic  nerve  is  performed  by  making  an  incision  over  the  course 
of  the  nerve  about  the  centre  of  the  thigh.  The  skin,  superficial  structures,  and  deep  fascia 
having  been  divided,  the  interval  between  the  inner  and  outer  hamstrings  is  to  be  defined,  and 
these  muscles  respectively  pulled  inward  and  outward  with  retractors.  The  nerve  will  be  found  a 
little  to  the  inner  side  of  the  Biceps.  It  is  to  be  separated  from  the  surrounding  structures,  hooked 
up  with  the  finger,  and  stretched  by  steady  and  continuous  traction  for  two  or  three  minutes. 
The  sciatic  nerve  may  also  be  stretched  by  what  is  known  as  the  "dry"  plan.  The  patient  is 
laid  on  his  back,  the  foot  is  extended,  the  leg  flexed  on  the  thigh,  and  the  thigh  strongly  flexed 
on  the  abdomen.  While  the  thigh  is  maintained  in  this  position  the  leg  is  forcibly  extended  to 
its  full  extent,  and  the  foot  as  fully  flexed  on  the  leg.     This  last-named  method  is  uncertain. 

The  position  of  the  external  popliteal  nerve,  close  behind  the  tendon  of  the  Biceps  on  the  outer 
side  of  the  ham,  should  be  remembered  in  subcutaneous  division  of  the  tendon.    After  it  is  divided, 


THE   FIRST    OB    OLFACTORY  NERVE  1019 

a  cord  often  rises  up  close  beside  it,  which  might  be  mistaken  for  a  small  undivided  portion  of 
the  tendon,  and  the  surgeon  might  be  tempted  to  reintroduce  his  knife  and  divide  it.  This  must 
never  be  done,  as  the  cord  is  the  external  popliteal  nerve,  which  becomes  prominent  as  soon  as 
the  tendon  is  divided. 


THE  CEREBRAL  OR  CRANIAL  NERVES  (NERVI  CEREBRALES). 

The  cranial  nerves  arise  from  some  part  of  the  cerebro-spinal  centre,  and  are 
transmitted  through  foramina  in  the  base  of  the  cranium.  They  have  been  named 
numerically,  according  to  the  order  in  which  they  pass  through  the  dura  mater 
hning  the  base  of  the  skull.  Other  names  are  also  given  to  them,  derived  from 
the  parts  to  which  they  are  distributed  or  from  their  functions.  Taken  in  their 
order,  from  before  backward,  they  are  as  follows: 

1st.    Olfactory.  7th.  Facial  (Portio  dura). 

2d.    Optic.  8th.  Auditory  (Portio  mollis). 

3d.    Motor  oculi.  9th.  Glosso-pharyngeal. 

4th.  Trochlear  (Pathetic).  10th.  Pneumogastric  (or  Vagus). 

5th.  Trifacial  (Trigeminus).  11th.  Spinal  accessory. 

6th.  Abducent.  12th.  Hypoglossal. 

All  the  cranial  nerves  are  connected  to  some  part  of  the  surface  of  the  brain. 
This  is  termed  their  superficial  or  apparent  origin.  But  their  fibres  may,  in  all 
cases,  be  traced  deeply  into  the  substance  of  the  brain  and  to  some  special  centre  of 
gray  matter,  termed  a  nucleus.  This  is  called  their  deep  or  real  origin.  The  nerves, 
after  emerging  from  the  brain  at  their  apparent  origin,  pass  through  foramina  or 
tubular  prolongations  in  the  dura  mater,  leave  the  skull  through  foramina  in  its 
base,  and  pass  to  their  final  distribution. 

THE  FIRST  OR  OLFACTORY  NERVE  (N.  OLFACTORIUS)  (Fig.  660). 

The  olfactory  nerves  are  the  special  nerves  of  the  sense  of  smell,  and  are 
about  twenty  in  number  on  each  side.  These  filaments  constitute  the  first  or 
olfactory  nerves.  They  are  given  off  from  the  under  surface  of  the  olfactory  bulb, 
an  oval  mass  of  a  grayish  color,  which  rests  on  the  cribriform  plate  of  the  eth- 
moid bone,  and  forms  the  anterior  expanded  extremity  or  a  slender  process  of 
brain-substance,  named  the  olfactory  tract.  The  olfactory  tract  and  bulb  have 
already  been  described  (p.  880).  The  olfactory  tubercle  {irigonum  olfactorium) 
is  a  small  triangular  mass  of  gray  matter  between  the  diverging  roots  of  the  optic 
tract  (p.  881). 

Each  nerve  is  surrounded  by  tubular  prolongations  from  the  dura  mater  and 
pia  mater,  the  former  being  lost  on  the  periosteum  lining  the  nose,  the  latter  in 
the  neurilemma  of  the  nerve.  The  nerves,  as  they  enter  the  nares,  are  divisible 
into  two  groups:  an  inner  group,  larger  than  those  on  the  outer  wall,  spread  out 
over  the  upper  third  of  the  septum;  and  an  outer  set,  which  is  distributed  over 
the  superior  turbinated  bone,  and  the  surface  of  the  ethmoid  in  front  of  it.  As 
the  filaments  descend,  they  unite  in  a  plexiform  network,  and  are  believed  by 
most  observers  to  terminate  by  becoming  continuous  with  the  deep  extremities 
of  the  olfactory  cells. 

The  olfactory  nerves  differ  in  structure  from  other  nerves  in  being  composed 
exclusively  of  non-medullated  fibres.  They  are  deficient  in  the  white  substance 
of  Schwann,  and  consist  of  axis-cylinders,  with  a  distinct  nucleated  sheath, 
in  which  there  are,  however,  fewer  nuclei  than  in  ordinary  non-medullated 
fibres. 


1020 


THE   NERVOUS  SYSTEM 


The  Olfactory  Path  (Figs.  660  and  661). — Impressions  from  the  upper  portion 
of  the  Schneiderian  mucous  membrane  pass  along  the  olfactory  nerves,  reach  the 
olfactory  bulb,  and  traverse  the  olfactory  tract  to  the  cerebral  hemisphere  of 
the  same  side.     The  cortical  area  of  the  sense  of  smell  is  in  the  uncus  hip- 


FiG.  660. — The  olfactory  bulb  and  tract.  A,  Schneiderian  membrane  in  nose  in  which  lies  peripheral  olfac- 
tory neurone;  B,  glomerulus  of  olfactory  bulb;  C,  mitral  cells  with  dendrites  in  B  and  axones  in  D  olfactory 
lobe;  E,  granule  cells;  F,  cells  in  olfactory  lobe;  H,  G,  fibres  of  olfactory  tract.     (Ramon  y  Cajal.) 


pocampi.  Impressions  which  are  conveyed  by  the  internal  root  pass  to  Broca's 
area  which  is  in  front  of  the  inner  root  of  the  olfactory  tract,  to  the  anterior 
extremity  of  the  gyrus  fornicatus,  the  cingulum,  and  the  uncinate  fasciculus  to 
the  cortical  centre  (Santee).      Impressions  travelling  by  the  middle  root  reach 


Fig.  661. — The  olfactory  system  and  tracts.  Bol,  olfactory  bulb;  Pol,  olfactory  tract;  Rolp,  deep  olfactory 
fibres;  Roli,  internal  olfactory  fibres;  Role,  external  olfactory  fibres.  The  deep  fibres  pass  to  the  thalamus  (Th) 
and  its  nuclei;  Tc,  tuber  cinereum;  Tm,  tuber  mamillare;  and  to  tsc,  taenia  semicircularis,  and  tth,  taenia 
thalami;  also  into  the  anterior  commissure,  coa.  The  internal  olfactory  fibres  pass  into  the  striae  of  Lancisi, 
sL,  and  thus  to  the  fasciola  cinerea,  Fc.  The  external  olfactory  fibres  pass  directly  to  the  uncinate  gyrus,  U.  Tg, 
fornix  from  the  carpus  mamillare  (Tm)  to  Ammon's  horn  (Cg);  NA,  nucleus  amygdalae;  Cing,  cingulum;  Cc, 
corpus  callosum;  Fc,  fasc.  cinerea;  FG,  Gudden's  fasciculus;  FM,  fasc.  retroflexus  of  Meynert;  Na,  ant.  nuc.  of 
thalamus;  Gip,  interpeduncular  ganglion;  Gh,  ganglion;  habenula;  Qa,  Qp,  corp.  quadrigemina;  Po,  pons;  VA, 
fascic.  Vicq,  d'Azyr.     (Dejerine.) 

the  trigone  and  then  pass  to  the  cortical  centre,  as  do  those  by  way  of  the  inter- 
nal root,  or  they  reach  it  by  way  of  the  anterior  commissure  (Santee).  The  outer 
root  conducts  impulses  directly  to  the  cortical  area.  Fig.  661  shows  the  olfac- 
tory path  according  to  Dejerine. 


THE  SECOND    OB    OPTIC   NERVE 


1021 


Surgical  Anatomy. — Destruction  of  the  olfactory  tract  of  one  side  causes  loss  of  smell  {anos- 
mia) on  the  side  of  the  injury,  because  the  olfactory  tract  is  uncrossed.  In  severe  injuries  to  the 
head  the  olfactory  bulb  may  become  separated  from  the  olfactory  nerves,  thus  producing  loss 
of  the  sense  of  smell,  and  with  this  a  considerable  loss  in  the  sense  of  taste,  as  much  of  the  per- 
fection of  the  sense  of  taste  is  due  to  the  sapid  substances  being  also  odorous  and  simultaneously 
exciting  the  sense  of  smell.  When  the  sense  of  smell  is  lost,  an  individual  cannot  distinguish 
the  pavor  of  food,  but  he  can  distinguish  that  a  substance  is  salt,  or  sweet,  or  bitter,  or  acid. 
The  most  usual  cause  of  injury  to  the  olfactory  nerve  is  fracture  of  the  base  of  the  skull,  the 
line  of  fracture  passing  through  the  cribriform  plate  of  the  ethmoid  bone,  but  a  blow  upon  the 
face,  forehead,  or  back  of  the  head,  which  does  not  produce  fracture  may  injure  the  nerve. 


THE  SECOND  OR  OPTIC  NERVE  (N.  OPTICUS)   (Fig.  662). 


The  second  or  optic  nerve,  the  special  nerve  of  the  sense  of  sight,  is  distributed 
exclusively  to  the  eyeball.  It  joins  the  eyeball  about  one-eighth  of  an  inch  to  the 
inner  side  of  the  axis  of  the  globe,  penetrates  the  fibrous  coat  and  the  vascular 
tunic,  and  at  the  optic  disk  is  expanded  and  forms  part  of  the  retina.  The  nerves 
of  opposite  sides  are  connected  together  at  the  commissure,  and  from  the  back 
of  the  commissure  they  may  be  traced  to  the 
brain,  under  the  name  of  the  optic  tracts. 

The  Optic  Tract. — The  optic  tract,  at  its 
connection  with  the  brain,  is  divided  into  two 
bands,  external  and  internal.  The  external 
band  is  the  larger;  it  arises  from  the  external 
geniculate  body  and  from  the  under  part  of  the 
pulvinar  of  the  optic  thalamus,  and  is  partly 
continuous  with  the  brachium  of  the  anterior 
or  upper  quadrigeminal  body.  The  internal 
band  curves  around  the  crusta,  and  passes 
beneath  the  internal  geniculate  body,  with 
which  it  is  connected,  and  then  appears  to  lose 
itself  in  the  brachium  of  the  posterior  or  infe- 
rior quadrigeminal  body.  The  fibres  by  which 
it  is  connected  to  the  internal  geniculate  body 
are  merely  commissural,  forming  part  of  Gud- 


den's  commissure.      From  this  origin  the  tract 


Fig. 


662. — The  left  optic  nerve  and  optic 
tracts. 


winds  obliquely  across  the  under  surface  of 
the  crus  cerebri,  in  the  form  of  a  flattened  band,  and  is  attached  to  the  crus  by 
its  anterior  margin.     It  then  assumes  a  cylindrical  form,  and,  as  it  passes  for- 
ward, *is  connected  with  the  tuber  cinereum  and  lamina  cinerea.     It  finally  joins 
with  the  tract  of  the  opposite  side  to  form  the  optic  commissure. 

The  Optic  Commissure  (chiasma  opticum)  (P'igs.  662  and  663,  and  p.  882) 
is  somewhat  quadrilateral  in  form,  rests  upon  the  olivary  eminence  and  on  the 

anterior  part  of  the  diaphragma  sellae,  being  bounded, 

above,  by  the  lamina   cinerea  ;   behind  by  the  tuber 

cinerereum;  on  either  side  by  the  anterior  perforated 

space.     Within  the  commissure,  the  optic  nerves  of 

the  two  sides  undergo  a  partial  decussation  (Figs.  663 

and  664).     The  fibres  which  form  the  inner  margin  of 

each  tract  and  posterior  part  of  the  commissure  have 

no  connection  with   the   optic    nerves.     They  simply 

pass   across    the    commissure   from    one    hemisphere 

of  the  brain  to  the  other,  and  connect  the  internal  geniculate  bodies  of  the  two 

sides.     They  are  known  as  the  inter-cerebral  fibres  of  the  optic  commissure  or  the 

commissure  of  Gudden.      The  remainder  and  principal  part  of  the  optic  com- 


FiG.  663. — Course  of  the  fibres 
in  the  optic  commissure. 


1022  THE  NERVOUS   SYSTEM 

missure  consists  of  two  sets  of  fibres,  crossed  and  uncrossed.  The  crossed  fibres, 
which  are  the  more  numerous,  occupy  the  central  part  of  the  chiasma,  and  pass 
from  the  optic  tract  of  one  side  to  the  optic  nerve  of  the  other,  decussating  in 
the  commissure  with  similar  fibres  of  the  opposite  tract.  The  uncrossed  fibres 
occupy  the  outer  part  of  the  chiasma,  and  pass  from  the  tract  of  one  side  to  the 
nerve  of  the  same  side.* 

The  great  majority  of  the  fibres  of  the  optic  nerve  consist  of  the  afferent  axones 
of  nerve-cells  in  the  retina.  Some  few,  however,  are  efferent  fibres,  and  grow  out 
from  the  brain.  The  afferent  fibres  end  in  arborizations  around  the  cells  in  the 
external  geniculate  body,  pulvinar,  nucleus  of  the  motor  oculi  nerve,  and  the 
upper  quadrigeminal  body.  The  external  geniculate  body  and  pulvinar  are  some- 
times termed  the  lower  visual  centres.  From  these  nuclei  other  fibres  are  pro- 
longed to  the  cortical  half -visual  centre,  which,  according  to  most  observers,  is 
situated  in  the  cuneus,  and  probably  also,  to  a  small  extent,  in  the  curved  portion 
of  the  occipital  lobe  (Fig.  664). 

It  should  be  stated  that  some  fibres  are  detached  from  the  optic  tract,  and  pass 
through  the  crus  cerebri  to  the  nucleus  of  the  third  nerve.  These  fibres  are  small, 
and  may  be  regarded  as  afferent  branches  for  the  sphincter  pupillae  and  ciliary 
muscles.  Other  fibres  pass  to  the  cerebellum  through  its  superior  peduncles,  while 
others,  again,  are  lost  in  the  pons. 

The  optic  nerves  arise  from  the  forepart  of  the  commissure,  and,  diverging 
from  one  another,  become  rounded  in  form  and  firm  in  texture,  and  are  enclosed  in 
a  sheath  derived  from  the  pia  mater  and  arachnoid.  As  each  nerve  passes  through 
the  corresponding  optic  foramen  it  receives  a  sheath  from  the  dura  mater;  and  as 
it  enters  the  orbit  this  sheath  subdivides  into  two  layers,  one  of  which  becomes  con- 
tinuous with  the  periosteum  of  the  orbit;  the  other  forms  the  proper  sheath  of  the 
nerve  and  surrounds  it  as  far  as  the  sclerotic.  The  nerve  passes  forward  and  out- 
ward through  the  cavity  of  the  orbit,  pierces  the  sclerotic  and  choroid  coats  at  the 
back  part  of  the  eyeball,  about  one-eighth  of  an  inch  to  the  nasal  side  of  its  centre, 
and  expands  into  the  retina.  A  small  artery,  the  arteria  centralis  retinae,  per- 
forates the  optic  nerve  a  little  behind  the  globe,  and  runs  along  its  interior  in  a 
tubular  canal  of  fibrous  tissue.  It  supplies  the  inner  surface  of  the  retina,  and  is 
accompanied  by  corresponding  veins. 

The  Optic  Path  (Fig.  664). — Impulses  of  sight  originate  in  the  retina.  From 
the  right  half  of  each  retina  impulses  pass  by  way  of  the  optic  nerves  to  the  right 
optic  tract.  From  the  left  half  of  each  retina  impulses  pass  by  way  of  the  optic 
nerves  to  the  left  optic  tract.  Impulses  from  the  nasal  half  of  each  retina  pass 
by  decussated  fibres  to  the  opposite  optic  tract.  Impulses  from  the  temporal 
half  of  the  retina  pass  by  unflecussated  fibres  to  the  optic  tract  of  the  same  side, 
although  a  few  fibres  may  cross  farther  back  through  the  quadrigeminal  bodies. 
From  the  optic  tract  impulses  pass  to  the  external  geniculate  body,  pulvinar, 
upper  quadrigeminal  body,  and  nucleus  of  the  motor  oculi  nerve.  From  the 
external  geniculate  body  and  pulvinar  impulses  pass  by  way  of  the  optic  radiatus 
through  the  posterior  segment  of  the  internal  capsule  to  the  half-vision  centre  in 
the  cuneus  and  the  convexity  of  the  occipital  lobe.  The  superior  quadrigeminal 
body  and  the  nucleus  of  the  third  nerve  produce  ocular  reflexes  and  the  pupil- 
lary reflex. 

Surgical  Anatomy. — The  optic  nerve  is  peculiarly  liable  to  become  the  seat  of  neuritis^  or 
undergo  atrophy  in  affections  of  the  central  nervous  system,  and,  as  a  rule,  the  pathological 
relationship  between  the  two  affections  is  exceedingly  difficult  to  trace.  There  are,  however, 
certain  points  in  connection  with  the  anatomy  of  this  nerve  which  tend  to  throw  light  upon  the 
frequent  association  of  these  affections  with  intracranial  disease:    (1)  From  its  mode  of  develop- 

^  A  specimen  of  congenital  absence  of  the  optic  commissure  is  to  be  found  in  the  Museum  of  the  Westminster 
Hospital.     See  also  Henle,  Nervenlehre,  p.  393,  ed  2. — Ed.  of  15th  English  edition. 


THE  SECOND    OB    OPTIC   NERVE 


1023 


ment  and  from  its  structure  the  optic  nerve  must  be  regarded  as  a  prolongation  of  the  brain-sub- 
stance, rather  than  as  an  ordinary  cerebro-spinal  nerve.  (2)  As  it  passes  from  the  brain  it  receives 
sheaths  from  the  three  cerebral  membranes --a  perineural  sheath  from  the  pia  mater,  an  inter- 
mediate sheath  from  the  arachnoid,  and  an  outer  sheath  from  the  dura  mater,  which  is  also  con- 
nected with  the  periosteum  as  it  passes  through  the  optic  foramen.  These  sheaths  are  separated 
from  each  other  by  spaces  which  communicate  with  the  subdural  and  subarachnoid  spaces 
respectively.  The  innermost  or  perineural  sheath  sends  a  process  around  the  arteria  centralis 
retinae  into  the  interior  of  the  nerve,  and  enters  intimately  into  its  structure.  Thus  inflammatory 
affections  of  the  meninges  or  of  the  brain  may  readily  extend  themselves  along  these  spaces  or 
along  the  interstitial  connective  tissue  in  the  nerve. 

The  course  of  the  fibres  in  the  optic  commissure  has  an  important  pathological  bearing,  and 
has  been  the  subject  of  much  controversy.  Microscopic  examination,  experiments,  and  pathology 
all  seem  to  point  to  the  fact  that  there  is  a  partial  decussation  of  the  fibres,  each  tract  supplying 


[left  eyeI 

f      RIGHT     1 
1          EYE         1 

/^^^MACOLA    LUTEA 

UNCROSSED    FIBRES 

FROM 

LEFT    HALf\ 

Ov 

yy'Xv 

OF    LEFT    RETINA   TO 

LEFT 

centres 

^B^ 

^ CHIASMA 

CROSSED    FIBRES    FROM 

LEFT 

HALF^                A 

#^ 

JRE\C\S» 

OF   RIGHT  i?ETINA   TO 
TRES 

LEFT 

""T  iS 

^r/G U  D  D  E  N 
^OMMISSl 

Aanterioro) 

laUADPl^ 

^GEMINA'^ 


.INTERNAL  GENICULATE  BODY 
AND    ITS    NERVE    CELLS 

-EXTERNAL  GENICULATE  BODY 
AND    ITS   NERVE   CELLS 


POSTERIOR  aUADRISEMINA^ 


CONNECTING    LEFT   SIDE    OF    BRAIN 
WITH   LEFT    HALF    OF    RETINA  AND  I 
CONSEQUENTLY     RIGHT     HALF   OF  I 
FIELD    OF   VISION  J 


loPTIC    RADIATION 


Fig.  664. — Diagram  of  the  course  of  the  optic  fibres.     (W.  Keiller  in  Gerrish's  Anatomy.) 


the  corresponding  half  of  each  eye,  so  that  the  right  tract  supplies  the  right  half  of  each  eye, 
and  the  left  tract  the  left  half  of  each  eye.  At  the  same  time,  Charcot  believes — and  his  view 
has  met  with  general  acceptation-  -that  the  fibres  which  do  not  decussate  at  the  optic  commis- 
sure have  already  decussated  in  the  corpora  quadrigemina,  so  that  lesion  of  the  cerebral  centre 
of  one  side  causes  complete  blindness  of  the  opposite  eye,  because  both  sets  of  decussating  fibres 
are  destroyed.  Whereas  should  one  tract — say  the  right  —be  destroyed  by  disease,  there  will  be 
blindness  of  the  right  half  of  both  retinae. 

An  antero-posterior  section  through  the  commissure  would  divide  the  decussating   filwes, 
and  would  therefore  produce  blindness  of  the  inner  half  of  each  eye;  while  a  section  at  the  mar- 
gin of  the  side  of  the  optic  commissure  would  produce  blindness  of  the  external  half  of  the  retina . 
of  the  same  side. 

The  optic  nerve  may  also  be  affected  in  injuries  or  diseases  involving  the  orbit,  in  fractures 
of  the  anterior  fossa  of  the  ba.se  of  the  skull,  in  tumors  of  the  orbit  itself,  or  those  invading  this 
cavity  from  neighboring  parts. 


1024 


THE  NERVOUS  SYSTEM 


Infratrochlear 
nerve. 


THE  THIRD  OR  MOTOR  OCULI  NERVE  (N.  OCULOMOTORIUS) 

(Figs.  665,  666,  669). 

The  third  or  motor  ocuH  nerve  supplies  all  the  muscles  of  the  orbit  except  the 
Superior  oblique  and  External  rectus;  it  also  supplies,  through  its  connection 
with  the  ciliary  ganglion,  the  Sphincter  muscle  of  the  iris  and  the  Ciliary  muscle. 
It  is  rather  a  large  nerve,  of  rounded  form  and  firm  texture. 

Its  apparent  origin  is  from  the  inner  surface  of  the  crus  cerebri,  immediately  in 
front  of  the  pons  Varolii.  The  deep  origin  may  be  traced  through  the  substantia 
nigra  and  tegmentum  of  the  crus  to  a  nucleus  situated  on  either  side  of  the  median 
line  beneath  the  floor  of  the  aqueduct  of  Sylvius  (Fig.  613).  The  nucleus  of  the 
third  nerve  also  receives  fibres  from  the  sixth  nerve  of  the  opposite  side.  These 
will  be  referred  to  again  in  the  description  of  the  latter  nerve.      The  nucleus  of 

the  third  nerve,  considered  from  a 
physiological  standpoint,  can  be 
subdivided  into  several  smaller 
groups  of  cells,  each  group  con- 
trolling a  particular  muscle.  The 
nerves  to  the  different  muscles 
appear  to  take  their  origin  from 
before  backward,  as  follows:  In- 
ferior oblique.  Inferior  rectus, 
Superior  rectus  and  Levator  pal- 
pebrae,  Internal  rectus;  while  from 
the  anterior  end  of  the  nucleus  the 
fibres  for  accommodation  and  for 
the  Sphincter  pupillae  take  their 
origin. 

On  emerging  from  the  brain,  the 
nerve  is  invested  with  a  sheath  of 
pia  mater,  and  enclosed  in  a  pro- 
longation from  the  arachnoid.  It 
passes  between  the  superior  cere- 
bellar and  posterior  cerebral  arte- 
ries, and  then  pierces  the  dura 
mater  in  front  of  and  external  to 
the  posterior  clinoid  process,  pass- 
ing between  the  two  processes  from 
the  free  and  attached  borders  of 
the  tentorium,  which  are  prolonged 
forward  to  be  connected  with  the 
anterior  and  posterior  clinoid  pro- 
cesses of  the  sphenoid  bone.  It 
passes  along  the  outer  wall  of  the 
cavernous  sinus  (Figs.  454  and  455);  above  the  other  orbital  nerves,  receiving  in 
its  course  one  or  two  filaments  from  the  cavernous  plexus  of  the  sympathetic,  and 
a  communicating  branch  from  the  first  division  of  the  fifth.  It  then  divides 
into  two  branches,  which  enter  the  orbit  through  the  sphenoidal  fissure,  between 
th^  two  heads  of  the  External  rectus  muscle  (Fig.  665).  On  passing  through 
the  fissure,  the  nerve  is  placed  below  the  fourth  and  the  frontal  and  lachrymal 
branches  of  the  ophthalmic  nerve,  and  has  passing  between  its  two  divisions  the 
nasal  nerve  (Fig.  675). 

The  Superior  Division  (ramus  superior)  (Fig.  666). — The  superior  division,  the 
smaller,  passes  inward  over  the  optic  nerve,  and  supplies  the  Superior  rectus  and 
Levator  palpebrae. 


Fig.  665.- 


Motor  root.   /    W — Eeciirrent  filament 
Sensory  root.  to  dura  mater. 

-Nerves  of  the  orbit,  seen  from  above. 


THE   FOURTH    OB    TROCHLEAR    NERVE 


1025 


The  Inferior  Division  {ramus  inferior)  (Fig.  666) . — The  inferior  division,  the  larger, 
divides  into  three  branches.  One  passes  beneath  the  optic  nerve  to  the  Internal 
rectus;  another,  to  the  Inferior  rectus;  and  the  third,  the  longest  of  the  three, 
passes  forward  between  the  Inferior  and  External  recti  to  the  Inferior  oblique. 
From  this  latter  a  short,  thick  branch,  radix  brevis  ganglii  ciliaris,  is  given  off 
to  the  lower  part  of  the  lenticular  ganglion  and  forms  its  short   or  motor  root 


LEVATOR    PALPEBniE. 


OBLIQUUS 
INFERIOR. 


Tig.  666. — Plan  of  the  motor  oculi  nerve.     (The  lenticular  ganglion  is  not  shown  in  normal  position.     If  it  were 
the  short  root  would  enter  the  inferior  angle.)     (After  Flower.) 

(Figs.  666,  669,  and  670).  It  also  gives  off  one  or  two  filaments  to  the  Inferior 
rectus.  All  these  branches  enter  the  muscles  on  their  ocular  surface,  except  that 
to  the  Inferior  oblique,  which  enters  its  posterior  border. 

Surgical  Anatomy. — Paralyse  of  the  third  nerve  may  be  the  result  of  many  causes :  as  cere- 
bral disease;  conditions  causing  pressure  on  the  cavernous  sinus;  periostitis  of  the  bones  entering 
into  the  formation  of  the  sphenoidal  fissure;  fracture  of  the  orbit.  It  results,  when  complete,  in 
(1)  ptosis,  or  drooping  of  the  upper  eyelid,  in  consequence  of  the  Levator  palpebrae  being  par- 
alyzed; (2)  external  strabismus,  on  account  of  the  unopposed  action  of  the  External  rectus  muscle, 
which  is  not  supplied  by  the  third  nerve,  and  is  not  therefore  paralyzed ;  (3)  dilatation  of  the  pupil, 
because  the  sphincter  fibres  of  the  iris  are  paralyzed;  (4)  lo.ss  of  power  of  accommodation,  as 
the  sphincter  pupillae,  the  ciliary  muscle,  and  the  Internal  rectus  are  paralyzed;  (5)  slight  promi- 
nence of  the  eyeball,  owing  to  most  of  its  muscles  being  relaxed.  Occasionally  paralysis  may 
affect  only  a  part  of  the  nerve;  that  is  to  say,  there  may  be,  for  example,  a  dilated  and  fixed 
pupil,  with  ptosis,  but  no  other  signs.  Irritation  of  the  nerve  causes  spasm  of  one  or  other  of 
the  muscles  supplied  by  it;  thus,  there  may  be  internal  strabismus  from  spasm  of  the  Internal 
rectus;  accommodation  for  near  objects  only  from  spasm  of  the  Ciliary  muscle,  or  contraction  of 
the  pupil  (myosis),  from  irritation  of  the  sphincter  of  the  pupil. 


THE  FOURTH  OR  TROCHLEAR  NERVE  (N.  TROCHLEARIS)  (Figs.  665  and  669). 

The  fourth  or  trochlear  nerve  or  Patheticus,  the  smallest  of  the  cranial  nerves, 
supplies  the  Superior  oblique  muscle. 

The  apparent  origin,  at  the  base  of  the  brain,  is  on  the  outer  side  of  the  crus 
cerebri,  just  in  front  of  the  pons  Varolii,  but  the  fibres  can  be  traced  backward 
behind  the  corpora  quadrigemina  to  the  valve  of  Vieussens,  on  the  upper  surface 
of  which  the  two  nerves  decussate,  decussatio  nervonun  trochlearium.  Its  deep 
origin  may  be  traced  to  a  nucleus  in  the  floor  of  the  aqueduct  of  Sylvius  imme- 
diately below  that  of  the  third  nerve,  with  which  it  is  continuous  (Fig.  618). 

Emerging  from  the  upper  end  of  the  valve  of  Vieussens,  the  nerve  is  directed 
outward  across  the  superior  peduncle  of  the  cerebellum,  and  then  winds  forward 

65 


1026  '  THE  NERVOUS  SYSTEM 

around  the  outer  side  of  the  crus  cerebri,  immediately  above  the  pons  VaroHi, 
pierces  the  dura  mater  in  the  free  border  of  the  tentorium  cerebelH,  just  behind, 
and  external  to,  the  posterior  cHnoid  process,  and  passes  forward  in  the  outer 
wall  of  the  cavernous  sinus,  between  the  third  nerve  and  the  ophthalmic  division 
of  the  fifth  (Figs.  454  and  455).  It  crosses  the  third  nerve  and  enters  the  orbit' 
through  the  sphenoidal  fissure  (Fig.  675).  It  now  becomes  the  highest  of  all 
the  nerves,  lying  at  the  inner  extremity  of  the  fissure  internal  to  the  frontal 
nerve.-  In  the  orbit  it  passes  inward,  above  the  origin  of  the  Levator  pal- 
pebrae,  and  finally  enters  the  orbital  surface  of  the  Superior  oblique  hiuscle. 
In  the  outer  wall  of  the  cavernous  sinus  this  nerve  is  not  infrequently  blended 
with  the  ophthalmic  division  of  the  fifth. 

Branches  of  Communication. — In  the  outer  wall  of  the  cavernous  sinus  it 
receives  some  filaments  from  the  cavernous  plexus  of  the  sympathetic.  In  the 
sphenoidal  fissure  it  occasionally  gives  off  a  branch  to  assist  in  the  formation  of 
the  lachrymal  nerve. 

Branches  of  Distribution. — It  gives  off  a  recurrent  branch,  which  passes 
backward  between  the  layers  of  the  tentorium,  dividing  into  two  or  three 
filaments  which  may  be  traced  as  far  back  as  the  wall  of  the  lateral  sinus. 

Surgical  Anatomy. — The  fourth  nerve  when  'paralyzed  causes  loss  of  function  in  the  Superior 
obHque,  so  that  the  patient  is  unable  to  turn  his  eye  downward  and  outward.  Should  the  patient 
attempt  to  do  this,  the  eye  on  the  affected  side  is  twisted  inward,  producing  diplopia  or  double 
vision.  Accordingly,  it  is  said  that  the  first  symptom  of  this  disease  which  presents  itself  is 
giddiness  when  going  down  hill  or  in  descending  stairs,  owing  to  the  double  vision  induced  by 
the  patient  looking  at  his  steps  while  descending. 

THE  FIFTH,  TRIGEMINAL  OR  TRIFACIAL  NERVE  (N.  TRIGEMINUS) 

(Figs.  665,  667  668,  669,  670,  671,  672,  673,  674). 

The  fifth,  trigeminal  or  trifacial  nerve  is  the  largest  cranial  nerve.  It  resembles 
a  spinal  nerve  (1)  in  arising  by  two  roots;  (2)  in  having  a  ganglion  developed  on 
its  posterior  root;  and  (3)  in  its  function,  since  it  is  a  compound  nerve.  It  is  the 
great  sensory  nerve  of  the  head  and  face  and  the  motor  nerve  of  the  muscles 
of  mastication.  Its  upper  two  divisions,  portio  major,  are  entirely  sensory,  the 
third  division,  portio  minor,  is  partly  sensory  and  partly  motor.  It  arises  by  two 
roots:  of  these  the  anterior  is  the  smaller,  and  is  the  motor  root  (Fig.  613);  the 
posterior,  the  larger  and  sensory  root.  Its  superficial  origin  is  from  the  side  of 
the  pons  Varolii,  nearer  to  the  upper  than  the  lower  border  (Fig.  613).  The 
smaller  root  consists  of  three  or  four  bundles ;  the  larger  root  consists  of  numer- 
ous bundles  of  fibres,  varying  in  number  from  seventy  to  a  hundred.  The  two 
roots  are  separated  from  one  another  by  a  few  of  the  transverse  fibres  of  the 
pons.  The  deep  origin  of  the  larger  or  sensory  root  is  chiefly  from  a  long  tract 
in  the  medulla,  the  lower  sensory  nucleus,  which  is  continuous  below  with  the 
substantia  gelatinosa  of  Rolando  (Fig.  607).  The  fibres  from  this  nucleus  form 
the  so-called  ascending  root  of  the  fifth  nerve  (Fig.  607) ;  they  pass  upward  through 
the  pons  and  join  with  fibres  from  the  locus  caeruleus  or  upper  sensory  nucleus 
(Fig.  613),  which  is  situated  to  the  outer  side  of  the  nucleus,  from  which  the  lower 
part  of  the  motor  root  takes  origin.  The  deep  origin  of  the  smaller  or  motor 
root  is  derived  partly  from  a  nucleus  embedded  in  the  gray  matter  of  the  upper 
part  of  the  floor  of  the  fourth  ventricle  and  partly  from  a  collection  of  nerve- 
cells  situated  at  the  side  of  the  aqueduct  of  Sylvius,  from  which  the  fibres  pass 
downward  under  the  name  of  the  descending  root  of  the  fifth  nerve  (Fig.  613). 

The  two  roots  of  the  nerve  pass  forward  below  the  tentorium  cerebelli  as  it 
bridges  over  the  notch  on  the  inner  part  of  the  superior  border  of  the  petrous  por- 
tion of  the  temporal  bone  (Fig.  668) ;  they  then  run  between  the  bone  and  the  dura 


THE   FIFTH,    TRIGEMINAL    OB    TRIFACIAL    NERVE        1027 


mater  to  the  apex  of  the  petrous  portion  of  the  temporal  bone,  where  the  fibres  of 
the  sensory  root  form  the  large  semilunar  or  Gasserian  ganglion  (Figs.  667  and  668), 
while  the  motor  root  passes  beneath  the  ganglion  without  having  any  connection 
with  it,  and  joins  outside  the  cranium  with  one  of  the  trunks  derived  from  it 
(Figs.  667  and  668). 


OCULOMOTOR  TROCHLEAR   ABDUCENS 
NERVE  NERVE    NERVE 


MOTOR  PORTION 
OF  FIFTH   NERVE 


SENSORY   PORTION 
OF  FIFTH  NERVE 


SEMILUNAR    NERVE 

(Gasserian  ganglion) 


SUPERIOR 

MAXILLARY 

NERVE 


MANDIBULAR 
NERVE 


Fig.  667. — The  right  semilunar  or  Gasserian  ganglion,  viewed  from  the  medial  side.     (Spalteholz.) 

The  Gasserian  or  Semilunar  Ganglion^  {ganglion  semilunare)  (Figs.  667, 668, 
669,  670,  671,  672,  and  673). — The  Gasserian  or  semilunar  ganglion  is  lodged  in  an 
osteo-fibrous  space,  the  cavum  Meckelii 
(Figs.  545  and  668),  near  the  apex 
of  the  petrous  portion  of  the  temporal 
bone.  The  ganglion  is  of  somewhat 
crescentic  form,  with  its  convexity 
turned  forward.  Its  upper  surface 
is  intimately  adherent  to  the  dura 
mater.  Besides  the  small  or  motor 
root,  the  large. superficial  petrosal  nerve 
lies  underneath  the  ganglion. 

Branches  of  Communication. — This 
ganglion  receives  on  its  inner  side 
filaments  from  the  carotid  plexus  of 
the  sympathetic. 

Branches  of  Distribution. — It  gives 
off  minute  branches  to  the  ten- 
torium cerebelli  and  the  dura  mater 
in  the  middle  fossa  of  the  cranium. 
From  its  anterior  border,  which  is  di- 
rected forward     and    outward,     three    Fig.  668.— The  course  of  the  motor  root  of  the  fifth  nerve. 

'  (Poirier  and  Charpy.) 

large    branches    proceed  —  the    oph- 
thalmic, superior  maxillary,  and  inferior  maxillary.     The  ophthalmic  and  superior 
maxillary  consist  exclusively  of  fibres  derived  from  the  larger  root  and  ganglion, 
and  are   solely  nerves  of    common    sensation.      The  third  division,  or  inferior 

'  A  Viennese  anatomist,  Raimund  BaUhasar  Hirsch  (1765),  was  the  first  who  recognized  the  ganglionic  nature 
of  the  swelling  on  the  sensory  root  of  the  fifth  nerve,  and  called  it,  in  honor  of  his  otherwise  unknown  teacher, 
Jon.  Laur.  Gasser,  the  "  Ganglion  Gasseri."  .Julius  Casserius,  whose  name  is  giv«n  to  the  musculo-cutaneous 
nerve  of  the  arm.  was  professor  at  Padua,  1545-1605.  (See  Hyrtl,  Lehrbuch  der  Anatomic,  p.  895  and  p.  55.) — 
Ed.  of  15th  English  edition. 


SENSORY  ROOT. 
DIVIDED 


SUPERIOR 
PETROSAL  SINUS 


SEVENTH  AND 
EIGHTH   NERVES 


1028 


THE  NERVOUS  SYSTEM 


maxillary,  is  joined  outside  the  cranium  by  the  motor  root.  This,  therefore, 
strictly  speaking,  is  the  only  portion  of  the  fifth  nerve  which  can  be  said  to 
resemble  a  spinal  nerve. 

Ophthalmic  Nerve  (n.ophthalmic^is)  (Figs.  665, 667,  668,  669,  670,  671,  672,  and 
673). — The  ophthalmic,  or  first  division  of  the  fifth,  is  a  sensory  nerve.  It  supplies 
the  eyeball,  the  lachrymal  gland,  the  mucous  lining  of  the  eye  and  nasal  fossae,  and 
the  integument  of  the  eyebrow,  forehead,  and  nose  (Fig.  674).  It  is  the  smallest 
of  the  three  divisions  of  the  fifth,  arising  from  the  upper  part  of  the  Gasserian 
ganglion.  It  is  a  short,  flattened  band,  about  an  inch  in  length,  which  passes  for- 
ward along  the  outer  wall  of  the  cavernous  sinus  (Figs.  454  and  455) ,  below  the  other 
nerves  (Fig.  667),  and  just  before  entering  the  orbit,  through  the  sphenoidal  fissure, 
divides  into  three  branches — lachrymal,  frontal,  and  nasal  (Figs.  665,  669,  670,  671). 

Branches  of  Communication. — The  ophthalmic  nerve  gives  off  in  the  cavernous 
sinus  a  branch  to  the  dura  mater  {n.  tentorii),  is  joined  by  filaments  from  the 
cavernous  plexus  of  the  sympathetic,  and  gives  off  minute  branches  to  communi- 
cate with  the  third  and  sixth  nerves,  and  not  infrequently  with  the  fourth. 


Internal  carotid  artery 
and  carotid  plexus. 


Fig.  669. — Nerves  of  the  orbit  and  ophthalmic  ganglion,  side  view. 

Branches  of  Distribution. — It  gives  off  recurrent  filaments  which  pass  between 
the  layers  of  the  tentorium,  and  then  divide  into — 

Lachrymal.  Frontal.  Nasal. 

The  Lachrymal  Nerve  {n.  lacrimalis)  (Figs.  665,  669,  670,  and  671).— The 
lachrymal  is  the  smallest  of  the  three  branches  of  the  ophthalmic.  It  sometimes 
receives  a  filament  from  the  fourth  nerve,  but  this  is  possibly  derived  from  the 
branch  of  communication  which  passes  from  the  ophthalmic  to  the  fourth.  It 
passes  forward  in  a  separate  tube  of  dura  mater,  and  enters  the  orbit  through  the 
narrowest  part  of  the  sphenoidal  fissure  (Fig.  675) .  In  the  orbit  it  runs  along  the 
upper  border  of  the  External  rectus  muscle,  with  the  lachrymal  artery,  and  com- 
municates with  the  temporo-malar  branch  of  the  superior  maxillary  nerve.  It 
enters  the  lachrymal  gland  and  gives  off  several  filaments,  which  supply  the 
gland  and  the  conjunctiva.  Finally,  it  pierces  the  superior  palpebral  ligament, 
and  terminates  in  the  integument  of  the  upper  eyelid,  joining  with  filaments  of 
the  facial  nerve.  The  lachrymal  nerve  is  occasionally  absent,  when  its  place  is 
taken  by  the  temporal  branch  of  the  superior  maxillary.  Sometimes  the  latter 
branch  is  absent,  and  a  continuation  of  the  lachrymal  is  substituted  for  it. 


THE  FIFTH,    TRIGEMINAL    OB    TRIFACIAL    NERVE'      1029 


Fig.  670. — Plan  of  the  fifth  cranial  nerve.  (The  lenticular  ganglion  is  displaced  from  its  normal  position. 
The  portion  where  the  short  root  enters  is  really  the  inferior  angle;  in  the  diagram  it  is  the  superior  angle.) 
(After  Flower.) 


1030  THE   NERVOUS  SYSTEM 

The  Frontal  Nerve  (n.  frontalis)  (Figs.  665,  669,  and  670). — The  frontal  is  the 
largest  division  of  the  ophthalmic,  and  may  be  regarded,  both  from  its  size  and 
direction,  as  the  continuation  of  the  nerve.  It  enters  the  orbit  above  the  muscles, 
through  the  sphenoidal  fissure  (Fig.  675) ,  and  runs  forward  along  the  middle  line, 
between  the  Levator  palpebrae  and  the  periosteum.  Midway  between  the  apex  and 
the  base  of  the  orbit  it  divides  into  two  branches,  supratrochlear  and  supra-orbital. 

The  Supratrochlear  Branch  (n.  supratrochlear  is)  (Figs.  665  and  670),  the  smaller 
of  the  two,  passes  inward,  above  the  pulley  of  the  superior  oblique  muscle,  and 
gives  off  a  descending  filament,  which  joins  with  the  infratrochlear  branch  of  the 
nasal  nerve.  It  then  escapes  from  the  orbit  between  the  pulley  of  the  Superior 
oblique  and  the  supraorbital  foramen,  curves  up  on  to  the  forehead  close  to  the 
bone,  ascends  beneath  the  Corrugator  supercilii  and  Occipito-frontalis  muscles, 
and,  dividing  into  branches  which  pierce  these  muscles,  it  supplies  the  integu- 
ment of  the  lower  part  of  the  forehead  on  either  side  of  the  middle  line  and 
sends  filaments  to  the  conjunctiva  and  skin  of  the  upper  lid. 

The  Supraorbital  Branch  (n.  supraorbitalis)  (Figs.  675  and  670)  passes  forward 
through  the  supraorbital  foramen,  and  gives  off,  in  this  situation,  palpebral  fila- 
ments to  the  upper  eyelid.  It  then  ascends  upon  the  forehead,  and  terminates  in 
cutaneous  and  pericranial  branches. 

The  cutaneous  branches,  two  in  number,  an  inner  and  an  outer,  supply  the  integ- 
ument of  the  cranium  as  far  back  as  the  vertex.  They  are  at  first  situated  beneath 
the  Occipito-frontalis,  the  inner  branch  perforating  the  frontal  portion  of  the 
muscle,  the  outer  branch  its  tendinous  aponeurosis. 

The  pericranial  branches  are  distributed  to  the  pericranium  over  the  frontal  and 
parietal  bones. 

The  Nasal  Nerve  (n.  nasociliaris)  (Figs.  665,  669,  and  670). — The  nasal  nerve 
is  intermediate  in  size  between  the  frontal  and  lachrymal,  and  more  deeply  placed 
than  the  other  branches  of  the  ophthalmic.  It  enters  the  orbit  by  way  of  the 
sphenoidal  fissure  (Fig.  675)  between  the  two  heads  of  the  External  rectus, 
and  passes  obliquely  inward  across  the  optic  nerve,  beneath  the  Superior  rectus 
and  Superior  oblique  muscles,  to  the  inner  wall  of  the  orbit,  where  it  passes 
through  the  anterior  ethmoidal  foramen,  and,  entering  the  cavity  of  the  cranium, 
traverses  a  shallow  groove  on  the  front  of  the  cribriform  plate  of  the  ethmoid 
bone,  and  passes  down,  through  the  slit  by  the  side  of  the  crista  galli,  into  the 
nose  (Fig.  672),  where  it  divides  into  two  branches,  an  internal  and  an  external 
branch.  The  internal  branch  {rami  nasales  mediates)  supplies  the  mucous  mem- 
brane near  the  forepart  of  the  septum  of  the  nose.  The  external  branch  (rami 
nasales  laterales)  descends  in  a  groove  on  the  inner  surface  of  the  nasal  bone,  and 
supplies  a  few  filaments  to  the  mucous  membrane  covering  the  forepart  of  the 
outer  wall  of  the  nares  as  far  as  the  inferior  spongy  bone ;  it  then  leaves  the  cavity 
of  the  nose,  between  the  lower  border  of  the  nasal  bone  and  the  upper  lateral 
cartilage  of  the  nose,  and,  passing  down  beneath  the  Compressor  nasi,  supplies 
the  integument  of  the  ala  and  the  tip  of  the  nose,  joining  with  the  facial  nerve. 

Branches. — The  branches  of  the  nasal  nerve  are  the  ganglionic,  ciliary,  and  infra- 
trochlear. 

The  Ganglionic  Branch,  or  the  long  root  of  the  ciliary  ganglion  (radix  longa  ganglii 
ciliaris)  (Figs.  666,  669,  and  670),  is  a  slender  branch,  about  half  an  inch  in 
length,  which  usually  arises  from  the  nasal  nerve,  between  the  two  heads  of  the 
External  rectus  muscle.  It  passes  forward  on  the  outer  side  of  the  optic  nerve, 
and  enters  the  postero-superior  angle  of  the  ciliary  ganglion,  forming  its  long 
root.  It  is  sometimes  joined  by  a  filament  from  the  cavernous  plexus  of  the 
sympathetic  or  from  the  superior  division  of  the  third  nerve. 

The  Long  Ciliary  Nerves  (nn.  ciliares  longi)  (Fig.  670),  two  or  three  in  number, 
are  given  off  from  the  nasal  as  it  crosses  the  optic  nerve.     They  join  the  sliort 


THE  FIFTH,    TRIGEMINAL    OB    TRIFACIAL    NERVE       1031 

ciliary  nerves  (Figs.  666,  669,  and  670)  from  the  ciliary  ganglion,  pierce  the  pos- 
terior part  of  the  sclerotic,  and,  running  forward  between  it  and  the  choroid,  are 
distributed  to  the  ciliary  muscle,  iris,  and  cornea. 

The  Infratrochleax  Branch  (n.  injratrochlearis)  (Figs.  665  and  670)  "is  given  off 
just  before  the  nasal  nerve  passes  through  the  anterior  ethmoidal  foramen.  It 
runs  forward  along  the  upper  border  of  the  Internal  rectus  muscle,  and  is  joined, 
beneath  the  pulley  of  the  Superior  oblique,  by  a  filament  from  the  supratrochlear 
nerve.  It  then  passes  to  the  inner  angle  of  the  eye,  and  supplies  the  integument 
of  the  eyelids  and  side  of  the  nose,  the  conjunctiva,  the  lachrymal  sac,  and  the 
caruncula  lacrimalis. 

Connected  with  the  three  divisions  of  the  fifth  nerve  are  four  small  ganglia. 
With  the  first  division  is  connected  the  ophthalmic  ganglion;  with  the  second 
division,  the  spheno-palatine  or  Meckel's  ganglion;  and  with  the  third,  the  otic  and 
submaxillary  ganglia.  All  the  four  receive  sensory  filaments  from  the  fifth  nerve, 
and  motor  and  sympathetic  filaments  from  various  sources;  these  filaments  are 
called  the  roots  of  the  ganglia. 

The  Ophthalmic,  Lenticular  or  Ciliary  Ganglion  {ganglion  cUiare)  (Figs.  666,  669, 
and  670)  is  a  small,  quadrangular,  flattened  ganglion,  of  a  reddish-gray  color,  and 
about  the  size  of  a  pin's  head,  situated  at  the  back  part  of  the  orbit  between  the 
optic  nerve  and  the  External  rectus  muscle,  lying  generally  on  the  outer  side  of 
the  ophthalmic  artery.  It  is  enclosed  in  a  quantity  of  loose  fat,  which  makes  its 
exposure  by  dissection  somewhat  difficult. 

Its  branches  of  communication  or  roots  are  three,  all  of  which  enter  its  posterior 
border.  One,  the  long  or  sensory  root  {radix  longa  ganglii  ciliaris),  is  derived 
from  the  nasal  branch  of  the  ophthalmic  and  joins  the  superior  angle  of  the 
ganglion.  The  second,  the  short  or  motor  root  {radix  hrevis  ganglii  ciliaris),  is  a 
short,  thick  nerve,  occasionally  divided  into  two  parts,  which  is  derived  from  the 
branch  of  the  third  nerve  to  the  Inferior  oblique  muscle,  and  is  connected  with 
the  inferior  angle  of  the  ganglion.  The  third,  the  sympathetic  root  {radix  sympa- 
thetica ganglii  ciliaris),  is  a  slender  filament  from  the  cavernous  plexus  of  the 
sympathetic.  This  is  frequently  blended  with  the  long  root,  though  it  some- 
times passes  to  the  ganglion  separately.  According  to  Tiedemann,  this  ganglion 
receives  a  filament  of  communication  from  the  spheno-palatine  ganglion. 

Its  branches  of  distribution  are  the  short  ciliary  nerves  {nn.  ciliares  breves)  (Figs. 
666,  669,  and  670) .  These  are  delicate  filaments,  from  six  to  ten  in  number,  which 
arise  from  the  forepart  of  the  ganglion  in  two  bundles,  connected  with  its  superior 
and  inferior  angles;  the  lower  bundle  is  the  larger.  They  run  forward  with  the 
ciliary  arteries  in  a  wavy  course,  one  set  above  and  the  other  below  the  optic 
nerve,  and  are  accompanied  by  the  long  ciliary  nerves  from  the  nasal  nerve 
They  pierce  the  sclerotic  at  the  back  part  of  the  globe,  pass  forward  in  delicate 
grooves  on  its  inner  surface,  and  are  distributed  to  the  Ciliary  muscle,  iris,  and 
cornea.  Tiedemann  has  described  one  small  branch  as  penetrating  the  optic 
nerve  with  the  arteria  centralis  retinae. 

The  circular  fibres  of  the  iris  are  innervated  by  the  third  nerve;  the  radiating 
fibres  are  innervated  by  the  sympathetic. 

The  Superior  Maxillary  Nerve  (n.  maxillaris)  (Figs.  667,  668,  669,  670,  671, 
and  672). — The  superior  maxillary  or  second  division  of  the  fifth  is  a  sensory  nerve. 
It  is  intermediate,  both  in  position  and  size,  between  the  ophthalmic  and  inferior 
maxillary.  It  commences  at  the  middle  of  the  Gasserian  ganglion  as  a  flattened 
plexiform  band  (Fig.  667),  and,  passing  horizontally  forward,  it  leaves  the  skull 
through  the  foramen  rotundum  (Fig.  668),  where  it  becomes  more  cylindrical  in 
form  and  firmer  in  texture.  It  then  crosses  the  spheno-maxillary  fossa  (Fig.  67), 
enters  the  orbit  through  the  spheno-maxillary  fissure,  traverses  the  infraorbital 
canal  in  the  floor  of  the  orbit,  and  appears  upon  the  face  of  the  infraorbital  fora- 


1032  THE  NERVOUS  SYSTEM 

men.  After  it  enters  the  infraorbital  canal  the  nerve  is  usually  called  the  infra- 
orbital (n.  infraorbitalis),  and  the  infraorbital  nerve  is  the  terminal  branch  of 
the  superior  maxillary  nerve  (Fig.  671) .  At  its  termination  the  nerve  lies  beneath 
the  Levator  labii  superioris  muscle,  and  divides  into  a  leash  of  branches,  which 
spread  out  upon  the  side  of  the  nose,  the  lower  eyelid,  and  upper  lip,  joining 
with  filaments  of  the  facial  nerve. 

Branches  of  Distribution. — The  branches  of  this  nerve  may  be  divided  into  four 
groups:  1.  Those  given  off  in  the  cranium.  2.  Those  given  off  in  the  spheno- 
maxillary fossa.    3.  Those  in  the  infraorbital  canal.    4.  Those  on  the  face. 

In  the  cranium      .     .     .     Meningeal. 

{Orbital  or  temporo-malar. 
Spheno-palatine. 
Posterior  superior  dental. 

T  p        1  •,  1  1  f  Middle  superior  dental. 

Intraorbital  canal    >    .     .  i   a    .     •        ^      •      j^i 

(  Anterior  superior  dental. 

(  Palpebral. 

On  the  face ^  Nasal. 

I  Labial. 

The  Meningeal  Branch  (ii.  meningeus  medius). — The  meningeal  branch  is  given 
off  by  the  superior  maxillary  nerve  directly  after  its  origin  from  the  Gasserian 
ganglion;  it  accompanies  the  middle  meningeal  artery  and  supplies  the  dura 
mater  of  the  middle  fossa  of  the  base  of  the  skull. 

The  Orbital  or  Temporo-malar  Branch  (w.  zygomaticus)  (Figs.  669,  670,  and  671). 
— The  orbital  or  temporo-malar  branch  arises  in  the  spheno-maxillary  fossa, 
enters  the  orbit  by  the  spheno-maxillary  fissure,  and  divides  at  the  back  of  that 
cavity  into  two  branches,  temporal  and  malar. 

The  Temporal  Branch  {ramus  zygomaticoiemporalis)  runs  in  a  groove  along  the 
outer  wall  of  the  orbit  (in  the  malar  bone),  receives  a  branch  of  communication 
from  the  lachrymal,  and,  passing  through  a  foramen  in  the  malar  bone,  enters  the 
temporal  fossa.  It  ascends  between  the  bone  and  the  substance  of  the  Temporal 
muscle,  pierces  this  muscle  and  the  temporal  fascia  about  an  inch  above  the 
zygoma,  and  is  distributed  to  the  integument  covering  the  temple  and  side  of 
the  forehead,  communicating  with  the  facial  and  the  auriculo-temporal  branch  of 
the  inferior  maxillary  nerve.  As  it  pierces  the  temporal  fascia  it  gives  off  a 
slender  twig,  which  runs  between  the  two  layers  of  the  fascia  to  the  outer  angle 
of  the  orbit. 

The  Malar  Branch  (ramus  zygomatico facialis)  passes  along  the  external  inferior 
angle  of  the  orbit,  emerges  upon  the  face  through  a  foramen  in  the  malar  bone, 
and,  perforating  the  Orbicularis  palpebrarum  muscle,  supplies  the  skin  on  the 
prominence  of  the  cheek,  where  it  is  named  the  subcutaneous  malae.  It  joins  with 
the  facial  and  the  palpebral  branches  of  the  superior  maxillary. 

The  Spheno-palatine  Branches  (nvi.  sphenopalatini)  (Figs.  670  and  671). — The 
spheno-palatine  branches,  two  in  number,  descend  to  the  spheno-palatine 
ganglion,  of  which  ganglion  they  are  the  sensory  or  short  roots. 

The  Posterior  Superior  Dental  Branches  (rami  alveolares  swperixires  posteriores) 
(Figs.  670  and  671). — The  posterior  superior  dental  branches  arise  from  the  trunk 
of  the  nerve  just  as  it  is  about  to  enter  the  infraorbital  canal ;  they  are  generally 
two  in  number,  but  sometimes  arise  by  a  single  trunk,  and  immediately  divide 
and  pass  downward  on  the  tuberosity  of  the  superior  maxillary  bone.  They  give 
off  several  twigs  to  the  gums  and  neighboring  parts  of  the  mucous  membrane  of 
the  cheek,  superior  gingival  branches  (rami  gingivales  superiores).  They  then 
enter  the  posterior  dental  canals  on  the  zygomatic  surface  of  the  superior  maxil- 
lary bone,  and,  passing  from  behind  forward   in  the  substance   of   the  bone. 


THE  FIFTH,     TRIGEMINAL    OB    TRIFACIAL    NERVE        1033 


communicate  with  the  middle  dental  nerve  by  a  plexus  formation,  and  give  off 
branches  to  the  lining  membrane  of  the  antrum  and  three  twigs  to  each  of  the 
molar  teeth.  These  twigs  enter  the  foramina  at  the  apices  of  the  fangs  and 
supply  the  pulp. 

The  Middle  Superior  Dental  Branch  {ramus  alveolaris  superior  medius)  (Fig. 
670). — The  middle  superior  dental  branch  is  given  off  from  the  superior  maxil- 
lary nerve  in  the  back  part  of  the  infraorbital  canal,  and  runs  downward  and 
forward  in  a  special  canal  in  the  outer  wall  of  the  antrum  to  supply  the  two 
bicuspid  teeth.  It  communicates  with  the  posterior  and  anterior  dental  branches 
by  a  plexus  formation.  At  its  point  of  communication  with  the  posterior 
branch,  above  the  root  of  the  second  bicuspid  tooth,  is  a  slight  thickening  which 
has  received  the  name  of  the  ganglion  of  Valentin ;  and  at  its  point  of  commu- 
nication with  the  anterior  branch  is  a  second  enlargement,  which  is  called  the 
ganglion  of  Bochdalek.    Neither  of  these  is  probably  a  true  ganglion. 


Sensory  root 
Motor  root. 


Auriculo-  temporal  J 
nerve. 


Fig.  671. — Distribution  of  the  second  and  third  divisions  of  the  fifth  nerve  and  submaxillary  ganglion. 


The  Anterior  Superior  Dental  Branch  (ramus  alveolaris  superior  anteriores)  (Fig. 
670). — The  anterior  superior  dental  branch,  of  large  size,  is  given  oft'  from  the 
superior  maxillary  nerve  just  before  its  exit  from  the  infraorbital  foramen;  it 
enters  a  special  canal  in  the  anterior  wall  of  the  antrum,  and  divides  into  a  series 
of  branches  which  supply  the  incisor  and  canine  teeth.  It  communicates  with 
the  middle  dental  nerve  by  a  plexus,  and  gives  off  a  nasal  branch,  which  passes 
through  a  minute  canal  into  the  nasal  fossa,  and  supplies  the  mucous  membrane 
of  the  forepart  of  the  inferior  meatus  and  the  floor  of  the  cavity,  communi- 
cating with  the  nasal  branches  from  Meckel's  ganglion. 

The  superior  dental  plexus  (plexus  dentalis  superior)  is  formed  by  twigs  of  the 
three  superior  dental  nerves.    From  the  plexus  come  the  nerves  which  supply  the 


1034  THE  NERVOUS   SYSTEM 

teeth  of  the  upper  jaw  {rami  dentales  superiores)  and  the  gums  (rami  gingivales 
super  lores). 

The  branches  upon  the  face  are  known  as  the  rami  n.  infraorbitalis  (Fig.  671). 
There  are  three  sets  of  them. 

The  Palpebral  Branches  (rami  palpehrales  inferiores). — The  palpebral  branches 
pass  upward  beneath  the  Orbicularis  palpebrarum  muscle.  They  supply  the 
integument  and  conjunctiva  of  the  lower  eyelid,  with  sensation,  joining  at 
the  outer  angle  of  the  orbit  with  the  facial  nerve  and  the  malar  branch  of  the 
orbital. 

The  Nasal  Branches  (rami  nasales  interni). — The  nasal  branches  pass  inward; 
they  supply  the  integument  of  the  side  of  the  nose  and  join  with  the  nasal  branch 
of  the  ophthalmic. 

The  Labial  Branches  (rami  labiales  superiores). — The  labial  branches,  the 
largest  and  most  numerous,  descend  beneath  the  Levator  labii  superioris  muscle, 
and  are  distributed  to  the  integument  of  the  upper  lip,  the  mucous  membrane 
of  the  mouth,  and  the  labial  glands. 

All  these  branches  are  joined,  immediately  beneath  the  orbit,  by  filaments  from 
the  facial  nerve,  forming  an  intricate  plexus,  the  infraorbital  plexus. 

The  Spheno-palatine  or  Meckel's  Ganglion  (ganglion  sphenopalatinum)  (Figs. 
670  and  672). — The  spheno-palatine  ganglion,  the  largest  of  the  cranial  ganglia, 
is  deeply  placed  in  the  spheno-maxillary  fossa,  close  to  the  spheno-palatine  fora- 
men. It  is  triangular  or  heart-shaped,  of  a  reddish-gray  color,  and  is  situated  just 
below  the  superior  maxillary  nerve  as  it  crosses  the  fossa. 

Branches  of  Commiinication. — Like  the  other  ganglia  of  the  fifth  nerve,  it  pos- 
sesses a  motor,  a  sensory,  and  a  sympathetic  root.  Its  sensory  root  is  derived 
from  the  superior  maxillary  nerve  through  its  two  spheno-palatine  branches 
(p.  1032).  These  branches  of  the  nerve  are  given  off  in  the  spheno-maxillary  fossa 
and  descend  to  the  ganglion.  Their  fibres,  for  the  most  part,  pass  in  front  of  the 
ganglion,  as  they  proceed  to  their  destination,  in  the  palate  and  nasal  fossa,  and 
are  not  incorporated  in  the  ganglionic  mass ;  some  few  of  the  fibres,  however,  enter 
the  ganglion,  constituting  its  sensory  root.  Its  motor  root  is  derived  from  the  facial 
nerve  through  the  large  superficial  petrosal  nerve,  and  its  sympathetic  root  from 
the  carotid  plexus,  through  the  large  deep  petrosal  nerve.  These  two  nerves  join 
together  before  their  entrance  into  the  ganglion  to  form  a  single  nerve,  the  Vidian. 

The  Large  or  Great  Superficial  Petrosal  Branch  (n.  petrosus  superficialis  major) 
(Fig.  676)  is  given  off  from  the  geniculate  ganglion  of  the  facial  nerve  in  the 
aquaeductus  Fallopii ;  it  passes  through  the  hiatus  Fallopii ;  enters  the  cranial 
cavity,  and  runs  forward,  being  contained  in  a  groove  on  the  anterior  surface 
of  the  petrous  portion  of  the  temporal  bone  and  lying  beneath  the  dura  mater. 
It  then  enters  the  cartilaginous  substance  which  fills  in  the  foramen  lacerum 
medium  basis  cranii,  and,  joining  with  the  large  deep  petrosal  branch,  forms  the 
Vidian  nerve. 

The  Large  or  Great  Deep  Petrosal  Branch  (n.  petrosus  profundus)  (Fig.  677)  is 
given  off  from  the  carotid  plexus  of  the  sympathetic  upon  the  internal  carotid 
artery,  and  runs  through  the  carotid  canal  on  the  outer  side  of  the  internal  carotid 
artery.  It  then  enters  the  cartilaginous  substance  which  fills  in  the  foramen 
lacerum  medium  basis  cranii,  and  joins  with  the  large  superficial  petrosal  nerve 
to  form  the  Vidian. 

The  Vidian  Nerve  (n.  canalis  pterygoidei)  (Figs.  670  and  672),  formed  in  the 
cartilaginous  substance  which  fills  in  the  middle  lacerated  foramen  by  the  junc- 
tion of  the  two  preceding  nerves,  passes  forward,  through  the  Vidian  canal,  with 
the  artery  of  the  same  name,  and  is  joined  by  a  small  ascending  nervous  branch, 
the  sphenoidal  branch,  from  the  otic  ganglion.  Finally,  it  enters  the  spheno-maxil- 
lary fossa,  and  joins  the  posterior  angle  of  Meckel's  ganglion. 


J 


THE    FIFTH,   TRIGEMINAL    OB    TRIFACIAL    NERVE        1035 

Branches  of  Distribution  of  the  Spheno -palatine  Ganglion. — Its  branches  of  distri- 
bution are  divisible  into  four  groups:  ascending,  which  pass  to  the  orbit;  descend- 
ing, to  the  palate;  internal,  to  the  nose;  and  posterior  branches,  to  the  pharynx  and 
nasal  fossae. 

The  Ascending  Branches  (rami  orbitales)  are  two  or  three  delicate  filaments,  which 
enter  the  orbit  by  the  spheno-maxillary  fissure,  and  supply  the  periosteum.  Accord- 
ing to  Luschka,  some  filaments  pass  through  foramina  in  the  suture  between  the 
OS  planum  of  the  ethmoid  and  frontal  bones  to  supply  the  mucous  membrane  of 
the  posterior  ethmoidal  and  sphenoidal  sinuses. 

The  Descending  or  Palatine  Branches  (nn.  palatini)  (Figs.  670  and  672)  are  dis- 
tributed to  the  roof  of  the  mouth,  the  soft  palate,  tonsil,  and  lining  membrane  of 
the  nose.  They  are  almosta  direct  continuation  of  the  spheno-palatine  branches 
of  the  superior  maxillary  nerve,  and  are  three  in  number — anterior,  middle,  and 
posterior. 


Termination  o, 

naso-palatine 

nerve 


Fig.  672. — The  spheno-palatine  or  Meckel's  ganglion  and  its  branches. 

The  anterior  or  large  palatine  nerve  (n.  palatinus  anterior)  descends  through 
the  large  posterior  palatine  canal,  emerges  upon  the  hard  palate  at  the  posterior 
palatine  foramen,  and  passes  forward  through  a  groove  in  the  hard  palate  nearly 
as  far  as  the  incisor  teeth.  It  supplies  the  gums,  the  mucous  membrane  and  glands 
of  the  hard  palate,  and  communicates  in  front  with  the  termination  of  the  naso- 
palatine nerve  (p.  1036) .  While  in  the  posterior  palatine  canal  it  gives  off  inferior 
nasal  branches  (rami  nasales  posteriores  injeriores),  which  enter  the  nose  through 
openings  in  the  palate  bone,  and  ramify  over  the  inferior  turbinated  bone,  the 
middle  and  the  inferior  meatus ;  and  at  its  exit  from  the  canal  a  palatine  branch 
is  distributed  to  both  surfaces  of  the  soft  palate. 

The  middle  or  external  palatine  nerve  (n.  palatinus  Tnedius)  descends  through 
one  of  the  accessory  palatine  canals,  distributing  branches  to  the  uvula,  tonsil, 
and  soft  palate.     It  is  occasionally  wanting. 

The  posterior  or  small  palatine  nerve  (n.  palatinus  posterior)  descends  with  a 
minute  artery  through  the  small  posterior  palatine  canal,  emerging  by  a  separate 


1036  'I'HE  NERVOUS  SYSTEM 

opening  behind  the  posterior  palatine  foramen.  It  supphes  the  Levator  palati 
and  Azygos  uvulae  muscles/  the  soft  palate,  tonsil,  and  uvula.  T.'he  middle  and 
posterior  palatine  join  with  the  tonsillar  branches  of  the  glosso-pharyngeal  to  form 
the  plexus  around  the  tonsil,  the  circulus  tonsillaris. 

The  Internal  Branches  are  distributed  to  the  septum  and  outer  wall  of  the  nasal 
fossae.    They  are  the  posterior  superior  nasal  and  the  naso-palatine. 

The  posterior  superior  nasal  branches  {rami  nasales  posteriores  superiores),  three 
in  number,  enter  the  back  part  of  the  nasal  fossa  by  the  spheno-palatine  foramen. 
They  supply  the  mucous  membrane  covering  the  superior  and  middle  spongy  bones, 
and  that  lining  the  posterior  ethmoidal  cells,  a  few  being  prolonged  to  the  upper 
and  back  part  of  the  septum. 

The  naso-palatine  nerve  (n.  nasopalatinus)  has  been  called  the  nerve  of  Scarpa 
and  also  the  nerve  of  Cotunnius.  It  enters  the  nasal  fossa  through  the  spheno- 
palatine foramen,  and  passes  inward  across  the  roof  of  the  nose,  below  the  orifice 
of  the  sphenoidal  sinus,  to  reach  the  septum ;  it  then  runs  obliquely  downward  and 
forward  along  the  lower  part  of  the  septum,  to  the  anterior  palatine  foramen, 
lying  between  the  periosteum  and  mucous  membrane.  It  descends  to  the  roof  of 
the  mouth  through  the  anterior  palatine  canal  (Fig.  672).  The  two  nerves  are  here 
contained  in  separate  and  distinct  canals,  situated  in  the  intermaxillary  suture,  and 
termed  the  foramina  of  Scarpa,  the  left  nerve  being  usually  anterior  to  the  right 
one.  In  the  mouth  they  become  united,  supply  the  mucous  membrane  behind 
the  incisor  teeth,  and  join  with  the  anterior  palatine  nerve.  The  naso-palatine 
nerve  furnishes  a  few  small  filaments  to  the  mucous  membrane  of  the  septum. 

The  Posterior  Branches  are  the  pharyngeal  or  pterygo -palatine  and  the  upper 
posterior  nasal  branches. 

The  pharyngeal  or  pterygo-palatine  nerve  (Figs.  670  and  672)  is  a  small  branch 
arising  from  the  back  part  of  the  spheno-palatine  ganglion,  being  generally  blended 
with  the  Vidian  nerve.  It  passes  through  the  pterygo-palatine  canal  with  the 
pterygo-palatine  artery,  and  is  distributed  to  the  mucous  membrane  of  the  upper 
part  of^  the  pharynx,  behind  the  Eustachian  tube. 

The  upper  posterior  nasal  branches  are  a  few  twigs  given  off  from  the  posterior 
part  of  the  spheno-palatine  ganglion,  which  run  backward  in  the  sheath  of  the 
Vidian  nerve  to  the  mucous  membrane  at  the  back  part  of  the  roof,  septum,  and 
superior  meatus  of  the  nose  and  that  covering  the  end  of  the  Eustachian  tube. 

The  Mandibular  or  Inferior  Maxillary  Nerve  (n.  mandibular  is)  (Figs.  667, 
669,  670,  and  671). — The  inferior  maxillary  or  third  division  of  the  fifth  nerve  dis- 
tributes branches  to  the  teeth  and  gums  of  the  lower  jaw,  the  integument  of  the 
temple  and  external  ear,  the  lower  part  of  the  face  and  lower  lip,  and  the  muscles 
of  mastication ;  it  also  supplies  the  tongue  with  a  large  branch.  It  is  the  largest  of 
the  three  divisions  of  the  fifth,  and  is  made  up  of  two  roots :  a  large  or  sensory  root, 
proceeding  from  the  inferior  angle  of  the  Gasserian  ganglion ;  and  a  small  or  motor 
root,  which  passes  beneath  the  ganglion  and  unites  with  the  sensory  root  just  after 
its  exit  from  the  skull  through  the  foramen  ovale  (Figs.  667,  668,  670,  and  671). 
Immediately  beneath  the  base  of  the  skull  this  nerve  divides  into  two  trunks, 
anterior  and  posterior.  Previous  to  its  division  the  primary  trunk  gives  off  from 
its  inner  side  a  recurrent  branch  and  the  nerve  to  the  Internal  pterygoid  muscle. 

The  Recurrent  or  Meningeal  Branch  (w.  spinosus). — The  recurrent  or  meningeal 
branch  is  given  off  directly  after  the  exit  of  the  mandibular  nerve  from  the  foramen 
ovale.  It  passes  backward  into  the  skull  through  the  foramen  spinosum  with  the 
middle  meningeal  artery.  It  divides  into  two  branches,  anterior  and  posterior,  which 
accompany  the  main  divisions  of  the  artery  and  supply  the  dura  mater.    The  pos- 

]  It  is  probable  that  this  is  not  the  true  motor  supply  to  these  muscles,  but  that  they  are  supplied  by  the 
spinal  accessory  through  the  pharyngeal  plexus. — Ed.  of  15th  English  edition. 


I 


THE  FIFTH,    TRIGEMINAL    OR    TRIFACIAL   NERVE        1037 

terior  branch  also  supplies  the  mucous  lining  of  the  mastoid  cells.  The  anterior 
branch  communicates  with  the  meningeal  branch  of  the  superior  maxillary  nerve. 

The  Internal  Pterygoid  Nerve  (w.  pterygoideus  internus)  (Fig.  670) . — The  internal 
pterygoid  nerve,  given  off  from  the  inferior  maxillary  previous  to  its  division,  is 
intimately  connected  at  its  origin  with  the  otic  ganglion.  It  is  a  long  and  slender 
branch,  which  passes  inward  to  enter  the  deep  surface  of  the  Internal  pterygoid 
muscle. 

The  anterior  and  smaller  division  of  the  inferior  maxillary  nerve,  which  receives 
nearly  the  whole  of  the  motor  root  of  the  fifth  nerve,  divides  into  branches  which 
supply  the  muscles  of  mastication.  They  are  the  masseteric,  deep  temporal,  buccal, 
and  external  pterygoid  branches  (Figs.  670  and  671). 

The  Masseteric  Branch  [n.  massetericus)  passes  outward,  above  the  External 
pterygoid  muscle,  in  front  of  the  temporo-mandibular  articulation  and  behind  the 
tendon  of  the  temporal  muscle;  it  crosses  the  sigmoid  notch  with  the  masseteric 
artery,  to  the  deep  surface  of  the  Masseter  muscle,  in  which  it  ramifies  nearly  as 
far  as  its  anterior  border.  It  occasionally  gives  a  branch  to  the  Temporal  muscle, 
and  a  filament  to  the  articulation  of  the  jaw. 

The  Deep  Temporal  Branches  {nn.  temporales  profundi),  two  in  number,  anterior 
and  posterior,  supply  the  deep  surface  of  the  Temporal  muscle.  The  posterior 
branch  (n.  temporalis  profundus  posterior),  of  small  size,  is  placed  at  the  back  of 
the  temporal  fossa.  It  is  sometimes  joined  with  the  masseteric  branch.  The 
anterior  branch  (n.  temporalis  profundus  anterior)  is  frequently  given  off  from  the 
buccal  nerve;  it  is  reflected  upward,  at  the  pterygoid  ridge  of  the  sphenoid,  to  the 
front  of  the  temporal  fossa.  Sometimes  there  are  three  deep  temporal  branches, 
and  if  this  maintains  the  third  branch,  the  middle  deep  temporal,  passes  outward 
above  the  External  pterygoid  muscle,  and  runs  upward  on  the  bone  to  enter  the 
deep  surface  of  the  Temporal  muscle. 

The  Buccal  or  Buccinator  Branch  (n.  huccinatorius)  passes  forward  between  the 
two  heafls  of  the  External  pterygoid,  and  downward  beneath  the  inner  surface  of 
the  coronoid  processes  of  the  lower  jaw,  or  through  the  fibres  of  the  Temporal 
muscle,  to  reach  the  surface  of  the  Buccinator  muscle,  upon  which  it  divides  into 
a  superior  and  an  inferior  branch.  It  gives  a  branch  to  the  External  pterygoid 
during  its  passage  through  that  muscle,  and  a  few  ascending  filaments  to  the 
Temporal  muscle,  one  of  which  occasionally  joins  with  the  anterior  branch  of  the 
deep  temporal  nerve.  The  superior  or  upper  branch  supplies  the  integument  and 
upper  part  of  the  Buccinator  muscle,  joining  with  the  facial  nerve  around  the 
facial  vein.  The  inferior  or  lower  branch  passes  forward  to  the  angle  of  the  mouth ; 
it  supplies  the  integument  and  Buccinator  muscle,  as  well  as  the  mucous  membrane 
lining  the  inner  surface  of  that  muscle,  and  joins  the  facial  nerve.^ 

The  External  Pterygoid  Nerve  (n.  pterygoideus  externus)  is  most  frequently 
derived  from  the  buccal,  but  it  may  be  given  off  separately  from  the  anterior 
trunk  of  the  mandibular  nerve.     It  enters  the  muscle  on  its  inner  surface. 

The  posterior  and  larger  division  of  the  inferior  maxillary  nerve  is  for  the  most  part 
sensory,  but  receives  a  few  filaments  from  the  motor  root.  It  divides  into  three 
branches:  auriculo -temporal,  lingual  (gustatory),  and  inferior  dental  (Figs.  670,  671). 

The  Auriculo-temporal  Nerve  {n.  auriculotemporalis)  (Fig.  673)  generally  arises 
by  two  roots,  between  which  the  middle  meningeal  artery  passes.  It  runs  back- 
ward beneath  the  External  pterygoid  muscle  to  the  inner  side  of  the  neck  of  the 
lower  jaw.  It  then  turns  upward  with  the  temporal  artery,  between  the  external 
ear  and  the  condyle  of  the  jaw,  under  cover  of  the  parotid  gland,  and,  escaping 
from  beneath  this  structure,  ascends  over  the  zygoma  and  divides  into  two  tem- 
poral branches. 

'There  seems  to  be  no  reason  to  doubt  that  the  branch  supplying  the  Buccinator  muscle  is  entirely  a  nerve  of 
ordinary  sensation,  and  that  the  true  motor  supply  of  this  muscle  is  from  the  facial. — Ed.  of  15th  English  edition. 


1038  THE   NERVOUS   SYSTEM 

The  branches  of  communication  are  with  the  facial  and  with  the  otic  ganglion. 
The  branches  of  communication  with  the  facial  {rami  anastomotici  cum  n.  faciali), 
usually  two  in  number,  pass  forward  from  behind  the  neck  of  the  condyle  of  the 
jaw,  to  join  this  nerve  at  the  posterior  border  of  the  Masseter  muscle.  They 
form  one  of  the  principal  branches  of  communication  between  the  facial  and  the 
fifth  nerve.  The  filaments  of  communication  with  the  otic  ganglion  are  derived 
from  the  commencement  of  the  auriculo-temporal  nerve. 

The  branches  of  distribution  are — 

Anterior  auricular.  Articular. 

Branches  to  the  meatus  auditorius.  Parotid. 

Superficial  temporal. 

The  anterior  auricular  branches  (nn.  auriculares  anteriores)  are  usually  two  in 
number.  They  supply  the  front  of  the  upper'part  of  the  pinna,  being  distributed 
principally  to  the  skin  covering  the  front  of  the  helix  and  tragus. 

Branch  to  the  external  auditory  meatus  (w.  meatus  auditorii  externi)  divides  into 
two.  The  two  nerves  enter  the  canal  between  the  bony  and  cartilaginous  portion 
of  the  meatus.  They  supply  the  skin  lining  the  meatus;  the  upper  one  sending 
a  filament  to  the  membrana  tympani  {ramus  memhranae  tijvipani). 

A  branch  to  the  temporo-mandibular  articulation,  the  articular  branch,  is  usually 
derived  from  the  auriculo-temporal  nerve. 

The  parotid  branches  {rami  parotidei)  supply  the  parotid  gland. 

The  superficial  temporal  branches  {rami  temporales  super fi dales)  accompany  the 
temporal  artery  to  the  vertex  of  the  skull,  and  supplies  the  integument  of  the  tem- 
poral region,  communicating  with  the  facial  nerve,  and  with  the  temporal  branch 
of  the  temporo-malar,  from  the  superior  maxillary. 

The  Lingual  Nerve  or  Gustatory  Nerve  (n.  lingualis)  (Figs.  670  and  671). — The 
lingual  or  gustatory  nerve  supplies  the  papillae  and  mucous  membrane  of  the 
anterior  two-thirds  of  the  tongue.  It  is  deeply  placed  throughout  the  whole  of  its 
course.  It  lies  at  first  beneath  the  External  pterygoid  muscle,  together  with  the 
inferior  dental  nerve,  being  placed  to  the  inner  side  of  this  nerve,  and  is  occasion- 
ally joined  to  it  by  a  branch  which  may  cross  the  internal  maxillary  artery.  The 
chorda  tympani  nerve  also  joins  it  at  an  acute  angle  in  this  situation.  The  nerve 
then  passes  between  the  Internal  pterygoid  muscle  and  the  inner  side  of  the 
ramus  of  the  jaw,  and  crosses  obliquely  to  the  side  of  the  tongue  over  the  Superior 
constrictor  of  the  pharynx  and  the  Stylo-glossus  muscles,  and  then  between  the 
Hyo-glossus  muscle  and  the  deep  part  of  the  submaxillary  gland;  the  nerve  finally 
runs  across  Wharton's  duct,  and  along  the  side  of  the  tongue  to  its  apex,  lying 
immediately  beneath  the  mucous  membrane. 

The  branches  of  communication  are  with  the  facial  through  the  chorda  tympani, 
with  the  inferior  dental  and  hypoglossal  nerves,  and  the  submaxillary  ganglion.  The 
chorda  tympani  branch  of  the  facial  joins  the  lingual  nerve  under  the  external 
pterygoid  muscle  and  is  distributed  with  the  lingual  to  the  tongue.  The  hypo- 
glossal nerve  and  the  lingual  nerve  lie  near  together,  over  the  Hyo-glossus  muscle, 
and  the  two  nerves  are  joined  by  loops  {rami  anastomotici  cum  n.  hypoglosso). 
The  branches  to  the  submaxillary  ganglion  are  two  or  three  in  number;  those 
connected  with  the  hypoglossal  nerve  form  a  plexus  at  the  anterior  margin  of  the 
Hyo-glossus  muscle. 

The  branches  of  distribution  supply  the  mucous  membrane  of  the  mouth,  the 
gums,  the  sublingual  gland,  the  filiform  and  fungiform  papillae  and  mucous  mem- 
brane of  the  tongue;  the  terminal  filaments  communicate,  at  the  tip  of  the  tongue, 
with  the  hypoglossal  nerve.  The  lingual  fibres  are  fibres  of  common  sensation. 
The  chorda  tympani  fibres  which  join  the  lingual  nerve  are  probably  taste- 
fibres. 


THE   FIFTH,   TRIGEMINAL    OB    TRIFACIAL    NERVE        1039 

The  Inferior  Dental  Nerve  (n.  alveolaris  inferior)  (Figs.  670  and  671). — The 
inferior  dental  is  the  largest  of  the  branches  of  the  inferior  maxillary  nerve.  It 
passes  downward  with  the  inferior  dental  artery,  at  first  beneath  the  External 
pterygoid  muscle,  and  then  between  the  internal  lateral  ligament  and  the  ramus 
of  the  jaw  to  the  dental  foramen.  It  then  passes  forward  in  the  dental  canal  of  the 
inferior  maxillary  bone,  lying  beneath  the  teeth,  as  far  as  the  mental  foramen, 
where  it  divides  into  two  terminal  branches,  incisor  and  mental. 

The  Branches  of  the  inferior  dental  are:  the  mylo-hyoid,  dental,  incisor,  and 
mental. 

The  Mylo-hyoid  (n.  mylohyoidetis)  is  derived  from  the  inferior  dental  just  as  that 
nerve  is  about  to  enter  the  dental  foramen.  It  descends  in  a  groove  on  the  inner 
surface  of  the  ramus  of  the  jaw,  in  which  it  is  retained  by  a  process  of  fibrous  mem- 
brane. It  reaches  the  under  surface  of  the  Mylo-hyoid  muscle,  and  supplies  it  and 
the  anterior  belly  of  the  Digastric. 

The  Dental  Branches  supply  the  molar  and  bicuspid  teeth.  They  correspond 
in  number  to  tiie  fangs  of  those  teeth :  each  nerve  entering  the  orifice  at  the  point 
of  the  fang  and  supplying  the  pulp  of  the  tooth. 

The  Incisor  Branch  is  continued  onward  within  the  bene  to  the  middle  line,  and 
supplies  the  canine  and  incisor  teeth. 

The  dental  branches  and  the  incisor  branch  form  a  plexus  (plexus  dentalis  infe- 
rior), and  from  this  plexus  come  the  branches  to  the  teeth  (rami  dentales  inferiores) 
and  to  the  gums  (rami  gingivales  inferiores). 

The  Mental  Branch  (n.  mentalis)  emerges  from  the  bone  at  the  mental  foramen, 
and  divides  beneath  the  Depressor  anguli  oris  muscle  into  two  or  three  branches; 
one  descends  to  supply  the  skin  of  the  chin,  and  another  (sometimes  two)  ascends 
to  supply  the  skin  and  mucous  membrane  of  the  lower  lip.  These  branches  com- 
municate freely  with  the  facial  nerve. 

Two  small  ganglia  are  connected  with  the  inferior  maxillary  nerve — the  otic 
with  the  trunk  of  the  nerve,  and  the  submaxillary  with  its  lingual  branch. 

Otic  or  Arnold's  Ganglion  (ganglion  oticum)  (Figs.  670  and  673). — The  otic  or 
Arnold's  ganglion  is  a  small,  oval-shaped,  flattened  ganglion  of  a  reddish-gray 
color,  situated  immediately  below  the  foramen  ovale,  on  the  inner  surface  of  the 
inferior  maxillary  nerve,  and  round  the  origin  of  the  internal  pterygoid  nerve.  It 
is  in  relation,  externally,  with  the  trunk  of  the  inferior  maxillary  nerve,  at  the 
point  where  the  motor  root  joins  the  sensory  portion;  internally,  with  the  car- 
tilaginous part  of  the  Eustachian  tube,  and  the  origin  of  the  Tensor  palati  muscle; 
behind,  it  lies  in  the  middle  meningeal  artery. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  internal 
pterygoid  branch  of  the  inferior  maxillary  nerve  by  two  or  three  short  delicate 
filaments.  From  this  nerve  the  ganglion  may  obtain  a  motor  root,  and  possibly 
also  a  sensory  root,  as  these  filaments  from  the  nerve  to  the  Internal  pterygoid 
perhaps  contain  sensory  fibres.  The  otic  ganglion  communicates  with  the  glosso- 
pharyngeal and  facial  nerves  through  the  small  superficial  petrosal  nerve  (Figs.  673 
and  676)  continued  from  the  tympanic  plexus,  and  through  this  communication 
it  probably  receives  its  sensory  root  from  the  glosso -pharyngeal  and  its  motor  root 
from  the  facial ;  its  communication  with  the  sympathetic  is  effected  by  a  filament 
from  the  plexus  surrounding  the  middle  meningeal  artery.  The  ganglion  also 
communicates  with  the  auriculo-temporal  nerve  (ramus'  anastomoticus  cum  n. 
auricidotemporali).  This  communicating  filament  is  probably  a  branch  from  the 
glosso-pharyngeal  which  passes  to  the  ganglion,  and  through  it  and  the  auriculo- 
temporal nerve  to  the  parotid  gland.  A  slender  filament,  the  sphenoidal,  ascends 
from  it  to  the  Vidian  nerve. 

Branches  of  Distribution. — Its  branches  of  distribution  are  a  filament  to  the 
Tensor  tympani  (n.  tensoris  tympani)  and  one  to  the  Tensor  palati  (n.  tensoris  veil 


1040 


THE   NEBVOUS  SYSTEM 


palatini).  The  former  passes  backward  on  the  outer  side  of  the  Eustachian  tube; 
the  latter  arises  from  the  ganghon,  near  the  origin  of  the  internal  pterygoid  nerve, 
and  passes  forward.  The  fibres  of  these  nerves  are,  however,  mainly  derived 
from  the  nerve  to  the  Internal  pterygoid  muscle.  It  also  gives  off  a  small  com- 
municating branch  to  the  chorda  tympani  {ramus  anastomoticus  cum  n.  chorda 
tymyani). 

The  Submaxillaxy  Ganglion  {ganglion  submaxillare)  (Figs.  670  and  671). — The 
submaxillary  ganglion  is  of  small  size,  fusiform  in  shape,  and  situated  above  the 
deep  portion  of  the  submaxillary  gland,  near  the  posterior  border  of  the  Mylo-hyoid 
muscle,  being  connected  by  filaments  with  the  lower  border  of  the  lingual  or 
gustatory  nerve. 

Branches  of  Communication. — This  ganglion  is  connected  with  the  lingual  nerve 
by  a  few  filaments  {rami  communicantes  cum  n.  linguxili),  which  join  it  separately 
at  its  fore  and  back  part.  It  also  receives  a  branch  from  the  chorda  tympani,  by 
which  it  communicates  with  the  facial,  and  communicates  with  the  sympathetic 
by  filaments  from  the  sympathetic  plexus  around  the  facial  artery. 


Fig.  673. — The  otic  ganglion  and  its  branches. 

Branches  of  Distribution. — These  are  five  or  six  in  number;  they  arise  from  the 
lower  part  of  the  ganglion,  and  supply  the  mucous  membrane  of  the  mouth  and 
Wharton's  duct,  some  being  lost  in  the  submaxillary  gland  {rami  submaxillares). 
The  branch  of  communication  from  the  lingual  nerve  to  the  forepart  of  the  gan- 
glion is  by  some  regarded  as  a  branch  of  distribution,  by  which  filaments  of  the 
chorda  tympani  pass  from  the  ganglion  to  the  lingual  nerve,  and  by  it  are  con- 
veyed to  the  sublingual  gland  and  the  tongue. 

Summary  of  the  Distribution  and  Connections  of  the  Fifth  Nerve. — It  is  the  chief 
sensory  nerve  of  the  face,  the  anterior  half  of  the  scalp,  the  mouth,  nasal  cavity, 
lips,  teeth,  anterior  two-thirds  of  the  tongue,  orbit,  and  eyeball.  The  clearly 
defined  cutaneous  distributions  of  the  branches  are  shown  in  Fig.  674.  The 
motor  portion  of  the  nerve  supplies  the  muscles  of  mast'cation,  the  mylo-hyoid, 
and  the  anterior  belly  of  the  digastric.  By  way  of  branches  from  the  otic 
ganglion  it  supplies  the  Tensor  tympani  and  Tensor  palati  muscles,  and  by 
way  of  branches  from  the  spheno-palatine  ganglion  perhaps  supplies  the  Levator 
palati  and  Azygos  uvulae  muscles,  although  it  is  more  probable  that  these  muscles 


THE   FIFTH,     TRIGEMINAL    OB    TRIFACIAL    NERVE       1041 

receive  their  motor  influence  by  the  spinal  accessory  through  the  pharyngeal 
plexus.  The  ganglia  associated  with  the  nerve  create  communications  with  the 
sympathetic,  the  motor  oculi,  the  facial,  and  the  glosso-pharyngeal,  and  through 
these  ganglia,  as  Prof,  Cunningham  says,  "  important  organs,  areas,  and  muscles  " 
are  innervated.  The  trigeminal  communicates  many  times  with  the  facial,  and 
thus  gives  sensory  fibres  to  the  "  muscles  of  expression  supplied  by  the  facial 
nerve."^ 


LACHRYMAL  N. 


SUPRATROCHLEAR  N 
SUPRAORBITAL  N. 


INFRATROCHLEAR  N 


NASAL  NERVE 


BUCCAL  NERVE 


MENTAL  NERVE- 


TEMPORAL  BR. 
OF  TEMPORO-MALAR 


MALAR  BR.   OF 
TEMPORO-MALAR 


AURICULO-TEMPORAL 
NERVE 


Fig.  674. — Sensory  areas  of  the  head,  showing  the  general  distribution  of  the  three  divisions  of  the  fifth 
nerve.     Gerrish's  Anatomy.      (Modified  from  Testut.) 

Surface  Marking. — It  will  be  seen  from  the  above  description  that  the  three  terminal  branches 
of  the  three  divisions  of  the  fifth  nerve  emerge  from  foramina  in  the  bones  of  the  skull  and  pass 
on  to  the  face:  the  terminal  branch  of  the  first  division  emerging  through  the  supraorbital 
foramen ;  that  of  the  second  through  the  infraorbital  foramen ;  and  the  third  through  the  mental 
foramen.  The  supraorbital  foramen  is  situated  at  the  junction  of  the  internal  and  middle 
third  of  the  supraorbital  arch.  If  a  straight  line  is  drawn  from  this  point  to  the  lower  border 
of  the  inferior  maxillary  bone,  so  that  it  passes  between  the  two  bicuspid  teeth  of  the  lower  jaw, 
it  will  pass  over  the  infraorbital  and  mental  foramina,  the  former  being  situated  about  one 
centimetre  (two-fifths  of  an  inch)  below  the  margin  of  the  orbit,  and  the  latter  varying  in  posi- 
tion according  to  the  age  of  the  individual.  In  the  adult  it  is  midway  between  the  upper  and 
lower  borders  of  the  inferior  maxillary  bone;  in  the  child  it  is  nearer  the  lower  border;  and  in  the 
edentulous  jaw  of  old  age  it  is  close  to  the  upper  margin. 

Surgical  Anatomy. — In  fracture  of  the  hose  of  the  skulL  the  fifth  nerve  or  one  of  its  branches 
may  be  injured.  It  seems  certain  that  occasionally,  though  seldom,  the  fifth  nerve  may  be 
actually  divided  by  such  an  injury.  The  fifth  nerve  may  be  affected  in  its  entirety,  or  its  sensory 
or  motor  root  may  be  affected,  or  one  of  its  primary  main  divisions.  In  injury  to  the  sensory  root 
there  is  anaesthesia  of  the  half  of  the  face  on  the  side  of  the  lesion,  with  the  exception  of  the  skin 
over  the  parotid  gland;  insensibility  of  the  conjunctiva,  followed,  if  the  eye  is  not  temporarily 
protected  with  a  watch-glass,  by  destructive  inflammation  of  the  cornea,  partly,  it  is  held,  from 
loss  of  trophic  influence,  and  partly,  it  is  certain,  from  the  irritation  produced  by  the  presence 
of  foreign  bodies  on  it,  which  are  not  perceived  by  the  patient,  and  therefore  not  expelled  by 
the  act  of  winking;  dryness  of  the  nose,  loss  to  a  considerable  extent  of  the  sense  of  taste,  and 
diminished  secretion  of  the  lachrymal  and  salivary  glands.  In  injury  to  the  motor  root  there  is 
impaired  action  of  the  lower  jaw  from  paralysis  of  the  muscles  of  mastication  on  the  affected  side. 

The  fifth  nerve  is  often  the  seat  of  neuralgia,  and  each  of  the  three  divisions  has  been  divided 
or  a  portion  of  the  nerve  excised  for  this  affection.    The  supraorbital  nerve  may  be  exposed 


1  Cunningham's  Text-book  of  Anatomy. 
66 


1042  THE   NERVOUS   SYSTEM 

by  making  an  incision  an  inch  and  a  half  in  length  along  the  supraorbital  margin  below  the 
eyebrow,  which  is  to  be  drawn  upward,  the  centre  of  the  incision  corresponding  to  the  supra- 
orbital notch.  The  skin  and  Orbicularis  palpebrarum  having  been  divided,  the  nerve  can  be 
easily  found  emerging  from  the  notch  and  lying  in  some  loose  cellular  tissue.  It  should  be  drawn 
up  by  a  blunt  hook  and  divided,  or,  what  is  better,  a  portion  of  it  should  be  removed.  The 
infraorbital  nerve  has  been  divided  at  its  exit  by  an  incision  on  the  cheek;  or  the  floor  of  the 
orbit  has  been  exposed,  the  infraorbital  canal  opened  up,  and  the  anterior  part  of  the  nerve 
resected;  or  the  whole  nerve,  together  with  Meckel's  ganglion  as  far  back  as  the  foramen  rotun- 
dum,  has  been  removed.  This  latter  operation,  though  undoubtedly  a  severe  proceeding,  appears 
to  have  been  followed  by  better  results  than  has  nerve  resection.  The  operation  is  performed 
as  follows:  The  superior  maxillary  bone  is  first  exposed  by  a  T-shaped  incision,  one  limb  of 
the  incision  passing  along  the  lower  margin  of  the  orbit,  the  other  from  the  centre  of  the  first 
cut  vertically  down  the  cheek  toward  the  angle  of  the  mouth.  The  nerve  is  then  found,  is  divided, 
and  a  piece  of  silk  is  tied  to  it  as  a  guide.  A  small  trephine  (one-half  inch)  is  then  applied 
to  the  bone  below,  but  including  the  infraorbital  foramen,  and  the  antrum  opened.  The 
trephine  is  now  applied  to  the  posterior  wall  of  the  antrum,  and  the  spheno-maxillary  fossa 
exposed.  The  infraorbital  canal  is  now  opened  up  from  below  by  fine  cutting-pliers  or  a 
chisel,  and  the  nerve  drawn  down  into  the  trephine  hole,  it  being  held  on  the  stretch  by 
means  of  the  piece  of  silk;  it  is  severed  with  fine  curved  scissors  as  near  the  foramen  rotundura 
as  possible,  any  branches  coming  off  from  the  ganglion  being  also  divided.'  The  mental 
branch  of  the  inferior  dental  nerve  may  be  divided  at  its  exit  from  the  foramen  through  an 
incision  made  through  the  mucous  membrane  where  it  is  reflected  from  the  alveolar  process  on 
to  the  lower  lip ;  or  a  portion  of  the  trunk  of  the  inferior  dental  nerve  may  be  resected  through 
an  incision  on  the  cheek  through  the  Masseter  muscle,  exposing  the  outer  surface  of  the  ramus  of 
the  jaw.  A  trephine  is  then  applied  over  the  position  of  the  inferior  dental  foramen  and  the 
outer  table  removed,  so  as  to  expose  the  inferior  dental  canal.  The  nerve  is  dissected  out  of 
the  portion  of  the  canal  exposed,  and,  having  been  divided  after  its  exit  from  the  mental  foramen, 
it  is  by  traction  on  the  end  exposed  in  the  trephine-hole,  drawn  out  entire,  and  cut  off  as  high  up 
as  possible.^  The  inferior  dental  nerve  has  also  been  divided  through  an  incision  within  the  mouth, 
the  bony  point  guarding  the  inferior  dental  foramen  forming  the  guide  to  the  nerve.  The  buccal 
nerve  may  be  divided  by  an  incision  through  the  mucous  membrane  of  the  mouth  and  the  Buc- 
cinator muscle  just  in  front  of  the  anterior  border  of  the  ramus  of  the  lower  jaw  (Stimson). 

In  inveterate  neuralgia  of  one  or  two  of  the  branches  of  the  fifth  nerve  a  peripheral  opera- 
tion may  cure  the  case,  but  seldom  does.  It  often  gives  relief,  perhaps  for  months.  In  neuralgia 
of  the  second  division  or  third  division,  or  of  the  second  division  and  third  division.  Abbe,  of 
New  York,  opens  the  skull  and  divides  the  nerve  or  nerves  by  an  intracranial  operation, 
removes  a  piece  of  nerve  so  as  the  foramen  of  exit  is  empty,  and  covers  the  foramen  with  rubber 
tissue,  to  hinder  regrowth  of  the  nerve.  Other  operators,  after  removing  a  piece  from  each 
nerve,  have  plugged  the  foramina  of  the  exit  with  dentists'  cement  or  silver-foil. 

Rose's  method  of  neurectomy  is  very  valuable  for  neuralgia  of  the  second  division.  It  is  a 
modification  of  the  Braun-Lossen  method.  The  infraorbital  nerve  is  exposed,  a  ligature  is 
tied  about  it,  the  roof  of  the  infraorbital  canal  is  chiselled  open,  and  the  nerve  is  freed  as  far 
back  as  possible.  An  incision  is  made  from  below  the  external  angular  process  outward  along 
the  zygoma  to  in  front  of  the  lobule  of  the  ear,  downward  to  just  above  the  angle  of  the  jaw, 
and  forward  for  two  inches.  The  flap  is  raised  and  the  zygoma  is  exposed.  The  root  of  the 
zygoma  is  drilled  at  two  points,  and  the  zygomatic  process  of  the  temporal  bone  is  drilled  at  two 
points.  The  bone  is  sawed  in  two  places  between  the  drill-holes.  The  freed  arch  is  lifted  down 
and  back,  the  tendon  of  the  temporal  muscle  is  drawn  backward,  and  the  pterygo-maxillary 
fossa  is  thus  exposed.  The  internal  maxillary  artery  is  divided  between  two  ligatures.  The 
External  pterygoid  muscle  is  separated  from  the  greater  wing  of  the  sphenoid  and  from  the  root 
of  the  external  pterygoid  process.  The  superior  maxillary  nerve  is  grasped  and  twisted  off  as 
near  the  ganglion  as  possible.  The  entire  nerve  is  then  drawn  back  from  the  infraorbital  foramen 
and  removed.  The  wound  is  then  closed.  If  the  third  division  is  also  haunted  by  neuralgia, 
it  too  should  be  removed  a   ew  weeks  after  the  performance  of  Rose's  operation. 

If  a  peripheral  operation  fails,  or  if  all  the  branches  of  the  fifth  are  involved,  the  Gasserian 
ganglion  must  be  removed  or  the  sensory  root  of  the  fifth  must  be  divided,  as  suggested  by 
Frazier  and  Spiller. 

Removal  of  the  Gasserian  ganglion  was  suggested  by  J.  Ewing  Mears  in  1884,  and  was  first 
carried  out  by  Rose  in  1890. 

The  method  chiefly  in  vogue  was  devised  by  Hartley,  and  was  first  performed  by  him  in  1891. 
An  osteoplastic  flap  is  made  in  front  of  the  ear,  the  dura  is  exposed  and  lifted.  Following  Krause's 
advice,  the  third  division  is  exposed  and  clamped.  The  second  division  is  exposed  and  damped. 
The  nerves  are  loosened  from  their  beds  and  then  are  rolled  about  the  clamps.     This  twisting 

^  Carnochan,  American  Journal  of  the  Medical  Sciences,  1858,  p.  136. 

^  Mears,  Transactions  of  the  American  Surgical  Association,  vol.  ii.  p.  469, 


THE   SIXTH   OB    ABDUCENT  NERVE  IO43 

pulls  out  the  ganglion  intact  along  with  the  motor  root,  and  also  the  sensory  root  from  the 
pons. 

A  difficulty  in  the  Hartley  operation  is  the  danger  of  division  of  the  meningeal  artery.  If 
this  happens,  the  surgeon  may  be  able  to  arrest  bleeding  and  proceed  with  the  operation.  If 
the  vessel  is  torn  off  at  the  foramen  spinosum,  it  will  be  necessary  to  pack  the  wound  and  post- 
pone any  further  operative  manipulation  for  forty-eight  hours. 

Dr.  Harvey  Gushing  has  modified  Hartley's  operation  by  trephining  the  wall  of  the  temporal 
fossa  very  low  down.  He  opens  the  skull  below  the  arch  of  the  meningeal  vessels,  and  thus  avoids 
the  meningeal  at  the  foramen  spinosum,  and  also  the  sulcus  arteriosus  of  the  parietal  bone. 

After  the  removal  of  the  ganglion.  Professor  Keen,  in  order  to  prevent  undue  inflammation  of 
the  eye,  sews  the  eyelids  of  the  affected  side  together,  leaving  a  space  open  at  each  angle,  and 
covers  the  eye  with  a  watch-crystal.  Boracic  acid  solution  is  flushed  into  the  opening  at  the  external 
angle  at  frequent  intervals.    The  stitches  are  removed  from  the  lid  in  from  eight  to  ten  days. 

The  lingual  (gustatory)  nerve  is  occasionally  divided  with  the  view  of  relieving  the  pain  in 
cancerous  disease  of  the  tongue.  This  may  be  done  in  that  part  of  its  course  where  it  lies  below 
and  behind  the  last  molar  tooth.  If  a  line  is  drawn  from  the  middle  of  the  crown  of  the  last 
molar  tooth  to  the  angle  of  the  jaw,  it  will  cross  the  nerve,  which  lies  about  half  an  inch  behind 
the  tooth,  parallel  to  the  bulging  alveolar  ridge  on  the  inner  side  of  the  body  of  the  bone.  If 
the  knife  is  entered  three-quarters  of  an  inch  behind  and  below  the  last  mokr  tooth  and  carried 
down  to  the  bone,  the  nerve  will  be  divided.  Hilton  divided  it  opposite  the  second  molar  tooth, 
where  it  is  covered  only  by  the  mucous  membrane,  and  Lucas  pulls  the  tongue  forward  and  over 
to  the  opposite  side,  when  the  nerve  can  be  seen  standing  out  as  a  firm  cord  under  the  mucous 
membrane  by  the  side  of  the  tongue  and  can  be  easily  seized  with  a  sharp  hook  and  divided  or 
a  portion  excised.  This  is  a  simple  enough  operation  on  the  cadaver,  but  when  the  disease  is 
extensive  and  has  extended  to  the  floor  of  the  mouth,  as  is  generally  the  case  when  division  of 
the  nerve  is  thought  of,  the  operation  is  not  practicable. 

THE  SIXTH  OR  ABDUCENT  NERVE  (N.  ABDUCENS)  (Fig.  669). 

The  sixth  or  abducent  nerve  suppHes  the  External  rectus  muscle.  Its  super- 
ficial origin  is  by  several  filaments  from  the  constricted  part  of  the  pyramid,  close 
to  the  pons,  or  from  the  lower  border  of  the  pons  itself,  in  the  groove  between  this 
body  and  the  medulla.  Its  deep  origin  is  from  the  upper  part  of  the  floor  of  the 
fourth  ventricle,  close  to  the  median  line,  beneath  the  eminentia  teres  (Fig.  613.) 

From  the  nucleus  of  the  sixth  nerve  fibres  pass  through  the  posterior  longitudinal 
bundle  to  the  oculo-motor  nucleus  of  the  opposite  side  and  into  the  third  nerve, 
along  which  they  are  carried  to  the  Internal  rectus  muscle.  The  External  rectus 
of  one  eye  and  the  Internal  rectus  of  the  other  may  therefore  be  said  to  receive 
their  nerves  from  the  same  nucleus — a  factor  of  great  importance  in  connection 
with  the  conjugate  movements  of  the  eyeball,  and  one  that  may  explain  certain 
paralytic  phenomena  of  the  Recti  muscles,  which  are  often  associated  with  lesions 
in  the  pons. 

The  nerve  pierces  the  dura  mater  on  the  basilar  surface  of  the  sphenoid  bone, 
runs  through  a  notch  immediately  below  the  posterior  clinoid  process,  and  enters 
the  cavernous  sinus.  It  passes  forward  through  the  sinus,  lying  on  the  outer  side 
of  the  internal  carotid  artery  (Fig.  454).  It  enters  the  orbit  through  the  sphenoid 
fissure,  and  lies  above  the  ophthalmic  vein,  from  which  it  is  separated  by  a  lamina 
of  dura  mater  (Fig.  675) .  It  then  passes  between  the  two  heads  of  the  External 
rectus  muscle,  and  is  distributed  to  that  muscle  on  its  ocular  surface. 

Branches  of  Communication. — It  is  joined  by  several  filaments  from  the 
carotid  and  cavernous  plexuses,  and  by  one  from  the  ophthalmic  nerve. 

Relations  to  Each  Other  of  the  Third,  Fourth,  Ophthalmic  Division  of  the  Fifth  and 
Sixth  Nerves  as  They  Pass  to  the  Orbit. — The  third,  the  fourth,  the  ophthalmic 
division  of  the  fifth,  and  the  sixth  nerves,  as  they  pass  to  the  orbit,  bear  a  certain 
relation  to  each  other  in  the  cavernous  sinus,  at  the  sphenoidal  fissure,  and  in  the 
cavity  of  the  orbit,  which  will  now  be  described. 

In  the  Cavernous  Sinus  (Figs.  454  and  455)  the  third,  fourth,  and  ophthalmic 
division  of  the  fifth  are  placed  on  the  outer  wall  of  the  sinus,  in  their  numerical 


1044 


THE  NERVOUS  SYSTEM 


Frontal. 


order,  both  from  above  downward  and  from  within  outward.  The  sixth  nerve 
lies  at  the  outer  side  of  the  internal  carotid  artery.  As  these  nerves  pass  for- 
ward to  the  sphenoidal  fissure,  the  third  and  fifth  nerves  become  divided  into 
branches,  and  the  sixth  nerve  approaches  the  rest,  so  that  their  relative  position 
becomes  considerably  changed. 

In  the  Sphenoidal  Fissure  (Fig.  675)  the  fourth  nerve  and  the  frontal  and 
lachrymal  branches  of  the  ophthalmic  division  of  the  fifth  lie  upon  the  same 
plane,  the  former  being  most  internal,  the  latter  external,  and  they  enter  the  cavity 
of  the  orbit  above  the  muscles.  The  remaining  nerves  enter  the  orbit  between 
the  two  heads  of  the  External  rectus  muscle.     The  superior  division  of  the  third 

nerve  is  the  highest  of  these;  beneath 
Lachrymal.  this   Hes   the   nasal    branch   of   the 

ophthalmic  nerve;  then  the  inferior 
division  of  the  third  nerve;  and  the 
sixth  nerve  lowest  of  all. 

In  the  Orbit  (Figs.  665  and  669) 
the  fourth  nerve  and  the  frontal  and 
lachrymal  divisions  of  the  ophthalmic 
nerve  lie  on  the  same  plane  immedi- 
ately beneath  the  periosteum,  the 
fourth  nerve  being  internal  and  rest- 
ing on  the  Superior  oblique  muscle, 
the  frontal  nerve  resting  on  the  Le- 
vator palpebrae  muscle,  and  the  lach- 
rymal nerve  on  the  External  rectus 
muscle.  Next  in  order  comes  the  superior  division  of  the  third  nerve,  lying 
immediately  beneath  the  Superior  rectus  muscle,  and  then  the  nasal  branch  of 
the  ophthalmic  nerve,  crossing  the  optic  nerve  from  the  outer  to  the  inner  side 
of  the  orbit.  Beneath  these  is  found  the  optic  nerve,  surrounded  in  front  by  the 
ciliary  nerves,  and  having  the  lenticular  ganglion  on  its  outer  side,  between  it  and 
the  External  rectus  muscle.  Below  the  optic  nerve  is  the  inferior  division  of  the 
third  nerve  and  the  sixth  nerve,  which  lies  on  the  outer  side  of  the  orbit. 


Fia.  675.- 


'' Superior  division  of  Sd, 
Nasal. 
Inferior  division  of  Sd. 
6th. 
Ophthalmic  vein. 


-Relations  of  structures  passing  through 
the  sphenoidal  fissure. 


Surgical  Anatomy. — It  is  often  stated  that  the  sixth  nerve  is  more  frequently  involved  in 
fractures  of  the  base  of  the  skull  than  any  other  of  the  cranial  nerves.  As  a  matter  of  fact,  however, 
it  is  injured  in  only  about  2  per  cent,  of  cases  of  fracture  of  the  skull  (Putscher).  Cases  have  been 
reported  in  which  the  nerve  was  actually  ruptured.  The  nerve  may  be  injured  by  traction, 
pressure  of  a  blood  clot,  of  a  tumor,  or  of  an  arterio-venous  aneurism.  The  result  of  paralysis  of 
this  nerve  is  internal  or  convergent  squint.  When  injured  so  that  its  function  is  destroyed,  there 
is,  in  addition  to  the  paralysis  of  the  External  rectus  muscle,  often  a  certain  amount  of  contrac- 
tion of  the  pupil,  because  some  of  the  sympathetic  fibres  to  the  radiating  muscle  of  the  iris  pass 
along  with  this  nerve. 


THE  SEVENTH  OR  FACIAL  NERVE  (N.  FACIALIS)  (Figs.  676,  677,  678). 


The  seventh  or  facial  nerve  or  Portio  Dura  is  the  motor  nerve  of  all  the  muscles 
of  expression  in  the  face,  and  of  the  Platysma  and  Buccinator;  the  muscles  of 
the  External  ear;  the  posterior  belly  of  the  Digastric,  and  the  Stylo-hyoid.  Its 
chorda  tympani  branch  is  the  nerve  of  taste  for  the  anterior  two-thirds  of  the 
tongue  and  the  vaso-dilator  nerve  of  the  submaxillary  and  sublingual  glands;  its 
tympanic  branch  supplies  the  Stapedius. 

Its  superficial  origin  is  from  the  upper  end  of  the  medulla  oblongata,  in  the 
groove  between  the  olivary  and  restiform  bodies.  Its  deep  origin  is  from  a  nucleus 
situated  in  the  floor  of  the  fourth  ventricle,  beneath  the  superior  fovea  (Fig.  613). 


THE   SEVENTH    OB    FACIAL    NEBVE  1045 

The  facial  nucleus  is  deeply  placed  in  the  reticular  formation  of  the  lower  part  of 
the  pons,  a  little  external  and  ventral  to  the  nucleus  of  the  sixth  nerve.  From  this 
origin  the  fibres  pursue  a  curved  course  in  the  substance  of  the  pons.  They  first 
pass  backward  and  inward,  and  then  turn  upward  and  forward,  forming  the  fas- 
ciculus teres,  which  produces  an  eminence,  the  eminentia  teres,  on  the  floor  of  the 
fourth  ventricle,  and  finally  bend  sharply  downward  and  outward  around  the  upper 
end  of  the  nucleus  of  origin  of  the  sixth  nerve,  to  reach  their  superficial  origin 
between  the  olivary  and  restiform  bodies.  From  the  nucleus  of  the  third  nerve 
some  fibres  arise  which  descend  in  the  posterior  longitudinal  bundle  and  join  the 
facial  just  before  it  leaves  the  pons;  these  fibres  are  said  to  supply  the  anterior 
belly  of  the  Occipito-frontalis, 
the  Orbicularis  palpebrarum,  and 
the  Corrugator  supercilii,  as  these  External  petrosal.. 

muscles   have   been   observed   to        f^^l^^^l^^ffZlir 

escape   paralysis  in  lesions  of    the     Intumescentia  ganglio/ormis 

nucleus  of  the  facial  nerve. 

The  auditory  nerve  {portio  mol- 
lis) lies  to  the  outer  side  of  the 

facial  nerve  ;  and  between  the  two        ^'^-  676.-The  course^and^onnecUon^of  the  facial  nerve 

is  a  small  fasciculus,  the  pars  in- 
termedia of  Wrisberg  (n.  intermedius),  which  arises  from  the  medulla  and  joins 
the  facial  nerve  in  the  internal  auditory  meatus.    The  deep  origin  of  the  pars 
intermedia  is  from  the  upper  end  of  the  nucleus  of  the  glosso-pharyngeal  nerve, 
and  at  its  emergence  it  is  frequently  connected  with  both  nerves. 

The  pars  intermedia  may  be  regarded  as  the  sensory  root  of  the  facial  nerve, 
analogous  to  the  sensory  root  of  the  fifth,  and  its  real  nucleus  of  origin  would  then 
consist  of  the  geniculate  ganglion. 

The  facial  nerve,  firmer,  rounder,  and  smaller  than  the  auditory,  passes  forward 
and  outward  upon  the  middle  peduncle  of  the  cerebellum,  and  enters  the  internal 
auditory  meatus  with  the  auditory  nerve.  Within  the  meatus  the  facial  nerve 
lies  in  a  groove  along  the  upper  and  anterior  part  of  the  auditory  nerve  and  the 
pars  intermedia  is  placed  between  the  two,  and  joins  the  inner  angle  of  the  geni- 
culate ganglion.  Occasionally  a  few  of  its  fibres  pass  into  the  auditory  nerve. 
Beyond  the  ganglion  its  fibres  are  generally  regarded  as  forming  the  chorda 
tympani. 

At  the  bottom  of  the  meatus  the  facial  nerve  enters  the  aquaeductus  Fallopii, 
and  follows  the  course  of  that  canal  through  the  petrous  portion  of  the  temporal 
bone,  from  its  commencement  at  the  internal  meatus  to  its  termination  at  the  stylo- 
mastoid foramen  (Figs.  49  and  676).  It  is  at  first  directed  outward  between  the 
cochlea  and  vestibule  toward  the  inner  wall  of  the  tympanum;  it  then  bends  sud- 
denly backward  and  arches  downward  behind  the  tympanum  to  the  stylo-mastoid 
foramen.  At  the  point  in  the  aqueduct  of  Fallopius  where  the  nerve  changes  its 
direction  (geniculum  n.  facialis),  it  presents  a  reddish  gangliform  swelling,  the  genic- 
ulate ganglion  {ganglion  geniculi),  which  is  also  called  the  intumescentia  ganglio- 
formis  (Fig.  676).  The  geniculate  ganglion  receives  a  branch  from  the  vestibular 
division  of  the  auditory  nerve,  which  probably  carries  fibres  of  the  pars  intermedia. 
On  emerging  from  the  stylo-mastoid  foramen  the  facial  nerve  runs  forward  in  the 
substance  of  the  parotid  gland,  crosses  the  external  carotid  artery,  and  divides 
behind  the  ramus  of  the  lower  jaw  into  two  primary  branches,  temporo-facial 
and  cervico-facial,  from  which  numerous  offsets  are  distributed  over  the  side  of 
the  head,  face,  and  upper  part  of  the  neck,  supplying  the  superficial  muscles 
in  these  regions.  As  the  primary  branches  and  their  offsets  diverge  from  each 
other,  they  present  somewhat  the  appearance  of  a  bird's  claw;  hence  the  name  of  pes 
anserinus  is  given  to  the  divisions  of  the  facial  nerve  in  and  near  the  parotid  gland. 


1046 


THE  NERVOUS  SYSTEM 


In  the  internal  auditory  meatus 


Branches  of  Communication  (Fig.  677). — The  communications  of  the  facial 
nerve  may  be  thus  arranged: 

'  With  the  auditory  nerve.  The  pars 
intermedia,  which  is  between  the 
facial  and  auditory,  gives  branches 
to  both.  The  branch  given  to  the 
auditory  accompanies  it  for  a  certain 
distance,  and  then  departs  from  it  to 
join  the  geniculate  ganglion. 

With  the  auditory  as  explained  above. 

With  Meckel's  ganglion  by  the  large 
superficial  petrosal  nerve. 

With  the  otic  ganglion  by  the  small 
superficial  petrosal  nerve. 

With  the  sympathetic  on  the  middle 
meningeal  artery  by  the  external 
superficial  petrosal  nerve. 

With  the  auricular  branch  of  the  pneu- 
mogastric. 

With  the  glosso-pharyngeal. 

With  the  pneumogastric. 

With  the  auricularis  magnus. 

With  the  auriculo-temporal. 

With  the  small  occipital. 

With  the  three  divisions  of  the  fifth. 

With  the  superficial  cervical. 


From  the  geniculate  ganglion 


In  the  Fallopian  aqueduct     . 

At  its  exit  from  the  stylo-mastoid 
foramen   .  .  .  .  . 

Behind  the  ear    .  .  .  . 

On  the  face  .  .  .  . 

In  the  neck  .  .  .  . 


In  the  internal  auditory  meatus  some  minute  filaments  pass  between  the  facial 
and  auditory  nerves. 

Opposite  the  hiatus  Fallopii,  the  gangliform  enlargement  on  the  facial  nerve 
communicates  with  Meckel's  ganglion  by  means  of  the  large  superficial  petrosal 
nerve,  which  forms  its  motor  root;  with  the  otic  ganglion,  by  the  small  superficial 
petrosal  nerve;  and  with  the  sympathetic  filaments  accompanying  the  middle 
meningeal  artery,  by  the  external  petrosal  nerve  (Bidder).  From  the  gangliform 
enlargement,  according  to  Arnold,  a  twig  is  sent  back  to  the  auditory  nerve.  Just 
before  the  facial  nerve  emerges  from  the  stylo-mastoid  foramen  it  generally  receives 
a  twig  of  communication  from  the  auricular  branch  of  the  pneumogastric. 

After  its  exit  from  the  stylo-mastoid  foramen,  it  sends  a  twig  to  the  glosso- 
pharyngeal, another  to  the  pneumogastric  nerve,  and  communicates  with  the  great 
auricular  branch  of  the  cervical  plexus,  with  the  auriculo-temporal  branch  of  the 
inferior  maxillary  nerve  in  the  parotid  gland,  with  the  small  occipital  nerve 
behind  the  ear,  on  the  face  with  the  terminal  branches  of  the  three  divisions  of 
the  fifth,  and  in  the  neck  with  the  transverse  cervical. 

Branches  of  Distribution  (Fig.  677). — ^The  branches  of  distribution  of  the 
facial  nerves  may  be  thus  arranged : 

f  Tympanic,  to  the  Stapedius  muscle. 
•-  Chorda  tympani. 
Posterior  Auricular. 


Within  the  aquaeductus  Fallopii 


At  its  exit  from  the  stylo-mastoid 
foramen  .  .  .  .  . 


On  the  face 


Digastric. 

Stylo-hyoid. 

f  Temporal. 
f  Temporo-facial   j  Malar. 
J  I  Infraorbital. 

f  Buccal. 
Supram  axillary. 
Inframaxillarv. 


THE  SEVENTH    OB    FACIAL    NERVE 


1047 


The  branches  of  the  two  terminal  divisions  form  the  parotid  plexus  {^plexus  paro- 
iideus) . 

The  Tympanic  Branch  (n.  5topec?fM5)  (Fig.  677). — The  tympanic  brancli  arises 
from  the  nerve  opposite  the  pyramid;  it  passes  through  a  small  canal  in  the 
pyramid  and  supplies  the  Stapedius  muscle. 

The  Chorda  Tympani  (Figs.  671,  676,  and  677). — The  chorda  tympani  is  given 
off  from  the  facial  as  it  passes  vertically  downward  at  the  back  of  the  tympanum, 
about  a  quarter  of  an  inch  before  its  exit  from  the  stylo-mastoid  foramen.  It 
passes  from  below  upward  and  forward  in  a  distinct  canal,  and  enters  the  cavity 
of  the  tympanum  through  an  aperture  {iter  chordae  posterius)  on  its  posterior  wall 
between  the  opening  of  the  mastoid  cells  and  the  attachment  of  the  membrana 
tympani, and  becomes  invested  with  mucous  membrane.  It  passes  forward  through 
the  cavity  of  the  tympanum,  between  the  fibrous  and  mucous  layers  of  the  mem- 
brana tympani,  and  over  the  handle  of  the  malleus,  emerging  from  that  cavity 


To  Auditory 


Vidinn, 
Large  Deep  Petromxl 


Digastric 
Stylo-hyoid' 


Supramaxillary 
Inframaxillary 


Fig.  677. — Plan  of  the  facial  nerve. 


through  a  foramen  at  the  inner  end  of  the  Glaserian  fissure,  which  is  called  the 
canal  of  Hugmer  {iter  chordae  anterius).  It  then  descends  between  the  two 
Pterygoid  muscles,  meets  the  lingual  nerve  at  an  acute  angle,  and  accompanies 
it  to  the  submaxillary  gland ;  part  of  it  then  joins  the  submaxillary  ganglion ;  the 
rest  is  continued  onward  through  the  muscular  substance  of  the  tongue  to  the 
mucous  membrane  covering  its  anterior  two-thirds.  A  few  of  its  fibres  probably 
pass  through  the  submaxillary  ganglion  to  the  sublingual  gland.  Before  joining 
the  lingual  nerve  it  receives  a  small  communicating  branch  from  the  otic  ganglion. 
As  already  stated,  the  chorda  tympani  nerve  is  by  many  regarded  as  the  con- 
tinuation of  the  pars  intermedia  of  Wrisberg. 

The  Posterior  Auricular  Nerve  {n.  auricularis  posterior)  (Figs.  634, 677,  and  678) . — 
The  posterior  auricular  nerve  arises  close  to  the  stylo-mastoid  foramen,  and  passes 
upward  in  front  of  the  mastoid  process  and  between  the  mastoid  process  and  the 
external  ear,  where  it  is  joined  by  a  filament  from  the  auricular  branch  of  the 
pneumogastric  (Fig.  684),  and  communicates  with  the  mastoid  branch  of  the  great 


1048 


THE  NERVOUS   SYSTEM 


auricular  and  with  the  small  occipital.  As  it  ascends  between  the  external  auditory 
meatus  and  the  mastoid  process  it  divides  into  two  branches,  the  auricular  and 
the  occipital  branches. 

The  Auricular  Branch  supplies  the  Retrahens  auriculam  and  the  small  muscles 
on  the  cranial  surface  of  the  pinna. 

The  Occipital  Branch  {ramus  occipitalis),  the  larger,  passes  backward  along  the 
superior  curved  line  of  the  occipital  bone,  and  supplies  the  occipital  portion  of  the 
Occipito-frontalis. 

The  Digastric  Branch  of  the  Facial  Nerve  (ramus  digastricus) . — The  digastric 
branch  usually  arises  by  a  common  trunk  with  the  Stylo-hyoid  branch;  it  divides 
into  several  filaments,  which  supply  the  posterior  belly  of  the  Digastric;  one  of 
these  perforates  that  muscle  to  join  the  glosso-pharyngeal  nerve  {ramus  anasto- 
unoticus  cum  n.  glossopharyngeo) . 


Tenninationa 
of  supratrochlear. 

of  infratrochlear 
of  nasal. 


Fig.  678. — The  nerves  of  the  scalp,  face,  and  side  of  the  neck. 

The  Stylo-hyoid  Branch  (ramus  stylohyoideus). — The  stylo-hyoid  branch  is  a 
long,  slender  branch,  which  passes  inward,  entering  the  Stylo-hyoid  muscle  about 
its  middle. 

The  Temporo-facial  Division  (Figs.  677  and  678). — The  temporo-facial,  the  larger 
of  the  two  terminal  branches  of  the  facial,  passes  upward  and  forward  through 


THE   SEVENTH    OR    FACIAL    NERVE  1049 

the  parotid  gland,  crosses  the  external  carotid  artery  and  temporo-maxillary  vein, 
and  passes  over  the  neck  of  the  condyle  of  the  jaw,  being  connected  in  this  situation 
with  the  auriculo-temporal  branch  of  the  inferior  maxillary  nerve,  and  divides 
into  branches  which  are  distributed  over  the  temple  and  upper  part  of  the  face; 
these  are  divided  into  three  sets — temporal,  malax,  and  infraorbital. 

The  Temporal  Branches  {rami  temporales)  cross  the  zygoma  to  the  temporal 
region,  supplying  the  Attrahens  and  Attollens  auriculam  muscles,  and  join  with 
the  temporal  branch  of  the  temporo-malar  division  of  the  superior  maxillary, 
and  with  the  auriculo-temporal  branch  of  the  inferior  maxillary.  The  more  ante- 
rior branches  supply  the  frontal  portion  of  the  Occipito-frontalis,  the  Orbicularis 
palpebrarum,  and  Corrugator  supercilii  muscles,  joining  with  the  supraorbital 
an(l  lachrymal  branches  of  the  ophthalmic. 

The  Malar  Branches  (rami  zygomatici)  pass  across  the  malar  bone  to  the  outer 
angle  of  the  orbit.  Where  they  supply  the  Orbicularis  palpebrarum  muscle,  join- 
ing with  filaments  from  the  lachrymal  nerve;  others  supply  the  lower  eyelid, 
joining  with  filaments  of  the  malar  branch  (subcutaneous  malae)  of  the  superior 
maxillary  nerve. 

The  Infraorbital  Branches  (rami  huccales) ,  of  larger  size  than  the  rest  of  the  malar 
branches,  pass  horizontally  forward  to  be  distributed  between  the  lower  margin  of 
the  orbit  and  the  mouth.  The  superficial  branches  run  beneath  the  skin  and 
above  the  superficial  muscles  of  the  face,  which  they  supply;  some  branches  are 
distributed  to  the  Pyramidalis  nasi,  joining  at  the  inner  angle  of  the  orbit  with  the 
infratrochlear  and  nasal  branches  of  the  ophthalmic.  The  deep  branches  pass 
beneath  the  Zygomatici  and  the  Levator  labii  superioris,  supplying  the  Levator 
anguli  oris,  the  Levator  labii  superioris  alaeque  nasi  and  the  small  muscles  of  the 
nose,  and  form  a  plexus,  infraorbital  plexus,  by  joining  with  the  branches  of  the 
infraorbital  branch  of  the  superior  maxillary  nerve  and  the  buccal  branches  of 
the  cervico-facial. 

The  Cervico-facial  Division. — The  cervico-facial  division  of  the  facial  nerve 
passes  obliquely  downward  and  forward  through  the  parotid  gland,  crossing  the 
external  carotid  artery.  In  this  situation  it  is  joined  by  branches  from  the  great 
auricular  nerve.  Opposite  the  angle  of  the  lower  jaw  it  divides  into  branches 
which  are  distributed  on  the  lower  half  of  the  face  and  upper  part  of  the  neck. 
These  may  be  divided  into  three  sets — buccal,  supramaxillary,  and  inframaxillary. 

The  Buccal  Branches  (rami  huccales)  cross  the  Masseter  muscle.  They  supply 
the  Buccinator  and  Orbicularis  oris,  and  join  with  the  infraorbital  branches  of 
the  temporo-facial  division  of  the  nerve,  and  with  filaments  of  the  buccal  branch 
of  the  inferior  maxillary  nerve. 

The  Supramaxillary  or  Supramandibular  Branch  (ramus  marginalis  mandibulae) 
passes  forward  beneath  the  Platysma  and  Depressor  anguli  oris,  supplying  the 
muscles  of  the  lower  lip  and  chin,  and  communicating  with  the  mental  branch  of 
the  inferior  dental  nerve. 

The  Inframaxillary,  Inframandibular  or  Cervical  Branch  (ramu^  colli)  runs  for- 
ward beneath  the  Platysma,  and  forms  a  series  of  arches  across  the  side  of  the 
neck  over  the  suprahyoid  region.  A  branch  descends  vertically  to  join  with  the 
superficial  cervical  nerve  from  the  cervical  plexus;  others  supply  the  Platysma. 

Surgical  Anatomy. — The  facial  nerve  is  more  frequently  paralyzed  than  any  of  the  other 
of  the  cranial  nerves.  The  paralysis  may  depend  either  upon  (1)  central  causes — i.  e.,  blood-clots 
or  intracranial  tumors  pressing  on  the  nerve  before  its  entrance  into  the  internal  auditory  meatus. 
It  is  also  one  of  the  nerves  involved  in  bulbar  paralysis.  Or  (2)  it  may  be  paralyzed  in  its  pass- 
age through  the  petrous  bone  by  damage  due  to  middle-ear  disease  or  by  fractures  of  the  base. 
Or  (3)  it  may  be  affected  at  or  after  its  exit  from  the  stylo-mastoid  foramen.  This  is  commonly 
known  as  BelVs  paralysis.  It  may  be  due  to  exposure  to  cold  or  to  injury  of  the  nerve,  either 
from  accidental  wounds  of  the  face  or  during  some  surgical  operation,  as  removal  of  parotid 
tumors,  opening  of  abscesses,  or  operations  on  the  lower  jaw. 


1050  ^^^  NERVOUS  SYSTEM 

When  the  cause  is  central,  the  sixth  nerve  is  usually  paralyzed  as  well,  and  there  is  also  hemi- 
plegia on  the  opposite  side.  In  these  cases  the  electric  reactions  are  the  same  as  in  health; 
whereas,  when  the  paralysis  is  due  to  a  lesion  in  the  course  of  the  nerve,  the  reactions  of  degenera- 
tion develop,  \^'hen  the  nerve  is  paralyzed  in  the  petrous  bone,  in  addition  to  the  paralysis  of  the 
muscles  of  expression,  there  is  loss  of  taste  in  the  anterior  part  of  the  tongue,  and  the  patient  is 
unable  to  recognize  the  difference  between  bitters  and  sweets,  acids  and  salines,  from  involvement 
of  the  chorda  tympani.  The  mouth  is  dry,  because  the  salivary  glands  are  not  secreting;  the  sense 
of  hearing  is  affected  from  paralysis  of  the  Stapedius,  but  there  is  not  hemiplegia.  When  the 
cause  of  the  paralysis  is  from  fracture  of  the  base  of  the  skull,  the  auditory  nerve  and  the  petrosal 
nerves,  which  are  connected  with  the  intumescentia  ganglioformis,  are  also  involved.  When  the 
injury  to  the  nerve  is  after  its  exit  from  the  stylo-mastoid  foramen,  all  the  muscles  of  expression, 
except  the  Levator  palpebrae,  together  with  the  posterior  belly  of  the  Digastric  and  Stylo-hyoid, 
are  paralyzed.  There  is  smoothness  of  the  forehead,  and  the  patient  is  unable  to  frown;  the 
eyelids  cannot  be  closed,  and  the  lower  lid  droops,  so  that  the  punctum  is  no  longer  in  contact 
with  the  globe,  and  the  tears  run  down  the  cheek;  there  is  smoothness  of  the  cheek  and  loss  of 
the  naso-labial  furrow;  the  nostril  of  the  paralyzed  side  cannot  be  dilated;  the  mouth  is  drawn 
to  the  sound  side,  and  there  is  inability  to  whistle;  food  collects  between  the  cheek  and  gum 
from  paralysis  of  the  Buccinator. 

The  facial  nerve  is  at  fault  in  cases  of  so-called  histrionic  spasm,  which  consists  in  an  almost 
constant  and  uncontrollable  twitching  of  the  muscles  of  the  face.  This  twitching  is  sometimes 
so  severe  as  to  cause  great  discomfort  and  annoyance  to  the  patient  and  to  interfere  with  sleep, 
and  for  its  relief  the  facial  nerve  has  been  stretched.  The  operation  is  performed  by  making 
an  incision  behind  the  ear  from  the  root  of  the  mastoid  process  to  the  angle  of  the  jaw.  The 
parotid  is  turned  forward,  and  the  dissection  carried  along  the  anterior  border  of  the  Sterno- 
mastoid  muscle  and  mastoid  process  until  the  upper  border  of  the  posterior  belly  of  the  Digas- 
tric is  found.  The  nerve  is  parallel  to  this  on  about  a  level  with  the  middle  of  the  mastoid  process. 
When  found,  the  nerve  may  be  stretched  by  passing  a  blunt  hook  beneath  it  and  pulling  it 
forward  and  outward.  Too  great  force  must  not  be  used,  for  fear  of  permanent  injury  to  the 
nerve.  In  facial  palsy  of  extracerebral  origin  it  may  be  advisable  to  expose  the  nerve,  cut  it 
across,  and  anastomose  the  distal  end  of  the  paralyzed  nerve  to  the  spinal  accessory,  or,  better, 
to  the  hypoglossal  nerve  (facio-accessory  anastomosis  or  facio-hypoglossal  anastomosis).  The 
idea  was  first  proposed  by  Ballance,  and  has  been  put  in  practice  by  Ballance  and  Stewart, 
Keen,  Gushing,  Faure,  Kennedy  and  others. 

THE  EIGHTH  OR  AUDITORY  NERVE  (N.  AOUSTIOUS)   (Fig.  679). 

The  eighth  or  auditory  nerve  or  Portio  Mollis  is  the  special  nerve  of  the  sense 
of  hearing,  being  distributed  exclusively  to  the  internal  ear.  It  is  soft  in  texture; 
hence  the  name,  fortio  mollis,  and  is  destitute  of  neurilemma. 

The  Origin  of  the  Eighth  Nerve. — The  eighth  nerve  consists  of  two  sets  of 
fibres,  which,  although  differing  in  their  central  connections,  are  both  concerned  in 
the  transmission  of  afferent  impulses  from  the  internal  ear  to  the  medulla  and  pons, 
and  from  there,  by  means  of  new  fibres  which  arise  from  collections  of  gray  matter 
in  these  structures,  to  the  cerebrum  and  cerebellum.  One  set  of  fibres  forms  the 
vestibular  root,  another  set  forms  the  cochlear  root  of  the  nerve.  At  its  con- 
nection with  the  brain  the  eighth  nerve  occupies  the  groove  between  the  pons 
and  medulla,  where  it  is  situated  between  the  restiform  body,  which  is  behind, 
and  the  seventh  nerve,  which  is  in  front. 

Vestibular,  Nexal  or  Ventral  Root  (radix  vestibularis)  (Fig.  613). — The  fibres  of  this 
root  enter  the  medulla  to  the  inner  side  of  those  of  the  cochlear  root,  and  pass 
between  the  restiform  body,  which  is  to  their  outer  side,  and  the  inferior  root  of  the 
fifth,  which  lies  to  their  inner  side.  They  then  divide  into  an  ascending  and  a 
descending  set.  The  fibres  of  the  latter  end  by  arborizing  around  the  cells  of  the 
internal  nucleus,  which  is  situated  in  the  trigonum  acustici  in  the  floor  of 
the  fourth  ventricle.  The  ascending  fibres  either  end  in  the  same  manner  or  in  the 
external  nucleus,  which  is  situated  to  the  outer  side  of  the  trigonum  acustici  and 
farther  from  the  ventricular  floor.  It  is  described  as  consisting  of  two  parts,  an 
inner,  the  nucleus  of  Deiters,  and  an  outer,  the  nucleus  of  Bechterew.  Some  of  the 
axones  of  the  cells  of  the  external  nucleus,  and  possibly  also  of  the  internal  nucleus, 
are  continued  upward  through  the  restiform  body  to  the  roof  nuclei  of  the  opposite 


THE   EIGHTH    OB    AUDITORY  NERVE 


1051 


side  of  the  cerebellum,  to  which  also  are  prolonged  other  fibres  of  the  vestibular 
root  without  undergoing  a  relay  in  the  nuclei  of  the  medulla.  A  second  set  of 
fibres  from  the  internal  and  external  nuclei  end  partly  in  the  tegmentum,  while 
the  remainder  ascend  in  the  posterior  longitudinal  bundle  to  arborize  around  the 
nuclei  of  the  oculo-motor  nerve. 

Cochleax,  Dorsal  or  Lateral  Root  {radix  cochlearis)  (Fig.  613). — This  part  of  the 
nerve  is  placed  externally  to  the  vestibular  root.  Its  fibres  end  in  two  nuclei, 
one  of  which,  the  accessory  nucleus,  lies  immediately  in  front  of  the  restiform 
body;  the  other,  the  tuberculum  acusticum,  somewhat  to  its  outer  side. 

The  striae  acusticae  or  medullary  striae  are  the  axones  of  the  cells  of  the  tuber- 
culum acusticum.  They  pass  backward  and  inward  over  the  restiform  body,  and 
across  the  floor  of  the  fourth  ventricle  toward  the  middle  line.  Here  they  dip  into 
the  substance  of  the  pons,  to  end  around  the  cells  of  the  superior  olive  of  the  same 
or  opposite  side.  There  are,  however,  other  fibres,  and  these  are  both  direct  and 
crossed,  which  do  not  arborize  around  the  tegmental  nuclei,  but  pass  into  the  lat- 


FiG.  679. — Distribution  of  the  auditory  nerve.     (Semidiagrammatic.)     (Testut.) 

eral  fillet.  The  cells  of  the  accessory  nucleus  give  origin  to  fibres  which  pass  trans- 
versely in  the  pons  and  constitute  the  trapezium.  The  description  given  as  to  the 
mode  of  ending  of  the  striae  acusticae  is  applicable  to  that  of  the  trapezoid  fibres — 
viz.,  around  the  cells  of  the  superior  olive  or  of  the  trapezoid  nucleus  (which  lies 
ventral  to  the  olive)  of  the  same  or  opposite  side,  while  others,  crossed  or  uncrossed, 
pass  directly  into  the  lateral  fillet. 

If  the  further  connections  of  the  cochlear  nerve  of  one  side,  say  the  left,  are 
considered,  it  is  found  that  they  lie  to  the  outer  side  of  the  main  sensory  tract,  the 
fillet,  and  are  therefore  termed  the  lateral  fillet.  The  fibres  comprising  the  left 
lateral  fillet  arise  in  the  superior  olive  or  trapezoid  nucleus  of  the  same  or  opposite 
side,  while  others  are  the  uninterrupted  fibres  already  alluded  to,  and  these  are 
either  crossed  or  uncrossed,  the  former  being  the  axones  of  the  cells  of  the  right 
accessory  nucleus  or  of  the  cells  of  the  right  tuberculum  acusticum,  while  the  latter 
are  derived  from  the  same  cells  of  the  left  side.  In  the  upper  part  of  the  fillet 
there  is  a  collection  of  nerve-cells,  the  nucleus  of  the  fillet  (fila  anastomotica) ,  around 


1052 


THE  NEBVOUS  SYSTEM 


the  cells  of  which  some  of  the  fibres  arborize,  and  from  the  cells  of  which  axones 
originate  to  continue  upward  the  tract  of  the  lateral  fillet.  The  ultimate  ending 
of  the  left  lateral  fillet  is  partly  in  the  quadrigeminal  bodies  of  the  same  or  opposite 


SchlX. 


Fig.  680. — Diagram  of  the  central  auditory  tract  (direct  or  root-fibre  system):  N.c,  cochlear  nerve;  F.a., 
acoustic  tubercle;  v.K.,  ventral  nucleus;  c.t.,  trapezoid  body;  o.O.,  o.O.,  superior  olives;  R.,  raph6;  Schl.K., 
nucleus  of  the  lemniscus;  o.V..  pregeminum;  Ri.,  cortex,     (Rauber,  after  Held.) 


Fig.  681. — Diagram  of  the  central  auditory  tract  (system  of  the  second  order):  A''.c.,  cochlear  nerve;  v.K., 
ventral  nucleus;  c.t.,  trapezoid  body;  R.,  raph(?;  T.K.,  trapezoid  nucleus;  o.O.,  superior  olive;  T.a.,  acoustic 
tubercle;  S<.a.,  acoustic  striae;  /.<S.K.,  nucleus  of  the  lateral  lemniscus;  Ba.,  prepeduncle;  Bat.,  decussation  of 
the  prepeduncle;  o.V.,  pregeminum;  n.V.,  post-geminum;  Ri.,  cortex;  Rb.,  cortical  tract.    (Rauber,  after  Held.) 


I 


THE  EIGHTH   OB    AUDITORY  NERVE 


1053 


side,  while  the  remainder  of  the  fibres  ascend  in  the  posterior  Hmb  of  the  internal 
capsule  to  reach  the  first  and  perhaps  the  second  left  temporal  convolution. 

The  auditory  nerve  contains  a  few  afferent  fibres  which  arise  in  the  quadrigem- 
inal  bodies,  the  nucleus  of  the  lateral  fillet,  trapezoid  nucleus,  and  superior  olive. 

The  auditory  nerve  after  leaving  the  medulla  passes  forward  across  the  poste- 
rior border  of  the  middle  peduncle  of  the  cerebellum,  in  company  with  the  facial 
nerve,  from  which  it  is  partly  separated  by  a  small  artery,  the  auditory.  It  then 
enters  the  internal  auditory  meatus  with  the  facial  nerve.  In  the  meatus  it  divides 
into  its  two  branches,  the  inferior  or  cochlear  trunk  (n.  cochleae)  and  the  superior  or 
vestibular  trunk  (w.  vestihuli).  The  cochlear  trunk  is  a  continuation  of  the  cochlear 
root,  gives  branches  to  the  macula  acustica  of  the  saccule,  and  to  the  ampulla  of 
the  posterior  semicircular  canal,  and  then  passes  through  the  lamina  cribrosa 
to  the  labyrinth.  The  cochlear  nerve  is  distributed  to  the  modiolus  and  osseous 
spiral  lamina,  and  is  finally  distributed  to  the  organ  of  Corti.     The  vestibular 


mmm "^ 

TJL. 

Fig.  682. — Diagram  of  the  central  auditory  tract  (recurrent  system'):  v.K.,  ventral  nucleus;  c.t.,  trapezoid 
body;  R.,  rapW;  TK.,  trapezoid  nucleus;  o.O.,  superior  olive;  Ta.,  acoustic  tubercle;  Sia.,  acoustic  striae;  S.K., 
nucleus  of  the  lemniscus;  o.  V.,  pregeminum;  n.  F.,  post-geminum;  fli.,  coterx.     (Rauber,  after  Held.) 

trunk  is  a  continuation  of  the  vestibular  root.  In  the  internal  meatus  it  receives 
fibres  of  the  pars  intermedia  and  gives  a  branch  to  the  geniculate  ganglion  of 
the  facial  nerve  (Cunningham^  It  divides  into  three  branches,  which  pass 
through  the  lamina  cribrosa  and  are  distributed,  one  to  the  macula  acustica  of 
the  utricle  and  the  ampulla,  one  to  the  superior  semicircular  canal,  and  one  to 
the  external  semicircular  canal.  There  is  a  ganglion  on  the  vestibular  nerve 
called  the  vestibular  ganglion  (ganglion  vestihulare) ,  and  a  ganglion  on  the  cochlear 
nerve,  the  ganglion  of  Corti  (ganglion  spirale).  The  fibres  of  the  auditory  nerve 
proper  arise  in  these  ganglia;  the  vestibular  fibres  in  the  ganglion  vestibulare; 
the  cochlear  fibres  in  the  ganglion  spirale. 

The  Auditory  Paths  (Figs.  680,  681,  and  682).— There  are  two  auditory 
paths,  the  cochlear  or  central  auditory  path  and  the  vestibular  path. 

The  Cochlear  Path. — ^The  cochlear  path  conducts  impulses  of  hearing.  Such 
impulses  pass  from  the  organ  of  Corti  to  the  ganglion  of  Corti  (ganglion  spirale) 
and  then  by  the  cochlear  fibres  to  the  cochlear  nucleus  in  the  medulla.  The 
path  from  the  nucleus  to  the  cortical  auditory  centre  is  described  as  follows 


1054  THE  NERVOUS  SYSTEM 

by  Santee.^  Impulses  from  the  cochlear  nucleus  "run  either  lateral  and  dorsal 
to  the  restiform  body  and  cross  to  the  opposite  side  through  the  acustic  striae 
and  trapezium,  or  they  run  medial  to  the  restiform  body  and  enter  at  once  into 
the  trapezium.  By  either  course  they  reach  the  lateral  fillet,  and  chiefly  the  oppo- 
site one.  The  lateral  fillets  conduct  the  impulses  to  the  inferior  quadrigeminal 
bodies;  the  inferior  brachia  to  the  internal  geniculate  bodies,  and  the  acustic  radia- 
tion to  the  third  and  fourth  fifths  of  the  superior  temporal  and  to  the  transverse 
temporal  gyri  of  the  cerebrum." 

The  Vestibular  Path. — The  vestibular  path  conducts  impulses  of  equilibrium. 
Impulses  from  the  semicircular  canals,  utricle  and  saccule  pass  by  way  of  the 
vestibular  nerve  to  the  vestibular  nuclei  in  the  floor  of  the  fourth  ventricle  and  a 
spinal  nucleus  of  undetermined  situation.  From  these  nuclei  impulses  pass  to  the 
nuclei  in  the  opposite  side  of  the  cerebellum  by  one  of  two  routes.  Either  by  the 
opposite  medial  fillet  and  fibres  of  the  systems  of  Flechsig  or  through  the  acustico- 
cerebellar  tract  and  fibres  of  the  vestibular  nerve  in  the  restiform  body  to  the 
opposite  cerebellum  (nucleus  fastigii,  nucleus  globosus,  corpus  dentatum,  and 
cerebellar  cortex).^  From  the  cerebellum  impulses  pass  along  the  superior 
peduncle  to  "the  red  nucleus  and  optic  thalamus  of  both  sides  and  thence  to  the 
cortex.  They  may  excite  in  the  cerebellum  impulses  of  equilibration,  which 
descend  to  the  motor  nuclei  of  spinal  nerves  in  the  anterior  horns  of  gray  matter 
by  way  of  the  antero-lateral  descending  cerebellar  tracts"  (Santee). 

Surgical  Anatomy. — The  auditory  nerve  is  frequently  injured,  together  with  the  facial  nerve, 
in  fractures  of  the  middle  fossa  of  the  base  of  the  skull  implicating  the  internal  auditory  meatus. 
The  nerve  may  be  either  torn  across,  producing  permanent  deafness,  it  may  be  bruised  or  it  may 
be  pressed  upon  by  extra vasated  blood  or  inflammatory  exudation,  when  the  deafness  will  in  all 
probability  be  temporary.  The  nerve  may  also  be  injured  by  violent  blows  on  the  head  without 
fracture,  and  deafness  may  follow  loud  explosions  of  dynamite,  etc.,  probably  from  some  lesion 
of  this  nerve,  which  is  more  liable  to  be  injured  than  the  other  cranial  nerves  on  account  of 
its  structure.  The  test  that  the  nerve  is  destroyed  and  that  the  deafness  is  not  due  to  some 
lesion  of  the  auditory  apparatus  is  obtained  by  placing  a  vibrating  tuning-fork  on  the  head. 
The  vibrations  will  be  heard  in  cases  where  the  auditory  apparatus  is  at  fault,  but  not  in  cases 
of  destruction  of  the  auditory  nerve. 

THE  NINTH  OR  GLOSSO-PHARYNGEAL  NERVE  (N.  GLOSSOPHARYNGEUS) 

(Figs.  683,  684,  685). 

The  ninth  or  glosso-pharyngeal  nerve  is  distributed,  as  its  name  implies,  to 
the  tongue  and  pharynx,  being  the  nerve  of  ordinary  sensation  to  the  mucous 

membrane  of  the  pharynx,  fauces,  and  tonsil ;  and  the 
juffuiaraan^.  ncrvc  of  taste  to  all  parts  of  the  tongue  to  which  it  is 

distributed. 

Its  superficial  origin  is  by  three  or  four  filaments, 
closely  connected  together,  from  the  upper  part  of  the 
medulla  oblongata,  in  the  groove  between  the  olivary 
and  restiform  body  (Fig.  683).  Its  deep  origin  (Fig. 
613)  may  be  traced  through  the  fasciculi  of  the  lateral 
tract  to  three  different  sources:  (1)  some  of  the  fibres 
may  be  traced  to  a  nucleus  of  gray  matter  at  the  lower 
Fig.  683— Origin,  ganRiia,  and    part  of  the  floor  of  the   fourth  vcntriclc  beneath  the 

communicationof  the  ninth,  tenth,     •     i?      •        p  /r.\      ,^  i       j^  11  1  •    j. 

and  eleventh  cranial  nerves.  mtcrior  lovea;  (2)  othcrs  may  DC  traced  downward  mto 

the  funiculus  solitarius,  a  rounded  bundle  of  fibres  in  the 
lower  part  of  the  medulla,  commencing  immediately  above  the  decussation  of  the 
pyramids  (these  fibres  have  not  been  distinctly  traced  to  cells);  (3)  a  third  set  of 

1  Anatomy  of  the  Brain  and  Spinal  Cord.  *  Sante3,  loc.  cit. 


THE  NINTH    OR    GL08SO- PHARYNGEAL    NERVE 


1055 


Fig.  684. — Plan  of  the  glosso-pharyngeal,  pneumogastric,  and  spinal  accessory  nerves.      (After  Flower.) 


1056  THE  NERVOUS  SYSTEM 

fibres  takes  origin  from  the  cells  of  the  nucleus  ambiguus.  This  nucleus  is 
situated  Sv^me  distance  from  the  floor  of  the  fourth  ventricle  and  lies  slightly 
internal  to  the  inferior  fovea.  It  gives  origin  to  the  motor  branches  of  the  glosso- 
pharyngeal and  vagus,  and  to  the  bulbar  part  of  the  spinal  accessory.  The  real 
origin  of  the  sensory  fibres  of  the  glosso-pharyngeal  must  be  looked  for  in  the 
jugular  and  petrosal  ganglia  which  are  developed  from  the  neural  crest. 

From  its  superficial  origin  it  passes  outward  across  the  flocculus,  and  leaves  the 
skull  at  the  central  part  of  the  jugular  foramen,  in  a  separate  sheath  of  the  dura 
mater,  external  to  and  in  front  of  the  pneumogastric  and  spinal  accessory  nerves 
(Fig.  685).  In  its  passage  through  the  jugular  foramen  it  grooves  the  lower 
border  of  the  petrous  portion  of  the  temporal  bone,  and  at  its  exit  from  the  skull 
passes  forward  between  the  jugular  vein  and  internal  carotid  artery,  and  descends 
in  front  of  the  latter  vessel,  and  beneath  the  styloid  process  of  the  temporal  bone 
and  the  muscles  connected  with  it,  to  the  lower  border  of  the  Stylo-pharyngeus 
muscle.  The  nerve  now  curves  inward,  forming  an  arch  on  the  side  of  the  neck, 
and  lying  upon  the  Stylo-pharyngeus  muscle  and  the  Middle  constrictor  of  the 
pharynx.  It  then  passes  beneath  the  Hyoglossus  muscle,  and  is  finally  distributed 
to  the  mucous  membrane  of  the  fauces  and  base  of  the  tongue,  and  the  mucous 
glands  of  the  mouth  and  tonsil. 

In  passing  through  the  jugular  foramen  the  nerve  presents,  in  succession,  two 
gangliform  enlargements.  The  superior  and  smaller  is  called  the  jugular  ganglion ; 
the  inferior  and  larger,  the- petrous  ganglion  or  the  ganglion  of  Andersch. 

The  Superior  or  Jugular  Ganglion  (Ganglion  Superius  n.  Glossopharsmgei) 

(Fig.  684). 

The  superior  or  jugular  ganglion  is  situated  in  the  upper  part  of  the  groove  in 
which  the  nerve  is  lodged  during  its  passage  through  the  jugular  foramen.  It  is 
of  very  small  size,  and  involves  only  the  lower  part  of  the  trunk  of  the  nerve. 
It  is  usually  regarded  as  a  segmentation  from  the  lower  ganglion. 

The  Inferior  or  Petrous  Ganglion  (Ganglion  Petrosum  n.  Glossopharjmgei) 

(Figs.  683  and  684). 

The  inferior  or  petrous  ganglion  is  situated  in  a  depression  in  the  lower  border 
of  the  petrous  portion  of  the  temporal  bone;  it  is  larger  than  the  superior  ganglion 
and  involves  the  whole  of  the  fibres  of  the  nerve.  From  this  ganglion  arise 
those  filaments  which  connect  the  glosso-pharyngeal  with  the  pneumogastric  and 
sympathetic  nerves. 

Branches  of  Communication  (Fig.  684). — The  branches  of  communication 
are  with  the  pneumogastric,  sympathetic,  and  facial. 

The  branches  to  the  pneumogastric  are  two  filaments,  arising  from  the  petrous 
ganglion,  one  of  which  passes  to  the  auricular  branch  of  the  pneumogastric,  and 
one  to  the  upper  ganglion  of  the  pneumogastric. 

The  branch  to  the  sympathetic,  also  arising  from  the  petrous  ganglion,  is  con- 
nected with  the  superior  cervical  ganglion. 

The  branch  of  communication  with  the  facial  perforates  the  posterior  belly  of 
the  Digastric  muscle.  It  arises  from  the  trunk  of  the  nerve  below  the  petrous 
ganglion,  and  joins  the  facial  just  after  its  exit  from  the  stylo-mastoid  foramen. 

Branches  of  Distribution  (Fig.  684).— The  branches  of  distribution  are  the 
tympanic,  carotid,  pharyngeal,  muscular,  tonsillar,  and  lingual. 

The  Tympanic  Branch  or  Jacobson's  Nerve  (n.tympanicus). — The  tympanic  branch 
or  Jacobson's  nerve  arises  from  the  petrous  ganglion,  and  enters  a  small  bony 
canal  in  the  lower  surface  of  the  petrous  portion  of  the  temporal  bone,  the  lower 


THE    TENTH    OB    PNEUMOGASTBIC  NEBVE  1057 

opening  of  which  is  situated  on  the  bony  ridge  which  separates  the  carotid  canal 
from  the  jugular  fossa.  It  ascends  to  the  tympanum,  enters  that  cavity  by  an 
aperture  in  its  floor  close  to  the  inner  wall,  and  divides  into  branches  which  are 
contained  in  grooves  upon  the  surface  of  the  promontory.  These  branches  form 
a  tympanic  plexus  (plexus  tympanicus).  This  plexus  gives  off  (1)  the  greater 
part  of  the  small  superficial  petrosal  nerve  (Fig.  677) ;  (2)  a  branch  to  join  the 
great  superficial  petrosal  nerve;  and  (3)  branches  to  the  tympanic  cavity,  all  of 
which  will  be  described  in  connection  with  the  anatomy  of  the  ear. 

The  Carotid  Branches  (n.  caroticotympanicus  superior  and  n.  caroticotympanicus 
inferior). — The  carotid  branches  descend  along  the  trunk  of  the  internal  carotid 
artery  as  far  as  its  commencement,  communicating  with  the  pharyngeal  branch 
of  the  pneumogastric  and  with  branches  of  the  sympathetic. 

The  Pharyngeal  Branches  (rami  pharyngei)(F[g.684). — The  pharyngeal  branches 
are  three  or  four  filaments  which  unite  opposite  the  Middle  constrictor  of  the 
pharynx  with  the  pharyngeal  branches  of  the  pneumogastric  and  sympathetic 
nerves  to  form  the  pharjmgeal  plexus,  branches  from  which  perforate  the  muscular 
coat  of  the  pharynx  to  supply  the  muscles  and  mucous  membrane. 

The  Muscular  Branch  (ramu^  stylopharyngeus). — The  muscular  branch  is  dis- 
tributed to  the  Stylo-pharyngeus  muscle. 

The  Tonsillar  Branches  (rami  tonsillares). — The  tonsillar  branches  supply  the 
tonsil,  forming  a  plexus  (circulus  tonsillaris)  around  this  body,  from  which 
branches  are  distributed  to  the  soft  palate  and  fauces,  where  they  communicate 
with  the  palatine  nerves. 

The  Lingual  Branches  (rami  linguales). — The  lingual  branches  are  two  in  num- 
ber: one  supplies  the  circumvallate  papillae  and  the  mucous  membrane  covering 
the  surface  of  the  base  of  the  tongue;  the  other  perforates  its  substance,  and 
supplies  the  mucous  membrane  and  follicular  glands  of  the  posterior  one-third 
of  the  tongue  and  communicates  with  the  lingual  nerve. 

The  Gustatory  Path. — The  impressions  of  taste  reach  the  glosso-pharyngeal 
nucleus  in  the  medulla  in  two  ways.  From  the  posterior  one-third  of  the  tongue 
and  from  the  palate  they  reach  the  nucleus  by  the  ninth  nerve.  From  the  anterior 
two-thirds  of  the  tongue  impulses  of  taste  are  conveyed  by  the  chorda  tympani 
and  pars  intermedia.  From  the  glosso-pharyngeal  nucleus  gustatory  impressions 
pass  by  way  of  the  medial  fillet  to  the  optic  thalamus  of  the  opposite  side,  and 
from  the  optic  thalamus  through  the  inferior  lamina  of  the  internal  capsule  to  the 
gyrus  hippocampi,  where  the  cortical  gustatory  centre  is  situated. 

Surgical  Anatomy. — Injury  may  produce  hemorrhage  about  the  roots  of  the  nerve.  Bergmann 
reported  such  a  case.  The  patient  died  from  oedema  of  the  glottis  after  presenting  evidences 
of  disorder  of  speech  and  difficulty  in  swallowing. 

THE  TENTH  OR  PNEUMOGASTRIC  NERVE  (N.  VAGUS)  (Figs.  683,684,  685). 

The  tenth  or  pneumogastric  nerve  has  a  more  extensive  distribution  than  any 
of  the  other  crainal  nerves,  passing  through  the  neck  and  thorax  to  the  upper  part 
of  the  abdomen.  It  is  composed  of  both  motor  and  sensory  fibres.  It  supplies 
the  organs  of  voice  and  respiration  with  motor  and  sensory  fibres,  and  the  pharynx, 
oesophagus,  stomach,  and  heart  with  motor  fibres.  Its  superficial  origin  (Fig.  683) 
is  by  eight  or  ten  filaments  from  the  groove  between  the  olivary  and  the  restiform 
body  below  the  glosso-pharyngeal;  its  deep  origin  (Fig.  613)  may  be  traced  through 
the  fasciculi  of  the  medulla  to  a  nucleus  of  gray  matter,  the  nucleus  vagi,  at  the  lower 
part  of  the  floor  of  the  fourth  ventricle  beneath  the  ala  cinerea  below  and  continu- 
ous with  the  nucleus  of  origin  of  the  glosso-pharyngeal.  In  addition  to  this  a  few 
fibres  pass  into  the  funiculus  solitarius,  and  others  into  the  nucleus  ambiguus  or 

67 


1058 


THE   NERVOUS  SYSTEM 


Qlosso-phaiynaeal.  v 

Pneumogastric.   ~-~, 

Spinal  accessory. 


accessory  vagal  nucleus.    The  real  origin  of  the  sensory  fibres  of  the  vagus  is  to  be 
found  in  the  cells  of  the  ganglia  on  the  nerve — viz.,  the  ganglion  of  the  root  and 

the  ganglion  of  the  trunk.  The 
filaments  become  united  and 
form  a  flat  cord,  which  passes 
outward  beneath  the  flocculus 
to  the  jugular  foramen,  through 
which  it  emerges  from  the  cran- 
ium (Fig.  685).  In  passing 
through  this  opening  the  pneu- 
mogastric accompanies  the  spi- 
nal accessory,  being  contained  in 
the  same  sheath  of  dura  mater 
with  it,  a  membranous  septum 
separating  them  from  the  glosso- 
pharyngeal, which  lies  in  front 
(Fig.  685).  The  nerve  in  this 
situation  presents  a  well-marked 
ganglionic  enlargement,  which 
is  called  the  superior  ganglion, 
jugular  ganglion,  or  the  ganglion 
of  the  pneumogastric;  to  it  the 
accessory  part  of  the  spinal  ac- 
cessory nerve  is  connected  by 
one  or  two  filaments.  After  the 
exit  of  the  nerve  from  the  jugular 
foramen  the  nerve  is  joined  by 
the  accessory  portion  of  the 
spinal  accessory,  and  enlarges 
into  a  second  gangliform  swell- 
ing, called  the  inferior  ganglion 
or  the  ganglion  of  the  trunk  of 
the  nerve,  through  which  the 
fibres  of  the  spinal  accessory 
pass  unchanged,  being  prin- 
cipally distributed  to  the  pha- 
ryngeal and  superior  laryngeal 
branches  of  the  vagus;  but  some 
of  the  filaments  from  it  are  con- 
tinued into  the  trunk  of  the 
vagus  below  the  ganglion,  to  be 
distributed  with  the  recurrent 
laryngeal  nerve,  and  probably 
also  with  the  cardiac  nerves. 
The  vagus  nerve  passes  verti- 
cally down  the  neck  within  the 
sheath  of  the  carotid  vessels  lying 
between  the  internal  carotid 
artery  and  the  internal  jugular 
vein  as  far  as  the  thyroid  cartil- 
age, and  then  between  the  same 
vein  and  the  common  carotid  to  the  root  of  the  neck  (Fig.  685).  From  here 
the  course  of  the  nerve  differs  on  the  two  sides  of  the  body. 

On  the  right  side  (Fig.  685)  the  nerve  passes  across  the  subclavian  artery  between 


Fig.  685. — Course  and  distribution  of  the  ninth,  tenth,  and 
eleventh  nerves. 


THE    TENTH    OB    PNEUMOGASTBIC  NERVE  1059 

it  and  the  right  innominate  vein,  and  descends  by  the  side  of  the  trachea  to  the  hack 
part  of  the  root  of  the  hing,  where  it  spreads  out  in  a  plexiform  network,  the  pos- 
terior pulmonary  plexus  (plexus  pulmonalis  posterior),  from  the  lower  part  of  which 
two  corfls  descend  upon  the  oesophagus,  on  which  tube  they  divide,  forming,  with 
branches  from  the  opposite  nerve,  the  oesophageal  plexus  (p/exM5  gulae) ;  below,  these 
branches  are  collected  into  a  single  cord,  which  runs  along  the  back  part  of  the 
oesophagus,  enters  the  abdomen,  and  is  distributed  to  the  posterior  surface  of 
the  stomach,  joining  the  left  side  of  the  solar  plexus,  and  sending  filaments  to  the 
splenic  plexus  and  a  considerable  branch  to  the  coeliac  plexus. 

On  the  left  side  the  pneumogastric  nerve  enters  the  chest  between  the  left  carotid 
and  subclavian  arteries,  behind  the  left  innominate  vein.  It  crosses  the  arch  of 
the  aorta  and  descends  behind  the  root  of  the  left  lung,  forming  the  anterior  pul- 
monary plexus  {plexus  pulvfionalis  anterior),  and  along  the  anterior  surface  of  the 
oesophagus,  where  it  unites  with  the  nerve  of  the  right  side  in  forming  the  plexus 
gulae.  It  passes  to  the  stomach,  distributing  branches  over  the  anterior  surface  of 
that  viscus,  some  extending  over  the  great  cul-de-sac,  and  others  along  the  lesser 
curvature.  Filaments  from  these  branches  enter  the  gastro-hepatic  omentum  and 
join  the  hepatic  plexus. 

The  Ganglion  of  the  Root  of  the  Pneumogastric  Nerve  (Ganglion  Jugulare) 

(Fig.  684). 

The  ganglion  of  the  root  or  the  jugular  ganglion  is  of  a  grayish  color,  circular 
in  form,  about  two  lines  in  diameter,  and  resembles  the  ganglion  on  the  large, 
root  of  the  fifth  nerve. 

Connecting  Branches. — To  this  ganglion  the  accessory  portion  of  the  spinal 
accessory  nerve  is  connected  by  several  delicate  filaments;  it  also  has  a  communi- 
cating twig  with  the  petrous  ganglion  of  the  glosso-pharyngeal,  with  the  facial 
nerve  by  means  of  its  (the  ganglion's)  auricular  branch,  and  with  the  sympa- 
thetic by  means  of  an  ascending  filament  from  the  superior  cervical  ganglion. 

The  Ganglion  of  the  Trunk  of  the  Pneumogastric  Nerve  (Ganglion  Nodosum) 

(Fig.  684). 

The  ganglion  of  the  trunk  or  the  inferior  ganglion  is  a  plexiform  cord,  cylindrical 
in  form,  of  a  reddish  color,  and  about  an  inch  in  length;  it  involves  the  whole  of 
the  fibres  of  the  nerve,  and  passing  through  it  is  the  accessory  portion  of  the  spinal 
accessory  nerve,  which  blends  with  the  pneumogastric  below  the  ganglion,  and  is 
then  principally  continued  into  its  pharyngeal  and  superior  laryngeal  branches. 

Connecting  Branches  (Fig.  684).— This  ganglion  is  connected  with  the  hypo- 
glossal, the  superior  cervical  ganglion  of  the  sympathetic,  and  the  loop  between 
the  first  and  second  cervical  nerves. 

The  branches  of  the  pneumogastric  are — 

T     .1      •       1      r  i  Meningeal. 

In  the  lugular  lossa  .  •     1  a     •     i 


In  the  neck 


In  the  thorax 


•^  Auricular. 
Pharyngeal. 
Superior  laryngeal. 
Recurrent  laryngeal. 
Cervical  cardiac. 
Thoracic  cardiac. 
Anterior  pulmonary. 
Posterior  pulmonary. 
.  Oesophageal. 
In  the  abdomen        .  .  .         Gastric. 


The  Meningeal  Branch  {ramus  meningeus). — The  meningeal  branch  is  a  recurrent 
filament  given  off  from  the  ganglion  of  the  root  in  the  jugular  foramen.    It  passes 


1060  THE  NERVOUS  SYSTEM 

backward,  and  is  distributed  to  the  dura  mater  lining  the  posterior  fossa  of  the 
base  of  the  skull. 

The  Auricular  Branch  or  Arnold's  Nerve  {ramus  auricularis)  (Fig.  684). — The 
auricular  branch  or  Arnold's  nerve  arises  from  the  ganglion  of  the  root,  and  is 
joined  soon  after  its  origin  by  a  filament  from  the  petrous  ganglion  of  the  glosso- 
pharyngeal; it  passes  outward  behind  the  jugular  vein,  and  enters  a  small  canal 
on  the  outer  wall  of  the  jugular  fossa.  Traversing  the  substance  of  the  tem- 
poral bone,  it  crosses  the  aquaeductus  Fallopii  about  two  lines  above  its  termina- 
tion at  the  stylo-mastoid  foramen;  here  it  gives  off  an  ascending  branch,  which 
joins  the  facial;  the  continuation  of  the  nerve  reaches  the  surface  by  passing 
through  the  auricular  fissure  between  the  mastoid  process  and  the  external  audi- 
tory meatus,  and  divides  into  two  branches,  one  of  which  communicates  with  the 
posterior  auricular  nerve,  while  the  other  supplies  the  integument  at  the  back 
part  of  the  pinna  and  the  posterior  part  of  the  external  auditory  meatus. 

The  Pharyngeal  Branch  {ramus  pharyngeus). — The  pharyngeal  branch,  the  prin- 
cipal motor  nerve  of  the  pharynx,  arises  from  the  upper  part  of  the  ganglion  of  the 
trunk  of  the  pneumogastric.  It  consists  principally  of  filaments  from  the  accessory 
portion  of  the  spinal  accessory;  it  passes  across  the  internal  carotid  artery  to  the 
upper  border  of  the  Middle  constrictor  of  the  pharynx,  where  it  divides  into 
numerous  filaments  which  join  with  those  from  the  glosso-pharyngeal,  the  supe- 
rior laryngeal  (its  external  branch),  and  sympathetic,  to  form  the  pharyngeal  plexus 
{plexus  pharyngeus),  from  which  branches  are  distributed  to  the  muscles  and 
mucous  membrane  of  the  pharynx  and  the  muscles  of  the  soft  palate.  From  the 
pharyngeal  plexus  a  minute  filament  is  given  off,  which  descends  and  joins  the 
hypoglossal  nerve  as  it  winds  around  the  occipital  artery. 

The  Superior  Laryngeal  Nerve  {n.  laryngeus  superior)  (Figs.  683,  684,  and  685). — 
It  is  larger  than  the  preceding,  and  arises  from  the  middle  of  the  ganglion  of  the 
trunk  of  the  pneumogastric.  It  consists  principally  of  filaments  from  the  accessory 
portion  of  the  spinal  accessory.  In  its  course  it  receives  a  branch  from  the  supe- 
rior cervical  ganglion  of  the  sympathetic.  It  descends  by  the  side  of  the  pharynx 
behind  the  internal  carotid  artery,  where  it  divides  into  two  branches,  the  external 
and  internal  laryngeal.  This  nerve  is  the  nerve  of  sensation  of  the  larynx,  and 
also  supplies  the  crico-thyroid  muscle.  Exner  has  pointed  out  that  the  superior 
laryngeal  nerve  innervates  to  some  extent  the  muscles  supplied  by  the  inferior 
laryngeal,  and  this  fact  explains  why  division  of  the  inferior  laryngeal  nerve  is  not 
of  necessity  followed  by  complete  paralysis  of  the  muscles  it  supplies. 

The  External  Laryngeal  Branch  of  the  Superior  Larjmgeal  {ramus  externum)  (Fig. 
685) ,  the  smaller,  descends  by  the  side  of  the  larynx,  beneath  the  Sterno-thyroid, 
to  supply  the  Crico-thyroid  muscle.  It  gives  branches  to  the  pharyngeal  plexus 
and  the  Inferior  constrictor,  and  communicates  with  the  superior  cardiac  nerve, 
behind  the  common  carotid. 

The  Internal  Larjmgeal  Branch  of  the  Superior  Larjmgeal  {ramus  internus) 
descends  to  the  opening  in  the  thyro-hyoid  membrane,  through  which  it  passes 
with  the  superior  laryngeal  artery,  and  is  distributed  to  the  mucous  membrane  of 
the  larynx.  A  small  branch  communicates  with  the  recurrent  laryngeal  nerve. 
The  branches  to  the  mucous  membrane  are  distributed,  some  in  front  to  the  epi- 
glottis, the  base  of  the  tongue,  and  the  epiglottidean  glands;  while  others  pass 
backward,  in  the  aryteno-epiglottidean  fold,  to  supply  the  mucous  membrane 
surrounding  the  superior  orifice  of  the  larynx,  as  well  as  the  membrane  which 
lines  the  cavity  of  the  larynx  as  low  down  as  the  vocal  cord.  The  filament  which 
joins  with  the  recurrent  laryngeal  descends  beneath  the  mucous  membrane  on  the 
inner  surface  of  the  thyroid  cartilage,  where  the  two  nerves  become  united. 

The  Inferior  or  Recurrent  Laryngeal  Branch  of  the  Pneumogastric  {n.  laryngeus 
inferior)  (Figs.  684  and  685). — The  inferior  or  recurrent  laryngeal  branch,  so 
called  from  its  reflected  course,  is  the  motor  nerve  of  the  larvnx.     It  arises  on 


I 


THE    TENTH    OR    PNEUMOGASTBIC   NERVE  1061 

the  right  side,  in  front  of  the  subclavian  artery;  winds  from  before  backward 
around  that  vessel,  and  ascends  obliquely  to  the  side  of  the  trachea,  behind 
the  common  carotid  artery  and  behind  or  in  front  of  the  inferior  thyroid  artery. 
On  the  left  side  it  arises  in  front  of  the  arch  of  the  aorta,  and  winds  from 
before  backward  around  the  aorta  at  the  point  where  the  remains  of  the  ductus 
arteriosus  are  connected  with  it,  and  then  ascends  to  the  side  of  the  trachea. 
The  nerve  on  each  side  ascends  in  the  groove  between  the  trachea  and  oesophagus, 
and,  passing  under  the  lower  border  of  the  Inferior  constrictor  muscle,  enters  the 
larynx  behind  the  articulation  of  the  inferior  cornu  of  the  thyroid  cartilage  with 
the  cricoid,  being  distributed  to  all  the  muscles  of  the  larynx  except  the  Crico- 
thyroid. It  communicates  with  the  superior  laryngeal  nerve  and  gives  off  a  few 
filaments  to  the  mucous  membrane  of  the  lower  part  of  the  larynx. 

The  recurrent  laryngeal,  as  it  winds  around  the  subclavian  artery  and  aorta, 
gives  off  several  cardiac  filaments,  which  unite  with  the  cardiac  branches  from 
the  pneumogastric  and  sympathetic.  As  it  ascends  in  the  neck  it  gives  off  oesoph- 
ageal branches,  more  numerous  on  the  left  than  on  the  right  side,  which  supply 
the  mucous  membrane  and  muscular  coat  of  the  oesophagus;  tracheal  branches  to 
the  mucous  membrane  and  muscular  fibres  of  the  trachea;  and  some  pharyngeal 
filaments  to  the  Inferior  constrictor  of  the  pharynx. 

The  Cervical  Cardiac  Branches  {rami  cardiaci  superiores)  (Fig.  684). — The  cer- 
vical cardiac  branches,  two  or  three  in  number,  arise  from  the  pneumogastric,  at 
the  upper  and  lower  part  of  the  neck. 

The  Superior  Branches  are  small,  and  communicate  with  the  cardiac  branches 
of  the  sympathetic.    They  can  be  traced  to  the  great  or  deep  cardiac  plexus. 

The  Inferior  Branches,  one  on  each  side,  arise  at  the  lower  part  of  the  neck, 

just  above  the  first  rib.    On  the  right  side  this  branch  passes  in  front  or  by  the 

'side  of  the  arteria  innominata,  and  communicates  with  one  of  the  cardiac  nerves 

proceeding  to  the  great  or  deep  cardiac  plexus.    On  the  left  side  it  passes  in  front 

of  the  arch  of  the  aorta  and  joins  the  superficial  cardiac  plexus. 

The  Thoracic  Cardiac  Branches  (rami  cardiaci  inferiores)  (Fig.  684) . — The  thoracic 

[cardiac  branches,  on  the  right  side,  arise  from  the  trunk  of  the  pneumogastric 

as  it  lies  by  the  side  of  the  trachea,  and  from  its  recurrent  laryngeal  branch,  but 

on  the  left  side  from  the  recurrent  nerve  only;  passing  inward,  they  terminate 

in  the  deep  cardiac  plexus. 

The  Anterior  Pulmonary  Branches  (Fig.  684). — The  anterior  pulmonary  branches, 
two  or  three  in  number,  and  of  small  size,  are  distributed  on  the  anterior  aspect 
of  the  root  of  the  lungs.  They  join  with  filaments  from  the  sympathetic,  and  form 
the  anterior  pulmonary  plexus  (plexus  pulmonalis  anterior). 

The  Posterior  Pulmonary  Branches(Fig.  684). — The  posterior  pulmonary  branches, 
more  numerous  and  larger  than  the  anterior,  are  distributed  on  the  posterior  aspect 
of  the  root  of  the  lung;  they  are  joined  by  filaments  from  the  third  and  fourth 
(sometimes  also  from  the  first  and  second)  thoracic  ganglia  of  the  sympathetic, 
and  form  the  posterior  pulmonary  plexus  (plexus  pulmonalis  posterior).  Branches 
from  both  plexuses  accompany  the  ramification  of  the  air-tubes  through  the  sub- 
stance of  the  lungs  (rami  bronchiales  anteriores  and  rami  bronchiales  posteriores). 

The  Oesophageal  Branches  (rami  oesophagei). — The  oesophageal  branches  are 
given  off  from  the  pneumogastric  both  above  and  below  the  pulmonary  branches. 
The  lower  are  more  numerous  and  larger  than  the  upper.  They  form,  together 
with  branches  from  the  opposite  nerve,  the  oesophageal  plexus  (plexus  gulae). 
From  this  plexus  branches  are  distributed  to  the  back  of  the  pericardium. 

The  Gastric  Branches  (rami  gastrici)  (Figs.  684  and  685. — The  gastric  branches 
are  the  terminal  filaments  of  the  pneumogastric  nerve.  The  nerve  on  the  right 
side  is  distributed  to  the  posterior  surface  of  the  stomach.  The  right  pneumo- 
gastric sends  branches  to  the  coeliac  plexus  (rami  coeliaci),  to  the  splenic  plexus 
(rami  lienales),  and  to  the  renal  plexus  (rami  renales).     The  nerve  on  the  left 


1062  THE   NEBVOUS   SYSTEM 

side  is  distributed  over  the  anterior  surface  of  the  stomach,  some  filaments  {rami 
hepatici)  passing  across  the  great  cul-de-sac,  and  others  along  the  lesser  curva- 
ture. They  unite  with  branches  of  the  right  nerve  and  with  the  sympathetic, 
some  filaments  passing  through  the  lesser  omentum  to  the  hepatic  plexus. 

Surgical  Anatomy. — The  laryngeal  nerves  are  of  considerable  importance  in  considering 
some  of  the  morbid  conditions  of  the  larynx.  When  the  peripheral  terminations  of  the  superior 
laryngeal  nerve  are  irritated  by  some  foreign  body  passing  over  them,  reflex  .spasm  of  the  glottis 
is  the  result.  When  the  trunk  of  the  same  nerve  is  pressed  upon  by,  for  instance,  a  goitre  or 
an  aneurism  of  the  upper  part  of  the  carotid,  we  have  a  peculiar  dry,  brassy  cough.  When  the 
nerve  is  paralyzed,  we  have  anaesthesia  of  the  mucous  membrane  of  the  larynx,  so  that  foreign 
bodies  can  readily  enter  the  cavity,  and,  in  consequence  of  its  supplying  the  crico-thyroid  muscle, 
the  vocal  cords  cannot  be  made  tense,  and  the  voice  is  deep  and  hoarse.  Paralysis  of  the  supe- 
rior laryngeal  nerves  may  be  the  result  of  bulbar  paralysis,  may  be  a  sequel  to  diphtheria,  when 
both  nerves  are  usually  involved,  or  it  may,  though  less  commonly,  be  caused  by  the  pressure 
of  tumors  or  aneurisms,  when  the  paralysis  is  generally  unilateral.  Irritation  of  the  inferior 
laryngeal  nerves  produces  spasm  of  the  muscles  of  the  larynx.  When  both  the  recurrent 
nerves  are  paralyzed,  the  vocal  cords  are  motionless  in  the  so-called  cadaveric  position^that 
is  to  say,  in  the  position  in  which  they  are  found  in  ordinary  tranquil  respiration — neither  closed 
as  in  phonation,  nor  open  as  in  deep  inspiratory  effort.  When  one  recurrent  nerve  is  paralyzed, 
the  cord  of  the  same  side  is  motionless,  while  the  opposite  cord  crosses  the  middle  line  to  accom- 
modate itself  to  the  affected  one ;  hence  phonation  is  present,  but  the  voice  is  altered  and  weak 
in  timbre.  The  recurrent  laryngeal  nerves  may  be  paralyzed  in  bulbar  paralysis  or  after  diph- 
theria, when  the  paralysis  usually  affects  both  sides;  or  they  may  be  affected  by  the  pressure 
of  aneurisms  of  the  aorta,  innominate  or  subclavian  arteries;  by  mediastinal  tumors;  by  bron- 
chocele;  or  by  cancer  of  the  upper  part  of  the  oesophagus,  when  the  paralysis  is  often  unilat- 
eral.   The  nerve  may  be  accidentally  divided  during  the  operation  for  goitre. 

It  is  a  well-recognized  fact  that  disease  or  injury  of  the  vagus  may  induce  serious  symptoms. 
Bruising  may  cause  such  symptoms;  so  may  injury  of  the  nerve  by  a  stab,  a  bullet,  or  during 
surgical  operations.  Either  accidental  ligation  or  crushing  with  clamp  forceps  is  particularly 
dangerous.  Michaux  accidentally  ligated  the  vagus,  and  the  patient  became  comatose  and 
ceased  to  breathe,  but  was  restored  on  removing  the  ligature.  Tillmanns,  while  removing  a 
cancer,  accidentally  caught  and  crushed  a  portion  of  the  nerve  in  a  clamp,  and  both  pulse  and 
respiration  ceased.  The  clamp  was  removed,  the  patient  was  restored  with  difficulty,  and  the 
nerve  was  sutured.  Recovery  followed.  It  thus  becomes  evident  that  division  of  the  vagus  on 
one  side  is  not,  as  was  so  long  taught,  a  necessarily  fatal  accident;  in  fact,  it  is  sometimes  under- 
taken deliberately  in  removing  tumors  adherent  to  the  nerve.  Division  of  a  nerve  which  has 
been  long  compressed  is  probably  not  so  dangerous  as  division  of  a  healthy  nerve,  as  in  the  former 
case  the  opposite  vagus  has  probably  assumed  some  of  its  colleague's  duties.  A  number  of  cases 
of  deliberate  division  have  been  reported.  Twenty-three  cases  are  referred  to  in  the  system  of 
surgery  by  von  Bergmann  and  Mikulicz,  and  twelve  of  them  died,  but  in  none  of  the  deaths  was 
the  removal  of  the  vagus  the  apparent  cause  of  the  fatality.  The  editor  of  this  American  edition 
of  "Gray"  has  seen  three  cases:  One  was  operated  upon  by  Dr.  W.  Joseph  Hearn,  one  by  Dr. 
Melvin  Franklin,  and  one  by  the  editor.  All  three  recovered,  and  not  one  presented  any 
serious  disturbance,  although  each  had  hoarseness  and  weakness  of  voice. 

One  would  assume  that  after  division  of  the  pneumogastric  below  the  superior  laryngeal  nerve  i 
and  above  the  recurrent  laryngeal  nerve  (the  region  usually  attacked)  that  there  would  be 
paralysis  of  all  the  muscles  of  one  side  of  the  larynx,  except  the  crico-thyroid,  and  wide- 
spread aberration  evinced  by  disturbances  of  the  heart,  stomach,  and  lungs.  As  a  matter  of  fact,^  * 
this  has  not  been  the  case.  It  might  be  and  probably  would  be  the  case,  were  a  healthy  nerve 
divided;  but  the  surgeon  who  deliberately  divides  the  nerve  does  so  during  the  removal  of  a 
tumor  which  has  long  made  pressure.  In  jnost  cases  there  is  no  change  in  the  pulse  orj 
respiration.  In  some  cases  dysphagia  and  pneumonia  arise,  but  they  may  be  due  to  other  causes 
than  pneumogastric  injury  (the  formidable  nature  and  the  duration  of  the  operation — ^thej 
ligation  of  vessels  of  large  size — the  age  of  the  subject). 

Laryngeal  symptoms,  to  a  greater  or  less  degree,  are  always  noted.  The  difference  in  the] 
degree  of  the  palsy  is  explainable  when  we  recall  Exner's  statement  that  the  muscles  supplied] 
by  the  recurrent  laryngeal  also  receive  some  innervation  from  the  superior  laryngeal.  In  fact,] 
Mills  points  out  that  a  portion  of  the  recurrent  laryngeal  has  been  resected  without  completely 
paralyzing  the  muscles  supposed  to  be  supplied  solely  by  the  recurrent  laryngeal.  The  laryngeal  ] 
symptoms  result  from  unilateral  laryngeal  paralysis,  in  which  there  is  paralysis  of  the  muscles  1 
which  open  the  glottis.  The  voice  may  be  lost  or  may  be  hoarse.  Usually,  after  a  time,  this  is, 
to  a  great  extent,  compensated  for  by  the  opposite  vocal  cord,  although  the  voice  may  alway] 
remain  weak,  and  the  patient  will  tire  easily  on  talking.  If  both  pneumogastrics  were  to  bej 
divided  death  would  ensue. 


THE   ELEVENTH    OR    SPINAL    ACCESSORY  NERVE        1063 

THE  ELEVENTH  OR  SPINAL  ACCESSORY  NERVE  (N.  ACCESSORIUS) 

(Figs.  683,  684,  685). 

The  eleventh  or  spinal  accessory  nerve  consists  of  two  parts:  one  the  accessory 
part  to  the  vagus,  and  the  other  the  spinal  portion. 

The  Bulbar  or  Accessory  Part  of  the  Spinal  Accessory  Nerve. 

The  bulbar  or  accessory  part  is  the  smaller  of  the  two.  It  is  accessory  to  the 
vagus.  Its  superficial  origin  (Fig.  683)  is  by  four  or  five  delicate  filaments  from 
the  side  of  the  medulla,  below  the  roots  of  the  vagus.  Its  deep  origin  (Fig.  613) 
may  be  traced  to  a  nucleus  of  gray  matter  at  the  back  of  the  medulla,  dorso-lateral 
to  the  hypo-glossal  nucleus,  and  extending  as  far  down  as  the  intermedio-lateral 
tract  of  the  spinal  cord.  It  passes  outward  to  the  jugular  foramen,  where  it  inter- 
changes fibres  with  the  spinal  portion  or  becomes  united  to  it  for  a  short  distance; 
it  is  also  connected,  in  the  foramen,  with  the  upper  ganglion  of  the  vagus  by  one 
or  two  filaments.  It  then  passes  through  the  foramen  (Fig.  685) ,  and  becoming 
again  separated  from  the  spinal  portion  it  is  continued  over  the  surface  of  the 
ganglion  of  the  trunk  of  the  vagus,  being  adherent  to  its  surface,  and  is  distributed 
principally  to  the  pharyngeal  and  superior  laryngeal  branches  of  the  pneumogastric 
(Fig.  684) .  Through  the  pharyngeal  branch  it  probably  supplies  the  muscles  of 
the  soft  palate.  Some  few  filaments  from  it  are  continued  into  the  trunk  of  the 
vagus  below  the  ganglion,  to  be  distributed  with  the  recurrent  laryngeal  nerve, 
and  probably  also  with  the  cardiac  nerves. 

The  Spinal  Portion  of  the  Spinal  Accessory  Nerve. 

The  spinal  portion  is  firm  in  texture.  Its  superficial  origin  (Fig.  683)  is  by 
several  filaments  or  rootlets  from  the  lateral  tract  of  the  cord,  as  low  down  as 
the  sixth  cervical  nerve.  Its  deep  origin  (Fig.  613)  may  be  traced  to  the  inter- 
medio-lateral tract  of  the  gray  matter  of  the  cord.  The  rootlets  of  origin  join  and 
form  a  trunk  which  ascends  in  the  subdural  space  between  the  ligamentum  den- 
ticulatum  and  the  posterior  roots  of  the  spinal  nerves,  enters  the  skull  through  the 
foramen  magnum,  and  is  then  directed  outward  to  the  jugular  foramen,  through 
which  it  passes,  lying  in  the  same  sheath  as  the  pneumogastric,  but  separated  from 
it  by  a  fold  of  the  arachnoid.  In  the  jugular  foramen  it  receives  one  or  two 
filaments  from  the  accessory  portion.  At  its  exit  from  the  jugular  foramen  it 
passes  into  the  neck  and  becomes  the  external  branch  {ramus  externum)  (Figs.  634, 
684,  and  685).  It  passes  backward,  either  in  front  of-  or  behind  the  internal 
jugular  vein,  and  descends  obliquely  behind  the  Digastric  and  Stylo-hyoid  muscles 
to  the  upper  part  of  the  Sterno-mastoid  muscle.  It  pierces  that  muscle,  and 
passes  obliquely  across  the  posterior  triangle,  to  terminate  in  the  deep  surface  of 
the  Trapezius  muscle.  This  nerve  gives  several  branches  to  the  Sterno-mastoid 
muscle  during  its  passage  through  it,  and  joins  in  its  substance  with  branches 
from  the  second  cervical,  which  supply  the  muscle.  In  the  posterior  triangle  it 
joins  with  the  second  and  third  cervical  nerves,  while  beneath  the  Trapezius  it 
forms  a  sort  of  plexus  with  the  third  and  fourth  cervical  nerves,  and  from  this 
plexus  fibres  are  distributed  to  the  muscle. 

Surgical  Anatomy. — Division  of  the  external  branch  of  the  spinal  accessory  nerve  causes 
paralysis  of  the  Sterno-cleido-mastoid  and  Trapezius  muscles;  not  absolute  paralysis,  for  these 
muscles  also  receive  nerves  from  the  cervical  plexus.  In  cases  of  spasmodic  torticollis  in  which 
all  palliative  treatment  has  failed,  division  or  excision  of  a  portion  of  the  external  branch  of  the 
spinal  accessory  nerve  has  been  suggested  by  Keen.  This  may  be  done  either  along  the  anterior  or 
posterior  border  of  the  Sterno-mastoid  muscle.    The  former  operation  is  performed  by  making 


1064 


THE    NERVOUS  SYSTEM 


an  incision  from  the  apex  of  the  mastoid  process,  three  inches  in  length,  along  the  anterior  border 
of  the  Sterno-mastoid  muscle.  The  anterior  border  of  the  muscle  is  defined  and  pulled  back- 
ward, so  as  to  stretch  the  nerve,  which  is  then  to  be  sought  for  beneath  the  Digastric  muscle, 
about  two  inches  below  the  apex  of  the  mastoid  process.  The  other  operation  consists  in 
making  an  incision  along  the  posterior  border  of  the  muscle,  so  that  the  centre  of  the  incision 
corresponds  to  the  middle  of  this  border  of  the  muscle.  The  superficial  structures  having  been 
divided  and  the  border  of  the  muscle  defined,  the  nerve  is  to  be  sought  for  as  it  emerges  from 
the  muscle  to  cross  the  occipital  triangle.  When  found,  it  is  to  be  traced  upward  through  the 
muscle,  and  a  portion  of  it  is  excised  above  the  point  where  it  gives  off  its  branches  to  the  Sterno- 
mastoid.  In  this  operation  one  of  the  descending  branches  of  the  superficial  cervical  plexus  is 
liable  to  be  mistaken  for  the  nerve. 


THE  TWELFTH  OR  HYPOGLOSSAL  NERVE  (N.  HYPOGLOSSUS^ 

(Figs.  686,  687). 

The  twelfth  or  hypoglossal  nerve  is  the  motor  nerve  of  the  tongue.    Its  super^ 
ficial  origin  is  by  several  filaments,  from  ten  to  fifteen  in  number,  from  the  groove 


To  Dura-mater 


•  To  Ganglion  on  Trunk  of  Vagua 


To  Anterior  Belly  of  Omo-hyoid 


To  Stemo-hyoid 
To  Stemo-thyrotd 
To  posterior  EclUj  of  Omo-hyoid 

Fig.  686. — Plan  of  the  hypoglossal  nerve. 


between  the  pyramidal  and  olivary  bodies  of  the  medulla,  in  a  continuous  line 
with  the  anterior  roots  of  the  spinal  nerves.  Its  deep  origin  can  be  traced  to  a 
nucleus  of  gray  matter  (trigonum  hypoglossi)  on  the  floor  of  the  fourth  ventricle 
(Fig.  613). 

The  filaments  of  this  nerve  are  collected  into  two  bundles,  which  perforate  the 
dura  mater  separately,  opposite  the  anterior  condyloid  foramen,  and  unite  together 
after  their  passage  through  it.     In  those  cases  in  which  the  anterior  condyloid 


THE    TWELFTH   OB    HYPOGLOSSAL   NERVE 


1065 


foramen  in  the  occipital  bone  is  double,  these  two  portions  of  the  nerve  are  sepa- 
rated by  the  small  piece  of  bone  which  divides  the  foramen.  The  nerve  descends 
almost  vertically  to  a  point  corresponding  with  the  angle  of  the  jaw.  It  is  at  first 
deeply  seated  beneath  the  internal  carotid  artery  and  internal  jugular  vein,  and  is 
intimately  connected  with  the  pneumogastric  nerve  (Fig.  687) ;  it  then  passes  for- 
ward between  the  vein  and  artery,  and  lower  down  in  the  neck  becomes  superficial 
below  the  Digastric  muscle.  The  nerve  then  loops  around  the  occipital  artery, 
and  crosses  the  external  carotid  and  its  lingual  branch  below  the  tendon  of  the 
Digastric  muscle.  It  passes  beneath  the  tendon  of  the  Digastric,  the  Stylo-hyoid, 
and  the  Mylo-hyoid  muscles,  lying  between  the  last-named  muscle  and  the  Hyo- 


FiG.  687. — Hypoglossal  nerve,  cervical  plexus,  and  their  branches. 

glossus  (Fig.  687) ,  and  communicates  at  the  anterior  border  of  the  Hyo-glossus 
with  the  lingual  or  gustatory  nerve  (Fig.  686) ;  it  is  then  continued  forward  in  the 
fibres  of  the  Genio-hyoglossus  muscle  as  far  as  the  tip  of  the  tongue,  distributing 
branches  to  its  muscular  substance. 

Branches  of  Communication  (Fig.  686). — The  branches  of  communication  are 
— with  the 


Pneumogastric. 
Sympathetic. 


First  and  Second  Cervical  Nerves. 
Lingual  (gustatory). 


The  first  mentioned  takes  place  close  to  the  exit  of  the  nerve  from  the  skull, 
numerous  filaments  passing  between  the  hypoglossal  and  the  ganglion  of  the  trunk 


1066  THE   NERVOUS  SYSTEM 

of  the  pneuraogastric  through  the  mass  of  connective  tissue  which  here  unites  the 
two  nerves.  It  also  communicates  with  the  pharyngeal  plexus  by  a  minute  filament 
as  it  winds  around  the  occipital  artery. 

The  communication  with  the  sympathetic  takes  place  opposite  the  atlas  vertebra 
by  branches  derived  from  the  superior  cervical  ganglion,  and  in  the  same  situa- 
tion the  nerve  is  joined  by  filaments  derived  from  the  loop  connecting  the  first 
two  cervical  nerves. 

The  communication  with  the  lingual  (gustatory)  takes  place  near  the  anterior 
border  of  the  Hyo-glossus  muscle  by  numerous  filaments  which  ascend  upon  it. 

Branches  of  Distribution  (Fig.  686). — The  branches  of  distribution  are — the 

Meningeal.  Thyro-hyoid. 

Descendens  hypoglossi.  Muscular. 

Meningeal  Branches  (Fig.  686). — As  the  hypoglossal  nerve  passes  through  the 
anterior  condyloid  foramen  it  gives  off,  according  to  Luschka,  several  filaments  to 
the  dura  mater  in  the  posterior  fossa  of  the  base  of  the  skull ;  these  filaments  are 
probably  derived  from  a  branch  which  passes  from  the  first  cervical  nerve  to  the 
hypoglossal  nerve. 

The  Descendens  Hypoglossi  (ramus  descendens)  (Figs.  686  and  687). — The 
descendens  hypoglossi,  long  called  the  descendens  noni,  is  a  long  slender  branch, 
which  quits  the  hypo-glossal  where  it  turns  around  the  occipital  artery.  It  con- 
sists mainly  of  fibres  which  pass  to  the  hypoglossal  from  the  first  and  second 
cervical  nerves  in  the  above-mentioned  communication.  It  descends  in  front  of 
or  within  the  sheath  of  the  common  carotid  artery,  giving  off  a  branch  to  the 
anterior  belly  of  the  Omo-hyoid,  and  then  joins  the  communicating  branches 
from  the  second  and  third  cervical  nerves,  just  below  the  middle  of  the  neck,  to 
form  a  loop,  the  ansa  hypo-glossi.  From  the  convexity  of  this  loop  branches  pass 
to  supply  the  Sterno-hyoid,  Sterno-thyroid,  and  the  posterior  belly  of  the  Omo- 
hyoid. According  to  Arnold,  another  filament  descends  in  front  of  the  vessels  into 
the  chest,  and  joins  the  cardiac  and  phrenic  nerves. 

The  Thyro-hyoid  Branch  (ramus  thyreohyoideus)  (Fig,  686). — The  thyro-hyoid 
is  a  small  branch  arising  from  the  hypoglossal  near  the  posterior  border  of  the 
Hyo-glossus;  it  passes  obliquely  across  the  great  cornu  of  the  hyoid  bone  and 
supplies  the  Thyro-hyoid  muscle. 

The  Muscular  Branches  (Fig.  686). — The  muscular  branches  are  distributed  to 
the  Stylo-glossus,  Hyo-glossus,  Genio-hyoid,  and  Genio-hyo-glossus  muscles.  At 
the  under  surface  of  the  tongue  numerous  slender  branches  (rami  linguales)  pass 
upward  into  the  substance  of  the  organ  to  supply  its  intrinsic  muscles. 

Surgical  Anatomy. — A  wound  in  the  submaxillary  region  may  injure  the  hypoglossal  nerve 
and  result  in  motor  paralysis  of  the  corresponding  half  of  the  tongue.  The  hypoglossal  nerve  is 
an  important  guide  in  the  operation  of  ligation  of  the  lingual  artery  (see  page  604i  It  runs  forward 
on  the  Hyo-glossus  muscle  just  above  the  great  cornu  of  the  hyoid  hone,  and  forms  the  upper 
boundary  of  the  triangular  space  in  which  the  artery  is  to  be  sought  for  by  cutting  through  the 
fibres  of  the  Hyo-glossus  muscle. 


THE  SYMPATHETIC  NERVE  (SYMPATHICUS)  (Fig.  688). 

The  sympathetic  nervous  system  consists  of  (1)  a  series  of  ganglia  (ganglia  trunci 
sympathici)  connected  together  by  a  great  ganglionic  cord,  the  gangliated  cord 
(truncus  sympathicus) ,  extending  from  the  base  of  the  skull  to  the  coccyx,  one 
gangliated  cord  on  each  side  of  the  middle  line  of  the  body,  partly  in  front  and 
partly  on  each  side  of  the  vertebral  column ;  (2)  of  three  great  gangliated  plexuses 
(plexus  sympathici)  or  aggregations  of  nerves  and  ganglia,  situated  in  front  of 


THE  SYMPATHETIC  NERVE 


1067 


the  spine  in  the  thoracic,  abdominal, 
and  pelvic  cavities  respectively;  (3)  of 
smaller  or  terminal  ganglia,  situated  in 
relation  with  the  abdominal  viscera  ; 
and  (4)  of  numerous  nerve-fibres.  These 
latter  are  of  two  kinds  :  communicating, 
by  which  the  ganglia  communicate  with 
each  other  and  with  the  cerebro-spinal 
nerves  ;  and  distributory,  supplying  the 
internal  viscera  and  the  coats  of  the 
blood-vessels. 

Each  gangliated  cord  may  be  traced 
upward  from  the  base  of  the  skull 
into  the  cranial  cavity  by  an  ascending 
branch,  which  passes  through  the  caro- 
tid canal,  forms  a  plexus  on  the  internal 
carotid  artery  and  in  the  cavernous 
sinus  (Fig.  692),  and  communicates 
with  certain  cranial  nerves  (p.  1073). 
According  to  some  anatomists,  the  two 
cords  are  joined,  at  their  cephalic  ex- 
tremities, by  these  ascending  branches 
communicating  in  a  small  ganglion, 
the  ganglion  of  Ribes,  situated  upon  the 
anterior  communicating  artery.  Upon 
the  gangliated  cord  are  ganglia  dis- 
tinguished as  cervical,  dorsal,  lumbar, 
and  sacral,  and  except  in  the  neck  they 


Fig.  688. — The  sympathetic  ners'e,  reduced  in  size 
from  Byron  Robinson's  life-size  drawing  of  a  dissection 
made  by  himself. 

l.-VIII.,  cervical  nerves;  2  a,  2  h,\  c,  \  d,  brachial 
plexus;  1,  spinal  accessory  nerve  (XI.  nerve);  2,  hypo- 
glossal nerve  (XII.  nerve);  3,  vagus  nerve  (X.  nerve); 
4,  descendens  nomi  nerve;  5,  laryngeal  nerve;  6,  supe- 
rior cervical  ganglion;  7,  middle  cervical  ganglion;  8,  9, 
inferior  cervical  ganglion;  10,  two  superior  cardiac 
nerves;  11,  two  middle  cardiac  nerves;  12,  two  ganglia 
on  10  and  11;  13,  branch  connecting  the  inferior  cervi- 
cal ganglion  to  phrenic  nerve;  14,  I.  dorsal  nerve;  15, 
left  subclavian  artery;  16,  carotid  artery;  17,  right  sub- 
clavian artery;  18,  Wrisberg's  ganglion;  19,  a,  sym- 
pathetic branches  to  the  heart;  19,  three  inferior  car- 
diac nerves.  The  phrenic  nerve  in  this  subject  arose 
from  the  III.,  IV.,  and  V.  cervical  nerves;  20  to  39, 
lateral  chain  of  sympathetic  ganglia;  40,  left  recurrent 
laryngeal  nerve;  41,  superior  splanchnic  nerve;  42,  mid- 
dle splanchnic  nerve;  43,  inferior  splanchnic  nerve;  44, 
45,  aortic  branches  from  the  lateral  chain  of  ganglia;  45 
to  56,  intercostal  nerve;  57,  diaphragmatic  ganglion; 
58,  right  vagus  nerve;  59,  left  vagus  nerve;  60,  nerve 
joining  the  vagi;  61,  coeliac  axis;  62,  phrenic  artery  sur- 
rounded by  the  phrenic  plexus,  which  is  connected 
with  the  phrenic  ganglion  (57);  63.  64,  abdominal 
brain  (ganglion  coeliacum);  65,  renal  ganglion,  I.  L. , 
ILL.,  III.  L.,  IV.  L.,  V.L.,  lumbar  nerves;  66,  right 
superior  splanchnic  nerve;  67,  seven  nerves  passing 
to  the  adrenal;  68,  rich  me.«hwork  of  nerves  surround- 
ing left  renal  artery;  69,  right  renal  ganglion;  70,  71, 
ovarian  ganglion;  72,  aortic  plexus;  73,  inferior  mesen- 
teric ganglion;  74,  hypogastric  plexus;  75,  76,  77,  pel- 
vic brain  (cervico-vaginal  ganglion).  At  75  branches 
from  the  pelvis  brain  are  emitted  to  rectum,  vagina, 
and  bladder.  At  76  the  branches  from  the  II.,  III., 
and  IV.  sacral  nerves  join  the  pelvic  brain.  At  77  the 
uterine  nerves  are  emitted  to  supply  the  uterus;  78, 
oviducal  nerves;  79,  uterine  nerves;  80,  bladder;  81 , 
vagina;  82,  83,  rectum;  I.  S.,  II.  S.,  III.  S.,  IV.  S.,  sacral 
nerves;  84,  arteria  uterina  ovarica.  The  right  lumbar 
lateral  chain  is  not  numbered;  85,  nerves  to  levator  ani; 
//.  and  Hy.,  ileo-hypogastric;  /?'.,  ileo-inguinal;  Ec, 
external  cutaneous;  .4c.,  anterior  crural;  Obi.,  Obtura- 
tor; G.  C,  genito-crural;  G.  S.,  great  sciatic. 


1068  THE  NERVOUS   SYSTEM 

correspond  pretty  nearly  in  number  to  the  vertebrae  against  which  they  lie. 
They  may  be  thus  arranged: 

Cervical  portion  ....       3  pairs  of  ganglia. 

Dorsal  "  .  .         .  .12 

Lumbar         "  .  .  .  .4 

Sacral  '*  .  .  .      4  or     5 

In  the  neck  they  are  situated  in  front  of  the  transverse  processes  of  the  verte- 
brae; in  the  dorsal  region,  in  front  of  the  heads  of  the  ribs;  in  the  lumbar  region, 
on  the  sides  of  the  bodies  of  the  vertebrae;  and  in  the  sacral  region,  in  front  of  the 
sacrum.  As  the  two  cords  pass  into  the  pelvis  they  converge  and  unite  together 
in  a  single  ganglion,  the  coccygeal  ganglion  or  ganglion  impar  (ganglion  coccygeum 
impar)  placed  in  front  of  the  coccyx.  Each  ganglion  may  be  regarded  as  a  dis- 
tinct centre,  and,  in  addition  to  its  branches  of  distribution,  possesses  also  branches 
of  communication  which  communicate  with  other  ganglia  and  with  the  cerebro- 
spinal nerves. 

The  branches  of  communication  between  the  ganglia  (Figs.  689  and  690)  are 
composed  of  gray  nerve-fibres  (gray  rami  comm,unicantes)  and  white  nerve-fibres 
(white  rami  communicantes) ,  the  latter  being  continuous  with  those  fibres  of  the 
spinal  nerves  which  pass  to  the  ganglia. 

The  three  great  gangliated  plexuses  (collateral  ganglia)  are  situated  in  front  of 
the  spine  in  the  thoracic,  abdominal,  and  pelvic  regions,  and  are  named,  respec- 
tively, the  cardiac,  the  solar  or  epigastric,  and  the  hsrpogastric  plexus.  They  consist 
•of  collections  of  nerves  and  ganglia,  the  nerves  being  derived  from  the  gangliated 
cords  and  from  the  cerebro-spinal  nerves.  They  distribute  branches  to  the 
viscera. 

Smaller  or  Terminal  ganglia  are  also  found  lying  amidst  the  nerves,  some  of  them 
of  microscopic  size,  in  certain  viscera — as,  for  instance,  in  the  heart,  the  stomach, 
.and  the  uterus.  They  serve  as  additional  centres  for  the  origin  of  nerve-fibres. 
There  are  numerous  special  ganglia  connected  with  the  cranial  nerves. 

These  ganglia  have  been  described  in  a  previous  section  (see  ophthalmic 
^ganglion,  otic  ganglion,  spheno-palatine  ganglion,  and  submaxillary  ganglion). 

The  branches  of  distribution  derived  from  the  gangliated  cords,  from  the  pre- 
vertebral plexuses,  and  also  from  the  smaller  ganglia,  are  principally  destined 
for  the  blood-vessels  and  thoracic  and  abdominal  viscera,  supplying  the  involun- 
tary muscular  fibre  of  the  coats  of  the  vessels  and  the  hollow  viscera,  and  the 
secreting  cells,  as  well  as  the  muscular  coats  of  the  vessels  in  the  glandular  viscera. 

Structure  of  the  Sympathetic  System.— The  svm pathetic  system  is  not,  as 
was  so  long  taught,  an  independent  system.  It  receives  fibres  from  the  cerebro- 
spinal system  and  arranges  them  for  distribution  to  the  splanchnic  blood-vessels 
and  the  viscera.  It  receives  fibres  from  the  viscera  and  transmits  them  to  the 
■cerebro-spinal  system,  and  it  transmits  fibres  by  way  of  the  spinal  nerves  to 
unstriped  muscles,  to  vessels,  and  to  glands.  It  is  simply  an  arrangement  of  spinal 
nerves  to  permit  of  the  re-arrangement  and  transmission  of  impulses.  In  order 
to  effect  this,  the  spinal  nerves  are  connected  with  a  series  of  ganglia,  which  possess 
a  certain  power  of  government  or  automatic  action.  In  the  sympathetic  system 
non-medullated  fibres  predominate.  The  individual  nerve-fibres  are  smaller  in 
diameter  than  those  of  the  cerebro-spinal  system,  and  the  fibres  are  interrupted 
by  nerve-cells  contained  in  a  ganglia  chain,  known  as  the  gangliated  cord,  and  are 
also  sometimes  interrupted  in  gangliated  plexuses  and  in  terminal  ganglia.  The 
sympathetic  nerves  have  a  notable  disposition  to  form  plexuses.  It  is  important  to 
note  that  not  all  of  the  visceral  branches  of  the  spinal  nerves  join  the  gangliated 
cord — for  instance,  the  visceral  branches  of  the  third  and  fourth  sacral  do  not. 
The  majority,  but  not  all,  of  the  sympathetic  fibres  are  non-medullated  (fibres  of 


THE  SYMPATHETIC  NERVE  1069 

Remak),  but  in  the  adult  true  non-medullated  fibres  are  found  only  in  the  sym- 
pathetic system.  These  fibres  are  of  smaller  diameter  than  spinal  nerve-fibres,  and 
are  prolongations  of  axones  of  sympathetic  ganglia  cells.  Each  fibre  is  surrounded 
by  connective-tissue  structure  which  resembles  the  neurilemma,  which  contains 
numerous  nuclei,  and  which  is  a  prolongation  of  the  capsule  of  a  sympathetic  cell 
capsule. 

A  sympathetic  nerve  consists  of  numerous  non-medullated  and  some  medullated 
fibres.  The  connective  tissue  which  separates  the  nerve-bundles  carries  blood- 
vessels and  nervi  nervorum,  but  no  lymph  vessels. 

The  sympathetic  ganglia  contain  multipolar  cells  which  are  smaller  than  those 
of  the  spinal  ganglia.  Each  cell  contains  two  nuclei,  and  is  surrounded  by  a  deli- 
cate capsule  of  connective  tissue.    The  cell  gives  off  one  axone  and  several  short 


POSTERIOR  ROOT 


POSTERIOR  PRIMARY 
DIVISION 


NTERIOR  ROOT\ 


SPLANCHNIC  EFFERENT  FIBRESi 
SYMPATHETIC  GANGLION 


ANTERIOR  PRIMARY 
DIVISION 


^SPLANCHNIC  AFFERENT  FIBRES 

"Fio.  689. — The  white  ramus  communicans  (schematic).     (After  Cunningham.) 

dendrites.  The  axone  is  non-medullated  when  it  begins  and  may  remain  so  or 
may  become  medullated.  Fibres  which  take  origin  from  sympathetic  axones, 
the  commissural  fibre,  may  pass  to  an  adjacent  ganglion  cell,  may  pass  toward  the 
centre  central  fibre  or  gray  ramus  commimicans,  or  may  pass  toward  the  periphery, 
peripheral  fibre,  and  reach  certain  glands,  or  to  unstriped  muscle  of  blood-vessels, 
intestines,  iris,  etc.     The  fibres  passing  to  glands  are  called  secretory  fibres. 

The  dendrites  of  a  sympathetic  ganglion  cell  form  arborizations  about  other 
ganglion  cells.  The  sympathetic  ganglia  contain  fibres,  as  well  as  cells.  Some  of 
the  fibres  are  medullated  and  some  are  non-medullated,  the  latter  taking  origin 
from  the  sympathetic  ganglion  cells,  the  former  being  motor  and  sensory  cere- 
brospinal fibres  which  have  reached  the  sympathetic  by  the  rami  communi- 
cantes.^ 

'  Histology  and  Microscopic  Anatomy,  by  Szymonowicz.      Translated  and  edited  by  John  Bruce  MacCallura. 


1070 


THE  NERVOUS  SYSTEM 


The  medullated  fibres,  the  white  rami  communicantes  or  the  visceral  branches  of 
the  spinal  nerves  (Figs.  689  and  690)  originate  from  the  anterior  divisions  of  certain 
spinal  nerves.  Two  groups  of  them  can  be  recognized,  one  group  coming  from 
the  nerves  from  the  first  or  second  dorsal  to  the  second  or  third  lumbar  nerves; 
another  group  from  the  second  or  third  lumbar  to  the  third  or  fourth  sacral.    The 


COMMISSURAL 
FIBRE 


aftNSLION   CCIXS 
OU^      AND   AX0N3 


Fio.  690. — Scheme  of  the  constitution  and  connections  of  the  gangliated  cord  of  the  sympathetic.  The 
gangliated  cord  is  indicated  on  the  right  with  the  arrangement  of  the  fibres  arising  from  the  ganglion  cells.  _  On 
the  left  the  roots  and  trunks  of  spinal  nerves  are  shown,  with  the  arrangement  of  the  white  ramus  communicans 
above  and  the  gray  ramus  below.     (Cunningham.) 

visceral  branches  of  the  third  and  fourth  sacral  do  not  join  the  gangliated  cord ;  the 
other  visceral  branches  do  join  it.  The  fibres  of  the  visceral  branches  of  the  spinal 
nerves  are  derived  from  both  the  anterior  and  the  posterior  nerve-roots,  but  more 
largely  from  the  anterior  than  from  the  posterior.  The  visceral  fibres  of  the  anterior 
roots  are  axones  of  nerve-cells  of  the  spinal  cord,  and  by  way  of  the  white  rami  enter 
into  the  sympathetic  ganglia.     Some  of  them  end  and  form  networks  about  the 


THE   CEBVICAL    PORTION    OF    THE    GANGLIATED    COBD     1071 

ganglia  cells.  Others  pass  up  or  down  and  end  in  an  adjacent  ganglion.  Others 
pass  through  a  ganglion  of  the  gangliated  cord  and  end  in  a  peripheral  ganglion 
with  non-medullated  fibres,  which  take  origin  from  ganglia  of  the  gangliated  cord. 
The  fibres  of  the  white  ramus  which  pass  through  the  ganglion  and  go  to  the 
periphery  are  known  as  the  splanchnic  efferent  fibres,  and  constitute  the  secretory 
fibres  of  the  splanchnic  glands  and  the  motor  fibres  of  the  muscular  tissue  of 
splanchnic  blood-vessels  and  viscera.  The  visceral  fibres  of  the  posterior  nerve- 
roots  aid  in  the  formation  of  the  white  rami  and  arise  as  axones  of  nerve-cells  in 
the  spinal  ganglia  on  the  posterior  roots,  pass  through  the  ganglia  of  the  sympa- 
thetic cord,  but  do  not  terminate  in  them,  and  leave  the  ganglion  directly  to  pass 
through  a  peripheral  ganglion  to  be  distributed  to  the  periphery  or  ascend  or 
descend  to  an  adjacent  ganglion  and  pass  through  this  to  a  collateral  ganglion,  and 
from  that  to  the  periphery.  They  constitute  the  splanchnic  afferent  fibres,  the 
sensory  fibres  of  the  viscera. 

The  non-medullated  fibres  take  origin  from  the  cells  of  the  sympathetic  gan- 
glia and  are  axones  of  these  cells.  Some  help  to  form  the  commissure,  which 
joins  a  ganglion  to  adjacent  ganglia  and  end  as  networks  about  the  cells  of  an 
adjacent  ganglion.  Others  run  to  the  periphery  and  help  to  form  the  splanchnic 
efferent  branches.  Some  pass  from  the  ganglia  to  the  spinal  nerve-roots  and  to 
the  anterior  and  posterior  divisions  of  the  nerves.  The  latter  are  the  gray  rami 
communicantes  (Fig.  690),  largely  composed  of  non-medullated  but  containing 
some  medullated  fibres.  They  give  branches  to  the  somatic  part  of  the  nerves 
and  not  the  visceral,  and  furnish  secretory  fibres  and  fibres  to  unstriated  muscle 
and  minute  branches  to  the  membranes  which  enwrap  the  nerve-roots.  The 
commissures  of  the  gangliated  cord  are  composed  of  white  and  gray  fibres. 
The  former  consist  of  both  splanchnic  efferent  and  splanchnic  afferent  fibres.  The 
latter  are  axones  from  sympathetic  ganglion  cells,  and  some  of  these  are  truly  com- 
missural, but  others  pass  up  or  down  the  cord  and  through  a  ganglion  and  become 
branches  which  go  to  the  periphery. 

From  the  above  it  becomes  evident  that  the  peripheral  branches  of  the  sym- 
pathetic contain  white  fibres,  which  are  composed  of  splanchnic  efferent  and 
splanchnic  afferent  branches  and  also  contain  splanchnic  efferent  gray  fibres. 
Fig.  690,  from  Cunningham's  Text-hook  of  Anatomy,  exhibits  the  constitution 
and  connections  of  the  gangliated  cord  of  the  sympathetic. 

THE  GANGLIATED  CORD   (TRUNCUS  SYMPATHICUS). 

The  Cervical  Portion  (Pars  Cervicalis)  of  the  Gangliated  Cord. 

The  cervical  portion  of  the  gangliated  cord  is  to  be  regarded  as  a  prolongation 
upward  of  the  primitive  sympathetic  along  the  great  vessels  of  the  neck  (Prof. 
Cunningham).  It  is  not  connected  to  the  cervical  spinal  nerves  by  white  rami 
communicantes.  It  obtains  its  spinal  fibres  from  the  upper  dorsal  nerves.  These 
fibres  ascend  in  the  commissure  of  the  gangliated  cord  and  join  the  cells  of  the 
cervical  ganglia.  From  the  cervical  ganglia  come  fibres  to  the  unstriped  muscle 
(veins  and  arteries  of  the  head,  neck,  and  limbs,  and  to  the  skin  of  the  head  and 
neck,  secretory  fibres  to  the  salivary  glands  and  fibres  to  the  heart).  The  fibres 
to  the  vessels  are  called  vasomotor  nerves,  and  the  fibres  to  the  heart  are  called 
cardio-motor  nerves.  In  the  neck  the  gangliated  cord  is  situated  behind  the  carotid 
vessels  and  upon  the  muscles  in  front  of  the  vertebrae,  and  runs  from  the  root 
of  the  neck  to  the  base  of  the  skull,  being  continuous  below  with  the  thoracic 
gangliated  cord  and  ending  above  in  the  carotid  plexus.  There  are  usually  three 
ganglia  on  each  side,  each  of  which  is  distinguished,  according  to  its  position,  as 
the  superior,  middle  and  inferior  cervical  ganglion. 


1072 


THE  NERVOUS  SYSTEM 


The  Superior  Cervical  Ganglion  {ganglion  cervicale  superius)  (Figs.  691,  692, 
and  693) . — ^^Fhe  superior  cervical  ganglion,  the  largest  of  the  three,  is  about  three- 


Superior  cervical  ganglion. 


Middle  cervical  ganglion. 


Inferior  cerdccd  ganglion 


Pharyngeal  branches. 


Cardiac  branches. 


Deep  cardiac  plexus. 

Superficial  cardiac  plexus. 


Solar  plexus. 


Aortic  plexus. 


Hypogastnc  plexus. 


Sacral  ganglia. 


Ganglion  impar 


Fig.  691. — The  sympathetic  nerve. 


THE    CERVICAL   PORTION    OF    THE    QANGLIATED    CORD     1073 

quarters  of  an  inch  in  length.  It  is  placed  opposite  the  second  and  third  cervical 
vertebrae.  It  is  of  a  reddish-gray  color,  is  usually  fusiform  in  shape,  is  sometimes 
broad  and  flattened,  and  is  occasionally  constricted  at  intervals,  so  as  to  give  rise  to 
the  opinion  that  it  consists  of  the  coalescence  of  several  smaller  ganglia;  and  it  is 
usually  believed  that  it  is  formed  by  the  coalescence  of  the  four  ganglia  correspond- 
ing to  the  four  upper  cervical  nerves.  It  is  in  relation,  in  front,  with  the  sheath 
of  the  internal  carotid  artery  and  internal  jugular  vein;  behind,  it  lies  on  the 
Rectus  capitis  anticus  major  muscle.  It  is  connected  to  the  middle  cervical  gan- 
glion by  the  commissure  of  the  gangliated  cord. 

Branches  (Fig.  693). — The  branches  of  the  superior  cervical  ganglion  are  central 
and  peripheral. 

Central  or  Communicating  Branches. — 1.  Gray  rami  communicantes  arise  in  the 
ganglion  and  pass  to  the  first, second,  third,  and  fourth  cervical  nerves.  2.  Branches 
are  given  off  to  certain  cranial  nerves  in  the  neck  (Figs.  692  and  693) .  What  is 
known  as  the  jugular  nerve  {n.  jugularis)  (Fig.  693)  passes  to  the  ganglion  on  the 
trunk  of  the  vagus,  a  branch  from  the  ganglion  passes  to  the  ganglia  on  the  root  of 
the  pneumogastric  (Fig.  693)  and  to  the  petrosal  ganglion  of  the  glosso-pharyngeal 
(F'ig.  693),  and  a  branch  goes  to  the  hypoglossal  (Fig.  693). 

Peripheral  Branches. — These  branches  may  be  divided  into  superior,  internal 
and  anterior. 

The  Superior  Branch  of  the  Superior  Cervical  Ganglion  or  the  Internal  Carotid 
Branch  (n.  caroticus  internus)  (Fig.  692)  appears  to  be  a  direct  prolongation  of  the 
ganglion.  It  is  soft  in  texture  and  of  a  reddish  color.  It  ascends  by  the  side  of 
the  internal  carotid  artery,  and,  entering  the  carotid  canal  in  the  temporal  bone, 
divides  into  two  branches,  which  lie,  one  on  the  outer,  and  the  other  on  the  inner, 
side  of  that  vessel. 

The  outer  branch,  the  larger  of  the  two,  distributes  filaments  to  the  internal 
carotid  artery  and  forms  the  internal  carotid  plexus. 

The  inner  branch  also  distributes  filaments  to  the  internal  carotid,  and,  con- 
tinuing onward,  forms  the  cavernous  plexus. 

The  Internal  Carotid  Plexus  (plexus  caroticus  internus)  (Figs.  691,  692, 
and  693) . — The  carotid  plexus  is  situated  on  the  outer  side  of  the  internal  carotid 
artery.  Filaments  from  this  plexus  occasionally  form  a  small  gangliform  swelling 
on  the  under  surface  of  the  artery,  which  is  called  the  carotid  ganglion.  The  internal 
carotid  plexus  communicates  with  the  Gasserian  ganglion,  with  the  sixth  nerve, 
and  the  spheno-palatine  ganglion,  and  distributes  filaments  to  the  wall  of  the 
carotid  artery  and  to  the  dura  mater  (Valentin),  while  in  the  carotid  canal  it 
communicates  with  Jacobson's  nerve,  which  is  the  tympanic  branch  of  the  glosso- 
pharyngeal. 

The  communicating  branches  with  the  sixth  nerve  (Fig.  693)  consist  of  one  or 
two  filaments  which  join  that  nerve  as  it  lies  upon  the  outer  side  of  the  internal 
carotid.  Other  filaments  are  also  connected  with  the  Gasserian  ganglion.  The 
communication  with  the  spheno-palatine  ganglion  is  effected  by  a  branch,  the 
large  deep  petrosal  nerve  (Fig.  677),  which  is  given  off  from  the  plexus  on 
the  outer  side  of  the  artery,  ancl  which  passes  through  the  cartilage  filling  up  the 
foramen  lacerum  medium,  and  joins  the  large  superficial  petrosal  from  the  facial 
to  form  the  Vidian  nerve  (Figs.  670,  672,  and  677) .  The  Vidian  nerve  then  pro- 
ceeds along  the  pterygoid  or  Vidian  canal  to  the  spheno-palatine  ganglion.  The 
commimication  with  Jacobson's  nerve  is  effected  by  two  branches,  one  of  which 
is  called  the  deep  petrosal  nerve,  and  the  other  the  carotico-tympanic  nerve;  the 
latter  may  consist  of  two  or  three  delicate  filaments. 

The  Cavernous  Plexus  (plexus  cavernosus)  (Figs.  692 and  693). — The  cavern- 
ous plexus  is  situated  below  and  internal  to  that  part  of  the  internal  carotid  which  is 
placed  by  the  side  of  the  sella  turcica  in  the  cavernous  sinus,  and  is  formed  chiefiy 

68 


1074 


THE   NERVOUS  SYSTEM 


by  the  internal  division  of  the  ascending  branch  from  the  superior  cervical  ganglion. 
It  communicates  with  the  third,  the  fourth,  the  ophthalmic  division  of  the  fifth, 
and  the  sixth  nerves,  and  with  the  ophthalmic  ganghon,  and  distributes  filaments 
to  the  wall  of  the  internal  carotid  and  to  the  pituitary  body.  The  branch  of  com- 
munication with  the  third  nerve  (Fig.  693)  joins  it  at  its  point  of  division;  the 
branch  to  the  fourth  nerve  (Fig.  693)  joins  it  as  it  lies  on  the  outer  wall  of  the 
cavernous  sinus;  other  filaments  are  connected  with  the  under  surface  of  the  trunk 
of  the  ophthalmic  nerve;  and  a  second  filament  of  communication  joins  the  sixth 
nerve  (Fig.  693). 

The  filament  of  connection  with  the  ophthalmic  ganglion  (Figs.  666  and  693) 
arises  from  the  anterior  part  of  the  cavernous  plexus;  it  accompanies  the  nasal 
nerve  or  continues  forward  as  a  separate  branch. 


EXTERNAL 
RECTUS 

MUSCLE 


OPHTHALMIC 
GANGLION 

SENSORY  ROOT 

OF  OPHTHALMIC 

GANGLION 


OPHTHALMIC 

GASSERIAN 
GANGLION 

[turned  forward) 

GREAT  DEEP 
PETROSAL 

TEMPORO- 

MAXILLARY 

ARTICULATION 


SMALL  DEEP 
PETROSAL 


MOTOR   ROOT  OF 

OPHTHALMIC  GANGLION 

UPPER    BRANCH 

OF  THIRD 

LOWER   BRANCH 

OF  THIRD 

SYMPATHETIC  ROOT  OF 
OPHTHALMIC  GANGLION 
THIRD  NERVE 

OPHTHALMIC 
ARTERY 


PITUITARY 
f  BODY 

CAVERNOUS 
PLEXUS 

SIXTH  NERVE 


COMMUNICATING 
BRANCH  TO  SIXTH 


INFERIOR       INTERNAL 
COROTICOTYMPANIC  CAROTID 

ARTERY 


INTERNAL 
CAROTID  PLEXUS 
NTERNAL 
CAROTID  BRANCH 
OF  SUPERIOR 
CERVICAL  GANGLION 
SUPERIOR 
CERVICAL 
GANGLION 


Fig.  692. — The  cephalic  portion  of  the  sympathetic  nervous  system,  seen  obliquely  from  above  and  behind. 

(Toldt.) 

Terminal  Branches  of  the  Carotid  and  Cavernous  Plexuses. — The  terminal 
filaments  from  the  carotid  and  cavernous  plexuses  are  prolonged  along  the  internal 
carotid,  forming  plexuses  which  entwine  around  the  cerebral  and  ophthalmic 
arteries;  along  the  former  vessels  they  may  be  traced  on  to  the  pia  mater;  along 
the  latter,  into  the  orbit,  where  they  accompany  each  of  the  subdivisions  of  the 
vessel,  a  separate  plexus  passing,  with  the  arteria  centralis  retinae,  into  the  interior 
of  the  eyeball.  The  filaments  prolonged  on  to  the  anterior  communicating  artery 
form  a  small  ganglion,  the  ganglion  of  Ribes,*  which  serves,  as  mentioned  above, 
to  connect  the  sympathetic  nerves  of  the  right  and  left  sides. 

The  so-called  Inferior  or  Descending  Branch  of  the  Superior  Cervical  Ganglion 
communicates  with  the  middle  cervical  ganglion.  It  is  the  commissure  of  the 
gangliated  cord. 


^  The  existence  of  this  ganglion  is  doubted  by  some  observers. — Ed.  of  15th  English  edition. 


THE   CERVICAL   PORTION   OF    THE    GANGLIATED    CORD     1075 


Fig.  693. — Plan  of  the  cervical  portion  of  the  sympathetic.     (After  Flower.) 


1076 


THE   NERVOUS  SYSTEM 


The  Internal  Branches  of  the  Superior  Cervical  Ganglion  are  three  in  number — the 
pharyngeal,  laryngeal  and  superior  cardiac  nerve. 

The  pharyngeal  branches  (rami  pharyngei)  (Figs.  691  and  693)  pass  inward  to  the 
side  of  the  pharynx,  where  they  join  with  branches  from  the  glosso-pharyngeal, 
pneumogastric,  and  external  laryngeal  nerves  to  form  the  pharjmgeal  plexus 
(plexus  pharyngeuLs). 
The  laryngeal  branches  unite  with  the  superior  laryngeal  nerve  and  its  branches. 
The  superior  cardiac  nerve  or  the  nervus  superficialis  cordis  {n.  cardiacus  supe- 
rior) (Figs.  691  and  693)  arises  by  two  or  more  branches  from  the  superior  cervical 
ganglion,  and  occasionally  receives  a  filament  from  the  cord  of  communication 
between  the  first  and  second  cervical  ganglia.  It  runs  down  the  neck  behind  the 
common  carotid  artery,  lying  upon  the  Longus  colli  muscle,  and  crosses  in  front  of 
the  inferior  thyroid  artery  and  recurrent  laryngeal  nerve.  The  right  superior  cardiac 
nerve,  at  the  root  of  the  neck,  passes  either  in  front  of  or  behind  the  subclavian 
artery,  and  along  the  arteria  innominata,  to  the  back  part  of  the  arch  of  the  aorta, 
where  it  joins  the  deep  cardiac  plexus.  This  nerve,  in  its  course,  is  connected  with 
other  branches  of  the  sympathetic;  about  the  middle  of  the  neck  it  receives  fila- 
ments from  the  external  laryngeal  nerve;  lower  down  it  obtains  one  or  two  twigs 
from  the  pneumogastric;  and  as  it  enters  the  thorax  it  is  joined  by  a  filament 
from  the  recurrent  laryngeal.  L'ilaments  from  thig  nerve  communicate  with  the 
thyroid  branches  from  the  middle  cervical  ganglion.  The  left  superior  cardiac 
nerve,  in  the  chest,  runs  by  the  side  of  the  left  common  carotid  artery  and  in 
front  of  the  arch  of  the  aorta  to  the  superficial  cardiac  plexus,  but  occasionally  it 
passes  behind  the  aorta  and  terminates  in  the  deep  cardiac  plexus. 

The  Anterior  Branches  of  the  Superior  Cervical  Ganglion  {nn.  carotid  extcrni) 
(Fig.  693)  ramify  upon  the  external  carotid  artery  and  its  branches,  forming  around 
each  a  delicate  plexus,  on  the  nerves  composing  which  small  ganglia  are  occasion- 
ally found.  The  plexuses  accompanying  some  of  these  arteries  have  important 
communications  with  other  nerves.  That  suiTounding  the  external  carotid  artery 
{plexus  caroticus  eodernus)  is  connected  with  the  branch  of  the  facial  nerve  to  the 

Stylo-hyoid  muscle  ;  that  surrounding  the 
facial  artery  communicates  with  the  sub- 
maxillary ganglion  by  one  or  two  filaments; 
and  that  accompanying  the  middle  menin- 
geal artery  sends  offsets  which  pass  to  the 
otic  ganglion  and  to  the  geniculate  gan- 
glion of  the  facial  nerve  and  constitute  the 
external  superficial  petrosal  nerve  (Fig.  677). 
The  Middle  Cervical  or  Thyroid  Gan- 
glion {ganglion  cervical  medium)  (Figs.  391 
and  693). — The  middle  cervical  or  thyroid 
ganglion  is  the  smallest  of  the  three  cervical 
ganglia,  and  is  occasionally  altogether  want- 
ing. It  varies  somewhat  in  position,  but  in 
most  individuals  is  placed  opposite  the  sixth  cervical  vertebra,  usually  upon,  or 
close  to,  the  inferior  thyroid  artery;  hence  the  name,  thyroid  ganglion,  assigned  to 
it  by  Haller.  It  is  probably  formed  by  the  coalescence  of  two  ganglia  corre- 
sponding to  the  fifth  and  sixth  cervical  nerves. 

It  communicates  above  with  the  superior  cervical  ganglion  and  below  with 
the  inferior  cervical  ganglion  by  means  of  the  commissure  of  the  gangliated  cord. 
The  Central  Communicating  Branches  (Fig.  693). — The  central  communicating 
branches  are:  1.  Gray  rami  communicantes  passing  from  the  ganglion  to  the 
anterior  divisions  of  the  fifth  and  sixth  cervical  nerves.  2.  The  subclavian  loop  or 
the  ansa  of  Vieussens  {ansa  suhclavia)  (Fig.  694)  arises  from  the  ganglion,  passes 


MIDDLE  CERVICAL  GANGLION 


SUBCLAVIAN  LOOP 


INFERIOR  CERVICAL 
GANGLION 


Fig.  694. — The  subclavian  loop  passing  from  the 
middle  to  the  inferior  cervical  ganglia. 


THE    CERVICAL    PORTION   OF    THE    GANGLIATED    CORD     1077 

down  over  the  front  and  under  the  subclavian  artery  and  runs  back  to  join  the 
inferior  cervical  ganglion.  It  gives  branches  to  the  artery.  In  some  cases  this 
nerve  takes  origin  from  the  sympathetic  trunk  below  the  ganglion. 

The  Peripheral  Branches. — The  peripheral  branches  are  the  thyroid  and  the 
middle  cardiac  nerve. 

I'he  Thyroid  Branches  (Fig.  693)  are  small  filaments  which  accompany  the  in- 
ferior thyroid  artery  to  the  thyroid  gland,  forming  the  inferior  thyroid  plexus 
{plexus  thyreoideus  mferior) ;  they  communicate,  on  the  artesy,  with  the  superior 
cardiac  nerve,  and,  in  the  gland,  with  branches  from  the  recurrent  and  external 
laryngeal  nerves. 

The  Middle  or  Great  Cardiac  Nerve  (n.  cardiacus  niedius)  (Figs.  691  and  693),  the 
largest  of  the  three  cardiac  nerves,  arises  from  the  middle  cervical  ganglion  or  from 
the  cord  between  the  middle  and  inferior  ganglia.  On  the  right  side  it  descends 
behind  the  common  carotid  artery,  and  at  the  root  of  the  neck  passes  either  in 
front  of  or  behind  the  subclavian  artery;  it  then  descends  on  the  trachea,  receives 
a  few  filaments  from  the  recurrent  laryngeal  nerve,  and  joins  the  right  side  of  the 
deep  cardiac  plexus.  In  the  neck  it  communicates  with  the  superior  cardiac  and 
recurrent  laryngeal  nerves.  On  the  left  side  the  middle  cardiac  nerve  enters  the 
chest  between  the  left  carotid  and  subclavian  arteries,  and  joins  the  left  side  of 
the  deep  cardiac  plexus.  If  the  middle  cervical  ganglion  is  absent,  the  above- 
named  branches  arise  from  the  gangliated  cord. 

The  Inferior  Cervical  Ganglion  (ganglion  cervicale  inferius)(Figs.  691  and  693). 
— The  inferior  cervical  ganglion  is  situated  between  the  base  of  the  transvetse  pro- 
cess of  the  last  cervical  vertebra  and  the  neck  of  the  first  rib  on  the  inner  side 
of  the  superior  intercostal  artery.  Its  form  is  irregular;  it  is  larger  in  size  than  the 
preceding,  and  is  frequently  joined  with  the  first  thoracic  ganglion.  It  is  prob- 
ably formed  by  the  coalescence  of  two  ganglia  which  correspond  to  the  two  last 
cervical  nerves.  It  joins  the  middle  ganglion  above  and  the  first  thoracic  ganglion 
below  by  the  commissural  cord,  and  is  usually  also  joined  to  the  middle  ganglion 
by  the  subclavian  loop. 

The  Central  Communicating  Branches. — Its  central  communicating  branches  are: 
1.  Gray  rami  communicantes  passing  to  the  anterior  divisions  of  the  seventh  and 
eighth  cervical  nerves  (Fig.  693) .  2.  The  subclavian  loop  (Fig.  694) ,  which  has 
been  previously  described  and  which  passes  under  and  in  front  of  the  subclavian 
artery  to  reach  the  middle  cervical  ganglion  or  the  commissural  cord. 

The  Peripheral  Branches. — The  peripheral  branches  are:  1.  Vascular.  The 
vertebral  plexus  (plexus  vertebralis)  (Fig.  693)  lies  upon  the  vertebral  artery  and  its 
branches  in  the  neck  and  in  the  cranial  cavity.  The  subclavian  plexus  (plexus 
subclavius)  (Fig.  693)  arises  from  the  subclavian  loop,  which  may  be  regarded  as 
a  branch  of  the  inferior  or  of  the  middle  ganglion.  2.  Cardiac.  The  inferior  or 
minor  cardiac  nerve  (n.  cardiacus  inferior)  (Fig.  693)  arises  from  the  inferior  cervical 
or  first  thoracic  ganglion.  It  passes  down  behind  the  subclavian  artery  and  along 
the  front  of  the  trachea  to  join  the  deep  cardiac  plexus.  It  communicates  freely 
behind  the  subclavian  artery  with  the  recurrent  laryngeal  and  middle  cardiac  nerves. 

Surgical  Anatomy. — The  situation  of  the  cervical  sympathetic  makes  wounds  of  it  rare. 
Thirteen  cases  of  sympathetic  traumatic  injury  were  collected  by  Seeligmiiller.  In  ten  cases 
paralysis  existed;  in  three,  irritation.  Tumors  of  the  neck  may  cause  irritation  or  paralysis.  In 
irritation  of  the  sympathetic  the  corresponding  side  of  the  face  becomes  pale,  the  pupil  dilates, 
the  palpebral  fissure  widens,  and  the  eyeball  protrudes.  In  many  cases  there  is  acceleration 
of  the  heart  beats.  In  paralysis  of  the  sympathetic  the  pupil  contracts,  the  palpebral  fissure  is 
narrowed  by  partial  ptosis,  the  corresponding  side  of  the  face  reddens,  there  is  an  increase  in 
the  flow  of  tears,  and  recession  of  the  eyeball. 

The  surgeon  occasionally  resects  the  sympathetic.  Jonnesco  recommends  bilateral  removal 
of  the  superior  cervical  ganglia  for  glaucoma,  and  bilateral  removal  of  all  the  cervical  sympa- 
thetic ganglia  for  epilepsy  and  for  exophthalmic  goitre. 


1078 


THE    NERVOUS  SYSTEM 


The  Thoracic  Portion  (Pars  Thoracalis)  of  the  Gangliated  Cord  (Fig.  695). 

The  thoracic  portion  of  the  ganghated  cord  consists  of  a  series  of  gangha 
which  usually  correspond  in  number  to  that  of  the  vertebrae,  but,  from  the  occa- 
sional coalescence  of  two,  their  number  is  uncertain.  These  ganglia  are  placed 
on  each  side  of  the  spine,  resting  against  the  heads  of  the  ribs,  and  are  covered  by 


THORACIC  NERVES. 
RAMI  COMMUNICANTES' 


INFERIOR    CER- 
VICAL  GANGLION 


VISCERAL 
BRANCHES 


SPLANCHNIC 

GANGLION 

GREAT 

SPLANCHNIC 


SMALL 
SPLANCHNIC 


RIGHT    PNEU- 
MOGASTRIC 


SMALL 
SPLANCHNIC 


BRANCH  OF    PNEUMOaASTRIO 
TO  SEMILUNAR  GANGLION 

CELIAC    AXIS 


SEMILUNAR  GANGLION 
SUPERIOR  MESENTERIC 
ARTERY  AND   PLEXUS 

LAR     PLEXUS 


QUADRATUS, 
LUMBORUM 


RENAL    PLEXUS 

Fig.  695. — Plan  of  the  right  sympathetic  cord  and  splanchnic  nerves.     (Testut.) 


the  pleura  costalis;  the  last  two  ganglia  are,  however,  anterior  to  the  rest,  being 
placed  on  the  side  of  the  bodies  of  the  eleventh  and  twelfth  dorsal  vertebrae.  The 
ganglia  are  small  in  size  and  of  a  grayish  color.  The  first  ganglion,  larger  than 
the  rest,  is  of  an  elongated  form  and  is  frequently  blended  with  the  last  cervical 
ganglion.  They  are  connected  together  by  cord-like  prolongations  from  the  sub- 
stance. In  the  thorax  each  thoracic  or  dorsal  spinal  nerve,  with  occasionally  the 
exception  of  the  first,  sends  a  visceral  branch  or  white  ramus  communicans  to  the 
thoracic  gangliated  cord  (Figs.  693  and  695) .     As  Prof.  Cunningham  points  out, 


THE  LUMBAR   PORTION  OF    THE    GANGLIATED    CORD     1079 

the  white  rami  "separate  into  two  main  streams  in  relation  to  the  sympathetic 
cord.  Those  of  the  upper  five  nerves  are,  for  the  most  part,  directed  upward  in 
the  ganghated  cord  to  be  distributed  through  the  cervical  part  of  the  sympathetic 
in  the  manner  already  described.  The  white  rami  of  the  lower  thoracic  nerves 
are,  for  the  most  part,  directed  downward  in  the  lower  part  of  the  sympathetic 
cord,  and  its  branches,  to  be  distributed  to  the  abdomen;  at  the  same  time  some 
of  their  fibres  are  directly  associated  with  the  supply  of  certain  thoracic  viscera — 
lungs,  aorta,  oesophagus.'"  The  white  rami  are  composed  of  splanchnic  afferent 
fibres  and  somatic  and  splanchnic  efferent  fibres. 

Central  Communicating  Branches. — 1.    White  rami  communicantes  (see  above). 

2.  Gray  rami  commmiicantes  arise  from  each  one  of  the  thoracic  ganglia,  pass  back- 
ward with  the  white  rami,  and  enter  into  the  anterior  divisions  of  the  thoracic  nerves. 

Peripheral  Branches  (Fig.  693). — 1.  Aortic  Branches  (Fig.  693)  come  off  from  the 
first  five  or  six  upper  ganglia.  They  send  filaments  to  the  aorta  and  its  branches, 
to  the  vertebral  bodies,  and  to  the  vertebral  ligaments.  The  aortic  branches  help 
to  form  the  thoracic  aortic  plexus  (plexus  aorticus  thoracalis) .  This  plexus  is  com- 
pleted by  branches  from  the  cardiac  plexus. 

2.  Pulmonary  Branches  (Fig.  693)  come  off  from  the  third  and  fourth  and  some- 
times from  the  first  and  second  ganglia. 

3.  The  Splanchnic  Nerves  (Figs.  688,  691,  and  695). — From  the  six  or  seven  lower 
ganglia  and  from  the  commissural  cord  a  number  of  large  white  branches  arise. 
They  give  filaments  to  the  aorta  and  unite  to  form  the  three  splanchnic  nerves  on 
each  side.  These  are  namefl  the  great,  the  lesser,  and  the  smallest  or  renal  splanchnic. 

The  superior  or  great  splanchnic  nerve  (n.  splanchnicus  major)  is  of  a  white 
color,  firm  in  texture,  and  presents  a  marked  contrast  to  the  ganglionic  nerves. 
It  is  formed  by  branches  from  the  thoracic  ganglia  between  the  fifth  or  sixth 
and  the  ninth  or  tenth,  but  the  fibres  in  the  higher  roots  may  be  traced  upward 
in  the  sympathetic  cord  as  far  as  the  first  or  second  thoracic  ganglion.  These 
roots  unite  to  form  a  large  round  cord  of  considerable  size.  It  descends  obliquely 
inward  in  front  of  the  bodies  of  the  vertebrae  along  the  posterior  mediastinum, 
perforates  the  crus  of  the  Diaphragm,  and  terminates  in  the  semilunar  ganglion  of 
the  solar  plexus  (Fig.  695),  distributing  filaments  to  the  renal  and  suprarenal  plexus. 

The  middle,  lesser  or  small  splanchnic  nerve  (n.  splanchnicus  minor)  is  formed 
by  filaments  from  the  tenth  and  eleventh  ganglia,  and  from  the  cord  betweer^  them. 
It  pierces  the  Diaphragm  with  the  preceding  nerve,  and  joins  the  solar  plexus 
(Fig.  695).  It  communicates  in  the  chest  with  the  great  splanchnic  nerve,  and 
occasionally  sends  filaments  to  the  renal  plexus. 

The  inferior,  smallest,  least  or  renal  splanchnic  nerve  (n.  splanchnicus  imus)  arises 
from  the  last  thoracic  ganglion,  and,  piercing  the  Diaphragm,  terminates  in  the 
renal  plexus  and  lower  part  of  the  solar  plexus.  It  occasionally  communicates  with 
the  preceding  nerve  (Fig.  688). 

A  striking  analogy  appears  to  exist  between  the  splanchnic  and  the  cardiac 
nerves.  The  cardiac  nerves  are  three  in  number;  they  arise  from  the  three  cer- 
vical ganglia,  and  are  distributed  to  a  large  and  important  organ  in  the  thoracic 
cavity.  The  splanchnic  nerves,  also  three  in  number,  are  connected  probably 
with  all  the  dorsal  ganglia,  and  are  distributed  to  important  organs  in  the  abdom- 
inal cavity. 

The  Lumbar  Portion  (Pars  Lumbalis)  of  the  Gangliated  Cord  (Figs.  688,  691). 

The  lumbar  portion  of  the  gangliated  cord  is  situated  in  front  of  the  vertebral 
column  along  the  inner  margin  of  the  Psoas  muscle.    It  consists  usually  of  hnr 

'  Text-book  of  Anatomy. 


X080  ^^^  NERVOUS  SYSTEM 

ganglia,  but  there  may  be  as  many  as  eight,  connected  together  by  intergangHonic 
cords.  The  gangha  are  of  small  size,  of  a  grayish  color,  shaped  like  a  barleycorn, 
and  placed  much  nearer  the  median  line  than  the  thoracic  ganglia.  Sometimes 
several  ganglia  are  fused  together. 

It  is  connected  with  the  thoracic  portion  by  a  thin  commissure,  which  passes 
back  of  or  through  the  Diaphragm.  It  is  connected  with  the  sacral  portion  by 
a  commissure  which  is  under  the  connnon  iliac  artery. 

The  upper  lumbar  ganglia  or  the  upper  portion  of  the  gangliated  cord  receives 
white  rami  communicantes  from  the  first  two  or  three  lumbar  spinal  nerves. 

Central  Communicating  Branches. — Gray  rami  communicantes  pass  irregularly  from 
the  gangliated  cord  to  the  anterior  divisions  of  the  lumbar  spinal  nerves,  the  gray 
rami  accompanying  the  white  rami. 

From  the  situation  of  the  lumbar  ganglia  these  branches  are  longer  than  in  the 
other  regions.  They  are  usually  two  in  number  from  each  ganglion,  but  their 
connection  with  the  spinal  nerves  is  not  so  uniform  as  in  other  regions.  They 
accompany  the  lumbar  arteries  around  the  sides  of  the  bodies  of  the  vertebrae, 
passing  beneath  the  fibrous  arches  from  which  some  of  the  fibres  of  the  Psoas 
muscle  arise. 

Peripheral  Branches. — Some  branches  pass  inward,  in  front  of  the  aorta,  and 
help  to  form  the  abdominal  aortic  plexus  {plexus  aorticus  ahdominalis)  (Fig.  691), 
which  plexus  is,  however,  developed  chiefly  by  filaments  from  the  coeliac  plexus. 
Other  branches  descend  in  front  of  the  common  iliac  arteries,  and  join  over  the 
promontory  of  the  sacrum,  helping  to  form  the  h3rpogastric  plexus  {'plexus  hypo- 
gastricus)  (Fig.  691).  Numerous  delicate  filaments  are  also  distributed  to  the 
bodies  of  the  vertebrae  and  the  ligaments  connecting  them. 

Pelvic  or  Sacral  Portion  (Pars  Sacralis)  of  the  Gangliated  Cord  (Figs.  688, 691). 

The  pelvic  portion  of  the  gangliated  cord  is  situated  in  front  of  the  sacrum 
along  the  inner  side  of  the  anterior  sacral  foramina.  It  consists  of  four  or  five 
small  ganglia  on  each  side,  connected  together  by  interganglionic  cords.  Below,, 
these  cords  converge  and  unite  on  the  front  of  the  coccyx  by  means  of  a  small 
ganglion,  the  coccygeal  ganglion  or  ganglion  impar  {ganglion  coccygeum  impar} 
(Fig.  691) .  The  commissural  cord  joins  the  pelvic  portion  to  the  lumbar  portion 
of  the  gangliated  cord.  Like  the  cervical  portion  and  the  lower  lumbar  portion 
the  sacral  portion  receives  no  white  rami  communicantes. 

The  visceral  branches  of  the  third  sacral,  and  usually  of  the  second  and  fourth 
sacral  spinal  nerves,  are  not  connected  with  the  ganglionic  cord. 

Central  Communicating  Branches. — Gray  rami  communicantes,  which  arise  in  the 
sacral  ganglia  and  pass  to  the  anterior  divisions  of  the  sacral  and  coccygeal  nerves. 

Peripheral  Branches. — 1.  Visceral  branches  arise  from  the  upper  portion  of  the 
gangliated  cord  and  pass  to  the  pelvic  plexus.    • 

2.  Parietal  branches  communicate,  on  the  front  of  the  sacrum,  with  the  correspond- 
ing branches  from  the  opposite  side;  some,  from  the  first  two  ganglia,  pass  to  join 
the  pelvic  plexus,  and  others  form  a  plexus  which  a,ccompanies  the  middle  sacral 
artery  and  sends  filaments  to  the  coccygeal  gland. 


THE  GREAT  PLEXUSES  OF  THE  SYMPATHETIC  (Fig.  688). 

The  great  plexuses  of  the  sympathetic  are  the  large  aggregations  of  nerves, 
and  ganglia,  previously  alluded  to,  situated  in  the  thoracic,  abdominal,  and  pelvic 
cavities  respectively.  From  them  are  derived  the  branches  which  supply  the 
viscera. 


THE  PULMONARY  PLEXUS  1081 

The  Cardiac  Plexus  (Plexus  Cardiacus)  (Figs.  688,  691). 

The  cardiac  plexus  is  situated  at  the  base  of  the  heart,  and  is  divided  into  a 
superficial  paxt,  which  Kes  in  the  concavity  of  the  arch  of  the  aorta,  and  a  deep 
paxt,  which  lies  between  the  trachea  and  aorta.  The  two  plexuses  are,  however, 
closely  connected. 

The  Great  or  Deep  Cardiac  Plexus. — The  great  or  deep  cardiac  plexus, 
the  plexus  magnus  profundus  of  Scarpa,  is  situated  in  front  of  the  trachea  at  its 
bifurcation,  above  the  point  of  division  of  the  pulmonary  artery  and  behind  the 
arch  of  the  aorta.  It  is  formed  by  the  cardiac  nerves  derived  from  the  cervical 
ganglia  of  the  sympathetic  and  the  cardiac  branches  of  the  recurrent  laryngeal 
and  pneumogastric.  The  only  cardiac  nerves  which  do  not  enter  into  the  forma- 
tion of  this  plexus  are  the  left  superior  cardiac  nerve  and  the  inferior  cervical 
cardiac  branch  from  the  left  pneumogastric. 

The  branches  from  the  right  side  of  this  plexus  pass,  some  in  front  of,  and 
others  behind,  the  right  pulmonary  artery;  the  former,  the  more  numerous,  trans- 
mit a  few  filaments  to  the  anterior  pulmonary  plexus,  and  are  then  continued 
onward  to  form  part  of  the  left  or  anterior  coronary  plexus ;  those  behind  the  pul- 
monary artery  distribute  a  few  filaments  to  the  right  auricle,  and  are  then  con- 
tinued onward  to  form  a  part  of  the  right  or  posterior  coronary  plexus. 

The  branches  from  the  left  side  of  the  deep  cardiac  plexus  distribute  a  few 
filaments  to  the  superficial  cardiac  plexus,  to  the  left  auricle  of  the  heart,  and  to 
the  anterior  pulmonary  plexus,  and  then  pass  on  to  form  the  greater  part  of  the 
posterior  coronary  plexus. 

The  Anterior  or  Left  Coronary  Plexus  {plexus  coronarius  cordis  anterior).— The 
anterior  or  left  coronary  plexus  is  formed  chiefly  from  the  superficial  cardiac 
plexus,  but  receives  filaments  from  the  deep  cardiac  plexus.  Passing  forward 
between  the  aorta  and  pulmonary  artery,  it  accompanies  the  left  coronary  artery 
on  the  anterior  surface  of  the  heart. 

The  Posterior  or  Right  Coronary  Plexus  (plexus  coronarius  cordis  posterior). — 
The  posterior  or  right  coronary  plexus  is  chiefly  formed  by  filaments  prolonged 
from  the  left  side  of  the  deep  cardiac  plexus,  and  by  a  few  from  the  right  side. 
It  surrounds  the  branches  of  the  coronary  artery  at  the  back  of  the  heart,  and 
its  filaments  are  distributed  with  those  vessels  to  the  muscular  substance  of  the 
ventricles. 

The  Superficial  or  AnteriorCardiac  Plexus. — The  superficial  or  anterior  cardiac 
plexus  lies  beneath  the  arch  of  the  aorta,  in  front  of  the  right  pulmonary  artery.  It 
is  formed  by  the  left  superior  cardiac  nerve,  the  left  (and  occasionally  also  the  right) 
inferior  cervical  cardiac  branches  of  the  pneumogastric,  and  filaments  from  the 
deep  cardiac  plexus.  A  small  ganglion,  the  cardias  ganglion  of  Wrisberg  (ganglion 
cardiacum  [Wrishergi])  is  occasionally  foimd  connected  with  these  nerves  at  their 
point  of  junction.  This  ganglion,  when  present,  is  situated  immediately  beneath 
the  arch  of  the  aorta,  on  the  right  side  of  the  ductus  arteriosus.  The  superficial 
cardiac  plexus  forms  the  chief  part  of  the  anterior  coronary  plexus,  and  several 
filaments  pass  along  the  pulmonary  artery  to  the  left  anterior  pulmonary  plexus. 

Valentin  has  described  nervous  filaments  ramifying  under  the  endocardium; 
and  Remak  has  found,  in  several  mammalia,  numerous  small  ganglia  on  the  car- 
diac nerves,  both  on  the  surface  of  the  heart  and  in  its  muscular  substance. 

The  Pulmonary  Plexus  (Plexus  Pulmonalis). 

The  larger  posterior  pulmonary  plexus  is  situated  back  of  the  root  of  the  lung. 
It  is  formed  by  the  pneumogastric  nerve  and  branches  from  the  second,  third,  and 
fourth  thoracic  sympathetic  ganglia.     It  sends  branches  along  the  bronchi  and 


1082 


2HE   NERVOUS  SYSTEM 


blood-vessels  into  the  lung  and  some  fibres  pass  to  the  front  of  the  root  of  the 
lung  to  form  the  anterior  pulmonary  plexus.  1'he  smaller  anterior  pulmonaxy 
plexus  is  in  front  of  and  above  the  root  of  the  lung.  It  is  formed  on  each  side  by 
the  fibres  from  the  posterior  pulmonary  plexus.  '^I'he  left  plexus  receives  branches 
from  the  superficial  cardiac  plexus.  The  anterior  plexus  supplies  the  structures 
of  the  root  of  the  lung. 

The  Oesophageal  Plexus  (Plexus  Oesophageus). 

The  oesophageal  plexus  is  in  the  posterior  mediastiimm  and  surrounds  the 
oesophagus.     It  is  formed  by  the  pneumogastric  nerves  which  have  come  from 


SOLAR      LEFT 
PLEXUS      PNEUMOGASTRIC 


HEPATIC 
PLEXUS 


COMMON 
BILE-DUCT 


SUPERIOR 

MESENTERIC 

PLEXUS 

ABDOMINAL 

AORTIC 

PLEXUS 


SUPRARENAL 
PLEXUS 


GREAT 
SPLANCHNIC 


SEMILUNAR 
GANGLION 


SUPERIOR 

MESENTERIC 

GANGLION 


SPERMATIC 
PLEXUS 


LUMBAR 
GANGLIA 


INFERIOR 

MESENTERIC 

PLEXUS 


Fig. 


The  semilunar  ganglia  with  the  sympathetic  plexuses  of  the  abdominal  viscera  radiating  from 
the  ganglia.     (Toldt.) 


the  posterior  pulmonary  plexuses,  and  by  fibres  from  the  great  splanchnic  nerve 
and  ganglion.  The  oesophageal  plexus  is  usually  considered  as  a  portion  of  the 
pneumogastric  nerve  (p.  1061). 


THE  EPIGASTRIC   OB   SOLAR   PLEXUS 


1083 


The  Epigastric  or  Solar  Plexus  (Plexus  Coeliacum)  (Figs.  688,  691,  696,  697). 

The  epigastric  or  solar  plexus  supplies  all  the  viscera  in  the  abdominal  cavity. 
It  consists  of  a  great  network  of  nerves  and  ganglia,  situated  behind  the  pancreas 


Diaphragmatic  ganglion 
Suprarenal  capsule. 

Great 

splanchni 
nerve. 

Right 
semilunar 
ganglion. 

Renal  ganglion 
Small  splanchnic  nerve. 


Hepatic 


Renal  artery. 
Gangliaied  cord. 

Communicating  branch. 


■Left  semilunar  ganglion. 
Superior  mesenteric  artery. 
Great  splanchnic  nerve. 
Small  splanchnic  nerve. 

Renal  ganglion. 


Renal  artery. 
Supenor  mesenteric  ganglion. 


Branch  to  aortic  plexus. 


Branch  to  aortic  plexus. — 


Gangliated  cord  of 
sympathetic. 


Inferior  mesenteric  artery. 


Inferior  myenteric  ganglion. 


Sacra-vertebral  angle. 
Common  iliac  vein. 
Common  iliac  artery. 


Fig.  697. — Lumbar  portion  of  the  gangliated  cord,  with  the  solar  and  hypogastric  plexuses.     (After  Henle.) 


1084  THE  NERVOUS  SYSTEM 

and  the  lesser  peritoneal  cavity  and  in  front  of  the  aorta  and  crura  of  the  Dia- 
phragm. It  surrounds  the  coeliac  axis  and  root  of  the  superior  mesenteric  artery, 
extending  downward  as  low  as  the  pancreas  and  outward  to  the  suprarenal  cap- 
sules. This  plexus,  and  the  ganglia  connected  with  it,  receive  the  great,  the  small 
and  the  least  splanchnic  nerves  of  both  sides,  and  some  filaments  from  the  right 
pneumogastric  nerve.  It  distributes  filaments  which  accompany,  under  the  name 
of  plexuses,  all  the  branches  from  the  front  of  the  abdominal  aorta. 

Of  the  ganglia  of  which  the  solar  plexus  is  partly  composed  the  principal  are 
the  two  semilunar  ganglia  {ganglia  coeliaca)  (Figs.  688,  696,  and  697),  which  are 
situated  one  on  each  side  of  the  plexus,  and  are  the  largest  ganglia  in  the  body. 
They  are  large,  irregular,  gangliform  masses  formed  by  the  aggregation  of  smaller 
ganglia,  having  interspaces  between  them.  They  are  situated  in  front  of  the 
crura  of  the  Diaphragm,  close  to  the  suprarenal  capsules:  the  one  on  the  right 
side  lies  beneath  the  inferior  vena  cava;  the  upper  part  of  each  ganglion  is  joined 
by  the  greater  splanchnic  nerve,  and  to  the  inner  side  of  each  the  branches  of  the 
solar  plexus  are  connected. 

From  the  epigastric  or  solar  plexus  are  derived  the  following: 

Phrenic  or  Diaphragmatic  plexus.  C  Gastric  plexus. 

Suprarenal  plexus.  Cceliac  plexus  <  Splenic  plexus. 

Renal  plexus.  (  Hepatic  plexus. 

Spermatic  plexus.  Superior  mesenteric  plexus. 

Aortic  plexus. 

The  Phrenic  Plexus  (plexus  phrenicus)  (Fig.  696). — The  phrenic  plexus  accom- 
panies the  phrenic  artery  to  the  Diaphragm,  which  it  supplies,  some  filaments 
passing  to  the  suprarenal  capsule.  It  arises  from  the  upper  part  of  the  semilunar 
ganglion,  and  is  larger  on  the  right  than  on  the  left  side.  It  receives  one  or  two 
branches  from  the  phrenic  nerve.  In  connection  with  this  plexus,  on  the  right 
side,  at  its  point  of  junction  with  the  phrenic  nerve,  is  a  small  ganglion,  the 
diaphragmatic  or  phrenic  ganglion  (ganglion  phrenicum)  (Fig.  697) .  This  ganglion 
is  placed  on  the  under  surface  of  the  Diaphragm,  near  the  right  suprarenal  capsule. 
Its  branches  are  distributed  to  the  inferior  vena  cava,  suprarenal  capsule,  and 
hepatic  plexus.     There  is  no  ganglion  on  the  left  side. 

The  Suprarenal  Plexus  (plexus  suprarenalis)  (Fig.  696) . — The  suprarenal  plexus 
is  formed  by  branches  from  the  solar  plexus,  from  the  semilunar  ganglion,  and 
from  the  phrenic  and  great  splanchnic  nerves,  a  ganglion  being  formed  at  the 
point  of  junction  of  the  latter  nerve.  It  supplies  the  suprarenal  capsule.  The 
branches  of  this  plexus  are  remarkable  for  their  large  size  in  comparison  with 
the  size  of  the  organ  they  supply. 

The  Renal  Plexus  (plexus  renalis)  (Figs.  696  and  697). — The  renal  plexus  is 
formed  by  filaments  from  the  solar  plexus,  the  outer  part  of  the  semilunar 
ganglion,  and  the  aortic  plexus.  It  is  also  joined  by  filaments  from  the  lesser  and 
smallest  splanchnic  nerves.  The  nerves  from  these  sources,  fifteen  or  twenty  in  num- 
ber, have  numerous  ganglia  developed  upon  them.  They  accompany  the  branches 
of  the  renal  artery  into  the  kidney,  some  filamentson  the  right  side  being  distributed 
to  the  inferior  vena  cava,  and  others,  on  both  sides,  to  the  spermatic  plexuses. 

The  Spermatic  Plexus  (plexus  spermaticus)  (Fig.  696). — ^The  spermatic  plexus 
is  derived  from  the  renal  plexus,  receiving  branches  from  the  aortic  plexus.  It 
accompanies  the  spermatic  vessels  to  the  testes. 

The  Ovarian  Plexus  ('plexus  arteriae  ovaricae). — In  the  female  the  ovarian  plexus 
is  distributed  to  the  ovaries  and  fundus  of  the  uterus. 

The  Coeliac  Plexus  (plexus  coeliacus). — The  coeliac  plexus,  of  large  size,  is  a 
direct  continuation  frorn  the  solar  plexus;  it  surrounds  the  coeliac  axis  and  sub- 
divides into  the  gastric,  hepatic,  and  splenic  plexuses.    It  receives  branches  from 


THE    HYPOGASTRIC  PLEXUS  1085 

the  lesser  splanchnic  nerves,  and,  on  the  left  side,  a  filament  from  the  right  pneu- 
mogastric. 

The  Gastric  or  Coronary  Plexus  (plexus  gastricus  superior)  (Fig.  696)  accompanies 
the  gastric  artery  along  the  lesser  curvature  of  the  stomach,  and  joins  with  branches 
from  the  left  pneumogastric  nerve.     It  is  distributed  to  the  stomach. 

The  Splenic  Plexus  (plexus  lienalis)  (Fig.  696)  is  formed  by  branches  from  the 
coeliac  plexus,  the  left  semilunar  ganglion,  and  from  the  right  pneumogastric 
nerve.  It  accompanies  the  splenic  artery  and  its  branches  to  the  substance  of 
the  spleen,  giving  off,  in  its  course,  filaments  to  the  pancreas,  the  pancreatic  plexus, 
and  the  left  gastro-epiploic  plexus,  which  accompanies  the  gastio-epiploica  sinistra 
artery  along  the  convex  border  of  the  stomach. 

The  Hepatic  Plexus  (plexus  hepaticus)  (Fig.  696),  the  largest  offset  from  the 
coeliac  plexus,  receives  filaments  from  the  left  pneumogastric  and  right  phrenic 
nerves.  It  accompanies  the  hepatic  artery,  ramifying  in  the  substance  of  the  liver 
upon  its  branches  and  upon  those  of  the  vena  portae. 

Branches  from  this  plexus  accompany  all  the  divisions  of  the  hepatic  artery. 
Thus  there  is  a  pyloric  plexus  accompanying  the  pyloric  branch  of  the  hepatic, 
which  joins  with  the  gastric  plexus  and  pneumogastric  nerves.  There  is  also  a 
gastro-duodenal  plexus,  which  subdivides  into  the  pancreatico-duodendal  plexus, 
which  accompanies  the  pancreatico-duodenal  artery,  to  supply  the  pancreas  and 
duodenum,  joining  with  branches  from  the  mesenteric  plexus.  The  gastro-epi- 
ploic plexus,  which  accompanies  the  right  gastro-epiploic  artery  along  the  greater 
curvature  of  the  stomach,  and  which  is  said  to  anastomose  with  branches  from 
the  splenic  plexus,  is  in  reality  derived  from  the  splenic  plexus.  A  cystic  plexus, 
which  supplies  the  gall-bladder,  also  arises  from  the  hepatic  plexus  near  the  liver. 

The  Superior  Mesenteric  Plexus  (plexus  rnesentericv^  superior)  (Fig.  696) . — The 
superior  mesenteric  plexus  is  a  continuation  of  the  lower  part  of  the  great  solar 
plexus,  receiving  a  branch  from  the  junction  of  the  right  pneumogastric  nerve  with 
the  coeliac  plexus.  It  surrounds  the  superior  mesenteric  artery,  which  it  accom- 
panies into  the  mesentery,  and  divides  into  a  number  of  secondary  plexuses,  which 
are  distributed  to  all  the  parts  supplied  by  the  artery — viz.,  pancreatic  branches  to 
the  pancreas;  intestinal  branches,  which  supply  the  whole  of  the  small  intestine; 
and  ileo-colic,  right  colic,  and  middle  colic  branches,  which  supply  the  corresponding 
partsof  the  large  intestine.  The  nerves  composing  this  plexus  are  white  in  color  and 
firm  in  texture,  and  have  numerous  ganglia  developed  upon  them  near  their  origin. 

The  Abdominal  Aortic  Plexus  (plexus  aorticus  abdomiualis)  (Figs.  691,  696,  and 
697). — The  abdominal  aortic  plexus  is  formed  by  branches  derived,  on  each  side, 
from  the  solar  plexus  and  the  semilunar  ganglia,  receiving  filaments  from  some 
of  the  lumbar  ganglia.  It  is  situated  upon  the  sides  and  front  of  the  aorta, 
between  the  origins  of  the  superior  and  inferior  mesenteric  arteries.  From  this 
plexus  arise  part  of  the  spermatic,  the  inferior  mesenteric,  and  the  hypogastric 
plexuses;  and  it  distributes  filaments  to  the  inferior  vena  cava. 

The  Inferior  Mesenteric  Plexus  (plexus  mesentericus  inferior)  (Fig.  696)  is  derived 
chiefly  from  the  left  side  of  the  aortic  plexus.  It  surrounds  the  inferior  mesenteric 
artery,  and  divides  into  a  number  of  secondary  plexuses,  which  are  distributed  to 
all  the  parts  supplied  by  the  artery — viz.,  the  left  colic  and  sigmoid  plexuses,  which 
supply  the  descending  and  sigmoid  flexure  of  the  colon;  and  the  superior  haem- 
orrhoidal  plexus  (plexus  haemorrhoidalis  superior),  which  supplies  the  upper  part 
of  the  rectum  and  joins  in  the  pelvis  with  branches  from  the  pelvic  plexus. 

The  Hypogastric  Plexus  (Plexus  Hypogastricus)  (Figs.  688,  691,  697). 

The  hypogastric  plexus  supplies  the  viscera  of  the  pelvic  cavity.  It  is  situated 
in  front  of  the  promontory  of  the  sacrum,  between  the  two  common  iliac  arteries, 


1086  THE  NERVOUS  SYSTEM 

and  is  formed  by  the  union  of  numerous  filaments,  which  descend  on  each  side 
from  the  abdominal  aortic  plexus  and  from  the  lumbar  ganglia.  This  plexus  con- 
tains no  evident  ganglia;  it  bifurcates,  below,  into  two  lateral  portions,  which 
form  the  pelvic  plexuses. 

The  Pelvic  or  Sacral  Plexus  (Plexus  Sacralis). 

The  pelvic  plexus,  sometimes  called  the  inferior  hjrpogastric,  supplies  the  viscera 
of  the  pelvic  cavity,  is  situated  at  the  side  of  the  rectum  in  the  male,  and  at  the 
side  of  the  rectum  and  vagina  in  the  female.  It  is  formed  by  a  continuation  of  the 
hypogastric  plexus,  by  branches  from  the  second,  third,  and  fourth  sacral  nerves, 
and  by  a  few  filaments  from  the  first  two  sacral  ganglia.  At  the  point  of  junction 
of  these  nerves  small  ganglia  are  found.  From  this  plexus  numerous  branches  are 
distributed  to  all  the  viscera  of  the  pelvis.  They  accompany  the  branches  of  the 
internal  iliac  artery. 

The  Inferior  Haemorrhoidal  Plexus  {'plexus  haemorrhoidalis  inferior). — The  infe- 
rior haemorrhoidal  plexus  arises  from  the  back  part  of  the  pelvic  plexus.  It 
supplies  the  rectum,  joining  with  branches  of  the  superior  haemorrhoidal 
plexus. 

The  Vesical  Plexus  (plexus  vesicalis). — The  vesical  plexus  arises  from  the  fore- 
part of  the  pelvic  plexus.  The  nerves  composing  it  are  numerous,  and  contain 
a  large  proportion  of  spinal  nerve-fibres.  They  accompany  the  vesical  arteries, 
and  are  distributed  at  the  side  and  base  of  the  bladder.  Numerous  filaments  also 
pass  to  the  vesiculae  seminales  and  vasa  deferentia;  those  accompanying  the  vas 
deferens  join,  on  the  spermatic  cord,  with  branches  from  the  spermatic  plexus. 

The  Prostatic  Plexus  {'plexus  prostaticus). — ^The  prostatic  plexus  is  continued 
from  the  lower  part  of  the  pelvic  plexus.  The  nerves  composing  it  are  of  large 
size.  They  are  distributed  to  the  prostate  gland,  vesiculae  seminales,  and  erectile 
structure  of  the  penis.  The  nerves  supplying  the  erectile  structure  of  the  penis 
consist  of  two  sets,  the  small  and  large  cavernous  nerves.  They  are  slender  fila- 
ments, which  arise  from  the  forepart  of  the  prostatic  plexus,  and,  after  joining 
with  branches  from  the  internal  pudic  nerve,  pass  forward  beneath  the  pubic 
arch. 

The  Small  Cavernous  Nerve  {n.  cavernosus  penis  minor)  perforates  the  fibrous 
covering  of  the  penis  near  its  roots. 

The  Large  Cavernous  Nerve  {n.  cavernosus  penis  'major)  passes  forward  along  the 
dorsum  of  the  penis,  joins  with  the  dorsal  branch  of  the  pudic  nerve,  and  is  dis- 
tributed to  the  corpora  cavernosa  and  corpus  spongiosum. 

The  uterine  and  vaginal  plexuses  in  reality  constitute  one  plexus,  the  utero- 
vaginal plexus  -{plexus  uterovaginalis). 

The  Vaginal  Plexus  arises  from  the  lower  part  of  the  pelvic  plexus.  It  is  lost 
on  the  walls  of  the  vagina,  being  distributed  to  the  erectile  tissue  at  its  anterior 
part  and  to  the  mucous  membrane.  The  nerves  composing  this  plexus  contain, 
like  the  vesical  nerves,  a  large  proportion  of  spinal  nerve-fibres. 

The  Uterine  Plexus  arises  from  the  upper  part  of  the  pelvic  plexus  above  the 
point  where  the  branches  from  the  sacral  nerves  join  the  plexus.  Its  branches 
accompany  the  uterine  arteries  to  the  sides  of  the  organ  between  the  layers  of  the 
broad  ligaments,  and  are  distributed  to  the  cervix  and  lower  part  of  the  body  of 
the  uterus,  penetrating  its  substance. 

Other  filaments  pass  separately  to  the  body  of  the  uterus  and  the  Fallopian 
tube. 

Branches  from  the  plexus  accompany  the  uterine  arteries  into  the  substance 
of  the  uterus.    Upon  these  filaments  ganglionic  enlargements  are  found. 


THE  OEGANS  OF  SPECIAL  SENSE. 


THE  Organs  of  the  Senses  are  five  in  number — viz.,  those  of  Taste,  of  Smell, 
of  Sight,  of  Heaxing,  and  of  Touch. 


THE  TONGUE  (LINGUA)  (Fig.  698). 

The  tongue  is  a  very  mobile  muscular  organ,  undergoing  changes  in  length  and 
width  at  every  contraction  of  its  muscle.  It  is  the  organ  of  the  special  sense  of 
taste,  and  is  also  an  organ  of  speech,  mastication,  and  deglutition.  It  is  situated 
in  the  floor  of  the  mouth,  in  the  interval  between  the  two  lateral  portions  of  the 
body  of  the  lower  jaw,  and  when  at  rest  is  about  three  and  one-half  inches  in 
length.     We  describe  the  body,  base,  apex,  dorsum,  margin,  and  inferior  surface. 

The  Body  {corpus  linguae).- — The  body  forms  the  great  bulk  of  the  organ 
and  is  composed  of  striated  muscle. 

The  Base  or  Root  {radix  linguae). — The  base  or  root  is  directed  backward,  and 
connected  with  the  os  hyoideum  by  the  Hyo-glossi  and  Genio-hyo-glossi  muscles 
and  the  hyo-glossal  membrane;  with  the  epiglottis  by  three  folds  of  mucous  mem- 
brane, the  glosso-epiglottic  folds;  with  the  soft  palate  by  means  of  the  anterior 
pillars  of  the  fauces;  and  with  the  pharynx  by  the  Superior  constrictors  and  the 
mucous  membrane. 

The  Apex  or  Tip  {apex  linguae). — The  apex  or  tip  is  thin  and  narrow,  and  is 
directed  forward  against  the  inner  surface  of  the  lower  incisor  teeth. 

The  Dorsum  of  the  Tongue  {dorsum  linguae). — The  dorsum  when  the  tongue 
of  a  living  person  is  at  rest  is  markedly  arched  from  before  backward.  On  the 
dorsum  is  a  median  longitudinal  raph6  {sulcus  medianu^  linguae).  This  slight 
depression  terminates  posteriorly  in  the  depression  known  as  the  foramen  caecum 
(foramen  caecum  linguae  [Morgagni{\),  from  which  a  shallow-shaped  groove,  the 
sulcus  terminalis  of  His,  runs  outward  and  forward  on  each  side  to  the  lateral 
margin  of  the  tongue.  The  part  of  the  dorsum  of  the  tongue  in  front  of  this 
groove,  known  as  the  anterior  or  oral  part,  forming  about  two-thirds  of  its  upper 
surface,  is  rough  and  covered  with  papillae;  the  posterior  third  of  the  dorsum 
is  back  of  the  sulcus  terminalis,  is  known  as  the  posterior  or  pharyngeal  portion,  is 
smoother,  and  contains  numerous  muciparous  glands  and  lymphoid  follicles. 

The  Margin  of  the  Tongue  (margo  lateralis  linguae). — ^The  margin  of  the 
tongue  is  free  in  front  of  the  anterior  arch  of  the  palate.  Just  in  front  of  the 
arch  are  several  vertical  folds,  the  folia  linguae. 

The  Under  or  Inferior  Surface  (fades  inferior  linguae). — The  under  or 
inferior  surface  of  the  tongue  is  connected  with  the  lower  jaw  by  the  Genio-hyo- 
glossi  muscles,  from  its  sides  the  mucous  membrane  is  reflected  to  the  inner  sur- 
face of  the  gums;  and  from  its  under  surface  on  to  the  floor  of  the  mouth,  where, 
in  the  middle  line,  it  is  elevated  into  a  distinct  vertical  fold,  the  fraenum  linguae 
(frenulum  linguae).  To  each  side  of  the  fraenum  is  a  slight  fold  of  the  mucous 
membrane,  the  plica  fimbriata,  the  free  edge  of  which  exhibits  a  series  of  fringe- 
like processes. 

The  tip  of  the  tongue,  part  of  the  under  surface,  its  sides,  and  dorsum  are  free. 

(  1087 ) 


1088 


THE    ORGANS   OF  SPECIAL    SENSE 


Structure  of  the  Tongue. — The  tongue  is  partly  invested  by  mucous  mem- 
brane and  a  submucous  fibrous  layer.  It  consists  of  symmetrical  halves,  sepa- 
rated from  each  other,  in  the  middle  line,  by  a  fibrous  septum.  Each  half  is  com- 
posed of  muscular  fibres  arranged  in  various  directions  (page  398),  containing 
much  interposed  fat,  and  supplied  by  vessels  and  nerves. 

The  Mucous  Membrane  {tunica  mucosa  linguae). — The  mucous  membrane 
invests  the  entire  extent  of  the  free  surface  of  the  tongue.  On  the  dorsum  it  is 
thicker  behind  than  in  front,  and  is  continuous  with  the  sheath  of  the  muscles 
attached  to  it,  through  the  submucous  fibrous  layer.  On  the  under  surface  of  the 
organ,  where  it  is  thin  and  smooth,  it  can  be  traced  on  each  side  of  the  fraenum 


PHARYNX 


—EPIGLOTTIS. 


CIRCUM- 
VALLATE 
PAPILLyC. 


Fig.  698. — Upper  surface  of  the  tongue. 

through  the  ducts  of  the  submaxillary  and  the  sublingual  glands.     As  it  passes 
over  the  borders  of  the  organ  it  gradually  assumes  a  papillary  character. 

Structure. — The  structure  of  the  mucous  membrane  of  the  tongue  differs  in 
different  parts.  That  covering  the  under  surface  of  the  organ  is  thin,  smooth, 
and  identical  in  structure  with  that  lining  the  rest  of  the  oral  cavity.  The  mucous 
membrane  covering  the  tongue  behind  the  foramen  caecum  and  sulcus  terminalis 
is  thick  and  freely  movable  over  the  subjacent  parts.  It  contains  a  large  number 
of  lymphoid  follicles  (folliculi  linguales),  which  together  constitute  what  is  some- 
times termed  the  lingual  tonsil  (tonsilla  lingualis).  Each  follicle  forms  a  rounded 
•eminence,  the  centre  of  which  is  perforated  by  a  minute  orifice  leading  into  a 


THE    TONGUE 


1089 


funnel-shaped  cavity  or  recess;  around  this  recess  are  grouped  numerous  oval  or 
rounded  nodules  of  lymphoid  tissue,  each  enveloped  by  a  capsule  derived  from 
the  submucosa,  while  opening  into  the  bottom  of  the  recesses  are  also  seen  the 
ducts  of  mucous  glands  {glandulae  linguales).  The  mucous  membrane  on  the 
anterior  part  of  the  dorsum  of  the  tongue  is  thin  and  intimately  adherent  to  the 
muscular  tissue,  and  covered  with  minute  eminences,  the  papillae  of  the  tongue. 
It  consists  of  a  layer  of  connective  tissue,  the  corium  or  mucosa,  supporting  numer- 
ous papillae,  and  covered,  as  well  as  the  papillae,  with  epithelium. 

The  epithelium  is  of  the  scaly  variety,  like  that  of  the  epidermis.  It  covers  the 
free  surface  of  the  tongue,  as  maybe  readily  demonstrated  by  maceration  or  boiling, 
when  it  can  be  easily  detached  entire ;  it  is  much  thinner  than  that  of  the  skin ;  the 
intervals  between  the  large  papillae  are  not  filled  up  by  it,  but  each  papilla  has 
a  separate  investment  from  root  to  summit.  The  deepest  cells  may  sometimes  be 
detached  as  a  separate  layer,  corresponding  to  the  rete  mucosum,  but  they  never 
contain  coloring  matter. 

The  Corium. — The  corium  consists  of  a  dense  feltwork  of  fibrous  connective 
tissue,  with  numerous  elastic  fibres,  firmly  connected  with  the  fibrous  tissue  form- 
ing the  septa  between  the  muscular  bundles  of  the  tongue.  It  contains  the  ramifi- 
cations of  the  numerous  vessels  (Fig.  699)  and  nerves  from  which  the  papillae  are 
supplied,  large  plexuses  of  lymphatic  vessels,  and  the  glands  of  the  tongue. 


Filiform. 


Fungiform. 


Secondary 
papillae. 


Circumvallate. 


Artery 
Vein 


Fig.  699. — Three  kinds  of  papillae,  magnified. 


The  Papillae  of  the  Tongue  (papillae  linguales)  (Figs.  698,  699,  700,  and  701).— 
These  are  papillary  projections  of  the  corium.  They  are  thickly  distributed  over 
the  anterior  two-thirds  of  the  upper  surface  of  the  tongue,  giving  to  it  its  char- 
icteristic  roughness.  The  varieties  of  papillae  met  with  are — the  papillae  maximae 
k  circumvallate  papillae,  papillae  mediae  or  fimgiforme  papillae,  papillae  minimae, 
)nical  or  filiforme  papillae,  and  papillae  simplices  or  simple  papillae. 
The  Papillae  Maximae  or  Circumvallate  Papillae  (papillae  vallatae)  (Figs.  698,  699, 
ind  700)  are  of  large  size,  and  vary  from  eight  to  twelve  in  number.  They  are 
Situated  at  the  back  part  of  the  dorsum  of  the  tongue,  near  its  base,  in  front  of 
the  foramen  caecum  and  sulcus  terminalis,  forming  a  row  on  each  side,  which, 
'running  backward  and  inward,  meet  in  the  middle  line,  like  the  two  lines  of  the 
letter  V  inverted  \.  Each  papilla  consists  of  a  projection  of  mucous  membrane 
from  -Jjj.  to  ^  of  an  inch  wide,  attached  to  the  bottom  of  a  cup-shaped  depression  of 
the  mucous  membrane ;  the  papilla  is  in  shape  like  a  truncated  cone,  the  smaller 
end  being  directed  downward  and  attached  to  the  tongue,  the  broader  part  or 
base  projecting  on  the  surface  and  being  studded  with  numerous  small  secondary 
papillae  (Fig.  699),  which,  however,  are  covered  by  a  smooth  layer  of  the  epithe- 
lium. The  cup-shaped  depression  forms  a  kind  of  fossa  around  the  papilla, 
having  a  circular  margin  of  about  the  same  elevation  covered  with  smaller  papillae. 

G9 


1090 


THE    ORGANS    OF  SPECIAL   SENSE 


Immediately  behind  the  apex  of  the  V  is  the  foramen  caecum,  mentioned  above. 
This  foramen,  according  to  His,  represents  the  remains  of  the  invagination  which 
forms  the  median  rudiment  of  the  thyroid  body,  and  which  for  a  time  opens  by 
a  duct,  the  thyroglossal  duct,  on  to  the  dorsum  of  the  tongue.  It  may  extend 
downward  toward  the  hyoid  bone.     Kanthack,  however,  disputes  this  view.^ 

The  Fungiform  Papillae  or  Papillae  Mediae  (papillae  fungiformes  et  papillae  len- 
ticulares)  (Fig.  699) ,  more  numerous  than  the  preceding,  are  scattered  irregularly 
and  sparingly  over  the  dorsum  of  the  tongue,  but  are  found  chiefly  at  its  sides 
and  apex.  They  are  easily  recognized  among  the  other  papillae,  by  their  large 
size,  rounded  eminences,  and  deep-red  color.  They  are  narrow  at  their  attach- 
ment to  the  tongue,  but  broad  and  rounded  at  their  free  extremities,  and  are 
covered  with  secondary  papillae.    Their  epithelial  investment  is  very  thin. 

The  Conical  or  Filiform  Papillae  or  Papillae  Minimae  {papillae  conicae  et  papillae 
filiformes)  (Fig.  699)  cover  the  anterior  two-thirds  of  the  dorsum  of  the  tongue. 
They  are  very  minute,  more  or  less  conical  or  filiform  in  shape,  and  arranged  in  lines 
corresponding  in  direction  with  the  two  rows  of  the  papillae  circumvallatae,  except- 
ing at  the  apex  of  the  organ,where  their  direction  is  transverse.  Projecting  from  their 
apices  are  numerous  filiform  processes  or  secondary  papillae;  these  are  of  a  whitish 
tint,  owing  to  the  thickness  and  density  of  the  epithelium  of  which  they  are  com- 
posed, and  which  has  here  undergone  a 
peculiar  modification,  the  cells  having  be- 
come cornified  and  elongated  into  dense, 
imbricated,  brush-like  processes.  They 
contain  also  a  number  of  elastic  fibres,  which 
render  them  firmer  and  more  elastic  than 
the  papillae  of  mucous  membrane  generally. 
Simple  Papillae,  similar  to  those  of  the  skin, 
cover  the  whole  of  the  mucous  membrane  of 
the  tongue,  as  well  as  the  larger  papillae. 
They  consist  of  closely  set,  microscopic  ele- 
vations of  the  corium,  containing  a  capillary 
loop,  covered  by  a  layer  of  epithelium. 

Structure  of  the  Papillae  (Figs.  699  and  700). 
— ^The  papillae  apparently  resemble  in  struc- 
ture the  papillae  of  the  cutis,  consisting  of  a 
cone-shaped  projection  of  connective  tissue, 
covered  with  a  thick  layer  of  squamous  epi- 
thelium, and  contain  one  or  more  capillary 
loops,  amongst  which  nerves  are  distributed 
in  great  abundance.  If  the  epithelium  is 
removed,  it  will  be  found,  however,  that  they  are  not  simple  elevations  like  the 
papillae  of  the  skin,  for  the  surface  of  each  is  studded  with  minute  conical  pro- 
cesses of  the  mucous  membrane,  which  form  secondary  papillae  (Todd  and  Bow- 
man). In  the  papillae  circumvallatae  the  nerves  are  numerous  and  of  large  size;  in 
the  papillae  fungiformes  they  are  also  numerous,  and  terminate  in  a  plexiform  net- 
work, from  which  brush-like  branches  proceed ;  in  the  papillae  filiformes  their  mode 
of  termination  is  uncertain.  Buried  in  the  epidermis  of  the  papillae  circumvallatae,. 
and  in  some  of  the  fungiformes,  are  certain  peculiar  bodies,  called  taste-buds^  (Fig. 
701).  Each  is  flask-like  in  shape,  the  broad  base  resting  on  the  corium,  and  the 
neck  opening  by  an  orifice,  the  gustatory  pore,  between  the  cells  of  the  epithelium. 


Fig.  700. — Circumvatlate  papillae  of  tongue  of 
rabbit,  showing  position  of  taste-goblets.  a. 
Duct  of  gland,  d.  Serous  gland,  p.  Taste-buds. 
I.  Primary  septa,  and  I',  secondary  sepia,  of 
papillae,  n.  Medullated  nerve.  if.  Muscular 
fibres.     (StiJhr.) 


'  Journal  of  Anatomy  and  Physiology,  1891. 

'  These  bodies  are  also  found  in  considerable  numbers  at  the  side  of  the  base  of  the  tongue,  just  in  front  of  the- 
anterior  pillars  of  the  fauces,  and  also  on  the  posterior  surface  of  the  epiglottis  and  anterior  surface  of  the  soft 
palate.— Ed.  of  15th  English  edition. 


THE    TONGUE  1091 

They  are  formed  by  two  kinds  of  cells,  supporting  cells  and  gustatory  cells.  The 
supporting  cells  are  mostly  arranged  like  the  staves  of  a  cask,  and  form  an  outer 
envelope  for  the  bud.  Some,  however,  are  found  in  the  interior  of  the  bud  between 
the  gustatory  cells.  The  gustatory  cells  occupy  the  central  portion  of  the  bud; 
they  are  spindle-shaped,  and  each  possesses  a  large  spherical  nucleus  near  the 
middle  of  the  cell.  Until  recently  the  teaching  was  as  follows:  The  peripheral 
end  of  the  cell  terminates  as  the  gustatory  pore  in  a  fine,  hair-like  filament,  the 
gustatory  hair.  The  central  process  passes  toward  the  deep  extremity  of  the  bud, 
and  there  ends  in  a  single  or  bifurcated  varicose  filament,  which  was  formerly 
supposed  to  be  continuous  with  the  terminal  fibril  of  a  nerve;  the  investigations 
of  Lenhossek  and  others  would  seem  to  prove,  however,  that  this  is  not  so,  but 
that  the  nerve-fibrils  after  losing  their  medullary  sheaths  enter  the  taste-bud,  and 


Gustatory  hairs  Taste  pore 


Epithelium 


Taste  bud 


Tunica  propria—^ 
Fig.  701. — Taste-buds  Irom  the  papilla  foliaia  of  a  rabbit,     a  sou.     i .Szymonowicz.) 

terminate  in  a  fine  extremity  between  the  gustatory  cells.  Other  nerve-fibrils 
may  be  seen  ramifying  between  the  cortical  cells  and  terminating  in  fine  extrem- 
ities; these,  however,  are  believed  to  be  nerves  of  ordinary  sensation,  and  not 
gustatory.  It  is  now  not  believed  that  the  epithelia  of  the  taste-buds  are  directly 
connected  with  the  nerve-fibres  by  long  processes.  "The  latest  researches  have 
shown  that  dendrites  of  sensory  neurones  (sensory  nerves)  enter  the  taste-buds 
and  end  free  in  telodendria.  The  latter  surround  the  neuro-epithelial,  and,  to 
some  extent,  the  sustentacular  cells,  their  relations  depending  on  contact."^ 

Glands  of  the  Tongue. — The  tongue  is  provided  with  mucous  and  serous  glands. 
The  mucous  glands  are  similar  in  structure  to  the  labial  and  buccal  glands.  They 
are  found  especially  at  the  back  part,  behind  the  circumvallate  papillae,  but  are 
also  present  at  the  apex  and  marginal  parts.  In  connection  with  these  glands 
special  ones  have  been  described  by  Blandin  and  Nuhn.  They  are  known  as  the 
glands  of  Nuhn  and  Blandin  or  apical  glands  (glandulae  linguales  anteriores  of  Nuhn 
mid  Blandin)  (Fig.  702).  They  are  situated  near  the  apex  of  the  tongue  on  either 
side  of  the  fraenum,  and  each  is  covered  over  by  a  fasciculus  of  muscular  fibre 
derived  from  the  Stylo-glossus  and  Inferior  lingualis  muscles.  Each  gland  is  from 
half  an  inch  to  nearlv  an  inch  lonff  and  about  the  third  of  an  inch  broad.  It  has 
from  four  to  six  ducts,  which  open  on  the  under  surface  of  the  apex. 

The  Serous  Glands  or  Glands  of  v.  Ebner  occur  only  at  the  back  of  the  tongue  in 
the  neighborhood  of  the  taste-buds,  their  ducts  opening  for  the  most  part  into  the 

'  Text-book  of  Histology.     By  A.  A.  Bohm  and  M.  von  Davidoff.     Edited  by  G.  Carl  Huber. 


1092 


THE    ORGANS    OF   SPECIAL    SENSE 


fossae  of  the  papillae  cireumvallatae.  These  glands  are  racemose,  the  duct  branch- 
ing into  several  minute  ducts,  which  terminate  in  alveoli  lined  by  a  single  layer 
of  more  or  less  columnar  epithelium.  Their  secretion  is  of  a  watery  nature,  and 
probably  assists  in  the  distribution  of  the  substance  to  be  tasted  over  the  taste- 
area  (Ebner). 

The  Hyo-glossal  membrane  is  a  strong  fibrous  lamina  which  is  derived  from  the 
septum  of  the  tongue  and  which  connects  the  under  surface  of  the  base  of  the 
tongue  to  the  body  of  the  hyoid  bone.  This  membrane  receives,  in  front,  some 
of  the  posterior  fibres  of  the  Genio-hyo-glossi  muscles. 

The  Vessels  of  the  Tongue. — The  arteries  of  the  tongue  are  derived  from  the 
lingual,  the  facial,  and  ascending  pharyngeal.  The  veins  of  the  tongue  open  into 
the  internal  jugular. 

The  lingual  artery  (Fig.  704)  on  each  side  passes  forward  beneath  the  Hyo- 
glossus  muscle  and  courses  to  the  apex  of  the  tongue,  between  the  Genio-glossus 
and  the  Inferior  lingual  muscles,  about  one-eighth  of  an  inch  from  the  surface. 
It  divides  into  the  ranine  (Fig.702  )  and  sublingual  (Fig.  704).  Near  the  apex  a 
branch  is  given  off  from  the  ranine  artery,  which  penetrates  the  septum  and  joins 
a  like  branch  from  the  other  side.     The  dorsalis  linguae  is  a  branch  of  the  lingual 


Bristles 
in  ducts 
"N  of  glands. 

Glands  of 
Blandin 
or  Niihn. 


Lingual  nerve.        Ranine  artery. 


Fig.  702. — Under  surface  of  tongue,  showing  position  and  relations  of  gland  of  Blandin  or  Nuhn. 
a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 


(Prom 


supplying  the  posterior  part  of  the  tongue,  and  rami  from  the  tonsillar  branch 
of  the  facial  go  to  the  same  region.  A  network  of  capillary  vessels  is  placed 
beneath  the  epithelium. 

The  ranine  veins  lie  to  the  sides  of  the  fraenum  underneath  the  mucous  mem- 
brane. Each  ranine  vein  runs  backward,  superficial  to  and  upon  the  Hyo-glossus 
muscle  and  near  to  the  hypo-glossal  nerve.  The  venae  comites  of  the  lingual  artery 
usually  join  the  ranine  vein,  and  the  trunk  opens  into  the  internal  jugular  vein, 
but  the  vessels  may  open  separately  into  the  jugular  (Fig.  445). 

The  Muscles  of  the  Tongue. — The  muscular  fibres  of  the  tongue  run  in  various 
directions.  These  fibres  are  divided  into  two  sets,  Extrinsic  and  Intrinsic,  which 
have  already  been  described  (pp.  396,  397,  398,  399,  and  400). 


THE    TONGUE 


1093 


The  Extrinsic  come  from  the  Stylo-glossus,  Hyo-glossus,  Genio-glossus, 
Palato-glossus,  and  Chondro-glossus.  The  Intrinsic  muscles  are  the  Superior 
lingualis  (m.  longitiulinalis  superior),  the  Inferior  lingualis  (m.  longitudinalis 
inferior),  the  Transverse  lingual  (m.  transversus  linguae),  and  the  Vertical  lingual 
(m.  verticalis  linguae).  The  outer  or  cortical  portion  of  the  tongue  is  composed 
chiefly  of  longitudinal  fibres.  The  central  or  medullary  portion  is  composed  chiefly 
of  vertical  and  transverse  fibres  and  is  divided  into  two  parts  by  a  vertical  sep- 
tum {septum,  linguae),  which  is  a  fibrous  structure,  begiiming  at  the  apex  and 
passing  back.  As  it  approaches  the  back  it  becomes  narrower  vertically  and 
broadens  out  transversely  to  form  the  hyo-glossal  membrane.  The  fibrous  septum 
is  well  displayed  by  making  a  vertical  section  of  the  tongue. 

The  Lymphatic  Vessels  of  the  Tongue  (Fig.  491). — The  lymphatic  vessels  from 
the  anterior  half  of  the  tongue  pass  to  the  submaxillary  lymph  glands. 

Lymph  vessels  from  the  posterior  half  of  the  tongue  are  connected  with  satellite 
glands  on  the  Hyo-glossus  muscle  and  terminate  in  the  deep  cervical  glands.  The 
last-named  lymph- vessel  accompanies  the  ranine  vein.  The  lingual  lymphatics 
arise  from  a  network  beneath  the  epithelium.  Across  the  anterior  two-thirds 
of  the  tongue  there  is  little  or  no  lymphatic  connection  between  the  two  sides; 
in  the  posterior  one-third  there  is  free  connection. 


SUPERIOR 

LONGITUDINALIS 

MUSCLE 

VrRTICALIS, 
LINGUiE  MUSCLE 

TRANSVERSUS 
LINGU£  MUSCLE 

INFERIOR 

LONGITUDINALIS 

MUSCLE 


STYLOGLOSSUS 
MUSCLE 


DEEP  LINGUAL 
ARTERY 


SUBLINGUAL 
GLAND 

GENIOGLOSSUS 
MWSCLE 


Fig.  703. — Frontal  section  through  the  body  of  the  tongue  of  a  new-born  babe.     X  3.     (Spalteholz.) 


The  Nerves  of  the  Tongue  (Fig.  704). — The  nerves  of  the  tongue  are  five  in  num- 
ber in  each  half;  the  lingual  branch  of  the  inferior  maxillary  division  of  the  fifth, 
which  is  distributed  to  the  papillae  at  the  forepart  and  sides  of  the  tongue,  and 
forms  the  nerve  of  ordinary  sensibility  for  its  anterior  two-thirds;  the  chorda 
t3mipani,  which  runs  in  the  sheath  of  the  lingual,  is  generally  regarded  as  the 
nerve  of  taste  for  the  same  area;  the  lingual  branch  of  the  glosso-pharyngeal,  which 
is  distributed  to  the  mucous  membrane  at  the  base  and  sides  of  the  tongue,  and 
to  the  papillae  circumvallatae,  and  which  supplies  both  sensory  and  gustatory 
filaments  to  this  region;  the  h3rpo-glossal  nerve,  which  is  the  motor  nerve  to  the 
muscular  substance  of  the  tongue;  and  the  internal  laryngeal  branch  of  the  superior 
laryngeal,  which  sends  some  fine  branches  to  the  root  near  to  the  epiglottis. 
Sympathetic  filaments  also  pass  to  the  tongue  from  the  nervi  molles  on  the 
lingual  and  other  arteries  supplying  it.  Some  of  the  nerves  end  free  between  the 
cells  of  epithelium;  others  terminate  as  end  organs  (Meissner's  corpuscles  and 
the  end-bulbs  of  Krause),  and  in  taste-buds  as  sensory  dendrites. 

Surgical  Anatomy. — The  diseases  to  which  the  tongue  is  liable  are  numerous,  and  its  .sur- 
gical anatomy  is  of  importance,  since  any  or  all  the  structures  of  which  it  is  composed — muscles, 
connective  ti.ssue,  mucous  membrane,  glands,  vessels,  nerves,  and  lymphatics — may  be  the  .seat 
of  morbid  changes.    It  is  not  often  the  seat  of  congenital  defects,  though  a  few  cases  of  vertical 


1094 


THE    ORGANS    OF  SPECIAL    SENSE 


deft  have  been  recorded,  and  it  is  occasionally,  though  much  more  rarely  than  is  commonly  sup- 
posed, the  seat  of  tongue-tie,  from  shortness  of  the  fraenum. 

There  is,  however,  one  condition  which  must  be  regarded  as  congenital,  though  not  uncom- 
monly it  does  not  exhibit  the  significant  changes  until  a  year  or  two  after  birth.  This  is  an 
enlargement  of  the  tongue  which  is  due  primarily  to  a  dilatation  of  the  lymph-channels  and  a 
greatly  increased  development  of  the  lymphatic  tissue  throughout  the  tongue  {macrogloasia) .  This 
is  often  aggravated  by  inflammatory  changes  induced  by  injury  or  exposure,  and  the  tongue  may 
assume  enormous  dimensions  and  hang  out  of  the  mouth,  giving  the  child  an  imbecile  expression. 
The  treatment  consists  in  excising  a  V-shaped  portion  and  bringing  the  cut  surfaces  together 
with  deeply  placed  silver  sutures.  Compression  has  been  resorted  to  in  some  cases  with  occa- 
sional success,  but  it  is  difficult  to  apply.  Acute  inflammation  of  the  tongue  (acute  glossitis), 
which  may  be  caused  by  injury  or  the  introduction  of  some  septic  or  irritating  matter,  and  it 
is  attended  by  great  swelling  from  infiltration  of  the  connective  tissue  of  the  tongue;  this  con- 
nective tissue  is  present  in  considerable  quantity.  The  great  swelling  renders  the  patient 
incapable  of  swallowing  or  speaking,  and  may  seriously  impede  respiration.  The  condition  may 
eventuate  in  suppuration  and  the  formation  of  an  acute  abscess.  Chronic  abscess,  which  has 
been  mistaken  for  cancer,  may  also  occur  in  the  sul)stanfi'  of  the  tongue. 


f^uhlingual 
artery. 


Glosso-nharyn- 
geal  nerve. 


Fig.  704.- 


Internal  laryngeal 

branch  of  the 

superior  laryngeal 

nerve. 


-Under  surface  of  tongue,  showing  the  di-i  i  ibution  of  nerves  to  this  organ, 
in  the  Museum  of  the  Royal  (JoUege  of  Surgeons  of  tugland.) 


(From  a  preparation 


The  mucous  membrane  of  the  tongue  may  become  chronically  inflamed,  and  presents  different 
appearances  in  different  stages  of  the  disease,  to  which  the  terms  leucoplakia,  psorias,  and 
ichthyosis  have  been  given. 

The  tongue,  being  very  vascular,  is  often  the  seat  of  naevoid  growths,  and  these  have  a  tendency 
to  grow  rapidly. 

The  tongue  is  frequently  the  seat  of  ulceration,  which  may  arise  from  many  causes,  as  from 
the  irritation  of  jagged  teeth,  dyspepsia,  tuberculosis,  syphilis,  and  cancer.  Of  these  the  cancerous 
ulcer  is  the  most  important,  and  probably  also  the  most  common.  The  variety  is  the  squamous 
epithelioma,  which  soon  develops  into  an  ulcer  with  an  indurated  base.  It  produces  great  pain, 
which  speedily  extends  to  all  parts  supplied  with  sensation  by  the  fifth  nerve,  especially  to  the 


THE  NOSE  1095 

region  of  the  ear.  The  pain  in  these  cases  is  conducted  to  the  ear  and  temporal  region  by  the 
hngual  nerve,  and  from  this  nerve  pain  radiates  to  the  other  branches  of  the  inferior  maxillary 
nerve,  especially  the  auriculo-temporal.  Possibly  pain  in  the  ear  itself  may  be  due  to  implication 
of  the  fibres  of  the  glosso-pharyngeal  nerve,  which  by  its  tympanic  branch  reaches  the  tympanic 
plexus.  Cancer  of  the  tongue  spreads  through  the  organ  very  rapidly  because  of  the  almost 
constant  muscular  movements. 

Cancer  of  the  tongue  may  necessitate  removal  of  a  part  or  the  whole  of  the  organ,  and  many 
different  methods  have  been  adopted  for  its  excision.  It  may  be  removed  from  the  mouth  by 
the  ecraseur  or  the  scissors.  The  better  method  is  by  the  scissors,  usually  known  as  Whitehead's 
method.  The  mouth  is  widely  opened  with  a  gag  the  tongue  is  transfixed  with  a  stout  silk  liga- 
ture, by  which  to  hold  and  make  traction  on  it  and  the  reflection  of  mucous  membrane  from 
the  tongue  to  the  jaw,  and  the  insertion  of  the  Genio-hyo-glossi  first  divided  with  a  pair  of 
curved  blunt  scissors.  The  Palato-glossi  are  aiso  divided.  The  tongue  can  now  be  pulled  well 
out  of  the  mouth.  The  base  of  the  tongue  is  cut  through  by  a  series  of  short  snips,  each  bleed- 
ing vessel  being  dealt  with  as  soon  as  divided,  until  the  situation  of  the  ranine  artery  is  reached. 
The  remaining  undivided  portion  of  tissue  is  to  be  seized  with  a  pair  of  Wells's  forceps,  the  tongue 
removed,  and  the  vessel  secured.  In  the  event  of  the  ranine  artery  being  accidentally  injured 
early  in  the  operation,  hemorrhage  can  be  at  once  controlled  by  passing  two  fingers  over  the 
dorsum  of  the  tongue  as  far  as  the  epiglottis  and  dragging  the  root  of  the  tongue  forcibly  forward. 

In  cases  where  the  disease  is  confined  to  one  side  of  the  anterior  portion  of  the  tongue  this 
operation  may  be  modified  by  splitting  the  tongue  down  the  centre  and  removing  only  the  affected 
half.  If  the  posterior  portion  of  the  tongue  is  attacked  oy  cancer  the  entire  tongue  must  be 
removed,  even  if  but  one  side  of  the  organ  is  apparently  involved.  The  exchange  of  lymph 
between  the  halves  of  the  posterior  portion  of  the  tongue  makes  it  certain  that  the  opposite  half 
becomes  involved  soon  after  the  origin  of  the  disease.  Whatever  operation  is  performed  for 
cancer  of  the  tongue,  the  glands  must  be  removed  ''rom  both  sides  of  the  neck.  This  is  to'  be 
done,  even  if  but  one  side  of  the  tongue  is  removed.  Kocher,  after  performing  a  preliminary  trache- 
otomy, removes  the  tongue  from  the  neck;  by  an  incision  taken  ^rom  near  the  lobule  of  the  ear, 
down  the  anterior  border  of  the  Sterno-mastoid  to  the  level  of  the  great  cornu  of  the  hyoid  bone, 
then  forward  to  the  body  of  the  hyoid  bone,  and  upward  to  near  the  symphysis  of  the  jaw.  The 
lingual  artery  is  now  secured  and  by  a  careful  dissection  the  submaxillary  lymphatic  glands 
and  the  tongue  removed.  Regnol'  advocated  the  removal  of  the  tongue  by  a  semilunar  incision 
in  the  submaxillary  triangle  along  the  )ine  of  the  lower  jaw,  and  a  vertical  incision  from  the 
centre  of  the  semilunar  one  backward  to  the  hyoid  bone.  Care  must  be  taken  not  to  carry  the 
first  incision  too  far  backward,  so  as  to  wound  the  facial  arteries.  The  tongue  is  thus  reached 
through  the  floor  of  the  mouth  pulled  out  through  the  external  incision,  and  removed  with  the 
knife.  The  great  objection  to  this  operation  is  that  all  the  muscles  which  raise  the  hyoid 
bone  and  larynx  are  divided,  and  that  therefore  the  movements  of  deglutition  and  respiration  are 
interfered  with. 

Finally,  where  both  sides  of  the  floor  of  the  mouth  are  involved  in  the  disease,  or  where  very 
free  access  is  required  on  account  of  the  extension  backward  of  the  disease  to  the  pillars  of  the 
fauces  and  the  tonsil,  or  where  the  lower  jaw  is  involved,  the  operation  recommended  by  Syme 
must  be  performed.  This  is  done  by  an  incision  through  the  central  line  of  the  lip-  across  the 
chin,  and  down  as  far  as  the  hyoid  bone.  The  iower  jaw  is  sawed  through  at  the  symphysis,  and 
the  two  halves  of  the  bone  forcibly  separated  from  each  other.  The  mucous  membrane  is  sepa- 
rated from  the  bone,  and  the  Genio-hyo-glossi  detached  from  the  bone,  and  the  Hyo-glossi 
divided.  The  tongue  is  then  drawn  forward  and  removed  close  to  its  attachment  to  the  hyoid 
bone.  Adjacent  lymph  glands  can  be  removed,  and  if  the  bone  is  implicated  in  the  dis- 
ease, it  can  also  be  removed  by  freeing  it  from  the  soft  parts  externally  and  internally,  and 
making  a  second  section  with  the  saw  beyond  the  diseased  part. 

Formerly  many  surgeons  before  removing  the  tongue  performed  a  preliminary  tracheotomy: 
(1)  to  prevent  blood  entering  the  air-passages;  and  (2)  to  allow  the  patient  to  breathe  through 
the  tube  and  not  inspire  air  which  had  passed  over  a  sloughy  wound,  and  which  was  loaded  with 
septic  organisms  and  ikely  to  induce  septic  pneumonia.  By  operating  with  the  patient  in  the 
Trendelenburg  position,  the  blood  is  caused  to  flow  away  from  the  air-passages.  By  the  judicious 
use  of  iodoform  the  evil  mentioned  secondly  may  be  obviated,  and  the  preliminary  tracheotomy  is 
now  usually  dispensed  with. 

THE  NOSE. 

The  nose  is  the  peripheral  portion  of  the  organ  of  smell  (organon  olfactus) :  by 
means  of  the  peculiar  properties  of  its  nerves  it  protects  the  lungs  from  the  inhala- 
tion of  deleterious  gases  and  assists  the  organ  of  taste  in  discriminating  the  prop- 
erties of  food.  The  organ  of  smell  consists  of  two  parts;  one  external,  the  outer 
nose;  the  other  internal,  the  nasal  fossae. 


1096 


THE    ORGANS   OF  SPECIAL    SENSE 


THE  OUTER  NOSE  (NASUS  EXTERNUS). 

The  outer  nose  is  the  more  anterior  and  prominent  part  of  the  organ  of  smell. 
Of  a  triangular  form,  it  is  directed  downward,  and  projects  from  the  centre  of 
the  face,  immediately  above  the  upper  lip.  Its  summit  or  root  {radix  nasi)  is 
connected  directly  with  the  forehead.  Its  inferior  paxt  or  base  (basis  nasi)  pre- 
sents two  elliptical  orifices,  the  nostrils  or  anterior  nares  (nares),  separated  from 
each  other  by  an  antero-posterior  septum,  the  mobile  septum  or  columna  nasi 
(septum  mobile  nasi).  The  margins  of  the  nostrils  are  provided  with  a  number 
of  stiff  hairs  or  vibrissae,  which  arrest  the  passage  of  foreign  substances  carried 
with  the  current  of  air  intended  for  respiration.  The  point  (apex  nasi)  is  the  free 
extremity  of  the  nose.  The  lateral  surfaces  of  the  nose  form,  by  their  union  in 
the  middle  line,  the  dorsum  (dorsum  nasi),  the  direction  of  which  varies  considerably 
in  different  individuals.  The  portion  of  the  dorsum  over  the  nasal  bones  is  the 
bridge.  Each  lateral  surface  terminates  below  in  a  rounded  eminence,  the  wing 
or  ala  nasi,  which,  by  its  lower  margin  (margo  nasi),  forms  the  outer  boundary 
of  the  corresponding  nostril.    Above  the  ala  is  a  depression,  the  alar  sulcus. 


Seen  from  below. 


Side  view. 


Lower  lateral  cartilage. 


Sesamoid  cartilages. 


Figs.  705  and  706. — Cartilages  of  the  nose. 

Structure. — The  nose  is  composed  of  a  framework  of  bones  and  cartilages,  the 
latter  being  slightly  acted  upon  by  certain  muscles.  It  is  covered  externally  by  the 
integument,  internally  by  mucous  membrane,  and  is  supplied  with  vessels  and  nerves. 

The  Bony  Framework. — The  bony  framework  occupies  the  upper  part  of  the 
organ ;  it  consists  of  the  nasal  bones  and  the  nasal  processes  of  the  superior  maxillary 
bones  (pp.  104  and  109). 

The  Cartilaginous  Framework  (cartilagines  nasi)  (Figs.  705  and  706). — The  car- 
tilaginous framework  consists  of  five  pieces,  the  two  upper  and  the  two  lower 
lateral  cartilages  and  the  cartilage  of  the  septum. 

The  Upper  Lateral  Cartilage  (cartilago  nasi  lateralis)  of  each  side  is  situated  below 
the  free  margin  of  the  nasal  bone.  It  is  flattened  and  triangular  in  shape.  Its  ante- 
rior margin  is  thicker  than  the  posterior,  and  continuous  with  the  cartilage  of  the 
septum.  Its  posterior  margin  is  attached  to  the  nasal  process  of  the  superior 
maxillary  and  nasal  bones.  Its  inferior  margin  is  connected  by  fibrous  tissue  with 
the  lower  lateral  cartilage;  one  surface  is  turned  outward,  the  other  inward  toward 
the  nasal  cavity. 


THE    OUTER    NOSE  1097 

The  Lower  Lateral  Cartilage,  the  Cartilage  of  the  Aperture  or  the  Greater  Alar  Car- 
tilage (cartilago  alaris  major)  of  each  side  consists  of  two  thin,  flexible  plates  situated 
immediately  below  the  preceding,  and  bent  upon  themselves  in  such  a  manner  as 
to  form  the  inner  and  outer  walls  of  the  orifice  of  the  nostril.  The  portion  which 
forms  the  inner  wall  {crus  mediale),  thicker  than  the  rest,  is  loosely  connected  with 
the  corresponding  portion  of  the  opposite  cartilage,  and  forms  a  small  part  of  the 
columna.  Its  inferior  border,  free,  rounded,  and  projecting,  forms,  with  the  thick- 
ened integument  and  subjacent  tissue  and  the  corresponding  parts  of  the  opposite 
side,  the  mobile  septum.  The  part  of  the  cartilage  which  forms  the  outer  wall  {crus 
later  ale)  is  curved  to  correspond  with  the  ala  of  the  nose;  it  is  oval  and  flattened, 
narrow  behind,  where  it  is  connected  with  the  nasal  process  of  the  superior  maxilla 
by  a  tough  fibrous  membrane,  in  which  are  found  three  or  four  small  cartilaginous 
plates,  the  sesamoid,  accessory  quadrate  or  lesser  alar  cartilages  {cartilagines  alares 
minores).  Above,  it  is  connected  by  fibrous  tissue  to  the  upper  lateral  cartilage 
and  front  part  of  the  cartilage  of  the  septum;  below,  it  falls  short  of  the  margin 
of  the  nostril;  the  ala  being  formed  by  dense  cellular  tissue  covered  by  skin.  In 
front  the  lower  lateral  cartilages  are  separated  by  a  notch  which  corresponds 
with  the  point  of  the  nose. 

The  Triangular  Cartilage  of  the  Septum  {cartilago  septi  nasi)  (Figs.  705  and  707) 
is  somewhat  quadrilateral  in  form,  thicker  at  its  margins  than  at  its  centre,  and 
completes  the  separation  between  the 
nasal  fossae  in  front.  Its  anterior 
margin,  thickest  above,  is  connected 
with  the  nasal  bones,  and  is  continuous 
with  the  anterior  margins  of  the  two 
upper  lateral  cartilages.  Below,  it  is 
connected  to  the  inner  portions  of  the 
lower  lateral  cartilages  by  fibrous 
tissue.  Its  posterior  margin  is  con- 
nected with  the  perpendicular  lamella 
of  the  ethmoid ;  its  inferior  margin  with 
the  vomer  and  the  palate  processes  of 
the  superior  maxillary  bones  (Fig.  103). 

It  may  be  prolonged  backward 
(especially  in  children)  for  some  dis- 
tance between  the  vomer  and  perpen- 
dicular   plate  of    the  ethmoid,  forming      ^'''-  707.-Bones  and^cartUa^es^of  septum  of  the  nose. 

what  is  termed  the  sphenoidal  process 

{processus  sphenoidalis  septi  cartilaginei) .  The  septal  cartilage  does  not  reach 
as  far  as  the  lowest  part  of  the  nasal  septum.  This  is  formed  by  the  inner 
portions  of  the  lower  lateral  cartilages  and  by  the  skin ;  it  is  freely  movable,  and 
hence  is  termed  the  mobile  septum  {septum  mobile  nasi). 

Along  the  lower  margin  of  the  anterior  half  of  the  cartilage  of  the  septum  is 
another  cartilage  which  is  attached  to  the  vomer  and  is  known  as  the  vomerine 
cartilage  or  cartilage  of  Jacobson  {cartilago  vomeronasalis) . 

These  various  cartilages  are  connected  to  each  other  and  to  the  bones  by  a  tough 
fibrous  membrane,  which  allows  the  utmost  facility  of  movement  between  them. 

The  Muscles  of  the  Nose. — The  muscles  of  the  nose  are  situated  beneath  the 
integument;  they  are  (on  each  side)  the  Pyramidalis  nasi,  the  Levator  iabii  supe- 
riores  alaeque  nasi,  the  Dilatator  naris,  anterior  and  posterior,  the  Compressor 
nasi,  the  Compressor  narium  minor,  and  the  Depressor  alae  nasi.  They  have  been 
previously  described  (p.  375). 

The  Integument  covering  the  dorsum  and  sides  of  the  nose  is  thin,  and  loosely 
connected  with  the  subjacent  parts;  but  the  integument  of  the  tip  and  the  alae  of 


1098 


THE    ORGANS    OF   SPECIAL    SENSE 


the  nose  is  thicker  and  more  firmly  adherent,  and  is  furnished  with  a  large  number 
of  sebaceous  follicles,  the  orifices  of  which  are  usually  very  distinct. 

The  Mucous  Membrane  lining  the  interior  of  the  nose  is  continuous  with  the 
skin  externally  and  with  the  mucous  membrane  which  lines  the  nasal  fossae  within. 

The  Arteries  of  the  Outer  Nose. — The  arteries  of  the  nose  are  the  lateralis  nasi  from 
the  facial,  and  the  inferior  artery  of  the  septum  from  the  superior  coronary,  which 
supply  the  alae  and  septum,  the  sides  and  dorsum  being  supplied  from  the  nasal 
branch  of  the  ophthalmic  and  the  infraorbital. 

The  Veins  of  the  Outer  Nose. — The  veins  of  the  nose  terminate  in  the  facial  and 
ophthalmic. 

The  Lymphatics  of  the  Outer  Nose. — These  vessels  are  shown  in  Figs.  487,  489, 
and  490.     They  empty  chiefly  into  the  submaxillary  lymph  glands. 

The  Nerves  of  the  Outer  Nose. — The  nerves  for  the  muscles  of  the  nose  are  derived 
from  the  facial,  while  the  skin  receives  its  branches  from  the  infraorbital,  infra- 
trochlear,  and  nasal  branches  of  the  ophthalmic. 


THE  NASAL  FOSSAE   (CAVUM  NASI). 

The  nasal  fossae  are  two  irregular  cavities  situated  in  the  middle  of  the  face, 
one  on  each  side  of  the  middle  line,  and  extending  from  before  backward.  They 
open  in  front,  when  the  soft  parts  are  in  place,  by  the  two  nostrils  or  anterior  nares, 
and  terminate,  behind,  in  the  naso-pharynx  by  the  posterior  nares. 


OPENINGS   OF   POSTERIOR 
ETHMOIDAL   CELLS 


SPHENOIDAL 
SINUS 


Fio.  708. — External  wall  of  right  nasal  fossa,  parts  of  the  turbinates  having  been  cut  away  to  show  the 
orifices  of  the  sinuses  which  open  into  the  meatuses.     (Testut.) 

The  Anterior  Nares  {nares). — The  anterior  nares  are  somewhat  pear-shaped' 
apertures,  each  measuring  about  one  inch  antero-posteriorly  and  half  an  inch 
transversely  at  their  widest  part.  The  nasal  fossae  in  the  dry  skull  open  in  front 
by  the  anterior  nasal  aperture  (apertura  pyriformis). 

The  Posterior  Nares  (choanae). — The  posterior  nares  are  two  oval  openings, 
which  are  smaller  in  the  living  or  recent  subject  than  in  the  skeleton,  because  they 


THE   NASAL    FOSSAE 


1099 


are  narrowed  by  the  mucous  membrane.  Each  measures  an  inch  in  the  vertical 
and  half  an  inch  in  the  transverse  direction  in  a  well-developed  adult  skull. 

For  the  description  of  the  bony  boundaries  of  the  nasal  fossae  see  section  on 
Osteology  (p.  143). 

Inside  the  aperture  of  the  nostril  is  a  slight  dilatation,  the  vestibule  (vestibulum 
nasi),  which  extends  as  a  small  pouch,  the  ventricle,  toward  the  point  of  the  nose. 
Above  and  behind  the  vestibule  is  surrounded  by  a  prominence  (limen  nasi). 
Below  the  prominence  the  vestibule  is  lined  with  skin;  above  and  behind  it  the 
fossa  is  lined  with  mucous  membrane.  The  fossa,  above  and  behind  the  vestibule, 
has  been  divided  into  two  parts:  an  olfactory  portion  (regio  olfactoria),  a  slit-like 
cavity,  comprising  the  upper  and  central  part  of  the  septum  and  probably  the 
superior  turbinated  bone,  and  a  respiratory  portion  (regio  respiratoria) ,  which  com- 
prises the  rest  of  the  fossa. 


Eye-ball 


Oroove  (hiatus  semilunaris) 
leading  to  injunditndum 
Middle  turbinated  bone 

Middle  meatus 
Antrum  of  Highmore 
Inferior  meatus 

Inferior  turbinated  bone 


(  Buccal  cavity 


Space  between  cheek  and  gum 
Molar  tooth,  upper  jaw 


Hoot  of  molar  tooth 


Fig. 


Inferior  dental  Jierve 


709. — Tran.sverse  vertical  section  of  the  nasal  fossae.     The  section  is  made  anterior  to  the  superior 
turbinated  bones.     (Cryer.) 


Outer  Wall  (Figs.  708,  709).— The  superior,  middle,  and  inferior  meatus  {meatus 
nasi  superior,  medius  and  inferior)  are  described  on  pages  144  and  145.  The 
sphenoidal  air  sinus  opens  into  the  spheno-ethmoidal  recess  (recessu^  sphenoethmoid- 
alis),  a  narrow  recess  above  the  superior  turbinated  bone  (Fig.  708).  The  posterior 
ethmoidal  cells  open  into  the  front  and  upper  part  of  the  superior  meatus  (Fig.  708). 
On  raising  or  cutting  away  the  middle  turbinated  bone  the  outer  wall  of  the  middle 
meatus  is  fully  exposed  (Figs.  708  and  709)  and  presents  (1)  a  rounded  elevation, 
termed  the  bulla  ethmoidalis,  opening  on  or  immediately  above  which  are  the  orifices 
of  the  middle  ethmoidal  cells;  (2)  a  deep,  narrow,  curved  groove,  in  front  of  the  bulla 
ethmoidalis,  termed  the  hiatus  semilunaris,  into  which  the  anterior  ethmoidal  cells 


1100  THE    ORGANS    OF  SPECIAL    SENSE 

and  the  antrum  of  Highmore  {sinus  maxillaris)  open,  the  orifice  of  the  latter  being 
placed  near  the  level  of  its  roof.  The  middle  meatus  is  prolonged,  above  and  in 
front,  into  the  infundibulum  (infundibulum  ethmoidale) ,  which  leads  into  the  frontal 
sinus.  The  anterior  extremity  of  the  meatus  is  continued  into  a  depressed  area 
which  lies  above  the  vestibule  and  is  named  the  atrium  (atrium  meatus  medii 
nasi).  The  nasal  duct  opens  into  the  anterior  part  of  the  inferior  meatus,  the 
opening  being  frequently  overlapped  by  a  fold  of  mucous  membrane,  and  from 
the  orifice  of  the  duct  a  groove  leads  downward  and  forward. 

The  Inner  Wall  (Fig.  709). — The  inner  wall  or  septum  is  frequently  more  or  less 
deflected  from  the  mesial  plane  (Figs.  101  and  709),  thus  limiting  the  size  of  one 
fossa  and  increasing  that  of  the  other.  Ridges  or  spurs  of  bone  growing  outward 
from  the  septum  are  also  sometimes  present.  Immediately  over  the  incisive 
foramen  at  the  lower  edge  of  the  cartilage  of  the  septum  a  depression,  the  naso- 
palatine recess  [recessus  naso'palatinus) ,  may  be  seen.  In  the  septum  close  to  this 
recess  a  minute  orifice  may  be  discerned ;  it  leads  into  a  blind  pouch,  the  rudi- 
mentary organ  of  Jacobson  (organon  vomeronasale) ,  which  is  well  developed  in 
some  of  the  lower  animals,  but  is  rudimentary  in  man.  The  organ  is  supported 
by  a  plate  of  cartilage,  distinct  from  the  cartilage  of  the  septum,  the  cartilage  of 
Jacobson  (p.  1097).  The  cartilage  of  Jacobson  is  to  the  outer  side  of  the  lower 
edge  of  the  cartilage  of  the  septum.  The  diverticulum  opens  anteriorly  near  the 
floor  of  the  nose  and  close  by  Stenson's  foramen.  Just  below  the  opening  of 
the  blind  pouch  is  an  elevation,  the  eminence  of  Jacobson. 

The  Mucous  Membrane  (memhrana  mucosa  nasi), — The  mucous  membrane  lining 
the  nasal  fossae  is  called  the  pituitary,  from  the  nature  of  its  secretion;  or  Schneide- 
rian,  from  Schneider,  the  first  anatomist  who  showed  that  the  secretion  proceeded 
from  the  mucous  membrane,  and  not,  as  was  formerly  imagined,  from  the  brain. 
It  is  intimately  adherent  to  the  periosteum  or  perichondrium,  over  which  it  lies. 
It  is  continuous  externally  with  the  skin  through  the  anterior  nares,  and  with  the 
mucous  membrane  of  the  naso-pharynx  through  the  posterior  nares.  From  the 
nasal  fossae  its  continuity  may  be  traced  with  the  conjunctiva  through  the  nasal 
duct  and  lachrymal  canals;  with  the  linmg  membrane  of  the  tympanum  and  mas- 
toid cells  through  the  Eustachian  tube;  and  with  the  frontal,  ethmoidal,  and 
sphenoidal  sinuses,  and  the  antrum  of  Highmore  through  the  several  openings  in 
the  meatuses.  The  mucous  membrane  is  thickest  and  most  vascular  over  the 
turbinated  bones.  It  is  also  thick  over  the  septum,  but  in  the  intervals  between 
the  spongy  bones  and  on  the  floor  of  the  nasal  fossae  it  is  very  thin.  Where  it 
lines  the  various  sinuses  and  the  antrum  of  Highmore  it  is  thin  and  pale. 

Owing  to  the  great  thickness  of  this  membrane,  the  nasal  fossae  are  much, 
narrower,  and  the  turbinated  bones,  especially  the  lower  ones,  appear  larger  and 
more  prominent  than  in  the  skeleton.  From  the  same  circumstances  also  the 
various  apertures  communicating  with  the  meatuses  are  considerably  narrowed 
or  completely  closed.  The  vestibule  is  lined  by  modified  skin,  and  contains  hairs 
(vibrissas)  which  guard  the  entrance  of  the  nostril. 

Structure  of  the  Mucous  Membrane  (Fig.  710). — The  epithelium  covering  the; 
mucous  membrane  differs  in  its  character  according  to  the  functions  of  the  part  of 
the  nose  in  which  it  is  found.  In  the  respiratory  portion  of  the  nasal  cavity  the 
epithelium  is  columnar  and  ciliated.  Interspersed  among  the  columnar  ciliated 
cells  are  goblet  or  mucin  cells,  while  between  their  bases  are  found  smaller  pyra- 
midal cells.  In  this  region,  beneath  the  epithelium  and  its  basement  membrane, 
is  a  fibrous  layer  infiltrated  with  lymph-corpuscles,  so  as  to  form  in  many  parts 
a  diffuse  adenoid  tissue,  which  is  particularly  plentiful  in  children,  and  beneath 
this  a  nearly  continuous  layer  of  smaller  and  larger  glands,  some  mucous  and  some 
serous,  the  ducts  of  which  open  upon  the  surface.  In  the  respiratory  portion  of 
the  mucous  membrane  there  is  an  extensive  anastomosing  plexus  of  veins,  which 


THE   NASAL    FOSSAE 


1101 


in  some  regions  forms  a  distinct  cavernous  tissue  (plexus  cavernosus  concharum). 
The  cavernous  tissue  is  particularly  distinct  over  the  inferior  turbinated  bones. 
In  the  olfactory  region  the  mucous  membrane  is  yellowish  in  color  and  the  epi- 
thelial cells  are  columnar  and  non-ciliated ;  they  are  of  two  kinds,  supporting  cells 
and  olfactory  cells. 

The  Supporting  Cells  contain  oval  nuclei,  situated  in  the  deeper  parts  of  the  cells; 
the  free  surface  of  each  cell  presents  a  sharp  outline,  and  its  deep  extremity  is 
prolonged  into  a  process  which  runs  inward,  branching  to  communicate  with 
similar  processes  from  neighboring  cells,  so  as  to  form  a  network  in  the  deep  part 
of  the  mucous  membrane.  Lying  between  these  central  processes  of  the  support- 
ing cells  are  a  large  number  of  spindle-shaped  cells,  the  olfactory  cells,  which  con- 
sist of  a  large  spherical  nucleus  surrounded  by  a  small  amount  of  granular  proto- 
plasm, and  possessing  two  processes,  of  which  one  runs  outward  between  the 
columnar  epithelial  cells,  and  projects  on  the  surface  of  the  mucous  membrane 
as  a  fine,  hair-like  process,  the  olfactory  hair;  the  other  or  deep  process  runs  inward, 
is  frequently  beaded  like  a  nerve-fibre,  and  is  believed  by  most  observers  to  be  in 
connection  with  one  of  the  terminal  filaments  of  the  olfactory  nerve. .  Beneath  the 


Fig.  710. — Section  of  the  olfactory  mucous  membrane;  a,  epithelium;  b,  glands  of  Bowman;  c,  nerve  bundles. 

(Cadiat.) 

epithelium,  extending  through  the  thickness  of  the  mucous  membrane,  is  a  layer 
of  tubular,  often  branched,  glands,  the  glands  of  Bowman  (glandulae  olfactoriae), 
identical  in  structure  with  serous  glands. 

The  Arteries  of  the  Nasal  Fossae. — The  arteries  of  the  nasal  fossae  are  the  anterior 
and  posterior  ethmoidal,  from  the  ophthalmic,  which  supply  the  ethmoidal  cells, 
frontal  sinuses,  and  roof  of  the  nose;  the  spheno-palatine,  from  the  internal  maxil- 
lary, which  supplies  the  mucous  membrane  covering  the  spongy  bones,  the 
meatuses,  and  septum;  the  inferior  artery  of  the  septum,  from  the  superior 
coronary  of  the  facial;  and  the  infraorbital  and  alveolar  branches  of  the  internal 
maxillary^  which  supply  the  lining  membrane  of  the  antrum.  The  ramifications 
of  these  vessels  form  a  close,  plexiform  network,  beneath  and  in  the  substance  of 
the  mucous  membrane. 

The  Veins  of  the  Nasal  Fossae. — The  veins  of  the  nasal  fossae  form  a  close,  cav- 
ernous-like network  beneath  the  mucous  membrane.  This  cavernous  appearance 
is  especially  well  marked  over  the  lower  part  of  the  septum  and  over  the  middle 
and  inferior  turbinated  bones.  Some  of  the  veins  pass,  with  those  accompanying 
the  spheno-palatine  artery,  through  the  spheno-palatine  foramen;  and  others, 
through  the  alveolar  branch,  to  join  the  facial  vein;  some  accompany  the  eth- 


1102 


THE   ORGANS    OF  SPECIAL   SENSE 


Fig.  711. — Nerves  of  septum  of  nose.     Right  side. 


moidal  arteries,  and  terminate  in  the  ophthalmic  vein;  and,  lastly,  a  few  com- 
municate with  the  veins  in  the  interior  of  the  skull,  through  the  foramina  in  the 
cribriform  plate  of  the  ethmoid  bone,  and  the  foramen  caecum. 

The  Lymphatics  of  the  Nasal  Fossae. — The  lymphatics  can  be  injected  from  the 
subdural  and  subarachnoid  spaces,  and  form  a  plexus  in  the  superficial  portion  of 
the  mucous  membrane.    The  lymph  is  drained  partly  into  one  or  two  glands  which 

lie  near  the  great  cornu  of  the  hyoid 
bone  and  partly  into  a  gland  situated  in 
front  of  the  axis. 

The  Nerves  of  the  Nasal  Fossae  (Fisr, 
711). — ^The  nerves  are:  the  olfactory, 
the  nasal  branch  of  the  ophthalmic,  fila- 
ments from  the  anterior  dental  branch  of 
the  superior  maxillary,  the  Vidian,  the 
naso-palatine,  descending  anterior  pala- 
tine, and  nasal  branches  of  Meckel's 
ganglion.  The  olfactory,  the  special 
nerve  of  the  sense  of  smell,  is  distributed 
to  the  olfactory  region,  and  has  been 
already  referred  to  (p.  1019).  The  nasal 
branch  of  the  ophthalmic  division  of  the 
fifth  nerve  distributes  filaments  to  the 
forepart  of  the  septum  and  outer  wall 
of  the  nasal  fossae.  Filaments  from  the 
anterior  dental  branch  of  the  superior  maxillary  supply  the  inferior  meatus  and 
inferior  turbinated  bone.  The  Vidian  nerve  supplies  the  upper  and  back  part  of 
the  septum  and  superior  spongy  bone,  and  the  upper  anterior  nasal  branches 
from  the  spheno -palatine  ganglion  have  a  similar  distribution.  The  naso-palatine 
nerve  supplies  the  middle  of  the  septum.  The  larger  or  anterior  palatine  nerve 
supplies  the  lower  nasal  branches  to  the  middle  and  lower  spongy  bones. 

Surgical  Anatomy. — Instances  of  congenital  deformity  of  the  nose  are  occasionally  met  with, 
such  as  complete  absence  of  the  nose,  an  aperture  only  being  present;  or  perfect  development 
on  one  side,  and  suppression  or  malformation  on  the  other;  or  there  may  be  imperfect  apposi- 
tion of  the  nasal  bones,  so  that  the  nose  presents  a  median  cleft  or  furrow.  Deformities  which 
have  been  acquired  are  much  more  common,  such  as  flattening  of  the  nose  (saddle  nose),  the  result 
of  syphilitic  necrosis,  imperfect  development  of  the  nasal  bones  in  cases  of  congenital  syphilis,  or 
a  lateral  deviation  of  the  nose  the  result  of  fracture. 

The  skin  over  the  alae  and  tip  of  the  nose  is  thick  and  closely  adherent  to  subjacent  parts. 
Inflammation  of  this  part  is  therefore  very  painful,  on  account  of  the  tension.  The  skin  is  largely 
supplied  with  blood,  and,  the  circulation  here  being  terminal,  vascular  engorgement  is  liable  to 
occur,  especially  in  women  at  the  menopause  and  in  both  sexes  from  disorders  of  digestion,  exposure 
to  cold,  etc.  The  skin  of  the  nose  also  contains  a  large  number  of  sebaceous  follicles,  and  these,  as 
a  result  of  intemperance,  are  apt  to  become  affected,  and  the  nose  becomes  reddened,  congested, 
and  irregularly  swollen.  To  this  condition  the  term  grog-blossom  is  popularly  applied.  In  some 
of  these  cases  there  is  enormous  hypertrophy  of  the  skin  and  subcutaneous  tissues,  producing 
pendulous  masses,  termed  lipomata  nasi.  Ordinary  epithelioma  and  rodent  ulcer  may  attack 
the  nose,  the  latter  being  the  more  common  of  the  two.  Lupus  and  syphilitic  ulceration  fre- 
quently attack  the  nose,  and  may  destroy  the  whole  of  the  cartilaginous  portion.  In  fact,  lupus 
vulgaris  begins  more  frequently  on  the  ala  of  the  nose  than  in  any  other  situation. 

Cases  of  congenital  occlusion  of  one  or  both  nostrils,  or  adhesion  between  the  ala  and  septum 
may  occur,  and  may  require  immediate  operation,  since  the  obstruction  much  interferes  with 
sucking.    Bony  closure  of  the  posterior  nares  may  also  occur. 

To  examine  the  na^al  cavities,  the  head  should  be  thrown  back  and  the  nose  drawn  upward, 
the  parts  being  dilated  by  some  form  of  speculum.  They  can  also  be  examined  with  the  little  finger 
or  a  probe,  and  in  this  way  foreign  bodies  detected.  A  still  more  extensive  examination  can  be 
made  by  Roux's  operation,  which  was  introducerl  for  the  cure  of  ozwna.  This  operation  enables 
the  surgeon  to  remove  any  dead  bone  which  may  be  present  in  this  disease.  The  cartilaginous 
framework  of  the  nose  is  lifted  up  by  an  incision  made  inside  the  mouth,  through  the  junction 


THE  EYE  1103 

of  the  upper  lip  with  the  bone;  the  septum  nasi  and  the  lateral  cartilages  are  divided  with  strong 
scissors  till  the  anterior  nares  are  completely  exposed.  The  posterior  nares  can  be  explored  by 
the  aid  of  reflected  light  from  the  mouth,  by  which  the  posterior  nares  can  be  illuminated.  The 
examination  is  very  difficult  to  carry  out,  and,  as  a  rule,  sufficient  information  regarding  the 
presence  of  foreign  bodies  or  tumors  in  the  naso-pharynx  can  be  obtained  by  the  introduction 
of  the  finger  behind  the  soft  palate  through  the  mouth.  The  septum  of  the  nose  may  be  dis- 
placed or  deviate  from  the  middle  line:  this  may  be  the  result  of  an  injury  or  from  some  con- 
genital defect  in  its  development;  in  the  latter  case  the  deviation  usually  occurs  along  the  line 
of  union  of  the  vomer  and  mesethmoid,  and  rarely  occurs  before  the  seventh  year.  Sometimes 
the  deviation  may  be  so  great  that  the  septum  may  come  in  contact  with  the  outer  wall  of  the 
nasal  fossa,  and  may  even  become  adherent  to  it,  thus  producing  complete  obstruction.  Per- 
foration of  the  septum  is  not  an  uncommon  affection  and  may  arise  from  several  causes:  syphilitic 
or  tuberculous  ulceration,  blood-tumor  or  abscess  of  the  septum,  and  especially  in  workmen 
exposed  to  the  vapor  of  bichromate  of  potash,  from  the  irritating  and  corrosive  action  of  fumes. 
When  small,  the  perforation  may  cause  a  peculiar  whistling  sound  during  respiration.  When 
large,  it  may  lead  to  the  falling  in  of  the  bridge  of  the  nose. 

Epistaxis  is  a  very  common  affection  in  children.  It  is  rarely  of  much  consequence,  and  will 
almost  always  subside,  but  in  the  more  violent  hemorrhages  of  later  life  it  may  be  necessary 
to  plug  the  posterior  nares.  In  performing  this  operation  it  is  desirable  to  remember  the  size 
of  the  posterior  nares.  A  ready  method  of  regulating  the  size  of  the  plug  to  fit  the  opening 
is  to  make  it  of  the  same  size  as  the  terminal  phalanx  of  the  thumb  of  the  patient  to  be  oper- 
ated on. 

Nasal  polypus  is  a  very  common  disease,  and  presents  itself  in  three  forms:  the  gelatinous, 
the  fibrous,  and  the  malignant.  The  first  is  by  far  the  most  common.  It  grows  from  the  mucous 
membrane  of  the  outer  wall  of  the  nasal  fossa,  where  there  is  an  abundant  layer  of  highly  vas- 
cular submucous  tissue;  rarely  from  the  septum,  where  the  mucous  membrane  is  closely  adher- 
ent to  the  cartilage  and  bone,  without  the  intervention  of  much,  if  any,  submucous  tissue.  The 
most  common  seat  of  gelatinous  polyps  is  probably  the  middle  turbinated  bone.  The  fibrous 
polypus  generally  grows  from  the  base  of  the  skull  behind  the  posterior  nares  or  from  the  roof 
of  the  nasal  fossae.  The  malignant  polypi,  both  sarcomatous  and  carcinomatous,  may  arise 
in  the  nasal  cavities  and  the  naso-pharynx;  or  they  may  originate  in  the  antrum,  and  protrude 
through  its  inner  wall  into  the  nasal  fossa. 

Rhinoliths  or  nose-stones  may  sometimes  be  found  in  the  nasal  cavities.  They  arise  from 
the  deposition  of  phosphate  of  lime  upon  either  a  foreign  body  or  a  piece  of  inspissated  secretion. 

The  nasal  passages  furnish  a  secretion  of  their  own  and  receive  secretion  from  other  parts 
(tears  and  secretions  of  the  accessory  sinuses).  The  nasal  cavities  contain  the  ethmoidal  laby- 
rinths, the  lateral  masses  of  the  ethmoid  (which  form  the  superior  and  middle  turbinated  bones), 
and  the  inferior  turbinated  bones.  The  nasal  cavity  is  surrounded  by  three  pairs  of  pneumatic 
spaces,  the  accessory  sinuses.  These  are  the  maxillary  sinuses,  the  frontal  sinuses,  and  the 
cells  of  the  ethmoidal  labyrinth.  The  lachrymal  duct  opens  into  the  inferior  meatus.  Inflam- 
mation of  the  air-cells  may  follow  inflammation  of  the  nasal  mucous  membrane  or  bone  disease. 
One  set  of  cells  or  many  may  suffer.  Suppuration  may  occur.  Pus  may  be  blocked  up  and 
retained.  Dead  bone  may  form.  The  most  serious  conditions  may  follow  (abscess  of  brain, 
sinus  thrombosis,  septicaemia),  and  an  operation  is  necessary  to  obtain  relief. 


THE  EYE. 

The  eyeball  or  globe  (hulhus  oculi)  (Figs.  712  and  716)  is  contained  in  the  ante- 
rior part  of  the  cavity  of  the  orbit.  In  this  situation  it  is  securely  protected  from 
injury,  whilst  its  position  is  such  as  to  ensure  the  most  extensive  range  of  sight. 
It  is  acted  upon  by  numerous  muscles,  by  which  it  is  capable  of  being  directed 
to  different  parts;  it  is  supplied  by  vessels  and  nerves,  and  is  additionally  pro- 
tected in  front  by  the  orbital  margins,  eyelids,  etc. 

The  eyeball  is  embedded  in  the  fat  of  the  orbit,  but  is  partly  surrounded  by 
a  thin  membranous  sac,  the  capsule  of  T^non,  which  isolates  it,  so  as  to  allow 
of  free  movement. 

The  Fascia  or  Capsule  of  T^non  (fascia  hulhi  [Tenon%\)  (Figs.  712  and 
713). — The  fascia  or  capsule  of  Tenon  consists  of  a  thin  membrane  which 
envelops  the  eyeball  from  the  optic  nerve  to  the  ciliary  region,  separating  it  from 
the  orbital  fat  and  forming  a  socket  in  which  it  plays.  Its  inner  surface  is  smooth, 
and  is  in  contact  with  the  outer  surface  of  the  sclerotic,  the  perisclerotic  or  supra- 


1104 


THE    ORGANS    OF  SPECIAL    SENSE 


scleral  lymph-space  only  intervening.    This  lymph-space  is  continuous  with  the 
subdural  and  subarachnoid  spaces,  and  is  traversed  by  delicate  bands  of  con- 


OPTIC   NERVE 


CAPSULE 
OF  TENON 


Fig.  712. — The  right  eye  in  sagittal  section,  showing  the  capsule  of  Tenon  (seniidiagrammatic).    (Testut.) 


nective  tissue  which  extend  between 
the  capsule  and  the  sclerotic.  This 
lymph-space  forms  a  flexible  pocket, 
in  which  the  globe  rotates.  The  cap- 
sule of  Tenon,  with  the  globe,  forms 
a  ball-and-socket  joint  (Deaver). 
The  capsule  is  perforated  behind  by 
d  the  ciliary  vessels  and  nerves  and  by 
the  optic  nerve,  being  continuous  with 
the  sheath  of  the  latter.  In  front  it 
blends  with  the  ocular  conjunctiva, 
and  with  it  is  attached  to  the  ciliary 
region  of  the  eyeball.  It  is  perforated 
by  the  muscles  which  move  the  eye- 
ball and  on  to  each  muscle  it  sends 
a  tubular  sheath.  The  sheath  of  the 
Superior  oblique  is  carried  as  far  as 

Fig.  713^ -The  capsule  of  T^non.     The  aponeurosis  is  the  fibrOUS  DulleV  of  that  mUSclc;  that 

seen  trom  behind  forward  on  the  posterior  hemisphere  of  ,        .     „    ^^          ^  ,.                        ,                  » 

theglobe:  a,  cellulo-fibrous  intermuscular  laminae;  6,  deep  On   the   interior  ObliqUC    reaCheS  aS  tar 

leaf  of  the  sheath  incised  at  the  point  where  it  leaves  the  .i         a                j?    .i             u"i     i.           U"    U    U 

muscle  to  fold  itself  on  the   posterior   hemisphere  when  aS   the    tlOOr    Ot    the  OrDlt,    tO   WhlCh   it 

it  forms  the  posterior  capsule;  d,  partly  incised;  c,  serous  ',,^„   ^(s   „    ^K^        T^U^   oU^o+Uc    nn    i\\a 

membrane.     (Poirier  and  Charpy.)  glVCS  OIT   a   Slip.       i  he  ShCathS  OU    thC 

recti  are  gradually  lost  in  the  peri- 
mysium, but  they  give  off  important  expansions.  The  expansion  from  the 
Superior  rectus  blends  with  the  tendon  of  the  Levator  palpebrae;  that  of  the 


THE  EYE 


1105 


Inferior  rectus  is  attached  to  the  inferior  tarsal  plate.  These  two  recti,  therefore, 
will  exercise  some  influence  on  the  movements  of  the  eyelids.  The  expansions 
from  the  sheaths  of  the  Internal  and  External  recti  are  strong,  especially  the  one 
from  the  latter  muscle,  and  are  attached  to  the  lachrymal  and  malar  bones  respec- 
tively. As  they  probably  check  the  action  of  these  two  recti,  they  have  been 
named  the  internal  and  external  check  ligaments. 

Lockwood  has  also  described  a  thickening  of  the  lower  part  of  the  capsule  of 
Tenon,  which  he  has  named  the  suspensory  ligament  of  the  eye.  It  is  slung  like  a 
hammock  below  the  eyeball,  being  expanded  in  the  centre  and  narrow  at  its 
extremities,  which  are  attached  to  the  malar  and  lachrymal  bones  respectively.^ 

The  anterior  one-third  of  the  globe  is  covered  by  the  conjunctiva,  or  mucous 
membrane,  reflected  from  the  inner  surfaces  of  the  lids  (Fig.  715).   A  lateral  view 


VISUAL 

OPTIC 

AXIS 

AXIS 

POSTERIOR  CHAMBER 

/^>^ 

-^SlT^v. 

OF  EYE           . 

X^NT.     c\h 

AM  B  E  R^V 

\ 

OCULAR 
CONJUNCTIVA 

CILIARY        -"^^^  ^ji^K^ 

''^          OF  the! 

EYE                    ^ 

^ 

"N;;^^/ 

p  R  o  c  E  s  s  ■~>7<r^ra\'^ 

t^A 

N     S          ^^^ 

5^   \^X       CILIARY 
^^g--^i^-r-M  U  SC  LE 

J^ 

"**^^^^^\         PARS  CILIARI8 

\ 

y^ 

^5^.      ^      RETINAE 

ZONULE  „J--J^'^ 

^^^^^,y^ 

^^\ 

OF  ZINN        [ff 

— 

%  .\— ORA  SERRATA 

EQUATORIAL 


V  ITR  EOUS 


DIAMETER 


BODY" 


PARS  OPTICA 
RETIN/E 


SCLEROTIC 


OPTIC, 

papilla' 


OPTIC 
EXCAVATION 


^YELLOW 
SPOT 


EXTERNAL 
AXIS 


Fig.  714. — The  right  eye  in  horizontal  section.     (Toldt.) 

of  the  globe  shows  that  it  is  composed  of  segments  of  two  spheres  of  different  sizes 
(Figs.  712,  714,  715,  and  716).  The  anterior  segment  is  one  of  a  small  sphere,  and 
forms  about  one-sixth  of  the  eyeball.  It  is  more  prominent  than  the  posterior  seg- 
ment, which  is  one  of  a  much  larger  sphere,  and  forms  about  five-sixths  of  the  globe. 
The  segment  of  the  larger  sphere  is  opaque,  and  formed  by  the  sclerotic,  the  tunic 
of  protection  to  the  eyeball ;  the  smaller  sphere  is  transparent,  and  formed  by  the 
cornea.  Between  the  small,  anterior  or  corneal  segment,  and  the  large,  posterior 
or  scleral  segment,  is  a  shallow  and  narrow  groove,  the  scleral  sulcus  {sulcus  sclerae). 
The  anterior  pole  is  the  centre  of  the  anterior  portion  of  the  cornea.  The  posterior 
pole  is  the  centre  of  the  posterior  portion  of  the  sclerotic.     A  straight  line  joining 


*  See  a  paper  by  C.  B.  Lockwood,  Journal  of   Anatomy  and  Physiology,  vol.  xx.,  part  i.  p.  1. — Ed.  of   15th 
English  edition. 

70 


1106 


THE    ORGANS   OF  SPECIAL   SENSE 


these  two  poles  is  the  sagittal  or  optic  axis  {axis  optica)  (Fig.  714).  A  line  drawn 
around  the  eyeball  equally  distant  at  all  points  from  the  two  poles  is  called  the 
equatorial  diameter  or  the  equator  (Fig.  714).  The  plane  of  the  equator  divides 
the  globe  in  an  anterior  and  a  posterior  hemisphere.  Meridians  may  be  drawn  from 
one  pole  to  the  other  at  right  angles  to  the  equator.  The  visual  axis  (linea  visus) 
(Fig.  714)  passes  in  a  straight  line  from  the  first  nodal  point  on  the  cornea  to  the 
fovea  centralis  of  the  yellow  spot  on  the  retina.  A  nodal  point  is  the  point  of  inter- 
section of  convergent  rays  with  the  visual  axis.    The  first  nodal  point  is  6.9685  mm. 


POSTERIOR  CH,^MBER 


Fig.  715.- 


-Diagram  of  a  horizontal  section  of  the  right  eye,  showing  the  upper  surface  of  the  lower 
segment.      (Testut.) 


behind  the  summit  of  the  cornea.  The  axes  of  the  eyeballs  are  nearly  parallel, 
and  therefore  do  not  correspond  to  the  axes  of  the  orbits,  which  are  directed 
outward.  The  optic  nerves  follow  the  direction  of  the  axes  of  the  orbits,  and 
are  therefore  not  parallel;  each  nerve  enters  its  eyeball  about  1  mm.  below  and 
3  mm.  to  the  inner  or  nasal  side  of  the  posterior  pole  (Fig.  714).  The  eyeball 
measures  rather  more  in  its  transverse  and  antero-posteror  diameters  than  in  its 
vertical  diameter,  the  former  amounting  to  nearly  an  inch,  the  latter  to  about 
nine-tenths  of  an  inch.  The  diameters  in  the  female  are  somewhat  less  than 
in  the  male. 
The  eyeball  is  composed  of  three  investing  tunics  and  of  three  refracting  media. 


THE    SCLERA 


1107 


THE  TUNICS  OF  THE  EYE. 

From  without  inward  the  three  tunics  are: 

I.  Sclerotic  Coat  and  Cornea. 
II.  Choroid,  CiUary  Body,  and  Iris. 
III.  Retina. 

I.  The  Fibrous  or  External  Coat:  The  Sclerotic  and  Cornea 
(Tunica  Fibrosa  Oculi). 

The  sclerotic  and  cornea  (Figs.  714,  715,  and  716)  form  the  external  tunic  of 
the  eyeball;  they  are  essentially  fibrous  in  structure,  the  sclerotic  being  opaque, 
and  forming  the  posterior  five-sixths  of  the  globe;  the  cornea,  which  forms  the 
remaining  sixth,  being  transparent. 

The  Sclera  or  Sclerotic  Coat  {axXrjpoc:,  hard).— The  sclera  or  sclerotic  coat 
has  received  its  name  from  its  extreme  density  and  hardness;  it  is  a  firm,  unyield- 
ing, opaque,  fibrous  membrane,  forming  the  posterior  five-sixths  of  the  outer  coat 


Canal  of  Schlemm. 


Posterior 
chamber. 

Ciliary 

body. 


Retina.  \ 


Choroid 
coat. 


Ciliary 
processes. 


Canal  of 
Petit. 


rectus 
musde. 


and  serving  to  maintain  the  form  of  the  globe.  It  is  much  thicker  behind  than  in 
front.  Its  external  surface  is  of  a  white  color,  and  is  in  contact  with  the  inner 
surface  of  the  capsule  of  Tdnon,  a  lymph-space  intervening;  it  is  quite  smooth, 
except  one-quarter  of  an  inch  back  of  the  sclero-corneal  junction,  at  the  points 
where  the  Recti  and  Obliqui  muscles  are  inserted  into  it,  and  its  anterior  part  is 
covered  by  the  conjunctival  membrane  (Fig.  744) ;  hence  the  whiteness  and  bril- 
liancy of  the  front  of  the  eyeball.  Its  inner  surface  is  stained  a  brown  color,  marked 
by  grooves,  in  which  are  lodged  the  ciliary  nerves  and  vessels  (Figs.  719,  724,  and 
725) ;  the  inner  surface  of  the  sclera  is  loosely  connected  by  three  layers  of  exceed- 


1108  ^'^^    ORGANS   OF  SPECIAL   SENSE 

ingly  fine  cellular  pigmented  tissue  {lamina  fusca)  with  the  outer  surface  of  the 
choroid,  an  extensive  lymph-space,  the  perichoroidal  space  (spatium  perichorioideale) 
(Figs.  727and  744)  intervening  between  the  sclerotic  and  choroid.  Behind  the  sclera 
is  pierced  by  the  optic  nerve  (n.  opticus) ,  and  is  continuous  with  the  fibrous  sheath 
of  the  nerve,  which  is  derived  from  the  dura  mater  (Fig.  721).  At  the  point  where 
the  optic  nerve  passes  through  the  sclerotic,  the  lamina  fusca  is  represented  by  an 
arrangement  of  the  fibrous  tissue  which  forms  a  thin  network,  the  cribriform  lamina 
{lamina  cribrosa  sclerae)  (Fig.  731) ;  the  minute  orifices  in  this  network  serve  for  the 
transmission  of  separate  bundles  of  nervous  filaments,  and  the  fibrous  septa  divifl- 
ing  them  from  one  another  are  continuous  with  the  membranous  processes  which 
separate  the  bundles  of  nerve-fibres.  One  of  these  openings  {porus  opticus),  larger 
than  the  rest,  occupies  the  centre  of  the  lamella;  it  transmits  the  arteria  centralis 
retinae  to  the  interior  of  the  eyeball  (Fig.  731).  Around  the  cribriform  lamella  are 
numerous  small  apertures  for  the  transmission  of  the  ciliary  nerves  and  the  short 
ciliary  arteries,  and  about  midway  between  the  margin  of  the  cornea  and  the  entrance 
of  the  optic  nerve  are  four  or  five  large  apertures,  for  the  transmission  of  veins  {venae 
vorticosae)  (Fig.  721) .  In  front,  the  fibrous  tissue  of  the  sclerotic  is  continuous  with 
the  substantia  proporia,  the  cornea  by  direct  continuity  of  tissue  (Fig,  744) ,  but  the 
opaque  sclerotic  slightly  overlaps  the  outer  surface  of  the  transparent  cornea.  In 
the  depths  of  the  line  of  junction  between  the  cornea  and  the  sclera  there  is  a  circular 
canal,  the  canal  of  Schlemm  {sinu^  venosus  sclerae)  (Figs.  716,  723,  727,  and  744). 
This  canal  receives  the  sclera  veins  (Fig.  723)  and  communicates  internally  by  num- 
erous minute  openings  in  the  pectineal  ligament  of  the  iris  (Fig.  744)  with  the  ante- 
rior chamber  of  the  eyeball.     These  openings  are  the  spaces  of  Fontana  (Fig.  727). 

Structure. — The  sclerotic  is  formed  of  white  fibrous  tissue  intermixed  with  fine 
elastic  fibres,  and  of  flattened  connective-tissue  corpuscles,  some  of  which  are  pig- 
mented, contained  in  cell-spaces  between  the  fibres  (Figs.  720  and  731).  These 
fibres  are  aggregated  into  bundles,  some  of  which  are  arranged  in  layers  having  an 
equatorial  direction,  but  most  of  which  are  arranged  in  layers  lying  in  meridian  lines. 
The  sclera  is  joined  to  the  choroid  by  three  thin  layers  of  loose  connective  tissue  con- 
taining pigment  cells,  the  lamina  fusca  {lamina  fasciae  sclerae)  (Fig.  724) .  Where 
the  optic  nerve  passes  through  the  sclera  there  is  very  thin  network  to  represent  the 
lamina  fusca.  This  network  is  the  lamina  cribrosa  (Fig.  731).  The  muscles  of 
the  eyeball  are  attached  to  the  sclera  (Figs.  715,  716,  and  744),  and  their  tendons 
enter  among  the  bundles  of  fibrous  connective  tissue.  The  conjunctiva  covers  the 
anterior  portion  of  the  sclera  and  is  attached  to  it  by  submucous  tissue  (Figs.  715 
and  727) .  The  sclera  yields  gelatin  on  boiling.  Its  vessels  (Figs.  721  and  723)  are  not 
numerous,  the  capillaries  being  of  small  size  and  uniting  at  long  and  wide  intervals. 
It  obtains  arterial  blood  from  the  short  posterior  ciliary  and  the  anterior  ciliary 
arteries.  The  venous  blood  is  removed  by  the  venae  vorticosae  and  the  anterior  ciliary 
veins.  There  are  lymph-spaces  between  the  cells  which  empty  into  the  periscleral 
(Fig.  712  and  p.  1104)  and  perichoroidal  lymph-spaces  (Fig.  727).  Its  nerves  are 
derived  from  the  ciliary  nerves  (Fig.  719).  They  lose  their  medullary  sheaths  and 
enter  among  the  bundles  of  fibrous  tissue,  but  it  is  not  known  how  they  terminate. 

The  Cornea  (Figs.  712,  715,  and  721). — The  cornea  is  the  projecting  transparent 
part  of  the  external  tunic  of  the  eyeball,  and  forms  the  anterior  sixth  of  the  globe.  It 
is  almost,  but  not  quite,  circular  in  shape,  occasionally  a  little  broader  in  the  transverse 
than  in  the  vertical  direction.  It  is  convex  anteriorly,  and  projects  forward  from 
the  sclerotic  in  the  same  manner  that  a  watch-glass  does  from  the  case.  Its  degree 
of  curvature  varies  in  different  individuals,  and  in  the  same  individual  at  different 
periods  of  life,  it  being  more  prominent  in  youth  than  in  advanced  life,  when  it 
becomes  flattened.  Usually  the  curvature  is  slightly  greater  in  the  vertical  plane 
than  in  the  horizontal  plane;  at  its  centre  than  at  its  periphery,  and  at  its  temporal 
than  at  its  nasal  side.    The  cornea  is  dense  and  of  uniform  thickness  throughout; 


THE    CORNEA 


1109 


its  posterior  surface  is  perfectly  circular  in  outline,  and  exceeds  the  anterior  sur- 
face slightly  in  extent,  from  the  latter  being  overlapped  by  the  sclerotic.  The 
anterior  surface  is  covered  with  conjunctiva  (Fig.  727). 

Structure  (Fig.  717). — The  cornea  consists  of  five  layers — namely:  (1)  the  anterior 
or  epithelial  layer;  (2)  the  anterior  elastic  layer;  (3)  the  substantia  propria;  (4) 
the  posterior  elastic  layer;  (5) 'the  posterior  or  endothelial  layer. 

Anterior 
epithelium 

Anterior 


■""^-w.    I  ■>!  elastic 

membrane 


-j 


L. 


^        J    V  Substantia 
~^"^,   f  propria 


mmmm 


FiQ.  717. — Vertical  section  through  the  cornea  of  a  newborn  child.     X  200. 


Posterior 
epithelium 
(Saymonowicz.) 


(1)  The  Anterior  Layer  (epithelium  corneae)  is  composed  of  stratified  epithelium 
and  is  continuous  with  the  cells  of  the  conjunctiva  at  the  borders  of  the  cornea. 
There  are  from  five  to  eight  strata  of  nucleated  cells  in  the  anterior  layer.  The 
deepest  cells  are  columnar.  Above  the  columnar  cells  are  several  layers  of 
polygonal  cells,  most  of  which  have  finger-like  processes  and  are  called  prickle 
cells.  At  the  surface  the  cells  and  nuclei  become  flat.  The  anterior  epithelial 
layer  prevents  the  absorption  of  the  fluid  of  the  tears. 

(2)  The  Anterior  Elastic  or  Anterior  Limiting  Layer  or  Bowman's  Membrane  (lamina 
elastica  anterior)  is  less  than  half  the  thickness  of  the  layer  of  stratified  epithelium. 


1110 


THE   ORGANS    OF  SPECIAL   SENSE 


It  differs  in  some  essential  respects  from  true  elastic  tissue.  It  shows  evidences 
of  fibrillary  structure,  and  does  not  have  a  tendency  to  curl  inward  or  to  undergo 
fracture  when  detached  from  the  other  layers  of  the  cornea.  It  consists  of  ex- 
tremely close  interwoven  fibrils,  similar  to  those  found  in  the  rest  of  the  cornea 
proper,  but  contains  no  corneal  corpuscles.  It  ought,  therefore,  to  be  regarded 
as  a  part  of  the  proper  tissue  of  the  cornea. 

(3)  The  Substantia  Propria  or  proper  substance  of  the  cornea  forms  the  main 
thickness  of  that  structure.  It  is  fibrous,  tough,  unyielding,  perfectly  transparent, 
and  continuous  with  the  sclerotic.  It  is  composed  of  about  sixty  flattened  lamellae, 
superimposed  one  on  another.  These  lamellae  are  made  up  of  bundles  of  modified 
connective  tissue,  the  fibres  of  which  are  directly  continuous  with  the  fibres  of  the 
sclerotic.  The  fibres  of  each  lamella  are  for  the  most  part  parallel  with  each 
other;  those  of  alternating  lamellae  at  right  angles  to  each  other.  Fibres,  however, 
frequently  pass  obliquely  from  one  lamella  to  the  next  {fihrae  arcuatae). 

The  lamellae  are  connected  with  each  other  by  an  interstitial  cement-substance, 
in  which  are  spaces,  the  corneal  spaces,  cell  spaces  or  lacunae  (Fig.  718).  The 
spaces  are  stellate  in  shape,  and  have  numerous  offsets  or  canaliculi  (Fig.  718), 
by  which  they  communicate  with  each  other.  Each  space  contains  a  cell,  the 
corneal  corpuscle  (Fig.  718),  which  resembles  in  form  the  space  in  which  it  is 


Lymph  eannUculi 


Corneal  cell  in 
lymph  sjyace 


Fig.  718. — From  a  horizontal  section  of  an  ox's  cornea.     Positive  picture  of  the  canal  system  demonstrated 
by  the  gold  chloride  method.     X  450.     (Szymonowicz.) 

lodged,  but  it  does  not  entirely  fill  it,  the  remainder  of  the  space  containing 
lymph.  In  the  aged  the  margin  of  the  cornea  becomes  opaque  gray.  This  rim 
is  called  the  arcus  senilis,  and  is  due  to  fat  deposit  in  the  lamellae  and  corneal 
corpuscles. 

(4)  The  Posterior  Elastic  Lamina,  the  Membrane  of  Descemet,  or  the  Membrane 
of  Demours  {lamina  elastica  'posterior),  which  covers  the  proper  structure  of  the 
cornea  behind,  presents  no  structure  recognizable  under  the  microscope.  It 
consists  of  an  elastic,  and  perfectly  transparent  homogeneous  membrane,  of 
extreme  thinness,  which  is  not  rendered  opaque  by  either  water,  alcohol,  or  acids. 
It  is  very  brittle,  but  its  most  remarkr.ble  property  is  its  extreme  elasticity,  and 
the  tendency  which  it  presents  to  curl  up,  or  roll  upon  itself,  with  the  attached 
surface  innermost,  when  separated  from  the  proper  substance  of  the  cornea.  Its 
use  appears  to  be  (as  suggested  by  Dr.  Jacob)  "to  preserve  the  requisite  perma- 
nent correct  curvature  of  the  flaccid  cornea  proper." 

At  the  margin  of  the  cornea  this  posterior  elastic  membrane  breaks  up  into  fibres 
to  form  a  reticular  structure  at  the  outer  angle  of  the  anterior  chamber,  the  intervals 
between  the  fibres  forming  small  cavernous  spaces,  the  spaces  of  Fontana  (spatia 


THE   CHOROID  1111 

anguli  iridis)  (Fig.  727).  These  little  recesses  communicate  with  a  circular  canal 
in  the  deeper  parts  of  the  corneo-scleral  junction.  This  is  the  canal  of  Schlemm 
(sinus  venosus  sclerae)  (Figs.  716,  723,  and  727) ;  it  communicates  internally  with 
the  anterior  chamber  through  the  spaces  of  Fontana,  and  externally  with  the 
scleral  veins.  Some  of  the  fibres  of  this  reticulated  structure  are  continued  into 
the  front  of  the  iris,  forming  the  ligamentum  pectinatum  iridis;  while  others  are 
connected  with  the  forepart  of  the  sclerotic  and  choroid. 

(5)  The  Posterior  Layer  or  the  Corneal  Endothelium  (endothelium  camerae  ante- 
rioris)  lines  the  aqueous  chamber  and  prevents  the  absorption  of  the  aqueous 
humor.  It  covers  the  posterior  surface  of  the  elastic  lamina,  is  reflected  on  to 
the  front  of  the  iris,  and  also  lines  the  spaces  of  Fontana.  It  consists  of  a  single 
layer  of  polygonal  flattened  transparent  nucleated  cells,  similar  to  those  lining 
other  serous  cavities. 

Arteries  and  Nerves. — The  foetal  cornea  contains  blood-vessels  which  pass  from 
the  margin  almost  to  the  centre.  The  adult  cornea  contains  no  blood-vessels, 
except  at  its  margin.  The  capillaries  from  the  sclera  and  conjunctiva  form  loops 
at  the  corneal  margin,  and  many  of  these  loops  enter  the  cornea  for  a  distance  of 
1  mm.  (Fig.  723).  The  balance  of  the  cornea  is  non-vascular  and  obtains  its 
nourishment  from  the  lymph  in  the  lacunae  and  canaliculi.  Lymphatic  vessels 
have  not  as  yet  been  demonstrated  in  it,  but  are  represented  by  the  channels  in 
which  the  bundles  of  nerves  run;  these  channels  are  lined  by  endothelium  and  are 
continuous  with  the  cell-spaces.  The  nerves  are  numerous,  twenty-four  to  thirty- 
six  in  number  (Kolliker),  forty  to  forty-five  (Waldeyer  and  Siimisch);  they  are 
derived  from  the  ciliary  nerves;  they  form  the  annular  plexus  (plexus  annularis), 
at  the  corneal  margin,  and  enter  the  laminated  tissue  of  the  cornea,  lose  their 
medullary  sheaths,  and  ramify  throughout  the  substantia  propria  as  the  funda- 
mental plexus  or  the  plexus  of  the  stroma.  From  this  deep  plexus  come  perforating 
fibres  (fibrae  perforantes) ,  which  pass  through  the  anterior  elastic  lamina  and  form 
the  subepithelial  plexus,  and  from  it  fibrils  are  given  off  which  ramify  between 
the  epithelial  cells,  forming  a  network  which  is  termed  the  intra-epithelial  plexus. 
Nerve-fibres  from  the  annular  plexus  and  from  the  plexus  of  the  stroma  come 
into  close  relation  with  the  corneal  corpuscles. 

Dissection. — In  order  to  separate  the  sclerotic  and  cornea,  so  as  to  expose  the  second  tunic, 
the  eyeball  should  be  immersed  in  a  small  vessel  of  water  and  held  between  the  finger  and  thumb. 
The  sclerotic  is  then  carefully  incised,  in  the  equator  of  the  globe,  till  the  choroid  is  exposed. 
One  blade  of  a  pair  of  probe-pointed  scissors  is  now  introduced  through  the  opening  thus  made, 
and  the  sclerotic  divided  around  its  entire  circumference,  and  removed  in  separate  portions. 
The  front  segment  being  then  drawn  forward,  the  handle  cf  the  scalpel  should  be  pressed  gently 
against  it  at  its  connection  with  the  iris,  and,  these  being  separated,  a  quantity  of  perfectly  trans- 
parent fluid  will  escape;  this  is  the  aqueous  humor.  In  the  course  of  the  dissection  the  ciliary 
nerves  (Fig.  719)  may  be  seen  lying  in  the  loose  cellular  tissue  between  the  choroid  and  sclerotic 
or  continued  in  delicate  grooves  on  the  inner  surface  of  the  latter  membrane. 

II.  The  Choroid,  Ciliary  Body,  and  Iris,  the  Tunica  Media,  the  Uveal  Tract 
(Tunica  Vasculosa  Oculi)  (Figs.  714,  716,  719,  724,  744). 

The  second  or  middle  tunic  of  the  eye  is  formed  from  behind  forward  by  the 
choroid,  the  ciliary  body,  and  the  iris. 

The  choroid  is  the  vascular  and  pigmentary  tunic  of  the  eyeball,  investing  the 
posterior  five-sixths  of  the  globe,  and  extending  as  far  forward  as  the  ora  serrata 
of  the  retina;  the  ciliary  body  connects  the  choroid  to  the  circumference  of  the 
iris.  The  iris  is  the  circular  muscular  septum,  which  hangs  vertically  behind  the 
cornea,  presenting  in  its  centre  a  large  rounded  aperture,  the  pupil. 

The  Choroid  (chorioidea). — The  choroid  is  a  thin,  highly  vascular  membrane, 
of  a  dark-brown  or  chocolate  color,  which  invests  the  posterior  five-sixths  of  the 


1112 


THE    ORGANS    OF   SPECIAL    SENSE 


globe,  and  is  pierced  behind  by  the  optic  nerve,  and  in  this  situation  is  firmly 
adherent  to  the  sclerotic.     It  is  thicker  behind  than  in  front.     Externally,  it  is 

loosely  connected  by  the  lamina 
fusca  with  the  inner  surface  of  the 
sclerotic  (p.  1108).  Its  inner  sur- 
face is  attached  to  the  retina. 

Structure  (Fig.  720).— The  choroid 
consists  of  a  dense  capillary  plexus 
and  of  small  arteries  and  veins, 
carrying  the  blood  to  and  returning 
it  from  this  plexus  (Fig.  723),  and  of 
branched  and  pigmented  cells  which 
lie  in  connective  tissue.  There  are 
three  layers  in  the  choroid.  Named 
from  without  inward,  they  are  the 
lamina  suprachorioidea,  the  choroid 
proper,  and  lamina  basalis  (Fig.  720) . 
(1)  The  Lamina  Suprachorioidea 
is  on  the  external  surface,  that  is, 
the  surface  next  to  the  sclerotic. 

It  resembles  the  lamina  fusca  of 

the   sclerotic.      It   is   composed  of 

delicate  non-vascular  lamellae,  each 

lamella  consisting  of  a  network  of 

fine  elastic  fibres,  among  which  are 

branched  pigment-cells.  The  spaces 

between  the  lamellae  are  lined  by 

endothelium,  and  open  freely  into  the  perichoroidal  lymph-space,  which,  in  its 

turn,  communicates  with  the  periscleral  space  by  the  perforations  in  the  sclerotic 

through  which  the  vessels  and  nerves  are  transmitted. 

(2)  The  Choroid  Proper  is  internal  to  the  lamina  suprachorioidea.  In  consequence 
of  the  small  arteries  and  veins  of  the  choroid  proper  being  arranged  on  the  outer 
surface  of  the  capillary  network,  it  is  customary  to  describe  this  as  consisting  of 
two  layers:  the  outermost  (lamina  vasculosa),  composed  of  small  arteries   and 

Pigment  layer 
of  retina 


Fig.  719. — The  choroid  and  iris.     (Enlarged.) 


Lamina  supra- 
chorioidea 


Part  of  the 
sclera 


Fig.  720. — Vertical  section  through  the  chorioidea  and  a  part  of  the  sclera  of  an  ape.     X  440.      (Szymonowicz.) 


veins,  with  pigment-cells  interspersed  between  them,  and  the  inner  (lamina 
choriocapillaris) ,  consisting  of  a  capillary  plexus.  The  external  layer  of  the  choroid 
proper  or  the  lamina  vasculosa  consists,  in  part,  of  the  larger  branches  of  the  short 


THE    CHOROID 


1113 


posterior  ciliaxy  arteries  (Figs.  721,  723,  and  725),  which  run  forward  between  the 
veins,  before  they  bend  inward  to  terminate  in  the  capillaries;  but  this  layer  is 


VENA 
VORTICOSA 


SCLEROTIC 


CILIARY    ARTERY 


POSTERIOR 
CILIARY 
ARTERIES 

Fig.  721. — Vessels  and  nerves  of  the  choroid  and  iris,  seen  from  above, 
been  largely  removed.     (Testut.) 


The  sclerotic  and  cornea  have 


formed  principally  of  veins,  which  have  a  whirl-like  arrangement  and  empty  into 
four  or  five  large  equidistant  trunks,  the  venae  vorticosae  (Figs.  721,  722,  and  723), 
which  pierce  the  sclerotic  midway 
between  the  margin  of  the  cornea 
and  the  entrance  of  the  optic 
nerve.  Around  the  veins  are 
l3nnph-spaces.  Interspersed  be- 
tween the  vessels  are  dark  star- 
shaped  pigment-cells,  the  offsets 
from  which,  communicating  with 
similar  branchings  from  neigh- 
boring cells,  form  a  delicate  net- 
work or  stroma,  which  toward 
the  inner  surface  of  the  choroid 
lo.ses  its  pigmentary  chraacter. 
The  internal  layer  of  the  choroid 
proper  consists  of  an  exceedingly 
fine  capillary  plexus,  formed  by 
the  short  ciliary  vessels (Fig.723), 
and  is  known  as  the  tunic  of 
Ruysch  (lamina  choriocapillaris) . 
The  network  is  close,  and  finer  at  the  hinder  part  of  the  choroid  than  in  front. 
About  half  an  inch  behind  the  cornea  its  meshes  become  larger,  and  are  continuous 


Fig.  722. — The  veins  of  the  choroid.     (Enlarged.) 


1114 


THE    ORGANS   OF  SPECIAL   SENSE 


with  those  of  the  ciUary  processes.  These  two  laminae  are  connected  by  an  interme- 
diate stratum,  which  is  destitute  of  pigment-cells  and  consists  of  fine  elastic  fibres. 
On  the  inner  surface  of  the  lamina  choriocapillaris  is  a  very  thin,  structureless, 
or,  according  to  Kolliker,  faintly  fibrous  membrane,  called  the  lamina  basalis 
or  membrane  of  Bruch;  it  is  closely  connected  with  the  stroma  of  the  choroid,  and 
separates  it  from  the  pigmentary  layer  of  the  retina. 


hff, 


Cornea 


Fig.  723. — Diagram  of  the  blood-vessels  of  the  eye,  as  seen  in  a  horizontal  section.     (Leber,  after  StShr.) 

Course  of  vasa  centralia  retinae:  n,  arteria,  a\  vena  centralis  retinae;  p,  anastomosis  with  vessels  of  outer 
coats;  y,  anastomosis  with  branches  of  short  posterior  ciliary  arteries;  (],  anastomosis  with  chorioideal  vessels. 

Course  of  vasa  cihar.  postic.  brev. :  I,  arteriae,  and  Ij,  venae  ciliar.  postic.  brev.;  II,  episcleral  artery; 
II],  episcleral  vein;  III,  capillaries  of  lamina  choriocapillaris. 

Course  of  vasa  ciliar.  postic.  long.:  1,  a.  ciliar.  post,  longa;  2,  circulus  iridis  major  cut  across;  3,  branches  to 
ciliary  body;  4,  branches  to  iris. 

Course  of  vasa  ciUar.  ant.:  a,  arteria,  a\,  vena  ciliar.  ant.;  b,  junction  with  the  circulus  iridis  major;  c,  junc- 
tion with  lamina  choriocapill.;  d,  arterial,  and  dj,  venous  episcleral  branches;  e,  arterial,  and  Cj,  venous  branches 
to  conjunctiva  sclerae;  /,  arterial,  and/i,  venous  branches  to  corneal  border;  V,  vena  vorticosa;  S,  transverse 
section  of  sinus  venosus  sclerae. 

Tapetum  (lucidum). — This  name  is  applied  to  the  iridescent  appearance  which 
is  seen  in  the  outer  and  posterior  parts  of  the  choroid  of  many  animals,  but  not 
in  man. 

The  ciliary  body  should  now  be  examined.  It  may  be  exposed,  either  by  detaching  the  iris 
from  its  connection  with  the  Ciliary  muscle,  or  by  making  a  transverse  section  of  the  globe,  and 
examining  it  from  behind. 


THE    CILIARY   BODY  1115 

The  Ciliary  Body  (corpus  ciliare)  (Fig.  716). — The  ciliary  body  or  cyclon  joins 
the  choroid  to  the  margin  of  the  iris.  It  is  in  reahty  a  process  of  the  choroid 
or  uveal  tract  and  comprises  the  orbiculus  ciliaris,  the  ciliary  processes,  and  the 
Ciliary  muscle. 

The  Orbiculus  Ciliaris  or  Annulus  Ciliaris  (Figs.  724,  726,  and  742).— The 
orbiculus  ciliaris  is  a  zone  of  about  one-sixth  of  an  inch  in  width,  directly  con- 
tinuous with  the  anterior  part  of  the  choroid.  The  lamina  basalis  presents 
numerous  ridges  arranged  in  a  radial  manner.  The  depressions  between  the 
ridges  are  filled  with  retinal  pigment  epithelium  (Szymonowicz).  The  orbiculus 
contains  no  lamina  choriocapillaris. 

The  Ciliary  Processes  (processus  ciliares)  (Figs.  714,  716,  726,  and  744). — The 
ciliary  processes  are  formed  by  the  plaiting  and  folding  inward  of  the  various 
layers  of  the  choroid — i.  e.,  the  choroid  proper  and  the  lamina  basalis — at  its 
anterior  margin,  and  are  received  between  corresponding  foldings  of  the  suspen- 
sory ligament  of  the  lens,  thus  establishing  a  connection  between  the  choroid  and 
inner  tunic  of  the  eye.  They  are  arranged  in  a  circle,  and  form  a  sort  of  plaited 
frill,  the  corona  ciliaris,  behind  the  iris, 
round  the  margin  of  the  lens  (Figs.  726 

and  744).    They  vary  between  sixty  and  ""*\%\\         .cm a r is* 

eighty  in  number,  lie  side  by  side,  and  ciliary  Jpl!^^^^/      .orbiculus 

may  be  divided  into  large  and  small;  -li^s^samn^ — .^^ciliaris 

the  latter,  consisting  of  about  one-third 
of  the  entire  number,  are  situated  in  the      l^^BBilli    l™"''W1liiHE^^*^^°lVJ'J°" 

'  *t^«^^^^BB»lHi\.  liiJll^^m.^S^     SMOOTH 


spaces  between  the  former,  but  without       ^S^BK^mlimlMUS^^^    portion 

'-  I  1  r^^^         1  ^^f^^^^aMHHHHi^rX  O^  CHOROID 

regular  alternation,  i  he  larger  processes 
are  each  about  one-tenth  of  an  inch  in 
length,  and  are  attached  by  their  per- 
iphery to  three  or  four  of  the  ridges  of 
the  orbiculus  ciliaris,  and  are  continu-  cornea  (pos 

ous  with  the  layers  of  the  choroid;  the  terior surface)" 

Opposite   margin    is  free,  and    rests   upon        Fig.  724.— The  middle  or  vascular  coat  of  the  eyeball 

the  circumference  of    the   lens.     Their  IKlnd^b^f^^^'^ffoidu' '^'' ^"'^  °'"'^"*'^" '"■°" 
anterior  surface   is  turned    toward   the 

back  of  the  iris,  with  the  circumference  of  which  they  are  continuous.     The 
posterior  surface  is  connected  with  the  suspensory  ligament  of  the  lens. 

Structure. — The  ciliary  processes  are  similar  in  structure  to  the  choroid,  but  the 
vessels  are  larger,  and  have  chiefly  a  longitudinal  direction.  They  are  the  most 
vascular  portion  of  the  eyeball.  The  processes  are  covered  on  their  inner  surface 
by  two  strata  of  black  pigment-cells,  which  are  continued  forward  from  the  retina, 
and  are  named  the  pars  ciliaris  retinae  (Figs.  720  and  727) .  In  the  stroma  of  the 
ciliary  processes  there  are  also  stellate  pigment-cells,  which,  however,  are  not  so 
numerous  as  in  the  choroid  itself. 

The  Ciliary  Muscle  or  Bowman's  Muscle  (m.  ciliaris)  (Figs.  719,  721,  725, 
727,  728,  and  729). — The  ciliary  muscle  consists  of  unstriped  fibres;  it  forms 
a  grayish,  semitransparent,  circular  band,  about  one-eighth  of  an  inch  broad, 
on  the  outer  surface  of  the  forepart  of  the  choroid,  between  the  choroid  and 
the  iris  and  back  of  the  sclero-corneal  junction.  It  is  thickest  in  front  and 
gradually  becomes  thinner  behind.  It  consists  of  two  sets  of  fibres,  radiating  and 
circular. 

The  Radiating  Fibres  (fibrae  meridianales  [Bruckei])  (Figs.  727  and  744) ,  much 
the  more  numerous,  arise  at  the  point  of  junction  of  the  cornea  and  sclerotic,  and 
partly  also  from  the  ligamentum  pectinatum  iridis,  and,  passing  backward,  are 
attached  to  the  choroid  opposite  to  the  ciliary  processes.  One  bundle,  according 
to  Waldeyer,  is  continued  backward  to  be  inserted  into  the  sclerotic. 


1116 


THE    ORGANS    OF   SPECIAL    SENSE 


The  Circular  Fibres  (fibrae  circulares  [Mulleri])  (Figs.  727  and  744)  are  internal  to 
the  radiating  ones  and  to  some  extent  unconnected  with  them,  and  have  a  circular 
course  around  the  attachment  of  the  iris.  They  are  sometimes  called  the  "ring 
muscle"  of  Muller,  and  were  formerly  described  as  the  ciliary  ligament.  They  are 
well  developed  in  hypermetropic,  but  are  rudimentary  or  absent  in  myopic  eyes. 


Anterior  ciliary  artery. 


Short  ciliary  arteri 


ior  ciliary  artery. 


Fig.  725. — The  arteries  of  the  choroid  and  iris.     The  .sclerotic  has  been  mostly  removed.     (Enlarged.) 


The  Ciliary  muscle  is  admitted  to  be  the  chief  agent  in  accommodation — i.  e.,  in 
adjusting  the  eye  to  the  vision  of  near  objects.  Bowman  believed  that  this  was 
effected  by  its  compressing  the  vitreous  body,  and  so  causing  the  lens  to  advance. 
At  the  present  time  all  agree  that  the  chief  element  in  accommodation  is  altered 
curvature  of  the  lens,  but  there  is  diversity  of  opinion  as  to  the  manner  in  which 


ORBICULARIS 
CILIARIS 


CILIARY 
PROCESSES 


s  (poste- 
lor  surface) 


EQUATOR 
OF  LENS 


Fig.  726. — -A  portion  of  the  corona  ciliaris  magnified.     The  ciliary  processes  and  the  ciliary  folds.     (Toldt.) 

this  is  accomplished.  The  view  which  now  prevails  is  that  of  Helmholtz.  He 
maintained  that  in  an  unaccommodated  eye  the  capsule  and  suspensory  ligament 
of  the  lens  are  tense,  and  their  pressure  flattens  the  anterior  surface  of  the  lens, 
and  parallel  rays  (and  rays  from  objects  far  off  are  practically  parallel)  "are 
focused  on  the  retina  without  any  sense  of  effort."^ 

"In  accommodation  for  a  near  object  the  meridional  or  antero-posterior  fibres 


'  Stewart,  Manual  of  Physiology. 


THE  IRIS 


1117 


of  the  ciliary  muscle  by  their  contraction  pull  forward  the  choroid  and  relax  the 
suspensory  ligament.  The  elasticity  of  the  lens  at  once  causes  it  to  bulge  forward 
till  it  is  again  checked  by  the  tension  of  the  capsule."*  The  pupil  is  at  the  same 
time  slightly  contracted. 

The  Iris  {iris,  a  rainbow)  (Figs.  716, 719,  721,  723,  724,  727,  728,  729,  730,  and 
744). — The  iris  has  received  its  name  from  its  various  colors  in  different  individ- 
uals. It  is  a  thin,  circular-shaped,  contractile  curtain,  suspended  in  the  aqueous 
humor  behind  the  cornea,  and  in  front  of  the  lens,  being  perforated  a  little  to  the 
nasal  side  of  its  centre  by  a  circular  aperture,  the  pupil  (pupilla)  (Fig.  730) ,  for 
the  transmission  of  light.  The  pupil  of  a  living  person  varies  in  size  under  the 
influence  of  light  and  in  efforts  at  accommodation.  In  looking  at  a  near  object  the 
pupil  is  small ;  in  looking  at  a  distant  object  it  is  large.  In  light  the  pupil  contracts, 
in  darkness  it  dilates;  hence  the  pupil  is  a  window  which  permits  light  to  pass  into 
the  interior  of  the  eye.  The  size  of  this  window  depends  on  the  contraction  or 
relaxation  of  the  iris.     The  iris  divides  the  aqueous  chamber  (the  space  between 


Circ.  fibres 
of  sclerotic. 


Circ.  fibres   / 
of  Ciliary  mttscle. 


Radiating 

fibres  of 

Ciliary  muscle. 


( Pars  ciliaris 
\      retinae. 


Fig.  727. — Section  of  the  eye,  showing  the  relations  of  the  cornea,  sclerotic,  and  iris,  together  with  the  Ciliary- 
muscle  and  the  cavernous  spaces  near  the  angle  of  the  anterior  chamber.      (Waldeyer.) 

the  cornea  and  lens)  into  an  anterior  chamber  and  a  posterior  chamber  which  com- 
municate through  the  pupil  (Figs.  714  and  716).  By  its  circumference  or  ciliary  mar- 
gin (marge  ciliaris)  (Figs.  727  and  728)  the  iris  is  continuous  with  the  ciliary  body, 
and  it  is  also  connected  with  the  posterior  elastic  lamina  of  the  cornea  by  means  of 
the  pectinate  ligament  (ligamentum  'pectinatum  iriclis)  (Fig.  744).  The  pectinate 
ligament  of  the  iris  is  derived  from  the  posterior  elastic  layer  of  the  cornea.  This 
layer  divides  into  numerous  fibrillae  and  some  of  them  reach  the  iris,  and  bridge 
the  angle  between  the  cornea  and  base  of  the  iris  (Deaver).  The  fibrillae  which 
reach  the  iris  constitute  the  ligament.  In  this  ligament  are  numerous  lymph- 
spaces,  the  spaces  of  Fontana  (spatia  anguli  iridis  \Fontanae\)  (Fig.  727),  and 
they  join  the  canal  of  Schlemm  to  the  anterior  chamber  of  the  eye.  The  inner  or 
free  edge  of  the  iris  forms  the  margin  of  the  pupil,  and  is  called  the  pupillary 
margin  (margo  pupillaris)  (Fig.  728).     The  surfaces  of  the  iris  are  flattened,  and 


*  Stewart,  Manual  of  Physiology. 


1118 


THE    ORGANS   OF  SPECIAL    SENSE 


look  forward  and  backward,  the  anterior  toward  the  cornea,  the  posterior  toward 
the  ciHary  processes  and  lens.  The  iris  is  pigmented  and  the  color  of  an  individual's 
eyes  depends  upon  this  pigment.  The  anterior  surface  (fades  anterior)  (Figs.  728 
and  744)  of  the  iris  is  variously  colored  in  different  individuals,  and  is  marked  by 
lines  which  converge  toward  the  pupil.  The  posterior  surface  (fades  posterior)  (Figs. 
726  and  744)  is  of  a  deep-purple  tint,  from  being  covered  by  two  layers  of  pig- 
mented, columnar  epithelium,  which  layers  are  continuous  posteriorly  with  the 
pars  ciliaris  retinae.  This  pigmented  epithelium  is  termed  the  pars  iridica  retinae, 
though  it  is  sometimes  named  uvea,  from  its  resemblance  in  color  to  a  ripe  grape. 
Structure. — The  iris  is  composed  of  the  following  structures: 

1.  In  front  is  a  layer  of  flattened  endothelial  cells  placed  on  a  delicate  hyaline 
basement-membrane.  This  layer  is  continuous  with  the  endothelial  layer  covering 
the  membrane  of  Descemet,  and  in  men  with  dark-colored  irides  the  cells  contain 
pigment-granules. 

2.  Stroma  (stroma  iridis). — The  stroma  consists  of  fibres  and  cells.  The  former 
are  made  of  fine,  delicate  bundles  of  fibrous  tissue,  of  which  some  few  fibres  have 


CILIARY  GANGLIATED 
PLEXUS 


CILIARY  MARGIN 
OF   IRIS 


^'\1/?^i         ATTACHED 


CILIARY  ZONE 
OF   IRIS 


REMNANT  OF 

CORNEAL 

MARGIN 


CIRCULUS 
MINOR' 


PUPILLARY  ZONE 
OF   IRIS 


CONTRACTINQ 
FOLDS  OF  IRIS 

VASCULAR 
EMINENCES 


LARGE 
PIGMENT-CELL 


FREE  BORDER 
"OF  PIGMENTARY 
LAYER 

Fig.  728. — Section  of  the  iris.     Anterior  surface  magnified.     (Toldt.) 


PUPILLARY 
MARGIN 


a  circular  direction  at  the  circumference  of  the  iris,  but  the  chief  mass  consists  of 
fibres  radiating  toward  the  pupil.  They  form,  by  their  interlacement,  a  delicate 
mesh,  in  which  the  vessels  and  nerves  are  contained.  Interspersed  between  the 
bundles  of  connective  tissue  are  numerous  branched  cells  with  fine  processes. 
Many  of  them  in  dark  eyes  contain  pigment-granules,  but  in  blue  eyes  and  the 
pink  eyes  of  albinos  they  are  unpigmented. 

3.  The  Muscular  Fibre  is  involuntary  and  consists  of  circular  and  radiating 
fibres.  The  circular  fibres  (m.  sphincter  pupillae)  surround  the  margin  of  the  pupil 
on  the  posterior  surface  of  the  iris,  like  a  sphincter,  forming  a  narrow  band  about 
one-thirtieth  of  an  inch  in  width,  those  near  the  free  margin  being  closely  aggre- 
gated; those  more  external  somewhat  separated,  and  forming  less  complete  circles. 
The  radiating  fibres  (m.  dilator  pupillae)  converge  from  the  circumference  toward 
the  centre,  and  blend  with  the  circular  fibres  near  the  margin  of  the  pupil.  These 
fibres  are  regarded  by  some  as  elastic,  not  muscular,  but  Grunnert  positively 
demonstrated  them.^  The  fibres  are  very  small  and  are  placed  between  the 
stroma  and  the  posterior  layer  of  endothelium. 


'  Von  Graefe's  Arch.  f.  Ophthal.,  Bd.  xlvii. 


THE   IBIS 


1119 


4.  Pigment. — The  situation  of  the  pigment-cells  differs  in  different  irides.  In 
the  various  shades  of  blue  eyes  the  only  pigment-cells  are  several  layers  of  small 
round  or  polyhedral  cells  filled  with  dark  pigment,  situated  on  the  posterior  surface 


CILIARY 
GANGLIATED 


ADICLE8 
THE 
VEINS 


Fig.  729. — The  ciliary  gangliated  plexus  and  the  ciliary  nerves  entering  the  plexus.     Outer  surface  of  the 
middle  or  vascular  coat  of  the  eyeball.    (Toldt.) 

of  the  iris  and  continuous  with  the  pigmentary  lining  of  the  ciliary  processes.  The 
color  of  the  eye  in  these  individuals  is  due  to  this  coloring-matter  showing  more 
or  less  through  the  texture  of  the  iris.    In  the  albino  even  this  pigment  is  absent. 


ANTERIOR    CILIARY    ARTERIES 


LONG   CILIARY 
ARTERY 


ANTERIOR  CILIARY  ARTERIES 

Fig.  730. — Iris,  front  view.     (Testut.) 


In  the  gray,  brown,  and  black  eye  there  are,  as  mentioned  above,  pigment-granules 
to  be  found  in  the  cells  of  the  stroma  and  in  the  endothelial  layers  on  the  front  of 
the  iris;  to  these  the  dark  color  of  the  eye  is  due.  • 


1120  THE    ORGANS    OF  SPECIAL    SENSE 

The  Arteries  of  the  Iris  (Figs.  723,  725,  727,  and  739).— The  arteries  of  the  iris  are 
derived  from  the  long  posterior  ciliary  and  anterior  ciliary  and  f  ron)  the  vessels  of  the 
ciliary  processes  (see  p.  1 1 15).  The  long  posterior  ciliaxy  arteries  (Figs.  721  and  723) , 
two  in  number,  pass  through  the  sclera,  one  on  the  inner  and  one  on  the  outer  side 
of  the  optic  nerve,  and  pass  forward  between  the  sclera  and  choroid,  and,  having 
reached  the  attached  margin  of  the  iris  (Figs.  721  and  730), divide  into  an  upper  and 
a  lower  branch,  and,  encircling  the  iris,  anastomose  with  corresponding  branches 
from  the  opposite  side ;  into  this  vascular  zone  {circulus  arteriosus  major)  (Fig.  744) 
the  anterior  ciliary  arteries  (Fig.  744) ,  from  the  lachr3mial  and  anterior  ciliary  from  the 
muscular  branches  of  the  ophthalmic,  pour  their  blood.  From  this  zone  vessels  con- 
verge to  the  free  margin  of  the  iris,  and  these  communicate  by  branches  from  one 
to  another  and  thus  form  a  second  zone  {circulus  arteriosus  minor)  in  this  situation. 
The  veins  pass  toward  the  ciliary  margin  and  communicate  with  the  veins  of  the 
ciliary  processes  and  of  the  canal  of  Schlemm  (Figs.  721  and  723). 

The  Nerves  of  the  Choroid  and  Iris  (Figs.  719,  721,  and  729). — The  nerves  of  the 
choroid  and  iris  are  the  short  ciliary,  the  ciliary  branches  of  the  lenticular  ganglion, 
and  the  long  ciliary  from  the  nasal  branch  of  the  opthalmic  division  of  the  fifth.  They 
pierce  the  sclerotic  around  the  entrance  of  the  optic  nerve,  and  run  forward  in  the 
perichoroidal  lymph-space  in  which  they  form  a  plexus,  from  which  plexus  filaments 
pass  to  supply  the  blood-vessels  of  the  choroid.  After  reaching  the  iris  they  form 
a  plexus  around  its  attached  margin ;  from  this  are  derived  non-medullated  fibres 
which  terminate  in  the  circular  and  radiating  muscular  fibres.  Their  exact  mode 
of  termination  has  not  been  ascertained.  Other  fibres  from  the  plexus  terminate 
in  a  network  on  the  anterior  surface  of  the  iris.  The  fibres  derived  from  the  motor 
root  of  the  lenticular  ganglion  (third  nerve)  supply  the  circular  fibres,  while  those 
derived  from  the  sympathetic  supply  the  radiating  fibres. 

Membrana  Pupillaris. — In  the  foetus  the  pupil  is  closed  by  a  delicate  transparent 
vascular  membrane,  the  membrana  pupillaris,  which  divides  the  space  into  which 
the  iris  is  suspended  into  two  distinct  chambers.  This  membrane  contains  numer- 
ous minute  vessels,  continued  from  the  margin  of  the  iris  to  those  on  the  front  part 
of  the  capsule  of  the  lens.  These  vessels  have  a  looped  arrangement,  and  converge 
toward  each  other  without  anastomosing.  Between  the  seventh  and  eighth  months 
the  membrane  begins  to  disappear,  by  gradual  absorption  from  the  centre  toward 
the  circumference,  and  at  birth  only  a  few  fragments  remain.  It  is  said  some- 
times to  remain  permanent  and  produce  blindness. 

III.  The  Tunica  Interna  or  Retina  (Figs.  723,  731,  733). 
The  retina  is  a  delicate  nervous  membrane,  in  which  the  fibres  of  the  optic  nerve 
are  spread  out  and  upon  the  surface  of  which  the  images  of  external  objects  are 
received.  Its  outer  surface  is  in  contact  with  the  choroid ;  its  inner  with  the  vitreous 
body.  Behind,  it  is  continuous  with  the  optic  nerve;  it  gradually  diminishes  in 
thickness  from  behind  forward;  and,  in  front,  extends  nearly  as  far  as  the  ciliary 
body,  where  it  appears  to  terminate  in  a  jagged  margin,  the  ora  serrata  (Figs.  723, 
742,  and  744) .  Here  the  nervous  tissues  of  the  retina  end,  but  a  thin  prolongation 
of  the  membrane  extends  forward  over  the  back  of  the  ciliary  processes  and  iris, 
forming  the  para  ciliaris  retinae  and  pars  iridica  retinae  already  referred  to  (Figs.  727 
and  744) .  This  forward  prolongation  consists  of  the  pigmentary  layer  of  the  retina, 
together  with  a  stratum  of  columnar  epithelium.  The  portion  back  of  the  ora 
serrata  is  called  the  physiological  retina  {jpars  optica  retinae)  (Fig.  744) .  The  retina 
is  soft,  semitransparent,  and  of  a  purple  tint  in  the  fresh  state,  owing  t(  the  presence 
of  a  coloring-material  named  rhodopsin  or  visual  purple;  but  it  soon  becomes 
clouded,  opaque,  and  bleached  when  exposed  to  sunlight.  Exactly  in  the  centre 
of  the  front  surface  of  the  posterior  part  of  the  retina,  corresponding  to  the  visual 
axis,  and  at  a  point  in  which  the  sense  of  vision  is  most  perfect,  is  an  oval  yellowish 


THE    TUNICA    INTERNA    OB    RETINA 


1121 


spot,  called,  after  its  discoverer,  the  yellow  spot  of  Sbminerring  (macula  lutea)  (Figs. 
714  and  733),  having  a  central  depression,  the  fovea  centralis.  The  retina  in  the 
situation  of  the  fovea  centralis  is  exceedingly  thin,  and  the  dark  color  of  the  choroid 
is  distinctly  seen  through  it;  so  that  it  presents  more  the  appearance  of  a  foramen, 
and  hence  the  name  foramen  of  Sommerring  at  first  given  to  it.  It  exists  only  in 
man,  the  quadrumana,  and  some  saurian  reptiles.  About  one-eighth  of  an  inch  (3 
mm.)  to  the  nasal  side  of  the  yellow  spot  and  one-twenty-fourth  of  an  inch  below 
it,  is  the  point  of  entrance  of  the  optic  nerve,  the  optic  disk  (porus  opticus)  (Figs. 
731  and  733).  The  circumference  of  the  optic  disk  is  slightly  raised  so  as  to  form 
an  eminence,  the  optic  papilla  (colliculus  nervi  optici);  the  central  portion  is 
depressed  and  is  called  the  optic  cup  (excavatio  papillae  nervi  optici).  The  arteria 
centralis  retinae  pierces  its  centre.  This  is  the  only  part  of  the  surface  of  the  retina 
from  which  the  power  of  vision  is  absent,  and  is  termed  the  blind  spot. 


OPTIC 
LAMINA  CRIBROSR      PAPILLA 


POSTERIOR 
SHORT  CILIARY     ^ 
ARTERY  AND 
VEIN 

PIAL 
SHEATH 

DURAL 
SHEATH 
ARACHNOID 
SHEATH' 

INTERVAGINAL 
SPACES 


eUNDLCS  OF  CENTRAL  ARTERY  AND 

OPTIC  NERVE  VEIN  OF  RETINA 

IIG.  731. — The  terminal  portion  of  the  optic  nerve  and  its  entrance  into  the  eyeball,  in  horizontal  section.  (Toldt.) 
Structure. — The  optical  portion  of  the  retina  is  an  exceedingly  complex  structure, 
nd,  when  examined  microscopically  by  means  of  sections  made  perpendicularly 
E)  its  surface,  is  found  to  consist  of  many  layers  of  nervous  structure.  These  ner- 
ous  structures  are  bound  together  and  supported  by  the  sustentacular  fibres. 
?here  are  three  layers:  a  middle  or  neuro-epitiielial  layer,  an  inner  layer,  and  an 
outer  or  pigmentary  layer.  The  neuro-epithelial  layer  is  subdivided  into  four  and 
the  middle  layer  into  six  layers;  hence  the  retina  consists  of  eleven  layers.  The 
layers  from  within  outward  are  as  follows  (Figs.  732,  734,  735,  and  736) : 

1.  Membrana  limitans  interna. 

2.  Layer  of  nerve-fibres  (stratum  opticum). 

3.  Ganglionic  layer,  consisting  of  nerve-cells. 

4.  Inner  molecular,  or  plexiform,  layer. 

5.  Inner  nuclear  layer,  or  layer  of  inner  granules. 

6.  Outer  molecular,  or  plexiform,  layer. 

7.  Henle's  fibre-layer. 

8.  Outer  nuclear  layer,  or  layer  of  outer  granules. 

9.  Membrana  limitans  externa. 

10.  Jacob's  membrane  (layer  of  rods  and  cones). 

11.  Pigmentary  layer  (tapetum  nigrum). 
71 


1.  Inner  layer 


2.  Neuro-epithelial  layer 


3.  Outer  laver 


1122 


THE    ORGANS    OF  SPECIAL   SENSE 


1.  The  Membrana  Limitans  Interna  (Figs.  732,  734,  and  735),  is  the  most  internal 
layer  of  the  retina,  and  is  in  contact  with  the  hyaloid  membrane  of  the  vitreous 


Fibre  of  Muller.- 


Pigmentary  layer.- 


Jacob's  membrane. 


Membrana  limitans  extei^na. 


Outer  nuclear  layer. 


Outer  molecular  layer. 


Inner  nuclear  layer. 


Inner  molecular  layer. 

Ganglionic  layer. 
Layer  of  nerve-fibres. 


Membrana  limitans  interna. 


Fig.  732. — The  layers  of  the  retina  with  the  exception  of  Henle's  fibre-layer.    (Diagrammatic.)  (After  Schultze.) 

humor.  It  is  derived  from  the  sup- 
porting framework  of  the  retina,  with 
which  tissue  it  will  be  described. 

2.  The  Layer  of  Nerve-fibres  (Figs. 
732,  734,  and  735)  is  formed  by 
the  expansion  of  the  optic  nerve. 
This  nerve  passes  through  all  the 
other  layers  of  the  retina,  except 
the  membrana  limitans  interna,  to 
reach  its  destination.  As  the  nerve 
passes  through  the  lamina  cribrosa  of 
the  sclerotic  coat,  the  fibres  of  which 
it  is  composed  lose  their  medullary 
sheaths  and  are  continued  onward, 
through  the  choroid  and  retina,  as 
simple   axis-cylinders.     When   these 

^"SL7LYf^o?tfe\yTbaii"bTntrttA^^^^^^  non-medulkted  fibres  reach  the  in 

ternal  surface  of  the  retina,  they  radi 
ate  from  their  point  of  entrance  over  the  surface  of  the  retina,  become  grouped  in 
bundles,  and  in  many  places,  according  to  Michel,  arranged  in  plexuses.     Most 
of  the  fibres  in  this  layer  are  centripetal,  and  are  the  direct  continuations  of  the 


THE    TUNICA    INTERNA    OB    RETINA 


1123 


axis-cylinder  processes  of  the  cells  of  the  next  layer,  A  few  of  the  fibres  are 
centrifugal,  which  are  axis-cylinders  of  ganglion-cells  within  the  brain.  The  cen- 
trifugal fibres  in  the  layer  of  nerve-fibres  pass  through  it  and  the  next  succeeding 
layer  to  ramify  in  the  inner  molecular  and  inner  nuclear  layers,  where  they  termi- 
nate in  enlarged  extremities.  The  layer  is  thickest  at  the  optic  nerve  entrance, 
and  gradually  diminishes  in  thickness  toward  the  ora  serrata. 

3.  The  Ganglionic  Layer  or  the  Inner  Ganglionic  Layer  (Figs.  732,  734,  and  735) 
consists  of  a  single  layer  of  large  ganglion-cells;  except  in  the  macula  lutea, 
where  there  are  several  strata.  The  cells  are  somewhat  flask-shaped,  the  rounded 
internal  margin  of  each  cell  resting  on  the  preceding  layer  and  sending  off  an  axone 
which  is  prolonged  as  a  nerve-fibre  into  the  fibrous  layer.  From  the  opposite 
extremity  numerous  thicker  processes  (dendrites)  extend  into  the  inner  molecular 
layer,  where  they  branch  out  into  flattened  arborizations  at  different  levels.  The 
ganglion-cells  vary  much  in  size,  and  the  dendrites  of  the  smaller  ones,  as  a  rule. 


r 


TTI 


■¥ 


P 


Figs.  734  and  735. — Vertical  sections  of  the  human  retina.  Fig.  734,  half  an  inch  from  the  entrance  of  the 
optic  nerve.  Fig.  735,  close  to  the  latter.  1.  Layer  of  rods  and  cones,  Jacob's  membrane,  bounded  underneath 
by  the  membrana  limitans  externa.  •  2.  Outernuclear  layer.  3.  Outer  molecular  layer.  4.  Inner  nuclear  layer. 
5.  Inner  molecular  layer.  6.  Ganglionic  layer.  7.  Layer  of  nerve  fibres.  8.  Sustentacular  fibres  of  MUller. 
9.  Their  attachment  to  the  membrana  limitans  interna. 

arborize  in  the  inner  molecular  layer  as  soon  as  they  enter  it ;  while  the  processes 
of  the  larger  cells  ramify  close  to  the  inner  nuclear  layer. 

4.  The  Inner  Molecular,  the  Plexiform  or  the  Inner  Reticular  Layer  (Fig.  732,  734, 
and  735)  is  made  up  of  a  dense  reticulum  of  minute  fibrils,  formed  by  the  inter- 
lacement of  the  dendrites  of  the  ganglion-cells  with  those  of  the  cells  contained  in 
the  next  layer,  immediately  to  be  described.  Within  the  reticulum  formed  by 
these  fibrils  a  few  branched  spongioblasts  are  sometimes  embedded. 

5.  The  Inner  Nuclear  or  Inner  Granular  Layer  (Figs.  732,  734,  and  735)  is  made  up 
of  a  number  of  closely  packed  cells,  of  which  there  are  three  different  kinds.  (1)  A 
large  number  of  oval  cells,  which  are  commonly  regarded  as  bipolar  nerve-cells,  and 
are  much  more  numerous  than  either  of  the  other  kind.  They  each  consist  of  a 
large  oval  body  placed  vertically  to  the  surface,  and  containing  a  distinct  nucleus. 
The  protoplasm  is  prolonged  into  two  processes ;  one  of  these  passes  inward  into  the 
inner  molecular  layer,  is  varicose  in  appearance,  and  ends  in  a  terminal  ramification, 
which  is  often  in  close  proximity  to  the  ganglion-cells  (Fig.  736,  i,  c).  The  outer 
process  passes  outward  into  the  outer  molecular  layer,  and  there  breaks  up  into  a 


1 


THE    ORGANS   OF  SPECIAL    SENSE 


1 


THE    TUNICA    INTERNA     OB    BETINA  .        1125 

number  of  branches.  According  to  Cajal,  there  are  two  varieties  of  these  pipolar 
cells :  one  in  which  the  outer  process  arborizes  around  the  knobbed  ends  of  the 
rod-fibres,  and  the  inner  around  the  cells  of  the  ganglionic  layer;  these  he  calls  rod- 
bipolars  (Fig.  736,  i) ;  the  others  are  those  in  which  the  outer  process  breaks  up  in 
a  horizontal  ramification,  in  contact  with  the  end  of  a  cone-fibre ;  these  are  the 
cone-bipolaxs,  and  their  inner  process  breaks  up  into  its  terminal  ramifications  in 
the  inner  molecular  layer  (Fig.  736,  i).  (2)  At  the  innermost  part  of  this  inner 
nuclear  layer  is  a  stratum  of  cells,  which  are  named  Cajal  amacrine  cells,  from  the 
fact  that  they  have  no  axis-cylinder  process,  but  they  give  a  number  of  short  proto- 
plasmic processes  which  extend  into  the  inner  molecular  layer  and  there  ramify 
(Fig.  736,  i).  There  are  also  at  the  outermost  part  of  this  layer  some  cells,  the 
processes  of  which  extend  into  and  ramify  in  the  outer  molecular  layer.  These 
are  the  horizontal  cells  of  Cajal.  (3)  Some  few  cells  are  also  found  in  this  layer, 
connected  with  the  fibres  of  Miiller  and  will  be  described  with  those  structures. 

6.  The  Outer  Molecular  or  Outer  Reticular  Layer  or  the  Plexiform  Layer  (Figs. 
732,  734,  and  735)  is  much  thinner  than  the  inner  molecular  layer;  but,  like  it, 
consists  of  a  dense  network  of  minute  fibrils,  derived  from  the  processes  of  the 
horizontal  cells  of  the  preceding  layer  and  the  outer  processes  of  the  bipolar  cells, 
which  ramify  in  it,  forming  arborizations  around  the  ends  of  the  rod-fibres  and 
with  the  branched  foot-plates  of  the  cone-fibres. 

7.  Henle's  Fibre  Layer  is  a  non-granular  layer  in  the  neighborhood  of  the  macula 
lutea,  and  is  produced  by  elongations  from  the  inner  segments  of  rod-fibres  and 
cone-fibres. 

8.  The  Outer  Nuclear  or  Outer  Granular  Layer  (Figs.  732,  734,  and  735),  like  the 
inner  nuclear  layer,  contains  several  strata  of  clear  oval  nuclear  bodies ;  they  are 
of  two  kinds,  and  on  account  of  their  being  respectively  connected  with  the  rods 
and  cones  of  Jacob's  membrane  (rod-fibres  and  cone-fibres)  are  named  rod- 
granules  and  cone-granules. 

The  rod-granules  are  much  the  more  numerous,  and  are  placed  at  different  levels 
throughout  the  layer.  Their  nuclei  present  a  peculiar  cross-striped  appearance, 
and  prolonged  from  either  extremity  of  the  granule  is  a  fine  process;  the  outer 
process  is  continuous  with  a  single  rod  of  Jacob's  membrane;  the  inner  passes 
inward  toward  the  outer  molecular  layer  and  terminates  in  an  enlarged  extremity. 


DESCRIPTION  OF  FIG.  736. 

I.  Section  of  the  dog's  retina,  a.  Cone-fibre,  b.  Rod-fibre  and  nucleus,  e,  d.  Bipolar  cells  (inner  granules) 
with  vertical  ramification  of  outer  processes  destined  to  receive  the  enlarged  ends  of  rod-fibres. 
e.  Bipolar.s  with  flattened  ramification  for  ends  of  cone-fibres.  /.  Giant  bipolar  with  flattened  raniifica- 
tion.  fir.  Cell  sending  a  neurone  or  nerve-fibre  process  to  the  outer  molecular  layer,  h.  Amacrine  cell 
with  diffuse  arborization  in  inner  molecular  layer,  i.  Nerve-fibrils  passing  to  outer  molecular  layer. 
j.  Centrifugal  fibres  passing  from  nerve-fibre  layer  to  inner  molecular  layer,  m.  Nervts-fibril  passing 
into  inner  molecular  layer,     n.  Ganglionic  cells. 

II.  Horizontal  or  basal  cells  of  the  outer  molecular  layer  of  the  dog's  retina.  A.  Small  cell  with  dense  arbori- 
zation. B.  Large  cell,  lying  in  inner  nuclear  layer,  but  with  its  processes  branching  in  the  outer 
molecular,     a.  Its  horizontal  neurone.     C.  Medium-sized  cell  of  the  same  character. 

III.  Cells  from  the  retina  of  the  ox.     a.  Rod-bipolars  with  vertical  arborizations.     6,  c,  d,  e.  Cone-bipolars  with 

horizontal  ramification  of  outer  process,  h.  Cell  lying  on  the  outer  surface  of  the  outer  molecular 
layer,  and  ramifying  within  it.  i,3,in,.  Amacrine  cells  within  the  substance  of  the  inner  molecular 
layer. 

IV.  Neurones  or  axis-cylinder  processes  belonging  to  horizontal  cells  of  the  outer  molecular  layer,  one  of  them, 

6,  ending  in  a  close  ramification  at  a. 

V.  Nervous  elements  connected  with  the  inner  molecular  layer  of  the  ox's  retina.      A.  Amacrine  cell,  with 

long  processes  ramifying  in  the  outermost  stratum.  B.  Large  amacrine  with  thick  processes  ramifying 
in  second  stratum.  C.  Flattened  amacrine  with  long  and  fine  processes  ramifying  mainly  in  the  first 
and  fifth  strata.  D.  Amacrine  with  radiating  tuft  of  fibrils  destined  for  third  stratum.  E.  Large 
amacrine,  with  processes  ramifying  in  fifth  stratum.  F.  Small  amacrine,  branching  into  second 
stratum.  G,  h.  Other  amacrines  destined  for  fourth  stratum,  a.  Small  ganglion-cell  sending  its  pro- 
cesses to  fourth  stratum,  b.  A  small  ganglion-cell  with  ramifications  in  three  strat.^.  C.  A  small  cell 
ramifying  ultimately  in  first  stratum,  d.  A  medium-sized  ganglion-cell  ramifying  in  fourth  stratum. 
e.  Giant-cell,  branching  in  third  stratum.     /.  A  bistratified  ceil  ramifying  in  second  and  fourth  strata. 

VI.  Amacrines  and  ganglion-cells  from  the  dog.      A.  Amacrine  with  radiating  tuft.     B.  Large  amacrine  passing 

to  third  stratum,  c  and  G.  Small  amacrines  with  radiations  in  second  stratum.  F.  Small  amacrine 
passing  to  third  .stratum.  D.  Amacrine  with  diffuse  arborization.  E.  Amacrine  belonging  to  fourth 
.stratum,  a,  d,  e,  g.  Small  ganglion-cells  ramifying  in  various  strata.  b,f.  Large  ganglion-cells  show- 
ing two  different  characters  of  arborization,  i.  Bistratified  cell. 
VII.  Amacrines  and  ganglion-cells  from  the  dog.  A,  B,  C.  Small  amacrines  ramifying  in  middle  of  molecular 
layer,  b,  d,  g,  h,  i.  Small  ganglion-cells  showing  various  kinds  of  arborization.  /.  A  larger  cell,  similar 
in  character  to  g,  but  with  longer  branch,  a,  t^.  e.  Giant-cells  with  thick  branches  ramifying  in  the 
first,  second,  and  third  layers.     L,  L.  Ends  of  bipolars  branching  over  ganglion-cells. 


1126 


THE   ORGANS    OF  SPECIAL    SENSE 


and  is  embedded  in  the  tuft  into  which  the  outer  process  of  the  rod-bipolars  break 
up.    In  its  course  it  presents  numerous  varicosities. 

The  cone-granules,  fewer  in  number  than  the  rod-granules,  are  placed  close  to  the 
membrana  limitans  externa,  through  which  they  are  continuous  with  the  cones  of 
Jacob's  membrane.  They  do  not  present  any  cross-striping,  but  contain  a  pyri- 
form  nucleus  which  almost  completely  fills  the  cell.  From  their  inner  extremity  a 
thick  process  passes  inward  to  the  outer  molecular  layer,  upon  which  it  rests  by  a 
somewhat  pyramidal  enlargement,  from  which  are  given  off  numerous  fine  fibrils, 

A    B 


External 
segment' 


Intermediary 

disc 
Elliptoid- 


I 

EQy. 
I  l()i«. 


Myoid- 
Nucletis — 


Fig.  737.— The  cells  of  the  rods  of  the 
retina  in  the  frog.  A,  red  rod;  JS,  green 
rod.     (Poirier  and  Charpy.) 

which  enter  the  outer  molecular 
layer,  where  they  come  in  con- 
tact with  the  outer  processes  of 
the  cone-bipolars. 

9.  The  Membrana  Limitans 
Externa  (Figs.  732, 734,  and  735) , 
like  the  membrana  limitans  in- 
terna, is  derived  from  the  fibres 
of  Miiller,  with  which  structures 
it  will  be  described. 

10.  Jacob's  Membrane  or  the 
Layer  of  Rods  and  Cones  (Figs. 
732,  734,  and  735)  consists  of 
visual  cells,  and  the  elements 
which  compose  it  are  of  two 
kinds,  rod-cells  and  cone-cells, 
the  former  being  much  more 
numerous  than  the  latter. 

The  rod-cells  (Fig.  737)  are  of  nearly  uniform  size,  and  arranged  perpen- 
dicularly to  the  surface.  A  rod-cell  consists  of  a  rod  and  a  rod-fibre,  and  the 
fibre  contains  the  nucleus.  The  rods  are  cylindrical  and  each  consists  of  two  por- 
tions, an  outer  segment  and  an  inner  segment,  which  are  of  about  equal  length. 
The  segments  differ  from  each  other  as  regards  refraction  and  in  their  behavior 
with  coloring  reagents,  the  inner  portion  becoming  stained  by  carmine,  iodine,  etc., 
the  outer  portion  remaining  unstained  with  these  reagents,  but  staining  yellowish- 
brown  with  osmic  acid .  The  outer  portion  of  each  rod  is  marked  by  transverse  striae, 
and  is  made  up  of  a  number  of  thin  disks  superimposed  on  one  another.    It  also 


Fig.  738. — Cones  in  the  different  regions  of  the  retina.  /,  near 
the  ora  serrata;  //,  at  3  mm.  from  the  ora  serrata;  ///,  at  an 
equal  distance  from  the  ora  serrata  and  the  papilla;  IV,  at  the 
periphery  of  the  fovea  centralis;  V,  in  the  fovea  centralis;  Vf,  at 
the  centre  of  the  fovea  centralis;  E,  length  of  the  external  seg- 
ment; /,  length  of  internal  segment;  D,  diameter  of  the  internal 
segment.     (Poirier  and  Charpy.) 


THE    TUNICA    INTERNA    OR   RETINA  1127 

exhibits  faint  longitudinal  markings.  The  inner  portion  of  each  rod,  at  its  deeper 
part  where  it  is  joined  to  the  outer  process  of  the  rod-granule,  is  indistinctly  gran- 
ular; its  more  superficial  part  presents  a  longitudinal  striation,  being  composed  of 
fine,  bright,  highly  refracting  fibres.  In  most  vertebrates  the  outer  portion  of  the 
inner  segment  contains  a  fibrous  body,  the  ellipsoid  of  Krause.  The  visual  purple,  or 
rhodopsin,  is  found  only  in  the  outer  segments  of  the  rods.  At  its  inner  end  each  rod 
is  prolonged  into  a  very  fine  fibre,  the  rod-fibre,  which  contains  a  nucleus,  and  which 
terminates  in  the  outer  nuclear  layer,  being  somewhat  enlarged  at  its  termination. 

The  cone-cells  (Fig.  738)  are  conical  or  flask-shaped,  their  broad  ends  resting 
upon  the  membrana  limitans  externa,  the  narrow  pointed  extremity  being  turned 
to  the  choroid.    Each  cone-cell  consists  of  two  parts,  the  cone  and  the  cone-fibre. 

The  cones  are  shorter  than  the  rods  and  exhibit  an  outer  and  an  inner  segment. 

The  outer  segment  is  a  short  conical  process,  which,  like  the  outer  segment  of  a 
rod,  presents  transverse  striae.  The  inner  segment  resembles  the  inner  portion 
of  the  rods  in  structure,  presenting  a  superficial  striated  and  deeper  granular  part; 
but  differs  from  it  in  size,  being  bulged  out  laterally  and  presenting  a  flask  shape. 

The  inner  segment  of  the  cone,  as  does  the  rod,  contains  an  ellipsoid  of  Krause. 
Each  cone  is  prolonged  into  a  cone-fibre,  and  at  the  junction  of  the  cone  with  the 
fibre  is  the  nucleus  of  the  cone-cell.  The  cone-fibre  passes  to  the  outer  nuclear 
layer,  and  terminates  as  an  expansion  from  which  very  minute  fibrils  are  given  off. 
The  chemical  and  optical  characters  of  the  rod-cells  and  cone-cells  are  identical. 

1 1 .  The  Pigmentary  Layer  or  Tapetum  Nigrum  (Fig.  732) . — The  most  external  layer 
of  the  retina,  formerly  regarded  as  a  part  of  the  choroid,  consists  of  a  single  layer 
of  hexagonal  epithelial  cells,  loaded  with  pigment-granules.  Each  cell  contains  a 
flattened  nucleus  in  the  outer  portion  of  the  cell  which  is  free  from  pigment  at  this 
point.  These  cells  are  smooth  externally,  where  they  are  in  contact  with  the 
choroid,  but  internally  they  are  prolonged  into  fine,  straight  processes,  which 
extend  between  the  rods,  this  being  especially  the  case  when  the  eye  is  exposed  to 
light.  The  pigment  changes  its  position  under  the  influence  of  light,  and  is  dis- 
tributed through  the  entire  cell.  In  the  eyes  of  albinos,  the  cells  of  the  pigmentary 
layer  are  present,  but  they  contain  no  coloring-matter.  In  the  eyes  of  many 
mammals  also,  as  in  the  horse,  and  many  of  the  carnivora,  there  is  no  pigment 
in  the  cells  of  this  layer,  and  the  choroid  possesses  a  beautiful  iridescent  lustre, 
which  is  termed  the  tapetum  lucidum. 

Supporting  Framework  of  the  Retina. — Almost  all  these  layers  of  the  retina  are 
connected  together  by  a  supporting  framework,  formed  by  the  supporting  cells  or 
supporting  fibres  of  Miiller  or  radiating  fibres,  from  which  the  membrana  limitans 
interna  et  externa  are  derived.  These  fibres  are  found  stretched  between  the  two 
limiting  layers  (Fig.  732),  "like  columns  between  a  floor  and  a  roof,"  and  they 
Dass  through  all  the  nervous  layers  except  Jacob's  membrane.  Each  commences 
on  the  inner  surface  of  the  retina  by  a  conical  hollow  base,  which  sometimes 
contains  a  spheroidal  body  which  stains  deeply  with  hsematoxylin,  the  edges  of 
the  bases  of  adjoining  fibres  being  united  and  thus  forming  a  boundary  line,  which 
is  the  membrana  limitans  interna.  As  they  pass  through  the  nerve-fibre  and  gan- 
glionic layers  they  give  off  few  lateral  branches ;  in  the  inner  nuclear  layer  they  give 
off  numerous  lateral  processes  for  the  support  of  the  inner  granules,  while  in  the 
outer  nuclear  layer  they  form  a  network,  the  fibre-baskets,  around  the  rod  and 
cone-fibrils,  and  unite  to  form  the  external  limiting  membrane  at  the  bases  of 
the  rods  and  cones.  In  the  inner  nuclear  layer  each  fibre  of  Miiller  presents  a  clear 
oval  nucleus,  which  is  sometimes  situated  at  the  side  of,  sometimes  altogether 
within,  the  fibre.    The  supporting  framework  of  the  retina  contains  neuroglia  cells. 

The  Path  of  Light  Stimuli. — The  stimulus  is  first  received  by  the  rod  and  cone- 
cells  (the  visual  cells),  and  is  transmitted  to  the  bipolar  cells  of  the  inner  nuclear 
layer  and  then  to  the  cells  of  the  ganglionic  layer,  which  send  fibres  by  way  of  the 
optic  nerve  to  the  brain. 


1128  THE    ORGANS    OF  SPECIAL    SENSE 

Macula  Lutea  and  Fovea  Centralis. — The  structure  of  the  retina  at  the  yellow 
spot  presents  some  modifications.  In  the  macula  lutea  (1)  the  nerve-fibres  are 
wanting  as  a  continuous  layer;  (2)  the  ganglionic  layer  consists  of  several  strata 
of  cells,  instead  of  a  single  layer;  (3)  in  Jacob's  membrane  there  are  no  rods,  but 
only  cones,  and  these  are  longer  and  narrower  than  in  other  parts;  and  (4)  in  the 
outer  nuclear  layer  there  are  only  cone-fibres,  which  are  very  long  and  arranged 
in  curved  lines.  At  the  fovea  centralis  the  only  parts  which  exist  are  the  cones 
of  Jacob's  membrane,  the  outer  nuclear  layer,  the  cone-fibres  of  which  are  almost 
horizontal  in  direction,  and  an  exceedingly  thin  inner  granular  layer,  the  pigment- 
ary layer,  which  is  thicker  and  its  pigment  more  pronounced  than  elsewhere.  The 
color  of  the  macula  seems  to  imbue  all  the  layers  except  Jacob's  membrane;  it  is 
of  a  rich  yellow,  deepest  toward  the  centre,  and  does  not  appear  to  consist  of 
pigment-cells,  but  simply  a  staining  of  the  constituent  parts. 

At  the  Ora  Serrata  (Fig.  723)  the  nervous  layers  of  the  retina  terminate  abruptly, 
and  the  retina  is  continued  onward  as  a  single  layer  of  elongated  colunmar  cells 
covered  by  the  pigmentary  layer.  This  prolongation  is  known  as  the  pars  ciliaris 
retinae  (Fig.  727) ,  and  can  be  traced  forward  from  the  ciliary  processes  on  to  the 
back  of  the  iris,  where  it  is  termed  the  pars  iridica  retinae  or  uvea. 

From  the  description  given  of  the  nervous  elements  of  the  retina  it  will  be 
seen  that  there  is  no  direct  continuity  between  the  structures  which  form  its  differ- 
ent layers  except  between  the  ganglionic  and  nerve-fibre  layers,  the  majority 
of  the  nerve-fibres  being  formed  of  the  axones  of  the  ganglionic  cells.  In  the 
inner  molecular  layer  the  dendrites  of  the  ganglionic  layer  interlace  with  those 

of  the  cells  of  the  inner  nuclear  layer,  while  in  the 
outer  molecular  layer  a  like  synapsis  occurs  between 
the  processes  of  the  inner  granules  and  the  rod  and 
cone  elements. 

The  Arteria  Centralis  Retinae  (Figs.  723  and  731) 
and  its  accompanying  vein,  vena  centralis  retinae, 
pierce  the  optic  nerve,  and  enter  the  globe  of  the  eye 
through  the  porus  opticus.  It  immediately  bifurcates 
into  an  upper  and  a  lower  branch,  and  each  of  these 
mo^ve'd  STh^eVin'thrfresh'^state".  ^g^i"  dividcs  iuto  an  inner  or  nasal,  and  an  outer  or 
with  the  saucer-shaped  hollow  in  which  temporal,  brauch,  which  at  first  run  between  the 

the  lens  lies.      Seen  obliquely  from  the    ,        /^  .  ,  , 

side  and  before.   (Toidt.)  hyaloid  membrane  and  the  nervous  layer;  but  they 

soon  enter  the  latter,  and  pass  forward,  dividing 
dichotomously.  From  these  branches  a  minute  capillary  plexus  is  given  off,  which 
does  not  extend  beyond  the  inner  nuclear  layer.  The  macula  receives  small  twigs 
from  the  temporal  branches  and  others  directly  from  the  central  artery;  these  do 
not,  however,  reach  as  far  as  the  fovea  centralis,  which  has  no  blood-vessels.  The 
branches  of  the  arteria  centralis  retinae  do  not  anastomose  with  each  other — in  other 
words,  they  are  "terminal  arteries."  In  the  foetus,  a  small  vessel  passes  forward, 
through  the  hyaloid  canal  in  the  vitreous  body,  to  the  posterior  surface  of  the  cap- 
sule of  the  lens  (Fig.  715) . 

THE   REFRACTING  MEDIA. 

The  Refracting  media  are  three,  viz.: 

Aqueous  humor.  Vitreous  body.  Crystalline  lens. 

I.  The  Aqueous  Humor  (Humor  Aqueus). 

The  aqueous  humor  completely  fills  the  lymph  space  known  as  the  aqueous 
chamber,  the  space  which  is  bounded  in  front  by  the  cornea  and  behind  by  the  lens 
and  its  suspensory  ligament  and  the  ciliary  body  (Fig.  744) .   The  aqueous  chamber 


FOSSA 
PATELLARIS 


VITREOUS 
BODY 


THE    VITREOUS  BODY  1129 

is  partly  divided  by  the  iris  into  two  communicating  parts,  the  anterior  and  posterior 
chambers  (Figs.  714,  715,  and  744.)  The  posterior  chamber  (cumera  oculi  posterior) 
is  only  a  narrow  chink  between  the  peripheral  part  of  the  iris,  the  suspensory 
ligament  of  the  lens,  and  the  ciliary  processes.  The  anterior  chamber  (cumera  oculi 
anterior  is  bounded  in  front  by  the  cornea  and  behind  by  the  iris.  The  external 
angle  of  the  anterior  chamber  is  bounded  by  the  periphery  of  the  cornea  and  of 
the  iris.  It  is  called  the  angle  or  sinus  of  the  anterior  chamber  or  the  filtration  angle 
(angulus  iridic) .  It  is  by  way  of  the  filtration  angle  that  any  excess  of  aqueous 
humor  passes  by  way  of  the  spaces  of  Fontana  and  the  canal  of  Schlemm  (Fig. 
727)  to  the  anterior  ciliary  veins  and  relieves  tension.  The  aqueous  humor  is 
small  in  quantity  (scarcely  exceeding,  according  to  Petit,  four  or  five  grains  in 
weight),  has  an  alkaline  reaction,  in  composition  is  little  more  than  water,  less 
than  one-fiftieth  of  its  weight  being  solid  matter,  chiefly  chloride  of  sodium. 

In  the  adult,  these  two  chambers  communicate  through  the  pupil;  but  in  the 
foetus  of  the  seventh  month,  when  the  pupil  is  closed  by  the  membrana  pupillaris, 
the  two  chambers  are  quite  separate. 

II.  The  Vitreous  Body  (Corpus  Vitreum)  (Figs.  712,  715,  739). 

The  vitreous  body  forms  about  four-fifths  of  the  entire  globe.  It  is  composed  of 
a  jelly-like  tissue  containing  98  per  cent,  water,  some  salts,  and  a  little  albumin, 
and  called  the  vitreous  humor  (humor  vitreum),  connective-tissue  fibres,  and 
connective-tissue  cells.  It  fills  the  concavity  of  the  retina,  and  is  hollowed  in 
front,  forming  a  deep  concavity,  the  fossa  patellaris  (fossa  hyaloidea)  (Fig.  739), 
for  the  reception  of  the  lens.  It  is  perfectly  transparent,  of  the  consistence 
of  thin  jelly,  and  is  composed  of  an  albuminous  fluid  enclosed  in  a  delicate 
transparent  membrane,  the  hyaloid  membrane  (membrana  hyaloidea),  the  outside 
of  which  is  in  contact  with  the  membrana  limitans  interna  of  the  retina.  It 
has  been  supposed  by  Hannover,  that  from  its  inner  surface  numerous  thin 
lamellae  (stroma  vitreum)  are  prolonged  inward  in  a  radiating  manner,  forming 
spaces  in  which  the  fluid  is  contained.  In  the  adult,  these  lamellae  cannot  be 
detected  even  after  careful  microscopic  examination  in  the  fresh  state,  but  in  prep- 
arations hardened  in  weak  chromic  acid  it  is  possible  to  make  out  a  distinct 
lamellation  at  the  periphery  of  the  body;  and  in  the  foetus  a  peculiar  fibrous 
texture  pervades  the  mass,  the  fibres  joining  at  the  numerous  points,  and  pre- 
senting minute  nuclear  granules  at  their  point  of  junction.  In  the  centre  of 
the  vitreous  humor,  running  from  the  entrance  of  the  optic  nerve  to  the  posterior 
surface  of  the  lens,  is  a  canal,  filled  with  fluid  and  lined  by  a  prolongation  of  the 
hyaloid  membrane.  This  is  the  canal  of  Stilling,  the  hyaloid  canal,  or  the  canal  of 
Cloquet  (canalis  hyaloideus)  (Fig.  715),  which  in  the  embryonic  vitreous  humor 
conveyed  the  minute  vessel  from  the  central  artery  of  the  retina  to  the  back  of 
the  lens. 

The  hyaloid  membrane  encloses  the  whole  of  the  vitreous  humor.  In  front  of 
the  ora  serrata  it  is  thickened  by  the  accession  of  radial  fibres  and  is  termed  the 
zonule  of  Zinn  (zonula  ciliaris)  (Figs.  742  and  744).  It  presents  a  series  of  radially 
arranged  furrows,  in  which  the  ciliary  processes  are  accommodated  and  to  which 
they  are  adherent,  as  evidenced  by  the  fact  that  when  removed  some  of  their  pig- 
ment remains  attached  to  the  zonule.  The  zonule  of  Zinn  splits  into  two  layers,  one 
of  which  is  thin  and  lines  the  fossa  patellaris;  the  other  is  named  the  suspensory 
ligament  of  the  lens ;  it  is  thicker,  and  passes  over  the  ciliary  body  to  be  attached 
to  the  capsule  of  the  lens  a  short  distance  in  front  of  its  equator.  Scattered  and 
delicate  fibres  are  also  attached  to  the  region  of  the  equator  itself.  This  ligament 
retains  the  lens  in  position,  and  is  relaxed  by  the  contraction  of  the  radial  fibres 
of  the  Ciliary  muscle,  so  that  the  lens  is  allowed  to  become  more  convex.   Behind 


1130 


THE    ORGANS    OF  SPECIAL   SENSE 


the  suspensory  ligament  there  is  a  sacculated  canal,  the  canal  of  Petit  (spaiia 
zonularia);  which  encircles  the  margin  of  the  lens  and  which  can  be  easily  inflated 
through  a  fine  blow-pipe  inserted  through  the  suspensory  ligament.  It  is  bounded 
in  front  by  the  anterior  layer  of  the  suspensory  ligament  of  the  lens,  behind  by  the 
hyaloidea  membrana,  and  internally  by  the  capsule  of  the  lens.  The  canal  of 
Petit  is  a  lymph-space.  All  the  spaces  of  the  canal  of  Petit  communicate  with  the 
posterior  chamber  of  the  eye. 

In  the  foetus,  the  centre  of  the  vitreous  humor  presents  the  hyaloid  canal  or 
canal  of  Stilling,  already  referred  to,  which  transmits  a  minute  artery,  the 
hyaloid  artery,  to  the  capsule  of  the  lens.  In  the  adult,  no  vessels  penetrate  its 
substance,  although  a  lymph  channel  remains ;  so  that  its  nutrition  must  be  car- 
ried on  by  the  vessels  of  the  retina  and  ciliary  processes,  situated  upon  its  exterior. 

III.  The  Crystalline  Lens  (Lens  Crystallina)  (Figs.716,723,740,741,742,743,744). 

The  crystalline  lens,  enclosed  in  its  capsule,  is  situated  immediately  behind  the 
pupil,  in  front  of  the  vitreous  body,  and  is  encircled  by  the  ciliary  processes,  which 
slightly  overlap  its  margin. 

The  capsule  of  the  lens  (capsula  lentis)  (Fig.  744)  is  a  transparent,  highly  elastic, 
and  brittle  membrane,  which  closely  surrounds  the  lens,  and  is  composed  in  part  of 


Fig.  740. — The  crystalline  lens,  hardened 
and  divided.    (Enlarged.) 


ANTERIOR 
SURFACE 


ANTERIOR 
POLE 


POSTERIOR 
SURFACE 


^POSTERIOR 
A        POLE 

AXIS  OF 
LENS 


Fig.  741. — The  term.s  used  in  the  orientation  of  the  lens.  (Toldt.) 


cuticular  and  in  part  of  connective  tissue.  It  is  not  white  fibrous  tissue,  and  is  not 
true  elastic  tissue  (Szymonowicz).  Its  outer  surface  is  composed  of  lamella  and 
possesses  transverse  striations.  It  rests,  behind,  in  the  fossa  patellaris  in  the  fore- 
part of  the  vitreous  body  (Fig.  739) ;  in  jront,  it  is  in  contact  with  the  free  border 
of  the  iris,  this  latter  receding  from  it  at  the  circumference,  thus  forming  the 
posterior  chamber  of  the  eye  (Fig.  744) ;  and  it  is  retained  in  its  position  chiefly  by 
the  suspensory  ligament  of  the  lens,  already  described  (Fig,  744).  The  capsule  is 
much  thicker  in  front  than  behind,  and  when  ruptured  the  edges  roll  up  with  the 
outer  surface  innermost,  like  the  elastic  lamina  of  the  cornea. 

The  substance  of  the  lens  {substantia  lentis)  is  an  epithelial  structure  and  takes 
origin  from  the  ectoderm.  It  consists  early  in  development  of  transparent 
cylindrical  cells,  which  at  a  later  period  become  higher  at  the  posterior  surface 
of  the  lens.  Eventually  very  long  cells  form;  they  are  known  as  lens-fibres  (fibrae 
lentis),  and  are  joined  by  a  cement  substance.  The  adult  lens  consists  of  lens- 
fibres,  the  anterior  surface  being  covered  by  one  layer  of  cubical  epithelial  cells, 
known  as  lens  epithelium  (epithelium  lentis).  This  layer  extends  to  the  margin  of 
the  lens,  at  which  point  the  cells  gain  in  height  and  form  lens-fibres.  The  lens- 
fibres  at  the  margin  are  nucleated,  the  others  are  not.  The  lens-fibres  run  as 
meridians  from  the  anterior  surface  backward.  There  is  no  epithelium  on  the 
posterior  surface. 


THE    CRYSTALLINE    LENS 


1131 


In  the  foetus,  a  small  branch  from  the  arteria  centralis  retinae  runs  forward, 
as  already  mentioned,  through  the  vitreous  humor  to  the  posterior  part  of  the 
capsule  of  the  lens,  where  its  branches  radiate  and  form  a  plexiform  network, 
which  covers  its  surface,  and  they  are  continuous  around  the  margin  of  the  capsule 
with  the  vessels  of  the  pupillary  membrane  and  with  those  of  the  iris.  In  the  adult 
no  vessels  enter  its  substance. 

Structure. — The  lens  is  a  transparent,  biconvex  body,  the  convexity  being  greater 
on  the  posterior  than  on  the  anterior  surface  (Fig.  741).    The  central  points  of  its 


CORONA 
CILIARIS 


ORBICULARIS 
CILIARIS 


Fig.  742. — The  zonule  of  Zinn  or  the  suspensory  ligament  of  the  lens  viewed  from  behind  in  connection 
with  the  lens  and  the  ciliary  body.     (Toldt.) 

anterior  and  posterior  surfaces  are  known  as  its  anterior  and  posterior  poles  (polus 
anterior  leniis  et  polus  posterior  lentis)  (Fig.  741).  It  measures  from  9  to  10  mm. 
in  the  transverse  diameter,  and  about  4  mm.  in  the  antero-posterior.  It  consists 
of  concentric  layers  (Fig.  740)  of  which  the  external  in  the  fresh  state  are  soft  and 
easily  detached  {substantia  corticalis)  (Fig.  744) ;  those  beneath  are  firmer,  the  cen- 
tral ones  forming  a  hardened  nucleus  (nucleus  lentis)  (Fig.  740),  These  laminae 
are  best  demonstrated  by  boiling  or  immersion  in  alcohol,  and  consist  of  minute 
parallel  fibres,  which  are  hexagonal  prisms,  the  edges  being  dentated,  and  the 


Fig.  743. — Diagram  to  show  the  direction  and  arrangement  of  the  radiating  lines  on  the  front  and  back  of 
the  foetal  lens.     A,  from  the  front;  B,  from  the  back. 


dentations  fitting  accurately  into  each  other;  their  breadth  is  about  g  ^q  q-  of  an 
inch.  Faint  lines  radiate  from  the  anterior  and  posterior  poles  to  the  circumference 
of  the  lens.  In  the  adult  there  may  be  six  or  more  of  these,  but  in  the  foetus  they  are 
only  three  in  number  and  diverge  from  each  other  at  angles  of  120°  (Fig.  743).  On 
the  anterior  surface  one  line  ascends  vertically  and  the  other  two  diverge  down- 
ward and  outward.  On  the  posterior  surface  one  ray  descends  vertically  and 
the  other  two  diverge  upward.  They  correspond  with  the  free  edges  of  an  equal 
number  of  septa  in  the  lens,  along  which  the  ends  of  the  lens-fibres  come  into 


1132 


THE    OBGANS   OF  SPECIAL    SENSE 


apposition  and  are  joined  together  by  transparent  amorphous  substance.  The 
fibres  run  in  a  curved  manner  from  the  septa  on  the  anteror  surface  to  those  on 
the  posterior  surface.  No  fibres  pass  from  pole  to  pole,  but  they  are  arranged 
in  such  a  way  that  fibres  which  commence  near  the  pole  on  the  one  aspect  of 
the  lens  terminate  near  the  peripheral  extremity  of  the  plane  on  the  other,  and 
vice  versa.  Each  fibre  of  the  outer  layers  of  the  lens  contains  a  nucleus,  and 
these  nuclei  form  a  layer,  the  nuclear  layer  on  the  surface  of  the  lens.  The  nuclear 
layer  is  most  distinct  toward  the  circumference  of  the  lens. 


INSERTION  OF 

TENDON  OF  SUPERIOR. 

RECTUS  MUSCLE 


PARS  OPTICA 
RETIN>E 
ORA  SERRATA 
PARS  CILIARIS  RETIN/E 


CONJUNCTIVA 
EPISCLERAL 
CONNECTIVE 
TISSU 
LIGAMENTUM 
PECTINATUM 
IRIDIS 
RIMA 
CORNEALIS! 

EDGE  OF 
CORNEA        m 

IRIS  (ante-   y| ' 
rior  surface) 


POSTERIOR 
SURFACE 
OF  CORNEA 
EPITHELIUM  — 
OF  CORNEA 
ANTERIOR- 
ELASTIC 
LAMINA 


EPITHELIUM  OF 
S  CAPSULE 
CAPSULE 
OF  LENS 


CORTICAL  SUB8TANCC 
OF  LENS 


NUCLEUS 
OF  LENS 


POSTERIOR  ELASTIC 
LAMINA 


STROMA   OF  IRIS 
SPHINCTER       PIGMENTARY 
OF  PUPIL      LAYERS  OF  IRIS 


Fig.  744. — The  upper  half  of  a  sagittal  section  through  the  front  of  the  eyeball.     (Toldt.) 


The  changes  'produced  in  the  lens  by  age  are  the  following: 

In  the  foetus  its  form  is  nearly  spherical,  its  color  of  a  slightly  reddish  tint,  it 
is  not  perfectly  transparent,  and  is  so  soft  as  to  break  down  readily  on  the  slightest 
pressure. 

In  the  adult  the  posterior  surface  is  more  convex  than  the  anterior;  it  is  color- 
less, transparent,  and  firm  in  texture. 

In  old  age  it  becomes  flattened  on  both  surfaces,  slightly  opaque,  of  an  amber 
tint,  and  increases  in  density. 

Arteries  of  the  Globe  of  the  Eye. — The  arteries  of  the  globe  of  the  eye  are  the  short 
posterior  ciliary,  long  posterior  ciliary,  and  anterior  ciliary  arteries,  and  the  arteria 
centralis  retinae. 


THE    CRYSTALLINE   LENS  1133 

The  short  posterior  ciliary  arteries  {aa.  ciliares  posterior es  breves)  (Figs.  721,  723, 
and  725)  are  from  eight  to  sixteen  in  number.  They  arise  from  the  ophthalmic 
branch  of  the  internal  carotid,  pass  through  the  sclerotic  coat  near  the  optic 
nerve,  and  are  distributed  to  the  choroid. 

There  are  two  long  posterior  ciliary  arteries  (aa.  ciliares  posteriores  longae)  (Figs. 
721,  723,  and  730) ,  one  on  each  side  of  the  optic  nerve.  They  are  branches  of  the 
ophthalmic.  They  pass  through  the  sclerotic  external  to  the  short  ciliary  arteries, 
and  extend  forward  in  the  choroid.  In  the  ciliary  body  they  form  an  anastomosis 
with  the  anterior  ciliary  arteries.  The  anastomosis  is  known  as  the  circulum  iridis 
major  (Figs.  723  and  744).  Branches  from  this  circle  pass  to  the  iris,  and  at  the 
periphery  of  the  sphincter  of  the  iris  form  the  circulum  iridis  minor.  The  muscular 
branches  and  the  lachrymal  branch  of  the  ophthalmic  give  off  the  anterior  ciliary 
arteries  {aa.  ciliares  anieriores) ,  six  or  eight  in  number.  They  pass  along  tendons 
of  the  muscles  of  the  eyeball,  reach  the  sclera,  and  pass  upon  the  sclera  to  the 
corneal  margin  (Fig.  730).  Branches  are  given  off  which  pass  backward  to  supply 
the  anterior  half  of  the  sclera,  and  which  are  known  as  episcleral  arteries  {aa. 
episclerales)  (Fig.  723).  Two  branches  are  given  off  which  pass  forward  to  the 
conjunctiva  bulbi,  which  are  known  as  the  anterior  conjunctival  arteries  {aa.  con- 
junctivales  anieriores),  which  anastomose  with  the  posterior  conjunctival  branches 
from  the  palpebral  arteries,  and  which  give  branches  to  the  delicate  vascular  net- 
work of  the  corneal  margin  which  is  in  the  annulus  conjunctivae  (Spalteholz). 
Eight  or  even  more  branches  form  the  anterior  ciliary  arteries.  They  pass  through 
the  sclerotic  near  the  sclero-corneal  junction,  and  participate  in  the  formation  of  the 
circulum  iridis  major. 

The  Veins  of  the  Globe  of  the  Eye  (Figs.  721,  722,  and  723).— The  veins  are  seen 
on  the  outer  surface  of  the  choroid.  They  have  a  whorl-like  formation  and  empty 
into  four  or  five  large  veins,  the  venae  vorticosae.  These  four,  five,  or  six  equidistant 
venae  vorticosae  pierce  the  sclerotic  midway  between  the  margin  of  the  cornea 
and  the  entrance  of  the  optic  nerve,  and  empty  into  the  ophthalmic  vein.  Another 
set  of  veins  accompany  the  anterior  ciliary  arteries,  and  are  known  as  the  anterior 
ciliary  veins  {vv.  ciliares  anieriores).  They  are  derivatives  of  the  venous  sinus  of 
the  sclera  in  the  canal  of  Schlemm.  They  form  a  circular  plexus.  They  receive 
vessels,  the  ciliary  muscle,  and  pass  through  the  sclera  close  to  the  corneal  margin. 
Posterior  ciliary  veins  {vv.  ciliares  posieriores)  receive  vessels  which  gather  venous 
blood  from  the  outer  surface  of  the  sclera  near  the  optic  nerve.  The  posterior 
ciliary  veins  join  anteriorly  with  the  venae  vorticosae.  After  emerging  from  the 
sclera  they  receive  anterior  conjunctival  branches,  and  by  means  of  episcleral 
veins  communicate  Avith  the  venae  vorticosae. 

The  Lymphatic  Passages  of  the  Eyeball. — The  conjunctiva  contains  lymph- 
vessels.     The  eyeball  contains  lymph-spaces,  but  no  lymph- vessels 

There  are  two  sets  of  lymph-spaces  in  the  eyeball,  the  anterior  and  posterior. 

The  anterior  lymph-spaces  are  the  spaces  of  the  cornea,  of  the  iris,  of  the 
anterior  chamber,  and  of  the  posterior  chamber. 

The  lymph  from  the  intralamellar  lymph-spaces  of  the  cornea  enters  the  con- 
junctival lymphatics  at  the  margin  of  the  cornea. 

The  lymph-spaces  of  the  iris  open  into  the  anterior  chamber  by  the  crypts  of 
the  iris  and  at  the  margin  of  the  iris  join  the  spaces  of  Fontana. 

The  aqueous  humor  fills  the  anterior  and  posterior  chambers,  but  is  furnished 
by  the  vessels  in  the  posterior  chamber;  in  part  by  the  vessels  of  the  ciliary  body, 
and  in  part  by  the  vessels  of  the  posterior  surface  of  the  iris.  The  lymph  thus 
secreted  passes  by  way  of  the  pupil  into  the  anterior  chamber,  and  then  is  taken 
up  by  the  spaces  of  Fontana,  the  canal  of  Schlemm,  and  the  anterior  ciliary  veins .^ 

'  Deaver's  Anatomy. 


1134  THE    ORGANS   OF  SPECIAL  SENSE 

The  posterior  lymph -spaces  are  the  hyaloid  canal,  the  perichoroidal  lymph- 
space,  the  space  of  Tenon,  the  intervaginal  space  of  the  optic  nerve,  and  the  supra- 
vaginal space  (Deaver). 

The  hyaloid  canal  (Figs.  712  and  715)  passes  between  the  posterior  surface  of 
the  lens  and  the  optic  disk.  In  the  embryo  the  canal  holds  an  artery,  the  hyaloid 
artery.  During  development  the  artery  disappears,  but  a  lymph  channel  remains. 
The  hyaloid  canal  opens  into  the  intervaginal  space  of  the  optic  nerve.  Between 
the  sclerotic  and  the  choroid  is  the  perichoroidal  lymph-space  (Fig.  744).  It  is 
around  the  choroid  vessels  and  the  venae  vorticosae,  and  empties  into  Tenon's 
space  by  means  of  openings  through  the  sclera  about  the  venae  vorticosae. 

Tenon's  space  (Figs.  712  and  713)  is  between  the  sclera  and  the  capsule  of  Tenon. 
It  receives  lymph  from  the  perichoroidal  space,  and  empties  into  the  supra- 
vaginal space. 

The  optic  nerve  (Fig.  731)  has  a  sheath  of  dura  and  a  sheath  of  pia,  and 
between  these  sheaths  is  the  intervaginal  lymph-space.  It  is  divided  by  a  pro- 
longation of  the  cerebral  arachnoid  into  a  subdm:al  space  and  a  subarachnoid 
space,  which  empty  into  the  corresponding  spaces  of  the  membranes  of  the  brain. 

The  supravaginal  space  is  between  the  dural  portion  of  the  sheath  of  the  optic 
nerve  and  a  posterior  prolongation  of  Tenon's  capsule.^ 

The  Nerves  of  the  Globe  of  the  Eye. — ^The  long  ciliary  nerves  (nn.  ciliaris  longi), 
two  in  number,  are  derived  from  the  nasal  branch  of  the  ophthalmic  and  the 
short  ciliary  nerves  {nn.  ciliares  breves) ,  twelve  to  fifteen  in  number,  are  derived 
from  the  ciliary  or  ophthalmic  ganglion.  Both  the  long  and  short  ciliary  nerves 
perforate  the  sclera  in  the  neighborhood  of  the  optic  nerve  (Fig.  721).  They  pass 
along  the  perichoroidal  lymph-space,  forming  a  plexus,  and  send  filaments  to  the 
choroid  vessels.  In  front  of  the  Ciliary  muscle  they  form  a  second  plexus,  and 
from  it  come  branches  which  go  to  the  Ciliary  muscle  and  the  muscular  fibres  and 
vessels  of  the  iris,  sclera,  choroid,  ciliary  body,  and  iris  (Fig.  729).  The  ciliary 
nerves  supply  the  cornea.  The  circular  fibres  of  the  iris  are  innervated  by  the 
third  nerve  and  the  radiating  fibres  by  the  sjonpathetic. 

Surgical  Anatomy. — From  a  surgical  point  of  view  the  cornea  may  be  regarded  as  consist- 
ing of  three  layers:  (1)  of  an  external  epithelial  layer,  developed  from  the  epiblast,  and  continu- 
ous with  the  external  epithelial  covering  of  the  rest  of  the  body,  and  therefore  in  its  lesions  resem- 
bling those  of  the  epidermis ;  (2)  of  the  cornea  proper,  derived  from  the  mesoblast,  and  associated 
in  its  diseases  with  the  fibro- vascular  structures  of  the  body;  and  (3)  the  posterior  elastic  layer 
with  its  endothelium,  also  derived  from  the  mesoblast  and  having  the  characters  of  a  serous 
membrane,  so  that  inflammation  of  it  resembles  inflammation  of  the  other  serous  and  synovial 
membranes  of  the  body. 

The  cornea  contains  no  blood-vessels,  except  at  its  periphery,  where  numerous  delicate  loops, 
derived  from  the  anterior  ciliary  arteries,  may  be  demonstrated  on  the  anterior  surface  of  the 
cornea.  The  rest  of  the  cornea  is  nourished  by  lymph,  which  gains  access  to  the  proper  sub- 
stance of  the  cornea  and  the  posterior  layer  through  the  spaces  of  Fontana.  This  lack  of  a  direct 
blood-supply  renders  the  cornea  very  apt  to  inflame  in  the  cachectic  and  ill-nourished.  In  spite 
of  the  absence  of  blood-vessels,  wounds  of  the  cornea  usually  heal  rapidly.  A  wound  which  pene- 
trates the  cornea  opens  the  anterior  chamber,  and  aqueous  humor  escapes.  An  ulcer  may  also 
open  the  anterior  chamber.  Through  a  wound  or  a  perforated  ulcer  the  pupillary  margin  of  the 
iris  may  prolapse.  A  trivial  injury  of  the  cornea  is  repaired  by  transparent  tissue.  A  severe 
injury  is  repaired  by  fibrous  tissue,  and  opacity  results.  A  slight  opacity  resembling  a  cloud  of 
gray  smoke  is  called  nebula;  a  more  marked  white  opacity  is  called  leucoma. 

In  abscess  of  the  cornea  pus  gravitates  between  the  layers  to  the  lower  part  of  the  cornea  and 
the  purulent  collection  assumes  a  crescentic  shape  (onyx). 

The  arcus  senilis,  seen  in  the  aged,  is  a  condition  of  haziness  or  opacity  at  the  corneal  margin 
due  to  fatty  degeneration  of  the  tissue  of  the  cornea.  It  signifies  interference  with  the  blood- 
supply,  because  of  senile  degeneration  of  adjacent  vessels.  In  cases  of  granular  lids  there  is  a 
pecuHar  affection  of  the  cornea,  called  pannus,  in  which  the  anterior  layers  of  the  cornea  become 
vascularized,  and  a  rich  network  of  blood-vessels  may  be  seen  on  the  cornea;  and  in  interstitial 
keratitis  new  vessels  extend  into  the  cornea,  giving  it  a  pinkish  hue,  to  which  the  term  salmon 
patch  is  applied.    The  cornea  is  richly  supplied  with  nerves,  derived  from  the  ciliary  nerves,  which 

1  For  the  lymphatic  channels  of  the  eyeball  see  Deaver's  Surgical  Anatomy,  vol.  ii.  p.  392. 


THE    CRYSTALLINE   LENS  1135 

enter  the  cornea  through  the  forepart  of  the  sclerotic  and  form  plexuses  in  the  stroma,  terminating 
between  the  epithelial  cells  by  free  ends  or  in  corpuscles.  In  cases  of  glaucoma  the  ciliary  nerves 
may  be  pressed  upon  as  they  course  between  the  choroid  and  sclerotic  (Fig.  719),  and  in  conse- 
quence of  the  [pressure  upon  them,  the  cornea,  to  which  they  are  distributed,  becomes  anaes- 
thetic. When  a  scar  forms  on  the  cornea  and  the  iris  becomes  adherent,  the  scar  and  the  iris, 
and  sometimes  even  the  lens,  may  bulge  forward  from  intraocular  tension.  This  condition 
is  staphyloma  of  the  cornea.  In  conditions  of  impaired  nutrition  the  cornea  may  be  bulged  for- 
ward by  intraocular  pressure.  The  line  of  least  resistance  is  a  little  below  the  centre  of  the 
cornea,  and  it  is  bulged  forward  and  strongly  curved.  This  condition  is  known  as  conical  cornea. 
The  sclerotic  has  very  few  blood-vessels  and  nerves.  The  blood-vessels  are  derived  from  the 
anterior  ciliary,  and  form  an  open  plexus  in  its  substance.  As  they  approach  the  corneal  margin 
this  arrangement  is  peculiar.  Some  branches  pass  through  the  sclerotic  to  the  ciliary  body;  others 
become  superficial  and  lie  in  the  episcleral  tissue,  and  form  arches,  by  anastomosing  with  each 
other,  some  little  distance  behind  the  corneal  margin.  From  these  arches  numerous  straight 
vessels  are  given  off,  which  run  forward  to  the  cornea,  forming  its  marginal  plexus.  In  inflamma- 
tion of  the  sclerotic  and  episcleral  tissue  these  vessels  become  conspicuous,  and  form  a  pinkish 
zone  of  straight  vessels  radiating  from  the  corneal  margin,  commonly  known  as  the  zone  of  ciliary 
injection.  In  inflammation  of  the  iris  and  ciliary  body  this  zone  is  present,  since  the  sclerotic 
speedily  becomes  involved  when  these  structures  are  inflamed.  But  in  inflammation  of 'the  cornea 
the  sclerotic  is  seldom  much  affected,  though  the  cornea  and  sclerotic  are  structurally  continuous. 
This  would  appear  to  be  due  to  the  fact  that  the  nutrition  of  the  cornea  is  derived  from  a  different 
source  from  that  of  the  sclerotic.  The  sclerotic  may  be  ruptured  subcutaneously  without  any 
laceration  of  the  conjunctiva,  and  the  rupture  usually  occurs  near  the  corneal  margin,  where 
the  tunic  is  thinnest.  It  may  be  complicated  with  lesions  of  adjacent  parts — laceration  of  the 
choroid,  retina,  iris,  or  suspensory  ligament  of  the  lens — and  is  then  often  attended  with  hemor- 
rhage into  the  anterior  chamber,  which  masks  the  nature  of  the  injury.  In  some  cases  the  lens 
has  escaped  through  the  rent  in  the  sclerotic,  and  has  been  found  under  the  conjunctiva.  Wounds 
of  the  sclerotic,  if  they  do  not  perforate,  usually  heal  readily.  If  they  extend  through  the  sclerotic 
they  cause  diminished  tension,  are  always  dangerous,  and  are  often  followed  by  inflammation, 
suppuration,  and  by  sympathetic  ophthalmia.  The  sclerotic  may  be  weakened  by  injury,  inflam- 
mation, etc.,  and  the  weakened  portion  may  bulge  from  intraocular  pressure,  and  even  a  healthy 
sclera  may  bulge  from  excessive  intraocular  pressure.  According  to  its  situation  the  lesion  is 
known  as  ciliary  staphyloma,  equatorial  staphyloma,  or  posterior  staphyloma. 

One  of  the  functions  of  the  choroid  is  to  provide  nutrition  for  the  retina  and  to  convey  ves- 
sels and  nerves  to  the  ciliary  body  and  iris.  Inflammation  of  the  choroid  is  therefore  followed 
by  grave  disturbance  in  the  nutrition  of  the  retina,  and  is  attended  with  early  interference  with 
vision.  Purulent  choroiditis  is  not  confined  to  the  choroid;  the  retina,  the  vitreous,  and  the  entire 
uveal  tract  become  involved,  and  even  other  structures  may  suffer.  In  its  diseases  it  bears  a  con- 
siderable analogy  to  those  which  affect  the  skin,  and,  like  it,  is  one  of  the  places  from  which 
melanotic  sarcomata  may  grow.  These  tumors  contain  a  large  amount  of  pigment  in  their  cells, 
and  grow  only  from  those  parts  where  pigment  is  naturally  present.  The  choroid  may  be  ruptured 
without  injury  to  the  other  tunics,  as  well  as  participating  in  general  injuries  of  the  eyeball.  In 
cases  of  uncomplicated  rupture  the  injury  is  usually  at  its  posterior  part,  and  is  the  result  of  a 
blow  on  the  front  of  the  eye.  It  is  attended  by  considerable  hemorrhage,  which  for  a  time  may 
obscure  vision,  but  in  most  cases  this  is  restored  as  soon  as  the  blood  is  absorbed. 

The  iris  is  the  seat  of  a  malformation,  termed  coloboma,  which  consists  in  a  deficiency  or 
cleft,  which  in  a  great  number  of  cases  is  clearly  due  to  an  arrest  in  development.  In  these  cases 
it  is  found  at  the  lower  aspect,  extending  directly  downward  from  the  pupil,  and  the  gap  fre- 
quently extends  through  the  choroid  to  the  entrance  of  the  optic  nerve.  In  some  rarer  cases  the 
gap  is  found  in  other  parts  of  the  iris,  and  is  then  not  associated  with  any  deficiency  of  the  choroid. 
The  iris  is  abundantly  supplied  with  blood-vessels  and  nerves,  and  is  therefore  very  prone  to 
become  inflamed.  And  when  inflamed,  in  consequence  of  the  fact  that  the  iris  and  ciliary  body  are 
continuous,  and  that  their  vessels  communicate,  iritis  is  usually  associated  with  cyclitis,  the  dis- 
ease being  called  irido-cyclitis.  And,  in  addition,  inflammation  of  adjacent  structures,  the  cornea 
and  sclerotic,  is  apt  to  spread  into  the  iris.  The  iris  is  covered  with  endothelium,  and  partakes  of 
the  character  of  a  serous  membrane,  and,  like  these  structures,  is  liable  to  pour  out  a  plastic  exuda- 
tion when  inflamed,  and  contract  adhesions,  either  to  the  cornea  in  front  (synechia  anterior),  or 
to  the  capsule  of  the  lens  behind  (synechia  posterior).  In  iritis  the  lens  may  become  involved, 
and  the  condition  known  as  secondary  cataract  may  be  set  up.  Tumors  occasionally  commence  in 
the  iris;  of  these,  cysts,  which  are  usually  congenital  and  sarcomatous  tumors,  are  the  most  common 
and  require  removal.  Gummata  are  not  unfrequently  found  in  this  situation.  In  some  forms 
of  injury  of  the  eyeball,  as  the  impact  of  a  spent  shot,  the  rebound  of  a  twig,  or  a  blow  with  a 
whip,  the  iris  may  be  detached  from  the  Ciliary  muscle,  the  amount  of  detachment  varying  from 
the  slightest  degree  to  the  separation  of  the  whole  iris  from  its  ciliary  connection. 

The  Argyll-Robertson  pupil  shows  no  reaction  to  light,  but  retains  reaction  to  accommodation 
and  vision  remains  good. 


1136 


THE    ORGANS   OF  SPECIAL   SENSE 


The  retina,  with  the  exception  of  its  pigment-layer  and  its  vessels,  is  perfectly  transparent, 
and  is  invisible  when  examined  by  the  ophthalmoscope,  so  that  its  diseased  conditions  are 
recognized  by  its  loss  of  transparency.  In  retinitis,  for  instance,  there  is  more  or  less  dense  and 
extensive  opacity  of  its  structure,  and  not  unfrequently  extravasations  of  blood  into  its  sub- 
stance. Hemorrhages  may  also  take  place  into  the  retina  from  rupture  of  a  blood-vessel  without 
inflammation. 

In  o-ptic  neuritis,  pajnllitis,  or  choked  disk,  the  ophthalmoscope  shows  increase  in  vascularity, 
and  swelling  and  opacity  of  the  nerve,  which  extend  beyond  the  disk  margins.  Optic  atrophy 
is  apt  to  follow.     (Fig.  745  shows  a  normal  optic  disk.) 

The  retina  may  become  displaced  from  effusion  of  serum  between  it  and  the  choroid  or  by 
blows  on  the  eyeball,  or  may  occur  without  apparent  cause  in  progressive  myopia,  and  in  this 
case  the  ophthalmoscope  shows  an  opaque,  tremulous  cloud.  Glioma,  a  form  of  sarcoma,  and 
essentially  a  disease  of  early  life,  is  occasionally  met  with  in  connection  with  the  retina. 

The  lens  has  no  blood-vessels,  nerves,  or  connective  tissue  in  its  structure,  and  therefore  is 
not  subject  to  those  morbid  changes  to  which  tissues  containing  these  structures  are  liable.  It 
does,  however,  present  certain  morbid  or  abnormal  conditions  of  various  kinds.  Thus,  variations 
in  shape,  absence  of  the  whole  or  a  part  of  the  lens,  and  displacements  are  amongst  its  congenital 
dejects.  Opacities  may  occur  from  injury,  senile  changes,  malnutrition,  or  errors  in  growth  or 
development.  An  opacity  of  the  capsule,  of  the  lens,  or  of  both,  is  known  as  a  cataract.  Senile 
changes  may  take  place  in  the  lens,  impairing  its  elasticity  and  rendering  it  harder  than  in  youth. 


Fig.  745. — Ophthalmoscopic  appearances  of  healthy 
fundus  in  a  person  of  very  fair  complexion.  Scleral 
ring  well  marked.  Left  eye,  inverted  image.  (Wecker 
and  Jaeger.) 


Fig.  746. — Ophthalmoscopic  appearance  of  severe 
recent  papillitis.  Several  elongated  patches  of  blood 
near  border  of  disk.     (After  Hughlings  Jackson.) 


so  that  its  curvature  can  only  be  altered  to  a  limited  extent  by  the  Ciliary  muscle.  And,  finally, 
the  lens  may  be  dislocated  or  displaced  by  blows  upon  the  eyeball,  and  its  relations  to  surround- 
ing structures  altered  by  adhesions  or  the  pressure  of  new  growths. 

There  are  two  particular  regions  of  the  eye  which  require  special  notice :  one  of  these  is  known 
as  the  "  filtration  area,"  and  the  other  as  the  "  dangerous  area."  The  filtration  area  is  the  circum- 
corneal  zone  immediately  in  front  of  the  iris.  Here  are  situated  the  cavernous  spaces  of 
Fontana,  which  communicate  with  the  canal  of  Schlemm,  through  which  the  chief  transudation 
of  fluid  from  the  eye  is  now  believed  to  take  place.  The  dangerous  area  of  the  eye  is  the  region 
in  the  neighborhood  of  the  ciliary  body,  and  wounds  or  injuries  in  this  situation  are  peculiarly 
dangerous;  for  inflammation  of  the  ciliary  body  is  liable  to  spread  to  many  of  the  other  structures 
of  the  eye,  especially  to  the  iris  and  choroid,  which  are  intimately  connected  by  nervous  and 
vascular  supplies.  Moreover,  wounds  which  involve  the  ciliary  region  are  especially  liable  to  be 
followed  by  sympathetic  ophthalmia,  in  which  destructive  inflammation  of  one  eye  is  excited  by 
some  irritation  in  the  other. 

Emmetropia  is  normal  vision.  In  normal  vision  the  practically  parallel  light  rays  from  distant 
objects  focus  on  the  retina  without  effort;  divergent  rays  from  near  objects  are  focused  on  the 
retina  by  an  effort  of  accommodation. 

Hyperopia  or  hypermetropia  is  far-sightedness.  In  this  condition  the  retina  is  in  front  of  the 
principal  focus  when  the  eye  is  at  rest.  The  patient  endeavors  to  correct  the  failure  by  constant 
and  tiresome  efforts  at  accommodation.  The  condition  is  usually  due  to  inordinate  shortness  of 
the  axis  of  the  eye,  but  may  be  due  to  loss  of  the  lens,  decreased  convexity  of  the  refractive  sur- 
faces, or  lessened  refractive  power  in  the  refractive  media  of  the  eye.  It  is  corrected  by  the  use 
of  convex  glasses. 


THE   EYELID  II37 

Myopia  is  near-sightedness.  In  this  condition  the  rays  of  light  come  to  a  focus  in  front  of  the 
retina,  and  the  patient  is  subjected  to  continued  eye-strain.  It  is  usually  due  to  too  great  length 
of  the  axis  of  the  eye,  but  may  result  from  increase  in  refractive  power  of  refractive  media.  It  is 
corrected  by  concave  glasses.  Sometimes,  as  a  person  with  hyperopia  begins  to  age,  an  increased 
refractive  power  of  the  lens  causes  myopia.  The  occurrence  of  myopia  in  a  hyperopic  eye  is 
called  second  sight,  and  it  enables  the  individual  to  cease  wearing  convex  glasses. 

Exenteration  of  the  contents  of  the  orbit  means  removal  of  all  the  contents  except  those  at  the 
orbital  apex.    Even  the  periosteum  is  taken  away.    It  is  performed  for  malignant  disease. 

Evisceration  of  the  eyeball  is  performed  by  making  a  circular  incision  at  the  corneal  margin  and 
removing  the  internal  and  middle  coats  and  the  contents  of  the  globe.  The  sclera  is  not  removed. 
A  glass  ball  is  inserted  into  the  scleral  sheath,  and  the  sclera  is  closed  over  the  ball  by  vertical 
stitches,  and  the  conjunctiva  is  closed  over  it  by  transverse  stitches.  The  operation  is  performed 
for  leucoma  or  staphyloma  of  the  cornea.  An  artificial  eye  (a  shell)  is  placed  over  the  stump 
when  healing  is  complete. 

Enucleation,  or  excision  of  the  eyeball,  differs  from  exenteration  of  the  orbital  contents  in  the 
fact  that  only  the  eyeball  is  removed.  A  circular  incision  through  the  ocular  conjunctiva 
is  carried  around  and  near  to  the  corneal  margin.  The  conjunctiva  and  capsule  of  T^non  are 
pushed  back  and  the  Rectus  muscles  are  clamped  and  divided  back  of  the  clamp.  Traction 
is  made  upon  the  glol)e  in  a  forward  and  inward  direction,  and  the  optic  nerve  and  adjacent 
structures  are  cut  with  scissors  from  the  outer  aspect  of  the  globe.  The  eye  is  then  pulled  out  of 
the  orbit,  antl  all  structures  which  tend  to  retain  it  are  divided.  The  stumps  of  the  Recti  muscles 
are  sewed  together. 

THE  APPENDAGES  OF  THE  EYE  (TUTAMINA  OOULI). 

The  appendages  of  the  eye  include  the  eyebrows,  the  eyelids,  the  conjunctiva, 
and  the  lachrymal  apparatus — viz.,  the  lachrymal  gland,  the  lachrymal  sac,  and  the 
nasal  duct. 

The  Eyebrow  (Supercilium) . 

The  eyebrows  are  two  arched  eminences  of  integument  which  surmount  the 
upper  circumference  of  the  orbit  on  each  side,  and  support  numerous  short,  thick 
hairs,  directed  obhquely  on  the  surface.  The  hairs  may  entangle  foreign  bodies 
and  lessen  somewhat  the  force  of  blows.  In  structure  the  eyebrows  consist  of 
thickened  integument,  connected  beneath  with  the  Orbicularis  palpebrarum, 
Corrugator  supercilii,  and  Occipito-frontalis  muscles.  These  muscles  serve,  by 
their  action  on  this  part,  to  control  to  a  certain  extent  the  amount  of  light 
admitted  into  the  eye. 

The  Eyelid  (Palpebra)  (Figs.  747,  748). 

The  eyelids  are  two  thin,  movable  folds  placed  in  front  of  the  eye,  and  by  closure 
protecting  the  eye  from  injury.  The  eyelids  are  composed  of  skin,  superficial 
fascia,  and  alveolar  tissue,  fibres  of  the  Orbicularis  palpebrarum  muscle,  palpebral 
and  orbito-tarsal  ligaments,  tarsal  cartilages,  and  conjunctiva.  The  upper  lid 
also  contains  the  Levator  labii  superioris  muscle.  In  the  lids  are  blood-vessels, 
lym])h-vessels,  nerves,  and  Meibomian  glands.  There  are  two  lids,  the  upper 
(palpebra  superior)  and  the  lower  (palpebra  inferior).  The  upper  lid  is  the  larger 
and  the  more  movable  of  the  two,  and  is  furnished  with  a  separate  elevator 
muscle,  the  Levator  palpebrae  superioris.  Each  lid  consists  of  two  portions.  The 
part  near  the  orbital  margin,  "whose  groundwork  is  formed  merely  by  the  thin 
palpebral  fascia  (septum  orhitale),"^  is  called  the  orbital  portion  (pars  orbitalis). 
The  part  in  which  the  tarsus  lies  is  called  the  tarsal  portion  (pars  tarsalis) .  Between 
the  two  portions  in  each  lid  is  a  sulcus,  called,  in  the  upper  lid,  the  superior  orbito- 
palpebral  sulcus  (sulcus  orbitopalpehralis  superior),  and,  in  the  lower  lid,  the  inferior 
orbito -palpebral  sulcus  (sulcus  orbitopalpebralis  inferior).     When  the  eyelids  are 

•  An  Atlas  of  Human  Anatomy.    By  Carl  Toldt,  assisted  by  A.  D.  Rosa.     Translated  by  M.  Eden  Paul. 

72 


1138 


THE    ORGANS    OF  SPECIAL   SENSE 


opened  an  elliptical  space,  the  interpalpebral  slit  {jissura  palpebrarum),  is  left 
between  their  margins,  the  angles  of  which  correspond  to  the  junction  of  the  upper 
and  lower  lids,  and  are  called  canthi. 

The  Canthi. — The  outer  canthus  {angulus  oculi  lateralis)  is  more  acute  than  the 
inner,  and  the  lids  here  lie  in  close  contact  with  the  globe;  but  the  inner  canthus 
(angulus  oculi  medialis)  is  prolonged  for  a  short  distance  inward  toward  the  nose. 
The  two  lids  are  separated  at  the  inner  canthus  by  a  triangular  space,  the  lacus 
lacrimalis.  At  the  commencement  of  the  lacus  lacrimalis,  on  the  margin  of  each 
eyelid,  is  a  small  conical  elevation,  the  lachrymal  papilla,  the  apex  of  which  is 
pierced  by  a  small  orifice,  the  punctum  lacrimale  (Fig.  751),  the  commencement  of 
the  lachrymal  canal  (Fig.  750) .  When  the  lids  are  closed  a  space  remains  between 
them  and  the  globe  to  permit  of  the  flow  of  tears  inward  (rivus  lacrimalis). 

The  Eyelashes  (cilia)  (Fig.  748). — The  eyelashes  are  attached  to  the  free  edges  of 
the  eyelids;  they  are  short,  thick,  curved  hairs,  arranged  in  a  double  or  triple  row 
at  the  margin  of  the  lids;  those  of  the  upper  lid,  more  numerous  and  longer  than 
the  lower,  curve  upward;  those  of  the  lower  lid  curve  downward.  Because  of  this 
arrangement  the  two  sets  do  not  interlace  in  closing  the  lids.  Near  the  attachment 
of  the  eyelashes  are  the  openings  of  sebaceous  glands  {glandulae  sebaceae)  (Fig.  748) 
and  of  a  number  of  glands,  glands  of  Moll  {glandulae  ciliares  [Molli])  (Fig.  748), 
arranged  in  several  rows  close  to  the  free  margin  of  the  lid.  They  are  regarded  as 
enlarged  and  modified  sweat-glands.  On  the  inner  surface  are  the  Meibomian 
glands  (glandulae  tarsales  \_Meibomi\)  (Fig.  750).  Internal  to  the  openings  of  the 
lachrymal  canaliculi  there  are  neither  lashes  nor  Meibomian  glands. 


LACHRYMAL  ARTERY. 
AND  NERVE 


EXTERNAL  LATERALr 
LIGAMENT 


i SUPRAORBITAL  VES- 
SELS AND  NERVE 


LACHRYMAL  SAC 

NTERNAL  LATE- 
RAL LIGAMENT 


Fig,  747. — The  tarsi  and  their  ligaments.     Right  eye,  front  view.     (Testut.) 


Structure  of  the  Eyelids  (Fig.  748) . — The  eyelids  are  composed  of  the  following 
structures,  taken  in  their  order  from  without  inward: 

Integument,  areolar  tissue,  fibres  of  the  Orbicularis  muscle,  tarsal  plate,  and 
its  ligament.  Meibomian  glands,  and  conjunctiva.  The  upper  lid  has,  in  addition, 
the  aponeurosis  of  the  Levator  palpebrse. 

The  integument  is  extremely  thin,  and  continuous  at  the  margin  of  the  lids  with 
the  conjunctiva. 

The  subcutaneous  areolar  tissue  is  very  lax  and  delicate,  seldom  contains  any 
fat,  and  is  extremely  liable  to  serous  infiltration. 

The  fibres  of  the  Orbicularis  muscle,  where  they  cover  the  palpebrae  (m.  ciliaris 
[Riolani]),  are  thin,  pale  in  color,  and  possess  an  involuntary  action. 


THE  EYELID 


1139 


The  tarsal  plates  are  two  thin  elongated  plates  of  dense  connective  tissue  about 
an  inch  in  length.  They  are  placed  one  in  each  lid,  contributing  to  their  form 
and  support. 

The  superior  tarsal  plate,  superior  tarsus  or  superior  tarsal  body  {tarsus  superior) 
(Fig.  747) ,  the  larger,  is  of  a  semilunar  form,  about  one-third  of  an  inch  in 
breadth  at  the  centre,  and  becoming  gradually  narrowed  at  each  extremity.  To 
the  anterior  surface  of  this  plate  the  aponeurosis  of  the  Levator  palpebrae  is 
attached. 

The  inferior  tarsal  plate,  inferior  tarsus  or  inferior  tarsal  body  (tarsus  inferior) 
(Fig.  747),  the  smaller  of  the  two,  is  thinner  and  of  an  elliptical  form. 

The  free  or  ciliary  margin  of  these  plates  is  thick,  and  presents  a  perfectly 
straight  edge.  The  attached  or  orbital  margin  is  connected  to  the  circumference  of 
the  orbit  by  the  fibrous  membrane  of  the 
lids,  with  which  it  is  continuous.  The 
outer  angle  of  each  plate  is  attached  to 
the  malar  bone  by  the  external  tarsal  or 
external  lateral  ligament,  or  the  external 
palpebral  ligament  or  raph^  (ligamentum 
pilpe'ralis  lateralis) (Fig.  747).  The  inner 
angles  of  the  two  plates  terminate  at  the 
commencement  of  the  lacus  lacrimalis; 
they  are  attached  to  the  nasal  process 
of  the  superior  maxilla  by  the  internal 
tarsal  or  internal  lateral  or  internal  palpe- 
bral ligament  or  the  tendo  oculi  (ligamen- 
tum palpebrals  mediale)  (Fig.  747). 

The  fibrous  membrane  of  the  lids  con- 
stitutes the  orbito-tarsal  ligaments  or  the 
palpebral  fasciae.  In  reality  these  so-called 
ligaments  are  fascial  expansions  situated 
one  in  each  lid,  and  are  attached  margin- 
ally to  the  edge  of  the  orbit,  where  they 
are  continuous  with  the  periosteum.  The 
superior  ligament  blends  with  the  tendon 
of  the  Levator  palpebrae,  the  inferior  with 
the  inferior  tarsal  plate.  Externally  the 
superior  and  inferior  ligaments  fuse  to 
form  the  external  tarsal  ligament  or  raph6 
just  referred  to ;  internally  they  are  much 
thinner,  and,  becoming  separated  from 
the  internal  tarsal  ligament,  are  fixed  to 
the  lachrymal  bone  immediately  behind 
the  lachrymal  sac.  Together  the  liga- 
ments  form    an    incomplete     septum,    the        Fig.  748. — Vertical  section  through  the  upper  eye- 

,  ..    ,  ^  ,         ,  7  •,    7  \         1  •    1      •      lid.    a.  Skin.    b.  Orbicularis  palpebrarum.     6'.  Mar- 

Orbltal   septum   (septum    Orbltale),  which    is    ginal  fasciculus  of   orbicularis  (ciliary   bundle).     C. 

J!,      11.1  1  1  I'l      Levator  palpebrae.    d.  Conjunctiva,  e.  Tarsal  plate. 

perforated  by  the  vessels  and  nerves  which  /.  Meibomian  gland,  g.  Sebaceous  gland,  h.  Eye- 
pass  from  the  orbital  cavity  to  the  face  'K^!irior\!A^.^ir\M^^^  '' 
and  scalp. 

The  Meibomian  or  Tarsal  Glands  (glandulae  tarsales  [Meibomi])  (Figs.  748  and 
750). — The  Meibomian  or  tarsal  glands  are  situated  upon  the  inner  surface  of  the 
eyelids  between  the  tarsal  plates  and  conjunctiva,  and  may  be  distinctly  seen 
through  the  mucous  membrane  on  everting  the  eyelids,  presenting  the  appearance 
of  parallel  strings  of  pearls.  They  are  about  thirty  in  number  in  the  upper  eyelid, 
and  somewhat  fewer  in  the  lower.     They  are  embedded  in  grooves  in  the  inner 


1140  THE    ORGANS   OF  SPECIAL   SENSE 

surface  of  the  tarsal  plates,  and  correspond  in  length  with  the  breadth  of  each  plate; 
they  are,  consequently,  longer  in  the  upper  than  in  the  lower  eyelid.  Their  ducts 
open  on  the  free  margin  of  the  lids  by  minute  foramina,  which  correspond  in  num- 
ber to  the  follicles.  The  use  of  their  secretion  is  to  prevent  adhesions  of  the  lids. 
Structure  of  the  Meibomian  Glands. — These  glands  are  a  variety  of  the  cutaneous 
sebaceous  glands,  each  consisting  of  a  single  straight  tube  or  follicle,  having  a 
csecal  termination,  and  with  numerous  small  secondary  follicles  opening  into  it. 
The  tubes  consist  of  basement-membrane,  lined  at  the  mouths  of  the  tubes  by 
stratified  epithelium;  the  deeper  parts  of  the  tubes  and  the  secondary  follicles  are 
lined  by  a  layer  of  polyhedral  cells.  They  are  thus  identical  in  structure  with  the 
sebaceous  glands. 

The  Conjunctiva  (Figs.  714,  715,  727,  749). 

The  conjunctiva  is  the  mucous  membrane  of  the  eye.  It  lines  the  inner  surface 
of  the  eyelids,  is  reflected  over  the  forepart  of  the  sclerotic  and  cornea,  and  joins 
the  lids  to  the  eyeball.  In  each  of  these  situations  its  structure  presents  some 
peculiarities. 

The  Palpebral  Portion  {tunica  conjunctiva  palpebrarum)  (Fig.  750) . — The  palpe- 
bral portion  of  the  conjunctiva  lines  the  posterior  surface  of  the  lids.  It  is  thick, 
opaque,  highly  vascular,  and  covered  with  numerous  papillae,  its  deeper  parts 
presenting  a  considerable  amount  of  lymphoid  tissue.  At  the  margin  of  the  lids 
it  becomes  continuous  with  the  lining  membrane  of  the  ducts  of  the  Meibomian 
glands,  and,  through  the  lachrymal  canals,  with  the  lining  membrane  of  the 
lachrymal  sac  and  nasal  duct.  At  the  outer  angle  of  the  upper  lid  the  lachrymal 
ducts  open  on  its  free  surface;  and  at  the  inner  angle  of  the  eye  it  forms  a  semi- 
lunar fold,  the  plica  semilunaris  {plica  semilunaris  conjunctivae)  (Fig.  751).  The 
folds  formed  by  the  reflection  of  the  conjunctiva  from  the  lids  on  to  the  eye  are 
called  the  superior  and  inferior  palpebral  folds,  the  former  being  the  deeper  of  the 
two.     These  folds  form  the  superior  and  inferior  conjunctival  fornix  (Fig.  749). 

The  Bulbar  Portion  {tunica  conjunctiva  hulhi). — Upon  the  sclerotic  the  conjunc- 
tiva is  loosely  connected  to  the  globe;  it  becomes  thinner,  loses  its  papillary  struc- 
ture, is  transparent,  and  only  slightly  vascular  in  health.  Upon  the  cornea  the  con- 
junctiva consists  only  of  epithelium,  constituting  the  ante- 
rior layer  of  the  cornea  (conjunctival  epithelium)  already 
described  (p.  1109).  Lymphatics  arise  in  the  conjunc- 
tiva in  a  delicate  zone  around  the  cornea,  from  which  the 
vessels  run  to  the  ocular  conjunctiva. 

Fornix  of  Conjunctiva.  —  At  the  point  of  reflection  of 
each  fold  of  the  conjunctiva  from  the  lid  on  to  the  globe 
of  the  eye  a  pocket  or  arch  is  formed.    These  arches  are 
INFERIOR  FORNIX      temicd  the  fornix  conjunctivae  (Fig.  749). 
Fig.  749.— Sagittal  section       Glauds  of  Conjunctiva. — In  the  conjunctiva  there  are  a 

of  eye,  showing  superior  and  iii-i  i  ij.i 

inferior  fornices  of  the  con-  numbcr  of  mucous  glauds  which  are  much  convoluted. 
They  are  chiefly  found  in  the  upper  lid.  Other  glands, 
analogous  to  lymphoid  follicles,  and  called  by  Henle  trachoma  glands,  are  found 
in  the  conjunctiva,  and,  according  to  Stromeyer,  are  chiefly  situated  near  the 
inner  canthus  of  the  eye.  They  were  first  described  by  Brush,  in  his  description 
of  Peyer's  patches  of  the  small  intestines,  as  "  identical  structures  existing  in  the 
under  eyelid  of  the  ox." 

The  Nerves  of  the  Conjunctiva. — ^The  nerves  in  the  conjunctiva  are  numerous  and 
form  rich  plexuses.  According  to  Krause,  they  terminate  in  a  peculiar  form  of 
tactile  corpuscle,  which  he  terms  the  terminal  bulb. 

The  OarunculaLacrimalis. — The  caruncula  lacrimalis  is  a  small,  reddish,  conical- 
shaped  body,  situated  at  the  inner  canthus  of  the  eye,  and  filling  up  the  small 


SUPERIOR  FORNIX 


THE    LACHRYMAL    APPARATUS 


1141 


triangular  space  in  this  situation,  the  lacus  lacrimalis.  It  consists  of  an  island 
of  skin  containing  sebaceous  and  sweat-glands,  and  is  the  source  of  the  whitish 
secretion  which  constantly  collects  at  the  inner  angle  of  the  eye.  A  few  slender 
hairs  are  attached  to  its  surface.  On  the  outer  side  of  the  caruncula  is  a  slight 
semilunar  fold  of  conjunctiva,  the  concavity  of  which  is  directed  toward  the 
cornea;  it  is  called  the  plica  semilunaris  (Fig.  751).  Miiller  found  smooth  mus- 
cular fibres  in  this  fold,  and  in  some  of  the  domesticated  animals  a  thin  plate  of 
cartilage  has  been  discovered.  This  structure  is  considered  to  be  the  rudiment 
of  the  third  eyelid  in  birds,  the  membrana  nictitans. 

The  Lachrymal  Apparatus  (Apparatus  Lacrimalis)  (Figs.  750,  751). 

The  lachrymal  apparatus  consists  of  the  lachrymal  gland,  which  secretes  the 
tears,  and  its  excretory  ducts,  which  convey  the  fluid  to  the  surface  of  the  eye. 
This  fluid  is  carried  away  by  the  lachrymal  canals  into  the  lachrymal  sac,  and  along 
the  nasal  duct  into  the  cavity  of  the  nose. 

The  Lachrymal  Glands  (glandula  lacrimalis). — The  lachrymal  gland  is  lodged 
in  a  depression  at  the  outer  angle  of  the  orbit,  on  the  inner  side  of  the  external 


Puncta  lachrymalia. 


Fig.  750. — The  Meibomian  glands,  etc.,  seen  from  the  inner  surface  of  the  eyelids. 

angular  process  of  the  frontal  bone.  It  is  of  an  oval  form,  about  the  size  and 
shape  of  an  almond.  Its  upper  convex  surface  is  in  contact  with  the  periosteum 
of  the  orbit,  to  which  it  is  connected  by  a  few  fibrous  bands.  Its  under  concave 
surface  rests  upon  the  convexity  of  the  eyeball  and  upon  the  Superior  and  External 
recti  muscles.  Its  vessels  and  nerves  enter  its  posterior  border,  whilst  its  anterior 
margin  is  closely  adherent  to  the  back  part  of  the  upper  eyelid,  where  it  is  covered 
to  a  slight  extent  by  the  reflection  of  the  conjunctiva.  The  forepart  of  the  gland 
is  separated  from  the  rest  by  a  fibrous  septum;  hence  it  is  sometimes  described  as 
a  separate  lobe,  called  the  inferior  lachrymal  gland,  palpebral  portion  of  the  gland, 
or  the  accessory  gland  of  Rosenmuller  (glandula  lacrimalis  inferior),  the  back  part 
of  the  gland  then  being  called  the  superior  lachrymal  gland  (glandula  lacrimalis 
superior).  The  ducts  of  the  lachrymal  gland,  from  six  to  twelve  in  number, 
run  obliquely  beneath  the  mucous  membrane  for  a  short  distance,  and,  separating 
from  each  other,  open  by  a  series  of  minute  orifices  on  the  upper  and  outer  half  of 
the  conjunctiva  near  its  reflection  on  to  the  globe.  These  orifices  are  arranged  in 
a  row,  so  as  to  disperse  the  secretion  over  the  surface  of  the  membrane. 

Structure  of  the  Lachrymal  Gland. — In  structure  and  general  appearance  the 
lachrymal  resembles  the  serous  salivary  glands.    In  the  recent  state  the  cells  are  so 


1142 


THE  ORGANS    OF  SPECIAL    SENSE 


Fig.  751. — The  lachrymal  apparatus.     Right  side. 


crowded  with  granules  that  their  Hmits  can  hardly  be  defined.    Each  cell  contains 
an  oval  nucleus,  and  the  cell-protoplasm  is  finely  fibrillated. 

The  Lachrymal  Canaliculi  or  Canals  (Fig.  751)  commence  at  the  minute  orifices, 
puncta  lacrimalia,  on  the  summit  of  a  small  conical  elevation,  the  lachrymal  papilla 
or  caruncle  {carunculus  lacrimalis),  seen  on  the  margin  of  the  lids  at  the  outer  ex- 
tremity of  the  lacus  lacrimalis.  The  superior  canal  (ductus  lacrimalis  superior),  the 
smaller  and  shorter  of  the  two,  at  first  ascends,  and  then  bends  at  an  acute  angle, 
and  passes  inward  and  downward  to  the  ampulla.     The  inferior  canal  (ductus 

lacrimalis  inferior)  at  first  descends, 
and  then,  abruptly  changing  its  course, 
passes  almost  horizontally  inward  to 
the  ampulla.  These  canals  are  dense 
and  elastic  in  structure  and  somewhat 
dilated  at  their  angle.  The  rtiucous 
membrane  is  covered  with  scaly  epi- 
thelium. The  two  canals  join  in  a 
dilatation,  the  ampulla  (ampulla  ductus 
lacrimalis),  which  empties  into  the 
lachrymal  sac. 

The  Lachrymal  Sac  (saccus  lacri- 
malis) (Fig.  751). — The  lachrymal  sac  is 
the  upper  dilated  extremity  of  the  nasal 
duct,  and  is  lodged  in  a  deep  groove 
formed  by  the  lachrymal  bone  and  the 
nasal  process  of  the  superior  maxillary 
bone.  It  is  oval  in  form,  its  upper  ex- 
tremity being  closed  in  and  rounded, 
whilst  below  it  is  continued  into  the  nasal  duct.  It  is  covered  by  a  fibrous 
expansion  derived  from  the  tendo  oculi,  and  on  its  deep  surface  it  is  crossed  by 
the  Tensor  tarsi  muscle  (Horner's  muscle,  p.  371),  which  is  attached  to  the  ridge 
on  the  lachrymal  bone. 

Structure. — It  consists  of  a  fibrous  elastic  coat,  lined  internally  by  mucous  mem- 
brane, the  latter  being  continuous,  through  the  ampulla  and  lachrymal  canals, 
with  the  mucous  lining  of  the  conjunctiva,  and,  through  the  nasal  duct,  with  the 
pituitary  membrane  of  the  nose. 

The  Nasal  Duct  (ductus  nasolacrimalis)  (Fig.  751). — The  nasal  duct  is  a 
membranous  canal,  about  three-quarters  of  an  inch  in  length,  which  extends  from 
the  lower  part  of  the  lachrymal  sac  to  the  inferior  meatus  of  the  nose,  where  it 
terminates  by  a  somewhat  expanded  orifice,  provided  with  an  imperfect  valve,  the 
valve  of  Hasner  (plica  lacrimalis  [Hasneri]),  formed  by  the  mucous  membrane.  It 
is  contained  in  an  osseous  canal  formed  by  the  superior  maxillary,  the  lachrymal, 
and  the  inferior  turbinated  bones,  is  narrower  in  the  middle  than  at  each  extrem- 
ity, and  takes  a  direction  downward,  backward,  and  a  little  outward.  It  is  lined 
by  mucous  membrane,  which  is  continuous  below  with  the  pituitary  lining  of 
the  nose.  The  membrane  in  the  lachrymal  sac  and  nasal  duct  is  covered  with 
columnar  epithelium,  as  in  the  nose.     This  epithelium  is  in  places  ciliated. 

Surface  Form. — The  palpebral  fissure,  or  opening  between  the  eyelids,  is  elliptical  in  shape, 
and  differs  in  size  in  different  individuals  and  in  different  races  of  mankind.  In  the  Mongolian 
races,  for  instance,  the  opening  is  very  small,  merely  a  narrow  fissure,  and  this  makes  the  eye- 
ball appear  small  in  these  races,  whereas  the  size  of  the  eye  is  relatively  very  constant.  The 
normal  direction  of  the  fissure  is  slightly  oblique,  in  a  direction  upward  and  outward,  so  that  the 
outer  angle  is  on  a  slightly  higher  level  than  the  inner.  This  is  especially  noticeable  in  the  Mon- 
golian races,  in  whom,  owing  to  the  upward  projection  of  the  malar  bone  and  the  shortness  of 
the  external  angular  process  of  the  frontal  bone,  "the  tarsal  plate  of  the  upper  lid  is  raised  at  its 
outer  part  and  gives  an  oblique  direction  to  the  palpebral  fissure. 


THE   LACHRYMAL   APPARATUS  1143 

When  the  eyes  are  directed  forward,  as  in  ordinary  vision,  the  upper  part  of  the  cornea  is 
covered  by  the  upper  hd,  and  the  lower  margin  of  the  cornea  corresponds  to  the  level  of  the 
lower  lid,  so  that  about  the  lower  three-fourths  of  the  cornea  is  exposed  under  ordinary  circum- 
stances. On  the  margins  of  the  lids,  about  a  quarter  of  an  inch  from  the  inner  canthus,  are  two 
small  openings,  the  puncta  lacrimalia,  the  commencement  of  the  lachrymal  canals.  They  are 
best  seen  by  everting  the  eyelids.  In  the  natural  condition  they  are  in  contact  w^ith  the  con- 
junctiva of  the  eyeball,  and  are  maintained  in  this  position  by  the  Tensor  tarsi  muscle,  so  that 
the  tears  running  over  the  surface  of  the  globe  easily  find  their  way  into  the  lachrymal  canals. 
The  position  of  the  lachrymal  sac  into  which  the  canals  open  is  indicated  by  a  little  tubercle, 
which  is  plainly  to  be  felt  on  the  lower  margin  of  the  orbit.  The  lachrymal  sac  lies  immediately 
above  and  to  the  inner  side  of  this  tubercle,  and  a  knife  passed  through  the  skin  in  this 
situation  would  open  the  cavity.  The  position  of  the  lachrymal  sac  may  also  be  indicated  by 
the  tendo  oculi  or  internal  tarsal  ligament.  If  both  lids  be  drawn  outward,  so  as  to  tense  the 
skin  at  the  inner  angle,  a  prominent  cord  will  be  seen  beneath  the  tightened  skin.  This  is  the 
tendo  oculi,  which  lies  immediately  over  the  lachrymal  sac,  bisecting  it,  and  thus  forming  a  useful 
guide  to  its  situation.  A  knife  entered  immediately  beneath  the  tense  cord  would  open  the 
lower  part  of  the  sac.  A  probe  introduced  through  this  opening  can  be  readily  passed  down- 
ward through  the  duct  into  the  inferior  meatus  of  the  nose.  The  direction  of  the  duct  is  down- 
ward, outward,  and  backward,  and  this  course  should  be  borne  in  mind  in  passing  the  probe, 
otherwise  the  point  may  be  driven  through  the  thin  bony  walls  of  the  canal.  A  convenient 
plan  is  to  direct  the  probe  in  such  a  manner  that  if  it  were  pushed  onward  it  would  strike 
the  first  molar  tooth  of  the  lower  jaw  on  the  same  side  of  the  body.  In  other  words,  the 
surgeon  standing  in  front  of  his  patient  should  carry  in  his  mind  the  position  of  the  first 
molar  tooth,  and  should  push  his  probe  onward  in  such  a  way  as  if  he  desired  to  reach  this 
structure. 

Beneath  the  internal  angular  process  of  the  frontal  bone  the  pulley  of  the  Superior  oblique 
viuscle  of  the  eye  can  be  plainly  felt  by  pushing  the  finger  backward  between  the  upper  and  inner 
angle  of  the  eye  and  the  roof  of  the  orbit;  passing  backward  and  outward  from  this  pulley,  the 
tendon  can  be  felt  for  a  short  distance. 

Surgical  Anatomy. — The  eyelids  are  composed  of  various  tissues,  and  consequently  are  liable 
to  a  variety  of  diseases.  The  skin  which  covers  them  is  exceedingly  thin  and  delicate,  and  is 
supported  on  a  quantity  of  loose  and  lax  subcutaneous  tissue  which  contains  no  fat.  In  conse- 
quence of  this  it  is  very  freely  movable,  and  is  liable  to  be  drawn  down  by  the  contraction  of 
neighboring  cicatrices.  Such  contractions  may  produce  an  eversion  of  the  lid  known  as  ectropion. 
Inversion  of  the  lids  (entropion)  from  spasm  of  the  Orbicularis  palpebrarum  or  from  chronic 
inflammation  of  the  palpebral  conjunctiva  may  also  occur.  In  some  individuals  there  is  an  extra 
row  of  eyelashes  on  the  inner  margin  of  the  lid,  directed  toward  the  cornea  (distichiasis).  Trich- 
iasis is  a  condition  in  which  the  lashes  are  directed  toward  the  eye,  but  there  is  not  inversion  of 
the  lid.  The  eyelids  are  richly  supplied  with  blood,  and  are  often  the  seat  of  vascular  gro\yths, 
such  as  ncpvi.  Rodent  ulcer  also  frequently  commences  in  this  situation.  The  loose  cellular  tissue 
beneath  the  skin  is  liable  to  become  extensively  infiltrated  either  with  blood  or  inflammatory 
products,  producing  very  great  swelling.  Even  from  very  slight  injuries  to  this  tissue  the  extrava- 
sation of  blood  may  be  so  great  as  to  produce  considerable  swelling  of  the  lids  and  complete 
closure  of  the  eye,  and  the  same  is  the  case  when  inflammatory  products  are  poured  out.  The 
follicles  are  liable  to  become  inflamed,  constituting  the  disease  known  as  marginal  blepharitis, 
blepharitis  ciliaris,  or  ''  blear-ei/e."  Irregular  or  disorderly  growth  of  the  eyelashes  not  unfre- 
quently  occurs,  some  of  them  being  turned  toward  the  eyeball  and  producing  inflammation  and 
follicles  of  the  eyelashes  or  the  sebaceous  glands  associated  with  these  follicles  may  be  the  seat  of 
inflammation,  constituting  the  ordinary  hordeolum  or  "siij."  The  Meibomian  glands  are  affected 
in  the  so-called  "  tarsal  tumor;"  the  tumor,  according  to  some,  being  caused  by  the  retained  secre- 
tion of  these  glands ;  by  others  it  is  believed  to  be  a  neoplasm  connected  with  the  gland.  The  Orbic- 
ularis palpebrarum  may  be  the  seat  of  spasm  (blepharospasm),  either  in  the  form  of  slight  quiv- 
ering of  the  lids  or  repeated  twitchings,  most  commonly  due  to  errors  of  refraction  in  children, 
or  more  continuous  spasm,  due  to  some  irritation  of  the  fifth  or  seventh  cranial  nerves.  The 
Orbicularis  may  be  paralyzed,  generally  associated  with  paralysis  of  the  other  facial  muscles. 
Under  these  circumstances  the  patient  is  unable  to  close  the  lids,  and  if  he  attempts  to  do  so, 
rolls  the  eyeball  upward  under  the  upper  lid.  The  tears  overflow  from  displacement  of  the  lower 
lid,  and  the  conjunctiva  and  cornea,  being  constantly  exposed  and  the  patient  being  unable  to 
wink,  become  irritated  from  dust  and  foreign  bodies.  As  a  result  there  may  be  ulceration  of 
the  cornea,  and  possibly  eventually  complete  destruction  of  the  eye.  In  paralysis  of  the  Levator 
palpebrae  superioris  there  is  drooping  of  the  upper  eyelid  (ptosis)  and  other  symptoms  of  impli- 
cation of  the  third  nerve.  The  eyelids  may  be  the  seat  of  bruises,  wounds,  or  bums.  After 
wounds  or  burns  adhesions  of  the  margins  of  the  lids  to  each  other  or  adhesion  of  the  lids  to 
the  globe  may  take  place.  The  eyelids  are  sometimes  the  seat  of  emphysema  after  fracture  of 
some  of  the  thin  bones  forming  the  inner  wall  of  the  orbit.  If  shortly  after  such  an  injury  the 
patient  blows  his  nose,  air  is  forced  from  the  nostrils  through  the  lacerated  structure  into  the 


1144  THE    ORGANS    OF   SPECIAL    SENSE 

connective  tissue  of  the  eyelids,  which  suddenly  swell  up  and  present  the  peculiar  crackling  on 
pressure  which  is  characteristic  of  this  affection. 

Foreign  bodies  frequently  get  into  the  conjunctival  sac  and  cause  great  pain,  especially  if 
they  come  in  contact  with  the  corneal  surface,  during  the  movements  of  the  lid  and  the  eye  on 
each  other.  The  conjunctiva  is  frequently  involved  in  severe  injuries  of  the  eyeball,  but  is  seldom 
ruptured  alone;  the  most  common  form  of  injury  to  the  conjunctiva  alone  is  from  a  burn,  either 
from  fire,  strong  acids,  or  lime.  In  these  cases  union  is  liable  to  take  place  between  the  eyelid 
and  the  eyeball.  The  conjunctiva  is  often  the  seat  of  inflammatio7i  arising  from  many  different 
causes,  and  the  arrangement  of  the  conjunctival  vessels  should  be  remembered  as  affording  a 
means  of  diagnosis  between  this  condition  and  injection  of  the  sclerotic,  which  is  present  in 
inflammation  of  the  deeper  structures  of  the  globe.  The  inflamed  conjunctiva  is  bright  red;  the 
vessels  are  large  and  tortuous,  and  greatest  at  the  circumference,  shading  off  toward  the  corneal 
margin;  they  anastomose  freely  and  form  a  dense  network,  and  they  can  be  emptied  by  gentle 
pressure. 

The  lachrymal  gland  is  occasionally,  though  rarely,  the  seat  of  inflammaiion  (dacryoadenitis), 
either  acute  or  chronic;  it  is  also  sometimes  the  seat  of  tumors,  benign  or  malignant,  and  for  these 
may  require  removal.  This  may  be  done  by  an  incision  through  the  skin  just  below  the  eyebrow; 
and  the  gland,  being  invested  with  a  special  capsule  of  its  own,  may  be  isolated  and  removed 
without  opening  the  general  cavity  of  the  orbit.  The  canaliculi  may  be  obstructed,  either  as  a 
congenital  defect  or  by  some  foreign  body,  as  an  eyelash  or  a  dacryolith,  causing  the  tears  to  run 
over  the  cheek.  The  canaliculi  may  also  become  occluded  as  the  result  of  burns  or  injury;  over- 
flow of  tears  may  in  addition  result  from  deviation  of  the  puncta  or  from  chronic  inflammation 
of  the  lachrymal  sac.  When  there  is  failure  of  the  lachrymal  tubes  to  drain  off  the  tears  and 
the  fluid  gathers  beneath  and  flows  over  the  lids,  the  condition  is  known  as  epiphora  or  stilli- 
cidium.  This  latter  condition  is  set  up  by  some  obstruction  to  the  nasal  duct  frequently  occurring 
in  tuberculous  subjects.  In  consequence  of  this  the  tears  and  mucus  accumulate  in  the  lachrymal 
sac,  distending  it.  Suppuration  in  the  lachrymal  sac  (dacryocystitis)  is  sometimes  met  with; 
this  may  be  the  sequel  of  a  chronic  inflammation ;  or  may  occur  after  some  of  the  eruptive  fevers 
in  cases  where  the  lachrymal  passages  were  previously  quite  healthy.  It  may  lead  to  lachrymal 
fistula. 

THE  EAR  (ORGANON  AUDITUS). 

The  organ  of  hearing  is  divisible  into  three  parts — the  external  eax,  the  middle 
eax  or  tympanum,  and  the  internal  ear  or  labyrinth. 

THE  EXTERNAL  EAR  (AURIS  EXTERNA). 

The  external  ear  consists  of  an  expanded  portion  named  pinna  or  am'icle,  and 
the  auditory  canal  or  meatus.  The  former  serves  to  collect  the  vibrations  of  the  air 
by  which  sound  is  produced;  the  latter  conducts  those  vibrations  to  the  tympanum. 

The  Pinna  or  Auricle  (Auricula)  (Fig.  752). 

The  pinna  or  auricle  is  attached  to  the  side  of  the  head  midway  between  the 
forehead  and  occiput.  "Its  level  is  indicated  by  horizontal  lines  extending  back- 
ward from  the  eyebrows  above  and  from  the  tip  of  the  nose  below."^  It  is  of  an 
ovoid  form,  with  its  larger  end  directed  upward.  Its  outer  surface  is  irregularly 
concave,  directed  slightly  forward.  The  angle  which  it  bears  to  the  head  is  called 
the  cephalo -auricular  angle.  In  some  cases  this  angle  is  almost  absent.  In  others 
it  is  nearly  a  right  angle.  The  pinna  of  one  side  may  vary  in  size,  shape,  and 
angle  from  the  pinna  of  the  other  side.  The  pinna  of  a  woman  is  apt  to  be  smaller 
than  that  of  a  man,  and  is  less  often  deformed.  The  outer  surface  of  the  pinna 
presents  numerous  eminences  and  depressions  which  result  from  the  foldings  of  its 
fibro-cartilaginous  element.  To  each  of  these,  names  have  been  assigned.  Thus 
the  external  prominent  rim  of  the  auricle  is  called  the  helix.  Another  curved  prom- 
inence, parallel  with  and  in  front  of  the  helix,  is  called  the  antihelix;  this  bifurcates 
above  and  forms  the  crura,  which  encloses  a  triangular  depression,  the  fossa  of  the 
antihelix  (fossae  triangularis  [auriculae]).    The  narrow  curved  depression  between 

'  Arthur  Hensman  in  Henry  Morris'  Human  Anatomy. 


THE  PINNA    OB    AUBICLE 


1145 


the  helix  and  antihelix  is  called  the  fossa  of  the  helix  or  the  scaphoid  fossa  (scapha) ; 
the  antihelix  describes  a  curve  around  a  deep,  capacious  cavity,  the  concha  auriculae, 


darwinian 
tubercle: 


FOSSA 
TRIANGULARIS 


CRURA  OF 
ANTIHELIX 


SCAPHOID 

FOSSA  -.  ''  I 


POSTERIOR 

AURICULAR 

SULCUS 


INCISURA 
ANTERIOR 


TUBERCULUM 
SUPRATRAGICUM 


EXTERNAL 
AUDITORY 
MEATUS 


INCISURA 
INTERTRAGICA 


CAVUM   CONCHAE 

Fig.  752. — The  right  pinna  or  auricle,  \'iewed  from  without. 


(Spalteholz.) 


INSERTION 

OF  SUPERIOR 

AURICULAR 

MUSCLE 

INSERTION 

OF  ANTERIOR 

AURICULAR 

MUSCLE 

OBLIQUE 

AURICULAR 

MUSCLE 


which  is  partially  divided  into  two  parts  by  the  cms  of  the  helix,  or  the  commence- 
ment of  the  helix;  the  upper  part  is  termed  the  cymba  conchae,  the  lower  part  the 
cavum  conchae.  In  front  of  the 
concha,  and  projecting  backward 
over  the  meatus,  is  a  small  pointed 
eminence,  the  tragus,  so  called  from 
its  being  generally  covered  on  its 
under  surface  with  a  tuft  of  hair 
resembling  a  goat's  beard.  Oppo- 
site the  tragus,  and  separated  from 
it  by  a  deep  notch  (incisuria  inter- 
tragica)  is  a  small  tubercle,  the 
antitragus.  Below  this  is  the  lobule 
(lohulus  auriculae),  composed  of 
tough  areolar  and  adipose  tissue, 
wanting  the  firmness  and  elasticity 
of  the  rest  of  the  pinna.  Some- 
times the  lobule  does  not  hang 
freely,  but  is  adherent.  Where 
the  helix  turns  downward  a  small 
tubercle,  the  tubercle  of  Darwin  {tuherculum  auriculae  [Darwini]),  is  frequently  seen. 
This  tubercle  is  very  evident  about  the  sixth  month  of  fcetal  life;  at  this  stage 
the  human  pinna  has  a  close  resemblance  to  that  of  some  of  the  adult  monkeys. 


INSERTION  OF 

POSTERIOR 

AURICULAR 

MUSCLE 

TRANSVERSE 

AURICULAR 

MUSCLE 


CARTILAGE 

OF  EXTERNAL 

AUDITORY 

MEATUS 


Fig.  753. — The  cartilages  of  the  right  auricle,  isolated,  with 
the  muscles,  viewed  from  the  inside.     (Spalteholz.) 


1146 


THE    ORGANS    OF  SPECIAL   SENSE 


The  cranial  surface  of  the  pinna  presents  elevations  which  correspond  to  the 
depressions  on  its  outer  surface  and  after  which  they  are  named,  e.  g.,  eminentia 
conchae,  eminentia  fossae  triangularis,  etc. 

The  eminentia  conchae  and  the  fossae  triangularis  are  separated  by  a  furrow 
(sulcus  antihelicis  transversus) ,  which  corresponds  to  the  inferior  crus  of  the  anti- 
heUx,  or  groove  (sulcus  cruris  helicis),  and  upon  the  eminence  there  is  a  vertical 
ridge,  the  ponticulus,  which  indicates  the  point  of  insertion  of  the  Retrahens 
auriculam  muscle. 

Structure  of  the  Pinna. — The  pinna  is  composed  of  a  thin  plate  of  yellow 
fibro-cartilage,  covered  with  integument,  and  connected  to  the  surrounding  parts 
by  the  extrinsic  ligaments  and  muscles,  and  to  the  commencement  of  the  external 
auditory  canal  by  fibrous  tissue. 

The  Integument. — The  integument  is  thin,  closely  adherent  to  the  cartilage,  and 
covered  with  hairs  furnished  with  sebaceous  glands,  which  are  most  numerous  in 
the  concha  and  scaphoid  fossa.  The  hairs  are  most  numerous  and  largest  on  the 
tragus  and  antitragus. 

The  Cartilage  of  the  Pinna  (cartilago  auriculae)  (Fig.  754).— The  cartilage  of  the 
pinna  consists  of  one  single  piece;  it  gives  form  to  this  part  of  the  ear,  and  upon  its 

surface  are  found  all  the  eminences 
and  depressions  above  described. 
It  does  not  enter  into  the  construc- 
tion of  all  parts  of  the  auricle ;  thus 
it  does  not  form  a  constituent  part 
of  the  lobule;  it  is  deficient  also 
between  the  lamina  of  the  tragus 
and  beginning  of  the  crus  helix,  the 
notch  between  (incisura  terminalis 
awm)them  being  filled  up  V)y  dense 
fibrous  tissue.  At  the  front  part  of 
the  pinna,where  the  helix  bends  up- 
ward, is  a  small  projection  of  car- 
tilage, called  the  spine  of  the  helix 
(spina  helicis),  while  the  lower  part 
of  the  helix  is  prolonged  downward 
as  a  tail-like  process,  the  cauda 
helicis;  this  is  separated  from  the 
antihelix  by  a  fissure,  the  fissura  antitragohelicina.  The  fissures  of  Santorini  are 
usually  two  in  number:  one  in- the  substance  of  the  tragus,  which  partially  separates 
the  different  parts,  and  one  in  the  cartilage  of  the  meatus.  The  fissure  of  the  helix 
is  a  short  vertical  slit,  situated  at  the  forepart  of  the  pinna.  Another  fissure,  the 
fissure  of  the  tragus,  is  seen  upon  the  anterior  surface  of  the  tragus.  Anteriorly 
and  inferiorly  the  cartilage  of  the  pinna  is  continuous  with  the  cartilage  of  the 
external  auditory  meatus  by  a  cartilaginous  isthmus  (isthmus  cartilaginis  auris). 
Some  authors  regard  the  tragus  as  part  of  the  cartilage  of  the  meatus.  The 
cartilage  of  the  pinna  is  very  pliable,  elastic,  of  a  yellowish  color  and  belongs  to 
that  form  of  cartilage  which  is  known  under  the  name  of  yellow  fibro-cartilage. 
The  Ligaments  of  the  Tinna.  (ligamenti  auricularia  [Valsalvae]). — The  ligaments 
of  the  pinna  consist  of  two  sets:  1.  The  extrinsic  set,  or  those  connecting  it  to  the 
side  of  the  head.  2.  The  intrinsic  set,  or  those  connecting  the  various  parts  of  its 
cartilage  together. 

The  Extrinsic  Ligaments,  the  most  important,  are  three  in  number:  superior, 
anterior,  and  posterior.  The  superior  ligament  (ligamentum  auriculare  superius) 
extends  from  the  suprameatal  spine  to  the  spine  of  the  helix.  The  anterior  ligament 
(ligamentum  auriculare  anterius)  extends  from  the  spina  helicis  and  tragus  to  the 


FISSURA 

ANTirnAGICO- 

HELICINA 

CAUDA 
HE 


TRIANGULAR 
FOSSA 


SPINE   OF 
HELIX 

RUS  OF 
ELIX 

LAMINA 

TRAGI 

INCISURA 

TERMINALIS 

AURIS 


ANTITRAGUS 


Fig.  754.— The  right  ear  cartilages,  isolated,  viewed  from 
without.     (Spalteholz.) 


THE    PINNA     OB   AURICLE 


1147 


root  of  the  zygoma.  The  posterior  ligament  (ligamentum  auriculare  posterius) 
passes  from  the  posterior  surface  of  the  concha  to  the  outer  surface  of  the  mastoid 
process  of  the  temporal  bone. 

The  chief  Intrinsic  Ligaments  are:  (1)  a  strong  fibrous  band,  stretching  across 
from  the  tragus  to  the  commencement  of  the  heHx,  completing  the  meatus  in  front, 
and  partly  encircling  the  boundary  of  the  concha;  and  (2)  a  band  which  extends 
between  the  antihelix  and  the  cauda  helicis.  Other  less  important  bands  are 
found  on  the  cranial  surface  of  the  pinna. 

The  Muscles  of  the  Pinna  (Figs.  753  and  755). — The  muscles  of  the  pinna  consist 
of  two  sets :  1.  The  extrinsic,  which  connect  it  with  the  side  of  the  head,  moving  the 
pinna  as  a  whole — viz.,  the  Attollens,  Attrahens,  and  Retrahens  auriculam  (p.  369). 
2.  The  intrinsic,  which  extend  from  one  part  of  the  auricle  to  another,  viz. : 


Helicis  major. 
Helicis  minor. 
Tragicus. 


Antitragicus. 
Transversus  auriculae. 
Obliquus  auriculae. 


vertical  band  of  muscular 
It  arises,  below,  from  the 


The  Helicis  Major  (m.  helicis  major)  is  a  narrow 
fibres,  situated  upon  the  anterior  margin  of  the  helix 
Cauda  helicis,  and   is   inserted   into 
the  anterior  border  of  the  helix,  just 
where  it  is  about  to  curve  backward. 
It  is  pretty  constant  in  its  existence. 

The  Helicis  Minor  (m.  helicis  minor) 
is  an  oblique  fasciculus  which  covers 
the  crus  helicis. 

The  Tragicus  (m.  tragicus)  is  a 
short,  flattened  band  of  muscular 
fibres  situated  upon  the  outer  surface 
of  the  tragus,  the  direction  of  its 
fibres  being  vertical. 

The  Antitragicus  (m.  antitragicus) 
arises  from  the  outer  part  of  the  anti- 
tragus;  its  fibres  are  inserted  into  the 
cauda  helicis  and  antihelix.  This 
muscle  is  usually  very  distinct. 

The  Transversus  Auriculae  (m. 
transversus  auriculae)  is  placed  on 
the  cranial  surface  of  the  pinna.  It 
consists  of  scattered  fibres,  partly 
tendinous  and  partly  muscular,  ex- 
tending from  the  convexity  of  the 
concha  to  the  prominence  corre- 
sponding with  the  groove  of  the  helix. 

The  Obliquus  Auriculae  (Tod)  (m. 
obliquus  auriculae)  consists  of  a  few 

fibres  extending  from  the  upper  and  back  part  of  the  concha  to  the  convexity 
immediately  above  it. 

The  Arteries  of  the  Pinna. — The  arteries  of  the  pinna  are  the  posterior  auricular 
from  the  external  carotid,  the  anterior  auricular  from  the  temporal  and  an  auric- 
ular branch  from  the  occipital  artery. 

The  Veins  of  the  Pinna. — The  veins  of  the  pinna  accompany  the  corresponding 
arteries. 

The  Lymphatics  of  the  Pinna. — The  lymphatics  enter  into  the  pre-auricular  glands 
and  the  glands  upon  the  Sterno-mastoid  muscle  at  its  insertion. 


Fig.  755. — The  muscles  of  the  pinna. 


1148 


THE   ORGANS   OF  SPECIAL   SENSE 


The  Nerves  of  the  Pinna. — The  nerves  of  the  pinna  are:  the  auricularis  magnus, 
from  the  cervical  plexus ;  the  auricular  branch  of  the  pneumogastric ;  the  auriculo- 
temporal branch  of  the  inferior  maxillary  nerve;  the  occipitalis  minor  from  the 
cervical  plexus,  and  the  occipitalis  major  or  internal  branch  of  the  posterior 
division  of  the  second  cervical  nerve.  The  muscles  of  the  pinna  are  supplied  by 
the  facial  nerv^e. 


The  External  Auditory  or  External  Acoustic  Canal  or  External  Auditory 

Meatus  (Meatus  Acusticus  Externus  or  Meatus 

Auditorius  Externus). 

The  external  auditory  or  acoustic  canal  or  meatus  extends  from  the  bottom 
of  the  concha  to  the  membrana  tympani  (Figs.  752,  756,  and  757).  It  is  about 
an  inch  and  a  half  in  length  if  measured  from  the  tragus;  from  the  bottom  of 
the  concha  its  length  is  about  an  inch.  It  forms  a  sort  of  S-shaped  curve,  and  is 
directed  at  first  inward,  forvi'ard,  and  slightly  upward  {"pars  externa);  it  then 
passes  inward  and  backward  {'pars  media),  and  lastly  is  carried  inward,  forward, 
and  slightly  downward  {pars  interna).  It  forms  an  oval  cylindrical  canal,  the 
greatest  diameter  being  in  the  vertical  direction  at  the  external  orifice,  but  in  the 

Cartilage  of 
the  pinna  ' 

Promont. 


Int.  carot.  a.  \  '•»  ;'  /  ;7?S>_: 

Membrana         /  '  ;5 Ifi'Ast^ 
tympani        /       ^' '"'■". %i'3jl\ 

Cartilage  of  the  ext.    a!j -flMJ 
auditory  meatus 

Fig.  756. — Transverse  section  of  external  auditory  meatus  and  tympanum.     Left  side.     (Gegenbauer.) 

transverse  direction  at  the  tympanic  end.  It  presents  two  constrictions,  one 
near  the  inner  end  of  the  cartilaginous  portion,  and  another,  the  isthmus,  in  the 
osseous  portion,  about  three-quarters  of  an  inch  from  the  bottom  of  the  concha. 
The  membrana  tympani  (Figs.  756  and  757),  which  occupies  the  termination  of  the 
meatus,  is  directed  obliquely,  in  consequence  of  which  the  floor  of  the  canal  is 
longer  than  the  roof,  and  the  anterior  wall  longer  than  the  posterior.  The  auditory 
canal  is  formed  partly  by  cartilage  and  membrane,  partly  by  bone,  and  is  lined  by 
perichondrium  and  periosteum,  which  is  covered  with  skin. 

The  Cartilaginous  Portion  {meatus  acusticus  externum  cartilagineus) . — The  car- 
tilaginous portion  is  about  one-third  of  an  inch  (8  mm.)  in  length;  it  is  formed 
by  the  cartilage  of  the  pinna,  prolonged  inward,  and  firmly  attached  to  a  greater 
portion  of  the  circumference  of  the  auditory  process  of  the  temporal  bone.  The 
cartilage  is  deficient  at  its  upper  and  back  part,  its  place  being  supplied  by  fibrous 
membrane.  This  part  of  the  canal  is  rendered  extremely  movable  by  two  or 
three  deep  fissures,  the  fissures  of  Santorini  {incisurae  cartilaginis  meatus  acu^stici 
externi  [Santorini^ ,  v/hich  extend  through  the  cartilage  in  a  vertical  direction. 
It  is  firmly  attached  at  its  lower  and  front  part  to  the  posterior  root  of  the  zygoma 
and  to  the  lateral  edge  of  the  tympanic  portion  of  the  temporal  bone. 


THE   EXTERNAL    AUDITORY  MEATUS 


1149 


The  Osseous  Portion  {meatus  acusticus  extemus  osseus). — The  osseous  por- 
tion is  about  two-thirds  of  an  inch  (16  mm.)  in  length,  and  narrower  than  the 
cartilaginous  portion.  It  is  directed  inward  and  a  little  forward,  forming  a  slight 
curve  in  its  course,  the  convexity  of  which  is  upward  and  backward.  Its  inner 
end,  which  communicates,  in  the  dry  bone,  with  the  cavity  of  the  tympanum,  is 
smaller  than  the  outer  and  sloped,  the  anterior  wall  projecting  beyond  the  poste- 
rior about  two  lines;  it  is  marked,  except  at  its  upper  part,  by  a  narrow  groove, 
the  tympanic  sulcus  (.sulcus  tympanicus),  for  the  insertion  of  the  membrana  tym- 
pani.  Its  outer  edge  is  dilated  and  rough  in  the  greater  part  of  its  circumference, 
for  the  attachment  of  the  cartilage  of  the  pinna.  Its  vertical  transverse  section 
is  oval,  the  greatest  diameter  being  from  above  downward.  The  front  and  lower 
parts  of  this  canal  are  formed  by  a  curved  plate  of  bone,  which,  in  the  fcetus, 
exists  as  a  separate  ring  {annulus  tympanicus),  incomplete  at  its  upper  part.  (See 
Section  on  Osteology.) 


FENESTRA  OVALIS 
LOSEO  BY  STAPES 


Fig.  757. 


-Vertical  section  through  the  external  auditory  meatus  and  tympanum,  passing  in  front  of  the 
fenestra  ovalis.     (Testut.) 


The  Skin  of  the  Meatus. — The  skin  lining  the  meatus  is  a  prolongation  of  the 
external  skin;  it  is  thin,  adheres  closely  to  the  cartilaginous  and  osseous  portions 
of  the  tube,  and  covers  the  surface  of  the  membrana  tympani,  forming  a  very 
thin  outer  layer.  After  maceration  the  thin  pouch  of  epidermis,  when  withdrawn, 
preserves  the  form  of  the  meatus.  In  the  thick  subcutaneous  tissue  of  the  cartil- 
aginous part  of  the  meatus  are  numerous  ceruminous  glands  (glandulae  ceruminosae) 
which  secrete  the  ear-wax.  They  resemble  in  structure  sweat-glands,  and  their 
ducts  open  on  the  surface  of  the  skin. 

Relations  of  the  Meatus. — In  front  of  the  osseous  part  is  the  glenoid  fossa,  which 
receives  the  condyle  of  the  mandible  (Fig.  759),  which,  however,  is  separated  from 
the  cartilaginous  part  by  the  retromandibular  part  of  the  parotid  gland.  The 
movements  of  the  jaw  influence  to  some  extent  the  lumen  of  the  cartilaginous 
portion.  Behind  the  osseous  part  are  the  mastoid  air-cells,  separated  from  it 
by  a  thin  layer  of  bone  (Fig.  46). 

The  Arteries  of  the  External  Meatus. — The  arteries  supplying  the  external  meatus 
are  branches  from  the  posterior  auricular,  internal  maxillary,  and  superficial 
temporal. 


1150  THE   ORGANS    OF  SPECIAL    SENSE 

The  Veins  of  the  External  Meatus. — Veins  accompany  the  corresponding  arteries 
and  pass  to  the  internal  maxillary,  temporal,  and  posterior  auricular  veins. 

The  Lymphatics  of  the  External  Meatus. — The  lymphatics  accompany  the  veins 
and  enter  the  parotid  and  posterior  auricular  lymph-glands. 

The  Nerves  of  the  External  Meatus. — The  nerves  are  derived  from  the  auriculo- 
temporal branch  of  the  inferior  maxillary  nerve,  the  auricularis  magnus,  and  the 
auricular  branch  of  the  pneumogastric. 

Surface  Form. — The  point  of  junction  of  the  osseous  and  cartilaginous  portions  of  the  tube 
is  an  obtuse  angle,  which  projects  into  the  canal  at  its  antero-inferior  wall.  This  produces  a 
sort  of  constriction  in  this  situation,  and  renders  it  the  narrowest  portion  of  the  canal — an  impor- 
tant point  to  be  borne  in  mind  in  connection  with  the  presence  of  foreign  bodies  in  the  ear. 
The  cartilaginous  is  connected  to  the  bony  part  by  fibrous  tissue,  which  renders  the  outer  part 
of  the  tube  very  movable,  and  therefore  by  drawing  the  pinna  upward  and  backward  the  canal 
is  rendered  almost  straight.  At  the  external  orifice  are  a  few  short,  crisp  hairs  which  serve  to 
prevent  the  entrance  of  small  particles  of  dust,  flies  or  other  insects.  In  the  external  auditory 
meatus  the  secretion  of  the  ceruminous  glands  serves  to  catch  any  small  particles  which  may 
find  their  way  into  the  canal,  and  prevent  their  reaching  the  membrana  tympani,  where  their 
presence  might  excite  irritation.  In  young  children  the  meatus  is  short,  the  osseous  part 
being  very  deficient,  and  consisting  merely  of  a  bony  ring  (annulus  tympanicus),  which  supports 
the  membrana  tympani.  In  the  fcetus  the  osseous  part  is  entirely  absent.  The  shortness  of  the 
canal  in  children  should  be  borne  in  mind  in  introducing  the  aural  speculum,  so  that  it  shall  not 
be  pushed  in  too  far,  at  the  risk  of  injuring  the  membrana  tympani;  indeed,  even  in  the  adult  the 
speculum  should  never  be  introduced  beyond  the  constriction  which  marks  the  junction  of  the 
osseous  and  cartilaginous  portions.  In  using  this  instrument  it  is  advisable  that  the  pinna 
should  be  drawn  upward,  backward,  and  a  little  outward,  so  as  to  render  the  canal  as  straight  as 
possible,  and  thus  assist  the  operator  in  obtaining,  by  the  aid  of  reflected  light,  a  good  view  of 
the  membrana  tympani.  Just  in  front  of  the  membrane  is  a  well-marked  depression,  situated 
on  the  floor  of  the  canal  and  bounded  by  a  somewhat  prominent  ridge;  in  this  foreign  bodies 
may  become  lodged.  By  aid  of  the  speculum,  combined  with  traction  of  the  auricle  upward 
and  backward,  the  whole  of  the  membrana  tympani  is  rendered  visible.  It  is  a  pearly-gray  mem- 
brane, slightly  glistening  in  the  adult,  placed  obliquely,  so  as  to  form  with  the  floor  of  the  meatus 
a  very  acute  angle  (about  55  degrees),  while  with  the  roof  it  forms  an  obtuse  angle.  At  birth  it 
is  more  horizontal — being  situated  in  almost  the  same  plane  as  the  base  of  the  skull.  About 
midway  between  the  anterior  and  posterior  margins  of  the  membrane,  and  extending  from  the 
centre  obliquely  upward,  is  a  reddish-yellow  streak;  this  is  the  handle  of  the  malleus,  which  is 
inserted  into  the  membrane  (Fig.  760).  At  the  upper  part  of  this  streak,  close  to  the  roof  of  the 
meatus,  a  little  white  rounded  prominence  is  plainly  to  be  seen;  this  is  the  processus  brevis  of 
the  malleus,  projecting  against  the  membrane.  The  membrana  tympani  does  not  present  a 
plane  surface;  on  the  contrary,  its  centre  is  drawn  inward,  on  account  of  its  connection  with  the 
handle  of  the  malleus,  and  thus  the  external  surface  is  rendered  concave. 

THE  MIDDLE  EAR,  DRUM  OR  TYMPANUM  (AURIS  MEDIA) 

(Figs.  756,  757,  758,  762). 

The  middle  ear  or  tympanum  is  an  irregular  cavity,  compressed  from  without 
inward,  and  is  situated  within  the  petrous  portion  of  the  temporal  bone.  It  is 
placed  above  the  jugular  fossa;  the  carotid  canal  lying  in  front,  the  mastoid  cells^ 
behind,  the  external  auditory  meatus  externally,  and  the  labyrinth  internally.  It  is 
lined  with  mucous  membrane,  is  filled  with  air,  and  communicates  with  the  mas- 
toid cells,  and  with  the  naso-pharynx  by  the  Eustachian  tube.  The  tympanum  is 
traversed  by  a  chain  of  movable  bones,  which  connect  the  membrana  tympani 
with  the  labyrinth,  and  serve  to  convey  the  vibrations  communicated  to  the  mem- 
brana tympani  across  the  cavity  of  the  tympanum  to  the  external  ear.  In  shape 
it  is  roughly  biconcave,  the  concave  surfaces  being  placed  vertically  and  forming 
the  external  and  internal  walls.  The  cavity  forms  an  angle  of  45  degrees  with  the 
median  plane  (Spalteholz). 

The  Tympanic  Cavity  (cavum  tympani)  (Figs.  762  and  763) . — The  tympanic 
cavity  consists  of  two  parts:  the  atrium  or  tympanic  cavity  proper  (Fig.  763), 
opposite  the  tympanic  membrane,  and  the  attic  or  epitympanic  recess  or  aditus 
ad  antrum  {recessus  epitympanicus)  (Figs.  761  and  762),  above  the  level  of  the 


THE   MIDDLE   EAR,    DRUM    OR    TYMPANUM 


1151 


upper  part  of  the  membrane;  the  latter  contains  the  upper  half  of  the  malleus 
and  the  greater  part  of  the  incus.  The  diameter  of  the  tympanic  cavity, 
including  the  attic,  measures  about  f  inch  (15  mm.)  vertically  and  trans- 
versely. From  without  inward  it  measures  about  \  inch  (6  mm.)  above  and  \ 
inch  (4  mm.)  below;  opposite  the  centre  of  the  tympanic  membrane  it  is  only 
about  -^  inch  (2  mm.).  It  is  bounded  externally  by  the  membrana  tympani  and 
meatus;  internally,  by  the  outer  surface  of  the  internal  ear;  and  communicates 
behind  with  the  mastoid  antrum  and  through  it  with  the  mastoid  cells;  and  in 
front  with  the  Eustachian  tube  and  canal  for  the  Tensor  tympani.  Its  roof  and 
floor  are  formed  by  thin  osseous  laminae,  the  one  forming  the  roof  being  a  thin 
plate  situated  on  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone, 
close  to  its  angle  of  junction  with  the  squamous  portion  of  the  same  bone. 

The  Roof  of  the  Tympanum  (paries  tegmentalis). — The  roof  of  the  tympanum 
is  broad,  flattened,  and  formed  of  a  thin  plate  of  bone  (tegmen  tympani)  (Fig. 
762),  which  separates  the  cranial  and  tympanic  cavities.  It  is  prolonged  back- 
ward so  as  to  roof  in  the  mastoid  antrum;  it  is  also  carried  forward  to  cover  in 
the  canal  for  the  Tensor  tympani  muscle. 

The  Floor  (paries  jugularis)  (Fig.  762). — The  floor  is  narrow,  and  is  separated 
by  a  thin  plate  of  bone  (Jundus  tympani)  from  the  jugular  fossa.    It  frequently 


Chorda  tympani 


Fig.  758. — View  of  the  inner  wall  of  the  tympanum  (enlarged). 


presents  numerous  small  notches  in  the  bone  (cellulae  tympanicae).  There  is  one 
small  aperture  in  the  floor.  It  is  near  the  inner  wall  and  is  the  opening  of  the 
canaliculus  tympanicus,  for  the  transmission  of  Jacobson's  nerve  (n.  tympanicus). 
On  the  floor  near  the  posterior  wall  there  is  often  to  be  found  a  slight  bony 
projection  (prominentia  styloideae). 

The  Outer  Wall  (Fig.  757). — The  outer  wall  is  formed  mainly  by  the  membrana 
tympani,  partly  by  the  ring  of  bone  into  which  this  membrane  is  inserted.  The 
part  formed  by  the  membrana  tympanum  is  called  the  paries  membranaceus.  This 
ring  of  bone  is  incomplete  at  its  upper  part,  forming  a  notch,  the  notch  of  Rivinus 
(incisura  tympanica  [Rivini])  (Fig.  760).  The  anterior  edge  of  the  notch  is 
known  as  the  spina  tympanica  major,  the  posterior  edge  as  the  spina  tympanica 
minor.  The  groove  for  the  reception  of  the  membrana  tympani  is  the  sulcus 
tympanicus.  Close  to  the  notch  are  three  small  apertures:  the  iter  chordae  pos- 
terius,  the  Glaserian  fissure,  and  the  iter  chordae  anterius. 

The  iter  chordae  posterius  or  the  tympanic  aperture  (canaliculus  chordae  tympani) 
(Fig.  761)  is  in  the  angle  of  junction  between  the  posterior  and  external  walls  of 
the  tympanum,  immediately  behind  the  membrana  tympani  and  on  a  level  with  the 
upper  end  of  the  handle  of  the  malleus;  it  leads  into  a  minute  canal,  which  descends 


1152  THE    ORGANS    OF  SPECIAL    SENSE 

in  front  of  the  aquaeductus  Fallopii,  and  terminates  in  the  aqueduct  near  the 
stylomastoid  foramen.  Through  it  the  chorda  tympani  nerve  enters  the  tym- 
panum. 

The  Glaserian  or  petro-tympanic  fissure  (fissura  petrotympanica  [Glaseri])  (Fig. 
761)  opens  just  above  and  in  front  of  the  ring  of  bone  into  which  the  membrana 
tympani  is  inserted;  in  this  situation  it  is  a  mere  sHt  about  a  hne  in  length.  It 
lodges  the  long  process  and  anterior  ligament  of  the  malleus,  and  gives  passage 
to  the  tympanic  branch  of  the  internal  maxillary  artery. 

The  iter  chordae  anterius  (Fig.  761)  is  seen  at  the  inner  end  of  the  preceding 
fissure;  it  leads  into  a  canal,  the  canal  of  Huguier,  which  runs  parallel  with  the 
Glaserian  fissure.     Through  it  the  chorda  tympani  nerve  leaves  the  tympanum. 

The  outer  wall  bounds  the  epitym panic  recess  externally. 

The  Internal  Wall  of  the  Tympanum  (paries  lahyrinthica)  (Figs.  758  and  762). — 
The  internal  wall  of  the  tympanum  is  adjacent  to  the  labyrinth,  is  vertical  in  direc- 
tion, and  looks  directly  outward.    It  presents  for  examination  the  following  parts: 

Fenestra  ovalis.  Promontory. 

Fenestra  rotunda.  Ridge  of  the  aquaeductus  Fallopii. 

Prominence  of  the  external  semicircular  canal. 

The  Fenestra  Ovalis,  the  Oval  or  the  Vestibular  Window  {fenestra  vestibuli)  (Fig. 
758)  is  a  reniform  opening  leading  from  the  tympanum  into  the  vestibule.  It 
is  situated  in  the  depths  of  a  fossa  (fossula  fenestrae  vestibuli).  Its  long  diameter 
is  directed  horizontally,  and  its  convex  border  is  upward.  The  opening  in  the 
recent  state  is  occupied  by  the  base  of  the  stapes  (Figs.  757  and  763),  which  is 
connected  to  the  margin  of  the  foramen  by  an  annular  ligament. 

The  Fenestra  Rotunda,  the  Round  or  Cochlear  Window  (fenestra  cochleae)  (Fig. 
758)  is  an  aperture  placed  at  the  bottom  of  a  funnel-shaped  depression  (fossula 
fenestrae  cochleae)  leading  into  the  cochlea.  It  is  situated  below  and  rather 
behind  the  fenestra  ovalis,  from  which  it  is  separated  by  a  rounded  elevation,  the 
promontory;  at  its  border  is  a  narrow  ridge  of  bone  (crista  fenestrae  cochleae),  and 
it  is  closed  in  the  recent  state  by  a  membrane,  the  membrane  of  Scarpa  or  the 
secondary  ear-drum  membrane  (membrana  tympani  secundaria).  This  membrane 
is  concave  toward  the  tympanum,  convex  toward  the  cochlea.  It  consists  of 
three  layers:  the  external  or  mucous,  derived  from  the  mucous  lining  of  the 
tympanum;  the  internal,  from  the  lining  membrane  of  the  cochlea;  and  an  inter- 
mediate or  fibrous  layer. 

The  Promontory  (promontorium)  (Fig.  762)  is  a  rounded  hollow  prominence, 
formed  by  the  projection  outward  of  the  first  turn  of  the  cochlea;  it  is  placed 
between  the  fenestrae,  and  is  furrowed  on  its  surface  (sulcus  promontorii)  for  the 
lodgement  of  the  tympanic  plexus.  A  minute  spicule  of  bone  frequently  connects 
the  promontory  to  the  pyramid. 

The  Rounded  Eminence  of  the  Aquaeductus  Fallopii  (prominentia  canalis  facialis) 
(Fig.  762) ,  the  prominence  of  the  bony  canal  in  which  the  facial  nerve  is  contained, 
traverses  the  inner  wall  of  the  tympanum  above  the  fenestra  ovalis,  and  behind 
that  opening  curves  nearly  vertically  downward  along  the  posterior  wall. 

Just  above  the  eminence  of  the  aquaeductus  Fallopii  the  wall  is  bulged  by  the 
external  semicircular  canal  (prominentia  canalis  semicircularis  lateralis). 

The  Posterior  Wall  of  the  Tympanum  (paries  mastoidea)  (Fig.  762). — The  pos- 
terior wall  of  the  tympanum  is  wider  above  than  below,  and  the  lower  portion  of 
the  posterior  wall  contains  many  tympanic  cells.  The  posterior  wall  presents  for 
examination  the — 

Opening  of  the  antrum.  Prominentia  styloideae. 

Fossa  incudis.  Pyramid. 

Apertura  tympanica  canaliculi  chordae. 


THE  MIDDLE   EAR,    DRUM    OB    TYMPANUM  1153 

The  Opening  of  the  Antrum  is  a  large  irregular  aperture,  which  extends  back- 
ward from  the  epitympanic  recess  and  leads  into  a  considerable  air  space,  the 
mastoid  antrum  {antrum  tympanicum) ,  which  is  the  entrance  to  the  mastoid  cells 
(p.  87).  The  antrum  communicates  with  large  irregular  cavities  contained 
in  the  interior  of  the  mastoid  process,  the  mastoid  air-cells.  These  cavities  vary 
considerably  in  number,  size,  and  form;  they  are  lined  by  mucous  membrane 
continuous  with  that  lining  the  cavity  of  the  tympanum. 

The  Fossa  Incudis  (Fig.  762)  is  placed  in  the  posterior  and  inferior  part  of  the 
epitympanic  recess.    It  lodges  the  short  process  of  the  incus. 

The  Prominentia  Styloideae  is  sometimes  seen  below  the  apertura  tympanica 
canaliculi  chordae.  It  is  a  prominence  produced  by  a  prolongation  of  the  styloid 
process. 

The  Pyramid  (eminentia  pyramidalis)  (Fig.  758)  is  a  conical  eminence  situated 
immediately  behind  the  fenestra  ovalis,  and  in  front  of  the  vertical  portion  of  the 
eminence  above  described ;  it  is  hollow  in  the  interior,  and  contains  the  Stapedius 
muscle;  its  summit  projects  forward  toward  the  fenestra  ovalis,  and  presents  a 
small  aperture  which  transmits  the  tendon  of  the  muscle.  The  cavity  in  the 
pyramid  is  prolonged  into  a  minute  canal,  which  communicates  with  the  aquae- 
ductus  Fallopii  and  transmits  the  nerve  which  supplies  the  Stapedius. 

The  Apertura  Tympanica  Canaliculi  Chordae  is  just  back  of  the  posterior  edge  of  the 
tympanic  membrane,  nearly  level  with  the  superior  end  of  the  manubrium  mallei. 

The  Anterior  Wall  of  the  Tympanum  (paries  carotica). — ^The  anterior  wall  of 
the  tympanum  is  bony  on  its  lower  portion.  Its  upper  part  is  the  tympanic 
opening  of  the  Eustachian  tube.  The  long  anterior  wall  contains  tympanic 
cells.  The  anterior  wall  is  wider  above  than  below;  it  corresponds  with  the 
carotid  canal,  from  which  it  is  separated  by  a  thin  plate  of  bone  (Fig.  762),  per- 
forated by  the  canaliculi  caroticotympanici,  which  transmit  the  tympanic  branch 
of  the  internal  carotid  artery  and  the  carotico-tympanic  nerves.  It  presents  for 
examination  the — 

Canal  for  the  Tensor  tympani.  Orifice  of  the  Eustachian  tube. 

The  processus  cochleariformis. 

The  orifice  of  the  canal  for  the  Tensor  tympani  and  the  orifice  of  the  Eustachian 
tube  are  situated  at  the  upper  part  of  the  anterior  wall,  being  incompletely  sepa- 
rated from  each  other  by  a  thin,  delicate,  horizontal  plate  of  bone,  the  processus 
cochleariformis  (septum  canalis  musculotubarii)  (Figs.  49  and  758).  The  canalis 
musculotubarius  is  divided  by  this  long  process  into  the  canal  for  the  Tensor 
tympani  and  the  canal  for  the  Eustachian  tube.  These  canals  run  from  the 
tympanum  forward,  inward,  and  a  little  downward,  to  the  retiring  angle  between 
the  squamous  and  petrous  portions  of  the  temporal  bone. 

The  Canal  for  the  Tensor  Tympani  (semicanalis  m.  tensoris  tympani)  (Figs.  49, 
758,  and  762)  is  the  superior  and  the  smaller  of  the  two;  it  is  rounded  and  lies 
beneath  the  forward  prolongation  of  the  tegmen  tympani.  It  extends  on  to  the 
inner  wall  of  the  tympanum  and  ends  immediately  above  the  fenestra  ovalis.  The 
processus  cochleariformis  passes  backward  below  this  part  of  the  canal,  forming 
its  outer  wall  and  floor;  it  expands  above  the  anterior  extremity  of  the  fenestra 
ovalis  and  terminates  by  curving  outward  so  as  to  form  a  pulley  over  which  the 
tendon  passes.  The  bony  wall  of  this  canal  is  incomplete,  and  the  osseous  vacancy 
is  filled  by  tough  connective  tissue. 

The  Eustachian  Tube  or  Ear  Trumpet  (tuba  auditiva  [Eustachii])  (Figs.  49, 
758,  and  759)  is  the  channel  through  which  the  tympanum  communicates  with 
the  pharynx.  Its  length  is  an  inch  and  a  half  (36  mm.),  and  its  direction 
downward,  inward,  and  forward,  forming  an  angle  of  about  45  degrees  with 
the  sagittal  plane  and  one  of  from  30  to  40  degrees  with  the  horizontal  plane. 

73 


1154 


THE    ORGANS    OF  SPECIAL    SENSE 


The  canal  for  the  Eustachian  tube  (semicanalis  tuhae  auditivae)  (Fig.  759)  is  formed 
partly  of  bone,  partly  of  cartilage  and  fibrous  tissue. 

The  Osseous  Portion  {"pars  ossea  tuhae  auditivae  or  semicanalis  tuhae  auditivae) 
is  about  half  an  inch  in  length.  It  is  the  outer  portion  of  the  tube.  It  commences 
in  the  anterior  wall  of  the  tympanum,  below  the  processus  cochleariformis  {ostium 
tympanicum  tuhae  auditivae),  and,  gradually  narrowing,  terminates  at  the  angle 
of  junction  of  the  petrous  and  squamous  portions  of  the  temporal  bone,  its 
extremity  presenting  a  jagged  margin  which  serves  for  the  attachment  of  the 
cartilaginous  portion.  The  roof  of  the  osseous  portion  is  the  tegmen  tympani. 
The  inner  wall  is  formed  in  part  by  the  inner  wall  of  the  tympanum  and  in  part 
by  the  canal  for  the  Tensor  tympani  muscle.  The  outer  wall  is  the  tympanic 
portion  of  the  temporal  bone.  The  floor  is  a  groove  which  near  the  tympanum 
contains  the  openings  of  air-cells  {ceUulae  pneuviatici  tubarii). 


MEMBRANA 
TYMPANI 


PHARYNGEAL  OPEN- 
ING  OF  TUBE 


Fig.  759. — Eustachian  tube,  laid  open  by  a  cut  in  its  long  axis.     (Testut.) 


The  Cartilaginous  Portion  (pars  cartilaginea  tuhae  auditivae),  about  an  inch  in 
length,  is  formed  of  a  triangular  plate  of  elastic  fibro-cartilage  (cartilago  tuhae 
auditivae),  the  apex  of  which  is  attached  to  the  margin  of  the  inner  extremity  of 
the  osseous  canal,  while  its  base  lies  directly  under  the  mucous  membrane  of 
the  naso-pharynx,  where  it  forms  an  elevation  or  cushion  above  and  behind  the 
pharyngeal  orifice  of  the  tube.  The  upper  edge  of  the  cartilage  is  curled  upon 
itself,  being  bent  outward  so  as  to  present  on  transverse  section  the  appearance  of 
a  hook  (lamina  lateralis) ;  a  groove  or  furrow  is  thus  produced,  which  opens  below 
and  externally,  and  this  part  of  the  canal  is  completed  by  fibrous  membrane.  On 
transverse  section  the  cartilage  exhibits  the  laminae  which  above  are  continuous 
with  each  other:  the  hard,  thick  lamina  medialis  and  the  thin  and  hooked  lamina 
lateralis.  The  cartilage  of  the  Eustachian  tube,  with  a  hood  plate  of  cartilage, 
forms  the  posterior  portion  of  the  inner  wall  (the  lamina  medialis).  The  cartilage 
is  fixed  to  the  base  of  the  skull,  and  lies  in  a  groove  (sulcus  tuhae  auditivae) 
between  the  petrous-temporal  and  the  greater  wing  of  the  sphenoid;  this  groove 
ends  opposite  the  middle  of  the  internal  pterygoid  plate,  in  a  projection,  the 


THE  MIDDLE   EAR,    DRUM    OB    TYMPANUM 


1155 


processus  tubarius.  At  the  pharyngeal  orifice  the  entire  wall  of  the  tube  is  cartil- 
aginous, hut  the  breadth  of  the  cartilage  progressively  lessens  as  the  isthmus  is 
approached.  Here  and  there  the  cartilage  is  deficient  or  pieces  lie  separate  from 
the  rest,  the  spaces  between  the  islands  being  occupied  by  fibrous  tissue.  The  Ten- 
sor palati  muscle  is  placed  to  the  outer  side  of  the  tube.  The  fibres  of  the  muscle 
which  take  origin  from  the  lamina  lateralis  are  known  as  the  dilator  tubae  muscle  of 
Rudinger.  The  Tensor  palati  muscle  and  the  mucous  membrane  of  the  pharynx  lie  to 
the  inner  side  of  the  tube.  The  under  and  outer  portion  of  the  canal  is  completed 
by  the  membranous  part  {lamina  membranacea) ,  which  is  a  strong  fibrous  mem- 
brane, passing  between  the  two  margins  of  the  cartilage.  It  is  thin  above,  but  thick 
below,  and  the  thick  portion  is  called  the  fascia  salpingopharyngea  of  Trbltsch, 
and  from  it  arise  some  fibres  of  the  Tensor  palati  (m.  salpingopharyngeus).  The 
cartilaginous  and  bony  portions  of  the  tube  are  not  in  the  same  plane,  the  former 


POSTERIOR    TYMPANO- 
MALLEOLAR  FOLD 


FLACCID  PORTION   OF 
MEMBRANA  TYMPANI 


POSTERIOR 

TYMPANIC. 

SPINC 


EXTERNAL 
AUDITORY- 
MEATUS 


MARGIN    OF 
MEMBRANA 

TYMPANI  ' 
OR  LIMBUS 


MALLEOLAR 
PROMINENCE. 


NOTCH  OF 
RIVINUS 


ANTERIOR 
TYMPANO- 
MALLEOLAR 
FOLD 

HANDLE    OF 
MALLEOLUS 
SEEN  THROUGH 
MEMBRANE 


TENSE  PORTION 
OF  MEMBRANA 
TYMPANI 


I  Fig.  760. — The  right  membrana  tympani,  viewed  from  the  outside,  from  in  front,  and  from  below.    (Spalteholz.) 


^■inclining  downward  a  little  more  than  the  latter.  They  join  each  other  at  a  large 
^■obtuse  angle,  open  below.  The  diameter  of  the  canal  is  not  uniform  throughout, 
^^being  greatest  at  the  pharyngeal  orifice  and  least  at  the  junction  of  the  bony  and 
cartilaginous  portions,  where  it  is  named  the  isthmus  (isthmus  tubae  audiiivae) ; 
it  again  expands  somewhat  as  it  approaches  the  tympanic  cavity.  The 
position  and  relations  of  the  pharyngeal  orifice  (ostium  pharyngeum  tubae 
aiuliticae)  are  described  with  the  anatomy  of  the  naso-pharynx.  Through  this 
canal  the  mucous  membrane  of  the  pharynx  is  continuous  with  that  which  lines 
the  tympanum.  The  mucous  membrane  is  covered  with  ciliated  epithelium  and 
is  thin  in  the  osseous  portion,  while  in  the  cartilaginous  portion  it  contains  many 
mucous  glands  and  near  the  pharyngeal  orifice  a  considerable  amount  of  adenoid 
tissue,  which  has  been  named  by  Gerlach  the  tube-tonsil.  The  tube  is  opened 
during  deglutition  by  the  Salpingo-pharyngeus  and  Dilator  tubae  muscles. 

The  Drumhead  or  Membrana  Tympani  (Figs.  757,  759,  760,  and  761).— The 
membrana  tympani  or  drumhead  separates  the  cavity  of  the  tympanum  from 


1156 


THE    ORGANS    OF  SPECIAL  SENSE 


the  bottom  of  the  external  meatus.  It  is  a  thin,  semi-transparent  membrane, 
nearly  oval  in  form,  somewhat  broader  above  than  below,  and  directed  very 
obliquely  downward  and  inward,  so  as  to  form  an  angle  of  about  55  degrees 
with  the  floor  of  the  meatus  (Fig.  757) .  The  antero-inferior  portion  is,  there- 
fore, placed  at  the  greatest  distance  from  the  external  orifice  of  the  meatus.  It 
is  asserted  that  in  musicians  the  membrana  tympani  is  placed  more  nearly  per- 
pendicular, and  that  in  deaf-mutes  and  cretins  it  is  placed  more  obliquely  than 
the  usual  55  degrees.  In  a  newborn  child  the  membrana  tympani  is  almost  hori- 
zontal. The  greatest  diameter  of  the  membrana  tympani  is  from  9  to  10  mm.; 
its  least  diameter  is  from  8  to  9  mm.^  The  greater  part  of  its  circumference  (limhus 
membranae  tympanae)  is  thickened  to  form  an  annular  ring  (annulus  fibrocartil- 
agineus),  which  is  fixed  in  a  groove,  the  sulcus  tympanicus,  at  the  inner  extremity 


SUPERIOR   LIGAMENT 
OF    MALLEOLUS 


EPITYMPANIC 
RECESS 


ANTERIOR  LIGAMENT 

AND   ANTERIOR 

PROCESS  OF 

MALLEOLUS 

INSERTION 
OF  TENSOR 
TYMPAN 
MUSCL 


GLASSCrtlAN 
FISSURE 


NCCK  OF 

MALLEUSV    ,f 


ARTICULAR   SURFACE 
TOR   BODY  OF  INCUS 


FLACCID  PORTION  OF 
MEMBRANA  TYMPANI 


POSTERIOR 

TYMPANIC 

SPINE 


TYMPANIC 
ORIFICE 
OF  CANAL 
FOR   CHORDA 
TYMPANI 
NERVE 


EUSTACHIAN 
TUBE 


TENSE  PORTION   OF 
MEMBRANA  TYMPANI 


Fig.  761. — The  right  membrana  tympani  with  the  hammer  and  the  chorda  tympani,  viewed  from  within, 
from  behind,  and  from  above.      (Spalteholz.) 

of  the  external  meatus.  This  sulcus  is  deficient  superiorly  at  the  incisure  or  notch 
of  Rivinus  (incisura  tym'panica  \Rivini\)  (Fig.  760) .  From  the  extremities  of  the 
notch  (spinae  tympanicae)  two  folds  pass  and  converge  to  the  short  process  of  the 
malleus  (Fig.  760) .  One  is  known  as  the  anterior  tympanomalleolar  fold  or  ligament 
(plica  membrana  tyrnpani  anterior).  The  other  is  known  as  the  posterior  tympano- 
malleolar fold  or  ligament  (plica  membrana  tympani  posterior).  These  are  not  to 
be  confused  with  the  anterior  and  posterior  malleolar  folds  (p.  1162).  The  small, 
somewhat  triangular  part  of  the  membrane  situated  above  these  folds  is  lax  and 
thin,  and  is  named  the  flaccid  portion  or  the  membrana  flaccida  of  Shrapnell  (Figs. 
760  and  761).  In  it  a  small  orifice  is  sometimes  seen,  which  is  of  artificial  and 
pathological  formation.  The  larger  lower  portion  of  the  drum  membrane  is 
stretched  tightly,  and  is  called  the  tense  portion  or  pars  tensa  (Figs.  760  and  761). 


'  Prof.  Cunningham's  Text-book  of  Anatomy. 


THE  MIDDLE   EAR,    DRUM    OB    TYMPANUM 


1157 


The  handle  of  the  malleus  is  firmly  attached  to  the  inner  aspect  of  the  mem- 
brana  tympani  as  far  as  its  centre  (Fig.  761).  It  draws  the  central  part  of  the 
membrane  inward  and  makes  its  outer  aspect  concave.  The  most  depressed  part 
of  the  concavity  is  called  the  umbo  or  navel  {umbo  membranae  tymj)anae)(Fig.  760). 
The  walls  of  the  umbo  are  convex  outward. 

On  the  outer  surface  of  the  drum  membrane  a  light  stripe  (stria  malleolaris)  is 
seen.  It  runs  from  in  front  and  above  downward  and  backward,  and  is  produced 
by  the  handle  of  the  malleus,  showing  through  the  membrane  (Fig.  760). 

Structure. — This  membrane  is  composed  of  three  layers:  an  external  (cw^icw/ar), 
a  middle  {fibrous),  and  an  internal  (mucous).  The  cuticular  lining  (stratum  cuia- 
neum)  is  derived  from  the  integument  lining  the  meatus.  The  fibrous  or 
middle  layer  (membrana  propria)  consists  of  two  strata:  an  external,  of  radiating 
fibres  (stratum  radiatum),  which  diverge  from  the  handle  of  the  malleus,  and  an 

JUNCTION   BETWEEN   MAS- 
^===_  TOID  ANTRUM   AND 

ePITYMPANIC  RECESS 
TEGMEN 
TYMPANI 

EPITYMPANIC 
RECESS 

PROMINENCE  OF  EXTERNAL 
SEMICIRCULAR  CANAL 

PROMINENCE  OF  AQUEDUCT 
OF  FALLOPIUS 

TENDON   OF 
STAP.EDIUS  MUSCLE 
PLICA 
STAPEDIUS 

PROCESSUS 

'm'iff^m'g^mm^  /  cochleariformis 

W'^^Wf^^^L  /  /  ^^  TENSOR  TYMPANI 

^mmmoi.        l  /  ^  muscle  (cut  through) 


WALL  OF 
LABYRINTH 


posterior 
sinus 

pyramidal 
eminence 

tympanic 

SINUS 


Fig.  762. 


"it"iiiii'Mr"'^i""~~iii '"" '  /  I         \  ==^ 

FOSSULA   OF  JUGULAR  TYMPANIC 

FENESTRA  ROTUNDA  WALL  PLEXUS 

-The  medial  wall  and  part  of  the  posterior  and  anterior  walls  of  the  right  tympanic  cavity,  lateral 
view.     (Spalteholz.) 


internal,  of  circular  fibres  (stratum  circulare),  which  are  plentiful  around  the  cir- 
cumference, but  sparse  and  scattered  near  the  centre  of  the  membrane.  Branched 
or  dendritic  fibres,  as  pointed  out  by  Griiber,  are  also  present,  especially  in  the 
posterior  half  of  the  membrane.  Both  muscular  layers  are  connected  to  the 
annulus  fibrocartilagineus,  and  both  are  absent  in  the  pars  flaccida.  The  inner 
or  epithelial  layer  is  mucous  membrane  (stratum  mucosum),  which  is  a  portion 
of  the  mucous  membrane  of  the  drum  cavity. 

The  Arteries  are  derived  from  the  deep  auricular  branch  of  the  internal  maxil- 
lary, which  ramifies  beneath  the  cuticular  layer  and  from  the  stylo-mastoid  branch 
of  the  posterior  auricular  and  tympanic  branch  of  the  internal  maxillary,  which 
are  distributed  on  the  mucous  surface.  The  arteries  of  the  cutaneous  set  anas- 
tomose with  the  arteries  of  the  mucous  set  by  minute  branches  which  penetrate 
the  drum  membrane  near  its  margin.  The  superficial  veins  open  into  the  external 
jugular;  those  on  the  mucous  surface  drain  themselves  partly  into  the  lateral 
sinus  and  veins  of  the  dura  mater  and  partly  into  a  plexus  on  the  Eustachian  tube. 


1158 


THE    OBGANS    OF  SPECIAL   SENSE 


The  outer  surface  of  the  drum  membrane  receives  its  nervous  supply  from  the 
auriculo-temporal  branch  of  the  inferior  maxillary  and  the  auricular  branch  of 
the  vagus.  The  inner  surface  is  supplied  by  the  tympanic  branch  of  the  glosso- 
pharyngeal. 

There  are  two  sets  of  lymphatics,  the  cutaneous  and  mucous,  which  freely 
communicate.  The  spaces  between  the  dendritic  fibres  of  Griiber  are  lymph- 
spaces  (Kessel). 

The  Ossicles  of  the  Tympanum  (Ossicula  Auditus)  (Fig.  763). 

The  tympanum  contains  in  its  upper  part  a  chain  of  movable  bones,  three  in 
number,  the  malleus,  incus,  and  stapes.    The  first  is  attached  to  the  membrana 

tympani,  the  last  to  the  fenestra  ovalis.  The 
incus  is  placed  between  the  two,  and  is  con- 
nected to  both  by  delicate  articulations. 

The  Malleus  or  Hammer  (Fig.  764).— The 
malleus  or  hammer,  so  named  from  its  fancied 
resemblance  to  a  hammer,  is  placed  farthest  in 
front  and  outward.  It  consists  of  a  head,  neck, 
and  three  processes — the  handle  or  manubrium, 
the  processus  gracilis,  and  the  processus  brevis. 
The  Head  (capitulum  mallei). — The  head  is 
the  large  upper  extremity  of  the  bone,  and  is 
situated  in  the  epitympanic  recess  (Fig.  761). 
It  is  oval  in  shape,  and  articulates  posteriorly 
with  the  incus,  being  free  in  the  rest  of  its  ex- 
tent. The  facet  for  articulation  with  the  incus 
is  covered  with  cartilage,  is  constricted  near 
the  middle,  and  is  divided  by  a  ridge  into  an 
upper,  larger,  and  a  lower,  lesser  part,  which 
form  nearly  a  right  angle  with  each  other.  Op- 
posite the  constriction  the  lower  margin  of  the 
facet  projects  in  the  form  of  a  process,  the 
cog-tooth  or  spur  of  the  malleus.  On  the  back 
of  the  head  below  the  spur  is  a  crest  (crista 
mallei),  to  which  the  posterior  ligament  of  the  malleus  is  attached. 

The  Neck  (collum  mallei). — The  neck  is  the  narrow  contracted  part  just  beneath 
the  head;  and  below  this  is  a  prominence,  to  which  the  various  processes  are 
attached.  The  outer  surface  of  the  neck  faces  the  membrana  flaccida.  The 
chorda  tympani  nerve  crosses  the  inner  surface'  (Fig.  761). 

The  Handle  or  Manubrium  (manubrium  mallei).— The  manubrium  is  a  vertical 
process  of  bone,  which  is  connected  by  its  outer  margin  with  the  fibrous  layer  of 
the  membrana  tympani,  its  entire  length  being  fastened  to  the  fibrous  layer  of 
the  drum  membrane  by  its  own  periosteum  and  by  a  layer  of  cartilage  (Griiber) 
(Figs.  761  and  763).  It  is  directed  downward,  inward,  and  backward;  it  decreases 
in  size  toward  its  extremity,  where  it  is  curved  slightly  forward,  and  is  flattened 
from  within  outward,  The  handle  forms  a  variable  angle  with  the  head  of  the 
hammer.  It  averages  about  130  degrees,  but  is  always  greater  in  the  right  ear 
than  in  the  left.  It  forms  an  angle  with  the  horizontal,  averaging  on  the  right 
side  50  degrees  and  on  the  left  side  45  degrees  (Spalteholz).  Internally  the 
handle  is  covered  by  the  mucous  membrane  of  the  tympanum.  On  the  inner 
side,  near  its  upper  end,  is  a  slight  projection,  into  which  the  tendon  of  the 
Tensor  tympani  is  inserted  (Fig.  761). 

The  Processus  Gracilis  or  Long  Process  (processus  anterior  [Folii]). — The  pro- 
cessus gracilis  is  a  long  and  very  delicate  process,  which  passes  from  the  front  of 


Fig.  763. — Chain  of  ossicles  and  their  liga^ 
ments,  seen  from  the  front  in  a  vertical,  tranS' 
verse  section  of  the  tympanum.     (Testut.) 


THE    OSSICLES    OF  THE    TYMPANUM 


1159 


the  neck  forward  and  outward  to  the  Glaserian  fissure,  to  which  it  is  connected 
by  hgamentous  fibres.  In  the  foetus  this  is  the  longest  process  of  the  malleus,  and 
is  in  direct  continuity  with  the  cartilage  of  Meckel. 

The  Processus  Brevis  {processus  lateralis). — The  processus  brevis  is  a  slight 
conical  projection,  which  springs  from  the  root  of  the  manubrium ;  it  is  directed 
outward,  and  is  attached  to  the  upper  part  of  the  tympanic  membrane  by  cartilage 
and  to  the  margins  of  the  notch  of  Rivinus  by  the  two  malleolar  folds. 


j^HfM     AURICULAR 

■PH_  SURFACE 

^^^^3m 

^Kfl        FOR  BODY 

^^^^ 

^^Jg        OF  INCUS 

TOOTH^^ 

:Migea 

OR  COG        \^k 

WgL     INSERTION  OF 

^BV     EXTERNAL 

NECK^H 

^^f       LIGAMENT 

HL       OF  MALLEUS 

INSERTION         1^ 

^^^^^^ 

OF  TENSOR        L  -g 

^^^^^B 

TYMPANI     J^  ^ 

^^^PP'^ 

MUSCLEjf^^ 

l^^^l 

^SHOHT 

PROCESS 

^^MANUBRIUM 

Fig.  764. — The  right  malleus:  a,  viewed  from  in  front;  b,  viewed  from  behind.     (Spaltehols.) 

The  Incus  or  Anvil  (Fig.  765). — The  incus  or  anvil  has  received  its  name  from 
its  supposed  resemblance  to  an  anvil,  but  it  is  more  like  a  bicuspid  tooth  with  two 
roots,  which  differ  in  length,  and  are  widely  separated  from  each  other.  It  con- 
sists of  a  body  and  two  processes.  The  body  and  the  short  process  are  placed  in 
the  epitympanic  recess  (Fig.  763) . 

The  Body  {corpus  incudis). — The  body  is  somewhat  quadrilateral,  but  compressed 
laterally.  On  its  anterior  surface  is  a  deeply  concavo-convex  facet,  which  articu- 
lates with  the  head  of  the  malleus,  and  the  lower  part  is  hollowed  for  the  spur  of  the 
malleus.  In  the  fresh  state  the  articular  surface  is  covered  with  cartilage  and  the 
joint  is  lined  with  synovial  membrane. 


ARTICULAR  SURFACE 
FOR  HEAD  OF  MALLEUS 


ARTICULAR 
SURFACE  FOR 
HEAD  OF 
MALLEUS 


LENTICULAR 
PROCESS 


Fig.  765. — The  right  incus:  a,  lateral  view;  h,  medial  and  front  view.     (Spalteholz.) 


Processes. — The  two  processes  diverge  from  one  another  at  an  angle  of  from 
90  to  100  degrees. 

The  Short  Process  {cms  breve),  somewhat  conical  in  shape,  projects  neai-ly 
horizontally  backward,  and  articulates  with  a  depression,  the  incus  fossa  {fossa 
incudis),  in  the  lower  and  back  part  of  the  epitympanic  recess. 

The  Long  Process  {crus  longum),  longer  and  more  slender  than  the  preceding, 
descends  nearly  vertically  behind  and  parallel  to  the  handle  of  the  malleus,  and, 


1160  THE    ORGANS    OF  SPECIAL    SENSE 

bending  inward,  terminates  in  a  rounded  globular  projection,  the  os  orbiculare  or 
lenticular  process  {processus  lenticularis) ,  which  is  tipped  with  cartilage,  and  articu- 
lates with  the  head  of  the  stapes.  In  the  foetus  the  os  orbiculare  exists  as  a  separate 
bone. 

The  Stapes  or  Stirrup  (Fig.  766). — The  stapes  or  stirrup,  so  called  from  its 
close  resemblance  to  a  stirrup,  consists  of  a  head,  neck,  two  crura,  and  a  base. 

The  Head  (capitulum  stapedis). — The  head  presents  a  depression,  tipped  with 
cartilage,  which  articulates  with  the  os  orbiculare. 

The  Neck. — ^The  neck,  the  constricted  part  of  the  bone  succeeding  the  head, 
receives  the  insertion  of  the  Stapedius  muscle. 

The  Crura. — ^The  two  crura  {crus  anterius  and  crus  posterius)  diverge  from  the 
neck  and  are  connected  at  their  extremities  by  a  flattened,  oval-shaped  plate,  the 
foot-plate  or  base  (basis  stapedis),  which  forms  the  foot-plate  of  the  stirrup  and 
is  fixed  to  the  margin  of  the  fenestra  ovalis  by  ligamentous  fibres.  The  foot- 
plate almost  fills  the  oval  window  (Fig.  757.  Of  the  two  crura,  the  anterior  is 
shorter  and  less  curved  than  the  posterior.    In  a  recent  specimen  a  membrane  will 

be  observed  filling  the  space  between  the 
crura  and  the  foot-plate.  This  mem- 
brane is  connective  tissue  and  is  called 


GROOVE  FOR  0  ^Yyq  membrana  obturatoria  stapedis.    The 


OBTURATOR 


OP  s^^'yy^^   ^^^^^©    stirrup  lies  practically  horizontal. 
*'*^"Rus^f        ^J  POSTERIOR  I    "  Articulations  of  the  Ossicles  of  the  Tym- 

DA«r  or       panum   (articulationes  ossiculorum  audi- 
tus)  (Fig.  763). — These  small  bones  are 
BASE  OF  STAPES  couuccted  with  each  other  and  with  the 

Fig.  766. — The  right  stirrup:  o,  viewed  from  above;  11        i>    i       ^  1       !•  1 

b,  medial  vein.    (Spaitehoiz.)  walls  oi  the  tympanum  by  ligaments,  and 

are  moved  by  small  muscles.  There  is  an 
articulation  between  the  head  of  the  hammer  and  the  body  of  the  anvil ;  one 
between  the  os  orbiculare  of  the  anvil  and  the  head  of  the  stirrup;  and  there  is  a 
syndesmosis  between  the  margins  of  the  oval  window  and  the  base  of  the  stirrup. 
The  bones  are  fastened  in  the  tympanum,  the  handle  of  the  hammer  being 
fastened  in  the  drum  membrane  and  the  base  of  the  stirrup  to  the  oval  window. 
The  articular  surfaces  of  the  malleus  and  incus  and  the  orbicular  process  of  the 
incus  and  head  of  the  stapes  are  covered  with  cartilage,  connected  together  by 
delicate  capsular  ligaments  and  lined  by  synovial  membrane. 

Ligaments  Connecting  the  Ossicula  with  the  Walls  of  the  Tympanum  (ligamenta 
ossiculorum  auditus). — The  malleus  is  fastened  to  the  wall  of  the  tympanum  by 
three  ligaments:  the  anterior,  superior,  and  external  ligaments. 

The  Anterior  Ligament  of  the  Malleus  (ligamentum  mallei  anterius)  consists  of 
two  parts,  the  band  of  Meckel  and  the  anterior  ligament  of  Helmholtz. 

The  band  of  Meckel  is  attached  to  the  base  of  the  processus  gracilis  and  passes 
through  the  Glaserian  fissure  to  reach  the  spine  of  the  sphenoid.  It  was  formerly 
described  by  Sommering  as  a  muscle,  and  it  was  called  the  laxator  tympani 
muscle.  It  is  now,  however,  believed  by  most  observers  to  consist  of  ligamentous 
fibres  only. 

The  anterior  ligament  of  Helmholtz  extends  from  the  anterior  margin  of  the 
notch  of  Rivinus  to  the  anterior  portion  of  the  malleus,  just  above  the  processus 
gracilis. 

The  Superior  Ligament  of  the  Malleus  (ligamentum  mallei  superius)  is  a  delicate 
round  bundle  of  fibres  which  descends  perpendicularly  from  the  roof  of  the  epi- 
tympanic  recess  to  the  head  of  the  malleus.  It  is  sometimes  called  the  suspensory 
ligament. 

The  External  Ligament  of  the  Malleus  (ligamentum  mallei  laterale)  is  a  triangular 
plane  of  fibres  passing  from  the  posterior  part  of  the  notch  in  the  tympanic  ring 


THE    OSSICLES    OF    THE    TYMPANUM  ngi 

(incisura  Rivini)  to  the  crest  of  the  malleus.  The  posterior  portion  of  the  external 
ligament  is  sometimes  called  the  posterior  ligament  of  Helmholtz  (ligamentum 
mallei  posterius  [Hehnholtzi]).  The  malleus  rotates  around  an  axis  composed  of 
the  external  and  anterior  ligaments,  hence  these  two  ligaments  constitute  what 
Helmholtz  called  the  axis  ligament  of  the  malleus. 

The  incus  is  fastened  to  the  wall  of  the  tympanum  by  two  ligaments,  the  poste- 
rior and  the  superior. 

The  Posterior  Ligament  of  the  Incus  (ligamentum  incudis  posterius)  is  a  short, 
thick,  ligamentous  band  which  connects  the  extremity  of  the  short  process  of  the 
incus  to  the  posterior  and  lower  part  of  the  epitympanic  recess,  near  the  margin 
of  the  opening  of  the  mastoid  cells. 

A  Superior  Ligament  of  the  Incus  (ligamentum  incudis  superius)  has  been 
described  by  Arnold,  but  it  is  little  more  than  a  fold  of  mucous  membrane. 

The  inner  surface  and  the  circumference  of  the  base  of  the  stapes  are  covered  with 
hyaline  cartilage,  and  the  annular  ligament  of  the  stapes  (ligamentum  annulare  haseos 
stapedis)  connects  the  circumference  of  the  base  to  the  margin  of  the  fenestra  ovalis. 

The  Muscles  of  the  Tympanum  (m.  ossiculorum  auditus). — The  muscles  of  the 
tympanum  are  two: 

Tensor  tympani.  Stapedius. 

The  Tensor  Tympani  (m.  tensor  tympani)  (Fig.  762) ,  the  larger,  is  contained  in 
the  bony  canal  above  the  osseous  portion  of  the  Eustachian  tube,  from  which  it 
is  separated  by  the  processus  cochleariformis.  It  arises  from  the  under  surface  of 
the  petrous  bone,  from  the  cartilaginous  portion  of  the  Eustachian  tube,  and  from 
the  osseous  canal  in  which  it  is  contained.  Passing  backward  through  the  canal, 
it  terminates  in  a  slender  tendon  which  enters  the  tympanum  and  makes  a  sharp 
bend  outward  around  the  extremity  of  the  processus  cochleariformis,  and  is 
inserted  into  the  handle  of  the  malleus  near  its  root.  Its  nerve-supply  is  from 
the  motor  root  of  the  fifth  cranial  nerve  by  way  of  the  otic  ganglion. 

The  Stapedius  {m.  stapedius)  (Fig.  762)  arises  from  the  side  of  a  conical  cavity 
hollowed  out  of  the  interior  of  the  pyramid;  its  tendon  emerges  from  the  orifice 
at  the  apex  of  the  pyramid,  and,  passing  forward,  is  inserted  into  the  neck  of  the 
stapes.  Its  surface  is  aponeurotic,  its  interior  fleshy,  and  its  tendon  occasionally 
contains  a  slender  bony  spine,  which  is  constant  in  some  mammalia.  It  is 
supplied  by  the  tympanic  branch  of  the  facial  nerve. 

Actions. — The  Tensor  tympani  draws  the  handle  of  the  malleus  inward  and 
thus  heightens  the  tension  of  the  drum  membrane.  It  also  causes  slight  rotation 
of  the  bone  around  its  long  axis.  When  the  Stapedius  contracts  it  draws  the 
head  of  the  stirrup  backward,  and  in  consequence  the  anterior  end  of  the  foot- 
plate passes  outward  toward  the  tympanum,  and  the  posterior  end  inward  toward 
the  vestibule,  and  the  annular  ligament  is  made  tense. 

Movements  of  the  Ossicles  of  the  Tympanum. — The  chain  of  bones  is  a  lever-like 
arrangement,  by  means  of  which  the  vibrations  of  the  membrana  tympani  are 
transferred  to  the  membrane  covering  the  oval  window,  and  from  this  to  the  peri- 
lymph in  the  labyrinth.  When  the  drum  membrane  moves  inward,  the  handle 
of  the  malleus  moves  with  it.  The  movement  of  the  malleus  moves  the  incus,  and 
the  movement  of  the  incus  drives  the  foot  of  the  stapes  toward  the  labyrinth. 
When  the  handle  of  the  malleus  moves  inward,  the  spur  on  the  head  becomes 
locked  with  the  body  of  the  incus.  During  outward  movement  it  is  unlocked. 
The  ordinary  outward  movement  of  the  drum  membrane  causes  the  above- 
described  movements  to  be  reversed.  When  there  is  overforcible  outward  move- 
ment the  incus  does  not  go  outward  quite  as  far  as  the  malleus,  but  slides  at  the 
joint  between  the  malleus  and  incus.  This  reluctance  of  the  incus  saves  the  foot 
of  the  stapes  from  being  pulled  away  from  the  oval  window. 


IIQ2  THE    0BGAN8    OF  SPECIAL   SENSE 

The  Mucous  Membrane  of  the  Tympanum  {tunica  mucosa  tympanica). — The 
mucous  membrane  of  the  tympanum  is  continuous  with  the  mucous  membrane 
of  the  naso-pharynx  through  the  Eustachian  tube,  and  is  firmly  united  to  the 
periosteum.  It  invests  the  ossicula,  and  the  muscles  and  nerves  contained  in  the 
tympanic  cavity;  forms  the  internal  layer  of  the  membrana  tympani,  and  the  outer 
layer  of  the  membrana  tympani  secundaria,  and  is  reflected  into  the  mastoid 
antrum  and  air-cells,  which  it  lines  throughout.  It  forms  several  vascular  folds 
(plicae),  which  extend  from  the  walls  of  the  tympanum  to  the  ossicles.  In  these 
folds  the  ossicles  are  enveloped. 

The  anterior  malleolar  fold  (plica  malleolaris  anterior)  comes  off  from  the  mem- 
brana tympani  between  the  anterior  edge  of  the  notch  of  Rivinis  and  the  handle 
of  the  malleus,  envelops  the  processus  gracilis  of  the  malleus,  the  anterior  liga- 
ment of  the  malleus,  and  the  anterior  portion  of  the  chorda  tympani  nerve,  and 
terminates  in  a  free  concave  edge  (Spalteholz).  The  posterior  malleolar  fold  (plica 
malleolaris  posterior)  is  the  larger  of  the  two.  It  comes  off  from  the  margin  of  the 
notch  of  Rivinis,  envelops  the  external  ligament  of  the  malleus,  the  posterior  part 
of  the  chorda  tympani  nerve,  is  attached  to  the  handle  of  the  malleus,  and  ends 
in  a  free  concave  margin  (Spalteholz).  The  fold  of  the  incus  (plica  incudis)  takes 
origin  from  the  roof  of  the  epitympanic  recess  and  passes  to  the  body  and  short 
process  of  the  incus;  and  a  similar  fold  passes  from  the  head  of  the  malleus  to  the 
anterior  wall  of  the  epitympanic  recess.  The  entire  stapes,  with  its  obturator 
membrane,  is  enwrapped  by  the  fold  of  the  stapes  (plica  stapedis).  This  fold  also 
ensheaths  the  tendon  of  the  stapedius  muscle  and  often  reaches  to  the  posterior 
wall  of  the  cavity  of  the  tympanum.  The  mucous  membrane  over  the  round 
window  forms  the  membrana  tympani  secundaria.  These  folds  separate  off  pouch- 
like cavities,  and  give  the  interior  of  the  tympanum  a  somewhat  honey-comb 
appearance.  One  of  these  pouches  is  well  marked — viz.,  the  pouch  of  Prussak, 
which  lies  between  the  neck  of  the  malleus  and  the  membrana  flaccida. 

The  inferior  external  pouch  of  the  tympanum  or  the  pouch  of  Prussak  (recessus 
membranae  tympani  superior)  is  between  the  flaccid  portion  of  the  membrana 
tympani,  the  external  ligament  of  the  malleus,  and  the  neck  of  the  mal- 
leus. The  anterior  and  posterior  malleolar  folds  with  the  tympanic  membrane 
form  two  pouches.  These  are  the  anterior  and  posterior  pouches  or  recesses  of 
Troltsch  (recessus  membranae  tympani,  anterior  and  posterior).  The  anterior  pouch 
is  blind  above  and  has  a  slit-like  opening  below.  The  posterior  pouch  is  con- 
tinued into  the  blind  superior  pouch  of  the  drum  membrane.  In  the  tympanum 
this  membrane  is  pale,  thin,  slightly  vascular,  and  covered  for  the  most  part  with 
columnar  ciliated  epithelium,  but  that  covering  the  pyramid,  ossicula,  and  mem- 
brana tympani  possesses  a  flattened,  non-ciliated  epithelium.  In  the  antrum  and 
mastoid  cells  its  epithelium  is  also  non-ciliated.  In  the  osseous  portion  of  the 
Eustachian  tube  the  membrane  is  thin ;  but  in  the  cartilaginous  portion  it  is  very 
thick,  highly  vascular,  covered  with  ciliated  epithelium,  and  provided  with  numer- 
ous mucous  glands. 

The  Arteries  of  the  Tympanum. — The  arteries  supplying  the  tympanum  are  six 
in  number.  Two  of  them  are  larger  than  the  rest — viz.,  the  tympanic  branch  of 
the  internal  maxillary,  which  enters  by  way  of  the  Glaserian  fissure  and  supplies 
the  membrana  tympani ;  and  the  stylo-mastoid  branch  of  the  posterior  auricular, 
which  passes  through  the  stylo-mastoid  foramen  and  the  aqueduct  of  Fallopius, 
and  supplies  the  inner  wall  and  floor  of  the  tympanum,  the  mastoid  cells,  and 
antrum  and  the  Stapedius  muscle.  This  vessel  anastomoses  around  the  drum 
membrane  with  the  tympanic.  The  middle  meningeal  sends  a  small  branch  to 
the  Tensor  tympani  muscle  near  its  origin.  The  petrosal  branch  of  the  middle 
meningeal  enters  the  tympanum  by  way  of  the  hiatus  Fallopii.  Minute  branches 
from  the  posterior  branch  of  the  middle  meningeal  pass  through  the  petro- 


THE  INTERNAL    EAR    OR    LABYRINTH  1153 

squamous  fissure  and  are  distributed  to  the  antrum  and  epitympanie  recess 
(Cunningham).  Two  tympanic  branches  come  off  from  the  internal  carotid 
artery  in  its  course  through  the  carotid  canal.  A  branch  from  the  ascending 
pharyngeal  and  another  from  the  Vidian,  accompany  the  Eustachian  tube.  The 
two  tympanic  branches  from  the  internal  carotid  are  given  off  in  the  carotid  canal 
and  perforate  the  thin  anterior  wall  of  the  tympanum. 

The  Veins  of  the  Tympanum. — The  veins  of  the  tympanum  terminate  in  the 
pterygoid  plexus,  the  middle  meningeal  vein,  and  the  superior  petrosal  sinus. 

The  Nerves  of  the  Tympanum. — The  nerves  of  the  tympanum  constitute  the 
tympanic  plexus  {'plexus  tympanicus  [Jacobsoni]) ,  which  ramifies  upon  the  surface 
of  the  promontory  (Fig.  7G2).  The  plexus  is  formed  by  (1)  the  tympanic  branch  of 
the  glosso-pharyngeal ;  (2)  the  small  deep  petrosal  nerve;  (3)  the  small  super- 
ficial petrosal  nerve;  and  (4)  a  branch  which  joins  the  great  superficial  petrosal. 

The  Tympanic  Branch  of  the  Glosso-pharyngeal  or  Jacobson's  Nerve  (n.  tympan- 
icus)  enters  the  tympanum  by  an  aperture  in  its  floor  close  to  the  inner  wall  and 
divides  into  branches,  which  ramify  on  the  promontory  and  enter  into  the  forma- 
tion of  the  plexus.  The  small  deep  petrosal  nerve  {n.  petrosus  profundus),  from 
the  carotid  plexus  of  the  sympathetic,  passes  through  the  wall  of  the  carotid  canal, 
and  joins  the  branches  of  Jacobson's  nerve.  The  branch  to  the  great  superficial 
petrosal  passes  through  an  opening  on  the  inner  wall  of  the  tympanum  in  front 
of  the  fenestra  ovalis.  The  small  superficial  petrosal  nerve  (w.  petrosus  super- 
ficialis  minor),  derived  from  the  otic  ganglion,  passes  through  a  foramen  in  the 
middle  fossa  of  the  base  of  the  skull  (sometimes  through  the  foramen  ovale), 
passes  backward  and  enters  the  petrous  bone  through  a  small  aperture,  situ- 
ated external  to  the  hiatus  Fallopii  on  the  anterior  surface  of  this  bone;  it  then 
courses  downward  through  the  bone,  and,  passing  by  the  gangliform  enlargement 
of  the  facial  nerve,  receives  a  connecting  filament  from  it  (Fig.  676)  and  enters  the 
tympanic  cavity,  where  it  communicates  with  Jacobson's  nerve,  and  assists  in 
forming  the  tympanic  plexus. 

The  branches  of  distribution  of  the  tympanic  plexus  are  distributed  to  the 
mucous  membrane  of  the  tympanum ;  one  special  branch  passing  to  the  fenestra 
ovalis,  another  to  the  fenestra  rotunda,  and  a  third  to  the  Eustachian  tube.  The 
small  superficial  petrosal  may  be  looked  upon  as  a  branch  from  the  plexus  to  the 
otic  ganglion. 

In  addition  to  the  tympanic  plexus  there  are  the  nerves  supplying  the  muscles. 
The  Tensor  tympani  is  supplied  by  a  branch  from  the  third  division  of  the  fifth 
through  the  otic  ganglion,  and  the  Stapedius  by  the  tympanic  branch  of  the  facial. 

The  chorda  tympani  (Figs.  758  and  761)  crosses  the  tympanic  cavity.  It  is  given 
off  from  the  facial  as  it  passes  vertically  downward  at  the  back  of  the  tympanum, 
about  a  quarter  of  an  inch  before  its  exit  from  the  stylo-mastoid  foramen.  It  passes 
from  below  upward  and  forward  in  a  distinct  canal,  and  enters  the  cavity  of  the 
tympanum  through  an  aperture,  iter  chordae  posterius,  already  described  (p.  1151), 
and  becomes  invested  with  mucous  membrane.  It  passes  forward,  through  the 
cavity  of  the  tympanum,  crossing  internal  to  the  membrana  tympani  and  over 
the  handle  of  the  malleus  to  the  anterior  inferior  angle  of  the  tympanum,  and 
emerges  from  that  cavity  through  the  iter  chordae  anterius  or  canal  of  Huguier 
(p.  1152) .  It  is  invested  by  the  fold  of  mucous  membrane  already  mentioned,  and 
therefore  lies  between  the  mucous  and  fibrous  layers  of  the  membrana  tympani. 


THE  INTERNAL  EAR  OR  LABYRINTH  (AURIS  INTERNA). 

The  internal  ear  is  the  essential  part  of  the  organ  of  hearing,  receiving  the 
ultimate  distribution  of  the  auditory  nerve.     It  is  called  the  labyrinth,  from  the 


1164 


THE    ORGANS    OF  SPECIAL   SENSE 


complexity  of  its  shape,  and  consists  of  two  parts:  the  osseous  labyrinth,  a  series 
of  cavities  channelled  out  of  the  substance  of  the  petrous  bone,  and  the  membranous 
labyrinth,  the  latter  being  contained  within  the  former. 

The  Osseous  Labyrinth  (Labyrinthus  Osseus)  (Fig.  767). 

The  osseous  labyrinth  consists  of  three  parts:  the  vestibule,  semicircular  canals, 
and  cochlea.  These  are  cavities  hollowed  out  of  the  substance  of  the  bone,  and 
lined  by  periosteum.  A  clear  fluid  is  contained  in  the  space  between  the  osseous 
labyrinth  and  the  membranous  labyrinth.  The  space  is  called  the  perilymph 
space,  and  the  fluid  is  called  perilsntnph  or  liquor  Cotunnii. 

The  Vestibule  (vestibulum)  (Figs.  763  and  767). — The  vestibule  is  the  common 
central  cavity  of  communication  between  the  parts  of  the  internal  ear.  It  is  situated 
on  the  inner  side  of  the  tympanum,  behind  the  cochlea,  and  in  front  of  the  semi- 
circular canals.  It  is  somewhat  ovoidal  in  shape  from  before  backward,  flattened 
from  within  outward,  and  measures  about  one-fifth  of  an  inch  from  before  back- 


Opening  of  aqueductus  vestibuli, 
Bi^istle  passed  through  foramen  rotundum 

Opening  of  aqueductus  cochlex. 
Fig.  767. — The  osseous  labyrinth  laid  open  (enlarged). 

ward,  as  well  as  from  above  downward,  and  about  one-eighth  of  an  inch  from  with- 
out inward.  On  its  outer  or  tympanic  wall  is  the  fenestra  ovalis  (fenestra  vestibuli), 
closed,  in  the  recent  state,  by  the  base  of  the  stapes,  and  its  annular  ligament. 
On  its  inner  wall,  at  the  forepart,  is  a  small  circular  depression,  fovea  hemi- 
sphaerica  or  spherical  recess  (recessus  sphaericus),  in  which  the  saccule  is  placed. 
This  recess  is  perforated,  at  its  anterior  and  inferior  part,  by  about  a  dozen  minute 
holes  (macula  cribrosa  media),  for  the  passage  of  filaments  of  the  auditory  nerve 
to  the  saccule.  Above  and  behind  this  depression  is  an  oblique  ridge,  the  crista 
vestibuli.  The  anterior  extremity  of  the  crista  vestibuli  is  the  shape  of  a  triangle, 
and  is  called  the  P3n:amid  (pyramis  vestibuli).  This  ridge  bifurcates  posteriorly  to 
enclose  a  small  depression,  the  recessus  cochlearis  of  Reichert,  which  is  perforated 
by  eight  small  holes  for  the  passage  of  filaments  of  the  auditory  nerve  which 
supply  the  posterior  end  of  the  ductus  cochlearis.  An  oval  depression  is  placed 
in  the  roof  and  inner  wall  of  the  vestibule  above  and  behind  the  crista  vestibuli. 
It  is  called  the  fovea  hemielliptica,  elliptical  recess  or  spherical  recess  (recessus 
ellipticus),  and  receives  the  utricle.  The  pyramid  and  the  adjacent  elliptical 
recess  are  perforated  by  numerous  minute  foramina  (macula  cribrosa  superior), 


THE    OSSEOUS  LABYRINTH  1165 

The  openings  in  the  pyramid  transmit  filaments  from  the  vestibular  nerve  to  the 
utricle;  the  openings  in  the  elliptical  recess  transmit  filaments  from  the  vestibular 
nerve  to  the  ampullae  of  the  superior  and  external  semicircular  canals.  Below  and 
behind  the  elliptical  recess  is  a  groove  which  deepens  into  a  canal  and  is  called 
the  aquaeductus  vestibuli.  This  canal  passes  to  the  posterior  surface  of  the  petrous 
portion  of  the  temporal  bone  and  opens  as  a  mere  crack  between  the  internal 
auditory  meatus  and  the  groove  for  the  lateral  sinus.  It  transmits  a  small  vein, 
and  contains  a  tubular  prolongation  of  the  lining  membrane  of  the  vestibule,  the 
ductus  endolymphaticus,  which  ends  in  a  cul-de-sac  between  the  layers  of  the  dura 
mater  within  the  cranial  cavity.  Behind,  the  semicircular  canals  open  into  the 
vestibule  by  five  orifices.  In  front  is  an  elliptical  opening,  which  communicates 
with  the  scala  vestibuli  of  the  cochlea  by  an  orifice,  apertura  scalae  vestibuli  cochleae. 
This  opening  is  bounded  below  by  a  thin  plate  of  bone  (lamina  spiralis  ossea), 
which  takes  origin  from  the  vestibular  floor  external  to  the  spherical  recess  and 
in  the  cochlea  forms  the  bony  portion  of  the  partition  between  the  scala  tympani 
and  the  scala  vestibuli.  In  the  anterior  portion  of  the  vestibular  floor  is  a  fissure 
(fissiira  vestibuli),  which  passes  into  the  bony  part  of  the  canal  of  the  cochlea. 
The  external  boundary  of  this  fissure  is  a  small,  thin  plate  of  bone  (lamina  spiralis 
secundaria). 

The  Semicircular  Canals  (canales  semicirculares  ossei)  (Fig.  767)  .—The  serai- 
circular  canals  are  three  bony  canals  situated  above  and  behind  the  vestibule.  They 
are  of  unequal  length,  compressed  from  side  to  side,  and  each  describes  the  greater 
part  of  a  circle.  They  measure  about  one-twentieth  of  an  inch  in  diameter,  and 
each  presents  a  dilatation  at  one  end,  called  the  ampulla  ossea,  which  measures 
more  than  twice  the  diameter  of  the  tube.  These  canals  open  into  the  vestibule 
by  five  orifices,  one  of  the  apertures  being  common  to  two  of  the  canals. 

The  Superior  Semicircular  Canal  (canalis  semicircularis  superior). — The  superior 
semicircular  canal  is  vertical  in  direction,  and  is  placed  transversely  to  the  long 
axis  of  the  petrous  portion  of  the  temporal  bone,  on  the  anterior  surface  of  which 
its  arch  forms  a  round  projection.  It  describes  about  two-thirds  of  a  circle.  Its 
outer  extremity,  which  is  ampullated,  communicates  by  a  distinct  orifice  with  the 
upper  part  of  the  vestibule;  the  opposite  end  of  the  canal,  which  is  not  dilated, 
joins  with  the  corresponding  part  of  the  posterior  canal  to  form  the  cnis  commune, 
which  opens  into  the  upper  and  inner  part  of  the  vestibule. 

The  Posterior  Semicircular  Canal  (canalis  semicircularis  posterior). — ^The  posterior 
semicircular  canal,  also  vertical  in  direction,  is  directed  backward,  nearly  parallel 
to  the  posterior  surface  of  the  petrous  bone ;  it  is  the  longest  of  the  three ;  its  ampul- 
lated end  commences  at  the  lower  and  back  part  of  the  vestibule,  its  opposite  end 
joining  to  form  the  common  canal  already  mentioned.  In  the  wall  of  the  ampulla 
of  the  posterior  canal  are  a  number  of  small  openings  (macula  cribrosa  inferior) 
for  the  entrance  of  nerves  to  the  ampulla. 

The  External  or  Horizontal  Canal  (canalis  semicircularis  lateralis). — The  external 
or  horizontal  canal  is  the  shortest  of  the  three,  its  arch  being  directed  outward  and 
backward;  thus  each  semicircular  canal  stands  at  right  angles  to  the  other  two. 
Its  ampullated  end  corresponds  to  the  upper  and  outer  angle  of  the  vestibule,  just 
above  the  fenestra  ovalis,  where  it  opens  close  to  the  ampuUary  end  of  the  superior 
canal ;  its  opposite  end  opens  by  a  distinct  orifice  at  the  upper  and  back  part  of  the 
vestibule. 

The  Cochlea  (Figs. 767,768,769,  and  770). — The  cochlea  bears  some  resemblance 
to  acommon  snail-shell ;  it  forms  the  anterior  partof  the  labyrinth,  is  conical  in  form, 
and  placed  almost  horizontally  in  front  of  the  vestibule;  its  apex  is  directed  forward 
and  outward,  with  a  slight  inclination  downward,  toward  the  upper  and  front  part 
of  the  inner  wall  of  the  tympanum ;  its  base  corresponds  with  the  anterior  depression 
at  the  bottom  of  the  internal  auditory  meatus,  and  is  perforated  by  numerous 


1166 


THE    ORGANS    OF  SPECIAL    SENSE 


apertures  for  the  passage  of  the  cochlear  divisions  of  the  auditory  nerve.    It  meas- 
ures nearly  a  quarter  of  an  inch  (5  mm.)  from  base  to  apex,  and  its  breadth  across 


Fig.  768. — Osseous  cochlea  in  vertical  section.     The  broken,  white  lines  indicate  the  position  of  the  basilar 
membrane  of  the  canal  of  the  cochlea.     Semidiagrammatic.      (Testut.) 

the  base  is  somewhat  greater  (about  9  mm.).  It  consists  of  a  conical-shaped 
central  axis,  the  modiolus  or  columella;  of  a  canal,  the  bony  canal  of  the  cochlea,  the 
inner  w^all  of  which  is  formed  by  the  central  axis,  wound  spirally  around  it  for  two 


BASIS 
MODIOLI 


CANALIS  CANALIS  LON- 
SPIRALIS  GITUDINALIS 
MODIOLI  MODIOLI 


COMPACT  BONY 
SUBSTANCE  OF 

CAPSULE  OF       SULCUS  FOR  LARGE  SUPCR- 
lAL  PETROSAL  NERVE 


ALL  SUPER- 
L  NERVE 


TEGMCN 
TYMPANI 

SEMICANAL 

FOR  TENSOR 

TYMPANI 

MUSCLE 

GLASSERIAN 

FISSURE 


EMICANAL  OF 
USTACHIAN 
TUBE 


LAMINA 

SPIRALIS 

OSSEA 


LAMINA  SPIRALIS 
SECUNDARIA 


Fig.  769. — Vertical  section  through  the  right  cochlea,  medial  portion,  viewed  from  the  lateral  side.    (Spalteholz.) 


turns  and  three-quarters,  from  the  base  to  the  apex,  and  of  a  delicate  lamina,  the 
lamina  spiralis  ossea,  which  projects  from  the  modiolus,  and,  following  the  windings 


THE   OSSEOUS  LABYRINTH  1167 

of  the  canal,  partially  subdivides  into  two.  In  the  recent  state  certain  mem- 
branous layers  are  attached  to  the  free  border  of  this  lamina,  which  project  into 
the  canal  and  completely  separate  it  into  two  passages,  which,  however,  com- 
municate with  each  other  at  the  apex  of  the  modiolus  by  a  small  opening,  named 
the  helicotrema. 

The  Modiolus  (Figs.  769  and  770). — The  modiolus  or  columella  is  the  central  axis 
or  pillar  of  the  cochlea.  It  is  conical  in  form,  and  extends  from  the  base  to  the  apex 
of  the  cochlea.  Its  base  (basis  modioli)  is  broad,  and  appears  at  the  bottom  of  the 
internal  auditory  meatus,  where  it  corresponds  with  the  area  cochleae.  It  is  per- 
forated by  numerous  orifices,  which  transmit  filaments  of  the  cochlear  division 
of  the  auditory  nerve,  the  nerves  for  the  first  turn  and  a  half  being  transmitted 
through  the  foramina  of  the  tractus  spiralis  foraminosus ;  the  fibres  for  the  apical 
turn  passing  up  through  the  foramen  centrale.  The  foramina  of  the  tractus 
spiralis  foraminosus  pass  up  through  the  modiolus  and  successively  bend  out- 
ward to  reach  the  attached  margin  of  the  lamina  spiralis  ossea.  Here  they  become 
enlarged,  and  by  their  apposition  form  a  spiral  canal  (canalis  spiralis  modioli), 
which  follows  the  course  of  the  attached  margin  of  the  lamina  spiralis  ossea  and 
lodges  the  ganglion  of  Corti  (ganglion  spirale  cochleae).  The  foramen  centrale  is 
continued  as  a  canal  up  the  middle  of  the  modiolus  to  its  apex,  and  from  this  canal 
numerous  minute  foramina  pass  outward  to  the  unattached  edge  of  the  lamina 
spiralis.  In  the  foramina  are  vessels  and  nerves.  The  axis  diminishes  rapidly 
in  size  in  the  second  and  succeeding  coil. 


Fig.  770. — The  cochlea  laid  open  (enlarged). 

The  Bony  Canal  or  the  Spiral  Canal  of  the  Cochlea  {canalis  spiralis  cochleae)  (Fig. 
770). — The  bony  canal  of  the  cochlea  takes  two  turns  and  three-quarters  round  the 
modiolus.  The  first  turn  of  the  canal  is  called  the  basal  coil,  the  second  is  called  the 
central  coil,  the  third  turn  is  called  the  apical  coil.  The  promontory  on  the  inner  wall 
of  the  tympanic  cavity  is  caused  by  the  basal  coil.  The  bony  canal  of  the  cochlea  is 
a  little  over  an  inch  in  length  (about  30  mm.),  and  diminishes  gradually  in  size  from 
the  base  to  the  summit,  where  it  terminates  in  a  cul-de-sac,  the  cupola  (cwpw/a),  which 
forms  the  apex  of  the  cochlea.  The  commencement  of  this  canal  is  about  the 
tenth  of  an  inch  in  diameter;  it  diverges  from  the  modiolus  toward  the  tympanum 
and  vestibule,  and  presents  three  openings.  One,  the  fenestra  rotunda,  commu- 
nicates with  the  tympanum ;  in  the  recent  state  this  aperture  is  closed  by  a  mem- 
brane, the  membrana  t3anpani  secundaria.  Another  aperture,  of  an  elliptical  form, 
enters  the  vestibule.  The  third  is  the  aperture  of  the  aquaeductus  cochleae,  leading 
to  a  minute  funnel-shaped  canal,  which  opens  on  the  basilar  surface  of  the  petrous 
bone  internal  to  the  jugular  fossa,  and  transmits  a  small  vein,  and  also  forms 
a  communication  between  the  subarachnoidean  space  of  the  skull  and  the  peri- 
lymph contained  in  the  scala  tympani. 

The  Lamina  Spiralis  Ossea. — The  lamina  spiralis  ossea  is  a  bony  shelf  or  ledge 
which  projects  outward  from  the  modiolus  into  the  interior  of  the  spiral  canal, 


1168 


THE    ORGANS    OF  SPECIAL    SENSE 


and,  like  the  canal,  takes  two  and  three-quarter  turns  around  the  modiolus.  It 
reaches  about  half-way  toward  the  outer  wall  of  the  spiral  tube,  and  partially 
divides  its  cavity  into  two  passages  or  scalae,  of  which  the  upper  is  named  the 
scala  vestibuli,  while  the  lower  is  termed  the  scala  tympani.  Near  the  summit  of 
the  cochlea  the  lamina  terminates  in  a  hook-shaped  process,  the  hamulus  (hamulus 
laminae  spiralis),  which  assists  in  forming  the  boundary  of  a  small  opening,  the 
helicotrema,  by  which  the  two  scalae  communicate  with  each  other.  From  the 
canalis  spiralis  modioli  numerous  foramina  pass  outward  through  the  osseous 
spiral  lamina  as  far  as  its  outer  or  free  edge.  In  the  lower  part  of  the  first  turn 
a  second  bony  lamina  (lamina  spiralis  secundaria)  projects  inward  from  the 
outer  wall  of  the  bony  tube;  it  does  not,  however,  reach  the  primary  osseous  spiral 
lamina,  so  that  if  viewed  from  the  vestibule  a  narrow  fissure,  the  fissura  vestibuli, 
is  seen  between  them. 

The  membrana  basilaris  (Fig.  768)  is  stretched  from  the  unattached  edge  of 
the  lamina  spiralis  ossea  to  the  outer  wall  of  the  cochlea.     The  lamina  spiralis 


NERVE  OF  AMPULLA 
OF  SUPERIOR  CANAL 


AMPULLA  OF  SUPERIOR 
MEMBRANOUS  CANAL 


SUPERIOR 

TERMINAL 

BRANCH  OF 

VESTIBULAR 

NERVE 


DUCTUS 
COCHLEARIS 


COCHLEAR 
NERVE 


ACOUSTIC 
NERVE 


VESTIBULAR 
NERVE 


VESTIBULAR 
GANGLION 


NERVE  OF        NERVE  OF  AMPULLA         SACCULE  AM  PU  LLA  OF  POSTE  RIOR 

SACCULE     OF  POSTERIOR  CANAL  MEMBRANOUS  CANAL 

Fig.  771. — The  right  membranous  labyrinth  of  an  adult,  isolated,  medial  and  posterior  view. 


DUCT  OF 
SUPERIOR 
SEMICIRCULAR 
CANAL 


AMPULLA  OF 
EXTERNAL 
MEMBRANOUS 
CANAL 


DUCT  OF 
EXTERNAL 
SEMICIRCULAR 
CANAL 


CPUS 

COMMUNE 

DUCT  OF 

POSTERIOR 

SEMICIRCULAR 

CANAL 


DUCTUS    ENDO. 
LYMPHATICUS 


(Spalteholz.) 


makes  an  incomplete  septiun  between  the  scala  tympani  and  scala  vestibuli;  the 
membrana  basilaris  completes  the  septum.  Even  with  the  perfected  septum  the 
two  scalae  communicate  at  the  apex  of  the  cochlea  by  means  of  the  helicotrema. 
The  Fundus  of  the  Internal  Auditory  Meatus  {fundus  meatus  acustici  irdemi). — 
This  structure  is  the  inner  wall  of  the  vestibule  and  the  base  of  the  modiolus.  A 
transverse  ridge  {crista  transversa)  maps  it  off  into  two  parts,  the  fossula  superior 
and  the  fossula  inferior.  The  facial  area  {area  n.  facialis)  is  in  the  anterior  portion 
of  the  fossula  superior.  The  opening  seen  here  is  the  beginning  of  the  aqueduct 
of  Fallopius  (canalis  facialis)  for  the  transmission  of  the  facial  nerve.  The  superior 
area  of  the  vestibule  (area  vestibularis  superior)  is  the  posterior  portion  of  the  fossula 
superior.  Here  the  nerves  perforate  which  supply  the  utricle  and  the  ampullae  of 
the  superior  and  external  semicircular  canals  (Cunningham),  The  area  cochleae 
is  the  anterior  portion  of  the  fossula  inferior.  In  it  is  the  canalis  centralis  for  the 
nerve-fibres  to  the  apical  turn  of  the  cochlea;  and  the  tractus  spiralis  foraminosa 
for  the  transmission  of  nerves  to  the  first  turn  and  a  half  of  the  cochlea.     The 


THE    MEMBRANOUS   LABYRINTH 


1169 


inferior  area  of  the  vestibule  {area  vestibularis  inferior)  is  back  of  the  area  cochleae 
and  a  ridge  separates  the  two.  It  transmits  nerves  to  the  saccule.  At  the  posterior 
part  of  the  fossula  inferior  is  a  solitary  foramen,  the  foramen  singulare,  which 
transmits  nerves  to  the  ampulla  of  the  posterior  semicircular  canal. 

The  Membranous  Labyrinth  (Labyrinthus  Membranaceus)  (Figs.  771,  772). 

The  membranous  labyrinth  is  contained  within  the  bony  cavities  just  described, 
having  the  same  general  form  as  the  cavities  in  which  it  is  contained,  though 
considerably  smaller,  being  separated  from  the  bony  walls  by  a  quantity  of  fluid, 
the  perilymph  or  liquor  Gotunnii  (perihjmpha) .  It  does  not,  however,  float  loosely 
in  this  fluid,  but  in  places  is  fixed  to  the  walls  of  the  cavity.  The  membranous 
sac  contains  fluid,  the  endolymph  {endohjm'pha) ,  and  on  the  sac  the  ramifications 
of  the  auditory  nerve  are  distributed. 

Within  the  osseous  vestibule  the  membranous  labyrinth  does  not  quite  preserve 
the  form  of  the  bony  cavity,  but  presents  two  membranous  sacs,  the  utricle  and 
the  saccule. 


Ampullae 


Ductus 
Endolymphaticus 

Fio.  772. — The  membranous  labyrinth  (enlarged). 


The  Utricle  (utriculus). — The  utricle  is  the  larger  of  the  two,  of  an  oblong 
form,  compressed  laterally,  and  occupies  the  upper  and  back  part  of  the  vestibule, 
lying  in  contact  with  the  fovea  semi-elliptica  and  the  part  below  it.  The  highest 
portion  of  the  utricle  is  called  the  recess  {recessus  utriculi);  it  is  placed  in  the 
elliptical  recess,  and  opening  into  it  are  the  ampulla  of  the  superior  and  external 
semicircular  canals.  The  central  portion  of  the  recess  of  the  utricle  receives  upon 
the  side  the  external  semicircular  canal.  This  opening  has  not  an  ampulla.  The 
superior  sinus  is  a  prolongation  upward  and  backward  from  the  central  portion  of 
the  utricle  and  in  the  superior  sinus  the  crus  commune  and  the  superior  and 
posterior  semicircular  canals  open.  The  lower  and  inner  portion  of  the  utricle 
is  the  inferior  sinus,  and  into  it  the  ampulla  of  the  posterior  semicircular  canal 
opens.  The  floor  and  anterior  wall  of  the  recess  of  the  utricle  are  much  thicker 
than  elsewhere,  and  form  the  macula  acustica  utriculi,  which  receives  the  utricular 
filaments  of  the  auditory  nerve  and  has  attached  to  its  internal  surface  a  layer  of 
calcareous  particles  which  are  called  otoliths.  The  cavity  of  the  utricle  communi- 
cates behind  with  the  membranous  semicircular  canals  by  five  orifices.  From 
its  anterior  wall  is  given  off  a  small  canal  (dvchis  utriculosaccularis) ,  which  joins 
with  a  canal  from  the  saccule,  the  ductus  endolymphaticus.  The  utricle  is  joined 
to  the  bony  wall  by  numerous  fibrous  bands. 

74 


1170  THE    ORGANS    OF  SPECIAL   SENSE 

The  Saccule  (sacculus). — The  saccule  is  the  smaller  of  the  two  vesicular  sacs; 
it  is  globular  in  form,  lies  in  the  elliptical  recess  near  the  opening  of  the  scala 
vestibuli  of  the  cochlea.  Its  anterior  part  exhibits  an  oval  thickening,  the  macula 
acustica  sacculi,  to  which  are  distributed  the  saccular  filaments  of  the  auditory 
nerve.  Its  cavity  does  not  directly  communicate  with  that  of  the  utricle.  From 
the  posterior  wall  is  given  off  a  canal,  the  ductus  endolymphaticus.  This  duct 
passes  along  the  aquaeductus  vestibuli  and  ends  in  a  blind  pouch  on  the  posterior 
surface  of  the  petrous  portion  of  the  temporal  bone,  where  it  is  in  contact  with 
the  dura  mater.  The  upper  extremity  of  the  saccule  looks  upward  and  back- 
ward and  forms  the  sinus  utricularis  sacculi.  This  lies  in  contact  with  but  is  not 
a  part  of  the  wall  of  the  utricle.  The  vestibule  contains  the  closed  end  of  the 
ductus  cochlearis.  This  is  known  as  the  caecum  vestibulare.  The  ductus  coch- 
learis  lies  below  the  saccule  in  what  Reichert  described  as  the  recessus  cochlearis, 
and  it  enters  the  spiral  canal.  From  the  lower  part  of  the  saccule  a  short  tube, 
the  canalis  reunions  of  Hensen  (ductus  reuniens  [Henseni]),  passes  downward 
and  outward  to  open  into  the  ductus  cochlearis.  The  saccule  is  held  in  posi- 
tion by  numerous  fibrous  bands  which  pass  between  the  saccule  and  the  bony 
wall. 

The  Membranous  Semicircular  Canals  (ductus  semicirculares).— The  mem- 
branous semicircular  canals  are  about  one-third  the  diameter  of  the  osseous  canals, 
but  in  number,  shape,  and  general  form  they  are  precisely  similar,  and  present 
at  one  end  within  the  osseous  ampulla  a  membranous  ampulla.  These  ampullae 
are  called  ampullae  membranaceae.  The  canals  open  by  five  orifices  into  the  utricle, 
one  opening  being  common  to  two  canals.  In  the  ampullae  the  wall  is  thickened, 
and  projects  into  the  cavity  as  a  fiddle-shaped,  transversely  placed  elevation,  the 
septum  transversum,  in  which  the  nerves  end. 

The  membranous  canals  are  attached  here  and  there  to  the  bone  by  numerous 
fibrous  bands,  the  so-called  ligaments  (ligamenta  lahyrinthi  canaliculorum). 

Structure. — ^The  walls  of  the  utricle,  saccule,  and  membranous  semicircular 
canals  consist  of  three  layers.  The  outer  layer  is  a  loose  and  flocculent  struc- 
ture, apparently  composed  of  ordinary  fibrous  tissue,  containing  blood-vessels 
and  pigment-cells  analogous  to  those  in  the  pigment  coat  of  the  retina.  The 
middle  layer,  thicker  and  more  transparent,  bears  some  resemblance  to  the 
hyaloid  membrane,  but  it  presents  on  its  internal  surface,  especially  in  the  semi- 
circular canals,  numerous  papilliform  projections,  and,  on  the  addition  of  acetic 
acid,  presents  an  appearance  of  longitudinal  fibrillation  and  elongated  nuclei. 
The  inner  layer  is  formed  of  polygonal  nucleated  epithelial  cells.  The  raphe  of 
each  semicircular  canal  is  a  line  upon  the  concave  side  of  the  canal.  Along  the 
raph^  the  height  of  the  epithelial  cells  is  distinctly  increased.  In  the  ampullae 
adjacent  to  the  cristae  acusticae  the  cells  are  cylindrical  and  constitute  the 
plana  semilunata.  In  the  maculae  of  the  utricle  and  saccule,  and  in  the  trans- 
verse septa  of  the  ampullae  of  the  canals,  the  middle  coat  is  thickened  and  the 
epithelium  is  columnar,  is  increased  in  height,  and  passes  into  the  neuro-epithe- 
lium.    The  neuro -epithelium  consists  of  supporting  cells  and  hair-cells. 

1.  The  supporting  cells  are  long,  wider  at  the  ends  than  in  the  centre,  contain  an 
oval  nucleus,  and  the  lower  end  of  the  cell  is  fissured. 

2.  The  hair-cells  are  columnar,  with  bulged  lower  ends  and  free  upper  ends. 
The  bulged  lower  ends,  each  of  which  contains  a  spherical  nucleus,  do  not  reach 
higher  than  the  middle  of  the  epithelial  layer.  Each  free  upper  end  is  surmounted 
by  a  long,  tapering  filament.  These  filaments  constitute  auditory  hair,  and  they 
project  into  the  cavity.  The  filaments  of  the  auditory  nerve  enter  these  parts, 
and,  having  pierced  the  outer  and  thickened  middle  layer,  they  lose  their  medul- 
lary sheath,  and  their  axis-cylinders  divide  into  three  or  four  branches  at  the 
larger  and  deeper  ends  of  the  hair-cells.    These  branches  form  a  horizontal  plexus 


THE   MEMBRANOUS    LABYRINTH 


1171 


{stratum  plexiforme).  "These  surround  the  hair-cells  like  the  calyx  of  a  flower, 
and  give  off  ascending  branches,  which,  however,  do  not  reach  the  surface.  In 
this  way  one  branch  usually  comes  in  contact  with  many  hair-cells."^ 


Fig.  773. — Floor  of  scala  media,  showing  the  organ  of  C!orti,  etc. 

Numerous  small  prismatic  bodies  termed  statoliths,  otokonien  crystals  or  otoliths, 
and  consisting  of  a  mass  of  minute  crystalline  grains  of  carbonate  of  lime,  held 


COCHLEAR    NCRVE 
AND    GANGLION 


Fig.  774. — Cochlea  in  transverse  section.     Observe  especially  the  canal  of  the  cochlea,  which  is  a  part  of 
the  membranous  labyrinth.      (Testut.) 

together  in  a  mesh  of  delicate  fibrous  tissue,  are  contained  in  the  walls  of  the 
utricle  and  saccule  opposite  the  distribution  of  the  nerves.     The  membrane  is 

'  Histology  and  Microscopic  Anatomy.     By  Dr.  Ladislaus  Szymonowicz.     Translated    and  edited  bv  John 
Biuce  MacCallum,  M.D.  ■^   """" 


]172  THE    ORGANS    OF  SPECIAL   SENSE 

called  the  otolith  membrane.  A  calcareous  material  is  also,  according  to  Bowman, 
sparingly  scattered  in  the  cells  lining  the  ampullae  of  the  semicircular  canals.  The 
conical  thickening  in  the  ampulla  corresponds  to  the  otohth  membrane  and  is 
called  the  cupola. 

The  Membranous  Cochlea  Ductus  Cochlearis  or  Scala  Media  consists  of  a  spirally 
arranged  tube  enclosed  in  the  bony  canal  of  the  cochlea  and  lying  along  its  outer 
wall.  It  begins  as  a  blind  end  in  the  recessus  cochlearis  of  the  vestibule.  This 
beginning  is  the  caecum  vestibulare.  It  ascends  inside  the  bony  cochlea  and  termi- 
nates at  the  apex  of  the  cochlea  by  a  blind  end,  the  lagena  {caecum  cwpulare).  The 
manner  in  which  it  is  formed  will  now  be  described. 

The  osseous  spiral  lamina,  as  above  stated,  extends  only  part  of  the  distance  be- 
tween the  modiolus  and  the  outer  bony  wall  of  the  cochlea.  A  membrane,  the  basilar 
membrane  (membrana  basilaris)  (Fig.  773),  stretches  from  its  free  edge  to  the  outer 
wall  of  the  cochlea,and  completes  the  roof  of  the  scala  tympani.  A  second  and  more 
delicate  membrane,  the  membrane  of  Reissner  {membrana  vestibularis  [Reissneri]) 
(Fig. 773), extends  from  the  thickened  periosteum  covering  the  lamina  spiralis  ossea 
to  the  outer  wall  of  the  cochlea,  to  which  it  is  attached  at  some  little  distance  above 
the  membrana  basilaris.  A  canal  is  thus  shut  off  between  the  scala  tympani  below 
and  the  scala  vestibuli  above;  this  is  the  membranous  canal  of  the  cochlea  {ductus 
cochlearis  or  scala  media)  (Fig.  774).  It  is  triangular  on  transverse  section,  its  roof 
being  formed  by  the  membrane  of  Reissner,  its  outer  wall  by  the  periosteum  which 
lines  the  bony  canal,  and  its  floor  by  the  membrana  basilaris,  and  the  outer  part 
of  the  lamina  spiralis  ossea,  on  the  former  of  which  is  placed  the  organ  of  Corti. 
Reissner's  membrane  is  thin  and  homogeneous,  and  is  covered  on  its  upper  and 
under  surfaces  by  a  layer  of  epithelium.    The  periosteum,  which  forms  the  outer 

wall  of  the  ductus  cochlearis,  is  greatly 
NERVE-FIBRES  PASSING  OUT        thickcncd   aud   altered  in  character, 

GANGLION      SPIRAL      BETWEEN   TH  E  TWO    LAYERS  OF  _  1  •  11       1        1 

spiRALE  FIBRES  LAMINA  SPIRALIS  OSSEA  ^^^^  formmg  what  iscallcd  the  spiral  liga- 
ment of  the  cochlea  {ligamentum  spirals 
cochleae)  (Fig.773) .  It  projects  inward 
below  as  a  triangular  prominence,  the 
crista  basilaris,  which  gives  attach- 
ment to  the  outer  edge  of  the  mem- 
brana basilaris, and  immediately  above 
which  is  a  concavity,  the  sulcus  spiralis 
extemus  (Fig.  773) .  The  upper  por- 
,.,,  .^,     tion  of  the  ligamentum  spirale  con- 

FiG.  775. — Part  of  the  cochlear  nerve,  highly  magnified.  .  ^  .,,  '^■,  •, 

(Henie.)  tauis    numcrous  capillary  loops  and 

small  blood-vessels,  and  forms  what 
is  termed  the  stria  vascularis.  The  stria  is  limited  below  by  a  prominence  {promi- 
nentia spiralis),  in  which  a  blood-vessel  {vas  prominens)  is  distinctly  visible. 

The  lamina  spiralis  ossea  (Fig.  774)  consists  of  two  plates  of  bone  extending 
outward;  between  these  are  the  canals  for  the  transmission  of  the  filaments  of  the 
auditory  nerve.  On  the  upper  plate  of  that  part  of  the  osseous  spiral  lamina 
which  is  outside  Reissner's  toembrane  the  periosteum  is  thickened  to  form  the 
limbus  laminae  spiralis,  and  this  terminates  externally  in  a  concavity,  the  sulcus 
spiralis  intemus,  which  presents,  on  section,  the  form  of  the  letter  C;  the  upper 
part  of  the  letter,  formed  by  the  overhanging  extremity  of  the  limbus,  is  named 
the  labium  vestibulare ;  the  lower  part,  prolonged  and  tapering,  is  called  the  labium 
tympanicum,  and  is  perforated  by  4000  foramina  {foramina  nervosa)  for  the  pass- 
age of  the  cochlear  nerves.  Externally,  the  labium  tympanicum  is  continuous 
with  the  membrana  basilaris.  The  upper  surface  of  the  labium  vestibulare  is 
intersected  at  right  angles  by  a  number  of  furrows,  between  which  are  numerous 
elevations;  these  present  the  appearance  of  teeth  along  the  free  margin  of  the 


THE   MEMBRANOUS   LABYRINTH 


1173 


labium,  and  have  been  named  by  Huschke  the  auditory  teeth.  There  are  7000 
auditory  teeth.  The  basilar  membrane  may  be  divided  into  two  areas,  inner  and 
outer.  The  inner  is  thin,  and  is  named  the  zona  arcuata  or  zona  tecta  (Fig.  773) ;  it 
supports  the  organ  of  Corti.  The  outer  is  thicker  and  striated,  and  is  termed 
the  zona  pectinata.    The  under  surface  of  the  membrane  is  covered  by  a  layer  of 

Outer  hair  cells. 
Membrana  tectoria. 


Limbus. 


Cells  of  Deiters. 
Outer  rod. 
Basilar  membrane. 
Fig.  776. — Section  through  the  organ  of  Corti.     Magnified.     (G.  Retzius.) 


-  - -=  SVo  =  000  „'=i'o  o  o  0  »<> 


Nerve  fibres. 


vascular  connective  tissue.    One  of  these  vessels  is  somew^hat  larger  than  the  rest, 
and  is  named  the  vas  spirale  (Fig.  776) ;  it  lies  below^  Corti's  tunnel. 

Organ  of  Corti^  (organon  spirale  [Cortii])  (Figs.  773,  774,  776,  and  777). — The 
inner  part  of  the  membrana  basilaris — that  is,  the  part  directed  toward  the  canal 
of  the  ductus  cochiearis — is  covered  with  epithelium,  which  is  largely  neuro-epithe- 


INTERNAL   AUDI-_ 
TORY    CELLS 


BASILAR    MEMBRANE 


Fig.  777. — Organ  of  Corti.     Diagrammatic  view  of  a  small  portion.     (Testut.) 

Hum.  It  forms  the  organ  of  Corti.  In  this  lie  the  terminations  of  the  cochlear 
nerve.  It  appears  at  first  sight  as  a  papilla,  winding  spirally  throughout  the 
whole  length  of  the  ductus  cochiearis,  from  which  circumstance  it  has  been  desig- 
nated the  papilla  spiralis.  More  accurately  viewed,  it  is  seen  to  be  composed 
of  a  remarkable  arrangement  of  cells,  which  may  be  likened  to  the  keyboard  of  a 


'  Corti's  original  paper  is  in  the  Zeitschrift  f.  Wissen.  Zool.,  iii.,  109. 


1174 


THE    ORGANS   OF  SPECIAL   SENSE 


pianoforte.  The  organ  of  Corti  consists  of  an  inner  'part  and  an  outer  part.  Each 
part  contains  auditory  cells  and  supporting  cells.  Of  these  cells,  the  two  central 
ones  are  rod-like  bodies  and  are  called  the  inner  and  outer  rods  of  Corti.  They  are 
placed  on  the  basilar  membrane,  at  some  little  distance  from  each  other,  but  are 
inclined  toward  each  other,  so  as  to  meet  at  their  opposite  extremities,  and  form 
a  series  of  arches  roofing  over  a  minute  tunnel,  the  canal  or  tunnel  of  Corti, 
between  them  and  the  basilar  membrane,  which  ascends  spirally  through  the 
whole  length  of  the  cochlea. 

The  inner  rods  (Fig.  776),  some  6000  in  number,  are  more  numerous  than  the 
outer  ones,  and  rest  on  the  basilar  membrane,  close  to  the  labium  tympanicum; 
they  project  obliquely  upward  and  outward,  and  terminate  above  in  expanded 
extremities  which  resemble  in  shape  the  upper  end  of  the  ulna,  with  its  sigmoid 
cavity,  coronoid  and  olecranon  processes.  On  the  outer  side  of  the  rod,  in  the 
angle  formed  between  it  and  the  basilar  membrane,  is  a  nucleated  mass  of  proto- 
plasm; while  on  the  inner  side  is  a  row  of  epithelial  cells,  inner  hair-cells  (Fig. 
776),  surmounted  by  a  brush  of  fine,  stiff,  hair-like  processes.  On  the  inner  side 
of  these  cells  are  two  or  three  rows  of  columnar  supporting  cells,  which  are 
continuous  with  the  cubical  cells  lining  the  sulcus  spiralis  internus. 


Fig.  778. — Longitudinal  section  of  the  cochlea,  showing  the  relations  of  the  scalae,  the  ganglion  spirale,  etc. 
S.  v.,  Scala  vestibuli.  S.  T.,  Scala  tympani.  S.  M.,  Scala  media.  L.  S.,  Ligamentum  spirale.  G.  S.,  Ganglion 
spirale. 


The  outer  rods  (Fig.  776) ,  numbering  about  4000,  also  rest  by  a  broad  foot  on 
the  basilar  membrane;  they  incline  upward  and  inward,  and  their  upper  extremity 
resembles  the  head  and  bill  of  a  swan ;  the  back  of  the  head  fitting  into  the  con- 
cavity— the  analogue  of  the  sigmoid  cavity — of  one  or  more  of  the  internal  rods, 
and  the  bill  projecting  outward  as  a  phalangeal  process  of  the  membrana  reticu- 
laris, presently  to  be  described. 

In  the  head  of  these  outer  rods  is  an  oval  portion,  where  the  fibres  of  which 
the  rod  appears  to  be  composed  are  deficient,  and  which  stains  more  deeply  with 
carmine  than  the  rest  of  the  rod.  At  the  base  of  the  rod,  on  its  internal  side — 
that  is  to  say,  in  the  angle  formed  by  the  rod  with  the  basilar  membrane — is  a 
similar  protoplasmic  mass  to  that  found  on  the  outer  side  of  the  base  of  the  inner 
rod ;  these  masses  of  protoplasm  are  probably  the  undifferentiated  portions  of  the 
cells  from  which  the  rods  are  developed.  External  to  the  outer  rod  are  three  or 
four  successive  rows  of  epithelial  cells,  more  elongated  than  those  found  on  the 


THE  MEMBRANOUS  LABYRINTH  1175 

internal  side  of  the  inner  rod,  but,  like  them,  furnished  with  minute  hairs  or  cilia. 
These  are  termed  the  outer  hair-cells,  in  contradistinction  to  the  inner  hair-cells 
above  referred  to.  There  are  about  12,000  outer  hair-cells,  and  about  3500  inner 
hair-cells. 

The  hair-cells  are  somewhat  oval  in  shape;  their  free  extremities  are  on  a 
level  with  the  heads  of  Corti's  rods,  and  from  each  some  twenty  fine  hairlets 
project  and  are  arranged  in  the  form  of  a  crescent,  the  concavity  of  which  opens 
inward.  The  deep  ends  of  the  cells  are  rounded  and  contain  large  nuclei;  they 
reach  only  as  far  as  the  middle  of  Corti's  rods,  and  are  in  contact  with  the  rami- 
fications of  the  nervous  filaments.  Between  the  rows  of  the  outer  hair-cells 
are  rows  of  supporting  cells,  called  the  cells  of  Deiters;  their  expanded  bases  are 
planted  on  the  basilar  membrane,  while  their  opposite  ends  present  a  clubbed 
extremity  or  phalangeal  process.  Immediately  to  the  outer  side  of  Deiters's  cells 
are  some  five  or  six  rows  of  columnar  cells,  the  supporting  cells  of  Hensen.  Their 
bases  are  narrow,  while  their  upper  parts  are  expanded  and  form  a  rounded 
elevation  on  the  floor  of  the  ductus  cochlearis.  The  columnar  cells  lying  outside 
Hensen's  cells  are  termed  the  cells  of  Claudius.  A  space  is  seen  between  the 
outer  rods  of  Corti  and  the  adjacent  hair-cells;  this  is  called  the  space  of  Nuel. 

The  lamina  reticularis  or  membrane  of  Kblliker  is  a  delicate  framework  per- 
forated by  rounded  holes.  It  extends  from  the  inner  rods  of  Corti  to  the  external 
row  of  the  outer  hair-cells,  and  is  formed  by  several  rows  of  "minute  fiddle- 
shaped  cuticular  structures"  called  phalanges,  between  which  are  circular 
apertures  containing  the  free  ends  of  the  hair-cells.  The  innermost  row  of  phal- 
anges consists  of  the  phalangeal  processes  of  the  outer  rods  of  Corti;  the  outer 
pows  are  formed  by  the  modified  free  ends  of  Deiters's  cells. 

Covering  over  these  structures,  but  not  touching  them,  is  the  membrana  tectoria 
or  membrane  of  Corti  (Figs.  773  and  776),  which  is  attached  to  the  vestibular  sur- 
face of  the  lamina  spiralis  close  tp  the  attachment  of  the  membrane  of  Reissner. 
It  is  thin  near  its  inner  margin,  and  overlies  the  auditory  teeth  of  Huschke.  Its 
outer  half  is  thick,  and  along  its  lower  edge,  opposite  the  inner  hair-cells,  is  a 
clear  band,  named  Hensen's  stripe.  Externally,  the  membrane  becomes  much 
thinner,  and  is  attached  to  the  outer  row  of  Deiters's  cells  (Retzius). 

The  fibres  from  the  cochlear  nerve  enter  the  organ  of  Corti  as  axis-cylinders, 
which  pass  directly  to  the  deepest  portions  of  the  inner  and  outer  hair-cells  by 
way  of  the  canal  of  Corti  or  by  the  space  of  Nuel.  The  terminations  arborize 
about  the  lower  portions  of  the  hair-cells  and  end  on  the  surfaces  of  the  hair-cells. 

The  inner  surface  of  the  osseous  labjrrinth  is  lined  by  an  exceedingly  thin  fibro- 
serous  membrane,  analogous  to  a  periosteum,  from  its  close  adhesion  to  the 
inner  surfaces  of  these  cavities,  and  performing  the  office  of  a  serous  membrane  by 
its  free  surface.  It  lines  the  vestibule,  and  from  this  cavity  is  continued  into  the 
semicircular  canals  and  the  scala  vestibuli  of  the  cochlea,  and  through  the  helico- 
trema  into  the  scala  tympani.  A  delicate  tubular  process  is  prolonged  along  the 
aqueduct  of  the  vestibule  to  the  inner  surface  of  the  dura  mater.  This  membrane 
is  continued  across  the  fenestra  ovalis  and  fenestra  rotunda,  and  consequently  has 
no  communication  with  the  lining  membrane  of  the  tympanum.  Its  attached 
surface  is  rough  and  fibrous,  and  closely  adherent  to  the  bone;  its  free  surface  is 
smooth  and  pale,  covered  with  a  layer  of  epithelium,  and  secretes  a  thin,  limpid 
fluid,  the  aqua  labyrinth!,  liquor  Cotunnii  or  perilymph  (Blainville). 

The  scala  media  is  closed  above  and  below.  The  upper  blind  extremity  is 
termed  the  lagena,  and  is  attached  to  the  cupola  at  the  upper  part  of  the  helico- 
trema;  the  lower  end  is  lodged  in  the  recessus  cochlearis  of  the  vestibule.  Near 
this  blind  extremity,  the  scala  media  receives  the  canalis  reunions  of  Hensen  (Fig. 
772),  a  very  delicate  canal,  by  which  the  ductus  cochlearis  is  brought  into  con- 
tinuity with  the  saccule. 


1176  THE   ORGANS   OF  SPECIAL   SENSE 

The  Arteries  of  the  Labyrinth. — The  arteries  of  the  labyrinth  are  the  internal 
auditory,  from  the  basilar,  and  the  stylo-mastoid,  from  the  posterior  auricular. 
The  internal  auditory  divides  at  the  bottom  of  the  internal  auditory  meatus 
into  two  branches,  cochlear  and  vestibular. 

The  cochlear  artery  divides  into  numerous  minute  branches,  which  enter 
foramina  in  the  tractus  spiralis  foraminosa  and  course  in  the  lamina  spiralis  ossea 
to  reach  the  membranous  structures.  The  largest  of  the  cochlear  branches  is  in 
the  canalis  centralis. 

The  vestibular  branches  accompany  the  nerves,  and  supply  the  membranous 
structures  in  the  vestibule  and  semicircular  canals.  Two  arteries  go  to  each 
canal.  The  two  vessels  enter  opposite  extremities  of  the  canal,  and  anastomose 
at  the  summit  of  the  canal.  The  vestibular  vessels  form  a  minute  capillary  net- 
work in  the  substance  of  each  membranous  labyrinth. 

The  Veins  of  the  Labyrinth. — The  veins  of  the  vestibule  and  semicircular  canals, 
the  auditory  veins,  accompany  the  arteries,  and  receive  those  of  the  cochlea  at  the 
base  of  the  modiolus,  to  form  the  internal  auditory  vein  {vv.  auditivae  internae), 
which  opens  into  the  posterior  part  of  the  inferior  petrosal  sinus  or  into  the  lateral 
sinus. 

The  Nerves  of  the  Labyrinth. — The  auditory  nerve  (n.  acusticus),i\\e  special  nerve 
of  the  sense  of  hearing,  divides,  at  the  bottom  of  the  internal  auditory  meatus, 
into  two  branches,  the  cochlear  and  vestibular. 

The  Vestibular  Nerve  {n.  vestibularis),  the  posterior  of  the  two,  presents,  as  it  lies 
in  the  internal  auditory  meatus,  a  ganglion,  the  vestibular  ganglion  or  the  ganglion 
of  Scarpa  {ganglion  vestihulare) ;  the  nerve  divides  into  three  branches  which  pass 
through  minute  openings  at  the  upper  and  back  part  of  the  bottom  of  the  meatus 
{area  vestibular  ^posterior),  and,  entering  the  vestibule,  are  distributed  to  the  utricle 
and  to  the  ampulla  of  the  external  and  superior  semicircular  canals. 

The  nervous  filaments  enter  the  ampullary  enlargements  opposite  the  septum 
transversum,  and  arborize  around  the  hair-cells.  In  the  utricle  and  saccule  the 
nerve-fibres  pierce  the  membrana  propria  of  the  maculae,  and  end  in  arborizations 
around  the  hair-cells. 

The  Cochlear  Nerve  {n.  cochlearis)  gives  off  the  branch  to  the  saccule,  the  fila- 
ments of  which  are  transmitted  from  the  internal  auditory  meatus  through  the 
foramina  of  the  area  vestibularis  inferior,  which  lies  at  the  lower  and  back  part 
of  the  floor  of  the  meatus.  It  also  gives  off  the  branch  for  the  ampulla  of  the 
posterior  semicircular  canal,  which  leaves  the  meatus  through  the  foramen  singulare. 

The  rest  of  the  cochlear  nerve  divides  into  numerous  filaments  at  the  base 
of  the  modiolus;  those  for  the  basal  and  middle  coils  pass  through  the  foramina 
in  the  tractus  foraminosus,  those  for  the  apical  coil  through  the  canalis  centralis, 
and  the  nerves  bend  outward  to  pass  between  the  lamellae  of  the  osseous  spiral 
lamina.  Occupying  the  spiral  canal  of  the  modiolus  is  the  spiral  ganglion  or  gan- 
glion of  Corti  {ganglion  spirale),  consisting  of  bipolar  nerve-cells,  which  really  con- 
stitute the  true  cells  of  origin  of  this  nerve,  one  pole  being  prolonged  centrally  to 
the  brain  and  the  other  peripherally  to  the  hair-cells  of  Corti's  organ.  Reaching  the 
outer  edge  of  the  osseous  spiral  lamina,  the  nerve  fibres  pass  through  the  foramina 
in  the  labium  tympanicum,  where  they  lose  their  axis-cylinders.  They  enter  the 
organ  of  Corti  and  pass  directly  to  the  deep  portions  iDf  the  inner  and  outer  hair-cells 
by  way  of  the  canal  of  Corti  and  the  space  of  Nuel.  The  terminations  arborize 
about  the  lower  portions  of  the  hair-cells  and  end  in  the  surfaces  of  the  cells. 

Surgical  Anatomy. — Malformations,  such  as  imperfect  development  of  the  external  parts, 
absence  of  the  meatus,  or  supernumerary  auricles,  are  occasionally  met  with.  Or  the  pinna  may 
present  a  congenital  fistula,  which  is  due  to  defective  closure  of  the  first  visceral  cleft,  or  rather 
of  that  portion  of  it  which  is  not  concerned  in  the  formation  of  the  Eustachian  tube,  tympanum, 
and  meatus.    In  some  cases  the  cephalo-auricular  angle  is  almost  absent;  in  others  it  is  nearly 


THE  MEMBRANOUS   LABYRINTH  1177 

a  right  angle.  Projecting  ears  and  long  ears  are  said  by  some  observers  to  be  more  common 
among  degenerates,  criminals,  and  the  insane  than  among  the  normal,  the  non-criminal,  and 
the  sane.  The  skin  of  the  auricle  is  thin  and  richly  supplied  with  blood,  but  in  spite  of  this  it 
is  frequently  the  seat  of  frost-bite,  due  to  the  fact  that  it  is  much  exposed  to  cold,  and  lacks  the 
usual  underlying  subcutaneous  fat  found  in  most  other  parts  of  the  body.  A  collection  of  blood 
is  sometimes  found  between  the  cartilage  and  perichondrium  {haematoma  auris),  usually  the 
result  of  traumatism,  but  not  necessarily  due  to  this  cause.  It  is  said  to  occur  most  frequently 
in  the  ears  of  the  insane.  Keloid  sometimes  grows  in  the  auricle  around  the  puncture  made  for 
ear-rings,  and  epithelioma  occasionally  affects  this  part.  Deposits  of  urate  of  soda  are  often  met 
with  in  the  pinna  in  gouty  subjects. 

The  external  auditory  meatus  can  be  most  satisfactorily  examined  by  light  reflected  down  a 
funnel-shaped  speculum;  by  gently  moving  the  latter  in  different  directions  the  whole  of  the 
canal  and  membrana  tympani  can  be  brought  into  view.  The  points  to  be  noted  are:  the  pres- 
ence of  wax  or  foreign  bodies,  the  size  of  the  canal,  and  the  condition  of  the  membrana  tympani. 
The  accumulation  of  wax  is  often  the.  cause  of  deafness,  and  may  give  rise  to  very  serious  conse- 
quences, causing  ulceration  of  the  membrane  and  even  absorption  of  the  bony  wall  of  the  canal. 
Foreign  bodies  are  not  infrequently  introduced  into  the  ear  by  children,  and,  when  situated  in 
the  first  portion  of  the  canal,  may  be  removed  with  tolerable  facility  by  means  of  a  minute  hook 
or  loop  of  fine  wire,  the  parts  being  illuminated  with  reflected  light;  but  when  they  have  slipped 
beyond  the  narrow  middle  part  of  the  meatus,  their  removal  is  in  nowise  easy,  and  attempts  to  effect 
it,  in  inexperienced  hands,  may  be  followed  by  destruction  of  the  membrana  tympani  and  possibly 
injury  of  the  contents  of  the  tympanum.  The  calibre  of  the  external  auditory  canal  may  be  nar- 
rowed by  inflammation  of  its  lining  membrane,  running  on  to  suppuration;  by  periostitis;  hy  polypi, 
sebaceous  tumors, und  exostoses.  The  membrana  tympani,  when  seen  in  a  healthy  ear,  "reflects 
light  strongly,  and,  owing  to  its  peculiar  curvature,  presents  a  bright  spot  of  triangular  shape  at  its 
lower  and  anterior  portion."  From  the  apex  of  this,  proceeding  upward  and  slightly  forward,  is 
a  white  streak  formed  by  the  handle  of  the  malleus,  while  near  the  upper  part  of  the  membrane 
may  be  seen  a  slight  projection,  caused  by  the  short  process  of  the  malleus.  In  disease  alterations 
in  color,  lustre,  curvature  or  inclination,  and  perforation  must  be  noted.  Such  perforations  may 
be  caused  by  a  blow,  a  loud  report,  a  wound,  or  as  the  result  of  suppuration  in  the  middle  ear. 

The  upper  wall  of  the  meatus  is  separated  from  the  cranial  cavity  by  a  thin  plate  of  bone; 
the  anterior  wall  is  separated  from  the  temporo-mandibular  joint  and  parotid  gland  by  the  bone 
forming  the  glenoid  fossa;  and  the  posterior  wall  is  in  relation  with  the  mastoid  cells;  hence 
inflammation  of  the  external  auditory  meatus  may  readily  extend  to  the  membranes  of  the  brain, 
to  the  temporo-mandibular  joint,  or  to  the  mastoid  cells;  and,  in  addition  to  this,  blows  on  the 
chin  may  cause  fracture  of  the  wall  of  the  meatus. 

The  nerves  supplying  the  meatus  are  the  auricular  branch  of  the  pneumogastric,  the  auriculo- 
temporal, and  the  auricularis  magnus.  The  connections  of  these  nerves  explain  the  fact  of  the 
occurrence,  in  cases  of  any  irritation  of  the  meatus,  of  constant  coughing  and  sneezing  from 
implication  of  the  pneumogastric,  or  of  yawning  from  implication  of  the  auriculo-temporal.  No 
doubt  also  the  association  of  earache  with  toothache  in  cancer  of  the  tongue  is  due  to  implication 
of  the  same  nerve,  a  branch  of  the  fifth,  which  supplies  also  the  teeth  and  the  tongue.  The 
vessels  of  the  meatus  and  membrana  tympani  are  derived  from  the  posterior  auricular,  temporal, 
and  internal  maxillary  arteries.  The  upper  half  of  the  membrana  tympani  is  much  more  richly 
supplied  with  blood  than  the  lower  half.  For  this  reason,  and  also  to  avoid  the  chorda  tympani 
nerve  and  ossicles,  incisions  through  the  membrane  should  be  made  at  the  lower  and  posterior 
part. 

The  principal  point  in  connection  with  the  surgical  anatomy  of  the  tympanum  is  its  relations 
to  other  parts.  Its  roof  is  formed  by  a  thin  plate  of  bone,  which,  with  the  dura  mater,  is  all  that 
separates  it  from  the  temporal  lobe  of  the  brain.  Its  floor  is  immediately  above  the  jugular 
fossa  and  the  carotid  canal,  the  fossa  being  behind  and  the  canal  in  front.  Its  posterior  wall  pre- 
sents the  openings  of  the  mastoid  cells.  On  its  anterior  wall  is  the  opening  of  the  Eustachian 
tube.  Thus  it  follows  that  in  disease  of  the  middle  ear  we  may  get  subdural  abscess,  septic 
meningitis,  or  abscess  of  the  cerebrum  or  cerebellum  from  extension  of  the  inflammation  through 
the  bony  roof;  thrombosis  of  the  lateral  sinus,  with  or  without  pyaemia,  by  extension  through  the 
floor;  or  mastoid  abscess  by  extension  backward.  In  addition  to  this,  we  may  get  fatal  hemorrhage 
from  the  internal  carotid  in  destructive  changes  of  the  middle  ear;  and  in  throat  disease  we  may 
get  the  inflammation  extending  up  the  Eustachian  tube  to  the  middle  ear.  The  Eustachian  tube 
is  accessible  from  the  nose.  If  the  nose  and  mouth  be  closed  and  an  attempt  made  to  expire  air,  a 
sense  of  pressure  with  dulness  of  hearing  is  produced  in  both  ears,  from  the  air  finding  its  way  up 
the  Eustachian  tube  and  bulging  out  the  membrana  tympani.  During  the  act  of  swallowing,  the 
pharyngeal  orifice  of  the  tube,  which  is  normally  closed,  is  opened,  probably  by  the  action  of 
the  Dilator  tubea  muscle.  This  fact  was  employed  by  Politzer  in  devising  an  easy  method  of 
inflating  the  tube.  The  nozzle  of  an  india-rubber  syringe  is  inserted  into  the  nostril ;  the  patient 
takes  a  mouthful  of  water  and  holds  it  in  his  mouth,  both  nostrils  are  closed  with  the  finger  and 
thumb  to  prevent  the  escape  of  air,  and  the  patient  is  then  requested  to  swallow ;  as  he  does  so  the 


1178 


THE    ORGANS   OF  SPECIAL  SENSE 


surgeon  squeezes  the  bulb  and  the  air  is  forced  out  of  the  syringe  into  his  nose,  and  is  driven  into 
the  Eustachian  tube,  which  is  now  open.  The  impact  of  the  air  against  the  membrana  tympani 
can  be  heard  by  the  surgeon,  if  the  membrane  is  intact,  sound  being  conveyed  by  means  of  a 
piece  of  india-rubber  tubing,  one  end  of  which  is  inserted  into  the  meatus  of  the  patient's  ear,  the 
other  into  that  of  the  surgeon.  The  direct  examination  of  the  Eustachian  tube  is  made  by  the 
Eustachian  catheter.  This  is  passed  along  the  floor  of  the  nostril,  close  to  the  septum,  with 
the  point  touching  the  floor,  to  the  posterior  wall  of  the  pharynx.  When  this  is  felt,  the  catheter 
is  to  be  withdrawn  about  half  an  inch,  and  the  point  rotated  outward  through  a  quarter  of  a 
circle,  and  pushed  again  slightly  backward,  when  it  will  enter  the  orifice  of  the  tube,  and  will 
be  found  to  be  caught,  and  air  forced  into  the  catheter  will  be  heard  impinging  on  the  tympanic 
membrane  if  the  ears  of  the  patient  and  surgeon  are  connected  by  an  india-rubber  tube. 


THE  SKIN  (INTEGUMENTUM  COMMUNE). 

The  skin  covers  the  body  surface  and  is  continuous  with  the  mucous  membrane 
at  the  origin  and  termination  of  the  ahmentary  canal  and  at  the  openings  of  other 
canals.  The  skin  is  a  protective  coat,  a  regulator  of  body-temperature,  contains 
multitudes  of  the  terminations  of  sensory  nerves,  and  is  the  seat  of  the  organ  of 
touch  (organon  tactus).  These  nerve-terminations  are  connected  with  nerve-fibres  of 
temperature,  pressure,  and  pain.  Connected  with  the  skin  are  sweat-glands  which 
have  important  excretory  functions  and  sebaceous  glands.  From  its  superficial  part 
come  appendages,  the  hairs,  and  nails.  The  skin  is  elastic  and  varies  in  thickness 
from  0.5  mm.  to  4  mm.  It  is  thinnest  in  the  eyelids  and  prepuce,  and  thickest  over 
the  back  of  the  neck,  back  of  the  shoulders,  palms  of  the  hands,  and  soles  of  the 
feet.  Its  color  depends  in  part  on  the  blood  within  it,  and  in  part  upon  pigment. 
The  deepest  hue  is  about  the  anus,  in  the  genital  region,  in  the  axillae,  over  the 
mammary  glands,  and  in  the  parts  exposed  to  air,  light,  and  varied  temperatures. 
The  color  varies  with  age,  being  pinkish  in  extreme  youth  and  becoming  yellow 
in  old  age.  It  varies  with  exposure  and  with  climate,  being  deepest  in  those  who 
brave  all  weathers  and  temperatures  and  in  those  who  dwell  beneath  a  tropical  sun. 

It  also  varies  with  race,  and  this  is 
so  well  recognized  that  races  are  class- 
ified by  the  color  of  the  skin  into  the 
Black,White,Yellow,  and  Brown  races. 
The  color  of  the  skin  is  also  affected 
in  certain  diseases;  being  extremely 
pale  in  anaemia,  brown  in  Addison's 
disease,  yellow  in  jaundice,  etc. 

In  most  situations  the  skin  is  mova- 
ble, but  in  some  it  is  attached  closely 
to  underlying  structures,  and  is  con- 
sequently immovable  on  the  scalp, 
the  palms  of  the  hands,  the  soles  of 
the  feet,  and  the  outer  portion  of  the 
pinna  of  the  ear.  The  skin  is  fairly 
smooth,  but  close  examination  dis- 
closes multitudes  of  openings,  creases, 
furrows,  depressions,  folds,  and  hairs. 
Hair-follicles  open  upon  the  surface, 
and  the  ducts  of  sebaceous  glands 
and  of  sweat-glands  perforate  the  skin. 
About  the  joints  are  folds  of  skin  (retinacula  cutis),  and  temporary  folds  or 
wrinkles  are  created  by  the  contraction  of  superficial  muscles.  The  facial  wrinkles 
of  advancing  years  are  due  to  habitual  expression  and  loss  of  skin  elasticity.  A 
dimple  is  a  permanent  pit  or  depression  due  to  adhesion  of  the  surface  to  parts 
beneath.    The  ridges  and  furrows  on  the  palms,  soles,  and  flexor  aspects  of  the 


LONGITUDINAL 
FURROWS 


RIDGES  OF  SKIN 

INTERRUPTED  BY 

LONGITUDINAL 

FURROWS 


FURROWS 
OF  SKIN 


FLEXION    FURROWS 
OPPOSITE  THE 
FLEXURE  OF 
THE  JOINT 


Fig.  779. — The  furrows  and  ridges  of  the  surface  of  the 
skin  from  the  palm  or  surface  of  the  middle  finger.    (Toldt.) 


THE  SKIN 


1179 


digits  are  permanent,  and  over  the  palmar  surface  of  the  digits  they  are  arranged 
in  definite  forms  which  endure  through  life  and  are  so  distinctive  that  they  have 
been  utilized  by  police  officials  in  determining  the  identity  of  individuals.  These 
folds  are  due  to  the  papillae  of  the  skin  being  arranged  in  rows;  some  of  the  papillae 
proliferate,  and  linear  depressions  occur  in  the  horny  layer  (Philippson). 


Fig.  780. — Anterior  surface.  Fig.  781. — Posterior  surface. 

The  general  course  of  the  connective-tissue  bundles  of  the  corium,  determined  by  the  direction  assumed  by  the 

linear  clefts  made  in  the  skin  when  it  is  punctured  by  a  round  awl.     (Langer.) 

Fig.  779  shows  skin  ridges  (cristae  cutis),  skin  furrows  (sulci  cutis),  furrows 
opposite  joints  due  to  acts  of  flexion,  and  called  flexure  furrows,  and  longitudinal 
furrows. 

When  the  skin  is  punctured  by  a  round  awl  it  tends  to  split  in  a  definite 
direction,  which  direction  varies  with  the  region  stabbed.    These  clefts  are  known 


1180 


THE  ORGANS    OF  SPECIAL   SENSE 


as  the  lines  of  cleavage  of  Langer  (Figs.  780  and  781),  and  depend  upon  the 
arrangement  of  the  connective-tissue  bundles  of  the  corium.  These  connective- 
tissue  bundles  certainly  influence  the  formation  of  folds  and  furrows.  In  many 
portions  of  the  body  the  cutaneous  surface  is  divided  by  linear  furrows  into  irregu- 
larly shaped  areas  (Fig.  782).  The  skin  consists  of  two  layers:  a  superficial  layer, 
the  epidermis,  and  a  deep  layer,  the  corium  or  dermis. 

The  Corium,  Cutis  Vera,  Dermis  or  True  Skin  (Figs.  783,  784,  and  786)  is  a 
connective-tissue  structure  which  arises  from  the  mesoderm.  It  consists  espe- 
cially of  connective  tissue  and  elastic  fibres;  it  contributes  elasticity  to  the  skin, 
and  is  the  seat  of  the  sensitive  layer.  The  corium  is  composed  of  two  layers, 
the  reticular  and  the  papillary. 


MOUTH  OF  ^^c 
HAIR-FOLLICLES'-*..^/' 


-..FURROW 

""of  skin 


Fig.  782. — The  furrows  of  the  skin  and  the  areas  which  these  furrows  delimit,  reproduced  from  an  impression  of 

the  dorsal  surface  of  the  wrist.      (Toldt.) 

The  Deep  or  Reticular  Layer  or  Tunica  Propria  {stratum  reticulare)  rests  upon 
the  subcutaneous  tissue.  It  passes  superficially  into  the  papillary  layer,  and  at 
most  places  into  the  subcutaneous  tissue  without  a  sharp  line  of  differentiation. 
At  some  places,  for  instance  in  the  nipple,  the  deep  layer  of  the  corium  rests 
upon  a  layer  of  muscular  fibre.    In  the  face  this  muscle-fibre  is  striated  and  sends 


FURROWS.OF  SKIN 


RIDGES  OF  SKIN 


/      STRATUM 
IDERMIS'j       STRATUM 

ORIUM  I 


TOUCH  CORPUSCLEv 


STRATUM  CORNEUS  f 


LUCIDUM 
RETE  MUCOSUM 


STRATUM     PAPILLARE 


STRATUM    RETICULARE 


SUBCUTANEOUS 
AREOLAR  tissue' 


ORIFICE   OF 

SUDORIFEROUS 

DUCT 

SUDORIFEROUS 

DUCT 

CAPILLARY 
LOOP  OF 
PAPILLA 


BLOODVESSELS 
OF   CORIUM 

BODY  OF 

SUDORIFEROUS 

GLAND 


Fig.  783. — Vertical  section  through  the  skin  of  the  finger-tip.     The  layers  of  the  epidermis  and  of  the  corium. 
The  subcutaneous  areolar  tissue.     The  sudoriferous  or  sweat-gland.     (Toldt.) 

prolongations  to  the  papillary  layer;  in  the  nipple  and  scrotum  it  is  non-striated. 
The  reticular  layer  is  composed  of  bundles  of  white  fibrous  tissue,  arranged  in  a 
network.  In  the  meshes  of  the  network  are  fat,  blood-vessels,  lymphatics,  seba- 
ceous glands,  sweat-glands,  and  hair-follicles. 

The  Subcutaneous  Areolar  Tissue  or  Tela  Subcutanea  (panniculus  adiposus)  con- 
nects, the  skin  to  the  parts  beneath ;  it  is  composed  of  bundles  of  connective  tissue 


THE   SKIN 


1181 


ARRECTOR 
PIL>    MUSCLE 


CORIUM       EPIDERMIS 


which  cross  repeatedly  and  form  spaces.  In  almost  all  regions  the  spaces  contain  fat, 
but  in  the  scrotum  and  external  ear  they  do  not  contain  fat.  When  the  connective- 
tissue  fibres  of  the  panniculus  adiposus  are  long  and  nearly  parallel  to  the  skin- 
surface  the  skin  becomes  wrinkled;  when  they  are  short  and  nearly  at  right  angles 
to  the  surface,  the  skin  cannot  wrinkle. 

The  Superficial  or  Papillaxy  Layer  or  Corpus  Papillare  of  the  Corium  (stratum  papil- 
lare)  lies  just  beneath  the  epidermis,  contains  the  papillae,  and  is  composed  of  a 
network  of  fine  bundles  of  fibrous  tissue.  The  papillae  are  composed  of  fine 
strands  of  connective  tissue  and  elastic 
tissue.  They  project  from  the  corium 
beneath  the  epidermis  and  enter  into 
depressions  of  the  epidermis.  They  vary 
greatly  in  size,  averaging  y^  of  an  inch 
in  height  and  2-5-0"  of  ^^i  i'^ch  in  width  at 
the  base.  In  the  face,  especially  in  the 
eyelids,  they  are  insignificant.  On  the 
glans  penis,  the  palms  of  the  hands,  and 
the  soles  of  the  feet,  and  in  the  nipples, 
they  are  large.  In  the  palmar  surfaces 
of  the  hands  and  fingers  and  the  plantar 
surfaces  of  the  feet  and  toes  they  pro- 
duce permanent  ridges  (Fig.785).  A  ridge 
is  composed  of   two   or  more  rows  of 

papillae,  and    the  ducts  of    sweat-glands        Fig.  784.— vertical  section  through  the  skin  of  the 

„. v.A.„, „„„,„    ^e    »^„„CU„„     ^^A    trunk  in  the  region  of  the  arch  of  the  ribs.     One  of 

emerge     between    rows    Ot    papillae,   and    the  small  hairs  is  seen  in  longitudinal  section.  (Toldt.) 

open  on  the  curved  surface  ridges  (Fig. 

785).  Most  of  the  papillae  contain  loops  of  capillaries,  and  are  called  vascular 
papillae.  Some  contain  nerve-terminations  and  are  called  nervous  papillae.  Be- 
tween the  papillary  layer  of  the  corium  and  the  epidermis  is  a  very  thin  and 
structureless  membrane  called  the  basal  membrane. 


SUDORIFEROUS      SUBCUTANEOUS 
GLANDS      AREOLAR  TISSUE 


PAPILL>E 
CORIUM 


SUDORIFEROUS 
DUCTS 


Fig.  785. — The  furrows  and  ridges  of  true  skin  on  the  palmar  surface  of  one  of  the  fingers,  the  epidermis 

having  been  removed.     (Toldt.) 

The  Cuticle,  Scarf  Skin  or  Epidermis  (Figs.  783,  784,  786,  and  787).— The 
cuticle,  scarf  skin  or  epidermis  is  composed  of  layers  of  epithelium  and  is 
derived  from  the  ectoderm.  The  epithelium  is  stratified,  and  there  are  no 
blood-vessels.  Two  layers  can  be  readily  made  out,  the  superficial  or  homy 
layer  and  the  deeper  or  Malpighian  layer. 

The  Homy  Layer  {stratum  corneum). — I'he  horny  layer  is  formed  by  several 
layers  of  non-nucleated  scaly  cells.  The  cells  consist  of  keratin.  The  surface 
cells  of  the  horny  layers  are  being  constantly  rubbed  oft',  and  are  being  replaced 
by  cells  from  the  Malpighian  layer,  which  are  converted  into  keratin  as  they  near 
the  surface. 


1182 


THE    OBGANS    OF  SPECIAL   SENSE 


The  Malpighian  Layer. — The  Malpighian  layer  of  the  epidermis  is  divided  into 
four  layers,  named,  from  without  inward,  the  stratum  lucidum,  the  stratum  granu- 
losum,  the  stratum  mucosum,  and  the  stratum  germinativum. 

The  Stratum  Lucidum  is  not  classified  by  all  writers  as  part  of  the  Malpighian 
layer.  Some  anatomists  classify  it  as  a  separate  layer.  It  is  here  regarded  as  the 
most  superficial  part  of  the  Malpighian  layer.  It  consists  of  several  layers  of  flat 
cells,  the  nuclei  of  which  are  beginning  to  disappear.  The  cells  contain  eleidin 
granules.    In  regions  where  the  epidermis  is  thin  the  stratum  lucidum  is  absent. 

The  Stratum  Granulosum  consists  of  several  layers  of  nucleated  flat  cells,  con- 
taining kerato hyaline  granules.  These  granules  are  probably  formed  from  the 
disintegrating  nucleus,  and  in  the  stratum  lucidum  are  converted  into  eleidin. 


Fibrous 
tissue 


Sebaceous 
Olands 


Sweat-Olands 


Nutrient  Artery 


Fig.  786. — A  sectional  view  of  the  skin  (magnified). 


The  Mucous  Layer,  the  Stratum  Spinosum  or  the  Stratum  Mucosum  consists  of 
numerous  layers  of  nucleated,  polygonal,  spine-shaped  cells  known  as  prickle  cells 
or  finger  cells.  Between  the  cells  of  the  stratum  mucosum  are  spaces  containing 
pigment  granules  and  leukocytes.  Processes  from  the  prickle-cells  join  adjacent 
cells.  This  layer  contains  numerous  connective-tissue  fibres  arranged  in  a  net- 
work, and  known  as  epidermic  fibrils. 

The  Stratum  Cylindricum  or  Stratum  Germinativum  is  composed  of  cylindrical  or 
prickle-cells,  the  points  of  which  are  directed  downward.  Fine  fibrils  pass  up 
from  the  corium  between  the  cells,  and  there  is  cement-substance  as  well  between 
them. 

Pigmentation  of  the  Skin. — As  previously  stated,  in  certain  regions  the  skin  of  the 
white  race  is  brown  because  of  pigmentation  (areolae,  nipples,  around  the  anus, 
axillae,  scrotum,  labia  majora).    This  is  due  to  pigment  within  the  epithelial  and 


THE   SKIN 


1183 


connective-tissue  cells  of  the  papillary  layer  of  the  corium,  and  in  the  basal  cells 
of  the  epidermis.  There  are  few  or  none  of  these  pigmented  cells  in  the  stratum 
corneum  of  one  of  the  Caucasian  race. 


Stratum  corneum. -l 


Stratum  lucidumA 
Stratum  grannlosum.  f 


Stratum  mucosum 
Malpighii. ' 


Stratum  germinativum. 


-Nerve-fibrU$. 


Fig.  787. — Section  of  epidermis.     (Ranvier.) 


"In  negroes  and  other  colored  races  the  deep  pigmentation  is  due  to  a  similar 
distribution  of  the  pigment  granules  in  the  entire  epidermis;  but  even  here  the 
pigmentation  decreases  toward  the  surface,  although  the  uppermost  cells  of  the 


Fig.  788. — Microscopic  section  of  skin,  showing  the  epidermis  and  derma  ;  a  hair  in  its  follicle  ; 
the  Erector  pili  muscle  ;  sebaceous  and  sudoriferous  glands. 

stratum  corneum  always  contain  some  pigment.  The  nuclei  of  the  cells  are  always 
free  from  coloring  matter.  The  question  as  to  the  origin  of  the  pigment  is  as  yet 
unsolved."^ 


A  Text-book  of  Histology.    By  A.  A.  BiJhm  and  M.  von  Davidoff.    Translated  and  edited  by  G.  Carl  Huber. 


1184 


THE    ORGANS    OF  SPECIAL   SENSE 


The  Arteries  and  Veins  of  the  Skin  (Fig.  789). — The  arteries  supplying  the  skin 
vary  in  number,  and  vary  much  in  size,  being  largest  in  regions  exposed  to 
pressure,  as  the  skin  of  the  palms,  soles,  and  buttocks.  The  arteries  enter  the 
skin  from  a  network  in  the  subcutaneous  tissue,  and  by  an  anastomosis  in  the 
deepest  part  of  the  corium  form  a  network  {rete  arteriosum  cutaneum).  The  vessels 
send  branches  to  the  fat  and  to  the  sweat-glands.  Branches  from  the  network  just 
described  ascend  and  form  a  second  network  in  the  corium  beneath  the  papillae. 
This  is  called  the  subpapillary  network  {rete  arteriosum  suhpapillare).  From  this  net- 
work fine  capillary  vessels  pass  into  the  papillae,  forming,  in  the  smaller  papillae, 
a  single  capillary  loop,  but  in  the  larger  a  more  or  less  convoluted  vessel.  From 
this  network  branches  go  to  the  hair-follicles  and  sebaceous  glands.  The  blood 
from  the  papillae  passes  into  a  plexus  (rete  venosum)  beneath  the  papillae.  This 
communicates  with  another  plexus  {rete  venosum),  between  the  corium  and  sub- 


RETE 
VENOSUM 


SUBPAPILLARY 
NETWORK 


EPIDERMIS 
—  PAPILLARY  LAYER" 


RETE 
VENOSUM 


RETE    ARTERIOSUM 
CUTANEUM 


SUBCUTANEOUS 
TISSUE 


RETE 
VENOSUM 


Fig.  789. — The  distribution  of  the  blood-vessels  in  the  skin  of  the  sole  of  the  foot.     (Spalteholz.) 


cutaneous  tissue.  In  some  regions  one  or  more  retia  are  interposed  between  these 
two.  The  veins  from  the  sweat-glands,  sebaceous  glands,  superficial  fat,  and  hair- 
follicles  are  received  by  the  retia  venosa.  From  the  deepest  rete  veins  pass  to  the 
subcutaneous  tissue,  and  these  veins  enter  the  large  subcutaneous  veins. 

The  Lymphatics  of  the  Skin. — There  are  numerous  lymphatics  supplied  to  the 
skin  which  form  two  networks,  superficial  and  deep,  communicating  with  each 
other  and  with  the  lymphatics  of  the  subcutaneous  tissue  by  oblique  branches. 
They  originate  in  the  cell-spaces  of  the  tissue. 

The  Nerves  of  the  Skin. — The  nerves  of  the  skin  terminate  partly  in  the  epidermis 
(Figs.  783  and  787)  and  partly  in  the  cutis  vera  (Fig.  783) .  The  former  are  pro- 
longed into  the  epidermis  from  a  dense  plexus  in  the  superficial  layer  of  the  corium 
and  terminate  between  the  cells  in  bulbous  extremities;  or,  according  to  some 
observers,  in  the  deep  epithelial  cells  themselves.  The  latter  terminate  in  end- 
bulbs,-  touch-corpuscles,  or  Pacinian  bodies  (Fig.  783),  in  the  manner  already 
described;  and,  in  addition  to  these,  a  considerable  number  of  fibrils  are  distrib- 
uted to  the  hair-follicles,  which  are  said  to  entwine  about  the  follicle  in  a  circular 


THE  NAILS 


1185 


manner.  Other  nerve-fibres  are  supplied  to  the  plain  muscular  fibres  of  the  hair- 
follicles  (arrectores  pili)  and  to  the  muscular  coat  of  the  blood-vessels.  These  are 
probably  non-medullated  fibres. 

The  Appendages  of  the  Skin. 

The  appendages  of  the  skin  are  the  nails,  the  hairs,  the  sudoriferous  and  seba- 
ceous glands,  and  their  ducts. 

The  nails  and  hairs  are  peculiar  modifications  of  the  epidermis,  consisting 
essentially  of  the  same  cellular  structure  as  that  tissue. 


Eponychium, 

Nail. 

Stratum 

MalpighiiJ 

Stratum  corneum 

of  the  nail 

groove. 


Fig.  790. 


-Longitudinal  section  through  human  nail  and  its  nail  groove  (sulcus). 
Davidoff's  Histology. 


Stratum 
corneum. 

'--'Iratuin 
granulosum. 

Corium. 


Blood-vessel. 


(From  Bohm  and 


The  Nails  (ungues)  (Figs.  790,  791,  792, 793,  794,  and  795).— The  nails  are  flat- 
tened, elastic  structures  of  a  horny  texture,  placed  upon  the  dorsal  surface  of  the 
terminal  phalanges  of  the  fingers  and  toes.  Each  nail  is  convex  on  its  outer  sur- 
face, concave  within.  Its  chief  mass,  called  the  body  (corpus  unguis),  lies  upon 
the  nail-bed.  The  free  edge  is  called  the  margo  liber.  Each  lateral  margin  (margo 
lateralis),  like  the  proximal  short  edge  of  the  nail  (margo  occultus),  lies  in  a  groove 
of  the  cutis,  the  ungual  fold  (sulcus  matricis  unguis).  The  ungual  wall  (vallum 
unguis)  overlies  the  lateral  and  posterior  edges.  The  nail  is  implanted  by  means 
of  a  portion,  called  the  root  (radix  unguis),  into  a  groove  in  the  skin.  The  root  is 
beneath  the  ungual  wall  and  is  composed  of  cells  which  have  not  yet  become 

Nail 

Stratum  Malpighii. 

Nail  wail. 

Nail  groove. 

'num. 
Blood-  vessel. 


Fig.  791. — Transverse  section  through  human  nail  and  its  sulcus.     (From  Biihm  and  Davidoff's  Histology.) 

horny.  It  is  white  in  color.  The  nail  has  a  very  firm  adhesion  to  the  cutis  vera, 
being  accurately  moulded  upon  the  surface  of  the  true  skin,  as  the  epidermis  is  in 
other  parts.  The  part  of  the  cutis  beneath  the  body  and  root  of  the  nail  is  called 
the  matrix  (matrix  unguis),  because  it  is  the  part  from  which  the  nail  is  produced. 
Corresponding  to  the  body  of  the  nail,  the  matrix  is  thick,  and  raised  into  a  series 
of  longitudinal  ridges  (cristae  matricis  unguis),  which  are  very  vascular,  and  the 
color  is  seen  through  the  transparent  tissue.  Behind  this,  near  the  root  of  the 
nail,  the  papillae  are  small,  less  vascular,  and  have  no  regular  arrangement,  and 
here  the  tissue  of  the  nail  is  somewhat  more  opaque;  hence  this  portion  is  of  a 
whiter  color,  and  is  called  the  lunula  on  account  of  its  crescentic  shape. 


1186 


THE    ORGANS    OF  SPECIAL    SENSE 


The  cuticle,  as  it  passes  forward  on  the  dorsal  surface  of  the  finger  or  toe,  is 
attached  to  the  surface  of  the  nail,  a  little  in  advance  of  the  nail  root;  at  the 
extremity  of  the  finger  it  is  connected  with  the  under  surface  of  the  nail  a  little 
behind  its  free  edge.  The  cuticle  and  the  horny  substance  of  the  nail  (both  epi- 
dermic structures)  are  thus  directly  continuous  with  each  other.  The  nails  con- 
sist of  a  greatly  thickened  stratum  lucidum,  the  stratum  corneum  forming  merely 


SULCUS  OF 
MATRIX 


LATERAL 
MARGIN 


THIRD^, 

phalanx' 


PERIOSTEU 


OF  FINOrP 


Fig.  792. — Transverse  section  through  the  nail  and  the  terminal  portion  of  the  ring  finger.     (Toldt.) 


the  thin  cuticular  fold  (eponychium)  which  overlaps  the  lunula.  The  cells  have 
a  laminated  arrangement,  and  are  essentially  similar  to  those  composing  the 
epidermis.  The  deepest  layer  of  cells,  which  lie  in  contact  with  the  papillae 
of  the  matrix,  are  columnar  in  form  and  arranged  perpendicularly  to  the  surface; 
those  which  succeed  them  are  of  a  rounded  or  polygonal  form,  the  more  superficial 
ones  becoming  broad,  thin,  and  flattened,  and  so  closely  compacted  as  to  make  the 


matrix  of  nail 


FREE  EDGE 


ridges  of 
matrix 


SULCUS  OF 
MATRIX 


NAIL  FOLD 


CONCEALED  MARGIN 


Fig.  793. — The  finger  nail  com- 
pletely isolated,  seen  from  the  con- 
vex side.     (Toldt.) 


NAIL  WALL 


Fig  794.— The  matrix  of 
the  nail  or  nail-bed,  with  the 
nail-fold  and  nail-walls  dis- 
played by  the  removal  of  the 
epidermic  portion  of  the  nail 
or  nail  proper  and  the  sur- 
rounding epidermis.     (Toldt.) 


SULCUS  OF 
MATRIX 


Fig.  795. — Matrix  of  the 
nail  with  partly  opened  mar- 
ginal groove  of  the  nail-bed. 
(Toldt.) 


limits  of  each  cell  very  indistinct.  It  is  by  the  successive  growth  of  new  cells  at 
the  root  and  under  surface  of  the  body  of  the  nail  that  it  advances  forward  and 
maintains  a  due  thickness,  while,  at  the  same  time,  the  growth  of  the  nail  in  the 
proper  direction  is  secured.  As  these  cells  in  their  turn  become  displaced  by 
the  growth  of  new  ones,  they  assume  a  flattened  form,  and  finally  become  closely 
compacted  together  into  a  firm,  dense,  horny  texture.    In  chemical  composition  the 


THE   HAIRS 


1187 


NECK  OF 
HAIR-FOLLICLE 


INNE 
ROOT-SHEATH 


OUTER 
ROOT-SHEATH 


SEBACEOUS 
GLAND 


nails  resemble  the  upper  layers  of  the  epidermis,  containing,  however,  a  some- 
what larger  proportion  of  carbon  and  sulphur  (Mulder). 

The  Hairs  (pi7i)(Figs.  784, 786, 788,  796, 797,  and  798).— The  hairs  are  peculiar 
modifications  of  the  epidermis,  and  consist  essentially  of  the  same  structure  as 
that  membrane.  They  are  found  on  nearly  every  part  of  the  surface  of  the  body, 
excepting  the  palms  of  the  hands,  soles  of  the  feet,  the  vermilion  borders  of  the 
lips,  the  dorsal  surfaces  of  the  phalanges,  the  nipples,  the  inner  surface  of  the 
prepuce,  and  the  glans  penis.  Hairs  include  hairs  of  the  head  (ca'pilla) ;  of  the  eye- 
brows (supercilia) ;  of  the  beard  (barba) ;  of  the  ears  (tragi) ;  of  the  nostrils (vibrissae) ; 
the  oyelashes  (cilia) ;  hairs  of  the  axilla  (hirci) ;  pubes  (pubes) ;  and  the  small  hairs 
of  the  skin  or  woolly  hairs  (lanugo). 
They  vary  much  in  length,  thick- 
ness, and  color  in  different  parts  of 
the  body  and  in  different  races  of 
mankind.  In  some  parts,  as  in  the 
skin  of  the  eyelids,  they  are  so  short 
as  not  to  project  beyond  the  follicles 
containing  them;  in  others,  as  upon 
the  scalp,  they  are  of  considerable 
length;  again,  in  other  parts,  as  the 
eyelashes,  the  hairs  of  the  pubic  re- 
gion, and  the  whiskers  and  beard, 
they  are  remarkable  for  their  thick- 
ness. Straight  hairs  are  stronger 
than  curly  hairs,  and  present  on 
transverse  section  a  cylindrical  or 
oval  outline;  curly  hairs,  on  the 
other  hand,  are  flattened.  The  hairs 
are  usually  oblique  to  the  surface 
from  which  they  arise  (Fig.  784). 
Their  direction  depends  upon  the 
region  from  which  they  spring,  being 
fairly  regular  in  certain  regions. 
Thus  are  formed  hair-streams  (flu- 
mina  pilonim)  and  hair-whirlpools 
(vortices  pilorum). 

A  hair  consists  of  the  root,  the 
part  implanted  in  the  skin;  the  shaft 
or  stem,  the  portion  projecting  from 
its  surface;  and  the  point. 

The  Root  of  the  Hair  (radix  pili) 

nrp'^pnts  nt  it«  pvfrpmi+v  a  KiilKr^iic  Fig.  796.— A  hair  of  the  head  still  in  the  course  of  growth, 
presents   ai    us   exiremiiy  a    DUIDOUS  with  hair-bulb  in  longitudinal  section      (Toldt.) 

enlargement,  the  hair-bulb   (bulbus 

pili)  (Figs.786  and  796) , which  is  whiter  in  color  and  softer  in  texture  than  the  shaft, 
and  is  lodged  in  a  follicular  involution  of  the  epidermis  called  the  hair-follicle  (folli- 
culus  pili)  (Figs.  784  and  788).  When  the  hair  is  of  considerable  length  the  follicle 
extends  into  the  subcutaneous  cellular  tissue  (Fig.  786).  The  hair-follicle  com- 
mences on  the  surface  of  the  skin  with  a  funnel-shaped  opening,  and  passes  inward 
in  an  oblique  or  curved  direction — the  latter  in  curly  hair — to  become  dilated  at 
its  deep  extremity  or  fundus  (fundus  folliculi  pili),  where  it  corresponds  with  the 
bulbous  condition  of  the  hair  which  it  contains.  It  has  opening  into  it,  near  its 
free  extremity,  the  orifices  of  the  ducts  of  one  or  more  sebaceous  glands  (Figs. 
786,  788,  796,  and  797).  At  the  bottom  of  each  hair-follicle  is  a  small  conical, 
vascular  eminence  or  papilla,  the  hair-papilla  (papilla  pili)  (Figs.  796  and  797), 


OUTER 
FIBROUS   LAYER 


INNER 
FIBROUS  LAYER 


FUNDU 
I-IAIR-FOLLI 


1188 


THE    ORGANS    OF  SPECIAL   SENSE 


similar  in  every  respect  to  the  papillae  found  upon  the  surface  of  the  skin ;  it  is 
continuous  with  the  dermic  layer  of  the  follicle,  is  highly  vascular,  and  is  prob- 
ably supplied  with  nervous  fibrils.  In  structure  the  hair-follicle  consists  of  two 
coats— an  outer  or  dermic,  and  an  inner  or  epidermic  (Figs.  796  and  798). 

The  Outer  or  Dermic  Coat  is  formed  mainly  of  fibrous  tissue;  it  is  continuous 
with  the  corium,  is  highly  vascular,  and  is  supplied  by  numerous  minute  nervous 
filaments.  It  consists  of  three  layers.  The  most  internal,  the  cuticular  lining 
of  the  follicle,  consists  of  a  hyaline  basement-membrane,  the  hyaline  layer,  having 
a  glassy,  transparent  appearance,  which  is  well  marked  in  the  larger  hair-follicles,. 
but  is  not  very  distinct  in  the  folUcles  of  minute  hairs.  It  is  continuous  with  the 
basement-membrane  of  the  surface  of  the  corium.  External  to  this  is  the  inner 
fibrous  layer,  a  compact  layer  of  fibres  and  spindle-shaped  cells  arranged  circularly 
around  the  follicle.  This  layer  extends  from  the  bottom  of  the  follicle  as  high  as 
the  entrance  of  the  ducts  of  the  sebaceous  glands.  Externally  is  the  outer  fibrous 
layer,  a  thick  layer  of  connective  tissue,  arranged  in  longitudinal  bundles,  forming 
a  more  open  texture  and  corresponding  to  the  reticular  part  of  the  corium.  In  this 
are  contained  the  blood-vessels  and  nerves. 


CPIOERMIS.— ' 


CORIUM-   % 


SUBCUTANEOUS    '^' 
AREOLAR  TISSUE 


RETINACULA 
OF  SKIN 


OCC I  PITO- FRONTAL 
APONEUROSIS 


ARRECTOR 
PILI   MUSCLE 

SEBACEOUS 

GLAND 

i^     SUDORIFEROUS 
GLAND 

—  HAIR-FOLLICLE 

ROOT 

HAIR-KNOB 
;  HAIR-BULB 


p;  PAPILLA 
OF  HAIR 


Fig.  797. — Vertical  section  through  the  skin  of  the  head.     The  hair.s  of  the  head  in  longitudinal  section.    (Toldt.) 

The  Inner  or  Epidermic  Layer  is  closely  adherent  to  the  root  of  the  hair,  so  that 
when  the  hair  is  plucked  from  its  follicle  this  layer  most  commonly  adheres 
to  it  and  forms  what  is  called  the  root-sheath.  It  consists  of  two  strata,  named 
respectively  the  outer  and  inner  root-sheaths;  the  former  of  these  corresponds  with 
the  Malpighian  layer  of  the  epidermis,  and  resembles  it  in  the  rounded  form  and 
soft  character  of  its  cells;  at  the  bottom  of  the  hair-follicle  these  cells  become  con- 
tinuous with  those  of  the  root  of  the  hair.  The  inner  root-sheath  consists  of  a 
delicate  cuticle  next  the  hair,  composed  of  a  thin  layer  of  imbricated  scales  having 
a  downward  direction,  so  that  they  fit  accurately  over  the  upwardly  directed 
imbricated  scales  of  the  hair  itself;  then  of  one  or  two  layers  of  horny,  flattened 
nucleated  cells,  known  as  Huxley's  layer;  and  finally  of  a  single  layer  of  horny 
oblong  cells  without  visible  nuclei,  called  Henle's  layer. 

The  hair-follicle  contains  the  root  of  the  hair,  which  terminates  in  a  bulbous 
extremity,  and  is  excavated  so  as  to  exactly  fit  the  papilla  from  which  it  grows. 
The  bulb  is  composed  of  polyhedral  epithelial  cells,  which  as  they  pass  upward 
into  the  root  of  the  hair  become  elongated  and  spindle-shaped,  except  some  in  the 
centre  which  remain  polyhedral.     Some  of  these  latter  cells  contain  pigment- 


THE   HAIRS 


1189 


granules,  which  give  rise  to  the  color  of  the  hair.  It  occasionally  happens  that 
these  pigment-granules  completely  fill  the  cells  of  the  medullary  substance  in 
the  centre  of  the  bulb,  which  gives  rise  to  the  dark  tract  of  pigment  often  found, 
of  greater  or  less  length,  in  the  axis  of  the  hair. 

The  Stem  or  Shaft  of  the  Hair  (scapus  pill)  (Fig.  796),  consists  of  a  central  pith  or 
medulla,  the  fibrous  part  of  the  hair,  and  the  true  cuticle  externally.  The  medulla 
(substantia  medullaris  pili)  occupies  the  centre  of  the  shaft  and  ceases  toward  the 
point  of  the  hair.  It  is  usually  wanting  in  the  fine  hairs  covering  the  surface  of 
the  body,  and  commonly  in  those  of  the  head.  It  is  found  in  the  shafts  of  all  thick 
hairs  and  in  the  deeper  parts  of  the  root  of  most  hairs.  It  is  more  opaque  and 
deeper  colored  when  viewed  by  transmitted  light  than  the  fibrous  part;  but  when 
viewed  by  reflectefl  light  it  is  white.  It  is  composed  of  rows  of  polyhedral  cells, 
which  contain  granules  of  eleidin  and  frecjuently  air-bubbles.  The  fibrous  portion 
or  cortical  substance  of  the  hair  (substantia  corticalis  pili)  constitutes  the  chief  part 
of  the  shaft;  its  cells  are  elongated  and  unite  to  form  flattened  fusiform  fibres. 
Between  the  fibres  are  found  minute  spaces  which  contain  either  pigment-granules 
in  dark  hair  or  minute  air-bubbles  in  white  hair.    In  addition  to  this  there  is  also  a 


CUTICLE  OF 
ROOT   SHEATH  '^ 


INNER 
FIBROUS  -«^'   1 

OUTER  / 

FIBROUS ■ 

LAYER        h 


OOT-SHEATH 


CR 
ROOT-SHCATH 


^  MEDULLARY 
SUBSTANCE 


x  FIBROUS 
SUBSTANCE 


Fig.  798  — \  moustache  hair  with  its  hair-follicle  in  transver«e  section.     (Toldt.) 


diffused  pigment  contained  in  the  fibres.  The  cells  which  form  the  outer  hair  mem- 
brane or  true  cuticle  (cuticula  pili)  consist  of  a  single  layer  which  surrounds  those  of 
the  fibrous  part;  they  are  converted  into  thin,  flat  scales,  having  an  imbricated 
arrangement. 

Connected  with  the  hair-follicles  are  minute  bundles  of  involuntary  muscular 
fibres,  termed  arrectores  pili  (mm.  arredores  pilorum)  (Figs.  784  and  796).  They 
arise  from  the  superficial  layer  of  the  corium,  and  are  inserted  into  the  outer 
surface  of  the  hair-follicle,  below  the  entrance  of  the  duct  of  the  sebaceous  gland. 
They  are  placed  on  the  side  toward  which  the  hair  slopes,  and  by  their  action 
elevate  the  hair.*  When  the  hair  is  elevated  a  depression  forms  over  the  seat  of 
origin  of  the  muscle,  and  the  parts  about  the  hair  are  elevated.  This  condition  is 
known  as  goose-skin.  It  is  probable  that  the  contraction  of  these  muscles  aids  in 
emptying  sebaceous  glands. 

Blood-vessels  and  Nerves  (Fig.  786). — A  hair-follicle  possesses  a  rich  network  of 
capillaries  about  the  hyaline  membrane,  and  capillary  loops  pass  to  the  papilla. 

'  Arthur  Thomson  suggests  that  the  contraction  of  these  muscles  on  follicles  which  contain  weak,  flat  hairs 
will  tend  to  produce  a  permanent  curve  in  the  follicle,  and  this  curve  will  Be  impressed  on  the  hair  which  is 
moulded  within  it,  so  that  the  hair,  on  emerging  through  the  skin,  will  be  curled.  Curved  hair-follicles  are 
characteristic  of  the  scalp  of  the  Bushman. —  I'^d.  of  loth  English  edition. 


1190  THE    ORGANS   OF  SPECIAL   SENSE 

We  have  little  knowledge  as  to  nerve-terminations  of  the  human  hair.  "In  other 
mammals  the  nerves  end  below  the  sebaceous  glands.  Medullated  fibres  lose 
their  medullary  sheaths,  divide,  and  penetrate  to  the  hyaline  membrane.  Here 
some  of  the  branches  encircle  the  hair,  while  others  end  freely  on  the  hyaline 
membrane  as  naked  axis-cylinders.  These  branch  regularly  and  run  parallel  to 
the  long  axis  of  the  hair."^ 

The  Sudoriferous  or  Sweat-glands  {glandulae  siidoriferae)  (Figs.  783,  7S4, 786, 
788,  and  797). — The  sudoriferous  or  sweat-glands  are  the  organs  by  which  a  large 
portion  of  the  aqueous  and  gaseous  materials  is  excreted  by  the  skin.  They  are 
found  in  almost  every  part  of  this  structure,  being  absent  on  the  red  border  of  the 
lips,  the  glans  penis,  and  inner  surface  of  the  prepuce.  On  the  eyelids  they  are  some- 
what modified,  and  are  called  ciliary  glands  {glandulae  ciliares  [Molli]) ;  about  the 
anus  they  are  extremely  large,  and  are  called  circumanal  glands  (glandulae  circum- 
anales).  The  sweat-glands  are  situated  in  small  pits  below  the  under  surface  of  the 
corium,  or,  more  frequently,  in  the  subcutaneous  areolar  tissue,  surrounded  by  a 
quantity  of  adipose  tissue.  They  are  small,  lobular,  reddish  bodies,  consisting  of 
a  single  convoluted  tube,  from  which  the  efferent  duct  {ductus  sudor  if  eru.'i)  proceeds 
upward  through  the  corium  and  cuticle.  The  duct  in  the  corium  has  true  walls;  in 
the  epidermis  it  has  not  individual  walls,  but  is  simply  an  epidermic  tube.  It 
becomes  somewhat  dilated  at  its  extremity,  and  opens  on  the  surface  of  the  cuticle  by 
an  oblique  valve-like  aperture  (poru^  sudorijerus).  The  duct,  as  it  passes  through 
the  epidermis,  presents  a  spiral  arrangement,  being  twisted  like  a  corkscrew,  in 
those  parts  where  the  epidermis  is  thick;  where,  however,  the  epidermis  is  thin,  the 
spiral  arrangement  does  not  exist.  In  the  superficial  layers  of  the  corium  the  duct 
is  straight,  but  in  the  deeper  layers  it  is  convoluted  or  even  twisted.  The  spiral 
course  of  these  ducts  is  especially  distinct  in  the  thick  cuticle  of  the  palm  of  the 
hand  and  sole  of  the  foot.  The  size  of  the  glands  varies.  They  are  especially 
large  in  those  regions  where  the  flow  of  perspiration  is  copious,  as  in  the 
axillae,  where  they  form  a  thin,  mamillated  layer  of  a  reddish  color,  which 
corresponds  exactly  to  the  situation  of  the  hair  in  this  region ;  they  are  large  also  in 
the  groin.  Their  number  varies.  They  are  most  numerous  on  the  palm  of  the  hand, 
presenting,  according  to  Krause,  2800  orifices  on  a  square  inch  of  the  integument, 
and  are  rather  less  numerous  on  the  sole  of  the  foot.  In  both  of  these  situations 
the  orifices  of  the  ducts  are  exceedingly  regular,  and  open  on  the  curved  surface 
ridges.  In  other  situations  they  are  more  irregularly  scattered,  but  the  number 
in  a  given  extent  of  surface  presents  a  fairly  uniform  average.  In  the  neck  and 
back  they  are  least  numerous,  their  number  amounting  to  417  on  the  square  inch 
(Krause).  Their  total  number  is  estimated  by  the  same  writer  at  2,381,248,  and, 
supposing  the  aperture  of  each  gland  to  represent  a  surface  of  ^  of  a  line  in 
diameter,  he  calculates  that  the  whole  of  these  glands  would  present  an  evap- 
orating surface  of  about  eight  square  inches.  Each  gland  consists  of  a  single 
tube  intricately  convoluted,  terminating  at  one  end  by  a  blind  extremity,  and 
opening  at  the  other  end  upon  the  surface  of  the  skin. 

The  wall  of  the  tubercle  of  the  secreting  coil  is  lined  with  cubical  epithelial 
cells,  external  to  these  is  a  layer  of  smooth  muscle-cells,  and  more  externally  a 
layer  of  connective  tissue,  the  membrana  propria.  The  duct  in  the  corium,  in 
contrast  to  the  secreting  coil,  has  no  layer  of  muscle-cells,  but  instead  a  second 
layer  of  epithelial  cells  covered  by  connective  tissue.  As  previously  stated,  the 
duct  becomes  spiral  in  the  epidermis,  its  own  wall  disappears,  and  the  channel 
is  bounded  by  epidermic  cells. 

Blood-vessels  and  Nerves. — The  blood-vessels  are  branches  from  the  subcuta- 
neous vessels  and  the  arterial  plexus  of  the  deep  part  of  the  corium.     Numerous 

'  Histology  and  Microscopic  Anatomy.      By  Dr.  Ladislaus  Szymonowicz.     Translated  and  edited  by  John 
Bruce  MacCallum,  M.D. 


THE  SEBACEOUS    GLANDS  1191 

non-medullated  nerve-fibres  lie  upon  the  membrana  propria  of  a  sweat-gland. 
From  them  fibrils  pass  inward  and  terminate  by  end-bulbs  upon  the  cells  of  the 
gland. 

The  Sebaceous  Glands  (glandulae  sebaceae). — The  sebaceous  glands  are  small, 
sacculated,  glandular  organs,  lodged  in  the  substance  of  the  corium.  They  are 
found  in  most  parts  of  the  skin,  and  are  usually  connected  with  hair-follicles. 
This  connection  is  so  common  that  they  are  sometimes  called  hair-follicle  glands. 
They  are  found  in  some  regions  which  are  devoid  of  hairs — the  vermilion  borders 
of  the  lips,  the  labia  minora,  the  glans  penis,  and  prepuce.  These  glands  are  espe- 
cially abundant  in  the  scalp  and  face;  they  are  also  very  numerous  around  the 
apertures  of  the  anus,  nose,  mouth,  and  external  ear;  but  are  wanting  in  the  palms 
of  the  hands  and  soles  of  the  feet.  Each  gland  consists  of  a  single  duct,  more  or 
less  capacious,  which  terminates  in  a  cluster  of  small  secreting  pouches  or  saccules. 
The  sacculi  connected  with  each  duct  vary,  in  number,  as  a  rule,  from  two  to  five, 
but  in  some  instances  may  be  as  many  as  twenty.  They  are  composed  of  a  trans- 
parent, colorless  membrane,  enclosing  a  number  of  epithelial  cells.  Those  of 
the  outer  or  marginal  layer  are  small  and  polyhedral,  and  are  continuous  with 
the  lining  cells  of  the  duct.  The  remainder  of  the  sac  is  filled  with  larger  cells, 
containing  fat,  except  in  the  centre,  where  the  cells  have  become  broken  up,  leav- 
ing a  cavity  containing  their  debris  and  a  mass  of  fatty  matter,  which  constitutes 
the  sebaceous  secretion.  The  orifices  of  the  ducts  open  most  frequently  into  the 
hair-follicles,  but  occasionally  upon  the  general  surface,  as  in  the  labia  minora  and 
the  free  margins  of  the  lips.  On  the  nose  and  face  the  glands  are  of  large  size, 
distinctly  lobulated,  and  often  become  much  enlarged  from  the  accumulation  of 
pent-up  secretion.  The  largest  sebaceous  glands  are  those  found  in  the  eyelids — 
the  Meibomian  glands. 


THE  ORGANS  OF  DIGESTION. 


THE  Apparatus  for  the  Digestion  of  the  Food  (apparatus  digestorius)  consists 
of  the  alimentary  canal  and  of  certain  accessory  organs. 

THE  ALIMENTARY  CANAL. 

The  alimentary  canal  is  a  musculo-membranous  tube,  about  thirty  feet  in 
length,  extending  from  the  mouth  to  the  anus,  and  lined  throughout  its  entire 
extent  by  mucous  membrane.  It  has  received  different  names  in  the  various  parts 
of  its  course;  at  its  commencement,  the  mouth,  we  find  provision  made  for  the 
mechanical  division  of  the  food  {mastication),  and  for  its  admixture  with  a  fluid 
secreted  by  the  salivary  glands  (in salivation) ;  beyond  this  are  the  pharynx  and 
the  oesophagus,  the  organs  which  convey  the  food  (deglutition)  into  that  part  of 
the  alimentary  canal,  the  stomach,  in  which  the  principal  chemical  changes  occur, 
and  in  which  the  reduction  and  solution  of  the  food  take  place;  in  the  small  intes- 
tines the  nutritive  principles  of  the  food,  the  chyle,  are  separated,  by  its  admixture 
with  the  bile,  pancreatic  and  intestinal  fluids,  from  that  portion  which  passes  into 
ihe  large  intestine,  most  of  which  is  expelled  from  the  system. 


Alimentary  Canal. 

Duodenum, 

Mouth. 

Small  intestine 

'  Jejunum. 

Pharynx. 

Oesophagus. 

Stomach. 

Large  intestine 

I  Ileum. 

Caecum. 
'   Colon. 
,  Rectum. 

Teeth. 

Accessory  Organs. 

(  Parotid. 

Liver. 

Salivary  glands 

'  Submaxillary. 
,  Sublingual. 

Pancreas. 
Spleen. 

THE  MOUTH,  ORAL  OR  BUCCAL  CAVITY  (CAVUM  ORIS). 

The  mouth  is  placed  at  the  commencement  of  the  alimentary  canal;  it  is  a 
nearly  oval-shaped  cavity,  in  which  the  mastication  and  insalivation  of  the  food 
take  place  (Figs.  799,  818,  and  824). 

The  aperture  of  the  mouth  (rima  oris)  is  bounded  by  the  lips.  The  angle  of  the 
mouth  (angulus  oris)  is  formed  on  each  side  by  the  meeting  of  the  upper  and 
lower  lips  (commissura  labiorum).  When  at  rest  with  the  lips  in  contact,  the  rima 
is  a  slightly  curved  line.  Every  movement  which  the  lips  make  alters  the  shape 
of  the  rima.  When  the  mouth  is  closed  the  floor  and  roof  are  usually  in  contact 
and  its  sides  are  approximated  to  the  dental  arches.    The  mouth  consists  of  two 

(1193) 


1194 


THE   ORGANS   OF  DIGESTION 


SALtVARY 
GLANDS 


PHARYNX 


STOMACH 


PANCREAS 


parts:  an  outer,  smaller  portion,  the  vestibule,  and  an  inner,  larger  part,  the  cavity 

proper  of  the  mouth. 

The  Vestibule  (vestibulum  oris). — The  vestibule  is  a  slit-like  space,  bounded 

in  front  and  laterally  by  the  Hps  and  cheeks;  behind  and  internally  by  the  gums 

and  teeth.  Above  and  below  it  is  limited 
by  the  reflection  of  the  mucous  membrane 
from  the  lips  and  cheeks  to  the  gum  cover- 
ing the  upper  and  lower  alveolar  arch  re- 
spectively. It  receives  the  secretion  from  the 
parotid  glands,  and  communicates,  when  the 
jaws  are  closed,  with  the  cavum  oris  by  an 
aperture  on  each  side  behind  the  wisdom 
teeth. 

The  Cavity  of  the  Mouth  Proper  (cavum 
oris  'propriu7n). — The  cavity  of  the  mouth 
proper  is  bounded  laterally  and  in  front 
by  the  alveolar  arches  with  their  contained 
teeth  ;  behind  it  communicates  with  the 
pharynx  by  a  constricted  aperture  termed 
the  isthmus  faucium.  It  is  roofed  in  by  the 
hard  and  soft  palate.  The  greater  part  of  the 
floor  is  formed  by  the  tongue,  the  remainder 
being  completed  by  the  reflection  of  the  mu- 
cous membrane  from  the  sides  and  under 
surface  of  the  tongue  to  the  gum  lining  the 
inner  aspect  of  the  mandible.  It  receives 
the  secretion  from  the  submaxillary  and 
sublingual  glands. 

The  Mucous  Membrane. — The  mucous 
membrane  lining  the  mouth  is  continuous 
with  the  integument  at  the  free  margin  of 
the  lips  and  with  the  mucous  lining  of  the 
pharynx   behind;  it  is   of  a  rose-pink  tinge 

during  life,  and  very  thick  where  it  covers  the  hard  parts  bounding  the  cavity. 

It  is  covered  by  stratified  epithelium. 


SM-ALL 
INTESTINE 


_  ANUS 
Fig.  799. — Diagram  of  the  alimentary  tube  and 
its  appendages.     (Testut.) 


The  Lips  (Labia  Oris). 


The  lips  are  two  fleshy  folds  which  surround  the  orifice  of  the  mouth,  formed 
externally  by  integument  and  internally  by  mucous  membrane,  between  which  are 
found  the  Orbicularis  oris  muscle  (Fig.  263) ,  the  coronary  vessels  (Fig.  395) ,  some 
nerves  (Fig.  395),  areolar  tissue,  and  fat,  and  numerous  small  labial  glands. 
The  upper  Up  is  called  the  labium  superius;  the  lower  lip  is  called  the  labium 
inferius.  The  inner  surface  of  each  lip  is  connected  in  the  middle  line  to  the  gum 
of  the  corresponding  jaw  by  a  fold  of  mucous  membrane,  the  frenulum  (frenulum 
labii  swperioris  and  frenulum  labii  inferioris).  The  frenulum  labii  superioris  is 
the  larger  of  the  two.  On  each  side,  external  to  the  angle  of  the  mouth,  the  lips 
become  continuovis  (commissura  lahiorum). 

The  Labial  Glands  (glandulae  lahiales)  (Fig.  395). — The  labial  glands  are  situated 
between  the  mucous  membrane  and  the  Orbicularis  oris  muscle  around  the  orifice 
of  the  mouth.  They  are  rounded  in  form,  about  the  size  of  small  peas,  and  their 
ducts  open  by  minute  orifices  upon  the  mucous  membrane.  In  structure  they 
resemble  the  salivary  glands. 


THE    TEETH  1195 

The  Cheeks  (Buccae). 

The  cheeks  form  the  sides  of  the  face  and  are  continuous  in  front  with  the  Hps. 
They  are  composed  externally  of  integument,  internally  of  mucous  membrane, 
and  between  the  two  of  a  muscular  stratum,  besides  a  large  quantity  of  fat,  areolar 
tissue,  vessels,  nerves,  and  buccal  glands. 

The  Mucous  Membrane. — ^The  mucous  membrane  lining  the  cheek  is  reflected 
above  and  below  upon  the  gums,  where  its  color  becom-es  lighter;  it  is  continuous 
behind  with  the  lining  membrane  of  the  soft  palate.  Opposite  the  second  molar 
tooth  of  the  upper  jaw  is  a  papilla,  the  summit  of  which  presents  the  aperture  of 
the  duct  of  the  parotid  gland  {ductus  parotideus  [Sienonis])  (Fig.  824.)  The  prin- 
cipal muscle  of  the  cheek  is  the  Buccinator,  but  numerous  other  muscles  enter  into 
its  formation — viz.,  the  Zygomatici,  Risorius  Santorini,  and  Platysma  myoides. 

The  Buccal  Glands  (glandulae  huccales). — The  buccal  glands  are  placed  in  the 
submucous  tissue  between  the  mucous  membrane  and  Buccinator  muscle;  they 
are  similar  in  structure  to  the  labial  glands,  but  smaller.  Four  or  five  glands  of 
larger  size  than  the  previously  mentioned  glands  are  placed  beneath  the  mucous 
membrane  in  the  neighborhood  of  the  last  molar  tooth.  They  are  called  the 
molar  glands  (glandidae  molar es).  Their  ducts  open  into  the  mouth  opposite  the 
last  molar  tooth. 

The  Gums  (Gingiva). 

The  gums  are  composed  of  a  dense  fibrous  tissue  closely  connected  to  the 
periosteum  of  the  alveolar  processes  and  surrounding  the  necks  of  the  teeth.  They 
are  covered  by  smooth  and  vascular  mucous  membrane,  which  is  remarkable  for 
its  limited  sensibility.  Around  the  necks  of  the  teeth  this  membrane  presents 
numerous  fine  papillae;  and  from  this  point  it  is  reflected  into  the  alveolus,  where 
it  is  continuous  with  the  periosteal  membrane  lining  that  cavity. 

The  Teeth  (Dentes). 

The  human  subject  is  provided  with  two  sets  of  teeth,  which  make  their  appear- 
ance at  different  periods  of  life.  The  first  set  appear  in  childhood,  and  are  called 
the  temporary,  deciduous  or  milk  teeth.    The  second  set  are  named  permanent. 

The  temporary  teeth  are  twenty  in  number — four  incisors,  two  canine,  and  four 
molars  in  each  jaw  (Figs.  800  and  817). 

The  permanent  teeth  are  thirty-two  in  number — four  incisors  (two  central  and  two 
lateral),  two  canines,  four  bicuspids,  and  six  molars  in  each  jaw  (Figs.  802  and  806). 

General  Characters  (Fig.  807). — Each  tooth  consists  of  three  portions;  the 
crown  or  body  {corona  dentis),  projecting  above  the  gum;  the  root  or  fang  {radix 
dentis),  entirely  concealed  within  the  alveolus;  and  the  neck  (collum  dentis),  the 
constricted  portion,  between  the  root  and  crown. 

Surfaces. — The  surfaces  of  a  tooth  are  named  thus:  that  which  comes  in  con- 
tact with  the  teeth  of  the  opposite  jaw  is  the  grinding  or  masticating  surface  {fades 
masticatoria) ;  that  which  touches  the  next  tooth  in  the  same  row  is  the  contact 
surface  {fades  contactus).  That  surface  which  is  toward  its  predecessor  is  called 
the  proximal  surface  (in  incisors  and  canines,  fades  iiiedialis;  in  molars  and  pre- 
molars, fades  anterior).  That  surface  which  is  toward  its  successor  is  called  the 
distal  surface  (in  incisors  and  canines,  fades  lateralis;  in  molars  and  premolars, 
fades  'posterior).  That  which  looks  toward  the  lips  and  cheek  is  the  labial  or 
buccal  surface  {fades  labialis).  That  toward  the  tongue  is  the  lingual  surface 
{fades  lingualis).  In  part  this  method  of  designation  applies  to  the  roots  as  well 
as  to  the  crowns  of  teeth. 


1196 


THE    ORGANS    OF  DIGESTION 


The  Roots  of  the  Teeth.— The  roots  of  the  teeth  are  firmly  implanted  within  the 
sockets  or  alveoli  of  the  jaws  {alveoli  deniales)  (see  pp.  109  and  124).  These  depres- 
sions are  lined  with  periosteum,  called  the  pericementum,  which  is  reflected  on  to  the 
tooth  at  the  point  of  the  root  and  covers  it  as  far  as  the  neck.  This  is  the  root 
membrane  {'periosteum  alveolar e).  At  the  margin  of  the  alveolus  the  periosteum 
becomes  continuous  with  the  fibrous  structure  of  the  gums. 

Right  upper. 


Fia.  800. — Deciduous  teetli.     Left  side. 


Fig.  801. — Deciduous  teeth.     Lingual  view. 


Temporary,  Deciduous  or  Milk  Teeth  {denies  decidui)  (Figs.  800, 801,  and  817). 
— The  temporary  or  milk  teeth  are  smaller,  but  resemble  in  form  those  of  the  per- 
manent set.  The  neck  is  more  marked,  owing  to  the  greater  degree  of  convexity 
of  the  labial  and  lingual  surfaces  of  the  crown.  The  hinder  of  the  two  temporary 
molars  is  the  largest  of  all  the  deciduous  teeth,  and  is  succeeded  by  the  second 
bicuspid.  The  first  upper  molar  has  only  three  cusps — two  labial,  one  lingual;  the 
second  upper  molar  has  four  cusps.  The  first  lower  molar  has  four  cusps;  the 
second  lower  molar  has  five.  The  roots  of  the  temporary  molar  teeth  are  smaller 
and  more  diverging  than  those  of  the  permanent  set,  but  in  other  respects  bear  a 
strong  resemblance  to  them. 


Fig.  802. — Permanent  teeth,  right  side.     (Burchard.) 

Permanent  Teeth  {denies  permanentes)  (Figs.  802,  803,  804,  and  806).  The 
Incisors  {denies  incisivi). — The  incisors  or  cutting  teeth  are  so  named  from  their 
presenting  a  sharp  cutting  edge,  adapted  for  incising  the  food.  They  are  eight  in 
number,  and  comprise  the  four  front  teeth  in  each  jaw. 

The  crown  is  directed  almost  vertically  and  is  spade-like  in  form ;  it  has  the  form 
of  a  truncated  cone  whose  top  has  been  compressed  into  a  sharp  horizontal  cutting 


THE   TEETH 


1197 


edge.  Before  being  subjected  to  attrition  this  edge  presents  three  small  elevations. 
The  labial  surface  is  convex,  and  marked  by  free  longitudinal  ridges  extending 
from  the  edge  tubercles  toward  the  neck  of  the  tooth.  The  lingual  surface  is  con- 
cave, and  is  marked  by  two  marginal  ridges  extending  from  an  encircling  ridge 
at  the  neck  to  the  angles  of  the  cutting  edge  of  the  tooth.  The  ridge  at  the  neck 
is  termed  the  cingulum  or  basal  ridge.  The  mesial  and  distal  surfaces  are  triangular, 
the  apex  of  the  triangle  being  at  the  cutting  edge.  The  neck  of  the  tooth  is 
constricted.  The  root  is  long,  single,  and  has  the  form  of  a  transversely  flattened 
cone,  thicker  before  than  behind.    The  root  may  be  curved. 

The  Incisors  of  the  Upper  Jaw  are  altogether  larger  and  stronger  than  those  of 
the  lower  jaw,  the  central  incisors  being  larger  and  flatter  than  the  lateral  incisors. 
They  are  directed  obliquely  downward  and  forward. 

The  Incisors  of  the  Lower  Jaw  are  smaller  and  flatter  than  the  upper,  and  the 
elevations  upon  their  lingual  faces  are  not  marked.  The  two  central  are  smaller 
than  the  two  lateral  incisors,  being  the  smallest  of  all  the  teeth.  The  roots  of  these 
teeth  are  flattened  laterally. 

I 


Fig.  803. — Right  half  of  upper  jaw  (from  below), 
with  the  corresponding  teeth.  The  letters  and  numbers 
point  to  the  classes  of  teeth  and  the  numbers  in 
classes. 


Fig.  804. — Right  half  of  lower  jaw,  with  the  cor- 
responding teeth.  The  letter  and  numbers  point  to 
the  various  cusps  or  their  modifications  on  the  dif- 
ferent teeth.     (Burchard.) 


The  Canine  Teeth  or  Cuspidati  {denies  canini). — The  canine  teeth  are  four  in 
number,  two  in  the  upper,  two  in  the  lower  jaw — one  being  placed  distal  to  each 
lateral  incisor.  They  are  larger  and  stronger  than  the  incisors,  especially  in  the 
roots,  which  are  deeply  implanted  and  each  causes  a  well-marked  prominence 
of  the  process  at  the  place  of  insertion. 

The  crown  is  large,  of  spear-head  form,  and  its  very  convex  labial  surface  is 
marked  by  three  longitudinal  ridges.  The  concave  lingual  surface  is  also  marked 
by  three  ridges  which  unite  at  a  basal  ridge.  The  point  or  cusp  is  longer  than  in 
the  other  teeth,  and  is  the  point  of  division  between  a  short  mesial  and  a  long 
distal  cutting  edge.    These  two  edges  form  an  obtuse  angle  with  each  other. 

The  root  is  single,  oval,  or  elliptical  on  transverse  section,  and  is  longer  and  more 
prominent  than  the  roots  of  the  incisors. 

The  Upper  Canines  or  cuspids,  vulgarly  called  the  eye  teeth,  are  larger  and  longer 
than  the  two  lower,  and  in  occlusion  are  distal  to  them  to  the  extent  of  half  the 
width  of  the  crown. 

The  Lower  Canines,  vulgarly  called  the  stomach  teeth,  have  the  general  form  of 
the  upper  cuspids,  but  their  lingual  surfaces  are  much  more  flattened,  owing  to 


1198  THE    ORGANS   OF  DIGESTION 

the  absence  of  the  elevations  marking  the  upper.  Their  roots  are  more  flattened 
and  may  be  bifid  at  their  apices. 

The  Bicuspid  Teeth  or  the  Premolars  {denies  fremolares). — The  bicuspid  teeth 
are  eight  in  number,  four  in  each  jaw;  they  are  placed  distal  to  the  cuspid  teeth, 
two  upon  each  side  of  the  jaw.    They  are  double  cuspids  in  form. 

The  crown  is  surmounted  by  two  cusps,  one  buccal  and  one  lingual,  separated 
by  a  groove,  the  buccal  being  more  prominent  and  larger  than  the  lingual.  The 
lower  bicuspids  are  not  truly  bicuspid,  the  first  having  but  a  primitive  lingual  cusp, 
the  second  having  the  lingual  cusp  divided  into  two  sections— t.  e.,  it  is  usually 
tricuspid.  The  necks  of  the  teeth  are  oval;  the  roots  are  single  and  laterally  com- 
pressed, that  of  the  first  upper  bicuspid  being  frequently  bifid.  The  first  upper 
bicuspid  is  usually  the  largest  of  the  series.  The  roots  of  the  lower  bicuspids  are 
less  compressed  and  more  rounded. 

The  Molar  Teeth,  the  Multicuspidati  or  Grinders  (denies  molares). — The  molar 
teeth  are  the  largest  and  strongest  teeth  of  the  denture.  They  are  adapted  by 
their  forms  for  the  crushing  and  grinding  of  the  food.  They  are  twelve  in  number, 
six  in  each  jaw,  three  being  placed  posterior  to  each  second  bicuspid. 

The  crowns  are  cuboidal  in  form,  are  convex  buccally  and  lingually;  they  are 
flattened  mesially  and  distally.  They  are  formed  by  the  fusion  of  three  primitive 
cuspids  in  the  upper  and  four  in  the  lower.  To  these  are  added  in  the  first  and 
second  upper  molars  a  disto-lingual  tubercle,  and  in  the  first  and  third  molars  of 
the  lower  jaw  a  disto-buccal  tubercle.  The  unions  of  the  primitive  forms  are 
marked  by  sulci.  The  necks  of  these  teeth  are  large  and  rhomboidal  in  form. 
The  roots  of  the  upper  molars  are  three  in  number — one  large  lingual  or  palatal 
root,  and  two  smaller  buccal  roots.  In  the  lower  molars,  two  roots  are  found,  a 
mesial  and  a  distal,  each  of  which  is  much  flattened  from  before  backward. 

The  First  Molar  Teeth  are  the  largest  of  the  dental  series;  they  have  four  cusps 
on  the  upper  and  five  in  the  lower — three  buccal  and  two  lingual. 

The  Second  Molars  are  smaller;  the  crowns  of  the  upper  are  compressed  until  the 
disto-lingual  cusp  is  reduced.  The  crowns  of  the  lower  are  almost  rectangular, 
with  a  cusp  at  each  angle. 

The  Third  Molars  are  called  the  wisdom  teeth  or  dentes  sapientae  {denies  seroiini), 
from  their  late  eruption;  they  have  three  cusps  upon  the  upper  and  five  upon  the 
lower.  The  three  roots  of  the  upper  are  frequently  fused  together,  forming  a 
grooved  cone,  which  is  usually  curved  backward.  The  roots  of  the  lower,  two 
in  number,  are  compressed  together,  and  curve  backward. 

Arrangement  of  the  Teeth.^ — The  human  teeth  are  arranged  in  two  parabolic 
arches,  the  upper  row  or  arch  {arcus  dentalis  superior)  being  larger,  its  teeth  over- 
lapping the  lower  row  or  arch  {arcus  dentalis  inferior).  The  average  distance 
between  the  centres  of  the  condyles  of  the  inferior  maxillary  bones  is  about  four 
inches,  which  is  also  the  distance  from  either  of  these  points  to  the  line  of  junction 
between  the  lower  incisor  teeth.  Whether  the  jaw  be  large  or  small,  the  equilateral 
triangle  indicated  is  included  in  it;  the  range  of  size  is  between  three  and  one-half 
and  four  and  one-half  inches. 

Owing  to  the  smaller  sizes  of  the  lower  incisors,  the  teeth  of  the  lower  jaw  are 
each  one-half  a  tooth  in  advance  of  its  upper  fellow,  so  that  each  tooth  of  the  dental 
series  has  two  antagonists,  with  the  exception  of  the  lower  central  incisors  and 
upper  third  molars  (Figs.  805  and  806). 

The  grinding  faces  of  the  upper  bicuspids  and  molars  curve  progressively  upward 
and  point  outward,  the  first  molar  being  at  the  lowest  point  of  the  curve,  the  third 
molar  at  the  highest.  The  curve  of  the  lower  dental  arch  is  the  reverse,  the  first 
molar  at  its  deepest  part,  the  third  molar  at  its  extremity.    The  greater  the  depth 

•  After  Dr.  W.  G.  A.  Bonwill. 


THE    TEETH 


1199 


to  which  the  upper  incisors  overlap  the  lower,  the  more  marked  this  curve  and 
the  more  pointed  are  the  cusps  of  the  grinding  teeth. 


Fig.  805. — View  of  teeth  in  situ,  with  the  external  plates  of  the  alveolar  processe.s  removed.     (Cryer.) 


Fig.  806.— Front  and  side  views  of  the  teeth  and  jaws.     (Cryer.) 


The  movement  of  the  human  mandible  is  forward  and  downward,  the  resultant 
of  these  directions  being  an  oblique  line,  upon  an  average  of  35  degrees  from 
the  horizontal  plane/    When  the  lower  jaw  is  advanced  until  the  cutting  edges  of 


'  W.  E.  Walker,  Dental  Cosmos,  1896. 


1200 


THE    ORGANS   OF  DIGESTION 


the  incisors  are  in  contact,  the  jaws  are  separated,  but  at  the  highest  point  of  the 
lower  arch  its  third  molar  advances,  and  meets  and  rests  upon  a  high  point,  the 
second  molar  of  the  upper  arch,  and  thus  undue  strain  upon  the  incisors  is  obviated. 
In  the  lateral  movements  of  the  mandible  but  one  side  is  in  effective  action  at 
one  time;  the  oblique  positions  of  the  cusps  of  the  opposite  teeth  are  such  that 


Fig.  807. — Vertical  section  of  a  molar  tooth. 

when  either  side  is  in  action  the  other 
is  balanced  at  two  or  more  points. 

There  is  an  anatomical  correspond- 
ence between  the  forms  and  arrange- 
ment of  the  teeth,  the  form  of  the  con- 
dyle of  the  mandible,  and  the  muscular 
arrangement.  Individuals  who  have 
teeth  with  long  cusps  have  the  head  of 
the  bone  much  rounded  from  before 
backward,  and  have  a  preponderance 
of  the  direct  over  the  oblique  muscles 
of  mastication,  and  vice  versa;  teeth 
with  short  or  no  cusps  are  associated 
with  a  flattened  condyle  and  strong 
oblique  muscles. 

Very  great  aberrations  in  the  dental 
arrangement  are  frequently  followed  by 
accommodative  changes  in  the  heads  of 
the  mandible. 

Structure  of  the  Teeth.  The  Dental 
Pulp  (pulpa  dentis).  —  A  longitudinal 
section  of  a  tooth  will  show  the  pres- 
ence of  a  central  chamber  having  the 
general  form  of  the  crown  of  the  tooth. 
Processes  of  the  chamber  pass  from  its 
body,  one  for  each  root  and  down  each 
root,  and  open  at  the  apex  by  a  minute 
orifice.  This  cavity  is  known  as  the  pulp-chamber  or  pulp-cavity  (cavum  dentis) 
(Figs.  807  and  808) .  The  minute  canal  in  each  root  is  called  the  pulp-canal  or  root- 
canal  (canalis  radicis  dentis).  The  foramen  at  the  apex  of  the  root  is  the  apical 
foramen  (foramen  apicis  dentis).  The  cavity  contains  a  soft,  vascular,  and  sensitive 
organ  called  the  dental  pulp  [pulpa  dentis) .  It  is  made  up  of  fibrous  cellular  con- 
nective tissue,  the  fibres  of  which  are  extremely  fine,  and  contains  numerous  blood- 
vessels and  nerves,  which  enter  by  way  of  the  apical  foramina.  It  has  not  been 
proved  that  there  are  lymphatics  in  the  dental  pulp,  although  some  authors  assert 
that  they  exist  (Wangermann  and  others).  It  seems  to  have  been  proved  that  the 
spaces  between  the  fibres  of  the  pulp  communicate  with  the  lymphatic  system.  The 
periphery  of  the  pulp  is  bounded  by  a  layer  of  cells  arranged  like  columnar  epithe- 
lium, each  cell  sending  one  or  more  branched  processes  through  the  basic  substance 


Fig.  808.  —  Vertical  section  of  a  tooth  in  situ  (15 
diameters).  C  is  placed  in  the  pulp-cavity,  opposite 
the  cervi.x  or  neck  of  the  tooth  ;  the  part  above  is  tho 
crown,  that  below  is  the  root  (fang).  1.  Enamel  with 
radial  and  concentric  markings.  2.  Dentine  with 
tubules  and  incremental  lines.  3.  Cement  or  crusta 
jietrosa,  with  bone  corpuscles.  4.  Dental  periosteum. 
5.  Bone  of  lower  jaw. 


THE    TEETH 


1201 


of  the  dentine.  These  processes  constitute  the  dentine  fibres.  Other  processes  come 
off  from  the  cells  which  pass  in  the  direction  of  the  pulp  and  surround  it.  The 
cells  at  the  periphery  of  the  pulp  are  the 
dentine -forming  cells,  the  odontoblasts  of  Wal- 
deyer.  The  blood-vessels  break  up  into  in- 
numerable capillary  loops  which  lie  beneath 
the  layer  of  odontoblasts.  The  nerve-fibrils 
break  up  into  numberless  non-medullary  fila- 
ments, which  spread  out  beneath  the  odonto- 
blasts, and  probably  send  terminal  filaments 
to  the  extreme  periphery  of  the  pulp  outside 
the  odontoblasts. 

The  matrix  cells  and  their  processes  are 
irregularly  arranged  in  the  body  of  the  pulp, 
but  in  the  canal  portion  the  fibrillae  are  in  the 
direction  of  the  axis  of  the  root. 

The  Solid  Portion  of  the  Tooth.— The  sec- 
tion will  exhibit  three  hard  tissues  in  a  tooth : 
one,  the  proper  dental  substance,  forming  the 
greater  mass   of   the   tooth;   hence  its  name      tt     onn    i?  a     *•     *u      u 

o  \  Fig.  809. — From  a  ground-section  through 

dentine    or   ivory.  The    dentine    upon    the    ex-  the    parts  of    a  dentine,   near  the  pulp,   of   a 

,                         •  1           1       I     1                 1                     II      1  human  canine  tooth  which  has  been  impreg- 

pOSed     crown     is  sheathed     by     a     layer    called  nated  with  pigment.    The  dental  canallcuU  are 

7i                       ,        ,1  1       ,•             !•     .1                 ,      •  cut  acro.ss  and  are    joined    together    by  side 

the  enamel  ;  the  dentine  or    the   root    is  en-  branches,    x  4oo. 

closed  in  a  distinct  tissue,  the  cementum  or 

crusta  petrosa ;  both  cementum  and  enamel  are  thinnest  at  the  neck  and  thickest 

upon  their  distal  portions. 


~   i-A^/f^J^ 


Fig.  810. — Longitudinal  ground-section  through  the  apex  of  a  canine  tooth  from  a  three-and-a-half-year-okl 
boy.  The  entrance  of  the  dental  canaliculi  between  the  enamel  prisms  and  the  course  taken  by  the  latter  are 
shown.     X  135.     (Szymonowicz.) 

76 


1202 


THE    OBGANS    OF  DIGESTION 


The  Ivory  or  Dentine  (suhstantiae  eburnea)  (Figs.  808,  809,  810,  and  811)  forms 
the  principal  mass  of  a  tooth;  in  its  central  part  is  the  cavity  enclosing  the  pulp.  It 
is  a  modification  of  osseous  tissue,  from  which  it  differs,  however,  in  the  fact  that 
it  does  not  contain  cells  placed  in  cavities,  but  the  cells  lie  in  the  periphery  of  the 
pulp,  against  but  not  in  the  dentine.  The  dentine  contains  the  processes  of  the 
cells,'  which  are  known  as  dental  or  dentinal  fibres.  On  microscopic  examination 
it  is'  seen  to  consist  of  a  number  of  minute  wavy  and  branching  tubes  having 
distinct  parietes.  They  are  called  the  dentinal  tubuli  or  dental  canals,  and  are 
embedded  in  a  dense  homogeneous  substance,  the  intertubular  tissue. 

The  dentinal  tubuli  (canaliculi  dentales)  (Fig.  811)  are  placed  parallel  with  one 
another,  and  open  at  their  inner  ends  into  the  pulp-cavity.  In  their  course  to  the 
periphery  they  present  two  or  three  curves,  and  are  twisted  on  themselves  in  a  spiral 
direction.  The  direction  of  these  tubes  varies;  they  are  vertical  in  the  upper  por- 
tion of  the  crown,  oblique  in  the 
neck  and  upper  part  of  the  root, 
and  toward  the  lower  part  of  the 
root  they  are  inclined  downward. 
The  tubuli,  at  their  commence- 
ment, are  about  -^-^-^  of  an  inch  in 
diameter;  in  their  course  they  di- 
vide and  subdivide  dichotomously, 
so  as  to  give  to  the  cut  surface  of 
the  dentine  a  striated  appearance. 
From  the  sides  of  the  tubes,  espe- 
cially in  the  root,  ramifications  of 
extreme  minuteness  are  given  off, 
which  join  together  in  loops  in  the 
intertubular  substance,  or  termin- 
ate in  small  dilatations,  from  which 
branches  are  given  off.  Near  the 
pulp  the  lateral  branches  are  few 
and  are  almost  at  right  angles  to 
the  canals.  Nearer  the  periphery 
the  lateral  branches  are  more  nu- 
merous, and  they  come  off  at 
acute  angles.  The  terminations  of 
the  chief  canals  at  the  periphery 
vary.  In  the  crown  they  break  up 
into  branches  like  fingers  just  be- 
neath the  enamel.  Some  of  these 
finger-like  branches  leave  the  den- 
tine and  enter  the  cement  substance  between  enamel  prisms.  The  majority  of 
the  chief  canals  end  in  blind  extremities  at  the  margin  of  the  enamel  and  do  not 
enter  this  structure.  In  the  lower  portion  of  the  tooth  the  chief  canals  do  not 
emerge  from  the  dentine,  but  end  at  the  margin  of  the  cement  in  blind  extremities. 
They  may  reach  the  spaces  of  the  granular  sheath.  Near  the  periphery  of  the 
dentine  of  the  crown  the  finer  ramifications  of  the  tubuli  pass  through  a  layer  of 
irregular  branched  spaces  which  communicate  with  each  other.  These  are  called 
the  interglobular  spaces  of  Gzermak  (spatia  interglohularia)  (Fig.  811,  /).  These 
spaces  are  gaps  in  the  dentine  due  to  failure  of  calcification  and  are  filled  with 
uncalcified  dentine.  The  outer  part  of  the  dentine  in  the  lower  portion  of  the 
tooth  contains  a  layer  of  interglobular  spaces  known  as  the  granular  layer  or 
granular  sheath  of  Tomes.  The  dentinal  tubuli  have  comparatively  thick  walls, 
and  contain  slender  cylindrical  prolongations  from  the  processes  of  the  cells  of 


Fig.  811. — Ground-section  through  the  root  of  a  human 
premolar.  D,  dentine  ;  K,  cement  corpusebs  ;  0,  osteoblasts  ; 
Ep.,  remains  of  Hertwig's  epithelial  sheath,  200  diameters  ; 
J,  interglobular  spaces.     (Riise.) 


THE    TEETH 


1203 


the  pulp-tissue  already  mentioned,  and  first  described  by  Mr.  Tomes  and  named 
Tomes's  fibres  or  dentinal  fibres.  These  dentinal  fibres  are  analogous  to  the  soft 
contents  of  the  canaliculi  of  bone.  Between  Tomes's  fibres  and  the  ivory  around 
the  canals  there  is  a  tissue  which  is  markedly  resistant  to  the  action  of  acids — the 
dentinal  sheath  of  Neumann. 

The  intertubular  substance  or  tissue  is  translucent  and  contains  the  chief  part 
of  the  earthy  matter  of  the  dentine.  After  the  earthy  matter  has  been  removed 
by  steeping  a  tooth  in  weak  acid  the  animal  basis  remaining  may  be  torn  into 
laminae  which  run  parallel  with  the  pulp-cavity  across  the  direction  of  the  tubules. 
These  laminae  show  the  method  of  growth  to  be  by  deposition  of  successive  strata 
of  dentine.  Fibrils  have  been  found  in  tho  matrix  of  the  intertubular  substance, 
and  are  probably  continuous  with  the  dentinal  fibres  of  Tomes.  In  a  dry  tooth  a 
section  of  dentine  often  displays  a  series  of  lines — the  incremental  lines  of  Salter — 
which  are  parallel  with  the  laminae  above  mentioned.  These  lines  are  caused  by 
two  facts:  (1)  The  imperfect  calcification  of  the  dentinal  laminae  immediately 
adjacent  to  the  line.  (2)  The  drying  process,  which  reveals  these  defects  in  the 
calcification.  These  lines  are  wide  or  narrow  according  to  the  number  of  laminae 
involved,  and  along  their  course,  in  consequence  of  the  imperfection  in  the  calci- 
fying process,  little  irregular  cavities  are  left,  which  are  the  interglobular  spaces 
already  referred  to.  They  have  received  their  name  from  the  fact  that  they  are 
surrounded  by  minute  nodules  or  globules  of  dentine.  Other  curved  lines  may 
be  seen  parallel  to  the  surface.  These  are  the  concentric  lines  of  Schreger,  and  are 
due  to  the  optical  effect  of  simultaneous  curvature  of  the  dentinal  tubules. 


Fig.  812. — Enamel  prisms  (350  diameters).     A,  fragments  and  single  fibres  of  the  enamel  isolated  by  the  action 
of  hydrochloric  acid,    li,  surface  of  a  small  fragment  of  enamel,  showing  the  hexagonal  ends  of  the  fibres. 

Chemical  Composition. — According  to  Berzelius  and  Bibra,  dentine  consists 
of  twenty-eight  parts  of  animal  and  seventy-two  of  earthy  matter.  The  animal 
matter  is  resolvable  by  boiling  into  gelatin.  The  earthy  matter  consists  of  phos- 
phate and  carbonate  of  calcium,  with  a  trace  of  fluoride  of  calcium,  phosphate  of 
magnesia,  and  other  salts. 

The  Enamel  (substantia  adamantina)  (Figs.  808,  810,  and  812)  is  the  hardest  and 
most  compact  part  of  a  tooth,  and  forms  a  thin  crust  over  the  exposed  part  of 
the  crown  as  far  as  the  commencement  of  the  root.  It  is  thickest  on  the  grind- 
ing surface  of  the  crown  until  worn  away  by  attrition,  and  becomes  thinner  toward 
the  neck.  It  consists  of  a  congeries  of  minute  hexagonal  rods,  columns,  or  prisms 
known  as  enamel  fibres  or  enamel  prisms  (prismata  adamantina)  (Fig.  812).  In 
general,  they  lie  parallel  with  one  another,  resting  by  one  extremity  upon  the 
dentine,  which  presents  a  number  of  minute  depressions  for  their  reception,  and 


1204  THE   ORGANS   OF  DIGESTION 

forming  the  free  surface  of  the  crown  by  the  other  extremity.  There  are  occa- 
sional collections  of  prisms  which  run  diagonally.  The  prisms  are  directed 
vertically  on  the  summit  of  the  crown,  horizontally  at  the  sides;  they  are  about 
the  ysVo"  of  ^^  ^'^^'^^  ^"  diameter,  and  pursue  a  more  or  less  wavy  course.  By 
reflected  light  radial  striations  are  visible.  These  are  Schreger's  lines,  and  are 
due  to  the  fact  that  the  prisms  take  an  undulatory  course  and  those  of  two  layers 
may  have  opposite  directions.  Another  series  of  lines,  having  a  brown  appear- 
ance from  pigmentation,  and  denominated  the  parallel  striae  or  brown  striae  of 
Retzius  or  the  colored  lines,  are  seen  on  a  section  of  the  enamel.  These  lines 
are  concentric  and  cross  the  enamel  rods.  They  are  caused  by  the  mode  of 
enamel  deposition.  Inasmuch  as  the  enamel  columns,  when  near  the  dentine, 
cross  each  other  and  only  become  parallel  farther  away,  a  series  of  radial  mark- 
ings, light  and  dark  alternately,  is  obtained  (Fig.  808).  The  enamel  prisms  are 
themselves  calcified  and  are  fixed  to  each  other  by  a  very  small  amoimt  of  cement 
substance.  Numerous  minute  interstices  intervene  between  the  enamel-fibres 
near  their  dentinal  surface.  It  is  noted  that  some  of  the  dentinal  canals  at  the 
crown  penetrate  a  certain  distance  between  the  rods  of  the  enamel  (Fig.  810).  No 
nutritive  canals  exist  in  the  enamel,  except  the  very  few  dentinal  canals  which  at 
the  crown  penetrate  a  short  distance,  and  these  are  found  only  in  a  small  area. 

Chemical  Composition. — According  to  Bibra,  enamel  consists  of  96.5  per  cent, 
of  earthy  matter  and  3.5  per  cent,  of  animal  matter.  The  earthy  matter  consists 
of  the  phosphate  and  the  carbonate  of  calcium,  with  traces  of  fluoride  of  calcium, 
phosphate  of  magnesia,  and  other  salts. 

The  enamel  of  a  recently  erupted  tooth  is  covered  by  a  membrane,  the  thick- 
ness of  which  is  ^Vfo"  ^^  ^^  inch.  It  is  known  as  enamel  cuticle  or  Nasmyth's  mem- 
brane (cuticula  dentis).  It  is  probably  the  most  recent,  and  hence  an  uncalcified, 
or  partly  calcified  enamel  layer.  Some  believe  it  to  be  a  product  of  the  outer  layer 
of  the  cells  of  the  enamel  organ. 

The  Cortical  Substance,  Cementum  or  Crusta  Petrosa  (substantia  ossea)  (Figs.  808 
and  81 1)  is  disposed  as  a  thin  layer  on  the  roots  and  neck  of  a  tooth,  from  the  termi- 
nation of  the  enamel  as  far  as  the  apex  of  the  root,  where  it  is  usually  very  thick.  At 
the  neck  it  overlays  a  slight  margin  of  enamel.  In  structure  and  chemical  com- 
position it  is  true  bone.  It  contains,  sparingly,  the  lacunae  and  canaliculi  which 
characterize  true  bone;  the  lacunae  placed  near  the  surface  have  the  canaliculi  radi- 
ating from  the  side  of  the  lacunae  toward  the  periodontal  membrane  or  dental 
periosteum,  and  those  more  deeply  placed  join  with  adjacent  dentinal  tubuli.  The 
teeth  of  the  young  usually  contain  Haversian  systems  in  the  thicker  portions  of 
the  cementum.  The  neck  of  the  tooth  does  not  contain  lacunae.  The  cementum 
is  occasionally  laminated.  Sharpey's  fibres  (p.  37)  are  very  numerous.  Some  of 
the  lacunae  of  the  cementum  receive  dentinal  tubes  from  the  dentine. 

As  age  advances  the  cement  increases  in  thickness,  and  gives  rise  to  those  bony  growths,  or 
exostoses,  so  common  in  the  teeth  of  the  aged;  the  pulp-cavity  becomes  also  partially  filled  up 
by  a  hard  substance  intermediate  in  structure  between  dentine  and  bone  (the  osteo-dentine  of 
Owen;  the  secondary  dentine  of  Tomes).  It  is  formed  by  the  odontoblasts,  the  dental  pulp 
lessening  in  volume. 

Development  of  the  Teeth  (Figs.  813,  814,  815,  and  816).— The  teeth  are  an 
evolution  from  the  dermoid  system,  and  not  of  the  bony  skeleton;  they  are  devel- 
oped from  two  of  the  blastodermic  layers,  the  epiblast  and  mesoblast.  From  the 
former  the  enamel  is  developed;  from  the  latter  the  dentinal  pulp,  dentine,  cemen- 
tum, and  pericementum.  It  is  customary  to  view  the  development  of  the  per- 
manent and  temporary  teeth  as  separate  studies. 

The  earliest  evidence  of  tooth-formation  in  the  human  embryo  is  observed 
about  the  seventh  week.  The  mucous  membrane  covering  the  embryonic  jaws  is 
seen  to  rise  as  a  longitudinal  ridge  along  the  summit  of  each  jaw.    This  ridge  is 


THE    TEETH 


1205 


the  maxillary  rampart  of  Kblliker  and  Waldeyer.  A  transverse  section  through  the 
jaw  will  show  the  elevation  to  be  due  to  a  linear  and  outlined  activity  of  the 
germinal  epithelial  layer;  a  corresponding  epithelial  growth  is  seen  to  sink  as  a 
band  into  the  mesoblastic  tissue  beneath.  This  band  is  called  the  dental  lamina 
or  dental  band.  The  local  cell-activity  continues,  and  in  its  descent  the  band 
appears  to  meet  with  a  resistance  which  causes  a  flattening  of  its  extremity  into  a 
continuous  lamina.  From  the  inner  (toward  the  tongue)  edge  of  the  lamina 
epithelial  cords  are  given  off,  ten  in  number,  one  for  each  temporary  tooth. 


Fig.  813. — Diagram  of  method  of  development  of  the  teeth.  1.  Early  stage.  4.  Later  stage.  2,  3.  Inter- 
mediate stages.  «.  Common  dental  germ.  o.  Special  dental  germ  (milk).  &.  Special  dental  germ  (permanent), 
p.  Papilla,     e.  Dental  furrow.     (Gegenbauer.) 

The  growth  of  each  cord  continues,  and  each  expands  into  a  flask-like  form,  the 
walls  covered  by  a  layer  of  germinal  cells,  its  interior  by  swollen  mature  cells. 
The  ingrowing  bulb  is  now  seen  to  flatten  upon  its  lower  surface,  as  though  it  had 
met  with  an  outlined  resistance  from  the  mesoblastic  tissue  beneath.  The  epithelial 
ingrowth  assumes  the  general  form  of  the  several  teeth;  it  is  the  enamel-organ  of 
the  tooth  (Fig.  813).  The  cellular  tissue  of  the  jaw  beneath  the  cap  of  the  enamel- 
organ  grows  and  projects  into  the  cap.  This  projection  is  the  dentine  papilla 
(papilla  dentis).  At  this  period  the  mesoblastic  tissue  around  each  enamel-organ 
is  seen  to  become  differentiated  into  fibrous  tissue  surrounding  the  enamel-organs, 


Dental  furrow 


Remains  of  ' '  neck ' '  of 
enamel  organ,  or  of  the 
common  dental  germ 


Permanent  special 

dental  germ 


Meckel's  cartilage. 


Internal  enamel  layer, 
or  adamantoblasts 


Dental  sac 


Enamel  pulp 
External  enamel 
layer 
Papilla 


Lower  jaw. 


Fig.  814. — Vertical  section  of  the  inferior  maxilla  of  an  early  human  foetus.     (Magnified  25  diameters.) 

but  at  some  distance  from  them.  Islets  of  bone  are  also  seen  to  be  forming  the 
beginning  of  the  bony  maxillae. 

The  indentation  of  the  base  of  the  enamel-organ  continues  until  it  assumes 
the  form  of  the  future  teeth.  The  cells  bounding  the  organ  assumes  a  cylindrical 
form ;  the  cells  of  the  interior  become  much  expanded,  and  irregular  in  size  and 
form. 

The  mesoblastic  tissue  underlying  the  enamel-organ  is  much  condensed;  evi- 
dences of  cellular  differentiation  and  a  vascular  system  appear.    Bone  continues  to 


1206 


THE   ORGANS   OF  DIGESTION 


develop  until  all  of  the  tooth-follicles  are  embraced  in  a  gutter  of  bone.  From  the 
lingual  side  of  the  cords  of  the  temporary  teeth  epithelial  buds  are  given  off,  which 
sink  into  the  raesoblastic  tissue  and  form  the  enamel-organs  of  the  permanent 
teeth.  The  condensation  of  fibrous  tissue  continues  until  each  embryonic  tooth  is 
enveloped  in  a  sac,  the  dental  sac  (Fig.  814) ;  this,  together  with  all  of  its  contents, 
is  called  the  dental  follicle. 

The  tooth  which  is  undergoing  development  with  its  enamel-organ  and  dentine 
papilla  is  known  as  the  tooth  germ.  This  tooth  germ  is  encompassed  and  shut  off 
from  surrounding  structures  by  the  bag  of  membranous  structure  known  as  the 
dental  sac. 

The  cells  of  the  enamel-organ  now  undergo  a  series  of  differentiations:  the 
inner  layer,  arranged  as  columnar  epithelium,  are  the  enamel  cells,  or  ameloblasts. 
The  layer  is  called  the  ameloblastic  or  enamel-forming  layer  (Figs.  814  and  815). 
The  cells  of  the  outer  wall  remain  cuboidal;  the  cells  which  lie  between  become 
much  distended,  and  on  account  of  their  appearance  when  seen  in  section  this 
portion  of  the  organ  is  called  the  enamel  jelly  or  the  stellate  reticulum.  The  layer  of 
cells  immediately  contiguous  to  the  ameloblasts  form  a  layer  called  the  stratum 
intermedium  (Fig.  815  A,  D). 


Dentine. 


Enamel. 


Fig.  815. — A.  Section  through  tooth-follicle — human  canine  seven  and  one-half  months.  A.  Follicular  wall. 
B.  Outer  epithelial  coat.  C.  Stellate  reticulum.  D.  Stratum  intermedium.  E.  Ameloblasts.  F.  Odonto- 
blasts.    O.  Pulp. 

B.  Diagram  after  Williams  (Dental  Cosmos,  1896),  mode  of  enamel  deposition.  A.  Blood-supply  to  B,  secret- 
ing papillae.  C.  Layer  of  ameloblasts  containing  enamel  globules  and  droplets  of  calcoglobulin.  D.  Enamel- 
globules  dep'osited.  E.  Formed  dentine.  F.  Forming  dentine.  O.  Layer  of  odontoblasts.  H.  Blood-supply 
to  odontoblastic  layer. 


The  enclosed  mesoblastic  papilla  (the  future  dental  jmlp)  has  its  peripheral  cells, 
which  are  called  odontoblasts,  differentiated  into  columnar  bodies  disposed  as  a 
layer,  each  cell  having  a  large  nucleus.  The  vascular  supply  of  the  pulp  is  now 
well  marked.  A  section  of  a  follicle  at  this  period  will  exhibit  the  follicular  wall 
springing  from  the  base  of  the  dental  papilla  and  having  a  well-marked  blood- 
supply.  The  bony  alveolar  walls  are  well  outlined,  and  evidences  of  a  periosteum 
appear  (Figs.  814  and  815). 

Development  of  Enamel  (Fig.  815  B).— In  point  of  time,  the  deposition  .of  den- 
tine actually  begins  before  that  of  enamel,  so  that  the  first-formed  layer  of  enamel 
is  deposited  against  a  layer  of  immature  dentine.  The  enamel  is  built  up  of  two 
distinct  substances — globules  of  uniform  size  which  are  formed  by  the  amelo- 
blasts, and  a  cementing  substance,  probably  an  albuminate  of  calcium  (calco- 
globulin), the  basis  of  all  the  calcified  tissues.    At  the  ends  of  the  ameloblasts. 


THE    TEETH  1207 

next  to  the  dentine,  the  secretion  of  calco-globulin  is  deposited,  and  into  the 
plastic  mass  the  enamel-globules  are  extruded,  each  globule  remaining  con- 
nected with  the  ameloblasts  by  plasmic  strings,  which  also  join  the  globules 
laterally.^ 

The  first  deposit  of  enamel  begins  in  the  tips  of  the  cusps,  and  is  quickly  fol- 
lowed by  a  disappearance  of  the  stellate  reticulum  at  that  point;  the  stellate  retic- 
ulum appears  to  atrophy,  so  that  the  vascular  follicular  wall  is  brought  into 
direct  apposition  with  the  stratum  intermedium,  which  becomes  differentiated  into 
a  glandular  (secreting)  tissue  which  elaborates  the  calcic  albuminous  basis  of  the 
enamel.  The  secretion  passes  from  the  cells  of  the  stratum  intermedium  through  a 
membrane  into  the  ameloblasts,  where  it  is  in  part  combined  with  the  cellular 
globules,  and  irregular  masses  of  it  are  extruded  as  cementing  substance.  The 
deposition  continues  until  the  enamel-cap  has  its  typical  form.  The  deposition 
of  the  layers  of  globules  is  indicated  by  parallel  lines  transverse  to  the  axes  of  the 
enamel-rods.  At  the  completion  of  amelification  the  ameloblasts  ai£  partially 
calcified  and  form  the  enamel  cuticle  or  Nasmyth's  membrane  {cuticula  dentis). 

Formation  of  Dentine. — The  layer  of  columnar  cells  bounding  the  periphery  of 
the  pulp,  the  odontoblasts,  are  in  apposition  with  a  plexus  of  capillary  vessels 
(Fig.  816).  Each  cell  is  a  secreting  body  which  selects  the  material  for  dentine- 
building.  Against  the  layer  of  ameloblasts 
covering  the  dental  papilla  the  odontoblasts 
deposit  globules,  of  the  calcium  albuminate, 
and  receding  as  the  deposits  are  made,  leave 
one  or  more  protoplasmic  processes  in  the 
calcic  deposit.  These  are  known  as  Tomes 's 
fibres.  The  process  continues  until  the  normal 
dentine  thickness  is  formed.  The  deposit  is 
laid  down  in  a  scaffolding  of  finely  fibrillated 
tissue.  The  layer  of  formative  cells  remains  p,^  gie.-Part  of  section  of'  developing 
constant.    The  remains  of  the  dentine  papilla   tooth  of  young  rat  showing  the  mode  of 

,  ,    ^    '^  .  deposition  of  the  dentine  (highly  magnified). 

constitute    the   pulp    and    lie    in  the  pulp-cavity  «•    Outer   layer    of     fully-calcified    dentine. 

,        .,  oAn\  ^       *^  "^  0.  Uncalcified  matrix  with  a  few  nodules  of 

(p.   12UU).  calcareous    matter.       c.    Odontoblasts    with 

■a  J.-  e     n  a.  TT      x     •  ±  processes  extending  into  the  dentine,  d.  Pulp. 

Formation    of      CementUm. nertWlg    asserts  The  section  is  stained  with  carmine,  which 

that  the  epithelial  edge  of  the  enamel  organ    co^ors^he,  uncalcified  matrix,  but  not  the  cai- 

formed  by  the  inner  and  outer  epithelial  layers 

of  the  organ  grows  downward,  or  rather  the  developing  tooth  grows  upward  until 

the  future  root-form  of  the  tooth  is  outlined  by  a  double  layer  of  epithelial  cells, 

constituting  the  root-sheath  of  Hertwig.    The  growth  of  the  alveolar  process  is 

synchronous. 

Upon  the  pulp  side  of  the  sheath  a  layer  of  odontoblasts  is  developed;  upon 
the  outer  side  the  fibrous  encasement  becomes  closely  attached  to  the  sheath  and  a 
layer  of  osteogenetic  cells  is  differentiated.  These  cells  are  called  cementoblasts. 
The  growth  of  the  dentine  of  the  root  is  exactly  similar  to  the  growth  of  that  of 
the  crown.  The  epithelial  sheath  undergoes  atrophic  changes,  leaving  the  epithe- 
lial whorls  which  remain  in  the  pericementum.  The  cementum  is  developed  as 
subperiosteal  bone.  The  cementum  over  the  apex  of  the  root  is  not  formed  until 
after  the  eruption  of  the  tooth. 

Formation  of  Alveoli. — By  the  time  the  crowns  of  the  teeth  have  formed,  each 
is  enclo.sed  in  a  loculus  of  bone  Avhich  has  developed  around  it  and  at  some  distance 
from  it;  the  loculus  is  open  at  the  top  toward  the  gums,  where  it  is  closed  by 
fibrous  tissue;  the  developing  permanent  tooth  is  contained  in  the  same  loculus, 
but  is  later  separated  from  the  temporary  tooth  by  a  growth  of  bone.    The  alveolar 

'  J.  L.  Williams,  Dental  Cosmos,  1896. 


1208  THE    ORGANS    OF  DIGESTION 

process  is  not  completed  until  after  the  eruption  of  the  teeth.  During  eruption 
that  portion  of  the  process  overlying  the  crown  undergoes  absorption,  and  as  soon 
as  the  immature  tooth  has  erupted  the  alveolar  process  is  developed  about  the  root, 
whose  formation  is  also  completed  after  eruption. 

Development  of  the  Permanent  Teeth. — The  permanent  teeth  as  regards  their 
development  may  be  divided  into  two  sets:  (1)  those  which  replace  the  temporary 
teeth,  and  which,  like  them,  are  ten  in  number;  these  are  the  successional  perma- 
nent teeth;  and  (2)  those  which  have  no  temporary  predecessors,  but  are  super- 
added at  the  back  of  the  dental  series.  These  are  three  in  number  on  either  side 
in  each  jaw,  and  are  termed  the  superadded  permanent  teeth.  They  are  the  three 
molars  of  the  permanent  set,  the  molars  of  the  temporary  set  being  replaced  by 
the  premolars  or  bicuspids  of  the  permanent  set. 

The  Development  of  the  Successional  Permanent  Teeth — the  ten  anterior  ones 
in  either  jaw — will  be  first  considered.  As  already  stated,  the  germ  of  each 
milk  tooth  is  a  special  thickening  of  the  "free"  edge  of  the  common  dental  germ 
or  dental  lamina.  In  like  manner  is  formed  the  special  dental  germ  of  each  of 
the  successional  permanent  teeth.  But  these  thickenings  are  not  at  the  "free" 
edge  of  the  dental  lamina,  but  occur  behind  and  lateral  to  each  of  the  milk-tooth 
germs  (Fig.  813).  There  are  ten  of  these,  and  they  appear  in  order,  about  the 
sixteenth  week,  on  each  side,  the  central  incisor  germs  being  the  first. 

These  special  dental  germs  now  go  through  the  same  transformations  as 
were  described  in  connection  with  those  of  the  milk  teeth,  and  the  changes  also 
eventuate  in  the  germs  becoming  enamel  organs;  that  is,  they  recede  into  the 
substance  of  the  gum  behind  the  germs  of  the  temporary  teeth.  As  they  recede 
they  become  flask-shaped,  form  an  expansion  of  their  distal  extremity,  and  finally 
meet  a  papilla,  which  has  been  formed  in  the  mesoblast,  just  in  the  same 
manner  as  was  the  case  in  the  temporary  teeth.  The  apex  of  the  papilla  inden- 
tates  the  dental  germ,  which  encloses  it,  and  forming  a  cap  for  it,  undergoes 
analogous  changes  to  those  described  in  the  development  of  the  milk  teeth,  and 
becomes  converted  into  the  enamel,  whilst  the  papilla  forms  the  dentine  of  the 
permanent  tooth.  In  its  development  it  becomes  enclosed  in  a  dentinal  sac  which 
adheres  to  the  hack  of  the  sac  of  the  temporary  tooth.  The  sac  of  each  perma- 
nent tooth  is  also  connected  with  the  fibrous  tissue  of  the  gum  by  a  slender  band 
of  the  gubernaculum,  which  passes  to  the  margin  of  the  jaw  behind  the  correspond- 
ing milk  tooth  (see  above). 

The  Superadded  Permanent  Teeth — three  on  each  side  in  each  jaw — arise  from 
successive  extensions  backward — i.  e.,  along  the  line  of  the  jaw — of  the  common 
dental  germ  from  the  back  part  of  the  special  dental  germ  of  the  immediately 
preceding  tooth.  During  the  fourth  month  or  seventeenth  week,  in  that  portion 
of  the  common  dental  germ  which  lies  behind — i.  e.,  lateral  to  the  special  dental 
germ  of  the  last  temporary  molar  tooth,  and  which  has  hitherto  remained  imal- 
tered — there  is  developed  the  special  dental  germ  of  the  first  permanent  molar 
into  which  a  papilla  projects.  In  a  similar  manner,  about  the  fourth  month  after 
birth  the  second  molar  is  formed,  and  about  the  third  year  the  third  molar. 

Eruption. — When  the  calcification  of  the  different  tissues  of  the  milk  tooth 
is  sufficiently  advanced  to  enable  it  to  bear  the  pressure  to  which  it  will  be  after- 
ward subjected,  its  eruption  takes  place,  the  tooth  making  its  way  through  the 
gum.  The  gum  is  absorbed  by  the  pressure  of  the  crown  of  the  tooth  against  it, 
which  is  itself  pressed  up  by  the  increasing  size  of  the  fang.  At  the  same  time 
the  septa  between  the  dentinal  sacs,  at  first  fibrous  in  structure,  ossify  and  thus 
form  the  loculi  or  alveoli ;  these  firmly  embrace  the  necks  of  the  teeth  and  afford 
them  a  solid  basis. 

Previous  to  the  permanent  teeth  penetrating  the  gum,  the  bony  partitions 
which  separate  their  sacs  from  the  deciduous  teeth  are  absorbed,  the  roots  of 


THE   TEETH 


1209 


the  temporary  teeth  disappear  by  absorption  through  the  agency  of  particular 
mukinucleated  cells,  called  odontoclasts,  which  are  developed  at  the  time  in  the 
neighborhood  of  the  root,  and  the  permanent  teeth  become  placed  under  the 
loose  crown  of  the  deciduous  teeth;  the  latter  finally  become  detached,  and  the 
permanent  teeth  take  their  place  in  the  mouth  (Fig.  817). 


Fig.  817. — The  milk-teeth  in  a  child  of  about  four  years.    The  permanent  leeii;  .iio  .  ci  ii  in  their  alveoli.    (Cryer.) 


Calcification  of  the  permanent  teeth  proceeds  in  the  following  order:  First 
molar,  soon  after  birth;  the  central  incisor,  lateral  incisor,  and  cuspid,  about  six 
months  after  birth;  the  bicuspids,  at  the  second  year  or  later;  second  molar,  end 
of  second  year;  third  molar,  about  the  twelfth  year. 

The  Eruption  of  the  Temporary  Teeth  commences  at  the  seventh  month,  and  is 
complete  about  the  end  of  the  second  year. 

The  periods  for  the  eruption  of  the  temporary  set  are  (C.  S.  Tomes) — 


Lower  central  incisors 

Upper  incisors    ..... 

Lower  lateral  incisors  and  first  molars 
Canines      ...... 

Second  molars    ..... 


6  to     9  months. 
8  to  10       '■ 

15  to  21       " 

16  to  20       " 
20  to  24       " 


The  Eruption  of  the  Permanent  Teeth  takes  place  at  the  following  periods,  the 
teeth  of  the  lower  jaw  preceding  those  of  the  upper  by  a  short  interval : 


C^  years,  first  molars. 
7th  year,  two  middle  incisors. 
8th  year,  two  lateral  incisors. 
9th  year,  first  bicuspid. 


10th  year,  second  biscuspid. 
11th  to  12th  year,  canine, 
12th  to  13th  year,  second  molars. 
17th  to  21st  year,  third  molars. 


1210 


THE    OBGANS    OF   DIGESTION 


The  Palate  (Palatum). 

The  palate  forms  the  roof  of  the  mouth;  it  consists  of  two  portions,  the  hard 
palate  in  front,  the  soft  palate  behind. 

The  Hard  Palate  {^palatum  durum)  (Figs.  818  and  819). — The  hard  palate  is 
bounded  in  front  and  at  the  sides  by  the  upper  alveolar  arches  and  gums.  In 
front  and  to  the  sides  it  is  continuous  with  the  gums;  behind,  it  is  continuous 
with  the  soft  palate.  It  is  formed  by  the  palate  processes  of  the  superior  maxil- 
lary bones  and  the  palate  processes  of  the  palate  bones  (Fig.  72) ,  It  is  covered  by  a 
dense  structure  formed  by  the  periosteum  and  mucous  membrane  of  the  mouth, 
which  are  intimately  adherent,  particularly  to  the  front  and  sides,  by  means  of 


ANTERIOR 
PILLAR 


POSTERIOR 
PILLAR 


Fig.  818. 


-Antero-inferior  surface  of  the  soft  palate.     The  tongue  has  been  removed,  so  that  the  pharyngeal 
isthmus  is  distinctly  seen.     (Luschka.) 


a  layer  of  fibrous  tissue.  Along  the  middle  line  is  a  linear  ridge  or  raphe  (raphe 
palati),  which  terminates  anteriorly  in  a  small  papilla,  the  incisive  papilla  (papilla 
incisiva),  corresponding  with  the  inferior  opening  of  the  anterior  palatine  fossa. 
This  papilla  receives  filaments  from  the  naso-palatine  and  anterior  palatine 
nerves.  The  incisive  papilla  in  a  recently  born  child  is  continuous  with  the 
gum  and  the  frenulum  of  the  upper  lip.  On  either  side  and  in  front  of  the  raphe 
the  mucous  membrane  is  thick,  pale  in  color,  and  corrugated;  these  corruga- 
tions, which  are  composed  of  fibrous  tissue,  are  the  palatine  rugae  (plicae  pala- 
tinae  transversae) .  In  very  young  children  the  rugae  are  distinct  and  definite. 
In  the  aged  they  are  indistinct.  Behind,  it  is  thin,  smooth,  and  of  a  deeper 
color;  it  is  covered  with  squamous  epithelium,  and  the  fibrous  tissue  beneath  it 


THE  PALATE 


1211 


contains  many  mucous  glands,  the  palatine  glands  (glandulae  palatinae) .  The 
palatine  vessels  and  nerves  lie  in  the  fibrous  tissue  beneath  the  mucous  membrane. 
The  Soft  Palate  or  Velum  Pendulum  Palati  (palatum  molle)  (Figs.  818,  819, 
and  824). — The  soft  palate  is  a  movable  fold  suspended  from  the  posterior  border 
of  the  hard  palate,  and  forming  an  incomplete  septum  between  the  mouth  and 
pharynx.  It  consists  of  a  fold  of  mucous  membrane  enclosing  muscular  fibres, 
an  aponeurosis,  vessels,  nerves,  adenoid  tissue,  and  mucous  glands.  When 
occupying  its  usual  position  it  is  relaxed  and  pendent  and  its  oral  surface  is 
concave,  continuous  with  the  roof  of  the  mouth,  and  marked  by  a  median  ridge 
or  raphe,  which  indicates  its  original  separation  into  two  lateral  halves.  Its 
pharyngeal  surface  is  convex,  and  continuous  with  the  mucous  membrane  cover- 


ANTERIOR 
PALATINE  CANAL 


i PALATINE 

ANDS 


DESCENDING 

PALATINE 

ARTERV 


Fig.  819. — The  palatine  vault  on  the  right  side  of  the  mucous  membrane  has  been  removed.     The  left  side  shows 
the  mucous  membrane  and  the  glandular  layer.     (Poirier  and  Charpy  ) 


ing  the  floor  of  the  posterior  nares.  Its  anterior  or  upper  border  is  attached  to 
the  posterior  margin  of  the  hard  palate,  and  its  sides  are  blended  with  the 
pharynx.  Its  posterior  or  lower  border  is  free.  The  posterior  portion  of  the 
soft  palate  is  known  as  the  vail  of  the  palate  (velum  palatinum)  and  terminates 
posteriorly  and  externally  on  each  side  in  a  free  margin,  the  posterior  arch  of 
the  palate. 

Hanging  from  the  middle  of  its  lower  border  is  a  small,  conical-shaped,  pen- 
dulous process,  the  uvula  (uvula  palatina).  The  uvula  varies  greatly  in  length  in 
different  individuals.  It  is  composed  of  glands  and  connective  tissue,  contains  a 
prolongation  of  the  Azygos  uvulae  muscle  and  is  covered  with  mucous  membrane, 
and  arching  outward  and  downward  from  the  base  of  the  uvula  on  each  side  are 
two  curved  folds  of  mucous  membrane,  containing  muscular  fibres,  called  the 
arches  or  pillars  of  the  soft  palate  or  pillars  of  the  fauces  (arcus  palatini). 


1212  THE    ORGANS   OF  DIGESTION 

The  Anterior  Pillax  {arcus  glossopalatinus)  (Figs.  818  and  824). — The  anterior 
pillar  on  each  side  runs  downward,  outward,  and  forward  to  the  side  of  the  base 
of  the  tongue.  These  pillars  are  formed  by  the  projection  of  the  Palato-glossi 
muscles,  covered  by  mucous  membrane. 

The  Posterior  Pillax  (arcus  pharijngopalatinus)  (Figs.  818  and  824). — The  pos- 
terior pillar  on  each  side  is  nearer  to  its  opposite  arch  than  is  the  anterior  pillar  to  its 
opposite.  These  pillars  are  larger  than  the  anterior;  they  run  downward,  outward, 
and  backward  to  the  sides  of  the  pharynx,  and  are  formed  by  the  projection  of  the 
Palato-pharyngei  muscles,  covered  by  mucous  membrane.  The  anterior  and  pos- 
terior pillars  are  separated  below  by  a  triangular  interval  in  which  the  tonsil  is  lodged. 

The  space  left  between  the  arches  of  the  palate  on  the  two  sides  is  called  the 
isthmus  of  the  fauces  {isthmus  faucium).  It  is  bounded,  above,  by  the  free  margin 
of  the  soft  palate;  below,  by  the  back  of  the  tongue;  and  on  each  side  by  the 
pillars  of  the  fauces  and  the  tonsils.  Through  this  isthmus  the  mouth  com- 
municates with  the  pharynx. 

The  Mucous  Membrane  of  the  Soft  Palate. — The  mucous  membrane  of  the  soft 
palate  is  thin,  and  covered  with  squamous  epithehum  on  both  surfaces,  excepting 
near  the  orifice  of  the  Eustachian  tube,  where  its  epithelium  is  columnar  and 
ciliated.^  Beneath  the  mucous  membrane  on  the  oral  surface  of  the  soft  palate 
is  a  considerable  amount  of  adenoid  tissue.  The  palatine  glands  form  a  con- 
tinuous layer  on  the  pharyngeal  surface  and  around  the  uvula. 

The  Aponeurosis  of  the  Soft  Palate. — The  aponeurosis  of  the  soft  palate  is  a  thin 
but  firm  fibrous  layer  attached  above  to  the  posterior  border  of  the  hard  palate, 
and  becoming  thinner  toward  the  free  margin  of  the  velum.  Laterally,  it  is  con- 
tinuous with  the  pharyngeal  aponeurosis.  It  forms  the  framework  of  the  soft 
palate,  and  is  joined  by  the  tendons  of  the  Tensor  palati  muscles. 

The  Muscles  of  the  Soft  Palate. — The  muscles  of  the  soft  palate  are  six  on  each 
side:  the  Levator  palati,  Tensor  palati,  Azygos  uvulae,  Palato-glossus,  Palato- 
pharyngeus  and  Salpingo-pharjmgeus  (see  pp.  403,  404,  405,  and  406).  The  follow- 
ing is  the  relative  position  of  these  structures  in  a  dissection  of  the  soft  palate 
from  the  posterior  or  naso-pharyngeal  to  the  anterior  or  oral  surface:  Imme- 
diately beneath  the  pharyngeal  mucous  membrane  is  a  thin  stratum  of  mus- 
cular fibres,  the  posterior  fasciculus  of  the  Palato-pharyngeus  muscle,  joining 
with  its  fellow  of  the  opposite  side  in  the  middle  line.  This  posterior  fasciculus 
is  joined  by  the  Salpingo-pharyngeus  muscle.  Beneath  this  are  the  Azygos  uvulae 
and  Salpingo-pharsmgeus  muscles,  consisting  of  two  rounded  fleshy  fasciculi, 
placed  side  by  side  in  the  median  line  of  the  soft  palate.  Next  comes  the  aponeu- 
rosis of  the  Levator  palati,  joining  with  the  muscle  of  the  opposite  side  in  the  mid- 
dle line.  Fourthly,  the  anterior  fasciculus  of  the  Palato-pharyngeus,  thicker  than 
the  posterior,  and  separating  the  Levator  palati  from  the  next  muscle,  the  Tensor 
palati.  This  muscle  terminates  in  a  tendon  which,  after  winding  around  the  hamu- 
lar  process  of  the  internal  pterygoid  plate  of  the  sphenoid  bone,  expands  into  a 
broad  aponeurosis  in  the  soft  palate,  anterior  to  the  other  muscles,  which  have 
been  enumerated.  Finally,  we  have  a  thin  muscular  stratum,  the  Palato-glossus 
muscle,  placed  in  front  of  the  aponeurosis  of  the  Tensor  palati,  and  separated  from 
the  oral  mucous  membrane  by  adenoid  tissue. 

The  Blood-vessels  of  the  Palate  (Fig.  819) . — The  palate  is  supplied  with  blood  by 
branches  of  the  posterior  or  descending  palatine  branch  of  the  internal  maxillary  artery 
(a.  'palatina  descendens)  and  of  the  ascending  or  anterior  palatine  branch  of  the  facial 
artery  (a.  j>alatina  ascendens).  The  posterior  palatine  artery  divides  into  the  great 
and  small  palatine  arteries  {aa.  falatinae  major  et  minor),  which  run  through  the 

'  According  to  Klein,  the  mucous  membrane  on  the  nasal  surface  of  the  soft  palate  in  the  foetus  is  covered 
throughout  by  columnar  ciliated  epithelium,  which  subsequently  becomes  squamous  ;  and  some  anatomists 
state  that  it  is  covered  with  columnar  ciliated  epithelium,  except  at  its  free  margin,  throughout  life. — Ed.  of 
15th  English  edition. 


THE    TONSIL  1213 

palatine  canals  and  after  emerging  give  off  branches.  Branches  from  the  small 
palatine  go  to  the  soft  palate,  the  large  branch  passes  forward  on  the  hard  palate 
near  the  alveolar  margin.  The  ascending  palatine  branch  of  the  facial  lies  upon 
the  medial  surface  of  the  Tensor  palati  muscle  and  is  distributed  to  the  soft  palate 
and  pharynx.  A  palatine  vein  corresponding  to  the  descending  palatine  artery 
opens  into  the  anterior  facial  vein.  The  pharyngeal  veins  also  receive  palatine  veins. 

The  Nerves  of  the  Palate. — The  large  posterior  palatine  nerve  emerges  from  the 
posterior  palatine  canal  and  accompanies  the  posterior  palatine  artery.  The  naso- 
palatine nerve  emerges  from  the  foramen  of  Scarpa  and  is  distributed  to  the  anterior 
portion  of  the  hard  palate.  The  soft  palate  is  supplied  by  the  small  posterior 
palatine  and  the  accessory  palatine  nerves. 

The  Tonsil  or  Amygdala  {tonsilla  palatina)  (Figs.  818  and  824).— The  tonsils 
or  amygdalae  are  two  prominent  bodies  situated  one  on  each  side  of  the  fauces, 
between  the  anterior  and  posterior  pillars  of  the  soft  palate.  They  are  of  a 
rounded  form,  and  vary  considerably  in  size  in  different  individuals.  A  recess, 
the  supra-tonsillar  fossa  (fossa  supratonsillaris) ,  may  be  seen,  directed  upward 
and  backward  above  the  tonsil.  His  regards  this  as  the  remains  of  the  lower  part 
of  the  second  visceral  cleft.  The  recess  is  covered  by  a  fold  of  mucous  mem- 
brane termed  the  plica  triangularis.  Externally  the  tonsil  is  covered  with  a  fibrous 
capsule  which  joins  the  aponeurosis  of  the  pharynx.  The  outer  surface  of  the 
capsule  is  in  relation  with  the  inner  surface  of  the  Superior  constrictor  muscle 
of  the  pharynx,  to  the  outer  side  of  which  is  the  Internal  pterygoid  muscle.  The 
ascending  palatine  artery  is  close  to  the  outer  surface  of  the  tonsil,  the  Superior 
constrictor  muscle  of  the  pharynx  and  the  tonsillar  capsule  intervening.  The 
tonsillar  artery,  which  is  sometimes  a  branch  of  the  ascending  palatine,  is  also 
close  to  the  outer  surface  of  the  tonsil.  The  internal  carotid  artery  lies  behind 
and  to  the  outer  side  of  the  tonsil,  and  nearly  an  inch  (20  to  25  mm.)  distant  from 
it.  It  corresponds  to  the  angle  of  the  lower  jaw.  The  surface  of  the  tonsil 
which  looks  toward  the  pharynx  presents  from  twelve  to  fifteen  orifices,  each 
leading  into  a  small  recess  or  crypt  (fossula  tonsillaris).  From  the  crypts 
numerous  follicles  branch  out  into  the  substance  of  the  tonsil  by  means  of  very 
irregular  channels.  The  crypts  are  lined  with  stratified  pavement  epithelium. 
The  epithelium  of  the  crypts  exhibits  marked  degenerative  changes.  The 
degeneration  causes  the  formation  of  numerous  communicating  spaces,  which 
contain  leukocytes  and  lymphocytes.  The  crypts  are  surrounded  with  lymphoid 
tissue.  In  this  are  numerous  lymphoid  follicles  (noduli  lymphatici),  which  are 
placed  in  the  submucous  tissue.  These  follicles  are  analogous  to  those  of 
Peyer's  glands  and  consist  of  adenoid  tissue.  No  openings  from  the  capsules 
into  the  follicles  can  be  recognized.     They  contain  a  thick  grayish  secretion. 

The  Blood-vessels  of  the  Tonsil. — The  arteries  supplying  the  tonsils  are  the 
dorsalis  linguae  from  the  lingual,  the  ascending  palatine  and  tonsillar  from  the 
facial,  the  ascending  pharyngeal  from  the  external  carotid,  the  descending  palatine 
branch  of  the  internal  maxillary,  and  a  twig  from  the  small  meningeal.  The  veins 
terminate  in  the  tonsillar  plexus,  on  the  outer  side  of  the  tonsil,  and  the  tonsillar 
plexus  joins  the  pharyngeal  plexus,  which  communicates  with  the  pterygoid  plexus 
of  the  internal  jugular  or  facial  vein. 

L3rmphatics  of  the  Tonsil. — Surrounding  each  follicle  is  a  close  plexus  of  lym- 
phatic vessels.  From  these  plexuses  the  lymphatic  vessels  pass  to  the  submaxillary 
lymph  glands  below  the  angle  of  the  jaw.  From  the  submaxilliary  glands  lymph 
passes  to  the  deep  cervical  glands. 

The  Nerves  of  the  Tonsil. — A  branch  from  the  glosso -pharyngeal  nerve  by  uniting 
with  branches  of  the  pharyngeal  plexus  forms  the  tonsillar  plexus.  The  pharyn- 
geal plexus  is  formed  by  the  pharyngeal  branches  of  the  glosso-pharyngeal  and 
superior  cervical  ganglions  and  the  pharyngeal  branch  of  the  vagus. 


1214 


THE    ORGANS    OF   DIGESTION 


The  Salivary  Glands  (Fig.  820). 

Numerous  glands  exist  in  the  lips,  cheeks,  palate,  and  tongue,  but  by  the  term 
salivary  glands  are  usually  understood  the  three  chief  glandular  masses  on  each 
side  of  the  face.  These  are  the  principal  salivary  glands.  They  communicate 
with  the  mouth,  pour  their  secretion  into  its  cavity,  and  are  named  respectively 
the  parotid,  submaxillary,  and  sublingual. 

The  Parotid  Gland  (glandulae  parotis)  (Fig.  646). — The  parotid  gland,  so 
called  from  being  placed  near  the  ear  (napd,  near;  o2>c,  ciroc,  the  ear),  is  the 
largest  of  the  three  salivary  glands,  varying  in  weight  from  half  an  ounce  to  an 
ounce.  It  lies  upon  the  side  of  the  face  immediately  below  and  in  front  of  the 
external  ear.  It  is  limited  above  by  the  zygoma;  below,  by  the  angle  of  the  jaw 
and  by  a  line  drawn  between  the  angle  and  the  mastoid  process:  anteriorly,  it 


Fig.  820. — The  salivary  glands. 

extends  to  a  variable  extent  over  the  Masseter  muscle ;  posteriorly,  it  is  bounded 
by  the  external  meatus,  the  mastoid  process,  and  the  Sterno-mastoid  and  Digastric 
muscles,  slightly  overlapping  the  two  muscles. 

Its  anterior  surface  is  grooved  to  embrace  the  posterior  margin  of  the  ramus  of 
the  lower  jaw,  and  advances  forward  beneath  the  ramus,  between  the  two  Ptery- 
goid muscles  and  superficial  to  the  ramus  over  the  Masseter  muscle.  Its  outer 
surface  is  triangular  and  convex,  slightly  lobulated,  is  covered  by  the  integument 
and  parotid  fascia,  and  has  one  or  two  lymphatic  glands  resting  on  it.  Its  inner 
surface  (processus  retromandihularis)  extends  deeply  into  the  neck  by  means  of 
two  large  processes,  one  of  which  dips  behind  the  styloid  process  and  projects 
beneath  the  mastoid  process  and  the  Sterno-mastoid  muscle;  the  other  is  situated 
in  front  of  the  styloid  process,  and  passes  into  the  back  part  of  the  glenoid 
fossa,  behind  the  articulation  of  the  lower  jaw.  The  structures  passing  through 
the  parotid  gland  are — the  external  carotid  artery,  giving  off  its  three  terminal 


THE  SALIVARY   GLANDS  1215 

branches :  the  posterior  auricular  artery  emerges  from  the  gland  behind ;  the  super- 
ficial temporal  artery  above;  the  transverse  facial,  a  branch  of  the  temporal,  in  front; 
and  the  internal  maxillary  winds  through  it  as  it  passes  inward,  behind  the  neck 
of  the  jaw.  Superficial  to  the  external  carotid  is  the  trunk  formed  by  the  union 
of  the  temporal  and  internal  maxillary  veins;  a  branch,  connecting  this  trunk 
with  the  internal  jugular,  also  passes  through  the  gland.  The  gland  is  also 
traversed  by  the  facial  nerve  and  its  branches,  which  emerge  at  its  anterior 
border;  branches  of  the  great  auricular  nerve  pierce  the  gland  to  join  the  facial, 
and  the  auriculo -temporal  branch  of  the  inferior  maxillary  nerve  emerges  from  the 
upper  part  of  the  gland.  The  internal  carotid  artery  and  internal  jugular  vein  lie 
close  to  its  deep  surface.  The  triangular  space  occupied  by  the  greater  part  of 
the  gland  is  bounded  in  front  by  the  posterior  margin  of  the  ramus  of  the  jaw 
and  the  internal  pterygoid  muscle,  and  behind  by  the  anterior  edge  of  the  Sterno- 
cleido-mastoid  muscle,  the  tympanic  portion  of  the  temporal  bone  and  the  car- 
tilaginous portion  of  the  external  auditory  meatus.  Its  floor  is  formed  by  the 
anterior  and  posterior  walls  of  the  space  which  meet  about  the  styloid  process. 
These  walls  are  composed  of  fascia  derived  from  the  deep  cervical  fascia.  The 
remaining  side  of  the  space  is  external  and  is  formed  by  fascia,  derived  from  the 
deep  cervical  fascia  and  called  the  parotid  fascia.  This  space  is  called  the  parotid 
recess.  Sir  Frederick  Treves^  denies  that  the  fascial  covering  of  the  space  is 
complete.  He  says  it  is  deficient  above  between  the  anterior  edge  of  the  styloid 
process  and  the  posterior  border  of  the  external  pterygoid  muscle.  A  portion 
of  the  gland  does  not  occupy  the  space,  but  projects  forward  over  the  Masseter 
muscle.     This  projecting  portion  is  the  facial  process. 

Lymph-glands,  known  as  the  parotid  lymph-glands,  are  in  and  about  the  parotid 
gland,  some  being  embedded  in  the  outer  surface  of  the  parotid  fascia,  others 
being  in  the  inner  surface  of  the  fascia,  others  in  the  gland  itself,  particularly 
along  the  temporo-maxillary  vein  and  external  carotid  artery.  They  receive 
lymph  from  the  anterior  and  lateral  portions  of  the  scalp,  both  eyelids,  a  portion 
of  the  cheek,  the  root  of  the  nose,  the  outer  portion  of  the  external  ear,  the  soft 
palate,  the  posterior  nares,  and  the  external  auditory  meatus.  The  vessels  from 
them  empty  into  the  superficial  cervical  glands  and  the  superior  deep  cervical 
glands.  Between  the  parotid  gland  and  the  pharynx  are  the  subparotid  glands. 
They  receive  lymph  from  the  nasal  fossae,  naso-pharynx  and  Eustachian  tube,  and 
vessels  from  the  glands  take  lymph  to  the  deep  cervical  glands.^ 

The  Duct  of  the  Parotid  Gland,  called  the  Parotid  Duct  or  Stenson's  Duct  (ductus 
farotideus  [Stenonis])  (Fig,  820). — The  duct  of  the  parotid  gland  is  about  two 
inches  and  a  half  in  length.  It  commences  by  numerous  branches  from  the  ante- 
rior part  of  the  gland,  crosses  the  Masseter  muscle,  and  at  its  anterior  border  dips 
down  into  the  substance  of  the  Buccinator  muscle,  which  it  pierces;  it  then  runs 
for  a  short  distance  obliquely  forward  between  the  Buccinator  muscle  and  the 
mucous  membrane  of  the  mouth,  and  opens  upon  the  inner  surface  of  the  cheek 
by  a  small  orifice  opposite  the  second  molar  tooth  of  the  upper  jaw  (Fig.  824). 
Upon  the  beginning  of  Stenson's  duct  there  is  often  an  accessory  parotid  gland 
(glandulae  parotis  accessor ia),  which  is  often  called  the  socia  parotidis.  It  is  a 
portion  of  the  facial  process'.  It  is  a  detached  portion  of  gland,  and  has  a  duct 
which  opens  into  Stenson's  duct.  This  accessory  gland  occasionally  exists  as  a 
separate  lobe,  just  beneath  the  zygomatic  arch.  In  this  position  it  has  the  trans- 
verse facial  artery  above  it  and  some  branches  of  the  facial  nerve  below  it. 

Surface  Form. — The  direction  of  the  duct  corresponds  to  a  line  drawn  across  the  face  about 
a  finger's  breadth  below  the  zygoma;  that  is,  from  the  lower  margin  of  the  concha  to  midway 
between  the  free  margin  of  the  upper  lip  and  the  ala  of  the  nose. 

1  Applied  Anatomy.  ^  Poirier  and  Cun^o,  Human  Anatomy. 


1216  THE    ORGANS    OF  DIGESTION 

Structure  of  the  Parotid  Duct.— The  parotid  duct  is  dense,  it  is  of  considerable 
thickness,  and  its  canal  is  about  the  size  of  a  crowquill;  but  at  vis  orifice  on  the 
inner  aspect  of  the  cheek  its  lumen  is  greatly  reduced  in  size.  The  duct  consists 
of  an  external  or  fibrous  coat,  of  considerable  density,  containing  contractile 
fibres,  and  of  an  internal  or  mucous  coat  lined  with  short  columnar  epithelium. 

Vessels  and  Nerves. — The  arteries  supplying  the  parotid  gland  are  derived  from 
the  external  carotid,  and  from  the  branches  given  off  by  that  vessel  in  or  near  its 
substance.  The  veins  empty  themselves  into  the  external  jugular  through  some 
of  its  tributaries.  The  lymphatics  terminate  in  the  superficial  cervical  and  the 
deep  cervical  glands,  passing  in  their  course  through  several  lymphatic  glands 
placed  on  the  surface  and  in  the  substance  of  the  parotid.  The  nerves  are 
derived  from  the  plexus  of  the  sympathetic  on  the  external  carotid  artery,  the 
facial,  the  auriculo -temporal,  and  great  auricular  nerves.  It  is  probable  that  the 
branch  from  the  auriculo-temporal  nerve  is  derived  from  the  glosso-pharyngeal 
through  the  otic  ganglion.  At  all  events,  in  some  of  the  lower  animals  this  has 
been  proved  experimentally  to  be  the  case. 

The  Parotid  Capsule. — The  parotid  gland  is  enclosed  by  two  layers  of  the  parotid 
fascia  {fascia  parotideomasseterica) ,  which  almost  completely  encompass  the 
gland.  The  sheath  is  incomplete  at  one  area  toward  the  pharyngeal  wall  (see 
p.  1215). 

The  parotid  fascia  comes  from  the  deep  cervical  fascia.  The  external  layer 
covers  the  gland.  The  internal  layer  lines  the  parotid  recess.  The  external  layer 
is  the  structure  usually  spoken  of  as  the  parotid  fascia.  Anteriorly  it  joins 
the  fascia  of  the  masseter;  below  it  is  continuous  v/ith  the  deep  cervical  fascia; 
above  it  is  attached  to  the  zygoma;  behind  it  is  adherent  to  the  external  auditory 
meatus  and  sheath  of  the  Sternomastoid.  The  deep  layer  is  adherent  above  to  the 
external  auditory  meatus  and  back  of  the  glenoid  fossa;  internally  to  the  styloid 
process;  below  it  is  continuous  with  the  deep  cervical  fascia.  The  stylomaxillary 
or  stylomandibular  ligament  comes  off  from  the  parotid  fascia. 

The  Submaxillary  Gland  (glandula  submaxillar  is)  (Fig.  820). — The  submax- 
illary gland  is  situated  below  the  jaw,  in  the  anterior  part  of  the  submaxillary 
triangle  of  the  neck.  It  is  irregular  in  form  and  weighs  about  two  drachms 
(8  to  10  grammes).  It  is  covered  by  the  integument,  Platysma,  deep  cervical 
fascia,  and  the  body  of  the  lower  jaw,  corresponding  to  a  depression  on  the 
inner  surface  of  the  body  of  the  mandible,  and  lies  upon  the  Mylo-hyoid,  Hyo- 
glossus,  and  Stylo-glossus  muscles,  a  portion  of  the  gland  passing  beneath  the 
posterior  border  of  the  Mylo-hyoid.  In  front  of  it  is  the  anterior  belly  of  the 
Digastric  muscle;  behind,  it  is  separated  from  the  parotid  gland  by  the  stylo- 
maxillary ligament,  and  from  the  sublingual  gland  in  front  by  the  Mylo-hyoid 
muscle.  The  facial  artery  lies  embedded  in  a  groove  in  its  posterior  and  upper 
border.  A  process  is  given  off  from  the  deep  surface  of  the  anterior  portion  of 
the  gland.  This  is  the  deep  process  (Cunningham),  and  it  passes  with  the  duct 
beneath  the  Mylo-hyoid  muscle. 

The  Duct  of  the  Submaxillary  Gland  or  Wharton's  Duct  (ductus  suhmaxillaris 
\Whartoni\). — The  duct  of  the  submaxillary  gland  is  about  two  inches  in  length, 
and  its  walls  are  much  thinner  than  those  of  the  parotid  duct.  It  commences  by 
numerous  branches  from  the  deep  portion  of  the  gland  which  lies  on  the  upper 
surface  of  the  Mylo-hyoid  muscle,  and  passes  forward  and  inward  between  the 
Mylo-hyoid  and  the  Hyo-glossus  and  Genio-hyo-glossus  muscles,  then  between  the 
sublingual  gland  and  the  Genio-hyo-glossus  muscle,  and  opens  by  a  narrow  orifice 
on  the  summit  of  a  small  papilla  (caruncula  sublingualis)  at  the  side  of  the  fraenum 
linguae.  On  the  Hyo-glossus  muscle  it  lies  between  the  lingual  and  hypoglossal 
nerves,  but  at  the  anterior  border  of  the  muscle  it  crosses  under  the  lingual  nerve, 
and  is  then  placed  above  it. 


THE   SALIVARY    GLANDS 


1217 


Vessels  and  Nerves. — The  arteries  supplying  the  submaxillary  gland  are  branches 
of  the  facial  and  lingual.  Its  veins  follow  the  course  of  the  arteries.  The  lymph- 
.atics  drain  into  the  submaxillary  lymph -glands.  There  are  no  lymphatic  glands 
in  this  salivary  gland.  The  nerves  are  derived  from  the  submaxillary  ganglion, 
through  which  it  receives  filaments  from  the  chorda  tympani  of  the  facial  and 
from  the  lingual  branch  of  the  inferior  maxillary,  sometimes  from  the  mylo-hyoid 
branch  of  the  inferior  dental,  and  from  the  sympathetic. 

The  Sublingual  Gland  {glandula  sublingualis)  (Fig.  820). — The  sublingual 
gland  is  the  smallest  of  the  salivary  glands.  It  is  situated  beneath  the  mucous 
membrane  of  the  floor  of  the  mouth,  at  the  side  of  the  fraenum  linguae,  in  contact 
with  the  inner  surface  of  the  lower  jaw,  close  to  the  symphysis.  It  is  narrow, 
flattened,  in  shape  somewhat  like  an  almond,  and  weighs  about  a  drachm.  It 
is  in  relation,  above,  with  the  mucous  membrane;  below,  with  the  Mylo-hyoid 
muscle;  in  front,  with  the  depression  on  the  side  of  the  symphysis  of  the  lower 
jaw,  and  with  its  fellow  of  the  opposite  side;  behind,  with  the  deep  part  of  the 
submaxillary  gland;  and  internally,  with  the  Genio-hyo-glossus,  from  which  it 
is  separated  by  the  lingual  nerve  and  Wharton's  duct.  Its  excretory  ducts  or 
ducts  of  Rivinus  (ductus  sublingualis  minores)  are  from  eight  to  twenty  in  number. 


Crescent  of  Gianuzsi. 


/^olivary  duct. 


Fig.  821. — A  highly  magnified  section  of  the  submaxillary  giand  of  the  dog,  stained  with  carmine.     (Kolliker.) 


They  open  separately  into  the  mouth  back  of  Wharton's  duct  and  upon  a  fold 
of  mucous  membrane  known  as  the  plica  sublingualis.  The  plica  sublingualis  is 
an  elevated  crest  of  mucous  membrane  caused  by  the  projection  of  the  gland  on 
either  side  of  the  fraenum  linguae.  One  or  more  ducts  sometimes  join  to  form 
a  tube  which  opens  into  the  Whartonian  duct  or  remains  independent,  opening 
close  to  Wharton's  duct  on  the  sublingual  papilla.  This  single  duct  is  called 
the  duct  of  Bartholin  (ductus  sublingualis  major). 

Vessels  and  Nerves. — The  sublingual  gland  is  supplied  with  blood  from  the 
sublingual  and  submental  arteries.     Its  nerves  are  derived  from  the  lingual. 

Structure  of  Salivary  Glands  (Fig.  821). — The  salivary  glands  are  compound 
racemose  glands,  consisting  of  numerous  lobes,  which  are  made  up  of  smaller 
lobules  connected  together  by  dense  areolar  tissue,  vessels,  and  ducts.  Each 
lobule  consists  of  the  ramifications  of  a  single  duct,  dividing  frequently  like  the 
branches  of  a  tree,  the  branches  terminating  in  dilated  ends  or  alveoli,  on  which 
the  capillaries  are  distributed.  These  alveoli,  however,  as  Pfliiger  points  out, 
are  not  necessarily  spherical,  though  sometimes  they  assume  that  form;  some- 
times they  are  perfectly  cylindrical,  and  very  often  they  are  mutually  com- 
pressed. The  alveoli  are  enclosed  by  a  basement  membrane  which  is  continuous 
with  the  membrana  propria  of  the  duct.      It  presents   a  peculiar  reticulated 

77 


1218  THE    ORGANS    OF  DIGESTION 

structure,  having  the  appearance  of  a  basket  with  open  meshes,  and  consisting 
of  a  network  of  branched  and  flattened  nucleated  cells. 

The  alveoli  of  the  salivary  glands  are  of  two  kinds,  which  differ  both  in  the 
appearance  of  their  secreting  cells,  in  their  size,  and  in  the  nature  of  their  secre- 
tion. The  one  variety  secretes  a  ropy  fluid  which  contains  mucin,  and  such 
alveoli  have  therefore  been  named  the  mucous  alveoli,  whilst  the  other  secretes  a 
thinner  and  more  watery  fluid,  which  contains  serum-albumin,  and  alveoli  of 
this  variety  have  been  named  serous  or  albuminous  alveoli.  The  sublingual  gland 
may  be  regarded  as  an  example  of  the  former  variety,  the  parotid  of  the  latter. 
The  submaxillary  is  of  the  mixed  variety,  containing  both  mucous  and  serous 
alveoli,  the  latter,  however,  preponderating. 

Both  varieties  of  alveoli  are  lined  by  cells,  and  it  is  by  the  character  of  these 
cells  that  the  nature  of  the  gland  is  chiefly  to  be  determined.  In  addition,  how- 
ever, the  alveoli  of  the  serous  glands  are  smaller  than  those  of  the  mucous  ones. 

The  Mucous  Alveoli. — The  cells  in  the  mucous  alveoli  are  spheroidal  in  shape, 
glassy,  transparent,  and  dimly  striated  in  appearance.  The  nucleus  is  usually 
situated  in  the  part  of  the  cell  which  is  next  the  basement  membrane,  against 
which  it  is  sometimes  flattened.  The  most  remarkable  peculiarity  presented  by 
these  cells  is,  that  they  give  off  an  extremely  fine  process  which  is  curved  in  a 
direction  parallel  to  the  surface  of  the  alveolus,  lies  in  contact  with  the  membrana 
propria,  and  overlaps  the  process  of  neighboring  cells.  The  cells  contain  a  quan- 
tity of  mucin,  to  which  their  clear,  transparent  appearance  is  due. 

Here  and  there  in  the  alveoli  are  seen  peculiar  half-moon-shaped  bodies  lying 
between  the  cells  and  the  membrana  propria  of  the  alveolus.  They  are  termed 
the  crescents  of  Gianuzzi  or  the  demilunes  of  Heidenhain  (Fig.  821),  and  are  com- 
posed of  polyhedral  granular  cells,  which  Heidenhain  regards  as  young  epithelial 
cells  destined  to  supply  the  place  of  those  salivary  cells  which  have  undergone 
disintegration.    This  view,  however,  is  not  accepted  by  Klein. 

Serous  Alveoli. — In  the  serous  alveoli  the  cells  almost  completely  fill  the  cavity, 
so  that  there  is  hardly  any  lumen  perceptible.  Instead  of  presenting  the  clear, 
transparent  appearance  of  the  cells  of  the  mucous  alveoli,  they  present  a  granular 
appearance,  due  to  distinct  granules  of  an  albuminous  nature  embedded  in  a  closely 
reticulated  protoplasm.  The  ducts  which  originate  from  the  alveoli  are  lined  at 
their  commencement  by  epithelium  which  differs  little  from  the  pavement  type. 
As  the  ducts  enlarge,  the  epithelial  cells  change  to  the  columnar  type,  and  the  part 
of  the  cells  next  the  basement-membrane  is  finely  striated.  The  lobules  of  the 
salivary  glands  are  richly  supplied  with  blood-vessels  which  form  a  dense  network 
in  the  interalveolar  spaces.  Fine  plexuses  of  nerves  are  also  found  in  the  inter- 
lobular tissue.  The  nerve-fibrils  pierce  the  basement-membrane  of  the  alveoli, 
and  end  in  branched  varicose  filaments  between  the  secreting  cells.  There  is  no 
doubt  that  ganglia  are  to  be  found  in  some  salivary  glands  in  connection  with  the 
nerve-plexuses  in  the  interlobular  tissue;  they  are  to  be  found  in  the  submaxillary, 
but  not  in  the  parotid. 

In  the  submaxillary  and  sublingual  glands  the  lobes  are  larger  and  more  loosely 
united  than  in  the  parotid. 

Mucous  Glands. — Besides  the  salivary  glands  proper,  numerous  other  glands 
are  found  in  the  mouth.  They  appear  to  secrete  mucus  only,  which  serves  to  keep 
the  mouth  moist  during  the  intervals  of  the  salivary  secretion,  and  which  is  mixed 
with  that  secretion  in  swallowing.  Many  of  these  glands  are  found  at  the  posterior 
part  of  the  dorsum  of  the  tongue,  behind  the  circumvallate  papillae,  and  also  along 
its  margins  as  far  forward  as  the  apex.^     Others  lie  around  and  in  the  tonsil 

'  It  has  been  shown  by  Ebner  that  many  of  these  glands  open  into  the  trenches  around  the  circumvallate 
papillae,  and  that  their  secretion  is  more  watery  than  that  of  ordinary  mucou's  glands.  He  supposes  that  they 
assist  in  the  more  rapid  distribution  of  the  substance  to  be  tasted  over  the  region  where  the  special  apparatus  of 
the  sense  of  taste  is  situated. — Ed.  of  15th  English  edition. 


THE  SALIVARY   GLANDS  1219 

between  its  crypts,  and  a  large  number  are  present  in  the  soft  palate.  These 
glands  are  of  the  ordinary  compound  racemose  type.  Behind  the  tip  of  the 
tongue  on  each  side,  external  to  the  anterior  extremity  of  the  genio-glossus  muscle, 
is  a  mucous  gland,  the  gland  of  Nuhn  and  Blandin  {glandula  lingualis  anterior). 
Its  lower  surface  is  partly  covered  by  muscular  fibres  from  the  inferior  lingualis 
and  styloglossus  muscles,  and  it  opens  by  several  ducts. 

Surface  Form. — The  orifice  of  the  mouth  is  bounded  by  the  lips,  two  thick,  fleshv  folds 
covered  externally  by  integument  and  internally  by  mucous  membrane,  and  consisting  of 
muscles,  vessels,  nerves,  areolar  tissue,  and  numerous  small  glands.  The  size  of  the  orifice  of 
the  mouth  varies  considerably  in  different  individuals,  but  seems  to  bear  a  close  relation  to  the 
size  and  prominence  of  the  teeth.  Its  corners  correspond  pretty  accurately  to  the  outer  border 
of  the  canine  teeth.  In  the  Ethiopian  tribes  the  front  teeth  are  large  and  inclined  for- 
ward, the  mouth  is  large;  and  this,  combined  with  the  thick  and  everted  lips  which  appear  to 
be  associated  with  prominent  teeth,  gives  to  the  negro's  face  much  of  the  peculiarity  by  which 
it  is  characterized.  The  smaller  teeth  and  the  slighter  prominence  of  the  alveolar  arch  of  the 
more  highly  civilized  races  render  the  orifice  of  the  mouth  much  smaller,  and  thus  a  small 
mouth  is  an  indication  of  intelligence,  and  is  regarded  as  an  evidence  of  the  higher  civilization 
of  the  individual. 

Upon  looking  into  the  mouth,  the  first  thing  we  may  note  is  the  tongue,  the  upper  surface 
of  which  will  be  seen  occupying  the  floor  of  the  cavity.  This  surface  is  convex,  and  is  marked 
along  the  middle  line  by  a  raphe  which  divides  it  into  two  symmetrical  portions.  The  anterior 
two-thirds  is  rough  and  studded  with  papillae;  the  posterior  third  smooth  and  tuberculated, 
and  covered  by  numerous  glands  which  project  from  the  surface.  Upon  raising  the  tongue 
the  mucous  membrane  which  invests  the  upper  surface  may  be  traced  covering  the  sides  of  the 
under  surface,  and  then  reflected  over  the  floor  of  the  mouth  on  to  the  inner  surface  of  the 
lower  jaw,  a  part  of  which  it  covers.  As  it  passes  over  the  borders  of  the  tongue  it  changes  its 
character,  becoming  thin  and  smooth  and  losing  the  papillae  which  are  to  be  seen  on  the  upper 
surface.  In  the  middle  line  the  mucous  membrane  on  the  under  surface  of  the  tip  of  the  tongue 
forms  a  distinct  fold,  the  jraenum  linguae,  by  which  this  organ  is  connected  to  the  symphysis 
of  the  jaw.  Occasionally  it  is  found  that  this  fraenum  is  rather  shorter  than  natural,  and, 
acting  as  a  bridle,  prevents  the  complete  protrusion  of  the  tongue.  When  this  condition  exists 
and  an  attempt  is  made  to  protrude  the  organ,  the  tip  will  be  seen  to  remain  buried  in  the 
floor  of  the  mouth,  and  the  dorsum  of  the  tongue  is  rendered  very  convex,  and  more  or  less 
extruded  from  the  mouth;  at  the  same  time  a  deep  furrow  will  be  noticed  to  appear  in  the 
middle  line  of  the  anterior  part  of  the  dorsum.  Sometimes,  a  little  external  to  the  fraenum, 
the  ranine  vein  may  be  seen  immediately  beneath  the  mucous  membrane.  The  corresponding 
artery,  being  more  deeply  placed,  does  not  come  into  view,  nor  can  its  pulsation  be  felt  with  the 
finger.  On  either  side  of  the  fraenum,  in  the  floor  of  the  mouth,  is  a  longitudinally  elevation  or 
ridge,  produced  by  the  projection  of  the  sublingual  gland,  which  lies  immediately  beneath  the 
mucous  membrane.  And  close  to  the  attachment  of  the  fraenum  to  the  tip  of  the  tongue  may 
be  seen  on  either  side  the  slit-like  orifices  of  Wharton's  ducts,  into  which  a  fine  probe  may  be 
passed  without  much  diflUculty.  By  everting  the  lips  the  smooth  mucous  membrane  lining  them 
may  be  examined,  and  may  be  traced  from  them  on  to  the  outer  surface  of  the  alveolar  arch. 
In  the  middle  line,  both  of  the  upper  and  lower  lip,  a  small  fold  of  mucous  membrane  passes 
from  the  lip  to  the  bone,  constituting  the  fraena;  these  are  not  so  large  as  the  fraenum  linguae. 
By  pulling  outward  the  angle  of  the  mouth,  the  mucous  membrane  lining  the  cheeks  can  be 
seen,  and  on  it  may  be  perceived  a  little  papilla  which  marks  the  position  of  the  orifice  of  Sten- 
son's  duct — the  duct  of  the  parotid  gland.  The  exact  position  of  the  orifice  of  the  duct  will  be 
found  to  be  opposite  the  second  molar  tooth  of  the  upper  jaw.  The  introduction  of  a  probe 
into  this  duct  is  attended  with  considerable  difficulty.  The  teeth  are  the  next  objects  which 
claim  our  attention  upon  looking  into  the  mouth.  These  are,  as  stated  above,  ten  in  either  jaw 
in  the  temporary  set,  and  sixteen  in  the  permanent  set.  The  gums,  in  which  they  are  implanted, 
are  dense,  firm,  and  vascular. 

At  the  back  of  the  mouth  is  seen  the  isthmus  of  the  fauces,  or,  as  it  is  popularly  called,  "  the 
throat:"  this  is  the  space  between  the  pillars  of  the  fauces  on  either  side,  and  is  the  means 
by  which  the  mouth  communicates  with  the  pharynx.  Above,  it  is  bounded  by  the  soft  palate, 
the  anterior  surface  of  which  is  concave  and  covered  with  mucous  membrane,  which  is  con- 
tinuous with  that  lining  the  roof  of  the  mouth.  Projecting  downward  from  the  middle  of 
its  lower  border  is  a  conical-shaped  projection,  the  uvula.  On  either  side  of  the  isthmus  of  the 
fauces  are  the  anterior  and  posterior  pillars,  formed  by  the  Palato-glossus  and  Palato-pharyn- 
geus  muscles  respectively,  covered  over  by  mucous  membrane.  Between  the  two  pillars  on  either 
side  is  situated  the  tonsil.  The  extirpation  of  this  body  is  not  unattended  with  danger  of 
hemorrhage.  Dr.  Weir  has  stated  that  he  believes  that  when  hemorrhage  occurs  after  their 
removal  it  arises  from  one  of  the  palatine  arteries  having  been  wounded.    These  vessels  are 


1220  THE    ORGANS    OF  DIGESTION 

large:  they  lie  in  the  muscular  tissue  of  the  palate,  and  when  wounded  are  constantly  exposed 
to  disturbance  from  the  contraction  of  the  palatine  muscles.  The  vessels  of  the  tonsil,  Dr.  Weir 
states,  are  small  and  lie  in  the  soft  tissue,  and  readily  contract  when  wounded. 

When  the  mouth  is  wide  open  a  prominent  tense  fold  of  mucous  membrane  may  be  seen  and 
felt,  extending  upward  and  backward  from  the  position  of  the  fang  of  the  last  molar  tooth 
to  the  posterior  part  of  the  hard  palate.  This  is  caused  by  the  pterycjo-maxillary  ligament, 
which  is  attached  by  one  extremity  to  the  apex  of  the  internal  pterygoid  plate,  and  by  the  other 
to  the  posterior  extremity  of  the  mylo-hyoid  ridge  of  the  lower  jaw.  It  connects  the  Buccinator 
with  the  Superior  constrictor  of  the  pharynx.  The  fang  of  the  last  molar  tooth  indicates  the 
position  of  the  lingual  (gustatory)  nerve  where  it  is  easily  accessible,  and  can  with  readiness 
be  divided  in  cases  of  cancer  of  the  tongue  (see  page  1043).  On  the  inner  side  of  the  last  molar 
tooth  we  can  feel  the  hamular  process  of  the  internal  pterygoid  plate  of  the  sphenoid  bone, 
around  which  the  tendon  of  the  Tensor  palati  plays.  The  exact  position  of  this  process  is  of 
importance  in  performing  the  operation  of  staphylorrhaphij.  About  one-third  of  an  inch  in 
front  of  the  hamular  process,  and  the  same  distance  directly  inward  from  the  last  molar  tooth, 
is  the  situation  of  the  opening  of  the  posterior  palatine  canal,  through  which  emerges  the  pos- 
terior or  descending  palatine  branch  of  the  internal  maxillary  artery  and  one  of  the  descending 
palatine  nerves  from  Meckel's  ganglion.  The  exact  position  of  the  opening  on  the  subject  may 
be  ascertained  by  driving  a  needle  through  the  tissues  of  the  palate  in  this  situation,  when  it 
will  be  at  once  felt  to  enter  the  canal.  The  artery  emerging  from  the  opening  runs  forward  in  a 
groove  in  the  bone  just  internal  to  the  alveolar  border  of  the  hard  palate,  and  may  be  wounded 
in  the  operation  for  the  cure  of  cleft  palate.  Under  these  circumstances  the  palatine  canal  may 
require  plugging.  By  introducing  the  finger  into  the  mouth  the  anterior  border  of  the  coronoid 
process  of  the  jaw  can  be  felt,  and  it  is  especially  prominent  when  the  jaw  is  dislocated.  By 
throwing  the  head  well  back  a  considerable  portion  of  the  posterior  wall  of  the  pharynx  may  be 
seen  through  the  isthmus  faucium,  and  on  introducing  the  finger  the  anterior  surface  of  the 
bodies  of  the  upper  cervical  vertebrae  may  be  felt  immediately  beneath  the  thin  muscular 
stratum  forming  the  wall  of  the  pharynx.  The  finger  can  be  hooked  around  the  posterior 
border  of  the  soft  palate,  and  by  turning  it  forward  the  posterior  nares,  separated  by  the 
septum,  can  be  felt,  or  the  presence  of  any  adenoid  or  other  growths  in  the  naso-pharynx  can 
be  ascertained. 

THE  PHARYNX  (Figs.  818,  824,  825). 

The  pharynx  (from  (fdf)irf^,  the  throat)  is  that  part  of  the  ahmentary  canal 
which  is  placed  behind  and  communicates  with  the  nose,  mouth,  and  larynx.  It 
is  a  musculo-membranous  tube,  somewhat  conical  in  form,  with  the  base  upward 
and  the  apex  downward,  extending  from  the  under  surface  of  the  skull  to  the  level 
of  the  cricoid  cartilage  in  front  and  that  of  the  intervertebral  disk  between  the  fifth 
and  sixth  cervical  vertebrae  behind. 

The  pharynx  is  about  four  inches  and  a  half  in  length,  and  broader  in  the  trans- 
verse than  in  the  antero-posterior  diameter.  Its  greatest  breadth  is  opposite  the 
cornua  of  the  hyoid  bone;  its  narrowest  point,  at  its  termination  in  the  oesophagus. 
It  is  attached,  above,  to  the  periosteum  of  the  petrous  portion  of  the  temporal 
bone  and  of  the  basilar  process  of  the  occipital  bone.  To  the  pharyngeal  tubercle 
of  the  basilar  process  of  the  occipital  bone  the  raphe  of  the  Constrictor  muscles  is 
attached.  It  is  bounded  above  by  the  body  of  the  sphenoid  as  well  as  by  the  basilar 
process  of  the  occipital;  below,  \i  is  continuous  with  the  oesophagus;  'posteriorly,  it 
is  connected  by. loose  areolar  tissue  with  the  cervical  portion  of  the  vertebral 
column  and  the  Longi  colli  and  Recti  capitis  antici  muscles;  this  areolar  tissue  is 
contained  in  what  is  called  the  retro-pharyngeal  space  (spatia  retropharyngeus) ; 
anteriorly,  it  is  incomplete,  the  gap  being  occupied  by  the  cavities  of  the  nose, 
mouth, and  larynx.  Anteriorly, it  is  attached  in  succession  to  the  Eustachian  tube, 
the  internal  pterygoid  plate,  the  pterygo-maxillary  ligament,  the  posterior  termi- 
nation of  the  mylo-hyoid  ridge  of  the  lower  jaw,  the  mucous  membrane  of  the 
mouth,  the  base  of  the  tongue,  hyoid  bone,  the  thyroid  and  cricoid  cartilages; 
laterally,  it  is  connected  to  the  styloid  processes  and  their  muscles,  and  is  in  con- 
tact with  the  common  and  internal  carotid  arteries,  the  internal  jugular  veins, 
and  the  glosso-pharyngeal,  pneumogastric,  hypoglossal,  and  sympathetic  nerves, 
and  above  with  a  small  part  of  the  Internal  pterygoid  muscles.    When  the  pharynx 


THE  PHARYNX 


1221 


is  at  rest  the  anterior  and  posterior  walls  are  near  together.  Above  the  larynx 
they  do  not  come  in  contact,  but  leave  a  channel  for  air;  below  the  larynx  they 
lie  in  contact,  but  open  for  the  passage  of  food.  It  has  seven  openings  com- 
municating with  it — the  two  posterior  nares,  the  two  Eustachian  tubes,  the 
mouth,  larynx,  and  oesophagus.  The  pharynx  may  be  subdivided  from  above 
downward  into  three  parts,  nasal,  oral,  and  laryngeal. 

The  Nasal  Part  {pars  nasalis  pharyngis)  (Fig.  824) . — The  nasal  part  of  the 
pharynx  or  naso-phar3mx  lies  behind  the  nose  and  above  the  level  of  the  soft  palate; 
it  differs  from  the  two  lower  parts  of  the  tube  in  that  its  cavity  always  remains 
patent.  In  front  it  communicates  through  the  posterior  nares  (choanae)  (Fig.  825) 
with  the  nasal  fossae.  On  its  lateral  wall  is  the  pharyngeal  orifice  of  the  Eustachian 
tube  (ostium  pharyngeum  tubae  auditivae)  (Figs.  822  and  823) ,  which  presents  the 
appearance  of  a  vertical  or  triangular  cleft  bounded  above  and  behind  by  a  firm 
prominence.  The  anterior  portion  of  the  prominence (/a6 mm  anterius)\s  the  smaller 
portion.  The  posterior  portion  {labium  posterius)  is  large  and  thick,  is  called  the 
Eustachian  cushion  {torus  tubarius),  and  is  caused  by  the  inner  extremity  of  the  caf*- 
tilage  of  the  tube  impinging  on  the  deep  surface  of  the  mucous  membrane (Fig.823). 
A  vertical  fold  of  mucous  membrane,  the  salpingo-pharyngeal  fold  {plica  salpingo- 


ORIFICE   OF 
EUSTACHIAN 

I    TUBE 

§     PHARYNGEAL 


SALPINGO- 

NASAL  FOLD 

EUSTACHIAN 

CUSHION 

SALPINGO-. 
PALATINE  FOLD 


Fig.  822. — Pharyngeal  tonsil  in  an  adult. 
(Escat.) 


Fig.  823. 


SALPINGO-PHARYN- 
GEAL FOLD 

-The  posterior  lateral  cavity  of  the  naso- 
pharynx.    (Escat). 


pharyngea)  (Fig.  823),  stretches  from  the  lower  part  of  the  cushion  to  the  pharynx; 
it  contains  the  Salpingo-pharyngeus  muscle.  A  second  and  smaller  mucous  fold 
may  be  seen  stretching  from  the  upper  part  of  the  cushion  to  the  palate,  the 
salpingo-palatine  fold  (plica  salpingopalatina)  (Fig.  823) .  Behind  the  orifice  of  the 
Eustachian  tube  is  a  deep  recess,  the  lateral  recess  or  fossa  of  Rosenmiiller  (recessus 
pharyngeus)  (Fig.  823),  which  represents  the  remains  of  the  upper  part  of  the  sec- 
ond branchial  cleft.  The  posterior  wall  of  the  naso-pharynx  is  directed  upward  and 
forward,  and  it  meets  the  superior  wall  at  an  angle.  This  rounded  area  of  meet- 
ing is  the  vault  of  the  pharynx  (fornix  pharyngis).  On  the  posterior  wall,  at  the 
level  and  above  the  level  of  the  orifices  of  the  Eustachian  tubes,  there  is  a  col- 
lection of  lymphoid  tissue.  This  is  particularly  marked  in  children,  and  almost 
or  quite  disappears  in  the  aged.  Over  it  the  mucous  membrane  is  thick  and 
in  folds.  This  collection  of  lymphoid  tissue  is  the  pharyngeal  tonsil  {tonsilla 
pharyngea)  (Fig.  822) .  The  naso-pharynx  communicates  with  the  oral  pharynx 
through  an  aperture  between  the  soft  palate  and  the  posterior  pharyngeal  wall. 
This  aperture  is  the  isthmus  of  the  pharynx  (isthmus  pharyngonasalis). 

The  Oral  Part  (pars  oralis  pharyngis). — The  oral  part  of  the  pharynx  reaches 
from  the  soft  palate  to  the  level  of  the  hyoid  bone.  It  opens  anteriorly,  through 
the  isthmus  faucium,  into  the  mouth,  while  in  its  lateral  wall,  between  the  two 


1222 


THE    ORGANS    OF  DIGESTION 


pillars  of  the  fauces,  is  the  tonsil.  A  triangular  area  on  the  lateral  wall  is  known  as 
the  sinus  tonsillaris  (Fig.  824).  It  is  bounded  anteriorly  by  the  anterior  palatine 
arch,  posteriorly  by  the  posterior  palatine  arch,  and  below  by  the  side  of  the 
pharyngeal  portion  of  the  tongue. 

The  LarjOlgeal  Part  {'pars  laryngea  pharyngis). — The  laryngeal  part  of  the 
pharynx  is  that  division  which  lies  behind  the  larynx ;  it  is  wide  above  where  it  is  con- 
tinuous with  the  oral  portion  while  below  at  the  lower  border  of  the  cricoid  cartilage 
it  becomes  continuous  with  the  oesophagus.  In  front  it  presents  the  triangular 
aperture  of  the  larynx,  the  base  of  which  is  directed  forward  and  is  formed  by  the 
epiglottis,  while  its  lateral  boundaries  are  constituted  by  the  aryteno-epiglottidean 
folds.    On  either  side  of  the  laryngeal  orifice  is  a  recess,  termed  the  sinus  pyri- 


OPENING  OF 

8TENSON-S 

DUCT 


GCNIO- 
HYOGLOSSUS 

MUSCLE 


PHARYNGEAL 
BURSA 


ORIFICE    OF 
EUSTACHIAN  TUBE 


PHARYNGEAL 
TONSIL 


SOFT    PALATE 
NASOPHARYNX 


ANTERIOR    PALA- 
TINE ARCH 
POSTERIOR  PALA- 
TINE ARCH 
TONSIL 
CAVITY  OF 
PHARYNX 
TONSILLAR 
SINUS 


POSTERIOR   PALA.' 
TINE  ARCH 


EPIGLOTTIS 


SINUS 

PYRIFORMIS. 

ARYTENO- 

EPIGLOTTIC 

FOLD 

CUNEIFORMI 

CARTILAGE 


ARYTENOID- 
CARTILAGE 


OESOPHAGUS 


RING  OF 
TRACHEA 


Fig.  824. — Sagittal  median  section  of  the  head  and  neck.    The  head  i.s  thrown  backward  into  complete  extension, 
which  explains  the  relations  between  the  lower  jaw  and  the  hyoid  bone  as  seen  in  the  figure.     (Luschka.) 

formis  (recessus  piriformis)  (Fig.  824) ;  it  is  bounded  internally  by  the  aryteno- 
epiglottidean  fold,  externally  by  the  thyroid  cartilage  and  thyro-hyoid  membrane. 
In  the  anterior  part  of  the  sinus  pyriformis  is  a  fold  (plica  nervi  laryngei),  which 
passes  downward  and  inward.  Extending  outward  from  the  epiglottis  on  each 
side  is  a  fold,  the  pharjmgo-epiglottic  fold  (plica  pharyngoepigloitica).  This  ascends 
in  the  lateral  wall  of  the  pharynx,  nearly  to  the  posterior  arch  of  the  fauces. 

Structure. — The  constrictors  of  the  pharynx  (see  p.  400)  are  surrounded  by 
a  sheath  of  thin  fascia,  the  bucco-pharyngeal  fascia  (Cunningham).    Forward  pro- 


THE  PHARYNX 


1223 


longations  of  this  fascia  overlay  the  Buccinator  muscles.  The  connective  tissue  of 
the  retro-pharyngeal  space  joins  the  bucco-pharyngeal  fascia  to  the  prevertebral 
fascia,  and  it  is  attached  by  areolar  tissue  to  the  other  structures  to  which  the 
pharynx  is  in  contact  (Cunningham).  The  pharynx  is  composed  of  three  coats 
— fibrous,  mucous  and  muscular. 

The  Pharyngeal  Aponeurosis  or  Fibrous  Coat  is  situated  between  the  mucous 
and  muscular  layers.  It  is  thick  above,  where  the  muscular  fibres  are  wanting,  and 
is  firmly  connected  to  the  periosteum  of  the  basilar  process  of  the  occipital  and 
petrous  portion  of  the  temporal  bones.  It  is  united  to  the  Eustachian  tube,  pos- 
terior nares,  and  other  points  which  the  pharynx  joins.  It  is  thicker  above  than 
below,  and  above  the  sinuses  of  Alorgagni  there  is  no  muscular  coat,  and  the  wall 


Fig.  825. — The  anterior  suilacu  m  i  ue  i^hiirynx.      (Sappcy.) 


of  the  pharynx  is  composed  of  aponeurosis  and  mucous  membrane.  As  it  descends 
it  diminishes  in  thickness,  and  is  gradually  lost.  It  is  strengthened  posteriorly  by 
a  strong  fibrous  band  which  is  attached  above  to  the  pharyngeal  spine  on  the  under 
surface  of  the  basilar  portion  of  the  occipital  bone,  and  passes  downward,  forming 
a  median  raphe,  which  gives  attachment  to  the  Constrictor  muscles  of  the  pharynx. 
The  Mucous  Coat  {tunica  mucosa).— The  mucous  coat  is  continuous  with  that 
lining  the  Eustachian  tubes,  the  nares,  the  mouth,  and  the  larynx.  In  the  naso- 
pharynx it  is  covered  by  columnar  ciliated  epithelium ;  in  the  buccal  and  laryngeal 
portions  the  epithelium  is  of  the  s(|uamous  variety.  Beneath  the  mucous  membrane 
are  found  racemose  mucous  glands  (glandulae  pharyngeae);  they  are  especially 
numerous  at  the  upper  part  of  the  pharynx  around  the  orifices  of  the  Eustachian 
tubes.    Throughout  the  pharynx  are  also  numerous  crypts  or  recesses,  the  walls 


1224  THE    ORGANS   OF  DIGESTION 

of  which  are  surrounded  by  lymphoid  tissue  similar  to  that  found  in  the  tonsils. 
Across  the  back  part  of  the  pharyngeal  cavity,  between  the  two  Eustachian  tubes, 
a  considerable  mass  of  this  tissue  exists,  and  has  been  named  the  pharyngeal  tonsil 
(Fig.  822).  Above,  this  in  the  middle  line  is  an  irregular,  flask-shaped  depres- 
sion of  the  mucous  membrane,  extending  up  as  far  as  the  basilar  process  of  the 
occipital  bone.  It  is  known  as  the  pharjmgeal  bursa  (bursa  pharyngea) ,  and  was 
regarded  by  Luschka  as  the  remains  of  the  diverticulum,  which  is  concerned  in 
the  development  of  the  anterior  lobe  of  the  pituitary  body.  Other  anatomists 
believe  that  it  is  connected  with  the  formation  of  the  pharyngeal  tonsils.  The 
muscular  coat  (tunica  muscularis  fharyngis)  has  been  already  described  (p.  400). 
The  sinuses  of  Morgagni,  referred  to  on  a  previous  page  (p.  402  and  Fig.  277), 
are  intervals  between  the  Superior  constrictor  muscles  and  the  basilar  process 
of  the  occipital  bone. 

The  Lymphatic  Pharyngeal  Ring. — This  name  was  applied  by  Waldeyer  to  the 
lymphatic  structure  gathered  into  a  sort  of  ring  about  the  pharynx.  There  are 
three  chief  collections  of  this  tissue  on  each  side.  The  first  is  known  as  the  lingual 
tonsil  (p.  1088);  the  second  as  the  palatine  tonsil  (p.  1212);  and  the  third  as  the 
pharyngeal  tonsil  (p.  1221). 

Surgical  Anatomy  of  the  Mouth,  Cheeks,  Lips,  Gums,  Tonsils,  Palate,  Salivary  Glands, 
and  Pharynx. — The  duct  of  a  salivary  gland  may  be  blocked  by  a  calculus,  and  the  condition 
is  often  productive  of  severe  pain. 

A  wound  of  Stenson's  duct  or  of  the  parotid  gland  may  be  followed  by  a  salivary  -fistula. 

The  parotid  recess  is  completely  lined  by  fascia,  excej)t  above.  "Between  the  anterior  edge 
of  the  styloid  process  and  the  posterior  border  of  the  external  pterygoid  muscle  there  is  a  gap 
in  the  fascia,  through  which  the  parotid  space  communicates  with  the  connective  tissue  about 
the  pharynx."' 

This  explains  why  there  is  frequently  swelling  of  the  parotid  region  in  post-pharyngeal  abscess. 
A  parotid  abscess  rarely  bursts  through  the  skin;  it  may  pass  into  the  temporal  fossa,  may 
enter  the  zygomatic  fossa,  may  advance  toward  the  mouth,  pharynx,  or  neck.  Because  of  the 
situation  of  thi  gland,  a  parotid  abscess  may  cause  inflammation  of  the  temporo-mandibular 
joint  or  periostitis  of  the  bone  about  the  meatus,  and  may  even  burst  into  the  external  auditory 
meatus  (Treves). 

The  facial  nerve  passes  through  the  gland,  and  inflammation  or  tuberculosis  of  the  gland 
may  cause  facial  palsy.  Some  enlargements  of  the  parotid  region  are  due  to  inflammation  of 
the  parotid  lymph-glands,  and  these  glands  may  become  tuberculous. 

Mumps  is  characterized  by  acute  inflammation  of  the  parotid  gland. 

Various  tumors  occur  in  the  parotid  (fibroma,  sarcoma,  carcinoma,  enchondroma,  etc.). 
Most  parotid  tumors  contain  more  or  less  cartilage.  Complete  extirpation  of  the  parotid  gland 
surgically  is  certainly  extremely  difficult,  and  Treves  and  others  maintain  that  it  is  impossible. 

Ranula  is  a  salivary  cyst  of  the  floor  of  the  mouth,  due  to  occlusion  of  ducts  of  the  sublingual 
gland  or  the  duct  of  the  submaxillary  gland.  Mucous  cysts  occur  in  the  mouth.  A  mucous  cyst 
of  the  gland  of  Nuhn  and  Blandin  is  on  the  under  surface  of  the  tongue  near  the  apex.  A 
dermoid  cyst  of  the  base  of  the  tongue  is  occasionally  encountered.     It  is  of  congenital  origin. 

What  is  known  as  the  sublingual  bursa  is  an  epithelial-lined  space,  said  to  exist  between 
the  mucous  membrane  of  the  floor  of  the  mouth  and  the  Genio-hyo-glossus  muscle.  When 
acutely  inflamed,  it  produces  rapidly  a  marked  swelling  called  acute  ranula.  Incomplete 
closure  of  the  oral  end  of  the  thyro-glossal  duct  causes  thyro-glossal  fistula.  If  the  oral  end  closes, 
but  a  portion  of  the  duct  below  remains  unobliterated,  a  thyro-glossal  cyst  forms.  Such  a  cyst 
or  fistula  is  always  in  the  median  line.  The  reader  will  remember  that  this  duct  runs  from  the 
foramen  caecum  to  the  isthmus  of  the  thyroid  gland. 

Hare-lip  is  considered  on  pp.  110  and  111. 

The  lower  lip,  more  commonly  than  any  other  structure,  gives  origin  to  cancer.  The  upper 
lip  is  not  nearly  so  often  affected.  Blocking  of  mucous  glands  of  the  lips  causes  mucous  cysts. 
A  scar  of  the  lip  or  about  the  lip  disturbs  this  structure  and  pulls  it  far  out  of  place.  Thus 
great  deformity  is  produced.     Burns  particularly  induce  hideous  cicatricial  contraction. 

Plastic  operations  in  this  region  are  often  successful,  because  of  the  great  vascularity  of  the 
parts,  and  because  adjacent  parts  admit  of  being  stretched  and  pulled  in. 

Cleft  palate  is  a  by  no  means  rare  congenital  deformity.  The  cleft  is  in  the  middle  line. 
It  may  be  a  mere  cleft  of  the  uvula,  it  may  be  limited  to  the  soft  palate,  or  it  may  involve 

'  Applied  Anatomy.     By  Sir  Frederick  Treves. 


THE    OESOPHAGUS  1225 

the  hard  palate  to  but  not  including  the  alveolus.  It  may  pass  through  the  alveolus,  but  if  it 
does  so  it  ceases  to  be  median  at  this  point,  and  follows  the  line  of  suture  between  the  incisive 
bone  and  the  superior  maxillary  (pp.  110  and  111).  In  a  complete  cleft  palate  there  is  apt 
to  be  hare-lip  at  the  end  of  the  palate  cleft.  This  cleft  in  the  lip  is  not  median,  but  is  at  the 
termination  of  the  palate  cleft.  If  the  cleft  of  a  cleft  palate  runs  along  each  side  of  the 
incisive  bone,  the  bone  is  isolated  from  the  superior  maxillary.  In  such  a  case  double  hare-lip 
results. 

When  a  tonsil  enlarges  it  projects  inward.  The  deafness  which  so  often  attends  hypertrophy 
of  the  tonsil  is  not  due  to  blocking  of  the  Eustachian  orifice  by  the  tonsil,  but  is  due  to  thicken- 
ing of  the  mucous  membrane  lining  the  tube  itself.  The  profuse  bleeding  which  sometimes 
follows  an  operation  for  the  removal  of  the  tonsil  is  very  seldom  due  to  injury  of  the  internal 
carotid  artery,  but  is  due  to  injury  of  the  ascending  pharyngeal  artery  (p.  621)  or  one  of  the 
palatine  arteries. 

The  internal  carotid  artery  is  in  close  relation  with  the  pharynx,  so  that  its  pulsations  can 
be  felt  through  the  mouth.  It  has  been  occasionally  wounded  by  sharp-pointed  instruments 
introduced  into  the  mouth  and  thrust  through  the  wall  of  the  pharynx.  In  aneurism  of  this 
vessel  in  the  neck  the  tumor  necessarily  bulges  into  the  pharynx,  as  this  is  the  direction  in 
which  it  meets  with  the  least  resistance,  nothing  lying  between  the  vessel  and  the  mucous 
membrane  except  the  thin  Constrictor  muscle,  whereas  on  the  outer  side  there  is  the  dense 
cervical  fascia,  the  muscles  descending  from  the  styloid  process,  and  the  margin  of  the  Sterno- 
mastoid  muscle. 

The  mucous  membrane  of  the  pharynx  is  very  vascular,  and  is  often  the  seat  of  inflamma- 
tion, frequently  of  a  septic  character,  and  dangerous  on  account  of  its  tendency  to  spread  to  the 
larynx.  On  account  of  the  tissue  which  surrounds  the  pharyngeal  wall  being  loose  and  lax,  the 
inflammation  is  liable  to  spread  through  it  far  and  wide,  extending  downward  into  the  posterior 
inediastinum  along  the  oesophagus.  Abscess  may  form  in  the  connective  tissue  behind  the 
pharynx,  between  it  and  the  vertebral  column,  constituting  what  is  known  as  retro-pharyngeal 
abscess.  This  is  most  commonly  due  to  caries  of  the  cervical  vertebrae,  but  may  also  be  caused 
by  suppuration  of  a  lymphatic  gland  which  is  situated  in  this  position  opposite  the  axis,  and 
which  receives  lymphatics  from  the  nares,  or  by  gumma  or  by  acute  pharyngitis.  In  these 
cases  the  pus  may  be  easily  evacuated  by  an  incision,  with  a  guarded  bistoury,  through  the 
mouth,  but,  for  aseptic  reasons,  it  is  desirable  that  the  abscess  should  be  opened  from  the  neck. 
In  some  instances  this  is  perfectly  easy;  the  abscess  can  be  felt  bulging  at  the  side  of  the  neck 
and  merely  requires  an  incision  for  its  relief;  but  this  is  not  always  so,  and  then  an  incision 
should  be  made  along  the  posterior  border  of  the  Sterno-mastoid  and  the  deep  fascia  should 
be  divided.  A  director  is  now  to  be  inserted  into  the  wound,  the  forefinger  of  the  left  hand 
being  introduced  into  the  mouth  and  pressure  made  upon  the  swelling.  This  acts  as  a  guide, 
and  the  director  is  to  be  pushed  onward  until  pus  appears  in  the  groove.  A  pair  of  sinus  forceps 
are  now  inserted  along  the  director  and  the  opening  into  the  cavity  dilated. 

Foreign  bodies  not  infrequently  become  lodged  in  the  pharynx  and  most  usually  at  its  termi- 
nation at  about  the  level  of  the  cricoid  cartilage,  just  beyond  the  reach  of  the  finger,  as  the 
distance  from  the  arch  of  the  teeth  to  the  commencement  of  the  oesophagus  is  about  six  inches. 

Hypertrophy  of  the  adenoid  tissue  of  the  naso-pharynx  produces  groups  of  hypertrophic 
masses  known  as  adenoids.  A  child  with  adenoids  has  a  cough,  and  when  awake  or  asleep, 
breathes  noisily  and  with  the  mouth  open.  The  voice  is  muffled,  the  hearing  is  impaired,  the 
expression  is  vacant,  the  mind  is  dull,  and  the  tonsils  are  enlarged. 


THE  OESOPHAGUS  (Figs.  826,  827,  828,  829). 

The  oesophagus  (ouo,  ocom,  I  carry;  (fayelh,  to  eat)  or  gullet  is  a  muscular 
canal,  averaging  about  nine  or  ten  inches  in  length,  extending  from  the  pharynx 
to  the  stomach.  It  commences  at  the  upper  border  of  the  cricoid  cartilage,  oppo- 
site the  intervertebral  disk  between  the  fifth  and  sixth  cervical  vertebrae  descends, 
along  the  front  of  the  spine  through  the  posterior  mediastinum,  passes  through 
the  Diaphragm,  and,  entering  the  abdomen,  terminates  in  the  stomach  wall  at  the 
point  known  as  the  cardia  opposite  the  tenth  dorsal  vertebra  or  possibly  opposite 
the  intervertebral  disk  between  the  tenth  and  eleventh  dorsal  vertebrae.  The 
general  direction  of  the  oesophagus  is  vertical,  but  it  presents  two  or  three  slight 
curves  in  its  course.  At  its  commencement  it  is  placed  in  the  median  line,  but 
it  inclines  to  the  left  side  as  far  as  the  root  of  the  neck,  gradually  passes  to  the 
middle  line  again,  and  finally  again  deviates  to  the  left  as  it  passes  forward  to 


1226 


THE    ORGANS    OF   DIGESTION 


the  oesophageal  opening  of  the  Diaphragm  {hiatus  oesophageus) .  The  oesophagus 
also  presents  an  antero-posterior  flexure,  corresponding  to  the  curvature  of  the 
cervical  and  thoracic  portions  of  the  spine.  It  is  the  narrowest  part  of  the  alimen- 
tary canal,  being  most  contracted  at  its  commencement  and  at  the  point  where 
it  passes  through  the  Diaphragm. 

The  diameter  of  the  largest  portion  of  the  oesophagus  where  it  is  contracted  is 
about  half  an  inch;  when  it  is  fully  dilated,  an  inch  or  even  more. 

In  the  neck  the  oesophagus,  when  at  rest,  is  flattened,  the  anterior  and  posterior 
walls  approaching  each  other.  The  canal  in  the  neck  is  round  or  oval,  and  the 
lumen  is  stellate  (Cunningham).  The  oesophagus  is  somewhat  constricted  at  three 
points.  One  constriction  is  at  the  very  beginning  of  the  tube;  another  is  where 
the  left  bronchus  crosses  it;  another  is  at  the  point  where  the  oesophagus  passes 
through  the  Diaphragm.  The  tube  at  each  constricted  point  is  distinctly  flattened. 
The  diameter  of  each  of  these  constricted  parts  is  slightly  under  one-half  inch, 
the  diameter  of  the  rest  of  the  tube  when  contracted  is  one-half  inch,  but  when 
dilated  may  reach  or  exceed  one  inch.     The  average  distance  from  the  upper 


AZYGOS  VeiN 


^  ARTERY 


BRONCHUS 


PULMONARY 


'CESOPHAGUS 


Fig.  826. — Pleural  cul-de-sac  of  the  posterior  mediastinum. 


incisor  teeth  to  the  beginning  of  the  gullet  is  about  six  inches;  the  average  dis- 
tance from  the  incisor  teeth  to  the  cardiac  opening  of  the  stomach  is  fifteen  or 
sixteen  inches.  The  portion  of  the  oesophagus  which  is  in  the  neck  is  called 
the  cervical  portion  (pars  cervicalis) ;  the  portion  in  the  thorax,  the  thoracic  portion 
(pars  thoracalis),  and  the  portion  which  lies  in  the  oesophageal  opening  of  the 
Diaphragm,  the  diaphragmatic  portion.  The  margin  of  the  oesophageal  orifice  is 
narrow  in  front,  thicker  behind  and  to  the  sides.  Behind  and  to  the  sides  the 
diaphragmatic  portion  of  the  oesophagus  is  about  half  an  inch  in  length.  In 
front  there  is  only  a  thin  edge  of  Diaphragm  in  contact  with  the  gullet.  The 
oesophagus  is  connected  to  the  margins  of  the  diaphragmatic  orifice  by  connec- 
tive tissue.  The  so-called  abdominal  portion  of  the  oesophagus  (pars  ahdominalis) 
is  not  over  half  an  inch  in  length,  and  is  limited  to  the  small  portion  of  the  ante- 
rior and  left  lateral  surface  observed  when  a  stomach  which  is  completely 
empty  is  drawn  downward  with  considerable  force.  The  abdominal  portion  of 
the  oesophagus  is  covered  with  peritoneum;  the  corresponding  portions  of  the 
right  lateral  and  posterior  walls  are  not  covered  by  peritoneum.  This  uncov- 
ered portion  of  the  oesophagus  runs  downward  and  to  the  left  and  lies  directly 


THE    OESOPHAGUS 


1227 


behind  the  oesophageal  groove  on  the  posterior  surface  of  the  left  lobe  of  the 
liver,  but  does  not  actually  touch  the  groove,  which  in  reality  holds  the  thick, 
right  edge  of  the  oesophageal  opening  of  the  Diaphragm.  When  the  stomach  is 
distended  the  abdominal  portion  of  the  gullet  ceases  to  exist  and  becomes  part 
of  the  stomach  wall. 

Relations. — In  the  neck  the  oesophagus  is  in  relation,  in  front,  with  the  trachea, 
and  it  is  connected  to  the  posterior  wall  of  the  trachea  by  areolar  tissue.  At  the 
lower  part  of  the  neck,  where  it  projects  to  the  left 
side,  it  is  in  relation  in  front  with  the  thyroid  gland 
and  thoracic  duct;  behind,  it  rests  upon  the  vertebral 
column  and  Longi  colli  muscles;  on  each  side,  it  is  in 
relation  with  the  common  carotid  artery  (especially  the 
left,  as  the  gullet  inclines  to  that  side)  and  part  of  the 
lateral  lobes  of  the  thyroid  gland;  the  recurrent  laryn- 
ijeal  nerves  ascend  between  it  and  the  trachea. 

In  the  thorax,  it  is  at  first  situated  a  little  to  the  left 
of  the  median  line;  it  then  passes  behind  the  aortic 
arch,  being  separated  from  it  by  the  trachea,  and  de- 
scends in  the  posterior  mediastinum,  along  the  right 
side  of  the  aorta,  nearly  to  the  Diaphragm,  where  it 
passes  in  front  and  a  little  to  the  left  of  the  artery, 
previous  to  entering  the  abdomen.  It  is  in  relation, 
in  front,  with  the  trachea,  the  arch  of  the  aorta,  the 
left  common  carotid  and  left  subclavian  arteries,  which 
incline  toward  its  left  side,  the  left  bronchus,  the 
pericardium,  and  the  Diaphragm;  behind,  it  rests 
upon  the  vertebral  column,  the  Longi  colli  muscles, 
the  right  intercostal  arteries,  and  the  vena  azygos 
minor;  and  below,  near  the  Diaphragm,  upon  the  front 
of  the  aorta;  laterally,  it  comes  in  contact  with  both 
pleurae,  especially  with  the  left  pleura  above  and  the 
right  pleura  below;  it  overlaps  the  vena  azygos  major, 
which  lies  on  its  right  side,  while  the  descending  aorta 
is  placed  on  its  left  side.  The  pneumogastric  nerves 
descend  in  close  contact  with  it,  the  right  nerve  pass- 
ing down  behind,  and  the  left  nerve  in  front  of  it,  each 
nerve  spreading  out  into  a  plexus,  the  oesophageal 
plexus,  around  the  tube.  The  two  jjlexuses  are  joined 
to  each  other.  The  right  nerve  forms  the  posterior 
oesophageal  plexus  (plexus  oesophageus  poterior) ; 
the  left  nerve  the  anterior  oesophageal  plexus  (plexus 
oesophageus  anterior). 

In  the  lower  part  of  the  posterior  mediastinum  the 
thoracic  duct  lies  to  the  right  side  of  the  oesophagus  ;  higher  up,  it  is  placed 
behind  it,  and,  crossing  about  the  level  of  the  fourth  dorsal  vertebra,  is  continued 
upward  on  its  left  side. 

Above  the  aortic  arch  and  the  arch  of  the  great  azygos  vein  above  the  root 
of  the  right  lung,  the  pleurae  are  close  to  but  not  in  actual  contact  with  the 
oesophagus. 

Below  the  arch  of  the  great  azygos  vein  the  right  side  of  the  oesophagus  is 
covered  with  pleura  nearly  to  the  diaphragmatic  opening.  The  posterior  surface 
of  the  gullet  also  may  be  covered  with  pleura.  Below  the  arch  of  the  aorta  on 
the  left  side  the  pleura  covers  only  a  small  portion  of  the  oesophagus,  that  is,  a 
portion  of  the  left  wall,  a  little  above  the  diaphragmatic  opening. 


Fig.  827. — The  supports  of  the 
oesophagus  at  the  aorta  in  an  in- 
fant.     (Poirier  and  Charpy.) 


122S 


THE    ORGANS    OF  DIGESTION 


Anomalies. — There  may  be  openings  of  the  oesophagus  into  the  trachea.  A 
diverticulum  or  pressure  pouch  may  exist.  Such  a  pouch  is  usually  placed  upon 
the  posterior  wall  near  the  pharynx.  There  may  be  congenital  constriction,  tubular 
or  annular. 

Structure. — The  oesophagus  is  fastened  to  adjacent  structures  by  connective 
tissue  called  the  tunica  adventitia.  The  tube  has  three  coats — an  external  or 
muscular,  a  middle  or  areolar,  and  an  internal  or  mucous  coat. 

The  Muscular  Coat  {tunica  muscularis). — The  muscular  coat  is  composed  of  two 
planes  of  fibres  of  considerable  thickness,  an  external  plane  of  longitudinal  and 
an  internal  plane  of  circular  fibres. 


LEFT 

PULMONARY 

ARTERY 

LEFT  LUNG 
LEFT  BRONCHI 

THORACIC  CANAL 


VAGUS  NERVE 
PLEURA 


AZYGOS  VEIN 


PHARYNX 


SUPERIOR  LARYN- 
mij         GEAL  NERVE 


INTERNAL 
JUGULAR  VEIN 
TRACHEA 
INFERIOR 
THYROID  ARTERY 

RECURRENT 

NERVE 

SUBCLAVICULAR 

ARTERY 

RIGHT  CEPHALIC 

TRUNK 

ESOPHAGUS 

VAGUS  NERVC 

—AZYGOS  VEIN 

BRONCHIAL 
i-ARTERY 

RIGHT  PUL- 
MONARY VEIN 

T-RIGHT  LUNG 


INFERIOR 
VENA   CAVA 


DIAPHRAGM 


Fig.  828. — The  position  and  relation  of  the  oesophagus  in  the  cervical  reRion  and  in  the  posterior  mediastinum. 

Seen  from  behind.    (Poirier  and  Charpy.) 

The  Longitudinal  Fibres  are  arranged,  at  the  commencement  of  the  tube,  in  three 
fasciculi:  one  in  front,  which  is  attached  to  the  vertical  ridge  on  the  posterior 
surface  of  the  cricoid  cartilage;  and  one  at  each  side,  which  is  continuous  with 
the  fibres  of  the  Inferior  constrictor  of  the  pharynx  ;  as  they  descend  they 
blend  together  and  form  a  uniform  layer,  which  covers  the  outer  surface  of  the 
tube. 

Accessory  slips  of  muscular  fibres  are  described  by  Cunningham  as  passing 
between  the  oesophagus  and  the  left  pleura  (m.  pleurooesophageus),  where  it  covers 
the  thoracic  aorta,  or  between  the  oesophagus  and  the  root  of  the  left  bronchus 
(m.  bronchooesophageus),  or  the  back  of  the  pericardium,  as  well  as  other  still  more 


THE    OESOPHAGUS 


1229 


rare  accessory  fibres.  In  Fig.  829,  taken  from  a  dissection  in  the  Museum  of  the 
Royal  College  of  Surgeons  of  England,  several  of  these  accessory  slips  may  be  seen 
passing  from  the  oesophagus  to  the  pleura,  and  two  slips  passing  to  the  back  of 
the  trachea  just  above  its  bifurcation.  These  slips  of  muscular  fibres  which  pass 
to  adjacent  structures  give  suppoit  to  the  oesophagus.  Below,  the  longitudinal 
fibres  of  the  oesophagus  are  continued  into  the  longitudinal  fibres  of  the  stomach. 

The  Circular  Fibres  are  continuous  above  with  the  Inferior  constrictor  of  the 
pharynx;  their  direction  is  transverse  at  the  upper  and  lower  parts  of  the  tube, 
but  oblique  in  the  central  part.  Below,  the  circular  fibres  pass  into  the  circular 
and  oblicpie  fibres  of  the  stomach. 

The  muscular  fibres  in  the  upper  part  of  the  oesophagus  are  of  a  red  color,  and 
consist  chiefly  of  the  striped  variety,  but  below  they  consist  for  the  most  part  of 
involuntary  muscular  fibre.  At  the  cardia  they  act 
as  a  sphincter  to  solid  food.  Some  maintain  that 
this  sphincter  is  closed  tonically,  others  that  it  opens 
and  closes  rhythmically  during  gastric  digestion. 

The  Submucous  or  Areolar  Coat  {tela  suhmucosa). — 
The  submucous  or  areolar  coat  connects  loosely  the 
mucous  and  muscular  coats.  It  consists  of  dense 
connective  tissue  and  contains  blood-vessels,  nerves, 
and  oesophageal  glands  {glandulae  oesophageae) .  The 
glands  are  mucous  glands  and  are  found  through- 
out the  length  of  the  gullet.  The  ducts  of  the  glands 
pass  through  the  muscularis  mucosae.  These  ducts 
are  surrounded  by  adenoid  tissue. 

The  Mucous  Coat  (tunica  mucosa). — The  mucous 
coat  is  thick,  of  a  reddish  color  above  and  pale 
below.  It  is  disposed  in  longitudinal  folds,  which 
disappear  on  distention  of  the  tube.  Its  surface  is 
studded  with  minute  papillae,  and  is  covered  through- 
out with  a  thick  layer  of  stratified  pavement  epithe- 
Hum.  The  mucous  coat  contains  glands  which  differ 
from  the  mucous  glands  of  the  submucous  tissue. 
They  are  branched  and  tubular  (Hewlett)  and  are 
called  the  superficial  glands.  There  are  two  chief 
groups  of  superficial  glands;  one  near  the  beginning, 
and  the  other  near  the  termination  of  the  oesophagus. 
The  ducts  of  the  superficial  glands  are  not  sur- 
rounded by  lymphoid  tissue  (Hewlett).  Beneath  the 
mucous  membrane,  between  it  and  the  submucous 
coat,  is  a  layer  of  longitudinally  arranged  non-striped 
muscular  fibres.  This  is  the  muscularis  mucosae 
(lamina  muscularis  mucosae) .    At  the  commencement 

•  .    •         I  .  1  J.     1    u  f  J. ,  1     of  the  Royal  College  of  teurgeons  of 

it  is  absent,  or  only  represented  by  a  tew  scattered   England.) 
bundles;  lower  down  it  forms  a  considerable  stratum. 

Vessels  of  the  Oesophagus. — The  larger  vessels  are  in  the  submucosa  and  send 
branches  to  the  mucosa  and  muscularis.  The  arteries  supplying  the  oesophagus 
are  derived  from  the  inferior  th3n:oid  branch  of  the  thyroid  axis  of  the  subclavian, 
from  the  descending  thoracic  aorta  and  the  bronchial  arteries,  and  from  the  gastric 
branch  of  the  cceliac  axiss  and  from  the  left  inferior  phrenic  of  the  abdominal  aorta. 
They  have  for  the  most  part  a  longitudinal  direction.  The  veins  are  gathered  into 
a  plexus  on  the  outer  surface  of  the  oesophagus.  This  plexus  receives  the  venous 
blood  from  the  walls  of  the  tube.  From  the  lower  portion  of  the  plexus  branches 
go  to  the  coronary  vein  of  the  stomach.     Higher  up  branches  go  to  the  azygos  veins 


Fig.  829.  —  Accessorj'  muscular 
fibres  between  the  oesophagus  and 
pleura,  and  oesophagus  and  trachea. 
(From  a  preparation  in  the  Museum 


1230  THE    ORGANS    OF  DIGESTION 

and  thyroid  veins.  In  this  manner  a  communication  is  opened  between  the  portal 
veins  and  the  systemic  veins. 

Lymphatics  of  the  Oesophagus. — ^The  lymphatics  drain  into  the  inferior  deep 
cervical  glands  and  the  glands  of  the  posterior  mediastinum. 

Nerves  of  the  Oesophagus. — The  nerves  are  derived  from  the  pneumogastric  and 
from  the  sympathetic;  they  form  a  plexus  in  which  are  groups  of  ganglion-cells 
between  the  two  layers  of  the  muscular  coats.  From  this  fibres  pass  to  supply 
the  muscle,  and  others  go  to  the  submucous  tissue  to  form  a  secondary  plexus. 
It  is  usual  to  regard  the  plexus  as  consisting  of  two  parts,  an  anterior  oesophageal 
plexus,  derived  from  the  left  pneumogastric,  and  a  posterior  oesophageal  plexus, 
derived  from  the  right  pneumogastric.  These  two  plexuses  are  in  the  posterior 
mediastinum;  they  communicate  with  each  other  and  contain  sympathetic  fibres. 

Movements  and  Innervation  of  the  Oesophagus. 

Movements. — When  liquid  is  swallowed  it  is,  as  pointed  out  by  Kronecker  and  Meltzer, 
suddenly  forced  into  the  gullet  by  the  contraction  of  the  Mylo-hyoid  muscle,  the  tube  playing 
a  prr.ctically  passive  part.'  In  the  passage  of  solid  and  semisolid  food  the  oesophagus  con- 
tracts. It  does  not  contract,  as  was  once  thought,  in  sections,  but  there  is  a  peristaltic  wave. 
'The  wave  at  a  given  point  lasts  in  the  neck  region  about  3.5  seconds,  and  from  five 
to  nine  seconds  in  the  thoracic  region.^  The  lower  end  of  the  oesophagus  or  cardia  has  a 
sphincter,  the  cardiac  sphincter.  It  is  usually  taught  that  this  sphincter  is  tonically  contracted. 
When  a  mouthful  of  food  is  swallowed  it  rests  above  the  sphincter  for  a  moment  and  is  then 
forced  through  by  muscular  contractions  (Kronecker  and  Meltzer).  If  several  acts  of  swallow- 
ing follow  each  other  rapidly  the  sphincter  relaxes  so  that  there  is  no  resistance  to  the  passage 
of  food.  In  cats  Dr.  Walter  B.  Cannon^  has  demonstrated  "rhythmical  relaxations  of  the 
cardia,  so  that  fluid  food  streams  from  the  stomach  into  the  oesophagus  even  above  the  level 
of  the  heart,  then  is  pressed  into  the  stomach  again  by  a  peristaltic  wave,  only  to  be  released 
a  moment  later  to  pour  into  the  oesophagus  anew." 

Innervation. — There  is  in  the  oesophagus  a  local  reflex,  but  peristalsis  is  dominated  by  the 
central  nervous  system.  "It  seems  probable  that  the  peristaltic  contractions  of  the  oesophagus, 
to  be  efficient,  must  be  supported  by  nervous  influences  from  outside.  In  this  respect  the 
oesophagus  is  different  from  the  remainder  of  the  alimentary  canal."* 

Surgical  Anatomy. — The  relations  of  the  oesophagus  are  of  considerable  practical  interest 
to  the  surgeon,  as  he  is  frequently  required,  in  cases  of  stricture  of  this  tube,  to  dilate  the  canal 
by  a  bougie,  when  it  is  of  importance  that  the  direction  of  the  oesophagus  and  its  relations 
to  surrounding  parts  should  be  remembered.  In  cases  of  malignant  disease  of  the  oesophagus, 
where  its  tissues  have  become  softened  from  infiltration  of  the  morbid  deposit,  the  greatest 
care  is  requisite  in  directing  the  bougie  through  the  strictured  part,  as  a  false  passage  may  easily 
be  made,  and  the  instrument  may  pass  into  the  mediastinum,  or  into  one  or  the  other  pleural 
cavity,  or  even  into  the  pericardium.  ^ 

The  student  should  also  remember  that  obstruction  of  the  oesophagus,  and  consequent 
symptoms  of  stricture,  are  occasionally  produced  by  aneurism  of  some  part  of  the  aorta  press- 
ing upon  the  tube.    In  such  a  case  the  passage  of  a  bougie  could  only  hasten  the  fatal  issue. 

In  passing  a  bougie  the  left  forefinger  should  be  introduced  into  the  mouth  and  the  epiglottis 
felt  for,  care  being  taken  not  to  throw  the  head  too  far  backward.  The  bougie  is  then  to  be 
passed  beyond  the  finger  until  it  touches  the  posterior  wall  of  the  pharynx.  The  patient  is 
now  asked  to  swallow,  and  at  the  moment  of  swallowing  the  bougie  is  passed  gently  down- 
ward, all  violence  being  carefully  avoided. 

It  occasionally  happens  that  a  foreign  body  becomes  impacted  in  the  oesophagus  and  can 
neither  be  brought  upward  nor  moved  downward.  When  all  ordinary  means  for  its  removal 
have  failed,  and  the  body  is  lodged  above  the  lower  one-third  of  the  gullet,  external  oesopha- 
gotomy  is  performed.  If  the  foreign  body  is  lodged  in  the  lower  one-third  of  the  gullet  the 
stomach  is  opened  {gaslrotomy)  and  the  foreign  body  is  extracted.  If  the  foreign  body  is 
allowed  to  remain  lodged  in  the  oesophagus,  extensive  inflammation  and  ulceration  may 
ensue.  In  one  case  the  foreign  body  ultimately  penetrated  the  intervertebral  substance,  and 
destroyed  life  by  inflammation  of  the  membranes  and  substance  of  the  cord. 

The  operation  of  oesophagotomy  is  thus  performed:  The  patient  being  placed  upon  his 
back,  with  the  head  and  shoulders  slightly  elevated,  an  incision,  about  four  inches  in  length, 

^  Recent  Advances  in  the  Knowledt^e  of  the  Movements  and  Innervation  of  the  Alimentary  Canal.  By  Walter 
li.  Cannon,  M.D.,  in  Medical  News,  May  20,  1905. 

•  Ibid.  3  Ibid.  *  Ibid. 


THE  ABDOMEN  1231 

should  be  made  on  the  left  side  of  the  trachea,  from  the  thyroid  cartilage  downward,  dividing 
the  skin,  Platysma,  and  deep  fascia.  The  edges  of  the  wound  being  separated,  the  Omo-hyoid 
muscle  should,  if  necessary,  be  divided,  and  the  fibres  of  the  Sterno-hyoid  and  Sterno-thyroid 
muscles  drawn  inward;  the  sheath  of  the  carotid  vessels,  being  exposed,  must  be  drawn  out- 
ward, and  retained  in  that  position  by  retractors:  the  oesophagus  will  now  be  exposed,  and 
should  be  divided  over  the  foreign  body,  which  can  then  be  removed.  Great  care  is  necessary 
to  avoid  wounding  the  thyroid  vessels,  the  thyroid  gland,  and  the  laryngeal  nerves. 

The  oesophagus  may  be  obstructed  not  only  by  foreign  bodies,  but  also  by  changes  in  its 
coats,  producing  stricture,  or  by  pressure  on  it  from  without  of  new-growths  or  aneurism,  etc. 

The  different  forms  of  stricture  are:  (1)  the  spasmodic,  occurring  in  neurotic  individuals,  and 
intermittent  in  character,  so  that  the  dysphagia  is  not  constant.  Spasmodic  stricture  of  the 
oesophagus  sometimes  occurs  in  cases  of  cancer  of  the  stomach  and  cancer  of  the  liver; 
(2)  fibrous,  due  to  cicatrization  after  injuries,  such  as  swallowing  corrosive  fluids  or  boiling 
water;  and  (3)  malignant,  usually  epitheliomatous,  in  its  nature.  Cancer  is  most  common 
either  at  the  upper  end  of  the  tube,  opposite  to  the  cricoid  cartilage,  or  at  its  lower  end  at  the 
cardiac  orifice.  Cicatricial  stricture  may  be  treated  by  gradual  dilatation.  If  a  stricture  is 
impassible  from  above,  the  stomach  may  be  opened,  an  instrument  passed  from  below,  and  a 
string  used  to  divide  the  stricture. 

The  operation  of  oesophagostomy  has  occasionally  been  performed  in  cases  where  the  stric- 
ture in  the  oesophagus  is  at  the  upper  part,  with  a  view  to  making  a  permanent  opening  below 
the  stricture  through  which  to  feed  the  patient,  but  the  operation  has  been  far  from  a  suc- 
cessful one,  and  the  risk  of  setting  up  diffuse  inflammation  in  the  loose  planes  of  connective 
tissue  deep  in  the  neck  is  so  great  that  it  would  appear  to  be  better,  if  any  operative  interference 
is  undertaken,  with  the  idea  of  forming  a  mouth  to  introduce  food,  to  perform  gastrostomy. 
The  operation  of  oesophagostomy  is  performed  in  the  same  manner  as  ocsophagotomy,  but  the 
edges  of  the  opening  in  the  oesophagus  are  stitched  to  the  skin  incision.  Gastrostomy  is 
the  only  operation  to  be  thought  of  in  malignant  stricture. 


THE  ABDOMEN. 

The  abdomen  (from  ahdo,  I  put  away  or  hide,  or  possibly  from  adeps,  fat)  is 
the  largest  cavity  in  the  body.  It  is  of  an  oval  form,  the  extremities  of  the  oval 
being  directed  upward  and  downward;  the  upper  one  being  formed  by  the  under 
surface  of  the  Diaphragm,  the  lower  by  the  upper  concave  surface  of  the  Levator 
ani  muscles.  In  order  to  facilitate  description,  it  is  artificially  divided  into  two 
parts:  an  upper  and  larger  part,  the  abdomen  proper;  and  a  lower  and  smaller 
part,  the  pelvis.  These  two  cavities  are  not  separated  from  each  other,  but  the 
limit  between  them  is  marked  by  the  brim  of  the  true  pelvis.  The  space  is  wider 
above  than  below,  and  measures  more  in  the  vertical  than  in  the  transverse 
diameter. 

The  abdomen  proper  differs  from  the  other  great  cavities  of  the  body  in  being 
bounded  for  the  most  part  by  muscles  and  fasciae,  so  that  it  can  vary  in  capacity 
and  shape  according  to  the  condition  of  the  viscera  which  it  contains;  but,  in 
addition  to  this,  the  abdomen  varies  in  form  and  extent  with  age  and  sex  (Fig. 
831).  In  the  adult  male,  with  moderate  distention  of  the  viscera,  it  is  oval  or 
barrel-shaped,  but  at  the  same  time  flattened  from  before  backward.  In  the  adult 
female,  with  a  fully  developed  pelvis,  it  is  conical  with  the  apex  above,  and  in 
young  children  it  is  conical  with  the  apex  below. 

Boundaries. — The  boundary  between  the  thorax  and  abdomen  is  the  Dia- 
phragm. This  muscle  forms  a  dome  over  the  abdomen,  and  the  cavity  extends 
high  into  the  bony  thorax,  reaching  to  the  level  of  the  junction  of  the  fourth  costal 
cartilages  with  the  sternum.  The  lower  end  of  the  abdomen  is  limited  by  the 
structures  which  clothe  the  inner  surface  of  the  bony  pelvis,  principally  the  Leva- 
tores  ani  and  Coccygei  muscles  on  either  side.  These  muscles  are  sometimes 
termed  the  Diaphragm  of  the  pelvis.  The  abdomen  proper  is  bounded  in  front  and 
at  the  sides  by  the  lower  ribs,  the  abdominal  muscles,  and  the  venter  ilii;  behind, 
by  the  vertebral  column  and  the  Psoas  and  Quadratus  lumborum  muscles;  above, 
by  the  Diaphragm;  below,  by  the  brim  of  the  pelvis.    The  muscles  forming  the 


1232 


THE    ORGANS    OF  DIGESTION 


boundaries  of  the  cavity  are  lined  upon  their  inner  surface  by  a  layer  of  fascia, 
differently  named,  according  to  the  part  which  it  covers. 


Fig.  830. — Topography  of  thoracic  and  abdominal  viscera. 


THE  ABDOMEN  1233 

The  abdomen  contains  (Fig.  830)  the  greater  part  of  the  alimentary  canal; 
some  of  the  accessory  organs  to  digestion — viz.,  the  liver  and  pancreas,  the  spleen, 
the  kidneys,  and  suprarenal  capsules.  Most  of  these  structures,  as  well  as  the 
wall  of  the  cavity  in  which  they  are  contained,  are  covered  by  an  extensive  and 
complicated  serous  membrane,  the  peritoneum  (Fig.  853.) 

The  Apertures  in  the  Walls  of  the  Abdomen. — The  apertures  found  in  the  walls  of 
the  abdomen,  for  the  transmission  of  structures  to  or  from  it,  are  the  umbilicus,  for 
the  transmission  (in  the  foetus)  of  the  umbilical  vessels;  the  caval  opening  in  the 
Diaphragm,  for  the  transmission  of  the  inferior  vena  cava;  the  aortic  opening,  for 
the  passage  of  the  aorta,  vena  azygos  major,  and  thoracic  duct;  and  the  oesophageal 
opening,  for  the  oesophagus  and  pneumogastric  nerves.  Below,  there  are  two 
apertures  on  each  side:  one  for  the  passage  of  the  femoral  vessels,  and  the  other 
for  the  transmission  of  the  spermatic  cord  in  the  male,  and  the  round  ligament  in 
the  female. 


Male  Type 


Infantile  Type 


Female  Type 


A  B  C 

Fig.  831. — Schematic  outlines  of  the  abdomen. 

Regions  (Fig.  832). — For  convenience  of  description  of  the  viscera,  as  well  as 
of  reference  to  the  morbid  conditions  of  the  contained  parts,  the  abdomen  is  arti- 
ficially divided  into  nine  regions.  Thus,  if  two  circular  lines  are  drawn  around 
the  body,  the  one  through  the  extremities  of  the  ninth  ribs  where  they  join  their 
costal  cartilages,  and  the  other  through  the  highest  points  of  the  crests  of  the  ilia, 
the  abdominal  cavity  is  divided  into  three  zones^an  upper,  a  middle,  and  a 
lower.  If  two  parallel  lines  are  drawn  perpendicularly  upward  from  the  centre  of 
Poupart's  ligament,  each  of  these  zones  is  subdivided  into  three  parts — a  middle 
and  two  lateral.* 

The  middle  region  of  the  upper  zone  is  called  the  epigastric  {liz't,  over;  yaaxrjpy 
the  stomach);  and  the  two  lateral  regions,  the  right  and  left  hypochondriac  {biio^ 
under;  -j^oi^dtioi,  the  cartilages).  The  central  region  of  the  middle  zone  is  the 
mesogastric  or  umbilical;  and  the  two  lateral  regions,  the  right  and  left  lumbar.  The 
middle  region  of  the  lower  zone  is  the  hypogastric  or  pubic  region ;  and  the  lateral 
regions  are  the  right  and  left  inguinal  or  iliac.  The  viscera  contained  in  these 
different  regions  are  the  following  (Fig.  832) : 

'  Anatomists  are  far  from  agreed  as  to  the  best  method  of  subdividing  the  abdominal  cavity.  Cunningham 
suggests  that  the  lower  line  should  encircle  the  body  on  a  level  with  the  highest  point  of  the  iliac  crest,  as  seen 
from  the  front — a  point  corresponding  with  a  prominent  tubercle  on  the  outer  lip  of  the  iliac  crest  about  two 
inches  behind  the  anterior  superior  spine.  Addison  (Journal  of  Anatomy  and  Physiology,  vols,  xxxiv.  and 
x.\xv.),  in  a  careful  analysis  of  the  abdominal  viscera  in  forty  subjects,  adopts  the  following  line?  :  (1)  a 
median,  from  the  symphysis  pubis  to  the  ensiform  cartilage;  (2)  two  lateral  lines  drawn  vertically  through  a  point 
midway  between  the  anterior  superior  iliac  spine  and  the  symphysis  jjubis  ;  (3)  an  upper  transverse  line  half-way 
between  the  symphysis  pubis  and  the  suprasternal  notch;  and  (4)  a  lower  transverse  line  midway  between  the 
last  and  the  upper  border  of  the  symphysis  pubis. — Ed.  of  15th  English  edition. 

.Joessel  draws  a  line  through  the  cartilaginous  ends  of  the  tenth  ribs:  a  line  through  the  two  anterior  superior 
spines  of  the  ilia.  On  each  side  he  carries  a  per|)endicular  line  from  the  iliopectineal  eminence  to  the  hori- 
zontal line  connecting  the  tenth  ribs.      By  this  plan  the  highest  plane  is  subcostal. 


78 


1234 


THE    ORGANS   OF  DIGESTION 


Right  Hypochondriac. 

The  greater  part  of  the 
right  lobe  of  the  Hver, 
the  hepatic  flexure  of  the 
colon,  and  part  of  the 
right  kidney. 


Right  Lumbar. 

Ascending  colon,  part 
of  the  right  kidney,  and 
some  convolutions  of  the 
small  intestines. 


Right  Inguinal  or  Iliac. 

The  caecum  and  ver- 
miform appendix  and  a 
portion  of  the  ascending 
colon. 


Epigastric  Region. 

The  greater  part  of  the 
stomach,  including  both 
cardiac  and  pyloric  ori- 
fices, the  left  lobe  and 
part  of  the  right  lobe  of 
the  Hver  and  the  gall- 
bladder, the  pancreas,  the 
duodenum,  the  supra- 
renal capsules,  and  parts 
of  the  kidneys. 

Umbilical  Region. 

The  transverse  colon, 
part  of  the  great  omentum 
and  mesentery,  transverse 
part  of  the  duodenum, 
and  some  convolutions  of 
the  jejunum  and  ileum, 
and  part  of  both  kidneys. 

Hypogastric  Region. 

Convolutions  of  the 
small  intestines,  the  blad- 
der in  children,  and  in 
adults  if  distended,  and 
the  uterus  during  preg- 
nancy. 


Left  Hypochondriac. 

The  fundus  of  the 
stomach,  the  spleen,  the 
extremity  of  the  pancreas, 
the  splenic  flexure  of  the 
colon,  and  part  of  the 
left  kidney. 


Left  Lumbar. 

Descending  colon,  part 
of  the  omentum,  part  of 
the  left  kidney,  and  some 
convolutions  of  the  small 
intestines. 


Left  Inguinal  or  Iliac. 

Sigmoid  flexure  of  the 
colon  and  a  portion  of 
the  descending  colon. 


If  the  anterior  abdominal  wall  is  reflected  in  the  form  of  four  triangular  flaps 
by  means  of  vertical  and  transverse  incisions — the  former  from  the  ensiform  car- 
tilage to  the  symphysis  pubis,  the  latter  from  flank  to  flank  at  the  level  of  the 
umbilicus — the  abdominal  or  peritoneal  cavity  is  freely  opened  into  and  the 
contained  viscera  are  in  part  exposed.^ 

Above  and  to  the  right  side  is  the  liver,  situated  chiefly  under  the  shelter  of 
the  right  ribs  and  their  cartilages,  but  extending  across  the  middle  line,  and  reach- 
ing for  some  distance  below  the  level  of  the  ensiform  cartilage.  Below  and  to  the 
left  of  the  liver  is  the  stomach,  from  the  lower  border  of  which  an  apron-like  fold 
of  peritoneum,  the  great  omentum,  descends  for  a  varying  distance,  and  obscures, 
to  a  greater  or  lesser  extent,  the  other  viscera  (Fig.  861).  Below  it,  however,  some 
of  the  coils  of  the  small  intestine  can  generally  be  seen,  while  in  the  right  and  left 
iliac  regions  respectively  the  caecum  and  the  sigmoid  flexm-eof  thecolon  are  exposed. 
The  bladder  occupies  the  anterior  part  of  the  pelvis,  and,  if  distended,  will  project 
above  the  symphysis  pubis;  the  rectum  lies  in  the  concavity  of  the  sacrum,  but 
is  usually  obscured  by  the  coils  of  the  small  intestine. 

If  the  stomach  is  followed  from  left  to  right  it  will  be  found  to  be  continuous 
with  the  first  part  of  the  small  intestine,  or  duodenum,  the  point  of  continuity  being 
marked  by  a  thickened  ring  which  indicates  the  position  of  the  pyloric  valve. 
The  duodenum  passes  toward  the  under  surface  of  the  liver,  and  then,  curving 
downward,  is  lost  to  sight.     If,  however,  the  great  omentum  be  thrown  upward 


'It  must  be  borne  in  mind  that,  although  the  term  abdominal  cavity  is  used,  there  is,  under  normal  con- 
ditions, only  a  potential  cavity  or  lymph-space,  since  the  viscera  are  everywhere  in  contact  with  the  parietes. — 
Ed.  of  15th  English  edition. 


THE  ABDOMEN 


1235 


over  the  chest,  the  terminal  part  of  the  duodenum  will  be  observed  passing  across 
the  spine  toward  the  left  side,  where  it  becomes  continuous  with  the  coils  of  the 
small  intestine.  These  measure  some  twenty  feet  in  length,  and  if  followed  down- 
ward will  be  seen  to  end  in  the  right  iliac  fossa  by  opening  into  the  caecum,  the 
commencement  of  the  large  intestine.  From  the  caecum  the  large  intestine  takes 
an  arched  course,  passing  at  first  upward  on  the  right  side,  then  across  the  middle 
line  and  downward  on  the  left  side,  and  forming  respectively  the  ascending,  trans- 
verse, and  descending  parts  of  the  colon.  In  the  left  iliac  region  it  makes  still 
another  bend,  the  sigmoid  flexure,  and  then  follows  the  curve  of  the  sacrum  as 
far  as  the  lectum. 


Limit  of 


Fig.  832. — The  regions  of  the  abdomen  and  their  contents.     Edge  of  costal  cartilages  in  dotted  outline. 


The  spleen  lies  behind  the  stomach  in  the  left  hypochondriac  region,  and  may 
be  in  part  expo.sed  by  pulling  the  stomach  over  toward  the  right  side. 

The  glistening  appearance  of  the  deep  surface  of  the  abdominal  wall  and  of 
the  exposed  viscera  is  due  to  the  fact  that  the  former  is  lined  and  the  latter  more 
or  less  completely  covered  by  a  serous  membrane,  the  peritoneum. 

Development  of  the  Alimentary  Canal,  Viscera  and  Peritoneum. — When 
the  paraxial  mesoblast  of  the  embryo  has  developed  a  series  of  transverse  seg- 
mentations it  becomes  converted  into  a  row  of  dark,  square  segments  known  as 
the  proto vertebrae  or  the  mesoblastic  somites,  which  are  separated  by  clear,  trans- 
verse intervals.  They  appear  first  in  the  region  that  is  to  become  the  neck,  and 
from  there  extend  back  along  the  entire  length  of  the  trunk.  These  bodies  are 
not  solely  the  representatives  of  the  future  permanent  vertebrae,  but  differentiate 
partly  into  muscles  and  true  skin. 

On  each  side  of  the  protovertebrae  the  lateral  mesoblast  splits  into  two  layers. 


1236  THE    ORGANS    OF  DIGESTION 

The  upper  layer  is  applied  to  the  epiblast,  and  forms  with  it  the  somatopleure  or 
body-wall.  The  lower  layer  becomes  adherent  to  the  hypoblast,  and  forms  the 
splanchnopleure  or  wall  of  the  alimentary  canal.  The  space  between  these  two 
layers  is  the  caelum  or  the  pleuroperitoneal  cavity.  This  body-cavity  is  of  large 
size  in  the  early  stages  of  the  development  of  the  embryo. 

Anteriorly — or,  if  the  body  is  in  the  erect  posture,  superiorly — there  is  developed 
a  comparatively  large  space  called  the  pericardiothoracic  cavity;  and  a  transverse 
fold  develops,  which  marks  off  this  cavity  from  the  future  abdominal  cavity.  This 
fold,  with  many  veins  of  large  size,  develops  into  the  primary  Diaphragm,  although 
its  dorsal  part  remains  incomplete.  The  dorsal  part  is  completed  at  a  later  period, 
constituting  the  Diaphragm  as  we  see  it  in  the  adult.  As  Dr.  Frederick  J.  Brock- 
way  expresses  it :  "The  Diaphragm  is  thus  made  up  of  a  ventral,  younger  part,  and 
a  dorsal,  older  part.  When  this  posterior  part  fails  to  develop,  there  is  opportunity 
for  a  congenital  diaphragmatic  hernia  to  be  present." 

The  pericardiothoracic  cavity  becomes  divided  into  three  cavities,  and  the  two 
lateral  ones  are  for  a  time  contirmous  with  the  abdominal  cavity.  This  continuation 
is,  however,  but  temporary,  and  they  are  afterward  separated.  In  this  manner, 
four  large  serous  sacs  are  formed.     The  two  lateral   thoracic  sacs  are  known  as 


Fig.  833. — Diagrammatic  outline  of  a  longitudinal  vertical  section  of  the  chick  on  the  fourth  day.  ep.  Epi- 
blast. »m.  Somatic  me.soblast.  hti.  Hypoblast,  vm.  Visceral  mesoblast.  o/.  Cephalic  fold.  pf.  Caudal  fold. 
am.  Cavity  of  true  amnion,  ys.  Yolk-sac.  i.  Intestine.  «.  Fore-gut.  a.  Future  anus,  still  closed,  m.  The 
mouth,  vie.  The  mesentery,  al.  The  allantoic  vesicle,  pp.  Space  between  inner  and  outer  folds  of  amnion. 
(From  Quain's  Anatomy,  Allen  Thomson.) 

the  pleural  sacs,  and  are  lined  with  the  pleura;  the  median  thoracic  sac  is  the 
pericardial  sac,  and  is  lined  with  the  pericardium ;  and  the  abdominal  sac  forms  the 
abdominal  cavity,  and  is  lined  with  the  peritoneum. 

The  primitive  alimentary  canal,  which  was  formed  early  by  the  closure  within 
the  embryo  of  a  portion  of  the  blastodermic  vesicle,  consists  of  three  parts :  first, 
the  fore-gut,  within  the  cephalic  flexure,  dorsal  to  the  heart;  second,  the  mid-gut, 
opening  freely  into  the  yolk-sac;  and  third,  the  hind-gut,  within  the  caudal  flexure. 
In  the  fore-gut  are  developed  the  back  portion  of  the  mouth,  the  tongue,  the 
pharynx,  the  oesophagus,  the  stomach,  the  larger  part  of  the  duodenum,  and  the 
organs  that  have  grown  out  from  these  structures.  The  hind-gut  forms  a  portion 
of  the  colon  and  the  rectum,  with  the  exception  of  the  latter's  anal  end ;  and  the 
mid-gut  gives  rise  to  the  remainder  of  the  digestive  tube. 

Development  of  the  Alimentary  Canal. — The  fore-gut  and  hind-gut  end 
blindly,  there  being  at  first  neither  mouth  nor  anus  (Figs.  833  and  834).  The  upper 
part  of  the  fore-gut  becomes  dilated  to  form  the  pharynx,  in  relation  to  which  the 
branchial  arches  are  developed  (Fig.  836);  the  succeeding  part  remains  tubular, 
and  with  the  descent  of  the  stomach  is  elongated  to  form  the  oesophagus.  Soon 
a  fusiform  dilatation,  the  future  stomach,  makes  its  appearance,  and  beyond 
this  the  mid-gut  opens  freely  into  the  yolk-sac  (Figs.  836  and  837). 

This  opening  is  at  first  wide,  but,  as  the  body-walls  close  in  around  the  umbilicus, 
it  is  gradually  narrowed  into  a  tubular  stalk,  the  yolk-stalk  or  vitello-intestinal  duct. 


THE  ABDOMEN 


1237 


At  this  stage,  therefore,  the  aHmentary  canal  forms  a  nearly  straight  tul)e  in  front 
of  the  notochord  and  primitive  aorta  (Fig.  834).     From  the  stomach  to  the  rectum 


Amnion 


V'.'-'v:  •  .>'.'-';V<^/.";. 


'Allantoia 
Hind-gut 


Fore-gut  /  Heart 

Chorda  Dorsalis 


Fig.  834. — Diagram  of  a  longitudinal  section  of  a  mannmalian  embryo.     Very  early.     (After  Quain.) 

it  is  attached  to  the  notochord  by  a  band  of  mesoblast,  from  which  the  common 
mesentery  of  the  gut  is  subsequently  developed.  The  stomach  undergoes  a  further 
dilatation,  and  its  two  curvatures  can  be  recognized  (Figs.  838  and  841),  the 
greater  directed  toward  the  verte- 
bral column  and  the  lesser  toward 
the  anterior  wall  of  the  abdomen, 
while  of  its  two  surfaces  one  looks 
to  the  right  and  the  other  to  the  left. 
The  mid-gut  also  undergoes  great 
elongation,  and  forms  a  V-shaped 
loop  which  projects  downward  and 
forward ;  from  the  bend  or  angle  of 
the  loop  the  vitello-intestinal  duct 
passes  to  the  umbilicus  (Fig.  841). 
For  a  time  a  part  of  the  loop  ex- 
tends beyond  the  abdominal  cavity 
into  the  umbilical  cord,  but  by 
the  end  of  the  third  month  this 
is  withdrawn.  With  the  length- 
ening of  the  tube,  the  mesoblast, 
which  attaches  it  to  the  future  ver- 
tebral column  and  which  carries  the 
blood-vessels  for  the  supply  of  the 
gut,  is  thinned  and  drawn  out  to 
form  the  primitive  or  common  me- 
sentery. The  portion  of  this  mesentery  which  is  attached  to  the  greater  curva- 
ture of  the  stomach  is  named  the  mesogastrium,  and  the  parts  which  suspend 


Fig. 


In  A 


835. — Early  form  of  the  alimentary  canal, 
front  view  and  in  B  an  antero-posterior  section  are  repre- 
sented, a.  Four  pharyngeal  or  visceral  plates,  b.  The 
pharynx,  c,  c.  The  commencing  lungs.  d.  The  stomach. 
/,  /.  The  diverticula  connected  with  the  formation  of  the 
liver,  g.  The  yolk-sac  into  which  the  middle  intestinal  groove 
opens,  h.  The  posterior  part  of  the  intestine.  (From  Kiilliker, 
after  Bischoff.) 


1238 


THE   ORGANS    OF   DIGESTION 


the  colon  and  rectum  are  respectively  termed  the  mesocolon  and  mesorectum 
(Fig.  841).  About  the  sixth  week  a  lateral  diverticulum  makes  its  appear- 
ance a  short  distance  beyond  the  vitello-intestinal  duct,  and  indicates  the  future 
caecum  or  boundary  between  the  small  and  the  large  intestine.  This  caecal  divertic- 
ulum has  at  first  a  uniform  calibre,  but  its  blind  extremity  remains  rudimentary 
and  forms  the  vermiform  appendix  (Figs.  841  and  842).  Changes  also  take  place 
in  the  position  and  direction  of  the  stomach.  It  falls  over  on  to  its  right  sur- 
face, which  henceforth  is  directed  backward,  while  its  original  left  surface  looks 
forward;  further,  its  greater  curvature  is  drawn  downward  and  to  the  left,  away 
from  the  vertebral  column,  while  its  lesser  curvature  is  directed  upward,  and  the 
commencement  of  the  duodenum  is  pushed  over  to  the  right  side  of  the  middle 
line.  The  mesogastrium,  being  attached  to  the  greater  curvature,  must  necessarily 
follow  its  movements,  and  hence  it  becomes  greatly  elongated  and  drawn  outward 


Midbrain. 


Cerebellum 


Pharyngeal  septum.-. 

Pharynx.- 

Auditory  pit: 

Aortic  bulb: 
Stomach.'- 


/Optic  vesicle. 


Stomodseum. 
Ventricle. 


Cloacal  dilatation- 
of  hind-gut. 


Allantoic  stalk 
Umbilical  vein 


Liver, 


,Mid-gut  and  yolk 
stalk. 


Hiad-gut. 


Allantois. 
Umbilical  artery. 


Fig.  836. — Human  embryo,  about  fifteen  days  old.     Brain  and  heart  represented  from  right  side  ; 
alimentary  canal  and  yolk-sac  in  mesial  section.     (After  His.) 

from  the  vertebral  column,  and,  like  the  stomach,  what  was  originally  its  right 
surface  is  now  directed  backward  and  its  left  forward.  In  this  way  a  pouch,  the 
bursa  omentalis,  is  formed  behind  the  stomach;  this  pouch  is  the  future  lesser  sac 
of  the  peritoneum,  and  it  increases  in  size  as  the  alimentary  tube  undergoes  further 
development;  the  entrance  to  the  pouch  constitutes  the  future  foramen  of  Winslow 
(Figs.  838,  842,  and  845).  The  remainder  of  the  mid-gut  becomes  greatly 
increased  in  length,  so  that  the  tube  is  coiled  on  itself,  and  this  increase  in  length 
demands  a  corresponding  increase  in  the  width  of  the  intestinal  attachment  of 
the  mesentery,  so  that  it  becomes  plaited  or  folded. 

At  this  stage  the  small  and  the  large  intestines  are  attached  to  the  vertebral 
column  by  a  common  mesentery,  the  coils  of  the  small  intestine  falling  to  the  right 
of  the  middle  line,  while  the  large  intestine  lies  on  the  left  side.^ 


'  Sometimes  this  condition  persists  throughout  life,  and  it  is  then  found  that  the  duodenum  does  not  cros» 
from  the  right  to  the  left  side  of  the  vertebral  column,  but  lies  entirely  on  the  right  side  of  the  mesial  plane, 
where  it  is  continued  into  the  jejunum  ;  the  arteries  to  the  small  intestine  (rami  intestiui  tenuis)  also  arise  from 
the  right  instead  of  the  left  side  of  the  superior  mesenteric  artery. 


THE  ABDOMEN 


1239 


The  gut  now  becomes  rotated  upon  itself,  so  that  the  large  intestine  is  carried 
over  in  front  of  the  small  intestine,  and  the  caecum  is  placed  immediately  below 


Rathke's  pouch 
Notochord.        {pituitary  involution). 


Lunfi  diver-. - 
ticulum. 

Stomach | 

Liver.  - 


Opening  into, 
yolk  sac. 


Allantois- 


Blind  portion  of 
hind-gut. 

an  duct. 


Lung  diverticuluni 
(Esophagus 


Omphalo- 
mesenteric 
duct. 

Allantois. 


Median  rudiment  of 
I  thyroid  gland. 
I       /Mandibular  arch. 
Notochord. 


Rathke's 

~  ~ pouch 
(pituitary 
involution). 


Blind  portion  of 
"hind-gut. 


Wolffian  duct. 


Fio.  837. — Sketches  in  profile  of  two  stages  in  the  development  of  the  human  alimentary  canal. 
Fig.  A  X  30.     Fig.  B  X  20.     (His.) 

the  liver;  about  the  sixth  month  the  caecum  descends  into  the  right  iliac  fossa, 
and  the  large  intestine  now  forms  an  arch  consisting  of  the  ascending,  transverse, 
and  descending  portions  of  the  colon — the  transverse  portion  crossing  in  front 


1240 


THE   ORGANS   OF  DIGESTION 


of  the  duodenum  and  lying  just  below  the  greater  curvature  of  the  stomach; 
within  this  arch  the  coils  of  the  small  intestine  are  disposed  (Fig.  842).  Some- 
times the  downward  progress  of  the  caecum  is  arrested,  so  that  in  the  adult  it 
may  be  found  lying  immediately  below  the  liver  instead  of  in  the  right  iliac  region. 


Trachea.--^ 
(Esophagus. 

Stomach. -- 
Bile  duct 


^-shaped  loop 
of  mid-gut.' 

Vitello-intesti)ial  duct.- 
Cloaca.- 


-Lung. 


-Trachea. 


-Pancreas. 


-Lung. 
—  CEsophagus, 


-Stomach. 


Fig.  838.— Front  view  of  two  successive  stages  in  the  development  of  the  alim3ntary  canal.     (His.) 

Further  changes  take  place  in  the  bursa  omentalis  and  in  the  common  mesen- 
tery, and  give  rise  to  the  peritoneal  relations  seen  in  the  adult.    The  bursa  omen- 
talis, which  at  first  reaches  only  as  far  as  the  greater  curvature  of  the  stomach, 
grows  downward  to  form  the  great  omentum, 
and  this  downward  extension   lies   in  front  of 
the  transverse  colon  and  the  coils  of  the  small 
intestine.     The  anterior  layer  of  the  transverse  *  ;«.-x  „  .. 

1        '       ,  n  •!••<.  1      *  ' i:^mi^K  Right 

mesocolon  is  at  nrst  quite  distinct  from  the  poste-  /  j^m^^iupmrenai 

rior  wall  of  the  bursa  omentalis,  but  ultimately  '  "  ^^■^  '"ps«e 


Liver 


Lesser      ''^j™ 


Stomach 


Right 
nprarenal 
vapsute 


L^ft 

suprarenal 

capsule 


Liver 


Fig.  839. — Schematic  and  enlarged  cross-section  through 
the  body  of  a  human  embryo  in  the  region  of  the  mesogas- 
trium.     Beginning  of  third  month.      (Toldt.) 


Fig.  840. — Same  section  as  in  Fig.  661   at  end 
of  third  month.      (Toldt.) 


the  two  blend,  and  hence  the  great  omentum  appears  as  if  attached  to  the  trans- 
verse colon  (Figs.  845,  846,  and  847).    The  mesentery  of  the  duodenum,  in  which 


THE  ABDOMEN 


1241 


the  rudiment  of  the  pancreas  is  enclosed,  disappears,  and  so  this  part  of  the  gut 
becomes  fixed  to  the  posterior  abdominal  wall,  and  the  pancreas  lies  entirely 
behind  the  peritoneal  membrane.    The  mesenteries  of  the  ascending  and  descend- 


Anterior  part  of  mesogastrium.- 


"Aorta. 

•Spleen. 
"Mesogastrium. 
Cieliac  axis. 

I'liiicreas. 


Superior  mesenteric 
-     artery. 


--,-  —yj— Mesentery. 


mesenteric  artery. 


Jlind-gut. 


Fig.  841. — Abdominal  part  of  alimentary  canal  anil  its  attachment  to  the  primitive  or  common  mesentery. 
Human  embryo  of  six  weeks.     (After  Toldt.)     (From  Kollmann's  ILntwickelungsgeschichte.) 

ing  parts  of  the  colon  disappear  in  the  majority  of  cases,  while  that  of  the  small 
intestine  assumes  the  oblique  attachment  characteristic  of  its  adult  condition. 

The  small  omentum  is  formed  by  a  thinning  of  the  mesoblast  or  anterior  primitive 
mesentery,  which  attaches  the  lesser  curvature  of  the  stomach  to  the  anterior 
abdominal  wall.    By  the  subsequent  growth  of  the  liver  this  leaf  of  mesoblast  is 


Duodenum. 


Small 
intestine. 

Yolk-stalk.: 


Rectum. 


Yolk-stalk. 


—Rectum. 


Fig.  842. — Illustrating  two  stages  in  the  development  of  the  human  alimentary  canal  and  its  mesentery. 
The  arrow  indicates  the  entrance  to  the  bursa  omentalis. 

divided  into  two  parts — viz.,  the  small  omentum  between  the  stomach  and  liver, 
and  the  falciform  ligament  between  the  liver  and  the  abdominal  wall  and  Dia- 
phragm (Fig.  844). 


1242 


THE    ORGANS    OF   DIGESTION 


The  anus  is  developed  as  a  slight  invagination  of  the  epiblast  a  short  distance 
in  front  of  the  posterior  end  of  the  hind-gut.  This  invagination  is  termed  the 
proctodaeum,  the  mesoblast  between  it  and  the  hypoblastic  hning  of  the  hind- 
gut  is  thinned,  and  ultimately  the  septum  breaks  down  and  disappears,  and  the 
hind-gut  opens  on  the  surface;  into  this  part  of  the  hind-gut  the  urinary  and 
generative  organs  open  for  a  time,  and  so  constitutes  a  common  cloaca.  The 
small  portion  of  the  hind-gut  behind  the  orifice  of  the  anus  is  named  the  c&udal 
or  post-anal  gut;  it  communicates  with  the  neural  tube  by  means  of  a  canal,  the 

neurenteric  canal,  already  referred  to.  Ultimately  the 
post-anal  gut  becomes  obliterated,  and  it,  together  with 
the  neurenteric  canal,  finally  disappears. 

The  peritoneal  cavity  is  the  space  left  between  the 
visceral  and  parietal  layers  of  the  mesoblast,  and  the 
serous  membrane  is  develped  from  these  layers. 

The  tongue  originates  from  the  floor  of  the  pharynx. 
The  anterior  or  papillary  portion  first  appears  as  a 
rounded  elevation,  the  tuberculum  impar,  between  the  ven- 
tral ends  of  the  mandibular  and  hyoid  arches  (Fig.  848). 
Between  the  third  and  fourth  arches  a  second  larger 
elevation  arises,  in  the  centre  of  which  is  a  median  groove 
or  furrow.  This  second  elevation  is  termed  the  furcula, 
and  from  it  the  epiglottis  is  developed,  while  the  median 
furrow  becomes  the  entrance  to  the  larynx  (Fig.  849). 
The  tuberculum  impar  and  the  furcula  are  at  first  in 
apposition,  but  are  soon  separated  by  a  ridge  produced 
by  the  forward  growth  of  the  second  and  third  arches. 
This  ridge  gives  rise  to  the  posterior  part  of  the  tongue 
and  extends  forward  in  the  form  of  a  V,  so  as  to  em- 
brace between  its  two  limbs  the  tuberculum  impar.  At 
T?      oA->    J?-    ,   J-      ■.•      the  apex  of  the  V  there  is  a  pit-like  invagination  to  form 

Fig.    843. — Final    disposition  •ini  -i  t  ii-i 

of  the  intestines  and  their  vas-   the  middle  thvroid  rudimcut,  and  this  depression  persists 

cular  relations.     A.   Aorta.     H.  ,i        p  "^  f  xV.  j     Ix         T'U  '  if  xU 

Hepatic  artery,    s.  Splenic  art-   as  the  lorameu  caccum  of  the  adult.      ine  union  ot  the 

ery.     A/.,  Co/.  Branches  of  supe-     .  ±         e    j1        i  •      •      i*       ^     i  •        xi  i     Ij. 

rior   mesenteric    artery,     m,  m'.     tWO   partS   Ot    the   tOUgUC   IS   indicated    CVCU    in    the   adult 

ar'te^^'^cjonnisct)  '"^^«'^*«"''   by  a  V-shapcd  dcpressiou,  the  apex  of  which  is  at  the 


f^eptam  fransversum. 


Aorta. 


Liver 


tnum 
(anterior  part) 


Umbilical  vein. 


Umbilical  cord 


Mesogastrium 
{posterior  part). 

Stomach. 


Intestinal 

y/shaped  loop. 
Mesentery. 


Colon. 


Fig.  844. — The  primitive  mesentery  of  a  six  weeks'  human  embryo,  half  schematic.     (Kollmann.) 


foramen  caecum,  while  the  two  limbs  run  outward  and  forward  parallel  to  but 
a  little  behind  the  circumvallate  papillae,  which  are  therefore  developed  from 


THE  ABDOMEN 


1243 


the  tuberculum  impar  (Figs.  848,  849,  and  850).  The  tonsils  are  developed  from 
the  second  branchial  cleft,  and  make  their  appearance  between  the  fourth  and 
fifth  months. 

The  liver  arises  in  the  form  of  two  diverticula  or  hollow  outgrowths  from  the 
ventral  surface  of  that  portion  of  the  fore-gut  which  afterward  becomes  the 


Mesoaastrhm 
anterius. 


Umbilical  vein . 


Border  of  the  anterior 
mesogastritan. 


Storaach 


■  Bursa  omeHtalis. 


Pancreas. 

Mesogastrium 
posterius. 

Duodenum. 


f    Great  omentum. 

Transverse 
mesocolon. 

Transverse  colon. 


Fig.  845. — Schematic  figure  of  the  bursa  omentalis  etc      Human  embryo  of  eight  weeks.     (Kollmann.; 

duodenum  (Figs.  836  and  837).  The  outgrowths,  which  represent  the  right  and 
the  left  lobes,  respectively,  of  the  adult  liver,  give  off  solid  buds  of  cells,  which  grow 
into  columns  or  cylinders;  these  unite  with  one  another  in  every  direction  to  form 
a  close  network,  in  the  meshes  of  which  are  contained  the  capillar^  blood-vessels. 


stomach 

Oreaier  curvature 
Anterior  lamella  of  greater  omentum 
Posterior  lamella  oj  greater  omentum 

Transvase  colon 


Greater  omentum 


Diaphragm 


Liver 


Lesser  omentum 


Pancreas 


Transverse  mesocolon 
Duodenum 


Mesentery 


Small  intestine 


Fig.  846. — Illustrating  the  development  of  the  bursa  omentalis,  cavity  of  the  great  omentum  or  lesser  sac. 
Foetal  stage.     *  Lesser  sac.     (Hertwig.) 

Some  of  these  columns  become  hollowed  out  and  form  the  bile-ducts,  while  the 
remainder  constitute  the  secreting  structure.  The  minute  ducts  thus  produced 
unite  to  form  the  right  and  left  hepatic  ducts;  while  the  common  bile-duct  is  devel- 
oped as  a  protrusion  from  the  duodenal  wall,  and  as  it  grows  the  liver  becomes 
shifted  away  from  the  duodenum.    The  gall-bladder  and  cystic  duct  are  formed  by 


1244 


THE    ORGANS    OF  DIGESTION 


a  hollow  evagination  from  the  wall  of  the  common  bile-duct.     About  the  third 
month  the  liver  almost  fills  the  abdominal  cavity.    From  this  period  the  relative 


stomach 

Oreater  curvature 

Posterior  lamella  of  greater  omentum- 

Transverse  colon 


Oreater  omentuvi 


Diaphragm 
Liver 

Lesser  omentum 


Pancreas 

Part  of  omentum  enclosing  pancreas 

Transverse  mesocolon 

Duodenum 


Mesentery 


Small  intestine 

Fig.  847.— Development  of  bursa  omentalis.     Infantile  .stage.     Great  omentum  covers  the  intestine.?  and  has 
fused  with  the  transverse  mesocolon.     Pancreas  is  free  from  peritoneum  posteriorly.     (Hertwig.) 

development  of  the  liver  is  less  active,  more  especially  that  of  the  left  lobe,  which 
now  becomes  smaller  than  the  right;  but  up  to  the  end  of  foetal  life  the  liver 
remains  relatively  larger  than  in  the  adult. 


Mandibular  arch. 
Hyoid  arch. 


Third  arch. 
Fourth  arch. 


Fig.  848.^ — The  floor  of  the  pharynx  of  a  human  embryo  about  fifteen  days  old.      X  50.     (From  His.) 

The  pancreas  is  also  an  early  formation,  being  far  advanced  in  the  second 
month.  It  originates  as  a  hollow  projection  from  the  hypoblast  of  the  dorsal  wall 
of  the  duodenum  (Figs.  837  and  838),  opposite  the  hepatic  diverticula,  which,  as 


Tuberculum  impar 
{papillary  part  of  tongue). 


Posterior  part  of  tongue. 

i 
I 

Furcula. 


Entrance  to  larynx.. ^-^^-L^ 


Mandibular  arch. 


•Hyoid  arch. 


Third  arch. 
Fourth  arch. 


•  -  Lung. 
Fig.  849. — The  floor  of  the  pharynx  of  a  human  embryo  about  twenty-three  days  old.     X  30.      (From  His.) 

we  have  already  seen,  spring  from  its  ventral  wall.    This  hollow  process  grows 
between  the  two  layers  of  the  dorsal  mesentery  and  sends  out  offshoots,  which 


THE   PERITONEUM 


1245 


branch  abundantly  and  form  a  complicated  tubular  gland.  As  torsion  of  the 
stomach  takes  place,  the  pancreas  assumes  a  transverse  position  and  becomes  fixed 
across  the  dorsal  wall  of  the  abdomen,  the  posterior  layer  of  its  mesentery  under- 
going absorption.  Its  duct  ultimately  opens  into  the  duodenum  together  with  the 
common  bile-duct. 

The  spleen,  on  the  other  hand,  is  of  mesoblastic  origin,  for  there  is  never  any 
connection  between  the  intestinal  cavity  and  the  substance  of  this  organ.  It 
originates  in  the  mesenteric  fold  which  connects  the  stomach  to  the  vertebral 
column  (mesogastrium)  (Fig.  841). 

Papillary  portion  of  tongue. 


•"i— Mandibular  arch. 


'Hyoid  arch. 


Foramen  csecum.     Posterior  part     third  arch, 
of  tongue. 
Fig.  850. — Floor  of  mouth  of  an  embryo  slightly  older  than  that  shown  in  Fig.  849.     X  16.     (From  His.) 


THE  PERITONEUM  (TUNICA  SEROSA). 

During  life  and  in  the  uncut  corpse  the  peritoneal  cavity  (cavum  peritonaei)  is 
air-tight.  It  is  not  a  real  cavity,  as  muscular  tension  and  atmospheric  pressure 
permit  no  vacant  space  to  form.  When  the  surgeon  or  anatomist  opens  the 
abdomen,  the  peritoneal  cavity  is  at  that  moment  produced. 

The  peritoneum  (from  Tiefu,  abovt,  and  rtcuto,  I  stretch)  is  the  largest  serous 
membrane  in  the  body,  and  consists,  in  the  male,  of  a  closed  sac,  a  pait  of  which 
is  applied  against  the  abdominal  parietes,  while  the  remainder  is  reflected  over 
the  contained  viscera.  In  the  female  the  peritoneum  is  not  a  closed  sac,  since  the 
free  extremities  of  the  Fallopian  tubes  open  directly  into  the  peritoneal  cavity. 
The  portion  of  the  peritoneum  applied  against  the  abdominal  parietes  consti- 
tutes the  parietal  peritoneum;  the  portion  reflected  over  the  viscera,  the  visceral 
peritoneum.  The  free  surface  of  the  membrane  is  smooth,  covered  by  a  layer  of 
flattened  endothelium,  and  lubricated  by  a  small  cavity  of  serous  fluid.  Hence 
the  viscera  can  glide  freely  against  the  wall  of  the  cavity  or  upon  one  another  with 
the  least  possible  amount  of  friction.  Its  attached  surface  is  rough,  being  con- 
nected to  the  viscera  and  inner  surface  of  the  parietes  by  means  of  areolar  tissue 
termed  the  subserous  areolar  tissue  (tela  subserosa).  The  parietal  portion  is  loosely 
connected  with  the  fascia  lining  the  abdomen  and  pelvis,  but  more  closely  to  the 
under  surface  of  the  Diaphragm  and  also  in  the  middle  line  of  the  abdomen. 

The  peritoneum  differs  from  the  other  serous  membranes  of  the  body  in  pre- 
senting a  much  more  complex  arrangement — an  arrangement  which  can  only 
be  clearly  understood  by  following  the  changes  which  take  place  in  the  alimentary 
canal  during  its  development;  and  therefore  the  student  is  advi.sed  to  preface  his 
study  of  the  peritoneum  by  reviewing  the  remarks  on  Embryology. 

Structure  of  the  Peritoneum.— It  is  a  thin,  glistening  serous  membrane  and 
consists  of  a  connective-tissue  layer  and  one  layer  of  flat  endothelial  cells  upon  the 
free  surface  of  the  membrane.  The  connective-tissue  layer  consists  of  bundles  of 
connective  tissue  which  contain  many  connective-tissue  cells  and  ela.stic  fibres. 
It  contains  a  multitude  of  lymph-spaces,  lymph-vessels,  and  lymph-capillaries. 


1246 


THE   ORGANS    OF  DIGESTION 


Beneath  the  peritoneum  is  a  layer  of  lax  and  spongy  connective  tissue  which  serves 
to  bind  the  serous  membrane  to  parts  beneath.  This  layer  is  called  the  subserous 
connective  tissue.  In  some  regions  it  is  plentiful;  in  others,  as  over  the  liver  and 
intestine,  it  is  very  scantily  developed.  The  endothelial  cells  are  flat  and  polyg- 
onal. Some  hold  that  they  are  joined  together  by  cement-substance.  Byron 
Robinson  asserts  that  there  is  no  cement-substance,  but  rather  an  organized  con- 
nection between  the  protoplasmic  processes  of  adjacent  cells. 

On  the  surface  of  the  endothelium  between  the  cells  numerous  apertures  or 
interruptions  are  to  be  seen.  Some  of  these,  the  stomata,  are  surrounded  by  a 
ring  of  cubical  endothelium  (Fig.  851),  and  communicate  with  lymphatic  capil- 
laries ;  others,  the  stigmata  or 
pseudostomata,  are  mere  interrup- 
tions in  the  endothelial  layer,  and 
are  occupied  by  processes  of  the 
branched  connective-tissue  cor- 
puscle of  the  subjacent  tissue. 
Stomata  are  particularly  numer- 
ous in  the  region  of  the  Dia- 
phragm and  are  relatively  scanty 
in  the  region  of  the  pelvis. 

The  amount  of  fluid  contained 
in  the  closed  sac  is,  in  most 
cases,  only  sufficient  to  moisten 
the  surface,  but  not  to  furnish  any 
appreciable  quantity  of  liquid. 
When  a  small  quantity  can  be 
collected,  it  is  found  to  resemble 
lymph,  and,  like  that  fluid,  coagu- 
lates spontaneously;  but  when 
secreted  in  large  quantities,  as 
in  dropsy,  it  is  a  more  watery 
fluid,  but  still  contains  a  con- 
siderable amount  of  proteid  which  is  coagulated  on  boiling. 

The  peritoneum  is  a  Ijnnph-sac  and  its  walls  contain  a  great  quantity  of  lym- 
phatic structures.  In  the  subserous  tissue  the  numerous  lymph-spaces  obtain 
fluid  from  the  peritoneal  cavity  by  way  of  the  stomata  of  the  endothelial  coat, 
and  from  these  lymph-spaces  lymph-vessels  take  origin.  Byron  Robinson  points 
out  that  the  lymphatic  system  of  the  peritoneum  consists  of:  1.  Interstitial 
lymph-spaces.  2.  Non-valved  capillaries.  3.  Valved  lymphatic  channels.  The 
subendothelial  interstitial  lymph-spaces  intercommunicate  and  can  take  up  an 
immense  quantity  of  fluid  from  the  peritoneal  cavity.  Normally  the  spaces  contain 
both  nutrient  material  and  waste  products.  Through  these  spaces  blood  capil- 
laries pass,  and  from  these  spaces  lymph-capillaries  come.  Lymphatics  are  par- 
ticularly plentiful  in — 1,  the  tendinous  portion  of  the  Diaphragm;  2,  the  ligamenta 
lata;  3,  the  omentum;  4,  the  ventral  surface  of  the  small  intestine;  5,  the  liver  and 
spleen.^ 

The  lymph  from  this  region  reaches  the  mediastinal  or  diaphragmatic  glands. 
The  serous  surface  of  the  Diaphragm  is  the  region  chiefly  efficient  in  absorption 
from  the  peritoneum,  and  there  is  a  current  in  the  peritoneal  cavity  directed  toward 
the  Diaphragm.^  Absorption  is  very  rapid  from  the  peritoneal  cavity.  Fluid  equalling 
from  3  to  8  per  cent,  of  the  body-weight  can  be  absorbed  in  one  hour.  There  are  a 
multitude  of  nerves  in  the  peritoneum,  and  it  seems  probable  that  each  endothelial 


Fig.  851. — Part  of  peritoneal  surface  of  the  central  tendon  of 
Diaphragm  of  rabbit,  prepared  with  nitrate  of  silver,  s.  Stomata. 
I.  Lymph-channels,  t.  Tendon-bundles.  The  stomata  are  sur- 
rounded by  germinating  endothelial  cells.  (From  Handbook  for 
the  Physiological  Laboratory,  Klein.) 


'  Tlie  Peritoneum.     By  Byron  Robinson. 


2  Ibid. 


THE  PERITONEUM  1247 

cell  receives  a  nerve  ending.  The  minute  arteries  of  the  peritoneum  are  surrounded 
by  nerve-plexuses.  According  to  Byron  Robinson/  the  nerves  of  the  peritoneum  are : 
1.  Medullated.  2.  Non-medullated.  3.  Fibres  of  Remak.  4.  The  Vater-Pacinian 
corpuscles  and  other  varieties  of  nerve  endings.  5.  Nerve-cells.  The  visceral 
peritoneum  contains  many  more  nerves  than  the  parietal  peritoneum. 

The  parietal  peritoneum  (peritonaeum  parietale)  lines  the  wall  of  the  abdominal 
cavity.  The  visceral  peritoneum  (peritonaeum  viscerate)  covers  the  viscera.  Back 
of  the  parietal  peritoneum  is  a  space,  the  retro -peritoneal  space  (spatium  retro- 
peritonaeale) ,  which  contains  the  great  vessels  and  nerves,  the  suprarenal  cap- 
sules, the  kidney,  and  ureters  (Figs.  853,  854,  855,  856,  and  857). 

We  describe  the  peritoneum  as  consisting  of  two  sacs,  a  greater  sac  and  a  lesser  sac 
(Fig.  853) .  The  larger  part  of  the  abdominal  cavity  is  lined  by  the  greater  sac,  as  most 
of  the  viscera  are  covered  h\  it.  The  lesser  sac  is  placed  largely  behind  the  stomach. 
These  two  sacs  are  not  two  distinct  cavities  which  communicate.  They  constitute 
one  cavity,  a  portion  of  which  has  been  formed  into  a  diverticulum  or  recess  by  a 
process  of  constriction,  the  result  of  changes  produced  in  the  position  of  adjacent 
viscera  by  development.  Prof.  Birmingham  says:  "  If  the  great  sac  be  compared 
to  a  bag,  the  lesser  sac  might  be  represented  as  a  pocket  lying  behind,  and  open- 
ing into  it  by  a  narrow  orifice,  the  foramen  of  Winslow,  on  its  posterior  wall."' 
The  greater  sac  lines  the  walls  of  the  abdominal  cavity  and  covers  the  viscera 
which  are  invested  by  peritoneum,  except  the  posterior  portion  of  the  stomach, 
the  suprarenal  capsule  of  the  left  side,  the  superior  surface  of  the  pancreas,  the 
Spigelian  lobe  and  the  caudate  lobes  of  the  liver,  and  portions  of  the  spleen,  left 
kidney,  and  transverse  colon,  which  are  covered  by  peritoneum  of  the  lesser  sac' 

To  trace  the  continuity  of  the  membrane  from  one  viscus  to  another,  and  from 
the  viscera  to  the  parietes,  it  is  necessary  to  follow  its  reflections  in  the  vertical 
and  horizontal  directions,  and  in  doing  so  it  matters  little  where  a  start  is  made. 

If  the  stomach  is  drawn  downward,  a  fold  of  peritoneum  will  be  seen  stretching 
from  its  lesser  curvature  to  the  transverse  fissure  of  the  liver  (Figs.  853  and  859). 
This  is  the  gastro-hepatic  or  lesser  omentum  (omentum  minus),  and  consists  of  two 
layers;  these,  on  being  traced  downward,  split  to  envelop  the  stomach,  covering 
respectively  its  anterior  and  posterior  surfaces.  At  the  greater  curvature  of  the 
stomach  they  again  come  into  contact  and  are  continued  downward  in  front  of 
the  transverse  colon,  forming  the  anterior  two  layers  of  the  great  or  gastro-colic 
omentum  (omentum  majus)  (Figs.  853  and  861).  Reaching  the  free  edge  of  this  fold 
they  are  reflected  upward  as  its  two  posterior  layers,  and  thus  the  great  omentum 
consists  of  four  layers  of  peritoneum.  Followed  upward  the  two  posterior  layers 
separate  so  as  to  enclose  the  transverse  colon,  above  which  they  once  more  come  into 
contact  and  pass  backward  to  the  abdominal  wall  as  the  transverse  mesocolon 
(mesocolon  transversum)  (Fig.  853) .  Reaching  the  abdominal  wall  about  the  level  of 
the  transverse  part  of  the  duodenum,  the  two  layers  of  the  transverse  mesocolon 
become  separated  from  each  other  and  take  different  directions;  the  upper  or  ante- 
rior layer,  known  as  the  ascending  layer  of  the  transverse  mesocolon,  ascends  in  front 
of  the  pancreas,  and  its  further  course  will  be  followed  presently  (Fig.  853) .  The 
lower  or  posterior  layer  is  carried  downward,  as  the  anterior  layer  of  the  mesentery, 
by  the  superior  mesenteric  vessels  to  the  small  intestine,  around  which  it  may  be 
followed  and  subsequently  traced  upward  as  the  posterior  layer  of  the  mesentery  to 
the  abdominal  wall.  From  the  posterior  abdominal  wall  it  sweeps  downward  over 
the  aorta  into  the  pelvis,  where  it  invests  the  first  part  of  the  rectum  and  attaches  it 
to  the  front  of  the  sacrum  by  a  fold  termed  the  mesorectum  (Fig.  863,  p.  1259). 
Leaving  first  the  sides  and  then  the  front  of  the  second  part  of  the  rectum  it  is 
reflected  on  to  the  back  of  the  bladder,  and,  after  covering  the  posterior  and 

'  The  Peritoneum.     By  Byron  Robinson.  -  Prof.  Cunningham's  Text-book  of  Human  Anatomy. 

^  Ibid. 


1248  THE    ORGANS    OF   DIGESTION 

upper  aspects  of  this  viscus,  is  carried  by  the  urachus  and  obliterated  hypogastric 
arteries  as  folds,  on  to  the  posterior  surface  of  the  anterior  abdominal  wall  (Fig. 
852).  The  fold  upon  the  urachus  is  the  plica  urachi  i'plica  umhilicalis  media); 
the  fold  on  each  obliterated  hypogastric  artery  is  the  plica  hypogastrica  (plica 
umbilicalis  lateralift).  Between  the  rectum  and  bladder  it  forms  a  pouch,  the 
recto-vesical  pouch  (excavatio  rectovesicalis) ,  bounded  on  the  sides  by  two  cres- 
centic  or  semilunar  folds  {'plicae  rectovesicales) ,  which  pass  from  the  posterior 
surface  of  the  bladder  to  the  sides  of  the  rectum;  the  bottom  of  this  pouch  is 
about  on  a  level  with  the  middle  of  the  vesiculae  seminales — i.  e.,  three  inches  or 
so  from  the  orifice  of  the  anus.  When  the  bladder  is  distended  the  peritoneum 
is  carried  up  with  the  expanded  viscus,  so  that  a  considerable  part  of  the  anterior 
surface  of  the  latter  lies  directly  against  the  abdominal  wall  without  the  inter- 
vention of  the  peritoneal  membrane.  When  the  bladder  is  empty  the  peri- 
toneum forms  a  transverse  fold  over  its  upper  surface  (plica  vesicalis  transversa) . 

In  the  female  the  peritoneum  is  reflected  from  the  rectum  on  to  the  upper  part 
of  the  posterior  vaginal  wall,  forming  the  recto-vaginal  pouch  or  pouch  of  Douglas 
(excavatio  rectouterina)  (Fig.  853).  In  the  pouch  of  Douglas  are  two  folds  of  peri- 
toneum (plica  rectouterinae) ,  which  begin  at  the  posterior  surface  of  the  cervix, 
extend  back  to  the  sides  of  the  rectum,  and  bound  above  the  deepest  portion  of  the 
pouch.  The  pouch  is  then  carried  over  the  posterior  aspect  and  fundus  of  the  uterus 
on  to  its  anterior  surface,  which  it  covers  as  far  as  the  junction  of  the  body  and 
cervix  uteri,  forming  here  a  second  but  shallower  depression,  the  utero-vesical 
pouch  (excavatio  vesicouterina) .  It  is  also  reflected  from  the  sides  of  the  uterus  to 
the  lateral  wall  of  the  pelvis  on  each  side  as  an  expanded  fold,  the  broad  ligament  of 
the  uterus  (ligamenum  latum  uteri),  in  the  free  margin  of  each  broad  ligament  can 
be  felt  a  thickened  cord-like  structure,  the  Fallopian  tube  (tuba  uterina  [Fallopii]). 

When  the  peritoneum  lining  the  anterior  abdominal  wall  is  examined  from 
behind,  it  is  noticed  that  certain  structures  which  lie  in  front  of  it  form  five  peri- 
toneal ridges  (Fig.  852).  The  structure  in  the  middle  line  is  the  urachus,  which  is 
the  remains  of  the  foetal  allantois.  In  the  adult  it  is  a  fibrous  cord  which  passes  from 
the  umbilicus  to  the  summit  of  the  bladder.  This  cord  is  slender  above,  but  broader 
below.  External  to  the  urachus  are  the  fibrous  cords  which  resulted  from  oblit- 
eration of  the  hypogastric  arteries  (arteriae  umbilicales).  These  cords  become  more 
slender  as  they  ascend  toward  the  sides  of  the  urachus  and  pass  to  the  umbilicus. 
More  external  still  are  the  folds  formed  by  the  deep  epigastric  arteries.  The  fold 
over  each  epigastric  artery  is  the  plica  epigastrica;  the  fold  over  each  obliterated 
hypogastric  artery  is  the  plica  umbilicalis  lateralis;  the  fold  over  the  obliterated 
urachus  is  the  plica  umbilicalis  media. 

The  five  peritoneal  ridges  formed  by  the  above-named  structures  create  three 
peritoneal  fossae  on  each  side,  called  the  inguinal  fossae  or  pouches  (fovea  inguinales) . 
The  external  inguinal  fossa  (fovea  inguinalis  lateralis)  is  external  to  the  deep  epi- 
gastric artery  and  corresponds  to  the  internal  abdominal  ring.  There  is  a  funnel- 
shaped  depression  in  its  floor  marking  the  point  at  which  the  inguinal  process 
passed  down.  This  depression,  if  marked,  predisposes  to  oblique  inguinal  hernia. 
The  middle  inguinal  fossa  (fovea  inguinalis  medialis)  is  placed  between  the  deep 
epigastric  arteries  and  the  obliterated  hypogastric  vessels.  The  internal  inguinal 
fossa  or  the  supravesical  fossa  (fovea  supravesicalis)  is  between  the  obliterated 
hypogastric  artery  and  the  urachus.  Just  beneath  the  inner  termination  of  Pou- 
part's  ligament  there  is  another  fossa,  the  femoral  or  crural  fossa  (fovea  femoralis), 
which  corresponds  to  the  situation  of  the  femoral  ring.  The  obliterated  hypo- 
gastric artery  is  to  the  inner  side  of  this  fossa. 

On  following  the  parietal  peritoneum  upward  on  the  back  of  the  anterior 
abdominal  wall  it  is  seen  to  be  reflected  around  a  fibrous  band,  the  ligamentum 
teres  or  obliterated  umbilical  vein  (Figs.  855, 856,  and  857),  which  reaches  from  the 


THE  PEBITONEUM 


1249 


umbilicus  to  the  under  surface  of  the  liver.  Here  the  membrane  forms  a  somewhat 
triangular  fold ,  the  falciform  or  suspensory  ligament  of  the  liver  (ligamenhim  falciforme 
hepatis),  which  attaches  the  upper  and  anterior  surfaces  of  that  organ  to  the  Dia- 
phragm and  abdominal  wall.  With  the  exception  of  the  line  of  attachment  of  this 
ligament  the  peritoneum  covers  the  under  surface  of  the  anterior  part  of  the  Dia- 
phragm and  is  reflected  from  it  on  to  the  upper  surface  of  the  liver  as  the  anterior  or 
superior  layer  of  the  coronary  ligament  {ligamenhim  coronarium  hepatic  anterior). 
Covering  the  upper  and  anterior  surfaces  of  the  liver  it  is  reflected  around  its  sharp 
margin  on  to  its  under  surface  as  far  as  the  transverse  fissure,  where  it  is  continuous 


Plica  umhilicalis 
lateralis 


Plica  umhilicalis 
media 


Peritoneu 


Vas 
deferens 


Middle 
inguinal 
fossa 
Deep 
inguinal 
fossa 
Superior 
vesical 
artery 

Fig.  852. — Posterior  view  of  the  abdominal  wall  in  its  lower   half.     The  peritoneum  is  in  place  and  the 
various  cords  are  shining  through.     (Joessel.) 

with  the  anterior  layer  of  the  small  omentum  from  which  a  start  was  made  (Fig.  853) . 
The  posterior  layer  of  this  omentum  is  carried  backward  from  the  transverse  fissure 
over  the  under  surface  and  Spigelian  lobe  of  the  liver,  and  is  then  reflected,  as  the 
posterior  or  inferior  layer  of  the  coronary  ligament  (ligamentum  coronarium  hepatis 
posterior),  on  to  the  Diaphragm  and  is  prolonged  downward  over  the  pancreas  to 
become  continuous  with  the  ascending  layer  of  the  transverse  mesocolon  (Fig.  853). 
Between  the  two  layers  of  the  coronary  ligament  there  is  a  triangular  surface  of  the 
liver  which  is  devoid  of  peritoneum ;  it  is  named  the  bare  area  of  the  liver,  and  is 
attached  to  the  Diaphragm  by  connective  tissue.    If,  however,  the  two  layers  of  the 

79 


1250  THE    ORGANS   OF  DIGESTION 

coronary  ligaments  are  traced  toward  the  right  and  left  margins  of  the  liver,  they 
approach  each  other,  and,  ultimately  fusing,  they  form  the  right  and  left  lateral 
ligaments  of  the  liver  and  attach  its  right  and  left  lobes  respectively  to  the  Dia- 
phragm. 

If  the  small  omentum  is  followed  toward  the  right  side  it  is  seen  to  form  a 
distinct  free  edge  around  which  its  anterior  and  posterior  layers  are  continuous 
with  each  other  and  between  which  are  situated  the  portal  vein,  hepatic  artery,  and 
bile-duct.  If  the  finger  is  introduced  behind  this  free  edge,  it  passes  through  a 
somewhat  constricted  ring,  the  foramen  of  Winslow  {foramen  epiploicum  [Wins- 
lowi])  (Figs.  853,  855,  and  858).  This  is  the  communication  between  what  are 
termed  the  greater  and  lesser  sacs  of  the  peritoneum  and  has  the  following  bound- 
aries: in  front,  the  free  edge  of  the  gastro-hepatic  omentum.  This  free  edge  is 
called  the  ligamentum  hepatoduodenale.  The  gastro-hepatic  omentum  has  the 
portal  vein,  hepatic  artery,  and  bile-duct  between  its  two  layers  (Fig.  859) ;  behind 
the  foramen  of  Winslow  is  the  vena  cava  inferior;  above,  are  the  Spigelian  and 
caudate  lobes  of  the  liver;  below,  the  duodenum  and  the  hepatic  artery,  as  the  latter 
passes  forward  and  upward  from  the  coeliac  axis. 

The  lesser  peritoneal  cavity  or  the  lesser  sac  of  the  peritoneum  (bursa  omentalis) 
(Figs.  853,  855,  and  858),  therefore,  lies  behind  the  small  omentum  and  has  the 
following  dimensions:  above,  it  is  limited  by  the  portion  of  the  liver  w^hich  lies 
behind  the  transverse  fissure;  below,  it  extends  downward  into  the  great  omentum, 
reaching,  in  the  foetus,  as  far  as  its  free  edge  (Fig.  846) ;  in  the  adult,  however,  its 
vertical  extent  is  limited  by  adhesions  between  the  layers  of  the  omentum.  In  front, 
it  is  bounded  by  the  small  omentum,  stomach,  and  anterior  two  layers  of  the  great 
omentum;  behind,  by  the  two  posterior  layers  of  the  great  omentum,  the  transverse 
colon,  and  ascending  layer  of  the  transverse  mesocolon  which  passes  upward  in  front 
of  the  pancreas  as  far  as  the  posterior  surface  of  the  liver.  Laterally  the  lesser 
sac  reaches  from  the  foramen  of  Winslow  on  the  right  side  as  far  as  the  spleen  on 
the  left  (recessus  lienalis)  (Fig.  860),  where  it  is  limited  by  the  lieno-renal  liga- 
ment. The  extent  of  the  lesser  sac  and  its  relations  to  surrounding  parts  can  be 
definitely  made  out  by  tearing  through  the  small  omentum  and  inserting  the 
hand  through  the  opening  thus  made.  A  passage  (vestibulum  bursae  omentalis) 
leads  out  from  the  foramen  of  Winslow  over  the  head  of  the  pancreas  to  the  left  as 
far  as  the  median  vascular  gastro-pancreatic  fold  (plica  gastropancreatica)  (Fig.  858) . 
This  fold  carries  the  gastric  artery  and  the  coronary  vein.  From  the  vestibule 
there  is  a  narrow  and  upward  prolongation  behind  the  lesser  omentum  and  cau- 
date lobe  of  the  liver  and  in  front  of  the  lumbar  portion  of  the  Diaphragm. 
This  prolongation  is  the  superior  omental  recess  {recessus  superior  omentalis). 
The  chief  part  of  the  lesser  peritoneal  cavity  extends  downward  from  the  gastro- 
pancreatic  fold  and  is  called  the  inferior  omental  recess  {recessus  omentalis  infe- 
rior). The  constriction  which  separates  the  two  recesses  is  due  to  the  passage 
around  the  lesser  sac  and  to  the  front  of  the  gastric  and  hepatic  arteries.  "The 
former  winds  around  its  left  side,  the  latter  around  its  right,  and  each  raises  up  a 
fold  of  peritoneum  which  projects  strongly  into  the  sac  and  partially  divides  it 
into  two.  "I  A  small  projection  of  the  lesser  sac  passes  to  the  right  side  behind 
the  beginning  of  the  duodenum.  The  splenic  artery  in  its  course  to  the  spleen 
lies  back  of  the  posterior  layer  of  the  lesser  sac. 

It  should  be  stated  that  during  a  considerable  part  of  foetal  life  the  transverse 
colon  is  suspended  from  the  posterior  abdominal  wall  by  a  mesentery  of  its  own — 
the  two  posterior  layers  of  the  great  omentum  passing,  at  this  stage,  in  front  of  and 
above  the  colon  (Fig.  846).  This  condition  sometimes  persists  throughout  adult 
life,  but  as  a  rule  adhesion  occurs  between  the  mesentery  of  the  transverse  colon 

'  Prof.  Cunningham's  Text-book  of  Human  Anatomy. 


THE  PERITONEUM 


1251 


and  the  posterior  layer  of  the  great  omentum,  with  the  result  that  the  colon 
appears  to  receive  its  peritoneal  covering  by  the  splitting  of  the  two  posterior 
layers  of  the  latter  fold. 

In  addition  to  tracing  the  peritoneum  vertically,  it  is  necessary  to  trace  it  hori- 
zontally (Figs.  854,  855,  856,  and  857).  If  this  is  done  below  the  transverse  colon, 
the  circle  is  extremely  simple,  as  it  includes  only  the  greater  sac  of  the  peri- 
toneum (Fig.  854).  Above  the  level  of  the  transverse  colon  the  arrangement  is 
more  complicated,  on  account  of  the  existence  of  the  two  sacs.  • 

Starting  from  the  linea  alba,  below  the  level  of  the  transverse  colon,  and  tracing 
the  continuity  in  a  horizontal  direction  to  the  right,  the  peritoneum  covers  the 
internal  surface  of  the  abdominal  wall  almost  as  far  as  the  anterior  border  of 
the  Quadratus  lumborum  muscle;  it  encloses  the  caecum,  and  is  reflected  over  the 


LESSER 
OMENTUM 


STOMACH 

TRANSVERSE 

MESOCOLON 

GREAT 

OMENTUM 


SMALL 
INTESTINE 


SMALL  SAC 

FORAMEN   OFWINSLOW, 
WITH   ARROW   PASSED 
THROUGH   IT 


PANCREAS 

THIRD  PART  OF 
DUODENUM 
TRANSVERSE 
COLON 


MESENTERY 


POUCH  OF 
DOUGLAS 


Fig.  853. — Diagrammatic  mesial  section  of  the  female  body,  to  show  the  peritoneum  on  vertical  tracing.  The 
great  sac  of  the  peritoneum  is  black  and  is  rejjresented  as  being  much  larger  than  in  nature;  the  small  sac  is  very 
darkly  shaded;  the  peritoneum  on  section  is  shown  as  a  white  Une,  and  a  white  arrow  is  passed  through  the  fora- 
men of  Winslow  from  the  great  into  the  small  sac.      (Cunningham.) 

sides  and  anterior  surface  of  the  ascending  colon,  fixing  it  to  the  abdominal  wall, 
from  which  it  can  be  traced  over  the  kidney  to  the  front  of  the  bodies  of  the  ver- 
tebrae. It  then  passes  along  the  mesenteric  vessels  to  invest  the  small  intestine, 
and  back  again  to  the  spine,  forming  the  mesentery,  between  the  layers  of  which 
are  contained  the  mesenteric  blood-vessels,  nerves,  lacteals,  and  glands.  Lastly, 
it  passes  over  the  left  kidney  to  the  sides  and  anterior  surface  of  the  descending 
colon,  and,  reaching  the  abdominal  wall,  is  continued  along  it  to  the  middle  line 
of  the  abdomen. 

Above  the  transverse  colon  (Fig.  855)  the  peritoneum  can  be  traced,  forming 
the  greater  and  lesser  cavities,  and  their  communication  through  the  foramen  of 
Winslow  can  be  demonstrated.  Commencing  in  the  middle  line  of  the  abdomen, 
the  membrane  may  be  traced  lining  its  anterior  wall,  and  sending  a  process  back- 


1252 


THE   ORGANS    OF  DIGESTION 


ward  to  encircle  the  obliterated  umbilical  vein  (the  round  ligament  of  the  liver), 
forming  the  falciform  or  longitudinal  ligament  of  the  liver.    Continuing  its  course 


Sfcfrntrnj   Aorta 


Small      Lymphatic    Vena  cava   Ascending 
intestine        node  inferior  colon 


Peritoneum 


Mesocolon 
{imperfect) 


Psoas 


Right 
kidney 


Left  kidney 


Fig.  854. — Peritoneal  reflection  in  a  transverse  section  of  a  lumbar  region  below  the  transverse  colon. 
Seen  from  above.     Schematic.     (Tillaux.) 

to  the  right,  it  is  reflected  over  the  front  of  the  upper  part  of  the  right  kidney, 
across  the  vena  cava  inferior  and  aorta,  and  over  the  left  kidney  to  the  hilum  of 


Vessels  in  lesser 
omentum 


Liq.  teres 


Aorta 


inferior 


Fio.  855. — Transverse  section  of  peritoneum  above  the  transverse  colon.     The  arrow  points  to  the  lesser 
sac  and  passes  through  the  foramen  of  Vi'inslow. 

the  spleen,  forming  the  anterior  layer  of  the  lieno-renal  ligament,  the  posterior 
layer  being  formed  by  the  termination  of  the  cul-de-sac  of  the  greater  cavity 


THE   PERITONEUM 


1253 


between  the  kidney  and  spleen.    From  the  hilum  of  the  spleen  it  is  reflected  to  the 
stomach,  forming  the  posterior  layer  of  the  gastro -splenic  omentum  (ligamentum 


lAg.  teres 


Vensrls  in  tesser 
omentum 


Fig.  856. — Horizontal  section  through  the  abdomen  at  the  level  of  the  foramen  of  Winslow. 
(Modified  from  Godlee.) 

gastrolienale) .    It  covers  the  posterior  surface  of  the  stomach,  and  from  its  lesser 
curvature  it  passes  around  the  portal  vein,  hepatic  artery,  and  bile-duct,  and  back 


Lesser  omentnm. 


ROUND    LIGAMENT    OF    LIVER. 


Hepatic  artery,  portal 
I  vein,  and  hepatic  duct. 


Gastro-splenic 
omentum 


LiENO-RENAL  LIGAMENT.     AMominnl  aorto  Vena  cava. 

Fig.  857. — Transverse  section  of  peritoneum. 

again  to  the  stomach,  as  the  lesser  omentum,  and  thus  it  forms  the  anterior  boun- 
dary of  the  foramen  of  Winslow.     It  now  covers  the  front  of  the  stomach,  and 


1254 


THE    ORGANS    OF  DIGESTION 


upon  reaching  the  cardiac  extremity  it  passes  to  the  hilum  of  the  spleen,  form- 
ing the  anterior  layer  of  the  gastro-splenic  omentum.  From  the  hilum  of  the 
spleen  it  can  be  traced  over  the  surface  of  this  organ,  to  which  it  gives  a  serous 
covering;  it  is  then  reflected  from  the  posterior  border  of  the  hilum  on  to  the  left 
kidney,  forming  the  posterior  layer  of  the  lieno-renal  ligament. 

Numerous  folds,  formed  by  the  peritoneum,  extend  between  the  various  organs  or 
connect  them  to  the  parietes.  These  serve  to  hold  the  organs  in  position,  and  at  the 
same  time  enclose  the  vessels  and  nerves  proceeding  to  each  part.  Some  of  these 
folds  are  called  ligaments,  such  as  the  ligaments  of  the  liver  and  the  false  ligaments 
of  the  bladder.  Others,  which  connect  certain  parts  of  the  intestine  with  the 
abdominal  wall,  constitute  the  mesenteries;  and  lastly,  those  which  proceed  from 
the  stomach  to  certain  viscera  in  its  neighborhood  are  called  omenta. 


PapiU4iry  tiihercle 

Cut  edge  of  peritoneum 


Spleen  covered 
by  peritoneum 


Descending, 
duodenum 


Cut  edge  of  peritoneum 

Fig.  858. — Bursa  omentalis,  opened  from  the  front  by  an  incision  through  the  gastro-coHc  omentum.     A  probe 
passes  through  the  foramen  of  Winslow  and  rests  on  the  gastro-pancreatic  fold.     (Henle.) 

The  Ligaments  of  the  Peritoneum. — The  ligaments,  formed  by  folds  of  the  peri- 
toneum, include  those  of  the  Uver,  spleen,  bladder,  and  uterus.  They  will  be 
found  described  with  their  respective  organs. 

The  Omenta. — The  omenta  are:  the  lesser  omentum,  the  great  omentum,  and  the 
gastro-splenic  omentum. 

The  Lesser  or  Gastro-hepatic  Omentum  (omentum  minus)  (Figs.  853  and  858)  is  the 
duplicature  which  extends  between  the  transverse  fissure  of  the  liver  and  the  right 
side  of  the  abdominal  portion  of  the  oesophagus,  the  lesser  curvature  of  the  stomach, 
and  the  upper  portion  of  the  superior  surface  of  the  duodenum.  The  portion  going 
to  the  oesophagus  and  stomach  is  called  the  hepato-gastric  ligament  (ligamentum 
hepatogastricum).  The  division  of  the  ligament  which  goes  to  the  oesophagus  is 
strong  and  dense;  the  division  which  goes  to  the  lesser  curvature  of  the  stomach 
is  thin  and  relaxed.  The  portion  of  the  lesser  omentum  which  goes  to  the 
duodenum  is  continuous  with  the  first-named  portion.      It  is  called  the  hepato- 


THE  PERITONEUM 


1255 


duodenal  ligament  (ligamentum  hepatoduodenale) .  The  right  margin  of  this  liga- 
ment is  free  and  concave.  The  hepato-colic  ligament  {ligamentum  hepatocoli- 
cum)  is  not  invariably  present.    It  is  a  fold  of  the  hepato-duodenal  ligament  and 


HEPATIC 
DUCT 


ROUND  OMENTAL 

LIGAMENT      TUBEBOSITY   GASTRIC 

IMPRESSION 


POSTERIOR  LAYER 
OF  LESSER 
OMENTUM 

OESOPHAGUS 


CYSTIC  DUCT 


DUODENAL 
IMPRESSION' 

FREE  EDGE 
OF  LESSER 
OMENTUM 


PORTAL 
VEIN 


COMMON 
BILE-DUCT 


PANCREATIC   DUCT 


PYLORUS 

RIGHT  GASTRO- 
EPIPLOIC ARTERY 
SUPERIOR  PANCREATICO- 
DUODENAL ARTERY 


Fig.  859.- 


-Structure  between  the  layers  of  the  lesser  omentum.     The  liver  has  been  raised  up,  and  the 
anterior  layer  of  the  omentum  removed.     Semidiagrammatic.     (Cunningham.) 


runs  from  the  posterior  surface  of  the  gall-bladder  to  the  descending  portion  of 
the  duodenum  or  possibly  to  the  transverse  colon.  From  the  free  margin  of  the 
termination  of  the  hepato-duodenal  ligament  a  fold  often  passes  to  the  front 


RENAL  SURFACE 

POUCH  OF  GREATER  SAC 

— LlENO-RENAL  LIGAMENT 

PHRENIC  SURFACE 

GASTRO-SPLENIC 

OMENTUM 

POUCH  OF  GREATER  SAC 

GASTRIC  SURFACE 


Fig.  860.- 


-Horizontal  section  through  the  stomach,  pancreas,  spleen,  and  the  left  kidney  to  .show  peritoneal 
reflections  at  the  hilum  of  the  spleen.     (G.  S.  H.) 


of  the  right  kidney.  It  is  known  as  the  duodeno-renal  ligament  (ligamentum 
duodenorenale) .  The  lesser  omentum  is  extremely  thin,  and  consists  of  two  layers 
of  peritoneum;  that  is,  the  two  layers   covering  respectively  the  anterior  and 


1256  THE    ORGANS    OF  DIGESTION 

posterior  surfaces  of  the  stomach.  The  posterior  layer  is  part  of  the  wall  of  the 
lesser  peritoneal  cavity;  the  anterior  layer,  of  the  greater  peritoneal  cavity.  When 
the  two  layers  reach  the  lesser  curvature  of  the  stomach,  they  join  together  and 
ascend  as  the  double  fold  to  the  transverse  fissure  of  the  liver;  to  the  left  of  this 
fissure  the  double  fold  is  attached  to  the  fissure  of  the  ductus  venosus  as  far  as 
the  Diaphragm,  where  the  two  layers  separate  to  embrace  the  end  of  the  oesoph- 
agus. At  the  right  border  the  lesser  omentum  is  free,  and  the  two  layers  of 
which  it  is  composed  are  continuous.  The  anterior  layer,  which  belongs  to  the 
greater  sac,  turns  around  the  hepatic  vessels  to  become  continuous  with  the  poste- 
rior layer  belonging  to  the  lesser  one.  They  here  form  a  free,  rounded  margin, 
which  contains  between  its  layers  the  hepatic  axtery,  the  common  bile-duct,  the 
portal  vein,  lymphatics,  and  the  hepatic  plexus  of  nerves  (Fig.  859) — all  these  struc- 
tures being  enclosed  in  loose  areolar  tissue,  called  Glisson's  capsule.  Between  the 
layers  where  they  are  attached  to  the  stomach  lie  the  gastric  artery  and  the  pyloric 
branch  of  the  hepatic  artery,  anastomosing  with  it.  From  the  left  side  of  the 
greater  curvature  of  the  stomach  a  fold  passes  to  the  gastric  surface  of  the  spleen, 
covers  the  spleen,  and  passes  from  the  renal  surface  of  the  spleen  around  the 
left  kidney  to  the  Diaphragm.^  The  fold  passing  to  the  spleen  is  known  as  the 
gastro-splenic  ligament  or  the  gastro-splenic  omentum  (ligamentum  gastrolienale) 
(Fig.  860).  The  portion  passing  to  the  Diaphragm  is  known  as  the  spleno- 
phrenic  ligament  {ligamentum  phrenicolienale) .  The  gastric  veins  or  vasa  brevia 
pass  from  the  left  side  of  the  greater  curvature  of  the  stomach  toward  the 
spleen  in  the  gastro-splenic  omentum. 

The  Great  or  Gastro-colic  Omentum  {omentum  majus)  (Figs.  853  and  861)  is  the 
largest  peritoneal  fold.  It  consists  of  four  layers  of  peritoneum,  two  of  which 
descend  from  the  stomach,  one  from  its  anterior,  the  other  from  its  posterior 
surface,  and,  uniting  at  its  lower  border,  descend  in  front  of  the  small  intestines, 
sometimes  as  low  down  as  the  pelvis;  they  then  turn  upon  themselves,  and  ascend 
again  as  far  as  the  transverse  colon,  where  they  separate  and  enclose  that  part 
of  the  intestine.  These  separate  layers  may  be  easily  demonstrated  in  the  young 
subject,  but  in  the  adult  they  are  more  or  less  inseparably  blended.  At  the  free 
margins  the  two  outer  layers  and  the  two  inner  layers  become  continuous.  The 
left  border  of  the  great  omentum  is  continuous  with  the  gastro-splenic  omentum; 
its  right  border  extends  as  far  only  as  the  duodenum.  The  great  omentum  is 
usually  thin,  presents  a  cribriform  appearance,  and  always  contains  some  adipose 
tissue,  which  in  fat  subjects  accumulates  in  considerable  quantity.  Between  its 
two  anterior  layers  is  the  anastomosis  between  the  right  and  left  gastro-epiploic 
arteries.  In  opening  the  abdomen  the  great  omentum  is  rarely  found  spread  out 
evenly  over  the  intestines.  It  often  projects  between  intestinal  coils,  or  is  largely 
gathered  in  some  one  region,  or  is  pushed  in  front  of  the  stomach  by  distention 
of  the  colon. 

The  lower  portion  of  the  lesser  sac  of  the  peritoneum  continues  for  a  distance 
between  the  ascending  and  descending  layers  of  the  great  omentum  (Fig.  853). 
The  portion  of  the  lesser  peritoneal  cavity  within  the  great  omentum  is  more  or 
less  obliterated  in  the  adult  by  adhesion  between  its  opposing  layers.  At  birth 
the  omentum  is  very  short  and  barely  reaches  the  umbilicus.  In  adults  its  length 
varies  greatly.  In  some  individuals  it  is  very  short;  in  others  it  passes  into  the 
pelvis.  Mr.  Lockwood  points  out  that  in  persons  under  forty-five  years  of  age 
the  omentum  can  rarely  be  pulled  down  below  the  level  of  the  pubic  spine;  in 
older  persons  it  generally  can. 

The  Gastro-splenic  Omentum  is  the  fold  which  connects  the  margins  of  the 
hilum  of  the  spleen  to  the  cul-de-sac  of  the  stomach,  being  continuous  by  its  lower 

'  Spalteholz,  Hand  Atlas  of  Human  Anatomy.     Translated  and  edited  by  Prof.  Lewellys  F.  Barker. 


THE   PERITONEUM 


1257 


border  with  the  great  omentum.  It  was  described  as  the  gastro-splenic  liga- 
ment (Fig.  860). 

The  Mesenteries. — The  mesenteries  are:  the  mesentery  proper,  the  transverse 
mesocolon,  the  sigmoid  mesocolon,  the  mesorectum  (p.  1259),  and  the  mesentery  of 
the  vermiform  appendix.  In  addition  to  these  there  are  sometimes  present  an 
ascending  and  a  descending  mesocolon. 

The  Mesentery  (mesenterium)  (/.tiaoii  ivvspou)  (Figs.  853,  862,  and  863),  so  called 
from  being  connected  to  the  middle  of  the  cylinder  of  the  small  intestine,  is  the 
broad  fold  of  peritoneum  which  connects  the  convolutions  of  the  jejunum  and 
ileum  with  the  posterior  wall  of  the  abdomen.  It  consists  of  a  layer  of  connec- 
tive tissue,  each  side  of  which  is  covered  with  peritoneum.      In  the  connective 


Fig.  861. — The  great  omentum  as  seen  from  the  front.     (Testut.) 

tissue  there  are  fatty  masses.  Its  root  (radix  mesenterii),  the  part  connected  with 
the  vertebral  column,  is  narrow,  about  six  inches  in  length,  and  directed  obliquely 
from  the  left  side  of  the  second  lumbar  vertebra  to  the  right  sacro-iliac  symphysis 
(Fig.  863).  Its  intestinal  border  is  vastly  broader  (measures  about  twenty  feet); 
and  here  its  two  layers  separate  so  as  to  enclose  the  intestine,  and  form  its  peri- 
toneal coat.  Its  breadth,  between  its  vertebral  and  intestinal  border,  is  about 
eight  inches.  Its  upper  border  is  continuous  with  the  under  surface  of  the  trans- 
verse mesocolon;  its  lower  border,  with  the  peritoneum  covering  the  caecum  and 


1258 


THE    ORGANS   OF  DIGESTION 


ascending  colon.  The  origin  of  the  mesentery  above  is  just  beyond  the  termina- 
tion of  the  duodenum,  and  it  terminates  below  in  the  angle  formed  by  the  junction 
of  the  ileum  and  the  colon.  It  serves  to  retain  the  small  intestines  in  their  position, 
and  contains  between  its  layers  the  mesenteric  vessels  and  nerves,  the  lymphatic 
vessels  and  mesenteric  glands.  These  glands  number  from  50  to  150.  Occa- 
sionally congenital  mesenteric  openings  exist.  In  stout  individuals  the  mesentery 
contains  much  fat.  If  there  is  much  fat  the  mesentery  is  not  translucent;  if 
there  is  little  fat  it  is  translucent.  It  may  be  actually  transparent  above  and 
translucent  or  opaque  below.  The  thinnest  part  of  the  mesentery  is  above.  As 
we  descend  it  becomes  thicker,  because  of  the  presence  of  fat,  fibrous  ligament, 
and  muscular  tissue.^ 


Mesentery 
{Itft  leaf) ' 


Root  of  mesen- 
tery 


Ileum 

Sigmoid  flexure 
Csscum- 


Duodenum 


Fig    862  —Mesentery 


Small  intestine  pushed  to  the  light  and  abrne 


CliUaux  ) 


In  most  cases  the  peritoneum  covers  only  the  front  and  sides  of  the  ascending 
and  descending  parts  of  the  colon.  Sometimes,  however,  these  are  surrounded  by 
the  serous  membrane  and  attached  to  the  posterior  abdominal  wall  by  an  ascending 
mesocolon  (mesocolon  ascendens)  and  a  descending  mesocolon  (mesocolon  descendens) 


'  Intestinal  Localization.    By  Geo.  H.  Monks,  Annals  of  Surgery,  October,  1903. 


THE  PERITONEUM 


1259 


respectively.  At  the  place  where  the  transverse  colon  turns  downward  to  form  the 
descending  colon,  a  fold  of  peritoneum  is  continued  to  the  under  surface  of  the 
Diaphragm  opposite  the  tenth  and  eleventh  ribs.  This  is  the  phreno-colic  ligament 
(ligamentum  phrenicocolicum) ;  it  passes  below  the  spleen,  and  serves  to  support 
this  organ,  and  therefore  it  has  received  the  secontl  name  of  sustentaculum  lienis. 
The  Transverse  Mesocolon  (mesocolon  transversum)  (Fig.  863)  is  a  broad  fold, 
which  connects  the  transverse  colon  to  the  posterior  wall  of  the  abdomen.  It  is 
formed  by  the  two  ascending  or  posterior  layers  of  the  great  omentum,  which,  after 


Right  lateral 
ligament  of  liver. 


Falciform  ligament 
of  liver. 


Left  lateral 
ligament  of  liver. 


Tena  cava  inferior 

(Esophagtu 
Right  phrenic  artery 

Coronary  artery  -< 

Hepatic  artery 

Splenic  artery 

Pancreas     — 

Inf.  pane. -duo.  artery 

Colica  medta 

Superior  mesenteric 

Duodenum  (3rd  part) 

Ao  ta 

Duodenum  (2nd  pat  t) 

Bight  and  left  kidneys 

Superior  mesenteric 

Aorta 


Colica  sinistra 

Colica  dextra. 

Vasa  intestini.  \ 

Sigmoid  artery. 
Sup.  hemorrhoidal  artery. 


Common  iliac  artery.'"    " 


Internal  iliac  artery.— — 

External  iliac  artery. " 

Epigastric  artery.  — 
Bladder.  " 


Peritoneum. 
Extraperitoneal  HsnM* 

^  Diaphragmatic  end  of 
(f astro- hepatic  omentum, 
istro'phrenic  ligament. 


G astro-splenic  omentum* 
Foramen  of  Winslow. 
Duodenum  (fst  part).. 


Costo-colic  ligament. 
Dot  between  two  anterior 
layers  of  great  omentum. 
Transverse  meso-colon. 

Bare  surface  for  descend^ 
ing  colon. 


The  two  layers  of  the 
mesentery  proper. 


Bare  surface  for  oACtnd* 
ing  colon. 


Sigmoid  meso-colon. 

Bare  surface  for  ccecum. 
.Veso-rectum. 

5  Bare  surface  for  2nd  part 
i    of  rectum. 
I  Left  lateral  false  liga- 
i    ment  of  bladder. 


Fio.  863. 


-Diagram  devised  by  Dr.  Del^pine  to  show  the  lines  along  which  the  peritoneum  leaves  the  wall 
of  the  abdomen  to  invest  the  viscera. 


separating  to  surround  the  transverse  colon,  join  behind  it,  and  are  continued 
backward  to  the  spine,  where  they  diverge  in  front  of  the  duodenum.  This  fold 
contains  between  its  layers  the  vessels  which  supply  the  transverse  colon. 

The  Sigmoid  Mesocolon  {mesocolon  sigmoideum)  (Fig.  863)  is  the  fold  of  peri- 
toneum which  retains  the  sigmoid  flexure  in  connection  with  the  left  iliac  fossa. 
This  portion  of  intestine  remains  always  freely  movable. 

The  Mesorectum  is  really  only  the  lower  portion  of  the  sigmoid  mesocolon.  It 
is  the  name  formerly  given  to  the  narrow  fold  which,  according  to  the  old  defini- 


1260 


THE    ORGANS    OF  DIGESTION 


tion  of  the  rectum,  connects  the  upper  part  of  the  rectum  with  the  front  of  the 
sacrum.     It  contains  the  superior  hemorrhoidal  vessels. 

The  Mesoappendix  or  Mesentery  of  the  Vermiform  Appendix  (mesenteriolum  pro- 
cessus vermiformis)  (Fig.867)is  a  double  fold  of  peritoneum  which  usually  completely 
surrounds  the  vermiform  appendix.  It  is  usually  described  as  a  triangular  fold, 
and  at  a  glance  it  appears  so,  but  Jonnesco  points  out  that  it  has  four  borders:  a 
superior  or  mesenteric  border;  a  right  or  csecal;  a  left  or  free,  and  an  inferior 
or  appsndicular.  One  of  the  borders  is  often  extremely  short.  The  upper  sur- 
face of  the  mesoappendix  is  continuous  with  the  lower  surface  of  the  mesentery 
proper  and  with  the  left  or  internal  fold  of  the  peritoneum  covering  the  caecum. 
The  lower  surface  of  the  mesoappendix  is  continuous  with  the  right  or  external 
fold  of  peritoneum  covering  the  caecum.  As  a  rule,  the  entire  appendix  is  covered 
with  peritoneum;  sometimes  a  portion  of  the  base  is  uncovered,  and  this  portion  of 
the  diverticulum  is  then  extraperitoneal.  The  tip  is  never  extraperitoneal.  The 
mesoappendix  may  be  attached  to  the  entire  length  of  the  appendix,  but,  as  a 
rule,  the  tip  is  free.  In  fact,  one-third,  one-half,  or  two-thirds  may  be  free  and 
occasionally  the  mesoappendix  is  a  mere  vestige.  Between  the  two  peritoneal 
layers  of  the  mesoappendix  there  is  connective  tissue,  and  often  fat.  In  the 
connective  tissue  are  the  appendicular  blood-vessels,  lymph-vessels,  and  nerves. 

The  Appendices  Epiploicae  are  small  pouches  of  the  peritoneum  filled  with  fat 
and  situated  along  the  colon  and  upper  part  of  the  rectum.  They  are  chiefly 
appended  to  the  transverse  colon. 


INFERIOR 

MESENTERIC 

VEIN 


SUPERIOR 
DUODENAL 
FOLD 


SUPERIOR 
DUODENAL 
FOLD 


INFERIOR 

DUODENAL 

FOLD 

INFERIOR 

DUODENAL 

FOLD 

ARTERIA 

COLICA 

SINESTRA 


Fig.  864. — Superior  and  inferior  duodenal  fossa.     (Poirier  and  Charpy.; 


Retro-peritoneal  Fossae.— In  certain  parts  of  the  abdominal  cavity  there  are 
recesses  of  peritoneum  forming  culs-de-sac  or  pouches,  which  are  of  surgical  inter- 
est in  connection  with  the  possibility  of  the  occurrence  of  retro-peritoneal  hernia. 
One  of  these,  which  was  previously  described,  is  the  lesser  sac  of  the  peritoneum 
(Figs.  853  and  855),  which  may  be  regarded  as  a  recess  of  peritoneum  through  the 
foramen  of  Winslow,  in  which  a  hernia  may  take  place,  but  there  are  several 
others,  of  smaller  size,  which  require  mention. 

These  recesses  of  fossae  may  be  divided  into  three  groups,  viz.:  (1)  the  duodenal 
fossae;  (2)  pericaecal  fossae;  and  (3)  the  intersigmoid  fossa. 

1.  Duodenal  Folds  and  Fossae.— Moynihan  has  described  no  less  than  nine  fossae 
as  occurring  in  the  neighborhood  of  the  duodenum.  Three  of  these  are  fairly 
constant.  Five  of  the  fossae  are  here  considered,  (a)  The  inferior  duodenal 
fossa  or  fossa  of  Treitz  (Fig.  864)  is  the  most  constant  of  all  the  peritoneal  fossae 
in  this  region,  being  present  in  from  70  to  75  per  cent,  of  cases.     It  is  situated 


THE   PERITONEUM 


1261 


opposite  the  third  lumbar  vertebra  on  the  left  side  of  the  ascending  portion  of  the 
duodenum.  The  opening  into  the  fossa  is  directed  upward,  and  is  bounded  by  a 
thin,  sharp  fold  of  peritoneum  with  a  concave  free  upper  margin.  This  fold  of 
peritoneum  is  called  the  inferior  duodenal  fold  (plica  duodenomesocolica) .  The 
tip  of  the  index  finger  introduced  into  the  fossa  under  the  fold  passes  some  little 
distance  up  behind  the  ascending  or  fourth  portion  of  the  duodenum.  One  margin 
of  the  fold  is  attached  to  the  ascending  portion  of  the  duodenum;  another  margin 
is  attached  to  the  parietal  peritoneum.  (/>)  The  superior  duodenal  fossa  (Fig.  864) 
is  the  next  most  constant  pouch  or  recess,  being  present  in  from  40  to  50  per  cent, 
of  cases.  It  often  coexists  with  the  inferior  one,  and  its  orifice  looks  downward, 
in  the  opposite  direction  to  the  preceding  fossa.  It  lies  to  the  left  of  the  ascend- 
ing portion  of  the  duodenum.  It  is  bounded  in  front  by  the  superior  duodenal  fold 
(plica  duodenojejunalis),  which  is  triangular  and  has  a  free  semilunar  base;  to  the 


RIGHT  RETHO- 

OUODENAL 

WALL 

INFERIOR 

DUODENAL 

ANGLE 


INFERIOR 

MESENTERIC 

VEIN 

PARIETAL   FOLD 
OF  DUODENUM 


LEFT  COLIC 
ARTERY 


INFERIOR  MESEN- 
TERIC ARTERY 


^ 


Fig.  865. — Retro-duodenal  fossa.     (Poirier  and  Charpy.) 

right  it  is  blended  with  the  peritoneum  covering  the  ascending  duodenum,  and  to 
the  left  with  the  peritoneum  covering  the  perirenal  tissues.  The  fossa  is  bounded 
in  front  by  the  superior  duodenal  fold;  behind  by  the  second  lumbar  vertebra;  to 
the  right  by  the  duodenum.  Its  depth  is  2  cm.,  and  it  terminates  in  the  angle 
formed  by  the  left  renal  vein  crossing  the  aorta.  This  fossa  is  of  importance,  as 
it  is  in  relation  with  the  inferior  mesenteric  vein;  that  is  to  say,  the  vein  almost 
always  corresponds  to  the  line  of  union  of  the  superior  duodenal  fold  with  the 
posterior  parietal  peritoneum,  (c)  The  duodeno-jejunal  fossa  or  mesocolic  fossa 
(recessus  duodenojejunalis)  is  formed  where  the  duodeno-jejunal  angle  enters  the 
root  of  the  transverse  mesocolon.  There  are  two  forms:  (1)  a  single  fossa  and  (2) 
a  double  fossa.  It  can  be  seen  by  pulling  the  jejunum  downward  and  to  the  right, 
after  the  transverse  colon  has  been  pulled  upward.  It  will  appear  as  an  almost 
circular  opening,  looking  downward  and  to  the  right,  and  bounded  by  two  free 
borders  or  folds  of  peritoneum,  the  duodeno-mesocolic  ligaments.  The  opening 
admits  the  little  finger  into  the  fossa  to  the  depth  of  from  2  to  3  cm.     The  fossa 


1262 


THE   ORGANS    OF  DIGESTION 


is  bounded  above  by  the  pancreas,  to  the  right  by  the  aorta,  and  to  the  left  by  the 
kidney;  beneath  is  the  left  renal  vein.  The  fossa  exists  in  from  15  to  20  per 
cent,  of  cases,  and  has  never  yet  been  found  in  conjunction  with  any  other  form 
of  duodenal  fossa,  {d)  Paraduodenal  fossa  or  the  fossa  of  Landzert  {recessus  diio- 
denojejunalis)  is  most  distinct  in  the  infant,  and  is  to  the  left  of  the  ascending 
portion  of  the  duodenum.    The  fold  of  peritoneum  to  its  outer  side  and  above  is 


ANTERIOR 
ILCOOCCAL 


ANTERIOR 

ILEOCiECAL 

FOSSA 


INFERIOR 

ILEOCiECAL 

FOLD 


Fig.  866.— Anterior,  sometimes  called  superior,  ileo-csecal  fossa.     (Poirier  and  Charpy.) 

produced  by  the  inferior  mesenteric  vein.  Its  lower  limit  is  a  fold  called  the 
mesenterico-mesocolic  fold,  (e)  The  retroduodenal  fossa  (Fig.  865)  was  described 
in  1893  by  Jonnesco.  It  is  a  peritoneal  cul-de-sac,  sometimes  found  behind  the 
horizontal  and  ascending  portions  of  the  duodeimm. 

2.  Pericsecal  Folds  and  Fos'ae. — There  are  at  least  three  pouches  or  recesses  to  be 
found  in  the  neighborhood  of  the  caecum,  which  are  termed  pericsecal  fossae.     (1) 


I  LEO- APPENDICULAR 
FOSSA 


W"  MESENTERY 

APPENDICULAR 
ARTERY 

ILEO-APPENDICULAR 
ARTERY 


MESO-APPENDIX 


Fig.  867. — Ileo-appendicular  or  inferior  ileo-cfecal  fossa.  The  caecum  and  ascending  colon  have  been 
drawn  outward  and  downward,  the  ileum  upward  and  backward,  and  the  apoendix  downward  (Poirier 
and  Charpy.) 

The  ileo-colic  fossa  or  superior  ileo-csecal  (recessus  ileocaecalis  superior)  (Fig.  866) 
is  formed  by  a  fold  of  peritoneum,  the  ileo-colic  fold,  arching  over  a  branch  of 
the  ileo-colic  artery,  which  supplies  the  ileo-colic  junction,  and  appears  to  be  the 
direct  continuation  of  the  artery.  The  fossa  is  a  narrow  chink  situated  between 
the  ileo-colic  fold  in  front,  and  the  mesentery  of  the  small  intestine,  the  ileum, 


THE  PERITONEUM 


1263 


and  a  small  portion  of  the  caecum  behind.  (2)  The  ileo-csecal,  inferior  ileo-csecal 
or  ileo-appendicular  fossa  (recessus  ileocaecalis  inferior)  (Fig.  867)  is  situated  behind 
the  angle  of  junction  of  the  ileum  and  caecum.  It  is  formed  by  a  fold  of  peritoneum, 
the  ileo-caecal  fold  {plica  ileocaecalis),  which  Treves  called  the  "bloodless  fold." 
Tuffier  denies  its  non-vascularity,  and  Lockwood  and  RoUeston  state  that  it  con- 
tains fat,  muscular  fibres,  and  arteries  and  veins  derived  from  the  appendicular  ves- 
sels and  the  anterior  and  posterior  ileo-csecal  vessels.^  The  upper  border  of  the  fold 
is  attached  to  the  ileum,  opposite  its  mesenteric  attachment,  and  the  lower  border, 
passing  over  the  ileo-cfecal  junction,  joins  the  mesentery  of  the  appendix,  and 
sometimes  the  appendix  itself;  hence  this  fold  is  sometimes  called  the  ileo-appen- 
dicular fold.  Between  the  ileo-cfecal  fold  and  the  mesentery  of  the  vermiform 
appendix  is  the  ileo-caecal  fossa.  It  is  bounded  above  by  the  posterior  surface  of 
the  ileum  and  the  mesentery;  in  front  and  below  by  the  ileo-cfecal  fold,  and  behind 
by  the  upper  part  of  the  mesentery  of  the  appendix.  (3)  The  retro-caecal  or  retro-colic 


ILEO-APPENDICULAR 


ILEO-APPENDICULAR 
FOSSA 

MESO-APPENOIX 


NFERIOR 
CiECAL  FOLD 


RETRO-OECAL 
FOSSA 


Fig.  868. — The  retro-cscal  fossa.     The  ileum  and  cwcum  are  drawn  backward  and  upward.     (Souligoux.) 

fossae  {recessus  retrocae sails)  (Fig.  868)  are  situated  behind  the  caecum  and  ascend- 
ing colon.  There  may  be  no  fossa  present.  There  may  be  one  fossa;  there  are 
usually  two  (external  and  internal  retrocolic  fossae) ;  occasionally  there  are  more 
than  two.^  The  fossae  are  brought  into  view  by  raising  the  caecum.  According  to 
Berry,  one  or  other  of  the  fossa  is  present  in  30  per  cent,  of  cases.  Treves  thinks 
the  retrocolic  fossae  are  extremely  rare.  There  may  be  one  fossa  (20  per  cent,  of 
cases)  or  two  fossae  (10  per  cent,  of  cases).  If  there  is  but  one  fossa  it  is  the 
internal  that  exists  three  times  as  often  as  the  external.  The  retro-colic  space, 
if  present,  varies  nuich  in  size  and  extent.  In  some  cases  it  is  sufficiently  large 
to  admit  the  index  finger  and  extends  upward  behind  the  ascending  colon  in 
the  direction  of  the  kidney;  in  others  it  is  merely  a  shallow  depression.  The 
external  retro-colic  fossa  is  bounded  and  formed  by  two  folds:  one,  the  external 
parieto-colic  fold  or  the  superior  csecal  fold,  which  is  the  outer  layer  of  the  ascend- 
ing mesocolon,  and  is  attached  by  one  edge  to  the  abdominal  wall  from  the 
lower  border  of  the  kidney  to  the  iliac  fossa  and  by  the  other  to  the  postero- 


The  Ccecal  Folds  and  Fossae.      By  Richard  J.  k.  Berry. 


2  Ibid. 


1264  THE    ORGANS    OF   DIGESTION 

external  aspect  of  the  colon;  and  the  other,  the  internal  paxieto-colic  fold  or  inferior 
caecal  fold,  which  is  the  inner  layer  of  the  ascending  mesocolon.  The  internal 
retrocolic  fossa  is  bounded  externally  by  the  internal  parieto-colic  fold,  and  is 
bounded  internally  by  the  mesenterico-parietal  fold,  which  is  the  insertion  of  the 
mesentery  into  the  iliac  fossa. 

3.  The  Intersigmoid  Fossa  {recessus  intersigmoideus) . — The  intersigmoid  fossa 
is  constant  in  the  foetus  and  common  during  infancy,  but  disappears  in  a  large 
percentage  of  cases  as  age  advances.  Upon  drawing  the  sigmoid  flexure  upward, 
the  left  surface  of  the  sigmoid  mesocolon  is  exposed,  and  on  it  will  be  seen  a 
funnel-shaped  recess  of  the  peritoneum,  lying  on  the  external  iliac  vessels,  in  the 
interspace  between  the  Psoas  and  Iliacus  muscles.  This  is  the  orifice  leading  to 
the  fossa  intersigmoidea,  which  lies  behind  the  sigmoid  mesocolon,  and  in  front  of 
the  parietal  peritoneum.  This  fossa  is  produced  by  the  incomplete  fusion  in  the 
foetus  of  the  descending  mesocolon  with  the  parietal  peritoneum.  The  fossa  varies 
in  size;  in  some  instances  it  is  a  mere  dimple,  whereas  in  others  it  will  admit  the 
whole  of  the  index  finger. 

Any  of  these  fossae  may  be  the  site  of  a  retro -peritoneal  hernia.  The  pericecal 
fossae  are  of  especial  interest,  because  hernia  of  the  vermiform  appendix  frequently 
takes  place  into  one  of  them,  and  may  there  become  strangulated.  The  presence 
of  these  pouches  also  explains  the  course  which  pus  has  been  known  to  take  in 
cases  of  perforation  of  the  appendix,  where  it  travels  upward  behind  the  ascending 
colon  as  far  as  the  Diaphragm.^ 

Surgical  Anatomy. — Study  of  the  lymphatics  of  the  peritoneum  by  Byron  Robinson  and 
others  shows  that  absorption  takes  place  most  rapidly  from  the  region  of  the  Diaphragm,  less 
rapidly  but  still  very  actively  from  the  region  of  the  small  intestine,  slowly  from  the  pelvic 
region.  Clinically  we  know  that  pelvic  peritonitis  is  not  nearly  so  dangerous  as  peritonitis 
in  the  small  intestine  or  Diaphragm  areas,  and  that  peritonitis  in  the  region  of  the  Diaphragm 
is  the  most  fatal  form  of  the  infection.  After  abdominal  operations  in  infected  cases,  it  is 
well  to  elevate  the  head  of  the  bed  {Fowler's  position),  so  as  to  obtain  the  aid  of  gravity  in 
draining  septic  fluids  away  from  the  dangerous  region  and  toward  the  safer  region.^  In  areas 
in  which  absorption  is  rapid,  protective  exudation  is  not  apt  to  form.  In  areas  in  which 
absorption  is  slow,  inflammatory  exudation  is  apt  to  circumscribe  the  area  and  prevent  dift'u- 
sion.  After  an  operation  in  a  non-infected  case,  if  salt  solution  has  been  left  in  the  abdominal 
cavity  because  of  shock  or  hemorrhage,  raising  the  foot  of  the  bed  will  aid  rapid  absorption 
of  the  fluid  by  favoring  the  natural  current  toward  the  Diaphragm  and  hurrying  the  fluid  to  a 
region  in  which  absorption  is  rapid. 

The  great  omentum  stores  up  fat,  and,  being  movable,  it  is  able  to  pass  to  different  parts 
of  the  peritoneal  cavity.  Dr.  Byron  Robinson,  in  his  work  on  the  Peritoneum,  describes  its 
functions  as  follows:  ''The  omentum  is  the  great  protector  against  peritoneal  infectious 
invasions.  It  builds  barriers  of  exudates  to  check  infection.  It  is  like  a  man-of-war, 
ready  at  a  moment's  notice  to  move  to  invaded  parts.  It  circumscribes  abscesses;  it  repairs 
visceral  wounds,  and  prevents  adhesions  of  mobile  viscera  to  the  anterior  abdominal  wall. 
It  resists  infectious  invasions  by  typical  peritoneal  exudates,  and  not  by  succumbing  to  absorbed 
sepsis.    It  is  a  director  of  peritoneal  fluids,  a  peritoneal  drain." 

In  abdominal  wounds  the  omentum  often  protrudes:  This  structure  frequently  constitutes 
or  is  part  of  a  hernia,  and  is  almost  invariably  present  in  umbilical  hernia.  As  a  result  of 
inflammation,  it  may  become  adherent  to  adjacent  structures.  Adhesions  may  be  of  service  by 
matting  together  the  intestines  and  circumscribing  infections.  They  may  be  harmful  by 
constricting  the  bowels  and  producing  obstruction.  A  portion  of  the  omentum  may  become 
adherent  to  some  other  part  and  form  a  band,  and  under  this  band  the  gut  may  be  caught  and 
strangulated.  Omentum  may  adhere  to  and  plug  a  perforation  in  a  hollow  viscus,  and  the  sur- 
geon may  utilize  it  for  the  same  purpose,  or  to  cover  a  raw  surface  or  overlie  a  suture  line.  The 
omentum  may  be  in  the  surgeon's  way  while  operating.  If  it  is,  the  patient  is  placed  in  the 
Trendelenburg  position  (pelvis  elevated). 

Any  tear  or  opening  found  by  the  surgeon  in  the  great  omentum  must  be  closed  with  sutures, 
because  of  the  danger  that  intestine  might  enter  and  be  caught  in  such  an  opening.  A  tumor 
cut  off  from  its  proper  blood-supply,  for  instance,  an  ovarian  cyst  with  a  twisted  pedicle,  may 
continue  to  receive  nourishment  from  adherent  omentum,  and  gangrene  may  thus  be  prevented. 

'  On  the  anatomy  of  these  fossae,  see  the  Arris  and  Gale  Lectures  by  Moynihan,  1899. 
-  George  R.  Fowler,  in  Medical  Record,  April  14,  1900. 


THE  PERITONEUM 


1265 


The  lax  character  and  shifting  tendency  of  the  subserous  tissue  explains  the  occurrence  of 
ptosis  of  the  abdominal  viscera  and  kidneys. 

The  vast  number  of  nerves  in  the  peritoneum  accounts  for  the  profound  shock  which  follows 
a  wound,  attends  an  intraperitoneal  calamity,  or  which  develops  from  infection.  An  infective 
process  of  any  portion  of  the  peritoneum  produces  pain  and  reflex  symptoms  (vomiting, 
abdominal  rigidity,  intestinal  paresis,  etc.). 

The  parietal  peritoneum  is  very  sensitive  to  pain,  but  not  to  touch;  hence,  after  injecting  a 
local  anaesthetic  and  opening  the  abdomen,  a  fairly  satisfactory  exploration  can  be  made  with 
the  finger. 

The  intestine,  the  mesentery,  the  stomach,  the  anterior  margin  of  the  liver,  and  the  gall-bladder 
are  insensitive,  and  may  be  cut  or  even  burned  without  pain.' 

Viscera  which  obtain  their  innervation  purely  from  visceral  nerves  are  insensitive;  those  which 
receive  branches  from  somatic  nerves  are  sensitive  (Lennander). 

The  oblique  origin  of  the  mesentery  causes  this  structure  to  form  a  sort  of  shelf.  A  hemor- 
rhage or  extravasation  into  the  abdomen,  to  the  right  of  the  mesentery,  tends  to  flow  into  the 
right  iliac  fossa;  one  occurring  on  the  left  side  flows  into  the  pelvis.  Monks  points  out  that  in 
flushing  the  abdominal  cavity  the  tube  should  not  be  aimlessly  introduced,  but  should  utilize 
the  mesentery  on  each  side  of  an  intestinal  loop,  to  ''  conduct  the  tip  of  the  irrigating  tube  to  the 
bottom  of  the  two  fossae."^  Monks  also  shows  how  the  mesentery  can  be  utilized  to  determine 
the  direction  of  an  intestinal  loop: 

"Now,  let  us  suppose  that  the  surgeon  has  between  his  fingers  a  loop  of  bowel,  and  wishes 
to  determine  its  direction.  He  knows  that  one  side  of  the  loop  is  the  left  side  of  the  intestine, 
and  that  the  corresponding  side  of  the  mesentery,  if  closely  followed  down  to  the  mesenteric 
root,  will  conduct  him  into  the  left  fossa;  he  also  knows  that  the  other  side  of  the  bowel  is  its 
right  side,  and  that  the  mesentery  on  that  side  will  conduct  him  into  the  right  fossa.     Now, 


Fig.  869. — A  loop  of  intestine,  the  middle  of  which  is  exactly  three  feet  from  the  end  of  the  duodenum.  The 
gut  is  of  large  size.  The  mesenteric  loops  are  primary,  and  the  vasa  recta  large,  long,  and  regular  in  distribu- 
tion. The  translucent  spaces  (lunettes)  between  the  ves.sels  are  extensive.  Below,  the  mesentery  is  streaked 
with  fat.  The  veins,  which  had  a  distribution  similar  to  the  arteries,  are  for  simplicity  omitted  from  this  and 
from  the  subsequent  drawings.  (The  subject  from  which  the  specimen  was  taken  was  a  male  aged  forty  years, 
with  rather  less  than  the  usual  amount  of  fat.  The  entire  length  of  the  intestine  was  twenty-three  feet. 
(Monks.) 

if  his  finger  goes  into  the  great  fossa  on  the  left  side  of  the  abdomen,  after  having  closely  fol- 
lowed the  mesentery  down  to  its  root  and  arranged  his  loop  to  be  parallel  with  that  root,  he  then 
knows  that  the  left  and  right  sides  of  the  intestine  face  to  the  left  and  right  sides  of  the  abdomen 
respectively,  and  that  the  end  of  the  loop  which  points  downward  is  the  end  nearest  the  ileo- 
csecal  valve.  He  can  determine  the  direction  of  the  gut  in  a  similar  way  in  case  his  finger  enters 
the  right  fossa.  All  this  would  seem  very  simple  were  it  not  for  the  twists  in  mesentery  and 
intestine,  which  tend  to  mislead  one.  A  little  practice  will  usually  enable  one  to  recognize  a  twist 
in  the  mesentery.  This  should  be  untwisted  by  rotation  of  the  gut,  after  which  the  direction  is 
determined  by  another  palpation  of  the  mesenteric  root."^ 


'  Dr.  K.  E  L.  Lennander,  in  Mittheilungen  aus  dem  Grenzgebrieten  der  Medecin  und  Chirurgie,  1902,  Band  x. 
Heft  1.  2. 

2  Intestinal  Localization,  by  George  H.  Monks,  Annals  of  Surgery,  October  1903. 
^  Annals  of  Surgery,  October,  1903. 

80 


1266 


THE    ORGANS   OF  DIGESTION 


The  studies  made  of  the  arrangement  and  variations  of  the  loops  of  the  mesenteric  vessels  by 
Dr.  Thomas  Dwight'  have  been  utilized  and  expanded  by  Dr.  George  H.  Monks  in  laying  down 


Fig.  870. — A  loop  of  intestine  at  six  feet.  As  compared  with  Fig.  869  the  gut  is  somewhat  smaller.  The 
vascularity  of  the  intestine  and  mesentery  is  less.  Secondary  loops  are  a  prominent  feature.  The  vasa  recta 
are  smaller.  The  lunettes  are  also  present,  but  are  not  so  large  as  in  Fig.  869.  (The  subject  was  a  male  aged 
about  thirty-five  years,  with  an  average  amount  of  fat.  The  entire  length  of  the  intestine  was  twenty  feet. 
(Monks.) 

rules  for  the  determination  of  the  exact  portion  of  small  intestine  which  may  be  in  the  surgeon's 
hand.^     His  views  are  as  follows: 

"  General  Vascularity  of  the  Mesentery  near  the  Bowel. — Opposite  the  upper  part  of  the  bowel  the 
mesenteric  vessels  are  distinctly  larger  than  opposite  any  other  part  of  it.    These  vessels  grow 


Fig.  871. — A  loop  of  intestine  at  nine  feet.  The  secondary  loops  are  large;  the  vasa  recta  are  somewhat 
irregular  and  show  branches.  No  lunettes  are  present,  and  the  mesentery  is  streaked  with  fat,  and  is,  therefore, 
somewhat  opaque.     (The  specimen  was  taken  from  the  same  subject  which  furnished  Fig.  869.      (Monks.) 

smaller  and  smaller  as  we  pass  downward  until  the  lower  third  of  the  gut  is  reached,  where  they 
remain  about  the  saTne  size  as  far  as  the  ileo-csecal  valve.    The  arrangement  of  the  mesenteric 


'  Reports  of  the  Meeting  of  American  Anatomists,  1897. 


Annals  of  Surgery,  1903. 


THE  PERITONEUM 


1267 


vessels  has  some  features  which  intimately  concern  the  subject  in  hand,  and  which  I  shall  describe 
with  some  detail.  Diagrammatically  speaking,  the  main  branches  of  the  superior  mesenteric 
artery  unite  with  each  other  by  means  of  loops,  which  are  called  for  convenience  'primary  loops;' 
in  some  parts  of  the  tube,  '  secondary  loops,'  and  even,  occasionally,  '  tertiary  loops'  are  super- 


Fro.  872.— A  loop  of  intestine  at  twelve  feet.  The  vessels  are  smaller.  The  primary  loops  are  lost  in  the  f^f 
rrL^nerim'.^^^''  ^?"  *^'"J.'^''-^  loops  are  visible.  ^  The  va.sa  recta  are  shorte^.'^ScTrf  frregS  ar  and  branchi^' 
(Ihe  specimen  came  from  the  same  subject  which  furnished  Figs.  869  and  871.)        (Monks  )  orancning. 

imposed  upon  the.se.    From  the.se  loops  little  straight  vessels— the  vasa  recta  already  referred  to 
^vf^u  lu ^  T''  "R?."  ^^^""^  ^^""^  r^mxl^,  alternating,  as  a  rule,  as  to  the  side  of  the  intestine 

which  they  supply.    The  mesenteric  veins  are  arranged  in  a  manner  somewhat  similar  to  the 
arteries. 


Fig.  873.  — .\  loop  of  intestine  at  seventeen  feet.     The  mesentery  is  ooaaue    and  small  f  qK=  r^t  f„f  \. :„  i 

appear  along  the  mesenteric  border  of  the   gut.      The  vesWls  are  reoresPnteH  hV  ^t.^whof  v     .  §"*  ^? 

"  The  Loops  of  the  Mesenteric  Vessels  (Figs.  869,870,  871,  872,  and  873).— Opposite  the  upper 
part  of  the  bowel  there  are  only  primary  loops.  Occasionally  a  secondary  loop  appears  but  it 
IS  small  and  insignificant  as  compared  with  the  primary  loops,  which  are  large  and  quite  regular 
As  we  proceed  down  the  bowel  secondary  loops  becom'e  more  numerous,  larger,  and  approach 


1268  THE    ORGANS   OF  DIGESTION 

nearer  to  the  bowel  than  the  primary  loops  in  the  upper  part.  As  a  rule,  secondary  loops 
become  a  prominent  feature  at  about  the  fourth  foot.  As  we  continue  farther  downward,  the 
secondary  loops  (and,  possibly,  tertiary  loops)  become  still  more  numerous  and  the  primary 
loops  smaller,  the  loops  all  the  time  getting  nearer  and  nearer  to  the  gut.  Opposite  the  lower 
part  of  the  gut  the  loops  generally  lose  their  characteristic  appearance,  and  are  represented  by 
a  complicated  network. 

"  The  Vasa  Recta. — Opposite  the  upper  part  of  the  intestine  the  vasa  recta  are  from  three  to 
five  centimetres  long,  when  the  loop  of  small  intestine  to  which  they  run  is  lifted  up  so  as  to 
put  them  gently  on  the  stretch.  They  are  straight,  large,  and  regular,  and  rarely  give  off  branches 
in  the  mesentery.  In  the  lower  third  they  are  very  short,  being  generally  less  than  one  centimetre 
in  length.  Here  they  are  less  straight,  smaller,  less  regular,  and  have  frequent  branches  in  the 
mesentery." 


Fig.  874. — A  loop  of  intestine  at  twenty  feet.  The  gut  appears  to  be  thick  and  large.  The  mesentery  is 
quite  fat  and  opaque,  and  large  and  numerous  fat-tabs  are  present.  The  vessels,  which  are  complicated,  are 
seen  with  difficulty,  and  are  represented  by  mere  grooves  in  the  fat.  (The  subject  was  a  stout  woman,  and  the 
entire  length  of  the  gut  was  twenty-one  feet.)     (Monks.) 

The  translucency  of  the  mesentery  varies  greatly;  in  some  parts  it  may  be  almost  transparent, 
in  others  almost  or  quite  opaque.  Its  thinnest  part  is  above.  It  is  thickened  below  by  fat,  fibrous 
tissue,  and  muscular  tissue.  In  very  fat  subjects  it  may  be  impossible  to  see  the  vessels  (Monks). 
According  to  Monks,  if  a  loop  is  raised  and  looked  at  against  the  light  close  to  the  gut  ''  little 
transparent  spaces"  are  seen  between  the  vasa  recta,  and  even  in  the  thickest  mesentery;  some 
of  these  ''lunettes"  exist  along  the  upper  portion  of  the  intestine.  As  we  descend  in  our  exam- 
ination, they  grow  smaller  and  become  fatty,  and  disappear  about  the  eighth  foot  of  the  intes- 
tine.' The  same  author  shows  that  the  mesentery  of  the  lower  third  of  the  intestine,  except  in 
the  thinnest  individuals,  contains  little  collections  of  fat  on  the  border  of  the  mesentery,  which 
project  toward  the  bowel  and  may  even  extend  upon  it. 

THE  STOMACH  (VENTRICULUS)  (Figs.  861,  875,  876,  878,  879). 

The  stomach  is  the  principal  organ  of  digestion.  It  is  the  most  dilated  part  of 
the  aUmentary  canal,  and  is  situated  between  the  termination  of  the  oesophagus 
(cardia)  and  the  commencement  of  the  small  intestine.  Its  form  varies  because 
of  varied  conditions,  but,  as  a  rule,  it  is  somewhat  pyriform.  It  is  placed,  in 
part,  immediately  behind  the  anterior  wall  of  the  abdomen  and  beneath  the 
Diaphragm.  Viewing  the  stomach  from  in  front  it  appears  that  the  right  margin 
of  the  oesophagus  is  continued  downward  as  the  upper  two-thirds  of  the  lesser 
curvature  of  the  stomach,  the  remaining  third  of  this  border  bending  sharply 

'  Annals  of  Surgery,  October,  1903. 


THE  STOMACH  1269 

backward  and  to  the  right,  to  complete  the  smaller  curvature  (Fig.  875).  The 
greater  curvature  begins  at  the  left  border  of  the  termination  of  the  oesophagus  in 
a  somewhat  acute  angle;  it  then  passes  upward  and  to  the  left  to  the  under  surface 
of  the  Diaphragm,  with  which  it  lies  in  contact  for  some  distance,  and  then  sweeps 
downward  with  a  convexity  to  the  left,  and,  continued  across  the  middle  line  of  the 
body,  finally  turns  upward  and  backward,  to  terminate  at  the  commencement  of 
the  small  intestine.  It  will  thus  be  seen  that  the  stomach  may  be  divided  into  a 
fundus  (fundus  ventriculi)  and  a  middle  portion  or  body  (corpus  ventriculi).  The 
portion  of  the  body  adjacent  to  the  cardia  being  known  as  the  cardiac  portion  (pars 
cardiaca),  the  long  axis  of  which  is  directed  downward  with  a  slight  inclination 
forward  and  to  the  right;  and  the  portion  adjacent  to  the  pylorus  being  known 
as  the  pyloric  portion  (pars  pylorica),  the  long  axis  of  which  is  horizontal  with 
an  inclination  backward.  Of  the  two  openings,  the  cardiac  orifice,  by  which  it 
communicates  with  the  oesophagus,  is  situated  slightly  to  the  left  of  the  middle 
line  of  the  body  to  the  right  of  the  fundus,  or  dilated  upper  extremity  of  the 
stomach,  and  is  directed  downward ;  the  other, 

the  pyloric  orifice,  by  which  it  communicates  Fundus 

with  the  small  intestine,  is  on  a  lower  plane, 
close  to  the  right  of  the  mid-line,  and  looks      Cardiac  onfice^ 
directly  backward. 

Relations  of    the  Stomach. — The  stomach       Lesser  curvature^ 

lies  in  a  space  or  chamber  called  the  stomach 

chamber  (Fig.  861) .  When  distended  the  viscus 

completely  fills  the  space.    When  the  stomach 

is  empty  it  lies  upon  the  floor  of  the  chamber, 

and  the  portion  it  has  vacated  is  occupied  by       Antrum 

the  transverse  colon,  which  ascends  in  front  of       pylori 

the   stomach    and    finally  gets   above    it.       The  Fi«.  875.-Diagrammatic  outline  of  the 

anterior  wall  of  the  stomach  chamber  is  formed 

by  the  anterior  abdominal  wall.  The  roof  is  formed  by  the  under  surface  of  the 
Diaphragm  and  the  under  surface  of  the  left  lobe  of  the  liver.  The  floor  is  formed 
by  the  left  suprarenal  capsule  and  the  summit  of  the  left  kidney,  the  gastric  face 
of  the  spleen,  the  upper  surface  of  the  pancreas,  the  transverse  mesocolon,  and 
the  colon  .^ 

Surfaces. — The  stomach  has  two  surfaces,  called  anterior  and  posterior  surfaces, 
and  two  borders,  termed  the  greater  and  lesser  curvatures. 

In  regard  to  the  so-called  anterior  and  posterior  surfaces  of  the  stomach,  it 
must  be  borne  in  mind  that  these  names  are  not  strictly  correct,  as  the  anterior 
surface  has  a  certain  amount  of  inclination  upward  and  the  posterior  downward. 

The  Anterior,  Upper  or  Parietal  Surface  (paries  anterior). — The  anterior  surface 
is  directed  forward  and  to  the  right  side.  It  has  a  somewhat  flattened  appearance 
when  the  stomach  is  empty,  but  when  it  is  full  the  surface  becomes  convex.  It  is 
in  relation  with  the  Diaphragm;  the  thoracic  wall  formed  by  the  anterior  parts  of 
the  seventh,  eighth,  and  ninth  ribs  of  the  left  side;  the  left  lobe  of  the  liver;  and 
the  anterior  abdominal  wall.  Between  the  part  covered  by  the  liver  and  that 
covered  by  the  left  ribs  there  is  a  triangular  segment  of  the  anterior  wall  of  the 
stomach,  which  is  in  contact  with  the  abdominal  wall  and  is  the  only  part  of  the 
stomach  which  is  visible  when  the  abdominal  wall  is  removed  and  the  viscera 
allowed  to  remain  in  situ.  Its  area  is  about  40  sq.  cm.,  and  it  is  of  great  impor- 
tance to  the  surgeon,  as  the  stomach  can  readily  be  reached  in  this  situation. 
Occasionally  the  transverse  colon  may  be,  found  lying  in  front  of  the  lower  part 
of  the  anterior  surface  of  the  stomach.  The  whole  of  this  surface  of  the  stomach 
is  covered  by  peritoneum. 

'  Prof.  Birmingham  in  Prof.  Cunningham's  Text-book  of  Anatomy. 


1270  '^HE    OBGANS    OF  DIGESTION 

The  Posterior,  Lower  or  Visceral  Surface  {'paries  'posterior). — The  posterior  sur- 
face of  the  stomach  is  directed  backward  and  to  the  left.  It  is  in  relation  with 
the  Diaphragm,  the  gastric  surface  of  the  spleen,  the  left  suprarenal  capsule,  the 
upper  part  of  the  left  kidney,  the  anterior  surface  of  the  pancreas,  the  splenic 
flexure  of  the  colon,  and  the  ascending  layer  of  the  transverse  mesocolon.  These 
structures  form  a  shallow  concavity  or  bed,  on  which  this  surface  of  the  stomach 
rests.  The  transverse  mesocolon  intervenes  between  the  stomach  and  the  duodeno- 
jejunal junction  and  commencement  of  the  ileum.  Its  greater  curvature  is  in 
relation  with  the  transverse  colon  and  has  attached  to  it  the  anterior  two  layers 
of  the  great  omentum.  Almost  the  whole  of  this  surface  is  covered  with  peri- 
toneum, but  behind  the  cardiac  orifice  there  is  a  small  portion  of  the  stomach 
which  is  uncovered  by  peritoneum  and  is  in  contact  with  the  Diaphragm  and  fre- 
quently with  the  upper  portion  of  the  left  suprarenal  capsule. 

The  Lesser  Curvature  {curvatura  ventriculi  Tninor). — The  lesser  curvature  of  the 
stomach  extends  between  the  cardiac  and  pyloric  orifices  along  the  right  border 
of  the  organ.  It  descends  in  front  of  the  left  crus  of  the  Diaphragm,  along  the  left 
side  of  the  eleventh  and  twelfth  dorsal  vertebrae,  and  then  turning  to  the  right  it 
crosses  the  first  lumbar  vertebra  and  ascends  to  the  pylorus.  It  gives  attachment 
to  the  two  layers  of  the  gastro-hepatic  omentum,  between  which  blood-vessels  and 
lymphatics  pass  to  reach  the  organ. 

The  Greater  Curvature  {curvatura  ventriculi  major). — The  greater  curvature  of 
the  stomach  is  directed  to  the  left,  and  is  four  or  five  times  as  long  as  the  lesser 
curvature.  Starting  from  the  cardiac  orifice,  it  forms  an  arch  to  the  left  with  its 
convexity  upward,  the  highest  point  of  which  is  on  a  level  with  the  costal  cartilage 
of  the  sixth  rib  of  the  left  side.  It  then  passes  nearly  straight  downward,  with  a 
slight  convexity  to  the  left,  as  low  as  the  costal  cartilage  of  the  ninth  rib,  and  then 
turns  to  the  right  to  end  at  the  pylorus.  As  it  crosses  the  median  line  the  lowest 
edge  of  the  greater  curvature  is  about  two  fingers'  breadth  above  the  umbilicus. 
The  lower  part  of  the  greater  curvature  gives  attachment  to  the  two  anterior 
layers  of  the  great  omentum,  between  which  layers  vessels  and  lymphatics  pass 
to  the  organ. 

The  Gardia  (Fig.  876) . — ^The  cardia  is  the  point  at  which  the  oesophagus  enters 
the  stomach  wall.  The  opening  is  called  the  cardiac  orifice  or  the  oesophageal 
opening.     At  the  cardia  the  circular  muscular  fibres  constitute  a  sphincter. 

The  Cardiac  Orifice  (Fig.  876) . — The  cardiac  orifice  is  the  opening  by  which  the 
oesophagus  communicates  .with  the  stomach.  It  is  therefore  sometimes  termed 
the  oesophageal  opening.  It  is  the  most  fixed  part  of  the  stomach,  and  is  situated 
about  two  inches  below  the  highest  part  of  the  fundus  on  a  level  with  the  body 
of  the  tenth  or  eleventh  dorsal  vertebra  to  the  left  and  a  little  in  front  of  the  aorta. 
This  would  correspond  on  the  anterior  surface  of  the  body  to  the  articulation  of 
the  seventh  left  costal  cartilage  to  the  sternum.  It  is  placed  far  oif  from  the  surface 
and  is  at  least  four  inches  back  of  the  seventh  left  chondro-sternal  articulation. 

The  Pylorus  (Fig.  876). — The  pylorus  is  the  point  at  which  the  stomach  passes 
into  the  duodenum.  The  opening  of  communication  is  called  the  pyloric  orifice. 
At  the  pylorus  the  muscular  fibres  constitute  a  sphincter. 

The  Pyloric  Orifice  (Fig.  876) . — The  pyloric  orifice  communicates  with  the  duo- 
denum, the  aperture  being  guarded  by  a  valve  (Fig.  877).  Its  position  varies  with 
the  movements  of  the  stomach.  When  the  stomach  is  empty  the  pylorus  is  situ- 
ated just  to  the  right  of  the  median  line  of  the  body,  on  a  level  with  the  upper 
border  of  the  first  lumbar  vertebra.  On  the  anterior  surface  of  the  body  its  posi- 
tion would  be  indicated  by  a  point  one  inch  below  the  tip  of  the  ensiform  cartilage 
and  a  little  to  the  right.  As  the  stomach  becomes  distended  the  pylorus  moves  to 
the  right,  and  in  a  fully  distended  stomach  may  be  situated  two  or  three  inches 
to  the  right  of  the  median  line.     The  direction  of  the  pylorus  is  upward  and  to 


THE   STOMACH 


1271 


the  right,  which  position  prevents  "the  weight  of  the  gastric  contents  bearing 
directly  on  the  sphincter  apparatus."^  The  pylorus  is  on  a  somewhat  higher  level 
than  the  lowest  point  of  the  stomach.  Near  the  pylorus  the  stomach  frequently 
exhibits  a  slight  dilatation,  which  is  named  the  antrum  of  the  pylorus  {antrum 
pyloricum).  The  pylorus  is  indicated  by  a  constriction,  the  direction  of  which 
is  circular.  The  pylorus  lies  upon  the  neck  of  the  pancreas  behind.  Above  it 
and  in  front  of  it  is  the  liver. 

The  size  of  the  stomach  varies  considerably  in  different  subjects.  When  mod- 
erately distended  its  greatest  length,  from  the  top  of  the  fundus  to  the  lowest  part 
of  the  greater  curvature,  is  from  ten  to  twelve  inches  and  its  diameter  at  the 
widest  part  from  four  to  five  inches.  The  distance  between  the  two  orifices  is  three 
to  six  inches,  and  the  measurement  from  the  anterior  to  the  posterior  wall  three 
and  a  half  inches.  Its  weight,  according  to  Clendinning,  is  about  four  ounces  and 
a  half,  and  its  capacity  in  the  adult  male  is  five  to  eight  pints.  The  stomach  of  a 
newborn  child  holds  about  one  ounce. 


Cystic  duct. 


Fig.  876. — The  mucous  membrane  of  the  stomach  and  duodenum  with  the  bile-ducts. 

Alterations  in  Position. — There  is  no  organ  in  the  body  the  position  and  connections  of  which 
present  such  frequent  alterations  as  the  stomach.  When  empty,  it  lies  at  the  back  part  of  the 
abdomen,  some  distance  from  the  surface,  and  is  in  the  left  hypochondriac  region  and  the  left 
portion  of  the  epigastric  region.  Its  fundus  is  directed  upward  and  backward  toward  the  Dia- 
phragm. The  long  axis  of  the  viscus  is  nearly  horizontal.  Its  pyloric  end  is  directed  upward 
and  backward,  is  situated  close  to  or  very  slightly  to  the  right  of  the  middle  line,  covered  in  front 
by  the  left  lobe  of  the  liver,  and  being  on  a  level  with  the  first  lumbar  vertebra.  When  empty, 
the  stomach  assumes  a  more  or  less  cylindrical  form,  especially  noticeable  at  its  pyloric  end.  The 
entire  viscus  is  small  and  contracted,  and  the  pyloric  region  resembles  the  intestine.  When  the 
stomach  is  distended,  its  surfaces,  which  are  flattened  when  the  organ  is  empty,  become  convex 
and  the  shape  becomes  pyriform.    The  viscus  becomes  very  oblique  and  approaches  the  vertical, 

'  W.  J.  Mayo,  Medical  Record.  June  11,  1904. 


1272 


THE    ORGANS   OF    DIGESTION 


its  long  axis  being  downward,  forward,  and  to  the  right.  The  greater  curvature  is  elevated  and 
carried  forward,  so  that  the  anterior  surface  is  turned  more  or  less  upward  and  the  posterior 
surface  downward,  and  the  stomach  is  brought  well  against  the  anterior  wall  of  the  abdomen.  Its 
fundus  expands  and  rises  considerably  above  the  level  of  the  cardiac  orifice;  in  doing  this  the 
Diaphragm  is  forced  upward,  contracting  the  cavity  of  the  chest;  hence  the  dyspnoea  complained 
of,  from  inspiration  being  impeded.  The  apex  of  the  heart  is  also  tilted  upward;  hence  the 
oppression  in  this  region  and  the  palpitation  experienced  in  extreme  distention  of  the  stomach. 
The  left  lobe  of  the  liver  is  pushed  to  the  right  side.  When  the  stomach  becomes  distended 
the  change  in  the  position  of  the  pylorus  is  very  considerable;  it  is  shifted  to  the  right,  some 
two  or  three  inches  from  the  median  line,  and  lies  under  cover  of  the  liver,  near  the  neck  of  the 
gall-bladder.  In  consequence  of  the  distention  of  the  stomach  the  lesser  cul-de-sac  bulges  over 
the  pylorus,  concealing  it  from  view,  and  causing  it  to  undergo  a  rotation,  so  that  its  orifice  is 
directed  backward.  When  the  stomach  is  greatly  distended  its  lower  border  may  enter  the 
umbilical  and  the  left  lumbar  regions.  During  inspiration  the  stomach  is  displaced  downward 
by  the  descent  of  the  Diaphragm,  and  it  is  elevated  by  the  pressure  of  the  abdominal  muscles  dur- 
ing expiration.  Pressure  from  without,  as  from  tight  lacing,  pushes  the  stomach  down  toward  the 
pelvis.  In  fact,  in  the  female,  because  of  tight  lacing,  the  stomach  may  be  to  the  left  side  of  the 
vertebral  column  and  nearly  vertical  in  direction,  the  lower  portion  being  sharply  angled  upward 
toward  the  pylorus,  which  lies  underneath  the  liver.  Besides  the  angulation,  the  lower  end,  the 
stomach  may  have  a  median  constriction,  and  there  may  even  be  an  hour-glass  stomach.  The 
descent  of  the  stomach  from  tight  lacing  may  cause  the  pancreas  to  become  nearly  vertical.  In 
disease  the  position  and  connection  of  the  stomach  may  be  greatly  changed,  from  the  accumula- 
tion of  fluid  in  the  chest  or  abdomen,  or  from  alteration  in  size  of  any  of  the  surrounding  viscera. 
Variations  according  to  Age. — In  an  early  period  of  development  the  stomach  is  vertical,  and  in 
the  newborn  child  it  is  more  vertical  than  later  on  in  life,  as  owing  to  the  large  size  of  the  liver 
it  is  more  pushed  over  to  the  left  side  of  the  abdomen,  and  the  whole  of  the  anterior  surface  is 
covered  by  the  left  lobe  of  this  organ. 


Fig.  877. — Diafi:rammatic  view 
of  the  coats  of  the  stomach,  duo- 
denum, and  pylorus.  The  ridge  is 
the  pyloric  valve.  (Allan  Thom- 
son.) 


On  looking  into  the  pyloric  end  of  the  stomach,  the  mucous  membrane  is  found 
projecting  inward  in  the  form  of  a  circular  fold,  the  pyloric  valve  (Fig.  877),  leaving 

a  narrow  circular  aperture,  about  half  an  inch  in 
diameter,  by  which  the  stomach  communicates  with 
the  duodenum. 

The  Pyloric  Valve  (valvula  pylori)  (Fig.  877) . — The 
pyloric  valve  is  formed  by  a  reduplication  of  the  mucous 
membrane  of  the  stomach,containing  numerous  circular 
fibres,  which  are  aggregated  into  a  thick  circular  ring, 
the  pyloric  sphincter  (ni.  sphincter  pylori) ;  the  longitu- 
dinal fibres  and  serous  membrane  being  continued 
over  the  fold  without  assisting  in  its  formation  (Fig.  877) . 
The  pylorus  is  normally  kept  closed  by  the  action  of 
this  aggregation  of  circular  fibres  which  constitutes  the 
Sphincter  muscle.  During  the  early  stage  of  digestion 
it  remains  closed,  but  after  a  time  opens  now  and  then.  The  opening  becomes 
more  frequent  and  the  period  of  patency  is  prolonged  as  digestion  advances. 

The  diameter  of  the  pylorus  is  uncertain.  It  is  usually  said  to  be  half  an  inch. 
But  it  is  closed  when  the  pylorus  is  at  rest,  and  it  can  certainly  dilate  even  in 
a  child  to  at  least  an  inch  and  let  bodies  of  this  size  pass  through. 

The  Peritoneum. — The  great  omentum  comes  off  from  the  greater  curvature  of 
the  stomach  and  passes  to  the  transverse  colon.  The  lesser  omentum  comes  off 
from  the  lesser  curvature  and  passes  to  the  liver.  The  gastro -splenic  ligament  or 
omentum  passes  from  the  under  surface  of  the  stomach  just  below  the  greater 
curvature  to  the  spleen.  A  fold  of  peritoneum  passes  up  from  the  stomach  along 
the  left  side  of  the  oesophagus  to  the  Diaphragm.  This  is  the  gastro -phrenic 
ligament. 

Supports  of  the  Stomach. — The  stomach  lies  on  the  bed  of  the  stomach  cham- 
ber, which  was  described  on  p.  1269.  The  great  omentum  gives  no  support  to 
the  stomach,  neither  does  the  gastro-splenic  ligament,  because  of  the  movability 
of  the  spleen.     The  lesser  omentum  does  give  support  to  the  stomach  and  so  do 


THE   STOMACH 


1273 


the  gastro -phrenic  ligament  and  the  hepato -duodenal  ligament.  The  two  chief 
points  of  support  are  the  attachment  of  the  oesophagus  to  the  Diaphragm  and 
the  fixation  of  the  duodenum  to  the  front  of  the  vertebral  column. 

Structure. — The  wall  of  the  stomach  consists  of  four  coats:  serous,  muscular, 
areolar,  and  mucous,  together  with  vessels  and  nerves. 

The  Peritoneal  or  Serous  Coat  {tunica  serosa).— Th&  peritoneal  or  serous  coat 
covers  the  entire  surface  of  the  organ,  excepting  along  the  greater  and  lesser 
curvatures,  at  the  points  of  attachment  of  the  greater  and  lesser  omenta;  at 
each  curvature  the  two  layers  of  peritoneum  leave  a  small  triangular  space,  to 
which  the  peritoneum  is  not  attached,  although  it  is  attached  in  front  of  it  and 
back  of  it.  Along  these  spaces  the  nutrient  vessels  and  nerves  pass.  On  the 
posterior  surface  of  the  stomach,  close  to  the  cardiac  orifice  and  below  and  to 
the  left  of  it,  there  is  a  smaller  triangular  area  uncovered  by  peritoneum,  where 
the  organ  is  in  contact  with  the  under  surface  of  the  Diaphragm,  and  it  may  be 


Fig.  878. — The  superficial  muscular  layer  of  the  stomach,  viewed  from  above  and  in  front.     (Spalteholz.) 

with  the  left  suprarenal  body  and  the  summit  of  the  left  kidney.  When  the 
stomach  is  moderately  distended  this  uncovered  area  measures  about  one  and  a 
half  inches  from  above  downward,  and  about  two  inches  from  before  backward. 
At  the  left  angle  of  this  uncovered  area  the  insertion  of  the  great  omentum 
begins.    At  the  right  angle  the  gastric  artery  reaches  the  stomach. 

The  Muscular  Coat  {tunica  muscularis)  (Figs.  878  and  879). — The  muscular  coat 
is  situated  immediately  beneath  the  serous  covering,  to  which  it  is  closely  connected. 
It  consists  of  three  sets  of  fibres — longitudinal,  circular,  and  oblique. 

The  Longitudinal  Fibres  {stratum  longitudinale)  are  most  superficial;  they  are 
continuous  with  the  longitudinal  fibres  of  the  oesophagus,  radiating  in  a  stellate 


1274 


THE    ORGANS    OF  DIGESTION 


manner  from  the  cardiac  orifice.  They  are  most  distinct  along  the  curvatures, 
especially  the  lesser,  but  are  very  thinly  distributed  over  the  surfaces.  At  the 
pyloric  end  they  are  more  thickly  distributed,  and  continuous  with  the  longitudinal 
fibres  of  the  small  intestine.  The  bundles  of  longitudinal  muscle-fibre  on  the  upper 
and  lower  surfaces  of  the  pylorus  are  particularly  firm  and  distinct,  and  are  called 
the  pyloric  ligaments  (ligamenta  pylori). 

The  Circular  Fibres  (stratum  circulare)  form  a  uniform  layer  over  the  whole 
extent  of  the  stomach,  except  the  fundus,  beneath  the  longitudinal  fibres.  At  the 
pylorus  they  are  most  abundant,  and  are  aggregated  into  a  circular  ring  or  sphinc- 
ter (w.  sphincter  pylori),  which  projects  into  the  cavity,  and  forms,  with  the  fold 
of  mucous  membrane  covering  its  surface,  the  pyloric  valve  {valvula  pylori)  (Fig. 
877).    They  are  continuous  with  the  circular  fibres  of  the  oesophagus. 


Fig.  879.- — The  middle  and  deep  muscular  layer  of  the  stomach,  viewed  from  above  and  in  front.     (Spalteholz.) 


The  Oblique  Fibres  {fibrae  ohliquae)  arise  at  the  left  side  of  the  cardia  from  the 
circular  fibres  of  the  oesophagus.  The  fibres  pass  down  in  the  anterior  and  pos- 
terior walls.  Those  of  the  anterior  wall  are  parallel  to  the  lesser  curvature  and 
almost  reach  the  pylorus.  Those  of  the  posterior  wall  are  more  nearly  transverse 
to  the  long  axis  of  the  stomach  (Spalteholz).  These  fibres  gradually  assume  the 
direction  of  the  circular  fibres  and  terminate  in  them.  The  layer  of  oblique  fibres 
is  beneath  the  circular  layer.  Certain  oblique  muscular  fibres  encircle  the  fundus 
of  the  stomach  in  a  series  of  rings. 

The  Areolar  or  Submucous  Coat  {tela  submucosa). — The  areolar  or  submucous 
coat  consists  of  loose,  filamentous,  areolar  tissue,  connecting  the  mucous  and 
muscular  layers.  It  supports  the  blood-vessels  previous  to  their  distribution  to 
the  mucous  membrane;  hence  it  is  sometimes  called  the  vascular  coat. 


THE  STOMACH 


1275 


The  Mucous  Membrane  {tunica  mucosa)  (Figs.  880,  881,  and  882). — The 
mucous  membrane  is  thick;  its  surface  smooth,  soft,  and  velvety.  In  the  fresh 
state  it  is  of  a  pinkish  tinge  at  the  pyloric  end,  and  of  a  red  or  reddish-brown 


Gastric  Areas.  Rugce. 

i"iG.  880. — Mucous  membrane  of  the  stomach,  from  the  pars  pylorica,  viewed  from  the  surface.    X  5.  (Spalteholz.) 


color  over  the  rest  of  the  surface.  In  in- 
fancy it  is  of  a  brighter  hue,  the  vascular 
redness  being  more  marked.  It  is  thin  at 
the  cardiac  extremity,  but  thicker  toward 
the  pylorus.  During  the  contracted  state 
of  the  organ  it  is  thrown  into  numerous 
plaits  or  rugae  {'plicae  mucosae)  (Figs.  880 
and  882  A),  which  for  the  most  part  have  a 
longitudinal  direction,  and  are  most  marked 
toward  the  lesser  end  of  the  stomach  and 
along  the  greater  curvature,  and  which 
contain  also  submucous  tissue.  These 
folds  are  entirely  obliterated  when  the 
organ  becomes  distended.  A  constant  fold 
exists  at  the  pylorus  (Fig.  877).  It  is  called 
the  pyloric  valve,  and  is  produced  by  the 
presence  beneath  it  of  the  Sphincter  muscle. 
Besides  the  large  folds  or  rugae  and  the 
pyloric  valve,  there  are  numerous  small 
elevations  of  mucous  membrane  known  as 
gastric  areas  {areas  gastricae),  which  are 
partly  separated  from  each  other  by  furrows 
and  which  vary  greatly  in  shape  (Fig.  880) . 
According  to  Spalteholz,  each  one  of  these 
elevations  has  an  area  of  several  square 
millimetres. 


Ridges  between  the  alveoli. 
K 


Gastric  alveoli. 


Fig.  881. — Mucous  membrane  of  the  stomach, 
from  the  pars  pylorica,  viewed  from  the  surface.  X 16. 
(Spalteholz.) 


1276 


THE    ORGANS    OF  DIGESTION 


Structure  of  the  Mucous  Membrane. — When  examined  with  a  lens  the 
inner  surface  of  the  mucous  membrane  presents  a  pecuHar  honeycomb  appear- 


MAMMILUE    V.S 


MOUTHS  or  GASTRIC 

GLANDS,  WITH  GLAND 

TUBES  AT  BOTTOM 


DEPRESSION  BETWEEN 
TWO  MAMMILUE 


MOUTH  OF 
GASTRIC  GLAND 


Fig.  882. — The  mucous  membrane  of  the  stomach.  A,  natural  size;  B,  magnified  25  diameters.  In  ^  the 
rugae  and  the  mammillated  surface  are  shown.  In  B  the  gland  mouths  (foveolae  gastricae),  with  the  gland  tubes 
leading  from  some  of  them,  and  the  ridges  separating  the  mouths  (plica  villosae)  are  seen.     (Cunningham.) 


Fig.  883.— Pyloric  gland. 


Fig.  884. — Peptic  gastric  gland. 


ance,  from  being  covered  with  small  shallow  depressions  or  alveoli  {foveolae 
gastricae)  (Figs.  881  and  882,  B)  of  a  polygonal  or  hexagonal  form,  which  vary 


THE  STOMACH  1277 

from  -j^-Q  to  2-5T  of  an  inch  in  diameter,  and  are  separated  by  slightly  elevated 
ridges  {plicae  villosae).  The  ridges  are  most  distinct  at  the  pylorus.  These 
foveolae  are  within  the  areae  gastricae.  The  ridges  on  section  resemble  villi.  In 
the  bottom  of  the  alveola  are  seen  the  orifices  of  minute  tubes,  the  gastric  glands 
(Fig.  882  B),  which  are  placed  perpendicularly  side  by  side  throughout  the 
entire  substance  of  the  mucous  membrane.  The  surface  of  the  mucous  membrane 
of  the  stomach  is  covered  by  a  single  layer  of  columnar  epithelium;  it  lines  the 
alveoli,  and  also  for  a  certain  distance  the  mouths  of  the  gastric  glands.  This 
epithelium  commences  very  abruptly  at  the  cardiac  orifice,  where  the  cells  sud- 
denly change  in  character  from  the  stratified  epithelium  of  the  oesophagus.  The 
cells  are  elongated,  and  consist  of  two  parts,  the  inner  or  attached  portions 
being  granular,  and  the  outer  or  free  parts  being  clear  and  occupied  by  a  muco- 
albuminous  substance. 

The  Gastric  Glands. — ^The  gastric  glands  are  of  three  kinds:  the  true  gastric 
glands,  the  pyloric  glands,  and  the  cardiac  glands. 

The  True  Gastric  Glands  (Fig.  884)  are  called  also  the  oxyntic  glands,  the  fundus 
glands,  and  the  peptic  glands  (glandulae  gastricae  propriae).  They  are  distributed 
throughout  the  entire  fundus  and  body,  and  maybe  found  even  at  the  pylorus.  They 
are  tubular  in  character,  and  are  formed  of  a  delicate  basement-membrane,  lined 
with  epithelium.  The  basement-membrane  consists  of  flattened  transparent  endo- 
thelial cells,  with  processes  which  extend  between  and  support  the  epithelium.  Into 
the  crypt  of  a  true  gastric  gland  three  or  more  caecal  tubes,  branched  or  unbranched, 
empty.  The  duct,  however,  in  these  glands  is  shorter  than  in  the  other  variety, 
sometimes  not  amounting  to  more  than  one-sixth  of  the  whole  length  of  the  gland; 
it  is  lined  throughout  by  columnar  epithelium.  At  the  point  where  the  terminal 
tubes  open  into  the  duct,  and  which  is  termed  the  neck,  the  epithelium  alters,  and 
consists  of  short  columnar  or  polyhedral,  granular  cells,  which  almost  fill  the  tube, 
so  that  the  lumen  becomes  suddenly  constricted,  and  is  continued  down  as  a  very 
fine  channel.  They  are  known  as  the  chief  or  the  peptic  or  the  central  cells  of  the 
glands,  and  furnish  pepsin.  Between  these  cells  and  the  basement-membrane  are 
found  other  darker  granular-looking  cells,  studded  throughout  the  tubes  at  inter- 
vals, and  giving  it  a  beaded  or  varicose  appearance.  These  are  known  as  the 
parietal  or  oxyntic  cells.  Some  of  the  parietal  cells  empty  directly  into  the  lumen 
of  the  gland  by  secretory  capillaries;  others  empty  by  a  duct  which  divides  into 
secretory  capillaries.  The  parietal  cells  secrete  the  acid  of  the  gastric  juice. 
Between  the  glands  the  mucous  membrane  consists  of  a  connective-tissue  frame- 
work with  lymphoid  tissue.  In  places  this  latter  tissue,  especially  in  early  life,  is 
collected  into  little  masses,  which  to  a  certain  extent  resemble  the  solitary  glands 
of  the  intestine,  and  are  by  some  termed  the  lenticular  glands  of  the  stomach.  They 
are  not,  however,  so  distinctly  circumscribed  as  the  solitary  glands. 

The  Pyloric  Glands  {glandulae  pyloricae)  (Fig.  883)  are  the  branched  tubular 
glands,  and  secrete  mucus. 

They  are  placed  most  plentifully  about  the  pylorus,  but  between  the  fundus  and 
pylorus,  in  the  region  known  as  the  transitional  or  intermediate  zone,  both  true 
gastric  glands  and  pyloric  glands  are  found.  Each  pyloric  gland  consists  of  two 
or  three  short,  closed  tubes  opening  into  a  common  duct,  the  external  orifice  of 
which  is  situated  at  the  bottom  of  an  alveolus.  The  caecal  tubes  are  wavy,  and 
are  of  about  equal  length  with  the  duct.  The  tubes  and  duct  are  lined  through- 
out with  epithelium,  the  duct  being  lined  by  columnar  cells  continuous  with  the 
epithelium  lining  the  surface  of  the  mucous  membrane  of  the  stomach,  the  tubes 
with  shorter  and  more  cubical  cells,  which  are  finely  granular.  The  pyloric 
glands  branch  more  frequently,  are  more  curved  in  direction,  and  open  into 
deeper  foveolae  than  the  true  gastric  glands  (Szymonowicz).  They  contain  only 
chief  or  peptic  cells  and  do  not  possess  parietal  cells. 


1278 


THE    ORGANS    OF   DIGESTION 


PLEXUS 

BENEATH  THE 
EPITHELIUM 


CLANDULAR 
PLEXUS 


The  Cardiac  Glands  are  found  about  the  oesophageal  orifice.     They  resemble 

the  pyloric  glands. 

Beneath  the  mucous  membrane,  and  between  it  and  the  submucous  coat,  is  a 

thin  stratum  of  involuntary  muscular  fibre  {muscularis  mucosae),  which  in  some 

parts  consists  only  of  a  single  longitudinal  layer;  in  others,  of  two  layers,  an  inner 

circular,  and  an  outer  longitudinal. 

Vessels  and  Nerves, — The  arteries  supplying  the  stomach  are — the  gastric  or 

coronary,  the  pyloric  and  the  right  gastro -epiploic  branch  of  the  gastro-duodendal,  the 

left  gastro -epiploic  and  vasa  brevia  from 
the  splenic.  The  gastric  artery  passes  to  the 
lesser  curvature  just  below  the  cardia.  It 
gives  off  the  oesophageal  branch,  and  passes 
from  left  to  right  along  the  lesser  curva- 
ture of  the  stomach  beneath  the  perito- 
neimi  between  the  two  layers  of  the  lesser 
omentum  and  upon  the  wall  of  the  stomach. 
It  may  in  this  course  be  a  single  vessel,  or 
may  divide  into  two  branches,  which  run 
along  each  side  of  the  lesser  curvature  (Fig. 
886).  If  there  is  a  single  artery  it  gives  off 
six  or  seven  descending  branches  to  the  an- 
terior wall  and  about  the  same  number  to 

Fig.  SSS.-TerminationsTTthe  blood-vessels  in    the  pOStCHOr  Wall  of    the   stoiuach.       It  alsO 

andcharpy.r*'™^'"^"^"^^''^  ^*'°'"^*'^"    ^^'''"^''  g^^cs  branches  to  the  lesser  omentum.     If 

two  vascular  arches  form,  one  gives  branches 
to  the  anterior  wall  of  the  stomach,  the  other  to  the  posterior  wall,  and  both  to 
the  lesser  omentum.  The  termination  of  the  gastric  anastomoses  with  the 
pyloric  branch  or  two  rami  of  the  pyloric  branch  of  the  hepatic  artery.  From 
each  arch  six  or  seven  descending  branches  come  off  to  the  anterior  and  posterior 


ARTERIOLE 

PLEXUS  OF 

BLOODVESSELS 

IN  SUBMUCOUS 

TISSUE 


SPLENIC 
ARTERY 


GASTRO- DUODENAL 
ARTERY 


RIGHT  GASTRO- 
EPIPLOIC ARTERY 


LEFT  GASTRO- 
EPIPLOIC ARTERY 


Fig.  886. — The  arteries  of  the  anterior  surface  of  the  stomach.     (Poirier  and  Charpy.) 


walls  of  the  stomach.  The  gastro -duodenal  artery  is  given  off  by  the  hepatic. 
From  the  gastro-duodenal  comes  the  right  gastro-epiploic.  The  left  gastro- 
epiploic comes  from  the  splenic.  The  right  gastro-epiploic  artery  passes  from 
right  to  left   in   the   gastro-colic  omentum  below  the  greater  curvature  of  the 


THE  STOMACH  1279 

stomach.  The  left  gastro-epiploic  artery  passes  forward  in  the  gastro-splenic 
ligament  to  below  the  greater  curvature  of  the  stomach,  and  passes  from  left  to 
right  along  that  curvature  in  the  gastro-colic  omentum,  and  joins  the  right  gastro- 
epiploic artery.  The  gastro-epiploic  arteries  are  not  upon  but  are  distinctly 
below  the  stomach  wall.  From  them  numerous  gastric  branches  are  sent  to  the 
anterior  and  posterior  walls  of  the  stomach,  and  they  anastomose  with  branches 
of  the  gastric  and  pyloric.  Vasa  brevia,  four  or  five  in  number,  arise  from  the 
splenic,  pass  forward  in  the  gastro-splenic  ligament,  and  supply  the  fundus. 
The  arteries  of  the  stomach  lie  first  beneath  the  peritoneum,  but  soon  enter  the 
muscular  coat,  supply  it,  pierce  it,  ramify  in  the  submucous  coat,  and  are  finally 
distributed  to  the  mucous  membrane.  The  arrangement  of  the  vessels  in  the 
mucous  membrane  is  somewhat  peculiar  (Fig.  885).  The  arteries  break  up  at 
the  base  of  the  gastric  tubules  into  a  plexus  of  fine  capillaries  which  run  upward 
between  the  tubules,  anastomosing  with  each  other,  and  ending  in  a  plexus  of 
larger  capillaries,  which  surround  the  mouths  of  the  tubes  and  also  form  hexagonal 
meshes  around  the  alveoli. 

The  capillary  networks  about  the  glands  give  origin  to  the  veins.  The  various 
small  veins  unite  and  form  a  plexus  in  the  submucous  tissue  (Fig.  885).  From  this 
plexus  come  branches  which  pass  through  the  muscular  coat  and  terminate  in  the 
right  gastro-epiploic  branch  of  the  superior  mesenteric,  the  left  gastro-epiploic  branch 
of  the  splenic,  the  veins  to  the  splenic  which  correspond  to  the  vasa  brevia  arteries, 
and  the  gastric  or  coronary  branch  of  the  portal. 

The  lymphatics  (Figs.  507  and  508)  arise  in  the  mucous  membrane  and  terminate 
in  a  network  in  the  submucous  tissue.  From  this  network  trunks  arise  which 
perforate  the  muscular  coat  in  the  regions  of  the  curvatures  and  terminate  in  the 
sero-muscular  collecting  trunks.^ 

According  to  Cuneo,  there  are  three  groups  of  these  collectors.  Those  from  the 
lesser  curvature  pass  to  the  point  where  the  gastric  artery  reaches  the  stomach  and 
enter  the  glands  along  the  gastric  artery.  Those  from  the  greater  curvature  pass 
from  left  to  right  and  enter  the  sub-pyloric  glands.  Those  from  the  fundus  pass 
from  right  to  left  and  end  in  the  splenic  glands.  Cuneo  further  pointed  out  that 
the  region  drained  by  the  collectors  of  the  lesser  curvature  is  divided  from  the 
others  by  the  line  shown  in  Fig.  507.  This  division  exists  on  both  surfaces  of 
the  stomach.  The  limit  between  the  collectors  which  drain  into  the  splenic 
glands  and  those  which  drain  into  the  sub-pyloric  glands  is  also  shown  in 
Fig.  507.  Along  the  lesser  curvature  the  lymph-glands  are  few  in  number  and 
are  limited  to  the  pyloric  region,  and  the  lymph- vessels  are  placed  directly  upon 
the  stomach  wall.  The  lymph-glands  and  vessels  are  not  upon  but  are  distinctly 
below  the  greater  curvature. 

The  subserous  and  submucous  lymphatic  networks  of  the  stomach  communi- 
cate with  the  corresponding  networks  of  the  oesophagus,  but  in  all  probability  do 
not  communicate  with  the  networks  of  the  duodenum. 

The  nerves  of  the  stomach  come  from  the  right  and  left  pneumogastrics  and  from 
the  solar  plexus  of  the  sympathetic.  The  left  pneumogastric  passes  to  the  front 
of  the  stomach,  and  the  right  nerve  passes  to  the  back,  and  they  unite  with  the 
fibres  of  the  sympathetic.  The  fibres  thus  formed  are  mostly  non-meduUated. 
They  form  Auerbach's  plexus  in  the  muscular  coat  between  the  circular  and  lon- 
gitudinal fibres  and  Meissner's  plexus  in  the  submucous  coat,  the  latter  plexus 
being  formed  by  fibres  from  the  former.  Fibres  from  Meissner's  plexus  ramify 
in  the  submucous  coat  and  terminate  in  the  muscularis  mucosae  and  the  mucous 
membrane,  branches  passing  to  the  gastric  glands  and  to  just  beneath  the 
epithelium. 

*  The  Lymphatics.     By  Poirier.  Cuneo,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


1280  THE   ORGANS   OF  DIGESTION 

Movements  and  Innervation  of  the  Stomach. 

Movements. — It  has  apparently  been  demonstrated  that  the  stomach  "consists  of  two  parts 
physiologically  distinct."'  The  cardiac  portion  of  the  stomach  is  a  food  reservoir  in  which 
salivary  digestion  continues;  the  pyloric  portion  is  the  seat  of  active  digestion.  Cannon  affirms 
that  there  are  no  peristaltic  waves  in  the  cardiac  portion,  but  that  as  the  food  passes  from  the 
pyloric  portion  into  the  intestines,  tonic  contraction  of  the  muscles  of  the  fundus  squeezes  the 
contents  of  the  pyloric  portion.  Moritz,  Levan,  and  Cannon  assert  that  muscular  activity  is 
chiefly  manifested  in  the  pyloric  portion.  In  this  portion  during  digestion  there  is  a  succes- 
sion of  peristaltic  waves,  which  waves  in  the  human  being  pass  at  the  rate  of  three  per  minute 
(Moritz).  Cannon  points  out  that  the  efficiency  of  peristalsis  in  mixing  the  food  depends 
upon  the  contraction  of  the  pyloric  sphincter.  So  long  as  the  sphincter  holds,  each  constric- 
tion-ring coursing  from  the  middle  to  the  end  of  the  stomach  presses  the  food  into  a  blind  pouch; 
the  food,  unable  to  escape  through  the  pyloric  opening,  has  as  its  only  outlet  the  opening  in 
the  advancing  ring.  This  is  an  admirable  device  for  bringing  the  food  under  the  influence  of 
the  glandular  secretions  of  the  pyloric  region.  For,  as  a  constriction  occurs,  the  secreting  sur- 
face enclosed  by  the  narrowed  muscular  ring  is  pressed  close  around  the  food  within  the  ring. 
As  the  constriction  advances  it  continually  presses  inward  fresh  glandular  tissue,  and  further- 
more, as  the  constriction  advances,  a  thin  stream  of  food  is  continuously  forced  back  through 
the  ring  and  thus  past  the  mouths  of  the  glands.  The  old  view  that  the  pyloric  sphincter  only 
opens  after  several  hours'  continuance  of  the  process  of  digestion  and  that  then  the  stomach 
empties  at  once  is  incorrect.  It  is  emptied  in  small  amounts  which  escape  at  frequent  intervals 
because  of  the  intermittent  opening  of  the  pylorus.  When  the  pylorus  is  open  a  wave  of  peri- 
stalsis forces  some  of  the  material  from  the  stomach  into  the  duodenum  (Cannon). 

Cannon  is  of  the  opinion  that  the  pyloric  sphincter  is  caused  to  relax  by  the  presence  of  free 
hydrochloric  acid  in  the  pyloric  portion  of  the  stomach.  When  the  pylorus  is  open  acid  chyme 
passes  into  the  duodenum  and  acid  in  the  duodenum  causes  the  pylorus  to  close.  The  acid 
in  the  duodenum  causes  a  flow  of  alkaline  pancreatic  juice  and  the  acid  is  neutralized.  "As 
the  neutralizing  proceeds  the  stimulus  closing  the  pylorus  is  weakened  until  the  acid  in  the 
stomach  again  opens  the  sphincter."^ 

Innervation. — The  stomach,  as  previously  shown,  has  nervous  plexuses  in  its  walls  and  is 
connected  to  the  brain,  spinal  cord,  and  sympathetic  system.  It  is  probable  that  gastric  peri- 
stalsis is  due  to  a  local  reflex  from  Auerbach's  plexus  (Magnus),  the  local  reflex  being  inaugu- 
rated by  local  stimulation,  which  stimulation,  in  the  words  of  Bayliss  and  Starling,  "produces 
excitation  above  and  inhibition  below  the  excited  spot."*  Reversed  peristalsis  cannot  occur 
if  "the  reflex  mechanism  is  intact"  (Cannon).  Cannon  in  the  previously  quoted  article  states 
that  cutting  the  vagus  or  splanchnic  nerves  does  not  destroy  the  reflex  mechanism  of  the  pylorus, 
but,  nevertheless,  it  is  markedly  affected  by  the  central  nervous  system. 

Surface  Form  (see  p.  1271). — The  cardiac  orifice  corresponds  to  the  articulation  of  the 
seventh  left  costal  cartilage  with  the  sternum.  The  pyloric  orifice  of  the  empty  stomach  is  in 
a  vertical  line  drawn  from  the  right  border  of  the  sternum,  two  and  a  half  or  three  inches  below 
the  level  of  the  sterno-xiphoid  articulation.  According  to  Braune,  when  the  stomach  is  dis- 
tended, the  pylorus  moves  considerably  to  the  right,  as  much  sometimes  as  three  inches.  The 
fundus  of  the  stomach  reaches,  on  the  left  side,  as  high  as  the  level  of  the  sixth  costal  cartilage 
of  the  left  side,  being  a  little  below  and  behind  the  apex  of  the  heart.  The  portion  of  the  distended 
stomach  which  is  in  contact  with  the  abdominal  walls,  and  is  therefore  accessible  for  opening  in 
the  operations  of  gastrotomy  and  gastrostomy,  is  represented  by  a  triangular  space,  the  base  of 
which  is  formed  by  a  line  drawn  from  the  tip  of  the  tenth  costal  cartilage  on  the  left  side  to  the 
tip  of  the  ninth  costal  cartilage  on  the  right,  and  the  sides  by  two  lines  drawn  from  the  extremity 
of  the  eighth  costal  cartilage  on  the  left  side  to  the  ends  of  the  base  line. 

Surgical  Anatomy. — Operations  on  the  stomach  are  frequently  performed,  ulcers  are  excised, 
malignant  growths  are  removed  with  the  associated  lymphatic  involvement,  the  entire  stomach 
may  be  removed  for  cancer,  etc.  By  ''  gastrotomy"  is  meant  an  incision  into  the  stomach  for  the 
removal  of  a  foreign  body,  or  the  arrest  of  hemorrhage  or  for  exploration,  the  opening  being 
immediately  afterward  closed — in  contradistinction  to  " gastrostomy"  the  making  of  a  more  or 
less  permanent  fistulous  opening.  Gastrotomy  is  probably  best  performed  by  an  incision  in  the 
linea  alba,  especially  if  the  foreign  body  is  large.  The  cut  may  reach  from  the  ensiform  car- 
tilage to  the  umbilicus.  The  incision  may  be  made  over  the  body  itself,  where  this  can  be  felt, 
or  by  one  of  the  incisions  for  gastrostomy,  to  be  mentioned  shortly.  The  peritoneal  cavity 
is  opened,  and  the  point  at  which  the  stomach  is  to  be  incised  decided  upon.  This  portion  is 
then  brought  out  of  the  abdominal  wound  and  sponges  carefully  packed  around.  The  stomach 
is  now  opened  by  a  transverse  incision  and  the  foreign  body  extracted.  The  wound  in  the 
stomach  is  then  closed  by  Lembert  sutures — i.  e.,  by  sutures  passed  through  the  peritoneal, 

1  Walter  B.  Cannon,  Medical  News,  May  20,  1905,  2  Ibid.  *  Ibid. 


MOVEMENTS   AND   INNERVATION    OF    THE   STOMACH     1281 

muscular  and  submucous  coats  in  such  a  way  that  the  peritoneal  surfaces  on  each  side  of  the 
wound  are  brought  into  apposition.  Gastrostomy  was  formerly  done  in  two  stages  by  the  direct 
method.  The  first  stage  consisted  in  opening  the  abdomen,  drawing  up  the  stomach  into  the 
external  wound,  and  fixing  it  there;  and  the  second  stage,  performed  from  two  to  four  days 
afterward,  consisted  in  opening  the  stomach.  The  operation  is  now  done  by  a  valvular  method. 
The  following  plan  is  known  as  the  Ssabanejew-Frank  operation.  An  incision  is  commenced 
opposite  the  .eighth  intercostal  space,  two  inches  to  the  left  of  the  median  line,  and  carried 
downward  for  three  inches.  By  this  incision  the  fibres  of  the  Rectus  muscle  are  exposed  and 
these  are  separated  from  each  other  in  the  same  line.  The  posterior  layer  of  the  sheath,  the 
transversalis  fascia  and  the  peritoneum,  are  then  divided,  and  the  peritoneal  cavity  is  opened. 
Instead  of  the  above  incision,  the  curved  incision  of  Fenger  can  be  made  at  the  margin  of  the 
left  costal  cartilages.  The  anterior  wall  of  the  stomach  is  now  seized  and  drawn  out  of  the 
wound  and  a  silk  suture  passed  through  its  submucous,  muscular,  and  serous  coats  at  the  point 
selected  for  opening  the  viscus.  This  is  held  by  an  assistant  so  that  a  long  conical  divertic- 
ulum of  the  stomach  protrudes  from  the  external  wound,  and  the  parietal  peritoneum  and 
the  posterior  layer  of  the  sheath  of  the  rectus  are  sutured  to  the  base  of  the  cone.  A  second 
incision  is  made  through  the  skin,  over  the  margin  of  the  costal  cartilage,  above  and  a  little  to  the 
outer  side  of  the  first  incision.  If  Fenger's  incision  were  used,  the  second  incision  should  be 
above  the  margin  of  the  cartilages.  With  a  pair  of  dressing  forceps  a  track  is  made  under  the 
skin  through  the  subcutaneous  tissue  from  the  one  opening  to  the  other  and  the  diverticulum  of 
the  stomach  is  drawn  along  this  track  by  means  of  the  suture  inserted  into  it ;  so  that  its  apex 
appears  at  the  second  opening.  A  small  perforation  is  now  made  into  the  stomach  through 
this  protruding  apex  and  its  margin  carefully  and  accurately  sutured  to  the  margin  of  the 
external  wound.  The  remainder  of  this  incision  and  the  whole  of  the  first  incision  are  then 
closed  in  the  ordinary  way  and  the  wound  dressed. 

In  cases  of  (jastric  ulcer,  perforation  sometimes  takes  place,  and  this  was  formerly  regarded 
as  an  almost  fatal  complication.  In  the  present  day,  by  opening  the  abdomen  and  closing 
the  perforation,  which  is  generally  situated  on  the  anterior  surface  of  the  stomach,  a  consider- 
able percentage  of  cases  are  cured,  provided  the  operation  is  undertaken  within  twelve  to  fifteen 
hours  after  the  perforation  has  taken  place.  The  opening  is  best  closed  by  bringing  the  peri- 
toneal surfaces  on  either  side  into  apposition  by  means  of  Lembert  sutures. 

Pylorectomy  or  excision  of  the  pylorus  is  performed,  particularly  for  early  cancer,  but  is  also 
done  for  cicatricial  stricture  and  for  ulcer.  The  mortality  after  operation  for  cancer  was,  until 
recently,  very  great,  but  of  late  years  it  has  been  notably  reduced,  though  it  is  still  much  higher 
than  that  which  follows  operation  for  any  non-malignant  condition. 

In  operating  for  cancer,  bear  in  mind  Cun^o's  study  of  the  lymphatics  (page  806).  These 
observations  indicate  that  the  fundus  and  two-thirds  of  the  greater  curvature  are  free  from 
lymphatic  involvement  in  pyloric  cancer.'  In  every  operable  case  of  cancer  of  the  pylorus  the 
entire  lesser  curvature  must  be  removed  up  to  the  gastric  artery  (Mikulicz's  point),  and  the 
greater  curvature  must  be  removed  to  the  left  of  the  involved  glands  (Hartmann's  rule). 

Gastro-enterostomy  is  an  operation  which  establishes  a  fistulous  communication  between  the 
stomach  and  jejunum.  The  operation  is  often  called  gastro-jejunostomy.  The  opening  may  be 
made  upon  either  the  anterior  or  the  posterior  wall  of  the  stomach,  between  the  cardia  and  the 
seat  of  pyloric  disease.  The  operation  is  employed  for  stricture  of  the  pylorus  (benign  or 
malignant),  and  occasionally  for  ulcer  of  the  stomach. 

Loreta's  operation  is  digital  divulsion  of  the  pylorus  for  cicatricial  stricture,  the  stomach  being 
incised  transversely  near  the  pylorus  to  admit  the  finger,  and  the  wound  in  the  stomach  being 
sutured  after  division  has  been  effected.  The  operation  has  been  abandoned,  because  contraction 
recurs. 

Pyloroplasty,  or  the  Heineke-Mikulicz  operation,  displaced  Loreta's  operation.  In  this  pro- 
cedure an  incision  is  made  through  the  stricture  in  the  direction  of  the  long  axis  of  the  stomach 
and  bowel.  By  making  traction  on  each  side  of  the  incision,  the  longitudinal  wound  assumes  a 
vertical  direction,  and  sutures  are  inserted  so  as  to  close  the  wound  in  a  vertical  line.  The  method 
of  pyloroplasty  devised  by  Finney,  of  Baltimore,  makes  a  large  permanent  opening  at  the 
most  dependent  part  of  the  stomach,  and  is  the  most  satisfactory  method  of  which  we  are 
possessed.^ 

Total  gastrectomy  is  the  removal  of  the  entire  stomach.  It  is  only  used  for  cancer.  It  was  first 
performed  by  Conner,  of  Cincinnati.  The  first  successful  operation  was  done  by  Schlatter,  of 
Zurich,  in  1898.  A  number  of  successes  have  been  reported.  It  is  a  justifiable  operation  only  in 
a  case  in  which  almost  the  entire  stomach  is  cancerous,  in  which  the  viscus  is  movable,  in  which 
there  are  no  secondary  deposits,  and  no  irremovable  diseased  glands. 

Gastro-gastrostomy  is  an  operation  employed  in  hour-glass  stomach.  In  this  operation  an 
anastomosis  is  made  between  the  pyloric  and  cardiac  ends  of  the  stomach. 

'  William  J.  Mayo,  Annals  of  Surgery,  March,  1904. 
*  Johns  Hopkins  Hospital  Bulletin,  July,  1902. 

81 


1282  THE    ORGANS    OF  DIGESTION 

Gastroplication  is  the  operation  of  suturing  the  stomach  wall  into  folds  or  reefs,  in  order  to 
lessen  its  size.    It  is  employed  in  some  cases  of  gastric  dilatation. 

Gastroptosis  is  a  condition  in  which  the  stomach  is  displaced  downward.  In  some  of  these 
cases  the  greater  curvature  almost  reaches  the  level  of  the  symphysis  pubis,  and  the  lesser  curva- 
ture is  midway  between  the  umbilicus  and  ensiform  cartilage.  The  condition  is  usually  associated 
with  enteroptosis  and  movable  kidney  (nephroptosis).  In  this  condition  the  gastro-hepatic 
omentum  and  the  gastro-phrenic  ligament  are  pulled  upon  and  lengthened.  The  best  operation 
for  gastroptosis  was  devised  by  Beyea.  He  applies  sutures  so  as  to  make  folds  in  and  thus  shorten 
the  stretched  ligament  and  omentum.  Thus  the  stomach  is  elevated  to  its  proper  position,  and 
its  mobility  is  not  lessened,  as  it  is  in  other  operations  which  suture  it  to  the  abdominal  wall. 


THE  SMALL  INTESTINE   (INTESTINUM  TENUE). 

The  small  intestine  is  a  convoluted  tube,  extending  from  the  pylorus  to  the 
ileo-caecal  valve,  where  it  terminates  in  the  large  intestine.  It  fills  up  the  greater 
part  of  the  abdominal  cavity  and  of  the  pelvic  cavity.  It  is  about  twenty  feet  in 
length/  and  gradually  diminishes  in  size  from  its  commencement  to  its  termina- 
tion. The  diameter  of  the  duodenum  is  almost  two  inches;  the  diameter  of  the 
lower  portion  of  the  small  intestine  is  little  more  than  one  inch.  It  is  contained 
in  the  central  and  lower  part  of  the  abdominal  cavity,  and  is  surrounded  above 
and  at  the  sides  by  the  large  intestine;  a  portion  of  it  extends  below  the  brim  of 
the  pelvis  and  lies  in  front  of  the  rectum;  it  is  in  relation,  in  front,  with  the  great 
omentum  and  abdominal  parietes;  and  connected  to  the  spine  by  a  fold  of  peri- 
toneum, the  mesentery  (p.  1257) .  The  small  intestine  is  divisible  into  three  portions 
— the  duodenum,  the  jejunum,  and  ileum. 

The  Duodenum  (Figs.  887,  892,  893,  894,  895). 

The  duodenum  has  received  its  name  from  being  about  equal  in  length  to  the 
breadth  of  twelve  fingers  (ten  inches).  It  is  the  shortest,  the  widest,  and  the  most 
fixed  part  of  the  small  intestine,  being  closely  and  firmly  attached  to  the  posterior 
abdominal  wall.  It  does  not  possess  a  mesentery.  Somewhat  more  than  the 
upper  half  of  the  duodenum  is  placed  in  the  epigastric  region;  the  remainder  is  in 
the  umbilical  region.  The  duodenum,  with  the  exception  of  the  ascending  portion, 
is  to  the  right  of  the  median  line.  Its  course  presents  a  remarkable  curve,  which 
in  the  adult,  as  regards  the  greater  part  of  its  extent,  is  horseshoe-shaped,  though 
sometimes,  in  consequence  of  the  transverse  portion  being  very  short  or  alto- 
gether wanting,  it  partakes  more  of  the  character  of  the  letter  V.  The  opening 
of  the  horseshoe  being  directed  upward  and  to  the  left.  In  children  up  to 
the  age  of  about  seven  the  duodenum  is  annular.  The  two  extremities  of 
the  duodenum  are  nearly  on  the  same  level,  the  exit  being  slightly  lower  than  the 
entrance.  The  two  ends  are  about  two  inches  apart;  and  between  them  it 
describes  a  regular  curve  embracing  the  head  of  the  pancreas,  the  neck  of  which 
lies  between  the  two  extremities  of  the  ring. 

In  the  adult  the  course  of  the  duodenum  is  as  follows:  commencing  at  the 
pylorus  the  direction  of  the  first  portion  depends  upon  the  amount  of  distention 
of  the  stomach  and  therefore  upon  the  position  of  the  pylorus.  When  the  stomach 
is  empty  and  the  pylorus  is  situated  at  the  right  of  the  upper  border  of  the  first 
lumbar  vertebra,  it  is  nearly  horizontal  and  transverse;  but  where  the  stomach  is 
distended,  in  consequence  of  the  alteration  of  the  position  of  the  pylorus  to  the 
right  the  proximal  end  of  the  duodenum  also  becomes  altered  in  position,  while  the 

I  Treves  states  that  in  one  hundred  cases  the  average  length  of  the  small  intestine  in  the  adult  male  was  22 
feet  6  inches,  and  in  the  adult  female  23  feet  4  inches  ;  but  that  it  varies  very  much,  the  extremes  in  the  male 
being  31  feet  10  inches  in  one  case  and  15  feet  6  inches  in  another,  a  difference  of  over  15  feet.  He  states  that 
he  has  convinced  himself  that  the  length  of  the  bowel  is  independent,  in  the  adult,  of  age,  height,  and  weight. — 
liiD.  of  15th  English  edition. 


THE  DUODENUM 


1283 


distal  end  remains  fixed  and  the  direction  of  this  portion  of  the  bowel  is  now 
antero-posterior.    Whether  directed  transversely  or  antero-posteriorly,  it  reaches 


Tributary  to  vena  cava. 


Hepatic  artei-y,  portal 
vein,  and  bile  duct 


Supra- renal 
capsule 


■a  of  Diaphragm. 
Gastric  artery. 


Bight 

renal 

vessels 


enic 
artery. 

ilenic 
vein. 


Fto  887  —Relations  of  duodenum,  pancreas,  and  spleen.     (From  a  cast  by  Professor  Birmingham.') 
'      The  dotted  line  represents  the  hne  of  attachment  of  the  transverse  mesocolon. 

the  under  surface  of  the  liver,  where  it  takes  a  sharp  curve  and  descends  along  the 
right  side  of  the  vertebral  column,  for  a  variable  distance,  generally  to  the  body  of 

1  In  the  subject  from  which  the  cast  was  taken  the  left  kidney  was  lower  than  normal. 


1284 


THE    ORGANS    OF  DIGESTION 


the  fourth  lumbar  vertebra.  It  now  takes  a  second  bend,  and  passes  across  the 
front  of  the  vertebral  cohimn  from  right  to  left  and  finally  ascends  on  the  left  side 
of  the  vertebi-ai  column  and  aorta  to  the  level  of  the  upper  border  of  the  second 
lumbar  vertebra  and  there  terminates  in  the  jejunum.  As  it  unites  with  the 
jejunum  it  often  turns  abruptly  forward,  forming  the  duodeno-jejunal  angle.    Prof. 


Omentum  Minus 


Lesser  Sac 


<» 


of  .Tl■*.'!'s^ 


'':f^. 


—Hepatic 

Artery 


Portal 
Vein 


••      '^     y  ■' Greater  \  ^^^ 


Omentum      'l ' 
Majlis     Transverse  Mesocolon 
Fig.  888. — Diagram  of  cross-section  of  the  first 
part  of    the  duodenum,   to  show  its   peritoneal 
relations. 


Fig.  889. — Diagram  of  cross-section  of  the  second  part 
of  the  duodenum,  to  show  its  peritoneal  relations. 
(Gerrish.) 


Birmingham  points  out  that  the  incomplete  ring  formed  by  the  duodenum  does 
not  lie  throughout  in  the  same  plane.  "  Its  greater  part  is  placed  in  a  transverse 
vertical  plane;  the  middle  portion  bends  strongly  backward,  around  the  right  side 
of  the  vena  cava,  and  lies  almost  in  a  sagittal  plane."^    From  the  above  descriotion 


eRY 


AUSi-N"? 


AORTA,     VENA     CAVA. 
AND     RIGHT     CRUS 

Fig.  890.— Diagram  of  the  third  part  of  the 
duodenum,  to  show  its  peritoneal  relations. 
(Gerrish.) 


Fig.  891. — Diagram  of  the  fourth  part  of  the  duodenum, 
to  show  its  peritoneal  relations.     (Gerri.sh.) 


it  will  be  seen  that  the  duodenum  may  be  divided  for  purposes  of  description 
into  four  portions — superior,  descending,  transverse  and  ascending. 

The  First  or  Superior  Portion  (pars  superior)  (Figs.  887,  892,  and  894)  is 
very  variable  in  length,  but  is  usually  estimated  as  being  about  two  inches. 
Beginning  at  the  pylorus,  it  ends  at  the  level  of  the  neck  of  the  gall-bladder. 


1  Prof.  Cunningham's  Text-book  of  Anatomy. 


THE   DUODENUM  1285 

When  the  stomach  is  empty  this  portion  of  the  duodenum  is  horizontal  and 
transverse;  when  the  stomach  is  distended  it  extends  from  before  backward.  It 
is  the  most  movable  of  the  four  portions.  It  is  almost  completely  covered  by  peri- 
toneum derived  from  the  two  layers  of  the  lesser  omentum.  A  small  part  of  its 
posterior  surface  is  not  completely  covered  by  peritoneum  (Fig.  888).  The  first 
inch  of  the  superior  portion  of  the  duodenum  is  completely  covered  by  perito- 
neum ;  the  lesser  omentum  is  attached  above  and  the  greater  omentum  below  (Fig. 
888).  The  other  portion  has  only  its  anterior  wall  covered  by  peritoneum.  The 
'posterior  and  lateral  surfaces  are  uncovered  by  peritoneum  and  are  near  the  neck 
of  the  gall-bladder  and  the  inferior  vena  cava.  The  first  portion  of  the  duo- 
denum is  in  such  close  relation  with  the  gall-bladder  that  it  is  usually  found  to 
be  stained  by  bile  after  death,  especially  on  its  anterior  surface.  It  is  in  relation 
above  and  in  front  with  the  quadrate  lobe  of  the  liver,  lying  in  a  slight  con- 
cavity, the  impressio  duodenalis.  It  is  also  in  relation  above  in  part  with  the 
gall-bladder;  behind  with  the  gastro-duodenal  artery,  the  common  bile-duct,  and 
the  vena  porta;  and  below  with  the  head  of  the  pancreas.  The  superior  portion 
of  the  duodenum  crosses  the  transverse  fissure  of  the  liver,  and  by  means  of 
the  superior  flexure  of  the  duodenum  (flexura  duodeni  superior)  passes  into  the 
second  or  descending  portion  beneath  the  caudate  lobe. 

The  Second  or  Descending  Portion  {j)ars  descendens)  (Figs.  887,  892,  and  894) 
is  between  three  and  four  inches  in  length,  and  extends  from  the  neck  of  the  gall- 
bladder on  a  level  with  the  first  lumbar  vertebra  along  the  right  side  of  the  verte- 
bral column  as  low  as  the  body  of  the  fourth  lumbar  vertebra.  It  is  crossed  in 
its  middle  third  by  the  transverse  colon,  the  posterior  surface  of  which  is  uncovered 
by  peritoneum  and  is  connected  to  the  duodenum  by  a  small  quantity  of  connective 
tissue.  The  portions  of  the  descending  part  of  the  duodenum  above  and  below 
this  interspace  are  named  the  supracolic  and  infracolic  portions,  and  are  covered 
in  front  by  peritoneum  (Fig.  889).  The  right  side  of  the  supracolic  portion  is 
covered  by  peritoneum  derived  from  the  anterior  surface  of  the  right  kidney,  the 
left  side  of  the  same  portion  being  covered  by  the  peritoneum  forming  the  lesser 
sac.  The  infracolic  part  is  covered  by  the  right  leaf  of  the  mesentery.  Pos- 
teriorly the  descending  portion  of  the  duodenum  is  uncovered  by  peritoneum. 
The  descending  portion  of  the  duodenum  is  in  relation,  in  front,  with  the  trans- 
verse colon,  and  above  this  with  the  right  lobe  of  the  liver,  where  it  lies  in  the 
impressio  duodenalis  for  the  second  part  of  the  duodenum;  behind  with  the  front  of 
the  right  kidney,  to  which  it  is  connected  by  loose  areolar  tissue,  the  renal  vessels 
and  the  vena  cava  inferior;  at  its  inner  side  is  the  head  of  the  pancreas,  and  the 
ductus  communis  choledochus;  to  its  outer  side  is  the  hepatic  flexure  of  the  colon. 
The  common  bile-duct  passes  downward  behind  the  first  portion  of  the  duodenum, 
descends  to  the  inner  side  of  the  second  portion,  is  joined  by  the  pancreatic  duct, 
and  the  two  ducts  perforate  the  inner  side  of  this  portion  of  the  intestine  obliquely, 
and  empty  into  the  duodenum  by  a  common  opening  or  by  two  openings  at  the 
summit  of  a  papilla,  some  three  or  four  inches  below  the  pylorus.  The  relations 
of  the  second  part  of  the  duodenum  to  the  right  kidney  present  considerable 
variations.  The  descending  portion  passes  into  the  transverse  portion  by  means 
of  the  flexura  duodeni  inferior. 

The  Third,  Pre-aortic,  Horizontal  or  Transverse  Portion  {pars  horizontalis 
inferior)  (Figs.  887,  892,  and  894)  varies  much  in  length;  when  the  duodenum 
assumes  the  ordinary  horseshoe  form,  it  measures  from  two  to  three  inches;  but 
when  it  presents  the  rarer  V-shaped  form,  it  is  practically  wanting  or  very  much 
reduced  in  length.  The  transverse  portion  is  described  as  the  horizontal  part  of 
the  ascending  or  last  portion  by  those  author ;  who  divide  the  duodenum  into  three 
parts  instead  of  four.  It  commences  at  the  right  side  of  the  fourth  lumbar  vertebra 
and  passes  from  right  to  left,  with  a  slight  inclination  upward,  in  front  of  the  great 


1286 


THE    ORGANS    OF   DIGESTION 


vessels  and  crura  of  the  Diaphragm,  and  ends  in  the  fourth  portion  in  front  of  or 
just  to  the  left  of  the  abdominal  aorta.  It  is  crossed  by  the  superior  mesenteric 
vessels  and  mesentery.  The  'posterior  surface  rests  upon  the  aorta,  the  vena  cava 
inferior,  and  the  crura  of  the  Diaphragm.  By  its  upper  surface  this  portion  of 
the  duodenum  is  in  relation  with  the  head  of  the  pancreas.  The  front  of  the 
third  portion  of  the  duodenum  is  covered  by  peritoneum  except  where  the  mesen- 
teric vessels  and  root  of  the  mesentery  cross  it  (Fig.  890).  The  left  side  of  the 
termination  of  the  ascending  portion  is  also  covered  by  peritoneum,  and  in  this 
region  the  duodenal  fossae  are  found  (p.  1260). 

The  Fourth  or  Ascending  Portion  of  the  Duodenum  (pars  ascendens)  (Figs. 
887,  892,  and  894)  is  about  two  inches  long.  It  ascends  on  the  left  side  of  the 
vertebral  column  and  aorta,  as  far  as  the  level  of  the  upper  border  of  the  second 
lumbar  vertebra,  where  it  turns  abruptly  to  the  right  and  forward  to  become  the 
jejunum,  forming  the  duodeno-jejunal  angle  or  flexure  (flexura  duodenojejunalis) 


CELLULAR  MEMBRANE 

CONNECTING  THE    PARTS 

OFTHE   DUODENAL  RING 

BEHIND  THE   PANCREAS 


DIAPHRAGM 


CCELIAC  AXIS 


GANGLION  OF 
CCELIAC   PLEXUS 
SUPERIOR    MESEN- 
TERIC ARTERY 

SUSPENSORY 
MUSCLE  OF 
DUODENUM 


Fig.  892. — Suspensory  muscle  of  the  duodenum  or  muscle  of  Treitz.     (Poirier  and  Charpy.) 


(Fig.  892).  It  is  covered  entirely  in  front  and  partly  at  the  sides  by  peritoneum, 
derived  from  the  left  portion  of  the  mesentery  (Fig.  891).  The  superior  mesen- 
teric artery  and  vein  are  in  front  of  it.  It  touches  the  left  kidney,  slightly  over- 
lapping its  inner  margin,  and  rests  upon  the  left  crus  of  the  Diaphragm. 

The  first  part  of  the  duodenum,  as  stated  above,  is  somewhat  movable,  but  the 
rest  is  practically  fixed  and  is  bound  down  to  neighboring  viscera  and  the  posterior 
abdominal  wall  by  the  peritoneum.  In  addition  to  this,  the  fourth  part  of  the 
duodenum  and  the  duodeno-jejunal  flexure  is  further  bound  down  and  fixed  by  a 
structure  called  the  Suspensory  muscle  of  the  duodenum  or  the  suspensory  ligament  of 
Treitz  (to.  suspensorius  duodeni)  (Fig.  892).  This  structure  commences  in  the  con- 
nective tissue  around  the  coeliac  axis  and  left  crus  of  the  Diaphragm,  and  passes 
downward  to  be  inserted  into  the  superior  border  of  the  duodeno-jejunal  curve  and 
a  part  of  the  ascending  duodenum,  and  from  this  it  is  continued  into  the  mesentery. 
It  possesses,  according  to  Treitz,  some  few  plain  muscular  fibres  mixed  with  the 


THE    DUODENUM 


1287 


fibrous  tissue,  of  which  it  is  principally  made  up.    It  is  of  little  importance  as  a 
muscle,  but  acts  as  a  suspensory  ligament. 


VALVU 
CONNIVEN 


CARUNCULA 
MAJOR 


SOUND   IN    DUG 
TUS  CHOLEDOCHUS 


CARUNCULA   MINOR 
OF  SANTORINI 


SOUND  IN 
DUCTUS  CHOLEDOCHUS 

lio.  893. — The  interior  of  the  duodenum.     (Spalteholz.) 


SOUND  IN 
ACCESSORY 
PANCREATIC 
DUCT  OF 
SANTORINI 


LONGITUDINAL 
FOLD 


VALVULAE 
CONNIVENTE8 


Portal  vein 
Hepatic  duct 
Cystic  duct 


Hepatic  artery — -V^  - 
Hight  svprnrenal,  _^m 
capsule 

Pyloric  orifice- 
Right  gastro-epipluic 
artery 


Superior  mesenteric 

vein  fM 


Spermatic  itb&ds  \    Spermatic  vessels 

Inferior  mesenteric  artery 

Fig.  894. — The  duodenum,  its  four  parts  marked  n,  b,  c,  d.     The  liver  is  lifted  up  ;  the  greater    art  of  the 
stomach  is  removed,  broken  lines  indicating  its  former  position.      (Testut.) 


128S 


THE    ORGANS    OF  DIGESTION 


Interior  of  the  Duodenum  (Fig.  893). — In  the  beginning  of  the  duodenum  valvulae 
conniventes  are  absent.  They  begin  to  appear  in  the  lower  half  of  the  first  portion, 
being  at  first  trivial  elevations  irregularly  placed.  They  become  higher,  regular, 
and  more  numerous  lower  down,  and  near  the  termination  of  the  duodenum  are 
strongly  marked  and  closely  placed  transverse  or  spiral  folds  (Fig.  893  and 
p.  1291).  In  the  descending  portion  (Fig.  893)  to  the  side  and  rear  is  a  longi- 
tudinal fold  {flica  longitudinalis  duodeni),  which  is  formed  by  the  projection  of 
the  bile-duct  and  pancreatic  duct  beneath  the  mucous  membrane. 

The  caxuncula  major  of  Santorini  or  the  bile  papilla  is  a  projection  or  tit  in  the 
lower  part  of  the  longitudinal  fold.  At  the  summit  of  this  papilla  are  seen  two 
openings,  if  the  bile-duct  and  pancreatic  duct  have  not  united,  or  one  common 
opening  for  both  of  them,  if  they  have  united.  One  inch  above  and  half  an  inch 
or  more  in  front  of  the  bile  papilla  is  a  much  smaller  papilla,  the  caruncula  minor 
of  Santorini  (papilla  duodeni  [Santorini^),  on  the  summit  of  which  the  accessory 
pancreatic  duct  of  Santorini  opens. 

Structure  of  the  Duodenum. — The  peritoneal  coat  {tunica  serosa)  has  been  de- 
scribed. The  muscular  coat  (tunica  muscidaris)  is  practically  identical  with  the 
muscular  coat  of  the  balance  of  the  intestine.    The  bile-duct  and  pancreatic  duct 


FIRST 

GASTRO- 

GASTRO- 

INFERIOR 

PART  OF 

DUOOENAL 

DUODENAL 

CCELIAC 

PANCREATICO 

DUODENUM 

\ 

ARTERY 

\    ^ 

VEI^ 

AXIS 

DUODENAL 
VEIN 

PANCREATICO- 
DUODENAL 
SUPERIOR 
ARTERY 


DUCTUS 
CHOLEDOCHUS 


ANASTOMOSIS  OF  THE 
TWO  PANCREATICO- 
DUODENAL ARTERIES 


Fig.  835. — The  blood-vessels  of  the  duodenum.     (Poirier  and  Charpy.) 


pass  through  it.  The  submucous  coat  {tela  suhmucosa)  contains  lymph-nodes  and 
glands  of  Brunner  (glandulae  duodenales).  These  glands  are  particularly  plenti- 
ful in  the  first  half  of  the  duodenum  (p.  1295).  The  mucous  membrane  is 
thicker  in  the  duodenum  than  in  the  rest  of  the  small  intestine,  is  covered  with 
villi,  and  from  the  lower  half  of  the  first  portion  down  is  formed  into  circular 
folds  or  valvulae  conniventes.  In  the  descending  part  it  exhibits  the  previously 
described  longitudinal  fold. 

Vessels  and  Nerves. — The  arteries  (Fig.  895)  supplving  the  duodenum  are  the 
pyloric  and  pancreatico -duodenal  branches  of  the  hepatic,  and  the  inferior  pancreatico- 
duodenal branch  of  the  superior  mesenteric.  The  veins  (Fig.  895)  correspond  to 
the  arteries.  The  superior  duodenal  vein  passes  into  the  superior  mesenteric,  and 
the  inferior  duodenal  vein  passes  into  the  portal.  The  lymphatics  pass  along  with 
the  pancreatico-duodenal  arteries,  glands  being  present  here  and  there,  and 
terminate  in  the  glands  about  the  coehac  axis.  The  duodenal  fossae  are  described 
on  p.  1260.     The  nerves  are  derived  from  the  solar  plexus. 


THE  JEJUNUM  AND    ILEUM  1289 

The  Jejunum  and  Ileum  (Figs.  862,  864,  865,  867,  892). 

The  remainder  of  the  small  intestine  from  the  termination  of  the  duodenum 
comprises  the  jejunum  and  ileum;  the  former  name  being  given  to  the  upper  two- 
fifths  and  the  latter  to  the  remaining  three-fifths.  Spalteholz  and  others  call  all  of 
the  small  intestine  below  the  duodenum  the  intestinum  tenue  mesenteriale.  There 
is  no  morphological  line  of  distinction  between  the  jejunum  and  ileum,  and  the 
division  is  arbitrary;  but  at  the  same  time  it  must  be  noted  that  the  character  of 
the  intestine  gradually  undergoes  a  change  from  the  commencement  of  the  jeju- 
num to  the  termination  of  the  ileum,  so  that  a  portion  of  the  bowel  taken  from 
these  two  situations  would  present  characteristic  and  marked  differences.  These 
are  briefly  as  follows: 

Differences  between  the  Jejunum  and  Ileum. — If  the  jejunum  high  up  is  con- 
trasted with  the  ileum  low  down,  it  is  noted  that  the  former  is  thicker,  of  greater 
diameter,  contains  more  blood-vessels,  and  hence  is  more  distinctly  red,  has  well- 
marked  valvulae  conniventes,  but  a  few  small-sized  Peyer's  patches,  and  the  villi 
are  short  and  broad.  In  the  ileum  large  Peyer's  patches  are  present  in  numbers, 
and  the  villi  are  thin  (Prof.  Birmingham). 

The  Jejunum  {intestinum  jejunum). — The  jejunum,  which  derives  its  name 
from  the  Latin  word  jejunus  (empty),  because  it  was  formerly  supposed  to  be 
empty  after  death,  is  wider,  its  diameter  being  about  one  inch  and  a  half,  and  is 
thicker,  more  vascular,  and  of  a  deeper  color  than  the  ileum,  so  that  a  given  length 
weighs  more.  Its  valvulae  conniventes  are  large  and  thickly  set  and  its  villi  are 
larger  than  in  the  ileum.  The  glands  of  Peyer  are  almost  absent  in  the  upper  part 
of  the  jejunum,  and  in  the  lower  part  are  less  frequently  found  than  in  the  ileum, 
and  are  smaller  and  tend  to  assume  a  circular  form.  Brunner's  glands  are  only 
found  in  the  upper  part  of  the  jejunum.  By  grasping  the  jejunum  between  the 
finger  and  thumb  the  valvulae  conniventes  can  be  felt  through  the  walls  of  the 
gut;  these  being  absent  in  the  lower  part  of  the  ileum,  it  is  possible  in  this  way 
to  distinguish  the  upper  from  the  lower  part  of  the  small  intestine. 

The  Ileum  {intestinum  ileum). — The  ileum  (so  called  from  the  Greek  w^ord 
ttktiv,  to  twist,  on  account  of  its  numerous  coils  and  convolutions)  is  placed 
below  and  to  the  right  of  the  jejunum.  It  is  narrower,  its  diameter  being  one  inch 
and  a  quarter,  and  its  coats  are  thinner  and  less  vascular  than  those  of  the  jejunum. 
It  possesses  but  few  valvulae  conniventes,  and  they  are  small  and  disappear  entirely 
toward  its  lower  end,  but  Peyer's  patches  are  larger  and  more  numerous.  The 
jejunum  for  the  most  part  occupies  the  umbilical  and  left  iliac  regions,  while  the 
ileum  occupies  chiefly  the  umbilical,  hypogastric,  right  iliac,  and  pelvic  regions, 
and  terminates  in  the  right  iliac  fossa  by  opening  into  the  inner  side  of  the  com- 
mencement of  the  large  intestine.  The  upper  portion  of  the  jejunum  passes  to 
the  left  of  the  duodeno-jejunal  flexure,  and  is  in  relation  with  the  under  surface 
of  the  pancreas  and  the  transverse  mesocolon.  The  lower  portion  of  the  ileum  is 
in  the  pelvis  and  rises  from  above  the  brim,  passing  upward,  backward,  and  to  the 
right  to  reach  the  ileo-caecal  opening.  Treves  points  out  that  another  portion  of 
the  small  intestine  may  be  in  the  pelvis,  viz.,  the  portion  with  the  longest  mesentery. 
This  is  a  portion  somewhere  between  a  point  six  feet  from  the  duodenum  and  a 
point  eleven  feet  from  the  duodenum.  The  jejunum  and  ileum  are  attached  to  the 
posterior  abdominal  wall  by  an  extensive  fold  of  peritoneum,  the  mesentery  (p.  1257), 
which  allows  the  freest  motion,  so  that  each  coil  can  accommodate  itself  to  changes 
in  form  and  position.  The  mesentery  is  fan-shaped;  its  posterior  border,  about 
six  inches  in  length,  is  attached  to  the  abdominal  wall  from  the  left  side  of  the 
second  lumbar  vertebra  to  the  right  iliac  fossa  (Fig.  862).  Its  length  is  about  eight 
inches  from  its  commencement  to  its  termination  at  the  intestine,  and  it  is  rather 
longer  about  its  centre  than  at  either  end  of  the  bowel.    According  to  Lockwood, 


1290  THE    0RGAN8    OF  DIGESTION 

it  tends  to  increase  in  length  as  age  advances.  Between  the  two  layers  of  which 
it  is  composed  are  contained  blood-vessels,  nerves,  lacteals,  and  lymphatic  glands, 
together  with  a  variable  amount  of  fat. 

Meckel's  Diverticulum  {diverticulum  ilei). — Occasionally  there  may  be  found 
connected  with  the  lower  part  of  the  ileum,  on  an  average  about  three  feet  from 
its  termination,  a  blind  diverticulum  or  tube,  varying  in  length,  but  averaging 
about  two  inches,  and  being  of  about  the  same  diameter  as  the  piece  of  intestine  of 
which  it  is  a  part.  Sometimes  only  a  portion  of  the  proximal  end  is  open  and 
the  balance  of  the  structure  is  obliterated  and  shrunk  to  a  fibrous  cord.  In  other 
cases  the  diverticulum  is  actually  of  greater  diameter  than  the  intestine.  It 
usually  is  at  a  right  angle  to  the  intestine,  but  may  take  almost  any  direction. 
In  most  cases  it  has  a  mesentery.  It  is  attached  to  and  communicates  with  the 
lumen  of  the  bowel  by  one  extremity,  and  by  the  other  is  unattached  or  may  be 
connected  with  the  abdominal  wall  or  with  some  other  portion  of  the  intestine 
by  a  fibrous  band.  This  is  Meckel's  diverticulum,  and  represents  the  remains  of 
the  vitelline  or  omphalo-mesenteric  duct,  the  duct  of  communication  between  the 
umbilical  vesicle  and  the  alimentary  canal  in  early  foetal  life. 

Structure  of  the  Small  Intestine,  including  the  Duodenum. — The  wall  of 
the  small  intestine  is  composed  of  four  coats — serous,  muscular,  axeolar  or  sub- 
mucous, and  mucous. 

The  Serous  Coat  {tunica  serosa). — The  relation  of  the  peritoneum  to  the  duod- 
enum has  been  described.  The  remaining  portion  of  the  small  intestine  is  sur- 
rounded by  the  peritoneum,  excepting  along  its  attached  or  mesenteric  border; 
here  a  space  is  left  for  the  vessels  and  nerves  to  pass  to  the  gut. 

The  Muscular  Coat  {tunica  muscularis). — The  muscular  coat  consists  of  two 
layers  of  fibres,  an  external  or  longitudinal  layer  and  an  internal  or  circular 
lajer. 

The  Longitudinal  Fibres  {stratum  longitudinale)  are  thinly  scattered  over  the 
surface  of  the  intestine,  and  are  more  distinct  along  its  free  border. 

The  Circular  Fibres  {stratum  circidare)  form  a  thick,  uniform  layer;  they  sur- 
round the  cylinder  of  the  intestine  in  the  greater  part  of  its  circumference,  and  are 
composed  of  plain  muscle-cells  of  considerable  length.  The  muscular  coat  is 
thicker  at  the  upper  than  at  the  lower  part  of  the  small  intestine. 

The  Areolar  or  Submucous  Coat  {tela  suhmucosa). — The  areolar  or  submucous 
coat  connects  together  the  mucous  and  muscular  layers.  It  consists  of  loose, 
filamentous  areolar  tissue,  which  forms  a  bed  for  the  subdivision  of  the  nutrient 
vessels,  previous  to  their  distribution  to  the  mucous  surface. 

The  submucous  coat  contains  lymph-nodules  {noduli  lymphatici).  Each  nodule 
is  pyramidal  or  pear-shaped,  and  the  apex  lies  in  the  mucous  membrane  and  forms 
a  rounded  elevation.  These  rounded  elevations  mark  the  solitary  glands  and 
Peyer's  patches  (Figs.  896,  898,  and  905),  and  in  nowise  resemble  villi.  In  the 
duodenum  the  submucous  tissue  contains  the  duodenal  glands.  The  submucous 
tissue  is  prolonged  into  the  valvulae  conniventes.  It  contains  blood-vessels,  Meiss- 
ner's  plexus  of  nerves,  and  lymph-vessels. 

The  Mucous  Membrane  {tunica  mucosa). — The  mucous  membrane  is  thick  and 
highly  vascular  at  the  upper  part  of  the  small  intestine,  but  somewhat  paler  and 
thinner  below.  It  consists  of  the  following;  structures:  next  the  areolar  or  sub- 
mucous  coat  is  a  layer  of  unstriped  muscular  fibres,  the  muscularis  mucosae ;  internal 
to  this  is  a  quantity  of  retiform  tissue,  enclosing  in  its  meshes  lymph-corpuscles, 
and  in  which  the  blood-vessels  and  nerves  ramify.  Lastly,  a  basement-membrane, 
supporting  a  single  layer  of  epithelial  cells,  which  throughout  the  intestines  are 
columnar  in  character.  They  are  granular  in  appearance,  and  each  possesses  a 
clear,  oval  nucleus.  At  their  superficial  or  unattached  end  they  present  a  distinct 
layer  of  highly  refracting  material,  marked  by  vertical  striae,  which  were  formerly 


THE   JEJUNUM   AND    ILEUM 


1291 


believed  to  be  minute  channels  by  which  the  chyle  was  taken  up  into  the  interior 
of  the  cell,  and  by  them  transferred  to  the  lacteal  vessels  of  the  mucous  membrane. 


MOUTHS    OF    GLANDS  SOLITARY  GLAND 

OF    LIEBERKUHN 

Fig.  896. — Free  surface  of  the  mucous  membrane  of  the  small  intestine,  showing  villi,  solitarj'  glands, 
and  openings  of  the  intestinal  glands.     Semidiagrammatic.     (Testut.) 

The  mucous  membrane  presents  for  examination  the  following  structures  con- 
tained within  it  or  belonging  to  it: 


Valvulae  conniventes. 

Villi. 

Simple  follicles. 


Duodenal  glands. 

T         I    ,  •         J  1      f  Solitary  glands. 
Lymphatic  nodules  i  „        /  •     ,      i      i 

''     ^  C  i  eyer  s  or  agmmate  glands. 


The  Valvulae  Conniventes  or  the  Valves  of  Kerkring  {'plicae  circulares  [Kerkringi]) 
(Fig.  897)  are  large  folds  or  valvular  flaps  projecting  into  the  lumen  of  the  bowel. 
They  are  composed  of  reduplications  or  folds  of  the  mucous  membrane,  the  two 
layers  of  the  fold  being  bound  together  by  submucous  tissue;  they  contain  no 
muscular  fibres,  and,  unlike  the  folds  in 
the  stomach,  they  are  permanent,  and 
are  not  obliterated  when  the  intestine  is 
distended.  The  majority  extend  trans- 
versely across  the  cylinder  of  the  intestine 
for  about  one-half  or  two-thirds  of  its 
circumference,  but  some  form  complete 
circles,  and  others  have  a  spiral  direc- 
tion; the  latter  usually  extend  a  little 
more  than  once  around  the  bowel,  but 
occasionally  two  or  three  times.  The 
spiral  arrangement  is  the  characteristic 
one  of  the  shark  family  of  fishes.  The 
larger  folds  are  about  one-third  of  an 
inch  in  depth  at  their  broadest  part;  but 
the  greater  number  are  of  smaller  size. 
The  larger  and  smaller  folds  alternate 
with  each  other.  They  are  not  found  at  the  commencement  of  the  duodenum, 
but  begin  to  appear  about  one  or  two  inches  beyond  the  pylorus.  In  the  lower 
part  of  the  descending  portion,  below  the  point  where  the  bile  and  pancreatic 
ducts  enter  the  intestine,  they  are  very  large  and  closely  approximated.  In 
the  transverse  portion  of   the  duodenum  and  upper  half  of  the  jejunum  they 


Fig.  897. — Valvulae  conniventes  in  the  upper  part 
of  the  small  intestine.     (Poirier  and  Charpy.) 


1292 


THE    ORGANS    OF   DIGESTION 


are  large  and  numerous;  and  from  this  point,  down  to  the  middle  of  the  ileum, 
they  diminish  considerably  in  size.  In  the  lower  part  of  the  ileum  they  almost 
entirely  disappear;  hence  the  comparative  thinness  of  this  portion  of  the  intes- 
tine as  compared  with  the  duodenum  and  jejunum.  The  valvulae  conniventes 
retard  the  passage  of  the  food  along  the  intestine,  and  afford  a  more  extensive 
surface  for  absorption. 

The  Vim  {villi  intestinales)  (Figs.  896,  898,  899,  900,  and  905)  are  minute,  highly 
vascular  processes,  never  larger  than  one  millimetre,  projecting  from  the  mucous 
membrane  of  the  small  intestine  throughout  its  whole  extent,  and  giving  to  its 
surface  a  velvety  appearance.  They  spring  from  the  valvulae  conniventes  and  also 
from  the  spaces  between  them.  In  shape,  according  to  Rauber,  they  are  short 
and  leaf-shaped  in  the  duodenum,  tongue-shaped  in  the  jejunum,  and  filiform 


MUCOUS   CO/^T 


PLANE    OF    MU- 
COUS   SURFACE 


Fig.  898. — Mucosa  of  small  intestine  in  ideal  vertical  cross-section.     (Testut,  after  Heitzmann.) 

in  the  ileum.  They  are  largest  and  most  numerous  in  the  duodenum  and 
jejunum,  and  become  fewer  and  smaller  in  the  ileum.  Krause  estimates  their 
number  in  the  upper  part  of  the  small  intestine  at  from  fifty  to  ninety  in  a  square 
line;  and  in  the  lower  part  from  forty  to  seventy,  the  total  number  for  the  whole 
length  of  the  intestine  being  about  four  millions. 

Structure  of  the  Villi  (Figs.  899  and  900). — The  structure  of  the  villi  has 
been  studied  by  many  eminent  anatomists.  We  shall  here  follow  the  description 
of  Watney,^  whose  researches  have  a  most  important  bearing  on  the  physiology  of 
that  which  is  the  peculiar  function  of  this  part  of  the  intestine,  the  absorption  of  fat. 

The  essential  parts  of  a  villus  are— the  lacteal  vessel,  the  blood-vessels,  the 
epithelium,  the  basement-membrane  and  muscular  tissue  of  the  mucosa,  these 
structures  being  supported  and  held  together  by  retiform  lymphoid  tissue. 

Phil.  Trans.,  vol.  clxv.  part  ii. 


THE  JEJUNUM  AND    ILEUM 


1293 


Fig.  899. — Diagrammatic  section  of  a  villus,  ep.  Epithelium  only  partially  shaded  in.  I.  Central  chyle- 
vessel  ;  the  cells  forming  the  vessel  have  been  less  shaded  to  distinguish  them  from  the  cells  of  the  parenchyma 
of  the  villus,  m.  Muscle-fibres  running  up  by  the  side  of  the  chyle-ves.sel.  It  will  be  noticed  that  each  muscle- 
fibre  is  surrounded  by  the  reticulum,  and  by  this  reticulum  the  muscles  are  attached  to  the  cells  forming  the 
membrana  propria,  as  at  e',  or  to  the  reticulum  of  the  villus.  Ic.  Lymph-corpuscles,  marked  by  a  spherical 
nucleus  and  a  clear  zone  of  protoplasm.  /'.  Upper  limit  of  the  chyle-vessel,  e,  e,  e'.  Cells  forming  the  mem- 
brana propria.  It  will  be  seen  that  there  is  hardly  any  difference  between  the  cells  of  the  parenchyma,  the  endo- 
thelium of  the  upper  part  of  the  chyle-vessel,  and  the  cells  of  the  membrana  propria.  V.  Blood-vessels,  z.  Dark 
line  at  base  of  the  epithelium  formed  by  the  reticulum.  It  will  be  seen  that  the  reticulum  penetrates  between 
all  the  other  elements  of  the  villus.  The  reticulum  contains  thickenings  or  "  nodal  points."  The  diagram  shows 
that  the  cells  of  the  upiser  part  of  the  villus  are  larger  and  contain  a  larger  zone  of  protoplasm  than  those  of  the 
lower  part.  The  cells  of  the  upper  part  of  the  chyle-vessel  differ  somewhat  from  those  of  the  lower  part  in  that 
they  more  nearly  resemble  the  cells  of  the  parenchyma.     (Watney.) 


Lymph  trunk 


Lymph  trunk. 


-  -  Capillaries. 


Small  artery. '  Lymphatic  plexus. 

Fig.  900.— Villi  of  small  intestine.     (Cadiat.) 


1294 


THE    ORGANS    OF   DIGESTION 


These  structures  are  arranged  in  the  following  manner:  situated  in  the  centre 
of  the  villus  is  the  lacteal,  terminating  near  the  summit  in  a  blind  extremity; 
running  along  this  vessel  are  unstriped  muscular  fibres;  surrounding  it  is  a  plexus 
of  capillary  vessels,  the  whole  being  enclosed  by  a  basement-membrane,  and  cov- 
ered by  columnar  epithelium.  Those  structures  which  are  contained  within  the 
basement-membrane — namely,  the  lacteal,  the  muscular  tissue,  and  the  blood- 
vessels— are  surrounded  and  enclosed  by  a  delicate  reticulum  which  forms  the 
matrix  of  the  villus,  and  in  the  meshes  of  which  are  found  large,  flattened  cells 
with  oval  nuclei,  and,  in  smaller  numbers,  lymph-corpuscles.  These  latter  are 
to  be  distinguished  from  the  larger  cells  of  the  villus  by  their  behavior  with 
reagents,  by  their  size,  and  by  the  shape  of  the  nucleus,  which  is  spherical. 
Transitional  forms,  however,  of  all  kinds  are  met  with  between  the  lymph-cor- 
puscles and  the  proper  cells  of  the  villus.  Nerve-fibres  are  contained  within  the 
villi;  they  form  ramifications  throughout  the  reticulum. 

The  lacteals  are  in  some  cases  double,  and  in  some  animals  multiple.  Situated 
in  the  axis  of  the  villi,  they  commence  by  dilated  caecal  extremities  near  to,  but 
not  quite  at,  the  summit  of  the  villus.  The  walls  are  composed  of  a  single  layer 
of  endothelial  cells,  the  interstitial  substance  between  the  cells  being  continuous 
with  the  reticulum  of  the  matrix. 


CALCIFORM 
CELL 


GLANDULAR 
CELL 


Fig.  901. — Section  of  a  gland  of  Lieberkiihn  in  the  mouse. 
(Paneth.) 


Fio.   902. — Transverse  section  of  crypts  of 
Lieberkiihn.     (Klein  and  Noble  Smith.) 


The  muscular  fibres  are  derived  from  the  muscularis  mucosae,  and  are  arranged 
in  bundles  around  the  lacteal  vessel,  extending  from  the  base  to  the  summit  of  the 
villus,  and  giving  off  laterally  individual  muscle-cells,  which  are  enclosed  by  the 
reticulum,  and  by  it  are  attached  to  the  basement-membrane. 

The  blood-vessels  form  a  plexus  between  the  lacteal  and  the  basement-mem- 
brane, and  are  enclosed  in  the  reticular  tissue;  in  the  interstices  of  the  capillary 
plexus,  which  they  form,  are  contained  the  cells  of  the  villus. 

These  structures  are  surrounded  by  the  basement-membrane,  which  is  made 
up  of  a  stratum  of  endothelial  cells,  and  upon  which  is  placed  a  layer  of  columnar 
epithelium.  The  reticulum  of  the  matrix  is  continuous  through  the  basement- 
membrane  (that  is,  through  the  interstitial  substance  between  the  individual 
endothelial  cells)  with  the  interstitial  cement  substance  of  the  columnar  epithelial 
cells  on  the  surface  of  the  villus.  Thus  we  are  enabled  to  trace  a  direct  continuity 
between  the  interior  of  the  lacteal  and  the  surface  of  the  villus  by  means  of  the 
reticular  tissue,  and  it  is  along  this  path  that  the  chyle  passes  in  the  process  of 
absorption  by  the  villi;  that  is  to  say,  it  passes  first  of  all  into  the  columnar 


THE  JEJUNUM  AND   ILEUM 


1295 


epithelial  cells,  and,  escaping  from  them,  is  carried  into  the  reticulum  of  the  villus, 
and  thence  into  the  central  lacteal. 

The  Simple  Follicles,  Intestinal  Glands,  Crypts  or  Glands  of  Lieberkiihn  (glandulae 
intestinales  [Lieberkuhrii])  (Figs.  901,  902,  and  905)  are  found  in  considerable 
numbers  over  every  part  of  the  mucous  membrane  of  the  small  intestine.  They 
consist  of  minute  tubular  depressions  of  the  mucous  membrane,  arranged  per- 
pendicularly to  the  surface,  upon  which  they  open  by  small  circular  apertures. 
They  may  be  seen  with  the  aid  of  a  lens,  their  orifices  appearing  as  minute  dots 
scattered  between  the  villi  (Fig.  896).  Their  walls  are  thin,  consisting  of  a  base- 
ment-membrane lined  by  columnar  epithelium,  and  covered  on  their  exterior  by 
capillary  vessels. 

The  Duodenal  or  Brunner's  Glands  (glandulae  duodenales  [Brunneri])  are  limited 
to  the  duodenum  and  commencement  of  the  jejunum.  They  are  small,  flattened, 
granular  bodies  embedded  in  the  submucous  areolar  tissue,  and  open  upon  the 
surface  of  the  mucous  membrane  by  minute  excretory  ducts.  They  are  most 
numerous  and  largest  near  the  pylorus.  They  are  small,  compound,  acino-tubular 
glands,  and  much  resemble  the  small  glands  which  are  found  in  the  mucous  mem- 


,JU 


Capillary  network. 


Fi».  903. — Transverse  section  through  the  equatorial  plane 
of  three  of  Peyer's  follicles  from  the  rabbit. 


Fig.  904. — Patch  of  Peyer's  glands, 
lower  part  of  the  ileum. 


From  the 


brane  of  the  mouth.  They  are  believed  by  Watney  to  be  direct  continuations  of 
the  pyloric  glands  of  the  stomach.  They  consist  of  a  number  of  tubular  alveoli, 
lined  by  epithelium,  and  opening  by  a  single  duct  on  the  inner  surface  of  the 
intestine. 

The  Lymph  Nodules  (noduli  lymphatici)  are  small  pyriform  structures.  The 
bodies  of  the  nodes  are  in  the  submucous  coat;  the  apices  are  in  the  mucous  mem- 
brane, which  is  thrown  by  them  into  rounded  elevations.  They  are  divided  into 
solitary  glands  and  Peyer's  glands. 

The  solitary  glands  (noduli  lymphatici  solitarii)  (Figs.  896  and  898)  are  found 
scattered  throughout  the  mucous  membrane  of  the  small  intestine  and  the  large 
intestine.  In  the  small  intestine  they  are  most  numerous  in  the  lower  part  of  the 
ileum,  upon  and  between  the  valvulae  conniventes.  They  are  small,  round,  whitish 
bodies,  from  one-twenty-fourth  of  an  inch  to  one-quarter  of  an  inch  in  diameter. 
Their  free  surface  is  covered  with  villi,  and  each  gland  is  surrounded  by  the 


1296  THE    OBGANS    OF  DIGESTION 

openings  of  the  follicles  of  Lieberkiihn.  They  are  now  recognized  as  lymph- 
nodules.  They  consist  of  a  dense  interlacing  retiform  tissue  closely  packed  with 
lymph-corpuscles  and  permeated  with  an  abundant  capillary  network.  The  inter- 
spaces of  the  retiform  tissue  are  continuous  with  larger  lymph-spaces  at  the  base 
of  the  gland,  through  which  they  communicate  with  the  lacteal  system.  They 
are  situated  partly  in  the  submucous  tissue,  partly  in  the  mucous  membrane, 
whence  they  form  slight  projections  of  its  epithelial  layer,  after  having  pene- 
trated the  muscularis  mucosae.  The  villi  situated  on  them  are  generally  absent 
from  the  very  summit  (or  "cupola,"  as  Frey  calls  it)  of  the  gland. 

Peyer's  glands,  Peyer's  patches,  the  agminated  glands  or  the  tonsillae  intestinales 
(noduli  lymphatici  aggregati  [Peyeri])  (Figs.  903,  904,  and  905)  may  be  regarded  as 
aggregations  of  solitary  glands,  forming  circular  or  oval  patches  from  twenty-five 
to  forty  in  number,  and  varying  in  length  from  half  an  inch  to  four  inches.  They 
are  largest  and  most  numerous  in  the  ileum.  In  the  lower  part  of  the  jejunum 
they  are  small,  of  a  circular  form,  and  few  in  number.  They  are  occasionally  seen 
in  the  duodenum.     They  are  placed  lengthwise  in  the  intestine,  and  are  situated 


INTESTINAL  VILLUS 


GLAND  OF  LIEBERKUHN 


CHYLI  FERGUS 
DUCT 


SUMMIT   OF 
FOLLICLE 


MIDDLE    FOLLICULAR 
ZONE 


PERIFOLLICULAR 
LYMPHATIC  ZONE 


INFERIOR   LYM- 
PHATIC PLEXUS 


Fig.  905. — Vertical  cell  of  a  Peyer's  patch  in  a  man  with  the  lymphatic  vessels  injected.     (Frey.) 

in  the  portion  of  the  tube  most  distant  from  the  attachment  of  the  mesentery. 
Each  patch  is  formed  of  a  group  of  the  above-described  solitary  glands  covered 
with  mucous  membrane,  and  in  almost  every  respect  are  similar  in  structure  to 
them.  They  do  not,  however,  as  a  rule,  possess  villi  on  their  free  surface.  Each 
patch  is  surrounded  by  a  circle  of  the  crypts  of  Lieberkiihn.  They  are  best  marked 
in  the  young  subject,  becoming  indistinct  in  middle  age,  and  sometimes  altogether 
disappearing  in  advanced  life.  They  are  largely  supplied  with  blood-vessels, 
which  form  an  abundant  plexus  around  each  follicle  and  give  off  fine  branches 
which  permeate  the  lymphoid  tissue  in  the  interior  of  the  follicle.  The  lacteal 
plexuses  which  are  found  throughout  the  small  intestine  are  especially  abundant 
around  these  patches;  here  they  form  rich  plexuses  with  sinuses  around  the  glands 
(Fig.  905),     In  typhoid  fever  there  is  ulceration  of  Peyer's  patches. 

Vessels  and  Nerves. — The  arteries  {vasa  intestini  tenuis)  are  branches  of  the 
superior  mesenteric  (Fig.  420)  and  ascend  within  the  mesentery,  forming  single, 
double,  or  even  tertiary  loops  (Figs.  869,  870,  871,  872,  873,  874,  and  906).  The 
terminal  branches  reach  the  intestine,  and  each  branch  divides  into  two,  one  going 
to  each  side  of  the  intestine  and  passing  transversely  around  it.     At  first  they  are 


THE   JEJUNUM  AND    ILEUM 


1297 


directly  beneath  the  peritoneum,  but  after  a  time  they  pass  to  the  submucosa 
and  form  a  plexus,  from  which  branches  go  to  the  mucous  membrane.  Some 
of  these  enter  the  villi;  others  form  plexuses  about  the  glands  of  Lieberkiihn 
(Birmingham). 


Fig.  906. — A  loop  of  small  intestine,  showing  the  mode  of  distribution  of  the  arteries.     (Testut.) 

Dr.  George  H.  Monks*  points  out  that  opposite  the  upper  portion  of  the  bowel 
the  mesenteric  vessels  form  only  primary  loops;  as  we  pass  down  secondary  loops 
appear,  become  larger  and  more  and  more  numerous,  and  actually  prominent 
features  about  the  fourth  foot.  As  we  descend  the  secondary 
loops  become  larger  and  more  numerous  and  the  primary 
become  smaller.  All  the  time  the  loops  get  nearer  and 
nearer  to  the  bowel.  Tertiary  loops  may  appear.  Opposite 
the  lower  part  of  the  ileum  the  loops  cease  to  be  character- 
istic and  they  form  a  network.  (Monks's  views  are  fully 
set  forth  on  pp.  1266,  1267,  and  1268.)  In  the  upper  part 
of  the  gut  the  vasa  recta  are  from  3  to  5  cm.  long,  when  the 
loop  of  small  intestine  to  which  they  run  is  lifted  up  so  as 
to  put  them  gently  on  the  stretch.  They  are  straight,  large, 
and  regular,  and  rarely  give  off  branches  in  the  mesentery. 
In  the  lower  third  they  are  very  short,  being  generally  less 
than  1  cm.  in  length.  Here  they  are  less  straight,  smaller, 
less  regular,  and  have  frequent  branches  in  the  mesentery. 

The  veins  correspond  to  the  arteries,  and  the  venous 
blood  passes  to  the  superior  mesenteric  vein,  which,  it  will  be 
remembered,  unites  with  the  splenic  vein  to  form  the  portal 
vein.    The  mesenteric  veins  are  devoid  of  valves. 

The  lacteals  are  lymphatics  (Figs.  898,  899,  900,  and 
905)  which  arise  in  the  villi.  Lymphatics  also  begin  in 
sinuses  at  the  base  of  the  solitary  glands  and  as  lymph- 
nodes  in  the  submucous  coat.  Peyer's  patches  are  aggre- 
gations of  lymph-nodes.     There  is  an  extensive  lymphatic 

1  •       .1  I  ,  ,1  •       ,1  1,1"  i"c  vim  oi  I  lie  small  in- 

plexus  m  the  submucous  coat,  another  in  the  muscular  coat,  testineof  arabbit.  (Muiier.) 
another  under   the    peritoneum.      The   submucous  plexus 

is  formed  by  lymphatics  from  the  villi  and  mucous  membrane.  This  plexus 
is  joined  by  lymphatics  from  the  bases  of  the  solitary  glands,  and  the  lymph 
passes  by  vessels  to  larger  vessels  at  the  mesenteric  border  of  the  gut.  The 
muscular    lymphatics    are    placed    between    the  two    muscular    layers.     They 


I  '       'i<<7 .       .N(>r\  (■  ciiilings 
in  the  villi  of  the  small  in- 


1  Annals  of  Surgery,  May,  1903. 
82 


1298 


THE    ORGANS    OF  DIGESTION 


form  a  plexus  and  communicate  freely  with  the  lymphatics  from  the  mucous 
membrane,  and  empty  themselves  in  the  same  manner  into  the  commencement 


Fig.  908. — Meissner's  plexus. 


Multipolar  ganglion- cells. 


Single  ganglion-cell. 


Fig.  909.— Meissner's  plexus.     (Klein  and  Noble  Smith.) 


THE  LARGE  INTESTINE 


1299 


of  the  lacteal  vessels  at  the  attached  border  of  the  gut.  The  vessels  from  all 
sources  of  lymphatic  supply  pass  up  between  the  two  layers  of  the  mesentery, 
being  connected  with  the  mesenteric  glands  (Fig.  509) ,  and  unite  to  form  a  trunk, 
the  intestinal  Ijrmphatic  trunk,  which  opens  into  the  receptaculum  chyli,  or  the 
vessels  unite  to  form  several  trunks,  which  open  separately  into  the  receptaculum 
chyli. 

The  nerves  of  the  small  intestine  (Figs.  907,  908,  and  909)  are  derived  from  the 
coeliac  plexus  about  the  superior  mesenteric  artery,  which  is  one  of  the  divisions 
of  the  solar  plexus.  They  pass  along  within  the  mesentery  with  the  superior  mesen- 
teric artery  and  reach  the  intestine.  They  pass  to  the  plexus  of  nerves  and  ganglia 
situated  between  the  circular  and  longitudinal  muscular  fibres  (Auerbach's  plexus), 
from  which  the  nervous  branches  are  distributed  to  the  muscular  coats  of  the 
intestine.  From  this  plexus  a  secondary  plexus  is  derived  (Meissner's  plexus). 
It  is  formed  by  branches  which  have  perforated  the  circular  muscular  fibres 
(Fig.  909).  This  plexus  lies  between  the  muscular  and  mucous  coats  of  the  intes- 
tine. It  is  -also  gangliated,  and  from  it  the  ultimate  fibres  pass  to  the  muscularis 
mucosae,  to  the  villi,  and  to  the  mucous  membrane.  The  nerves  of  the  intestine 
are  non-medullated,  and  some  of  the  fibres  are  derived  from  the  pneumogastric. 

THE  LARGE  INTESTINE  (INTESTINUM  CRASSUM)  (Figs.  799, 861, 865, 910,  911). 

The  large  intestine  extends  from  the  termination  of  the  ileum  to  the  anus.  It 
is  about  five  feet  or  more  in  length,  being  one-fifth  of  the  whole  extent  of  the 


SACCULATIONS 


APPENDICES  CPIPLOICAE 


Fig.  910. — Large  intestine.     A  piece  of  transverse  colon  from  a  child  two  years  old.     The  three  chief  charac- 
teristics of  the  large  intestine — sacculation,  taeniae  and  appendices  epiploicae — are  shown.     (Cunningham.) 


MUSCULAR    BAND 


intestinal  canal.  It  is  largest  at  its  com- 
mencement at  the  caecum,  and  gradually 
diminishes  as  far  as  the  rectum,  where 
there  is  a  dilatation  of  considerable  size 
just  above  the  anus.  The  diameter  of  the 
distended  caecum  is  usually  about  three 
inches;  the  diameter  of  the  descending 
colon  is  about  one  and  a  half  inches. 
The  large  intestine  differs  from  the  small 
intestine  in  its  greater  size,  its  more 
fixed  position,  its  sacculated  form  (Figs. 
910 and  911),  and  in  possessing  certain  ap- 
pendagesto  its  external  coat,  the  appendices 
epiploicae  (Fig.  910).  The  appendices 
epiploicae  are  peritoneal  pouches  con- 
taining fat,  unless  the  subject  is  greatly 

wasted;  they  protrude  here  and  there  from  the  peritoneal  coat  of  the  entire  large 
bowel,  except  the  rectum,  and  are  particularly  frequent  along  the  anterior  longi- 


MUSCULAR 
BAND 


MUSCULAR 
BAND 


Fig.  911. — Segment  of  large  intestine,  showing  the 
characteristic  features  of  its  structure.    (Testut.) 


1300 


THE    ORGANS    OF  DIGESTION 


tudinal  band.  Further,  the  longitudinal  muscular  fibres  of  the  large  intestine  do 
not  form  a  continuous  layer  around  the  gut,  but  are  arranged  in  three  longitudinal 
bands  or  taeniae  {taeniae  coli)  (Fig.  91 1) .  The  large  intestine,  in  its  course,  describes 
an  arch,  which  surrounds  the  convolutions  of  the  small  intestine.  It  commences 
in  the  right  inguinal  region,  in  a  dilated  part,  the  caecum.  It  ascends  through  the 
right  lumbar  and  right  hypochondriac  regions  to  the  under  surface  of  the  liver; 
it  here  takes  a  bend  to  the  left,  the  hepatic  flexure,  and  passes  transversely  across 
the  abdomen  on  the  confines  of  the  epigastric  and  umbilical  regions,  to  the  left 
hypochondriac  region;  it  then  bends  again,  the  splenic  flexure,  and  descends 
through  the  left  lumbar  region  to  the  left  iliac  fossa,  where  it  becomes  convoluted, 
and  forms  the  sigmoid  flexure ;  finally  it  enters  the  pelvis,  and  descends  along  its 
posterior  wall  to  the  anus.  The  large  intestine  is  divided  into  the  caecum,  colon, 
and  rectum. 

The  Caecum  (Intestinum  Caecum)  (Figs.  912,  913). 

The  caecum,  the  commencement  of  the  large  intestine,  is  the  large  blind  pouch, 
or  cul-de-sac,  situated  below  the  ileo-caecal  valve.  Its  name  is  derived  from 
caecus,  blind.     Its  blind  end  or  fundus  is  directed  downward,  and  its  open  end 

upward,  communicating  directly  with  the 
colon,  of  which  this  blind  pouch  appears  to 
be  the  beginning  or  head,  and  hence  the  old 
name  caput  caecum  coli  was  applied  to  it. 
An  incomplete  groove  marks  the  upper  limit 
of  the  caecum.  This  groove  is  at  the  level 
of  the  opening  of  the  ileum.  When  the 
caecum  is  contracted  it  bends  on  this  groove 
as  on  a  hinge  and  forms  an  angle  with  the 
ascending  colon.  In  the  contracted  caecum 
sacculations  are  but  slightly  evident;  in  the 
distended  caecum  they  are  definite.  Its  size 
is  variously  estimated  by  different  authors, 
but  on  an  average  it  may  be  said  to  be  two 
and  a  half  inches  in  length  and  three  in 
breadth.  In  435  careful  autopsies,  Byron 
Robinson  found  the  caecum  and  appendix 
congenitally  absent  in  one  case.^  The  same 
author  says  that  excessively  large  caeca  are 
found  in  a  little  less  than  one-third  of  all 
autopsies.  A  large  caecum  may  be  four 
inches  in  width,  entirely  surrounded  by  peri- 
toneum and  usually  is  excessively  mobile. 
Sometimes  an  excessively  small  caecum  is 
encountered.  According  to  Byron  Robinson,  this  results  from  diminution  of  the 
blood-supply  during  the  axial  rotation  and  caecal  descent  of  development.  An 
adult  caecum  may  be  only  one  inch  in  width  and  one-half  an  inch  in  length,  and  it 
is  usually  devoid  of  mobility.  It  is  situated  in  the  right  iliac  fossa,  above  the  outer 
half  of  Poupart's  ligament,  usually  rests  on  the  Ilio-psoas  muscle,  the  iliac  fascia 
intervening,  and  lies  immediately  behind  the  abdominal  wall.  The  right  side  of 
the  caecum  is  in  contact  with  the  outer  wall  of  the  abdomen,  and  the  outer  aspect 
of  the  anterior  wall  of  the  caecum  is  in  contact  with  the  anterior  abdominal  wall 
(Spalteholz).     When  the  caecum  is  full  the  small  intestine  lies  in  front  of  the  left 


Fig.  912. — The  caecum  and  colon  laid  open 
to  show  the  ileo-caecal  valve. 


1  St.  Louis  Courier  of  Medicine,  October-December,  1902. 


k 


THE    CAECUM  1301 

side  and  lower  portion  of  the  anterior  caecal  wall.  If  the  caecum  is  empty  the 
small  intestine  lies  in  front  of  its  anterior  wall,  and  the  lower  end  is  on  a  higher 
level  than  when  this  portion  of  the  gut  is  full.  In  15  per  cent,  of  cases  the  caecum 
is  covered  by  the  omentum  (Byron  Robinson).  Byron  Robinson  describes  four 
positions  of  the  caecum:  1.  On  the  Psoas  muscle.  2.  To  the  right  of  the  Psoas 
muscle.  3.  In  the  pelvis.  4.  The  potential  position,  in  which  it  lies  free  in  the 
abdominal  cavity.  It  may  be  found  in  various  positions  in  the  abdomen, 
because  of  elongation  of  the  fixation  apparatus.  The  commonest  position  is  on  the 
Psoas  muscle,  and  this  position  is  even  more  common  in  men  than  in  women.  It 
is  twice  as  often  in  the  pelvis  in  women  as  in  men — 20  per  cent,  of  cases  in  the 
former;  10  per  cent,  in  the  latter.  As  a  rule,  it  is  entirely  enveloped  on  all  sides 
by  peritoneum,  but  in  a  certain  number  of  cases  (6  per  cent.,  according  to  Berry) 
the  peritoneal  covering  is  not  complete,  so  that  a  small  portion  of  the  upper  end 
of  the  posterior  surface  is  uncovered  and  connected  to  the  iliac  fascia  by  connec- 
tive tissue.  As  a  matter  of  fact,  there  is  no  real  mesocaecum — meaning  by  the  term 
a  peritoneal  fold  which  holds  the  caecum  to  the  dorsal  wall  of  the  abdomen — except 
when  there  is  failure  in  development.  The  normal  caecum  is  completely  invested 
by  peritoneum  from  the  beginning.  Originally  the  caecum  receives  its  blood  along 
a  single  peritoneal  fold,  the  ileo-caecal  fold,  which  is  a  simple  mesentery.  As 
development  advances,  this  simple  mesentery  becomes  a  double  fold  and  prac- 
tically bloodless,  and  is  replaced  by  two  vascular  folds,  the  meso appendix  to 
the  left  and  the  mesenterico-colicum  to  the  right.  The  mobility  of  the  caecum 
varies.  Very  small  caeca  are  fixed.  In  most  cases  the  caecum  lies  quite  free  in  the 
abdominal  cavity  and  enjoys  a  considerable  amount  of  movement.  Sometimes 
it  is  excessively  mobile,  and  in  such  cases  is  usually  also  of  large  size.  Such 
mobility  is  due  to  a  stretched  fixation  apparatus.  A  very  large  and  mobile 
caecum  may  be  made  to  come  in  contact  with  any  abdominal  viscus  and  may 
enter  any  hernial  sac  on  either  side.  As  a  rule,  when  the  caecum  is  large  and  mobile, 
it  is  found  in  the  pelvis  or  in  the  middle  of  the  abdomen  (Byron  Robinson).  It 
is  to  be  remembered  that  a  mobile  caecum  carrying  with  it  the  appendix  may 
pass  to  almost  any  region  of  the  abdomen.  Sometimes  the  caecum  fails  to  descend 
or  only  descends  a  part  of  the  way  during  development,  the  axial  rotation  of  the 
intestinal  tract  having  been  arrested.  In  such  a  case  it  may  terminate  at  the 
level  of  the  gall-bladder,  and  the  ascending  colon  is  absent.  In  310  adult  males 
Byron  Robinson  found  8  per  cent,  with  undescended  caecum  and  appendix. 
Non-descent  is  found  in  less  than  4  per  cent,  of  adult  females.  A  partbj  descended 
caecum  usually  lies  upon  the  right  kidney. 

The  caecum  varies  in  shape,  but,  according  to  Treves,  in  man  it  may  be  classified 
under  one  of  four  types  (Fig.  913).  In  early  foetal  life  it  is  short,  conical,  and 
broad  at  the  base,  with  its  apex  turned  upward  and  inward  toward  the  ileo-caecal 
junction.  It  then  resembles  the  caecum  of  some  of  the  monkey  tribe,  e.  g.,  Man- 
gabey  monkey.  As  the  foetus  grows  the  caecum  increases  in  length  more  than  in 
breadth,  so  that  it  forms  a  longer  tube  than  in  the  primitive  form  and  without  the 
broad  base,  but  with  the  same  inclination  inward  of  the  apex  toward  the  ileo- 
caecal  junction.  This  form  is  seen  in  others  of  the  monkey  tribe,  e.  g.,  the  spider 
monkey.  As  development  goes  on,  the  lower  part  of  the  tube  ceases  to  grow  and 
the  upper  part  becomes  greatly  increased,  so  that  at  birth  there  is  a  narrow  tube, 
the  vermiform  appendix,  hanging  from  a  conical  projection,  the  caecum.  This  is 
the  infantile  form,  and  as  it  persists  throughout  life,  in  about  2  per  cent,  of 
cases,  it  is  regarded  by  Treves  as  the  first  of  his  four  types  of  human  caeca.  The 
caecum  is  conical  and  the  appendix  rises  from  its  apex.  The  three  longitudinal 
bands  start  from  the  appendix  and  are  equidistant  from  each  other.  In  the  second 
type,  the  conical  caecum  has  become  quadrate  by  the  growing  out  of  a  saccule  on 
either  side  of  the  anterior  longitudinal  band.    These  saccules  are  of  equal  size, 


1302 


THE    ORGANS    OF   DIGESTION 


and  the  appendix  arises  from  between  them,  instead  of  from  the  apex  of  a  cone. 
This  type  is  found  in  about  3  per  cent,  of  cases.  The  third  type  is  the  normal  type 
of  man.  Here  the  two  saccules,  which  in  the  second  type  were  uniform,  have 
grown  at  unequal  rates:  the  right  with  greater  rapidity  than  the  left.  In  conse- 
quence of  this  an  apparently  new  apex  has  been  formed  by  the  growing  downward 
of  the  right  saccule,  and  the  original  apex,  with  the  appendix  attached,  is  pushed 
over  to  the  left  toward  the  ileo-caecal  junction.  The  three  longitudinal  bands  still 
start  from  the  base  of  the  appendix,  but  they  are  now  no  longer  equidistant  from 
each  other,  because  the  right  saccule  has  grown  between  the  anterior  and  postero- 
external bands,  pushing  them  over  to  the  left.  This  type  occurs  in  about  90  per 
cent,  of  cases.    The  fourth  type  is  merely  an  exaggerated  condition  of  the  third; 


Fig.  913. — The  four  types  of  caecum. 

the  right  saccule  is  still  larger,  and  at  the  same  time  the  left  saccule  has  been 
atrophied,  so  that  the  original  apex  of  the  caecum,  with  the  appendix,  is  close  to 
the  ileo-caecal  junction,  and  the  anterior  band  courses  inward  to  the  same  situa- 
tion.    This  type  is  present  in  about  4  per  cent,  of  cases. 

Supports  of  the  Caecum. — According  to  Byron  Robinson,^  the  caecum  is  main- 
tained in  position  by  the  mesocolon  and  a  peritoneal  fold,  the  right  phrenico -colic 
ligament,  which  arises  from  the  hepato-duodenal  and  hepato-renal  ligaments.  It 
receives  support  from  the  connective  tissue  about  vessels  and  nerves,  and 
inconstantly  from  folds  which  fixes  it  in  the  iliac  fossa  and  in  the  region  of  the 
vena  cava. 

1  St.  Louis  Courier  of  Medicine,  October- December,  1902. 


THE   CAECUM  1303 

The  Interior  of  the  Caecum. — In  the  interior  of  the  caecum  are  seen  depressions 
which  correspond  to  the  surface  haustra,  and  semilunar  folds  (plicae  semilunares 
coli)  (Fig.  912),  which  correspond  to  the  transverse  surface  constrictions.  There 
are  three  openings  in  the  caecum:  that  into  the  colon;  that  into  the  ileum,  which 
is  guarded  by  the  ileo-caecal  valve  (p.  1308) ;  and  that  into  the  appendix,  which 
may  be  guarded  by  the  valve  of  Gerlach. 

Pericaecal  Folds  and  Fossae. — See  p.  1262,  and  Figs.  866,  867,  and  868. 

The  Vermiform  Appendix  {processus  vermiformis)  (Figs.  866, 867, 868, 913, 914, 
915,  916,  and  918)  . — The  vermiform  appendix  is  found  only  in  man,  the  higher 
apes,  and  the  wombat,  although  in  certain  rodents  a  somewhat  similar  arrangement 
exists.  In  carnivorous  animals  the  caecum  is  very  slightly  developed;  in  her- 
bivorous animals  (with  a  simple  stomach)  it  is,  as  a  rule,  extremely  large.  It  has 
been  suggested  that  the  vermiform  process  in  man  is  the  degenerated  remains  of  the 
herbivorous  caecum,  which  has  been  replaced  by  the  carnivorous  form.^  The 
vermiform  appendix  is  a  long,  narrow,  worm-shaped,  musculo-membranous  tube, 
which  starts  from  what  was  originally  the  apex  of  the  caecum.  After  development 
has  advanced  the  vermiform  appendix  comes  off,  as  a  rule,  from  the  inner  side  of 
the  posterior  wall  of  the  caecum  that  is  below  and  behind  the  termination  of  the 
ileum.  This  origin  usually  corresponds  to  McBumey's  point,  which  is  in  the 
abdominal  wall,  midway  between  the  umbilicus  and  the  anterior  superior  iliac 
spine  and  which  is  the  usual  seat  of  the  greatest  tenderness  in  appendicitis.  The 
origin  of  the  appendix  varies  with  the  type  of  caecum  present.  These  variations 
are  shown  in  Fig.  913.  In  the  foetal  or  infantile  type  of  appendix  it  arises  from 
the  apex  of  the  caecum;  in  the  second  type  of  caecum  it  arises  between  the  two 
caecal  sacculi ;  in  the  third  type  it  arises  between  a  large  outer  and  a  small  inner  sac- 
culus;  and  on  the  posterior  wall  of  the  caecum,  the  excessive  growth  of  the  anterior 
wall  having  caused  the  appendix  to  originate  posteriorly;  in  the  fourth  type  there  is 
no  internal  sacculus,  and  the  appendix  arises  from  the  posterior  caecal  wall  behind 
the  ileo-caecal  junction  (p.  1302).  The  movable  portion  of  the  appendix  may  be 
met  with  in  different  situations.  "It  may  pass  upward  and  in  front  of  the  caecum 
and  colon,  upward  and  behind  the  caecum,  and  even  behind  the  colon  between  the 
two  layers  of  the  mesocolon ;  upward  and  to  the  inner  side,  or  upward  and  to  the  outer 
side  of  the  caecum  and  colon.  It  may  pass  to  the  left  under  the  ileum  and  mesentery, 
upward  and  to  the  left  or  downward  and  to  the  left  into  the  true  pelvis.  It  may  pass 
directly  downward  under  the  caecum.  It  may  pass  to  the  right  in  front  of  or  back 
of  the  caecum.  It  may  occupy  any  one  of  the  caecal  fossae  (p.  1262) ,  but  most  often 
enters  the  ileo-caecal  fossa.  In  unusual  cases  the  appendix  is  found  in  the  inguinal 
canal  as  a  portion  of  or  the  sole  contents  of  a  hernia;  adherent  to  the  parietal  peri- 
toneum in  front  of  or  to  the  side  of  the  caecum,  or  "behind  the  peritoneum,  below 
the  caecum,  adherent  to  the  under  surface  of  the  caecum  and  in  contact  with  its 
muscular  wall  and  covered  by  its  peritoneal  coat."^  When  the  caecum  is  mobile 
the  appendix  may  be  found  almost  anywhere  within  the  abdomen.  When  the 
caecum  is  undescended  the  appendix,  of  course,  shares  in  the  failure  to  descend, 
and  may  be  below  the  gall-bladrler  or  in  front  of  the  right  kidney,  and  may  pass 
in  several  directions:  upward  behind  the  caecum;  to  the  left  behind  the  ileum  and 
mesentery;  or  downward  and  inward  into  the  true  pelvis.  It  varies  from  one-half 
an  inch  to  nine  inches  in  length,  its  average  being  about  three  inches.  Its  diameter 
is  from  one-eighth  inch  to  one-quarter  inch.  The  operating  surgeon  may  occa- 
sionally fail  to  find  an  appendix  buried  in  one  of  the  caecal  fossae,  and  may  con- 
clude that  the  diverticulum  is  absent.  As  a  matter  of  fact,  unless  the  colon  is  also 
absent,  it  seems  doubtful  if  the  appendix  is  ever  absent,  except  as  a  result  of  dis- 

1  Cunningham's  Text-book  of  Anatomy. 
*  Deaver's  Surgical  Anatomy. 


1304  THE    ORGANS    OF   DIGESTION 

ease.  This  view  is  maintained  by  Lockwood  and  RoUeston/  by  Kelynack,^  and 
others.  It  is  asserted  by  some  that  the  appendix  is  absent  five  times  out  of  10,000 
autopsies.  It  is  retained  in  position  by  a  fold  of  peritoneum  derived  from  the  left 
leaf  of  the  mesentery,  which  forms  a  mesentery  for  it,  and  is  called  the  meso- 
appendix  (p.  1260,  and  Figs.  866,  867,  and  868).  In  color  the  healthy  appendix  is 
yellowish-pink,  is  soft  and  smooth  to  the  touch,  and  the  "subperitoneal  vessels 
are  barely  visible."'  The  canal  of  the  appendix  is  small  and  extends  throughout 
the  whole  length  of  the  tube.  The  walls  of  the  healthy  diverticulum  are  thick, 
and  the  diameter  of  the  lumen  is  usually  trivial  as  compared  with  the  diameter  of 
the  appendix  itself.  The  lumen  of  the  appendix  communicates  with  the  caecum 
by  an  orifice  which  is  placed  Vjelow  and  behind  the  ileo-caecal  opening  (Fig.  919). 
It  is  sometimes  guarded  above  and  to  the  left  side  by  a  semilunar  fold  of  mucous 
membrane,  the  valve  of  Gerlach  (valvula  processus  vermiformis) .  The  valve  is 
inconstant,  and  is  never  perfect.  It  is  stated  that  the  appendix  tends  to  undergo 
obliteration  as  an  involution  change  in  a  functionless  organ.  The  lumen  rarely 
contains  foreign  bodies  after  death,  but  often  contains  fecal  concretions.  Certain 
it  is  that  in  25  per  cent,  of  necropsies  upon  adults  or  elderly  people  the  lumen 
is  found  to  be  partially  or  completely  occluded. 


LEOCOLIC  ARTERY 


ANTERIOR  ILEO- 
CAECAL  ARTERY 


ANTERIOR  CAECAL 
ARTERY 


APPENDICULAR 
ARTERY 

APPENDIX 
VERMIFORMIS 

Fig.  914. — Arteries  of  the  caecum  and  of  the  appendix  vermiformis  and  of  the  terminal  portion  of  the  ileum. 

(Poirier  and  Charpy.) 

Structure  of  the  Appendix  (Fig.  917). — The  coats  of  the  appendix  correspond  to 
the  coats  of  the  bowel:  serous,  muscular  (the  outer  layer  of  longitudinal,  the  inner 
of  circular  fibres),  submucous,  and  mucous.  In  the  deepest  portion  of  the  mucous 
coat,  against  the  submucous  coat,  are  the  unstriated  fibres  constituting  the  mus- 
cularis  mucosae.  The  muscularis  mucosae  is  often  present  in  some  regions  and 
absent  in  others.     It  may  not  be  present  at  all. 

The  Outer  or  Serous  Coat  usually  completely  covers  the  appendix  and  has  a 
definite  mesentery,  the  mesoappendix  (p.  1260).  Occasionally  the  base  of  the 
appendix  is  not  surrounded  by  peritoneum,  but  is  extraperitoneal,  lying  in  the 
retroperitoneal  tissue.  The  appendiculo -ovarian  ligament  of  Clado  is  occasionally 
present  in  females.  It  is  a  prolongation  of  the  mesoappendix  which  passes  into 
the  broad  ligament,  and  is  extremely  thin,  and  its  fine  connective-tissue  fibres 
send  prolongations  into  the  longitudinal  muscle-fibres  of  the  appendix.  Ix)ck- 
wood  points  out  that  the  subperitoneal  tissue  of  the  meso-appendix  and  ''the 
blood-vessels,  nerves,  and  lymphatics  which  it  contains  are  very  intimately  con- 
nected with  the  submucosa.  This  union  takes  place  at  certain  large  gaps  in  the 
muscular  coats.     These  gaps  serve  for  the  transmission  of  blood-vessels,  nerves, 

1  Journal  of  Anatomy  and  PhysioloKv,  1891.  vol.  xxvi. 

"  A  Contribution  to  the  Pathology  of  the  Vermiform  Appendix. 

"  Lockwood  on  Appendicitis. 


THE    CAECUM 


1305 


and  lymphatics  from  the  mesoappendix  to  the  mucous  coat.  They  are  situated 
at  the  junction  of  the  mesoappendix  with  the  appendix."^ 

The  Longitudinal  Muscular  Layer  is  thin  and  irregularly  distributed,  and  in  certain 
regions  may  be  excessively  thin  or  actually  absent,  and  between  the  fibres  are  the 
blood-vessels,  nerves,  and  lymphatics  passing  from  the  subperitoneal  tissue  to  the 
mucous  coat. 

The  Circular  Fibres  are  much  better  developed  than  the  longitudinal  fibres,  and, 
according  to  Lockwood,  the  layer  is  1  mm.  thick.  Ijarge  gaps  are  found  here  and 
there  for  the  passage  of  vessels,  lymphatics,  and  nerves  to  and  from  the  meso- 
appendix and  the  mucous  membrane,  and  a  few  vessels  pierce  the  fibres  at 
other  points  (Lockwood). 

The  Submucous  Coat  varies  greatly  in  thickness.  It  contains  blood-vessels, 
nerves,  and  lymphatics,  and  some  lymphoid  follicles. 

The  Mucous  Membrane  (Fig.  915)  is  covered  by  columnar 
epithelial  cells  and  contains  numerous  solitary  lymph- 
follicles,  some  glands  of  Lieberkiihn,  surrounded  by 
lymphoid  tissue,  blood-vessels,  lymphatics,  and  nerves. 

The  muscularis  mucosae  may  be  absent,  may  be  scanty 
or  may  be  distinct.  The  lymphoid  follicles  are  visible  to 
the  naked  eye  (Fig.  915).  Some  of  them  are  in  the  sub- 
mucosa,  some  of  them  chiefly  in  the  mucosa,  the  bases  of 
the  latter,  however,  being  in  the  submucosa.  Lockwood 
estimates  that  an  appendix  three  and  a  half  inches  in 
length  contains  from  150  to  200  follicles. 

Blood-vessels  of  the  Caecum  and  Appendix  (Figs.  914, 916, 
932,  and  933). — The  ileo-colic  artery  in  the  ileo-colic  angle 
gives  off  the  anterior  and  posterior  ileo-caecal  arteries.  The 
anterior  ileo-caecal  runs  down  over  the  front  of  the  ileum 
and  supplies  the  ileum,  and  sends  off  a  terminal  branch, 
the  anterior  caecal  artery, which  supplies  the  anterior  surface 
of  the  caecum  and  of  a  portion  of  the  ascending  colon,  and 
to  the  upper  and  lower  margins  of  the  ileo-caecal  valve.  It 
sends  no  branch  to  the  appendix.  The  arteries  of  the  ap- 
pendix come  from  the  posterior  ileo-caecal  artery.  This 
vessel,  after  arising  from  the  ileo-colic  artery,  passes  back 

of  the  termination  of  the  ileum  and  gives  branches  to  the  face'of  the~vermiform"appen- 
lower  end  of  the  ileum  back  of  a  portion  of  the  ascending  ^^'^^    (B«°'*'»y  ^^^  ^'^^^-^ 
colon  and  to  the  lower  margin  of  the  ileo-caecal  valve, 

where  they  anastomose  with  the  valvular  branches  from  the  anterior  ileo-caecal 
(Lockwood).  From  the  posterior  ileo-caecal  comes  the  posterior  caecal  branch, 
which  passes  over  the  posterior  and  inner  portion  of  the  caecum  near  the  base 
of  the  appendix  and  sends  one  or  two  branches  to  the  appendix.  The  chief  blood- 
supply  of  the  appendix  is  the  appendicular  artery,  which  comes  off  the  beginning 
of  the  posterior  ileo-caecal  or,  occasionally,  from  the  termination  of  the  ileo-colic. 
If  there  is  a  distinct  mesoappendix  the  largest  branch  of  the  artery  passes  along 
its  free  edge.  If  the  mesoappendix  is  absent  or  rudimentary  the  artery  usually 
lies  upon  the  appendix  from  base  to  tip  beneath  the  peritoneum. 

Lockwood  points  out  that  the  appendicular  artery  as  it  enters  the  mesoappen- 
dix divides  into  three  branches.  The  largest  branch  runs  along  the  free  edge, 
and  from  this  the  tip  of  the  appendix  obtains  its  blood-supply;  "the  other  two 
reach  the  appendix  at  intervals  of  half  an  inch."^  When  the  branches  reach 
the  appendix  they  divide  and  pass  around  it  in  the  subperitoneal  coat  and  send 


*  Appendicitis,  its  Pathology  and  Surgery.     By  Charles  Barrett  Lockwood. 


2  Ibid. 


1306 


THE    ORGANS    OF  DIGESTION 


branches  through  the  muscular  gaps  to  enter  and  pass  through  the  submucous 
coat. 

In  females  there  is  occasionally  some  additional  blood-supply  through  a  branch 
of  the  ovarian  artery  in  the  appendiculo-ovarian  ligament. 

The  veins  of  the  appendix  are  numerous,  thin  walled,  and  large.  Veins  from 
the  submucous  plexus  pass  through  the  muscular  gaps  and  enter  the  subperi- 


ILEOCOLIC  ARTERY 
AND  VEIN 


POSTERIOR 

ILEOCAECAL 

ARTERY 

AND    VEIN 

ILEAC   BRANCH 


APPENDICULAR 

ARTERY  AND 

VEIN 


ASCENDINQ 
COLON 


Fig.  916. — Arteries  and  veins  of  the  caecum  and  vermiform  appendix  seen  from  behind.     (Poirier  and  Charpy.) 

toneal  plexus.  Veins  from  the  subperitoneal  plexus  pass  into  veins  in  the  meso- 
appendix  which  correspond  to  but  do  not  really  accompany  the  arteries  (liOck- 
wood).  Most  of  the  veins  of  the  mesoappendix  pass  to  the  posterior  ileo-caecal 
vein,  though  some  pass  directly  to  the  caecal  vein.  These  veins  are  radicles  of 
the  portal  system. 


EPITHELIUM 


Fig.  917. — Transverse  section  of  the  vermiform  appendix  of  man.     (Kolliker.) 

Lymphatic  System  of  the  Caecum  and  Appendix  (Fig.  918). — Surrounding  the  base 
of  each  lymph-foUicle  in  the  submucous  tissue  of  the  appendix  is  a  lymph-space, 
which  Lockwood  calls  the  follicular  or  basilar  lymph-sinus.  This  sinus  communi- 
cates with  the  lymphatics  of  the  submucous  coat,  "which  again  communicate 
freely  through  the  hiatus  muscularis  with  those  of  the  peritoneum  and  of  the 
mesoappendix."^   The  collecting  trunks  from  the  caecum  and  appendix  follow  the 


^  Appendicitis,  its  Patholoey  and  Surgery.    By  Charles  Barrett  Lockwood. 


THE    CAECUM 


1307 


blood-vessels  (Fig.  918).     The  anterior  collecting  trunks  of  the  caecum   pass 
through  several  small  glands  in  the  anterior  ileo-caecal  fold,  and  terminate  in 


ILEOCAECAL 


ANTERIOR 

LYMPHATICS 

OFCAECUM 


GLAND  OF 
APPENDIX 


Fig.  918. — Lymphatics  of  the  caecum  and  appendix,  anterior  view.     (Poirier  and  Charpy.) 


glands  along  the  ileo-colic  artery  (Fig.  918).     The  posterior  collecting  trunks 
pass  through  some  small  glands  and  terminate  in  glands  along  the  ileo-colic 
artery.    The  appendicular  collecting  trunks  enter  the  mesoappendix.   There  are 
usually  four  of  them,  sometimes  five.     Some 
of  them  traverse  a  gland  constantly  present 
at  the  ileo-caecal  angle  (Clado).  Another  gland 
is  constant.     It  is  situated  beneath  the  ileo- 
colic fossa  (Lockwood  and  RoUeston).     The 


ORIFICE  or\ 

APPENDIX 


Fig.  919. 


-Ileo-caecal  valve  of  the  circular  type. 
(Poirier.) 


Fig.  920. — Vertical  section  through  the  caecum 
and  ileo-caecal  valve.     (Gegenbauer.) 


editor  subscribes  to  Lockwood's  statement  that  in  appendicitis  there  is  often  a 
chain  of  inflamed  glands  along  the  inner  side  of  the  ascending  colon  behind  the 


1308 


THE    ORGANS    OF    DIGESTION 


ascending  mesocolon.     Hence  this  is  one  road  taken  by  the  lymphatics  of  the 
appendix.     The  others  pass  to  the  mesenteric  glands. 

The  Ileo-caeeal  Valve  or  the  Valve  of  Bauhin  (valvula  coli)  (Figs.  919, 920, 
921,  and  922). — The  lower  end  of  the  ileum  terminates  by  opening  into  the  inner 
and  back  part  of  the  large  intestine,  at  the  point  of  junction  of  the  caecum  with  the 
•  colon.  The  opening  is  guarded  by  a  valve,  consisting  of  two  semilunar  segments, 
an  upper  or  colic  segment  {labium  superius)  and  a  lower  or  caecal  segment  (labimn 
inferius),  which  project  into  the  lumen  of  the  large  intestine.  The  upper  one, 
nearly  horizontal  in  direction,  is  attached  by  its  convex  border  to  the  point  of 
junction  of  the  ileum  with  the  colon;  the  lower  segment,  which  is  more  concave 
and  longer,  is  attached  to  the  point  of  junction  of  the  ileum  with  the  caecum. 
At  each  end  of  the  aperture  the  two  segments  of  the  valve  coalesce,  and  are  con- 
tinued as  a  narrow  membranous  ridge  around  the  canal  for  a  short  distance.  Each 
ridge  is  known  as  the  retinaculum  or  frenulum  of  the  valve  {frenulum  valvulae  coli). 
The  left  or  anterior  end  of  the  aperture  is  rounded ;  the  right  or  posterior  is  narrow 


Fig.  921. — Caecum  and  vermiform  appendix.  1, 
ileum  ;  2,  orifice  of  valve  ;  3,  inferior  segment  ; 
4,  superior  segment  ;  5,  long  muscular  fibres  from 
ileum  ;  6,  cul-de-sac  of  caecum  ;  7,  appendix  ;  8, 
posterior  taenia ;  9,  internal  taenia ;  10,  anterior 
taenia;  11,  sacculus.     (Sappey.) 


Fig.  922. — Ileo-caecal  valve.  1,  edge  of  caecum  ;  2, 
orifice  of  valve  ;  3,  inferior  segment  ;  4,  superior  seg- 
ment ;  5  and  6,  fraena  ;  7,  appendix  ;  8,  mouth ;  9, 
semilunar  fold  ;  10,  posterior  taenia  ;  11,  12,  12,  ante- 
rior taenia  ;  13,  internal  taenia.      (Sappey.) 


and  pointed.  In  the  formation  of  the  valve  the  termination  of  the  small  intestine 
invaginates  for  a  short  distance  into  the  lumen  of  the  large  intestine  (Fig.  920), 
the  invaginated  portion  of  the  wall  of  the  small  intestine  uniting  with  a  corre- 
sponding portion  of  the  wall  of  the  large  intestine. 

Each  segment  of  the  valve  is  formed  by  a  reduplication  of  the  mucous  mem- 
brane and  of  the  circular  muscular  fibres  of  the  intestine,  the  longitudinal  fibres 
and  peritoneum  being  continued  uninterruptedly  across  from  one  portion  of  the 
intestine  to  the  other.  When  the  longitudinal  fibres  and  peritoneum  are  divided 
or  removed,  the  ileum  may  be  drawn  outward,  and  all  traces  of  the  valve  will 
be  lost,  the  ileum  appearing  to  open  into  the  large  intestine  by  a  funnel-shaped 
orifice  of  large  size. 

The  surface  of  each  segment  of  the  valve  directed  toward  the  ileum  possesses 
villi,  and  presents  the  characteristic  structure  of  the  mucous  membrane  of  the 
small  intestine;  while  that  turned  toward  the  large  intestine  is  destitute  of  villi, 
and  marked  with  the  orifices  of  the  numerous  tubular  glands  peculiar  to  the 
mucous  membrane  of  the  large  intestine.    These  differences  in  structure  continue 


THE    COLON  1309 

as  far  as  the  free  margins  of  the  valve.  When  the  caecum  is  distended  it  is  sup- 
posed that  the  margins  of  the  opening  are  approximated  so  as  to  prevent  reflux 
into  the  ileum.  It  is  known,  however,  that  a  very  large  enema  which  distends 
the  caecum  and  colon  may  in  part  enter  the  ileum,  being  driven  there  by  waves 
of  reversed  peristalsis.  The  valve  resists,  but  a  certain  amount  of  pressure  over- 
comes it.  Some  believe  that  the  so-called  ileo-caecal  valve  is  not  a  valve,  but  a 
distinct  sphincter.  This  has  been  demonstrated  to  be  true  in  cats  and  dogs,  but 
lacks  demonstration  in  man  (p.  1323). 

The  Colon. 

The  colon  is  divided  into  four  parts — the  ascending,  transverse  and  descending 
colon,  and  the  sigmoid  flexure. 

The  Ascending  Colon  {colon  ascendens). — The  ascending  colon  is  smaller  than 
the  caecum,  with  which  it  is  continuous.  It  passes  upward,  from  its  commence- 
ment at  the  frenula  of  the  caecum,  opposite  the  ileo-caecal  valve,  to  the  under  sur- 
face of  the  right  lobe  of  the  liver,  on  the  right  of  the  gall-bladder,  where  it  is  lodged 
in  a  shallow  depression  on  the  liver,  the  impressio  colica;  here  it  bends  abruptly 
inward  to  the  left,  forming  the  hepatic  flexure  {flexura  coli  dextra).  It  is  retained 
in  contact  with  the  posterior  wall  of  the  abdomen  by  the  peritoneum,  which  covers 
its  anterior  surface  and  sides,  its  posterior  surface  being  connected  by  loose  areolar 
tissue  with  the  Quadratus  lumborum  and  Transversalis  muscles,  and  with  the 
front  of  the  lower  and  outer  part  of  the  right  kidney  (Fig.  923).  Sometimes  the 
peritoneum  almost  completely  invests  it,  and  forms  a  distinct  but  short  meso- 
colon* (p.  1259).  It  is  in  relation,  in  front,  with  the  convolutions  of  the  ileum  and 
the  abdominal  parietes. 

The  Transverse  Colon  (colon  transversum)  (Fig.  858). — The  transverse  colon, 
the  longest  part  of  the  large  intestine,  passes  transversely  from  right  to  left  across 
the  abdomen,  opposite  the  confines  of  the  epigastric  and  umbilical  zones,  into  the 
left  hypochondriac  region,  where  it  curves  downward  beneath  the  lower  end  of 
the  spleen,  forming  the  splenic  flexure  (flexura  coli  sinistra).  In  its  course  the 
transverse  colon  describes  an  arch,  the  concavity  of  which  is  directed  backward 
toward  the  vertebral  column  and  a  little  upward;  hence  the  name  transverse  arch 
of  the  colon.  This  is  the  most  movable  part  of  the  colon,  being  almost  completely 
invested  by  peritoneum,  and  connected  to  the  spine  behind  by  a  large  and  wide 
duplicature  of  that  membrane,  the  transverse  mesocolon  (Fig.  863).  The  trans- 
verse colon  is  in  relation,  by  its  upper  surface  with  the  liver  and  gall-bladder,  the 
great  curvature  of  the  stomach,  and  the  lower  end  of  the  spleen;  by  its  under  sur- 
face, with  the  small  intestines;  by  its  anterior  surface,  with  the  anterior  layers 
of  the  great  omentum  and  the  abdominal  parietes;  its  posterior  surface  on  the 
right  side  is  in  relation  with  the  second  portion  of  the  duodenum,  and  on  the  left 
side  is  in  contact  with  some  of  the  convolutions  of  the  jejunum  and  ileum. 

The  Descending  Colon  (colon  descendens). — The  descending  colon  passes 
downward  through  the  left  hypochondriac  and  lumbar  regions  along  the  outer 
border  of  the  left  kidney.  At  the  lower  end  of  the  kidney  it  turns  inward  toward 
the  outer  border  of  the  Psoas  muscle,  along  which  it  descends  to  the  crest  of  the 
ilium,  where  it  terminates  in  the  sigmoid  flexure.  At  its  commencement  it  is  con- 
nected with  the  Diaphragm  by  a  fold  of  peritoneum,  the  phreno-colic  ligament 
(see  p.  1259).     It  is  retained  in  position  by  the  peritoneum,  which  covers  its 

'  Treves  states  that  after  a  careful  examination  of  one  hundred  subjects,  he  found  that  in  fifty-two  there  wa» 
neither  an  ascending  nor  a  descending  mesocolon.  In  twenty-two  there  was  a  descending  mesocolon,  but  no 
trace  of  a  corresponding  fold  on  the  other  side.  In  fourteen  sub.iects  there  was  a  mesocolon  to  both  the  ascend- 
ing and  the  descending  segments  of  the  bowel  ;  while  in  the  remaining  twelve  there  was  an  ascending  mesocolon, 
but  no  corresponding  fold  on  the  left  side.  It  follows,  therefore,  that  in  performing  lumbar  colostomy  a  meso- 
colon may  be  expected  on  the  left  side  in  36  per  cent,  of  all  ca.ses,  and  on  the  right  in  26  per  cent.  (The  Anat- 
omy of  the  Intestinal  Canal  and  Peritoneum  in  Man,  1885,  p.  55.) — Ed.  of  15th  English  edition. 


1310 


THE    ORGANS    OF   DIGESTION 


anterior  surface  and  sides,  its  posterior  surface  being  connected  by  areolar  tissue 
with  the  outer  border  of  the  left  kidney,  and  the  Quadratus  lumborum  and 


Posterior 

Middle  lamella  of 

lamella  of  lumbai  fascia 

.   ,    .             lumbal  / 

Antenor         f^^^^^  /_ 
lamella  of 
lumbar  fascia. 


QUADRATUS    LUMBORUM. 


LATISSIMUS 
DORSI. 


Fig.  923. — Diagram  of  the  relations  of  the  large  intestine  and  kidneys,  from  behind. 


Transversalis  muscles  (Fig.  863).  It  is  smaller  in  calibre  and  more  deeply  placed 
than  the  ascending  colon,  and  is  more  frequently  covered  with  peritoneum  on  its 
posterior  surface  than  the  ascending  colon  (Treves). 


THE    COLON 


1311 


DESCENDING  COLON 


The  Sigmoid  Flexure,  Pelvic  Colon  or  Sigmoid  Colon  {colon  sigmoideum) 
(Figs,  924,  925,  926,  and  927)  is  the  narrowest  part  of  the  colon;  it  is  situated  in 
the  left  iliac  fossa,  commencing  from  the  termina-  ,       , 

tion  of  the  descending  colon,  at  the  margin  of  the 
crest  of  the  ilium,  and  then  forming  a  loop,  which 
varies  in  length  and  position,  and  which  terminates 
in  the  rectum  at  the  level  of  the  attachment  of  the 
mesentery  upon  the  front  of  the  third  sacral  verte- 
bra. It  passes  downward  about  two  inches  parallel 
to  the  outer  border  of  the  Psoas  muscle,  then  taking 
a  transverse  direction  enters  the  cavity  of  the  pelvis, 
crosses  this  cavity  from  left  to  right  and  a  little 
upward  to  the  lower  margin  of  the  right  iliac  fossa; 
"from  this  point  it  passes  downward,  backward, 
and  inward  along  the  anterior  surface  of  the  sacrum 
to  its  junction  with  the  rectum."^  It  is  surrounded 
with  the  peritoneum  and  is  attached  to  the  poste-  ^'''semiiTagr^riTcl^^cSst^^^ 


Fig.  925. — Sigmoid  colon  and  rectum,  front  view.     The  broken  lines  indicate  the  situation  of  the  concealed  part 
of  the  sigmoid  colon.     The  small  intestine  is  drawn  away,  and  the  anus  is  turned  forward.    (Testut.) 

rior  abdominal  wall  by  the  mesosigmoid,  a  continuation  of  the  mesocolon,  but 
which  greatly  exceeds  the  latter  in  length,  hence  the  sigmoid  is  the  most  mobile 


^  Tuttle,  Diseases  of  the  Anus,  Rectum,  and  Pehdc  Colon. 


1312 


THE    ORGANS    OF  DIGESTION 


portion  of  the  large  intestine.  Tuttle  divides  the  sigmoid  into  four  portions.  The 
first  or  vertical  portion;  the  second  or  transverse  portion;  the  third  portion,  which  is  a 
loop  and  is  concave  upward  if  the  sigmoid  occupies  the  pelvis,  and  is  concave  down- 
ward if  it  occupies  the  abdomen;  the  fourth  portion,  which  is  curved  irregularly  in 
the  hollow  of  the  sacrum,  and  which  joins  the  rectum  as  often  from  the  right  as 
from  the  left.  When  the  sigmoid  is  lifted  up  and  to  the  right  and  the  mesosigmoid 
is  put  slightly  upon  the  stretch,  an  opening  is  seen  at  the  parietal  border  of  the  left 
layer  of  the  mesosigmoid.  This  opening  leads  into  a  cul-de-sac,  the  intersigmoid 
fossa.  When  the  sigmoid  is  empty  most  of  it  falls  into  the  recto-vesical  or  recto- 
vaginal space  (Fig.  925).  When  distended  it  mounts  up  into  the  abdomen, reaching 
to  or  even  above  the  umbilicus.  The  sigmoid  flexure  is  in  relation  in  front  with 
the  small  intestine  and  abdominal  parietes.  The  sigmoid  mesocolon  is  attached 
to  a  line  running  downward  and  inward  from  the  crest  of  the  ilium,  across  the 
Psoas  muscle  (Fig.  863). 

The  Rectum  (Intestinum  Rectum)  (Figs.  924,  925,  926,  927,  928,  929). 

The  rectum  is  the  terminal  part  of  the  large  intestine,  and  extends  from  the 
termination  of  the  sigmoid  flexure  to  the  level  of  the  semilunar  valves  of  Mor- 


URETHRA 

PROSTATE 

GLAND 

TRANSVERSE 

PERrN>EI 

MUSCLE 


EXTERNAL 

SPHINCTER 

MUSCLE 


Fig.  926. — Sagittal  section  in  the  median  line  of  the  pelvis.      (Poirier  and  Charpy.) 


gagni.  The  sigmoid  flexure  terminates  at  the  level  of  the  attachment  of  the 
mesentery  in  front  of  the  third  sacral  vertebra.  This  definition  is  practical  and 
useful.  It  was  suggested  by  Sir  Frederick  Treves.  "  It  gives  to  the  organ 
definite  limits;  it  separates  the  mobile  from  the  immobile  portion  of  the  gut;  it 
marks  the  line  where  the  course  of  the  blood -supply  changes;  it  indicates  the 


THE   RECTUM 


1313 


point  where  the  three  longitudinal  muscular  bands  of  the  colon  spread  out  and 
become  more  or  less  equally  distributed  around  the  gut;  and,  finally,  it  marks  a 
point  at  which  there  is  always  a  decided  narrowing  in  cahbre,  indicating  the 
juncture  of  the  rectum  with  the  pelvic  colon."^  The  old  division  added  to  this 
the  so-called  first  part  of  the  rectum,  which  we  consider  as  part  of  the  sigmoid  colon. 
The  rectum  is  divided  into  two  portions,  a  superior  and  an  inferior.  The  supe- 
rior or  sacrococcygeal  portion  of  the  rectum  (flexura  sacralis)  curves  downward 
with  the  concavity  forward  and  upward  in  front  of  the  sacrum  and  coccyx,  and 
is  continued  as  far  as  the  apex  of  the  prostate  gland,  about  an  inch  in  front  of 
the  tip  of  the  coccyx.  The  inferior  or  prostatic  portion  (flexura  perinealis)  begins 
at  this  point.  The  bowel  is  directed  downward  and  backward,  being  convex  in 
front,  and  terminates  at  the  beginning  of  the  anus  at  the  level  of  the  semilunar 
valves  of  Morgagni.  The  inferior  or  prostatic  portion  of  the  rectum  is  described 
by  Symington  as  the  anal  canal. 


RECTAL  FOLD 


CUL-DE-SAC_^ 
OF  DOUGLAS     W\ 


RECTO- 
VAGINAL 
SEPTUM 


,/    VESICO-UTEHINE 
CUL-DE-SAC 


Fig.  927.— -Median  sagittal  section  of  tlie  female  pelvis.      (Luschka.) 

Curves  of  the  Rectum. — It  will  be  seen,  therefore,  that  the  rectum  presents  two 
antero-posterior  curves:  the  first,  with  its  convexity  backward,  is  due  to  the  con- 
formation of  the  sacro-coccygeal  column,  and  represents  the  arc  of  a  circle,  the 
centre  of  which  is  opposite  the  third  sacral  vertebra.  The  lower  one  has  its 
convexity  forward,  and  is  angular.  Its  centre  corresponds  to  a  line  drawn 
between  the  anterior  parts  of  the  ischial  tuberosities.  Two  lateral  curves  are  also 
described:  the  one  to  the  right,  opposite  the  junction  of  the  third  and  fourth  sacral 
vertebrae;  the  other  to  the  left,  opposite  the  sacro-coccygeal  articulation.  They 
are  of  little  importance. 

The  adult  rectum  as  here  described  has  a  length  of  from  four  to  six  inches  in  men, 
and  from  three  and  five-eighths  to  five  and  one-eighth  inches  in  women.  Accord- 
ing to  Tuttle  the  length  of  the  rectum  depends  to  some  degree  on  the  size  of  the 


1  A  Treatise  on  Diseases  of  the  Anus,  Rectum,  and  Pelvic  Colon.    By  James  P.  Tuttle. 

83 


1314 


THE    0BGAN8    OF   DIGESTION 


Fig.  928. — Diagram  of  rectum,  showing  Hous- 
ton's valves  in  the  interior.     (Cunningham.) 


subject,  and  is  somewhat  greater  in  the  old  than  in  the  young.  The  prostatic  portion 
is  the  narrowest  portion  of  the  rectum.  The  widest  part  of  the  rectum  is  the  ampulla 
recti  just  above  the  anal  canal  (Figs.  926  and  927).  The  prostatic  portion  has  no 
peritoneal  investment  whatever  and  includes  the  lower  two  inches  of  the  superior 
portion  of  the  rectum.  When  the  rectum  is  empty  it  is  a  mere  slit,  the  anterior  and 
posterior  walls  being  in  contact.  When  distended  it  is  "irregularly  cylindrical" 
(Tuttle).  At  and  above  the  level  of  the  third  sacral  vertebra  the  gut  is  entirely  sur- 
rounded by  peritoneum,  and  there  is  a  mesosigmoid.  This  is  the  mesorectum  of 
those  who  describe  the  lower  pelvic  colon  as  the  first  part  of  the  rectum.  At  the  level 

of  the  third  sacral  vertebra  the  true  rectum 
begins,  and  the  true  rectum  has  no  meso- 
rectum. The  rectum  is  covered  in  front  and 
laterally  by  peritoneum  at  its  upper  part  ; 
gradually  the  peritoneum  leaves  its  sides, 
and  about  an  inch  above  the  prostate  is  re- 
flected from  the  anterior  surface  of  the  bowel 
on  to  the  posterior  wall  of  the  bladder  in 
the  male,  and  the  upper  fifth  of  the  posterior 
wall  of  the  vagina  in  the  female,  forming 
the  recto-vesical  or  recto-vaginal  pouche  {ex- 
cavatio  reciovesicalis  and  excavatio  rectoute- 
rina),  as  the  case  may  be  (Fig.  853).  The 
balance  of  the  rectum  has  no  peritoneal  cov- 
ering. The  level  at  which  the  peritoneum 
leaves  the  anterior  wall  of  the  rectum  to  be 
reflected  on  to  the  viscus  in  front  of  it  is  of 
considerable  importance  from  a  surgical 
point  of  view,  in  con1i,ection  with  removal  of  the  lower  part  of  the  rectum.  It  is 
higher  in  the  male  than  in  the  female.  In  the  former  the  height  of  the  recto- 
vesical pouch  is  about  three  inches;  that  is  to  say,  the  height  to  which  an  ordinary 
index  finger  can  reach  from  the  anus.  In  the  female  the  height  of  the  recto- 
vaginal pouch  is  about  two  and  a  quarter  inches  from  the  anal  orifice. 

The  upper  or  sacro-coccygeal  portion  of  the  rectum  is  in  relation,  in  front,  in 
the  male,  with  the  recto-vesical  pouch,  the  triangular  portion  of  the  base  of  the 
bladder,  the  vesiculae  seminales,  and  vasa  deferentia,  and  more  anteriorly  with 
the  under  surface  of  the  prostate.  In  the  female,  with  the  posterior  wall  of  the 
vagina  below,  and  the  recto-vaginal  pouch  above,  in  which  are  some  convolutions 
of  the  small  intestine  (Fig.  927).  To  the  sides  below  the  peritoneal  reflections, 
the  rectum  is  surrounded  by  cellular  tissue  in  which  on  each  side  lie  the  lateral 
sacral  artery  and  the  bifurcated  hypogastric  plexus.  This  portion  of  the  rectum  is 
separated  from  the  sacrum  and  coccyx  by  an  interval,  the  retro-rectal  space,  which 
is  filled  with  cellular  tissue.  The  superior  portion  of  the  distended  rectum  is  in  con- 
tact posteriorly  and  on  each  side  with  the  sacral  plexus,  ganglia  of  the  sympathetic, 
and  the  fascial  origin  of  the  pyramidalis  muscle  (Tuttle).  The  lower  or  prostatic 
portion  in  men  is  in  relation  anteriorly  with  the  prostate  gland  and  the  membranous 
urethra;  in  women  with  the  posterior  wall  of  the  vagina.  The  lower  end  of  the 
rectum  takes  a  backward  turn,  and  the  uro-genital  organs  turn  forward;  the  inter- 
vening space  is  called  the  perineum.  In  the  female,  the  fibro-fatty  and  muscular 
tissue  which  occupies  this  space  is  called  the  perineal  body.  The  prostatic  portion 
of  the  rectum  is  invested  by  the  Internal  sphincter,  supported  by  the  Levatores 
ani  muscles,  and  surrounded  at  its  termination  by  the  External  sphincter;  in  the 
empty  condition  it  presents  the  appearance  of  a  longitudinal  slit.  Posteriorly 
the  lower  part  of  the  rectum  is  in  contact  with  cellular  tissue,  which  separates  it 
from  the  coccygeal  gland  and  the  coccyx. 


THE   RECTUM 


1315 


Supports  of  the  Rectum. — The  rectum  as  it  has  been  described  in  these  pages  is  a 
fixed  tube.  The  upper  portion  of  the  rectum  is  supported  by  "the  inferior  mesen- 
teric arteries  and  the  fibrous  sheaths  which  surround  them"  (Tuttle);  by  the  peri- 
toneal folds  which  attach  it  to  the  sacrum ;  and  by  the  peritoneal  folds  which  pass 
in  front  to  the  bladder  (plicae  redovesicales) ,  or  to  the  uterus  (plicae  rectouterinae) , 
and  laterally  to  the  pelvis.  The  middle  of  the  rectum  receives  some  support 
from  the  lateral  sacral  arteries  and  their  fibrous  sheaths.  The  lower  portion  of  the 
rectum  is  supported  by  the  Levator  ani,  External  sphincter,  and  Recto-coccygeus 
muscles. 

Blood-vessels  and  Lymphatics  of  Rectum. — See  pp.  1320  and  1322. 

Nerves  of  Rectum. — See  p.  1322. 

Structure  of  Rectum. — See  p.  1316. 


RECTAL  VALVES 


A  B 

Fig.  929. — The  anal  canal  and  lower  part  of  the  rectum  in  the  foetus.  A,  aged  four  to  five  months  ;  B,  six 
months  ;  C,  nine  months.  In  each  the  anal  canal  is  distinctly  marked  off  from  the  rectum  proper  ;  the  columns 
of  Morgagni  and  the  rectal  valves  are  distinct.     (Cunningham.) 


The  Common  Anal  Canal  (pars  analis  recti)  (Figs.  929  and  930). — The  anal 
canal  is  the  third  portion  of  the  rectum  of  the  older  descriptions.  It  begins 
where  the  true  rectum  ends.    This  canal  is  the  portion  of  the  intestinal  tract  which 


LONGITUDINAL 

FIBRES  OF 

RECTUM 


PART  OF 

LEVATOR  AN. 

INTERNAL 

SPHINCTER 


ANAL  CANAL 


RUG>e  OF 
MUCOUS 
MEMBRANE 

COLUMNS  OF 
MORGAGNI 


ANAL  VALVES 


Fig.  930  — The  interior  of  the  anal  canal  and  lower  part  of  the  rectum,  showing  the  columns  of  Morgagni  and 
the  anal  valves  between  their  lower  ends.  The  columns  were  more  numerous  in  the  specimen  than  usual. 
(Cunningham.) 

is  below  the  distribution  of  genuine  mucous  membrane,  and  is  just  posterior  to 
the  middle  of  a  line  drawn  from  one  tuberosity  to  the  other.  It  lies  between  the 
true  skin  and  the  upper  borders  of  the  semilunar  valves  of  Morgagni.  When  at 
rest  it  is  a  mere  slit  placed  antero-posteriorly.  The  external  opening  of  the  anal 
canal  is  the  anus.  The  skin  about  the  anus  is  pigmented,  is  thrown  into  radi- 
ating folds  by  the  contraction  of  the  External  sphincter  muscle,  and  contains 
hairs,  sebaceous  glands,  and  sudoriparous  glands  (glandulae  circumanales). 
Ascending  into  the  canal,  it  alters  its  character  and  becomes  muco-outaneous, 


1316  THE    ORGANS    OF   DIGESTION 

and  true  mucous  membrane  appears  at  the  rectum  proper.  Back  of  the  anus  is 
a  median  cutaneous  fold  passing  posterior  to  the  coccyx  and  called  the  anal  raphe. 
In  front  of  the  anus  is  a  median  fold  which,  in  the  female,  passes  forward  and 
merges  with  the  labia  major  and  in  the  male  continues  into  the  raph^  of  the 
scrotum.  This  is  called  the  perineal  raph6.  The  length  of  the  anal  canal  is  three- 
quarters  to  one  inch.  "Its  circumference  varies  from  3  cm.  (one  and  three- 
sixteenths  inches)  in  normal  condition  to  15  cm.  (five  and  five-sixteenths  inches) 
in  disease,  following  injury  or  vicious  practices.  The  average  anus  will  admit  a 
cylinder  of  65  mm.  in  circumference  without  rupturing  the  mucous  membrane."^ 
Relations  of  the  Anil  Canal. — It  is  surrounded  by  the  external  and  internal 
sphincter  muscles,  and  above  by  the  Levatores  ani.  To  each  side  is  the  ischio- 
rectal fossa  containing  fat.  Between  the  anal  canal  and  the  coccyx  is  a  collec- 
tion of  muscular  fibres  and  connective  tissue,  the  ano-coccygeal  body  of  Symington. 
In  front,  in  the  male,  is  the  bulb  of  the  urethra  and  the  base  of  the  triangular 
ligament  ;  in  the  female,  is  the  perineal  body,  which  separates  the  anus  from 
the  vagina.    There  are  three  layers  in  the  wall  of  the  anal  canal: 

1.  The  muco-cutaneous  layer,  which  contains  glands,  blood-vessels,  and  numer- 
erous  nerve-endings.  The  lower  portion  is  covered  with  pavement-epithelium, 
but  gradually  there  is  a  transition,  and  at  the  beginning  of  the  rectum  proper  the 
epithelium  is  entirely  columnar.  The  valves  of  Morgagni,  the  anal  valves  or  the  semi- 
lunar valves  (Figs.  930  and  931)  are  in  the  upper  portion  of  the  anal  canal  between 
the  lower  ends  of  the  columns  of  Morgagni  (Figs.  930  and  931).  Above  the  valves 
the  canal  is  lined  by  transitional  mucous  membrane,  below  them  by  modified  skin. 

The  ano-rectal  line  is  not  straight,  but  is  irregularly  dentated  by  trivial  eleva- 
tions, each  of  which  is  papilliform  at  its  summit.  According  to  Tuttle,  these 
elevations  number  from  five  to  eight.  About  one-fifth  of  an  inch  below  the  ano- 
rectal line  is  the  depression  known  as  Hilton's  white  line  (annulus  haemorrhoidalis) 
(Fig.  931).  This  line  is  somewhat  indistinct  to  sight,  but  can  always  be  felt  with 
the  finger.  It  marks  the  junction  of  the  External  with  the  Internal  sphincter. 
Above  Hilton's  line  are  some  mucous  crypts  and  also  dilatations  produced  by  the 
internal  haemorrhoidal  plexus  of  veins  (Fig.  931). 

2.  The  fibro-cellular  layer  is  beneath  the  mucous  membrane.  Above  Hilton's 
line  it  is  composed  of  cellular  tissue;  below  it  is  a  thin  fascia-like  layer  which  joins 
the  superficial  fascia. 

The  anal  canal  is  surrounded  by  longitudinal  fibres  from  the  rectum,  fibres  from 
the  licvator  ani,  the  lower  portion  of  the  Internal  sphincter,  and  particularly  by 
the  External  sphincter. 

Blood-vessels,  Lymphatics,  and  Nerves  of  Anus. — See  pp.  1321  and  1322. 

Structure  of  Large  Intestine  (including  the  Rectum  and  Anal  Canal). — The 
large  intestine  has  four  coats — serous,  muscular,  areolar  or  submucous  and  mucous. 

The  Serous  Coat  (tunica  serosa). — The  serous  coat  is  derived  from  the  peritoneum, 
and  invests  the  different  portions  of  the  large  intestine  to  a  variable  extent.  The 
caecum  is  completely  covered  by  the  serous  membrane,  except  in  a  small  percent- 
age of  cases  (5  or  6  per  cent.),  where  a  small  portion  of  the  upper  end  of  the  pos- 
terior surface  is  uncovered.  The  ascending  and  descending  colon  are  usually 
covered  only  in  front  and  at  the  sides;  a  variable  amount  of  the  posterior  surface 
is  uncovered.  The  transverse  colon  is  almost  completely  invested,  the  parts  corre- 
sponding to  the  attachment  of  the  great  omentum  and  transverse  mesocolon  being 
alone  excepted.  The  sigmoid  flexure  is  completely  surrounded,  except  along  the 
line  to  which  the  sigmoid  mesocolon  is  attached.  The  upper  two-thirds  of  the 
rectum  is  covered  in  front  and  laterally  by  the  peritoneum,  but  not  posteriorly, 
between  the  two  posterior  folds  of  peritoneum,  the  so-called  mesorectum;  later 

1  Diseases  of  the  Anus,  Rectum,  and  Pelvic  Colon.     By  James  P.  Tuttle. 


THE   RECTUM  1317 

it  is  covered  only  on  its  anterior  surface;  and  the  lower  portion  is  entirely 
devoid  of  any  serous  covering.  In  the  course  of  the  colon  the  peritoneal  coat  is 
thrown  into  a  number  of  small  pouches  filled  with  fat,  called  appendices  epiploicse. 
They  are  chiefly  appended  to  the  transverse  colon,  and  are  particularly  numerous 
along  the  anterior  band. 

The  Muscular  Coat  {tunica  muscularis). — The  muscular  coat  consists  of  an 
external  longitudinal  and  an  internal  circular  layer  of  muscular  fibres. 

The  Longitudinal  Fibres,  although  found  to  a  certain  extent  all  around  the 
intestine,  do  not  form  a  uniform  layer  over  the  whole  surface  of  the  large 
intestine.  In  the  caecum  and  colon  they  are  especially  collected  into  three  flat 
longitudinal  bands  or  taeniae  {taeniae  coli)  (Figs.  910  and  911),  each  being  about 
half  an  inch  in  width.  These  bands  commence  at  the  base  of  the  vermiform 
appendix,  which  structure  is  surrounded  by  a  uniform  layer  of  longitudinal 
muscular  fibres.  The  bands  pass  from  the  base  of  the  appendix  to  the  rectum. 
At  this  point  they  broaden,  fuse,  and  surround  the  rectum.  On  the  ascend- 
ing, descending,  and  sigmoid  colon  the  mesocolic  band  {taenia  mesocolica)  is 
posterior  and  internal;  the  omental  band  {taenia  omentalis)  is  posterior  and 
external;  the  free  band  {taenia  libera)  is  anterior.  On  the  transverse  colon  the 
taenia  libera  is  inferior;  the  taenia  mesocolica  is  posterior;  the  taenia  omentalis 
is  anterior  and  superior.  These  bands  are  one-sixth  shorter  than  the  other  coats 
of  the  intestine  to  which  they  are  applied,  and  serve  to  produce  the  sacculi  (Fig. 
911),  which  are  characteristic  of  the  caecum  and  colon;  accordingly,  when  they 
are  dissected  off,  the  tube  can  be  lengthened,  and  its  sacculated  character  becomes 
lost.  The  sacculations  are  called  haustra  coli.  There  are  three  rows  of  the  sac- 
culations separated  from  each  other  by  the  longitudinal  bands.  These  pouches 
are  also  subdivided  by  transverse  furrows  which  correspond  to  concave  folds  of 
mucous  membrane,  called  semilunar  folds  {plicae  semilunares  coli) .  In  the  sig- 
moid flexure  the  longitudinal  fibres  become  more  scattered;  but  upon  its  lower 
part,  and  around  the  rectum,  they  spread  out  and  form  a  layer  which  completely 
encircles  this  portion  of  the  gut,  but  is  thicker  on  the  anterior  and  posterior 
surfaces,  where  two  accentuations  exist,  than  on  the  lateral  surfaces.  In  the 
rectum  the  external  fibres  of  the  longitudinal  layer  descend  and  are  inserted  into 
the  fascia  covering  the  Levator  ani  muscle.  The  middle  fibres  are  mingled  with 
descending  fibres  of  the  Levator  ani  and  terminate  by  attachment  to  the  rectal 
wall.  The  internal  fibres  descend  between  the  External  and  Internal  sphincter 
muscles  and  are  inserted  into  the  superficial  fascia  around  the  anal  margin. 
The  lower  part  of  the  rectum  is  surrounded  by  the  Levator  ani  muscle  (p.  451). 
In  addition  to  the  muscular  fibres  of  the  bowels,  two  bands  of  plain  muscular 
tissue  are  to  be  noted.  They  arise  from  the  front  of  the  second  and  third  coccy- 
geal vertebrae,  and  pass  downward  and  forward  to  blend  with  the  longitudinal 
muscular  fibres  on  the  posterior  wall  of  the  rectum.  Each  is  known  as  the  recto- 
coccygeal muscle  (m.  rectococcygeus) . 

The  Circular  Fibres  form  a  thin  layer  over  the  caecum  and  colon,  being  especially 
accumulated  in  the  intervals  between  the  sacculi.  In  the  rectum  the  circular  fibres 
constitute  a  thick  coat  at  some  portions  of  the  circumference  and  a  thinner  coat 
at  others.  The  circular  fibres  are  thickened  at  every  flexure.  The  thickenings 
only  partly  surround  the  gut,  and  hence  are  not  to  be  considered  as  additional 
sphincters.  Tuttle  calls  them  the  semicircular  muscles  of  the  rectum.  These  semi- 
circular muscles  are  opposite  the  insertion  of  Houston's  valves.  At  the  lower  end 
of  the  rectum  the  circular  fibres  become  very  numerous  and  constitute  the  Internal 
sphincter  muscle  (m.  sphincter  ani  internus)  (Fig.  930).  Tuttle  describes  it  as  fol- 
lows: "This  muscle,  composed  of  an  aggregation  of  circular  fibres,  begins  about 
4  cm.  above  the  anal  margin,  and  gradually  increases  in  thickness  until  it  reaches 
the  ano-rectal  line,  after  which  it  thins  out  again  and  disappears  about  the  middle 


1318 


THE    ORGANS    OF   DIGESTION 


of  the  anal  canal.  Its  width  from  above  downward  averages  1  to  3  cm.  (three-fifths 
of  an  inch  to  one  and  one-fifth  inches).  Its  thickness  is  so  variable  that  no  accurate 
measurement  can  be  given.  Its  lower  fibres  are  below  and  within  the  grasp  of  the 
External  sphincter,  from  which  it  is  separated  by  a  narrow  zone  of  connective 
tissue.  A  depressed  zone,  not  always  perceptible  to  the  eye,  but  appreciable 
by  digital  touch,  marks  the  line  of  division  between  these  two  muscles."^  The 
Internal  sphincter  is  an  involuntary  muscle.  The  external  sphincter  muscle  is 
not  a  portion  of  the  wall  of  the  bowel.     It  is  described  on  pages  450  and  451. 

The  Areolax  Coat  or  Submucous  Coat  {tela  suhmucosa). — The  areolar  or  sub- 
mucous coat  connects  the  muscular  and  mucous  layers  closely  together.  This  coat 
is  thicker,  looser,  and  more  elastic  in  the  rectum  than  elsewhere.  In  this  coat  are 
the  blood-vessels,  nerves,  and  lymphatics. 

The  Mucous  Membrane  {tunica  mucosa). — The  mucous  membrane,  in  the  caecum 
and  colon,  is  pale,  smooth,  destitute  of  villi,  and  raised  into  numerous  crescentic 
folds  which  correspond  to  the  intervals  between  the  sacculi.  In  the  rectum  it  is 
thicker,  of  a  darker  color,  more  vascular,  and  connected  loosely  to  the  muscular 
coat,  as  in  the  oesophagus. 

The  rectum  contains  certain  horizontal  folds.  Most  of  them  disappear  when 
the  gut  is  distended,  but  some  of  them  do  not  disappear,  but  remain  as  distinct 


MUCOUS 
MEMBRANE 


DILATATION 

OF   VEINS~ 

COLUMNS  OF. 

MORGAGNI 

VALVE    OF 

MORGAGN 


HILTON'S 
WHITE  LINE 


MUSCULAR  WALL 
OF  RECTUM 


INTERNAL  HEMOR- 
RHOIDAL  PLEXUS 

DILATATION 
OF  VEIN 

COMMUNICATION    BE- 
TWEEN    INTERNALANB 
EXTERNAL  HEMOR- 
RHOIDAL   PLEXUS 
INTERNAL 
SPHINCTER 

EXTERNAL 
SPHINCTER 

LONGITUDINAL 
TENDINOUS  FIBRES 

SUBCUTANEOUS 
CELLULAR  TISSUE 


Fig.  931.— -Inner  wall  of  the  lower  end  of  the  rectum  and  anus.  On  the  right  the  mucous  membrane  has 
been  removed  to  show  the  dilatation  of  the  veins  and  how  they  pass  through  the  muscular  wall  to  anastomose 
with  the  external  haemorrhoidal  plexus.     (Luschka.) 

folds  with  free  crescentic  edges.  These  permanent  folds  were  first  described  by 
Houston,  of  Dublin,  and  are  known  as  rectal  valves  or  Houston's  valves  {'plicae 
iransversales  recti)  (Figs.  928  and  929).  Each  fold  surrounds  more  than  one- 
third  of  the  gut,  and  is  composed  of  mucous  membrane,  submucous  tissue,  and 
a  layer  from  the  circular  muscular  layer  of  the  gut.  There  may  be  three,  four,  or 
five  of  these  folds.  Three  of  them  are  constant.  One  is  on  the  right  rectal  wall, 
about  the  point  of  peritoneal  reflection;  another  is  on  the  left  side,  about  one 
inch  above  the  margin  of  the  anal  canal.  A  third  is  on  the  rectal  wall,  either 
toward  the  right  or  left,  at  the  point  where  the  rectum  joins  the  front  of  the 
sigmoid.  These  shelf-like  valves  are  not  perfectly  flat,  for  on  the  superior  surface 
of  each  is  a  depression. 

The  borders  of  a  valve  are  thinner  than  its  base  and  are  very  flexible.  These 
valves  support  the  mass  of  faces  as  it  descends,  and  give  to  it  a  rotary  motion 

1  Diseases  of  the  Anus,  Rectum,  and  Pelvic  Colon.     By  James  P.  Tuttle. 


THE    RECTUM  I3I9 

(Tuttle).  In  the  lower  end  of  the  rectum  the  mucous  membrane  forms  longi- 
tudinal folds  known  as  the  columns  of  Morgagni  or  the  rectal  columns  (columnae 
redales  [Morgagni])  (Figs.  930  and  931).  There  are  from  five  to  ten  of  these 
folds,  each  of  which  is  about  one-half  an  inch  long,  and  they  contain  longitudinal 
muscle-fibres.  They  are  most  prominent  when  the  sphincter  contracts.  The  base 
of  each  column  helps  to  form  the  upper  margin  of  the  anal  canal.  The  outer  angle 
of  each  column  below  passes  into  a  semilunar  valve.  The  grooves  between  the 
columns  are  shallow  above  and  deeper  below,  and  end  in  the  semilunar  valves. 
The  semilunar  valves,  valves  of  Morgagni  or  anal  valves  (Figs.  930  and  931)  are  folds 
which  stretch  from  the  base  of  one  column  to  another,  and  form  the  anal  pockets 
or  crypts  of  Morgagni  {sinus  redales).  These  pockets  are  about  5  mm.  in  depth. 
They  are  most  marked  posteriorly  (Ball),  but  none  exists  in  either  the  anterior 
or  posterior  commissure  (Tuttle).  Below  the  sinuses  is  the  white  line  of  Hilton 
{annulus  haemorrhoidalis)  (Fig.  931),  which  reaches  to  the  region  where  hair  and 
sebaceous  glands  appear. 


Fig.  932. — The  arterial  circulation  in  the  dorsal  pcsterior  surface  of  the  caecum  and  appendix.  A,  ileo-colic 
artery;  B  and  F,  posterior  caecal  artery;  C,  appendicular  artery;  E,  appendicular  artery  for  free  end;  H ,  artery 
for  basal  end  of  api>endix;  1,  ascending  or  right  colon;  2,  external  sacculus  of  the  caecum;  3,  appendix;  6,  ileum; 
D,  arteries  on  the  dorsal  surface  of  the  ileum.     (Byron  Robinson.) 

As  in  the  small  intestine,  the  raucous  membrane  consists  of  a  muscular  layer,  the 
muscularis  mucosae  (Fig.  935) ;  of  a  quantity  of  retiform  tissue  in  which  the  vessels 
ramify;  of  a  basement-membrane  and  epithelium,  which  is  of  the  columnar  variety, 
and  exactly  resembles  the  epithelium  found  in  the  small  intestine.  In  the  rectum 
the  epithelial  cells  are  columnar;  at  the  lower  end  of  the  tube,  however,  they  begin 
to  change  into  stratified  polyhedrons  and  prisms.  The  mucous  membrane  of  the 
large  intestine  presents  for  examination  simple  follicles  and  solitary  glands. 

The  simple  Follicles,  Intestinal  Glands,  Crypts  or  Glands  of  Lieberkiihn  (glandulae 
iniestinales  [Lieberkuhni])  (Fig.  935)  are  minute  tubular  prolongations  of  the 
mucous  membrane  arranged  perpendicularly,  side  by  side,  over  its  entire  sur- 
face; they  are  longer,  more  numerous,  and  are  placed  in  much  closer  apposition 
than  those  of  the  small  intestine;  and  they  open  by  minute  rounded  orifices  upon 
the  surface,  giving  it  a  cribriform  appearance. 


1320 


THE    ORGANS    OF  DIGESTION 


The  Solitary  Glands  {iioduli  lymphatici  solitarii)  (Fig.  935)  in  the  large  intes- 
tine are  most  abundant  in  the  caecum  and  vermiform  appendix,  but  are  irregu- 
larly scattered  also  over  the  rest  of  the  intestine.  They  are  similar  to  those  of  the 
small  intestine. 

Vessels  of  the  Large  Intestine. — The  arteries  supplying  the  large  intestine  give 
off  large  branches,  which  ramify  between  the  muscular  coats  supplying  them, 
and,  after  dividing  into  small  vessels  in  the  submucous  tissue,  pass  to  the 
mucous  membrane.  The  caecum,  the  appendix,  and  the  ileo-caecal  valve  are  sup- 
plied by  the  branches  from  the  anastomotic  loops  between  the  right  colic  and  ileo- 


FiG.  933. — The  arterial  blood-supply  of  the  anterior  (ventral)  surface  of  the  caecum  and  appendix.  A,  ileo- 
colic artery;  B,  caecal-appendicular  artery;  D,  anterior  caecal  artery;  F  and  G,  appendicular  artery.  Note  that 
the  caecal  and  appendicular  arteries  anastomose  by  fine  capillaries,  both  ventral  and  dorsally;  C,  iliac  artery; 
1,  right  colon;  2,  external  sacculus  of  caecum  (to  right  of  taenium  coh);  3,  appendix;  4,  Iliac,  and  5,  Psoas  muscles. 
(Byron  Robinson.) 


colic  branches  of  the  superior  mesenteric  artery  (Figs.  932  and  933).  In  males  the 
sole  blood-supply  of  the  appendix  is  by  the  appendicular  artery  from  the  posterior 
ileo-caecal  branch  of  the  ileo-caecal  artery  (Fig.  933).  In  the  female  the  appendix 
occasionally  receives  an  additional  vessel  along  the  appendiculo-ovarian  ligament 
from  the  ovarian  artery.  The  ascending  colon  is  supplied  by  the  right  colic,  and  the 
transverse  colon  by  the  middle  colic  branch  of  the  superior  mesenteric.  The 
descending  colon  is  supplied  by  the  left  colic  branch  of  the  inferior  mesenteric, 
and  the  sigmoid  flexure  by  the  sigmoid  branches  of  the  inferior  mesenteric.  The 
rectum  (Fig.  934)  is  supplied  mainly  by  the  superior  haemorrhoidal  branch  of  the 
inferior  mesenteric,  but  also  at  its  lower  end  by  the  middle  haemorrhoidal  from 
the  internal  iliac,  and  the  inferior  haemorrhoidal  from  the  pudic  artery.    The  supe- 


THE    RECTUM 


1321 


SUPERIOR 

EMORRHOIDAL 
EIN 


SUPERIOR 

HEMORRHOIDAL 

ARTERY 


rior  haemorrhoidal,  the  continuation  of  the  superior  mesenteric,  divides  into  two 
branches,  which  run  down  either  side  of  the  rectum  to  within  about  five  inches 
of  the  anus;  they  here  spHt  up  into  about  six  branches,  which  pierce  the 
muscular  coat  and  descend  between  it  and  the  mucous  membrane  in  a  longi- 
tudinal direction,  parallel  with  each  other  as  far  as  the  Internal  sphincter,  where 
they  anastomose  with  the  other  haemorrhoidal  arteries  and  form  a  series  of  loops 
around  the  anus.  The  veins  of  the  large  intestine  correspond  to  the  arteries  and 
join  the  superior  and  inferior  mesenteric  veins  which  join  the  portal  vein.  The  veins 
of  the  rectum  (Fig.  934)  coi»mence  in  a  plexus  of  vessels  which  surrounds  the  lower 
extremity  of  the  intestinal  canal.  In  the  vessels  forming  this  plexus  are  small 
saccular  dilatations  just  within  the  margin  of  the  anus  (Figs.  931  and  934); 
from  it  about  six  vessels  of  considerable  size  are  given  off.  These  ascend  between 
the  muscular  and  mucous 
coats  for  about  five  inches, 
running  parallel  to  each 
other  ;  they  then  pierce  the 
muscular  coat,  and,  by  their 
union,  form  a  single  trunk, 
the  superior  haemorrhoidal 
vein,  which  empties  into  the 
inferior  mesenteric  branch  of 
the  portal  vein.  This  arrange- 
ment is  termed  the  haemor- 
rhoidal plexus  (Fig.  473);  it 
communicates  with  the  tribu- 
taries of  the  middle  and  infe- 
rior haemorrhoidal  veins  at  its 
commencement,  and  thus  a 
communication  is  established 
between  the  systemic  and 
portal  circulations.  The  in- 
ferior haemorrhoidal  veins 
empty  into  the  internal  pudic 
veins,  and  the  middle  haemor- 
rhoidal veins  empty  into  the 
internal  iliac  veins. 

The  Lymphatics  of  the  Large 
Intestine .  —  The  lymphatics 
of  the  large  intestine  begin 
in  the  mucous  membrane  and 
form  an  extensive  plexus  in 
the  submucosa.  There  are 
also  lymphatics  more  deeply 
seated,  beneath  the  simple 
follicles.  Those  from  the 
ascending  colon  and  trans- 
verse  colon    open    into    the 

glands  Wnthin  the   mesocolon       _  Fig.  934.— The  blood-vessels  of  the  rectum  and  anus,  showing  the 
1    1      ,  .      ,    .1  I  ,  distribution  and  anastomosis  on  the  posterior  surface  near  the  termi- 

and    benmci  the  colon  (meSO-    nation  of  the  gut.     (Poirier  and  Charpy.) 

colic    glands),    from    which 

glands  trunks  pass  to  the  superior  mesenteric  glands.  The  lymphatics  from  the 
transverse  colon  join  with  lymph-vessels  of  the  great  omentum,  and  hence  com- 
municate with  the  lymphatics  of  the  greater  curvature  of  the  stomach.  The  lymph 
from  the  descending  colon,  from  the  sigmoid  and  from  the  pelvic  colon  passes  to 


MIDDLE 

HEMORRHOIDAL 

ARTERY 


NFERIOR 
HEMORRHOIDAL 
ARTERY 


1322 


THE    ORGANS    OF  DIGESTION 


the  glands  along  the  inferior  mesenteric  artery.  The  lymphatics  of  the  rectum 
pass  first  to  the  rectal  glands,  which  lie  on  the  muscular  coat  of  the  rectum,  next  to 
the  glands  which  lie  back  of  the  rectum  along  the  superior  haemorrhoidal  artery, 
and  finally  to  the  sacral  glands.  Lymphatics  from  the  skin  of  the  anus  pass 
with  the  lymphatics  of  the  skin  to  the  superficial  inguinal  glands.  Lymphatics 
from  the  anus  between  the  skin  margin  and  Hilton's  white  line  pass  to  the  hypo- 
gastric glands. 

The  Nerves  of  the  Anus  and  Rectum. — The  nerves  of  the  anus  and  rectum  are 
derived  from  both  the  sympathetic  and  cerebro-spin^  system.  The  chief  supply 
of  the  rectum  is  from  the  mesenteric,  sacral,  and  hypogastric  plexuses  of  the  sympa- 
thetic. It  also  obtains  small  branches  from  the  third,  fourth,  and  fifth  sacral  nerves. 
The  lower  part  of  the  rectum  is  much  more  sensitive  than  the  upper  part. 
The  muscles  of  the  anus  and  rectum  are  supplied  "  from  the  intricate  plexuses 
formed  by  the  second,  third,  fourth,  and  fifth  sacral  nerves"  (Tuttle).  The 
External  sphincter  is   supplied  by  nerves   which  contain  motor,   sensory,  and 

Surface  of  mucous  membrane, 
u-iih  openings  of  Lieberkuhn's 
follicles. 


Lieberkiihn's  follicles. 


Sri   Muscularis  mucosae  (two  layers). 


^     ^1  Submucous  conjieclive  tissue. 


Solitary  gland. 

Fig.  935. — Minute  structure  of  large  intestine. 

sympathetic  fibres.  These  nerves  come  from  three  sources.  "Two  filaments 
from  the  branches  formed  by  the  third,  fourth,  and  fifth  sacral  nerves  extend 
transversely  across  the  ischio-rectal  fossa  and  distribute  themselves  to  the  middle 
portion  of  the  muscle  and  to  the  peri-anal  cutaneous  surface;  a  filament  which 
comes  off  from  the  internal  pudic  just  before  its  division  into  terminal  branches 
supplies  the  anterior  portion  of  the  muscle,  and  is  called  the  anterior  sphincterian 
nerve ;  while  a  filament  coming  off  from  the  fifth  and  sixth  sacral  nerves  passes 
down  into  the  hollow  of  the  sacrum,  between  the  I^evator  ani  muscle  and  the  recto- 
coccygeus  ligament,  and  finally  reaches  the  posterior  superficial  surface  of  the 
External  sphincter."*  The  spinal  centre  for  the  nerves  of  the  anus  and  rectum  is 
opposite  the  first  lumbar  vertebra,  and  is  in  practically  the  same  region  as  the 
centre  for  the  genito-urinary  organs. 

Movements  and  Innervation  of  the  Intestines. 

Movements. — As  the  small  intestine  is  devoid  of  any  sphincter  arrangement  peristalsis  cannot 
mix  the  food  as  it  does  in  the  pyloric  portion  of  the  stomach.  The  process  by  which  the  food  is 
mixed  with  the  secretions  and  is  brought  against  the  intestinal  v.all  for  absorption  is  called 
by  Cannon  "rhythmic  segmentation."     Rhythmic  motions,  according  to  Cannon,  "mix  the 


1  Diseases  of  the  Anus,  Rectum,  and  Pelvic  Colon.     By  James  P.  Tuttle 


MOVEMENTS  AND    INNERVATION   OF    THE   INTESTINES     1323 

food  and  expose  it  to  the  mucosa  without  advancing  it  appreciaiely  along  the  canal."'  In  this 
process  constrictions  occur  in  the  circular  fibres,  with  the  result  that  a  collection  of  stationary 
food  is  divided  into  a  number  of  segments.  In  the  middle  of  each  segment  constrictions  ap})ear 
and  the  earlier  constrictions  relax.  Then  the  later  constrictions  relax  and  the  earlier  reappear 
and  so  on  until  the  food  is  thoroughly  mixed  with  digestive  secretions.  Finally  the  food  is 
driven  on  by  peristalsis  coming  again  to  rest  and  being  again  subjected  to  "  rhythmic  segmenta- 
tion."^ Cannon  says  that  in  the  duodenum  "rhythmic  segmentation"  lasts  for  several  minutes, 
but  in  other  parts  of  the  intestine  it  may  continue  for  half  an  hour  or  more,  the  food  which  is 
being  subjected  to  it  scarcely  moving  along  the  canal.  Cannon  infers  that  in  man  there  are 
from  seven  to  eight  segmentations  per  minute  in  a  given  area.  It  is  probable  that  there  is  a 
sphincter  action  at  the  ileo-caecal  opening. 

Cannon  divides  the  large  intestine  into  two  parts:  a  distal  part,  in  which  the  material  is  hard 
and  lumpy  and  is  "advanced  by  rings  of  tonic  contraction,"  and  a  proximal  part,  in  which 
the  material  is  soft.  In  this  part  "the  common  movements  are  waves  of  constriction  running 
backward  toward  the  caecum."^  The  resistance  of  the  valve  or  sphincter  enables  reversed 
peristalsis  or  antiperistalsis  to  mix  the  food.  When  more  food  enters  from  the  small  intestine, 
antiperistalsis  ceases,  tonic  contraction  of  the  caecum  and  proximal  portion  of  the  colon  occurs, 
some  of  the  food  is  merged  into  the  transverse  colon,  and  antiperistalsis  again  begins  to  act 
on  what  remains.*  The  above  facts  have  been  observed  in  animals  and  are  probably  true  in 
man. 

Innervation. — The  pneumogastric  fibres  of  the  small  intestine  seem  to  excite  contraction  of 
the  circular  fibres  after  a  brief  preliminary  period  of  inhibition.*  Some  observers  maintain 
that  the  splanchnic  fibres  are  inhibitory,  but  others  claim  that  they  are  also  motor.  The  local 
reflex  of  the  small  intestine  is  in  Auerbach's  plexus.  Cannon  quotes  Bayliss  and  Starling  to 
the  effect  that  the  pelvic  visceral  nerves  to  the  large  intestine,  "arising  like  the  vagus  from  the 
central  nervous  system,  are  augmentary  nerves,  whereas  the  supply  from  the  sympathetic  sys- 
tem is  purely  inhibitory  in  its  action."**  It  is  further  contended  that  the  pelvic  visceral  nerves 
are  distributed  to  the  distal  colon  only.  "The  region  of  antiperistalsis  does  not,  therefore, 
receive  motor  impulses  from  the  pelvic  nerves."' 

Surface  Form. — The  coils  of  the  small  intestine  occupy  the  front  of  the  abdomen  below  the 
transverse  colon,  and  are  covered  more  or  less  completely  by  the  great  omentum.  For  the  most 
part  the  coils  of  the  jejunum  occupy  the  left  side  of  the  abdominal  cavity — i.  e.,  the  left  lumbar 
and  inguinal  regions  and  the  left  half  of  the  umbilical  region — whilst  the  coils  of  the  ileum  are 
situated  to  the  right,  in  the  right  lumbar  and  inguinal  regions,  in  the  right  half  of  the  umbilical 
region,  and  also  in  the  hypogastric  region.  The  caecum  is  situated  in  the  right  inguinal  region. 
Its  position  varies  slightly,  but  the  mid-point  of  a  line  drawn  from  the  anterior  superior  spinous 
process  of  the  ilium  to  the  symphysis  pubis  will  about  mark  the  middle  of  its  lower  border.  It  is 
comparatively  superficial.  From  it  the  ascending  colon  passes  upward  through  the  right  lumbar 
and  hypochondriac  regions,  and  becomes  more  deeply  situated  as  it  ascends  to  the  hepatic  flexure, 
which  is  deeply  placed  under  cover  of  the  liver.  The  transverse  colon  crosses  the  belly  trans- 
versely on  the  confines  of  the  umbilical  and  epigastric  regions,  its  lower  border  being  on  a  level 
slightly  above  the  umbilicus,  its  upper  border  just  below  the  greater  curvature  of  the  stomach. 
The  splenic  flexure  of  the  colon  is  situated  behind  the  stomach  in  the  left  hypochondrium,  and 
is  on  a  higher  level  than  the  hepatic  flexure.  The  descending  colon  is  deeply  seated,  passing 
down  through  the  left  hypochondriac  and  lumbar  regions  to  the  sigmoid  flexure,  which  is  situ- 
ated in  the  left  inguinaf  region,  and  which  can  be  felt  in  thin  persons,  with  relaxed  abdominal 
walls,  rolling  under  the  fingers  when  empty,  and  when  distended  forming  a  distinct  bulge.  The 
position  of  the  base  of  the  vermiform  appendix  is  indicated  by  a  point  two  inches  from  the 
anterior  superior  spinous  process  of  the  ilium,  on  a  line  drawn  from  this  process  to  the  umbilicus. 
This  is  known  as  McBurney's  point.  Another  mode  of  defining  the  position  of  the  base  of  the 
appendix  is  to  draw  a  line  between  the  anterior  superior  spines  of  the  ilia  and  marking  the  point 
where  this  line  intersects  the  right  semilunar  line. 

Upon  introducing  the  finger  into  the  rectum,  the  membranous  portion  of  the  urethra  can 
be  felt,  if  an  instrument  has  been  introduced  into  the  bladder,  exactly  in  the  middle  line;  behind 
this  the  prostate  gland  can  be  recognized  by  its  shape  and  hardness  and  any  enlargement  detected; 
behind  the  prostate  the  fluctuating  wall  of  the  bladder  when  full  can  be  felt,  and  if  thought 
desirable  it  can  be  tapped  in  this  situation;  on  either  side  and  behind  the  prostate  the  vesiculae 
seminales  can  be  readily  felt,  especially  if  enlarged  by  tuberculous  disease.  Behind,  the  coccyx 
is  to  be  felt,  and  on  the  mucous  membrane  one  or  two  of  Houston's  folds.  The  ischio-rectal 
fossae  can  be  explored  on  either  side,  with  a  view  to  ascertaining  the  presence  of  deep-seated 
collections  of  pus.  Finally,  it  will  be  noted  that  the  finger  is  firmly  gripped  by  the  sphincter  for 
about  an  inch  up  the  bowel.    By  gradual  dilatation  of  the  sphincter,  the  whole  hand  can  be 

'  Medical  News,  May  20,  1905.  -  Walter  B.  Cannon,  in  Medical  News,  May  20,  1305. 

»  Medical  News,  May  20,  1905.  ■•  Ibid. 

*  Bayliss  and  Starling,  Journal  of  Physiology,  1899. 

6  Medical  News,  May  20,  1905.  Walter  B.  Caunon,  Medical  News,  May  20,  1905. 


1324  THE    ORGANS    OF  DIGESTION 

introduced  into  the  rectum  so  as  to  reach  the  descending  colon.    This  method  of  exploration  is 
not  at  the  present  day  employed  for  diagnostic  purposes. 

Surgical  Anatomy. — The  small  intestine  is  much  exposed  to  injury,  but,  in  consequence 
of  its  elasticity  and  the  ease  with  which  one  fold  glides  over  another,  it  is  not  so  frequently  rup- 
tured as  would  otherwise  be  the  case.  Any  part  of  the  small  intestine  may  be  ruptured,  bui 
probably  the  most  common  situation  is  the  transverse  duodenum,  on  account  of  its  being  more 
fixed  than  other  portions  of  the  bowel,  and  because  it  is  situated  in  front  of  the  bodies  of  the 
vertebrae,  so  that  if  this  portion  of  the  intestine  is  struck  a  sharp  blow,  as  from  the  kick  of  a 
horse,  it  is  unable  to  glide  out  of  the  way,  but  is  compressed  against  the  bone  and  lacerated. 
Wounds  of  the  intestine  sometimes  occur.  If  the  wound  is  a  small  puncture,  under,  it  is  said, 
three  lines  in  length,  there  may  be  no  extravasation  of  the  contents  of  the  bowel.  The  mucous 
membrane  becomes  everted  and  perhaps  plugs  the  little  opening.  The  bowels,  therefore,  may  be 
punctured  with  a  fine  capillary  trocar,  in  cases  of  excessive  distention  of  the  intestine  with  gas,  with- 
out much  danger  of  extravasation.  A  longitudinal  wound  gapes  more  than  a  transverse  wound, 
owing  to  the  greater  thickness  of  the  circular  muscular  coat.  In  closing  a  wound  of  the  intestine, 
use  Lembert's  inversion  sutures,  which  bring  the  peritoneal  surfaces  in  contact.  Halsted  showed 
us  that  these  sutures  must  include  the  tough  submucous  coat.  The  portions  of  intestine  which  lie 
in  the  pelvis  are  inflamed  in  pelvic  peritonitis  and  become  embedded  in  adhesions.  The  portions 
of  intestine  which  may  be  present  are  the  termination  of  the  ileum,  the  portion  of  small  intestine 
with  the  largest  mesentery  (Treves),  the  rectum,  and  the  pelvic  colon.  The  small  intestine,  and 
most  frequendy  the  ileum,  may  become  strangulated  by  internal  bands,  or  through  apertures, 
normal  or  abnormal.  The  bands  may  be  formed  in  several  different  ways:  they  may  be  old  peri- 
toneal adhesions  from  previous  attacks  of  peritonitis;  or  adherent  omentum  from  the  same 
cause;  or  the  band  may  be  formed  by  Meckel's  diverticulum,  which  has  contracted  adhesions  at 
its  distal  extremity;  or  the  band  may  be  the  result  of  the  abnormal  attachment  of  some  normal 
structure,  as  the  adhesion  of  two  appendices  epiploicae,  or  an  adherent  vermiform  appendix  or 
Fallopian  tube.  Iniussusception  or  invagination  of  the  small  intestine  may  take  place  in  any  part 
of  the  jejunum  and  ileum,  but  the  most  frequent  situation  is  at  the  ileo-caecal  valve,  the  valve 
forming  the  apex  of  the  entering  tube.  This  form  may  attain  great  size,  and  it  is  not  uncom- 
mon in  these  cases  to  find  the  valve  projecting  from  the  anus.  Stricture,  the  impaction  of 
foreign  bodies,  and  twisting  of  the  gut  (volvulus)  may  lead  to  intestinal  obstruction.  Volvulus  is 
most  common  in  the  sigmoid  flexure.  Meckel's  diverticulum  may  itself  become  twisted  and 
strangulated. 

Resection  of  a  portion  of  the  intestine  may  be  required  in  cases  of  gangrenous  gut;  in  cases- 
of  intussusception;  for  the  removal  of  new  growth  in  the  bowel;  in  dealing  with  artificial  anus^ 
and  in  cases  of  rupture.  The  operation  is  termed  enterectomy,  and  is  performed  as  follows:  the 
abdomen  having  been  opened  and  the  amount  of  bowel  requiring  removal  having  been  deter- 
mined upon,  the  gut  must  be  clamped  on  either  side  of  this  portion  in  order  to  prevent  the  escape 
of  any  of  the  contents  of  the  bowel  during  the  operation.  The  portion  of  bowel  is  then  separated 
above  and  below  by  means  of  scissors.  If  the  portion  removed  is  small,  it  may  be  simply  removed 
from  the  mesentery  at  its  attachment  and  the  bleeding  vessels  tied;  but  if  it  is  large,  it  will  be 
necessary  to  remove  also  a  triangular  piece  of  the  mesentery,  and  having  secured  the  vessels, 
suture  the  cut  edges  of  this  structure  together.  The  surgeon  then  proceeds  to  unite  the  cut 
ends  of  the  bowel  together.  He  may  do  it  by  the  operation  termed  end-to-end  anastomosis. 
There  are  many  ways  of  doing  this,  which  may  be  divided  into  two  classes:  one,  where  the  anas- 
tomosis is  made  by  means  of  some  mechanical  appliance,  such  as  Murphy's  button,  or  one  of 
the  forms  of  decalcified  bone  bobbins;  and  the  other,  where  the  operation  is  performed  by 
simply  suturing  the  ends  of  the  bowel  in  such  a  manner  that  the  peritoneum  covering  the  free 
divided  ends  of  the  bowel  is  brought  into  contact,  so  that  speedy  union  may  ensue. 

In  some  cases  after  resection  each  open  end  of  the  gut  is  closed,  the  side  of  the  terminal  portion 
is  sutured  to  the  side  of  the  initial  portion,  a  fistula  is  made  in  each,  and  the  suturing  is  com- 
pleted so  as  to  cause  the  two  fistulae  to  correspond.  A  permanent  side-to-side  opening  is 
thus  made.  Lateral  anastomosis  without  resection  may  be  practised  between  two  pieces  of 
intestine,  in  order  to  side-track  an  intervening  portion,  which  is  the  seat  of  malignant  disease  or 
of  an  artificial  anus.  Complete  exclusion  of  a  portion  of  intestine  is  performed  for  irremovable 
tumors  or  persistent  fsecal  fistulae  of  the  large  intestine.  The  intestine  is  cut  through  above  and 
below  the  diseased  area  and  the  ends  of  the  healthy  gut  are  united  to  each  other,  or  the  larger 
end  is  closed,  an  opening  is  made  into  the  side  of  the  larger  end  and  the  smaller  end  is  implanted 
in  it  {lateral  implantation).  The  two  ends  of  the  excluded  portion  are  fastened  to  the  skin  and 
are  left  open. 

In  ascites  resulting  from  cirrhosis  of  the  liver  benefit  occasionally  follows  the  performance  of 
Talma's  operation  (epiplopexy) .  The  abdomen  is  opened  and  the  omentum  is  sutured  to  the 
anterior  abdominal  wall  or  in  the  abdominal  wound  in  the  hope  of  establishing  a  more  free 
communication  between  the  portal  and  systemic  circulations,  thus  lowering  portal  pressure. 

External  hernia  is  considered  on  page  1325. 

By  the  term  internal  hernia,  we  mean  hernia  into  the  foramen  of  Winslow,  into  the  retro- 


MOVEMENTS  AND   INNERVATION    OF    THE   INTESTINES     1325 

duodenal  fossa,  into  the  retro-caecal  fossa,  or  into  the  intersigmoid  fossa.  Such  a  hernia  produces 
the  symptoms  of  acute  strangulation  of  the  intestine. 

In  fyphoid  fever  there  is  ulceration  of  Peyer's  patches.  One  of  these  ulcers  may  perforate. 
The  only  chance  for  life  is  immediate  laparotomy  and  closure  of  the  perforation.  This  saves 
one-fifth,  or  possibly  one-third,  of  the  cases.  The  incision  is  made  to  expose  the  lower  ileum,  as 
in  the  vast  majority  of  cases  the  perforation  is  in  this  portion  of  the  gut. 

Ulcer  of  the  duodenum  is  more  common  than  used  to  be  thought.  The  portion  of  the  duo- 
denum between  the  pylorus  and  the  bile  papilla  is  about  four  inches  in  length,  and  is  called  by 
the  Mayo  brothers  the  veMibule  of  the  duodenum.  Here  the  acid  gastric  juice  enters  and  may  pro- 
duce an  ulcer.  The  portion  of  the  duodenum  below  the  vestibule  is  not  liable  to  ulcer,  because 
it  is  protected  by  the  alkaline  bile  and  pancreatic  juice. 

A  duodenal  ulcer  may  perforate  a  large  duodenal  vessel  and  cause  death  from  hemorrhage, 
or  may  perforate  the  intestine  and  produce  septic  peritonitis.  A  perforated  ulcer  is  treated 
by  laparotomy  and  closure  of  the  perforation.  Occasionally  ulceration  of  the  duodenal  glands 
(Curling's  ulcer)  may  occur  in  cases  of  burns,  but  is  not  a  very  common  complication. 

The  vermiform  api)endix  is  very  liable  to  become  inflamed,  the  condition  being  known  as 
appendicitis.  This  condition  may  be  set  up  by  a  catarrhal  inflammation  arising  in  the  appen- 
dix or  derived  from  the  colon.  It  may  remain  catarrhal  and  then  subside.  It  may  become 
purulent  or  may  be  purulent  from  the  beginning.  Anything  which  lessens  vital  resistance 
makes  the  appendix  a  ready  prey  to  bacteria.  Among  causes  which  lessen  resistance  are  faecal 
concretions,  twists  of  the  mesoappendix  cutting  off  the  blood-suj>ply,  bruises  inflicted  by  the  Psoas 
muscle  (Byron  Robinson),  blocking  of  the  outlet  of  the  appendix  by  catarrhal  exudate,  concre- 
tions, proliferated  lymphoid  tissue,  or  adhesions.  Appendicitis  may  arise  by  the  appendix  becom- 
ing twisted,  owing  to  the  shortness  of  its  mesentery,  in  consequence  of  distention  of  the  caecum. 
As  the  result  of  inflammation,  its  blood-supply,  which  is  mainly  through  one  large  artery  running 
in  the  mesoappendix,  becomes  interfered  with.  Again,  in  rarer  cases,  the  inflammation  is  set 
up  by  the  impaction  of  a  solid  mass  of  faeces  or  a  foreign  body  in  the  appendix.  The  inflammation 
may  result  in  ulceration  and  perforation,  or  in  gangrene  of  the  appendix  the  appendix  may  be 
blocked  and  full  of  pus,  or  abscess  may  form  outside  of  it  (appendicular  abscess).  These  con- 
ditions require  prompt  operative  interference,  and  in  cases  of  recurrent  attacks  of  appendicitis  it 
is  advisable  to  remove  this  diverticulum  between  the  attacks.  In  external  hernia  the  ileum 
is  the  portion  of  bowel  most  frequently  herniated.  When  a  part  of  the  large  intestine  is 
involved,  it  is  usually  the  caecum,  and  this  may  occur  even  on  the  left  side.  In  some  few  cases 
the  vermiform  appendix  has  been  the  part  implicated  in  cases  of  strangulated  hernia,  and  has 
given  rise  to  serious  symptoms  of  obstruction.  The  diameter  of  the  large  intestine  gradually 
diminishes  from  the  caecum,  which  has  the  greatest  diameter  of  any  part  of  the  bowel,  to  the 
point  of  junction  of  the  sigmoid  flexure  with  the  rectum,  at  or  a  little  below  which  point  stricture 
most  commonly  occurs  and  diminishes  in  frequency  as  one  proceeds  upward  to  the  caecum. 
When  distended  by  some  obstruction  low  down,  the  outline  of  the  large  intestine  can  be  defined 
throughout  nearly  the  whole  of  its  course — all,  in  fact,  except  the  hepatic  and  splenic  flexures, 
which  are  more  deeply  placed ;  the  distention  is  most  obvious  in  the  two  flanks  and  on  the  front 
of  the  abdomen  just  above  the  umbilicus.  The  caecum,  however,  is  that  portion  of  the  bowel 
which  is,  of  all,  most  distended.  It  sometimes  assumes  enormous  dimensions,  and  has  been 
known  to  give  way  from  the  distention,  causing  fatal  peritonitis.  The  hepatic  flexure  and  the  right 
extremity  of  the  transverse  colon  are  in  close  relationship  with  the  liver,  and  abscess  of  this  viscus 
sometimes  bursts  into  the  gut  in  this  situation.  The  gall-bladder  may  become  adherent  to  the 
colon,  and  gall-stones  may  find  their  way  through  into  the  gut,  where  they  may  become  impacted 
or  may  be  discharged  per  anum.  The  mobility  of  the  sigmoid  flexure  renders  it  more  liable  to 
become  the  seat  of  a  volvulus  or  twist  than  any  other  part  of  the  intestine.  It  generally  occurs 
in  patients  who  have  been  the  subjects  of  habitual  constipation,  and  in  whom,  therefore,  the 
mesosigmoid  is  elongated.  The  gut  at  this  part  being  loaded  with  faeces,  from  its  weight  falls 
over  the  gut  below,  and  so  gives  rise  to  the  twist. 

The  surgical  anatomy  of  the  rectum  is  of  considerable  importance.  There  may  be  congenital 
malformation  due  to  arrest  or  imperfect  development.  Thus,  there  may  be  no  invagination  of 
the  epiblast,  and  consequently  a  complete  absence  of  the  anus;  or  the  hind-gut  may  be  imper- 
fectly developed,  and  there  may  be  an  absence  of  the  rectum,  though  the  anus  is  developed; 
or  the  invagination  of  the  epiblast  may  not  communicate  with  the  termination  of  the  hind-gut 
from  want  of  solution  of  continuity  in  the  septum  which  in  early  foetal  life  exists  between  the 
two.  The  mucous  membrane  is  thick  and  but  loosely  connected  to  the  muscular  coat  beneath 
and  thus  favors  prolapse,  especially  in  children  The  vessels  of  the  rectum  are  arranged  as 
mentioned  above,  longitudinally,  and  are  contained  in  the  loose  cellular  tissue  between  the 
mucous  and  muscular  coats,  and  receive  no  support  from  surrounding  tissues,  and  this  favors 
varicosity.  Moreover,  the  veins,  after  running  upward  in  a  longitudinal  direction  for  about  five 
inches  in  the  submucous  tissue,  pierce  the  muscular  coats,  and  are  liable  to  become  constricted 
at  this  point  by  the  contraction  of  the  muscular  wall  of  the  gut.  In  addition  to  this  there  are  no 
valves  in  the  superior  hemorrhoidal  veins,  and  the  vessels  of  the  rectum  are  placed  in  a  depen- 


1326  THE    ORGANS    OF  DIGESTION 

dent  position,  and  are  liable  to  be  pressed  upon  and  obstructed  by  hardened  faeces.  The  anatom- 
ical arrangement,  therefore,  of  the  hemorrhoidal  vessels  explains  the  great  tendency  to  the 
occurrence  of  piles.  The  presence  of  the  Sphincter  ani  is  of  surgical  importance,  since  it  is  the 
constant  contraction  of  this  muscle  which  prevents  an  ischio-rectal  abscess  from  healing  and 
tends  to  cause  a  fistula.  Also,  the  reflex  contraction  of  this  muscle  is  the  cause  of  the  severe  pain 
complained  of  in  fissure  of  (he  anus.  The  relations  of  the  peritoneum  to  the  rectum  are  of 
importance  in  connection  with  the  operation  of  removal  of  the  lower  end  of  the  rectum  for 
malignant  disease.  The  membrane  gradually  leaves  the  rectum  as  it  descends  into  the  pelvis; 
first  leaving  its  posterior  surface,  then  the  sides,  and  then  the  anterior  surface  to  become 
reflected  in  the  male  on  to  the  posterior  wall  of  the  bladder,  forming  the  recto-vesical  pouch,  and 
in  the  female  on  to  the  posterior  wall  of  the  vagina,  forming  Douglas's  pouch.  The  recto-vesical 
pouch  of  peritoneum  extends  to  within  three  inches  from  the  anus,  so  that  it  is  not  desirable 
to  remove  more  than  two  and  a  half  inches  of  the  entire  circumference  of  the  bowel,  for  fear 
of  the  risk  of  opening  the  peritoneum.  When,  however,  the  disease  is  confined  to  the  poste- 
rior surface  of  the  rectum,  or  extends  farther  in  this  direction,  a  greater  amount  of  the  poste- 
rior wall  of  the  gut  may  be  removed,  as  the  peritoneum  does  not  extend  on  this  surface  to  a 
lower  level  than  five  inches  from  the  margin  of  the  anus.  The  recto-vaginal  or  Douglas's  pouch 
in  the  female  extends  somewhat  lower  than  the  recto-vesical  pouch  of  the  male,  and  therefore 
it  is  advisable  to  remove  a  less  length  of  the  tube  in  this  sex.  Of  recent  years,  however,  much 
more  extensive  operations  have  been  done  for  the  removal  of  cancer  of  the  rectum,  and  in  these 
the  peritoneal  cavity  has  necessarily  been  opened.  If,  in  these  cases,  the  opening  is  plugged 
with  iodoform  gauze  until  the  operation  is  completed  and  then  the  edges  of  the  wound  in  the 
peritoneum  is  accurately  brought  together  with  sutures,  no  evil  result  appears  to  follow.  For 
cases  of  cancer  of  the  rectum  which  are  too  low  to  be  reached  by  abdominal  section,  and  too 
high  to  be  removed  by  the  ordinary  operation  from  below,  Kraske  has  devised  an  operation 
which  goes  by  his  name.  The  patient  is  placed  on  his  right  side  and  an  incision  is  made  from 
the  second  sacral  spine  to  the  anus.  The  soft  parts  are  now  separated  from  the  back  of  the 
left  side  of  the  sacrum  as  far  as  its  left  margin,  and  the  greater  and  lesser  sacro-sciatic  liga- 
ments are  divided.  A  portion  of  the  lateral  mass  of  the  sacrum,  commencing  on  the  left  border 
at  the  level  of  the  third  posterior  sacral  foramen,  and  running  downward  and  inward  through 
the  fourth  foramen  to  the  cornu,  is  now  cut  away  with  a  chisel.  The  left  side  of  the  wound 
being  now  forcibly  drawn  outward,  the  whole  of  the  rectum  is  brought  into  view,  and  the  dis- 
eased portion  can  be  removed,  leaving  the  anal  portions  of  the  gut,  if  healthy.  The  two  divided 
ends  of  the  gut  can  perhaps  then  be  approximated  and  sutured  together.  Kraske's  operation  is 
in  many  cases  preceded  by  the  performance  of  iliac  colostomy.  In  cancer  high  up  in  the 
rectum  removal  of  the  growth  through  the  abdomen  is  sometimes  practised,  the  divided  lower 
end  of  the  rectum  being  sutured  to  the  divided  upper  end  (Weir's  operation). 

The  colon  frequently  requires  opening  in  cases  of  intestinal  obstruction,  and  by  some  sur- 
geons this  operation  is  performed  in  cases  of  cancer  of  the  rectum,  as  soon  as  the  disease  is 
recognized,  in  the  hope  that  the  rate  of  growth  may  be  retarded  by  removing  the  irritation  pro- 
duced by  the  passage  of  fecal  matter  over  the  diseased  surface.  The  operation  of  colostomy  may 
be  performed  either  in  the  inguinal  or  lumbar  region;  but  inguinal  colostomy  (Maydl's  opera- 
tion) has  at  the  present  day  superseded  the  lumbar  operation.  The  main  reason  for  preferring 
this  operation  is  that  a  spur-shaped  process  can  be  formed  which  prevents  any  fecal  matter  find- 
ing its  way  past  the  artificial  anus  and  becoming  lodged  on  the  diseased  structures  below.  The 
sigmoid  flexure  being  surrounded  by  peritoneum,  a  coil  can  be  drawn  out  of  the  wound,  and 
when  it  is  opened  transversely  a  spur  is  formed,  and  this  prevents  any  fecal  matter  finding  its 
way  from  the  gut  above  the  opening  into  that  below.  The  operation  is  performed  by  making  an 
incision  two  or  three  inches  in  length  from  a  point  one  inch  internal  to  the  anterior  superior 
spinous  process  of  the  ilium,  parallel  to  Poupart's  ligament.  The  various  layers  of  abdominal 
muscles  are  cut  through,  and  the  peritoneum  opened  and  sewed  to  the  external  skin.  The  sigmoid 
flexure  is  now  sought  for,  and  pulled  out  of  the  wound  and  fixed  by  pushing  a  glass  bar  through 
a  slit  in  the  mesocolon.  The  two  parts  of  the  loop  are  sutured  together.  The  intestine  is  now 
sutured  to  the  parietal  peritoneum.  The  wound  is  dressed,  and  either  immediately  or  between 
the  second  to  the  fourth  day,  according  to  the  requirements  of  the  case,  the  protruded  coil  of 
intestine  is  opened.     It  is  opened  transversely  with  the  Paquelin  cautery. 


THE  LIVER  (HEPAR)  (Figs.  936,  937,  938,  939). 

The  liver  is  the  largest  gland  in  the  body,  and  is  situated  in  the  upper  and 
right  part  of  the  abdominal  cavity,  occupying  almost  the  whole  of  the  right  hypo- 
chondrium,  the  greater  part  of  the  epigastrium,  and  extending  into  the  left  hypo- 
chondrium  as  far  as  the  mammary  hne.    In  the  male  it  weighs  from  fifty  to  sixty 


THE  LIVER  1327 

ounces;  in  the  female,  from  forty  to  fifty.  It  is  relatively  much  larger  in  the  foetus 
than  in  the  adult,  constituting,  in  the  former,  about  one-eighteenth,  and  in  the 
latter,  about  one-thirty-sixth  of  the  entire  body-weight.  Its  greatest  transverse 
measurement  is  from  eight  to  nine  inches.  Vertically,  near  its  lateral  or  right 
surface,  it  measures  about  six  or  seven  inches,  while  its  greatest  antero-posterior 
diameter  is  on  a  level  with  the  upper  end  of  the  right  kidney  and  is  from  four  to 
five  inches.  Opposite  the  vertebral  column  its  measurement  from  before  backward 
is  reduced  to  about  three  inches.  Its  consistence  is  that  of  a  soft  solid;  it  is, 
however,  friable  and  easily  lacerated;  its  color  is  a  dark  reddish-brown,  and  its 
specific  gravity  is  1.05. 

To  obtain  a  correct  idea  of  its  shape,  it  must  be  hardened  in  situ,  and  it  will 
then  be  seen  to  present  the  appearance  of  a  wedge,  the  base  of  which  is  directed 
to  the  right  and  the  thin  edge  toward  the  left.  Symington  describes  its  shape  as 
that  "of  a  right-angled  triangular  prism  with  the  right  angles  rounded  off."  It 
possesses  five  surfaces,  viz.,  a  superior,  inferior,  anterior,  posterior,  and  a  right  lateral 
surface. 

Gall-bladder. 


RIGHT   LATERAL 

LIGAMENT. 

LEFT    LATERAL ( 
LIGAMtNT. 

Fig.  936. — The  liver.     Upper  surface.     (Drawn  from  His's  models.) 

The  superior  and  anterior  surfaces  are  separated  from  each  other  by  a  thick 
rounded  border,  and  are  attached  to  the  Diaphragm  and  anterior  abdominal  wall 
by  a  triangular  or  falciform  fold  of  peritoneum,  the  suspensory  or  falciform  liga- 
ment, which  divides  the  liver  into  two  unequal  parts,  termed  the  right  and  left 
lobes  (Figs.  936,  940,  and  941).  Except  along  the  line  of  attachment  of  this  liga- 
ment to  the  liver,  the  superior  and  anterior  surfaces  are  covered  by  peritoneum. 

The  Superior  Area  or  Surface  (fades  superior)  (Fig.  936). — The  superior 
area  or  surface  comprises  a  part  of  both  lobes.  Spalteholz  considers  as  parts  of 
the  superior  surface  the  right  surface  and  the  anterior  surface.  The  superior  sur- 
face is  convex,  and  fits  under  the  vault  of  the  Diaphragm ;  its  central  part,  however, 
presents  a  shallow  depression,  the  cardiac  depression  (impressio  cardiaca),  which 
corresponds  with  the  position  of  the  heart  on  the  upper  surface  of  the  Diaphragm. 
It  is  separated  from  the  anterior,  posterior,  and  lateral  surfaces  by  thick,  rounded 
borders.  Its  left  extremity  is  continued  into  the  under  surface  by  a  prominent 
sharp  margin. 

The  Anterior  Area  or  Surface. — The  anterior  area  or  surface  is  large  and 
triangular  in  shape,  comprising  also  a  part  of  both  lobes.    It  is  directed  forward. 


1328 


THE    ORGANS   OF  DIGESTION 


and  the  greater  part  of  it  is  in  contact  with  the  Diaphragm,  which  separates  it 
from  the  right  lower  ribs  and  their  cartilages.     In  the  middle  line  it  lies  behind 


Gi'eat  splanchnic 

nerve  piercing 

crua. 


Rcceptdculum 
chyli 


Semilunar 
ganglion. 


(heat  iplanchmc 

neiu  piercing 

uus 

'Semilunar 
ganglion 


Fig.  937. — The  relations  of  the  viscera  and  large  vessels  of  the  abdomen.     (Seen  from  behind, 
the  last  dorsal  vertebra  being  well  raised.) 

the  ensiform  cartilage,  to  the  left  of  which  it  is  protected  by  the  seventh  and 
eighth  left  costal  cartilages.  In  the  angle  between  the  diverging  rib  cartilages 
of  opposite  sides  the  anterior  surface  is  in  contact  with  the  abdominal  wall.      It 


THE    LIVER  1329 

is  continuous  with  the  inferior  surface  by  a  sharp  margin,  and  with  the  superior 
and  lateral  surfaces  by  thick  rounded  borders. 

The  Lateral  or  Right  Area  or  Surface  (Figs.  936  and  938).— The  lateral  or 
right  area  or  surface  is  convex  from  before  backward  and  slightly  so  from 
above  downward.  It  is  directed  toward  the  right  side,  forming  the  base  of  the 
wedge,  and  lies  against  the  lateral  portion  of  the  Diaphragm,  which  separates 
it  from  the  lower  part  of  the  left  pleura  and  lung,  outside  which  are  the  right 
costal  arches  from  the  seventh  to  the  eleventh  inclusive. 

The  Under  or  Visceral  Area  or  Surface  {jades  inferior)  (Figs.  938  and  939). — 
The  under  or  visceral  area  or  surface  is  uneven,  concave,  directed  downward  and 
backward  and  to  the  left,  and  is  in  relation  with  the  stomach  and  duodenum,  the 
hepatic  flexure  of  the  colon,  and  the  right  kidney.  The  surface  is  divided  by  a 
longitudinal  fissure  into  a  right  and  a  left  lobe,  and  is  almost  completely  invested 
by  peritoneum;  the  only  parts  where  this  covering  is  absent  are  where  the  gall- 
bladder is  attached  to  the  liver  and  at  the  transverse  fissure,  where  the  two  layers 
of  the  lesser  omentum  are  separated  from  each  other  by  the  blood-vessels  and 
duct  of  the  viscus.  The  under  surface  of  the  left  lobe  presents  to  the  right  and 
near  the  centre  a  rounded  eminence,  the  omental  tuberosity  {tuher  omentale)  (Fig. 
938),  which  is  in  contact  with  the  lesser  omentum.  It  is  surrounded  by  a  broad 
depression,  the  gastric  surface  or  impression  (impressio  gastrica),  with  which  the 
stomach  is  in  contact.  Between  the  gall-bladder  and  the  left  lobe  is  the  quad- 
rate lobe.  The  quadrate  lobe  is  bounded  to  the  left  by  the  umbilical  fissure  or  the 
fissure  of  the  umbilical  vein  (fossa  venae  umbilicalis) ,  which  is  the  anterior  portion 
of  the  longitudinal  fissure  and  lodges  the  round  ligament  (ligamentum  teres) .  The 
under  surface  of  the  right  lobe  is  divided  into  two  unequal  portions  by  a  fossa, 
which  lodges  the  gall-bladder  and  is  called  the  fossa  vesicalis  (fossa  vesicae  felleae) ; 
the  portion  to  the  left,  the  smaller  of  the  two,  is  somewhat  oblong  in  shape,  its 
antero-posterior  diameter  being  greater  than  its  transverse.  It  is  known  as  the 
quadrate  lobe  (lobus  quadratus),  and  is  in  relation  with  the  pyloric  end  of  the 
stomach  (impressio  pylorica)  and  the  first  portion  of  the  duodenum.  The  portion 
of  the  under  surface  of  the  right  lobe  to  the  right  of  the  fossa  vesicalis  presents 
two  shallow  concave  impressions,  one  situated  behind  the  other,  the  two  being 
separated  by  a  ridge.  The  anterior  of  these  two  impressions,  the  colic  impression 
(impressio  colica),  is  produced  by  the  hepatic  flexure  of  the  colon;  the  posterior, 
the  renal  impression  (impressio  renalis),  is  occupied  by  the  upper  end  of  the 
right  kidney  (Fig.  938).  To  the  inner  side  of  the  latter  impression  is  a  third 
and  slightly  marked  impression,  lying  between  it  and  the  neck  of  the  gall- 
bladder. This  is  caused  by  the  second  portion  of  the  duodenum,  and  is  known 
as  the  duodenal  impression  (impressio  duodenalis).  Just  in  front  of  the  vena  cava 
is  a  narrow  strip  of  liver  tissue,  the  caudate  lobe,  which  connects  the  right  infe- 
rior angle  of  the  Spigelian  lobe  to  the  under  surface  of  the  right  lobe.  Imme- 
diately below  it  is  the  foramen  of  Winslow. 

The  Posterior  Area  or  Surface  (fades  posterior)  (Figs.  937  and  939). — The 
posterior  area  or  surface  is  rounded  and  broad  behind  the  right  lobe,  but  narrow 
on  the  left.  Over  a  large  part  of  its  extent  it  is  not  covered  by  peritoneum ;  this 
uncovered  area  (Fig.  938)  is  about  three  inches  broad,  and  is  in  direct  contact  with 
the  Diaphragm,  being  united  to  it  by  areolar  tissue.  In  this  tissue  are  numerous 
small  veins  which  join  the  portal  circulation  to  the  systemic  circulation.  The 
uncovered  area  is  marked  off  from  the  upper  surface  by  the  line  of  reflection  of 
the  upper  or  anterior  layer  of  the  coronary  ligament.  It  is  in  the  same  way 
marked  off  from  the  under  surface  of  the  liver  by  the  line  of  reflection  of  the  lower 
layer  of  the  coronary  ligament  (Fig.  940).  In  its  centre  the  posterior  surface  is  deeply 
notched  for  the  vertebral  column  and  crura  of  the  Diaphragm,  and  to  the  right 
of  this  it  is  indented  for  the  inferior  vena  cava  (fossa  venae  cavae),  which  is  often 

84 


1330 


THE    ORGANS    OF  DIGESTION 


partly  embedded  in  its  substance.  Close  to  the  right  of  this  indentation  and 
immediately  above  the  renal  impression  is  a  small  triangular  depressed  area,  the 
suprarenal  impression  (impressio  suprarenalis)  (Fig.  938),  the  greater  part  of  which 
is  devoid  of  peritoneum ;  it  lodges  the  right  suprarenal  capsule,  which  is  inserted 
between  the  liver  and  Diaphragm.  To  the  left  of  the  fossa  for  the  inferior  vena 
cava  is  the  Spigelian  lobe,  which  lies  between  the  fissure  for  the  vena  cava  and  the 
fissure  for  the  ductus  venosus.  Below  and  in  front  it  projects  and  forms  part  of  the 
posterior  boundary  of  the  transverse  fissure.  Here,  to  the  right,  it  is  connected 
with  the  under  surface  of  the  right  lobe  of  the  liver  by  the  caudate  lobe,  and  to 
the  left  it  presents  a  tubercle,  the  tuberculum  papillare  (Fig.  938).  It  is  opposite 
the  tenth  and  eleventh  dorsal  vertebrae,  and  rests  upon  the  aorta  and  crura  of  the 
Diaphragm,  being  covered  by  the  peritoneum  of  the  lesser  sac.  The  lobe  is 
nearly  vertical  in  position,  and  is  directed  backward;  it  is  longer  from  above 
downward  than  from  side  to  side,  and  is  somewhat  concave  in  the  transverse 
direction.  On  the  posterior  surface  to  the  left  of  the  Spigelian  lobe  is  a  groove^ 
the  oesophageal  groove  (impressio  oesophagea),  indicating  the  position  of  the 
abdominal  portion  of  the  oesophagus  (Fig.  938). 


Suprarenal 
impression 
{non-peritoneal), 

Suprarenal 
impression 
(peritoneal). 
Tuberculum 
cav  datum. 


Tuberculum 
papillare. 

Umbilical  fissure.  Transverse  fissure. 

Fig.  938. — The  liver.     Posterior  and  inferior  surfaces.     (Drawn  from  His's  models.) 

Prof.  Cunningham  divides  the  liver  into  two  surfaces,  a  visceral  and  a  parietal, 
and  subdivides  the  parietal  surface  into  a  posterior  area  and  superior  area,  an  ante- 
rior area  and  a  right  area.  The  parietal  surface  is  separated  from  the  visceral 
surface  by  the  inferior  border  or  margin. 

The  inferior  border  or  margin  (margo  inferioris) ,  posteriorly,  is  rather  ill  defined. 
It  is  the  lower  margin  of  the  posterior  surface;  it  follows  the  line  of  rib  and  is  in 
contact  with  the  right  kidney.  At  the  right  side  the  lower  margin  is  thick  and 
distinct,  and,  as  a  rule,  projects  slightly  below  the  thorax.  The  front  of  the 
inferior  margin  is  called  the  anterior  margin  (margo  anterior).  It  is  a  sharp  edge 
which,  on  inspiration,  corresponds  to  an  oblique  line  on  the  abdominal  wall 
drawn  from  "a  point  half  an  inch  below  the  margin  of  the  ribs  (tip  of  tenth 
costal  cartilage),  on  the  right  side,  to  a  point  an  inch  below  the  nipple  on  the 
left,  and  extending  down  in  the  middle  line  to  a  point  half-way  between  the 
gladiolus  and  the  umbilicus."^ 

In  men  the  anterior  margin  of  the  liver  often  corresponds  to  the  lower  margin 
of  the  ribs,  but  in  women  and  children  it  is  usually  below  the  ribs  in  the  line 


'  Ambrose  Birmingham,  in  Cunningham's  Text-book  of  Anatomy. 


THE   LIVER 


1331 


indicated  above.  Opposite  the  attachment  of  the  falciform  Hgament  the  anterior 
border  often  exhibits  a  deep  notch,  the  umbilical  notch  (incisura  umhilicalis), 
which  is  the  anterior  end  of  the  fossa  venae  umbihcahs.  Another  notch,  some- 
times present,  corresponds  to  the  fundus  of  the  gall-bladder,  and  is  known  as  the 
notch  of  the  gall-bladder  {incisura  vesicae  jelleae). 

The  left  extremity  of  the  inferior  margin  of  the  liver  is  thin  and  flattened  from 
above  downward.  The  margin  passes  posteriorly  around  the  free  end  of  the  left 
lobe  and  terminates  posteriorly  at  the  oesophageal  groove. 

Fissures. — Five  fissures  are  seen  upon  the  under  and  posterior  surfaces  of  the 
liver,  which  serve  to  divide  it  into  five  lobes.  They  are:  the  umbilical  fissure, 
the  fissure  of  the  ductus  venosus,  the  transverse  fissure,  the  fissure  for  the  gall-bladder, 
and  the  fissure  for  the  inferior  vena  cava.  They  are  arranged  in  the  form  of  the 
letter  H.  The  left  limb  of  the  H  is  known  as  the  longitudinal  fissure.  The 
right  limb  is  formed  in  front  by  the  fissure  for  the  gall-bladder,  and  behind 
by  the  fissure  for  the  inferior  vena  cava;  these  two  fissures  are  separated  from 
each  other  by  the  caudate  lobe.  The  connecting  bar  of  the  H  is  the  transverse  or 
portal  fissure.  It  separates  the  quadrate  lobe  in  front  from  the  caudate  and 
Spigelian  lobes  behind. 

(Esophageal  groove.        Portal  vein.         Suprarenal  impression. 

,^{<0VE.RED     By  RIGHT    LATERAL 


LIGAMENTUM 
TERES. 


Hepatic  artery. 

Common  bile-dtict. 
Fig.  939. — Posterior  and  under  surfaces  of  the  liver.     (From  Ellis.) 

The  Longitudinal  Fossa  or  Fissure  (fossa  longitudinalis  sinistra). — The  longi- 
tudinal fissure  is  a  deep  groove,  which  extends  from  the  notch  on  the  anterior 
margin  of  the  liver  to  the  upper  border  of  the  posterior  surface  of  the  organ.  It 
separates  the  right  and  left  lobes;  the  Transverse  Fissure  (Fig.  938)  joins  it,  at 
right  angles,  and  divides  it  into  two  parts.  The  anterior  part  is  called  the  um- 
bilical fossa  or  fissTure  (fossa  venae  umhilicalis)  (Fig.  938) ;  it  is  deeper  than  the 
posterior,  and  lodges  the  umbilical  vein  in  the  foetus,  and  its  remains  (the  round 
ligament)  in  the  adult;  the  posterior  part  contains  the  ductus  venosus,  and  is 
known  as  the  fissure  of  the  ductus  venosus.  This  fissure  lies  between  the  quadrate 
lobe  and  the  left  lobe  of  the  liver,  and  is  often  partially  bridged  over  by  a 
prolongation  of  the  hepatic  substance,  the  pons  hepatis. 

The  Fissure  or  Fossa  of  the  Ductus  Venosus  (fossa  ductus  venosi)  (Fig.  938)  is 
the  back  part  of  the  longitudinal  fissure,  and  is  situated  mainly  on  the  posterior 
surface  of  the  liver.     It  lies  between  the  left  lobe  and  the  lobe  of  Spigelius.     It 


1332  THE    ORGANS   OF  DIGESTION 

lodges  in  the  foetus  the  ductus  venosus,  and  in  the  adult  a  slender  fibrous  cord, 
the  obliterated  remains  of  that  vessel. 

The  Transverse  or  Portal  Fissure  {"porta  hepatis)  (Fig.  938). — The  transverse  or 
portal  fissure  is  a  short  but  deep  fissure,  about  two  inches  in  length,  extending 
transversely  across  the  under  surface  of  the  left  portion  of  the  right  lobe,  nearer  to 
its  posterior  surface  than  its  anterior  border.  It  joins,  nearly  at  right  angles,  with 
the  longitudinal  fissure,  and  separates  the  quadrate  lobe  in  front  from  the  cau- 
date and  Spigelian  lobes  behind.  By  the  older  anatomists  this  fissure  was  con- 
sidered the  gateway  (porta)  of  the  liver;  hence  the  large  vein  which  enters  at  this 
fissure  was  called  the  portal  vein  (Fig.  939).  Besides  this  vein,  the  fissure  trans- 
mits the  hepatic  artery  and  nerves,  and  the  hepatic  duct  and  lymphatics.  At 
their  entrance  into  the  fissure,  the  hepatic  duct  lies  in  front  and  to  the  right, 
the  hepatic  artery  to  the  left,  and  the  portal  vein  behind  and  between  the  duct 
and  artery. 

The  Fossa  or  Fissure  for  the  Gall-bladder  (fossa  vesicae  felleae). — The  fossa  or 
fissure  for  the  gall-bladder  is  a  shallow,  oblong  fossa,  placed  on  the  under  surface 
of  the  right  lobe,  parallel  with  the  longitudinal  fissure.  It  extends  from  the 
anterior  free  margin  of  the  liver,  which  is  notched  for  its  reception,  to  the  right 
extremity  of  the  transverse  fissure. 

The  Fissure  or  Fossa  for  the  Inferior  Vena  Cava  (fossa  venae  cavae)  (Fig.  938).— 
The  fissure  or  fossa  for  the  inferior  vena  cava  is  a  short,  deep  fissure,  in  some  cases 
a  complete  canal,  in  consequence  of  the  substance  of  the  liver  occasionally  sur- 
rounding the  vena  cava.  It  extends  obliquely  upward  from  the  lobus  caudatus, 
which  separates  it  from  the  transverse  fissure,  on  the  posterior  surface  of  the  liver, 
and  separates  the  Spigelian  from  the  right  lobe.  On  slitting  open  the  inferior 
vena  cava  the  orifices  of  the  hepatic  veins  will  be  seen  opening  into  this  vessel  at 
its  upper  part,  after  perforating  the  floor  of  this  fissure. 

Lobes. — The  lobes  of  the  liver,  like  the  ligaments  and  fissures,  are  five  in 
number — the  right  lobe,  the  left  lobe,  the  lobus  quadratus,  the  lobus  Spigelii,  and 
the  lobus  caudatus,  the  last  three  being  merely  parts  of  the  right  lobe. 

The  Right  Lobe  (lobus  hepatis  dexter)  (Figs.  936  and  938) . — The  right  lobe  is 
much  larger  than  the  left;  the  proportion  between  them  being  as  six  to  one.  It 
occupies  the  right  hypochondrium,  and  is  separated  from  the  left  lobe,  on  its  upper 
and  anterior  surfaces  by  the  falciform  ligament;  on  its  under  and  posterior  surfaces 
by  the  longitudinal  fissure;  and  in  front  by  the  umbilical  notch.  It  is  of  a  some- 
what quadrilateral  form,  its  under  and  posterior  surfaces  being  marked  by  three 
fissures — the  transverse  fissure,  the  fissure  for  the  gall-bladder,  and  the  fissure  for 
the  inferior  vena  cava,  which  separate  its  left  part  into  three  smaller  lobes — the 
lobus  Spigelii,  lobus  quadratus,  and  lobus  caudatus.  On  it  are  seen  four  shallow 
impressions:  one  in  front,  for  the  hepatic  flexure  of  the  colon;  a  second  behind, 
for  the  right  kidney;  a  third  internal,  between  the  last-named  and  the  gall-bladder, 
for  the  second  part  of  the  duodenum;  and  a  fourth  on  its  posterior  surface,  for  the 
suprarenal  capsule. 

The  Lobus  Quadratus  or  Square  Lobe  (Figs.  938  and  939)  is  situated  on  the 
under  surface  of  the  right  lobe,  is  bounded  in  front  by  the  inferior  margin  of  the 
liver;  behind,  by  the  transverse  fissure;  on  the  right,  by  the  fissure  of  the  gall- 
bladder; on  the  left,  by  the  umbilical  fissure. 

The  Lobus  Spigelii  (lobus  caudatus  [Spigeli])  (Figs.  938  and  939)  is  situated 
upon  the  posterior  surface  of  the  right  lobe  of  the  liver.  It  looks  directly  back- 
ward, and  is  nearly  vertical  in  direction.  It  is  bounded,  above,  by  the  upper  layer 
of  the  coronary  ligament;  below,  by  the  transverse  fissure;  on  the  right,  by  the 
fissure  for  the  vena  cava;  and  on  the  left,  by  the  fissure  for  the  ductus  venosus. 
Its  left  upper  angle  forms  part  of  the  groove  for  the  oesophagus.  What  is  here 
called  the  lobus  Spigelii,  Spalteholz  calls  the  lobus  caudatus  of  Spigelius. 


THE   LIVER  1333 

The  Lobus  Caudatus  or  Tuberculum  Caudatum  (processus  caudatus)  (Fig.  938),  or 
tailed  lobe,  is  a  small  elevation  of  the  hepatic  substance  extending  obliquely  out- 
ward, from  the  lower  extremity  of  the  Spigelian  lobe  to  the  under  surface  of  the 
right  lobe.  It  is  situated  behind  the  transverse  fissure,  and  separates  the  fissure 
for  the  gall-bladder  from  the  commencement  of  the  fissure  for  the  inferior  vena 
cava.  What  is  here  called  the  lobus  caudatus,  Spalteholz  calls  the  processus 
caudatus  of  the  lobus  caudatus  of  Spigelius. 

The  Left  Lobe  (lobus  hepatis  sinister)  (Figs.  936  and  938). — The  left  lobe  is 
smaller  and  more  flattened  than  the  right.  It  is  situated  in  the  epigastric  and 
left  hypochondriac  regions.  Its  upper  surface  is  slightly  convex;  its  under  sur- 
face is  concave,  and  presents  a  shallow  depression  for  the  stomach,  the  gastric 
impression.  This  is  situated  in  front  of  the  groove  for  the  oesophagus,  and  is 
separated  from  the  longitudinal  fissure  by  the  omental  tuberosity,  which  lies  against 
the  small  omentum  and  lesser  curvature  of  the  stomach.  The  posterior  end  of 
the  left  lobe  frequently  exhibits  a  flat  projection,  composed  of  connective  tissue, 
and  called  the  appendix  fibrosa  hepatis.  In  the  adult,  portions  only  of  bile-ducts 
are  present  in  it.  In  the  newborn  it  is  a  definite  portion  of  secreting  liver  substance, 
which  later  undergoes  connective-tissue  transformation. 

Ligaments. — The  liver  is  connected  to  the  under  surface  of  the  Diaphragm 
and  the  anterior  walls  of  the  abdomen  and  the  inferior  vena  cava  by  six  ligaments, 
four  of  which  are  peritoneal  folds;  the  other  two,  which  are  the  round  ligament 
and  the  ligament  of  the  ductus  venosus,  are  fibrous  cords,  resulting  from  the 
obliteration  of  foetal  vessels.  These  ligaments  are  the  falciform,  two  lateral, 
coronary,  round,  and  the  ligament  of  the  ductus  venosus.  It  is  also  attached  to  the 
lesser  curvature  of  the  stomach  by  the  gastro-hepatic  or  small  omentum. 

CORONARY  ^ ii^fg^,     SPIGELIAN  LEFT 

LI<.AMENT^><C^    «ss^=SJ«^ffl!s'm_     tO,BE  ""^LATERAL 

LIGAMENT 


RIGHT 
LATERAL. 
LIGAMENT 


FALCIFORM 
LIGAMENT 


Fig.  940. — The  peritoneal  ligaments  of  the  liver.     (Schematic.)     (Poirier  and  Charpy.) 

The  Falciform,  Broad  or  Suspensory  Ligament  (ligamentum  falciforme  hepatis) 
(Figs.  936,  940,  and  941). — The  falciform  or  suspensory  Hgament  is  a  broad  and 
thin  antero-posterior  peritoneal  fold,  falciform  in  shape,  its  base  being  directed 
downward  and  backward,  its  apex  upward  and  backward.  It  is  attached  by  one 
margin  to  the  under  surface  of  the  Diaphram,  and  the  posterior  surface  of  the 
sheath  of  the  right  Rectus  muscle  to  within  one  inch  of  the  umbilicus;  by  its 
hepatic  margin  it  extends  from  the  notch  on  the  anterior  margin  of  the  liver,  as 
far  back  as  its  posterior  surface. 

The  free  edge  or  base  of  the  falciform  ligament  reaches  from  a  little  above  and  to 
the  right  of  the  umbilicus  to  the  umbilical  fissure  on  the  anterior  margin  of  the  liver. 
This  free  edge  contains  between  its  folds  the  round  ligament  of  the  liver.  On  the 
posterior  surface  of  the  liver  the  two  peritoneal  folds  which  constitute  the  falci- 
form ligament  separate,  the  right  fold  passing  into  the  upper  fold  of  the  coronary 
ligament,  the  left  fold  passing  into  the  upper  fold  of  the  left  lateral  ligament. 


1334 


THE    ORGANS    OF  DIGESTION 


The  Lateral  Ligaments  (Figs.  936  and  940). — The  lateral  ligaments  are  two  in 
number,  and  are  called  the  right  and  left  lateral  ligaments. 

The  Right  Lateral  Ligament  (liganientum  triancjulare  dexirum)  (Figs.  936  and 
940)  is  in  reality  the  right  extremity  of  the  coronary  ligament.  This  ligament  is 
triangular  in  form,  runs  from  the  liver  to  the  Diaphragm,  and  is  formed  by  the 
apposition  of  the  upper  and  lower  layers  of  the  coronary  ligament.  It  is 
attached  to  the  liver  between  its  lateral  and  inferior  surfaces. 

The  Left  Lateral  Ligament  (ligamentum  trlangulare  sinistrum)  (Figs.  936  and 
940)  is  also  formed  by  apposition  of  the  upper  and  lower  layers  of  the  coronary 

ligament.     It  is  triangular  in  form. 


runs 


Fig.  941. — Diagram  to  show  the  relations  o/  the  falci- 
form or  suspensory  and  round  ligaments  to  the  liver  and 
the  abdominal  wall.     (Gerrish.) 


from  the  liver  to  the  Dia- 
phragm, and  is  longer  than  the  right 
lateral  ligament.  It  is  attached  to 
the  upper  surface  of  the  left  lobe, 
where  it  lies,  in  front  of  the  oesopha- 
geal opening  in  the  Diaphragm. 

The  Coronary  Ligament  {ligamentum 
coronarium  hepatis)  (Figs.  936  and 
940). — The  coronary  ligament  con- 
nects the  posterior  surface  of  the  liver 
to  the  Diaphragm.  It  is  formed  by 
the  reflection  of  the  peritoneum  from 
the  Diaphragm  on  to  the  upper  and 
lower  margins  of  the  posterior  sur- 
face of  the  liver.  The  coronary  liga- 
ment consists  of  two  layers,  which 
are  continuous  on  each  side  with  the 
lateral  ligaments,  and,  in  front,  with 
the  falciform  ligament.  Between  the  layers  a  large  triangular  area  is  left  un- 
covered by  peritoneum,  and  is  connected  to  the  Diaphragm  by  firm  areolar  tissue. 
The  Round  Ligament  {ligamentmn  teres  hepatis)  (Figs.  939  and  941). — The 
round  hgament  is  a  fibrous  cord  resulting  from  the  obliteration  of  the  foetal  umbil- 
ical vein.  It  ascends  from  the  umbilicus,  in  the  free  margin  of  the  falciform 
ligament,  to  the  notch  in  the  anterior  border  of  the  liver,  from  which  it  may  be 
traced  along  the  umbilical  fissure  on  the  under  surface  of  the  liver,  to  the  left 
branch  of  the  portal  vein. 

The  Ligament  of  the  Ductus  Venosus  {ligamentum  venosum  [.4ranfi{])  is  com- 
posed of  slender  bundles  of  fibrous  tissue,  and  results  from  the  obliteration  of  the 
ductus  venosus  of  the  foetus.  It  arises  from  the  left  branch  of  the  portal  vein, 
almost  opposite  the  insertion  of  the  round  ligament,  passes  backward  in  the  fissure 
of  the  ductus  venosus,  and,  as  it  emerges  from  the  liver,  is  attached  to  the  vena  cava. 
Support  and  Movability  of  the  Liver. — The  liver  is  movable  within  certain 
narrow  limits.  It  moves  with  respiration.  On  inspiration  it  moves  down  with 
the  Diaphragm  to  distinctly  below  the  costal  arch  in  the  right  nipple  line. 
Much  discussion  has  taken  place  as  to  what  supports  the  liver  in  place.  Syming- 
ton asserted  that  the  ligaments  do  not  give  support,  because  they  lie  relaxed. 
Other  observers  (Graham,  Steele)  apparently  demonstrate  that  the  peritoneal 
ligaments  do  give  some  support  to  the  liver.  The  connective  tissue  which  unites 
the  uncovered  area  of  the  right  lobe  of  the  liver  to  the  Diaphragm  and  the  hepatic 
veins  which  join  the  vena  cava  (Faure)  do  give  distinct  support.  The  chief  factor 
in  the  support  of  the  liver  is  the  intra-abdominal  pressure  resulting  from  the 
tonic  contraction  of  the  abdominal  muscles.  When  abdominal  tension  is  normal 
the  intestines  are  driven  up  and  become  a  bed  for  the  Uver.  Intrahepatic  vascular 
tension  aids  in  supporting  the  liver  (Glenard). 


THE   LIVER 


1335 


Abnormalities  of  the  Liver. — The  liver  may  be  divided  into  many  lobules,  and 
such  lobulation  is  most  evident  on  the  parietal  surface  of  the  right  lobe.  I^obula- 
tion  is  probably  a  pathological  change.  Occasionally  the  right  lobe  is  small  and 
the  left  large. 

The  editor,  in  performing  an  abdominal  operation,  encountered  a  liver  the 
left  lobe  of  which  was  so  large  and  the  right  so  small  as  to  suggest  transposition 
or  rotation  of  the  organ.  Such  a  change  may  result  from  abnormality  of  the 
foetal  circulation  or  from  syphilitic  disease  of  the  right  lobe,  producing  cicatricial 
contraction.^  The  left  lobe  may  be  very  small;  sometimes  it  is  rudimentary. 
When  the  left  lobe  is  very  small  an  unusual  amount  of  stomach  is  visible,  and  the 
entire  gall-bladder  can  be  seen  from  the  front.  In  such  a  case  the  gall-bladder  is 
usually  displaced  and  it  may  actually  "lie  with  its  long  axis  in  the  transverse  axis 
of  the  body."^' 


DIAPHRAGMATIC 
GROOVE 


Fig.  942. — Deformed  female  liver.     (Poirier  and  Charpy.) 


Atrophy  of  the  left  lobe  is  usually  a  congenital  defect,  but  may  result  from 
syphilis.  Small  accessory  lobes,  about  one  inch  in  length,  are  not  uncommon,  and 
they  are  most  often  met  with  on  the  visceral  surface  of  the  right  lobe.  "When 
markedly  pedunculated,  they  may  form  accessory  livers.  The  Spigelian  lobe  is 
sometimes  curiously  pedunculated."^ 

Accessory  livers  are  fragments  of  hepatic  tissue  or  rests,  which  are  entirely 
separated  from  the  liver.  They  are  seldom  met  with.  When  they  do  exist  their 
mo.st  common  situation  is  in  the  suspensory  ligament,  but  they  have  been  found 
in  the  great  omentum,  in  the  peritoneum,  wall  of  the  gall-bladder,  and  in  other 
situations.  They  may  be  congenital  or  may  be  due  to  atrophy  of  the  pedicle  of  an 
accessory  lobe  or  of  a  pedunculated  lobe.  Tight  lacing  alters  the  shape  and  posi- 
tion of  the  liver  (Fig.  942).  It  may  flatten  the  dome  and  increase  the  length  of 
the  anterior  surface,  this  change  being  especially  obvious  in  the  right  lobe,  and  a 
costal  groove  may  be  formed  by  the  pressure  of  a  rib.  "When  the  elongated 
right  lobe  passes  over  the  right  kidney,  there  is  atrophy  of  the  hepatic  substance 


1  H.  D.  RoUeston  on  Diseases  of  the  Liver. 


2  Ibid. 


8  Ibid. 


1336  THE   ORGANS    OF  DIGESTION 

and  thickening  of  the  capsule,  which  is  opaque  and  forms  a  hinge-Hke  Hgament 
between  the  main  part  of  the  right  lobe  above  and  the  constricted  lower  portion. 
This  lobe  is  variously  termed  partial  hepatoptosis,  constriction  lobe,  or  the  sus- 
tentacula! formation  of  the  right  lobe  (Hertz).  The  constriction  furrow  is  pro- 
duced by  the  pressure  of  the  corset  in  front  and  the  resistance  of  the  kidney 
behind.  The  constriction  lobe  tapers  to  a  point,  so  that  the  shape  of  the  liver,  as 
seen  from  the  front,  is  that  of  a  right-angled  triangle,  with  the  apex  downward."^ 
The  condition  resembles  Riedel's  lobe.  The  left  lobe  may  also  project  down, 
but  not  so  markedly.  Tight  lacing  may  cause  the  entire  organ  to  occupy  a  level 
higher  than  normal.  Such  a  liver  is  thick  and  excessively  convex  above  and 
thin  below,  and  reaches  to  or  laps  over  the  spleen.  In  severe  cases  the  superior 
surface  is  thrown  into  antero-posterior  creases  or  folds.  Linguiform  or  tongue-like 
lobe,  Riedel's  lobe  or  floating  lobe  (Fig.  942),  may  be  congenital,  may  be  due  to  tight 
lacing,  or  may  arise  in  cholelithiasis  or  cholecystitis  from  the  traction  of  adhesions. 
Such  a  lobe  comes  off  from  the  right  lobe.  It  may  be  a  tapering  mass  of  liver 
tissue,  it  may  have  a  thin  pedicle  of  liver  tissue,  or  its  pedicle  may  be  merely  a 
double  fold  of  peritoneum.  The  gall-bladder  may  lie  upon  its  under  surface,  or 
may  be  placed  to  the  left  of  it. 

Vessels. — ^The  blood-vessels  connected  with  the  liver  are  the  hepatic  artery,  the 
portal  vein  and  the  hepatic  veins. 


Fig.  943. — Schematic  section  of  the  liver.    The  fibron  tunic  shown  in  black  and  tne  capsule  of  Glisson  in  red. 

The  Hepatic  Artery  and  Portal  Vein  (Figs.  418,  419,  489,  and  944),  accompanied 
by  numerous  lymphatics  and  nerves,  ascend  to  the  transverse  fissure  between  the 
layers  of  the  gastro-hepatic  omentum,  and  in  front  of  the  foramen  of  Winslow. 
The  hepatic  duct,  lying  in  company  with  them,  descends  from  the  transverse  fissure 
between  the  layers  of  the  same  omentum.  The  relative  position  of  the  three 
structures  in  the  lesser  omentum  (Fig.  859)  is  as  follows :  the  hepatic  duct  lies  to 
the  right,  the  hepatic  artery  to  the  left,  and  the  portal  vein  behind  and  between 
the  other  two.  They  enter  the  transverse  fissure  in  the  above-described  order,  but 
in  that  fissure  undergo  rearrangement,  the  duct  being  in  front,  the  artery  in  the 
middle,  and  the  vein  behind.  The  artery,  the  vein,  and  the  duct  divide  into  a 
right  and  left  branch  and  several  smaller  branches,  and  within  the  organ  the 
vessels  from  the  three  sources  accompany  each  other  and  divide  at  the  same 
points;  so  each  branch  of  the  portal  vein  is  accompanied  by  a  branch  of  the 
hepatic  artery  and  of  the  duct.  They  are  enveloped  in  a  loose  areolar  tissue,  the 
capsule  of  Glisson  (Fig.  943) ,  which  accompanies  the  vessels  in  their  course  through 
the  'portal  canals  in  the  interior  of  the  organ. 

The  Hepatic  Veins  (Fig.  421).— The  hepatic  veins  convey  the  blood  from  the  liver. 
They  commence  in  the  substance  of  the  Hver,  in  the  capillary  terminations  of  the  por- 
tal vein  and  hepatic  artery;  these  tributaries,  gradually  uniting,  usually  form  three 

1  Rolleston,  on  Diseases  of  the  Liver. 


THE   LIVER 


1337 


veins,  which  converge  toward  the  posterior  surface  of  the  liver  and  open  into  the 
portion  of  the  inferior  vena  cava  situated  in  the  groove  at  the  back  part  of 
this  organ.  Of  these  three  veins,  one  from  the  right  and  another  from  the  left 
lobe  open  obliquely  into  the  vena  cava;  that  from  the  middle  of  the  organ  and 
lobus  Spigelii  having  a  straight  course. 

The  hepatic  veins  have  very  little  cellular  investment;  what  there  is  binds  their 
parietes  closely  to  the  walls  of  the  canals  through  which  they  run;  so  that,  on 
section  of  the  organ,  these  veins  remain  widely  open  and  solitary  (Fig.  946), 
and  may  be  easily  distinguished  from  the  branches  of  the  portal  vein  (Fig.  947), 
which  are  more  or  less  collapsed,  and  always  accompanied  by  an  artery  and  duct. 
The  hepatic  veins  are  destitute  of  valves. 

Structure. — The  substance  of  the  liver  is  composed  of  lobules  held  together  by 
extremely  fine  areolar  tissue,  and  of  the  ramifications  of  the  portal  vein,  hepatic 
duct,  hepatic  artery,  hepatic  veins,  lymphatics,  and  nerves,  the  whole  being 
invested  by  a  serous  and  a  fibrous  coat. 


COMMON    DUCT 


FORAMEN  OF 
WINSLOW 


DUODENUM 


Fig.  944. — The  relations  of  the  vessels  as  they  pass  into  the  transverse  fissure  of  the  liver.    (Poirier  and  Charpy.) 


The  Serous  Coat  {tunica  serosa). — The  serous  coat  is  derived  from  the  perito- 
neum, and  invests  the  greater  part  of  the  surface  of  the  organ.  It  is  intimately 
adherent  to  the  fibrous  coat. 

The  Areolar  or  Fibrous  Coat  {capsula  fibrosa  [Glissoni]). — The  areolar  or  fibrous 
coat  lies  beneath  the  serous  investment  and  covers  the  entire  surface  of  the  organ. 
It  is  difficult  of  demonstration,  excepting  where  the  serous  coat  is  deficient.  At 
the  transverse  fissure  it  is  thick  and  evident,  is  known  as  the  capsule  of  Glisson, 
and  envelops  the  vessels  which  enter  the  liver  and  passes  with  them  along  the 
portal  canals.  The  areolar  tissue  which  surrounds  and  binds  together  the  liver 
lobules  is  continuous  with  the  areolar  coat. 

The  Lobules  (lobuli  hepatis)  (Fig.  049). — The  lobules  form  the  chief  mass  of 
the  hepatic  substance ;  they  may  be  seen  either  on  the  surface  of  the  organ  or  by 
making  a  section  through  the  gland.  They  are  small  granular  bodies  about  the  size 
of  a  millet-seed,  measuring  from  one-twentieth  to  one-tenth  of  an  inch  in  diameter. 
In  the  human  subject  their  outline  is  very  irregular,  but  in  some  of  the  lower 


1338 


THE    OBGANS    OF   DIGESTION 


animals  (for  example,  the  pig)  they  are  well  defined,  and  when  divided  transversely 
have  a  polygonal  outline.  If  divided  longitudinally  they  are  more  or  less  foliated 
or  oblong.  The  bases  of  the  lobules  are  clustered  around  the  smallest  radicles 
of  the  hepatic  veins  (sublobular  veins),  to  which  each  is  connected  by  means  of  a 
small  branch  which  issues  from  the  centre  of  the  lobule  (intralobular  vein).  The 
remaining  part  of  the  surface  of  each  lobule  is  imperfectly  isolated  from  the  sur- 
rounding lobules  by  a  thin  stratum  of  areolar  tissue  in  which  are  ducts  and  a  plexus 
of  vessels,  the  interlobular  plexus  (Figs.  948  and  949) .  In  some  animals,  as  the 
pig,  the  lobules  are  completely  isolated  one  from  another  by  this  interlobular  areolar 
tissue. 

If  one  of  the  sublobular  veins  be  laid  open,  the  bases  of  the  lobules  may  be 
seen  through  the  thin  wall  of  the  vein  on  which  they  rest,  arranged  in  the  form 
of  a  tessellated  pavement,  the  centre  of  each  polygonal  space  presenting  a  minute 
aperture,  the  mouth  of  an  intralobular  vein  (Fig.  946). 

Microscopic  Appearance. — Each  lobule  is  composed  of  a  mass  of  cells,  hepatic 
cells  (Fig.  945) ,  surrounded  by  a  dense  capillary  plexus,  composed  of  vessels  which 


ABC  C 

Fig.  945. — The  hepatic  cells  at  different  stages  of  digestion.     (Heidenhain.) 

penetrate  from  the  circumference  to  the  centre  of  the  lobule,  and  terminate  in  a 
single  straight  central  vein,  which  runs  through  its  centre,  to  open  at  its  base  into 
one  of  the  radicles  of  the  hepatic  vein.  Between  the  cells  are  also  the  minute  com- 
mencements of  the  bile-ducts.  Therefore  in  the  lobule  we  have  all  the  essentials  of 
a  secreting  gland;  that  is  to  say:  (1)  cells,  by  which  the  secretion  is  formed;  (2) 
blood-vessels,  in  close  relation  with  the  cells,  containing  the  blood  from  which 
the  secretion  is  derived;  and  (3)  ducts,  by  which  the  secretion,  when  formed,  is 
carried  away.    Each  of  these  structures  will  have  to  be  further  considered. 

(1)  The  Hepatic  Cells  are  epithelial  in  nature  and  of  more  or  less  spheroidal  form, 
but  may  be  rounded,  flattened,  or  many-sided  from  mutual  compression.  They 
vary  in  size  from  the  ywot  ^^  ^^e  yoVo"  ^^  ^^  ^^^^  ^^  diameter.  They  consist  of  a 
honeycomb  network  (Klein)  without  any  cell-wall,  and  contain  one  or  sometimes 
two  distinct  nuclei.  In  the  nucleus  is  a  highly  refracting  nucleolus  with  granules. 
Embedded  in  the  honeycomb  network  are  numerous  yellow  particles,  the  coloring 
matter  of  the  bile,  and  oil-globules.  The  cells  adhere  together  by  their  surfaces  so 
as  to  form  rows,  which  radiate  from  the  centre  to  the  circumference  of  the  lobules.* 
As  stated  above,  they  are  the  chief  agents  in  the  secretion  of  the  bile. 

(2)  The  Blood-vessels. — ^The  blood  in  the  capillary  plexus  around  the  liver-cells 
is  brought  to  the  liver  principally  by  the  portal  vein,  but  also  to  a  certain  extent 
by  the  hepatic  artery.  For  the  sake  of  clearness  the  distribution  of  the  blood 
derived  from  the  hepatic  artery  may  be  considered  first. 

The  Hepatic  Artery,  entering  the  liver  at  the  transverse  fissure  with  the  portal 
vein  and  hepatic  duct,  ramifies  with  these  vessels  through  the  portal  canals.  It 
gives  off  vaginal  branches  which  ramify  in  the  capsule  of  Glisson,  and  appear  to 
be  destined  chiefly  for  the  nutrition  of  the  coats  of  the  large  vessels,  the  ducts, 

'  Del6pine  states  that  there  are  evidences  of  the  arrangement  of  these  cells  in  the  form  of  columns,  which 
form  tubes  with  narrow  lumina  branching  from  terminal  bile-ducts.  This  branching  is  evidenced  by  a  diverg- 
ence of  the  columns  from  lines  extending  between  adjacent  portal  vessels.  The  columns  of  cells  group  around 
terminal  bile-ducts,  and  not  around  the  so-called  intralobular  veins.  (Lancet,  1895,  vol.  i.  p.  1254.) — Ed.  of  15tn 
English  edition. 


THE   LIVER 


1339 


and  the  investing  membranes  of  the  Hver.  It  also  gives  off  capsular  branches 
which  reach  the  surface  of  the  organ,  terminating  in  the  fibrous  coat  in  stellate 
plexuses.  Finally  it  gives  off  interlobular  branches  {rami  arteriosi  interlohulares) 
which  form  a  plexus  on  the  outer  side  of  each  lobule,  to  supply  its  wall  and  the 
accompanying   bile-ducts.     From  this  plexus  lobular  branches  enter  the  lobule 


Hepatic 


Portal  vein. 


Orifices  of  intralohidar  reins. 

Fig.  946. — Longitudinal  section  of  an  hepatic 
vein.     (After  Kiernan.) 


Portion  of 

canal  from 

which  vein 

has  been 

removed- 


Fig.  947. — Longitudinal  section  of  a  small  portal 
vein  and  canal.      (After  Kiernan.) 


and  end  in  the  capillary  network  between  the  cells.     Some  anatomists,  however, 
doubt  whether  it  transmits  any  blood  directly  to  the  capillary  network. 

The  Portal  Vein  also  enters  at  the  transverse  fissure  and  runs  through  the 
portal  canals,  enclosed  in  Glisson's  capsule,  dividing  into  branches  in  its  course. 


Intralobular  vein. 


Trunk  of  intralobulctr 
vein. 


Fig.  948. — Horizontal  section  of  liver  (dog.) 


which  finally  break  up  into  a  plexus,  the  interlobular  plexus,  in  the  interlobular 
spaces.  In  their  course  these  branches  receive  the  vaginal  and  capsular  veins, 
corresponding  to  the  vaginal  and  capsular  branches  of  the  hepatic  artery  (Fig. 
947).  Thus  it  will  be  seen  that  all  the  blood  carried  to  the  liver  by  the  portal  vein 
and  hepatic  artery,  except  perhaps  that  derived  from  the  interlobular  branches  of 


1340 


THE    ORGANS   OF  DIGESTION 


the  hepatic  artery,  directly  or  indirectly  finds  its  way  into  the  interlobular  plexus. 
From  this  plexus  the  blood  is  carried  into  the  lobule  by  fine  branches  which  pierce 
its  wall  and  then  converge  from  the  circumference  to  the  centre  of  the  lobule,  form- 


FiQ.  949. — Horizontal  section  of  a  liver  lobule.     1,  central  vein  ;  2,  converging  vessels  ;  3,  interlobular  plexus. 

(Poirier  and  Charpy.) 

ing  a  number  of  converging  vessels  which  are  connected  by  transverse  branches 
(Figs.  948  and  949).  In  the  interstices  of  the  network  of  vessels  thus  formed  are 
situated,  as  before  said,  the  liver-cells :  and  here  it  is  that  the  blood  is  brought  into 


Fig.  950. — X-ray  picture  of  the  bile-ducts  and  the  pancreatic  ducts.     (Byron  Robinson.) 

intimate  connection  with  the  liver-cells  and  the  bile  is  secreted.  Arrived  at  the 
centre  of  a  lobule,  all  these  minute  vessels  empty  themselves  into  one  vein,  of 
considerable  size,  which  runs  down  the  centre  of  the  lobule  from  apex  to  base 
and  is  called  the  intralobulax  or  central  vein  {vena  interlobularis)  (Fig.  949) .    At  the 


THE  LIVER 


1341 


base  of  the  lobule  this  vein  opens  directly  into  the  sublobulax  vein,  with  which  the 
lobule  is  connected,  and  which,  as  before  mentioned,  is  a  radicle  of  the  hepatic  vein. 
The  sublobular  veins,  uniting  into  larger  and  larger  trunks,  end  at  last  in  the  hepatic 
veins,  which  do  not  receive  any  intralobular  veins.  Finally,  the  hepatic  veins,  as 
mentioned  on  page  767,  converge  to  form  three  large  trunks  which  open  into  the 
inferior  vena  cava,  while  that  vessel  is  situated  in  the  fissure  appropriated  to  it 
at  the  back  of  the  liver. 

(3)  The  Ducts. — Having  shown  how  the  blood  is  brought  into  intimate  relation 
with  the  hepatic  cells  in  order  that  the  bile  may  be  secreted,  it  remains  now  only 
to  consider  the  way  in  which  the  secretion,  having  been  formed,  is  carried  away. 
Several  views  have  prevailed  as  to  the  mode  of  origin  of  the  hepatic  ducts;  it 
seems,  however,  to  be  clear  that  they  commence  by  little  passages  which  are 
formed  between  the  cells,  and  which  have  been  termed  intercellular  biliary  pass- 
ages, bile-capillaries  or  bile-canaliculi  {ductus  biliferi).  These  passages  are  merely 
little  channels  or  spaces  left  between  the  contiguous  surfaces  of  two  cells  or  in  the 


Biliary 
duct. 


Hepatic 
cells. 


Capillary. 


Fio.  951. — Section  of  liver. 


Bili 


Fig.  952. — A  transverse  section  of  a  small  portal  canal 
and  its  vessels.  1,  portal  vein  ;  2,  interlobular  branches; 
3,  vaginal  branches  ;  4,  hepatic  duct ;  5,  hepatic  artery. 
(After  Kiernan.) 


angle  where  three  or  more  liver-cells  meet  (Fig.  951),  and  it  seems  doubtful 
whether  there  is  any  delicate  membrane  forming  the  wall  of  the  channel. 
Heidenhain,  however,  thinks  they  have  coats.  The  channels  thus  formed  radi- 
ate to  the  circumference  of  the  lobule,  and,  piercing  its  wall,  form  a  plexus 
(interlobular)  between  the  lobules.  From  this  plexus  interlobular  ducts  (ductus 
interlobular es)  are  derived  which  pass  into  the  portal  canals,  become  enclosed  in 
Glisson's  capsule,  and,  accompanying  the  portal  vein  and  hepatic  artery  (Fig. 
952),  join  with  other  ducts  to  form  two  main  trunks,  the  right  and  left  branches  of 
the  hepatic  duct,  which  leave  the  liver  at  the  transverse  fissure,  and  by  their  union 
form  the  hepatic  duct. 

Structure. — The  coats  of  the  smallest  biliary  ducts,  which  He  in  the  inter- 
lobular spaces,  are  a  connective-tissue  coat,  in  which  are  muscle-cells,  arranged 
both  circularly  and  longitudinally,  and  an  epithelial  layer,  consisting  of  short 
columnar  cells.  In  the  larger  ducts,  which  lie  in  the  portal  canals,  there  are  a 
number  of  orifices  disposed  in  two  longitudinal  rows,  which  were  formerly  regarded 
as  the  openings  of  mucous  glands,  but  which  are  merely  the  orifices  of  tubular 
recesses.  They  occasionally  anastomose,  and  from  the  sides  of  them  saccular 
dilatations  are  given  off. 

Lsrmphatics  of  the  Liver  (Fig.  506) . — The  lymphatics  in  the  substance  of  the  liver 
commence  in  lymphatic  spaces  around  the  capillaries  of  the  lobules ;  they  accompany 


1342  THE   ORGANS    OF  DIGESTION 

the  vessels  of  the  interlobular  plexus,  often  enclosing  and  surrounding  thera. 
These  unite  and  form  larger  vessels,  which  run  in  the  portal  canals,  enclosed  in 
Glisson's  capsule,  and  emerge  at  the  portal  fissure  to  be  distributed  in  the  manner 
described.  Other  superficial  lymphatics  arise  from  the  superficial  lobules,  pass 
under  the  peritoneum,  and  form  a  close  plexus,  where  this  membrane  covers 
the  liver.  The  first-named  group  of  lymphatics  give  origin  to  the  deep  collecting 
trunks,  the  second  to  the  superficial  collecting  trunks.  According  to  Poirier, 
Cuneo  and  Delamare,^  one  group  of  deep  collecting  trunks  accompanies  the  portal 
vein,  there  being  fifteen  to  eighteen  of  them  emerging  from  the  transverse  fissure. 
They  empty  into  the  glands  of  the  hilum.  Another  group  accompanies  the  hepatic 
veins.  There  are  five  or  six  trunks  which  pass  through  the  Diaphragm  and  ter- 
minate in  the  glands  about  the  vena  cava  {intrathoracic  glands).  According  to  the 
above-cited  authorities,  the  superficial  trunks  of  the  superior  surface  are  divided 
into  posterior,  anterior,  and  superior  trunks.  Some  of  the  posterior  trunks  ter- 
minate in  the  glands  about  the  coeliac  axis,  others  in  the  glands  about  the  lower 
portion  of  the  vena  cava  in  the  thorax;  others  in  the  glands  about  the  abdominal 
portion  of  the  oesophagus.  The  anterior  trunks  which  are  limited  to  the  right 
lobe  pass  to  the  glands  of  the  hilum.  The  superior  trunks  ascend  in  the  suspen- 
sory ligament.  Some  pass  to  the  glands  about  the  vena  cava,  just  above  the 
Diaphragm;  others  to  the  hepatic  glands.  The  balance  unite  to  form  a  very  large 
trunk,  which  passes  through  the  Diaphragm  and  divides  into  branches  which  enter 
the  glands  back  of  the  base  of  the  ensiform  cartilage. 

Nerves  of  the  Liver. — The  nerves  of  the  liver  are  derived  from  the  left  pneumo- 
gastric  and  the  solar  plexus  of  the  sympathetic.  The  branches  of  the  pneumo- 
gastric  ascend  from  in  front  of  the  stomach  within  the  lesser  omentum.  The 
sympathetic  nerves  pass  along  the  hepatic  artery  from  the  coeliac  plexus.  The 
nerves  enter  the  liver  at  the  transverse  fissure  and  accompany  the  vessels  and 
ducts  to  the  interlobular  spaces.  Here,  according  to  Korolkow,  the  medullated 
fibres  are  distributed  almost  exclusively  to  the  coats  of  the  blood-vessels;  while 
the  non-medullated  fibres  enter  the  lobules  and  ramify  between  the  cells. 

The  Excretory  Apparatus  of  the  Liver. 

The  excretory  apparatus  of  the  liver  consists  of  (1)  the  hepatic  duct,  which, 
as  we  have  seen,  is  formed  by  the  junction  of  the  two  main  ducts,  which  pass 
out  of  the  liver  at  the  transverse  fissure,  and  are  formed  by  the  union  of  the  bile- 
capillaries;  (2)  the  gall-bladder,  which  serves  as  a  reservoir  for  the  bile;  (3)  the 
cystic  duct,  which  is  the  duct  of  the  gall-bladder;  and  (4)  the  common  bile-duct, 
formed  by  the  junction  of  the  hepatic  and  cystic  ducts. 

The  Hepatic  Duct  (ductus  hepaticus)  (Figs.  953,  954,  and  956). — Two  main 
trunks  of  nearly  equal  size  issue  from  the  liver  at  the  transverse  fissure,  one  from 
the  right,  the  other  from  the  left  lobe ;  these  unite  to  form  the  hepatic  duct,  which 
then  passes  downward  and  to  the  right  for  about  an  inch  and  a  half  or  two 
inches,  between  the  layers  of  the  lesser  omentum,  where  it  is  joined  at  an  acute 
angle  by  the  cystic  duct,  and  so  forms  the  ductus  communis  choledochus.  The 
hepatic  duct,  as  it  descends  from  the  transverse  fissure  of  the  liver,  between  the 
two  layers  of  the  lesser  omentum,  lies  in  company  with  the  hepatic  artery  and 
portal  vein  (Fig.  944). 

The  Gall-bladder  (vesica  fellea)  (Figs.  859,  861,  938,  944,  and  953).— The 
gall-bladder  is  the  reservoir  for  the  bile;  it  is  a  conical  or  pear-shaped  musculo- 
membranous  sac,  lodged  in  a  fossa  on  the  under  surface  of  the  right  lobe  of  the 
liver,  and  fixed  in  it  by  connective  tissue,  and  extending  from  near  the  right 
extremity  of  the  transverse  fissure  to  the  anterior  border  of  the  organ.     It  is 

1  The  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE   EXCRETORY  APPARATUS    OF    THE    LIVER 


1343 


about  four  inches  in  length,  one  inch  in  breadth  at  its  widest  part,  and  holds  from 
eight  to  ten  drachms.  It  is  divided  into  a  fundus,  body,  and  neck.  The  fundus 
{fundus  vesicae  felleae),  or  broad  extremity,  is 
directed  downward,  forward,  and  to  the  right, 
and  projects  beyond  the  anterior  border  of  the 
liver;  the  body  (corpus  vesicae  felleae)  and  neck 
(collum  vesicae  felleae)  are  directed  upward  and 
backward  to  the  left.  The  neck  of  the  gall- 
bladder is  on  a  slightly  higher  level  than  the 
lowest  point  of  the  gall-bladder;  thus  the  weight 
of  the  bile  is  away  from  rather  than  toward 
the  outlet.  The  upper  surface  of  the  gall- 
bladder is  attached  to  the  liver  by  connective 
tissue  and  vessels.  The  under  surface  is 
covered  by  peritoneum,  which  is  reflected  on  to 
it  from  the  surface  of  the  liver.  Occasionally 
the  whole  of  the  organ  is  invested  by  the  ser- 
ous membrane,  and  is  then  connected  to  the 
liver  by  a  kind  of  mesentery. 

Relations. — The  body  of  the  gall-bladder  is 
in  relation,  by  its  upper  surface,  with  the 
liver,  to  which  it  is  connected  by  areolar  tissue 
and  vessels  ;  by  its  under  surface,  with  the 
commencement  of  the  transverse  colon  ;  and 
farther  back,  with  the  upper  end  of  the  de- 
scending portion  of  the  duodenum  or  some- 
times with  the  pyloric  end  of  the  stomach  or 
the  first  portion  of  the  duodenum.  The  fundus 
is  completely  invested  by  peritoneum  ;  it  is  in 
relation,  in  front,  with  the  abdominal  parietes, 
immediately  below  the  ninth  costal  cartilage;  Fig. 953.— The  gaii-biadder  and  bUe-ducts, 

,     ,  .      ,         .^%      .,        .  1        p    ,1  1  cut  through.     (Spalteholz.) 

behmd,  witn  the  transverse  arch  01  the  colon. 

The  neck  is  narrow,  and  curves  upon  itself  like  the  letter  S;  at  its  point  of 

connection  with  the  cystic  duct  it  presents  a  well-marked  constriction. 

When  the  gall-bladder  is  distended  with  bile  or  filled  with  calculi,  the  fundus  may  be  felt 
through  the  abdominal  parietes,  especially  in  an  emaciated  subject;  the  relations  of  this  sac  will 
also  serve  to  explain  the  occasional  occurrence  of  abdominal  biliary  fistulae,  through  which  biliary 
calculi  may  pass  out,  and  of  the  passage  of  calculi  from  the  gall-bladder  into  the  stomach,  duod- 
enum, or  colon,  which  occasionally  happens. 

Structure. — The  gall-bladder  consists  of  three  coats — serous,  fibrous  and  mus- 
cular, and  mucous. 

The  External  or  Serous  Coat  (tunica  serosa  vesicae  felleae)  is  derived  from  the  peri- 
toneum; it  completely  invests  the  fundus,  but  covers  the  body  and  neck  only  on 
their  under  surfaces. 

The  Fibro -muscular  Coat  (tunica  muscularis  vesicae  felleae)  is  a  thin  but  strong 
layer  which  forms  the  framework  of  the  sac,  consisting  of  dense  fibrous  tissue  which 
interlaces  in  all  directions  and  is  mixed  with  plain  muscular  fibres  which  are  dis- 
posed chiefly  in  a  longitudinal  direction,  a  few  running  transversely. 

The  Internal  or  Mucous  Coat  (tunica  mucosa  vesicae  felleae)  is  loosely  connected 
with  the  fibrous  layer.  It  is  generally  tinged  with  a  yellowish-brown  color,  and 
is  everywhere  elevated  into  minute  rugae,  by  the  union  of  which  numerous  meshes 
are  formed,  the  depressed  intervening  spaces  having  a  polygonal  outline.  The 
meshes  are  smaller  at  the  fundus  and  neck,  being  most  developed  about  the  centre 


k 


1344 


THE    ORGANS   OF   DIGESTION 


of  the  sac.  Opposite  the  neck  of  the  gall-bladder  the  mucous  membrane  projects 
inward  in  the  form  of  oblique  ridges  or  folds,  forming  a  sort  of  screw-like  or  s'pirul 
valve  (Fig.  953). 

The  mucous  membrane  is  covered  with  columnar  epithelium,  and  secretes  an 
abundance  of  thick  viscid  mucus;  it  is  continuous  through  the  hepatic  duct  with 
the  mucous  membrane  lining  the  ducts  of  the  liver,  and  through  the  ductus  com- 
munis choledochus  with  the  mucous  membrane  of  the  duodenum. 

The  Cystic  Duct  (ductus  cysticus). — The  cystic  duct,  the  smallest  of  the  three 
biliary  ducts,  is  about  an  inch  and  a  half  in  length.  It  passes  obliquely  downward 
and  to  the  left  from  the  neck  of  the  gall-bladder,  and  joins  the  hepatic  duct  to  form 
the  common  bile-duct.    It  lies  in  the  gastro-hepatic  omentum  in  front  of  the  portal 


HEPATIC 
DUCT 


DUCT  OF 
WIRSUNG 


SPHINCTER  OF 
DUCT  OF  WIRSUNG 


COMMON 
DUCT 


SPHINCTER  OF 
COMMON    DUCT 


Fig.  955. 


-The  sphincter  of  the  common  bile-duct. 
(Poirier  and  Charpy.) 


PANCREATIC 
OUCT 


AMPULLA 
OF  VATER 


WALL  OF 
DUODENUM 


vein,  the  hepatic  artery  lying  to  its  left 
side.  The  mucous  membrane  lining  its  in- 
terior is  thrown  into  a  series  of  crescentic 
folds,  from  five  to  twelve  in  number,  similar 
to  those  found  in  the  neck  of  the  gall-blad- 
der. They  project  into  the  duct  in  regular 
succession,  and  are  directed  obliquely  round 
the  tube,  presenting  much  the  appearance 
of  a  continuous  spiral  valve  {valvula  spiralis 
[Heisteri])  (Fig.  953).  When  the  duct  is 
distended,  the  spaces  between  the  folds 
are  dilated,  so  as  to  give  to  its  exterior 
a  sacculated  appearance. 

The  Ductus  Communis  Choledochus  or 
Common  Bile-duct  (ductus  choledochus) 
Figs.  953  and  954) ,  the  largest  of  the  three, 
is  the  common  excretory  duct  of  the  liver  and  gall-bladder.  It  is  about  three 
inches  in  length,  is  of  the  diameter  of  a  goose-quill,  and  is  formed  by  the  junction 
of  the  cystic  and  hepatic  ducts. 

It  descends  within  the  two  layers  and  along  the  right  border  of  the  lesser  omen- 
tum behind  the  first  portion  the  duodenum,  in  front  of  the  portal  vein,  and  to  the 
right  of  the  hepatic  artery  (Fig.  859) ;  then  passes  either  between  the  pancreas 
and  descending  portion  of  the  duodenum,  or  through  the  head  of  the  pancreas. 
In  fifty-eight  dissections  Prof.  Biingner  found  that  it  passed  through  the  pan- 
creas fifty-five  times  and  over  the  head  only  three  times.  Even  when  it  passes 
through  the  pancreas  it  almost  always  joins  the  pancreatic  duct  outside  of  the 
gland.  It  descends  by  the  right  side  of  the  pancreatic  duct  and  passes  with  it 
obliquely  through  the  wall  of  the  descending  portion  of  the  duodenum  between 
the  mucous  and  muscular  coats  in  the  submucous  tissue  for  one-half  to  three- 


FiG.  954. — The  biliary  ducts.     Schematic. 
(Poirier  and  Charpy.) 


THE  EXCRETORY  APPARATUS    OF    THE   LIVER  1345 

quarters  of  an  inch.  The  two  ducts  usually  unite  just  before  opening  into  the 
duodenum  (Figs.  954,  955,  and  957),  but  may  remain  independent  throughout. 
The  ampulla  of  Vater  (Fig.  954)  is  the  cavity  formed  by  the  fusion  of  the  two 
ducts,  and  is  much  larger  than  the  opening  on  the  bile-papilla.  The  two  ducts 
open  by  a  common  orifice,  or  by  two  separate  orifices,  upon  the  summit  of  a  papilla, 
situated  at  the  inner  side  of  the  descending  portion  of  the  duodenum,  a  little 
below  its  middle  and  about  three  or  four  inches  below  the  pylorus.  The  muscle 
of  the  common  duct  has  a  certain  amount  of  sphincter  power  (Fig.  955),  which 
serves  to  prevent  the  entrance  of  duodenal  contents  through  the  small  aperture, 
but  is  not  sufficiently  powerful  to  prevent  the  flow  of  bile  and  pancreatic  juice. 
Structure. — The  coats  of  the  large  biliary  ducts  are  an  external  or  fibrous  and 
an?intemal  or  mucous.    The  fibrous  coat  is  composed  of  strong  fibro-areolar  tissues, 


CIRCULAR 
MUSCULAR 
FIBRES 
MUCOUS 
COAT 


LONGITUDINAL 
MUSCULAR  FIBRES 

ACCESSORY 

PANCREATIC 

DUCTS 


BILE-DUCT 


PANCREATIC 
DUCT 


Fig.  957. — Diagram  showing  the  bile  and 
pancreatic  ducts  piercing  the  wall  of  the 
duodenum  obliquely.     (Cunningham.) 

with  a  certain  amount  of  mus- 
cular tissue  arranged,  for  the 
most  part,  in  a  circular  manner 
around  the  duct.  The  mucous 
coat  is  continuous  with  the  lin- 
ing membrane  of  the  hepatic 
ducts  and  gall-bladder,  and 
also  with  that  of  the  duodenum ; 
and, like  the  mucous  membrane 
of  these  structures,  its  epithe- 
lium is  of  the  columnar  variety. 
It  is  provided  with  numerous 
mucous  glands,  which  are  lobu- 
lated  and  open  by  minute  orifices  scattered  irregularly  in  the  larger  ducts.  It  is 
questionable  if  the  smallest  biUary  ducts,  which  lie  in  the  interlobular  spaces,  have 
any  coats.  Heidenhain  thinks  they  have  a  connective-tissue  coat,  in  which  are 
muscle-cells  arranged  both  circularly  and  longitudinally,  and  an  epithelial  layer, 
consisting  of  short  columnar  cells. 

Dimensions  of  the  Bile-ducts. — ^The  hepatic  duct  is  about  two  inches  in  length, 
and  its  lumen  is  one-sixth  of  an  inch  in  diameter.  The  cystic  duct  is  about  one 
and  one-half  inches  in  length,  and  its  lumen  one-twelfth  of  an  inch  in  diameter. 
The  common  duct  is  about  three  inches  in  length,  and  its  lumen  is  one-quarter  of 
an  inch  in  diameter.  The  duodenal  opening  is  smaller  than  the  common  duct. 
The  ducts  are  capable  of  considerable  distention,  but  the  duodenal  opening  can- 
not be  dilated  (HyrtH. 

85 


Fig.  956. — Part  of  the  bile-duct  and  the  pancreatic  ducts.  C 
and  B,  calculi;  Sa,  Santorini's  duct;  P,  pancreatic  duct;  III  and 
I  V,  ducts  from  the  right  and  left  lobes  of  the  liver;  //,  cystic  duct; 
C,  gall-bladder;  .,4,  common  duct.      (Byron  Robinson.) 


1346 


THE    ORGANS   OF  DIGESTION 


Blood-vessels,  Lymphatics  and  Nerves  of  the  Gall-bladder  and  Bile-ducts. — The  cystic 
artery  (Fig.  418),  a  branch  from  the  right  division  of  the  hepatic,  supphes  the  gall- 
bladder and  cystic  duct  with  blood.  It  passes  along  the  cystic  duct,  and  on  reach- 
ing the  gall-bladder  divides  into  an  upper  branch  and  a  lower  branch.  The  upper 
branch  lies  between  the  gall-bladder  and  the  liver  and  sends  branches  to  each. 
The  lower  branch  is  between  the  peritoneum  and  the  wall  of  the  gall-bladder. 
The  cystic  veins  empty  into  the  portal  vein.  The  common  duct  receives  branches 
from  the  superior  pancreatico -duodenal  artery.  There  is  a  submucous  lymphatic  net- 
work and  a  muscular  lymphatic  network.  The  lymphatics  are  much  less  numer- 
ous at  the  fundus  of  the  gall-bladder  than  at  the  neck  or  in  the  extra-hepatic  ducts. 
The  collecting  trunks  (Fig.  506)  end  in  glands  along  the  cystic  and  common  ducts, 
and  these  glands  are  in  communication  with  the  duodenal  lymphatics  and  the 
lymphatics  from  the  head  of  the  pancreas.  The  nerves  of  the  gall-bladder  and 
bile-ducts  come  from  the  coeliac  plexus  of  the  sympathetic.  The  adjacent  peri- 
toneum is  plentifully  supplied  with  nerves  (Byron  Robinson). 

The  Bile  {]el) . — The  bile  is  a  reddish-brown  or  greenish  fluid.  It  contains  pig- 
ments (bilirubin  and  biliverdin),  fats  and  soaps,  cholesterin,  sodium  salts  of  glyco- 
cholic  and  taurochohc  acid,  lecithin,  and  nucleo-albumin  furnished  by  the  mucous 
membrane.  There  are  also  present  COg;  chlorides,  carbonates,  phosphates,  and 
sulphates  of  the  alkalies  and  of  calcium,  and  iron.  The  amount  normally 
secreted  is  from  one  pint  to  one  and  one-half  pints  in  the  twenty-four  hours. 

Siuface  Relations. — The  liver  is  situated  in  the  right  hypochondriac  and  the  epigastric 
regions,  and  is  moulded  to  the  arch  of  the  Diaphragm.  In  the  greater  part  of  its  extent  it  lies 
under  cover  of  the  lower  ribs  and  their  cartilages,  but  in  the  epigastric  region  it  comes  in  con- 
tact with  the  abdominal  wall,  in  the  subcostal  angle.  The  upper  limit  of  the  right  lobe  of  the 
liver  may  be  defined  in  the  middle  line  by  the  junction  of  the  mesosternum  with  the  ensiform 
cartilage;  on  the  right  side  the  line  must  be  carried  upward  as  far  as  the  fifth  rib  cartilage 
in  the  line  of  the  nipple  and  then  downward  to  reach  the  seventh  rib  at  the  side  of  the  chest. 
The  upper  limit  of  the  left  lobe  may  be  defined  by  continuing  this  line  to  the  left  with  an  inclina- 
tion downward  to  a  point  about  two  inches  to  the  left  of  the  sternum  on  a  level  with  the  sixth 
left  costal  cartilage.  The  lower  limit  of  the  liver  may  be  indicated  by  a  line  drawn  half  an  inch 
below  the  lower  border  of  the  thorax  on  the  right  side  as  far  as  the  ninth  right  costal  cartilage, 
and  thence  obliquely  upward  across  the  subcostal  angle  to  the  eighth  left  costal  cartilage.  A 
slight  curved  line  with  its  convexity  to  the  left  from  this  point — i.  e.,  the  eighth  left  costal 
cartilage — to  the  termination  of  the  line  indicating  the  upper  limit  will  denote  the  left  margin  of 
the  liver.  The  fundus  of  the  gall-bladder  approaches  the  surface  behind  the  anterior  extremity 
of  the  ninth  costal  cartilage,  close  to  the  outer  margin  of  the  Right  rectus  muscle. 

It  must  be  remembered  that  the  liver  is  subject  to  considerable  alterations  in  position,  and 
the  student  should  make  himself  acquainted  with  the  different  circumstances. under  which  this 
occurs,  as  they  are  of  importance  in  determining  the  existence  of  enlargement  or  other  diseases 
of  the  organ. 

Its  position  varies  according  to  the  posture  of  the  body.  In  the  erect  position  in  the  adult 
male  the  edge  of  the  liver  projects  about  half  an  inch  below  the  lower  edge  of  the  right  costal 
cartilages,  and  its  anterior  border  can  be  often  felt  in  this  situation  if  the  abdominal  wall  is  thin. 
In  the  supine  position  the  Hver  gravitates  backward  and  recedes  above  the  lower  margin  of  the 
ribs,  and  cannot  then  be  detected  by  the  finger.  In  the  prone  position  it  falls  forward,  and  can 
then  generally  be  felt  in  a  patient  with  loose  and  lax  abdominal  walls.  Its  position  varies  also 
with  the  ascent  or  descent  of  the  Diaphragm.  In  a  deep  inspiration  the  liver  descends  below 
the  ribs;  in  expiration  it  is  raised  behind  them.  Again,  in  emphysema,  where  the  lungs  are 
distended  and  the  Diaphragm  descends  very  low,  the  liver  is  pushed  down;  in  some  other  dis- 
eases, as  phthisis,  where  the  Diaphragm  is  much  arched,  the  liver  rises  very  high  up.  Pressure 
from  without,  as  in  tight  lacing,  by  compressing  the  lower  part  of  the  chest,  displaces  the  liver 
considerably,  its  anterior  edge  often  extending  as  low  as  the  crest  of  the  ilium;  and  its  convex 
surface  is  often  at  the  same  time  deeply  indented  from  the  pressure  of  the  ribs.  Again,  its  posi- 
tion varies  greatly  according  to  the  greater  or  less  distention  of  the  stomach  and  intestines. 
When  the  intestines  are  empty  the  liver  descends  in  the  abdomen,  but  when  they  are  distended 
it  is  pushed  upward.  Its  relations  to  surrounding  organs  may  also  be  changed  by  the  growth  of 
tumors  or  by  collections  of  fluid  in  the  thoracic  or  abdominal  cavities. 

Surgical  Anatomy. — Movable  liver  or  hepatopfosis  is  a  rare  condition,  in  which  the  liver 
moves  or  can  be  moved  from  its  normal  position.    It  is  due  to  lessened  tone  of  the  abdominal 


THE   EXCRETORY  APPARATUS    OF    THE   LIVER  1347 

muscles  and  relaxation  of  the  liver  supports.  In  movable  liver  the  organ  may  be  rotated  on  its 
vertical  axis  or  on  its  transverse  axis.  Tongue-like  lobes  have  been  referred  to.  On  account  of 
its  large  size,  its  fixed  position,  and  its  friability,  the  liver  is  more  frequently  ruptured  than 
any  of  the  abdominal  viscera.  The  rupture  may  vary  considerably  in  extent,  from  a  slight 
scratch  to  an  extensive  laceration  completely  through  its  substance,  dividing  it  into  two  parts. 
Sometimes  an  internal  rupture  without  laceration  of  the  peritoneal  covering  takes  place,  and 
such  injuries  are  most  susceptible  of  repair;  but  small  tears  of  the  surface  may  also  heal;  when, 
however,  the  laceration  is  extensive,  death  usually  takes  place  from  hemorrhage,  on  account 
of  the  fact  that  the  hepatic  veins  are  contained  in  rigid  canals  in  the  liver-substance  and  are 
unable  to  contract,  and  are  moreover  unprovided  with  valves.  The  liver  may  also  be  torn 
by  the  end  of  a  broken  rib  perforating  the  Diaphragm.  The  liver  may  be  injured  by  stabs 
or  other  punctured  wounds,  and  when  these  are  inflicted  through  the  chest-wall  both  pleural 
and  peritoneal  cavities  may  be  opened  up  and  both  lung  and  liver  be  wounded.  In  cases  of 
wound  of  the  liver  from  the  front,  jirotrusion  of  a  part  of  this  viscus  may  take  place,  but  can  gen- 
erally easily  be  replaced.  In  cases  of  laceration  of  the  liver,  when  there  is  evidence  that  bleeding 
is  going  on,  the  abdomen  must  be  opened,  the  laceration  sought  for,  and  the  bleeding  arrested. 
This  may  be  done  temporarily  by  introducing  the  forefinger  into  the  foramen  of  Winslow  and 
placing  the  thumb  on  the  gastro-hepatic  omentum  and  compressing  the  hepatic  artery  and  portal 
vein  between  the  two.  Any  bleeding  points  can  then  be  seen.  Bleeding  is,  if  possible,  arrested 
by  suture  ligatures.  The  edges  of  a  small  laceration  are  simply  brought  together  and  sutured  by 
means  of  a  blunt,  curved,  round  needle  passed  from  one  side  of  the  wound  to  the  other.  All  sutures 
must  be  passed  before  any  are  tied,  and  this  must  be  done  with  the  greatest  gentleness,  as  the  liver 
substance  is  very  friable.  If  suture  fails  the  actual  cautery  may  succeed.  When  the  laceration  is  ex- 
tensive, the  liver  is  sutured  to  the  abdominal  wall  to  hold  it  firm  when  pressure  is  applied,  and  then 
the  laceration  is  packed  with  a  piece  of  iodoform  gauze,  the  end  of  which  is  allowed  to  hang  out 
of  the  external  wound.  Abscess  of  the  liver  is  of  not  infrequent  occurrence,  and  may  open  in  many 
different  ways  on  account  of  the  relations  of  this  viscus  to  other  organs.  Thus  it  may  burst  into 
the  lung,  the  pus  being  coughed  up,  or  into  the  stomach;  the  pus  perhaps  being  vomited,  it  may 
burst  into  the  colon  or  into  the  duodenum,  or,  by  perforating  the  Diaphragm,  it  may  empty 
itself  into  the  pleural  cavity.  Frequently  it  makes  its  way  forward,  and  points  on  the  anterior 
abdominal  wall,  and  finally  it  may  burst  into  the  peritoneal  or  pericardiac  cavity.  Abscesses 
of  the  liver  require  opening,  and  this  must  be  done  by  an  incision  in  the  abdominal  wall,  in  the 
thoracic  wall,  or  in  the  lumbar  region,  according  to  the  direction  in  which  the  abscess  is  tracking. 
The  incision  through  the  abdominal  wall  is  to  be  preferred  when  possible.  The  abdominal  wall 
is  incised  over  the  swelling,  and  unless  the  peritoneum  is  adherent,  gauze  is  packed  all  around 
the  exposed  liver  surface  and  the  abscess  opened,  if  deeply  seated,  preferably  by  the  thermo- 
cautery. Hydatid  cysts  are  more  often  found  in  the  liver  than  in  any  other  of  the  viscera.  The 
reason  of  this  is  not  far  to  seek.  The  embryo  of  the  egg  of  the  taenia  echinococcus  being  liberated 
in  the  stomach  by  the  disintegration  of  its  shell,  bores  its  way  through  the  gastric  walls  and 
usually  enters  a  blood-vessel,  and  is  carried  by  the  blood-stream  to  the  hepatic  capillaries,  where 
its  onward  course  is  arrested,  and  where  it  undergoes  development  into  the  fully  formed  hydatid. 
Tumors  of  the  liver  have  recently  been  subjected  to  surgical  treatment  by  removal  of  a  portion 
of  the  organ.  The  abdomen  is  opened  and  the  diseased  portion  of  liver  exposed;  the  circulation 
is  controlled  by  compressing  the  portal  vein  and  the  hepatic  artery  in  the  gastro-hepatic  omen- 
tum and  a  wedge-shaped  portion  of  liver  containing  the  tumor  removed;  the  divided  vessels 
are  ligated  and  the  cut  surfaces  brought  together  and  sutured  in  the  manner  directed  above. 

when  the  r/all-bladder  or  one  of  its  main  ducts  is  ruptured,  which  may  occur  independently 
of  laceration  of  the  liver,  death  usually  occurs  from  peritonitis.  If  the  symptoms  have  led  to 
the  performance  of  a  laparotomy  and  a  small  rent  is  found,  it  should  be  sutured;  if  an  exten- 
sive opening  is  found  the  gall-bladder  should  be  removed.  If  the  cystic  duct  is  torn,  its  intes- 
tinal end  must  be  closed  and  the  gall-bladder  removed.  In  rupture  of  either  of  the  other 
ducts,  sim]ily  provide  for  free  drainage. 

The  gall-bladder  may  become  distended  with  bile  in  cases  of  obstruction  of  its  duct  or  of  the 
common  bile-duct,  or  it  may  become  distended  from  a  collection  of  gall-stones  within  its  interior, 
thus  forming  a  large  tumor.  The  swelling  due  to  distention  with  bile  is  pear-shaped,  and  pro- 
jects downward  and  forward  to  the  umbilicus.  It  moves  with  respiration,  since  it  is  attached  to 
the  liver.  To  relieve  a  ]>atient  of  gall-stones,  the  gall-bladder  must  be  opened  and  the  gall-stones 
removed.  The  operation  is  performed  by  an  incision  two  or  three  inches  long  in  the  right  semi- 
lunar line,  commencing  at  the  costal  margin.  The  peritoneal  cavity  is  opened,  and,  the  tumor 
having  been  found,  gauze  pads  are  packed  around  it  to  protect  the  peritoneal  cavity,  and  it  is 
aspirated.  When  the  contained  fluid  has  been  evacuated  the  flaccid  bladder  is  drawn  out  of 
the  abdominal  wound  and  its  wall  incised  to  the  extent  of  an  inch;  any  gall-stones  in  the 
bladder  are  now  removed  and  the  interior  of  the  sac  sponged  dry.  If  the  case  is  one  of 
obstruction  of  the  duct,  an  attempt  must  be  made  to  dislodge  the  stone  by  manipulation  through 
the  wall  of  the  duct;  or  it  may  be  crushed  from  without  by  the  fingers  or  carefully  padded  for- 
ceps.   If  this  does  not  succeed,  the  safest  plan  is  to  incise  the  duct,  extract  the  stone,  close 


1348 


THE   ORGANS   OF  DIGESTION 


the  incision  in  the  duct  by  fine  sutures  in  two  layers  and  employ  drainage.  After  all  obstruction 
has  been  removed,  four  courses  are  open  to  the  surgeon:  1.  The  wound  in  the  gall-bladder 
may  be  at  once  sewed  up,  the  organ  returned  into  the  abdominal  cavity,  and  the  external  incision 
closed.  2.  The  edges  of  the  incision  in  the  gall-bladder  may  be  sutured  to  the  fascia  of  the  ex- 
ternal wound,  and  a  fistulous  communication  established  between  the  gall-bladder  and  the  exte- 
rior; this  fistulous  opening  usually  closes  in  the  course  of  a  few  weeks.  3.  The  gall-bladder  may 
be  connected  with  the  intestinal  canal,  preferably  the  duodenum,  by  means  of  a  lateral  anasto- 
mosis; this  is  known  as  cholecystenterostomy.  4.  The  gall-bladder  may  be  completely  removed 
(cholecystectomy).  Plan  2  is  usually  followed.  Plan  4  is  employed  when  the  coats  of  the 
gall-bladder  are  seriously  diseased.  Plan  2  is  employed  in  obstruction  of  the  common  duct  by 
malignant  disease. 

If  a  stone  blocks  the  diverticulum  of  Vater  and  if  the  common  bile-duct  and  the  pancreatic 
duct  empty  into  the  diverticulum,  it  is  evident  that  both  ducts  will  be  blocked.  It  has  been 
demonstrated  that  in  such  a  case  the  pressure  urging  the  bile  onward  is  sufficient  to  overcome 
the  pressure  in  the  pancreatic  duct  and  drive  bile  into  the  ducts  of  the  pancreas,  the  result, 
perhaps,  being  disastrous  inflammation  of  the  pancreas. 

Septic  trouble  arises  more  rapidly  when  a  stone  is  blocked  in  the  duct  than  when  stones  merely 
block  the  gall-bladder,  because  the  first-named  part  is  richer  in  lymphatics  (Murphy). 


THE  PANCREAS  (Figs.  958,  959,  960,  961). 

Dissection. — The  pancreas  may  be  exposed  for  dissection  in  three  diflFerent  ways:  1.  By 
raising  the  liver,  drawing  down  the  stomach,  and  tearing  through  the  gastro-hepatic  omentum 
and  the  ascending  layer  of  the  transverse  mesocolon.  2.  By  raising  the  stomach,  the  arch  of 
the  colon,  and  great  omentum,  and  then  dividing  the  inferior  layer  of  the  transverse  mesocolon 
and  raising  its  ascending  layer.  3.  By  dividing  the  two  layers  of  peritoneum,  which  descend 
from  the  great  curvature  of  the  stomach  to  form  the  great  omentum;  turning  the  stomach 
upward,  and  then  cutting  through  the  ascending  layer  of  the  transverse  mesocolon  (see  Fig.  853). 

The  Pancreas  {Tiav-xfjsa^,  all  flesh)  is  a  compound  racemose  gland,  analo- 
gous in  its  structure  to  the  saUvary  glands,  though  softer  and  less  compactly 
arranged  than  those  organs.  It  is  long  and  irregularly  prismatic  in  shape,  and 
has  been  compared  to  a  human  or  a  dog's  tongue ;  it  is  of  reddish-white  color. 
Its  right  extremity  being  broad,  is  called  the  head.  The  right  half  of  the  head 
above  is  continuous  with  the  neck,  which  connects  the  head  to  the  main  portion 
of  the  organ,  the  body.  The  neck  is  a  slight  constriction  or  thin  part  of  the  gland, 
placed  in  front  of  the  portal  vein,  and  connecting  the  head  to  the  body.  The  left 
half  of  the  head  is  separated  from  the  neck  by  a  notch,  the  incisura  pancreaticus. 
The  body  of  the  gland  gradually  tapers  into  an  extremity  directed  to  the  left,  and 
called  the  tail.  The  pancreas  is  placed  transversely  across  the  posterior  wall  of 
the  abdomen,  at  the  back  of  the  epigastric  and  left  hypochondriac  regions.  Its 
length  varies  from  five  to  six  inches,  its  breadth  is  an  inch  and  a  half,  and  its  thick- 
ness from  half  an  inch  to  an  inch,  being  greater  at  its  right  extremity  and  along 
its  upper  border.  Its  weight  varies  from  two  to  three  and  a  half  ounces,  but  it 
may  reach  six  ounces. 

The  Right  Extremity  or  Head  of  the  Pancreas  (caput  pancreatis)  (Fig.  958) 
is  shaped  like  the  head  of  a  hammer,  being  elongated  both  above  and  below;  it 
is  flattened  from  before  backward,  and  conforms  to  the  whole  concavity  of  the 
duodenum,  which  is  slightly  overlapped  by  it.  The  anterior  surface  near  its  left 
border  exhibits  a  notch,  the  incisura  pancreatis,  which  contains  the  superior  mesen- 
teric vessels.  The  notch  marks  the  separation  of  the  inferior  portion  of  the  head, 
which  is  known  as  the  uncinate  process  of  Winslow  {processus  uncinaius  \Winslowi\), 
which  rests,  below,  upon  the  inferior  portion  of  the  duodenum,  and,  above,  is 
pushed  up  back  of  the  upper  portion.  The  lower  end  of  the  head  is  crossed  by 
the  transverse  colon  and  its  mesocolon.  Behind,  the  head  of  the  pancreas  is  in 
relation  with  the  inferior  vena  cava,  the  left  renal  vein,  the  right  crus  of  the 
Diaphragm,  and  the  aorta.  The  common  bile-duct  descends  behind,  between 
the  duodenum  and  pancreas,  or  in  the  substance  of  the  gland;  and  the  pan- 


THE  PANCREAS 


1349 


creatico-duodenal  artery  descends  in  front  between  the  same  parts.     The  head  of 
the  pancreas  is  closely  adherent  to  the  duodenum. 


Fig.  958. — The  pancreas  and  its  relations. 
Gastric  artery.    ^^aU^       W>i      Lower  end  of  oesophagus. 


Inferior  mesenteric 
artery. 


-:ij_j.j,_iinr  mesenteric 
artery. 


Spermatic  vessels. 


Fig.  959. — The  duodenum  and  pancreas.  The  Uver  has  been  Hfted  up  and  the  greater  part  of  the  stomach 
removed:  a,  portal  vein;  6,  hepatic  duct;  c,  cystic  duct;  d,  hepatic  artery;  e,  right  sui)rarenal  capsule; 
/,  pyloric  orifice  ;  g,  right  gastro-epiploic  artery  ;  h,  superior  mesenteric  vein  ;  i,  left  crus  of  diaphragm  ;  j,  left 
suprarenal  capsule  ;  k,  splenic  vein  ;  I,  splenic  artery;  m,  duodeno-jejunal  junction  ;  a,  b,  c,  d,  the  four  portions 
of  the  duodenum.     (Testut.) 


1350 


THE    ORGANS   OF  DIGESTION 


The  Neck  of  the  Pancreas  is  about  an  inch  long,  and  passes  upward  and  for- 
ward to  the  left,  having  the  first  part  of  the  duodenum  above  it,  and  the  ter- 
mination of  the  fourth  portion  below.  It  lies  in  front  of  the  commencement  of 
the  portal  vein,  and  is  grooved  on  the  right  by  the  gastro-duodenal  and  superior 
pancreatico-duodenal  arteries.    The  pylorus  hes  just  above  it. 

The  Body  (corpus  pancreatis)  and  Tail  (cauda  pancreatis)  of  the  Pancreas  are 
somewhat  prismatic  in  shape,  and  have  three  surfaces:  anterior,  posterior,  and 
inferior. 

The  Anterior  Surface  (fades  anterior). — The  anterior  surface  is  somewhat  con- 
cave, and  is  covered  by  the  posterior  surface  of  the  stomach  which  rests  upon  it, 
the  two  organs  being  separated  by  the  lesser  sac  of  the  peritoneum.  At  its  right 
extremity  there  is  a  well-marked  prominence,  called  by  His  the  omental  tuberosity 
(tuber  omentale). 

The  Posterior  Surface  (fades  posterior). — The  posterior  surface  is  separated  from 
the  vertebral  column  by  the  aorta,  the  splenic  vein,  the  left  kidney  and  its  vessels, 
the  left  suprarenal  capsule,  the  pillars  of  the  Diaphragm,  and  the  origin  of  the 
superior  mesenteric  artery. 

The  Inferior  Surface  (fades  inferior)  (Fig,  959). — The  inferior  surface  is  narrow, 
and  lies  upon  the  duodeno-jejunal  flexure  and  on  some  coils  of  the  jejunum;  its  left 
extremity  rests  on  the  splenic  flexure  of  the  colon, 

^„„^  FIRST  FOLD 

^     \,t-=;^^^^OF  DUODENUM 

ACCESSORY 
PANCREATIC 
DUCT 

COMMON 
BILE-DUCT 


HEAD  OF^^^  ^^^^BRANCH  OF 

PANCREAS    ^^teKia^^ai^       ACCESSORY 
DUCT 

Fig.  960. — The  pancreas  and  duodenum  from  behind,  with  the  pancreatic  duct  exposed.  The  superior 
mesenteric  vessels  are  also  shown  in  section,  passing  forward,  surrounded  by  the  recurved  portion  of  the  head  of 
the  pancreas.     (Cunningham.) 

The  Superior  Border  (margo  superior)  (Fig.  959). — The  superior  border  of  the 
body  is  blunt  and  flat  to  the  right;  narrow  and  sharp  to  the  left,  near  the  tail.    It 
commences  to  the  right  in  the  omental  tuberosity,  and  is  in  relation  with  the 
coeliac  axis,  from  which  the  hepatic  artery  courses  to  the  right  just  above  the  gland, , 
while  the  splenic  branch  runs  in  a  groove  along  this  border  to  the  left. 

The  Anterior  Border  (margo  anterior). — The  anterior  border  is  the  position  where 
the  two  layers  of  the  transverse  mesocolon  separate;  the  one  passing  upward  in 
front  of  the  anterior  surface,  the  other  backward  below  the  inferior  surface 
(Fig,  853), 

The  lesser  end  or  tail  of  the  pancreas  is  narrow;  it  extends  to  the  left  as  far  as 
the  lower  part  of  the  inner  aspect  of  the  spleen,  and  its  end  is  directed  upward  and 
to  the  left  (Fig.  959), 

Birmingham  describes  the  body  of  the  pancreas  as  projecting  forward  as  a 
prominent  ridge  into  the  abdominal  cavity  and  forming  a  sort  of  shelf  on  which  the 
stomach  hes.  He  says:  "The  portion  of  the  pancreas  to  the  left  of  the  middle  line 
has  a  very  considerable  antero-posterior  thickness;  as  a  result  the  anterior  surface 
is  of  considerable  extent,  it  looks  strongly  upward,  and  forms  a  large  and  important 
part  of  the  shelf.  As  the  pancreas  extends  to  the  left  toward  the  spleen  it  crosses 
the  upper  part  of  the  kidney,  and  is  so  moulded  on  to  it  that  the  top  of  the  kidney 


THE  PANCBEA8 


1351 


forms  an  extension  inward  and  backward  of  the  upper  surface  of  the  pancreas  and 
extends  the  bed  in  this  direction.  On  the  other  hand,  the  extremity  of  the  pan- 
creas comes  in  contact  with  the  spleen  in  such  a  way  that  the  plane  of  its  upper 
surface  runs  with  little  interruption  upward  and  backward  into  the  concave  gastric 
surface  of  the  spleen,  which  completes  the  bed  behind  and  to  the  left,  and,  running 
upward,  forms  a  partial  cap  for  the  wide  end  of  the  stomach."^  An  occasional 
anomaly  is  a  pancreas  prolonged  in  front  of  the  duodenum  or  actually  embracing 
it  (annular  pancreas). 

Peritoneal  Relations  (Fig.  853). — The  transverse  mesocolon  is  attached  to  the 
anterior  border  of  the  pancreas,  from  the  tail  to  the  neck  of  the  gland,  and  the  two 
layers  of  the  mesocolon  separate.  The  anterior  layer  which  comes  from  the  lesser 
peritoneum  covers  part  of  the  anterior  surface  and  the  superior  surface ;  the  poste- 
rior layer,  which  comes  from  the  greater  omentum,  covers  the  rest  of  the  anterior 
surface  and  the  inferior  surface.    The  posterior  surface  is  devoid  of  peritoneum. 


RECTUS    MUSCLE. 


8th  Costal  Cartilage. 

7th  Costal  Cartilage. 


Rib. 


..'Sth,  Rib. 


■9th  Rib. 


10th  Rib. 


Abdominal  Aorta. 


12th  Rib.    nth  Rib. 


Fig.  961. 


-Transverse  section  through  the  middle  of  the  first  lumbar  vertebra,  showing  the  relations 
of  the  pancreas.      (Braune.) 


There  is  in  front  of  the  head  and  at  the  anterior  margin  a  narrow  strip  of  pancreas, 
which  remains  uncovered  by  peritoneum  and  which  corresponds  to  the  cellular 
tissue  of  the  mesocolon. 

The  principal  excretory  duct  of  the  pancreas,  called  the  pancreatic  duct  or  canal 
of  Wirsung  {ductus  'pancreaticus  [Wirsungi])  (Figs.  956,  958,  and  960),  from  its 
discoverer,  extends  transversely  from  left  to  right  through  the  substance  of  the 
pancreas.  In  order  to  expose  it,  the  superficial  portion  of  the  gland  must  be 
removed.  It  commences  by  the  junction  of  the  small  ducts  of  the  lobules  situated 
in  the  tail  of  the  pancreas,  and,  running  from  left  to  right  through  the  body,  it  con- 
stantly receives  the  ducts  of  the  various  lobules  composing  the  gland.  Consider- 
ably augmented  in  size,  it  reaches  the  neck,  and  turning  obliquely  downward,  back- 
ward, and  to  the  right,  it  comes  into  relation  with  the  common  bile-duct,  lying  to 


1  Journal  of  Anatomy  and  Physiology,  vol.  xxxi.  part  i.  p.  102. 


1352  "IHE   ORGANS   OF   DIGESTION 

its  left  side;  leaving  the  head  of  the  gland,  it  passes  very  obliquely  through  the 
mucous  and  muscular  coats  of  the  duodenum,  and  usually  terminates  by  an  orifice 
common  to  it  and  the  ductus  communis  choledochus  upon  the  summit  of  an  ele- 
vated papilla,  situated  at  the  inner  side  of  the  descending  portion  of  the  duodenum, 
three  or  four  inches  below  the  pylorus  (Figs.  954,  955,  and  957). 

Sometimes  the  pancreatic  duct  and  ductus  communis  choledochus  open  sepa- 
rately into  the  duodenum  (Fig.  893) .  In  about  one-fifth  of  the  subjects  there  is  an 
accessory  duct,  which  is  given  off  from  the  canal  of  Wirsung  in  the  neck  of  the  pan- 
creas and  passes  horizontally  to  the  right  to  open  into  the  duodenum  about  an 
inch  above  the  orifice  of  the  main  duct.  This  is  known  as  the  duct  of  Santorini 
(ductus  pancreaiicus  accessorius  \Santorini\)  (Figs.  956,  957,  and  960). 

The  pancreatic  duct,  near  the  duodenum,  is  about  the  size  of  an  ordinary  quill; 
its  walls  are  thin,  consisting  of  two  coats,  an  external  fibrous  and  an  internal 
mucous ;  the  latter  is  smooth,  and  furnished  near  its  termination  with  a  few  scat- 
tered follicles. 

Structure. — In  structure,  the  pancreas  resembles  the  salivary  glands.  It  differs 
from  them,  however,  in  certain  particulars,  and  is  looser  and  softer  in  its  texture. 
It  is  not  enclosed  in  a  distinct  capsule,  but  is  surrounded  by  areolar  tissue,  which 
dips  into  its  interior,  and  connects  together  the  various  lobules  of  which  it  is  com- 
posed. Each  lobule,  like  the  lobules  of  the  salivary  glands,  consists  of  one  of  the 
ultimate  ramifications  of  the  main  duct,  terminating  in  a  number  of  caecal  pouches 
or  alveoli,  which  are  tubular  and  somewhat  convoluted.  The  minute  ducts  con- 
nected with  the  alveoli  are  narrow  and  lined  with  flattened  cells.  They  are  the 
secreting  end  tubules.  The  narrow  ducts  which  come  from  the  end  tubules  are 
lined  with  flat  epithelial  cells.  The  alveoli  are  almost  completely  filled  with  secret- 
ing cells,  so  that  scarcely  any  lumen  is  visible.  In  the  centre  of  the  end  tubules 
flat  cells  are  frequently  found.  They  are  continuations  into  the  tubules  of  the 
duct  epithelium.  These  cells  are  known  as  the  centro-acinar  cells  of  Langerhans. 
The  true  secreting  cells  which  line  the  wall  of  the  alveolus  are  very  characteristic. 
They  are  columnar  or  rounded  in  shape  and  present  two  zones:  an  outer  one 
clear  and  finely  striated  next  the  basement-membrane,  and  an  inner  granular 
one  next  the  lumen.  The  highly  refracting  granules  are  known  as  zymogen 
granules.  During  digestion  the  granules  gradually  disappear  and  the  cells  become 
clear.  During  fasting  the  granular  zone  occupies  more  than  one-half  of  the  cell 
(Szymonowicz).  In  some  secreting  cells  of  the  pancreas  is  a  spherical  mass, 
staining  more  easily  than  the  rest  of  the  cells;  this  is  termed  the  paranucleus,  and 
is  believed  to  be  an  extension  from  the  nucleus.  The  connective  tissue  among  the 
gland  tubules  and  alveoli  presents  in  certain  parts  collections  of  cells,  which  are 
termed  inter-alveolar  cell-islets,  intertubular  cell-masses  or  islands  of  Langerhans. 
Opie  points  out  that  they  are  most  common  in  the  splenic  end  of  the  pancreas. 
The  cells  of  the  islands  are  smaller  than  the  secreting  cells  of  the  alveoli,  and 
are  arranged  in  layers  with  intervening  spaces.  The  islands  are  surrounded  by 
fine  connective  tissue.  The  spaces  in  the  islands  contain  capillaries.  There 
are  no  ducts  in  the  islands  of  Langerhans.  Their  function  is  to  furnish  the 
internal  secretion  of  the  pancreas. 

Blood-vessels,  Lymphatics,  and  Nerves. — The  arteries  of  the  pancreas  come  from 
the  superior  pancreatico -duodenal  branch  of  the  gastro -duodenal;  the  inferior  pan- 
creatico-duodenal  branch  of  the  superior  mesenteric;  the  inferior  pancreatic  branch  of 
the  superior  mesenteric;  pancreatic  branches  of  the  hepatic  and  pancreatic  branches 
of  the  splenic.  In  a  few  cases  a  large  artery,  the  pancreatica  magna,  accompanies 
the  pancreatic  duct.  In  most  cases  there  is  no  such  vessel.  The  veins  are  the 
anterior  pancreatico -duodenal  branch  of  the  superior  mesenteric;  the  posterior  pancre- 
atico-duodenal  branch  and  other  pancreatic  branches  of  the  portal;  and  pancreatic 
branches  of  the  splenic.     The  lymphatics  arise  in  a  network   about  the  lobules. 


THE  SPLEEN  I353 

Numerous  collecting  trunks  pass  to  the  surface  of  the  pancreas,  anastomose  with 
each  other,  and  enter  into  glands  about  the  pancreas.  The  splenic  glands  receive 
most  of  the  trunks.  Others  are  received  by  glands  along  the  aorta  (Sappey), 
glands  at  the  origin  of  the  superior  mesenteric  artery,  and  glands  along  the  pan- 
creatico-duodenal  vessels.^  The  nerves  come  from  the  coeliac,  superior  mesenteric, 
and  splenic  plexuses. 

The  Pancreatic  Juice. — The  pancreatic  juice  is  a  clear,  somewhat  viscid  alkaline 
liquid.  Its  specific  gravity  is  about  1030.  The  solid  matter  consists  chiefly  of 
proteids,  and  amounts  to  about  10  per  cent,  of  a  sample  of  the  juice.^  The  juice 
contains  a  ferment  which  breaks  up  fat,  a  ferment  which  converts  starch  into 
sugar,  a  ferment  which  curdles  milk,  and  a  ferment  which  digests  proteid  material. 

Surface  Form.— The  pancreas  lies  in  front  of  the  second  lumbar  vertebra,  and  can  some- 
times be  felt,  in  emaciated  subjects,  when  the  stomach  and  colon  are  empty,  by  making  deep 
pressure  in  the  middle  line  about  three  inches  above  the  umbilicus. 

Surgical  Anatomy. — Of  late  years  our  knowledge  of  the  structure,  functions,  and  diseases 
of  the  pancreas  has  been  notably  increased,  and  surgeons  have  begun  to  operate  for  certain 
pancreatic  diseases.  It  is  occasionally  the  seat  of  cancer,  which  usually  affects  the  head  or 
duodenal  end,  and  therefore  often  speedily  involves  the  common  bile-duct,  leading  to  persistent 
jaundice.  Cancer  of  the  pancreas  may  be  primary  or  secondary.  Primary  sarcoma  is  very 
unusual;  secondary  sarcoma  is  more  common,  but  cancer  is  far  commoner  than  either  form  of 
sarcoma.  Adenoma  may  also  occur.  Cases  are  on  record  of  the  successful  removal  of  tumors  of 
the  pancreas,  but  the  operations  are  very  dangerous,  are  extremely  difficult,  and  are  seldom 
attempted.  The  pancreas  may  be  ihe  seat  of  sy^philitic  or  tuberculous  disease.  As  a  result  of 
pancreatic  injury,  there  may  be  elusion  into  the  lesser  peritoneal  cavity.  The  lesser  cavity 
becomes  distended,  and  the  fluid  of  this  pseudo-cyst  may  contain  pancreatic  juice  (Jordan  Lloyd). 
True  cysts  of  the  pancreas  are  occasionally  found.  Pancreatic  cysts  may  result  from  blocking 
of  the  duct,  from  epithelial  proliferation,  from  traumatism  and  hemorrhage,  or  from  hydatid  dis- 
ease. Congenital  cysts  may  occur,  and  cystic  carcinoma  is  sometimes  encountered.  Cysts  of  the 
pancreas  may  present  in  the  epigastric  region  above  and  to  the  right  of  the  umbilicus.  The 
fluid  in  these  cysts  contains  some  of  the  pancreatic  secretion.  A  pancreatic  cyst  is  best  treated 
by  opening  the  abdomen,  suturing  the  cyst  to  the  skin,  opening  the  cyst  and  providing  for  drainage. 
Complete  extirpation  of  the  cyst  is  invariably  difficult  and  is  usually  impossible.  It  has  been 
said  that  the  pancreas  is  the  only  abdominal  viscus  which  has  never  been  found  in  a  hernial  pro- 
trusion; but  even  this  organ  has  been  found,  in  company  with  other  viscera,  in  rare  cases  of 
diaphragmatic  hernia.  The  pancreas  has  been  known  to  become  invaginated  into  the  intestine, 
and  portions  of  tue  organ  have  sloughed  ofi".  In  cases  of  excision  of  the  pylorus  great  care  must 
be  exercised  to  avoid  wounding  the  pancreas,  as  the  escape  of  the  pancreatic  fluid  may  be  attended 
with  serious  and  even  with  fatal  results,  peritonitis  and  fat  necrosis,  and  gangrene  being  caused. 

Rupture  of  the  pancreas  as  a  solitary  result  of  traumatism  is  very  unusual,  but  is  more  common 
in  violent  injuries  which  rupture  the  liver  and  spleen  as  well.  An  injury  which  lacerates  the 
pancreas  and  permits  blood  and  pancreatic  juice  to  flow  into  the  lesser  peritoneal  cavity  is  usually 
rapidly  fatal,  but  may  not  be.  The  foramen  of  Winslow  may  be  occluded  by  inflammation,  and 
a  pseudo-cyst  may  form.  In  severe  laceration  of  the  pancreas  alone,  it  would  be  proper  to  open 
the  abdomen,  ligature  bleeding  vessels,  suture  the  pancreas,  and  drain  the  lesser  peritoneal  cavity 
posteriorly.  A  gun-shot  wound  of  the  pancreas  requires  posterior  drainage.  Every  eftort  must 
be  made  in  a  pancreatic  wound  to  rapidly  get  rid  of  pancreatic  fluid  by  drainage  from  the 
wound  area,  as  this  fluid  is  extremely  irritant  and  may  cause  gangrene. 

Inflammation  of  the  pancreas  is  due  to  infection.  Occasionally  it  seems  to  follow  the  entrance 
of  bile  into  the  pancreatic  duct,  because  of  plugging  of  the  ampulla  with  a  calculus  (Halsted, 
Opie).  Hemorrhage  into  the  pancreas  is  frequent  in  acute  pancreatitis,  and  fat  necrosis  is  common 
in  the  fat  of  the  mesentery,  subperitoneal  tissue,  omentum,  and  other  parts.  Acute  pancreatitis 
may  be  recovered  from  if  the  abdomen  is  opened,  the  pancreas  incised,  and  drainage  employed. 

In  chronic  interstitial  pancreatitis  of  the  head  of  the  pancreas  the  gall-duct  is  apt  to  become 
blocked,  and  the  disease  is  frequently  mistaken  for  cancer.  Cure  may  follow  opening  and  drain- 
age of  the  gall-bladder. 

THE  SPLEEN  (LIEN)  (Figs.  958.  959,  961). 

The  spleen  belongs  to  that  class  of  bodies  which  are  known  as  ductless  glands. 
It  is  probably  related  to  the  blood-vascular  system,  but  in  consequence  of  its 

1  Poirier,  Cun(5o,  and  Delamare  on  the  Lymphatics.     Edited  and  translated  by  Cecil  H.  Leaf. 
*  Robson  and  Moyniham  on  Disease.s  of  the  Pancreas. 


1354 


THE   ORGANS  OF  DIGESTION 


anatomical  relationship  to  the  stomach  and  its  physiological  relationship  to  the 
liver  it  is  convenient  to  describe  it  in  this  section.  It  is  situated  principally  in  the 
posterior  portion  of  the  left  hypoohondriac  region,  its  upper  and  inner  extremity 
extending  into  the  epigastric  region;  lying  between  the  fundus  of  the  stomach 
and  the  Diaphragm.  If  the  abdomen  is  opened  a  spleen  of  ordinary  size  is  not 
visible  from  the  front,  as  it  is  placed  between  the  left  kidney.  Diaphragm,  and 
stomach.  It  moves  with  the  respiratory  movements  and  with  the  movements  of 
the  stomach.  It  is  the  largest  of  the  so-called  ductless  glands,  and  varies  greatly 
in  size.  Usually  it  measures  some  five  inches  in  length.  It  is  of  an  oblong, 
flattened  form,  soft,  of  very  brittle  consistence,  highly  vascular,  and  of  a  dark- 
purplish  color. 

Surfaces.  The  External  or  Phrenic  Surface  (fades  diaphragmatica). — The  exter- 
nal or  phrenic  surface  is  convex,  smooth,  and  is  directed  upward,  backward,  and 
to  the  left,  except  at  its  upper  end,  where  it  is  directed  slightly  inward.  It  is  in 
relation  with  the  under  surface  of  the  Diaphragm,  which  separates  it  from  the 
eighth,  ninth,  tenth,  and  eleventh  ribs  of  the  left  side,  and  in  part  from  the  lower 

border  of  the  left  lung  and  pleura.  It  is 
to  be  remembered  that  not  only  are  the 
peritoneum  and  the  Diaphragm  between 
the  spleen  and  the  ribs,  but  also  the  cavity 
of  the  left  pleura  and  a  portion  of  the  left 
lung. 

The  Internal  Surface. — The  internal  sur- 
face is  concave,  and  divided  by  a  ridge 
into  an  anterior  or  larger,  and  a  posterior  or 
smaller  portion. 

The  Anterior  Portion  of  the  internal  sur- 
face or  the  gastric  surface  (fades  gastrica), 
which  is  directed  forward  and  inward,  is 
broad  and  concave,  and  is  in  contact  with 
the  posterior  wall  of  the  great  end  of  the 
stomach;  and  below  this  with  the  tail  of 
the  pancreas.  It  presents  near  its  inner 
border  a  long  fissure,  termed  the  hilum 
(hilus  lienis).  This  is  pierced  by  several 
irregular  apertures,  for  the  entrance  and 
exit  of  vessels  and  nerves. 

The   Posterior   Portion    of    the  internal 

surface  or  the  renal  surface  (fades  renalis) 

is  directed  inward  and  downward.     It  is 

somewhat  flattened,  does  not  reach  as  high 

as  the  gastric  surface,  is  considerably  narrower  than  the  latter,  and  is  in  relation 

with  the  upper  part  of  the  outer  surface  of  the  left  kidney  and  occasionally  with 

the  left  suprarenal  capsule. 

The  upper  end  of  the  spleen  (extremitas  superior)  is  directed  inward,  toward  the 
vertebral  column,  where  it  lies  on  a  level  with  the  eleventh  dorsal  vertebra.  The 
lower  end  (extremitas  inferior),  sometimes  termed  the  basal  surface,  is  flat,  triangular 
in  shape,  and  rests  upon  the  splenic  flexure  of  the  colon  and  the  phreno-colic  liga- 
ment, and  is  generally  in  contact  with  the  tail  of  the  pancreas.  The  anterior  border 
(margo  anterior)  is  free,  sharp,  and  thin,  and  is  often  notched,  especially  below.  It 
separates  the  phrenic  surface  from  the  gastric  surface.  The  posterior  border  (margo 
posterior)  is  more  rounded  and  blunter  than  the  anterior.  It  separates  the  renal 
portion  of  the  internal  surface  from  the  phrenic  surface.  It  corresponds  to  the 
lower  border  of  the  eleventh  rib  and  lies  between  the  Diaphragm  and  left  kidney. 


Fig.  962. — The  spleen,  showing  its  gastric  and 
renal  surfaces.     (Testut.) 


THE  SPLEEN 


1355 


The  internal  border  is  the  name  sometimes  given  to  the  ridge  which  separates  the 
renal  and  gastric  portions  of  the  internal  surface. 

The  spleen  is  surrounded  by  peritoneum,  except  at  the  hilum  and  the  serous 
membrane,  is  firmly  adherent  to  its  capsule,  and  is  held  in  position  by  two  folds 
of  this  membrane:  one,  the  lieno-renal  ligament  (ligamentum  phrenicolienale)  (Figs. 
857  and  860),  is  derived  from  the  layers  of  peritoneum  forming  the  greater  and 
lesser  sacs,  where  they  come  into  contact  between  the  left  kidney  and  the  spleen. 
Between  its  two  layers  the  splenic  vessels  pass;  the  second,  the  gastro -splenic 
omentum  (ligamentum  gastrolienale),  also  formed  of  two  layers,  derived  from  the 
greater  and  lesser  sacs,  respectively,  where  they  meet  between  the  spleen  and 
stomach  (Fig.  860).  Between  these  two  layers  run  the  vasa  brevia  of  the 
splenic  artery  and  vein.  The  spleen  is  also  supported  by  the  phreno-colic  ligament 
(ligamentum  phrenicocolicum),  upon  which  its  lower  end  rests. 

The  size  and  weight  of  the  spleen  are  liable  to  very  extreme  variations  at  dif- 
ferent periods  of  life,  in  different  individuals,  and  in  the  same  individual  under 
different  conditions.    In  the  adult,  in  whom  it  attains  its  greatest  size,  it  is  usually 


Fig.  963. — Transverse  section  of  the  spleen,  showing  the  trabecular  tissue  and  the  splenic  vein  and 

its  tributaries. 


about  five  inches  in  length,  three  inches  in  breadth,  and  an  inch  or  an  inch  and  a 
half  in  thickness,  and  weighs  about  seven  ounces.  At  birth,  its  weight,  in  propor- 
tion to  the  entire  body,  is  almost  equal  to  what  is  observed  in  the  adult,  being  as 
1  to  350;  while  in  the  adult  it  varies  from  1  to  320  to  1  to  400.  In  old  age,  the  organ 
not  only  decreases  in  weight,  but  decreases  considerably  in  proportion  to  the 
entire  body,  being  as  1  to  700.  The  size  of  the  spleen  is  increased  during  and 
after  digestion,  and  varies  considerably  according  to  the  state  of  nutrition  of  the 
body,  being  large  in  highly  fed,  and  small  in  starved  animals.  In  intermittent 
and  other  fevers  it  becomes  much  enlarged,  weighing  occasionally  from  eighteen 
to  twenty  pounds. 

Frequently  in  the  neighborhood  of  the  spleen,  and  especially  in  the  gastro- 
splenic  and  great  omenta,  small  nodules  of  splenic  tissue  may  be  found,  either 
isolated,  or  connected  to  the  spleen  by  thin  bands  of  splenic  tissue.  Every  such 
nodule  is  known  as  a  supernumerary  or  accessory  spleen  (lien  accessorius).  Accessory 
spleens  vary  in  size  from  that  of  a  pea  to  that  of  a  plum. 


1356  '^HE    ORGANS   OF  DIGESTION 

Support  and  Movability  of  the  Spleen. — The  spleen  is  normally  movable 
within  certain  narrow  limits.  It  moves  with  respiration  and  with  stomach  move- 
ments. It  is  supported  by  ligaments  (p.  1355).  An  unduly  movable  spleen  is 
called  a  movable  spleen.  In  order  that  a  spleen  shall  become  unduly  movable, 
the  ligaments  must  stretch,  and  this  stretching  is  often  effected  when  the  organ 
is  greatly  enlarged,  but  even  an  apparently  normal  spleen  may  become  movable. 
Movable  spleen  is  usually  associated  with  movable  left  kidney. 

Stnicture. — The  spleen  is  invested  by  two  coats — an  external  serous  and  an 
internal  fibro-elastic  coat. 

The  External  or  Serous  Coat  {tunica  serosa). — The  external  or  serous  coat  is 
derived  from  the  peritoneum;  it  is  thin,  smooth,  and  in  the  human  subject  is  inti- 
mately adherent  to  the  fibro-elastic  coat.  It  invests  the  entire  organ,  except  at 
the  places  of  its  reflection  on  to  the  stomach  and  Diaphragm  and  at  the  hilum. 

The  Fibro-elastic  Coat  {tunica  albuginea). — The  fibro-elastic  coat  forms  the 
framework  of  the  spleen.  It  is  composed  of  connective  tissue  containing  muscle- 
cells  and  elastic  fibres,  and  it  invests  the  organ  as  a  capsule,  and  at  the  hilum  is 
reflected  inward  upon  the  vessels  in  the  form  of  sheaths.  From  these  sheaths,  as 
well  as  from  the  inner  surface  of  the  fibro-elastic  coat,  numerous  small  fibrous 
bands,  trabeculae  {trabeculae  lienis)  (Figs.  963  and  964),  are  given  off  in  all  direc- 
tions; these  uniting,  constitute  the  framework  of  the  spleen.  This  framework 
resembles  a  sponge-like  material,  consisting  of  a  number  of  small  spaces  or 
areolae  formed  by  the  trabeculae,  which  are  given  off  from  the  inner  surface  of  the 
capsule,  or  from  the  sheaths  prolonged  inwardly  on  the  blood-vessels.  The  spaces 
or  areolae  contain  the  adenoid  material  known  as  splenic  pulp  {pulpa  lienis). 

The  proper  coat,  the  sheaths  of  the  vessels  and  the  trabeculae,  consist  of  a 
dense  mesh  of  white  and  yellow  elastic  fibrous  tissues,  the  latter  decidedly  pre- 
dominating. It  is  owing  to  the  presence  of  this  tissue  that  the  spleen  possesses 
a  considerable  amount  of  elasticity,  which  allows  of  the  very  great  variations  in 
size  that  it  presents  under  certain  circumstances.  In  addition  to  these  con- 
stituents of  this  tunic,  there  is  found  in  man  a  small  amount  of  non-striped  mus- 
cular fibre,  and  in  some  mammalia  {e.  g.,  dog,  pig,  and  cat)  a  very  considerable 
amount,  so  that  the  trabeculae  appear  to  consist  chiefly  of  muscular  tissue.  It  is 
probably  because  of  this  muscular  structure  that  the  spleen  exhibits,  when  acted 
upon  by  the  galvanic  current,  faint  traces  of  contractility. 

The  proper  substance  of  the  spleen  or  splenic-pulp  is  a  soft  mass  of  a  dark 
reddish-brown  color,  resembling  gruraous  blood.  When  a  thin  section  is  exam- 
ined under  a  microscope,  it  is  found  to  consist  of  a  number  of  branching 
cells  and  an  intercellular  substance.  The  cells  are  connective-tissue  corpuscles, 
and  have  been  named  the  sustentacular  or  supporting  cells  of  the  pulp.  The 
processes  of  these  branching  cells  communicate  with  each  other,  thus  forming  a 
delicate  reticulated  tissue  in  the  interior  of  the  areolae  formed  by  the  trabeculae  of 
the  capsule;  so  that  each  primary  space  may  be  considered  to  be  divided  into  a 
number  of  smaller  spaces  by  the  junction  of  these  processes  of  the  branching 
corpuscles.  These  secondary  spaces  contain  blood,  in  which,  however,  the  white 
corpuscles  are  found  to  be  in  larger  proportions  than  in  ordinary  blood.  The 
sustentacular  cells  are  either  small  uni-nucleated  or  larger  multi-nucleated  cells; 
they  do  not  stain  deeply  with  carmine,  like  the  cells  of  the  Malpighian 
bodies,  presently  to  be  described  (W.  Miiller),  but  like  them  they  possess  amoe- 
boid movements  (Cohnheim).  In  many  of  them  may  be  seen  deep  red  or 
reddish-yellow  granules  of  various  sizes  which  present  the  characters  of  the 
hsematin  of  the  blood.  Sometimes,  also,  unchanged  blood-disks  are  seen  included 
in  these  cells,  but  more  frequently  blood-disks  are  found  which  are  altered  both 
in  form  and  color.  In  fact,  blood-corpuscles  in  all  stages  of  disintegration  may 
be  noticed  to  occur  within  them.    Klein  has  recently  pointed  out  that  sometimes 


THE  SPLEEN 


1357 


these  cells  in  the  young  spleen  contain  a  proliferating  nucleus;  that  is  to  say, 
the  nucleus  is  of  large  size,  and  presents  a  number  of  knob-like  projections, 
as  if  small  nuclei  were  budding  from  it  by  a  process  of  gemmation.  This  obser- 
vation is  of  importance,  as  it  may  explain  one  possible  source  of  the  colorless 
blood-corpuscles. 

The  interspaces  or  areolae  formed  by  the  framework  of  the  spleen  are  thus  filled 
by  a  delicate  reticulum  of  branched  connective-tissue  corpuscles,  the  interstices  of 
which  are  occupied  by  blood,  and  in  which  the  blood-vessels  terminate  in  the 
manner  now  to  be  described. 

Blood-vessels  of  the  Spleen. — The  splenic  artery  (Fig.  961)  is  remarkable  for  its 
large  size  in  proportion  to  the  size  of  the  organs,  and  also  for  its  tortuous  course. 
It  divides  into  six  or  more  branches,  which  enter  the  hilum  of  the  spleen  and 
ramify  throughout  its  substance,  receiving  sheaths  from  the  involution  of  the 
external  fibrous  tissue.    Similar  sheaths  also  invest  the  nerves  and  veins. 

Each  branch  runs  in  the  transverse  axis  of  the  organ  from  within  outward, 
diminishing  in  size  during  its  transit,  and  giving  off  in  its  passage  smaller  branches, 
some  of  which  pass  to  the  anterior,  others  to  the  posterior  part.    These  ultimately 


Fig.  964. — Transverse  section  of  the  human  spleen,  showing  the  distribution  of  the  splenic  artery 

and  its  branches. 

leave  the  trabecular  sheaths,  and  terminate  in  the  proper  substance  of  the  spleen 
in  small  tufts  or  pencils  of  minute  arterioles,  which  open  into  the  interstices 
of  the  reticulum  formed  by  the  branched  sustentacular  cells  (Figs.  964,  965,  and 
966).  Each  of  the  larger  branches  of  the  artery  supplies  chiefly  that  region  of  the 
organ  in  which  the  branch  ramifies,  having  no  anastomosis  with  the  majority 
of  the  other  branches. 

The  arterioles  (Fig.  966),  supported  by  the  minute  trabeculae,  traverse  the  pulp 
in  all  directions  in  bundles  or  pencilli  of  straight  vessels.  Their  external  coat,  on 
leaving  the  trabecular  sheaths,  consists  of  ordinary  connective  tissue,  but  it  grad- 
ually undergoes  a  transformation,  becomes  much  thickened,  and  is  converted  into 
a  lymphoid  material.^  This  change  is  effected  by  the  conversion  of  the  con- 
nective tissue  into  a  lymphoid  tissue,  the  bundles  of  connective  tissue  becoming 
looser  and  laxer,  their  fibrils  more  delicate,  and  containing  in  their  interstices 
an  abundance  of  lymph-corpuscles  (W.  Miiller).  This  lymphoid  material  is  sup- 
plied with  blood  by  minute  vessels  derived  from  the  artery  with  which  they  are 


1  According  to  Klein,  it  is  the  sheath  of  the  small  vessel  which  undergoes  this  transformation,  and  forms  a 
^'  solid  mass  of  adenoid  tissue  which  surrounds  the  vessel  like  a  cylindrical  sheath."  (Atlas  of  Histology,  p.  424.) 


1358 


THE    ORGANS   OF   DIGESTION 


in  contact,  and  which  terminates  by  breaking  up  into  a  network  of  capillary 
vessels. 

The  altered  coat  of  the  arterioles,  consisting  of  lymphoid  tissue  (Fig.  966),  pre- 
sents here  and  there  thickenings  of  a  spheroidal  shape,  the  Malpighian  bodies  of  the 
spleen  (noduli  lymphatici  lienales  [Malpighii])  (Fig.  965) .  These  bodies  vary  in  size 
from  about  the  y^^  of  an  inch  to  the  yj-  of  an  inch  in  diameter.  They  are  merely 
local  expansions  or  hyperplasiae  of  the  lymphoid  tissue  of  which  the  external  coat  of 
the  smaller  arteries  of  the  spleen  is  formed.  They  are  most  frequently  found  sur- 
rounding the  arteriole,  which  thus  seems  to  tunnel  them,  but  occasionally  they  grow 
from  one  side  of  the  vessel  only,  and  present  the  appearance  of  a  sessile  bud  grow- 
ing from  the  arterial  wall.  Klein,  however,  denies  this,  and  says  it  is  incorrect  to 
describe  the  Malpighian  bodies  as  isolated  masses  of  adenoid  tissue,  but  that  they 
are  always  formed  around  an  artery,  though  there  is  generally  a  greater  amount  on 
one  side  than  on  the  other,  and  that,  therefore,  in  transverse  sections  the  artery  in 
the  majority  of  cases  is  found  in  an  eccentric  position.  These  bodies  are  visible  to 
the  naked  eye  on  the  surface  of  a  fresh  section  of  the  organ,  appearing  as  minute 

dots  of  semi-opaque  whitish  color  in  the  dark 
substance  of  the  pulp.  In  minute  structure  they 
resemble  the  adenoid  tissue  of  lymphatic  glands, 
consisting  of  a  delicate  reticulum  in  the  meshes 
of  which  lie  ordinary  lymphoid  cells. 

The  reticulum  of  the  tissue  is  made  up  of  ex- 
tremely delicate  fibrils,  and  is  comparatively 
open  in  the  centre  of  the  corpuscle,  becoming 
closer  at  the  periphery  of  the  body.  The  cells 
which  it  encloses,  like  the  supporting  cells  of  the 
pulp,  are  possessed  of  amoeboid  movements,  but 
when  treated  with  carmine  become  deeply 
stained,  and  can  thus  easily  be  recognized  from 
those  of  the  pulp. 

The  arterioles  terminate  in  capillaries,  which 
traverse  the  pulp  in  all  directions;  their  walls 
become  much  attenuated,  lose  their  tubular 
character,  and  the  cells  of  the  lymphoid  tissue 
of  which  they  are  composed  become  altered;  presenting  a  branched  appearance 
and  acquiring  processes  which  are  directly  connected  with  the  processes  of  the 
sustentacular  cells  of  the  pulp  (Fig.  966).  In  this  manner  the  capillary  vessels 
terminate,  and  the  blood  flowing  through  them  finds  its  way  into  the  interstices 
of  the  reticulated  tissue  formed  by  the  branched  connective-tissue  corpuscles  of 
the  splenic  pulp.  Thus  the  blood  passing  through  the  spleen  is  brought  into 
intimate  relation  with  the  elements  of  the  pulp,  and  no  doubt  undergoes  important 
changes. 

After  these  changes  have  taken  place  the  blood  is  collected  from  the  interstices 
of  the  tissue  by  the  rootlets  of  the  veins  (Fig.  963) ,  which  commence  much  in  the 
same  way  as  the  arteries  terminate.  Where  a  vein  is  about  to  originate  the  con- 
nective-tissue corpuscles  of  the  pulp  arrange  themselves  in  rows  in  such  a  way  as  to 
form  an  elongated  space  or  sinus.  They  become  changed  in  shape,  being  elongated 
and  spindle-shaped,  and  overlap  each  other  at  their  extremities.  They  thus  form 
a  sort  of  endothelial  lining  of  the  path  or  sinus,  which  is  the  radicle  of  a  vein. 
On  the  outer  surface  of  these  cells  are  seen  delicate  transverse  lines  or  markings 
vvhich  are  due  to  minute  elastic  fibrillae  arranged  in  a  circular  manner  around  the 
smus.  Thus  the  channel  obtains  a  continuous  external  investment,  and  grad- 
ually becomes  converted  into  a  small  vein,  which  after  a  time  presents  a  coat  of 
ordinary  connective  tissue,  lined  by  a  layer  of  fusiform  endothelial  cells  which  are 


Fig.  965. — Part  of  a  Malpighian  body 
of  the  spleen  of  man.  a,  arterial  branch 
in  longitudinal  section  ;  b,  adenoid  tissue, 
still  containing  the  lymph-corpuscles  ;  only 
their  nuclei  are  shown  ;  r,  adenoid  reticu- 
lum, the  lymph-corpuscles  accidentally  re- 
moved.    (Klein  and  Noble  Smith.) 


THE   SPLEEN 


1359 


continuous  with  the  supporting  cells  of  the  pulp.  The  smaller  veins  unite  to  form 
larger  ones  which  do  not  accompany  the  arteries,  but  soon  enter  the  trabecular 
sheaths  of  the  capsule,  and  by  their  junction  form  from  six  or  more  branches  which 
emerge  from  the  hilum  and,  uniting,  form  the  splenic  vein,  the  largest  radicle  of 
the  portal  vein  (Figs.  958  and  962). 

The  veins  are  remarkable  for  their  numerous  anastomoses,  while  the  arteries 
hardly  anastomose  at  all. 

The  lymphatics  originate  in  two  ways — i  .e.,  from  the  sheaths  of  the  arteries 
and   in  the   trabecula?.     The  former  trunks  are  the  deep  collecting  trunks,  and 


Supporting  cell. 


Vessel  undergoing  lymphoid  change. 


Vessel  continuous 
with  processes  of 
supporting  cells. 


Supporting  cell. 


Fig.  966. — Section  of  spleen,  showing  the  termination  of  the  small  blood-vessels. 


accompany  the  blood-vessels ;  the  latter  pass  to  the  superficial  lymphatic  plexus, 
which  may  be  seen  on  the  surface  of  the  organ.  The  two  sets  communicate  in 
the  interior  of  the  organ.  The  deep  trunks  at  the  hilum  number  from  five  to 
ten,  and  terminate  in  the  splenic  glands.  The  superficial  trunks  also  pass  to  the 
hilum  and  terminate  in  the  splenic  glands. 

The  nerves  are  derived  from  the  splenic  plexus,  which  is  part  of  or  connected 
with  the  solar  plexus.     The  nerves  enter  the  spleen  with  the  vessels. 

Surface  Form. — ^The  spleen  is  situated  under  cover  of  the  ribs  of  the  left  side,  being  sepa- 
rated from  them  by  the  Diaphragm,  and  above  by  a  small  portion  of  the  lower  margin  of  the 
left  lung  and  pleura.  Its  position  corresponds  to  the  eighth,  ninth,  tenth,  and  eleventh  ribs. 
It  is  placed  very  obliquely.  "  It  is  oblique  in  two  directions  — viz.,  from  above  downward  and 
outward,  and  also  from  above  downward  and  forward"  (Cunningham).  "  Its  highest  and 
lowest  points  are  on  a  level  respectively  with  the  ninth  dorsal  and  first  lumbar  spines;  its  inner 
end  is  distant  about  an  inch  and  a  half  from  the  median  plane  of  the  body,  and  its  outer  end 
about  reaches  the  mid-axillary  line"  (Quain). 

Surgical  Anatomy. — Injury  of  the  spleen  is  less  common  than  that  of  the  liver,  on  account 
of  its  protected  situation  and  connections.  It  may  be  ruptured  by  direct  or  indirect  violence, 
torn  by  a  broken  rib,  or  injured  by  a  punctured  or  gunshot  wound.  When  the  organ  is  enlarged 
the  chance  of  rupture  is  increased.  The  great  risk  is  hemorrhage,  owing  to  the  extreme  vascu- 
larity of  the  organ,  and  the  absence  of  a  proper  system  of  capillaries.  The  injury  is  not,  how- 
ever, necessarily  fatal,  and  this  would  appear  to  be  due  in  a  great  measure  to  the  contractile 
power  of  its  capsule,  which  narrows  the  wound  and  thus  antagonizes  the  escape  of  blood.  In 
cases  in  which  the  symptoms  suggest  such  an  injury  and  indicate  danger  to  life,  laparotomy  must 
be  performed ;  and  if  the  hemorrhage  cannot  be  arrested  by  ordinary  surgical  methods  the  spleen 
must  be  removed.  The  spleen  may  become  displaced,  producing  great  pain  from  stretching  of 
the  vessels  and  nerves,  and  this  dislocation  may  render  necessary  removal  of  the  organ.  The 
spleen  may  become  enormously  enlarged  in  certain  diseased  conditions,  such  as  ague,  leukaemia, 
syphilis,  valvular  disease  of  the  heart,  or  without  any  obtainable  history  of  previous  disease. 
It  may  also  become  enlarged  in  lymphadenoma  as  a  part  of  a  general  blood  disease.  In  these 
cases  the  mass  may  fill  the  abdomen  and  extend  into  the  pelvis,  and  may  be  mistaken  for 
ovarian  or  uterine  disease. 


1360  THE    ORGANS   OF  DIGESTION 

The  spleen  is  sometimes  the  seat  of  cystic  tumors,  especially  hydatids,  and  of  abscess.  These 
cases  require  treatment  by  incision  and  drainage;  and  in  abscess  great  care  must  be  taken  if 
there  are  no  adhesions  between  the  spleen  and  abdominal  cavity,  to  prevent  the  escape  of  any 
of  the  pus  into  the  peritoneal  cavity.  If  possible,  the  operation  should  be  performed  in  two 
stages.  Sarcoma  and  carcinoma  are  occasionally  found  in  the  spleen,  but  very  rarely  as  a  primary 
disease.  In  movable  spleen,  if  the  organ  is  normal,  follow  the  advice  of  Ilydygier  and  loosen 
the  parietal  peritoneum  to  make  a  pocket,  place  the  spleen  in  the  pocket,  and  pass  sutures  through 
the  parietal  peritoneum  and  the  splenic  ligaments.    A  movable  diseased  spleen  should  be  removed. 

Extirpation  of  the  spleen  has  been  performed  for  wounds  or  injuries,  floating  spleen,  simple 
hypertrophy,  and  leukismic  enlargement;  but  in  the  latter  case  the  operation  is  now  regarded 
as  unjustifiable,  as  it  is  practically  certain  to  terminate  fatally.  The  incision  is  best  made  in 
the  left  semilunar  line:  the  spleen  is  isolated  from  its  surroundings,  and  the  pedicle  transfixed 
and  ligatured  in  two  portions,  before  the  tumor  is  turned  out  of  the  abdominal  cavity,  if  this  is 
possible,  so  as  to  avoid  any  traction  on  the  pedicle,  which  may  cause  tearing  of  the  splenic  vein  and 
which  inevitably  induces  grave  shock.  In  applying  the  ligatures  the  surgeon  must  not  include 
the  tail  of  the  pancreas,  and  in  lifting  out  the  organ  care  must  be  taken  to  avoid  rupturing  the 
capsule. 


THE  ORGANS  OF  VOICE  AND  RESPIMTION. 


THE  LARYNX. 


^F^HE  Larynx  is  the  organ  of  voice,  placed  at  the  upper  part  of  the  air-passage. 
JL  It  is  situated  between  the  trachea  and  base  of  the  tongue,  at  the  upper  and 
forepart  of  the  neck,  where  it  forms  a  considerable  projection  in  the  middle  line. 
On  either  side  of  it  lie  the  great  vessels  of  the  neck;  behind,  it  forms  part  of  the 
boundary  of  the  pharynx,  and  is  covered  by  the  mucous  membrane  lining  that 
cavity.  Its  vertical  extent  corresponds  to  the  fourth,  fifth,  and  sixth  cervical  ver- 
tebrae, but  it  is  placed  somewhat  higher  in  the  female  and  also  during  childhood. 
In  infants  between  six  and  twelve  months  of  age  Symington  found  that  the  tip  of 


Fig.  967. — Sagittal  section  of  a  man  twenty-one  years  of  age.     (After  W.  Braune.) 


the  epiglottis  was  a  little  above  the  level  of  the  cartilage  between  the  odontoid 
process  and  body  of  the  axis,  and  that  between  infancy  and  adult  life  the  larynx 
descends  for  a  distance  equal  to  two  vertebral  bodies  and  two  intervertebral  disks. 
The  movements  of  the  head  affect  the  position  of  the  larynx.  When  the  head  is 
drawn  back,  the  larynx  is  lifted,  and  when  the  chin  approaches  the  chest  the 
larynx  is  depressed.  During  swallowing  the  larynx  moves  distinctly;  during  sing- 
ing it  moves  slightly.    The  larynx  is  suspended  by  the  stylo-hyoid  ligament,  the 

86  ( 1361  ) 


1362  'J'HE   ORGANS   OF    VOICE  AND    BESPIBATION 

muscles  of  the  upper  border  of  the  hyoid  bone,  the  Stylo-pharyngeus  and  Palato- 
pharyngeus  muscles.  According  to  Sappey,  the  average  measurements  of  the  adult 
larynx  are  as  follows: 

In  males.  In  females. 

Vertical  diameter      .          .  .  .44  mm.                   36  mm. 

Transverse  diameter           .  .  .     43     "                     41     " 

Antero-posterior  diameter  .  .     36     "                     26     " 

Circumference            .          .  .  .    136     *'  112     " 

Until  puberty  there  is  no  marked  difference  between  the  larynx  of  the  male 
and  that  of  the  female.  In  the  latter  its  further  increase  in  size  is  only  slight, 
whereas  in  the  former  it  is  great;  all  the  cartilages  are  enlarged,  and  the  thyroid 
becomes  prominent  as  the  pomum  Adami  in  the  middle  line  of  the  neck,  while 
the  length  of  the  glottis  is  nearly  doubled. 

The  larynx  is  broad  above,  where  it  presents  the  form  of  a  triangular  box, 
flattened  behind  and  at  the  sides,  and  bounded  in  front  by  a  prominent  vertical 
ridge.  Below,  it  is  narrow  and  cylindrical.  It  is  composed  of  cartilages,  which 
are  connected  together  by  ligaments  and  moved  by  numerous  muscles.  It  is  lined 
by  mucous  membrane,  which  is  continuous  above  with  that  lining  the  pharynx  and 
below  with  that  of  the  trachea. 

In  the  median  line  of  the  neck  the  larynx  has  in  front  of  it  the  skin  and  cer- 
vical fascia.  There  is  often  a  bursa  between  the  skin  and  fascia  over  the  most 
prominent  part  of  the  larynx.  It  is  called  the  bursa  subcutanea  prominentiae 
larsmgeae.  It  is  present  particularly  in  men,  and  is  seldom  found  in  the 
young  or  in  women.  The  larynx  is  covered  to  each  side  by  the  thyroid  gland, 
and  the  Sterno-hyoid,  Sterno-thyroid,  Thyro-hyoid,  and  Omo-hyoid  muscles,  and 
the  Inferior  constrictors  of  the  pharynx.  Posterior  is  the  laryngeal  portion  of  the 
pharynx. 

The  Cartilages  of  the  Larynx  {cartilagines  lanjngis). — The  cartilages  of  the 
larynx  are  nine  in  number,  three  single,  and  three  pairs: 

Thyroid.  Two  Arytenoid. 

Cricoid.  Two  Cornicula  Laryngis. 

Epiglottis.  Two  Cuneiform. 

The  Thyroid  Cartilage  (cartilago  thyreoidea)  (Figs.  968  and  969) . — The  thyroid 
cartilage  (from  dvpeo^,  a  shield)  is  hyaline  cartilage  and  is  the  largest  cartilage 
of  the  larynx.  It  is  at  the  anterior  and  upper  portion  of  the  larynx.  It  con- 
sists of  two  lateral  lamellae  or  alae,  united  at  an  acute  angle  in  front,  forming  a 
vertical  projection  in  the  middle  line,  which  is  prominent  above  and  called  the 
pomum  Adami  (prominentia  laryngea).  This  projection  is  subcutaneous,  is  more 
distinct  in  the  male  than  in  the  female,  and  is  often  separated  from  the  integu- 
ment by  a  bursa,  the  bursa  subcutanea  prominentiae  laryngeae. 

Each  lamella  is  quadrilateral  in  form.  Its  outer  surface  (Fig.  968)  presents 
an  oblique  ridge  (linea  ohliqua),  which  passes  downward  and  forward  from  a 
tubercle  situated  near  the  root  of  the  superior  cornu,  the  superior  tubercle  (tuber- 
culum  thyreoideum  superius),  to  a  small  tubercle  near  the  anterior  part  of  the 
lower  border,  the  inferior  tubercle  (tuherculum  thyreoideum  inferius).  This  ridge 
gives  attachment  to  the  Sterno-thyroid  and  Thyro-hyoid  muscles,  and  the  portion 
of  cartilage  included  between  it  and  the  posterior  border  gives  attachment  to 
part  of  the  Inferior  constrictor  muscle.  Just  below  each  superior  tubercle  there 
is  often  an  opening,  the  thyroid  foramen  (foramen  thyreoideum). 

The  anterior  borders  of  the  alae  of  the  thyroid  cartilage  which  are  continuous 
below  are  separated  above  by  a  V-shaped  notch,  the  thsrroid  notch  (incisura  thy- 
reoidea [superior] ) . 


THE   LABYNX 


1363 


The  Inner  Surface  (Fig.  969)  of  each  ala  is  smooth,  slightly  concave,  and 
covered  by  mucous  membrane  above  and  behind;  but  in  front,  in  the  receding 
angle  formed  by  their  junction,  are  attached  the  epiglottis,  the  true  and  false 
vocal  cords,  the  Thyro-arytenoid  and  Thyro-epiglottidean  muscles,  and  the 
thyro-epiglottidean  ligament. 

The  Upper  Border  or  Margin  of  the  Thyroid  Cartilage  (Fig.  969)  is  sinuously  curved, 
being  concave  at  its  posterior  part,  just  in  front  of  the  superior  cornu,  then  rising 
into  a  convex  outline,  which  dips  in  front  to  form  the  sides  of  the  thyroid  notch, 
in  the  middle  line,  immediately  above  the  pomum 
Adami.     This  border  gives  attachment  through- 
out its  whole  extent  to  the  th3nro-hyoid  or  hyo- 
thyroid  membrane  (membrana  hyothyreoidea) . 

The  Lower  Border  or  Margin  (Fig.  969)  is  nearly 
straight  in  front,  but  behind,  close  to  the  cornu, 
it  is  concave.  It  is  connected  to  the  cricoid  cartil- 
age, in  and  near  the  median  line,  by  the  middle 
portion  of  the  crico-thyroid  membrane  (membrana 
cricothyreoidea) ;  and,  on  either  side,  by  the 
Crico-thyroid  muscle. 

The  Posterior  Borders  (Fig.  969)  are  thick  and 
rounded,  and  each  terminates  above,  in  a  superior 
cornu  {cornu  swperius),  and  below,  in  an  inferior 
cornu  {cornu  injerius).  The  two  superior  cornua 
are  long  and  narrow,  directed  upward,  backward, 
and  inward,  and  terminate  in  conical  extremities, 
which  give  attachment  to  the  lateral  thyro-hyoid 
ligaments.  The  two  inferior  cornua  are  short 
and  thick;  they  pass  downward,  with  a  slight  in- 
clination forward  and  inward,  and  each  presents 
on  its  inner  surfaces  a  small  oval  articular  facet 
for  articulation  with  the  side  of  the  cricoid  cartil- 
age (Fig.  968) .  The  posterior  border  receives  the 
insertion  of  the  Stylo-pharyngeus  and  Palato-pharyngeus  muscles  on  each  side. 

During  infancy  the  alae  of  the  thyroid  cartilage  are  joined  to  each  other  by  a 
narrow,  lozenge-shaped  strip,  named  the  intrath3n:oid  cartilage.  This  strip  extends 
from  the  upper  to  the  lower  border  of  the  thyroid  cartilage  in  the  middle  line, 
and  is  distinguished  from  the  alae  by  being  more  transparent  and  more  flexible. 

The  Cricoid  Cartilage  {cartilago  cricoidea)  (Figs.  968,  969,  and  971). — The  cri- 
coid cartilage  is  so  called  from  its  resemblance  to  a  signet  ring  {xpixo(;,  a  ring). 
It  is  smaller,  but  thicker  and  stronger  *  than  the  thyroicl  cartilage,  and  forms  the 
lower  and  back  part  of  the  cavity  of  the  larynx.  It  is  hyaline  cartilage  and  con- 
sists of  two  parts:  a  quadrate  portion,  situated  behind,  and  a  narrow  ring  or 
arch,  one-fourth  or  one-fifth  the  depth  of  the  posterior  part,  situated  in  front. 
The  posterior  square  portion  rapidly  narrows  at  the  sides  of  the  cartilage,  at  the 
expense  of  the  upper  border,  into  the  anterior  portion. 

Its  Posterior  Portion  or  Lamina  {lamina  cartilaginis  cricoideae)  is  very  deep  and 
broad,  and  measures  from  above  downward  about  an  inch  {2  to  3  cm.) ;  it  presents, 
on  its  posterior  surface,  in  the  middle  line,  a  vertical  ridge  for  the  attachment  of 
the  longitudinal  fibres  of  the  oesophagus;  and  on  either  side  a  broad  depression 
for  the  Crico-arytenoideus  posticus  muscle. 

Its  Anterior  Portion  or  Arcus  {arcus  cartilaginis  cricoideae)  is  narrow  and  convex, 
and  measures  vertically  about  one-fourth  or  one-fifth  of  an  inch  (5  to  7  cm.); 
it  affords  attachment  externally  in  front  and  at  the  sides  to  the  Crico-thyroid 
muscles,  and,  behind,  to  part  of  the  Inferior  constrictor. 


Fig.  968 


Side  view  of  the  thyroid 
and  cricoid  cartilages. 


1364 


THE    ORGANS   OF    VOICE  AND    RESPIRATION 


Epiglottis. 


At  the  point  of  junction  of  the  posterior  quadrate  portion  with  the  rest  of  the 
cartilage  is  a  small  round  elevation,  for  articulation  with  the  inferior  cornu  of  the 
thyroid  cartilage. 

The  Lower  Border  of  the  cricoid  cartilage  is  horizontal,  and  connected  to  the 
upper  ring  of  the  trachea  by  fibrous  membrane  (Figs.  968  and  970). 

Its  Upper  Border  is  directed  obliquely  upward  and  backward,  owing  to  the 
great  depth  of  the  posterior  surface.    It  gives  attachment,  in  front,  to  the  middle 

portion  of  the  crico-thyroid  mem- 
brane ;  at  the  sides,  to  the  lateral 
portion  of  the  same  membrane 
and  to  the  lateral  Crico-arj'tenoid 
muscle;  behind,  it  presents,  in  the 
middle,  a  shallow  notch,  and  on 
each  side  of  this  is  a  smooth,  oval 
surface,  directed  upward  and  out- 
ward, for  articulation  with  the 
arytenoid  cartilage. 

The  Inner  Surface  of  the  cricoid 
cartilage  is  smooth,  and  lined  with 
mucous  membrane. 

The  ArTtenoid  Cartilages  (cartil- 
agines  arytaenoideae)  (Figs.  969, 
972,  and  976).— The  arytenoid 
cartilages  are  so  called  from  the 
resemblance  they  bear,  when  ap- 
proximated, to  the  mouth  of  a 
pitcher  {a.i>bxmva,  a  pitcher).  They 
are  two  in  number,  and  situated 
at  the  upper  border  of  the  cricoid 
cartilage,  at  the  back  of  the  larynx 
in  the  interval  between  the  poste- 
rior borders  of  the  alae  of  the  thy- 
roid cartilages.  Each  cartilage  is 
in  form  a  three-sided  pyramid,  and 
presents  for  examination  three  sur- 
faces, a  base,  and  an  apex. 

The  Posterior  Surface  is  trian- 
gular, smooth,  concave,  and  gives 
attachment  to  the  transverse  por- 
tion of  the  Arytenoid  muscle. 

The  Anterior  or  External  Surface 
is  somewhat  convex  and  rough.  It 
presents,  near  its  apex,  a  small 
elevation,  the  colliculus ;  from  this  a 
ridge  (crista  arcuata)  passes  back- 
ward and  then  forward  and  down- 
ward into  a  sharp-pointed  process,  the  vocal  process.  This  ridge  separates  a 
deep  depression  above,  the  fovea  triangularis,  from  a  broader  and  shallower  depres- 
sion below,  the  fovea  oblonga.  A  short  distance  above  the  base  a  small  tubercle 
gives  origin  to  the  ligament  of  the  false  vocal  cord,  the  superior  thyro-arytenoid 
ligament.  To  the  outer  part  of  the  ridge,  as  well  as  the  surface  above  and  below, 
is  attached  the  Thyro-arytenoid  muscle. 

The  Internal  Surface  is  narrow,  smooth,  and  flattened,  covered  by  mucous 
membrane,  and  forms  the  lateral  boundary  of  the  respiratory  part  of  the  glottis. 


Posterior 
surface. 


Thyroid. 


Cornicula  laryngis. 
Cuneiform  cartilage. -^^^    ^       « 

f  J^        ^ 

Arytenoid,     l^ji^ 


Insertion  of 

CRICO-ARYTENOIDEUS 
POSTICUS  ET  LATERALIS 


Cricoid. 
Articular  facet  for 
arytenoid  cartilage. 

Articular  facet  for 
inferior  cornu  of 
thyroid  cartilage. 


Fig.  969. — The  cartilages  of  the  larynx.     Posterior  view. 


Arytenoid  cartilages,  base. 


THE   LARYNX  1365 

The  Base  (basis)  of  each  cartilage  is  broad,  and  presents  a  concave  smooth  sur- 
face, for  articulation  with  the  cricoid  cartilage.  Two  of  its  angles  require  special 
mention:  the  external  angle,  which  is  short,  rounded,  and  prominent,  projects 
backward  and  outwartl,  and  is  termed  the  muscular  process  (processus  muscularis), 
from  receiving  the  insertion  of  the  Posterior  and  Lateral  crico-arytenoid  muscles. 
The  anterior  angle,  also  prominent,  but  more  pointed,  projects  horizontally  forward, 
and  gives  attachment  to  the  inferior  thy ro- arytenoid  ligament,  the  supporting  liga- 
ment of  the  true  vocal  cord.  This  angle  is  called  the  vocal  process (proce^^ws  vocalis). 

The  Apex  of  each  cartilage  is  pointed,  curved  backward  and  inward,  and  sur- 
mounted by  a  small  conical,  cartilaginous-nodule,  the  comiculum  laryngis,  articu- 
lated with  or  united  to  the  arytenoid  cartilage. 

The  Comicula  Laryngis  or  Cartilages  of  Santorini  (cartilagines  corniculatae)  (Figs. 
969  and  975) . — The  cornicula  laryngis  are  two  small  conical  nodules,  consisting  of 
white  fibro-cartilage,  which  articulate  with  the  summit  of  the  arytenoid  cartilages 
and  serve  to  prolong  them  backward  and  inward.  To  them  are  attached  the  aryteno- 
epiglottidean  folds.     They  are  sometimes  united  to  the  arytenoid  cartilages. 

The  Cuneiform  Cartilages  or  Cartilages  of  Wrisberg  (cartilagines  cuneiformes) 
(Figs,  969  and  971). — The  cuneiform  cartilages  are  two  small,  elongated,  cartil- 
aginous bodies,  placed  one  on  each  side,  in  the  fold  of  mucous  membrane  which 
extends  from  the  apex  of  the  arytenoid  cartilage  to  the  side  of  the  epiglottis,  and  is 
called  the  aryteno-epiglottidean  fold  (plica  aryepiglottica)  (Fig.  971) ;  they  give 
rise  to  small  whitish  elevations  on  the  inner  surface  of  the  mucous  membrane, 
just  in  front  of  the  arytenoid  cartilages. 

The  Epiglottis  or  the  Cartilage  of  the  Epiglottis  (cartilago  epiglottica)  (Figs.  967, 969^, 
970,  971,  972,  and  975). — The  epiglottis  is  a  thin,  flexible  lamella  of  fibro-cartilage, 
of  a  yellowish  color,  shaped  like  a  leaf,  and  placed  behind  the  tongue  in  front  of 
the  superior  opening  of  the  larynx.  Its  free  extremity,  which  is  directed  upward, 
is  broad  and  rounded,  and  often  notched;  its  attached  part  (petiolus  epiglottidis) 
is  long,  narrow,  and  connected  to  the  receding  angle  between  the  alae  of  the 
thyroid  cartilage,  just  below  the  median  notch,  by  a  long,  narrow  ligamentous 
band,  the  thjrro-epiglottic  ligament  (ligamentum  thyreoepiglotticum)  (Fig.  972).  It 
is  also  connected  to  the  posterior  surface  of  the  body  of  the  hyoid  bone  by  an 
elastic  ligamentous  band,  the  hyo -epiglottic  ligament  (ligamentum  hyoepiglotticum) . 

Its  Anterior  or  Lingual  Surface  is  curved  forward,  toward  the  tongue,  and  cov- 
ered at  its  upper,  free  part  by  mucous  membrane,  which  is  reflected  on  to  the 
sides  and  base  of  the  organ,  forming  a  median  and  two  lateral  folds,  the  glcsso- 
epiglottidean  folds  (plicae  glossoepiglotticae)  (Fig.  971).  The  median  glosso-epiglot- 
tidean  fold  (plica  glossoepiglottica  mediana)  contains  the  elastic  glosso-epiglottic 
ligament  (ligamentum  glossoepiglotticum) .  Each  lateral  glosso-epiglottidean  fold 
(plica  glossoepiglottica  lateralis)  runs  from  the  front  and  side  of  the  base  of  the 
epiglottis  to  the  side  of  the  tongue.  The  depression  between  the  epiglottis  and 
the  base  of  the  tongue  on  each  side  of  the  median  fold  is  named  the  vallecula 
epiglottica.  The  lower  part  of  the  anterior  surface  of  the  epiglottis  lies  behind  the 
hyoid  bone,  the  thyro-hyoid  membrane,  and  upper  part  of  the  thyroid  cartilage, 
but  is  separated  from  these  structures  by  a  mass  of  fatty  tissue. 

Its  Posterior  or  Laryngeal  Surface  is  smooth,  concave  from  side  to  side,  concavo- 
convex  from  above  downward;  its  lower  part  projects  backward  as  an  elevation, 
the  tubercle  or  cushion  (tuberculum  epiglotticum)  (Fig.  970) ;  when  the  mucous  mem- 
brane is  removed,  the  surface  of  the  cartilage  is  seen  to  be  studded  with  a  number 
of  small  mucous  glands,  which  are  lodged  in  little  pits  upon  its  surface.  To  its 
sides  the  aryteno-epiglottidean  folds  (plicae  aryepiglotticae)  are  attached  (Fig.  971). 

Structure. — The  cuneiform  cartilages,  the  epiglottis,  and  the  apices  of  the 
arytenoids  are  composed  of  yellow  elastic  cartilage,  which  shows  little  tendency  to 
calcification;  on  the  other  hand,  the  thyroid,  cricoid,  and  the  greater  part  of  the 


1366  THE    ORGANS    OF    VOICE   AND    BESPIBATION 

arytenoids  consist  of  hyaline  cartilage,  and  become  more  or  less  ossified  as  age 
advances.  Ossification  commences  about  the  twenty-fifth  year  in  the  thyroid  car- 
tilage, somewhat  later  in  the  cricoid  and  arytenoids;  by  the  sixty-fifth  year  these 
cartilages  may  be  completely  converted  into  bone.  The  cornicula  laryngis  consist 
of  white  fibro-cartilage,  which  becomes  osseous  about  the  seventieth  year. 

Ligaments,  Joints,  and  Membranes  of  the  Larjmx. — The  ligaments  of  the  larynx 
are  extrinsic — i.  e.,  those  connecting  the  thyroid  cartilage  and  epiglottis  with  the 
hyoid  bone,  and  the  cricoid  cartilage  with  the  trachea;  and  intrinsic,  those  which 
connect  the  several  cartilages  of  the  larynx  to  each  other. 

The  ligaments  connecting  the  thyroid  cartilage  with  the  hyoid  bone  are  three 
in  number — the  thyro-hyoid  membrane,  and  the  two  lateral  thyro-hyoid  ligaments. 

The  Thyro-hyoid  or  Hyo-th3n:oid  Membrane  or  Ligament  {riiemhrana  hyothyreoidea) 
(Fig.  972)  is  a  broad,  fibro-elastic,  membranous  layer,  attached  below  to  the 
upper  border  of  the  thyroid  cartilage,  and  above  to  the  posterior  border  of  the 
body  and  greater  cornua  of  the  hyoid  bone,  passing  behind  the  postero-inferior 
surface  of  the  hyoid,  and  being  separated  from  this  surface  by  a  synovial  bursa 
(bursa  m.  sternohyoidei) ,  which  facilitates  the  upward  movement  of  the  larynx 
during  deglutition.  The  membrane  is  thicker  in  the  middle  line  than  at  either 
side.  This  thickening  is  due  to  elastic  fibres,  and  constitutes  the  middle  thjrro- 
hyoid  ligament  (ligamentum  hyothyreoideum  medium).  On  each  side  the  posterior 
extremity  of  the  membrane  is  thickened  by  elastic  fibres,  constituting  the  lateral 
thjnro-hyoid  ligament  {ligamentum  hyothyreoideum  laterale).  The  thyro-hyoid 
membrane  is  pierced  on  each  side  by  the  superior  laryngeal  vessels  and  the 
internal  laryngeal  nerve.  The  anterior  surface  of  the  thyro-hyoid  membrane  is 
in  relation  with  the  Thyro-hyoid,  Sterno-hyoid,  and  Omo-hyoid  muscles  and  with 
the  body  of  the  hyoid  bone.  The  two  lateral  ligaments  are  rounded,  elastic  cords, 
which  pass  between  the  superior  cornua  of  the  thyroid  cartilage  and  the  extremi- 
ties of  the  greater  cornua  of  the  hyoid  bone.  A  small  cartilaginous  nodule  {car- 
tilago  triticea),  sometimes  bony,  is  frequently  found  in  each. 

The  Membrana  Quadrangularis  is  an  elastic  membrane  containing  numerous 
glands.  The  fibres  of  the  membrane  run  in  part  downward  and  in  part  down- 
ward and  backward.  The  membrane  on  each  side  arises  in  front  and  above  at 
the  lateral  margin  of  the  cartilage  of  the  epiglottis,  below  at  the  posterior  surface 
of  the  angle  of  the  thyroid  cartilage  and  becomes  attached  behind  to  the  cornicula 
laryngis  and  to  the  inner  margins  of  the  arytenoid  cartilages.^  The  membranes 
converge  below  and  medianward.  The  ligamentum  ventriculare  is  the  superior 
end  of  the  membrane  (Spalteholz) .  The  fibres  constituting  the  ligamentum  ven- 
triculare are  given  off  at  the  thyroid  cartilage  above  the  ligamentum  vocale  and 
pass  horizontally  backward  to  the  medial  margin  of  the  fovea  triangularis  of  the 
arytenoid  cartilage.^  The  epiglottis  is  connected  to  the  tongue  by  the  three 
glosso-epiglottidean  folds  of  mucous  membrane,  which  may  also  be  considered 
as  extrinsic  ligaments  of  the  epiglottis. 

The  Glosso-epiglottidean  Folds  or  Ligaments  (plicae  epiglotticae)  (Fig.  971)  num- 
ber three.  The  middle  glosso-epiglottidean  fold  (plica  glossoepigloitica  mediana) 
passes  from  the  middle  of  the  anterior  free  surface  of  the  epiglottis  to  the  base 
of  the  tongue.  It  contains  the  glosso -epiglottic  ligament.  The  lateral  glosso- 
epiglottidean  or  the  phar3mgo-epiglottidean  fold  (plica  glossoepigloitica  lateralis) 
on  each  side  passes  from  the  side  of  the  epiglottis  to  the  side  of  the  base  of  the 
tongue  and  to  the  pharyngeal  wall.  On  each  side  between  the  median  and  lateral 
folds  is  a  depression,  the  vallecula  epiglottica. 

The  Hyo-epiglottic  Ligament  ((ligamentum  hyoepiglotticum)  is  an  elastic  band, 
which  extends  from  the  anterior  surface  of  the  epiglottis,  near  its  apex,  to  the 

I  l^*?*^  Atlas  of  Human  Anatomy.   By  Werner  Soalteholz.     Translated  and  edited  by  Lewellys  F.  Barker. 
bpalteholz  s  Hand  Atlas  of  Human  Anatomy.      Translated  and  edited  by  Lewellys  F.  Barker. 


THE   LARYNX 


1367 


upper  border  of  the  body  of  the  hyoid  bone.  The  epiglottis  is  attached  to  the 
thyroid  cartilage,  below  and  behind  the  superior  thyroid  notch,  by  the  strong 
and  elastic  thyro-epiglottic  ligament  (ligamentum  thyreoepiglotticum)  (Fig.  972). 
Between  the  epiglottis,  the  hyo-epiglottic  ligament  and  the  thyro-hyoid  membrane 
is  a  triangular  space  containing  fat  on  each  side  of  the  median  line. 

The  ligaments  connecting  the  thyroid  cartilage  to  the  cricoid  are  also  three  in 
number — the  crico-thjnroid  membrane  and  the  capsular  ligaments. 

The  Crico-th3n:oid  Membrane (conii^  elasticus)  (Figs.968  and  975)  is  an  elastic  mem- 
brane which  passes  radially  from  the  posterior  surface  of  the  angle  of  the  thyroid 
cartilage  to  the  upper  margin  of  the  arch  of  the  cricoid  cartilage  and  to  the  vocal 
processes  of  the  arytenoid  cartilages.  It  is  composed  mainly  of  yellow  elastic 
tissue.  It  consists  of  three  parts,  a  central  triangular  portion  and  two  lateral 
portions.  The  central  part  {ligamentum  cricothyreoideum  medium)  is  thick  and 
strong,  narrow  above  and  broadening  out  below.  It  connects  together  the  con- 
tiguous margins  of  the  thyroid  and  cricoid  cartilages.  It  is  convex,  concealed  on 
each  side  by  the  Crico-thyroid  muscle,  but  subcutaneous  in  the  middle  line;  it  is 
crossed  horizontally  by  a  small  anastomotic  arterial  arch,  formed  by  the  junction 
of  the  two  crico-thyroid  arteries.  The  lateral  portions  are  thinner  and  lie  close 
under  the  mucous  membrane  of  the  larynx.  They  extend  from  the  superior 
border  of  the  cricoid  cartilage  to  the  inferior  margin  of  the  true  vocal  cords  with 
which  they  are  continuous.  On  each  side  are  the  uppermost  fibres  from  the 
inferior  thyro-arytenoi^  ligament  (ligamentum  vocale). 

The  lateral  portions  are  lined  internally  by  mucous  membrane,  and  are  sepa- 
rated from  the  thyroid  cartilage  by  the  lateral  Crico-arytenoid  and  Thyro-aryte- 
noid  muscles.  This  membrane 
and  the  muscles  just  men- 
tioned reduce  greatly  the  inte- 
rior of  the  larynx.  The  crico- 
thyroid membrane  with  the 
membrana  quadrangularis  con- 
stitute the  membrana  elastica 
laryngis. 

The  Crico-th37roid  Articulation 
(articulatio  cricothyreoidea)  (Fig. 
968) ,  on  each  side  of  the  inferior 
cornu  of  the  thyroid,  with  the 
cricoid  cartilage  on  each  side. 
A  loose  synovial  membrane  (cap- 
sula  articularis  cricothyreoidea) 
encloses  the  articulation. 

The  synovial  capsule  is 
strengthened  by  the  ligamenta 
ceratocricoidea,which  pass  from 
the  lesser  cornu  of  the  thyroid 
to  the  lamina  of  the  cricoid 
cartilage. 

The  Crico-arytenoid  Articula- 
tion    (articulatio      cricoarytae- 

noidea)  (Fig.  969)  on  each  side  is  between  the  articular  surface  of  the  arytenoid 
cartilage  and  the  arytenoid  articular  surface  of  the  cricoid  cartilage. 

The  ligaments  connecting  the  arytenoid  cartilages  to  the  cricoid  are  on  each 
side  a  capsular  ligament  (capsula  articularis  cricoarytaenoidea)  and  a  posterior 
crico-arytenoid  ligament  (ligamentum  cricoarytaenoideum  posterius).  The  capsular 
ligaments  are  thin   and  loose  capsules  attached  to  the  margin  of  the  articular 


ARYTENO- 
EPIGLOTTIDEUS 


CRIC 
THYREOIDEI 


LARYNGEAL 
SACCULE 


NFERIOR 
VOCAL   CORD 


Fig.  970. —  Coronal  section  of  larynx,  rear  view  of  front  half. 
(Testut.) 


1368  THE    ORGANS   OF    VOICE  AND    BESPIBATION 

surfaces ;  they  are  lined  internally  by  synovial  membrane.  The  posterior  crico- 
arytenoid ligaments  extend  from  the  cricoid  to  the  inner  and  back  part  of  the  base 
of  the  arytenoid  cartilage. 

The  Orico-tracheal  Ligament  (ligamentum  cricotracheale)  connects  the  cricoid 
cartilage  with  the  first  ring  of  the  trachea.  It  resembles  the  fibrous  membrane 
which  connects  the  cartilaginous  rings  of  the  trachea  to  each  side. 

There  is  on  each  side  an  articulation  between  the  arytenoid  cartilage  and  the 
cartilage  of  Santorini  {synchondrosis  arycorniculala).  The  cartilage  of  Santorini  is 
somewhat  movable  and  is  fixefl  to  the  arytenoid  by  lax  connective  tissue.  From 
each  cartilage  of  Santorini  a  band  of  connective  tissue  runs  down  to  the  lamina 
of  the  cricoid  cartilage  and  to  the  pharyngeal  mucous  membrane.  Beneath  the 
arytenoid  muscles  the  ligaments  from  the  two  sides  join  and  pass  down  together. 
Thus  is  formed  a  Y-shaped  ligament  called  the  ligamentum  comiculopharyngeum. 
The  portion  between  the  cricoid  cartilage  and  the  mucous  membrane  of  the 
pharynx  is  sometimes  called  the  ligamentum  cricopharjmgeum. 

Interior  of  the  Larynx  (Figs.  970,  971,  and  972).— The  cavity  of  the  larynx 
(cavum  laryngis)  extends  from  the  superior  aperture  of  the  larynx  to  the  lower 
border  of  the  cricoid  cartilage.  It  is  divided  into  two  parts  by  the  projection 
inward  of  the  true  vocal  cords,  between  which  is  a  narrow  triangular  fissure  or 
chink,  the  rima  glottidis.  It  is  further  subdivided  by  the  false  vocal  cords.  So 
we  consider  the  larynx  as  divided  into  a  portion  above  the  false  cords,  a  por- 
tion between  the  false  and  true  vocal  cords,  and  a  portion  below  the  true  cords. 
The  entrance  of  the  first  compartment  is  the  superior  aperture  of  the  larynx. 

The  Superior  Aperture  of  the  Larjmx  {aditus  laryngis). — The  superior  aperture 
of  the  larynx  (Figs.  970  and  971)  is  a  triangular  or  cordiform  opening,  wide  in  front, 
narrow  behind,  and  sloping  obliquely  downward  and  backward.  It  is  bounded, 
in  front,  by  the  epiglottis;  behind,  by  the  apices  of  the  arytenoid  cartilages  and 
the  cornicula  laryngis ;  and  laterally,  by  a  fold  of  mucous  membrane,  enclosing 
ligamentous  and  muscular  fibres,  stretched  between  the  sides  of  the  epiglottis 
and  the  apices  of  the  arytenoid  cartilages;  these  are  the  aryteno-epiglottidean 
folds  (Figs.  971  and  972),  on  the  margins  of  which  the  cuneiform  cartilages  form 
more  or  less  distinct  whitish  prominences. 

The  small  gap  between  the  cartilages  of  Santorini  is  called  the  incisura  inter- 
arytaenoidea.  On  the  pharynx,  on  either  side  of  the  posterior  portion  of  the  superior 
aperture  of  the  larynx,  is  a  recess,  called  the  sinus  pyriformis. 

Upper  Compartment  or  Vestibule  of  the  Laryngeal  Ca,witj(vestibulum  laryngis)  (Figs. 
970  and  972) . — The  vestibule  is  the  portion  between  the  superior  opening  and  the 
false  vocal  cords.  It  is  much  narrower  below  than  above.  It  is  bounded  anteriorly 
by  the  mucous  membrane-covered  epiglottis.  The  lower  part  of  the  epiglottis 
exhibits  a  prominence  called  the  cushion  or  tubercle  {tvberculum  epiglotticum)  (Fig. 
970) .  The  lateral  wall  of  the  vestibule  on  each  side  is  the  aryteno-epiglottidean  fold 
(plica  aryepiglottica)  (Fig.  972),  which  extends  from  the  summit  of  the  arytenoid 
cartilage  forward,  upward,  and  outward  to  the  margin  of  the  epiglottis,  and  which 
contains  fibres  of  the  Thyro-epiglottideus  and  Arytenoideus  muscles  (muscidus 
arytaenoepiglottidean).  Near  the  posterior  end  of  the  fold  are  two  trivial  elevations : 
the  anterior  elevation  is  caused  by  the  prominence  of  the  cuneiform  cartilage,  and 
is  called  the  cuneiform  tubercle  of  Wrisberg  (tuberculum  cuneiforme  [Wrisbergi]) ;  the 
posterior  elevation  is  caused  by  the  anterior  margin  of  the  arytenoid  cartilage  and 
the  cartilage  of  Santorini,  and  is  called  the  comical  tubercle  of  Santorini  {tuberculum 
corniculatum  [Santorini]).  Between  these  elevations  is  a  groove,  the  filtrum  ven- 
triculi  of  Merkel,  which  passes  into  the  space  between  the  false  and  true  vocal  cords. 
The  anterior  elevation  passes  into  the  false  vocal  cord,  the  posterior  elevation 
into  the  true  vocal  cord.  The  posterior  portion  of  the  laryngeal  vestibule  is  the 
narrow  space  between  the  upper  portions  of  the  arytenoid  cartilages. 


THE   LARYNX 


1369 


The  Middle  Compaxtment  of  the  Larynx  (Figs.  970  and  972) . — This  lies  between  the 
false  vocal  cords  above  and  the  true  vocal  cords  below.  It  is  the  smallest  of  the  laryn- 
geal compartments.  It  opens  into  the  vestibule  by  the  way  of  the  gap  between  the 
false  vocal  cords,  which  is  called  the  false  glottis ;  it  opens  into  the  lower  compart- 
ment of  the  larynx  by  way  of  the  space  between  the  true  vocal  cords,  the  true  glottis. 

The  True  Glottis. — The  true  glottis  is  the  apparatus  for  producing  tone  and  is 
formed  by  the  true  vocal  cords. 

The  Chink  of  the  Glottis  {rima  glottidis)  (Figs.  970  and  971).— The  chink  of  the 
glottis  is  the  elongated  fissure  or  chink  between  the  inferior  or  true  vocal  cords  in 
front,  and  between  the  bases  and  vocal  processes  of  the  arytenoid  cartilages  behind. 
It  is  therefore  frequently  subdivided  into  an  anterior,  interligamentous  or  vocal  por- 
tion, the  glottis  vocalis  ('pars  intermemhranacea) ,  and  a  posterior,  intercartilaginous 
or  respiratory  portion,  the  glottis  respiratoria  {jpars  intercartilaginea).  Posteriorly  it  is 
limited  by  the  mucous  membrane  passing  between  the  arytenoid  cartilages.  The 
vocal  portion  averages  about  three-fifths  of  the  length  of  the  entire  aperture.  It 
is  the  narrowest  part  of  the  cavity  of  the  larynx,  and  its  level  corresponds  to  the 


APEX    OF   SUP.   HORN    OF 
THYROID    CARTILAGE 


LUM 
S 
El  FORM 
RTILAGE 
TENO-EPIGLOT- 

OIAN   FOLD 
PEX    OF  GREAT 
ORN    OF   HVOlO 


LATERAL   GLOSSO-  MIDDLE    GLOSSO- 

CPIGLOTTIDIAN   FOLD      EPIGLOTTIDIAN  FOLD 

Fig.  971. — Larynx,  viewed  from  above. 


(Testut.) 


bases  of  the  arytenoid  cartilages.  Its  length,  in  the  male,  measures  rather  less 
than  an  inch  (20  to  25  mm.);  in  the  female  it  is  shorter  by  5  or  6  mm.,  or  three 
lines.  The  width  and  shape  of  the  rima  glottidis  vary  with  the  movements  of  the 
vocal  cords  and  arytenoid  cartilages  during  respiration  and  phonation.  In  the 
condition  of  rest — i.  e.,  when  these  structures  are  uninfluenced  by  muscular  action, 
as  in  quiet  respiration,  the  glottis  vocalis  is  triangular,  with  its  apex  in  front  and 
its  base  behind,  the  latter  being  represented  by  a  line  about  8  mm.  long,  connect- 
ing the  anterior  extremities  of  the  vocal  processes,  while  the  inner  surfaces  of  the 
arytenoids  are  parallel  to  each  other,  and  hence  the  glottis  respiratoria  is  rectan- 
gular. During  extreme  adduction  of  the  cords,  as  in  the  emission  of  a  high  note, 
the  glottis  vocalis  is  reduced  to  a  linear  slit  by  the  apposition  of  the  cords,  while 
the  glottis  respiratoria  is  triangular,  its  apex  corresponding  to  the  anterior  extrem- 
ities of  the  vocal  processes  of  the  arytenoids,  which  are  approximated  by  the 
inward  rotation  of  the  cartilages.  Conversely  in  extreme  abduction  of  the  cords, 
as  in  forced  inspiration,  the  arytenoids  and  their  vocal  processes  are  rotated  out- 
ward, and  the  glottis  respiratoria  is  triangular  in  shape,  but  with  its  apex  directed 
backward.  In  this  condition  the  entire  glottis  is  somewhat  lozenge-shaped,  the 
sides  of  the  glottis  vocalis  diverging  from  before  backward,  those  of  the  glottis 


1370 


THE   ORGANS    OF    VOICE  AND    RESPIRATION 


respiratoria  diverging  from  behind  forward,  the  widest  part  of  the  aperture  corre- 
sponding with  the  attachment  of  the  cords  to  the  vocal  processes/ 

The  Superior  or  False  Vocal  Cords(p/?cae  ventriculares)  (Figs,  970, 971,  and  972),  so 
called  because  they  are  not  directly  concerned  in  the  production  of  the  voice.  Each 
is  a  thick  fold  of  mucous  membrane,  enclosing  a  narrow  band  of  fibrous  tissue,  the 
superior  thyro-ar3rtenoid  ligament  {ligamentum  ventriculare) ,  which  is  attached  in 
front  to  the  angle  of  the  thyroid  cartilage  immediately  below  the  attachment  of  the 
epiglottis,  and  behind  to  the  anterior  surface  of  the  arytenoid  cartilage.  The  lower 
border  of  this  ligament,  enclosed  in  mucous  membrane,  forms  a  free  crescentic 
margin,  which  constitutes  the  upper  boundary  of  the  ventricle  of  the  larynx.  The 
false  vocal  cord  contains  the  lower  part  of  the  membrana  quadrangularis  with 
the  ligamentum  ventriculare,  the  muscle  ventricularis  and  laryngeal  glands. 

The  Inferior  or  True  Vocal  Cords  (plicae  vocales)  (Figs.  970, 971,  972,  and  976),  so 
called  from  their  being  concerned  in  the  production  of  sound.     Each  is  a  strong 


\ 


VJ\\  EPIQl-OTTIO 
^^1  CARTILAGE 


•"HYRO-HYO 


THYRO-EPIGLOT 
TIC   LIGAMENT 


ARYTENO-EPI- 
GLOTTIDIAN  FOLD 


Fig.  972.— Sagittal  section  of  larynx,  right  half.     (Testut.) 

band,  the  inferior  thyro-arytenoid  ligament  (Zijamen/ww  voca/e) ,  covered  on  its  sur- 
face by  a  thin  layer  of  mucous  membrane.  Each  ligament  consists  of  a  band  of 
yellow  elastic  tissue,  attached  in  front  to  the  depression  between  the  alae  of  the 
thyroid  cartilage,  and  behind  to  the  anterior  angle  of  the  base  of  the  arytenoid. 
This  angle  is  called  the  vocal  process.  Its  lower  border  is  continuous  with  the 
thin  lateral  part  of  the  crico-thyroid  membrane.  Its  upper  bortler  forms  the  lower 
boundary  of  the  ventricle  of  the  larynx.  Externally,  the  Thyro-arytenoideus 
muscle  lies  parallel  with  it.  It  is  covered  internally  by  mucous  membrane,  which  is 
extremely  pale,  thin,  and  closely  adherent  to  its  surface.  The  upper  margin  of 
the  true  vocal  cord  is  covered  with  mucous  membrane,  and  is  the  lower  boundary 
of  the  ventricle  of  the  larynx.  Over  the  vocal  process  it  is  yellowish  {macula 
flava).  The  true  vocal  cord  contains  the  upper  part  of  the  crico-thyroid  mem- 
brane with  the  ligamentum  vocale  and  the  muscle  vocalis. 


^  On  the  shape  of  the  rima  glottidis,  in  the  various  conditions  of  breathing  and  speaking,  see  Czermak,  On  the 
Laryngoscope,  translated  for  the  New  Sydenham  Society. — Ed.  of  15th  English  edition. 


THE   LARYNX 


1371 


The  Ventricle  of  the  Larynx  or  Laryngeal  Sinus  (ventricidus  laryngis  [Morgagnii]) 
(Figs.  970  and  972)  is  an  oblong  fossa,  situated  between  the  superior  and  inferior 
vocal  cords  on  each  side,  and  extending  nearly  their  entire  length.  This  fossa  is 
bounded,  above,  by  the  free  crescentic  edge  of  the  superior  vocal  cord;  below,  by 
the  straight  margin  of  the  inferior  vocal  cord;  externally,  by  the  mucous  mem- 
brane covering  the  corresponding  Thyro-arytenoideus  muscle.  The  anterior  part 
of  the  ventricle  leads  up  by  a  narrow  opening  into  a  caecal  pouch  of  mucous 
membrane  of  variable  size,  called  the  lar3mgeal  pouch. 

The  Laryngeal  Saccule  or  Pouch  (appendix  ventriculi)  (Fig.  970),  or  laryngeal 
pouch,  is  a  membranous  sac,  placed  between  the  superior  vocal  cord  and  the  inner 
surface  of  the  thyroid  cartilage,  occasionally  extending  as  far  as  its  upper  border 
or  even  higher;  it  is  conical  in  form,  and  curved  slightly  backward.  On  the  surface 
of  its  mucous  membrane  are  the  openings  of  sixty  or  seventy  mucous  glands,  which 
are  lodged  in  the  submucous  areolar  tissue.  This  sac  is  enclosed  in  a  fibrous  cap- 
sule, continuous  below  with  the  superior  thyro-arytenoid  ligament;  its  laryngeal 
surface  is  covered  by  the  Aryteno-epiglottideus  inferior  muscle  (compressor  sacculi 
laryngis  of  Hilton) ;  while  its  exterior  is  covered  by  the  Thyro-arytenoideus  and 
Thyro-epiglottideus  muscles.  These  muscles  compress  the  sacculus  laryngis,  and 
discharge  the  secretion  it  contains  upon  the  vocal  cords,  the  surfaces  of  which  it  is 
intended  to  lubricate. 


STCRNO- 

THYREOtDEUS 


Fig.  973. — Muscles  of  larynx,  front  view.  The  sterno- 
thyroids and  right  thyro-hyoid  have  been  removed. 
(Testut.) 


Fig.  974. — Muscles  of  larynx,  from  behind. 

(Testut.) 


The  Lower  Compartment  of  the  Larynx  (Figs.  970  and  972) . — This  space  is  just 
beneath  the  true  vocal  cords  and  leads  into  the  trachea.  It  is  called  the  additus  glot- 
tidis  inferior.  Above,  on  cross-section,  it  is  oval;  below,  it  is  round.  It  is  bounded 
by  the  inner  surface  of  the  crico-thyroid  membrane  and  the  cricoid  cartilage. 

Muscles  of  the  Larynx  (muscuH  laryngis). — We  do  not  consider  all  muscles 
which  are  attached  to  laryngeal  cartilages  as  laryngeal  muscles.  Some  muscles 
so  attached  in  reality  belong  to  other  regions,  for  instance,  the  Inferior  constric- 
tor, the  Stylo-pharyngeus,  the  Sterno-thyroid,  the  Thyro-hyoid,  and  the  Palato- 
pharyngeus.     The  muscles  which  really  belong  to  the  larynx  are  called  intrinsic. 

Four  muscles  of  the  vocal  cords  and  rima  glottidis  are  paired  and  one  is  single. 


1372 


THE   ORGANS    OF    VOICE  AND   RESPIRATION 


The  paired  muscles  are  the  crico-thyroid,  the  posterior  crico-arytenoid,  the 
lateral  crico-arytenoid,  and  the  thyro-arytenoid.  The  single  muscle  is  the  aryte- 
noideus. 

A  Crico-thyroid  (w.  cricothyreoideus)  (Figs.  968,  970,  and  973)  is  placed  on  each 
side.  It  is  triangular  in  form,  and  situated  at  the  forepart  and  side  of  the  cricoid 
cartilage.  It  arises  from  the  front  and  lateral  part  of  the  cricoid  cartilage;  its 
fibres  diverge,  passing  obliquely  upward  and  outward  to  be  inserted  into  the  lower 
border  of  the  thyroid  cartilage  and  into  the  anterior  border  of  the  lower  cornu. 

The  inner  borders  of  these  two  muscles  are  separated  in  the  middle  line  by  a 
triangular  interval  occupied  by  the  central  part  of  the  crico-thyroid  membrane. 
The  Posterior  Crico-arytenoid  (m.  cricoarytaenoideus  posterior)  {Figs.  974,  975,  and 

976),  a  paired  muscle,  arises  from  the 
broad  depression  occupying  each  lat- 
eral half  of  the  posterior  surface  of  the 
cricoid  cartilage;  its  fibres  pass  up- 
ward and  outward,  converging  to  be 
inserted  into  the  outer  angle  (muscu- 


FiG.  975. 


-Muscles  of  larynx.     Side  view.     Right  ala 
of  thyroid  cartilage  removed. 


Fig.  976. 


-Interior  of  the  larynx,  seen  from  above. 
(Enlarged.) 


lar  process)  of  the  base  of  the  arytenoid  cartilage.    The  upper  fibres  are  nearly 
horizontal,  the  middle  oblique,  and  the  lower  almost  vertical.^ 

The  Ar3rtenoideus  (Figs.  972,  974,  975,  and  976)  is  a  single  muscle  filling  up  the 
posterior  concave  surface  of  the  arytenoid  cartilages.  It  arises  from  the  posterior 
surface  and  outer  border  of  one  arytenoid  cartilage,  and  is  inserted  into  the  corre- 
sponding parts  of  the  opposite  cartilage.  It  consists  of  three  planes  of  fibres,  two 
oblique  and  one  transverse.  The  oblique  fibres  (m.  arytaenoideus  obliquus),  the 
most  superficial,  form  two  fasciculi,  which  pass  from  the  base  of  one  cartilage  to 
the  apex  of  the  opposite  one.  The  transverse  fibres  (m.  arytaenoideus  transversus) , 
the  deepest  and  most  numerous,  pass  transversely  across  between  the  two  cartil- 
ages; hence  the  Arytenoideus  was  formerly  considered  as  three  muscles,  the  trans- 

'  Merkel,  of  Leipzig,  has  described  a  muscular  slip  which  occasionally  extends  between  the  outer  border  of  the 
posterior  surface  of  the  cricoid  cartilage  and  the  posterior  margin  of  the  inferior  cornu  of  the  thyroid  ;  this  he 
calls  the  "  Musculus  kerato-cricoideus."  It  is  not  found  in  every  larynx,  and  when  present  exists  usually  only 
on  one  side,  but  is  occasionally  found  on  both  .sides.  Sir  William  Turner  (Edinburgh  Medical  Journal,  February, 
1860)  states  that  it  is  found  in  about  one  case  in  five.  Its  action  is  to  fix  the  lower  horn  of  the  thyroid  cartilage 
backward  and  downward,  opposing  in  some  measure  the  part  of  the  Crico-thyroid  muscle,  which  is  connected  to 
the  anterior  margin  of  the  horn. — Ed.  of  15th  English  edition. 


THE  LARYNX  1373 

verse  and  the  two  oblique.  A  few  of  the  oblique  fibres  are  around  the  outer  margin 
of  the  cartilage,  and  blend  with  the  Thyro-arytenoid  in  the  aryteno-epiglottidean 
fold,  and  are  called  the  Aryteno-epiglottideus  muscles. 

In  order  to  expose  the  rest  of  the  muscles  of  the  larynx  the  thyroid  cartilage 
of  one  side  must  be  removed.  Begin  by  taking  away  the  crico-thyroid  muscle, 
then  dividing  the  lateral  thyro-hyoid  ligament;  disarticulate  the  inferior  cornu  of 
the  thyroid  cartilage  from  the  cricoid  cartilage,  then  carefully  cut  through  the 
thyroid  cartilage  a  short  distance  from  its  union  with  its  twin.  The  following 
muscles  will  then  be  exposed  after  a  little  cleaning:  the  Lateral  crico-thyroid, 
the  Thyro-arytenoid,  the  Thyro-epiglottideus. 

The  Lateral  Crico-arytenoid  {m.  cricoarytenoideus  lateralis)  (Figs.  975  and  976), 
a  paired  muscle,  is  smaller  than  the  preceding,  and  of  an  oblong  form.  It  arises 
from  the  upper  border  of  the  side  of  the  cricoid  cartilage,  and,  passing  obliquely 
upward  and  backward,  is  inserted  into  the  muscular  process  of  the  arytenoid 
cartilage  in  front  of  the  posterior  Crico-arytenoid  muscle. 

The  Thyro-arytenoid  (m.  thyroarytaenoideus) (Figs.  975  and  976),  a  paired  muscle, 
is  broad  and  flat.  It  lies  parallel  with  the  outer  side  of  the  true  vocal  cord.  It 
arises  in  front  from  the  lower  half  of  the  receding  angle  of  the  thyroid  cartilage, 
and  from  the  crico-thyroid  membrane.  Its  fibres  pass  backward  and  outward,  to 
be  inserted  into  the  base  and  anterior  surface  of  the  arytenoid  cartilage.  This 
muscle  consists  of  two  fasciculi.^  The  inner  or  inferior  fasciculus  (m.  vocalis),  the 
thicker,  is  prismatic  in  shape  and  is  inserted  into  the  vocal  process  of  the  aryte- 
noid cartilage,  and  into  the  adjacent  portion  of  its  anterior  surface;  it  lies  parallel 
with  the  true  vocal  cord,  to  which  it  is  adherent.  This  fasciculus  on  its  deeper 
surface  gives  off  some  fibres  which  are  attached  to  the  true  vocal  cord.  These 
are  called  the  ary-vocalis  (Ludwig).  The  outer  or  superior  fasciculus,  the  thinner, 
is  inserted  into  the  anterior  surface  and  outer  border  of  the  arytenoid  cartilage 
above  the  preceding  fibres;  it  lies  on  the  outer  side  of  the  sacculus  laryngis,  imme- 
diately beneath  the  mucous  membrane.^ 

The  muscles  of  the  epiglottis  are  the — 

Thyro-epiglottideus.  Aryteno-epiglottideus  superior. 

Aryteno-epiglottideus  inferior. 

The  Thyro-epiglottideus  (w.  thyroeyiglotticus)  is  a  delicate  fasciculus,  which 
arises  from  the  inner  surface  of  the  thyroid  cartilage,  just  external  to  the  origin  of 
the  Thyro-arytenoid  muscle,  of  which  it  is  sometimes  described  as  a  part,  and 
spreads  over  the  outer  surface  of  the  sacculus  laryngis;  some  of  its  fibres  are  lost 
in  the  aryteno-epiglottidean  fold,  while  the  others  are  continued  forward  to  the 
margin  of  the  epiglottis. 

The  Aryteno-epiglottideus  (Figs.  970  and  975)  is  properly  divided  into  two 
muscles,  a  superior  and  an  inferior. 

The  Ar3rteno-epiglottideus  superior  consists  of  a  few  delicate  muscular  fasciculi, 
which  arise  from  the  apex  of  the  arytenoid  cartilages,  and  become  lost  in  the 
fold  of  mucous  membrane,  the  aryteno-epiglottidean  fold,  extending  between  the 
arytenoid  cartilage  and  the  side  of  the  epiglottis. 

The  Aryteno-epiglottideus  inferior,  the  Compressor  sacculi  laryngis  of  Hilton,  arises 
from  the  arytenoid  cartilage,  just  above  the  attachment  of  the  superior  vocal  cord ; 
passing  forward  and  upward, it  spreads  out  upon  the  anterior  surface  of  the  epiglot- 
tis.   This  muscle  is  separated  from  the  preceding  by  an  indistinct  areolar  interval.^ 

'  Henle  describes  these  two  portions  as  separate  muscles,  under  the  names  of  the  External  and  Internal  thyro- 
arytenoid.— Ed.  of  15th  English  edition. 

*  Luschka  has  described  a  small  but  fairly  constant  muscle  as  the  Arytenoideus  rectus.  It  is  attached  below 
to  the  po.sterior  concave  surface  of  the  arytenf)id  cartilage,  beneath  the  Arytenoideus  muscle,  and,  passing 
upward,  emerges  at  the  upper  border  of  this  mu.scle,  and  is  inserted  into  the  posterior  surface  of  the  cartilage  of 
Santorini  (Anatomy,  by  Hyrtl,  p.  718).  — En.  of  15th  English  edition. 

^  MuscuLUS  TRiTiCEO-OLOSsus.  Bochdalek,  .Ir.  (Prager  Vierteljahrsschrift,  1866,  2d  part)  describes  a  muscle 
hitherto  entirely  overlooked,  except  by  Henle,  who  makes  a  brief  statement  in  his  Anatomy,  which  arises  from 
the  nodule  of  cartilage  (corpus  triticeum)  in  the  posterior  thyro-hyoid  ligament,  and  passes  forward  and  upward 
to  enter  the  tongue  along  with. the  Hyo-glos.sus  muscle.  He  met  with  this  muscle  eight  times  in  twenty-two  sub- 
jects.    It  occurred  in  both  sexes,  sometimes  on  both  sides,  at  others  on  one  only. — Ed.  of  15th  English  edition. 


1374  THE    ORGANS    OF   VOICE  AND    RESPIRATION 

Actions. — In  considering  the  action  of  the  muscles  of  the  larynx,  they  may 
be  conveniently  divided  into  two  groups,  viz.:  1.  Those  which  open  and  close 
the  glottis.    2.  Those  which  regulate  the  degree  of  tension  of  the  vocal  cords. 

1.  The  muscles  which  open  the  glottis  are  the  two  Posterior  crico-arytenoids; 
and  those  which  close  it  are  the  Arytenoideus  and  the  two  Lateral  crico-arytenoids. 
2.  The  muscles  which  regulate  the  tension  of  the  vocal  cords  are  the  two  Crico- 
thyroids, which  tense  and  elongate  them,  and  the  two  Thyro-arytenoids,  which 
relax  and  shorten  them.  The  Thyro-epiglottideus  is  a  depressor  of  the  epiglottis, 
and  the  Aryteno-epiglottideus,  superior  and  inferior,  constrict  the  superior  aper- 
ture of  the  larynx. 

The  Posterior  crico-arytenoids  separate  the  chordae  vocales,  and  consequently  open  the  glottis, 
by  rotating  the  arytenoid  cartilages  outward  around  a  vertical  axis  passing  through  the  crico- 
arytenoid joints,  so  that  their  vocal  processes  and  the  vocal  cords  attached  to  them  become  widely 
separated. 

The  Lateral  crico-arytenoids  close  the  glottis  by  rotating  the  arytenoid  cartilages  inward  so 
as  to  approximate  their  vocal  processes. 

The  Arytenoideus  muscle  approximates  the  arytenoid  cartilages,  and  thus  closes  the  opening 
of  the  glottis,  especially  at  its  back  part. 

The  Crico-thyroid  muscles  produce  tension  and  elongation  of  the  vocal  cords.  This  is  eflfected 
as  follows:  the  thyroid  cartilage  is  fixed  by  its  extrinsic  muscles;  then  the  Crico-thyroid  muscles, 
when  they  act,  draw  upward  the  front  of  the  cricoid  cartilage,  and  so  depress  the  posterior  por- 
tion, which  carries  with  it  the  arytenoid  cartilages,  and  thus  elongate  the  vocal  cords. 

The  Thyro-arytenoid  muscles,  consisting  of  two  parts  having  different  attachments  and 
different  directions,  are  rather  complicated  as  regards  their  action.  Their  main  use  is  to  draw 
the  arytenoid  cartilages  forward  toward  the  thyroid,  and  thus  shorten  and  relax  the  vocal  cords. 
But,  owing  to  the  connection  of  the  inner  portion  with  the  vocal  cord,  this  part,  if  acting  sepa- 
rately, is  supposed  to  modify  its  elasticity  and  tension,  and  the  outer  portion,  being  inserted 
into  the  outer  part  of  the  anterior  surface  of  the  arytenoid  cartilage,  may  rotate  it  inward,  and 
thus  narrow  the  rima  glottidis  by  bringing  the  two  cords  together. 

The  Thyro-epiglottidei  may  depress  the  epiglottis;  they  assist  in  compressing  the  sacculi 
laryngis.  The  Aryteno-epiglottideus  superior  constricts  the  superior  aperture  of  the  larynx, 
when  it  is  drawn  upward,  during  deglutition.  The  aryteno-epiglottideus  inferior,  together  with, 
some  fibres  of  the  Thyro-arytenoidei,  compress  the  sacculus  laryngis. 

The  Mucous  Membrane  of  the  Laxynx  is  continuous  above  with  that  lining  the 
mouth  and  pharynx,  and  it  is  prolonged  through  the  trachea  and  bronchi  into  the 
lungs.  It  lines  the  posterior  surface  and  the  anterior  part  of  the  upper  surface  of 
the  epiglottis,  to  which  it  is  closely  adherent.  In  the  rest  of  the  larynx,  above  the 
true  vocal  cords,  it  is  lax  and  rests  upon  a  considerable  submucous  layer.  The 
mucous  membrane,  with  the  submucous  coat,  ligamentous  and  muscular  fibres,, 
forms  the  aryteno-epiglottidean  folds,  which  folds  are  the  lateral  boundaries  of  the 
superior  aperture  of  the  larynx.  It  lines  the  whole  of  the  cavity  of  the  larynx; 
forms  by  its  reduplication  the  chief  part  of  the  superior  or  false  vocal  cord ;  and, 
from  the  ventricle,  is  continued  into  the  sacculus  laryngis.  It  is  then  reflected 
over  the  true  vocal  cords,  where  it  is  thin  and  very  intimately  adherent;  covers 
the  inner  surface  of  the  crico-thyroid  membrane  and  cricoid  cartilage;  and  is 
ultimately  continuous  with  the  lining  membrane  of  the  trachea.  The  forepart  of 
the  anterior  surface  and  the  upper  half  of  the  posterior  surface  of  the  epiglottis, 
the  upper  part  of  the  aryteno-epiglottidean  folds,  and  the  true  vocal  cords  are 
covered  by  stratified  squamous  epithelium;  the  rest  of  the  laryngeal  mucous 
membrane  is  covered  by  columnar  ciliated  cells. 

The  mucous  membrane  above  the  rima  glottidis  is  extremely  sensitive,  and 
during  life  the  lightest  touch  of  a  foreign  body  produces  cough. 

Glands. — The  mucous  membrane  of  the  larynx  is  furnished  with  numerous 
muciparous  glands,  the  orifices  of  which  are  found  in  nearly  every  part;  they 
are  very  numerous  upon  the  epiglottis,  being  lodged  in  little  pits  in  its  substance; 
they  are  also  found  in  large  numbers  along  the  posterior  margin  of  the  aryteno- 
epiglottidean  fold,  in  front  of  the  arytenoid  cartilages,  where  they  are  termed  the 


THE  LARYNX 


1375 


arjrtenoid  glands.    They  exist  also  in  large  numbers  upon  the  inner  surface  of  the 
sacculus  laryngis.    None  are  found  on  the  surface  of  the  true  vocal  cords. 

Vessels  and  Nerves. — The  arteries  of  the  larjmx  (Fig.  977)  are  the  larj^ngeal 
branches  derived  from  the  superior  and  inferior  thyroid.  The  superior  laryngeal  artery 
from  the  superior  th3a"oid  courses  along  by  the  internal  laryngeal  nerve;  the  inferior 
laryngeal  artery  from  the  inferior  thyroid  courses  along  with  the  recurrent  laryngeal 
nerve.  The  veins  accompany  the  arteries;  those  accompanying  the  superior  laryn- 
geal artery  join  the  superior  thyroid  vein  which  opens  into  the  internal  jugular 
vein;  while  those  accompanying  the  inferior  laryngeal  artery  join  the  inferior 
thyroid  vein  which  opens  into  the  innominate  vein.  The  laryngeal  lymphatics  arise 
from  a  network  in  the  mucous  membrane.  This  network  is  divisible  into  two 
portions,  a  superior  and  an  inferior,  which  are  to  be  regarded  as  almost  inde- 
pendent areas.  The  superior  region  includes  all  of  the  "laryngeal  mucous 
membrane  above  the  glottis,  epiglottis,  aryteno-epiglottidean  folds,  interarytenoid 
region,  and  superior  vocal  cords."^     The  inferior  area  is  the  laryngeal  mucous 

Superior 

thyroid 

artery. 


Superior 

—laryngeal 

artery. 


Fig.  977. — The  origin  and  distribution  of  the  arteriey  of  the  larynx.     (Luschka.) 

membrane  below  the  glottis.  The  lymphatics  of  one-half  of  the  larynx  do  uut 
communicate  with  those  of  the  other  half  in  the  median  line  in  front,  but  do 
in  the  median  iine  behind.  The  eiferent  vessels  from  the  superior  network 
accompany  the  superior  laryngeal  artery,  pierce  the  thyro-hyoid  membrane, 
and  divide  into  three  sets.  One  or  two  lymphatic  vessels  pass  upward  and 
terminate  in  a  gland  slightly  below  the  posterior  belly  of  the  Digastric  muscle. 
A  group  of  vessels  passes  horizontally  outward  to  terminate  in  the  glands 
situated  on  the  internal  jugular  vein  on  a  level  with  the  bifurcation  of  the 
common  carotid  artery.  Another  group  descends  and  empties  into  the  internal 
jugular  group  of  glands  at  a  lower  level  than  the  horizontal  vessels.  Trunks  from 
the  inferior  network  of  the  laryngeal  mucous  membrane  form  two  groups.  The 
anterior  or  supracricoid  group  consists  of  three  trunks  which  pass  through  the  crico- 
thyroid membrane,  to  empty  into  the  pre-laryngeal  glands,  the  pre-tracheal  gland, 
and  the  middle  and  lower 'deep  cervical  glands.^    The  posterior  group  consists 


1  Philio  R.  W.  De  Santi  in  the  Lancet,  June  18,  1904. 


2  Poirier,  Cun<So,  Most,  De  Santi. 


1376  THE    ORGANS    OF   VOICE  AND   BESPIBATION 

of  "from  three  to  five  trunks,  which  pass  over  the  crico-tracheal  fascia  at  the 
junction  of  the  lateral  and  posterior  aspects  of  the  trachea,"^  and  terminate  in 
the  recurrent  glands  about  the  recurrent  laryngeal  nerve.  The  nerves  are  derived 
from  the  internal  and  external  laryngeal  branches  of  the  superior  laryngeal  nerve, 
from  the  inferior  or  recurrent  lar3mgeal,  and  from  the  sympathetic.  The  internal 
larvngeal  nerve  is  almost  entirely  sensory,  but  some  motor  filaments  are  said  to  be 
carried  by  it  to  the  Arytenoideus  muscle.  It  divides  into  a  branch  which  is  dis- 
tributed to  both  surfaces  of  the  epiglottis,  a  second  to  the  aryteno-epiglottidean 
folds,  and  a  third,  the  largest,  which  supplies  the  mucous  membrane  over  the 
back  of  the  larynx  and  communicates  with  the  recurrent  laryngeal.  The  external 
laryngeal  nerve  supplies  the  Crico-thyroid  muscle.  The  recurrent  laryngeal 
passes  upward  under  the  lower  border  of  the  Inferior  constrictor,  and  enters  the 
larynx  between  the  cricoid  and  thyroid  cartilages.  It  supplies  all  the  muscles  of 
the  larynx  except  the  Crico-thyroid  and  part  of  the  Arytenoideus.  The  sensory 
branches  of  the  laryngeal  nerves  form  subepithelial  plexuses,  from  which  fibres 
ascend  to  end  between  the  cells  covering  the  mucous  membrane. 

Over  the  posterior  surface  of  the  epiglottis,  in  the  aryteno-epiglottidean  folds, 
and  less  regularly  in  some  other  parts,  taste-buds,  similar  to  those  in  the  tongue, 
are  found. 

THE  TRACHEA  AND  BRONCHI  (Fig.  978). 

The  trachea  or  windpipe  is  a  cartilaginous  membranous,  elastic,  cylindrical 
tube,  flattened  posteriorly,  which  extends  from  the  lower  part  of  the  larynx,  on  a 
level  with  the  sixth  cervical  vertebra,  to  opposite  the  body  of  the  fourth,  or  some- 
times of  the  fifth,  dorsal  vertebra,  where  it  divides  (bifurcatio  tracheae)  into  two 
bronchi,  one  for  each  lung.  This  point  is  at  the  level  of  the  spine  of  the  fourth 
dorsal  vertebra.  The  trachea  is  found  to  be  more  deeply  placed  the  lower  down 
it  is  examined.  It  is  in  the  median  line,  deviating  below  a  very  little  to  the  right 
side.  When  a  cross-section  is  made  of  the  trachea  it  is  seen  that  its  anterior  and 
lateral  walls  are  rounded,  but  its  posterior  wall  is  flat  (Fig.  982).  The  largest 
diameter  of  the  tube  is  the  middle;  from  this  point  the  diameter  diminishes  toward 
the  bronchi  and  toward  the  laryngeal  end.  The  trachea  measures  about  four 
inches  and  a  half  in  length;  its  diameter  from  side  to  side  is  from  three-quarters 
of  an  inch  to  an  inch,  being  always  greater  in  the  male  than  in  the  female. 

Relations. — The  anterior  surface  of  the  trachea  is  convex,  and  covered  in  the 
neck,  from  above  downward,  by  the  isthmus  of  the  thyroid  gland,  the  inferior 
thyroid  veins,  the  arteria  thyroidea  ima  (when  that  vessel  exists),  the  Sterno-hyoid 
and  Sterno-thyroid  muscles,  the  cervical  fascia,  and  more  superficially,  by  the 
anastomosing  branches  between  the  anterior  jugular  veins:  in  the  thorax  it  is 
covered  from  before  backward  by  the  first  piece  of  the  sternum,  the  remains  of  the 
thymus  gland,  the  left  innominate  vein,  the  arch  of  the  aorta,  the  innominate  and 
left  common  carotid  arteries,  and  the  deep  cardiac  plexus.  Posteriorly,  it  is  in 
relation  with  the  oesophagus ;  laterally,  in  the  neck,  it  is  in  relation  with  the  com- 
mon carotid  arteries,  the  lateral  lobes  of  the  thyroid  gland,  the  inferior  thyroid 
arteries,  and  recurrent  laryngeal  nerves;  and,  in  the  thorax,  it  lies  in  the  upper 
part  of  the  interpleural  space,  that  is,  in  the  superior  mediastinum,  and  is  in  relation 
on  the  right  to  the  pleura  and  right  vagus,  and  near  the  root  of  the  neck  to  the 
innominate  artery;  on  its  left  side  are  the  recurrent  laryngeal  nerve,  the  aortic 
arch,  the  left  common  carotid  and  subclavian  arteries. 

The  Right  Bronchus  (bronchus  dexter). — The  unbranched  portion  of  the  right 
bronchus,  wider,  shorter,  and  more  vertical  in  direction  than  the  left,  is  about 
an  inch  in  length,  and  enters  the  hilum  of  the  right  lung  opposite  the  fifth  dorsal 

1  De  Santi,  in  the  Lancet,  June  18,  1904. 


THE    TRACHEA    AND   BRONCHI 


1377 


vertebra.  It  forms  an  angle  to  the  median  plane  of  about  29  degrees.  The  vena 
azygos  major  arches  over  it  from  l^ehind ;  and  the  right  pulmonary  artery  lies  below 
and  then  in  front  of  it.  About  three-quarters  of  an  inch  from  its  commencement 
it  gives  off  a  branch  to  the  upper  lobe  of  the  right  lung.  This  is  termed  the 
eparterial  branch  {ramus  hronchialis  eparterialis) ,  because  it  is  given  off  above 
the  right  pulmonary  artery.    The  bronchus  now  passes  below  the  artery,  and  is 


Superior^ 
Cornu.  ' 


Fig.  978.- 


-  Front  view  of  cartilages  of  larynx;  the  trachea  and  bronchi  (the  right  bronchus  is  not  shown  as 
steep  as  it  really  is. 


known  as  the  hyparterial   branch  {ramus   branchialis   hyparterialis) .     It  divides 
into  two  branches  for  the  middle  and  lower  lobs. 

If  a  transverse  section  of  the  trachea  is  made  a  short  distance  above  its  point 
of  bifurcation,  and  a  bird's-eye  view  taken  of  its  interior  (Fig.  982),  the  septum 
placed  at  the  bottom  of  the  trachea  and  separating  the  two  bronchi  will  be  seen 
to  occupy  the  left  of  the  median  line,  and  the  right  bronchus  appears  to  be  a 
more  direct  continuation  than  the  left,  so  that  any  solid  body  dropping  into  the 
trachea  would  naturally  be  directed  toward  the  right  bronchus.  This  tendency  is 
aided  by  the  larger  size  of  the  right  tube  as  compared  with  its  fellow.    This  fact 

87 


1378 


THE    ORGANS    OF   VOICE  AND    RESPIRATION 


serves  to  explain  why  a  foreign  body  in  the  trachea  more  frequently  falls  into  the 
right  bronchus  than  into  the  left/ 

The  Left  Bronchus  (bronchus  sinister). — The   left  bronchus   is  smaller  and 
longer  than  the  right,  being  nearly  two  inches  in  length.    It  forms  an  angle  to  the 

median  plane  of  about  46  degrees.  It  is  slightly 
curved  and  enters  the  root  of  the  left  lung,  oppo- 
site the  sixth  dorsal  vertebra,  about  an  inch 
lower  than  the  right  bronchus.  It  passes  l^e- 
neath  the  arch  of  the  aorta,  crosses  in  front  of 
the  oesophagus,  the  thoracic  duct,  and  the  de- 
scending aorta,  and  has  the  left  pulmonary  artery 
lying  at  first  above,  and  then  in  front  of  it.  The 
left  bronchus  has  no  branch  corresponding  to 
the  eparterial  branch  of  the  right  bronchus,  and 
therefore  it  has  been  supposed  by  some  that 
there  is  no  upper  lobe  to  the  left  lung,  but  that 
the  so-called  upper  lobe  corresponds  to  the 
middle  lobe  of  the  right  lung.  The  left  bron- 
chus does  have  an  hyparterial  branch. 

When  the  main  or  stem  bronchus  enters  the 
lung  on  each  side  it  appears  to  divide  into  nearly 
equal  branches  at  the  root  of  the  lung,  but  a 
somewhat  similar  arrangement  to  what  is  found 
in  many  animals  may  be  made  out  where  each 
main  bronchus  passes  downward  and  backward 
toward  the  extremity  of  the  lower  lobe,  and  ends 
near  the  posterior  surface  of  the  base  of  the  lung, 
a  portion  of  pulmonary  substance  which  is  be- 
tween the  Diaphragm  and  the  wall  of  the  chest. 
It  gives  off  four  branches,  or  lateral  bronchi 
{rami  hronchiales) ,  at  intervals  in  two  directions,  dorsally  and  ventrally,  and,  in 
addition,  accessory  branches,  which  arise  from  the  front  of  the  bronchus  and 
pass  mesially  and  dorsally  into  the  inferior  lobe.  In  the  right  bronchus  the 
first  ventral  branch  supplies  the  middle  lobe,  the  other  three  and  all  the  dorsal 
going  to  the  lower  lobe;  in  the  left  bronchus,  the  first  ventral  branch  sup- 
plies the  middle  lobe,  the  other  three  and  all  the  dorsal  going  to  the  lower 
lobe;  in  the  left  bronchus,  the  first  central  supplies  the  superior  lobe,  and  all  the 
others,  both  ventral  and  dorsal,  go  to  the  lower  lobe.  The  dorsal  and  ventral 
branches  divide  into  smaller  branches,  and  these  again  into  smaller  branches  or 
bronchioles  (Fig.  981).  Each  bronchiolus  divides  into  minute  branches  (bronchioli 
respiratorii)  (Fig.  981),  the  walls  of  which  show  numerous  areas  of  bulging  called 
alveoli  (Fig.  981).  From  the  bronchioli  respiratorii  come  the  terminal  branches 
of  the  bronchi.  These  terminal  branches  are  the  alveolar  ducts  (ductuli  alveolares), 
and  they  are  bulged  by  numerous  alveoli  (Fig.  981).  They  connect  by  openings 
at  their  termination  with  several  cavities  of  irregular  form,  which  are  called  atria. 
Each  atrium  is  connected  with  several  or  many  larger  cavities,  known  as  sacculi 
alveolares,  air-cells,  or  air-sacs  (infundihula).  The  entire  surface  of  the  air-sacs  is 
filled  with  small  cavities,  the  pulmonary  alveoli  (alveoli  pulmonis).  An  alveolar 
duct  with  its  branches  forms  a  pulmonary  lobule  (lobulv^  pulmonis)  (Fig.  980). 

Structure  of  the  Trachea. — The  trachea  is  composed  of  imperfect  cartilagin- 
ous rings,  fibrous  membrane,  muscular  fibres,  mucous  membrane,  and  glands. 

The  Cartilages. — The  cartilages  vary  from  sixteen  to  twenty  in  number;  each 
forms  an  imperfect  ring,  which  surrounds  about  two-thirds  of  the  cylinder  of  the 


Fio.  979.- 


-Internal  surface  of  the  bronchi. 
(Poirier  and  Charpy.) 


^  Reigel  asserts  that  the  entrance  of  a  foreizn  body  into  the  left  bronchus  is  bv  no  means  so  infrequent  as  ia 
generally  supposed.     See  also  Med.-Chir.  Transactions,  vol.  Ixxi.  p.  121. ^Ed.  oi  15th  English  edition. 


THE    TRACHEA    AND    BRONCHI 


1379 


trachea,  being  imperfect  behind,  where  the  tube  is  completed  by  fibrous  mem- 
brane. The  cartilages  are  placed  horizontally  above  each  other,  separated  by 
narrow  membranous  intervals.  They  measure  about  two  lines  in  depth,  and  half 
a  line  in  thickness.  Their  outer  surfaces  are  flattened,  but  internally  they  are 
convex,  from  being  thicker  in  the  middle  than  at  the  margins.  Two  or  more  of 
the  cartilages  often  unite,  partially  or  completely,  and  are  sometimes  bifurcated 
at  their  extremities.  They  are  highly  elastic,  but  sometimes  become  calcified  in 
advanced  life.    In  the  right  bronchus  the  cartilages  vary  in  number  from  six  to 

eight;  in  the  left,  from  nine  to  twelve.  They 
are  shorter  and  narrower  than  those  of  the 
trachea.  The  peculiar  cartilages  are  the  first 
and  the  last. 

The  First  Cartilage  is  broader  than  the  rest, 
and  sometimes  divided  at  one  end;  it  is  con- 
nected   by  fibrous  membrane  with  the  lower 


NTERLOBULAR 


ALVEOLI 
DUCT 


BRONCHIOLE 


RESPIRATORY 
BRONCHIOLE 


Fig.  980. — A  pulmonary  lobule.     (Poirier  and 

Charpy.) 


Fig.  981. — The  terminal  bronchial  tubes.    The  respiratory 
bronchiole  and  alveoli.    (Poirier  and  Charpy.) 


Right. 


border  of  the  cricoid  cartilage,  with  which  or  with  the  succeeding  cartilage  it  is 
sometimes  blended. 

The  Last  Cartilage  is  thick  and  broad  in  the  middle,  in  consequence  of  its  lower 
border  being  prolonged  into  a  triangular  hook-shaped  process  which  curves  down- 
ward and  backward  between  the  two  bronchi.    It  terminates  on  each  side  in  an 

imperfect  ring  which  encloses  the  com- 
mencement of  the  bronchi.  The  cartil- 
age above  the  last  is  somewhat  broader 
than  the  rest  at  its  centre. 

The  Fibrous  Membrane. — The  cartil- 
ages are  enclosed  in  an  elastic  fibrous 
membrane  which  forms  a  double  layer, 
one  layer,  the  thicker  of  the  two,  passing 
over  the  outer  surface  of  the  ring,  the 
other  over  the  inner  surface;  at  the 
upper  and  lower  margins  of  the  cartilages 
these  two  layers  blend  together  to  form  a 
single  membrane,  which  connects  the  rings  one  with  another.  They  are  thus,  as 
it  were,  embedded  in  the  membrane.  In  the  space  behind,  between  the  extremi- 
ties of  the  rings,  the  membrane  forms  a  single  distinct  layer. 

The  Muscular  Fibres. — The  muscular  fibres  are  disposed  in  two  layers,  longi- 
tudinal and  transverse 


Fig.  982. — Transverse  section  of  the  trachea,  just 
above  its  bifurcation,  with  a  bird's-eye  view  of  the 
interior. 


1380  THE    ORGANS   OF   VOICE   AND   BE8PIBATI0N 

The  Longitudinal  Fibres  are  the  most  external,  and  consist  merely  of  a  few  scat- 
tered longitudinal  bundles  of  fibres. 

The  Transverse  Fibres  constitute  the  Trachealis  muscle  of  Todd  and  Bowman.  The 
most  internal  form  a  thin  layer  which  extends  transversely  between  the  ends  of 
the  cartilages  and  the  intervals  between  them  at  the  posterior  part  of  the  trachea. 
The  muscular  fibres  are  of  the  unstriped  variety. 

The  Mucous  Membrane. — The  mucous  membrane  is  continuous  above  with  that 
of  the  larynx,  and  below  with  that  of  the  bronchi.  Microscopically,  it  consists  of 
areolar  and  lymphoid  tissue,  and  presents  a  well-marked  basement-membrane, 
supporting  a  layer  of  columnar,  ciliated  epithelium,  between  the  deeper  ends  of 
which  are  smaller  triangular  cells,  the  bases  of  which,  often  branched,  are  attached 
to  the  basement-membrane.  These  triangular  cells  are  mucus-secreting,  and  may 
be  seen  as  goblet-cells  or  chalice-cells  when  their  contents  have  been  discharged. 
In  the  deepest  part  of  the  mucous  membrane,  and  especially  between  the  mucous 
and  submucous  layers,  longitudinally  arranged  fibres  are  very  abundant  and  form 
a  distinct  layer. 

The  Tracheal  Glands  (glandulae  tracheales). — The  tracheal  glands  are  found  in 
great  abundance  at  the  posterior  part  of  the  trachea.  They  are  racemose  glands, 
and  consist  of  a  basement-membrane  lined  by  columnar  mucus-secreting  cells. 
They  are  situated  at  the  back  of  the  trachea,  outside  the  layer  of  muscular  tissue, 
between  it  and  the  outer  fibrous  layer.  Their  excretory  ducts  pierce  the  muscular 
and  inner  fibrous  layers,  and  pass  through  the  submucous  and  mucous  layers  to 
open  on  the  surface  of  the  mucous  membrane.  Some  glands  of  smaller  size  are 
also  found  at  the  sides  of  the  trachea,  between  the  layers  of  fibrous  tissue  con- 
necting the  rings,  and  others  immediately  beneath  the  mucous  coat.  The  secre- 
tion from  these  glands  serves  to  lubricate  the  inner  surface  of  the  trachea. 

Vessels  and  Nerves. — The  trachea  is  supplied  with  blood  by  the  inferior  thy- 
roid arteries.  The  veins  terminate  in  the  thyroid  venous  plexus.  The  nerves 
are  derived  from  the  pneumogastric  and  its  recurrent  branches  and  from  the 
sympathetic. 

Lymphatic  Glands. — The  trachea  is  surrounded  by  lax  connective  tissue  which 
contains  numerous  lymph  glands,  known  as  the  peritracheo-bronchial  glands.  They 
are  divided  into  four  groups  (Bar^ty).  A  group  to  the  right  side,  in  the  angle 
between  the  trachea  and  right  bronchus  and  ascending  to  the  region  of  the  sub- 
clavian vessels.  A  group  to  the  left  side,  in  the  angle  formed  by  the  trachea  and 
left  bronchus,  and  ascending  to  about  the  arch  of  the  aorta  and  the  recurrent 
laryngeal  nerve.  The  two  groups  just  described  are  usually  called  tracheal  glands 
(lymphoglandulae  tracheales).  A  third  group  is  in  the  angle  formed  by  the  bifur- 
cation of  the  trachea.  These  constitute  the  bronchial  glands  (lymphoglandulae 
bronchiales).  They  number  ten  or  twelve  (Cuneo).  A  fourth  group,  the  inter- 
bronchial  glands,  are  found  in  angles  of  bifurcation  of  the  larger  bronchi  in  the 
lung  parenchyma.  Very  early  in  life  the  peritracheo-bronchial  glands  become 
dark  or  even  black  from  the  deposition  of  carbonaceous  substance  brought  by 
the  leukocytes  from  the  bronchial  tubes.     This  condition  is  called  anthracosis. 

Surface  Form. — In  the  middle  line  of  the  neck  some  of  the  cartilages  of  the  larynx  can  readily 
be  distinguished.  In  the  receding  angle  below  the  chin  the  hyoid  bone  can  easily  be  made 
out,  and  a  finger's  breadth  below  it  is  the  pomum  Adami,  the  prominence  between  the  upper 
borders  of  the  two  alae  of  the  thyroid  cartilage.  About  an  inch  below  this,  in  the  middle  line,  is 
a  depression  corresponding  to  the  crico-thyroid  space,  in  which  the  operation  of  laryngotomy  is 
performed.  This  depression  is  bounded  below  by  a  prominent  arch,  the  anterior  ring  of  the 
cricoid  cartilage,  below  which  the  trachea  can  be  felt,  though  it  is  only  in  the  emaciated  adult 
that  the  separate  rings  can  be  distinguished.  The  lower  part  of  the  trachea  is  not  easily  made 
out,  for  as  it  descends  in  the  neck  it  takes  a  deeper  position,  and  is  farther  removed  from  the 
surface.  The  level  of  the  vocal  cords  corresponds  to  the  middle  of  the  anterior  margin  of  the 
thyroid  cartilage. 


I 


THE   TRACHEA    AND    BRONCHI  1381 

With  the  laryngoscope,  the  following  structures  can  be  seen:  The  base  of  the  tongue  and 
the  upper  surface  of  the  epiglottis,  with  the  glosso-epiglottic  ligaments;  the  superior  aperture  of 
the  larynx,  bounded  on  either  side  by  the  aryteno-epiglottidean  folds,  in  which  may  be  seen  two 
rounded  eminences  corresponding  to  the  cornicula  and  cuneiform  cartilages.  Beneath  these,  the 
true  and  false  vocal  cords,  with  the  ventricle  between  them.  Still  deeper,  the  cricoid  cartilage 
and  some  of  the  anterior  parts  of  the  rings  of  the  trachea,  and  sometimes,  in  deep  inspiration,  the 
bifurcation  of  the  trachea. 

Surgical  Anatomy. — Foreign  bodies  often  find  their  way  into  the  air-passages.  These  may 
be  either  large  soft  substances,  as  a  piece  of  meat,  which  may  become  lodged  in  the  upper  aper- 
ture of  the  larynx  or  in  the  rima  glottidis,  and  cause  speedy  suffocation  unless  rapidly  got  rid  of, 
or  unless  an  opening  is  made  into  the  air-passages  below,  so  as  to  enable  the  patient  to  breathe. 
Smaller  bodies,  frequently  of  a  hard  nature,  such  as  cherry-  or  plum-stones,  small  pieces  of  bone, 
buttons,  etc.,  may  find  their  way  through  the  rima  glottidis  into  the  trachea  or  bronchus,  or  may 
become  lodged  in  the  ventricle  of  the  larynx.  The  dangers  then  depend  not  so  much  upon  the 
mechanical  obstruction  as  upon  the  spasm  of  the  glottis  which  they  excite  from  reflex  irritation. 
When  lodged  in  the  ventricle  of  the  larynx,  they  may  jiroduce  very  few  symptoms  beyond  sudden 
loss  of  voice  or  alteration  in  the  voice  sounds,  immediately  following  the  inhalation  of  the  foreign 
body.  When,  however,  they  are  situated  in  the  trachea,  they  are  constantly  striking  against 
the  vocal  cords  during  expiratory  efforts,  and  produce  attacks  of  dyspntra  from  spasm  of  the 
glottis.  When  lodged  in  the  bronchus,  they  usually  become  fixed  there,  and,  occluding  the 
lumen  of  the  tube,  cause  a  loss  of  the  respiratory  murmur  on  the  affected  side,  which  is,  as  stated 
above,  more  often  the  right. 

Beneath  the  mucous  membrane  of  the  upper  part  of  the  air-passages  there  is  a  considerable 
amount  of  submucous  tissue  which  is  liable  to  become  much  swollen  from  effusion  in  inflamma- 
tory affections,  constituting  the  disease  known  as  "  oedema  of  the  glottis."  This  effusion  does 
not  extend  below  the  level  of  the  true  vocal  cords,  on  account  of  the  fact  that  the  mucous  mem- 
brane is  closely  adherent  to  these  structures,  without  the  intervention  of  any  submucous  tissue. 
So  that,  in  cases  of  this  disease  in  which  it  is  necessary  to  open  the  air-passages  to  prevent  suffo- 
cation, the  operation  of  laryngotomy  is  sufficient. 

Chronic  laryngitis  is  an  inflammation  of  the  mucous  glands  of  the  larynx,  which  occurs  in 
those  who  speak  much  in  public,  and  is  known  as  "  clergyvian's  sore  throat."  It  is  due  to  the 
dryness  induced  by  the  large  amount  of  cold  air  drawn  into  the  air-passages  during  prolonged 
speaking,  which  incites  increased  activity  in  the  mucous  glands  to  keep  the  parts  moist,  and 
this  eventually  terminates  in  inflammation  of  these  structures. 

Ulceration  of  the  larynx  may  occur  from  syphilis,  either  as  a  superficial  ulceration,  or  from 
the  softening  of  a  gumma;  from  tuberculous  disease  (laryngeal  phthisis),  or  from  malignant 
disease  (epithelioma). 

The  air-passages  may  be  opened  surgically  in  two  different  situations:  through  the  crico- 
thyroid membrane  (laryngotomy),  or  in  some  part  of  the  trachea  (tracheotomy);  and  to  these 
some  surgeons  have  added  a  third  method,  by  opening  the  crico-thyroid  membrane  and 
dividing  the  cartilage  with  the  upper  ring  of  the  trachea  (laryngo-tracheotomy). 

Laryngotomy  is  anatomically  the  more  simple  operation:  it  can  readily  be  performed,  and 
should  be  employed  in  those  cases  where  the  air-passages  require  opening  in  an  emergency  for 
the  relief  of  some  sudden  obstruction  to  respiration.  The  crico-thyroid  membrane  is  very 
superficial,  being  covered  only  in  the  middle  line  by  the  skin,  superficial  fascia,  and  the  deep 
fascia.  On  each  side  of  the  middle  line  it  is  also  covered  by  the  Sterno-hyoid  and  Sterno-thyroid 
muscles,  which  diverge  from  each  other  at  their  upper  parts,  leaving  a  slight  interval  between 
them.  On  these  muscles  rest  the  anterior  jugular  veins.  The  only  vessel  of  any  importance 
in  connection  with  this  operation  is  the  crico-thyroid  artery,  which  crosses  the  crico-thyroid 
membrane,  and  which  may  be  wounded,  but  rarely  gives  rise  to  any  trouble.  The  operation 
is  performed  thus:  the  head  being  thrown  back  and  steadied  by  an  assistant,  the  finger  is  passed 
over  the  front  of  the  neck,  and  the  crico-thyroid  depression  felt  for.  A  vertical  incision  is  then 
made  through  the  skin,  in  the  middle  line  over  this  spot,  and  carried  down  through  the  fascia 
until  the  crico-thyroid  membrane  is  exposed.  A  cross-cut  is  then  made  through  the  membrane, 
close  to  the  upper  border  of  the  cricoid  cartilage,  so  as  to  avoid,  if  possible,  the  crico-thyroid 
artery,  and  a  tracheotomy  tube  is  introduced.  It  has  been  recommended,  as  a  more  rapid  way 
of  performing  the  operation,  to  make  a  transverse  instead  of  a  longitudinal  cut,  through  both  the 
superficial  and  deep  structures,  and  thus  to  open  at  once  the  air-passages.  It  will  be  seen, however, 
that  in  opening  in  this  way  the  anterior  jugular  veins  would  be  in  danger  of  being  wounded. 

Tracheotomy  may  be  performed  either  above  or  below  the  isthmus  of  the  thyroid  body,  or 
this  structure  may  be  divided  and  the  trachea  opened  behind  it. 

The  isthmus  of  the  thyroid  gland  usually  crosses  the  second  and  third  rings  of  the  trachea; 
along  its  upper  border  is  frequently  to  be  found  a  large  transverse  communicating  branch  between 
the  superior  thyroid  veins;  and  the  isthmus  itself  is  covered  by  a  venous  plexus  formed  between 
the  thyroid  veins  of  the  opposite  sides.  Theoretically,  therefore,  it  is  advisable  to  avoid  dividing 
this  structure  in  opening  the  trachea. 


1382  THE    OBGANS    OF    VOICE  AND    RESPIRATION 

Above  the  isthmus  the  trachea  is  comparatively  superficial,  being  covered  by  the  skin,  super- 
ficial fascia,  deep  fascia,  Sterno-hyoid  and  Sterno-thyroid  muscles,  and  a  second  layer  of  the 
deep  fascia,  which,  attached  above  to  the  lower  border  of  the  hyoid  bone,  descends  beneath  the 
muscles  to  the  thyroid  body,  where  it  divides  into  two  layers  and  enclose  the  isthmus. 

Below  the  isthmus  the  trachea  lies  much  more  deeply,  and  is  covered  by  the  Sterno-hyoid 
and  the  Sterno-thyroid  muscles  and  a  quantity  of  loose  areolar  tissue  in  which  is  a  plexus  of 
veins,  some  of  them  of  large  size;  they  converge  to  two  trunks,  the  inferior  thyroid  veins,  which 
descend  on  either  side  of  the  median  line  on  the  front  of  the  trachea  and  open  into  the  innomi- 
nate veins.  In  the  infant  the  thymus  gland  ascends  a  variable  distance  along  the  front  of  the 
trachea,  and  opposite  the  episternal  notch  the  windpipe  is  crossed  by  the  left  innominate  vein. 
Occasionally,  also,  in  young  subjects,  the  innominate  artery  crosses  the  tube  obliquely  above 
the  level  of  the  sternum.  The  thyroidea  ima  artery,  when  that  vessel  exists,  passes  from  below 
upward  along  the  front  of  the  trachea. 

From  these  observations  it  must  be  evident  that  the  trachea  can  be  more  readily  opened 
above  than  below  the  isthmus  of  the  thyroid  body. 

Tracheotomy  above  the  isthmus  is  performed  thus;  the  patient  should,  if  possible,  be  laid 
on  his  back  on  a  table  in  a  good  light.  A  pillow  is  to  be  placed  under  the  shoulders  and  the 
head  thrown  back  and  steadied  by  an  assistant.  The  surgeon  standing  on  the  right  side  of  his 
patient  makes  an  incision  from  an  inch  and  a  half  to  two  inches  in  length  in  the  median  line  of 
the  neck  from  the  top  of  the  cricoid  cartilage.  The  incision  must  be  made  exactly  in  the  middle 
line,  so  as  to  avoid  the  anterior  jugular  veins,  and  after  the  superficial  structures  have  been 
divided  the  interval  between  the  Sterno-hyoid  muscles  must  be  found,  the  raphe  divided,  and 
the  muscles  drawn  apart.  The  lower  border  of  the  cricoid  cartilage  must  now  be  felt  for,  and 
the  upper  part  of  the  trachea  exposed  from  this  point  downward  in  the  middle  line.  Bose  has 
recommended  that  the  layer  of  fascia  in  front  of  the  trachea  should  be  divided  transversely  at 
the  level  of  the  lower  border  of  the  cricoid  cartilage,  and,  having  been  seized  with  a  pair  of 
forceps,  pressed  downward  with  the  handle  of  the  scalpel.  By  this  means  the  isthmus  of  the 
thyroid  gland  is  depressed,  and  is  saved  from  all  danger  of  being  wounded,  and  the  trachea  is 
cleanly  exposed.  The  trachea  is  now  transfixed  with  a  sharp  hook  and  drawn  forward  in  order 
to  steady  it,  and  is  then  opened  by  inserting  the  knife  into  it  and  dividing  the  two  or  three  upper 
rings  from  below  upward.  If  the  trachea  is  to  be  opened  below  the  isthmus,  the  incision  to 
expose  it  must  be  made  from  a  little  below  the  cricoid  cartilage  to  the  top  of  the  sternum. 

In  the  child  the  trachea  is  smaller,  more  deeply  placed,  and  more  movable  than  in  the  adult. 
In  fat  or  short-necked  people,  or  in  those  in  whom  the  muscles  of  the  jieck  are  prominently 
developed,  the  trachea  is  more  deeply  placed  than  in  others. 

A  portion  of  the  larynx  or  the  whole  of  it  has  been  removed  or  malignant  disease,  laryn- 
gectomy. 

Some  surgeons  do  preliminary  tracheotomy,  insert  a  Trendelenburg  cannula  to  prevent  the 
flow  of  blood  downward  into  the  lungs,  and  then  remove  the  larynx.  Other  surgeons  do  not 
employ  preliminary  tracheotomy. 

Perier's  method  of  laryngectomy  is  as  follows:  Make  a  vertical  incision  in  the  median  line 
from  the  level  of  the  hyoid  bone  to  below  the  level  of  the  cricoid  cartilage.  Make  a  transverse 
incision  at  each  end  of  the  vertical  incision.    This  makes  an  I-shaped  wound. 

Separate  the  soft  parts  from  the  larynx  and  upper  part  of  the  trachea,  and  separate  these  two 
structures  from  the  oesophagus.  After  arresting  bleeding,  divide  the  trachea  below  the  cricoid 
cartilage,  introduce  a  special  cinnula,  complete  the  removal  of  the  larynx,  suture  the  opening  of 
the  trachea  to  the  lower  r.ngleof  the  wound,  and  close  the  rest  of  the  wound  after  securing  drainage. 
In  malignant  disease  of  the  larynx  the  associated  lymphatic  glands  must  be  removed. 

Partial  laryngectomy,  according  to  Sir  F.  Semon,  is  the  removal  of  not  less  than  one  wing  of 
the  thyroid  cartilage.  Removal  of  a  lesser  piece  of  the  thyroid  or  of  a  bit  of  the  arytenoid  or 
cricoid  he  considers  with  the  operation  of  thyrotomy. 

THE  PLEURAE  (Figs.  983,  984,  985,  986,  987). 

Each  lung  is  invested,  upon  its  external  surface,  by  an  exceedingly  delicate 
serous  membrane,  the  pleura,  which  encloses  the  organ  as  far  as  its  root,  and  is 
then  reflected  upon  the  inner  surface  of  the  thorax.  The  portion  of  the  serous 
membrane  investing  the  surface  of  the  lung  and  dipping  into  the  fissures  between 
its  lobes  is  called  the  pulmonary  pleura  or  the  visceral  layer  of  the  pleura  (pleura 
pulmonalis)  (Fig.  983),  while  that  which  lines  the  inner  surface  of  the  chest  is  called 
the  parietal  layer  of  the  pleura  (pleura  parietalis)  (Fig.  983).  The  two  layers  join  at 
the  hilum  of  the  lung.    The  space  between  these  two  layers  is  called  the  cavity  of  the 


THE   PLEURAE 


1383 


pleura  (cavum  pleurae),  and  contains  a  very  little  clear  fluid.     It  must  be  borne 
in  mind  that  in  the  healthy  condition  the  two  layers  are  in  contact,  and  there 


TRfANGULARIS    STERNI 

Internal  Mammary  Vessels 


L^t  Phrenic  Nerve 


Pleura  Pulmonalis. 

Pleura  Costalis. 


^^'^-^--{'•''"mLS 


Diicf. 


Vena  Azygos  Major)  p^^^^^,.^^ 
eumnaas'tric  rtervex  > 


Pneumnaa. 


Fig.  983. — A  transverse  section  of  the  thorax,  showing  the  relative  position  of  the  viscera  and  the 

reflections  of  the  pleurae. 

is  no  real  cavity  until  the  lung  becomes  collapsed  and  separates  from  the  wall 
of  the  chest.  Each  pleura  is  therefore  a  shut  sac,  one  occupying  the  right,  the 
other  the  left  half  of  the  thorax,  and  they  are  perfectly  separate  from  each  other. 


SCALENUS 
MINIMUS 


SYMPATHETIC 
GANGLION 


Fig.  984. — The  dome  of  the  pleura.     (Poirier  and  Charpy.) 


The  two  pleurae  do  not  meet  in  the  middle  line  of  the  chest,  excepting  anteriorly 
opposite  the  second  and  third  pieces  of  the  sternum — a  space  being  left  between 


1384 


THE    ORGANS    OF    VOICE   AND    RESPIRATION 


them,  which  contains  all  the  viscera  of  the  thorax  excepting  the  lungs;  this  is  the 
mediastinum. 

Reflections  of  the  Pleurae  (Fig.  983).    The  Pleura  Pulmonalis  (Fig.  983).  -The 
pleura  pulmonalis  is  closely  attached  to  the  surface  of  the  lung  and  enters  into  the 


costapleural 
ligament' 


SCALENUS 
MINIMUS 
MUSCLE 


Fig.  985. — The  supports  of  the  pleural  dome.     The  oesophagus,  trachea  and  arteries  have  been  cut  and  pulled 
aside  to  show  the  pleural  reinforcements.     (Poirier  and  Charpy.) 


SYMPATHETIC 
GANGLION 


FIRST 

THORACIC 

NERVC 


LONGUS  COLLI 
MUSCLE 


SIBSON-S 
APONEUROSIS 


Fig.  987. — Section  of   the  wall   of  the 
Fig.  986. — The  supports  of  the  pleural  dome.     (Poirier  and  thorax,  showing  the  phrenico-costal  sinus. 

Charpy.)  (Poirier  and  Charpy.) 

depths  of  the  interlobar  fissures.    It  leaves  the  lung  surface  at  the  hilum,  covers  the 
root  of  the  lung  for  a  little  way  (Figs.  990  and  991),  and  then  passes  into  the  medi- 


THE   PLEURAE  1385 

astinal  pleura.  Between  the  hilum  and  the  mediastinal  pleura  there  is  a  thickened 
pleural  fold,  triangular  in  outline,  and  called  the  ligamentum  pulmonale  or  the 
ligamentum  latum  pulmonis  (Figs.  990  and  991).  It  is  formed  by  the  two  layers  of 
the  pulmonary  pleura  coming  in  contact  below  the  root  of  the  lung.  This  fold 
passes  from  the  lower  part  of  the  inner  pulmonary  surface  to  the  pericardium, 
and  the  lower  border  is  free  or  attached  to  the  diaphragmatic  pleura.  In  the 
right  lung  the  origin  of  this  ligament  is  in  front  of  the  groove  for  the  azygos 
vein;  in  the  left  lung  it  is  in  front  of  the  groove  for  the  thoracic  aorta. 

The  Pleura  Parietalis. — The  pleura  parietalis  is  a  continuous  membrane,  but 
for  convenience  is  divided  into  the  cervical  pleura,  costal  pleura,  mediastinal  pleura, 
and  diaphragmatic  pleura. 

The  Cervical  Pleura  or  Dome  of  the  Pleura  or  Cupola  (cupula  pleurae)  (Fig.  986)  is 
the  dome-shaped  roof  of  the  cavity  of  the  pleura.  It  projects  above  the  apex  of  the 
lung  to  the  neck  of  the  first  rib.  As  the  first  rib  is  placed  obliquely,  the  dome  of  the 
pleura  reaches  from  one  inch  to  two  inches  above  the  anterior  extremity  of  the  first 
rib,  and  from  one-half  an  inch  to  one  and  one-half  inches  above  the  clavicle.  On  the 
outer  side  of  the  cervical  pleura  are  the  Scalenus  anticus  and  medius  muscles.  Just 
below  the  apex,  on  the  anterior  and  inner  surface,  is  a  groove  for  the  subclavian 
artery,  which  vessel  passes  over  it  in  an  arch  (Fig.  984) .  A  little  below  the  groove 
for  the  subclavian  artery  is  a  broader  and  shallower  groove  for  the  innominate  and 
subclavian  veins.  Above  the  subclavian  artery  and  in  front  and  above  the  cervical 
pleura  are  the  cords  of  origin  of  the  brachial  plexus  and  the  inferior  cervical  gan- 
glion (Fig.  984) .  The  dome  is  strengthened  and  kept  in  place  by  Sibson's  aponeurosis 
or  the  vertebro-pleural  ligament  (Figs.  985  and  986) .  This  comes  from  a  little  piece 
of  muscle,  the  Scalenus  minimus  muscle,  which  originates  from  the  transverse  pro- 
cess of  the  seventh  cervical  vertebra,  broadens  and  becomes  aponeurotic  as  it  de- 
scends, and  is  inserted  into  the  inner  margin  of  the  first  rib  (Figs.  984  and  985).  It 
is  also  strengthened  by  the  costa-pleural  ligament  (Fig.  985),  from  the  inner  surface 
of  the  neck  of  the  first  rib  to  the  pleura,  and  by  fibrous  bands  which  pass  to  the 
tissue  about  the  subclavian  sheath,  trachea,  and  oesophagus  (Fig.  985). 

The  Costal  Pleura  (pleura  costalis)  (Fig.  983)  is  the  shortest  portion  of  the 
pleura  and  is  connected  to  the  parts  it  covers  by  the  endothoracic  fascia  {fascia 
endothoracica) ,  a  layer  of  connective  tissue  which  is  much  thicker  back  of  the  rib 
cartilages  than  it  is  posteriorly.  The  costal  pleura  covers  the  inner  surface  of  part 
of  the  sternum,  the  costal  cartilages,  ribs,  and  Intercostal  muscles,  and  the  sides 
of  the  bodies  of  the  dorsal  vertebrae.  This  layer  is  loosely  attached  except  as  it 
passes  from  the  heads  of  the  ribs  to  the  vertebrae,  where  it  is  firmly  adherent. 

The  Mediastinal  Pleura  (pleura  mediasiinalis)  (Fig.  985)  covers  the  septum  of  the 
mediastiinnn,  which  intervenes  between  the  two  pleural  cavities.  The  mediastinal 
pleura  extends  from  the  inner  surface  of  the  anterior  wall  of  the  thorax  to  the 
vertebrae.  It  is  continuous  in  front  and  back  with  the  costal  pleura  of  the  same 
side,  the  lines  of  junction  being  known,  respectively,  as  the  anterior  line  of  pleural 
reflection  and  the  posterior  line  of  pleural  reflection.  Below  the  mediastinal  pleura 
passes  into  the  diaphragmatic  pleura  of  the  same  side.  The  portion  of  the  medi- 
astinal pleura  which  fuses  with  the  parietal  layer  of  the  pericardium  is  called  the 
pericardial  pleura  (pleura  pericardiaca). 

Above  the  root  of  the  lung  the  mediastinal  pleura  passes  back  directly  to  the 
vertebrae.  "  In  this  region  the  left  mediastinal  pleura  is  applied  to  the  arch  of  the 
aorta  and  the  phrenic  and  vagus  nerves;  to  the  left  innominate  vein,  the  left 
superior  intercostal  vein,  and  the  left  common  carotid,  and  left  subclavian  arteries; 
to  the  oesophagus  and  the  thoracic  duct.  The  right  mediastinal  pleura,  on  the  other 
hand,  is  applied,  above  the  level  of  the  root  of  the  lung,  to  the  upper  part  of  the 
vena  cava  and  right  innominate  vein;  to  the  right  innominate  artery;  to  the  vena 
azygos  major,  as  it  hooks  forward  above  the  bronchus;  to  the  vagus  and  phrenic 


1386  THE    ORGANS    OF    VOICE  AND    BESPIBATION 

nerves;  and  to  the  right  side  of  the  trachea."^  Upon  the  pericardium  the  phrenic 
nerve  is  covered  by  the  pleura.  Back  of  the  root  of  the  lung  and  the  pulmonary 
ligament,  the  right  mediastinal  pleura  passes  back  to  the  vertebrae  to  the  left  of  the 
oesophagus;  the  left  mediastinal  pleura  passes  back  over  the  descending  aorta, 
and  just  above  the  Diaphragm  and  in  front  of  the  aorta  over  the  lower  end  of  the 
oesophagus. 

The  Diaphragmatic  Pleura  {pleura  diaphragmatica)  (Figs.  987  and  988)  covers 
the  upper  surface  of  the  Diaphragm  outside  of  the  base  of  the  pericardium,  but 
does  not  completely  cover  it;  for  it  does  not  pass  into  the  interval  between  the 
wall  of  the  thorax  and  Diaphragm,  and  before  this  point  is  reached  becomes 
continuous  with  the  costal  pleura. 

The  reflection  to  the  costal  pleura  begins  by  the  sternum,  at  the  lower  margin  of 
the  sixth  rib;  takes  place  at  the  junction  of  the  cartilage  of  the  rib  with  the  seventh 
rib;  posteriorly,  it  takes  place  at  the  lower  margin  of  the  twelfth  dorsal  vertebra. 

In  the  front  of  the  chest,  where  the  parietal  layer  of  the  pleura  is  reflected  back- 
ward to  the  pericardium,  the  two  pleural  sacs  are  in  contact  for  a  considerable 
extent.  At  the  upper  part  of  the  chest,  behind  the  manubrium,  they  are  not  in 
contact;  the  point  of  reflection  being  represented  by  a  line  drawn  from  the  sterno- 
clavicular articulation  to  the  mid-point  of  the  junction  of  the  manubrium  to  the 
body  of  the  sternum.  From  this  point  the  two  pleurae  descend  in  close  contact  to 
the  level  of  the  fourth  costal  cartilages  Here  the  line  of  reflection  on  the  right  side 
is  continued  downward  in  nearly  a  straight  line  to  the  lower  end  of  the  gladiolus  and 
then  turns  outward  behind  the  costal  cartilage  of  the  sixth  rib,  continuing  to 
descend  and  to  run  outward,  it  passes  behind  the  descending  part  of  the  seventh 
costal  cartilage,  and  mests  the  axillary  line  at  the  junction  of  the  eighth  rib  with 
the  cartilage.  The  line  of  reflection  continues  to  descend  till  it  reaches  its  lowest 
point  at  the  tenth  rib.  This  point  is  in  the  axillary  line,  while  on  the  left  side 
the  line  of  reflection  diverges  outward,  so  that  opposite  the  seventh  cartilage  it  is 
about  three-quarters  of  an  inch  from  the  left  border  of  the  sternum.  It,  how- 
ever, always  extends  considerably  farther  over  the  pericardium  than  the  corre- 
sponding lung.  From  this  joint  the  reflections  of  the  two  sides  are  practically 
the  same.  The  lower  limit  of  the  pleura  is  on  a  considerably  lower  level  than 
the  lower  limit  of  the  lung,  but  does  not  extend  to  the  attachment  of  the  Dia- 
phragm, so  that  below  the  line  of  reflection  of  the  pleura  from  the  chest  wall 
on  to  the  Diaphragm  the  latter  is  in  direct  contact  with  the  rib  cartilages  and 
the  Internal  intercostal  muscles.  In  ordinary  inspiration  the  thin  margin  of  the 
base  of  the  lung  does  not  extend  as  low  as  the  line  of  pleural  reflection,  with  the 
result  that  the  costal  and  diaphragmatic  pleura  are  here  in  contact,  the  narrow 
slit  between  the  two  being  termed  the  phrenico-costal  sinus  {sinus  phrenicocos- 
talis)  (Fig.  987) .  A  similar  condition  exists  behind  the  sternum  and  rib  cartilages, 
where  the  anterior  thin  margin  of  the  lung  falls  short  of  the  line  of  pleural  reflec- 
tion, and  where  the  slit-like  cavity  between  the  two  layers  of  pleura  forms  what  is 
sometimes  called  the  costo-mediastinal  sinus  {sinus  costomediastinalis). 

Along  the  line  of  reflection  of  the  diaphragmatic  pleura  a  dense  fascia  passes 
from  the  costal  cartilages  and  the  uncovered  portion  of  the  Diaphragm  to  the 
costal  pleura.  This  serves  to  hold  it  in  place.  It  is  named  by  Cunningham  the 
phrenico-pleural  fascia. 

The  inner  surface  of  the  pleura  is  smooth,  polished,  and  moistened  by  a  serous 
fluid;  its  outer  surface  is  intimately  adherent  to  the  surface  of  the  lung,  and  to  the 
pulmonary  vessels  as  they  emerge  from  the  pericardium;  it  is  also  adherent  to  the 
upper  surface  of  the  Diaphragm;  throughout  the  rest  of  its  extent  it  is  somewhat 
thicker,  and  may  be  separated  from  the  adjacent  parts  with  extreme  facility. 

1  Cunningham's  Text-book  of  Anatomv. 


THE  MEDIASTINAL   SPACE    OB   MEDIASTINUM  1387 

The  right  pleural  sac  is  shorter,  wider,  and  reaches  higher  in  the  neck  than 
the  left. 

Structure  of  the  Pleura. — The  pleura  is  composed  of  connective  tissue  con- 
taining much  elastic  tissue,  its  free  surface  being  covered  with  flat  endothelial  cells. 
It  is  fastened  to  adjacent  structures  by  subserous  areolar  tissue.  The  subserous 
tissue  of  the  visceral  pleura  is  continuous  with  the  areolar  tissue  of  the  lung. 

Vessels  and  Nerves. — The  arteries  of  the  pleura  are  derived  from  the  intercostal, 
the  internal  mammary,  the  musculo-phrenic,  thymic,  pericardiac,  and  bronchial. 
The  veins  correspond  to  the  arteries.  The  lymphatics  are  very  numerous  in  the 
pleura  antl  subserous  tissue.  Many  of  them  are  in  direct  communication  with  the 
pleural  cavity  by  stomata  between  the  endothelial  cells.  Stomata  are  absent  in 
the  mediastinal  pleura  and  over  the  ribs  (Dyskowsky).  The  lymphatics  of  the 
visceral  layer  empty  into  the  superficial  pulmonary  trunks;  the  lymphatics  of  the 
costal  pleura  empty  into  the  intercostal  trunks;  of  the  diaphragmatic  pleura,  into 
the  diaphragmatic  trunks;  of  the  mediastinal  pleura,  into  the  posterior  mediastinal 
glands.^  The  nerves  are  derived  from  the  phrenic  and  sjrmpathetic  (Luschka). 
KoUiker  states  that  nerves  accompany  the  ramification  of  the  bronchial  arteries 
in  the  pleural  pulmonalis. 

Surgical  Anatomy.^ — In  operations  upon  the  kidney  it  must  be  borne  in  mind  that  the  pleura 
may  sometimes  extend  below  the  level  of  the  last  rib,  and  may  therefore  be  opened  in  these 
operations,  especially  when  the  last  rib  is  removed,  in  order  to  give  more  room.  It  is  best  to 
keep  the  incision  at  least  one  inch  below  the  last  rib,  enlarging  the  wound  afterward,  when  the 
finger  can  be  introduced  as  a  guide. 

In  wounds  of  the  Diaphragm  the  pleura  may  be  injured.  In  operations  about  the  root  of 
the  neck,  especially  in  the  removal  of  glands  and  the  ligation  of  the  first  part  of  the  subclavian 
artery,  the  pleura  may  be  injured. 

Punctured  wounds  of  the  root  of  the  neck  are  apt  to  reach  the  pleura. 

Empyema  is  a  surgical  disease.  In  acute  empyema  the  treatment  is  drainage.  A  portion  of 
the  fifth  or  sixth  rib  in  the  axillary  line  is  removed  by  subperiosteal  resection,  the  pleura  is 
opened,  and  a  tube  is  introduced.  In  chronic  empyema  the  lung  is  contracted  and  adherent  and 
cannot  expand;  hence  drainage  will  not  cure  it.  It  is  necessary  to  perform  multiple  rib  resec- 
tion in  order  to  permit  the  chest-wall  to  sink  in  and  obliterate  the  cavity,  which,  as  the  lung 
is  unable  to  expand,  it  cannot  do.  The  necessary  operation  may  be  the  operation  of  Estlander, 
or  the  operation  of  Schede,  or  the  operation  of  Fowler  (page  166). 

If  a  large  wound  admits  suddenly  a  quantity  of  air  into  the  pleura,  dangerous  or  fatal  pneumo- 
thorax arises,  and  the  lung  collapses.  This  is  best  met  during  operations  by  using  the  Fell- 
O'Dwyer  apparatus  for  artificial  respiration  as  advised  by  Matas.'^  This  apparatus  keeps  the 
lung  expanded,  in  spite  of  the  entrance  of  air  into  the  pleural  sac.  In  surgical  pneumothorax 
the  lung  may  be  sutured  to  the  chest-wall,  so  as  to  block  the  opening.  Sometimes,  in  order  to 
arrest  dangerous  pulmonary  bleeding,  a  surgeon  dehberately  induces  pneumothorax,  in  hope  that 
the  collapse  of  the  lung  will  arrest  bleeding. 

When  an  abscess  of  the  liver  is  posterior  and  on  the  dorsum,  transpleural  hepatotomy  is  per- 
formed. A  portion  of  the  tenth  and  eleventh  ribs  below  the  angle  of  the  scapula  is  removed. 
As  a  rule,  the  pleura  is  found  obliterated  at  this  point.  If  it  is  opened,  it  is  at  once  sutured  or 
closed  with  gauze  packing.  The  exposed  Diaphragm  is  incised,  and,  as  it  is  usually  adherent 
to  the  liver,  the  abscess  cavity  is  entered.  If  it  is  not  adherent,  the  liver  is  exposed  and  the 
abscess  sought  for  with  an  aspirating-needle. 

THE  MEDIASTINAL  SPACE,  INTERPLEURAL  SPACE  OR 
MEDIASTINUM. 

The  mediastinum  is  the  space  left  in  the  median  portion  of  the  chest  by  the  non- 
approximation  of  the  two  pleurae.  It  extends  from  the  sternum  in  front  to  the 
spine  behind.  Within  it  are  the  contents  of  the  thorax  excepting  the  lungs.  The 
mediastinum  may  be  divided  for  purposes  of  description  into  two  parts — an 
upper  portion,  above  the  upper  level  of  the  pericardium,  which  is  named  the 

1  Poirier,  Cun<5o,  and  Delamare  on  the  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 
'^  Annals  of  Surgery,  April,  1899. 


1388 


THE    ORGANS    OF    VOICE   AND   RESPIRATION 


superior  mediastinum  (Struthers);  and  a  lower  portion,  below  the  upper  level  of 
the  pericardium.  This  lower  portion  is  again  subdivided  into  three — that  part 
which  contains  the  pericardium  and  its  contents,  the  middle  mediastinum;  that 
part  which  is  in  front  of  the  pericardium,  the  anterior  mediastinum;  and  that  part 
which  is  behind  the  pericardium,  the  posterior  mediastinum. 


Fig.  988. — The  posterior  mediastinum. 


The  Superior  Mediastinum  (Fig.  989)  .—The  superior  mediastinum  is  that  por- 
tion of  the  interpleural  space  which  lies  above  the  upper  level  of  the  pericardium, 
between  the  manubrium  sterni  in  front  and  the  upper  dorsal  vertebrae  behind.  It  is 
bounded  below  by  a  plane  passing  backward  from  the  junction  of  the  manubrium 
and  gladiolus  sterni  to  the  lower  part  of  the  body  of  the  fourth  dorsal  vertebra, 


THE   MEDIASTINAL    SPACE    OR   MEDIASTINUM 


1389 


and  laterally  by  the  lungs  and  pleurae.  It  contains  the  origins  of  the  Sterno-hyoid 
and  Stern o-thyroid  muscles  and  the  lower  ends  of  the  Longus  colli  muscles;  the 
arch  of  the  aorta;  the  innominate,  the  thoracic  portion  of  the  left  carotid  and  sub- 
clavian arteries;  the  upper  half  of  the  superior  vena  cava  and  the  innominate 
veins,  and  the  left  superior  intercostal  vein;  the  pneumogastric,  cardiac,  phrenic, 
and  left  recurrent  laryngeal  nerves;  the  trachea,  oesophagus,  and  thoracic  duct; 
the  remains  of  the  thymus  gland  and  some  lymphatic  glands. 

The  Anterior  Mediastinum  (Fig.  983). — The  anterior  mediastinum  is  bounded 
in  front  by  the  sternum,  on  each  side  by  the  pleura,  and  behind  by  the  pericardium. 
It  is  narrow  above,  but  widens  out  a  little  below,  and,  owing  to  the  oblique  course 
taken  by  the  left  pleura,  it  is  directed  from  above  obliquely  downward  and  to  the 
left.  Its  anterior  wall  is  formed  by  the  left  Triangularis  sterni  muscle  and  the 
fifth,  sixth,  and  seventh  left  costal  cartilages.  It  contains  a  quantity  of  loose 
areolar  tissue,  some  lymphatic  vessels  which  ascend  from  the  convex  surface  of  the 
liver,  two  or  three  lymphatic  glands  (anterior  mediastinal  glands),  and  the  small 
mediastinal  branches  of  the  internal  mammary  artery. 


Left  Inom-     Left  Carotid      Thymus        Pneumogastric 
inate  Vem.  Artery.  Gland.  Nerve. 


Pneumoqastric 
Nerve. 


Vertebral 

Artery 

Left  Stiblcavian_ 
Artery. 

Oesophagus.'  — 


Internal  Mammary 
Artery. 


Right  Innom- 
inate Vein. 


Trachea. 


2nd  Rih. 


oi  d  Rib. 
Fig.  989. — Transverse  section  through  the  second  dorsal  vertebra.     (Braune.) 

The  Middle  Mediastinum  (Fig.  983). — The  middle  mediastinum  is  the 
broadest  part  of  the  interpleural  space.  It  contains  the  heart  enclosed  in  the 
pericardium,  the  ascending  aorta,  the  lower  half  of  the  superior  vena  cava,  with 
the  vena  azygos  major  opening  into  it,  the  bifurcation  of  the  trachea  and  the  two 
bronchi,  the  pulmonary  artery  dividing  into  its  two  branches  and  the  right  and 
left  pulmonary  veins,  the  phrenic  nerves,  and  some  bronchial  lymphatic  glands. 

The  Posterior  Mediastinum  (Figs.  983  and  987). — The  posterior  mediastinum 
is  an  irregular  triangular  space  running  parallel  with  the  vertebral  column;  it  is 
bounded  in  front  by  the  pericardium  and  roots  of  the  lungs,  behind  by  the  verte- 
bral column  from  the  lower  border  of  the  fourth  dorsal  vertebra,  and  on  either 
side  by  the  pleura.  It  contains  the  descending  thoracic  aorta,  the  greater  and 
lesser  azygos  veins,  the  pneumogastric  and  splanchnic  nerves,  the  oesophagus, 
thoracic  duct,  and  some  lymphatic  glands. 


1390 


THE    ORGANS    OF    VOICE    AND    BESPIBATION 


Blood-vessels. — The  areolar  tissue  of  the  anterior  mediastinum  receives  numer- 
ous mediastinal  branches  from  the  internal  mammary  artery.  The  areolar  tissue 
of  the  posterior  mediastinum  receives  mediastinal  branches  from  the  descending 
thoracic  aorta.  The  lowest  mediastinal  vessels  lie  upon  the  Diaphragm  and  are 
called  superior  phrenic  arteries.  The  vena  cava  and  internal  mammary  veins 
receive  mediastinal  branches. 

The  anterior  mediastinal  lymphatic  glands  are  in  the  upper  portion  of  the  anterior 
mediastinum.  They  are  five  or  six  in  number  and  are  placed  in  front  of  the  trans- 
verse arch  of  the  aorta.  Chains  of  glands  run  up  from  them  to  the  root  of  the 
neck.  On  the  right  side  glands  are  in  front  of  the  right  innominate  vein,  between 
the  artery  and  vein  and  behind  the  artery.  On  the  left  side  they  are  around  the 
left  common  carotid  and  left  subclavian  arteries.^ 

The  posterior  mediastinal  glands  are  around  the  oesophagus,  particularly  in  front 
of  it.    The  peritracheo -bronchial  glands  have  been  described. 


THE  LUNGS  (PULMONES)  (Figs.  983,  990,  991,  992,  993,  994,  995). 

The  lungs  are  the  essential  organs  of  respiration;  they  are  two  in  number, 
placed  one  on  each  side  of  the  chest,  separated  from  each  other  by  the  heart  and 
other  contents  of  the  mediastinum.    A  healthy  lung  hangs  free  within  the  pleural 


LIGAMENTUM 
LATUM    PULMONIS 

Fig.  990. — The  right  lung.     The  inner  or  mediastinal  surface,  with  the  hilum  laid  bare  by  the  removal  of  the 
structures  forming  the  root  of  the  lung.     (Toldt.) 

cavity.  It  is  suspended  by  the  root  and  by  the  ligamentum  pulmonis.  In  many 
cases  examined  the  lung  does  not  hang  free,  but,  as  a  result  of  former  pleurisy, 
an  area  of  the  pulmonary  pleura  is  adherent  to  the  parietal  pleura.  Each  lung  is 
conical  in  shape,  and  presents  for  examination  an  apex,  a  base,  two  borders,  and 
two  surfaces. 

The  Apex  {ajpex  'pulmonis). — The  apex  forms  a  tapering  cone  which  extends 
into  the  root  of  the  neck  about  an  inch  to  two  inches  above  the  level  of  the  anterior 

1  Poirier,  Cun6o,  and  Delamare  on  the  Lymphatics.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE   LUNGS 


1391 


extremity  of  the  first  rib.  The  brachial  plexus  is  in  close  proximity  to  this  por- 
tion of  the  lung. 

The  Base  (basis  pulmonis). — The  base  is  broad,  concave,  and  rests,  by  its 
diaphragmatic  surface  {fades  diaphragmatica),  upon  the  convex  surface  of  the 
Diaphragm,  which  separates  the  right  lung  from  the  upper  surface  of  the  right 
lobe  of  the  liver  and  the  left  lung  from  the  upper  surface  of  the  left  lobe  of  the 
liver,  the  fundus  of  the  stomach,  and  spleen;  its  circumference  is  thin,  and 
projects  for  some  distance  into  the  phrenico-costal  sinus  of  the  pleura,  between 
the  lower  ribs  and  the  costal  attachment  of  the  Diaphragm,  extending  lower 
down  externally  and  behind  than  in  front. 

Surfaces.  The  External,  Costal  or  Thoracic  Surface  (fades  costalis)  (Figs.  994 
and  995). — The  external,  costal,  or  thoracic  surface  is  smooth,  convex,  of  con- 
siderable extent,  and  corresponds  to  the  form  of  the  cavity  of  the  chest,  being 
deeper  behind  than  in  front.  In  a  hardened  specimen  this  surface  has  grooves 
and  bulgings  on  it,  corresponding  to  the  ribs  and  intercostal  spaces. 


ROOT  OF 
LUNG 


SUBCLAVIAN 
GROOVE 


PULMONARY 
ARTERY 


BRONCHUS 


PULMONARY 
VEINS 


IRONCHIAL 
ARTERIES 


BRONCHIAL 

LYMPHATIC 

GLAND 


LIGAMENTUM 

LATUM 

PULMONIS 


CARDIAC 
DEPRESSION 


INFERIOR 
BORDER 


Fig.  991.— The  left  lung.     The  inner  or  mediastinal  surface,  with  the  root  of  the  lung  cut  across.     (Toldt.) 


The  Inner  or  Mediastinal  Surface  (fades  mediastinalis)  (Figs.  990  and  991). — The 
inner  or  mediastinal  surface  is  concave.  It  presents  in  front  a  depression  corre- 
sponding to  the  convex  surface  of  the  pericardium,  and  behind  a  deep  fissure,  the 
hilum  (hilus  pidmonalis) .  In  the  hilum  lie  the  bronchi,  vessels,  nerves,  and 
lymph-nodes,  which  together  constitute  the  root  of  the  lung.  On  the  inner  and 
anterior  surface,  a  little  below  the  apex,  is  a  groove,  the  subclavian  groove  (sulcus 
subclavius),  for  the  subclavian  artery.  A  little  lower  is  a  broader  and  shallower 
groove  for  the  innominate  and  subclavian  veins.  The  pleura  lies  between  the 
lungs  and  these  vessels.  In  front  of  the  hilum  and  below  it  is  a  depression  for 
the  heart  (impressio  cardiaca).  It  is  deeper  on  the  left  than  on  the  right  side. 
On  the  right  side  it  passes  into  the  groove  from  the  superior  vena  cava  and  the 
vena  azygos  major.  On  the  left  side,  behind  the  hilum,  is  a  groove  for  the 
thoracic  aorta;  on  the  right  side  a  groove  for  the  oesophagus. 


1392 


THE    ORGANS    OF    VOICE  AND   RESPIRATION 


Borders.  The  Inferior  Border  (margo  inferior). — The  inferior  border  is  the  line 
of  junction  of  the  costal  and  diaphragmatic  surfaces.  Posteriorly,  it  is  rounded 
and  broad,  and  is  received  into  the  deep  concavity  on  either  side  of  the  spinal 
column  (Fig.  996).  It  is  much  longer  than  the  anterior  border,  and  projects, 
below,  into  the  phrenico-costal  sinus. 


Fig.  992. — Front  \  iew  of  the  heart  and  lungs. 


The  Anterior  Border  (margo  anterior). — The  anterior  border  is  thin  and  sharp, 
overlaps  the  front  of  the  pericardium,  and  is  projected  into  the  costo-medi- 
astinal  sinus  of  the  pleura.  The  anterior  border  of  the  right  lung  is  almost 
vertical;  that  of  the  left  presents,  below,  an  angular  notch,  the  incisura  cardiaca, 
into  which  the  heart  and  pericardium  are  receivefl.  A  projection  from  the 
upper  lobe  omes  forward  beneath  the  cardiac  notch;  it  is  called  the  lingula 
pulmonis. 

The  Lobes  of  the  Lungs  (Figs.  994  and  995).— Each  lung  is  divided  into  two 
lobes,  an  upper  (lohus  superior)  and  a  lower  (lobus  inferior),  by  a  long  and  deep 
fissure  (incisura  interlobaris) ,  which  extends  from  the  upper  part  of  the  posterior 
border  of  the  organ  about  three  inches  from  its  apex,  downward  and  forward  to 
the  lowest  part  of  the  lung  just  external  to  its  anterior  border.  This  fissure  pene- 
trates nearly  to  the  root.  The  upper  lobe  is  the  smaller;  the  lower  lobe  is  the 
larger.  In  the  right  lung  the  upper  lobe  is  partially  subdivided  by  a  second  and 
shorter  fissure,  which  extends  almost  horizontally  forward  from  the  middle  of 
the  preceding  to  the  anterior  margin  of  the  organ,  marking  off  a  small  triangular 
portion,  the  middle  lobe  (lohus  medium). 

The  right  lung  is  the  larger  and  heavier;  it  is  broader  than  the  left,  owing  to 
the  inclination  of  the  heart  to  the  left  side;  it  is  also  shorter  by  an  inch,  in 


THE  LUNGS 


1393 


consequence  of  the  Diaphragm  rising  higher  on  the  right  side  to  accommodate 
the  Hver. 


ENTRANCE    OF 
VENA     AZYGOS 
BRANCH    OF    PUL- 
MONARY   ARTERY 


Fig.  993. — Pulmonary  veins,  seen  in  a  dorsal  view  of  the  heart  and  lungs.  The  lungs  have  been  pulled 
away  from  the  median  line,  and  a  part  of  the  right  lung  has  been  cut  away  to  display  the  air-ducts  and  blood- 
vessels.    (Testut.) 


Fio.  994. — The  right  lung.     The  outer  or  costal 
surface.     (Toldt.) 


Fig.  995. — The  left  lung.     The  outer  or  costal 
surface.    (Toldt.) 


The  Root  of  the  Lung  (radix  pulmonis)  (Figs.  990,  991,  992,  and  993).— A 
little  above  the  middle  of  the  inner  surface  of  each  lung,  and  nearer  its  posterior 

88 


1394  THE    ORGANS   OF    VOICE  AND   BESPIBATION 

than  its  anterior  border,  is  its  root,  by  which  the  lung  is  connected  to  the  heart 
and  the  trachea.  The  root  is  formed  by  the  bronchial  tube,  the  pulmonary 
artery,  the  pulmonary  veins,  the  bronchial  arteries  and  veins,  the  pulmonary 
plexus  of  nerves,  lymphatics,  bronchial  glands,  and  areolar  tissue,  all  of  which 
are  enclosed  by  a  reflection  of  the  pleura.  The  root  of  the  right  lung  lies  behind 
the  superior  vena  cava  and  ascending  portion  of  the  aorta,  and  below  the  vena 
azygos  major.  The  root  of  the  left  lung  passes  beneath  the  arch  of  the  aorta 
and  in  front  of  the  descending  aorta;  the  phrenic  nerve  and  the  anterior  pulmo- 
nary plexus  lie  in  front  of  each,  and  the  pneumogastric  and  posterior  pulmonary 
plexus  behind  each. 

The  chief  structures  composing  the  root  of  each  lung  are  arranged  in  a  similar 
manner  from  before  backward  on  both  sides — viz.,  the  two  pulmonary  veins  in  front ; 
the  pulmonary  artery  in  the  middle;  and  the  bronchus,  together  with  the  bronchial 
vessels,  behind.  From  above  downward,  on  the  two  sides,  their  arrangernent  differs, 
thus:  On  the  right  side  their  position  is — bronchus,  pulmonary  artery,  pulmonary 
veins;  but  on  the  left  side  their  position  is — pulmonary  artery,  bronchus,  pulmo- 
nary veins.  It  should  be  noted  that  the  entire  right  bronchus  does  not  lie  above 
the  right  pulmonary  artery,  but  only  its  eparterial  branch  (see  p.  1377),  which 
passes  to  the  upper  lobe  of  the  right  lung;  the  divisions  of  the  bronchus  for  the 
middle  and  lower  lobes  lie  below  the  artery. 

The  true  weight  of  the  human  lungs  as  ascertained  in  the  bodies  of  criminals 
executed  by  electricity,  in  which  the  mode  of  death  is  attended  by  a  nearly  bloodless 
condition  of  the  lungs,  is  215  grams  (7^  ounces)  for  the  left  lung  and  240  grams 
(8^  ounces)  for  the  right  lung  (E.  A.  Spitzka,  Amer.  Jour,  of  Anat.,  iii.,  1,  p.  v.). 
Ordinarily,  with  the  vascular  channels  more  or  less  filled  with  blood  and  serum, 
the  two  lungs  together  weigh  about  42  ounces,  the  right  lung  being  2  ounces 
heavier  than  the  left,  but  much  variation  is  met  with  according  to  the  amount  of 
blood  or  serous  fluid  they  may  contain.  The  lungs  are  heavier  in  the  male  than 
in  the  female.     The  specific  gravity  of  the  lung-tissue  varies  from  0.345  to  0.746. 

The  color  of  the  lungs  at  birth  is  a  pinkish-white;  in  adult  life  a  dark  slate- 
color,  mottled  in  patches;  and  as  age  advances  this  mottling  assumes  a  black 
color.  The  coloring  matter  consists  of  granules  of  a  carbonaceous  substance 
deposited  in  the  areolar  tissue  near  the  surface  of  the  organ.  It  increases  in 
quantity  as  age  advances,  and  is  more  abundant  in  males  than  in  females.  The 
posterior  surface  of  the  lung  is  usually  darker  than  the  anterior. 

The  surface  of  the  lung  is  smooth,  shining,  and  marked  out  into  numerous 
polyhedral  spaces,  indicating  the  lobules  of  the  organ;  the  area  of  each  of  these 
spaces  is  crossed  by  numerous  lighter  lines. 

The  substance  of  the  lung  is  of  a  light,  porous,  spongy  texture;  it  floats  in 
water  and  crepitates  when  handled,  owing  to  the  presence  of  air  in  the  tissue;  it 
is  also  highly  elastic;  hence  the  collapsed  state  of  these  organs  when  they  are 
removed  from  the  closed  cavity  of  the  thorax. 

The  Fcetal  Lung. — After  respiration  has  been  established,  the  lung  fills  the 
pleural  cavity.  In  the  foetus,  as  the  lung  has  never  been  distended  with  air 
and  has  never  received  a  large  amount  of  blood,  it  is  gathered  into  a  small  mass 
at  the  back  of  the  thorax.     It  will  sink  in  water  and  feels  solid  to  the  touch. 

Structure. — The  structure  of  the  lung  is  such  that  the  blood  brought  by  the 
pulmonary  artery  comes  into  close  relation  with  the  air  which  enters  from  the 
bronchioles.  The  blood  gives  materials  to  the  air,  and  the  air  gives  elements  to 
the  blood,  and  the  process  of  respiration  causes  the  dark  blood  brought  from  the 
heart  by  the  pulmonary  artery  to  return  to  the  heart  as  red  blood  in  the  pulmonary 
vein.  The  lungs  are  composed  of  an  external  serous  coat,  a  subserous  areolar  tissue, 
and  the  pulmonary  substance  or  parenchyma. 

The  Serous  Coat. — The  serous  coat  is  thin,  transparent,  and  invests  the  entire 
organ  as  far  as  the  root.     It  is  known  as  the  pulmonary  pleura  (p.  1384). 


THE  LUNGS  I395 

The  Subserous  Areolar  Tissue. — The  subserous  areolar  tissue  contains  a  large 
proportion  of  elastic  fibres;  it  invests  the  entire  surface  of  the  lung,  and  extends 
inward  between  the  lobules,  and  at  the  hilum  forms  the  pulmonary  scaffold  or 
framework. 

The  Paxenchyma. — The  parenchyma  is  composed  of  lobules  which,  although 
closely  connected  together  by  an  interlobular  areolar  tissue,  are  quite  distinct  from 
one  another,  and  may  be  teased  asunder  without  much  difficulty  in  the  foetus. 
The  lobules  vary  in  size;  those  on  the  surface  are  large,  of  pyramidal  form,  with 
the  bases  turned  toward  the  surface;  those  in  the  interior  are  smaller  and  of  various 
forms.  Each  lobule  is  composed  of  one  of  the  ramifications  of  a  bronchial  tube 
and  its  terminal  air-cells,  and  of  the  ramifications  of  the  pulmonary  and  bronchial 
vessels,  lymphatics,  and  nerves,  all  of  these  structures  being  connected  together  by 
areolar  tissue. 

The  Bronchus  (pp.  1377  and  1378)  (Figs.  980,  981,  and  982).— The  bronchus, 
upon  entering  the  substance  of  the  lung,  divides  and  subdivides  bipinnately, 
throughout  the  entire  organ.  Sometimes  three  branches  arise  together,  and  occa- 
sionally small  lateral  branches  are  given  off  from  the  sides  of  a  main  trunk.  Each 
of  the  smaller  subdivisions  of  the  bronchi  enters  a  pulmonary  lobule,  and  is  termed 
a  lobular  bronchial  tube  or  bronchiole  (bronchioli).  Each  bronchiole  divides  into 
minute  branches  {bronchioli  respiratorii) ,  the  walls  of  which  now  begin  to  present 
irregular  dilatations,  bronchial  alveoli.  These  are  present  at  first  sparingly  and  on 
one  side  of  the  tube  only,  but  as  it  proceeds  onward  these  dilatations  become  more 
numerous  and  surround  the  tube  on  all  sides,  so  that  it  loses  its  cylindrical  char- 
acter. The  terminal  branches  come  from  the  bronchioli  respiratorii.  These 
terminal  branches  are  called  the  alveolar  ducts  or  alveolar  passages  {ducivli  alveo- 
lares).  The  alveolar  ducts  show  numerous  alveoli  (Fig.  981)  ar.d  join  with  cav- 
ities called  atria.  Each  atrium  joins  several  larger  cavities,  the  air-cells  or  air-sacs 
(infundibula) .  The  numerous  small  cavities  on  the  surface  of  the  air-sacs  are 
the  pulmonary  alveoli  (alveoli  pulmonis) .  The  bronchiole  now  becomes  widened 
out  and  terminates  in  an  irregular  cul-de-sac,  the  air  cell,  air  sac  alveolus  or  infun- 
dibulum.  The  walls  of  the  infundibulum  are  closely  beset  in  all  directions  by  pul- 
monary alveoli  or  pulmonary  air  cells.  Professor  Gerrish  remarks  that  the  first  of 
the  alveoli  seen  on  the  bronchioles  before  the  coreal  ends  are  formed  would  seem 
an  effort  on  the  part  of  nature  to  form  an  infundibulum  before  all  the  necessary 
conditions  are  favorable. 

Changes  in  the  Structure  of  the  Bronchi  in  the  Lungs. ^Within  the  lungs  the 
bronchial  tubes  are  circular,  not  flattened  (Fig.  982),  and  present  certain  pecu- 
liarities of  structure. 

In  the  Lobes  of  the  Lungs. — In  the  lobes  of  the  lungs  the  following  changes 
take  place:  The  cartilages  are  not  imperfect  rings,  but  consist  of  thin  laminae, 
of  varied  form  and  size,  scattered  irregularly  along  the  sides  of  the  tube,  being 
most  distinct  at  the  points  of  division  of  the  bronchi.  They  may  be  traced  into 
tubes,  the  diameter  of  each  of  which  is  only  one-fourth  of  a  line.  Beyond  this 
point  the  tubes  are  wholly  membranous.  The  fibrous  coat  is  continued  into  the 
smallest  ramifications  of  the  bronchi.  The  muscular  coat  is  disposed  in  the  form 
of  a  continuous  layer  of  annular  fibres,  which  may  be  traced  upon  the  smallest 
bronchial  tubes,  and  consists  of  the  unstriped  variety  of  muscular  tissue.  The 
mucous  membrane  lines  the  bronchi  and  their  ramifications  throughout,  and  is 
covered  with  columnar  ciliated  epithelium. 

In  the  Lobules  of  the  Lung. — In  the  lobular  bronchial  tubes  and  in  the  infun- 
dibula the  following  changes  take  place:  The  muscular  tissue  begins  to  disap- 
pear, so  that  in  the  infundibula  there  is  scarcely  a  trace  of  it.  The  fibrous  coat 
becomes  thinner,  and  degenerates  into  areolar  tissue.  The  epithelium  becomes 
non-ciliated  and  flattened.    This  occurs  gradually;  thus,  in  the  lobular  bronchioles 


1396  THE    ORGANS    OF   VOICE  AND   RESPIRATION 

patches  of  non-ciliated  flattened  epithelium  may  be  found  scattered  among  the 
columnar  ciliated  epithelium;  then  these  patches  of  non-ciliated  flattened  epithe- 
lium become  more  and  more  numerous,  until  in  the  infundibula  and  air-cells  all 
the  epithelium  is  of  the  non-ciliated  pavement  variety.  In  addition  to  these  flat- 
tened cells,  there  are  small  polygonal  granular  cells  in  the  air-sacs,  in  clusters  of 
two  or  three,  between  the  others. 

The  air-cells  are  small,  polyhedral  recesses  composed  of  a  fibrillated  connec- 
tive tissue  and  surrounded  by  a  few  involuntary  muscular  and  elastic  fibres.  Free 
in  their  cavity  are  to  be  seen  under  the  microscope  granular,  rounded,  amoeboid 
cells  (eosinophile  leukocytes),  often  containing  carbonaceous  particles.  The  air- 
cells  are  well  seen  on  the  surface  of  the  lung,  and  vary  from  -^^  to  y^  of  an 
inch  in  diameter,  being  largest  on  the  surface  at  the  thin  borders  and  at  the  apex, 
and  smallest  in  the  interior. 

Mucous  Glands. — In  the  larger  bronchi  the  mucous  membrane  contains  goblet 
cells.  When  the  tubes  diminish  to  1  mm.  in  diameter  the  glands  grow  fewer. 
In  the  smaller  bronchi  there  are  no  mucous  glands. 

Vessels  of  the  Lungs. — The  pulmonary  artery  (Figs.  992  and  993)  conveys  the 
venous  blood  to  the  lungs;  it  divides  into  branches  which  accompany  the  bronchial 
tulles,  and  terminates  in  a  dense  capillary  network  upon  the  walls  of  the  inter- 
cellular passages  and  air-cells.  In  the  lung  the  branches  of  the  pulmonary  artery 
are  usually  above  and  in  front  of  a  bronchial  tube,  the  vein  below. 

The  pulmonary  capillaries  form  plexuses  which  lie  immediately  beneath  the 
mucous  membrane  in  the  walls  and  septa  of  the  air-cells  and  of  the  infundibula. 
In  the  septa  between  the  air-cells  the  capillary  network  forms  a  single  layer.  The 
capillaries  form  a  very  minute  network,  the  meshes  of  which  are  smaller  than  the 
vessels  themselves;^  their  walls  are  also  exceedingly  thin.  The  arteries  of  neigh- 
boring lobules  are  independent  of  each  other,  but  the  veins  freely  anastomose 
together. 

The  pulmonary  veins  commence  in  the  pulmonary  capillaries,  the  radicles 
coalescing  into  larger  branches,  which  run  along  through  the  substance  of  the 
lung,  independently  from  the  minute  arteries  and  bronchi.  After  freely  commu- 
nicating with  other  branches  they  form  large  vessels,  which  ultimately  come  into 
relation  with  the  arteries  and  bronchial  tubes,  and  accompany  them  to  the  hilum 
of  the  organ.  Finally  they  open  into  the  left  auricle  of  the  heart,  conveying 
oxygenated  blood  to  be  eventually  distributed  to  all  parts  of  the  body  by  the  aorta. 

The  bronchial  arteries  supply  blood  for  the  nutrition  of  the  lung.  The  thoracic 
aorta  usually  gives  off  two  left  bronchial  arteries.  The  single  right  bronchial 
artery  usually  arises  from  the  first  right  aortic  intercostal,  but  sometimes  from 
the  superior  left  bronchial  artery,  or  from  the  aorta.  In  the  root  of  the  lung 
they  are  posterior  to  the  bronchus,  they  accompany  the  bronchial  tubes,  supply 
the  tubes  and  pulmonary  tissue,  and  give  branches  to  the  walls  of  the  larger 
pulmonary  vessels,  the  oesophagus,  pericardium,  and  bronchial  glands.  Those 
supplying  the  bronchial  tubes  form  a  capillary  plexus  in  the  muscular  coat,  from 
which  branches  are  given  off  to  form  a  second  plexus  in  the  mucous  coat.  This 
plexus  communicates  with  branches  of  the  pulmonary  artery,  and  empties  itself 
into  the  pulmonary  vein.  Others  are  distributed  in  the  interlobular  areolar  tissue, 
and  terminate  partly  in  the  deep,  partly  in  the  superficial,  bronchial  veins.  Lastly, 
some  ramify  upon  the  surface  of  the  lung  beneath  the  pleura,  where  they  form  a 
capillary  network.  There  may  be  but  one  bronchial  artery;  there  may  be  three 
or  four. 

The  bronchial  veins  are  not  found  in  the  walls  of  the  very  small  bronchi.  The 
small  bronchial  veins  run  along  by  the  front  and  back  of  the  median  sized  and 

1  The  meshes  are  only  0.002'"  to  0.008'"  in  width,  while  the  vessels  are  0.003'"  to  0.005'"  (KSlliker,  Human 
Microscopic  Anatomy). — Ed.  of  15th  English  edition. 


THE  LUNGS  I397 

larger  tubes,  and  from  two  trunks  at  the  root  of  each  lung.  These  vessels  termi- 
nate on  the  right  side  in  the  vena  azygos  major,  and  on  the  left  side  in  the  superior 
intercostal  or  left  upper  azygos  vein.  Tracheal  and  posterior  mediastinal  veins 
open  into  the  bronchial  veins.  The  venous  blood  from  the  smaller  tubes  passes 
to  the  pulmonary  veins. 

The  lymphatics  begin  in  networks  about  the  lobules  and  form  networks  about 
the  bronchi  and  beneath  the  bronchial  mucous  membrane.  The  superficial  col- 
lecting trunks  arise  about  the  lobules  and  beneath  the  pleura.  According  to 
Sappey,  the  superficial  trunks  from  the  upper  lobe  begin  on  the  costal  surface; 
one  set  passes  around  the  anterior  border,  another  set  around  the  posterior 
border,  and  a  third  into  the  incisura  interlobaris.  The  same  observer  says  that  the 
superficial  trunks  from  the  middle  lobe  unites  with  the  trunks  from  the  upper  and 
lower  lobes;  and  the  superficial  trunks  from  the  lower  lobe,  like  those  of  the  upper 
lobe,  are  in  three  sets.  One  set  passes  around  the  posterior  margin,  one  around  the 
anterior  margin,  and  one  into  the  incisura  interlobaris.  All  of  the  superficial  trunks 
convey  lymph  to  the  glands  of  the  hilum.  Some  of  the  deep  collecting  trunlcs  begin 
by  the  sides  of  the  small  bronchi;  others  course  along  by  the  pulmonary  veins 
or  pulmonary  arteries.  All  of  them  pass  to  the  glands  of  the  hilum.  The  glands 
of  the  hilum  are  in  communication  with  the  peritracheo-bronchial  glands.^ 

Nerves. — The  lungs  are  supplied  from  the  anterior  and  posterior  pulmonary 
plexuses,  formed  chiefly  by  branches  from  the  sympathetic  and  pneumogastiic. 
The  filaments  from  these  plexuses  accompany  the  bronchial  tubes,  and  are  lost 
upon  them.     Small  ganglia  are  found  upon  these  nerves. 

Surface  Form. — The  apex  of  the  lung  is  situated  in  the  neck,  behind  the  interval  between  the 
two  heads  of  origin  of  the  Sterno-mastoid  muscle.  The  height  to  which  it  rises  above  the  clavicle 
varies  very  considerably,  but  is  generally  about  one  inch.  It  may,  however,  extend  as  much  as 
an  inch  and  a  half  or  an  inch  and  three-quarters,  or,  on  the  other  hand,  it  may  scarcely  project 
above  the  level  of  this  bone.  In  order  to  mark  out  the  anterior  margin  of  the  lung,  a  line  is 
to  be  drawn  from  the  apex-point,  one  inch  above  the  level  of  the  clavicle,  and  rather  nearer  the 
posterior  than  the  anterior  border  of  the  Sterno-mastoid  muscle,  downward  and  inward  across 
the  sterno-clavicular  articulation  and  first  piece  of  the  sternum  until  it  meets,  or  almost  meets, 
its  fellow  of  the  other  side  opposite  the  articulation  of  the  manubrium  and  gladiolus.  From  this 
point  the  two  lines  are  to  be  drawn  downward,  one  on  either  side  of  the  mesial  line  and  close  to 
it,  as  far  as  the  level  of  the  articulation  of  the  fourth  costal  cartilages  to  the  sternum.  From 
here  the  two  lines  diverge;  the  left  is  to  be  drawn  at  first  passing  outward  with  a  slight  inclina- 
tion downward,  and  then  taking  a  bend  downward  with  a  slight  inclination  outward  to  the  apex 
of  the  heart,  and  thence  to  the  sixth  costo-chondral  articulation.  The  direction  of  the  anterior 
border  of  this  part  of  the  left  lung  is  denoted  with  sufficient  accuracy  by  a  curved  line  with  its 
convexity  directed  upward  and  outward  from  the  articulation  of  the  fourth  right  costal  cartilage 
of  the  sternum  to  the  fifth  intercostal  space,  an  inch  and  a  half  below  and  three-quarters  of  an 
inch  internal  to  the  left  nipple.  The  continuation  of  the  anterior  border  of  the  right  lung  is 
marked  by  a  prolongation  of  its  line  from  the  level  of  the  fourth  costal  cartilages  vertically 
downward  as  far  as  the  sixth,  when  it  slopes  off  along  the  line  of  the  sixth  costal  cartilage  to  its 
articulation  with  the  rib. 

The  lower  border  of  the  lung  is  marked  out  by  a  slightly  curved  line  with  its  convexity  down- 
ward from  the  articulation  of  the  sixth  costal  cartilage  to  its  rib  to  the  spinous  process  of  the 
tenth  dorsal  vertebra.  If  vertical  lines  are  drawn  downward  from  the  nipple,  the  mid-axillary 
line,  and  the  apex  of  the  scapula,  while  the  arms  are  raised  from  the  sides,  they  should  intersect 
this  convex  line,  the  first  at  the  sixth,  the  second  at  the  eighth,  and  the  third  at  the  tenth  rib. 
It  will  thus  be  seen  that  the  pleura  extends  farther  down  than  the  lung,  so  that  it  may  be 
wounded,  and  a  wound  may  pass  through  its  cavity  into  the  Diaphragm,  and  the  abdominal 
viscera  may  be  injured  without  the  lung  being  involved. 

The  posterior  border  of  the  lung  is  indicated  by  a  line  drawn  from  the  level  of  the  spinous 
process  of  the  seventh  cervical  vertebra,  down  either  side  of  the  spine,  corresponding  to  the 
costo-vertebral  joints  as  low  as  the  spinous  process  of  the  tenth  dorsal  vertebra.  The  trachea 
bifurcates  opposite  the  spinous  process  of  the  fourth  dorsal  vertebra,  and  from  this  point  the  two 
bronchi  are  directed  outward. 

"The  position  of  the  great  fissure  of  the  lungs  may  be  indicated  by  a  line  drawn  from  the  third 

1  The  Lymphatics,  by  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


1398 


THE   ORGANS    OF    VOICE  AND   RESPIRATION 


dorsal  spine  obliquely  downward  in  such  a  manner  as  to  reach  the  sixth  rib  close  to  the  mid- 
clavicular line.  The  interlobar  fissure  between  the  upper  and  middle  lobes  of  the  right  lung 
corresponds  to  a  line  drawn  from  the  apex  of  the  axilla  almost  horizontally  to  the  sternum, 
reaching  the  latter  at  about  the  level  of  the  fourth  costal  cartilage"  (Erendrath). 


Recur, 
lar.  nen 


Epart. 
hronchtis 


Pulm. 
veins 


1 1)1  iiiiu  n  Ju) 
oesophagus 

Fig.  996. — Thoracic  contents  seen  from  behind.     (Joessel.) 


Surgical  Anatomy. — The  lungs  may  be  wounded  or  torn  in  three  ways:  (1)  By  compres- 
sion of  the  chest,  without  any  injury  to  the  ribs.  (2)  By  a  fractured  rib  penetrating  the  lung. 
(3)  By  stabs,  gunshot  wounds,  etc. 


THE   LUNGS  1399 

The  first  form,  where  the  lung  is  ruptured  by  external  compression  without  any  fracture  of 
the  ribs,  is  very  rare,  and  usually  occurs  in  young  children,  and  affects  the  root  of  the  lung — 
i.  e.,  the  most  fixed  part — and  thus,  implicating  the  great  vessels,  is  frequently  fatal.  It  would 
seem  to  be  a  most  unusual  injury,  and  the  exact  mode  of  its  causation  is  difficult  to  understand. 
The  probable  explanation  is  that  immediately  before  the  compression  is  applied  a  deep  inspira- 
tion is  taken  and  the  lungs  are  fully  inflated ;  owing  then  to  spasm  of  the  glottis  at  the  moment 
of  compression,  the  air  is  unable  to  escape  from  the  lung,  the  lung  is  not  able  to  recede,  and 
consequently  gives  way. 

In  the  second  variety,  when  the  wound  in  the  lung  is  produced  by  the  penetration  of  a  broken 
rib,  both  the  pleura  costalis  and  the  pleura  pulmonalis  must  necessarily  be  injured,  and  conse- 
quently the  air  taken  into  the  wounded  air-cells  may  find  its  way  through  these  wounds  into  the 
cellular  tissue  of  the  parietes  of  the  chest.  This  it  may  do  without  collecting  in  the  pleural  cavity; 
the  two  layers  of  the  pleura  are  so  intimately  in  contact  that  the  air  may  pass  straight  through 
from  the  wounded  lung  into  the  subcutaneous  tissue.  Emphysema  constitutes,  therefore,  an 
important  sign  of  injury  to  the  lung  in  cases  of  fracture  of  the  ribs.  Pneumothorax,  or  air  in  the 
pleural  cavity,  is  much  more  likely  to  occur  in  injuries  to  the  lung  of  the  third  variety;  that  is 
to  say,  from  external  wounds,  from  stabs  and  gunshot  injuries,  in  which  cases  air  passes  either 
from  the  wound  of  the  lung  or  from  an  external  wound  into  the  cavity  of  the  pleura  dur- 
ing the  respiratory  movements.  In  these  cases  there  is  generally  no  emphysema  of  the  sub- 
cutaneous tissue  unless  the  external  wound  is  small  and  valvular,  so  that  the  air  drawn  into  the 
wound  during  inspiration  is  then  forced  into  the  cellular  tissue  around  during  expiration  because 
it  cannot  escape  from  the  external  wound.  Occasionally  in  wounds  of  the  parietes  of  the  chest 
no  air  finds  its  way  into  the  cavity  of  the  pleura,  because  the  lung  at  the  time  of  the  accident 
protrudes  through  the  wound  and  blocks  the  opening.  This  occurs  where  the  wound  is  large, 
and  constitutes  a  so-called  hernia  of  the  lung.  True  hernia  of  the  lung  occurs,  though  very 
rarely,  after  wounds  of  the  chest-wall,  when  the  wound  has  healed  and  the  cicatrix  sub- 
sequently yields  from  the  pressure  of  the  viscus  behind.  It  forms  a  globular,  elastic,  crepi- 
tating swelling,  which  enlarges  during  expiratory  efforts,  falls  during  inspiration,  and  disappears 
on  holding  the  breath.  Wounds  of  the  lung  may  produce  dangerous  or  fatal  hemorrhage  into 
the  pleural  sac.  In  many  cases  the  bleeding  is  spontaneously  arrested;  in  others  the  surgeon 
must  interfere  to  save  life.  In  some  cases  air  has  been  admitted  by  intercostal  incision  and  the 
insertion  of  a  tube,  and  pulmonary  collapse  has  arrested  bleeding.  In  other  cases  it  is  necessary 
to  resect  portions  of  several  ribs,  and  stop  bleeding  by  ligatures  or  suture  ligatures.  In  one 
<;ase  of  a  furious  secondary  hemorrhage  following  a  gunshot  wound,  the  editor  resected  several 
ribs,  packed  the  pleural  cavity  about  the  lung  with  sterile  gauze,  to  obtain  a  base  of  support,  and 
then  arrested  the  bleeding  by  packing  iodoform  gauze  against  the  firmly  supported  lung.  This 
patient  recovered. 

Incision  of  the  lung  (pneumotomy)  is  performed  for  pulmonary  abscess  (either  tuberculous  or 
pyogenic),  pulmonary  gangrene,  hydatid  cysts,  and  bronchiectasis.  In  pulmonary  abscess, 
locate  the  area  by  physical  signs  and  the  a^-ray,  resect  a  portion  of  a  rib  over  it,  and  note  if  the 
pleura  is  adherent.  If  it  is  adherent,  continue  the  operation.  If  it  is  not  adherent,  insert  stitches 
of  catgut  through  the  two  layers  of  pleura  and  the  superficial  part  of  the  lung,  so  as  to  encircle 
a  considerable  area,  and  then  wait  several  days  for  adhesions  to  form.  Adhesions  protect  the 
pleura  from  infection,  and,  by  keeping  air  from  the  pleural  sac,  prevent  pneumothorax.  When 
ready  to  continue  the  operation,  locate  the  abscess  with  an  aspirating-needle  and  syringe,  open 
it  with  a  cautery  at  a  dull-red  heat,  and  drain  by  means  of  a  tube. 

Pneumotomy  is  very  unsatisfactory  in  tuberculous  cavities  and  bronchiectasis.  In  tubercu- 
losis, excision  of  the  diseased  area  (pneumectomy)  has  been  employed,  but  it  is  not  to  be  advised. 


THE  DUCTLESS  GLANDS. 


THESE  glands  do  not  possess  excretory  ducts.  They  furnish  materials  which 
are  added  to  the  blood  or  lymph  as  it  passes  through  them.  The  material 
from  each  gland  is  known  as  an  internal  secretion.  Some  of  these  secretions  are 
powerful  materials  and  influence  profoundly  the  body  nutrition.  The  ductless 
glanfls  are  usually  given  as  follows:  the  spleen,  the  lymphatic  glands,  the  pineal 
gland,  the  pituitary  body,  the  suprarenal  capsules,  the  thyroid  gland,  the  para-thyroids, 
the  thymus,  the  carotid  body,  and  the  coccygeal  body.  The  lymphatic  glands  were 
described  in  a  special  section  (p.  772).  The  lymphatic  glands  are  not  con- 
sidered to  be  really  glands,  but,  nevertheless,  as  lymph  passes  through  the  lymph 
glands,  it  receives  a  product  of  the  glands,  namely,  lymphocytes.  There  is  no 
evidence  that  the  spleen  furnishes  an  active  internal  secretion,  and  this  organ 
has  been  studied  with  the  abdominal  viscera.  The  pineal  gland  (p.  905)  and 
pituitary  body  (p.  882)  were  considered  with  the  brain.  The  suprarenal  capsules 
(p.  1428)  are  described  with  the  kidneys.  Some  glands,  for  instance,  the  liver, 
pancreas  and  testicle,  have  an  external  secretion  and  also  an  internal  secretion. 


THE  THYROID  BODY  OR  GLAND  (GLANDULA  THYREOIDEA) 

(Fig.  997). 

The  thyroid  gland  is  an  extremely  vascular  body,  situated  at  the  front  and 
sides  of  the  neck,  and  extending  upward  upon  each  side  of  the  larynx.  It  is  a 
single  gland,  varying  greatly  in  size  in  different  individuals.  It  is  larger  relatively 
in  females  and  in  children  than  in  men.  It  is  frequently  asymmetrical.  In  early 
embryonal  life  the  gland  has  a  duct,  the  thyro-glossal  duct  (ductus  thyreoglossus) , 
which  passes  from  the  isthmus  of  the  thyroid  to  the  foramen  caecum  of  the  dorsum 
of  the  tongue.  The  lumen  of  this  duct  is  obliterated  early  and  becomes  a  cord  of 
epithelium.  The  lower  portion  of  the  duct  often  remains  open  for  a  little  way. 
The  upper  portion  remains  as  the  foramen  caecum.  The  situation  of  this  obliter- 
ated foetal  duct  may  be  marked  by  the  third  or  middle  lobe  of  the  thyroid  gland. 
The  thyroid  surrounds  the  upper  portion  of  the  trachea  like  a  horseshoe.  It  con- 
sists of  two  lateral  lobes  connected  across  the  middle  line  by  a  narrow  transverse 
portion,  the  isthmus. 

The  weight  of  the  gland  is  somewhat  variable,  but  is  usually  about  one  ounce. 
It  is  somewhat  heavier  in  the  female,  in  whom  it  becomes  enlarged  during  men- 
struation and  pregnancy.    As  age  advances  the  weight  of  the  thyroid  diminishes. 

The  color  of  the  thyroid,  as  seen  from  the  surface,  is  reddish-blue.  The  gland  is 
surrounded  by  a  closely  adherent  thin  connective-tissue  capsule  of  the  pre-tracheal 
layer  of  deep  cervical  fascia.  From  the  inner  surface  of  the  capsule  come  delicate 
septa,  which  enter  into  the  thyroid  body  and  separate  it  into  lobes  and  also  sepa- 
rate the  lobes  into  lobules.  The  blood-vessels  lie  beneath  the  capsule.  The  ante- 
rior and  lateral  portions  of  the  gland  are  covered  by  the  capsule.  "  Passing  around 
the  side  of  the  gland  to  its  posterior  surface,  this  capsule  then  splits  into  two  por- 
tions. One  remains  in  contact  with  the  glanfl  and  invests  its  posterior  surface. 
The  other,  the  thicker  of  the  two,  passes  to  the  posterior  surface  of  the  pharynx 

( 1401 ) 


1402 


THE   DUCTLESS    GLANDS 


and  oesophagus,  thus  enclosing  them  with  the  larynx,  trachea,  and  thyroid  gland, 
in  a  common  sheath."^ 

The  lateral  lobes  are  conical  in  shape,  the  apex  of  each  being  directed  upward 
and  outward  as  far  as  the  junction  of  the  middle  with  the  lower  third  of  the  thy- 
roid cartilage;  the  base  looks  downward,  and  is  on  a  level  with  the  fifth  or  sixth 
tracheal  ring.  The  summit  of  the  lateral  lobe  not  unusually  is  pointed  and  reaches 
to  the  level  of  the  oblique  line  upon  the  ala  of  the  thyroid  cartilage  or  even  higher. 
The  right  is,  as  a  rule,  somewhat  larger  than  the  left  lobe.    The  lower  portion  of 

the  gland,  when  the  head  is  extended,  is  about 
one  inch  above  the  upper  margin  of  the  ster- 
num; when  the  head  is  flexed,  it  is  at  the  level 
of  the  upper  border  of  the  sternum  or  even 
below  and  behind  it.  The  portion  of  the 
lateral  lobe  above  the  level  of  the  superior 
border  of  the  isthmus  is  called  the  upper  horn, 
the  portion  below  the  level  of  the  inferior  mar- 
gin of  the  isthmus  is  called  the  lower  horn.  The 
lower  horn  "is  usually  much  smaller  than  the 
upper  horn ;  frequently  it  is  altogether  absent."^ 
At  the  inner  and  posterior  part  of  each  lateral 
lobe  is  the  hilum.  At  the  hilum  the  inferior 
thyroid  artery  passes  into  the  gland.  "Here 
the  recurrent  laryngeal  nerve  comes  into  close 
contact  with  the  gland,  lying  in  the  space  be- 
tween it  and  the  trachea  and  oesophagus."' 

The  external  or  superficial  surface  is  convex, 
and  covered  by  the  skin,  the  superficial  fascia, 
the  deep  fascia,  the  Sterno-mastoid,  the  anterior 
belly  of  the  Omo-hyoid,  the  Sterno-hyoid  and 
Sterno-thyroid  muscles,  and  beneath  the  last- 
named  muscles  by  the  pre-tracheal  layer  of  the 
deep  fascia,  which  forms  a  capsule  for  the 
gland. 

The  deep  or  internal  surface  is  moulded 
over  the  underlying  structures — viz.,  the  thy- 
roid and  cricoid  cartilages,  the  trachea,  the 
inferior  constrictor  and  posterior  part  of  the 
Crico-thyroid  muscles,  the  oesophagus  (par- 
ticularly on  the  left  side  of  the  neck),  the  supe- 
rior and  inferior  thyroid  arteries,  and  the  recurrent  laryngeal  nerves. 

The  deep  surface  of  each  lobe  is  fixed  by  bands  of  fibrous  tissue  passing  from 
the  capsule  of  the  isthmus  and  lateral  lobes  to  the  sides  of  the  cricoid  cartilage  and 
the  posterior  fascia  of  the  trachea.  These  bands  are  called  the  lateral  or  suspen- 
sory ligaments.  Because  of  this  fixation  to  the  larynx  and  trachea  by  the  capsule 
and  by  the  lateral  ligaments,  the  thyroid  gland  moves  with  the  trachea  and  ascends 
during  the  act  of  swallowing.  The  recurrent  laryngeal  nerve  on  each  side  is  in 
contact  with  the  outer  and  posterior  surface  of  the  suspensory  ligament. 

The  anterior  border  is  thin,  and  inclines  obliquely  from  above  downward  and 
inward  toward  the  middle  line  of  the  neck,  while  the  posterior  border  is  thick  and 
overlaps  the  common  carotid  artery.  Each  lobe  is  about  two  inches  in  length,  its 
greatest  width  is  about  one  inch  and  a  quarter,  and  its  thickness  about  three- 
quarters  of  an  inch.    The  posterior  border  is  over  the  common  carotid  artery  and 


Fig.  997.— The  thyroid  gland.    (Spalteholz.) 


1  Diseases  of  the  Thyroid  Gland.     By  James  Berry. 


«  Ibid. 


8  Ibid. 


THE   THYROID   BODY  OB    GLAND  1403 

touches  the  oesophagus  and  pharynx.  The  carotid  artery  usually  makes  a  groove 
upon  the  gland. 

The  Isthmus  (isthmus  glandulae  thyreoidea), — The  isthmus  connects  the  lower 
third  of  the  two  lateral  lobes;  it  measures  about  half  an  inch  in  breadth  and  the 
same  in  depth,  and  usually  covers  the  second  and  third  rings  of  the  trachea,  but 
sometimes  also  the  first  and  fourth  rings.  Its  situation  presents,  however,  many 
variations,  a  point  of  importance  in  the  operation  of  tracheotomy.  In  the  middle 
line  of  the  neck  it  is  covered  by  the  skin  and  fascia,  and  close  to  the  middle  line, 
on  either  side,  by  the  Sterno-hyoid  muscle.  Across  its  upper  border  run  branches 
of  the  superior  thyroid  artery  and  vein;  at  its  lower  border  is  a  branch  of  the 
inferior  thyroid  veins.  Sometimes  the  isthmus  is  altogether  wanting,  the  two 
lateral  lobes  being  completely  separate. 

The  third,  pjnramidal  or  middle  lobe  is  called  the  pyramid  of  Lalouette.  It  is  not 
constant,  but  is  frequently  found.  Occasionally  it  arises  from  the  upper  part  of 
the  isthmus,  or  from  the  adjacent  portion  of  either  lobe,  but  most  commonly  from 
the  left  lobe,  and  ascends  in  front  of  the  thyroid  cartilage  in  the  direction  of  the 
middle  of  the  hyoid  bone.  It  may  reach  the  bone  or  may  not  reach  it.  If  it 
reaches  the  bone  it  is  attached  to  it.  If  it  does  not  reach  the  bone,  fibrous  tissue, 
which  often  contains  muscle,  is  prolonged  from  the  tip  of  the  pyramid  to  the 
back  of  the  bone  or  to  the  thyro-hyoid  membrane.  The  pyramid  is  occasionally 
quite  detached,  or  divided  into  two  or  more  parts,  or  altogether  wanting, 

A  few  muscular  bands,  derived  from  the  Thyro-hyoid  muscles,  are  occasionally 
found  attached,  above,  to  the  body  of  the  hyoid  bone,  and  below  to  the  isthmus 
of  the  gland  or  its  pyramidal  process.  These  form  a  muscle,  which  was  named 
by  Soemmerring  the  Levator  glandulae  thyreoidae. 

Accessory  Thyroids  {glandulae  thyreoideae  accessoriae). — Frequently  small 
isolated  masses  of  thyroid  tissue  exist.  They  are  found  particularly  about  the 
lateral  lobes  of  the  thyroid  gland  in  the  sides  of  the  neck  or  just  above  the  hyoid 
bone,  and  are  called  accessory  thyroids.  Accessory  thyroids  may  also  exist  by  the 
side  of  the  pyramidal  lobe  or  upon  the  trachea,  as  low  even  as  the  level  of  the  arch 
of  the  aorta.  These  isolated  portions  of  gland  tissue  represent  isolated  portions 
of  the  median  thyroid  rudiment.  Sometimes  accessory  thyroid  tissue  is  found 
in  the  root  of  the  tongue  or  in  the  interior  of  the  larynx.  Berry  points  out  that  a 
distinction  must  be  made  between  true  congenital  accessory  thyroids  and  masses 
of  encapsuled  thyroid  tissue  which  "have  been  extruded  from  the  gland." 

Structure  of  the  Th3n:oid  (Fig.  998). — The  thyroid  body  is  invested  by  a  thin 
capsule  of  connective  tissue  which  projects  into  its  substance  as  a  framework  and 
imperfectly  divides  it  into  masses  of  irregular  form  and  size,  known  as  lobules. 
More  slender  septa  separate  the  secretory  alveoli  from  one  another.  When  the 
organ  is  cut  into,  it  is  of  a  brownish-red  color,  and  is  seen  to  be  made  up  of  a 
number  of  closed  vesicles  or  alveoli  containing  a  yellow  glairy  fluid  and  separated 
from  each  other  by  intermediate  connective  tissue. 

According  to  Baber,  who  has  published  some  important  observations  on  the 
minute  structure  of  the  thyroid,^  the  vesicles  of  the  thyroid  of  the  adult  animal 
are  generally  closed  cavities;  but  in  some  young  animals  {e.g.,  young  dogs)  the 
vesicles  are  more  or  less  tubular  and  branched.  This  appearance  he  supposes 
to  be  due  to  the  mode  of  growth  of  the  gland,  and  merely  indicating  that  an 
increase  in  the  number  of  vesicles  is  taking  place.  Each  vesicle  is  lined  by  a  single 
layer  of  epithelium,  the  cells  of  which  are  cubical  or  cylindrical.  Between  the 
epithelial  cells  exists  a  delicate  reticulum.  The  vesicles  are  of  various  sizes  and 
shapes,  and  contain  as  a  normal  product  a  viscid,  homogeneous,  semi-fluid, 
slightly  yellowish  material  which  frequently  contains  blood,  the  red  corpuscles  of 


1  Researches  on  the  Minute  Structure  of  the  Thyroid  Glands,  Phil.  Trans.,  part  iii.,  1881, 


k 


1404 


THE   DUCTLESS    GLANDS 


which  are  found  in  it  in  various  stages  of  disintegration  and  decolorization,  the 
yellow  tinge  being  probably  due  to  the  hoemoglobin,  which  is  thus  set  free  from 
the  colored  corpuscles.  This  normal  product  is  known  as  colloid  material,  and  it 
is  secreted  by  the  epithelium.  What  part  if  any  the  colloid  plays  in  the  formation 
of  the  internal  secretion  of  the  gland  is  not  known.  It  is  cjuite  possible  that  the 
colloid  corresponds  to  the  external  secretion  of  glands  with  ducts  and  that  the 
true  internal  secretion  passes  directly  into  the  capillaries  which  form  a  network 
about  the  alveoli  (Szymonowicz),  or  passes  into  the  lymphatics.  In  the  thyroid 
gland  of  the  dog,  Baber  has  found  large  round  cells,  parenchymatous  cells,  each 
provided  with  a  single  oval-shaped  nucleus,  which  migrate  into  the  interior 
of  the  gland-vesicles.  Between  the  thyroid  vesicles  in  the  human  being  are  col- 
lections of  romid  cells.  They  are,  in  reality,  miniature  vesicles,  and  are  much 
more  numerous  in  youth  than  in  old  age. 

The  capillary  blood-vessels  form  a  dense  plexus  in  the  connective  tissue  around 
the  vesicles,  between  the  epithelium  of  the  vesicles  and  the  endothelium  of  the 
lymph-spaces,  which  latter  surround  a  greater  or  smaller  part  of  the  circumference 


Vesicle. 


Lymphatic  vessel. 


Wall  of  gland-vesicle 


Fig.  998. — Minute  structure  of  the  thyroid.     From  a  transverse  section  of  the  thyroid  of  a  dog. 

diagrammatic.     (Baber.) 


Semi- 


of  the  vesicles.  These  lymph-spaces  empty  themselves  into  Isrmphatic  vessels 
which  run  in  the  interlobular  connective  tissue,  not  uncommonly  surrounding  the 
arteries  which  they  accompany,  and  communicate  with  a  network  in  the  capsule 
of  the  gland.  Small  glands  may  be  connected  with  this  network.  Baber  has 
found  in  the  lymphatics  of  the  thyroid  a  viscid  material  which  is  morphologically 
identical  with  the  normal  constituent  of  the  vesicle. 

Vessels  and  Nerves.—The  arteries  (Figs.  392  and  393;  see  also  p.  602)  supply- 
ing the  thyroid  are  the  superior  thyroid  from  the  external  carotid,  and  the  inferior 
thyroid  from  the  thyroid  axis  of  the  first  part  of  the  subclavian.  Sometimes  there 
is  an  additional  vessel,  the  thyroidea  media  or  ima,  usually  arising  from  the 
innominate  artery,  but  sometimes  from  the  arch  of  the  aorta  or  the  common  caro- 
tid. It  ascends  upon  the  front  of  the  trachea.  The  superior  thyroid  artery  reaches 
the  summit  of  the  upper  horn  of  the  gland,  and  usually  at  this  point  gives  off  a 
vessel  which  courses  down  the  posterior  surface  of  the  gland.  The  main  trunk 
passes  downward  and  inward  at  the  junction  of  the  inner  and  anterior  border  of 
the  upper  horn,  giving  branches  to  adjacent  structures  and  sending  branches  over 


THE   THYROID    BODY  OR    GLAND  1405 

the  anterior  surface  of  the  thyroid  gland.  It  reaches  the  isthmus  and  crosses 
the  isthmus  at  its  upper  border  to  anastomose  with  the  artery  from  the  other  side. 
The  inferior  thyroid  artery,  which  is  usually  larger  than  the  superior,  after  it 
has  passed  posterior  to  the  sheath  of  the  carotid  and  the  sympathetic  nerve,  reaches 
the  posterior  surface  of  the  gland.  At  this  point  branches  are  given  off;  some  pass 
into  the  hilum;  the  others  go  to  the  posterior  surface  of  the  gland.  The  relation 
of  the  artery  to  the  recurrent  laryngeal  nerve  is  very  important  to  the  surgeon. 
"Usually  the  main  trunk  of  the  artery  passes  behind  the  nerve;  sometimes  the 
artery  breaks  up  before  reaching  the  nerve ;  in  this  case  one  or  more  of  the  branches 
may  pass  in  front  of  it.  Much  less  commonly  the  main  trunk  or  all  its  branches 
will  be  found  to  lie  in  front  of  the  nerve. "^  If  the  thyroidea  ima  is  present  it  goes 
to  the  lower  part  of  the  gland.  The  larger  branches  of  the  thyroid  arteries  are 
beneath  the  capsule  and  upon  the  surface  of  the  gland;  smaller  branches  pass  to 
the  interior  of  the  gland  (Berry).  The  arteries  are  remarkable  for  their  large 
size  and  frequent  anastomoses. 

The  thyroid  veins  (Figs.  447  and  448;  see  also  p.  731)  form  a  plexus  upon  the 
surface  of  the  gland  and  beneath  the  capsule.  Here  and  there  veins  pass  through 
the  capsule  and  go  to  adjacent  venous  trunks.  Berry,  accepting  Kocher's  descrip- 
tion, notes  the  following  veins:  The  superior  thyroid  vein  runs  with  the  superior 
thyroid  artery  and  passes  to  the  internal  jugular  vein.  A  transverse  vein  of  the 
upper  border  of  the  isthmus  joins  the  two  superior  thyroid  veins.  A  single  vein, 
the  middle  thyroid,  sometimes  emerges  from  the  side  of  the  gland  and  passes  to 
the  internal  jugular.  Usually,  however,  instead  of  this  single  vein  there  are  two 
veins,  the  superior  and  inferior  accessory  thj^rroids.  The  superior  accessory  thyroid 
emerges  from  the  outer  side  of  the  upper  horn,  below  the  apex,  and  passes  to  the 
internal  jugular.  The  inferior  accessory  thjrroid  emerges  from  the  posterior  and 
inferior  portion  of  the  gland  and  passes  to  the  internal  jugular.  The  veins  from  the 
lower  border  of  the  gland  vary  greatly.  A  vein  passes  vertically  down  on  each  side 
in  front  of  the  trachea  from  the  isthmus  and  from  the  inner  side  of  the  inferior  horn. 
It  is  called  by  Kocher  the  thyroidea  ima.  The  vein  of  the  left  side  passes  to  the  left 
innominate;  the  vein  of  the  right  side  passes  to  the  right  innominate  or  left  innom- 
inate. As  Berry  points  out,  the  vein  of  one  side  may  be  small  or  may  be  absent, 
or  the  two  veins  may  unite  and  form  one  vein  which  enters  the  left  innominate. 
An  inferior  thyroid  vein  is  often  present.  It  is  of  small  size,  emerges  at  the  inferior 
and  external  part  of  the  gland,  and  passes  to  the  corresponding  innominate  vein.^ 

The  lymphatics  are  numerous  and  of  large  size.  Collecting  trunks  arise  from  a 
network  within  the  capsule.  Some  trunks  ascend  from  the  upper  margin  of  the 
isthmus  and  reach  the  gland  in  front  of  the  larynx ;  others  ascend  along  the  superior 
thyroid  artery  and  reach  the  glands  at  the  bifurcation  of  the  carotid.  Descending 
trunks  from  the  lower  margin  of  the  isthmus  reach  the  glands  in  front  of  the 
trachea;  trunks  from  the  side  of  the  gland  descend  to  the  glands  about  the  recur- 
rent laryngeal  nerve  .^ 

The  nerves  are  derived  from  the  middle  and  inferior  cervical  ganglia  of  the  sym- 
pathetic, and  from  the  inferior  lar3nigeal  nerves.  Probably  there  is  also  a  branch 
from  each  superior  laryngeal  nerve. 

Surgical  Anatomy. — The  thyroid  gland  may  be  congenitally  absent,  and  when  it  is  the  indi- 
vidual suffers  from  the  worst  form  of  cretinism.  One  lobe  may  he  congenitally  absent,  but 
this  will  provoke  no  trouble  unless  the  other  lobe  undergoes  atrophy. 

Complete  removal  of  the  thyroid  and  parathyroids  will  produce  operative  myxoedema  (cachexia 
strumi'priva) ,  unless  accessory  thyroids  enlarge  and  perform  the  functions  of  the  thyroid. 

The  thyroid  gland  may  be  congenitally  enlarged.  The  gland  tends  to  atrophy  in  old  age. 
It  is  atrophied  in  myxoedema  and  cretinisin.  Some  forms  of  thyroid  enlargement  are  called 
goitre. 

1  Diseases  of  the  Thyroid  Gland.    By  James  Berry.  -Ibid. 

^  The  Lymphatics.    By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


1406 


THE   DUCTLESS    GLANDS 


When  all  parts  of  the  gland  enlarge  the  condition  is  known  as  'parenchymatous  goitre. 

Adenomatous  goitre  consists  of  an  adenoma  or  of  adenomata.  In  cystic  goitre  there  is  one 
or  more  cysts  due  to  cystic  degeneration  of  adenomata  or  to  fusion  of  adjacent  follicles. 

A  pulsating  goitre  is  one  which  receives  impulses  from  the  carotid  pulsations.  In  a  fibroid 
goitre  there  is  increase  of  interstitial  connective  tissue.  A  goitre  which  passes  back  of  the  sternum 
IS  known  as  substernal  or  intrathoracic.  A  goitre  may  extend  back  of  the  trachea  or  back  of 
the  oesophagus. 

Exophthalmic  goitre,  Graves's  disease  or  Basedow's  disease,  is  a  remarkable  disease.  Its  three 
chief  symptoms  are  enlargement  of  the  thyroid,  or  goitre ;  prominence  of  the  eyeballs,  or  exoph- 
thalmos, and  very  rapid  pulse,  or  tachycardia.  Dyspnoea,  tremor,  and  various  other  symptoms 
are  usually  found.  The  thyroid  gland  may  be  the  seat  of  a  carcinoma  or  sarcoma  {malignant 
goitre),  syphilitic  or  tuberculous  disease,  ordinary  inflammation,  suppuration,  or  hydatid  disease; 
For  the  relief  of  ordinary  goitre  various  methods  have  been  employed.  Tapping,  injection  of 
astringents,  simple  incision,  and  the  seton  are  obsolete.  Ligature  of  the  thyroid  arteries  is  rarely 
performed  as  a  curative  measure.  The  superior  and  inferior  thyroids  of  one  side  have  been  tied 
in  some  cases;  all  four  thyroids  in  other  cases.  Jaboulay  has  performed  exothyropexy.  In  this 
operation  the  gland  is  dislocated  from  its  bed,  brought  out  of  the  wound,  and  left  exposed,  in 
hope  that  it  will  atrophy 

Division  of  the  isthmus  is  occasionally  practised  to  relieve  dyspnoea.  The  operation  some- 
times succeeds,  but  often  fails. 

Extirpation  of  one-half  or  two-thirds  of  the  gland  is  a  very  successful  operation.  Removal  of 
the  entire  gland  with  the  parathyroids  will  be  followed  by  operative  myxoedema. 

In  extirpating  a  lobe  of  the  thyroid  great  care  must  be  taken  to  avoid  tearing  the  capsules,  as  if 
this  happens  the  gland-tissue  bleeds  profusely.  The  thyroid  arteries  should  be  ligatured  on  the 
diseased  side  before  an  attempt  is  made  to  remove  the  mass,  and  in  ligaturing  the  inferior  thy- 
roid the  position  of  the  recurrent  laryngeal  nerve  must  be  borne  in  mind,  so  as  not  to  include 
it  in  the  ligature. 

A  cystic  or  solid  tumor  of  the  thyroid  may  be  removed  by  intra  glandular  enucleation.  If 
operation  becomes  necessary  in  exophthalmic  goitre,  partial  extirpation  is  usually  preferred. 

Bilateral  extirpation  of  the  cervical  ganglia  of  the  sympa- 
thetic (sympathectomy  or  Jonnesco's  operation)  has  been 
practised  by  some  surgeons  for  exophthalmic  goitre.  The 
value  of  the  procedure  is  uncertain. 

Parathyroids  (Fig.  999).— If  the  thyroid  gland 
has  been  carefully  detached,  two  round  bodies 
of  small  size  may  be  found  embedded  upon  the 
trachea  or  upon  the  surface  of  the  lateral  lobe  of 
the  gland,  between  the  terminal  branches  of  the 
inferior  thyroid  artery.  "These  are  the  para- 
thyroids, about  the  size  of  orange-seeds,  and 
brownish-red  in  color."^  These  masses  are  con- 
stant in  man  and  are  more  distinct  in  infants 
than  in  adults.  Although  the  parathyroids  lie 
on  or  in  the  thyroid,  they  are  always  completely 
separated  from  it  by  capsules  of  connective 
tissue.  The  parathyroids  are  divided  from  their 
situation  into  external  and  internal.  The  former, 
usually  two  in  number,  are  situated,  one  on  each 
side,  in  relation  to  the  postero-internal  surface 
of  the  lateral  lobe;  sometimes  they  are  duplicated. 
The  latter,  also  usually  two  in  number,  are  placed 
one  in  or  on  each  lateral  lobe,  generally  near  its 
mesial  surface. 

Structure. — The  structure  of  the  parathyroids 

is  different  from  that  of  the  thyroid.    They  are 

composed  of  solid  masses  of  epithelial  cells  arranged  in  a  more  or  less  columnar 

fashion   with    numerous    intervening   capillaries.     The   columns   of   the   para- 


FiG.  999.— The  position  of  the  parathy- 
roid glands.  View  from  behind.  (Zucker- 
kandl.) 


*  Practical  Anatomy.    By  Prof.  Alfred  W.  Hughes. 


THE    THYMUS    GLAND 


1407 


thyroids  anastomose.  There  is  much  lymphoid  tissue  connected  with  the 
columns.  Some  regard  the  parathyroids  as  embryonic  portions  of  the  thyroid. 
This  view  seems  to  gain  probabihty  from  the  statement  that  after  complete 
thyroidectomy,  the  parathyroids  having  been  left,  these  structures  increase  in 
size,  and  apparently  prevent  operative  myxoedema.  If  they  are  also  removed, 
myxoedema  arises.  Nevertheless,  MacCallum  says  "there  is  no  histological  proof 
that  parathyroid  tissue  can  ever  become  converted  into  thyroid  tissue."  Most 
observers  regard  the  parathyroids  as  distinct  glands  possessed  of  a  special  func- 
tion. Certain  it  is,  as  Gley  and  others  have  shown,  removal  of  the  parathyroids 
from  herbivora  leaving  the  thyroid  intact  is  followed  by  spasms,  tetany,  etc.,  just 
as  complete  thyroidectomy  is  followed  by  such  symptoms  in  carnivora.^ 


THE  THYMUS  GLAND  (Fig.  1000). 

The  thymus  gland  is  a  temporary  organ,  attaining  its  full  size  at  the  end  of  the 
second  year,  when  it  ceases  to  grow  and  remains  practically  stationary  until 
puberty,  at  which  period  it  rapidly  degenerates.  It  does  not  entirely  disappear, 
for  the  shrunken  and  degenerated  mass,  even  later  in  life,  maintains  a  likeness  to 
the  original  form  and  retains  within  its  substance  small  portions  of  thymus  tissue 
(Waldeyer).    If  examined  when  its  growth  is  most  active,  it  will  be  found  to  con- 


FiG.  1000. — The  thymus  gland  in  an  infant  two  months  old.     (Poiricr  and  Charpy.) 


sist  of  two  lateral  lobes  placed  in  close  contact  along  the  middle  line,  situated 
partly  in  the  superior  mediastinum,  partly  in  the  neck,  and  extending  from  the 
level  of  the  fourth  costal  cartilage  upward  as  high  as  the  lower  border  of  the 
thvroid  gland.  It  is  covered  by  the  sternum  and  by  the  origins  of  the  Sterno- 
hyoid and  Sterno-thyroid  muscles.     Below,  it  rests  upon  the  pericardium,  being 

1  Internal  Secretions.     By  William  Hanna  Thom.«on.     New  York  Medical  Journal,  November  19,  1904. 


1408 


THE   DUCTLESS    GLANDS 


separated  from  the  arch  of  the  aorta  and  great  vessels  by  a  layer  of  fascia.  In  the 
neck  it  lies  on  the  front  and  sides  of  the  trachea,  behind  the  Sterno-hyoid  and 
Sterno-thyroid  muscles.  The  two  lobes  generally  differ  in  size;  they  are  occa- 
sionally united  so  as  to  form  a  single  mass,  and  are  sometimes  separated  by  an 
intermediate  lobe.  The  thymus  is  of  a  pinkish-gray  color,  is  soft  and  is  lobu- 
lated  on  its  surfaces.  It  is  about  two  inches  in  length,  one  and  a  half  inches 
in  breadth  below,  and  about  three  or  four  lines  in  thickness.  At  birth  it  weighs 
about  half  an  ounce. 

Structure  (Figs.  1001  and  1002) . — Each  lateral  lobe  is  composed  of  numerous 
lobules  held  together  by  delicate  areolar  tissue,  the  entire  gland  being  enclosed  in 
an  investing  capsule  of  a  similar  but  denser  structure.  The  primary  lobules  vary 
in  size  from  a  pin's  head  to  a  small  pea,  and  are  made  up  of  a  number  of  small 
nodules  or  follicles  which  are  irregular  in  shape  and  are  more  or  less  fused 
together,  especially  toward  the  interior  of  the  gland.  Each  follicle  consists  of  a 
medullary  and  cortical  portion,which  differ  in  many  essential  particulars  from  each 
other.    The  cortical  portion  is  mainly  composed  of  lymphoid  cells  supported  by  a 

delicate  reticulum.  In  addition  to  this  reticulum,  of 
which  traces  only  are  found  in  the  medullary  portion, 
there  is  also  a  network  of  finely  branched  cells  which 
is  continuous  with  a  similar  network  in  the  medul- 
lary portion.  This  network  forms  an  adventitia  to 
the  blood-vessels.  In  the  medullary  portion  there 
are  but  few  lymphoid  cells,  but  there  are,  especially 
toward  the  centre,  granular  cells  and  concentric 
corpuscles.  The  granular  cells  are  rounded  or 
flask-shaped  masses  attached  (often  by  fibrillated 
extremities)  to  blood-vessels  and  to  newly  formed 
coimective  tissue.  The  concentric  corpuscles  are 
composed  of  a  central  mass  consisting  of  one  or 
more  granular  cells,  and  of  a  capsule  which  is 
formed  of  epithelioid  cells  which  are  continuous 
with  the  branched  cells  forming  the  network  men- 
tioned above. 

Each  follicle  is  surrounded  by  a  capillary  plexus 

from  which  vessels  pass  into  the  interior  and  radiate 

Fig.  1001.— Minute  structure  of  thy-   ^^om  the  periphery  toward  the  centre,  and  form  a 

Ty.ntt-S^l'lpW'in  length!   ^^^^nd  zouc  just  withiu  the  margin  of  the  medullary 

portion.  In  the  centre  of  the  medulla  there  are  very 
few  vessels,  and  they  are  of  minute  size. 

Watney  has  made  the  important  observation  that 
haemoglobin  is  found  in  the  thymus  either  in  cysts 
or  in  cells  situated  near  to  or  forming  part  of  the 
concentric  corpuscles.  This  haemoglobin  varies 
from  granules  to  masses  exactly  resembling  colored  blood -corpuscles,  oval  in  the 
bird,  reptile,  and  fish;  circular  in  all  mammals  except  in  the  camel.  Dr.  Watney 
has  also  discovered  in  the  lymph  issuing  from  the  thymus  similar  cells  to  those 
found  in  the  gland,  and,  like  them,  containing  haemoglobin  either  in  the  form  of 
granules  or  masses.  From  these  facts  he  arrives  at  the  physiological  conclusion 
that  the  thymus  is  one  source  of  the  colored  blood-corpuscles. 

Vessels  and  Nerves. — The  arteries  supplying  the  thymus  are  derived  from 
the  internal  mammary  and  from  the  superior  and  inferior  th3n'oid.  The  veins 
terminate  in  the  two  innominate  veins,  and  in  the  internal  mammary  and  the 
thyroid  veins.  The  lymphatics  are  of  large  size,  arise  in  the  substance  of  the 
gland,  and  are  said  to  terminate  in  the  internal  jugular  vein.     The  nerves  are 


showing  the  bud-Uke  lobuH  and  gland 
ular  elements.  2,  cells  of  the  thymu;-, 
mostly  from  a  man  ;  a,  free  nuclei  ; 
h,  small  cells  ;  c,  larger  ;  d,  larger,  with 
oil-globules,  from  the  ox  ;  e,  i,  cells 
completely  filled  with  fat,  at  /  without 
a  nucleus  ;  g,  h,  concentric  bodies  ;  a, 
an  encapsulated  nucleated  cell ;  h,  a 
composite  structure  of  a  similar  nature. 


THE    CAROTID    GLAND    OB    CAROTID    BODY 


1409 


exceedingly  minute;  they  are  derived  from  the  pneumogastxic  and  sympathetic. 
Branches  from  the  descendens  hypoglossi  and  phrenic  reach  the  investing  cap- 
sule, but  do  not  penetrate  into  the  substance  of  the  gland. 


Artery. 


Artery 


Fig.  1002. — Minute  structure  of  the  thymus  gland.  Follicle  of  injected  thymus  from  a  calf,  four  days  old, 
slightly  diagramniatic,  magnified  about  .50  diameters.  The  large  vessels  are  dispo.sed  in  two  rings,  one  of  which 
surrounds  the  follicle,  the  other  lies  just  within  the  margin  of  the  medulla.  A  and  B,  from  thymus  of  camel, 
examined  without  addition  of  any  reagent.  Magnified  about  400  diameters.  A,  large  colorless  cell  containing 
small  oval  masses  of  haemoglobin.  Similar  cells  are  found  in  the  lymph-glands,  spleen,  and  medulla  of  bone  ; 
B,  colored  blood-corpuscles.     (Watney.) 


THE  CAROTID  GLAND  OR  CAROTID  BODY  (GLOMUS  CAROTICUM). 

This  body,  when  present,  lies  in  the  carotid  bifurcation,  to  the  inner  side  of  the 
common  carotid  below  the  bifurcation,  or  on  the  posterior  surface  of  the  internal  or 
of  the  external  carotid.  It  is  often  absent.  It  lies  in  fatty  tissue  and  is  surrounded 
by  a  fibrous  capsule  which  is  attached  to  the  carotid  sheath.  The  carotid  gland 
is  about  the  size  of  a  grain  of  corn;  it  is  oval  in  shape  and  reddish-brown  in  color. 
The  capsule  of  the  gland  sends  septa  inward.  The  septa  divide  the  organ  into 
follicles  or  cell-balls.  These  cell-balls  are  composed  of  endothelial  cells  and  are 
associated  with  blood  capillaries.  A  branch  (or  branches)  from  the  carotid  artery 
enters  the  carotid  gland,  and  the  gland  is  closely  connected  with  the  carotid 
plexus  of  the  ssrmpathetic.  (This  structure  has  been  recently  studied  by  John 
Funke,^  Reclus  and  Chevasson,^  Paltauf,  Kartschenko,  and  Marchand.) 

Surgical  Anatomy. — Tumors  may  arise  from  this  structure.  Such  a  tumor  is  apt  to  be 
above  the  level  of  the  upper  margin  of  the  thyroid  cartilage  and  in  most  cases  it  moves  with 
each  arterial  beat. 


'  American  Medicine,  vol.  viii.,  No.  3. 


8  Bull,  et  mem.  de  la  Soc.  de  chir.  de  Paris,  1903,  No.  18. 

89 


1410  THE  DUCTLESS    GLANDS 

THE  COCCYGEAL  GLAND  OR  COCCYGEAL  BODY  OR  LUSCHKA'S 
GLAND  (GLOMUS  COCCYGEUM). 

Lying  near  the  tip  df  the  coccyx  in  a  small  tendinous  interval  formed  by  the 
union  of  the  Levator  ani  muscles  and  just  above  the  coccygeal  attachment  of 
the  Sphincter  ani,  is  a  small  conglobate  body  about  as  large  as  a  lentil  or  a  pea, 
first  described  by  Luschka,'  and  named  by  him  the  coccygeal  gland.  Its  most 
obvious  connections  are  with  the  arteries  of  the  part.  It  is  similar  in  structure 
to  the  carotid  body. 

Structure. — It  consists  of  a  congeries  of  small  arteries  with  little  aneurismal 
dilatations  derived  from  the  middle  sacral  and  freely  communicating  with  each 
other.  These  vessels  are  enclosed  in  one  or  more  layers  of  polyhedral  granular 
cells,  and  the  whole  structure  is  invested  in  a  capsule  of  connective  tissue  which 
sends  in  trabeculae,  dividing  the  interior  into  a  number  of  spaces  in  which  the 
vessels  and  cells  are  contained.  Nerves  pass  into  this  little  body  from  the  sympa- 
thetic, but  their  mode  of  termination  is  unknown.  Macalister  believes  the  glom- 
erulus of  vessels  "consists  of  the  condensed  and  convoluted  metameric  dorsal 
arteries  of  the  caudal  segments  embedded  in  tissue  which  is  possibly  a  small  per- 
sisting fragment  of  the  neurenteric  canal."  It  resembles  the  carotid  gland  in 
structure,  and  is  probably  one  of  the  ductless  glands. 

1  Der  Hirnanhang  und  die  Steissdriise  des  Menschen,  Berlin,  1860;  Anatomic  des  Menschen,  Tubingen,  1864, 
vol.  ii.  pt.  2,  p.  187. 


THE  UUIMRY  OEGANS. 


THE  KIDNEYS  (RENES)  (Figs.  1003,  1004,  1005). 

THE  Kidneys  are  large  glands.  They  are  two  in  number,  and  are  situated 
in  the  back  part  of  the  abdomen,  near  the  spinal  column.  Their  function  is 
to  separate  from  the  blood  certain  materials  which,  when  dissolved  in  a  quantity 
of  water,  also  separated  from  the  blood  by  the  kidneys,  constitute  the  urine. 

They  are  placed  in  the  loins,  one  on  each  side  of  the  vertebral  column,  behind 
the  peritoneum,  and  are  surrounded  by  a  mass  of  fat  and  loose  areolar  tissue,  which 


TERMINAL 

PART  OF 

PROSTATE 

VEIN 

ORIGIN   OF 

DUCTUS    YMy. 
CHOLEOOCHUS    flV' 


FIBROUS 

CAPSULE 

PELVIS  OF 

KIDNEY 


RIGHT 

SPERMATIC 

VEIN 


LEFT 

SPERMATIC 
ARTERY 
AND  VEIN 


FIBROUS 

SUBPERITONEAL 

LAMINA 


Fig.  1003. — The  situation,  direction,  forms,  and  supports  of  the  kidney.     (Sappey.) 

constitutes  the  fatty  capsule  (capsula  adi/posa)  (Figs.  1008  and  1009).  There  are 
two  distinct  layers  in  this  fatty  capsule.  The  superficial  fatty  layer  is  the  pararenal 
fat.^  Keen  calls  this  layer  the  transversalis  layer  of  fat,  because  it  is  derived  from  the 
transversalis  fascia.^  The  deeper  and  thicker  perirenal  layer  is  the  fxue  perinephric 
fat  (Fig.  1009).  The  deeper  layer  of  fat  completely  surrounds  the  kidney,  and  is 
somewhat  adherent  to  the  fibrous  renal  capsule.     The  fat  about  the  kidney  does 

1  See  Gerota,  Arch.  f.  Anatomic.  Leipzic,  1895;  Zuckerkandl,  Medizinische  Jahrbiicher,  Vienna,  1883. 
*  W.  W.  Keen,  in  American  Medicine,  January  31,  1903. 

(1411) 


1412 


THE    UBINABY  OBQANS 


not  look  like  fat  in  other  regions,  but  is  soft,  delicate,  and  of  a  canary  yellow 
color.  These  two  layers  are  separated  by  a  layer  of  connective  tissue,  which  is 
the  posterior  layer  of  the  perirenal  fascia,  and  is  called  by  Zuckerkandl  the  retro-renal 
fascia  {jascia  retrorenalis)  {Y\g.  1008).  The  true  capsule  of  the  kidney  [tunica 
fibrosa)  is  thin,  smooth,  and  glistening.  The  inner  part  of  this  capsule  {tunica 
muscularis)  contains  unstriated  muscle  fibres.  The  true  capsule  can  be  easily 
separated  from  the  underlying  glandular  structure.  The  upper  extremity  of  the 
kidney  is  on  a  level  with  the  upper  border  of  the  twelfth  dorsal  vertebra,  the  lower 
extremity  on  a  level  with  the  third  lumbar  vertebra  (Fig.  1006).  The  right  kidney 
is  usually  on  a  slightly  lower  level  than  the  left,  probably  on  account  of  the  vicinity 
of  the  liver.    In  the  female  the  kidneys  are  a  little  lower  than  in  the  male. 

Each  kidney  is  about  four  and  a  half  inches  in  length,  two  to  two  and  a  half  in 
breadth,  and  rather  more  than  one  inch  in  thickness.  The  left  is  somewhat  longer, 
though  narrower,  than  the  right.  The  weight  of  the  kidney  in  the  adult  male  varies 
from  4^  ounces  to  6  ounces;  in  the  adult  female,  from  4  ounces  to  b\  ounces.  The 
combined  weight  of  the  two  kidneys  in  proportion  to  the  body  is  about  1  in  240. 


Fig.  1004. — Anterior  surface  of  the  kidney. 
(Bourgery.) 


Fig.  1005. 


-Posterior  surface  of  the  kidney. 
(Bourgery.) 


The  kidney  has  the  characteristic  form  of  a  "flattened  bean"  (Spalteholz).  It 
is  flattened  on  its  sides  and  presents  at  one  part  of  its  circumference  a  hollow. 
It  is  larger  at  its  upper  than  at  its  lower  extremity.  The  kidney  presents  for  exam- 
ination two  surfaces,  two  borders,  and  an  upper  and  lower  extremity. 

Surfaces.  The  Anterior  Surface  {jades  anterior)  (Figs.  1003  and  1004).— Its  ante- 
rior surface  is  convex,  looks  forward  and  outward,  and  is  partially  covered  by  peri- 
toneum. The  right  kidney  in  its  upper  three-fourths  is  in  contact  with  the  pos- 
terior part  of  the  under  surface  of  the  right  lobe  of  the  liver.  This  area  of  the  right 
kidney  is  flattened  {impressio  hepatica).  Toward  its  inner  border  it  is  covered  by 
the  second  part  of  the  duodenum,  while  its  lower  and  outer  part  is  in  relation  with 
the  hepatic  flexure  of  the  colon.  The  relation  of  the  second  part  of  the  duodenum 
to  the  front  of  the  right  kidney  is  a  varying  one.  The  left  kidney  is  covered  above 
by  the  posterior  surface  of  the  stomach,  below  the  stomach  by  the  pancreas,  behind 
which  are  the  splenic  vessels.  The  region  in  contact  with  the  stomach  is  markedly 
depressed  {impressio  gastrica).    Its  lower  half  is  in  contact  with  some  of  the  coils 


THE    KIDNEYS 


1413 


of  the  small  intestine  and  sometimes  with  the  third  part  of  the  duodenum.  Near 
its  outer  border  the  anterior  surface  lies  behind  the  spleen  and  the  splenic  flexure 
of  the  colon. 


Fig.  1006. — Posterior  surface  of  the  kidneys.      (Poirier  and  Cliarpy.) 


Fig.  1007. — Relation  of  the  kidney  to  the  vertebral  column,  ribs,  muscles,  and  lumbo-costal  ligaments. 

CPoirier  and  Charpy.) 


1414 


THE    U BINARY   ORGANS 


The  kidneys  are  partly  covered  in  front  by  peritoneum  and  partly  uncovered. 
On  the  right  kidney,  the  hepatic  area,  that  is  to  say  that  portion  of  the  kidney 
which  produces  the  renal  impression  on  the  liver,  is  covered  by  peritoneum,  which 
therefore  separates  the  kidney  from  the  liver;  the  duodenal  and  colic  areas  are  not 
peritoneal,  and  these  structures  are  connected  to  the  kidney  by  loose  connective 
tissue;  at  the  lower  and  inner  extremity  is  a  small  area,  the  mesocolic  area,  which 
is  covered  by  a  layer  of  peritoneum  of  the  greater  sac  and  by  the  colic  vessels. 
On  the  left  kidney  the  gastric  area  is  covered  by  the  peritoneum  of  the  lesser  sac; 
the  pancreatic  and  colic  areas  are  non-peritoneal ;  while,  as  on  the  right  side,  at  the 
lower  and  inner  extremity,  is  an  area,  mesocolic  area,  which  is  covered  by  the 
peritoneum  of  the  greater  sac  and  by  the  colic  vessels. 

The  Posterior  Surface  {jades  'posterior)  (Fig.  1005) . — The  posterior  surface  of  the 
kidney  is  flatter  than  the  anterior  and  is  directed  backward  and  inward.    It  is 


ELEVENTH 
RIB 


TWELFTH 
RIB 


POSTERIOR 

LAMELLA  OF 

PERIRENAL 

FASCIA 


FAT  BEHIND 
PERIRENAL 

FASCIA        /'      I 


PERITONEUM 

VESSELS  OF 
HILUM   OF 
KIDNEY 


«/'  SECTION 
OF  COLON 


ANTERIOR 
LAMELLA  O 
PERIRENAt 
FASCIA 


PERITONEUM 

TRUE 

PERINEPHRITIC 

FAT 


Fig.  1008. — Longitudinal  section,  showing  the 
arrangement  of  the  capsule  of  the  kidney. 
(After  Gerota.) 


__  QUADRATUS  LUM- 

"SACRO-LUM BALIS      BORUM  MUSCLE 
GROUP 

Fig.  1009. — ^Transverse  section,  showing  the  relations 
of  the  capsule  of  the  kidney  and  the  two  layers  of  fat. 
(After  Gerota.) 


entirely  devoid  of  peritoneal  covering,  being  embedded  in  areolar  and  fatty  tissue. 
It  lies  upon  the  Diaphragm,  the  anterior  layer  of  the  lumbar  aponeurosis,  the 
external  and  internal  arcuate  ligaments,  the  Psoas  and  Transversalis  muscles, 
one  or  two  of  the  upper  lumbar  arteries,  the  last  dorsal,  ilio-hypogastric,  and 
ilio-iiiguinal  nerves.  The  lumbo-costal  ligaments  overlie  the  posterior  surface  of 
the  kidney  (Fig.  1007).  The  right  kidney  rests  upon  the  twelfth  rib  (Fig.  1007), 
the  left  usually  on  the  eleventh  and  twelfth  ribs.  The  Diaphragm  separates  the 
kirlney  from  the  pleura  as  the  pleura  dips  down  to  form  the  phrenico -costal  sinus 
(Fig.  987),  but  frequently  the  muscular  fibres  of  the  Diaphragm  are  defective  or 
absent  over  a  triangular  area  immediately  above  the  external  arcuate  ligament, 
and  when  this  is  the  case  the  perirenal  areolar  tissue  is  in  immediate  apposition 
with  the  diaphragmatic  pleura.  In  the  lower  part  of  the  posterior  surface  of  the 
kidney  is  an  impression  produced  by  the  Quadratus  lumborum  muscle  and  called 


THE   KIDNEYS  1415 

the  impressio  musculaxis.  A  little  internal  to  this  a  flattening,  caused  by  the  Psoas 
muscle,  is  often  recognizable.  At  the  upper  part  of  the  posterior  surface  is  a  sulcus 
produced  by  contact  with  the  Diaphragm. 

Borders.  The  External  Border  (margo  lateralis)  (Figs.  1004  and  1005). — The 
external  border  is  convex,  and  is  directed  outward  and  backward,  toward  the 
postero-lateral  wall  of  the  abdomen.  On  the  left  side  it  is  in  contact,  at  its  upper 
part,  with  the  spleen  (Fig.  1003). 

The  Internal  Border  (margo  medialis)  (Figs.  1004  and  1005). — The  internal  bor- 
der is  concave,  and  is  directed  forward,  inward,  and  a  little  downward.  It  presents 
a  deep  longitudinal  fissure,  bounded  by  a  prominent  overhanging  anterior  and 
posterior  lip.  This  fissure  is  named  the  hilum  (Jiilus  renalis)  (Fig.  1010),  and 
allows  of  the  passage  of  the  vessels,  nerves,  and  ureter  into  and  out  of  the  kidney. 

Extremities.  The  Superior  Extremity  (extremitas  superior) (Figs.  1004  and  1005. 
— The  superior  extremity,  directly  slightly  inward  as  well  as  upward,  is  thick  and 
rounded,  and  is  surmounted  by  the  suprarenal  capsule  (Fig.  1010),  which  covers 
also  a  small  portion  of  the  anterior  surface. 

The  Inferior  Extremity  (extremitas  inferior)  (Figs.  1004  and  1005). — The  inferior 
extremity,  directed  a  little  outward  as  well  as  downward,  is  smaller  and  thinner 
than  the  superior.     It  extends  to  within  two  inches  of  the  crest  of  the  ilium. 

At  the  hilum  of  the  kidney  the  relative  position  of  the  main  structures  passing 
into  and  out  of  the  kidney  is  as  follows:  the  vein  is  in  front,  the  artery  in  the 
middle,  and  the  duct  or  ureter  behind  and  toward  the  lower  part  (Fig.  1005).  By 
a  knowledge  of  these  relations  the  student  may  distinguish  between  the  right  and 
left  kidney.  The  kidney  is  to  be  laid  on  the  table  before  the  student  on  its 
posterior  surface,  with  its  lower  extremity  toward  the  observer — that  is  to  say, 
with  the  ureter  behind  and  below  the  other  vessels;  the  hilum  will  then  be  directed 
to  the  side  to  which  the  kidney  belongs. 

General  Structure  of  the  Kidney. — The  kidney  is  surrounded  by  a  distinct 
investment  of  fibrous  tissue  (tunica  fibrosa),  which  forms  the  firm,  smooth,  true 
capsule  covering  the  entire  organ.  The  capsule  passes  over  the  margins  of  the 
hilum,  enters  the  interior  of  the  kidney,  and  covers  the  wall  of  the  sinus.  The 
true  capsule  is  closely  and  firmly  adherent  to  the  renal  pelvis  where  it  is  attached 
to  the  sinus.  It  closely  invests  it,  but  can  be  easily  stripped  off,  in  doing  which, 
however,  numerous  fine  processes  of  connective  tissue  which  pass  to  the  intrarenal 
connective  tissue  and  numerous  small  blood-vessels  are  torn  through.  Beneath 
this  fibrous  layer  a  thin  wide-meshed  network  of  unstriped  muscular  fibre  forms 
an  incomplete  covering  to  the  organ.  When  the  true  capsule  is  stripped  off,  the 
surface  of  the  kidney  is  found  to  be  smooth,  even,  and  of  a  deep-red  color. 

In  infants  fissures  extending  for  some  depth  may  be  seen  on  the  surface  of  the 
organ,  a  remnant  of  the  lobular  construction  of  the  gland  (Fig.  1027).  The  kid- 
ney is  dense  in  texture,  but  is  easily  lacerable  by  mechanical  force.  In  order  to 
obtain  a  knowledge  of  the  structure  of  the  gland,  a  vertical  section  must  be  made 
from  its  convex  to  its  concave  border,  and  the  loose  tissue  and  fat  removed 
around  the  vessels  and  the  excretory  duct  (Fig.  1010).  It  will  be  then  seen  that 
the  kidney  consists  of  a  central  cavity  surrounded  at  all  parts  but  one  by  the 
proper  kidney-substance.  This  central  cavity  is  called  the  sinus  (sinus  renalis), 
and  is  lined  by  a  prolongation  of  the  fibrous  coat  of  the  kidney,  which  enters 
through  a  longitudinal  fissure,  the  hilum  (hilus  renalis)  (Fig.  1010),  which  is 
situated  at  that  part  of  the  cavity  which  is  not  surrounded  by  kidney  structure. 
Through  this  fissure  the  blood-vessels  of  the  kidney  and  its  excretory  duct  pass, 
and  therefore  these  structures,  upon  entering  the  kidney,  are  contained  within  the 
sinus  (Fig.  1004).  The  excretory  duct  or  ureter,  after  entering,  dilates  into  a  wide, 
funnel-shaped  sac  named  the  pelvis  (pelvis  renalis)  (Figs.  1010  and  1011).  This 
divides  into  two  or  three  tubular  divisions,  which  subdivide  into  several  short, 


1416 


THE    URINARY   ORGANS 


truncated  branches  named  calices  or  infundibula  {calyces  renales),  all  of  which 
are  contained  in  the  central  cavity  of  the  kidney  (Figs.  1010  and  1011).  The 
blood-vessels  of  the  kidney,  after  passing  through  the  hilum,  are  contained  in 
the  sinus  or  central  cavity,  lying  between  its  lining  membrane  and  the  excretory 
apparatus,  before  entering  the  kidney-substance  (Fig.  1011). 

This  central  cavity,  as  before  mentioned,  is  surrounded  on  all  sides  except  at 
the  hilum  by  the  substance  of  the  kidney,  which  is  at  once  seen  to  consist  of  two 
parts — viz.,  of  an  external  granular  investing  part,  which  is  called  the  cortical 
portion  {substantia  corticalis) ;  and  of  an  internal  part,  the  medullary  portion  {sub- 
stantia medullaris) ,  made  up  of  a  number  of  dark-colored  pyramids,  with  their 
bases  resting  on  the  cortical  part  and  their  apices  converging  toward  the  centre, 
where  they  form  prominent  papillae,  the  renal  papillae  {papillae  renales),  which 
project  into  the  interior  of  the  calices  (Fig.  1010). 


SUPERIOR 
EXTREMITY 


CUT  SURFACE 
OF  KIDNEY 


Fig.  1010.— Vertical  section  of  kidney. 


INFERIOR 
EXTREMITY 

Fig.  1011. — The  right  kidney  with  its  pelvis  exposed,  viewed 
from  behind.     (Spalteholz.) 


The  cortical  substance  (Figs.  1010  and  1017)  is  of  a  bright  reddish-brown  color, 
soft,  granular,  and  easily  lacerable.  It  is  found  everywhere  immediately  beneath 
the  capsule,  and  is  seen  to  extend  in  an  arched  form  over  the  base  of  each  medul- 
lary pyramid.  Prolongations  of  the  cortical  substance  pass  between  the  pyramids 
toward  the  renal  sinus.  These  prolongations  are  the  cortical  columns  or  the  columns 
of  Bertin  {columnae  renales)  (Fig.  1010,  B  B).  The  columns  contain  blood-vessels, 
nerves,  and  lymphatics.  The  base  of  each  pyramid  (basis  pyramidis)  is  known 
as  the  intermediate  zone.  That  portion  of  the  cortical  substance  which  stretches 
from  one  cortical  column  to  the  next,  and  intervenes  between  the  base  of  the 
pyramid  and  the  capsule  (marked  by  the  dotted  line  extending  from  A  to  A'  in  Fig. 
1010),  is  called  a  cortical  arch,  the  depth  of  which  varies  from  a  third  to  half  an  inch. 

The  medullary  substance  (Figs.  1010  and  1017),  as  before  stated,  is  seen  to  con- 
sist of  red-colored,  striated,  conical  masses,  the  pyramids  of  Malpighi  {pyramides 


THE  KIDNEYS 


1417 


renales)  (Fig.  1010),  the  number  of  which,  varying  from  eight  to  eighteen,  corre- 
sponds to  the  number  of  lobes  of  which  the  organ  in  the  foetal  state  is  composed. 
The  pyramids  are  composed  of  straight  tubes  which  pass  between  the  apices  of 
the  papillae  and  the  cortical  margin.  They  enter  the  cortex  in  masses  called  the 
pyramids  of  Ferrein  (see  below).  The  sides  of  the  pyramids  of  Malpighi  are  con- 
tiguous with  the  cortical  columns,  while  the  apices,  known  as  the  papillae  of  the 
kidney  (papillae  renales)  (Figs.  1010  and  1014),  project  into  the  calices  of  the 
ureter,  each  calyx  receiving  two  or  three  papillae.  Radiating  from  the  bases  of 
the  pyramids  of  Malpighi  are  ridges  of  cortical  substance  with  distinct  depres- 
sions between  them.  These  ridges  are  the  medullary  rays  (pars  radiate)  or  P3n:a- 
mids  of  Ferrein  (Figs.  1013  and  1017).  The  labyrinth  of  the  cortex  (Fig.  1013)  is 
constituted  by  the  kiflney  substance  between  the  rays.     The  pyramids  of  Ferrein 

look  like  direct   continuations  of   the  medullary  sub-  

stance,  but,  in  reality,  they  are  in  the  cortex,  and  are 
formed  by  the  straight  tubes  extending  in  masses  into 
the  cortex.  The  pyramids  of  Ferrein  are  much  smaller 
than  the  pyramids  of  Malpighi.  In  the  columns  of 
Bertin  blood-vessels,  nerves,  and  lymphatics  pass  to  and 
emerge  from  the  sinus  by  way  of  small  foramina.  The 
summit  of  a  papilla  contains  a  number  of  orifices  of 
papillary  ducts.  Such  an  area  is  called  an  area  cribrosa 
(Fig.  1014). 

These  two  parts,  cortical  and  medullary,  so  dissimilar 
in  appearance,  are  very  similar  in  structure,  being 
made  up  of  urinary  tubes  and  blood-vessels  united  and 
bound  together  by  a  connecting  matrix  or  stroma. 

Minute  Anatomy. — The  uriniferous  tubes,  urinary  canals 
or  tubuli  urinif eri  {tvbuli  renales)  (Figs.  1012  and  1017), 
of  which  the  kidney  is  for  the  most  part  made  up, 
commence  in  the  cortical  portion  of  the  kidney.  Each 
tubule  begins  between  the  medullary  rays  (Fig.  1013) 
in  a  sac,  Bowman's  capsule  or  the  Malpighian  capsule 
(see  below) .  The  tubules,  as  a  rule,  after  pursuing 
a  very  circuitous  course  through  the  cortical  and  medul- 
lary parts  of  the  kidney,  finally  terminate  at  the  apices 
of  the  Malpighian  pyramids  by  open  mouths,  so  that 
the  fluid  which  they  contain  is  emptied  into  the 
dilated  extremity  of  the  ureter  contained  in  the  sinus 
of  the  kidney.  "  If  the  surface  of  one  of  the  papillae 
is  examined  with  a  lens,  it  will  be  seen  to  be  studded 
over  with  a  number  of  small  depressions  (foramiria 
papillaria),  from  sixteen  to  twenty  in  number,  and  in 
a  fresh  kidney,  upon  pressure  being  made,  fluid  will 
be  seen  to  exude  from  these  depressions.  They  are  the  orifices  of  the  tubuli 
uriniferi,  which  terminate  in  this  situation.  The  tubuli  uriniferi  begin  in  the  cortex 
as  the  Malpighian  bodies  or  corpuscles  (corpuscula  renis)  (Figs.  1012,  1013,  1015, 
1016,  and  1018),  which  are  smaU  rounded  masses,  varying  in  size,  but  average 
about  yfg-  of  an  inch  in  diameter.  They  are  of  a  deep-red  color,  and  are  found 
only  in  the  cortical  portion  of  the  kidney.  Each  of  these  little  bodies  is  composed 
of  two  parts — a  central  glomerulus  of  vessels,  called  a  Malpighian  tuft,  and  a  mem- 
branous envelope,  the  Malpighian  capsule  or  capsule  of  Bowman  (capsida  glomeruli), 
which  latter  is  a  small  pouch-like  commencement  of  a  uriniferous  tubule. 

The  Malpighian  Tuft  or  Vascular  Glomerulus  (Figs.  1015,  1016,  1017,  1022,  and 
1023)  is  a  network  of  convoluted  capillary  blood-vessels  held  together  by  scanty 


Fig.  1012. — Plan  of  uriniferous 
tubes.  A  A ,  Malpighian  bodies  ; 
B  B,  margin  of  medullary  struc- 
ture ;    C,   C.  C,   loop.s  of  Henle  ; 

D,  D,   D,   straight  tubes  cut  off  ; 

E,  commencing    straight   tubes  ; 

F,  termination  of  straight  tube  or 
the  excretory  tube. 


1418 


THE     URINARY   ORGANS 


connective  tissue  and  grouped  into  from  two  to  five  lobules.  This  capillary  net- 
work is  derived  from  a  small  arterial  twig,  the  afferent  vessel,  which  pierces  the  wall 
of  the  capsule,  generally  at  a  point  opposite  that  at  which  the  latter  is  connected 
with  the  tube;  and  the  resulting  efferent  vessel  emerges  from  the  capsule  at  the  same 


TUNICA.. 
ALBUGINEA 


LABYBINTH 
OF  CORTEX 


MEDULLARY    .. 
RAYS 


INTERLOBULA 
VEIN 


f-jL,  CONVOLUTED 


^_      MALPIGHIAN 
JZ'^  CORPUSCLES 


interlobular 
--''artery 


AREA  CRIBROSA 


EXCRETORY 
TUBULES 


Fig.  1013. — Part  of  a  section  through  the  cortex  of  the  kidney  in  the  direction  of  the  straight  tubules.     (Toldt.) 

point.  The  afferent  vessel  is  usually  the  larger  of  the  two  (Fig.  1015).  The  Mal- 
pighian  or  Bowman's  capsule  (capsula  glomeruli)  (Figs.  1015, 1016,  and  1017),  which 
surrounds  the  glomerulus,  is  formed  of  a  hyaline  membrane  supported  by  a  small 
amount  of  connective  tissue  which  is  continuous  with  the  connective  tissue  of  the 

tube.  It  is  lined  on  its  inner  surface 
with  a  layer  of  squamous  epithelial 
cells  which  are  reflected  from  the 
lining  membrane  on  to  the  glomerulus 
at  the  point  of  entrance  or  exit  of  the 
afferent  and  efferent  vessels.  The 
whole  surface  of  the  glomerulus  is 
covered  with  a  continuous  layer  of 
the  same  cells  on  a  delicate  support- 
ing membrane,  which  with  the  cells 
dips  in  between  the  lobules  of  the 
glomerulus,  closely  surrounding  them 
(Fig.  1016).  Thus,  between  the 
glomerulus  and  the  capsule  a  space 
is  left,  forming  a  cavity  lined  by  a 
continuous  layer  of  cells,  which 
varies  in  size  according  to  the  state 
of  secretion  and  the  amount  of  fluid 
present  in  it.  The  cells,  as  above 
stated,  are  squamous  in  the  adult, 
but  in  the  foetus  and  young  subject  they  are  polyhedral  or  even  columnar. 

The  Tubuli  Uriniferi,  commencing  in  the  Malpighian  bodies,  in  their  course 
present  many  changes  in  shape  and  direction  (tubuli  renales  contorti),  and  are 


WALL  OF  RENAL  CALYX 

Fig.  1014. — Area  cribrosa  of  renal  papilla.      (Toldt.) 


THE   KIDNEYS 


1419 


contained  partly  in  the  medullary  and  partly  in  the  cortical  portions  of  the  organ. 
At  the  junction  of  a  tubule  with  the  Malpighian  capsule  there  is  a  somewhat 
constricted  portion  which  is  termed  the  neck  (Fig.  1018).  Beyond  this  the  tubule 
becomes  convoluted,  and  pursues  a  considerable  course  in  the  cortical  structure, 
constituting  the  proximal  or  first  convoluted  tubule  (Figs.  1017  and  1018).  After  a 
time  the  convolutions  disappear,  and  the  tubule  approaches  the  medullary  portion 
of  the  kidney  in  a  more  or  less  spiral  manner.  This  section  of  the  tubule  has 
been  called  the  spiral  tube  of  Schachowa  (Fig.  1018).  Throughout  this  portion 
of  their  course  the  tubuli  uriniferi  have  been  contained  entirely  in  the  cortical 
structure,  and  have  presented  a  pretty  uniform  calibre.  They  now  enter  the 
medullary  portion,  and  suddenly  become  much  smaller,  quite  straight  in  direc- 
tion (tubidi  renales  recti),  and  each  tubule  dips  down  for  a  variable  depth  into 
the  pyramids,  constituting  the  descending  limb  of  Henle's  loop  (Figs.  1017  and 
1018).  Bending  on  itself,  it  forms  a  kind  of  loop  near  the  apex  of  the  pyramid, 
the  loop  of  Henle,  and,  reascending,  becomes  suddenly  enlarged  and  again  spiral 
in  direction,  forming  the  ascending  limb  of  Henle's  loop  (Figs.  1017  and  1018), 


Fig.  1015. — Minute  structure  of  kidney. 


Bowman'i 
capsule. 


-.-)  Vascular 
glomerulus. 


Fig.  1016. — Malpighian  body. 


and  re-enters  the  cortical  structure.  This  portion  of  the  tubule  does  not  present 
a  uniform  calibre,  but  })ecomes  narrower  as  it  ascends  and  irregular  or  somewhat 
spiral  in  outline  (Fig.  1018).  As  a  narrow  tube  it  enters  the  cortex  and  ascends 
for  a  short  distance,  when  it  again  becomes  dilated,  irregular,  and  angular.  This 
section  is  termed  the  irregular  tubule  (Fig.  1018);  it  terminates  in  a  convoluted 
tubule  which  exactly  resembles  the  proximal  convoluted  tubule;  and  is  called  the 
distal  or  second  convoluted  tubule  (Figs.  1017  and  1018).  This  again  terminates 
in  a  narrow  curved  or  junctional  tubule,  which  enters  the  straight  or  collecting 
tube. 

Each  straight  collecting  or  receiving  tube  (Figs.  1012,  1017,  and  1018)  com- 
mences by  a  small  orifice  on  the  summit  of  a  papilla,  thus  opening  and  discharg- 
ing its  contents  into  the  interior  of  one  of  the  calices.  Traced  into  the  substance 
of  the  pyramid,  these  tubes  are  found  to  run  from  apex  to  base,  dividing 
dichotomously  in  their  course  and  slightly  diverging  from  each  other.  Thus 
dividing  and  subdividing,  they  reach  the  base  of  the  pyramid,  and  enter  the 
cortical  structure  greatly  increased  in  number.  Upon  entering  the  cortical  por- 
tion they  continue  a  straight  course  for  a  variable  distance,  and  are  arranged  in 
groups,  several  of  these  groups  corresponding  to  a  single  pyramid.  The  tubes  in 
the  centre  of  the  group  are  the  longest,  and  reach  almost  to  che  surface  of  the  kid- 
ney, while  the  external  ones  are  shorter,  and  advance  only  a  short  distance  into 
the  cortex.  In  consequence  of  this  arrangement  the  cortical  portion  presents  a 
number  of  conical  masses,  the  apices  of  which  reach  the  periphery  of  the  organ, 


1420 


THE    URINARY   ORGANS 


and  the  bases  are  applied  to  the  medullary  portion.  These  are  termed  the  medul- 
laxy  rays  or  the  pjrramids  of  Ferrein  (Fig.  1013;  also  p.  1417).  As  they  run  through 
the  cortical  portion  the  straight  tubes  receive  on  either  side  the  curved  extremity 
of  the  convoluted  tubes,  which,  as  stated  above,  commence  at  the  Malpighian 
bodies.  Each  collecting  tube  receives  a  number  of  tubules,  and  several  collecting 
tubes  unite  together  to  form  a  papillary  duct  (Fig.  1017)  and  open  by  a  foramen 
(Fig.  1014)  at  the  surface  of  the  papilla. 


Cortex 


Medullary 


Medulla 


terlob- 
ularis 


Fig.  1017. — Diagrammatic  representation  of  the  course  of  the  urinary  canals  (left)  and  the  kidney  vessels 
(right).  The  arteries  are  red,  the  veins  blue;  capsules  of  Bowman,  convoluted  tubules  I.  order  and  loops  of 
Henle  are  black;  convoluted  tubules  II.  order  and  collecting  tubules  gray.  I..  II.,  III.,  IV.,  four  kidney 
lobules:  a,  vas  afferens;  e,  vas  efferens.  1,  Bowman's  capsule;  2,  convoluted  tubule  I.  order;  3,  descending 
limb  of  loop  of  Henle;  4,  ascending  limb  of  loop  of  Henle;  5,  convoluted  tubule  II.  order;  6,  7,  collecting 
tubules;  8,  papillary  duct.     (Szymonowicz.) 


It  will  be  seen  from  the  above  description  that  there  is  a  continuous  series 
of  tubes  from  their  commencement  in  the  Malpighian  bodies  to  their  termina- 
tion at  the  orifices  on  the  apices  of  the  pyramids  of  Malpighi,  and  that  the  urine. 


THE   KIDNEYS 


1421 


1^0^  Junctional 

conyo-  tubaie. 

luted  t 
tubule. 


the  secretion  of  which  commences  in  the  capsule,  finds  its  way  through  these 
tubes  into  the  caHces  of  the  kidney,  and  so  into  the  ureter.  To  recapitulate: 
the  tube  first  presents  a  con- 
stricted portion,  (1)  the  neck. 
2.  It  forms  a  wide  convoluted 
tube,  the  proximal  convoluted 
tube.  3.  It  becomes  spiral,  the 
spiral  tubule  of  Schachowa.  4.  It 
enters  the  medullary  structure 
as  a  narrow,  straight  tube,  the 
descending  limb  of  Henle's  loop. 

5.  Forming  a  loop  and  becom- 
ing dilated,  it  ascends  somewhat 
spirally,  and,  gradually  dimin- 
ishing in  calibre,  again  enters 
the  cortical  structure,  the  as- 
cending limb   of    Henle's    loop. 

6.  It  now  becomes  irregular 
and  angular  in  outline,  the 
irregular  tubule.  7.  It  then  be- 
comes convoluted,  the  distal 
convoluted  tubule.  8.  Diminish- 
ing in  size,  it  forms  a  curve,  the 
curved  or  junctional  tubule.  9. 
Finally,  it  joins  a  straight  tube, 
the  straight  collecting  tube, which 
is  continued  downward  through 
the  medullary  substance  and 
joins  other  straight  tubes  to 
form    a  papillary   duct,    which 

opens  in  a  foramen  at  the  apex         Fig.   lOlS.— Uriniferous  tube.      For  the  sake  of  clearness  the 
/-kf   Q   r»A7ramirl  epithelial  cells  have  been  represented  more  highly  magnified  than 

a  pyramiQ.*  the  tubes  in  which  they  are  contained. 


Descending  limb  \ 
of  Henle's  loop.  J 


Fig.  1019.'— Longitu-  Fio.  1020.— Longitu- 
dinal section  of  Henle's  dinal  section  of  straight 
descending  limb:  a,  tube:  i,  cylindrical  or 
membrana  propria  ;  b,  cubical  epithelium  ;  b, 
epithelium.  membrana  propria. 


Fig.  1021. — Transverse  section  of  pyramidal  substance  of 
kidney  of  pig,  the  blood-vessels  of  which  are  injected:  n,  large 
collecting  tube  cut  across,  lined  with  cylindrical  epithelium; 
h,  branch  of  collecting  tube  cut  across,  lined  with  epithelium 
with  shorter  cylinders;  c  and  rf.  Henle's  loops  cut  across  ;  e, 
blood-vessels  cut  across  ;  D,  connective-tissue  ground-sub- 
stance. 


The  Tubuli  Uriniferi:  their  Structure  (Figs.  1019,  1020,  and  1021. — 
The  tubuli  uriniferi  consist  of  basement-membrane  lined  with  epithelium.     The 


1  From  Handbook  for  the  Physiological  Laboratory. 


1422 


THE    URINARY    ORGANS 


epithelium  varies  considerably  in  different  sections  of  the  uriniferous  tubes.  In 
the  neck  the  epithelium  is  continuous  with  that  lining  the  Malpighian  capsule, 
and,  like  it,  consists  of  flattened  cells  with  an  oval  nucleus  (Fig.  1016).  The  cells 
are,  however,  very  indistinct  and  difficult  to  trace,  and  the  tube  has  here  the 
appearance  of  a  simple  basement-membrane  unlined  with  epithelium.  In  the 
proximal  convoluted  tubule  and  the  spiral  tubule  of  Schachowa  the  epithelium  is 
polyhedral  in  shape,  the  sides  of  the  cells  not  being  straight,  but  fitting  into 
each  other,  and  in  some  animals  so  fused  together  that  it  is  impossible  to  make 
out  the  lines  of  junction.  In  the  human  kidney  the  cells  often  present  an  angular 
projection  of  the  surface  next  the  basement-membrane.  These  cells  are  made 
up  of  more  or  less  rod-like  fibres,  which  rest  by  one  extremity  on  the  basement- 
membrane,  whilst  the  other  projects  toward  the  lumen  of  the  tube.  This  gives 
to  the  cells  the  appearance  of  distinct  striation.  In  the  descending  limb  of  Henle's 
loop  the  epithelium  resembles  that  found  in  the  Malpighian  capsule  and  the 
commencement  of  the  tube,  consisting  of  flat  transparent  epithelial  plates  with 
an  oval  nucleus  (Fig.  1019).  In  the  ascending  limb,  on  the  other  hand,  the 
cells  partake  more  of  the  character  of  those  described  as  existing  in  the  prox- 
imal convoluted  tubule,  being  polyhedral   in  shape  and  presenting  the  same 

appearance  of  striation.   The 
6    B       c  _6 


nucleus,  however,  is  not  situ- 
ated in  the  centre  of  the  cell, 
but  near  the  lumen  (Fig. 
1021).  After  the  ascending 
limb  of  Henle's  loop  becomes 
narrower  upon  entering  the 
cortical  structure,  the  stria- 
tion appears  to  be  confined 
to  the  outer  part  of  the  cell; 
at  all  events,  it  is  much  more 
distinct  in  this  situation,  the 
nucleus,  which  appears  flat- 
tened and  angular,  being  still 
situated  near  the  lumen.  In 
the  irregular  tubule  the  cells 
undergo  a  still  further  change, 
becoming  very  angular,  and 
presenting  thick  bright  rods 
or  markings,  which  render  the 
striation  much  more  distinct 


a  A 

Fig.  1022. — Diagrammatic 
sketch  of  the  blood- ves.sels  of 
the  kidney. 


Fig.  1023.— a  portion  of  Fig.  1022 

enlarged.     (The  references  are  the 

same.) 

A,  a,    interlobar  artery  and  vein,  the  former  giving  off  the  renal  ,             .                         ,                   j.'             e 

afferents,  the  latter  receiving  the  renal  efferents  ;  b,  b,  interlobular  than    lU    any   Othcr   SCCtlOU    OI 

artery  and  vein,  the  latter  commencing  from  the  stellate  veins,  and  ,i              •                ■     i      i               y        ii 

receiving   branches   from  the  plexus  around  the  tubuli  contorti,  the  tnC    UriUary   lUDUlCS.        in    lUe 

former  giving  off  renal  afferents  ;  c,  straight   tube,    surrounded   by  j:qJ.„1     r>nnvnliit<^fJ     tnhlllp    tliA 

tubuh  contorti,  with  which  it  communicates,  as  more  fully  .shown  in  liioiai     ».,«jii  vi^nutou     iiiuuic     nio 

Fig.  1023  ;  n,  margin  of  meduUarv  substance  ;  e,  e,  e,  receiving  tubes  oniflitiliiiin        •ir»rkf»ar«!       in      Kf» 

cut  off;  F, /,  arteriolae  et  venae  rectae,  the  latter  arising  from  (G)  the  epiiuetiuiii       cippcdis       lu      uc 

plexus  at  the  medullary  apex;  X,  vascular  glomerulus;  w,  the  arcuate  somewhat      similar      tO       that 

artery  and  vein.  .                                                mi 

which  has  been  described  as 
existing  in  the  proximal  convoluted  tubule,  but  presents  a  peculiar  refractive 
appearance.  In  the  curved  tubule,  just  before  its  entrance  into  the  straight 
collecting  tube,  the  epithelium  varies  greatly  as  regards  the  shape  of  the  cells, 
some  being  angular  with  short  processes,  others  spindle-shaped,  others  poly- 
hedral. 

In  the  straight  tubes  the  epithelium  is  more  or  less  columnar;  in  its  papillary 
portion  the  cells  are  distinctly  columnar  and  transparent  (Fig.  1020),  but  as  the 
tube  approaches  the  cortex  the  cells  are  less  uniform  in  shape;  some  are  poly- 
hedral, and  others  angular  with  short  processes. 


THE  KIDNEYS 


1423 


The  Renal  Blood-vessels. — The  kidney  is  plentifully  supplied  with  blood  by 
the  renal  artery  (Figs.  422,  423,  1005,  and  1011),  a  large  offset  of  the  abdominal 
aorta.  Previously  to  entering  the  kidney,  each  artery  divides  into  four  or  five 
branches,  which  are  distributed  to  its  substance.  At  the  hilum  these  branches 
lie  between  the  renal  vein  and  ureter,  the  vein  being  in  front,  the  ureter  behind. 
Each  vessel  gives  off  a  small  branch  to  the  suprarenal  capsules,  the  ureter,  and 
the  surrounding  cellular  tissue  and  muscles.  It  has  been  pointed  out  by  Hyrtl 
(p.  679)  that  the  renal  artery  gives  off  a  branch  which  divides  and  supplies  the 
dorsal  portion  of  the  kidney  and  a  branch  which  divides  and  supplies  the  ventral 
portion  of  the  kidney  (Figs.  422  and  423).  Between  these  two  vascular  systems 
is  a  non-vascular  zone,  called  by  Byron  Robinson  the  exsanguinated  renal 
zone  of  Hyrtl  (Figs.  422  and  423).  It  "  is  one-half  inch  dorsal  to  the  lateral 
longitudinal  renal  border."^  Frequently  there  is  a  second  renal  artery,  which  is 
given  off'  from  the  abdominal  aorta  at  a  lower  level,  and  supplies  the  lower  por- 
tion of  the  kidney.  It  is  termed  the  inferior  renal  artery.  The  branches  of  the 
renal  arteries  pass  to  the  kidney  substance  between  the  pyramids  and  are 
known  as  interlobar  arteries  (arteriae  interlobares  renis)  (Figs.  1013,  1017,  1024, 
and  1025).  At  the  junction  of  the  cortical  and  medullary  portions  these  vessels 
turn  and  for  a  short  distance  pursue  a  course  parallel  to  the  kidney  surface. 
There  are  thus  formed  a  series  of  incomplete  vascular  arches  across  the  bases 
of  the  pyramids,  the  arcuate  arteries  (arteriae  arciforvies)  (Figs.  1017,  1022,  and 
1023).  From  these  arches  two  sets  of  vessels  come.  The  vessels  of  one  set  go 
to  the  periphery  and  enter  the  labyrinth,  those  of  the  other  set  pass  toward  the 
c?ntre  and  enter  the  intermediate  zone  of  the  medulla.  These  last  vessels  are 
the  arteriolae  recti  (Figs.  1017,  1022,  and  1023). 
Bfcause  of  these  vessels  the  kidney  exhibits  stria- 
tions  on  section.  Each  of  the  arteriolae  recti 
in  the  medulla  divides  into  numerous  small 
branches  which  are  nearly  parallel  to  each  other 


Figs.  1024  and  1025. — Lobar  circulation.     Interlobar 
circulation.    (Poirier  and  Charpy.) 


Fig.  1026. — Diagrammatic  representation 
of  the  blood-vessels  in  the  substance  of  the 
cortex  of  the  kidney:  m,  region  of  the 
medullary  ray  ;  b,  region  of  the  tortuous 
portion  of  the  tubules ;  ai,  interlobular 
artery;  rt,  interlobular  vein;  ?o,  vas  affer- 
ens  ;  gl,  glomerulus  ;  ve,  vas  efferens  ;  vz, 
venous  twig  of  the  interlobularis.  (From 
Ludwig,  in  Strieker's  Handbook.) 


and  supply  the  tubules  of  this  region.  The  arteries  which  arise  from  the  arches 
and  pass  to  the  periphery  are  the  interlobular  arteries  {arteriae  inierlobidares) 
(Figs.  1017,  1022,  1023,  and  1026).  They  traverse  the  labyrinth  and  pass  toward 
the  surface  of  the  kidney.  A  number  of  short  branches,  the  vasa  afferentia,  are 
given  off  by  the  interlobular  arteries  (Figs.  1017,  1022,  1023,  and  1026).  Each 
afferent  vessel  passes  to  a  capsule  of  Bowman.  On  reaching  the  capsule  the 
vessel  forms  a  capillarv  mass,  the  glomerulus,  which  is  within  the  invaginated 
capsule  (Figs.  1016,  1017,  1023,  and  1026) . 


1  Byron  Robinson,  p.  679. 


1424 


THE    URINARY    ORGANS 


Emerging  from  each  glomerulus  is  a  small  vessel,  the  vas  efEerens  (Figj.  1015, 
1016,  1017,  1023,  and  1026).  This  vessel  divides  into  capillaries  which  are  dis- 
tributed to  the  tubules  of  the  labyrinth  and  medullary  rays.  Blood  is  gathered 
from  the  capillaries  about  the  tubules  by  veins  which  correspond  to  the  inter- 
lobular arteries  and  arteriolae  recti.  These  veins  form  a  set  of  arches  across 
the  bases  of  the  pyramids.  From  the  arches  veins  arise  and  pass  between  the 
pyramids  to  the  sinus  of  the  kidney,  where  they  unite  and  form  branches  of 
the  renal  vein. 

Nerves  of  the  Kidney. — The  nerves  of  the  kidney,  although  small,  are  about 
fifteen  in  number.  They  have  small  ganglia  developed  upon  them,  and  are  derived 
from  the  renal  plexus,  which  is  formed  by  branches  from  the  solar  plexus,  the 
lower  and  outer  part  of  the  semilunar  ganglion  and  aortic  plexus,  and  from  the 
lesser  and  smallest  splanchnic  nerves.  They  communicate  with  the  spermatic 
plexus,  a  circumstance  which  may  explain  the  occurrence  of  pain  in  the  testicle  in 
affections  of  the  kidney.  So  far  as  they  have  been  traced,  they  seem  to  accompany 
the  renal  artery  and  its  branches,  but  their  exact  mode  of  termination  is  not 
known. 

The  Lymphatics. — The  lymphatics  consist  of  a  superficial  and  deep  set. 
The  superficial  lymphatics  are  just  beneath  the  capsule.    From  them  come  two 
sets  of  collecting  trunks  (Sappey).    One  set  joins  the  deep  collectors  by  entering 

the  kidney  substance  or  passing  to  the  hilum.    Another 
set  pass  into  the  lymphatics  of  the  fatty  capsule. 

The  deep  collectors  emerge  from  the  hilum  and  lie 
about  the  renal  artery  and  vein.  From  the  right  kidney 
some  of  the  trunks  pass  to  the  glands  about  the  vena 
cava  and  possibly  also  in  the  glands  in  front  of  the 
aorta.  Others  end  in  the  glands  back  of  the  vena  cava 
(Stahr). 

From  the  left  kidney  the  trunks  pass  to  the  glands 
which  lie  along  the  left  side  of  the  abdominal  aorta.^ 
The  lymphatics  of  the  fatty  capsule  of  the  kidney  pass 
to  the  same  glands  as  do  the  deep  collectors  of  the 
kidney  (Stahr). 

Connective  Tissue  or  Intertubular  Stroma. — Although 
the  tubules  and  vessels  are  closely  packed,  a  certain 
small  amount  of  connective  tissue,  continuous  with  the 
capsule,  binds  them  firmly  together.  This  tissue  was 
first  described  by  Goodsir,  and  subsequently  by  Bow- 
man. Ludwig  and  Zawarykin  have  observed  distinct  fibres  passing  around  the 
Malpighian  bodies,  and  Henle  has  seen  them  between  the  straight  tubes  com- 
posing the  medullary  structure. 

Variations  and  Abnormalities. — Congenital  absence  of  the  kidney  has  been 
observed.  Not  unusually  one  kidney  is  considerably  larger  than  the  other;  occa- 
sionally one  is  very  large  and  the  other  is  very  small,  from  atrophy,  the  large 
organ  having  become  large  in  response  to  a  functional  need,  which  causes  it  to 
compensate  for  the  insufficiency  of  the  small  kidney.  If  a  kidney  is  removed 
surgically,  the  other  kidney  enlarges.  As  previously  stated,  the  kidneys  of  the 
foetus  and  of  the  young  child  show  distinct  fissures  which  makes  each  organ 
lobulated  (Fig.  1027).  The  adult  kidneys  frequently  exhibit  remains  of  these 
fissures.  A  horseshoe  kidney  is  a  condition  in  which  the  lower  poles  of  the  two 
kidneys  are  united  by  kidney  structure,  the  bond  of  union  crossing  the  middle  line. 
The  strip  of  kidney  tissue  which  effects  the  junction  may  be  slight  in  amount, 


riG.1027. — Foetal  kidney,  showing 
lobes.     (Testut.) 


1  The  Lymphatics.    By  Poirier,  Cun^o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE  KIDNEYS  1425 

considerable,  or  extensive.     Sometimes  the  two  kidneys  are  completely   fused 
together  into  one  large  organ  with  two  ureters. 

Surface  Form. — The  kidneys,  being  situated  at  the  back  part  of  the  abdominal  cavity  and 
deeply  placed,  cannot  be  felt  unless  enlarged  or  misplaced.  They  are  situated  on  the  confines 
of  the  epigastric  and  umbilical  regions  internally,  with  the  hypochondriac  and  lumbar  regions 
externally.  The  left  is  somewhat  higher  than  the  right.  According  to  Morris,  the  position  of 
the  kidney  may  be  thus  defined:  Anteriorly:  "1.  A  horizontal  line  through  the  umbilicus  is 
below  the  lower  edge  of  each  kidney.  2.  A  vertical  line  carried  upward  to  the  costal  arch  from 
the  middle  of  Poupart's  ligament  has  one-third  of  the  kidney  to  its  outer  side  and  two-thirds  to 
its  inner  side — i.  e.,  between  this  line  and  the  median  line  of  the  body."  In  adopting  these  lines 
it  must  be  borne  in  mind  that  the  axes  of  the  kidneys  are  not  vertical,  but  oblique,  and  if  con- 
tinued upward  would  meet  about  the  ninth  dorsal  vertebra.  Posteriorly:  The  upper  end  of  the 
left  kidney  would  be  defined  by  a  line  drawn  horizontally  outward  from  the  spinous  process  of  the 
eleventh  dorsal  vertebra,  and  its  lower  end  by  a  point  two  inches  above  the  iliac  crest.  The  right 
kidney  would  be  half  to  three-quarters  of  an  inch  below.  Morris  lays  down  the  following  rules 
for  indicating  the  position  of  the  kidney  on  the  posterior  surface  of  the  body:  "  1.  A  line  parallel 
with,  and  one  inch  from,  the  spine,  between  the  lower  edge  of  the  tip  of  the  spinous  process 
of  the  eleventh  dorsal  vertebra  and  the  lower  edge  of  the  spinous  process  of  the  third  lumbar 
vertebra.  2.  A  line  from  the  top  of  this  first  line  outward  at  right  angles  to  it  for  two  and  three- 
quarter  inches.  3.  A  line  from  the  lower  end  of  the  first  transversely  outward  for  two  and  three- 
quarter  inches.  4.  A  line  parallel  to  the  first  and  connecting  the  outer  extremities  of  the  second 
and  third  lines  just  described." 

The  hilum  of  the  kidney  lies  about  two  inches  from  the  middle  line  of  the  back,  at  the  level 
of  the  spinous  process  of  the  first  lumbar  vertebra. 

Surgical  Anatomy. — Cases  of  congenital  absence  of  a  kidney,  of  atrophy  of  a  kidney,  and 
of  horseshoe  kidney  are  of  great  importance,  and  must  be  duly  taken  into  account,  when  neph- 
rectomy is  contemplated.  A  more  common  malformation  is  where  the  two  kidneys  are  jused 
together.  They  may  be  only  joined  together  at  their  lower  ends  by  means  of  a  thick  mass  of 
renal  tissue,  so  as  to  form  a  horseshoe-shaped  body,  or  they  may  be  completely  united,  forming 
a  disk-like  kidney,  from  which  two  ureters  descend  into  the  bladder.  These  fused  kidneys  are 
generally  situated  in  the  middle  line  of  the  abdomen,  but  may  be  misplaced  as  well. 

One  or  both  kidneys  may  be  misplaced  as  a  congenital  condition,  and  remain  fixed  in  this 
abnormal  position.  They  are  then  very  often  misshapen.  They  may  be  situated  higher  or  lower 
than  normal  or  removed  farther  from  the  spine  than  usual  or  they  may  be  displaced  into  the 
iliac  fossa,  over  the  sacro-iliac  joint,  on  to  the  promontory  of  the  sacrum,  or  into  the  pelvis 
between  the  rectum  and  bladder  or  by  the  side  of  the  uterus.  In  these  latter  cases  they  may 
give  rise  to  very  serious  trouble.  The  kidney  may  also  be  misplaced  as  a  congenital  condition, 
but  may  not  be  fixed.  It  is  then  known  as  a  floating  kidney.  It  is  believed  to  be  due  to  the 
fact  that  the  kidney  is  completely  enveloped  by  peritoneum,  which  then  passes  backward  to  the 
spine  as  a  double  layer,  forming  a  mesonephron,  which  permits  of  movement  taking  place.  The 
kidney  may  also  be  misplaced  as  an  acquired  condition;  in  these  cases  the  kidney  is  mobile  in 
the  tissues  by  which  it  is  surrounded,  either  moving  in  or  moving  with  its  fatty  capsule.  This 
condition  is  known  as  movable  kidney  (nephroptosis),  and  is  more  common  in  the  female  than 
in  the  male,  and  on  the  right  than  the  left  side.  If  a  displaced  kidney  becomes  fixed  in  an 
abnormal  position,  it  is  said  to  be  dislocated.  Movable  kidney  cannot  be  distinguished  from 
floating  kidney  until  the  kidney  is  exposed  by  incision.  Other  malformations  are  the  persist- 
ence of  the  foetal  lobulation;  the  presence  of  two  pelves  or  two  ureters  to  the  one  kidney.  In 
some  rare  instances  a  third  kidney  may  be  present. 

The  kidney  is  embedded  in  a  large  quantity  of  loose  fatty  tissue,  and  is  but  partially  covered 
by  peritoneum;  hence,  rupture  of  this  organ  is  not  nearly  so  serious  an  accident  as  rupture  of 
the  liver  or  spleen,  since  the  extravasation  of  blood  and  urine  which  follows  is,  in  the  majority 
of  cases,  outside  the  peritoneal  cavity.  Occasionally  the  kidney  may  be  bruised  by  blows  in  the 
loin  or  by  being  compressed  between  the  lower  ribs  and  the  ilium  when  the  body  is  violently 
bent  forward.  This  is  followed  by  a  little  transient  hwmatvria,  which,  however,  speedily  passes 
off.  Occasionally,  when  rupture  involves  the  pelvis  of  the  kidney  or  the  commencement  of  the 
ureter,  this  duct  may  become  blocked,  and  hydronephrosis  follows. 

The  loose  cellular  tissue  around  the  kidney  may  be  the  seat  of  suppuration,  constituting 
perinephritic  abscess.  This  may  be  due  to  injury,  to  disease  of  the  kidney  itself,  or  to  'extension 
of  inflammation  from  neighboring  parts.  The  abscess  may  burst  into  the  pleura,  causing 
empyema;  into  the  colon  or  bladder;  or  may  point  externally  in  the  groin  or  loin.  Tumors  of  the 
kidney,  of  which,  perhaps,  sarcoma  in  children  is  the  most  common,  may  be  recognized  by  their 
position  and  fixity;  by  the  resonant  colon  lying  in  front  of  it;  by  their  not  moving  with  respira- 
tion; and  by  their  rounded  outline,  not  presenting  a  notched  anterior  margin  like  the  spleen,  with 
which  they  are  most  likely  to  be  confounded.  The  examination  of  the  kidney  should  be  bimanual ; 
that  is  to  say,  one  hand' should  be  placed  in  the  flank  and  firm  pressure  made  forward,  v.hib 

90 


1426  THE    URINARY   ORGANS 

the  other  hand  is  buried  in  the  abdominal  wall,  over  the  situation  of  the  organ.  Manipulation 
of  the  kidney  frequently  produces  a  peculiar  sickening  sensation  and  some  faintness. 

The  kidney  has,  of  late  years,  been  frequently  attacked  surgically.  It  may  be  exposed  and 
opened  for  exploration  or  the  evacuation  of  pus  {nephrotomy);  it  may  be  incised  for  the  removal 
of  stone  (nephro-lithotomy);  it  may  be  sutured  when  wounded  (nephrorrhaphy);  it  may  be  fixed 
in  place  by  sutures  (nephropexy)  or  gauze  pads  when  movable  or  floating;  or  it  may  be  removed 
(nephrectomy). 

The  kidney  may  be  exposed  either  by  a  lumbar  or  abdominal  incision.  The  operation  is 
best  performed  by  a  lumbar  incision,  except  in  a  case  of  very  large  tumor  or  of  wandering  kid- 
ney with  a  loose  mesonephron,  on  account  of  the  advantages  which  it  possesses  of  not  opening 
the  peritoneum  and  of  affording  admirable  drainage.  It  may  be  performed  either  by  an  oblique 
a  vertical,  or  a  transverse  incision.  A  common  incision  for  exposing  the  kidney  begins  an  inch 
below  the  twelfth  rib  at  the  margin  of  the  Erector  spinae  muscle  and  passes  obliquely  down- 
ward and  forward,  exposing  the  anterior  border  of  the  Latissimus  dorsi  and  the  posterior  border 
of  the  Internal  oblique.  The  surgeon  divides  the  posterior  leaflet  of  the  lumbar  fascia,  draws  aside 
or  incises  the  Quadratus  lumbonim,  and  cuts  the  anterior  leaflet  of  the  lumbar  fascia  and  also  the 
transversalis  fascia.  He  opens  the  fatty  capsule  down  to  the  kidney  and  strips  it  from  the  true 
capsule,  bringing  the  kidney  outside  of  the  body  for  inspection.  The  vertical  incision  at  the 
edge  of  the  Erector  spinae  muscle  is  frequently  used.  A  gridiron  or  muscle-splitting  operation 
is  used  by  some  in  order  to  avoid  the  division  of  nerves,  vessels,  and  muscular  fibre. 

The  abdominal  operation  is  best  performed  by  an  incision  in  the  linea  semilunaris  on  the 
side  of  the  kidney  to  be  removed,  as  recommended  by  Langenbuch;  the  kidney  is  then  reached 
from  the  outer  side  of  the  colon,  ascending  or  descending,  as  the  case  may  be,  and  the  vessels 
of  the  colon  are  not  interfered  with.  If  the  incision  were  made  in  the  linea  alba,  the  kidney 
would  be  reached  from  the  inner  side  of  the  colon,  and  the  vessels  running  to  supply  the  colon 
would  necessarily  be  interfered  with.  The  incision  is  made  of  varying  length  according  to  the 
size  of  the  kidney,  and  commences  just  below  the  costal  arch.  The  abdominal  cavity  is  opened. 
The  intestines  are  held  aside,  and  the  outer  layer  of  the  mesocolon  incised,  sO  that  the  fingers 
can  be  introduced  behind  the  peritoneum  and  the  renal  vessels  are  sought  for.  These  vessels 
are  then  to  be  ligatured:  if  tied  separately,  care  must  be  taken  to  ligature  the  artery  first.  The 
kidney  must  now  be  enucleated,  and  the  vessels  and  the  ureter  divided,  and  the  latter  disinfected 
and  tied,  and,  if  it  is  thought  necessary,  stitched  to  the  edge  of  the  wound. 

THE  URETER  (Figs.  1004,  1005,  1006,  1011,  1028,  1029). 

The  ureters  are  the  two  tubes  which  conduct  the  urine  from  the  kidneys  into 
the  bladder.  The  ureter  commences  within  the  sinus  of  the  kidney  by  a  number 
of  short  truncated  branches,  the  calices  or  infundibula,  which  unite  either  directly 
or  indirectly  to  form  a  dilated  pouch,  the  pelvis  (Fig.  1010),  from  which  the  ureter, 
after  passing  through  the  hilum  of  the  kidney,  descends  to  the  bladder.  The  calices 
are  cup-like  tubes  encircling  the  apices  of  the  Malpighian  pyramids ;  but  inasmuch 
as  one  calyx  may  include  two  or  even  more  papillae,  their  number  is  generally 
less  than  the  pyramids  themselves.  The  calices  vary  in  number  from  eight  to 
eighteen.  These  calices  converge  into  two  or  three  tubular  divisions  which  by 
their  junction  form  the  pelvis  or  dilated  portion  of  the  ureter.  The  portion  last 
mentioned,  where  the  pelvis  merges  into  the  ureter  proper,  is  found  opposite 
the  spinous  process  of  the  first  lumbar  vertebra,  in  which  situation  it  is  accessible 
behind  the  peritoneum  (Fig.  1006). 

The  Ureter  Proper. — The  ureter  proper  is  a  cylindrical  membranous  tube, 
about  sixteen  inches  in  length  and  of  the  diameter  of  a  goosequill,  extending  from 
the  pelvis  of  the  kidney  to  the  bladder.  Its  course  is  obliquely  downward  and 
inward  through  the  lumbar  region  (pars  abdominalis)  (Fig.  1029),  into  the  cavity  of 
the  pelvis  (pars  pe/yma)  (Fig.  1029), where  it  passes  downward,  forward,  and  inward 
across  that  cavity  to  the  base  of  the  bladder,  into  which  it  then  opens  by  a  con- 
stricted orifice  (orificium  ureteris)  (Fig.  1045),  after  having  passed  obliquely  for 
nearly  an  inch  between  its  muscular  and  mucous  coats  (Fig.  1028) .  The  lower 
part  of  the  abdominal  portion  of  the  ureter  exhibits  a  spindle-shaped  dilatation. 

Relations  (Fig.  1029). — In  its  course  it  rests  upon  the  Psoas  muscle,  being 
covered  by  the  peritoneum,  and  crossed  obliquely,  from  within  outward,  by  the 


THE    URETER 


1427 


spermatic  vessels ;  the  right  ureter  is  crossed  by  the  branches  of  the  mesenteric 
arteries,  which  are  distributed  to  the  ascending  colon,  and  the  left  ureter  by  those 
for  the  descending  colon;  the  right  ureter  lying  close  to  the  outer  side  of  the  infe- 
rior vena  cava.  Opposite  the  first  piece  of  the  sacrum  it  crosses  either  the  common 
or  external  iliac  artery  and  vein,  lying  behind  the 
ileum  on  the  ricjht  side  and  behind  the  sigmoid 
flexure  of  the  colon  on  the  le]t  side.  In  the  pelvis 
it  enters  the  posterior  false  ligament  of  the  bladder, 
below  the  obliterated  hypogastric  artery,  the  vas 
deferens  in  the  male  passing  between  it  and  the 
bladder.  In  the  female  the  ureter  is  to  the  inner 
side  of  the  uterine  artery  at  the  wall  of  the  pelvis, 
it  passes  forward  and  inward  below  the  posterior 
layer  of  the  broad  ligament  running  through  the 
parametrium,  passing  along  the  side  of  the  neck 
of  the  uterus  and  upper  part  of  the  vagina, 
being  in  contact  with  the  anterior  and  lateral 
vaginal  walls  and  being  crossed  anteriorly  by 
the  uterine  artery  (Fig.  1099).    At  the  base  of  the 

bladder  the  ureter  is  situated  about  two  inches  from  its  fellow:  lying,  in  the  male, 
about  an  inch  and  a  half  from  the  vesical  orifice  of  the  urethra,  at  one  of  the 
posterior  angles  of  the  trigone  (Fig.  1045). 

Structure. — The  ureter  is  composed  of  three  coats — fibrous,   muscular,   and 


Fig.  1028. — Diagram  showing  method 
of  entrance  of  the  ureter  into  the  blad- 
der.    (F.  H.  Gerrish.) 


mucous. 


RIGHT  URETER  PSOAS  MUSCLE 

LEFT  URETER 


ASCENDING 
COLON 


APPENDIX  (drawn 
up  under) 


SUPERIOR 

HEMORRHOIDAL 

ARTERY 


U^ 


ARTERY  TO 

SIGMOID 

FLEXURE 


Fig.  1029. — The  relations  of  the  pelvic  mesocolon  with  the  wall,  the  iliac  sigmoid  and  superior  hemorrhoidal 
arteries  and  the  ureter.      (Poirier  and  Charpy.) 

The  Fibrous  Coat  (tunica  adventitia). — The  fibrous  coat  is  the  same  throughout 
the  entire  length  of  the  duct,  being  continuous  at  one  end  with  the  fibrous  capsule 
of  the  kidney  at  the  floor  of  the  sinus,  while  at  the  other  it  is  lost  in  the  fibrous 
structure  of  the  bladder. 


1428 


THE    UBINABY   OBGANS 


The  Muscular  Coat  {tunica  muscularis). — In  the  pelvis  of  the  kidney  the  mus- 
cular coat  consists  of  two  layers,  longitudinal  and  circular:  the  longitudinal  fibres 
become  lost  upon  the  sides  of  the  papillae  at  the  extremities  of  the  calices;  the 
circular  fibres  may  be  traced  surrounding  the  medullary  structure  in  the  same 
situation.  In  the  ureter  proper  the  muscular  fibres  are  very  distinct,  and  are 
arranged  in  three  layers — an  external  longitudinal  {stratum  externum),  a  middle 
circular  {stratum  medium),  and  an  internal  layer  {stratum  internum),  less  distinct 
than  the  other  two,  but  having  a  general  longitudinal  direction.  According  to 
Kolliker,  this  internal  layer  is  only  found  in  the  neighborhood  of  the  bladder. 

The  Mucous  Coat  {tunica  mucosa). — The  mucous  coat  is  smooth,  and  presents  a 
few  longitudinal  folds  which  become  effaced  by  distention.  It  is  continuous  with 
the  mucous  membrane  of  the  bladder  below,whilst  it  is  prolonged  over  the  papillae 
of  the  kidney  above.  Its  epithelium  is  of  a  peculiar  character,  and  resembles  that 
found  in  the  bladder.  It  is  known  by  the  name  of  transitional  epithelium.  It  con- 
sists of  several  layers  of  cells,  of  which  the  innermost — that  is  to  say,  the  cells  in 
contact  with  the  urine — are  quadrilateral  in  shape,  with  concave  margins  on  their 
outer  surface,  into  which  fit  the  rounded  ends  of  the  cells  of  the  second  layer. 
These,  the  intermediate  cells,  more  or  less  resemble  columnar  epithelium,  and  are 
pear-shaped,  with  a  rounded  internal  extremity  which  fits  into  the  concavity  of 
the  cells  of  the  first  layer,  and  a  narrow  external  extremity  which  is  wedged  in 
between  the  cells  of  the  third  layer.  The  external  or  third  layer  consists  of  conical 
or  oval  cells  varying  in  number  in  different  parts,  and  presenting  processes  which 
extend  down  into  the  basement-membrane. 

Vessels  and  Nerves. — The  arteries  supplying  the  ureter  are  branches  from  the 
renal,  spermatic,  internal  iliac,  and  inferior  vesical. 

The  nerves  are  derived  from  the  inferior  mesenteric,  spermatic,  and  pelvic  plexuses. 

Surgical  Anatomy. — Subcutaneous  rupture  of  the  ureter  is  not  a  common  accident,  but  occa- 
sionally occurs  from  a  sharp,  direct  blow  on  the  abdomen,  as  from  the  kick  of  a  horse.  The  ureter 
may  be  either  torn  completely  across,  or  only  partially  divided,  and,  as  a  rule,  the  peritoneum 
escapes  injury.  If  torn  completely  across  the  urine  collects  in  the  retroperitoneal  tissues;  if  it 
is  not  completely  divided,  the  lumen  of  the  tube  may  become  obstructed  and  hydro-nephrosis  or 
pyo-nephrosis  results.  The  ureter  may  be  accidentally  xvounded  in  some  abdominal  operations; 
if  this  should  happen,  the  divided  ends  must  be  sutured  together,  or,  failing  to  accomplish  this, 
the  upper  end  must  be  implanted  into  the  bladder  or  the  intestine. 


THE  SUPRARENAL  CAPSULE  OR  GLAND  (6LANDULA 
SUPRARENALIS)  (Figs.  1010,  1030, 1031). 

The  suprarenal  capsules  belong  to  the  class  of  ductless  glands.  They  are  two 
small  flattened  bodies,  of  a  yellowish  color,  situated  at  the  back  part  of  the  abdo- 
men, behind  the  peritoneum,  and  immediately  above  and  in  front  of  the  upper 
end  of  each  kidney;  hence  their  name.  The  right  one  (Fig.  1030)  is  somewhat 
triangular  in  shape,  bearing  a  resemblance  to  a  cocked  hat;  the  left  (Fig.  1031)  is 
more  semilunar,  usually  larger  and  placed  at  a  higher  level  than  the  right.  They 
vary  in  size  in  different  individuals,  being  sometimes  so  small  as  to  be  scarcely 
detected;  their  usual  size  is  from  an  inch  and  a  quarter  to  nearly  two  inches  in 
length,  rather  less  in  width,  and  from  two  to  three  lines  in  thickness.  Their 
average  weight  is  from  one  to  one  and  a  half  drachms  each. 

Relations. — The  relations  of  the  suprarenal  capsules  differ  on  the  two  sides  of 
the  body. 

The  Right  Suprarenal  (Fig.  1030). — The  right  suprarenal  is  roughly  triangular  in 
shape,  its  angles  pointing  upward,  downward,  and  outward.  It  presents  two  sur- 
faces for  examination,  an  anterior  and  a  posterior.     The  anterior  surface  {fades 


THE   SUPRARENAL    CAPSULE    OR    GLAND 


1429 


anterior)  presents  two  areas,  separated  by  a  furrow,  the  hilum  {hilus  glandulae 
suprarenalis) :  one  area  occupying  about  one-third  of  the  whole  surface,  is  situ- 
ated above  and  internally;  it  is  depressed,  uncovered  by  peritoneum,  and  is  in 
contact  in  front  with  the  posterior  surface  of  the  right  lobe  of  the  liver,  and  along 
its  inner  border  with  the  inferior  vena  cava;  the  remaining  area  is  elevated,  and 
is  divided  into  a  non-peritoneal  portion,  in  contact  with  the  hepatic  flexure  of 
the  duodenum,  and  a  portion  covered  by  peritoneum  forming  the  hepato-renal 
fold.  The  posterior  siirface  (fades  posterior)  is  slightly  convex,  and  rests  upon 
the  Diaphragm.  The  base  (basis  glandulae  suprarenalis)  is  concave,  and  is  in 
contact  with  the  upper  end  and  the  adjacent  part  of  the  anterior  surface  of  the 
kidney. 

The  Left  Suprarenal  (Fig.  1031). — The  left  suprarenal  is  crescentic  in  shape,  its 
concavity  being  adapted  to  the  upper  end  of  the  left  kidney.    It  presents  an  inner 


ANTERIOR 
SURFACE 


SUPRARENAL 
VEIN 


SUPRARENAL 

VEIN 


SUPRARENAL 
ARTERY 


SUPRARENAL 
ARTERY 


Fig.  1030. — The  right  suprarenal  gland. 
(Spalteholz.) 


Fig.  1031. — The  left  suprarenal  gland. 
(Spalteholz.) 


border  which  is  convex,  and  an  outer  which  is  concave ;  its  upper  border  is  narrow, 
and  its  lower  rounded.  Its  anterior  surface  (fades  anterior)  presents  two  areas:  an 
upper  one,  covered  by  the  peritoneum  forming  the  lesser  sac,  which  separates  it 
from  the  cardiac  end  of  the  stomach  and  to  a  small  extent  from  the  superior 
extremity  of  the  spleen;  and  a  lower  one,  which  is  in  contact  with  the  pancreas 
and  splenic  artery,  and  is  therefore  not  covered  by  the  peritoneum.  A  hilum  is 
present,  as  in  the  right  suprarenal.  Its  posterior  surface  (fades  posterior)  presents 
a  vertical  ridge,  which  divides  it  into  two  areas.  The  ridge  lies  in  the  sulcus 
between  the  kidney  and  crus  of  the  Diaphragm,  while  the  area  on  either  side  of 
it  lies  on  these  parts  respectively;  the  outer  area,  which  is  thin,  resting  on  the 
kidney,  and  the  inner  and  smaller  area  resting  on  the  left  crus  of  the  Diaphragm. 
The  surface  of  the  suprarenal  gland  is  surrounded  by  areolar  tissue  containing 
much  fat,  and  closely  invested  by  a  thin  fibrous  coat,  which  is  difficult  to  remove, 
on  account  of  numerous  fibrous  processes  and  vessels  which  enter  the  organ 
through  the  furrows  on  its  anterior  surface  and  base. 

Accessory  Suprarenal  Glands  (glandulae  suprarenales  accessoriae). — Small 
accessory  suprarenals  are  often  to  be  found  in  the  connective  tissue  around  the 
suprarenals.  The  smaller  of  these,  on  section,  show  a  uniform  surface,  but  in 
some  of  the  larger  a  distinct  medulla  can  be  made  out. 

Structure  (Figs.  1032,  1033,  and  1034). — On  making  a  perpendicular  section 
(Fig.  1032) ,  the  suprarenal  gland  is  seen  to  consist  of  two  substances — external  or 
cortical  and  internal  or  medullary.  The  former,  which  constitutes  the  chief  part  of 
the  organ,  is  of  a  deep-yellow  color.     The  medullary  substance  is  soft,  pulpy, 


1430 


THE    URINARY  ORGANS 


and  of  a  dark-brown  or  black  color,  whence  the  name  atxabiliary  capsules  formerly 
given  to  these  organs.  In  the  centre  is  often  seen  a  space,  not  natural,  but 
formed  by  breaking  down  after  death  of  the  medullary  substance. 

The  Cortical  Portion  (substantia  corticalis)  (Fig.  1032). — The  cortical  substance 
consists  chiefly  of  narrow  columnar  masses  placed  perpendicularly  to  the  surface. 
This  arrangement  is  due  to  the  disposition  of  the  capsule,  which  sends  into  the 
interior  of  the  gland  processes  passing  in  vertically  and  communicating  with  each 
other  by  transverse  bands  so  as  to  form  spaces 
which  open  into  each  other.     These  spaces  are  mM 

of  slight  depth  near  the  surface  of  the  organ,  ililliififli 

so  that  there  the  section  somewhat  resembles  a 
net;  this  is  termed  the  zona  glomenilosa ;  but 
they  become  much  deeper  or  longer  farther  in, 
so  as  to  resemble  pipes  or  tubes  placed  endwise, 


^^Capsule. 

Zona 
glomerulosa. 


Zona 
fasdculata. 


Connective 
tissue. 


Gland 
llT     cylinders. 


Fig.  1033. — Minute  structure  of  suprarenal 
capsule. 


FrameworTc. 


Zona  reticularis. 


Medulla. 


/    --Nuclei. 


Capillary. 


Fig.  1032.- 


-  Vertical  section  of  the  suprarenal  capsule. 
Elberth,  in  Strieker's  Manual.) 


(From 


Fig.  1034. — Minute  structure  of  suprarenal 
capsule. 


the  zona  fasciculata.  Still  deeper  down,  near  the  medullary  part,  the  spaces 
become  again  of  small  extent;  this  is  named  the  zona  reticularis.  These  processes 
or  trabeculae,  derived  from  the  capsule  and  forming  the  framework  of  the  spaces, 
are  composed  of  fibrous  connective  tissue  with  longitudinal  bundles  of  unstriped 
muscular  fibres.  Within  the  interior  of  the  spaces  are  contained  groups  of  poly- 
hedral cells,  which  are  finely  granular  in  appearance,  and  contain  a  spherical 
nucleus,  and  not  infrequently  fat-globules.  These  groups  of  cells  do  not  entirely 
fill  the  spaces  in  which  they  are  contained,  but  between  them  and  the  trabeculae 
of  the  framework  is  a  channel  which  is  believed  to  be  a  lymph-path  or  sinus, 
and  which  communicates  with  certain  passages  between  the  cells  composing  the 


THE    CAVITY    OF   THE   PELVIS  1431 

group.  The  lymph-path  is  supposed  to  open  into  a  plexus  of  efferent  lymphatic 
vessels  which  are  contained  in  the  capsule. 

The  Medullary  Portion  (substantia  medullaris)  (Fig.  1032). — In  the  medullary 
portion  the  fibrous  stroma  seems  to  be  collected  together  into  a  much  closer 
arrangement,  and  forms  bundles  of  connective  tissue  which  are  loosely  applied 
to  the  large  plexus  of  veins  of  which  this  part  of  the  organ  mainly  consists.  In 
the  interstices  lie  a  number  of  cells  compared  by  Frey  to  those  of  columnar  epithe- 
lium. They  are  coarsely  granular,  do  not  contain  any  fat-molecules,  and  some 
of  them  are  branched.  Luschka  has  affirmed  that  these  branches  are  connected 
with  the  nerve-fibres  of  a  very  intricate  plexus  which  is  found  in  the  medulla;  this 
statement  has  not  been  verified  by  other  observers,  for  the  tissue  of  the  medullary 
substance  is  less  easy  to  make  out  than  tliat  of  the  cortical,  owing  to  its  rapid 
decomposition. 

Vessels  and  Nerves. — The  numerous  arteries  which  enter  the  suprarenal  bodies 
from  the  sources  mentioned  below  penetrate  the  cortical  part  of  the  gland,  where 
they  break  up  into  capillaries  in  the  fibrous  septa,  and  these  converge  to  the  very 
numerous  veins  of  the  medullary  portion,  which  are  collected  together  into  the 
suprarenal  vein,  which  usually  emerge  as  a  single  vessel  from  the  centre  of  the 
gland. 

The  arteries  supplying  the  suprarenal  capsules  are  three  in  number  and  of  large 
size;  they  are  derived  from  the  aorta,  the  phrenic,  and  the  renal;  they  subdivide 
into  numerous  minute  branches  previous  to  entering  the  substance  of  the  gland. 

The  suprarenal  vein  returns  the  blood  from  the  medullary  venous  plexus,  and 
receives  several  branches  from  the  cortical  substance ;  it  emerges  from  the  hilum 
and  opens  on  the  right  side  into  the  inferior  vena  cava,  on  the  left  side  into  the 
renal  vein. 

The  lymphatics  form  several  collections  which  are  about  the  beginning  of  the 
suprarenal  vein.  They  terminate  in  the  glands  to  the  correspojiding  side  of  the 
aorta. 

The  nerves  are  exceedingly  numerous,  and  are  derived  from  the  solar  and 
renal  plexuses,  and,  according  to  Bergmann,  from  the  phrenic  and  pneumo gastric 
nerves.  They  enter  the  lower  and  inner  part  of  the  capsule,  traverse  the  cortex, 
and  terminate  about  the  cells  of  the  medulla.  They  have  numerous  small  ganglia 
developed  upon  them,  from  which  circumstance  the  organ  has  been  conjectured 
to  have  some  function  in  connection  with  the  sympathetic  nervous  system. 


THE  CAVITY  OF  THE  PELVIS. 

The  cavity  of  the  pelvis  is  that  part  of  the  general  abdominal  cavity  which  is 
below  the  level  of  the  ilio-pectineal  lines  and  the  promontory  of  the  sacrum. 

Boundaries. — It  is  bounded  behind  by  the  sacrum,  the  coccyx,  the  Pyriformis 
muscles,  and  the  great  sacro-sciatic  ligaments;  in  front  and  at  the  sides  by  the 
portions  of  the  innominate  bones  below  the  ilio-pectineal  lines.  In  front  and 
to  the  sides  the  bony  sides  of  the  pelvic  cavity  are  partly  covered  by  the  internal 
Obturator  muscles,  and  internal  to  these  muscles  by  the  parietal  part  of  the 
pelvic  fascia.  Above,  it  communicates  with  the  cavity  of  the  abdomen;  and 
below,  the  outlet  is  closed  by  the  triangular  ligament,  the  Levatores  ani  and 
Coccygei  muscles,  and  the  visceral  layer  of  the  pelvic  fascia,  which  is  reflected 
from  the  wall  of  the  pelvis  on  to  the  viscera. 

Contents. — The  viscera  contained  in  this  cavity  are — the  urinary  bladder,  the 
rectum,  and  some  of  the  generative  organs  peculiar  to  each  sex,  and  some  convo- 
lutions of  the  small  intestines.  The  pelvic  viscera  are  partially  covered  by  the 
peritoneum,  and  supplied  with  blood-vessels,  lymphatics,  and  nerves. 


1432 


THE    URINARY    ORGANS 


THE  URINARY  BLADDER  (VESICA  URINARIA)  (Figs.  1037,  1038,  1054,  1055). 

The  urinary  bladder  is  the  reservoir  for  the  urine.  It  is  a  musculo-membranous 
sac  situated  in  the  pelvis,  behind  the  pubes,  and  in  front  of  the  rectum  in  the  male, 
the  cervix  uteri  and  vagina  intervening  between  it  and  that  intestine  in  the  female. 
The  shape,  position,  and  relations  of  the  bladder  are  greatly  influenced  by  age. 


Fig.  1035. — The  empty  bladder.      (Poirier  and  Charpy.) 


Fig.  1036. — Modifications  of  form  of  the  blad- 
der during  distention  (Poirier  and  Charpy.) 


'■!s  '  '  [JlJ^pace  of 


^Suspensory 
ligament 

\\ 


Fossa  navicularis.' 
Fig.  1037. — Vertical  section  of  bladder,  penis,  and  urethra. 

sex,  and  the  degree  of  distention  of  the  organ.  During  infancy  it  is  conical  in 
shape,  and  projects  above  the  symphysis  pubis  into  the  hypogastric  region.  In  the 
adult,  when  quite  empty  and  contracted  (Figs.  1035  and  1036),  it  is  cup-shaped, 
and  on  vertical  median  section  its  cavity,  with  the  adjacent  portion  of  the  urethra, 
presents  a  Y-shaped  cleft,  the  stem  of  the  Y  corresponding  to  the  urethra.     It  is 


THE    URINARY   BLADDER 


1433 


placed  deeply  in  the  pelvis,  flattened  from  before  backward,  and  reaches  as  high  as 
the  upper  border  of  the  symphysis  pubis.  When  slightly  distended,  it  has  a  rounded 
form,  and  is  still  contained  within  the  pelvic  cavity  (Fig.  1036),  and  when  greatly 
distended  (Figs.  1036  and  1037),  it  is  ovoid  in  shape,  rising  into  the  abdominal 
cavity,  and  often  extending  nearly  as  high  as  the  umbilicus.  It  is  larger  in  its  verti- 
cal diameter  than  from  side  to  side,  and  its  long  axis  is  directed  from  above 
obliquely  downward  and  backward,  in  a  line  directed  from  some  point  between 
the  symphysis  pubis  and  umbilicus  (according  to  its  distention)  to  the  end  of  the 
coccyx.     The  bladder,  when  distended,  is  slightly  curved  forward  toward  the 


Peritoneur], 


Vesicula  seminalis. 
Symphysis  pubis. 


Dorsal  vein  of  penis 

Septum  pectiniforme.'-''  "y/^. 
Urethra.  "'' 


Jtecto-vesicai 
\y/pouch. 


Prostate 
gland. 


Sphincter  ani. 


Fig.  1038. — Vertical  median  section  of  the  male  pelvis.     (Henle.) 

anterior  wall  of  the  abdomen,  so  as  to  be  more  convex  behind  than  in  front.  In 
the  fem.ale  it  is  larger  in  the  transverse  than  in  the  vertical  diameter,  and  its 
capacity  is  said  to  be  greater  than  in  the  male.^  When  moderately  distended,  it 
measures  about  five  inches  in  length,  and  three  inches  across,  and  the  ordinary 
amount  which  it  can  contain  without  serious  discomfort  is  about  a  pint. 

The  bladder  is  divided  for  purposes  of  description  into  a  superior,  an  antero- 
inferior, and  two  lateral  surfaces,  a  base  or  fundus,  and  a  summit  or  apex. 

Surfaces.  The  Superior  or  Abdominal  Surface  (Figs.  852,  1037,  1038,  and  1055). 
— The  superior  or  abdominal  surface  is  entirely  free,  and  is  covered  throughout  by 


1  According  to  Henle,  the   bladder  is  considerably   smaller  in  the    female  than  in  the  male.- 
English  eciiticiii. 


-En.  of    15th 


1434 


THE    UBINARY   ORGANS 


peritoneum.  It  looks  almost  directly  upward  into  the  abdominal  cavity,  and  extends 
in  an  antero-posterior  direction  from  the  apex  to  the  base  of  the  bladder.  It  is  in 
relation  with  the  small  intestine  and  sometimes  with  the  sigmoid  flexure,  and,  in 
the  female,  with  the  uterus.  On  each  side,  in  the  male,  a  portion  of  the  vas 
deferens  is  in  contact  with  the  hinder  part  of  this  surface,  lying  beneath  the 
peritoneum. 

The  Antero-inferior  or  Pubic  Surface  (Figs.  1037,  103S,  and  1055). — The  antero- 
inferior or  pubic  surface  looks  downward  and  forward.  In  the  undistended 
condition  it  is  uncovered  by  peritoneum,  and  is  in  relation  with  the  Obturator 
internus  muscle  on  each  side,  with  the  recto-vesical  fascia,  and  anterior  true 
ligaments  of  the  bladder.  It  is  separated  from  the  body  of  the  pubis  by  a  tri- 
angular interval,  the  space  of  Retzius,  occupied  by  fatty  tissue.     As  the  bladder 


Vermiform  appendix. 


External  iliac 
artery. 


Anterior  crural 
nerve. 


External  oblique 
muscle. 


Profunda  vessels,    levator  ani.        Corpora         Urethra. 

cavernosa. 
Fig.  1039. — Frontal  section  of  the  lower  part  of  the  abdomen.    Viewed  from  in  front.     (Braune.) 

ascends  into  the  abdominal  cavity  during  distention  the  distance  between  its  apex 
and  the  umbilicus  is  necessarily  diminished,  and  the  urachus  (Fig.  852  and  1055) 
is  thus  relaxed;  so  that,  instead  of  passing  directly  upward  to  the  umbilicus,  it 
descends  first  on  the  upper  part  of  the  anterior  surface  of  the  bladder,  and  then, 
curving  upward,  ascends  on  the  back  of  the  abdominal  wall.  The  peritoneum, 
which  follows  the  urachus,  thus  comes  to  form  a  pouch  (plica  vesicalis  transversa) 
of  varying  depth  betv/een  the  anterior  surface  of  the  viscus  and  the  abdominal 
wall  (Fig.  1038).  The  fold  passes  to  the  neighborhood  of  the  internal  abdom- 
inal rings.  Thus,  when  the  bladder  is  distended,  the  upper  part  of  its  anterior 
surface  is  in  relation  with  the  urachus  and  is  covered  by  peritoneum.  The  lower 
part  of  its  anterior  surface,  a  distance  of  about  two  inches  above  the  symphysis 
pubis,  is  devoid  of  peritoneum,  and  is  in  contact  with  the  abdominal  wall. 


THE    URINARY  BLADDER  1435 

The  Lateral  Surfaces. — The  lateral  surfaces  are  covered  behind  and  above  by 
peritoneum,  which  extends  as  low  as  the  level  of  the  obliterated  hypogastric 
artery;  below  and  in  front  of  this,  these  surfaces  are  uncovered  by  peritoneum, 
and  are  separated  from  the  Levatores  ani  muscles  and  walls  of  the  pelvis  by  a 
quantity  of  loose  areolar  tissue  containing  fat.  In  front  this  surface  is  connected 
to  the  recto-vesical  fascia  by  a  broad  expansion  on  either  side,  the  lateral  true 
ligaments.  The  vas  deferens  crosses  the  hinder  part  of  the  lateral  surface  obliquely, 
and  passes  between  the  ureter  and  the  bladder.  When  the  bladder  is  empty  the 
peritoneum  descends  on  the  pelvic  wall  as  low  as  the  lateral  border  of  the  bladder 
and  enters  a  groove  known  as  the  paravesical  fossa.  The  lateral  surfaces,  the 
pubic  surface,  and  the  abdominal  surface  together  constitute  the  body  of  the 
bladder  (corpus  vesicae). 

The  Fundus  or  Base  (fundus  vesicae)  (Figs.  1038, 1052,  and  1055). — The  fundus 
or  base  is  directed  downward  and  backward,  and  is  partly  covered  by  peritoneum 
and  is  in  part  not  covered  by  it.  In  the  male  the  upper  portion,  to  within  about 
an  inch  and  a  half  of  the  prostate,  is  covered  by  the  recto-vesical  pouch  of  peri- 
toneum (Fig.  855) .  The  lower  part  is  in  direct  contact  with  the  anterior  wall  of 
the  second  part  of  the  rectum  and  the  vesiculae  seminales  and  vasa  deferentia 
(Figs.  1052  and  1054).  The  ureters  enter  the  bladder  at  the  upper  part  of  its 
base,  about  an  inch  and  a  half  above  the  base  of  the  prostate  gland  (Fig.  1045). 
The  portion  of  the  bladder  in  relation  with  the  rectum  corresponds  to  a  trian- 
gular space,  bounded,  below,  by  the  prostate  gland;  above,  by  the  recto-vesical 
fold  of  the  peritoneum;  and  on  each  side,  by  the  vesicula  seminalis  and  vas 
deferens.  It  is  separated  from  direct  contact  with  the  rectum  by  the  recto- 
vesical fascia.  When  the  bladder  is  very  full,  the  peritoneal  fold  is  raised  with 
it,  and  the  distance  between  its  reflection  and  the  anus  is  about  four  inches;  but 
this  distance  is  much  diminished  when  the  bladder  is  empty  and  contracted.  In 
the  female,  the  base  of  the  bladder  is  connected  to  the  anterior  aspect  of  the  cervix 
uteri  by  areolar  tissue,  and  is  adherent  to  the  anterior  wall  of  the  vagina  (Fig. 
853) .  Its  upper  surface  is  separated  from  the  anterior  surface  of  the  body  of 
the  uterus  by  the  utero-vesical  pouch  of  the  peritoneum  (Fig.  853) . 

The  so-called  neck  or  cervix  of  the  bladder  (collum  vesicae)  is  the  point  of  com- 
mencement of  the  urethra;  there  is,  however,  no  tapering  part,  which  would 
constitute  a  true  neck,  but  the  bladder  suddenly  contracts  to  the  opening  of  the 
urethra  (Fig.  1038).  In  the  male  it  is  surrounded  by  the  prostate  gland  and  its 
direction  is  oblique  when  the  individual  is  in  the  erect  posture  (Figs.  1037  and 
1038).     In  the  female  its  direction  is  obliquely  downward  and  forward. 

The  Summit  or  Apex  (vertex  vesicae). — The  summit  or  apex  is  the  portion 
of  the  bladder  which  when  that  organ  is  empty  or  nearly  empty  is  nearest  to 
the  upper  border  of  the  symphysis.  It  is  directed  upward  and  forward.  In  a 
distended  bladder  the  apex  is  well  above  the  pubes  in  the  abdominal  cavity. 

The  Urachus  or  Middle  Umbilical  Ligament  (ligamentum  umbilicale  medium) 
(Fig.  1055). — The  urachus  is  a  connective-tissue  cord  and  is  the  obliterated 
remains  of  the  tubular  canal  of  the  allantois,  which  existed  in  the  embryo,  and 
a  portion  of  which  expanded  to  form  the  bladder.  It  passes  upward,  from  the 
apex  of  the  bladder,  between  the  trans versalis  fascia  and  peritoneum,  to  the 
umbilicus,  becoming  thinner  as  it  ascends.  It  is  composed  of  fibrous  tissue, 
mixed  with  plain  muscular  fibres.  The  urachus  causes  the  formation  of  a  peri- 
toneal fold,  the  plica  umbilicalis  media  (Fig.  852).  On  each  side  of  it  is  placed  a 
fibrous  cord,  the  obliterated  portion  of  the  hypogastric  artery,  which,  passing 
upward  from  the  side  of  the  bladder,  approaches  the  urachus  above  its  summit. 
Over  each  cord  is  the  fold  known  as  the  plica  umbilicalis  lateralis  (Fig.  852).  In 
the  infant,  at  birth,  the  urachus  is  occasionally  found  pervious,  so  that  the  urine 
escapes  at  the  umbilicus,  and  calculi  have  been  found  in  its  canal. 


1436 


THE    URINARY   ORGANS 


Ligaments. — The  bladder  is  retained  in  its  place  by  ligaments,  which  are  divided 
into  true  and  false.  The  true  ligaments  are  five  in  number:  two  anterior,  two 
lateral,  and  the  urachus.  The  false  ligaments,  also  five  in  number,  are  formed  by- 
folds  of  the  peritoneum. 

The  two  anterior  true  ligaments,  the  pubo-prostatic  or  pubo-vesical  ligaments  {liga- 
menta  puboprostatica)  extend  from  the  back  of  the  ossa  pubis,  one  on  each  side  of 
the  symphysis,  to  the  front  of  the  neck  of  the  bladder,  over  the  anterior  surface  of 
the  prostate  gland.  These  ligaments  are  formed  by  the  recto-vesical  fascia,  and 
contain  a  few  muscular  fibres  prolonged  from  the  bladder. 

The  two  lateral  true  ligaments,  formed  by  expansions  from  the  fascia  lining  the 
lateral  wall  of  the  pelvis,  are  broader  and  thinner  than  the  preceding.  They 
are  attached  to  the  lateral  parts  of  the  prostate  gland  and  to  the  sides  of  the  base  of 
the  bladder. 


Fig.  1040.— Fibres  of  the  exteral 
longitudinal  layer.  (Poirier  and 
Charpy.) 


Fig.  1041. — Fibres  of  the  middle 
or  circular  layer.  (Poirer  and 
Charpy.) 


Fig.  1042.— Fibres  of  the  inter- 
nal longitudinal  layer.  (Poirier 
and  Charpy.) 


The  urachus  or  middle  umbilical  ligament  is  the  fibro-muscular  cord  already  men- 
tioned, extending  between  the  summit  of  the  bladder  and  the  umbilicus.  It  is  broad 
below,  at  its  attachment  to  the  bladder,  and  becomes  narrower  as  it  ascends. 

The  two  posterior  false  ligaments  pass  forward,  in  the  male,  from  the  sides  of 
the  rectum  (plicae  rectovesicales) ;  in  the  female,  from  the  sides  of  the  uterus  (plicae 
rectouterinae) ,  to  the  posterior  and  lateral  aspect  of  the  bladder;  they  form  in 
the  male  the  lateral  boundaries  of  the  recto-vesical  pouch  (excavatio  rectovesicalis) 
(Figs.  926  and  1038) ;  they  form  in  the  female  the  lateral  boundaries  of  the  pouch  or 
cul-de-sac  of  Douglas  (excavatio  rectouterina  [Douglasi])  (Figs.  853  and  927).  The 
posterior  false  ligaments  contain  the  obliterated  hypogastric  arteries  and  the 
ureters,  together  with  vessels  and  nerves.  In  the  base  of  each  fold  is  smooth 
muscle-fibre,  the  Recto-vesical  muscle  (m.  rectovesicalis). 

The  two  lateral  false  ligaments  are  reflections  of  the  peritoneum,  from  the 
iliac  fossae  and  lateral  walls  of  the  pelvis  to  the  sides  of  the  bladder.  Each 
lateral  false  ligament  (ligamentum  umhilicale  laterale)  passes  in  front  into  the  plica 
umbilicalis  lateralis  over  the  corresponding  hypogastric  artery.  The  two  lateral 
reflections  of  peritoneum  are  continuous  in  front  of  the  apex  vesicae,  at  which 
point  the  peritoneum  passes  upon  the  urachus. 

The  superior  or  anterior  false  ligament  or  the  suspensory  ligament  (plica  umhilicalis 
media)  is  the  prominent  fold  of  peritoneum  extending  from  the  summit  of  the  blad- 
der to  the  umbilicus.     It  is  carried  off  from  the  bladder  by  the  urachus  and  the 


THE    URINARY  BLADDER  I437 

obliterated  hypogastric  arteries.  The  peritoneal  fold  over  each  obliterated  hypo- 
gastric artery  is  called  the  plica  mnbilicalis  lateralis  (Fig.  852),  and  is  the  pro- 
longation forward  of  the  ligamentum  umbilicale  laterale.  Besides  the  true  and 
false  ligaments,  the  bladder  receives  support  from  the  fibrous  tissue  and  unstriated 
muscle  about  the  seminal  vesicles,  and  terminations  of  the  ureters  and  vasa  defer- 
entia.  In  the  female  the  connection  with  the  anterior  vaginal  wall  supports  the 
base  of  the  bladder.  In  both  sexes  the  most  solidly  fixed  part  of  the  bladder  is 
about  the  orifice  of  the  urethra. 

Structure. — The  bladder  is  composed  of  four  coats — serous,  muscular,  sub- 
mucous, and  mucous. 

The  Serous  Coat  {tunica  serosa). — The  serous  coat  is  partial,  and  derived  from  the 
peritoneum.  It  invests  the  superior  surface  and  the  upper  part  of  the  lateral  surfaces 
and  base,  and  is  reflected  from  these  parts  on  to  the  abdominal  and  pelvic  walls. 

The  Muscular  Coat  {tunica  muscularis)  (Figs.  1040,  1041,  and  1042). — The  mus- 
cular coat  consists  of  three  layers  of  unstriped  muscular  fibre:  an  external  layer, 
composed  of  fibres  having  for  the  most  part  a  longitudinal  arrangement;  a  middle 
layer,  in  which  the  fibres  are  arranged,  more  or  less,  in  a  circular  manner;  and  an 
internal  layer,  in  which  the  fibres  have  a  general  longitudinal  arrangement. 

The  fibres  of  the  external  longitudinal  layer  {stratum  externum)  arise  from  the 
posterior  surface  of  the  body  of  the  os  pubis  in  both  sexes  (m.  pubovesicalis) ,  and 
in  the  male  aris?  also  from  the  adjacent  part  of  the  prostate  gland  and  its  capsule. 
They  pass,  in  a  more  or  less  longitudinal  manner,  up  the  anterior  surface  of  the 
bladder,  over  its  apex,  and  then  descend  along  its  posterior  surface  to  its  base, 
where  they  become  attached  to  the  prostate  in  the  male  and  to  the  front  of  the  vagina 
in  the  female.  At  the  sides  of  the  bladder  the  fibres  are  arranged  obliquely  and 
intersect  one  another.  The  external  lorgitudinal  layer  has  been  named  the 
Detrusor  urinae  muscle. 

The  middle  circular  layers  {stratum  medium)  are  very  thinly  and  irregularly 
scattered  on  the  body  of  the  organ,  and,  though  to  some  extent  placed  transversely 
to  the  long  axis  of  the  bladder,  are  for  the  most  part  arranged  obliquely.  Toward 
the  lower  part  of  the  bladder,  f  round  the  neck  and  the  commencement  of  the 
urethra,  they  are  disposed  in  a  thick  circular  layer,  forming  the  sphincter  vesicae, 
which  is  continuous  with  the  muscular  fibres  of  the  prostate  gland. 

The  internal  longitudinal  layer  {stratum  internum)  is  thin,  and  its  fasciculi  have 
a  reticular  arrangement,  but  with  a  tendency  to  assume  for  the  most  part  a  longi- 
tudinal direction.  Two  bands  of  oblique  fibres,  originating  behind  the  orifices  of 
the  ureters,  converge  to  the  back  part  of  the  prostate  gland,  and  are  inserted,  by 
means  of  a  fibrous  process,  into  the  middle  lobe  of  that  organ.  They  are  the 
muscles  of  the  ureters,  described  by  Sir  C.  Bell,  who  supposed  that  during  the  con- 
traction of  the  bladder  they  served  to  retain  the  oblique  direction  of  the  ureters, 
and  so  prevent  the  reflux  of  the  urine  into  them. 

The  Submucous  Coat  {tela  suhmucosa). — The  submiucous  coat  consists  of  a  layer 
of  areolar  tissue  connecting  together  the  muscular  and  mucous  coats,  and  inti- 
mately united  to  the  latter. 

The  Mucous  Coat  {tunica  mucosa). — The  mucous  coat  is  thin,  smooth,  and  of  a 
pale  rose  color.  It  is  continuous  above  through  the  ureters  with  the  lining  mem- 
brane of  the  uriniferous  tubes,  and  below  with  that  of  the  urethra.  Except  at  the 
trigone,  it  is  connected  very  loosely  to  the  muscular  coat  by  a  layer  of  areolar  tissue, 
and  is  therefore  thrown  into  folds  or  rugae  when  the  bladder  is  empty  (Fig. 
1046).  The  mucous  membrane  over  the  trigone  never  presents  rugae.  The 
epithelium  covering  it  is  of  the  transitional  variety,  consisting  of  a  superficial 
layer  of  polyhedral  flattened  cells,  each  with  one,  two,  or  three  nuclei  (Fig.  1043) ; 
beneath  these  is  a  stratum  of  large  club-shaped  cells  with  the  narrow  extremity  of 
each  cell  directed  downward  and  wedged  in  between  smaller  spindle-shaped  cells, 


1438 


THE    UBINABY   0BGAN8 


each  an  oval  nucleus  (Fig.  1044).  There  are  no  true  glands  in  the  mucous  mem- 
brane of  the  bladder,  though  certain  mucous  follicles  which  exist,  especially  near 
the  neck  of  the  bladder,  have  been  regarded  as  such. 

Objects  Seen  on  the  Inner  Surface. — Upon  the  inner  surface  of  the  bladder  are 
seen  the  mucous  membrane,  orifices  of  the  ureters,  the  trigone,  and  the  commencement 
of  the  urethra. 


Fig.  1043.— Superficial  layer  of  the  epithelium  of 
the  bladder.  Composed  of  polyhedral  cells  of  vari- 
ous sizes,  each  with  one,  two,  or  three  nuclei.  (Klein 
and  Noble  Smith.) 


Fig.  1044. — Deep  layers  of  epithelium  of  bladder, 
showing  large  club-shaped  cells  above,  and  smaller, 
more  spindle-shaped  cells  below,  each  with  an  oval 
nucleus.     (Klein  and  Noble  Smith.) 


The  Mucous  Membrane. — The  mucous  membrane  of  the  empty  bladder  is  thrown 
into  folds  or  rugae,  except  over  the  trigone,  where  it  is  firmly  adherent  to  the 
muscular  coat  and  is  smooth  (Figs.  1045  and  1046).  The  folds  disappear  when 
the  bladder  is  distended. 

The  Orifices  of  the  Ureters  (Figs.  1045  and  1046) . — These  are  situated  at  the  base 
of  the  trigone,  being  distant  from  each  other  about  two  inches  when  the  bladder  is 


RIDQC   FORMtD  BY 
I— INTERURETERAL 
MUSCLE 


Fig.  1045. — The  interior  of  the  bladder,  showing  the  vesical  trigone.      (Poirier  and  Charpy.) 

moderately  distended.  Each  orifice  is  about  an  inch  and  a  half  from  the  base  of  the 
prostate  and  the  commencement  of  the  urethra  in  the  moderately  distended  bladder. 
The  Vesical  Trigone  or  the  Trigonum  Vesicae  (Fig.  1045)  is  a  triangular  smooth 
surface,  with  the  apex  directed  forward,  situated  at  the  base  of  the  bladder,  imme- 
diately behind    the  urethral  orifice.    It  is  paler  in  color  than  the  rest   of  the 


THE    UBINABY  BLADDER 


1439 


interior,  and  never  presents  any  rugae,  even  in  the  collapsed  condition  of  the 
organ,  owing  to  the  intimate  adhesion  of  its  mucous  membrane  to  the  subjacent 
tissue.  It  is  bounded  at  each  posterior  angle  by  the  orifice  of  a  ureter,  and  in 
front  by  the  orifice  of  the  urethra.  Projecting  from  the  lower  and  anterior  part  of 
the  bladder,  and  reaching  to  the  orifice  of  the  urethra,  is  a  slight  elevation  of 
mucous  membrane,  particularly  prominent  in  old  persons,  called  the  uvula  vesicae. 
It  is  formed  by  a  thickening  of  the  submucous  tissue. 

Stretching  from  one  ureteral  opening  to  the  other  is  a  smooth,  slightly  curved 
ridge,  the  convexity  of  which  is  toward  the  urethra.  It  is  produced  by  transverse 
muscle-fibres  beneath  the  mucous  membrane.  The  outer  prolongations  of  this 
ridge  beyond  the  ureteral  orifices  are  called  the  ureteral  folds  {'plicae  uretericae). 
They  are  created  by  the  ureters  as  they  traverse  the  bladder  wall.  About  the 
ureteral  orifice  are  slight  radial  folds  of  mucous  membrane,  which  are  continuous 
with  the  longitudinal  folds  of  the  prostatic  urethra.  "  In  the  empty  bladder  the 
ureteral  orifice  and  the  openings  of  the  two  ureters  lie  at  the  angles  of  an  approxi- 
mately equilateral  triangle,  whose  sides  are  about  one  inch  in  length.  When  the 
bladder  is  distended  the  distance  between  the  openings  may  be  increased  to  one 
and  a  half  inches  or  more."^ 


LONGITUDINAL 
FIBRES 


CIRCULAR 
FIBRES 


TRIGONE 

TRANSVERSE 

FIBRES  OF 

TRIGONE 

LONGITUDINAL 

FIBRES  OF 

TRIGONE 


EJACULATORY 
DUCT 


Fia.  1046.— The  internal  surface  of  the  bladder.     (Poirier  and  Charpy), 

The  muscles  of  the  ureters  were  referred  to  on  p.  1437. 

The  internal  urethral  orifice  {orificium  urethrae  internum)  is  sickle-shaped  and 
is  surrounded  by  a  circular  prominence  (annulus  urethralis),  which  is  most  distinct 
in  the  male. 

Vessels  and  Nerves.— The  arteries  (Fig.  424)  supplying  the  bladder  are  the 
superior,  middle,  and  inferior  vesical  in  the  male,  with  additional  branches  from 
the  uterine  and  vaginal  in  the  female.  They  are  all  derived  from  the  anterior 
trunk  of  the  internal  iliac.  The  obturator  and  sciatic  arteries  also  supply  small 
visceral  branches  to  the  bladder.  The  veins  form  a  complicated  plexus  around  the 
neck,  sides,  and  base  of  the  bladder  (Fig.  474).  The  veins  communicate  below 
with  the  plexus  about  the  prostate  and  terminate  in  the  internal  iliac  vein. 

The  lymphatics  form  two  plexuses,  one  in  the  muscular  and  another  in  the  sub- 
mucous coat.  They  accompany  the  blood-vessels.  The  mucous  membrane  of 
the  bladder  contains  no  lymphatics  whatever  (Sappey).  The  must;ular  tissue 
contains  a  few  lymphatics.    The  subperitoneal  tissues  contain  the  usual  number. 


1  Professor  A.  Francis  Dixon,  in  Prof.  D.  J.  Cunningham's  Text-book  of  Anatomy. 


1440  THE    URINARY   ORGANS 

The  collecting  trunks  from  the  anterior  surface  terminate  in  the  external  iliac 
glands.  The  trunks  from  the  posterior  surface  terminate  in  the  internal  iliac 
glands,  the  hypogastric  glands  and  the  glands  in  front  of  the  sacral  promontory. 

The  nerves  are  derived  from  the  pelvic  plexus  of  the  sympathetic  and  from  the 
third  and  fourth  sacral  nerves ;  the  former  supplying  the  upper  part  of  the  organ, 
the  latter  its  base  and  neck.  According  to  F.  Darwin,  the  sympathetic  fibres  have 
ganglia  connected  with  them,  which  send  branches  to  the  vessels  and  to  the 
muscular  coat. 

Surface  Form. — The  surface  form  of  the  bladder  varies  with  its  degree  of  distention  and 
under  other  circumstances.  In  the  young  child  it  is  represented  by  a  conical  figure,  the  apex 
of  which,  even  when  the  viscus  is  empty,  is  situated  in  the  hypogastric  region,  about  an  inch 
above  the  level  of  the  symphysis  pubis.  In  the  adult,  when  the  bladder  is  empty,  its  apex  does 
not  reach  above  the  level  of  the  upper  border  of  the  symphysis  pubis,  and  the  whole  organ  is 
situated  in  the  pelvis;  the  neck,  in  the  male,  corresponding  to  a  line  drawn  horizontally  backward 
through  the  symphysis  a  little  below  its  middle.  As  the  bladder  becomes  distended,  it  gradually 
rises  out  of  the  pelvis  into  the  abdomen,  and  forms  a  swelling  in  the  hypogastric  region,  which  is 
perceptible  to  the  hand  as  well  as  to  percussion.  In  extreme  distention  it  reaches  into  the  umbil- 
ical region.  Under  these  circumstances  the  lower  part  of  its  anterior  surface,  for  a  distance 
of  about  two  inches  above  the  symphysis  pubis,  is  closely  applied  to  the  abdominal  wall,  without 
the  intervention  of  peritoneum,  so  that  it  can  be  tapped  by  an  opening  in  the  middle  line  just 
above  the  symphysis  pubis,  without  any  fear  of  wounding  the  serous  membrane.  When  the 
rectum  is  distended,  the  prostatic  portion  of  the  urethra  is  elongated  and  the  bladder  lifted  out 
of  the  pelvis  and  the  peritoneum  pushed  upward.  Advantage  is  taken  of  this  by  some  surgeons 
in  performing  the  operation  of  suprapubic  cystotomy.  The  rectum  is  distended  by  an  India- 
rubber  bag,  which  is  introduced  into  this  cavity  empty,  and  is  then  filled  with  ten  or  twelve  ounces 
of  water.  If  now  the  bladder  is  injected  with  about  half  a  pint  of  some  antiseptic  fluid,  it  will 
appear  above  the  pubes  plainly  perceptible  to  the  sight  and  touch.  The  peritoneum  will  be 
pushed  out  of  the  way,  and  an  incision  three  inches  long  may  be  made  in  the  linea  alba,  from 
the  symphysis  pubis  upward,  without  any  great  risk  of  wounding  the  peritoneum.  Other  sur- 
geons object  to  the  employment  of  this  bag,  as  its  use  is  not  imattended  with  risk,  and  because 
it  causes  pressure  on  the  prostatic  veins  and  hence  produces  congestion  of  the  vessels  over  the 
bladder  and  a  good  deal  of  venous  hemorrhage. 

When  distended,  the  bladder  can  be  felt  in  the  male,  from  the  rectum,  behind  the  prostate, 
and  fluctuation  can  be  perceived  by  a  bimanual  examination,  one  finger  being  introduced  into  the 
rectum  and  the  distended  bladder  being  tapped  on  the  front  of  the  abdomen  with  the  finger 
of  the  other  hand.  This  portion  of  the  bladder — that  is,  the  portion  felt  in  the  rectum  by  the 
finger — is  uncovered  by  peritoneum. 

Surgical  Anatomy. — A  certain  defect  of  development  in  which  the  bladder  is  implicated  is 
known  under  the  name  of  extroversion  of  the  bladder.  In  this  condition  the  lower  part  of  the 
abdominal  wall  and  the  anterior  wall  of  the  bladder  are  wanting,  so  that  the  posterior  surface 
of  the  bladder  presents  on  the  abdominal  surface,  and  is  pushed  forward  by  the  pressure  of  the 
viscera  within  the  abdomen,  forming  a  red,  vascular  protrusion,  on  which  the  openings  of  the 
ureters  are  visible.  The  penis,  except  the  glans,  is  rudimentary  and  is  cleft  on  its  dorsal  sur- 
face, exposing  the  floor  of  the  urethra — a  condition  known  as  epispadias.  The  pelvic  bones 
are  also  arrested  in  development  (see  page  220). 

The  bladder  may  be  ruptured  by  violence  applied  to  the  abdominal  wall  when  the  viscus  is 
distended  without  any  injury  to  the  bony  pelvis,  or  it  may  be  torn  in  case  of  fracture  of  the 
pelvis.  The  rupture  may  be  either  intraperitoneal  or  extraperitoneal — that  is,  may  implicate  the 
superior  surface  of  the  bladder  in  the  former  case,  or  one  of  the  other  surfaces  in  the  latter. 
Rupture  of  the  antero-inferior  surface  alone  is,  however,  very  rare.  Until  recently  intraperi- 
toneal rupture  was  uniformly  fatal,  but  now  abdominal  section  and  suturing  the  rent  with  Lem- 
bert  sutures  often  saves  the  patient.  The  sutures  are  inserted  only  through  the  peritoneal  and 
muscular  coats  in  such  a  way  as  to  bring  the  serous  surfaces  at  the  margins  of  the  wound  into 
apposition,  and  one  is  also  inserted  just  beyond  each  end  of  the  wound.  The  bladder  should  be 
tested  as  to  whether  it  is  water-tight  before  closing  the  external  incision. 

The  muscular  coat  of  the  bladder  undergoes  hypertrophy  in  cases  in  which  there  is  any  per- 
sistent obstruction  to  the  flow  of  urine.  Under  these  circumstances  the  bundles  of  which  the 
muscular  coat  consists  become  much  increased  in  size,  and,  interlacing  in  all  directions,  give  rise 
to  what  is  known  as  the  fasciculated  bladder.  Between  these  bundles  of  muscular  fibres  the  mucous 
membrane  may  bulge  out,  forming  sacculi,  constituting  the  sacculated  bladder,  and  in  these 
little  pouches  phosphatic  concretions  may  collect,  forming  encysted  calculi.  The  mucous  mem- 
brane is  very  loose  and  lax,  except  over  the  trigone,  to  allow  of  the  distention  of  the  viscus. 

Various  forms  of  tumors  have  been  found  springing  from  the  wall  of  the  bladder.    The  inno- 


THE    MALE    URETHRA 


1441 


cent  tumors  are  the  papilloma  and  the  mucous  polypus,  arising  from  the  mucous  membrane; 
the  fibrous  tumor,  from  the  submucous  tissue;  and  the  myoma,  originating  in  the  muscular 
tissue;  and,  very  rarely,  dermoid  tumors,  the  exact  origin  of  which  it  is  difficult  to  explain. 
Of  the  malignant  tumors,  epitheliomata  are  the  most  common,  but  sarcomata  are  occasionally 
found  in  the  bladders  of  children. 

Puncture  of  the  bladder  is  performed  above  the  pubes  without  wounding  the  peritoneum. 
Puncture  by  the  rectum  is  not  now  performed,  as  a  permanent  fistula  may  be  left  from  abscess 
forming  between  the  rectum  and  the  bladder;  or  pelvic  cellulitis  maybe  set  up;  moreover,  it  is 
exceedingly  inconvenient  to  keep  a  cannula  in  the  rectum.  In  some  cases  in  performing  this 
operation  the  recto-vesical  pouch  of  peritoneum  has  been  wounded,  inducing  fatal  peritonitis. 
The  operation,  therefore,  has  been  abandoned.  Suprapubic  cystotomy  is  considered  above  under 
the  heading  of  Surface  Form.  This  operation  may  be  employed  to  permit  of  the  removal  of  a 
calculus  and  is  then  called  suprapubic  lithotomy. 


THE  MALE  URETHRA  (URETHRA  VIRILIS)  (Figs.  1047, 1048, 1049, 1050, 1054). 

The  urethra  in  the  male  extends  from  the  neck  of  the  bladder  at  the  internal 
orifice  of  the  urethra  (orificium  urethrae  internum)  to  the  meatus  urinarius,  the 
external  orifice  of  the  urethra  (orificium  urethrae 
externum),  at  the  end  of  the  penis.  The  in- 
ternal orifice  has  been  described  (p.  1439).  The 
urethra  presents  a  double  curve  in  the  flaccid 
state  of  the  penis  (Fig.  1054),  but  in  the  erect 
state  of  this  organ  it  forms  only  a  single  curve, 
the  concavity  of  which  is  directed  upward.  Its 
length  varies  from  eight  to  nine  inches;  and  it 
is  divided  into  three  portions,  the  prostatic, 
membranous,  and  spongy,  the  structure  and  re- 
lations of  which  are  essentially  different.  Ex- 
cept during  the  passage  of  the  urine  or  semen, 
the  urethra  is  a  mere  cleft  or  slit,  transverse,  T- 
shaped  or  crescentic  (Fig.  1049),  with  its  upper 
and  under  surfaces  in  contact.  At  the  meatus 
urinarius  the  slit  is  vertical,  and  in  the  prostatic 
portion  somewhat  arched  (Fig.  1049). 

The  First  or  Prostatic  Portion  (pars  pros- 
iatica)  (Figs.  1037, 1047,  1048,  1055,  and  1056). 
— The  first  or  prostatic  portion  is  the  widest  and  Corpus 
most  dilatable  part  of  the  canal.  It  is  between 
the  internal  orifice  of  the  urethra  and  the  supe- 
rior layer  of  the  triangular  ligament  and  is  within 
the  pelvic  cavity.  It  passes  between  the  two 
lateral  lobes  of  the  prostate  gland,  from  the  base 
to  the  apex  of  the  gland,  lying  nearer  its  ante- 
rior than  its  posterior  surface.  The  gland  seems 
to  completely  surround  this  portion  of  the 
urethra  (Fig.  1053),  but  the  glandular  matter  of 
the  gland  does  not  (Fig,  1051) .  The  gland  is  like 
a  buckle  open  in  front,  and  the  open  part  of  the 
buckle  is  closed  by  the  prostatic  muscle.  The 
prostatic  urethra  is  about  an  inch  and  a  quarter 
in  length;  the  form  of  the  canal  is  spindle- 
shaped,  being  wider  in  the  middle  than  at  either 

extremity,  and  narrowest  below,  where  it  joins  the  membranous  portion.  Except 
during  the  passage  of  fluid,  the  canal  is  in  a  collapsed  state,  the  anterior  wall  resting 
upon  the  posterior  wall  (Fig.  1049),  and  the  mucous  membrane  exhibiting  longitu- 

91 


Glans. 


Fossa 
tiavic. 


MeatuLS. 


Fig.  1047. — The  male  urethra,  laid  open  on 
its  anterior  (upper)  surface.     (Testut.) 


1442 


THE    UBINABY   OBGANS 


dinal  folds.  When  distended,  the  largest  portion  of  the  prostatic  urethra  has  a 
diameter  of  about  one-third  of  an  inch.  A  transverse  section  of  the  canal  as  it 
lies  in  the  prostate  is  horseshoe-shape  J,  the  convexity  being  directed  forward 
(Fios.  1049  and  1051).  The  direction  of  the  canal  is  nearly  vertical,  there  being 
a  slight  curve,  which  is  concave  forward  (Figs.  1037  and  1038j. 

Upon  the  posterior  wall  or  floor  of  the  canal  is  a  narrow  longitudinal  ridge,  the 
crest  of  the  urethra  {crista  urethralis) ,  formed  by  an  elevation  of  the  mucous  mem- 
brane and  its  subjacent  tissue  (Fig.  1047).  This  crest  begins  at  the  uvula  vesicae, 
and  passes  through  the  prostatic  portion  and  into  the  membranous  portion  of  the 
urethra  (Fig.1056),  and  usually  bifurcates  at  its  distal  end ;  it  contains,  according  to 
Kobelt,  muscular  and  erectile  tissues.  On  this  longitudinal  ridge  is  an  enlargement, 
the  verumontanum  or  caput  gallinaginis  (colliculus  seminalis)  (Figs.  1047  and  1056). 
When  distended,  it  may  serve  to  prevent  the  passage  of  the  semen  backward  into 
the  bladder.  On  each  side  of  the  verumontanum  is  a  slightly  depressed  fossa,  the 
floor  of  which  is  perforated  by  numerous  apertures,  the  orifices  of  the  prostatic  ducts 
(Figs.  1047  and  1056),  from  the  lateral  lobes  of  the  glands;  the  ducts  of  the  middle 


MUSCULAR  WALL 
OF  BLADDER 


PROSTATIC 
SINUS 


LONGITUDINAL  MUS- 
CLES OF  URETHRA 


Fig.  1048. — Proximal  portion.^  of  urethra  with  surrounding  parts.     (After  Testut.) 

lobe  open  behind  the  verumontanum.  At  the  forepart  of  the  verumontanum,  in  the 
middle  line,  is  a  depression,  the  prostatic  sinus,  prostatic  utricle,  prostatic  vesicle, 
uterus  masculinus  or  sinus  pocularis  {utriculus  prostaticus)  (Yigs.lOSS  and  1056) ;  and 
upon  or  within  its  margins  are  the  slit-like  openings  of  the  ejaculatory  ducts  (diwtus 
ejaculatorii)  (Fig.  1056).  The  sinus  pocularis  forms  a  cul-de-sac  about  a  quarter  of 
an  inch  in  length,  which  runs  upward  and  backward  in  the  substance  of  the  pros- 
tate behind  the  transverse  band  of  prostatic  tissue  which  joins  the  lateral  lobes 
behind  the  posterior  wall  of  the  urethra ;  its  prominent  anterior  wall  partly  forms 
the  verumontanum.  Its  walls  are  composed  of  fibrous  tissue,  muscular  fibres, 
and  mucous  membrane,  and  numerous  small  glands  open  on  its  inner  surface. 
It  has  been  called  by  Weber,  who  discovered  it,  the  uterus  masculinus,  from  its 
being  developed  from  the  united  lower  ends  of  the  atrophied  Miillerian  ducts, 
and  therefore  being  homologous  with  the  uterus  and  vagina  in  the  female. 

The  Second,  Muscular  or  Membranous  Portion(par5  membranacea)  (FigsA047, 
1048,  and  1056)  extends  downward  and  forward  between  the  apex  of  the  prostate 
and  the  bulb  of  the  corpus  spongiosum.  It  is  the  narrowest  part  of  the  canal  (except- 
ing the  meatus),  and  measures  three-quarters  of  an  inch  along  its  upper,  and  half 
an  inch  along  its  lower,  surface,  in  consequence  of  the  bulb  projecting  backward 


THE   3fALE    UBETHBA 


1443 


•aS^J 


beneath  it.  Its  anterior  concave  surface  is  placed  about  an  inch  below  and  behind 
the  pubic  arch,  from  which  it  is  separated  by  the  dorsal  vessels  and  nerves  of  the 
penis,  and  some  muscular  fibres.  Its  posterior  convex  surface  is  separated  from 
the  rectum  by  a  triangular  space,  which  constitutes  the  perineum.  The  membra- 
nous portion  of  the  urethra  lies  chiefly  between  the  inferior  and  superior  layers  of 
the  triangular  ligament(Fig.309) .  The  termination  of  this  part  of  the  urethra  is  over- 
lapped by  the  bulb,  and  is  in  front  of  the  triangular  ligament 
(Fig.  309j.  As  it  pierces  the  inferior  layer,  the  fibres  around 
the  opening  are  prolonged  over  the  tube  and  fix  the  two  struc- 
tures firmly  to  each  other.  The  membranous  urethra  is  sur- 
rounded by  cavernous  tissue  and  by  the  Compressor  urethrae 
muscle  (m.  sphincter  urethrae  membrc.naceae)[F\g.3lO) .  On  the 
floor  of  the  membranous  urethra  is  the  anterior  extremity  of 
the  crista  urethralis.  Behind  this  part  of  the  urethra,  on  each 
side  of  the  middle  line,  are  Cowper's  glands  (Figs.  308  and  1056). 
The  canal  enters  the  bulb  a  little  in  front  of  the  posterior 
extremity,  and  the  anterior  wall  or  roof  of  the  membranous 
urethra  is  a  little  longer  than  the  posterior  wall  or  floor.  The 
backward  projection  of  the  bulb  hangs  over  most  of  the  floor 
of  the  membranous  urethra  (Figs.  308,  309,  1047,  1056,  and 
1058).  When  the  urethra  is  empty  the  mucous  membrane  of 
the  second  part  is  thrown  into  longitudinal  folds,  which  are 
obliterated  by  distention. 

The  Third,  Penile,  Pendulous,  Cavernous  or  Spongy 
Portion  (pars  cavernosa)  (Figs.  1037, 1047, 1048,  and  1050)  is 
the  longest  part  of  the  urethra,  and  is  contained  in  the  corpus 


I 


RIGHT  LIP  OF  MEATUS 


PREPUCE  RETRACTED- 

LATERAL   LACUNA 
UPPER  WALL  OF  URETHRA- 

SPONGY  BODY — cot  surfaea- 


-SKIN 

-SIDE  OF  URETHRA 

-LARGE   LACUNA 

_SPONQY  BODY — cut  SUrfaCS 


MEDIAN   LACUN>C 


CORPUS 

SPONGIOSUM 


Fig.  1050.- 


-The  distal  portion  of  the  male  urethra,  laid  open  on  its  posterior 
(under)  surface,  showing  the  lacunae.     (Testut.) 


^'i'^'^ni 


xs 


Fig.  1049.  —  Cross-sec- 
tionsof  the  male  urethra  at 
various  distances  from  its 
free  end,  showing  marked 
alterations  of  form.  (Tes- 
tut.) 


spongiosum.  It  is  about  six  inches  in  length,  and  extends  from  the  termination 
of  the  membranous  portion  to  the  meatus  urinarius.  It  is  surrounded  throughout 
its  entire  course  by  the  erectile  tissue  of  the  corpus  spongiosum  and  glans  penis. 
Its  proximal  end  is  fixed  in  position  and  unchangeable  in  direction.  Its  distal  end 
is  movable  and  changeable  in  direction.  Commencing  just  below  the  triangular 
ligament  it  is  first  directed  forward  through  the  bulb;  it  then  passes  downward 
and  forward,  the  turn  beginning  at  the  seat  of  attachment  of  the  suspensory 
ligament  of  the  penis  (Fig.  1037) .  The  direction  of  the  third  portion  of  the  urethra 
is  changed  by  alterations  in  the  position  of  the  penis.  When  the  canal  is  closed  the 
anterior  and  posterior  walls  are  in  contact  (roof  and  floor),  except   in  the  glans 


1444  THE    URINARY   ORGANS 

penis,  where  the  lateral  walls  come  together.  "Thus  the  first  part  of  the  canal 
when  empty  is  represented  in  cross-section  by  a  transverse  slit,  and  the  terminal 
part  by  a  vertical  slit  "^  (Fig.  1049).  The  calibre  of  the  spongy  urethra  varies  in 
different  portions  of  the  tube.  It  is  of  larger  diameter  in  the  bulb  (bulbous  por- 
tion of  urethra)  and  in  the  glans  than  between  these  two  points.  In  the  body  of 
the  penis  the  canal  is  of  uniform  size,  and  is  about  one-quarter  of  an  inch  in 
diameter.  The  fossa  naviculaxis  (fossa  navicularis  urethrae  [Morgagni])  is  an 
oblong  dilatation  of  the  terminal  portion  of  the  penile  urethra  (Figs.  1037,  1047, 
and  1060).  In  the  front  of  the  fossa  navicularis  there  is  a  transverse  fold  of 
mucous  membrane,  the  valve  of  Guerin  (valvulae  fossae  navicularis).  It  is  part 
of  a  distinct  depression  or  pocket.  The  fossa  navicularis  opens  anteriorly  by 
the  meatus  urinarius. 

The  meatus  urinarius  or  external  orifice  of  the  urethra  (orificium  urethrae  externum) 
(Figs.  1047  and  1059)  is  the  most  contracted  part  of  the  urethra;  it  is  a  vertical  slit 
(Fig.  1049), about  three  lines  in  length,bounded  on  each  side  by  a  small  lip  or  labium. 

The  inner  surface  of  the  lining  membrane  of  the  urethra,  especially  on  the  floor 
of  the  spongy  portion,  presents  the  orifices  of  numerous  mucous  glands  (Fig.  1050) 
situated  in  the  submucous  tissue,  and  named  the  glands  of  Littx^  (glandulae  ure- 
thrales).  A  number  of  little  recesses  or  follicles,  called  lacmiae  (lacunae  urethrales), 
open  into  the  penile  urethra.  Some  of  the  glands  of  Littreopen  into  the  lacunae; 
some  do  not.  They  vary  in  size,  and  their  orifices  are  directed  forward,  so  that  they 
may  easily  intercept  the  point  of  a  catheter  in  its  passage  along  the  canal.  One 
of  these  lacunae,  larger  than  the  rest,  is  situated  in  the  upper  surface  of  the  fossa 
navicularis,  about  half  an  inch  from  the  orifice;  it  is  called  the  lacuna  magna  (Fig. 
1060) .  Into  the  bulbous  portion  are  found  opening  the  ducts  of  Cowper's  glands. 

Structure. — The  urethra  is  composed  of  a  continuous  mucous  membrane, 
supported  by  a  submucous  tissue  which  connects  it  with  the  various  structures 
through  which  it  passes. 

The  Mucous  Coat. — The  mucous  coat  forms  part  of  the  genito-urinary  mucous 
membrane.  It  is  continuous  with  the  mucous  membrane  of  the  bladder,  ureters, 
and  kidneys;  externally  with  the  integument  covering  the  glans  penis;  and  is  pro- 
longed into  the  ducts  of  the  glands  which  open  into  the  urethra — viz.,  Cowper's 
glands  and  the  prostate  gland — into  the  vasa  deferentia  and  the  seminal  vesicles 
through  the  ejaculatory  ducts.  The  mucous  membrane  is  arranged  in  longitudinal 
folds  when  the  tube  is  empty.  Small  papillae  are  found  upon  it  near  the  orifice, 
and  its  epithelial  lining  is  of  the  columnar  variety,  excepting  near  the  meatus, 
where  it  is  squamous. 

The  Glands  and  Crypts  of  the  Urethral  Mucous  Membrane  (Fig.  1049). — There  is  a 
pocket,  the  lacuna  magna  (Fig.  1060) ,  opening  to  the  front  in  the  upper  wall  of  the 
fossa  navicularis.  The  fossa  is  bounded  by  the  valve  of  Guerin  (valvulae  fossa  7iavic- 
ularis) .  The  lacunae  of  Morgagni  are  in  the  spongy  urethra  back  of  the  valve  of 
Guerin.  The  lacunae  look  forward.  The  largest  of  them  is  on  the  roof  of  the  fossa 
navicularis,  one  and  one-half  inches  from  the  orifice  (see  above).  Some  of  the 
lacunae  receive  the  secretion  from  the  glands  of  Littre;  others  do  not,  because  some 
of  the  glands  open  on  the  free  surface.  The  larger  lacunae  are  one-third  of  an  inch 
deep  and  are  placed  in  a  longitudinal  row  upon  the  anterior  wall.  The  smaller 
lacunae  are  in  longitudinal  rows  at  the  sides  of  the  tube.  The  glands  of  Morgagni 
are  present  throughout  the  urethra,  except  in  its  most  anterior  part.  In  the  prostatic 
urethra  they  are  arranged  in  rows.  In  the  membranous  urethra  they  are  scat- 
tered irregularly.  In  the  spongy  portion  they  are  most  numerous  on  the  anterior 
wall  and  are  more  plentiful  on  the  sides  than  on  the  floor.  Besides  the  lacunae  and 
racemose  glands,  there  are  the  opening  of  the  prostatic  glands,  the  ejaculatory 
ducts,  Cowper's  glands,  and  the  opening  of  the  sinus  pocularis. 

1  Professor  A.  Francis  Dixon,  in  Professor  D.  J.  Cunningham's  Text-book  of  Anatomy. 


I 


THE   MALE    URETHRA  I445 

The  Submucous  Tissue. — The  submucous  tissue  consists  of  a  vascular  erectile 
layer.  It  contains  the  glands  of  Littre,  especially  in  the  posterior  part.  These 
glands  are  lined  with  cylindrical  epithelium  and  enter  the  submucous  coat. 

The  Muscular  Layer. — The  muscular  layer  is  continuous  with  the  muscle  of  the 
prostate  and  bladder.  It  is  composed  of  non-striated  muscle  arranged  in  an 
outer  layer  of  circular  fibres  {stratum  circulare)  and  an  inner  layer  of  longitudinal 
fibres  (stratum  longitudinale).  It  is  placed  external  to  the  submucous  coat.  In 
the  penile  urethra  there  is  only  a  thin  layer  of  longitudinal  fibres.  In  the  mem- 
branous urethra  and  the  prostatic  urethra  there  are  two  layers  of  muscle,  an  inner 
thin  layer  of  longitudinal  fibres  and  a  thicker  layer  of  circular  fibres.  The  longi- 
tudinal fibres,  when  contracted,  shorten  the  urethra  and  increase  its  diameter. 
The  circular  fibres  are  in  a  state  of  tonic  contraction  and  close  the  urethra.  In 
fact,  they  constitute  the  real  sphincter  (Zeissl,  Zuckerkandl).  The  so-called 
sphincter  of  the  urethra,  the  Accelerator  urinae,  is  a  voluntary  muscle  and  is  not 
the  real  sphincter.  Outside  of  the  muscular  layer  of  the  urethra  is  the  tissue 
of  the  corpus  spongiosum. 

Surgical  Anatomy. — The  urethra  may  be  ruptured  by  the  patient  falling  astride  of  any  hard 
substance  and  striking  his  perinseum,  so  that  the  urethra  is  crushed  against  the  pubic  arch. 
Bleeding  will  at  once  take  place  from  the  urethra,  and  this,  together  with  the  bruising  in  the 
perinseum  and  the  history  of  the  accident,  will  at  once  point  to  the  nature  of  the  injury. 

Rupture  of  the  urethra  leads  to  exiravasation  of  urine.  In  rupture  back  of  the  superior  layer 
of  the  triangular  ligament  the  urine  usually  follows  the  rectum  and  reaches  the  margin  of  the 
anus.  Rupture  between  the  two  layers  of  the  triangular  ligament  liberates  urine  between  the 
two  layers,  where  it  remains  until  a  path  of  exit  is  made  by  suppuration  or  the  surgeon's  knife. 
In  rupture  in  front  of  the  anterior  layer  of  the  ligament  the  urine  passes  into  the  scrotum  and 
may  mount  up  to  the  abdomen  between  the  symphysis  and  the  pubic  spine,  between  which 
points  the  deep  layer  of  the  superficial  fascia  is  not  attached.  It  cannot  pass  to  the  thigh  nor 
cross  the  mid-line,  because  the  fascia  is  attached  to  the  fascia  lata  and  at  the  mid-line. 

The  surgical  anatomy  of  the  urethra  is  of  considerable  importance  in  connection  with  the 
passage  of  instruments  into  the  bladder.  Otis  was  the  first  to  point  out  that  the  urethra  is 
capable  of  great  dilatation,  so  that,  excepting  through  the  external  meatus,  an  instrument  corre- 
sponding to  18  English  gauge  (29  French)  can  usually  be  passed  without  damage.  The  orifice 
of  the  urethra  is  not  so  dilatable,  and  therefore  may  require  slitting,  although  the  introduction 
of  the  Oberlander  dilator,  which  is  expanded  after  introduction,  renders  slitting  of  the  meatus 
seldom  necessary  in  cases  of  chronic  gonorrhoea.  A  recognition  of  this  dilatability  caused  Bige- 
low  to  very  considerably  modify  the  operation  of  lithotrity  and  introduce  that  of  litholapaxy. 
In  passing  a  fine  catheter,  the  point  of  the  instrument  after  it  has  passed  the  lacuna  magna 
should  be  kept  as  far  as  possible  along  the  upper  wall  of  the  canal,  as  the  point  is  otherwise 
very  liable  to  enter  one  of  the  lacunae.  Stricture  of  the  urethra  is  a  disease  of  very  common 
occurrence,  and  is  generally  situated  in  the  spongy  portion  of  the  urethra,  most  commonly  in 
the  bulbous  portion,  just  in  front  of  the  membranous  urethra,  but  in  a  very  considerable  num- 
ber of  cases  in  the  penile  or  ante-scrotal  part  of  the  canal.  Even  in  a  normal  urethra,  and  very 
markedly  in  an  inflamed  urethra,  a  bougie  encounters  resistance  behind  the  bulb.  This  is 
usually  supposed  to  be  due  to  spasm  of  the  Compressor  urethrae  muscle. 

In  irrigation  of  the  urethra  by  gravity  fluid  tends  to  block  at  the  same  point,  especially  if  it  is 
thrown  in  suddenly  or  forcibly.  If  a  reservoir  is  raised  seven  and  one-half  feet  from  the  floor, 
and  if  a  patient  sits  on  a  chair  or  lies  upon  a  bed,  fluid  can  be  readily  made  to  pass  by  hydraulic 
pressure  from  the  meatus  to  the  bladder.  Spasm  may  temporarily  prevent  the  inflow,  but  the 
weight  of  the  column  of  fluid  soon  tires  out  the  muscle  and  causes  it  to  relax.  Relaxation 
is  favored  by  having  the  patient  take  slow,  deep  breaths  and  make  efforts  at  urination 
(Valentine). 

Chronic  gonorrhoea  is  frequently  kept  up  by  persistent  inflammation  of  the  ducts  and  follicles  in 
the  mucous  membrane.  This  condition  is  known  as  chrome  glandular  urethritis  or  para- 
urethritis. In  these  crypts  and  glands  gonococci  may  remain  when  gonorrhoea  appears  to  have 
passed  away,  and  from  time  to  time  reinfection  of  the  urethra  may  arise  from  such  a  source. 

Median  urethrotomy  or  perineal  section  is  opening  of  the  membranous  urethra.  Through  such 
an  opening  the  bladder  can  be  drained  and  explored,  and  the  operation  is  sometimes  called 
median  cystotomy. 

In  lateral  lithotomy  the  knife  enters  the  membranous  urethra  and  strikes  the  groove  of  the 
staff.  Its  edge  is  then  turned  toward  the  left  ischial  tuberosity  and  is  carried  along  the  groove 
into  the  bladder,  dividing  the  membranous  urethra,  the  prostatic  urethra,  the  posterior  layer  of 
the  triangular  ligament,  the  Compressor  urethrae  muscle,  anterior  fibres  of  the  Levator  ani 
muscle  and  the  left  lobe  of  the  prostate  gland. 


1446  THE    UBINARY   ORGANS 

THE  FEMALE  URINARY  BLADDER. 

The  female  bladder  is  situated  at  the  anterior  part  of  the  pelvis.  It  is  in  relation,  in 
front,  with  the  symphysis  pubis ;  behind,  with  the  utero-vesical  pouch  of  peritoneum, 
which  separates  it  from  the  body  of  the  uterus;  its  base  lies  in  contact  with  the 
connective  tissue  in  front  of  the  cervix  and  upper  part  of  the  vagina.  Laterally, 
is  the  recto-vesical  fascia.  The  bladder  is  said  by  some  anatomists  to  be  larger  in 
the"  female  than  in  the  male.  At  any  rate,  it  does  not  rise  above  the  symphysis 
pubis  till  more  distended  than  in  the  male,  but  this  is  perhaps  owing  to  the  more 
capacious  pelvis  rather  than  to  its  being  of  actually  larger  size.  It  is  described 
in  the  section  on  the  Bladder  (p.  1431). 

THE  FEMALE  URETHRA  (URETHRA  MULIEBRIS). 

The  female  urethra  is  a  narrow  membranous  canal,  about  an  inch  and  a  half  in 
length,  extending  from  the  internal  urethral  orifice  (orificium  urethrae  internum) 
at  the  neck  of  the  bladder  to  the  vestibule  of  the  vagina,  where  it  ends,  being 
called  at  its  termination  the  external  orifice  of  the  urethra  or  the  meatus  urinarius 
{orificium  urethrae  externum).  The  meatus  is  usually  a  vertical  slit.  Tiie 
urathra  is  placed  behind  the  symphysis  pubis,  embedded  in  the  anterior  wall 
of  the  vagina;  and  its  direction  is  obliquely  downward  and  forward,  its  course 
being  slightly  curved,  the  concavity  directed  forward  and  upward.  Its  diameter 
when  undilated  is  about  a  quarter  of  an  inch.  The  urethra  perforates  both 
layers  of  the  triangular  ligament,  and  its  external  orifice  is  situated  directly  in 
front  of  the  vaginal  opening  and  about  an  inch  behind  the  glans  clitoridis.  Except 
above,  the  posterior  wall  of  the  urethra  is  firmly  connected  to  the  anterior  wall 
of  the  vagina. 

Structure. — The  urethra  consists  of  three  coats:  muscular,  erectile,  and  mucous. 

The  Muscular  Coat  (tunica  muscularis) . — The  muscular  coat  is  continuous  witli 
that  of  the  bladder;  it  extends  the  whole  length  of  the  tube,  and  consists  of  an 
internal  layer  of  non-striated  longitudinal  fibres  {stratum  longitudinale)  and  an 
external  layer  of  non-striated  circular  fibres  {stratum  circulare).  Superficial  to  the 
circular  fibres  "lies  a  layer  of  cross-striped  muscle-fibres,  which  form  a  closed  ring 
near  the  bladder  only."^ 

The  Submucous  Coat  {tunica  submucosa). — Internal  to  the  muscular  coat  is  the 
submucous  coat,  which  contains  a  venous  plexus,  networks  from  which  pass 
between  the  muscular  layers  and  impart  to  these  layers  an  erectile  or  spongy 
nature  {corpus  spongiosum  urethrae).  In  addition  to  this,  between  the  two  layers 
of  the  triangular  ligament,  the  female  urethra  is  surrounded  by  the  Compressor 
urethrae  muscle,  as  in  the  male. 

The  Mucous  Coat  tunica  mucosa). — The  mucous  coat  is  pale,  continuous  exter- 
nally with  that  of  the  vulva,  and  internally  with  that  of  the  bladder.  It  is  thrown 
into  longitudinal  folds,  one  of  which,  placed  along  the  floor  of  the  canal,  extends 
from  the  vesical  trigone  almost  to  the  external  orifice  of  the  urethra.  It  is  called 
the  crest  {crista  urethralis).  The  outline  of  the  urethra  is  stellate  when  collapsed, 
because  of  the  formation  of  numerous  longitudinal  folds.  It  is  lined  by  laminated 
epithelium,  which  becomes  transitional  near  the  bladder.  Many  mucous  glands 
open  into  the  urethra,  and  there  are  numerous  lacunae.  External  to  the  external 
orifice,  on  each  side,  a  group  of  mucous  glands  opens  by  a  common  duct,  the 
ductus  para-urethralis. 

The  urethra,  because  it  is  not  surrounded  by  dense  resisting  structures,  as  in  the  male,  admits 
of  great  dilatation,  which  enables  the  surgeon  to  remove  with  considerable  facility  calculi  or 
other  foreign  bodies  from  the  cavity  of  the  bladder. 

'  Hand  Atlas  of  Human  Anatomy.  By  Prof.  Werner  Spalteholz.  Translated  and  edited  by  Prof.  Lewellys  F. 
Barker. 


THE  MALE  OEGANS  OF  GENERATION. 


PROSTATIC 
MUSCLE 


GLANDULAR 
TISSUE 


THE  PROSTATE  GLAND  (PROSTATA)  (Figs.  1048,  1051,  1052,  1053,  1054, 

1055,  1056,  1057). 

THE  prostate  gland  {Ttimarrjiu,  to  stand  before)  is  a  structure  accessory  to  the 
true  generative  organs  and  furnishes  a  viscid,  opalescent  secretion  in  which 
spermatozoids  will  live  (W.  G.  Richardson).  It  is  a  pale,  firm,  partly  glandular 
and  partly  muscular  body,  which  is 
placed  immediately  below  the  neck  of  the 
bladder  and  about  the  commencement  of 
the  urethra  in  the  male.  The  prostate 
appears  to  completely  surround  the  first 
portion  of  the  urethra  (Figs.  1053  and 
1057),  but  the  glandular  matter  does  not 
in  reality  completely  surround  the  tube 
(Figs.  1051  and  1057).  As  Spalteholz 
says,  it  partly  surrounds  it  as  a  broad 
clasp,  o'pen  in  front.  This  opening  in  the 
glandular  tissue  is  closed,  and  a  com- 
plete ring  is  established  about  the  urethra 
by  the  prostatic  muscle  (m.  prostaticus) 
Figs.  1051  and  1057).  This  muscle  below  is  composed  of  striated  fibres  and 
is  continuous  with  the  Compressor  urethrae  {m.  sphincter  urethrae  memhranacea) ; 


UTBICLC 

Fig.  1051. — Section  of  the  prostate. 


MUSCULAR 
LAYER  OF 
URETHRA 
URETHRA 


EJACULATORV 
DUCT 

(Jarjavay.) 


PROSTATIC 
MUSCLE 


COMPRESSOR 
URETHRAE    MUSCLE 


SUPERFICIAL 
TRANSVERSE 
PERINEAL 
MUSCLE 


TRANSVERSE 
PERINEAL  LIGAMENT 

Fig.  1052.— Side  view  of  the  position  of  the  prostate.     (Poirier  and  Charpy.) 

above  it  is  composed  of  non-striated  muscle,  and  is  continuous  with  the  circular 
muscular  fibres  of  the  bladder  which  surround  the  ii^ternal  urethral  orifice  and 

^^  (  1447  ) 


1448 


THE   MALE    ORGANS   OF    GENERATION 


constitute  the  Sphincter  vesica?  (Fig.  1052).  The  general  course  of  the  fibres  is 
transverse,  with  radiations  into  the  gland  substance.  The  apex  of  the  gland  for 
about  one-quarter  of  an  inch  is  completely  surrounded  by  the  muscle  (Fig.  1052). 


VAS 
DEFERENS 


PROSTATE 

Fig.  1053. — Prostate  with  seminal  vesicles  and  seminal  ducts,  viewed  from  in  front  and  above. 


(Spalteholz.) 


Ascending  from  the  apex  the  fibres  cover  for  a  short  distance  only  the  front  of  the 
gland  and  are  attached  at  the  sides  to  the  fascia  (Fig.  1052) .    Higher  up  the  muscle 


AMPULLA 

OF  VAS 

DEFERENS 


VAS 
DEFERENS 

EJACULATORY 
DUCT 
PROSTATIC 
UTRICLE 
PROSTATE 
GLAND 
COWPER 
GLAND 


PERITONEUM 


! URETHRA 


CORPUS 
SPONGIOSUM 


CORPUS 
CAVERNOSUM 


HYDATID  OF 
MORGAGNI 


Fig.  1054. — Diagrammatic  representation  of  the  male  reproduction  organs  and  their  relations  to  the  bladder 
and  the  urethra.     Lateral  view.      (Toldt.) 


passes  between  the  sheath  and  the  capsule  and  ascends  to  the  base  of  the  prostate, 
uniting  the  sheath  to  the  capsule  along  the  mid-line  in  front.  The  prostate  is  placed 
in  the  pelvic  cavity,  behind  the  lower  part  of  the  symphysis  pubis,  and  above  the 


THE  PROSTATE    GLAND 


1449 


deep  layer  of  the  triangular  ligament,  and  rests  upon  the  rectum,  through  which 
it  may  be  distinctly  felt,  especially  when  enlarged  (Fig.  1055.) 

The  ejaculatory  ducts  (Figs.  1053,  1054,  and  1056)  enter  the  prostate  at  the  margin 
which  separates  the  base  from  the  posterior  surface  of  the  gland ;  they  pass  down- 
ward, inward,  and  forward  through  the  prostate,  and  open  into  the  prostatic 
urethra.  The  prostate  when  surrounded  by  its  sheath  resembles  a  chestnut  in 
shape.  When  dissected  out  from  its  sheath  and  capsule  and  from  the  Prostatic 
muscle,  it  resembles  an  "open  clasp"  or  horseshoe.    The  sheath  of  the  prostate 


LEC^T   COMMON 
ILIAC    VEIN 


Fig.  1055. — Sagittal  section  of  the  lower  part  of  a  male  trunk,  the  right  segment.     (Testut.) 

is  derived  from  the  recto-vesical  fascia.  It  is  called  the  prostatic  fascia  (fascia  pro- 
statae),  is  distinct  and  dense,  and  covers  the  entire  prostate,  except  at  the  apex  and 
at  the  attachment  of  the  base  of  the  prostate  to  the  neck  of  the  bladder.  The  pros- 
tatic fascia  is  a  distinct  structure,  though  it  is  thin.  The  veins  of  the  prostatic 
plexus  lie  in  the  layers  of  the  sheath,  "and  are  everywhere  separated  from  the 
prostatic  capsule  proper  by  a  layer  of  this  sheath."^  In  an  enlarged  prostate 
the  sheath  is  thick  and  fibrous.  It  is  very  difficult  to  shell  out  a  normal  prostate 
from  its  sheath,  but  it  is  easy  to  shell  out  an  enlarged  prostate.  Within  the  pros- 
tatic sheath  (which,  be  it  remembered,  carries  the  veins)  is  the  true  or  proper  capsule 

1  J.  W.  Thomson  Walker,  in  the  British  Medical  Journal,  July  9,  1904. 


1450 


THE   MALE    ORGANS    OF   GENERATION 


of  the  prostate.  The  true  capsule  is  a  continuous  investment  from  the  entrance 
of  the  urethra  above  to  the  triangular  hgament  below.  It  is  thin,  but  firm  and 
fibrous.     It  is  not  everywhere  absolutely  distinct  from  the  sheath,  but  may  be  fused 


EJACULATOBY 
DUCT 


MOUTH    OF   EJACU- 

LATORY    DUCT 
VERUMONTANUM- — 


PROSTATE — CUT  SURFACE 
OPENINGS    OF 
PROSTATIC  DUCTS 


MEMBRANOUS    URETHRA 


DUCT   OF   COWPERS 

GLAND— LAID   BARE 


A    RIDGE    OF 

MUCOSA 
BULBOUS 
URETHRA 

CORPUS    SPON- 
GIOSUM— CUT  SURFACE 


Fig.  1056. — Proximal  portion  of  the  urethra,  laid  open  by  a  median,  anterior  cut.     (Testut.) 


Fig.  1057. — Transverse  section  of  normal  prostate  through  the  middle  of  the  verumontanum,  from  a  subject 
aged  nineteen  years:  a,  longitudinal  section  of  ducts  leading  from  the  lobules  of  the  pro.static  glands  ;  6,  veru- 
montanum ;  c,  .sinus  pocularis  ;  d,  urethra  ;  e,  ejaculatory  ducts  ;  /",  arteries,  veins,  and  venous  sinuses  in  sheath 
of  prostate  ;  (i,  nerve  trunks  in  sheath  ;  h,  point  of  origin  of  fibro-muscular  bands  encircling  urethra  ;  i,  zone  of 
striated  voluntary  muscle  on  superior  surface.      (Drawn  from  Erdinger  projection  apparatus.)      (Taylor.) 


THE   PROSTATE    GLAND  1451 

with  it  here  and  there,  and  many  bands  of  fibres  run  from  the  sheath  to  the  capsule/ 
The  capsule  is  continuous  with  the  stroma  of  the  gland  and  cannot  be  stripped  off  as 
can  the  kidney  capsule.  Any  attempt  to  strip  off  the  capsule  tears  away  fragments 
of  gland.  The  capsule  is  composed  of  fibrous  tissue  and  unstriated  muscle-fibres. 
From  its  deep  surface  the  capsule  is  continuous  with  the  stroma  of  the  prostate  (W.  G. 
Richardson).  Sir  Henry  Thompson,  half  a  century  ago,  pointed  out  the  distinction 
between  true  capsule  and  sheath,  and  suggested  these  names.  The  prostate  is  divided 
for  study  into  a  base,  apex,  posterior  surface,  anterior  surface,  and  lateral  surfaces. 

The  Base  {basis  prostatae). — The  base  is  directed  upward,  and  is  situated 
immediately  below  the  base  of  the  bladder.  It  is  in  contact  with  and  supports  the 
base  of  the  bladder.  The  external  longitudinal  muscular  layer  of  the  bladder  is 
attached  to  the  posterior  portion  of  the  base  of  the  prostate,  and  some  of  the  fibres 
reach  and  adhere  to  the  true  capsule.  The  anterior  portion  of  the  base  is  called 
the  isthmus  (isthmus  prostatae)  (Fig.  1053). 

The  Apex  (apex  prostatae). — The  apex  is  directed  downward  and  rests  upon 
the  deep  layer  of  the  triangular  ligament.  The  apex  is  fixed,  except  for  the  slight 
mobility  of  the  triangular  ligament ;  the  rest  of  the  gland  is  somewhat  movable. 

Surfaces. — The  Posterior  Surface  (fades  posterior). — The  posterior  surface  is 
flattened,  marked  by  a  slight  longitudinal  furrow,  and  rests  on  the  second  part  of 
the  rectum,  and  is  distant  about  one  inch  and  a  half  from  the  anus.  At  the  upper 
and  posterior  border  of  the  gland  are  the  seminal  vesicles.  Their  direction  is 
downward  and  inward;  in  fact,  almost  transverse. 

The  Anterior  Surface  (facies  anterior). — The  anterior  surface  is  convex,  and  placed 
about  three-fourths  of  an  inch  behind  the  pubic  symphysis, from  which  it  is  separated 
by  a  plexus  of  veins  and  a  quantity  of  loose  fat.  It  is  connected  to  the  pubic  bone 
on  either  side  by  the  pubo -pro static  ligament.   It  is  shorter  than  the  posterior  surface. 

The  Lateral  Surfaces. — The  lateral  surfaces  are  prominent,  and  are  covered  by 
the  anterior  portions  of  the  Levatores  ani  muscles,  which  are,  however,  separated 
from  the  gland  by  a  plexus  of  veins. 

The  prostate  measures  about  an  inch  and  a  half  transversely  at  the  base,  an 
inch  in  its  antero-posterior  diameter,  and  an  inch  and  a  quarter  in  its  vertical 
diameter.  Its  weight  is  about  four  and  a  half  drachms.  It  is  held  in  position 
by  the  anterior  ligaments  of  the  bladder  (ligamenta  puboprostatica) ;  by  the  deep 
layer  of  the  triangular  ligament,  which  invests  the  commencement  of  the  mem- 
branous portion  of  the  urethra  and  prostate  gland ;  and  by  the  anterior  portions  of 
the  Levatores  ani  muscles,  which  pass  backward  from  the  os  pubis  and  embrace 
the  sides  of  the  prostate.  These  portions  of  the  Levatores  ani,  from  the  support 
they  afford  to  the  prostate,  are  named  the  Levator  prostatae. 

The  prostate  consists  of  two  lateral  lobes  and  a  middle  lobe. 

The  Lateral  Lobes  (lobus  dexter  et  sinister). — The  two  lateral  lobes  are  of 
equal  size,  separated  by  a  deep  notch  above,  and  by  a  furrow  upon  the  anterior 
and  posterior  surfaces  of  the  gland,  which  indicates  the  bilobed  condition  of  the 
organ  in  some  animals.  At  the  upper  and  posterior  portion  of  the  prostate  the 
two  lobes  are  united  by  two  bands  of  gland-tissue.  One  of  these  bands  is  in  front 
of  the  ejaculatory  ducts,  the  other  is  below  them.  "The  upper  limit  of  the  gland 
is  thus  in  the  form  of  a  horseshoe,  open  in  front.  "^  Below  the  level  of  the  prostatic 
ducts  the  prostate  and  urethra  are  in  relation,  but  are  not  closely  connected. 
Above  this  level  the  connection  is  intimate  (J.  W.  Thomson  Walker). 

The  So-called  Middle  Lobe  (lobv^  medius). — The  middle  lobe  is  not  in  reality  a 
lobe,  and  the  name  is  usually  employed  to  describe  an  enlargement  of  the  region  of 
the  prostate  on  the  posterior  portion  of  the  urethra  in  front  of  the  ejaculatory  ducts. 
The  so-called  third  or  middle  lobe  is  an  abnormal  condition.  It  is  due  to  enlargement 
of  the  transverse  band  of  prostatic  tissue  which  joins  the  lateral  lobes  beneath  the 

>  W.  G.  Richardson  on  the  Development  and  Anatomy  of  the  Prostate  Gland. 
2  J.  W.  Thomson  Walker,  in  the  British  Medical  Journal,  July  9,  1904. 


1452  THE  MALE    ORGANS  OF    GENERATION 

base  of  the  bladder,  behind  the  posterior  wall  of  the  urethra  and  in  front  of  the  e jacu- 
latory  ducts.  This  mass  of  tissue  is  beneath  the  uvula  vesicae.  Walker  points  out 
that  frequently  nodules  of  enlarged  prostate  protrude  into  the  bladder^ being  covered 
only  by  bladder  mucous  membrane.  This  is  accomplished  by  the  enlarging  pros- 
tate forcing  its  way  through  the  lumen  of  the  vesical  sphincter  and  dilating  it, 
and  separating  and  passing  between  the  strands  of  tiie  internal  longitudinal 
muscle  of  the  bladder.  "  The  so-called  middle  lobe  is  formed  by  the  protrusion  of 
a  nodule  between  the  two  bands  of  muscle  which  pass  into  the  trigone  from  the 
ureters,  and  unite  on  the  posterior  wall  of  the  prostatic  urethra."^ 

The  urethra  passes  forward  between  the  lateral  lobes  of  the  prostate.  The 
prostate  is  perforated  by  the  ejaculatory  ducts.  The  urethra  usually  lies  on  the 
level  of  the  junction  of  the  anterior  and  middle  thirds  of  a  lateral  lobe.  The 
ejaculatory  ducts  pass  obliquely  downward  and  forward  through  the  posterior 
part  of  the  prostate,  and  open  into  the  prostatic  portion  of  the  urethra. 

Structure  (Fig.  1057) . — As  previously  stated  (p.  1449),  the  prostate  is  surrounded 
by  a  sheath  from  the  recto- vesical  fascia,  and  possesses  also  a  true  capsule. 

The  glands  of  the  prostate  are  of  the  branched  tubular  variety  and  number 
forty  or  fifty.  Many  of  the  ducts  join  and  form  from  fifteen  to  twenty-five  smaller 
ducts,  which  empty  into  the  prostatic  urethra,  to  the  sides  of  the  verumontanum 
(Fig.  1056).  The  ducts  and  glands  are  lined  with  cubical  epithelium.  The 
prostatic  secretion  or  prostatic  fluid  (succus  prostaticus)  is  a  viscid,  opalescent, 
serous  secretion,  alkaline  in  reaction,  containing  a  ferment,  but  no  mucus.  The 
substance  of  the  prostate  is  of  a  pale,  reddish-gray  color,  of  great  density  and 
not  easily  torn.    It  consists  of  glandular  substance  and  muscular  tissue. 

The  muscular  tissue,  according  to  KoUiker,  constitutes  the  proper  stroma  of 
the  prostate,  the  connective  tissue  being  very  scanty,  and  simply  forming  thin 
trabeculae  between  the  muscular  fibres,  in  which  the  vessels  and  nerves  of  the 
gland  ramify.  The  true  capsule  is  continuous  with  the  stroma.  The  stroma  lies 
between  the  glandular  substance  and  strands  of  stroma  pass  in  convergent  lines 
toward  the  prostatic  urethra,  especially  toward  the  dorsum  of  the  urethra.  These 
strands  or  septa  divide  the  prostate  into  small  irregular  subdivisions  called  lobules. 
Next  to  the  urethra,  the  stroma  forms  a  thick  layer.  As  age  advances  the  inter- 
stitial tissue  of  the  prostate  increases  and  the  glandular  substance  shrinks. 

Vessels  and  Nerves. — The  arteries  supplying  the  prostate  are  derived  from  the 
internal  pudic,  inferior  vesical,  and  middle  haemorrhoidal.  Branches  of  the  vessels 
enter  the  gland  in  the  septa  between  the  lobules  and  send  off  minute  branches  to  the 
lobules  (Walker).  The  veins  form  a  plexus  around  the  sides  and  base  of  the  gland 
between  layers  of  the  fascial  sheath;  they  receive  in  front  the  dorsal  vein  of  the 
penis,  and  terminate  in  the  internal  iliac  vein.  The  lymphatics  of  the  prostate 
begin  as  networks  about  the  acini  of  the  gland,  pass  to  beneath  the  capsule,  and 
form  another  network,  and  from  this  peripheral  network  collecting  trunks  arise. 
Several  trunks  pass  from  the  posterior  portion  of  the  gland.  One  trunk  passes  to 
the  external  iliac  glands,  one  to  the  internal  iliac  glands,  and  several  end  in  the 
lateral  sacral  glands,  and  the  glands  of  the  sacral  promontory.  An  anterior  trunk 
is  joined  by  lymphatics  from  the  membranous  urethra  and  prostatic  urethra  and 
passes  to  a  gland  on  the  internal  pudic  artery.^  The  nerves  are  derived  from  the 
hypogastric  plexus. 

Surgical  Anatomy. — The  relation  of  the  prostate  to  the  rectum  should  be  noted :  by  means  of 
the  finger  introduced  into  the  gut  the  surgeon  detects  enlargement  or  other  disease  of  the  prostate; 
he  can  feel  the  apex  of  the  gland,  which  is  the  guide  to  Cock's  operation  for  stricture;  he  is  enabled 
also  by  the  same  means  to  direct  the  point  of  a  catheter  when  its  introduction  is  attended  with 
difficulty  either  from  injury  or  disease  of  the  membranous  or  prostatic  portions  of  the  urethra. 
When  the  finger  is  introduced  into  the  bowel  the  surgeon  may,  in  some  cases,  especially  in  boys, 

1  J.  W.  Thomson  Walker,  in  the  British  Medical  Journal,  July  9,  1904. 
-  Poirier  and  Charpy.     Human  Anatomy. 


THE   PENIS  1453 

learn  the  position,  as  well  as  the  size  and  weight,  of  a  calculus  in  the  bladder.  In  the  operation 
for  the  removal  of  a  calculus,  if,  as  is  not  unfrequently  the  case,  the  stone  should  be  lodged 
behind  an  enlarged  prostate,  it  may  be  displaced  from  its  position  by  pressing  upward  the  base 
of  the  bladder  from  the  rectum.  The  prostate  gland  is  occasionally  the  seat  of  suppuration,  either 
due  to  injury,  gonorrhoea,  or  tuberculous  disease.  The  gland  is  enveloped  in  a  dense  unyield- 
ing capsule,  which  determines  the  course  of  an  abscess,  and  also  explains  the  great  pain  which  is 
present  in  acute  inflammation.  The  abscess  most  frequently  bursts  into  the  urethra,  the  direc- 
tion in  which  there  is  least  resistance,  but  may  occasionally  burst  into  the  rectum,  or  more  rarely 
in  the  perinanun.  In  advanced  life  the  prostate  often  becomes  considerably  enlarged,  and  may 
project  into  the  bladder  so  as  to  impede  the  passage  of  the  urine.  According  to  Dr.  Messer's 
researches,  conducted  at  Greenwich  Hospital,  it  would  seem  that  such  obstruction  exists  in  20 
per  cent,  of  all  men  over  sixty  years  of  age.  The  prostate  may  be  enlarged  by  the  growth  of 
innocent  tumors,  adenomata,  fibromata,  myomata,  and  myofibromata.  The  entire  gland  may 
be  hypertrophied.  A  tumor  may  be  encapsulated,  but  often  is  surrounded  by  an  area  of  hyper- 
plasia of  prostatic  tissues,  and  usually  the  area  of  hyper[)lasia  is  much  more  extensive  than  the 
tumor.  A  tumor  may  be  beneath  the  mucous  membrane,  deep  in  the  gland,  or  beneath  the 
sheath.  The  growth  called  the  third  lobe  is  submucous.  In  some  cases  the  enlargement  affects 
principally  the  lateral  lobes,  which  may  undergo  considerable  enlargement  without  causing  much 
inconvenience.  In  other  cases  it  would  seem  that  the  nodule  forms  the  so-called  middle  lobe, 
and  even  a  small  enlargement  of  this  character  may  act  injuriously,  by  forming  a  sort  of  valve 
over  the  urethral  orifice,  preventing  the  passage  of  the  urine,  and  the  more  the  patient  strains, 
the  more  completely  will  it  block  the  opening  into  the  urethra.  In  consequence  of  the  enlarge- 
ment of  the  prostate  a  pouch  is  formed  at  the  base  of  the  bladder  behind  the  projection,  in  which 
urine  collects  and  cannot  entirely  be  expelled.  The  urine  becomes  decomposed  and  ammoniacal, 
and  leads  to  cystitis.  If  the  prostate  enlarges  the  urethra  is  lengthened,  often  dilated,  altered 
in  shape,  or  distorted. 

The  relation  of  the  enlarged  prostate  to  the  neck  of  the  bladder  is  greatly  altered  from  the 
relation  of  the  normal  prostate.  Normally,  it  is  extra  vesical ;  when  enlarged  it  may  encapsule 
"the  neck  of  the  bladder  in  a  cuff-like  manner,  extending  several  inches  upward  on  its  wall," 
and  often  it  protrudes  "into  the  vesical  cavity,  carrying  on  its  surface  the  mucosa  vesicae."^  In 
many  cases  of  prostatic  enlargement  the  gland  should  be  removed  (prostatectomy).  One  method 
is  enucleation  through  a  suprapubic  incision;  another  method  is  enucleation  through  a  perineal 
incision;  another  method  is  carried  out  by  both  incisions  (the  combined  method). 

The  Bottini  operation  is  prostatotomy,  effected  by  a  special  instrument  for  the  purpose  of 
cauterizing  the  gland  and  thus  causing  shrinking. 

In  elderly  individuals  the  gland  tubules  may  form  round,  indurated,  and  sometimes  calcified 
masses,  about  1  mm.  in  diameter,  and  called  prostatic  stones. 

COWPER'S  GLANDS  (GLANDULAE  BULBO-URETHRALES) 

(Figs.  1056,  1063). 

Cowper's  glands  are  two  small,  rounded,  and  somewhat  lobulated  bodies  of 
a  yellow  color,  about  the  size  of  peas,  placed  behind  the  forepart  of  the  mem- 
branous portion  of  the  urethra,  between  the  two  layers  of  the  triangular  ligament. 
They  lie  close  above  the  bulb,  and  are  enclosed  by  the  transverse  fibres  of  the 
Compressor  urethrae  muscle.  Their  existence  is  said  to  be  constant;  they  gradually 
diminish  in  size  as  age  advances. 

Structure. — Each  gland  consists  of  several  lobules  held  together  by  a  fibrous 
investment.  Each  lobule  consists  of  a  number  of  acini  lined  by  columnar  epithe- 
lial cells,  opening  into  one  duct,  which,  joining  with  the  ducts  of  other  lobules 
outside  the  gland,  form  a  single  excretory  duct  (ductus  excretorius) .  The  excretory 
duct  of  each  gland,  nearly  an  inch  in  length,  passes  obliquely  forward  beneath 
the  mucous  membrane,  and  opens  by  a  minute  orifice  on  the  floor  of  the  bulbous 
portion  of  the  urethra. 

THE  PENIS  (Figs.  1058,  1059,  1060,  1061,  1062,  1063). 

The  penis  is  a  long  body  of  prismatic  shape  placed  below  and  in  front  of  the 
symphysis  pubis.  It  surrounds  the  greatest  length  of  the  urethra.  It  consists 
of  a  root,  body,  and  extremity  or  glans  penis.    The  root  and  the  posterior  portion 

'  .John  B.  Murphy,  in  the  Journal  of  the  American  Medical  Association,  May  28,  1904. 


1454 


THE   MALE    ORGANS    OF    GENERATION 


of  the  body  lie  beneath  the  scrotum  and  the  integument  of  the  perinseum  (Fig. 

1054),  and  are  firmly  fixed  to  the  triangular  ligament,  the  pubic  bones,  and  the 

symphysis;  hence  this  portion  of  the  organ 
is  called  the  fixed  portion  {'pars  fxa)  (Fig. 
309).     The  balance  of  the  organ  is  free 


FOSSA  OF  __  MO 
FRAENUM  ~ 


PREPUCE 
RETRACTED 


Fig.  1058. — The  penis,  proximal  portion,  seen 
from  below.      (Testut.) 


rMEDIAN    GROOVE 


™    -  FRAENUM 


Fig.  1059. — Glans  penis,  tui.Ioi  -urface.     (Testut.) 


'DISTAL  PART  OF  SEP- 
TUM PECTINIFORM 


SSA    NAVI 
U  LA  R I S 


-  FRENUM 
_VALVE    OF  LA- 
CUNA   MAGNA 

—LEFT  SIDE  OF  URETHRA 
-FLOOR  OF  URETHRA 

LACUNA    MAGNA 


and  movable  (Fig.  1054),  and  is  called  the  mobile  portion  (pars  mobilis).    When 

the  penis  is  relaxed  there  is  an  angle  between  the   fixed  and  mobile  portions; 

when  the  penis  is  erect,  the  angle  disappears. 

The  Root  (radix  penis). — The  root  is  firmly  connected  to  the  rami  of  the  os 

pubis  and  iscliium  by  two  strong  tapering,  fibrous  processes,  the  crura  (Figs.  1058, 

1062,  and  1063),  and  to  the  front  of  the  symphysis  pubis  by  the  suspensory  liga- 
^^^^^jg  ment  (Fig.  1001),  a  strong  band 

of  fibrous  tissue  which  passes 
downward  from  the  front  of 
the  symphysis  pubis  to  the  root 
of  the  penis. 

The  extremity,  acorn  or 
glans  penis  (Figs.  1059  and 
1060j  presents  the  form  of  an 
obtuse  cone,  flattened  from 
above  downward.  At  its  sum- 
mit is  a  vertical  fissure,  the  ex- 
ternal orifice  of  the  urethra  or 
the  meatus  urinarius  (orificium 
ureihrae  externum).  The  base 
of  the  glans  forms  a  rounded 
projecting  border,  the  corona 
glandis,  and  behind  the  corona 
is  a  deep  constriction,  the  cer- 
vix or  neck  (collum  glandis). 
Upon  both  the  corona  and  neck 
numerous  small  sebaceous 
glands  are  found,  the  glandulae 

Tysonii  odoriferae.^     They  secrete  a  sebaceous  matter  of  very  peculiar  odor,  which 

probably  contains  caseine  and  becomes  easily  decomposed. 

1  Stieda  (Comptes-rendus  du  XII.  Congres  International  de  M^decine.  Mo.<?cow.  1897)  asserts  that  Tyson's 
glands  are  never  found  on  the  corona  glandis,  and  that  what  have  hitherto  been  mistaken  for  glands  are  really 
Jarge  papillae.— Ed.  of  15th  English  edition. 


PREPUCE 
RETRACTED 


CAVERNOSUM  CORPUS 

SPONGIOSUM 


Fig.  1060.- 


-The  penis,  distal  end,  in  sagittal  section  one-twelfth  inch 
at  left  of  middle  line.      (Testut  ) 


THE   PENIS 


1455 


The  Body  of  the  Penis  (corpus  penis). — The  body  of  the  penis  is  the  part 
between  the  root  and  extremity.  In  the  flaccid  condition  of  the  organ  it  is  cyHn- 
drical,  but  when  erect  it  has  a  triangular  prismatic  form  with  rounded  angles,  the 
broadest  side  being  turned  upward,  and  called  the  dorsum  penisi.  The  lower  sur- 
face of  the  body  of  the  penis  is  called  the  urethral  surface  {fades  urethralis).  The 
body  is  covered  by  integument,  and  contains  in  its  interior  a  large  portion  of  the 
urethra.  The  integument  covering  the  penis  is  remarkable  for  its  thinness,  its 
dark  color,  its  looseness  of  connection  with  the  deeper  parts  of  the  organ,  and  for 
the  absence  of  adipose  tissue.  At  the  root  of  the  penis  the  integument  is  contin- 
uous with  that  upon  the  pubes  and  scrotum,  and  at  the  neck  of  the  glans  it  leaves 
the  surface  and  becomes  folded  upon  itself  to  form  the  prepuce  (praeputium)  (Fig. 
1059) .  The  internal  layer  of  the  prepuce  is  attached  behind  to  the  cervix  or  neck 
(Fig.  1059),  and  approaches  in  character  to  a  mucous  membrane;  from  the  cervix 
it  is  reflected  over  the  glans  penis,  and  at  the  meatus  urinarius  is  continuous  with 
the  mucous  lining  of  the  urethra. 

The  integument  covering  the  glans  penis  contains  no  sebaceous  glands,  but 
projecting  from  its  free  surface  are  a  number  of  small,  highly  sensitive  papillae. 


SUPERFICIAL 

FIBRES  OF 

SUSPENSORY 

LIGAMENT 

DEEP    FIBRES 

OF  SUSPENSORY 

LIGAMENT 

DORSAL  VEIN 

DORSAL  ARTERY 

DORSAL  NERVE 


PERITONEUM 


ANTERIOR 
LIGAMENT 
OF  BLADDER 

SUBPUBIC 
LIGAMENT 

ERECTA  PENIS 
MUSCLE 


Fig.  1061. — The  suspensory  ligament.      (Poirier  and  Charpy.) 

At  the  back  part  of  the  meatus  urinarius  a  fold  of  mucous  membrane  passes 
backward  to  the  bottom  of  a  depressed  raph^,  where  it  is  continuous  with  the 
prepuce;  this  fold  is  termed  thefraenum  {frenulum  praeputii).  The  skin  of  the  penis 
covers  the  mobile  parts  of  the  organ.  It  is  thin,  extremely  elastic,  and  contains  very 
few  hairs.  Beneath  the  skin  of  the  penis  is  the  dartos  layer  (Figs.  1061  and  1068), 
continuous  with  the  scrotal  dartos,  containing  chiefly  non-striated  muscular  fibres 
arranged  longitudinally.  It  passes  forward  to  the  orifice  of  the  prepuce,  and 
then  turns  backward,  growing  thinner  and  thinner,  and  finally  disappearing  at 
the  cervix.  Beneath  the  dartos  and  extending  forward  to  the  orifice  of  the  pre- 
puce is  a  sheath  of  areolar  tissue.  It  is  a  lax  sheath  rich  in  elastic  tissue  and 
containing  almost  no  fat.  The  superficial  vessels  and  nerves  are  in  the  areolar 
sheath.  Beneath  the  areolar  sheath  of  €  e  penis,  from  the  corona  to  the  root,  is 
the  fascia  of  the  penis  (fascia  penis)  (Fig.  1068).  It  covers  the  organ  from  the  root 
to  the  corona,  and  also  covers  the  dorsal  artery,  veins,  and  nerves.  It  is  continuous 
behind  with  the  superficial  perineal  fascia  and  suspensory  ligament.  It  is  com- 
posed chiefly  of  elastic  tissue. 

Structure  of  the  Penis. — The  penis  is  composed  of  a  mass  of  erectile  tissue 
enclosed  in  three  cylindrical  fibrous  compartments.     Of  these,  two,  the  corpora 


1456 


THE  MALE    ORGANS    OF   OENEMATION 


cavernosa,  are  placed  side  by  side  along  the  upper  part  of  the  organ;  the  third,  or 
corpus  spongiosum,  encloses  the  urethra  and  is  placed  below. 

The  Two  Corpora  Cavernosa  (corpora  cavernosa  penis)(Figs.  1062  and  1063). — The 
two  corpora  cavernosa  form  the  chief  part  of  the  body  of  the  penis.  They  consist  of 
two  fibrous  cylindrical  tubes,  placed  side  by  side,  and  intimately  connected  along 
the  median  line  for  their  anterior  three- 
fourths,  whilst  at  their  back  part  they 
separate  from  each  other  to  form  the 
crura  penis,  which  are  two  strong  taper- 
ing fibrous  processes  or  roots  firmly  -<r --^^  in  .  « 
connected  to  the  rami  of  the  os  pubis  (f  K^  (  uTV  \  ,  /  f-" 
and  ischium  -(Figs.  1058,  1062,  and  ^^Aa,J3  \:%^J, 
1063).     Each   crus   commences    by 


VAS 
DEFERENS 


CORONA. 
GLANDIS 


Fig.  1062. — The  penis,  with  the  pubic  bones,  seen 
from  before  and  below.     (Toldt.) 


EXTERNAL   ORIFICE 
OF  URETHRA 

Fig. 1063. — The  penis,  with  the  urethra,  Cowper  s 
glands,  the  ijrostate  gland, and  the  seminal  vesicles, 
seen  from  below  and  behind.     (Toldt). 


THE   PENIS 


1457 


blunt-pointed  process  in  front  of  the  tuberosity  of  the  ischium,  and  before  its  junc- 
tion with  its  fellow  to  foi'in  the  body  of  the  penis  it  presents  a  slight  enlargement, 
named  by  Kobelt  the  bulb  of  the  corpus  cavemosum.  Just  beyond  this  point  they 
become  constricted,  and  retain  an  e(|ual  diameter  to  their  anterior  extremity,  where 
they  form  a  single  rounded  end  which  is  received  into  a  fossa  in  the  base  of  the  glans 
penis  (Figs.  1060  and  1062).  A  median  groove  on  the  upper  surface  lodges  the 
dorsal  arteries,  nerves,  and  veins  of  the  penis  (Figs.  1066,  1067,  and  1068),  and  the 
groove  on  the  under  surface  receives  the  corpus  spongiosum  (Fig.  1062).  The  root 
of  the  penis  is  connected  to  the  symphysis  pubis  by  the  suspensory  ligament. 

Structure  (Fig.  1068). — Each  corpus  cavernosum  is  composed  of  erectile  tissue. 
The  erectile  tissue  is  surrounded  by  a  strong  fibrous  envelope,  the  tunica  albuginea, 
corporum  cavernosum,  consisting  of  two  sets  of  fibres — the  one,  longitudinal  in  direc- 
tion, being  common  to  the  two  corpora  cavernosa,  and  investing  them  in  a  com- 
mon covering;  the  other,  internal,  circular  in  direction,  and  being  proper  to  each 
corpus  cavernosum.  The  internal  circular  fibres  of  the  two  corpora  cavernosa 
form,  by  their  junction  in  the  mesial  plane,  an  incomplete  partition  or  septum, 
the  septum  penis,  between  the  two  bodies. 


SUSPENSORY 
LIGAMtNT 


Fig.  1064. — The  dartos.    (Poirier  and  Charpy.) 


Fifi.  1065. — From  the  peripheral  portion  of  the  corpus 
cavernosum  penis  under  a  low  magnifying  power.  1,  o, 
capillar.y  network;  6,  cavernou.s  spaces;  2,  connection  of 
the  arterial  twigs  (a)  with  the  cavernous  spaces.  (Copied 
from  Langer.) 


The  septum  between  the  two  corpora  cavernosa  is  thick  and  complete  behind, 
but  in  front  it  is  incomplete,  and  consists  of  a  number  of  vertical  bands,  which  are 
arranged  like  the  teeth  of  a  comb,  whence  the  name  which  it  has  received,  septum 
pectiniforme.  These  bands  extend  between  the  dorsal  and  the  urethral  surface 
of  the  corpora  cavernosa.  The  fibrous  investment  of  the  corpora  cavernosa  is 
extremely  dense,  of  considerable  thickness,  and  consists  of  bundles  of  shining 
white  fibres,  with  an  admixture  of  well-developed  elastic  fibres,  so  that  it  is  pos- 
sessed of  great  elasticity. 

From  the  interna!  surface  of  the  fibrous  envelope,  as  well  as  from  the  sides  of 
the  septum,  are  given  off  a  number  of  bands  or  cords  which  cross  the  interior  of 
each  crus  in  all  directions,  subdividing  it  into  a  number  of  separate  compart- 

U2 


1458  THE  MALE    ORGANS    OF   GENERATION 

ments,  and  giving  the  entire  structure  a  spongy  appearance.  These  bands  and 
cords  are  called  trabeculae  corporum  cavemosum,  and  consist  of  white  fibrous 
tissue,  elastic  fibres,  and  plain  muscular  fibres.  In  them  are  continued  numer- 
ous arteries  and  nerves. 

The  component  fibres  of  which  the  trabeculae  are  composed  are  larger  and 
stronger  around  the  circumference  than  at  the  centre  of  the  corpora  cavernosa; 
they  are  also  thicker  behind  than  in  front.  The  interspaces,  on  the  contrary,  are 
larger  at  the  centre  than  at  the  circumference,  their  long  diameter  l)eing  directed 
transversely;  they  are  largest  anteriorly.  They  are  called  cavernous  spaces  and 
are  occupied  by  venous  blood,  and  are  lined  by  a  layer  of  flattened  cells  similar 
to  the  endothelial  lining  of  veins  (Fig.  1065). 

The  whole  of  the  structure  of  the  corpora  cavernosa  contained  within  the 
fibrous  sheath  consists,  therefore,  of  a  sponge-like  tissue  the  areolar  spaces  of 
which  freely  communicate  with  each  other  and  are  filled  with  venous  blood. 
The  spaces  may  therefore  be  regarded  as  large  cavernous  veins. 

The  arteries  bringing  the  blood  to  these  spaces  are  the  arteries  of  the  corpora 
cavernosa  and  branches  from  the  dorsal  artery  of  the  penis,  which  perforate  the 
fibrous  capsule,  along  the  upper  surface,  especially  near  the  forepart  of  the  organ. 

These  arteries  on  entering  the  cavernous  structure  divide  into  branches  which 
are  supported  and  enclosed  by  the  trabeculae.  Some  of  these  terminate  in  a 
capillary  network,  the  branches  of  which  open  directly  into  the  cavernous  spaces 
(Fig.  1065) ;  others  assume  a  tendril-like  appearance,  and  form  convoluted  and 
somewhat  dilated  vessels,  which  were  named  by  Miiller  helicine  arteries  (arteriae 
helicinae).  They  project  into  the  spaces,  and  from  them  are  given  off  small 
capillary  branches  to  supply  the  trabecular  structure.  They  are  bound  down  in 
the  spaces  by  fine  fibrous  processes,  and  are  more  abundant  in  the  back  part  of  the 
corpora  cavernosa. 

The  blood  from  the  cavernous  spaces  is  returned  by  a  series  of  vessels,  some  of 
which  emerge  in  considerable  numbers  from  the  base  of  the  glans  penis  and  con- 
verge on  the  dorsum  of  the  organ  to  form  the  deep  dorsal  vein;  others  pass  out  on  the 
upper  surface  of  the  corpora  cavernosa  and  join  the  dorsal  vein;  some  emerge  from 
the  under  surface  of  the  corpora  cavernosa,  and,  receiving  branches  from  the  corpus 
spongiosum,  wind  around  the  sides  of  the  penis  to  terminate  in  the  dorsal  vein; 
but  the  greater  number  pass  out  at  the  root  of  the  penis  and  join  the  prostatic  plexus. 

The  Corpus  Spongiosum  (corpus  cavemosum  urethrae)  (Figs.  1060,  1062,  and 
1063). — The  corpus  spongiosum  encloses  the  urethra,  and  is  situated  in  the  groove 
on  the  under  surface  of  the  corpora  cavernosa  penis.  It  commences  posteriorly 
below  the  superficial  layer  of  the  triangular  ligament  of  the  urethra,  between 
the  diverging  crura  of  the  corpora  cavernosa,  where  it  forms  a  rounded  enlarge- 
ment, the  bulb  of  the  urethra  (hulhus  urethrae),  and  terminates  anteriorly  in  another 
expansion,  the  glans  penis  (Figs.  1059,  1060,  1062,  and  1063),  which  overlaps  the 
anterior  rounded  extremity  of  the  corpora  cavernosa.  The  central  portion,  or  body 
of  the  corpus  spongiosum,  is  cylindrical,  and  tapers  slightly  from  behind  forward. 

The  Bulb  of  the  Urethra  (Figs.  1058,  1062,  and  1063)  varies  in  size  in  different 
subjects;  it  receives  a  fibrous  investment  from  the  superficial  layer  of  the  triangular 
ligament,  and  is  surrounded  by  the  Accelerator  urinae  muscle.  The  urethra  enters 
the  bulb  nearer  its  upper  than  its  lower  surface,  being  surrounded  by  a  layer  of 
erectile  tissue,  a  thin  prolongation  of  which  is  continued  backward  around  the 
membranous  and  prostatic  portions  of  the  canal  to  the  neck  of  the  bladder,  lying 
between  the  two  layers  of  muscular  tissue.  The  portion  of  the  bulb  below  the 
urethra  presents  a  partial  division  into  two  lobes  (hemisphaeria  hulhi  urethrae), 
being  marked  externally  by  a  linear  raphe,  whilst  internally  there  projects,  for  a 
short  distance,  a  thin  fibrous  median  septum  {septum  hulhi  urethrae),  which  is  more 
distinct  in  earlv  life. 


THE  PENIS 


1459 


Structure. — The  corpus  spongiosum  consists  of  a  strong  fibrous  envelope 
enclosing  a  trabecular  structure,  which  contains  in  its  meshes  erectile  tissue.  The 
fibrous  envelope  is  thinner,  whiter  in  color,  and  more  elastic  than  that  of  the  corpora 


CAVERNOUS 
BRANCH 


DORSAL  ARTCRV 


CORPUS  CAVERNOSUM 


INTERNAL  PUDIC 


'^i-'V^ 


Fig.  1066. — Diagram  of  the  arteries  of  the  penis.     (Testut.) 


cavernosa  of  the  penis.  The  trabeculae  are  more  delicate,  more  nearly  uniform 
in  size,  and  the  meshes  between  them  smaller  than  in  the  corpora  cavernosa, 
their  long  diameter,  for  the  most  part,  corresponding  with  that  of  the  penis. 
The  external  envelope  or  outer  coat  of  the  corpus  spongiosum  is  formed  partly 
of  unstriped  muscular  fibre,  and  a 
layer  of  the  same  tissue  immediately 
surrounds  the  canal  of  the  urethra. 

Ligaments  of  the  Penis. — The  sus- 
pensory ligament  (ligamentum  siis- 
'pensorium  'penis)  (Fig.  1061)  is  firm 
and  fibrous.  It  passes  from  the  front 
of  the  symphysis  pubis  to  the  tunica 
albuguinea  of  the  corpora  cavernosa. 
The  ligamentum  fundiforme  penis 
(P'ig.  1058),  formerly  called  the  sus- 
pensory ligament,  arises  from  the 
linea  alba,  sheath  of  the  rectus, 
superficial  fascia,  and  symphysis 
pubis,  and  surrounds  the  penis  in 
a  loop,  being  attached  more  distal- 
w^ard  than  is  the  suspensory  liga- 
ment, and  usually  passes  into  the 
scrotum.  It  is  composed  of  elastic 
tissue. 

Vessels  and  Nerves  of  the  Penis. — 
The  arteries  (Fig.  1066)  of  the  penis 
come  from  branches  of  the  internal 
pudic  artery.  The  deep  arteries  of 
the  penis  give  the  chief  supply  to 
the  erectile  tissue  of  the  corpora 
cavernosa,  and  the  dorsal  artery  also 
sends  branches  to  it ;  the  artery  of 
the  bulb  (p.  691)  supplies  the  erectile 

tissue  of  the  corpus  spongiosum.  The  chief  blood-supply  of  the  glans  is  from 
the  dorsal  artery  (p.  692).  In  the  trabeculae  the  arteries  are  very  small  and  often 
twisted.  The  twisted  vessels  are  called  helicine  arteries.  The  small  arteries 
open  directly  into  the  venous  spaces.     The  veins  of  the  penis  empty  directly  into 


UPERFICIAL   DORSAL  VEIN 
EXTERNAL    PUDIC    VEIN 

OBTURATOR    VEIN 


Fig.  1067.— Veins  of  the  penis.      (Testut.) 


1460  THE  MALE    ORGANS   OF   GENERATION 

the  prostatic  plexus  or  into  the  deep  dorsal  vein,  which  empties  into  the  prostatic 
plexus.  On  each  side  of  the  deep  dorsal  vein  is  a  dorsal  artery  and  external 
to  each  dorsal  artery  is  a  dorsal  nerve  (Fig.  106S).  The  superficial  dorsal  vein 
(Figs.  1067  and  1068),  receiving  small  veins  from  the  prepuce,  passes  back 
beneath  the  skin,  reaches  the  symphysis  and  divides  into  two  branches,  each  of 
which  passes  to  the  corresponding  superficial  external  pudic  vein. 

The  lymphatics  of  this  region  have  been  studied  carefully  by  Poirier,  Cun^o, 
and  ITelamare,^  which  book  I  have  freely  used. 

The  lymphatics  of  the  skin  of  the  penis  and  prepuce  are  continuous  (Fig.  501). 
Those  on  the  internal  surface  of  the  prepuce  are  continuous  with  those  of  the  glans. 
The  trunks  of  the  cutaneous  lymphatics  anastomose  with  each  other,  ascend  by 
the  dorsal  vein,  and  terminate  in  the  inguinal  glands.     The  trunks  from  the  glans 

converge  toward  the  frsenum  ;   they 

'sVL^JEl'N"""'  then  ascend  to  the  median  part  of 

the  corona,  and  the  vessels  of  the  two 

/^<^;;^|^^^^^\  sides    unite.      Several  collectors  as- 

so PE R F?c\TCZTi^. ^^fe^J^^^^i^r  tIssu e"   ccud  ou  thc  dorsum  to  the  inguinal 

and  femoral  glands. 
*RTEHY   T¥v^5f^/^§|^fM??Pii/ii;i  I  The  superior  wall  of  the  anterior 

portion  of  the  urethra  is  drained  by 
the  lymphatic  trunks  from  the  glans. 
From  the  rest  of  the  penile  urethra 


SUPERFICIAL   DOR- 
SAL  VEIN 
DORSAL  ARTERY      |     .DEEP   DORSAL   VEIN 

CORPUS  cavernosum: 


DEEP 
FASCIA 


""'"-ANTER^R'sifANc"''^''  ^PuRETHRA  thc  lymphatlcs  uultc  with  the  trunks 

SPONGIOSUM  from  the  penis,  and  most  of  them  ter- 

FiG.  1068.— The  penis  in  transverse  section,  showing  minatc    ill     the    Same    WaV,    althoUffh 

the  blood-vessels.     (Testut.)  <•       i  i  i 

one  or  them  passes  between  the 
Recti  muscles  and  terminates  in  the  deeper  external  iliac  glands  or  in  the 
"internal  retro-crural  gland. "^ 

The  trunks  from  the  bulb  and  membranous  urethra  terminate  in  the  external 
iliac  glands,  the  "internal  retro-crural  gland,"  and  the  glands  along  the  internal 
pudic  artery  (Poirier,  Cuneo,  and  Delamare).  The  trunks  from  the  prostatic 
urethra  join  the  trunks  from  the  prostate  gland. 

The  nerves  are  derived  from  the  internal  pudic  nerve  and  the  pelvic  plexus.  On 
the  glans  and  bulb  some  filaments  of  the  cutaneous  nerves  have  Pacinian  bodies 
connected  with  them,  and,  according  to  Krause,  many  of  them  terminate  in  a 
peculiar  form  of  end-bulb. 

Surgical  Anatomy. — It  is  occasionally  necessary  to  remove  a  penis  for  malignant  disease. 
Usually,  removal  of  the  ante-scrotal  portion  is  all  that  is  necessary,  but  sometimes  it  is  requisite 
to  remove  the  whole  organ  from  its  attachment  to  the  rami  of  the  ossa  pubis  and  ischia.  The 
former  operation  is  performed  either  by  cutting  off  the  whole  of  the  anterior  part  of  the  penis 
with  one  sweep  of  the  knife,  or,  what  is  better,  cutting  through  the  corpora  cavernosa  from  the 
dorsum,  and  then  separating  the  corpus  spongiosum  from  them,  dividing  it  at  a  level  nearer  the 
glans  penis.  The  mucous  membrane  of  the  urethra  is  then  slit  up,  and  the  edges  of  the  flap 
attached  to  the  external  skin,  in  order  to  prevent  contraction  of  the  orifice,  which  would  other- 
wise take  place.  The  vessels  which  require  ligature  are  the  two  dorsal  arteries  of  the  penis,  the 
arteries  of  the  corpora  cavernosa,  and  the  artery  of  the  septum.  When  the  entire  organ  requires 
removal  the  patient  is  placed  in  the  lithotomy  position,  and  an  incision  is  made  through  the 
skin  and  subcutaneous  tissue  around  the  root  of  the  penis,  and  carried  down  the  median  line  of 
the  scrotum  as  far  as  the  perinaeum.  The  two  halves  of  the  scrotum  are  then  separated  from 
each  other,  and  a  catheter  having  been  introduced  into  the  bladder  as  a  guide,  the  spongy  por- 
tion of  the  urethra  below  the  triangular  ligament  is  separated  from  the  corpora  cavernosa  and 
divided,  the  catheter  having  been  withdrawn  just  behind  the  bulb.  The  suspensory  ligament 
is  now  severed,  and  the  crura  separated  from  the  bone  with  a  periosteum  scraper,  and  the  whole 
penis  removed.  The  membranous  portion  of  the  urethra,  which  has  not  been  removed,  is  now 
to  be  attached  to  the  skin  at  the  posterior  extremity  of  the  incision  in  the  perinseum.  The 
remainder  of  the  wound  is  to  be  brought  together,  free  drainage  being  provided  for. 

1  Translated  and  edited  by  Cecil  H.  Leaf. 

*  The  Lymphatics.     By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


DESCENT   OF   THE   TESTIS 


1461 


THE   TESTICLES  (TESTES)  AND  THEIR  COVERINGS  (Figs.  1071,  1072). 

The  testicles  are  two  glandular  organs,  which  secrete  the  semen;  they  are  situ- 
ated in  the  scrotum,  being  suspended  by  the  spermatic  cords.  At  an  early  period 
of  foetal  life  the  testes  are  contained  in  the  abdominal  cavity,  behind  the  peri- 
toneum, but  they  subsequently  descend  into  the  scrotum. 


DESCENT  OF  THE  TESTIS  (DESCENDUS  TESTIS). 

Each  testis  at  an  early  period  of  foetal  Ufe  is  placed  at  the  back  part  of  the 
abdominal  cavity,  behind  the  peritoneum,  in  front  and  a  little  below  the  kidney. 
The  anterior  surface  and  sides  are  invested  by  peritoneum.  At  about  the  third 
month  of  intra-uterine  life  a  peculiar  structure,  the  gubemaculum  testis,  makes  its 
appearance.  This  structure  is  at  first  a  slender  band  which  extends  from  the 
situation  of  the  internal  ring  to  the  epididymis  and  body  of  the  testicle,  and  is 
then  continued  upward  in  front  of  the  kidney  toward  the  Diaphragm.  As  devel- 
opment advances  the  peritoneum  covering  the  testicle  encloses  it  and  forms  a 
mesentery,  the  mesorchium,  which  also  encloses  the  gubemaculum  and  forms  two 
folds — one  above  the  testicle,  and  the  other  below  it.  The  one  above  the  testicle  is 


STOMOSIS 
VEINS 


Fig.  1069. — Vaginal  tunics  of  the  testicle. 
(Poirier  and  Charpy.) 


Fig.  1070. — Ligament  of  the  scrotum. 
(Poirier  and  Charpy.) 


the  plica  vascularis,  and  contains  ultimately  the  spermatic  vessels;  the  one  below, 
the  plica  gubernatrix,  contains  the  lower  part  of  the  gubemaculum,  which  has  now 
grown  into  a  thick  cord ;  it  terminates  below  at  the  internal  ring  in  a  tube  of  peri- 
toneum, the  processus  vaginalis,  which  now  lies  in  the  inguinal  canal.  The  lower 
part  of  the  gubemaculum  by  the  fifth  month  has  become  a  thick  cord,  whilst  the 
upper  part  has  disappeared.  The  lower  part  can  now  be  seen  to  consist  of  a  cen- 
tral core  of  unstriped  muscle-fibre,  and  outside  this  of  a  firm  layer  of  striped 
elements,  connected,  behind  the  peritoneum,  with  the  abdominal  wall.  Later  on, 
about  the  sixth  month,  the  lower  end  of  the  gubemaculum  can  be  traced  into  the 
inguinal  canal,  extending  to  the  pubes,  and,  at  a  later  period,  to  the  bottom  of 
the  scrotum.  The  fold  of  peritoneum  constituting  the  processus  vaginalis  pro- 
jects itself  downward  into  the  inguinal  canal,  forming  a  gradually  elongating 
depression  or  cul-de-sac,  which  eventually  reaches  the  bottom  of  the  scrotum.  This 
cul-de-sac  is  now  invaginated  by  the  testicle,  as  the  body  of  the  foetus  grows,  for  the 
gubemaculum  does  not  grow  commensurately  with  the  growth  of  other  parts,  and 
therefore  the  testicle,  being  attached  by  the  gubemaculum  to  the  bottom  of  the 


1462  THE  MALE    ORGANS    OF    GENERATION 

scrotum,  is  prevented  from  rising  as  the  body  grows,  and  is  drawn  first  into  the 
inguinal  canal,  and  eventually  into  the  scrotum.  By  the  eighth  month  the  tes- 
ticle has  reached  the  scrotum,  preceded  by  the  lengthened  pouch  of  peritoneum, 
the  processus  vaginalis,  which  communicates  by  its  upper  extremity  with  the 
peritoneal  cavity.  Just  before  birth  the  upper  part  of  the  pouch  usually  becomes 
closed,  and  this  obliteration  extends  gradually  downward  to  within  a  short  dis- 
tance of  the  testis.  The  process  of  peritoneum  surrounding  the  testis,  which  is  now 
entirely  cut  off  from  the  general  peritoneal  cavity,  constitutes  the  tunica  vaginalis.^ 

Mr.  Jacobson^  says  that  the  attachments  of  the  gubernaculum  above  are  to 
the  vas,  the  epididymis,  and  afterward  to  the  testicle.  The  lower  attachments 
of  the  gubernaculum,  some  of  which  are  temporary,  are  the  abdominal  wall, 
pubes  and  root  of  the  scrotum,  Scarpa's  triangle,  perina:^um  and  scrotum.  The 
remains  of  the  scrotal  fibres  constitute  a  so-called  ligament  of  the  scrotum  or 
the  mesorchium,  which  causes  adhesion  between  the  testicle  and  skin  (Fig.  1070). 

In  the  female,  a  small  cord,  corresponding  to  the  gubernaculum  in  the  male, 
descends  to  the  inguinal  region  and  ultimately  forms  the  round  ligament  of  the 
uterus.  A  pouch  of  peritoneum  accompanies  it  along  the  inguinal  canal,  analogous 
to  the  processus  vaginalis  in  the  male ;  it  is  called  the  canal  of  Nuck. 

Surgical  Anatomy. — Abnormalities  in  the  formation  and  in  the  descent  of  the  testicle  may 
occur.  The  testicle  may  fail  to  be  developed,  or  it  may  be  fully  developed  and  the  vas  deferens 
may  be  undeveloped  in  whole  or  in  part;  or,  again,  both  testicle  and  vas  deferens  may  be  fully 
developed,  but  the  duct  may  not  become  connected  to  the  gland.  The  testicle  may  fail  in  its 
descent  (cryptorchismus)  or  it  may  descend  into  some  abnormal  position  (ectopia  testis) .  Thus  it 
may  be  retained  in  the  position  where  it  was  primarily  developed,  below  the  kidney;  or  it  may 
descend  to  the  internal  abdominal  ring,  but  fail  to  pass  through  this  opening;  it  may  be  retained 
in  the  inguinal  canal,  which  is  perhaps  the  most  common  position;  or  it  may  pass  through  the 
external  abdominal  ring  and  remain  just  outside  it,  failing  to  pass  to  the  bottom  of  the  scrotum. 
On  the  other  hand,  it  may  get  into  some  abnormal  position;  it  may  pass  the  scrotum  and  reach 
the  perinseum,  or  it  may  fail  to  enter  the  inguinal  canal,  and  may  find  its  way  through  the  fem- 
oral ring  into  the  crural  canal,  and  present  itself  on  the  thigh  at  the  saphenous  opening.  Ectopia 
testis  is  due  to  the  absence,  overdevelopment  or  malposition  of  some  portion  of  the  gubernacu- 
lum. There  is  still  a  third  class  of  cases  of  abnormality  in  the  position  of  the  testicle,  where  the 
organ  has  descended  in  due  course  into  the  scrotum,  but  is  malplaced.  The  most  common  form 
of  this  is  where  the  testicle  is  inverted;  that  is  to  say,  the  organ  is  rotated,  so  that  the  epididymis 
is  connected  to  the  front  of  the  scrotum,  and  the  body,  surrounded  by  the  tunica  vaginalis,  is 
directed  backward.  In  these  cases  the  vas  deferens  is  to  be  felt  in  the  front  of  the  cord.  The 
condition  is  of  importance  in  connection  with  hydrocele  and  haematocele,  and  the  position  of 
the  testicle  should  always  be  carefully  ascertained  before  performing  any  operation  for  these 
affections.  Again,  more  rarely,  the  testicle  may  be  reversed.  This  is  a  condition  in  which  the 
top  of  the  testicle,  indicated  by  the  globus  major  of  the  epididymis,  is  at  the  bottom  of  the 
scrotum,  and  the  vas  deferens  comes  off  from  the  summit  of  the  organ. 

THE  COVERINGS  OF  THE  TESTICLE  (Fig.  1073). 
The  coverings  of  the  testicle  are  the  following: 

Skin        ]      a      * 
T-.    -        y     Scrotum. 
Dartos    j 

Intercolumnar  or  External  spermatic  fascia. 

Cremasteric  fascia. 

Infundibuliform  or  Fascia  propria  (Internal  spermatic  fascia). 

Tunica  vaginalis. 

The  Testicular  Bag  or  Scrotum  (Figs.  1071  and  1072).— The  testicular  bag  or 
scrotum  is  a  cutaneous  pouch  which  contains  the  testes  and  part  of  the  spermatic 
cords.     It  is  divided  on  its  surface  into  two  lateral  portions  by  a  median  line  or 

1  The  obliteration  of  the  process  of  peritoneum  which  accompanies  the  cord,  and  is  hence  called  the  funicular 
■process,  is  often  incomplete.     See  section  on  Inguinal  Hernia. 
^  Diseases  of  the  Male  Organs  of  Generation. 


THE    COVERINGS    OF    THE    TESTICLE 


1463 


raph^  {raphe  scroti),  which  is  continued  forward  to  the  under  surface  of  the  penis 
and  backward  along  the  middle  line  of  the  perinseum  to  the  anus.  Of  these  two 
lateral  portions,  the  left  is  usually  longer  than  the  right,  and  corresponds  with  the 
usual  greater  length  of  the  spermatic  cord  on  the  left  side.  Its  external  aspect  varies 
under  different  circumstances:  thus  under  the  influence  of  warmth  and  in  old  and 
debilitated  persons  it  becomes  elongated  and  flaccid,  but  under  the  influence  of  cold 
and  in  the  young  and  robust  it  is  short,  corrugated,  and  closely  applied  to  the 
testes.     The  wrinkles  in  the  scrotum  are  called  rugae. 

The  scrotum  consists  of  two  layers,  the  integument  and  the  dartos. 


RIGHT   INGUINAL   CANAL 

(opened; 


CREMASTERIC  MUSCLE- 
AND    FASCIA 
INTERCOLUMNAR 
FASCIA 


fpERSJSTENT  SEROUS 
—  ■<        CAVITY  AROUND 

(^OORO EXCEPTIONAL 


TUNICA  VAGINALIS 

PARIETAL  LAYER 
INFUNOIBULIFORM 

FASCIA 
NO N- PEDUNCULATED 
HYDATID 


RIGHT    HALF   OF   SCROTUM     SKIN 


LEFT    HALF   OF   SCROTUM 


Fig.  1071. — The  scrotum.     On  the  left  side  the  cavity  of  the  tunica  vaginalis  has  been  opened  ;  on  the 
right  side  only  the  layers  superficial  to  the  cremaster  have  been  removed.     (Testut.) 

The  Integument. — The  integument  is  very  thin,  of  a  brownish  color,  and  gen- 
erally thrown  into  folds  or  rugae.  It  is  provided  with  sebaceous  follicles,  the 
secretion  of  which  has  a  pecidiar  odor,  and  is  beset  with  thinly-scattered,  crisp 
hairs,  the  roots  of  which  are  seen  through  the  skin. 

The  Dartos  {tunica  dartos)  (Figs.  1064  and  1071). — The  dartos  is  a  thin  layer  of 
loose  tissue,  endowed  with  contractility;  it  forms  the  proper  tunic  of  the  scrotum, 
is  continuous  around  the  base  of  the  scrotum,  with  the  two  layers  of  the  super- 
ficial fascia  of  the  groin  and  perinaeum,  and  sends  inward  a  distinct  septum, 
the  septum  of  the  scrotum  {septum  scroti)  (Fig.  1071),  which  divides  it  into  two 
cavities  for  the  two  testes,  the  septum  extending  between  the  raphe  and  the 
under  surface  of  the  penis  as  far  as  its  root. 

The  dartos  is  closely  united  to  the  skin  externally,  but  connected  with  the 


1464 


THE    MALE    ORGANS    OF    GENERATION 


subjacent  parts  by  delicate  areolar  tissue,  upon  which  it  glides  with  the  greatest 
facility.  The  dartos  is  very  vascular,  and  consists  of  a  loose  areolar  tissue  con- 
taining unstriped  muscular  fibre,  but  no  fat.  Its  contractibility  is  slow,  and 
excited  by  cold  and  mechanical  stimuli,  but  not  by  electricity. 

The  Intercolumnar  or  Spermatic  Fascia  (Fig.  1071). — The  intercolumnar 
fascia  is  a  thin  membrane  derived  from  the  margin  of  the  pillars  of  the  external 
abdominal  ring,  during  the  descent  of  the  testis  in  the  foetus,  which  is  prolonged 
downward  around  the  surface  of  the  cord  and  testis.     It  is  separated  from  the 


EXTERNAL 

ABDOMINAL 

RING 


ACCESSORY 

SLIP  OF 

ORIGIN  OF- 

CREMASTER 

MUSCLE 


SPERMATIC 
CORD 


CREMASTER. 
MUSCLE 


SEPTUM 
SCROTUM 


AS 
DEFERENS 


SPERMATIC 
ARTERY 


NERVE-FILAMENTS 
OF  SPERMATIC 
PLEXUS 

DEFERENTIAL 
ARTCRY 


INFUNDIBULIFORM 
FASCIA 


SPERMATIC 
PLEXUS 

EPIDIDYMIS 
PARIETAL 
LAYER   OF 
TUNICA 
VAGINALI 


Fig.  1072.— The  scrotum.  The  penis  has  been  turned  upward,  and  the  anterior  wall  of  the  scrotum  has  been 
removed.  On  the  right  side,  the  spermatic  cord,  the  infundibuliform  fascia  and  the  Cremaster  muscle  are  dis- 
played; on  the  left  side,  the  infundibuliform  fascia  has  been  divided  by  a  lonRitudinal  incision  passing  along  the 
front  of  tlie  cord  and  the  testicle,  and  a  portion  of  the  parietal  layer  of  the  tunica  vaginalis  has  been  removed  to 
display  the  testicle  and  a  portion  of  the  head  of  the  epididymis,  which  are  covered  by  the  visceral  layer  of  the 
tunica  vaginalis.      (Toldt.) 

dartos  by  loose  areolar  tissue,  which  allows  of  considerable  movement  of  the 
latter  upon  it,  but  is  intimately  connected  with  the  succeeding  layers. 

The  Cremasteric  Fascia  (jascia  cremasterica)  (Figs.  1071  and  1072).— The 
cremasteric  fascia  consists  of  scattered  bundles  of  muscular  fibres,  the  Cremaster 
muscle  (m.  cremaster)  (Figs.  1071  and  1072)  connected  together  into  a  continuous 
covering  by  intermediate  areolar  tissue.  The  muscular  fibres  are  continuous 
with  the  lower  border  of  the  Internal  oblique  muscle. 


THE    COVERINGS    OF    THE    TESTICLE 


1465 


The  Infundibuliform  Fascia  {tunica  vaginalis  communis  [testis  et  funiculi  sper- 
maiici])(F'igs.  1071  and  1071). — The  infundibuliform  fascia  is  a  thin  membranous 


Skin. 

Dartos. 

External  spermatic  fascia. 

Cremasteric  fascia. 

Infundibuliform  fascia. 

Parietal  tunica  vaginalis. 

Visceral  tunica  vaginalis. 

Tunica  vascnlosa.. 

Tunica  albuginea. 


A  lobule  of  the  testicle..  Am 


A  septum. 

Mediastinum. 

Digital  fossa. 

Spermatic  vein. 

Epididymis. 

Vas  deferens. 

Artery  to  vas. 

Spermatic  artery. 

Internal  cremastev 

muscle. 


Fig.  1073. — Transverse  section  through  the  left  side  of  the  scrotum  and  the  left  testicle.     The  sac  of  the 
tunica  vaginalis  is  represented  in  a  distended  condition.     (Del6pine.) 

layer,  which  loosely  invests  the  surface  of  the  cord.  It  is  a  continuation  downward 
of  the  fascia  transversalis.  Beneath  it  is  a  quantity  of  loose  connective  tissue  which 
connects  this  layer  of  fascia  with  the  spermatic  cord  and  posterior  parts  of  the  tes- 


SPERMATIC 
ARTERY 


ANTERIOR 

GROUP  OF 

VEINS 


.CREMASTERIC 
ARTERY 


deferential 
'artery 

SEMINAL 

"duct 


POSTERIOR 
-GROUP  OF 
VEINS 


STOMOSIS 
NS 


Fig.  1074.  — The  arteries  of  the  testicle  and  the  cord.      (Poirier  and  Charpy.) 

tide.  This  connective  tissue  is  continuous  above  with  the  subserous  areolar  tissue  of 
the  abdomen.    These  two  layers,  the  infundibuliform  fascia  and  the  tissue  beneath 


1466 


THE   MALE    ORGANS    OF    GENERATION 


it,  are  known  collectively  as  the  fascia  propria.  The  infundibuliform  fascia  com- 
pletely encloses  the  testicle  and  epididymis  and  is  fused  with  the  parietal  lamina 
of  the  tunica  vaginalis  propria  testis. 

The  Tunica  Vaginalis  {tunica  vaginalis  propria  testis). — The  tunica  vagi- 
nalis is  described  with  the  testis  (p.  1469.) 

Vessels  and  Nerves. — The  arteries  supplying  the  coverings  of  the  testis  are: 
the  superficial  and  deep  external  pudic,  from  the  femoral;  the  superficial  perineal 
branch  of  the  internal  pudic;  and  the  cremasteric  branch  from  the  deep  epigastric. 
The  veins  follow  the  course  of  the  corresponding  arteries.  The  lymphatics  term- 
inate in  the  inguinal  glands.  The  nerves  are:  the  ilio-inguinal  branch  of  the 
lumbar  plexus,  the  two  superficial  perineal  branches  of  the  internal  pudic  nerve, 
the  inferior  pudenal  branch  of  the  small  sciatic  nerve,  and  the  genital  branch  of 
the  genito-crural  nerve. 


TRANSVERSALIS 
FASCIA 


DEEP 

EPIGASTRIC 

ARTERY 


LIGAMENT 
OF  CLOQUET 


SPERMATIC 
ARTERY 

PAMPINIFORM 
PLEXUS 


SPERMATIC 
CORD 


Fig.  1075. — The  spermatic  cord  and  the  ligament  of  Cloquet.     (Poirier  and  Charpy.) 


THE    SPERMATIC    CORD    (FUNICULUS    SPERMATICUS) 

(Figs.  1071,  1072,  1075,  1076). 

The  spermatic  cord  extends  from  the  internal  abdominal  ring,  where  the 
structures  of  which  it  is  composed  converge,  to  the  back  part  of  the  testicle.  In 
the  abdominal  wall  the  cord  passes  obliquely  along  the  inguinal  canal,  lying  at 
first  beneath  the  Internal  oblique  muscle  and  upon  the  fascia  transversalis ;  but 
nearer  the  pubes  it  rests  upon  Poupart's  ligament,  having  the  aponeurosis  of 
the  External  oblique  in  front  of  it  and  the  conjoined  tendon  behind  it.  It  then 
escapes  at  the  external  ring,  and  descends  nearly  vertically  into  the  scrotum.  The 
left  cord  is  usually  rather  longer  than  the  right,  consequently  the  left  testis 
generally  hangs  somewhat  lower  than  its  fellow. 

Structure. — The  spermatic  cord  contains  the  spermatic  duct,  the  deferential 
artery  and  veins,  the  spermatic  artery,  the  pampiniform  plexus  of  veins,  the  sper- 
matic plexus,  and  the  deferential  plexus  of  the  sympathetic  nerve,  lymphatics,  and 
the  cord-like  remnant  of  the  funicular  process  of  peritoneum  called  the  ligament 


THE   SPERMATIC    COBD 


1467 


of  Cloquet  (Fig.  1075) .  All  the  above  structures  are  held  together  by  connective 
tissue.  These  structures  are  ensheathed  by  the  infundibuliform  process  of  the  trans- 
versalis  fascia  {tunica  vaginalis  communis  [testis  et  funiculi  spermatid])  (Fig.  1075 
and  p.  1064) .  This  fascia  is  thin  above  and  thicker  below,  and  encloses  the  testicle 
and  epididymis,  as  well  as  the  cord,  being  firmly  adherent  to  the  parietal  layer  of 
the  vaginal  tunic  of  the  testicle  and  with  the  posterior  portion  of  the  testicle  and 
epididymis.  Upon  this  fascia  are  the  fibres  of  the  Cremaster  muscle,  which  spring 
from  the  internal  oblique,  and  in  this  fascia  are  the  cremasteric  artery,  the  genital 
branch  of  the  genito-crural  nerve,  and  external  spermatic  veins.  This  fascia  is 
surrounded  by  the  intercolumnar  or  spermatic  fascia  (fascia  or emasterica[Cooperi]), 
which  is  distinct  above,  but  not  below. 

Vessels  and  Nerves  of  the  Spermatic  Oord.^The  arteries  (Figs.  1074  and  1080)  of 
the  cord  are:  the  spermatic,  from  the  aorta;  the  artery  of  the  vas  deferens,  from 
the  superior  vesical;  the  cremasteric,  from  the  deep  epigastric. 


VAS 
DEFERENS 


SPERMATIC 
CORD 


Fig.  1076. — The  spermatic  cord  in  the  inguinal  canal.    (Poirier  and  Charpy.) 

The  spermatic  artery  (a.  spermatica  interna)  arises  from  the  abdominal  aorta 
below  the  renal  artery,  descends  by  the  Psoas  muscle,  crosses  the  ureter  and 
external  iliac  vessels,  meets  the  vas  deferens  at  the  internal  abdominal  ring, 
escapes  from  the  abdomen  at  the  internal  or  deep  abdominal  ring,  and  lying  in 
front  of  the  vas  deferens  accompanies  the  other  constituents  of  the  spermatic  cord 
along  the  inguinal  canal  and  through  the  external  abdominal  ring  into  the  scrotum. 
It  then  descends  to  the  testicle,*  and,  becoming  tortuous,  divides  into  several 
branches,  two  or  three  of  which,  the  epididymal  branches,  accompany  the  vas 
deferens  and  supply  the  epididymis,  anastomosing  with  the  artery  of  the  vas 
deferens  and  the  cremasteric  artery;  others,  the  glandular  branches,  pierce  the  back 
of  tlie  tunica  albuginea  and  supply  the  substance  of  the  testis. 

The  artery  of  the  vas  deferens,  a  branch  of  the  superior  vesical,  is  a  long  slender 
vessel  which  accompanies  the  vas  deferens,  ramifying  upon  the  coats  of  that  duct, 
and  anastomosing  with  the  spermatic  artery  and  the  cremasteric  artery  near  the 
testis. 


1468 


THE  MALE   ORGANS    OF    GENERATION 


The  cremasteric  artery  (a.  spermatica  externa)  is  a  branch  of  the  deep  epigas- 
tric artery.  It  accompanies  the  spermatic  cord  and  suppHes  the  Cremaster 
muscle  and  other  coverings  of  the  cord,  anastomosing  with  the  spermatic  and 
deferential  arteries. 

The  spermatic  veins  (Figs.  1074,  1075,  1076,  and  1077)  emerge  from  the  back  of 
the  testis  and  receive  tributaries  from  the  epididymis;  they  unite  and  form  a  con- 
voluted plexus,  the  pampiniform  plexus  {plexus  pampiniformis) ,  which  forms  the 
chief  mass  of  the  cord ;  the  vessels  composing  this  plexus  are  very  numerous,  and 
ascend  along  the  cord  in  front  of  the  vas  deferens ;  below  the  external  or  super- 


FiG.  1077. — Spermatic  veins.      (Testut.) 

ficial  abdominal  ring  they  unite  to  form  three  or  four  veins,  which  pass  along  the 
inguinal  canal,  and,  entering  the  abdomen  through  the  internal  or  deep  abdominal 
ring,  coalesce  to  form  two  veins.  These  again  unite  to  form  a  single  vein,  which 
opens  on  the  right  side  into  the  inferior  vena  cava  at  an  acute  angle,  and  on  the 
left  side  into  the  renal  vein  at  a  right  angle. 

The  lymphatic  vessels  of  the  scrotum  terminate  in  the  superficial  inguinal 
glands.  The  lymphatics  of  the  testicle  join  the  lymphatics  of  the  epididymis  and  of 
the  visceral  layer  of  the  vaginal  tunic  of  the  testicle,  and  ascend  in  the  spermatic 
cord.  They  reach  the  lumbar  region  along  the  spermatic  blood-vessels  and  ter- 
minate in  the  juxta-aorta  glands,  and  sometimes  in  the  glands  in  front  of  the 
aorta.    The  lymphatics  of  the  seminal  duct  pass  to  the  external  iliac  glands. 


THE    TESTICLES  1469 

The  nerves  are  the  spermatic  plexus  from  the  sympathetic,  joined  by  filaments 
from  the  pelvic  plexus  which  accompany  the  artery  of  the  vas  deferens. 
The  Ligament  of  the  Scrotum.— See  Fig.  1070  and  p.  1462. 

Surgical  Anatomy. — The  scrotum  forms  an  admirable  covering  for  the  protection  of  the 
testicle.  This  body,  lying  suspended  and  loose  in  the  cavity  of  the  scrotum,  and  surrounded  by 
a  serous  membrane,  is  capable  of  great  mobility,  and  can  therefore  easily  slip  about  within  the 
scrotum,  and  thus  avoid  injuries  from  blows  or  squeezes.  The  skin  of  the  scrotum  is  very 
elastic  and  capable  of  great  distention,  and  on  account  of  the  looseness  and  amount  of  subcu- 
taneous tissue  the  scrotum  becomes  greatly  enlarged  in  cases  of  cedema,  to  which  this  part  is 
especially  liable  on  account  of  its  dependent  position.  The  scrotum  is  frequently  the  seat  of 
epithelioma;  this  is  no  doubt  due  to  the  rugae  on  its  surface,  which  favor  the  lodgement  of  dirt, 
and  this,  causing  irritation,  is  the  exciting  cause  of  the  disease.  Cancer  was  especially  common 
in  chimney-sweeps  from  the  lodgement  of  soot.  The  scrotum  is  also  the  part  most  frequently 
affected  by  elephantiasis. 

On  account  of  the  looseness  of  the  subcutaneous  tissue  considerable  extravasations  of  blood 
may  take  place  from  very  slight  injuries.  It  is  therefore  generally  recommended  never  to  apply 
leeches  to  the  scrotum,  since  they  may  lead  to  considerable  ecchymosis,  but  rather  to  puncture 
one  or  more  of  the  superficial  veins  of  the  scrotum  in  cases  where  local  bloodletting  from  this 
part  is  judged  to  be  desirable.  The  muscular  fibre  in  the  dartos  causes  contraction  and  consider- 
able diminution  in  the  size  of  a  wound  of  the  scrotum,  as  after  the  operation  of  castration,  and 
is  of  assistance  in  keeping  the  edges  together  and  covering  the  exposed  parts. 


THE  TESTICLES  (TESTES)  (Figs.  1069,  1071,  1072,  1078,  1079). 

The  testicles  are  suspended  in  the  scrotum  by  the  spermatic  cords.  As  the  left 
spermatic  cord  is  rather  longer  than  the  right  one,  the  left  testicle  hangs  somewhat 
lower  than  its  fellow.  Each  gland  is  of  an  oval  form,  compressed  laterally,  and 
having  an  oblique  position  in  the  scrotum,  the  upper  extremity  (extremitiis  superior) 
being  directed  forward  and  a  little  outward,  the  lower  extremity  (extremitus  infe- 
rior), backward  and  a  little  inward;  the  anterior  convex  border  (margo  anterior) 
looks  forward  and  downward;  the  posterior  or  straight  border  (margo  posterior), 
to  which  the  cord  is  attached,  backward  and  upward. 

The  anterior  border  and  lateral  surfaces  (fades  lateralis  et  fades  medialis),  as  well 
as  both  extremities  of  the  organ,  are  convex,  free,  smooth,  and  invested  by  the 
visceral  layer  of  the  tunica  vaginalis.  The  posterior  border,  to  which  the  cord  is 
attached,  receives  only  a  partial  investment  from  that  membrane.  Lying  upon 
the  outer  edge  of  this  posterior  border  is  a  long,  narrow,  flattened  body,  named, 
from  its  relation  to  the  testis,  the  epididymis  (ocdopio^,  testis)  (Figs.  1078  and  1079). 
The  curve  of  the  epididymis  is  convex  outward  and  backward.  It  consists  of 
a  central  portion  or  body  (corpus  epididymidis) ;  an  upper  enlarged  extremity,  the 
head  or  globus  major  (caput  epididymidis) ;  and  a  lower  pointed  extremity,  the  tail 
or  globus  minor  (cauda  epididymidis).  The  globus  major  is  directed  inward  and 
is  intimately  connected  with  the  upper  end  of  the  testicle  by  means  of  its  efferent 
ducts,  and  the  globus  minor  is  connected  with  its  lower  end  by  cellular  tissue  and  a 
reflection  of  the  tunica  vaginalis.  The  globus  minor  bends  suddenly  and  passes 
into  the  seminal  duct,  the  direction  of  which  is  upward  and  backward.  The  outer 
surface  and  upper  and  lower  ends  of  the  epididymis  are  free  and  covered  by 
serous  membrane;  the  body  is  also  completely  invested  by  it,  excepting  along  its 
posterior  border,  and  between  the  body  and  the  testicle  is  a  pouch  or  cul-de-sac, 
named  the  digital  fossa  (sinus  epididymidis).  Above  this  fossa  is  a  fold  of  the 
timica  vaginalis,  which  is  called  the  ligamentum  epididymidis  superior,  and  below 
it  is  another  fold,  the  ligamentum  epididymidis  inferior.  The  epididymis  is  con- 
nected to  the  back  of  the  testis  by  a  fold  of  the  serous  membrane.  Attached  to 
the  upper  end  of  the  testis,  close  to  the  globus  major,  is  a  small  body.  It  is  oblong 
in  shape  and  has  a  broad  base.  Attached  to  the  globus  major  of  the  epididymis 
is  another  small  body,  which  is  pear-shaped  and  has  a  stalk.    These  bodies  are 


1470 


THE  MALE    ORGANS   OF    GENERATION 


believed  to  be  the  remains  of  the  upper  extremity  of  the  Miillerian  duct,  and  are 
termed  the  hydatids  of  Morgagni;  some  observers,  however,  regard  the  stalked 
hydatid  as  being  a  rudiment  of  the  pronephros.  The  body  with  a  broad  base  is 
the  non-pedunculated  hydatid  (appendix  testis  [Morgagnii])  (Figs.  1071  and  1078} ; 


Spermatic  cord. 


Artery  of 
cord. 


Tunica  vaginalis, 
parietal  layer. 

Non-pedunculated 
hydatid 
Digital 
foasa. 


Fig.  1078. — The  testis  in  situ,  the  tunica  vaginalis 
having  been  laid  open. 


MEDIASTINUM 
TESTIS 


ALBUGINEA 


Fig.  1079. --Frontal  section  of    the  testicle  and 
epididymis.      (Poirier  and  Charpy.) 


Tunica  Vaffinaiit. 
Timica  Albuginea. 


Ductidi 
efferentes. 


Tubuli 

seminiferi 

recti. 


the  pear-shaped  body  is  the 
pedunculated  hydatid  (appendix 
epididymidis) .  When  the  tes- 
ticle is  removed  from  the  body, 
the  position  of  the  vas  deferens, 
on  the  posterior  surface  of  the 
testicle  and  inner  side  of  the 
epididymis,  marks  the  side  to 
which  the  gland  has  belonged. 

Size  and  Weight. — The  aver- 
age dimensions  of  this  gland 
are  from  one  and  a  half  to  two 
inches  in  length,  one  inch  in 
breadth,  and  an  inch  and  a 
quarter  in  the  antero-postcrior 
diameter,  and  the  weight  varies 
from  six  to  eight  drachms,  the 
left  testicle  being  a  little  the 
larger. 

The  Tunics  of  the  Testicle.— 
The  testis  is  invested  by  three  tu- 
nics— the  tunica  vaginalis,  tunica 
albuginea,  and  tunica  vasculosa. 
The  Proper  Sheath  of  the  Testicle  or  the  Tunica  Vaginalis  (tunica  vaginalis  propria 
testis)  (Figs.  1069,  1071, 1072, 1073,  and  1080)  is  the  serous  covering  of  the  testicle 
and  epididymis.  It  is  a  pouch  of  serous  membrane,  derived  from  the  peritoneum 
(processus  vaginalis  peritonaei)  during  the  descent  of  the  testis  in  the  foetus  from 
the  abdomen  into  the  scrotum.    After  its  descent  that  portion  of  the  pouch  which 


Fig.  1080. 


-Vertical  section  of  the  testicle,  to  show  the  arrange- 
ment of  the  ducts. 


THE    TESTICLES  1471 

extends  from  the  internal  ring  to  near  the  upper  part  of  the  gland,  the  funicular 
process,  becomes  obliterated,  the  lower  portion  remaining  as  a  shut  sac  {tunica 
vaginalis  propria  testis),  which  invests  the  outer  surface  of  the  testis,  and  is  reflected 
on  to  the  internal  surface  of  the  scrotum;  hence  it  may  be  described  as  consisting 
of  a  visceral  and  parietal  portion. 

The  Visceral  Portion  (lamina  visceralis)  of  the  tunica  vaginalis  propria  covers 
the  outer  surface  of  the  testis,  as  well  as  the  epididymis,  connecting  the  latter  to 
the  testis  by  means  of  a  distinct  fold.  From  the  posterior  border  of  the  gland  it 
is  reflected  on  to  the  internal  surface  of  the  infundibuliform  process  of  the  trans- 
veisalis  fascia,  and  between  the  tunic  and  the  fascia  is  a  layer  of  unstriated 
muscle  fibres,  the  Internal  cremaster  muscle  (Fig.  1073). 

The  Parietal  Portion  {lamina  parietalis)  of  the  tunica  vaginalis  propria  is  the 
reflected  portion.  It  is  far  more  extensive  than  the  visceral  portion,  extending 
upward  for  some  distance  in  front  and  on  the  inner  side  of  the  cord,  and  reaching 
below  the  testis.  The  inner  surface  of  the  tunica  vaginalis  is  free,  smooth,  and 
covered  by  a  layer  of  endothelial  cells.  The  interval  between  the  visceral  and 
parietal  layers  of  this  membrane  constitutes  the  cavity  of  the  tunica  vaginalis  and 
contains  a  small  amount  of  serous  fluid. 

The  obliterated  portion  of  the  pouch  may  generally  be  seen  as  a  fibro-cellular 
thread,  the  ligament  of  Cloquet  {rudimentum  processus  vaginalis)  (Fig.  1075),  lying  in 
the  loose  areolar  tissue  around  the  spermatic  c«rd ;  sometimes  this  may  be  traced 
as  a  distinct  band  from  the  upper  end  of  the  inguinal  canal,  where  it  is  connected 
with  the  peritoneum,  down  to  the  tunica  vaginalis;  sometimes  it  gradually  becomes 
lost  on  the  spermatic  cord.  Occasionally  no  trace  of  it  can  be  detected.  In  some 
eases  it  happens  that  the  pouch  of  peritoneum  does  not  become  obliterated,  but 
the  sac  of  the  peritoneum  communicates  with  the  tunica  vaginalis.  This  may 
give  rise  to  one  of  the  varieties  of  oblique  inguinal  hernia;  or  in  other  cases  the 
pouch  may  contract,  but  not  become  entirely  obliterated ;  it  then  forms  a  minute 
canal  leading  from  the  peritoneum  to  the  tunica  vaginalis.^ 

The  Tunica  Albuginea  (Figs.  1073,  1079,  and  1080j. — The  tunica  albuginea  is 
the  fibrous  covering  of  the  testis.  It  is  a  dense  fibrous  membrane,  of  a  bluish-white 
color,  composed  of  bundles  of  white  fibrous  tissue,  which  interlace  in  every  direc- 
tion. Its  outer  surface  is  covered  by  the  tunica  vaginalis,  except  at  the  points  of 
attachment  of  the  epididymis  to  the  testicle,  and  along  its  posterior  border,  wiiere 
the  spermatic  vessels  enter  the  gland.  This  membrane  surrounds  the  glandular 
structure  of  the  testicle,  and  at  its  posterior  border  forms  a  projection,  triangular 
in  shape  and  cellular  in  structure,  which  is  reflected  into  the  interior  of  the  gland, 
forming  an  incomplete  vertical  septum,  called  the  mediastinum  testis. 

The  Mediastinum  Testis  (corpus  Highmori)  (Figs.  1073, 1079,  and  1080)  extends 
from  the  upper,  neaily  to  the  lower,  extremity  of  the  gland,  and  is  wider  above 
than  below\  From  the  front  and  sides  of  this  septum  numerous  slender  fibrous 
cords  and  imperfect  septa,  called  the  trabeculae  {septula  testis)  (Fig.  1080),  are 
given  ofi^,  which  radiate  toward  the  surface  of  the  organ,  and  are  attached  to  the 
inner  surface  of  the  tunica  albuginea.  This  scaffolding  of  connective  tissue  divides 
the  parenchyma  (parenchyma  testis)  of  the  organ  into  a  number  of  incomplete 
spaces,  which  are  somewhat  cone-shaped,  being  broad  at  their  bases  at  the  sur- 
face of  the  gland,  and  becoming  narrower  as  they  converge  to  the  mediastinum. 
The  mediastinum  supports  the  blood-vessels,  lymphatics,  and  ducts  of  the  testis 
in  their  passage  to  and  from  the  substance  of  the  gland,  and  contains  numerous 
fine  canals,  into  which  open  the  very  small  tubules  of  the  proper  substance  of 
the  testicle. 

'  It  is  recorded  that  in  the  post-mortem  examination  of  Sir  Astley  Cooper  a  minute  funicular  canal  was  found 
on  each  side  of  the  body.  Sir  Astley  Cooper  states  that  when  a  student  he  suffered  from  inguinal  hernia  ;  prpb- 
ablv  this  was  of  the  congenital  variety,  and  the  canal  found  after  death  was  the  remains  of  the  one  down  which 
the" hernia  travelled  (Lancet,  1824,  vol.  ii.  p.  116.). — Ed.  of  15th  English  edition. 


1472  THE  MALE   ORGANS    OF   GENERATION 

The  Tunica  Vasculosa  (Fig.  1073). — The  tunica  vasculosa  is  the  vascular  layer -jI 
the  testis,  and  consists  of  a  plexus  of  blood-vessels  held  together  by  a  delicate 
areolar  tissue.  It  covers  the  inner  surface  of  the  tunica  albuginea  and  the  dif- 
ferent septa  in  the  interior  of  the  gland,  and  therefore  forms  an  internal  invest- 
ment to  all  the  spaces  of  which  the  gland  is  composed. 

Structure  of  the  Testicle  and  Epidid3nms  (Fig.  1080).— The  glandular  struc-' 
ture  of  the  testis  consists  of  numerous  lobules  {lohvli  testis).  Their  number,  in  a 
single  testis,  is  estimated  by  Berres  at  250,  and  by  Krause  at  400.  They  differ  in  size 
according  to  their  position,  those  in  the  middle  of  the  gland  being  larger  and  longer. 
The  lobules  are  conical  in  shape,  the  base  of  each  being  directed  toward  the  circum- 
ference of  the  organ,  the  apex  toward  the  mediastinum.  Each  lobule  is  contained  in 
one  of  the  intervals  between  the  fibrous  cords  and  vascular  processes  which  extend 
between  the  mediastinum  testis  and  the  tunica  albuginea,  and  consists  of  from  one 
to  mree  or  more  minute  convoluted  tubes,  which  anastomose  with  each  other,  the 
tubuli  seminiferi  contort!.  The  contorted  tubes  imite  at  the  apex  of  the  lobules  and 
form  the  straight  tubes  (tuhuli  seminiferi  recti).  The  straight  tubes  pass  into  the 
mediastinum  testis  and  form  the  network  known  as  the  rete  testis  of  Haller  (Fig. 
1080).  The  rete  testis  is  lined  with  flattened  epithelium.  The  tubes  are  lined  with 
columnar  ciliated  epithelium.  The  efferent  ducts  (ducti  efferentes  testis)  (Fig.  1080), 
about  twelve  to  fifteen  in  number,  arise  from  the  rete.  The  contorted  tubes  may 
be  separately  unravelled  by  careful  dissection  under  water,  and  may  be  seen  to 
commence  either  by  free  caecal  ends  or  by  anastomotic  loops.  The  total  number  of 
tubes  is  considered  by  Munro  to  be  about  300  and  the  lengtii  of  each  about  sixteen 
feet;  by  Lauth  their  number  is  estimated  at  840,  and  their  average  length  two  feet 
and  a  quarter.  The  diameter  varies  from  -^^  to  yir  of  an  inch.  The  tubuli  are 
pale  in  color  in  early  life,  but  in  old  age  they  acquire  a  deep-yellow  tinge  from 
containing  much  fatty  matter.  Each  tube  consists  of  a  basement  layer,  formed 
of  epithelioid  cells  united  edge  to  edge,  outside  of  which  are  other  layers  of 
flattened  cells  arranged  in  interrupted  laminae,  which  give  to  the  tube  an  appear- 
ance of  striation  in  cross-section.  The  cells  of  the  outer  layers  gradually  pass 
into  the  interstitial  tissue.  Within  the  basement-membrane  are  epithelial  cells 
arranged  in  several  irregular  layers,  which  are  not  always  clearly  separated ,  but 
which  may  be  arranged  in  three  different  groups.  Among  these  cells  may  be  seen 
the  spermatozoids  in  different  stages  of  development.  1.  Lining  the  basement- 
membrane  and  forming  the  outer  zone  is  a  layer  of  cubical  cells,  with  small 
nuclei;  these  are  known  as  the  lining  cells  or  spermatogonia.  The  nucleus  of  some 
of  them  may  be  seen  to  be  in  the  process  of  indirect  division  {karyokinesis) ,  and 
in  consequence  of  this  daughter  cells  are  formed,  which  constitute  the  second  zone. 
2.  Within  this  first  layer  is  to  be  seen  a  number  of  larger  cells  with  clear  nuclei, 
arranged  in  two  or  three  layers;  these  are  the  intermediate  cells  or  spermatocytes. 
Most  of  these  cells  are  in  a  condition  of  karyokinetic  division,  and  the  cells  which 
result  from  this  division  form  those  of  the  next  layer,  the  spermatoblasts  or  sperma- 
tids. 3.  The  third  layer  of  cells  therefore  consists  of  the  spermatoblasts  or  sperma- 
tids, and  each  of  these,  without  further  subdivision,  becomes  a  spermatozoid.  Tliey 
are  ill-defined  granular  masses  of  protoplasm,  of  an  elongated  form,  with  a  nucleus 
which  becomes  the  head  of  the  future  spermatozoid.  In  addition  to  these  three 
layers  of  cells  others  are  seen,  which  are  termed  the  supporting  cells,  or  cells  of 
Sertoli.  They  are  elongated  and  columnar,  and  project  inward  from  the  basement- 
membrane  toward  the  lumen  of  the  tube.  They  give  off  numerous  lateral  branches, 
which  form  a  reticulum  for  the  support  of  the  three  groups  of  cells  just  described. 
As  development  of  the  spermatozoids  proceeds  the  latter  group  themselves  around 
the  inner  extremities  of  the  supporting  cells.  The  nuclear  part  of  the  sperma- 
tozoid, which  is  partly  embedded  in  the  supporting  cell,  is  differentiated  to  form  the 
head  of  the  spermatozoid,  while  the  cell  protoplasm  becomes  lengthened  out  to 


THE   TESTICLES  I473 

form  the  middle  piece  and  tail,  the  latter  projecting  into  the  lumen  of  the  tube. 
Ultimately  the  heads  are  separated  and  the  spermatozoids  are  set  free. 

Spermatogenesis. — The  stages  in  the  development  of  the  spermatozoids  are  as 
follows:  The  spermatogonia  become  enlarged  to  form  the  spermatocytes,  and 
each  spermatocyte  subdivides  into  two  cells,  and  each  of  these  again  divides  into 
two  spermatids  or  young  spermatozoids,  so  that  the  spermatocyte  gives  origin  to 
four  spermatozoids. 

The  process  of  spermatogenesis  bears  a  close  relation  to  that  of  maturation  of 
the  ovum.  The  spermatocyte  is  equivalent  to  the  immature  ovum.  It  undergoes 
subdivision,  and  ultimately  gives  origin  to  four  spermatozoids,  each  of  which  con- 
tains, therefore,  only  one-fourth  of  the  chromatin  elements  of  the  nucleus  of  the 
spermatocyte.  In  the  process  of  maturation  of  the  ovum  its  nucleus  divides,  one- 
half  being  extended  as  the  first  polar  body.  The  remaining  half  of  the  nucleus 
again  subdivides,  one-half  being  extended  as  the  second  polar  body.  The  portion 
of  the  nucleus  which  is  retained  to  form  the  female  pronucleus  of  the  now  matured 
ovum  contains,  therefore,  only  one-fourth  of  the  chromatin  elements  of  the 
original  nucleus,  and  thus  the  spermatozoid  and  the  matured  ovum,  so  far  as 
their  nuclear  elements  are  concerned,  may  be  regarded  as  of  the  same  morpho- 
logical value. 

The  tubules  are  enclosed  in  a  delicate  plexus  of  capillary  vessels,  and  are  held 
together  by  an  intertubular  connective  tissue,  which  presents  large  interstitial 
spaces  lined  by  endothelium,  which  are  believed  to  be  the  rootlets  of  lymphatic 
vessels  of  the  testis. 

The  Aberrant  Ducts  of  the  Epididymis  {ductuli  aherrantes)  are  tortuous  and  end 
in  blind  extremities.  The  superior  aberrant  duct  {ductus  aherrans  superior)  is  in  the 
globus  major  and  joins  the  rete  testis.  The  inferior  aberrant  duct  (ductus  aherrans 
inferior)  (Fig.  1080)  is  in  the  tail  of  the  epididymis,  and  takes  origin  from  the 
duct  of  the  epididymis  or  the  seminal  duct.  It  is  a  persistent  canal  of  the  Wolffian 
body.  It  extends  up  the  cord  for  two  or  three  inches  and  terminates  by  a  blind 
extremity,  which  is  occasionally  bifurcated.  It  may  be  as  much  as  fourteen 
inches  in  length.     Its  structure  is  similar  to  that  of  the  seminal  duct. 

The  Seminal  Duct  or  Vas  Deferens  {ductus  deferens)  (Figs.  1074,  1075,  1076, 1080, 
1081,  and  1118). — The  seminal  duct  or  vas  deferens,  the  excretory  duct  of  the  testis, 
is  the  continuation  of  the  epididymis.  Commencing  at  the  lower  part  of  the  globus 
minor,  it  ascentls  along  the  posterior  border  of  the  testis  and  inner  side  of  the  epi- 
didymis, and  along  the  back  part  of  the  spermatic  cord,  through  the  inguinal  canal 
to  the  internal  or  deep  abdominal  ring.  From  the  ring  it  curves  around  the  outer 
side  of  the  internal  epigastric  artery  and  vein,  crosses  the  external  iliac  vessels,  and 
descends  into  the  pelvis  at  the  side  of  the  bladder;  it  arches  backward  and  down- 
ward to  its  base,  crossing  over  the  obliterated  hypogastric  artery  and  to  the  inner 
side  of  the  ureter.  At  the  base  of  the  bladder  it  lies  between  that  viscus  and  the 
rectum,  nmning  along  the  inner  border  of  the  seminal  vesicle.  Behind  the  bladder 
it  becomes  enlarged  and  sacculated,  forming  the  ampulla  (ampulla  ductus  deferentis) 
(Fig.  1081),  and  then,  becoming  narrowed  at  the  base  of  the  prostate,  unites  with 
the  duct  of  the  seminal  vesicle  to  form  the  ejaculatory  duct  (Fig.  1082) .  From  the 
internal  abdominal  ring  to  the  middle  of  the  ampulla  the  seminal  duct  is  beneath 
the  peritoneum.  The  vas  deferens  offers  a  hard  and  cord -like  sensation  to  the 
fingers;  it  is  about  two  feet  in  length,  of  cylindrical  form,  and  about  a  line  and 
a  quarter  in  diameter.  Its  walls  are  dense,  measuring  one-third  of  a  line,  and  its 
canal  is  extremely  small,  measuring  about  half  a  line. 

Structure. — The  vas  deferens  consists  of  three  coats:  1.  An  external  or  areolar 
coat  (tunica  adventitia).  2.  A  muscular  coat  (tunica  muscularis) ,  which  in  the 
greater  part  of  the  tube  consists  of  two  layers  of  unstriped  muscular  fibre :  an  inner 
layer  of  thin  longitudinal  fibres  (stratum,  internum)  existing  only  at  the  beginning, 

93 


1474  TJJE  31  ALE    ORGANS   OF   GENERATION 

a  thick  layer  of  circular  fibres  {stratum  medium),  and  a  thick  external  layer  of 
longitudinal  fibres  {stratum  externum).  3.  An  internal  or  mucous  coat  {tunica 
mucosa),  which  is  pale,  and  arranged  in  longitudinal  folds;  its  epithelial  cells  are 
of  the  columnar  variety. 

Organ  of  Giraldes  {paradidymis). — This  term  is  applied  to  a  small  body  of 
rounded  shape  in  the  lower  end  of  the  spermatic  cord,  in  front  of  the  blood- 
vessels. It  consists  of  a  small  collection  of  minute  vesicles  and  a  small  collection 
of  convoluted  tubules.  These  tubes  are  lined  with  columnar  ciliated  epithelium, 
and  probably  represents  the  remains  of  a  part  of  the  Wolffian  body. 

Surgical  Anatomy. — Abnormalities  in  the  descent  and  position  of  the  testicle  have  been 
discussed  (p.  1462).  The  testicle  may  require  removal  for  malignant  disease,  tuberculous  disease, 
cystic  disease,  in  cases  of  large  hernia  testis,  and  in  some  instances  of  incompletely  descended  or 
misplaced  testicles.  The  operation  of  double  castration  has  also  been,  during  the  last  few  years, 
performed  for  enlargement  of  the  prostate  gland;  for  it  has  been  found  that  removal  of  the  tes- 
ticles is  followed  by  very  rapid  and  often  considerable  diminution  in  the  size  of  the  prostate. 
The  operation  is,  however,  one  of  severity,  and  is  frequently  followed  by  death  in  these  cases, 
performed,  as  it  necessarily  is,  in  old  men.  Reginald  Harrison  has  proposed  to  substitute  for  it 
excision  of  a  portion  of  each  vas  deferens  {vasectomy).  The  operation  of  castration  is  a  com- 
paratively simple  one.  An  incision  is  made  into  the  cavity  of  the  tunica  vaginalis  from  the 
external  ring  to  the  bottom  of  the  scrotum.  The  coverings  are  shelled  off  the  organ,  and  the 
mesorchium,  stretching  between  the  back  of  the  testicle  and  the  scrotum,  divided.  The  cord  is 
then  isolated,  and  an  aneurism  needle,  armed  with  a  double  ligature,  passed  under  it,  as  high 
as  is  thought  necessary,  and  the  cord  tied  in  two  places,  and  divided  between  the  ligatures. 
Sometimes,  in  cases  of  malignant  disease,  it  is  desirable  to  open  the  inguinal  canal  and  tie  the 
cord  as  near  the  internal  abdominal  ring  as  possible. 

A  collection  of  serous  fluid  in  the  sac  of  the  vaginal  tunic  of  the  testicle  is  known  as  an  ordinary 
or  testicular  hydrocele.  In  congenital  hydrocele  a  communication  remains  between  the  tunica 
vaginalis  testis  and  the  peritoneal  cavity.  This  communication  should  have  closed  during 
development.  In  infantile  hydrocele  the  tunica  vaginalis  and  part  of  the  funicular  process  are 
distended  with  fluid,  but  the  funicular  process  is  closed  above  and  the  cavity  of  the  hydrocele 
does  not  communicate  with  the  peritoneal  cavity.  In  encysted  hydrocele  of  the  cord  the  funicular 
process  is  closed  above  and  below,  but  between  these  points  is  not  obliterated.  In  funicular 
hydrocele  the  funicular  process  is  closed  below  and  open  above.  Congenital  hydrocele  can 
usually  be  cured  by  the  application  of  a  truss.  This  obliterates  the  upper  end  of  the  funicular 
process,  and  the  obliteration  once  begun  may  proceed  to  completion.  If  it  does  not,  the  condi- 
tion has  become  an  infantile  hydrocele.  An  infantile  hydrocele  can  usually  be  cured  by  multiple 
punctures  or  tapping.  The  same  is  true  of  encysted  hydrocele  of  the  cord.  In  hydrocele  of  the 
funicular  process  wear  a  truss  for  a  time  and  then  tap.  In  ordinary  testicular  hydrocele  incise 
and  pack,  or  incise  and  suture,  the  cut  edge  of  the  parietal  layer  of  the  tunic  to  the  skin,  or  extir- 
pate the  parietal  layer  of  the  tunic.  A  successful  method  is  that  of  Longuet.  He  makes  an 
incision,  pulls  out  the  testicle,  and  allows  all  the  coats  except  the  skin  to  fall  behind  and  make 
a  sheath  for  the  cord.  These  coats  are  held  behind  by  one  catgut  suture.  A  bed  is  made  for 
the  testicle  beneath  the  skin  toward  the  septum  of  the  scrotum.  The  testicle  is  rotated  on  its 
long  axis  and  placed  in  the  bed,  and  the  skin  is  sutured  above  it.  This  operation  is  known 
as  extraserous  transposition.  If  a  portion  of  bowel  enters  an  open  vaginal  process  the  condition 
is  congenital  hernia. 

In  infantile  hernia  the  funicular  process  is  closed  above  but  not  below,  and  the  hernia  descends 
in  a  special  sac  back  of  the  vaginal  tunic.  If  the  hernia  pushes  down  on  the  vaginal  process  and 
causes  it  to  double  on  itself  the  condition  is  encysted  infantile  hernia. 

The  Semen  and  the  Spermatozoids. — Semen  consists  of  spermatozoids  with  liquids 
and  solids.  Part  of  the  semen  comes  from  the  testicles,  most  of  it  from  accessory 
glands — that  is,  from  the  glands  of  the  seminal  ducts,  the  seminal  vesicles,  the  pros- 
tate gland,  and  Cowper's  glands.  Semen  is  a  viscid,  whitish  fluid,  of  alkaline 
reaction  and  characteristic  odor.  It  contains  water  and  about  18  per  cent,  of 
solid  matter.  In  this  solid  matter  are  fat,  cholesterin,  lecithin,  proteids,  nuclein, 
xanthin,  chlorides,  sulphates,  and  phosphates  of  sodium  and  potassium.  Bott- 
cher's  crystals,  which  can  be  obtained  from  semen,  are  composed  of  phosphate  of 
spermine.  Spermine  is  a  nitrogenous  substance.  The  fluid  portion  of  semen 
carries  and  probably  nourishes  the  living  cells  known  as  spermatozoids. 


THE   SEMINAL     VESICLES 


1475 


The  spermatozoids  (Fig.  1081)  are  minute,  thread-like  bodies,  which  constitute  the 
essential  elements  of  the  semen.  Each  consists  of  a  head,  a  middle  piece  or  body, 
and  an  elongated  filament  or  tail.  The  head,  on  surface  view, appears  oval  in  shape, 
but  if  seen  in  profile  it  is  narrow  and  pointed  at  its  free  end.  It  represents  the 
modified  nucleus  of  the  spermatid,  and  consists  chiefly  of  chromatin,  and  so 
stains  readily  with  nuclear  reagents;  it  is  covered  by  a  thin  cap  of  protoplasm. 
The  body  is  a  short  cylindrical  or  conical  piece,  inter- 
vening between  the  head  and  tail,  and  is  therefore 
sometimes  spoken  of  as  the  intermediate  segment. 
The  tail  is  about  four  times  the  combined  lengths  of 
the  head  and  body;  its  terminal  part  is  extremely  fine, 
and  is  named  the  end-piece.  Contained  within  the 
body  and  tail  is  an  axial  filament,  surrounded,  except 
in  the  end-piece,  by  a  thin  layer  of  protoplasm;  this 
axial  filament  terminates  just  below  the  head  in  a 
rounded  knob  or  button.  In  virtue  of  their  tails, 
w'hich  act  as  propellers,  the  spermatozoids,  in  the 
fresh  condition,  are  capable  of  free  movement,  and 
if  placed  in  favorable  surroundings  {e.  g.,  in  the 
female  passages)  may  retain  their  vitality  for  some 
davs  or  even  weeks. 


.Head 


3iiddle 
'  piece 


'Main  piece 


Head' 


Middle 
piece 


of 
the 
tail 


..^End  piece    J 


THE    SEMINAL   VESICLES    (VESICULAE 
SEMINALES)  (Figs.  1082,  1083). 

The  seminal  vesicles  are  two  lobulated  membran- 
ous pouches  placed  between  the  base  of  the  bladder 

J    ,1  ,  •  •       i!        J.1  Fig.  1081. — Spermatozoid  of  man. 

and  the  rectum,  serving  as  reservoirs  tor  the  semen,  At  the  left  a  surface  view  is  shown ; 
and  secreting  a  fluid  to  be  added  to  the  secretion  of  S;y^^o1.f4%!'af[er  SiusV'"''- 
the  testicles.    Each  sac  is  somewhat  pyramidal  in 

form,  the  broad  end  being  directed  backward  and  the  narrow  end  forward  toward 
the  prostate.  It  measures  about  two  and  a  half  inches  in  length,  about  five  lines 
in  breadth,  and  two  or  three  lines  in  thickness.  They  vaiy,  however,  in  size,  not 
only  in  different  individuals,  but  also  in  the  same  individual  on  the  two  sides.  The 
upper  surface  is  in  contact  with  the  base  of  the  bladder,  extending  from  near  the 
termination  of  the  ureters  to  the  base  of  the  prostate  gland.  The  under  surface 
rests  upon  the  rectum,  from  which  it  is  separated  by  the  recto- vesical  fascia. 
Their  posterior  extremities  diverge  from  each  other.  Their  anterior  extremities 
are  pointed,  and  converge  toward  the  base  of  the  prostate  gland,  where  each  joins 
with  the  corresponding  seminal  duct  to  form  the  ejaculatory  duct.  Along  the 
inner  margin  of  each  vesicle  runs  the  enlarged  and  convoluted  vas  deferens.  The 
inner  border  of  the  vesicle  and  the  corresponding  seminal  duct  form  the  lateral 
boundaries  of  a  triangular  space,  limited  behind  by  the  recto-vesical  peritoneal 
fold;  the  portion  of  the  bladder  included  in  this  space  rests  on  the  rectum. 

Each  vesicle  consists  of  a  single  tube,  coiled  upon  itself  and  j^iving  off  several 
irregular  caecal  diverticula  (Fig.  1082) ,  the  separate  coils,  as  well  as  the  diverticula, 
being  connected  together  by  fibrous  tissue.  When  uncoiled  this  tube  is  about  the 
diameter  of  a  quill,  and  varies  in  length  from  four  to  six  inches;  it  terminates  pos- 
teriorly in  a  cul-de-sac;  its  anterior  extremity  becomes  constricted  into  a  narrow 
straight  duct,  the  excretory  duct  (ductus  excretorius)  (Fig.  1083),  which  joins  vvith 
the  corresponding  seminal  duct,  and  forms  the  ejaculatory  duct. 

The  Ejaculatory  Ducts  (ductus  ejaculatorii)  (Fig.  1083). — The  ejaculatory  ducts 
are  two  in  number,  one  on  each  side.  Each  duct  is  formed  by  the  junction  of  the  duct 
of  the  seminal  vesicle  with  the  seminal  duct.    Each  duct  is  about  three-quarters  of 


1476 


THE  3fALE    ORGANS    OF   GENERATION 


MUSCULAR 
TUNIC 


VA3 

DCFEi^ENS 


an  inch  in  length;  it  commences  at  the  base  of  the  prostate,  and  runs  forward  and 
downward  between  the  middle  and  lateral  lobes  of  that  gland,  and  along  the  side  of 

the  sinus  pocularis,  to  termi- 
nate by  a  separate  slit-like 
orifice  close  to  or  just  within 
the  margins  of  the  sinus.  The 
ductsdiminish  insizeand  also 
converge  toward  their  termi- 
nation. 

Structure. — The  seminal 
vesicles  are  composed  of  three 
coats:  an  external  or  areolar 
{tunica  adventitia) ;  a  middle 
or  muscular  coat  {tunica  mus- 
cM/an'.s),  which  is  thinner  than 
m  the  seminal  duct,  and  is 
arranged  in  two  layers,  an 
outer,  longitudinal,  and  inner, 
circular;  an  internal  or  mucous 
coat  (tunica  mucosa),  which 
is  pale,  of  a  whitish-brown 
color,  and  presents  a  delicate 
reticular  structure,  like  that 
seen  in  the  gall-bladder,  but 
the  meshes  are  finer.  The 
epithelium  is  columnar. 

The  coats  of  the  ejacula- 
tory  ducts  are  extremely  thin. 
They   are:   an  outer    fibrous 


COWPER'S 
GLANDS 


EXCRETORY 
DUCT 


Fig.  1082. — The  urinary  bladder,  distended,  with  surrounding  struc- 
tures, viewed  from  behind.     (Spalteholz.) 


layer,  which  is  almost  entirely 
lost  after  the  entrance  of  the 
duct  into  the  prostate;  a 
layer  of  muscular  fibres,  con- 
sisting of  an  outer  thin  circu- 
lar and  an  inner  longitudinal 
layer;  and  the  mucous  mem- 
brane. 

Vessels  and  Nerves. — The 
arteries  supplying  the  vesic- 
ulae  seminales  are  derived 
from  the  middle  and  inferior 
vesical  and  middle  haemor- 
rhoidal.  The  veins  and  lym- 
phatics accompany  the  arte- 
ries. The  lymphatics  anas- 
tomose on  the  surface  of  the 
vesicle.  The  trunks  from  this 
network  anastomose  with  the 
lymphatics  of  the  bladder 
and  prostate,  and  [)ass  to  the 
external  and  internal  iliac  glands.    The  nerves  are  derived  from  the  pelvic  plexus. 

Surgical  Anatomy. — The  vesiculae  seminales  are  often  the  seat  of  an  extension  of  the  dis- 
ease in  cases  of  tuberculosis  of  the  testicle,  and  should  always  be  examined  through  the  rectum 
before  coming  to  a  decision  with  regard  to  castration  in  this  affection.  The  vesicles  have  been 
deliberately  extirpated  for  local  tuberculosis.  In  gonorrhoea  the  seminal  vesicles  may  become 
acutely  inflamed  {acute  seminal  vesiculitis).  Chronic  seminal  vesiculitis  may  follow  the  acute 
form  or  may  arise  insidiously  during  gonorrhoea. 


XCRETORY 
DUCT 

EJACULATORY 
DUCT 


SINUS 
POCULARIS 


Fig.  1083. — The  ejaculatory  ducts  viewed  from  in  front  and  above. 
(Spalteholz.) 


THE  FEMLE  ORGANS  OE  GENERATION. 


EXTERNAL  ORGANS  (PARTES  GENITALES  EXTERNAE  MULIEBRES). 

THE  external  organs  of  generation  in  the  female  are:  the  mons  Veneris,  the 
labia  majora  and  minora,  the  clitoris,  the  meatus  urinarius,  and  the  orifice  of 
the  vagina.  The  term  vulva  {pudendum  muliebre),  as  generally  applied,  includes 
all  of  these  parts. 


FALLOPIAN  TUBE 


INFUNDIBULUM  OF 
FALLOPIAN  TUBE 


PAVILION  OF. 
FALLOPIAN  TUBE 


ORGAN  OF 
ROSENMULLER 


VESTIBULE   OF  VAGINA 

Fig.  1084.— Diagrammatic  representation  of  the  female  reproductive  organs  and  their  relations  to  the  bladder 

and  urethra,  lateral  view.     (Toldt.) 

THE  MONS  VENERIS  (MONS  PUBIS)  (Figs.  1085,  1086). 

The  mons  Veneris  is  the  rounded  eminence  in  front  of  the  pubic  symphysis, 
formed  by  a  collection  of  fatty  tissue  beneath  the  integument.  It  becomes  covered 
with  hair  at  the  time  of  puberty. 


THE  LARGE  LIPS  OR  LABIA  MAJORA  (LABIA  MAJORA  PUDENDI) 

(Figs.  1085,  1086,  1087). 

The  large  lips  or  labia  majora  are  two  prominent  longitudinal  cutaneous  folds 
extending  downward  from  the  mons  Veneris  to  the  anterior  boundary  of  the 
perinseum,  and  enclosing  the  common  urino-sexual  opening.  Each  labium  ma  jus 
{labium  majus  pudendi)  has  two  surfaces,  an  outer,  which  is  pigmented  and 

(1477) 


1478 


THE  FEMALE    ORGANS   OF   GENERATION 


covered  with  strong,  crisp  hairs;  and  an  inner,  which  is  smooth  and  is  beset  with 
large  sebaceous  follicles  and  is  continuous  with  the  genito-urinary  mucous  tract; 
between  the  two  there  is  a  considerable  quantity  of  areolar  tissue,  fat,  and  a 
tissue  resembling  the  dartos  of  the  scrotum,  besides  vessels,  nerves,  and  sweat  and 
sebaceous  glands.  Between  the  labia  majora  is  the  pudendal  slit  {rima  pudendi). 
The  labia  are  thicker  in  front,  where  they  form  by  their  meeting  the  anterior 
commissure  (commissura  labiorum  anterior).  Posteriorly  they  are  not  really 
joined,  but  appear  to  become  lost  in  the  neighboring  integument,  terminating 
close  to,  and  nearly  parallel  with,  each  other.  Together  with  the  connecting  skin 
between  them,  they  form  the  posterior  commissure  (commissura  labiorum  posterior), 
or  posterior  boundary  of  the  vulval  orifice.     The  interval  between  the  posterior 


MONS  VENERIS 


PREPUCE  OF 
CLITORIS 


POSTERIOR 

COMMISSURE- 

OF  VULVA 


ANTERIOR 
COMMISSURE 


PERINEUM 


POST-ANAL. 
FURROW 


Fig.  1085. — The  female  pudendum  or  vulva  with  the  labia  majora.     (Toldt.) 

commissure  and  the  anus,  about  an  incli  to  an  inch  and  a  quarter  in  length, 
constitutes  the  obstetric  perinseum.  The  fourchette  (frenulum  labiorum  pudendi) 
(Fig.  1086)  is  the  anterior  edge  of  the  perinseum,  and  between  it  and  the  hymen 
is  a  depression,  the  fossa  navicularis  of  the  vulva  or  the  vestibule  of  the  vagina  (fossa 
navicularis  vestibuli  vaginae)  (Fig.  1086).  The  labia  majora  correspond  to  the 
scrotum  in  the  male. 


THE  SMALL  LIPS,  NYMPHAE  OR  LABIA  MINORA  (LABIA  MINORA  PUDENDI) 

(Figs.  1085,  1086,  1087). 

The  small  lips  are    two  small  cutaneous    folds,  situated  within    the   labia 
majora,  and  extending  from  the  clitoris  obliquely  downward,  outward,  and  back- 


THE    CLITORIS 


1479 


ward  for  about  an  inch  and  a  half  on  each  side  of  the  orifice  of  the  vagina, 
between  which  and  the  labia  majora  they  are  lost  in  women  who  have  borne 
children.  In  women  who  have  not  borne  children  they  unite  behind  and  usually 
form  a  fold  {frenulum  lahiorum  piuiendi).  Behind  this  fold  is  the  fossa  navicularis. 
Anteriorly,  each  lip  divides  into  two  limbs.     The  external  limbs  unite  over  the 


VVONS    VENERIS 


ORIFICE  % 
OF  VAGINA 


rossA 

NAVICULARIS 


FiQ.  1086. — The  vulva.     External  female  organs  of  generatign. 

glans  clitoris  to  form  the  prepuce  of  the  clitoris  (praepuiium  clitoridis)  (Fig.  1086). 
The  internal  limbs  meet  and  unite  beneath  the  glans  clitoris  and  are  attached 
to  the  under  surface  of  the  glans  to  form  the  fraenum  (frenulum  clitoridis).  The 
nymphae  are  really  modified  skin.  Their  internal  surfaces  have  numerous  seba- 
ceous follicles  (glandulae  vestibidares  minores). 


THE  CLITORIS  (Figs.  1086,  10S7,  1089). 


Tlie  clitoris  is  an  erectile  structure  analogous  to  the  corpora  cavernosa  of  the 
penis.  It  is  situated  beneath  the  anterior  commissure,  partially  hidden  between 
the  anterior  extremities  of  the  labia  minora.  It  is  connected  to  the  rami  of  the 
OS  pubis.    It  consists  of  two  corpora  cavernosa,  each  of  which  {corpus  cavernosum 


1480 


THE  FEMALE    ORGAN^S   OF   GENERATION 


clitoridis)  passes  behind  into  the  eras  {cms  clitoridis).  Each  crus  is  attached 
to  the  ramus  of  the  pubis  and  ischium;  the  body  (corpus  clitoridis)  is  short 
and  concealed  beneath  tlie  labia;  the  free  extremity  (glans  clitoridis)  is  a  small 
rounded  tubercle,  consisting  of  spongy  erectile  tissue,  and  is  highly  sensitive.  It 
is  provided,  like  the  penis,  with  a  suspensory  ligament  (ligamentum  suspensorium 
clitoridis),  and  with  two  small  muscles,  the  Erectores  clitoridis,  which  are  inserted 
into  the  crura  of  the  clitoris.    The  two  corpora  cavernosa  are  composed  of  erectile 


POSTERIOR 
Vo  R  N  I X 


ANTERIOR 
FORNIX 


Fig.  1087. 


-Sagittal  section  of  the  lower  part  of  a  female  trunk,  right  segment, 
intestine.     (Testut.) 


SM.  INT..  small 


tissue  enclosed  in  a  dense  layer  of  fibrous  membrane,  united  together  along  their 
inner  surfaces  by  an  incomplete  fibrous  pectiniform  septum. 

To  each  crus  of  the  clitoris  goes  a  branch  from  the  internal  pudic  artery,  which 
branch  is  known  as  the  deep  artery  of  the  clitoris.  The  dorsal  arteries  of  the  clitoris 
(arteriae  dorsalis  clitoridis)  from  the  internal  pudic  send  branches  to  the  glans. 
The  nerves  of  the  clitoris  consist  of  the  dorsal  nerves  of  the  clitoris  from  the 
internal  pudic  nerve  and  sympathetic  fibres  from  the  hypogastric  plexus. 


THE    HYMEN 


1481 


THE  VESTIBULE   (VESTIBULUM  VAGINAE). 

The  vestibule  of  English  and  American  writers  is  a  triangular  smooth  surface 
between  the  clitoris  and  the  entrance  of  the  vagina  (Fig.  1086).  It  is  bounded 
on  each  side  by  the  nymphae.  The  vestibule  of  the  vagina  is  understood  by  the 
Germans  to  be  the  space  at  the  sides  of  the  vaginal  orifice  enclosed  by  the  labii 
minora,  as  well  as  the  space  in  front  of  the  vagina.^ 


Seclum 


Ovary, 


Fig.  1088. — Female  pelvic  organs  in  situ,  seen  from  above.     (Bardeleben.) 


rail- 


ORIFICE  OF  THE  URETHRA  OR  THE  MEATUS  URINARIUS  (ORIFICIUM 
URETHRAE  EXTERNUM)  (Figs.  1086,  1089). 


The  external  orifice  of  the  urethra  or  the  meatus  urinarius  is  situated  at  the 
back  part  of  the  vestibule,  about  an  inch  below  the  clitoris  and  near  the  margin 
of  the  vagina,  surrounded  by  a  prominent  elevation  of  the  mucous  membrane. 
Below  the  meatus  urinarius  is  the  orifice  of  the  vagina  (orificium  vaginae)  (Fig.  1086) , 
more  or  less  closed  in  the  virgin  by  a  membranous  fold,  the  hymen  (Fig.  1086). 


THE  HYMEN  (Figs.  1086,  1090). 

The  hymen  varies  much  in  shape.  Its  commonest  form  is  that  of  a  ring, 
generally  broadest  posteriorly;  sometimes  it  is  represented  by  a  semilunar  fold, 
with  its  concave  margin  turned  toward  the  pubes.  A  complete  septum  stretched 
across  the  lower  part  of  the  vaginal  orifice  is  called  an  imperforate  hymen.     Occa- 


1  See  note  89  by  Dr.  M.  Eden  Paul,  in  vol.  iv.  of  Toldt's  Atlas. 


1482 


THE  FEMALE    ORGANS    OF    GENERATION 


sionally  the  hymen  is  cribriform,  or  its  free  margin  forms  a  membranous  fringe, 
or  it  may  be  entirely  absent.  It  may  persist  after  copulation,  so  that  it  cannot 
be  considered  as  a  test  of  virginity.  After  rupture  of  the  hymen  the  small  rounded 
elevations  known  as  the  canmculae  myrtiformes  are  found  as  the  remains  of  the 
structure. 


GLANDS  OF  BARTHOLIN  (GLANDULA  VESTIBULARIS  MAJOR 
[BARTHOLINIp   (Fig.  1089). 

On  each  side  of  the  posterior  part  of  the  commencement  of  the  vagina  is  a 
round  or  oblong  body,  of  a  reddish-yellow  color,  and  of  the  size  of  a  horse-bean, 


SUSPENSORY  LIGAMENT 
OF    CLITORIS 


CLANS  OF 
CLITORIS 

SPHINCTER 
VAGINAE 
MUSCLE 

ERECTOR 

CLITORIDIS 

MUSCLE 

ORIFICE    OF 

URETHRA 

LABIA, 
MINORA 

CARUNOULAE 
MYRTIFORMES 
SPHINCTER 
VAGINAE- 
MUSCLE 


TRANSVERSE 
PERINEI 
MUSCLE 


EXCRETORY 
DUCT 


G  LA N  D  OF 
BARTHOLIN 


OMPRESSOR 
URETHRAE  MUSCLE 


TRANSVERSE 
PERINEI  MUSCLE 


Fig.  1089. — The  female  external  organs  of  generation  dissected.     (Spalteholz.) 


analogous  to  Cowper's  gland  in  the  male.  It  is  called  the  gland  of  Bartholin,  the 
gland  of  Duvemey,  the  vulvo-vaglnal  gland  or  the  suburethral  gland  (glandula  vestibu- 
laris major  [Bartholini]).  Bartholin's  gland  lies  partly  in  the  inferior  or  anterior 
leaf  of  the  triangular  ligament.  The  posterior  portion  of  the  bulbous  vestibuli 
and  the  Bulbo-cavernous  muscle  partly  cover  it.  Each  gland  opens  by  means  of 
a  long  single  duct  immediately  external  to  the  hymen,  in  the  angle  or  groove 
between  it  and  the  nympha  (Fig.  1090). 


THE    VAGINA 


1483 


CRESCENTIC  FRrNGED  BILABIAL  BIPERFORATE 

Fig.  1090. — Varieties  of  hymen.     (Testut,  after  Roze.) 


CRIBRIFORM 


THE  VAGINAL  BULB  OR  BULB  OF  THE  VESTIBULE  (BULBUS  VESTIBULI) 

(Fig.  1089). 

Extending  from  the  clitoris,  along  either  side  of  the  vestibule  (the  term  vestibule 
being  used  according  to  the  German  nomenclature)  (p.  1481),  and  lying  a 
little  behind  the  nymphae,  are  two  large  oblong  masses,  about  an  inch  in  length, 
consisting  of  a  plexus  of  veins  enclosed  in  a  thin  layer  of  fibrous  membrane. 
This  plexus  is  superficial  to  the  triangular  ligament,  and  it  is  covered  externally 
and  inferiorly  by  the  Bulbo-cavernous  muscle.  These  bodies  are  narrow  in  front, 
rounded  below,  and  are  connected  with  the  crura  of  the  clitoris  and  rami  of  the 
pubes;  they  are  termed  by  Kobelt  the  bulbi  vestibuli,  and  he  considers  them 
analogous  to  the  bulb  of  the  corpus  spongiosum  in  the  male.  Immediately  in 
front  of  these  bodies  is  a  smaller  venous  plexus,  continuous  with  the  bulbi  ves- 
tibuli behind  and  the  glans  clitoridis  in  front;  it  is  called  by  Kobelt  the  pars  inter- 
media, and  is  considered  by  him  as  analogous  to  that  part  of  the  body  of  the  corpus 
spongiosum  which  immediately  succeeds  the  bulb.  The  bulb  receives  its  blood 
from  the  artery  of  the  bulb  {arteria  bulbi  vestibuli),  which  is  a  branch  of  the  internal 
pudic. 

INTERNAL  ORGANS  (PARTES  GENITALES  INTERNAE  MULIEBRIS). 

The  internal  organs  of  generation  are — the  vagina,  the  uterus  and  its  appendages, 
the  Fallopian  tubes,  the  ovaries  and  their  ligaments. 


THE  VAGINA  (Figs.  1084,  1087,  1093). 

The  vagina  extends  from  the  vulva  to  the  uterus.  It  is  situated  in  the  cavity 
of  the  pelvis,  behind  the  bladder  and  in  front  of  the  rectum.  Its  direction  is 
curved  upward  and  backward,  at  first  in  the  line  of  the  pelvic  outlet,  and  afterward 
in  that  of  the  axis  of  the  cavity  of  the  pelvis.  Its  walls  are  ordinarily  in  contact, 
and  its  usual  shape  on  transverse  section  is  that  of  an  H,  the  transverse  limb 
being  slightly  curved  forward  or  backward,  whilst  the  lateral  limbs  are  somewhat 
convex  toward  the  median  line.  Its  length  is  about  two  and  a  half  inches  along 
its  anterior  wall  (paries  anterior),  and  three  and  a  half  inches  along  its  posterior 
wall  {paries  posterior).  It  is  constricted  at  its  commencement,  and  becomes 
dilated  medially,  and  narrowed  near  its  uterine  extremity;  it  surrounds  the  vaginal 


1484  THE  FEMALE    ORGANS   OF    GENERATION 

portion  of  the  cervix  uteri,  a  short  distance  from  the  os,  its  attachment  extending 
higher  up  on  the  posterior  than  on  the  anterior  wall  of  the  uterus  (Fig.  1096). 

The  vaginal  axis  forms  with  the  uterine  axis  an  obtuse  angle  opening  forward, 
and,  as  a  rule,  a  little  greater  than  a  right  angle  (Fig.  1094).  The  fact  that  the 
attachment  of  the  vagina  to  the  cervix  is  above  the  external  os  causes  the  formation 
of  a  recess  between  the  cervix  and  vaginal  wall,  known  as  the  vaginal  fornix  {fornix 
vaginae).  This  recess  is  deeper  posteriorly  than  it  is  laterally  or  in  front.  The 
anterior  portion  of  the  fornix  is  called  the  anterior  fornix  (Fig.  1087).  The  pos- 
terior portion  is  called  the  posterior  fornix  (Fig.  1087).  The  right  and  left  portions 
are  called  the  right  and  left  lateral  fomices.  The  vagina  opens  into  the  uro-genital 
cleft,  between  the  labia  minora  and  back  of  the  urethra  and  clitoris.  It  opens  by 
the  vaginal  orifice  (orijicium  vaginae)  (Fig.  1086).  In  the  virgin  the  opening  is 
partly  closed  by  the  hymen  (p.  1481).  After  rupture  of  the  hymen  atrophied 
fragments  of  the  torn  membrane  remain  around  the  vaginal  orifice,  and  are 
known  as  the  carunculie  myrtiformes  (carunculae  hymenales). 

Relations  (Fig^.  1084  and  1087). — The  upper  part  of  the  anterior  wall  of  the 
vagina  is  in  relation  with  the  base  of  the  bladder,  being  separated  from  that  viscus 
by  lax  connective  tissue.  Lower  down  the  middle  line  of  the  anterior  wall  and 
closely  joined  to  it  is  the  urethra.  The  upper  part  of  the  posterior  wall,  near 
the  middle  line,  is  covered  for  a  quarter  of  an  inch  or  more  with  peritoneum, 
which  forms  the  anterior  wall  of  the  depths  of  the  recto-vaginal  pouch  of  perito- 
neum or  pouch  of  Douglas  {excavatio  rectouterina  [Douglasi])  (Fig.  1096),  between 
the  uterus  and  vagina  and  the  rectum.  The  portion  of  the  posterior  wall  below 
the  level  of  the  pouch  of  Douglas  is  placed  close  to  the  rectum,  a  layer  of  pelvic 
fascia  intervening.  As  the  vaginal  orifice  is  neared,  the  rectum  and  vagina 
separate,  and  interposed  between  them  is  a  mass  of  fibro-fatty  tissue  called  the 
perinseum  or  perineal  body.  Its  sides  are  enclosed  between  the  Levatores  ani 
muscles.  The  ureter  toward  its  termination  (Fig.  1097)  lies  near  the  lateral  wall 
of  the  vagina,  passing  at  this  point  in  a  direction  downward,  inward,  and  slightly 
forward  to  reach  the  bladder.  The  vagina  near  its  termination  passes  through 
the  triangular  ligament,  and  upon  its  sides  are  the  bulbs  of  the  vestibule,  the 
glands  of  Bartholin,  and  the  Bulbo-cavernous  muscle. 

Structure. — The  vagina  consists  of  an  internal  mucous  lining,  of  a  muscular  coat, 
and  between  the  two  of  a  layer  of  erectile  tissue. 

The  Mucous  Membrane  (tunica  mucosa)  (Fig.  1093). — The  mucous  membrane  is 
continuous  above  with  that  lining  the  uterus.  Its  inner  surface  presents,  along 
the  anterior  and  posterior  walls,  a  longitudinal  ridge  or  raphd,  called  the  rugous 
columns  of  the  vagina  (columna  rugarum  anterior  et  posterior).  The  anterior 
column  extends  downward  as  far  as  the  external  orifice  of  the  urethra,  forming  the 
carina  urethralis  vaginae.  Numerous  transverse  ridges  or  rugae  {rugae  vaginales) 
extend  outward  from  the  raph^  on  either  side.  These  rugae  are  divided  by  fur- 
rows of  variable  depth,  giving  to  the  mucous  membrane  the  appearance  of  being 
studded  over  with  conical  projections  or  papillae;  they  are  most  numerous  near 
the  orifice  of  the  vagina,  especially  in  females  before  parturition.  The  epithelium 
covering  the  mucous  membrane  is  of  tlie  squamous  variety.  The  submucous  tissue 
is  very  loose  and  contains  numerous  large  veins,  which  by  their  anastomoses 
form  a  plexus,  together  with  smooth  muscular  fibres  from  the  muscular  coat;  it 
is  regarded  by  Gussenbauer  as  an  erectile  tissue  (see  p.  1485).  It  contains  a 
number  of  mucous  crypts,  but  no  true  glands. 

The  Muscular  Coat  {tunica  muscularis). — The  muscular  coat  consists  of  two 
layers:  an  external  longitudinal,  which  is  far  the  stronger,  and  an  internal  circular 
layer.  The  longitudinal  fibres  are  continuous  with  the  superficial  muscular  fibres 
of  the  uterus.  The  strongest  fasciculi  are  those  attached  to  the  recto-vesical  fascia 
on  each  side.    The  two  layers  are  not  distinctly  separable  from  each  other,  but 


THE    VAGINA 


1485 


are  connected  by  oblique  decussating  fasciculi  which  pass  from  the  one  layer  to 
the  other.  Above  the  triangular  ligament  the  fibres  are  non-striated ;  in  the  region 
of  the  ligament  they  show  striations.  In  addition  to  this  the  vagina  at  its  lower 
end  is  surrounded  by  a  band  of  striped  muscular  fibres,  the  sphincter  vaginae 
(p.  461).  External  to  the  muscular  coat  is  a  layer  of  connective  tissue  containing 
a  large  plexus  of  blood-vessels. 

The  Erectile  Tissue. — The  erectile  tissue  consists  of  a  layer  of  loose  connective 
tissue  situated  between  the  mucous  membrane  and  the  muscular  coat;  embedded 
in  it  is  a  plexus  of  large  veins,  and  numerous  bundles  of  unstriped  muscular  fibres 
derived  from  the  circular  muscular  layer.  The  arrangement  of  the  veins  is 
similar  to  that  found  in  other  erectile  tissues. 


EXTERNAL 
ILIAC  GLANDS 


INTERNAL 
ILIAC  GLANDS 


LATERAL 
SACRAL  GLANDS 


AFFERENTS 
TO  EXTERNAL 
ILIAC  GLANDS 


AFFERENTS 
TO   INTERNAL 
LIAC  GLANDS 


RETROVAGINAL 
NODULES 


Fig.  1091. — The  lymphatics  of  the  vagina.     Schematic.     (Poirier  and  Charpy.) 

Blood-vessels,  Nerves,  and  Lymphatics, — The  arteries  of  the  vagina  are  branches 
of  the  vesico-vaginal  artery;  the  vaginal  branch  of  the  uterine  artery  (p.  687),  and 
branches  of  the  internal  pudic  and  middle  haemorrhoidal.  The  veins  form  an  abund- 
ant plexus  around  the  wall  of  the  vagina  and  pass  to  the  internal  iliac  veins.  The 
lymphatics  (Fig.  1091)  arise  from  the  two  communicating  networks,  one  of  which  is 
below  the  mucous  membrane,  the  other  in  the  muscular  wall.  There  is  a  third  net- 
work around  the  vaginal  wall,  from  which  the  collectors  arise.  The  trunks  from  the 
upper  third  of  the  vagina  pass  to  the  external  iliac  glands ;  those  from  the  middle 
third  pass  to  the  internal  iliac  glands ;  those  from  the  lower  third  terminate  in  the 
glands  at  the  promontory  of  the  sacrum  or  in  the  lateral  sacral  glands.^  The  nerves 
come  from  the  third  and  fourth  sacral  nerves  and  from  the  utero-vaginal  and 
vesical  plexuses  of  the  ssrmpathetic. 


1  The  Lymphatics.    By  Poirier,  Cuneo,  and  Delamare.     Tran.slated  and  edited  by  Cecil  H.  Leaf. 


1486 


THE   FEMALE    ORGANS    OF    GENERATION 


THE  WOMB  OR  UTERUS  (Figs.  1084,  1087,  1088,  1092,  1097). 


The  uterus  is  the  organ  of  gestation,  receiving  the  fecundated  ovum  in  its  cavity, 
retaining  and  supporting  it  during  the  development  of  the  foetus,  and  becoming 
the  principal  agent  in  its  expulsion  at  the  time  of  parturition.  It  is  a  hollow 
muscular  organ.  The  non-pregnant  uterus  is  contained  in  the  cavity  of  the  pelvis 
betvi^een  the  bladder  and  rectum  (Figs.  1087  and  1088).  It  is  rarely  placed  exactly 
in  the  mid-line,  but  inclines  to  one  side  or  the  other,  more  often  to  the  left  than 
to  the  right.  The  walls  of  the  organ  are  extremely  thick.  The  uterus  is  movable 
as  a  whole,  and  the  body  of  the  uterus  is  movable  upon  the  neck.  Its  position 
varies  with  the  condition  of  adjacent  parts,  especially  the  bladder  and  rectum. 
The  cervix  is  more  firmly  fixed  than  the  body  and  fundus,  and  hence  the  latter 
vary  more  in  position  than  the  former.  Normally,  in  an  erect  individual,  with  the 
bladder  and  rectum  empty,  the  external  os  is  at  the  level  of  the  upper  surface  of 
the  pubic  symphysis  (Fig.  1084)  and  in  a  frontal  plane  passing  through  the  ischiatic 
spines.  The  long  axis  of  the  uterus  is  directed  forward  and  upward  (Fig.  1084), 
and  is  angled  where  the  body  and  cervix  join.    Hence,  normally,  with  the  bladder 


MESOVARIUM 


ANTERIOR        ISTHMUS   . 
BORDER    OF      FALLOPIAN 
OVARY  TUBE 


FALLOPIAN 
TUBE 


OVARIAN 
FIMBRIA 


ABDOMINAL 
ORIFICE 


LIGAMENT 
OF  OVAHV 


OF  OVARY  UTERINE 

EXTREMITY 

OF  OVARY 


VAGINAL 
PORTION  OF 
CERVIX 


ANTERIOR  LIP 
OF  CERVIX 

Fig.  1092.— The  uterus,  the  left  Fallopian  tube  and  the  left  ovary  in  their  connection  with  the  broad  ligament  of 
the  uterus,  which  has  been  fully  unfolded.     Seen  from  behind.     From  a  virgin,  aged  nineteen  years.  (Toldt.) 

empty,  the  uterus  is  anteverted  and  anteflexed.  When  the  bladder  fills  the  ante- 
version  and  anteflexion  are  almost  abolished.  If  the  bladder  is  overdistended  and 
the  rectum  is  empty,  the  uterus  is  pushed  strongly  backward,  so  that  its  long  axis 
corresponds  to  the  long  axis  of  the  vagina;  in  other  words,  it  is  retroverted. 

In  the  virgin  state  it  is  pear-shaped,  flattened  from  before  backward,  and 
is  retained  in  its  position  by  the  round  and  broad  ligaments  on  each  side,  and 
projects  into  the  upper  end  of  the  vagina  below  (Figs.  1092  and  1093).  Its  upper 
end,  or  base,  is  directed  upward  and  forward;  its  lower  end,  or  apex,  downward 
and  backward,  in  the  line  of  the  axis  of  the  inlet  of  the  pelvis.  It  therefore 
forms  an  angle  with  the  vagina,  since  the  direction  of  the  vagina  corresponds  to 
the  axis  of  the  cavity  and  outlet  of  the  pelvis.  The  non-pregnant  adult  uterus 
measures  about  three  inches  in  length,  two  inches  in  breadth  at  its  upper  part,  and 
nearly  an  inch  in  thickness,  and  it  weighs  from  an  ounce  to  an  ounce  and  a  half. 

It  consists  of  two  parts  (Fig.  1092) :  (1)  An  upper  and  larger  portion,  consisting 
of  the  body  and  fundus.  This  portion  is  flattened  from  before  backward.  (2)  A 
lower,  smaller,  and  cylindrical  portion,  the  cervix. 


THE    WOMB    OB    UTEBUS 


1487 


The  Fundus  (fundus  uteri)  (Fig.  1092). — The  fundus  is  the  upper  broad 
extremity  of  the  uterus.  If  a  line  is  drawn  from  the  uterine  opening  of  one 
Fallopian  tube  to  the  other,  the  portion  above  the  line  is  the  fundus.  The 
fundus  is  directly  continuous  with  the  body. 

The  Body  of  the  Uterus  (corpus  uteri)  (Fig.  1092). — The  body  of  the  uterus  is 
below  and  continuous  with  the  fundus.  In  outline,  when  seen  from  in  front  or 
behind,  it  resembles  a  triangle,  the  base  being  above  and  the  point  being  absent. 


GLANS 
CLITORIDIS 


EXTERNAL 
ORIFICE  OF 
URETHRA 


PARA-URETHRAL 
DUCT 


URETHRAL 
RIDGE 


POSTERIOR 
VAGINAL 
COLUMN 

ANTERIOR 
VAGINAL 
COLUMN 

TRANSVE 
RU 


VAGINAL 

PORTION  OF 

CERVIX 

SUPRAVAGINAL 
PORTION  OF- 
CERVIX 

Fig.  1093. — The  female  external  genital  organs  of  a  virgin  attached  to  the  vagina,  which  has  been  isolated 
anci  opened,  and  a  portion  of  the  cervix  uteri.      (Toldt.) 


The  anterior  surface  (fades  vesicalis)  passes  on  each  side  into  the  posterior  surface 
(fades  intestinalis)  by  the  lateral  border  (margo  lateralis) . 

The  body  gradually  narrows  from  the  fundus  to  the  neck.  Its  anterior  surface  is 
so  slightly  rounded  as  to  appear  flattened.  It  is  covered  by  peritoneum  (Fig.  1092), 
which  becomes  separated  from  it  at  its  union  with  the  cervix,  in  order  to  form  the 
utero-vesical  pouch,  which  lies  between  the  uterus  and  bladder  (Fig.  1096).  Its  pos- 
terior surface  is  more  rounded  than  the  anterior,  being  convex  transversely.     It  is 


1488 


THE   FEMALE   OBGAJ)^^.    OF   GENERATION 


covered  by  peritoneum  throughout  (Fig.  1097),  and  separated  from  the  rectum  by 
some  convolutions  of  the  small  intestine  (Fig.  1087).  The  peritoneum  which  covers 
the  posterior  surface  forms  most  of  the  anterior  wall  of  Douglas's  cul-de-sac 
(Figs.  853,  1096  and  1097,  and  p.  1248).  Its  lateral  margins  (Figs.  1092  and 
1097)  are  concave,  and  each  gives  attachment  to  the  Fallopian  tube  above,  the 
round  ligament  below,  and  in  front  of  this  the  ligament  of  the  ovary;  these 
structures  lie  between  the  layers  of  the  broad  ligament.    The  division  between  the 


GARTNER'S 
"DUCT 


Fig.  1094. — The  parovarium.     The  mesosalpinx  is  partly  removed.     (Poirier  and  Charpy.) 


the  body  and  the  cervix  is  indicated  externally  by  a  slight  constriction,  and  by  the 
reflection  of  the  peritoneum  from  the  anterior  surface  of  the  uterus  on  to  the  bladder, 
and  internally  by  a  narrowing  of  the  canal  called  the  internal  os  (Fig.  1095). 

The  Neck  or  Cervix  Uteri  (Figs.  1092  and  1095). — The  neck  or  cervix  uteri  is 
the  lower  constricted  segment  of  the  uterus;  around  its  circumference  is  attached 
the  upper  end  of  the  vagina  (Figs.  1087,  1092,  1093,  and  1096),  which  extends 
upward  a  greater  distance  behind  than  in  front.  The  neck  is  spindle-shaped  in 
those  who  have  had  no  children,  cylindrical  in  those  who  have  had  children. 


UTERINE 

ORIFICE   OF 

FALLOPIAN  TUBE 


ABDOMINAL 
ORIFICE 


HYDATID  OF 
MORGAQNI 


UTEROVAGINAL 

VENOUS 

PLEXUS 


\VAGINAL 
FORNIX 
OS    UTERI 
EXTERNUM 

Fig.  1095.  — The  uterus  and  the  right  Fallopian  tube  opened  from  behind.     (Toldt.) 

The  Supravaginal  Portion  (por^io  supravaginalis[cervicis])  (Figs.  1092  and  1096).— 
The  supravaginal  portion  is  not  covered  by  peritoneum  in  front;  a  pad  of  cellular 
tissue  is  interposed  between  it  and  the  bladder.  Behind,  the  peritoneum  is  extended 
over  it. 

The  Vaginal  Portion  (portio  vaginalis  cervicis)  (Figs.  1087, 1092,  1093,  and  1096). 
— The  vaginal  portion  is  the  lower  end  projecting  into  the  vagina.     It  is  round  or 


THE    WOMB    OR     UTERUS 


1489 


elliptical,  the  long  axis  of  the  elliptical  figure  being  transversely  placed.  On  its 
surface  is  a  small  aperture,  the  external  mouth  of  the  womb,  or  os  uteri,  or  external  os 
(orificium  uteri  externum)  (Figs.  1092,  1093, 1095,  and  1096),  generally  circular  in 
shape,  but  sometimes  oval  or  almost  linear.  If  a  woman  has  borne  children  the 
opening  is  transverse  and  the  margins  are  irregular.  The  margin  of  the  opening  is, 
in  the  absence  of  past  parturition  or 
disease,  quite  smooth.  This  aperture 
divides  the  vaginal  portion  of  the  cervix 
into  two  lips,  an  upper  or  posterior  lip 
(labium  posterius)  and  a  lower  or  an- 
terior lip  (labium  anierius).  On  each 
side  of  the  cervix  and  upper  portion  of 
the  vagina  there  is  a  space  containing 
bloodvessels  and  filled  with  loose  cellu- 
lar tissue.  This  loose  tissue  passes 
upward  between  the  layers  of  the  broad 
ligament  and  is  called  parametrium. 
On  each  side  of  the  cervix  and  three- 
quarters  of  an  inch  away  is  the  termi- 
nal portion  of  thecorresponding  ureter. 
Folds  and  Ligaments. — The  liga- 
ments of  the  uterus  are  eight  in  number.  Some  are  simple  folds  of  peritoneum; 
others  contain  connective  tissue  and  muscle.    The  ligaments  are  as  follows  :  one 


RECTAL    PERITONEUM 
CTOVAGINAL    POUCH 

ERIOR  AND  POS- 
IIOR  LAYERS  OP 
OAD    LIGAMENT 

VESICAL 
'ERITONEUM 

UTERO-VESICAL 
POUCH 

SUPRA-VAGINAL 
PORTION  OF 
CERVIX 


Fig.  1096. — The  cervix  uteri  and  upper  end  of  the 
vagina,  .showing  their  relations  to  the  peritoneum. 
Diagrammatic.     (Testut.) 


ROUND 

LIGAMENT. 


al  iliac 
tery. 


artery. 
Fig.  1097. — Douglas's  pouch.    (From  a  preparation  in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

anterior,  one  posterior,  two  lateral  or  broad,  two  sacro-uterine — all  these  being  formed 
of  peritoneum — and,  lastly,  two  round  ligaments. 

94 


1490 


THE  FEMALE    ORGANS    OF    GENERATION 


The  Anterior  Ligament  or  the  Utero-vesical  Fold  or  Vesico-uterine  Ligament  is 
reflected  on  to  the  bladder  from  the  front  of  the  uterus,  at  the  junction  of  the 
cervix  and  body.  It  forms  the  utero-vesical  pouch  (excavatio  vesicouterina)  (Figs. 
1096  and  1097). 

The  Posterior  Ligament  or  the  Recto-vaginal  Fold  passes  from  the  posterior  wall 
of  the  uterus  over  the  upper  fourth  of  the  vagina,  and  thence  on  to  the  rectum  and 
sacrum.  It  thus  forms  a  pouch,  called  the  recto-vaginal  pouch  or  Douglas's  pouch 
(Figs.  853,  1096,  and  1097),  the  boundaries  of  which  are,  in  front,  the  posterior 
wall  of  the  uterus,  the  supravaginal  portion  of  the  cervix,  and  the  upper  fourth  of 
the  vagina;  behind,  the  rectum  and  sacrum;  above,  the  small  intestine;  and, 
laterally,  the  folds  of  Douglas  or  recto-uterine  folds,  which  contain  the  sacro- 
uterine ligaments. 

The  Lateral  or  Broad  Ligament  (ligamenhim  latum  uteri)  (Figs.  1088,  1098, 
and  1104)  is  a  peritoneal  fold  which  passes  from  each  side  of  the  uterus  to  the 
lateral  wall  of  the  pelvis  as  high  as  the  external  iliac  vein.  From  this  region 
comes  the  peritoneal  fold  called  the  suspensory  ligament  of  the  ovary  (Fig.  1088) . 
The  two  broad  ligaments  form  a  septum  across  the  pelvis,  which  divides  that 
cavity  into  two  portions.  In  the  anterior  part  are  contained  the  bladder,  urethra, 
and  vagina;  in  the  posterior  part,  the  rectum.  In  the  uterus  normally  placed  the 
anterior  surface  of  the  broad  ligament  faces  forward  and  downward,  and  the  pos- 
terior surface  faces  upward  and  backward.    The  ligament  is  more  nearly  vertical 


GRAAFIAN 
FOLLICLE 


MCSOMCTRIUM' 


GRAAFIAN 
FOLLICLE 


STROMA   or 


Fig.  1098.— The  broad  ligament  of  the  uterus,  with 
the  mesovarium,  the  mesosalpinx,  the  ovary,  and 
the  Fallopian  tube  in  transverse  section.     (Toldt.) 


Fig.  1099. — Longitudinal  section  through  the  ovary. 
CToldt.) 


at  its  pelvic  insertion.  The  two  layers  of  the  broad  ligament  are  mostly  near 
to  each  other,  to  the  side  and  below  they  separate  and  pass  into  the  peritoneum 
of  the  lateral  pelvic  wall,  the  bladder  and  the  rectum.  Between  the  two  layers 
of  each  broad  ligament  are  contained — (1)  the  Fallopian  tube  superiorly;  (2)  the 
round  ligament;  (3)  the  ovary  and  its  ligament;  (4)  the  parovarium  or  organ  of 
Rosenmiiller,  and  the  paro-ophoron ;  (5)  loose  connective  tissue,  which  is  called 
parametrium;  (6)  unstriped  muscular  fibre;  and  (7)  blood-vessels  and  nerves.  The 
Fallopian  tube  is  in  the  free  edge  of  the  broad  ligament,  and  is  contained  in  a 
special  fold,  which  is  attached  to  the  part  of  the  ligament  near  the  ovary,  and  is 
known  by  the  name  of  the  mesosalpinx  (Figs.  1094,  1098,  and  1104).  If  the 
mesosalpinx  is  spread  out,  it  is  seen  to  be  roughly  triangular;  the  base  of  the 
triangle  is  outward,  the  apex  at  the  upper  and  outer  angle  of  the  uterus;  the 
upper  boundary  is  the  Fallopian  tube,  and  the  lower  boundary  is  the  ovary  and 
its  ligament.  Between  the  two  layers  of  the  mesosalpinx  are  the  parovarium  and 
the  paro-ophoron.  Between  the  fimbriated  extremity  of  the  tube  and  the  lower 
attachment  of  the  broad  ligament  is  a  concave  rounded  margin,  called  the  infun- 
dibulo-pelvic  ligament  (Fig.  1103). 


THE    WOMB    OB     UTEBU8  I49I 

The  ovary  lies  in  a  depression  of  the  broad  ligament  called  the  ovarian  bursa 
{bursa  ovarii)  (Figs.  1098  and  1104),  and  is  joined  to  the  ligament  by  a  short  fold, 
the  mesovarium  (Fig.  1104). 

The  mesovarium  passes  upward  from  the  posterior  surface  of  the  broad  liga- 
ment (Fig.  1098).  Beneath  the  mesovarium  is  a  larger  and  thicker  portion  of 
the  broad  ligament,  called  the  mesometrium  (Fig.  1098). 

The  Sacro-uterine  or  Utero-sacral  Ligaments  {plicae  rectouterinae)  are  contained 
in  the  peritoneal  folds  of  Douglas.  They  pass  from  the  second  and  third  bones 
of  the  sacrum,  downward  and  forward  on  the  lateral  aspects  of  the  rectum  to  be 
attached  one  on  each  side  of  the  uterus  at  the  junction  of  the  supravaginal  cervix 
and  the  body,  this  point  corresponding  internally  to  the  position  of  the  os 
internum.  They  contain  fibrous  tissue  and  unstriated  muscle-fibre.  Muscular 
fibres  from  the  uterine  wall  to  the  rectal  wall  constitute  the  Recto-uterinus  muscle 
{musculus  rectouterinus) .    This  muscle  is  part  of  the  sacro-uterine  ligaments. 

A  Round  Ligament  {ligamentum  teres)  (Figs.  1088,  1097,  1100,  and  1104)  is 
attached  on  each  side  of  the  uterus.  The  two  ligaments  are  rounded  cords, 
between  four  and  five  inches  in  length,  each  situated  between  the  layers  of  the 
broad  ligament  in  front  of  and  below  the  Fallopian  tube.  Commencing  at  the 
superior  angle  of  the  uterus,  this  ligament  passes  forward,  upward,  and  outward 
through  the  internal  abdominal  ring,  along  the  inguinal  canal,  to  the  labium 
majus,  in  which  it  becomes  lost.  The  round  ligament  consists  principally  of 
muscular  tissue  prolonged  from  the  uterus ;  also  of  some  fibrous  and  areolar  tissue, 
besides  blood-vessels  and  nerves,  enclosed  in  a  duplicature  of  peritoneum,  which 
in  the  foetus  is  prolonged  in  the  form  of  a  tubular  process  for  a  short  distance  into 
the  inguinal  canal.  This  process  is  called  the  canal  of  Nuck.  It  is  generally  oblit- 
erated in  the  adult,  but  sometimes  remains  pei-vious  even  in  advanced  life.  It 
is  analogous  to  the  peritoneal  pouch  which  precedes  the  descent  of  the  testis. 

The  Cavity  of  the  Uterus  {cavum  uteri)  (Fig.  1095) . — The  cavity  of  the  uterus 
is  small  in  comparison  with  the  size  of  the  organ,  because  of  the  great  thickness  of 
the  wall.  That  portion  of  the  cavity  which  corresponds  to  the  body  is  triangular, 
flattened  from  before  backward ,  so  that  its  anterior  and  posterior  walls  are  closely 
approximated,  and  having  its  base  directed  upward  toward  the  fundus.  At  each 
superior  angle  is  a  funnel-shaped  cavity,  which  constitutes  the  remains  of  one 
division  of  the  body  of  the  uterus  into  two  cornua,  and  at  the  bottom  of  each  cavity 
is  the  minute  orifice  of  the  Fallopian  tube.  At  the  inferior  angle  of  the  uterine 
cavity  is  a  small  constricted  opening,  smaller  and  more  nearly  circular  than  the 
external  os  uteri,  the  internal  orifice  of  the  uterus  or  internal  os  uteri  {orificium 
internum  uteri)  (Fig.  1095),  which  leads  into  the  cavity  of  the  cervix. 

The  Cavity  of  the  Cervix  or  Cervical  Canal  {canalis  cervicis  uteri)  (Fig.  1095). 
— The  cavity  of  the  cervix  or  cervical  canal  extends  from  the  internal  os  uteri  to 
the  external  os  uteri.  It  is  somewhat  fusiform,  flattened  from  before  backward, 
broader  at  the  middle  than  at  either  extremity,  and  communicates  below  with  the 
vagina.  The  wall  of  the  canal  presents,  anteriorly  and  posteriorly,  a  longitudinal 
column,  from  which  proceed  a  number  of  small  oblique  columns,  giving  the  appear- 
ance of  branches  from  the  stem  of  a  tree ;  and  hence  the  name  uterine  arbor  vitae 
{plicae  palmatae)  applied  to  it.  These  folds  usually  become  very  indistinct  after 
the  first  labor. 

Structure.— The  uterus  is  composed  of  three  coats:  an  external  or  serous  coat,  a 
middle  or  muscular  coat,  and  an  internal  mucous  or  coat. 

The  Serous  Coat  or  Perimetrium  {tunica  serosa)  (Figs.  1087, 1092,  1096,  and  1097). 
— The  serous  coat  is  derived  from  the  peritoneum;  it  invests  the  fundus  and  the 
whole  of  the  posterior  surface  of  the  uterus;  but  covers  the  anterior  surface  only  as 
far  as  the  junction  of  the  body  and  cervix.  In  the  lower  fourth  of  the  posterior 
surface  the  peritoneum,  though  covering  the  uterus,  is  not  closely  connected  with 


1492  THE  FEMALE   ORGANS    OF   GENERATION 

it,  being  separated  from  it  by  a  layer  of  loose  cellular  tissue  and  some  large  veins. 
At  the  lateral  margins  of  the  uterus  the  serous  coat  passes  on  to  the  broad  liga- 
ments. The  serous  coat  adheres  closely  to  the  uterus,  and  it  is  very  difficult  to 
separate  it  from  the  muscle. 

The  Muscular  Coat  {tunica  muscularis)  (Fig.  1095) . — The  muscular  coat  forms  the 
chief  bulk  of  the  substance  of  the  uterus.  In  the  unimpregnated  state  it  is  dense, 
firm ,  of  a  grayish  color,  and  cuts  almost  like  cartilage.  It  is  thick  opposite  the  middle 
of  the  body  and  fundus,  and  thin  at  the  orifices  of  the  Fallopian  tubes.  It  consists 
of  bundles  of  unstriped  muscular  fibres,  disposed  in  layers,  intermixed  with  areolar 
tissue,  blood-vessels,  lymphatic  vessels,  and  nerves.  The  muscular  tissue  is  dis- 
posed in  three  layers — external,  middle,  and  internal. 

The  external  layer  is  placed  beneath  the  peritoneum,  disposed  as  a  thin  plane 
on  the.  anterior  and  posterior  surfaces.  It  consists  of  fibres  which  pass  trans- 
versely across  the  fundus,  and,  converging  at  each  superior  angle  of  the  uterus, 
are  continued  on  the  Fallopian  tube,  the  round  ligament,  the  ligament  of  the 
ovary;  some  passing  at  each  side  into  the  broad  ligament,  and  others  running 
backward  from  the  cervix  into  the  sacro-uterine  ligaments.  The  fibres  of  the 
external  portion  of  the  outer  layer  (stratum  suhserosum)  are  longitudinal.  The 
fibres  of  the  inner  portion  of  the  outer  layer  {stratum  supravasculare)  are  partly 
circular  and  partly  longitudinal. 

The  middle  layer  of  fibres  {stratum  vasculare),  which  is  thickest,  presents  bundles 
of  circular  fibres  closely  connected  with  blood-vessels.  In  this  layer  are  most  of 
the  blood-vessels.  The  circular  fibres  about  the  internal  os  form  a  distinct 
sphincter.  Those  which  surround  the  orifices  of  the  Fallopian  tubes  are  arranged 
in  the  form  of  two  hollow  cones,  the  apices  of  which  surround  the  orifices  of  the 
Fallopian  tubes,  their  bases  intermingling  with  one  another  on  the  middle  of  the 
body  of  the  uterus. 

The  internal  or  deep  layer  {stratum  mucosum)  consists  of  longitudinal  fibres. 
Some  consider  the  deeper  portion  of  the  muscular  tissue  of  the  uterus  to  be  the 
muscularis  mucosae.  But  the  deep  portion  of  the  muscular  substance  is  con- 
tinuous with  the  more  superficial  portion,  and  there  is  no  submucous  coat  between 
the  muscle  and  the  mucous  membrane.  The  deeper  layer  of  muscular  fibres  of 
the  uterus  contains  connective  tissue  and  elastic  fibres.  The  muscular  tissue  of 
the  cervix  contains  more  connective  and  elastic  tissue  than  does  the  body  of  the 
uterus;  hence,  the  cervix  is  harder  and  stiffer  than  the  body. 

The  Mucous  Membrane  {tunica  mucosa)  (Fig.  1095). — The  mucous  membrane 
is  thin,  smooth,  and  closely  adherent  to  the  subjacent  muscular  tissue.  It  is 
continuous,  through  the  fimbriated  extremity  of  the  Fallopian  tubes,  with  the 
peritoneum,  and  through  the  os  uteri  with  the  lining  of  the  vagina. 

In  the  body  of  the  uterus  it  is  smooth,  soft,  of  a  pale-red  color  lined  with  columnar 
ciliated  epithelium,  and  presents,  when  viewed  with  a  lens,  the  orifices  of  numer- 
ous tubular  follicles  arranged  perpendicularly  to  the  surface.  It  is  unprovided 
with  any  submucosa,  but  is  intimately  connected  with  the  innermost  layer  of 
the  muscular  coat.  In  structure  its  corium  differs  from  ordinary  mucous  membrane, 
consisting  of  an  embryonic  nucleated  and  highly  cellular  form  of  connective  tissue, 
in  which  run  numerous  large  lymphatics.  In  it  are  the  tube-like  uterine  glands 
{glandulae  uterinae),  which  are  of  small  size  in  the  unimpregnated  uterus,  but 
shortly  after  impregnation  become  enlarged  and  elongated,  presenting  a  contorted 
or  waved  appearance  toward  their  closed  extremities,  which  reach  into  the  mus- 
cularis, and  may  be  single  or  bifid.  The  uterine  glands  consist  of  a  delicate 
membrane,  lined  with  epithelium,  which  becomes  ciliated  toward  the  orifices. 

In  the  cervix  the  mucous  membrane  is  sharply  difi'erentiated  from  that  of  the 
uterine  cavity.  It  is  thrown  into  numerous  oblique  ridges,  which  diverge  from  an 
anterior  and  posterior  longitudinal  raphe,  presenting  an  appearance  which  has 


THE    W03IB    OR     UTERUS  I493 

received  the  name  of  axbor  vitae.  In  the  upper  two-thirds  of  the  canal  the  mucous 
membrane  is  provided  with  numerous  deep  glandular  follicles  (glandulae  cervicales 
uteri),  which  secrete  a  clear  viscid  alkaline  mucus;  and  in  addition,  extending 
through  the  whole  length  of  the  canal,  are  a  variable  number  of  little  cysts,  pre- 
sumably follicles,  which  have  become  occluded  and  distended  with  retained  secre- 
tion. They  are  called  the  ovules  of  Naboth.  The  mucous  membrane  covering  the 
lower  half  of  the  cervical  canal  presents  numerous  papillae.  The  epithelium  of 
the  upper  two-thirds  is  cylindrical  and  ciliated,  but  below  this  it  loses  its  cilia,  and 
gradually  changes  to  squamous  epithelium  close  to  the  external  os. 

The  Uterus  at  Different  Ages. — The  uterus  of  the  foetus  is  in  the  abdominal  cavity 
projecting  above  the  brim  of  the  pelvis.  The  cervix  is  considerably  larger  than 
the  body.  At  birth  the  cervix  is  larger  relatively  than  in  the  adult;  there  is  no  dis- 
tinct internal  os  distinguishing  the  cavity  of  the  body  of  the  uterus  from  the  cavity  of 
the  cervix,  and  "  the  arbor  vitae  extends  throughout  the  whole  length  of  the  uterus."^ 
The  growth  of  the  uterus  is  slow  until  puberty  is  almost  reached,  when  for  a  time 
the  growth  is  rapid.  The  growth  of  the  uterine  body  causes  the  mucous  mem- 
brane of  this  part  to  lose  its  folds,  hence  the  arbor  vitae  disappears  from  the  body. 
In  a  woman  who  has  had  children  the  uterine  cavity  is  larger  than  in  a  woman 
who  has  never  borne  a  child.  In  advanced  years  the  uterine  wall  becomes  paler 
and  hard  and  rigid  from  atrophic  fibrous  changes.  A  more  distinct  constriction 
separates  the  body  and  cervix.  The  internal  os  frequently  and  the  external  os 
occasionally  are  obliterated  in  old  age. 

Abnormalities. — Very  rarely  the  uterine  cavity  is  divided  into  two  by  a  septum. 
Occasionally  the  condition  known  as  bicomate  uterus  exists.  In  this  condition 
each  lateral  angle  is  prolonged  into  a  horn  or  cornu.  The  uterus  is  formed  by  the 
union  of  the  two  ducts  of  Miiller,  and  failure  of  fusion  of  these  ducts  makes  a 
double  uterus  or  a  bicornate  uterus. 

Changes  at  a  Menstrual  Period. — For  several  days  before  the  menstrual  flow 
begins  the  mucous  membrane  increases  in  thickness  and  vascularity  and  its  sur- 
face is  cast  into  folds.  After  these  preparatory  changes  the  superficial  portions 
of  the  mucous  membrane  break  down  and  are  cast  off,  and  bleeding  begins.  At 
the  termination  of  menstruation  the  mucous  membrane  rapidly  regenerates.  At 
each  menstrual  period  from  100  to  200  grammes  of  blood  are  discharged.  The 
meaning  of  menstruation  is  uncertain.  Pfliiger  believes  the  wall  of  the  uterus  is 
made  raw,  so  that  if  an  impregnated  ovum  arrives  it  will  adhere.  Reichert  believes 
that  menstruation  means  that  no  impregnated  ovum  has  arrived  in  the  womb,  and 
hence  no  bed  is  needed  for  one. 

Changes  Induced  by  Pregnancy. — The  muscular  fibres  hypertrophy  enormously 
and  become  vastly  longer  and  broader.  There  is  a  great  increase  in  connective 
tissue,  and  new  connective-tissue  fibres  pass  between  bundles  of  muscle.  The 
peritoneal  coat  undergoes  hyperplasia.  It  remains  closely  adherent  to  the  uterus, 
except  over  the  lower  segment,  from  which  region  it  can  be  easily  stripped.  The 
blood-vessels  become  large  ancl  tortuous.  The  nerves  are  increased  in  length  and 
new  filaments  form.  The  lymphatics  undergo  hypertrophy  and  hyperplasia 
(Prof.  Barton  Cooke  Hirst).  The  uterus  becomes  spherical,  and  after  the  fourth 
month  ovoidal.  Early  in  pregnancy  the  increase  in  weight  causes  the  uterus 
to  descend  in  the  pelvis.  After  the  third  month  it  rises  progressively,  and  during 
the  ninth  month  the  fundus  reaches  the  epigastrium.  "Before  term  (four  weeks 
in  primiparae,  ten  days  or  one  week  in  multiparae)  the  fundus  sinks  again,  as 
the  presenting  part  and  lower  uterine  segment  become  engaged  in  the  pelvic 
cavity.  This  phenomenon  is  explained  by  contraction  of  the  overstretched 
abdominal  walls."^    The  womb  is  acutely  anteflexed  during  the  first  three  months 

I  Prof.  Francis  A.  Dixon  in  Prof.  Cunningham's  Text-book  of  Anatomy. 
«  A  Text-book  of  Obstetrics.     By  Prof.  Barton  Cooke  Hirst, 


1494 


THE   FEMALE    ORGANS    OF    GENERATION 


of  pregnancy.  After  this  period,  as  the  womb  rises,  the  anteflexion  is  diminished, 
but  some  degree  remains,  because  the  abdominal  walls  are  too  lax  to  hold  the 
organ  straight.  The  uterus  passes  somewhat  to  the  right  side  and  undergoes  a 
rotation  on  its  longitudinal  axis,  so  that  the  anterior  surface  looks  front  and  to  the 

-^^g^^'j^^^^r^'-^     Branches  to  tube. 
Branches  to  fundus. 


Fig.  1100. 


Vaginal  arteries. 
-The  arteries  of  the  internal  organs  of  generation  of  the  female,  seen  from  behind.    (After  Hyrtl.) 


right.  These  changes  in  position  are  caused  by  fecal  distention  of  the  sigmoid. 
The  intestines  are  above  and  back  of  the  uterus.  During  the  first  four  months  the 
cervix  softens  and  enlarges  somewhat.    The  length  of  the  cervical  canal  is  not 


VESSELS    FROM 
BODY  OF  FUNDUS 


VE88E 
FROM  TUB 


^, 


VESSELS  OF 
ROUND   LIGAMENT 


ANASTOMOSIS E   V 

OF  VESSELS 


VAGINAL, 
LYMPHATICS 


Fig.  1101. — The  lymphatic  vessels  of  the  uterus.     (Poirier  and  Charpy.) 

altered  during  pregnancy,  and  the  canal  does  not  dilate  until  labor  begins.  During 
pregnancy  the  cervical  glands  secrete  thick  mucus,  which  coagulates  and  occludes 
the  cervical  canal ;  the  round  ligaments  become  stronger,  and  the  layers  of  the 
broad  ligament  are  separated  toward  their  inner  portions  by  the  enlarging  womb. 


THE    W03IB    OB     UTERUS 


1495 


After  parturition  the  uterus  nearly  regains  its  former  size,  usually  weighing 
something  over  one  and  a  half  ounces;  but  its  cavity  is  larger  than  in  the  virgin 
state,  the  external  orifice  is  more  marked,  its  edges  present  a  fissured  surface,  its 
vessels  are  very  tortuous,  and  its  muscular  layers  are  more  defined. 

Vessels  and  Nerves  (Fig.  1100). — The  arteries  of  the  uterus  are  the  uterine,  from 
the  internal  iliac,  and  the  ovarian,  from  the  aorta.  They  are  remarkable  for  their 
tortuous  course  in  the  substance  of  the  organ  and  for  their  frequent  anastomoses. 
The  uterine  artery  reaches  the  lower  part  of  the  uterus  at  the  side  and  is  pro- 


JUXTA-»On^ 
GLAN 


VESSELS    FROM 
BODY  OF  UTERUS 


VESSELS    FRO 

NECK  OF  UTERU 

TO  LATERA 

SACRAL  GLAN 

VESSELS    FRO 

NECK  OF  UTEPU 


VESSELS 
ROUND   LIGAME 


XTA-AORTIC 
DS 


ELOF 
LLOPIAN  TUBE 


Fig.  1102.— The  lymphatics  of  the  internal  organs  of  generation  in  the  female.      (Poirier  and  Charpy.) 

longed  as  a  large  artery  to  the  body  and  fundus,  which  ascends  between  the 
layers  of  the  broad  ligament.  The  uterine  artery  gives  off  a  smaller  branch,  the 
cervical,  which  descends  to  supply  the  cervix  and  sends  cervico-vaginal  branches 
to  the  vagina.  The  azygos  arteries  of  the  vagina  come  from  the  cervico-vaginal 
reinforced  by  branches  of  the  vaginal  arteries  (Fig.  1104).  A  median  longitudinal 
vessel  is  formed  in  front  and  behind,  which  descends  in  the  vaginal  wall.  The 
termination  of  the  ovarian  artery  meets  the  termination  of  the  uterine  artery, 
and  forms  an  anastomotic  trunk  from  which  branches  are  given  off  to  supply 
the  uterus.     Dr.  Byron  Robinson,  instead  of  describing  the  uterine  and  ovarian 


1496  THE  FE3IALE    OBOANS    OF   GENERATION 

arteries  as  two  vessels,  describes  them  as  parts  of  one  vessel,  the  arteria  uterina 
ovarica  (p.  558).  The  veins  are  of  large  size,  and  correspond  with  the  arteries. 
In  the  impregnated  uterus  these  vessels  form  the  uterine  sinuses,  consisting  of 
the  lining  membrane^  of  the  veins  adhering  to  the  walls  of  the  canals  channelled 
through  the  substance  of  the  uterus.  They  terminate  in  the  uterine  plexuses, 
which  empty  into  the  internal  iliac  veins.  The  lymphatics  (Figs.  1101  and  1102) 
originate  from  three  networks,  a  muscular  network,  a  peritoneal  network,  and  a 
network  in  the  stroma.  The  trunks  from  these  networks  anastomose,  and  thus 
form  another  network  beneath  the  peritoneum,  and  from  the  fourth  network  the 
collectors  arise.  The  network  of  the  cervix  is  continuous  with  that  of  the  body. 
The  collecting  trunks  from  the  cervical  region  number  from  five  to  eight.  Some 
terminate  in  the  external  iliac  glands,  some  in  the  internal  iliac  glands,  some  in  the 
lateral  sacral  glands,  or  the  glands  of  the  promontory.  The  collecting  trunks  from 
the  body  terminate  chiefly  in  the  juxta-aortic  or  pre-aortic  glands,  but  some  termi- 
nate in  the  external  iliac  glands,  and  some  in  the  inguinal  glands.^  The  nerves  come 
chiefly  from  the  utero-vaginal  plexus,  which  continues  into  the  hypogastric  plexus 
and  receives  filaments  from  the  third  and  fourth  sacral  nerves.  The  uterus  also 
receives  direct  fibres  from  the  hjrpogastric  plexus    and  from  the  vesical  plexus. 

Surgical  Anatomy. — Pelvic  cellulitis  {parametritis)  is  inflammation  of  the  pelvic  cellular 
tissue.  It  is  due  to  sepsis,  and  its  usual  antecedent  is  uterine  sepsis.  A  laceration  of  the  cervix 
may  admit  bacteria.  An  abscess  may  form.  If  it  points  in  the  vagina  it  should  be  incised  through 
the  vaginal  wall.  The  uterus  may  require  removal  {hysterectomy)  in  cases  of  malignant  disease 
or  for  fibroid  tumors.  Carcinoma  is  the  most  common  form  of  malignant  disease  of  the  uterus, 
though  cases  of  sarcoma  do  occur.  Carcinoma  may  show  itself  either  as  a  columnar  carcinoma 
or  as  a  squamous  carcinoma ;  the  former  commencing  either  in  the  cervix  or  body  of  the  uterus,  the 
latter  always  commencing  in  the  epithelial  cells  of  the  mucous  membrane  covering  of  the  vaginal 
surface  of  the  cervix.  The  columnar  form  may  be  treated  in  the  early  stage,  before  fixation  has 
taken  place,  by  removal  of  the  uterus,  either  through  the  vagina  or  by  means  of  abdominal 
section.  The  former  operation  is  attended  by  the  smaller  death-rate.  Vaginal  hysterectomy 
may  be  performed  in  any  case  in  which  the  uterus  or  the  uterus  and  tumor  are  not  too  large  to  be 
withdrawn  through  the  vagina.  It  is  difficult  in  this  operation  to  deal  with  adhesions  and  other 
complications  in  the  upper  part  of  the  pelvis,  and  for  this  reason  many  surgeons  prefer  the  abdom- 
inal operation.  Vaginal  hysterectomy  is  performed  by  placing  the  patient  in  the  lithotomy  position 
and  introducing  a  large  duckbill  speculum  into  the  vagina.  The  cervix  is  then  seized  with  a  vol- 
sellum  and  pulled  down  as  far  as  possible  and  the  mucous  membrane  of  the  vagina  incised  around 
the  cervix  as  near  to  it  as  the  disease  will  allow,  especially  in  front,  where  the  ureters  are  in 
danger  of  being  wounded.  A  pair  of  dressing  forceps  are  then  pushed  through  into  Douglas's 
pouch  and  opened  sufficiently  to  allow  of  the  introduction  of  the  two  forefingers,  by  means  of 
which  the  opening  is  dilated  laterally  as  far  as  the  sacro-uterine  ligaments.  A  somewhat  similar 
proceeding  is  adopted  in  front,  but  here  the  bladder  has  to  be  separated  from  the  anterior  wall 
of  the  uterus  for  about  an  inch  before  the  vesico-uterine  fold  of  peritoneum  can  be  reached. 
This  is  done  by  carefully  burrowing  upward  with  a  director  and  stripping  the  tissues  off  the 
anterior  uterine  wall.  When  the  vesico-uterine  pouch  has  been  opened  and  the  opening  dilated 
laterally,  the  uterus  remains  attached  only  by  the  broad  ligaments,  in  which  are  contained  the 
vessels  that  supply  the  uterus.  Before  division  of  the  ligaments,  these  vessels  have  to  be  dealt 
with.  The  forefinger  of  the  left  hand  is  introduced  into  Douglas's  pouch  and  an  aneurism 
needle,  armed  with  a  long  silk  ligature,  is  inserted  into  the  vesico-uterine  pouch,  and  is  pushed 
through  the  broad  ligament  of  one  side  about  an  inch  above  its  lower  level  and  at  some  distance 
from  the  uterus.  One  end  of  the  ligature  is  now  pulled  through  the  anterior  opening,  and  in  this 
way  we  have  the  lowest  inch  of  the  broad  ligament,  in  which  is  contained  the  uterine  artery, 
enclosed  in  a  ligature.  This  is  tied  tightly,  and  the  operation  is  repeated  on  the  other  side.  The 
broad  ligament  is  then  divided  on  either  side,  between  the  ligature  and  the  uterus,  to  the  extent 
to  which  it  has  been  constricted.  By  traction  on  the  volsellum  which  grasps  the  cervix,  the  uterus 
can  be  pulled  considerably  farther  down  in  the  vagina,  and  a  second  inch  of  the  broad  ligament 
is  treated  in  a  similar  way.  This  second  ligature  will  embrace  the  pampiniform  plexus  of  veins 
and,  when  the  broad  ligament  has  been  divided  on  either  side,  it  will  be  found  that  a  third  liga- 
ture can  be  made  to  pass  over  the  Fallopian  tube  and  top  of  the  broad  ligament,  after  the  uterus 
has  been  dragged  down  as  far  as  possible.  After  the  third  ligature  has  been  tied  and  the  struc- 
tures between  it  and  the  uterus  divided,  this  organ  will  be  freed  from  all  its  connections  and  can 
be  removed  from  the  vagina.    This  canal  is  then  sponged  out  and  lighUy  dressed  with  gauze, 

1  The  Lymphatics.    By  Poirier,  Cun6o,  and  Delamare.     Translated  and  edited  by  Cecil  H.  Leaf. 


THE   FALLOPIAN    TUBE  I497 

no  sutures  being  used.  The  gauze  may  be  removed  at  the  end  of  the  second  day.  In  squamous 
epitheHoraa,  amputation  of  the  cervix  is  done  by  some  in  those  cases  where  the  disease  is  recog- 
nized before  it  has  invaded  the  walls  of  the  vagina  or  the  neighboring  broad  ligaments.  The 
operation  consists  in  removing  a  wedge-shaped  piece  of  the  uterus,  including  the  cervix,  through 
the  vagina  and  attaching  the  cut  surfaces  of  the  stump  to  the  anterior  and  posterior  vaginal  walls, 
so  as  to  prevent  retraction.  In  view,  however,  of  the  continuity  of  the  lymphatic  network  of  the 
cervix  with  the  lymphatics  of  the  body,  the  operation  is  insufficient  and  should  be  condemned. 
Complete  abdominal  hysterectomy  is  rarely  necessary,  except  for  malignant  disease.  In  this  opera- 
tion the  entire  uterus  is  removed.  The  preliminary  introduction  of  bougies  into  the  ureters  as 
practised  by  Kelly  and  Clark  enables  the  surgeon  to  readily  recognize  the  situations  of  these  tubes. 
After  the  abdomen  has  been  opened  the  uterine  vessels  are  secured  and  the  broad  ligaments 
divided  in  a  similar  manner  to  that  employed  in  vaginal  hysterectomy,  except  that  the  proceeding 
is  commenced  from  above.  When  the  first  two  ligatures  have  been  tied  and  the  broad  ligament 
divided,  it  will  be  found  that  the  uterus  can  be  raised  out  of  the  pelvis.  A  transverse  incision 
is  now  made  through  the  peritoneum,  where  it  is  reflected  from  the  anterior  surface  of  the  uterus 
on  to  the  back  of  the  bladder  and  the  serous  membrane  peeled  from  the  surface  of  the  uterus 
until  the  vagina  is  reached.  The  anterior  wall  of  this  canal  is  cut  across.  The  uterus  is  now 
turned  forward  and  the  peritoneum  at  the  bottom  of  Douglas's  pouch  incised  transversely,  and 
the  posterior  wall  of  the  vagina  cut  across  until  it  meets  the  incision  on  the  anterior  wall.  The 
uterus  is  now  almost  free,  and  is  held  only  by  the  lower  part  of  the  broad  ligament  on  either 
side,  containing  the  uterine  artery.  A  third  ligature  is  made  to  encircle  this,  and,  after  having 
been  tied,  the  structures  are  divided  between  the  ligature  and  the  uterus.  The  organ  can  now 
be  removed.  The  vagina  is  plugged  with  gauze,  and  the  external  wound  closed  in  the  usual 
way.  The  vagma  acts  as  a  drain,  and  therefore  the  opening  into  it  is  usually  left  unsutured.  In 
some  cases  of  uterine  fibroid  the  abdomen  is  opened  and  the  tumor  is  removed,  but  the  uterus  is 
not  taken  away.  This  operation  is  called  myomectomy.  This  operation  is  suited  only  to  solitary 
subperitoneal  or  interstitial  tumors  (Penrose). 

The  common  operation  for  uterine  fibroids  is  supravaginal  amputation.  The  uterus  is 
cut  away  and  the  cervical  flaps  are  sutured.  Before  the  technique  of  hysterectomy  was  per- 
fected and  before  myomectomy  was  devised  the  favorite  operation  for  uterine  fibroids  was 
salpinrp-oophorectomy,  and  by  it  a  large  majority  of  cases  operated  upon  were  cured.  When  it 
succeeds  a  premature  menopause  is  induced  and  the  tumor  shrinks.  The  operation  is  useless  if 
a  woman  is  past  the  menopause,  and  is  apt  to  fail  if  the  tumor  is  very  soft  or  very  large. 

THE  ADNEXA  OR  APPENDAGES  OF  THE  UTERUS. 

The  appendages  of  the  uterus  are  the  Fallopian  tubes,  the  ovaries  and  ovarian 
ligaments,  and  the  round  ligaments.  They  are  placed  in  the  following  order:  in 
front  is  the  round  ligament;  the  Fallopian  tube  occupies  the  upper  margin  of  the 
broad  ligament;  the  ovary  and  its  ligament  are  behind  and  below  both. 

THE    FALLOPIAN    TUBE    (TUBA    UTERINA    [FALLOPII]) 

(Figs.  1092,  1097,  1098,  1103,  1104). 

The  Fallopian  tubes  or  oviducts  convey  the  ova  from  the  ovaries  to  the  cavity 
of  the  uterus.  They  are  two  in  number,  one  on  each  side,  situated  in  the  upper 
margin  of  the  broad  ligament,  extending  from  each  superior  angle  of  the  uterus  to 
the  sides  of  the  pelvis.  Each  tube  is  about  four  inches  and  a  quarter  in  length, 
and  is  placed  in  a  fold  of  peritoneum,  which  is  part  of  the  broad  ligament  and  is 
called  the  mesosalpinx  (Fig.  1098).  Each  tube  is  described  as  consisting  of  four 
portions:  (1)  the  isthmus  (isthmus  tubae  uterinae)  (Fig.  1103),  or  inner  constricted 
third;  (2)  the  ampulla  (ampulla  tubae  uterinae) (¥\g.  1103),  or  outer  dilated  portion, 
which  curves  over  the  ovary ;  and  (3)  the  infundibulum,  the  funnel-like  expansion  of 
the  tube,  at  the  bottom  of  which  is  the  abdominal  orifice  or  pavilion  (ostium  abdom- 
inale  tubae  uterinae)  (Fig.  1103).  The  abdominal  orifice  has  a  small  diameter  (2 
mm.  when  relaxed  to  its  full  extent).  The  margin  of  the  infundibulum  is  rendered 
irregular  by  the  presence  of  numerous  small  processes,  the  fimbriae  (fimbriae  tubae). 
This  end  of  the  tube  is  called  the  fimbriated  extremity  (Fig.  1103),  because  of  these 
processes.  The  surfaces  of  the  fimbriae  looking  into  the  cavity  of  the  infundi- 
bulum are  covered  with  mucous  membrane  continuous  with  the  tubal  mucous 


1498 


THE  FEMALE    ORGANS    OF    GENERATION 


membrane.  The  outer  surfaces  are  covered  with  peritoneum.  One  of  the  fimbriae 
is  attached  to  the  ovary  and  is  called  the  ovarian  fimbria  {fimbria  ovarica)  (Fig. 
1103).  (4)  The  uterine  portion  of  the  tube  (pars  uterina)  (Fig.  1095)  is  in  the  uterine 
wall.  The  opening  into  the  uterus  {ostium  uterinum  tubae)  is  even  smaller  than 
the  abdominal  opening,  and  will  admit  only  a  small  bristle.  The  general  direc- 
tion of  the  Fallopian  tube  is  outward,  backward,  and  downward.  In  connec- 
tion with  the  fimbriae  of  the  Fallopian  tube  or  with  the  broad  ligament  close  to 
them  there  is  frequently  one  or  more  small  vesicles  floating  on  a  long  stalk  of 
peritoneum.  These  are  termed  the  hydatids  of  Morgagni  (appendices  vesiculosi). 
They  are  representative  of  small  portions  of  the  upper  extremity  of  the  Wolffian 
duct. 

Course  Pursued  by  the  Fallopian  Tube  (Figs.  1088  and  1103). — The  tube  on  each 
side  begins  at  the  upper  and  outer  angle  of  the  uterus  and  passes  outward  in  a 
horizontal  direction  toward  the  uterine  extremity  of  the  ovary.  It  then  bends 
almost  to  a  right  angle  and  ascends  close  to  the  pelvic  wall  and  in  front  of  the 
anterior  margin  to  the  tubal  extremity  of  the  ovary.  At  this  point  it  turns  sharply 


Fimbria  ovutica. 

Fig.  1103. — Uterine  appendages,  seen  from  behind.     (Henle.) 

downward  and  a  little  backward,  and  the  inner  surface  of  the  infundibulum  comes 
to  lie  upon  the  free  margin  and  the  posterior  portion  of  the  inner  surface  of  the 
ovary,  "The  fimbria  ovarica  thus  ascends  in  a  recurrent  direction  to  the  extrem- 
itas  tubaria."^ 

Structure. — ^The  Fallopian  tube  consists  of  three  coats — serous,  muscular,  and 
mucous. 

The  external  or  serous  coat  (tunica  serosa)  (Fig.  1098)  is  peritoneal.  Beneath 
this  lies  the  tunica  adventitia,  composed  of  lax  connective  tissue. 

The  middle  or  muscular  coat  (tunica  muscularis)  consists  of  an  external  longi- 
tudinal layer  (stratum  longitudinale) ,  and  an  internal  circular  layer  (stratum  cir- 
culare)  of  muscular  fibres  continuous  with  those  of  the  uterus. 

The  internal  or  mucous  coat  (tunica  mucosa)  is  continuous  with  the  mucous  lining 
of  the  uterus  and,  at  the  free  extremity  of  the  tube,  with  the  peritoneum.  It  is 
thrown  into  longitudinal  folds  (plicae  tubariae),  which  in  the  outer,  larger  part  of 
the  tube  or  ampulla  (plicae  ampullares)  are  much  more  extensive  than  in  the 
narrow  canal  of  the  isthmus  (plicae  isthmicae).  The  lining  epithelium  is  columnar 
and  ciliated.    This  form  of  ephithelium  is  also  found  on  the  inner  surface  of  the 

1  Spalteholz's  Atlas.     English  edition  by  Barker. 


THE    OVABY 


1499 


fimbriae,  while  on  the  outer  or  serous  surfaces  of  these  processes  the  epithelium 
gradually  merges  into  the  endothelium  of  the  peritoneum. 

Vessels  and  Nerves. — The  chief  artery  of  the  tube  is  the  tubal  branch  of  the 
uterine  artery  (ramus  tuharius)  (Fig.  1100).  It  also  receives  branches  from  the 
ovarian  (Fig.  1100).  Some  of  the  tubal  veins  empty  into  the  uterine  veins,  some 
into  the  ovarian  veins.  The  lymphatics  (Figs.  1101  and  1102)  coming  from  the 
tube  unite  with  the  trunks  coming  from  the  uterus  and  ovary  and  terminate  in 
the  juxta-aortic  glands.  The  nerves  come  from  the  same  plexuses  that  send 
branches  to  the  uterus  and  ovary. 

The  Epo-ophoron,  Parovarium  or  Organ  of  Rosenmiiller  (Figs.  1094, 1095,  and 
1103)  is  placed  in  the  mesosalpinx,  between  the  ovary  and  tube.  It  consists  of  a 
number  of  epithelial-lined  closed  tubes.  This  structure  can  be  readily  seen  if  the 
mesosalpinx  is  stretched  and  held  in  front  of  the  light.  One  of  these  tubes  runs 
parallel  to  the  Fallopian  tube  and  is  called  Gartner's  duct  {ductus  epoophori  longitu- 
dinalis).     A  number  of  tubes  (ductuli  transversi)  ascend  from  near  the  ovary  and 


Fimbrinted  extremity 
of  fiihe 


Fallopian  tube 


Broad  ligament, 
upper  part. 


\ 

Artery 
vein. 


Vagina,  anterior  wall. 


Fig.  1104. — The  uterus  and  its  appendages.  Posterior  view.  The  parts  have  been  somewhat  displaced  from 
their  proper  position  in  the  preparation  of  the  specimen;  thus  the  right  ovary  has  been  raised  above  the  Fallo- 
pian tube,  and  the  fimbriated  extremities  of  the  tubes  have  been  turned  upward  and  outward.  (From  a  prepa- 
ration in  the  Museum  of  the  Royal  College  of  Surgeons  of  England.) 

each  empties  into  Gartner's  duct  at  a  right  angle.  Gartner's  duct  is  a  portion  of 
the  Wolffian  duct,  which  has  persisted  and  is  represented  in  the  male  by  the  canal 
of  the  epididymis.  The  tubules  which  join  the  duct  "are  derived  from  the  meso- 
nephros  and  represent  the  vasa  efferentia  and  coni  vasculosi  of  the  testis,  and 
probably  also  the  ductuli  aberrantes  of  the  canal  of  the  epididymis."' 

The  Paro-ophoron  is  within  the  mesosalpinx,  but  is  nearer  to  the  uterus  than 
is  the  epo-ophoron.  It  consists  of  several  small  tubules,  which  can  be  seen  in  an 
adult  only  by  the  aid  of  a  pocket  lens.  They  are  visible  to  the  naked  eye  in  a  child 
at  birth.  It  represents  the  organ  of  Girald^s  in  the  male  and  is  derived  from  the 
mesonephros. 

THE  OVARY  (Figs.  1088,  1092,  1094,  1095,  1097,  1098,  1099,  1103,  1104). 

The  ovaries  (ovaria) ,  the  testes  muliebres  of  Galen,  are  two  in  number  and  are 
analogous  to  the  testes  in  the  male.     They  are  oval-shaped  bodies  of  an  elongated 


'  Prof.  Cunningham's  Text-book  of  Human  Anatomy. 


1500  THE  FEMALE    ORGANS    OF   GENERATION 

form,  flattened  from  above  downward,  situated  one  on  each  side  of  the  uterus, 
in  the  posterior  layer  of  the  broad  ligament  behind  and  below  the  Fallopian  tube. 
Each  ovary  is  connected  by  its  anterior  straight  margin  to  the  broad  ligament; 
by  its  lower  extremity  to  the  uterus  by  a  proper  ligament,  the  ligament  of  the 
ovaxy  (ligamentum  ovarii  proprium)  (Fig.  1103);  and  by  its  upper  end  to  the 
fimbriated  extremity  of  the  Fallopian  tube  by  the  ovarian  fimbria  (fimbria  ovarica) 
(Fig.  1103),  its  mesial  and  lateral  surfaces  and  posterior  convex  border  are  free 
(Fig.  1104).  The  ovaries  are  of  a  grayish-pink  color,  and  present  either  a  smooth 
or  a  puckered,  uneven  surface.  They  are  each  about  an  inch  and  a  half  in 
length,  three-quarters  of  an  inch  in  width,  and  about  a  third  of  an  inch  thick, 
and  weigh  from  one  to  two  drachms. 

The  exact  position  of  the  ovary  has  been  the  subject  of  considerable  difference 
of  opinion,  and  writers  are  in  conflict  as  to  what  is  to  be  regarded  as  the  normal 
position.  The  fact  appears  to  be  that  the  ovary  is  differently  placed  in  different 
individuals.  The  two  ovaries  are  seldom  placed  in  absolutely  identical  positions. 
Hasse  has  described  the  ovary  as  being  situated  with  its  long  axis  transverse,  or 
almost  transverse,  to  the  pelvic  cavity.  Schultze,  on  the  other  hand,  believes  that 
its  long  axis  is  antero-posterior.  Kolliker  asserts  that  the  truth  lies  between 
these  views,  and  that  the  ovary  is  placed  obliquely  in  the  pelvis,  its  long  axis 
lying  parallel  to  the  external  iliac  vessels,  with  its  surface  directed  inward  and  out- 
ward ,  and  its  convex  free  border  upward.  His  has  made  some  important  observa- 
tions on  this  subject,  and  his  views  are  largely  accepted.  He  teaches  that  the 
uterus  rarely  lies  symmetrically  in  the  middle  of  the  pelvic  cavity,  but  is  generally 
inclined  to  one  or  other  side,  most  frequently  to  the  left,  in  the  proportion  of  three 
to  two.  The  position  of  the  two  ovaries  varies  according  to  the  inclination  of  the 
uterus.  When  the  uterus  is  inclined  to  the  left,  the  ovary  of  this  side  lies  with 
its  long  axis  vertical  and  with  one  side  closely  applied  to  the  outer  wall  of  the 
pelvis,  while  the  ovary  of  the  opposite  side,  being  dragged  upon  by  the  inclina- 
tion of  the  uterus,  lies  obliquely,  its  outer  extremity  being  retained  in  close  appo- 
sition to  the  side  of  the  pelvis  by  the  infundibulo-pelvic  ligament.  When,  on 
the  other  hand,  the  uterus  is  inclined  to  the  right,  the  position  of  the  two 
ovaries  is  exactly  reversed,  the  right  being  vertical  and  the  left  oblique.  In 
whichever  position  the  ovary  is  placed,  the  Fallopian  tube  forms  a  loop  around  it, 
the  uterine  half  ascending  obliquely  over  it,  and  the  outer  half,  including  the 
dilated  extremity,  descending  and  bulging  freely  behind  it.  From  this  extremity 
the  fimbriae  pass  upward  on  to  the  ovary  and  closely  embrace  it. 

Waldeyer^  states,  as  the  result  of  the  examination  of  fifty  female  subjects, 
ranging  from  early  childhood  to  advanced  age,  that  the  ovary  "lies  on  the  lateral 
pelvic  wall  and  vertically  when  the  woman  takes  the  erect  posture."  Its  tubal 
extremity  is  near  the  external  iliac  vein;  its  uterine  end  is  directed  downward, 
while  the  Fallopian  tube  overlies  it  so  as  to  cover  it  on  its  medial  face  entirely  or 
nearly  so.  Its  convex  margin  looks  downward  and  backward  toward  the  pelvic 
cavity  and  rectum,  while  its  straight  margin  or  hilum  lies  laterally  on  the  pelvic 
wall  attached  to  the  mesosalpinx.  He  also  finds  that  it  lies  in  a  distinct  but 
shallow  groove  (fossa  ovarii)  limited  above  by  the  hypogastric  artery  and  below 
by  the  ureter,  in  such  a  manner  that  the  ureter  lies  along  the  convex  margin 
of  the  ovary,  and  the  hypogastric  artery  passes  near  the  hilum  or  straight  margin. 

The  ovary  possesses  two  poles  or  extremities:  (1)  An  outer,  superior  or  tubal 
extremity  (extremitas  tubaria  ovarii).  (2)  An  inner,  inferior  or  uterine  extremity 
(extremitas  uterina  ovarii).  The  ovary  has  two  surfaces,  an  inner  surface  (]acies 
medialis),  which  is  also  upper;  an  outer  surface  (facies  lateralis),  which  is  also 
lower.    The  posterior  or  free  border  (margo  liber)  is  markedly  convex.    The  anterior 

1  Journal  of  Anatomy  and  Physiology,  vol.  xxxii. 


THE   DESCENT   OF    THE    OVAltY  1501 

border  (margo  mesovaricus)  is  almost  straight  and  is  narrow.  The  anterior  border 
is  not  free,  but  is  joined  to  the  posterior  layer  of  the  broad  Ugament  by  a  peritoneal 
fokl  known  as  the  mesovarium.  There  is  a  groove  in  the  anterior  border  called  the 
hilum  (hilus  ovarii),  through  which  vessels  and  nerves  to  pass,  and  emerge  from 
the  ovary. 

Supports  and  Connections  of  the  Ovary. 

From  its  upper  extremity  a  peritoneal  fold  is  continuous  with  the  peritoneum 
over  the  iliac  vessels  and  Psoas  muscle.  It  is  called  the  ovario-pelvic  fold  or  the 
suspensory  ligament  (ligamenium  suspensorium  ovarii)  (Fig.  1088).  It  is  in  reality 
a  portion  of  the  broad  ligament,  and  within  it  are  the  ovarian  vessels  and  nerves. 
The  vessels  (Fig.  1104)  and  nerves  go  to  the  anterior  border  of  the  ovary  and  are 
surrounded  by  a  peritoneal  sheath  derived  from  the  posterior  layer  of  the  broad 
ligament ;  it  is  thus  evident  that  the  anterior  border  of  the  ovary  is  connected  to 
the  posterior  portion  of  the  broad  ligament  by  a  very  short  mesentery,  the  meso- 
varium^ (Fig.  1098).  The  ligament  of  the  ovary  or  ovarian  ligament  (Figs.  1088 
and  1103)  is  a  round,  cord-like  structure,  composed  chiefly  of  non-striated  muscle- 
fibres,  which  passes  between  the  two  folds  of  the  broad  ligament  from  the  lower 
extremity  of  the  ovary  to  the  lateral  angle  of  the  uterus.  The  ovarian  fimbria 
(Fig.  1103),  as  previously  stated,  passes  to  the  upper  extremity  of  the  ovary 
from  the  extremity  of  the    Fallopian  tube. 

The  Descent  of  the  Ovary. 

In  the  female  there  is  a  gubernaculum  which  effects  a  considerable  change  in 
the  position  of  the  ovary,  though  not  so  extensive  a  change  as  is  effected  upon  the 
male  testicle.  The  gubernaculum  in  the  female,  as  it  lies  on  either  side  in  con- 
tact with  the  fundus  of  the  uterus  formed  by  the  union  of  the  Miillerian  ducts, 
contracts  adhesions  to  this  organ  and  thus  the  ovary  is  prevented  from  descending 
below  this  level.  The  remains  of  the  gubernaculum — that  is  to  say,  the  part 
between  the  attachment  of  the  cord  to  the  uterus  to  its  termination  in  the  labium 
majus — ultimately  forms  the  round  ligament  of  the  uterus.  A  pouch  of  peri- 
toneum accompanies  it  along  the  inguinal  canal,  analogous  to  the  funicular  process 
in  the  male;  it  is  called  the  canal  of  Nuck.  In  rare  cases  the  gubernaculum  fails 
to  contract  adhesions  to  the  uterus,  and  then  the  ovary  descends  through  the 
inguinal  canal  into  the  labium  majus,  extending  down  the  canal  of  Nuck. 
Under  these  conditions,  the  position  of  the  ovary  resembles  the  position  of  the 
testicle  in  the  male. 

The  Ovary  at  Different  Ages. — The  ovary  of  childhood  is  smooth  and 
even.  The  rupture  of  Graafian  follicles,  repeated  many  times,  causes  the  surface 
of  the  ovary  to  become  pitted,  puckered,  fibrous,  and  uneven  in  old  age.  The  sur- 
face of  the  ovary  is  grayish-red  in  color.  The  corpus  luteum  of  a  non-pregnant 
woman  slowly  degenerates  and  disappears.  The  corpus  luteum  of  an  impreg- 
nated woman  enlarges  during  pregnancy. 

Structure  (Figs.  1098,  1099, 1105,  and  1106).— The  ovary  consists  of  a  number 
of  Graafian  follicles  or  vesicles  embedded  in  the  meshes  of  a  stroma  or  framework, 
and  invested  by  a  serous  covering  derived  from  the  peritoneum. 

Serous  Covering. — Though  the  investing  membrane  of  the  ovary  is  continuous 
with  the  peritoneum  near  the  hilum  of  the  ovary  (the  point  of  junction  being 
indicated  by  a  narrow  white  line),  it  differs  essentially  from  the  peritoneum, 
inasmuch  as  it  is  an  epithelial  st-^ucture  and  consists  of  a  single  layer  of  columnar 
epithelial  cells,  instead  of  the  flattened  endothelial   cells  of  other  parts  of  the 

1  Prof.  Cunningham's  Text-book  of  Anatomy. 


1502  THE  FEMALE    ORGANS    OF    GENERATION 

membrane;  this  has  been  termed  the  germinal  epithelium  of  Waldeyer,  and  gives 
to  the  surface  of  the  ovary  a  dull-gray  aspect  instead  of  the  shining  smoothness 
of  serous  membranes  generally. 

Stroma.— The  stroma  is  a  peculiar  soft  tissue,  abundantly  supplied  with  blood- 
vessels, consisting  for  the  most  part  of  spindle-shaped  cells,  with  a  small  amount 
of  ordinary  connective  tissue.  These  cells  have  been  regarded  by  some  anatomists 
as  unstriped  muscle-cells,  which,  indeed,  they  most  resemble  (His) ;  by  others  as 
connective-tissue  cells  (Waldeyer,  Henle,  and  Kolliker).  On  the  surface  of  the 
organ  this  tissue  is  much  condensed,  and  forms  a  layer  composed  of  short  connec- 
tive-tissue fibres,  with  fusiform  cells  between  them.  This  was  formerly  regarded 
as  a  distinct  fibrous  covering,  and  was  termed  the  tunica  albuginea,  but  is  nothing 
more  than  a  condensed  layer  of  the  stroma  of  the  ovary. 

Graafian  Follicles  or  Vesicles  (folliculi  oophori  vesiculori  [Graafi])  (Figs.  1105  and 
1106). — Upon  making  a  section  of  an  ovary  numerous  round  transparent  vesicles 
of  various  sizes  are  to  be  seen ;  they  are  the  Graafian  vesicles  or  ovisacs  containing 
the  ova.  Immediately  beneath  the  superficial  covering  is  a  layer  of  stroma,  in 
which  are  a  large  number  of  minute  vesicles  of  uniform  size,  about  y^^  of  an 
inch  in  diameter.  These  are  the  Graafian  vesicles  in  their  earliest  condition,  and 
the  layer  where  they  are  found  has  been  termed  the  cortical  layer.  They  are 
especially  numerous  in  the  ovary  of  the  young  child.  After  puberty  and  during  the 
whole  of  the  child-bearing  period  large  and  mature,  or  almost  mature.  Graafian 

vesicles  are  also  found  in  the  cortical 
layer  in  small  numbers,  and  also 
corpora  lutea,  the  remains  of  vesicles 
which  have  burst  and  are  undergoing 
atrophy  and  absorption.  Beneath 
this  superficial  stratum  other  large 
and    mature    Graafian   vesicles    are 


Granular  zone. 


Ovum. 


Peritoneum. 


Fig.  1105. — Section  of  the  ovary.  1,  outer  covering; 
1',  attached  border;  2,  central  stroma;  3,  peripheral 
stroma;  4,  blood-vessels;  5,  Graafian  follicles  in  their 
earliest  stage;  6,  7,  8,  more  advanced  follicles;  9,  an  almost 
mature  follicle;  9',  follicle  from  which  the  ovum  has 
escaped;  10,  corpus  luteum.     (After  Schron.) 


/    \  J    I      j       Coats  of  the 
Stroma  of  the  ovary  '      (  Graafian  vesicle 
w  ith  blood  vessels.    Membrav  a 
(iranulma. 

Fig.  1106. — Section  of  the  Graafian  vesicle. 
(After  von  Baer.) 


found  embedded  in  the  ovarian  stroma.  These  increase  in  size  as  they  recede 
from  the  surface  toward  a  highly  vascular  stroma  in  the  centre  of  the  organ, 
termed  the  medullary  substance  {zona  vasculosa  [Waldeyeri]).  This  stroma  forms 
the  tissue  of  the  hilum  by  which  the  ovary  is  attached,  and  through  which  the 
blood-vessels  enter;  it  does  not  contain  any  Graafian  vesicles. 

The  larger  Graafian  follicles  consist  of  an  external  fibro- vascular  coat  connected 
with  the  surrounding  stroma  of  the  ovary  by  a  network  of  blood-vessels;  and  an 
internal  coat,  named  the  ovicapsule,  which  is  lined  by  a  layer  of  nucleated  cells, 
called  the  membrana  granulosa.  The  fluid  contained  in  the  interior  of  the  vesicles 
is  transparent  and  albuminous,  and  in  it  is  suspended  the  ovum.  In  that  part  of 
the  mature  Graafian  vesicle  which  is  nearest  the  surface  of  the  ovary  the  cells 
of  the  membrana  granulosa  are  collected  into  a  mass  which  projects  into  the 
cavity  of  the  vesicle.  This  is  termed  the  discus  proligerus,  and  in  this  the  ovum 
is  embedded. 

The  ova  are  formed  from  the  germinal  epithelium  on  the  surface  of  the  ovary. 


THE   DESCENT   OF    THE    OVARY  1503 

This  becomes  thickened,  and  in  it  are  seen  some  cells  which  are  larger  and  more 
rounded  than  the  rest;  these  are  termed  the  primordial  ova.  The  germinal  epi- 
thelium grows  downward  in  the  form  of  tubes  or  columns,  termed  the  %gg  tubes 
of  Pfliiger,  into  the  ovarian  stroma,  which  grows  outward  between  the  tubes,  and 
ultimately  cuts  them  off  from  the  germinal  epithelium.  These  tubes  are  further 
subdivided  into  rounded  nests  or  groups,  each  containing  a  primordial  ovum  which 
undergoes  further  development  and  growth,  while  the  surrounding  cells  of  the  nest 
form  the  epithelium  of  the  Graafian  follicle. 

The  development  and  maturation  of  the  Graafian  vesicles  and  ova  continue 
uninterruptedly  from  puberty  to  the  end  of  the  fruitful  period  of  woman's  life, 
while  their  formation  commences  before  birth.  Before  puberty  the  ovaries  are 
small,  the  Graafian  vesicles  contained  in  them  are  disposed  in  a  comparatively 
thick  layer  in  the  cortical  substance;  here  they  present  the  appearance  of  a  large 
number  of  minute  closed  vesicles,  constituting  the  early  condition  of  the  Graafian 
vesicle;  many,  however,  never  attain  full  development,  but  shrink  and  disappear. 
At  puberty  the  ovaries  enlarge  and  become  more  vascular,  the  Graafian  vesicles 
are  developed  in  greater  abundance,  and  their  ova  are  capable  of  fecundation. 

Discharge  of  the  Ovum. — The  Graafian  vesicles,  after  gradually  approaching 
the  surface  of  the  ovary,  burst;  the  ovum  and  fluid  contents  of  the  vesicles  are 
liberated,  and  escape  on  the  exterior  of  the  ovary,  passing  thence  into  the  Fallopian 
tube.  This  is  effected  either  by  application  of  the  tube  to  the  ovary,  or  by  a 
curling  upward  of  the  fimbriated  extremity,  so  that  the  ovum  is  caught  as  it  falls. 

In  the  foetus  the  ovaries  are  situated,  like  the  testes,  in  the  lumbar  region,  near 
the  kidneys.  They  may  be  distinguished  from  those  bodies  at  an  early  period  by 
their  elongated  and  flattened  form,  and  by  their  position,  which  is  at  first  oblique 
and  then  nearly  transverse.    They  gradually  descend  into  the  pelvis. 

The  Round  Ligament  (p.  1491). 

Vessels  and  Nerves. — The  arteries  of  the  ovaries  (Figs.  1100  and  1104)  are  the 
ovarian  from  the  aorta,  corresponding  to  the  spermatic  arteries  in  the  male.  The 
ovarian  artery  on  each  side  enters  the  pelvis  in  the  fold  of  broad  ligament  known 
as  the  suspensory  ligament  of  the  ovary  and  enters  the  attached  border,  or  hilum, 
of  the  ovary.  The  ovarian  vessels  anastomose  about  the  hilum  with  branches  of 
the  uterine  artery.  The  veins  follow  the  course  of  the  arteries;  they  form  a  plexus 
near  the  ovarj,  the  pampiniform  plexus,  corresponding  to  a  like  structure  near  the 
male  testicle.  The  lymphatics  (Figs.  1101  and  1102)  terminate  in  the  glands  to 
the  corresponding  side  of  the  aorta,  and  they  anastomose  in  their  course  with 
trunks  from  the  uterine  fundus  and  Fallopian  tube.  The  nerves  come  from  the 
ovarian  plexus,  which  is  a  continuation  of  the  renal  plexus  along  the  ovarian  artery, 
and  from  the  aortic  plexus. 

Surgical  Anatomy  of  the  Appendages.— Ea-fra-uferme  pregnancy  most  commonly  occurs 
in  the  ampulla  of  the  tube.  The  product  of  the  conception  may  escape  through  the  ostium 
abdominale  or  the  walls  of  the  tube  may  rupture,  a  violent  hemorrhage  resulting. 

Pelvic  peritonitis  is  a  not  uncommon  'sequence  of  tubal  disease.  Salpingitis  is  inflarnmation 
of  the  mucous  coat  of  the  tube— interstitial  salpingitis  of  the  middle  coat,  perisalpingitis  of  the 
peritoneal  coat. 

If  inflammation  closes  the  uterine  and  the  abdominal  ends  of  the  tube,  mucus  gathers  and  dis- 
tends the  tube  {hydrosalpinx).    If  purulent  matter  gathers,  the  condition  is  known  as  pyosalpinx. 

An  ovary  may  fail  to  descend  and  remain  well  above  the  pelvic  brim ;  it  may  prolapse  mto 
Douglas's  pouch;  it  may  enter  the  sac  of  a  hernia;  it  may  inflame;  a  turnor  or  cyst  may  arise  from 
it.  A  solid  tumor  of  the  ovarv  may  be  a  fibroma,  a  sarcoma,  or  a  carcinoma.  "  Cysts  may  orig- 
inate in  anv  part  of  the  tubo-ovarian  structure;  as  the  cortical,  medullary,  or  parenchymatous 
portions  of' the  ovary;  in  the  structure  between  the  tube  and  ovary  known  as  the  Rosenmuller 
organ  or  parovarian'structures;  and  in  the  hydatid  of  Morgagni."i  Cysts  may  be  simple,  pro- 
liferating, or  dermoid;  unilocular  or  multildcular.     Glandular  proliferous  cysts,  papillary  pro- 

1  Text-book  of  Gynecology.    By  E.  E.  Montgomery. 


1504  THE  FE3IALE    ORGANS   OF    GENERATION 

Hferous  cysts,  dermoid  cysts,  and  parovarian  cysts  may  attain  a  large  or  even  an  enormous  size. 
The  operation  for  the  removal  of  an  ovarian  cyst  is  one  of  the  most  successful  of  the  major 
procedures  of  surgery. 

THE  MAMMARY  GLAND  (MAMMA)  (Figs.  1107,  1108,  1109,  1110). 

The  breasts,  mammaxy  glands  or  mammae  secrete  the  milk,  and  are  accessory 
glands  of  the  generative  system.  They  develop  fully  in  the  female,  but  remain 
permanently  rudimentary  in  the  male.  There  are  two  of  these  glands,  and 
they  are  situated  in  the  superficial  fascia  of  the  anterior  portion  of  the  thorax. 
Between  the  two  glands  and  in  front  of  the  sternum  is  a  groove,  the  bosom. 

Description  of  a  Well-developed  Breast. — Each  gland  appears  as  a  hemispher- 
ical body  projecting  from  the  front  of  the  thorax  beneath  the  skin  and  lying  over 
a  portion  of  the  Pectoralis  major  muscle  and  a  smaller  portion  of  the  Serratus 
magnus  muscle.  The  hemispherical  projection  extends  usually  from  the  margin 
of  the  sternum  to  the  axilla  and  from  the  level  of  the  second  rib  to  the  level  of 
the  sixth  rib,  or  from  the  third  rib  to  the  seventh  rib,  but  this  does  not  represent 
the  real  size  of  the  gland.  The  gland  is  much  larger  than  this,  being  rendered 
so  by  tails  or  prolongations  of  breast  tissue,  which  will  be  described  later  (p.  1505). 

The  Nipple  (papilla  mammae)  (Figs.  1107,  1108, 1109,  an;l  1110).— The  nipple 
projects  from  a  little  below  and  to  the  median  side  of  the  summit  of  the  hemi- 
sphere at  or  above  the  level  of  the  fifth  rib,  and  is  covered  with  thin  skin.  The 
right  nipple  may  not  exactly  correspond  in  situation  and  direction  to  the  left 
nipple.  The  nipple  varies  considerably  in  height  and  shape.  In  the  virgin  it  is 
usually  cylindrical  and  is  directed  forward  and  slightly  upward  and  outward. 
The  apex  of  the  nipple  is  rendered  rough  by  fissures  (Fig.  1107),  it  exhibits  a 
depression  in  which  are  the  openings  of  the  milk  ducts  (Fig.  1109),  and  its  cir- 
cumference is  thrown  into  concentric  ridges  (Fig.  1109).  The  nipple  is  surrounded 
by  a  darker  circular  wrinkled  area,  the  areola  (areola  mammae)  (Figs.  1107  and 
1108),  in  which  are  sweat-glands  and  on  which  are  twelve  or  fifteen  small 
rounded  elevations.  These  elevations  are  caused  by  cutaneous  sebaceous  glands 
which  in  structure  represent  a  transition  betvveen  sebaceous  and  mammary  glands. 
They  are  probai)ly  rudimentary  portions  of  the  mammary  gland  and  are  known 
as  the  glands  of  Montgomery  (glandulae  areolares)  (Fig.  1109).  The  color  of  the 
nipple  and  areola  varies  with  the  complexion  of  the  individual.  In  brunettes  it  is 
darker  than  in  blondes.  The  usual  color  of  the  nipple  in  a  young  woman  is  rosy- 
pink,  the  areola  being  of  a  darker  shade.  During  the  early  months  of  pregnancy 
the  nipple  and  areola  become  dark  brown  in  color,  the  areola  becomes  larger  in 
circumference  and  the  glands  of  Montgomery  increase  in  size  (Fig.  1110).  The 
nipple  contains  non-striated  muscle  and  mechanical  irritation  or  sexual  excitement 
makes  it  stiff  and  erect.  The  skin  covering  the  breast  is  clear,  soft,  and  delicate, 
and  subcutaneous  veins  are  often  visible.  The  skin  of  the  nipple  and  areola  is 
particularly  delicate. 

Variations  in  the  Mammae. — Before  puberty  the  glands  are  small,  of  the  infantile 
type,  grow  slowly,  and  differ  but  slightly  from  the  male  organs.  The  nipple  is 
small  and  flat  and  pale.  At  puberty  the  increase  in  the  size  of  the  breast  is  rapid 
and  considerable,  due  to  growth  of  gland  tissue  and  of  subcutaneous  fat.  During 
pregnancy  the  breasts  enlarge  greatly  and  remain  very  large  throughout  lactation. 
This  enlargement  is  due  to  new  gland  tissue  and  increased  vascularity.  Numerous 
blue  veins  are  visible  in  the  skin,  the  areola  darkens,  and  the  glands  of  Mont- 
gomery enlarge  (Fig.  1110).  During  lactation  the  associated  lymphatic  glands  may 
enlarge  (A.  Marmaduke  Sheild).  After  the  termination  of  lactation  the  breasts 
diminish  in  size.  They  do  not  become  as  small  as  the  virgin  breast,  are  apt  to  lose 
their  hemispherical  outlines,  and  cease  to  be  soft.    They  droop  as  flaccid  pendulous 


THE   3fA3IMABY    GLAND 


1505 


masses,  the  subcutaneous  fat  is  largely  gone,  and  the  outlines  of  the  lobular  breast 
tissue  can  be  seen  and  felt.  The  nipple  is  long  and  hangs  down  like  a  teat.  At 
the  menopause  the  breast  usually  shrinks.  In  some  cases,  however,  it  actually 
increases  in  size.  In  such  a  case,  although  the  gland  atrophies,  there  is  an  exten- 
sive deposit  of  fat.  In  old  age  the  glands  undergo  atrophy  and  largely  disappear, 
the  skin  is  flabby  and  thrown  into  wrinkles,  and  the  breasts  contain  very  little 
glandular  structure,  and  are  hard  from  the  presence  of  fibrous  tissue.  The  nipples 
become  pigmented  and  corrugated.  Women  vary  greatly  in  the  development  of 
the  breasts.  In  some  women  they  are  large,  firm,  and  well  proportioned;  in  others 
they  are  small,  flat,  or  atrophy  occurs  in  the  course  of  certain  bodily  diseases,  as 
phthisis,  and  certain  mental  diseases,  as  melancholia.  If  the  ovaries  are  ill- 
developed  the  breasts  remain  flat  and  small.  In  newly  married  women,  even 
though  pregnancy  does  not  exist,  the  breasts  often  develop  decidedly  and  rapidly. 
The  outline  and  direction  of  the  breast  and  also  of  the  nipple  may  be  altered  by 
corsets.    The  left  mamma  is  usually  somewhat  larger  than  the  right. 


Nipple. 


■Areola. 


Lactiferous 
duct. 


Lobule  unravelled 


Ampulla. 


/ 
Lobule 


Locidi  in  connective  tissue. 
Fig.  1107. — Dissection  of  the  lower  half  of  the  female  breast  during  the  period  of  lactation.     (From  Luschka.) 

One  gland  or  both  glands  may  be  entirely  absent,  the  nipple  being  also  absent. 
One  or  both  glands  may  be  absent,  one  or  both  nipples  being  present.  When  there 
is  only  one  nipple,  it  is  apt  to  be  the  left.  The  term  polymazia  (mammae  acces- 
soriae  muliehris)  means  the  presence  of  supernumerary  breasts,  with  or  without 
nipples.  Polythelia  means  the  presence  of  supernumerary  nipples,  the  associated 
glandular  structure  being  rudimentary.  There  may  be  one,  two,  or  several  super- 
numerary breasts,  and  when  more  than  one  exists,  are  usually  asymmetrical.  If 
one  is  functionally  active,  it  enlarges  during  pregnancy  and  furnishes  milk. 

Supernumerary  mammae  may  secrete  milk  or  may  be  without  function.  The 
most  common  situation  is  on  the  part  of  the  chest  below  and  to  the  inner  side  of 
the  normally  placed  gland.  They  may  also  exist  in  the  axilla,  the  abdomen,  the 
groin,  the  back,  and  the  thigh.  Many  cases  of  supposed  supernumerary  glands 
have  been  really  instances  in  which  moles,  warts,  or  sebaceous  cysts  have  been 
mistaken  for  breast  tissue,  but  some  cases  are  undoubted. 

95 


1506  THE  FEMALE   ORGANS    OF   GENERATION 

Prolongations  of  Mammary  Tissue. — As  previously  stated,  the  outlines  of 
the  breast  are  not  regular,  but  here  and  there  tails,  prolongations,  or  cusps  come  off 


CLAVICLC- 


PCCTORAUIS    MAJOR 


FIBROUS   SEPTUM 
GLAND    SUBSTANCE 

ADIPOSE    TISSUE 


THIRD    RIB 


AREOLAR    TISSUE 


FIRST 
RIB 


SECOND 

RIB 
ECTORALIS 
MINOR 
INTERCOSTALES 
SHEATH    OF    PEC- 
TORALIS    MAJOR 


UPERFICIAL 
FASCIA 


LUNG 

ADIPOSE    TISSUE 
HORIZONTAL    PLANE 
OF    NIPPLE 


FIFTH    RIB 


SIXTH    RIB 


Fig.  1108. — Right  breast  in  sagittal  section,  inner  surface  of  outer  segment.     (Testut.) 

from  and  are  true  portions  of  the  gland.    Two  or  even  more  prolongations  pass  to 
the  edge  of  the  sternum;  others  pass  toward  the  axilla,  the  clavicle,  and  the  origin 


SECONDARY    ARLOLA 


CONCENTRIC    , 
RIDGES  I 


Fig    1109. — Nipple  and  areola  of  a  virgin.     (Testut.) 


Fig.  1110. — Nipple  and  areolae  of  a  preg- 
nant woman.     (Testut.) 


of  the  external  oblique  muscle  from  the  ribs.     Underneath  the  mammary  gland 
prolongations  of  mammary  tissue  penetrate  the  pectoral  fascia   (Heidenhain). 


THE  MAM3IABY   GLAND 


1507 


If  one  of  the  glandular  cusps  is  of  considerable  size  it  is  called  an  outlying 
lobule. 

Structure  of  Mammary  Gland  and  Nipple  (Figs.  11 07  and  1 108)  .—The  glands  of 
the  breast  ( cor  p?^«  mammae)  rest  by  a  smooth  posterior  surface  upon  the  loose  pectoral 
fascia,  which  fastens  the  breast  to  the  muscle  beneath,  but  so  loosely  that  the  breast 
is  movable.  The  mamma  consists  of  gland-tissue;  of  fibrous  tissue,  connecting  its 
lobes,  of  fatty  tissue  in  the  intervals  between  the  lobes,  of  retinacula,  and  of  skin. 
The  gland-tissue,  when  freed  from  fibrous  tissue  and  fat,  is  of  a  pale  reddish  color, 
firm  in  texture,  in  general  circular  in  form,  with  prolongations  here  and  there,  flat- 
tened from  before  backward,  thicker  in  the  centre  than  at  the  circumference,  and 
presenting  several  inequalities  on  its  surface,  especially  in  front.  On  the  anterior 
surface  there  are  many  irregular  elevated  processes  with  deep  spaces  between 
them.  From  the  summits  of  the  elevations  connective-tissue  strands  (retinacula 
evils)  pass  to  the  true  skin.  The  glandular  structure  consists  of  numerous  lobes 
(lohi  mammae),  and  these  are  composed  of  lobules  (lobuli  mammae),  connected 
together  by  areolar  tissue,  blood-vessels,  and  ducts.  The  smallest  lobules  con- 
sist of  a  cluster  of  rounded  alveoli  (Fig.  1107),  which  open  into  the  smallest 
branches  of  the  excretory  ducts;  these  ducts,  uniting,  form  larger  ducts,  which 
terminate  in  single  canals.  Each  canal  is  called  a  lactiferous,  galactophorus  or 
mammillary  duct  (ductus  lactiferu^)  (Fig.  1107).  Each  lobe  possesses  one  lac- 
tiferous duct.  This  passes  to  the  apex  of  the  lobe  and  then  into  the  nipple. 
The  lactiferous  ducts  are  white  and  cord-like,  and  contrast  with  the  yellowish- 
red  tissue  of  the  gland  itself.  The  number  of  excretory  ducts  varies  from  fifteen 
to  twenty.  They  converge  toward  the  areola,  beneath  which  each  duct  forms 
a  spindle-shaped  dilatation,  the  ampulla  (sinus  lactiferans)  (Fig.  1107).  The 
ampullae  serve  as  reservoirs  for  the  milk.  At  the  base  of  the  nipple  the  ducts 
become  contracted  and  pursue  a  straight  course  to  its  summit,  perforating  it  by 
separate  orifices  considerably  narrower  than  the  ducts  themselves.  Each  orifice 
(porus  lactiferu^)  is  the  orifice  of  a  tube  which  drains  an  individual  lobe.  The 
ducts  are  composed  of  areolar  tissue,  with  longitudinal  and  transverse  elastic 
fibres;  muscular  fibres  are  entirely  absent;  their  mucous  lining  is  continuous,  at 
the  point  of  the  nipple,  with  the  integument.  The  epithelium  of  the  mammary 
gland  differs  according  to  the  state  of  activity  of  the  organ.  In  the  gland  of  a  woman 
who  is  not  pregnant  or  nursing  the  alveoli  are  very  small  and  solid,  being  filled 
with  a  mass  of  granular  polyhedral  cells.  During  pregnancy  the  alveoli  enlarge 
and  the  cells  undergo  rapid  multiplication.  At  the  commencement  of  lactation 
the  cells  in  the  centre  of  an  alveolus  undergo  fatty  degeneration,  and  are  elim- 
inated in  the  first  milk  as  colostrum-corpuscles.  The  peripheral  cells  of  the  alveolus 
remain,  and  form  a  single  layer  of  granular,  short  columnar  cells  lining  the  limit- 
ing membrana  propria.  The  single  nucleus  of  each  cell  divides  and  forms  two. 
In  the  protoplasm,  especially  in  the  end  of  the  cells  toward  the  alveolus, 
drops  of  fat  appear,  and  the  nucleus  toward  this  end  of  the  cell  also  becomes 
fatty. 

The  end  of  the  cell  toward  the  alveolus  breaks  down,  and  the  liberated  mate- 
rial constitutes  "  the  albuminous  ingredients  of  the  milk,  while  the  drops  of  fat 
become  the  milk-globules.  The  portion  of  the  cell  which  remains  forms  new 
cytoplasm,  and  the  same  process  is  repeated  over  and  over  again.  The  cells 
also  secrete  water  and  the  salts  which  are  found  in  the  milk."^ 

The  fibrous  tissue  (Fig.  1108)  invests  the  entire  surface  of  the  breast,  and  sends 
down  septa  between  its  lobes,  connecting  them  together. 

The  fatty  tissue  (Figs.  1107  and  1108)  surrounds  the  surface  of  the  gland  and 
occupies  the  interval  between  its  lobes.     It  usually  exists  in  considerable  abun- 

1  Human  Physiology.     By  Joseph  Howard  Raymond. 


1508 


THE   FEMALE    ORGANS    OF  GENERATION 


dance,  and  determines  the  form  and  size  of  the  gland.    There  is  no  fat  immediately 
beneath  the  areola  and  nipple. 


Fig.  1111. — The  lymphatic  vessels  of  the  anterior  surface  of  the  bieast;  the  subareolar  plexus  and  the 
trunks  which  run  from  it.     (tjappey.) 


DELTA- PECTORAL     HUMERAL  CHAIN 


—  MAMMARY  LYMPHATIC 
ENDING  IN  SUB- 
CLAVIAN GLANDS 


THORACIC 
CHAIN 

MAMMARY  COL- 
LECTING TRUNKS 


SUBAREOLAR 

PLEXUS 


CUTANEOUS  COLLECTING 

TRUNK  FROM  THE 

THORACIC  WALL 


CUTANEOUS  COL-  ^^  "VV- COLLECTING  TRUNKS 

LECTING  TRUNKS  \  V  PASSING  TO  INTERNAL 

MAMMARY  GLANDS 

Fig.  1112. — Lymphatics  of  the  breast  and  axillary  glands.     (Poirier  and  Charpy.) 

Vessels  and  Nerves. — The  arteries  supplying  the  mammary  gland  are  derived 
from  the  perforating  branches  of  the  internal  mammary,  long  thoracic  branches  of  the 


THE   MAM3IARY    GLAND  1509 

axillary,  and  branches  from  the  intercostals.  The  veins  describe  an  anastomotic 
circle  around  the  base  of  the  nipple,  called  by  Haller  the  circulus  venosus.  From 
this  large  branches  transmit  the  blood  to  the  circumference  of  the  gland  and  end 
in  the  axillary  and  internal  mammary  veins.  The  lymphatics  of  the  mammary 
gland  (Figs.  1111  and  1112)  and  mammary  region  have  been  previously  described 
(pp.  812,813,  and  814).  The  nerves  are  derived  from  the  fourth,  fifth,  and  sixth 
intercostal  nerves,  and  sympathetic  filaments  from  the  dorsal  cord  pass  to  the  breast 
along  the  branches  of  the  intercostal  nerves. 

Surgical  Anatomy. — Occasionally  the  mammary  gland  undergoes  enormous  hypertrophy. 
This  may  occur  at  any  age,  even  in  the  virgin.  The  physiological  enlargement  of  puberty  may 
become  excessive  or  the  physiological  enlargement  of  pregnancy  and  lactation  may  continue 
and  increase  after  the  termination  of  lactation.  The  chief  elements  in  the  enlargement  are  fat 
and  connective  tissue,  and  it  is  doubtful  if  there  is  extensive  reproduction  of  glandular  tissue. 

Abscess  of  the  breast  may  occur  at  any  age,  but  is  most  common  by  far  in  nursing  women. 
The  portals  are  opened  to  infection  by  a  crack  in  the  nipple  and  bacteria  are  carried  inward 
by  the  lymph- vessels.  In  some  cases  the  pus  gathers  beneath  the  skin  (supra-mammary  abscess), 
in  others  in  the  breast  tissue  (intra-mammary  abscess).  In  rare  cases  pus  gathers  beneath  the 
breast  (^retro-mammary  abscess).  In  intra-mammary  abscess  the  pus  burrows  through  the 
fibrous  septa  or  fascia  and  forms  numerous  channels,  and  such  a  channel  is  constricted  at  the 
point  where  it  passes  through  fascia  or  a  fibrous  septum,  as  an  hour-glas,''  is  constricted. 

In  every  patient  suffering  from  abscess  the  nipple  should  be  examined  for  a  sore  or  crack,  and 
the  area  when  found  should  be  treated  antiseptically.  A  supra-mammary  abscess  should  be 
opened  by  an  incision  radiating  from  the  nipple. 

In  intra-mammary  abscess  follow  the  advice  of  Sheild:  open  the  abscess  by  an  incision  radiating 
from  the  nipple,  insert  the  index  finger,  and  when  possible  pass  it  to  the  bottom  of  the  abscess 
and  carry  the  tip  from  the  depths  of  the  abscess  to  as  near  the  surface  as  possible.  At  this  point 
make  a  counter  opening.  The  finger  breaks  down  septa  which  cause  constriction  and  thus  con- 
verts the  tracking  sinuses  into  one  large  cavity.'     Drain  by  tubes. 

A  retro-mammary  abscess  is  opened  by  an  incision,  following  the  outline  of  the  breast  at  the 
thoraco-mammary  junction,  the  finger  being  pushed  through  the  incision  and  up  under  the  gland. 

Tuberculosis  of  the  breast  may  occur,  and  if  it  does,  cold  abscess  is  apt  to  form.  The  best 
treatment  is  removal  of  the  gland  and  the  associated  lymph  glands. 

Chronic  mastitis  is  a  condition  of  mammary  fibrosis,  most  common  in  neurotic  single  women, 
and  apt  to  be  associated  with  ovarian  or  uterine  disease. 

Malignant  dermatitis  or  Paget's  disease  of  the  nipple  is  a  chronic  condition  consisting  of 
epithelial  proliferation,  induration,  desquamation,  and  ulceration,  and  it  is  apt  to  be  followed 
by  epithelioma. 

Chancre  of  the  nipple  is  occasionally  met  with. 

Secondary  and  tertiary  syphilitic  lesions  are  seen  upon  the  skin  of  the  breast,  the  nipple,  and 
the  areola. 

Cysts  and  tumors  are  common  in  the  breast. 

There  may  be  cystic  degeneration  of  the  gland  in  women  near  the  menopause  (involution 
cysts);  a  lacteal  cyst;  a  hydatid  cyst;  an  adenoma  may  become  cystic. 

The  nipple  may  suffer  from  epithelioma,  myoma,  myxoma,  angioma,  papilloma,  or  fibroma. 

The  innocent  tumors  of  the  breast  are  fibro-adenoma,  cystic  adenoma,  myxoma,  and  angioma. 

The  skin  of  the  breast  may  suffer  from  any  form  of  growth  or  cyst  which  could  arise  from 
the  skin  of  another  part.  Malignant  tumors  of  the  glandular  structure  are  ten  times  as  frequent 
as  innocent  tumors.    Sarcoma  is  rare;  carcinoma  is  very  common. 

Carcinoma  of  the  breaM  has  occupied  much  of  the  attention  of  surgeons  during  recent  years. 
The  old  operation  was  uniformly  followed  by  recurrence.  The  modern  radical  operation  has 
been  evolved  from  the  studies  of  Moore,  the  younger  Gross,  Heidenhain,  Stiles,  Banks,  Halsted, 
and  others.  The  modern  operation  always  removes  at  least  the  skin  and  subcutaneous  tissue 
over  the  hemispherical  portion  of  the  breast,  the  outlying  lobules  of  the  breast,  the  pectoral  fascia, 
and  the  sternal  portion  of  the  great  Pectoral  muscle,  the  lymphatic  tracts  from  the  breast,  the 
lymphatic  glands  and  cellular  tissue  from  the  axilla,  and  from  beneath  the  latissimus  dorsi  muscle. 
The  pectoral  fascia  and  the  sternal  portion  of  the  great  Pectoral  muscle  must  come  away  in  eveiy 
case,  because  breast  tissue  may  pass  through  the  fascia.  The  entire  breast  must  be  removed, 
because  even  in  a  recent  case  the  entire  breast  is  regarded  as  infected.  The  clavicular  portion 
of  the  great  Pectoral  muscle  is  anatomically  distinct  from  the  sternal  portion  arid  its  removal  is 
not  imperative.  Some  operators  remove  the  lesser  Pectoral  muscle.  To  leave  it  is  of  no  value  to 
the  arm,  and  it  frequently  causes  an  annoying  rigid  band  anterior  to  the  axilla.    To  take  it  away 

1  Diseases  of  the  Breast.     By  A.  Marmaduke  Sheild. 


1510  THE    FEMALE    ORGANS    OF   GENERATION 

gives  ready  access  to  the  axillary  vessels  at  a  desirable  point  above.  The  sheath  of  the  axillary 
vein  should  be  removed  with  the  glands  and  cellular  tissue  of  the  axilla.  The  glands  receiving 
lymph  from  the  cancerous  area  must  be  removed,  of  course.  In  view  of  the  fact  that  in  an 
undetermined  percentage  of  cases  a  lymph  tract  passes  direct  to  the  subclavian  glands,  it  is 
evident  that  these  glands  may  become  infected  by  this  route  instead  of,  as  is  more  usual,  secondarily 
to  axillary  infection;  hence  it  seems  wiser  in  every  case  to  remove  the  cellular  tissue  and  glands 
from  the  subclavian  triangle.  All  of  these  structures  should  be  removed  as  one  piece,  in  order 
to  avoid  cutting  across  lymph  tracts  and  flooding  the  wound  with  carcinoma  cells  which  might 
adhere,  grow,  and  reproduce  cancer. 

Halsted's  operation  is  the  method  adopted  by  most  surgeons.  The  wound  cannot  be  com- 
pletely closed,  and  the  raw  spot  is  covered  at  once  or  later  with  Thiersch  skin  grafts.  (For  sur- 
gical considerations  regarding  the  lymphatics  in  mammary  carcinoma  see  page  814.) 

The  Male  Breast  {mamma  virilis). — The  male  breast  is  a  small  flat  struc- 
ture, consisting  chiefly  of  connective  tissue,  but  containing  some  branched  tubules. 
Un  'er  normal  circumstances  it  remains  permanently  of  the  infantile  type.  It 
possesses  a  nipple  which  is  much  smaller  than  that  of  the  female  breast,  and 
which  usually  lies  over  the  fourth  intercostal  space,  but  may  lie  over  the  fourth  or 
fifth  rib.  The  nipples  of  the  two  sides  are  rarely  placed  quite  symmetrically. 
Accessory  glands  and  accessory  nipples  are  as  common  among  males  as  females. 
The  male  breast  may  exhibit  some  evidence  of  temporary  functional  activity  at  birth 
and  at  puberty.     Cases  have  been  recorded  of  actual  lactation  by  the  male  breast. 

Surgical  Anatomy. — The  male  breasts  may  undergo  enormous  hypertrophy  (gynaecomazia). 
In  these  cases  the  penis  is  often  small  and  the  testicles  may  be  atrophied.  The  breasts  may 
be  absent  in  the  male.  Disease  of  the  male  breast  is  not  nearly  so  frequent  as  disease  of  the 
female  breast.  The  organ  may  be  the  seat  of  syphilis,  tuberculosis,  acute  or  chronic  mastitis, 
abscess  or  tumor.    A  number  of  cases  of  cancer  of  the  male  breast  have  been  recorded. 


THE  SUEGICAL  ANATOMY  OF  INGUINAL 
HEKNIA  AND  FEMORAL  HEENIA. 


Dissection  (Fig.  288). — For  dissection  of  the  parts  concerned  in  inguinal  hernia  a  male 
subject,  free  from  fat,  should  always  be  selected.  The  liody  should  be  placed  in  the  supine 
position,  the  abdomen  and  pelvis  raised  by  means  of  blocks  placed  beneath  them,  and  the  lower 
extremities  rotated  outward,  so  as  to  make  the  parts  as  tense  as  possible.  If  the  abdominal  walls 
are  flaccid,  the  cavity  of  the  abdomen  should  be  inflated  through  an  aperture  made  at  the  umbil- 
icus. An  incision  should  be  made  along  the  middle  line  from  a  little  below  the  umbilicus  to 
the  symphysis  pubis,  and  continued  along  the  front  of  the  scrotum,  and  a  second  incision  from 
the  anterior  superior  spine  of  the  ilium  to  just  below  the  umbilicus.  These  incisions  should 
divide  the  integument,  and  the  triangular-shaped  flap  included  between  them  should  be  reflected 
downward  and  outward,  when  the  superficial  fascia  will  be  exposed. 

The  Superficial  Fascia  of  the  Abdomen  (p.  433). — This,  over  the  greater  part  of 
the  abdominal  wall,  consists  of  a  single  layer  of  fascia,  which  contains  a  variable 
amount  of  fat ;  but  as  it  approaches  the  groin  it  is  easily  divisible  into  two  layers, 
between  which  are  found  the  superficial  vessels  and  nerves  and  the  superficial 
inguinal  lymphatic  glands. 

The  Superficial  Layer  of  the  Superficial  Fascia  or  the  Fascia  of  Camper  is  thick, 
areolar  in  texture,  containing  adipose  tissue  in  its  meshes,  the  quantity  of  which 
varies  in  different  subjects.  Below,  it  passes  over  Poupart's  ligament,  and  is  con- 
tinuous with  the  outer  layer  of  the  superficial  fascia  of  the  thigh.  In  the  male  this 
fascia  is  continued  over  the  penis  and  over  the  outer  surface  of  the  cord  to  the 
scrotum,  where  it  helps  to  form  the  dartos.  As  it  passes  to  the  penis,  and  over  the 
cord  to  the  scrotum  it  changes  its  character,  becoming  thin,  destitute  of  adipose 
tissue,  and  of  a  pale  reddish  color;  and  in  the  scrotum  it  acquires  some  involuntary 
muscular  fibres.  From  the  scrotum  it  may  be  traced  backward,  to  be  continuous 
with  the  superficial  fascia  of  the  perinseum.  In  the  female  this  fascia  is  continued 
into  the  labia  majora. 

The  hypogastric  branch  of  the  ilio-hjrpogastric  nerve  perforates  the  aponeurosis 
of  the  External  oblique  muscle  about  an  inch  above  and  a  little  to  the  outer  side  of 
the  external  abdominal  ring,  and  is  distributed  to  the  integument  of  the  hypogas- 
tric region. 

The  ilio-inguinal  nerve  escapes  at  the  external  abdominal  ring,  and  is  distributed 
to  the  integument  of  the  upper  and  inner  part  of  the  thigh,  to  the  scrotum  in  the 
male  and  to  the  labium  in  the  female. 

The  superficial  epigastric  artery  arises  from  the  femoral  about  half  an  inch 
below  Poupart's  ligament,  and,  passing  through  the  saphenous  opening  in  the  fascia 
lata,  ascends  on  to  the  abdomen,  in  the  superficial  fascia  covering  the  External 
oblique  muscle,  nearly  as  high  as  the  umbilicus.  It  distributes  branches  to  the 
superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and  the  integument, 
anastomosing  with  branches  of  the  deep  epigastric  and  internal  mammary 
arteries. 

The  superficial  circumflex  iliac  artery,  the  smallest  of  the  cutaneous  branches, 
arises  close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel 
with  Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches 
which  supply  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and 

(  1511  ) 


1512 


THE  SURGICAL    ANATOMY   OF   HERNIA 


the  integument,  anastomosing  with  the  deep  circumflex  iliac  and  with  the  gluteal 
and  external  circumflex  arteries. 


POUPART-S  INTERCOLUMNAR 

LIGAMENT  FIBRES 


FEMORAL 
RING 

GIMBERNAT-S. 
LIGAMENT 

SAPHENOUS 

OPENING 

FEMORAL 

VEIN 

LONG- 

SAPHENOUS 

VEIN 


EXTERNAL 
•ABDOMINAL 
RING 


_CRUS 
SUPERIOR 


Fig.  1113. — Right  external  abdominal  ring  and  saphenous  opening  in  the  male.    (Spalteholz.) 


,    EXTERNAL  OBLIQUE 

vreflected  downward) 


EXTERNAL  OBLIQUE 

(reflected  inward) 


POSTERIOR  WALL  OF 
INGUINAL  CANAL 


INTERNAL   ORIGIN 
OF  CRENASTER 


Fig.  1114.— Right  inguinal  canal  in  the  male.     Second  layer  viewed  from  in  front.     (Spalteholz.) 


APONEUROSIS    OF   THE  EXTERNAL    OBLIQUE   MUSCLE     1513 

The  superficial  external  pudic  (superior)  artery  arises  from  the  inner  side  of 
the  femoral  artery  close  to  the  preceding  vessels,  and,  after  passing  through  the 
saphenous  opening,  courses  inward  across  the  spermatic  cord,  to  be  distributed  to 
the  integument  on  the  lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male, 
and  the  labium  in  the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The  Superficial  Veins. — The  veins  accompanying  these  superficial  vessels  are 
usually  much  larger  than  the  arteries;  they  terminate  in  the  internal  saphenous  vein. 

The  superficial  inguinal  lymphatic  glands  are  placed  immediately  beneath  the 
integument,  are  of  large  size,  and  vary  from  ten  to  twenty  in  number  (p.  793). 


INTERNAL  OBLIQUE 

(reflected  inward) 


INTERNAL 
OBLIQUE 


EXTERNAL  OBLIQUE 

(reflected  inward) 


POSTERIOR 
WALL 


triangular 
"fascia 


Fig.  1115.— The  right  inguinal  canal  in  the  male.     Third  layer  viewed  from  in  front.     (Spalteholz.) 

The  Deep  Layer  of  the  Superficial  Fascia,  the  Fascia  of  Scarpa  or  the  Fascia  of  Cooper 
(p.  433)  is  thinner  and  more  membranous  in  character  than  the  superficial  layer. 
In  the  middle  line  it  is  intimately  adherent  to  the  linea  alba;  above,  it  is  continuous 
with  the  superficial  fascia  over  the  rest  of  the  trunk ;  below,  it  blends  with  the  fascia 
lata  of  the  thigh  a  little  below  Poupart's  ligament ;  below  and  internally,  in  the  male, 
it  is  continued  over  the  penis  and  over  the  outer  surface  of  the  cord  to  the  scrotum, 
where  it  helps  to  form  the  dartos.  From  the  scrotum  it  may  be  traced  backward 
to  be  continuous  wath  the  base  of  the  triangular  ligament  of  the  urethra.  In  the 
female  it  is  continuous  with  the  labia  majora. 

The  scrotum  is  a  cutaneous  pouch  which  contains  the  testes  and  part  of  the 
spermatic  cords,  and  into  which  an  inguinal  hernia  frequently  descends. 

The  Aponeurosis  of  the  External  Oblique  Muscle  (Fig.  1113). — This  is  a  thin 
but  strong  membranous  aponeurosis,  the  fibres  of  which  are  directed  obliquely 
downward  and  inward.    That  portion  of  the  aponeurosis  which  extends  between 


1514  1HE   SURGICAL    ANATOMY   OF   HERNIA 

the  anterior  superior  spine  of  the  ilium  and  the  spine  of  the  os  pubis  is  a  broad 
band,  folded  inward  and  continuous  below  with  the  fascia  lata;  it  is  called  Poupart's 
ligament  (Figs.  289,  1113,  1116,  1117,  1119,  1124,  1125).  The  portion  which  is 
reflected  from  Poupart's  ligament  at  the  spine  of  the  os  pubis,  along  the  pectineal 
line,  is  called  Gimbemat's  ligament  (Fig.  297,  340,  1113,  1124,  1125).  A  thin  fibrous 
band  extends  from  the  inner  end  of  Poupart's  ligament  and  Gimbernat's  ligament 
upward  and  inward  behind  the  inner  pillar  of  the  external  ring  to  the  anterior 
layer  of  the  rectus  sheath.  The  fibres  diverge  as  they  ascend.  This  band  is 
known  as  the  triangular  fascia  or  Co  lies 's  fascia  or  the  triangular  ligament  of  CoUes 
(Figs.  1115  and  1119). 

The  External  or  Superficial  Abdominal  Ring  {anmilus  inguinalis  subcutaneus) 
(Figs.  289  and  1113). — Just  above  and  to  the  outer  side  of  the  crest  of  the  os  pubis 
an  interval  is  seen  in  the  aponeurosis  of  the  External  oblique,  called  the  external 
abdominal  ring.  This  aperture  is  oblique  in  direction,  somewhat  triangular  in 
form,  and  corresponds  with  the  course  of  the  fibres  of  the  aponeurosis.  It  usually 
measures  from  base  to  apex  about  an  inch,  and  transversely  about  half  an  inch. 
It  is  bounded  below  by  the  crest  of  the  os  pubis;  above,  by  a  series  of  curved 
fibres,  the  intercolumnar  fibres,  which  pass  across  the  upper  angle  of  the  ring,  so  as 
to  increase  its  strength;  and  on  either  side  by  the  margins  of  the  opening  in  the 
aponeurosis,  which  are  called  the  columns  or  pillars  of  the  ring. 

The  External  Pillar,  which  at  the  same  time  is  inferior  {crus  injerius),  from  the 
obliquity  of  its  direction,  is  the  stronger;  it  is  formed  by  that  portion  of  Poupart's 
ligament  which  is  inserted  into  the  spine  of  the  os  pubis ;  it  is  curved,  so  as  to  form 
a  kind  of  groove,  upon  which  the  spermatic  cord  rests. 

The  Internal  or  Superior  Pillar  {criis  superius)  is  a  broad,  thin,  flat  band,  which 
is  attached  to  the  front  of  the  body  of  the  os  pubis,  interlacing  with  its  fellow  of 
the  opposite  side  in  front  of  the  symphysis  pubis,  that  of  the  right  side  being 
superficial. 

The  external  abdominal  ring  gives  passage  to  the  spermatic  cord  in  the  male 
and  round  ligament  in  the  female;  it  is  much  larger  in  men  than  in  women,  on 
account  of  the  large  size  of  the  spermatic  cord,  hence  the  great  frequency  of  inguinal 
hernia  in  men. 

The  Intercolumnar  Fibres  (fibrae  intercrurales)  (Fig.  1113)  are  a  series  of  curved 
tendinous  fibres  which  arch  across  the  lower  part  of  the  aponeurosis  of  the  Exter- 
nal oblique.  They  have  received  their  name  from  stretching  across  between  the 
two  pillars  of  the  external  ring ;  they  increase  the  strength  of  the  lower  part  of  the 
aponeurosis  and  prevent  the  divergence  of  the  pillars  from  one  another.  They 
are  thickest  below,  where  they  arise  from  Poupart's  ligament,  and  they  are 
inserted  into  the  linea  alba,  describing  a  curve,  with  the  convexity  downward. 
They  are  much  thicker  and  stronger  at  the  outer  angle  of  the  external  ring  than 
internally,  and  are  more  strongly  developed  in  the  male  than  in  the  female. 
These  intercolumnar  fibres,  as  they  pass  across  the  external  abdominal  ring,  are 
themselves  connected  together  by  delicate  fibrous  tissue,  thus  forming  a  fascia 
which,  as  it  is  attached  to  the  pillars  of  the  ring,  covers  it  in,  and  is  called  the 
intercolumnar  fascia.  This  intercolumnar  fascia  is  continued  downward  as  a 
tubular  prolongation  around  the  outer  surface  of  the  cord  and  testis,  and  encloses 
them  in  a  distinct  sheath;  hence,  it  is  also  called  the  external  spermatic  fascia. 
The  sac  of  an  inguinal  hernia  in  passing  through  the  external  abdominal  ring 
receives  an  investment  from  the  intercolumnar  fascia. 

If  the  finger  is  introduced  a  short  distance  into  the  external  ring  and  the  limb 
is  then  extended  and  rotated  outward,  the  aponeurosis  of  the  External  oblique, 
together  with  the  iliac  portion  of  the  fascia  lata,  will  be  felt  to  become  tense  and 
the  external  ring  much  contracted;  if  the  limb  is,  on  the  contrary,  flexed  upon  the 
pelvis  and  rotated  inward,  this  aponeurosis  will  become  lax,  and  the  external  ring 


THE    TRIANGULAR    FASCIA    OF    THE   ABDOMEN  1515 


sufficiently  enlarged  to  admit  the  finger  with  comparative  ease;  hence  the  patient 
should  always  be  put  in  the  latter  position  when  the  taxis  is  applied  for  the  reduc- 
tion of  an  inguinal  hernia,  in  order  that  the  abdominal  walls  may  be  relaxed  as 
much  as  possible. 

The  aponeurosis  of  the  External  oblique  should  be  removed  by  dividing  it  across  in  the  same 
direction  as  the  external  incisions,  and  reflecting  it  downward  and  outward;  great  care  is  requisite 
in  separating  it  from  the  aponeurosis  of  the  muscle  beneath.  The  lower  part  of  the  Internal 
obHque  and  the  Cremaster  are  then  exposed,  together  with  the  inguinal  canal,  which  contains 
the  spermatic  cord  (Fig.  1116).  The  mode  of  insertion  of  Poupart's  and  Gimbernat's  ligaments 
into  the  os  pubis  should  also  be  examined. 

Poupart's  Ligament  (ligamentum  inguinale  [Pouparti])  (Figs.  289, 1113,1116,1117, 
1 1 19, 1 124,  and  1 125)  or  the  crural  arch  is  the  lower  border  of  the  aponeurosis  of  the 
External  oblique  muscle,  which  extends  from  the  anterior  superior  spine  of  the  ilium 
to  the  spine  of  the  os  pubis.  From  this  latter  point  it  is  reflected  outward  to  be 
attached  to  the  pectineal  line  for  about  half  an  inch,  forming  Gimbernat's  ligament. 
Its  general  direction  is  curved  down- 
ward toward  the  thigh,  where  it  is  con- 
tinuous with  the  fascia  lata.  Its  outer 
half  is  rounded  and  oblique  in  direc- 
tion; its  inner  half  gradually  widens  at 
its  attachment  to  the  os  pubis,  is  more 
horizontal  in  direction,  and  lies  be- 
neath the  spermatic  cord. 

Gimbernat's  Ligament  (ligamentum 
lacunare  [Gimbernati])  (Figs.  289,  297, 
340,  1113,  1124,  and  1125)  is  that  por- 
tion of  the  aponeurosis  of  the  External 
oblique  muscle  which  is  reflected  up- 
ward and  outward  from  the  spine  of 
the  OS  pubis  to  be  inserted  into  the 
pectineal  line.  It  is  about  half  an 
inch  in  length,  larger  in  the  male  than 
in  the  female,  almost  horizontal  in 
direction  in  the  erect  posture,  and  of  a 
triangular  form,  with  the  base  directed 
outward.  Its  base  or  outer  margin  is 
concave,  thin,  and  sharp,  and  lies  in 
contact  with  the  femoral  sheath,  form- 
ing the  inner  boundary  of  the  femoral 
ling  (Fig.  1124).  Its  apex  corresponds 
to  the  spine  of  the  os  pubis.  Its  pos- 
terior margin  is  attached  to  the  pec- 
tineal line,  and  is  continuous  with  the 
pubic  portion  of  the  fascia  lata.  Its  anterior  margin  is  continuous  with  Poupart's 
ligament. 

The  Triangular  Fascia  of  the  Abdomen,  CoUes's  Fascia  or  the  Triangular  Ligament 
of  Colles  (ligamentum  inguinale  reflexum  [Collesi])  (Fig.  1115, 1116,  and  1119)  is  a 
band  of  tendinous  fibres,  of  a  triangular  shape,  which  is  attached  by  its  apex  to 
the  inner  end  of  Poupart's  ligament  and  to  Gimbernat's  ligament.  It  passes 
inward  beneath  the  spermatic  cord,  and  expands  into  a  somewhat  fan-shaped 
fascia,  lying  behind  the  inner  pillar  of  the  external  abdominal  ring  and  in  front 
of  the  conjoined  tendon,  and  interlaces  with  the  ligament  of  the  other  side  at  the 
linea  alba  in  the  anterior  layer  of  the  sheath  of  the  Rectus  muscle. 


Fig.  1116. — Inguinal  hernia.    Dissection  showing  the 
Internal  oblique  and  Cremaster. 


1516  THE   SURGICAL    ANATOMY   OF  HERNIA 

The  Ligament  of  Cooper.— See  Fig.  297  and  p.  437. 

The  Internal  Oblique  Muscle  (Figs.  1114,  1115,  and  1116)  has  been  previously- 
described  (p.  437).  The  part  which  is  now  exposed  is  pardy  muscular  and  partly 
tendinous  in  structure.  Those  fibres  which  arise  from  Poupart's  ligament,  few  in 
number  and  paler  in  color  than  the  rest,  arch  downward  and  inward  across  the 
spermatic  cord,  and,  becoming  tendinous,  are  inserted,  conjointly  with  those  of 
the  Transversalis,  into  the  crest  of  the  os  pubis  and  pectineal  line,  forming  what 
is  known  as  the  conjoined  tendon  of  the  Internal  oblique  and  Transversalis  (Figs. 
1116  and  1117).  This  tendon  is  inserted  immediately  behind  the  inguinal  canal 
and  external  abdominal  ring,  serving  to  protect  what  would  otherwise  be  a  weak 
point  in  the  abdominal  wall.  The  conjoined  tendon  is  sometimes  divided  into 
an  outer  and  an  inner  portion,  the  former  being  called  the  ligament  of  Hessel- 
bach  (ligamentum  interjoveolare)  (Fig.  292),  and  the  latter  the  ligament  of  Henle 
(Fig.  292).  Sometimes  the  conjoined  tendon  is  insufficient  to  resist  the  pressure 
from  within,  and  is  carried  forward  in  front  of  the  protrusion  through  the  exter- 
nal ring,  forming  one  of  the  coverings  of  direct  inguinal  hernia,  or  the  hernia 
forces  its  way  through  the  fibres  of  the  conjoined  tendon. 

The  Oremaster  (Figs.  1114  and  1116)  is  derived  from  the  lower  margin  of  the 
Internal  oblique,  of  which  muscle  it  is  in  reality  a  portion.  It  is  a  thin  muscular 
layer  composed  of  a  number  of  fasciculi.  It  arises  by  a  thick  external  bundle  of 
fibres  from  the  upper  portion  of  Poupart's  ligament,  being  connected  with  the 
Internal  oblique  muscle  and  also  occasionally  with  the  Transversalis.  It  arises 
also  by  a  thin  inner  bundle  of  fibres  from  the  anterior  layer  of  the  rectus 
sheath. 

The  thick  bundle  of  origin  is  on  the  lateral  surface;  the  thin  bundle  is  on  the 
medial  surface  of  the  spermatic  cord.  The  Cremaster  passes  along  with  the 
spermatic  cord,  and  descends  with  it  through  the  external  ring.  Upon  the  front  and 
sides  of  the  cord  both  bundles  spread  out  upon  the  vaginal  tunic  of  the  testicle 
and  epididymis,  and  form  a  series  of  loops  which  differ  in  thickness  and  length 
in  different  subjects.  These  loops  are  united  together  by  areoh:r  tissue,  and 
form  a  thin  covering  over  the  cord  and  testis,  the  cremasteric  fascia  (fascia 
cremasterica) . 

It  will  be  observed  that  the  Cremaster  is  a  separated  portion  of  the  Internal 
oblique.  This  fact  affords  an  easy  explanation  of  the  manner  in  which  the  testicle 
and  cord  are  invested  by  this  muscle.  At  an  early  period  of  foetal  life  the  testis  is 
placed  at  the  lower  and  back  part  of  the  abdominal  cavity,  but  during  its  descent 
toward  the  scrotum,  which  takes  place  before  birth,  it  passes  beneath  the  arched 
border  of  the  Internal  oblique.  In  its  passage  beneath  this  muscle  some  fibres 
are  derived  from  its  lower  part,  which  accompany  the  testicle  and  cord  into  the 
scrotum. 

It  occasionally  happens  that  the  loops  of  the  Cremaster  surround  the  cord,  some 
lying  behind  as  well  as  in  front.  It  is  probable  that  under  these  circumstances 
the  testis  in  its  descent  passes  through,  instead  of  beneath,  the  fibres  of  the  Internal 
oblique. 

In  the  descent  of  an  oblique  inguinal  hernia,  which  takes  the  same  course  as 
the  spermatic  cord,  the  Cremaster  muscle  forms  one  of  its  coverings.  This  muscle 
becomes  largely  developed  in  cases  of  hydrocele  and  large  old  scrotal  herniae.  No 
such  muscle  exists  in  the  female,  but  an  analogous  structure  is  developed  in  those 
cases  where  an  oblique  inguinal  hernia  descends  beneath  the  margin  of  the  Internal 
oblique. 

The  Internal  oblique  should  be  detached  from  Poupart's  ligament,  separated  from  the  Trans- 
versalis to  the  same  extent  as  in  the  previous  incisions,  and  reflected  inward  on  to  the  sheath 
of  the  Rectus  (Fig.  1117).  The  deep  circumflex  iliac  vessels,  which  lie  between  these  two  muscles, 
form  a  valuable  guide  to  their  separation. 


THE   INGUINAL     OB   SPERMATIC    CANAL 


1517 


The  Transversalis  Muscle  (Figs.  1115  and  1117)  has  been  previously  described 
(p.  442).  The  part  which  is  now  exposed  is  partly  muscular  and  partly  tendinous 
in  structure ;  it  arises  from  the  outer  third  of  Poupart's  ligament,  its  fibres  curve 
downward  and  inward,  and  are  inserted,  together  with  those  of  the  Internal 
oblique,  into  the  lower  part  of  the  linea  alba,  into  the  crest  of  the  os  pubis  and 
the  pectineal  line,  forming  what  is  known  as  the  conjoined  tendon  of  the  Internal 
oblique  and  Transversalis  (Figs.  1116  and  1117).  The  falx  aponeurotica  [inguinalis] 
is  a  collection  of  fibres  of  tendinous  consistence  in  the  inner  side  of  the  Trans- 
versalis insertion.  Between  the  lower  border  of  this  muscle  and  Poupart's 
ligament  a  space  is  left  in  which  is  seen  the  transversalis  fascia. 

The  Inguinal  or  Spermatic  Canal  {canalis  inguinalis)  (Figs.  1114,  1115,  and  1117) 
contains  the  spermatic  cord  in  the  male  and  the  round  ligament  in  the  female.  It 
is  an  oblique  canal,  about  an  inch  and  a  half  in  length,  directed  downward  and 
inward  and  placed  parallel  with,  and  a  little  above,  Poupart's  ligament.  It  com- 
mences above  at  the  internal  or  deep  abdominal  ring,  which  is  the  point  where 


Epigastric  artery. 


Fig.  1117. — Inguinal  hernia. 


Dissection  showing  the  Transversalis  muscle,  the  transversalis  fascia, 
and  the  internal  abdominal  ring. 


the  cord  enters  the  inguinal  canal,  and  terminates  below  at  the  external  or  super- 
ficial ring.  It  is  bounded,  in  front,  by  the  integument  and  superficial  fascia,  by 
the  aponeurosis  of  the  External  oblique  throughout  its  whole  length,  and  by  the 
Internal  oblique  for  its  outer  third;  behind,  by  the  triangular  fascia,  the  conjoined 
tendon  of  the  Internal  oblique  and  Transversalis,  transversalis  fascia,  and  the 
subperitoneal  fat  and  peritoneum;  above,  by  the  arched  fibres  of  the  Internal 
oblique  and  Transversalis;  below,  by  the  union  of  the  transversalis  fascia  with 
Poupart's  ligament.  That  form  of  hernia  in  which  the  intestine  follows  the  course 
of  the  spermatic  cord  along  the  inguinal  canal  is  called  oblique  inguinal  hernia. 

On  the  posterior  wall  of  the  inguinal  canal  is  seen  the  band  of  fibres  known  as 
the  ligament  of  Hesselbach  (ligamentum  interfoveolare  [Hesselbachi])  (Fig.  292). 
It  is  placed  in  front  of  the  deep  epigastric  artery.  The  fibres  come  from  the 
external  portion  of  the  lower  fibres  of  the  conjoined  tendon  (Fig.  1116)  and  pass 


1518  THE   SURGICAL    ANATOMY    OF  HERNIA 

downward  for  a  distance,  some  of  them  then  passing  outward  and  upward,  some 
of  them  downward  and  inward  to  the  inner  surface  of  Poupart's  Hgament. 

The  Transversalis  Fascia  (Figs.  297,  1117,  and  1125)  is  a  thin  aponeurotic  mem- 
brane which  lies  between  the  inner  surface  of  the  Transversalis  muscle  and  the 
peritoneum.  It  forms  part  of  the  general  layer  of  fascia  whicli  lines  the  interior 
of  the  abdominal  and  pelvic  cavities,  and  is  directly  continuous  with  the  iliac 
and  pelvic  fasciae. 

In  the  inguinal  region  the  transversalis  fascia  is  thick  and  dense  in  structure, 
and  joined  by  fibres  from  the  aponeurosis  of  the  Transversalis  muscle;  but  it 
becomes  thin  and  cellular  as  it  ascends  to  the  Diaphragm.  Below,  it  has  the 
following  attachments;  external  to  the  femoral  vessels  it  is  connected  to  the 
posterior  margin  of  Poupart's  ligament,  and  is  there  continuous  with  the  iliac 
fascia.  Internal  to  the  vessels  it  is  thin,  and  attached  to  the  os  pubis  and  pectineal 
line  behind  the  conjoined  tendon,  with  which  it  is  united;  and,  corresponding  to 
the  points  where  the  femoral  vessels  pass  into  the  thigh,  this  fascia  descends  in 
front  of  them,  forming  the  anterior  wall  of  the  femoral  sheath.  The  spermatic  cord 
in  the  male  and  the  round  ligament  in  the  female  pass  through  this  fascia;  the 
point  where  they  pass  through  is  called  the  internal  or  deep  abdominal  ring.  This 
opening  is  not  visible  externally,  owing  to  a  prolongation  of  the  transversalis  fascia 
on  the  structures  forming  the  infiindibuliform  fascia. 

The  Internal  or  Deep  Abdominal  Ring  (annulus  inguinalis  ahdcminalis)  (Figs.  297 
and  1117j  is  situated  in  the  transversalis  fascia,  midway  between  the  anterior  superior 
spine  of  the  ilium  and  symphysis  pubis,  and  about  half  an  inch  above  Poupart's 
ligament.  It  is  of  an  oval  form,  its  long  diameter  being  directed  upward  and 
downward;  it  varies  in  size  in  different  subjects,  and  is  much  larger  in  the  male 
than  in  the  female.  It  is  bounded  above  and  externally  by  the  arched  fibres  of 
the  Transversalis  muscle,  below  and  internally  by  the  deep  epigastric  vessels.  It 
transmits  the  spermatic  cord  in  the  male  and  the  round  ligament  in  the  female. 
From  its  circumference,  a  thin,  funnel-shaped  membrane,  the  infundibuliform  fascia, 
is  continued  around  the  cord  and  testis,  enclosing  them  in  a  distinct  pouch  (Fig. 
1117).  When  the  sac  of  an  oblique  inguinal  hernia  passes  through  the  internal  or 
deep  abdominal  ring,  the  infundibuliform  fascia  constitutes  one  of  its  coverings. 

The  Subperitoneal  Areolar  Tissue  or  the  Fascia  Propria  of  Cooper. — Between  the 
transversalis  fascia  and  the  peritoneum  is  a  quantity  of  loose  areolar  tissue.  In 
some  subjects  it  is  of  considerable  thickness  and  loaded  with  adipose  tissue. 
Opposite  the  internal  ring  it  is  continued  around  the  surface  of  the  cord,  forming 
a  loose  sheath  for  it. 

The  Deep  Epigastic  Artery  (Figs.  292  and  1118)  arises  from  the  external  iliac 
artery  a  few  lines  above  Poupart's  ligament.  It  at  first  descends  to  reach  this  liga- 
ment, and  then  ascends  obliquely  along  the  inner  margin  of  the  internal  or  deep 
abdominal  ring,  lying  between  the  transversalis  fascia  and  the  peritoneum,  and 
passing  upward  pierces  the  transversalis  fascia  and  enters  the  sheath  of  the  Rectus 
muscle  by  passing  over  the  semilunar  fold  of  Douglas.  Consequently  the  deep 
epigastric  artery  bears  a  very  important  relation  to  the  internal  abdom.inal  ring 
as  it  passes  obliquely  upward  and  inward  from  its  origin  from  the  external  iliac. 
In  this  part  of  its  course  it  lies  along  the  lower  and  inner  margin  of  the  internal 
ring  and  beneath  the  commencement  of  the  spermatic  cord.  At  its  commence- 
ment it  is  crossed  by  the  vas  deferens  in  the  male  and  by  the  round  ligament  in 
the  female. 

The  Peritoneum  (Fig.  1118),  corresponding  to  the  inner  surface  of  the  internal 
ring,  presents  a  well-marked  depression,  the  depth  of  which  varies  in  different 
subjects.  A  thin  fibrous  band  is  continued  from  it  along  the  front  of  the  cord 
for  a  variable  distance,  and  becomes  ultimately  lost,  the  ligament  of  Cloquet. 
This  is  the  remains  of  the  pouch  of  peritoneum  which,  in  the  foetus,  precedes 


THE   PERITONEUM 


1519 


the  cord  and  testis  into  the  scrotum,  the  obliteration  of  which  commences  soon 
after  birth.  In  some  cases  the  fibrous  band  can  only  be  traced  a  short  distance, 
but  occasionally  it  may  be  followed,  as  a  fine  cord,  as  far  as  the  upper  end  of  the 
tunica  vaginalis.  Sometimes  the  tube  of  peritoneum  is  closed  only  at  intervals 
and  presents  a  sacculated  appearance,  or  a  single  pouch  may  extend  along  the 
whole  length  of  the  cord,  which  may  be  closed  above,  or  the  pouch  may  be  directly 
continuous  with  the  peritoneum  by  an  opening  at  its  upper  part. 

In  the  female  foetus  the  peritoneum  is  also  prolonged  in  the  form  of  a  tubular 
process  for  a  short  distance  into  the  inguinal  canal.  This  process  is  called  the 
canal  of  Nuck.  It  is  generally  obliterated  in  the  adult,  but  sometimes  it  remains 
pervious  even  in  advanced  life. 


M.  iliacus 


External 
inguinal 
fossa. 


iliac        ^^^^Kl_2i;^_^  r,  xStSi^Mi^^T^l^f^  fn 

vein.  ^^^■■H^.v-.^  6  t.ADDER\  -..>r*7'»^     ^  ■'      , 

I  nor  vesical 

artery. 

^Middle  inguinal 

fossa. 

J.ntenial  iiKjuim' 

fo 

Fig.  1118. — Posterior  view  of  the  anterior  abdominal  wall  in  its  lower  half.     The  peritoneum  is  in  place, 
and  the  various  cords  are  shining  through.      (After  Joessel.) 

In  order  to  understand  the  relation  of  the  peritoneum  to  inguinal  hernia,  it  is 
necessary  to  view  the  anterior  abdominal  wall  from  its  internal  aspect,  when  it  will 
be  seen  as  shown  in  Fig.  1 1 18.  Between  the  upper  margin  of  the  front  of  the 
pelvis  and  the  umbilicus,  the  peritoneum,  when  viewed  from  behind,  will  be  seen 
to  be  raised  into  five  vertical  folds,  with  intervening  depressions,  by  more  or  less 
prominent  bands  which  converge  to  the  umbilicus.  One  of  these  is  situated  in  the 
median  line,  and  is  caused  by  the  urachus,  the  remnant  of  the  allantois;  it  extends 
from  the  summit  of  the  bladder  to  the  umbilicus.  The  fold  of  peritoneum  covering 
it  is  known  as  the  fold  of  the  urachus  or  the  plica  urachi  (plica  umbilicalis  media). 
On  either  side  of  this  is  a  prominent  band,  caused  by  the  obliterated  hypogastric 
artery,  which  extends  from  the  side  of  the  bladder  obliquely  upward  and  inward 
to  the  umbilicus.    This  is  covered  by  a  fold  of  peritoneum  which  is  known  as  the 


1520  THE    SURGICAL    ANATOMY    OF  HEBNIA 

hypogastric  fold  or  the  plica  hypogastrica  {'plica  umhilicalis  lateralis).  To  either 
side  of  these  three  cords  is  the  deep  epigastric  artery,  which  ascends  obliquely 
upward  and  inward  from  a  point  midway  between  the  symphysis  pubis  and  the 
anterior  superior  spine  of  the  ilium  to  the  semilunar  fold  of  Douglas,  in  front  of 
which  it  disappears.  It  is  covered  by  a  fold  of  peritoneum  which  is  known  as  the 
plica  epigastrica.  Between  these  raised  folds  are  depressions  of  the  peritoneum, 
constituting  so-called  fossae.  The  most  internal,  between  the  plica  urachi  and  the 
plica  hypogastrica,  is  known  as  the  internal  inguinal  fossa  {fovea  supravesicalis). 
The  middle  one  is  situated  between  the  plica  hypogastrica  and  the  plica  epigas- 
trica, and  is  termed  the  middle  inguinal  fossa  {fovea  inguinalis  mesialis).  The 
external  one  is  external  to  the  plica  epigastrica,  and  is  known  as  the  external 
inguinal  fossa  {fovea  inguinalis  lateralis).  Occasionally  the  deep  epigastric  artery 
corresponds  in  position  to  the  obliterated  hypogastric  artery,  and  then  there  is  but 
one  fold  on  each  side  of  the  middle  line,  and  the  two  external  fossae  are  merged 
into  one.  In  the  usual  condition  of  the  parts  the  floor  of  the  external  inguinal 
fossa  corresponds  to  the  internal  abdominal  ring,  and  into  this  fossa  an  oblique 
inguinal  hernia  descends.  To  the  inner  side  of  the  plica  epigastrica  are  the 
two  internal  fossae,  and  through  either  of  these  a  direct  hernia  may  descend,  as 
will  be  explained  in  the  sequel  (p.  1523).  The  whole  of  this  space,  that  is  to 
say,  the  space  between  the  deep  epigastric  artery,  the  margin  of  the  Rectus  and 
Poupart's  ligament,  is  commonly  known  as  Hesselbach's  triangle.  These  three 
depressions  or  fossae  are  situated  above  the  level  of  Poupart's  ligament,  and  in 
addition  to  them  is  another  below  the  ligament,  corresponding  to  the  position  of 
the  femoral  ring,  and  into  which  a  femoral  hernia  descends. 


INGUINAL  HERNIA. 

Inguinal  hernia  is  that  form  of  protrusion  which  makes  its  way  through  the 
abdomen  in  the  inguinal  region. 

There  are  two  principal  varieties  of  inguinal  hernia — external  or  oblique,  and 
internal  or  direct. 

External  or  oblique  inguinal  hernia,  the  more  frequent  of  the  two,  takes  the 
same  course  as  the  spermatic  cord.  It  is  called  external  from  the  neck  of  the  sac 
being  on  the  outer  or  iliac  side  of  the  deep  epigastric  artery. 

Internal  or  direct  inguinal  hernia  does  not  follow  the  same  course  as  the  cord, 
but  protrudes  through  the  abdominal  wall  on  the  inner  or  pubic  side  of  the  deep 
epigastric  artery. 

Oblique  Inguinal  Hernia. 

In  oblique  inguinal  hernia  (Fig.  1118)  the  intestine  or  omentum  escapes  from  the 
abdominal  cavity  at  the  internal  ring.  Before  it  is  a  pouch  of  peritoneum,  which 
forms  the  hernial  sac  (Fig.  1119,  A).  This  pouch  of  peritoneum  is  invested  by  the 
subserous  areolar  tissue,  and  is  enclosed  in  the  infimdibuliform  process  of  the  trans- 
versalis  fascia,  which  it  receives  as  it  enters  the  inguinal  canal.  In  passing  along  the 
inguinal  canal  the  hernia  displaces  upward  the  arched  fibres  of  the  Transversalis  and 
Internal  oblique  muscles,  and  is  imperfectly  surrounded  by  the  fibres  of  the  Cre- 
master  muscles,  the  coat  being  completed  by  the  cremasteric  fascia.  It  then  passes 
along  the  front  of  the  cord,  and  escapes  from  the  inguinal  canal  at  the  external 
ring,  receiving  an  investment  from  the  intercolumnar  fascia.  Lastly,  it  descends 
into  the  scrotum,  receiving  coverings  from  the  superficial  fascia  and  the  integument. 
^  The  coverings  of  this  form  of  hernia,  after  it  has  passed  through  the  external 
ring,  are,  from  without  inward,  the  integument,  superficial  fascia,  intercolumnar 


OBLIQUE   INGUINAL    HEBNIA 


1521 


fascia,  Cremaster  muscle  and  fascia,  infundibuliform  fascia,  subserous  areolar 
tissue,  and  peritoneum. 

This  form  of  hernia  lies  in  front  of  the  vessels  of  the  spermatic  cord  and  seldom 
extends  below  the  testis,  on  account  of  the  intimate  adhesion  of  the  coverings 
of  the  cord  to  the  tunica  vaginalis  (Fig.  1120,  A). 

The  seat  of  stricture  in  a  strangulated  oblique  inguinal  hernia  is  either  at  the 
external  ring,  in  the  inguinal  canal,  caused  by  the  fibres  of  the  Internal  oblique 
or  Trans versalis;  or  at  the  internal  ring,  most  frequently  in  the  latter  situation. 
If  it  is  situated  at  the  external  ring,  the  division  of  a  few  fibres  at  one  point  of 
its  circumference  is  all  that  is  necessary  for  the  replacement  of  the  hernia.  If 
in  the  inguinal  canal  or  at  the  internal  ring,  it  may  be  necessary  to  divide  the 


Fig.  1119. 


-Oblique  inguinal  hernia,  showing  its  various  coverings.     (From  a  preparation  in  the 
Museum  of  the  Royal  College  of  Surgeons.) 


aponeurosis  of  the  External  oblique  so  as  to  lay  open  the  inguinal  canal.  In 
dividing  the  stricture  the  direction  of  the  incision  should  be  upward. 

When  the  hernia  passes  along  the  inguinal  canal  and  escapes  from  the  external 
ring  into  the  scrotum,  the  condition  is  called  complete  oblique  inguinal  or  scrotal 
hernia  (Fig.  1120,  A).  If  the  hernia  does  not  escape  from  the  external  ring,  but  is 
retained  in  the  inguind  canal,  the  condition  is  called  incomplete  inguinal  hernia  or 
bubonocele.  In  each  of  these  cases  the  coverings  which  invest  the  intestine  cr 
omentum  will  depend  upon  the  extent  to  which  it  descends  in  the  inguinal  canal. 

There  are  some  other  varieties  of  oblique  inguinal  hernia  depending  upon  con- 
genital defects  in  the  processus  vaginalis.  The  testicle  in  its  descent  from  the 
abdomen  into  the  scrotum  is  preceded  by  a  pouch  of  peritoneum,  which  about 

96 


1522 


THE  SURGICAL   ANATOMY   OF   HERNIA 


the  period  of  birth  becomes  shut  off  from  the  general  peritoneal  cavity  by  a  closure 
of  that  portion  of  the  pouch  which  extends  from  the  internal  abdominal  ring  to 


— 1 Sac  of  hernia. 


Tallica 
vaginalis.'' 

A.  Common  scrotal  hernia. 


Tunica 
■—-vaginalis. 


B   Congenital  hernia. 


Sac  of  ^__ 
hernia. 


--Sac  of  hernia. 

Tunica 
'vaginalis. 


Tunica  vaginalis.~\~-M^^ 


)f  hernia. 


E.  Hernia  into  the  funicular  process. 
Fig.  1120. — Varieties  of  oblique  inguinal  hernia 


near  the  upper  part  of  the  testicle,  the  lower  portion  of  the  pouch  remaining  per- 
sistent as  the  tunica  vaginalis.     It  would  appear  that  this  closure  commences  at 


DIRECT  INGUINAL    HERNIA 


1523 


two  points — viz.,  at  the  internal  abdominal  ring  and  at  the  top  of  the  epididymis 
— and  gradually  extends  until,  in  the  normal  condition,  the  whole  of  the  inter- 
vening portion  is  converted  into  a  fibrous  cord.  From  failure  in  the  completion 
of  this  process  variations  in  the  relation  of  the  hernial  protrusion  to  the  testicle 
and  tunica  vaginalis  are  produced,  which  constitute  distinct  varieties  of  inguinal 
hernia,  and  which  have  received  separate  names  and  are  of  surgical  importance. 
These  are  congenital,  infantile,  encysted,  and  hernia  of  the  funicular  process. 

Congenital  Hernia  (Fig.  1120,  B). — Where  the  congenital  pouch  of  peritoneum 
which  precedes  the  cord  and  testis  in  its  descent  remains  patent  throughout  and 
is  unclosed  at  any  point,  the  cavity  of  the  tunica  vaginalis  communicates  directly 
with  the  cavity  of  the  peritoneum.  The  intestine  descends  along  this  pouch  into 
the  cavity  of  the  tunica  vaginalis,  which  constitutes  the  sac  of  the  hernia,  and  the 
gut  lies  in  contact  with  the  testicle. 

Infantile  and  Encysted  Hernia.— Where  the  congenital  pouch  of  peritoneum 
is  occluded  at  the  internal  ring  only,  but  remains  patent  throughout  the  rest  of 
its  extent,  two  varieties  of  oblique  inguinal  hernia  may  be  produced,  which  have 
received  the  names  of  infantile  and  encysted  hernia.  In  the  infantile  form  (Fig. 
1120,  C)  the  septum  which  closed  the  congenital  sac  above  and  the  peritoneum 
in  its  immediate  neighborhood  yields  and  forms  a  sac,  which  descends  behind  the 
tunica  vaginalis,  so  that  in  front  of  the  bowel  there  are  three  layers  of  perito- 
neum, the  two  layers  of  the  tunica  vaginalis  and  the  layer  of  the  proper  hemial 
sac.  In  the  encysted  form  (Fig.  1120,  D)  yielding  occurs  in  the  same  position  as 
in  the  infantile  form — namicly,  at  the  occluded  spot  in  the  pouch — and  a  sac  forms 
which  projects  into  and  not  behind  the  tunica  vaginalis,  as  in  the  infantile  form, 
and  thus  it  constitutes  a  sac  within  a  sac,  so  that  in  front  of  the  bowel  there  are  two 
layers  of  peritoneum — one  layer  of  the  tunica  vaginalis  and  one  of  true  hemial  sac. 

Hernia  into  the  Funicular  Process  (Fig.  1120,  £).— Where  the  congenital 
pouch  of  peritoneum  is  occluded  at  the  lower  point  only — that  is,  just  above  the 
testicle — the  intestine  descends  into  the  pouch  of  peritoneum  as  far  as  the  testicle, 
but  is  prevented  from  entering  the  sac  of  the  tunica  vaginalis  by  the  septum  which 
has  formed  between  it  and  the  pouch,  so  that  it  resembles  the  congenital  form  in 
all  respects,  except  that,  instead  of  enveloping  the  testicle,  that  body  can  be  felt 
below  the  rupture. 

Direct  Inguinal  Hernia. 

In  direct  inguinal  hernia  the  protrusion  makes  its  way  through  some  part  of 
the  abdominal  wall  internal  to  the  epigastric  artery. 

At  the  lower  part  of  the  abdominal  wall  is  a  triangular  space,  Hesselbach's 
triangle,  bounded  externally  by  the  deep  epigastric  artery,  internally  by  the 
margin  of  the  Rectus  muscle,  below  by  Poupart's  ligament  (Fig.  1118).  The  con- 
joined tendon  is  stretched  across  the  inner  two-thirds  of  this  space,  the  remaining 
portion  of  the  space  having  only  the  subperitoneal  areolar  tissue  and  the  trans- 
versalis  fascia  between  the  peritoneum  and  the  aponeurosis  of  the  External  oblique 
muscle. 

In  some  cases  the  hernial  protrusion  escapes  from  the  abdomen  on  the  outer 
side  of  the  conjoined  tendon,  pushing  before  it  the  peritoneum,  the  subserous 
areolar  tissue,  and  the  trans versalis  fascia.  It  then  enters  the  inguinal  canal, 
passing  along  nearly  its  whole  length,  and  finally  emerges  from  the  external  ring, 
receiving  an  investment  from  the  intercolumnar  fascia.  The  coverings  of  this 
form  of  hernia  are  precisely  similar  to  those  investing  the  oblique  form,  with  the 
insignificant  difference  that  the  infundibuliform  fascia  is  replaced  by  a  portion 
derived  from  the  general  layer  of  the  transversalis  fascia. 

In  other  cases — and  this  is  the  more  frequent  variety — the  hernia  is  either  forced 
through  the  fibres  of  the  conjoined  tendon  or  the  tendon  is  gradually  distended  in 


1524  ^^^  SURGICAL    ANATOMY    OF  HERNIA 

front  of  it  so  as  to  form  a  complete  investment  for  it.  The  intestine  then  enters 
the  lower  end  of  the  inguinal  canal,  escapes  at  the  external  ring  lying  on  the 
inner  side  of  the  cord,  and  receives  additional  coverings  from  the  superficial  fascia 
and  the  integument.  This  form  of  hernia  has  the  same  coverings  as  the  oblique 
variety,  excepting  that  the  conjoined  tendon  is  substituted  for  the  Cremaster,  and 
the  infundibuliform  fascia  is  replaced  by  a  portion  derived  from  the  general  layer 
of  the  trans versalis  fascia. 

The  difference  between  the  position  of  the  neck  of  the  sac  in  these  two  forms 
of  direct  inguinal  hernia  has  been  referred,  with  some  probability,  to  a  difference 
in  the  relative  positions  of  the  obliterated  hypogastric  artery  and  the  deep  epi- 
gastric artery.  When  the  course  of  the  obliterated  hypogastric  artery  corre- 
sponds pretty  nearly  with  that  of  the  deep  epigastric  the  projection  of  these 
arteries  toward  the  cavity  of  the  abdomen  produces  two  fossae  in  the  peritoneum. 
The  bottom  of  the  external  fossa  of  the  peritoneum  corresponds  to  the  position  of 
the  internal  abdominal  ring,  and  a  hernia  which  distends  and  pushes  out  the  peri- 
toneum lining  this  fossa  is  an  oblique  hernia.  When,  on  the  other  hand,  the 
obliterated  hypogastric  artery  lies  considerably  to  the  inner  side  of  the  deep  epi- 
gastric artery,  corresponding  to  the  outer  margin  of  the  conjoined  tendon,  it  divides 
the  triangle  of  Hesselbach  into  two  parts,  so  that  three  depressions  will  be  seen  on 
the  inner  surface  of  the  lower  part  of  the  abdominal  wall — viz.,  an  external  one  on 
the  outer  side  of  the  deep  epigastric  artery;  a  middle  one,  between  the  deep  epi- 
gastric and  the  obliterated  hypogastric  arteries;  and  an  internal  one,  on  the  inner 
side  of  the  obliterated  hypogastric  artery  (pp.  1519  and  1520).  In  such  a  case 
a  hernia  may  distend  and  push  out  the  peritoneum  forming  the  bottom  of  either 
fossa.  These  fossae  are  the  inguinal  fossae.  When  the  hernia  distends  and 
pushes  out  the  peritoneum  forming  the  botton  of  the  external  fossa,  it  is  an 
oblique  or  external  inguinal  hernia. 

When  the  hernia  distends  and  pushes  out  the  peritoneum  forming  the  bottom 
of  either  the  middle  or  the  internal  fossa,  it  is  a  direct  or  internal  hernia. 

The  anatomical  difference  between  these  two  forms  of  direct  or  internal  inguinal 
hernia  is  that,  when  the  hernia  protrudes  through  the  middle  fossa — that  is, 
the  fossa  between  the  deep  epigastric  and  the  obliterated  hypogastric  arteries — 
it  will  enter  the  upper  part  of  the  inguinal  canal ;  consequently  its  coverings  will  be 
the  same  as  those  of  an  oblique  hernia,  with  the  insignificant  difference  that  the 
infundibuliform  fascia  is  replaced  by  a  portion  derived  from  the  general  layer  of 
the  transversalis  fascia,  whereas  when  the  hernia  protrudes  through  the  internal 
fossa  it  is  either  forced  through  the  fibres  of  the  conjoined  tendon  or  the  tendon  is 
gradually  distended  in  front  of  it  so  as  to  form  a  complete  investment  for  it.  The 
intestine  then  enters  the  lower  part  of  the  inguinal  canal,  and  escapes  from  the 
external  abdominal  ring  lying  on  the  inner  side  of  the  cord. 

This  form  of  hernia  has  the  same  coverings  as  the  oblique  variety,  excepting 
that  the  conjoined  tendon  is  substituted  for  the  Cremaster,  and  the  infundibuli- 
form fascia  is  replaced  by  a  portion  derived  from  the  general  layer  of  the  fascia 
transversalis. 

The  seat  of  stricture  in  strangulation  in  both  varieties  of  direct  hernia  is  most 
frequently  at  the  neck  of  the  sac  or  at  the  external  ring.  In  that  form  of  hernia 
which  perforates  the  conjoined  tendon  it  not  unfrequently  occurs  at  the  edges  of 
the  fissure  through  which  the  gut  passes.  In  dividing  the  stricture  the  incision 
should  in  all  cases  be  directed  upward.^ 

If  the  hernial  protrusion  passes  into  the  inguinal  canal,  but  does  not  escape 

1  In  all  cases  of  inguinal  hernia,  whether  oblique  or  direct,  it  is  proper  to  divide  the  stricture  directly  upward: 
the  reason  of  this  is  obvious,  for  by  cutting  in  this  direction  the  incision  is  made  parallel  to  the  deep  epigastric 
artery — either  external  to  it  in  the  oblique  variety,  or  internal  to  it  in  the  direct  form  of  hernia — and  thus  all 
chance  of  wounding  the  vessel  is  avoided.  If  the  incision  was  made  outward,  the  artery  might  be  divided  if  the 
hernia  was  direct;  and  if  made  inward,  the  vessel  would  stand  an  equal  chance  of  injury  if  the  case  was  one  of 
oblique  inguinal  hernia. — Ed.  of  15th  English  edition. 


FEMORAL    HERNIA 


1525 


from  the  external  abdominal  ring,  it  forms  what  is  called  incomplete  direct  hernia. 
This  form  of  hernia  is  usually  of  small  size,  and  in  corpulent  persons  is  very 
difficult  of  detection. 

Direct  inguinal  hernia  is  of  much  less  frequent  occurrenee  than  the  oblique, 
their  comparative  frequency  being,  according  to  Cloquet,  as  one  to  five.  It  occurs 
far  more  frequently  in  men  than  in  women,  on  account  of  the  larger  size  of  the 
external  ring  in  the  former  sex.  It  differs  from  the  oblique  in  its  smaller  size  and 
globular  form,  dependent  most  probably  on  the  resistance  offered  to  its  progress 
by  the  transversalis  fascia  and  conjoined  tendon.  It  differs  also  in  its  position, 
being  placed  over  the  os  pubis  and  not  in  the  course  of  the  inguinal  canal.  The 
deep  epigastric  artery  runs  on  the  outer  or  iliac  side  of  the  neck  of  the  sac,  and  the 
spermatic  cord  along  its  external  and  posterior  side,  not  directly  behind  it,  as  in 
oblique  inguinal  hernia. 

FEMORAL  HERNIA. 

The  dissection  of  the  parts  comprised  in  the  anatomy  of  femoral  hernia  should  be  performed, 
if  possible,  upon  a  female  subject  free  from  fat.  The  subject  should  lie  upon  the  back;  a  block 
is  first  placed  under  the  pelvis,  the  thigh  everted,  and  the  knees  slightly  bent  and  retained  in 
this  position.  An  incision  should  then  be  made  from  the  anterior  superior  spinous  process  of 
the  ilium  along  Poupart's  ligament  to  the  symphysis  pubis;  a  second  incision  should  be  carried 
transversely  across  the  thigh  about  six  inches  beneath  the  preceding;  and  these  are  to  be  con- 
nected together  by  a  vertical  one  carried  along  the  inner  side  of  the  thigh  (Fig.  340).  These 
several  incisions  should  divide  merely  the  integument;  this  is  to  be  reflected  outward,  when  the 
superficial  fascia  will  be  exposed. 

The  Superficial  Fascia  forms  a  continuous  layer  over  the  whole  of  the  thigh, 
consisting  of  areolar  tissue,  containing  in  its  meshes  much  fat,  and  capable  of  being 
separated  into  two  or  more  layers,  between  which  are  found  the  superficial  vessels 
and  nerves.  It  varies  in  thickness  in  different  parts  of  the  limb.  In  the  groin 
it  is  thick,  and  the  two  layers  are  separated  from  one  another  by  the  superficial 
inguinal  lymphatic  glands,  the  internal  saphenous  vein,  and  several  smaller 
vessels.  One  of  these  layers,  the  superficial,  is  continuous  with  the  superficial 
fascia  of  the  abdomen. 

The  superficial  layer  should  be  detached  by  dividing  it  across  in  the  same  direction  as  the 
external  incisions;  its  removal  will  be  facilitated  by  commencing  at  the  lower  and  inner  angle  of 
the  space,  detaching  it  at  first  from  the  front  of  the  internal  saphenous  vein,  and  dissecting  it 
off  from  the  anterior  surface  of  that  vessel  and  its  tributaries;  it  should  then  be  reflected  out- 
ward in  the  same  manner  as  the  integument.  The  cutaneous  vessels  and  nerves  and  superficial 
inguinal  glands  are  then  exposed,  lying  upon  the  deep  layer  of  the  superficial  fascia.  These  are 
the  internal  saphenous  vein  and  the  superficial  epigastric,  superficial  circumflex  iliac,  and  super- 
ficial external  pudic  vessels,  as  well  as  numerous  lymphatics,  ascending  with  the  saphenous  vein 
to  the  inguinal  glands. 

The  internal  or  long  saphenous  vein  (Figs.  1121,  1122,  and  1123)  ascends  along 
the  inner  side  of  the  thigh,  and,  passing  through  the  saphenous  opening  in  the 
fascia  lata,  terminates  in  the  femoral  vein  about  an  inch  and  a  half  below  Poupart's 
ligament  (Fig.  1113).  This  vein  receives  at  the  saphenous  opening  the  superficial 
epigastric,  the  superficial  circumflex  iliac,  and  the  superficial  external  pudic  veins. 

The  superficial  external  pudic  artery  (superior)  arises  from  the  inner  side  of 
the  femoral  artery,  and,  after  passing  through  the  saphenous  opening,  courses 
inward  across  the  spermatic  cord,  to  be  distributed  to  the  integument  on  the 
lower  part  of  the  abdomen,  the  penis  and  scrotum  in  the  male  and  the  labium  in 
the  female,  anastomosing  with  branches  of  the  internal  pudic. 

The  superficial  epigastric  artery  arises  from  the  femoral  about  half  an  inch 
below  Poupart's  ligament,  and,  passing  through  the  saphenous  opening  in  the 
fascia  lata,  ascends  on  to  the  abdomen,  in  the  superficial  fascia  covering  the 
External  oblique  muscle,  nearly  as  high  as  the  umbilicus.    It  distributes  branches 


1526 


THE    SURGICAL   ANATOMY   OF  HERNIA 


to  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and  the  integu- 
ment, anastomosing  with  branches  of  the  deep  epigastric  and  internal  mammary 
arteries. 

The  superficial  circumflex  iliac  artery,  the  smallest  of  the  cutaneous  branches, 
arises  close  to  the  preceding,  and,  piercing  the  fascia  lata,  runs  outward,  parallel 
with  Poupart's  ligament,  as  far  as  the  crest  of  the  ilium,  dividing  into  branches 
which  supply  the  superficial  inguinal  lymphatic  glands,  the  superficial  fascia,  and 
the  integupient  of  the  groin,  anastomosing  with  the  deep  circumflex  iliac,  and  with 
the  gluteal  and  external  circumflex  arteries. 

The  Superficial  Veins  (Fig.  1121). — The  veins  accompanying  these  superficial 
arteries  are  usually  much  larger  than  the  arteries;  they  terminate  in  the  internal 
or  long  saphenous  vein  at  the  saphenous  opening. 
-  The  superficial  inguinal  lymphatic  glands. — See  p.  793. 


Fig.  1121. — Femoral  hernia.     Superficial  dissection. 


The  ilio-inguinal  nerve  arises  from  the  first  lumbar  nerve.  It  escapes  at  the 
external  abdominal  ring,  and  is  distributed  to  the  integument  of  the  upper  and 
inner  part  of  the  thigh — ^to  the  scrotum  in  the  male  and  to  the  labium  in  the 
female.  The  size  of  this  nerve  is  in  inverse  proportion  to  that  of  the  ilio-hypo- 
gastric  nerve.  Occasionally  it  is  very  small,  and  ends  by  joining  the  ilio-hypogastric ; 
in  such  cases  a  branch  of  the  ilio-hypogastric  takes  the  place  of  the  ilio-inguinal, 
or  the  latter  nerve  may  be  altogether  absent.  The  crural  branch  of  the  genito- 
crural  nerve  passes  along  the  inner  margin  of  the  Psoas  muscle,  beneath  Poupart's 
ligament,  into  the  thigh,  entering  the  sheath  of  the  femoral  vessels,  and  lying 


FEMORAL    HERNIA 


1527 


superficial  and  a  little  external  to  the  femoral  artery.  It  pierces  the  anterior  layer 
of  the  sheath  of  the  vessels,  and,  becoming  superficial  by  passing  through  the  fascia 
lata,  it  supplies  the  skin  of  the  anterior  aspect  of  the  thigh  as  far  as  midway 
between  the  pelvis  and  knee.  On  the  front  of  the  thigh  it  communicates  w^ith 
the  outer  branch  of  the  middle  cutaneous  nerve,  derived  from  the  anterior  crural. 
The  Deep  Layer  of  the  Superficial  Fascia  is  a  very  thin  fibrous  layer,  best  marked 
on  the  inner  side  of  the  long  saphenous  vein  and  below  Poupart's  ligament.  It  is 
placed  beneath  the  subcutaneous  vessels  and  nerves,  and  upon  the  surface  of  the 
fascia  lata,  to  which  it  is  intimately  adherent  at  the  lower  margin  of  Poupart's 
ligament.  It  covers  the  saphenous  opening  in  the  fascia  lata,  is  closely  united  to 
its  circumference,  and  is  connected  to  the  sheath  of  the  femoral  vessels  corre- 


FiG.  1122. — Femoral  hernia,  showing  fascia  lata  and  saphenous  opening. 


sponding  to  its  under  surface.  The  portion  of  fascia  covering  this  aperture  is 
perforated  by  the  internal  saphenous  vein  and  by  numerous  blood-  and  lymphatic 
vessels;  hence  it  has  been  termed  the  cribriform  fascia,  the  openings  for  these 
vessels  having  been  likened  to  the  holes  in  a  sieve.  The  cribriform  fascia  adheres 
closely  both  to  the  superficial  fascia  and  to  the  fascia  lata,  so  that  it  is  described 
by  some  anatomists  as  a  part  of  the  fascia  lata,  but  it  is  usually  considered  (as  in 
this  work)  as  belonging  to  the  superficial  fascia.  It  is  not  till  the  cribriform  fascia 
has  been  cleared  away  that  the  saphenous  opening  is  seen,  so  that  this  opening 
does  not  in  ordinary  cases  exist  naturally,  but  is  the  result  of  dissection  (p.  513).  A 
femoral  hernia  in  passing  through  the  saphenous  opening  receives  the  cribriform 
fascia  as  one  of  its  coverings. 


1528 


THE   SURGICAL    ANATOMY    OF   HERNIA 


The  deep  layer  of  superficial  fascia,  together  with  the  cribriform  fascia,  having 
been  removed,  the  fascia  lata  is  exposed. 

The  Fascia  Lata  has  been  already  described  with  the  muscles  of  the  front  of 
the  thigh  (p.  513).  At  the  upper  and  inner  part  of  the  thigh,  a  little  below 
Poupart's  ligament,  a  large  oval-shaped  aperture  is  observed  after  the  superficial 
fascia  has  been  cleared  away;  it  transmits  the  internal  saphenous  vein  and  other 
smaller  vessels,  and  is  called  the  saphenous  opening  (Fig.  1113).  In  order  the 
more  correctly  to  consider  the  mode  of  formation  of  this  aperture,  the  fascia  lata  in 
this  part  of  the  thigh  is  described  as  consisting  of  two  portions,  an  iliac  portion  and 
a  pubic  portion. 


Fig.  1123. — Femoral  hernia.     Iliac  portion  of  fascia  lata  removed,  and  sheath  of  femoral  vessels  and 

femoral  canal  exposed. 

The  iliac  portion  (Fig.  11 22)  is  all  that  part  of  the  fascia  lata  on  the  outer  side  of 
the  saphenous  opening.  It  is  attached  externally  to  the  crest  of  the  ilium  and  its 
anterior  superior  spine;  to  the  whole  length  of  Poupart's  ligament;  and  to  the 
pectineal  line  in  conjunction  with  Gimbernat's  ligament.  From  the  spine  of  the 
OS  pubis  it  is  reflected  downward  and  outward,  forming  an  arched  margin,  the 
outer  boundary  or  falciform  process  or  superior  comu  (cornu  superius)  (Fig.  1122) 
of  the  saphenous  opening.  This  margin  overlies  and  is  adherent  to  the  anterior 
layer  of  the  sheath  of  the  femoral  vessels;  to  its  edge  is  attached  the  cribriform 
fascia,  and  below  it  is  continuous  with  the  pubic  portion  of  the  fascia  lata. 

The  pubic  portion  of  the  fascia  lata  or  the  pectineal  fascia  (Fig.  1122)  is  situated 
at  the  inner  side  of  the  saphenous  opening;  at  the  lower  margin  of  this  aperture 
it  is  continuous  with  the  iliac  portion;  traced  upward,  it  covers  the  surface  of 
the  Pectineus,  Adductor  longus,  and  Gracilis  muscles;  and,  passing  behind  the 


FEMORAL    HERNIA  I529 

sheath  of  the  femoral  vessels,  to  which  it  is  locsely  united,  is  continuous  with 
the  sheath  ot  the  Psoas  and  Iliacus  muscles,  and  is  attached  above  to  the  ilio- 
pectmeal  hne,  where  it  becomes  continuous  with  the  fascia  covering  the  Iliacus 
muscle  From  the  description  it  may  be  observed  that  the  iliac  portion  of  the 
fascia  lata  passes  m  front  of  the  femoral  vessels  and  the  pubic  portion  behind 
them,  so  that  an  apparent  aperture  consequently  exists  between  the  two,  through 
which  the  internal  saphenous  vein  joins  the  femoral  vein. 

The  Saphenous  Opening  {jossa  ovalis)  (Figs.  1113,  1121,  1122,  and  1123)  is  an 
oval-shaped  aperture  measuring  about  an  inch  and  a  half  in  length  and  half  an 
inch  in  width.  It  is  situated  at  the  upper  and  inner  parts  of  the  front  of  the 
thigh,  below  Pouparts  ligament,  and  is  directed  obliquely  downward  and  out- 
ward. It  is  covered  by  the  cribriform  fascia  {jascia-  cribrosa),  a  portion  of  the 
deep  layer  of  the  superficial  fascia  of  the  thigh,  and  which  extends  from  the 
falciform  margin  to  the  pubic  portion  of  the  fascia  lata  or  the  pectineal  fascia. 

The  outer  margin  of  the  saphenous  opening  is  of  a  semilunar  form,  thin,  strong, 
sharply  defined,  and  lies  on  a  plane  considerably  anterior  to  the  inner  margin! 
If  this  edge  is  traced  upward,  it  will  be  seen  to  form  a  curved  elongated  process, 
the  falciform  process  or  superior  comu  (Fig.  1122),  which  ascends  in  front  of  the 
femoral  vessels,  and,  curving  inward,  is  attached  to  Poupart's  ligament  and  to  the 
spine  of  the  os  pubis  and  pectineal  line,  where  it  is  continuous  with  the  pubic  por- 
tion. If  traced  downward,  it  is  found  continuous  with  another  curved  margin, 
the  concavity  of  which  is  directed  upward  and  inward;  this  is  the  inferior  cornu 
of  the  saphenous  opening,  and  is  blended  with  the  pubic  portion  of  the  fascia 
lata  covering  the  Pectineus  muscle. 

The  inner  boundary  of  the  opening  (Figs.  1113  and  1122)  is  on  a  plane  posterior 
to  the  outer  margin  and  behind  the  level  of  the  femoral  vessels;  it  is  much  less 
prominent  and  defined  than  the  outer,  from  being  stretched  over  the  subjacent 
Pectineus  muscle.  It  is  through  the  saphenous  opening  that  a  femoral  hernia 
passes  after  descending  along  the  crural  canal. 

If  the  finger  is  introduced  into  the  saphenous  opening  while  the  limb  is  moved 
in  different  directions,  the  aperture  will  be  found  to  be  greatly  constricted  on 
extending  the  limb  or  rotating  it  outward,  and  to  be  relaxed  on  flexing  the  limb 
and  inverting  it;  hence  the  necessity  for  placing  the  limb  in  the  latter  position  in 
employing  the  taxis  for  the  reduction  of  a  femoral  hernia. 

The  iliac  portion  of  the  fascia  lata,  but  not  its  falciform  process,  should  now  be  removed  by 
detaching  it  from  the  lower  margin  of  Poupart's  ligament,  carefully  dissecting  it  from  the  sub- 
jacent structures,  and  turning  it  inward,  when  the  sheath  of  the  femoral  vessels  is  exposed, 
descending  beneath  Poupart's  ligament  (Fig.  1123). 

Poupart's  Ligament  (ligamentum  inguinale  [Pouparti])  (Figs.  289,  1113,  1116, 
1117,  1119,1122,  1123,  1124,  and  1125)  is  the  lower  border  of  the  aponeurosis 
of  the  External  oblique  muscle,  which  extends  from  the  anterior  superior  spine 
of  the  ilium  to  the  spine  of  the  os  pubis.  From  this  latter  point  it  is  reflected 
outward,  to  be  attached  to  the  pectineal  line  for  about  half  an  inch,  forming 
Gimbemat's  ligament.  Its  general  direction  is  curved  downward  toward  the  thigh, 
where  it  is  continuous  with  the  fascia  lata.  Its  outer  half  is  rounded  and 
oblique  in  direction.  Its  inner  half  gradually  widens  at  its  attachment  to  the 
OS  pubis,  is  more  horizontal  in  direction,  and  lies  beneath  the  spermatic  cord. 
Nearly  the  whole  of  the  space  included  between  Pcupart's  ligament  and  the 
innominate  bone  is  filled  in  by  the  parts  which  descend  from  the  abdomen  into 
the  thigh  (Figs.  297,  340,  and  1124).  The  outer  half  of  the  space  (lacuna  muscu- 
lorum) is  occupied  by  the  Iliacus  and  Psoas  muscles,  together  with  the  external 
cutaneous  and  anterior  crural  nerves.  The  pubic  half  of  the  space  (lacuna 
vasorum)  is  occupied  by  the  femoral  vessels  included  in  their  sheath,  a  small  oval- 
shaped  interval  existing  between  the  femoral  vein  and  the  inner  wall  of  the  sheath, 


1530 


THE  SURGICAL    ANATOMY   OF  HERNIA 


which  is  occupied  merely  by  a  little  loose  areolar  tissue,  a  few  lymphatic  vessels, 
and  occasionally  by  a  small  lymphatic  gland;  this  is  the  femoral  ring,  through 
which  the  gut  descends  in  femoral  hernia.  The  part  of  Poupart's  ligament  in 
front  of  the  femoral  or  crural  ring  is  called  the  superficial  crural  arch. 

Gimbemat's  Ligament  (ligamentum  lacunare  [Gimbernati])  (Figs.  297,340, 1113, 
1124,  an  1  1125)  is  that  part  of  the  aponeurosis  of  the  External  oblique  muscle 
which  is  reflected  backward  and  outward  from  the  spine  of  the  os  pubis,  to  be 
inserted  into  the  pectineal  line.  It  is  about  half  an  inch  in  length,  larger  in  the 
male  than  in  the  female,  almost  horizontal  in  direction  in  the  erect  posture,  and 
of  a  triangular  form,  with  the  base  directed  outward.  Its  base  or  outer  margin 
is  concave,  thin,  and  sharp,  and  lies  in  contact  with  the  femoral  sheath.  Its 
apex  corresponds  to  the  spine  of  the  os  pubis.  Its  posterior  margin  is  attached  to 
the  pectineal  line,  and  is  continuous  with  the  pubic  portion  of  the  fascia  lata.  Its 
anterior  margin  is  continuous  with  Poupart's  ligament. 

External 
Crural 

branch     Anterior  crural, 
of  genito- 


Poupart's  ligament 


cutaneous  nerve. 


Iliac  portion  of 
fascia  lata 


Femoral  vein. 
Femoi  al  t  ing. 

Gtmbet  naf  s 
liqament 


Femoral  arte^-T 
Fig.  1124. — Structures  which  pass  beneath  the  crural  arch. 

Femoral  Sheath  (Fig.  1124) . — The  femoral  or  crural  sheath  is  a  continuation  down- 
ward of  the  fasciae  that  line  the  abdomen,  the  transversalis  fascia  passing  down  in 
front  of  the  femoral  vessels,  and  the  iliac  fascia  descending  behind  them;  these 
fasciae  are  directly  continuous  on  the  iliac  side  of  the  femoral  artery,  but  a  small 
space  exists  between  the  femoral  vein  and  the  point  where  they  are  continuous  on 
the  pubic  side  of  that  vessel,which  constitutes  the  femoral  or  crural  canal  (Fig.  11 13). 
The  femoral  sheath  is  closely  adherent  to  the  contained  vessels  about  an  inch 
below  the  saphenous  opening,  being  blended  with  the  areolar  sheath  of  the  vessels, 
but  opposite  Poupart's  ligament  it  is  much  larger  than  is  required  to  contain  them; 
hence  the  funnel-shaped  form  which  it  presents.    The  outer  border  of  the  sheath 


FEMORAL    HERNIA 


1531 


is  perforated  by  the  genito-cniral  nerve.  Its  inner  border  is  pierced  by  the  internal 
saphenous  vein  and  numerous  lymphatic  vessels.  In  front  it  is  covered  by  the 
iliac  portion  of  the  fascia  lata;  and  behind  it  is  the  pubic  portion  of  the  same 
fascia. 

If  the  anterior  wall  of  the  sheath  is  removed  (Fig.  1113),  the  femoral  artery  and 
vein  are  seen  lying  side  by  side,  a  thin  septum  separating  the  two  vessels,  while 
another  septum  may  be  seen  lying  just  internal  to  the  vein,  and  cutting  off  a  small 
space  between  the  vein  and  the  inner  wall  of  the  sheath.  The  septa  are  stretched 
between  the  anterior  and  posterior  walls  of  the  sheath,  so  that  each  vessel  is 
enclosed  in  a  separate  compartment.  The  interval  left  between  the  vein  and  the 
inner  wall  of  the  sheath  is  not  filled  up  by  any  structure,  excepting  a  little  loose 
areolar  tissue,  a  few  lymphatic  vessels,  and  occasionally  by  a  small  lymphatic 
gland;  this  is  the  femoral  or  crural  canal  (Fig.  1113),  through  which  the  intestine 
descends  in  femoral  hernia. 

Deep  Crural  Arch, — Passing  across  the  front  of  the  femoral  sheath  on  the  abdom- 
inal side  of  Poupart's  ligament,  and  closely  connected  with  it,  is  a  thickened  band 
of  fibres  of  the  transversalis  fascia,  called  the  deep  crural  arch.  It  is  apparently  a 
thickening  of  the  transversalis  fascia,  joining  externally  to  the  centre  of  Poupart's 
ligament,  and  arching  across  the  front  of  the  crural  sheath,  to  be  inserted  by  a 
broad  attachment  into  the  pectineal  line  behind  the  conjoined  tendon.  In  some 
subjects  this  structure  is  not  very  prominently  marked,  and  not  infrequently  it  is 
altogether  wanting.  The  superficial  crural  arch  is  the  portion  of  Poupart's  liga- 
ment in  front  of  the  femoral  ring. 

The  Femoral  or  Crural  Canal  (canalis  femoralis)  (Figs.  297,  340,  and  1113)  is  the 
narrow  interval  between  the  femoral  vein  and  the  inner  wall  of  the  femoral  sheath. 
It  exists  as  a  distinct  canal  only  when  the  sheath  has  been  separated  from  the  vein 
by  dissection  or  by  the  pressure  of  a  hernia  or  tumor.  Its  length  is  from  a  quarter 
to  half  an  inch,  and  it  extends  from  the  femoral  ring  to  the  upper  part  of  the 
saphenous  opening. 

Its  anterior  wall  is  very  narrow,  and  formed  by  a  continuation  downward  of 
the  transversalis  fascia,  under  Poupart's  ligament,  covered  by  the  falciform 
process  of  the  fascia  lata. 

Its  posterior  wall  is  formed  by  a  continuation  downward  of  the  iliac  fascia  cover- 
ing the  pubic  portion  of  the  fascia  lata. 

Its  outer  wall  is  formed  by  the  fibrous  septum  separating  it  from  the  inner  side 
of  the  femoral  vein. 

Its  inner  wall  is  formed  by  the  junction  of  the  processes  of  the  transversalis 
and  iliac  fasciae,  which  form  the  inner  side  of  the  femoral  sheath,  and  lies  in 
contact  at  its  commencement  with  the  outer  edge  of  Gimbernat's  ligament. 

This  canal  has  two  orifices— an  upper  one,  the  femoral  or  crural  ring,  closed  by 
the  septum  crurale;  and  a  lower  one,  the  saphenous  opening,  closed  by  the  cribri- 
form fascia. 

The  femoral  or  crural  ring  (annulus  femoralis)  (Figs.  1113,  1124,  and  1125)  is 
the  upper  opening  of  the  femoral  canal,  and  leads  into  the  cavity  of  the  abdomen. 
It  is  bounded  in  front  by  Poupart's  ligament  and  the  deep  crural  arch;  behind, 
by  the  os  pubis,  covered  by  the  Pectineus  muscle  and  the  pubic  portion  of  the  fascia 
lata;  internally,  by  the  base  of  Gimbernat's  ligament,  the  conjoined  tendon,  the 
transversalis  fascia,  and  the  deep  crural  arch;  externally,  by  the  fibrous  septum 
lying  on  the  inner  side  of  the  femoral  vein.  The  femoral  ring  is  of  an  oval  form; 
its  long  diameter,  directed  transversely,  measures  about  half  an  inch,  and  it  is 
larger  in  the  female  than  in  the  male,  which  is  one  of  the  reasons  of  the  greater 
frequency  of  femoral  hernia  in  the  former  sex. 

Position  of  Parts  around  the  Ring. — The  spermatic  cord  in  the  male  and 
round  ligament  in  the  female  lie  immediately  above  the  anterior  margin  of  the 


1532 


THE  SURGICAL    ANATOMY   OF  HERNIA 


femoral  ring,  and  may  be  divided  in  an  operation  for  femoral  hernia  if  the  incision 
for  the  relief  of  the  stricture  is  not  of  limited  extent.  In  the  female  this  is  of  little 
importance,  but  in  the  male  the  spermatic  artery  and  vas  deferens  may  be  divided. 

The  femoral  vein  lies  on  the  outer  side  of  the  ring. 

The  deep  epigastric  artery  in  its  passage  upward  and  inward  from  the  external 
iliac  artery  passes  across  the  upper  and  outer  angle  of  the  crural  ring,  and  is 
consequently  in  danger  of  being  wounded  if  the  stricture  is  divided  in  a  direction 
upward  and  outward. 

The  communicating  branch  between  the  deep  epigastric  and  obturator  lies  in 
front  of  the  ring. 

The  circumference  of  the  ring  is  thus  seen  to  be  bounded  by  vessels  in  every 
part,  excepting  internally  and  behind  (Fig.  1125).  It  is  in  the  former  position  that 
the  stricture  is  divided  in  cases  of  strangulated  femoral  hernia. 

The  obturator  artery  (p.  688),  when  it  arises  by  a  common  trunk  with  the  deep 
epigastric  (p.  689),  which  occurs  once  in  every  three  subjects  and  a  half,  bears 
a  very  important  relation  to  the  crural  ring.     In  most  cases  it  descends  on  the 


Fig.  1125.— Hernia. 


The  relations  of  the  femoral  and  internal  abdominal  rings,  seen  from  within  the 
abdomen.     Right  side. 


inner  side  of  the  external  iliac  vein  to  the  obturator  foramen,  and  will  consequently 
lie  on  the  outer  side  of  the  crural  ring,  where  there  is  no  danger  of  its  being 
wounded  in  the  operation  for  dividing  the  stricture  in  femoral  hernia  (Fig.  427  A, 
p.  689).  Occasionally,  however,  the  obturator  artery  curves  along  the  free  margin 
of  Gimbernat's  ligament  in  its  passage  to  the  obturator  foramen;  it  would  conse- 
quently skirt  along  the  greater  part  of  the  circumference  of  the  crural  ring,  and 
could  hardly  avoid  being  wounded  in  the  operation  (Fig.  427  B,  p.  689). 

The  Crural  Septum  or  Septum  Crurale  (septum  femorale  muscuhis)  (Fig.  297). — 
The  femoral  ring  is  closed  by  a  thin  process  of  transversalis  fascia  containing  fat 
and  called,  by  J.  Cloquet,  the  septum  crurale.  This  serves  as  a  barrier  to  the 
protrusion  of  a  hernia  through  this  part.  Its  upper  surface  is  slightly  concave, 
and  supports  a  small  lymphatic  gland  (Fig.  1125),  by  which  it  is  separated  from 
the  subserous  areolar  tissue  and  peritoneum.  Its  under  surface  is  turned  toward 
the  femoral  canal.  The  septum  crurale  is  perforated  by  numerous  apertures  for 
the  passage  of  lymphatic  vessels  connecting  the  deep  inguinal  lymphatic  glands 
with  those  surrounding  the  external  iliac  artery. 


FEMORAL    HERNIA  I533 

The  size  of  the  femoral  canal,  the  degree  of  tension  of  its  orifices,  and  conse- 
quently the  degree  of  constriction  of  a  hernia,  vary  according  to  the  position  of 
the  limb.  If  the  leg  and  thigh  are  extended,  abducted,  or  everted,  the  femoral 
canal  and  its  orifices  are  rendered  tense  from  the  traction  on  these  parts  by  Pou- 
part's  ligament  and  the  fascia  lata,  as  may  be  ascertained  by  passing  the  finger 
along  the  canal.  If,  on  the  contrary,  the  thigh  is  flexed  upon  the  pelvis,  and  at 
the  same  time  adducted  and  rotated  inward,  the  femoral  canal  and  its  orifices 
become  considerably  relaxed;  for  this  reason  the  limb  should  always  be  placed  in 
the  latter  position  when  the  application  of  the  taxis  is  made  in  attempting  the 
reduction  of  a  femoral  hernia. 

The  subperitoneal  areolar  tissue  is  continuous  with  the  subserous  areolar  tissue 
of  surrounding  parts.  It  is  usually  thickest  and  most  fibrous  where  the  iliac  ves- 
sels leave  the  abdominal  cavity.  It  covers  over  the  femoral  ring,  the  small  interval 
on  the  inner  side  of  the  femoral  vein.  In  some  subjects  it  contains  a  considerable 
amount  of  adipose  tissue.  In  such  cases,  where  it  is  protruded  foi-ward  in  front 
of  the  sac  of  a  femoral  hernia,  it  may  be  mistaken  for  a  portion  of  omentum.  The 
peritoneum  lining  the  portion  of  the  abdominal  wall  between  Poupart's  ligament 
and  the  brim  of  the  pelvis  is  similar  to  that  lining  any  other  portion  of  the  abdom- 
inal wall,  being  very  thin.  Here  there  is  no  natural  aperture  for  the  escape  of 
intestine. 

Descent  of  the  Hernia. — From  the  preceding  description  it  follows  that  the 
femoral  ring  must  be  a  w^eak  point  in  the  abdominal  wall;  hence  it  is  that  when 
violent  or  long-continued  pressure  is  made  upon  the  abdominal  viscera  a  portion 
of  intestine  may  be  forced  into  it,  constituting  a  femoral  hernia;  and  the  changes 
in  the  tissues  of  the  abdomen  which  are  produced  by  pregnancy,  together  with  the 
larger  size  of  this  aperture  in  the  female,  serve  to  explain  the  frequency  of  this 
form  of  hernia  in  women. 

When  a  portion  of  the  intestine  passes  through  the  femoral  ring,  a  pouch  of 
peritoneum  lies  before  it,  which  forms  what  is  called  the  hernial  sac;  it  is  cov- 
ered by  the  subserous  areolar  tissue,  receives  an  investment  from  the  septum 
crurale,  and  descends  vertically  along  the  crural  canal  in  the  inner  compartment  of 
the  sheath  of  the  femoral  vessels  as  far  as  the  saphenous  opening;  at  this  point  it 
changes  its  course,  being  prevented  from  extending  farther  down  the  sheath  on 
account  of  the  narrowing  of  the  sheath  and  its  close  contact  with  the  vessels,  and 
also  from  the  close  attachment  of  the  superficial  fascia  and  crural  sheath  to  the 
lower  part  of  the  circumference  of  the  saphenous  opening;  the  hernia  is  conse- 
quently directed  forward,  pushing  before  it  the  cribriform  fascia,  and  then  curves 
upward  on  to  the  falciform  process  of  the  fascia  lata  and  lower  part  of  the  tendon 
of  the  External  oblique,  being  covered  by  the  superficial  fascia  and  integument. 
Wliile  the  hernia  is  contained  in  the  femoral  canal  it  is  usually  of  small  size, 
owing  to  the  resisting  nature  of  the  surrounding  parts;  but  when  it  has  escaped 
from  the  saphenous  opening  into  the  loose  areolar  tissue  of  the  groin,  it  becomes 
considerably  enlarged.  The  direction  taken  by  a  femoral  hernia  in  its  descent  is 
at  first  downward,  then  forward  and  upward;  this  should  be  borne  in  mind,  as 
in  the  application  of  the  taxis  for  the  reduction  of  a  femoral  hernia  pressure  should 
be  directed  in  the  reverse  order. 

Coverings  of  the  Complete  Hernia. — The  coverings  of  a  femoral  hernia,  from 
within  outward,  are— peritoneum,  subserous  areolar  tissue,  the  septum  crurale, 
crural  sheath,  cribriform  fascia,  superficial  fascia,  and  integument.* 


immedi 

SUrglCail  V  ,    lly     in    iiiiiy»/i  I  emu      Li/    »  t.»»iv,iii.^»^*       ,...w     ^-..■  — ^ '"'    ''      ~  '•  '  7  '  1  Ltr  •        c  iL  -i'  I  ~      1     *  I, 

account  of  the  ease  with  which  an  inexperienced  operator  may  mistake  the  fascia  for  the  peritoneal  sac  and  the 
contained  fat  for  omentum.  Anatomically,  this  fascia  appears  identical  with  what  is  called  m  the  text  sub- 
serous areolar  tissue,"  the  areolar  tissue  being  thickened  and  caused  to  assume  a  membranous  appearance  by 
the  pressure  of  the  hernia. — Ed.  of  15th  English  edition. 


1534  THE  SURGICAL    ANAT03IY    OF   HERNIA 

Varieties  of  Femoral  Hernia. — If  the  hernia  descends  along  the  femoral  canal  only 
as  far  as  the  saphenous  opening,  and  does  not  escape  from  this  aperture,  the  con- 
dition is  called  incomplete  femoral  hernia.  The  small  size  of  the  protrusion  in  this 
form  of  hernia,  which  is  due  to  the  firm  and  resisting  nature  of  the  canal  in 
which  it  is  contained,  renders  it  an  exceedingly  dangerous  variety,  from  the 
extreme  difficulty  of  detecting  the  existence  of  the  swelling,  especially  in  corpulent 
subjects.  The  coverings  of  an  incomplete  femoral  hernia,  named  from  without 
inward, are  as  follows :  the  integument,  superficial  fascia,  iliac  portion  of  fascia  lata, 
crural  sheath,  septum  crurale,  subserous  areolar  tissue,  and  peritoneum.  When, 
however,  the  hernia  protrudes  through  the  saphenous  opening  and  directs  itself 
forward  and  upward,  it  forms  a  complete  femoral  hernia,  the  coverings  of  which 
have  been  given  (p.  1533).  Occasionally  the  hernial  sac  descends  on  the  iliac 
side  of  the  femoral  vessels  or  in  front  of  these  vessels,  or  even  sometimes  behind 
them. 

The  seat  of  stricture  in  a  strangulated  femoral  hernia  varies ;  it  may  be  in  the 
peritoneum  at  the  neck  of  the  hernial  sac;  in  the  greater  number  of  cases  it  w^ould 
appear  to  be  at  the  point  of  junction  of  the  falciform  process  of  the  fascia  lata 
with  the  lunated  edge  of  Gimbernat's  ligament,  or  at  the  margin  of  the  saphenous 
opening  in  the  thigh.  The  stricture  should  in  every  case  be  divided  in  an  inward 
direction,  or  upward  and  inward,  and  the  extent  of  the  necessary  cut  in  the 
majority  of  cases  is  about  two  or  three  lines.  By  these  means  all  vessels  or 
other  structures  of  importance  in  relation  with  the  neck  of  the  hernial  sac  will 
be  avoided. 


SUEGICAL  ANATOIIY  OF  THE  PERINJIUM. 


Dissection. — The  student  should  select  a  well-developed  muscular  subject,  free  from  fat, 
and  the  dissection  should  be  commenced  early,  in  order  that  the  parts  may  be  examined  in  as 
recent  a  state  as  possible.  A  staff  having  been  introduced  into  the  bladder  and  the  subject 
placed  in  the  position  shown  in  Fig.  1126,  the  scrotum  should  be  raised  upward,  and  retained  in 
that  position,  and  the  rectum  moderately  distended  with  tow. 

The  Perinaeum  corresponds  to  the  inferior  aperture  or  outlet  of  the  pelvis.  Its 
deep  boundaries  are,  in  front,  the  pubic  arch  and  subpubic  ligament;  behind, 
the  tip  of  the  coccyx;  and  on  each  side,  the  rami  of  the  os  pubis  and  ischium,  the 
tuberosities  of  the  ischium,  and  great  sacro-sciatic  ligaments.  The  space  included 
by  these  boundaries  is  somewhat  lozenge-shaped,  and  is  limited  on  the  surface  of 


Fig.  1126. — Dissection  of  perinseum  and  ischio-rectal  region. 

the  body  by  the  scrotum  in  front,  by  the  buttocks  behind,  and  on  each  side  by  the 
inner  side  of  the  thigh.  A  line  drawn  transversely  between  the  anterior  parts  of 
the  tuberosities  of  the  ischium,  on  each  side,  in  front  of  the  anus,  divides  this  space 
into  two  portions.  The  anterior  portion  contains  the  penis  and  urethra,  and  is 
called  the  perinaeum  proper  or  genito-urinary  region.  The  posterior  portion  con- 
tains the  termination  of  the  rectum,  and  is  called  the  ischio-rectal  or  anal  region. 


ISCHIO-REOTAL  REGION. 

The  ischio-rectal  region  contains  the  termination  of  the  rectum  and  a  deep  fossa, 
filled  with  fat,  on  each  side  of  the  intestine,  between  it  and  the  tuberosity  of  the 
ischium;  this  is  called  the  ischio-rectal  fossa. 

The  ischio-rectal  region  presents  in  the  middle  line  the  aperture  of  the'anus; 
around  this  orifice  the  integument  is  thrown  into  numerous  folds,  which  are 
obliterated  on  distention  of  the  anus.  The  integument  is  of  a  dark  color,  con- 
tinuous with  the  mucous  membrane  of  the  rectum,  and  is  provided  with  numerous 

( 1535 ) 


1536  SURGICAL   ANATOMY    OF    THE   PERINEUM 

follicles,  which  occasionally  inflame  and  suppurate,  and  may  be  mistaken  for 
fistulae.  The  veins  around  the  margin  of  the  anus  are  occasionally  much  dilated, 
forming  a  number  of  hard  pendent  masses,  of  a  dark  bluish  color,  covered  partly 
by  mucous  membrane  and  partly  by  the  integument.  These  tumors  constitute  the 
disease  called  external  piles. 

Dissection  (Fig.  1126). — Make  an  incision  through  the  integument,  along  the  median  line, 
from  the  base  of  the  scrotum  to  the  anterior  extremity  of  the  anus:  carry  it  around  the  margins 
of  this  aperture  to  its  posterior  extremity,  and  continue  it  backward  to  about  an  inch  behind 
the  tip  of  the  coccyx.  A  transverse  incision  should  now  be  carried  across  the  base  of  the  scrotum, 
joining  the  anterior  extremity  of  the  preceding;  a  second,  carried  in  the  same  direction,  should 
be  made  in  front  of  the  anus;  and  a  third  at  the  posterior  extremity  of  the  first  incision.  These 
incisions  should  be  sufficiently  extensive  to  enable  the  dissector  to  raise  the  integument  from 
the  inner  side  of  the  thighs.  The  flaps  of  skin  corresponding  to  the  ischio-rectal  region  should 
now  be  removed.  In  dissecting  the  integument  from  this  region  great  care  is  recfuired,  otherwise 
the  Corrugator  cutis  ani  and  External  sphincter  will  be  removed,  as  they  are  intimately  adherent 
to  the  skin. 

The  Superficial  Fascia  is  exposed  on  the  removal  of  the  skin;  it  is  very  thick, 
areolar  in  texture,  and  contains  much  fat  in  its  meshes.  In  it  are  found  ramifying 
two  or  three  branches  of  the  perforating  cutaneous  nerve;  these  turn  around  the 
inferior  border  of  the  Gluteus  maximus  and  are  distributed  to  the  integument 
around  the  anus. 

In  this  region,  and  connected  with  the  lower  end  of  the  rectum,  are  four  muscles: 
the  Corrugator  cutis  ani;  the  two  Sphincters,  External  and  Internal;  and  the 
Levator  ani. 

These  muscles  have  been  already  described  (p.  449). 

The  Ischio-rectal  Fossa  {fossa  ischiorectalis)  (P'igs.  300  and  304)  is  situated 
between  the  end  of  the  rectum  and  the  ischial  tuberosity.  It  is  triangular  in  shape; 
its  base,  directed  to  the  surface  of  the  body,  is  formed  by  the  integument  of  the 
ischio-rectal  region;  its  apex,  directed  upward,  corresponds  to  the  point  of  division 
of  the  obturator  fascia  and  the  thin  membrane  given  off  from  it,  which  covers  the 
outer  surface  of  the  Levator  ani  (ischio-rectal  or  anal  fascia).  Its  dimensions  are 
about  an  inch  in  breadth  at  the  base  and  about  two  inches  in  depth,  being  deeper 
behind  than  in  front.  It  is  bounded,  internally,  by  the  Sphincter  ani,  Levator 
ani,  and  Coccygeus  muscles;  externally,  by  the  tuberosity  of  the  ischium  and  the 
obturator  fascia,  which  covers  the  inner  surface  of  the  Obturator  internus  muscle; 
in  front,  it  is  limited  by  the  line  of  junction  of  the  superficial  fascia  with  the  base 
of  the  triangular  ligament;  and  behind,  by  the  margin  of  the  Gluteus  maximifs 
muscle  and  the  great  sacro-sciatic  ligament.  This  space  is  filled  with  a  large  mass 
of  adipose  tissue,  which  explains  the  frequency  with  which  abscesses  in  the  neigh- 
borhood of  the  rectum  burrow  to  a  considerable  depth. 

If  the  subject  has  been  injected,  on  placing  the  finger  on  the  outer  wall  of  this 
fossa  the  internal  pudic  artery,  with  its  accompanying  veins  and  the  two  divisions 
of  the  nerve,  will  be  felt  about  an  inch  and  a  half  above  the  margin  of  the  ischiatic 
tuberosity,  but  approaching  nearer  the  surface  as  they  pass  forward  along  the 
inner  margin  of  the  pubic  arch.  These  structures  are  enclosed  in  a  sheath,  the 
fascial  canal  or  canal  of  Alcock  (Figs.  304  and  1131),  formed  by  the  obturator  fascia, 
the  pudic  nerve  lying  below  the  artery  and  the  dorsal  nerve  of  the  penis  above  it. 
Crossing  the  space  transversely,  about  its  centre  are  the  inferior  hemorrhoidal 
vessels  and  nerves,  which  are  distributed  to  the  integument  of  the  anus  and  to  the 
muscles  of  the  lower  end  of  the  rectum.  These  vessels  are  occasionally  of  large 
size,  and  may  give  rise  to  troublesome  hemorrhage  when  divided  in  the  operation 
of  lithotomy  or  in  that  for  fistula  in  ano.  At  the  back  part  of  this  space,  near 
the  coccyx,  may  be  seen  a  branch  of  the  fourth  sacral  nerve,  and  at  the  forepart  of 
the  space  the  superficial  perineal  vessels  and  nerves  can  be  seen  for  a  short  distance. 


THE   PERINEUM  PROPER    IN    THE    MALE  1537 

THE  PERIN-fflUM  PROPER  IN  THE  MALE. 

The  perineal  space  is  of  a  triangular  form;  its  deep  boundaries  are  limited, 
laterally,  by  the  rami  of  the  pubic  bones  and  ischia,  meeting  in  front  at  the  pubic 
arch;  behmd,  by  an  imaginary  transverse  line  extending  between  the  anterior 
parts  of  the  tuberosities  of  the  ischia.  The  lateral  boundaries  are,  in  the  adult, 
from  three  inches  to  three  inches  and  a  half  in  length,  and  the  base  from  two  to 
three  inches  and  a  half  in  breadth,  the  average  extent  of  the  space  being  two 
inches  and  three-quarters. 

The  variations  in  the  diameter  of  this  space  are  of  extreme  interest  in  connection  with  the 
operation  of  hthotomy  and  the  extraction  of  a  stone  from  the  cavity  of  the  bladder.  In  those 
cases  where  the  tuberosities  of  the  ischia  are  near  together  it  would  be  necessary  to  make  the 
incisions  in  the  lateral  operation  of  hthotomy  less  obhque  than  if  the  tuberosities  were  widely 
separated,  and  the  perineal  space  consequently  wider.  The  perinseum  is  subdivided  by  the 
median  raphe  into  two  equal  parts.  Of  these,  the  left  is  the  one  in  which  the  operation  of  lith- 
otomy is  performed. 

In  the  middle  line  the  perinseum  is  convex,  and  corresponds  to  the  bulb  of  the 
urethra.  The  skin  covering  it  is  of  a  dark  color,  thin,  freely  movable  upon  the 
subjacent  parts,  and  covered  with  sharp  crisp  hairs,  which  should  be  removed 
before  the  dissection  of  the  part  is  commenced.  In  front  of  the  anus  a  prominent 
line  commences,  the  raph^,  continuous  in  front  with  the  raphd  of  the  scrotum. 
The  skin  of  the  raphe  is  adherent  to  the  deep  layer  of  the  superficial  fascia. 

Upon  removing  the  skin  and  the  superficial  layer  of  the  superficial  fascia,  in  the 
manner  shown  in  Fig.  1126,  a  plane  of  fascia  will  be  exposed,  covering  in  the 
triangular  space  and  stretching  across  from  one  ischio-pubic  ramus  to  the  other. 
This  is  the  deep  layer  of  the  superficial  fascia  or  fascia  of  CcUes  (fascia  superficialis 
perinaei).  It  has  already  been  described  (p.  456).  It  is  a  layer  of  considerable 
strength,  and  encloses  and  covers  a  space  in  which  are  contained  muscles,  vessels, 
and  nerves.  It  is  continuous  in  front  with  the  fascia  of  the  penis  and  the  dartos 
of  the  scrotum ;  on  each  side  it  is  firmly  attached  to  the  margin  of  the  ischio-pubic 
ramus  and  to  the  tuberosity  of  the  ischium;  and  posteriorly  it  curves  down  behind 
the  Transversalis  perinaei  muscles  to  join  the  base  of  the  triangular  ligament. 

It  is  between  this  layer  of  fascia  and  the  triangular  ligament  of  the  urethra  that  extravasa- 
tion of  urine  most  frequently  takes  place  in  cases  of  rupture  of  the  urethra.  The  triangular 
ligament  of  the  urethra  (p.  459)  is  attached  to  the  ischio-pubic  rami,  and  in  front  to  the  subpubic 
ligament.  It  is  clear,  therefore,  that  when  extravasation  of  fluid  takes  place  between  these 
two  layers,  it  cannot  pass  backward,  because  the  two  layers  are  continuous  with  each  other 
around  the  Transversi  perinaei  muscles:  it  cannot  extend  laterally,  on  account  of  the  connection 
of  both  these  layers  to  the  rami  of  the  os  pubis  and  ischium ;  it  cannot  find  its  way  into  the  pelvis 
because  the  opening  into  this  cavity  is  closed  by  the  triangular  ligament,  and,  therefore,  so 
long  as  these  two  layers  remain  intact,  the  only  direction  in  which  the  fluid  can  make  its  way 
is  forward  into  the  areolar  tissue  of  the  scrotum  and  penis,  and  then  on  to  the  anterior  wall  of 
the  abdomen. 

\^^len  the  deep  layer  of  the  superficial  fascia  is  removed  (Fig.  1127),  a  space  is 
exposed,  between  this  fascia  and  the  triangular  ligament,  in  which  are  contained  the 
superficial  perineal  vessels  and  nerves  and  some  of  the  muscles  connected  with  the 
penis  and  urethra— viz.,  in  the  middle  line,  the  Accelerator  urinae;  on  each  side, 
the  Erector  penis;  and  behind,  the  transversus  perinaei;  together  with  the_ crura 
of  the  corpora  cavernosa  and  the  bulb  of  the  corpus  spongiosum.  Here  also  is  seen 
the  central  tendinous  point  of  the  perinaeum.  This  is  a  fibrous  point  in  the  middle 
line  of  the  perineum  between  the  urethra  and  the  rectum,  being  about  half  an  inch 
in  front  of  the  anus.  At  this  point  four  muscles  converge  and  are  attached— viz., 
the  External  sphimjter  ani,  the  Accelerator  urinae,  and  the  two  Transversi  perinaei 

97 


1538 


SURGICAL    ANAT03IY   OF    THE   PERINEUM 


muscles;  so  that  by  the  contraction  of  these  muscles,  which  extend  in  opposite 
directions,  it  serves  as  a  fixed  point  of  support. 

The  Accelerator  urinae,  the  Erector  penis,  and  the  Superficial  transversus 
perinaei  muscles  have  been  already  described  (p.  457).  They  form  a  triangular 
space  (Fig.  1127),  bounded,  internally,  by  the  Accelerator  urinae;  externally,  by 
the  Erector  penis;  and  behind,  by  the  Transversus  perinaei.  The  floor  of  this 
space  is  formed  by  the  triangular  ligament  of  the  urethra;  and  running  from, 
behind  forward  in  it  are  the  superficial  perineal  vessels  and  nerves,  and  the 
transverse  perineal  artery  coursing  along  the  posterior  boundary  of  the  space, 
on  the  Transversus  perinaei  muscle. 

The  Accelerator  urinae  and  Erector  penis  should  now  be  removed,  when  the  triangular  liga- 
ment of  the  urethra  will  be  exposed,  stretching  across  the  front  of  the  outlet  of  the  pelvis.  The 
urethra  is  seen  perforating  its  centre,  just  behind  the  bulb;  and  on  each  side  is  the  crus  penis, 
connecting  the  corpus  cavernosum  with  the  rami  of  the  ischium  and  os  pubis. 


Transversus  perinei 
superfidalis. 


GREAT  SACRO- 
SCIATIC   LIGAMENT. 


Superficial  perineal  artery. 
Superficial  perineal  nerve. 
Internal  piidic  nerve. 
Internal  pudic  artery. 


Fig.  1127. — The  superficial  muscles  and  vessels  of  the  perinsRum. 

The  Triangular  Ligament  or  the  Deep  Perineal  Fascia  (trigonum  urogenitale  or 
diaphragma  urogenitale)  (Figs.  309,  310,  and  1128),  which  has  been  already 
described  (p.  459),  consists  of  two  layers,  the  inferior  anterior  or  superficial  layer 
(fascia  trigoni  urogenitalis  inferior)  of  which  is  now  exposed.  It  is  united  to  the 
superior  or  deep  layer  behind,  but  is  separated  in  front  by  a  subfascial  space  in 
which  are  contained  certain  structures. 

The  inferior  layer  of  the  triangular  ligament  (Figs.  305  an  1  310)  consists  of  a 
strong  fibrous  membrane,  the  fibres  of  which  are  disposed  transversely,  which 
stretches  across  from  one  ischio-pubic  ramus  to  the  other  and  completely  fills  in 
the  pubic  arch;  it  is  attached  in  front  to  the  subpubic  ligament,  except  just  in  the 
centre,  where  a  small  interspace  is  left  for  the  dorsal  vein  of  the  penis.  In  the  erect 
position  of  the  body  it  is  almost  horizontal.  It  is  perforated  by  the  urethra  in  the 
middle  line,  and  on  each  side  of  the  urethral  opening  by  the  ducts  of  Cowper's 
glands  and  by  the  arteries  of  the  bulb;  in  front,  and  external  to  this,  by  the  artery 


THE   PERINEUM  PROPER  IN    THE   MALE  1539 

of  the  corpus  cavernosum,  immediately  before  this  vessel  enters  the  crus  penis 
Near  its  apex  the  ligament  is  perforated  by  the  termination  of  the  pudic  artery  and 
by  the  dorsal  nerve  of  the  penis.  The  apex  of  the  triangular  ligament  is  known  as 
the  transverse  perineal  ligament.  The  crura  penis  are  exposed,  lying  superficial  to 
this  ligament.  They  will  be  seen  to  be  attached  by  blunt-pointed  processes  to  the 
rami  of  the  os  pubis  and  ischium,  in  front  of  the  tuberosities,  and  passing  forward 
and  inward,  joining  to  form  the  body  of  the  penis.  In  the  middle  line  the  bulb  and 
corpus  spongiosum  are  exposed  by  the  removal  of  the  Accelerator  urinae  muscle. 
If  the  inferior  layer  of  the  triangular  ligament  is  detached  on  either  side, 
the  deep  perineal  interspace  will  be  exposed  and  the  following  parts  will  be  seen 
between  it  and  the  deep  layer  of  the  ligament:  the  subpubic  ligament  in  front, 
close  to  the  symphysis  pubis;  the  dorsal  vein  of  the  penis;  the  membranous  por- 
tion of  the  urethra  and  the  Compressor  urethrae  muscle;  Cowper's  glands  and 
their  ducts;  the  pudic  vessels  and  the  dorsal  nerve  of  the  penis;  the  artery  and 
nerve  of  the  bulb  and  a  plexus  of  veins. 


Anterior  layer  of 

deep  perineal  fascia  removed, 

showing 

.^COMPRESSOR   URETHR>E. 

Jnternal  pudic  artery. 
Artery  of  the  bulb. 
Cowper's  gland. 


Fig.  1128. — Deep  perineal  fascia.     On  the  left  side  the  anterior  layer  has  been  removed. 

The  superior,  deep,  or  posterior  layer  of  the  triangular  ligament  or  deep  perineal 
fascia  (fascia  trigoni  urogenitalis  superior)  {iig.  305)  is  derived  from  the  obturator 
fascia,  and  is  continuous  with  it  along  the  pubic  arch.  Behind,  it  joins  with  the 
inferior  layer  of  the  triangular  ligament,  and  is  continuous  with  the  anal  fascia. 
Above  it  is  the  prostate  gland  (Fig.  1129),  supported  by  the  anterior  fibres  of 
the  Levator  ani,  which  act  as  a  sling  for  the  gland  and  form  the  Levator  prostatae 
muscle.  The  superior  layer  of  the  triangular  ligament  is  continuous  around  the 
anterior  free  edge  of  this  muscle  with  the  layer  of  recto-vesical  fascia  covering 
the  prostate  gland.  The  superior  layer  of  the  triangular  ligament  is  perforated 
by  the  urethra.  Between  the  two  layers  of  the  triangular  ligament  are  situated 
the  membranous  part  of  the  urethra,  enveloped  by  the  Compressor  urethrae 
muscle  (Fig.  309);  the  ducts  of  Cowper's  glands;  the  arteries  to  the  bulb;  the 
pudic  vessels  and  the  dorsal  nerve  of  the  penis.  The  membranous  part  of  the 
urethra  is  about  three-quarters  of  an  inch  in  length,  and  passes  downward  and 


1540 


SURGICAL    ANATOMY   OF   THE  PERINEUM 


forward  behind  the  symphysis  pubis,  from  which  it  is  distant  about  an  inch.  It 
is  the  narrowest  part  of  the  tube,  and  is  enveloped,  as  has  already  been  stated, 
by  the  Compressor  urethrae  muscle. 

The  Compressor  urethrae  has  already  been  described  (p.  460).  In  addition  to 
this  muscle,  and  immediately  beneath  it,  circular  muscular  fibres  surround  the 
membranous  portion  of  the  urethra  from  the  bulb  in  front  to  the  prostate  behind, 
and  are  continuous  with  the  muscular  fibres  of  the  bladder.  These  fibres  are 
involuntary. 

Cowper's  glands  (Figs.  303,  1128,  and  1129)  are  situated  immediately  below 
the  membranous  portion  of  the  urethra,  close  behind  the  bulb,  and  below  the 
artery  of  the  bulb. 

The  Pudic  Vessels  (Figs.  1128  and  1129)  and  Dorsal  Nerve  of  the  Penis  (Fig.  310) 
are  placed  along  the  inner  margin  of  the  pubic  arch  (p.  1536). 

The  Artery  of  the  Bulb  (Figs.  1128  and  1129,  and  p.  691)  passes  transversely 
inward,  from  the  internal  pudic  artery  (p.  689)  along  the  base  of  the  triangular 


Avtery  of  corpus  cavernosum. 
Dorsal  artery  of  penis. 


Artery  of  bulb. 
Internal  pudic  artery, 


Cowper's  gland. 


Fig.  1129. — A  view  of  the  position  of  the  viscera  at  the  outlet  of  the  pelvis. 

ligament,  between  its  two  layers,  accompanied  by  a  branch  of  the  pudic  nerve. 
If  the  superior  layer  of  the  triangular  ligament  is  removed  and  the  crus  penis  of 
one  side  detached  from  the  bone,  the  under  or  perineal  surface  of  the  Levator 
ani  muscle,  covered  by  the  anal  fascia,  is  brought  fully  into  view  (Figs.  302, 
303,  and  304).  This  muscle,  with  the  triangular  ligament  in  front  and  the  Coc- 
cygeus  and  Pyriformis  behind,  closes  the  outlet  of  the  pelvis. 

The  Levator  ani  and  Coccygeus  muscles  have  already  been  described  (p.  451). 

Position  of  the  Viscera  at  the  Outlet  of  the  Pelvis.—  Divide  the  central  tendinous  point 
of  the  perinseum,  separate  the  rectum  from  its  connections  by  dividing  the  fibres  of  the  Levator 
ani,  which  descend  upon  the  sides  of  the  prostate  gland,  and  draw  the  gut  backward  toward  the 
coccyx,  when  the  under  surface  of  the  prostate  gland,  the  neck  and  base  of  the  bladder,  the 
vesiculse  seminales,  and  the  vasa  deferentia  will  be  exposed. 

The  Prostate  Gland  (p.  1129)  is  a  pale,  firm,  glandular  body  A^hich  is  placed 
immediately  below  the  neck  of  the  bladder,  around  the  commencement  of  the 


THE   PERINEUM  PROPER   IN   THE  MALE  1541 

urethra.  It  is  placed  in  the  pelvic  cavity,  behind  the  lower  part  of  the  sym- 
physis pubis,  above  the  superior  layer  of  the  triangular  ligament,  and  rests  upon 
the  rectum,  through  which  it  may  be  distinctly  felt,  especially  when  enlarged.  In 
shape  and  size  it  resembles  a  chestnut.  Its  base  is  directed  upward  toward  the 
neck  of  the  bladder.  Its  apex  is  directed  downward  to  the  deeper  layer  of  the 
triangular  ligament,  which  it  touches. 

Its  posterior  surface  is  smooth,  marked  by  a  slight  longitudinal  furrow,  and  rests 
on  the  second  part  of  the  rectum,  to  which  it  is  connected  by  areolar  tissue.  Its 
anterior  surface  is  flattened,  marked  by  a  slight  longitudinal  furrow,  and  placed 
about  three-quarters  of  an  inch  below  the  pubic  symphysis.  It  measures  about 
an  inch  and  a  half  in  its  transverse  diameter  at  the  base,  an  inch  in  its  antero- 
posterior diameter,  and  three-quarters  of  an  inch  in  depth.  Hence  the  greatest 
extent  of  incision  that  can  be  made  in  it  without  dividing  its  substance  completely 
across  is  obliquely  backward  and  outward.  This  is  the  direction  in  which  the 
incision  is  made  in  it  in  the  lateral  operation  of  lithotomy.  The  prostate  has  a 
sheath  derived  from  the  recto-vesical  fascia  (p.  1449). 

Above  the  prostate  a  small  triangular  portion  of  the  bladder  is  seen  (Fig.  1129), 
bounded,  in  front  and  below,  by  the  prostate  gland;  above,  by  the  recto-vesical  fold 
of  the  peritoneum;  on  each  side,  by  the  seminal  vesicle  and  the  vas  deferens.  It  is 
separated  from  direct  contact  with  the  rectum  by  the  recto-vesical  fascia.  The 
relation  of  this  portion  of  the  bladder  to  the  rectum  is  of  extrem.e  interest  to  the 
surgeon.  In  cases  of  retention  of  urine  this  portion  of  the  organ  is  found  pro- 
jecting into  the  rectum,  between  three  and  four  inches  from  the  margin  of  the 
anus,  and  may  be  easily  perforated  without  injury  to  any  important  parts.  This 
portion  of  the  bladder  was  consequently  selected  in  the  old  days  for  the  perform- 
ance of  the  now  obsolete  operation  of  tapping  the  bladder. 

Surgical  Anatomy.  Median  Lithotomy. — As  the  incision  is  in  the  raph^,  the  hemor- 
rhage is  trivial,  and  there  is  but  slight  risk  of  injuring  the  pelvic  fascia.  But  the  operation  gives 
little  room  for  manipulation  and  is  inadmissible  in  children,  because  in  them  dilatation  of  the 
wound  may  tear  the  bladder  loose  from  the  urethra.  A  risk  of  median  lithotomy  is  division  of 
the  artery  of  the  bulb. 

In  median  lithotomy  a  grooved  staff  is  introduced,  the  groove  being  median.  The  knife  is 
introduced  in  the  mid-line,  just  in  front  of  the  anal  m.argin,  and  hits  the  staff  near  the  apex 
of  the  prostate;  the  entire  length  of  the  membranous  urethra  is  cut  as  the  instrument  is  with- 
drawn. 

Parts  Divided. — Skin,'  superficial  fascia,  sphincter  ani  muscle,  central  tendon  of  the 
perinseum,  inferior  leaf  of  the  triangular  ligament,  membranous  urethra,  and  the  Compressor 
urethrae  muscle. 

Lateral  Lithotomy.—  The  operation  is  performed  on  the  left  side  of  the  perinseum,  as  this 
is  most  convenient  for  the  right  hand  of  the  operator.  A  grooved  staff  having  been  introduced 
into  the  bladder,  the  first  incision  is  commenced  midway  between  the  anus  and  the  back  of 
the  scrotum  {i.  e.,  in  an  ordinary  adult  perinseurn  about  an  inch  and  a  half  in  front  of  the  anus) 
a  litde  on  the  left  side  of  the  raphe,  and  is  carried  obliquely  backward  and  outward  to  midway 
between  the  anus  and  tuberosity  of  the  left  ischium.  The  incision  divides  the  integument  and 
superficial  fascia,  the  inferior  hemorrhoidal  vessels  and  nerves,  and  the  superficial  and  trans- 
verse perineal  vessels.  If  the  forefinger  of  the  left  hand  is  thrust  upward  and  forward  inlo 
the  wound,  pressing  at  the  same  time  the  rectum  inward  and  backward,  the  staff  may  be  felt  in 
the  membranous  portion  of  the  urethra.  The  finger  is  fixed  upon  the  staff",  and  the  structures 
covering  the  staff  are  divided  with  the  point  of  the  knife,  which  must  be  directed  along  the  groove 
toward  the  bladder,  the  edge  of  the  knife  being  turned  outward  and  backward,  dividing  in  its 
course  the  membranous  portion  of  the  urethra  and  part  of  the  left  lobe  of  the  prostate  gland 
to  the  extent  of  about  an  inch.  The  knife  is  then  withdrawn,  and  the  forefinger  of  the  left  hand  , 
passed  along  the  staff  into  the  bladder.  The  position  of  the  stone  having  been  ascertained,  the 
staff  is  to  be  withdrawn,  and  the  forceps  is  introduced  over  the  finger  into  the  bladder.  If  the 
stone  is  very  large,  the  opposite  side  of  the  prostate  may  need  to  be  notched  before  the  forceps 
is  introduced;  the  finger  is  now  withdrawn,  and  the  blades  of  the  forceps  opened  and  made  to 
grasp  the  stone,  which  must  be  extracted  by  slow  and  cautious  undulating  movements. 

Parts  Divided  in  the  Operation.— The  various  structures  divided  in  this  operation  are  as 
follows:  the  integument,  superficial  fascia,  inferior  hemorrhoidal  vessels  and  nerves,  and  prob- 


1542  SURGICAL    ANATOMY    OF    THE    PERINEUM 

ably  the  superficial  perineal  vessels  and  nerves,  the  posterior  fibres  of  the  Accelerator  urinae 
muscle,  the  Transversus  perinaei  muscle  and  artery,  the  triangular  ligament,  the  anterior  fibres  of 
the  Levator  ani  muscle,  part  of  the  Compressor  urethrae  muscle,  the  membranous  and  pros- 
tatic portions  of  the  urethra,  and  part  of  the  prostate  gland. 

Parts  to  be  Avoided  in  the  Operation. — In  making  the  necessary  incisions  in  the  perinseum  for 
the  extraction  of  a  calculus  the  following  parts  should  be  avoided:  The  primary  incision  should 
not  be  made  too  near  the  middle  line,  for  fear  of  wounding  the  bulb  of  the  corpus  spongiosum 
or  the  rectum ;  nor  too  far  externally,  otherwise  the  internal  pudic  artery  may  be  implicated  as  it 
ascends  along  the  inner  border  of  the  pubic  arch.  If  the  incisions  are  carried  too  far  forward, 
the  artery  of  the  bulb  may  be  divided ;  if  carried  too  far  backward,  the  entire  breadth  of  the  pros- 
tate and  neck  of  the  bladder  may  be  cut  through,  which  allows  the  urine  to  become  infiltrated 
behind  the  pelvic  fascia  into  the  loose  areolar  tissue  between  the  bladder  and  rectum,  instead 
of  escaping  externally;  diffuse  inflammation  is  consequently  set  up,  and  peritonitis,  from  the 
close  proximity  of  the  recto-vesical  peritoneal  fold,  is  the  result.  If,  on  the  contrary,  only  the 
anterior  part  of  the  prostate  is  divided,  the  urine  makes  its  way  externally,  and  there  is  less 
danger  of  infiltration  taking  place. 

During  the  operation  it  is  of  great  importance  that  the  finger  should  be  passed  into  the  bladder 
before  the  staff  is  removed;  if  this  is  neglected,  and  if  the  incision  made  in  the  prostate  and  neck 
of  the  bladder  is  too  small,  great  difficulty  may  be  experienced  in  introducing  the  finger  afterward; 
and  in  the  child,  where  the  connections  of  the  bladder  to  the  surrounding  parts  are  very  loose, 
the  force  made  in  the  attempt  is  sufficient  to  displace  the  bladder  upward  into  the  abdomen, 
out  of  the  reach  of  the  operator.  Such  a  proceeding  has  not  unfrequently  occurred,  producing 
the  most  embarrassing  results  and  total  failure  of  the  operation. 

It  is  necessary  to  bear  in  mind  that  the  arteries  in  the  perinseum  occasionally  take  an  abnormal 
course.  Thus  the  artery  of  the  bulb,  when  it  arises,  as  sometimes  happens,  from  the  pudic 
opposite  the  tuber  ischii,  is  liable  in  its  passage  forward  to  the  bulb  to  be  wounded  in  the 
operation  of  lithotomy.  The  accessory  pudic  may  be  divided  near  the  posterior  border  of  the 
prostate  gland,  if  this  gland  is  completely  cut  across;  and  if  the  prostatic  veins  are  of  large  size, 
and  give  rise,  when  divided,  to  troublesome  hemorrhage.  In  men  advanced  in  years  the  pros- 
tatic veins  are  very  apt  to  be  enlarged. 

Extravasation  of  Urine. — Extravasation  most  commonly  occurs  from  urethral  rupture, 
between  Colles's  fascia  and  the  triangular  ligament  of  the  urethra  (extravasation  in  front  of 
the  triangular  ligament).  The  adherence  of  these  two  fascial  layers  posteriorly  prevents  the 
urine  from  passing  backward.  The  urine  cannot  find  a  way  laterally,  because  both  layers  on 
each  side  are  attached  to  the  rami  of  the  pubes  and  ischium.  It  cannot  reach  the  pelvis,  because 
the  triangular  ligament  bars  the  way.  It  can  only  go  forward  if  the  two  fascial  layers  remain 
intact,  and  consequently  the  urine  passes  into  the  areolar  tissue  of  the  scrotum  beneath  the 
superficial  fascia  of  the  penis  and  of  the  anterior  abdominal  wall. 

Pus  and  blood  would  pursue  the  same  course  in  this  space.  Effusions  in  this  space  causes 
much  pain,  because  the  space  contains  the  three  long  scrotal  nerves. 

In  rupture  of  the  urethra  between  the  two  layers  of  the  triangular  ligament,  the  urine  remains 
in  this  situation  as  long  as  fascia  remains  intact.  If  suppuration  occurs,  destruction  of  fascia 
liberates  the  urine. 

In  rupture  behind  the  superior  layer  of  the  triangular  ligament  (extravasation  back  of  the 
triangular  ligament),  the  urine  passes  intD  the  ischio-rectal  fossa  and  upward  and  backward 
into  the  pelvis. 


THE  FEMALE  PERINiEUM. 

The  female  perinseum  presents  certain  differences  from  that  of  the  male,  in 
consequence  of  the  whole  of  the  structures  which  constitute  it  being  perforated 
in  the  middle  line  by  the  vulvo-vaginal  passage. 

The  Superficial  Fascia,  as  in  the  male,  consists  of  two  layers,  of  which  the 
superficial  one  is  continuous  with  the  superficial  fascia  over  the  rest  of  the  body, 
and  the  deep  layer,  corresponding  to  the  fascia  of  Colles  in  the  male,  is,  like  it, 
attached  to  the  ischio-pubic  rami,  and  in  front  is  continued  forward  through 
the  labia  majora  to  the  inguinal  region.  It  is  of  less  extent  than  in  the  male, 
in  consequence  of  being  perforated  by  the  aperture  of  the  vulva. 

On  removing  this  fascia  the  muscles  of  the  female  perinjeum,  which  have 
already  been  described  (p.  461),  are  exposed  (Figs.  311  and  1130).  The  Sphincter 
vaginae,  corresponding  to  the  Accelerator  urinae  in  the  male,  consists  of  an  atten- 


THE   FEMALE   PERINJEUM 


1543 


uated  plane  of  fibres,  forming  an  orbicular  muscle  around  the  orifice  of  the 
vagina,  instead  of  being  united  in  a  median  raphe,  as  in  the  male.  The  Erector 
clitoridis  is  proportionately  reduced  in  size,  but  differs  in  no  other  respect  from 
the  erector  penis,  and  the  Transversus  perinaei  is  similar  to  the  muscle  of  the 
same  name  in  the  male. 

The  triangular  ligament  (Fig.  1130)  is  not  strongly  marked  as  in  the  male. 
It  transmits  the  urethra  and  the  tube  of  the  vagina. 

The  Compressor  Urethrae  corresponds  with  the  Compressor  urethrae  in  the  male. 
It  arises  from  the  ischio-pubic  ramus,  and,  passing  inward,  its  anterior  fibres  blend 
with  the  muscle  of  the  opposite  side,  in  front  of  the  urethra;  its  middle  fibres,  the 
most  numerous,  are  inserted  into  the  side  of  the  vagina,  and  the  posterior  fibres 
join  the  central  point  of  the  perinseum. 


Suspensoi-p  ligavmit 
of  clitoris 


Glans  clitoris 


Erector 

clitoridie 

muscle 


Sphincter 

vaginae 

muscle 


Deep  perineal 
muscle,  with, 
its  under 
layer  of  fascia 
{the  triangular 
iigament) 


External 
obturator 
muscle 


Sacro- 
sciatic 
ligament 


Gluteus  mazimus 

muscle  ^^  ^^'^'^y^ 

Fig.  1130. — The  female  perinsDum  after  removal  of  the  skin  and  superficial  fascia 


External  sphincter 
ani  muscle 


(Bardeleben.) 


The  distribution  of  the  internal  pudic  artery  is  the  same  as  in  the  male  (p. 1540), 
and  the  pudic  nerve  has  also  a  similar  arrangement,  the  dorsal  nerve  being, 
however,  very  small  and  supplying  the  clitoris. 

The  corpus  spongiosum  is  divided  into  two  lateral  halves,  which  are  represented 
by  the  bulbi  vestibuli  and  partes  intermediales. 

The  Perineal  Body  fills  up  the  interval  between  the  lower  part  of  the  vagina 
and  the  rectum.     Its  base  is  covered  by  the  skin  lying  between  the  anus  and 


1544 


SURGICAL    ANATOMY    OF   THE   PERINEUM 


vagina  on  what  is  called  the  perinseum.  Its  anterior  surface  Hes  behind  the  pos- 
terior vaginal  wall,  and  its  posterior  surface  lies  in  front  of  the  anterior  rectal 
wall  and  the  anus.  It  measures  about  an  inch  and  a  quarter  from  before  back- 
ward, and  laterally  extends  from  one  tuberosity  of  the  ischium  to  the  other.  In  it 
are  situated  the  muscles  belonging  to  the  external  organs  of  generation.  Through 
its  centre  runs  the  transverse  perineal  septum,  which  is  of  great  strength  in  women, 
and  forms  on  either  side,  behind  the  posterior  commissure,  a  hard,  ill-defined 
body,  consisting  of  connective  tissue,  with  much  yellow  elastic  tissue  and  inter- 
lacing bundles  of  involuntary  muscular  fibres,  in  which  the  voluntary  muscles  of 
the  perineum  are  inserted. 

The  Pelvic  Fascia  (fascia  pelvis)  (Figs.  304  and  1131). — The  pelvic  fascia 
strengthens  the  floor  of  the  pelvis,  fastens  pelvic  structures  together,  and  supports 
the  nerves,  blood-vessels,  and  lymphatics.     It  is  connected  above  with  the  trans- 


Internal  pudic  vessels 
and  nerve. 


Tuberosity  of 
ischium. 

Fig.  1 131. — A  transverse  section  of  the  pelvis,  showing  the  pelvic  fascia  from  behind. 

versalis  fascia  and  the  iliac  fascia.  It  is  at  first  a  thin  membrane  and  covers  the 
inner  surface  of  the  pelvis,  being  attached  to  the  brim  for  a  short  flistance  at  the 
side  of  the  cavity  and  to  the  inner  surface  of  the  bone  around  the  attachment  of 
the  Obturator  internus.  At  the  posterior  portion  of  this  muscle  it  is  continued 
backward  as  a  very  thin  membrane  in  front  of  the  Pyriformis  muscle  to  the  front 
of  the  sacrum.  In  front,  as  it  descends,  it  gives  off  the  parietal  layer  of  the  pelvic 
fascia,  which  continues  as  the  obturator  fascia.  It  then  becomes  thicker  and  covers 
the  inner  and  upper  surface  of  the  Diaphragm  of  the  pelvis  as  far  as  the  white 
line  (arcus  tendineus  fasciae  pelvis).  The  portion  covering  the  superior  and  upper 
surface  of  the  pelvic  Diaphragm  is  the  inner  sheath  of  the  T^evator  ani  muscle  and 
is  called  the  visceral  layer  of  the  pelvic  fascia  or  the  recto-vesical  fascia  (fascia 
diaphragmatis  pelvis  superior).  The  white  line  is  a  rough  band  of  fascial  thick- 
ening, seen  in  the  pelvic  fascia  of  each  side.  It  indicates  the  line  of  separation 
between  the  pelvic  cavity  and  the  ischio-rectal  fossa.     It  passes  from  the  lower 


THE   FEMALE  PEBINJEUM 


1545 


portion  of  the  symphysis  pubis  outward  and. backward  to  the  spine  of  the  ischium. 
It  makes  the  attachment  of  the  levator  ani  muscle  to  the  pelvic  fascia.  At  the  white 
line  the  chief  mass  of  the  pelvic  fascia  passes  upon  the  pelvic  viscera  and  is  known 
as  the  fascia  endo-pelvica.  It  covers  portions  of  the  vagina,  rectum,  and  urinary 
bladder,  becomes  thinner  and  thinner,  and  is  gradually  lost.  Other  bands  of  fascia 
begin  at  the  white  line,  descend  on  the  inner  surface  of  the  recto-vesical  fascia,  and 
in  the  male  pass  to  the  tip  of  the  prostate  and  become  the  prostatic  fascia.  Between 
the  anterior  ends  of  the  two  white  lines  the  level  of  the  fascia  is  lower,  and  it  forms 
a  fossa,  bounded  on  the  sides  in  the  male  by  the  pubo-prostatic  ligaments  {liga- 
menta  p-uboprostatica  lateralia),  and  in  the  female  by  the  pubo-vesical  ligaments 
(ligamenta  jmbovesicalia  lateralia).  These  ligaments  are  called  the  lateral  true 
ligaments  of  the  bladder.  In  the  base  of  this  fossa  in  the  male  runs  the  anterior  true 
ligament  of  the  bladder  or  the  pubo-prostatic  ligament  (ligamentum  puboprostaticum 


Fig.  1132. — Side  view  of  the  pelvic  viscera  of  the  male  subject,  showing  the  pelvic  and  perineal  fasciae. 

medium),  and  in  the  female  the  anterior  true  vesical  ligament  (ligamentum  pubo- 
vesicale  medium).  These  ligaments  arise  from  the  lowest  portion  of  the  symphysis 
and  pass  to  the  urinary  bladder  and  prostate  in  the  male,  and  urinary  bladder  and 
urethra  in  the  female  (Spalteholz).  The  outer  surface  of  the  pelvic  Diaphragm  is 
covered  by  the  anal  fascia  or  the  ischio-rectal  fascia  (fascia  diaphragmatis  pelvis 
inferior).  ^  It  is  the  lower  or  outer  sheath  of  the  Levator  ani  muscle,  and  is  derived 
from  the  obturator  fascia.  The  space  between  the  obturator  fascia  and  the  anal 
fascia  is  pyramidal  and  is  called  the  ischio-rectal  fossa  (fossa  ischiorectalis). 

The  pelvic  fascia  does  not  completely  invest  the  bladder,  although  the  neck  and 
lateral  walls  lie  upon  the  Levator  ani  muscles,  and  the  lateral  true  ligaments  and 
the  anterior  ligament  ascend  upon  the  sides  and  front  of  the  bladder  and  are  lost 
upon  the  fibrous  coat  of  that  viscus.  The  sides  and  anterior  wall  have  a  fascial 
investment.    The  sheath  of  the  prostate  has  already  been  discussed  (p.  1449).    It  is 


1546  SURGICAL    ANATOMY   OF    THE   PERINEUM 

continuous  with  the  recto-vesical  fascia  and  the  anterior  true  hgament  of  the 
bladder. 

The  pelvic  fascia  is  composed,  according  to  Hughes,  of:  1.  The  fibrous  cap- 
sules of  the  pelvic  viscera.  2.  The  sheaths  of  the  Levator  ani  and  Coccygei 
muscles  (recto-vesical  and  anal  fasciae).  3.  The  sheath  of  the  Obturator  internus 
(obturator  fascia).  4.  Sheath  of  the  Compressor  urethrae  muscle  (the  triangular 
ligament).  5.  The  sheath  of  the  pelvic  aspect  of  the  Pyriformis  muscle.  The 
sacral  plexus  is  outside  this  sheath,  the  internal  iliac  vessels  inside  of  it.^  As  pre- 
viously stated,  the  pelvic  fascia  gives  off  the  obturator  fascia  and  the  recto-vesical 
fascia. 

The  Obturator  Fascia  {fascia  ohturatoria)  descends  and  covers  the  Obturator 
internus  muscle.  It  is  a  direct  continuation  of  the  parietal  pelvic  fascia  below 
the  white  line  above  mentioned,  and  is  attached  to  the  pelvic  arch,  the  ischial 
tuberosities,  and  to  the  margin  of  the  great  sacro-sciatic  ligaments.  This  fascia 
forms  a  canal  for  the  pudic  vessels  and  nerve  in  their  passage  forward  to  the 
perinaeum,  and  gives  off  a  thin  membrane  which  covers  the  perineal  aspect  of  the 
Levator  ani  muscle,  and  is  called  the  anal  or  ischio-rectal  fascia.  It  forms  the  inner 
boundary  of  the  ischio-rectal  fossa.  From  its  attachment  to  tlie  rami  of  the  os 
pubis  and  ischium  a  process  is  given  off  which  is  continuous  with  a  similar  process 
from  the  opposite  side,  so  as  to  close  the  front  part  of  the  outlet  of  the  pelvis,  form- 
ing the  deej)  layer  of  the  triangular  ligament. 

The  Recto-vesical  Fascia  or  the  Visceral  Layer  of  the  Pelvic  Fascia 
(fascia  endopelvica)  descends  into  the  pelvis  upon  the  upper  surface  of  the  Levator 
ani  muscle,  and  invests  the  prostate,  bladder,  and  rectum.  From  the  inner  sur- 
face of  the  symphysis  pubis  a  short  rounded  band  is  continued,  on  each  side  of 
the  middle  line,  to  the  upper  surface  of  the  prostate  and  neck  of  the  bladder,  form- 
ing the  pubo-prostatic  or  anterior  true  ligaments  of  the  bladder.  At  the  side  this 
fascia  is  connected  to  the  side  of  the  prostate,  enclosing  this  gland  and  the  vesico- 
prostatic  plexus  of  veins,  and  is  continued  on  to  the  side  of  the  bladder,  forming 
the  lateral  true  ligaments  of  the  organ.  Another  prolongation  invests  the  seminal 
vesicle,  and  passes  across  between  the  bladder  and  rectum,  being  continuous 
with  the  same  fascia  of  the  opposite  side.  Another  thin  prolongation  is  reflected 
around  the  surface  of  the  lower  end  of  the  rectum.  The  Levator  ani  muscle  arises 
from  the  point  of  division  of  the  pelvic  fascia,  the  visceral  layer  of  the  fascia 
descending  upon  and  being  intimately  adherent  to  the  upper  surface  of  the  muscle, 
while  the  under  surface  of  the  muscle  is  covered  by  a  thin  layer  derived  from  the 
obturator  fascia,  called  the  ischio-rectal  or  anal  fascia.  In  the  female  the  vagina 
perforates  the  recto-vesical  fascia  and  receives  a  prolongation  from  it. 

1  A  Manual  of  Practical  Anatomj'.     By  Prof.  Alfred  W.  Hughes;  edited  and  completed  by  Dr.  Arthur  Keith. 


CHEONOLOGIOAL  TABLE 

OF 

THE  DEVELOPMENT  OF  THE  FCETUS. 

(From  Beaunis  and  Bouchard.) 

First  Week. — During  this  period  the  ovum  is  in  the  Fallopian  tube.  Having  been  fertilized  in 
the  upper  part  of  the  tube,  it  slowly  passes  down,  undergoing  segmentation,  and  reaches 
the  uterus  probably  about  the  end  of  the  first  week.  During  this  time  it  does  not  undergo 
much  increase  in  size. 

Second  Week. — The  ovum  rapidly  increases  in  size  and  becomes  imbedded  in  the  decidua,  so 
that  it  is  completely  enclosed  in  the  decidua  reflexa  by  the  end  of  this  period.  An  ovum 
believed  to  be  of  the  thirteenth  day  after  conception  is  described  by  Reichert.  There  was 
no  appearance  of  any  embryonic  structure.  The  equatorial  margins  of  the  ovum  were  beset 
with  villi,  but  the  surface  in  contact  with  the  uterine  wall  and  the  one  opposite  to  it  were 
bare.  In  another  ovum,  described  by  His,  believed  to  be  of  about  the  fourteenth  day, 
there  was  a  distinct  indication  of  an  embryo.  There  was  a  medullary  groove  bounded  by 
folds.  In  front  of  this  a  slightly  prominent  ridge,  the  rudimentary  heart.  The  amnion 
was  formed  and  the  embryo  was  attached  by  a  stalk,  the  allantois,  to  the  inner  surface  of 
the  chorion.  It  may  be  said,  therefore,  that  these  parts,  the  amnion  and  the  allantois,  and 
the  first  rudiments  of  the  embryo,  the  medullary  groove,  and  the  heart,  are  formed  at  the 
end  of  the  second  week. 

Third  Week. — By  the  end  of  the  third  week  the  flexures  of  the  embryo  have  taken  place,  so 
that  it  is  strongly  curved.  The  protovertebral  disks,  which  begin  to  be  formed  early  in  the 
third  week,  present  their  full  complement.  In  the  nervous  system  the  primary  divisions 
of  the  brain  are  visible,  and  the  primitive  ocular  and  auditory  vesicles  are  already  formed. 
The  primary  circulation  is  established.  The  alimentary  canal  presents  a  straight  tube  com- 
municating with  the  yolk-sac.  The  branchial  arches  are  formed.  The  limbs  have  appeared 
as  short  buds.     The  Wolffian  bodies  are  visible. 

Fourth  Week. — The  umbilical  vesicle  has  attained  its  full  development.  The  caudal  extremity 
projects.  The  upper  and  the  lower  limbs  and  the  cloacal  aperture  appear.  The  heart  sep- 
arates into  a  right  and  left  heart.  The  special  ganglia  and  anterior  roots  of  the  spinal 
nerves,  the  olfactory  fossae,  the  lungs  and  the  pancreas  can  be  made  out. 

lYfth  Week. — The  allantois  is  vascular  in  its  whole  extent.  The  first  traces  of  the  hands  and 
feet  can  be  seen.  The  primitive  aorta  divides  into  aorta  and  pulmonary  artery.  The  duct 
of  Miiller  and  genital  gland  are  visible.  The  ossification  of  the  clavicle  and  the  lower  jaw 
commences.     The  cartilage  of  Meckel  occupies  the  first  post-oral  arch. 

Sixth  Week. — The  activity  of  the  umbilical  vesicle  ceases.  The  pharyngeal  clefts  disappear. 
The  vertebral  column,  primitive  cranium,  and  ribs  assume  the  cartilaginous  condition.  The 
posterior  roots  of  the  nerves,  the  membranes  of  the  nervous  centres,  the  bladder,  kidney, 
tongue,  larynx,  thyroid  body,  the  germs  of  teeth,  and  the  genital  tubercle  and  folds 
are  apparent. 

Seventh  Week. — The  muscles  begin  to  be  perceptible.  The  points  of  ossification  of  the  ribs, 
scapula,  shaft  of  humerus,  femur,  tibia,  palate,  and  uiiper  jaw  appear. 

Eighth  Week. — The  distinction  of  arm  and  forearm,  and  of  tnigh  and  leg,  is  apparent,  as  well  as 
the  interdigital  clefts.  The  capsule  of  the  lens  and  pupillary  membrane,  the  interventricu- 
lar and  commencement  of  the  interauricular  septum,  the  salivary  glands,  the  spleen,  and 
suprarenal  capsules  are  distinguishable.  The  larynx  begins  to  become  cartilaginous.  All 
the  vertebral  bodies  are  cartilaginous.  The  points  of  ossification  for  the  ulna,  radius,  fibula, 
and  ihum  make  their  appearance.  The  two  lialvcs  of  the  hard  i)alate  unite.  The 
sympathetic  nerves  are  now  for  the  first  time  to  be  discerned. 

*  [Eternod  {Anat.  Anzeiger,  Band  xv.,  ]898)  described  an  ovum  which  he  reconstructed.  It 
had  a  precise  history,  from  which  he  concluded  that  it  must  have  belonged  to  the  end  of  the  second 
or  the  beginning  of  the  third  week.  Including  the  villi  it  measured  10X8.2X6  mm.  It  was 
flattened  on  its  embryonal  side,  and  the  embryo  measured  1.3  mm.  The  amnion  was  completely 
formed  and  the  allantois  existed  as  a  long  canal.  The  vitelline  circulation  was  established  and  the 
villi  of  the  chorion  were  beginning  to  be  vascularized.  The  blastopore  still  opened  into  the  amniotic 
cavity,  with  the  primitive  groove  behind  it  and  the  rudimentary  groove  in  front.  The  notochord 
was  closing  in  and  all  three  layers  of  the  blastoderm  were  disiinct,  except  around  the  blastopore,  where 
they  formed  an  undivided  mass. — Ed.  of  1.5th  English  edition.] 

1547 


1548  THE  FCETUS. 

Ninth  Week. — The  corpus  striatum  and  the  pericardium  are  first  apparent.  The  ovarj'  and 
testicle  can  be  distinguished  from  each  other.  The  genital  furrow  appears.  The  osseous 
nuclei  of  the  bodies  and  arches  of  the  vertebrae,  of  the  frontal,  vomer,  and  malar  bones  of  the 
shafts  of  the  metacarpal  and  metatarsal  bones,  and  of  the  phalanges  appear.  The  union  of 
the  hard  palate  is  completed.     The  gall-bladder  is  seen. 

Third  Month. — The  formation  of  the  fcetal  placenta  advances  rapidly.  The  projection  of  the 
caudal  extremity  disappears.  It  is  possible  to  distinguish  the  male  and  female  organs  from 
each  other.  The  cloacal  aperture  in  divided  into  two  parts.  The  cartilaginous  arches  on  the 
dorsal  region  of  the  spine  close.  Tlie  points  of  ossification  for  the  occipital,  sphenoid, 
lachrymal,  nasal,  squamous  portion  of  temporal  and  ischium  appear,  as  well  as  the  orbital 
centre  of  the  superior  maxillary.  The  pons  Varolii  and  fissure  of  Sylvius  can  be  made  out. 
The  eyelids,  the  hair,  and  the  nails  begin  to  form.  The  mammary  gland,  the  epiglottis, 
and  prostate  are  beginning  to  develop.  The  union  of  the  testicle  with  the  canals  of  the 
Wolffian  body  takes  place. 

Fourth  Month. — The  closure  of  the  cartilaginous  arches  of  the  spine  is  complete.  Osseous 
points  for  the  first  sacral  vertebra  and  os  pubis  appear.  The  ossification  of  the  malleus  and 
incus  takes  place.  The  corpus  callosum,  the  membrana  lamina  spiralis,  the  cartilage  of 
the  Eustachian  tube,  and  the  tympanic  ring  are  seen.  Fat  is  first  developed  in  the  sub- 
cutaneous cellular  tissue.  The  tonsils  are  seen,  and  the  closure  of  the  genital  furrow  and 
the  formation  of  the  scrotum  and  prepuce  take  place. 

Fifth  Month. — The  two  layers  of  the  decidua  begin  to  coalesce.  Osseous  nuclei  of  the  axis  and 
odontoid  process,  of  the  lateral  points  of  the  first  sacral  vertebra,  of  the  median  points  of 
the  second,  and  of  the  lateral  masses  of  the  ethmoid  make  their  appearance.  Ossification 
of  the  stapes  and  the  petrous  bone  and  ossification  of  the  germs  of  the  teeth  take  place. 
The  germs  of  the  permanent  teeth  and  the  organ  of  Corti  appear.  The  eruption  of  hair  on 
the  head  commences.  The  sudoriferous  glands,  Brunner's  glands,  the  follicles  of  the  tonsil 
and  base  of  the  tongue,  and  the  lymphatic  glands  appear  at  this  period.  The  difiierentiatioa 
between  the  uterus  and  vagina  becomes  apparent. 

Sixth  Month. — The  points  of  ossification  for  the  anterior  root  of  the  transverse  process  of  the 
seventh  cervical  vertebra,  the  lateral  points  of  the  second  sacral  vertebra,  the  median  points 
of  the  third,  the  manubrium  sterni  and  the  os  calcis  appear.  The  sacro-vertebral  angle 
forms.  The  cerebral  hemispheres  cover  the  cerebellum.  The  papillae  of  the  skin,  the 
sebaceous  glands,  and  Peyer's  patches  make  their  appearance.  The  free  border  of  the 
nail  projects  from  the  corium  of  the  dermis.     The  walls  of  the  uterus  thicken. 

Seventh  Month. — The  additional  points  of  the  first  sacral  vertebra,  the  lateral  points  of  the 
third,  the  median  point  of  the  fourth,  the  first  osseous  point  of  the  body  of  the  sternum, 
and  the  osseous  point  for  the  astragalus  appear.  Meckel's  cartilage  disappears.  The 
cerebral  convolutions,  the  island  of  Reil,  and  the  tubercula  quadrigemina  are  apparent.  The 
pupillary  membrane  atrophies.  The  testicle  passes  into  the  vaginal  process  of  the 
peritoneum. 

Eighth  Month. — Additional  points  for  the  second  sacral  vertebra,  lateral  points  for  the  fourth 
and  median  points  for  the  fifth  sacral  vertebrae,  can  be  seen. 

Ninth  Month. — Additional  points  for  the  third  sacral  vertebra,  lateral  points  for  the  fifth, 
osseous  points  for  the  middle  turbinated  bone,  for  the  body  and  great  cornu  of  the  hyoid, 
for  the  second  and  third  pieces  of  the  body  of  the  sternum,  and  for  the  lower  end  of  the 
femur  appear.  Ossification  of  the  bony  lamina  spiralis  and  axis  of  the  cochlea  takes  place. 
The  eyelids  open,  and  the  testicles  are  in  the  scrotum. 


INDEX. 


Abdomen,  1231 

boundaries  of,  1231 
fascia  of,  deep,  433 
superficial,  433,  1511 
triangular,  1515 
lymphatics  of,  797,  800 
muscles  of,  432 

actions  of,  445,  449 
deep,  449 
dissection  of,  432 
superficial,  432 
surface  form  of,  448 
nerves  of,  cutaneous,  996 
regions  of,  1233 
veins  of,  755 
viscera,  1234 

walls  of,  apertures  in,  1233 
of,    lymphatic     vessels     of, 
deep,  801 
superficial,  801 
Abdominal  aorta,  668 
branches  of,  671 
relations  of,  669 
surface  marking  of,  670 
surgical  anatomv  of,  670 
aortic  plexus,  1080,  1085 
intercostal  nerves,  996 
muscles,  432 

portion  of  oesophagus,  1223 
ring,  external,  436,  1514 
internal,  446,  1518 
pillars  of,  1514 
sacs,  1236 

surface  of  bladder,  1433 

viscera,  position  of,  1234 

Abdomino-aortic  glands,  799 

-thoracic  arch,  165 
Abducent  nerve,  1043 
branches  of,  1043 
relations  of,  1043 
surgical  anatomy  of,  1044 
Abductor  hallucis  muscle,  544 
relations  of,  544 
indicis  nauscle,  499 
minimi  digiti  muscle,  foot,  545 
relations  of,  545 
hand,  498 

relations  of,  498 
pollicis  muscle,  495 
relations  of,  496 
Aberrant    ducts    of    epididymis, 

1472 
Absorbent  glands,  774 
Absorbents,  772 
Accelerator  urinse  muscle,  457 
Accessorius  ad  ilio-costalem  mus- 
cle, 419 
pedis,  546 
Accessorv  anterior  crural  nerve 
of  Winslow,  1004 
auditory  nuclei,  950 
chains  to  deep  cervical  glands, 

787 
cuneate  nucleus,  948 


Accessory    descending    palatine 
canals,  116 
gland  of  Rosenmiiller,  1141 
ligament  of  atlas,  276 
nucleus  of  eightli  nerve,  1051 
obturator  nerve,  1004 
olivary  nuclei,  951 
parotid  gland,  1215 
posterior  palatine  canals,  116, 

135 
processes,  57 
quadrate  cartilage,  1097 
suprarenal  glands,  1430 
thyroid  glands,  1403 
veins,  731 
Acervulus  cerebri,  906 
Acetabulum,  213 
fossa  of,  213 

ligaments  of,  transverse,  330 
Acoustic  canal,  external,  1148 

tubercle,  lateral,  950 
Acromial  angle,  176 
region,  fascia  of,  470 
muscles  of,  470 
actions  of,  471 
surgical  anatomy  of,  471 
thoracic  artery,  651 
Acromio-clavicular   articulation, 
299 
surface  form  of,  311 
surgical  anatomy  of,  301 
ligament,  inferior,  299 
superior,  299 
Acromion  process,  174 
Additus  glottidis  inferior,  1371 
Adductor  brevis  muscle,  520 
relations  of,  520 
canal,  698 
longus  muscle,  519 

relations  of,  519 

magnus  muscle,  520 

relations  of,  521 

minimus  muscle,  520 

obliquus  hallucis  muscle,  546 

pollicis  muscle,  497 

relations  of,  497    • 
transversus     hallucis    muscle, 
548 
relations  of,  548 
pollicis  muscle,  497 
relations  of,  497 
tubercle,  225 
Adipose  tissue,  pads  of,  263 
Aditus  ad  antrum,  87,  1150 
Adminiculum  linea*  albae,  437 
Afferent  nerve  tract,  961 

vessels  of  kidneys,  1423 
Agminated  glands,  1296 
Air  cells,  1396 

sinus,  82 
Ala  cinerea,  945 

lobuli  centralis,  928 
nasi,  1096 

artery  of,  607 
Alse  of  cerebellum,  928 
of  ethmoid,  99 


Alae  of  sacrum,  64 

of  vomer,  121,  143 
Alar  cartilage,  greater,  1097 
lesser,  1097 
ligaments,  278 
thoracic  artery,  651 
Alcock's  canal,  1011,  1536 
Alimentary  canal,  1193 

development  of,  1236 
Alveolar  artery,  615 
inferior,  614 
superior,  615 
ducts,  1378 
hare-lip.  111 
processes,  140 

of  superior  maxillary,  109 
Alveoli,  mucous,  1218 
pulmonary,  1378 
serous,  1218 
of  stomach,  1278 
of  teeth,  development  of,  1207 
Alveus,  896 

Amacrine  cells  of  retina,  1125 
Ameoblasts,  1206 
Amphiarthrosis,  264. 
AmpuUise  of  Fallopian  tube,  1497 
membranaceae,  1170 
ossea,  1165 
tubuli  lactiferi,  1507 
of  Vater,  1345 
Amygdalfv,  1213 

of  cerebellum,  931 
Amygdaloid  nucleus,  891 
Anal  canal,  1315 

areolar  coat  of,  1318 
mucous  membrane  of,  1318 
muscular  coat  of,  1317 
relations  of,  1316 
serous  coat  of,  1316 
structure  of,  1316 
submucous  coat  of,  1318 
fascia,  454,  1546 
pockets,  1319 
valves,  1319 
Anastomosis  of  arteries,  583 

circumpatellar,  711 
Anastomotic  vein  of  Trolard,  735 
Anastomotica  magna  of  brachial, 
656 
of  femoral,  707 
Anatomical  neck  of  humerus,  177 

of  scapula,  175 
Anconeus  muscle,  487 

relations  of,  487 
Andersch,  ganglion  cf,  1056 
Angle,  acromial,  176 
cephalo-auricular,  1144 
of  jaw,  124 
lateral,  inferior,  63 
of  Ludwig,  165 
nasal,  105 
of  OS  pubis,  212 
of  ribs,,  161 
Rolandic,  867 
sacro- vertebral.  61 
of  sternum,  157 

(  1549  ) 


1550 


INDEX 


Angle,  subscapular,  172 
Angular  artery,  607 
convolution,  876 
gyrus,  876 
process,  external,  80,  140 

internal,  80,  140 
vein,  726 
Ankle  bone,  244 
bursse  of,  543 

-joint,  articulations  of,  347 
ligaments  of,  347 
surface  form  of,  351 
surgical  anatomy  of,  351 
Annectant  gyrus,  deep,  867 
first,  876 
fourth,  877 
second,  876 
third,  877 
Annular  ligament  of  ankle,   an- 
terior, 541 
external,  542 
internal,  542 
of  radius  and  ulnar,  314 
of  stapes,  1161 
of  wrist,  anterior,  491 
posterior,  493 
plexus,  1111 
Annulus  ciliaris,  1115 

ovalis,  567 
Ano-coccygeal  body  of  Syming- 
ton, 1316 
Ansa  hypoglossi,  1066 
lenticularis,  915 
peduncularis,  892 
of  Vieussens,  1076 
Ante-cubital  glands,  789 
Anterior  angle  of  ribs,  161 

annular  ligament  of  ankle,  541 

of  wrist,  491 
atlanto-axial  ligament,  274 
atlo-axoid  ligament,  274 
auricular  artery,  611 

nerves,  1038 
bicipital  ridge,  179 
branches    of  superior   cervical 

ganglion,  1076 
cardiac  plexus,  1081 
carpal  arch,  659 
of  ulnar,  663 
cerebellar  notch,  926 
cerebral  artery,  626 
chamber  of  eye,  1129 
chondro-sternal  ligament,  288 

-xiphoid  ligament,  288 
choroid  artery,  628 
ciliary  arteries,  625 
clinoid  process,  131 
commissure  of  cerebrum,  896 

of  cord,  839 
common  ligament,  269 
communicating   artery   of   ul- 
nar, 662 
condyloid    foramen,    73,    133, 
136 
fossa,  136 
cornu  of  lateral  ventricle,  889 
coronary  plexus,  1081 
costo-vertebral  ligament,  284 

-xiphoid  ligament,  288 
crescentic  lobe,  928 
crucial  ligament,  337 
crural  nerve,  1004 

accessory,      of     Winslow, 
1004 
deep  cervical  vein,  733 
divisions    of    cervical    nerves, 
971 
of  coccygeal  nerves,  1009 
of  dorsal  nerves,  993 
of  lumbar  nerves,  998 
of  thoracic  nerves,  993 


Anterior  dental  canal,  107 
ethmoidal  canal,  82,  100 

cells,  101 

foramen,  82,  130,  141 

sinuses,  101 
extremity  of  ribs,  161 
facial  vein,  726 
femoral  region,  muscles  of,  512 
fontanelle,  78,  103 
fossa  of  skull,  130 
gluteal  line,  207 
humeral    region,    muscles    of, 

474 
inferior  cerebellar  artery,  640 

spinous  process  of  ilium,  210 
intercostal  arteries,  644 

veins,  752 
internal  frontal  artery,  627 
interosseous    artery    of    ulnar, 
662 

nerve,  987 
intersternal  ligament,  290 
intertrochanteric  line,  223 
jugular  vein,  728 
ligament  of  Helmholtz,  1160 

of  malleus,  1160 

of  wrist,  318 
longitudinal  ligament,  269 

spinal  veins,  754 
mediastinal  glands,  811 
mediastinum,  1389 
medullary  velum,  943 
meningeal  artery,  622 
nares,  142,  1098 
nasal  spine.  111,  139,  143 
occipito-atlantal  ligament,  276 
olfactory  lobule,  880 
orbital  convolution,  874 
palatine  canal,  143 

fossa,  110,  133 

nerve,  1035 
perforated  space,  881 
perforating  arteries,  644 
peroneal  artery,  718 
pillars  of  fornix,  895 

of  soft  palate,  1212 
pubic  ligament,  296 
pulmonary  nerves,  1061 

plexus,  1059,  1061,  1082 
radial  carpal  artery,  659 
radio-ulnar  ligament,  315 

region,  muscles  of,  479 
recurrent  tibial  artery,  713 
region  of  skull,  139 
root  of  spinal  nerves,  965 
sacral  foramina,  62 
sacro-coccygoal  ligament,  294 

-iliac  ligament,  292 

-sciatic  ligament,  293 
scapular   region,   muscles  of, 

471 
spinal  artery,  638 
sterno-clavicular  ligament,  298 

-costal  ligament,  288 
subarachnoid  space,  853 
superior  dental  nerve,  1033 

ligament,  285 

spinous  process  of  ilium,  210 
surface  of  liver,  1327 

of  stomach,  1269 
temporal  artery,  611,  640 

diploic  vein,  734 
thoracic  nerve,  984 
tibial  arterv,  711 

gland,  795 

nerve,  1016 

veins,  758 
tibio-fibular  region,  muscles  of, 
531 

-tarsal  ligament,  347 
triangle  of  neck,  616 


Anterior  tubercle  of  cervical  ver- 
tebra, 50 
of  optic  thalamus,  904 
tympano-malleolar     ligament. 

1156 
ulnar  recurrent  artery,  662 

vein,  745 
vertebral    region,    muscles   of, 
406 
vein,  733 
wall  of  tympanum,  1153 
Antero-lateral  fissure,  838 
fontanelle,  103 
ganglionic  arteries,  628 
tract  of  cord,  842 
-median  fissure,  837 

ganglionic  arteries,  627 
-posterior  diameter  of  pelvis, 
217 
Antihehx,  1144 
fossa  of,  1144 
Antitragicus  muscle,  1147 
Antitragus,  1145 
Antrum  of  Highmore,  108 
mastoid,  87 
opening  of,  1153 
of  pylorus,  1271 
tympanic,  87 
Anus,  1315 

arteries  of,  1320 
lymphatics  of,  809,  1321 
nerves  of,  1322 
veins  of,  1321 
Aorta,  587 

abdominal,  668 
arch  of,  591 

branches  of,  593 
peculiarities  of,  591,  593 
relations  of,  591 
surgical  anatomy  of,  592 
ascending,  588 
descending,  665 
sinus  of,  great,  589 
thoracic,  665 
transverse,  590 
Aortic  isthmus,  591 

opening  of  diaphragm,  429 

of  heart,  566 
semilunar  valves,  572 
sinus  of  Valsalva,  573 
spindle,  591 
vestibule  of  Sibson,  572 
Apertura  scaliE  vestibuli  cochleae, 
1165 
tympanica  canaliculi  chorda;, 
1153 
Aperture    of   nose,    cartilage    of, 

1097 
Apical  coil  of  cochlea,  1167 

glands,  1091 
Aponeurosis  of  external  oblique, 
434,  1513 
of  internal  oblique,  439 
palatine,  404 
pharyngeal,  402,  1223 
Sibson's,  1385 
of  soft  palate,  1212 
supra-hyoid,  394 
vertebral,  411,  416 
Apophysis,  34 
Appendages  of  eye,  1137 
of  skin,  1185 
of  uterus,  1497 
Appendices  epiploic^,  1260 
Appendicular  artery,  676 

vein,  768 
Appendiculo-ovarian  ligament  of 

Clado,  1304 
Appendix  of  auricle,  left,  568 
right,  565 
ensiform,  158 


INDEX 


1551 


Anoendix,  vermiform,  1303 

-viphoid,  158 
Aqueduct  of  Sylvius,  912 
Atjuaeductus    coclileai,    89,    136, 
1167 
Fallopii,  89 

eminence  of,  1152 
vestibuli,  89,  133,  1165 
Aqueous  chamber,  1128 

humor,  1128 
Arachnoid  of  brain,   851 
structure  of,  853 
of  cord,  834 

structure  of,  835 
vilH,  854 
Arangi,  body  of,  571 
Arantius,  ventricle  of,  944 
Arbor  vitae  of  cerebellum,  931 

of  uterus,  1492 
Arch  of  aorta,  591 
branches  of,  593 
peculiarities  of,  591,  593 
relations  of,  591 
surgical  anatomy  of,  592 
of  atlas,  51 

axillary,  413,  464,  646 
carpal,  anterior,  659 

posterior,  659 
crural,  deep,  44S,  1531 

superficial,  436,  1529 
palmar,  deep,  658 
superficial,  664 
plantar,  720 
pubic,  217 
supraorbital,  80 
tarsal,  inferior,  623 

superior,  623 
of  vertebra,  48 
zygomatic,  138 
Arciform  fibres  of  medulla,  942 
Arcuate  fibres  of  medulla,  942 
ligaments,  external,  427,  449 
internal,  427 
middle,  427 
Areus  senilis,  1110 
Area  of  Broca,  881 
cribrosa  media,  89 

superior,  89 
vestibularis,  inferior,  1176 
superior,  1176 
Areolae  of  bone,  primary,  44 
secondary,  45 
of  mamma,  1504 
Areolar  coat  of  anal  canal,  1318 
of  intestine,  large,  1318 

small,  1290 
of  liver,  1337 
of  cEsophagus,  1229 
of  rectum,  1318 
of  stomach,  1274 
tissue,  subcutaneoas,  1180 
subserous,  1245 
Arm,  arteries  of,  637 
bones  of,  177 
fascise  of,  474 
deep,  470 
superficial,  470 
lymphatics  of,  789 
muscles  of,  470,  474 
dissection  of,  470,  474 
surgical  anatomy  of,  478 
nerves  of,  977 
veins  of,  744 
Arnold's  ganglion,  1039 
branches  of,  1039 
nerve,  1060 

canal  for,  90 
ponticulus  of,  939 
Arteria  centralis  retinae,  626 

magna,  587 
Artcrise  hallucis,  716 


Arteriae  priuceps  cervicis,  609 
receptaculi,  622 
uterina  ovarica,  688 
Artery  or  arteries,  583 
alveolar,  615 

inferior,  614 

superior,  615 
anastomosis  of,  583 
anastomotica  magna  of  brach- 
ial, 656 
of  feinoral,  707 
angular,  607 
antero-lateral  ganglionic,  628 

-median  ganglionic,  627 
aorta,  587 

abdominal,  668 

arch  of,  591 

ascending,  588 

descending,  665 

thoracic,  665 
appendicular,  676 
arteriae  receptaculi,  622 
articular,  of  knee,  710,  711 
auditory,  639 
auricular,  anterior,  611 

posterior,  609 
axillary,  647 
azygos,  of  knee,  711 

of  vagina,  687 
basilar,  639 
brachial,  652 
of  brain,  cortical,  631 
bronchial,  666 
buccal,  615 
of  bulb,  691 
bulbar,  639 
calcanean,  external,  718 

internal,  719 
carotid,  common,  595 

external,  600 

internal,  619 
carpal  arch,  anterior,  659 
posterior,  657 

radial,  anterior,  659 
posterior,  659 

ulnar,  anterior,  663 
posterior,  663 
centralis  retinae,  626 
cerebellar,     anterior     inferior, 
640 

posterior  inferior,  639 

superior,  640 
cerebral,  anterior,  626 
of  cerebral  hemorrhage,  628 

middle,  627 

posterior,  640 
cervical,  ascending,  641 

deep,  646 

superficial,  642 

transverse,  642 
choroid,  anterior,  628 

posterior,  640 
ciliary,  625 
circle  of  Willis,  640 
circumflex,  of  arm,  651 

iliac,  deep,  697 
superficial,  704 

of  thigh,  705 
cochlear,  1176 
coccygeal,  692 
cccliac,  671 
colic,  left,  678 

middle,  676 

right,  675 
comes  nervi  ischiadic!,  693    ' 
mediana,  663 
phrenici,  644 
communicating,  anterior  cere- 
bral. 627 

to  deep  palmar  arch,  664 

posterior  cerebral,  628 


Artery  or  arteries,  communicat- 
ing, of  ulnar,  anterior,  662 
coronary,  671 

of  heart,  590 

of  Up,  inferior,  607 
superior,  607 
of  corpus  cavernosum,  691 
cremasteric,  696 
crico-thyroid,  602 
cystic,  674 
dental,  anterior,  605 

inferior,  614 

posterior,  615 
digital,  plantar,  659 

of  uhiar,  664 
dorsalis  hallucis,  716 

indicis,  659 

linguae,  603 

nasi,  625 

pedis,  714 

pollicis,  659 

scapulffi,  651 
of  dura  mater  of  brain,  848 
epigastric,  deep,  696 

internal,  696 

superficial,  704 

superior,  645 
ethmoidal,  623 
facial,  604 

transverse,  611 
femoral,  697 

common,  699 

deep,  704 
fibular,  superior,  713 
frontal,  611 

from  anterior  cerebral,  628 

from  middle  cerebral,  628 

from  ophthalmic,  625 
ganglionic,  postero-lateral,  640 

postero-median,  640 
gastric,  671,  674 
gastro-duodenalis,  673 

-epiploica  dextra,  673 
sinistra,  674 
gluteal,  694 

inferior,  693 
hemorrhoidal,  inferior,  690 

middle,  687 

superior,  678 
of  head,  595 
of  heart,  577 
hepatic,  672 
histology  of,  584 
hyoid  branch  of  lingual,  603 
of  superior  thyroid,  602 
hypogastric,  683 

in  foetus,  684 
ileo-colic,  675 
iliac,  circumflex,  deep,  697 
superficial,  704 

common,  681 

external,  694 

internal,  683 
ilio-lumbar,  693 
infra-hyoid  branch  of  superior 

thyroid,  602 
infraorbital,  615 
innominate,  593 
inosculation  of,  583 
intercostal,  667 

anterior,  644 

superior,  645 
interlobar,  1423 
interosseous,  of  foot,  715 
of  hand,  660 
ulnar,  662 
anterior,  662 
posterior,  663 
labial,  inferior,  607 
lachrymal,  623 
laryngeal,  inferior,  641 


1552 


INDEX 


Artery    or    arteries,    laryngeal, 

superior,  602 
lateralis  nasi,  607 
lenticulo-striate,  628 
lingual,  603 

deep,  604 
of  lower  extremity,  697 
lumbar,  680 
lymphatics  of,  586 
malar  from  lachrymal,  623 
malleolar,  713,  7i9 
mammary,  internal,  643 
mandibular,  614 
marginal,  590 
masseteric,  615 
mastoid,  609,  670 
maxillary,  external,  604 

internal,  612 
mediastinal,  644 

posterior,  666 
meningeal,  609,  610 

anterior,  622 

middle,  613 

from  occipital,  609 

from  pharyngeal,  610 

posterior,  638 

small,  614 

from  vertebral,  638 
mesenteric,  inferior,  677 

superior,  675 
metatarsal,  715 
musculo-phrenic,  644 
mylo-hyoid,  614 
nasal,  from  ophthalmic,  625 

of  septum,  inferior,  607 
superior,  615 
naso-palatine,  616 
of  neck,  595 
nerves  of,  586 
nutrient,  of  femur,  707 

of  fibula,  718 

of  humerus,  656 

of  tibia,  718 
obturator,  688 
occipital,  608 
cfisophageal,  641,  666 
ophthalmic,  622 
orbital,  611 

internal,  627 
ovarian,  680 
palatine,  ascending,  606 

descending,  615 

inferior,  606 

posterior,  615 
palmar  arch,  deep,  658 

superficial,  664 
palpebral,  external,  623 

internal,  623 
pancreatic,  674 
pancreatico-duodenalis,     infe- 
rior, 675 
superior,  674 
parietal,  611 

ascending,  628 
parieto-sphenoidal,  628 

-temporal,  628 
of  penis,  dorsal,  689,  1458 
perforating,  anterior,  644 

of  foot,  720 

of  hand,  660 

of  thigh,  706 
pericardiae,  644,  666 
of  pericardium,  561 
perineal,  superficial,  690 

transverse,  691 
peroneal,  717 

anterior,  718 

posterior,  718 
pharyngeal,   ascending,   610 
phrenic,  inferior,  680 

superior,  644 


Artery  or  arteries  of  pia  mater 

of  brain,  856 
plantar,  digital,  720 

external,  720 

internal,  719 
popliteal,  707 

postero-median  ganglionic,  628 
prevertebral,  610 
princeps  cervicis,  610 

hallucis,  716 

pollicis,  660 
profunda  of  arm,  inferior,  656 
superior,  655 

femoris,  704 
pterygo-palatine,  616 
pterygoid,  614 
pudic,  accessory,  690 

external,  deep.  704 
superficial,  704 

internal,  in  female,  692 
in  male,  689 
pulmonary,  587 
pyloric,  inferior,  673 

superior,  673 
radial,  657 
radialis  indicis,  660 
ranine,  604 
recurrent,  palmar,  660 

radial,  659 

tibial,  anterior,  713 
posterior,  713 

ulnar,  anterior,  662 
posterior,  662 
renal,  678 

inferior,  1423 
of  round  ligament,  688 
sacral,  lateral,  693 

middle,  681 
scapular,  posterior,  642 
sciatic,  692 
sigmoid,  678 
spermatic,  679 
spheno-palatine,  616 
spinal,  anterior,  638 

lateral,  638 

posterior,  639 
splenic,  674 
sternal,  644 

sterno-mastoid,  602,  609 
stylo-mastoid,  610 
subclavian,  631 
subcostal,  667 
sublingual,  604 
submaxillary,  606 
submental,  606 
subscapular,  651 
superficialis  vola?,  659 
supra-acromial,  642 

-hyoid,  603 
supraorbital,  623 
suprarenal,  678 
suprascapular,  641 
suprasternal,  642 
sural,  710 
tarsal,  715 
temporal,  61 1 

anterior,  611,  640 

deep,  614 

middle,  611 

posterior,  611,  640 
thoracic,  acromial,  651 

alar,  651 

long,  651 

superior,  650 
thyroid  axis,  640 

inferior,  641 

superior,  601 
of  thyroid  gland,  602 
thyroidea  ima,  594 
tibial,  anterior,  711 

posterior,  716 


Artery  or  arteries,  tibial,  recui- 
rent,  anterior,  713 
posterior,  713 
tonsillar,  606 
tracheal,  641 
transversalis  colli,  642 

humeri,  641 
of  trunk,  665 

tympanic,      from      ascending 
pliaryngeal,  610 
from  internal  carotid,  622 
from  internal  maxillarv,  613 
ulnar,  660 

recurrent,  anterior,  662 
posterior,  662 
umbilical,  in  foetus,  579,  685 
of  upper  extremity,  631 
uterine,  687 
vaginal,  687 
of  vas  deferens,  686 
vasa  brevia,  674 

intestini  tenuis,  675 
vasorum  of,  586 
vertebral,  637 
vesical,  inferior,  686 
middle,  686 
superior,  686 
Vidian,  616 
Arteriolae  recta;,  1423 
Arthrodia,  266 
Arthrology,  259 

Articular  arteries  of  knee,  azygos, 
711 
inferior,  711 
superior,  710 
cartilage,  259 
circumference  of  ulna,  189 
eminence  of  temporal  bone,  84 
lamella  of  bone,  259 
processes  of  a  vertebra,  49 
synovial  membrane,  262 
Articulations,  259 

acromio-clavicular,  299 
of  ankle-joint,  347 
astragalo-scaphoid,  354 
atlanto-axial,  276 
of  atlas  with  axis,  274 

with  occipital  bone,  276 
biaxial,  265 

calcaneo-astragaloid,  352 
-cuboid,  353 
-scaphoid,  353 
carpo-metacarpal,  321 
of  carpus,  319 
first  row,  319 
second  row,  319 
chondro-sternal,  288 
coccygeal,  294 
condyloid,  265 
costo-central,  283 
-chondral,  290 
-sternal,  287 
-transverse,  285 
-vertebral,  283 
crico-arytenoid,  1367 

-thyroid,  1367 
of  cuboid  with  cuneiform,  355 

with  scaphoid,  355 
of  elbow-joint,  308 
femoro-tibial,  335 
of  hip,  325 
immovable,  264 
interchondral,  289 
interneural,  272 
of  knee,  334 
of  lower  extremit}',  325 

jaw,  280 
metacarpo-phalangeal,  324 
metatarso-phalangeal,  359 
mixed,  264 
movable,  265 


INDEX 


1553 


Articulations,    occipito-atlantal, 
276 

-axial,  278 
of  ossa  pubis,  296 
of  ossicles  of  t3^mpanum,  1160 
of  pelvis,  292 
of  phalanges  of  foot,  359 

of  hand,  325 
radio-carpal,  317 

-ulnar,  313 
inferior,  315 
middle,  314 
superior,  314 
by  reciprocal  reception,  265 
of  ribs  with  vertebrcD,  283 
sacro-coccygeal,  294 

-iliac,  292 

-sciatic,  292 

-vertebral,  290 
of  sacrum  with  coccyx,  294 

and  ilium,  292 

and  iscliium,  292 
scapulo-clavicular,  299 
of  shoulder-joint,  303 
of  spine  with  cranium,  276 
sterno-clavicular,  297 
of  sternum,  290 
tarso-metatarsal,  357 
of  tarsus,  352 
temporo-mandibular,  280 

-maxillary,  138 
tibio-fibular,  345 

-tarsal,  347 
of  trunk,  269 
of  upper  extremity,  297 
of  vertebral  column,  269 

with  pelvis,  290 
of  wrist,  317 
Aryteno-epiglottidean      folds, 

1365 
-epiglottideus  muscle,  1373 
Arj'tenoid  cartilages,  1364 

apex  of,  1365 

base  of,  1365 

surfaces  of,  1364 
glands,  1375 
muscles,  1372 
Arytenoideus  muscle,  1372 
Ascending  aorta,  588 

branches  of,  590 

relations  of,  589 
cervical  artery,  641 
colon,  1309 

flexure  of,  hepatic,  1309 
frontal  artery,  628 

convolution,  872 
lumbar  vein,  753,  765 

right,  752 
mesocolon,  1258 
nerve  tract,  961 
oblique   muscle   of    abdomen, 

437 
palatine  artery,  606 
parietal  artery,  628 

convolution,  876 
pharjTigeal  artery,  610 
ramus  of  ischium,  212 

of  pubis,  213 
root  of  fifth  nerve,  948,  1026 
vena  cava,  764 
Association   fibres   of   cerebrum, 

916 
Astragalo-scaphoid   articulation, 
354 

ligament,  superior,  354 
Astragalus,  244 

articulations  of,  245 
body  of,  244 
head  of,  244 
neck  of,  244 
surfaces  of,  244,  245 


Asterion,  75,  138 
Atlanto-axial  ligament,  anterior, 
274 
posterior,  275 
-odontoid  joint  of  Cruveilhier, 
274 
Atlas,  50 

arches  of,  51 

attachment  of  muscles  to,  60 
development  of,  59 
lateral  masses  of,  51 
ligament  of,  transverse,  275 
processes  of,  51 
Atlo-axoid     ligament,     anterior, 
274 
posterior,  275 
Atrabiliary  capsules,  1430 
Atria  of  left  bronchus,  1378 
Atrium,  1150 

of  nasal  fossae,  1100 
meatus,  145 
Attic,  1150 

tympanic,  87 
AttoUens  auric  ulam  muscle,  369 

relations  of,  369 
Attrahens  auriculam  muscle,  369 

relations  of,  369 
Auditory  arteries,  1176 
internal,  639 
canal,  external,  1148 
meatus,  external,  138,  1148 
arteries  of,  1149 
cartilaginous    portion    of, 

1148 
lymphatics  of,  1150 
nerves  of,  1150 
osseous  portion  of,  1149 
relations  of,  1149 
skin  of,  1149 
surface  form  of,  1150 
veins  of,  1150 
internal,  133 
fundus  of,  1168 
nerve,  1050 
nuclei  of,  925 
origin  of,  1050 
roots  of,  1050,  1051 
surgical  anatomy  of,  1054 
nuclei,  950 

accessory,  950 
dorsal,  950 
inner,  950 
ventral,  950 
paths,  1053 
process,  88 
teeth,  1173 
veins,  1176 
Auerbach's  plexus,  1299 
Auricle  of  ear,  1144 
of  heart,  fibres  of,  575 
left,  568 

sinus  of,  568 
right,  565 
sinus  of,  565 
Auricular  appendices,  565 
appendix,  left,  568 

right,  565 
artery,  anterior,  611 
posterior,  609 
branches  of,  610 
branch  of  pneumogastric  nerve, 

1060 
fissure,  90,  136 
nerves,  anterior,  1038 
great,  972 
posterior,  1047 
region,  muscles  of,  369 
action  of,  369 
dissection  of,  369 
surface  of  sacrum,  63 
vein,  anterior,  726 

98 


Auricular  vein,  posterior,  727 
Auriculo-temporal  nerve,  1037 
-ventricular  groove    of    heart, 
565 
opening,  left,  569 
right,  566 
Axes  of  pelvis,  218 
Axilla,  dissection  of,  463 

ligament  of,  suspensory,  464 
surgical  anatomy  of,  645 
Axillary  arch,  413,  464,  646 
artery,  646 

branches  of,  650 
peculiarities  of,  649 
relations  of,  648 
surface  marking  of,  649 
surgical  anatomy  of,  649 
border  of  scapula,  174 
fascia,  463,  646 
•glands,  790 
space,  645 
veins,  747 

surgical  anatomy  of,  748 
Axis,  52 
apex  of,  52 

attachment  of  muscles  to,  60 
body  of,  52 
cerebro-spinal,  832 
coeliac,  671 
cylinder  of  nerve-fibre,  822 

of  Purkinje,  822 
development  of,  59 
ligament  of  malleus,  1161 
odontoid  process  of,  52 
cptic,  1106 
pedicles  of,  52 
processes  of,  53 
thoracic,  651 
thyroid,  640 
visual,  1106 
Axone  of  nerve-cells,  821 
Azygos  arteries,  articular,  711 
of  vagina,  687 
uvulsB  muscle,  405 

relations  of,  405 
veins,  752 
larger,  752 
left  lower,  753 
upper,  753 
right,  752 
smaller,  753 
surgical  anatomy  of,  753 


B 


Back,  fascia  of,  deep,  411 
superficial,  411 
muscles  of,  dissection  of,  420 
fifth  layer,  420 
first  layer,  410 
fourth  layer,  417 
second  layer,  414 
surface  forms  of,  424 
third  layer,  415 
Baillarger,  nerve-fibres  of,  920 
Band  of  Gennari,  918 
of  Giacomini,  879 
of  Meckel,  1160 
Bartholin,  duct  of,  1217 

glands  of,  1482 
Base  of  brain  881 
of  sacrum,  64 
of  skull,  130 
surfaces  of,  130 
Basi-hyal  of  hyoid  bone,  153 
Basil  coil  of  cochlea,  1167 
Basilar  artery,  639 
branches  of,  639 
groove,  75 
lymph-sinus,  1306 


1554 


INDEX 


Basilar    membrane    of   cochlea, 
1167 

process,  71 

sinus,  743 

suture,  128 

vein,  735 
Basilic  vein,  746 
median,  746 
Basis  vertebranum,  ven»,  753 
Basion,  73 

Basket-cells  of  cerebellum,  936 
Bauhin,  valve  of,  1308 
Beak  of  corpus  callosum,  886 
Beaunis   et    Bouchard,    table   of 

development   of    foetus    from, 

1547 
Bechterew,  nerve-fibres  of,  920 

nucleus  of,  926,  1050 
Bell,  respiratory  nerve  of,  exter- 
nal, 983 
internal,  974 
Bertin,  bones  of,  97 

columns  of,  1416 

ligament  of,  328 
Biaxial  articulation,  265 
Biceps  flexor  cubiti  muscle,  475 

muscles,  475,  529 
bursa  of,  476 
relations  of,  476,  530 
Bichat,  fissure  of,  900 
Bicipital  fascia,  476,  746 

groove,  179 

ridges,  179 

tuberosity,  190 
Bicornate  uterus,  1493 
Bicuspid  teeth,  1198 

valve,  672 
cusps  of,  572 
Bigelow,  ligament  of,  328 
Bile,  1346 

canaliculi,  1341 

-capillaries,  1341 

-duct,  common,  1344 
arteries  of,  1346 
dimensions  of,  1345 
lymphatics  of,  806,  1346 
nerves  of,  1346 
structure  of,  1345 
surgical  anatomy  of,  1347 
veins  of,  1346 

papilla,  1288 
Bipenniform  muscles,  363 
Bipolar  cells,  820 
Biventer  cervicis  muscle,  420 
Biventral  lobe  of  cerebellum,  931 
Bladder,  1431 

apex  of,  1435 

arteries  of,  1439 

base  of,  1435 

body  of,  1435 

cervix  of,  1435 

female,  1446 

fundus  of,  1435 

ligaments  of,  1435 

lymphatics  of,  802,  1439 

mucous  coat  of,  1437 
membrane  of,  1438 

muscular  coat  of,  1437 

neck  of,  1435 

nerves  of,  1440 

serous  coat  of,  1437 

structure  of,  1437 

submucous  coat  of,  1437 

summit  of,  1435 

surface  form  of,  1440 

surfaces  of,  1433 
inner,  1438 

surgical  anatomy  of,  1440 

trigone  of,  1438 

veins  of,  1439 
Blade  bone,  171 


Blind  spot,  1121 
Blood  supply  of  cord,  840 
Blood-vascular  system,  555 
Blood-vessels  of  bone,  39 
Bochdalek,  ganglion  of,  1033 
Body,  carotid,  1409 

cavernous,  artery  of,  691 

coccygeal,  1410 

pituitary,  882 

thyroid,  1401 

of  a  vertebra,  49 
Bones,  acetabulum,  213 

apophysis  of,  34 

areolae  of,  primary,  44 
secondary,  45 

astragalus,  244 

atlas,  50 

axis,  52 

of  Bertin,  97 

blood-vessels  of,  39 

breast,  155 

calcaneum,  242 

canalicuh  of,  46 

cancellous,  35 

carpus,  193 

chemical  composition  of,  41 

clavicle,  167 

coccyx,  65 

compact,  35 

cranial,  71 

cuboid,  245 

cuneiform  of,  foot,  247 
of  hand,  197 

diploe  of,  34 

ear,  1158 

eminences  and  depressions  of, 
34 

epactal,  103 

epicteric,  103 

epiphysis  of,  34 

ethmoid,  98 

of  face,  104 

femur,  221 

fibula,  237 

flat,  34 

of  foot,  239 

frontal,  79 

growth  of,  42 
of  hand,  193 

Haversian  canals  of,  38 
systems  of,  38 

humerus,  177 

hvoid,  153 

ilium,  207 

incus,  1158 

inter-maxillary,  110 

irregular,  34 

ischium,  210 

of   jaw,    upper,    changes   pro- 
duced in,  by  age,  112 

lachrymal,  112 

lacuniB  of,  38 

lamella  of,  38 
articular,  259 

of  leg,  230 

lingual,  153 

long,  33 

lymphatics  of,  41 

malar,  113 

malleus,  1158 

marrow  of,  36 

maxillary,  inferior,  122 
superior,  105 

medullary  spaces  of,  45 

metacarpal,  200 

metatarsal,  249 

mixed,  34 

nasal,  104 

navicular,  195,  246 

nerves  of,  41 

occipital,  71 


Bones,  orbicular,  1159 
OS  calcis,  242 

innominatum,  207 

magnum,  of  carpus,  199 
ossification  of,  42 

intracartilaginous,  43 

intramembranous,  43 
palate,  115 
parietal,  76 
patella,  230 
pelvic,  215 
periosteum  of,  37 
phalanges  of  foot,  252 

of  hand,  204 
pisiform,  197 
ploughshare,  120 
pre-maxillary,  110 
pubis,  212 
radius,  190 
ribs,  159 
sacrum,  61 
scaphoid,  of  foot,  246 

of  hand,  195 
scapula,  171 
semilunar,  196 
sesamoid,  257 
short,  33 
sphenoid,  92 

spongy,  97 
sternum,  155 
structure  of,  34 
supernumerary,  103 
surface  of,  34 
sutural,  103 
tarsus,  242 
temporal,  83 
thigh,  221 
tibia,  233 
trapezium,  198 
trapezoid,  198 
turbinated,  inferior,  119 

middle,  101 

sphenoidal,  143 

superior,  101 
tvmpanic  91 
ulna,  184 
unciform,  199 
veins  of,  41 

vertebra  prominens,  53 
vertebrae,  cervical,  49 

dorsal,  53 

lumbar,  56 

thoracic,  53 
vomer,  120 
wedge,  247 
Wormian,  103 
Bony  canal  of  cochlea,  1167 
Bosom,  1503 
Bowman's  capsule,  1418 
glands  of,  1101 
membrane,  1109 
muscle,  1115 
Brachiaof  corpora  quadrigemina, 

911 
Brachial  artery,  652 

branches  of,  655 

peculiarities  of,  653 

relations  of,  652 

surface  marking  of,  654 

surgical  anatomy  of,  654 
lymphatic  glands,  788 
plexus,  977 

branches  of,  981 

relations  of,  980 

surgical  anatomy  of,  991 
region,  anterior,  muscles  of  ,479 

posterior,  muscles  of,  486 
veins,  747 
Brachialis  anticus  muscle,  476 

relations  of,  476 
Brachio-cephalic  vein,  750 


INDEX 


1555 


IJrachium,  904 
Brain,  857 

arteries  of,  cortical,  631 

base  of,  881 

blood-vessels  of,  629 

capsule  of,  external,  894 
internal,  894 

commissures  of,  903 

communication  of  the  parts  of, 
863 

convolutions  of,  865 

development  of,  857 

dissection  of,  847 

dura  mater  of,  847 

ganglionic  vessels  of,  central, 
630 

general  considerations  and  di- 
visions of,  864 

gyri  of,  865 

hemispheres  of,  864 
surfaces  of,  under,  881 

infundibulum  of,  882 

little,  926 

lobes  of,  872 

membranes  of,  arachnoid,  861 

meninges  of,  847 

pia  mater  of,  854 

sand,  906 

ventricle  of,  fifth,  897 
lateral,  888 
third,  901 
Vergas,  896 

weight  of,  951 
Breast  bone,  155 
Bregma,  129 
Bregmatic  fontanelle,  103 
Breschet,  canals  of,  733 
Brim  of  pelvis,  217 
Broad  ligaments  of  liver,  1333 

of  uterus,  1490 
Broca,  area  of,  881 

"cap"  of,  874 

convolution  of,  874 
Bronchi,  1376 

relations  of,  1376 
Bronchial  arteries,  666 

branch  of  innominate,  594 

glands,  1380 

septum,  1380 

veins,  753 
Bronchus,  left,  1378 

right,  1376 
Brown  striae  of  Retzius,  1204 
Bruch,  membrane  of,  1114 
Brunner's  glands,  1295 
Bruns,  falciform  margin  of,  515 

space  of,  388 
Bubonocele,  1521 
Buccal  artery,  615 

cavity,  1193 

glands,  1195 

lymphatic  glands,  782 

nerve,  1037,  1049 
Buccinator  crest,  124 

glands,  782 

muscle,  380 

relations  of,  380 

nerve,  1037 
Bucco-pharvngeal     fascia,     380, 

388,  401,  "1222 
Bulb,  artery  of,  691 

surgical  anatomy  of,  691 

of  corpus  cavernosum,  1456 
spongiosum,  1457 

of  internal  jugular  vein,  729 

nerve  to,  1013 

olfactory,  880,  1019 

spinal,  938 

of  urethra,  male,  1458 

vaginal,  1483 
Bulbar  arteries,  639 


Bulbar  portion  of  conjunctiva, 
1140 

of  spinal    accessory  nerve, 
1063 
Bulbi  vestibuli,  1483 
Bulbo-cavernous  muscle,  457 
Bulla  ethmoidalis,  145,  1099 
Bundle  of  Vicq  d'Azvr,  883 
Burdach,  tract  of,  839,  843 
Bursse  of  ankle,  543 
anserina,  530 
of  biceps  muscle,  476 
of  coraco-brachialis    muscle, 

475 
of  elbow,  311 
of  extensor  carpi  radialis  bre- 

vior  muscle,  486 
of  foot,  543 

of  gastrocnemius  muscle,  534 
of  great  trochanter,  331 
gluteo-femoral,  331 
of  hand,  492 
of  hip,  330 

iliac,  subtendinous,  331 
ilio-pectineal,  330 
infrapatellar,  deep,  340 
infraspinatus,  305,  473 
ischio-gluteal,  331 
of  knee,  340 

of  latissimus  dorsi  muscle,  474 
obturator,  331 

intemus  muscle,  525 
olecranon,  311 

subcutaneous,  477 
ovarian,  1490 
patellar,  518 
pharyngeal,  1224 
prepatellar,  340 
of  pyriformis  muscle,  525 
of  semimembranous   muscle, 

531 
of  shoulder,  305 
stemo-hyoid,  391 
subacromial,  305,  471 
subcutanea  prominentise  larvn- 

gese,  1362 
subcutaneous  acromial,  305 

trochanteric,  331 
subdeltoid,  305,  471 
subscapular,  305,  472 
suprapatellar,  340 
synovial,  subcutaneous,  263 

subtendinous,  263 
of  tendo  Achillis,  535 
tibial,  subcutaneous,  340 
of  tibialis  anticus  muscle,  532 
wrist,  492 
Bursal  synovial  membrane,  263 


C-ECAL  fold,  inferior,  1264 

superior,  1263 
Csecum,  1300 

arterieg  of,  1305 

interior  of,  1303 

lymphatics  of,  1306 

supports  of,  1302 

veins  of,  1306 

vestibulare,  1170 
Cffilum,  1236 
Cajal,  horizontal  cells  of,  1125 

neurones  of,  919 
Calamus  scriptorius,  943 
Calcaneal  nerves,  external,  1014 

internal,  1015 
Calcanean  artery,  external,  718 

internal,  719 
Calcaneo-astragaloid      ligament, 

external,  352 


Calcaneo-astragaloid     ligament, 
internal,  352 
posterior,  352 

-cuboid  ligament,  internal,  353 
long,  353 
short,  353 
superior,  353 

-navicular  ligament,  353 

-plantar  nerve,  1015 

-scaphoid    ligament,  external, 
353 
inferior,  354 
internal,  354 
superior,  353 
Calcaneus,  242 

anterior  extremity  of,  242 

articulations  of,  244 

attachment  of  muscles  to,  244 

body  of,  242 

posterior  extremity  of,  242 

process  of,  greater,  243 
lesser,  243 

surfaces  of,  242,  243 

tuberosity  of,  243 
Calcar  avis,  889 

femorale,  227 
Calcarine  fissure,  870 
Calf  bone,  237 
Calices  of  kidney,  1415 
Callosal  convolution,  879 

sulcus,  879,  885 
Calloso-marginal  sulcus,  870 
Calvaria,  71 
Camper,  fascia  of,  433 
Canalis  centralis  cochlea;,  89 

reuniens  of  Hensen,  1170 

spiralis  modioli,  1169 
Canaliculi  of  bone,  46 
Canaliculus  tympanicus,  1151 
Canals,  acoustic,  external,  114& 

adductor,  698 

Alcock's,  1011,  1536 

alimentary,  1193 

anal,  1315 

of  appendix,  1304  ,. 

for  Arnold's  nerve,  90 

auditory,  1148 

of  Breschet,  733 

carotid,  136 

central,  of  cord,  840 

cervical,  1491 

for  chorda  tympani,  8 

of  Cloquet,  1129 

of  cochlea,  1167 
membranous,  1172 

crural,  1531 

dental,  1202 
anterior,  107 
inferior,  324 
posterior,  106 

diploic,  733 

ethmoidal,  82,  100 

for  Eustachian  tube,  1154 

fascial,  1536 

femoral,  509,  1531 

Haversian,  38 

of  Huguier,  84,  1047 

Hunter's,  521,  698 

hyaloid,  1129 

incisor,  110 

infraorbital,  107,  140 

inguinal,  448,  1517 

for  Jacobson's  nerve,  90 

lachrymal,  1142 

malar,  114 

medullary,  857 

naso-palatine,  121 

neural,  857 

neurenteric,  1242 

of  Nuck,  1462,  1501 

obturator,  525 


1556 


INDEX 


Canals,  palatine,  anterior,  143 
posterior,  107,  116 
accessory,  116,  135 
palato-maxillary,  107 
of  Petit,  1130 
pterygo-palatine,  135 
pterygoid,  135 
sacral,  64 

«f  Schlemm,  1108,  1111 
semicircular,  1165 
spermatic,  448,  1517 
spinal,  69 
of  Stilling,  1129 
for  tensor  tympani,  91,  1153 
-vertebral,  49 
A^idian,  96,  135 
Volkmann's,  38 
of  Wirsung,  1351 
Cancellous  bone,  35 

lamella;  of,  39 
'Canine  eminence,  106 
fossa,  106,  140 
teeth,  1197 
Canthi  of  eyelids,  1138 
■"Cap"  of  Broca,  874 
Capillaries,  liistology  of,  584 
Capitellum  of  humerus,  181 
Capsula  extrema,  894 
Capsular   ligaments.      See    Indi- 
vidual joints. 
Capsules,  atrabiliary,  1430 
Bowman's,  1418 
of  brain,  external,  894 
internal,  892 
fibres  of,  892 
cartilage,  260 
of  Glisson,  770,  1256,  1337 
of  kidneys,  fatty,  1411 

true,  1415 
of  lens,  1130 
parotid,  1216 
of  prostate  gland,  1449 
suprarenal,  1428 
of  Ttoon,  1103 
Caput,  cornu  of  cord,  839 

gallinaginis,  1442 
Cardia,  1270 

Cardiac  depression  of  liver,  1327 
ganglion  of  Wrisberg,  1081 
glands,  1278 
lymphatics,  815 
muscular  fibres,  361 
nerve,  cervical,  1061 
great,  1077 
inferior,  1077 
middle,  1077 
minor,  1077 
superior,  1076 
thoracic,  1061 
orifice  of  stomach,  1270 
plexus  of  nerves,  1081 
anterior,  1081 
deep,  1081 
great,  1081 
superficial,  1081 
portion  of  stomach,  1269 
veins,  770 
anterior,  771 
great,  770 
left,  771 
middle,  771 
posterior,  771 
right,  771 
Cardio-motor  nerves,  1071 
Carina  uretii rails  vagina;,  1484 
Carotico-tympanic  nerve,  1073 
Carotid  arteries,  common,  595 

branches    of,    occasional, 

598 
peculiarities  of,  598 
relations  of,  596 


Carotid  arteries,    common,   sur- 
face form  of,  598 
surgical  anatomy  of,  598 
external,  600 
branches  of,  601 
relations  of,  600 
surface  fonn  of,  601 
surgical  anatomy  of,  601 
internal,  619 

branches  of,  621 
cavernous  portion,  621 
cerebral  portion,  621 
cervical  portion  620 
peculiarities  of,  621 
petrous  portion,  620 
relations  of,  620 
surgical  anatomy  of,  621 

body,  1409 

canal,  136 

foramen,  external,  89 
internal,  88 

ganglion,  1073 

gland,  786,  1409 

surgical  anatomy  of,  1409 

groove,  93 

nerves,  1057 

plexus,  1073 

sheath,  388 

triangle,  inferior,  616 
superior,  394,  617 

tubercle,  51 
Carpal  arch,  anterior,  659 
posterior,  659 

artery,  radial,  anterior,  659 
posterior,  659 
ulnar,  anterior,  663 
posterior,  663 

bones,  development  of,  205 
Carpo-metacarpal    articulations, 

321 
Carpus,  193 

articulations  of,  319 
first  row,  319 
second  row,  319 

common  characters  of,  193 

ligaments  of,  319 

surface  form  of,  204 

surgical  anatomy  of,  204 
Cartilage,  259 

accessory  quadrate,  1097 

alar,  1097 

of  aperture  of  nose,  1097 

articular,  259 

arytenoid,  1364 

capsule,  260 

costal,  164 

cricoid,  1363 

cuneiform,  1365 

of  ear,  1146 

elastic,  260 

ensiform,  155 

of  epiglottis,  1365 

epiphysial,  36,  44 

fibro-,  260 

hyaline,  259 

intrathyroid,  1363 

of  Jacobson,  1097 

of  larynx,  1362 

of  nose,  1096 

permanent,  259 

of  pinna,  1146 

of  Santorini,  1365 

sesamoid,  1097 

spaces,  260 

temporarv,  259 

thyroid,  1362 

of  trachea,  1378 

triangular,  of  septum  of  nose, 
1097 

vomerine,  1097 

of  Wrisberg,  1365 


Cartilage,  xiphoid,  155 
Cartilaginous  isthmus  of  pinna, 
1146 

portion    of    Eustachian    tube, 
1154 
of  external  auditory  meatus 
1148 
Cartilago  triticea,  1365 
Caruncle,  lachrymal,  1142 
Caruncula  lacrimalis,  1140 

major  of  Santorini,  1288 

minor  of  Santorini,  1288 
Carunculse  mystiforma-,  1482 
Casserius,   perforating  nerve   of, 

985 
Cauda  equina,  1006 

helicis,  1146 
Caudal  gut,  1242 
Caudate  lobe  of  liver,  1333 

nucleus,  891 
bulb  of,  891 
head  of,  891 
surcingle  of,  891 
tail  of,  891 
Cava,  ascending,  764 

inferior,  764 

peculiarities  of,  764 

superior,  752 
Cave  of  Meckel,  848 
Cavernous  body,  artery  of,  691 

groove,  93 

nerves  of  penis,  1086 

plexus,  1073 

portion     of     internal     carotid 
artery,  621 
of  urethra,  1443 

sinus,  739 

surgical  anatomy  of,  740 
Cavity,  buccal,  1193 

of  cervix  uteri,  1491 

cotyloid,  213 

glenoid,  175 

of  larynx,  1368 

of  Meckel,  848 

of  mouth,  143 

nasal,  142 

oral,  1193 

of  pelvis,  1431 

pericardiothoracic,  1236 

of  pleura,  1382 

pleuroperitoneal,  1236 

sigmoid,  of  radius,  191 
of  ulna,  186 

of  thorax,  556 

of  tunica  vaginalis,  1470 

tympanic,  1150 

of  uterus,  1491 
Cavum  concha?,  1145 

Meckelii,  1027 

oris  proprium,  1193 
Cells,  amacrino,  1125 

basket,  936 

bipolar,  820 

centro-acinar,   of  Langerhans, 
1352 

of  Claudius,  1175 

column,  lateral,  846 

of  Deiters,  1175 

enamel,  1206 

ethmoidal,  82,  100 
posterior,  145 

of  Golgi,  821 

gustatory,  1091 

of  Hensen,  1175 

hepatic,  1338 

horizontal,  of  Cajal,  1125 

of  Martinotti,  921 

mastoid,  86 

multipolar,  820 

nerve,  820 
axone  of,  821 


Cells,  nerve,  dendrites  of,  821 
development  of,  823 
epitheliuni,  830 
olfactory,  1101 
oxyntic,  1277 
parietal,  1277 
peptic,  of  glands,  1277 
prickle,  1109 
of  Purkinje,  925 
of  Sertoli,  1472 
sphenoidal,  94 
unipolar,  820 
Cementum  of  teeth,  1204 
development  of,  1207 
Central  canal  of  cord,  840 
coil  of  cochlea,  1167 
ganglionic  vessels  of  brain,  630 
lobe  of  cerebrum,  878 
sulcus  of  Rolando,  867 
tendon  of  diaphragm,  429 
Centrifugal    projection   fibres   of 

cerebrum,  914 
Centripetal   projection   fibres   of 

cerebrum,  914 
Centro-acinar    cells    of    Langer- 

hans,  1352 
Centrum  ovale  majus  of  Vieus- 
sens,  886 
minus,  885 
vertebra,  48 
Cephalic  vein,  747 

median,  746 
Cephalo-auricular  angle,  1144 
Cerato-hyals  of  hyoid  bone,  154 
Cerebellar   arteries,    anterior   in- 
ferior, 640 
posterior  inferior,  639 
superior,  640 
columns,  843 
notch,  anterior,  926 

posterior,  926 
tract,    antero-lateral,    ascend- 
ing, 842 
descending,  843 
direct,  843 
dorso-lateral,  843 
path  of,  963 
veins,  deep,  736 
superficial,  736 
inferior,  736 
superior,  736 
Cerebellum,  926 
amygdala  of,  931 
corpus  dentatum  of,  937 
cortex  of,  936 
fibres  of,  932 
proper,  936 
fissures  of,  927 
fra^nulum  of,  928 
ganglion  of,  937 
gray  matter  of,  936 
hemispheres  of,  885,  926 
lamina  of,  927 
lobes  of,  926,  928 
nodules  of,  930 
peduncles  of,  932,  943 

superior,  910 
structure  of,  internal,  931 
surfaces  of,  inferior,  lobes  on, 
930 
under,  929 
upper,  927 
tonsil  of,  931 
uvula  of,  931 
vallecula  of,  926 
vermiform  process  of,  926 
weight  of,  938 
white  matter  of,  931 
Cerebral  artery,  anterior,  626 
branches  of,  626 
middle,  627 


INDEX 

Cerebral  arterv,  middle,  branches 
of,  628"^ 
posterior,  640 
convolutions,  857 
cranium,  71 

hemorrhage,  arteries  of,  628 
localization,  953 
lymphatic  vessels,  779 
nerves,  1019 
peduncles,  906 
portion     of     internal     carotid 

artery,  621 
veins,  734 
cortical,  735 
deep,  735 
inferior,  735 
median,  735 
superficial,  735 
superior,  735 
ventricles,  888 
Cerebro-cortico-pontal      nerve 

paths,  960 
Cerebro-spinal  axis,  832 

nervous    system,    structure 
of,  817 
Cerebrum,  commissure  of,  ante- 
rior, 896 
fibres  of,  914 
fissures  of,   longitudinal,   865, 

882 
gray  matter  of,  918 
hemispheres  of,  864 

constituent  parts  of,  864 
general     considerations     of, 

864 
surface  of,  865 

external,  lobes  on,  869 
mesial,  fissures  of,  869 

sulci  of,  869 
outer,  fissures  of,  865 

sulci  of,  865 
tentorial,  fissures  of,  869 
sulci  of,  869 
interior  of,  885 
parts  composing,  885 
peduncles  of,  882,  884 
structure  of,  913 
ventricles  of,  888,  900,  901 
white  matter  of,  913 
Ceruminous  glands,  1149 
Cervical  artery,  ascending,  641 
deep,  646 
superficial,  642 
transverse,  642 
canal,  1491 
cardiac  nerves,  1061 
fascia,  deep,  387 
superficial,  386 
surgical  anatomy  of,  389 
ganglion,  inferior,  1077 

branches,  central  commu- 
nicating, 1077 
peripheral,  1077 
middle,  1076 

branches  of,  central  com- 
municating, 1076 
peripheral,  1077 
superior,  1072 
branches  of,  1073 
central,  1073 
•  communicating,  1073 
peripheral,  1073 
surgical  anatomy  of,  1077 
glands,  deep,  786 

accessory  chains  to,  787 
lower,  787 
upper,  786 
superficial,  784 
anterior,  784 
nerves,  968 

divisions  of,  anterior,  971 


1557 

Cervical    nerves,    divisions    of, 
dorsal,  968 

from  facial  nerve,  1049 
posterior,  968 
roots  of,  968 
superficial,  973 
pleura,  1385 
plexus,  972 

branches,  deep,  974 

superficial,  972 
posterior,  970 
surgical  anatomy  of,  977 
portion     of     internal     carotid 
artery,  620 
of  oesophagus,  1226 
region,  superficial,  muscles  of, 

386 
rib,  53 
veins,  anterior  deep,  733 

posterior  deep,  733 
vertebra,  seventh,  53 
vertebrae,  49 
laminae  of,  49 
body  of,  49 
pedicles  of,  49 
processes  of,  50 
Cervicalis  ascendens  muscle,  419 
Cervico-facial  nerve,  1049 
Cervix  of  bladder,  1435 
comu  of  cord,  839 
uteri,  1488 

cavity  of,  1491 
Chassaignac's  tubercle,  69 
Check  ligaments,  278 

of  eye,  1105 
Cheeks,  1195 

mucous  membrane  of,  1195 
surgical  anatomy  of,  1224 
Chemical    composition  of   bone, 
41 
of  nervous  tissue,  824 
Chest,  155 

articulations  of,  159 
attachment  of  muscles  to,  159 
boundaries  of,  155 
development  of,  158 
structure  of,  158 
surface  form  of,  156 
surgical  anatomy  of,  165 
Chiasma    or    optic    commissure, 

1021 
Chink  of  glottis,  1369 
Choanse,  146 

Chondro-glossus  muscle,  397 
-sternal      ligament,     anterior, 
288 
interarticular,  288 
posterior,  288 
-xiphoid     ligament,     anterior, 
^     288 

"^posterior,  288 
Chorda  tympani  nerve,  1047 
Chordae  tendineae  of  left  ventri- 
cle, 573 
of  right  ventricle,  570 
Willisi,  737 
Choroid  arteries,  anterior,  628 
posterior,  640 
coat  of  eye,  1111 

structure  of,  1112 
fissure,  890,  900 
nerves  of,  1120 
plexus,  899 

of  body  of  ventricle,  900 
of  fourth  ventricle,  901 
of  lateral  ventricle,  900 
of  third  ventricle,  901 
vein,  735 
Chromatophile  granules,  820 
Chyli  receptaculum,  624 
Cilia,  or  eyelashes,  1137 


1558 


INDEX 


Ciliary  arteries,  anterior,  623 
long,  625 
short,  625 
body,  1115 
ganglion,  1031 

long  root  of,  1030 
glands,  1190 
ligament,  1116 
margin,  1117 
muscles,  1115 
nerves,  long,  1030 

short,  lOaO 
processes  of  eye,  1115 
structure  of,  1115 
Cingulum,  879,  918 
Circle  of  Willis,  629,  640 
Circular  sinus,  742 
Circulus  of  iris,  major,  625 
minor,  625 
tonsillaris,  1036 
Circumanal  glands,  1190 
Circumduction,  274 
Circumflex  arteries  of  arm,  651 
of  thigh,  705 
iliac  artery,  deep,  697 
superficial,  704 
vein,  deep,  759 
nerve,  984 

lower  branch,  985 
upper  branch,  985 
vein,  deep,  758 
superficial,  756 
Circumflexus  muscle,  404 

relations  of,  404 
Circumpatellar  anastomosis,  711 
Circumvallate  papillae  of  tongue, 

1089 
Cistern  of  Pecquet,  775 
Cisterna  basalis,  852 
magna,  853 
pontis,  853 
Clado,    appendiculo-ovarian    lig- 
ament of,  1304 
Clarke,     vesicular     column     of, 

843 
Claudius,  cells  of,  1175 
Claustrum,  894 
Clava  of  fasciculus  gracilis,  941 
Clavicle,  167 

articulations  of,  170 
attachment    of     muscles    to, 

170 
development  of,  170 
peculiarities  of,   in  sexes  and 

individuals,  170 
structure  of,  170 
surface  form  of,  170 
surgical  anatomy  of,  170 
Clavicular  facet,  157 
Clavi-pectoral  fascia,  467 
Clinoid  process,  anterior,  131 
middle,  93,  132 
posterior,  93,  132 
Clitoris,  1479 
arteries  of,  1480 
crus  of,  1480 
fraenum  of,  1479 
muscles  of,  461 
nerves  of,  1480 
dorsal,  1013 
prepuce  of,  1479 
Clivus,  93 

monticuli  of  cerebellum,  928 
Cloquet,  canal  of,  1129 
gland  of,  795,  798 
ligament  of,  1466 
septum  crurale  of,  509 
Coccygeal  artery,  693 
body,  1410 
gland,  1410 
ligament,  833 


Coccygeal  nerve,  divisions  of,  an- 
terior, 1009 
posterior,  1008 
Coccygeus  muscle,  455 
Coccyx,  65 

apex  of,  66 

articulation  of,  67 

attachment  of  muscles  to,  67 

base  of,  66 

borders  of,  66 

cornua  of,  66 

development  of,  66 

surfaces  of,  66 
Cochlea,  1165 

canal  of,  bony,  1167 
membranous,  1172 
spiral,  1167 

lamina  spiralis  of,  1167 

ligament  of,  spiral,  1172 

nerve,  1053 
Cochlear  artery,  1126 

path,  1053 

root  of  eighth  nerve,  1051 

window,  1152 
Coeliac  artery,  671 

axis,  671 

glands,  800 

plexus,  1061,  1084 
Colic  area  of  kidneys,  1414 

artery,  left,  678 
middle,  676 
right,  675 

glands,  808 

impression  of  liver,  1329 

plexus,  1085 
Collar  bone,  167 
Collateral  fissure,  871 

intercostal  artery,  668 
Colles'  fascia,  456,  1515 

ligament,  437 
CoUiculus  nervi  optici,  1364 
Colloid  material,  1404 
Colon,  1309 

ascending,   1309 

descending,  1309 

pelvic,  1311 

sigmoid,  1311 

surgical  anatomy  of,  1326 

transverse,  1309 
Colostrum  corpuscles,   1507 
Columella  cochleae,  1166 
Column   of  Marchi  and   Lowen- 

thal,  843 
Columna  nasi,  1096 
ColumniE  cameae  of  left  ventricle, 
573 
of  right  ventricle,  570 
Columns  of  Bertin,  1416 

cerebellar,  843 

of  Morgagni,  1319 

of  spinal  cord,  838 

of  vagina,  1484 
Comes  nervi  ischiadic! artery,  693 
mediana  artery,  663 
phrenici  artery,  644 
Comma  tract,  descending,  844 
Commissura  hippocampi,  896 
Commissural  fibres  of  cerebrum, 

916 
Commissure  of  brain,  anterior,  896 
gray,  903 
middle,  903 
posterior,  903 
soft,  903 

Gudden's,  912,  1021 

of  habenula,  904 

of  Mevnert,  908 

optic,"  131,  882,  1021 

of  spinal  cord,  839 
anterior,  839 
gray,  839 


Commissure  of  spinal  cord,  gray, 
anterior,  839 
posterior,  839 
posterior,  839 
white,  839 
Common  carotid  artery,  595 
facial  vein,  726 
femoral  artery,  699 
iliac  arteries,  681 
glands,  799 
vein,  764 
temporal  vein,  727 
ulnar  vein,  745 
Communicantes  hypoglossi  nerve, 

974 
Communicating    arteries,    ante- 
rior cerebral,  627 
posterior  cerebral,  628 
of  ulnar,  anterior,  662 
Compact  bone,  35 

longitudinal  section  of,  39 
transverse  section  of,  38 
Complexus  muscle,  420 

relations  of,  420 
Compressor  narium  minor  mus- 
cle, 376 
sacculi  laryngis,  1373 
urethrse  muscle  in  female,  462 
in  male,  460 
Conarium,  905 

Concentric  lines  of  Schreger,  1203 
Concha  auricula?,  1145 
Conducting  tracts  of  cord,  841 
Conductor  sonorus,  945 
Condyles  of  bones.     See  Bones. 
Condylic     portion     of     occipital 

bone,  71 
Condyloid  articulation,  265 
foramen,  anterior,  73,  133,  136 

posterior,  73,  133,  136 
fossa,  anterior,  136 

posterior,  136 
glands  of  Leaf,  795 
process,  125 
Cone-bipolars,  1125 

-granules  of  retina,  1126 
Cones  of  retina,  1126 
Congenital  hernia,  1523 
Conglobate  glands,  774 
Conical  papillte,  1090 
Conjugate  diameter  of  pelvis,  217 
Conjunctiva,  1140 

bulbar  portion  of,  1140 
fornix  of,  1140 
glands  of,  1140 
nerves  of,  1140 
palpebral  portion  of,  1140 
surgical  anatomy  of,  1144 
Connective    tissue,    subserous, 

1246 
Conoid  ligament,  300 

tubercle,  168 
Constriction  lobe  of  liver,  1336 
Constrictor  isthmi  faucium  mus- 
cle, 398,  405 
muscles,  inferior,  400 
middle,  401 
superior,  401 
urethrse  muscle  in  female,  462 
in  male,  460 
Conus  arteriosus,  569 

terminalis,  837 
Convolutions,  angular,  876 
of  brain,  865 
of  Broca,  874 
callosal,  879 
dentate,  879 
frontal,  872 
hippocampal,  879 
of  limbic  lobe,  879 
marginal,  873 


INDEX 


1559 


Convolutions,  occipital,  877 
occipito-temporal,  878 
orbital,  internal,  873 
parietal,  876 

ascending,  876 
post-parietal,  876 
precuneus,  877 
quadrati,  877 
subcalcarine,  877 
subcollateral,  878 
supramarginal,  876 
temporal,  877 
uncinate,  879 
Cooper,  ligament  of,  437,  448 
Coraco-acromial  ligament,  301 
-brachialis  muscle,  475 
bursa  of,  475 
relations  of,  475 
-clavicular  ligaraient,  300 
-humeral  ligament,  304 
Coracoid  ligament,  302 

process,  175 
Cord,  gangliated,  1071 

cervical  portion  of,  1071 
lumbar  portion  of,  1079 
pelvic  portion  of,  1080 
sacral  portion  of,  1080 
thoracic  portion  of,  1078 
spermatic,  1466 
spinal.     Sec  Spinal  cord, 
vocal,  1370 
Cordiform  tendon  of  diaphragm, 

429 
Corium,  1180 

corpus  papillare  of,  1181 
of  tongue,  1089 
Cornea,  1108 
arteries  of,  1111 
nerves  of,  1111 
structure  of,  1109 
Corneal  endothelium,  1111 

spaces,  1110 
Comical    tubercle    of    Sairtibrini, 

1368 
Cornicula  laryngis,  1365 
Cornu  ammonis,  897 
commissural  tract,  844 
of  lateral  ventricle,  889 
Cornua  of  coccyx,  66 
of  hyoid  bone,  154 
sacral,  62 
Corona  ciliaris,  1115 

glandis,  1454 
Coronal  suture,  78,  127 
Coronarv  artery,  671 
of  heart,  590 
descending,  590 
infundibular,  590 
marginal,  590 
peculiarities  of,  591 
transverse,  590 
of  lip,  inferior,  607 

superior,  607 
of  stomach,  671 
ligament  of  knee,  340 

of  liver,  1334 
plexus,  1085 
anterior,  1081 
left,  1081 
posterior,  1081 
right,  1081 
sinus,  567,  771 
valve,  567 
vein,  768 
left,  770 
small,  771 
Coronoid  fossa,  181 
process  of  jaw,  125 
of  ulna,  186 
Corpora  albicantia,  883 
bigemina,  911 


Corpora  cavernosa,  1455 
arteries  of,  1458 
bulb  of,  1456 
structure  of,  1457 
trabeculae  of,  1457 
veins  of,  1458 
geniculata,  911 
mammillaria,  883 

peduncles  of,  883 
quadrigemina,  907,  911 
brachia  of,  119 
structure  of,  911 
Corpus  albicans,  895 
Arantii,  571,  573 
callosum,  882,  S86 
beak  of,  886 
body  of.  886 
pad  of,  886 

peduncles  of,  882,  886 
rostrum  of,  886 
spleuium  of,  886 
cavernosum,  artery  of,  691 
dentatum  of  cerebellum,  937 

of  olive,  951 
fimbriatum,  890,  896,  898 
of  olivary  body,  951 
papillare  of  corium,  1181 
spongiosum,  1458 

structure  of,  1458 
striatum,  890 
Corpuscles  of  Ilerbst,  829 
Malpighian,  of  kidney,  1417 

of  spleen,  1358 
Pacinian,  828 
of  Purkinje,  936 
tactile,  827 
of  Vater,  828 
Corrugator    cutis     ani    muscle, 
449 
supercilii  muscle,  371 
relations  of,  371 
Cortex  of  cerebellum,  936 
of  cerebrum,  cells  of,  919 
gray  matter  of,  918 
nerve-fibres  of,  920 
Corti,  ganglion  of,  1053 
membrane  of,  1175 
organ  of,  1173 
rods  of,  1174 
tunnel  of,  1174 
Cortical  arteries  of  brain,  631 
cerebral  veins,  735 
portion  of  kidney,  1416 

of  suprarenal  capsule,  1430 
of  thymus  gland,  1408 
substance  of  teeth,  1204 
Costal  cartilages,  164 

attachment    of   muscles   to, 

164 
borders  of,  164 
extremities  of,  164 
surfaces  of,  164 
facet,  169 
pleura,  1385 
process,  50 
surface  of  lungs,  1391 
Costo-axillary  vein,  748 
-central  articulations,  283 
-chondral  articulations,  290 
-clavicular  ligament,  298 
-coracoid  ligament,  467 

membrane,  467 
-mediastinal  sinus,  1386 
-sternal  articulations,  287 
-transverse  articulations,  285 
foramen,  50 
ligament,  long,  285 
middle,  286 
posterior,  286 
-vertebral  articulations,  283 
ligament,  anterior,  284 


Costo-xiphoid     ligament,     ante- 
rior, 288 
posterior,  288 
Cotunnis,  nerve  of,  1036 
Cotyloid  cavity,  213 
ligament,  329 
notch,  213 
Cowper's  glands,  1453 

structure  of,  1453 
Cranial  bones,  71 
fossa,  143 
nerves,  1019 

path  of,  962 
reflex,  963 

region,  dissection  of,  366 
fascia  of,  superficial,  366 
lymphatics  of,  779 
vessels  of,  782 
sutures,  127 
Cranio-cerebral  topography,  954 
Cranium,  71 
cerebral,  71 
development  of,  102 
differences  in  size  and  form  of, 

146 
fasciae  of,  365 
lymphatics  of,  779 
membranous,  102 
muscles  of,  365 
Cremaster  muscle,  439,  1516 
Cremasteric  arterv,  696 

fascia,  1464,  1516 
Crescentric  lobe,  anterior,  928 

posterior,  928 
Crescents  of  Gianuzzi,  1218 
Crest,  buccinator,  124 
ethmoidal,  94 
falciform,  89     ■ 
frontal,  80,  130 
incisor,  111 
infratemporal,  95 
lachrymal,  113 

bone,  141 
nasal,  111,  116 
obturator,  213 
occipital,  external,  72,  136 

internal,  74,  133 
sphenoidal,  94 
supramastoid,  84,  137 
temporal,  76,  80,  84 
of  tibia,  234 

turbinated,  inferior,  107,  117 
superior,  117 
Cribriform  fascia,  512,  1527 
lamina,  1108 
plate,  130 

of  ethmoid,  99 
Crico-arytenoid     articulation, 
1367 
ligaments,  1367 
muscle,  lateral,  1373 
posterior,  1372 
-thyroid  artery,  602 
articulation,  1367 
membrane,  1367 
muscle,  1372 
-tracheal  ligament,  1368 
Cricoid  cartilage,  1 363 
borders  of,  1364 
surfaces  of,  1364 
Crista  falciformis,  89 
galli,  99,  130 
terminalis,  565 
vestibuli,  1164 
Crossed  descending  tract,  842 

pyramidal  tract,  842 
Crucial  ligaments  of  knee,  337 
Cruciform  ligament,  275 
Crura  ad  cerebrum,  932 
ad  medullam,  934 
ad  posterior,  934 


1560 


INDEX 


Crura  cerebri,  884 
of  diaphragm,  427 
of  penis,  1454 
Crural  arch,  deep,  448,  1531 
superficial,  436,  1529 
canal,  509,  1531 
nerve,  anterior,  1004 
ring,  437,  509,  1532 
septum,  1532 
sheath,  509 
Crureus  muscle,  517 
nerve  to,  1006 
relations  of,  517 
Crus     cerebri,    tegmentum    of, 
885 
of  helix,  1145 
Crusta  of  crus  cerebri,  907 

petrosa  of  teeth,  1204 
Cruveilhier,     atlanto-odontoid 
joint  of,  274 
glenoid  ligament  of,  359 
Crypts  of  Lieberkiihn,  1295 

of  Morgagni,  1319 
Crystalline  lens,  1130 
capsule  of,  1130 
substance  of,  1130 
structure  of,  1131 
Cuboid  bone,  245 

articulations  of,  246 
attachment  of    muscles    to, 

246 
surfaces  of,  245,  246 
tuberosity  of,  245 
Culmen      monticuli      cerebelli, 

928 
Cuneate  funiculus,  941 
lobe,  877 

nucleus,  accessory,  948 
tubercle,  941 
Cuneiform  bone,  foot,  247 
external,  248 

articulations  of,  249 
attachment  of  muscles 

to,  249 
surfaces  of,  248 
internal,  247 

articulations  of,  247 
attachment  of  muscles 

to,  247 
surfaces  of,  247 
middle,  248 

articulations  of,  248 
attachment  cif  muscles 

to,  248 
surfaces  of,  248 
of  hand,  197 

articulations  of,  197 
surfaces  of,  197 
cartilages,  1365 
tubercle  of  Wrisberg,  1368 
Cuneus,  875 

Cupola  of  cochlea,  1167,  1172 
Cushion  of  epiglottis,  1365 
Cusps  of  bicuspid  valve,  572 

of  tricuspid  valve,  570 
Cutaneous  nerve,  external,  985, 
1003 
internal,  986,  1004 
middle,  1004 
palmar,  987 
perforating,  1011 
Cuticle  of  skin,  1181 
Cutis  vera,  1180 
Cuvier,  duct  of,  561 
Cymba  conchffi,  1145 
Cystic  artery,  674 
duct,  1344 

plexus  of  nerves,  1085 
vein,  769 
Czermak,  interglobular  spaces  of, 
1202 


Dacryon,  141 
Dartos  of  scrotum,  1463 
Uarwin,  tubercle  of,  1.145 
Deciduous  teeth,  1196 
Decussatio    nervorum    trochlea- 

rium,  1025 
Decussation  of  fillet,  949 

of  pyramids,  947 
Deep  annectant  gyrus,  867 
anterior  thoracic  nerve,  984 
branches    of    cervical    plexus, 

974,  976 
cardiac  plexus,  1081 
cerebral  veins,  735 
cervical  artery,  646 
fascia,  387 
glands,  786 
circumflex  iliac  artery,  697 

vein,  759 
crural  arch,  448,  1531 
dorsal  vein  of  penis,  762 
epigastric  artery,  696 

vein,  759 
external  pudic  artery,  704 
fascia,  364 

of  arm,  470,  474 

of  back,  411 

of  femoral  region,   anterior, 

513 
of  forearm,  478 
of  leg,  532 
of  shoulder,  470 
of  thoracic  region,  anterior, 
463 
femoral  artery,  704 

lymphatic  glands,  795 
inguinal  lymphatic  glands,  795 
lymphatic  glands  of  upper  ex- 
tremity, 790 
vessels    of   abdominal    wall, 
801 
of  lower  extremity,  797 
of  upper  extremity,  792 
muscles  of  abdomen,  449 
palmar  arch,  658 
fascia,  493 
veins,  747 
parotid  lymphatic  glands,  782 
patellar  bursa,  518 
pectoral  fascia,  464 
perineal  fascia,  1538 
petrosal  nerve,  1073 
radial  veins,  747 
superficial  external   pudic   ar- 
tery, 704 
temporal  artery,  614 
nerves,  1037 
veins,  727 
transverse  fascia  of  leg,  537 
ulnar  veins,  747 
veins  of  foot,  758 

of  lower  extremity,  758 
of  upper  extremity,  747 
Deiters,  cells  of,  1175 
nucleus  of,  926,  1050 
process,  817 
Deltoid  eminence,  179 
impression,  179 
muscle,  470 

relations  of,  471 
tubercle,  168 
Demilunes  of  Heidenhain,  1218 
Demours,  membrane  of,  1110 
Dendraxones,  821 
Dendrites  of  nerve-cells,  821 
Dental  artery,  inferior,  614 
posterior,  615 
band,  1205 
canal,  1202 


Dental  canal,  anterior,  107 
inferior,  124 
posterior,  106 
fibres,  1202 
follicle,  1206 

lamina,  1205  » 

nerves,  anterior  superior,  1033 
inferior,  1039 
middle  superior,  1033 
posterior  superior,  1032 
periosteum,  1204 
plexus,  superior,  1033 
pulp,  1200 
sac,  1206 
tubuh,  1202 
Dentate  convolution,  879 
gray  matter  of,  921 
fascia,  879,  898 
fissure,  871,  879 
ligament,  835 
Dentinal    sheath    of    Neumann, 
1203 
tubuli,  1202 
Dentine,  1202 

development  of,  1207 
papilla,  1205 
Depression,  pterygoid,  125 

trigeminal,  88 
Depressions  of  bone,  34 
Depressor  ala;  nasi  muscle,  37S 
anguli  oris  muscle,  378 
relations  of,  378 
labii  inferioris  muscle,  378 
relations  of,  378 
Dermic  coat  of  hair-follicle,  1 188 
Dermis,  1180 

Descemet,  membrane  of,  1110 
Descendens     hypoglossi     nerve, 

1066 
Descending  aorta,  665 

branch    of    superior    cervical 

ganglion,  1074 
colon,  1309 
comma  tract,  844 
cornu  of  lateral  ventricle,  890 
mesocolon,  1258 
nerve  tract,  959 
oblique   muscle    of    abdomen, 

433 
palatine  artery,  615 
ramus  of  ischium,  211 

of  pubis,  213 
root  of  fifth  nerve,  1026 
Descent  of  ovary,  1501 
of  testicles,  1461 

surgical  anatomy  of,  1462 
Detrusor  urinse  muscle,  1437 
Development   of  alimentary  ca- 
nal, 1236 
of  alveoli  of  teeth,  1207 
of  atlas,  59 
of  axis,  59 
of  brain,  857 
of  carpal  bones,  205 
of  cementum,  1207 
of  clavicle,  170 
of  coccyx,  66 
of  cranium,  102 
of  dentine,  1207 
of  enamel,  1206 
of  ethmoid  bone,  101 
of  femur,  228 
of  fibula.  238 
of  foot,  253 
of  frontal  bone,  82 
of  humerus,  182 
of  hyoid  bone,  154 
of  inferior    turbinated     bone, 

120 
of  lachrymal  bone,  113 
of  liver,  1243 


INDEX 


1561 


Development  of  maxillary  bone, 
inferior,  125 

of  mesentery,  1237 

of  metacarpal  bones,  205 

of  metatarsal  bones,  253 

of  organs,  clironological  table 
of,  1547 

of  nasal  bones,  105 

of  nerve-cells,  823 
-fibres,  823 

of  occipital  bone,  75 

of  omentum,  1238 

of  OS  innominatum,  214 

of  palate  bone,  119 

of  pancreas,  1244 

of  parietal  bone,  78 

of  patella,  231 

of  peritoneal  cavitv,  1242 

of  peritoneum,  1234,  1242 

of  permanent  teeth,  1208 

of  phalanges  of  foot,  254 
of  hand,  206 

of  radius,  192 

of  ribs,  163 

of  sacrum,  64 

of  scapula,  175 

of  sphenoid  bone,  97 

of  spleen,  1245 

of  sternum,  158 

of  superior    maxillary    bones, 
112 

of  tarsal  bones,  253 

of  teeth,  1204 

of  temporal  bone,  91 

of  tibia,  236 

of  tongue,  1242 

of  tonsils,  1243 

of  ulna,  189 

of  vertebrse,  58 

of  viscera,  1234 

of  vomer,  122 

Wormian,  103 
Diagonal  sulcus,  868 
Diameter  of  pelvis,  217 
Diaphragm,  427 

actions  of,  430 

crura  of,  427 

lymphatics  of,  810 

nerves  of,  430 

openings  of,  429 
aortic,  429 
oesophageal,  430 
for  vena  cava,  430 

of  pelvis,  1231 

pillars  of,  427 

serous  membranes  of,  430 

tendons  of,  central,  429 
Diaphragma  selliE,  851,  882 
Diaphragmatic  ganglion,  1084 

hernia,  427 

lymphatic,  810 

pleura,  1386 

portion  of  a?sophagus,  1226 
Diaphysis,  34 
Diarthrosis,  265 
Diaxonic  cells,  821 
Digastric  branch  of  facial  nerve, 
1048 

fossa,  86,  123,  136 

lobe  of  cerebellum,  931 

muscle,  393 

relations  of,  394 

nerve,  from  facial,  1048 
Digestion,  organs  of,  1193 
Digital  arteries,  dorsal,  659 
of  ulna,  664 

fossa,  223 

nerves  of  foot,  1015 
hand,  987 
Dilator  naris  anterior  muscle,  376 
posterior  muscle,  376 


Dilator  tubse  muscle  of  Rudinger, 

1155 
Diploe,  34 

veins  of,  733 
Diploic  canals,  733 
veins,  frontal,  734 
occipital,  734 
parietal  external,  734 
temporal,  anterior,  734 
posterior,  734 
Direct  cerebellar  tract,  843 
inguinal  hernia,  1523 
pyramidal  tract,  842 
Disk,  interpubic,  296 
intervertebral,  270 
optic,  1121 
Dissection  of  axilla,  463 
of  brain,  847 

of  internal  oblique  muscle,  437 
of  muscles  of  abdomen,  432 
of  arm,  470 

of  auricular  region,  369 
of  back,  410,  414,  415,  417 
of  cranial  region,  366 
of  femoral  region,  anterior, 
512 
internal,  519 
posterior,  529 
of  fibular  region,  539 
of  forearm,  478,  482 
of  gluteal  region,  522 
of  hand,  491 
of  iliac  region,  508 
of  infra-hyoid  region,  391 
of  intermaxillary  region,  378 
of  lingual  region,  396 
of  mandibular  region,  377 
of  orbital  region,  372 
of  palatal  region,  403 
of  palpebral  region,  370 
of  pectoral  region,  463 
of  pharyngeal  region,  400 
of  plantar  region,  544,  545, 

546 
of  pterygo-mandibular      re- 
gion, 383 
of  radial  region,  484 
of  scapular  region,  anterior, 
471 
posterior,  472 
of  shoulder,  470 
of  superficial  cervical  region 

386 
of  supra-hyoid  region,  393 
of  tibio-fibular  region,  ante- 
rior, 532 
posterior,  534,  537 
of  pancreas,  1348 
of  perinseum,  1535 
of  popliteal  space,  707 
of  rectus  abdominis  muscle,  442 
of  sole  of  foot,  542 
of  spinal  cord,  832 
of  temporal  muscle,  382 
of  trans versalis  muscle,  441 
Diverticulum,  Meckel's,  1290 
Dorsal  artery  of  penis,  692 
auditory  nuclei,  950 
digital  arteries,  659 

veins,  745 
divisions    of    cervical    nerves, 

968 
interosseous  arteries,  659,  715 
nerves,  993 

of  clitoris,  1013 
divisions  of,  anterior,  993 

posterior,  993 
of  penis,  1013 
roots  of,  993 
region,  muscles  of,  543 
root  of  eighth  nerve,  1051 


Dorsal  root  of  spinal  nerves,  96S 
ulnar  vein,  745 
veins  of  penis,  deep,  762 

superficial,  762 
vertebrse,  53 
bodies  of,  53 
lamina  of,  54 
peculiar,  55 
pedicles  of,  54 
processes  of,  54 
Dorsalis  hallucis  artery,  716 
indicis  artery,  659 
linguae  artery,  603 
nasi  artery,  625 
pedis  artery,  714 

branches  of,  715 
peculiarities  of,  715 
relations  of,  714 
surface  marking  of,  715 
surgical  anatomy  of,  715 
pollicis  arteries,  659 
scapulae  artery,  651 
Dorsi-lumbar  nerve,  996 

-spinal  veins,  753 
Dorso-lateral  cerebellar  tract,  84$ 
-median  fissure,  838 
-ventral  fibres  of  cord,  841 
Dorsum  ephippii,  93,  152 
of  penis,  1455 
of  scapula,  172 
sella;,  93 
Douglas,  fold  of,  semilunar,  439,. 
444 
pouch,  1490 
Drumhead,  1155 
Duct  or  ducts,  aberrant,  of  epi- 
didymis,  1472 
alveolar,  1378 
of  Bartholin,  1217 
biliary,  1341 

of  Cuvier,  561  ^ 

cystic,  1344 
ejaculatory,  1476 
galactophorus,  1507 
Gartner's,  1499 
hepatic,  1342 
interlobular,  1341 
of  kidney,  1420 
lactiferous,  1507 
of  liver,  1341 
lymphatic,  right,  778 
mammillary,  1507 
nasal,  1142 
pancreatic,  1351 
parotid,  1215 
of  Rivinus,  1217 
seminal,  1472 
Stenson's,  1215 
of  submaxillary  gland,  121ft 
thoracic,  775 
thyroglossal,  1090,  1401 
Wharton's,  1216 
Ductless  glands,  1401 
Ductus  arteriosus,  579 

communis  choledoclms,  1344 
endolymphaticus,  89,  1165 
venosus,  fissure  of,  1331 
fossa  of,  1331 
Duodenal  area  of  kidney,  1414 
folds,  1260 
inferior,  1261 
superior,  1261 
fossse,  1260 
inferior,  1260 
superior,  1261 
glands,  1295 
impression  of  liver,  1329 
Duodeno-jejunal  fossa,  1261 
-mesocolic  ligaments,  1261 
-renal  ligament,  1255 
Duodenum,  1282 


1562 


INDEX 


13uodenum,  arteries  of,  1288 
ascending  portion  of,  1286 
descending  portion  of,  1285 
first  portion  of,  1284 
flexure  of,  superior,  1285 
fourth  portion  of,  1286 
horizontal  portion  of,  1285 
interior  of,  1288 
lymphatics  of,  1288 
muscular  coat  of,  1288 
nerves  of,  1288 
peritoneal  coat  of,  1288 
pre-aortic  portion  of,  1285 
«econd  portion  of,  1285 
structure  of,  1288 
submucous  coat  of,  1288 
superior  portion  of,  1284 
surgical  anatomy  of,  1325 
suspensory  muscle  of,  1286 
tliird  portion  of,  1285 
transverse  portion  of,  1285 
veins  of,  1288 
Dura  mater  of  brain,  847 
arteries  of,  848 
lymphatics  of,  849 
nerves  of,  849 
proctesses  of,  849 
structure  of,  848 
veins  of,  849 
sinuses  of,  736 
of  spinal  cord,  832 
structure  of,  834 
Duverney,  gland  of,  1482 


E 


Ear,  1144 

auditory    meatus,    external, 

1148 
auricle,  1144 
bones  of,  1158 
cartilages  of,  1146 
cochlea,  1165 
-drum  membrane,   secondary, 

1152 
-external,  1144 
auricle  of,  1144 
lobule  of,  1145 
internal,  1163 
labyrinth,  1163 

membranous,  1169 
osseous,  1164 
middle,  1150 
muscles  of  auricle,  1 147 

of  tympanum,  1157 
ossicula  of,  1158 
pinna  of,  1144 
semicircular  canals  of,  1165 
surgical  anatomy  of,  1176 
trumpet,  1153 
tympanum,  1150 
^.  Ebner,  glands  of,  1091 
Efferent  nerve  tract,  959 
Egg  tubes,  1502 
Eighth  nerve,  1050 
origin  of,  1050 
roots  of,  1050 
svirgical  anatomy  of,  1054 
Ejaculator  seminis  muscle,  457 

urinse  muscle,  457 
Ejaculatory  ducts,  1476 
Elastic  cartilage,  260 
tissue,  yellow,  261 
Elbow,  bend  of,  surgical  anatomv 
of,  653 
bone,  184 
bursa  of,  311 

-joint,  articulations  of,  308 
surface  form  of,  312 
surgical  anatomy  of,  312 


Elbow,    ligament    of,    anterior, 
309 
posterior,  309 
Eleventh  nerve,  1063 

surgical  anatomy  of,  1063 
Ellipsoid  of  Krause,  1127 
Elliptical  recess,  1164 
Eminence,  articular,  of  temporal 
bone,  84 

of  bone,  34 

canine,  106 

deltoid,  179 

frontal,  79 

ilio-pectineal,  210,  213 

of  Jacobson,  1100 

nasal,  79 

olivary,  93 

parietal,  76 
Eminentia  articularis,  84,  135 

collate  rails,  890 

conchae,  1146 

fossa;  triangularis,  1046 

teres,  945 
Emissary  veins,  743 

surgical  anatomy  of,  743 
Emulgent  vein,  766 
Enamel  cells,  1206 

cuticle,  1204 

fibres,  1203 

jelly,  1206 

-organ  of  tooth,  1205 

prisms,  1203 

of  teeth,  1203 

development  of,  1206 
Enarthrosis,  266 
Encephalon,  857 
Encysted  hernia,  1523 
End-bulb  of  Krause,  827 
Endocardium,  574 
Endo-gnathion,  111 
Endolymph,  1169 
Endoneurium,  825 
Endosteum,  36 
Endothelium,  corneal,  1111 
Endothoracic  fascia,  1385 
Ensiform  appendix,  158 
surfaces  of,  158 

cartilage,  155 
Eosinophiles,  56 
Epactal  bones,  103 
Eparterial   branch  of   bronchus, 

1377 
Epencephalon,  857 
E])endyma,  888 
Epicondyles,  181 
Epicondylic  ridge,  179 
Epicteric  bone,  103 
Epidermic    coat    of    hair-follicle, 

1188 
Epididymis,  1469 

aberrant  ducts  of,  1472 

structure  of,  1471 
Epidural  space,  833,  847 
Epigastric     artery,    deep,    696, 
1518 
peculiarities  of,  696 
surgical  anatomy  of,  697 
internal,  696 
superficial,  704 
superior,  645 

glands,  superior,  802 

plexus,  1083 

vein,  deep,  759 
Epiglottis,  1365 

cartilage  of,  1365 

cushion  of,  1365 

surfaces  of,  1365 
Epimysium,  361 
Epineurium,  825 
Epiotic  portion  of  temporal  bone, 

91 


Epiphysial  cartilage,  36 
Epiphysis  of  bone,  34 

cerebri,  905 
Epithelium.    See  Various  organs, 
germinal,  of  Waldeyer,  1501 
lens,  1130 
transitional,  1428 
Epitrochlea,  181 
Epitympanic  recess,  87,  1150 

space,  87 
Epo-ophoron,  1499 
Erectile  tissue  of  penis,  1457 

of  vagina,  1485 
Erector  clitoridis  muscle,  461 
penis  muscle,  458 
spinas  muscle,  417 
relations  of,  420 
Ethmo-frontal  suture,  130 

-sphenoidal,    130 
Ethmoid  bone,  98 

articulations  of,  102 
cribriform  plate  of,  99 
development  of,  101 
horizontal  lamina  of,  99 
infundibulum  of,  101 
lateral  mass  of,  100 
OS  planum  of,  100 
perpendicular      plate       of, 

100 
unciform  process  of,  100 
Ethmoidal  arteries,  623 
canals,  82,  100 
cells,  82,  100 

posterior,  145 
crest,  94 
foramina,  82 

anterior,  130,  141 
posterior,  130 
notch,  82 
process  of  inferior  turbinated, 

120 
sinuses,  101 
spine,  93,  130 
Eustachian  cushion,  1221 
tube,  1153 

canal  for,  1154 
cartilaginous    portion    of, 

1154 
osseous  portion  of,  1154 
valve,  567 
in  foetus,  578 
Excretory    apparatus    of    liver, 

1342 
Exo-gnathion,  111 
Expiration,  muscles  of,  432 
Expression,  muscles  of,  385 
Exsanguinated     renal     zone     of 

Hyrtl,  679,  1423 
Extensor  brevis  digitorum  mus- 
cle, 543 
pollicis  muscle,  489 
carpi  radialis  brevior  muscle, 
485 
bursa  of,  486 
longior  muscle,  485 
ulnaris  muscle,  487 
coccygeus  muscle,  422 
communis    digitorum    muscle, 
486 
relations  of,  487 
indicis  muscle,  490 
longus  digitorum  muscle,  533 

pollicis  muscle,  489 
minimi  digiti  muscle,  487 
ossis  metacarpi  pollicis,  489 
primi  internodii  pollicis  mus- 
cle, 489 
proprius  hallucis  muscle,  532 

relations  of,  533 
secundi  internodii  pollicis  mus- 
cle, 489 


INDEX 


1563 


External    abdominal    ring,    436, 
1514 
acoustic  canal,  1148 
angular  process,  80,  140 
annular  ligament,  542 
anterior  thoracic  nerve,  984 
arcuate  ligament,  427,  449 
auditory  canal,  1148 

meatus,  138,  1148 
bicipital  ridge,  179 
■calcaneal  nerves,  1014 
■calcanean  artery,  718 
•calcaneo-astragaloid  ligament, 
352 

-scaphoid  ligament,  353 
■capsule  of  brain,  894 
carotid  artery,  600 

foramen,  89 
circumflex  arterj'  of  thigh,  705 
condyle  of  femur,  226 
crucial  ligament,  337 
cutaneous  nerve,  985,  1003 
car,  1144 
cpicondyle,  181 
geniculate  body,  904,  912 
hiemorrhoidal  veins,  760 
iliac  artery,  694 

glands,  797 

vein,  759 
inguinal  fossa,  1520 

hernia,  1520 
interchondral  ligament,  290 
intercostal  muscle,  425 
jugular  vein,  728 
lateral  ligament,  280,  310 
malleolus,  238 

ligament  of,  1160 
mammary  artery,  651 
maxillary  artery,  604 
oblique  line,  123 

muscle,  433 

aponeurosis  of,  1513 
occipital  crest,  72,  136 

protuberance,  71,  136 
orbital  foramina,  95 
OS,  1489 

palatine  nerve,  1035 
palpebral  arteries,  623 
parietal  diploic  vein,  734 
parieto-occipital  sulcus,  867 
plantar  artery,  720 

nerve,  1016 
popliteal  nerve,  1016 
ptervgoid  muscle,  383 

nerve,  1037 

plate,  96 
pudic  artery,  deep,  704 
superficial,  704 
deep,  704 
saphenous  gland,  795 

vein,  756 
semicircular  canal,  1165 
semilunar  fibrocartilage,  339 
spermatic  fascia,  436,  1514 
sphincter  ani  muscle,  450 
supracondylar  ridge,  179 
tarsal  ligament,  370 
tuberosity  of  tibia,  233 
lilxtracranial  lymphatics,  780 
Extrinsic  muscles  of  tongue,  398 
Eye,  1103 

appendages  of,  1137 
aqueous  humor  of,  1128 
choroid,  1111 
ciliary  muscle,  1115 
conjunctiva,  1140 
cornea,  1108 
crystalline  lens,  1130 
globe  of,  arteries  of,  1132 

lymphatics  of,  1133 

nerves  of,  1134 


Eye,  globe  of,  veins  of,  1133 

iris,  1117 

lachrymal  apparatus,  1141 
glands,  1141 
sac,  1142 

nasal  duct,  1142 

pupil  of,  1117 

refracting  media  of,  1128 

retina,  1120 

sclera,  1107 

surgical  anatomy  of,  1134 

-teeth,  1197 

tunics  of,  1107 

uvea  of,  1118 

vitreous  body  of,  1129 
Eyeball,  coverings  of,  375 
Eyebrow,  1137 
Eyelashes,  1138 

surgical  anatomy  of,  1143 
Eyelid,  1137 

Meibomian  glands  of,  1139 

orbital  portion,  1137 

structure  of,  1138 

surface  form  of,  1143 

surgical  anatomy  of,  1143 

tarsal  portion,  1137 
Erythroblasts,  36 


Face,  arteries  of,  604 
bones  of,  104 
exterior  of,  veins  of,  725 
fasciae  of,  365 
lymphatics  of,  779 
muscles  of,  365 

surface  form  of,  385 
nerves  of,  1044 
veins  of,  726 
Facet,  clavicular,  157 

costal,  169 
Facial  artery,  604 

branches  of,  605 

relations  of,  605 

surgical  anatomy  of,  607 

transverse,  611 
bones,  104 
nerve,  1044 

branches  of,  1046 

nucleus  of,  925 

surgical  anatomy  of,  1049 
suture,  transverse,  128 
vein,  anterior,  726 

common,  726 

transverse,  727 

surgical  anatomy  of,  726 
Falciform  crest,  89 
ligament,  293 

of  liver,  1333 
process  of  fascia  lata,  515 
Fallopian  tube,  1497 

ampulla  of,  1497 

artery  of,  1498 

course  pursued  by,  1498 

fimbriae  of,  1497 

infundibulum  of,  1497 

isthmus  of,  1497 

lymphatics  of,  804,  1498 

nerve  of,  1499 

structure  of,  1498 

uterine  portion  of,  1497 

vein  of,  1498 
False  pelvis,  215 
ribs,  159 

vocal  cords,  1370 
Falx  cerebelli,  850 
cerebri,  849 
inguinalis,  448 
Fascia  or  fasciae,  361 
of  abdomen,  deep,  433 


Fascia   or    fasciae,    of   abdomen, 
superficial,  433,  1511 

triangular,  1515 
of  acromial  region,  470 
anal,  454,  1546 
of  arm,  474 

deep,  470 

superficial,  470 
axillary,  463,  646 
of  back,  deep,  411 

superficial,  411 
bicipital,  476,  746 
bucco-pharyngeal,    380,    388, 

401,  1222 
of  Camper,  433 
cervical,  deep,  387 

superficial,  386 
clavi-pectoral,  467 
of  CoUes,  456,  1515 
costo-coracoid,  467 
of  cranium,  365 
cremasteric,  1464,  1516 
cribriform,  512,  1527 
deep,  364 
dentate,  879,  898 
endo-pel-vica,  1544 
endothoracic,  1385 
of  face,  365 

of  femoral     region,     anterior, 
deep,  513 
superficial,  512 
of  foot,  541 
of  forearm,  478 
of  hand,  491 
of  hip,  522 
ihac,  508 
infraspinatus,  472 
infundibulifomi,  446,  1464 
intercolumnar,  436,  1463,  1514 
intercostal,  424 
ischio-rectal,  454,  1546 
lata,  513,  1527 

falciform  process  of,  1528 

iliac  portion,  514,  1528 

pubic  portion,  514,  1528 
of  leg,  532 

transverse,  537 
of  lo-wer  extremity,  507 
masseteric,  381 
of  neck,  385 
obturator,  1546 
of  orbit,  374 
palmar,  deep,  493 
palpebral,  1139 
parotid,  388,  1215 
parotideo-masseterica,  388 
pectoral,  deep,  464 
pelvic,  1544 

of  perinaeum    in    male,    deep, 
458,  1538 
superficial,  455 
phrenico-pleural,  1386 
plantar,  542 
pre-tracheal,  388 
prevertebral,  388 
of  quadratus  lumborum,  449 
recto- vesical,  1546 
retro-renal,  1412 
salpingopharyngea  of  Troltsch 

1155 
of  Scarpa,  433 
semilunar,  476 
of  shoulder,  deep,  470 

superficial,  470 
spermatic,  1463 

external,  436,  1514 
internal,  446 
middle,  440 
subscapular,  471 
superficial,  364 

of  cranial  region,  366 


1564 


INDEX 


Fascia  or  fasciae,  supraspinatus, 
472 
temporal,  381 
of  thigh,  512 

of  thoracic     region,     anterior, 
deep,  463 
superficial,  463 
of  thorax,  424 
transversalis,  445,  1517 
triangular,  437 
of  trunk,  410 
of  upper  extremity,  462 
Fascial  canal,  1536 
Fasciculi,  261 
Fasciculus  cuneatus,  941 
gracilis,  941 

clava  of,  941 
longitudinal,  inferior,  918 

superior,  918 
occipito-frontal,  918 
perpendicular,  918 
rectus,  918 
of  Rolando,  941 
teres,  945 
of  Turck,  842 
uncinate,  917 
Fasciola  cinerea,  879 
Fauces,  isthmus  of,  1212 

pillars  of,  1211 
Female  bladder,  1446 

organs  of  generation,  1477 
perinaeum,  1542 
urethra,  1446 
Femoral  artery,  697 

anastomotica  magna  of,  707 
branches  of,  704 
common,  699 
deep,  704 

peculiarities  of,  701 
superficial,  700 
surface  marking  of,  701 
surgical  anatomy  of,  701 
canal,  509,  1531 
cutaneous  nerves,  1011 
hernia,  1525 
complete,  1534 
coverings  of,  1533 
descent  of,  1533 
incomplete,  1533 
varieties  of,  1533 
ligament,  515 

lymphatic  glands,  deep,  795 
region,  anterior,  fascia  of,  deep, 
513 
superficial,  512 
surgical  anatomy  of,  515 
muscles  of,  512 
dissection  of,  512 
surgical  anatomy  of,  518 
internal,  muscles  of,  519 
dissection  of,  519 
surgical  anatomy  of,  522 
posterior,  muscles  of,  529 
dissection  of,  529 
surgical  anatomy  of,  531 
ring,  437,  509,  1532 
sheath,  509,  1530 
spur,  227 
vein,  758 
Femur,  221 

articulations  of,  228 
attachment  of  muscles  to,  229 
condyles  of,  225 
development  of,  228 
lower  extremity  of,  225 
shaft  of,  224 
borders  of,  225 
linea  aspera,  224 
surfaces  of,  225 
spiral  line  of,  223 
structure  of,  226 


Femur,  surface  form  of,  229 
surgical  anatomy  of,  229 
trochlea  of,  225 
tubercle  of,  223 
tuberosities  of,  226 
upper  extremity  of,  221 
head  of,  221 
neck  of,  222 
trochanters  of,  223 
Fenestra  ovalis,  1152 
rotunda,  1152,  1167 
Fenestrated  membrane  of  Henle, 

585 
Ferrein,  pyramids  of,  1417 
Fibre-baskets,  1127 
Fibres  of  auricles  of  heart,  575 
of  cerebellum,  peduncular,  932 
projection,  932 
proper,  936 
of  cerebrum,  association,  916 
commissural,  916 
peduncular,  914 
projection,  914 
transverse,  916 
of  cord,  dorso-ventral,  841 
longitudinal,  841 
oblique,  841 
transverse,  841 
dental,  1202 
enamel,  1203 

inter-cerebral,    of    optic    com- 
missure, 1021 
intercolumnar,  436 
of  internal    capsule    of    brain, 

892 
lens,  1130 
of  medulla,  arciform,  942 

arcuate,  942 
of  pons  Varolii,  923 
longitudinal,  923 
transverse,  923 
preanal,  of  levator  ani,  453 
prd-rectales,  454 
of  Remak,  823 
of  Sharpey,  37 
sustentacular,  1121 
of  tegmentum,  908 
of  ventricles  of  heart,  575 
Fibro-cartilage,  260 

circumferential,  261 
connecting,  261 
interarticular,  281,  298,  300 

triangular,  315 
intervertebral,  270 
semilunar,  337 
stratiform,  261 
-elastic  coat  of  spleen,  1356 
-muscular  coat  of  gall-bladder, 
1343 
Fibrous  band  of  Baillarger,  920 
of  Bechterew,  920 
coat  of  liver,  1337 
of  pharynx,  1223 
of  ureter,  1427 
membrane  of  trachea,  1379 
rings  of  heart,  574 
septum  of  tongue,  398 
sheaths  of  flexor  tendons,  545 
tissue,  white,  261 
Fibula,  237 

articulations  of,  238 
attachment  of  muscles  to,  239 
development  of,  238 
lower  extremity  of,  23*8 
nutrient  artery  of,  718 
oblique  line  of,  237 
shaft  of,  237 
borders  of,  237 
surfaces  of,  238 
styloid  process  of,  237 
surface  form  of,  239 


Fibula,  surgical  anatomy  of,  239 

upper  extremity  of,  237 
Fibular  artery,  superior,  713 
region,  muscles  of,  539 
actions  of,  540 
dissection  of,  539 
surgical  anatomv  of,  541 
Fifth  nerve,  1026 
nuclei  of,  925 
root  of,  ascending,  948 
semilunar  ganglion  of,  1027 
surface  marking  of,  1041 
surgical  anatomy  of,  1041 
ventricle,  897 
Filiform  papilla;  of  tongue,  109O 
Fillet,  decussation  of,  949 

of  gyrus  fornicatus,  879,  918 
interoUvary,  909,  949 
lateral,  885,  910 
lower,  910 
median,  910 
mesial,  910 
superior,  910 
upper,  910 
Filtrum    ventriculi    of     Merkel, 

1368 
Fimbria,  898 
Fimbriae  of  Fallopian  tube,  1497 

of  ovary,  1499 
Fimbrio-dentate  fissure,  898 
Finger,  index,  metacarpal  bone 
of,  202 
ligaments  of,  322 

superficial  transverse,  494 
little,  metacarpal  bone  of,  203 
middle,    metacarpal    bone    of, 

202 
ring,  metacarpal  bone  of,  203 
veins  of,  superficial,  745 
First  nerve,  1019 
Fissura  antitragohelicina,  1146 
prima,  881 
vestibuli,  1168 
Fissure  or  fissures,  antero-lateral, 
838 
antero-median,  837 
antitragohelicina,  1146 
auricular,  90,  136 
of  Bichat,  900 
of  brain,  865 
calcarine,  870 
callosal,  879 
of  cerebellum,  927,  930 
of  cerebrum,  longitudinal,  865 

882 
choroid,  890,  900 
collateral,  871 
of  cord,  837 
lateral  838 
dentate,  871,  879 
dorso-median,  838 
of  ductus  venosus,  1331 
fimbrio-dentate,  898 
of  gall-bladder,  1331 
Glaserian,  84,  1152 
hippocampal,  871,  879 
of  liver,  1331 

longitudinal,  1331 
transverse,  1332 
of  lung,  1392 
mammary,    prolongations    of, 

1505 
orbital,  96 

petro- tympanic,  84,  1152 
portal,  1332 
posterior  median,  838 
post-clival,  928 
-limbic,  871 
-nodular,  930 
-pvramidal,  930 
pre-cHval,  928 


INDEX 


1565 


Fissure     or    fissures,     pre-pvra- 
midal,  930 
pterygoid,  96 
ptervgo-maxillarv,  139 
of  Rolando,  867 " 
sphenoidal  96,  132 
spheno-maxillarv,  115,  138 
of  Santorini,  1146,  1148 
of  spinal  cord,  837 
of  Sylvius,  866,  884 
of  tragus,  1146 
umbilical,  1331 
ventro-median,  837 
Flat  bones,  34 

Flechsig,  fibrous  systems  of,  915 
Flexor  accessorius  muscle,  546 
brevis  digitorum  muscle,  544 
hallucis  muscle,  546 
minimi  digiti  m.uscle,   foot, 
547 
hand, 498 
pollicis  muscle,  497 
carpi  radialis  muscle,  479 

ulnaris  muscle,  480 
longus  digitorum  muscle,  538 
hallucis  muscle,  538 
pollicis  muscle,  482 
ossis   metacarpi    pollicis   mus- 
cle, 497 
profundus    digitorum    muscle, 

482 
sublimis  digitorum  muscle,  481 
tendons,  fibrous  sheaths  of,  545 
Flexure  of  colon,  hepatic,  1309 
sigmoid,  1311 
splenic,  1309 
of  duodenum,  superior,  1285 
of  large  intestine,  hepatic, 1300 
sigmoid,  1300 
splenic,  1300 
Floating  lobe  of  hver,  1336 
Floccular  fossa,  89,  133 
Flocculus,  931 

peduncle  of,  931 
Flood's  ligament,  304 
Foetal  circulation,  579 

lung,  1394 
Fold  of  Douglas,  semilunar,  439, 
444 
duodenal,  1260 
hypogastric,  1519 
ovario-pelvic,  1500 
recto-vaginal,  1490 
of  urachus,  1519 
utero- vesical,  1490 
of  uterus,  1489 
Folia  linguae,  1087 
Folium  cacuminis,  929 
Follicle,  dental,  1206 
simple,  1295,  1319 
Follicular  lymph-sinus,  1306 
Fontana,  spaces  of,  1110 
Fontanelles,  102 

anterior,  78 
Foot,  arteries  of,  714 
bones  of,  239 
bursfB  of,  543 
development  of,  253 
fascia;  of,  541 
ligaments  of,  541 
muscles  of,  541 
nerves  of,  1015 
phalanges  of,  252 

articulations  of,  359 
sole  of,  dissection  of,  542 
surface  form  of,  255,  360 
surgical  anatomy  of,  256,  360 
veins  of,  758 
Foramen,  96 

Cfficum,  80,  130,  1087 
carotid,  external,  89 


Foramen,  carotid,  internal,  88 
condyloid,    anterior,    73,    133, 
136 

posterior,  73,  133,  136 
costo-transverse,  50 
dental,  inferior,  124 
diaphragmatis  sellse,  883 
ethmoidal,  anterior,  130,  141 

posterior,  130,  141 
of  Huschke,  92 
infraorbital,  106,  140 
jugular,  73,  133 
of  Key  and  Retzius,  853 
lacerum  anterius,  96,  132 

medium,  132 

posterius,  133 
of  Langer,  464,  646,  791 
magnum,  72,  133 
of  Majendie,  834,  853 
malar,  113 
mastoid,  85,  138 
mental,  123,  140 
of  Monro,  889 
obturator,  214 
optic,  93,  131,  142 
ovale,  95,  132,  567 

in  foetus,  578 
palatine,  great,  116 

posterior,  135 
parietal,  76 
pterygo-palatine,  95 
quadratum  of  diaphragm,  430 
rotund um,  95,  132 
sacro-sciatic,  great,  211,  294 
singulare,  89,  1169 
of  Sommerring,  1121 
spheno-palatine,  119,  143 
spinal,  49,  132 
sternal,  157 
stylo-mastoid,  90,  135 
supratrochlear,  181 
supraorbital,  80,  140 
temporo-malar,  115 
thyroid,  214 
vertebral,  49 
vertebrarterial,  50 
Vesalii,  95,  132 
Foramina  of  diaphragm,  430 
ethmoidal,  82 
incisor,  110 
intervertebral,  49 
of  Key  and  Retzius,  834 
malar,  113 
olfactory,  143 
orbital,  external,  95 
sacral,  anterior,  62 

posterior,  63 
of  Scarpa,  110,  135,  1036 
of  Stenson,  110 
Thebesii,  567,  568,  771 
Fore-gut,  1236 
Forearm,  arteries  of,  657 
bones  of,  184 
fasciae  of,  478 
interosseous  veins  of,  747 
lymphatics  of,  788 
muscles  of,  478 

dissection  of,  478,  482 
nerves  of,  984 
veins,  744 
Fore-brain,  857 
Forel,  occipito-frontal  fasciculus 

of,  918 
Form  of  bones,  33 
Formatio  reticularis,  845,  948 

alba,  949 

grisea,  949       ' 
Fornix,  895 
body  of,  895 
of  conjunctiva,  1140 
lyra  of,  896 


Fornix,  pillars  of,  anterior,  895 

posterior,  896 
vaginal,  1484 
Fossa  or  fossae  of  acetabulum,213 
of  antihelix,  1144 
canine,  106,  140 
condyloid,  anterior,  136 

posterior,  136 
coronoid,  181 
cranial,  143 
digastric,  86,  123,  136 
digital,  223  /- 

duodenal,  1260 
duodeno-jejunal,  1261 
floccular,  89,  133 
glenoid,  84,  135 
of  heUx,  1145 
ileo-appendicular,  1263 

-Cffical,  1263 

-colic,  1262 
iliac,  209 

incisive,  106,  123,  139 
incudis,  1153 
infraspinous,  172 
inguinal,  1248,  1520 

external,  1520 

internal,  1520 

middle,  1520 
intersigmoid,  1312 
ischio-rectal,  1536 
jugular,  91 
lachrymal,  81 
of  Landzert,  1262 
longitudinal,  of  liver,  1331 
mandibular,  84 
mastoid,  86 
mesocolic,  1261 
myrtiform,  106 
nasal,  142,  1098 
navicularis  of  urethra,  1444 

of  vulva,  1478 
occipital,  133 
olecranon,  181 
orbital,  143 
ovalis,  567 

palatine,  anterior,  110,  133 
paraduodenal,  1262 
patellaris,  1129 
pericaecal,  1262 
pituitary,  93 
pterygoid,  96,  115 
radial,  181 
retro-caecal,  1263 

-colic,  1263 

-duodenal,  1262 

-peritoneal,  1260 
rhomboid,  inferior,  840 
of  Rosenmiiller,  1221 
of  Scapha,  1145 
scaphoid,  97,  135,  1145 
sigmoid,  86 
of  skull,  anterior,  130 

infratemporal,  138 

middle,  130 

orbital,  140 

pterygo-palatine,  139 

posterior,  132 

spheno-maxillary,  139 

temporal,  137 

zygomatic,  138 
spheno-maxillary,  115 
sublingual,  123 
submaxillary,  123 
subscapulus,  171 
supra-tonsillar,  1213 
supraspinous,  172 
temporal,  76 
of  Treitz,  1260 
trochanteric,  223 
trochlear,  82 
umbilical,  1331 


1566 


INDEX 


Fossula  inferior,  1168 

superior,  1168 
Fourchette,  1478 
Fourth  nerve,  1025 
ventricle,  942 

lining  membrane  of,  945 
roof  of,  943 
triangles  of,  945 
wall  of,  anterior,  944 
posterior,  943 
Fovea     centralis    retinae,     1121, 
1128 
hemielliptica,  1164 
hemispherica,  1164 
inguinalis  lateralis,  1520 

mesialis,  1520 
oblonga,  1364 
superior,  945 
supra- vesicularis,  1520 
triangularis,  1364 
Foveolas,  Howship's,  38 
Fraenulum  of  cerebellum,  928 

of  ileo-csecal  valve,  1308 
Fraenum  of  clitoris,  1479 

labii    superioris  et    inferioris, 

1194 
linguae,  1087 
of  penis,  1455 
Frontal  air  sinus,  82 
artery,  611 

from  anterior  cerebral,  ante- 
rior internal,  627 
inferior  internal,  627 
middle  internal,  627 
posterior  internal,  627 
from    middle    cerebral,    as- 
cending, 628 
inferior  external,  628 
from  ophthalmic,  625 
bone,  79 

horizontal  portion  of,  81 
articulations  of,  83 
attachment  of  muscles 

to,  83 
border  of,  82 
development  of,  82 
structure  of,  82 
orbital  portion  of,  81 
articulations  of,  83 
attachment  of  muscles 

to,  83 
border  of,  82 
development  of,  82 
structure  of,  82 
vertical  portion,  79 
border  of,  81 
structure  of,  81 
convolutions,  ascending,  872 
inferior,  873 
middle,  873 
superior,  873 
crest,  80,  130 
diploic  vein,  734 
eminence,  79 

horn  of  lateral  ventricle,  889 
lobe,  872,  884 
nerve,  1030 
operculum,  866,  874 
process  of  malar,  114 
spine,  80 
sulci,  868,  873 
suture,  79,  127 
vein,  725 
Frontalis  muscle,  368 
Fron to-parietal  suture,  127 
-malar  suture,  128 
-sphenoidal  suture,  128 
Fundamental  plexus,  1111 
Fundiform  ligament  of  Retzius, 

541 
Fundus  glands,  1277 


Fundus     of     internal     auditory 
meatus,  1168 

tympani,  1151 

of  uterus,  1487 
Fungiform    papillae    of     tongue, 

1090 
Funicular    process,    hernia    of, 

1523 
Funiculus,  cuneate,  941 

gracilis,  941 

of  Rolando,  941 

slender,  941 

teres,  945 

wedge-shaped,  941 
Furcula,  1242 
Furrow,  interarticular,  565 

sternal,  165 
Fusiform  muscles,  362 


G 


Galactophorus  duct,  1507 
Galen,  testes  muUebres  of,  1499 

veins  of,  735,  771 
Gall-bladder,   1342 

arteries  of,   1346 

body  of,   1343 

fibro-muscular  coat  of,  1343 

fissure  for,  1331 

fundus  of,  1343 

lymphatics  of,  1346 

mucous  coat  of,   1343 

neck  of,  1343 

nerves  of,   1346 

notch  of,  1331 

relations  of,   1343 

serous  coat  of,  1343 

structure  of,  1343 

surgical  anatomy  of,   1347 

veins  of,   1346 
Ganglia  of  nerves,  831 

semilunar,  of  abdomen,  1084 
of  spinal  nerves,  966 
Gangliated  cord,   1071 

cervical  portion  of,  1071 

lumbar  portion  of,   1079 

pelvic  portion  of,   1080 

sacral  portion  of,   1080 

thoracic  portion  of,   1078 
Ganglion  of  Andersch,   1056 
Arnold's,  1039 
of  Bochdalek,    1033 
cardiac,  of  Wrisberg,  1081 
carotid,  1073 
cephalic,  1031 
of  cerebellum,  937 
cervical,  inferior,  1077 

middle,   1076 

superior,   1072 
ciliarv,  1031 

long  root  of,   1030 
of  Corti,   1053 
diaphragmatic,   1084 
of  facial  nerve,  1045 
of  fifth  nerve,  1031 
Gasserian,  1027 
geniculate,  1034,  1045 
of  glosso-pharvngeal,  1056 
impar,  1068 
inferior,  1056 
interpeduncular,  910 
jugular,  1056 
lenticular,  1031 
lumbar,  1080 
Meckel's,  1034 
mesenteric,  1085 
ophthalmic,    1031 
otic,   1039 
petrous,  1056 
pharyngeal,  1073 


Ganglion,  phrenic,    1084 
of  pneumogastric,   1059 
of  portio  dura,  1045 
radicis  cochlearis,  950 
of  Ribes,  1067 
semilunar,  of  abdomen,  1084 

of  fifth  nerve,  1027 
spheno-palatinc,   1034 
of  spinal  nerves,  966 
submaxillary,    1040 
superior,   1056 
of  sympathetic  nerves,  107L 
thoracic,  1078 
thvroid,  1076 
of  Valentin,   1033 
vestibular,    1053 
Ganglionar  gray  matter,  922 
Ganglionic   arteries,   postero- 
lateral, 640 
postero-median,  640 
branch  of  nasal  nerve,  1030 
vessels  of  brain,  central,  630 
Gartner's  duct,   1499 
Gasserian  ganglion,    1027 

branches  of,  1027 
Gastric  area  of  kidnej^  1414 
artery,   671,   674 
glands,  800,   1277 

true,   1277 
impression,  1333 
nerves,   1061 
plexus,    1085 
surface  of  liver,  1329 

of  spleen,   1354 
veins,  768 
Gastro-colic   omentum,    1256 
-duodenal  plexus,   1085 
-duodenalis  artery,  673 
-epiploic  plexus,  1085 
left,   1085 
vein,  768 
-epiploica    dextra    arter}',  673 

sinistra  artery,  674 
-hepatic  omentum,   1254 
-splenic  ligament,   1256 
omentum,   1256 
Gastrocnemius  muscle,  534 

bursa  of,  534 
Gemellus  muscle,  inferior,  527 

superior,  526 
Generation,   organs  of,  develop- 
ment of,  1547 
female,  1477 
male,  1447 
Genial  gland,  782 

tubercles,   123 
Geniculate  body,  external,  904. 
912 
internal,  904,  912 
ganglion,   1034,   1045 
Genio-glossus  muscle,  396 
-hyo-glossus  muscle,  396 
-hyoid  muscle,  395 
Genito-crural  nerve,  1000 
crural  branch,   1000 
genital  branch,  1000 
Germ  of  corpus  callosum,  886 
Gerlach,  valve  of,  1303 
Germinal    epithelium    of    Wal- 

deyer,   1501 
Giacomioni,  band  of,  879 
Gianuzzi,  crescents  of,  1218 
Gimbernat's  ligament,  437,  1515 
Gingival     branches     of     dental 

nerves,  1032 
Ginglymus,  265 
Giraldes,  organ  of,  1473 
Girdle,  pelvic,  207 

shoulder,  207 
Glabella  of  frontal  bone,  80,  139 
Gladiolus,  157 


INDEX 


1567 


Gladiolus,  borders  o',   157 

surfaces  of,  157 
Glands,  absorbent,  774 
agminated,   1296 
apical,  1091 
arytenoid,  1375 
of  Bartholin,   1482 
of  biliary  duets,  1342 
of  Bowman,   1101 
Brunner's,  1295 
buccal,   1195 
cardiac,   1278 
carotid,  1409 
ceruminous,  1149 
ciliary,  1190 
circumanal,  1190 
coccygeal,   1410 
conglobate,  774 
Cowper's,    1453 
ductless,   1401 
duodenal,   1295 
of  Duvemey,  1482 
epiglottis,  1374 
fundus,   1277 
gastric,    1277 
intestinal,  1295,  1319 
labial,  1195 
lachrymal,  1141 
of  larynx,  1374 
lenticular,  of  stomach,  1277 
of  Lieberkiihn,   1295,  1319 
lingual,  1091 
of  Littr^,    1444 
Luschka's,  1410 
lymphatic,  774 
mammary,  1503 

lymphatics  of,  812 
Meibomian,  1139 
molar,  1195 
of  Moll,  1138 
of  Montgomery,  1504 
mucilaginous,  262 
mucous,  1218 

of  Nuhn  and  Blandin,  1091 
odoriferae,  1454 
oesophageal,  1230 
oxvntic,  1277 
of  Pacchioni,  737,  854 
palatal,  1211 
parotid,  1214 
peptic,  1277 
Peyer's,  1296 
pharyngeal,  1224 
pineal,  905 

peduncles  of,  895 
prostate,  1447 

lymphatic  vessels  of,  803 
pyloric,  1277 
of    Rosenmiiller,    accessory, 

1141 
salivary,  1214 
sebaceous,  1138,  1191 
solitary,  1295,  1320 
sublingual,  1217 
submaxillary,  1216 
subparotid,  1215 
suburethral,  1482 
sudoriferous,  1190 
suprarenal,  1428 
sweat,  1190 
tarsal,  1139 
thymus,  1407 
thyroid,  1401 

arteries  of,  602 

lymphatic  vessels  of,  782 

veins  of,  731 
of  tongue,  1091 
tracheal,  1380 
of  Tyson,  1454 
of  V.  Ebner,  1091 
vulvo-vaginal,  1482 


Glandulse  Pacchioni,  737,  854 

Tysonii  odoriferae,  1454 
Glans  clitoridis,  1480 

penis,  1454 
Glaserian  fissure,  84,  1152 
Gleno-humeral  ligament,  305 
Glenoid  cavitv,   175 
fossa,  84,  135 
ligament,  175 

of  Cruveilhier,  359 
tuberosity,  175 
Glisson,  capsule  of,  770,  1256, 

1337 
Globus    of      epididymis    major, 
1469 
minor,  1469 
Glosso-epiglottic  ligament,   1365 
-epiglottidean  folds,    1366 
-pharyngeal   nerve,    1054 
nuclei  of,  950 
surgical  anatomy  of,  1057 
Glottis,  cliink  of,  1369 
false,  1369 
respiratoria,  1369 
true,  1369 
vocalis,  1369 
Gluteal  artery,  694 
inferior,  693 
cutaneous  nerve,  1011 
glands,  797 
line,  anterior,  207 
inferior,  208 
posterior,  207 
nerve,  inferior,  1011 

superior,  1010 
region,    Ivmphatic    vessels    of, 
801  ' 
muscles  of,  522 
dissection  of,  522 
surgical  anatomy  of,  528 
ridge,  224 
veins,  761 
Gluteo-femoral  bursa,  331 
Gluteus  maximus  muscle,  522 
medius  muscle,  523 
minimus  muscle,  523 
Golgi,  cells  of,  821 

organ  of,  829 
GoU,  tract  of,  839,  843 
Gomphosis,  264 
Gonion,  124 
Graafian  vesicles,  1502 

membrana     granulosa      of, 

1502 
ovicapsule  of,  1502 
Gracilis  muscle,  519 
Grande  lobe  limbique,  878 
Grandy's  corpuscles,  827 
Granular  sheath  of  Tomes,  1202 
Gray  commissure   of  brain,  903 
of  cord,  839 
anterior,  839 
posterior,  839 
matter,  central,  922 
of  cerebellum,  936 
of  cerebrum,  918 
of  cortex,  918 
of  ganglia,  922 
of  medulla,  945 
of  pons,  924 
ventricular,  922 
nerve-fibres,  823 
substance  of  cord,  845 
anterior  horn,  845 
dorsal  horn,  845 
lateral  horn,  845 
nerve-cells  of,  845 

-fibres  of,  845 
posterior  horn,  845 
ventral  horn,  845 
Great  auricular  nerve,  972 


Great  cardiac  nerve,  1077 
plexus,  1081 
vein,  770 

deep  petrosal  nerve,    1034 

occipital  nerve,  969 

omentum,  1256 

sacro-sciatic  foramen,  294 
ligament,  292 

sciatic  nerve,  1013 

sinus  of  aorta,  589 

superficial  petrosal  nerve,  1034 
Greater  alar  cartilage,  1097 

wings  of  sphenoid,  95 
Grooves,  auriculo- ventricular  of 
heart,  565 

basilar,  75 

bicipital,  179 

caroti^,  93 

cavernous,  93 

of  cord,  837 

infraorbital,  107,  141 

interventricular,  568 
of  heart,  565 

intervertebral,  49 

lachrymal,  107,   109,   141,  143: 

musculo-spiral,  179 

mylo-hyoidean,  124 

naso-palatine,  121 

obturator,  211,  213 

occipital,  86 

optic,  93,  130,  131 

peroneal,  245 

popliteal,  226 

pterygopalatine,  116 

sacral,  63 

of  spinal  cord,  837 

subclavian,  169 

subcostal,  162 

ulnar,  182 

vertebral,  155 
Gubemaculum  testis,  1461 
Gudden's  commissure,  912,  1021 
Guerin,  valve  of,  1444 
Gulf  of  internal  jugular  vein,  72ft 
Gullet,  1225 
Gums,  1195 

surgical  anatomy  of,   1224 
Gustatory  cells,  1091 

hair,  1091 

nerve,  1038 

branches  of,  1038 

path,  1057 

pore,  1090 
Gyri  of  brain,  865 

brevis  insulse,  878 
Gyrus,  angular,  876 

annectant,  deep,  867 

cinguli,  879 

fomicatus,  fillet  of,  879,  91S 

lingual,  877 

longus  insulse,  870 

marginal,  875 

occipi to-temporal,  877 

post-central,  876 

prsecentral,  872 

rectus,  874 

subcallosus,  882 

supra-callosus,  88V 


HABENTJIiA,  904 

commissure  of,  904 
trigone  of,  904 
Hsemorrhoidal  artery,   inferior, 
690 
middle,  687 
superior,  678 
gland,  middle,  799 
nerve,  inferior,  1011 


1568 


INDEX 


Hacmorrhoidal    plexus,    inferior, 
1086 
superior,  1085 
veins,  external,  760 
inferior,  760,  1011 
middle,  760 
superior,  768 
surgical  anatomy  of,  761 
Hair,  1187 

bloodvessels  of,  1189 
-bulb,  1187 

coats  of,  dermic,  1188 
of,  epidermic,  1188 
cortical  substance  of,  1189 
-follicle,  1187 
gustatory,  1091 
nerves  of,  1189 
olfactory,  1101 
-papilla,  1187 
root  of,  1187 
shaft  of,  1189 
stem  of,  1189 
-streams,  1187 
-whirlpools,  1187 
Haller,  rete  testis  of,  1471 
Hamstring  muscles,  529 
Hamular  process  of  lachrymal, 
113 
of  sphenoid,  96 
Hamulus,  1168 
Hand,  arteries  of,  660 
bones  of,  193 

development  of,  205 
bursa  of,  492 
fasciae  of,  491 
ligaments  of,  319 
muscles  of,  491 

dissection  of,  491 
nerves  of,  from  median,  987 
from  radial,  991 
from  ulnar,  989 
phalanges  of,  204 
veins  of,  745 
Hard  palate,  1210 
Harmonia,  264 
Hasner,  valve  of,  1142 
Haustra  coli,  1317 
Haversian  canal,  38 
Head,  arteries  of,  595 
exterior  of,  veins  of,  725 
lymphatic  glands  of,  780 
muscles  of,  surface  form  of, 

385 
veins  of,  724 
Heart,  562 

arteries  of,  577 
auricles  of,  fibres  of,  575 
left,  568 

sinus  of,  568 
right,  565 
cavities  of,  capacity  of,  564 
circular  fibres  of,  575 
component  parts  of,  565 
endocardium,  574 
fat  upon,  564 
fibrous  rings  of,  574 
grooves  of,   auriculo-ventricu- 
lar,  565 
interventricular,  565 
infundibulum  of,  569 
lymphatics  of,  577 

muscular  fibres  of,  575 
myocardium,  574 
nerves  of,  577 
position  of,  562 
size  of,  564 
spiral  fibres  of,  575 
structure  of,  574 
muscular,  575 
surface  form  of,  577 
surgical  anatomy  of,  578 


Heart,  veins  of,  577 

ventricle  of,  fibres  of,  575 

right,  569 
ventricular  portion  of,  568 
vortex  of,  575 
weight  of,  564 
Heel  bone,  242 

Heidenhain,  demilunes  of,   1218 
Helicine  arteries,  1458 
Helicis  major  muscle,  1147 

minor  muscle,   1147 
Helicotrema  of  cochlea,  1167 
Helix,  1144 
crus  of,  1145 
fossa  of,  1145 
muscles  of,  1147 
spine  of,  1146 
Helmholtz,  ligaments  of,  1160 
Helwig,  tract  of,  triangular,  843 

951 
Hemispheres  of  brain,  surface  of, 
under,  881 
of  cerebellum,  885,  926 
of  cerebrum,   864 

constituent  parts  of,  864 
general  considerations  of, 

864 
surfaces  of,  865 

external,  lobes   on,  869 
mesial,  fissures  of,  869 

sulci  of,  869 
outer,  fissures  of,  865 

sulci  of,  865 
tentorial,     fissures     and 
sulci  of,  869 
Henle,  fenestrated  membrane  of, 
585 
ligament  of,   438,   442 
loop  of,  1419 
spine  of,  88 
Hensen,  canalis  reuniens  of,  1170 
cells  of,  1175 
node,  857 
stripe,  1175 
Hepatic  area  of  kidneys,  1414 
artery,  672 
cells,  1338 
ducts,  1342 
flexure  of  colon,   1309 

of  large  intestine,   1300 
glands,  801 
plexus,  1085 
veins,  767 
Hepato-colic  ligament,  1255 
-duodenal  ligament,  1255 
-gastric    ligament,    1254 
Herbst,  corpuscles  of,  829 
Hernia,  congenital,  1523 
diaphragmatic,  427 
encysted,  1523 
femoral,  1525 
of  funicular  process,  1523 
infantile,  1523 
inguinal,  1520 
direct,  1523 
external,  1520 
obhque,  1517,  1520 
scrotal,  1521 

surgical  anatomy  of,   1511 
Hesselbach,  ligament  of,  438, 
442,  1517 
triangle,  1520 
Hey,  ligament  of,  515 
Hiatus  Fallopii,  88 
sacralis,  62 
semilunar,  747,  1099 
tendineus,  521 
Highmore,  antrum  of,  108 
Hilton,  compressor  sacculi  laryn- 
gis  muscle  of,  1373 
white  line  of,  1319 


Hilum  of  kidney,   1415 
of  ovary,  1500 
of  spleen,  1354 
Hind-brain,  922 

-gut,  1236 
Hinge-joint,  265 
Hip,  articulations  of,  325 
bursa  of,  330 
fascise  of,  522 
ligaments  of,  326 
muscles  of,  522 
surface  form  of,  333 
surgical  anatomy  of,  333 
Hippocampal  convolution,  879 

fissure,  871,  879 
Hippocampus  major,  889,  897 

gray  matter  of,  921 
His,  sulcus  terminalis  of,  566 
Histology  of  arteries,  584 

of  capillaries,  584 
Hook  bone,  199 
Horizontal  cells  of  Cajal,   1125 
lamina  of  ethmoid,  99 
plate  of  palate  bone,  116 
semicircular  canal,   1165 
Horner's  muscle,  371 
Homy  layer  of  skin,   1181 
Horseshoe  kidney,   1424 
Houston's  valves,  1318 
Howship's  lacuna?,  38 
Huguier,  canal  of,  84,  1047 
Humeral  region,   anterior,   mus- 
cles of,  474 
posterior  muscles  of,  477 
Humerus,  177 

articulations  of,  183 
attachment    of     muscles    to, 

183 
capitellum  of,  181 
development  of,  182 
lower  extremity  of,  181 
nutrient  canal  of,  180 
shaft  of,   179 
structure  of,  182 
surface  form  of,  183 
surgical  anatomy  of,  183 
trochlea  of,  181 
tuberosities  of,  179 
upper  extremity  of,   177 
Humors  of  eye,  1128 
Hunter's  canal,  521,  698 
Huschke,  foramen  of,  92 
Hyaline  cartilage,  259 
Hyaloid  canal  of  eye,  1129 

membrane  of  eye,  1129 
Hydatids  of  Morgagni,   1469 
non-pedunculated,  1469 
pedunculated,  1469 
Hymen,  1481 

imperforate,  1481 
Hyo-epiglottic  ligament,  1365 
-glossus  muscle,  397 
-thyroid  membrane,   1366 
Hyoid  artery  of  lingual,  603 
of  superior  thyroid,  602 
bone,  153 

attachment  of  muscles  to, 

154 
basi-hyal  of,  153 
body  of,  153 
borders  of,  154 
surfaces  of,  153 
cornua  of,  greater,  154 

lesser,  154 
development  of,  154 
region,     infra-,     muscles    of, 
391 
supra-,  muscles  of,  393 
surface  form  of,  154 
surgical  anatomy  of,  154 
tubercle  of,  153 


INDEX 


1569 


Hvparterial  branch  of  bronchus, 

1377 
Hypochondriac  region,  1233 
Hypogastric  artery,  683 
in  fcEtus,  684 

fold,  1519 

nerve,  999 

plexus,  1080,  1085 

region,  1233 

vein,  760 
JHvpoglossal  nerve,  1064 

branches  of,  1065,  1066 
surgical  anatomy  of,  1066 

nucleus,  949 
JHvrtl,  exsanguinated  renal  zone 

of,  679,  1423 


Ileo-appendicular  fold,  1263 
fossa,  1263 
-caecal  fossa,  1263 
inferior,  1263 
superior,  1262 
valve,  1308 

frajnulum  of,  1308 
-colic  arterv,  675 
fold,  1262 
fossa,  1262 
Ileum,  1289 

Iliac   arteries,    circumflex,  deep, 
697 
superficial,  704 
common,  681 
branches  of,  682 
compression  of,  683 
peculiarities  of,  682 
surface  marking  of,  682 
surgical  anatomy  of,  682 
external,  694 

branches  of,  696 
relations  of,  694 
surface  marking  of,  682, 

695 
surgical  anatomy  of,  695 
internal,  683 

branches  of,  686 
peculiarities  of,  685 
relations  of,  683 
surface  form  of,  694 
surgical  anatomy  of,  685, 
694 
bursa,  subtendinous,  331 
fascia,  508 
fossa,  209 
furrow,  220 
glands,  797 
common,  799 
external,  797 
internal,  799 
Tierve,  999 

portion  of  fascia  lata,  1528 
region,  muscles  of,  508 

surgical  anatomy  of,  511 
vein,  circumflex,  deep,  759 
common,  764 

peculiarities  of,  764 
external,  759 
internal,  760 
Tliacus  muscle,  510 

relations  of,  511 
Ilio-capsularis  muscle,  511 
-coccygeus  muscle,  454 
-costalis  muscle,  419 
-femoral  ligament,  328 
-hypogastric  nerve,  999 
-inguinal  nerve,  999 
-lumbar  artery,  693 
ligament,  291 
veins,  764 


Ilio-pectineal  bursa,  330 
eminence,  210,  213 
ligament,  508 
line,  209 
-pelvic  glands,  797 
-sciatic  notch,  210 
-tibial  band,  234,  514 
-trochanteric  ligament,  329 
Ilium,  207 

borders  of,  210 
crest  of,  210 
dorsum  of,  207 
])rocesses  of,  210 
spine  of,  210 
surfaces  of,  207,  208 
venter  of,  209 
Impar  ganglion,  1068 
Imperforate  hj^men,  14S1 
Impression,  deltoid,  179 

gastric,  1333 
Incisive  fossa,  106,  123,  139 
Incisor  canal,  110 
crest,  111 
foramina,  110 
nerve,  1039 
teeth,  1196 
Incisura  cardiaca,  1392 
inter-arytaenoidea,  1368 
marsupialis,  926 
pancreatis,  1348 
semilunaris,  926 
Incremental     lines    of     dentine, 

1203 
Incus,  1159 
body  of,  1159 
ligaments  of,  1161 
processes  of,  1159 
Infantile  hernia,  1523 
Inferior  acromio-clavicular  liga- 
ment, 299 
alveolar  artery,  614 
branch     of    superior    cervical 

ganglion,  1074 
calcaneo-scaphoid  ligament, 
354 
surgical  anatomy  of,  354 
cardiac  nerve,  1077 
carotid  triangle,  616 
central  nucleus,  949 
cerebral  veins,  735 
cervical  ganglion,  1077 
constrictor  muscle,  400 

relations  of,  401 
coronary  artery  of  lip,  607 
dental  artery,  614 
canal,  124 
foramen,  124 
nerve,  1039 
ethmoidal  turbinate  bone,  101 
external  frontal  artery,  628 
frontal  convolution,  873 
gemellus  muscle,  527 
gluteal  artery,  693 
line,  208 
nerve,  1011 
hsemorrhoidal  artery,  690 
nerve,  1011 
plexus,  1086 
veins,  760 
internal  frontal  arteries,  627 
labial  artery,  607 
lachrymal  gland,  1141 
laryngeal  artery,  641 

veins,  751 
lateral  angle,  63 
lingualis  muscle,  399 
longitudinal  fasciculus,  918 

sinus,  738 
maxilla  bone,  122 

horizontal  portion  of,  122 
surfaces  of,  122 

99 


Inferior  maxillary  bone,  articula- 
tions of,  125 
attachment  of  muscles  to, 

125 
development  of,  125 
horizontal  portion  of,  bor- 
ders of,   124 
perpendicular  portion  of, 
124 
borders  of,   124 
processes  of,  125 
surfaces  of,  124 
nerve,  1036 
meatus  of  nose,  145 
medullary  velum,  943 
mesenteric  artery,  677 
plexus,  1085 
vein,  768 
nuchal  line,  72 
obliquus  oculi  rrmscle,  374 
occipital  convolution,  877 
fossa},   133 
sulcus,  877 
ophthalmic  vein,  741 
orbito-palpebral  sulcus,  1137 
palatine  artery,  606 
pancreatico-duodenal  artery, 

675 
parietal  convolution,  876 
petrosal  sinus,  742 
phrenic  arteries,  680 

veins,  767 
post-central  sulcus,  875 
profunda  artery,  656 
pubic  ligament,  296 
pudendal  nerve,  1011 
pyloric  artery,  673 
radio-ulnar  articulation,  315 
ramus  of  ischium,  212 

of  pubis,  213 
rectus  oculi  muscle,  373 
renal  artery,  1423 
rhomboid  fossa,  840 
sacro-sciatic  foramen,  294 
semilunar  lobe  of  cerebellum, 

931 
stephanion,  76 

superficial  cerebellar  veins,  736 
tarsal  arch,  623 
temporal  convolution,  877 

sulcus,  870 
thyroid  artery,  641 

veins,  751 
transverse  ligament,  302 
triangle  of  fourth  ventricle,  945 
turbinated  bone,  119 

articulations  of,  120 
borders  of,  120 
development  of,  120 
processes  of,  120 
surfaces  of,  120 
crest,  107,  117 
vena  cava,  764 

vermiform  process  of  cerebel- 
lum, 929 
vesical  artery,  686 

plexus,  762 
vocal  cords,  1370 
Infraclavicular  plexus,  792 
Infracostales  muscle,  425 
Infraglenoid  margin  of  tibia,  234 

tubercle,  174 
Infrahyoid  artery,  602 

region,  muscles  of,  391 
Infralaryngeal  glands,  787 
Inframandibular  nerve,   1049 
Inframaxillarv  glands,  782 

nerve,  1049 
Infraorbital  arterv,  615 
canal,  107,  140 
foramen,  106,  140 


1570 


INDEX 


Infraorbital  groove,  107,  141 

nerves,  plexus  of,  1049 
Infrapatellar  bursa,  340 
Infraspinatus  bursa,  315 
muscle,  472 
bursa  of,  473 
Infraspinous  fascia,  472 

fossa,  172 
Infrasternal  depression,  163 
Infratemporal  crest,  95 

fossa,  138 
Infratrochlear  nerve,  1031 
Infundibula  of  kidney,  1415 
Infundibular  artery,  590 
Infundibuliform  fascia,  446,  1464 
Inf  undibulo-pelvic  ligament,  1490 
Infundibulum  of  brain,  882 
of  ethmoid,  101 
of  Fallopian  tube,  1497 
of  heart,  569 
Ingrassias,  processes  of,  96 
Inguinal  canal,  448,  1517 
fossa,  1248 

external,  1520 
internal,  1520 
middle,  1520 
hernia,  1520 
direct,  1523 

incomplete,  1524 
oblique,  1517,  1520 
lymphatic  gland,  deep,  795 
superficial,  793 

surgical     anatomy    of, 
794 
region,  1233 
Inion,  71 

Inlet  of  pelvis,  217 
Innominate  artery,  593 
branches  of,  594 
peculiarities  of,  594 
relations  of,  593 
surgical  anatomy  of,  594 
bone,  207 
vein,  750 
left,  750 

peculiarities  of,  750 
right,  750 
Inosculation  of  arteries,  583 
Insertion  of  muscles,  363 
Inspiration,  muscles  of,  432 
■  Insula,  867,  878 
opercula  of,  878 
Integument  of  scrotum,  1463 
Inter-alveolar  cell  islets,  1352 
Interarticular    chondro-sternal 
ligament,  288 
fibro-cartilage,  281,  298,  300 

triangular,  315 
furrow,  565 
ligament,  284,  329 
septum,  565 

stemo-costal  ligament,  288 
Inter-brain,  901 
Intercarotid  body,  600 
Intercavernous  sinus,  742 
Intercerebral  fibres  of  optic  com- 
missure, 1021 
Intercellular     biliary     passages, 

1341 
Interchondral  articulations,  289 
ligament,  external,  290 
internal,  290 
Interclaviculer  ligament,  298 
Intercolumnar  fascia,  436,  1463, 
1514 
fibres,  436 
Intercondyloid  notch,  225 
Intercostal  arteries,  667 
anterior,  644 
collateral,  668 
superior,  645 


Intercostal  arteries,  surgical  ana- 
tomy of,  668 
fascia,  424 
glands,  810 
muscles,  425 

external,  425 
relations  of,  425 

internal,  425 
relations  of,  425 
nerves,  993 

abdominal,  996 

first,  995 

pectoral,  995 

surgical  anatomy  of,  996 
space,  155,  160 
veins,  752 

anterior,  752 

posterior,  752 

superior,  left,  752 
right,  752 
Intercosto-humeral  nerve,  995 
Interglobular  spaces  of  Czermak, 

1202 
Interlobar  arteries,  1423 
biliary  plexus,  1338 
ducts,  1341 
Inter-maxillary  bone,  110 

region,  muscles  of,  378 

suture,  139 
Intermediate  crusta  nerve  path, 

960 
glands,  791 
zone  of  kidney,  1416 
Internal    abdominal    ring,    446, 

1518 
angular  process,  80,  140 
annular  ligament,  542 
anterior  thoracic  nerve,  984 
arcuate  ligament,  427 
auditory  artery,  639 

meatus,  133 
bicipital  ridge,  179 
branches   of  superior  cervical 

ganglion,  1076 
calcaneal  nerve,  1015 
calcanean  artery,  719 
calcaneo-astragaloid  ligament, 
352 

-cuboid  ligament,  353 

-scaphoid  ligament,  354 
capsule  of  brain,  fibres  of,  892 
carotid  artery,  619 

foramen,  88 

plexus,  1073 
circumflex  artery  of  thigh,  705 
condyle  of  femur,  226 
crucial  Ugament,  337 
cutaneous  nerve,  986,  1004 
ear,  1163 
epicondyle,  181 
epigastric  artery,  696 
femoral  region,  muscles  of,  519 
geniculate  body,  904,  912 
iliac  arterv,  683 

glands,  '799 

vein,  760 
inguinal  hernia,  1520 
interchondral  ligament,  290 
intercostal  muscle,  425 
jugular  glands,  786 

vein,  729 
bulb  of,  729 
lateral  hgament,  280,  310 
malleolar  artery,  719 
malleolus,  235 
mammary  artery,  643 

vein,  750 
maxillary  artery,  612 

Ivmphatic  glands,  782 

vein,  727 
oblique  line,  123 


Internal    oblique    mu&cles,    437,, 
1516 
occipital  crest,  74,  113 

protuberance,  73 
orbital  arteries,  627 
convolution,  873 
OS,  1488 

palpebral  arteries,  623 
parieto-occipital    sulcus,    867,. 

870 
plantar  artery,  719 

nerve,  1015 
popliteal  nerve,  1014 
pterygoid  muscle,  383 
relations  of,  384 
ner\^e,  1037 
plate,  96 
pudic  artery  in  female,  692 
in  male,  689 
vein,  760 
rectus  oculi  muscle,  373 
respiratory  nerve  of  Bell,  974 
saphenous  nerve,  1005 

vein,  756 
semilunar  fibrocartilage,  338 
spermatic  fascia,  446 
sphincter  ani  muscle,  451 
structure  of  cerebellum,  931 
supracondylar  ridge,  180 
tarsal  ligament,  370 
tuberosity  of  tibia,  233 
wall  of  tympanum,  1152 
Intemasal  suture,  139 
Intemeural  articulations,  272 
Internodia  or  phalanges,  204 
Interolivary  fillet,  909,  949 
Interossci  muscles  of  foot,  548 
dorsal,  548 
plantar,  548 
of  hand,  499 
Interosseous  artery*'  of  ulnar,  662* 
anterior,  662 
posterior,  663 
arteries,  dorsal,  659,  715 

palmar,  660 
ligament,  286 
nerve,  anterior,  987 

posterior,  991 
sacro-iliac  ligament,  292 
veins  of  forearm,  747 
Interpalpebral  slit,  1138 
Interparietal  suture,  127 
Interpeduncular  ganglion,  910 

space  of  brain,  882,  906 
Interpleural  space,  1387 
Interpubic  disk,  296 
Intersigmoid  fossa,  1312 
Interspinales  muscle,  421 
Interspinous  ligaments,  273 

venous  plexus,  732 
Intersternal    ligament,    anterior, 
290 
posterior,  290 
Intertransversales  muscle,  422 
laterales  muscle,  422 
mediales  muscle,  422 
Intertransverse    ligaments,    273.. 

295 
Intertrochanteric   line,   anterior,. 
223 
posterior,  223 
Intertubular  cell-masses,  1352 

tissue,  1203 
Interventricular  grooves,  568 
of  heart,  565 
septum,  569 
Intervertebral  disks,  270 
structure  of,  271 
fibro-cartilages,  270 

structure  of,  271 
foramina,  49 


INDEX 


1571 


Intervertebral  grooves,  49 
notches,  49 
substances,  270 

structure  of,  271 
veins,  755 
Intestinal  glands,  1295,  1319 
Intestine,  large,  1299 

areolar  coat  of,  1318 
arteries  of,  1320 
flexure  of,  hepatic,  1300 
sigmoid,  1300 
splenic,  1300 
lymphatic    glands    of,    808, 
1321 
vessels  of,  809 
mucous  membrane  of,  1318 
muscular  coat  of,  1317 
serous  coat  of,  1316 
structure  of,  1316 
submucous  coat  of,  1318 
veins  of,  1321 
innervation  of,  1323 
movements  of,  1322 
small,  1282 

areolar  coat  of,  1290 
arteries  of,  1296 
lymphatic    glands    of,    807, 
1297 
vessels  of,  808 
mucous  membrane  of,   1290 
muscular  coat  of,  1290 
nerves  of,  1299 
serous  coat  of,  1290 
structure  of,  1290 
submucous  coat  of,  1290 
veins  of,  1297 
villi  of,  1292 
surface  form  of,  1323 
surgical  anatomy  of,  1324 
Intestinum    tenue    mesenteriale, 

1289 
Intracapsular  fracture,  229 
Intracartilaginous  ossification,  43 
Intraepithelial  plexus,  1111 
Intralobular  veins,  767 
Intramembranous  ossification,  43 
Intraparietal   sulcus   of   Turner, 

875 
Intrathyroid  cartilage,  1363 
Intrinsic  muscles  of  tongue,  398 
Intumescentia     ganglioformis, 

1045 
Involuntarv  muscles,  361 
Iris,  1117   "^ 

arteries  of,  1120 
muscular  fibres  of,  1118 
nerves  of,  1120 
pigment  of,  1119 
stroma  of,  1118 
structure  of,  1118 
Irregular  bones,  34 
Ischiatic  lymphatic  glands,  797 
Ischio-capsular  ligament,  328 
-gluteal  bursa,  331 
-rectal  fascia,  454,  1546 
fossa,  1536 

region,  muscles  of,  449 
surgical  anatomy  of,  1535 
Ischium,  210 
body  of,  210 
ramus  of,  ascending,  212 

descending,  211 
spine  of,  211 
tuberosity  of,  211 
Island  of^Langerhans,  1352 

of  Reil,  867,  878 
Isthmus,  aortic,  591 

of  auditory  canal,  1148 
cerebri,  906 
of  Fallopian  tube,  1497 
of  fauces,  1212 


Isthmus,  faucium,  1194 
of  pharynx,  1221 
of  prostate  gland,  1451 
rhombencephali,  857 
of  thyroid  gland,  1403 

Iter   a  tertio   ad   quartum   ven- 
triculum,  903,  912 
chordse  anterius,  1152 
posterius,  1151 

Ivory  of  teeth,  1202 


Jacob's  membrane,  1126 
Jacobson,  cartilage  of,  1097 
eminence  of,  1100 
nerve,  1056 

canal  for,  90 
organ  of,  rudimentary,  1100 
Jaw,  angle  of,  124 
bones,  upper,  105 
lower,  articulations  of,  280 
changes  produced  in,  by  age, 
125 
upper.     See  Maxillary  Bone. 
Jejunum,  1289 
Joints.    See  Articulations. 
Jugular  foramen,  73,  133 
fossa,  91 
ganglion,  1056 
glands,  internal,  786 
lymphatic  trunk,  787 
nerve,  1073 
process,  73 
tubercle,  74 
vein,  anterior,  728 
external,  728 

sinus  of,  728 
internal.  729 
bulb  of,  729 
sinus  of,  729 

surgical  anatomy  of,  732 
posterior  external,  728 
Juxta-aortic  glands,  left,  800 
right,  800 
-cervical  lymphatic  knot,  803 


Kerkhinq,  valves  of,  1291 
Key  and   Retzius,   foramina  of, 

834,  853 
Kidneys,  1411 

abnormalities  of,  1424 
areas  of,  1414 
arteries  of,  1422 
calices  of,  1415 
capsule  of,  fatty,  1411 

true,  1415 
connective  tissue  of,  1424 
cortical  substance  of,  1416 
ducts  of,  1420 
hilum  of,  1415 
infundibula  of,  1415 
intermediate  zone  of,  1416 
lymphatic  vessels  of,  804,  1424 
Malpighian  bodies  of,  1417 

capsule,  1417 

tuft  of,  1417 
medullary  substance  of,  1416 
minute  anatomy  of,  1417 
nerves  of,  1424 
papillffi  of,  1417 
pelvis  of,  1415 
pyramids  of  Ferrein,  1417 

of  Malpighi,  1416 
sinus  of,  141.5 
structure  of,  1415 
surface  form  of,  1425 


Kidneys,  surfaces  of,  1412 

surgical  anatomy  of,  1425 

tubuli  uriniferi,  1418 

variations  of,  1424 

veins  of,  1424 
Knee,  bursae  of,  340 

-cap,  230 

-joint,  surface  form  of,  343 
surgical  anatomy  of,  343 

ligaments  of,  334 
KoUiker,  membrane  of,  1175 
Krause,  ellipsoid  of,  1127 

end-bulbs  of,  827 


Labia  pudendi  majora,  1477 

minora,  1478 
Labial  arterv,  inferior,  607 
glands,  1194 
nerves,  1034 
Labii  cerebri,  885 
Labium  tympanicum,  1172 

vestibulare,  1172 
Labyrinth,  1163 
arteries  of,  1176 
membranous,  1169 
nerves  of,  1176 
osseous,  1164 
veins  of,  1176 
Lachrymal  apparatus,  1141 
artery,  623 

peculiarities  of,  623 
bone,  112 

articulations  of,  113 
attachment   of   muscles   to, 

113 
borders  of,  113 
crests  of,  141 
development  of,  113 
lesser,  113 
surfaces  of,  113 
canaliculi,  1142 
canals,  1142 
caruncle,  1142 
crest,  113 
fossa,  81 
glands,  1141 

structure  of,  1141 
surface  form  of,  1143 
surgical  anatomy  of,  1144 
groove,  107,  109,  141,  143 
nerve,  1028 
notch,  107 
papilla,  1138,  1142 
process  of  inferior  turbinated, 

120 
sac,  1142 

structure  of,  1142 
surface  form  of,  1143 
surgical  anatomy  of,  1144 
sulcus,  113 
tubercle,  109 
Lactiferous  duct,  1507 
Lacuna  magna,  1444 
Lacunae,  1110 
of  bone,  38 
Howship's,  38 
Lacus  lacrimalis,  1138 
Lagena,  1172 

Lalouette,  pyramid  of,  1403 
Lambda,  129 

Lambdoid  suture,  75,  7S,  128 
Lamella  of  bone,  articular,  259 
Lamina  basalis,  1114 
of  cerebellum,  927 
cinerea,  882 
of  cornea,  1109 
cribrosa,  89 
cribriform,  1108 


1572 


INDEX 


Lamina,  cribriform,  of  sclerotic, 
1108 
dental,  1205 

of  ethmoid,  horizontal,  99 
perpendicular,  100 
vertical,  100 
fusca,  1108 

posterior  perforated,  910 
reticularis,  1175 
septi  pellucidi,  889 
spiralis  ossea  of  cochlea  1167 
suprachorioidea,  1112 
terminalis,  882 
vasculosa,  1112 
of  vertebra,  34 
Lancisi,  nerve  of,  887 
Landzert,  fossa  of,  1262 
Langer,  foramen  of,  464,  646,  791 

lines  of  cleavage  of,  1180 
Langerhans,    centro-acinar    cells 
of,  1352 
islands  of,  1352 
Lantermann,  segments  of,  823 
Large,  deep  petrosal  nerve,  1034, 
1073 
intestine,  1299 
palatine  nerve,  1035 
superficial  petrosal  nerve,  1034 
Laryngeal  artery,  inferior,  641 
superior,  602 
nerve,  superior,  1060 
external,  1060 
internal,  1060 
pouch,  1371 
saccule,  1371 
sinus,  1371 

surface  of  epiglottis,  1365 
veins,  751 
Larynx,  1361 

aperture  of,  superior,  1368 
arteries  of,  1375 
cartilages  of,  1362 
cavity  of,   1368 
compartments  of,  1368 
lower,  1371 
middle,  1369 
glands  of,  1374 
joints  of,  1366 
ligaments  of,  1366 
lymphatics  of,  782,  1375 
membranes  of,  136 
mucous  membrane  of,  1374 
muscles  of,  1371 

action  of,   1374 
nerves  of,  1376 
rima  glottidis,  1369 
structure  of,  1365 
veins  of,  1375 
ventricle  of,  1371 
vocal  cords  of,  false,  1370 
true,  1369 
Lateral  acoustic  tubercle,  950 
angle,  inferior,  63 
cell  column,  846 
column  of  medulla,  945 
fillet,  885 

fissures  of  cord,  838 
ligament,  external,  280 
internal,  280 
of  liver,  1334 
of  wrist,  318 
masses  of  atlas,  51 
of  ethmoid,  100 
odontoid  ligaments,  278 
patellar  ligaments,  335 
region  of  skull,  136 
root  of  eighth  nerve,  1051 
sacral  artery,  693 

veins,  760 
sacro-coccygeal  ligament,  295 
sinus,  738 


Lateral  sinus,  surgical  anatomy 
of,  739 
spinal  arteries,  638 
surface  of  liver,  1329 
thoracic    region,    muscles     of, 

468 
tract  of  medulla,  945 
ventricle  of  brain,  888 
body  of,  889 
central  cavity  of,  889 
cornu  of,  anterior,  889 
descending,  890 
middle,  890 
posterior,  889 
horn  of,  frontal,  889 
occipital,  889 
temporal,  890 
vertebral    region,    muscles    of, 
408 
Lateralis  nasi  artery,  607 
Latissimus  dorsi  muscle,  413 

bursa  of,  474 
Leaf,  condyloid  glands  of,  795 

supracondyloid  glands  of,  795 
Left  bronchus,  1378 
cardiac  vein,  771 
colic  artery,  678 

plexus,  1085 
coronary  artery,  590 
plexus,  1081 
vein,  770 
gastro-epiploic  plexus,  1085 
innominate  vein,  750 
juxta-aortic  glands,  800 
lobe  of  liver,  1333 
lower  azygos  vein,  753 
marginal  vein,  771 
superior  intercostal  vein,   752 
upper  azygos  vein,  753 
Leg,  arteries  of,  711 
bones  of,  230 
fascise  of,  531 
ligaments  of,  325 
muscles  of,  531 
nerves  of,  1006 
veins  of,  755 
Lemniscus,  909,  949 
Lens,  crystalline,  1130 
epithelium,  1130 
fibres,  1130 

suspensory  ligament  of,  1129 
Lenticular  ganglion,  1031 

nucleus,  891 
TiCnticulo-striate  arteries,  628 
Lesser  internal  cutaneous  nerve, 
986 
omentupi,  1254 
sacro-sciatic  foramen,  294 

ligament,  293 
sciatic  nerve,  1011 
wing  of  sphenoid,  96 
Levator  anguli  oris  muscle,  377 
scapulae  muscle,  414 
ani  muscle,  451 

preanal  fibres  of,  453 
glanduliB    thyroidese     muscle, 

1403 
labii  inferioris  muscle,  378 
superior  alseque  nasi  muscle 

375 
superioris  muscle,  376 
menti  muscle,  378 
palati  muscle,  403 
palpebrae  muscle,  371 

superioris  muscle,  372 
prostatas,  454 
urethrse,  454 
Levatores  costarum  muscle,  426 
Lieberkiihn,  crvpts  of,  1295 

glands  of,  1295,  1319 
Lieno-renal  ligament,  1252,  1355 


Ligamenta  alaria,  340 

sacro-coccygea,  anterior,  452 
subflava,  272 

suspensoria  of  mamma,  463 
Ligamentous  action  of  muscles, 

268 
Ligaments,  261 

accessory,  of  atlas,  276 
of  acetabulum,  transverse,  330 
acromio-clavicular,    inferior, 
299 
superior,  299 
of  ankle,  347 
annular,  anterior,  541 
external,  542 
internal,  542 
of  radius,  314 
of  stapes,  1161 
anterior  common,  269 
longitudinal,  269 
superior,  285 
appendiculo-ovarian  of  Clado, 

1304 
arcuate,  external,  427,  449 
internal,  427 
middle,  427 
astragalo-scaphoid,  354 
atlanto-axial,  anterior,  274 

posterior,  275 
atlo-axoid,  anterior,  274 

posterior,  275 
of  axilla,  suspensory,  464 
of  Bertin,  328 
of  Bigelow,  328 
of  bladder,  false,  1436 

true,  1436 
broad,  of  liver,  1333 

of  uterus,   1490 
calcaneo-astragaloid,  external, 
352 
internal,  352 
posterior,  352 
-cuboid,  internal,  353 
long,  353 
short,  353 
superior,  353 
-navicular,  353 
-scaphoid,  external,  353 
inferior,  354 
internal,  354 
superior,  353 
capsular.  &ee  Individual  Joints, 
carpo-metacarpal,  313 
of  carpus,  319 
central,  of  spinal  cord,  835 
check,  278,  1105 
chondro-sternal,  anterior,  288 
interarticular,  288 
posterior,  288 
-xiphoid,  anterior,  288 
posterior,  288 
ciliarv,  1116 
of  Cloquet,  1466 
coccvgeal,  833 
Colles',  437 
conoid,  300 
of  Cooper,  437,  448 
coraco-acromial,  301 
-clavicular,  300 
-humeral,  304 
coracoid,  302 
costo-clavicular,  298 
-coracoid,  467 
-transverse,  long,  285 
middle,  286 
posterior,  286 
-vertebral,  anterior,  284 
-xiphoid,  anterior,  288 
posterior,  288 
cotyloid,  329 
crico-arytenoid,  1367 


INDEX 


1573 


Ligaments,  crico-tracheal,  1368 
cruciform,  275 
deltoid,  348 
dentate,  835 

dorsal.    iSee  Individual  Joints, 
duodeno-mesocolic,   1261 

-renal,  1255 
of  elbow,  anterior,  309 

posterior,  309 
femoral,  515 
of  fingers,  322 

superficial,  transverse,  494 
Flood's,  304 
of  foot,  547 

fundiform  of  Retzius,  541 
gastro-splenic,  1256 
Gimbernat's,  437,  1515 
gleno-humeral,  305 
glenoid,  175,  305 

of  Cruveilhier,  359 
glosso-epiglottic,  1366 
of  hand,  319 
of  Helmholtz,  1160 
of  Henle,  438,  442 
hepato-colic,  1255 

-duodenal,  1255 

-gastric,  1254 
of  Hesselbach,  438,  442,  1517 
of  Hev,  515 
of  hip,  326 
hyo-epiglottic,  1365 
ilio-femoral,  328 

-lumbar,  291 

-pectineal,  508 

-trochanteric,  329 
of  incus,  1161 
infundibulo-pelvic,  1490 
interarticular,  284,  329 
interchondral,  external,  290 

internal,  290 
interclavicular,  298 
interosseous.      See  Individual 

joints, 
interspinous,  273 
intersternal,  anterior,  290 

posterior,  290 
intertransverse,  273,  295 
intervertebral,  270 
ischio-capsular,  328 
of  jaw,  280 
of  knee,  334 

alar,  340 

anterior,  345 

coronary,  340 

crucial,  337 

mucosum,  334 

posterior,  335 

transverse,  340 
of  larynx,  1366 
lateral.    See  Individual  Joints. 
lieno-renal,  1252,  1355 
of  liver,  1333 

coronary,  1334 

falciform,  1333 

lateral,  of,  1334 
left,  1334 
right,  1.334 

round,  1334 

suspensory,  1333 
lumbo-sacral,  291 
of  Luschka,  558 
of  malleus,  1160 
metacarpal,  324 
metacarpo-phalangeal,  324 
metatarsal,  359 
metatarso-pharyngeal.  359 
nuchse,  273,  413 
oblique,  314 
obturator,  296 

occipito-atlantal,  anterior,  276 
posterior,  276 


Ligaments,  occipito-axial,  278 
odontoid,  lateral,  278 

middle,  279 
orbicular,  314 
orbito-tarsal,  1139 
of  ossicula,  1160 
palpebral,  1139 
of  patella,  335 
pelvis,  falciform,  293 

transverse,  459 
of  penis,  1458 

suspensory,  437 
perineal,  transverse,  459 
of  peritoneum,  1254 
of  phalanges  of  foot,  359 

of  hand,  325 
phreno-colic,  1259 
-pericardial,  559 
plantar,  long,  353 

short,  353 
posterior  common,  270 

longitudinal,  270 
Poupart's,  436,  1515 
pterygo-mandibular,  380 

-maxillary,  380 
pubic,  anterior,  296 
inferior,  296 
posterior,  296 
superior,  296 
pubo-capsular,  328 
-femoral,  328 
-prostatic,  1435,  1451 
-vesical,  1435 
radio-carpal,  319 
-ulnar,  annular,  314 
anterior,  315 
oblique,  314 
orbicular,  314 
round,  314 
posterior,  315 
rhomboid,  298 

sacro-coccygeal,   anterior,   294 
lateral,  295 
posterior,  294 
-iliac,  anterior,  292 
interosseous,  292 
long,  292 
obUque,  292 
posterior,  292 
short,  292 
-sciatic,  anterior,  293 
great,  292 
lesser,  293 
posterior,  292 
-uterine,  1490 
-vertebral,  291 
of  scapula,  301 
Schlemm's,  305 
of  shoulder,   303 
spino-glenoid,  302 
spiral,  of  cochlea,  1172 
spleno-phrenic,  1256 
sterno-clavicular,  anterior,  298 
posterior,  298 
-costal,  anterior,  288 
interarticular,  288 
posterior,  288 
-costo  pericardial,   559 
-pericardiac,  558 
of  stapes,  1161 
of  sternum,  290 
stylo-hyoid,  394 

-mandibular,  281,  388 
-maxillary,  281 
subpubic,  296 
suprascapular,  302 
supraspinous,  273 
suspensory,  of  clitoris,  437 
of  eye,  1105 
of  incus,  1161 
of  lens,  1129 


Ligaments,  suspensory,  of  liver, 

1333 

of  mamma,  463 

of  ovary,  1501 

of  penis,  437 

of  Treitz,  1286 
sutural,  259 
synovial,  262 
tarsal,  external,  370 

internal,  370 
of  thumb,  321 
thyro-epiglottic,  1367 

-hyoid,  1366 
tibio-tarsal,  anterior,  347 

posterior,  347 
transverse,  of  atlas,  275 

humeral,  305 

inferior,  302 

of  knee,  340 

superior,  of  scapula,  302 
trapezoid,  300 
tympano-malleolar,  1156 
utero-sacral,  1490 
of  uterus,  1489 

round,  1491 
of  vertebra;,  270 
vertebro-pericardial,  558 

-pleural,  1385 
vesico-uterine,  1490 
of  Winslow,  335 
of  Wrisberg,  339 
of  wrist,  318 

anterior,  318 

dorsal,  318 

lateral,  external,  318 
internal,  318 

posterior,  318 

volar,  318 
xipho-pericardial,  559 
Y-,  328 
of  Zinn,  373 
Ligamentum  arcuatum  exter- 
num, 427,  449 

internum,  427 
arteriosurn,  587 
conjugale,  284 
corniculopharyngpum,   1.368 
crico-pharyngeum,  1368 
denticulatum,  835 
epididymidis,  1469 
hepatoduodenale,  1250 
latum  pulmonalis,  1385 
mucosum,  340 
nuchse,  273,  413 
patella;,  335 

posticum  Winslowii,  335 
pulmonale,  1385 
spirale,  1172 
suspensorium,  279 
teres,  329 
ventriculare,  1366 
Light  stimuli,  path  of,  1127 
Ligula,  944 
Limbic  lobe,  878 

convolutions  of,  879 
Limbus  alveolaris,  124 
laminae  spiralis,  1172 
Limen  insulse,  878 
Limiting  sulcus  of  Reil,  867 
Linea  alba,  444 
aspera,  224 

external  lip  of,  224 

internal  lip  of,  224 
quadrati,  224 
splendens,  835 
Linse  semilunares,  445 

transverse,  of  abdomen,  445 
Line,  gluteal,  anterior,  207 

inferior,  208 

posterior,  207 
ilio-pectineal,  209 


1574 


INDEX 


Line,  nuchal,  inferior,  72 

superior,  72 
temporal,  76,  80 
Lingual  artery,  603 

branches  of,  603 

deep,  604 

relations  of,  603 

surgical  anatomy  of,  604 
bone,  153 
gyrus,  877 
nerve,  1038,  1057 

branches  of,  1038 
region,  muscles  of,  396 

dissection  of,  396 
tonsil,  1088 
veins,  729 
Lingualis  muscle,  inferior,  399 

superior,  399 

transverse,  399 

vertical,  399 
Lingula,  93,  280,  928,  944 

pulmonis,  1392 
Lips,  1194 

surgical  anatomy  of,  1224 
Liquor  Cotunnii,  1164 
Lissauer,  tract  of,  843 
Little  brain,  926 
Littr6,  glands  of,  1444 
Liver,  1326 

abnormalities  of,  1335 
accessory,  1335 
areolar  coat  of,  1337 
arteries  of,  1336 
development  of,  1243 
ducts  of,  1341 

excretory  apparatus  of,  1342 
fibrous  coat  of,  1337 
fissures  of,  1330 
hepatic  arteries,  1336 

ducts,  1336 

vein,  1336 
figaments  of,  1333 
lobes  of,  1332 
lobules  of,  1337 
lymphatics  of,  80S,  1341 
margins  of,  1330 
movabihty  of,  1334 
nerves  of,  1342 
portal  vein,  1336 
serous  coat  of,  1337 
structure  of,  1337 
support  of,  1334 
surface  relations  of,  1346 
surfaces  of,  1327,  1329 
surgical  anatomy  of,  1346 
veins  of,  1336 
Lobe  or  lobes,  biventral,  931 
of  brain,  872 
central,  878 

of  cerebellum,  926, 928, 930, 931 
crescentic,  anterior,  928 

posterior,  928 
cuneate,  877 
•digastric,  931 
frontal,  872,  884 
of  kidney,  1415 
limbic,  878 
of  liver,  1332 
of  lungs,  1392 
occipital,  876 
olfactory,  880 
orbital,  874 
parietal,  875 
post-central,  878 
pre-central,  878 
of  prostate  gland,  1451 
quadrate,  876 
semilunar,  inferior,  931 
slender,  931 
temporal,  877,  885 
temporo-sphenoidal,  877 


Lobe  or  lobes,  of  testicle,  1472 
of  thymus  gland,  1407 
of  thyroid  gland,  1403 
Lobule  of  ear,  1145 
of  kidney,  1415 
of  liver,  1337 
of  lungs,  1395 
of  mamma,  1506 
Lobuli  testis,  1472 
Lobulus  centralis,  928 
Locus  ca>ruleus,  945 
Long  bones,  33 

calcaneo-cuboid  ligament,  353 
ciliary  arteries,  625 

nerves,  1030 
plantar  ligament,  353 
sacro-iliac  ligament,  292 
saphenous  nerve,  1005 

vein,  756 
scrotal  nerve,  1011 
subscapular  nerve,  984 
thoracic  artery,  651 
nerve,  983 
vein,  748 
Longissimus  dorsi  muscle,  419 
Longitudinal  fasciculus,  inferior, 
918 
superior,  918 
fibres  of  cord,  841 
of  pons,  923 
dorsal,  924 
deep,  924 
middle,  924 
superficial,  924 
ventral,  924 
deep,  924 
fissure  of  cerebrum,  865,  882 
sinus,  inferior,  738 
superior,  78,  130,  736 
Longus  capitis  muscle,  406 

colli  muscle,  407 
Looped  tubes  of   Henle,  1419 
Louis,  angle  of,  157 
Lower  deep  cervical  glands,  787 
extremity,  arteries  of,  697 
articulations  of,  325 
bones  of,  206 
fasciae  of,  507 
ligaments  of,  325 
lymphatic  vessels  of,  797 
deep,  797 
superficial,  797 
muscles  of,  507 

surface  form  of,  549 
surgical  anatomy  of,  551 
nerves  of,  997 
veins  of,  755 
deep,  758 
superficial,  756 
jaw,  articulation  of,  280 
subscapular  nerve,  984 
visual  centre,  1022 
Ludovic,  angle  of,  157 
Lumbar  arteries,  680 
fascia,  416 
ganglia,  1085 
glands,  799 
nerves,  997 

divisions  of,  anterior,  998 

posterior.  997 
roots  of,  997 
plexus,  998 
branches,  999 
surgical  anatomy  of,  1017 
portion     of    gangliated    cord, 

1079 
region,  1233 
veins,  765 

ascending,  753,  765 
right,  752 
vertebrae,  56 


Lumbar  vertebrae,  body  of,  56 

fifth,  57 

laminai  of,  56 

pedicles  of,  56 

processes  of,  57 
Lumbo-iliac  ligament,  291 
-sacral  ligament,  291 

plexus,  998 
Lumbricales  muscle,  foot, -546 

hand,  499 
Lungs,  1390 

air-cells  of,  1396 
apex  of,  1390 
arteries  of,  1396 
base  of.  1391 
borders  of,  1392 
bronchus  of,  1395 
capillaries,  1396 
color  of,  1394 
fissures  of,  1392 
foetal,  1394 
lobes  of,  1392 
lobules  of,  1395 
lymphatics  of,  1396 
nerves  of,  1397 
parenchyma  of,  1395 
root  of,  1394 
serous  coat  of,  1394 
structure  of,  1394 
subserous  areolar  coat  of,  1394 
substance  of,  1394 
surface  form  of,  1397 
surfaces  of,  1391,  1394 
surgical  anatomy  of,  1397 
veins  of,  1396 
weight  of,  1394 
Lunula  of  nails,  1185 
Luschka,  gland  of,  1410 
ligament  of,  558 
vilU  of,  854 
Luys,  nucleus  of,  908,  910 
Lymph  canalicular  system,  772 
-capillaries,  772 
-glands,  parotid,  1215 
-nodes,  774 

perivascular,  772 
-spaces,  772 
Lymphatic  or  lymphatics,  772 
of  arm,  788 
of  arteries,  586 
of  bone,  41 
of  cord,  840 
of  cranial  region,  779 
duct,  right,  778 

tributaries  of,  779 
of  dura  mater  of  brain,  848 
extracranial,  780 
of  face,  779 
glands,  774 

of  abdomen,  797 

abdomino-aortic,  799 

along    mesenteric    arteries, 
800 

of  anus,  809 

axillarv,  790 

brachial,  788 

bronchial,  1380 

buccal,  782- 

buccinator,  782 

carotid,  786 

cervical,  deep,  786 
superficial,  784 

of  Cloquet.  795,  798 

ccpliac,  800 

colic,  808 

condyloid  of  Leaf,  795 

connected  with  ccBliac   axis 
and  branches,  800 

diaphragmatic,  810 

epigastric,  superior,  802 

of  face,  780 


INDEX 


1575 


IL ymphatic  or  lymphatics,  glands, 

femoral,  deep,  795 
gastric,  800 
genial,  782 
gluteal,  797 

haemorrhoidal,  middle,  799 
of  head,  780 
hepatic,  800 
hypogastric,  799 
iliac,  797 

common,  799 

external  797 

internal,  799 
ilio-pelv-ic,  797 
infralaryngeal,  787 
inframaxillary,  782 
inguinal,  deep,  795 

superficial,  793 
intercostal,  810 
intermediate,  791 
of  intestine,  large,  808 

small,  807 
ischiatic,  797 
jugular,  external,  784 

internal,  786 
juxta-aortic,  left,  800 

right,  800 
of  lower  extremity,  793 
lumbar,  799 
malar,  782 

mammary,  internal,  810 
mastoid,  780 
maxillary,  internal,  782 
mediastinal,  anterior,  Sll 

posterior,  812 
middle,  of  Stahr,  784 
of  neck,  784 
obturator,  798 
occipital,  780 
paramammary,  813 
parietal,  810  ' 
parotid,  781 

deep,  782 

superficial,  781 
pectoral,  790 
of  pelvis,  797 
peritracheo-bronchial,  812 
posterior     auricular     retro- 
auricular,  780 
post-pharyngeal,  785 
pre-aortic,  800 
pre-auricular,  781 
prelaryngeal,  787 
pretracheal,  787 
popliteal,  795 
rectal,  809 
retro-aortic,  800 

-crural,  798 

-pharyngeal,  785 
of  Ilosenmiiller,  795 
■    sacral,  799 
saphenous,  external,  795 
scapular,  790 
splenic,  800 
stemo-raastold,  786 
subclavian,  791 
submaxillary,  784 
submental,  785 
suboccipital,  780 
suborbital,  782 
subparotid,  782 
substerno-mastoid,  786 
supraclavicular,  787 
supracondyloid     of      Leaf, 

795 
supraepitrochlear,  789 
suprahyoid,  lateral,  784 

median,  785 
supramaxillary,  782 
■supratrochlear,  789 
surgical  anatomy  of,  774 


Lymphatic  or  lymphatics,  glands, 
of  thoracic  wall,  810 
tibial,  anterior,  795 
tracheal,  787 
of  upper  extremity,  788 

deep,  790 

superficial,  788 
visceral,  811 
zygomatic,  782 
pharyngeal  ring,  1224 
vessels  of  abdomen,  801 
walls  of,  deep,  801 

superficial,  801 
of  bile-ducts,  806 
of  bladder,  802 
cardiac,  815 
cerebral,  779 
of  cranial  region,  782 
of  face,  782 
of  Fallopian  tube,  804 
of  gluteal  region,  801 
of  head,  782 
of  heart,  577 
of  intestines,  large,  809 

small,  808 
of  kidney,  804 
of  larynx,  782 
of  leg.  797 
of  liver,  805 
of  lower  extremity,  797 

deep,  797 

superficial,  797 
of  lung,  815 
meningeal,  779 
of  mouth,  782 
of  neck,  779,  787 
of  nose,  interior  of,  782 
of  ffisophagus,  815 
of  ovary,  804 
of  pancreas,  807 
of  pelvis,  801 
of  penis,  801 
of  perinaium,  801 
of  peritoneum,  802 
of  pharynx,  782 
pleural,  815 
of  prostate  gland,  803 
pulmonary,  815 
of  scrotum,  801 
of  seminal  vesicles,  804 
of  spleen,  807 
of  stomach,  806 
of  suprarenal  capsule,  804 
of  testicle,  804 
of  thoracic  trachea,  815 

wall,  812 
thymic,  815 
of  thyroid  gland,  782 
of  tongue,  782 
of  umbilicus,  802 
of  upper  extremity,  792 

deep,  792 

superficial,  792 
of  ureter,  804 
of  urethra,  female,  803 

male,  803 
of  uterus,  803 
of  vagina,  804 
of  vas  deferens,  804 
Lyra  of  fornix,  896 


M 

Macui.a  acustica  sacculi,  1170 

cribrosa,  1164 

lutea,  1128 
Magnum  of  carpus,  199 
Majendie,  foramen  of,  834,  853 
Malar  bone,  113 

articulations  of,  115 


Malar  bone,  attachment  of  mus- 
cles to,  115 
borders  of,  115 
development  of,  115 
processes  of,  114 
surfaces  of,  113 
canal,  114 
foramen,  113 
glands,  782 
nerve,  1032,  1049 
process  of  superior  maxillary, 
109 
Male  breast,  1509 

surgical  anatomy  of,  1509 
organs  of  generation,  1447 
perinseum,  1537 
urethra,  1441 
Malleolar  artery,  713,  719 
Malleolus,  external,  238 

internal,  235 
Malleus,  1158 
handle  of,  1158 
head  of,  1158 
ligaments  of,  1160 
manubrium  of,  1158 
neck  of,  1158 
processes  of,  1158 
spur  of,  1158 
Malpighi,  pyramids  of,  1416 
Malpighian    bodies    of    kidney, 
1417 
of  spleen,  1358 
capsule,  1417 
layer  of  skin,  1182 
tuft,  1417 
Mamma,  1503 
areola  of,  1504 
arteries  of,  1508 
ligament  of,  suspensory,  463 
lobule  of,  1506 
lymphatics  of,  1508 
nerves  of,  1508 
variations  in,  1504 
veins  of,  1508 
Mammary  artery,  external,  651 
internal,  643 
branches  of,  644 
surgical  anatomy  of,  645 
glands,  1503 

description  of,  1503 
internal,  810 
lymphatics  of,  812 

surgical  anatomy  of,  814 
structure  of,  1505 
surgical  anatomy  of,  1508 
tissue,   prolongations  of,   1505 
vein,  internal,  750 
Mammillary  duct,  1507 

process  of  lumbar  vertebra,  57 
Mandible,  122 
Mandibular  artery,  614 
fossa,  84 
nerve,  1036 

region,  muscles  of,  377 
dissection  of,  377 
Manubrium  of  malleus,  1158 

of  sternum,   157 
Marchi  and  Lowenthal,  column 

of,  843 
Marginal  artery,  500 
convolution,  873 
gyrus,  875 
lobe,  857 
tract  of  Spitzka  and  Lissauer, 

843 
vein,  left,  771 
Marrow  of  bone,  36 
Marshall,  vein  of,  oblique,  771 

vestigial  fold  of,  561 
Martinotti,  cells  of,  921 
Masseter  muscle,  381 


1576 


INDEX 


Masseteric  artery,  615 
fascia,  381 
nerve,  1037 
vein,  727 
Mast-cells,  36 
Mastoid  air-cells,  1153 
antrum,  87 
arterv,  609,  610 
cells,'86 

foramen,  85,  138 
fossa,  86 

lymphatic  glands,  780 
nerves,  973 
process,  86,  138 
vein,  728 
Masto-occipital  suture,  75,   128 

-parietal  suture,  128 
Matrix  of  nails,  1185 
Maxillary  antrum,  orifice  of,  145 
artery,  external,  604 

internal,  612 
bone,  inferior,  122 

articulation  of,  125 
attachment  of  muscles  to, 

125 
development  of,  125 
horizontal  portion  of,  122 
borders  of,  124 
surfaces  of,  122 
perpendicular  portion  of, 
124 
borders  of,  124 
processes  of,  125 
surfaces  of,  124 
superior,  105 

articulations  of,  112 
attachment  of,  112 
body  of,  105 

surfaces  of,  106 
development  of,  112 
processes  of,   109 
hiatus,  107 

l3Tnphatic  glands,  internal,  782 
nerve,  inferior,  1036 
superior,  1031 

branches  of,  1032 
process  of  inferior  turbinated, 
120 
of  malar,  115 
of  palate  bone,  117 
region,  superior  muscles  of,  376 
sinus,  108 
tuberosity,  106 
vein,  internal,  727 
McBurney's  point,  1303 
Meatus,  auditory,  external,  88, 
138,  1148 
internal,  89,  133 
of  nose,  inferior,   145 
middle,  145 
superior,  101,  144 
urinarius,  male,  1444 
female,  1481 
Meckel,  band  of,  1160 
cavity  of,  848 
diverticulum,  1290 
ganglion,  1034 

branches  of,  1034,  1035 
Median  nerve,  986 
branches  of,  987 
vein,  745 
basilic,  746 
cephalic,  746 
cerebral,  735 
Mediastinal  arteries,  644 
posterior,  666 
glands,  anterior,  811 

posterior,  812 
pleura,  1385 

subpleural,  644 
space,  1387 


Mediastinal     surface     of     lungs, 

1391 
Mediastinum,  1388 
anterior,  1389 
arteries  of,  1390 
lymphatics  of,   1390 
middle,  1389 
posterior,  1389 
superior,  1388 
testis,  1471 
veins  of,  1390 
Medio-tarsal  joint,  350,  355 
Medulla  oblongata,  884,  938 

fibres  of,  942 

fissures  of,  939 

formatio  reticularis  of,  947 

funiculus  cuneatus,  941 
gracilis  of,  941 
of  Rolando,  941 

gray  matter  of,  945 

lateral  column  of,  940 
tract  of,  945 

oUvary  body  of,  941 

pyramid  of,  939 
raph6  of,  951 

restiform  body  of,  941 

structure  of,  internal,  945 

surfaces  of,  posterior,  941 

veins  of,  736 
spinalis,  884 
Medullary  canal,  857 

portion  of  suprarenal  capsule, 
1431 

of  thymus  gland,  1408 
spaces  of  bone,  45 
substance  of  kidneys,  1416 
tube,  857 
velum,  anterior,  943 

inferior,  943 

posterior,  943 

superior,  943 
Medullated  nerve-fibres,  822 
Medulli-spinal  veins,  755 
Meibomian  glands,  1139 

structure  of,  1140 

surgical  anatomy  of,  1143 
Membrana  basilaris,  1172 

cochlea  ductus  cochlearis,  1172 
elastica  laryngis,   1367 
flaccida  of  Shrapnell,  1156 
Umitans  externa  of  retina,1126 

interna,  1122 
nictitans,  1140 
pupillaris,  1120 
quadrangularis,  1366 
sacciformis,  317 
tectoria,  1175 
tympani,  1155 

arteries  of,  1157 

lymphatics  of,   1158 

nerves  of,  1158 

secundaria,  1167 

structure  of,  1157 

veins  of,  1157 
Membrane,  basilar,  1172 
Bowman's,  1109 
of  brain,  arachnoid,  851 

meningeal,  847 
of  Bruch,  1114 
of  choroid,  1112 
of  Corti,  1175 
costo-coracoid,  467 
crico-thyroid,  1367 
of  Demours,  1110 
of  Descemet,  1110 
fenestrated,  of  Henle,  585 
hyaloid,  1129 
hyo-thyroid,  1366 
of  Jacobs,  1126 
of  Kolliker,  1175 
Nasmyth's,  1204 


Membrane,  obturator,  525 

occipito-atlantal,  anterior,  276- 
posterior,  276 

otolith,  1172 

of  Reissner,  1172 

of  Scarpa,  1152 

of  Shrapnell,  1156 

of  spinal  cord,  832 
arachnoid,  834 
surgical  anatomv  of,  836- 

sutural,  264,  847 

synovial,  262 

tiiyro-hyoid,  1366 
Membranous  canal  of  cochlea,, 
1172 

cranium,  102 

labyrinth,  1169 

portion  of  urethra,  1442 

semicircular  canals,    1170- 
Meningeal  artery,  609,  610 
anterior,  622 
middle,  613 

surgical  anatomy  of,  614r 
posterior,  638 
small,  614 

lymphatic  vessels,  779 

membranes  of  brain,  847 

nerve,  1032 

veins,  730,  734 
Meninges  of  brain,  847 
Meningo-rachidian  veins,  754, 

833 
Menisco-femoral  joint,  342 

-tibial  joint,  342 
Meniscus,  281 
Mental  foramen,  123,  140 

nerve,  1039 

process,  122,  140 

protuberance,  122 

spines,  123 

tubercles,  122 
Merkel,     filtrum     ventriculi     of, 

1368 
Mesencephalon,  906 
Mesenteric  arteries,  glands  along, 
800 

artery,  inferior,  677 
superior,  675 

ganglion,  1085 

plexus,  inferior,  1085 
superior,  1085 

vein,  inferior,  768 
superior,  768 
Mesenterico-mesocolic  fold,  1262 

-parietal  fold,  1264 
Mesentery,  1257 

development  of,   1237 

glands,  807 

of  vermiform  appendix,   1260 
Mesoappendix,  1260 
Mesoblastic  somites,   1235 
Mesoca?cum,  1301 
Mesochorium,  1461 
Mesocolic  area  of  kidnev,  1414 

band,  1317 

fossa,  1261 
Mesocolon,   ascending,   1258 

descending,  1258 

sigmoid,  1259 

transverse,  1259,  1309 
Mesogastrium,  1237 
Mesognathion,  111 
Mesorectum,  1259 
Mesosalpinx,  1490 
Mesosternum,  159 
Mesovarium,  1490,  1500 
Metacarpal  bones,  200 

ligament,  transverse,  324 

spaces,  201 
Metacarpo-phalangeal  articula- 
tions, 324,  359 


INDEX 


1577 


Metacarpo-phalangeal     articula- 
tions, surface  form  of,  325 
Metacarpus,  200 

articulations  of,  20-1 
common  character  of,  200 
development  of,  205 
peculiar  characters  of,  201 
Metasternum,  159 
Metatarsal  artery,  715 
bones,  249 
fifth,  252 
first,  249 
fourth,  251 

peculiar  characters  of,  249 
second,  250 
third,  251 
ligament,  transverse,  359 
Metatarsus,  249 

articulations  of,  252 
common  characters  of,  249 
development  of,  253 
Metencephalon,  858 
Jkletopic  suture,  83,  127 
Mevnert,  commissure  of,  908 
Mid-brain,  906 

Middle  arcuate  ligament,  427 
cardiac  nerve,  1077 
cerebellar  peduncles,  934 
cerebral  artery,  627 
cervical  ganglion,  1076 
clinoid  processes,  93,  132 
colic  arterj^,  676 
commissure,  903 
constrictor  muscle,  401 
cornu     of     lateral    ventricle. 

890 
costo-transverse  ligament,  2S6 
cutaneous  nerve,  1004 
ear,  1150 
fossa  of  skull,  130 
frontal  convolution,  873 
haemorrhoidal  artery,  687 
gland,  799 
veins,  760 
inguinal  fossa,  1520 
internal  frontal  arterj^,  627 
meatus  of  nose,  145 
mediastinum,  1389 
meningeal  artery,  613 

veins,  734 
occipital  convolution,  877 

sulcus,  876 
odontoid  ligament,  52,  279 
palatine  nerve,    1035 
peduncle  of  cerebellum,  922 
sacral  artery,  681 

veins,  764 
spermatic  fascia,  440 
subscapular  nerve,  984 
superior  dental  nerve,   1033 
temporal  artery,  611 
convolution,  877 
vein,  727 
thyroid  vein,  730 
turbinated  bone,  107 
vesical  arterv,  686 
Mid-gut,  1236  " 
Milk  teeth,  1196 
Minor  cardiac  nerve,   1077 
Mitral  orifice,  568 
Mixed  bones,  34 
Mobile  septum,  1097 
Moderator  band,  570 
Modiolus,  1167 
Molar  glands,  1195 

teeth,  1198 
Moll,  glands  of,   1138 
Monoaxonic  cells,  821 
Monro,  foramen  of,  889 
Mons  Veneris,  1477 
Montgomery,  glands  of,  1504 


Monticulus  cerebelli,  927 
Morgagni,  columns  of,   1319 
crvpts  of,  1319 
hydatids  of,   1469 
sinus  of,  402 
valves  of,   1319 
Motor  oculi  nerve,   1024 

surgical      anatomy      of, 
1025 
projection  fibres  of  cerebrum 
914 
tract,  939 
Mouth,  1193 
angle  of,   1193 
aperture  of,   1193 
cavity  of,   143 
proper,  1194 
floor  of,  Ivmphatic  vessels  of, 

782 
mucous  membranes  of,   1194 
muscles  of,  376 
surface  form  of,    1219 
surgical  anatomy  of,  1224 
vestibule  of,   1194 
Movable  spleen,  1356 
Movements    admitted  in   joints, 

266 
Mucilaginous  glands,  262 
Mucous  alveoli,   1218 
coat  of  bladder,  1437 
of  gall-bladder,    1343 
of  oesophagus,   1229 
of  pharynx,  1223 
of  urethra,  1444,  1446 
glands  of  tongue,  1218 
Miiller's  muscle,  374 

"ring"  muscle,  1116 
Multifidus  spinae  muscle,  421 
Multipolar  cells,  820 
Muscle  or  muscles,  361 
of  abdomen,  432 
deep,  449 
superficial,  432 
abductor  hallucis,  544 
indicis,  499 
minimi  digiti,  foot,  544 

hand,  498 
pollicis,  495 
accelerator  urinse,  457 
accessorius    ad     ilio-costalem, 
419 
pedis,  546 
of  acromial  region,  470 
adductor  brevis,  520 
longus,  519 
magnus,  520 
minimus,  520 
obliquus  hallucis,   546 

pollicis,  497 
transversus  hallucis,  548 
pollicis,  497 
anconeus,  487 
antitragicus,  1147 
of  arm,  470,  474 
arytenoid,  1375 
aryteno-epiglottideus,  1373 
arytenoideus,  1372 
attoUens  auriculam,  369 
attrahens  auriculam,  369 
of  auricular  region,  369 
azvgos  uvula?,  405 
of  "back,  410 
biceps,  arm,  475 
flexor  cubiti,  475 
thigh,  520 
bipenniform,  363 
biventer  cervicis,  420 
Bowman's,  1115 
braehialis  anticus,  476 
buccinator,  380 
bulbo-cavernous,  557 


Muscle  or  muscles,  cervicalis  as- 
cendens,  419 
chondro-glossus,  397 
ciliary  of  eye,  1115 
circumflexus,  404 
coccygeus,  455 
complexus,  420 
compressor  narium  minor,  376 
nasi,  376 

sacculi  laryngis,  1373 
urethral  in  female,  462 
in  male,  460 
constrictor,    istlimi     faucium, 
398,  405 
pharyngeus,  inferior,  400 
middle,  401 
superior,  401 
urethrse  in  female,  462 
in  male,  460 
coraco-brachialis,  475 
corrugator  cutis  ani,  449 

supercilii,  371 
of  cranium,  365 
cremaster,  439,   1516 
crico-arytenoid,  posterior,  1372 

-thyroid,  1372 
crureus,  517 
deltoid,  470 
depressor  alse  nasi,  376 
anguli  oris,  378 
labii  inferioris,  378 
detrusor  urinse,    1437 
diaphragm,  427 
digastric,  393 
dilator  naris  anterior,  376 

posterior,  376 
of  dorsal  region,  543 
ejaculator  seminis,  457 

urinse,  457 
erector  clitoridis,  461 
penis,  458 
spina^,  417 
of  expression,  385 
of  expiration,  432 
extensor  brevis  digitorum,  543 
pollicis,  489 
carpi  radialis  brevior,  485 
longior,  485 
ulnaris,  487 
coccygis,  422 
communis  digitorum,  486 
indicis,  490 
longus  digitorum,  533 

polhcis,  489 
minimi  digiti,  487 
ossis  metacarpi  pollicis,  489 
primi  intemodii  pollicis,  489 
proprius  hallucis,  532 
secundi    intemodii    pollicis, 
489 
of  face,  365 

of  femoral  region,  anterior,  512 

internal,  519 

posterior,  529 

of  fibular  region,  539 

flexor  accessorius,  546 

brevis  digitorum,  544 

hallucis,  546 
minimi  digiti,  foot,  547 

hand,  498 
pollicis,  497 
carpi  radialis,  479 

ulnaris,  480 
longus  digitorum,  538 
hallucis,  538 
pollicis,  482 
ossis  metacarpi,  498 

pollicis,  496 
profundus  digitorum,  482 
sublimis  digitorum,  481 
of  forearm,  478 


1578 


INDEX 


Muscle  or  muscles,  of  foot,  541 
frontalis,  368 
fusiform,  362 
gastrocnemius,  534 
gemellus,  inferior  527 

superior,  526 
genio-glossus,  396 

-hvo-glossus,  396, 

-hyoid,  395 
of  gluteal  region,  522 
gluteus  maxiraus,  522 

medius,  523 

minimus,  523 
gracilis,  519 
hamstring,  529 
of  hand,  491 
of  head,  385 
helicis  major,  1147 

minor,  1147 
Hilton's,  1373 
of  hip,  522 
Horner's,  371 

of  humeral     region,     anterior, 
474 
posterior,  477 
Ihyo-glossus,  397 
of  iliac  region,  508 
"iiiacus,  510 
ilio-capsularis,  511 

-coccygeus,  454 

-costalis,  419 
infracostales,  425 
of  infra-hyoid  region,  391 
infraspinatus,  472 
insertion   of,  363 
of  inspiration,  432 
intercostal,  425 

external,  425 

internal,  425 
of  intermaxillary  region,  378 
interossei  of  foot,  548 

of  hand,  499 
interspinales,  421 
intertransversales,  422 

lateralis,  422 

mediales,  422 
involuntary,  361 
of  ischio-rectal  region,  449 
labial,  378 
of  larynx,  1373 
latissimus  dorsi,  413 
of  leg,  531 

levator  anguli  oris,  377 
scapulse,  414 

ani,  451 

■glandula;  thyroidea?,  1403 

labii  inferioris,  378    . 

inenti,  378 

superioris,  376 
ala?que  nasi,  375 

palati,  403 

palpebrse,  371 
superioris,  372 

prostata;,  454 

urethrte,  454 
levatores  costarum,  426 
ligamentous  action  of,  268 
of  lingual  region,  396 
lingualis,  inferior,  399 

superior,  399 

transverse,  399 

vertical,  399 
longissimus  dorsi,  419 
longus  capitis,  407 

colli,  407 
of  lower  extremity,  507 
lumbricales,  foot,  546 

hands,  497 
of  mandibular  region,  377 
masseter,  381 
of  maxillary  region,  376 


Muscle  or  muscles,  Miiller's,  374 
multifidus  spinae,  421 
mylo-hyoid,  394 
of  nasal  region,  375 
naso-labialis,  380 
of  neck,  385 
oblique,  ascending,  437 

descending,  433 

external,  433 

internal,  437,  1516 
obUquus  auriculae,  1147 

capitis  inferior,  422 
superior,  422 

oculi,  inferior,  374 

superior,  373 

obturator  externus,  528 

internus,  525 
occipitalis,  368 
occipito-frontalis,  367 
omo-hyoid,  393 
opponens  minimi  digiti,  498 

pollicis,  496 
orbicular,  363 
orbicularis  oris,  378 

palpebrarum,  370 
orbital,  374 

region,  372 
of  palatal  region,  403 
palato-glossus,  398,  405 

-pharyngeus,  405 
of  palmar  region,  middle,  499 
palmaris  brevis,  498 

longus,  480 
of  palpebral  region,  370 
pectineus,  519 
pectoralis  major,  464 

minor,  468 
of  pelvic  outlet,  449 
penniform,  363 
of  perinseum  in  female,  460 

in  male,  455 
peroneus  brevis,  540 

longus,  539 

tertius,  534 
of  pharjmgeal  region,  400 
pharyngo-glossus,  398 
of  plantar  region,  544 
plantaris,  536 
platysma  myoides,  386 
popliteus,  537 
pronator  quadratus,  483 

radii  teres,  479 
psoas  magnus,  509 

parvus,  510 
of  pterygo-mandibular  region, 

383 
pterygoid,  external,  383 

internal,  383 
pubococcygeus,  452 
pyramidalis  abdominis,  444 

nasi,  375 
pyriformis,  524 
quadratus  femoris,  527 

lumborum,  449 

menti,  378 
quadriceps  extensor,  516 
quadrilateral,  362 
of  radial  region,  484,  495 
of  radio-ulnar    region,    poste- 
rior, 486 
recto-urethralis,  454 

-uterinus,  1491 
rectus  abdominis,  442 

capitis  anticus  major,  406 
minor,  407 
lateralis,  407 
posticus  major,  422 
minor,  422 

femoris,  516 

oculi,  external,  373 
inferior,  373 


Muscle  or  muscles,  rectus  oculi, 
internal,  373 
superior,  373 
retrahens  auriculum,  369 
rhomboidal,  363 
rhomboideus  major,  414 

minor,  414 
"ring"  of  Miiller,  1116 
risorius,  380 
rotatores  spinse,  421 
sacro-lumbalis,  419 
salpingo-pharyngeus,  405 
Santorini's,  380 
sartorius,  516 
scalenus  anticus,  408 

medius,  408 

posticus,  409 
of  scapular    region,     anterior, 
471 
posterior,  472 
semicircular,  of  rectum,  1317 
semimembranosus,  530 
semispinalis  colli,  421 

dorsi,  421 
semitendinosus,  530 
serratus  magnus,  468 

posticus  inferior,  415 
superior,  415 
of  shoulder,  470 
skeletal,  361 
of  sole  of  foot,  544 
soleus,  535 
sphincter,  363 

ani,  external,  450 
internal,  451 

vaginae,  461 
spinalis  colli,  420 

dorsi,  419 
splenius,  416 

capitis,  416 

colh,  416 
,   sterno-cleido-mastoid,  389 

-hyoid,  391 

-mastoid,  389 

-thvroid,  392 
striated,  361 
striped,  361 
stylo-glossus,  397 

'-hyoid,  394 

-pharyngeus,  403 
subanconeus,  478 
subclavius,  468 
subcrureus,  518 
subscapularis,  471 
of  superficial    cervical    region, 

386 
supinator  longus,  484 

radii  brevis,  487 
of  supra-hyoid  region,  393 
supraspinales,  421 
supraspinatus,  472 
suspensory,  of  duodenum,  1286 
temporal,' 382 
of  temporo-mandibular  region 

381 
tensor  fascia?  fenioris,  515 

palati,  404 

tarsi,  371 

tympani,  1161 
teres  major,  474 

minor,  473 
of  thigh,  512 

of  thoracic     region,     anterior, 
463 
lateral,  468 
of  thorax,  424 
Ihyro-arytenoid,  1373 

-epiglottideus,   1373 

-hyoid,  392 
tibialis  anticus,  532 

posticus,  538 


INDEX 


1579 


Muscle    or     muscles,    of     tibio- 
fibular region,  531 
of  tongue,  400 
extrinsic,  398 
intrinsic,  391 
trachelo-mastoid,  419 
tragic  us,  1147 

transversalis   abdominis,    442, 
1516 
cervicis,  419 
colli,  419 
trans  versus  auriculje,  1147 
menti,  378 

perinei    superficialis,    in    fe- 
male, 460 
in  male,  457 
trapezius,  411 
triangular,  362 
triangularis  menti,  378 

stern i,  425 
triceps,  477 

-  extensor  cubiti,  477 
of  trunk,  410 
of  ulnar  region,  498 
unstriated,  361 
unstriped,  361 
of  upper  extremity,  462 
of  ureters,  1437 
vastus  externus,  517 

internus,  517 
of  vertebral    region,    anterior, 
406 
lateral,  408 
voluntary,  361 
zygomaticus  major,  377 
minor,  377 
Muscular  coat  of  anal  canal,  1317 
of  bladder,  1437 
of  duodenum,  1288 
of  intestine,  large,  1317 

small,  1290 
of  oesophagus,  1228 
of  rectum,  1317 
of  stomach,  1273 
of  vermiform  appendix,  1305 
portion  of  urethra,  1442 
structure  of  heart,  575 
substance  of  tongue,  398 
MuscuU   papillares  of    ventricle, 
left,  571 
right,  570 
pectinati  of  auricle,  left,  511 

right,  566 
pubo-vesicalis,  1437 
Musculo-cutaneous    nerve,    985, 
1017 
-phrenic  artery,  644 
-spiral  groove,  179 
nerve,  989 
branches  of,  990 
Myelencephalon,  938 
Mylo-hyoid  artery,  614 
muscle,  394 
ridge,  123 
-hyoidean  groove,  124 
Myocardium,  574 
Myrtiform  fossa,  106 


N 

Naboth,  ovules  of,  1492 
Nails,  1185 

body  of,  1185 

edge  of,  1185 

lunula  of,  1185 

matrix  of,  1185 

ridges  of,  1185 

ungual  fold  of,  1185 
wall  of,  1185 
Nares,  anterior,  142,  1098 


Nares,  posterior,  142,  1098 

septum  of,  142 
Nasal  angle,  105 

artery    from     internal    maxil- 
lary, 616 

from  ophthalmic,  625 

of  septum,  607 

transverse,  625 
bones,  104 

articulations  of,  105 

attachment    of   muscles   to, 
105 

borders  of,  105 

development  of,  105 

surfaces  of,  105 
cartilages,  1096 
cavity,  142 
crest.  111,  116 
duct,  1142 
fossae,  142,  1098 

arteries  of,  1101 

atrium  of,  1100 

inner  wall  of,  1100 

lymphatics  of,  1102 

mucous  membrane  of,  1100 

nerves  of,  1102 

outer  wall  of,  1099 

surgical  anatomy  of,  1102 

veins  of,  1101 
groove,  105 
nerve,  1030 

branches  of,  1030 
notch,  80 

portion  of  pharynx,  1221 
process,  80 

of  superior  maxillary,  109 
region,  muscles  of,  375 
slit,  143 
spine,  80 

anterior.  111,  139,  143 

posterior,  116,  135,  143 
venous  arch,  725 
Nasion,  80,  139 
Nasmyth's  membrane,  1204 
Naso-frontal  vein,  740 
-labial  ridge,  377 
-labialis  muscle,  380 
-maxillary  suture,  139 
-palatine  artery,  616 

canal,  121 

groove,  121 

nerve,  1036 

-pharynx,  1221 

Navicular  bone,  246 

articulations  of,  247 

attachment  of  muscles  to, 
247 

surfaces  of,  246 

tuberosity  of,  246 
Neck,  arteries  of,  595 
fasciae  of,  385 
lymphatic  glands  of,  779,  784 

vessels  of,  787 
muscles  of,  385 
triangles  of,  posterior,  618 

surgical  anatomy  of,  616 
veins  of,  724,  728 
N^laton's  fine,  229 
Nerve  or  nerves,  abducent,  1043 
ansa  hypoglossi,  1066 
of  arm,  977 
Arnold's,  1060 
of  arteries,  586 
articular,  of  anterior  tibial, 
1017 

of  auriculo-temporal,  1038 

of  great  sciatic,  1013 

of  internal  plantar,  1015 
popliteal,   1014 

of  peroneal,   1016 

of  posterior  tibial,  1015 


Nerve    or    nerves,    articular,    of 

ulnar,  988 
auditory,  1050 
auricular,  anterior,  1038 

of  pneumogastric,  1060 

posterior,  1047 
auriculo-temporal,  1037 
of  bones,  41 
buccal,   1037 

from  facial,  1049 
buccinator,  1037 
calcaneal,  external,  1014 

internal,  1015 
calcaneo-plantar,  1015 
cardiac,  cervical,  1061 

great,  1077 

inferior,  1077 

middle,  1077 

minor,  1077 

superior,  1076 

thoracic,  1061 
cardio-motor,  1071 
carotico-tympanic,  1073 
carotid,  1057 
cavernous,  large,  1086 

small,  1086 
-cells,  818 

axone  of,  821 

dendrites  of,  821 

development  of,  823 
cerebral,  1019 
cervical,  968,  1049 

superficial,  973 
cervico-facial,  1049 
chorda  tympani,  1038,  1047 
ciliary,  long,  1030 

short,  1031 
circumflex,  984 
coccygeal,  1006 
cochlear,  1053 

communicantes  hypoglossi,  974 
communicating,    fibular,    1014 

tibial,  1014 
of  Cotunnius,  1036 
cranial,  1019 

first,  880 
crural,  'anterior,  1004 

accessory  of  Winslow, 
1004 
cutaneous,  of  abdomen,  996 

external,  985,  1003 

internal,  986,  1004 

of  internal  plantar,  1015 

middle,  1004 

of  musculo-cutaneous,  1017 
-spiral,  991 

of  obturator,   1003 

palmar,  986 

of  perineal,  1013 

of  peroneal,  1016 

of  small  sciatic,  femoral, 
1011 
gluteal,  1011 
perineal,  1011 

of  supraorbital,  1030 

of  thorax,  995 

of  ulnar,  988 
dorsal,  989 
palmar,  988 
dental,  anterior  superior,  1033 

inferior,  1039 

middle  superior,   1033 

posterior  superior,    1032 
descendens  hypoglossi,  1066 

noni,  1066 
digastric,  from  facial,  1048 
digital,  foot,  1015 

hand,  987 
dorsal,  993 

of  clitoris,  1013 

of  penis,  1013 


1580 


INDEX 


Nerve  or  nerves, dorsi-lumbar,996 
of  dura  mater  of  brain,  849 
eighth,  1050 
eleventh,  1063 
-endings,  Ruffini's,  828 
-epithelium  cells,  830 
of  eyeball,  1021 
facial,  1044 

-fibre,   axis-cylinder  of,  822 
-fibres,  822 

development  of,  823 

medullated,  822 

non-medullated,  823 

of  retina,  1122 
fifth,  1026 
first,  1019 
of  foot,  1015 
fourth,  1025 
frontal,  1030 
ganglia  of,  831 
gastric,  1061 
genito-c  rural,  1000 
glosso-pharyngeal,  1054 
gluteal,  inferior,  1011 

superior,  1010 
gustatory,  1038 
hsemorrhoidal,   inferior,   1011 
of  heart,  577 
hypogastric,  999 
hypoglossal,  1064 
iliac,  999 
ilio-hypogastric,  999 

-inguinal,  999 
incisor,  1039 
inframandibular,  1049 
inframaxillary,  1049 
infraorbital,  1049 
infratrochlear,  1031 
intercostal,  993 
intercosto-humeral,  995 
interosseous,  anterior,  987 

of  anterior  tibial,   1017 

posterior,  991 
Jacobson's,  1056 
jugular,  1073 
labial,  1034 
of  labyrinth,  1176     ' 
lachrymal,  1028 
of  Lancisi,  887 

laryngeal,  inferior,  of  pneumo- 
gastric,  1060 

superior,  1060 
external,  1060 
internal,  1060 
lingual  of  fifth,  1038, 

of  glosso-pharyngeal,  1057 
lumbar,  997 
malar,  1049 

of  superior  maxillary,   1032 
mandibular,  1036 
masseteric,  1037 
mastoid,  973 
maxillary,  inferior,  1036 

superior,  1031 
median,  986 
meningeal,  1032 

from  hypoglossal,   1066 

of  internal  maxillary,  1036 

of  pneumogastric,  1059 
mental,  1039 
motor  oculi,  1024 
muscular,    of    anterior    tibial, 
1017 

of  external  plantar,   1016 

of  great  sciatic,  1013 

of  hypoglossal,  1066 

of  internal  plantar,  1015 
popliteal,    1014 

of  musculo-cutaneous,   1017 
-spiral,  990 

of  perineal,  1013 


Nerve    or    nerves,    muscular,   of 
posterior  tibial,    1014 

of  sciatic  plexus,  1010 

of  ulnar,  988 
musculo-cutaneous,  985,   1017 

-spiral,  989 
mylo-hyoid,  1039 
nasal,  1030 

from  Meckel's  ganglion,  1034 

ganglionic  branch  of,  1030 
naso-palatine,  1036 
ninth,  1054 
obturator,  1003 

accessory,  1004 
occipital,  from  facial,  1048 

great,  969 

small,  972 
oesophageal,  1061 
olfactorv,  880,  1019 
ophthalmic,  1028 
optic,  1021 
orbital,  of  superior  inaxillary, 

1032 
origin  of,  826 
palatine,  anterior,  1035 

external,  1035 

large,  1035 

middle,  1035 

posterior,  1035 

small,  1035 
palmar,  of  ulnar,  deep,  989 

superficial,  989 
palpebral,  1034 
parotid,  1038 
-paths,  959 

auditory,  1053 

cochlear,  1053 

gustatory,  1057 

vestibular,  1054 
perforating,  of  Casserius,  985 
of  pericardium,  561 
pericranial,  1030 
perineal,  1013 
peroneal,  1016 
petrosal,  deep,  1073 

great  deep,   1034 
superficial,  1034 

large  deep,  1034,  1073 
superficial,  1034 
pharyngeal,  1036,  1057,  1060 
phrenic,  974 

of  pia  mater  of  brain,  856 
plantar,  external,  1016 

internal,  1015 
plexus    of,    abdominal    aortic, 
1085 

annular,  1111 

brachial,  977 

cardiac,  1081 

carotid,  internal,  1073 

cavernous,  1073 

cervical,  972 

cceliac,  1061,  1084 

coUc,  left,  1085 

coronary,  1081,  1085 

cystic,  1085 

of  dental,  superior,  1033 

epigastric,  1083 

fundamental,  1111 

gastric,  1085 

gastro-duodenal,  1085 
-epiploic,  1085 
left,  1085 

hsemorrhoidal,  inferior,  1086 
superior,   1085 

hepatic,   1085 

hypogastric,  1085 

infraorbital,  1049 

intra-epithelial,  1111 

lumbar,  998 

mesenteric,  inferior,   1085 


Nerve  or  nerves,  plexus  of.  mes- 
enteric, superior,  1085 

oesophageal,   1059,  1061, 
1082 

ovarian,  1084 

pancreatic,  1085 

patellar,  1004 

peKdc,  1086 

pharyngeal,  1057 

phrenic,  1084 

prostatic,  1086 

pudendal,  1009 

pudic,  1009 

pulmonary,  1081 
anterior,  1059,  1061 
posterior,  1059,  1061 

pyloric,  1085 

renal,  1061,  1084 

sacral,  1009,  1086 

sciatic,  1009 

sigmoid,  1085 

solar,  1083 

spermatic,  1084 

splenic,  1061,  1085 

subclavian,  1077 

subepithelial,  1111 

suprarenal,  1084 

thoracic  aortic,  1079 

tympanic,  1057 

uterine,  1086 

utero-vaginal,  1086 

vaginal,  1086 

vertebral,  1077 

vesical,  1086 
pneumogastric,  1057 
popliteal,  external,  1016 

internal,  1014 
portio  dura,  1044 

mollis,  1045 
pterygoid,  external,  1037 

internal,  1037 
pterygo-palatine,  1036 
pudendal,  inferior,  1011 
pudic,  1011 
pulmonary,  anterior,  1061 

posterior,  1061 
radial,  991 

recurrent,    of    internal    maxil- 
lary, 1036 

laryngeal,  of  pneumogastric, 
1060 
respiratorv,  of   Bell,  external, 
983 
internal,  974 
sacral,  1006 
saphenous,  external,  1014 

internal,   1005 

long,  1005 

short,  1014 
scapular,  posterior,  982 
of  Scarpa,  1036 
sciatic,  great,  1013 

small,  1011 
scrotal,  long,  1011 
second,  1021 
seventh,  1044 
sixth,  1043 
spheno-palatine,  1032 
sphenoidal,  1039 
spinal,  964 

accessory,  1063 
-spindles,  829 
splanchnic,  1079 

renal,  1079 
stylo-hyoid,  1048 
subcutaneous  maliB,  1032 
suboccipital,  968 
subscapular,  984 
superficialis  colli,  973 
supra-acromial,  974 
I       supraclavicular,  974 


INDEX 


1581 


Nerve   or  nerves,  supramandib- 
ular,  1049 

supramaxillary,  1049 

supraorbital,  1030 

suprascapular,  983 

suprasternal,  974 

supratrochlear,  1030 

sural,   1016 

sympathetic,  1066 

temporal,    of    auriculo-tempo- 
ral,  1038 
deep,  1037 
from  facial,    1049 
of  superior  maxillary,   1032 

temporo-malar,  1032 

tenth,   1057 

termination  of,  826 
peripheral,  826 

third,  1024 

thoracic,  993 
anterior,  984 
long,  983 
posterior,  983 

thyro-hvoid,  1066 

thvroid,  1077 

tibial,  1014 
anterior,  1016 
posterior,  1014 

tonsillar,  1057 

trifacial,  1026 

trigeminal,  1026 

trochlear,  1025 

twelfth,  1064 

tympanic,  1056 
from  facial,  1047 

ulnar,  988 

-unit,  818 

vagus,  1057 

vasomotor,  1071 

vestibular,  1053 

Vidian,  1034 
Nervi  nervorum,  825 
Nervous  papillae,  1181 

system,  817 

cerebro-spinal,  structure  of, 
817 

tissue,   chemical  composition 
of,  824 

cutaneous  patelliB,  1005 

superficialis  cordis,  1076 
Neumann,    dentinal    sheath    of, 

1203 
Neural  arch,  34 

canal,  857 

tube,  857 
Neurenteric  canal,  1242 
Neurilemma  of  cord,  822 
Neuroblasts,  823 
Neuro-central  suture,  59 

-muscular  spindles,  829 

-tendinous  spindles,  829 
Neuroglia  of  cord,   840 
Neurokeratin,  823 
Neurones,  818 

of  Cajal,  919 

cell-bodies  of,  818 

theory  of,  821 
Nexal  root  of  eighth  nerve,  1050 
Nidus  avis  of  cerebellum,  931 
Ninth  nerve,  1054 

surgical  anatomy  of,   1057 
Nipple,   1504 

structure  of,  1505 
Nissl's  bodies,  820 
Nodal  point,  1106 
Nodules  of  cerebellum,  930 
Non-medullated  nerve-fibres,  823 
Nose,   1095 

aperture  of  cartilage  of,   1097 

arteries  of,  1098 

cartilage  of,  1096 


Nose,  dorsum  of,  1096 
fossae  of,  142,  1098 
integument  of,  1097 
interior  of,    lymphatic   vessels 

of,  782 
lymphatics  of,  1098 
meatus  of,  inferior,  145 
middle,  145 
superior,  101,  144 
mucous  membrane  of,   1098 
muscles  of,  1097 
nerves  of,  1098 
outer,   1096 
septum  of,  142 

cartilage  of,  triangular,  1097 
structure  of,  1096 
veins  of,  1098 
Notch  cerebellar,  anterior,  926 
posterior,  926 
cotyloid,  213 
ethmoidal,  82 
ilio-sciatic,  210 
intercondyloid,  225 
intervertebral,  49 
lachrymal,  107 
nasal,  80 
popliteal,  234 
pre-sternal,  157 
pre-occipital,  869 
pterygoid,  96 
of  Rivinus,  1151 
sacro-sciatic,  217 
great,  210 
lesser,  211 
scapular,  great,  173 
sigmoid,  125 
spheno-palatine,  118 
supraorbital,  80,  140 
suprascapular,  174 
suprasternal,  409 
thyroid,  1362 
Nuchal  line,  inferior,  72 
superior,  72 
plane,  72 
Nuck,  canal  of,  1462,  1501 
Nucleated  sheath  of  Schwann, 

822 
Nuclei,  auditory,  950 
of  auditory  nerve,  £25 
of  fifth  nerve,  925 
of  glosso-pharyngeal  nerve,  950 
of  optic   thalamus,  904 
of  vagus   nerve,   950 
Nucleus,     accessory,     of    eighth 
nerve,  1051 
amygdaloid,  891 
ambiguus,  950,  1056 
of  Bechterew,  926,   1050 
caudate,  891 
cuneate,  accessorv,  948 
of  Deiters,  926,  1050 
emboliformis,  938 
of  facial  nerve,  925 
fasciculi  gracilis,  941 
fastigii,  938 
globosus,  938 
hypoglossal,  949 
inferior  central,  949 
lentis,  1132 
lenticular,  890 
of  Luys,  908,  910 
of  olivary  body,  951 
accessory,  951 
superior,  925 
of  optic  thalamus.  904 
of  sixth  nerve,  925 
of  spinal  accessorv  nerve,  950 
of  Stilling,  red,  938 
of  tegmentum,  red,  908 
vagi,  1057 
Nuel,  space  of,  1175 


Nuhn    and    Blandin,    glands   of, 

1091 
Nutrient  arterv  of  femur,  707 

of  fibula,  718 

of  humerus,  656 

of  tibia,  719 
Nymphse,  1478 


Obelion,  129 
Obex,  944 

Oblique  diameter  of  pelvis,  217 
fibres  of  cord,  841 
inguinal  hernia,  1517,  1520 
complete,  1521 
incomplete,  1521 
ligament,  314 
line  of  clavicle,  168 
of  fibula,  237 
of  radius,  190 
of  tibia,  235 
muscles,  ascending,  437 
aponeurosis  of,  439 
descending,  433 
external,  433 

aponeurosis  of,  434 
internal,  437,  1516 
aponeurosis  of,  439 
dissection  of,  437 
ridges  of  scapula,  171 
of  trapezium,  198 
of  ulna,  188 
sacro-iliac  ligament,  292 
sinus  of  pericardium,  560 
vein  of  Marshall,  771 
Obliquus  auriculse  muscle,  1147 
capitis  inferior  muscle,  422 

superior  muscle.  422 
oculi  muscle,  inferior,  374 
superior,  373 
Obstetric  perinseum,  1478 
Obturator  artery,  688 
peculiarities  of,  689 
bursa,  331 
canal,  525 
crest,  213 

externus  muscle,  528 
fascia,  1546 
foramen,  214 
groove,  211,  213 
internus  muscle,  525 

bursa  of,  525 
ligament,  296 
membrane,  525 
nerve,  1003 

accessory,  1004 
vein,  761 
Occipital  artery,  608,  640 
branches  of,  609 
bone,  71 

angles  of,  75 
articulations  of,  76 
attachment  of  muscles  to,  76 
borders  of,  75 
development  of,  75 
structure  of,  75 
surfaces  of,  71 
convolution,  inferior,  877 
middle,  877 
superior,  877 
crest,  external,  72,  136 

internal,  74,  133 
diploic  vein,  734 
fossae,  inferior,  133 
groove,  86 

horn  of  lateral  ventncle,  889 
lobe,  876 

gray  matter  of,  921 
lymphatic  glands,  780 


1582 


INDEX 


Occipital  nerve,  branch  of  facial, 
1048 
great,  969 
small,  972 
protuberance,  external,  71,  136 

internal,  73 
sinus,  739 
sulci,  868,  876 
triangle,  618 
vein,  727 
Occipitalis  muscle,  368 
Occipito-atlantal  ligament,  ante- 
rior, 276 
»  posterior,  276 

-axial  ligament,  posterior,  278 
-frontal  fasciculus,  918 
-frontalis,  muscle,  367 

surgical  anatomy  of,  368 
-parietal  suture,  128 
-temporal  convolution,  878 
gyrus,  877 
sulcus,  870 
Occiput,  arteries  of,  608 
Odontoblasts,  1206 

of  Waldeyer,  1201 
Odontoclasts,  1209 
Odontoid  ligaments,  lateral,  278 
middle,  52,  279 
process  of  axis,  52 
Esophageal  arteries,  641,  666 
nerves,  1061 
opening  of  diaphragm,  430 

of  stomach,  1270 
plexus,  1059,  1061,  1082 
veins,  751 
CEsophagus,  1225 

abdominal  portion,  1226 
anomalies  of,  1228 
areolar  coat  of,  1229 
arteries  of,  1229 
cervical  portion,  1226 
diaphragmatic  portion,  1226 
innervation  of,  1230 
lymphatics  of,  815,  1230 
movements  of,  1230 
mucous  coat  of,  1229 
muscular  coats  of,  1228 
nerves  of,  1230 
relations  of,  1227 
structure  of,  1228 
submucous  coat  of,  1229 
surgical  anatomy  of,  1230 
thoracic  portion,  1226 
veins  of,  1229 
Olecranon  bursa,  311 
subcutaneous,  477 
fossa,  181 
process,  186 
Olfactory  bulb,  880,  1019 
gray  matter  of,  921 
cells,  1101 
fasciculus,  895 
foramina,  143 
hair,  1101 
lobe,  880 

anterior,  880 
posterior,  881 
nerve,  880,  1019 

surgical  anatomy  of,  1021 
path,  1020 
sulcus,  870,  874 
tract,  880,  1019 
tubercle,  881,  1019 
OUvary  body  of  medulla  oblon- 
gata, 941 
corpus  of,.  951 
nucleus  of,  951 
peduncles  of,  951 
bundle  of  cord,  843 
eminence,  93 
fasciculus,  910  I 


Olivary  nucleus  superior,  925 

process,  93,  131 
Omenta,  1254 
Omental  band,  1317 

tuberosity,  1329 
Omentum,  development  of,  1238 
gastro-colic,  1256 
-hepatic,  1254 
-splenic,  1256 
great,  1256 
lesser,  1254 
Omo-hyoid  muscle,  393 
Opercula  of  insula,  878 
Operculum,  frontal,  866,  874 
fronto-parietal,  866,  874 
orbital,  866,  874 
Ophryon,  80 
Ophthalmic  artery,  622 
branches  of,  622 
ganglion,  1031 
nerve,  1028 

branches  of,  1028 
veins,  740 
inferior,  741 
superior,  740 
Opisthotonic  portion  of  temporal 

bone,  91 
Opponens  minimi  digiti  muscle, 
foot,  547 
hand,  498 
pollicis  muscle,  496 
Optic  axis,  1106 
chiasma,  882 
commissure,  131,  882,  1021 

inter-cerebral  fibres  of,  1021 
cup,  1121 
disk,  1121 

foramen,  93,  96,  131,  142 
groove,  93,  130,  131 
lobes,  911 
nerve,  1021 

surgical  anatomy  of,  1022 
papilla,  1121 
path,  1022 
radiations,  905 
recess,  902 
thalamus,  903 

connections  of,  905 
nuclei  of,  904 
stalk  of,  905 
tubercle  of,  904 
tract,  884,  1021 
Ora  serrata,  1120 
Oral  cavity,  1193 

portion  of  pharynx,  1221 
of  tongue,  1087 
Orbicular  bone,  1159 
ligament,  314 
muscles,  363 
Orbicularis  oris  muscle,  378 
palpebrarum  muscle,  370 
external  portion  of,  370 
internal  portion  of,  370 
orbital  portion  of,  370 
palpebral  portion  of,  370 
Orbiculus  ciliaris,  1115 
Orbit,  140 

arteries  of,  623 
fasciae  of,  374 
margin  of,  106 
muscles  of,  374 
Orbital  arterv,  611 
internal,"  627 
branch  of  facial  nerve,  1032 
cavities,   140 

convolution,  anterior,  874 
internal,  873 
posterior,  874 
fascia,  375 
fissure,  96 
foramina,  95 


Orbital  fossie,  140,  143 
lobe,  874 
muscle,  374 
nerve,  1032 
operculum,  866,  874 
plates,  81 

process  of  malar,  114 
of  palate  bone,  118 
region,  muscles  of,  372 
action  of,  374 
dissection  of,  372 
surgical  anatomy  of,  375 
septum,  1139 
sinus,  118 
sulcus,  870,  874 
vein,  727 
Orbito-palpebral  sulcus,  inferior,, 
1137 
superior,  1137 
-tarsal  ligament,  1139 
Orbits,  140 
Organ  of  Corti,  1173 
of  Jacobson,  1100 
Organs  of  digestion,  1193 
of  generation,  female,  1477 

male,  1447 
of  Giraldes,  1473 
of  Golgi,  829 
of  respiration,  1361 
of  Rosenmiiller,  1499 
of  special  sense,  1087 
of  voice,   1361 
Orifice,  mitral,  568 

of  prostatic  ducts,  1442 
tricuspid,  567 
of  ureters,  1438 
Os  acetabulum,  213 
external,  1489 
incfe,  76 

innominatum,  207 
articulations  of,  215 
attachment   of   muscles   to, 

215 
development  of,  214 
ilium,  207 
ischion,  210 
pubis,  212 
structure  of,  214 
internal,   1488 
magnum  of  carpus,  199 
articulations  of,  199 
attachment  of  muscles  to,. 

199 
surfaces  of,  199 
planum  of  ethmoid,  100 
trigonum,  245 
uteri,  1489 
Ossa  pubis,  articulations  of,  296- 
angle  of,  212 
unguis,   113 
Osseous  labyrinth,  1164 

portion    of    Eustachian    tube, 
1154 
of  external  auditory  meatus,. 
1149 
Ossicles  of  tympanum,  1158 
articulations  of,  1160 
ligaments  of,  1160 
movements  of,  1161 
Ossification  of  bone,  42 
centre  of,  44 
intracartilaginous,  43 
intramembranous,  43 
of  spine,  60 
Osteo-dentine  of  Owen,  1204 
Osteoclasts,  36 
Osteology,  33 
Ostium  abdominale  of  Fallopian. 

tube,  1497 
Otic  ganglion,  1039 
branches  of,  1039 


INDEX 


158a 


Otokonien,  1171 
Otolith,  1169 

membrane,  1172 
Outlet  of  pelvis,  217 
Ova,  primordial,  1502 
Ovarian  arteries,  680 

bursa,  1490 

plexus,  1084 

veins,  766 
Ovario-pelvic  fold,  1500 
Ovary,  1499 

arteries  of,  1503 

at  different  ages,  1501 

connections  of,  1500 

descent  of,  1501 

fimbria  of,  1499 

hilum  of,  1500 

lymphatics  of,  1503 

lymphatic  vessels  of,  804 

nerves  of,  1503 

serous  covering  of,  1501 

stroma  of,  1501 

structure  of,  1501 

supports  of,  1500 

surgical  anatomy  of,  1503 

veins  of,  1503 
Ovicapsule  of   Graafian  follicles 

1502 
Ovules  of  Naboth,  1492 
Ovum,  discharge  of,  1503 
Oxvntic  cells,  1277 

glands,  1277 


Pacchion'Iax  depressions,  78 

glands,  737,  854 
Pacinian  corpuscles,  828 
Pads  of  adipose  tissue,  263 

corpus  callosum,  886 
Palatal  region,  muscles  of,  403 
dissection  of,  403 
surgical  anatomy  of,  406 
Palate,  1210 
bone,  115 

articulations  of,  119 
attachment  of  muscles  to, 

119 
development  of,  119 
horizontal  plate  of,  116 
borders  of,  116 
surfaces  of,  116 
perpendicular  plate  of,  117 
borders  of,  117 
surfaces  of,  117 
processes  of,  118 
tuberosity  of,  117,  135 
vertical  plate  of,  117 
borders  of,  117 
surfaces  of,  117 
hard,  1210 
muscles  of,  403 
soft,  1211 

surgical  anatomy  of,  1224 
vail  of,  1211 
Palatine  aponeurosis,  404 
artery,  ascending,  606 
descending,  615 
inferior,  606 
posterior,  615 
surgical  anatomy  of,  615 
canal,  anterior,  143 
posterior,   107,  116 
accessory,  116,  135 
foramen,  great,  116 

posterior,  135 
fossa,  anterior,  110,  133 
glands,  1211 
nerve,  anterior,  1035 
external,  1035 


Palatine  nerve,  large,  1035 
middle    1035 
posterior,  1035 
small,   1035 
process  of  superior  maxiilarv, 

120 
spine,   116 
Palato-glossus  muscle,  398,  405 
-maxillary  canal,  107 
-pharyngeiLs  muscle,  405 
Palmar  arch,  deep,  658 
superficial,  664 
surface  marking  of,  665 
surgical  anatomy  cf,  665 
cutaneous  nerve,  987 
fascia,  deep,  493 

surgical  anatomy  of,  494 
interosseous  arteries,  660 
plexus  of  nerves,  745 
recurrent  arteries,  660 
region,  middle,  muscles  of,  499 
veins,  747 
Palmaris  brevis  muscle,  498 

longus  muscle,  480 
Palpebral  arteries,  external,  623 
internal,  623 
cartilages  or  plates,  1139 
fascia?,   1139 
ligaments,  1139 
nerves,   1034 

portion  of  conjunctiva,  1140 
region,  muscles  of,  370 
dissection  of,  370 
Pampiniform  plexus  of  veins,  765 
Pancreas,  1348 
arteries  of,  1352 
body  of,  1350 
borders  of,  1350 
development  of,  1244 
dissection  of,  1348 
head  of,  1348 
lymphatic  vessels  of,  807 
lymphatics  of,  1352 
neck  of,  1350 
nerves  of,  1353 
peritoneal  relations  of,  1351 
structure  of,  1352 
surface  form  of,  1353 
surfaces  of,  1350 
surgical  anatomy  of,  1353 
tail  of,  1350 
veins  of,  1352 
Pancreatic  area  of  kidney,  1414 
artery,  674 
duct,  1351 
juice,  1353 

plexus  of  nerves,  1085 
of  veins,  768 
Pancreatic  a  magna  artery,  674 
Pancreatico-duodenal  artery, 
inferior,  675 
superior,  674 
plexus  of  nerves,  1085 
vein,  768 
Papilla,  bile,  1288 
dentine,  1205 
lachrj'mal,  1142 
spiralis,  1173 
PapillsB  circumvallate,  1089 
conical,  1090 
filiform,  1090 
fungiform,  1090 
raaximse,  1089 
media;,  1090 
minimsB,  1090 
of  tongue,  1089 
simple,  1090 
structure  of,  1090 
Papillary  layer  of  skin,  1187 
Paracentral  lobule,  875 
Paraduodenal  fossa,  1262 


Paramastoid  process,  73 
Paramedians  sulcus,  868 
Parametrium,  1489 
Paramammary  gland,  813 
Paranucleus,  1352 
Parathyroids,  1406 

structure  of,  1406 
Parenchyma  of  lungs,  1395 

of  testicle,   1471 
Paries  carotica,   1153 
jugularis,  1151 
labyrinthica.  1152 
mastoidea,  1152 
tegmentalis,  1151 
Parietal  artery,  611 

arteries,  ascending,  628 
bone,  76 

articulations  of,  79 
attachment  of  muscles  to, 

79 
development  of,  78 
surfaces  of,  76 
borders  of,  78 
cells  of  gastric  glands,  1277 
convolution,  ascending,  876 
inferior,  876 
superior,  876 
diploic  vein,  external,  734 
eminence,  76 
foramen,  76 
layer  of  pleura,  1385 
lobe,  875 
lymphatics,  810 
peritoneum,  1247 
portion    of    tunica    vaginalis, 

1470 
surface  of  liver,   1330 
of  stomach,  1269 
Parieto-colic  fold,  external,  1263 
internal,  1264 
-occipital  sulcus,  867 
external,  867 
internal,  867,  870 
•    -sphenoidal  artery,  628 

-temporal  artery,  628 
Paro-ophoron,  1499 
Parotid  capsule,  1216 
duct,  1215 

structure  of,  1216 
surface  form  of,   1215 
fascia,  388,  1215 
gland,  1214 

accessory,  1215 
arteries  of,  1216 
duct  of,  1215 
lymph,  1215 
lymphatics  of,  1216 
nerves  of,  1216 
veins  of,  1216 
lymphatic  glands,  781 
deep,  782 
superficial,  781 
nerves,  1038 
recess,  1215 
Paratideo-masseterica  fascia,  388 
Parovarium,  1499 
Pars  ciliaris  retinae,    1115,    1120 
intermedia  of  Wrisberg,   1045 
iridica  retinae,  1120 
Patella,  230 
apex  of,  231 
articulations  of,  231 
attachment  of  muscles  to,  231 
borders  of,  231 
development  of,  231 
ligaments  of,  335 
structure  of,  231 
surfaces  of,  231 
form  of,  231 
surgical  anatomy  of,  231 
Patellar  bursa,  deep,  518 


1584 


INDEX 


Patellar  plexus,  1004 
Path  of  light  stimuli,   1127 
Paths,  nerve,  auditory,  1053 
cochlear,  1053 
gustatory,  1057 
vestibular,  1054 
olfactory,  1020 
optic,  1022 
Pecquet,  reservoir  of,  775 
Pecten  ossis  pubis,  212 
Pectineus  muscle,  519 

nerve  to,  1005 
Pectoral  fascia,  deep,  464 
gland,  790 

intercostal  nerve,  995 
region,   dissection  of,  463 
ridge,  179 
Pectoralis  muscle,  major,  464 

minor,  468 
Peduncles  of  cerebellum,  932 
inferior,  935 
middle,  922,  934 
superior,  910,  932,  943 
cerebral,  906 
of  cerebrum,  882,  884 
■of  corpus  callosum,  882,  886 
■of  flocculus,  931 
of  mammillary  body,  883 
of  olive,   951 

of  perineal  gland,  895,  906 
Peduncular  fibres  of  cerebellum, 
932 
of  cerebrum,  914 
Pelvic  colon,  1311 
fascia,  1544 
girdle,  207 

ligament,  transverse,  459 
plexus,  1086 

portion  of  gangliated  cord,  1080 
Pelvis,  215 
axes  of,  218 
brim  of,  217 
cavity  of,  217,  1431 
boundaries  of,  1431 
contents  of,  1431 
■diameters  of,  217 
diaphragm  of,  1231 
■differences  between  male  and 

female,  219 
false,  215 
■of  kidney,  1415 
lower  circumference  of,  217 
lymphatic  vessels  of,  801 
lymphatics  of,  797 
muscles  of,  449 
■outlet  of,  217 
position  of,  218 
surface  form  of,  220 
surgical  anatomy  of,  220 
true,  216 

inlet  of,  217 

superior    circumference    of, 
217 
veins  of,  755 
Pendulous    portion    of    urethra, 

1443 
Penile  portion  of  urethra,  1443 
Penis,  1453 

arteries  of,  1459 

dorsal,  692 
body  of,  1455 

corpora  cavernosa  of,   1455 
corpus  spongiosum,  1458 
crura  of,  1454 
dorsum  of,  1455 
frsenum  of,  1455 
ligaments  of,  1459 
lymphatics  of,  1459 

vessels  of,   superficial,   801 
nerves  of,  1013,  1460 
dorsal,  1013 


Penis,  prepuce  of,  1455 
root  of,  1454 
septum  of,  1457 
structure  of,  1455 
surgical  anatomy  of,   1460 
veins  of,   1459 
dorsal,  deep,  762 
superficial,  762 
Penniform  muscles,  363 
Peptic  cells  of  glands,  1277 

glands,  1277 
Perforating     arteries,     anterior, 
644 
of  hand,  660 
of  thigh,  706 
cutaneous  nerve,  1011 
nerve  of  Casserius,  985 
Pericajcal  folds,  1262 

fossa},  1262 
Pericardiac  arteries,  644,  666 
Pericardial  pleura,  1385 

sac,  1236 
Pericardiothoracic    cavity,    1236 
Pericardium,  557 
arteries  of,   561 
fibrous  layer  of,   558 
nerves  of,  561 
serous,  560 
sinus  of,   oblique,  560 

transverse,  560 
structure  of,  558 
surgical  anatomy  of,  561 
vestigial  fold  of,  561 
Pericementum,  1196 
Perichondrium,  260 
Perichoroidal  space,  1108 
Pericranial  nerves,  1030 
Perilymph,  1164 

space,  1164 
Perimysium,  external,  361 

internal,  361 
Perineal  artery,   superficial,  690 
transverse,  691 
body,  1314,   1484,   1543 
cutaneous  nerve,  1011 
fascia,  deep,  1538 
ligament,  transverse,  459 
nerve,  1013 
Perineum,  1314,  1484 
dissection  of,  1535 
in  female,  1542 

muscles  of,  460 
lymphatic    vessels    of,    super- 
ficial, 801 
in  male,  1537 

central  tendinous  point  of, 

1537 
fascise  of,  455 
muscles  of,  455 
obstetric,  1478 
surgical  anatomy  of,   1535 
Perineurium,  825 
Periosteum,  37 
dental,  1204 
Peripheral   branches   of   lumbar 
portion  of  gangliated  cord, 
1080 
of  middle  cervical  ganglion, 

1077 
of  pelvic  portion  of  gangli- 
ated cord,  1080 
of  sacral  portion  of  gangli- 
ated cord,  1080 
of    superior     cervical     gan- 
glion, 1073 
of  thoracic  portion  of   gan- 
gliated cord,  1079 
terminations  of  nerves,  826 
Peritoneal    coat    of    duodenum, 
1288 
of  stomach,  1273 


Peritoneal  relations  of  pancreas,   "I 

1351 
Perisclerotic  lymph-space,  1103 
Peritoneum,  1245 

development  of,  1235,  1242 
ligaments  of,  1254 
lymphatic  vessels  of,  802 

surgical  anatomy  of,  802 
mesenteries  of,  1257 
omenta  of,  1254 
parietal,   1247 
structure  of,  1245 
surgical  anatomy  of,   1264 
visceral,   1247 
Peritracheo-bronchial      glands, 

812 
Perivascular   lymph-spaces,    772 
Permanent   teeth,   1196 
development  of,  1208 
eruption  of,  1209 
superadded,  1208 
Peroneal  artery,  717 
anterior,  718 
branches  of,  718 
peculiarities  of,  718 
posterior,  718 
relations  of,  718 
groove,  245 
nerve,  1016 
spine,  243 
tubercle,  243 
vein,  578 
Peroneus  brevis  muscle,  540 
longus  muscle,  539 
tertius  muscle,  534 
Perpendicular  line  of  ulna,  188 
plate  of  ethmoid,  100 
of  palate  bone,  117 
Pes  accessorius,  890 
anserinus,  1045 
of  crus  cerebri,  907 
hippocampi,  890 
Petit,  canal  of,  1130 

triangle  of,  435 
Petro-mastoid    portion    of   tem- 
poral bone,  91 
-occipital  fissure,  128 

suture,  75,  133 
-sphenoidal  fissure,  128 

suture,  136 
-squamous  sinus,  739 

suture,  88 
-tympanic  fissure,  84,  1152 
Petrosal  nerve,  deep,  1073 
great  deep,  1034 

superficial,  1034 
large  deep,  1034,  1073 
superficial,  1034 
process,  93 
sinus,  inferior,  742 
superior,  742 
Petrous,  ganglion,  1056 
branches  of,  1056 
portion   of    internal   carotid 
artery,  620 
of  temporal  bone,  136 
Peyer's  glands,  1296 

patches,  1296 
Phalanges  of  foot,  252 

articulations  of,  252,  359 
attachment  of  muscles  of, 

252 
development  of,  254 
of  hand,  204 

articulations  of,  204,  325 
attachment  of  muscles  to, 

204 
development  of,  206 
ligaments  of,  325 
Pharyngeal      aponeurosis,     402, 
1223 


INDEX 


1585 


Pharyngeal     artery,     ascending, 
610 
branches  of,  610 
surgical  anatomy  of,  611 
branch  of  pneumogastric  nerve 

1060 
bursa,  1224 
glands,  1222 
nerve,  1036,  1057 

plexus,  1057 
portion  of  tongue,  1087 
region,  muscles  of,  400 

dissection  of,  400 
ring,  lymphatic,  1224 
spine,  73,  135 
tonsil,  1221,  1224 
tubercle,  73 
veins,  730 

plexus  of,  730 
Fharyngo-epiglottic    fold,    1222 

-glossus  muscle,  398 
Pharynx,  1220 

aponeurosis  of,  1223 
arteries  of,  610 
fibrous  coat  of,  1223 
isthmus  of,  1221 
laryngeal  part,  1222 
lymphatic  vessels  of,  782 
mucous  coat  of,  1223 
muscles  of,  400 
nasal  part,  1221 
oral  part,  1221 
structure  of,  1222 
surgical  anatomy  of,  1224 
vault  of,  1221 
Philtrum,  380 
Phleboliths,  762 
Piirenic  arteries,  inferior,  680 
superior,  644 
ganglion,  1084 
hernia,  427 

nerve,  974  • 

plexus  of  nerves,  1084 
surface  of  spleen,   1354 
veins,  767 
Plirenico-costal  sinus,  1386,  1414 

-pleural  fascia,  1386 
Phreno-colic  ligament,   1259 
-pericardial  ligament,  559 
Physiological  retina,  1120 
Pia  mater  of  brain,  854 
arteries  of,  856 
nerves  of,  857 
veins  of,  856 
of  cord,  835 

structure  of,  835 
Pigmentary  layer  of  retina,  1127 
Pillars  of  fauces,  1211 
of  fornix,  anterior,  895 
posterior,  896 
Pineal  body,  905 
gland,  905 

peduncles  of,  895,  906 
structure  of,  906 
recess,  903 
stria;,  904 
Pinna  of  ear,  1144 
arteries  of,  1147 
cartilage  of,   1146 
integument  of,  1146 
ligaments  of,   1146 
lymphatics  of,   1147 
muscles  of,   1147 
nerves  of,   1148 
structure  of,   1146 
veins  of,   1147 
Pisiform  bone,   197 

articulations  of,  197 
attachment    of   muscles   to, 

197 
surfaces  of,  197 


Pit  of  stomach,  165 
Pituitary  body,  882 
structure  of,  883 
fossa,  93 
membrane,  1100 
Pivot-joint,  265 
Plane,  nuchal,  72 
Plantar  arch,  719 

arteries,  external,  720 
brandies  of,  720 
surface  marking  of,  720 
surgical  anatomy  of,  720 
internal,  719 

branches  of,  720 
surface  marking  of,  720 
surgical  anatomy  of,  720 
fascia,  542 

surgical  anatomy  of,  543 
ligaments,  long,  353 
superficial,  353 
short,  353 
nerves,  external,  1016 

internal,  1015 
region,  muscles  of,  544 

dissection  of,  544, 
veins,  758 
Plantaris  muscle,  536 
Planum  temporale,  76 
Plate,  cribriform  of  ethmoid,  99 
horizontal,  of  palate  bone,  116 
perpendicular,  of  ethmoid,  100 

of  palate  bone,   117 
pterygoid,  external,  96 

internal,  96 
vertical,  of  ethmoid,  100 
of  palate  bone,   117 
Platysma  myoides  muscle,  386 
Pleura;,  1382 

arteries  of,   1387 
cavity  of,   1382 
cervical,  1385 
costal,  1385 
diaphragmatic,  1386 
dome  of,  1385 
lymphatics  of,  1387 
mediastinal,  1385 
nerves  of,   1387 
parietal  layer  of,  1385 
pericardial,  1385 
pulmonary,  1385 
reflections  of,  1384 
structure  of,  1387 
surgical  anatomy  of,   1387 
veins  of,  1387 
visceral  layer  of,  1382 
Pleural  lymphatics,  815 

sacs,  1236 
Pleuroperitoneal  cavity,  123G 
riexus,  Auerbachi,  1299 
interlobular,  1338 
of  nerves,  abdominal  aortic, 
1080,  1085 
annular,  1111 
brachial,  977 
cardiac,  1081 
anterior,  1081 
deep,  1081 
great,  1081 
superficial,  1081 
carotid,  internal,  1073 
cavernous,  1073 
cervical,  972 

posterior,  900 
choroid,  899 
cceliac,  1061,  1084 
colic,  left,  1085 
coronarv,  1085 
cystic,  i085 
dental,  superior,  1033 
diaphragmatic,  1086 
epigastric,  1083 

100 


Plexus  of   nerves,  fundamental, 
1111 
gastric,  1085 
gastro-duodenal,  1085 
-epiploic,  1085 
left,  1085 
hajmorrhoidal,  inferior,  1086 

superior,  1085 
hepatic,  1085 
hypogastric,  1080,  1085 
infraorbital,  1049 
intra-epithelial,  1111 
lumbar,  998 
lumbo-sacral,  998 
magnus  profunda,  1081 
mesenteric,  inferior,  1085 

superior,  1085 
oesophageal,     1059,    1061, 

1082 
ovarian,  1084 
pancreatic,  1085 
pancreatico-duodenal,    1085 
patellar,  1004 
pelvic,  1086 
pharyngeal,  1057 
phrenic,  1084 
prostatic,  1086 
pudendal,  1009 
pudic,  1009 
pulmonary,  1059 
anterior,  1082 
posterior,  1081 
pyloric,  1085 
renal,  1061,  1084 
sacral,  1009,  1086 
sciatic,  1009 
sigmoid,  1085 
solar,  1083 
spermatic,  1084 
splenic,  1061,  1085 
subclavian,  1077 
subepithelial,  1111 
suprarenal,  1084 
thoracic  aortic,  1079 
tympanic,  1057 
uterine,  1086 
utero-vaginal,  1086 
vaginal,  1086 
vertebral,  1077 
vesical,  1086 
of  veins,  infraclavicular,  792 
palmar,  745 
pharyngeal,  730 
prostatic,  761 
prostatico-vesical,  761 
pterygoid,  727 
spermatic,  765 
spinal,  753 

subpleural  mediastinal,  644 
uterine,  763 
vaginal,  763 
venous,  interspinous,  732 

on  thyroid  body,  751 
vesical,  inferior,  762 
superior,  761 
Plica,  epigastrica,  1520 
fimbriata,  1087 
gubernatrix,  1461 
hypogastrica,  1519 
salpingopalatine,  1221 
salpingopharyngea,  1221 
semilunaris,  1140 
sublingualis,  1217 
triangularis,  1213 
urachi,  1519 
vascularis,  1461 
Pneumatic  spaces,  1103 
Pneumogastric  nerve,  1057 
ganglion  of  root  of,  1059 
surgical  anatomy  of,  1062 
of  trunk  of,"  1059 


1586 


INDEX 


Polyaxonic  cells,  821 
Polymazia,  1505 
Polythelia,  1505 
Pomum  Adami,  1362 
Pons  Tariiii,  883 
Varolii,  883,  922 
base  of,  922 
fibres  of,  923 
gray  matter  of,  924 
structure  of,  922 
surfaces  of,  922 
veins  of,  736 
Pontal  arteries,  639 
Ponticulus,  1146 
of  Arnold,  939 
Popliteal  artery,  707 
branches  of,  710 
contents  of,  708 
peculiarities  of,  709 
position  of  contained  parts, 

708 
surface  marking  of,  709 
surgical  anatomy  of,  709 
groove,  226 
line,  235 

lymphatic  glands,  795 
nerve,  external,  1016 
internal,  1014 
branches,  1014 
notch,  234 
space,  707 

boundaries  of,  707 
dissection  of,  707 
vein,  758 
Popliteus  muscle,  537 
Pore,  gustatory,  1090 
Portal  sinus,  769 
vein,  769 

system  of,  768 
Portio-dura    of    seventh    nerve, 
1044 
ganglia  of,  1045 
-mollis  of  auditory  nerve,  1045 
Post-anal  gut,  1242 
-central  gyrus,  876 
lobes,  878 
sulcus,  inferior,  875 
superior,  875 
-clival,  fissure,  928 
-glenoid  process,  84 
-gracile  fissure,  930 
-limbic  fissure,  871 
-nodular  fissure,  930 
-parietal  convolution,  876 
-pharyngeal  gland,  785 
-pyramidal  fissure,  930 
Posterior  auricular  artery,  609 
nerve,  1047 
vein,  727 
bicipital  ridge,  179 
calcaneo-astragaloid  ligament, 

352 
carpal  arch,  659 

artery  of  ulnar,  663 
cerebellar  notch,  926 
cerebral  artery,  640 
cervical  plexus,  970 
chondro-stemal  ligament,  288 

-xiphoid  ligament,  288 
choroid  artery,  640 
clinoid  process,  93,  132 
commissure  of  brain,  903 

of  cord,  839 
common  ligament,  270 
condyloid    foramen,    73,    133, 
136 
fossa,  136 
comu  of  lateral  ventricle,  889 

bulb  of,  889 
coronary  plexus,  1081 
costo-transverse  ligament,  286 


Posterior  costo-xiphoid  ligament, 
288 
crescentic  lobe,  928 
crucial  ligament,  337 
deep  cervical  vein,  733 
dental  canals,  106 
divisions  of  cervical  nerves,  968 
of  coccygeal  nerve,  1008 
of  dorsal  nerves,  993 

branches,    cutaneous, 
993 
external,  993 
internal,  993 
of  lumbar  nerves,  997 

branches,  external,  998 
internal,  998 
of  sacral  nerves,  1006 
lower,  1007 
upper,  1006 

branches,    external, 
1006 
internal,  1006 
ethmoidal  canal,  82,  100 
cells,  101,  145 
foramen,  82,  130,  141 
sinuses,  101 
external  jugular  vein,  728 
of  thoracic  nerves,  993 
branches,  cutaneous, 
993 
external,  993 
internal,  993 
extremity  of  ribs,  160 
head  of,  160 
neck  of,  160 
tuberosity  of,  161 
femoral  region,  muscles  of,  529 
fontanelle,  75,  103 
fossa  of  skull,  132  » 

gluteal  line,  207 
humeral  region,  muscles  of,477 
inferior  cerebellar  artery,  639 

spinous  process  of  ilium,  210 
intercostal  veins,  752 
internal  frontal  artery,  627 
interosseous  artery  of  ulna,  663 

nerve,  991 
intersternal  ligament,  290 
intertrochanteric  line,  223 
ligament  of  incus,  1161 
of  Winslow,  335 
of  wrist,  318 
longitudinal  ligament,  270 

spinal  veins,  755 
median  fissure,  838 

ganglionic  arteries,  640 
mediastinal  arteries,  666 

glands,  812 
mediastinum,  1389 
medullary  velum,  943 
meningeal  artery,  638 
nares,  142,  1098 
nasal  spine,  116,  135,  143 
occipito-atlantal  ligament,  276 

-axial  ligament,  278 
olfactory  lobule,  881 
orbital  convolution,  874 
palatine  arterv,  615 
canal,  107,  116 
canals,  accessory,  116,  135 
foramen,  135 
nerve,  1035 
perforated  lamina,  910 

space,  883 
peroneal  artery,  718 
pillar  of  soft  palate,  1212 
pillars  of  fornix,  896 
pubic  ligament,  296 
pulmonary  nerves,  ]061 

plexus,  1059,  1061,  1081 
radial  carpal  artery,  659 


Posterior,   radio-ulnar   ligament, 
315 
region,  muscles  of,  486 
recurrent  tibial  artery,  713 
root  of  spinal  nerves,  965 
sacral  foramina,  63 
sacro-coccygeal  ligament,  2^4: 
-iliac  ligament,  292 
-sciatic  ligament,  292 
scapular  artery,  642 
nerve,  982 

region,  muscles  of,  472 
semicircular  canal,  1165 
spinal  artery,  639 
sterno-clavicular  ligament,  29S 

-costal  ligament,  288 
subarachnoid  space,  852 
surface  of  liver,  1329 
of  stomach,  1270 
superior  dental  nerves,  1032 

spinous  process  of  ilium,  21(> 
temporal  artery,  611,  640 

diploic  vein,  734 
thoracic  nerve,  983 
tibial  artery,  716 
nerve,  1014 
veins,  758 
tibio-fibular  region,  muscles  of, 
534 
-tarsal  ligament,  347 
triangle  of  neck,  618 
tubercle  of  cervical  vertebra, 

50 
tympano-malleolar     ligament, 

1156 
ulnar  recurrent  artery,  662 

vein,  745 
vertebral  vein,  733 
wall  of  tympanum,  1152 
Postero-lateral  fontanelles,  103 
ganglionic  arteries,  640 
tract,  843 
-median     ganglionic     arteries, 
628 
tract,  843 
Pouch,  Douglas's,  1490 
of  Prussak,  1162 
recto-vaginal,  1490 
utero-vesical,  1487,  1490 
Poupart's  ligament,  436,  1515 
Prsecentral  gyrus,  872 
Pre-anal  fibres  of  levator  ani,  453 
-aortic  glands,  800 
-auricular    lymphatic    glands, 

781 
-central  lobe,  878 
sulci,  868 
sulcus,  872 
inferior,  872 
superior,  872 
-clival  fissure,  928 
-laryngeal  glands,  787 
-maxillarj'  bones,  110 
-occipital  notch,  869 
-patellar  bursa,  340,  518 
Precuneus  of  lobe  of  brain,  87ft 
Prepatellar  bursa,  518 
Prepuce  of  clitoris,  1479 

of  penis,  1455 
Pre-occipital  notch,  869 
-pyramidal  fissure,  930 
-sternal  notch,  157 
-sternum,  157 
-tracheal  fascia,  388 

glands,  787 
-vertebral  fascia,  388 
Prickle  cells,  1109 
Primitive  fibrillar  of  Schultze,  822 

sheath  of  Schwann,  822 
Primordial  ova,  1502 
Princeps  hallucis  artery,  716 


INDEX 


1587 


Princeps  pollicis  artery,  660 
Process   or  processes,   acromion, 

174 
alveolar,  140 
angular,  80 

external,  140 

internal,  140 
of  atlas,  51 
auditory,  88 
basilar,  73 
of  calcaneous,  greater,  243 

lesser,  243 
clinoid,  anterior,  131 

middle,  93,  132 

posterior,  93,  132 
cochleariform,  91,  1153 
condyloid  of  lower  jaw,  125 
coracoid,  175 

of  jaw,  125 

of  ulna,  186 
costal,  50 

ethmoidal,   of  inferior  turbin- 
ated, 120 
falciform,  515 
hamular,  of  lachr\'Tnal,  113 

of  sphenoid,  96 
of  inferior  turbinated  bone,  120 
of  Ingrassias,  96 
jugular,  73 

lachrymal,  of   inferior  turbin- 
ated, 120 
of  malar  bone,  114 
mammillary,  of  lumbar  verte- 

brje,  57 
mastoid,  86,  138 
mental,  122,  140 
nasal,  80 

odontoid,  of  axis,  52 
olecranon,  186 
olivary,  93,  131 
orbital,  118 

of  malar,  114 
of  palate  bone,  117 
petrosal,  93 
post-glenoid,  84 
pterygoid,  of  palate  bone,  117 

of  sphenoid  bone,  96 
sphenoidal,  1097 

of  palate,  118 
spinous,  of  ilium,  210 

of  sphenoid,  95 

of  tibia,  233 
stylohyal,  92 
styloid,  of  fibula,  237 

of  temporal  bone,  90 

of  ulna,  189 
of  superior  maxillary,  109,  110 
tympanohyal,  92 
unciform,  200 

of  ethmoid,  100 
vaginal,  of  sphenoid,  95 

of  temporal  bone,  89 
of  vertebrae,  articular,  49 
zygomatic,  84 
Processus  brevis  of  malleus,  1159 
cochleariformis,  91,  1153 
gracilis  of  malleus,  1158 
tubarius,  1155 
vaginalis,  1461 
Proctodseum,  1242 
Profunda  artery,  inferior,  656 

superior,  655 
femoris  artery,  704 

vein,  759 
Projection    fibres    of    cerebrum, 
914,  932 
centrifugal,  914 
centripetal,  914 
motor,  914 
sensory,  914 
Prominentia  styloidefE,  1153 


Promontory  of  sacrum,  61 

of  tympanum,  1152 
Pronator  quadratus  muscle,  483 
radii  teres  muscle,  479 

surgical     anatomy     of, 
479 
ridge,  188 
Pro-otic     portion     of     temporal 

bone,  91 
Prosencephalon,  864 
Prostate  gland,  1447 
apex  of,  1451 
arteries  of,  1452 
base  of,  1451 
capsule  of,  1449 
isthmus  of,  1451 
lobes  of,  1451 
lymphatics  of,  1452 

vessels  of,  803 
nerves  of,  1452 
sheath  of,  1449 
structure  of,  1452 
surfaces  of,  1451 
surgical  anatomy  of,  1452 
veins  of,  1452 
Prostatic  ducts,  orifices  of,  1442 
plexus  of  nerves,  1086 

of  veins,  761 
portion  of  rectvun,  1313 

of  urethra,  1441 
secretion,  1452 
sinus,  1442 
vesicle,  1442 
Prostatico-vesical  plexus,  761 

surgical  anatomy  of,  762 
Protovertebrse,  1235 
Protuberance,  mental,  122 
occipital,  external,  71,  136 
internal,  73 
Prussak,  pouch  of,  1162 
Psalterium,  896 
Pseudostomata,  1246 
Psoas  magnus  muscle,  509 

parvus  muscle,  500 
Pterion,  137 

ossicle,  83,  103 
Pterygoid  artery,  614 
canal,  135 
depression,  125 
fissure,  96 
fossa  of  jaw,  115 
of  sphenoid,  96 
muscles,  external,  383 

internal,  383 
nerve,  external,  1037 

internal,  1037 
notch,  96 
plate,  external,  96 

internal,  96 
plexus  of  veins,  727 
process  of  palate  bone,  117 

of  sphenoid  bone,  96 
ridge,  95,  137 
tubercle,  97 
Pterygo-mandibular    ligament, 
380 
region,  dissection  of,  383 
muscles  of,  383 

actions  of,  384 
nerves  of,  384 
-maxillary  fissure,  139 

ligament,  380 
-palatine  artery,  616 
canals,  135 
fossa,  139 
groove,  116 
nerve,  1036 
Pubic  arch,  217 

ligament,  anterior,  296 
inferior,   296 
posterior,   296 


Pubic  ligament,  superior,  296 
portion  of  fascia  lata,  1528 
surface  of  bladder,  1434 
Pubis,  212 
angle  of,  212 
body  of,  212 
ramus  of,  ascending,  213 

descending,  213 
spine  of, 
Pubo-capsular  ligament,  328 
-coccygeus  muscle,  452 
-femoral  ligament,  328 
-prostatic  ligament,  1435, 

1451 
-vesical  ligament,  1435 
muscle,  1437 
Pudendal  nerve,  inferior,  1011 
plexus  of  nerves,  1009 
sht,  1478 
Pudendum,  1477 
Pudic  artery,  accessory,  690 
external,  deep,  704 
superficial,  704 
internal,   in  female,  692^ 
in  male,  689 

branches  of,  690 
pecuUarities  of,  690 
surgical   anatomy   of, 
690 
nerve,  1011 

plexus  of,  1009 
vein,  internal,  760 
Pulmonary  alveoli,    1378 
artery,  587 
left,  587 
opening  of,  569 
right  of,  587 
branches  of    thoracic    portion 

of  gangliated  cord,  1079 
lymphatics,  815 
nerves,  anterior,  1061 

posterior,   1061 
pleura,    1385 
plexus,  1081 

anterior,  1059,  1061,  1082 
posterior,    1059,   1061,   1081 
sinuses  of  Valsalva,  571 
veins,  723 
Pulmonic  semilunar  valves,  571 
Pulp,  dental,  1200 
Pulvinar  of  optic  thalamus,  904 
Puncta  lacrimalia,  1142 

vasculosa,  885 
Punctum  jJacrimale,  1138 
Pupil  of  eye,  417 
Pupillary  margin,  1117 
Purkinje,  axis-cylinder  of,  822 
cells  of,  825 
corpuscles  of,  936 
Putamen,  892 

Pyloric  artery,  inferior,  673 
superior,  673 
glands,  1277 
orifice  of  stomach,  1270 
plexus,  1085 

portion  of  stomach,  1269 
sphincter,  1272 
valve,  1272 
Pylorus,  1270 

antrum  of,  1271 
Pyramids  of  Ferrein,  1417 
of  Lalouette,  1403 
lobe  of  cerebellum,  931 
of  Malpighi,  1417 
of  medulla,  939 
of  tympanum,  1153 
of  vestibule  of  ear,  1164 
Pyramidal  decussation,  947 
tract,  crossed,  842 
direct,  842 
luicrossed,  842 


1588 


INDEX 


Pyramidalis,  muscle,  444 

nasi  muscle,  375 
Pyriformis  muscle,  524 
bursa  of,  525 


Quadrate  lobe  of  liver,  1332 

lobule,  875 
Quadratus  femoris  muscle,  527 

lumborum,  fascia  of,  449 
muscle,  449 

Tnenti  muscle,  378 
relations  of,  378 
Quadriceps  extensor  muscle,  516 
Quadrigeminal  bodies,  911 
Quadrilateral,  muscles,  362 


Radial  artery,  657 
branches  of,  659 
peculiarities  of,  658 
relations  of,  657 
^surface  marking  of,  658 
surgical  anatomy  of,  658 
ifossa,  181 

head  of  humerus,  181 
nerve,  991 

recurrent  artery,  659 
region,  muscles  of,  484,  495 

dissection  of,  484 
vein,  745 
Radialis  indicis  artery,  660 
Radiations,  optic,  905 
Radio-carpal  articulations,  317 
surface  form  of,  318 
surgical  anatomy  of,  318 
-ulnar  articulation,  313 
inferior,  315 

surface  form  of,  317 
middle,  314 
superior,  314 

surface  form  of,  314 
surgical     anatomy     of, 
314 
ligaments,  annular,  314 
anterior,  315 
oblique,  314 
orbicular,  314 
posterior,  315 
round,  314 
region,  anterior,  muscles  of, 
479 
surgical     anatomy     of, 
484 
posterior,  muscles  of,  486 
surgical     anatomy     of, 
491 
Radius,  190 

articulations  of,  192 
attachment    of    muscles    to, 

192 
development  of,  192 
lower  extremitv  of,  191 
shaft  of,  190 

borders  of,  190,  191 
surfaces  of,  191 
sigmoid  cavity  of,  191 
structure  of,  192 
.surface  form  of,  192 
surgical  anatomy  of,  192 
upper  extremity  of,  190 
Rami  of  lower  jaw,  124 
Ramus    of    ischium,    ascending, 
212 
descending,  211 
of  pubis,  ascending,  213 
descending,  213 


Ranine  artery,  604 

vein,  729 
Raph6  of  corpus  callosum,  887 
of  medulla,  951 
of  palate,  1211 
of  perineum,  1537 
of  scrotum,  1463 
of  tongue,  1087 
Receptaculum  chyli,  775 
Recess,  epitympanic,  87 
Recessus  cochlearis  of  Reichert, 

1164 
Reciprocal    reception,     articula- 
tion by,  265 
Rectal  columns,  1319 
glands,  809 
valves,  1318 
Recto-urethralis  muscle,  454 
-uterinus  muscle,  1491 
-vaginal  fold,  1490 

pouch,  1314, 1490 
-vesical  fascia,  1546 
pouch,  1314 
Rectum,  1312 

areolar  coat  of,  1318 
arteries  of,  1320 
curves  of,  1313 
lymphatics  of,  809,  1321 
mucous  membrane  of,  1318 
muscular  coat  of,  1317 
nerves  of,  1322 
prostatic  portion  of,  1313 
sacrococcygeal    portion    of, 

1313 
serous  coat  of,  1316 
submucous  coat  of,  1318 
surface  form  of,  1323 
surgical  anatomy  of,  1325 
supports  of,  1315 
structure  of,  1316 
veins  of,  1321 
Rectus  abdominis  muscle,  442 
capitis  anticus  major  muscle, 
406 
minor  muscle,  407 
lateralis  muscle,  407 
posticus  major  muscle,  422 
minor  muscle,  422 
femoris  muscle,  516 
oculi  muscle,  external,  373 
inferior,  373 
internal,  373 
superior,  373 
Recurrent  artery,  palmar,  660 
radial,  659 
tibial,  anterior,  713 

posterior,  713 
ulnar,  anterior,  662 
posterior,  662 
laryngeal  nerve,  1060 
Red  nucleus  nerve-path,  960 
Reflections  of  pleura;,  1384 
Reflex  nerve-paths,  963 
Refracting  media  of  eye,  1128 
Reichert,  recessvis  cochlearis  of, 

1164 
Reil,  island  of,  867,  878 

sulcus  of,  limiting,  867,  878 
Reissner,  membrane  of,  1172 
Remak,  fibres  of,  823 
Renal  artery,  678 
inferior,  1423 
blood-vessels,  1422 
impression  of  liver,  1329 
plexus,  1061,  1084 
surface  of  spleen,  1354 
veins,  767 

zone  of  Hvrtl,  exsanguinated, 
1423 
Reservoir  of  Pecquet,  775 
Respiration,  muscles  of,  431 


Respiration,  organs  of,  I36I 
Respiratory    nerve    of    Bell,    ex- 
ternal, 983 
internal,  974 
Restiform  body  of  medulla,  941 
Rete  testis  of  Haller,  1471 
Retina,  1120 

nerve-fibres  of,  1122 
physiological,  1120 

pigmentary  layer  of,  1127 

rods  of,  1125 
structure  of,  1121 
supporting  framework  of,  1127 
Retinacula  of  capsular  ligament 
of  hip,  327 

patellae  mediale,  517 
Retrahens  auriculam  muscle,  309 
Retro-aortic  glands,  800 

-csecal  fossa,  1263 

-colic  fossa?,  1263 

-crural  glands,  798 

-duodenal  fossa,  1262 

-peritoneal  fossa;,  12C0 
space,  1247 

-pharyngeal  glands,  785 
space,  388,  1220 

-rectal  space,  1314 

-renal  fascia,  1412 

-sternal  glands,  810 
Retzius,  brown  stria?  of,  1204 

fundiform  Ugament  of,  541 

space  of,  1434 
Rhinencephalon,  880 
Rhodopsin,  or  visual  purple, 1120 
Rhombencephalon,  922 
Rhomboid  fossa,  inferior,  840 

impression,  169 

ligament,  298 
Rhomboidal  muscles,  363 
Rhomboideus  major  muscle,  414 

minor  muscle,  414 
Ribes,  ganglion  of,  1067 
Ribs,  159 

anterior  extremity  of,  161 

articulations  of,  283 

attachment  of  muscles  to,  164 

cervical,  53 

common  characters  of,  160 

development  of,  163 

false,  159 

floating,  160 

peculiar,  162 

posterior  extremity  of,  160 

shaft  of,  161 

structure  of,  163 

true,  159 
Ridges,  bicipital,  179 

epicondvlic,  179 

gluteal, '224 

mylo-hyoid,  123 

naso-labial,  377 

obUque,  of  trapezium,  198 
of  ulna,  188 

pectoral,  179 

pronator,  188 

pterygoid,  95,  137 

superciliary,  80 

supracondylar,  external,  179 
internal,"  180 

supraorbital,  140 

temporal,  76,  80 

trapezoid,  169 
Riedel's  lobe  of  liver,  1336 
Right    ascending    lumbar    vein, 
752 

azygos  vein,  752 

bronchus,  1376 

cardiac  vein,  771 

colic  artery,  675 

coronary  artery,  590 
plexus,  1081 


INDEX 


1589 


Right  innominate  vein,  750 

juxta-aortic  glands,  800 

lobe  of  liver,  1332 

lymphatic  duct,  778 

superior  intercostal  vein,  752 
Rima  glottidis,  1369 
Ring,  abdominal,  internal,  446 

crural,  437,  1532 

femoral,  437,  509,  1532 

fibrous,  of  heart,  574 

muscle  of  Miiller,  1116 
Risorius  muscle,  380 
Risus  sardonicus,  381 
Rivinus,  ducts  of,  1217 

notch  of,  1151 
Rod-bipolars,  1125 

-cells,  1126 

-fibre,  1126 

-granules,  1125 
Rolandic  angle,  867 
Rods  of  Corti,  1174 

of  retina,  1125 
Rolando,  fasciculus  of,  941 

fissure  of,  867 

funiculus  of,  941 

sulcus  of,  central,  867 

tubercle  of,  941 
Roots  of  auditory  nerve,  1050 

of  cervical  nerves,  968 

of  dorsal  nerves,  993 

of  eighth  nerve,  1050 

of  fifth  nerve,  ascending,  948, 
1026 
descending,  1026 

of  lumbar  nerve,  997 

of  lung,  1394 

of  penis,  1454 

of  pneumogastric   nerve,  gan- 
glion of,  1059 

of  sacral  nerves,  1006 

of  spinal  nerves,  965 
anterior,  965 
dorsal,  965 
posterior,  965 
ventral,  965 

of  thoracic  nerves,  993 

of  tongue,  1087 
Rosenmiiller,  fossa  of,  1221 

gland  of,  795 
accessory,  1141 

organ  of,  1499 
Rostrum     of    corpus    callosum, 
886 

of  sphenoid  bone,  94,  135 
Rotary  joint,  265 
Rotatores  spiiue  muscle,  421 
Round  ligament,  artery  of,  688 
of  liver,  1334 
of  uterus,  1491 
Roux's  amputation  of  foot,  256 
Rudimentary  organ  of  Jacobson, 

1100 
Rudinger,  dilator    tubie    mascle 

of,  1155 
Ruffini's  nerve-endings,  828 
Rugfe  of  scrotum,  1462 

of  stomach,  1275 

of  vagina,  1484 
Ruysch,  tunic  of,  1113 


S 


Sacs,  abdominal,  1236 

dental,  1206 

lachrymal,  1142 

pericardial,  1236 

pleural,  1236 
Saccule  of  vestibule.  1170 
Sacculi  alveolares,  1378 
Sacculus  laryngis,  1371 


Sacral  arterv,  lateral,  693 
middle,"  681 
canal,  64 
cornua,  62 
foramina,  anterior,  62 

posterior,  63 
groove,  63 

lymphatic  glands,  799 
nerve,  1006 

division  of,  anterior,  1007 

posterior,  1006 
roots  of,  1006 
plexus,  1009,  1086 
portion    of    gangliated    cord, 

1080 
veins,  lateral,  760 
middle,  764 
Sacro-coccygeal   ligament,   ante- 
rior, 294 
lateral,  295 
posterior,  294 
portion  of  rectum,  1313 
symphisis,  66 
-ihac  ligament,  anterior,  292 
interosseous,  292 
long,  292 
obUque,  292 
posterior,  292 
short  292 
-lumbalis  muscle,  419 
-sciatic    foramen,    great,    211, 
294 
inferior,  294 
lesser,  211,  294    . 
superiorj  294 
ligament,  anterior,  293 
great,  292 
lesser,  293 
posterior,  292 
notches,  217 
great,  210 
lesser,  211 
-uterine  ligaments,  1490 
-vertebral  angle,  61 
Sacrum,  61 
ala  of,  64 
apex  of,  64 
articulations  of,  65 
attachment  of  muscles  to,  65 
base  of,  64 
development  of,  64 
differences    in    the    male    and 

female,  64 
peculiarities  of,  64 
promontory  of,  61 
structure  of,  64 
surfaces  of,  61 
tuberosity  of,  63 
Saddle-joint,  265 
Sagittal  axis,  1106 
sulcus,  73,  80 
suture,  78,  127 
Salivary  glands,  1214 
structure  of,  1217 
surgical  anatomy  of,  1224 
Salpingo-palatine  fold,  1221 
-pharyngeal  fold,  1221 
-pharyngeus  muscle,  405 
Salter,     incremental     lines     of, 

1203 
Santorini,  cartilages  of,  1365 
comical  tubercle  of,  1368 
fissures  of,  1146,  1148 
muscle  of,  380 
Saphenous  gland,  externa,!,  795 
opening,  514,  1529 
nerve,  internal,  1005 

long,  1005 
vein,  external,  756 
internal,  756 
long,  756 


Saphenous  vein,  short,  756 

surgical  anatomy  of,  757 
Sarcolemma,  361 
Sardonic  laugh,  381 
Sartorius  muscle,  516 

nerve  to,  1005 
Scala  media,  1172 

tympani  of  cochlea,  1168 
vestibuli  of  cochlea,  1168 
Scalenus  muscles,  anticus,  408 
medius,  408 
posticus,  409 
Scalp,  skin  of,  366 
Scapha,  fossa  of.  1145 
Scaphoid  bone  of  foot,  246 
articulations  of,  247 
attachment  of  muscles  to, 

247 
surfaces  of,  246 
tuberositv  of,  246 
of  hand,  195 

articulations  of,  196 
attachment  of  muscles  to, 

196 
surfaces  of,  196 
fossa,  97,  135,  1145 
Scapula,  171 
angles  of,  174 
articulations  of,  176 
attachment  of  muscles  to,  176 
base  of,  174 
borders  of,  174 
development  of,  175 
dorsum  of,  172 
head  of,  174 
Ugaments  of,  301 
spine  of,  172 
structure  of,  175 
surface  form  of,  176 
surgical  anatomy  of,  177 
venter  of,  171 
Scapular  arteries,  posterior,  G42 
glands,  790 
nerve,  posterior,  982 
notch,  great,  173 
region,    anterior,    muscles    of, 
471 
dissection  of,  471 
posterior,  muscles  of,  472 
dissection  of,  472 
Scapulo-clavicular     articulation, 

299 
Scarf  skin,  1181 
Scarpa,  fascia  of,  433 

foramina  of,  110,  135,  1036 
membrane  of,  1152 
nerve  of,  1036 
triangle  of,  516,  697 
Schachowa,  spiral  tube  of,  1419 
Schindylesis,  264 
Schlemm,  canal  of,  1108,  1111 

ligament,  305 
Schneiderian  membrane,  1100 
Schreger,  concentric  lines  of,  1203 
ScKultze,  primitive  fibrillae  of,  822 
Schwann,    nucleated   sheath   of, 
822 
primitive  sheath  of,  822 
white  substance  of,  822 
Sciatic  artery,  692 
nerve,  great,  1013 

branches  of,  1013 
small,  1011 

branches  of.  1011 
notch,  great,  210 
plexus,  1009 
veins,  761 
Sclera,  1107 

structure  of,  lipS 
Scleral  sulcus,  1 105 
Sclerotic  coat,  1107 


1590 


INDEX 


Scrotal  hernia,  1521 
nerve,  long,  1011 
Scrotum,  1462 
arteries  of,  1465 
dartos  of,  1463 
integument  of,  1463 
lymphatic  vessels  of,  801 
lymphatics  of,  1466 
nerves  of,  1466 
raphe  of,  1463 
rugiB  of,  1462 
septum  of,  1463 
surgical  anatomy  of,  1469 
veins  of,  1466 
Sebaceous  glands,  1138,  1191 
Second  nerve,  1021 
Secondary  ear-drum  membrane, 

1152 
Segments  of  Lantermann,  823 
Sella  turcica,  93,  131 
Semen,  1474 

Semicircular  canals,  1165 
external,  1165 
horizontal,  1165 
membranous,  1170 
posterior,  1165 
superior,  1165 
muscles  of  rectum,  1317 
Semilunar  bone,  196 

articulations  of,  197 
surfaces  of,  196 
fascia,  476 
fibro-cartilages,  337 
external,  339 
internal,  338 
folds  of  colon,  1317 

of  Douglas,  439,  444 
ganglion  of  abdomen,  1084 

of  fifth  nerve,  1027 
hiatus,  145,  747 
lobe    of    cerebellum,    inferior, 

931 
valves,  aortic,  572 
pulmonic,  571 
Semimembranosus  muscle,  530 

bursa  of,  531 
Seminal  duct,  1472 
vesicles,  1475 
arteries  of,  1476 
lymphatic  vessels  of,  804 
lymphatics  of,  1476 
nerves  of,  1476 
structure  of,  1476 
surgical  anatomy  of,  1476 
veins  of,  1476 
Semispinalis  colli  muscle,  421 

dorsi  muscle,  421 
Semitendinosus  muscle,  530 
Sensory  decussation,  947 
nerve  tract,  961 
projection  fibres  of  cerebrum, 
914 
Septo-marginal  tract,  844 
Septum  atriorum,  567 
bronchial,  1380 
crurale,  1532 

of  Cloquet,  509 
interarticular,  565 
interventricular,  569 
lucidum,  889,  896 
of  nose,  142 

cartilage  of,  triangular,  1097 
orbital,  1139 
pectiniforme,  1457 
of  scrotum,  1463 
of  tongue,  fibrous,  398 
trans  versum,  1170 
Serous  coat  of  anal  canal,  1316 
of  bladder,  1437 
of  gall-bladder,  1343 
of  large  intestine,  1316 


Serous  coat  of  lungs,  1354 
of  rectum,  1316 
of  small  intestine,  1290 
of  spleen,  1356 
of  stomach,  1273 
of  vermiform     appendix, 
1304 

covering  of  ovary,  1501 

pericardium,  560 
Scrratus  magnus  muscle,  468 

posticus  inferior  muscle,  415 
superior  muscle,  415 
Sertoli,  cell  of,  1472 
Sesamoid  bones,  257 

cartilage,  1097 
Seventh  nerve,  1044 

surgical  anatomy  of,  1049 
Shaft  of  bone,  its  structure,  33 

of  hair,  1189 

of  ribs,  161 
Sharpey,  fibres  of,  37 
Shrapnell,  membrana  flaccida  of, 

1156 
Sheath,  carotid,  388 

dentinal,  of  Neumann,  1203 

femoral,  509,  1530 

of  flexor  tendons,  fibrous,  545 

granular,  of  Tomes,  1 202 

nucleated,  of  Schwann,  822 

primitive,  of  Schwann,  822 

of  prostate,  1449 

of  rectus  muscles,  443 
Shin  bone,  233 
Short  bones,  33 

calcaneo-cuboid  .ligament,  353 

ciliary  arteries,  625 

fibre  nerve  path,  960,  963 

plantar  ligament,  353 

sacro-iliac  ligament,  292 

saphenous  vein,  756 
Shoulder,  fascia  of,  deep,  470 
superficial,  470 

girdle,  167 

-joint,  articulations  of,  303 
bursai  of,  305 
surface  form  of,  307 
surgical  anatomj^  of,  307 

muscles  of,  470 
Sibson,  aortic  vestibule  of,  572 

aponeurosis,  1385 
Sigmoid  arteries,  678 

cavity  of  radius,  191 
of  ulna,  186 

colon,  1311 

flexure  of  colon,  1311 
of  large  intestine,  1300 

fossa,  86 

mesocolon,  1259 

notch  of  lower  jaw,  125 

plexus,  1085 

sinus,  739 

sulcus,  86 
Sinus  or  sinuses,  air,  82 

ala;  parvse,  740 

of  aorta,  great,  589 

basilar,  743 

cavernous,  739 

circular,  742 

confluence  of,  737 

coronary  vein,  567,  771 

costo-mediastinal,  1386 

of  dura  mater,  736 

ethmoidal,  101 

frontal,  80 

of  heart,  auricle  of,  left,  568 
right,  565 

intercavernous,  742 

of  jugular  vein,  external,  728 
internal,  729 

of  kidney,  1415 

laryngeal,  1371 


Sinus  or  sinuses,  lateral,  738 
longitudinal,  inferior,  738 

superior,  78,  130,  736 
maxillary,  108 
of  Morgagni,  402  ' 

of  nose,  80 
occipital,  739 
orbital,  118 
petro-squamous,  739 
petrosal,  inferior,  742 

superior,  742 
of  pericardium,  oblique,  560 

transverse,  560 
phrenico-costal,  1386,  1414 
pocularis,  1442 
portal,  769 
prostatic,  1442 
pyriformis,  1222,  1368 
sigmoid,  739 
spheno-parietal,  740 
sphenoidal,  94,  143 
straight,  738 
tonsillaris,  1222 
transverse,  743 

pericardial,  560 
utricularis  sacculi,  1170 
of  Valsalva,  aortic,  573 

pulmonary,  571 
venosus,  565 
Sixth  nerve,  1043 

branches  of,  1043 

nucleus  of,  925 

relations  of,  1043 

surgical      anatomy       of, 
1044 
Skeletal  muscles,  361 
Skin,  1178 

appendages  of,  1185 

arteries  of,  1184 

bone,  233 

cuticle  of,  1181 

epidermis,  1181 

folds  of,  1178 

furrows,  1179 

horny  layer  of,  1181 

lymphatics  of,  1184 

Malpigliian  laj'er  of,  1182 

nerves  of,  1184 

papillary  layer  of,  1181 

pigmentation  of,  1182 

ridges,  1179 

of  scalp,  366 

scarf,  1181 

stratum  cylindricum,  1182 

germinativum,  1182 

granulosum,  1182 

lucidum,  1182 

mucosum,  1182 

spinosum,  1182 
true,  1180 
veins  of,  1184 
Skull,  anterior  region  of,  139 
base  of,  130 
at  different  ages,  102 
fixed  point  for  measurement  of, 

149 
fossa  of,  anterior,  130 

infratemporal,  138 

middle,  130 

orbital,  140 

posterior,  132 

pterygo-palatine,  139 

spheno-maxillary,  139 

temporal,  137 

zygomatic,  138 
lateral  regions  of,  136 
sexual  differences  in,  102 
surface  form  of,  147 
surgical  anatomy  of,  149 
tables  of,  33 

vitreous,  34 


INDEX 


1591 


Skull,  vertex  of,  129 
Slender  funiculus,  941 

lobe  of  cerebellum,  931 
Small  coronary  vein,  771 
intestine,  1282 

lymphatic  glands  of,  807 
vessels  of,  808 
occipital  nerve,  972 
palatine  nerve,  1035 
sciatic  nerve,  1011 
Socia  parotidis,  1215 
Soft  commissure  of  brain,  903 
palate,  1211 

aponeurosis  of,  1212 
arches  of,  1211 
arteries  of,  1212 
.xnucoas  membrane  of,  1212 
muscles  of,  1212 
nerves  of,  1213 
pillars  of,  1211 
veins  of,  1213 
Solar  plexus,  1083 
Soleus  muscle,  535 
Solitary  glands,  1295,  1320 
Somatopleure,  1236 
Sommerring,  foramen  of,  1121 

yellow  spot  of,  1121 
Space  or  spaces,  axillary,  645 
of  Bruns,  388 
-cartilage,  260 
corneal,  1110 
epitympanic,  87 
of  Fontana,  1110 
intercostal,  160 
interglobular,    of    Czermak, 

1202 
Interpeduncular,  882 
interpleural,  1387 
mediastinal,  1387 
■of  Nuel,  1175 
perichoroidal,  1108 
perisclerotic,  1103 
pneumatic,  1103 
popliteal,  707 
retro-peritoneal,  1247 

-pharyngeal,  388,  1220 
of  Retzius,  1434 
suprascleral,  1104 
suprasternal,  388 
Special  sense,  organs  of,  1087 
Spermatic  arteries,  679 
canal,  448,  1517 
cord,  1466 

arteries  of,  1467 
lymphatics  of,  1468 
nerves  of,  1468 
structure  of,  1466 
surgical  anatomy  of,  1468 
veins  of,  1467 
iascia,  1463 

external,   1436,  1514 
internal,  446 
middle,  440 
plexus  of  nerves,  1084 

of  veins,  765 
vein,  765 

surgical  anatomy  of,  766 
■Spermatids,  1472 
^Spermatoblasts,  1472 
Spermatocytes,  1472 
Spermatogenesis,  1472 
Spermatogonia,  1472 
Spermatozoid,  1472,  1474 
Spheno-ethmoidal  recess,  145 
-maxillary  fLssure,  115,  138 

fossa,  115,  139 
-palatine  arterv,  616 
foramen,  119,  143 
ganglion,  1034 
ner\es,  1032 
notch,  118 


Spheno-parietal  sinus,  740 
suture,  128 
-phrenic  ligament,  1256 
Sphenoid  bone,  92 

articulations  of,  98 
attachment   of    muscles   to, 

98 
body  of,  92 

surfaces  of,  93 
development  of,  97 
greater  wings  of,  95 
circumference  of,  95 
surfaces  of,  95 
hamular  process  of,  96 
lesser  wings  of,  96 
pterygoid  process  of,  96 
rostrum  of,  94,  135 
Sphenoidal  cells,  94 
crest,  94 
fissure,  96,  132 
process,  1097 

of  palate  bone,  118 
sinuses,  94,  143 
spine,  95 
spongy  bones,  97 
turbinated  bones,  143 
Spherical  recess,  1164 
Sphincter  ani  muscle,   external, 
450 
internal,  451 
muscles,  363 
pyloris,  1272 
vaginae  muscle,  461 
Spigelian  lobe  of  liver,  1330 
Spina  tympanica  major,  1151 

minor,  1151 
Spinal  accessory  nerve,  1063 
accessory  portion,  1063 
bulbar  portion,  1063 
nucleus  of,  950 
spinal  portion,  1063 
surgical  anatomy  of,  1063 
arteries,  anterior,  638 
lateral,  638 
posterior,  639 
bulb,  938 
canal,  69 
column,  48 
cord,  836 

arachnoid  membrane  of, 

834 
blood  supply  of,  840 
central  canal  of,  840 
columns  of,  838 
commissure  of,  839 
comu  of,  caput,  839 

cervix,  839 
dissection  of,  832 
dura  mater  of,  832 
fibres  of,  841 
fissures  of,  837 
gray  substance  of,  845 
grooves  of,  837 
lymphatics  of,  840 
membranes  of,  832 
minute  anatomy  of,  840 
neuroglia  of,  840 
olivary  bundle  of,  843 
pia  mater  of,  835 
structure  of,  839 
tracts  of,  conducting,  841 

functions  of,  844 
veins  of,  755 
white  substance  of,  841 
cranial  reflexes,  963 
foramen,  49 
nerves,  964 

accessory,  1063 
distribution  of,  967 
ganglia  of,  966 
origin  of,  847 


Spinal   nerves,    points   of  emer- 
gence of,  967 
roots  of,  965 

reflexes,  963 

veins,  753 

longitudinal,  anterior,  754 

posterior,  755 
plexus  of,  753 
Spinalis  colli  muscle,  420 

dorsi  muscle,  419 
Spindle,  aortic,  591 
Spindles,  neuro-muscular,  829 

neuro-tendinous,  829 
Spine,  articulations  of,  276 

ethmoidal,  93,  130 

frontal,  80 

of  helix,  1146 

of  Henle,  88 

of  ischium,  211 

mental,  123 

nasal,  80 

anterior.  111,  139,  143 
posterior,  116,  135,  143 

palatine,  116 

peroneal,  243 

pharyngeal,  73,  135 

progress  of  ossification  in,  60 

of  pubis,  212 

of  scapula,  172 

sphenoidal,  95 

suprameatal,  88 
Spino-glenoid  ligament,  302 
Spinous  processes  of  ilium,  210 
of  tibia,  233 
of  vertebriB,  49 
Spiral  canal  of  cochlea,  1167 

ligament  of  cochlea,  1172 

line  of  femur,  223 

tube  of  Schachowa,  1419 
Splanchnic  nerv^es,  1079 
Splanchnopleure,  1236 
Spleen,  1353 

accessory,  1355 

arteries  of,  1357 

development  of,  1245 

fibro-elastic  coat  of,  1356 

hilum  of,  1354 

lymphatics  of,  807,  1359 

Malpighian  bodies  of,  807,  1358 

movability  of,  1356 

movable,  1356 

nerves  of,  1359 

serous  coat  of,  1356 

structure  of,  1356 

support  of,  1356 

surface  form  of,  1359 

surgical  anatomy  of,  1359 

veins  of,  1359 
Splenic  artery,  674 

flexure  of  colon,  1309 
of  large  intestine,  1300 

glands,  800 

plexus,  1061,  1085 

pulp,  1356 

vein,  768 
Splenium    of    corpus    callosum, 

886 
Splenius  muscle,  416 
Spongy  portion  of  urethra,  1443 

tissue  of  bone,  33 
Spur,  femoral,  227 
Squamo-parietal  suture,  128 

-sphenoidal  suture,  128 
Squamous    portion    of    occipital 
bone,  71 

suture,  85,  128 
Square  lobe  of  liver,  1332 
Stahr,  middle  gland  of,  784 
Stapedius  muscle,  1160 
Stapes,  1160 

base  of,  1160 


1592 


INDEX 


Stapes,  crura  of,  1160 

foot-plate,  1160 

head  of,  1160 

ligament  of,  1161 

neck  of,  1160 
Statoliths,  1171 
Stellate  ligament,  284 

reticulum,  1206 
Stenson,  duct  of,  1215 

foramina  of,  110 
Stephanion,  137 

inferior,  76 

superior,  76 
Sternal  arteries,  644 

foramen,  157 

furrow,  165 

glands,  810 

ribs,  159 
Stemo-clavicular     articulations, 
297 
surface  form  of,  299 
surgical  anatomy  of,  297 

-cleido-mastoid  muscle,  389 

-costal    ligament,     anterior, 
288 
interarticular,  288 
posterior,  288 

-costo     pericardial     ligament, 
559 

-hyoid  muscle,  391 

-mastoid  artery,  602,  609 
glands,  786 
muscle,  389 

surface  form  of,  391 
surgical  anatomy  of,  391 

-pericardiac  ligaments,  558 

-thyroid  muscle,  392 
Sternum,  155 

angle  of,  157 

articulations  of,  159,  290 

attachment  of  muscles  to,  159 

development  of,  158 

ensiform  appendix  of,  158 

gladiolus,  157 

ligaments  of,  290 

manubrium  of,  157 

structure  of,  158 

surface  form  of,  165 

surgical  anatomy  of,  165 

xiphoid  appendix  of,  158 
Stigmata,  1246 
Stilling,  canal  of,   1129 

nucleus  of,  red,  938 
Stomach,  1268 

alterations  in  position  of,  1271 

areolar  coat  of,  1274 

arteries  of,   1278 

body  of,  1269 

cardiac  orifice  of,   1270 
portion  of,  1269 

chamber,  1269 

curvatures  of,  1270 

fundus  of,  1269 

innervation  of,  1280 

IjTnphatic  vessels  of,  806,  1279 

movements  of,  1280 

mucous  membrane  of,  1275 

muscular  coat  of,   1273 

nerves  of,  1279 

oesophageal  opening  of,  1270 

peritoneal  coat  of,  1273 

pit  of,  165 

pyloric  orifice  of,  1270 
portion  of,  1269 

relations  of,  1269 

rugae  of,  1275 

serous  coat  of,  1273 

structure  of,  1273 

submucous  coat  of,  1274 

supports  of,   1272 

surface  form  of,  1280 


Stomach,  surfaces  of,  1269 
surgical  anatomy  of,  1280 
-teeth,  1197 
vascular  coat  of,  1274 
veins  of,  1279 
Stomata,  1246 
Straight  sinus,  738 
Stria  vascularis,  1172 
Striated  muscle,  361 
Striped  muscle,  361 
Stroma  of  iris,  1118 
of  ovarj%  1501 
plexus  of,  1111 
Stylo-glossus  muscle,  397 
-hyal  process,  92 
-hyoid  ligament,  394 
muscle,  394 

nerve,  from  facial,  1048 
-mandibular  ligament,  281,  388 
-mastoid  artery,  610 

foramen,  90,  135 
-maxillary  ligament,  281 
-pharyngeus  muscle,  403 
Styloid  process  of  fibula,  237 
of  temporal  bone,  90 
of  ulna,  189 
Subacromial  bursa,  305,  471 
Subanconeus  muscle,  478 
Subarachnoid  cisternge,  852 

space,  834,  852 
Subarachnoidean  areolar  tissue, 
851 
space,  834 
Subcalcarine  convolution,  877 
Subcallosal  gyrus,  882 
Subclavian  artery,  631 
branches  of,  637 
first  part  of,  left,  633 

right,  632 
peculiarities  of,  635 
second  part  of,  633 
surface  form  of,  635 
surgical  anatomy  of,  635 
third  part  of,  633 
glands,  791 
groove,  169 
loop,  1076 
muscle,  468 
plexus  of  nerves,  1077 
triangle,  618 
vein,  749 
Subclavius  muscle,  468 
Subcollateral  convolution,  878 
Subcostal  artery,  667 

groove,  162 
Subcrureus  mviscle,  518 
Subcutaneous     acromial     bursa, 
30B 
areolar  tissue,  1180 
olecranon  bursa,  477 
sjmovial  bursa,  263 
tibial  bursa,  340 
trochanteric  bursa,  331 
Subdeltoid  bursa,  305,  471 
Subdural  space,  834,  847 
Subepithelial  plexus,  1111 
Sublingual  artery,  604 
fossa,  123 
gland,  1217 
Sublobular  veins,  767 
Submaxillary  artery,  606 
fossa,  123 
ganglion,  1040 
arteries  of,  1217 
branches  of,  1040 
ducts  of,  1216 
glands,  784,  1216 
lymphatics  of,  1217 
nerves  of,  1217 
veins  of,  1217 
triangle,  394,  617 


Submaxillary  vein,  727 
Submental  artery,  606 

glands,  785 

vein,  727 
Suboccipital    Ij'mphatic    glands, 
780 

nerves,  968 

triangle,  423 
Suborbital  glands,  782 
Subparotid  glands,  1215 

lymphatic  glands,  782 
Subpleural    mediastinal    plexus, 

644 
Subpubic  ligament,  296 
Subscapular  angle,  172 

artery,  651 

bursa,  305 

fascia,  471 

fossa,  171 

nerves,  984 
Subscapularis  muscle,  471 
Subserous  areolar  coat  of  lungs, 
1394 
tissue,  1245 

connective  tissue,  1246 
Substantia  cinerea  glutinosa,  841 

ferruginea,  945 

glutinosa  centralis,  840 

nigra,  910 

propira  of  cornea,  1110 
Substerno-mastoid  glands,  785 
Subtendinous  iliac  bursa,  331 

synovial  bursa,  26.3 
Subthalamic  region,  905,  913 

tegmental  region,  885 
Suburethral  gland,  1482 
Sucking  pad,  380 
Suctorial  pad,  380 
Sudoriferous  glands,  1190 
Sulci,  occipital,  876 
Sulcus,  callosal,  879,  885 

calloso-marginal,  868,  870 

diagonalis,  8G8 

dorso-median,  838 

frontal,  873 

frontalis,  inferior,  868 
medius,  868,  873 
superior,  868 

interparietalis,  868 

intraparietal,  of  Turner,  875 

lachrymal,  113 

lateralis  mesencephali,  885 

nervi  oeulo-motorii,  885 

occipitalis  transversus,  868 

occipito-temporal,  870 

oculomotorius,  906 

olfactory,  870,  874 

orbital,  870,  874 

orbito-palpebral,  inferior,  1137 
superior,  1137 

paramedians,  868,  873 

parieto-occipital,  867 
internal,  870 

post-central,  875 
inferior,  868 
superior,  868 

posterior  median,  838 

precentral,  872 
inferior,  868 
superior,  868 

of  Reil,  limiting,  867,  878 

of  Rolando,  central,  867 

sagittal,  73,  80 

scleral,  1105 

sigmoid,  86 

spiralis  extemus,  1172 
intemus,  1172 

temporal,  877 
inferior,  868,  870 
superior,  868 

terminalis  of  His,  566,   1087 


INDEX 


1593 


Sulcus,  tri-radiate,  874 
tympanic,  1149 
tympanicus,  1151 
Superciliary  ridge,  80 
Superficial     anterior     thoracic 

nerve,  984 
branches    of    cervical    plexus, 

972 
cardiac  plexus,  1081 
cerebellar  veins,  736 
cerebral  veins,  735 
cervical  artery,  642 

fascia,  386 

glands,  784 

nerve,  973 

region,  inuscles  of,  386 
circumflex  iliac  artery,  704 

vein,  756 
crural  arch,  436,  1529 
dorsal  veins  of  penis,  762 
epigastric  artery,  704 
external  pudic  artery,  704 
fascia,  364 

of  abdomen,  433,  1511 

of  arm,  470 

of  back,  411 

of  cranial  region,  366 

of  femoral  region,  512 

of  periniEura  in  male,  455 

of  shoulder,  470 

of  thoracic  region,  463 
femoral  artery,  700 
inguinal  lymphatic  glands,  793 
long  plantar  ligament,  353 
lymphatic  glands  of  upper  ex- 
tremity, 788 

vessels  of  gluteal  region,  801 
of  lower  extremity,  797 
of  penis,  801 
of  perinseum,  801 
of  scrotum,  801 
of  upper  extremity,  792 
of  walls  of  abdomen,  801 
muscles  of  abdomen,  432 
palmar  arch,  664 
parotid  lymphatic  glands,  781 
perinea]  artery,  690 
sural  artery,  710 
Sylvian  vein,  735 
temporal  artery,  611 

nerves,  1038 

vein,  727 
transverse  ligament  of  fingers, 

494 
veins  of  fingers,  745 

of  foot,  756 

of  hand,  745 

of  lower  extremity,  756 

of  upper  extremity,  745 
Superficialis  colli  nerve,  973 

volje  artery,  659 
Superior  acromio-clavicular  lig- 
ament, 299 
astragalo-scaphoid      ligament, 

354 
branch    of    superior    cervical 

ganglion,  1073 
calcaneo-cuboid  ligament,  353 

-scaphoid  ligament,  353 
cardiac  nerve,  1076 
carotid  triangle,  394 
cerebellar  artery,  640 

peduncles,  932 
cerebral  veins,  735 
cervical  ganglion,  1072 
constrictor  muscle,  401 
coronary  artery  of  lip,  607 
dental  plexus,  l033 
epigastric  artery,  645 

glands,  802 
fibular  artery,  713 


Superior   flexure   of    duodenum, 

1285 
frontal  convolution,  873 
gemellus  muscle,  526 
gluteal  nerve,  1010 
hsemorrhoidal  artery,  678 

plexus  of  nerves,  1085 

veins,  768 
intercostal  artery,  645 

veins,  752 
lachrymal  gland,  1141 

nerve,  1060 
laryngeal  artery,  602 
ligament  of  incus,  1061 

of  malleus,  1160 
lingualis  muscle,  399 
longitudinal  fasciculus,  918 

sinus,  78,  130,  736 
maxillary  bones,  105 

nerve,  1031 

region,  muscles  of,  376 
meatus  of  nose,  101,  144 
mediastinum,  1388 
medullary  velum,  943 
mesenteric  artery,  675 

plexus  of  nerves,  1085 

vein,  768 
nuchal  line,  72 
obliquus  oculi,  muscle,  373 
occipital  convolution,  877 

sulcus,  876 
olivary  nucleus,  925 
ophthalmic  vein,  740 
orbito-palpebral  svdcus,  1137 
parietal  convolution,  876 
peduncle    of   cerebellum,    910, 

943 
petrosal  sinus,  742 
phrenic  artery,  644 

veins,  767 
post-central  sulcus,  875 
profunda  artery,  655 
pubic  ligament,  296 
pyloric  artery,  673 
radio-ulnar  articulation,  314 
ramus  of  ischium,  211 

of  pubis,  213 
rectus  oculi  muscle,  373 
sacro-sciatic  foramen,  294 
semicircular  canal,  1165 
stephanion,  76 
superficial  cerebellar  veins,  736 

external  pudic  artery,  704 
surface  of  Uver,  1327 
tarsal  arch,  623 
temporal  convolution,  877 
thoracic  artery,  650 
thvroid  artery,  601 

vein,  730 
transverse  ligament,  302 
triangle  of  fourth  ventricle,  945 
turbinated  bone,  101 

crest,  117 
vena  cava,  752 

vermiform  process  of  cerebel- 
lum, 927 
vesical  artery,  686 

plexus  of  veins,  761 
vocal  cords,  1370 
Supernumerary  bones,  103 

spleens,  1355 
Supinator  longus  muscle,  484 

radii  brevis  muscle,  487 
Supporting  cells  of  Hensen,  1175 
Supra-acromial  artery,  642 

nerves,  974 
Supracallosal  gyrus,  887 
Supraclavicular  glands,  787 

nerves,  974 
Supracondylar    ridge,    external, 
179 


Supracondylar    ridge,     internal, 

180 
Supracondvloid   glands  of  Leaf, 

795 
Supraepitrochlear  glands,  789 
Supraglenoid  tubercle,  175 
Suprahj'oid  aponeurosis,  394 
artery,  603 
glands,  lateral,  784 

median,  785 
region,  muscles  of,  393 
Supramandibular  nerves,  1049 
Supramarginal  convolution,  S76. 
Supramastoid  crest,  84,  137 
Supramaxillary    lymphatic 
glands,  782 
nerves,  1049 
Suprameatal  spine,  88 

triangle,  85 
Supraorbital  arch,  80 
artery,  623 
foramen,  80,  140 
nerve,  1030 
notch,  80,  140 
ridge,  140 
vein,  726 
Suprapatellar  bursa,  340,  518- 
Suprarenal  artery,  678 
capsule,  1428 
arteries  of,  1431 
left,  1429 

lymphatic  vessels  of,  804 
lymphatics  of,  1431 
nerves  of,  1431 
relations  of,  1428 
right,  1428 
structure  of,  1430 
veins  of,  1431 
glands,  1428 

accessory,  1430 
impression  of  liver,  1332 
plexus  of  nerves,  1084 
veins,  767 
Suprascapular  artery,  641 
ligament,  302 
nerve,  983 
notch,  174 
Suprascleral  lymph-space,  1104- 
Supraspinales  muscle,  421 
Supraspinatus  fascia,  472 

muscle,  472 
Supraspinous  fossa,  172 

Ugament,  273 
Suprasternal  artery,  642 
nerves,  974 
notch,  409 
space,  388 
Supratonsillar  fossa,  1213 
Supratrochlear  foramen,  181 
glands,  789 
nerve,  1030 
Supravaginal  portion  of  uterus,. 

1488 
Surface  form  of  abdominal  aorta,. 
670 
of  acromio-clavicular    artic- 
ulation, 301 
of  ankle-joint,  351 
of  axillary  arterv,  649 
of  bladde'r,  1440 
of  bones,  34 
of  brachial  artery,  654 
of  carotid  arteries,  common, 
598 
external,  601 
of  carpus,  204 
of  clavicle,  170 
of    common    iliac    arteries, 

682 
of  dorsalis  pedis  artery,  715» 
of  elbow-joint,  312 


1594 


INDEX 


Surface  form  of   external  audi- 
tory meatus  1050 
iliac  artery,  682,  695 

of  eyelids,  1142 

of  femoral  artery,  701 

of  femur,  229 

of  fibula,  239 

of  fifth  nerve,  1041 

of  foot,  255,  360 

of  heart,  577 

of  hip,  333 

of  humerus,  183 

of  hyoid  bone,  154 

of  inferior  radio-ulnar  artic- 
ulation, 317 

of  internal  iliac  artery,  694 

of  intestines,  1323 

of  kidney,  1425 

of  knee-joint,  343 

of  lachrymal  gland,  1143 
sac,  1143 

of  liver,  1346 

of  lungs,  1397 

of  metacarpo-phalangeal  ar- 
ticulation, 325 

-of  mouth,  1219 

•of  muscles  of  abdomen,  448 
of  back,  424 
of  face,  385 
of  head,  385 
of  lower  extremity,  549 
of  upper  extremit3%  500 
of  vertebral  region,  409 

■of  pancreas,  1353 

of  parotid  duct,  1215 

of  patella,  231 

of  pelvis,  220 

•of  plantar  arteries,  720 

of  popliteal  arterj',  709 

of  radial  artery,  658 

•of  radio-carpal  articulation, 
318 

■of  radius,  192 

of  rectum,  1323 

•of  scapula,  176 

of  shoulder-joint,  307 

of  skull,  147 

of  spleen,  1359 

of  sterno-clavicular     articu- 
lation, 299 
-mastoid  muscle,  391 

of  sternum,  165 

of  stomach,  1280 

of  subclavian  artery,  635 

of  superior    radio-ulnar    ar- 
ticulation, 314 

of  temporo-mandibular     ar- 
ticulations, 282 

of  tibial  artery,  anterior,712 
posterior,  717 

of  trachea,  1380 

of  trifacial  ners^e,  1041 

of  trigeminal  nerve,  1041 

of  ulnar  artery,  661 

of  vermiform  appendix,  1323 

of  vertebral  column,  69 
ISurgical  anatomy  of  abdominal 
aorta,  670 

of  abducent  nerve,  1044 

of  acromio-clavicular  articu- 
lation, 301 

of  ankle-joint,  351 

of  arch  of  aoria,  592 

of  artery  of  bulb,  691 

of  ascending  pharyngeal  ai- 
tery,  611 

of  auditory  nerve,  1054 

of  axilla,  645 

of  axillary  artery,  649 
vein,  748 

•of  azygos  veins,  753 


Surgical    anatomy    of    bend     of 

elbow,  653 
oi  bile-duct,  1347 
of  bladder,  1440 
of  brachial  artery,  654 

plexus,  991 
of  carotid  arteries,  common, 
598 
external,  601 
internal,  621 

gland,  1049 
of  carpus,  205 
of  cavernous  sinus,  740 
of  cervical  fascia,  389 

ganglion,  1077 

plexus,  977 
of  cheeks,  1224 
of  clavicle,  170 
of  colon,  1326 
of    common    iliac    arteries, 

682 
of  conjunctiva,  1144 
of    deep    epigastric    artery, 

697 
of  descent  of  testicles,  1462 
of  dorsalis  pedis  artery,  715 
of  duodenum,  1325 
of  ear,  1176 
of  eighth  nerve,  1054 
of  elbow-joint,  312 
of  eleventh  nerve,  1063 
of  emissary  veins,  743 
of  external  iliac  artery,  695 
of  eye,  1134 
of  eyelashes,  1143 
of  eyelids,  1143 
of  facial  artery,  607 

nerve,  1049 

veins,  726 
of  fascia  of  femoral  region, 

anterior,  515 
of  femoral  artery,  701 
of  femur,  229 
of  fibula,  239 
of  foot,  256,  360 
of  gall-bladder,  1347 
of  glosso-pharvngeal   nerve, 

1057 
of  gums,  1224 
of  hemorrhoidal  veins,  76 1 
of  heart,  578 
of  hernia,  1511 
of  hip,  333 
of  humerus,  183 
of  hyoid  bone,  154 
of  hypoglossal  nerve,  1066 
of  inferior  calcaneo-scaphoid 
ligament,  354 

thyroid  artery,  641 
of  innominate  artery,  594 
of  intercostal   artery,  668 

nerves,  996 
of  internal  iliac  artery,  685, 
694 

jugular  vein,   732 

mammary  artery,  645 

pudic  artery  in  male,  690 
of  intestines,  1324 
of  ischio-rectal  region,  1535 
of  kidney,  1425 
of  knee-joint,  343 
of  lachrymal  gland,   1144 

sac,  1144 
of  lateral  sinus,  739 
of  ligaments  of  vertebra,279 
of  lips,  1224 
of  lingual  artery,  604 
of  liver,  1346 
of  lumbar  plexus,   1017 
of  lungs,  1397 
of  lymphatic  glands,  774 


Surgical  anatomy  of  lymphatics 
of  mammary  gland,  814 
of  neck,  787 

of  upper  extremity,  792 
vessels  of  peritoneum,  802 
of  stomach,  806 
of  male  breast,  1509 
of  mammary  gland,   1508 
of  maxillary  arterj-,  exter- 
nal, 607 
of  Meibomian  glands,  1143 
of  membranes  of  cord,  836 
of  middle  meningeal  arterj-, 

614 
of  motor  oculi  nerve,  1025 
of  mouth,  1224 
of  muscles  of  acromial  re- 
gion, 471 
of  arm,  478 

of  femoral  region,  anterior, 
518 
internal,  522 
posterior,  531 
of  gluteal  region,  528 
of  iliac  region,  511 
of  lateral  thoracic  region, 

469 
of  leg,  541 

of  lower  extremity,  551 
of  orbital  region,  375 
of  palatal  region,  406 
of  radio-ulnar  region,  an- 
terior, 484 
posterior,  491 
of  tongue,  400 
of  upper  extremity,  503 
of  nasal  fossae,  1102 
of  ninth  nerve,  1057 
of  occipito-frontalis  muscle, 

368 
of  tt'sophagus,  1230 
of  olfactory  nerve,  1021 
of  optic  nerve,  1022 
of  ovary,  1503 
of  palate,  1224 
of  palatine  artery,  615 
of  palmar  fascia,  deep,  494 
of  pancreas,  1353 
of  patella,  231 
of  pelvis,  220 
of  penis,  1460 
of  pericardium,  561 
of  perinffium,  1535 
of  peritoneum,  1264 
of  pharynx,  1224 
of  phrenic  nerve,  976 
of  plantar  arteries,  720 

fascia,  543 
of  pleura,  1387 
of  pneumogastric  nerve, 

1062 
of  popliteal  artery,  709 
of  pronator  radii  teres  mus- 
cle, 479 
of  prostate  gland,  1452 
of  prostatico-vesical  plexus, 

762 
of  radial  artery,  658 
of  radio-carpal  articulation, 

318 
of  radius,  192 
of  rectum,  1325 
of  salivarj'  glands,   1224 
of  saphenous  veins,   757 
of  scapula,   177 
of  scrotum,  1469 
of  seminal  vesicles,  1476 
of  seventh  nerve,    1049 
of  shoulder-joint,  307 
of  sixth  nerve,   1044 
of  skull,  149 


INDEX 


1595 


^Surgical  anatomy  of    spennatic 
cord,  1468 
veins,  766 
of    spinal    accessory    nerve, 

1063 
of  spleen,  1359 
of  sternum,  165 
of    ste mo-clavicular    artic- 
ulation, 299 
-mastoid  muscle,  391 
of  stomach,  1280 
of  subclavian  artery,  635 
of  superficial  fascia  of  cra- 
nial region,  367 
inguinal  Ivmphatic  glands, 
794 
of  superior  radio-ulnar  artic- 
ulation, 314 
of  synovial  tendons  at  wrist, 

492 
of  tarsal  joint,  356 
of  tarsus,  256 
of  temporal  artery,  612 
of   temporo-mandibular   ar- 
ticulations, 282 
of  tenth  nerve,  1062 
of  testicles,  1473 
of  thoracic  aorta,  666 
of  thvroid  artery,   superior, 
603 
gland,  1405 
of  tibia,  239 
of  tibial  artery,  717 

anterior,  712 
of  tongue,  1093 
of  tonsils,  1224 
of  trachea,  1381 
of  triangles  of  neck,  616 
of  trochlear  nerve,   1026 
of  twelfth  nerve,  1066 
of  ulna,  192 
of  ulnar  artery,  661 
of  ureter,  1428 
of  urethra,  male,  1445 
of  utero-ovarian  artery,  688 
of  uterus,  1496 
_  of  vermiform  appendix, 
1325 
of  vertebral  artery,  639 
column,  69 
neck  of  humerus,   177 
of  scapula,  172 
^Suspensory   ligament  of  axilla, 
464 
of  clitoris,  437 
of  eve,  1105 
of  lens,  1129 
of  liver,  1333 
of  malleus,  1160 
of  mamma,  463 
of  ovary,  1501 
of  penis,  437 
of  Treitz,  1286 
muscle  of  duodenum,  1286 
Sustentacular  cells  of  spleen,1356 

fibres,  1121 
Sustentaculum  lienis,  1259 

tali,  255 
•Sutura,  264 
dentata,  264 
harmonia,  264 
limbosa,  264 
notha,  264 
serrata,  264 
squamosa,  264 
vera,  264 
'.Sutural  bones,  103 
ligament,  259 
membrane,  264,  847 
'Suture  or  sutures,  basilar,   128 
coronal,  78,  127 


Suture  or  sutures,  cranial,  126 
ethmo-frontal,  130 
-sphenoidal,  130 
frontal,  79,  127 
fronto-malar,  128 
-parietal,  127 
-sphenoidal,  128,  130 
intermaxillary,  139 
internasal,  139 
interparietal,  127 
lambdoid,  75,  78,   128 
masto-occipital,  75,  128 

-parietal,  128 
metopic,  83,  127 
naso-maxillary,  139 
occipi  to-parietal,  128 
petro-occipital,  75,  128,  133 
-sphenoidal,  128,  136 
-squamous,  88 
sagittal,  78,  127 
spheno-parietal,  128 
squamo-parietal,  128 

-sphenoidal,  128 

squamous,  85,  128 

transverse,  128 

facial,  128 

Sweat-glands,  1190 

Sylvian  point,  866 

vein,  superficial,  735 
Sylvius,  aqueduct  of,  912 

"fissure  of,  866,  884 
Symington,   ano-coccygeal  body 

of,  1316 
Sympathetic  nerve,  1066 
ganglion  of,  1078 
plexuses  of,  1080 
structure  of,  1068 
Svmphysis,  264,  267 
of  jaw,  122 
sacro-coccygeal,  66 
Synarthrosis,  264 
Synchondrosis,  264 
Syndesmo-odontoid  joint,  274 
Syndesmosis,  265 
Synovial  bursa,  263 
ligaments,  262 
membranes,  262 
articular,  262 
bursal,  263 

of    flexor    tendon    at  wrist, 
492 
surgical  anatomy  of, 
492 
vaginal,  263.    -See  also  Indi- 
vidual joints, 
sheaths,  263 
viUi,  262 
Systemic  arteries,  583 
"  veins,  724 


Tables  of  skull,  33 

Tabular  portion  of  occipital  bone, 

71 
Tactile  corpuscle,  827 
Tffinia  fornicis,  896,   898 

hippocampi,  896 

pontis,  8S3 

semicircularis,  891,  894 

thalami,  904 
Tapetum  of  choroid,  1114 

lucidum,  1127 

nigrum,  1127 
Tarsal  arch,  623 

artery,  715 

bones,  development  of,  253 

glands,  1139 

joint,  surgical  anatomy  of,  356 

ligament,  external,  370 
internal,  370 


Tarsal  plates  of  eyelid,  1139 
Tarso-metatarsal   articulations, 

357 
Tarsus,  242 

articulations  of,  352 
surface  form  of,  255 
surgical  anatomy  of,  256 
synovial  membrane  of,  352 
Tast«-buds,  1090 
Teeth,  1195 

arrangement  of,  1198 

auditory,  1173 

bicuspid,  1138 

canine,  1197 

cementum  of,  1204 

cortical  substance  of,  1204 

deciduous,  1196 

development  of,  1204 

enamel  of,  1203 

eruption  of,   1208 

eye,  1197 

general  characters  of,   1195 

grinders,  1198 

incisors,  1196 

ivory  of,  1202 

milk,  1196 

molar,  1198 

permanent,  1196 

superadded,  1208 
premolars,  1198 
roots  of,  1196 
soUd  portion  of,   1201 
stomach,  1197 
structure  of,  1200 
surfaces  of,  1195 
temporary,  1196 
Tegmen  tympani,  87 
Tegmental  region,   subthalamic, 

885 
Tegmentum,  908 
of  crus  cerebri,  885 
fibres  of,  908 
nucleus  of,  red,  908 
Tela  chorioidea  inferior,  856,  943 

superior,  854,  901 
subcutanea,  1180 
Temporal  artery,  611 

anterior,  611,  640 

from  internal  maxillary,  614 

middle,  611 

posterior,  611,  640 

surgical  anatomy  of,  612 
bone,  83 

articulations  of,  92 

attachment    of    muscles  to, 
92 

development  of,  91 

mastoid  portion  of,  85 

petrous  portion  of,  88,  136 

squamous  portion  of,  83 
convolution,  877 
crest,  76,  80,  84 
diploic  vein,  734 
fascia,  381 
fossa,  76,  137 

horn  of  lateral  ventricle,  890 
lines,  76,  80 
lobe,  885 
muscle,  382 

nerves,    from   auriculo-tempo- 
ral,  1038 

deep,  1037 

from  facial,  1032,  1049 
ridges,  76,  80 
sulci,  868 
sulcus,  first,  877 

fourth,  878 

inferior,  870 

second,  877 

third.  878 
veins,  727 


1596 


INDEX 


Temporary  teeth,  1196 

eruption  of,  1209 
Temporo-facial  nerve,  1032, 1049 
-malar  filaments,  115 
foramen,  115 
nerve,  1032 
mandibular  articulations,  280 
surface  form  of,  282 
surgical  anatomy  of,  282 
region,  muscles  of,  381 
-maxillarv  articulation,  138 

vein,  727 
sphenoidal  lobe,  877 
Tendo  Achillis,  535 
bursa  of,  535 
oculi,  370 
Tendons,  363 

of  diaphragm,  central,  429 

cordiform,  429 
flexor,  fibrous  sheaths  of,  545 
T6non,  capsule  of,  1103 
Tensor  fasciae  femoris  muscle,  515 
palati  muscle,  404 
tarsi  m.uscle,  371 
tympani  muscle,  1161 
canal  for,  1153 
Tenth  nerve,  1057 

surgical  anatomy  of,  1062 
Tentorium,  900 
cerebelli,  850 
Teres  major  muscle,  474 

minor  muscle,  473 
Testes  gubernaculum,  1461 
muliebres  of  Galen,  1499 
Testicles,  1460,  1469 
coverings  of,  1462 
descent  of,  1461 
gubernaculum  testis,  1461 
lobes  of,  1472 
lymphatic  vessels  of,  804 
mediastinum  testis,  1471 
parenchyma  of,  1471 
rete  testis,  1471 
sheaths  of,  proper,  1469 
size  of,  1469 
structure  of,  1471 
surgical  anatomy  of,  1473 
trabeculse  of,  1471 
tubuli  seminiferi  of,  1471 
tunica  albuginea,  1471 
vaginalis,  1470 
vasculosa,  1471 
tunics  of,  1469 
weight  of,  1469 
Testicular  bag,  1462 
Thalamencephalon,  901 
Thalmic  radiation,  905 
Thebesian  valve,  567,  771 
Thigh,  bones  of,  221 
fascia  of,  512 
muscles  of,  512 
Third  nerve,  1024 

ventricle  of  brain,  901 
Thoracic  aorta,  665 
branches  of,  666 
surgical  anatomy  of,  666 
artery,  acromial,  651 
alar,  651 
long,  651 
superior,  650 
axis,  651 

cardiac  nerves,  1061 
duct,  775 

structure  of,  778 
gangUon,  1078 
nerves,  993 
plexus,  1079 

divisions  of,  anterior,  993 

posterior,  993 
long,  983 
posterior,  983 


Thoracic  plexus,  roots  of,  993 
portion    of    gangliated    cord, 
1078 
of  oesophagus,  1226 
region,  anterior,  fascia  of,  deep, 
463 
superficial,  463 
muscles  of,  463 
lateral,  muscles  of,  468 

surgical  anatomy  of,469 
surface  of  lungs,  1391 
trachea,  lymphatic  vessels  of, 

815 
vein,  long,  748 
vertebrae,  53 
bodies  of,  53 
laminae  of,  54 
pedicles  of,  54 
processes  of,  54 
wall,  lymphatic  glands  of,  810 
vessels  of,  812 
Thoracico-epigastric  vein,  748 
Thorax,  155 

boundaries  of,  155 
cavity  of,  556 
fasciffi  of,  424 
lymphatics  of,  810 
muscles  of,  424 
nerves  of,  cutaneous,  995 
openings  of,  lower,  556 

upper,  556 
veins  of,  744 
Thumb,  ligaments  of,  321 
metacarpal  bone  of,  201 
muscles  of,  484 
Thymic  artery,  594 

lymphatic  vessels,  815 
Thymus  gland,  1407 
arteries  of,  1408 
lobes  of,  147 
lymphatics  of,  1048 
nerves  of,  1408 
structure  of,  1408 
veins  of,  1408 
Thyro-arytenoid  ligament,   infe- 
rior, 1370 
superior,  1370 
muscle,  1373 
-epiglottic  ligament,  1367 ' 
-epiglottideus  muscle,  1373 
-glossal  duct,  1090,  1401 
-hyals  of  hyoid  bone,  154 
-hj'oid  ligaments,  1366 
membrane,  1366 
muscle,  392 
nerve,  1066 
Thyroid  artery,  inferior,  641 

surgical  anatomy  of,  641 
superior,  601 

surgical  anatomy  of,  603 
axis,  640 
body,  1401 

venous  plexus  on,  751 
cartilage,  1362 
foramen,  214 
ganglion,  1076 
gland,  1401 

accessory,  1403 
arteries  of,  602,  1404 
color  of,  1401 
isthmus  of,  1403 
lobes  of,  1403 
lymphatic  vessels  of,  782 
lymphatics  of,  1405 
nerves  of,  1405 
structure  of,  1403 
surgical  anatomv  of,  1405 
veins  of,  731,  1405 
weight  of,  1401 
nerve,  1077 
notch,  1362 


Thyroid  veins,  accessory,  731 
inferior,  751 
middle,  730 
superior,  730 
Thyroidea  ima  artery,  594 

vein,  751 
Tibia,  233 

articulations  of,  236 
attachment  of  muscles  to,  236 
crest  of,  234 
development  of,  236 
lower  extremit}'  of,  235- 

surfaces  of,  235 
nutrient  artery  of,  719, 
oblique  line  of,  235 
shaft  of,  234 

surfaces  of,  234 
spinous  process  of,  233; 
structure  of,  236 
surface  form  of,  236 
tubercle  of,  234 
tuberosities  of,  233 
upper  extremity  of,  233' 
Tibial  artery,  anterior,  711 
branches  of,  712 
peculiarities  of,  712 
relations  of,  711 
surface  marking  of,  712 
surgical  anatomy  of,  712 
posterior,  716 
branches  of,  717 
peculiarities  of,  717 
relations  of,  716 
surface  marking  of,  717 
surgical  anatomy  of,  717 
recurrent,  anterior,  713 
posterior,  713 
bursa,  subcutaneous,  340 
gland,  anterior,  795 
nerve,  1014 
anterior,  1016 
posterior,  1014 
veins,  anterior,  758 
posterior,  758 
Tibialis  anticus  muscle,  532 
bursa  of,  532 
posticus  muscle,  538 
Tibio-fibular  articulation,  345 
region,  anterior,  muscles  of, 

531 
posterior,  muscles  of,  534 
-tarsal  ligament,  anterior,  347 
posterior,  347 
Tissue,  adipose,  pads  of,  263 
areolar,  subserous,  1245 
connective,  subserous,  1246 
elastic,  yellow,  261 
fibrous,  white,  261 
intertubular,  1203 
Tomes 's  fibres,  1203 

granular  sheath  of,  1202 
Tongue,  1087 

anterior  portion  of,  1087 
apex  or  tip  of,  1087 
arteries  oi,  1092 
base  or  root  of,  1087 
body  of,  1087 
corium  of,  1089 
development  of,  1242 
dorsum  of,  1087 
fibrous  septum  of,  398 
fraenum  of,  1087 
glands  of,  1091 
-like  lobe  of  liver,  1336 
lymphatics  of,  1093 
lymphatic  vessels  of,  7?2 
margin  of,  1087 
mucous  membrane  of,  1088 
muscles  of,  398,  1092 
extrinsic,  398 
fntrinsic,  398 


INDEX 


1597 


Tongue,  muscles  of,  surgical  ana- 
tomy of,  400 
nerves  of,  1093 
oral  portion  of,  1087 
papillae  of,  1089 
pharyngeal  portion  of,  1087 
posterior  portion  of,  1087 
raph6  of,  1087 
structure  of,  1088 
surface  of,  1087 
surgical  anatomy  of,  1093 
veins  of,  1092 
Tonsil,  1213 

arteries  of,  1213 
of  cerebellum,  931 
development  of,  1243 
lingua,  1088 
lymphatics  of,  1213 
nerves  of,  1213 
pharyngeal,  1221,  1224 
surgical  anatomy  of,  1224 
veins  of,  1213 
Tonsillar  artery,  606 

nerves,  1057 
Tooth  germ,  1206 
Torcular  Herophili,  74.  737 
Trabeculaj    corpus    cavernosum, 
1457 
of  spleen,  1356 
of  testicle,  1471 
Trachea,  1376 

arteries  of,  641,  1380 
cartilages  of,  1378 
fibrous  membrane  of,  1379 
lymphatics  of,  1380 
mucous  membrane  of,  1380 
muscular  fibres  of,  1378 
nerves  of,  1380 
relations  of,  1376 
structure  of,  1378 
surface  form  of,  1380 
surgical  anatomy  of,  1381 
thoracic,  lymphatic  vessels  of, 

815 
veins  of,  751,  1380 
Tracheal  arteries,  641 
glands,  787,  1380 
veins,  751 
Trachelo-mastoid  muscle,  419 
Tract  of  Burdach,  839,  843 

cerebellar,    antero-lateral,    as- 
cending, 842 
descending,  843 
direct,  843 
dorso-lateral,  843 
of  cord,  conducting,  841 

functions  of,  844 
cornu,  commissural,  844 
descending  comma,  844 

crossed,  842 
of  Goll,  839,  843 
of  Gowers,  842 
of  Helwig,  triangular,  951 
lateral,  of  medulla,  945 
marginal,  of  Spitzka  and  Lis- 

sauer,  843 
nerve,  afferent,  961 
ascending,  961 
descending,  959 
efferent,  959 
motor,  959 
sensory,  961 
olfactory,  880,  1019 
optic,  1021 
postero-lateral,  843 

-median,  843 
pyramidal,  crossed,  842 
'direct,  842 
uncrossed,  842 
■septo-marginal,  844 
triangular,  of  Helwig,  843 


Tractus  spiralis  foraminosus,  89 
Tragicus  muscle,  1147 
Tragus,  1145 

Transitional  epithelium,  1428 
Transversalis  cervicis  muscle, 419 
colli  artery,  642 

muscle,  419 
fascia,  445,  1517 
humeri  artery,  641 
muscle,  442,  1516 

relations  of,  442 
Transverse  cervical  artery,  642 
colon,  1309 

flexure  of,  splenic,  1309 
diameter  of  pelvis,  217 
facial  artery,  611 

suture,  128 

vein,  727 
fibres  of  cerebrum,  916 

of  coid,  841 

of  pons,  923 
foramen,  50 
humeral  ligament,  305 
ligament  of  acetabulum,  330 

of  atlas,  275 

inferior,  302 

of  knee,  340 

superior,  302 
lingualis  muscle,  399 
mesocolon,  1259,  1309 
metacarpal  ligament,  324 
pelvic  ligament,  459 
perineal  arter}"-,  691 

ligament,  459 
processes  of  a  vertebra,  49 
sinus,  743 

of  pericardium,  560 
suture,  128 
Transversus     auricula;     muscle, 

1147 
menti  muscle,  378 
perinei     superficialis     muscle, 

457,  460 
Trapezium  bone,  198 

articulations  of,  198 

attachment  of   muscles    to, 
198 

surfaces  of,  198 
Trapezius  muscles,  411 
Trapezoid  bone,  198 

articulations  of,  199 

surfaces  of,  198 
ligament,  300 
ridge,  168 
Treitz,  fossa  r  f,  1260 

suspensory  ligament  of,  1286 
Triangle  of  elbow,  653 
of  election,  617 

of  fourth  ventricle,  945 
Hesselbach's,  1520 
of  necessity,  616 
of  neck,  anterior,  616 

posterior,  618 

surgical  anatomy  of,  616 
occipital,  618 
Petit's,  435 
Scarpa's,  516,  697 
subclavian,  618 
submaxillary,  394,  617 
suboccipital,  423 
suprameatal,  85 
Triangular  cartilage  of  septum  of 

nose,  1097 
fascia  of  abdomen,  437,  1155 

of  urethra,  458 
interarticular   fibro-cartilage, 

315 
muscles,  362 
tract  of  Helwig,  843,  951 
Triangularis  menti  muscle,  378 
sterni  muscle,  425 


Triceps  extensor  cubiti  muscle, 

477 
Tricuspid  orifice,  567 

valve,  570 
Trifacial  nerve,   1026 

surface  marking  of,  1041 
surgical  anatomy  of,   1041 
Trigeminal  depression,  88 

nerve,  1026 

surface  marking  of,   1041 
surgical  anatomy  of,   1041 
Trigoid  bodies,  820 
Trigone  of  bladder,  1438 

of  habenula,  904 
Trigonum  acustici,  945 

nervi  hj'poglossi,  945 

olfactoriiun,  881 

vagi,  945 

ventriculi,  890 

vesicae,  1438 
Tri-radiate  sulcus,  874 

carotid,  inferior,  616 
superior,  394,  617 
Trochanter,  great,  223 
bursa  of,  331 

lesser,  223 

rudimental,  third,  224 
Trochanteric  fossa,  223 
Trochlea  of  femur,  225 

of  humerus,   181 
Trochlear  fossa,  82 

nerve,  1025 

surgical  anatomy  of,   1026 

surface  of  astragalus,  244 
Trochoid,  265 

Trolard,  anastomotic  vein  of,  735 
Troltsch,  recessus  of,  1162 
True  vocal  cords,   1370 
Trunk,  arteries  of,  665 

articulations  of,  269 

fasciae  of,  410 

muscles  of,  410 

of  pneumogastric  nerve,   gan- 
glion of,   1059 
Tube  or  tubes,  bronchial,  1376 

Eustachian,  1153 

Fallopian,  1497 

lymphatic  vessels  of,  804 

medullary,  857 

neural,  857 

spiral,  of  Schachowa,  1419 

tonsil,  1155 
Tuber  annulare,  922 

cinereum,  882 
Tubercle,  acoustic,  lateral,  950 

adductor,  225 

carotid,  51 

of  cervical  vertebra,  anterior, 
50 
posterior,  50 

Chassaignac's,  69 

conoid,  168 

comical,  of  Santorini,   1368 

cuneate,  941 

cuneiform,  of  Wrisberg,    13G8 

of  Darwin,  1145 

deltoid,  168 

egg,  1502 

of  epiglottis,  1365 

of  femur,  223 

genial,  123 

of  hyoid  bone,  153 

infragleniod,  174 

jugular,  74 

lachrymal,  109 

mental,  122 

of  navicular  bone,  246 

olfactory,  881,  1019 

of  optic  thalamus,  anterior,  904 

peroneal,  243 

pharyngeal,  73 


1598 


INDEX 


Tubercle,  pterygoid,  97 
of  quadratus,  225 
of  ribs,  161 
of  Rolando,  941 
of  scaphoid,  196 
supraglenoid,  175 
of  tibia,  234 
of  ulna,  186 
of  zygoma,  84 
Tubercula  quadrigemina,  911 
Tuberculum  acusticum,  945, 1051 
caudatum,  1333 
impar,  1242 
Tuberosity,  bicipital,  195 
of  calcaneus,  243 
of  cuboid,  245 
of  femur,  inner,  226 

outer,  226 
glenoid,  175 
of  humerus,  179 
of  ischium,  211 
maxillary,  106 
of  navicular  bone,  246 
of  palate  bone,  117,  135 
of  radius,  190 
of  ribs,  161 
of  sacrum,  63 
of  scaphoid  bone,  246 
of  tibia,  external,  233 
internal,  233 
Tubuli,  lactiferi,  1507 
seminiferi,  1471 
uriniferi,  1418 
Tunic  of  Ruysch,   1113 
Tunica  adventitia,   1228 
albuginea,  373,  1457,  1471 
interna,  1120 
propria,  1180 

vaginalis,  1462,  1465,  1469 
cavity  of,  1470 
parietal  portion  of,  1470 
visceral  portion  of,  1470 
vasculosa  testis,  1471 
Tunics  of  eye,  1107 

of  testicle,  1469 
Turbinated  bone,  inferior,  119 
articulations  of,  120 
development  of,  120 
surfaces  of,  120 
middle,  101 
sphenoidal,  143 
superior,  101 
crest,  107,  117 
Turck,   fasciculus  of,   842 
Turner,  intraparietal  sulcus  of, 

875 
Twelfth  nerve,  1064 

surgical  anatomy  of,  1066 
Tympanic  antrum,  87 
aperture,  1151 

artery  from  ascending  pharyn- 
geal, 610 
from  internal  carotid,  622 
maxillary,  613 
attic,  87 
cavity,  1150 
nerve,  1056 

from  facial,  1047 
plexus  of,  1057 
sulcus,  1149 
Tympanohyal  process,  92 
Tvmpanomalleolar  ligaments, 

1156 
Tympanum,  1150 
arteries  of,   1162 
cavity  of,  1150 
floor  of,  1151 
fundus  of,  1151 
mucous  membrane  of,  1162 
muscles  of,   1161 
nerves  of,   1163 


Tympanum,  ossicles  of,  1158 
pyramid  of,   1153 
roof  of,   1151 
veins  of,  1163 
walls  of,  1153 


Ulna,   184 

articulations  of,  189 

attachment  of  muscles  to,  189 

development  of,    189 

lower  extremity  of,   189 

shaft  of,   188 

structure  of,  189 

surface  form  of,   189 

surgical  anatomy  of,   192 

tubercle  of,  186 

upper  extremity  of,   184 

coronoid  process  of,  186 
olecranon  process  of,   186 
sigmoid  cavities  of,  186 
Ulnar  artery,  660 

peculiarities  of,  661 
surface  marking  of,   661 
surgical  anatomy  of,  661 
groove,  182 
nerve,  988 

region,  muscles  of,  498 
veins,  745 
Umbilical  arteries  in  fcBtus,  579, 
685 
fissure  of  liver,  1331 
fossa  of  liver,  1331 
notch,  1331 

region,  contents  of,  1234 
Umbilicus,  lymphatic  vessels  of, 

802 
Umbo,  1157 
Unciform  bone,   199 

articulations  of,  200 
attachment  of  muscles  to, 
200 
process  of  ethmoid,  100 
Uncinate  convolution,  879  '• 
fasciculus,  917 
process  of  Winslow,  1348 
Uncrossed  pyramidal  tract,  842 
Uncus,  879 

Ungual  phalanges,  204 
Unipolar  cells,  820 
Unstriated  muscle,  361 
Unstriped  muscle,  361 
Upper  deep  cervical  glands,  786 
extremity,  arteries  of,  631 
articulations  of,  297 
bones  of,  167 
fascige  of,  462 
lymphatic  glands  of,  788 

vessels  of,  792 
muscles  of,  462 
veins  of,  744 
subscapular  nerve,  984 
Urachus,  1435 
fold  of,  1519 
Ureter,  1426 

arteries  of,   1428 
fibrous  coat  of,   1427 
Ureteral  folds,   1439 
Ureters,  lymphatic  vessels  of,804 
muscular  coat  of,   1428 
mucous  coat  of,  1428 
nerves  of,  1428 
orifices  of,  1438 
relations  of,   1427 
structure  of,  1427 
surgical  anatomy  of,  1428 
Urethra,  female,   1446 

lymphatic  vessels  of,  803 
mucous  coat  of,   1446 


Urethra,    female,   muscular  coat 
of,   1446 
orifice  of,  1481 
structure  of,  1446 
submucoxis  coat  of,  1446 

male,  1441 
bulb  of,  1458 

cavernous  portion  of,  1443 
crest  of,  1442 
fossa  navicularis  of,  1444 
lymphatic  vessels  of,  803 
membranous     portion     of, 

1442 
mucous  coat  of,  1444 
muscular  layer  of,  1445 

portion  of,  1442 
pendulous  portion  of,  1443 
penile  portion  of,   1443 
prostatic  portion  of,  1441 
spongy  portion  of,   1443 
structure  of,  1444 
submucous  tissue  of,   1445 
surgical  anatomy  of,   1445 
Urinary  bladder.     See  Bladder. 

organs,  1411 
Uterine  artery,   687 

portion    of     Fallopian     tube, 
1497 

plexus  of  nerves,  1086 

veins,  763 

plexus  of,  763 
Utero-sacral  ligaments,   1490 

-vaginal  plexus,  1086 

-vesical  fold,    1490 
pouch,  1487,  1490 
Uterus,  1486 

abnormalities  of,  1493 

after  parturition,  1494 

appendages  of,  1497 

arbor  vitaj  of,   1492 

arteries  of,  1494 

bicornate,  1493 

body  of,  1487 

cavity  of,   1491 

changes  induced  bj'  pregnancv 
1493 
at  menstrual  period,  1493 

at  different  ages,  1493 

folds  of,  1489 

fundus  of,  1487 

ganglia  of,  1086 

ligainents  of,   1489 

lymphatic  vessels  of,  803,  1495 

masculinus,  1442 

mucous  membrane  of,  1492 

muscular  coat  of,  1491 

neck  of,  1488 

nerves  of,   1086,  1496 

structure  of,   1491 

supravaginal  portion  of,   148S 

surgical  anatomy  of,    1496 

vaginal  portion  of,   1488 

veins  of,  1495 
Utricle  of  vestibule,  1169 
Uvea,  1118 
Uvula  of  cerebellum,  931 

of  throat,  1211 

vesicae,  1439 


Vagina,  1483 
arteries  of,   1485 
azygos  arteries  of,   687 
columns  of,  1484 
erectile  tissue  of,    1485 
lymphatic  vessels  of,  804.  1485 
mucosa  intertubercularis,  304 

membrane   of,    1484 
muscular  coat  of,   1484 
nerves  of.   1485 


INDEX 


1599> 


Vagina,  orifice  of,  1481 

relations  of,   1484 

rugae  of,  1484 

structure  of,  1484 

veins  of,  1485 

vestibule  of,   1481 
Vaginal  artery,  687 

bulb,  1483 

fornix,  1484 

plexus  of  nerves,  1086 

portion  of  uterus,  1488 

process  of  temporal   bone,   89 

synovial  membrane,  263 

veins,  763 

plexuses  of,  763 
Vagus  nerve,  nuclei  of,  950 
Valentin,  ganglion  of,  1033 
Vallecula  of  cerebellum,  926 

epiglottica,  1365 

Sylvii,  856 
Valley  of  cerebellum,  926 
Valsalva,  sinuses  of,  aortic,  573 

pulmonary,  571 
Valve  or  valves,  anal,  1319 

of  Bauhin,  1308 

bicuspid,  572 

coronary,  567 

Eastacliian,  567 
in  foetus,  578 

of  Gerlach,  1303 

of  Guerin,  1444 

of  Hasner,  1142 

Houston's,  1318 

ileo-cffical,  1308  . 

of  Kerkring,  1291 

of  Morgagni,  1319 

pvloric,  1272 

rectal,  1318 

semilunar,  1319 
aortic,  572 
pulmonic,  571 

Thebesian,  567,  771 

tricuspid,  570 

of  Vieussens,  910,  933 
Valvulaj  conniventes,  1291 
Vas  deferens,  1472 
artery  of,  686 
lymphatic  vessels  of,  804 
structure  of,  1473 

spirale,  1173 
Vasa  brevia  arteries,  674 

intestini  tenuis  artery,  675 

vasorum  of  arteries,  586 
Vascular  papillae,  1181 

system  at  birth,  changes  in, 
581 
in  foetus,  578 
Vasomotor  nerves,   1071 
Vastus  extemus  muscle,  517 

internus  muscle,  517 
Vater,  ampulla  of,  1345 

corpuscles  of,  828 
Veins,  721 

of  abdomen,  755 

anastomotic,  of  Troland,  735 

angular,  726 

appendicular,  768 

of  arm,  744 

auricular,  727 

axillary,  747 

azygos,  752 
larger,  752 
left  lower,  753 

upper,  753 
right,  752 
smaller,  753 

basilar,  735 

basilic,  746 
median,  746 

brachial,  747 

brachio-cephalic,  750 


Veins  of  bones,  41 
bronchial,  753 
buccal,  726 
cardiac,  770 
cava,  inferior,  764 

superior,  752 
cephaUc,  747 

median,  746 
cerebellar,  736 
cerebral,  734 
cervical,  anterior,  deep,  733 

posterior,  deep,  733 
choroid,  735 
circumflex,  iliac,  759 

superficial,  756 
companion,  747 
coronary,  768 
costo-axillary,  748 
cystic,  769 
digital,  hand,  745 
of  diploe,  733 
dorsal,  of  penis,  762 
dorsi-spinal,  753 
of  dura  mater  of  brain,  849 
emissary,  743 
emulgent,  766 
epigastric,   deep,   759 

superficial,  756 
of  face,  exterior  of,  725 
facial,  726 
femoral,  758 

of  fingers,  superficial,  745 
of  foot,  758 
frontal,  725 
of  Galen,  735 
gastric,  768 
gluteal,  761 
haemorrhoidal,  external,    760 

inferior,  760 

middle,  760 

superior,    768 
of  hand,  superficial,   745 
of.  head,  724 
of  heart,  577 
hepatic,  767 
histology  of,  722 
hypogastric,  760 
iliac,  circumflex,  deep,  759 

common,  764 

external,  759 

internal,  760 
ilio-lumbar,  764 
innominate,  750 
intercostal,  752 
interosseous,  of  forearm,  747 
intervertebral,  755 
intralobular,  767 
jugular,  728 
laryngeal,  inferior,  751 
lingual,  729 

longitudinal,  inferior,  738 
of  lower  extremity,  755 
lumbar,  765 

ascending,  753,  765 
right,  752 
mammary,  internal,  750 
masseteric,  726 
maxillary,  internal,  727 
median,  745 
medulli-spinal,  755 
meningeal,  730,  734 
meningo-rachidian,  754,  833 
mesenteric,  768 
naso-frontal,  740 
of  neck,  725 
obturator,  761 
occipital,  727 
oesophageal,  751 
ophthalmic,  740 
orbital,  727 
ovarian,  766 


Veins,  palatine,  727 
palmar,  deep,  747 
pancreatic,  769 
of  pelvis,  755 
peroneal,  758 
pharyngeal,  730 
phrenic,  767 

of  pia  mater  of  brain,  856 
plantar,  758 
plexus  of,  palmar,  745 

pampinniform,  765 

pharyngeal,  730 

prostatic,  761 

prostatico-vesical,  761 

pterygoid,  727 

spermatic,  765 

spinal,  753 

on  thyroid  body,  751 

uterine,  763 

vaginal,  763 

vesical,  inferior,  763- 
superior,  761 
popliteal,  758 
portal,  769 

system  of,  768 
profunda  femoris,  759- 
pterygoid  plexus,  727 
pudic,  760 
pulmonary,  723 
pyloric,  768 
radial,  745 

deep,  747 
ranine,  729 
renal,  767 
sacral,  lateral,  760 

middle,  764 
saphenous,  756 
sciatic,  761 
spermatic,  765 
spinal,  753 
splenic,  768 
stylo-mastoid,  725 
subclavian,  749 
sublobular,  767 
submaxillary,  727 
submental,  727 
supraorbital,  726 
suprarenal,  767 
sylvian,  superficial,  735 
systemic,  724 
temporal,    727 
temporo-maxillary,  727 
thoracic,  long,  748 
thoracico-epigastric,  748 
of  thorax,  744 
thyroid,  accessory,  731 

gland,  731 

inferior,  751 

middle,  730 

superior,  730 
thvroidea  ima,  751 
tibial,  758 
tracheal,  751 
ulnar,  745 

of  upper  extremity,  744 
uterine,  763 
vaginal,  763 
ventricular,  735 
vermian,  735 

of  vertebrae,  bodies  of,  755 
vertebral,  732,  751 
Vidian,  730 
Velum  interpositum,  854,  901 
medullary,  943 
pendulum  palati,  1211 
Vena  azygos  major,  752 
minor,  753 

basis  vertebrae,  49,  755 
cava,  ascending,  764 
inferior,  764 

peculiarities  of,  764 


1600 


INDEX 


Vena  cava,  superior,  752 

magna  Galeni,  735 
Venae  basis  vertebrarum,  755 
comites,  723,  747 
corporis  striati,  735 
interlobulares  of  kidney,  1423 
Thebesii,  771 
vorticosse,  1113 
Venesection,  746 
Venous  arch,  nasal,  725 
plexus,  interspinous,  732 
on  thyroid  body,  751 
Venter  ilii,  209 

of  scapula,  171 
Ventral  auditory  nuclei,  950 
root  of  eighth  nerve,  1050 
of  spinal  nerve,  965 
Ventricle  of  Arantius,  944 
of  brain,  fifth,  897 
fourth,  943 
third,  901 
Verga's,  896 
of  heart,  fibres  of,  575 

left,  chordse  tendineae  of,  573 

columna;  carnea;  of,  573 
right,  568 

chordae  tendinese  of,  570 
columnse  carnese  of,  570 
of  larynx,  1371 
lateral,  888 
Ventricular  gray  matter,  922 
portion  of  heart,  568 
veins,  735 
Ventro-median  fissure,  837 
Verga's  ventricle,  896 
Vermian  vein,  735 
Vermiform  appendix,  1303 
arteries  of,  1305 
canal  of,  1304 
lymphatics  of,  1306 
mesentery  of,  1260 
mucous  membrane  of,  1305 
muscular  coat  of,  1305 
serous  coat  of,  1304 
structure  of,  1304 
submucous  coat  of,  1305 
surface  form  of,  1323 
surgical  anatomy  of,  1325 
veins  of,  1306 
process  of  cerebellum,  926 
Vertebrae,  48 

bodies  of,  veins  of,  755 
centrum  of,  48 
cervical,  49 

sev-enth,  53 
coccygeal,  61 
development  of,  58 
•dorsal,  53 
false,  61 

general  characters  of,  48 
immovable,  61 
ligaments  of,  270 
lumbar,  56 

process  of,  articular,  49 
spinous,  49 
transverse,  49 
prominens,  53 
sacral,  61 
structure  of,  58 
thoracic,  53 
Vertebral  aponeurosis,  411,  416 
artery,  637 

surgical  anatomy  of,  639 
border  of  scapula,  174 
canal,  49 
column,  48 

articulations  of,  269 
surface  form  of,  69 
surgical  anatomy  of,  69 
foramen,  49 
groove,  155 


Vertebral,  ligaments  of,  270 

plexus  of  nerves,  1077 

region,  anterior,  muscles  of,  406 
lateral,  muscles  of,  408 
muscles  of,  409 

ribs,  160 

vein,  732,  751 
Vertebrarterial  foramen,  50 
Vertebro-chondral  ribs,  160 

-pericardial  ligaments,  558 

-pleural  ligament,  1385 

-sternal  ribs,  159 
Vertex  of  skull,  129 
Vertical  lingualis  muscle,  399 

plate  of  palate  bone,  117 
Verumontanum,  1442 
Vesical  arteries,  686 

plexus  of  nerves,  1086 
of  veins,  inferior,  762 
superior,  761 

trigone,  1438 
Vesicle,  prostatic,  1442 
Vesicles,  Graafian,  1502 

seminal,  1475 
Vesico-uterine  ligament,  1490 
Vesicula  prostatica,  1441 
Vesicular  column  of  Clark,  846 
Vestibular  artery,  1176 

ganglion,  1053 

nerve,  1053 
path,  1054 

root  of  eighth  nerve,  1050 

window,  1152 
Vestibule,  aortic,  of  Sibson,  572 

of  ear,  1164 

of  mouth,  1194 

of  nose,  1099 

of  vagina,  1481 
Vestigial  fold  of  pericardium,  561 
Vibrissa,  1096 
Vicq  d'Azyr,  bundle  of,  883 
Vidian  artery,  616 

canal,  96,  135 

nerve,  1034 

veins,  730 
Vieussens,  ansa  of,  1076 

centrum  ovale  majus  of,  881 

valve  of,  910,  933 
Villi  of  small  intestine,  1292 

S3movial,  262 
Viscera,  development  of,  1235 
Visceral  cranium,  71 

layer  of  pleura,  1382 

lymphatics,  811 

peritoneum,  1247 

portion    of    tunica    vaginalis, 
1470 

surface  of  liver,  1329 
of  stomach,  1270 
Visual  axis,  1106 

centres,  1022 

purple,  1120 
Vitreous  bod.y,  1129 

humor  of  eye,  1129 

table  of  skull,  34 
Vocal  cords,  false,  1370 
true,  1370 

process,  1365 
Voice,  organs  of,  1361 
Volkmann's  canals,  38 
Voluntary  muscle,  361 
Vomer,  120 

alffi  of,  121,  143 

articulations  of,  122 

development  of,  122 

surfaces  of,  121 
Vomerine  cartilage,  1097 
Vortex  of  heart,  575 
Vulva,    fossa      navicularis     of, 

1478 
Vulvo-vaginal  gland,  1482 


Waldeyer,  germinal  epithelium 
of,  1501 
odontoblasts  of,  1201 
Wedge  bones,  247 

-shaped  funiculus,  941 
Wharton's  duct,  1216 
White  commissure  of  cord,  839 
fibrous  tissue,  261 
line  of  Hilton,  1319 
matter  of  cerebellum,  931 

of  cerebrum,  913 
nerve  fibres,  822 
substance  of  cord,  841 
of  Schwann,  822 
Willis,  circle  of,  629,  640 
Winslow,  accessory  anterior  cru- 
ral nerve  of,  1004 
ligament  of,  posterior,  335 
uncinate  process  of,  1348 
Wirsung,  canal  of,  1351 
Womb,  1486 
Worm  of  cerebellum,  926 
Wormian  bones,  103 

development  of,  103 
Wrisberg,    cardiac    ganglion    of, 
1081 
cartilages  of,  1365 
cuneiform  tubercle  of,  1368 
ligament  of,  339 
nerve  of,  986 
pars  intermedia  of,  1045 
Wrist,  articulations  of,  317 
bursa  of,  492 
-joint,  317 

ligament  of,  318 
surface  form  of,  318 
surgical  anatomy  of,  318 


XiPHo-PERicARDiAL,    ligament, 

559 
Xiphoid  appendix,  158 
surfaces  of,  158 

cartilage,  155 


Y-LIGAMENT,   328 

Yellow  elastic  tissue,  261 
spot  of  Sommerring,  1121 


Zinn,  ligament  of,  373 

zonule  of,  1129 
Zona  arcuata,  1173 

fasciculata,  1430 

glomerulosa,  1430 

incerta,  910 

orbicularis,  327 

pectinata,  1173 

reticularis,  1430 

tecta,  1173 
Zonula  ciliaris,  1129 
Zonule  of  Zinn,  1129 
Zygoma,  84 
Zygomatic  arch,  138 

fossa,  138 

lymphatic  glands,  782 

process  of  malar,  115 
of  temporal  bone,  84 
Zygomaticus  major  muscle,  377 

minor  muscle,  377 
Zymogen  granules,  1352 


UNIVERSITY  OF  CALIFORNIA 

Medical  Center  Library 

THIS  BOOK  IS  DUE  ON  THE  LAST  DATE  STAMPED  BELOW 

Books  not  returned  on  time  are  subject  to  a  fine  of  50c  per  volume  after 
the  third  day  overdue,  increasing  to  $1.00  per  volume  after  the  sixth  day. 
Books  not  in  demand  may  be  renewed  if  application  is  made  before  ex- 
piration of  loan  period. 


74978 


^-^^ 


